Research On Cross-layer Assisted Optimal Resource Allocation For The Next Generation Networks

The rapid development of the next generation wireless networks and the explosive growth of multimedia applications inevitably aggravate the contradiction between the limited wireless resource and the increasing Quality of Service (QoS) requirements of multimedia services. To alleviate this contradiction, cross-layer based resource allocation is proposed to improve the utilization efficiency of radio resource. It discards the layered design and treats all the layers jointly. In this way, the closely related information among all layers can be jointly adjusted to optimize the whole network performance. In this dissertation, under the guidance of information theory, optimization theory and effective capacity theory, the cross-layer based resource allocation for the next generation wireless networks is intensively investigated. The main contributions of this dissertation are as follows:The cross-layer based resource allocation strategy for single user systems is investigated. Two kinds of power control policies are proposed based on the effective capacity theory for traditional cellular networks and cognitive radio networks, respectively. In detail, for traditional cellular networks, we propose a power control policy to minimize the average transmit power subject to delay QoS constraints when employing continuous and discrete constellation multi-level quadrature amplitude modulation (MQAM) schemes. The cognitive radio networks considered allow co-existence of primary users (PUs) and secondary users (SUs) in the same frequency band. Based on the cross-layer model, we first propose the issue maximizing the effective capacity for the SU operating in a licensed band subject to the constraints of transmit power for the SU and average interference power for the PU. A scheme is introduced to decompose the optimization problem into two sub-problems to reduce the computational complexity of the overall optimization problem. Then the problem of minimizing the average interference power while ensuring the delay QoS requirements for the SU is investigated. The limits on the minimum average interference power at PU with some given delay QoS requirements at SU are derived.Considering a single-hop wireless clustered sensor network, we investigate the resource allocation with delay QoS guarantees for wireless multimedia sensor networks (WMSN) as an effort to reduce network energy consumption. In the network considered, the sensor nodes operating on time-division-multiple-access (TDMA) scheme communicate with the cluster head. To save transmit power, we formulate the problem to minimize the average power while fulfilling individual delay QoS constraints. To improve the network capacity, we formulate the issue on maximizing the system effective capacity subject to average power constraints. By employing the Lagrangian duality theory and the dual decomposition theory, two subgradient iteration algorithms are developed to obtain the globally optimal solutions. And the aforementioned resource allocation policies have been shown to be deterministic functions of delay QoS requirements and channel fading states.To improve the power efficiency in WiMAX networks, a joint power, bit and subcarrier assignment policy is proposed. Considering the real-time multimedia services supported in WiMAX networks, the proposed policy ensures delay-related QoS requirements with significant reduced power consumption. To this end, we develop a cross-layer framework in which orthogonal frequency division multiplexing (OFDM) is employed at the physical layer and queuing operation based on the proposed power, bit and subcarrier assignment policy is adopted at the data link layer. Based on the framework, the issue on minimizing the overall power consumption while satisfying the given effective capacity constraints is studied. The optimization problem is mathematically formulated and transformed to a convex optimization one by introducing a time-sharing factor. Based on karush-Kuhn-Tucher (KKT) optimality conditions, the power, bit and subcarrier assignment policy is derived. Both experimental and analytical results consistently show that the proposed policy gives a degree of freedom to WiMAX to save the transmit power.