Initial Access in 5G mm-Wave Cellular Networks

TL;DR

This paper surveys initial access techniques in 5G mmWave networks, analyzing coverage and delay to determine optimal strategies based on system parameters and SNR regimes.

Contribution

It provides a comprehensive comparison of recent initial access methods and offers guidelines for selecting the best approach depending on system conditions.

Findings

Iterative search reduces delay compared to exhaustive search in high SNR regimes.

Context information algorithms improve initial access efficiency in certain scenarios.

Optimal initial access strategy varies with target SNR and system parameters.

Abstract

The massive amounts of bandwidth available at millimeter-wave frequencies (roughly above 10 GHz) have the potential to greatly increase the capacity of fifth generation cellular wireless systems. However, to overcome the high isotropic pathloss experienced at these frequencies, high directionality will be required at both the base station and the mobile user equipment to establish sufficient link budget in wide area networks. This reliance on directionality has important implications for control layer procedures. Initial access in particular can be significantly delayed due to the need for the base station and the user to find the proper alignment for directional transmission and reception. This paper provides a survey of several recently proposed techniques for this purpose. A coverage and delay analysis is performed to compare various techniques including exhaustive and iterative search, and Context Information based algorithms. We show that the best strategy depends on the target SNR regime, and provide guidelines to characterize the optimal choice as a function of the system parameters.