TS V1.0.0 ( )

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1 TD SMG 947/97 DRAFT Technical Specification Digital cellular telecommunications system (Phase 2+); General Packet Radio Service (GPRS); Mobile Station (MS) - Base Station System (BSS) interface; Radio Link Control/ Medium Access Control (RLC/MAC) protocol () GLOBAL SYSTEM FOR MOBILE COMMUNICATIONS R European Telecommunications Standards Institute

2 2 Reference ICS: (xxxxxxxx.pdf) Keywords Digital cellular telecommunications system, Global System for Mobile communications (GSM), General Packet Radio Service (GPRS) ETSI Secretariat Postal address F Sophia Antipolis Cedex - FRANCE Office address 650 Route des Lucioles - Sophia Antipolis Valbonne - FRANCE Tel.: Fax: Siret N NAF 742 C Association à but non lucratif enregistrée à la Sous-Préfecture de Grasse (06) N 7803/88 X.400 c= fr; a=atlas; p=etsi; s=secretariat Internet secretariat@etsi.fr Copyright Notification No part may be reproduced except as authorized by written permission. The copyright and the foregoing restriction extend to reproduction in all media. European Telecommunications Standards Institute All rights reserved.

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4 4 Contents 1. Scope Scope of the Technical Specification Application to interface structure Test procedures Use of logical Channels Applicability of implementations Normative references Definitions and abbreviations Vocabulary Random values Layered overview of radio interface Layer Services Layer Functions Sequenced message transfer operation on packet data Service Primitives Definition of primitives Primitives offered to the LLC-sublayer Primitives offered to the MM-sublayer Definition of parameters Services required from physical layers Primitives types Radio block structure RLC data blocks Downlink RLC data block without polling Downlink RLC data block with polling Uplink RLC data block RLC control blocks Downlink RLC control block Uplink RLC control block MAC header and RLC data block header fields Uplink state flag (USF) field Retry (R) bit Stall indicator (SI) bit Power control field Final block indicator (FBI) bit Relative Reserved Block Frame (RRBF) field Countdown Value (CV) field Type (T) bit Supplementary/Polling (S/P) Bit TLLI Indicator (TI) bit Temporary Flow Identifier (TFI) field Extension (E) Bit Block Sequence Number (BSN) field More (M) bit Length Indicator (LI) field TLLI field RLC data field Control message contents field Introduction to the Medium Access Control (MAC) procedures General...30

5 5 6.2 MAC multiplexing principles Uplink State Flag Temporary Flow Identity Temporary Block Flow Medium access modes Packet mode Packet wait state Packet transfer state Packet combined mode MAC procedures in packet wait state Mobile station side Selection of primary PCCCH Actions taken by the mobile station at release of primary PCCCH Allocation/Release of secondary PCCCH(s) Listening to broadcast channels Discontinuous Reception (DRX) Paging procedures Measurements Network side System Information broadcasting Paging on PCCCH Allocation/Release of PCCCH in a cell Allocation of primary PCCCH Release of primary PCCCH Allocation/Release of secondary PCCCHs Medium Access Control (MAC) procedures for Temporary Block Flow (TBF) establishment TBF establishment initiated by the mobile station Entering the packet transfer state: packet access procedure Permission to access the network TBF establishment using one phase access Initiation of the packet immediate assignment procedure Access persistence control on PRACH Answer from the network On receipt of a PACKET CHANNEL REQUEST message Packet access queuing notification Packet access polling Packet access reject procedure Contention resolution One phase packet access completion Abnormal cases TBF establishment using two phase access Initiation of the Packet resource request procedure Answer from the network On receipt of a PACKET RESOURCE REQUEST message Contention resolution Two phase packet access completion Abnormal cases Procedure for measurement report TBF establishment initiated by the network Packet resource assignment Abnormal cases Initial timing advance estimation Paging procedures Paging procedure for RR connection establishment Paging initiation by the network Paging initiation using paging subchannel on CCCH Paging initiation using paging subchannel on PCCCH Paging initiation using PACCH Paging response Abnormal cases...47

6 Packet Paging procedure for TBF connection establishment Packet Paging procedure using paging subchannel on CCCH Packet Paging using paging subchannel on PCCCH Packet paging initiation by the network Indication of packet paging request on the mobile station side Packet Paging response Abnormal cases Packet PTM-M notification procedure Medium Access Control (MAC) Procedures in Packet Transfer Mode Transfer of RLC Data Blocks Downlink Packet Transfer MS Addressing Polling for Packet Ack/Nack Measurement windows Establishment of Uplink TBF Special Rules for Fixed Allocation Uplink Packet Transfer Dynamic Allocation MS Addressing PACCH Location Establishment of Downlink TBF Extended Dynamic Allocation Uplink Slot Allocation MS Addressing PACCH Location Establishment of Downlink TBF Measurement Windows Fixed Allocation Bitmap Usage PACCH Location Measurement Windows Establishment of Downlink TBF Packet Resource Reassignment Procedure for Uplink Dynamic Allocation Procedures Fixed Allocation Procedures Packet Resource Reassignment Procedure for Downlink TBF Release Procedures Uplink TBF Release Procedures Countdown procedure Downlink TBF Release Procedures Concurrent TBF procedures Semi-duplex and full duplex MS procedures Half duplex MS procedures Indication of Notification and Paging Information Queuing Notification Release Notifications Paging Notification Downlink Inactivity Period Notification Frequency Redefinition Procedure Abnormal cases Classmark Change Procedure Classmark interrogation procedure Classmark interrogation initiation Classmark interrogation completion Abnormal Release Procedures Abnormal Release with Return to (P)CCCH Abnormal Release with Random Access Abnormal Release with USF/TFI Reallocation...59

