Beginners Guide to Coverage vs Capacity for WLAN Designs
The idea for this blog came from a recent headache from a company looking to overhaul their current infrastructure. Currently using cost effective access points, they were looking for a solution that would cover more area (due to experiencing black spots) with half as many access points. After a lengthy discussion they seemed to get the idea that this is not quite how wireless works. But how does it work? Why upgrade from an entry level access point to an enterprise grade product if you going to have to buy a similar number of access points?
When designing a new wireless LAN, the variables to coverage are; the power settings (which are Country dependent), antenna gain, and the physical environment. The newer enterprise grade access points on the market will automatically adjust their settings for optimal coverage, but planning a wireless network has, unfortunately, never been as simple as drawing circles on a floor plan. Wireless surveys, and the documentation to understand the results, can go a long way to help creating a network that matches the initial expectations of your project. You will stand more of a chance implementing an effective WLAN when including heat maps and spectrum analysis from a professional survey, especially when VOIP is going to be a feature.
The location and number of access points required nowadays, depends on how many wireless clients will be using the network simultaneously, what they will be using the bandwidth for, and in where in the building (for density coverage). Looking at the design and layout of your project, you will know of the main areas that will be using wireless. For example, in Schools, there are large classrooms, assembly halls, canteens and playgrounds where students will gather using mobiles, tablets and possibly laptops. These environments have the potential to be a high density area for WLAN clients. We can no longer install an access point in a hallway, and record the signal while walking away until the final lingering strains of signal fade. Now you design for capacity as well (or at least you should).
In the early days, Wi-Fi was mostly used for web browsing and email by the rich and the famous. It was more of a convenience. Nowadays, there isn't a day that goes by where people won\'t automatically expect to be able to connect to Wi-Fi in some way, in order to automatically share the pictures of them enjoying a day out with their friends or stream a video of a cat falling off a fence on YouTube. And with every Smartphone able to support Wi-Fi and the carriers clamping down on data plans, users will look for any open Wi-Fi connection to save themselves money! This also needs to be taken into consideration for your design if the IT manager is allowing BYOD on a free network.
It\'s always good to plan for the users at the edge of the coverage area as well, as depending on the access point manufacturer you have chosen, they can experience a diminished performance and the overall capacity will suffer, even if you have great coverage to start off with. If you cut lower data rates out and decrease the coverage area, you can potentially increase throughput. If you allow the lower data rates, you can increase the coverage area of each access point but users will notice the difference as they walk half way between access points placed further away than usual. This then leaves you with the difficult conundrum of whose desk to put in this black spot as a punishment.
So what does all this mean? Do we have to spend more and buy more APs? Maybe.
But the network is there to be used, not just seen. Choosing an enterprise grade access point for your business can result in using less access points if the network is properly designed and configured, and this has been implemented on more than a few occasions. We can help design the network so that it provides a great end user experience and help boost productivity.