移动通信与仿真2-GPRS.ppt

GPRS - EDGE,吴伟民 电子与信息工程系 wuwmhust.edu.cn,2,GPRS - EDGE Overview GPRS Services,Network Architecture Um Interface (MS-Bss) 52- Multitrame Logical Channels Physical Channel GPRS Stack Layer SNDCP LLC,GPRS en mode Idle GPRS Network mode Classes des mobiles Multislot Class Session Management Evolution to EDGE Modulations GPRS vs EDGE EDGE: RLC/MAC,RLC / MAC TBF,3,GPRS: Overview,What is GPRS,General,But only applicable to specific services,Packet,Obviously,Radio,But much more,Service,But rather a transmission method,4,GPRS: Overview,Circuit vs. Packet,Circuit,Packet,5,GPRS: Overview,GPRS vs. non GPRS,Differences between GPRS and GSM,Warranty on traffic,Warranty on delay vs. Best effort,Charging on time vs. charging on volume,Radio resource sharing,Dedicated channels vs. Shared channels,Transmission mode in the network,Circuit 64 kbps vs. IP network User rate up to 160 kbps,6,GPRS: Overview,Circuit vs. Packet,Service (point to point protocol),GSM allows both circuit and packet service GPRS allows only packet service,Switch mode in the network,In MSC, circuit switch at 64 kbps In GPRS, datagram switch,Radio path transmission,GSM use a resource during the complete call (circuit) But data are always in packet format (burst),7,GPRS: Overview,Shared Channels,The equivalent of a TCH is allocated to 16 (max) multiplexed flows,Possible to allocate several such resources to one user (multi-slot),Release through timer,Independent handling of direction,WEB application traffic is not symmetrical Limitation through GSM symmetrical scheme,8,GPRS: Overview Location Area Code is relevant to LA (Location Area) inside a PLMN. Routing Area Code is relevant to RA (Routing Area) inside a LA.,PLMN A LAC A Cell C RAC A,RAC B,LAC B,PLMN B,Cell A,Cell B,9,IP,GPRS: Overview TCP/IP IP: Internet Protocol,To route datagram (32 bits address) through interconnected network segmentation TCP: Transmission Control Protocol Point to point transport,TCP,UDP,Numbering and acknowledge of data multiplexing UDP: User Datagram Protocol More simple than TCP,Local network protocol (GPRS),No acknowledgement Used for WAP,10,GPRS Network Architecture,GPRS network equipment,Radio sub-system,CCU: Channel Codec Unit,Part of the BTS mainly handling the physical layer,PCU: Packet Control Unit,Handles RLC and MAC layers,Switches,SGSN: Serving GPRS Support Node GGSN: Gateway GPRS Support Node,11,Um Interface (MS-BSS) MM Sub-Layer LLC,RR-SAP,GMMRR-SAP,GRR-SAP RR Management,Non -RR,PD,RR,RR,Upper Layer PDUs RLC/MAC,SAPI 0,SAPI 3,PBCCH,PCCCH,PACCH,PDTCH,BCCH,RACH PCH SDCCH AGCH,SACCH,FACCH,SDCCH,SACCH,Data Link Layer (signalling L2) PDCH PHYSICAL LINK LAYER,12,52 Multi-Trame TDMA Frame: Same as GSM technology New format : Multi-frame 52 (PDCH : Packet Data Channel) 1 Block ( 4 frames in continue),B 0,B 1,B 2,X,B 3,B 4,B 5,X,B 6,B 7,B 8,X,B 9,B 10,B 11,X,52 multiframe (duration 240 ms) Bn : Blocks X : Idle frames,13,Logical Channels PBCCH : Packet Broadcast Common Channel PCCCH : Packet Common Control Channel PAGCH : Packet Access Grant Channel,PPCH :,Packet Paging Channel,PRACH : Packet Random Access Channel PDTCH : Packet Data Transfer Channel PACCH : Packet Associated Control Channel PTCCH : Packet Timing advance Control Channel,14,Logical Channels, PBCCH + PCCCH + PDTCH + PACCH + PTCCH + PRACH, PCCCH + PDTCH + PACCH + PTCCH, PDTCH + PACCH + PTCCH,15,Logical Channels,Shared Channels Logical channels,PDTCH (Packet