Transcript gprs[1].
An Overview of GPRS Shourya Roy Pradeep Bhatt Gururaja K. 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. Motivation Speed Immediacy New and better applications User friendly billing GSM Architecture PSTN ISDN MS BTS GMSC BSC MSC BTS BSC EIR MS AUC HLR BTS MS VLR PDN GPRS Architecture Other GPRS PLMN Gp Gn SGSN BSC Gb Gf MS Gr Gs BTS BTS EIR GGSN Gc GGSN D MSC/VLR HLR Gi PDN Protocol Architechture Transmission Plane GPRS specifies a tunnel mechanism to transfer user data packets . Signalling Plane 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 attach GPRS detach GPRS detach can be initiated by the MS or the network. Session Management 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 type PDP address assigned to MS Requested QoS Address of the corresponding GGSN Session Management(Contd.) PDP-Address allocation: Static:Assigned by network operator of User’s home PLMN. Dynamic:Assigned by Corresponding GGSN. PDP Context Activation MS SGSN GGSN Activate PDP Context Request PDP type,PDP Address QoS Requested,Access Point,… Security Functions Create PDP Context Request PDP type,PDP Address QoS Negotiated,Access Point,… Activate PDP Context Accept PDP type,PDP Address QoS Negotiated,… Create PDP Context Response PDP type,QoS Negotiated,… Routing BSC BTS BSC BTS SGSN SGSN MS PLMN1 Intra-PLMN GPRS Backbone Inter-PLMN GPRS Backbone Gn Border Gateway Gn Intra-PLMN GPRS Backbone Gp Border Gateway Gn GGSN SGSN GGSN Gi Packet Data Network(PDN) Eg.Internet,Intranet Router LAN Host PLMN2 Location Management 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. Location Management(Contd.) A MS can be in 3 states: IDLE READY STANDBY Protocol Architechture Transmission Plane The protocols provide transmission of user data and its associated signalling Signalling Plane Comprises protocols for the control and support of functions of the transmission plane 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 LLC(MS-SGSN) RLC/MAC(MS-BSS) Physical layer PLL:channel coding,detection of errors, forward error correction, interleaving, detection of physical link congestion RFL:modulation and demodulation Network Layer (IP or X.25) Relay SNDCP LLC GTP GTP TCP/UDP TCP/UDP Relay RLC MAC PLL RFL BSSP BSSGP IP IP Network Service Network Service Data Link Service Data Link Layer Phy Layer Phy Layer Phy layer Phy Layer Gm BSS RLC :Radio link control PLL :Physical link layer RFL :Physical RF layer MAC:Medium access control Gb SGSN GGSN BSSGP:BSS GPRS Application protocol GTP :GPRS tunneling protocol TCP :Transmission control protocol UDP :user datagram protocol IP :Internet Protocol Transmission Plane Gi MS BSS Application Network Layer SNDCP LLC Relay RLC RLC MAC MAC PLL BSSGP Network Service PLL RFL RFL Um SNDCP:Subnetwork dependent convergence protocol LLC :Logical link control RLC :Radio link control PHY Layer SGSN BSS MS GMM/SM GMM/SM LLC Application LLC Application RLC MAC GSM/RF RLC MAC GSM RF Relay BSSGP BSSGP Network service Network layer Physical layer Phy Layer Um Gb GMM/SM:GPRS Mobilty Management and session Management Protocol GSM/RF:GSM physical layer(radio interface) I.e.PLL and RFL Signalling Plane:MSSGSN SGSN MSC/VLR BSSAP BSSAP SCCP SCCP MTP3 MTP3 MTP2 MTP2 Phy Layer Phy Layer Gs Signalling Plane SGSN MSC/VLR SGSN HLR(and EIR) MAP MAP TCAP TCAP SCCP SCCP MTP3 MTP3 MTP2 MTP2 Phy Layer Phy Layer Gr MAP TCAP SCCP MTP :Mobile Application Part :Transaction capabilities and application part :Signalling connection control part :Message transfer part Signalling Plane SGSNHLR/SGSNEIR GSM TDMA Frame Slots and Bursts 960 MHz 959.8 MHz 124 Time Slot 123 ... 200 KHz ... Downlink 1 2 3 4 5 6 7 2 935.2 MHz 935 MHz TDMA Frame 1 915 MHz 914.8 MHz 1 8 Data Burst = 156.25 bit periods 124 123 ... 200 KHz ... Uplink 1 2 3 4 5 6 7 1 8 2 890.2 MHz 890 MHz 1 TDMA Frame GPRS Air Inteface Time Slot Number 0 1 2 3 4 5 6 7 0 1 2 3 4 F1 Uplink F2 F3 Carrier Frequency F4 0 1 2 3 4 5 6 7 0 1 2 3 4 F1 F2 Downlink F3 F4 Voice User1 GPRS User1 Voice User2 GPRS User2 GPRS User3 GPRS Air Interface Master slave concept One PDCH acts as Master Master holds all PCCCH channels The rest of channels act as Slaves Capacity on demand PDCH(s) are increased or decreased according to demand Load supervision is done in MAC Layer GPRS Logical Channels Group Channel Packet data Traffic channel PDTCH Packet broadcast control channel PBCCH Packet common Control Channel (PCCCH) Packet Dedicated Control Channels Function Data Traffic Direction MS BSS Broadcast Control MS BSS PRACH Random Access MS BSS PAGCH Access Grant MS BSS PPCH Paging MS BSS PNCH Notification MS BSS PACCH Associated Control MS BSS PTCCH Timing Advance Control MS BSS Uplink Data Transfer MS PRACH or RACH PAGCH or AGCH PACCH PACCH PDTCH PACCH PDTCH PACCH BSS Packet channel Request Packet Immediate assignment Packet resource Request Packet resource assignment Random Access Frame Transmission Negative Acknowledgement Retransmission of blocks in error Acknowledgement Transmission Downlink Data Transfer MS BSS Packet paging request PPCH or PCH PRACH or RACH PAGCH or AGCH PACCH PACCH or PAGCH PDTCH PACCH PDTCH PACCH Packet channel Request Packet Immediate assignment Packet paging response Packet resource assignment Paging Frame Transmission Negative Acknowledgement Retransmission of blocks in error Acknowledgement Transmission 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 Improved Throughput Conclusion 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. References “General Packet Radio Service in GSM”, Jian Cai and David J. Goodman, Rutgers University, IEEE Communications Magazine, Oct 1997 http://www.comsoc.org/pubs/surveys/3q99issue/bett stetter.html http://www.wsdmag.com/2000/aug2200/38-45.html “Wireless Internet Access based on GPRS”, IEEE Personal Comm. April 2000.