Research On Resource Allocation For OFDM Wireless Network

The rapid development of the wireless networks and the explosive growth of multimediaapplications inevitably aggravate the contradiction between the limited spectrum resource and theincreasing quality of service (QoS) requirement of multimedia services. To alleviate the contradiction,the wireless network resource allocation technology becomes the hot research field recently. Due tothe distinct advantages of orthogonal frequency division multiplexing (OFDM), it provides flexiblefreedoms for resource allocation. Thus, resource allocation in OFDM system has attracted greatinterests in recent years. In this thesis, the resource allocation algorithms in OFDM wireless networksincluding cellular network, wireless local area network and wireless Mesh network are intensivelystudied. In this thesis, we make some improvements on the basis of previous work. The main work ofthis thesis are listed as follows:For the cellular network resource allocation problem of the uplink multiuser multi-inputmulti-output orthogonal frequency division multiplexing (MIMO-OFDM), a minimizing powerresource allocation algorithm based on limited feedback which considers the minimum transmissionrate requirement of each user and TCM is proposed. Firstly, the algorithm designs the codebook ofrate, power and equivalent channel quantization threshold utilizing the Lagrange multiplier methodand the Karush-Kuhn-Tucher condition of convex optimization theory. Secondly, the subcarriers areallocated according to current channel state information and the equivalent channel gain is quantized.Finally, the base station broadcasts the resource allocation solution to users. Proposed algorithm notonly saves efficiently the energy of cellular network, but also has advantage of limited feedback.For the cellular network resource allocation problem of the uplink multiuser MIMO-OFDM, amaximizing throughput resource allocation algorithm based on limited feedback which considers thebest effort service and TCM is proposed. Firstly, the algorithm defines the effective set oftransmission mode per user according to the code of transmission mode and the requirement of BER.Secondly, the function of link quality indicator is derived according to the Lagrange dual method andthe Karush-Kuhn-Tucher condition in convex optimization theory. Finally, updates the Lagrangemultipliers utilizing sub-gradient iterative method. Proposed algorithm not only improves the networkthroughput, but also has advantage of limited feedback.For the cellular network resource allocation problem of single user MIMO-OFDM, a maximizingthroughput resource allocation algorithm which considers the delay channel state information and channel coding is proposed. Firstly, the algorithm derives the constellation distance which guaranteesthe requirement of the user’s BER utilizing the delay channel state information from the perspectiveof coding gain. Secondly, it proves that the optimization problem is convex and the closed formsolution for optimal power and bit loading is derived according to the Lagrange multiplier method andthe Karush-Kuhn-Tucher condition of convex optimization theory. Finally, the resource allocationsolution is obtained through rounding bit and power adjustment. Proposed algorithm is close to theoptimal integer bit loading solution of single user and has advantage of low computationalcomplexity.For the cellular network resource allocation problem of the downlink multiuser MIMO-OFDM, aproportional fairness resource allocation algorithm which considers the delay channel stateinformation and users’ proportional rate weight is proposed. Firstly, the algorithm allocates the totalpower of base station equally across the subcarrier and maps each user into the corresponding virtualusers according to the users’ proportional rate weight. Secondly, it defines the subcarrier allocationcriteria of virtual users accessing time according to the concept of shadow price in operation research.Finally, it obtains the percentage of subcarrier accessing time in accordance with the subcarrierallocation criteria and shadow price classification. Proposed algorithm can improve the networkthroughput efficiently under the condition of guaranteeing the proportional fairness of users.For the wireless local area network resource allocation problem of the uplink multiuserMIMO-OFDM, cross-layer resource allocation algorithm with low complexity and improvedcross-layer resource allocation algorithm which consider multi-packet reception and the data packet’slength are proposed. Firstly, we study MIMO-OFDM transmission technology based on beamformingat the physical layer and the distributed coordination function (DCF) protocol based on multi-packetreception at the media access control (MAC) layer. Secondly, we propose a low complexity crosslayer resource allocation algorithm based on multi-packet reception according to the mathematicaloptimization model of Huang’s literature. This algorithm has a good compromise between networkperformance and computational complexity. Finally, in order to overcome the mathematicaloptimization model deficiency of Huang’s literature we substitute the total power of the network withthe maximum power of each user and propose an improved cross-layer resource allocation algorithmbased on multi-packet reception. This algorithm not only effectively improves the network throughput,but also reduces the average packet delay.For the resource allocation problem of the multi-hop wireless Mesh network based on OFDMtechnology, a joint power-timeslot-subcarrier resource allocation algorithm which considers the maximum transmission power constraint of each link and the real-time traffic transmission raterequirement of each link is proposed. Firstly, according to the characteristics of voice traffic and videotraffic the algorithm allocates the pair of timeslot-subcarrier for the real-time traffic of each link anddesigns the service differentiation mechanism for the voice traffic and video traffic of each link.Secondly, it allocates the remaining pairs of timeslot-subcarrier in the frame to the largest marginaleffect link in order to increase the network throughput of data traffic. Finally, water filling algorithmis performed in the power allocation stage. Proposed algorithm not only guarantees the QoSrequirement of voice traffic and video traffic, but also improves the throughput of data trafficeffectively.