In-Depth

Wireless DevelopmentJoining the wireless world

IT looks more closely at wireless options as network technologies and devices mature; a guide through the maze of hardware, software and communications options.

If there is an IT industry buzzword right now that is hotter than "wireless," word has not yet reached the ears of this writer. Industry watchers note that the term now rivals the power once commanded by ".com" to snare the attention and stir the imagination of corporate executives and IT managers. The promise offered by the emerging technologies clustered under this rubric is compelling, and it will not be long before virtually every enterprise will want the ability to access information and transact business beyond the constraints of wires and cables.

Corporate IT has been looking at wireless technology for several years now without actually doing much. Beyond the widespread use of pagers and cell phones, wirelessness has yet to have a real impact on the enterprise. A recent Meta Group study found that less than 5% of all corporations currently have a wireless application in place. The promise of wireless did not meet reality, and plans were forced to wait until technology advances to levels that now appear imminent.

Immature wireless networking technologies, and devices and software that are difficult to implement on a large scale have held back acceptance for years. Experts now say that the devices, some emerging software and new wireless networking schemes are convincing IT managers to take a closer and more serious look at implementing a system.

Experts say evidence of an impending wireless explosion is definitely strong. For example, Boston-based Aberdeen Group, a technology researcher, predicts that by 2004, 74 million people around the world will have wireless access to the Web. GartnerGroup, a research firm based in Stamford, Conn., predicts that 700 million cell phones will be in use worldwide by 2003, and 80% of those will have access to the Internet. Analysts at AMR Research, Boston, foresee a range of packaged application developers, ranging from suppliers of traditional ERP systems to e-commerce specialists, expanding product lines to include wireless technologies. Observers note that many systems integrators are rushing to add wireless practices to their offerings. And a whole new class of mobile specialists is looking to dominate the industry.

"That's a hell of a capability," said industry analyst Ken Dulaney, vice president of mobile computing at GartnerGroup, "and someone is going to figure out how to use it."

"If I were an IT manager," advised Joe Owen, CEO of XcelleNet, Alpharetta, Ga., a maker of software for managing wireless systems, "I'd be past the tire-kicking stage by now and at least experimenting with some kind of wireless implementation."

Good advice, experts say, but easier said than done. IT managers wading into the wonderful world of wireless quickly find themselves hip-deep in a river of diverse devices, sinking in a swamp of system protocols and positively drowning in acronyms. To make educated decisions for their organizations, they need to understand key concepts about a computing paradigm that is very much a work in progress, an immature market and a group of technologies that are still evolving.

"We've seen wireless deployed in public Internet companies for some time," said Jacob Christfort, vice president of product development and chief technical officer at Oracle Mobile, a division of Redwood Shores, Calif.-based Oracle Corp. Christfort is charged with building and hosting wireless applications for businesses. "But it's true that wireless [technology] hasn't been taken up in the enterprise nearly as fast. The problem is the complexity that IT managers have to manage."

The following overview is designed for organizations ready to dip their toes into the wireless torrent for the first time. It covers most of the wireless basics—systems, networks, devices, software and services—IT managers need to know about. And it includes some recommendations from industry analysts and vendors for implementing effective wireless strategies.

This is not everything you need to know, of course, but it is not a bad place to start.

Fixed, mobile or broadband
For this story, "wireless" refers to an array of products and standards that enable communications without, well, wires. That covers a lot of territory, and the term as it is being bandied about today is almost too general to be useful. Obviously a cellular telephone is a wireless device, but so are a garage door opener, a TV remote control and a baby monitor.

"There are so many definitions of 'wireless,'" said Bill O'Farrell, CEO of OpenAir.com, Boston, a provider of professional service automation applications using an application service provider (ASP) model. "It's amazing to me that anyone understands any of this. Do you mean a cell phone? A PalmPilot? A PC? It's totally confusing." OpenAir Wireless is a companion service to OpenAir.com, a company that makes it easier for Wireless Application Protocol (WAP)-enabled phone users to log hourly, flat rate, mileage and expense TimeBills in real time.

The maturity of some execs notwithstanding, IT managers will not be spending much time with the baby monitors. But they will be dealing with a variety of wireless systems, including fixed, mobile and broadband wireless.

