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Layer 1 Cấu trúc Bảng 4.3 Nhóm luật Tập đoàn di động Tham số luật di động Thông số Scrambling Mã 0 1 2 3 4 5 6 7 mã luật luật luật luật luật luật 0 1 2 3 4 5 6 7 Mã Associated dài cơ bản Midamble Mã mPL0 mPL1 mPL2 mPL3mPL4 mPL5 mPL6 mPL7 | Layer 1 Structure 53 Table 4.3 Code Groups and Cell Parameters Code Group Cell Parameter Associated Codes Scrambling Code Long Basic Midamble Code Short Basic Midamble Code 0 Code 0 mPL0 mSL0 1 Code 1 mPL1 mSL1 Group 0 2 Code 2 mPL2 mSL2 3 Code 3 mPL3 mSL3 4 Code 4 mPL4 mSL4 Group 1 5 Code 5 mPL5 mSL5 6 Code 6 mPL6 mSL6 7 Code 7 mPL7 mSL7 UEs will use the PRACH P for UL communication with UTRAN when they do not have a dedicated channelization code assigned such as during initial access to UTRAN. This results in the possibility of collision i.e. multiple UEs using the same PRACH P at the same time . For this reason a set of admissible channelization codes on the PRACH P is specified from which the UE randomly selects a code. The random selection is used to minimize the possibility of collision. The midamble is determined through a fixed association between the midamble and the channelization code 7 . The available midambles for PRACH P are from the long midamble set using either all eight shifts or only the four odd shifts from k 1 to 8. Using odd-only shifts is intended for larger cells whereby using only half of the available midamble shifts allows for double-length channel responses. For larger cells the effective number of available midamble shifts can be doubled from four to eight by using a second basic midamble sequence which is a time inverted or reverse version of the original basic midamble sequence. Since Random Access is used for initial access to UTRAN the UE does not have tight time synchronization with the UTRAN. For this reason PRACH P uses Type-3 bursts which have the larger guard period of 192 chips. This reduces the probability of the PRACH P transmission spilling into an adjacent timeslot. Power Control is not used on the PRACH P channel. Each PRACH P can be split into N-subchannels with the i-th subchannel using the frames with i SFN mod N with possible values of N being 1 2 4 or 8. The purpose of the subchannels is to reduce probability of .
