Delay-Throughput Tradeoff for Supportive Two-Tier Networks

TL;DR

This paper analyzes a two-tier wireless network with primary and secondary nodes, showing how secondary nodes can support primary traffic while maintaining optimal delay-throughput performance.

Contribution

It introduces a model for supportive two-tier networks with spectrum sharing, deriving throughput and delay tradeoffs for primary and secondary tiers.

Findings

Primary tier achieves throughput of Θ(1/ log n) per node.

Secondary tier maintains optimal delay-throughput tradeoff.

Supportive routing enables primary spectrum access without performance loss.

Abstract

Consider a static wireless network that has two tiers with different priorities: a primary tier vs. a secondary tier. The primary tier consists of randomly distributed legacy nodes of density $n$, which have an absolute priority to access the spectrum. The secondary tier consists of randomly distributed cognitive nodes of density $m=n^\beta$ with $\beta\geq 2$, which can only access the spectrum opportunistically to limit the interference to the primary tier. By allowing the secondary tier to route the packets for the primary tier, we show that the primary tier can achieve a throughput scaling of $\lambda_p(n)=\Theta(1/\log n)$ per node and a delay-throughput tradeoff of $D_p(n)=\Theta(\sqrt{n^\beta\log n}\lambda_p(n))$ for $\lambda_p(n)=O(1/\log n)$, while the secondary tier still achieves the same optimal delay-throughput tradeoff as a stand-alone network.