Wireless LANs and PANs

While mobile voice communications were one step in transforming the way people communicate, wireless data communications are set to go one step further, through network technologies such as wireless local area networks (WLANs) and personal area networks (PANs), enabling such possibilities as sending and receiving e-mails in a moving bus (see Box 2.1), accessing company data from a conference room, or sharing wireless Internet connections in the home. These networks are based on technologies that enable substitution for wider-scale networks at shorter geographical ranges, depending on the coverage afforded by the technology in question.

2.2.1 Different networks for different ranges

The networks with the largest coverage area are current 2G and future 3G mobile networks. 3G is expected to eventually provide full global roaming. A second group of networks covers a smaller area (around 100-150 metres) and includes WLANs. PANs are the networks with the shortest range of communication, covering an area of about ten metres (see Figures 2.3 and 2.6).

The various ranges make each network ideal for different types of traffic. The shorter-range PANs are perfect for cable replacement among peripherals, and other close point-to-point communications. WLANs are better suited for local, high-speed networking of buildings or homes. The broadest coverage, offered by 3G, is best for connecting away from buildings with WLANs, in more remote locations, or in transit. In general terms, the shorter the range, the faster the network and the cheaper the service will be.

While there are wireless technologies in development for all three sizes of networks, this section focuses on the two technologies that have the most immediate promise: wireless LANs and Bluetooth (a type of PAN).

Box 2.1: Broadband on the bus: The convergence of wireless LANs and 3G

The University of California San Diego introduced the world’s first CyberShuttle offering mobile, high speed Internet access to its passengers in April 2002. The bus travels for some 15 to 20 minutes between the campus and the nearest train station and users can connect to the Internet with a wireless-enabled laptop or PDA for the duration of the ride.

The wireless network consists of an 802.11b access point (WLAN) mounted in the bus. This access point is connected to the Internet. A CDMA2000 1xEV-DO wide area data network provides 2.4 Mbit/s transmission speed, allowing passengers to access their e-mail, browse the Web, and even enjoy high-speed audio/video streams. While the trip may be short in duration, it highlights the potential of service development as 3G and WLANs move closer towards convergence.

Source: UCSD/California Institute for Telecommunications and Information Technology.

Figure 2.3: Approximate wireless ranges

Note: Not to scale.

Source: ITU.

2.2.2 Introduction to wireless LANs

The rapid success of WLAN technology took most of the world by surprise. Even amid sluggish computer sales, users are buying up wireless networking equipment at a considerable rate. This is partly because, although wireless networking has been around for many years, it has only recently been available at an attractive price to consumers and businesses. WLANs have also found a particular market niche for households with several Internet users. By means of a WLAN router, each member of a household can have access to the Internet simultaneously through a single Internet connection. The connected computers throughout the house can share files and printers just as if they were connected via a traditional local area network (e.g. Ethernet), such as those typically used in the workplace.

Businesses and other institutions are also rapidly embracing wireless LANs, notably in older buildings, convention centres, schools, factories, and other locations where installing wiring poses a challenge. WLANs are also ideal for temporary use by conference attendees, as they can be set up quickly in conference rooms without the need for additional wiring. Wireless networks also perform a very important function for employees on the move, enabling them to roam with their laptop computer, while maintaining a connection to the Internet and the corporate Intranet. In addition, not only do WLANs allow numerous users connection via a single access point, but, once installed, further users can be added easily. This is particularly appealing in locations such as airports and cafés with high numbers of transient users.

Other, non-conventional business users are also finding wireless networks a valuable asset. For instance, shopping trolleys in grocery stores can be equipped with wireless devices that send signals back to the network and plot the course of shoppers as they make their way through the store. Managers can then adjust the placement of the most popular or profitable goods to the highest traffic areas.

The medical profession has also benefited from the growth of wireless technology. Doctors and nurses can carry personal digital assistants (PDAs) with wireless connections in order to access a patient’s medical records, rather than carrying multiple medical charts. Any changes in a patient’s status can be entered in the PDA at the patient’s bedside and relayed instantaneously back to the network for timely reports and analysis.¹⁹

2.2.3 The structure of a wireless LAN

A WLAN is defined as a local area network of which at least one segment uses wireless technology. Mobile devices access the “wired” network by connecting to an access point on the network. This access point is

CHAPTER TWO: TECHNOLOGIES AND APPLICATIONS 13 physically connected to the wired network and acts as a receiver and transmitter, passing traffic back and forth between the wired network and mobile clients equipped with wireless cards. It is worth noting that the phrase “wireless LAN” is somewhat of a misnomer, given that the wireless network typically forms part of a

“wired” LAN, to which it is connected.

