The Research Of Resource Allocation Algorithm For Multi-user OFDMA System

OFDMA system is developed on the basis of OFDM system, so it inheritsthe OFDM system’s ability to resist the great decline which is caused by thefrequency selective channel, and has high spectrum efficiency and information rate,besides it has its own advantage of multiuser diversity. In OFDMA system, resourceallocation has a very important impact on the entire system performance, which isone of hot topics in the study of the current content.In multiuser OFDMA system, when computing storage capacity in maximizingcapacity resource allocation algorithm, many of the existing literatures assume thateach subcarrier has equal gain, but those algorithms don’t make the system capacitymaximize. This paper presents a novel subcarrier and power allocation algorithmwhich based on channel capacity, we call it BCCF algorithm. This algorithm uses thewater-filling to calculate the channel capacity, and then allocates subcarriers based onchannel capacity. By using this method overcomes the disadvantage that allsubcarriers have the same power. Simulation results show that the algorithmcompared with WUF algorithm and WSA algorithm, the system capacity has beensignificantly improved, and reduces PAPR.BCCF algorithm is compared with the WUF algorithm and WSA algorithm,allocates the subcarriers on the basis of channel capacity, so improves the systemcapacity, but after allocates part of subcarriers, the required power of each subcarrieris not the same. Based on this, this paper puts forward a worst capacity firstallocation on the basis of iterative water-filling, we call it IWCF algorithm. Thealgorithm assumes that one subcarrier can only be allocated to one user to calculatethe capacity, and firstly assigns subcarriers to the user who has minimum capacity.The system performance of IWCF algorithm is better than BCCF algorithm. Whenthe number of users is different, the IWCF algorithm is compared with WUFalgorithm and WSA algorithm, the system capacity is improved by nearly11%, butthe complexity of algorithm basically remains unchanged. When the size of SNR is different, IWCF algorithm is compared to the WUF the system capacity increases bynearly15.7%, compared to the WSA algorithm improves by nearly12.2%.In addition, this paper presents an improved algorithm of the water-filling and anovel subcarrier allocation on the basis of this new water-filling resource allocationalgorithm. Improved water-filling algorithm solves the problem of using the averagepower to calculate the channel capacity. In the process of subcarrier allocation,through the improved algorithm of the water-filling makes the power baseline is aconstant, compared to the algorithms of each subcarrier allocated the samepower,this algorithm works better to meet the requirements of water-filling principle.Therefore, it is better to ensure the system capacity and maximize user fairness. Then,based on this improved algorithm of the water-filling, this paper proposes a newproportional rate limit subcarrier and power allocation algorithm. In the process ofsubcarrier allocation, the algorithm constantly corrects the power to subcarriers, thusmore accurately calculate the system capacity that each user will get. And based onthe user’s proportional rate constraints, finds the next user and assigns the desiredsub-carrier to it, so as to attain the user’s maximum fairness. As can be seen from theMATLAB simulation results that the total system capacity proposed in this algorithmis almost close to the average power algorithm, only average reduced about3%, butthe user fairness has greatly improved, which improves about99.20%.