One of the really neat features about using automated RF planning tools like Forsk Atoll is you’re able to get it to automatically try out tweaks and look at how that impacts performance.

In the past you’d adjust something, run the simulation again, look at the results and compare to what you had before,

Atoll’s ACP (Automatic Cell Planning) module allows you to automate this, and in most cases, it does a better job than I would!

Today we’ll look at Cell Site Selection in Atoll.

To begin with we’ll limit the computation area down to a polygon we draw around the area in question,

In the Geo tab we’ll select Zones -> Computation Zone and select Edit

We’ll create a new Polygon and draw around the area we are going to analyze. You can automate this step based on population levels, etc, if you’ve got that data present.

So now we’ve set our computation area to the selection, but if we didn’t do this, we’d be computing for the whole world, and that might take a while…

Generating Candidate Sites

Atoll sucks at this, I’ve found if your computation zone is set, and it’s not a rectangle, bad things happen, so I’ve written a little script to generate candidates for me.

Creating an new ACP Job

From the Network tab, right click on ACP Automatic Cell Planning and select New

Optimization Tab

Before we can define all the specifics of what we’re looking to plan / improve, we need to set some limits on the software itself and tell it what we’re looking to improve.

The resolution defines how precise the results should be, and the iterations defines how many changes the software should run through.

The higher the number of iterations, the better the results, but it’s not linear – The improvement between 1000 iterations and 1,000,000,000 iterations is typically pretty minor, and this is because ACP works kind of a “getting warmer” philosophy, where it changes a value up or down, looks at the overall result and then if the result was better, changes the value again until it stops getting better.

As I’m working in a fairly small area I’m going to set 100 iterations and a 50m resolution.

In the optimization tab we can also set constraints, for example we’re looking at where to place cell sites in an area, and as far as Atoll is concerned if we just throw hundreds of sites at an area we’ll have pretty good results, but the economics of that doesn’t work, so we can set constraints, for example for site selection we may want to set the max number of cell sites. As we are importing ~5k candidate locations, we probably don’t want to build 5k cell sites 20m apart, so set this to be a reasonable number for your geography.

When using ACP for Optimization as we can see later on, we can also set cost constraints regarding the cost to make changes, but for now this is just going to pick best cell sites locations for us.

Objectives Tab

Next up we’ll need to setup Automatic Cell Plannings’ objectives.

For ACP to be an effective tool we need to define what we’re looking for in terms of success, you can’t just throw it some values and say “Make it better” – we need to define what parameters we’re looking to improve. We do this by setting Objectives.

Your objectives are going to be based on your needs and wants, but for this example we’re building greenfield networks, so want to offer coverage over an area, as well as good RSRP and RSRQ, so we will set the objectives to Coverage of 95% of the Computation Zone for this post, with a secondary objective of increasing RSRP and RSRQ.

But today I’m modeling for coverage, so let’s set that:

As we’re planning for LTE we need to set the UE parameters, as I’m planning for a mobile network, I’ll need to set the service type and terminal.

Reconfiguration

Now we’ve defined the Objectives, it’s now time to define what values ACP can mess with to try and achieve these objectives, for some ACP runs you may be adjusting tilts or azimuths, swapping out antennas, etc, but today we’re looking for where we can put cell sites to be the most effective to serve our target area.

Now we import our candidate list. This might be a list of potential towers you can use, or in my case, for something greenfield, I’m just importing a list of points on a map every X meters to find the best locations to place towers.

From the “Reconfiguration”, we’ll select “Setup” to add the sites we want to evalute.

Atoll has “Automatic Candidate Positioning” which allows it to generate pins on the map, but I’ve not had any luck with it, instead I’m importing a list of candidates I’ve generated via a little Python script, so I’ll select “Import from File”.

Pick my file and set the parameters for importing the data like so.

Now we’ve got candidates for cell sites defined, we set the station template to populate and then we’re good to go.

Running ACP

Once you’ve tweaked all your ACP values as required, we can run the ACP job,

As ACP runs you’ll see a graph showing the objectives and the levels it needs to reach to satisfy them, this step can take a super dooper long time – Especially if your computation zone is large or your number of candidates is large.

But eventually we’ll be a lot older and wearier, but ACP will have completed, and we can checkout the Optimization it’s created.

In my case the objectives failed to be met, but that’s OK for me,

One it’s completed the Changes tab outlines the recommended changes, and the Objectives outlines how this has performed against the criteria we outlined at the start, and if we’re happy with the result, we can Commit the changes to put them on the map from the commit tab.

With that done I weed out the sites in impractical locations, the the ones in the sea…

Now we’ve got the sites plugged in, the next thing we’ll start doing is optimizing them.

When we’re dealing with greenfield builds like we are today, the “Move to highest location with X Meters” function is super useful. If you’ve got a high point on a property, we want to build our tower on the highest point, so the tower is moved to the highest point.

One thing to note is this just plans our grid. It won’t adjust azimuths, downtilts, etc, in one operation. We need to use another ACP operation to achieve that, and that’s the content of a different post!