Channel Estimation And Joint Detection Of TD-HSPA+ System

Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) proposed by China is one of 3G communication standards which is based on Time Division Duplexing (TDD) mode. TD-SCDMA adopts many advanced techniques, such as uplink synchronous CDMA, Smart Antenna, Joint Detection, Software Defined Radio, Baton Handover, Dynamic Channel Allocation and so on. TDD mode doesn't need symmetric spectrum, and the advantage of TD-SCDMA, the high spectrum efficiency, becomes more and more important as the spectrum resource becomes rarer. Meanwhile, the radio resource can be allocated between the uplink and the downlink with high flexibility, which is more suitable for the asymmetric traffics. As TD-SCDMA standard is widely accepted, most of the operators and the manufactories are making great efforts to research about it, which stimulates the development and evolution of TD-SCDMA including the TD-SCDMA phase, the Time Division-High Speed Packet Access (TD-HSPA) phase, the Time Division-High Speed Packet Access plus (TD-HSPA+) phase, and the Time Division-Long Term Evolution (TD-LTE) phase, followed by the B3G/4G phase. TD-HSPA phase imports High Speed Downlink Packet Access (HSDPA) and High Speed uplink Packet Access (HSUPA) and also take into account of the compatibility with other wireless wideband access techniques. TD-HSPA+ is the evolution of TD-HSPA., which wants to achieve higher system capacity and better QoS guarantee. The main innovation of TD-HSPA+ system is the adoption of Multiple Input Multiple Output (MIMO), which enhances the stability and speed of the communication system through the spatial diversity and multiplexing.The Channel Estimation is the premise of the reception of the signal. TD systems insert Midamble codes into every slot and the receiver gets the channel response through the known Midamble codes. The popular channel estimation algorithm is based on Steiner algorithm, which simplifies the procedure of getting the channel by using Fast Fourier Transform. But it can't eliminate the inter-cell interference.Joint Detection is one of key techniques of TD systems, which can reduce the Multiple Access Interference (MAI), Co-Channel Interference (CCI) and get the multiple code signals which are sent simultaneous at the same time. Minimum Mean Squared Error (MMSE) is widely used, and Zero-Forcing (ZF) and Match-Filtering (MF) are usually used as comparisons. However, most researches are based on one cell scenario. There are only few researches about multi-cell scenario.This paper analyzes the transmit model of the TD-HSPA+ system and the classic channel estimation and joint detection algorithms, and make a big improvement to the existing algorithms. It also considers the scenario which adopts MIMO in the TD-HSPA+system, presents some simulation results about the channel estimation and joint detection algorithms with different antenna configurations and working modes, and analyzes the performances of the channel estimation and joint detection in the TD-HSPA+system. The main innovations and contributions of this paper are:a) it improves the existing channel estimation algorithm by theoretical deduction and also reduces the effect of the noise to the accuracy of the channel estimation by post-processing the channel estimation results. b) it improves the existing joint detection algorithm and adds the procedure of selecting high interference users.