The success of WiFi is nothing short of outstanding. Who would have thought that wireless network operators would adopt the technology and deploy WiFi access nodes in their tens of thousands to off-load their wide area networks? But with more carrier WiFi being rolled out in addition to your typical enterprise and personal access nodes, how much WiFi is out there? How much interference does it generate? And what does that say about the future when it comes to unlicensed band spectrum utilization?
A program which started 11 years ago almost to a day, WiGLE (Wireless Geographic Logging Engine) has recorded over 74.6 million unique access networks to date around the world and has about 1.65 billion WiFi locations in its database collected from over 128,000 users.
So where are all these WiFi networks? WiGLE maps clearly show that the deployments concentrate in the urban areas of the world, particularly Western Europe, US and Canada and Japan, although I reckon that networks in developing countries may be under-represented because of fewer contributors to the program. Anyway, the WiFi network density is closely correlated with population density.
The majority of recorded networks (86.3%) operate in the ISM band while the U-NII bands account for 0.4%. The remainder 13.3% is unaccounted for (none shown for U-NII Worldwide band spanning 5.47 – 5.725 GHz). Operation in the non-overlapping channels 1, 6, and 11 account for 67.5% (channel 6 accounts for just over 27%). Nevertheless, this matches conventional knowledge of the ISM band being highly polluted with interference; not a surprise with over 86% of WiFi access nodes operating in this band.
| Band |
Frequency |
% of Systems |
| ISM |
2400 – 2500 MHz |
86.31% |
| U-NII-1 |
5150 – 5250 MHz |
0.21% |
| U-NII-2 |
5250 – 5350 MHz |
0.05% |
| U-NII-3 |
5725 – 5825 MHz |
0.14% |
Given these statistics, I believe it would be better for carrier WiFi networks to start making use of the U-NII bands which are far less polluted. Finalizing (end of 2012) and ratification (back end of 2013) of 802.11ac standard and availability of devices in 5 GHz will lead to increasingly higher utilization of the U-NII bands despite the requirement for Dynamic Frequency Selection (DFS) which requires systems to change channels upon detecting radar systems in parts of the U-NII band spectrum (country specific). Even today devices that support dual channel 2.4/5 GHz operation with 802.11n (e.g. iPhone 5, iPad, Samsung Galaxy S3 and Galaxy Tab are but a few to name) can take advantage of access nodes operating in the 5 GHz band. I would expect this trend to accelerate in the near future as subscribers discover the advantages of faster data services over the 5 GHz band.
I will expand further on the topic of interference in an upcoming entry, so stay tuned and come back soon to check it out!
World WiFi Deployment Map (Source: WiGLE)
USA WiFi Deployment Map (Source: WiGLE)
Europe WiFi Deployment Map (Source: WiGLE)
Thanks Frank, your insight is great and very relevant as always.
What is staggering is what gets achieved using just 100MHz of low power, interference ridden spectrum versus the gigahertz sitting there doing nothing.