CS 1 Wireless Communication and Mobile Programming Wireless
CS 1: Wireless Communication and Mobile Programming Wireless Technologies: General Packet Radio Service (GPRS) Dr. Khaled Mahmud Laurentian University International Global Experience Program Summer 2016
Agenda �GPRS Key features �Architecture �IP connections �Applications (c) Khaled Mahmud 2
Reference �Chapter 7 [TEL] �Web references �http: //www. radioelectronics. com/info/cellulartelecomms/gprs_tutorial. ph p �http: //en. wikipedia. org/wiki/General_Packet_Radio_Service �http: //en. wikipedia. org/wiki/GPRS_Core_Network (c) Khaled Mahmud 3
General Packet Radio Service (GPRS) �GPRS - 2. 5 G for GSM �First introduction of packet technology �Always On �Usage based charging (not time based) �First step toward 3 G evolution (c) Khaled Mahmud 4
Key Features of GPRS � Packet-based service � Usage-based charging � Best-effort service � Throughput and latency not controlled � Data rate: 56 -114 kbps �All new IP-based data infrastructure � Mobile set will have IP addresses � No changes to voice network � Employs the same physical channels of GSM � Only new GPRS logical channels are defined � Dynamic TDMA � Unused time slots are used when needed � Allocation to circuit switched services and GPRS is done dynamically based on capacity on demand (c) Khaled Mahmud 5
Key Parameters Parameter Specification Value Channel Bandwidth 200 k. Hz Modulation type GMSK Data handling Packet data Max (Theoretical) data rate 172 kbps (c) Khaled Mahmud 6
GPRS Network 2 G MS (voice only) NSS BSS E Abis PCU PSTN B BSC MS PSTN A MSC BTS Gs C VLR GMSC D SS 7 H Gb 2 G+ MS (voice & data) Gr HLR Au. C Gc Gi Gn BSS: Base Station System BTS: Base Transceiver Station BSC: Base Station Controller PCU: Packet Control Unit MS: Mobile Station (c) Khaled Mahmud SGSN NSS: Network Sub-System MSC: Mobile-service Switching Controller VLR: Visitor Location Register HLR: Home Location Register Au. C: Authentication Server GMSC: Gateway MSC IP PSDN GGSN SGSN: Serving GPRS Support Node GGSN: Gateway GPRS Support Node 7
GPRS System Structure (c) Khaled Mahmud 8
GPRS Network Enhancements �Overlaid on GSM network �No Change in GSM air interface �Enhanced set (GPRS-enabled) required �Small change in BTS/BSC/HLR �New packet-based nodes introduced (c) Khaled Mahmud 9
New Elements for GPRS Architecture � SGSN � Serving GPRS Support Node - this forms a gateway to the services within the network � Functions: packet switching, routing and transfer, mobility management, logical link management, authentication and charging � GGSN � Gateway GPRS Support Node which forms the gateway to the outside world � Functions: Routing, tunneling, PDP conversion, address conversion, authentication and charging � PCU � Packet Control Unit which differentiates whether data is to be routed to the packet switched or circuit switched networks (c) Khaled Mahmud 10
Serving GPRS Support Node (SGSN) � Main functions include � Attach/detach: Controls access to MSs connected to several BSCs (i. e. Routing area of the SGSN) � Router: Packet routing and transfer � Responsible for delivering packets to an MS of its routing area and from the MS to the Internet � Mobility management � Logical link management � Authentication � Charging data � There is a location register within the SGSN: It stores � Location information (e. g. , current cell, current VLR) � User profiles (e. g. , IMSI, packet addresses used) (c) Khaled Mahmud 11
Gateway GPRS Support Node (GGSN) � Logical interface between the GPRS network and the Internet (other corporate network) � Combination of Gateway, Router, Firewall � Hides internal network � Main functions include � Converts the PDN address (IP Address) of the MS to the IMSI � Routes the packet to the appropriate SGSN serving the MS (c) Khaled Mahmud 12
Packet Control Unit (PCU) �Hardware router �Usually built (added) to BSC �Differentiate data from CS network from PS network � Routes appropriately towards MSC or SGSN (c) Khaled Mahmud 13
GPRS Layered Protocol Structure (User Plane) Application IP / X. 25 Relay SNDCP LLC Relay RLC MAC GSM RF (PLL/RFL) MS PLL : RFL : FR : SNDCP: UDP : GTP : (c) Khaled Mahmud BSSGP GTP UDP/ TCP IP IP BSSGP Network Service L 2 L 1 bis L 1 GSM RF Um GTP BSS Gb Physical Link Layer Physical Radio Layer Frame Relay Subnetwork Dependent Convergence Protocol User Datagram Protocol GPRS Tunnelling Protocol SGSN BSSGP : LLC: Gn GGSN Gi BSS GPRS Protocol Logical Link Control 14
