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Wireless local area networks
The wireless local area network (WLAN) is a relatively new technology. Work to develop the WLAN standard (IEEE 802.11) was started in 1990 by the Institute of Electrical and Electronics Engineers Inc., a US-based professional engineering society, to exploit the Industrial, Scientific and Medical (ISM) frequency band for high-speed networking. Unlike most other radio frequencies which are tightly controlled and accessible only to specific licensed personnel, anyone with the appropriate equipment can use the ISM band. The IEEE completed the initial 802.11 standard in 1997 and this was followed in quick succession by an upgrade (IEEE 802.11b) which exploits new technology innovations to improve performance from two to 11 Mbps. Another upgrade (IEEE 802.11a) exploits the newly open ISM bands in the 5.3 to 5.8 GHz bands. To be released in 2007 is yet another variant (IEEE 802.11n) that exploits advanced digital signal processing technologies such as Multiple Input Multiple Output (MIMO) algorithms to bring WLAN data rates up from 54 Mbps to 110 Mbps and beyond. Fortunately, when developing these upgrades, the IEEE standards workgroups have ensured that there is backward compatibility between the new and old. This means that infrastructure installed before the release of these new standards can still work with equipment made to the newer WLAN standards.
Unlike mobile phones where the equipment supplier base is relatively small, the number of manufacturers supplying WLAN equipment is much larger. Many of these manufacturers originate from the Far East and they have a reputation for bringing out very cost competitive products. Competition to supply WLAN equipment is very intense and prices have come down to a point where they have become quite affordable to the masses. For example, currently it is possible to purchase a WLAN PC card for under USD 25 and the price is still dropping. One of the main reasons why WLAN has taken off is that Intel, the US-based computer chip giant, strongly endorsed the technology with its Centrino campaign to put WLAN capability into every notebook computer that is manufactured. The trend to WLAN-enable portable devices is spreading to Personal Digital Assistants (PDAs) and mobile phones. This trend points to a situation where sometime in the not too distant future, almost everyone will carry a WLAN-enabled end-user device everywhere he or she goes.
Recognizing the need to ensure that WLAN equipment from various WLAN manufacturers can work with each other, the leading players from the WLAN community set up a global non-profit organization called the Wi-Fi Alliance to drive the adoption of a single worldwide accepted standard for high-speed wireless local area networking. They created a logo which is affixed to products that have successfully gone through a rigorous certification programme designed to ensure inter-operability between products from different Wi-Fi manufacturers. Users have come to see the logo as a mark of quality and assurance that the product can work with Wi-Fi devices from other manufacturers that may be found in the home, at the office or in public hotspots.
The simplest Wi-Fi system is just a Wi-Fi card plugged or pre-built into a computer, establishing radio contact with a nearby Access Point (AP), which then provides onward connectivity to the global Internet. Because Wi-Fi operates in the unlicensed ISM band, regulators have imposed strict limits on the maximum permissible transmitter power3 for the Wi-Fi card and AP. This is so that the ISM band can be shared by as many people as possible and it is not monopolized by any one single user. The transmit power limitation in turn causes the maximum communication range between a Wi-Fi card and AP to be limited to about 100 metre. If there is no direct line of sight, say if there is a wall between the Wi-Fi card and the AP, the range may drop to below 10 metre. By default, all Wi-Fi cards and APs use omni-directional antennas because a user may approach an AP from any direction. In some special cases where it is desired to link two known fixed points together using Wi-Fi, it is possible to replace the omni-directional antennas with highly directional antennas and extend the range to tens of kilometres. In such situations care must be taken to align the two antennas for maximum effect and the user should note that the mobility capability of Wi-Fi is lost.
