| With the rapid development and the widely application of wireless communication, the desire for users to largely improve the transmission rate of wireless communication is getting much stronger than ever before. Multiple Input and Multiple Output (MIMO) technology can break through the traditional capacity limits of wireless communication systems. The spectrum efficiency can be greatly improved by setting multiple antennas without increasing the required bandwidth and transmitting power. However, it is not easy to design multiple antennas in a user equipment (UE), which limits its application in the uplink transmission, In the virtual MIMO (VMIMO) concept, multiple single-antenna UEs can be grouped together to transmit signals at the same time/frequency resources to improve the uplink system capacity. Therefore, it attracts the most attention. By allocating each user one or a group of subcarriers to realize multiple access scheme, Orthogonal Frequency Division Multiple Access (OFDMA) is the most effective way to realize multiuser multiplexing and access in Orthogonal Frequency Division Multiplexing (OFDM) systems. The combination of the advantages of VMIMO and OFDMA technique is suitable for the high data rate transmission for the next wireless communication systems.Future communication networks not only provide greater system capacity, but also ensure the needs of high-speed and wide coverage. The introduction of relay station (RS) technology to the current cellular system, can improve the cell-edge users'QoS, reduce the network investment and operation cost. And it also plays an important role in enhancing the system coverage. Therefore, the objective of this thesis is to investigate the user pairing scheduling algorithms for VMIMO system, and consider its extending applications in multi-hop relay networks.In this thesis, the principles of VMIMO-OFDMA are introduced firstly, and then the methods to research radio resource management, especially the user pairing algorithms are investigated in details. The simulation platform for VMIMO-OFDMA system is built up. Then several typical user pairing algorithms in single-hop, such as random pairing algorithm, orthogonal pairing algorithm, determinant pairing algorithm and adjustable determinant pairing algorithm are investigated and simulated to compare the algorithms'performance. Considering the traditional pairing algorithms which can't achieve the tradeoff between paired users'near far effect and system throughput, we propose a novel pairing scheduling scheme based on the SNR threshold combined with the proportional fair scheduling scheme. Simulation results show that the proposed scheme improves the system capacity without reducing the QoS for the users at the cell's edge. Meanwhile, it also reduces the interference of the adjacent cells and system lose rate. Therefore, it is suitable for the real system applications.Secondly, due to the user which has lower SNR (such as the user at the cell's edge) can't achieve high throughput, in this thesis, by analyzing the existed pairing algorithms, we consider the determinant pairing scheme for the relay system, and propose a cooperative relay pairing algorithm. Simulation results show that our algorithm can provide higher throughput for the user at the cell's edge compared to the traditional pairing algorithms and it also reduce the interference of the adjacent cells and gain more uplink system capacity. |
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