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Wireless Technologies
August 1999

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Liam Quinn, Senior Engineering Manager, Communication Technology Strategy
Frank Hanzlik, Group Manager, Communications, Internet Product Marketing
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The globalization of wireless communications is driving development of new standards and products that will soon bring dramatic changes to the wireless communications landscape. New and emerging wireless standards such as 802.11, HiperLAN/2, Bluetooth, HomeRF, and Wireless Application Protocol (WAP) will allow wireless communications between wired networks, mobile and desktop computers, cellular telephones, pagers, office machines, personal digital assistants (PDAs), and other hand-held digital devices.

These emerging wireless technologies use modulation techniques that provide a high level of security as well as resistance to interference from electronic devices and other users. Thus, more users can share a frequency band without interference. Moreover, these new technologies use unlicensed frequency bands, so there are no license restrictions for use of the frequency.

This white paper focuses on the technologies used for wireless network connections for computers and mobile digital devices other than cellular telephones and pagers. Wireless telephone and paging technologies are discussed because they are used in wide area networks (WANS) that connect local area networks (LANs) and personal area networks (PANs). Some of these technologies are also used for direct wireless connections to computers (DirectPC and other satellite services for example), and are involved in creating virtual private networks (VPNs) over the Internet. The paper concludes with Dell's plan for implementing wireless technologies in future products.

Why Wireless in Computer Networks?

In the past, wireless devices for computers were slow, had limited applications, were not usually interoperable, and were available from only a few vendors. Most wireless vendors specialized in a particular market segment, resulting in fragmented markets with prices that prevented widespread use of wireless technology in computer networks.

Today, emerging wireless standards and new products are making wireless communications available to a much broader customer base. In addition to these new wireless standards and products, other factors influencing the move to wireless network connections include:

  • Availability of a range of unlicensed frequencies in the 2.4 to 2.4835 gigahertz (GHz) industrial, scientific, and medical (ISM) band and in the 5-GHz band

  • Increased speed of the backbone data pipes that link wireless networks

  • Changing work patterns, a larger mobile work force, and globalization of e-commerce

With the new wireless products, mobile workers will be able to access corporate networks and the Internet from home or on the road without a physical network connection. Smart phones will be able to receive Internet data and link directly to computers, fax machines, and other office equipment. Computers and office machines can be networked in any size office without wires, and then linked to a wired network through an access device. Connections between wired networks can be wireless.

In the next 12 to 18 months, the speed of wireless devices will increase dramatically due to new wireless technologies. Most of these new devices will be interoperable or compatible because vendors are designing to the new standards. The best news for customers is that increased volumes are expected to cause a considerable decrease in the prices of wireless computer-related products.

Wireless Connections

Standardized protocols for wired WANs, LANs, and PANs, plus inexpensive interconnection hardware have made worldwide information sharing possible for some time. However, until recently, a network user's mobility was constrained by the need for a physical connection to a network. Typically, this physical connection is a network interface controller (NIC) and a cable. Alternatively, a modem can be used to link the computer to a remote network through the Public Switched Telephone Network (PSTN).

Recent developments in wireless technologies allow users who want more mobility to replace this physical network connection with a wireless link to a WAN, LAN, or PAN. A typical wireless link consists of a radio frequency (RF) or infrared (IR) transmitter/receiver module in a portable computer (or other digital device) linking the computer to a wired network through an access device as shown in Figure 1. The access device typically includes an RF or IR transmitter/receiver plus circuitry that permits connection to the wired network through a cable.

A computer user with a wireless connection is free to move about and still have access to network resources as long as the mobile computer is within range of the access device. The distance over which the computer and the access device can remain in contact varies depending on the type of wireless devices and the environment in which they are used.

Wireless Network Connection

Figure 1. Wireless Network Connection

Connections With Subscription Fees

Wireless connections can be categorized as subscription or nonsubscription. Subscription wireless services are services where a provider offers customers a package that includes use of a frequency band and other services for a periodic fee. Wireless services based on consumers paying a subscription fee for their use include:

  • Cellular paging and messaging services (one- and two-way)

  • Cellular telephone and data services, including computer connections over cellular networks

  • Satellite-based services such as DirectTV, DirectPC, telephone, and paging

Connections With No Subscription Fees

After a customer purchases the necessary hardware and software, there are no fees for using unlicensed frequency bands for wireless communications. Most wireless devices that operate in unlicensed frequency bands comply with one of the released or emerging standards listed in Table 1.

