ots between GSM and GPRS. TDMA 1 TDMA 2 TDMA 3 TDMA 4 Combined GSM/GPRS TS Configuration TCH/PDTCH GPRS TS (PDCH: packet switched) Possible configurations: PDTCH PCCCH/PDTCH PBCCH/PCCCH PBCCH/PCCCH/PDTCH Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Radio and MS-PCUSN Interfaces Chapter 6 The capacity-on-demand principle means that PDCHs do not need to be permanently allocated to support GPRS and the network allocates avail- able channels as required. Common control signaling required by GPRS in the initial phase of packet transfer is conveyed on the PCCH, when allo- cated to the network, or on the CCCH using GSM specifications. This saves on specific GPRS capacity for the Public Land Mobile Network (PLMN) operator. If the last available PCCH is allocated, then the mobile stations will perform a cell reselection. At least one PDCH, acting as the master channel, carries the PCCH as well as the PDTCH and PACCH. Other PDCHs, acting as slave channels, are used for data transfer and dedicated signaling. The possible configura- tions for the packet-switched channels (PDCHs) are PDTCH PCCCH + PDTCH PBCCH + PCCCH PBCCH + PCCCH + PDTCH These configurations will result in different packet channel multiplexing on the same PDCH. The fast release of the PDCH is an important feature that enables the dynamic sharing of the physical radio resources (RRs) between packet- and circuit-switched services. To enable this, three PDCH release options are available: Wait for assignments to terminate on that PDCH. Individually notify all users who have assignments on that PDCH. Broadcast the notification about deallocation. Packet Logical Channels- Multiframe Structure The packet channels carry either RLC data blocks or RLC/MAC control blocks (except PRACH and PTCCH UL, which use an access burst instead of normal bursts). Each of these radio blocks is mapped after 