AASERT95: Blind Adaptive Beamforming For Mobile Communications
Abstract
Space-time adaptive processing schemes effecting both equalization and interference cancellation for mobile narrowband digital communications under time-varying multipath conditions were developed. Interference cancellation was effected through the use of an "extended correlator" exploiting past symbol decisions to highly localize in time the contribution due to the desired signal. This facilitated a "dead" time zone during which the spatial correlation matrix of the interference could be estimated and used in an adaptive beamformer. Novel "sample-spaced" equalizer structures were developed based on the Zero-Forcing (ZF) criterion, the Minimum Mean Square Error (MMSE), and the Decision Feedback Equalization (DFE) criterion. For the case where: (1) the delay spread is on the order of T, where 1/T is the symbol rate, as would be the case in voice communications, (2) at least two spatially separated or polarization diverse antennas are available at the receiver, and (3) each baseband antenna output is oversampled sampled by a factor of 3 or 4, we showed that equalization may be effected via either the ZF, MMSE, or DFE criteria via a small set of "sample-spaced" taps encompassing the delay spread which is a fraction of T. This is in contrast to conventional equalization which employs symbol-spaced taps encompassing roughly the duration of the pulse symbol waveform, which is on the order of 10T, for example. As a result, the new "sample-spaced" equalizers have an inherent capability to better track time-varying multipath channels than conventional equalization schemes, as evidenced by extensive computer-based simulations.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 31, 1998
- Accession Number
- ADA360436
Entities
People
- Michael D. Zoltowski
Organizations
- Purdue University