Module2-IEEE Mobile Broadband-Mobile WiMAX

8/9/2019 Module2-IEEE Mobile Broadband-Mobile WiMAX

http://slidepdf.com/reader/full/module2-ieee-mobile-broadband-mobile-wimax 1/64

ITU Centres of Excellence for Europe

Mobile Broadband: LTE/LTE-Advanced,WiMAX and WLAN

Module 2:IEEE mobile broadband: Mobile WiMAX



1

Table of contents

2.1. IEEE standards for mobile broadband ...........................................................22.2. 3G Mobile WiMAX (IEEE 802.16e) ................................................................72.3. 4G Mobile WiMAX (IEEE 802.16m-2011) ....................................................132.4. Femto cells in advanced WiMAX systems ...................................................242.5. Mobile WiMAX network design and deployment..........................................292.6. WiMAX Interworking with LTE/LTE-Advanced networks..............................352.7. Mobile IP, IEEE 802.21 for seamless mobility..............................................39

2.7.1. Mobile IP............................................................................................392.7.2. IEEE 802.21.......................................................................................45

2.8. 4G regulation: Mobile WiMAX and LTE/LTE-Advanced...............................522.9. Business potential of Mobile WiMAX ...........................................................57References .........................................................................................................62



2

2.1. IEEE standards for mobile broadband

The biggest challenge in the delivery of broadband services directly tocustomers’ terminals represents the ‘last mile’ problem. It is solved by variousflavours of wired or wireless access technologies, depending on the populationdensity, required services and coverage area, existing infrastructure (e.g. cables,fibres, ducts), configuration of the terrain, etc., but the network dimensioning istypically carried out based on long-term service requirements. To meet thedemand for higher data rate communications a plethora of ‘last mile’ technologiesare used and under development based around different communicationstandards.

The IEEE Standards Association, a globally recognized standards-setting

body within IEEE, develops consensus standards through an open process thatengages industry and brings together a broad stakeholder community. IEEEstandards set specifications and best practices based on current scientific andtechnological knowledge. The IEEE-SA has a portfolio of over 900 activestandards and more than 500 standards under development (for moreinformation visit the IEEE-SA website).

In a way of the mobile broadband internet, IEEE 802 has developed analternative series of wireless Internet standards. The main intent is to bring tomarket low-cost products that serve customer needs. Much of the work involveslicense-exempt spectrum. This removes the spectrum acquisition costs from theeconomic picture. Furthermore, it weakens the concept of a monolithic ‘operator’

with strong control over the provided services. Instead, it opens up the market toenterprise and innovation. IEEE 802 wireless Internet technologies offer datarates much higher than those provided by even the fixed user case in IMT-2000;for example, the currently popular IEEE 802.11b standard supports 11 Mb/s,while the recent IEEE 802.11g speeds up to 54 Mb/s. The basic structures ofIEEE standards are not intended to offer the mobility of IMT-2000 in the sense ofproviding services to moving vehicles, although extensions to high mobility arecurrently under investigations, and they are not aimed at providing blanketcoverage to users at arbitrary locations within a city.

In this context, IEEE 802 LAN/MAN Standards Committee has developedthree standardization branches:

IEEE 802.16 and IEEE 802.20 wireless MAN (Metropolitan AreaNetwork) standards will support high-rate broadband-wireless-access services to buildings, mostly through rooftop antennas, fromcentral base stations.

IEEE 802.11 wireless LAN (Local Area Network) standards supportusers roaming within homes, office buildings, campuses, hotels,airports, restaurants, cafes, etc.

and IEEE 802.15 wireless PAN (Personal Area Network) standardswill support short-range links among computers, mobile telephones,peripherals, and other consumer electronics devices that are wornor carried.



3

IEEE 802.11 and 802.15 have worked particularly closely since they bothaddress unlicensed bands. IEEE 802.16 has historically dealt with licensedbands and been more independent. However, a new license-exempt project inIEEE 802.16 now requires it to coordinate more closely with the other twoworking groups. The IEEE 802.16 Working Group on Broadband WirelessAccess has completed 17 standards projects since 2001 toward the developmentand evolution of the IEEE 802.16 WirelessMAN® Standard for WirelessMetropolitan Area Networks. The Working Group currently has 437 individualmembers. It typically meets six times a year, around the globe (for more details,see http://wirelessman.org).

Furthermore in this section we shortly summarized the technologyaddressed by the different IEEE 802 wireless mobile broadband standardprograms, with particular attention to the IEEE 802.11 and IEEE 802.16, IEEE802.20 and IEEE 802.21 frameworks.

The IEEE 802.11 working group has produced a standard describing MAC(Medium Access Control) sublayer and multiple PHYs (PHYsical layers). IEEE802.11 also describes MAC management functionality. IEEE 802.11a, IEEE802.11b and IEEE 802.11g are additional PHY amendments to the basestandard (IEEE 802.11-1999). The existing standard and its amendmentsdescribe several Wireless LAN PHYs:

Infrared at 1 and, optionally, 2 Mb/s; Frequency hopping spread spectrum radio at 1 and, optionally, 2

Mb/s in the 2.4 GHz band; Direct sequence spread spectrum radios with data rates up to 11

Mb/s in the 2.4 GHz band (11b amendment, colloquially referred to

as ‘Wi-Fi’ (Wireless Fidelity)); Orthogonal frequency division multiplexing radios with data rates up

to 54 Mb/s in the 5-6 GHz band (11a amendment); Orthogonal frequency division multiplexing radios with data rates up

to 54 Mb/s in the 2.4 GHz band (11g amendment).Current work includes extending the MAC and MAC-management

functionality to provide expanded international operation and roaming, improvedsupport for quality of service, enhanced security, dynamic channel selection,transmit power control, and standardized communication between IEEE 802.11access points (11e amendment). Moreover, the IEEE 802.11 has a variety ofstandards (not only above given), each with a letter suffix. These cover

everything from the wireless standards themselves, to standards for securityaspects, quality of service and the like:

802.11a - Wireless network bearer operating in the 5 GHz ISM band withdata rate up to 54 Mbps

802.11b - Wireless network bearer operating in the 2.4 GHz ISM bandwith data rates up to 11 Mbps

802.11e - Quality of service and prioritisation802.11f - Handover802.11g - Wireless network bearer operating in 2.4 GHz ISM band with

data rates up to 54 Mbps



4

802.11h - Power control802.11i - Authentication and encryption802.11j - Interworking802.11k - Measurement reporting802.11n - Wireless network bearer operating in the 2.4 and 5 GHz ISM

bands with data rates up to 600 Mbps802.11s - Mesh networking802.11ac - Wireless network bearer operating below 6GHz to provide

data rates of at least 1Gbps per second for multi-station operation and 500 Mbpson a single link

802.11ad - Wireless network bearer providing very high throughput atfrequencies up to 60GHz

802.11af - Wi-Fi in TV spectrum white spaces (often called White-Fi)

Of these the standards that are most widely known are the network bearerstandards, 802.11a, 802.11b, 802.11g and now 802.11n. Their fundamentalcharacteristics are summarized in the Table 2.1.

Table 2.1. Summary of major IEEE 802.11 standards.

The newest IEEE standard in the WLAN category is 802.11n. It was

designed to improve on 802.11g in the amount of bandwidth supported byutilizing multiple wireless signals and antennas (MIMO technology) instead ofone. When this standard is finalized, 802.11n connections should support datarates of over 100 Mbps. 802.11n also offers somewhat better range over earlierWLAN standards due to its increased signal intensity. The IEEE 802.11nequipment will be backward compatible with 802.11g gear and for sure is one ofthe main IEEE standards for mobile broadband. More details about WLANbroadband access networks are given in Module 3.

The second main IEEE mobile broadband standard is IEEE 802.16, whichdefines the wireless metropolitan area network (MAN) technology which isbranded as WiMAX. The 802.16 includes two sets of standards, 802.16-2004



5

(802.16d) for fixed WiMAX, 802.16-2005(802.16e) for 3G mobile WiMAX and thenewest IEEE 802.16m-2011 for 4G Mobile WiMAX 2.0. The WiMAX wirelessbroadband access standard provides the missing link for the "last mile"connection in metropolitan area networks where DSL, Cable and otherbroadband access methods are not available or too expensive. WiMAX alsooffers an alternative to satellite Internet services for rural areas and allowsmobility of the customer equipment. Moreover, the IEEE 802.16m provides theperformance improvements necessary to support future advanced services andapplications for next generation broadband mobile communications. In October2010, ITU-R agreed to incorporate this technology (Mobile WiMAX 2.0 (IEEE802.16m-2011), also known as WirelessMAN-Advanced) into its IMT-AdvancedRecommendation specifying systems that support low to high mobilityapplications, a wide range of data rates in multiple user environments, high-quality multimedia applications, and significant improvements in performance andquality of service. More details about the 3G and 4G Mobile WiMAX is providedin the following sections.

On 11 December 2002, the IEEE Standards Board approved theestablishment of IEEE 802.20, the Mobile Broadband Wireless Access (MBWA)Working Group. The mission of IEEE 802.20 is to develop the specification for anefficient packet based air interface that is optimised for the transport of IP basedservices. The goal is to enable worldwide deployment of affordable, ubiquitous,always on and interoperable multi-vendor mobile broadband wireless accessnetworks that meet the needs of business and residential end user markets.Specification of physical and medium access control layers of an air interface forinteroperable mobile broadband wireless access systems, operating in licensed

bands below 3.5 GHz, optimised for IP-data transport, with peak data rates peruser in excess of 1 Mbit/s. It supports various vehicular mobility classes up to250 km/h in a MAN environment and targets spectral efficiencies, sustained userdata rates and numbers of active users that are all significantly higher thanachieved by existing mobile systems. The proposed standard will conform to theappropriate IEEE 802 functional requirements. Compatibility will be addressedduring development of the standard and any variance that may be required willbe clearly identified and justified. The standard will include the definition of acompliant management information base (MIB) in support of the PHY and MAClayer capabilities. The proposed standard is applicable to licensed spectrum andall issues of coexistence will be subject to the respective constraints imposed by

the spectrum license. Deployment related coexistence issues would beaddressed during the development of the proposed standard.

The main technical characteristics of IEEE 802.20 are: Frequency bandsbelow 3.5 GHz, peak data rates per user of 1 Mbps, vehicular mobility up to 250km/h, large cells (up to 15 km), spectral efficiencies about 1 bit/s/Hz/cell, supportof Real and Non-Real data traffic, use spread spectrum technologies (likeFrequency Hopping), OFDM carrier and adaptive antennas.

The main advantages of IEEE 802.20 are: Delivery of broadband to fastmoving users, up to 250 km/h; good QoS: connection oriented MAC supports



6

data, voice and video; the aim is to have transparent IP services over differentmobile wireless technologies; various modulation and transmission codes.

Unfortunately, on June 8, 2006, the IEEE-SA Standards Board directedthat all activities of the 802.20 Working Group be temporarily suspended untilOctober 1, 2006. The decision came from complaints of a lack of transparency.Later, IEEE 802.20 standard was put to hibernation on March 2011 due to lack ofactivity.

On the other side, the IEEE 802.21 working group (seewww.ieee802.org/21) started work in March 2004. More than 30 companies have

joined the working group. The group produced a first draft of the standardincluding the protocol definition in May 2005. The standard was publishedJanuary 2009. The main purpose of IEEE 802.21 (also called Media-IndependentHandovers (MIH)) is to enable handovers between heterogeneous technologies(including IEEE 802 and cellular technologies) without service interruption, henceimproving user experience of mobile terminals. A lot of functionalities required toprovide session continuity depend on complex interactions that are specific toeach particular technology.

The IEEE 802.21 provides a framework that allows higher levels tointeract with lower layers to provide session continuity without dealing with thespecifics of each technology. That is, the upcoming protocol can be seen as the”glue” between the IP centric world developed in IETF and the referencescenarios for future mobile networks currently being designed in 3GPP and3GPP2 or other technology specific solutions.

The main design elements of IEEE 802.21 can be classified into threecategories: a framework for enabling transparent service continuity while handing

over between heterogeneous access technologies; a set of handover-enablingfunctions; and a set of Service Access Points (SAPs). However, the section 2.7 isproviding greater details about IEEE 802.21.



7

2.2. 3G Mobile WiMAX (IEEE 802.16e)

The IEEE 802.16e has emerged as a strong candidate standard fornowadays 3G and future wireless systems primarily because it offers thepotential for high spectral efficiency, flexible spectrum options (e.g., 2–6 GHz),scalable carrier bandwidth options (e.g., from 1.25 MHz to 20 MHz), multipleduplexing options (time and frequency division duplex), varioussubchannelization options, and, unlike its IEEE 802.16 predecessors, mobility.Because of the recent emergence of IEEE 802.16e and the complexity it poses insystem analysis, there is little published work in the literature regarding the actualsystem capacity (throughput) performance of IEEE 802.16e for high data rateservices.

The true 3G Mobile WiMAX standard of 802.16e is divergent from FixedWiMAX. It attracted a significant number of Forum members towards anopportunity to substantively challenge existing 3G technology purveyors. Whileclearly based on the same OFDM base technology adopted in 802.16-2004, the802.16e version is designed to deliver service across many more sub-channelsthan the OFDM 256-FFT. It is important to note that both standards supportsingle carrier, OFDM 256-FFT and at least OFDMA 1K-FFT.

Moreover, the 802.16e standard adds OFDMA 2K-FFT, 512-FFT and 128-FFT capability. Sub-channelization facilitates access at varying distance byproviding operators the capability to dynamically reduce the number of channelswhile increasing the gain of signal to each channel in order to reach customers

farther away. The reverse is also possible. For example, when a user getscloser to a cell site, the number of channels will increase and the modulation canalso change to increase bandwidth. At longer ranges, modulations like QPSK(which offer robust links but lower bandwidth) can give way at shorter ranges to64 QAM (which are more sensitive links, but offer much higher bandwidth) forexample. Each subscriber is linked to a number of subchannels that obviatemulti-path interference. The upshot is that cells should be much less sensitive tooverload and cell size shrinkage during the load than before. Ideally, customersat any range should receive solid QoS without drops that 3G technology mayexperience. The 802.16e version of WiMAX also incorporates support formultiple-input-multiple-output (MIMO) antenna technology as well asBeamforming and Advanced Antenna Systems (AAS), which are all "smart"antenna technologies that significantly improve gain of WiMAX systems as wellas throughput.

The 802.16e standard is being utilized primarily in licensed spectrum forpure mobile applications. Many firms have elected to develop the 802.16estandard exclusively for both fixed and mobile versions. The 802.16e version ofWiMAX is the closest comparable technology to the emerging LTE mobilewireless standard. Or rather, it is more proper to say that LTE is the mostcomparable to Mobile WiMAX in terms of capabilities as well as technology. Thetwo competing technologies are really very much alike technically.



8

In the following we summarised the key advantages of the 3G MobileWiMAX (802.16e):

Mobile WiMAX physical layer is based on Scalable OFDMAtechnology.