Wi-Fi has made major in-roads into the Office, Home and Public Hotspot markets. In the Office market, some technology-savvy companies have Wi-Fi enabled their offices so that their employees can be more productive. Their employees can access corporate resources such as databases, e-mail and the Internet and conduct business transactions even when they are away from their desks. Wi-Fi is also taking root in the Home market. In places where broadband penetration is high, it has become quite widespread to use Wi-Fi to create a wireless home network so that members of a household can share one cable or DSL connection to the Internet. The third market segment is the Public Hotspot market. Public Hotspots are places where Wi-Fi APs have been put up and made available to the general public, sometimes for a fee, or for free, or in exchange for patronizing a business. These Hotspots can typically be found at coffee outlets, fast food chains, shopping malls, libraries and community centres. The public can use their personal Wi-Fi devices to access the Internet at these Public Hotspots.
Because Public Hotspots are relatively cheap and easy to set up, many community leaders see the potential of using Public Hotspots to bridge the digital divide. The city of Philadelphia, working with Earthlink Inc., a commercial Internet Service Provider (ISP), is one noteworthy example of such an effort. Philadelphia is deploying over 4,000 APs on lamp posts all over the city. The capital costs of the infrastructure will be shouldered by Earthlink while the city contributes access to its lamp posts and takes responsibility for obtaining approvals from relevant city departments for the service. Through this public-private collaboration, Philadelphia will be able to offer Wi-Fi Internet access to its needy residents for half the cost of normal commercial Internet access using cable or DSL technologies. The service is also putting pressure on the traditional ISPs to either improve their service offerings or drop their prices to compete. Alarmed by this impending threat to their business, incumbent broadband providers in Philadelphia have responded by pushing for State legislation to prevent City administrations from using public funds to deploy such networks because they supposedly represent unfair competition. We can expect a repeat of this legal battle in many of the cities trying to deploy cheap and affordable community Wi-Fi systems in the United States and elsewhere around the world. Regulators should monitor the case closely for clues on how they may handle a similar situation within their jurisdiction.
Following on the heels of Philadelphia is the city of San Francisco where they approved a joint bid by Google and Earthlink to offer free and paid Wi-Fi Internet access to city residents. The service will be funded through location-aware advertisements based on the context of the users. In Asia Pacific, Singapore announced its Wireless@Sg programme in December 2006, which will see the number of Public Hotspots in Singapore climb from 600 to 5,000 within one year. Through this service, residents and visitors will get to enjoy free basic rate Internet access for a period of three years.
Wi-Fi Public Hotspots are not just meant for cities in developed countries. First Mile Solutions (2003), a Cambridge-based company with close links to the Massachusetts Institute of Technology, has developed and launched several innovative mobile Wi-Fi Hotspot solutions for developing countries. One solution uses a store-and-forward technique for emails to be dropped and picked up by Wi-Fi equipped motorcycles (called 'Motomen') or trucks as they move in a circuit around a central hub that has an external Internet connection. Villages along the circuit can send and receive e-mail through these roving Wi-Fi carriers, albeit with some delay. Villagers can also access the Internet through content that has been previously downloaded and stored locally. This technology has brought some form of basic communications to rural towns and villages in Cambodia and India for a fraction of what a traditional communication system would have cost. Recently, Goswami and Purbo (2006) published a paper reviewing the uses of Wi-Fi in less developed nations and they highlighted certain 'innovative' uses of Wi-Fi to overcome the hostile market and regulatory environment in Indonesia. These innovations included the use of Wi-Fi to provide last mile access and as a low capacity backhaul technique to overcome infrastructure limitations in Indonesia. Many users also resorted to becoming unlicensed re-seller ISPs to recover their own costs.
Although Wi-Fi came into existence some 20 years after the mobile phone and it does not yet enjoy the widespread adoption of mobile phones, it is nevertheless a technology with tremendous potential for development. As mentioned earlier, a mobile phone requires a complex supporting infrastructure in the background for it to work. Creating that infrastructure requires government licensing, extensive capital expenditure, and detailed radio and network planning. Only large companies with significant capital resources are able to undertake these tasks. In contrast, a Wi-Fi system is much easier to set up. Many countries have created regulations to permit systems to operate in a relatively unconstrained manner in the ISM band. Such ISM systems, which include Wi-Fi, can operate without a specific radio frequency allocation or an operating license.4 Wi-Fi would never have taken off if each and every user had to apply for a license from their home regulator! It is also much easier to set up a Wi-Fi radio network because Wi-Fi uses a much simpler though admittedly less efficient radio channel access method to manage multiple users attempting to access the base station. This makes radio planning for Wi-Fi systems much simpler at the expense of certain performance parameters. Because of these features, Wi-Fi systems can be set up in a much shorter time using relatively less skilled human resources compared to mobile phone systems.
