Assessing the potential for interference between a spectrum licensed transmitter and RCS base/repeater/customer receivers under Part 2 of these Advisory Guidelines

Spectrum licensees will, in some cases, be required to assess the level of potential interference from a proposed spectrum licensed transmitter to each affected RCS site. Spectrum licensees will be responsible for ensuring that the level of interference is lower than the maximum long term[1] allowable interference appropriate to RCS receivers. The coordination procedure is set out in Part 2 of these Advisory Guidelines.

In many cases the levels of interference between RCS and spectrum licensed transmitters will be well within acceptable limits, and there will be no need to carry out the detailed coordination procedures set out in Part 2 of these Advisory Guidelines. Spectrum licensees can use the look-up table in Table 2 in Part 2 to determine if there is a need to carry out detailed coordination.

Recommendation ITU-R PN.526-3 should be used for calculating terrain loss between two sites. The interference path loss is modelled by diffraction over spherical earth or diffraction over obstacles (eg knife edge or multiple knife edge obstructions). The method is given in Schedule 2.

PART 2COORDINATION PROCEDURES

Interpretation

1. In this Part:

‘effective occupied bandwidth’ has the meaning it has in the Radiocommunications Spectrum Marketing Plan (500 MHz Band) 1996;

‘EIRP’ means equivalent isotropically radiated power;

‘horizontally radiated power’ has the meaning it has in Radiocommunications Spectrum Marketing Plan (500 MHz Band) 1996;

‘lower band’ has the meaning it has in Radiocommunications Spectrum Marketing Plan (500 MHz Band) 1996;

‘minimum distance’ means the distance worked out in accordance with clause 2;

‘upper band’ has the meaning it has in Radiocommunications Spectrum Marketing Plan (500 MHz Band) 1996.

Meaning of “minimum distance”

2. The minimum distance is, for a transmitter that is located at a height nearest to the value set out in an item in the left hand column of Table 2 below, with an EIRP for each 12.5 kHz of bandwidth nearest to the value set out in a column of the top row of the table  the distance in kilometres set out in that column of the item.

Table 2 Coordination Look-up Table

Coordination of RCS with spectrum licensed transmitters

3. (1) This clause applies to a person who is operating, or intends to operate, under a spectrum licence, a transmitter:

(a) that is located at a point that is at a distance that is equal to or less than the minimum distance from an RCS base receiver that is authorised to operate on the frequency:

(i) 501.9 Megahertz; or

(ii) 503.1 Megahertz; or

(iii) 504.3 Megahertz; or

(iv) 505.5 Megahertz; and

(b) that has its emission centre frequency plus or minus half the effective occupied bandwidth within plus or minus 910 kHz of any of the frequencies referred to in paragraph (a).

[NOTE: A list of RCS base/repeater/customer site coordinates operating in these bands is provided in Schedule 1. The site and frequency convention sense used in Schedule 1 is the same as that of the SMA's RADCOM database. A site name under the field A_SITE will correspond to a site with transmitting frequency A_FREQ and receiving frequency B_FREQ. eg. The receive frequency for site Cheviot Hills would be 511.9 MHz.

The field names A_STREET, B_STREET, A_ANT_TYPE and B_ANT_TYPE used in RADCOM should be used to determine whether A_SITE or B_SITE is an RCS base/repeater or an RCS customer station. eg. field antenna types of site A (A_ANT_TYPE) with U, T are associated with omni antenna, a base station site. Antenna type 4MP associated with ‘radio terminal’ is a 4 metre parabolic directional repeater antenna. Antenna type 15 1Y associated with ‘RCS subscribers’ is a 15 element directional customer Yagi antenna.

Only limited RADCOM fields are included in Schedule 1.]

(2) For the purposes of following the procedures set out in this clause, the person should:

(a) if a procedure involves calculations in relation to an RCS customer receiver, assume that the customer receiver:

(i) is located at the site of the RCS base station to which it relates; and

(ii) has an antenna with an antenna gain of 15 dBi and an antenna height of 10 metres;

(b) if a procedure involves calculations in relation to a transmitter that is operated in the upper band under a spectrum licence, assume that the transmitter is located at the site of the base station to which it relates. If there are emissions emanating from other sites that are likely to result in RCS levels of protection being exceeded then these should also be analysed.

(c) if a procedure involves calculations in relation to an RCS repeater station, take account of the directional characteristics of the antenna that is used in conjunction with the repeater station.

(3) The person should calculate the propagation loss in accordance with the following formula:

Lb = Lbf + Lt

where:

Lb = Propagation loss (dB)

Lbf = Free Space Loss (dB)

32.4 + 20 log(500 . d) where d = separation distance in kilometres

Lt = Terrain Loss modelled by spherical earth or knife edge or multiple knife edge diffractions (dB) as specified in ITU-R 526-3. [NOTE: See Schedule 2]

[NOTE: Apart from FSL, propagation loss associated with terrain will determine the required level of protection to RCS receivers. Long term terrain protection is associated with diffraction loss at an effective Earth's radius or k-factor and can be calculated as shown in Schedule 2. A k-factor of 3 which corresponds to a percentage of time greater than 20% (ITU-R Rec 758 and RALI FX3) is used in the analysis.]

(4) The person should calculate the level of unwanted power from the operation of the transmitter that is received by the RCS base receiver using the following formula:

Pu = EIRPt - Lb + Gr - Dr

where:

Pu = Unwanted Power (dBm/12.5 kHz)

EIRPt = proposed spectrum licensed horizontally radiated power for the transmitter (dBm/12.5 kHz EIRP) that is within the bandwidth of the RCS receiver and in the direction of the RCS receiver

Lb = Lbf + Lt

Gr = gain of RCS receiver antenna (dBi)

 for RCS base refer to RADCOM database (typically 8/11 dBi)

 for RCS repeater refer to RADCOM database (typically 17/20/23 dBi)

 for customer Gr = 15 dBi

Dr = Antenna Discrimination in the direction of spectrum licence transmitter (dB)

 for RCS base Dr = 0

 for RCS repeater refer Schedule 3

 for customer Dr = 0 dB (assume that customer antenna is pointing at spectrum licence transmitter)

(5) The level of unwanted power obtained using the formula in subclause (4) should be no greater than - 134.1 dBm/12.5 kHz.

[NOTE: The maximum value for permissible level of interference into a RCS receiver (IRCS) is worked out using the following formula:

IRCS(dBm/12.5 kHz) = RCS thermal noise - Noise for 1 dB degradation - bandwidth adjustment

= -106.5 -6 - 10 log (1820/12.5)

= -134.1 dBm]