On The Adaptive Resource Allocation Algorithms Based On Orthogonal Frequency Division Multiple Access (OFDMA)

Orthogonal frequency division multiple access (OFDMA) is a multiple access technique based on OFDM, also namely multiuser OFDM, which is the most effective way to realize multiuser multiplexing and access in OFDM systems. By allocating each user one or a group of subcarriers to realize multiple access scheme, the OFDMA is one of the important techniques in IEEE802.16 published, also in beyond 3G and 4G.Due to the time-varying characteristics and the frequency-selective fading of wireless channel, the adaptive resource allocation used in OFDMA can assign subcarriers to multi-user flexiblely according to the channel conditions, thus avoiding badly damaged channels, improving the transmit signal quality and spectral efficiency, and realizing adaptive optimization allocation. It is therefore the objective of this thesis to investigate the adaptive resource allocation algorithms for application in OFDMA.In this thesis, the characteristics of wireless fading channel and the principle of OFDMA are introduced firstly. Then the adaptive resource allocation algorithms in OFDMA are investigated in details. The allocation schemes concerned include the joint optimization allocation of subcarrier, bit and power. The overall objective of the allocation schemes is to determine the subcarriers assignment to each user, then determine the bit and transmit power assignment to each subcarrier, according to instantaneous fading characteristics of all users and the quality-of-service (QoS) requirements. The bit and power allocation algorithm for single-user and fixed resource allocation schemes in multiuser system are presented in the thesis. Then several typical adaptive resource allocation algorithms based on margin adaptive (MA) and rate adaptive (RA) optimization rule are analysed, simulated and compared. Meanwhile, based on the study of RA algorithms, an adaptive resource allocation algorithm of multi-service users with QoS guarantees is proposed. The proposed algorithm for real time users and non-real time users are investigated separately. Our analysis and simulation results show that, the proposed algorithm can satisfy the required bit error rate and data rate for both the real-time users and the non-real time users while maintaining proportional fairness among users. Besides, the bit correction algorithm is also investigated to ensure the full utilization of total transmit power while realizing integer bit allocation, resulting better and satisfactory performance.