Radio Resource Management And Optimization In Wireless Cooperative Networks

Through the collaboration of multiple hops and/or points, cooperative communication technology is able to make full use of the radio resource in the system and improve the spectral efficiency. However, because the new elements and communication mechanisms are introduced in, radio resource is far beyond the concept of the time and frequency domains. So this dissertation discussed the radio Resource Management and Optimization in Wireless Cooperative Networks.First, the feasibility of multi-hop transmission should be verified. This dissertation researched the relay deployment in wide area, Manhattan area and indoor area respectively, and the position, number, power and work mode of relay nodes in indoor environment are focused on. A mathematical model is designed for indoor area, where parameters are adaptive for practical systems. Moreover, a3-step method to research the deployment in indoor scenario is presented. The packet delay in relay-aided systems is also analyzed. According to the theoretical derivation and numerical results, it is believed that the relay networks are able to guarantee the QoS of real-time services through effective radio resource management mechanisms and functions in MAC layer.Second, this dissertation studied the interference model in type I relay based OFDM networks. It is found that SINR in the access links of most relay users are constrained by interference from eNBs, while for about8%direct UEs the major interference is from relay nodes. Therefore, a novel intra-cell frequency planning scheme based on interference coordination is exploited for cellular OFDM-Relay systems. A factor R, is introduced to model the interference in the2nd slot. According to R, and SINR the scheduler groups all the users into three sets. Furthermore, the total spectrum in the2nd slot is divided into three parts based on the size of user sets, so that the frequency recourses in access links are reused properly. The proposed method was evaluated in WINNER and LTE-A scenarios. Simulation results show that the proposed method enhances the system performance in terms of both system capacity and cell edge users’SINR with low overheads and computational complexity.Third, heterogeneous services in MIMO-Relay systems are investigated, and a utility based adaptive scheduling algorithm is proposed, which aims to maximize the user satisfaction as well as system spectral efficiency. Two factors ratio and w are introduced in order to differentiate QoS and users. A heterogeneous services spatial subchannel scheduling strategy is derived to decide the optimal bits of proper services loaded in spatial subchannels (according to Theorem4-1and Criterion4-1). A multiuser carrier scheduling algorithm is designed to allocate carriers to users (according to Theorem4-2and Algorithm4-1). Moreover, a suboptimal solution is also presented for the sake of decreasing computational complexity and processing delay. Simulation results show that the proposed strategy can guarantee QoS of multiple services with a tolerable decline in terms of spectral efficiency compared with traditional maximum carrier/interference (MCI) algorithm. Besides, the complexity can be reduced obviously by utilizing the suboptimal scheme, which achieves nearly the same performance compared with the optimal solution.Fourth, a joint cooperative set selection and resource allocation algorithm is exploited for single user (SU)-CoMP transmission. In the approach, the problem is divided into2separate decisions for the candidate cells and serving cell respectively. The processing unit (PU) decides "whether and which CoMP request should be answered" and "the resource allocation for the potential co-channel UE " according to the load of candidate cells and the throughput of cell edge UEs through the Algorithm5-1. In this way, the potential CoMP collision from different cells will be solved. Moreover, the probability that cells with light load approve CoMP requests is increaseed and therefore the load in the system is balanced. Simulation results show that both the system capacity and communication quality of cell edge users are enhanced. In the selection of transmission set and pairing users for multi user (MU)-CoMP scenarios, the concept "candidate pairing user set" is proposed to narrow the range of UEs who need to measure and feedback Hil. Based on the ability of different cells, a centralized and a distributed processing method and two algorithms are provided to calculate candidate paring user set. Besides, an extended approach called Cell-based is designed to further decrease the overheads. Simulation results show that the proposed schemes are able to improve both the cell average and the cell edge spectrum efficiency and achieve the similar performance compared with the full-CSI based one, while the overheads in both the backhaul and the air interface are decreased a lot.Fifth, a CoMP transmission mode management strategy based on semi-static user grouping is studied. After the analysis of the performance and calculating complexity of different transmission modes, it is decided to limit the mode management within user groups. The serving cells determine the transmission mode according to the statistical channel information feedback. Besides, the corresponding feedback mechanisms for cell edge UE and pairing UE are designed. The cell edge UE needs to feedback instant channel information of the links between it and the cells in its measurement set. As for the pairing UE, only in coherent-MU-joint transmission mode, the instant channel information of the link between it and the cell launching the CoMP request is needed; otherwise, the statistical channel information is enough. According to the simulation, it is proved that the proposed scheme is able to improve the system performance in terms of both the cell average spectral efficiency and the transmission quality of cell edge users while the users’feedback and the numbers of involved cells and users are cut down.Finally, the conclusion is presented in the end of this dissertation.