7 7 9. Radio Link Control (RLC) procedures in packet transfer mode Procedures and parameters for peer-to-peer operation Send state variable V(S) Acknowledge state variable V(A) Acknowledge state array V(B) Block sequence number BSN Receive state variable V(R) Receive state array V(N) Starting sequence number (SSN) and received block bitmap (RBB) Window Size Segmentation of LLC-PDUs into RLC Data Blocks Re-assembly of LLC-PDUs from RLC Data Blocks Operation during RLC/MAC control message transfer Operation during packet transfer Acknowledged mode operation Establishment of Temporary Block Flow Operation of uplink Temporary Block Flow Release of uplink Temporary Block Flow Operation of downlink Temporary Block Flow Release of downlink Temporary Block Flow Unacknowledged mode operation Operation of uplink Temporary Block Flow Release of uplink Temporary Block Flow Operation of downlink Temporary Block Flow Release of downlink Temporary Block Flow Abnormal release cases Abnormal release with hold timer Abnormal release with paging channel Abnormal release with channel access Abnormal release with cell reselection Message functional definitions and contents Handling of erroneous protocol data RLC/MAC control messages GPRS System information type GPRS System information type GPRS System information type 2bis GPRS System information type 2ter GPRS System information type GPRS System information type 3 bis GPRS System information type GPRS System information type GPRS System information type 5bis Packet Acknowledgement Packet Channel Request Packet Downlink Ack/Nack Packet Downlink Assignment Packet Downlink Reassignment Packet Dummy Control Block Packet Fixed Immediate Assignment Packet Fixed Assignment Packet Fixed Reassignment Packet Fixed Reassignment Packet Fixed Ack/Nack Packet Immediate Assignment Packet Paging Request Packet Paging Response Packet PDCH Release Packet Polling Packet Power/Timing Update Packet PRACH Parameters...106

8 Packet Queueing Notification Packet Reject Packet Resource Request Packet Suspend Notification Packet TBF Release Packet TBF Status Packet Timing Advance Access Packet Timing Advance Update Packet Uplink Ack/Nack Packet Uplink Assignment Packet Uplink Reassignment General message format and information elements coding Overview Message Type Other information elements Ack/Nack Description Acknowledgement Allocation Allocation Reference Channel Quality Report Channel Request Description Downlink Channel Description Embedded LLC Frame Fixed Channel Description Fixed Channel Description Fixed Channel Description Fixed Channel Description Fixed Channel Description MS Classmark MS Multislot Class MS Measurement capability MS Identity Packet Reject Cause Packet Request Reference Packet Timing Advance Power Control parameter Power Control parameters PRACH Control Parameters Priority level Ready Block Count Suspend Duration Suspend Request TBF Release Cause TBF Status Temporary Flow Identifier Temporary Queueing Identifier (TQI) Timeslot allocation Timing Advance List Uplink Channel Description Timers and counters Timers on the MS side Timers on the network side Other parameters Annex A (informative): Bibliography History

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10 10 Intellectual Property Rights

11 11 Foreword

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13 13 1. Scope This European Telecommunication Standard (ETS) specifies the procedures used at the radio interface (Reference Point Um, see GSM 04.02) for the General Packet Radio Service (GPRS) Medium Access Control /Radio Link Control (MAC/RLC) layer. When the notations for "further study" or "FS" or "FFS" are present in this ETS they mean that the indicated text is not a normative portion of this standard. These procedures are defined in terms of messages exchanged over the control channels of the radio interface. The control channels are described in GSM and in this ETS. The structured functions and procedures of this protocol and the relationship with other layers and entities are described in general terms in GSM This specification is applicable to the following GPRS Um functional layers: - Radio Link Control functions, - Medium Access Control functions, and - Physical Link Control functions. 1.1 Scope of the Technical Specification The procedures described in this ETS are for the RLC/MAC functions of the GPRS radio interface (Um). GSM contains functional procedures for the Logical Link Control (LLC) layer. 1.2 Application to interface structure The MAC/RLC procedures apply to the interface structures defined in GSM They use the functions and services provided by layer 1 defined in GSM GSM gives the general description of layer 3 including procedures, messages format and error handling. 1.3 Test procedures Test procedures of the GSM radio interface signalling are described in GSM and GSM 11.2x series. 1.4 Use of logical Channels The logical control channels are defined in GSM Two similar sets of logical channels are defined. The first set consists of the logical channels used for both circuit mode procedures and GPRS procedures: i) Broadcast Control CHannel (BCCH): downlink only, used to broadcast Cell specific information; ii) Paging CHannel (PCH): downlink only, used to send page requests to Mobile Stations (MSs); iii) Random Access CHannel (RACH): uplink only, used to request a Dedicated Control CHannel; iv) Access Grant CHannel (AGCH): downlink only, used to allocate a Dedicated Control CHannel; The second set of logical channels are used only by GPRS: i) Packet Broadcast Control CHannel (PBCCH): downlink only, used to broadcast Cell specific information; ii) Packet Paging CHannel (PPCH): downlink only, used to send page requests to Mobile Stations (MSs); iii) Packet Random Access CHannel (PRACH): uplink only, used to request a Dedicated Control CHannel;

