Traffic Allocation for Low-Latency Multi-Hop Networks with Buffers

TL;DR

This paper analyzes traffic allocation schemes in multi-hop mm-wave networks with buffers, deriving latency formulas, comparing local and global schemes, and providing insights for low-latency network design.

Contribution

It introduces a comprehensive formulation for latency in multi-hop buffer-aided networks and compares local and global traffic allocation schemes with analytical and simulation validation.

Findings

Global allocation reduces latency more than local allocation as relay nodes increase.

Latency decreases with more deterministic channels and optimal relay deployment.

As the number of channels grows, the performance gap between schemes widens.

Abstract

For millimeter-wave (mm-wave) buffer-aided tandem networks consisting of relay nodes and multiple channels per hop, we consider two traffic allocation schemes, namely local allocation and global allocation, and investigate the end-to-end latency of a file transfer. We formulate the problem for generic multi-hop queuing systems and subsequently derive closed-form expressions of the end-to-end latency. We quantify the advantages of the global allocation scheme relative to its local allocation counterpart, and we conduct an asymptotic analysis on the performance gain when the number of channels in each hop increases to infinity. The traffic allocations and the analytical delay performance are validated through simulations. Furthermore, taking a specific two-hop mm-wave network as an example, we derive lower bounds on the average end-to-end latency, where Nakagami-$m$ fading is considered. Numerical results demonstrate that, compared to the local allocation scheme, the advantage of global allocation grows as the number of relay nodes increases, at the expense of higher complexity that linearly increases with the number of relay nodes. It is also demonstrated that a proper deployment of relay nodes in a linear mm-wave network plays an important role in reducing the average end-to-end latency, and the average latency decays as the mm-wave channels become more deterministic. These findings provide insights for designing multi-hop mm-wave networks with low end-to-end latency.