Some of these new wireless products are based on standards that are under development but not yet approved. Most vendors who are basing products on unapproved standards claim that their products can be easily upgraded with a simple software or firmware change when the standard is approved.

Standard

Controlling Agency

802.11

Institute of Electrical and Electronics Engineers (IEEE)

HiperLAN, HiperLAN/2

European Telecommunications Standards Institute (ETSI) Broadband Radio Access Networks (BRAN) project

Bluetooth

Bluetooth Special Interest Group (SIG)

HomeRF

International Telecommunications Union`s (ITU's) HomeRF working group

Wireless Networks

The following sections describe the technologies involved in WANs, LANs, and PANs. The discussion of WANs is primarily an overview of wireless telephone and paging technologies and services. These technologies are included because WANs are often used to interconnect LANs and PANs, and the technologies used in WANs, LANs, and PANs will converge in the future. Networks are discussed in the order of their size.

WAN Technologies

The major wireless technologies for WANs include:

  • Analog and digital cellular telephone service.

  • One- and two-way paging. Bidirectional messaging service is also possible between pagers with the appropriate equipment and service.

  • Satellite links for computers. DirectPC is currently available, and other high-speed solutions are under development.

Cellular Telephone and Paging Overview

Figure 2 shows how cellular telephone and pager users are linked through the PSTN.

Typical Cellular Service

Figure 2. Typical Cellular Service

Table 2 briefly describes the major wireless telephone services used in the U.S. and many other parts of the world for the past several years. The cellular technologies described in Table 2 fall into the following categories:

  • Analog cellular in the 800-MHz frequency band

  • Digital cellular in the 800- and 900-MHz frequency bands

  • Personal Communications Systems (PCS) in the 1,800- and 1,900-MHz frequency bands

The first three entries in Table 2 are first-generation (1G) analog wireless services. The remaining entries are second-generation (2G) digital wireless services. These generations and the changes coming in the next generation are described in more detail later in this paper.

Network

Type of Service

Frequency Band

Multiple Access Method(s)

Description

Improved Mobile Telephone Service (IMTS)

Analog

800 MHz

Not applicable

First analog wireless telephone service in the U.S. Limited to six calls at one time in each service area.

Advanced Mobile Phone Service (AMPS)

Analog

800 MHz

IS-54 TDMA1 and FDMA2

Advanced analog mobile service. Uses a 50-MHz segment of the 800-MHz band to provide 832 analog channels. Two service providers are each assigned one half of the channels in each service area. Analog cellular systems that are similar to AMPs but not compatible include Total Access Communications System (TACS) in the United Kingdom, China, and other countries, and Nordic Mobile Telephone (NMT) in the Scandinavian countries.

Digital AMPS (D-AMPS)

Digital cellular

800 MHz

IS-136 TDMA and IS-95 CDMA3

First digital cellular service in the U.S. Provides 416 1.25-MHz channel pairs. Supports three subscribers per channel with TDMA and a variable number of subscribers per channel with CDMA.

Personal Communications Systems

PCS

900 MHz and 1,900 MHz

IS-136 TDMA

PCS networks in the U.S. provide narrowband digital communications in the 900-MHz band for paging, and broadband digital communications in the 1,900-MHz band for cellular telephone service. In the U.S., PCS 1,900 is the same as Global System for Mobile Communications (GSM) 1,900.

Global System for Mobile Communications

PCS

900 MHz, 1,800 MHz, and 1,900 MHz

IS-36 TDMA for 1,900 MHz in U.S.

GSM operates in the 900-, 1,800-, and 1,900-MHz, frequency bands. GSM 1,800 is widely used in Europe and throughout many parts of the world. In the U.S., GSM 1,900 is the same as PCS 1,900; thus, these two technologies are compatible.

Personal Digital Communications (PDC)

Digital cellular

900 MHz

TDMA4

PDC is used only in Japan and is rapidly being replaced with CDMA to alleviate overcrowding of PDC bandwidth.

1. Time division multiple access. Conforms to Telecommunications Industry Association (TIA) Interim Standard (IS)-54 or IS-95 in the U.S.
2. Frequency division multiple access.
3. Code division multiple access. Conforms to TIA IS-95 in the U.S.
4. Japanese TDMA is not compatible with IS-136 TDMA.