A fixed wireless system provides access to public voice and data networks through the use of wireless communications technology. "Fixed" refers to the stationary devices that make up the system. "Point-to-point" systems require a pair of antennas with no obstructions in between.

Mobile wireless refers, of course, to the use of wireless systems for connecting untethered devices, such as cell phones, laptops and PDAs.

"Point-to-multipoint" systems connect fixed wireless devices with mobile devices via several large antennas communicating with smaller receivers. "Portable wireless" is a term sometimes used to describe systems of autonomous, battery-powered devices outside the enterprise, including handheld cell phones and PCS units.

Fixed wireless devices are usually plugged into the local power grid; whereas mobile or portable wireless devices tend to be battery-powered. Although mobile and portable systems can be used in fixed locations, efficiency and bandwidth are compromised compared with fixed systems. Mobile or portable, battery-powered wireless systems can serve as emergency backups for fixed systems in case of a power blackout or natural disaster.

Finally, wireless broadband is used to describe wireless systems that transmit at higher rates. Wireless connections are generally slower than wireline systems. A land-based broadband system transmits at speeds in the T1 range and above. Wireless connections are considered broadband if they reach or exceed 250 kbps.

Wireless broadband connections are usually described as "fixed broadband," because they are only available in fixed wireless systems. It is really an extension of the point-to-point, wireless-LAN-bridging concept. The idea is to deliver high-speed and high-capacity connectivity that can be used for voice, multimedia and Internet access services. Wireless broadband is mainly used for connecting LANs to the Internet, but it may be used to connect multiple services (data, voice, video) over the same connection.

Getting started
Before any enterprise begins the process of evaluating the specific components of a wireless system, it should take some time to evaluate its own requirements and personnel. In other words, handing out BlackBerry wireless devices to the sales staff is not much of a wireless strategy.

"The first thing you need to think about is what really makes sense for your business," said Christfort. "I think that is where most people—particularly technical people—go wrong. Very often they are focused on the idea of, 'Are there some technologies that can I can buy that will automatically take some stock mobile?' What they end up doing is taking some applications mobile without considering the end users, and it ends up not working."

Christfort advises IT managers to remember that mobile technologies represent more than simply a different protocol, markup language and set of devices; it is also a completely different use context.

"You can't just think about taking the same stuff and shoving it into a mobile device," he said. "CIOs who really get it ask themselves what information their people in the field most often find themselves without. That's the information that you really want to deliver wirelessly."

Peter Firstbrook, research analyst with Stamford, Conn.-based Meta Group, agreed: "You have to start with the information and the people. What information do you have that is both highly valuable and highly variable? E-mail fits that category. Then you have to ask where [the people] are. And only then can you start thinking about what you'll need to get the information out to them."

A growing number of enterprises are extending the availability of corporate data and other high-value information to workers in the field through wireless systems. Wireless connectivity provides a remote link to the Internet, E-mail, corporate databases and other public and personal information.

A typical wireless system is made up of several components, including mobile computing devices, modems, middleware and networks. All components of a wireless system should be evaluated in terms of a company's specific needs and requirements.

Mobile computing devices
Mobile computing devices are everywhere these days. With millions of workers doing business far from the office, it is no wonder. Hardware developers have created a veritable cornucopia of untethered devices—from laptops to handhelds to smartphones—any of which IT managers may find themselves called upon to support with wireless connectivity. Many of these devices come with built-in wireless modems, or fit easily into add-ons. And they come ready to run wireless applications.

Deciding which devices to support can be a real challenge. Unlike desktop machines, which are relatively unvarying in form and function, mobile devices come with a wide range of features, functions and purposes. And the costs of these gizmos can vary just as widely, from a $200 pager to an $8,000 ruggedized laptop.

Enterprises will want to take into consideration the following factors to evaluate which mobile devices are appropriate for them: durability, form factor, battery life, operating system and support for peripheral devices.

Because the device is mobile and gets lugged around far from the safety of the office desktop, durability is almost the primary consideration. The precise durability required of the device depends on just how far from that desktop it will travel and how it will be used in the field. Will it spend most of its time nestled in the cozy inside pocket of a Brooks Brothers suitcoat, or will it be bouncing along muddy fields in the back seat of a Jeep? IT managers should carefully consider environmental elements such as physical shock, temperature extremes, exposure to water and the quality of the display in bright light.

