<p>Before starting a stream transmission, a server device (100) acquires a number of antenna combinations from a client device (200) and decides a training time t1 according to a maximum number of antenna combinations. The training time t1 is reported to client devices (200). Each of the client devices (200) decides a training time t2 required for estimating a transmission path state for each of the antenna combinations according to the training time t1. The server device (100) transmits a training signal for the training time t1. Each of the client devices (200) estimates a transmission path state for the training time t2 for each of antenna combinations by using the training signal and selects and sets an antenna combination according to the estimated transmission path state.</p>
