Suppression of multiple interferences for superposed multicarrier transmission

Superposed multicarrier transmission is proposed as one of the schemes that improve frequency utilization efficiency. In this scheme some wireless systems share the same spectrum, and interference suppression is necessary. One conventional scheme for the interference suppression applies the EM (Expectation Maximization) algorithm for the estimation of interference parameters, and another scheme iterates the estimation of the parameters based on undesired signal power. However, these schemes assume the same average power for all interferences, which makes accuracy of the estimated power decrease and results in degradation of BER (Bit Error Rate) when the average power of each interference is not same. In this paper, we propose a suppression schemes for multiple interferences with different average power levels. In our scheme, undesired signal power is averaged in both the time and the frequency domain, after which it is compared to threshold to determine if the corresponding subcarrier is superposed or not. According to the result of this comparison, the power of each interference is estimated. Furthermore, the threshold is iteratively recalculated when the estimated parameters are updated. Through simulations we show that the proposed scheme taking the different average power of interference into account shows better BER performance than that of conventional ones assuming the same average power of interference. In addition, we show that averaging undesired signal power in both the time and the frequency domain and iterative calculation of threshold lead to improvement of the accuracy of superposed band detection.