Diversity And Power Optimal Allocation Of The Cooperative Communication System

Multipath fading seriously degrades the performance of wireless communication systems. Diversity as an effective technology to against multipath fading includes time diversity, frequency diversity and spatial diversity, etc. With the development of wireless communications, spectrum resource becomes more and more expensive. Multiple-input multiple-output (MIMO) system was proposed as a candidate system for future which can provide diversity gains without extra spectrum utilization. However, the mobile device, such as cell phones, the sensor nodes, and so on can not install more antennas due to the size, power and other constraints. The cooperative diversity technology is the effective means which use wireless relay system to improve the capacity and reliability of wireless channel. Every user shares their antennas and forms Virtual Antenna Array (VAA), and then achievs distributed spatial diversity. Power is also the important resource in the wireless communication system. It is important to further enhance transmission rate with limited power by optimizing the allocation of power in the physical layer. This thesis describes the following work of the author:1, Basic cooperation diversity patterns and cooperation protocols are introduced. The performance of various cooperation diversity protocols are simulated and compared.2, Study of the traditional three-node cooperation communication system. We aim at the AF and DF relay protocol. When the total power is constant, optimize allocation of source node and relay's power.3, Study of optimization power allocation in the Distributed Cooperative Communication System. Firstly under the condition that relay's total power is constant, I study and compare three optimized power allocation schemes. Secondly when relay's total power is not limited, I study a new relay selection scheme which can save power.