The form factor also depends on the planned use for the wireless device, experts say. Managers should carefully evaluate the required size and weight, the ease of use and the input system, that is, buttons, keyboards or styli. There will be tradeoffs, which can best be made by researching a variety of issues, such as weight versus button size.

User opinions count here, too. Users are the ones that will be using the devices on a day-to-day basis. Buying a PDA for an individual is a lot like buying that person a pen—and you know what it is like to get stuck working with a pen you just do not like.

"People say that the problem with mobile is that there's not enough bandwidth to get the information to the devices," said Christfort. "That's crap. The screens on the devices are too small to support huge lumps of information. But you don't need big screens and WAP phones that display full-color Web pages. Keep in mind that, to make this work profitably, all you need to do is get a few critical pieces of information at the right time. Getting timely and accurate information into the hands of people who need it to make decisions is what this is all about."

Battery life can be a critical consideration, depending on how long the users of the system must operate the devices away from the power grid. Battery types are another consideration. If you are using a Palm V and the lithium ion battery starts to die, you need access to the charging cradle; if you are using a Palm III, you just pop in a couple of flashlight batteries and carry on.

If it is the type of device that recharges, it is important to consider how long it takes, whether it can plug into a car's cigarette lighter to be charged and whether it has a portable battery charger. Managers must also determine whether the modem can utilize the device's battery.

A continuing lack of standards makes selecting a mobile operating system a very tricky process for IT managers. There's little uniformity right now among disparate mobile device operating systems - and there are many more options than one might think. Proprietary systems abound, from Palm Inc.'s Palm OS to Windows CE from Microsoft Corp. When choosing mobile devices, managers must consider both the power of the OS and its compatibility with the applications they intend to run on it; they also have to do some guesswork about its future.

The decision also requires managers to understand all current and potential future application requirements. The decision must take into account any application's processor speed, RAM and hard-drive space requirements. In addition, managers must determine whether a system can support standard or proprietary specialized peripheral devices.

Choosing the correct modem is a key decision for ensuring a successful wireless strategy. Managers can choose from a host of modem technologies, including integrated, on-board modems and systems that can plug into modem modules. Many mobile devices are designed to work with specific wireless networks and have modems that support them exclusively. Others offer a world of choice among networks. The selection process should include a comparison of power requirements, whether an internal or external model is preferred, and replacement issues.

IT managers must remember that development and software considerations are the key factors in building a wireless network. "Hardware is important, certainly," said Gartner's Dulaney. "But too many people decide on the hardware up front. They don't consider preserving their software. But the software is going to be their most important investment—especially in an environment in which their hardware and user preferences are changing like crazy."

Mobile middleware
Chances are a corporate wireless system will be called upon to support more than one type of mobile device: laptops, cell phones, pagers and a few wireless PDAs thrown in just to irritate you. One way out of the proprietary OS/application dilemma is through a variety of emerging mobile middleware systems coming from established middleware suppliers and start-up developers (see related story, "Legacy goes wireless"). Middleware can provide platform independence and allow your applications to be ported to varying devices.

Middleware is, by definition, an enabling layer of software that resides between the applications, the heterogeneous operating systems, hardware platforms and communication protocols. Wireless middleware performs the same function in a wireless system. It creates a third tier in the system architecture that frees the applications from dependencies. The technology is designed to shield developers from the intricacies of a system's "plumbing" and enable communication between disparate networks.

Experts say wireless middleware can hide the complexity of wireless communications with simple APIs that make it easy to develop and deploy mobile applications. The technology can also offer support for multiple networks or operating systems, providing a common API.

But no matter how effective, Christfort warned, no middleware technology can circumvent the need for careful analysis of a company's mobile data needs.

"There are lots of companies out there with this middleware pitch that leaves people believing that they don't have to do anything to their existing applications [to make them mobile]," he said. "That's overselling it, and it's just not realistic. People have to understand that they have to do some work here. They really have to think about what kind of information is going to make a difference to the business in the hands of their [remote] employees."

Wireless application gateways
Gartner's Dulaney tracks a specific kind of wireless middleware called wireless application gateways, a term Gartner coined for a group of products that use XML and W3C-defined stylesheeting to provide a single interface for wireless applications.

"A big problem with wireless is the proliferation of dissimilar form factors, and the dissimilar resource characteristics that exist on these devices," Dulaney said. "Wireless application gateways adapt content to a particular device."