Multiple Access Methods

FDMA, TDMA, and CDMA are methods for multiplexing several telephone conversations onto a single analog or digital cellular channel. With these technologies, multiple users can share a single cellular channel, thus reducing congestion and providing access for more users. These techniques also allow data streams to be multiplexed over a cellular channel. Data transfers over cellular connections are discussed later in this paper.

FDMA, controlled by the TIA in the U.S., is used only with analog cellular systems. FDMA divides the available frequency band into segments, allocating a particular segment to each call.

TDMA, controlled by TIA IS-54 or IS-136, defines how a single cellular channel can be segmented into a series of time slots. Each time slot carries a specific user's information. IS-54 TDMA is used with analog service; IS-136 TDMA is used with digital service. IS-136 TDMA is the prevalent multiple access method in the U.S. at this time.

Digital cellular telephones designed for networks that use TDMA will not work in networks that use CDMA.

CDMA, also called CDMA 1, is controlled in the U.S. by TIA IS-95. CDMA defines how a single channel can be segmented into multiple channels using a pseudorandom signal (or code) to identify each user's information. Because CDMA spreads each call over the entire available frequency band, it is more immune to interference than TDMA and can support more users per channel in some situations. CDMA networks are not as widely used in the U.S. at this time.

Data Transfers Over Cellular Connections

Data can be transferred over an analog or digital cellular connection using Cellular Digital Packet Data (CDPD) technology. CDPD, developed by American Telephone and Telegraph (AT&T) in the mid-1990s, provides for wireless transmission of digital data over cellular channels. Currently, data transfers of up to 14.4 kilobits per second (Kbps) over a single cellular channel are possible with CDMA, whereas systems using TDMA are limited to 9.6 Kbps. CDPD is currently used primarily to transmit brief messages to PDAs and e-mail to cellular telephones, but it is not restricted to those uses.

Circuit-Switched Versus Packet-Switched Data

Data can be transmitted across cellular networks using either circuit-switched or packet-switched connections.

Circuit-switched connections are similar to telephone calls, where a temporary circuit is dedicated exclusively to the sending and receiving nodes for the duration of the data transfer. Circuit-switched connections are best suited for long file transfers because data is received in the order that it is sent and is unlikely to be separated or lost. With circuit-switched connections, customers are billed for the duration of the connection. This type of data transaction is typically routed through the PSTN.

Packet-switched connections, unlike circuit-switched connections, do not involve a dedicated circuit between two nodes. Instead, packet-switched connections allow multiple simultaneous users to access multiple locations across a network. Packets of data are sent from source to destination using the quickest route available. Each packet contains a source and destination address and is typically limited to 1,500 bytes of data. Using packet-switched connections can be much more efficient and cost-effective for short, bursty data such as e-mail and database queries. Customers are not billed for connection time, only for the amount of data transferred. Packet-switched data is typically routed over a high-speed public data network (PDN).

CDPD is a Transmission Control Protocol/Internet Protocol (TCP/IP)-based technology that supports Point-to-Point Protocol (PPP) and Serial Line Internet Protocol (SLIP) wireless connections to mobile devices. Cellular data service is widely available throughout the world from major service providers. With CDPD, data can be transferred over switched PSTN circuits or a packet-switched network as described in the sidebar, "Circuit-Switched Versus Packet-Switched Data." A higher-speed, packet-switched data service based on CDPD protocols will be available in the U.S. in the future.

GSM systems use a technology called GSM data for transferring data at up to 9.6 Kbps over switched circuits in a GSM cellular network. GSM networks do not offer packet switching at this time.

1G Wireless Services and Technologies

First-generation wireless services and technologies include analog cellular telephone and paging services and the technologies that support them. These services and technologies have been replaced with second-generation digital services and technologies in many cases.

2G Wireless Services and Technologies

The digital wireless services described in Table 2 and the technologies that support them are 2G technologies. Currently in use in the wireless communications industry, 2G technologies provide extensive coverage with a proven and reliable communications infrastructure; however, data transfer rates are limited, few security features are available, and subscriber fees are higher than those for wireline connections.

2.5G Wireless Services and Technologies

The next true generation of wireless technologies will be called third generation (3G); however, an interim step called 2.5G is planned for release in the second half of 1999 and the first half of 2000. Several new features will be available in 2.5G, including:

  • General Packet Radio Service (GPRS), a packet-based data transmission technology that will initially provide data transfer rates of up to 115 Kbps. GPRS will work with CDMA and TDMA, and it supports both the IP and X.25 communication protocols. Trials of GPRS will start in 2000 in the U.S.

