Q&A: Wi-Fi and the GSM Family of Technologies

What is Wi-Fi?

What are hot spots?

What are the differences between GSM and Wi-Fi?

What are the benefits of linking GSM and Wi-Fi?

How does a GSM operator deploy Wi-Fi?

Do any GSM operators currently offer Wi-Fi?

Which companies provide Wi-Fi certified products?

What is Wi-Fi?

Wireless Fidelity (Wi-Fi) is a catch-all term that refers to technologies based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards. Other common terms are "wireless LAN," which is short for wireless local area network (WLAN), "wireless Ethernet," and "hot spots," which are Wi-Fi access points (APs) that serve a public area, such as an airport, café, hotel or conference center.

There are multiple versions of the 802.11 standard. The four primary ones are:

• 802.11a: This technology uses the unlicensed 5.8 GHz band and delivers a maximum data rate of 54 Mbps.

• 802.11b: The most widely available of all Wi-Fi technologies in terms of devices and deployed hot spots, 802.11b supports peak data rates of 11 Mbps. 802.11b shares the unlicensed 2.4 GHz band with a wide variety of other technologies, including Bluetooth, cordless phones, microwave ovens and 802.11g.

• 802.11g: This relatively new technology uses the 2.4 GHz band and delivers peak rates of 54 Mbps.

• 802.11n: This forthcoming technology is expected to deliver peak throughput of 100 Mbps. Although 802.11n equipment, such as access points (APs) and modems, have been commercially available since 2004, they are based on unofficial, preliminary versions of the standard. When the 802.11n standard is ratified, these “pre-n” products, as they are known, might not be 100 percent compatible with or upgradeable to the official standard.

It is important to note the differences between Wi-Fi's peak throughputs and real-world averages. For example, although 802.11b has a theoretical maximum of 11 Mbps, more than half of that bandwidth is consumed by overhead such as encoding, leaving at most 5 Mbps of usable bandwidth.

Other key factors that can significantly affect Wi-Fi's real-world data rates are the number of simultaneous customers sharing the hot spot and the size of the "backhaul" connection between each Wi-Fi AP and the Internet. For example, a public hot spot provider might choose DSL or cable broadband for each backhaul rather than a T1 line. The T1 line typically provides more bandwidth to support the number of customers utilizing the particular AP. These factors are among the reasons why public Wi-Fi networks typically provide data rates that are only a small fraction of their peak speeds.

Return to top

What are hot spots?

Hot spots are public places where users with an 802.11 PC card modem, hybrid cellular/Wi-Fi handset or laptop with an embedded 802.11 modem get Internet access for free or for a fee. Hot spots typically are found in public areas such as airports, cafés and hotels. In 2006, the number of hot spots worldwide grew 47 percent to 1,437,000 according to ABI Research, an independent analyst firm. Nearly 75 percent are in Europe and North America, but by 2011, the Asia-Pacific region will have the most hot spots, ABI predicts.

The nickname “hot spot” reflects the fact that Wi-Fi signals have a range of about 200 feet, depending on factors such as interference and physical obstructions. (By comparison, GSM signals can travel several miles or more.) As a result, Wi-Fi typically provides spotty rather than seamless coverage, so users have to seek out a hot spot to connect. That is not the case with cellular technologies such as GPRS, EDGE and UMTS, where coverage typically is available throughout an entire market, such as a city and its suburbs. Cellular’s ubiquity is particularly attractive to business users because they can be productive in almost any environment, instead of wasting time looking for a hot spot.

Return to top

What are the differences between the GSM family of technologies and Wi-Fi?

There are several key differences, including coverage, roaming, interference protection, security, data rates and support for voice.

• Coverage: A Wi-Fi signal will provide coverage typically up to 200 feet from an AP, depending on factors such as walls, allowing only for stationary rather than mobile use. A GSM signal provides more widespread coverage of several miles or more from a cell site, depending on factors such as whether the cell site is located in a rural or urban area.
  
  Coverage is particularly important for data customers who want access from multiple locations in even a small geographic area, such as a downtown business district. Seamless Wi-Fi coverage in any public area is a rarity, and places with extensive Wi-Fi coverage usually are served by one operator in some areas and another operator in others. By comparison, a GSM operator that serves a particular market will cover all areas, such as its downtown, suburbs and outlying towns, which allows true mobility because connections are handed off seamlessly as customers move between cell sites. Thus, it is not economically viable for Wi-Fi to compete in the area of coverage technologies such as GPRS, EDGE and UMTS/HSDPA.

• Roaming: Spotty coverage highlights the need for roaming. When Wi-Fi customers try to connect in an area served by a Wi-Fi operator other than the one with which they have an account, they often have to go through a lengthy log-on process that includes using a credit card to pay for service. Roaming agreements between Wi-Fi operators eliminate those steps and make Wi-Fi more customer-friendly.
  
