Unsourced Random Access with Hardware Impairments

We consider unsourced random access for which the base station is equipped with a massive number of antennas and there are residual hardware impairments at both the base station and the user equipment. We divide the transmission frame into slots where each user sends a non-orthogonal pilot selected based on part of its message bits followed by its data bits encoded by a polar code. At the receiver side, we first identify the selected pilot sequences by a generalized orthogonal matching pursuit algorithm and estimate the user channels employing a newly developed hardware-impairment aware linear minimum mean-squared error solution. We then perform symbol estimation by maximal ratio combining and data decoding by a single-user polar decoder followed by successive interference cancellation in an iterative fashion. Numerical examples illustrate that hardware impairments degrade the system performance; however, the proposed solution alleviates this loss in terms of both energy efficiency and the number of supported active users.