Abstract-The performance of OFDM systems over a multipath channel can strongly degrade due to the propagation delay spread. The distortion of the received signal over the FFT window, is referred to as multipath noise. This work aims to determine analytically the performance loss due to multipath noise as a function of OFDM and channel parameters for narrowband OFDM systems. First, it is investigated whether it is possible to describe the multipath noise, varying over different OFDM packets due to the temporal variation of the channel, by an effective noise factor F delay , from which the loss factor is directly determined. Secondly, the theory of room electromagnetics is applied to develop a closed-form expression for F delay as a function of the OFDM and reverberation parameters. This analytical method is validated with excellent agreement. Finally, the loss factor is determined for IEEE 802.11 based on channel measurements in 2 large conference rooms, providing values up to 19 dB for an 800 ns cyclic prefix length.

In this paper, a path loss (PL) model for IEEE 802.11n in large conference rooms is proposed. The PL can be described accurately by a one-slope model with PL exponents varying from 1.2 to 1.7. The influence of humans (during a meeting) on the PL model is investigated. It was found that the PL exponent increases towards 2 in the presence of humans. Further, the effect of frequency (2.4/5 GHz), antenna configuration (SISO vs MIMO 2×2), bandwidth (20 vs 40 MHz) and transmit power on the required number of access points for wireless conferencing, total radiated power consumption and maximum throughput is investigated. This is done by link budget calculation, based on our proposed PL model as well as the IEEE 802.11 TGn channel model. In this evaluation, it was found that the two PL models predict some essentially different effects concerning throughput and radiated power.

Abstract-In this paper, a path loss (PL) model for 802.11n in large conference rooms is determined, based on PL measurements. The PL can be described accurately by a one-slope model with one standard deviation. PL exponents varying from 1.2 to 1.7 are found. Based on this PL model, the effect of frequency (2.4 vs 5 GHz), configuration (SISO vs MIMO (spatial diversity)), bandwidth (20 vs 40 MHz) and transmit power on number of access points, total power consumption and possible (physical) throughputs is investigated. According to the determined PL model, a higher range (by tuning the transmit power) requires less access points, as well as a lower total power consumption, due to a PL exponent lower than 2.

Abstract-The performance loss of 802.11 OFDM systems due to propagation delay spread has been analyzed as a function of OFDM parameters for a wide range of reverberation times. This analysis gives physical insight and solutions for the OFDM design to suppress the performance degradation.