3gpp Based LTE Network Architecture for Broad band ... · a)NAS signaling support: NAS (Non Access Stratum) sig- naling refers to the signaling layer being used between the Packet

3gpp Based LTE Network Architecturefor Broad band Wireless Communication

T.Vasu deva Reddy1, M.Obula Reddy2,B.Naresh kumar3,P.Kavitha Reddy4

1ECE Dept B V Raju Institute Of Technology,Narsapur , Medak(Dt),

2Associate professor, M.V.S T, Hyderabad3,4Dept of ECE,Associate professor,B V Raju Institute Of Technology,

Narsapur , Medak(Dt),[email protected],[email protected],[email protected],[email protected]

April 18, 2018

Abstract

Long Term Evaluation (LTE) Network is designed witha aim of providing higher data rates of uplink (Encode bto User E) & down link (UE to E node) speed of 100Mbps& data rates 50Mbs. It also supports for various band-widths ranging from 1.25MHZ to 20MHZ. In1991, 2G GSMNetworks are designed & deployed for the voice centric ser-vices based on circuit switched telephone network. Lateron GSM networks are improved for the packet based ser-vices with name of 2.5 GPRS. This network offers higherdata rates approximately 170 kbps. In 1999, 3G UniversalMobile Telecommunications System (UMTS) is designed tooffer higher data rates with 2Mbps for the pedestrian en-vironment. Later on it has improved to higher data ratesof High Speed Packet Access (HSPA) around 14mbps with

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International Journal of Pure and Applied MathematicsVolume 118 No. 24 2018ISSN: 1314-3395 (on-line version)url: http://www.acadpubl.eu/hub/Special Issue http://www.acadpubl.eu/hub/

back word compatibility. LTE network is designed and op-timized for internet protocol (IP) based networks. LTE net-works are targeted to provide various real time services likevoice, video telephony, etc and non real time services of filedown load, email ,sms, mms streaming, gaming, broad cast,multicast services and so on. This research paper describesthe overview of LTE network architecture for broad bandwireless communication

Key Words:LTE/3GPP, UMTS, UE, MM, E-Node B,SGW, PGW

1 INTRODUCTION

In 1991, 2G GSM network is designed for voice based service oncircuit switch network principle & supports less data rates of 9.6kbps for data communication services. It also enhanced for theSMS, Supplementary services, value added services like a ring backcaller tunes. Around 1995 packet based services are added on topGSM network with name of 2G GPRS services. In 1999 first 3GUMTS network designed and deployed in various parts of the world.3G UMTS network offers global roaming, improving voice quality,network capacity and data

communication services. In 3G UMTS, WCDMAradio accesstechnology with carrier bandwidth of 5MHZ is applied. Later on 3GUMTS networks are improved with data rates around 14 to15Mbpswith the help of advanced modulation like MIMO techniques. In2008, first LTE network specifications are released for the globalcommunity. Basically LTE

Fig 1: 3G UMTS High level Network components

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International Journal of Pure and Applied Mathematics Special Issue

network is designed with all IP core network, excluding the cir-cuit switched network. LTE network supports circuit switched ser-vices with the help of IP multimedia subsystem service platform.[1].In LTE Network, No Separate Radio Network Controller, all RNCfunctions are shifted to Encoder for reducing latency.

Fig 2: LTE Network, network nodes

2 Description of LTE network Nodes

and Device

Basically LTE network consists of UE, ENODEB, MME, SGW,PDNGW, and HSS.

2.1 User Equipment Functions (UE)

Contains the Universal Subscriber Identity Module (USIM) whichholds authentication information and Operator Specific informa-tion. Various services & applications supported by UE are Moni-tors radios and conveys performance to the Evolved Node B (eNB).Channel quality indicator (CQI) Supports LTE uplink and down-link air interface Maps upstream traffic into traffic classes that aredefined by upstream traffic flow templates

2.2 Enodeb/E-Utran functions [1]

The main features supported by the Endoeb are the following:a) Radio Bearer management: This includes Radio Bearer

setup and release and also involves radio resource management fea-tures for initial admission control and bearer allocation. This set offunctions is under the control of the MME through the S1 interfaceduring session Setup & release and modification phases.