14 14 iv) Packet Access Grant CHannel (PAGCH): downlink only, used to allocate a Dedicated Control CHannel; v) Packet Associated Control CHannel (PACCH): bi-directional, associated with a Temporary Block Flow (TBF); vi) Packet Cell Broadcast CHannel (PCBCH): downlink only used for general (not point to point) short message information. vii) Packet Notification CHannel (PNCH): downlink only, used to notify mobile stations of VBS (Voice Broadcast Service) calls or VGCS (Voice Group Call Service) calls. 1.5 Applicability of implementations

15 15 2. Normative references References may be made to: a) specific versions of publications (identified by date of publication, edition number, version number, etc.), in which case, subsequent revisions to the referenced document do not apply; or b) all versions up to and including the identified version (identified by "up to and including" before the version identity); or c) all versions subsequent to and including the identified version (identified by "onwards" following the version identity); or d) publications without mention of a specific version, in which case the latest version applies. A non-specific reference to an ETS shall also be taken to refer to later versions published as an EN with the same number. [1] GSM (ETR 350): "Digital cellular telecommunications system (Phase 2+); Abbreviations and acronyms". [2] GSM 02.60: "Digital cellular telecommunications system (Phase 2+); Stage 1 Service Description of the General Packet Radio Service (GPRS)". [3] GSM 03.60: "Digital cellular telecommunications system (Phase 2+); Stage 2 Service Description of the General Packet Radio Service (GPRS)". [4] GSM 03.64: "Digital cellular telecommunications system (Phase 2+); General Packet Radio Service (GPRS);Overall description of GPRS radio Interface; Stage 2". [5] GSM 04.03: " Digital cellular telecommunications system (Phase 2+);Mobile Station - Base Station System (MS - BSS) interface Channel structures and access capabilities ". [6] GSM (ETS ): "Digital cellular telecommunications system; Layer 1 General requirements". [7] GSM (ETS ): "Digital cellular telecommunications system (Phase 2+);Mobile radio interface layer 3 specification". [8] GSM 04.64: "Digital cellular telecommunications system (Phase 2+); General Packet Radio Service (GPRS); Logical Link Control (LLC)". [9] GSM 04.65: "Digital cellular telecommunications system (Phase 2+); General Packet Radio Service (GPRS); Subnetwork Dependent Convergence Protocol (SNDCP)". [10] GSM 05.01: "Digital cellular telecommunications system (Phase 2+); Physical layer on the radio path, General description". [11] GSM (ETS ): "Digital cellular telecommunications system (Phase 2+); Multiplexing and multiple access on the radio path". [12] GSM (ETS ): "Digital cellular telecommunications system (Phase 2+); Channel coding". [13] GSM (ETS ): "Digital cellular telecommunications system (Phase 2+); Modulation". [14] GSM (ETS ): "Digital cellular telecommunications system (Phase 2+); Radio transmission and reception". [15] GSM (ETS ): "Digital cellular telecommunications system (Phase 2+); Radio subsystem link control".

16 16 [16] GSM (ETS ): "Digital cellular telecommunications system (Phase 2+); Radio subsystem synchronisation".

17 17 3. Definitions and abbreviations Abbreviations used in this specification are listed in GSM Vocabulary The following terms are used in this Technical Specification: - idle mode: In this mode, the mobile station is not allocated any dedicated channel; the transfer of packet data PDUs is not possible; the mobile station listens to the CCCH and the BCCH; - packet mode: (only applicable for mobile stations supporting GPRS of class A, B or C): In this mode, the mobile station is prepared to transfer packet data PDUs on packet data physical channels, as defined in GSM The packet mode has two sub-states: - packet wait state: The mobile station is not allocated any radio resource on a packet data physical channel; it listens to the PBCCH and PCCCH or, if those are not provided by the network, to the BCCH and the CCCH; - packet transfer state: The mobile station is allocated radio resource on one or more packet data physical channels for the transfer of packet data PDUs; - packet combined mode: (only applicable for GPRS MS of Class A): In packet combined mode, the services and functions provided by the RLC/MAC layer in packet mode are combined with the services and functions provided by the RR procedures in one of the access modes amongst dedicated mode, group receive mode and group transmit mode, as defined in GSM Temporary Block Flow (TBF): A Temporary Block Flow (TBF) addressed with a unique Temporary Flow Identity (TFI) consists of a set of RLC data blocks (belonging to one or more LLC frames) transmitted sequentially within a single MAC channel assignment. - Uplink State Flag(USF): - The Uplink State Flag (USF) is used on PDCH channel(s) to allow multiplexing of uplink Radio blocks from different mobile stations. 3.2 Random values In a number of places in this Technical Specification, it is mentioned that some value must take a "random" value, in a given range, or more generally with some statistical distribution. For such random values refer to GSM section 2.1, Random values.

