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| This paper presents an analytical study on the outage performance of amplify-and-forward (AF) two-way relay system with multi-antenna relay node (RN).Two major bidirectional protocols, i.e., two time slots multiple access broadcast (MABC) protocol and three time slots time division broadcast (TDBC) protocol, are considered respectively. For both considerations, we first assume that instantaneous channel-state-information (CSI) is unavailable at RN, thus RN just simply uses the fixed relay gain derived from statistical CSI to scalethe received signals before forwarding.We then consider the scenario where RN can obtainthe instantaneous CSI to perform the zero-forcing (ZF) relayprecoding. The closed-form expressions ofoutage probability are derived for all cases.Based on these expressions,the diversity-multiplexing tradeoff (DMT) is further obtained for the MABC protocol.The analytical results show that, for non-precoding MABC scheme, the diversity order of 1 can only be obtainedand it is irrelevant to the relay antenna number M. While for theZF-precoding case, the diversity order of M-1 can be obtained. |
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| Keywords:Communications and information system, two-way relaying, physical layer network coding, precoding, outage probability. |
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