How to Set Density and Distance?

Two of the critical parameters for the EPFD(up) analysis are the non-GSO system’s density and distance fields. These are defined in Appendix 4 as:

A.4.b.7.b: the average number of associated earth stations with overlapping frequencies per square kilometre within a cell

A.4.b.7.c: the average distance, in kilometres, between co-frequency cells

These are used to create a deployment of non-GSO ES to use in the EPFD analysis.

The average distance is that between the centres of two co-frequency cells or beams, taking into account the frequency re-use between beams. If a system is using CDMA, so that all beams could be on the same frequency, then it is the average distance between adjacent beam centres. However if FDMA or TDMA/FDMA is used then there are likely to be beams between two co-frequency beams.

The access method should also be used to set the density taking into account the average distance between co-frequency cells. In particular, these two fields are used to calculate the number of co-frequency co-located non-GSO ES that can transmit simultaneously using:

NUM_ES = ES_DISTANCE * ES_DISTANCE * ES_DENSITY

If a non-GSO system is using TDMA or FDMA then only one of its ES will be transmitting at the same location and hence the density can be derived from the distance using:

ES_DENSITY = 1 / (ES_DISTANCE * ES_DISTANCE)

However if CDMA is being used so that there could be NCDMA non-GSO ES active co-frequency co-located at the same time then the density is:

ES_DENSITY = NCDMA / (ES_DISTANCE * ES_DISTANCE)

The NUM_ES is then used to adjust the non-GSO system ES EIRP mask to take account of there being potentially being multiple simultaneously active ES as in:

REP_e.i.r.p. = ES_e.i.r.p. + 10log10(NUM_ES)

Note that the density field is typically much less than 1 and SpaceCap V7 is required to enter this field (earlier versions required an integer).