A new upstream channel structure for asymmetric LMDS with CDMA

Abstract

We propose a method using coherent detection with a time division multiple pilot signal for each user in the reverse CDMA channel as the structure of reverse CDMA channel to apply CDMA to the upstream channel of bidirectional LMDS. By using coherent detection with a pilot signal in the reverse CDMA channel, the capacity can be improved when compared with noncoherent detection, but it is required to allocate a pilot signal for all users. Also, the interference is increased due to the need to continuously allocate the pilot signals. In this case the channel capacity is decreased. A method of pilot allocation is needed that reduce this interference and keep the synchronization effect using coherent detection. In the reverse link, where the pilot is allocated to each user at a different time and not overlapped is possible solution. This pilot is proposed, and its performance and capacity analyzed. The result is that the proposed method has a greater increased capacity compared with others.