Effects of detection threshold and frame size on duty cycle in GSM bands

Explosion in the demand for mobile applications and services necessitates the efficient utilization of the limited radio spectrum. Determination of a suitable detection threshold is an important aspect of spectrum occupancy measurement. Inappropriate choice of the threshold value may either increase the probability of false alarm or failure detection. However, the most appropriate threshold value is not yet clearly stated, though, the International Telecommunication Union (ITU) has provided a benchmark of 10 dB above the noise level as an acceptable threshold value. In this paper, the effects of energy detection threshold techniques on duty cycle in the GSM bands are examined. Spectrum measurements were conducted in the GSM 900 and 1800 MHz bands in Ilorin, Nigeria to cover a bandwidth of 105 MHz. Experimental results based on analytical method of determining noise level (theoretical) and those obtained based on actual measurements of the noise floor (measured) were analyzed. Findings indicated that the MaxNoise overestimates the occupancy values across all bands while the ITU 10 dB was found to be too conservative. Therefore, for optimum prediction, 5 dB above the measured average noise level should be considered as detection threshold. Furthermore, it was found that the number of frames of the sensing data do not have significant effect on the duty cycle.