The Research On Adaptive Modulation And Coding Technology And FPGA Design In Cognitive Radio

With the coming of the information age, radio communication is widely used inbattlefield. It is hard to use limited spectrum for wireless communication in a largescale.So it is urgent and serious to improve the utilization rate of spectrum while keepingthe communication stable. Cognitive radio is proposed in order to solve this problem. It iswidely studied because of its strong commonality and its ability to detect its surroundingsand to adjust its communication parameters self-adaptively. In this paper, we mainlystudied adaptive coded modulation in cognitive radio system, it matches channelvariation in time, and it balanced reliability requirement and higher band utilization rate.The main work in this paper can be summarized as follows:1) A detailed summary of cognitive radio and adaptive communications technologyresearch status. Compared the existing adaptive technique and summarized theiradvantages and disadvantages, illustrated the necessity of introducing the channel codingtechniques in adaptive modulation techniques. The basic principles and key technology ofACM were analyzed in detail.2) The low density parity check code (LDPC) was investigated, equivalence andcomplexity of encoding algorithm was deduced and analyzed in view of existingtraditional coding algorithm based on generator matrix and RU,the classical decodingalgorithms were analyzed, and the error performance were simulated. The LDPC codewas used in adaptive modulation technology, redundant code was used to improve systemreliability and anti-noise performance.3) When ACM system works, it needs to measure SNR to adjust code modulationmode. This paper studied the SNR estimation algorithm in detail, including the maximumlikelihood estimation (ML), subspace decomposition, polynomial fitting algorithm, thetheoretical derivation and performance simulation were introduced. The Kalman-filterwas used to predict the SNR. Simulation shows that: in the range of0~15dB, estimationerror is less than0.1dB, the error variance of prediction is less than0.16dB.4) One ACM system model using LDPC was proposed, mapping scheme betweeneach scenario and SNR range was determined using simulation, Finally, the ACM system was implemented using FPGA in the lab, and the implementation scheme of eachmodules was presented, a hardware platform was established. And it established the voicecommunication test platform using the high-fidelity voice chip TLV320AIC23, to verifythe effectiveness of adaptive coded modulation algorithm.