Research On Multi-Access Interference Cancellation Algorithm For FFH/MFSK Communication Systems

Frequency hopping spread spectrum communication is one of the spread spectrum communication technology, which is a multiple access technology, Frequency hopping coded division multiple access (FH-CDMA) communication can allow multiuser communication in the same bandwidth at the same time. Compare with direct-sequence coded division multiple access (DS-CDMA), frequency hopping spread spectrum communication technology have some important advantages. first, the frequency usages does not have to contiguous, frequency bands affected by severe fading or in use by another system can be avoided; secondly, FH-CDMA systems are less susceptible in general to the near-far problem than direct-sequence systems and don't request power control. Therefore, Frequency hopping communication is very suit for peer to peer networks without power control, such as frequency hopping communication for military,urgency Ad-hoc network for edge region. With the rapid development of wireless communication and the increasingly of society requests, frequency hopping communication has been received widely attention recently, and become an important technology for improving frequency efficiency and cancellation interference. Whereas,as the same DS-CDMA,FH-CDMA systems have been confronted with multiuser interference, cancellation multiuser interference is one of main technology for improving systems capacity and frequency efficiency. In this dissertation, We study on multi-access interference cancellation technology of fast frequency hopping multi-access/multiple level shift keying(FFH-MA/MFSK) systems, to improve system capacity and performance as low complexity. The main creation idea divided as bellow:First, we proposed a low complexity multistage iterative interference cancellation (MS-IIC)multiuser detection algorithm for fast FH-CDMA synchronous communication systems . according to the characteristic of linear detector, the one of key technology is correct estimate and cancel the multi-access interference, The existence detector with maximum logic rule deal with method is very simple and result in useful information loss,we first proposed a estimate method that exploit signal to interference plus noise power ratio(SINR). The detector can confirm the interference according to the estimate SINR, and then cancel the interference. Theory analysis and simulation results show that the proposed algorithm can improve the systems BER performances which don't increase computing complexity, espceily in the fading channel, its advantage is significant.Second, according to interference estimate question, a variety weighting factor adaptive multiuser detection(VW-MUD)algorithm is presented. The advantage of weighing is not estimate interference precisely, only choose a appropriate weighing factor,but the factor can influence severely the detection performance, furthermore,the optimization weighing factor is variety, a constant factor can't result a good performance. A real-time SINR estimate can realize a variety weighing factor and adaptive weighing factor; it can ensure the optimization systems performance. The results show that proposed algorithm has best convergence and BER performance compared with in existence multiuser detector.Third, a based-MMSE of majority blind and semi-blind multiuser detection algorithm of asynchronous fast-frequency hopping multiple access communication system is proposed, which exploit the difference of arrive time of asynchronous user and coordinate of signal energy of desired user. In asynchronous frequency hopping system, the receive Time-Frequency matrix will result much more spurious majority because of detector energy to spill over into nearby frequency bins, and result in more error. The proposed algorithm can average interference and cancel the influence of spill energy. Meanwhile, the proposed algorithm can realize blind detecte without any other user address information, and can obtain more performance gain with others user information.Moreover, we have researched on multi-antenna adaptive beamforming technology, and proposed a blind space-time multi-access interference algorithm for FFH-MA/MFSK peer to peer network. The algorithm use two filter group and constant power algorithm when the one in the information hopping bins, the other starts adjust weighing factor and estimate interference and noise power, it can increase convergence and avoid the beamforming error. The results show that output SINR gain has improved.