[논문 리뷰] Can Terahertz Provide High-Rate Reliable Low Latency Communications for Wireless VR?

Christina Chaccour, Mehdi Naderi Soorki외 3명|arXiv (Cornell University)|2020. 04. 30.

Millimeter-Wave Propagation and Modeling인용 수 33

한 줄 요약

본 논문은 wireless VR을 위한 새로운 terahertz 기반 모델을 제시하여 사용자 지연을 처리, 대기열, 및 다운링크 지연으로 분해하고, 꼬리 분포와 불안정한 경험의 위험을 분석하여 차단 및 분자 흡수의 영향을 받는 단거리 링크에서의 순간 신뢰성을 평가한다.

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.

연구 동기 및 목표

• Motivate the use of terahertz for wireless VR and identify key delay components.
• Introduce a novel VR delay model including processing, queuing, and downlink transmission delays.
• Derive the tail distribution of delay via moments to characterize extreme delay events.
• Apply risk-measure tools to assess the probability of unreliable user experience.
• Analyze how blockage density and molecular absorption influence reliability at terahertz frequencies.

제안 방법

• Define a VR request/response model with three delay components: processing, queuing, and downlink transmission.
• Derive the delay tail distribution using moment-based techniques to capture extreme events.
• Employ extreme value theory / risk analysis tools (e.g., CVaR-like metrics) to quantify unreliable-user-experience risk.
• Evaluate how terahertz-specific factors like blockage density and molecular absorption affect reliability in short-range links.
• Discuss implications for high-rate, low-latency wireless VR on terahertz channels.

실험 결과

연구 질문

• RQ1 What is the instantaneous reliability of terahertz links for wireless VR in short-range scenarios?
• RQ2 How does the delay tail behave, and what are the probabilities of extreme delays?
• RQ3 How do blockages and molecular absorption impact terahertz VR reliability?
• RQ4 Can risk-measure frameworks quantify the likelihood of an unreliable VR experience at terahertz frequencies?

주요 결과

• The delay tail distribution is derived via moments to characterize extreme delay events.
• The analysis provides insights on terahertz potential within short communication ranges given high susceptibility to blockages and molecular absorption.
• The study uses risk measures to examine the risk of unreliable user experience at terahertz frequencies.
• The results indicate that delay reliability is influenced by the density of blockages and molecular absorption, as captured by the proposed model.
• The framework enables assessment of instantaneous reliability for terahertz-based wireless VR.