4 Packet data logical channels

03.643GPPGeneral Packet Radio Service (GPRS)Overall description of the GPRS radio interfaceStage 2TS

NOTE: The text in this clause is informative. The normative text is in 3GPP TS 05.02 [11]. Where there is a conflict between these descriptions, the normative text has precedence.

4.1 General

This subclause describes the packet data logical channels that are supported by the radio subsystem. The packet data logical channels are mapped onto the physical channels that are dedicated to packet data.

The physical channel dedicated to packet data traffic is called a Packet Data Channel (PDCH).

4.2 Packet Common Control Channel (PCCCH) and Compact (CPCCCH)

PCCCH and CPCCCH comprises logical channels for common control signalling used for packet data as described in the following subclauses.

4.2.1 Packet Random Access Channel (PRACH) and Compact Packet Random Access Channel (CPRACH) – uplink only

PRACH and CPRACH are used by MS to initiate uplink transfer for sending data or signalling information. Packet Access burst and Extended Packet Access burst are used on PRACH. Extended Packet Access burst is used on CPRACH.

4.2.2 Packet Paging Channel (PPCH) and Compact Packet Paging Channel (CPPCH) – downlink only

PPCH and CPPCH are used to page an MS prior to downlink packet transfer. PPCH and CPPCH use paging groups in order to allow usage of DRX mode. PPCH can be used for paging of both circuit switched and packet data services. The paging for circuit switched services on PPCH is applicable for class A and B GPRS MSs in Network operation mode I, see 3GPP TS 03.60 [3].

4.2.3 Packet Access Grant Channel (PAGCH) and Compact Packet Access Grant Channel (CPAGCH) – downlink only

PAGCH and CPAGCH are used in the packet transfer establishment phase to send resource assignment to an MS prior to packet transfer.

4.2.4 Packet Notification Channel (PNCH) and Compact Packet Notification Channel (CPNCH) – downlink only

PNCH and CPNCH are used to send a PTM-M (Point To Multipoint – Multicast) notification to a group of MSs prior to a PTM-M packet transfer.

DRX mode shall be provided for monitoring PNCH and CPNCH. Furthermore, a “PTM-M new message" indicator may optionally be sent on all individual paging channels to inform MSs interested in PTM-M when they need to listen to PNCH and CPNCH.

The PTM-M service is not specified in GPRS Phase 1.

4.3 Packet Broadcast Control Channel (PBCCH) and Compact Packet Broadcast Control Channel (CPBCCH) – downlink only

PBCCH and CPBCCH broadcast packet data specific System Information. If PBCCH is not allocated, the packet data specific system information is broadcast on BCCH. For Compact, CPBCCH shall be allocated. CPBCCH and BCCH are mutually exclusive.

4.4 Packet Traffic Channels

4.4.1 Packet Data Traffic Channel (PDTCH)

PDTCH is a channel allocated for data transfer. It is temporarily dedicated to one MS or to a group of MSs in the PTM‑M case. In the multislot operation, one MS may use multiple PDTCHs in parallel for individual packet transfer.

All packet data traffic channels are uni-directional, either uplink (PDTCH/U), for a mobile originated packet transfer or downlink (PDTCH/D) for a mobile terminated packet transfer.

4.5 Packet Dedicated Control Channels

4.5.1 Packet Associated Control Channel (PACCH)

PACCH conveys signalling information related to a given MS. The signalling information includes e.g. acknowledgements and power control information. PACCH carries also resource assignment and reassignment messages, comprising the assignment of a capacity for PDTCH(s) and for further occurrences of PACCH. The PACCH shares resources with PDTCHs, that are currently assigned to one MS. Additionally, an MS that is currently involved in packet transfer, can be paged for circuit switched services on PACCH.

4.5.2 Packet Timing advance Control Channel, uplink (PTCCH/U)

PTCCH/U is used to transmit random access burst to allow estimation of the timing advance for one MS in packet transfer mode.

PTCCH/U shall not be used for DTM.

4.5.3 Packet Timing advance Control Channel, downlink (PTCCH/D)

PTCCH/D is used to transmit timing advance information updates to several MS. One PTCCH/D is paired with several PTCCH/U’s.

PTCCH/D shall be ignored by MS operating in DTM.