  However, although many Wi-Fi operators now support roaming, the geographic coverage in a city, country or region is nowhere near that of cellular technologies. For example, GSM's ubiquitous global footprint – with service available in more than 220 countries, as of 3Q 2006 – is supported by extensive regional, national and international roaming for voice and data. The GSM community has been expanding roaming since the technology launched commercially in 1991 – a head start of more than a decade compared to Wi-Fi.

• Protection from interference: Wi-Fi uses unlicensed spectrum, which means that services used in that spectrum have no regulatory recourse or protection against other interfering services. By comparison, GSM uses licensed spectrum, enabling GSM operators to provide consistent levels of service quality, which is particularly important for wireless services that cater to business and enterprise customers.

• Security: Wi-Fi devices use security standards such Wired Equivalent Privacy (WEP), Wi-Fi Protected Access (WPA) or WPA2 to overcome the technology’s inherent vulnerability to hacking and bandwidth-siphoning attacks called "warchalking" and "wardriving." However, these standards protect data only when they are used, and many Wi-Fi users do not use them. In enterprises, for example, usage of Wi-Fi security standards is low, according to an October 2006 report by In-Stat, an independent analyst firm. Consumers also frequently do not turn on the security features on their Wi-Fi devices because they are too difficult to configure, according to March 2006 report by ABI Research.
  
  By comparison, GSM-based data networks are inherently more secure than Wi-Fi networks due to security techniques built into the GSM standard by group such as the Third Generation Partnership Project (3GPP). GSM automatically provides end-to-end security features, so users do not have to configure them manually.

• Data rates: Although the most widely used Wi-Fi technology, 802.11b, supports peak data rates of 11 Mbps, more than half of that bandwidth is consumed by overhead such as encoding, leaving at most 5 Mbps of usable bandwidth. The remaining bandwidth often is reduced further by factors such as whether the hot spot provider chose DSL or cable broadband for each backhaul rather than a T1 line, which provides more bandwidth. By comparison UMTS/HSDPA provides average data rates of 550-800 Kbps, with peak speed in excess of 1 Mbps under favorable conditions. These speeds will increase to as much as 14 Mbps with planned enhancements to HSDPA.

• Support for voice: Wi-Fi supports voice over IP (VoIP), but the technology remains impractical for many consumers and businesses because it requires additional software. VoIP over Wi-Fi also has limited use. For example, a customer whose VoIP Wi-Fi handset or PDA works on a campus network cannot assume that his device will provide voice calls elsewhere, such as on a public hot spot. By comparison, a GSM phone provides voice service in more than 220 countries, as of 3Q 2006, regardless of whether the customer is at home, at work, indoors or outside.

Return to top

What are the benefits of linking GSM and Wi-Fi?

For GSM operators, the greatest benefit of adding Wi-Fi to their service offerings is flexibility. For example, many GSM operators see Wi-Fi as a complement for their GPRS, EDGE and/or UMTS/HSDPA networks, giving their customers more options for accessing the Internet and data services. By offering adjunct Wi-Fi services, GSM operators also can leverage the installed base of Wi-Fi PC card modems and laptops with embedded 802.11 modems. One example of this strategy is T-Mobile HotSpot, which launched in 2002 as a complement to the company’s GPRS network.

Another benefit is that customers who get a "bundle" of services from a single provider are less likely to switch to another provider. As an added incentive, some GSM operators send their customers a single monthly bill for GSM and Wi-Fi.

The GSM community is developing solutions that enable convenient switching between GSM-based and Wi-Fi networks. For example, in the near future, a GSM customer might install a special Wi-Fi AP in her home. When she drives up to her house while talking on her GSM/Wi-Fi handset and walks inside, the call is automatically and seamlessly switched to Wi-Fi. This approach benefits GSM operators by encouraging wireline displacement and by reducing the need for additional base stations to provide indoor coverage in every home.

Return to top

How does a GSM operator deploy Wi-Fi?

Mobile operators have two main options for offering Wi-Fi. The first is to build or buy a network of hot spots. One example of this strategy is T-Mobile HotSpot. The second option is to partner with a Wi-Fi operator and resell its service. Some GSM operators have used both options in order to offer their customers Wi-Fi service in as many places as possible.

A key issue is how the customer's handset, PDA or laptop chooses between the GPRS, EDGE or UMTS/HSDPA network and the Wi-Fi hot spot, especially when both services are available in the same area. The most popular solution is to install software on the customer's device that detects all available networks and then manages the connection. Depending on the arrangement between the GSM operator and the hot spot operator, the software might be configured to prefer the GPRS, EDGE or UMTS/HSDPA network when both are available and switch to the Wi-Fi network only in areas where GPRS, EDGE or UMTS/HSDPA is unavailable.

Return to top

Do any GSM operators currently offer Wi-Fi?

Several GSM operators worldwide offer Wi-Fi service. In the Americas, examples include Cingular Wireless, Rogers Wireless, Telefónica and T-Mobile.

Return to top

Return to Questions and Answers home page.