Data Detection for MIMO Broadcasting System with Decode-and-Forward Cooperation

We consider the data detection in a multiple-input multiple-output (MIMO) broadcasting system where the source simultaneously transmits multiple data streams to single-antenna receivers. To detect multiple data streams, conventional MIMO techniques require the receivers to have multiple receive antennas, the number of which is greater than or equal to the number of transmit antennas. However, user cooperation can be applied to combat this limitation. In this paper, we propose a user decode- and-forward (DF) cooperation scheme and the corresponding detection method. The transmission consists of two phases: source broadcasting and the user cooperation. During the user cooperation phase, a selected leader in the cooperation group collects the detections from the other users. The leader then obtains its final detection by using maximum likelihood (ML) criteria and broadcasts the results to all the other users in the cooperation group. Through simulations we show that the average symbol error performance of the proposed cooperation scheme are affected by several factors including the cooperation group size, the number of users activated for transmission and the length of the cooperation phase. With moderately large group size, the proposed system can potentially outperform the conventional system whose number of receive antennas are equal to the number of transmit antennas.