Statistical Analysis of Modern Communication Signals

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  • Author: Bob Muro

The latest wireless communication formats like DVB, DAB, WiMax, WLAN, and LTE cellular use OFDM modulation with multiple carriers to transmit digital information. OFDM is a multi-carrier modulation scheme with a large dynamic range requirement due to the high crest factor signal. The introduction of this digital transmission technology has made it necessary to deal with peak power levels up to 20 dB above the average value. All of the RF power components must be capable of handling these high voltage peaks to avoid break down, or flash over. The peak power of several interconnected transmitters can reach more than one hundred times the thermal or average power level and RF component selection should not be based solely on these average values. Short voltage spikes that rarely occur are critical when determining the power handling capability of the transmission system components. The crest factor, i.e. the ratio of the peak value to the average or RMS value, must be correctly determined in order to specify these components. Signals with these high peak-to-average ratios should be measured using a statistical approach rather than a single measurement because it is unlikely to capture one of these rare events with a single peak power acquisition.