The new technologies employed for Mobile WiMAX result in lowerequipment complexity and simpler mobility management due to theall-IP core network and provide Mobile WiMAX systems with manyother advantages over CDMA-based 3G systems.

Tolerance to Multipath and Self-Interference. Scalable Channel Bandwidth. Orthogonal Uplink Multiple Access. Support for Spectrally-Efficient TDD. Frequency-Selective Scheduling. Fractional Frequency Reuse. Fine Quality of Service (QoS). Advanced Antenna Technology.

IEEE 802.16e-2005 will initially operate in the 2.3 GHz, 2.5 GHz, 3.3 GHz,3.4-3.8 GHz spectrum bands. Support for additional bands will be added on thebasis of market demand and new spectrum allocations. The Release-1 of802.16e profiles will cover 5, 7, 8.75, and 10 MHz channel bandwidths forfrequency bands above.

Furthermore, in figure 2.1 we give the Reference Model of 3G mobileWiMAX.

Figure 2.1. 3G Mobile WiMAX Reference Model.

The WiMAX network reference model is composed of four logical parts: Mobile Stations (MS)—Comprises all user (subscriber) mobile devices,

such as cell phones, PDAs, and wireless laptops, and software neededfor communication with a wireless telephone network.



9

Network Access Provider (NAP)—Provides radio access functionality.Contains the logical representation of the functions of a NAP. Some ofthe functions included in the NAP are: access service network (ASN),802.16 interface with network entry and handover, ASN-GW(gateway), base stations (wireless towers), foreign agent (FA), QoSand policy enforcement, and forwarding to a selected CSN. A NAPmay have contracts with multiple NSPs.

Network Service Provider (NSP)—Provides IP connectivity services.Contains the logical representation of the functions of the NSP. Someof the functions included within the NSP are: connectivity servicenetwork (CSN), home agent (HA), visited and home AAA servers(VAAA or HAAA), connectivity to the Internet, IP address management,authentication, authorization, and accounting, and mobility androaming between ASNs. An NSP may have a contract with anotherNSP and may also have contracts between multiple NAPs.

Internet—Provides Internet content to a user/subscriber andconnectivity to a NSP.

Reference points (for example, R1 or R2) are conceptual links thatconnect two functional entities. Reference points represent a bundle of protocolsbetween peer entities (similar to an IP network interface). Interoperability isenforced through reference points without dictating how vendors implement theedges of those reference points.

R1—Represents the interface between the wireless device and thebase station.

R2—Represents the link between the MS (mobile station) and the CSN(connectivity service network). EAP traffic from the mobile station to the AAAserver traverses R2 and R3.

R3—Represents the link between the ASN (access service network)and the CSN. RADIUS traffic between the ASN-GW and the AAA servertraverses R3.

R4—Represents the link between an ASN and another ASN.R5—Represents the link between a CSN and another CSN.R6 – consists of a set of control and bearer plane protocols for

communication between the BS and the ASN GW. The bearer plane consists ofintra-ASN data path or inter-ASN tunnels between the BS and ASN GW. The

control plane includes protocols for IP tunnel management (establish, modify,and release) in accordance with the MS mobility events. R6 may also serve as aconduit for exchange of MAC states information between neighboring BSs.

R8 – consists of a set of control plane message flows and, in somesituations, bearer plane data flows between the base stations to ensure fast andseamless handover. The bearer plane consists of protocols that allow the datatransfer between Base Stations involved in handover of a certain MS. The controlplane consists of the inter-BS communication protocol defined in IEEE 802.16and additional set of protocols that allow controlling the data transfer between theBase Stations involved in handover of a certain MS.



10

Furthermore, on figure 2.2 are given two implementation scenarios: ASNscenario 1 and 2.

Figure 2.2. Illustration of the implementation scenarios.

The IEEE 802.16 mobile WiMAX standard allows data transmission using

multiple broadband frequency ranges. The original 802.16a standard specifiedtransmissions in the range 10 - 66 GHz, but 802.16d allowed lower frequenciesin the range 2 to 11 GHz. The lower frequencies used in the later specificationsmeans that the signals suffer less from attenuation and therefore they provideimproved range and better coverage within buildings. This brings many benefitsto those using these data links within buildings and means that external antennasare not required. Different bands are available for WiMAX applications in differentparts of the world. The frequencies commonly used are 3.5 and 5.8 GHz for802.16d and 2.3, 2.5 and 3.5 GHz for 802.16e but the use depends upon thecountries (see Table 2.2).

Furthermore, as one of the major goal of any network technology,including mobile WiMAX is delivering any existing service with good level of QoSsupport. In order to categorise the different types of QoS, there are five WiMAXQoS classes that have been defined. These WiMAX QoS classes are defined inthe table 2.3 below. As we said before, the 3G Mobile WiMAX introducesOFDMA and supports several key features necessary for delivering mobilebroadband services at vehicular speeds greater than 120 km/hr with QoScomparable to broadband wireline access alternatives.



11

Table 2.2. Major spectrum allocations for 3G mobile WiMAX worldwide.

Table 2.3. WiMAX QoS classes.



12

The WiMAX technology continues to evolve with the WiMAX Forum’sapproval of the Release-1 mobile WiMAX system performance profiles based onthe 802.16e-2005 amendment and beyond 4G Mobile WiMAX (IEEE 802.16m-2011, see the next section). With OFDMA, mobile WiMAX can meet the stringentrequirements necessary for the delivery of mobile broadband services in achallenging mobile environment. Many performance simulations are showing that3G mobile WiMAX provides superior throughput and spectral efficiencycompared to planned 3G CDMA-based enhancements, EVDO and HSPA. Theseadvantages will provide operators with added network capacity for the support ofvalue-added services with fewer base stations than alternative approaches thusresulting in lower network capital and operating costs.



13

2.3. 4G Mobile WiMAX (IEEE 802.16m-2011)

The IMT-Advanced requirements (defined and approved by ITU-R/Working Party 5D and published as Report ITU-R M.2134) are referred to astarget requirements in the IEEE 802.16m system requirement document and willbe evaluated based on the methodology and guidelines specified by Report ITU-R M.2135. A careful examination of the IMT-Advanced requirements reveals thatthey are a subset of, and less stringent than, the IEEE 802.16m systemrequirements; therefore, the IEEE 802.16m standard can qualify as an IMT-Advanced technology. Full backward compatibility and interoperability with thereference system is required for IEEE 802.16m systems, although the networkoperator can disable legacy support in Greenfield deployments. The reference

system is defined as a system that is compliant with a subset of the IEEE802.16e-2005 features (see the previous section). Furthermore, in Table 2.4 wesummarized the IEEE 802.16m baseline system requirements and thecorresponding requirements specified by Report ITU-R M.2134.

Table 2.4. IMT-Advanced and IEEE 802.16m system requirements.



14

The IEEE 802.16 standards describes medium-access-control (MAC) andphysical layer (PHY) protocols for fixed and mobile broadband wireless-accesssystems, including IEEE 802.16m. The MAC and PHY functions can be classifiedinto three categories, namely, data plane, control plane, and management plane(see Figure 2.3). The data plane comprises functions in the data processing pathsuch as header compression, as well as MAC and PHY data packet-processing

functions. A set of layer-2 (L2) control functions is required to support variousradio resource configuration, coordination, signaling, and management. This setof functions is collectively referred to as the control-plane functions. Amanagement plane also is defined for external management and systemconfiguration. Therefore, all management entities fall into the managementplanecategory. The IEEE 802.16m MAC layer is composed of two sublayers: theconvergence sublayer (CS) and the MAC common-part sublayer (MAC CPS).For convenience, MAC CPS functions are classified into two groups based ontheir characteristics as shown in Figure 2.3. The upper and lower classes arecalled the resource control and management functional group and the MACfunctional group, respectively. The control-plane functions and data-plane

functions also are classified separately. As shown in Figure 2.3, the radio-resource control and management functional group comprises several functionalblocks including:

Radio-resource management: This block adjusts radio networkparameters related to the traffic load and also includes the functions ofload control (load balancing), admission control, and interference control.

Mobility management: This block scans neighbor BSs and decideswhether an MS should perform a handover operation.

Network-entry management: This block controls initialization and accessprocedures and generates management messages during initializationand access procedures.



15

Figure 2.3. Illustration of the IEEE 802.16m protocol structure.

Location management: This block supports location-based service(LBS), generates messages including the LBS information, andmanages the location-update operation during idle mode.

Idle-mode management: This block controls idle-mode operation andgenerates the paging- advertisement message, based on a pagingmessage from the paging controller in the core network.

Security management: This block performs key management for securecommunication. Using a managed key, traffic encryption/ decryption andauthentication are performed.

System configuration management: This block manages system-configuration parameters and generates broadcast-control messages,such as a DL/UL channel descriptor.

Multicast and broadcast service (MBS): This block controls andgenerates management messages and data associated with the MBS.

Connection management: This block allocates connection identifiers(CIDs) during initialization/handover service-flow creation procedures;interacts with the convergence sublayer to classify MAC service dataunits (MSDUs) from upper layers; and maps MSDUs into a particulartransport connection.



16

Furthermore, the MAC functional group includes functional blocks that arerelated to physical layer and link controls such as:

PHY control: This block performs PHY signaling such as ranging,channel quality measurement/feedback (CQI), and hybrid automaticrepeat request (HARQ) acknowledgment (ACK) or negativeacknowledgment (NACK) signaling.

Control signaling: This block generates resource-allocation messagessuch as DL/UL medium-access protocol (MAP), as well as specificcontrol signaling messages, and other signaling messages not in theform of general MAC messages (e.g., a DL frame control header).

Sleep mode management: This block handles sleep mode operation andgenerates management messages related to sleep operation and cancommunicate with the scheduler block to operate properly according tothe sleep period.

Quality-of-service (QoS): This block performs rate control based on QoSinput parameters from the connection management function for eachconnection.

Scheduling and resource multiplexing: This block schedules andmultiplexes packets based on the properties of the connections.

Automatic repeat request (ARQ): This block performs the MAC ARQfunction. For ARQ-enabled connections, the ARQ block splits MSDUslogically and sequences logical ARQ blocks.

Fragmentation/packing: This block performs the fragmentation orpacking of MSDUs based on input from the scheduler block.

MAC PDU formation: This block constructs MAC protocol data units

(PDUs) so that a BS/MS can transmit user traffic or managementmessages via PHY channels.

The IEEE 802.16m protocol structure is similar to that of IEEE 802.16 withadditional functional blocks for new features including the following:

Relay functions: Relay functionality and packet routing in relay networks Self-organization and self-optimization functions: a plug-and-play form of

operation for an indoor BS (i.e., a femtocell). Multi-carrier functions: Control and operation of a number of adjacent or

non-adjacent radio-frequency (RF) carriers where the RF carriers can beassigned to unicast and/or multicast and broadcast services. A single

MAC instantiation is used to control several physical layers. If the MSsupports multi-carrier operation, it can receive control and signaling,broadcast, and synchronization channels through a primary carrier, andtraffic assignments can be made on the secondary carriers. Ageneralization of the protocol structure for multi-carrier support using asingle MAC instantiation is shown in Figure 2.4. The load-balancingfunctions and the RF-carrier mapping and control are performed by theradio-resource control and management functional class. From theperspective of an MS, the carriers utilized in a multi-carrier system canbe divided into two categories:



17

A primary RF carrier is the carrier that is used by the BS and theMS to exchange traffic and full PHY/MAC control information.

A secondary RF carrier is an additional carrier that the BS may usefor traffic allocations for mobile stations capable of multicarriersupport.

Figure 2.4. IEEE 802.16m multicarrier protocol stack and frame structure.

Based on the primary and/or secondary usage, the carriers of a multi-carrier system can be configured differently as follows: Fully configured carrier: A carrier for which all control channels

including synchronization, broadcast, multicast, and unicastcontrol signaling are configured. The information and parametersrelated to multi-carrier operation and the other carriers also canbe included in the control channels.

Partially configured carrier: A carrier with only essential control-

channel configuration to support traffic exchanges duringmulticarrier operation. If the user-terminal RF front end and/or itsbaseband is not capable of processing more than one RF carriersimultaneously, the user terminal may be allowed, in certainintervals, to monitor secondary RF carriers and to resumemonitoring of the primary carrier prior to transmission of thesynchronization, broadcast, and nonuser-specific controlchannels.

Multi-radio coexistence functions: Protocols for multi-radio coexistence,where the MS generates management messages to report theinformation about its co-located radio activities obtained from the inter-



18

radio interface, and the BS responds with the corresponding messagesto support multi-radio coexistence operation.

It is well known that the IEEE 802.16m uses OFDMA as the multipleaccess scheme in the DL and UL. It further supports both time-division duplex(TDD) and frequency-division duplex (FDD) schemes including the half-duplexFDD (HFDD) operation of the mobile stations in the FDD networks. Also, IEEE802.16m identified new frequency bands for FDD and TDD deployment ofsystems (see Table 2.5).

Table 2.5. IEEE 802.16m frequency bands



19

The frame structure attributes and baseband processing are common forboth duplex schemes. The super-frame is a new concept introduced in IEEE802.16m, where a super-frame is a collection of consecutive, equally-sized radioframes, where the beginning is marked with a super-frame header. The super-frame header carries short-term and long-term system configuration information(Figure 2.5). To decrease the air-link access latency, the radio frames are furtherdivided into a number of sub-frames where each sub-frame comprises an integernumber of OFDMA symbols. The transmission time interval is defined as thetransmission latency over the air-link and is equal to a multiple of sub-framelength (default one sub-frame).

Figure 2.5. The IEEE 802.16m frame structure for 5/10/20 MHz channel bandwidth.



20

There are three types of sub-frames depending on the size of the cyclic prefix: Type-1 subframe, which consists of six OFDMA symbols Type-2 subframe, which consists of seven OFDMA symbols Type-3 subframe, which consists of five OFDMA symbolsIn all of the sub-frame types, some of the symbols can be idle symbols. In the

basic frame structure, the super-frame length is 20 ms (comprising four radioframes), radio frame size is 5 ms (comprising eight sub-frames), and sub-framelength is 0.617 ms. The use of the subframe concept with the latter parameter setwould reduce the one-way air-link access latency from 18.5 ms (corresponding tothe reference system) to less than 5 ms. The concept of time zones that isapplied to both TDD and FDD systems was introduced in IEEE 802.16m. Thenew and legacy time zones are time-division multiplexed across the time domainfor the DL. For UL transmissions, both time- and frequency-division multiplexapproaches are supported for the multiplexing of legacy and new terminals. Thenon-backward compatible improvements and features are restricted to the newzones. All backward compatible features and functions are used in the legacyzones. In the absence of a legacy system, the legacy zones disappear, and theentire frame is allocated to the new zones.

