Tham khảo tài liệu 'mcgraw hill - 2002 - w-cdma and cdma2000 for 3g mobile networks_7', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 212 Chapter 6 an entire cell. Its per-slot data structure is shown in Figure 6-12. Each slot is 2 560 chips long. The spreading factor used on this channel is 128 and a total of only 20 bits is transmitted per slot. However the transmitter is turned off for the first 256 chips so that the primary and secondary synchronization channels can be transmitted during that period. Eighteen bits of data are then transmitted during the remaining 2 304 chips. Because there are 15 slots in a 10 ms frame the effective rate on this channel is 27 kb s. The broadcast channel which is mapped by this physical channel uses a fixed predetermined transport format combination. Secondary Common Control Physical Channel SCCPCH This physical channel transmits the information contents of two transport channels the FACH and the PCH. Unlike the primary common control physical channel the secondary common control physical channel may be transmitted in a narrow lobe and may use any transport format combination as indicated by the TFCI field. The two transport channels may be mapped either to the same SCCPCH or to two different SCCPCHs. Synchronization Channel SCH This channel is used by mobile stations for cell search. There are two synchronization channels the primary and the secondary. The primary synchronization channel transmits a modulated code called the primary synchronization code with a length of 256 chips during the first 256-chip period of each slot of a 10-ms 15-slot radio frame refer to Figure 6-12 . The PCCPCH is transmitted during the remaining period of each slot. Every cell in a UTRAN uses the same primary synchronization code. Figure 6-12 The per-slot data structure for the PCCPCH Transmitter turned off on this channel during this period Data - 18 bits 256 Chips 1 - 2304 Chips Universal Mobile Telecommunications System UMTS 213 The secondary SCH is constructed by repeating a sequence of modulated codes of 256 chips and is transmitted in parallel with the primary SCH that is on