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b) Radio interface transmission and reception: This in-cludes radio channel modulation/Demodulation as well as channelcoding and decoding[6,7].

c) Uplink and Downlink Dynamic radio resource man-agement and data packet scheduling: This is probably themost critical function which requires the eNodeB to cope with manydifferent constraints (like radio-link quality, user priority and re-quested Quality of Service). So as to be able to multiplex differentdata flows over the radio interface and make use of available re-sources in the most efficient way.

d) Radio Mobility management: This function relates toterminal mobility handling while the terminal is in an active state.This function implies radio measurement configuration and process-ing as well as the handover algorithms for mobility decision andtarget cell determination. Radio Mobility has to be distinguishedfrom Mobility Management in Idle, which is a feature handled bythe Packet Core.

e) User data IP header compression and encryption:This item is a key to radio interface data transmission. It answersto the requirements to maintain privacy over the radio interfaceand transmit IP packets in the most efficient way.

f) Network signaling security: Because of the sensitivityof signaling messages exchanged between the eNodeB itself andthe terminal or between the MME and the terminal, all this setof information is protected against eaves dropping and alteration.In addition, the eNodeB also supports some additional functions,which are less obvious but Still mandatory to make the overallsystem work

g) Scheduling and transmission of broadcast informa-tion: This function is present in most, if not all, of the cellularsystems. It refers to system information broadcasting so that idleterminals can learn network characteristics and be able to accessand register to it.

h)Scheduling and transmission of paging messages: Thisfunction is essential for the network to be able to set up mobileterminated sessions. In addition, paging is also used for non idlebut inactive terminals which the network needs to join.

i) Selection of MME at terminal attachment this nonessen-tial feature may be used to increase network resilience to EPC node

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failure, and also helps to cope up with network load management.It is part of the S1 flexibility.

2.3 MME Function [1]

The main features supported by the MME are the following:a)NAS signaling support: NAS (Non Access Stratum) sig-

naling refers to the signaling layer being used between the PacketCore and the terminal supporting functions such as network attach-ment and data session setup.

b)Active session mobility support: This refers to user con-text transfer in the case of active session mobility, either between2G and 3G systems (which involves user context transfer over theS3 interface) or between MME nodes (which involves S10 support).

c)Idle mode terminal Mobility Management: This func-tion is also known as terminal location tracking. It allows the EPCto know where to page terminals in case of user-terminated ses-sions. d)Authentication and Key Agreement (AKA) This refers touser and network-mutual Authentication and session key agreementbetween terminal and EPC.

e)Determination of Serving and PDN GW at bearerestablishment: This function is the EPC Equivalent of the GGSNselection function which is performed in 2G/GPRS and 3G/UMTSNetworks by the SGSN.

2.4 SGW functions [1]

The main features supported by the Serving GW are: Packet rout-ing between E-UTRAN and EPC.

Mobility anchoring: The Serving GW is actually theUser plane anchor point in case of active session mobility be-

tween 2G and 3G systems (which involves the S4 interface) or be-tween encoded in E-UTRAN.

a) PDNGW functions [1]The main PDN GW features arePacket routing between the EPC and external PDN (Packet

Data Network): In this context, PDN is a very generic term whichcovers any kind of IP network as well as IMS domain.

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b)Policy enforcement: Based on the rules provided by thePCRF.

