Adaptive frame structure and OFDMA resource allocation in mobile multi-hop relay networks

The objective of this thesis research is to optimize network throughput and fairness, and enhance bandwidth utilization in wireless mobile multi-hop relay (MMR) networks. To enhance bandwidth utilization, we propose an adaptive OFDMA frame structure which is used by the base station and the non-transparent relay stations. To optimize throughput and fairness, we develop an adaptive OFDMA allocation algorithm by using the proposed adaptive OFDMA frame. The effectiveness of the proposed schemes has been verified by numeric simulations.;Providing ubiquitous coverage with wireless metropolitan area networks (WMANs) can be costly, especially in sparsely populated areas. In this scenario, cheaper relay stations (RSs) can be used to provide coverage instead of expensive base stations (BSs). The RS extends the coverage area of traditional BSs. This sort of network is known as a wireless MMR network. This thesis focuses on MMR networks that use orthogonal frequency division multiple access (OFDMA) and time division duplex (TDD) as a multiple access scheme and a duplex communication technique (e.g., WiMAX). The use of OFDMA resources (e.g., OFDMA symbols and subcarriers) and how they are shared in current schemes can reduce system capacity and network throughput in certain scenarios. To increase the capacity of the MMR network, we propose a new protocol that uses an adaptive OFDMA frame structure for BSs and RSs. We also propose adaptive OFDMA resource allocation for subscriber stations (SSs) within a BS or RS. We derive the maximum OFDMA resources that RSs can be assigned and synchronize access zones and relay zones between a superior station and its subordinate RSs. This is bounded by three properties defined in this thesis: a data relay property, a maximum balance property, and a relay zone limitation property. Finally, we propose max-min and proportional fairness schemes that use the proposed adaptive frame structure. The proposed scheme is the first approach that incorporates the adaptive technique for wireless MMR networks. We evaluate our scheme using simulations and numerical analysis. Results show that our technique improves resource allocation in wireless MMR networks. Further, in asymmetric distributions of SSs between access zones and relay zones, the proposed OFDMA allocation scheme performs two times better than the non-adaptive allocation scheme in terms of average max-min fairness and 70% better in terms of average throughput.;However, the extension of the cell coverage of the BS by placing nt-RSs has two drawbacks: less bandwidth utilization of the nt-RSs and a decrease in the MMR network capacity. The reason for the lower bandwidth utilization is that nt-RSs can use only some amount of the bandwidth assigned by their superior station. The reason for the decreased network capacity is that the first hop nt-RSs are located near the cell boundary, where the signal strength between them and the BS is not sufficient and does not generate an efficient modulation scheme or coding rate. To overcome the first drawback, we introduce a local traffic concept, and to overcome the second, place transparent RSs (t-RSs). The reason for these is that the local traffic of nt-RSs is independent of their superior stations and the t-RSs can enhance the signal strength between the BS and the first-hop nt-RSs.