RT Journal Article
T1 Unsourced multiple access with random user activity
A1 Ngo, K. Hoang
A1 Lancho Serrano, Alejandro
A1 Giuseppe, Durisi
A1 Graell I Amat, Alexandre
AB To account for the massive uncoordinated random access scenario, which is relevant for the Internet of Things, Polyanskiy et al. (2017) proposed a novel formulation of the multiple-access problem, commonly referred to as unsourced multiple access, where all users employ a common codebook and the receiver decodes up to a permutation of the messages. In this paper, we extend this seminal work to the case where the number of active users is random and unknown a priori . We define a random-access code accounting for both misdetection (MD) and false alarm (FA), and derive a random-coding achievability bound for the Gaussian multiple access channel. Our bound captures the fundamental trade-off between MD and FA probabilities. It suggests that the lack of knowledge of the number of active users entails a small penalty in energy efficiency when the target MD and FA probabilities are high. However, as the target MD and FA probabilities decrease, the energy efficiency penalty becomes more significant. For example, in a typical IoT scenario with framelength 19200 complex channel uses and 25-300 active users in average, the required energy per bit to achieve both MD and FA probabilities below $10^{-1}$ , predicted by our bound, is only 0.5-;0.7 dB higher than that predicted by the bound in Polyanskiy et al. (2017) for a known number of active users. This gap increases to 3-4 dB when the target MD probability and/or FA probability is below $10^{-3}$ . Taking both MD and FA into account, we use our bound to benchmark the energy efficiency of slotted-ALOHA with multi-packet reception, of a decoder that simply treats interference as noise, and of some recently proposed unsourced multiple access schemes. Numerical results suggest that, when the target MD and FA probabilities are high, it is effective to estimate the number of active users, then treat this estimate as the true value, and use a coding scheme that performs well for the case of known number of active users. However, this approach becomes energy inefficient when the requirements on MD and FA probabilities are stringent.
PB IEEE
SN 0018-9448
YR 2023
FD 2023-07
LK https://hdl.handle.net/10016/38367
UL https://hdl.handle.net/10016/38367
LA eng
NO An earlier version of this paper was presented in part at the IEEE International Symposium on Information Theory (ISIT), Melbourne, VI, Australia, July 2021.
DS e-Archivo
RD 1 jul. 2024