GPRS Network Operation: GPRS Attach/ PDP Context Activation Activate PDP Context request [PDP type, PDP address, Qo. S requested, Access Point (GGSN), …] Authentication Create PDP Context request [PDP type, PDP address, Qo. S requested, Access Point, …] Activate PDP Context response [PDP type, PDP address, Qo. S negotiated, …] Activate PDP Context accept [PDP type, PDP address, Qo. S negotiated, …] MS is now visible to the PDN MS (c) Khaled Mahmud SGSN GGSN PDN 15
Packet Data Protocol (PDP) �GPRS can use various packet data protocols �IP �X. 25 �Frame Relay �MS can connect to the networks these protocols (c) Khaled Mahmud 16
PDP Context �Data structure present on both the SGSN and the GGSN �Contains the subscriber's session information when the subscriber has an active session �First activated when a mobile wants to use GPRS and make attach �Activation allocates a PDP context data structure in the visiting SGSN and the GGSN serving the subscriber's Access Point � Access Point Name: � IP network where the subscriber is connected � Example format: internet. mnc 012. mcc 345. gprs (c) Khaled Mahmud 17
Data in PDP Context �Subscriber's IP address �Subscriber's IMSI �Subscriber's Tunnel Endpoint ID (TEID) at the GGSN �Tunnel Endpoint ID (TEID) at the SGSN (c) Khaled Mahmud 18
Quality of Service (Qo. S) �GPRS allows definition of Qo. S profiles using these parameters: �Service precedence (priority) � Defines three levels: High, medium, low �Reliability � 3 classes are defined � Guarantees: probability of loss, duplication, mis-sequence, corruption �Delay � Defines: mean delay and 95 -percentile delay �Throughput � Defines maximum/peak bit rate and mean bit rate (c) Khaled Mahmud 19
Mobility Management �SGNS communicates with each other to update MS’s location in relevant registers �MS’s profiles is stored in VLR �Accessible by SGSN (via local MSC) �While MS is in a particular SGSN �A logical link is maintained �When MS moves out of the serving area of a SGSN �Logical link is terminated �Resources are released (c) Khaled Mahmud 20
Data Services in GPRS �Application Mode �GPRS device runs the end application �May use WAP �May connect to internet directly �Tunnel Mode �GPRS device works as a modem �Provides internet access �Other mobile device, e. g. laptop runs the application (c) Khaled Mahmud 21
Mobile Phone Classes �Class A: �Supports simultaneous CS (GSM) and PS (GPRS) traffic �Class B: �Supports CS or PS traffic, but does not maintain both kinds of traffic simultaneously �Class C: �Can operate only in one mode (either PS or CS) �User need to change mode manually (c) Khaled Mahmud 22
GPRS Bearer Services �SMS messaging and broadcasting �File manipulation functions �Active process block process �"Always on" internet access �Multimedia messaging service (MMS) �Push to talk over cellular (Po. C) �Internet applications for smart devices through wireless application protocol (WAP) �Point-to-point (P 2 P) service: inter-networking with the Internet (IP) �Point-to-Multipoint (P 2 M) service: point-to-multipoint multicast and point-to-multipoint group calls (c) Khaled Mahmud 23
GPRS-Specific Applications �Chat �Multimedia Services �Virtual Private Network (VPN) �Location-based Service and Telematics �Unified Messaging (c) Khaled Mahmud 24
Billing and Charging in GPRS �Usage based charging �Flat (fixed usage-based) charging �Other factors in charging: �Qo. S �Max allowed data rate �Charging Gateway Function (CGF) takes care of charging related usage information �Destination and source address �Usage of radio resource �Usage of external packet network �… (c) Khaled Mahmud 25
GSM Evolution for Data Access 2 Mbps UMTS 384 kbps 115 kbps EDGE GPRS 9. 6 kbps GSM 1997 2000 GSM evolution (c) Khaled Mahmud 2003+ 3 G 26
Enhanced Data rates for Global Evolution (EDGE ) �Increased data rates with GSM compatibility �Max 384 kbps �Still 200 KHz bands �Still FDMA/TDMA �Air interface changed a little �Shorter range (more sensitive to noise/interference) (c) Khaled Mahmud 27
Enhancement In EDGE � 8 -PSK modulation � 3 bits/symbol give 3 X data rate �Multiple coding scheme �Adaptive redundancy according to channel condition � 5 coding scheme for EDGE �Incremental redundancy �Retransmitted data is sent with higher channel coding rate and combined with the previously received data (c) Khaled Mahmud 28
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