Dulaney points to the way in which many organizations implement the enormously popular BlackBerry wireless handheld E-mail device from Waterloo, Ont.-based Research in Motion Ltd. as an example: "When people put BlackBerries into their [organizations], they typically put in a BlackBerry server, with links to Exchange, for example. Although it is a good product, that is exactly what companies should not do. That server is dedicated to supporting that one device over that one particular network.

"If you put in a wireless application gateway instead, you would be able to service the BlackBerry and any other devices wanting access to Exchange, as well as devices wanting access to other types of content, such as Web or database content."

Dulaney said that enterprises that do not adopt this kind of platform-neutral approach to their wireless implementations, will, in just a few years, find themselves managing 30 or 40 servers that deliver specific content through specific networks to specific devices.

"The sheer number of different formats and operating systems and networks is going to overwhelm any IT shop," he said.

Some of the 20+ vendors currently providing wireless application gateways include:

  • IBM Corp.
  • Brience Inc., San Francisco
  • ViaFone Inc., Redwood City, Calif.
  • AlterEgo Networks, Redwood City, Calif.
  • NetMorf Inc., Boston
  • iConverse, Waltham, Mass.

"The software is your most important investment," said Dulaney. "Your basic strategy should be to assume that you must build robust applications that can deal with any content delivered through any network to any device."

Wireless networks
Wireless networks can provide the connectivity among devices in a wireless system, and they come in a number of shapes, sizes and frequencies, experts say. "The network is one of the critical decisions you'll be making in this process," said Firstbrook. "Most of them are between nine and 19 kilobits.

Personal Area Networks (PANs) are wireless networks that can be installed within small office spaces, in which the connected devices are in close proximity. Today's PAN technologies include IrDA (infrared), which requires "line-of-sight" between the devices, usually a few feet apart, and Bluetooth, which supports multipoint, close-proximity wireless connectivity without the line-of-sight requirement.

"I think that Bluetooth is going to be one of the most important wireless technologies going forward," predicted Christfort. "IrDA is the Iridium of local area networking. It won't be around much longer."

Wireless Local-Area Networks (LANs) cover a greater area than PANs. But just like wired LANs, the enhanced systems can connect devices only within a contained geographical area, such as a corporate headquarters campus or a factory complex. Industry analysts at GartnerGroup expect that the market for installed wireless LANs will approach $35.8 billion by 2004.

In a sense, wireless LANs are bypassing the wide-area services the same way that cell phone service made satellite services like Iridium moot before they ever got deployed. Within a year most of the high-traffic areas like airports and convention centers will have wireless LAN access.

A Metropolitan Area Network (MAN) is designed to interconnect users with computer resources within a specific area. MANs cover an area larger than LANs, but smaller than Wide-Area Networks (WANs). The term is used to describe the interconnection of networks in a city into a single larger network.

MetriCom Inc., San Jose, Calif., maker of the Ricochet wireless modem, operates wireless MANs in about 14 cities, including San Francisco, Seattle and Washington D.C., to support only its Ricochet offering. Although it is restricted to downtown cores, it runs at a relatively blazing 128 kbps. MetriCom plans to have its networks rolled out to 48 major cities by the end of 2001, officials said.

Wireless WANs are said to offer cable-free connectivity beyond the coverage of a LAN. WANs can be private or public, and can be connected through leased lines or satellites. A wireless WAN offers connection rates ranging from 8 Kbps to 28.8 Kbps and can provide citywide or nationwide coverage. Typically, users are charged fees for airtime or the amount of data transmitted.

CDPD or SMR networks give wireless connectivity to courier drivers and police officers. The current trend is toward shared public networks, such as BellSouth. Typically, a wireless WAN consists of two or more wireless LANs.

"Last mile" refers to the connection between the customer and the telephone or cable company. The last mile has traditionally used copper-based telephone wire or coaxial cable, but wireless technologies offer alternative options in some locations.

It is not unusual to hear WAN solution vendors describing the "last mile" as anywhere from the last few hundred feet to the last 50 miles.

In many communities, last-mile technology represents a major remaining challenge to high-bandwidth applications such as on-demand television, fast Internet access and Web pages full of multimedia effects.

