Fastening the Initial Access in 5G NR Sidelink for 6G V2X Networks

TL;DR

This paper proposes innovative initial access techniques for 6G V2X networks that leverage probabilistic codebooks and position information to significantly reduce access trials, enhancing beam alignment in high-mobility scenarios.

Contribution

It introduces probabilistic codebook methods based on traffic data and map analysis to improve initial access speed without needing sensitive position data.

Findings

Probabilistic codebooks outperform 5G standard in reducing IA trials.

Position-based schemes achieve similar performance without sensitive info.

Non-uniform quantization improves beam selection accuracy.

Abstract

The ever-increasing demand for intelligent, automated, and connected mobility solutions pushes for the development of an innovative sixth Generation (6G) of cellular networks. A radical transformation on the physical layer of vehicular communications is planned, with a paradigm shift towards beam-based millimeter Waves or sub-Terahertz communications, which require precise beam pointing for guaranteeing the communication link, especially in high mobility. A key design aspect is a fast and proactive Initial Access (IA) algorithm to select the optimal beam to be used. In this work, we investigate alternative IA techniques to fasten the current fifth-generation (5G) standard, targeting an efficient 6G design. First, we discuss cooperative position-based schemes that rely on the position information. Then, motivated by the intuition of a non-uniform distribution of the communication directions due to road topology constraints, we design two Probabilistic Codebook (PCB) techniques of prioritized beams. In the first one, the PCBs are built leveraging past collected traffic information, while in the second one, we use the Hough Transform over the digital map to extract dominant road directions. We also show that the information coming from the angular probability distribution allows designing non-uniform codebook quantization, reducing the degradation of the performances compared to uniform one. Numerical simulation on realistic scenarios shows that PCBs-based beam selection outperforms the 5G standard in terms of the number of IA trials, with a performance comparable to position-based methods, without requiring the signaling of sensitive information.