Channel (broadcasting)

MIMO

Block (permutation group theory)

Computer network

Mathematics

Wireless

Algorithm

Random access

Statistics

Channel state information

Additive white Gaussian noise

Geometry

Polar code

Coherence (philosophical gambling strategy)

Computer science

Rayleigh fading

Theoretical computer science

Fading

Decoding methods

Transmission (telecommunications)

Telecommunications

In this work we treat the unsourced random access problem on a Rayleigh block-fading AWGN channel with multiple receive antennas. Specifically, we consider the slowly fading scenario where the coherence block-length is large compared to the number of active users and the message can be transmitted in one coherence block. Unsourced random access refers to a form of grant-free random access where users are considered to be a-priori indistinguishable and the receiver recovers a list of transmitted messages up to permutation. In this work we show that, when the coherence block length is large enough, a conventional approach based on the transmission of non-orthogonal pilot sequences with subsequent channel estimation and Maximum-Ratio-Combining (MRC) provides a simple energy-efficient solution whose performance can be well approximated in closed form. For the finite block-length simulations we use a randomly sub-sampled DFT matrix as pilot matrix, a low-complexity approximate message passing algorithm for activity detection and a state-of-the-art polar code with a successive-cancellation-list decoder as single-user error correction code. These simulations prove the scalability of the presented approach and the quality of the analysis.

Pilot-Based Unsourced Random Access with a Massive MIMO Receiver in the Quasi-Static Fading Regime