Satellites
Satellites—first used for intercontinental telecommunications before undersea fiber was available and for communication in remote areas, including islands and oceangoing ships—can facilitate wireless communications. By the end of 1997, more than 180 communications satellites had been deployed and the business today represents a sizeable and growing industry.

Geosynchronous satellites are set up to 22,300 miles above ground. They revolve around the earth at the same rate as the planet itself and can facilitate wireless communications. One frequency band is used for the satellite uplink, and another for the downlink. Satellites are great for data transmission, but not so hot for voice because of the time it takes for an electrical signal to make the trip into space and back. It only takes a half second, but that is enough of a lag that users notice it during a phone conversation.

Low-Earth Orbit satellites (LEOs) orbit at up to 900 miles above the earth and can communicate directly with handheld earthbound telephones. Because of their low orbit, these satellites move across the sky at high speeds, so they frequently need to hand off a call to a second satellite just rising over the horizon. Each LEO acts like the cell site, catching the call from earth and passing it to an earth-based switching system. Industry watchers expect to see 1,700 additional LEO systems deployed by 2005.

Wireless supply chain
"We have to say that [wireless] is a good technology for the long term," said Dulaney. "People will want to have access to information anytime anywhere, so it's going to happen. We do have to wait for things to mature. The networks have to get better, faster and more available. The devices have to be more stable. For now, we still have to glue a bunch of pieces together and it's still very complex to get it done."

Dennis Gaughan and Randy Weston, analysts at Boston-based AMR Research, believe one area where wireless systems currently impact the enterprise is in supply chain management. In a recent report, they wrote: "Maintaining strong relationships with a growing network of suppliers is a key component of a successful e-business. In addition to an organization's traditional supply base, there is a growing list of trading exchanges available to procure goods. As organizations look to minimize their inventory and streamline their supply chain, visibility becomes an essential factor for success."

Specifically, the two analysts point to an emerging class of supply chain management application called Supply Chain Event Management (SCEM). SCEM applications from vendors like Categoric Software Corp., Sterling, Va., or Vigilance Inc., Sunnyvale, Calif., are designed to smooth out potentially costly kinks in the supply chain. Dramatic glitches that cannot wait for E-mail—say, a steel supplier suddenly not being able to fulfill an automaker's order, without which production stops—can instantly be announced via (WAP) phones or two-way pagers. In this example, one manufacturer can turn to another quickly enough to keep the assembly line rolling. In an industry where production stoppages can cost a company millions of dollars, say AMR analysts, this kind of application will quickly become essential.

Gaughan and Weston also expect wireless to find its way into many other areas of business during the next two years. Areas such as Customer Relationship Management (CRM) and systems integration are ripe for the technology, they say. "Expect to see a lot of real work in the market in the coming year," said Weston. "The time for hype has passed. Now it's time to deliver the goods."

Beyond the promise—or hype—of wireless technologies is the bottom line.

"Whenever you're thinking about adopting a new technology," said O'Farrell, "you have to ask yourself the only question that really matters: Is it going to help me do it better, faster, or cheaper? The fact that the technology is wireless is interesting, but all that matters at the end of the day is that it's helping someone get the job done."

Talk the talk: Wireless glossary
802.11

In Wireless LAN (WLAN) technology, 802.11 refers to a family of specifications developed by a working group of the Institute of Electrical and Electronics Engineers (IEEE). There are three specifications in the family: 802.11, 802.11a and 802.11b.

The 802.11 and 802.11b specifications apply to wireless Ethernet LANs and operate at frequencies in the 2.4-GHz region of the radio spectrum. Data speeds are generally 1 or 2 Mbps for 802.11, and 5.5 Mbps or 11 Mbps for 802.11b, although speeds up to about 20 Mbps are realizable with 802.11b. The 802.11b standard is backward-compatible with 802.11. The modulation used in 802.11 has historically been Phase-Shift Keying (PSK). The modulation method selected for 802.11b is known as CCK (Complementary Code Keying), which allows higher data speeds and is less susceptible to multipath-propagation interference.

