2G Cellular Data Networks - h AcGeneral Packet Radio Service (GPRS) Enhanced Data Rates for GSM...

Wireless Communicationdata on cellular systems1

Dr. Martin LandHadassah CollegeSpring 2010

2G Cellular Data Networks



General Mobility IssuesRegistration and Authentication

User Locate local service provider access pointObtain network access

Service provider Locate mobile user within network for MS-terminated connectionsAuthenticate user access rights

HandoffUsers move between service access pointsService maintained when changing attachment point (location)

Roaming Handoff between service providersElaborate authentication and accounting



Standard IPUser

Connects to IP router by LAN or point-to-point connectionSends IP datagrams containing source and destination IP addressesReceives IP datagrams to (possibly temporary) dedicated IP address

IP address = network number.host numberRouter

Forwards datagram to next hop according to routing protocolRouting tables locate host by NETWORK NUMBER

Router

132.4.16.X X=1, 2, 3, ..., 254

1 2 3

Router

138.27.192.Y Y=1, 2, 3, ..., 254

1 2 3 138.27.192.87



Mobile IP (RFC 2002)Internet protocol supporting host mobility

Maintains TCP connections as host changes locationSupports authentication

Mobile host maintains single long-term IP addressVersion 4 IP address and address format are unaffected

Routing tunnel replaces standard IP routing

Router

132.4.16.X X=1, 2, 3, ..., 254

1 2 3

Router

138.27.192.Y Y=1, 2, 3, ..., 254

1 2 3

138.27.192.87



Mobile IP ⎯ Basic IdeaSimilar to

Call forwardingMail forwarding at

post officeMobile Node

Permanent IP address

Usual home service routerFinds mobile service routers when roaming

Home router and mobile service router coordinateIP datagrams

Sent to usual home routerForwarded by home router to mobile service routerForwarded to Mobile Node

IP datagram

IP datagram

IP datagram



Mobile IP EntitiesMobile Node (MN)

Host or router that can change its point of attachmentHome Address

Permanent IP address assigned to MNCorrespondent Node (CN)

Node that sends datagrams to MN home addressHome Agent (HA)

Maintains table of registered mobile nodes Forwards datagrams addressed to mobile node

Foreign Agent (FA)Delivers datagrams between MN and HA

Mobility AgentHA or FA supporting mobility

Care-of-Address (COA)FA address used to identify current location of MN



Mobile IP Service Definitions Principle Connection Services

Agent DiscoveryCare-of-Address DiscoveryRegistration

Principle Delivery ServicesEncapsulationTunnelingDecapsulation

Roaming and HandoffChange of Foreign AgentRoute Optimization



Agent DiscoveryMobility Agents broadcast availability

Home Agents (HA) Foreign Agents (FA)

Mobile Node (MN) looks for Local router services when connected to home networkForeign Agent (FA) services when connected to foreign network

FA advertises services



Care-of-Address DiscoveryMobile Node (MN)

Requests service from Foreign Agent (FA)Foreign Agent

Assigns Care-of-Address (COA) to MN FA can have 1 or more available COAsUsually FA assigns same COA to all MNs

MN requestsservice from FA



RegistrationForeign Agent

Requests Mobile IP support from MN’s Home AgentHome Agent

Agrees to provide Mobile IP supportMN

Registers COA with its HAHA forwards datagrams to FA

Datagrams for MN arrive at HA

MN registerswith FA and HA

FA forwardsrequest to HA

HA acceptsor rejects

FA informsMN of status



Establishment of Service in Mobile IP

MN in home network

MN in foreign network



Principle Delivery ServicesEncapsulation

Enclose IP datagram inside second IP datagram Inner IP header: addressed from CN to MNOuter IP header: addressed from HA to COA

TunnelingPath taken by encapsulated datagramFrom HA to FA

DecapsulationFA opens encapsulated datagram FA forwards original datagram to MNFA to MN forwarding works at DATA LINK LAYER

Standard routing would return datagram to Home Network



Mobile IP End-to-End Delivery

StandardIP datagram

From: CN IP addressTo: MN Home Address DATA

EncapsulatedIP datagram

From: HA IP addressTo: FA COA Address


StandardIP datagram


CN

MN

FA

HA



Roaming and Hand-OffRoaming MN

Moves to new attachment point (network)Requires change of FA

Multiple bindings Multiple COAs — old + newAvoid datagram lossAvoid too frequent registrations

