Cross-Layer Resource Allocation for MB-OFDM UWB Systems

The demand of wireless services is increasing and new generations of mobile radio systems are promising to provide higher data rates and a large variety of applications to mobile users. Besides, one of the major challenging problems in future wireless communication systems is how to offer the ability to transport multimedia services at different channel conditions and bandwidth capacities with various quality of service (QoS) requirements. However, this goal must be achieved under the constraint of limited available frequency spectrum because numerous licensed services and applications already exploit the spectral resource up to several gigahertz. Thereby, the multiple access and the coexistence are challenging matters for the next generation wireless communication systems. Two exciting solutions have recently risen to circumvent the limited frequency spectrum problem. The first solution is based on spectrum sensing and dynamic spectrum access (DSA) techniques to find available spectrum which can be used by a cognitive radio user without causing any harmful interference to licensed users. The other solution is to set up underlay communications that would allow so-called secondary users to judiciously exploit some frequency resource already allocated to licensed primary users such that the former does not impact on the quality of the communications of the latter significantly. The latter solution can namely be achieved by imposing tough radiation restrictions to the secondary users. In that context, ultra-wideband (UWB) has recently been attracting great interest as a suitable technology for unlicensed short range communications. With the data rate of several hundred Mbps, and the restricted power transmission, UWB demonstrates great potential in the coexistence issue and the support of multimedia services such as highdefinition television (HDTV), videos and music sharing, console gaming, etc., in home networks known as the wireless personal area network (WPAN). Given the power constraint and the extremely wide bandwidth of UWB, a fundamental problem arises is how to manage the multiple-user access to efficiently utilize the bandwidth, support the QoS requirements of multimedia applications and provide fairness among the existing users. Moreover, to this date, research works on resource allocation for UWB communications are still limited. Based on the WiMedia Alliance, solution proposed for the UWB communications, the objective of this chapter is to define a new approach for the spectrum sharing and multiple access problems in the scope of the resource allocation in UWB systems while taking into account the various system constraints. Thus, to deal with