There is a growing demand that future networks should be ubiquitous, pervasive and multimedia-capable, i.e. anyone should have broadband access at anytime and anywhere. This demands that the future network access should be broadband, high-speed, and with Quality of Service (QoS) support for various multimedia applications. This vision will not become true without the development of next-generation QoS-enabled broadband wireless access technologies given that the current access technologies (e.g. WiFi, GSM/GPRS/3G UMTS and DSL cable access) cannot sufficiently satisfy the above requirements. Orthogonal Frequency Division Multiple Access (OFDMA) technology has emerged as a most promising transmission technique candidate to be utilized for the next-generation broadband wireless access networks. Compared to conventional single-carrier systems, the orthogonal multi-carrier transmission scheme offers increased robustness to mitigate wireless multi-path distortion effects, and any subsets of the available subcarriers can be flexibly assigned to any users according to their specific QoS requirements.This proposal seeks to explore effective solutions for managing radio and transmission power resources to guarantee the QoS performance as perceived by users with minimum transmission power consumption for emerging OFDMA-based broadband wireless access systems. We plan to design a cross-layer optimization scheme, where subcarrier and power resources are optimally allocated by jointly considering the information from both physical and upper layers. Information theory and advanced queuing theory will be combined together for modelling wireless system dynamics. Specifically, a novel channel estimation method is to be investigated for physical layer to estimate channel state information, and then to be utilized to formulate a robust power bit loading model. An advanced Markov Modulated Poisson Process (MMPP) queuing model is to be created for modelling QoS performance of upper layer heterogeneous multimedia applications. At the scheduler, a cross-layer multi-objective optimization will then be formulated and low-complexity algorithms are sought to search optimal solutions of joint subcarrier and power allocation. The outcomes of this project will make a significant contribution toward acceleration of the rapid and ubiquitous deployment of emerging next-generation broadband wireless access systems in the UK and worldwide.