channel cod- ing and interleaving onto four radio frames (called radio blocks because they carry logical radio blocks). 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 Radio and MS-PCUSN Interfaces The mapping in time of the packet logical channels carried by the same PDCH is defined by a multiframe structure. The multiframe structure for PDCH consists of a cycle of 52 successive TDMA frames, divided into 12 blocks (of four frames each), and 4 idle frames. The multiplexing of the packet channels on a PDCH is not fixed like in the GSM system. It is man- aged by some parameters and the following block order: B0, B6, B3, B9, B1, B7, B4, B10, B2, B8, B5, and B11. For example, if the cell has four PBCCH blocks, those will be carried by the blocks B0, B6, B3, and B9 (on the same time slots indicated in SI 13 on BCCH). The idle frames are used by the mobile station for signal measurements and Base Station Identity Code (BSIC) decoding on the SCH of neighboring cells (idle 2 and 4) or for TA update (sending an access burst on PTCCH uplink in idle 1 or 3 and receiving an RLC/MAC control block on PTCCH DL in idle 1 and 3 of two successive multiframes, which equals four frames in total). The multiframe for PDCH consists of 52 TDMA frames, divided into 12 blocks of 4 frames (radio blocks) and 4 idle frames. This multiframe, shown in Figure 6-6, can be seen as two 26-frame multiframes on the GSM net- work, numbered from 0 to 51. The multiframe has a duration of 240 ms and 25.5 multiframes are counted as a superframe. Figure 6-6 Cycle of 52 TDMA frames divided in: The 52 multiframes Twelve radio blocks B0-B11 (of 4 consecutive frames) in GPRS. Four idle frames (X) TDMA Frame GPRS Time Slot (PDCH) 4.615 ms Idle Frames 012345670123456701234567 01234567891011121314 Frame Block Radio Blocks Downloaded from Digital Engineering Lib