HA Forwards each packet to multiple COAs

MNReceives packet at one COA

Route optimization after reconnection



Change of Foreign AgentCN HA FAold FAnew MN

IPdatagram

EncapsulatedIP

datagramIP

datagramMN changes

location

registration

registration

updateACK

EncapsulatedIP

datagram

IPdatagram

EncapsulatedIP

datagram

IP datagram

IPdatagram

IPdatagram

ACK

EncapsulatedIP

datagram



Triangle RoutingHome agent is bottleneck

Increases network load



Route Optimization

(1)IP

datagram

IPdatagrams (2b) W

arning(3) Binding Request(4) Binding U

pdate

(5)IP

datagram

HAFA

(2a) EncapsulatedIP datagram



Roaming Under Route Optimization



Voice/Data Interfaces in Cellular Network

Public SwitchedTelephone Network

(PSTN)

Frame Relay,ATM, IP

Circuit Mode Packet Mode

Serial Data onAnalog Modem

Analog Local Loop300 - 3300 Hz

Voice on AnalogTelephone

Voice on DigitalTelephone

Digital Local Loop (ISDN)64 kbps (DS-0)

Serial Dataon ISDN

Network provides dedicated point-to-pointSVC connections and charges for timeand distance of connection

Network provides packet forwarding over one-to-manySVC connections and charges for packet volume

Voice onAMPS

Serial Dataon Analog

AMPS Modem

T1/E1 DigitalConcentrator

Voice onTDMA, GSM,

CDMA

Serial Datain DigitalFrame

T1/E1 DigitalConcentrator

Packet Data inCDPD/GPRS/EDGE

Frame

PacketData

Frame Relay,ATM, IP

Frame Relay,ATM, IP



Data over AMPS

digital bits

modem

modulated(analog)

data

AMPS Networkanalog channels(300 - 3300 Hz)

digital bits

modem

modulated(analog)

data

POTS Networkanalog channels(300 - 3300 Hz)

modem

digital bits

PSTN



Cellular Circuit Mode Data Services

digital bits

POTS Networkanalog channel(300 - 3300 Hz)

modem

digital bits

digital bits

modem

ISDNdigital channel

(64 kbps)

digital bits

PSTN

Cellular Networkdigital voice/data

circuit mode channels(9.6 - 19.2 kbps)



Cellular Packet Mode Data Services

Internet

IPDatagrams

IPDatagrams

Cellular Networkdigital voice/data circuit mode channels

andpacket mode datagram forwarding

(19.2 kbps - 2 Mbps)Cellular service provider acts directly as ISP AMPS: CDPD

GSM: GPRS / EDGE

IPDatagrams

ISPUser makes dial-up call to Internet Service Provider (ISP)



Cellular Data Terminals

Laptop using cellular phone as modem

Laptop with integrated cellular modem

Smartphone with integrated cellular

modem



wWAN Services for Cellular Technologyd-AMPS (IS-136)

Circuit mode data over voice channelCellular Digital Packet Data (CDPD)End-of-life

GSMNative circuit mode data channelGeneral Packet Radio Service (GPRS)Enhanced Data Rates for GSM Evolution (EDGE)Evolution path — 3G

CDMACircuit mode data over voice channelIS-95BEvolution path — 3G



Cellular Digital Packet Data (CDPD)Packet Mode data on AMPS frequencies

Shares radio frequency channels with voice callsAMPS and d-AMPS compatible

First service 1993Considered 2.5G enhancement

Infrastructure additions to AMPS technologyData channel equipment in cellular networkInternal or external modem in mobile station

IP routing Exchange standard IP datagrams with InternetInternal CDPD network

Implements Mobile IP to tunnel IP datagrams

Full duplex transmission up to 19.2 kbps



CDPD Network Architecture

Base System(BS)

Base TransceiverSite (BTS)

BTSBase

StationController

(BSC)

Mobile SwitchingCenter (MSC)

PLMN

BSS

BS

Base Station Subsystem

Public Land Mobile Network

Internet(IS)

MD-IS

PSTN

MDBS

M-ES

F-ES

Internal CDPD IP Tunneling

Standard IP Routing

CELL

CLUSTER

M-ES



CDPD System Architecture ElementsMobile End Station (M-ES)Mobile Data Base Station (MDBS)