18 18 4. Layered overview of radio interface The RLC/MAC layer interacts with other entities as illustrated in Figure 4.1. Communication is performed via Service Access Points (SAPs) by means of Service primitives. Service primitives do not constrain implementations. SAPs defined in this ETS are: GRR-SAP and GMMRR-SAP. Through the GRR-SAP transfer of LLC frames is accomplished while GMMRR-SAP interacts with the RR-sublayer. MM-sublayer LLC sublayer RR-SAP GMMRR-SAP GRR-SAP RR-sublayer RR management RLC/MAC Data Link layer Physical layer Figure 4.1/GSM Layered overview and protocol structure of RR sublayer 4.1 Layer Services Backward error correction (ARQ) Segmentation/reassembly of LL-PDUs Handling of RLC Connection Establishment PDCH Allocation PDCH Reservation Handling of RLC Connection Release

19 19 PDCH Release PDCH Scheduling Handling of RLC Connection Failure Arbitration between many mobile stations trying to transmit simultaneously Mapping of information onto logical channels Mapping of broadcast info?? 4.2 Layer Functions Sequenced message transfer operation on packet data 4.3 Service Primitives Definition of primitives Primitives offered to the LLC-sublayer PRIMITIVE GRR-DATA-REQ GRR-DATA-IND GRR-UNITDATA-REQ GRR-UNITDATA-IND GRR-STATUS-IND Table: Primitives and parameters at GRR-SAP - MS side PARAMETER (message, inf. elements of message, other parameters) LLC PDU, Priority LLC PDU LLC PDU, Priority LLC PDU cause PRIMITIVE Table: Primitives and parameters at GRR-SAP - Network side PARAMETER (message, inf. elements of message, other parameters) GRR-DATA-REQ GRR-DATA-IND GRR-UNITDATA-REQ GRR-UNITDATA-IND GRR-STATUS-IND LLC PDU, TLLI, CI, DRX, MS CLM, QoS, Priority LLC PDU, TLLI, CI LLC PDU, TLLI, CI, DRX, MS CLM, QoS, Priority LLC PDU, TLLI, CI TLLI, cause GRR-DATA-REQ Request used by the LLC sublayer for acknowledged data transmission with a certain priority.

20 20 GRR-DATA-IND Indication used by RR to transfer received data to the LLC sublayer. GRR-UNITDATA-REQ Request used by the LLC sublayer for unacknowledged data transmission with a certain priority. GRR-UNITDATA-IND Indication used by RR to transfer received data to the LLC sublayer. GRR-STATUS-IND Indication used by RR to transfer RLC/MAC failures to the LLC sublayer Primitives offered to the MM-sublayer PRIMITIVE GMMRR-ASSIGN-REQ Table: Primitives and parameters at GMMRR-SAP - MS side PARAMETER (message, inf. elements of message, other parameters) newtlli GMMRR-PAGE-IND - PRIMITIVE GMMRR-PAGE-REQ Table: Primitives and parameters at GMMRR-SAP - Network side PARAMETER (message, inf. elements of message, other parameters) TLLI, IMSI, CI or CI-list or RAI, priority GMMRR-ASSIGN-REQ A new TLLI is assigned to the RR sublayer. GMMRR-PAGE-IND A RR-paging message has been received by the RR sublayer. GMMRR-PAGE-REQ Request by GMM to send a RR-paging message to the mobile station Definition of parameters 4.4 Services required from physical layers GPH-CONNECT (indication) GPH-READY-TO-SEND (indication) GPH-DATA (request, indication) GPH-RANDOM-ACCESS (request, indication, confirm??) Primitives types REQUEST The REQUEST primitive type is used when a higher layer is requesting a service from the next lower layer.

21 21 INDICATION The INDICATION primitive type is used by a layer providing a service to notify the next higher layer of activities related to the REQUEST primitive type. RESPONSE The RESPONSE primitive type is used by a layer to acknowledge receipt, from the next lower layer, of the RESPONSE primitive type. CONFIRM The CONFIRM primitive type is used by the layer providing the requested service to confirm that the activity has been completed.

22 22 5. Radio block structure A Radio Block consists of a MAC Header, a RLC Data Block or RLC/MAC Control Block, and a Block Check Sequence (BCS). The BCS is part of the physical layer and is not defined in this specification (see GSM 05.03). The Radio Block structure is shown in Figure 5.1. Radio Block T =0 RLC Hdr RLC Data Reser ved BCS MAC Header Radio Block RLC Data Block BCS is par t of physical link layer T =1 RLC/MAC Signalling information BCS MAC Header R L C/ MAC Cont r ol B l ock BCS is par t of physical link layer Figure 5.1/GSM Radio Block structure 5.1 RLC data blocks The RLC data block consists of an RLC Header, an RLC Data field, and Reserved bits. Each RLC data block may be encoded using any of the available channel coding schemes CS-1, CS-2, CS-3, or CS-4 (see GSM 05.03). RLC data blocks encoded using CS-1 do not contain Reserved bits. The size of the RLC data block and the value of the Reserved bits for each of the channel coding schemes is shown in Table 5.1. Channel Coding Scheme Table 5.1/GSM 04.60: RLC data block size RLC data block size (octets) Number of Reserved bits RLC data block size without Reserved bits (octets) CS CS / CS / CS / Downlink RLC data block without polling The Downlink RLC data block without polling is formatted as shown in Figure 5.2.

