Two-layer Coded Channel Access with Collision Resolution: Design and Analysis

by   MohammadReza Ebrahimi, et al.

We propose a two-layer coding architecture for communication of multiple users over a shared slotted medium enabling joint collision resolution and decoding. Each user first encodes its information bits with an outer code for reliability, and then transmits these coded bits with possible repetitions over transmission time slots of the access channel. The transmission patterns are dictated by the inner collision-resolution code and collisions with other users' transmissions may occur. We analyze two types of codes for the outer layer: long-blocklength LDPC codes, and short-blocklength algebraic codes. With LDPC codes, a density evolution analysis enables joint optimization of both outer and inner code parameters for maximum throughput. With algebraic codes, we invoke a similar analysis by approximating their average erasure correcting capability while assuming a large number of active transmitters. The proposed low-complexity schemes operate at a significantly smaller gap to capacity than the state of the art. Our schemes apply both to a multiple access scenario where number of users within a frame is known a priori, and to a random access scenario where that number is known only to the decoder. In the latter case, we optimize an outage probability due to the variability in user activity.


page 1

page 2

page 3

page 4


Unsourced Multiuser Sparse Regression Codes achieve the Symmetric MAC Capacity

Unsourced random-access (U-RA) is a type of grant-free random access wit...

Optimal Achievable Rates for Computation With Random Homologous Codes

Building on the framework of nested coset codes by Padakandla and Pradha...

LDPC Coded Multiuser Shaping for the Gaussian Multiple Access Channel

The joint design of input constellation and low-density parity-check (LD...

Minimum Feedback for Collision-Free Scheduling in Massive Random Access

Consider a massive random access scenario in which a small set of k acti...

Enabling LTE RACH Collision Multiplicity Detection via Machine Learning

The collision resolution mechanism in the Random Access Channel (RACH) p...

A Joint PHY and MAC Layer Design for Coded Random Access with Massive MIMO

Grant-free access schemes are candidates to support future massive multi...

Random Spreading for Unsourced MAC with Power Diversity

We propose an improvement of the random spreading approach with polar co...

Please sign up or login with your details

Forgot password? Click here to reset