Research On Resource Allocation Techniques In Wireless Network Coding Systems

Rapid development of radio wireless data services leads to more urgent requirement for radio communication experience with features of high data-rate, large coverage and low delay. Comprehensive study has been developed by the academic circles and telecommunication industry. By utilizing multiple-input multiple-output (MIMO), orthogonal frequency division multiplexing (OFDM), interference alignment (IA), wireless relay and etc, the link performance has been improved. In order to further enhance system spectrum efficiency, network coding (NC) has been considered to be introduced in various scenarios, which can decrease the transmission procedures due to the broadcast character of wireless propagation. Recently, wireless NC is one of major focuses for researchers, and has been widely accepted to be an important item in the next radio communication network specification.This dissertation is focused on the thesis of wireless NC resource allocation, and presents a thorough and comprehensive study on multiple user scheduling and pairing, relay location selection and power allocation algorithms for different NC scenarios. This dissertation is based on an extensive survey on the current literatures and is organized as follows. First, a novel user scheduling strategy is proposed for the uplink multiple access scenario; then, a new multi-user scheduling and pairing scheme is studied in the cellular two-way relay networks; finally, a simple two-way relay channel model is considered, the optimal relay location selection and power allocation strategies are analyzed. The major work and contribution of this dissertation consist in:1. Network coding scheduling algorithm in the uplink multiple access scenarioA novel network coding scheduling algorithm is proposed for uplink multiple access scenario. The algorithm always schedules the users with best channel condition, and the messages from the non-scheduled user can be transmitted by the relay user via physical network coding. Considering the impact of relay user channel condition, an improved scheme is addressed. The throughput and user delay are derived at first. Then, numerical results are shown to compare the performance of different scheduling schemes. The time division-synchronous code division multiple access (TD-SCDMA) system level simulation platform is built to evaluate the urban macro performance of the proposed scheme. It is shown from the results that network coding scheduling algorithm enhances system throughput while maintaining user fairness, moreover, it can provide better coverage for the users at the edge.2. Multi-user scheduling and pairing in two-way relay cellular modelWe consider two-way relay cellular model containing one base station and a single relay. Both of them are deployed with multiple antennas. Plenty of single antenna users are also located in the topology. By employing network coding and precoding, uplink and downlink information exchange for multi-pair data flows can be accomplished during two time slots. Channel-correlation-based selection (CCUS) algorithm is proposed in this dissertation. The proposed algorithm is carefully designed to decrease the multiple access interference and improve the coding gain at the base station and relay. The advantage of the CCUS algorithm is verified by the downlink analysis of sum rate and outage probability, meanwhile the computational complexity, signaling cost and user fairness of the proposed algorithm are also discussed and compared with the round robin (RR) and pure opportunistic (PO) scheme. It is shown from the mumerical results that the sum rate and outage probabilities of CCUS algorithm outperform other schemes for both uplink and downlink. Even when the user payload in the cells is low, better performance can be obtained by the CCUS algorithm, and with increasing the user number, the performance gain is more remarkable.3. Power allocation and relay positioning for two-way relay channelThis dissertation investigates a simple two-way relay scenario, where two source nodes communicate to each other via an intermediate relay. All the nodes are equipped with a single antenna. Considering symmetrical data traffic requirements, we derive a power allocation closed form expression to minimize the outage probability under the sum power constraints by convex optimization theory. It indicates that the optimal scheme is always to allocate one half sum power to the relay. Then, the relay positioning scheme are discussed, and the relay node is best positioned at the middle of the two end nodes. It is shown from the results that the optimal power allocation scheme can yield lower outage probability than the direct transmission. Furthermore, we extend the requirements to the asymmetrical data traffic. The power allocation and relay positioning strategies are investigated in order to minimize the power consumption. The relay operating region is identified in which relay-assisted transmission can yield higher energy efficiency than direct transmission. It is also pointed out that the relay node is best positioned at the middle of the two source nodes for any asymmetric traffic requirements.The research outputs related to this dissertation have been accepted as papers in institute of electrical and electronics engineers (IEEE) journals and conferences.