23 23 bit PC T = 0 USF MAC header TFI S/P= Octet 1 0 BSN E Octet 2 Length indicator M E Octet 3 (optional) Length indicator M E Octet 4 (optional) Octet 5 RLC data... Octet N-1 Octet N Reserved (if present) Figure 5.2/GSM Downlink RLC data block Downlink RLC data block with polling The Downlink RLC data block with polling is formatted as shown in Figure 5.3. bit FBI RRBF T = 0 USF MAC header TFI S/P= Octet 1 1 BSN E Octet 2 Length indicator M E Octet 3 (optional) Length indicator M E Octet 4 (optional) Octet 5 RLC data... Octet N-1 Octet N Reserved (if present) Figure 5.3/GSM Downlink RLC data block with polling Uplink RLC data block The Uplink RLC data block is formatted as shown in Figure 5.4. bit Countdown Value T = 0 spare SI R MAC header TFI TI Octet 1 BSN E Octet 2 Length indicator M E Octet 3 (optional) Length indicator M E Octet 4 (optional) Octet 5 \ TLLI Octet 6 } (optional) Octet 7 / Octet 8 / Octet 9 RLC data... Octet N-1 Octet N Reserved (if present) Figure 5.4/GSM Uplink RLC data block

24 RLC control blocks RLC/MAC control messages shall be transported within RLC control blocks. RLC control blocks shall always be encoded using the coding scheme CS-1 (see GSM 05.03) Downlink RLC control block The Downlink RLC control block is formatted as shown in Figure 5.5. bit Power control T = 1 USF MAC header Octet 1 Octet 2 Octet 3 Control Message Contents... Octet 21 Octet 22 Figure 5.5/GSM Downlink RLC control block Uplink RLC control block The Uplink RLC control block is formatted as shown in Figure Countdown value T = 1 spare R MAC header Octet 1 Octet 2 Octet 3 Control Message Contents... Octet 21 Octet 22 Figure 5.6/GSM Uplink RLC control block 5.3 MAC header and RLC data block header fields Uplink state flag (USF) field The USF field is sent in all downlink Radio Blocks and indicates the owner or use of the next uplink Radio Block on the same timeslot. The encoding of the USF field is described in Table 5.2. The USF assignment process are described in section 6.1.

25 25 Table 5.2/GSM USF field values Retry (R) bit bits Next uplink block frame MS with USF value 000 assigned shall transmit MS with USF value 001 assigned shall transmit MS with USF value 010 assigned shall transmit MS with USF value 011 assigned shall transmit MS with USF value 100 assigned shall transmit MS with USF value 101 assigned shall transmit If PCCCH timeslot, next uplink block frame is PRACH block, otherwise MS with USF value 110 assigned shall transmit No MS shall transmit The Retry (R) bit indicates whether the MS sent its last channel request message once time or whether it had to repeat the channel request during its most recent channel access. The MS shall send the same value for the R bit in each uplink Radio block of the TBF Stall indicator (SI) bit Table 5.3/GSM Retry (R) bit bit 1 Retry (R) bit 0 MS sent channel request message once 1 MS sent channel request message more than once The Stall indicator (SI) bit indicates whether the mobile s RLC transmit window can advance (i.e., is not stalled) or can not advance (i.e., is stalled). The MS shall set the SI bit in all uplink RLC data blocks Power control field Table 5.4/GSM Stall indicator bit bit 1 Stall indicator 0 MS RLC transmit window is not stalled 1 MS RLC transmit window is stalled The Power control (PC) field indicates the power level at which the Radio block was transmitted by the network. The value of PC is relative to the parameter BS_TXPWR_MAX. The network shall set the PC field to indicate the actual transmit power level. Table 5.5/GSM Power control field bits Power control BS_TXPWR_MAX BS_TXPWR_MAX - 2 db BS_TXPWR_MAX - 4 db BS_TXPWR_MAX - 6 db BS_TXPWR_MAX - 30 db Final block indicator (FBI) bit The Final block indicator (FBI) bit indicates that the downlink RLC data block is the last RLC data block of the downlink TBF.

26 26 Table 5.6/GSM Final block indicator bit bit 1 Final block indicator 0 Current block is not last RLC data block in TBF 1 Current block is last RLC data block in TBF Relative Reserved Block Frame (RRBF) field The RRBF value shall indicate the uplink block in which an uplink PACCH message is to be sent by the MS. The MS shall wait for the specified uplink Radio Block and then shall transmit one Radio Block on the PACCH timeslot. The MS need not monitor the USF bits in the downlink radio block before the uplink block it shall transmit. Table 5.7 indicates the number of TDMA frames the MS shall wait before transmitting. The delay is relative to the first TDMA frame (N) of the downlink block containing the RRBF value. Table 5.7/GSM Relative Reserved Block Frame (RRBF) field Countdown Value (CV) field bits Relative Reserved Block Frame uplink block with AFN = N+38 or N uplink block with AFN = N+8 or N uplink block with AFN = N uplink block with AFN = N+17 or N uplink block with AFN = N+21 or N uplink block with AFN = N uplink block with AFN = N+30 or N uplink block with AFN = N+34 or N+35 The Countdown Value (CV) field is sent by the MS to indicate the number of block frames of RLC data remaining for the current uplink TBF. CV is calculated according to the process described in section The CV field is 4 bits in length and is encoded as a binary number with range 1 to 15. The value 0 is used to indicate the final RLC data block of the uplink TBF. Table 5.8/GSM Countdown value (CV) field Type (T) bit bits Countdown value (CV) Final RLC data block Last blockframe of data nd to last block frame of data rd to last block frame of data th to last block frame of data th to last block frame of data The Type (T) bit shall indicate whether the Radio block is an RLC control block or an RLC data block. Table 5.9/GSM Type (T) bit bit 1 Type 0 Radio block contains an RLC data block 1 Radio block contains an RLC control block Supplementary/Polling (S/P) Bit The S/P bit is used to poll the MS to send the Packet Ack/Nack for Uplink Transfer message. The S/P bit also controls whether the Power control (PC) field or the Relative Reserved Block Frame (RRBF) and Final block indicator (FBI) bit

