Research On Cooperative Resource Allocation Scheme In Imt-advanced System

MIMO technology can effectively improve the wireless channel capacity and reliability. However, employing MIMO in actual system is difficult due to equipment size, hardware complexity and power cost limitations. To overcome this problem, cooperative diversity was proposed. In cooperative networks, the antennas of both a terminal and its partners form a virtual MIMO system, where the diversity gain is obtained and the transmission performance is improved. In addition, in order to provide the lots of data services and various multimedia multicast services, IMT-Advanced system provides a multi-BS cooperative multicast transmission mode. This mode can improve the SNR of the cell edge users and provide broadcast services over a large coverage area. It can also reduce the power consumption, the signal radiation and the electromagnetic pollution. Moreover, users do not need to handoff to a different frequency band to continue receiving the multicast signals when they enter an adjacent cell area. This paper investigates the unicast resource allocation issue for cooperative relay networks and the multicast resource allocation issue for multi-BS cooperative networks. The main contribution of the paper can be summarized as follows:1) A subcarrier and power allocation scheme for cooperative relay networks is proposed. The optimal solution of the combinable resource allocation has high computational complexity, so this paper proposes a sub-optimal resource allocation scheme. Firstly, a proportional subcarrier allocation strategy under the assumption of equal power distribution is proposed to achieve tradeoff between total throughput and fairness. Secondly, in order to further improve the system performance, a threshold is introduced into subcarrier allocation, where subcarriers and relays with bad performance are prevented from transmitting. Finally, water-filling method is adopted to distribute power to cooperative links in order to fully utilize the limited power. The system performance of the proposed schemes is significantly enhanced. If a suitable threshold is selected in subcarrier allocation, the total throughput can be increased.2) Two resource allocation schemes for cooperative multiuser networks are proposed. Firstly, under the constraint on the total power of BS and relays, an equal capacity increment (ECI) subcarrier allocation strategy is proposed, where each user has an equal capacity increment. The ECI improve the system throughput and achieve a reasonable fairness among the users at the same time. Next, the respective constraint on power of BS and each relay is considered to accord with the actual system. A subcarrier allocation strategy based on relay selection and limited feedback is proposed. The strategy decreases the uplink feedback cost at the expense of a small portion of throughput, and this performance advantage becomes more distinct with more users. Finally, a centralized and a distributed power allocation schemes based on water-filling method are proposed to achieve effective utilization of power.3) A multicast resource allocation scheme with QoS guarantee is proposed for multi-BS cooperative networks. The application of multi-BS cooperative multicast transmission is still restricted by a large number of feedbacks. Therefore, we design a user feedback control algorithm to reduce feedback load. The algorithm determines to which base stations users should report channel state information. Then, in order to achieve reasonable fairness among the multicast groups, a subcarrier allocation scheme with QoS guarantee is proposed according to the limited channel information and the QoS requirement of different multicast services. Finally, each BS distributes its power to each subcarrier by employing a new iterative water-filling power scheme and a fixed power iterative scheme. The proposed methods improve the multicast throughput and user satisfaction, and the fixed power iterative scheme is suitable in practice due to its low complexity.4) A multicast resource allocation scheme based on the layered coding is introduced for multi-BS cooperative networks. Wireless multicast service suffers from the capacity problem since the transmission rate is restricted by the worst users. Therefore, we encode the multicast data into a base layer and an enhancement layer, and propose a multi-layer multicast resource allocation scheme based on limited feedbacks and the enhancement layer users selection. The scheme guarantees the rate of base layer and improves the throughput of enhancement layer. In order to accord with the actual application, an open-loop semi-dynamic resource allocation scheme based on the network topology is proposed. The scheme avoids user feedback and decrease the resource real location frequency. It provides a reference for the practical application of multi-BS cooperative multicast system.