  • Voice over IP (VOIP) and multimedia services over IP will become practical with the higher data transfer rates afforded by GPRS. However, quality of service (QoS) will not be available until 3G.

3G Wireless Services and Technologies

3G wireless technologies will become available over a period of several years, beginning in 2000 in some countries and as late as 2002 in others. The governing standard for 3G technologies is the ITU's standard for International Mobile Telephony (IMT)-2000. This standard, which provides for commonality of design and worldwide compatibility between networks, is supported by the TIA in North America, ETSI in Europe, and the Association of Radio Industries and Businesses (ARIB) in Asia.

W-CDMA will be backward compatible with GPRS in GSM and PDC systems in Europe and Asia. CDMA2000 will be backward compatible with GPRS in IS-95 CDMA systems in North America.

Additional capacity, compatibility between worldwide wireless systems, and higher data transfer rates are the major thrusts of the 3G initiative. Data transfer rates of up to 2 megabits per second (Mbps) will be possible in fixed mode using wideband CDMA (W-CDMA), which is called CDMA2000 in North America. W-CDMA increases data transfer rates by using multiple 1.25-MHz cellular channels compared to the single channel currently used by IS-95 CDMA. Major service providers are already working on deployment of W-CDMA in Japan where existing cellular networks are severely overloaded due to the rapidly expanding number of users.

Satellite Communications

Geosynchronous earth orbit (GEO) satellites, orbiting over 22,000 miles above the earth, are used primarily for broadcast television. Although a GEO satellite's high altitude gives it a broad coverage area, the time it takes for a signal to travel to and from the satellite (signal latency) makes a GEO satellite undesirable for real-time voice or data communications. Moreover, the cost of access to communication channels on a GEO satellite is prohibitive for all but large businesses and consortiums.

Low earth orbit (LEO) satellites, orbiting the earth at an altitude of 400 to 1,000 miles, have a narrower coverage area than GEO satellites. Because of their lower altitude, signal latency is less of a problem and less power is required to transmit signals to and from a LEO satellite, resulting in a lower cost of service. Several industry groups are developing networks of LEO satellites to provide affordable global wireless communication services.

LAN Technologies

For wireless links, 802.11 specifies a carrier sense multiple access with collision avoidance (CSMA/CA) method compared to standard Ethernet's carrier sense multiple access with collision detection (CSMA/CD). The reason for this difference is that when a wireless node is transmitting data, it cannot detect another node transmitting at the same time.

Although there are some proprietary wireless LAN solutions, most are based on devices that conform to the IEEE 802.11 standard or the ETSI BRAN project's HiperLAN standard.

IEEE 802.11 Standard

The IEEE 802.11 standard specifies parameters for the physical layer (PHY) and the medium access control (MAC) layer of the seven-layer Open Systems Interconnect (OSI) model. The standard specifies three different transmission methods for the PHY, the layer responsible for transferring data between nodes. Two of the methods use spread spectrum RF signals in the 2.4- to 2.4835-GHz ISM band. The two RF methods transfer Ethernet data (no voice at this time) at 1 and 2 Mbps using 100 milliwatts (mw) of transmitter power. The third method, which transfers data over IR links, is discussed later in this paper.

Spread spectrum technology is a modulation technique that spreads data transmissions across the entire available frequency band in a prearranged scheme (similar to CDMA discussed earlier). This type of modulation makes the signal highly resistant to noise, interference, and snooping. Spread spectrum technology also permits many users to share a frequency band with minimal interference from other users and from devices such as microwave ovens. The two types of spread spectrum modulation specified by 802.11 are Direct Sequence Spread Spectrum (DSSS) and Frequency Hopping Spread Spectrum (FHSS). Brief descriptions of each follow.

DSSS

With DSSS, each bit to be transmitted is encoded with a redundant pattern called a chip, and the encoded bits are spread across the entire available frequency band. The chipping code used in a transmission is known only to the sending and receiving stations, making it difficult for an intruder to intercept and decipher wireless data encoded in this manner. The redundant pattern also makes it possible to recover data without retransmitting it if one or more bits are damaged or lost during transmission.

With DSSS, roaming is only possible between access points on the same channel, which makes DSSS less robust for roaming than FHSS. DSSS devices are capable of transmitting data up to 25 miles over point-to-point connections. Thus, they can be used as an alternative to leased lines or fiber-optic cables for bridging LAN segments in point-to-point or multipoint connections between buildings.