Data forwarding function in Base Transceiver Site (BTS)Intermediate Station (IS)

Standard IP network routers, switches, gatewaysMobile Data Intermediate Station (MD-IS)

Data forwarding function in Mobile Switching Center (MSC)Fixed End System (F-ES)

M-ES MDBS MD-IS IS F-ES

F-ES

upstreamradio

downstreamradio

IS

M-ES MDBS IS MD-IS

IS



Mobile Data Base Station (MDBS)Data forwarding function in Base Transceiver Site (BTS)

Manages data streams for all M-ESs in one cellTransmits and receives digital data in AMPS channels

Forward channelAnnounces channel availability to CDPD M-ESMDBS transmits data to all M-ESProvides ACK or NACK responses to M-ES packets

Reverse directionMDBS receives data from M-ES



Mobile Data Intermediate Stations (MD-IS) Located in Mobile Switching Center (MSC)Manages interface between CDPD and InternetHandles

TCP/IP to CDPD protocol conversionMobility Management using Mobile IP

Protects upstream elements from mobility issues

Mobility managementMD-ISs exchange location information about roamers

Mobile Network Location Protocol (MNLP)

Home MD-IS Default gateway for M-ES at homeHome Agent (HA) for roaming M-ES

Attached MD-ISForeign Agent (FA) for roaming M-ES



CDPD Protocol Layers

TCP

IP

SNDCP

MDLP

MAC

Physical(Radio)

DataLink

Network

MDLP

MAC

Physical(Radio)

IP IPData Link Data Link

Physical Physical

MDLP

TCP

IP

Data Link

Physical

IP

SNDCP

MDLP

TCP

IP

Data Link

Physical

Tunnel

IP Networking

TCPEnd-to-End Transport

M-ES MDBS IS MD-IS IS

Physical

Data Link

IP

Physical

Data Link

IP

Physical

Data Link

IP

F-ES

CDPD Internet

End-to-end transport of TCP segmentsInternet hops perform standard IP datagram routing and forwardingCDPD hops implement Mobile IP

MD-IS performs tunneling to M-ESMD-IS to MDBS to M-ES routing by IP address + phone number



Physical Medium Access Transmits over AMPS analog frequency channelsTransfers data packets on unused voice channels

Unused AMPS frequencies or d-AMPS time slots

Sniff and hopBase stations broadcast advertise available channelsMobile station listens for idle channelsWorks well with excess network capacity



MAC Protocol ⎯ Access Control in CDPDDigital Sense Multiple Access/Collision Detect (DSMA/CD)

Contention-based access among CDPD M-ESsExploits forward/reverse frequency pairing

Device senses the transmit medium Listens for Idle flag in forward

channel

If medium is IdleDevice sends data in reverse channelWaits for ACK from MDBS in forward channel

Collision ⎯ transmission from multiple sourcesMDBS returns Decode Failure flagRandom back-off period before trying again

Maximum transmit time of about 1 second per transmission

f3: idle flag

f1: busy flagf2: voice

f4: packet dataf3: ACK/NACK



Special CDPD ProtocolsSNDCP ⎯ Subnetwork Dependent Convergence Protocol

Maps user IP datagrams to an MDLP channelSession servicesSAR (Segmentation and Reassembly)M-ES uses SNDCP as tunnel to MD-IS

MDLP ⎯ Mobile Data Link ProtocolFramingDestination addressing

Encrypted IP address used as MAC layer address

Logical Link Control (LLC) functionsError control and flow control

CDPD MAC ⎯ DSMA-CDManages channel accessManages collision detection and packet retry process



M-ES in Home SystemF-ES places TCP segment into IP datagram addressed to M-ES

Network Entity Identifier (NEI)Standard IP address for M-ESAssigned by CDPD service provider

IP datagram routed through Internet to Home MD-ISHome MD-IS tunnels IP datagram to M-ES via MDBS

SNDCPOpens ports to M-ES for session serviceEncrypts IP datagramEncrypted form of NEI is Temporary Equipment Identifier (TEI)Performs SAR (Segmentation and Reassembly)Passes segments to MDLP

MDLP Builds data link frameAddressed to TEI Includes frame sequencing, flow control, and error control fieldsPasses MDLP frame to TCP/IP for transmission to MDBS