2.2.4 Types of wireless LAN

Like most emerging technologies that are typically based on a number of competing standards, of which only one or two are likely to survive, the arena of wireless networking is somewhat of a battleground in which the various contenders are jostling for the best position (see Table 2.2, which sets out the various wireless networking standards). In the North American market, the early favourite is 802.11b, a standard developed by the United States Institute of Electrical and Electronics Engineers (IEEE). It is also commonly known as Wi-Fi (Wireless Fidelity).²⁰ Strictly speaking, Wi-Fi is actually a certification that manufacturers can apply to their products once they pass the requisite interoperability criteria.²¹ Companies such as Apple, Cisco, Lucent, and 3Com support the Wi-Fi standard. Wi-Fi is very popular and controls the vast majority of the WLAN market despite some inherent security flaws. HomeRF follows closely, with the support of several other manufacturers including Motorola, Siemens, and Proxim.²²

While the standards debate between Wi-Fi and HomeRF continues in North America, Europe has been developing its own standard, known as HiperLAN. Founded by Tenovis (Bosch), Dell, Ericsson, Nokia, Telia, and Texas Instruments, HiperLAN is a consortium of equipment manufacturers hoping to recreate the Wi-Fi phenomenon using more recent technology.

Both HomeRF and HiperLAN incorporate quality of service (QoS) control in their standards while Wi-Fi does not. At present, this makes HomeRF and HiperLAN more suitable for time-sensitive data and video services: a few seconds’ delay in e-mail delivery does not have the same impact as a similar delay in a voice conversation. In order to enhance competitiveness, the IEEE is working on a standard called 802.11e, which will eventually add QoS elements to the Wi-Fi (802.11b) standard.²³

Table 2.2: Wireless networking standard comparisons

Name Speed Range Frequency Notes

802.11b (Wi-Fi) 11 Mbit/s 100 m 2.4 GHz Most popular and widespread²⁴ 802.11a 54 Mbit/s 50 m 5 GHz Newer, faster, higher frequency 802.11g 54 Mbit/ss 100 m 2.4 GHz Fast and should be compatible 802.11b 802.11e NA NA NA Improves 802.11 a, b and g with QoS RadioLAN 10 Mbit/s 35 m 5.8 GHz Specializes in wireless bridges HomeRF 1 Mbit/s 50 m 2.4 GHz Replaced by HomeRF2

HomeRF2 10 Mbit/s 100 m 2.4 GHz QoS, better encryption, not widespread HiperLAN2 54 Mbit/s 150 m 5 GHz European standard, QoS, for voice/video Bluetooth 1 Mbit/s 10 m 2.4 GHz Personal Area Network [not WLAN]

Infrared LAN 4 Mbit/s ~20 m 350’000 GHz Same room only, no negative health effects Source: ITU.

2.2.5 A question of frequencies

Competition between these standards is fuelled by the fact that they are essentially restricted to operating over one of two frequencies, 2.4 GHz or 5 GHz. The reason for this is that both of these frequencies have been set aside for public use in most parts of the world as “unlicensed spectrum”, setting wireless makers on their toes to take advantage of them. The 2.4 GHz band is the most popular among wireless devices, and carries with it inherent benefits and disadvantages. Although the equipment is among the cheapest and most widespread, many different technologies use the 2.4 GHz frequency (Bluetooth and HomeRF2 also use the 2.4 GHz frequency, in addition to microwave ovens and some types of cordless phone) and the band is becoming increasingly congested, resulting in the risk of interference and slower data transfer rates.

As a result, several standards, namely the 802.11a, RadioLAN and HiperLAN2 standards, have taken advantage of the less-crowded 5 GHz band (see Table 2.2). This band holds much promise because fewer devices operate in it, thereby avoiding some of the interference that affects the 2.4 GHz frequency. The 5 GHz band also has the advantage that the standards were developed later, and can accommodate faster speeds than earlier standards using the 2.4 GHz range. The quandary is, therefore, that the 5 GHz range standards are ideal, particularly given their capacity for higher speeds, but they cannot elbow their way to the top owing to competition from the proliferation of equipment and networks already operating in the 2.4 GHz band. Conversely, those operating in the 2.4 GHz band suffer from quality of service problems due to overcrowding.