FHSS

With FHSS, a transmitting and receiving station are synchronized to hop from channel to channel in a predetermined pseudorandom sequence. The prearranged hop sequence is known only to the transmitting and receiving station. In the U.S. and Europe, IEEE 802.11 specifies 79 channels and 78 different hop sequences. If one channel is jammed or noisy, the data is simply retransmitted when the transceiver hops to a clear channel.

As a result of its constant frequency shifting, FHSS is less susceptible to interference and is difficult for an intruder to intercept, making it very secure against snooping. Because interference is minimal with FHSS, multiple hopping sequences can typically be assigned in the same physical area, allowing more users to share the available bandwidth. With FHSS systems, users can roam between access points on different channels.

The Federal Communications Commission (FCC) has restricted data transfer rates with FHSS to 2 Mbps, so it is not included in the upcoming revision to the 802.11 standard. However, several companies have petitioned the FCC to permit FHSS operation at 11 Mbps.

802.11 Infrared

The third data transfer method supported by 802.11 uses the 300-GHz to 428-terahertz (THz) IR band to transmit data that conforms to the Infrared Data Association (IrDA) standard. 802.11 IrDA devices have a peak power rating of 2 watts (w) and use pulse position modulation of IR signals to transmit data at up to 155 Mbps.

IrDA devices use very high-frequency electromagnetic waves just below the visible light spectrum to transmit data, thus they are sensitive to environmental conditions such as bright lights or sunlight. IrDA transmissions are limited to line-of-sight, so they are very secure against snooping. However, they are generally limited to relatively short distances because infrared signals cannot travel through opaque objects. Hampered by lack of supporting application programs, IrDA has few supporters at this time.

802.11 Summary and Upcoming Revisions

The 802.11 standard currently provides for 1- and 2-Mbps data transfers using DSSS and FHSS, and 155 Mbps with IrDA. All of the 802.11 technologies are designed to be interoperable with wired Ethernet LAN networks and with other devices of the same type; however, 802.11 DSSS and FHSS systems are not interoperable. 802.11-compatible devices that operate at 1 Mbps and 2 Mbps are widely available today from several vendors.

IEEE working groups currently have two extensions to the 802.11 standard under development:

  • The first extension, designated 802.11b, upgrades data transfers to 11 Mbps in the 2.4-GHz frequency band using DSSS. (This extension will not support FHSS due to FCC restrictions.) Devices that operate at up to 11 Mbps are already available from a few vendors. Most of these vendors claim their devices will conform to 802.11b when it is approved, or be easily upgradeable through a software or firmware revision. 802.11b devices that operate at up to 11 Mbps are expected to be widely available in 2000, and prices are expected to drop as more vendors bring their products to the market.

  • The second extension, designated 802.11a, provides for data rates from 6 Mbps to 54 Mbps in the unlicensed 5-GHz frequency band using Orthogonal Frequency Division Multiplexing (OFDM), a spread spectrum technology developed by Wi-LAN, Inc. The IEEE 802.11a working group is working closely with the ETSI BRAN project to ensure compatibility between this extension to 802.11 and the ETSI BRAN HiperLAN/2 standard. The 802.11a extension is expected to be approved in 2000.

Operating at 11 Mbps, 802.11 will be a major enabler for widespread use of wireless communications in enterprise networks. Migration to the home environment is expected to follow as product volumes increase and prices decrease.

HiperLAN

The HiperLAN type 1 (HiperLAN/1) standard, which supports data transfers of up to 19 Mbps in the 5-GHz frequency band, is not widely used in the U.S. because HiperLAN devices are not compatible with 802.11 devices. However, the ETSI BRAN project is currently working on a HiperLAN/2 standard in which compatibility with the 802.11a standard is planned. The HiperLAN/2 standard, scheduled for release in 2000, provides for communications over distances of 200 meters (m) at 25 to 54 Mbps in the 5-GHz frequency band. Like 802.11a, HiperLAN/2 will use the OFDM technology. HiperLAN/2 will include QoS for voice transfers.

The ETSI BRAN project group is also working on Hiperaccess and Hiperlink standards. Hiperaccess is intended to provide 25-Mbps point-to-multipoint wireless service up to 5 kilometers (km) for residences, small businesses, and corporate campuses. Hiperlink is intended to provide wireless links between HiperLAN and Hiperaccess networks. These standards are still in the development stage.

