Coexistence of WLAN Network With Radar: Detection and Interference Mitigation

Abstract

Coexistence between 802.11 wireless local area network (WLAN) and radars operating in co/adjacent channel scenarios (notably 5GHz) is a problem of considerable importance that requires new innovations. We propose a modified Wi-Fi link design that mitigates the interference from a pulsed search radar such that the WLAN network continues to operate outside the exclusion region. For low density parity check encoding adopted in high throughput WLANs such as 802.11n and.11ac, the modified receiver includes a new interleaver and a log-likelihood ratio (LLR) mapping function to mitigate the impact of radar interference. Two detection approaches are proposed to detect the radar pulse interference to Wi-Fi; time domain cyclic prefix auto-correlation detection and frequency domain data subcarrier based detection. The detection approaches are derived analytically and their performances are evaluated via simulation. We investigate the impact of interleaver length and LLR mapping function parameters via simulations to obtain the desirable frame error rate. Under the known radar pulse arrival at the Wi-Fi receiver, the modified system can significantly mitigate the radar interference for all interference to noise ratio (INR) values by using the frame interleaver. Using the radar pulse detectors in the system, the modified system can mitigate the interference at high and low INRs, while it can partially mitigate the interference in the range of 3<INR<30 dB, especially at higher modulation and coding scheme.