VLs). The BSSGP also provides radio-related QoS and routing information to facilitate data transfer between the BSS and the SGSN. BSSGP uses a BSSGP Virtual Connection Identifier (BVCI) for informa- tion transfer between the SGSN and the BSS. The connection over the Gb, interface is called a BSSGP Virtual Connection (BVC). The BVC is made up of the BVCI and the Network Service Entity Identifier (NSEI). In the BSS, Figure 6-30 The BSSGP layer in Application relation to the other IP/X.25 layers. IP/X.25 Relay SNDCP SNDCP UDP/TCP Relay BSSGP BSSGP GSM RF GSM RF L1bis L1bis 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 Figure 6-31 The BSSGP provisioning of BVCI. Signaling Function BVCI 2 BVC 1 NS-VC PTP/PTM Functional Entities BVCI 1 Cell 1 Cell 2 BVC=BVCI+NSEI a BVCI is allocated for each cell that supports GPRS. For each new cell introduced in the BSS area, a new BVCI context is allocated. In the SGSN, the BVCI context consists of at least one queue for LLC-PDUs. In a BSS, a BVC is connected to a cell or to a functional entity such as a signaling entity. A signaling functional entity is used for the functions like paging. One or more signaling entities exist per BSS. The BVCs are stati- cally provisioned. Figure 6-31 shows the BSSGP with the provisioning of multiple BVCIs. Channel Coding Channel coding in basic GSM operation is performed using two codes: a block code and a convolutional code. The block code corresponds to the block code defined in the GSM Recommendations 05.03. The block code receives an input block of 240 bits and adds four zero tail bits at the end of the input block. The output of the block code is consequently a block of 244 bits. A convolutional code adds redundancy bits in order to protect the information. A convolutional encoder contains memory. This property Downloaded from Dig