aging access. (MS in standby) Paging PPCH (or PCH) Packet STANDBY Packet Channel Request PRACH (or RACH) Assignment Immediate PAGCH (or AGCH) Packet PDTCH Starts here Paging Response Frame) if MS is in READY ready state (TLLI) PAGCH (or AGCH) PDTCH starting TFI differentiates 2 ARFCN, MS Receiving blocks on the same PDCH Packet control acknowledgement PDTCH The network initiates transmission of a packet to a mobile station in the ready state by using the Packet Downlink Assignment message on PAGCH (or AGCH). This message includes the list of PDCHs that will be used for a downloading transfer; if available, timing advance and power control infor- mation are also included. The network sends the radio blocks belonging to one Temporary Block Flow on the assigned downlink channels, as shown in Figure 6-22. Timing Advance Updating Procedure The timing advance procedure is necessary because a proper value for tim- ing advance has to be used for the uplink transmission (radio data or con- trol blocks). Figure 6-23 provides a representation of the timing advance procedure. The mobile station's initial timing advance is calculated on the access burst the same as GSM. The estimated timing advance value is passed to the mobile station via the Packet Immediate Assignment mes- sage. The mobile station uses the value until continuous timing advance provides a new value. 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 Figure 6-22 BSC PCUSN Downlink data Network transfer. Network Data Block PDTCH Data Block PDTCH Data Block PDTCH Data Block PDTCH Temporary Packet Ack/Nack PACCH Data Block PDTCH Data Block PDTCH Data Block PDTCH Packet Resource Reassignment PACCH Packet Resource Reassignment Ack PACCH Data Block PDTCH Data Block (last, polling) PDTCH Final Packet Ack/Nack PACCH Figure 6-23 TA update 