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ACP WG-F/25 WP-10
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International Civil Aviation Organization
WORKING PAPER / ACP WG-F/25 WP-10
03rd October 2011

AERONAUTICAL COMMUNICATIONS PANEL (ACP)

24th MEETING OF WORKING GROUP F

Dakar, Senegal 10th-14th October 2011

Agenda Item x: / Adjacent compatibility study between radars and mobile networks around 2.7 GHz

ADJACENT SHARING ISSUE BETWEEN ATC PRIMARY RADAR (2700-2900 MHz AND MOBILE SERVICE BELOW (2500-2690 MHz)

(Presented by Eric Allaix)

SUMMARY
Since several months many theoretical studies and practical tests have been conducted on compatibility issues between new mobile services operating below 2.7 GHz and approach radars operating above 2.7 GHz.
The aim of this paper is first to inform WGF members on the ongoing work in Europe and the actions put in place in France on this issue and second to have some feedback, if any, on action engaged in other region.
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ACTION
WGF members are invited to take into accountthematerialprovidedinthispaper and to take appropriate action in order to ensure the protection of the 2.7-2.9 GHz band for the future.

1.CEPT studies

Working Group SE performed studies to assess the mutual compatibility between systems operating in the mobile service below 2.69 GHz and radars operating in the aeronautical radionavigation and radiolocation services above 2.7 GHz.

These studies have been conducted in such a way as to provide clear guidance on the issues that need to be addressed and their relative magnitude but should not be seen as providing definitive answers as to the additional isolation potentially required.

For the radar side, two main issues were raised:

a)In many cases, the radar receiver front end does not provide sufficient adjacent band rejection (i.e. there is a blocking issue). The studies have shown that additional isolation depending on the separation distance would be required between the mobile service base station and the radar. For an assumed separation distance of 1 km this additional required isolation is in the order of 30-60 dB depending on the radar characteristics such as antenna height, gain, radiation patterns, etc. The blocking effect from mobile user equipments operating in accordance with the FDD band-plan (in the 2500-2570 MHz band) is not a problem.

b)The unwanted emissions of the mobile service increase the noise level in the radar band which can desensitize the radar receiver. Based on the assumption that unwanted emissions of mobile equipment meet the regulatory limit of -30 dBm/MHz defined in ERC Recommendation 74-01, studies have shown that there would be a need of additional isolation depending on the separation distance. For a separation distance of 1 km this isolation would be in the order of 30-45 dB for the base station and 15-20 dB for the user equipment depending on the radar characteristics such as antenna height, gain, radiation patterns, etc..

The draft report that should be sent for public consultation by the end of october is attached to this paper.

2.Action at French level

To adress the issues presented above, it is important to note that both the impact of blocking and unwanted emissions have to be addressed at the same time.

Currently, it is planned in France (as in a number of administrations in Europe) to address the impact of blocking issue by increasing the radar adjacent band rejection capability through enhanced filtering where needed.

With regard to the unwanted emissions:

a)it is planned to impose to the base station more stringent unwanted emissions limits above 2.7 GHz compared to standards requirements on a case-by case basis, when appropriate. This approach has also been chosen by some other administrations. In practice, the level of unwanted emission of base stations will have to be below a certain level at the radar site.

b)With regard to the user terminal, the additional isolation cannot be achieved on a case by case basis due to the free circulation of handsets. Therefore, this improvement can only be achieved at the common European level through modification of mobile terminal standards. Measurements performed up to now on equipments (see the attachment) show that in practice, equipments perform better than required. This reduces the risk of interference on radars, but it also shows that mobile standards could be improved without impacting the technology. States are invited to support this modification since there is no regulatory certainty at present that the other actions will be sufficient to protect radars.

Furthermore it is planned in France to impose to the base station more stringent unwanted emissions limits above 2.7 GHz compared to standards requirements on a case-by case basis, when appropriate. This approach has also been chosen by some other administrations. In practice, the level of unwanted emission of base stations will have to be below a certain level at the radar site: mobile operators will have to ensure that the pfd level generated by a base station at the radar antenna port and in the frequency band of the S band radar will remain below -155 dBW/m²/MHz. This level apply at the radar, and therefore, it gives mobile operators the necessary flexibility for the deployment of base stations, taking into account the terrain, the buildings, the antenna orientation, and any other parameter that could contribute to respect that level at the radar antenna port.

3.Action by the Meeting

The ACP WGF members are invited to take into accountthematerialprovidedinthispaper and to take appropriate action in order to ensure the protection of the 2.7-2.9 GHz band for the future.