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Đó là dựa trên nguyên tắc đạt được liên tục chế biến với một số lượng lớn multicodes trong sử dụng, do đó hiển thị một số khác biệt cơ bản, nhưng cũng có một mức độ phổ biến, với công nghệ WCDMA trong các diễn đàn khác. | Physical Layer 115 Figure 6.11. Uplink dedicated channel structure The uplink DPCCH uses a slot structure with 15 slots over the 10 ms radio frame. This results in a slot duration of 2560 chips or about 666 ms. This is actually rather close to the GSM burst duration of 577 ms. Each slot has four fields to be used for pilot bits TFCI Transmission Power Control TPC bits and Feedback Information FBI bits. The pilot bits are used for the channel estimation in the receiver and the TPC bits carry the power control commands for the downlink power control. The FBI bits are used when closed loop transmission diversity is used in the downlink. The use of FBI bits is covered in the physical layer procedures section. There exist a total of six slot structures for uplink DPCCH. The different options are 0 1 or 2 bits for FBI bits and these same alternatives with and without TFCI bits. The TPC and pilot bits are always present and their number varies in such a way that the DPCCH slot is always fully used. It is beneficial to transmit with a single DPDCH for as long as possible for reasons of terminal amplifier efficiency because multicode transmission increases the peak-to-average ratio of the transmission which reduces the efficiency of the terminal power amplifier. The maximum user data rate on a single code is derived from the maximum channel bit rate which is 960 kbps with spreading factor 4. With channel coding the practical maximum user data rate for the single code case is in the order of 400-500 kbps. When higher data rates are needed parallel code channels are used. This allows up to six parallel codes to be used as explained in Section 6.3.3.2 raising the channel bit rate for data transmission up to 5740 kbps which can accommodate 2 Mbps user data or an even higher data rate if the coding rate is 2. Therefore it is possible to offer a user data rate of 2 Mbps even after retransmission. The achievable data rates with different spreading factors are presented in Table .
