Low Latency Communications for Wireless Networks:
Exploiting Traffic Characteristics

Project leader: Nikolaos Pappas
<nikolaos.pappas@liu.se>

September 19, 2019

1 Project background and industrial motives

The main goal of the next generation mobile communication is to provide seamless communication for a massive amount of devices building the Internet-of-Things (IoT) and at the same time to support the constantly increasing traffic demands originated from personal communications. The major difference between 5G and the previous generations is the native support of ultra reliability, low latency, and the massive access. Ultra-high reliability and ultra-low latency are required by several applications and services such as autonomous vehicles, factory automation, telepresence, smart grids etc.

One of the major impacts of 5G will be the transformation of the industrial production into Industry 4.0. The term Industry 4.0 captures the fourth industrial revolution that transforms industrial manufacturing systems into cyber-physical systems by introducing novel communications techniques such as 5G connectivity and cloud computing [1].

Latency is crucial in applications such as automated industrial production, automatic control, robotics, transportation, health-care, education etc. An indicative list of latency-constrained services that will be supported by 5G are given below [2]. Factory Automation includes real-time control of machines and systems for fast and massive production lines with limited human involvement has challenging requirements in terms of latency and reliability. The latency requirement for factory automation applications varies between 0.25 - 10 ms with a packet loss rate of 10-9. Autonomous driving and optimization of road traffic requires ultra reliable low latency communication. According to Intelligent Transport Systems (ITS), various cases including autonomous driving, road safety, and traffic efficiency services have different requirements. For these purposes, latency of 10 - 100 ms with packet loss rate of 10-3 - 10-5 is required. An important requirement for the utilization of robots and telepresence applications is remote-control with real-time feedback. System response times must be less than a few milliseconds including network delays. Communication infrastructure capable of proving this level of real-time capacity, high reliability/availability, and mobility support is to be addressed in 5G networks. In virtual and augmented reality, typical update rates of display for haptic information and physical simulation are in the order of 1000 Hz which allows round trip latency of 1 ms. Consistent local view of VR can be maintained for all users if and only if the latency of around 1 ms is achieved. In health care, tele-diagnosis and tele-surgery are probably the most important healthcare applications of low latency tactile Internet. These allow for remote physical examination, and remote surgery assisted by robots. Thus, sophisticated control with a round trip latency of 1 - 10 ms and very high reliability data transmission is crucial. Smart Grids have strict requirements of reliability and latency. The dynamic control allows 100 ms of end-to-end latency for switching on or off suppliers such as PV, windmill, etc. In case of a synchronous co-phasing of power suppliers such as generators, an end-to-end delay constraint of 1 ms is required. In education and training, low latency tactile Internet will assist remote training by haptic overlay of trainers and trainees. For these identical multi-modal human-machine interfaces, a round trip latency of 5 - 10 ms is allowed for perceivable visual, auditory, and haptic interaction.

From the above, it is clear that providing massive connectivity and also ultra-reliable and low latency wireless communications will be of major importance for the future wireless networks.

The International Telecommunication Union (ITU) defined three representative service categories according to data rates, latency, and reliability [3]. The enhanced mobile broadband (eMBB), the massive machine-type communication (mMTC), and the ultra-reliable and low latency communication (uRRLC).

Another way to distinguish the traffic is related to the content itself, if it is reusable or not. For example, voice calls or remote control signals are not-reusable content. On the other hand, most of the network traffic today is cacheable or reusable, which is approximately 60%, as stated in [4]. This is another important aspect that must be taken into account for the efficient design of networks in order to reduce the unnecessary transmissions and leave more resources for the non-reusable and critical content. Thus, Age of Information is expected to play a crucial role in that direction.

2 Long-term objectives of the project

The long term vision of the project is to establish a research group that performs fundamental research and in parallel can utilize the results into real life networks through the collaboration with leading industrial partners such as Ericsson. The goal of the project is to put Link÷ping University on the map for excellent research in the emerging area of Ultra Reliable and Low Latency Communications in Wireless Networks and also to establish the project leader and his collaborators among the world leading experts in this research area. This project will tackle important theoretical issues that need further investigation and at the same time these results can be utilized in order to provide solutions that will have a direct impact on practical wireless networks in the 5G and beyond era.

A summary of key steps taken towards realizing this vision are given below

3 Current project status and the results that have been achieved

Regarding the research results we have a rich set of publications both in top-tier journal and conferences as given in the section of publications. All the work packages progress well, more specifically, the related publications for each WP are given below

Below we highlight some of the most important findings during 2019. The works in [J18], [J20], [J21] consider optimal sampling to minimize the Age of Information in an IoT setup. Furthermore, the work in [C25] is one step closer to what is called "Effective Age", a metric that can enable context-aware communications.

4 Publications

References

[1]   A. E. Kal°r, R. Guillaume, J. J. Nielsen, A. Mueller, and P. Popovski, “Network slicing for ultra-reliable low latency communication in industry 4.0 scenarios,” arXiv preprint arXiv:1708.09132, 2017.

[2]   I. Parvez, A. Rahmati, I. Guvenc, A. I. Sarwat, and H. Dai, “A survey on low latency towards 5G: Ran, core network and caching solutions,” arXiv preprint arXiv:1708.02562, 2017.

[3]   M. Series, “IMT vision–framework and overall objectives of the future development of IMT for 2020 and beyond,” 2015.

[4]   C. V. Forecast, “Cisco visual networking index: Global mobile data traffic forecast update, 2015–2020 white paper,” Cisco Public Information, 2016.