27 27 are present in the MAC header octet. When the S/P bit is set to indicate polling, the RRBF fields indicates when the MS shall transmit the Packet Ack/Nack message TLLI Indicator (TI) bit Table 5.10/GSM S/P bit bit 1 S/P 0 no polling, PC field is present 1 polling, RRBF and FBI are present The TLLI Indicator (TI) bit indicates the presence of an optional TLLI field within the RLC data block. Table 5.11/GSM TLLI Indicator (TI) bit bit 1 TLLI indicator (TI) bit 0 TLLI field is not present 1 TLLI field is present Temporary Flow Identifier (TFI) field The TFI identifies the Temporary Block Flow (TBF) to which the RLC data block belongs. A unique TFI value is assigned to the MS by the network for each TBF. All data blocks belonging to the same TBF and control blocks for associated signalling will use the same TFI value. The TFI field is 7 bits in length and is encoded as a binary number with range 0 to Extension (E) Bit The Extension (E) bit is used to indicate the presence of an optional octet in the RLC data block header. If the E bit in octet 2 has the value 0 all of the octets of the RLC data field belong to one LLC frame. Table 5.12/GSM Extension (E) bit bit 1 E bit 0 No extension octet follows 1 Extension octet follows immediately Block Sequence Number (BSN) field The Block Sequence Number (BSN) field carries the unique sequence number of each RLC data block within the TBF. The BSN is 7 bits in length and is encoded as a binary number with range 0 to More (M) bit The M bit, along with the E bit and the Length Indicator (LI), are used to delimit LLC frames within a TBF. When the M bit is present it indicates whether or not another LLC frame follows the current one within the RLC data block. The function of the M and E bits when they occur in the same octet is defined in Table 5.13.

28 Length Indicator (LI) field Table 5.13/GSM M bit and E bit bit M E 0 0 no LLC data after the current LLC frame, no more extension octets 0 1 not used, reserved 1 0 a new LLC frame starts after the current LLC frame and continues until the end of the RLC information field, no more extension octets 1 1 a new LLC frame starts after the current LLC frame and ends before the end of the RLC information field, there is another extension octet The Length indicator is used to delimit LLC frames within the RLC data block. The Length indicator shall indicate the number of octets of the RLC data field that belong to the current LLC frame. The final RLC data block of a TBF shall have a Length indicator field unless the final LLC frame fills the RLC data block precisely. The LI field is 6 bits in length and shall be encoded as a binary number with range 0 to 63. Figure 5.7 provides an example of the use of the Length indicator in conjunction with the M and E bits. In the example, LLC frame 1 continues from a previous RLC data block and ends in the RLC data block shown. LLC frame 2 follows LLC frame 1 and is completely contained within the RLC data block. LLC frame 3 follows LLC frame 2 and continues into the next RLC data block. bit PC T = 0 USF MAC header TFI S/P= 0 Octet 1 BSN E = 1 Octet 2 Length indicator = 11 M= 1 E = 1 Octet 3 (optional) LLC frame 1 Length indicator = 25 M = 0 E =0 Octet 4 (optional) LLC frame 1 LLC frame 2... LLC frame 3 Octet 5... Octet 15 Octet 16 Octet 17 Octet 41 Octet 42 Octet Octet N-1 Octet N Figure 5.7/GSM Length indicator (LI) example LLC frame 2 LLC frame TLLI field The TLLI field contains a TLLI encoded as the contents of the TLLI information element defined in GSM The TLLI field shall contain a valid local TLLI assigned to the MS in the local Routeing Area. If the MS does not have a valid local TLLI, the TLLI field shall contain a valid foreign TLLI assigned to the MS in another Routeing Area. If the MS does not have a valid local TLLI or a valid foreign TLLI, the TLLI field shall contain a random TLLI.

29 RLC data field The RLC data field contains octets from one or more LLC frames. The RLC data field may contain parts of one or two LLC frames and all of an arbitrary number of LLC frames. The E bit, the M bit, and the Length Indicator delimit the RLC data field into LLC frames. If the last LLC frame of the TBF does not fill the entire RLC data field, an extension octet shall be used to indicate the number of valid RLC data octets and the remainder of the RLC data field shall be filled with filler octets with the value Only the last RLC data block of the TBF may contain filler octets Control message contents field The Control message contents field shall contain one RLC/MAC control message. Only one RLC/MAC control message shall be transported per Control message contents field (i.e., RLC control block). If the RLC/MAC control message does not fill the RLC control block, filler octets with value shall be used to fill the remainder of the RLC control block. The receiver of the RLC/MAC control message determines the length of the RLC/MAC control message by interpreting the RLC/MAC control message.

