Research On Downlink Resource Allocation For LTE System

Since the wireless communication channel is a time varying and frequency selective channel, how to improve the throughput and satisfy different people’s rate according to the instantaneous channel quality of system, is the key of resources allocation. Through analyzing the research status of resource allocation at home and abroad, the situation that most researches about resource allocation algorithms are based on the subcarrier, taking the subcarrier as the allocation unit now which is infeasible when the bandwidth is wide. So the article brings the idea of this allocation to the resource allocation algorithms based on RB (Resource Block) according to study the exiting allocation algorithms which base on subcarrier.The article focuses on the aspects as follows:(1) The optimization objective and method of the RA (Rate Adaptive) allocation are researched and the resource allocation on account of the requirement of the ratio is modeled.(2)The algorithms of the resource allocation based on subcarrier are studied. Aiming to an efficient RA algorithm, in order to enhance its fairness and drop its time complexity further, the article proposes an improved algorithm through improving the way of allocating the subcarriers and power. Among it, the subcarrier allocation includes pre-allocation and adjustment. In the pre-allocation, the priority is set on the basis of the average of SNR. The algorithm allocates the subcarriers the users need at once in the light of the priority, which reduces the number of cycles, so drops the time complexity. Then, it adjusts the subcarriers among the users to increase the satisfaction degree of their rate ratio, that is, the fairness, by means of setting the parameter. Because of the parameter’s tenability, the algorithm can adjust the value of the parameter to find the best value to meet different requirement according to the actual situation, simultaneously improving the overall performance. So the improved algorithms are more flexible. In the power allocation, it allocates power for each user directly according to the numbers of subcarriers they get. It simplifies the calculation process of the power, so the time complexity is decreased.(3)In order to adapt to the situation of the large bandwidth, the article expands the resource allocation based on subcarrier to which based on RB. As for the shortcomings of the overall power water-filling algorithm and user equal power allocation algorithm’s complexity and poor fairness, the article puts forward a improved algorithm whose time complexity is lower and fairness is higher. This improved algorithm adopts the idea of the modified subcarrier allocation to boost users’fairness. Due to the higher throughput of the overall power water-filling algorithm, the improved algorithm uses the idea of this algorithm. However, the original algorithm’s time complexity is higher, the article achieves to modify the way of implementation about it through sorting the RBs’corresponding users’channels only according to the situation of their allocation. It reduces the amount of computation, thereby decreases the time complexity.