Hybrid Active and Passive Antenna Selection for Backscatter-Assisted MISO Systems

Abstract

In this article, we propose and investigate hybrid active and passive antenna selection for backscatter-assisted multiple input and single output (MISO) systems. Specifically, each transmit antenna is allowed to work on either the active radio (AR) mode or the passive radio (PR) mode, which are respectively powered by the battery as in traditional communication and the external power source as in the backscatter communication (BackCom). The advantage is that the link reliability can be enhanced, and the power consumption can be opportunistically reduced by switching between the AR and the PR modes. Adaptive antenna selection is investigated and analyzed, where the antenna is selected over all combinations of antennas and their working modes. However, the antenna with the best channel quality will always be chosen. In order to circumvent this problem, two alternative schemes, referred to as reactive antenna selection and proactive antenna selection, are considered, where all antennas take turns to transmit/backscatter the signal. Specifically, in the reactive antenna selection scheme, the working mode for each antenna is determined by choosing the maximum value of the transmit power in the AR mode and the backscatter power in the PR mode. The working mode for the proactive antenna selection scheme is, however, chosen beforehand. Since the exact closed-form expression for the average symbol error rate (SER) is not attainable, approximations and their asymptotic performance are derived for proposed schemes. The power consumption is also analyzed. Simulation results demonstrate the correctness and the tightness of our analysis, and the effectiveness of proposed schemes.