Research Of Detection Algorithm Based On TDD-LTE Random Access

With the development of global mobile communication, people need more and more fornetwork information, the third generation of mobile communication cannot unable to meetthe needs of people, the3GPP went to many years of research and discussion, proposed theLTE communication protocol finally, the goal in achieving a more flexible system bandwidth,higher transmission rate and lower delay. Random access process is the first step of UEaccess communication network, so it directly affects the performance of the wholecommunication system.Rondom access detecting algorithm widely used in the LTE system is a time domaindetecting algorithm,which quot sampling techniques and frequency domain pointmultiplication is equivalent to the time domain convolution principle to reduce thecomputational complexity of the receiving end, and detection threshold to be adjustedaccording to the estimated noise power, which ensure the accuracy of the uplinksynchronization. The simulation results show that the detection probability of the existingalgorithm is superior to the reference value of the agreement under multipath fading channeland low SNR (signal to noise ratio). But existing PRACH detecting algorithm also havedefectives, it uses oversampling technique can reduce the complexity of implementation andimprove the time resolution, but also lead to the energy dispersion of the correlation valuepoint, in the case of high SNR can easily cause a false alarm; in addition, the low speedresdential use of unrestricted set, Doppler frequency offset caused by the user speed will leadto the uplift of false alarm in the case of high SNR.For this problem, this paper based on the research of PRACH detection algorithm usedin the LTE system, puts forward a method of increase circular shift (Ncs) detection windowwidth joint set secondary threshold, which can achieve the purpose of suppressing false alarm. Increase the Ncs detection window width can effectively reduce the false alarm which causedby sampling, set the secondary threshold can effectively suppress the false alarm whichcaused by Doppler shift frequency offset in high SNR. The simulation results show that thismethod meet the probability of missed alarm, at the same time, can well solve the problem offalse alarm increases in high SNR; and the simulation of short PRACH format under thealgorithm was carried out, the simulation results show that under the premise of no increaseof miss detection probability, the probability of false alarm is almost entirely suppressed.