Research On The Adaptive Duplex Technique

With the development of communications techniques, the relationship between communications networks and other networks especially Internet has become more and more compact, which enhance the user's demand of downlink transmission data and make rate of the uplink and downlink become asymmetric. Besides that, under the restriction of electromagnetic radiation, the rate of uplink and downlink are also asymmetric. By the calculation of human's SAR which is caused by uplink and downlink electromagnetic radiation, it shows that: under the restriction of electromagnetic radiation, the uplink transmission rate is limited; the downlink rate is much higher than that of uplink. So, the asymmetric characteristic between uplink and downlink for one user which take restriction of electromagnetic surrounding and human health into account will be very important in the future communication system.Adaptive technique change the system's parameter according to the channel condition and service demand to improve the efficiency of frequency usage. Nowadays, adaptive technique mainly concerns about link adaptive, in which the system adopt the adaptive technique according to the channel condition and resource of single transmission link to improve the throughput of single user. Duplex adaptive is introduced in this article, it is means that the system allocates the resource to uplink and downlink dynamically according to the characteristic of downlink and uplink to suit the asymmetric characteristic of future mobile communication system.Nowadays people mainly concern about duplex adaptive technique of TDD, the switch point of TDD adaptive technique is variable, the TDD adaptive technique can allocate the slot of uplink and downlink dynamically according to traffic conditions. But the variable switch point may cause crossed slot interfere, so how to avoid the crossed slot interfere is the key technique of TDD adaptive technique. This article introduce a scheme -- IRIM(Isolated-Region Interference Mitigation)to solve the crossed slot interference based on isolated area, the isolated area is determined by difference of pilot signal. In this article, simulation is done to prove this scheme, the simulation results shows that it can avoid the crossed slot interference of mobile stations efficiently and the isolated area is smaller than other schemes. What's more, it causes little infections to coverage of crossed slot.Besides TDD adaptive technique, the FDD adaptive technique is also reasonable, but the FDD adaptive has its special design method such as asymmetric bandwidth, asymmetric characteristics of service. This article introduces a novel adaptive asymmetric frequency division duplex. AFDD allocate the uplink (downlink) bandwidth according to the service circumstance, it divide the uplink (downlink) frequency into several frequency points, all the uplink (downlink) frequency points make up uplink (downlink) frequency pool, each cell use the frequency points dynamically according to the actual service circumstance. AFDD has the advantages of TDD and FDD, it can allocate the uplink and downlink frequency resource flexibly to suit the asymmetric characteristic of the future mobile communications system, it also has the advantages such as strong robustness, wide coverage.Combining with CDMA, this article analyze the improvement of AFDD\CDMA to FDD\CDMA in the area of system capability and coverage. We also analyze the radio resource management of AFDD\CDMA, and prove the call access control method—SNR based access control is most suitable to AFDD\CDMA system by simulation. As the OFDM is the core technique of future mobile communication system, this article also analyzes improvement of AFDD\OFDMA to FDD\OFDMA in the area of system capability, AFDD\OFDMA reduce the block rate compare to FDD\OFDMA and it is proved by mathematics analysis.