Measurements and models of radio frequency impulsive noise for indoor wireless communications

Abstract

Absfracf-This paper presents the results of average and impulsive noise measurements inside several office buildings and retail stores. The noise measurement system operated at 918 MHz, 2.44 GHz, and 4 GHz with a nominal 40 MHz 3 dB RF bandwidth. Omnidirectional and directional antennas were used to investigate the characteristics and sources of RF noise in indoor channels. Statistical analyses of the measurements are presented in the form of peak amplitude probability distributions, pulse duration distributions, and interarrival time distributions. Simple first-order mathematical models for these statistical characterizations are also presented. These analyses indicate that photocopiers, printers (both line printers and cash register receipt printers), elevators, and microwave ovens are significant sources of impulsive noise in office and retail environments.

Adaptive classification of interfering signals in a shared radio frequency environment

“…Measurements of impulsive noise due to photocopiers have been studied, and some limited information is available. The following are some observations we made from [6], [7]: * Impulsive noise inside buildings is very wide band, and pulse durations observed 38 are directly a function of the receiver bandwidth.…”

“…As for pulse duration, since the observation made in [7] used a bandpass filter with bandwidth 30 MHz, we need to estimate the pulse duration for bandwidths other than 30 MHz, which is done by assuming that the time-bandwidth product is constant (as we discussed in Section 5.1). Pulse duration statistic for the photocopier emissions in the 2.44 GHz band, using a bandpass filter with bandwidth 30 MHz, had a mean value of 143 ns, and we assume, for convenience, that the pulse durations are also exponentially distributed.…”

“…We would like the~tool to have the capability of correctly classifying the observed signal if the signal has been previously encountered by the tool, and the capability of 7 adaptive learning if the signal is new. We therefore conclude that the diagnostic tool should have two operating modes -the Learn7ing mode and the Diagnostic mode.…”

“…and that W << f. 7 We define the Fourier Transform of 2(t) as X(f) = fo x(t)e-i2ftdt and the Inverse Fourier…”

“…PhotoPulse takes the standard arguments L and bw, and the arguments z (the number of samples by which the pulse is delayed; corresponds to Tk) and theta (the phase offset O, of the first pulse). Since we have assumed that Ak is Gaussian, using the values of 12.7 dB, and 3.9 dB for the mean amplitude and standard deviation observed in [7] for photocopier emissions in the 2.44 GHz band, we generate a random variable with distribution N(1, .36) to represent Ak (this was done by converting the values 12.7 dB and 3.9 dB to a linear scale, and normalizing the mean to 1). Proposition 2.2 prescribed a :(t -Tk) in the form of response of a lowpass filter to a delayed ideal impulse, due to the assumptions made through Lemma 2.1.…”