Blind adaptive joint suppression of MAI and ISI in dispersive CDMA channels

The problem of blind adaptive suppression of both multiple-access interference (MAI) and intersymbol interference (ISI) in a high-rate dispersive CDMA network is considered. The dispersive CDMA channel is first cast within a multiple-input multiple-output (MIMO) model. It is then shown that the linear MMSE receiver can be expressed in terms of the signal subspace components of an augmented received signal, the desired user´s signature waveform and its channel response. The signal subspace components can be adaptively estimated using subspace tracking techniques. Moreover, it is shown that the desired user´s dispersive channel can also be estimated using a constrained adaptive filtering method. The proposed adaptive receiver employs a subspace tracker and a channel estimator, and forms the linear MMSE detector in closed-form based on the estimated subspace components and the channel response.