Data Traffic Channel) and PACCH (Packet Associated Control Channel),To convey user and signalling data,Multiplexed between 16 (or less) users Unidirectional (UL or DL),PTCCH (Packet Timing advance Control Channel),To manage timing advance,Divided into 16 bi-directional channels Fixed allocation,16,Logical Channels, Common Logical Channels (optional), PBCCH: trnasmits network description (Packet,System Information Type x), PCCCH, PPCH: equivalent to PCH, PAGCH: equivalent to AGCH, PRACH: equivalent to RACH (up to 11 bits),17,Physical Channel,Shared Channels Physical channels,PDCH (Packet Data Channel) is a physical channel PDCH is based on one frequency and one timeslot Logical channels are mapped onto physical channels PDCH is organized into blocks of 4 consecutive bursts,18,TBF : Temporary Block Flow,3GPP 44.060 Definition:,A Temporary Block Flow (TBF) is a connection used by the two RR entities to,support the unidirectional,transfer of upper layer PDUs on packet data,physical channels (PDCH),19,GPRS Stack Layers User Plane GPRS: Application,Appli,Control Plane GPRS: Control L3,IP-X25 SNDCP LLC RLC MAC L1 PDTCH TBF-User,PDTCH TBF - Control,SM | GSMS GMM LLC RLC MAC L1,Control Plane GPRS GRR RLC MAC L1 PBCCH / PCCCH PRACH PACCH /PTCCH,B 0,B 1,B 2,X,B 3,B 4,B 5,X,B 6,B 7,B 8,X,B 9,B 10,B 11,X,52 multiframe (duration 240 ms),20,GPRS User Plane,21,GPRS Control Plane,22,GPRS Control Plane,23,GPRS SNDCP Overview Multiplexing of several PDPs Between MS and SGSN: NSAPI Sequencing warranty for each PDP Access to LLC through several QoS profiles Segmentation / Re-assembly Compression IP header Data,MS: SNDCP,SGSN: SNDCP,24,GPRS MS IDENTITY,MS identities,IMSI: 8 bytes,Unique identity,Stored in the SIM card,P-TMSI (Packet Temporary Mobile Subscriber Identity): 4 bytes,Similar to TMSI,Used to avoid sending IMSI Allocated within a RA,TLLI (Temporary Logical Link Identity): 4 bytes,Used by RLC/MAC layers Derived from P-TMSI,P-TMSI signature: 3 bytes,Used to skip authentication procedure,25,GPRS MS IDENTITY TLLI: Temporary Logical Link Identifier Allocated by SGSN Using P-TMSI TLLI,LLC,LLE x: SAPIx LLE z: SAPI z,LLC,LLE x: SAPIx LLE z: SAPI z,LLE y: SAPI y,MS,LLE y: SAPI y,SGSN,DLCIx (Data Link Connection Identifier) TLLI+SAPI,26,GPRS MS IDENTITY,TLLI handling,GMM generates the TLLI,GMM sends the TLLI to RLC/MAC, LLC and L3 RR,Random TLLI,Used in case no P-TMSI is available Identifier + Random bits,Foreign TLLI,Used in case P-TMSI is available but assigned in a different RA Identifier + Bits derived from the P-TMSI,Local TLLI,Used in case P-TMSI is available and assigned in this RA Identifier + Bits derived from the P-TMSI,27,GPRS LLC Address Field,PD C/R X,X,SAPI,PD: Protolcole Discriminator, LLC= 0, Other = Invalid C/R = Command / Response,SAPI:,0001: GPRS Mobility Mgt: LLGMM 0010 : Tunnelling of Msg 2 :TOM2 0011 : User Data 3 : LL3 0101 : User Data 5 : LL5 0111 : SMS 1000 : Tunnelling of Msg 8 : TOM8 1001 : User Data 9 : LL9 1011 : User Data 11: LL11,28,GPRS LLC 3 Modes LLC,Protected Mode CRC-24bits Header + Data,Unprotected Mode CRC-24bits Header,Acknowledged Mode Err. Frames SGSN,T O M,S N D C P,G M M,S M S,T O M,S N D C P,G M M,S M S,LLC,LLC,RLC MAC GSM RF,RLC MAC GSM RF,BSSGP Netw. Serv. L1,BSSGP Netw. Serv. L1,MS,Um,BSS,Gb,29,1,1,1,1,0,1,GPRS LLC Control Field A Acknoledgement Request bit E Encryption function bit,8,7,6,5,4,3,2,1,Mn Unnumbured function bit,I format (I+S),0,A X