Capacity Analysis of Frequency Shift Based Backscatter Communication System

Abstract

Ambient backscatter is a new communication technology that enables connectivity between battery-free devices and off the shelf devices. To cancel self-interference from the wireless carrier signal without specific hardware, backscatter systems usually adopt to shift the carrier signal to another frequency band and keep the backscattered signals away from primary carrier signal. In this paper, we analyze the effect of frequency shift size on system capacity. We also build prototype backscatter system, consisting of a FPGA facilitated backscatter tag and WARP board as the transmitter. We conduct experiments with various frequency shift step sizes, and measure the PER of the tag under different experimental conditions. It is found that at most two concurrent tags can be supported in the 802.11b based backscatter communication systems when the carrier signal occupied one channel.