Impact of Ultra-Narrowband Interference on Wi-Fi Links: An Experimental Study

We develop a systematic methodology to experimentally investigate the impact of interference from a non-listen-before-talk ultra-narrowband (UNB) signaling technique on Wi-Fi links. The methodology is based on a worst-case interference scenario, and consists of three investigating steps. This methodology is then applied to a measurement setup to practically study the case of 100 bps UNB signals interfering with an IEEE 802.11n transmission in the 2.4GHz band. Five different Wi-Fi devices are tested. The UNB signal is generated in two modulation schemes, the on-off-keying (OOK) and the Gaussian minimum-shift-keying. Both single and multiple simultaneous UNB interferers are considered. An analysis of the measurement results shows that three of the tested Wi-Fi devices cannot coexist with the considered non-listen-before-talk UNB communication system. The throughput performance analysis of the other tested devices shows that the OOK-modulated UNB signal has the least interfering impact, and the Wi-Fi pilot subcarriers are the most vulnerable to UNB interference. However, if a single UNB interferer avoids these subcarriers and employs the OOK-modulation scheme, then wireless coexistence is possible as long as the signal-to-interference ratio of Wi-Fi to UNB is greater than 30dB, given that a drop to 75% of the maximum Wi-Fi throughput is acceptable.