Rate allocation in massive multiple access combining successive decoding with error control

Abstract

The Gaussian multiple access channel under asymptotically many code-division-multiple-access users and successive interference cancellation (SIC) is investigated in this work. Users transmit n-symbol packets and select their encoding rate as a function of their perfectly known channel gains. We address a theoretical study whereby the performance of employed encoding schemes is described by achievable second-order coding rates at blocklength n. Our contribution is twofold. Firstly, we formulate and solve an optimal control problem to maximize the asymptotic user-aggregate spectral efficiency (SE) for a one-iteration SIC. Secondly, we analyze the user-limit behavior of two-iteration SIC and propose a complexity-affordable vector optimization to maximize the user-aggregate SE. Reported results quantify the benefit of adopting a two-iteration SIC versus the blocklength.