The 5 GHz standards are also facing some competition from an old, revitalized foe. Just as 802.11a products (at 5 GHz) are coming onto the market, the IEEE is working on a standard known as 802.11g that offers the same speed as 802.11a, but which operates in the 2.4 GHz range. This standard will offer backward compatibility with the existing Wi-Fi infrastructure. Notwithstanding Wi-Fi’s position as the most popular of these standards to date, it may be some time before an effective standard materializes as a global favourite.

2.2.6 The advantages and disadvantages of WLANs

While wireless LANs can be extremely useful, by dint of their very nature, they can pose a higher security threat than their wired network counterparts. For instance, while access to an internal LAN usually requires penetration into a physical building, a wireless LAN can often be tapped into from outside the “wired”

building, or even from across the street. Therefore, without the proper safeguards, unsecured networks can become the target of unauthorized, and undesirable, infiltration and interception.

Most wireless networks have some level of encryption available to protect sensitive data. However, this encryption should only be considered as a first line of defence. The most popular wireless standard, Wi-Fi, uses WEP (Wired Equivalence Privacy), which was never intended to protect sensitive data. As its name implies, its main objective was limited to bringing the level of security up to the level used in a fixed network. WEP has some serious security flaws and has been shown to be vulnerable to programs like AirSnort (see Box 2.2). For most networks therefore, another form of encryption is desirable. Fortunately, there are many solutions for securing wireless networks such as the RADIUS (Remote Authentication Dial-In User Service) protocol and PPTP (Point-to-Point Tunneling Protocol), which offer end-to-end encryption. According to some estimates, however, more than 60 per cent of all wireless networks fail to make use even of the WEP encryption that comes built into their networks.²⁵ While WEP isn’t perfect, it should always be activated, apart from in exceptional cases, such as Internet access points designated exclusively for public use (e.g. Internet cafés and airports).

Some have speculated that 3G services will be squeezed out by WLANs as they proliferate around the world.

However, there are a number of applications and benefits that remain strictly within the realm of 3G, and are likely to guarantee its continued existence. For example, while WLANs offer speeds from five to 25 times faster than 3G, they are not suitable for exclusive use while in transport. 3G services, on the other hand, are ideal for communication in moving vehicles since mobile operators have hand-off technology already in place. 3G networks are also ideal for any outdoor applications away from WLAN infrastructure. Thus, rather than competing head on, WLANs and 3G networks are in fact complementary technologies, interlinking very different areas of a network. But it may be difficult to persuade 3G licence owners, who have paid billions of US dollars for spectrum, that they do not face a threat from companies exploiting unlicensed spectrum free of charge.

CHAPTER TWO: TECHNOLOGIES AND APPLICATIONS 15 Box 2.2: Stumbling, snorting, and “war driving” to a wireless network near you

“War drivers” are likely to have already scanned any existing wireless network and published their findings on the Web. In fact, they may have already drawn an “X” with the network’s information in chalk on the pavement outside to notify other wireless users of the network (see right-hand figure below). Without proper security, a wireless network is accessible to anyone with a laptop computer, a US$ 70 wireless card, and a free wireless scanning program such as NetStumbler.²⁶ War drivers are driving around in cities across the world trying to stumble on wireless networks, some for leisure, others for free Internet access, and others still for serious hacking.

The term “war driving” is derived from “war dialling,” a brute force method used by hackers for locating insecure computers by dialling through phone numbers. The newest incarnation is easier, cheaper, and much more popular than its namesake, and is currently more legal.

NetStumbler runs on a laptop and continually scans for wireless networks from a car being driven around, capturing information about all networks it comes across. War drivers can “discover” large numbers of networks in business districts in a matter of minutes. With an additional GPS connected to the computer, NetStumbler will pinpoint the physical location of the network on a map that can be loaded into national/worldwide databases on the Web and made available to anyone. The map below shows actual “war driving” results in San Francisco, California, in the United States. While a detected network is not necessarily invaded, war drivers report that the vast majority of networks use absolutely no encryption and leave their connections and networks wide open to the public. Many stumblers attach antennae to their computers and are able to connect to unsecured networks up to one kilometre away. Not only do these stumblers search out wireless networks, they publish their findings on the pavements where others can benefit from their results. This “war chalking” saves other passers-by the trouble of scanning for the network because the information they need to connect is literally written on the street.