Mobility and TunnelingEntire CDPD system is one Internet domain

Controlled by one MD-ISActs as an Internet subnetEnd-to-end tunnel (SNDCP and MDLP over TCP/IP) covers service areaTEI in MDLP packets permits mobile MAC-layer addressingTelephone number permits mobile physical layer addressing

BaseStation

Controller(BSC)


Internet(IS)

MD-IS

MDBS

M-ES

F-ES


Standard IP R

outing

IS



Mobility and TunnelingHandoff

M-ES moves between cells or between clusters End-to-end tunnel still covers service areaMDLP frames forwarded to new MDBS within TCP/IP frames

Mobility handled by telephone mobilityMDLP frames still addressed to same TEI

BaseStation

Controller(BSC)


Internet(IS)

MD-IS

MDBSM-ES

F-ES


Standard IP R

outing

IS

handoff



Roaming M-ESM-ES

Connects to network in non-home systemRegisters with local (attachment) MD-IS

Attachment MD-IS Exchanges location data with Home MD-IS

Mobile Network Location Protocol (MNLP)

Assigns roamer Subnetwork Point of Attachment (SNPA) addressFunctions as Mobile IP Foreign Agent (FA)

Home MD-IS Functions as Mobile IP Home Agent (HA)

F-ES Addresses TCP segment to M-ES NEI

IP datagram Routed through Internet to Home MD-ISHome MD-IS tunnels to attachment MD-IS using SNPAAttachment MD-IS tunnels IP datagram to M-ES via MDBS, SNDCP, MDLP



Mobile Station and Fixed Station

M-ES

MDBS

IS

MD-IS IS F-ES

MDBS IS MD-IS IS

HomeM-ES

M-ESSubdomain

Subdomain

1

2

3

4

5



M-ES in Roaming Subdomain and F-ES

M-ES

MDBS

IS

MD-IS IS F-ES

MDBS IS MD-IS IS

M-ES

RoamingM-ES

Subdomain

Subdomain

1

2

3 4 5

1

23

4

5

67

8



M-ES in Home Subdomain with Roaming M-ES

HomeM-ES

MDBS

IS

MD-ISIS

F-ES

MDBS IS MD-ISIS

M-ES

RoamingM-ES

Subdomain

Subdomain

1

23

45

61

23

4

5

67

8

910

11

12



General Packet Radio Service (GPRS)Provides packet mode data access for GSM

IP-based architectureConsidered 2.5G enhancement

IP datagrams separated from circuit mode traffic at cluster Packet Control Unit (PCU)

Packet mode function in BSC to handle IP datagrams

Circuit mode voice/data routed to MSC Forwarded to other MSC or PSTN

Packet mode data is routed to Serving GPRS Support Node (SGSN)Forwarded to Internet or X.25 PSDNPCU to SGSN runs IP over Frame Relay

Mobility managementCircuit mode traffic uses PSTN / PLMN routingPacket mode traffic uses IP routing



GSM Circuit Mode and GPRS Packet Mode Data



GPRS System Architecture

Base System(BS)

Base TransceiverSite (BTS)

BTS

BaseStation

Controller(BSC)


PLMN

BSS

Base System(BS)

MS

Base Station Subsystem

Public Land Mobile Network

FrameRelay

InternetServing GPRSSupport Node

(SGSN)

Gateway GPRSSupport Node

(GGSN)

PSTN

PacketControl

Unit (PCU)

GPRSBackbone

(IP)MS



GPRS Support NodesServing GPRS Support Node (SGSN)

Packet-switched version of MSCHandles packets to / from Mobile Stations (MS) Handles MS mobility management

Gateway GPRS Support Node (GGSN) Interfaces SGSNs to external IP networks Maintains routing information

Exterior gateway for GPRS networkAddress mapping (IP mobility)Routes incoming IP datagrams to appropriate PCU



GPRS Terminal ClassesClass A terminal

Supports simultaneous GPRS and GSM voice servicesClass B terminal

Supports GPRS or GSM voice service at one timeMonitor (on hold) one channel and operate second channel

