Introduction to Mobile Wireless Technology in eHealthehealth-spectrum.ca.com/support/secure/pdfs/mobile_wireless.pdf · Introduction to Mobile Wireless Technology in eHealth ... Introduction

Introduction to Mobile Wireless Technology in eHealth

Technical White Paper

Dan Seligman March 28 2006

CA Company Conficential

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1. Introduction This document presents a technical overview of the two dominant mobile wireless technologies currently in use worlwide, cdma2000 and UMTS. It is intended as technical background for development, support, product management, marketing and sales personnel. The document is divided into four sections. In the first we present a general background in the basics of mobile wireless technology. In the second and third sections we discuss cdma2000 and UMTS in turn, providing details on each technology and a discussion of how eHealth supports it. Finally we offer a series of use cases, common to both technologies, to show how eHealth reports can be used to address mobile wireless customer needs.

2. Background Mobile wireless technology supports hand-held telephones, laptop computers, and other mobile personal devices, connecting them to services and to each other via cellular communication over airwaves. Cellular technologies exploit the concept of frequency reuse, recognizing that the same frequency can be used to support multiple conversations provided the conversations are sufficiently separated in space. Communication takes place on reusable frequencies within a network of hexagonal cells. Since a signal cannot be guaranteed to drop off to zero at the boundary of a cell, the cells have to be configured so that two adjacent cells do not share a frequency. To this end, the available frequencies are divided into seven sets and the sets allocated to cells as shown in Figure 1.

Figure 1. Hexagonal Cells. The following three cellular access mechanisms have been used to permit a mobile device to access a cellular infrastructure:


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• Frequency Division Multiple Access (FDMA) allocates a frequency within a cell to a single call and modulates an analog signal. This approach, known as Frequency Division Multiple Access (FDMA), consumes an entire frequency for the duration of a call. Of all the cellular access methods, it is the least efficient in terms of utilization of the available frequencies.

• Time Division Multiple Access (TDMA) assigns a time slot within a frequency channel to a call.

Strictly speaking this access method is TDMA superimposed on FDMA and it represents a clear improvement over simple FDMA in terms of effective use of bandwidth.

• Code Division Multiple Access (CDMA) is a spread-spectrum technology that assigns a distinct

digital code to a call and supports all calls on a range of frequencies. A transmitter effectively encrypts the signal and a receiver decrypts it based on shared knowledge of the same digital code. CDMA has considerable advantages over TDMA and FDMA in terms of effective use of the spectrum and security. Spread-spectrum was originally developed for military use, which favors a signal spread out over a wide range of frequencies, making it harder for an unauthorized party to detect and decode than one confined to a narrow range.

Mobile wireless has evolved considerably since it first saw serious use in the 1980s and can be classified into three generations:

• 1G is based on FDMA and analog signaling. Its most common variants are (or were) Advanced Mobile Phone System (AMPS) in the United States and variations on Total Access Communication Systems (TACS) in Europe. It was designed for voice communication and can be made to handle data only incidentally.

• 2G is based on TDMA (superimposed over FDMA), or, alternatively, CDMA. Unlike 1G, it is a

digital technology which supports both voice and low speed data. The data features are suitable for fax and short messages, but not such data intensive services as Web browsing. The most popular 2G technology was developed in support of the General System for Mobile Communication (GSM). The European Union standardized on GSM early, with commercial networks in operation by 1991. As a result, Europe took an early lead in market penetration of mobile wireless devices. The terms 2G+ or 2.5G are used for services based on a 2G infrastructure that allow higher speed data of the order of fractional T1 speeds. Probably the most well-known 2.5G service is General Packet Radio Service (GPRS), an IP-based value-added service superimposed on a GSM network.

• 3G emphasizes data-oriented services and offers data rates of the order of Mbps based on CDMA.

Two standards dominate the 3G space, cdma2000 based on 1.25 Mhz transmission bandwidths and W-CDMA, based on 5 Mhz transmission bandwidths. Both use the same basic CDMA technology described above. cdma2000 is the dominant standard in the USA, South America and South Korea whereas most of the rest of the world uses W-CDMA. The GSM standard originally used FDMA/TDMA, as discussed above, but switched to W-CDMA when it developed the 3G Universal Mobile Telecommunications System (UMTS) standards.

This paper addresses cdma2000 in the next section and UMTS in the following section.

3. CDMA2000 3.1 cdma2000 History

cdma2000 is a family of 3G CDMA standards defined by the International Mobile Telecommunications-2000 (IMT-2000) Third Generation Partnership Project 2 (3GPP2) under the auspices of the International


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Telecommunications Union (ITU). cdma2000 builds on the 2G cdmaOne technology developed by the Telecommunications Industry Association (TIA/EIA). cdmaOne consists of three progressively improving standards, beginning with IS-95, designed for voice, evolving through IS-95A, which supports data at a maximum speed of 14.4 Kbps based on 1.25 Mhz channels, and culminating in IS-95B which supports packet-switched data services up to 64 kbps and is considered a 2.5G technology. There are four cdma2000 standards:

1. cdma2000 1x (also known as 1xRTT and 3G1x) uses a single 1.25 Mhz channel and offers peak data rates of 307 Kbps and average of 144 kbps packet data in a mobile environment

2. cdma2000 1xEV-DO (data only) offers both voice and high speed data (2.4 Mbps) support, using

a separate data overlay network. 1xEV-DO is not backward compatible with 1xRTT

3. cdma2000 1xEV-DV (data voice) offers integrated voice and data services at 3.09 Mbps using the same carrier and restoring backward compatibility with 1xRTT.