The 802.11a specification applies to wireless ATM systems and operates at radio frequencies between 5 and 6 GHz. A modulation scheme known as OFDM (Orthogonal Frequency-Division Multiplexing) makes possible data speeds as high as 54 Mbps, but most commonly, communications takes place at 6, 12, or 24 Mbps. (Source: whatis.com)

Advanced Mobile Phone Service (AMPS)
This is the original analog cellular standard, and, though digital networks are hot on its heels, it is still the most widely used system in the U.S. AMPS systems transmit voice communications as FM radio signals. Analog cellular operates in the 800 MHz frequency range and is available across 95% of the United States. (Also called Frequency Division Multiple Access, or FDMA.) Although AMPS is still in use, it is anticipated that it will be replaced by the United States Digital Cellular (USDC) standard.

Air Interfaces
Wireless communications systems use different access techniques, sometimes referred to as "air interfaces." These include AMPS, USDC, CDMA, GSM and CDPD.

BlackBerry
The BlackBerry is a handheld device made by Research In Motion (RIM) that competes with the Palm PDA and is marketed primarily for its wireless E-mail handling capability. Through partners, BlackBerry also provides access to other Internet services. Like the Palm, BlackBerry is also a Personal Digital Assistant (PDA) that can include software for maintaining a built-in address book and personal schedule. It can also be configured for use as a pager.

RIM provides software that forwards a user's incoming mail from a user's individual E-mail account or to a user's corporate E-mail address through a customer-selected wireless network to the BlackBerry, where it is stored and available for reading. Outgoing E-mail goes directly to the addressee from the BlackBerry, but a copy of the E-mail also goes to the user's home E-mail box. Additional software synchronizes address books and schedules with the desktop system.

Compared to the Palm, the BlackBerry is somewhat simpler and offers fewer options and applications. Its unnamed operating system apparently takes up a relatively small space on its 4 Mb flash memory, which is also used to store user data. Unlike the Palm, whose users write text using a stylus, BlackBerry provides a tiny keyboard that some users say is faster to use in spite of its size.

The BlackBerry device comes in two configurations, one with a slightly larger LCD display. (Source: whatis.com)

Bluetooth
Bluetooth is a short-range, wireless connection specification that describes how mobile phones, computers and PDAs can interact within a small space, such as a home or office. The technology requires that a low-cost transceiver chip be included in the mobile devices that are to be connected.

Bluetooth-enabled devices transmit and receive in a previously unused frequency band (2.45 GHz) that is available globally (with some variation of bandwidth in different countries). In addition to data, up to three voice channels are available in this band.

Each device has a unique 48-bit address from the IEEE 802 standard. Connections can be point-to-point or multipoint. The maximum range is 10 meters. Data can be exchanged at a rate of 1 Mbps (up to 2 Mbps in the second generation of the technology). A frequency hop scheme allows devices to communicate even in areas with a great deal of electromagnetic interference. Built-in encryption and verification is provided.

Cellular Digital Packet Data (CDPD)
CDPD is designed specifically for data transmission and is an overlay on existing AMPS cellular voice systems. Data transmissions take place during idle times on voice channels without adversely affecting voice quality. CDPD can coexist with TDMA and CDMA networks.

The major cellular players currently offer CDPD service in select metropolitan areas. Unfortunately, it is limited to 14.4 kbps. The CDPD carriers, including AT&T Wireless, Verizon Wireless, Ameritech, GTE Wireless and Cingular, now offer interoperability among carriers.

Circuit-switched data
"Circuit-switched" refers to a type of network in which the communication circuit (or path) is set up and dedicated to a particular interaction (or phone call). For the duration of the connection, all resources on that circuit are unavailable to other users. Voice calls using the Internet's packet-switched system are possible on a circuit-switched network. Each end of the conversation is broken down into packets that are reassembled at the other end.

Code Division Multiple Access (CDMA)
Also known as spread spectrum technology, CDMA uses a low-power signal that is "spread" across a wide bandwidth. With CDMA, a message is assigned a code, which identifies it to the correct receiving device. Using the identifying code and a low-power signal, a large number of calls can be carried simultaneously on the same group of channels.

CDMA has the widest frequency spectrum, but rather than using time or frequency to divide calls, CDMA fills the entire spectrum with coded data packets. The unique codes allow the receiving terminal to receive only packets intended for it. Once the packets arrive at the receiving terminal, they are reassembled into their original voice or data form. CDMA provides greater capacity than FDMA, TDMA or GSM.

Digital systems
Digital systems share the 800 MHz frequency band with analog and are usually available where analog service is offered. Unlike analog transmissions that are sent out as a continuously varying electrical signal in the shape of a wave, digital transmissions are a combination of on-and-off electrical pulses. Several air interfaces are used to implement digital cellular networks, including CDMA, TDMA, GSM and ESMR.

