A combination of soft and hard partial parallel interference cancellations (SHPPIC) for a multistage multiuser detector with amplitude and phase estimation is introduced in this paper. This scheme is appropriate for a digital video broadcasting-return channel via satellite (DVB-RCS) communication system when used together with the evolutionary satellite communication scheme that uses a combination of TDMA and CDMA (slotted CDMA). The outputs of the first stages are more deteriorated by multiple access interference (MAI) than by the thermal noise. This makes amplitude and phase estimation impractical in the first stages. Therefore, soft interference cancellation (IC) is used in the earlier stages since soft IC does not require the knowledge of the channel parameters. Once the performance of the soft multistage multiuser detector becomes more reliable (roughly equivalent to the performance of the decorrelator detector), the amplitude and phase of each user are estimated. Having these parameters estimated, the subsequent stages would be in the form of hard IC. The complexity of such a detector is linearly increased with the number of users. Also, a multistage hybrid interference cancellation (HIC) method for near-far conditions when the signals arrive at the receiver with different power levels, is presented.
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