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Midamble thực tế (đào tạo trình tự) m có nguồn gốc bằng cách định kỳ mở rộng vector Mã Midamble phức tạp của P chiều dài L chiều dài thích hợp (512 hoặc 256), xem Hình 3.5. Các midambles m (k) k = 1,. . . , K có thể được tạo ra bằng cách áp dụng thay đổi phần mở rộng định kỳ của MP Mã Midamble phức tạp. Kế hoạch này được minh họa trong hình 3.6. | 24 Fundamentals of TDD-WCDMA 1st part of TFCI 2nd part of TFCI Data symbols Midamble Data symbols GP 512 256 chips 2560 Tc 1st part of TFCI 2nd part of TFCI Data symbols Midamble Data symbols GP 512 256 chips TPC 2560 Tc Figure 3.4 Location of TPC and TFCI Signaling Bits Top Downlink Burst Bottom Uplink Burst where mi is -1. Define Complex Midamble Code vector corresponding to QPSK modulation as mP m- m . mP 3.2 where mi j i mi for i 1 . P 3.3 The actual midamble training sequence m is derived by periodically extending the Complex Midamble Code vector of length P to the appropriate length L 512 or 256 see Figure 3.5. Additional midambles m k k 1 . K may be generated by applying shifts to the periodic extension of the Complex Midamble Code mP. The scheme is illustrated in Figure 3.6. The first Kz midambles are generated by shifts of multiples of W chips whereas the second Kz midambles use an additional constant shift of S P K rounded to the lower integer. The midambles generated as above may be used when a timeslot carries more than one user. They may also be used in contention-based common access radio channels i.e. the Random Access Channel which will be introduced in Chapter 4 . The Network may allocate midambles to UEs in three different ways 1 UE specific midamble allocation 2 common midamble allocation and 3 Default midamble allocation based on a fixed relationship to the channelization code . mP m1 m2.mP part of mP mi m2.mL-p Figure 3.5 Midamble Generation by Periodic Extension of Complex Midamble Code TDMA Aspects 25 Figure 3.6 Generation of Multiple K 2K Midambles 3.2.3 Synchronization Bursts Although the standards do not classify synchronization bursts it is convenient here to describe radio bursts used for providing initial chip level and timeslot level synchronization to the UE see 4 Section 7 . There are two types of synchronization bursts called Primary Synchronization Burst and Secondary Synchronization Burst each of which is of 256 chips duration. .
