Study On Cross-Layer Design In MIMO Wireless Communication Systems

Future wireless communication systems face the great challenges of providing higher data rates and spectral efficiency with the limited frequency bandwidth, while guaranteeing quality of service (QoS). By adequately exploiting spatial resource, the multiple input multiple output (MIMO) technology has been shown to be able to multiply improve data transmission rate and significantly enhance link quality without additional bandwidth and power. MIMO has been adopted by a variety of wireless communication system standards, such as worldwide interoperability for microwave access (WiMAX) and 3GPP long time evolution (LTE). However, due to the dynamic-varying wireless communication environment, traditional hierarchical design is difficult to guarantee the diversity and variable QoS requirements of users. This problem entails the research focuses of this dissertation on the cross layer design in MIMO wireless communication systems. The main context includes following aspects:First, the cross-layer design for MIMO-AMC systems is studied on. The queuing characteristics of the MIMO-AMC systems under the conditions of unsaturated traffic and finite-length buffer are investigated. An optimal cross-layer design aiming at minimizing the overall packet loss rate (PLR) is proposed. The solution to the cross-layer design is modeled as a Markov decision process and utilizes the linear programming method to obtain the optimal adaptive transmission policy. Simulation results show the great decreasing of the system PLR compared with the traditional AMC scheme.Second, the automatic repeat request (ARQ) technology is introduced into the cross-layer design for MIMO-AMC systems. Based on the traditional cross-layer design, a novel cross-layer design applied for the actual MIMO systems is proposed. With the presence of imperfect CSI and other actual constraints, the cross-layer design uses Markov-chain-based analytical framework to investigate the performance of the systems and derive the close form expressions for the throughput, PLR and average delay, from which the overall system throughput is maximized under the specified QoS constraints. Simulation results demonstrate the verification of the performance analysis and show the extremely improvement of system throughput compared with the traditional cross-layer design.Third, aiming at the problem that wireless communication system can only guarantee statistical QoS, the combined effects of the physical layer transmission and the link layer packet queuing on the packet delay QoS of the MIMO systems are investigated. The analysis based on the effective bandwidth and effective capacity theory obtains the expression of the packet delay-bound QoS violation probability. Based on the expression, a novel cross-layer design is proposed to maximize the system effective throughput with the guarantees of the service delay QoS. Simulation results show that the proposed cross-layer design significantly improves the system performance in the condition of lower signal to noise ratio.Finally, the adaptive resource allocation problem for the MIMO systems in the presence of channel estimation error is analyzed. For the MIMO zero-forcing receivers, a novel algorithm of power allocation and adaptive modulation combining spatial water-filling theorem and bit allocation algorithm is proposed to maximize the system effective throughput in the conditions of the prescribed system packet error rate and limited transmit power. The numerical results show that the system effective throughput of the proposed algorithm is near optimal with acceptable implementation complexity. For the MIMO zero-forcing transmitter, a cross-layer adaptive resource allocation algorithm (CLARA) is proposed. The algorithm is effective in maximizing the system throughput, while also takes into account the fairness between users. Numerical results show the greatly improvement of the system effective throughput and guarantees of the users'fairness compared with the traditional resource allocation policy.A summarization about the cross-layer designs in MIMO systems is made in the end of this dissertation in which the future direction of the study is pointed out.