Research On Resource Mapping Of Frequency And Time Based On Power Control

In today’s society, the quality of the wireless channel is affected by many factors, which make the quality of channel have a big difference, and frequency resources will be more and more shortage.How to use the limited resources, improving the channel quality,and improving wireless resource utilization.LTE resource allocation methods has been the main factors that directly affects the system performance, which has become one of hot topics in the research of the current LTE system[1].The most current optimal allocation of resources of OFDMA system, always put the single subcarrier or the group of subcarriers as the smallest unit for resources allocation.However these resources allocation algorithm only from the point of view of frequency domain(subcarrier) to consider the allocation of resources, using of noncorrelation between multi-user diversity and subcarrier channel fading, while ignoring the temporal changes of fading channel, The actual channel is Short-term stability, study of time-frequency two-dimensional resource mapping algorithm is necessary, and more suitable for the actual system.This thesis firstly summarizes the LTE downlink physical layer, including LTE downlink frame structure, the physical resource unit, downlink multiple access methods, the definition of physical channel and downlink power control mode,and then introduces the factors affecting the quality of the wireless channel, which mainly include channel fading, time-varying and doppler effect, and the technology of OFDMA is studied. The third chapter research two kinds of wireless resource allocation algorithm on two-dimensional from time and frequency, and on this basis, from the angle of reducing power control, put forward a new frequency time frame mapping algorithm for radio resource mapping(TFM) and verify that the algorithm is suitable for LTE downlink system. At the same time TFM algorithm is improved for the fairness problem of TFM algorithm, and increased the part of scheduling algorithm.The focus of this study is the LTE downlink resource mapping based on OFDMA, considering that channel characteristics is constant within the coherent time, the new algorithm will select the user who can obtain the maximum channel gain for each subchannel and continuously allocation resource block for them. So that system can obtain larger throughput.At the same time, considering the coherence time is far greater than OFDM symbol period, it is not necessary to allocation power on each OFDM symbol, the new algorithm consider that it’s viable to allocate power only one time in a coherent time.The simulation results show that the number of allocating power of system has greatly reduced with the new algorithm,it greatly reduces times that the transmitter adjust the signal power, making the signal of receiver more stable, and it is conducive to the identify and receive signal for the receiver.