4. cdma2000 3x, the multicarrier option (MC-CDMA), also known as 3xRTT, uses three 1.25 Mhz

channels to support integrated voice and data . This was an earlier proposal that seemed to make sense prior to the advent of #2 and #3 and is not likely to be deployed commercially.

Indeed, only #1 and #2 seem to have any real traction in the marketplace. 3.2 cdma2000 Network Components

A Public Land Mobile Network (PLMN) -- cdma2000 or otherwise -- consists of two parts, a wireless infrastructure that permits a user with a mobile wireless device to access the network and a fixed infrastructure that provides support and connectivity to the wireless communication, as shown in Figure 2.

Figure 2. cdma2000 Mobile and Wired Infrastructures


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The wireless infrastructure – the Radio Access Network (RAN) -- consists of Base Transceiver Stations (BTS), one per cell, that communicate directly with the mobile wireless device over airwaves using CDMA as described earlier. A Base Station Controller (BSC) – sometimes called Radio Network Controller (RNC) -- is responsible for management of one or more BTSs. It connects directly to the BTSs via land lines and switches traffic either to a Mobile Switching Center (MSC) which places a voice call on the Public Switched Telephone Network (PSTN) or, alternatively, to the fixed infrastructure for data traffic or perhaps VoIP. This latter traffic is passed to a Packet Control Function (PCF), which relays it to a Packet Data Serviing Node which is effectively the access point to the fixed network infrastructure, an IP network. The PDSN and PCF communicate via the RAN-to-PDSN (R-P) interface, also called the A10/A11 interface, setting up Point-to-Point (PPP) connections between the cellular stations and the PDSN and establishing a tunnel for communication between the FA and HA Indeed the only truly wireless component of the network is the airlink between the mobile wireless station and the BTS. All other communication travels over fixed lines. The components in Figure 2 provide services in support of mobile wireless conversations, as described below. Packet Control Function The Packet Control Function or PCF performs a variety of functions associated with relaying packets between the BSC and the PDSN. It may actually be physically part of the BSC. It communicates with the BSC using the A8/A9 protocols and with the PDSN using A10/A11. The A8 protocol transports user data between the BSC and the PCF and A9 protocol provides the associated signaling. Similarly, the A10/A11 interface (also known as R-P interface for RAN-to-PDSN) supports the A10 protocol for transport of user data between the PCF and PDSN and the A11 protocol for the associated signaling. The PCF monitors registration lifetimes, renewing sessions as required, buffers data pending the availability of wireless channels and manages mobile packet data sessions. A packet data session represents a logical association between a mobile station and the PDSN. It is distinguished from a connection or Packet Data Service Instance (PDSI) which actually dedicates radio resources. A packet data session can be in any of three states: active, dormant or inactive. In the active or connected state there are one or more PDSIs allocated between the mobile station and the BTS. Each active PDSI has an associated A8 connection, A10 connection and active PPP link. In the dormant state, there is no traffic channel or A8 connection but there is an active A10 connection and an associated active PPP link. In the null or inactive state there is neither a traffic channel nor an A8 connection nor an A10 connection nor a PPP link. A mobile station is in the active state when there is data to send or receive. It goes into the dormant state when no data has been transmitted or received for a defined period of time and can return to the active state when there is data to send. Traffic is normally transmitted over the airwaves on dedicated traffic channels. However common channels can be used as well. The concept of a short data burst (SDB) permits small amounts of data to be transmitted over common channels. Packet Data Serving Node The Packet Data Serving Node (PDSN) provides mobile stations access to the wired infrastructure, effectively functioning as an access router to the IP network. The PDSN terminates the PPP connection from the mobile station, which spans the airlink, the BTS, the BSC, the PCF and all associated wired connections.


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The PDSN usually serves as a Foreign Agent in support of IP Mobility, permitting the mobile station to obtain a care-of address from the local PDSN and communicate via a tunnel with its Home Agent. In some cases the PDSN serves as a Home Agent as well. IP Mobility is discussed in some detail below. In the absence of the Foreign Agent feature, the PDSN can only support simple IP. Simple IP conversations, unlike mobile IP, cannot survive a move from the coverage are of one PDSN to another. Indeed, the PDSN, in conjunction with the PCF and the wireless infrastructure, is capable of supporting four levels of packet data service mobility, each representing a handoff of a mobile station from the coverage area of one device to that of another parallel device and preserving the associated conversation:

• mobility between BTSs. This is the lowest level of mobility. It changes the associated BTS within the area associated with a common BSC.