When it comes a word about modulation and coding in the IEEE 802.16mwe can say that it supports quadrature-phase shift keying (QPSK), 16-QAM, and64-QAM modulation schemes in the DL and UL. The performance of adaptivemodulation generally suffers from the power inefficiencies of multilevel-modulation formats. This is due to the variations in bit reliabilities caused by thebit-mapping onto the signal constellation. To overcome this issue, a constellationrearrangement scheme is utilized where a signal constellation of quadrature

amplitude modulation (QAM) signals between retransmissions is rearranged; thatis, the mapping of the bits onto the complex-valued symbols between successiveHARQ retransmissions is changed, resulting in averaging the bit reliabilities overseveral retransmissions and lower packet-error rates. The mapping of bits to theconstellation point depends on the constellation rearrangement type used forHARQ retransmissions and also can depend on the MIMO scheme. Thecomplex-valued modulated symbols are mapped to the input of the MIMOencoder. Incremental-redundancy HARQ is used in determining the startingposition of the bit selection for HARQ retransmissions.

Both convolutional code and convolutional turbo code with variable coderate and repetition coding are supported. The modulation and coding schemes

used in a data transmission are selected from a set of 16 modulation codingschemes (MCSs).

Furthermore, IEEE 802.16m supports several advanced multi-antennatechniques including ingle and multi-user MIMO (spatial multiplexing and beam-forming) as well as a number of transmit diversity schemes. In single-user MIMO(SU-MIMO) scheme only one user can be cheduled over one resource unit, whilein multi-user MIMO (MU-MIMO), multiple users can e scheduled in one resourceunit.

Single-user MIMO (SU-MIMO) schemes are used to improve the linkperformance, by providing robust transmissions with spatial diversity, or large



21

spatial multiplexing gain and peak data rate to a single MS, or beam-forminggain. Both open-loop SU-MIMO and closed-loop SU-MIMO is supported in 16m.For open-loop SU-MIMO, both spatial multiplexing and transmit diversityschemes are supported. For closed-loop SU-MIMO, codebook based pre-codingis supported for both TDD and FDD systems. CQI, PMI, and rank feedback canbe transmitted by the mobile station to assist the base station’s scheduling,resource allocation, and rate adaptation decisions. CQI, PMI, and rank feedbackmay or may not be frequency dependent. For closed-loop SU-MIMO, soundingbased pre-coding is supported for TDD systems.

On the other side, multi-user MIMO (MU-MIMO) schemes are used toenable resource allocation to communicate data to two or more MSs. MU-MIMOenhances the system throughput. Multi-user transmission with one stream peruser is supported in MU-MIMO mode. MU-MIMO includes the MIMOconfiguration of 2Tx antennas to support up to 2 users, and 4Tx or 8Tx antennasto support up to 4 users. Both unitary and non-unitary MU-MIMO linear pre-coding techniques are supported.

For open-loop MU-MIMO, CQI and preferred stream index feedback maybe transmitted to assist the base station’s scheduling, transmission modeswitching, and rate adaptation. The CQI is frequency dependent. For closed-loopmulti -user MIMO, codebook based pre-coding is supported for both TDD andFDD systems. CQI and PMI feedback can be transmitted by the mobile station toassist the base station’s scheduling, resource allocation, and rate adaptationdecisions. CQI and PMI feedback may or may not be frequency dependent. Forclosed-loop multi -user MIMO, sounding based pre-coding is supported for TDDsystems. In Figure 2.6 is given a basic comparison of SU-MIMO and MU-MIMO.

a) b)Figure 2.6. Examples of SU-MIMO (a)) and MU-MIMO (b)).

Multi-BS MIMO techniques are supported in IEEE 802.16m for improvingsector throughput and cell-edge throughput through multi-BS collaborativeprecoding, network coordinated beamforming, or inter-cell interference nulling.Both open-loop and closed-loop multi-BS MIMO techniques can be considered.For closed-loop multi-BS MIMO, CSI feedback via codebook based feedback or



22

sounding channel will be used. The feedback information may be shared byneighboring BSs via network interface. This places significant obligation in lowlatency backhauls. COMP - Coordinated multi-point (CoMP) is a new class oftransmission schemes for interference reduction in the 802.16m technology.Enabling features such as network synchronization, cell- and user-specific pilots,feedback of multicell channel state information and synchronous data exchangebetween the base stations can be used for interference mitigation and forpossible macro diversity gain. The collaborative MIMO (Co-MIMO) and theclosed-loop macro diversity (CL-MD) techniques are examples of the possibleoptions. For downlink Co-MIMO, multiple BSs perform joint MIMO transmissionto multiple MSs located in different cells. Each BS performs multi-user precodingtowards multiple MSs, and each MS is benefited from Co-MIMO by receivingmultiple streams from multiple BSs. For downlink CL-MD, each group ofantennas of one BS performs narrow-band or wide-band single-user precodingwith up to two streams independently, and multiple BSs (see Figure 2.7).

Figure 2.7. Multi BS-MIMO

In DL and UL different MIMO techniques are available in IEEE 802.16m.They are listed in Table 2.6 and 2.7 respectively.

Table 2.6. Supported MIMO techniques by IEEE 802.16m in DL



23

Table 2.7. Supported MIMO techniques by IEEE 802.16m in UL

Other key enhancements and features planned for the IEEE 802.16mamendment and 4G mobile WiMAX System includes:

Enhanced Multicast Broadcast Services (E-MBS) to provide greaterbroadcast and multicast spectral efficiency and support forswitching between broadcast and unicast services whether on thesame or on different frequencies.

Enhanced GPS-based and Non-GPS-based Location BasedServices (LBS) using triangulation schemes with < 30 secondslatency for location determination.

Self-Organizing Network (SON) features to enable self-configuration and self-optimization. Self-configuration enables trueplug and play of network nodes and cells as well as fastreconfiguration and compensation in cases of failure. Self-optimization ensures optimal network performance with respect toservice availability, QoS, network efficiency, and throughput underchanging traffic and environmental conditions.

Enhanced security with more advanced encryption schemesassuring confidentiality of user identity and user-generated datapackets (e.g. location privacy and user identity protection).

Mobility: An IEEE 802.16m mobile station will maintain aconnection up to 350 km/hr and in some cases 500 km/hrdepending on the operating frequency band.

In the following sections some of those advanced features of IEEE802.16m network design and deployment, like: E-MBS, Relaying, Femto-cellsand Self organizing networks and other will be overviewed in more details.



24

2.4. Femto cells in advanced WiMAX systems

Femtocells are viewed as a promising option for mobile operators toimprove coverage and provide high-data-rate services in a cost-effective manner.The idea is to overlay low-power and low-cost base station devices, Femto-APs,on the existing cellular network, where each Femto-AP provides high-speedwireless connection to subscribers within a small range. In particular, Femto-APscan be used to serve indoor users, resulting in a powerful solution for ubiquitousindoor and outdoor coverage, using a single access technology such as MobileWiMAX. Moreover, the femtocells in 802.16m are low powered access pointstypically used in home or SOHO to provide the access to closed or open group ofusers as configures by the subscribers. Femtocells are normally connected to

service provider’s network through broadband or other access technologies. Forthe femtocell BSs which can support Relay Link transmission, it may establishthe air interface connection with the overlapped macrocell BS for exchange ofcontrol messages.

Through deployment of a large number of Femto-APs, significant gain in areal capacity and indoor coverage can be achieved. In addition, Femto-APdeployments have several advantages over other technologies. First, they are acost-effective solution for indoor access since they are more likely to be deployedat places that need them most, and being a consumer device, the cost of aFemto-AP is expected to be under $200. Wireless operators save on backhaulcosts since Femto-AP traffic is carried over wired residential broadband

connections that connect to the IP backbone. The consumer can expectimproved data speeds and service quality, and longer battery life as it is nolonger necessary to connect to outdoor macro/micro BSs. Furthermore, Femto-APs enable the convergence of landline and mobile services since the samehandheld device can be used to access the broadband wireless connectionindoors and outdoors. In the future, it may also be possible to provide newservices such as indoor location finding, and fast music and video downloadswith Femto-APs deployed in advanced WiMAX systems.

To emphasize that the Femtocell BS (or Femto-AP) is intended to servepublic users, like public WLAN hot spot, or to serve closed subscriber group(CSG) that is a set of subscribers authorized by the femtocell BS owner or theservice provider. CSG can be modified by the service level agreement betweenthe subscriber and the access provider. Femtocells coupled with the features ofself organizing systems, automatic neighbor establishment, coverage andcapacity optimization, software up gradations and handover optimization will besupported in 16m to maximize the overall network performance. Note that SONfunctions are intended for any BSs (e.g. Macro, Relay, Femtocell) to automatethe configuration of BS and has remarkable ability to optimize networkperformance, coverage and capacity, but particularly are more important tofemtocell, since femtocell is typically installed by a subscriber. The scope of SONin IEEE 802.16m is limited to the measurement and reporting of air interface



25

performance metrics from MS/BS, and the subsequent adjustments of BSparameters.

Self organization can be divided into the following two; Initializing and configuring BSs automatically with minimum human

intervention ( Cell initialization, Neighbor discovery, and NeighborMacro BS Discovery)

Self-optimization from the BS/MS and fine tuning the BS parameters inorder to optimize the network performance which includes QoS,network efficiency, throughput, cell coverage and cell capacity.

An example network structure for an adnvanced WiMAX system withFemto-APs is illustrated in Figure 2.8.

Figure. 2.8. Illustration of WiMAX network with Femto-BS.

The WiMAX network consists of two components, the access servicenetwork (ASN) and connectivity service network (CSN). An all-IP networkstructure is applied in the ASN where both operator-owned macro/micro BSs and

customer owned Femto-APs are connected to local ISP networks to reduce thebackbone implementation cost. Typically, the IP networks to which macro/microBSs are connected are built and owned by operators, whereas Femto-APs arelikely to connect to IP networks provided by local DSL or cable companies. Incontrast, the CSN is an existing backend composed of servers such as anauthentication, authorization, and accounting (AAA) server, mobile IP (MIP),home agent (HA), and policy server. The interface between ASN and CSNoccurs at the ASN gateway (GW). Macro/micro BSs and Femto-APscommunicate with ASN gateways through the packet-switched IP network,enabling exchange of necessary information with servers within the CSN. TheASN gateways conduct tasks like location registration, authentication, paging



26

control, and service flow authorization. This WiMAX network architecture is flatcompared to typical cellular architectures (second/third generation [2G/3G]) sinceRNC functions are integrated into macro/micro BSs and Femto-APs. Thus,macro/micro BSs and Femto-APs in WiMAX networks should be moreautonomous. Additionally, such a system is more robust since each BS, eithermacro/micro or femto, can connect to multiple ASN GWs such that there is nosingle point of failure. The role of a Femto-AP in WiMAX network is the same asa macro/micro BS. A Session Initiation Protocol/IP multimedia subsystem(SIP/IMS) gateway is required to interwork with existing 2G/3G networks and thepublic switched telephone network (PSTN).

However, the developing a new technology is always a challenging task.In order for femtocells to be successful and provide significant capacity andcoverage gains, several technical issues need to be addressed. Furthermore wediscuss the technical challenges for femtocell deployments and possiblesolutions:

a) NETWORK ARCHITECTURE: It is important to decide what kind of networkstructure should be adopted by femtocells. Traditional 2G/3G networksutilize centralized devices, RNCs, to control their associated base stations.Typically, there is an RNC in charge of radio resource management of about100 BSs. Once Femto-APs are overlaid on the existing network, the numberof devices an RNC needs to control will increase on the order of hundredsto thousands or tens of thousands. Current network control entities may notbe scalable to handle so many devices. For advanced WiMAX networks,scalability is less of an issue because of the flat all-IP network architecture.In such a distributed control structure, more radio resource management

needs to be implemented at Femto-APs. Therefore, WiMAX Femto-APsneed to be more autonomous and powerful. In addition, the large neighbor(cells) list that needs to be kept at a BS for timely handover can becomedifficult to manage. The network architecture also needs to considerinfrastructure support for seamless mobility during handover. Managementprotocols used in DSL systems, like TR-069 customer premises equipment(CPE) WAN Management Protocol can be adopted for efficientmanagement of a large-scale femtocell network.

b) INTERFERENCE MANAGEMENT: In a hierarchical overlay network, whereWiMAX Femto-APs operate on the same frequency band as macro BSs, co-channel interference becomes an important factor that limits overall network

performance. When Femto-APs are installed indoors, however, walls help toalleviate the interference between macro BSs and Femto-APs. As thenumber of Femto-APs increase, the accumulated interference becomes aserious issue. At a minimum, power control is required in Femto-APs toavoid performance degradation to mobile terminals served by macro/microBSs. To guarantee close to 100 percent coverage, further interferencemitigation strategies such as fractional frequency reuse (FFR) could beapplied. In order to apply these more advanced interference mitigationstrategies, good synchronization is essential, as well as efficient means ofexchanging messages between macro BSs and Femto-APs.



27

c) SYNCHRONIZATION: Synchronization is required in order to havesuccessful handover between base stations. Furthermore, synchronizationis essential for interference management in outdoor systems using TDDsuch as the 2.5 GHz systems planned for the initial release of mobileWiMAX. In the existing 2G/3G BSs, there are high-accuracy oscillators thatare calibrated periodically by the timing signal sent from central controllerover very reliable links (T1 lines). This solution is not applicable to the all-IParchitecture of WiMAX networks. The synchronization requirement forWiMAX is less stringent than for 2G or 3G technology. The frequencyaccuracy suggested by the WiMAX Forum is less than 2 parts per million(ppm), whereas 0.05 ppm is required in Global System for MobileCommunications (GSM)/wideband code-division multiple access(WCDMA)/CDMA 2000 systems. Synchronization in time to about 1 µs mayalso be required for TDD operation. Candidate calibration strategies includeGPS and IEEE 1588. GPS is more accurate, and provides both time andlocation data. Localization may be a mandatory feature if operators want toavoid customers moving Femto-APs outside of their houses. However, GPSis more expensive and relies on GPS system availability. For indoorfemtocells, GPS is not suitable since it requires line of sight from thesatellite, which is difficult to achieve indoors. IEEE 1588, Precision TimingProtocol (PTP), is a more suitable solution for Femto-APs. It uses a master-slave structure. There is a master clock in the network providing timingreference to the slave clocks at Femto-APs. The timing signal is transmittedover IP/Ethernet backhaul. IEEE 1588 is a low-cost standalone solution thatachieves submicrosecond accuracy. Application of IEEE 1588 to TDD

WiMAX, which requires both time and frequency synchronization, is yet tobe demonstrated.

d) SECURITY AND PERFORMANCE: In traditional cellular systems BSs areconnected directly to the operator’s network. With the registration andauthentication process, the cellular operator can thus easily preventunauthorized users accessing its own network to ensure security. However,Femto-APs utilize local ISP networks, which may be different from theoperators’ network and are much more difficult to protect. The public IPnetwork can be accessed by almost everyone, including hackers whoattempt to eavesdrop on conversations or control the Femto-AP. Therefore,in addition to a more sophisticated registration and authentication process,

encryption of IP packets is necessary. Another issue with the IP network isthat a cellular operator has no control over the channel and cannot prioritizevoice packets from Femto-APs. To ensure system and user performance,collaboration and service level agreements between cellular and landlineoperators are required. For example, with higher priority given to voicepackets from Femto-APs, end-to-end quality of service can be guaranteed.

e) SELF-ORGANIZATION AND AUTONOMOUS OPERATION: as it wasmentioned before, the WiMAX networks require a higher level of self-organization at both macro/micro BSs and Femto-APs because of the flatnetwork architecture. For example, handover and radio resource



28

management (RRM) are directly controlled by the BSs and Femto-APs.Cooperation is required among BSs and Femto-APs for successfulhandover and RRM information exchange. The communication betweenBSs/Femto-APs can be over the landline or even over the air. Latency canbe an issue when sending control signals over the IP network. Fastercommunication can be carried out using the wireless medium, but the actualprocedures remain to be standardized. Besides the self-organizationfunctions shared with macro/micro BSs, a Femto-AP requires even higherautonomy since it should be a plug-and-play device that can integrate itselfinto the mobile network without user intervention. A configuration function inthe device should be capable of adjusting parameters under variousenvironments since the locations of Femto-APs cannot be planned inadvanced, as for macro/micro BSs. Also, the large number of Femto-APsdeployed within the network makes manual maintenance virtuallyimpossible. The possibility of updating firmware and software of the Femto-APs could be an important requirement.

