Adaptive Repetitions Strategies in IEEE 802.11bd

TL;DR

This paper investigates adaptive repetition strategies in IEEE 802.11bd, proposing methods to optimize packet retransmissions based on channel load, thereby improving decoding success under varying traffic conditions.

Contribution

It introduces two adaptive strategies for selecting packet repetitions using an adapted channel busy ratio, validated through network simulations.

Findings

Strategies maintain optimal transmission settings under variable traffic.

Adaptive methods improve decoding probability and reduce collisions.

Validation through detailed network-level simulations.

Abstract

A new backward compatible WiFi amendment is under development by the IEEE bd Task Group towards the so-called IEEE 802.11bd, which includes the possibility to transmit up to three repetitions of the same packet. This feature increases time diversity and enables the use of maximum ratio combining (MRC) at the receiver to improve the probability of correct decoding. In this work, we first investigate the packet repetition feature and analyze how it looses its efficacy increasing the traffic as an higher number of transmissions may augment the channel load and collision probability. Then, we propose two strategies for adaptively selecting the number of transmissions leveraging on an adapted version of the channel busy ratio (CBR), which is measured at the transmitter and is an indicator of the channel load. The proposed strategies are validated through network-level simulations that account for both the acquisition and decoding processes. Results show that the proposed strategies ensure that devices use optimal settings under variable traffic conditions.