30 30 6. Introduction to the Medium Access Control (MAC) procedures 6.1 General The Medium Access Control procedures include the functions related to the management of the common transmission resources, e.g. the physical channels and the radio link connections on packet data channels. The general purpose of the Medium Access Control procedures is to establish, maintain and terminate Temporary Block Flow (TBF) connections that allow a point-to-point transfer of signalling and user data in a cell from the network to a mobile station, or vice versa. A TBF is a physical connection used by the two peer entities to support the upper layers transfer of information on packet data channels. Moreover, the Medium Access Control procedures include the procedures for cell selection/reselection in packet mode. In particular, they include the reception of the BCCH and CCCH or PBCCH and PCCCH when no TBF is established, which permits automatic cell selection/reselection. 6.2 MAC multiplexing principles Uplink State Flag The Uplink State Flag (USF) is used on PDCH to allow uplink multiplexing of Radio blocks from different mobile stations (cf. TS GSM 05.02). In downlink blocks, the USF field carries the Uplink State Flag (USF) that is used to indicate the state of the corresponding uplink block, i.e. which mobile station may transmit within the next uplink RLC block period. It can acquire 8 different values (cf TS GSM 05.03). On PCCCH, one USF value is used to denote PRACH (USF=FREE). The other USF values USF=R1/R2/...R7 are used to reserve the uplink for different mobile stations. On PDCHs not carrying PCCCH, the eight USF values USF=R1/R2/.../R8 are used to reserve the uplink for different mobile stations. One USF value shall be broadcast even when the mobile station is using the uplink channel without having to monitor the uplink state flag. That in order to prevent collisions on uplink channel Temporary Flow Identity The method of implementing the selective ARQ protocol on the RLC level includes the assignment of a Temporary Flow Identity (TFI) to each Temporary Block Flow (TBF) transmitted to/from a mobile station. One TBF may comprise a number of LLC frames. The assigned TFI is unique among concurrent LLC frame transfer sequences on the same PDCH(s) and is used instead of the MS identity in the RLC/MAC layer. The same TFI may be used for two simultaneous TBFs, one in uplink and one in downlink. The TFI is assigned in a resource assignment message that precedes the transfer of LLC frames belonging to one TBF to/from the mobile station. The same TFI is included in every RLC header belonging to a particular TBF as well as in the control messages associated to the LLC frame transfer (e.g. acknowledgements) in order to address the peer RLC entities. The length of TFI is 7 bits which allows up to 128 simultaneous block flows (unique TFIs) in same direction on the same PDCH(s) Temporary Block Flow A Temporary Block Flow (TBF) provides a physical connection on one or more PDCH(s) and consists of a set of RLC data blocks (belonging to one or more LLC frames) transmitted sequentially within a single MAC channel assignment. A unique Temporary Flow Identity (TFI) is assigned by the network for each channel assignment, independently for uplink and downlink. All blocks belonging to the same flow will comprise the same TFI value. A TBF is temporary and exists only for the duration of the data transfer period (i.e. until all the RLC data blocks are correctly received or, in acknowledged mode, the transmitted data blocks are receipted by the other end).

31 31 The RLC control messages for associated signalling belonging to the TBF bear the same TFI. 6.3 Medium access modes The medium access modes defined in this TS constitutes an addition to the Radio Resource access modes, i.e. the idle mode, dedicated mode, and the group receive and group transmit modes defined in GSM Packet mode In packet mode, the RLC/MAC layer provides services for the transfer of LLC packet data PDUs on packet data channels. In packet mode, a mobile station can be in either of two substates: the packet wait state or the packet transfer state. The procedures in idle mode, dedicated mode, group receive and group transmit modes do not apply to a mobile station in packet mode, unless explicitly so stated in this TS Packet wait state In packet wait state, no TBF exist. The MAC procedures include (on the mobile station side) those for cell selection/reselection. The RLC/MAC entity indicates to the upper layers the unavailability of a BCCH/CCCH and of the cell change when decided by the RLC/MAC entity. Upper layers are advised of the BCCH or, alternatively, the PBCCH broadcast information when a new cell has been selected, or when a relevant part of this information changes. In packet wait state, upper layer can require the transfer of a PDU, which implicitly requires the establishment of a TBF Packet transfer state In packet transfer state, the TBF provides a physical point-to-point connection on one or more packet data channels for the transfer of packet data PDUs from the network to a mobile station, or vice versa. In packet transfer state, the RLC/MAC layer provides the following services (cf. clause 4): - transfer of packet data SDUs in acknowledged mode with a certain priority; - transfer of packet data SDUs in un-acknowledged mode with a certain priority; - automatic provision of TBF (establishment, maintaing and release); - automatic cell reselection and provision of TBF. - indication to upper layers of loss of the connection; Packet combined mode Only applicable for mobile stations supporting GPRS MS class A (cf. GSM 02.60). In packet combined mode, the services and functions provided by the RLC/MAC layer in packet mode are combined with the services and functions provided by the RR procedures in one of the access modes amongst dedicated mode, group receive mode and group transmit mode, as defined in GSM A TBF can be established and maintained in parallel with a RR connection or (if VBCS listening or VBS listening is supported) the listening to the downlink of a voice group call channel or a voice broadcast channel. Cell reselection in packet combined mode is co-ordinated and aligned with the cell reselection (handover) in dedicated mode, group receive mode or group transmit mode, as defined in GSM and in GSM

