Research On Cross-Layer Design Of Wireless Networks

People's requirements promote the rapid growth of wireless technologies for providing anytime, anywhere ubiquitous communications. With the increasing Quality of Service (QoS) requirement of multimedia traffics, the next generation wireless communication systems are required to utilize the radio resource in a more flexible and efficient way. The idea of cross-layer design discards the idea of layered design and views separate network layers as a whole to design and optimize while providing the QoS requirement of multimedia traffics.This thesis offers several novel approaches on cross-layer design in point-to-point wireless link, end-to-end networks as well as cooperative networks. The contents of this work are listed as follows:For cross-layer design in point-to-point wireless link, we consider the problem of jointly exploiting the error-correcting capability of the hybrid automatic repeat request (HARQ) protocol at the data link layer and the adaptation ability of the adaptive modulation and coding (AMC) scheme at the physical layer, in order to maximize the throughput for quality-of-service (QoS)-guaranteed traffic. The queueing behavior induced by both HARQ and AMC is analyzed with an embedded Markov chain and we derive the closed-form expressions for performance metrics such as packet loss rate, throughput and average delay. Then, we propose a cross-layer design algorithm, which can improve the system performance with the QoS constraints.For cross-layer design in end-to-end hybrid wired/wireless networks, we consider the problem of jointly optimization of AMC at the physical layer, HARQ at the data link layer and transmission control protocol (TCP) at the transport layer. First, the performances of transport, data link and physical layers are modeled by some classical models. Then, we study the interaction between transport layer, data link layer and physical layer via a fixed-point procedure. To maximize the end-to-end throughput for QoS-guaranteed traffic, we propose a cross-layer design which optimizes the target packet error rate (PER) for AMC as well as the maximum number of retransmission for HARQ.For cooperative networks, we propose a cross-layer design which combines AMC, cooperative diversity at the physical layer and HARQ at the data link layer. First, we provide theoretical analyses of conventional direct transmission scheme and cooperative transmission scheme with AMC and HARQ that include analytical expressions for the PER and spectral efficiency. Then we propose an opportunistic cooperative HARQ scheme which invokes cooperation based on the feedback channel state information. Numerical results demonstrate that the performance of the opportunistic cooperative HARQ scheme is equivalent to the cooperative transmission scheme while its cooperation cost is kept much lower compared with that of the cooperative transmission scheme.