Annex A:

Propagation measurements for ad-hoc deployment

A.1 Method

A number of propagation measurement campaigns have been carried out for ad-hoc deployment in UK and Finnish cities in the 3,4 GHz band. In general, the method used was as follows.

Transmitters were set up at typical CS locations chosen to illuminate the desired area. Transmitting antennas were either omnidirectional or "sectored"; for an omnidirectional antenna the typical gain was 10 dBi (achieved by the narrow vertical beamwidth). Somewhat higher gains are achievable with sectored antennas. Vertical polarization was used throughout. The radiated carrier was unmodulated, allowing the use of narrow receiver bandwidth to maximize dynamic range.

Received signal levels were measured at a vehicle equipped with a telescopic mast, at a large number of randomly chosen locations. The receiving antenna mounted on the mast was pointed at the CS location from each measurement point and the mast set to rooftop height to measure the signal level. The level was measured over a period of time to assess the variability of the signal. The receiving antenna gain was 18 dBi.

With the transmit power and receiver bandwidth used the total dynamic range possible was approximately 180 dB.

Separate tests have been done to characterize multipath propagation using wideband channel sounding and swept frequency measurements in cities in both the UK and Finland.

A.2 Results

Figure A.1 plots the measured path loss from one typical trial. For each measurement location, the median path loss and the path loss exceeded for 99 % of the measurement period are shown, as a function of the range of the point from the CS location. Also plotted is the free space path loss.

Figure A.1: path loss measurements

The results clearly show the large excess loss and variability expected when a LOS path cannot be guaranteed. It is obvious that the maximum possible system range will be required to maximize the probability of providing service at any particular point from the given CS.

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Multipath measurements have also shown that delay spread is found on a proportion of paths, with a maximum recorded delay spread of up to 4 s. The existence of multipath at any given TS location is unpredictable, and to maximize the service probability the system has to cope with this level of delay spread.

For P-MP systems in frequency bands at or above 10 GHz, line-of-sight conditions are an inevitable condition for each link. On the one hand this reduces coverage, because a prospective TS location can no longer be supplied by means of the physical effects of reflection or diffraction. This negative effect has to be taken into account. On the other hand the highly positive effect is a strong reduction of dynamic range of receive power in any CRS or TS. This is in contrast to the measurement results discussed above. In particular the impact of multipath transmission is reduced drastically because these unintended paths depend on reflection and/or diffraction and can be assumed to show considerably higher path loss than the wanted line-of-sight path. Hence all the negative effects of multipath propagation such as Intersymbol Interference and loss of power will be reduced in the higher frequency bands.

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