Olympic and paralympic games 2024, the competition of radio frequencies

Last summer, Paris hosted the Olympic and Paralympic Games, an international event that brought with it an unparalleled need to control radio frequencies and prevent both intentional and unintentional interference. This was the role of France’s National Frequency Agency (ANFR), which was having to increase its workforce accordingly. To meet this exceptional need, Télécom SudParis recruited and trained a number of students over several months to help with controlling frequencies.

In brief:

Assigning channels to different radio services was the first step in preventing interference.
ANFR had to be prepared to identify and act swiftly in the event of voluntary or involuntary interference.
Télécom SudParis trained students to bolster ANFR’s workforce during the 2024 Olympic and Paralympic Games.

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The Paris 2024 Olympic and Paralympic Games was a unique opportunity to promote inclusion, diversity and sporting excellence on a global scale. Preparing for this historic event had its share of difficulties, however. Between the efficient management of infrastructure, the need to guarantee the safety of athletes and the public in an uncertain global context, and questions relating to sustainability and the legacy left by this event, organizing the 2024 Olympic and Paralympic Games involved a series of logistical and preparatory challenges. These included controlling radio frequencies and preventing interference, whether intentional or unintentional, throughout the event.

Such interference may not necessarily stem from a malicious desire to jam communication systems – it could also be caused unintentionally by the inappropriate use of a device, set to a frequency allocated to another service, for example. “If the ‘hijacked’ channel was allocated in this time slot to a major television channel that was broadcasting live, we needed to be able to intervene quickly and efficiently,” says Nel Samama, Director of the Electronics and Physics Department (EPh) and researcher at Télécom SudParis specializing in radio waves.

For the event’s media coverage, it was therefore crucial to ensure that radio frequencies were properly allocated and used efficiently, and to identify potential sources of interference. Télécom SudParis was committed to this mission, training students for two consecutive years to reinforce the control teams at France’s National Frequency Agency (ANFR) last summer.

“Allocation” and “assignment”, a tightly-knit distribution of radio frequencies

Radio frequency (RF) allocation is the set of mechanisms for distributing frequencies between the various radiocommunication services. The main challenge is to avoid interference between broadcasts. The RF spectrum is first divided into bands, which are then allocated to specific services. In France, there are some ten frequency owners, including the Electronic Communications, Postal and Print Media Distribution Regulatory Authority (ARCEP), the Audiovisual and Digital Communication Regulatory Authority (ARCOM), the Civil Aviation Authority, the National Center for Space Studies (CNES), and the Ministries of Defense and the Interior.

These allocators then assign the RFs to radiocommunication services. For the Olympic and Paralympic Games, ARCEP regulated most telecommunications services, such as mobile telephony, broadcasting and satellite communications. These assignments also concerned all metrology systems, i.e. measurement tools that communicate wirelessly via radio links, such as scientific, geolocation and electronic measurement instruments. As with communications services, it was essential that these devices had interference-free access to their assigned frequencies, to guarantee that their measurements could be carried out.

ANFR certification, the golden ticket for radiocommunication services

The first solution for avoiding interference at this type of event, and in particular, interference between different services, is to assign channels for a given period, in a given location, and check that these assignments are respected. That was the role of ANFR, which coordinates RFs, manages allocation conflicts, and carries out compliance and control measures to ensure that channel usage rules are respected.

All players in the communication, audiovisual and metrology sectors must be certified to use their systems on various sites. This certification was issued by the Paris 2024 Organizing Committee for the Olympic and Paralympic Games (COJOP) after examination by ANFR. Each body, from every country, submitted its request, and ANFR then assigned channels according to need. Quite a challenging puzzle, given the scale of the event. Because although channels were not unique, and could be used in the north and south of France at the same time, demand was massive. “ANFR expected to receive between 50,000 and 75,000 requests for frequencies!” says Nel Samama.

General rehearsal before the 2024 Olympics for ANFR teams at the French Open (badminton), held from March 4 to 8, 2024 at the Adidas Arena in Paris. Credits: ANFR.

Risk of “static on the airwaves”

As well as checking that all equipment entering the site for the duration of the event is certified, ANFR had to deal with interference problems. Despite said certification and various technical standards and regulations, there were many potential sources of interference. “For example, the electronic components used in transmitting and receiving equipment are not always perfect, and sometimes generate parasitic signals that propagate into the atmosphere. This could manifest in a frequency being used by a team and could interfere with the signal,” says Ghalid Abib, radio frequency researcher at Télécom SudParis. Then, there was the possibility of an incorrectly tuned, faulty or uncertified transmitter, brought by a member of the public, or of course, malicious broadcasts.

Regardless of the nature of the interference, control teams needed to be able to detect it and launch corrective or coercive measures. This was an epic task, given the geographical distribution of the various sites. The event was hosted at some forty venues throughout the Île-de-France region, as well as in other cities in France and overseas, with some occurring simultaneously.

Students as back-up

“In anticipation of this need for human resources, the deputy director of ANFR contacted us, as he knew that Télécom SudParis had skills in this field,” says Nel Samama. “He came to us with the idea of involving students and teaching them the prerequisites of the trade.” With the support of the training department, a project team named Control and Teaching of Radio Frequencies (CERF) was set up to provide academic training for these students, as a precursor to the practical training provided by ANFR.

“We taught them the technical language and all the general theory they needed to quickly understand the nature and origin of interference in a practical situation,” says Ghalid Abib. During the CERF training, the young recruits reviewed the basics of RF: what a radio signal is, how it is broadcast, what are its effects, and how to characterize wireless communication. They also took more advanced technical courses on radio instrumentation and parameters, including RF receivers, spectrum analyzers, generators, antennas, and more.

“Being backstage at the Olympic and Paralympic Games is a once-in-a-lifetime opportunity!”

Given that the Télécom SudParis laboratory is well-resourced, the students had the opportunity to use cutting-edge equipment dedicated to radio systems, through practical exercises. On the program: detection of normal and abnormal operation of transceivers, use and characterization of antennas – which transmit and receive radio signals -, and direction-finding, to locate a source of disturbance. All this practical work culminates in a “foxhunt”: an exercise whereby a device emitting an unwanted signal was hidden on the premises. The students had to locate the device as quickly as possible using ANFR equipment.

Once the academic training completed, the students finished their practical training at ANFR, to familiarize themselves in greater depth with the various wireless radio instruments. Last summer, the 2024 Olympic and Paralympic Games marked the end of the CERF project-team which, according to its tutor Arthur Jovart (Training Department), has successfully completed its mission. “As well as learning many practical things, being behind-the-scenes at such an event is a once-in-a-lifetime experience for these students!” he says.

A popular training course

Launched during the 2022-2023 academic year for a trial run with around 20 students, last year’s CERF training welcomed approximately 70 students. The offer was presented to students from Télécom SudParis and Télécom Paris as a training course followed by a fixed-term contract/professional placement, and sparked a great deal of enthusiasm. ANFR had to select the future frequency controllers on the basis of their CVs and cover letters. The training, which complemented their engineering studies, was provided by Nel Samama and Ghalid Abib, along with Muriel Muller, Thierry Taillandier-Loize and Jose Rubio Hernan, also members of the EPh department. It took place over six half-days, combining theory and practical work.