Femtocell Opinion, comment and reviews

Wi-Fi has limits that small cells can capitalize on

Wi-Fi and small cellsEd Candy, Group CTO of Hutchison 3, said at last month's LTE World Summit that he thought Wi-Fi would "Asymptote to failure", a view he has held for several years. With Wi-Fi performance in some places becoming unworkable, is he right? I believe Wi-Fi does have a place in the overall solution, but can't solve capacity problems in cases of high traffic congestion and contention.

Some network operators believe Wi-Fi will rescue them from overwhelming demands on their mobile data networks, while others believe it will cut them out of the value chain. We've seen Wi-Fi become a standard feature of smartphones and tablets, often used to access higher speed services such as video, but it cuts out the network operator who has little or no visibility of what the end user is doing. We've looked at Wi-Fi congestion before in an article which also referenced last year's study by Qualcomm into the issue.

Wi-Fi in congested areas

What I believe Ed was referring to was that where larger numbers of Wi-Fi hotspots and users are competing in shared but uncontrolled spectrum, the throughput goes down for everyone. In the worst case, total capacity drops dramatically and nobody gets any reasonable throughput.

In some cases, you can pickup anything from 50 to 200 Wi-Fi hotspots all trying to share the same space. This is very true for conference venues, where it seems every booth has its own.

Another problem can be "pop-up Mi-Fi hotspots", where a portable Mi-Fi unit (effectively a standalone 3G data dongle combined with a Wi-Fi hotspot) can be turned on in any congested space and just adds to the problem.

Some "fireside" stories

I've heard of residents in terraced streets or apartments competing for Wi-Fi channels. Having set their broadband router for a particular free channel, it works well for a while until a neighbour decides to change the settings on their box. Neighbours can play hokey-cokey with their Wi-Fi settings, changing them on a regular basis to find a setting that works.

Others have installed multiple Wi-Fi hotspots in their homes, only to discover that overall throughput can be reduced as each box competes with the others.

My own experience in public areas such as airports and conferences is poor. Unless I'm are standing right next the hotspot itself, I don't expect much.

A hotel I stayed at recently appeared to have a Wi-Fi modem in every room, under the desk. My laptop could connect to that through the few inches of desktop of course, but my iPad wasn't reliable from other parts of the room. I'm pretty sure that would be down to interference rather than signal strength, and that there are technical solutions to that problem.

Wi-Fi does have its place

Clearly Wi-Fi works well in many circumstances. If you have a larger home or live in an area with fewer competing hotspots, then it works well. In offices and other buildings where there is a single owner (e.g. McDonalds), performance can be good.

Using Wi-Fi systems which are more sophisticated and designed for higher numbers of users, such as from Ruckus, Belair (now Ericsson) or Cisco, significantly improves the throughput and end user experience.

Since many of us would use smartphones, tablets and other wireless devices in the home or office – Wi-Fi clearly has an important position to handle that traffic.

Why new Wi-Fi features may not work so well

There have been several major advances with Wi-Fi technology in recent years. Newer versions incorporate many new features. Spectrum at 5GHz can be used in addition to the original 2.4GHz band. However, there are many devices in circulation which still use the older 802.11b specification and will continue to be used for years to come.

The issue here is that the latest Wi-Fi features are swamped by older devices, preventing them from delivering the higher speeds and capacity they are designed for.

Small Cells and Femtocells offer a co-ordinated approach

The difference that a small cell offers is that by operating in licensed spectrum, it can be co-ordinated with others sharing the same frequencies. Clusters of small cells work in harmony with each other, sharing traffic and capacity between themselves.

Many algorithms and further research into femtocells is being incorporated into higher capacity devices which allow them to perform more effectively.

A balanced solution

I expect that we might see several outcomes in the next few years:

  • Wi-Fi will continue to be successful in the homes, offices and other buildings where only one owner installs and maintains it and where these are physically spaced apart enough to avoid congestion from neighbours
  • Public access in dense urban and other high traffic areas will be dominated by co-ordinated small cells run by the cellular network operators.
  • In dense residential environments where Wi-Fi congestion grows, femtocells may be considered as an option because they would provide a more consistent throughput and end-user experience.

Always-on connection to data services is becoming a "must have" for many people these days. If Wi-Fi fails to deliver in certain situations, then more robustly engineered small cells have the technology to meet that demand.

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#1 Christian said: 
As an expert in the sort of interference that you're talking about, I don't see all that much difference between WiFi and small cells. The same interference is present for both, and the same sort of solutions apply inboth cases. I think WiFi will steal just as many cellular users as cellular steals from WiFi.
0 Quote 2012-06-07 04:53
#2 ThinkSmallCell said: 
@Christian: Without further details about your assumptions, I still have reservations. The specific difference with Wi-Fi is where there are many hotspots sharing the same spectrum in the same location operated by different people. This uncoordinated interference is surely more difficult to resolve than a single, co-ordinated grid of small cells operating in protected spectrum?

As above, I think there are some situations where Wi-Fi is a better solution and others where mobile technology will win out.
0 Quote 2012-06-07 19:22
#3 Adnan said: 
WiFi is by design contention based. 3GPP (LTE in particular) is managed access by eNB. So in busy areas, a managed approach is always better.
In the extreme, think of MWC and WiFi.
0 Quote 2012-06-09 08:40
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