The performance of OFDMA wireless systems using PF scheduling

Orthogonal Frequency Division Multiple Access (OFDMA) has gained a lot of attention from many researchers of wireless communications. OFDMA represents a promising multiple access scheme for high-data rate transmission over wireless channels as it combines the Orthogonal Frequency Division Multiplexing (OFDM) modulation and flexible and effective subcarrier allocation [1]. OFDMA inherits the favourable OFDM prosperities of high immunity to the multi-path fading and inter-symbol interference [2]-[3]. -- One main aspect related to OFDMA is scheduling. Scheduling in OFDMA systems is expected to manage multiple frequency subbands over time to deliver service to the system's users with specific quality requirements. Data rate, throughput, and fairness among users are key factors that specify how efficient a scheduling solution is. The Proportional Fair (PF) algorithm is an appealing scheduling scheme to improve the fairness among users without sacrificing the efficiency in terms of average throughput of the system [4]. -- This thesis focuses on OFDMA systems that utilize the PF algorithm to schedule the available time and frequency resources among users. The thesis studies the performance of OFDMA scheduling in terms of the throughput, fairness, and packet delay using computer simulations and analysis. -- Two dimensional (frequency and time) scheduling algorithms based on the PF algorithm are proposed, evaluated using computer simulations. The proposed solutions utilize the PF criterion to achieve high system throughput while maintaining fairness among users in the system. In order to support multimedia bursty traffic, our solutions allow frequency domain sharing so that more than one user can share a subband in each time frame, where a subband is formulated by grouping a number of subcarriers. We compare the performance of the proposed solutions with other candidate OFDMA scheduling algorithms in the literature. Results show that the proposed schemes outperform the other schemes in terms of the throughput and packet delay with comparable fairness performance. -- It is worth mentioning that, to the best of our knowledge, the performance of PF scheduling scheme for OFDMA systems is not determined analytically in previous work available in the literature, and it is usually found by simulations only. Hence, we analyze the proposed PF scheduling schemes for OFDMA systems and evaluate its performance analytically. We derive closed-form expressions for the average throughput, throughput fairness index, and packet end-to-end delay. Computer simulations are used for verification. It is found that the analytical results agree very well with the results from simulations, which verifies the correctness and accuracy of the analytical solution. In our opinion, deriving analytical expressions that reflect the performance of the PF scheduling algorithm is a significant contribution because it provides deeper insight and ameliorates the understanding of the PF scheduling algorithm behaviour and mechanism for OFDMA systems. This facilitates the process of pursuing future work and further studying and developing more efficient solution for OFDMA systems.