lues are possi- ble. Consequently, the TAI limitation is at most 16 mobile stations/time slots. Based on the USF limitation and future improvements (dynamic UL allocation), some manufacturers have split this limitation into a maximum of eight mobile stations on the uplink and eight mobile stations on the downlink using the same PDCH. 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 Uplink State Flag The USF gives successive UL access on a given PDCH to different mobile stations that have been allocated this same time slot (PDCH), when dynamic allocation is used for UL channel assignment. DL channel assign- ment has no specific limitation except the nonoverlapping between the DL bitmaps of different mobile stations communicating on the same PDCH (this bitmap remaining in the PCU). The USF is coded on 3 bits, SO 8 (23) different USF values are possible. Consequently, if dynamic allocation is used for UL network access, the USF limitation is eight mobile stations per time slot on the UL. RLC/MAC Block Network Layer Protocol Data Units (NL-PDU) are transmitted over the air interface by using the Logical Link Control (LLC) and the RLC/MAC pro- tocols. The Subnetwork-Dependent Convergence Protocol (SNDPC) trans- forms packets into LLC frames. LLC frames (currently variable up to a maximum of 1,600 octets) are then segmented into RLC data blocks (or RLC/MAC control blocks), which are formatted by the physical layer into blocks of four successive time slots on the same physical channel (one per frame), as shown in Figure 6-24. The rate of RLC/MAC data blocks is one block every 20 ms. Blocks (RLC/MAC PDU) RLC/MAC Block Figure 6-24 The RLC/MAC blocks. Info Field Info Field Info Field RLC/MAC Layer Normal Burst Normal Burst Normal Burst Normal Burst Physical Layer BCS = Block Check Sequence BH = Block Header D