WiFi! What is it good for?

Should we put WiFi on a pedestal or chuck it in the bin?

There are many arguments taking place about how the wireless networks of the future could or should operate, and whether or not they could be operated on a non-profit basis. The role of the technology nicknamed WiFi is most often mentioned in these arguments.

WiFi is able to take on some part of the task of delivering a telecommunications service. WiFi is cheap enough that the end-user can afford to buy a WiFi radio outright in a single payment and therefore not have to pay ongoing subscriptions. Because of this, it is often touted as being a cornerstone technology in a future telecommunications system where all bandwidth is provided free of charge and that requires no human administration. WiFi does have it's limits, and just as often as it is lauded, WiFi is derided for it's limitations and we are told that WiFi has no future at all.

Lets look at what WiFi can do, and look at what we expect from our telecommunications system.

A Communications service company can do any or all of these 3 things:

• Carry large amounts of data long distances between major city exchanges with single, high capacity links
• Carry medium amounts of data medium distances between suburban or small town exchanges with numerous medium capacity links
• Carry small amounts of data between suburban exhanges and end users with a vast network of "last mile" links - being copper lines or cell towers.
  

WiFi is completely unsuited to inter-city data transfer. It doesn't have the range, stability or bandwidth to accomplish such a task. Such a task still requires specialised telco equipment and major infrastructure, so end-users or community groups cannot hope to replicate this service using WiFi.

WiFi has a limited capability to achieve inter-suburb data transfer with fixed, point-to-point links. A network based on WiFi inter-suburb links can service a small number of users, but will become unreliable with too high a bandwidth load. Using WiFi as a point-to-point link system is relatively expensive - a separate radio with a large, high-gain antenna must be dedicated to each end of each link. A node that wants to make multiple links must buy a radio for each link - these costs add up quickly. Also, because of the limited bandwidth in the public 2.4GHz spectrum, there is a maximum number of radios that can operate at the one location - any more and the radios interfere with each other leading to degraded performance and diminishing bandwidth returns.

WiFi is not well-suited to point-to-multipoint links when used at the inter-suburb scale. WiFi was designed for short-range indoor deployments and does not efficiently or fairly manage network bandwidth from the central Access Point when the client radios are beyond receiving range of each other (the "Hidden Node" problem).

There are some proprietary midrange solutions that are within the price range of community groups that could achieve decent inter-suburb point-to-multipoint linkage. Motorola's Canopy system is one such solution. The Access Point cost is around the AU$1100 mark and the client radio is around the $350 mark. These costs are higher than what most end-users are willing to pay. Canopy heralds the widespread introduction of WiMax. It is unclear what impact WiMax will have on the wireless networking landscape. But it is unlikely that WiMax radios will be as cheap as WiFi radios in the short-to-medium term. It is also unlikely that WiMax client radios will offer a peer-to-peer or "adhoc" mode - if it does, the adhoc mode won't be capable of covering the same range as an Access Point. So all WiMax networks will rely on a dedicated central Access Point, and that Access Point will be an expensive piece of hardware - beyond the price-range of the average end-user and deliberately so. Working out a way to pay for Canopy/WiMax Access Points and how to find good places to put them becomes complicated in a non-profit model, but perhaps not impossible for a community organisation. In Australia the fact that the ACMA has some fairly strict rules regarding telco licencing and who is or isn't exempt from buying a licence makes matters even more complicated.

WiFi is best suited to achieve "Last Mile", intra-suburb linkage. WiFi operates best over short distances - the longer the link distance the smaller amount of bandwidth the link can carry. WiFi can cope well with network applications that don't concentrate many users bandwidth bandwidth upon a single node - one such example is Voice-Over-IP (VoIP) telephony. A single WiFi radio is cheap, low power consuming, and physically quite small. With a high-gain omnidirectional antenna attached, WiFi can enable neighborhood connectivity between any users in range of each other. An omnidirectional Wifi antenna is unobtrusive and could easily be mounted on the rooftop television antenna mast on any suburban household. A typical installation would have a minumum rooftop-to-rooftop omnidirectional range of a few hundred metres and a maximum omnidirectional range of roughly 2km, depending on surrounding tree and building heights.

WiFi's usefulness also benefits from the fact that it has a peer-to-peer or adhoc mode, so end-users are also able to act as network repeaters. This effectively makes every node a multipoint-to-multipoint repeater. Network that take advantage of this mode are called mesh networks. There are many successful, real-world examples of mesh networks - both commercial and non-profit. Freifunk.net in Germany and The Champaign-Urbana network in the USA are non-profit examples. Tropos and MeshDynamics are commercial examples. WiFi is a consumer-grade product which hasn't been considered suitable for mission critical applications. Mesh networks increase the reliability of a WiFi network by offering redundant paths that automaticlly bypass node failures or bandwidth choke points. Mesh networks are said to be "self-healing" and "failure-tolerant".

Mesh networks have proven their usefulness, but the technology is still in its infancy. There is yet to emerge a mesh protocol that is truly scalable, yet open-source programmers and academic researchers are refining existing protocols and are learning their limitations. It is only a matter of time before a mesh protocol appears that comes close to the ideal of being globally scalable with little or no human administration or centralised infrastructure. An example on the drawing board that aims to achieve this ideal is DART. However, if and when such a protocol appears, we must still keep in mind the capabilities and limitations of WiFi.

End users continue to pay subscription fees (line rentals) to use a reliable telecommunications service. The advent of WiFi and broadband Internet has opened up the possibility that there may be some way for end users to organise collectively to buy Internet bandwidth in bulk from a central supplier and use WiFi to distribute it amongst themselves - thereby freeing themselves from monthly line rentals. This method of receiving a telecommunications service is acceptable to technology hobbyists and early-adopters, but won't become mainstream until it can deliver a standard of service close to what most users expect from their present telco.

WiFi has its flaws, and it clearly isn't a "magic bullet" technology that can universally deliver everyone's telecommunications needs. But it clearly has it's capabilities, and it has popularised the concept of mesh networking. The idea of wide-area, zero-overhead, zero-admin networking is gaining momentum, and isn't going to go away. The technology can only improve and so with each generation of hardware and protocols we come closer to the ideal.

To telco planners, investors and government regulators: ignore or restrict WiFi at your peril. Networks serve their users best when people are allowed to use them the way they want to use them. WiFi is in the hands of end-users - WiFi can and will be used by them as a Last Mile replacement technology. Acceptable Usage Policies (AUPs) that restrict or prohibit end-users from sharing their bandwidth go against people's natural instincts to organise at a local level to share resources. Telcos that allow end-user bandwidth-redistribution have an enormous marketing advantage and will be seen to be technology innovators in the eyes of the public. Governments that legislate to allow and encourage community-organised data networks also stand to gain political capital - especially in areas that are under-served by commercially-oriented telcos.