N(S),X,N(S),N(R),N(R) Transmitter receive sequence nbr N(S) Transmitter send sequence number,N(R),S1,S2,N(U) Transmitter unconfirmed sequence,S format,1,0,A,X N(R),X,N(R) S1,S2,number P/F Poll Bit when issued as Command Final Bit when issued as Response,UI format U format,X X N(U) N(U) E PM P/F M4 M3 M2 M1,PM Protected Mode Bit Sn Supervisory function bit X Spare Bit,30,GPRS LLC,Control Field,8 0,7 A,6 X,5,4,3 N(S),2,1,1,N(S),X,N(R),2,N(R),1,1,3,X,X,X,K,4,I frame,R(1) R(2) R(3) R(4) R(5)R(6) R(7) R(8),SACK format,R(9) R(10)R(11)R(12)R(13) , R(16),R(253) R(254) R(255),X 36(max),1,0,A,X,X,N(R),1,N(R),1,1,2,S frame SACK format,R(1) R(2) R(3) R(4) R(5)R(6) R(7) R(8) R(9) R(10)R(11)R(12)R(13) R(16),R(253) R(254) R(255),X 34 (max),31,GPRS RLC/MAC Management of TBFs (Temporary Blocks Flows) Management of Logical Channels TBF has oneTFI, Unidirectionnal Identity allocated by network Coding Scheme:, CS 1 CS 2 CS 3 CS 4,Block Size : 22 octets, 9 kbit/s Block Size : 32 octets, 13.4 kbits/s Block Size : 38 octets, 15.6 kbits/s Block Size : 52 octets, 21.4 kbits/s,CS1,User data,Protection,CS2 CS3 CS4,32,GPRS RLC/MAC TBF Stands for Temporary Block Flow “Channel” allocated between the MS and the BSS to convey data Unidirectional (Uplink or Downlink) Release through timer,MS,TBF1 TBF1,TBF2,TBF2,BSS,33,GPRS RLC/MAC: Uplink TBF 3 Modes for TBF Uplink Allocation Static Allocation: a bitmap is sent to MS during,TBF establishment (1TS,1USF),Dynamic Allocation: MS sends 1 to 4 Blocks on reception USF Flag from Network Extended Dynamic Allocation: MS sends 1 to 4 Blocks on reception USF Flag from Network, But from 1 to N PDCHs, mandatory in MultiSlot 2 Types of TBF Uplink Establishment 1 phase access 2 phases access: mandatory for multi slot uplink transfer,34,GPRS RLC/MAC: Header of Uplink Data Block,Payload Type:, 00 RLC/MAC Data Block 01 RLC/MAC Control Block,Countdown Value,TFI: Temporary Flow Identity,BSN: Block Sequence Number, could be acknowledged by network,In sending Packet Uplink Ack/Nack message (including BSN(s) ACK-NACK),TLLI (optional),35,GPRS RLC/MAC: Header of Uplink Data Block Countdown Procedure Used by the MS to announce the end of the TBF BS_CV_MAX (See SI13) indicates when the Countdown Procedure shall be started While remaining RLC/MAC blocks BS_CV_MAX,CV = 15,If remaining RLC/MAC blocks BS_CV_MAX CV = remaining RLC/MAC blocks - 1 Last RLC/MAC block sent with CV=0 Two RLC/MAC blocks sent with same CV if two UL timeslots are allocated to the MS Resource request is not possible during Countdown Procedure New RLC/MAC blocks New TBF,36,GPRS RLC/MAC: Header of Downlink Data Block,Payload Type,S/P and RRBP: NW requires to MS for sending,Packet Control Acknowledgement control message,TFI: Temporary Flow Identity,BSN: Block Sequence Number, could be acknowledged by mobile,In sending Packet Downlink Ack/Nack message (including BSN(s) ACK-NACK),USF: Uplink State Flag,37,GPRS RLC/MAC: Header of Downlink Data Block,Uplink State Flag,Used to multiplex several users on the same PDCH,USF assigned to the MS during the assignment procedure USF present in each DL RLC/MAC block,USF of the MS present within DL RLC/MAC block,The MS can send an UL RLC/MAC block at next occurrence,The MS sends one or four UL RLC/MAC block depending on USF GRANULARITY,USF is allocated on a timeslot basis,The MS needs to monitor every allocated timeslot,USF=7 reserved for PRACH,38,GPRS RLC/MAC: Header of Downlink Data