Research On Relay Selection Based On Channel State Information Prediction

Cooperative relay technique is an important wireless communication technology, which can bring spatial diversity and improve spectrum efficiency, link reliability, as well as the flexibility of network configuration, etc. with great potential for application. Relay selection can affect the performance of cooperative communication system directly, which makes relay selection attract a wide spread attention. General cooperative relay selections often use outdated channel state information (CSI) which results from the delay during the process of relay selection and data transmission as the main basis of relay selection. Hence, the relay selection based on outdated CSI may not have ideal system performance. In this paper, we would like to provide precise CSI for relay selection by channel prediction, therefore, the research on relay selection based on channel prediction was carried out, the specific contribution as follows:(1) A channel state information prediction based on slope prediction and a relay selection were put forward. The channel prediction cuts the prediction range into several small enough time slice, and implements continuous prediction on the slope of channel first-order linear function with FIR Wiener prediction within these small segments of time. At the same time, the performance analysis of the relay selection method based on that channel prediction was carried out. The numerical results show that in the comparison experiments with the relay selection based on outdated channel state information, the proposed scheme can make the system Bits Error Ratio (BER) decline effectively.(2) To achieve the balance between predicting complexity and precision, a relay selection with low complexity was raised, in which predicted signal-to-noise ratio (SNR) can be obtained by adding the random number that follows a specific statistical distribution to the measured SNR, and the predicted SNR would be used for relay selection. Further performance analysis of the relay selection was made to achieve the expressions of outage probability and average bit error rate (ABER) of the system. The numerical results show that, the performances of outage and ABER of the proposed method are both superior to those of the relay selection based on minimum mean square error (MMSE) prediction. Besides, the complexity of the former is much lower than that of the latter. Particularly, the proposed algorithm can reduce the ABER and outage probability of the system in high correlated channel scenarios, respectively.(3) By extending the research from single user scenarios to multi-user scenarios, and taking the interference in multi-user communication into account, a multi-user relay selection based on predicted signal to interference plus noise ratio (SINR) was proposed. The proposed scheme produces a random number following a specific statistical distribution firstly, and then generates the predicted SINR by combining this random number with the measured SINR, through which relay selection is made. Meanwhile, the average bit error rate (BER) and the outage probability of the proposed scheme in multi-user cooperative communication system are analyzed. The numerical results show that, the above performance of the proposed scheme overmatches that of the multi-user relay selection based on outdated SINR, the effectiveness of the proposed scheme was validated accordingly.