• mobility between BSCs. Here we change BSCs but remain within the purview of a common PCF. • mobility between PCFs (A10/A11 interface) . Here the associated PCF is changed in a fashion

that is transparent to PPP session. The associated PDSN does not change. • mobility between PDSNs. The highest level of mobility permits changing PDSNs and requires

implementation of IP Mobility. Figure 3, lifted directly from Reference [6], illustrates the four levels of packet data mobility.

Figure 3. Packet Data Mobility Levels

Mobile Switching Center The Mobile Switching Center (MSC) is generally located at the service provider central office and switches traffic between the wireless network and the PSTN Home Location Register The Home Location Register (HLR) is a subscriber database. It is used by the MSC for authentication and registration purposes. An Authentication Center (AC) which provides authentication and encryption services may be collocated with the HLR


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Visitor Location Register The Visitor Location Register (VLR) is a visitor database maintained by the MSC to keep track of mobile wireless subscribers who have moved into the MSC’s area of responsibility. Indeed, the VLR may be collocated with the MSC. Authentication, Authorization and Accounting Servers Authentication, Authorization and Accounting (AAA) servers are used by the PDSN for security and accounting purposes. The PDSN/FA and the associated HA exchange Radius messages with AAA servers when initiating and terminating registrations. AAA servers are potentially collocated with the PDSN/FA and HA. 3.3 cdma2000 IP Communication

The wireless and fixed infrastructures permit a mobile wireless user to communicate with another user, wireless or not, or perhaps a network server, using the Internet Protocol. Thus an IP Path needs to be established between the mobile wireless user and the remote destination. To achieve this, cdma2000 needs to solve two IP datagram transport problems:

1. Transporting IP datagrams between the user and the PDSN across a wireless infrastructure

2. Transporting IP datagrams from the PDSN to the appropriate IP destination Problem 1 is solved via a system of protocol encapsulations. Problem 2 is solved by IP Mobility technology. We discuss each in turn Protocol Encapsulations To transport IP traffic between a mobile station and the PDSN, a Point-to-Point Protocol (PPP) connection is established across the airwaves, the BTS, the BSC, the PCF and all associated wired connections. PPP is an encapsulation protocol for exchanging multiprotocol datagrams between two peers over a point-to-point link. It supports full-duplex, bi-directional communication and delivers packets in order. PPP is actually two protocols:

• A link control protocol (LCP), which establishes a data link connection between the two peers

• A Network Control Protocol (NCP), which establishes a network layer connection on top of the data link connection. The NCP is specific to a network layer protocol. Since the only one used in this context is IP, the only NCP we are concerned with is the Internet Protocol Control Protocol (IPCP).

The A8/A9 and A10/A11 interfaces themselves utilize an underlying IP network. To transport the mobile wireless IP datagrams across tjos network, cdma2000 resorts to the Generic Routing Encapsulation Protocol (GRE). GRE permits encapsulation of a packet associated with one protocol within a packet associated with another protocol by first encapsulating it within a GRE packet. This set of protocol encapsulations is summarized in Figure 4. Withn the A8/A9 and A10/A11 interfaces we have IP encapsulated in PPP, which is encapsulated in GRE, which is, in turn, encapsulated within another IP header.


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Figure 4. Data Transport Protocol Stacks IP Mobility IP Mobility is a technology designed to solve the problem of routing IP traffic to nodes that change their points of attachment to the network. It was originally intended for stations which migrate from one access network to another in semi-permanent attachments, where a station might remain physically attached to a single point for a matter of hours, days or even weeks. A good example would be moving a laptop from a home office to a temporary office on the same corporate network. However with the advent of cellular technology, IP Mobility was adopted as a viable mechanism for handling mobile wireless where attachments are of considerably shorter duration. IP Mobility makes use of two types of network device, Home Agents (HA) and Foreign Agents (FA). Mobile stations register with HAs to obtain permanent IP addresses, called home addresses, by which they are known to other network users. They subsequently register with FAs to obtain care-of IP addresses through which they can communicate temporarily while they are in a particular geographic area. A tunnel supports traffic between the care-of address and the home address. Two protocols are designed to support IP Mobility, an Agent Discovery Protocol to permit a mobile station to find a Foreign Agent (or, indeed, a Home Agent) and a Registration Protocol through which a mobile station registers its care-of address with its Home Agent. The Agent Discovery protocol features an Agent Advertisement message used by a Foreign Agent to advertise its presence and an Agent Solicitation message used by a mobile station to solicit an Agent Advertisement message from a locally attached agent. The Registration Protocol is used by the mobile station to register its care-of address with its Home Agent and establish a tunnel. The Registration Protocol is fundamentally a simple request/reply protocol between the mobile station and Foreign Agent which, in turn, forwards messages to the Home Agent. Registration


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Replies can be successful or unsuccessful, the latter for a variety of reasons that are indicated by a message code. The Registration Protocol described in Reference [17] was co-opted by cdma2000 and forms the basis for the A11 signaling protocol. Registration activity falls into three categories, or types of request

• Initial registration, where a mobile station obtains a care-of address and establish a tunnel to its home agent

• Re-Registration, where the mobile station renews its care-of address and tunnel, as registrations have finite lifetimes, and

• De-Registration, where the mobile station releases the care-of address and tears down the tunnel There are a number of possible Registration Reply message codes, indicating either a successful registration or a registration denied for any of a variety of reasons [17] The net result of a successful registration is the creation of an encapsulating tunnel between the Home Agent and the Foreign Agent that transports datagrams addressed to the mobile station’s home address to the Foreign Agent and thence to the mobile station’s temporary care-of address where they are received by the mobile station. Mobile stations themselves transmit IP datagrams directly to the appropriate destination. Mobile IP traffic flow is summarized in Figure 5, taken from Reference [17].

