Research On Adaptive Modulation For MC-CDMA System

With the ever-increasing demand for the mobile communication service, the data rate of the next generation mobile communication system will be increased to a great extent. People have been beginning to research the 4G technologies. It is proved that CDMA combining with orthogonal frequency division multiplexing (OFDM), especially the technology called multi-carrier CDMA (MC-CDMA) can improve the integral system performance efficiently. This technology is regarded as the core solution for the 4G mobile communication system. Meanwhile, adaptive modulation technology is also regarded as an important way to improve data transmission rate and transmission quality, which is one of the key technologies for the next generation mobile communication system.As there is little research on adaptive modulation for MC-CDMA system, this thesis proposes two new adaptive bit and power allocation algorithm. These two algorithms are based on greedy allocation algorithm and theoretical allocation algorithm originally used in OFDM system respectively. With the branch subcarrier concept, they can be deployed to MC-CDMA system with either Orthogonal Restoring Combining (ORC) or Minimum Mean Square Error (MMSE) combining at the receiver, which aims to minimize the whole transmit power for a constant data rate and a target BER. Simulation results show that the two algorithm can achieve the same result. By the proposed algorithms, the required transmit power can be saved significantly compared with that of the conventional non-adaptive MC-CDMA system. Furthermore, we also compare the two algorithms with fix bit and adaptive power allocation...