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Employs digital modulation and advanced call processing capabilities
Ex: GSM, TDMA ,CDMA, Cordless Phones.
Dedicated control channel for voice, signal data.
Provides paging and other data services.
High data rate (N/W access.)
Uses MAHO (Mobile Assisted Hand Off) where mobile units performs the following functions:
reporting received power.
scanning adjacent base station.
data encoding and encryption.
Third Generation Wireless Networks
Aim: to provide single set of standards that can meet wide range of applications and provide universal access thru out the world.
Distinction between cordless and cellular phones disappear as personal handset provides access to voice, data and video services.
It uses broadband integrated service digital
N/W (ISDN) to provide internet for both fixed or mobile users.
Provides reliable transfer of information .
Fixed Network transmission Hierarchy Signal level Digital bit rate Equivalent voice ckts. Carrier system North America and Japan DS-0 64.0 Kbps 1 - DS-1 1.544 Mbps 24 T-1 DS-1c 3.152 Mbps 48 T-1c DS-2 6.312 Mbps 96 T-2 DS-3 44.736 Mbps 672 T-3 DS-4 274.176 Mbps 4032 T-4 CEPT( Europe and more other PTTs) 0 64.0 Kbps 1 - 1 2.048 Mbps 30 E-1 2 8.448 Mbps 120 E-1c 3 34.368 Mbps 480 E-2 4 139.264 Mbps 1920 E-3 5 565.148 Mbps 7680 E-4
Traffic Routing in Wireless Networks
There are three phases in circuit switching:
The telephone message is sent in one go, it is not broken up. The message arrives in the same order that it was originally sent.
In packet-based networks, the message gets broken into small data packets. These packets are sent out from the computer and they travel around the network seeking out the most efficient route to travel as circuits become available. This does not necessarily mean that they seek out the shortest route.
Each packet may go a different route from the others.
Packet Switching Packet Data Format Fields in a Typical packet data HEADER USER DATA TRAILER FLAG ADDRESS FIELD CONTROL FIELD INFORMATION FIELD FRAME CHECK SEQUENCE FIELD
Figure 17-3 Format of a Frame in X.25
Layers of X.25 Protocol
UNIT-4 PART -3
WIRELESS SYSTEMS & STANDARDS
Global System for Mobile (GSM)
CDMA Digital Cellular Standard
GSM Network Architecture
NSS MS MS BTS BSC GMSC IWF OMC BTS BSC MSC MSC A bis U m EIR HLR VLR VLR A BSS PDN ISDN, PSTN RSS radio cell radio cell MS AUC OSS signaling O
U m A bis A BSS radio subsystem MS MS BTS BSC BTS BTS BSC BTS network and switching subsystem MSC MSC Fixed partner networks IWF ISDN PSTN PDN SS7 EIR HLR VLR ISDN PSTN
voice and signaling encrypted on the wireless link (after successful authentication)
temporary identity TMSI (Temporary Mobile Subscriber Identity)
newly assigned at each new location update (LUP)
3 algorithms specified in GSM
A3 for authentication (“secret”, open interface)
A5 for encryption (standardized)
A8 for key generation (“secret”, open interface)
A3 and A8 available via the Internet
network providers can use stronger mechanisms
A3 RAND K i 128 bit 128 bit SRES* 32 bit A3 RAND K i 128 bit 128 bit SRES 32 bit SRES* =? SRES SRES RAND SRES 32 bit mobile network SIM AC MSC SIM K i : individual subscriber authentication key SRES: signed response
A8 RAND K i 128 bit 128 bit K c 64 bit A8 RAND K i 128 bit 128 bit SRES RAND encrypted data mobile network (BTS) MS with SIM AC BTS SIM A5 K c 64 bit A5 MS data data cipher key
What is GPRS?
A new bearer service for GSM that greatly improves and simplifies wireless access to packet data networks,e.g to the internet.
New and better applications
User friendly billing
GSM Architecture BTS MS BTS BTS MS BSC BSC MSC GMSC MS EIR VLR HLR AUC PSTN PDN ISDN
GPRS Architecture BTS BTS MS BSC Gb SGSN Gf Gs Gr D EIR MSC/VLR HLR Gc Gn GGSN Gi PDN Gp GGSN Other GPRS PLMN
GPRS specifies a tunnel mechanism to transfer user data packets .
GTP specifies a tunnel control management protocol.The signalling is used to create modify and delete tunnels.
