Cross-layer design for support of delay bound quality of service guarantees over fading channels.
Quality-of-service (QoS) guarantees have become critically important for the transmission of real-time multimedia traffic in next generation mobile wireless networks. The aim of this dissertation is to investigate the cross-layer design for support of delay bound QoS guarantees over fading channels. Providing diverse QoS guarantees presents a challenge due to the time-varying fading nature of wireless channels. Existing physical layer modelling is inadequate in supporting real time QoS metrics such as delay, hence adaptive techniques need to be extended to the upper-protocol layers. The first objective of this dissertation is to introduce a cross-layer design framework which investigates the impact of the physical layer on the data link delay bound QoS performance. At the physical layer, adaptive modulation and coding (AMC) is utilized for transmission over block fading channels. At the data link layer, the effective capacity approach is used to model the delay bound QoS performance subject to physical layer variations. The effects of varying physical layer parameters, such as average signal-to-noise ratio (SNR), the fading parameter for the kagami-𝑚 model, and target packet-error rate (PER), on the analytical delay bound performance are investigated and then validated by the simulation of a queuing system. Due to the cross-layer design framework, the system’s throughput has a significant impact on bounded delay at the data link layer. The switching levels of the conventional AMC scheme used in the first objective were fixed, subject to a target PER. However, fixed switching levels results in the system’s throughput limiting the delay bound performance. The second objective of this dissertation is to optimize the switching levels of the AMC scheme employed at the physical layer, by maximizing the average throughput, while maintaining the target PER constraint. The analytical and simulated results show that by optimizing the switching levels, a superior delay bound performance is achieved, when compared to the deterministic switching levels of the conventional AMC scheme used in the first objective.