Interference cancellation techniques for low power wireless sensors

Abstract

Non-coherent on-off keying (OOK) receivers are preferred in ultra low power (ULP) wireless devices as they consume less power when compared to receivers based on other modulation schemes. However, these devices are highly susceptible to co-channel interference (CCI). Therefore, interference cancellation (IC) techniques for ULP non-coherent OOK receivers are investigated in this thesis. Various IC techniques are discussed in literature. However, the non-coherent OOK receiver architecture calls for the design of new low complexity IC techniques. The main constraint of the system is imposed by the analog front end that uses a simple square law detector to down-convert the RF signals to baseband and there is also only single radio frequency (RF) chain. The challenge is to mitigate CCI under these constraints and improve the detection performance. The non-coherent detection of OOK signals requires the knowledge of the signal to noise ratio (SNR) of the incoming signal. Therefore, SNR estimation plays an important role in non-coherent OOK receivers. Thus the scope of this thesis is twofold. Firstly, the SNR estimation and non-coherent detection techniques are proposed for OOK signals. Secondly, the interference mitigation techniques are proposed for the case of continuous wave (CW) CCI and OOK modulated interferers. The problems of the proposed techniques for the case of M-ary phase shift keying (MPSK) modulated interferers are also investigated. Finally, the implementation of the SNR estimation techniques on real time hardware platform is discussed.