Registration of a Mobile Node
A mobile station must register itself with GPRS network.
GPRS detach can be initiated by the MS or the network.
After Successful attach a MS gets one or more Packet Data Protocol(PDP) address.This address is unique only for a particular session.
It consists of,
PDP address assigned to MS
Address of the corresponding GGSN
Static:Assigned by network operator of User’s home PLMN.
Routing PLMN1 PLMN2 MS BTS BSC SGSN Gn Intra-PLMN GPRS Backbone Gn Gn SGSN GGSN Gi Packet Data Network(PDN) Eg.Internet,Intranet Border Gateway Gp Inter-PLMN GPRS Backbone Border Gateway Intra-PLMN GPRS Backbone GGSN Router LAN Host SGSN BSC BTS
MS frequently sends location update messages to inform the SGSN where it is.
Determining frequency of update messages is non-trivial.
The location update frequency is dependent on the state of the MS.
A MS can be in 3 states:
The protocols provide transmission of user data and its associated signalling
Comprises protocols for the control and support of functions of the transmission plane
GPRS Backbone:SGSN GGSN
GTP tunnels the user packets and related signalling information between the GPRS support nodes.
Subnetwork dependent convergence protocol
It is used to transfer packets between SGSN and MS
Data link layer
PLL:channel coding,detection of errors, forward error correction, interleaving, detection of physical link congestion
RFL:modulation and demodulation
PLL RFL Phy Layer MAC Network Service Relay RLC BSSP Phy Layer Phy Layer Network Data Link Service Service BSSGP IP LLC TCP/UDP Relay SNDCP GTP Phy layer Data Link Layer IP TCP/UDP Network Layer (IP or X.25) GTP RLC :Radio link control BSSGP:BSS GPRS Application protocol PLL :Physical link layer GTP :GPRS tunneling protocol RFL :Physical RF layer TCP :Transmission control protocol MAC:Medium access control UDP :user datagram protocol IP :Internet Protocol Transmission Plane BSS SGSN GGSN Gm Gb Gi
PLL RFL RLC MAC LLC SNDCP Network Layer Application PLL PHY RFL Layer MAC Network Service Relay RLC BSSGP MS BSS SNDCP:Subnetwork dependent convergence protocol LLC :Logical link control RLC :Radio link control Um
Application Application LLC RLC MAC GSM/RF GMM/SM GSM RF Physical layer MAC Network service Relay RLC BSSGP Phy Layer Network layer BSSGP LLC GMM/SM MS BSS SGSN GMM/SM:GPRS Mobilty Management and session Management Protocol GSM/RF:GSM physical layer(radio interface) I.e.PLL and RFL Signalling Plane:MSSGSN Um Gb
PDCH(s) are increased or decreased according to demand
Load supervision is done in MAC Layer
Group Channel Function Direction Packet data Traffic channel PDTCH Data Traffic MS BSS Packet broadcast control channel PBCCH Broadcast Control MS BSS Packet common Control Channel (PCCCH) PRACH PAGCH PPCH PNCH Random Access Access Grant Paging Notification MS BSS MS BSS MS BSS MS BSS Packet Dedicated Control Channels PACCH PTCCH Associated Control Timing Advance Control MS BSS MS BSS
MS BSS PRACH or RACH PAGCH or AGCH Random Access Transmission Packet channel Request PACCH PACCH PDTCH PACCH PDTCH PACCH Packet Immediate assignment Packet resource Request Packet resource assignment Frame Transmission Negative Acknowledgement Retransmission of blocks in error Acknowledgement
PRACH or RACH PAGCH or AGCH Paging Transmission Packet channel Request PACCH PACCH or PAGCH PDTCH PACCH PDTCH PACCH Packet Immediate assignment Packet paging response Packet resource assignment Frame Transmission Negative Acknowledgement Retransmission of blocks in error Acknowledgement Packet paging request PPCH or PCH MS BSS
Multi Slot Operation
GPRS allows a mobile to transmit data in up to 8 PDCHs (eight-slot operation)
3-bit USF at beginning of each radio block in downlink points to next uplink radio block
Comparison with single-slot GSM
Higher delay at higher load
Low blocking rate
GPRS provides efficient access to Packet Data Networks.
Multislot operation in GPRS leads to efficient channel utilization.
GPRS is more effective for long data packet transmission than short ones.
“ General Packet Radio Service in GSM”, Jian Cai and David J. Goodman, Rutgers University, IEEE Communications Magazine, Oct 1997