The Radiotools Spectrum Management Suite

Until recently, Radiotools was the main Spectrum Management tool we use in the JRC.

Since April 2006 we've been steadily integrating ATDI's ICS Telecom into our planning processes. Radiotools is still in daily use as it's tightly integrated with what we do and we're finding some interesting "features" of Telecom that preclude our using it for some activities until we've worked out exactly what's happening.

Radiotools is a Unix-based RF planning tool custom-built for the industry by EA Technology and based on our earlier planning tools (170k Page size!), RFD1, Radio, SERV, which were among the first computerised RF planning tools in use. Ever. Radiotools uses the JRC Terrain Database which is a specially optimised for RF planning 500m terrain database of the UK giving comparible performance with the more common non-optimised 50m databases. This was the first UK Terrain Database and is still in use in the broadcast and spectrum management industries.

Propagation Prediction

(extract from the RFDesigner2 Manual)

Unlike microwave link and scanning telemetry link design, mobile radio systems require prediction of propagation losses on paths that are subject to significant obstruction. Also the prediction can only be, at best, a mean value since it is an environment in which there are local obstructions and reflections, and the signal is a summation of several paths resulting in a fading pattern at the wavelength scale. This signal variability, described by the Rayleigh function is not modelled within this design tool. What the prediction model does attempt to model is the effect of path obstructions primarily due to the terrain but also to take some account of the objects that exist on the ground, that is buildings or "clutter", the prediction taking account of the clutter insofar as it adds to, the mean value of loss.

The method of identifying and classifying features on the profile that are significant to propagation has been revised, as has the detail of the propagation algorithm itself. RFDesigner 1 used a method of radials out from a base station to cover the required area, and then interpolated values calculated along these radials to give a rectangular array of results. In RFDesigner II, the user defines the required resolution of predictions and a regular grid of points within the defined area has predictions calculated for them. This avoids the smoothing of predictions caused by interpolation.

The original release of RFDesigner II had a revised propagation algorithm that had been developed in the context of the availability 50m Digital Terrain Maps (DTM). In this release the propagation algorithm has reverted to that utilised in RFDesigner I, partially for compatibility with the large amount of design work undertaken with the earlier tool and because the new algorithm was found to be less accurate than the old when using 500m DTM. Since the 500m DTM is adequate for most situations, the use of 50m is seen as being restricted to rapidly varying terrain such as the valleys of South Wales.

Obstructions that are not described in a terrain height database, i.e. buildings and forests, can have a significant effect on propagation. Users had to make their own manual compensation in RFDesigner 1, but there is now a facility within RFDesigner II to represent building ground cover to allow additional loss to be attributed to areas of urbanisation. The database supplied with the tool is at 500m resolution and defines urban areas only. Rather than ascribe a loss to a specific area the clutter feature includes a representation of the mean height of obstacles and the mean distance from the mobile. This has an advantage in taking account of clutter obstructions to the path even when the mobile is not in the midst of clutter.

Defining the areas for which predictions are required.

In contrast to the limited facility of either predefined circular areas according to a simple cellular plan or user defined circular areas, the facility is provided within RFDesigner II to distort cell boundaries so that they become representations of the required service area. It is envisaged that description of the required service area in the form of a distorted cell, together with the ability to predict and display C/I ratios will allow more of the overall design and co-ordination to be supported directly by the design tool.