Effects of downlink intercell interference on MC-CDMA system performance

A multi-carrier code division multiple access (MC-CDMA) scheme is used in a multi-cellular environment in order to reduce the interference present in typical mobile systems. The conventional approach to limit the interference of the users in adjacent cells is frequency reuse (FR). In this paper, a new scheme-code reuse (CR)-is proposed in order to achieve a higher order of diversity. In this method, all the cells in the cluster use the total number of available carriers to transmit the users data signal. The distinction of the data signal of different users is made by using orthogonal Walsh-Hadamard codes for each user. A comparison between the frequency reuse and code reuse schemes is done as a function of the environment path loss, number of carriers, frequency gap between adjacent carriers, number of users and cluster size. The results obtained for a cluster size equal to four show that, increasing the number of carriers and the frequency gap between adjacent channels the performance of both schemes improve. When the number of carriers is increased, the best improvement is achieved for the CR scheme, while for the frequency gap increase it is the FR scheme that improves the most. When a cluster size equal to seven is considered, CR achieves a better performance than FR, since in this case, the co-channel interference is clearly reduced due to the larger distance between cells using the same codes