[BELLE HISTOIRE] A platform for testing the performance of new telecoms systems

" In the early 2000s, manufacturers were starting to use modeling languages for their embedded software, but they didn't have a tool for verifying how they worked," recalls Ludovic Apvrille, professor of embedded systems at Télécom Paris. " Now, before integrating a system into a device like a satellite, it's best to make sure it works properly.

After his post-doctorate, when he joined Télécom Paris, the researcher wanted to respond to this need with a toolbox to help design and verify embedded systems. The TTool platform was born. Initially offering simple models, this platform, which has been awarded the TSN Carnot Institute label, has gradually been enriched, including different hardware components, offering a growing number of simulation techniques, and supporting new languages.

Verifying the safety and security of embedded systems

TTool thus takes the form of a toolbox enabling, firstly, the modeling of an embedded system in a language derived from UML(Unified Modeling Language) or SysML(Systems Modeling Language), commonly used in systems engineering. A decisive first step. " The reliability of the results obtained depends, of course, on our algorithms, but also on the quality of the model produced," notes Ludovic Apvrille. " For each case, it is therefore essential to carry out this abstraction work, starting from the specifications or the code, in order to obtain a truly representative model. " By following the TTool documentation, the user can then describe all the functionalities of his system, which appear in the form of "boxes", linked together by arrows. And if in doubt, they can ask the platform team for help.

Once the model has been produced, TTool offers to test its safety, security and performance. What's the difference between the first two terms? " Safety refers to the absence of danger to users or major economic risk," explains Ludovic Apvrille. " For example, a train with safety problems is at risk of serious failure, up to and including an accident. To verify this property, the platform simulates all possible use cases, examining whether any of them could lead to such a catastrophic state.

Security refers to a system's ability to withstand computer attacks that could alter data or compromise confidentiality. " By default, TTool has a large arsenal of attack models, which it simulates to check whether or not an attacker can get in," explains Ludovic Apvrille. " And if a possible attack has been found, it describes the scenario step by step. This information can help the user to correct the flaw uncovered. However, they will need to check the security of the updated system, as a patch can sometimes be accompanied by new vulnerabilities...

Open source, a decisive asset for industrial partnerships

Features that make the platform unique? " There are other modeling and simulation tools, some of them developed by manufacturers," admits Ludovic Apvrille. " Nevertheless, to my knowledge, none has this ability to describe software and hardware components, with proof of safety, security and performance. " Not surprisingly, TTool is used by universities, research labs and industry alike. While it's difficult to know exactly who all the users are - the tool is available as a free download - the platform has particular appeal in the automotive, aerospace, rail and telecoms industries. For example, as part of the European EVITA project, in partnership with BMW, the use of TTool helped improve safety protocols designed for use in vehicles.

This success can also be attributed to an orientation taken from the outset of the adventure: free and open source software. " This is essential for us, and certainly for other companies using TTool," stresses Laurent Roullet, head of Nokia Bell Labs' Enterprise Industrial Platforms (EIP) research department. " As an industrial company, we can ill afford to share proprietary code. So when we work with the academic world, we need a shared development and testing environment, a requirement that open source meets perfectly. " Ideal conditions, therefore, for collaboration, as demonstrated by the Model-Oriented Programming (MOP) project, bringing together researchers from Télécom Paris and Nokia Bell Labs.

POM: assessing the performance of cloudified telecoms systems

" This project was prompted by a paradigm shift in telecoms: the advent of 'cloudification'," explains Laurent Roullet. " Until then, the main network functions were embedded in base stations. But the growing demands of the telecoms sector led industry players to move some of these functions to the cloud, in order to benefit from greater computing capacity. This new architecture also offered numerous advantages, such as lower hardware costs and greater agility. However, this approach also raises a number of questions: which functionalities should be deployed in the cloud, and which in the base stations? How can we design an optimal distributed system? With which components?

This is what the research team explored as part of the POM project, using TTool. On this occasion, the platform was updated to take into account essential cloud components, such as orchestration tools, which dynamically allocate resources according to load.

TTool, for example, has enabled us to test different designs for distributed telecoms systems and verify their ability to meet even the most demanding requirements. " Connectivity has become a fundamental issue for sectors such as manufacturing and transport," observes Laurent Roullet. " Telecom systems have everything it takes to meet this demand, but they have to adapt to requirements they didn't initially take on board, particularly in terms of operating reliability. They must also offer strict guarantees of throughput and delay - a connected industrial robot or autonomous vehicle must be able to make decisions in real time. Researchers were able to verify this with TTool.

What role for AI in TTool?

The POM project, for example, has delivered valuable results to Nokia Bell Labs, even if it will take time to integrate them. " Originally, our work focused on 5G, but in reality, it's 6G that will benefit from these advances," says Laurent Roullet. " And that's just as well: this next generation of mobile networks will be cloud-native. These results will also feed into other research projects, such as UNEXT - which aims to transform the network into a programmable operating system, inspired by UNIX - or initiatives around connected vehicles, a subject on which Nokia Bell Labs is very active.

On the TTool side, POM has enabled improvements to be made to the platform, which is always seeking to keep pace with changes in the sector. " For example, in the past, embedded systems were rarely connected," notes Ludovic Apvrille. " Today, given the new uses, particularly in industry, we have to add a network dimension, which is not easy, and take into account the variety of technologies: Wi-Fi, Bluetooth, LoRa..." TTool is thus subject to continuous improvement, with new functions regularly added, such as system cost evaluation, with the aim of optimizing the system.

AI has also recently made its appearance on the platform. But not at all levels. " We believe that today, AI is not sufficiently equipped to deal with complex verification issues," says Ludovic Apvrille. " As a result, in TTool, it only comes into play as a modeling assistant: it can guide the user and help him design his model. In short, we confine AI to its best role: that of supporting human expertise. "