Space-time processing for interference cancellation and equalization in narrowband digital communications
Abstract
Spatiotemporal processing schemes are presented that effect both equalization and interference cancellation for mobile narrowband digital communications in an urban cellular environment. The proposed schemes hold the greatest promise in terms of the trade-off amongst convergence rate, computational complexity, robustness to model mismatch, and symbol error performance for TDMA systems where the multipath time delay spread is less than the null-to-null mainlobe of the pulse symbol wave-form, as is the case with the IS-136 standard. Sampling at greater than the symbol rate and multiple beam channels are assumed so that equalization may be effected with sample-spaced taps encompassing a time duration roughly equal to the multipath time delay spread. This enables the scheme proposed to better track time-varying multipath channels than conventional equalization schemes employing symbol-spaced taps encompassing the effective time duration of the convolution of the pulse symbol waveform with the RF multipath channel. In addition to tracking the channel taps, the interference canceling beamforming weight vectors can also be tracked in a decision directed manner. Simulations are presented that demonstrate the efficacy of these algorithms. These simulations include a comparison of various equalizers, including decision feedback equalizers and zero forcing type equalizers.
Degree
Ph.D.
Advisors
Zoltowski, Purdue University.
Subject Area
Electrical engineering
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.