Figure 5. Mobile IP Traffic Flow

The above scheme directs, forward traffic, sent by the mobile station, through a tunnel but utilizes the bare IP network itself for reverse traffic, sent to the mobile station. Reverse tunneling is a variation on this scheme where both forward and reverse traffic are sent through a tunnel. Reverse tunneling has several advantages:

• Since the IP network never sees the mobile nodes IP address, private IP addresses can be used • A common tunnel with a common security scheme can be used for both forward and reverse

traffic, e.g., IPSec • The mobile node can join multicast groups in its home network

Reverse tunneling requires minor modifications to Registration Protocol and definition of several additional Registration Reply message codes.[16]


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Finally, some PDSNs distinguish between Open RP and Closed RP. They contain the same features and functions, but Open RP operates over the A10/A11 interface and uses the associated protocol stack. Closed RP uses the Layer 2 tunneling protocol (L2TP) 3.4 eHealth cdma2000 Reports

eHealth has certified a number of PDSNs, HAs, PCFs and associated devices. For most of these devices we offer Top N, Trend and At-a-Glance reports for the device and its components. eHealth gathers the necessary data from the devices via SNMP polling or, alternatively, via a specially constructed integration module, depending upon the capabilities of the device in question to transport management information While it has not been possible to provide a single common model for each type of device, there are strong similarities among the eHealth models for similar devices and these are reflected in the resultant reports. The following six elements are commonly found among supported PDSNs:

• Registration Protocol (RP) elements provide variables characteristic of the registration protocol exchange between mobile devices and the PDSN/FA (A10/A11). We normally support Open RP and, where appropriate, closed RP.

• Foreign Agent (FA) elements offer variables associated with mobile IP protocol exchanges between the FA and the HA in support of mobile IP devices.

• Point-to-Point Protocol (PPP) elements provides variables characteristic of PPP connections between IP devices and the PDSN.

• Authorization Server elements provide RADIUS authorization statistics for authorization servers co-located with the PDSN.

• Accounting Server elements provide RADIUS accounting statistics for accounting servers collocated with the PDSN. Sometimes the Authorization and Accounting servers are combined in AAA servers.

• IP Address Pool elements represent pools of IP addresses. The following elements are usually found among supported PCF devices:

• A8-A9 Interface elements contain statistics for the A8-A9 interfaces. • A10-A11 Interface elements contain statistics for the A10-A11 interfaces. • Mobile Aggregate Elements contain aggregate statistics associated with the underlying links

between mobile devices and PCFs. At the time of this writing eHealth supports the following cdma2000 devices, broken down by vendor: Cisco. eHealth supports the Cisco Packet Data Serving Node/ Foreign Agent (PDSN/FA) and Cisco Home Agent (HA) devices. Both are both essentially Cisco routers with some additional features that permit them to function as a PDSN/FA and HA respectively. Three platforms are supported: Cisco 7206VXR, Catalyst 6500 Series, and Cisco 7600 . CommWorks. Here eHealth supports a PDSN, an HA and a Home Agent Control Node (HACN). Lucent. eHealth supports the following Lucent PCF devices

• Lucent PCF which connects to the MSC via frame relay bearer channels.


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• Lucent E-PCF, which utilizes a physical Ethernet in support of the A8-A9 interface, hence the designation E-PCF.

• Lucent RNC, which combines RNC and PCF functions in a single chassis. The PCF is a Blade-PCF or B-PCF which occupies a single blade in the chassis. In general, multiple B-PCFs are co-resident within a single RNC.

Nortel. eHealth supports the Nortel PDSN/FA and HA. The PDSN-FA supports two types of R-P interface, the Open R-P interface based on A10/A11 and the Closed R-P interface based on the Layer 2 Tunneling Protocol (RFC 2661). Starent. The Starent ST16 can assume the roles of different GSM and CDMA devices. For the purposes of this project, we are interested in its CDMA capabilities, specifically its ability to support PDSN/FA and HA features, both of which are supported by eHealth. UT- Starcom. Here eHealth supports the UT-Starcom Packet Data Serving Node/ Foreign Agent (PDSN/FA), Home Agent (HA) and Home Agent Control Node (HACN). Figures 6, 7 and 8 are examples of At-a-Glance reports for the Lucent PCF element, the CommWorks PDSN PPP element and the Nortel PDSN FA element.


