Physical layer design and performance analysis for cooperative communication in wireless multi-hop networks

Abstract

Cooperative communication is an approach considered in the recent wireless communication research to be employed in a distributive multi-hop network. In cooperative communication, a “virtual” antenna array is composed by the single-antenna radios in cooperation, thus the benefit of classic multi-antenna communication can be obtained. Different cooperative communication schemes have specific purposes: cooperative diversity (CD) or cooperative transmission (CT) is intended to improve the reliability or loss rate of data transmission over fading channels, and virtual multiple-input-multiple-output (MIMO) or distributed spatial multiplexing (DSM) are intended to improve the throughput of data transmission. This research is primarily concerned with physical layer signal processing and performance analysis of different cooperative communication schemes in wireless multi-hop networks. Some practical issues in cooperative communication are addressed by this dissertation. One is the coordination overhead for CD, which involves control packets or signaling to determine the transmission parameters of each node in CD. This overhead makes the efficiency of CD doubtful. A new CD approach combining random delay and phase dithering is proposed for single-carrier frequency domain equalization (SC-FDE), which eliminates the overhead and keeps the constant envelop character of the transmitted signal. The approach is proved to be very robust in different channel models. The other issue is the multiple carrier frequency offsets (CFOs) problem, which originates from the distributed manner of the transmission. Specifically, a computationally efficient equalization algorithm which can compensate large multiple CFOs is developed for the orthogonal frequency division multiplexing (OFDM) DSM. The approach can also be generalized for such problems in frequency domain equalization. While SC-FDE is widely used in wideband wireless and MIMO systems, and surely finds its space in cooperative communication, the diversity analysis for it is still controversial. We carry out the analysis for point-to-point SC-FDE linear equalizer, and the approach is ready to be extended to the multi-antenna scenario. For multi-hop virtual MIMO and DSM, we are concerned about the problem on how to model and analyze or evaluate the network. We are especially interested in the multi-hop DSM scheme with amplify-and-forward (AF) relaying for its simplicity and low overhead cost in application. The closed form expression is found for the joint distribution of the nonzero eigenvalues of the equivalent MIMO channel matrix of the multi-hop network.