On the Applicability of Average Channel Capacity in Log-Normal Fading Environment

The statistical characterization of channel capacity in slow fading environment modeled by log-normal probability density function is considered. The probability density function of channel capacity is found to be positively skewed and significantly departs from bell shaped curve for higher values of σ _dB . The computation of first two moments of channel capacity provides a measure for relative fluctuation in terms of coefficient of variation (CV). It is noted that the value of CV is quite high in lower range of SNR and starts declining with increasing SNR. This may question the applicability of average channel capacity as a performance measure in slow fading scenario and accordingly a more appropriate measure is based on outage capacity. A simple procedure based on three-point estimate is outlined to obtain the approximate expression for higher order moments of channel capacity and they are found to be in excellent agreement with exact results.