This experimentation tri-operators was organized in order to very envisage the deployment of high speed portable in the band of the 800 MHz and also to have a technical expertise and operational, making it possible to treat under best the conditions the probable cases of jammings of the DVB by base stations of mobile telephony. The town of Saint-Etienne was selected by taking account of its specificities.
It is covered by a transmitter DVB of strong power, the Saint Étienne transmitter – Cross of Guizay, and by some controlled relay transmitters. In addition, it was retained because of its dense urban environment, of the geography of the city and the use for the diffusion of the DVB of a channel at high frequency (channel 59), likely to support, a priori, in the event of non-observance of the report of protection, the situation of jammings by base stations 4G, because of selectivity of receivers DVB and the possible saturation of the various equipment equipped with amplifiers in the chain of televisual reception.
Procedure of communication and assistance installation
In particular at the request of the Council, the starting of the experimentation in the town of Saint-Etienne was preceded by campaigns of information bound for the elected officials, the televiewers, the trade unions of condominium and the social lessors. A call number (0 970,818,818) was placed at the disposal by the ANFR to make it possible to the televiewers to announce the difficulties of reception of the DVB within the framework of the experimentation, essential component in the process to be able to treat jammings. This operation was the object of regular assessments of stage carried out by the ANFR towards the whole of the actors concerned of which the operators DVB and SCUMS.
The remediation of jammings
The cases of jammings indexed at the time of this program were in the near total of the cases related to the saturation of the equipment of reception DVB, the proximity of transmitter 4G of a reception DVB then causing a “dazzling” of the latter. The solution adopted in the event of proven jammingsofthis type is the installation of an adapted filter. Antennists, partners of the test, intervene then to insert a filter in the installation of reception of the television of the user. This technical intervention is assumption of responsibility by the telephone operators and thus does not engage any expenses for the televiewers insofar as the licences delivered by the ARCEP fix at the telecom operators an obligation of results. The Council of State called into question, on January 15th, 2014, the R20-44-26 article modified by the decree n°2012-951 of August 1st, 2012 – art 1 relating to the key of distribution of the financing of the collection and the treatment of the claims relating to jammings of the departments of communication audio-visual by the networks of the mobile service in band 800 MHz. It is important to note that the televiewers whose reception DVB is subjected to an interference with a telephone relay must initially make known themselves near the call center: 0970 818 818.
Assessment of the experimentation
The experimentation of diffusion of the signals 4G-800 MHz starting from the antenna-relays took place over one four months period going from April 2nd to August 2nd, 2013. With final, 70 stations LTE 800 MHz were commissioned. Lighting was carried out in a progressive way. As the service 4G was not yet commercially open in the town of Saint-Etienne, the traffic was simulated by the telecom operators during all the duration of the experimentation. At the end of the deployment, an estimated population of approximately 100,000 hearths was under the cover of the networks 4G 800 MHz.
The tests proceeded according to three successive phases:
- Phase 1 (from April 2nd to June 16th, 2013): the goal was to evaluate the level of disturbance of the relays 4G, to qualify the first complaints of televiewers and to test the approachs of remediation. 29 stations were thus commissioned in eleven weeks, with a power and a maximum load of traffic,
- Phase 2 (from June 17th to July 21st, 2013): acceleration of the lighting of the stations to reach 41 additional stations in four weeks, with a power and a maximum load of traffic. At the conclusion of this phase, 70 stations were commissioned,
- Phase 3 (from July 22nd to August 2nd, 2013): this last phase was intended to evaluate the operating process known as “idle” where the load of traffic simulated on the stations is worthless. This mode is of an interest for jammings because it causes an important variation of the emitted power, which can result in to disturb the installations of reception of the DVB.
During the experimentation, the call center of the ANFR received urban area inhabitant of Saint-Etienne nearly 2000 descriptions of televiewers confronted with problems of reception of the DVB. The first calls of the televiewers occurred quickly after the commissioning of the stations 4G-800 MHz. Following an analysis, the descriptions concerned more than 700 distinct addresses. The antennists who went to the residence of the televiewers finally characterized almost 500 really ascribable jammings with the emission of the antennas 4G-800 MHz. The disturbances, when they were jammings 4G-800 MHz indeed, profited from an not exceeding time of resolution most of the time, three working days. Among these jammings related to the 4G-800 MHz, almost 400 related to collective habitats and a hundred, individual habitats. By considering that a collective habitat gathers on average 13 hearths, the population having met disturbances and having actually announced them to the ANFR can be estimated at approximately 5000 hearths. In addition, this experimentation made it possible to determine that the maximum distance between a disturbing station 4G and the scrambled address are of approximately 1000 meters, the average distance to the disturbing station being approximately 300 meters.
The near total of the dysfunctions met (99%) was due to the electromagnetic signals 4G-800 MHz, saturating the installations with reception, causing disturbances even a total loss of the reception of the chains of the DVB. This problem was solved each time while inserting a suitable filter on these installations.
It is important to note, at the conclusion of this experimentation, that all the zones of the French territory are not equivalent taking into consideration risk of disturbance by the signals 4G-800 MHz: according to the level of field received in DVB and at the conclusion of the experiment of the operations of passage to the digital whole, each zone has its own criticality. Within this framework the experimentation of Saint-Etienne was regarded as with high criticality.
From its preparation, its organization and its unfolding, the experimentation of Saint-Etienne made it possible to answer the objectives which had been set, as well on the technical plan and operational as on that of the communication. It allowed a better knowledge of the qualification of jammings and their remediation, this within realistic times.