A Frequency Diversity Technique for Interference Mitigation in Coexisting Bluetooth and WLAN

Co-channel interference has become an important problem with the increasing deployment of wireless networks in the unlicensed frequency band. Most existing schemes aim to avoid collisions on Bluetooth devices by modifying their hop sequences in the presence of WLAN interference. We propose a frequency diversity technique for Bluetooth, namely dual channel transmission (DCT), which reduces packet error rate (PER) due to co-channel interference when multiple bluetooth piconets coexist with or without WLAN interference. The idea of DCT is to transmit the same packet on two distinct frequency hopped channels simultaneously and the power used in each channel is half of what would be used in single channel transmission (SCT). Since a packet is successfully received if at least one channel survives, the PER is reduced when multiple bluetooth piconets coexist. Meanwhile, the two channels of DCT are separated by at least 22 MHz so that bluetooth is also robust to WLAN interference. Theoretic analysis and numerical simulations show that PER for bluetooth with DCT is significantly lower than that with SCT, when a small number of piconets coexist in the presence of WLAN interference. Comparisons to other collision avoidance mechanisms also demonstrate the effectiveness of DCT.