Charging support: As being the EPC edge router, the PDN GWis in charge of applying specific data-flow charging rules.

c)IP address allocation for terminals: The IP address al-location is performed when the initial bearer is set up during thenetwork attachment procedure.

d) HSS functionsThe HSS (Home Subscriber Server) is the concatenation of the

HLR (Home Location Register) and the AuC (Authentication Cen-ter) two functions being already present in pre-IMS 2G/GSM and3G/UMTS networks[9]. The HLR part of the HSS is in chargeof storing and updating when necessary the database containing allthe user subscription information, including (list is non exhaustive):

e)User identification and addressing: This corresponds tothe IMSI (International Mobile Subscriber Identity) and MSISDN(Mobile Subscriber ISDN Number) or mobile telephone number.

f)User profile information: This includes service subscrip-tion states and user-subscribed Quality of Service information (suchas maximum allowed bit rate or allowed traffic class).The AuC partof the HSS is in charge of generating security information from useridentity keys. This security information is provided to the HLR andfurther communicated to other entities in the network. Securityinformation is mainly used for mutual network-terminal authenti-cation. Radio path ciphering and integrity protection, are used toensure data and signaling transmitted between the network and theterminal is neither eavesdropped nor altered.

3 Radio Interface Protocols:

The E-UTRAN Radio Layered Architecture:a)RRC LAYER: Starting from the top of the picture,the RRC layer (Radio Resource Control) supports all the signal-

ing procedures between the terminal and the eNodeB. This includesmobility procedures as well as terminal connection management.The signaling from the EPC Control plane (e.g. for terminal regis-tration or authentication) is transferred to the terminal through theRRC protocol, hence the link between the RRC and upper layers.

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Protocol layered structure in eNodeB for downlink channels asshown fig3

Fig 3: Protocol layered structure in eNodeB for downlink channels

b)PDCP Layer:The PDCP layer (whose main role consists of header compres-

sion and implementation of security such as encryption and in-tegrity) is offered to Radio Bearers by E-UTRAN lower layers. Eachof these bearers corresponds to a specific information flow such asUser plane data (e.g. voice frames, streaming data, IMS signaling)or Control plane signaling (such as RRC or NAS signaling issuedby the EPC). Due to their specific purpose and handling, Informa-tion flows generated by System Information Broadcast and .PagingFunctions are transparent to the PDCP layer.

c)RLC Layer:The RLC layer provides to the PDCP layer basic OSI-like Layer

2 services such as packet data segmentation and ARQ (AutomaticRepeat Request) as an error-correction mechanism. There is one-to-one mapping between each RLC input flow and Logical channelsprovided by RLC to the MAC layer.

d)MAC Layer:The MAC layers main task is to map and multiplex the logi-

cal channels onto the transport Channels after having performedpriority handling on the data flows received from the RLC layer.The flow being multiplexed on a single transport channel may beoriginated by a single user (e.g. one or more instances of DCCH

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and DTCH) or multiple users (e.g. several DTCH from differentusers). The MAC also supports HARQ (Hybrid ARQ), which isa fast repetition process. finally, the MAC delivers the transportflows to the PHY layer, which will apply the Channel coding andmodulation before transmission over the radio interface[6,7].

e) The Radio Channels:In general, it is critical, especially in the case of radio mobility,

that E-UTRAN signaling messages are transmitted as fast as pos-sible, using the best error-protection scheme. On the other hand,voice or data streaming applications can accept a reasonable frameloss due to radio transmission. Interactive connection-oriented ap-plications (such as Web browsing) are also different, as the end-to-end retransmission can help to recover from radio propagationissues. In order to be flexible and allow different schemes for datatransmission.

The E-UTRAN Specifications introduce several types of chan-nels:

a) The logical channels what is transmitted.b)The transport channels how it is transmitted.The physical & logical channels correspond to data-transfer ser-

vices offered by the radio interface protocols to upper layers. Ba-sically, there are only two types of logical channels: the controlchannels (for the transfer of Control plane information) and thetraffic channels (for the transfer of User plane information). Eachof the channels of these two categories corresponds to a certain typeof information flow[5].

