Research On Danamic Resource Allocation In MC-CDMA System

With the growing demand for high-speed wireless data services, the data rate of the next generation mobile communication system will be increased to a great extent.Multi-Carrier CDMA (MC-CDMA) has drawn significant interest as a major candidate for next generations of high data rate mobile networks. MC-CDMA is a multi-carrier transmission technique that might be viewed as a combined OFDM/CDMA communication system. Accordingly, MC-CDMA benefits from advantages of both technologies.The thesis mainly focuses on the dynamic carrier allocaiton and adaptive bit and power allcotion for MC-CDMA system.First, in accordance with its own characteristics and applicability of MC-CDMA systems, this paper migrates three algorithms and presents two new dynamic carrier allocation algorithms of low complexity, which try to maximize the capacity of the system under certain transmission power, compared with the (optimal) brute-force search algorithm, the complexity of these five algorithms are greatly reduced. But the performance of these five algorithms are close to the optimum, which are much higher than the traditional random assignment algorithm. The descending order of these algorithms according to performance are:ASA, GGSA, ESA, EUSA, SESA.Then, a new criteria with multi-user interference consideration are proposed and combined with above carrier allocation algorithms. The system performance has improved due to multi-user interference consideration. Influences of four different detection and combination methods on systems that based on the new criteria are also simualted and analysized.Finally, adapting the Chow's algorithm from OFDM systems to CDMA systems, this paper presents an adaptive bit and power allocation algorithm. The optimization objective is to maximize the margin under certain data rate and transmitting power. Simulation results show that the algorithm performance is much better than traditional fixed bit allocation algorithm. Furthermore, simulation results show that the performance of the adaptive modulation system using smaller spreading factors is better than that using bigger spreading factors.