User experience in public Free-WiFi

Today’s world lives in the paradigm that “WiFi = Internet & Internet = Life”. Therefore it is not surprising that governments around the world consider making WiFi a fundamental right of their citizens. In many ways, WiFi is today what electricity was in the 50s. Many cities around the world already offer Free-WiFi . We even see political parties include Free-WiFi in their election manifestos, especially in developing economies. Free-WiFi is bound to be a ubiquitous presence in our public spaces.

image-2

(Picture Courtesty @RealErlich)

However, how free is this Free-WiFi? What kind of a user-experience can one expect from Free-WiFi? Such questions are largely unanswered & unthought of under the pressure to show implementation. It is not very uncommon that one goes to a space which has Free-WiFi, spots a very good WiFi signal, but cannot even connect to the network. Connection reliability and performance requirements of most popular applications are beyond the capabilities of poorly implemented Free-WiFi networks. This results in high costs with near zero value add to the general public.

To address this issue, clearly defined SLAs are needed. These should incentivize integrators, set up expectations for users, and act as guidelines for administrators. Also this will result in proper planning of WiFi coverage and capacity. A closer look at the details on how WiFi works will help to understand the challenge better. WiFi works in 2 ISM bands; 2.4GHz and 5GHz. Each of these bands consists of many channels. Number of channels and channel center frequencies varies slightly from country to country. A typical 802.11n channel is of 40MHz of bandwidth and allows a maximum theoretical through put of 450 Mbps with a 3×3 MIMO antenna, at the physical layer. Practically, applications running on user’s devices can get around 220 to 270 Mbps. Does that imply that 200 users can be served 1 Mbps each on a single channel? Not really. Since users are independent of each other and their actions are not co-ordinated, many clients try to use the channel at the same time and these collisions, brings the efficiency of the channel down. Also typically there are resource limitations in the WiFi Access Point and rest of the WiFi infrastructure, which brings down the number of users that can be served by a single Access point over a single channel.

Graph below shows this more objectively. As the number of clients increases total throughput given by the Access Point decreases rapidly

image-1(measured using SWAT WiCheck multi-client emulator http://wicheck.alethea.in)

The degree of deterioration varies between different makes of Access Points and to some extent defines the difference between a consumer grade AP and an enterprise grade AP. Each AP OEM, has their own method to achieve the best result in the most cost effective way.

Solution to improving the efficiency of WiFi networks also needs a broader perspective. Starting point is definitely the allocation of more bandwidth to the ISM bands used by WiFi. World over WiFi ecosystem has been appealing to policy makers in their respective countries for more spectrum. Moving to newer and better standards (802.11ac) that allow much higher throughputs also will help.

Many describe WiFi as the new oxygen. As Free-WiFi networks increase their reach, need for increasing the efficiency of the network becomes more and more important. Each part of the ecosystem, starting from policy makers to OEMs and service provides needs to be sensitive about this and work as a team to find better solutions.

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