Purpose of these guidelines

The purpose of these advisory guidelines is to provide guidance to spectrum licensees in the 500 MHz bands (between 501-505 MHz and 511-515 MHz) on the operation of transmitters located within range of Telstra radio concentrator systems (RCS). These systems are used to deliver a telecommunications service to rural areas of inland Australia and their presence must be taken into account by spectrum licensees before operating their transmitters.

RCS follow frequency and cell plans that utilise frequencies for base transmitters in both the lower band (501-505 MHz) and upper band (511-515 MHz). Interference within the RCS network is controlled by the use of a cellular frequency re-use plan. Each RCS site is allocated a channel which results in acceptable co-channel and adjacent channel interference from other RCS sites.

Spectrum licensed transmitters do not follow the same cell plans as RCS and need to be specially coordinated in order to manage the level of interference to the RCS network. These advisory guidelines provide coordination procedures that spectrum licensees should follow in order to ensure that the power radiated from their transmitters in the direction of affected RCS sites is kept to an acceptable level.

The SMA does not intend to afford protection to receivers operated under spectrum licences from any interference they may encounter from RCS transmitters operated in accordance with their apparatus licence. The SMA also intends to afford protection, in accordance with these Advisory Guidelines, to RCS receivers from transmitters operated under a spectrum licence. Each case will be assessed on its merits.

Possible interference scenarios

The cellular implementation of RCS is such that an RCS base transmit frequency in one cluster of cells is never used by an RCS customer transmit frequency in another cluster. However, they can operate on either the lower band or the upper band. Table 1 below shows the affected frequency assignments for RCS base station, RCS customer and RCS repeaters.

Table 1 RCS frequency assignments

Note 1. Tx frequencies only shown for information purposes

Note 2. (2) Figures in brackets represent RCS channel numbers

As can be seen from Table 1 there are four affected RCS frequencies (channels) in each of the lower and upper bands. Under spectrum licensing, spectrum licensed transmitters may operate in the lower band or the upper band. This gives rise to two possible interference scenarios:

Scenario 1 Spectrum licensed transmitters operating in the lower band (501 - 505 MHz) with RCS base or repeater or customer receivers; and

Scenario 2 Spectrum licensed transmitters operating in the upper band (511 - 515 MHz) with RCS base or repeater or customer receivers.

Scenario 1 Co-ordination of spectrum licensed transmitters operating in the lower band (501-505 MHz) with RCS base or repeater or customer receivers.

RCS base station receivers with centre frequencies 501.9 MHz (ch 1) and 504.3 MHz (ch 3)

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RCS repeater station receivers with centre frequencies 501.9 MHz (ch 1), 503.1 MHz (ch 2), 504.3 MHz (ch 3) and 505.5 MHz (ch 4)

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RCS customer station receivers with centre frequencies 503.1 MHz (ch 2) and 505.5 MHz (ch 4)

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Scenario 2 Co-ordination of spectrum licensed transmitters operating in the upper band (511 - 515 MHz) with RCS base or repeater or customer receivers

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]

SCHEDULE 1

RCS SITE COORDINATES WITHIN 350 KM OF SPECTRUM LICENCE TRANSMITTER

SCHEDULE 2

CALCULATION OF TERRAIN LOSS BETWEEN A SPECTRUM LICENSED TRANSMITTER AND RCS BASE/REPEATER/CUSTOMER RECEIVERS

The terrain loss (Lt) may be calculated by using Method A or Method B below. Method A is only to be used where there are no terrain obstructions between the sites. Otherwise Method B should be used.

Method A: Diffraction over a spherical Earth ( or smooth earth diffraction loss)

Terrain loss due to diffraction over a spherical Earth is calculated using the formula below.

Lt = -(F(X) + G(Y1) + G(Y2)) (dB)

where:

Lt = smooth earth diffraction loss (dB)

X = the normalised length of the path between the antennas at normalised heights Y1 and Y2

= 2.2 f1/3 ae -2/3 d

Yn = 0.0096 f2/3ae -1/3 Hn

where:

ae = k r

r = 6370 km (earth radius)

k = equivalent earth radius factor (k=3 which represents

> 20% of time)

Hn = antenna height above spherical earth (m)

n = 1 for site 1 and

2 for site 2

d = path length (km)

f = frequency (MHz)

The distance term F(X) is given by

F(X) = 11 + 10 log (X) - 17.6 X (dB)

The height gain terms G(Y1) and G(Y2) are given by:

G(Yn) = 17.6 (Yn - 1.1)1/2 - 5 log (Yn - 1.1) - 8 for Yn > 2

G(Yn) = 20 log(Yn + 0.1 Yn3) for Yn < 2

Method B: Diffraction over obstacles and irregular terrain (single and multiple knife edge)

1. Single knife-edge obstacle

 = 0.0316 h ( (2 / ) (d1 + d2) / d1 d2)1/2

where:

d = length of path (km)

d1 and d2 = distances of the two ends of the path from the top of the obstacle (km)

h = height from the top of the obstacle (ho) to the straight line joining the two ends of the path. If the obstacle is below this line, h is negative. (m)

ho = fixed terrain height of obstacle (m) + terrain height correction due to k-factor (m). (k=3 which represents > 20% of time)

= (d1 d2)/(12.75 k)

 = wavelength (m)

For  greater than -0.7 an approximate value can be obtained from the expression:

Lt = 6.9 + 20 log((( - 0.1)2 +1) +  - 0.1)

2. Single rounded obstacle

Lt = J() + T(m,n)

where:

J() = single knife-edge obstacle loss calculated in 1. above.

T(m,n) = is the additional attenuation due to the curvature of the obstacle.

= 7.2 m1/2 - (2 - 12.5 n) m + 3.6 m3/2 -0.8 m2 for mn  4

= -6 - 20 log(mn) + 7.2 m1/2 - (2 - 17n)m + 3.6 m3/2 - 0.8 m2 for mn  4

where:

m = R ((d1 + d2)/d1 d2) / ( R /)1/3

n = h ( R /)2/3 / R

R = radius of a rounded obstacle (km)

d = length of path (km)

d1 and d2 = distances of the two ends of the path from the top of the obstacle (km)

h = height from the top of the obstacle (ho) to the straight line joining the two ends of the path. If the obstacle is below this line, h is negative. (m)

ho = fixed terrain height of obstacle (m) + terrain height correction due to k-factor (m). (k=3 which represents > 20% of time)

= (d1 d2)/(12.75 k)

 = wavelength (m)

3. Double isolated edges

Use Recommendation ITU-R PN.526-3

4. General method for one or more obstacles

Use Recommendation ITU-R PN.526-3

SCHEDULE 3

RCS ANTENNA PATTERNS

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Radiation Pattern Envelope for a 2MP RCS repeater antenna

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Radiation Pattern Envelope for a 3MP RCS repeater antenna

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Radiation Pattern Envelope for a 4MP RCS repeater antenna

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Radiation Pattern Envelope for a Yagi 15 dBi (E Plane) RCS repeater/customer antenna

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Radiation Pattern Envelope for a Yagi 15 dBi (H Plane) RCS repeater/customer antenna