Abstract
In this article we propose a space-time processing strategy for combined equalization and (co-channel) interference cancellation in mobile communications. The principle of this strategy is to decouple interference cancellation and signal equalization in two processing stages. The so-called decoupled space-time (D-ST) processing strategy consists of employing an antenna arrav or a space-time filter to cancel the co-channel interfer~r signals in the space domain or in the space-time domain and an equalizer to perform intersymbol interference suppression in the time domain. This is achieved by optimizing the effective channel impulse response of the user of interest in such a way that the signal-to-interference-plus-noise ratio (SINR) at the input of the equalizer is maximized. In this contribution the optimization criteria for the D-ST strategy are presented and optimum receiver settings are derived. The bit-error-rate (BER) performance of adaptive D-ST processing structures is evaluated by means of link-level simulations under the COST 259 channel model. The results show superior performance of the D-ST receiver structures as compared to conventional approaches.
Highlights
Current mobile communication systems have an increasing demand for user capacity and improved spectral efficiency
Observe that the UNIT-NORM CONSTRAINT (UNC) approximates the ST-minimum mean square error (MMSE) at low SNRs while at higher SNRs, the UNIT-TAP CONSTRAINT (UTC) and UNC exhibit similar performance
Reducing the number of sensors to 2, the output signal-to-interference-plus-noise ratio (SINR) for both decoupled space-time (D-ST) strategies still have a linear increase with the input SINR, while the ST-MMSE exhibits a floor aroundS dB
Summary
Current mobile communication systems have an increasing demand for user capacity and improved spectral efficiency. The TE can follow either an MMSE or an MLSE criterion in order to suppress residual lSI at the output of the array, Simultaneous CCI and lSI mitigation can be achieved with a linear space-time filter (STF), where a tap-delay-line filter is employed at each branch of the AA [4, 7J(Fig. 2). The selection of a given space-time processing algorithm or receiver configuration will depend on whether the propagation channel is more CCI- or lSI-limited [3]. In rich multi path scenarios with strong CCI signals and lSI the performance of space-time processing receivers can be severely degraded. The second stage consists of a non-linear TE that makes use of the ECIR to equalize the lSI channel of the desired user without noise enhancement.
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