Personal Communications Service (PCS) is an all-digital service specifically designed for U.S. operations and is available in metropolitan areas. The term "PCS" was coined by the Federal Communications Commission to describe a digital, two-way, wireless telecommunications system licensed to operate between 1850 and 1990 MHz. But the FCC's rules describe PCS as a broad family of wireless services without reference to spectrum band or technology.

Enhanced Data GSM Environment (EDGE)
EDGE is a faster version of the GSM wireless service. It is designed to deliver data at rates up to 384 Kbps and enable the delivery of multimedia and other broadband applications to mobile phone and computer users. The EDGE standard is built on the existing GSM standard, using the same TDMS frame structure and existing cell arrangements.

EDGE is expected to be commercially available this year, and it is regarded as an evolutionary standard on the way to Universal Mobile Telecommunications System.

Enhanced Specialized Mobile Radio (ESMR)
ESMR is a digital service that applies digital systems to traditional dispatch "specialized mobile radio" service spectrum (in the 800 and 900 MHz bands). By aggregating this spectrum, and applying a cellular-like digital network, an ESMR company is able to provide a cellular- or PCS-like voice and data messaging service. NEXTEL is an ESMR service.

Embedded wireless
Embedded computers are not immune from the wireless explosion. Vending machines now send messages when they are low on soda or change. Cars have wireless data modems that can disable themselves when they are stolen or open the doors when the driver leaves his keys in the ignition. And that's just the beginning. Any minute now, your refrigerator is going to start calling your PDA to tell you to stop for milk on the way home from work.

Global System for Mobile communications (GSM)
GSM is a type of TDMA digital wireless network that divides each carrier frequency into a number of time slots. But GSM has wider carrier frequencies and more time slots than TDMA, and it has encryption features. GSM is rapidly being deployed worldwide and is the standard in Europe at 900 MHz. In the U.S., carriers are deploying GSM at 1900 MHz, making GSM devices sold in the U.S. incompatible with their European counterparts.

The GSM standard was developed in Europe to standardize cellular communications among European countries. GSM has demonstrated substantial success and is now one of the world's most popular standards for new cellular radio and personal communications equipment.

Infrared Data Association (IrDA)
The IrDA is an industry-sponsored organization set up in 1993 to create international standards for the hardware and software used in infrared communication links. Infrared Radiation (IR) is the same technology used to control a TV set with a remote control.

Infrared has been playing an important role in wireless data communication because of the popularity of laptop computers, PDAs, digital cameras, mobile telephones, pagers and other devices. Many of the newer versions of these devices have an IR communications port.

IR can also be used for LAN connections. The maximum effective distance is somewhat less than 1.5 miles; the maximum projected bandwidth is 16 megabits per second. Since IR is a line-of-sight light transmission, it is sensitive to fog and other atmospheric conditions.

Last mile
"Last mile" refers to the connection between the customer and the telephone or cable company. The last mile has traditionally used copper-based telephone wire or coaxial cable, but wireless technologies offer alternative options in some locations.

Local Multipoint Distribution System (LMDS)
LMDS is a system for broadband microwave wireless transmission direct from a local antenna to homes and businesses within a line-of-sight radius. It is a solution to the so-called last-mile technology problem of economically bringing high-bandwidth services to users. LMDS is an alternative to installing optical fiber all the way to the user or to adapting cable TV for broadband Internet service.

Depending on the implementation, LMDS offers a bandwidth of up to 1.5 billion bits per second (1.5 Gbps) downstream to users and 200 million bits per second (200 Mbps) upstream from the user. A more typical data rate is 38 Mbps downstream. Some services offer both downstream and upstream service (symmetrical service); others offer downstream only (asymmetrical service). These obtain upstream using wire connections.

Local loop
"Local loops" are the lines between a customer and the telephone company's central office, often called the "last mile." Local loops use copper-based telephone wire.

Microwave
Microwave links are point-to-point wireless connections that require licenses. The available frequencies range from 1.7 GHz to 40 GHz. Most of the lower frequencies are used by carriers for backhaul networks, such as T3 connections at 45 Mbps. Although there is no upper limit on microwave connection speed, 155-Mbps is the current high end.

