Broadband Relay System Resource Allocation In Wireless Technology

Relay technique has been accepted as one of the cost-effective solutions to meet the requirement of the future wireless systems. It can reduce the transmis-sion distance and increase the amount of users under more favorable channel conditions, allowing for better channel quality and higher throughput. Mean-while, orthogonal frequency division multiplexing (OFDM), has emerged as one of the prime modem schemes for the future broadband wireless systems. By dividing the transmission channel into multiple orthogonal sub-channels (i.e. subcarrier), the inter-symbol interference (ISI) induced by multi-path fad-ing is overcome. Considering the advantages of both the relay and OFDM techniques, the integration of relay and OFDM into the future wireless sys-tems has been regarded as a promising way to increase capacity and enhance coverage.In the wireless relay-OFDM systems, well-designed radio resource allo-cation algorithms can introduce large system transmission rate gain. By using relay, which separates the single-hop transmission into multiple hops, the trans-mission from the source to the destination may cost more radio resource. For-tunately, it is possible to exploit larger multiuser diversity gain at the frequency domain in the wireless relay-OFDM systems as the frequency selectivity on the multiple hops is independent. Therefore, it is advisable to concentrate on the design of the radio resource allocation schemes that can achieve efficient resource usage on the multiple hops and exploit multiuser diversity gain of the systems.In this dissertation, we concentrate on the radio resource allocation tech-niques of the wireless relay-OFDM systems. Based on the system analysis, novel resource allocation algorithms are proposed, which can improve system performance. In order to verify the effectiveness of the proposed algorithms, we resort to both theoretical analysis and simulations.In the first part, the radio resource allocation problems of the wireless re-lay systems under flat fading channels are studied. In the researches, we focus on the multiple relays scenario. The related resource allocation problems are formulated and analyzed. By combing adaptive subframe allocation and in-cremental relaying, a high-efficient hybrid automatic repeat request (HARQ) mechanism for the relay systems is proposed. In the meantime, the optimal relay selection schemes that can maximize system transmit rate and keep load-ing balance among relay nodes are proposed. Moreover, the related system performances are analyzed theoretically.In the second part, the radio resource allocation problems of the wireless relay-OFDM systems in one single cell are investigated. First, the resource allocation in the single-relay-multiple-user scenario is analyzed. The optimal subcarrier allocation algorithms that can maximize system transmit rate and proportional fairness are proposed. Then, the joint subcarrier and power allo-cation schemes on both the downlink and uplink of the relay-OFDM systems are studied in the multiple-relay-multiple-user scenario. In order to achieve the optimal solutions, the decomposition methods in the convex optimization theory are utilized.In the third part, the radio resource allocation problems of the wireless relay-OFDM systems among multiple cells are analyzed. In order to achieve good tradeoff between resource usage efficiency and co-channel interference, both the intra-cell and the inter-cell radio resource allocation problems are in-vestigated. For the intra-cell radio resource allocation, a distributed subcarrier and power allocation algorithm is proposed. For the inter-cell radio resource al-location, the semi-static inter-cell interference coordination (ICIC) techniques are focused on. Three ICIC schemes are proposed, i.e. frequency domain ICIC scheme, time domain ICIC scheme and frequency-time domain ICIC scheme.In the last part, the radio resource allocation problems of the 3GPP LTE-Advanced systems with relay are studied. The discussions of the relay tech- niques in the 3GPP radio access network (RAN) group are summarized. Based on the analysis of the 3GPP LTE-Advanced systems with relay, several radio re-source allocation algorithms are proposed. System-level simulation platforms are built up to verify the effectiveness of the proposed algorithms.