Luís Jorge Gonçalves

Cognitive Radio Systems Evaluation: Measurement, Modeling, and Emulation Approach

A vertically integrated approach is presented to evaluate the performance of cognitive radio (CR) systems. The approach consists of three pillars: measurement, modeling, and emulation (MME). This integrated approach enables the reproduction of the radio environment in laboratory conditions and aims to guarantee the same performance results as one would obtain in the field. This article provides a detailed explanation for each pillar along with state-of-the-art overviews. Finally, a test bed based on the MME approach is presented.

GSM downlink spectrum occupancy modeling

In this article the spectrum occupancy of a GSM900 and a DCS1800 band as an analog power or binary quantized power is modeled. In the case of analog power it is presented histograms of the power distribution during one working day. In the case of quantized power it presents the two time statistics, the time period of opportunities distribution and the time between opportunities distribution. The measurement setup is standing in line of sight with the base station. Also, the measurement setup in terms of maximum sensitivity is described and analyzed. Spectrum non occupancy, for a working day, in terms of total time for the GSM900 band and for the DCS1800 band is given.

Frequency shift based multiple access interference canceller for DS-CDMA systems

The cyclostationary properties of direct sequence spread spectrum signals are well known. These cyclostationary properties imply a redundancy between frequency components separated by multiples of the symbol rate. We present a multiple access interference canceller that explores this property and applies it to UMTS-TDD. This frequency domain canceller acts on the spread signal in such a way that minimizes the interference and noise at its output (minimum mean squared error criterium). The performance is evaluated in two detector configurations: one including the frequency shift canceller (FSC) and the other plus a parallel interference canceller (PIC). The results are benchmarked against the performance of the conventional RAKE detector and the conventional PIC detector.

Multi-sensor frequency domain multiple access interference canceller for DS-CDMA systems

Direct sequence code division multiple access (DS-CDMA) signals exhibit cyclostationary properties which imply a redundancy between frequency components separated by multiples of the symbol rate. In this paper a multiple access interference canceller (frequency shift canceller) that explores this property is presented. This linear frequency domain canceller operates on the spread signal in such way that the interference and noise at its output is minimized (minimum mean squared error criterion). The frequency shift canceller (FSC) performance was evaluated for a UMTS-TDD scenario and multi-sensor configurations, where the cases of diversity and beamforming were considered. All these configurations are evaluated concatenated with a parallel interference canceller (PIC-2D). The results are benchmarked against the performance of the conventional RAKE-2D detector, the conventional PIC-2D detector and single user scenario, and we observe considerable performance gains with the FSC especially for the diversity case and a performance close to the single user case when it was evaluated jointly with PIC-2D.

Frequency domain equalizer for multirate UMTS-TDD systems

Direct-sequence spread spectrum (DS-SS) signals exhibit cyclostationary properties which imply a redundancy between frequency components separated by multiples of the symbol rate. In this paper we present a multiple access interference canceller that explores this property and applies to UMTS-TDD. This linear frequency domain canceller operates in the spreaded signal in such a way that the interference and noise at its output is minimized (minimum mean squared error criterium). The performance is evaluated in two configurations: one including the frequency shift canceller (FSC) and the other concatenated with parallel interference canceller (PIC). The results are benchmarked against the performance of the conventional RAKE detector and the conventional PIC detector.

Frequency shift based multiple access interference canceller for multirate UMTS-TDD systems

Direct sequence spread spectrum (DS-SS) signals exhibit cyclostationary properties which imply a redundancy between frequency components separated by multiples of the symbol rate. In this paper we present a multiple access interference canceller that explores this property and applies to UMTS-TDD This frequency domain canceller operates in the spreading signal in such way that the interference and noise at its output is minimized (minimum mean squared error criterion). The performance is evaluated in two configurations: one including the frequency shift canceller (FSC) and the other concatenated with the parallel interference canceller (PIC). The results are benchmarked against the performance of the conventional RAKE detector and the conventional PIC detector.