Logical control of E-UTRAN channels:a) The BCCH (Broadcast Control Channel): this channel is a

downlink common channel, used by the network to broadcast E-UTRAN system information to the terminals presents in the radiocell. This information is used by the terminal, e.g. to know servingcell network operator, to get information about the configuration ofthe cell common channels, how to access to the network, etc. b)ThePCCH (Paging Control Channel): the PCCH is a downlink commonchannel which transfers paging information to terminals presents inthe cell, e.g. in case of mobile terminated communication session.

c)The CCCH (Common Control Channel): The CCCH is a spe-cial kind of transport channel, used for communication betweenthe terminal and E-UTRAN when no RRC connection is available.

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Typically, this channel is used in the very early phase of a commu-nication establishment.

d)The MCCH (Multicast Control Channel): This channel isused for the transmission of MBMS (Multimedia Broadcast andMulticast Service) information from the network to one or severalterminals.

e)DCCH (Dedicated Control Channel): The DCCH is a point-to-point bi-directional channel supporting control information be-tween a given terminal and the network. In the DCCH context,the control information only includes the RRC and the NAS sig-naling. The Application-level signaling (such as SIP of RTCP) isnot handled by the DCCH.

E-UTRAN logical traffic channels:The DTCH (Dedicated Traffic Channel): The DCCH, the DTCH

is a point-to-point bidirectional Channel, used between a given ter-minal and the network. It can support the transmission of userdata, which include the data themselves as well as application-levelsignaling associated to the data flow[3]. The MTCH (MulticastTraffic Channel): A point-to-multipoint data channel for the trans-mission of traffic data from the network to one or several terminals.As for the MCCH, this channel is associated to the MBMS ser-vice[3].

E-UTRAN Transport ChannelsThe transport channels describe how and with what character-

istics data are transferred over the radio interface. For example,the transport channels describe how the data are protected againsttransmission errors, the type of channel coding, CRC protection orinterleaving which is being used, the size of data packets sent overthe radio interface, etc. All this set of information is known as theTransport Format. As in the specification, the transport channelsare classified into two categories:Downlink transport channels (fromthe network to the terminal Uplink transport channels (from theterminal to the network)[3].

E-UTRAN downlink transport channels:BCH (Broadcast Channel), associated to the BCCH logical

channel. The BCH has a fixed and predefined Transport Format,and shall cover the whole cellarea. PCH (Paging Channel) as-sociated to the BCCH.The DL-SCH (Downlink Shared Channel),which is used to transport user control or traffic data.

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MCH (Multicast Channel) which is associated to MBMSuser control of transport information

E-UTRAN uplink transport channels are:The UL-SCH (Uplink Shared Channel), which is the up-

link equivalent of the DL-SCHThe RACH (Random Access Channel) which is a specific

transport channel supporting limited control information, e.g. dur-ing the early phases of communication establishment or in case ofRRC state change. Physical channels: The physical channels arethe actual implementation of the transport channel over the radiointerface. They are only known to the physical layer of E-UTRANand their structures tightly dependent on physical interface OFDMcharacteristics [5].

Types Of physical channels defined in the downlinkPhysical Downlink Shared Channel (PDSCH) carries user data

and higher-layer SignalingPhysical Downlink Control Channel (PDCCH): This chan-

nel carries scheduling assignments for the uplink.Physical Multicast Channel (PMCH) bears Multicast/Broadcast

informationPhysical Broadcast Channel (PBCH) holds System Infor-

mation. Physical Control Format Indicator Channel (PC-FICH) This informs the UE about the Number of OFDM sym-bols used for the PDCCH. Physical Hybrid ARQ Indicator Chan-nel (PHICH): which carries ACK and NACK, NodeB responses touplink transmission, relative to the HARQ mechanism [5,6].

