Tracking mm-Wave channel dynamics: Fast beam training strategies under mobility

Abstract

Abstract-In order to cope with the severe path loss, millimeter-wave (mm-wave) systems exploit highly directional communication. As a consequence, even a slight beam misalignment between two communicating devices (for example, due to mobility) can generate a significant signal drop. This leads to frequent invocations of time-consuming mechanisms for beam re-alignment, which deteriorate system performance. In this paper, we propose smart beam training and tracking strategies for fast mm-wave link establishment and maintenance under node mobility. We leverage the ability of hybrid analogdigital transceivers to collect channel information from multiple spatial directions simultaneously and formulate a probabilistic optimization problem to model the temporal evolution of the mmwave channel under mobility. In addition, we present for the first time a beam tracking algorithm that extracts information needed to update the steering directions directly from data packets, without the need for spatial scanning during the ongoing data transmission. Simulation results, obtained by a custom simulator based on ray tracing, demonstrate the ability of our beam training/tracking strategies to keep the communication rate only 10% below the optimal bound. Compared to the state of the art, our approach provides a 40% to 150% rate increase, yet requires lower complexity hardware.

A Tutorial on Beam Management for 3GPP NR at mmWave Frequencies

“…The issue of designing efficient beam management solutions for mmWave networks is addressed in [32], in which the author designs a mobility-aware user association strategy to overcome the limitations of the conventional power-based association schemes in a mobile 5G scenario. Other relevant papers on this topic include [33], in which the authors propose smart beam tracking strategies for fast mmWave link establishment and maintenance under node mobility. In [34], the authors proposed the use of an extended Kalman filter to enable a static base station, equipped with a digital beamformer, to effectively track a mobile node equipped with an analog beamformer after initial channel acquisition, with the goal of reducing the alignment error and guarantee a more durable connectivity.…”

Efficient Beam Alignment for Millimeter Wave Single-Carrier Systems With Hybrid MIMO Transceivers

“…represents the correlation between the Doppler-rotated sequence x l s,i (t) given by (11) and the desired matched filter x * s,i (−t), and z c s,j (t) = z s,j (τ )x * s,i (τ − t)dτ denotes the noise at the output of the matched filter. The approximation (a) in (13) follows the fact that, the cross-correlations between different PN sequences are nearly zero, i.e., R x i ,i (t) = x s,i (τ )x * s,i (τ −t)dτ ≈ 0, for i = i.…”

“…As we explained in Section III-B, neglecting the effect of the noise, the output y s,i,j [k] is a Gaussian variables whose power is obtained by projecting the AoA-AoD-Delay PSF f p (φ, θ, τ ) along beamforming vectors u s,i and v s,j in the angular domain (due to g s,i,j :=ǔ s,i ⊗v * s,j ) and along the k-th slice corresponding to τ ∈ [kT c , (k + 1)T c ] in the delay domain, where the slicing in the delay domain results from the fact that the correlation function |R x l i,i (t)| between the Doppler-rotated sequence x l s,i (t) given by (11) and the desired matched filter x * s,i (−t) is well localized around t = 0; we refer to Fig. 1 (a) for an illustration.…”

Channel Fingerprint Based Beam Tracking for Millimeter Wave Communications

“…Many research efforts have been devoted to designing highefficient beam training schemes, such as using configurable beam width for adaptive beam search [2], sending pseudorandom beacons to apply compressive sensing techniques [3], double-link beam tracking to overcome the blockage problem [4], probabilistic beam tracking for hybrid beamforming architectures [5], adaptive beam tracking with the unscented kalman filter [6] and narrowing down the search range with the historical training results [7]. Channel fingerprints can also This act as useful historical information to aid beam tracking.…”