Research On The Application Of Precoding Technology In Cooperative Multi-point Transmission

As a potential future technology, cooperative multi-point transmission could improve the spectral efficiency, the coverage and the efficiency of handoff for users effectively. The paper mainly studied the precoding and related technologies for the uplink of cooperative multi-point transmission. According to the differences in complexity, the precoders are mainly classified into linear precoders and non-linear precoders. Linear precoders are realized relatively simply and rely on the channel information. The paper studied zero-forcing precoders and adaptive forward algorithm on relay nodes for the uplink of cooperative multi-point transmission in detail.There are three aspects of innovations in the paper:Firstly, the precoding technology is introduced into cooperative transmission with differential detection to combat performance degradation brought by differential detection. Monte Carlo simulation is conducted on the differential precoding transmission link of cooperative transmission, simulation results indicated that there is 3dB degradation in performance for differential reception. However, zero-forcing precoders will improve the performance of differential detection evidently. As accurate channel state information is unavailable in fast faded channels, the complexity of mobile terminals and the state of channels are both vital to the selection of transmission schemes.Secondly, the channel state based partial channel precoding is proposed to improve the performance of cooperative transmission. The performance of zero-forcing precoders is effectively improved by the proposed algorithm, which makes the simple and excellent linear precoders more available in practical application. In order to restrain the transmitting power in the procedure of zero-forcing precoding on the uplink, the transmitting power is usually normalized and the normalized factors of undesirable channels are huge. The proposed partial channel precoding algorithm selects the precoding channels adaptively, thus the performance of zero-forcing precoding is improved. Simulation results testify the performance of the proposed algorithm under amplify-forward and decode-forward transmission, and there is 0.8dB performance gain.Lastly, the adaptive forward algorithm is studied in detail, the proposed algorithm will decrease the performance loss brought by the single forward algorithm on all relay nodes. The reliability of amplify-forward and decode-forward algorithm is concluded for the uplink of multi-user cooperation. Simulation results indicated that the proposed adaptive forward algorithm acquired distinct improvement in cooperative communication, which means that it will be valuable to be applied in realistic communications.