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In this paper, we investigate a cooperative system consisting of one source-destination pair equipped with single antenna and L relays equipped with M antennas as wireless access points. We propose a new relay selection scheme for this system based on partial relay selection, where the best relay is selected according to the instantaneous and one-hop channel state information (CSI). We use maximal ratio combining (MRC) and maximal ratio transmitting (MRT) at relays to obtain the maximal achievable received signal-to-noise ratio (SNR). Close-form expressions for the outage probability and symbol error rate (SER) are derived. High SNR analysis is tightly approximated to explicitly characterize the diversity order and array gain. Monte Carlo simulations verify our analytical results. Results show that the diversity order increases with the antenna numbers at the selected relay according to M. For partial relay selection, two available relays are enough to get the array gain, and impacts of relay locations are also discussed in this paper.