Energy-efficient Transmission Technology And Performance Analysis In Wireless Cooperative Multicast Systems

Wireless multicast/broadcast is a point to multipoint service which sends the same data from a single source to multiple destinations, thereby enabling the sharing of network resources and improving the utilization of radio resources. With the widespread deployment of wireless networks, rapid performance improvement of devices, and rapid growth of wireless subscribers, wireless multicast/broadcast service has become one of the hot spots in wireless networks. In particular, with the development of wireless cooperative communication, transmission efficiency of wireless multicast network is further promoted, e.g., extending the life of the wireless sensor network under the same power.This dissertation investigates energy-efficient transmission technology in wireless cooperative multicast systems, including the performance analysis of hybrid multicast and opportunistic unicast transmission with decord-and-forward (DF) and amplify-and-forward (AF) relaying, energy-efficient cooperative broadcast transmission, and randomized distributed space-time-code (RDSTC) based cooperative broadcast transmission. The main contributions of this dissertation are described as follows:(1) In the context of Rayleigh fading channel, depending on the model of wireless cooperative multicast, and jointly considering the direct link and relay link, the received signal-to-noise ratio (SNR) distributions of the selected user in the multicast and opportunistic unicast transmission with DF and AF relaying are derived, and thus their performances in terms of ergadic capacity and outage probability can be analyzed and evaluated using the SNR ditributions.Specifically, a hybrid multicast and opportunistic unicast transmission scheme is proposed in wireless cellular network and its performance over Rayleigh fading channel is analyzed and evaluated, and some distribution functions are derived such as the SNR distributions for the selected user in the multicast and unicast transmission.(2) An energy-efficient cooperative broadcast transmission mechanism based on multilevel virtual MIMO is proposed so as to meet the demand of low energy consumption in clustered wireless sensor networks.In this mechanism, multilevel cooperative broadcast technologies based on virtual MISO are discussed in clustered wireless sensor networks, one of which we focus on is power allocation so as to improve the energy efficiency of the whole network. In view of the Cumulative Increment Algorithm (CIA), we present the modified centralized algorithm (MCA) and the modified distributed algorithm (MDA) in order to minimize the total transmission power by the iteration and accumulation of signal energy at each node. Specifically, in MCA more than one VMISO transmission is realized by power allocation at each iteration with knowledge of the whole channel state information (CSI). Also, MDA is introduced with knowledge of intra-cluster CSI so as to facilitate implementation. There performance analyses show that energy-efficient cooperative broadcast is realized in MCA and MDA.(3) For the purpose of reducing energy consumption and signaling overhead, a cooperative broadcast transmission mechanism is studied based on counter and randomized distributed space-time code (RDSTC).In this mechanism, energy consumption is significantly reduced by the introduction of the counter to limit the number of rebroadcast and the randomized distributed space-time code (RDSTC) to reduce signaling overhead. There are two distributed algorithms:A-DSTC and A-RDSTC, where A-DSTC refers to the algorithm with distributed space-time code and A-RDSTC denotes the Algorithm with RDSTC. Wether or not a cluster head rebroadcasts depends on the number of the same broadcast message it overhears, which limits the nmber of rebroadcast so as to reduce the total transmission power. Especially in the A-RDSTC algorithm, RDSTC eliminates the concentration of code word (or antenna) allocation process, which decreases the signaling overhead and thus further makes a decline in the total energy consumption. In addition, the A-RDSTC algorithm not only saves more transmission power by power control based on the number of collaborating nodes, but also reduces the interference while increasing energy efficiency.