The blossoming industrial activities arise from the potentially high gains incoverage and capacity expected from femtocell deployments, as well as the largenumber of deployments anticipated. Some research reports are forecasting thatby 2012 there will be 36 million shipments with an installed base of nearly 70million femtocells serving over 150 million users. Unsatisfactory coverage andthe increasing number of high-data-rate applications are two of the driving forcesfor femtocell development in advanced Mobile WiMAX systems. Femto-APsimprove coverage and provide huge areal capacity gain through spatial reuse ofthe available bandwidth, as well as spectral efficiency enhancement. Although

femtocells offer the aforementioned advantages, there are several technicalchallenges remaining to be overcome before Femto-APs are widely adopted inthe market. These include innovative algorithms for management of large-scaleFemto-AP networks, advanced interference mitigation methods to ensuresatisfactory coverage when Femto-APs are densely deployed, and seamlessroaming outdoors and indoors. In the future, increasing efforts should be devotedto femtocell research in advanced WiMAX systems, in order to accelerate itssuccess.



29

2.5. Mobile WiMAX network design and deployment

As Along with traditional factors such as link budgets and signal-to-noiseratio (SNR), design and deployment considerations for Mobile WiMAX systemsshould include the cost-saving opportunities offered by the 802.16e/m standard.For example, the standards are allowing for the use of low-cost chipsets andenables flexible bandwidth scalability. Furthermore we will provide an overview ofthese and other considerations involved in deploying Mobile WiMAX systems.

Fact is that a wide variety of technical points need to be considered whendesigning a Mobile WiMAX network. Designing, deploying and managing anywireless and mobile system requires clear objectives to be identified from theoutset; like: definition of the service area, the projected number of mobile users,

their distribution, spectrum availability, system usage, growth rate, and thenetwork interconnect agreement, numbering, and outing policy for inter=networkaccess and roaming. The QoS of Mobile WiMAX network is a critical aspect ofradio planning, which determines the level of service that users will experiencewhen they access the network for multimedia services. The carefully formulateddesign criteria such as link-budgets, targeted service classes, coverage thresholdlevels for different service types, an appropriate propagation model for theavailable spectrum and an appropriate channel allocation strategy can help insatisfying the technical and business goals. A significant consideration is theefficiency (cost and performance) involved in providing coverage and capacity,while avoiding the build-out of a large number of new cell sites.

In Figure 2.9 is given the natural flow of activities performed in the MobileWiMAX network planning, starting from gathering the marketing and designrequirement input and satisfying and design requirement input and satisfying thebusiness model to providing a normal cell plan using a network planning tool.

The first item to consider is the link budget — the loss and gain sum ofsignal strength through the varying medium of the transmission path. The linkbudget determines the maximum cell radius for an adequate service-levelagreement (SLA). Additionally a good SNR is critical for the system to perform atthe optimum level. As mentioned earlier, the 802.16e and the 802.16m standardswill reduce the cost of mobile deployments by enabling VARs to use the chipsetsoriginally intended for laptops and PDAs. These chipsets can be leveraged in the

manufacture of indoor and outdoor fixed customer premises equipment forWiMAX. IEEE 802.16e and 802.16m are offering the critical advantage ofallowing the operator to think about cost savings for serving large coverageareas. Another benefit of the 802.16e OFDMA specification is that the bandwidthof the system is easily scalable because of the fixed relationship between theoccupied bandwidth and the OFDM symbol sample rate. While several samplerates are enabled by the 802.16e standard’s specification of fast Fouriertransform (FFT) sizes of 128, 512, 1024, and 2048, the subcarrier separation andsymbol duration remain constant as the deployment bandwidth changes. Theability to scale while maintaining constant symbol duration provides moreflexibility in equipment components. Most importantly, operators can deploy



30

systems today and grow system bandwidth in the future at lower cost-withoutimpact to earlier deployments.

Figure 2.9. Mobile WiMAX network dimensioning and planning processes

Wireless design criteria vary across four types of environments:1) Dense Urban: A city center with many businesses and high-density

residential units represents a challenge due to multipath effects among themulti-story buildings.

2) Urban: Surrounding a city center, average building heights may be lowerthan the mast of a base station, but the propagation environment remainsequally challenging.

3) Suburban: With lower-density housing (primarily single-family dwellings)and fewer businesses, average building heights are much lower than basestation towers and structures are more spread out, thus creating a morefavourable propagation environment.

4) Rural: Where homes are far apart and businesses widely scattered, thisenvironment offers no obstruction to wireless propagation so long as theterrain is flat.

To take full advantage of WiMAX scalability, system operators need to usethe right software tools to predetermine coverage boundaries. These toolsperform propagation simulation and drive tests. Careful deployment planning iscritical in order to have room to scale, anticipating growing customer demandswhile ensuring a quality user experience. This planning is especially important inurban areas, where deployments are most likely to be driven by capacityrequirements.



31

Population density and population growth rates are easily obtained for anymetropolitan area by referring to census data. When considering mobile servicesthe addressable market can be assumed to be any individual within a certain agegroup. The specific age group targeted may differ from operator to operatorbased on planned services and population density data.

A 3-sector base station is standard for cellular and PCS systems, and italso suits WiMAX systems (Figure 2.10). To make best use of the availablewireless spectrum, Mobile WiMAX systems can utilize both sector and frequencyreuse. Sector reuse is using one sector to cover multiple areas, at least one ofwhich is closer to another base station. Frequency reuse is using a frequency toserve multiple sectors that do not mutually interfere. With a frequency reuse of 1,each of a BS’s three sectors use the same channel (thus effectively combiningthe three sectors into a single sector). A frequency reuse of 3 eliminates co-channel interference at the sector boundaries. This reuse also significantlydecreases co-channel interference between neighboring cells due to theincreased spatial separation for channels operating at the same frequency -provided that the cell sector boundaries are properly aligned. Getting the rightalignment involves down-tilting antennas and performing drive tests to see ifeach sector covers the proposed azimuths. The inherent properties of MobileWiMAX’s OFDMA scheme controls adjacent channel interference (ACI) at thesector boundaries.

Figure 2.10. 3-Sector Wireless System with Frequency ReuseCalculations for link margins and SNR must include a number of factors,

mostly related to the deployment environment and quality of service goals. Thechosen Mobile WiMAX implementation technology strongly influences thesetradeoffs. Because of the importance of good reception inside buildings andvehicles, penetration loss must be taken into account by utilizing thenormalization factor (n-factor) for a given medium. The n-factor depends on themodulation and is used to achieve the same average power for all mappings.The modulation is based on Quadrature Amplitude Modulation (QAM) with 2Mpoints constellation, where M is the number of bits transmitted per modulated



32

symbol. For Mobile WiMAX downlinks, 4QAM (QPSK, M = 2) and 16QAM (M=4)are mandatory, while 64QAM (M=6) is optional. For uplinks, 4QAM is mandatoryand 16QAM is optional. As a propagation model for making calculations, MobileWiMAX deployments can take advantage of the Modified Hata COST 231 model.This widely used version of the COST 231 model is suitable for mobileapplications in the 1900 MHz band and acceptable for the 2500 MHz and 3500MHz bands.

Another factor is antenna gain, which can be used to increase coveragewith the trade-off that increasing gain decreases the carrier-to-interference-plus-noise ratio (CINR). A CINR of 25 dB or better is normal. Other link parametersincluding fade margins and interference margins are assumed to be the same foreach of the frequency bands — 2.5 GHz, 3.5 GHz and eventually 5.8 GHzbands.

On the other hand, the intelligent relays are an effective technology toachieve important deployment tools to provide cost-effective methods ofdelivering high data rate and avoid coverage holes in deployments areas. Inaddition, upgrading the networks in order to support higher data rates isequivalent to an increase of signal-to-interference plus noise ratio (SINR) at thereceivers’ front-end. Also, through deployment the network providers have toavoid coverage area holes. A traditional solution to increase the receiver’s SINRis to deploy additional BSs or repeaters to serve the coverage area holes withrequired data rates. In most of the cases, the cost of the BS is relatively high andarranging backhauls quickly might be a challenge in serving coverage holes. Bynow industry has used RF repeaters; however repeater has the problem ofamplifying the interference and has no intelligence of signal control and

processing. In order to achieve a more cost effective solution, relay stations (RS)capable of decoding and forwarding the signals from source to destinationthrough radio interface would help operators to achieve higher SINR in costeffective manner. Relay stations do not need a wire-line backhaul; thedeployment cost of RSs is expected to be much lower than the cost of BSs. Thesystem performance could be further improved by the intelligent resourcescheduling and cooperative transmission in systems employing intelligent relays.

Moreover, deploying RS can improve IEEE 802.16m network in differentdimensions. The following figure 2.11 illustrates the different benefits that can beachieved by deploying RS within an IEEE802.16m network.

Figure 2.11. Relay usage in IEEE 802.16m.



33

Another key advantage in Mobile WiMAX 2.0 are the Enhanced multicastand broadcast services (E-MBS). They are point-to-multipoint communicationsystems where data packets are transmitted simultaneously from a single sourceto multiple destinations. The E-MBS content is transmitted over an area identifiedas a zone. An E-MBS zone is a collection of one or more IEEE 802.16m BSstransmitting the same content. The contents are identified by the same identifiers(IDs). Each ABS capable of E-MBS service can belong to one or more E-MBSzones. Each E-MBS Zone is identified by a unique E-MBS_Zone ID. An IEEE802.16m MS can continue to receive the E-MBS within the E-MBS zone inConnected State or Idle State. Moreover, the 802.16m BS may provide E-MBSservices belonging to different E-MBS zones (i.e. the ABS locates in theoverlapping E-MBS zone area). E-MBS data bursts may be transmitted in termsof several sub-packets, and these sub-packets may be transmitted in differentsub-frame and to allow 802.16m MSs combining but without anyacknowledgement from 802.16m MSs.

Finally, the location is seen as one the major new business model driversin advanced Mobile WiMAX Networks. A major difference between mobilebroadband networks and fixed networks is that the former can be subject tolocation changes. This provides a huge opportunity for location based services(LBS) which have very broad potential to integrate with high performance mobileservices. General LBS include the updating of maps, provision of information onthe location of shops, service points, etc., depending on the location of the user.As LBS become more intuitive to use, require regular updates when on the moveand have access to the sophistication of applications like Google Maps andGoogle Earth, they are expected to drive network traffic to considerable volumes.

Operators are strongly interested in LBS as a route to providing truepersonalized services, and, with true broadband connectivity, they will be able totake advantage of devices with embedded GPS to offer their own and third partyservices, e.g. using Google Maps or similar. Services such as these raise thepossibility of new business models to be developed for charging users orspecialist service providers for use of network capacity. As it is well known theIEEE 802.16m supports basic MAC and PHY features to support both use cases,with or without use of GPS or equivalent satellite based location solution. Theservice can be provided to:

The end user providing the AMS with value added services. External emergency or lawful interception services. The network operator using the location information for network

operation and optimization.In order to enhance location based service, 802.16m MS should send

report location-related information which includes the location information or themeasurement for determining location in response to the request of 802.16m BS.In addition, LBS are supported for 802.16m MS in connected state as well as idlestate. For the connected state, AMS can report location information when it isneeded. For the idle state, 802.16m MS should perform network re-entry toreport location information when it is needed. The 802.16m MS positioning isperformed by using measurement methods, such as TDOA, TOA, AOA, and etc.,



34

whose relevant location-related parameters may include cell-ID, RSSI, CINR,RD, RTD, angle, and Spatial Channel Information. These parameters areexchanged between the 802.16m MS and its serving/attached or/andneighboring 802.16m BSs/ARSs. Location determination methods contain GPSbased methods, assisted GPS and not GPS based. In figure 2.12 thearchitecture for LBS in IEEE 802.16m is presented.

Figure. 2.12. Architecture for LBS.

We can summarize that when considering Mobile WiMAX deploymentfactors such as link budgets and SNR as it was described before, one of themost important factors is the technology used to implement base stations, relays

and subscriber equipments. The main focus of Mobile WiMAX radio networkdesign, deployment and optimization is expected to be on areas such as: thesub=carrier allocation scheme, neighbour list definition, zoning definition for thefrequency reuse of 1 and channel measurements. The network performanceoptimisation involves establishing the end-to-end key performance indicators(KPIs), and service integrity for monitoring the new QoS and perceived the enduser. It is always beneficial to have a proactive performance monitoring systemsin place to ensure the set design standards are always met.

.



35

2.6. WiMAX Interworking with LTE/LTE-Advanced networks

The main challenges in wireless mobile interworking of connecting thecellular network with the other wireless networks include issues like: security,seamless handover, location and emergency services, cooperation, and QoSprovisioning. The developed interworking mechanisms, that is, unlicensed mobileaccess (UMA), IP Multimedia Subsystem (IMS), and Media independenthandover (MIH), due to the characteristics of wireless channel, need to beanalyzed and tested under various circumstances.