32 MAC procedures in packet wait state Mobile station side In packet wait state the mobile station listens either to the BCCH or in case when PCCCH is allocated in the cell to the PBCCH and to the paging sub-channel for the paging group the mobile station belongs to. The mobile station also measures the radio propagation for connection with other cells Selection of primary PCCCH When no PCCCH is allocated in a cell all GPRS mobile stations shall camp on CCCH as they normally do in Idle state. When the network indicates the existence of and the channel description for a PCCCH in the System Information TYPE 13 message on extended BCCH as specified in TS GSM 04.08, all GPRS mobile stations in Packet Wait state shall leave the CCCH and camp on the PCCCH. The first PCCCH allocated in a cell will be the primary PCCCH carrying the PBCCH. The mobile station shall then read all relevant system information from PBCCH Actions taken by the mobile station at release of primary PCCCH The network may on PBCCH indicate that the primary PCCCH shall be released. The network also indicates the absolute time (in frame number) for this configuration change. A mobile station shall then read the absolute time for that configuration change on PBCCH. Until that time occurs, the mobile station shall continue to supervise it s paging group on PPCH. When that time occurs, the mobile station shall again read the PBCCH and confirm that the configuration change is still valid. If still valid, the mobile station shall return to CCCH and there read the BCCH information for calculation of it s new paging sub channel as specified in TS GSM Allocation/Release of secondary PCCCH(s) The network may on PBCCH indicate that one or more secondary PCCCH(s) shall be allocated (or released). The network also indicates the absolute time (in frame number) for this configuration change. A mobile station shall then read the absolute time for that configuration change on PBCCH. When that time occurs, the mobile station shall read the PBCCH again and confirm that the configuration change is still valid. If still valid, the mobile station shall calculate it s new paging subchannel as specified in TS GSM Listening to broadcast channels When the decision to change cells is taken, the mobile station switches to the BCCH of the new cell. The broadcast information is then checked to verify the allowance to camp on this cell. A GPRS mobile station in Packet Wait state also checks if the cell is supporting GPRS and if a GPRS control channel is allocated. If GPRS is not supported or a PCCCH not allocated, the mobile station remains listening to BCCH (as defined in GSM 04.08). If the new cell has a PCCCH allocated the mobile station switches to that channel and reads all relevant GPRS specific information from PBCCH. The broadcast information is then evaluated and proper actions are taken. Similarly, physical contexts are updated (list of neighbouring cells frequencies, thresholds for some actions, etc. (cf. GSM 05.08)). As long as the PCCCH is provided in the cell, the mobile station camps on that channel. When all relevant GPRS System Information has been read once, the mobile station only needs to read the GPRS System Information TYPE 1 message which contains an Information Changed indication that relevant information has been changed in any other system information message on PBCCH or BCCH. The indication is a 2 bit counter for each broadcast channel which is stepped each time the system information is changed. If the mobile station discovers that the 'Information Changed indication has changed it's value the mobile station shall again read the corresponding broadcast channel (cf ). The GPRS specific broadcast information on BCCH is specified in GSM NOTE 1: The requirements on the mobile station to read the system information broadcast on PBCCH are specified in GSM

33 Discontinuous Reception (DRX) A mobile station can negotiate its own DRX parameters. The mobile station may choose to use DRX or not in packet wait state. If used, the mobile station is only required to monitor the PCH (if locked to CCCH) or the PPCH (if locked to PCCCH) blocks belonging to its own paging group. It can then also determine if non DRX mode shall be kept a certain time after leaving transfer state. A mobile station in non-drx mode is required to monitor every PCH block (if locked to CCCH) or PPCH block (if locked to PCCCH) which it has assigned to. GSM gives a detailed description of the DRX function Paging procedures A mobile station in packet wait state monitors the paging sub channels on either PCH ( see GSM 04.08) or PPCH. The paging sub channels are monitored according to the paging group the mobile station belongs to and the current DRX parameters. The paging group is calculated from information received on BCCH if the mobile station is locked to CCCH or from PBCCH if the mobile station is locked to PCCCH as specified in GSM and in GSM On either of PCH or PPCH the mobile station can receive paging requests for both RR connection establishment and for downlink packet transfer. The mobile station shall also support both extended paging and paging reorganisation when indicated either on PCH (if the mobile station is locked to CCCH) or on PPCH (if the mobile station is locked to PCCCH) (cf. clause 7.4 and TS GSM 04.08) Measurements Measurements are treated to assess the need of a cell change as specified in GSM Normally the mobile station takes the decision to change cell. Optionally and when a PCCCH is allocated in the cell, the network can request the mobile station to start sending measurement reports and only perform network controlled and ordered cell reselection.. For Power Control purposes the mobile station shall in wait state periodically measure the downlink Rx signal level and quality from its serving cell. The mobile station shall also measure the interference signal strength on certain channels which may be indicated on the BCCH and PBCCH. If no channels are indicated, the mobile station shall not perform these interference signal measurements ( see GSM 05.08) Network side System Information broadcasting In cells supporting GPRS, GPRS specific system information is broadcast. If a PCCCH is established in a cell, the required GPRS system information is broadcast on PBCCH. In that case the system information broadcast on BCCH indicates that a PBCCH is allocated and it s location. System information sent on BCCH is further specified in TS GSM GPRS SYSTEM INFORMATION TYPE 1 to 3 messages, and optionally TYPE 2bis, 2ter, 3bis, 4, 5 and 5bis and further types are regularly broadcast by the network on the PBCCH. Based on this information the mobile station is able to decide whether and how it may gain access to the system via the current cell. The GPRS System Information TYPE 1 message contains common parameters and control channel information for GPRS. In the TYPE 1 message it is also indicated with an Information Changed -flag when relevant information has been changed in other system information messages on either BCCH or PBCCH which requires that the mobile station updates this information. Consequently when a mobile station has read all the GPRS System Information messages once, only the TYPE 1 message needs to be read until a Information Changed is indicated. The BCCH information supervised through the BCCH_INF_CHANGED flag is: The RACH parameters CELL_BAR_ACCESS, CALL_REESTABLISHMENT_ALLOWED and EMERGENCY_ CALL_ALLOWED; The CCCH Control Channel description parameters ATTACH/DETACH_ALLOWEDand the T3212 Timer for Periodic Updating.