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Figure 6. Lucent PCF At-a-Glance Report


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Figure 7. CommWorks PPP At-a-Glance Report


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Figure 8. Nortel PDSN Foreign Agent At-a-Glance Report

4. UMTS

4.1 UMTS History Universal Mobile Telecommunications System (UMTS) is the set of of technical specifications based on GSM defined by the IMT-2000 3rd Generation Partnership Project (3GPP). UMTS evolved from 2G GSM in four distinct stages:

1. Global System for Mobile Communication (GSM) was originally a 2G technology in support of digital cell phones using FDMA/TDMA. Like other 2G technologies it handled voice and low-speed data

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2. General Packet Radio Service (GPRS) was a 2.5 G technology based on GSM which, in theory, supports data up to 115 kbps and is designed to utilize the Internet Protocol.

3. Enhanced Data GSM Environment (EDGE) is an improvement over GPRS and represents a 3G

technology with data rates up to 384 kbps. 4. Universal Mobile Telecommunication System (UMTS) represents the next stage in GSM

evolution. Here the FDMA/TDMA technology gives way to Wideband CDMA (W-CDMA) over 5 Mhz channels. It supports 144 kbps for mobile users and up to 2 Mbps for stationary and slow moving users. In addition, UMTS supports quality of service traffic classes.

4.2 UMTS Networks Like cdma2000, a UMTS PLMN has two parts, a wireless infrastructure that permits a user with a mobile wireless device to access the network and a fixed infrastructure that provides support and connectivity, as shown in Figure 9 where we depict the wireless and fixed parts of a General Packet Radio Service (GPRS).in support of a Public Land Mobile Network (PLMN).

Figure 9. UMTS Mobile and Wired Infrastructures


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General Packet Radio Service (GPRS) is an IP packet service based on 2.5G/3.0G GSM. The wireless infrastructure is similar to that of cdma2000. Central to the operation of GPRS are two devices within the fixed infrastructure: the Serving GPRS Support Node (SGSN) and the Gateway GPRS Support Node (GGSN). SGSNs permit mobile stations to communicate with remote services by exchanging information with GGSNs. The GGSNs are gateways to networks and services external to the fixed wireless network. SGSNs communicate with GGSNs via the GPRS Tunneling Protocol (GTP), which tunnels IP traffic through the network infrastructure. The tunnel is set up between the SGSN and GGSN and permits communication between a mobile user and a remote service or application designated by an Access Point Name (APN). A tunnel is established when an SGSN activates a Packet Data Protocol (PDP) context with a GGSN. A PDP context is a set of agreed upon parameters for communication between a mobile station and a fixed network. This GPRS fixed infrastructure has remained essentially unchanged through the GPRS, EDGE and UMTS stages of GSM, although the wireless infrastructure has evolved somewhat. The upgrade from EDGE to UMTS requires replacing the GSM EDGE Radio Access Network (GERAN) with the UMTS Terrestrial Radio Access Network (UTRAN), i.e., replacing Base Tranceiver Stations (BTS) with Node B units and Base Station Controllers with Radio Network controllers (RNC). Node B is a radio unit largely equivalent to a BTS. It communicates with mobile stations over a well defined interface using W-CDMA and performs services that include rate adaptation and error correction. The Radio Network Controller (RNC) controls the Node B units and is largely equivalent to a BSC. It is tasked with management of radio resources and responsible for channel allocation, segmentation and reassembly and managing connections, congestion, and handovers. A variety of protocol and tunnel configurations can be constructed to provide an IP path from mobile station to an APN over the UTRAN and fixed infrastructure. One common approach is to establish a PPP connection (see section 3.3 for a discussion of PPP) from the mobile station to the GGSN with unencapsulated IP routing from the GGSN to the APN. An alternative might be to extend the PPP connection to the external network by means of the L2TP or some similar tunneling protocol. Figure 10, lifted from Reference [4] depicts the associated protocol stacks, along with some defined interfaces. The Packet Data Convergence Protocol (PDCP) performs data transfer, maintains sequence numbers and, in some cases, provides data compression. PPP can be incorporated on top of it to provide a foundation for IP traffic.

Figure 10. UMTS Protocol Stacks Following are brief descriptions of the major components within the fixed infrastructure of a UMTS network:


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Serving GPRS Support Node The Serving GPRS Support Node (SGSN) tracks mobile systems and provides security and access control. It represents the point of access to the wired network from a particular serving area within the wireless infrastructure and:

• exchanges IP packets with mobile stations within its serving area • detects newly-arrived mobile stations within its serving area • queries Home Location Registers (see below) for information on new subscribers • registers new subscribers

Gateway GPRS Support Node The Gateway GPRS Support Node (GGSN) is a gateway device that permits communication with users and external networks. It represents the endpoint of the GTP tunnel from the SGSN. The GGSN is the point of access to an external network for a particular mobile station. It identifies the services accessed as Access Point Names (APN). Mobile Services Switching Center The Mobile Services Switching Center (MSC) performs telephone switching functions. It is responsible for switching calls to and from other MSCs, the fixed infrastructure, and the PSTN. Home Location Register The Home Location Register (HLR) collects PLMN subscriber information and stores it in a central database. Visitor Location Register The Visitor Location Register (VLR) is a distributed database which contains information on visiting subscribers, i.e., subscribers from another PLMN which have roamed into the PLMN coverage area. The VLR is collocated with the MSC. Equipment Identity Register The Equipment Identity Register (EIR) is an equipment inventory database that serves as proof against theft or unauthorized use. Authentication Center The Authentication Center (AuC) provides authentication and encryption services to each call and is associated with the Home Location Register. Charging Gateway Function The CGF Charging Gateway Function (CGF) collects charging records from SGSNs and GGSNs.