The physical channels defined in the uplinkPhysical Uplink Shared Channel (PUSCH): Carries user

data and higher-layer Signaling.Physical Uplink Control Channel (PUCCH) Channel car-

ries uplink control information,Including ACK and NACK responses from the terminal to down-

link transmission, relative to the HARQ mechanismPhysical Random Access Channel (PRACH) which car-

ries the random access preamble sent by terminals to access to thenetwork[5,6]

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FIG 4:ENODEB CHANNEL MAPPING

4 DIFFERENT NETWORK ARCHI-

TECTURE S FOR LTE

Basically LTE network consists of access network and packet basedcore network [1], which is connected to IMS service platform. 3GppLTE group specifies various Network architectures like a simple LTEhome network, LTE roaming network, Inter operability of 2G/3GUMTS networks, Interoperability with other Non 3Gpp networksof WLAN, WIMAX etc in both trusted and non trusted modes.The following section shows various network architect models [8,9].Merging the two gateways [4]

Fig 5: Merging S1 Control AND User plane

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Fig 6: EPC roaming architecture home-routed traffic

Fig 7: EPC roaming architecture local breakout

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Fig 8: Non-3GPP Access Architecture

The EPC architecture for trusted WLAN access

Fig 9: HSS Interface Architecture:

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Fig 10: Interface of HSS with MME

V. Important EPC protocol stack: The following sections showsthe various protocol stack for the LTE network & Control planebetween UE, eNodeB and MME [2]

Fig 11: GTP based protocol stack

Basically in GTP based protocol stack defined for different inte-faces with various parameters according to interface requiremenets.MME MME (S10), MME¡-¿SGW(S11), Serving GW PDN GW(S5/S8)

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Fig 12: MMEHSS (S6a) protocol stack

User Plane Protcol Stack UE eNodeB Serving GW PDNGW (GTP-U)

Fig13: interfacing of UE with PDN GW

5 Typical Signaling flows

The following sections shows various signaling flows

a) Subscriber registration

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Fig 14: Subscriber registration

b). Subscriber Deregistration

Fig 15: Subscriber Deregistration

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Fig 16: Service Request Architecture

6 Conclusion

In this paper addressesd overview of LTE network Acrchitecture,Scheduling and transmission, Types Of physical channels, logicalcontrol data rates,protocol tacks,some of the improtant signalingflows.

A. Abbreviations and Acronyms 3GPP : Third GenerationPartnership Project3 3GPP2 : 3rd Generation Partnership Project2 ARQ : (Automatic Repeat Request). CQI : Channel QualityIndicator. eNodeB : evolved NodeB. EPC : Evolved Packet CoreEPS : Evolved Packet System HLR : Home Location Register HSS: Home Subscriber Server

References

[1] Pierre Lescuyer and Thierry Lucidarme, Evolved Packet Sys-tems (EPS), John Wiley & Sons Ltd, 2008

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[2] Magnus Olsson, Stefan Rommer , Catherine Mulligan , Shab-nam Sultana , Lars Frid, SAE and the Evolved Packet Core:Driving the Mobile Broadband Revolution, Academic Press; 1edition (1 August 2009)

[3] TS23.401 (rel 8), GPRS Enhancements for E-UTRAN Access

[4] TS23.402, Architecture Enhancements for Non-3GPP Accesses

[5] TS3GPP 36.201, LTE Physical Layer: General Description

[6] TS 36.211,Physical Channels and Modulation

[7] TS 36.212, Multiplexing and Channel Coding

[8] Erik Dahlman, Stefan Parkvall, Johan Skold, 4G: LTE/LTE-Advanced for Mobile Broadband– Academic Press, 21-Mar-2011 - Technology & Engineering.

[9] Harri Holma, Antti Toskala , LTE for UMTS: Evolution toLTE-Advanced, Wiley; 2 editions, (April 25, 2011)

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3gpp Based LTE Network Architecture for Broad band ... · a)NAS signaling support: NAS (Non Access Stratum) sig- naling refers to the signaling layer being used between the Packet