Key Technologies Of Adaptive Resource Allocation In MIMO-OFDM Systems

With the rapid rise of mobile Internet, the data services represented by broadband multimedia services have gradually become the mainstream. The demand for wireless access rate has risen sharply. The resources of available spectrums are increasingly strained. Without additional power and transmission bandwidth, using MIMO-OFDM technology to improve the spectrum efficiency has become the top choice for next-generation wireless transmission technology. Adaptive resource allocation technology is one of the core technologies for MIMO-OFDM system to guarantee transmission performance. The performance of the algorithms related to this technology will have direct influences on the validity and reliability of the whole system. The thesis, taking this technology as the starting point, centers around such aspects as the allocation of subcarriers, modulation mode, transmit power and other resources in the single-user MIMO-OFDM system, the multi-user MIMO-OFDM system and the multi-user MIMO-OFDM system with imperfect CSI feedback. The main points are as follows:1. The thesis conducts researches about the single-user adaptive resource allocation technology. In order to simplify the complex adaptive bit and power allocation algorithm which takes the minimized bit error rate as the optimization objective, the thesis improves the current efficient Fisher algorithm from two different perspectives. One is to put forward a frequency selective fading degree estimation-based adaptive bit and power allocation algorithm according to the influences of frequency selective fading degree on the adaptive bit and power allocation. The simulation results show that when the threshold is selected appropriately, the algorithm can not only guarantee the system BER performance but also reduce effectively the amount of calculation. The other is to put forward a cluster random select-based efficient subband adaptive bit and power allocation algorithm according to the idea of subband. Theoretical analyses and simulation results, this algorithm can improve the screening efficiency without changing the system BER performance and adjust flexibly the complexity of the algorithm by choosing different cluster width, thus making a good compromise between performance and the calculation amount.2. The thesis carries out a study of the multi-user adaptive resource allocation technology. In the allocation of adaptive subcarriers, bit and power, which takes the minimized transmit power as the optimization objective, there are the problem of equality among customers and the demand for different service qualities. To deal with such problems and demands, the thesis puts forward a low complex proportional fairness-based adaptive subcarrier, bit and power allocation algorithm. Theoretical analyses and simulation results show that this algorithm can guarantee the BER performance of the system, significantly reduce the computational complexity and make the system capacity allocated to each user fairly and reasonably.3. The thesis investigates the multi-user adaptive resource allocation technology which brings in the imperfect CSI feedback. In the multi-user system with feedback delays, channel estimation errors, quantization errors and feedback errors, to solve the problem of adaptive subcarrier, bit and power allocation which takes the maximized system capacity as the optimization objective, the thesis puts forward an algorithm based on the switching between the adaptive transmission mode and the non-adaptive transmission mode. The simulation results show that this algorithm can both guarantee the capacity performance of the system and simplify the system structure effectively, thus enhancing the work efficiency.