Design Of Radio Frequency Front-end And Study Of Space-time Code Technique In Wireless Cooperative Communications System

The neighboring nodes in a wireless cooperative communication systems form avirtual multiple-antenna environment by making use of the shared antennas.Cooperative communication systems can overcome the signal fading effectively inpropagated process and let the single-antenna cooperative communication systemsachieve the same spatial diversity gain of multiple-antenna systems, as well as thereliability and bandwidth efficiency. However, affected by miniaturization andanti-jamming ability, the hardware platform is one of key technologies restricting thepracticality of cooperative communications systems. Moreover, in traditionalcooperative communications systems based on space-time code, the relay nodes arerequired to be controlled intensively, leading to the cost of network capacity and theefficiency of the systems. The dissertation focuses on these two key problems, and themain work of this dissertation is listed as follows:1. The whole structure of wireless cooperative communications system based onsoftware defined radio is designed. After introducing two main designment of RFfront-end, we accomplish designing scheme, analysing feasibility, selecting chips andimplementing the scheme. At last, the circuit and drives of the RF front-end aredesigned and realized. The proposed RF front-end has some advantages such asminiaturization, high-bandwith and simple operation.2. According to designed RF front-end, the dissertation analyses the advantagesand disadvantages of two classical Automatic Gain Control(AGC)，and proposes amixed AGC scheme taking the characters of platform, which can control the gain ofreceived signal rapidly and correctly, and enlarge the dynamic range; Considering theinfluence of transmit-receive switch plan on network throughput rate, one kind plancalled rapid transmit-receive switch plan is proposed, and it can improve the networkthroughput rate.3. In the case of designed scene, the cooperative communication systems are tested.The testing channel model and method are given, and results are analyzed. The testresults show that the designed platform can meet the needs, and the implementedmethods can improve the reliability and efficiency of RF front-end.4. The dissertation studies RDSTBC because DSTBC needs to control relay nodeintensively. The RDSTBC plan solves the problem well and persistent connection.According to the constrained problem of random matrix of RDSTBC, an improvedalgorithm is proposed and solves the problem well. The improved random distributedAlamouti code is implemented on the platform.