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4.3 UMTS Interfaces

The network components described above communicate with each other over a set of defined interfaces, shown in Figure 11, adapted from Reference [4].

Figure 11. UMTS Interfaces

Of particular importance is the Gateway Tunneling Protocol, used to cross the Gn and Gp interfaces. This protocol was designed to permit communication between two Gateway Serving Nodes (SGSN or GGSN). The Gn interface supports communication between two GSNs in the same PLMN while the Gp interface uses the same protocol to support communication between GSNs in different PLMNs. In both cases the GTP protocol sits on top of an IP protocol stack. In the case of Gn, the traffic is all internal to a single IP network, while in the case of Gp the traffic has to traverse a border gateway between the two networks. The Ga interface (SGSN-CGF, GGSN-CGF) uses the GTP’ protocol, a variation on GTP, to send accounting records for billing purposes. The GPRS Tunneling Protocol (GTP) is concerned with creating/updating/deleting PDP contexts and exchanging data between two GSNs. It sits on top of the protocol stack shown in Figure 12.


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Figure 12. GTP Protocol Stack

PDP contexts are data structures maintained by mobile stations and relevant GSNs for each active session. They support a variety of management parameters including address, sequencing, tunnelling, QoS and APN information. Particularly important structures within PDP contexts are Quality of Service profiles which permit a user to associate quality of service characteristics with a session. Such parameters as precedence, delay, reliability and throughput can be configured with a variety of settings to allow four traffic classes:

• Conversational, characterized by short delays and minimal delay variation (jitter), and suitable for such services as voice, voice-over-IP and video conferencing

• Streaming, characterized by one-way transport of data and minimal delay variation, and suitable for such applications as real-time audio or real-time video.

• Interactive, with limitations on round-trip delay and low bit error rates, and suitable for such applications as web browsing and server access.

• Background, with low bit error rates but no strict requirements on delay or delay variation, and suitable for such applications as email, SMS, and downloads of database information

4.4 eHealth UMTS Reports In the UMTS space, eHealth has certified several GGSNs, where we offer Top N, Trend and At-a-Glance reports for the device and its components. As with cdma2000, eHealth gathers the necessary data from the devices via SNMP polling or, alternatively, via a specially constructed integration module, depending upon the capabilities of the device in question to transport management information As with cdma2000, it has not been possible to provide a single common GGSN model, but there are strong similarities among the eHealth GGSN models which are reflected in the associated reports. In general, the data models are hierarchical and contain elements with information on

• the GTP protocol itself, typically variables associated with context manipulation and throughput • QoS classes associated with the GTP protocol • the various tunneling technologies used • resource utilization such as CPU and memory • pooled resources such as IP addresses or bandwidth


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• communication with a remote server or APN At the time of this writing eHealth supports the following UMTS devices, all GGSNs: Cisco. Here we offer GTP statistics and detailed QoS statistics based on three alternative QoS schemes Ericsson/Juniper. Here eHealth provides GTP statistics. Nortel. Here we support an extensive model of the Nortel Univity GGSN, with elements that offers information on the GTP Protocol, detailed statistics on the various QoS traffic classes, GTP accounting, Radius accounting, CGF servers, APNs, IP address pools, and a variety of associated services Figure 13 is an example of a GTP Tunnel element At-a-Glance report.

Figure 13. Nortel GTP Tunnel Element At-a-Glance Report


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5. Use Cases eHealth mobile wireless reports are designed for the use of mobile wireless service providers. We define several roles within the service provider environment and show how the available reports can be used to address their needs. The roles are as follows:

• service provider account managers who want to provide mobile wireless services on top of their IP network infrastructures and sell these services to enterprises.

• service provider production managers who want to oversee the operation of the service at a high level and determine if it is functioning properly or requires attention

• service provider operations personnel who need to detect and correct operational problems before they become critical.

• service provider capacity planners who want to see trends in their customer base and call volumes so they can plan accordingly.

Account managers Probably the most critical problem service provider account managers face is the need to convince their enterprise customers that their service offering is robust, reliable and cost effective. Ideally the enterprise customer would like to see a single report that gives an overview of an entire mobile wireless installation. Such a report would contain panels that depict performance with respect to service level agreements on performance metrics including availability and call quality. Alternatively, reports that depict the aggregate performance of the various network components at a high level might be of interest. These would feature drilldowns to detailed reports on the performance of the various individual devices and components. Detailed reports on the various devices can be presented to a customer to focus attention on performance variables associated with mobile IP figures of merit. While eHealth does not at present support a single report that yields an a overview of the entire mobile wireless configuration, high level reports on, say, the PDSNs or the GGSNs or their subordinate elements are available in the form of Top N reports that might be configured to show the customer the type and volume of work that each device is handling, e.g.,

• registrations requests (total/successful/unsuccessful) • volume of traffic (packets and bytes) crossing critical interfaces • number of extant registrations or active PDP contexts • registered mobiles and active sessions

These Top N reports feature drilldowns to At-a-Glance reports for more detail on particular devices or elements of interest. Production Managers The production manager is concerned with the overall performance of the network and desires to answer the following questions:

1. Is the network close to hitting capacity limits? 2. What components are underutilized? overutilized? 3. Are customers able to access the network? How many users are refused access? 4. Are customers getting good service? degraded service?

