In part one of this article I explained the need for a designed solution to a "worst case" scenario wireless environment. The worst case was an apartment complex where every resident would have their own high performance wireless access point and the wireless networks would be overlapping eahc other everywhere. The challenge was to make it work as well as possible so that the owner of the complex and the cable Internet provider could sell it as a managed service.
As a result of each apartment having its own wireless access point there was going to be multiple overlapping RF cells. With this much overlapping RF I knew I would certainly see co-channel interference or contention (channels reused within the same space which is a wifi no no) in the 2.4 GHz channel space.
I knew I would also probably run into adjacent channel interference or contention (very close neighboring channels adjacent to each other which is another Wi-Fi no no) in the 5GHz spectrum. To address this I recommended the following in the design;
Each residential gateway unit would require a static channel assigned to each radio; 2.4GHz and 5 GHz.
All auto radio management on the gateway units would need to be turned off completely.
The lowest data rates for both 2.4GHz and 5 GHz radios would need to be removed. This would mean disabling data rates less than 12Mbps on the 2.4 & 5GHz radios.
The default power level assignment for each radio would need to be at its lowest possible.
Channel widths for the radios would need to be 20MHz for 2.4GHz and 20MHz for 5GHz.
The project started off with a predictive design using a site survey and planning software. Access points were placed in the software application with respect to the locations where the service provider had located the low voltage enclosure that would house the gateway units within each apartment.
(Remember that I had no say in how many access points there would be or where they would be located) Channel assignments were allocated using an auto channel planning function of the software and then doing some spot checking.
The spot checking was done to make sure I did not have any overlapping channels from units above, below or adjacent to any of the apartments. Static channel plans is not something I am used to doing as most Enterprise class WLAN equipment has automated RF adjustment features that take care of assigning channels and power levels.
In this environment however I am not sure that automated RF features would have been of any help. As difficult as the planning of static channels in both spectrums is it was definitely necessary in an effort to make this the best coordinated effort I could.
Once I had tweaked the design and adjusted it as much as I could it was then presented to the customer. We had a conference call to discuss the items I felt needed to be addressed and any of the customers concerns and questions were answered.
From this call the next steps in the process were laid out. The customer would be taking the design on-site to implement my recommendations and we would set a time for a site visit to validate and verify the implementation.
In part 3 of this article I will visit how the implementation of the design was carried out, how the design was validated, and what tests I used to verify my assumptions on-site. Stay posted for part 3.