16-03-2011, 09:50 AM
RK-5GPRSFinal.ppt (Size: 210.5 KB / Downloads: 151)
Constraints with existing network
• Data Rates too slow – about 9.6 kbps
• Connection setup time too long
• Inefficient resource utilization for bursty traffic
• Proves expensive for bursty traffic utilization
• No efficient method for packet transfers
Comparison of GSM & GPRS
GPRS in INDIA
BPL Mobile
Bharti Cellular
Hutchison Max
Hutchison Essar
Idea Cellular
What is GPRS ?
General Packet Radio Service (GPRS) is a new bearer service for GSM that greatly improves and simplifies wireless access to packet data networks
GPRS applies packet radio principal to transfer user data packets in an efficient way b/w MS & external packet data network
Benefits of GPRS
New Data Services
High Speed (Data Rate 14.4 – 115 kbps)
Efficient use of radio bandwith (Statistical Multiplexing)
Circuit switching & Packet Switching can be used in parallel
Constant connectivity
Statistical Multiplexing
Salient Features of GPRS
Important step on the path to 3G
Standardized by ETSI
GPRS is an overlay network over the GSM
Provides Data Packet delivery service
Support for leading internet communication protocols
Billing based on volume of data transferred
Utilizes existing GSM authentication and privacy procedures.
High Data Rate
GPRS uses radio channel i.e. 200 kHz wide
Radio channel carries digital data stream of 271 kbps
This rate is divided into 8 time slots each carrying 34 kbps per time slot
Data rate 14 kbps per time slot achieved after corrections
GPRS can combine upto 8 time slots giving data rate of 114 kbps
GPRS Services
Offers end-to-end packet switched data transfer
• Bearer Services
• PTP - Point-To-Point service (CLNS mode)
• PTM - Point-To-Multipoint service(CONS Mode)
• PTM-M Multicast service
• PTM-G Group call service
• Supplementary Services
• SMS Short Message Service
• CFU Call Forwarding Unconditional
• CFNRc Call Forwarding on mobile subscriber not reachable
• CUG Closed User Group
• Tele action, access to data bases
• Quality of Service
• GPRS allows defining QoS profiles
• Service precedence, reliability, delay,throughput
GPRS Terminals
Class A
– MS supports simultaneous operation of GPRS and GSM services
Class B
– MS able to register with the n/w for both GPRS & GSM services simultaneously. It can only use one of the two services at a given time.
Class C
– MS can attach for either GPRS or GSM services
– GPRS Network Elements
GPRS Architecture is same as GSM except few hardware modifications :
GPRS includes GSNs
SGSN : Serving GPRS Support Node
GGSN : Gateway GPRS Support Node
GPRS Register
GSM SYSTEM ARCHITECTURE
GPRS SYSTEM ARCHITECTURE
Interfaces
Gb – Connects BSC with SGSN
Gn – SGSN – SGSN/GGSN (in the same network)
Gp – SGSN –GGSN (in different networks)
Gf – For equipment querying at registering time
Gi – Connects PLMN with external Packet Data Networks (PDNs)
Gr – To exchange User profile between HLR & SGSN
Gs – To exchange Database between SGSN & MSC
Gd – Interface between SMS & GPRS
SGSN – Serving GPRS Support Node
• Delivers data packets to mobile stations & vice-versa
• Detect and Register new GPRS MS in its serving area
• Packet Routing, Transfer & Mobility Management
• Authentication, Maintaining user profiles
• Its location register stores location info. & user profiles
• GGSN – Gateway GPRS Support Node
• Interfaces GPRS backbone network & external packet data networks
• Converts the GPRS packets from SGSN to the PDP format
• Converts PDP addresses change to GSM addresses of the destination user
• Stores the current SGSN address and profile of the user in its location register
• Performs authentication
• Many-to- many relations among SGSNs & GGSNs
GPRS Register
GPRS Register is integrated with GSM-HLR.
Maintains the GPRS subscriber data and Routing information.
Stores current SGSN address
GPRS Backbone Network
GSNs are connected through IP based backbone
Two Backbones:
• Intra PLMN backbone networks that connects GSNs of the same PLMN & are private IP networks
• Inter PLMN backbone networks that connects GSNs of the different PLMN. Roaming agreement is necessary
GPRS Tunneling protocol (GTP)
PLMN- Inter PLMN interconnect are called Border gateways (performs security functions to protect Intra- PLMN backbone against unauthorized users and attacks).
GPRS BACKBONE NETWORK
Protocol Stack
SNDCP - Sub Network Dependent Convergence Protocol
Used to transfer data packets between SGSN and MS
Multiplexing of several connections of network layer onto one logical connection of underlying LLC layer
Compression and decompression of user data and header information
Data Link layer
Divided into two sub layers :
• LLC layer (between MS-SGSN)
• RLC/MAC (between MS-BSS)
LLC-Logical Link Control
Establishes highly reliable logical link between MS & its assigned SGSN
Works either in acknowledged or unacknowledged modes
Data confidentiality is ensured by ciphering functions
RLC/MAC Layer
Radio Link Control(RLC)
Establish a reliable link between MS & BSS
Segmentation and reassembly of LLC frames into RLC data blocks