Beyond digital interference cancellation Joint RF-baseband interference cancellation to reduce receiver complexity and power consumption

Joint RF-baseband interference cancellation to reduce receiver complexity and power consumption. Summary One of the major drawbacks towards the realization of MIMO and multi-sensor wireless communication systems is that multiple antennas at the receiver each have their own separate radio frequency (RF) front ends and analog to digital converter (ADC) units, leading to increased circuit size and power consumption. Improvements in RF and ADC technology happen at a much slower pace when compared to digital circuits, so that this problem is likely to be more critical in future. In a dense multiuser wireless communication setup, these multiple RF front ends and ADCs spend most of their power in processing signals from interfering users. The purpose of this research is to look at alternative mobile receiver archi-tectures, from the joint perspective of a digital signal processing engineer as well as that of an RF designer. We start by specifying the need for a communion of RF and DSP techniques. We propose that advanced signal processing algorithms can be used in combination with existing circuit configurations, such as integrated phased arrays and multi-channel feedback ADCs, to perform analog interference cancellation. Interference cancellation allows for a reduced number of receiver chains and low resolution ADCs, hence reduced circuit size and power consumption. In summary, the research addresses the following questions: 1. Can we potentially reduce the cost and power dissipation of MIMO trans-ceivers, by optimization across the RF-baseband borderline? 2. Can we design a flexible baseband platform that is tailored to low power circuits, demonstrating a potential for low cost in a dense multiuser setup? One approach to cancel interference in RF and to reduce the number of receiver chains in antenna array systems is to design RF phase shift combiners. An alternative is to integrate existing ADCs with a feedback beamformer (this setup i SUMMARY ii is especially compatible with Sigma-Delta ADCs) to identify and cancel the in-terferer. Interference cancellation in the RF and in the mixed signal components of the receiver allows ADC units to represent the desired user more effectively for a fixed precision. For both the above mentioned architectures, we consider the hardware limitations and propose closed form solutions minimizing the overall mean squared distortion between the transmitted signals and its received estimate, and illustrate significant power savings in the receiver. In both the cases we also specify approximate solutions, when the closed form solutions are not feasible. Given …