The new 5G radio techniques will considerably improve communications; latency and reliability are key to answering the demands of communication in industrial environments.
1. Understanding the challenges of the robotic domain in an industrial environment
This article focuses on robots operating in an industrial environment with a 5G wireless connection. Standards organizations and verticals (manufacturing, for example) have defined the requirements for a robot to work with wireless communications as follows: the packet transmission time between robot and base station of less than 1 millisecond and packet loss probability of one in a hundred thousand. These figures are obtained with Ethernet (wired) technology, but the objective for the industry of the future is to remove all the cables since it will enable flexible reconfiguration of machines and predictable maintenance.
Wi-Fi cannot easily meet these requirements because transmissions can suffer from interference. 5G is the right wireless solution for industrial robotics, particularly if we couple it with mobile edge computing solutions.
2. A demonstration visualizing the impact of 5G when controlling robots
The following video demonstration presents an industrial mobile network that provides connectivity to robots in 4G or 5G networks in order to compare their performance. To create this demonstration, we integrated a system level simulator specially developed for low-latency communications, and then the latency obtained was integrated into a 3D visualization module. Both tools were developed at Orange Labs.
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As can be observed, robots over 4G work very slowly, which means it is impossible for them to perform complex tasks, and this will reduce their global productivity. On the other hand, the robots in 5G have a fluid, fast and perfectly synchronized behavior, which enables the completion of complex tasks. This is possible thanks to the use of URLLC (Ultra Reliable and Low Latency Communication) technological building blocks as explained below.
3. What are the low latency techniques introduced by 5G?
The new mobile generation is introducing new features that enable reaching communication latencies lower than 1 millisecond. Some of them are:
- Larger space between frequency carriers (High Sub-Carrier Spacing - SCS)
5G uses as reference the radio frame structure of 4G, which has a duration of 10 milliseconds, containing 10 slots of 1 millisecond each. In 4G, the scheduling is done on a slot basis, which means that the slot is the minimum granularity in which we can schedule a user. Augmenting the space between carriers means that in 1 millisecond it will be possible to accommodate several slots. For example, in a 1 millisecond time period, only one slot can be transmitted with 15 kHz SCS; however, 2 slots can be fitted with 30 kHz SCS, 4 slots with 60 kHz SCS, and even 8 slots with 120 kHz SCS. The main advantage of having more slots per sub-frame is having more scheduling opportunities and, therefore, more re-transmission possibilities, which is crucial for increasing reliability.
- A smaller slot size (with 7, 4 or 2 symbols)
In 4G, the slot duration is fixed to 14 symbols, and in the case of 5G, the number of symbols per slot can be configured either to a “standard” 14 symbol slot as in 4G, or to a smaller slot of 2, 4, or 7 symbols: this is the concept of “mini-slot.” A mini-slot can start at any symbol without waiting for the start of a slot boundary. Thus, the mini-slot feature supports transmissions shorter than the regular slot duration and allows transmissions to start immediately. Mini-slot is defined by:
K –> identifies the slot
S –> identifies the starting symbol relative to the start of the slot
L –> identifies the number of consecutive symbols counting from S
- More flexible duplexing in FDD and TDD
In radio communications, when a packet is transmitted, an acknowledgment response is required. In 5G, the timing relation between the reception of data and the transmission of the acknowledgment has been optimized with respect to 4G. In 4G, when information is sent in slot n, the acknowledgement for that information is sent only in subframe n + 4. With 5G, the acknowledgment can be transmitted in sub-frame n + 1, 2, 3 or 4; this will be chosen depending on the UE processing capability and the network load.
These three techniques are the most significant ones that have been integrated within the 5G standards and that help in reducing latency, which will allow us to respond to future industry demands.
It is clear that 5G is a perfect technology to meet the increasingly technologically-demanding Industry 4.0, and its implementation in industry will be another significant step in the digital industrial revolution.
I received my telecommunication and electronic engineering degree from Instituto Superior Politcnico José Antonio Echeverria, La Habana, Cuba, in 2007 and the PhD at the Dept. of Signal Theory and Communications (TSC) of the Technical University of Catalonia (UPC) in 2012. In 2012 I joined Orange Labs as a research engineer. My research topics of interest are on mobile communication systems design, especially for critical communication. I am also interested by energy saving techniques and sustainable development.