Research On Energy-e±cient Transmission Schemes For Cooperative MIMO Sensor Networks

Wireless sensor network, which is considered as a novel technology about acquiring and processing information, has gain more and more attention from academy and industry. It is declared as one of the most important technologies for the 21st century. Wireless sensor networks is formed by a large number of self-organized tiny sensor nodes which consist of sensing, data processing and wireless communication components. It can sense the fields or surveil objects and transmit the collected information to the remote subscriber (SINK) in an cooperative and real-time manner.Wireless sensor networks has found more and more applications in daily life, for example, sensor node can measure the signal of heat, ultra-red, sonar, light and vibrating wave by using its embedded various kinds of sensors, so that it can explore a lot of kinds of phenomenons that we have interest in, including the temperature, humidity, noise, pressure, the component of soil, the size, speed and direction of a moving object. However, most sensor nodes have a small physical size and are mainly driven by battery. And it is impractical to recharge the battery for most application environments. So, energy-efficiency is one of the most important performance for the wireless sensor networks. We can say that, energy-efficient design should be considered in all layers of WSNs, from the hardware to the application.Cooperative (Virtual) MIMO technique which is considered as one of the energy-efficient transmission technologies, has gained more and more attention in recent years. Due to the dense deployment of sensor nodes, the cooperative MIMO technique can save the energy consumption and guarantee the reliable communication in a multi-path fading environment by allowing individual single-antenna nodes to cooperate on information transmission and reception. The application of Cooperative MIMO technique to wireless sensor network faced several problems, for example:How to choose proper MIMO codec algorithm for different applications.How will different MIMO codec algorithm take effects on the cooperative MIMO schemes design.How to choose the cooperative transmit/receive nodes effectively.How to extend the network lifetime, meanwhile maximizing the utility of the whole network (which depends on the amount of data that the network collected and transmit)To answer the above problems, this thesis addresses on the cooperative MIMO technologies in the WSN. The contents of this thesis include the following issues:(l)Research on STBC based cooperative MIMO transmission scheme. (2) Research on distributed V-BLAST based cooperative MIMO transmission scheme. (3) Research on joint network utility and lifetime optimization in cooperative MIMO sensor networks.The work in this thesis has been supported by the National Science Foundation of China "Information Processing and Transmission on Reconstructible MIMO-based Wireless Sensor Networks" (No.60572049) and " Research on Key Issues on Cognitive Radio Networks" (No.60602029) respectively.The contributions of this thesis include:1. Research on STBC based cooperative MIMO transmission scheme: For the applications in which the sensor nodes have sufficient processing ability, we design a distributed STBC based cooperative MIMO transmission scheme(ECCM). By jointly optimizing the number of clusters, cooperative nodes and the transmission rates, simulation results show that the performance of energy efficiency and the network lifetime can be remarkably improved.2. Research on distributed V-BLAST based cooperative MIMO transmission scheme: For the applications in which the communications are mainly between low-end nodes (data collecting node with strict energy constraints) and high-end nodes (e.g SINK node with less energy constraints), we first propose the criterion to choose the cooperative nodes, and then we propose a V-BLAST(Vertical-Bell Labs Layered Space-Time) algorithm based cooperative MIMO transmission protocol。Simulation results show that the proposed transmission protocol can offer significant energy savings compared to LEACH and almost the same energy efficiency as the existing STBC-based cooperative MIMO transmission scheme. And its feature that does not require any joint encoding at the transmit side make it more feasible in the scenario in which the communications are mainly between low-end nodes (data collecting node with strict energy constraints) and high-end nodes.3. Research on joint network utility and lifetime optimization in cooperative MIMO sensor networks: For some applications such as video and audio sensor networks, the amount of collected and transferred data is of great importance to guarantee the QoS. In order to achieve the optimal trade-off, we propose a distributed joint optimization algorithm that could turn the primal centralized optimization problem into several distributed problems that could be calculated on different virtual MIMO nodes. Simulation results show that, by using our distributed algorithm, the cooperative MIMO nodes in the network can converge to the optimal source data rate and transmit power. The Pareto optimal tradeoff between the network utility and the network lifetime can be achieved.