Research On Key Techniques Of Radio Resource Management In Distributed Antennas

Distributed antenna technology can enhance dramatically spectrum efficiency of wireless communication systems and be viewed as a remarkable feature of the fourth generation mobile communication system. Radio resource management (RRM) plays a vital role in distributed antenna system (DAS) and directly affects the performance of the system.Due to distributed antennas, the traditional base-station-centered cell is replaced with the user-centered virtual cell (VC) and the space/antenna resource allocation problem is introduced. It makes the OFDM resource allocation problem more complex. Therefore, some RRM techniques based on distributed antenna, including antenna selection, admission control and OFDM resource allocation, are explored in this dissertation.First, an antenna dynamic selection algorithm is proposed based on the transmit power minimization for the uplink in CDMA distributed antenna system. By making a tradeoff between received bit signal-to-interference plus noise ratio and complexity of receiver, we select dynamically the antennas in VC so that the average transmit power of mobile terminals could be minimized under guaranteeing quality of service of users.Second, we provide an admission control algorithm based on interference power estimation for the uplink in TDD-CDMA distributed antenna system. Using interference power estimation method in CDMA system, we derive the uplink load factor based on distributed antennas and establish a mathematical model to estimate the interference power. Then the admission control algorithm is based on this model.Next, a resource allocation algorithm is presented based on graph theory method for the downlink in multi-user OFDM distributed antenna system. According to the optimal resource allocation strategy in the single cell OFDM cellular system, we construct a directed graph and transform the resource allocation problem into a linear optimal distribution problem in network flows. Then the resource allocation algorithm is given to maximize system rate capacity under guaranteeing the minimum number of subcarriers for each user.Finally, resource allocation algorithms are proposed based on shared criterion for the downlink in multi-user OFDM distributed antenna system. In the first algorithm, each subcarrier may be allocated to multiple users through different distributed antenna. Then, by imposing limitation on rate deterioration due to co-channel interference, we improve this algorithm so as to make a tradeoff between the rate capacity and user fairness.In this dissertation, we provide some methods for the research on RRM based on distributed antennas and make a supplement to the existing RRM algorithms. The proposed algorithms are of some values to theory and practice.