simultaneouslyClass C terminal

Supports only one service at a time



GPRS System Elements



GPRS System Elements

Authentication Center AUC

Service Order GatewaySOG

Border GatewayBG

Call Detail RecordCDR

Charging GatewayCG

Gateway GPRS Support NodeGGSN

Serving GPRS Support NodeSGSN

Base Station SubsystemBSS

Visitor Location RegisterVLR

Home Location RegisterHLR

Base Station ControllerBSC

Base Transceiver SiteBTS



GPRS System Architecture

BTS MSCBS

Internet

SGSN

GGSN

PSTN

BSCGPRS

BackboneMS

PLMN - 1

GGSN

BTS MSCBS

SGSN

BSCMS

BTS MSCBS

SGSN

BSCGPRS

BackboneMS

PLMN - 2

GPRSBackbone

BorderGateway

BorderGateway



GPRS Architecture Protocol Stack

From Internetor X.25

MS to SGSN Tunnel SGSN to GSSN Tunnel

MS to BSS Tunnel BSS to SGSN Tunnel



GPRS Protocol Structure — 1Fixed-system application sends data to MS

IP datagrams or X.25 packetsBasic hops

Internet → GGSN → SGSN → BSS → MSGGSN → SGSN

L1L1

Standard user IP datagrams from InternetIP

GGSNSGSN

L2L2

IPIPStandard TCP/IP and infrastructure protocols

TCP/UDPTCP/UDP

GPRS Tunneling Protocol (GTP)GTP header added to user IP datagram

Call Data Records (CDR) for billingHandles call failure

GTPGTP



GPRS Protocol Structure — 2SGSN-to-MS Tunnel

Logical Link Control (LLC)LLC headerFlow controlError controlLink control

Sub-Network Dependent Convergence Protocol (SNDCP)

SNDCP headerEncapsulates GTP + user IP datagrams Provides

Session servicesSAR (Segmentation and Reassembly)

Maps user IP datagrams to LLC channel

BSS SGSN

L1bis

NW

BSSGP

LLC

SNDCP

L1

MS

L2

IP

TCP/UDP

LLC

GTPSNDCP



GPRS Protocol Structure — 3SGSN to BSS

Frame Relay packets

Maps BSSGP signaling to Frame Relay signaling

Map LLC packets to BSSGPBase Station System GPRS Protocol (BSSGP) Processes routing and QoS information Routing layer for Frame Relay signaling Call setup / control signaling over Frame Relay

SGSN

L1bis

NW

BSSGP

LLC

SNDCP

L1L1bis

BSS

L2NW

IPBSSGP

TCP/UDP

GTP



GPRS Protocol Structure — 4BSS to MS

GSM Radio Frequency (RF)MS allocated 1 to 8 GSM time slots 18 kbps per time slot ⇒ 18 kbps to 144 kbps

Media Access Control (MAC)Between MS and BSSControls access to GPRS

Radio Link Control (RLC)MS-to-BSS Logical Link Control Flow control, error control, link control

BSSGP

RF

MAC

RLC

BSS

RF

MAC

LLC

RF

MS

MAC

RLC

SNDCP

IP



GPRS Connection Process



GPRS Connection ProcessMS switches on and sends GPRS attach requestUser Registration — 1

Associate PLMN address with Packet Data Protocol (PDP) address PDP address — Static or dynamic IP or X.25 addressPLMN address — International Mobile Subscriber ID (IMSI)

AuthenticationBSC queries Home Location Registers (HLR) — 2HLR updates Visitor Location Registers (VLR) — 3

Call Admission Control (CAC) — 4Determines required network resourcesGrants resources if available

Routing — hop-by-hop IP datagram or X.25-PLP deliveryRouting tables in GSN (GGSN or SGSN)

Address conversion / VC mappingGSN handles compression and encryption



Enhanced Data Rates for GSM Evolution (EDGE)Standard: GPRS-136HS

Formally defined as 3G enhancement to GPRSConsidered 2.75G enhancement

Uses enhanced modulation techniqueTransmits 60 kbps in each time slot8 slots × 60 kbps/slot = 480 kbpsUses 384 kbps for user data

Planned (but not relevant)CDPD Gateway d-AMPS Gateway using Voice Over IP (VoIP)



Short Message Service (SMS)Transmission of short text messages

Up to 160 bytes of alphanumeric data160 English ASCII characters16-bit unicode for non-English alphabets ⇒ 80 characters

GSM permits message concatenation

Supported by GSM, d-AMPS, and CDMA

Out-of-band signalingSMS sent over signaling channel — not traffic channelSMS can be sent during a voice callShort messages do not create a heavy traffic load



SMS in GSM Architecture

GMSCSMSC

IWMSC

SME

SMSC

SME: Short Messaging EntitySMSC: Short Message Service CenterGMSC: Gateway Message Service CenterIWMSC: Interworking Message Service Center



