Channel Time-variance for Fixed Wireless Communications: Modeling and Impact

S. Thoen, L. Van der Perre, and M. Engels (Belgium)



In this paper, we propose a new stochastical model for the time-variance of indoor channels. In the classical Jakes’ Doppler spectrum, the receiver (or the transmitter) is assumed to move at a certain speed. However, in some wireless sys tems, such as WLANs, both the transmitter and the receiver are stationary and time-variations are actually due to moving reflectors. A novel stochastical model for this sort of time varying channels is introduced which can be employed to more accurately simulate the performance of fixed wireless commu nication systems. To demonstrate the practical importance of the proposed model and the impact of time variations, both adaptive loading and SDMA for OFDM-based WLAN, de scribed in [1, 2] respectively [3, 4], are used as case-studies. The results show that the actual time-variations to be expected in practical WLANs are 5 times smaller than what is predicted by the classical Jakes’ spectrum.

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