ranet OMC-R Gateway <<<<<<<< iii uni Dynamic Host Configuration Protocol (DHCP) To provide automatic addressing and readdressing for mobile hosts TDMA-GPRS Physical Channel Capacity The Time Division Multiple Access (TDMA) frame structure for GPRS is the same as for GSM and is shown in Figure 3-10. The sequence of all time slots in a particular position of each TDMA frame is defined to be a physical channel. A physical channel that has been allocated to GPRS service is called a Packet Data Channel (PDCH). As we shall see later, various combi- nations of the logical channels can be mapped onto a single physical chan- nel. Physical channels can also be grouped to provide higher data transmission rates. GPRS provides for flexible allocation of physical channels to GPRS ser- vice. The GPRS traffic load in a given cell varies as a function of time. The network has the option of dynamically changing the number of physical channels allocated to GPRS depending on the demand. 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. System Architecture Chapter 3 TDMA Frame Figure 3-10 The physical channels. Slot 8 Slot 1 Slot 2 Slot 3 Slot 4 Slot 5 Slot 6 Slot 7 Slot 8 Slot 1 Slot 8 Slot 1 Slot 2 Slot 3 Slot 4 Slot 5 Slot 6 Slot 7 Slot 8 Slot 1 = Other Physical Channel = Packet Data Channel GPRS Logical Channels In GSM terms, a logical channel refers to a flow of information between entities for a particular purpose. Logical channels are carried within the physical channels (such as PDCHs). The following logical channels are defined and shown in Figure 3-11 for GPRS: Packet Broadcast Control Channel (PBCCH) Packet Broadcast Control Channel (PBCCH) is a downlink function used for broadcast of system information to the mobile stations in a cell. If the PBCCH is not used in a cell, then regular Broadcast Control Channel (BCCH) may be used to send packet data-spec