The fact that war drivers are looking for wireless networks in neighbourhoods as well as business districts highlights the need for vigilant security on all wireless networks. Passive security won’t keep up with active stumblers. All unsecured networks are at risk, even those using WEP encryption on the most popular Wi-Fi equipment. This is due to the fact that war drivers and stumblers armed with another free program, called AirSnort, can take advantage of a design flaw in the WEP standard for Wi-Fi networks and obtain encryption keys. AirSnort passively monitors transmissions and can easily compute the encryption key when it gathers between 100 Mb and 1 Gb of network traffic, often possible within one day of heavy network activity.²⁷

It is therefore vital to secure wireless networks with supplementary encryption. Even casual home users with no

“sensitive” data should at least use the highest level of WEP. One consoling factor is there are so many networks that are left wide open, that WEP may indeed keep hackers moving on, if only temporarily. Fortunately for the smaller user, there are many security solutions available to encourage war drivers to keep driving, looking for other targets.

Map showing detected WLANs in San Francisco, California, United States, and chart of “war chalking” codes.

Note: SSID stands for Service Set ID, in other words the name of the network.

Source: DIS, http://www.dis.org/wl/maps (right-hand graphic); War chalking results adapted from blackbeltjones.com.

While both WLANs and 3G services make a niche in the market, several other technologies are drastically increasing the range of wireless networks. Mesh and ad hoc networks are evolving that turn all users into network transmitters, thus quickly expanding the wireless network beyond its fixed roots. At the same time, new directional antennae for mobile base stations are also rapidly increasing the range of mobile networks.²⁸ These new technologies could give wireless networks the final push they need to be able to offer truly seamless connectivity.

2.2.7 Bluetooth and PANs

An Ericsson trademark, Bluetooth²⁹ was developed by a consortium including IBM, Intel, Nokia, Toshiba and Ericsson. The Bluetooth Special Interest Group (SIG)³⁰ was formed in 1998 to promote the technology and included over 2’500 member companies in April 2002. The technology was first designed to replace proprietary cables, connectors linking electronic devices such as mobile phones and laptop computers. This concept has expanded to include desktop PCs, digital cameras, MP3 players, PC monitors, and PDAs. The advantages go beyond eliminating awkward cables to the provision of local on-demand wireless connection from device to device as well as between devices and network resources. Bluetooth uses a combination of circuit and packet technologies, and slots can be reserved for both synchronous and asynchronous transmission. Devices can establish and maintain seven simultaneous connections. The system consists of a radio, a baseband, link management and host terminal interface functions. At a current maximum speed of 1 Mbit/s, the data rate for Bluetooth is higher than the maximum data rate on GPRS and 3G networks, but lower than current WLAN standards. Due to its low radio power, Bluetooth is ideal for small, battery-powered personal devices.

The promise of Bluetooth is in its ability to offer a universal means for devices to connect to one another.

Instead of having a multitude of protocols and connections such as Serial, Parallel, IEEE 1394/Firewire/iLink, USB, Ethernet/RJ45, PCMCIA, Compact Flash, Smart Media and others, enabled devices will all be able to communicate in close range over a Bluetooth wireless connection. Just as the Internet’s TCP/IP protocol opened up communication between different types of computer operating systems, (e.g. Macintosh, Windows, UNIX, etc.) Bluetooth should be able to offer the same interoperability for a wide range of devices.

A number of compelling Bluetooth applications are now appearing on the market. PC connections allow for accessories such as a keyboard, mouse, or monitor to be connected wirelessly, as well as other non-traditional devices. Video camera manufacturers have introduced Bluetooth-enabled cameras that can transfer video between the camera and the computer wirelessly. Bluetooth is also making its way into mobile phones equipped with 2G and 3G connections, giving them an Internet connection to share with any other

A number of compelling Bluetooth applications are now appearing on the market. PC connections allow for accessories such as a keyboard, mouse, or monitor to be connected wirelessly, as well as other non-traditional devices. Video camera manufacturers have introduced Bluetooth-enabled cameras that can transfer video between the camera and the computer wirelessly. Bluetooth is also making its way into mobile phones equipped with 2G and 3G connections, giving them an Internet connection to share with any other