Table 2.8. LTE/LTE-Advanced and WiMAX technical specifications

LTE (3GPP Rel-8) LTE-Advanced(3GPP Rel-10)

WiMAX 802.16e(R1.0)

WiMAX 802.16m(R2.0)

Physical layer DL: OFDMAUL : SC-FDMA

DL: OFDMAUL: SC-FDMA

DL : OFDMAUL : OFDMA

DL: OFDMAUL: OFDMA

Duplex mode FDD and TDD FDD and TDD TDD FDD and TDDUser Mobility 350 km/h 350 km/h 60 to 120 km/h 350 km/h

Channel Bandwidth 1.4, 3, 5, 10, 15, 20MHz

Aggregates compo-nents of R8

3.5, 5, 7, 8.75, 10MHZ

5,10,20, 40 MHZ

Peak Data Rates DL: 302 MbpsUL: 75 Mbps

DL: 1 GbpsUL: 300 Mbps

DL: 46 MbpsUL: 4 Mbps

DL: 350 MbpsUL: 200 Mbps

Spectral Efficiency DL: 1.91bps/HzUL: 0.72 bps/Hz

DL: 30 bps/HzUL: 15 bps/Hz

DL: 1.91bps/HzUL: 0.84 bps/Hz

DL: 2.6 bps/HzUL: 1.3 bps/Hz

Latency Link Layer < 5 msHandoff < 50ms

Link Layer < 5 msHandoff < 50ms

Link Layer = 20 msHandoff =35 to

50ms

Link Layer< 10msHandoff < 30ms

VoIP Capacity 80 users per sec-tor/MHz (FDD)

>80 users per sec-tor/MHz (FDD)

20 users per sec-tor/MHz (TDD)

>30 users per sec-tor/MHz (TDD)

Furthermore in Table 2.8 the general technical specification of theLTE/LTE-Advanced and WiMAX with comparisions are given. Both LTE andWiMAX use orthogonal Frequency Division Multiplexing (OFDMA) in theDownload but LTE uses Single Carrier Frequency Division Multiple Access (SC-FDMA). So, in the LTE uplink signal achieves saving power capacity withoutdegrading system flexibility and performance. There is provision of both TDD andFDD in WiMAX802.16m (R2.0) but current market of WiMAX is based on

802.16e. So, in this case we can say WiMAX uses TDD and LTE uses both TDDand FDD. User mobility and Data rate is higher in LTE than the commercialWiMAX. The latency requirement in the WiMAX and LTE specifications is smallenough to support real-time applications, such as voice applications. A voiceapplication could tolerate a delay of between 50 and 200 ms without the userperceiving a decrease in quality. Low latency is thus essential in these mobilebroadband standards. The low latency is also coupled with high data rates tosatisfy bandwidth-intensive applications. Both standards support mobility in thatusers can carry the device traveling at speeds of up to 350 km/h. So, users on ahigh-speed train, for example, could connect to a 4G network.



36

The main difference between WiMAX and LTE is that WiMAX benefitsfrom its earlier development and deployment, while LTE has the advantage ofbeing developed by telecommunications companies who get to choose whichtechnology to deploy. WiMAX jump started the mobile broadband market.According to the WiMAX Forum, WiMAX has about 592 deployments world widewith more than 10 million subscribers. Also, WiMAX has spectrum allocated for itin 149 countries, and many telecommunications companies are involved inWiMAX activities. However, now that LTE’s development has picked up, sometelecommunications companies have backed away from WiMAX. Recently, Ciscoannounced that it will discontinue offering WiMAX base stations and will focus onradio agnostic IP core solutions. Alcatel-Lucent made a similar announcement.However, companies such as Clear wire that have invested in WiMAX don’t haveto discontinue their offerings. WiMAX could coexist in the broadband arena withLTE, and moreover we expect the ITU to include that coexistence of those twotechnologies in its recommendations for IMT-Advanced. However, this doesn’tnecessarily mean that WiMAX or LTE will prevail at that time, as we’ve learnedfrom previous ITU recommendations. The IMT-2000 (3G) recommended severalindependent technologies that meet the same goals. For example, in 2007, ITUadded OFDM as part of 3G at the request of IEEE. Thus, ITU can includemultiple standards in its recommendation, which means the real battle betweenWiMAX and LTE will be how successfully they’re deployed and used. LTEsupports handover and roaming with the 3GGP mo-bile networks but withWiMAX these services are not easy to achieve. From telecom operator point ofview, the roaming service generates numerous benefits for operators. It extendsthe coverage of the operator using the network of other carriers, it generates

more benefits of visitors from other carriers and it provides to users an importantservice i.e. user can travel far away from his operator.

However, both WiMAX and LTE/LTE-Advanced use IP backbone for theaccess part. So, there is not any problem in access part, it is easily upgradablebut we have to careful about the core elements. The deployment of an integratedarchitecture that allows users to seamlessly switch between these two types ofnetworks would present several advantages to both users and service providers.By offering integrated LTE/WiMAX services, users would benefit from theenhanced performance and high data rate of such combined service. For theproviders, this could capitalize on their investment, attract a wider user base andultimately facilitate the ubiquitous introduction of high speed wireless data. The

required LTE access network may be owned either by the WiMAX operator or byany other party, which then requires proper rules and Service Level Agreements(SLAs) set up for smooth interworking on the basis of business and roamingagreements between the LTE and mobile WiMAX operators. In [20], authorsproposed integrating architecture of the WiMAX and LTE.

In Figure 2.13, the Mobile WiMAX supports access to a variety of IPmultimedia services via WiMAX radio access technologies which is called AccessService Network (ASN). The ASN is owned by a Network Access Provider (NAP)and comprises one or more BS and one or more ASN gateways (ASN-GW) thatform the radio access network. Access control and traffic routing for Mobile



37

Stations (MSs) in Mobile WiMAX is entirely handled by the Connectivity ServiceNetwork (CSN), which is owned by a Network Service Provider (NSP), and pro-vides IP connectivity and all the IP core network functions.

Figure 2.13. Example of WiMAX-LTE/LTE-Advanced Integrating Architecture.

The LTE network may be owned either by the NAP or by any other part inwhich case the interworking is enabled and governed by appropriate businessand roaming agreement.3GPP and Mobile WiMAX accesses are integrated

through the Evolved Packet Core (EPC). 3GPP access connections aresupported by the Serving Gateway (SGW), and Mobile WiMAX accesses areconnected to the Packet Data Network Gateway (PGW). Specifically, the legacyserving GPRS support node (SGSN) is connected to the SGW. New logicalentities are also added to the system architecture. The ANDSF is an entity thatfacilitates the discovery of the target access. The target access supported by theANDSF can be either a 3GPP or Mobile WiMAX cell. This entity is introduced by3GPP in order to minimize the impacts on the use of radio signals. The use ofradio signals for neighbor cell discovery requires the User Equipment (UE) toutilize multiple antennas, which result in power consumption. Moreover, if the cellinformation is not broadcast, the UE is unable to acquire the appropriate target

cell information. Optionally, the ANDSF can provide additional information aboutneighbor cells, such as QoS capabilities, which cannot be distributed by radiosignals due to high data demand. Integration architecture proposed in Figure2.13 is basically interworking between WiMAX and LTE/LTE-Advanced. Innetwork transition from WiMAX to LTE can be run in parallel both networksutilizing all the existing elements of the WiMAX including certain elements of theLTE/LTE-Advanced so that it solves the problem of service interruption inswitchover the system and subscribers get experience from both technology forcertain period.

On the other side, the network management is also the important factor tobe considered while moving from one network to the other network. There might



38

be some difficulty in handling by the same network management system aftermoving from WiMAX to LTE/LTE-Advanced or vice versa, but there can be usedexisting network management system. Existing network management systemcan use after switching towards the LTE/LTE-Advanced and it can be used fortraffic handling from one network to the other network during switch over.

Although WiMAX and LTE/LTE-Advanced are based on the samefundamental mobile wireless standard, they have difference inperformance likepeak data rate, user mobility, power consumption, handover, roaming facilitiesetc. But the main difference between two technologies is: LTE/LTE-Advancedsystems are increasing theri momentum in the current 4G wireless technologyand Mobile WiMAX is losing the current market day by day. In this scenario, anyof the operators wants to sustain in the market for the future. Due to competeionin the 4G wireless technology of Mobile WiMAX and LTE/LTE-Advanced in thecurrent market, WiMAX operators are in confusion of their future. Moreover, thereare some recommendations for current WiMAX operators to move their networktowards the TD-LTE so that they can survive in the current 4G wirelesstechnology, they can save cost in migrating their network from one technology toanother technology and they can use same spectrum after migrating to theadvanced network technology.



39

2.7. Mobile IP, IEEE 802.21 for seamless mobility

In this section we will describe the Mobile IP support together with theIEEE 802.21 standard for seamless mobility.

2.7.1. Mobile IP

The Mobile IP is officially known as "Internet Protocol Mobility Support." Itis an area under rapid development and one of the factors driving therequirements to redevelop the Internet Protocol as IPv6. Generally, Mobile IP canbe thought of as the cooperation of three major subsystems. First, there is adiscovery mechanism defined so that mobile terminals can determine their newattachment points (new IP addresses) as they move from place to place within

the Internet. Second, once the mobile terminal knows the IP address at its newattachment point, it registers with an agent representing it at its home network.Lastly, mobile IP defines simple mechanisms to deliver datagrams to the mobilenode when it is away from its home network.

In the beginning of this sub-section, it is a good idea to frame thediscussion by setting some terminology, adapted from the mobile IPspecification. Mobile IP introduces the following new functional entities:

Mobile node - A host or router that changes its point of attachment fromone network or subnetwork to another, without changing its IP address.A mobile node can continue to communicate with other Internet nodes atany location using its (constant) IP address.

Home agent - A router on a mobile node’s home network which deliversdatagrams to departed mobile nodes, and maintains current location

information for each. Foreign agent - A router on a mobile node’s visited network which

cooperates with the home agent to complete the delivery of datagramsto the mobile node while it is away from home.

A mobile node has a home address, which is a long-term IP address on itshome network. When away from its home network, a care-of address isassociated with the mobile node and reflects the mobile node’s current point ofattachment. The mobile node uses its home address as the source address of allIP datagrams it sends, except where otherwise required for certain registration

request datagrams.The following terms are frequently used in connection with Mobile IP:• Agent advertisement - Foreign agents advertise their presence by

using a special message, which is constructed by attaching a specialextension to a router advertisement, as described in the next section.

• Care-of-address - The termination point of a tunnel toward a mobilenode, for datagrams forwarded to the mobile node while it is away fromhome. There are two different types of care-of-address (CoA): a foreignagent care-of address is an address of a foreign agent with which themobile node is registered; a collocated care-of address is an externally



40

obtained local address which the mobile node has associated with oneof its own network interfaces.

• Correspondent node - A peer with which a mobile node iscommunicating. A correspondent node may be either mobile orstationary.

• Mobility agent - Either a home agent or a foreign agent.• Mobility binding - The association of a home address with a care-of

address, along with the remaining lifetime of that association.• Mobility security association - A collection of security contexts

between a pair of nodes which may be applied to mobile IP protocolmessages exchanged between them. Each context indicates anauthentication algorithm and mode (as described in the fourth section), asecret (a shared key, or appropriate publiciprivate key pair), and a styleof replay protection in use.

To emphasize that nowadays we have two types of Mobile IP protocolversions: Mobile IPv4 (MIPv4) and Mobile IPv6 (MIPv6). MIPv4 is a popularmobility protocol used in the current IPv4 networks, but with the next generationnetworks emerging developments, there are the IPv6 networks, and the MIPv6protocol. MIPv6 is design to deal with mobility and to overcome some problemssuffered by MIPv4. Although MIPv6 shares many features with MIPv4, there aresome differences between them (discussed later in this sub-section). The mostsignificant difference between MIPv4 and MIPv6 is that MIPv6 is integrated intothe base IPv6 protocol and not an add-on feature, as is the case with IPv4 andMIPv4. Because most Internet devices will soon be mobile, it is important that all

devices are inherently designed to be mobile and IPv6/MIPv6 allows for this.Furthermore, we will elaborate the three general functions in Mobile IPv4.Those related functions are:

Agent Discovery - Mobility agents advertise their availability on eachlink for which they provide service.

Registration - When the mobile node is away from home, it registersits CoA with its home agent.

Tunneling - In order for datagrams to be delivered to the mobilenode when it is away from home, the home agent has to tunnel thedatagrams to the care-of address.

The following will give a rough outline of operation of the Mobile IPv4

protocol, making use of the above-mentioned operations. Figure 2.14 may beused to help envision the roles played by the entities.Mobility agents make themselves known by sending agent advertisement

messages. An impatient mobile node may optionally solicit an agentadvertisement message. After receiving an agent advertisement, a mobile nodedetermines whether it is on its home network or a foreign network. A mobile nodebasically works like any other node on its home network when it is at home.



41

Figure 2.14. Mobile IP packet flow.

When a mobile node moves away from its home network, it obtains a CoAon the foreign network, for instance, by soliciting or listening for agentadvertisements, or contacting DHCP or Point-to-Point Protocol (PPP). Whileaway from home, the mobile node registers each new CoA with its home agent,possibly by way of a foreign agent. Figure 2.15 illustrated the Mobile IPregistration process. IP packets sent to the mobile node’s home address areintercepted by its home agent, tunneled by its home agent to the CoA, receivedat the tunnel endpoint (at either a foreign agent or the mobile node itself), and

finally delivered to the mobile node. In the reverse direction, datagrams sent bythe mobile node are generally delivered to their destination using standard IProuting mechanisms, not necessarily passing through the home agent.

Figure 2.15. Mobile IP registration process.

When the home agent tunnels a datagram to the CoA, the inner IP headerdestination (i.e., the mobile node’s home address) is effectively shielded fromintervening routers between its home network and its current location. At theCoA, the original datagram exits from the tunnel and is delivered to the mobilenode. It is the job of every home agent to attract and intercept datagrams that are



42

destined to the home address of any of its registered mobile nodes. In Figure2.16, the tunneling process in Mobile IPv4 is plotted.

Figure 2.16. Mobile IP tunneling process.

The home agent basically does this by using a minor variation on proxyAddress Resolution Protocol (ARP), and to do so in the natural model it has tohave a network interface on the link indicated by the mobile node’s homeaddress. However, the latter requirement is not part of the mobile IPspecification. When foreign agents are in use, similarly, the natural model of

operation suggests that the mobile node be able to establish a link its foreignagent. Other configurations are possible, however, using protocol operations notdefined by (and invisible to) mobile IP. Notice that, if the home agent is the onlyrouter advertising reachability to the home network, but there is no physical linkinstantiating the home network, then all datagrams transmitted to mobile nodesaddressed on that home network will naturally reach the home agent without anyspecial link operations.

On the other hand, Mobile IPv6 is the next generation mobile protocol andin the near future, all nodes/routers are going to become more faster and the newtechnologies are going to reduce the Internet delay and will provide advancedmobility management. IETF (Internet Engineering Task Force) expects that the

IPv6 protocol will replace the IPv4 protocol in the near future. Although spacedoes not permit a full exposition of the details of the proposed MIPv6, someoverall discussion is certainly in order.

The Mobile IPv6 uses the experiences gained from the design anddevelopment of Mobile IPv4 together with the new IPv6 protocol features. MobileIPv6 shares many features with Mobile IPv4, but the protocol is now fullyintegrated into IPv6 and provides many improvements over Mobile IPv4. Themajor differences between Mobile IPv4 and Mobile IPv6 are:

Support for "Route Optimisation": This feature is now built in as afundamental part of the Mobile IPv6 protocol. In Mobile Ipv4 the route



43

optimisation feature is being added on as an optional set of extensionsthat may not be supported by all IP nodes.

