Research On Radio Resource Allocation Technology In B3G Mobile Communication Systems

The next generation mobile communication system as the update of the current 2G and 3G mobile communication system can provide reliable and high-speed data transmission while supporting a large number of subscribers and ensuring the fulfillment of quality-of-service (QoS) requirements. Multiple-input multiple-output (MIMO) and orthogonal frequency division multiplexing (OFDM) technologies become research hotspot recently and are known as the most promising physical technologies for B3G/4G broadband wireless mobile communication systems. In this dissertation the radio resource allocation technologies in B3G mobile communication system, which would include OFDMA and SDMA technologies, are discussed.Channel model provides the foundation for radio resource allocation in wireless communication systems. In this dissertation, the propagation characteristics of OFDM/MIMO channels are summarized and OFDM/MIMO channel models are introduced based on the work of pioneer researchers. After discussing the various multiple access mode in OFDM systems, the radio resource management models for OFDMA systems are established and the research mothod, classified into the optimization theory, of radio resource allocation for multiuser OFDM systems are summarized and discussed.Proportional fair algorithm is a popular algorithm to improve system throughput and maintain the user's fairness. In this dissertation, the proportional fair algorithms for OFDMA systems (MPF) are studied and a reduced-complexity MPF scheduling algorithm is proposed assuming equally power distribution among subcarriers. Compared with traditional MPF algorithm, the proposed mothod can gain better system throughput and the result fairness curve is more close to the 3GPP fairness curve.The system should provide various services and different users may have different QoS requirements, which further complicates the problem of resource allocation. Based on multilevel grouping mothod, a radio resource allocation algorithm is researched for OFDMA system, and an adaptive subcarrier allocation, bit loading scheme supporting various services is proposed. The simulation results suggest that the proposed algorithm outperforms the conventional algorithm based on subcarrier swapping.Cochannl interference is the main barrier for frequency planning in OFDMA cellular systems. To effectively reuse the subcarrier and depress cochannel interference, RNC must collect subcarrier information of all cells, which will result in overload signaling and high computational complexity. In this dissertation, the cell-based distributed channel allocation scheme are studied. The proposed scheme, combining channel gain revising and power water-filling, can improve system performance while keep the low signaling overhead.In conventional multiuser MIMO-OFDM system, no more than one user can use the same subcarrier, which would restrict the accommodated user number in system. In this dissertation, an OFDM-SDMA scheme is studied. Considering the user's spatial correlation, the subcarrier and spatial signature can be used simultaneously for multiple access. The proposed scheme can choose a group of nearly orthogonal users by revised Gram-Schmidt process. The simulation results show that the proposed scheme can choose the proper user group to share the same subcarrier and can enhance the admittance capacity.