The next generation wireless systems are expected to provide universal personal and multimedia communications without regard to the users' mobility and location. These services will include heterogeneous classes of traffics such as voice, file transfer, web browsing, wireless multimedia, teleconferencing, and interactive games, etc. The major challenges we are confronted with include the harsh wireless channel, scarce resources such as power and spectrum, and very diverse QoS (Quality of Services) requirements. This stimulates the development of intelligent resource management algorithms to achieve efficient utilization of radio resources, provide QoS differentiation and guarantees, and ultimately enable ubiquitous and high-rate communications over a limited frequency spectrum....[ Read more ]

The next generation wireless systems are expected to provide universal personal and multimedia communications without regard to the users' mobility and location. These services will include heterogeneous classes of traffics such as voice, file transfer, web browsing, wireless multimedia, teleconferencing, and interactive games, etc. The major challenges we are confronted with include the harsh wireless channel, scarce resources such as power and spectrum, and very diverse QoS (Quality of Services) requirements. This stimulates the development of intelligent resource management algorithms to achieve efficient utilization of radio resources, provide QoS differentiation and guarantees, and ultimately enable ubiquitous and high-rate communications over a limited frequency spectrum.

In this thesis, we will present joint MAC-PHY layer resource allocation algorithms for OFDM systems. OFDM is recently recognized as one of the leading candidates for supporting the next generation wireless communication systems. Building our work upon a multiuser OFDM architecture, we will maximize the overall power or spectral efficiency by exploiting the inherent system diversity in the frequency, time, space, and user domains through an intelligent management of bandwidth allocation, multiple access, adaptive modulation and coding, along with power allocation. Particularly, we will propose dynamic resource allocation algorithms for four multiuser OFDM systems. These are 1) uncoded system; 2) coded system; 3) MIMO system; and 4) packet-switched system.

For the multiuser uncoded OFDM system, we propose for downlink transmission a low-complexity resource allocation algorithm that includes dynamic cell selection, adaptive modulation, and adaptive subcarrier allocation. We then extend the work to the TCM encoded OFDM system, in which the SER, BER, and BPS performance as well as the optimal switching levels are derived. For MIMO/OFDM systems, we propose for the uplink transmission three low-complexity subcarrier-bit-and-power allocation algorithms when different receiver structures are adopted at the BS. These algorithms exploit the additional space domain freedom and present intelligent SDMA solutions. Finally, we extend our work to the cross-layer design and optimization of packet-switched networks. In this algorithm, the bandwidth and power allocation in the PHY and MAC layers are designed within an integrated framework to take advantages of the inter-dependencies between the two layers. The proposed algorithm not only exploits the time- and frequency-varying channel conditions, but also takes advantage of the random packet arrival and the dynamic queueing behavior.

Numerical results and comparisons with various conventional non-adaptive and adaptive systems are provided to demonstrate the potential of our proposed techniques. It is shown that the proposed resource allocation algorithms substantially improve the system spectral/power efficiencies as well as system performance given that the QoS guarantees for each user are ensured.