In Mobile IPv6 (also integrated in the IPv6) a new feature is specifiedthat allows Mobile Nodes and Mobile IP to coexist efficiently with routersthat perform "ingress filtering" [RFC2267]. The packets sent by a MobileNode can pass normally through ingress filtering routers. This can beaccomplished due to the fact that the CoA is used as the SourceAddress in each packet’s IP header. Moreover, the Mobile Node’s homeaddress is carried in the packet in a Home Address destination option.This allows the use of the care-of address in the packet to betransparent above the IP layer, e.g., TCP.

By using the CoA as the Source Address in each packet's IP header therouting of multicast packets sent by a Mobile Node is simplified. InMobile IPv6 the Mobile Node will not anymore have to tunnel multicastpackets, as specified in Mobile IPv4, to its Home Agent. Moreover, theuse of the Home Address option allows the home address to be used butstill be compatible with multicast routing that is based in part, on thepacket's Source Address.

In Mobile IPv6 the functionality of the Foreign Agents can beaccomplished by IPv6 enhanced features, such as Neighbour Discoveryand Address Autoconfiguration [RFC1971]. Therefore, there is no needto deploy Foreign Agents in Mobile IPv6.

The Mobile IPv6, unlike Mobile IPv4, uses IPsec for all securityrequirements such as sender authentication, data integrity protection,and replay protection for Binding Updates (which serve the role of both

registration and Route Optimisation in Mobile IPv4). In Mobile IPv4 thesecurity requirements are provided by its own security mechanisms foreach function, based on statically configured mobility securityassociations.

In mobile IPv6 a mechanism is provided to support bidirectional (i.e.,packets that the router sends are reaching the Mobile Node, and packetsthat the Mobile Node sends are reaching the router) confirmation of aMobile Node's ability to communicate with its default router in its currentlocation. This bidirectional confirmation can be used to detect the “blackhole” situation, where the link to the router does not work equally well inboth directions. In contrast, Mobile IPv4 does not support bidirectional

confirmation, but only the forward direction (packets from the router arereaching the Mobile Node) is confirmed, and therefore the black holesituation may not be detected.

Mobile IPv6 and IPv6 use the source routing feature. This feature makesit possible for a Correspondent Host to send packets to a Mobile Nodewhile it is away from its home network using an IPv6 Routing headerrather than IP encapsulation, whereas Mobile IPv4 must useencapsulation for all packets. However, in Mobile IPv6 the Home Agentsare allowed to use encapsulation for tunneling. This is required, duringthe initiation phase of the binding update procedure.



44

In Mobile IPv6 the packets which arrive at the home network and aredestined for a Mobile Node that is away from home, are intercepted bythe Mobile Node’s Home Agent using IPv6 Neighbor Discovery[RFC1970] rather than ARP [RFC826] as is used in Mobile IPv4.

The source routing (routing header) feature in Mobile IPv6 removes theneed to manage "tunnel soft state", which was required in Mobile IPv4due to limitations in ICMP error procedure for IPv4. In Mobile IPv4 anICMP error message that is created due to a failure of delivering an IPpacket to the Care-of Address, will be returned to the home network, butwill may not contain the IP address of the original source of the tunnelledIP packet. This is solved in the Home Agent by storing the tunnelinginformation, i.e., which IP packets have been tunnelled to which Care-ofAddress, called tunneling soft state.

In IPv6 a new routing procedure is defined called any-cast. This featureis used in Mobile IPv6 for the dynamic Home Agent address discoverymechanism. This mechanism returns one single reply to the MobileNode, rather than the corresponding Mobile IPv4 mechanism that usedIPv4 directed broadcast and returned a separate reply from each HomeAgent on the Mobile Node's home sub-network. The Mobile IPv6mechanism is more efficient and more reliable. This is due to the factthat only one packet need to be replied to the Mobile Node.

In Mobile IPv6 an Advertisement Interval option on RouterAdvertisements (equivalent to Agent Advertisements in Mobile IPv4) isdefined, that allows a Mobile Node to decide for itself how many RouterAdvertisements (Agent Advertisements) it is tolerating to miss before

declaring its current router unreachable. All Mobile IPv6 control traffic can be piggybacked on any existing IPv6

packets. This can be accomplished by using the IPv6 destinationoptions. In contrary, for Mobile IPv4 and its Route Optimisationextensions, separate UDP packets were required for each controlmessage.

In Mobile IPv6 supports Hierarchical Mobile IPv6 (HIPv6) plus FastHandovers for Mobile IPv6 (FHIPv6). HMIPv6 is a localized mobilitymanagement proposal that aims to reduce the signaling load due to usermobility. The mobility management inside the local domain is handled bya Mobility Anchor Point (MAP). Mobility between separate MAP domains

is handled by MIPv6. Moreover, the HMIPv6 presents the followingadvantages: it includes a mechanism to reduce the signaling load incase of handoffs within the same domain and may improve handoffperformance reducing handoff latency and packet losses since intra-domain handoffs are performed locally. However, since the periodic BUsare not reduced but the ones due to handoffs, the gain depends on themobility of the mobile nodes. On the other hand, FHIPv6 protocolenables mobile nodes to quickly detect that it has moved to a newsubnet by providing the new access point and the associated subnetprefix information when the mobile node is still connected to its current



45

subnet. For instance, a mobile node may discover available accesspoints using link-layer specific mechanisms (i.e., a "scan" in WLAN) andthen request subnet information corresponding to one or more of thosediscovered access points. The mobile node may do this after performingrouter discovery or at any time while connected to its current router.

Moreover, in comparison to Mobile IPv4 protocol, Mobile IPv6 protocol canprovide mobility support that combines the experience gained in the design ofMobile IPv4 and the new features of the IPv6 protocol. Some of the Mobile IPv4open issues, i.e., Triangle routing, Mobility routing crossings in an Intranet, RSVPoperation over IP tunnels, Inefficient maintenance of simultaneous bindings,Ingress filtering, Minimize the number of required trusted entities andAuthentication are partially solved. Most of the solutions provided in Mobile IPv6are mainly generated for Mobile IPv4. However, it is expected that some of these

(above mentioned) solutions, after some minor modifications, can also be appliedfor Mobile IPv6.The goal for Mobile IPv6 is to provide provides seamless mobility for next

generation mobile services and applications and across several accesstechnologies such as WCDMA, WiMAX 802.16m, WLAN 802.11m, LTE-Advanced and other 4G access networks. Undoubtedly, Mobile IPv6, along withfast-handoffs and context transfer mechanisms will be essential for the largescale deployment of real-time services (such as VoIP) and broadcast services in4G networks.

2.7.2. IEEE 802.21

The IEEE 802.21 working group was initiated in 2004, and the latest draftversion of the standard was accepted as a new standard by the IEEE-SAStandards Board in November 2008. The standard was published in January2009. It is anticipated that actual deployment of the standard will take place atthe earliest in late 2009–2010. The Figure 2.17 illustrates the progress towardthe IEEE 802.21-2008 standard.

Figure 2.17. Timeline of the IEEE 802.21-2008 Standardization.

IEEE 802.21-2008, also known as Media-Independent Handover (MIH)Services, features a broad set of properties that meet the requirements ofeffective heterogeneous handovers. It allows for transparent service continuityduring handovers by specifying mechanisms to gather and distribute informationfrom various link types to a handover decision maker. The collected informationcomprises timely and consistent notifications about changes in link conditionsand available access networks. We must to emphasize that the scope of IEEE



46

802.21-2008 is restricted to access technology-independent handovers. Intra-technology handovers, handover policies, security mechanisms, media-specificlink layer enhancements to support IEEE 802.21-2008, and Layer 3 (L3) andupper-layer enhancements are outside the scope of IEEE 802.21-2008.

IEEE 802.21 facilitates a variety of handover methods, including both hardhandovers and soft handovers. A hard handover, also known as "break-before-make" handover, typically implies an abrupt switch between two access points,base stations, or, generally speaking, PoAs. Soft handovers require theestablishment of a connection with the target PoA while still routing traffic throughthe serving PoA. In soft ("make-before-break") handovers, mobile nodes remainbriefly connected with two PoAs. Note, however, that depending on servicerequirements and application traffic patterns, hard handovers may often gounnoticed. For example, web browsing and audio/video streaming withprebuffering can be accommodated when handing over between different PoAsin the range of one network by employing mechanisms that allow transferring thenode connection context from one PoA to another quickly.

The main design elements of the IEEE 802.21 reference model can beclassified into three categories: a framework for enabling transparent servicecontinuity while handing over between heterogeneous access technologies; a setof handover-enabling functions; and a set of Service Access Points (SAPs). Therole of the IEEE 802.21 standard within the framework of IEEE and its newfunctions is illustrated in Figure 2.18.

Figure 2.18. Illustration of the IEEE 802.21 MIH reference model.

Moreover, the IEEE 802.21 specifies a framework that enablestransparent service continuity while a mobile node switches betweenheterogeneous access technologies. The consequences of a particular handoverneed to be communicated and considered early in the process and, clearly,before the handover execution. In soft handovers, it is crucial that servicecontinuity, during and after the handover, is ensured without any userintervention. To this end, IEEE 802.21 specifies essential mechanisms to gatherall necessary information required for an affiliation with a new access pointbefore breaking up the currently used connection. Interactive applications, such



47

as VoIP, are typically the most demanding in terms of handover delays, and high-quality VoIP calls can be served only by soft handovers. On the other hand,video streaming can accommodate hard handovers, as long as the verticalbreak-before-make handover delay does not exceed the application bufferinterval delay. In the case of hard handovers, handover preparation signaling caninitiate the connection context transfer from the serving PoA to the target PoAbeforehand. For instance, lack of the required level of QoS support or lowavailable capacity in a candidate access network may lead the network selectingentity to prevent a planned handover. On the other hand, for example, increasingdelay, jitter, or packet-loss rates in the currently serving network may degradethe perceived QoS throughout the network, or only for a particular application,triggering the mobility manager to start assessing the potential of candidatetarget access networks and subsequently initiate an IEEE 802.21-assistedhandover.

Also, IEEE 802.21 allows the reception of dynamic information about theperformance of the serving network and other networks in range. In other words,IEEE 802.21 provides methods for continuous monitoring of available accessconditions. However, IEEE 802.21 does not specify any methods for collectingthis dynamic information at the link layer.

Furthermore, the EEE 802.21 defines a set of handover-enablingfunctions, which are specified with respect to existing network elements in theprotocol stack, and introduces a new logical entity called Media-IndependentHandover Function (MIHF). The MIHF logically resides between the link layerand the network layer. It provides, among others, abstracted services to entitiesresiding at the network layer and above, called MIH Users (MIHUs). MIHUs are

anticipated to make handover and link-selection decisions based on their internalpolicies, contextÂ and the information received from the MIHF. To this end, theprimary role of the MIHF is to assist in handovers and handover decision makingby providing all necessary information to the network selector or mobilitymanagement entities. The latter are responsible for handover decisionsregardless of the entity position in the network. The MIHF is not meant to makeany decisions with respect to network selection.

SAPs with associated primitives between the MIHF and MIHUs(MIH_SAP) give MIHUs access to the following services that the MIHF provides:

The Media-Independent Event Service (MIES) provides event reportingabout, for example, dynamic changes in link conditions, link status, and

link quality. Events can be both local and remote. Remote events areobtained from a peer MIHF entity.

The Media-Independent Command Service (MICS) enables MIHUs tomanage and control the parameters related to link behavior andhandovers. MICS provides a set of commands for accomplishing that, aswe will see later in this article. Commands can be both local and remote.The information obtained with MICS is dynamic.

The Media-Independent Information Service (MIIS) allows MIHUs toreceive static information about the characteristics and services of theserving network and other available networks in range. This information



48

can be used to assist in making a decision about which handover target tochoose and to make preliminary preparations for a handover.

On the other hand, there is a need for defining a separate technology-dependent interface, which is specific to the corresponding media typesupported, between the MIHF and the lower layers (MIH_LINK_SAP). Theprimitives associated with the MIH_LINK_SAP enable MIHF to receive timely andconsistent link information and control link operation during handovers. Forexample, the currently supported link layers include wired and wireless mediatypes from the IEEE family of standards (for example, 802.3, 802.11, 802.15, and802.16), as well as those defined by the Third-Generation Partnership Project(3GPP) and Third-Generation Partnership Project 2 (3GPP2). Besides these,IEEE 802.21 specifies a media-independent SAP (MIH_NET_SAP), whichprovides transport services for Layer 2 (L2) and Layer 3 (L3) MIH message

exchange with remote MIHFs. Functions over the LLC_SAP are not specified inIEEE 802.21.Figure 2.19 presents the messages directions of each MIHF service class,

including both local and remote events and commands. The MIHF can subscribeto particular sets of events from a peer MIHF. Remote commands are initiated bylocal MIHUs and are conveyed to the peer MIHF through the local MIHF. Finally,MIIS information can be obtained through queries to the local database and toremote Information Servers.

Figure 2.19. MIHF Services.

In order to use and provide MIHF services, MIHF entities need to be

configured appropriately. IEEE 802.21 defines three service managementfunctions: MIH capability discovery, MIH registration, and MIH event subscription.MIHF may discover other MIHF entities and their capabilities using the MIHcapability discovery procedure. Depending on the information obtained from thisprocedure, the local MIHF can determine which peer MIHFs it should registerwith. The MIH capability discovery function uses the MIH protocol (introduced inthe following section) at Layer 2 or Layer 3, and media-specific Layer 2broadcast messages are allowed. For example, an MIHF can listen to media-specific broadcast messages, such as IEEE 802.11 beacons, or media-independent Layer 2 MIH_Capability_Discover broadcast messages, because anMIHF entity residing in the network may announce its existence and capabilities



49

periodically. MIHF can also send MIH_Capability_Discover request messagesusing multicast or unicast to detect peer MIHFs in a solicited way. For instance,MIHF can send a request by unicast for obtaining the capabilities of a specificIEEE 802.21 network entity. In this case, only the IEEE 802.21 network entityaddressed should respond to these request messages.

MIH registration is a symmetric procedure by which two peer MIHFsauthenticate and can then communicate with each other in a more trustedmanner. After MIH registration is completed, the two peer MIHF entities cansymmetrically request services from their registered peer. Note that MIHregistration is not necessary for obtaining some level of support from a peerMIHF. However, by registering and authenticating, peer MIHFs typically will getaccess to much more extensive information. That is, although the MIHF residingon the mobile node may be able to access information services from the network-side MIHFs without registration and authentication, the available information maybe only a subset of that provided after authenticating.

Finally, MIH event subscription enables MIHUs to subscribe to a particularset of events provided by MIES from the local or peer MIHF. Event subscriptionfrom a peer MIHF requires registration and knowledge about its capabilities. Thesubscription contains only the list of events the MIHU is interested in. Note thatevent sources may not be necessarily capable of providing all events that thesubscriber is interested in subscribing to. Each subscription request is matchedby a confirmation message from the event source indicating the events approvedfor subscription.

