Multi-Element Adaptive Arrays with Tapped Delay Lines for Interference Mitigation in IEEE 802.11G OFDM Systems

In the unlicensed ISM wireless band, signals that use Orthogonal Frequency Division Multiplexing (OFDM) and OFDM with Cyclic Prefix Code (OFDM-CPC) present interference to other wireless users. We analyze the interference these broadband signals cause and contrast the results to that of narrowband interferers. Multi-element adaptive antennas with tapped-delay-lines are used to mitigate multiple interferers. It is shown that the number of delay line taps required to effectively mitigate the effect of multiple interferers increases as the number of interferers and array elements increases. For example, a 3-element array needs only 3 taps per element while a 6-element array needs 9 taps per element for interference mitigation.