| In most digital communication systems the modulated signal is transmitted through impaired channels. The channel impairments include additive white gaussian noise (AWGN), multipath, and fading. The impaired channels are modeled by their impulse responses. Several mathematical models that characterize the time varying behavior of the channel have been developed. Multipath is the process whereby a signal arrives at the receiver via different propagation paths at different delays. Signal fading occurs because the components usually have different carrier phase offsets, which causes the transmitted signals to destructively add. The delay of the reflected paths is known as delay spread, and is measured in nanoseconds. This delay spread can introduce inter-symbol interference (ISI) at the receiver. ISI is introduced if the symbol period is shorter than the delay spread of the channel. A multipath channel model will be presented in this paper. The model is statistically verified using a Simulink/Matlab platform. The model is applied to a wireless local area networks channel for IEEE 802.11, IEEE 802.11a, and IEEE 802.11b applications. The transceiver for each of these WLAN applications are modeled. The effect of delay spread for these transceiver waveforms using the multipath channel model will be presented. Bit error rate curves for IEEE 802.11, IEEE 802.11a, and IEEE 802.11b for various delay spreads will be presented. |
