A distributed antenna system (DAS) is very attractive, since it can reduce transmit power by shortening the distance between antenna elements (AEs) and the mobile station. This paper investigates the channel capacity of the DAS over a multi-path frequency-selective fading channel. We first show that the optimal power allocation solution to approaching the channel capacity is unrealistic for the practical DAS. Then, a near-optimal scheme is given through maximally tightening the upper bound of the channel capacity. Approximate analytical results are obtained through the use of the central-limit theorem. Both simulation and theoretical results are presented to show that the channel capacity can be greatly enhanced by the proposed power allocation schemes. Moreover, the bit error rate performance is analyzed for the proposed scheme.

The physical-layer network coding (PNC) becomes a popular research topic, and the multiuser PNC network is still an open issue. This paper investigates the uniquely-decodable codes (UDC) by using Iterative construction algorithm, and applies the generated UDC to the multiuser PNC network that based on amplify-and- forward (AF) criterion. Due to the attractive features of UDC, the sum data rate can increase with the number of users log-linearly. Moreover, only two time slots are needed for any user node to obtain the data sequences transmitted by an arbitrary user, no matter of the users' number. It is also illustrated that the theoretical bit error rate (BER) of the proposed scheme, which can compare with the traditional PNC scheme in both simulated and theoretical results.