LC Data Unit Spare RLC Data Block Payload Downlink RLC/MAC Block MAC Header Control Header RLC/MAC Signaling Information RLC/MAC Control Block Table 6-1 Uplink state flag is used to indicate which mobile station is allocated the GPRS resource. Radio Link Control (RLC) Layer Supplementary/Polling bit is used to indicate whether the RRBP field is active. Relative Reserved Block Period is used to specify that a single uplink block is being used as a Packet Associated Control Channel (PACCH). Payload type Payload type defines the type of information in the payload area: either data or signaling information. Stall Indicator is used to signal whether the transmission has stalled. Countdown This is sent by the mobile station (on the uplink) to the network so value that the network can calculate the number of radio blocks remaining in the current uplink allocation of resources. Retry bit indicates whether the mobile station was transmitted on the channel. 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 Radio Link Control (RLC) Layer The RLC layer is primarily responsible for segmenting and reassembling data sent over the air interface. The frames used in the LLC layer are much too big to send over the air. Thus, the RLC layer segments or breaks the LLC frame into blocks, and encapsulates each block forming an RLC block. A BSN designates each RLC block. The BSN is contained in a field of the block header. Upon receipt of an RLC block, the RLC layer reverses the action required to send the data. First, the BSN is used to arrange the RLC block in sequential order. Then the header is stripped off the block and the blocks are reassembled into LLC frames. This layer supports two modes of operation: acknowledged and unac- knowledged. The acknowledged mode enables selective retransmission. In this mode, the BSN is als