Questions 1 and 2 can be addressed with a series of Top N reports on

• PDSNs, featuring such variables as CPU load, memory utilization, current RP sessions


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• PCF resource elements on such variables as processor occupancy and memory utilization • GGSN GTP elements, featuring PDP context statistics • GGSN Resource elements on CPU and memory utilizations • GGSN QoS elements on bandwidth used and available • Routers on CPU load, memory utilization • critical LAN/WAN interfaces on interface utilization

Questions 3 and 4 can also be addressed with Top N reports, in this case on

• PDSN RP elements for such variables as registration requests denied and active/dormant RP sessions

• PCF A8-A9 elements to report on A8 connections denied, A8 reconnection failures, active A8 sessions, A8 reconnection successes

• GGSN GTP elements for variables such as PDUs in error, PDP contexts rejected or failed From the Top N reports, a user can drill down to relevant At-a-Glance reports to examine problem elements. From the At-a-Glance reports, the user can drill down further to Trend reports on problematical variables. Operations Personnel Operations personnel are interested in monitoring the network to ensure service quality, network robustness and reliability. They are concerned with ensuring that service quality is acceptable. Useful in this regard are the overview reports described above as well as routine reports on quality and the various network components and data streams to see how things are going. Service provider operations personnel are concerned with ensuring that service level agreements are kept and, to this end, need reports that depict performance variables with superimposed thresholds that represent service level agreements. Relevant SLA variables include volume, delay and drops. An important concern of the operations personnel is providing proactive service assurance by identifying problems in and separating intermittent problems from more serious ones. There is a need to distinguish momentary effects from true performance degradation to avoid the unnecessary effort of fixing, replacing or upgrading a component that is, in fact, functioning properly. To this end “intelligent” alarms are needed, i.e., notifications that are triggered only when an effect is deemed to be serious and not momentary or intermittent. Such alarms are needed for all supporting devices and equipment to indicate when their performance is reaching a critical threshold. Performance variables subject to alarm thresholding environment include: In particular the operations staff requires Live Exceptions that indicate SLA violations and provide warnings for near-SLA violations. Examples follow: PCF

• Major CPU overload (major) • Minor CPU overload (minor) • Unusually high traffic volume (warning)

PDSN:

• Unusually high number of active RP connections (warning) • Too many registration requests denied (major)

HA

• Too many mobile IP registration requests failed (major) • IP address pool empty (major)


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GGSN

• Too many PDP contexts rejectecd or failed (major) • Too many GTP data PDUs received in error (Major) • CPU utilization too high (warning) • Remaining pool bandwidth in bits too low (warning) •

Similar Live Exceptions on more traditional network variables are also of interest, e.g.:

• device availability • router CPU utilization • memory utilixation • line utilization • errors • discards

To these might be added routine At-a-Glance reports on critical elements, such as PDSNs and GGSNs and their subordinate elements to get some idea of how well the devices are performing Capacity Planners The capacity planner needs to evaluate the existing network in terms of resource utilization to determine if there is spare capacity that can be allocated to mobile wireless traffic and to get some idea of where and when system bottlenecks might occur and to determine when upgrades are needed. For these purposes, historical performance reports on network components are needed, with the ability to

• extrapolate historical behavior to the future in order to determine when critical thresholds will be crossed, and

• depict “what if” scenarios to better understand the alternatives available. Such reports should help determine whether additional capacity in the form of new or upgraded PDSNs, PCFs, GGSNs, routers, switches, or LAN/WAN links will be needed. We can address the capacity planner’s problem with eHealth Trend and What-If reports on variables that relate to capacity such as CPU utilization, memory utilization, IP address pool utilization and any other type of physical or logical resource utilization. These reports single out individual variables, depict historical behavior, and permit trend projection and what-if analyses.

6. References [1] 3rd Generation Partnership Project; Technical Specification Group Core Network and Terminals; General Packet Radio Service (GPRS); GPRS Tunnelling Protocol (GTP) across the Gn and Gp interface (Release 7), 3GPP TS 29.060 v7.0.0 (2005-12) [2] 3rd Generation Partnership Project; Technical Specification Group Core Network and Terminals; Mobile radio interface Layer 3 specification; Core network protocols; Stage 3 (Release 7) 3GPP TS 24.008 v7.2.0 (2005-12) [3] 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; General Packet Radio Service (GPRS); Service description; Stage 1 (Release 6), 3GPP TS 22.060 v6.0.0 (2003-03)


