inning of a number of well-defined time-intervals, relative to the frame boundary of the received BCH of the current cell. The access slot timing and structure are identical to those defined for the RACH. Figure 4.8 illustrates the structure of the CPCH access transmission. The PCPCH access transmission consists of one or several Access Pream- bles [A-P] of length 4096 chips, one Collision Detection Preamble (CD-P) of length 4096 chips, a DPCCH Power Control Preamble (PC-P) which is either 0 slots or 8 slots in length, and a message of variable length Nx10 ms. Message Part 4096 chips 0 or 8 slots N* 10 msec Access Preamble Control Part Collision Detection Data part Preamble Figure 4.8 Structure of the CPCH access transmission. 4.3.3.2.1 CPCH Access -Power Control and Detection Preamble Parts Like in the RACH, the access CPCH preamble uses signature sequences, but the number of sequences can be lower. The scrambling codes may differ from the gold codes segment used in the RACH or could be the same scrambling code. Table 4.12 defines the DPCCH fields form the CPCH PC-P part. The power control preamble length parameter takes the values 0 or 8 slots, as set by the higher layers. When the power control preamble length is set to 8 slots, pilot bit patterns from slot #0 to slot #7 defined in Table 4.8 shall be used for CPCH PC-P. Table 4.12 DPCCH Fields for CPCH Power Control Preamble Segment Chan- Channel Bits/ Bits/ Npilot NTFCI format nel bit symb. rate (ksps) (kbps) The UMTS Network and Radio Access Technology Also like in the RACH, the detection CPCH preamble uses signature sequences. However, the scrambling code set differs from the gold code segment used to form the RACH scrambling code. 4.3.3.2.2 CPCH Message Part With similar message part structure of the RASH, each CPCH message part consists of up to N_Max_frames¹ 10 ms frames, with a 10 ms frame split into 15 slots, each having Tslot = 2560 chips length. In addition, every slot consists of a data part that carries higher layer information and a control part t