city Timeslots are always allocated to the GPRS territory unless pre-empted by CSW traffic (Figure 2.31). Dedicated GPRS Capacity A number of TCHs can be dedicatedly reserved for GPRS use and are thereby removed for circuit switched traffic. Additional GPRS Capacity Additional timeslots, over and above the default territory, may be used by GPRS traffic if circuit switched traffic permits. Parameter Planning Circuit Switched TRX 1 CCCH TS TS TS TS TS TS TS Territory TRX 2 TS TS TSTSTSTSTSTS Packet Switched Territory Additional Default Dedicated Capacity Capacity Capacity Territory border moves based on Circuit Switched traffic load Figure 2.31 EGPRS territory Maximum GPRS Capacity This is the maximum number of timeslots in a given cell that can be used up for GPRS traffic. GPRS Traffic Preference This decides if GPRS traffic should be assigned to the BCCH carrier prior to other TCH carriers within the same cell. Territory Update Guard Time This determines a timer value, i.e. the guard time between two subsequent territory updates. Intracell Handover for a GPRS Territory Upgrade During the GPRS territory upgrade procedure, CSW calls in timeslots to be included in the territory are handed over to other available timeslots in the same cell (Figure 2.32). Signalling Capacity in the GPRS Network The negotiation between the terminal and the base station has to be considered in order to understand the extra load placed on the existing GSM signalling channels, unless separate channels for the GPRS are used. Figure 2.33 introduces this new set of logical GPRS radio interface channels. B = BCCH TSL BCCC CCC S = SDCCH TSL C = CSW call SCC C CC DefaultGPRScapacity 20% CCC C DedicatedGPRScapacity = 10% Free TSLsforCSW = 3 \CddDDD = GSM territory GPRS territory upgrade = GPRS territory Figure 2.32 EGPRS territory upgrade Radio Network Planning and Optimisation GPRS Air Interface Logical Channels Common Channels Dedicated Channels PCCCH Packet Common Control Broadcast Channels Channels DOWNLINK ONLY (can be combined with CCCH) P