The Media-Independent Handover Protocol (MIHP) specifies the rules andservices for unified communication between peer MIHFs. The protocol defines

the message format, header, and encoding format and is meant to be used solelyfor communicating with peer MIHF entities. For internal communication noparticular encoding is dictated.

MIH protocol messages can be carried over Layer 2 management frames,Layer 2 data frames, or over Layer 3/IP transport. Note that cellular technologiesdo not provide Layer 2 transport without changes in their protocol stack.

The MIH protocol messages, or frames, comprise a header part and aTLV-encoded payload part. The MIHF frame header consists of eight octets.Figure 2.20 illustrates the MIH protocol header indicating the corresponding bitlength for each field in parentheses.

Figure 2.20. Illustration of the MIH Protocol Header.



50

The Version field in the MIH frame header specifies the version of the MIHprotocol used. The two Ack fields are for acknowledgement purposes and arediscussed later in the article. The Unauthenticated Information Request (UIR)flag indicates that the response message may be sent with a limited lengthbecause of the nature of unauthenticated message exchange. Recall that whenan MIHF issues requests without registering first with its peer, it may receive lessinformation than if it had registered earlier. If this flag is set, then the informationincluded in the response message may not reflect the complete informationavailable to registered MIHFs. The More Fragments (M) and Fragment Number(FN) fields are used in message fragmentation.

The MIH Message ID field comprises three subfields. The ServiceIdentifier (SID) field indicates the MIHF service class (MIES, MICS, MIIS, orService Management) that this message belongs to. The Operation code(Opcode) specifies whether the message is a request, response, or indication.The Action Identifier (AID) is related with and scoped by the SID. For instance, ifthe SID indicates MIES, AID points to the actual event type. The Variable LoadLength field contains the total length of the variable, TLV-encoded payloadcarried by this message frame.

The MIH protocol messages use the Transaction ID and MIHF ID fields asidentifiers, but only the former is included in the header. The Transaction ID fieldis an identifier that helps to match each request, response, or indication messagewith its acknowledgement.

The payload part contains service-specific messages encoded in TLVformat. The first two TLVs in the payload part (not shown in Figure 2.20) shouldbe the Source Identifier and Destination Identifier, which are both the same data

type as the MIHF ID. Every MIHF must have a unique MIHF ID, which may beassigned to it at configuration time. The MIHF ID shall be invariant and could be,for example, a Fully Qualified Domain Name (FQDN) or Network AccessIdentifier (NAI). The MIHF ID is used during the MIH registration phase and isappended to the payload part of every message requiring endpoint identification.In broadcast messages, the Destination Identifier TLV is defined as zero length.

The Figure 2.21 shows the message structure consisting of the MIHProtocol header, source and destination identifiers, and service-specific TLVs. InTLV encoding, the Type field (1 octet) denotes the parameter type, the Lengthfield (variable octets) indicates the length of the Value field, and the Value field(variable octets) carries the actual value of the parameter.

Figure 2.21. The MIH Protocol Frame Structure.

Acknowledging MIH messages is not mandatory. Still, the MIH protocoldoes support the use of acknowledgements to ensure reliable messageexchange. The sender MIHF can set the ACK-Req field to instruct the receiver to



51

return an acknowledgement with ACK-Rsp bit set. The MIH Message ID andTransaction ID must be the same in the request message and itsacknowledgement. An acknowledgement message may carry no payload. Note,however, that despite employing these two ID fields, the MIH protocol does notspecify any further mechanisms for reliable authentication or shielding messageexchanges from third parties.

Finally, we anticipate that its adoption in the near future will allow for betternetwork resource usage and permit multi-access devices to select the networkaccess best suited for their communication needs. After motivating the needs fora standard to cope with heterogeneous network handovers, we introduced theIEEE 802.21 Reference Model and the MIH Services. We briefly presented theMIH Protocol, although a more thorough description calls for a separate overviewarticle.

We expect that in the future, when IEEE 802.21 MIH is widely deployed,there will be significant efforts to further amend and extend it in order to providefor even better services. In fact, because security mechanisms are outside thescope of the base IEEE 802.21 standard, the work on defining a security-relatedextension to IEEE 802.21 (IEEE P802.21a) has already begun. Moreover,another amendment (IEEE P802.21b) that deals with handovers with downlink-only technologies, such as Digital Video Broadcasting (DVB), has also beenintroduced (see: www.ieee802.org/21 for more information about theamendments). Nevertheless, it remains uncertain whether vendors will stand bythis promising standard and incorporate it in future products and solutions.



52

2.8. 4G regulation: Mobile WiMAX and LTE/LTE-Advanced

The Mobile WiMAX and LTE/LTE-Advanced are well positioned to drivethe global evolution towards pervasive mobile broadband internetcommunications with market acceptance, rich ecosystems, and promisingeconomies of scale. On the other side, two essentials for a healthy wireless andmobile broadband technology environment include well-developed technologystandards and a fair market regulatory environment with carefully allocatedspectrum resources.

The shift to 4G (towards Mobile WiMAX and LTE/LTE-Advanced) will begradual, along with continued operation and coexistence with 2G and 3Gnetworks and services. As the 4G world materializes it will increasingly do so

based on mobile operators using spectrum across multiple existing and newspectrum bands. As mobile operators tread the 4G path they will be forced tofocus on using their existing 2G and 3G spectrum resources in different waysand in different combinations. At the same time, operators are vying for newspectrum allocations to meet increasing network coverage and capacitydemands dictated by the mobile Internet.

Not all spectrum is equal, it is the sum of the parts – spectrumcombinations in different bands – that will shape the fortunes of mobile operators.The operators who succeed in 4G deployment and delivery will be those that canbuild and augment sufficient spectrum holdings in both lower and upperfrequency bands. As a consequence vendors must evolve equipment to flexibly

support multi-mode and multi-band functionality so that service providers canoperate efficiently and transparently across bands. Moreover, Figure 2.22presents a view of the spectrum combinations that will characterize the emerging4G regulation landscape.

Figure 2.22. Mobile Broadband Internet and 4G radio spectrum combinations.

At the ITU World Radiocommunication Conference 2007 (WRC-07), themembers addressed radio spectrum for upcoming 4G systems (IMT-Advanced).



53

The new spectrum is spread across five additional bands in portions of the 400 to700 MHz and 2.3, 2.5, and 3.5 GHz bands 4G systems and their backwardcompatibility to 3G will force multiple band and multiple front end products tomeet the diverse requirements of regional carriers. The recommendations fromWRC- 07 are included in Table 2.9.

Table 2.9. The frequencies added for 4G services from WRC-07

The bands below 1 GHz are a cost-effective way to provide IMT servicesin sparsely populated regions in developed and undeveloped countries. Thebands above 1 GHz are preferable for providing continuous blocks of spectrumfor future broadband wireless systems such as IMT-Advanced (4G). Among thebands being proposed, the newly identified 3.4 to 3.6 GHz band could prove tobe the most attractive for implementing 4G bands in the future. It should beapparent that whatever solutions we bring to the market, the ability to be able tocustomize and adapt the front end for a particular combination of frequencies will

be a worthwhile investment due to the complexities involved. In Figure 2.23 oneview of possible band combinations required in mobile devices and embeddedmodems are given. Different analysis may come to different weightings forregional splits, but the daunting number of band combinations should not be lost.

Figure 2.23. 3G/4G Band Combination Forecast by Volume



54

Furthermore, successful conclusions were reached on over 30 separateitems on the latest WRC-12 (mentioned in the previous module), even if in somecases that conclusion was not to change the Radio Regulations. The headlineshave been taken by the decision, following pressure from African and Arabcountries, to extend the mobile radio allocation in Europe, Africa and the MiddleEast down from 790 MHz to (provisionally) 694 MHz, and identify this allocationfor 4G. The formal agenda of the WRC did not allow for this and Europeancountries were not ready to take that decision. The resulting compromise is avery unusual arrangement. The new allocation, by way of a WRC Resolution,becomes effective from the end of the next WRC (scheduled for late 2015) andwill be subject to technical and regulatory conditions to be developed in theintervening period.

However, making a new allocation to mobile does not necessarily meanthat the band will become available. Regulators will face major policy decisionson the relative priority of mobile and broadcasting 4G services. Even if thedecisions come down in favor of mobile, it will need the concerted effort of anumber of countries within a region to bring about substantial change. Wherethere are existing broadcasting services – as throughout Europe – these wouldneed to be re-arranged to clear the spectrum. This would require difficultnegotiations to be held with neighboring countries. And there will be significantcross-border constraints imposed by those countries that keep broadcasting andother services in the band (including aeronautical radars in some places). So itremains to be seen for how long the apparent success of the WRC remains onlyon paper. The writing however is on the wall, and many will not want to seeEurope being the only part of the world without access to this valuable resource

for mobile services.Another contentious issue at WRC-12 concerned changes to the

regulations governing satellite networks using the geostationary orbit. Theconference considered many proposals aimed at reducing the number of “papersatellites”, i.e. internationally coordinated orbital slots for systems that are notsubsequently brought into use. There was also debate on ensuring “equitableaccess” to the geostationary orbit. The eventual outcome was some clarificationof the definitions of “bringing into use” and other procedures. These issues didnot attract so many headlines, and the detailed changes agreed will requirecarefully analysis to reveal the real consequences, but the potential impact onthose in the satellite communications business could be very considerable

indeed. That was clear from the intense discussions and close attention paid tothese issues. Finally WRC-12 established the agenda for the next WRC in 2015.Included in a long list of issues is a wide-ranging item to consider the growingspectrum demands of mobile broadband internet. This does not specify anypotential target bands for new 4G spectrum and so will lead to a great deal ofwork and close scrutiny by all of the communities that could be affected –broadcasting, satellite, navigation etc. An illustration of all WRC-12 issues isgiven in Figure 2.24.



55

Figure 2.24. Illustration of the WRC-12 Issues.

Globally, provisioned network capacity to handle the explosive growth ofbroadband data traffic is forecasted to increase by forty times between 2010 and2015. As operators evolve towards meeting increasing capacity demands andless are coverage limited, narrow band allocations in lower frequency ranges willattract a lower market premium price than has been the case in the past. This is

not to imply that lower frequencies are no longer valuable. However, theiroptimized use will be in combination with higher band frequencies such as withinthe coveted 2.6 GHz range, where significant bandwidth resources are beingavailed. There is a discernable trend of regulators moving to combined spectrumallocation models. For example, Germany’s auction of 358.8 MHz of spectrumacross 4 bands – 800 MHz, 1800 MHz, 2100 MHz and 2.5 GHz concluded inMay 2010. There are numerous other cases where simultaneous allocation ofspectrum across multiple bands is under consideration including Jordan, which isexamining permission for 3G service delivery at 900 MHz and 1800 MHz. Theregulator is also consulting on future allocations at 800 MHz, 2.3 GHz, 2.5 GHz,and 1785-1805 MHz and re-banding at 3.5 GHz and 3.6 GHz. In Switzerlandthere are plans to reallocate and newly assign spectrum across multiple bands:800 MHz, 900 MHz, 1800 MHz, 2100 MHz and 2.5 GHz.

However, regardless of the spectrum allocation formats – simultaneous orsequential - spectrum reform requires planning for the allocation and re-assignment of spectrum across multiple bands. This is irrespective of licenserenewal dates, new licensing timeframes or the availability of new spectrum formobile services. A detailed spectrum reform roadmap will recognize theinterdependencies between different spectrum bands and increase the level ofcertainty for operators in understanding how much spectrum is prospectivelyavailable, under what conditions, and in which bands.



56

Before regulators embark on either spectrum reform or the allocation ofnew 4G spectrum sources suitable for mobile services, a granular understandingof the status quo is critical. Where a registry of spectrum distribution and use isnot in place this action becomes an urgent priority. Such a spectrum audit musttake account of spectrum that is used or reserved for public authorities along withresources allocated for commercial purposes other than communications.

Finally we can conclude that, the spectrum reform is a priority globally.This is driven in large part by the burgeoning of mobile broadband and theprogression towards 4G (Mobile WiMAX and LTE/LTE-Advanced). Greaterregulatory certainty around band re-planning and the structure of new spectrumallocations is demanded as operators seek a firm basis upon which to assessfuture bandwidth requirements and how they can be met. Rearrangement ofcurrent bands allocated to mobile services and the release of unallocatedspectrum will present different challenges and degrees of challenges in differentnations. However, at the very least, all nations need to move to auditingspectrum distribution and use across multiple bands and public and privatesector players. This view of the status quo then provides the basis for band re-planning as deemed necessary and the development of approaches to theallocation of vacated or new spectrum. Regulators have an urgent required todevelop a multi-band plan-irrespective of existing license expiry dates and thetiming of availability of new spectrum earmarked for mobile services.

Regulators are confronted with a daunting set of legacy issues that needto be addressed, along with priorities for 4G spectrum reform priorities and theneed to set critical conditions related to new spectrum allocations. As 4Gspectrum agendas are developed, these often overlapping issues, priorities and

policy approaches must all be considered.



57

2.9. Business potential of Mobile WiMAX

A few years ago, the technology promised to change the economics ofInternet access by providing faster, more efficient broadband service overunprecedented distances and growing into a ubiquitous open wireless network.Despite the challenges it has faced in reaching these ambitious goals, MobileWiMAX has several strengths that make it a viable option to alternativetechnologies. Therefore, business technology decision makers would be wise notto dismiss Mobile WiMAX.

As we can recognize, Mobile WiMAX is not a service which would fit in theshoes of or replace any previously available services or technologies. It hascapabilities, by keeping the users connected at high bit rates of, say, 1Mbps

each, a new ecosystem of “applications space,” which is beyond the domain ofexisting cellular mobile, wireless, or fixed wireless technologies. The operatorsventuring out on WiMAX need to recognize this potential and not be content withthe traditional revenue streams, but to create new services, new domains ofapplications which not only attract users but also generate entirely new sourcesof revenue. Hence the answer to the question “Is there is business case forMobile WiMAX?” is Yes; traditional services such as VoIP, broadband, and datalinks alone make it viable in most situations. But operators can create a biggerbusiness opportunity by entering the domain of community-based services suchas instant messaging, presence, active directories, video and audio bloggingwith IMPS, TV broadcast and multicast services, video on demand and push

video, music downloads, RSS feeds to mobile devices, and mobile broadband. Inmost cases, this will require the operators to venture into areas which aremultidisciplinary, such as design of mobile devices, software clients, and networkarchitectures that enable them to step out of legacy TDM-based networks. Manydeveloping countries and rural communities everywhere are today bereft of anyreliable broadband connectivity and nothing is on the horizon in the near term. Itis no surprise, therefore, that some of the major installations have becomeoperational in these locales and more are on the way.

