Taking the measurements

There are three steps in the measurement process:

  • an initial desktop assessment to determine likely measurement locations
  • broadband measurements of all mobile phone downlinks in the vicinity of the base station
  • final measurements at five selected locations.

Suitability of a location is primarily determined by ability to access the areas expected to have the highest levels and good line of sight to the antennas. This initial assessment is done using aerial photographs, street maps and model calculations. At this stage of the process more than five potential locations may be considered. A site visit is used to confirm the suitability of the locations.

Preliminary measurements to assess the suitability of the site were conducted by ARPANSA staff. Broadband measurements of all mobile phone downlinks were recorded whilst walking the streets surrounding the base station. These measurements in conjunction with model calculations and line of sight considerations are used to select five measurement locations.

The final measurements were conducted by consultants from companies appointed by ARPANSA and accredited by the National Association of Testing Authorities (NATA). The data were obtained following the ARPANSA measurement protocol.

Five locations were nominated by ARPANSA in the vicinity of each base station to provide an indication of the broad-scale variation (figure 1). At each of these five locations the RF EME levels were measured at seven positions spaced over a few square metres to explore the small-scale variation and to reduce the chances of a local minima due to destructive interference skewing the results (figure 2). In all cases the average RF power flux density was to be measured over a period of at least one minute.

The RF power flux density (averaged over at least one minute) in each mobile phone downlink frequency band was measured at seven positions around the primary measurement location only. These measurements include contributions from phone traffic on the target base station and may also include signals from other nearby base stations. The smallest and largest values recorded for each frequency band are reported.

The RF power flux density (averaged over at least one minute) in the control channels and pilot signals for the services at the target base station were measured at seven positions in all five measurement locations. These measurements are designed to include only traffic independent levels arising from the target base station. The smallest and largest values for each Operator and Service are reported.

Primary measurment image

Figure 1. Measurement locations in relation to the base station antenna pattern as seen from above. The predicted RF levels are shown by colour: white and blue represent lower values whilst orange and red indicate higher values. The ideal place for the Primary Measurement (Location 1) is at the point with the highest predicted value. Secondary Measurements are made at points closer, further and to the left and right of Location 1. In practice it is rarely possible to obtain such a neat symmetry of measurement locations.

Sampling positions

Figure 2a. Sampling of local variation at each measurement location as seen from above (not to scale). The initial measurement location is indicated by the red spot in the centre of the measurement points. Four of the six measurement points for the structured sampling surrounding the initial measurement location are indicated in blue (labelled Left, Right, Forward and Backward).

Sampling locations from the side

Figure 2b. Sampling of local variation at each measurement location as seen from the side (not to scale). The initial measurement location is indicated by the red spot in the centre of the measurement points. Four of the six measurement points for the structured sampling surrounding the initial measurement location are indicated in blue (labelled Up, Down, Forward and Backward).

Preliminary measurements

Preliminary measurements to assess the suitability of the site were conducted by ARPANSA staff. Broadband measurements of all mobile phone downlink frequencies were recorded whilst walking the streets surrounding the base station. These measurements in conjunction with model calculations and line of sight considerations were used to select five measurement locations.

The map below shows the preliminary broadband measurements conducted by ARPANSA whilst walking the streets surrounding the base station. These values include contributions from phone traffic on the network and may include contributions from other nearby base stations. The location of the base station is indicated by the green triangle ( Green triangle ) and the measured values are represented by blue circles ( Blue circle ) sized relative to the measured RF level.

Preliminary measurements

At this site the base station antennas are situated on the exterior of a large building with the antennas for each sector widely separated. Due to the topography of this inner city site only one sector was explored and very few locations provided line of sight to the antennas. For these reasons the site was deemed to not be amenable to measurement using the current ARPANSA measurement protocol.