[Paper Review] Distributed SIR-Aware Opportunistic Access Control for D2D Underlaid Cellular Networks

Chen, Zheng, Marios Kountouris|arXiv (Cornell University)|Oct 10, 2014

Cooperative Communication and Network Coding11 references3 citations

TL;DR

This paper proposes a distributed, SIR-aware opportunistic access control scheme for D2D underlaid cellular networks that maximizes area spectral efficiency by enabling D2D links to transmit only when their estimated signal-to-interference ratio (SIR) exceeds an adaptive threshold. The key contribution is deriving optimal SIR thresholds using stochastic geometry, with the conditional SIR threshold outperforming unconditional and channel-aware schemes in coverage probability, spectral efficiency, and sum rate across dense and sparse networks.

ABSTRACT

In this paper, we propose a distributed interference and channel-aware opportunistic access control technique for D2D underlaid cellular networks, in which each potential D2D link is active whenever its estimated signal-to-interference ratio (SIR) is above a predetermined threshold so as to maximize the D2D area spectral efficiency. The objective of our SIR-aware opportunistic access scheme is to provide sufficient coverage probability and to increase the aggregate rate of D2D links by harnessing interference caused by dense underlaid D2D users using an adaptive decision activation threshold. We determine the optimum D2D activation probability and threshold, building on analytical expressions for the coverage probabilities and area spectral efficiency of D2D links derived using stochastic geometry. Specifically, we provide two expressions for the optimal SIR threshold, which can be applied in a decentralized way on each D2D link, so as to maximize the D2D area spectral efficiency derived using the unconditional and conditional D2D success probability respectively. Simulation results in different network settings show the performance gains of both SIR-aware threshold scheduling methods in terms of D2D link coverage probability, area spectral efficiency, and average sum rate compared to existing channel-aware access schemes.

Motivation & Objective

• To address interference management in dense D2D underlaid cellular networks where D2D links share spectrum with cellular users.
• To improve D2D area spectral efficiency and link coverage probability through intelligent, distributed access control.
• To derive optimal SIR thresholds that maximize throughput while accounting for interference from both cellular and D2D sources.
• To enable decentralized operation by providing locally computable threshold values based on SIR estimation.
• To evaluate the performance gains of SIR-aware over channel-aware and non-adaptive access schemes.

Proposed method

• Models D2D transmitter locations as a homogeneous Poisson Point Process (PPP) to enable stochastic geometry-based interference analysis.
• Proposes a distributed access control where each D2D link activates if its estimated SIR exceeds a threshold, computed based on local channel and interference estimates.
• Derives two expressions for the optimal SIR threshold: one using unconditional D2D success probability and another using conditional success probability to account for link quality of active links.
• Uses analytical expressions for D2D coverage probability and area spectral efficiency (ASE) derived via stochastic geometry to optimize the activation threshold.
• Applies an approximation to the conditional success probability to enable practical, decentralized computation of the optimal threshold.
• Employs simulation in varying D2D densities to compare performance against channel-aware and non-adaptive access schemes.

Experimental results

Research questions

• RQ1 How can distributed SIR-aware opportunistic access control maximize D2D area spectral efficiency in underlaid cellular networks?
• RQ2 What is the optimal SIR threshold for D2D link activation that maximizes throughput, and how can it be computed in a decentralized manner?
• RQ3 How does the use of conditional versus unconditional success probability affect the performance of SIR-aware access control?
• RQ4 What performance gains does SIR-aware access offer over channel-aware and non-adaptive access schemes in terms of coverage probability and sum rate?
• RQ5 How do network density and target SIR levels influence the effectiveness of the proposed threshold scheduling?

Key findings

• The SIR-aware opportunistic access scheme with conditional optimal SIR threshold achieves the highest performance in terms of D2D link coverage probability and area spectral efficiency.
• The conditional SIR threshold outperforms the unconditional threshold because it better captures the link quality of active D2D links, improving accuracy in performance prediction.
• The proposed SIR-aware scheme significantly outperforms channel-aware access schemes in both sparse and dense D2D networks, with gains evident from a D2D density of $\lambda = 4 \times 10^{-5}$.
• In dense networks ($\lambda = 6 \times 10^{-5}$), the performance gap between conditional and unconditional SIR thresholds narrows for high target SIR values ($\beta > 12$ dB), indicating reduced approximation error.
• The SIR-aware scheme with conditional threshold achieves performance close to the experimental optimum, validating the analytical approximation.
• The optimal SIR threshold is adaptive and depends on network density and target SIR, with the conditional method enabling earlier activation (e.g., at $-2$ dB) compared to the unconditional method ($12$ dB in sparse networks).