Furthermore, we can clearly say that there can be multiple businessmodels for the introduction of both Fixed WiMAX and Mobile WiMAX services. Byproviding a wide coverage, instantly available connectivity, with QoS andsecurity, it is an enabler for many applications, which would otherwise beunviable with wire-line connectivity. Many of the applications which today usesatellite VSAT networks (for want of better wireless technologies) can nowmigrate to WiMAX. Examples of applications that can be implemented usingWiMAX are:

Private networks (bank ATMs, retail, remote display TV screens, etc.) Video surveillance networks, public safety services Tracking systems Small business data services (ADSLequivalents) Personal broadband Mobile video multicast



58

Remote WiFi hotspot enabling VoIPphone booths, video phones Satellite news gathering for news, weather, reality, and current affairs

channels User-generated content with high resolution

These services can be classified into different categories based onrequirements for bandwidth, latency, and jitter. These values are important as thescheduling of service flows in Mobile WiMAX takes into account theserequirements.

The model used would depend on the territories where such deploymentis done, the local regulations, and the existing infrastructure fortelecommunications and broadband services. Any deployments will depend onthe resources available and their costs such as licensed spectrum, which we

discuss in the next section. In some cases, such resources may actually permitor limit the capability of an operator to offer such services.On the other side, the costing of resources is an important driver of any

business plan. As in the case of any wireless technology, the ownership andcosts of licensed spectrum are the factors which have a major bearing on theviability of a Mobile WiMAX network. Of course, it is also possible to useunlicensed spectrum with IEEE 802.16-2004 technology, and this indeed is anenabler of WiMAX connectivity in rural areas with low attendant costs. Moreover,the use of unlicensed spectrum in urban areas has many limitations and acommercial service is better provided with licensed spectrum.

Broadband spectrum in most countries is now priced attractively in order

to promote the growth of wireless access and is also more easily available thanthe spectrum for 3G technologies, which is a competitor in some ways for thebroadband-based services. For example, in India, the WiMAX-licensed slots (2-7MHz for FDD and 7MHz for TDD) were allocated in the 3.3–3.4GHz band on afirst come first-served basis. The slots now stand allotted to over 20 operators indifferent parts of the country. The spectrum charges (called royalty) works out to$1800 per 7MHz TDD spectrum channel for each link of up to 25 Km. Thus for abase station with three sectors, the cost is $5400 per annum. A city with 20 basestations would need $108 000 as spectrum charges. Spectrum in the 2.4GHzband (2.469–2.69) for Mobile WiMAX is planned to be allotted in the near future.

In the USA, the bulk of the spectrum in the 2.5GHz band is held by Sprint

and Clearwire. The 2.3 GHz licensed and 5GHz unlicensed bands can be usedcurrently, before the auction of the 700MHz bands in 2008makes availableadditional capacity. There are different criteria for considering the spectrumcosts. One method is cost of spectrum per base station, as used in somecountries. In other cases, the spectrum is allocated across various regions. Acompany needs to get a license for all the regions in order to cover the entirecountry. For example, in Germany, licenses for 28 regions were auctioned for 56million Euros to three companies (nationwide) and some regional licensees. Thelicenses were for 21MHz each or 4 channels of 5MHz to each licensee or 12channels nationwide. This gives a figure of about 4.5 million Euros per 5MHz(FDD) for 28 regions ($0.5 per person based on a population of 8.5 million).



59

Assuming that such coverage requires 5000 base stations, the cost per basestation for 5MHz works out to $900per base station or $1800for 10MHz.

In Japan, the spectrum is allotted based on a pricing of $500,000 per MHzfor the whole of Japan. This works out to $2.5million per year for the entirecountry (10 million population) for 5MHz or $0.25 per individual covered per year.

Recognizing that there are large variations in cost to reckon with, we have,however, taken a figure of $2000 per base station per month as the spectrumcost per 10MHz, with a coverage of 50sq km for the business case recognizingthat any higher costs will need to be offset by higher priced offerings.

Furthermore, with data being the primary offering in some business plans,the cost of internet bandwidth is also an important factor. Internet bandwidth ispriced in the range of $350–1000 per Mbps per month for backbone connectivity.The prices in the lower range of $350 are in the United States, while higherprices such as $1000 prevail in some Asian and African countries. These pricesare based on DS3 (45Mbps)-derived pricings.

The cost of the CPE is an important consideration for a viable business. Itis also important to identify and validate the type of CPEs which will be used in agiven network even though all the devices conforming to the WiMAX Forumapproved profiles and with certified equipment are expected to be able tooperate. The CPE devices which have initially become available are for the data-centric applications and may consist of either an outdoor unit mounted with theantennas or an indoor unit with inbuilt antennas such as a WiMAX mobilehandset. A typical crash of the CPE prices, which follows a large volume growth,is yet to be witnessed in the Mobile WiMAX arena. Hence, CPEs with prices inthe $200–400 range are the norm.

Moreover, let we see something about the key suppliers of Mobile WiMAXnetwork equipment. In the main, the infrastructure vendors that remain mostcommitted to Mobile WiMAX are those that have managed to attract the majorityof Mobile WiMAX contracts. The top Mobile WiMAX players include: Motorola,Samsung, Huawei, Alvarion, ZTE and Alcatel-Lucent. In contrast, Nortel simplyexited the business, while Nokia Siemens Networks (NSN) finally decided toresell Alvarion’s Mobile WiMAX solutions instead of relying on in-house systemsas initially planned. However, there may not be enough room for all of today’sWiMAX infrastructure vendors in the future. Over a dozen companies arecurrently competing for contracts, yet even the much larger UMTS/HSPAinfrastructure market is currently dominated by just four players Ericsson, NSN,

Alcatel-Lucent and Huawei). All the main vendors with ambitions in MobileWiMAX promote their end-to-end capabilities - from network infrastructure toend-user devices, and from systems integration services to applications.However, the key difference between the vendors is the extent to which they relyon in-house development and capabilities. When a technology is new (such aswas the case with Mobile WiMAX three to four years ago), in-house end-to-endcapabilities are a strong competitive advantage. These capabilities help toensure that customers have good levels of system stability, resulting in a betterend-user experience.



60

This is one of the factors behind early Mobile WiMAX contracts — such asthat for Sprint — going to end-to-end providers such as Motorola and Samsung(see our interview on page 4 for more details). These contracts, in turn, helped toestablish these vendors as early market leaders. However, given the fact thatMobile WiMAX is maturing (and more certified interoperable products from avariety of vendors are now available) this advantage is eroding over time.

Among service providers, one of the original key market drivers forWiMAX was the strong belief that WiMAX chips would follow the sameevolutionary path as WiFi. Therefore, they would eventually be built into themajority of laptops. For service providers, the intended ubiquity of WiMAX wouldmean lower costs, thus less need for subsidization and a wider potentialcustomer base. Unfortunately, the reality has been quite different. At the peak ofthe hype surrounding WiMAX, embedded laptops were expected by 2007 withvolumes ramping up to achieve high market penetration quickly. However, thefirst laptops with embedded WiMAX are only now coming to the market, and inlimited numbers. Nonetheless, several device vendors have recently reportedpositive signs of growing WiMAX demand. Chipset supplier Sequans hasannounced that it shipped its millionth WiMAX chipset in June 2009, whileBeceem shipped more than 1 million WiMAX terminal chips in Q3 2009 alone.On the device side, Motorola announced at the 4G World event in September2009 that it had shipped its millionth WiMAX end-user device. Several industrysources have also confirmed a rapid decrease in mobile WiMAX device prices.Price points as low as $50 for a USB modem have been mentioned in relation toupcoming WiMAX projects in India.

A number of key market opportunities in emerging markets remain open to

mobile WiMAX, most notably in India. The reasons are the following: Untapped demand exists today that cannot be met by fixed alternatives.

This means that wireless operators using WiMAX can avoid a host ofchallenges faced by their fixed-line rivals trying to penetrate these areas,such as the high cost of laying cables. For example, Yota in Russia lookslike the success story the WiMAX community has been long awaiting. In amarket where broadband penetration is low and 3G is just beginning roll out,the operator, after only three months of operation, has attracted more than100,000 subscribers in just four cities.

A number of mobile operators in emerging markets (even those with 3Gspectrum) may consider mobile WiMAX as a better alternative to DSL in

rural areas than HSPA, due to potential spectrum capacity constraints.Mobilink in Pakistan and Globe Telecom in the Philippines are goodexamples of this phenomenon.

Therefore, the outlook for mobile WiMAX depends heavily on its successin penetrating emerging markets. As Figure 2.25 illustrates, by 2014 the majorityof Mobile WiMAX connections are expected to come from such markets.

On the other hand, Mobile WiMAX has applications in many other areas,each of which can be a standalone business by itself. This includes applicationssuch as rural connectivity and VoIP, providing rural broadband over large areas,providing dedicated networks for special applications such as security, data



61

gathering networks, bank networks, and many others. Owing to the large andreliable coverage it replaces many applications which were earlier provided usingsatellites. However, the biggest opportunity in the near term is to use these eitherfor enriching legacy applications for high-quality triple-play services or to providemulticast video and “on-demand” services (VoD) for mobile devices. In themedium to long term, a new ecosystem with open architecture mobile devicesparalleling the cellular mobile networks, but without the legacy architectures andproprietary elements, is on the horizon. New players not currently owningtelecom networks are expected to take this initiative.

Figure 2.25. Worldwide Mobile WiMAX Connection Forecasts.

Overall, competing head-to-head with existing players and technologiesrequires deep pockets to expand the coverage footprint, while at the same timespending heavily on marketing. In order to focus entirely on services, someWiMAX operators, like Sprint, have decided to opt for an approach more akin tothat of a mobile virtual network operator (MVNO) model.

Therefore, it is likely that Mobile WiMAX will remain a niche technology inmost developed markets. The greatest opportunities exist in the USA andadvanced markets of Asia. However, in all cases, the availability of the rightspectrum at the right price will be critical.



62

References

[1] Roger B. Marks, "IEEE STANDARD 802.16 FOR GLOBAL BROADBANDWIRELESS ACCESS", Session: “The Future of Wireless”, ITU Telecom World2003, Geneva, Switzerland, 12-18 October 2003.

[2] IEEE Computer Society and the IEEE Microwave Theory and TechniquesSociety: “IEEE Std 802.16m-2011 Standard for local and metropolitan areanetworks”, 2011.

[2] Chris Thomas, Raj Jain, “802.16m and WiMAX Release 2.0”, 2010.

[3] Yaghoobi, Hassan, "Mobile WiMAX Update and IEEE 802.16m," IEEE, 2009.

[4] IEEE 802.11n-2009—Amendment 5: Enhancements for Higher Throughput.

IEEE-SA. 29 October 2009.[5] Broadcom corporation, “802.11n: Next-Generation Wireless LANTechnology”, April 2006.

[6] A. Bacioccola, C. Cicconetti, C. Eklund, L. Lenzini, Z. Li, E. Mingozzi, "IEEE802.16: History, Status and Future Trends", Computer Communications, Volume33, Issue 2, Pages 113-123, 15 February 2010.

[7] Thomas Paul and Tokunbo Ogunfunmi , “Wireless LAN Comes of Age:Understanding the IEEE 802.11n Amendment”, IEEE Circuits and SystemsMagazine Vol. 8(1), pp. 28-54, 2008.

[8] Srinivasan, Roshni (ed), Hamiti, Shkumbin (ed), "IEEE 802.16m SystemDescription Document (SDD)," IEEE 802.16 Task Group m, September 2009.

[9] Shantanu Pathak and Shagun Batra, "Next Generation 4G WiMAX Networks -IEEE 802.16 Standard", Sundarapandian et al. (Eds), pp. 507–518, CS & IT-CSCP 2012

[10] Bjoern Dusza, Christoph Ide and Christian Wietfeld, "A Measurement BasedEnergy Model for IEEE 802.16e Mobile WiMAX Devices", IEEE 75th VTC 2012 -Spring.

[11] IEEE Std 802.16m-2011, (Amendment to IEEE Std 802.16-2009), IEEE 3Park Avenue, NY, USA, 6 May 2011.

[12] IEEE Computer Society and the IEEE Microwave Theory and TechniquesSociety: “IEEE Std 802.16m-2011 Standard for local and metropolitan areanetworks”, 2011.

[13] Chris Thomas, Raj Jain, “802.16m and WiMAX Release 2.0”, 2010.

[14] Yaghoobi, Hassan, "Mobile WiMAX Update and IEEE 802.16m," IEEE,March 2009.

[15] Srinivasan, Roshni (ed), Hamiti, Shkumbin (ed), "IEEE 802.16m SystemDescription Document (SDD)," IEEE 802.16 Task Group m, September 2009.

[16] http://www.beyond4g.org/mimo-schemes-in-16m-wimax-2-0



[17] PicoChip, “The Case for Home Base Stations,” Apr. 2007.

[18] ABI Research, “Femtocell Research Service,” 2nd qtr., 2007.

[19] Shu-ping Yeh and Shilpa Talwar, "WiMAX Femtocells: A Perspective onNetwork Architecture, Capacity, and Coverage", IEEE CommunicationsMagazine, pp.:58-65, October 2008.

[20] Tara A. Yahiya and Hakima Chaouchi, “On the Integration of LTE and MobileWiMAXNetworks," 19th Intrnational Confe-rence on Computer communicationand Networks, April 2010.

[21] Shyam S. Wagle, Minesh Ade, and M. Ghazanfar Ullah, "Network Transitionfrom WiMAX to LTE", Journal of Computing, VOL 3, ISSUE 1, January 2011,ISSN 2151-9617, pp.:66-70.

[22] Perkins, C., E., “Mobile IP”, IEEE Communications Magazine, May 1997.

[23] RFC 3344: IP Mobility Support for IPv4.

[24] RFC 3775: Mobility Support in IPv6.

[25] RFC 4140: Hierarchical Mobile IPv6 Mobility Management (HMIPv6).

[26] RFC 4068: Fast Handovers for Mobile IPv6.

[27] RFC2002: IP Mobility Support.

[28]http://www.cisco.com/web/about/ac123/ac147/archived_issues/ipj_12-2/122_ieee.html

[29] A. de la Oliva, and alt. "A case study: IEEE 802.21 enabled mobile terminalsfor optimized WLAN/3G handovers", Mobile Computing and CommunicationReview, Vol. 11, No.2, April 2007.

[30] Antonio de la Oliva, Telemaco Melia, Albert Banchs, Ignacio Soto and AlbertVidal, "IEEE 802.21 (Media Independent Handover services) Overview", IEEEWireless Communication, Volume 15, Issue 4, August 2008.

[31] Doug Gray, "Mobile WiMAX: A Performance and Comparative Summary",WiMAX Forum, September 2006.

[32]https://itunews.itu.int/En/2061-World-Radiocommunication-Conference-2012.note.aspx

[33]http://www.itu.int/ITU-R/index.asp?category=conferences&rlink=wrc-12&lang=en&general-information=1

[34]http://wwwen.zte.com.cn/endata/magazine/ztetechnologies/2011/no1/articles/ 201101/t20110117_201776.html

[35] http://www.realwireless.biz/2012/02/21/wrc-12-final-update-the-outcome/

[36] htt // f b t /T l P /Wi P1 ht l

Documents

Module2-IEEE Mobile Broadband-Mobile WiMAX