Block Uplink State Flag MS1 is assigned USF1 MS2 is assigned USF2 DOWNLINK,USF7,USF7,USF1,USF2,USF1,USF7,USF1,USF2,USF7,UPLINK,MS1 MS2,BSN,BSN,BSN,BSN,BSN,39,GPRS RLC/MAC: Header of Control Block,Uplink,Payload Type,Downlink,Payload Type,S/P and RRBP: NW requires to MS for sending,Packet Control Acknowledgement control message,TFI (Optional): Temporary Flow Identity,USF: Uplink State Flag,40,GPRS Network Mode,Network Mode of Operation (NMO broadcasted within SI13),NMO2: no co-ordination,Double registration,Location Updating AND Attach or RAU IMSI Detach AND GPRS Detach,No Paging co-ordination,Impossible to receive a CS Paging during a GPRS transfer,NMO1: co-ordination,Single registration,Combined procedures,Paging co-ordination,CS Paging are sent on PACCH during a GPRS transfer,41,Classes the Mobiles,MS class,Class A,Mobile registered in both modes,Able to perform both operations simultaneously (GSM call + Retrieve an email),Technically very difficult (2 radios needed),Class B,Mobile registered in both modes,Only one service at one time (either call OR email) Priority for GSM,Class C,Mobile registered in one mode (GSM or GPRS),42,GPRS: MultiSlot Class,43,Session Management Overview Used to manage PDP contexts Activation Deactivation Modification PDP context: logical association between a MS and PDN (Public Data Network) running across a GPRS network The PDP context defines aspects such as: Routing,QoS Security,PDP1 / APN1,PDP1 / APN1,Billing,PDP2 / APN2,PDP2 / APN2,Etc,44,EDGE,Enhanced Data rates for GSM Evolution Appeared in Release 99,Increase data rate on air interface Rate can be multiplied by 3,IR HARQ AMC Important modification related to signal processing Few modifications within RLC/MAC(Increase ARQ window size, Compressed ACK) LLC and SNDCP: same as GPRS,45,Modulation GPRS vs EDGE,GMSK Vs. 8PSK,GMSK: Gaussian Minimum Shift Keying,1 bit onto one symbol,8PSK: 8 Phase Shift Keying,3 bits onto one symbol, Transfer rate * 3,46,Modulation GPRS vs EDGE,Reduced decision interval and therefore more affected by noise Need robust radio link,47,Modulation GPRS vs EDGE,More complicated signal processing to differentiate the constellation,48,EDGE: RLC/MAC,Modulation and Coding Schemes GPRS: 4 Coding Schemes (CS1 to CS4),8PSK: 9 Modulation and Coding Schemes (MCS),49,EDGE: RLC/MAC,EGPRS block structure,EGPRS uses the GSM Normal Burst for data transfer 4 Normal Bursts used to form a Radio Block,Stealing bits,In GSM, used to indicate FACCH,In GPRS and EGPRS, used to indicate coding scheme,Stealing bits are combined with the encrypted bits Table gives the MCS used and header type,CS1 always used for RLC/MAC Control Blocks,50,EDGE: RLC/MAC Downlink RLC/MAC Header Type 1 Used for MCS7, MCS8 and MCS9 Two RLC blocks per radio block,EGPRS Supplementary Polling (requests Ack/Nack and its type),Temporary Flow Identifier,Uplink State Flag (which TBF is allowed to send on next block),Block Sequence Number 1 Block Sequence Number 2 Coding and Puncturing Scheme (channel coding and puncturing used for the data part),51,EDGE: RLC/MAC,Downlink RLC/MAC Header Type 2,Used for MCS5 and MCS6,Downlink RLC/MAC Header Type 3 Used for MCS1, MCS2, MCS3 and MCS4,Split Block indicator,(indicates if some user data is retransmitted,using 2 blocks,resegmentation),52,EDGE: RLC/MAC,Uplink RLC/MAC Header,Type 1,Rtransimit Block (indicates whether any of the RLC data blocks have,been sent previously),Type 2,Type 3,