Multichannel Multipoint Distribution Service (MMDS)
MMDS is a broadcasting and communications service that operates in the ultra-high-frequency (UHF) portion of the radio spectrum between 2.1 and 2.7 GHz. MMDS is also known as wireless cable.

In MMDS, a medium-power transmitter is located with an omnidirectional broadcast antenna at or near the highest topographical point in the intended coverage area. The workable radius can reach up to 70 miles in flat terrain (significantly less in hilly or mountainous areas). Each subscriber is equipped with a small antenna, along with a converter that can be placed next to or on top of a conventional TV set. There is a monthly fee, similar to satellite TV service.

The MMDS frequency band has room for several dozen analog or digital video channels, along with narrowband channels that can be used by subscribers to transmit signals to the network. The narrowband channels were originally intended for use in an educational setting (so-called wireless classrooms). The educational application has enjoyed some success, but conventional TV viewers prefer satellite TV services, which have more channels.

Narrow-band Advanced Mobile Phone Service (NAMPS)
NAMPS is a variation on AMPS that uses a narrower bandwidth and has greater data capabilities.

Packet-switched
"Packet-switched" describes the type of network in which relatively small units of data, called packets, are routed through a network based on the destination address contained within each packet. Breaking communication down into packets allows the same data path to be shared among many users in the network. This type of communication between sender and receiver is known as "connectionless" (rather than dedicated). Most traffic over the Internet uses packet switching and the Internet is basically a connectionless network.

Ricochet
Ricochet, by MetriCom, is a packet-switched, wireless service with coverage in the Washington D.C., San Francisco and Seattle areas. Ricochet is unique because it uses unlicensed radio spectrum, which enables it to provide unlimited usage. In a partnership with electric utility companies, Ricochet mounts micro-cells on power poles and street lighting. Service is oriented towards consumers, offering flat rate pricing for access to the Internet.

Spread spectrum
Spread spectrum is currently the most widely used transmission technique for wireless LANs. It was initially developed by the military to avoid jamming or eavesdropping on signals. This is done by spreading the signal over a range of frequencies which consist of the Industrial, Scientific and Medical (ISM) bands of the electromagnetic spectrum. The ISM bands include the frequency ranges at 902 MHz to 928 MHz and at 2.4 GHz to 2.484 GHz, which do not require an FCC license.

Time Division Multiple Access (TDMA)
TDMA is designed to increase channel capacity by chopping the signal into pieces and assigning each one to a different time slot, each of which constitutes an independent telephone circuit and lasts a fraction of a second. Using TDMA, a single channel can be used to handle simultaneous transmissions.

United States Digital Cellular (USDC)
USDC, also known as IS-54 (Interim Standard 54), was developed to replace the AMPS standard, particularly in urban areas where AMPS did not provide adequate channel capacity. USDC allows the coexistence of AMPS so that providers can gradually phase out AMPS as needed.

Universal Mobile Telecommunications System (UMTS)
UMTS is a third-generation (3G), broadband, packet-based transmission of text, digitized voice, video and multimedia at data rates up to and possibly higher than 2 Mbps. Based on the GSM communication standard, UMTS offers a consistent set of services to mobile computer and phone users no matter where they are located in the world. Major standards bodies and manufacturers endorse UMTS.

Nortel Networks and British Telecom are currently conducting trials of UMTS technology, using advanced mobile phone/computing device prototypes. It may become the standard for mobile users around the world by 2002.

Wireless Application Service Provider (WASP)
A Wireless Application Service Provider (WASP) is part of a growing industry sector resulting from the convergence of two trends: wireless communications and the outsourcing of services. A WASP performs the same service for wireless clients as a regular Application Service Provider (ASP) does for wired clients: it provides Web-based access to applications and services that would otherwise have to be stored locally. The main difference with WASP is that it enables customers to access the service from a variety of wireless devices, such as the smartphone and the PDA. (Source: whatis.com)

Wireless Application Protocol (WAP)
WAP is a specification for a set of communication protocols to standardize the ways wireless devices can be used for Internet access. WAP supports wireless access to things like E-mail, the Web, newsgroups and Internet Relay Chat. Four companies conceived WAP: Ericsson Motorola, Nokia and Unwired Planet (which became Phone.com and recently merged with Software.com to become Openwave).

—John K. Waters

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