SMS NodesShort Messaging Entity (SME)

Any entity that can receive or send short messagesFixed network elementMobile StationAnother service center

Short Message Service Center (SMSC)Store and forwarding of SMS between SME and MS

Gateway Message Service Center (GMSC)Receives SMS from SMSCInterrogates HLR for routing informationDelivers SMS to MSC for destination SME

Interworking Message Service Center (IWMSC)Receives SMS from MSC Delivers SMS to appropriate SMSC for forwarding



SMS Delivery to MS

SME SMSC HLR MSC VLR BSSSMS

Submit RouteRequest

Route

SMSForward

MS

UserInfo

ACK

UserInfo Page

ACKACK

SMSForward SMS

Forward

ACKACK

DeliveryReport

DeliveryReport



High Speed Circuit Switched Data (HSCSD)Circuit Switched Data (CSD)

14.4 kbps circuit mode data connection in 2G GSM User data replaces digitized voice in 1 time slot

High Speed Circuit Switched Data (HSCSD)2.5G enhancementUp to 8 slots (full user frame) allocated to one data channelUp to 115.2 kbps

Transparent data transmissionUser data stream can contain signaling to network

Allows dynamic reconfiguration of data connection (data rate, QoS) HSCSD data frames carry data sub-stream numbers

Maintains order of transmission over GSMNon-transparent data transmission

Only user data in data streamNo signaling or reconfiguration

LLC functions performed by GSM protocols



2.5G Cellular VideoVideo conferencing

MS-to-MS or MS-to-PC audio / video connectionVideo conference

Technology demonstrated in 1926Commercial systems available since 1964

AT&T lost $250 million (in 1965 dollars) on Picture Phone

Personal feel of cellular call may overcome customer resistance

Live video streamingTV broadcasting to telephonesVideo-on-Demand (VOD)



Protocol Options for Digital VideoDigital multimedia streaming options for fixed terminals

Circuit-switched technologyCompressed video over 64 kbps ISDN High quality video over B-ISDN (ATM-based) networksUsed by corporate networks and news reportingNot widely adopted by home users

Packet-switched technologyIP based H.323 protocol for video call (also used in Voice Over IP)Widely implemented

Digital multimedia streaming options for mobile terminalsPacket-switched technology

Video over H.323 over cellular IP (GPRS/EDGE/UTMS)

Circuit-switched technologyCompressed video over High Speed Circuit Switched Data (HSCSD)



Protocol Options for Cellular Digital VideoCellular IP

Fine for non-real-time services with bursty dataWeb browsingSMS/MMS

Cannot provide QoS required for non-bursty videoLow transmission delay and jitterTraffic and mobility variations make delay highly variable

HSCSD providesDedicated channel with no delay variationHigh availabilityStable bit rate for constant bit rate (CBR) video data



3G-324M Protocol for VideoDefines required services for multimedia calls

Call set-upCall routingFrame structureFrame multiplexingVoice and image coordinationCall security

Specifies profiles for existing standardsH.223 Multiplexing and De-multiplexingH.245 Call ControlH.263 Video Codec



3G-324M FunctionsH.223 Multiplexing Protocol

Divides the HSCSD channel into subchannelsAssigns subchannels to voice, audio, control, and dataSegmentation and Reassembly (SAR)

Provides low delay and low overhead

Determines procedures depending on system error rateH.245 Control Protocol

Procedures for setting up and controlling video callsControl message definitions and structuresError control and flow control for digital video packets

H.263 Video CodingEncoding procedures for video channels Mandates widely used standard codecsPermits optional codecs such as MPEG-4



3G-324M System Architecture

Call Signaling Dialing number Call acceptanceEstablishing bearer channel

Multiplexer

and

Demultiplexer

(H.223)

HSCSD

Transparent64 kbps

synchronouslink

VideoCodec

AudioCodec

CallControl(H.245)

Camera

Screen

Microphone

Speaker

OperatingSystem

Call ControlExchange terminal capabilitiesDetermine session masterOpen audio and video logical

channels

2G Cellular Data Networks - h AcGeneral Packet Radio Service (GPRS) Enhanced Data Rates for GSM...

Documents

Transcript of 2G Cellular Data Networks - h AcGeneral Packet Radio Service (GPRS) Enhanced Data Rates for GSM...