Mobile phone base stations can cost up to USD 100,000 per unit, whereas a high-grade Wi-Fi AP can be purchased for only about USD 5,000 per unit. This is because the technology used in Wi-Fi is less complex and there is much greater competition in the Wi-Fi market. The severe competition has resulted in price wars and breakthrough innovations that bring better value to Wi-Fi users. In the 10 years since its introduction, Wi-Fi's data rate improved from 1 Mbps to 54 Mbps. During that same period, the mobile phone's data rate improved only from 40 Kbps to 384 Kbps.
Possibly because of these factors and the fact that there is much more competition for the supply of Wi-Fi services, Wi-Fi tends to offer much better value than mobile phones. With Wi-Fi, data rates tend to be much higher and prices much lower. For example, under Singapore's Wireless@Sg Wi-Fi service, users can connect at 512 Kbps for free, whereas a mobile phone call would cost SGD 0.20 per minute and a 40 Kbps GPRS data connection would cost SGD 0.0037 per kilobyte transferred. While it has become quite common for Wi-Fi operators to offer unlimited data plans, mobile phone operators tend to charge for the amount of data carried or by connection time. Both of these charging methods can expose the user to a very large bill at the end of the month.
On top of the endorsement by Intel and the emergence of Public Hotspots, several new developments have given Wi-Fi a further boost. These include the launch of Skype, a Voice over Internet Protocol (VoIP) technology for making phone calls over the Internet. Skype managed to attract over 130 million registered users since its launch in 2003 because it offers free on-net telephone calls and very affordable off-net calls. On-net calls are calls between two people connected via the Internet using their Skype IDs. Off-net calls are calls between a Skype user and someone with a normal fixed-line or mobile telephone number. Equipment manufacturers are rushing to put Wi-Fi capabilities into devices such as notebook computers, tablet personal computers, game machines, cordless phones, PDAs and even mobile phones, to exploit use of Hotspots and services such as Skype. With the number of Public Hotspots growing, interesting new Wi-Fi devices being introduced and with the availability of services such as Skype, more and more people are acquiring Wi-Fi-enabled devices to take advantage of this trend. In time, Wi-Fi may come to challenge mobile phones as the dominant means of communication in the world.
However, some of the weaknesses of Wi-Fi systems should be noted. First, Wi-Fi is primarily a short-range system. Thus, building an infrastructure that can provide seamless coverage similar to that of a mobile phone system in a reasonably-sized city would require the deployment of tens, if not hundreds of thousands, of Wi-Fi Hotspots. The backhaul connectivity costs and maintenance requirements of such a system are not trivial and may come to dominate the operating expenses of the Wi-Fi service provider.
Second, Wi-Fi is not able to provide the seamless connectivity that mobile phones seem to do so well; it is able to provide only nomadic access capability. Once a Wi-Fi end-user device moves out of range of the AP it is associated with, connectivity is lost and the link is broken. It has to search for and establish a new connection with another AP whose signals it can detect. There is no automatic handover or mobility capability.
Third, unlike with mobile phones where there are only a limited number of operators per geographical region, there are usually many more smaller and independent Wi-Fi operators in a geographical region. Each of these may have a different sign-on mechanism and they are likely to issue a log-in identity that is unique to their system. Unlike with mobile phones where a single identity suffices for travel around the world, a traveller using Wi-Fi may pass through several of these Wi-Fi operators and thus end up with a whole bunch of different log-in identities and an assortment of bills at the end of his or her journey.
Fourth, many Wi-Fi operators have adopted simplified log-in processes that may have security weaknesses. In these implementations, data exchanges between the end-user device and the AP are unencrypted and unscrupulous people could eavesdrop on the data conversation and extract information that is private to the user.