Tdd Mode Of Baseband Signal Synchronization Algorithm On The Dsp Implementation

TDD(Time Division Duplexing), corresponding to FDD, is one kind of LTEtechnology. It’s a kind of duplex mode of communication system, receiving andtransmitting at the different slots in the same frequency channel, separating channels ofreceiving and transmitting by guaranteeing the time. TDD has great advantage on it’sflexibility that nothing can compare with. It needs only one asymmetric frequencyband, and it can make full use of the radio spectrum.The real time demodulation of a QPSK signal with the sample rate between1Mbpsand2Mbps is required in this subject, using a variety of demodulation techniques tofinally recovery the sending data, while at the same time keep the BER and frame lossrate to be less than107at a switching rate of4KHz, when there’s no noise or otherinterference. MATLAB, CCS and other software tools are used for simulation in thissubject, and DM6437is used in the emulation and the optimization of the code.we use the symbol synchronization technology to build the whole basebanddemodulation system，remove the symbol timing error produced by the differentsampling time of the sending end and the receiving end. The traditional Gardneralgorithm is used in symbol synchronization, and also improved on this basis. At last,evaluating the performance of the whole system by a series of error computing.The experiment is completed on DM6437, and cache, DMA are enabled in thisalgorithm for optimizing, so that the system can demodulate at a sample rate of3Mbps,while the bit error rate and frame loss rate is about107in both the state of noise of nohigher than20dB and the state of phase error of no higher than5°.