Low-Latency Networking: Where Latency Lurks and How to Tame It

Abstract

While the current generation of mobile and fixed communication networks has been standardized for mobile broadband services, the next generation is driven by the vision of the Internet of Things and mission critical communication services requiring latency in the order of milliseconds or submilliseconds. However, these new stringent requirements have a large technical impact on the design of all layers of the communication protocol stack. The cross layer interactions are complex due to the multiple design principles and technologies that contribute to the layers' design and fundamental performance limitations. We will be able to develop low-latency networks only if we address the problem of these complex interactions from the new point of view of sub-milliseconds latency. In this article, we propose a holistic analysis and classification of the main design principles and enabling technologies that will make it possible to deploy low-latency wireless communication networks. We argue that these design principles and enabling technologies must be carefully orchestrated to meet the stringent requirements and to manage the inherent trade-offs between low latency and traditional performance metrics. We also review currently ongoing standardization activities in prominent standards associations, and discuss open problems for future research.

Age-Delay Tradeoffs in Single Server Systems

“…Age-delay tradeoff: We consider Poisson update generation. Let S AoI and F SAoI denote the service time random variable and its distribution, respectively, that solves (4). We argue that as AoI → A min in (4) we must have E S 2 AoI → +∞.…”

“…Information freshness and low latency communication is gaining increasing relevance in many futuristic communication systems, such as industrial automation, autonomous driving, tele-surgery, financial markets, and virtual reality [4]- [7]. The latency requirements vary depending on the application.…”

“…The latency requirements vary depending on the application. While applications such as autonomous driving, tele-surgery, virtual reality, financial markets are envisioned to require a latency of a few milliseconds, other systems such as industry automation, control signalling in power grids aim at a latency of 10-100 milliseconds [4], [5]. In many of these applications, seeking the most recent status update is crucial to the overall system performance.…”

Minimizing Age of Information With Power Constraints: Multi-User Opportunistic Scheduling in Multi-State Time-Varying Channels

“…The forthcoming Industrial 4.0 revolution brings more stringent data freshness requirement to support the higher level automated applications such as industrial manufacturing and factory automation [2]. In many of these applications, the monitor or the central controller collects data from sensors tracking real-time processes via time-varying wireless links [3].…”

“…Finally, an asymptotically optimal truncated policy that can satisfy the hard bandwidth constraint is built upon the optimal solution to each of the decoupled single-sensor. Our investigation shows that to obtain a small AoI performance: (1) The scheduler exploits good channels to schedule sensors supported by limited power; (2) Sensors equipped with enough transmission power are updated in a timely manner such that the bandwidth constraint can be satisfied.…”