Research On The Time Acquistion And Mai Suppression Of IDMA System

Interleave-Division Multiple Access (IDMA) originating from CDMA is proposedby Prof. Li Ping coming from City University of Hong Kong, which uses random chip-level interleavers to separate different users. IDMA has been thought a potential newmultiple-access technology, not only for its many advantages inherited from CDMA, inparticular, diversity against fading and mitigation of the worst-case other-cell user inter-ference problem, but also for its high spectral efficiency, improved performance and ca-pacity and low receiver complexity with a new simple Chip-by-Chip Iterative Multi-userDetection scheme.For these advantages, IDMA are thought a potential new multiple-access technology.In this paper, three issues are studied. Firstly, the time acquisition technology of theIDMA system is talked. Secondly, we settle the problem that the detection time is toolong to be accepted for high speed communication system. Besides, the issue that the costof the IMUD technology is too complexity for the down-link system is talked at last.In this paper ,firstly, the advantages and disadvantages of IDMA system based onstudies of the structure and algorithm are analyzed. In the low Signal-to-Noise(SNR)condition, the time acquisition of IDMA system is difficult and the existing solution istoo complexity. For this issue ,three new schemes are proposed, which are the sliding-correlation on interlavers, M-average scheme and Spreading-IDMA scheme.Besides, theacquisition probability, false-alarm probability, the average acquisition time and the al-gorithm complexity are analyzed and compared respectively. Analysis and simulationresults show that, among the three schemes, S-IDMA scheme compete on its near - opti-mum acquisition probability, lowest average acquisition time and lowest algorithm com-plexity. Moreover, the issue that the detection time of the IMUD receiver is too long isalso solved by the S-IDMA scheme.MUD technology plays an important role to suppress the mulitple user interfer-ence(MAI). However, the cost of the traditional MUD algorithm is too high to practice,especially in downlink of the cellular System. So does the IDMA system, which is fa-mous for its low cost even though.For the IDMA system ,the total cost,which is linerwithK, iso(K). As K is usually a large number in the practical system, the structure andcomputational complexity is still too huge for a small MS to utilize the traditional MUD method.As a substitute, a novel idea, part-MUD is proposed. And based on the new idea,a novel CDMA downlink system, Group-CDMA, is proposed. Analysis and simulationresults show that the BER performance and system capacity is promoted several timesthan CDMA system with a little complexity's raise.