[论文解读] Can Terahertz Provide High-Rate Reliable Low Latency Communications for Wireless VR?

Christina Chaccour, Mehdi Naderi Soorki+3 more|arXiv (Cornell University)|Apr 30, 2020

Millimeter-Wave Propagation and Modeling被引用 33

一句话总结

本论文提出了一种基于太赫兹的无线VR新模型，将用户延迟分解为处理、排队和下行延迟，然后分析尾部分布和不可靠体验的风险，以评估在受阻塞和分子吸收影响的短距离链路中的瞬时可靠性。

ABSTRACT

Wireless virtual reality (VR) imposes new visual and haptic requirements that are directly linked to the quality-of-experience (QoE) of VR users. These QoE requirements can only be met by wireless connectivity that offers high-rate and high-reliability low latency communications (HRLLC), unlike the low rates usually considered in vanilla ultra-reliable low latency communication scenarios. The high rates for VR over short distances can only be supported by an enormous bandwidth, which is available in terahertz (THz) frequency bands. Guaranteeing HRLLC requires dealing with the uncertainty that is specific to the THz channel. To explore the potential of THz for meeting HRLLC requirements, a quantification of the risk for an unreliable VR performance is conducted through a novel and rigorous characterization of the tail of the end-to-end (E2E) delay. Then, a thorough analysis of the tail-value-atrisk (TVaR) is performed to concretely characterize the behavior of extreme wireless events crucial to the real-time VR experience. System reliability for scenarios with guaranteed line-of-sight (LoS) is then derived as a function of THz network parameters after deriving a novel expression for the probability distribution function of the THz transmission delay. Numerical results show that abundant bandwidth and low molecular absorption are necessary to improve the reliability. However, their effect remains secondary compared to the availability of LoS, which significantly affects the THz HRLLC performance. In particular, for scenarios with guaranteed LoS, a reliability of 99.999% (with an E2E delay threshold of 20 ms) for a bandwidth of 15 GHz along with data rates of 18.3 Gbps can be achieved by the THz network (operating at a frequency of 1 THz), compared to a reliability of 96% for twice the bandwidth, when blockages are considered.

研究动机与目标

• 激发在无线VR中使用太赫兹技术并识别关键的延迟分量。
• 引入一个新颖的VR延迟模型，包含处理、排队和下行传输延迟。
• 通过矩来推导延迟的尾部分布，以表征极端时延事件。
• 应用风险度量工具来评估不可靠用户体验的概率。
• 分析阻塞密度和分子吸收如何影响太赫兹频率下的可靠性。

提出的方法

• 定义一个具有三个延迟分量的VR请求/响应模型：处理、排队和下行传输。
• 使用基于矩的方法推导延迟尾部分布，以捕捉极端事件。
• 利用极值理论/风险分析工具（如CVaR-like指标）来量化不可靠用户体验的风险。
• 评估太赫兹特定因素，如阻塞密度和分子吸收，如何影响短距离链路的可靠性。
• 讨论太赫兹信道下高数据速率、低时延无线VR的影响。

实验结果

研究问题

• RQ1 在短距离场景下，太赫兹链路用于无线VR的瞬时可靠性是多少？
• RQ2 延迟尾部如何行为，以及极端时延的概率是多少？
• RQ3 阻塞和分子吸收如何影响太赫兹VR的可靠性？
• RQ4 风险度量框架是否能够量化太赫兹频率下不可靠VR体验的可能性？

主要发现

• 通过矩推导出延迟尾部分布，以表征极端时延事件。
• 该分析在强阻塞和分子吸收易感性下，提供了太赫兹在短距离通信中的潜力的见解。
• 该研究使用风险度量来评估太赫兹频率下不可靠用户体验的风险。
• 结果表明，延迟可靠性受阻塞密度和分子吸收的影响，如所提出模型所捕捉。
• 该框架能够评估基于太赫兹的无线VR的瞬时可靠性。