Capacity of Backscatter Communication Systems With Tag Selection

In backscatter communication (BackCom) systems, the system performance is susceptible to the double fading channels. In this paper, we investigate the capacity performance of BackCom systems via multiple tags, where the tag corresponding to the maximum signal-to-noise ratio (SNR) is selected to combat the double fading. Although the exact ergodic capacity does not admit a closed-form expression, we derive its approximation by exploiting the extreme value theory, which shows that the capacity scales as <inline-formula><tex-math notation="LaTeX">$\log \log N$</tex-math></inline-formula> with <inline-formula><tex-math notation="LaTeX">$N$</tex-math></inline-formula> denoting the number of tags. Simulation results confirm the tightness of the approximate ergodic capacity, and the correctness of the capacity scaling law.