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Notes on coordination

Whenever two or more radio stations in the same general vicinity share spectrum, there is the potential for radio interference from the transmitter of one station to the receiver of another station.

Coordination of a proposed radio station with existing or already proposed fixed stations or satellite earth stations that may be in conflict with the proposed station is required to ensure that aggregate radio interference limits into or from such stations for the type of services employed are not exceeded.

Harmonious coexistence of radio stations is ensured by appropriate combinations of antenna discrimination, signal characteristics, natural shielding, and of separations in distance, frequency, polarization, and possibly time, to meet specified interference criteria.

In some extreme cases, extraordinary measures at one or other or both of the affected stations, such as a relaxation of the system performance, a change in the signal characteristics, additional repeater stations, artificial shielding, or interference cancellers may have to be taken. In general, however, successful radio frequency coordination is usually possible without recourse to such extreme measures.

There are two distinct areas of frequency coordination: domestic is undertaken by the applicant, while international is undertaken by the Department.

Domestic Coordination

Domestic coordination of radio station frequencies is the responsibility of the applicant with parties or agencies operating existing and proposed terrestrial radio facilities. These latter parties and agencies shall be identified by the applicant based upon assumed overlapping spectrum with the proposed station within its coordination area.

The coordination requirements for proposed stations in the fixed service are determined on the basis of a preliminary analysis carried out by the applicant. This analysis determines potential conflicts with existing or registered stations based on such parameters as frequency, distance, antenna characteristics, carrier to interference criteria, etc.

For satellite earth stations, the coordination area around the earth station is determined by ITU Radio Regulations, Appendix 7 procedures.

International Coordination

The procedures for international coordination between stations in the fixed service are established by bilateral agreements. For coordination between a station in the fixed service and a station in the space radiocommunication service, ITU Radio Regulations, Appendix 7 apply.

International coordination will be undertaken by the Department. However, the applicant may wish to initiate preliminary investigations internationally. The Department should be informed of all such investigations. To determine if your system will require US coordination, review the criteria for coordination as specified in the Terrestrial Radiocommunication Agreements and Arrangements (TRAA). Notwithstanding the need to consult with the TRAA, generally, for frequencies under 18 GHz, the coordination distance is 120 km from the US border; for frequencies over 18 GHz, the coordination distance is 60 km from the US border.

Receivers do not cause interference. Any emission from a receiver is considered insignificant and therefore not coordinated. There is a requirement, however, to protect receive sites from interference. This is achieved by associating the endpoint or link receiver to the transmitter site being coordinated. Indicating the receiver's location or the transmitter's coverage area in the proposal permits technical staff to protect the receiver site from future US assignments. Similarly, although a receive frequency may be part of an ALS record sent for coordination, this receive frequency is not sent with the coordination message. Consequently, to achieve protection for the receiver station it is necessary to coordinate one of its end points.

If coordination is not required, determine whether protection is required. If protection from future American assignments is required, coordinate the system. An example of this is found with systems whose ERP is less than 5 watts. Under Arrangement A of the 1962 Agreement, these systems do not require coordination. However, if they are not coordinated, they cannot be protected from US systems.

If a station is outside the coordination zone, it could still be a source or recipient of potential interference to or from an American operation. If this is suspected, the assignment should be coordinated. Outside the coordination zone, coordination may not technically be required; however, should interference arise it must be resolved. The rule is usually first come, first served. If this potential can be detected in advance, the work required to correct the problem is significantly reduced.

If the applicant is willing to accept higher interference levels than those recommended for the equipment, the Department should be so informed. Licences for "unprotected" assignments are issued to stations whose operators waive any claim to protection of received signals in order to expedite the coordination process.

In some circumstances, licences may also be issued on a "no-interference no-protection" basis (that is, the applicant guarantees that they will cause no interference, and their use of the frequency is not protected). If, subsequently, such stations are found to cause harmful interference to a protected station, the interfering station will be required to take corrective action or to cease transmission.