Adaptive Modulation And Resource Allocation For MC-CDMA

MC-CDMA is one of the key technologies in the fourth generation. It units OFDM and CDMA together and potentially offers the advantages of both technologies. It shows the advantages in well adaptive flexibility,high bandwidth efficiency,strong ability in resisting code-interference and frequency-slective fading,high capability of the system,and so on.MC-CDMA can convert the frequency- selective-fading channel propagation of the broadband to flat channel of the subcarriers, the subcarriers can be adaptively loaded according to their states. This would improve the performance. So the the adaptive modulation and resource allocation is investigated in this paper.Firstly ,the fundamental principle of OFDM and CDMA is introduced in this paper and the three combine methods of the two are introduced following. By comparing the three methods with each other, we find that MC-CDMA offers more advantages. And then the the channel of OFDM and MC-CDMA is annalyzed according to the channel model of the radio communication. The channels of MC-CDMA and OFDM can be described as parallel Gauss channels, so the theory of adaptive technology can be found.Secondly, the downlink of MC-CDMA is established in the MATLAB environment. The greedy algorithm is analyzed and simulated base on the concept of the equivalent sub-carrier. The greedy algorithm is optimized in this paper following, as the all bits would be assigned is distributed to the every sub-channel averagely, and then adjust the bit number of each sub-chnnel according to their states. Then, the two methods are compared with each other by simulation.Lastly, the realization of assigning resource adaptively in the MC-CDMA system is analyzed. The ACG/RCG algorithm of the OFDM can assign the sub-carriers adaptively and improve the performance. How to realize the two algorithms in the MC-CDMA system is investigated in this paper. Then simulate the two algorithms in MATLAB environment.