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[4] 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; General Packet Radio Service (GPRS); Service description; Stage 2 (Release 6), 3GPP TS 23.060 v6.11.0 (2005-12) [5] 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Quality of Service (QoS); concepts and architecture (Release 6), 3GPP TS 23.107 v6.3.0 (2005-06) [6] 3rd Generation Partnership Project 2, Interoperability Specification (IOS) for cdma2000 Access Network Interfaces — Part 1 Overview, 3GPP2 A.S0011-C, Version 2.0, December 2005 [7] 3rd Generation Partnership Project 2, Interoperability Specification (IOS) for cdma2000 Access Network Interfaces — Part 2 Transport, 3GPP2 A.S0012-C, Version 2.0, December 2005 [8] 3rd Generation Partnership Project 2, Interoperability Specification (IOS) for cdma2000 Access Network Interfaces — Part 3 Features, 3GPP2 A.S0013-C, Version 2.0, December 2005 [9] Cisco Systems, Cisco Gateway GPRS Support Node 4.0 Data Sheet, copyright © 1992-2003 Cisco Systems, Inc. [10] Cisco Systems, Cisco IOS Mobile Wireless Configuratiion Guide, Mobile Wireless Overview, © 1992-2005 Cisco Systems, Inc, http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fmwire_c/mwcfbkov.pdf

[11] Cisco Systems, Overview of GSM, GPRS, and UMTS, Cisco Cisco Mobile Exchange (CMX) Solutions Guide 0l-2947-01, Chapter 2, © 1992--2006 Cisco Systems, Inc. http://www.cisco.com/univercd/cc/td/doc/product/wireless/moblwrls/cmx/mmg_sg/cmxgsm.pdf [12] Salih Ergut, Overview of 3G Packet Data, Powerpoint presentation, 7/16/2003, http://adaptive.ucsd.edu/2003_salih_3Gdata.ppt [13] D. Farinacci et al, Generic Routing Encapsulation (GRE), RFC 2784, March 2000 [14] Joel Kaufman and Tom Hayes, The Mobile Wireless Business, Wireless Business Plan [date unknown]

[15] G. McGregor, The PPP Internet Protocol Control Protocol (IPCP), RFC 1332, May 1992 [16] G. Montenegro, Editor, Reverse Tunneling for Mobile IP, revised, RFC 3024, January 2001 [17] C. Perkins, Ed., IP Mobility Support for IPv4, RFC 3344, August 2002 (lineal descendant of RFC 2002, which is the RFC actually referenced in the 3GPP2 standards) [18] Radcom, Ltd., Introduction to CDMA2000 1x/1x-EV-DO, © RADCOM Ltd., August 2003, http://www.vicom.com.au/downloads/IntroductiontoCDMA2000.pdf [19] Dan Seligman, Computer Associates Product Approach Specification, eHealth Support for the Lucent CDMA 1X RNC, Version 1.1, 12/20/05 [20] Dan Seligman, Computer Associates Product Approach Specification, eHealth Support for the Lucent E-PCF, Version 1.1, 09/13/05 [21] Dan Seligman, Concord Communications Product Approach Specification, Emerging Technologies, Cisco/Ericsson-Juniper GGSN, Version 1.1, 02/29/04


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[22] Dan Seligman, Concord Communications Product Approach Specification, Emerging Technologies, Cisco GGSN, Version 2.2, 05/03/05 [23] Dan Seligman, Computer Associates Product Approach Specification, Emerging Technologies, Nortel Univity GGSN, Version 3.1, 01/06/06 [24] Dan Seligman, Computer Associates Product Approach Specification, Emerging Technologies, Starent ST16 V5.0 Bulk Stats Support for eHealth 5.7, Version 1.3, 03/20/06 [25] Dan Seligman, Computer Associates Product Approach Specification, UT Starcom TC2K PDSN, HA and HACN, Version 1.1, 09/19/05 [26] Dan Seligman, Concord Communications Product Approach Specification, Emerging Technologies, Cisco PDSN/FA and HA, Version 1.1, 02/09/04 [27] Dan Seligman, Concord Communications Product Requirements Specification, Emerging Technologies, Voice Over IP, Version 0.0, 03/31/03 [28] Dan Seligman, Customized Support for CommWorks PDSN with Mobile IP Support, memo, Fri 4/11/2003 2:43 PM [29] Dan Seligman, Introduction to Wireless Technology, Technical White Paper, February 20, 2002 [30] Dan Seligman, Mobile Wireless Strategic Certification of the Lucent PCF, memo, Tuesday, June 11, 2002 9:54 AM [31] Dan Seligman, Nortel PDSN-FA and HA Approach, Version 1.1, May 23, 2003 [32] Siemens, Comparison of W-CDMA and cdma2000, © Siemens AG 2002 [33] W. Simpson, Editor, The Point-to-Point Protocol (PPP), RFC 1661, July 1994 [34] Tektronix, CDMA Network Technologies: A Decade of Advances and Challenges, Technical Brief, © 2003 Tektronix, 2FW-16904-0, http://www.tek.com/Measurement/App_Notes/2F_16904/eng/2FW_16904_0.pdf [35] Wikipedia, http://en.wikipedia.org/wiki/Main_Page

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