network (micro cells/macro cells/routing area size) will have a significant impact on the CCCH load. Parameter Planning CHANNEL REQUEST IMMEDIATE ASSIGNMENT PACKET RESOURCE REQUEST (OPTIONAL) PACCH PACKET UPLINK ASSIGNMENT (OPTIONAL) PACCH Figure 2.34 Packet data transfer: uplink initiated Packet Paging Request Packet Paging Request CHANNEL REQUEST IMMEDIATE ASSIGNMENT DATA BLOCK (last) PDTCH PACKET UPLINK ACK/NACK PACCH PACKET CONTROL ACK PACCH LLC PDU Figure 2.35 Packet data transfer: downlink initiated Radio Network Planning and Optimisation Table 2.18 Resource requirement for an EGPRS event GPRS attach (no authentication) GPRS attach (authentication) GPRS detach (MO, or mobile originated) PDP (Packer Data Protocol) context activation (MO) Paging Cell update Routing area update SMS (MT, or mobile terminated) (with paging) SMS (MT) (without paging) SMS (MO) (with stats report) SMS (MO) (without stats report) Channel Combinations In the existing GSM infrastructure, timeslots 0 and 1 in the first carrier are usually needed for the use of all of the above-mentioned channels. Due to capacity constraints, there are two main configurations of these channels: combined channel structure; uncombined channel structure. Combined Configuration The combined configuration combines the Broadcast Control Channel (BCCH) with the Stand-alone Dedicated Control Channel (SDCCH). This configuration occupies only one timeslot and is usually used with cells having up to two carriers requiring limited signalling capacity. The 51-frame multiframe is shown in Figure 2.36 and indicates the location of the signalling channels for both the uplink and downlink Combined CCCH /SDCCH / 4 Multiframe Downlink 51 TDMA frames = 235 ms sbbbbccccf SCCCCCCCC fs tt fsttttttttfs SSSSSSSS Uplink CHANNELS f = FCCH b = BCCH RACCH S = SCH/SACCH C = CCCH t = SDCCH/4 Figure 2.36 Combined BCCH/SDCCH structure Parameter Planning BCCH/CCCH Multiframe Downlink 51 TDMA frames = 235 ms bbbbcccc scccccccc f scccccccc Uplink CHANNELS f =FCCH b = BCCH r = RACCH S = SC