PAN Technologies

PANs are generally very small networks, covering only a personal work space, an office, or a meeting room. The major advantages of PANs are freedom from cables, automatic data synchronization between computers, and easy sharing of data between workers in a meeting room or small area. Bluetooth and HomeRF are the most popular technologies for PANs at this time. Although 802.11 IrDA is suitable for PANs under certain conditions, it currently has little support.

Bluetooth

Bluetooth is the name adopted by a consortium of wireless equipment manufacturers who are working on a global standard for low-cost wireless voice and data communications. The Bluetooth SIG is currently working on a specification for wireless data transmissions in the 2.4-GHz ISM frequency band using FHSS technology. The Bluetooth technology is based on a short-range radio transmitter/receiver that is built into small application-specific integrated circuits (ASICs) and embedded in supported devices.

Initially, Bluetooth devices will have 1 mw of transmitter power and will be capable of symmetrical data transfers of up to 432 Kbps and asymmetrical transfers of up to 721 Mbps over distances of up to 10 m. The Bluetooth specification permits increasing transmitter power to 100 mw, which will increase its range to 100 m. The Bluetooth specification also supports up to three independent voice channels.

Bluetooth devices will use short data packets and hop between frequencies at up to 1,600 hops per second, a much higher rate than 802.11 devices. The Bluetooth group claims that the higher hop rate and shorter data packets make this technology more robust than 802.11. The Bluetooth SIG and the IEEE 802.11 working group are cooperating to ensure that there will be no unfavorable interaction between the two technologies. Dell is working with both groups to ensure that its customers can use both technologies in their networks with no interference problems between the two technologies.

Bluetooth technology enables a user to replace the various cables between devices and create a totally wireless network in a residence or small business where all devices are within 10 m of each other. Using Bluetooth technology, devices such as cellular telephones, portable computers, fax machines, printers, and so on can communicate without the need for cables.

Bluetooth can provide automatic synchronization of data between devices. For example, a traveler can configure his/her desktop computer, portable computer, cellular telephone, and PDA to automatically synchronize calendars and address lists when returning to the office from a trip.

If users set up their devices to do so, a Bluetooth-equipped device can automatically establish a connection with another Bluetooth device as soon they are within range. Because the Bluetooth technology supports both point-to-point and point-to-multipoint connections, several very small networks (piconets) can be established and linked together in an ad hoc network called a scatternet. Figure 3 shows how two piconets can link together to form a PAN.

Bluetooth Piconet Connections

Figure 3. Bluetooth Piconet Connections

An example of where Bluetooth would be the ideal technology is a large meeting room where portable computer users need to share files or a database. With Bluetooth technology in the portable computers, the computers can link to form a piconet as soon as users turn on computer power and authorize the connection.

Although Bluetooth is not interoperable with the IEEE 802.11 standard, it uses the same TCP/IP protocol. Interoperability with 802.11 devices can be provided through bridge access devices.

The Bluetooth group is encouraging vendors to integrate the technology into their products by offering the technology free of royalty fees. The Bluetooth specification 1.0 was released in July 1999. Announcements of computer-related products are expected to begin in late 1999. The first Bluetooth products will be Universal Serial Bus (USB)-based or integrated on PC Cards or mini peripheral component interconnect (PCI) cards. Bluetooth transceivers will be integrated directly on mobile computer system boards and in other wireless devices in the future.

HomeRF

The HomeRF working group, sponsored by the ITU, is developing a standard for inexpensive RF voice and data communications. When the standard is approved, HomeRF technology will be available free to promote market growth.

The HomeRF specification provides for wireless Ethernet data transmissions of up to 800 Kbps at distances up to 40 m with 100 mw of transmitter power. The specification also provides for four PCS-quality voice channels for telephones, and a short-range, low-power mode for digital devices such as PDAs. Based on the Shared Wireless Access Protocol (SWAP), HomeRF will operate in the 2.4-GHz ISM band using a frequency-hopping technique where devices change channels at 50 hops per second. The SWAP specification is a hybrid, borrowing its PHY layer from 802.11 and its voice protocols from the European Digital Cordless Telephone (DECT) standard. PHY layer requirements are more relaxed in the SWAP specification, allowing vendors to make HomeRF devices less expensive than 802.11 devices.

Although HomeRF's data rate brings it close to Bluetooth performance, Bluetooth currently has more industry backing.

Wireless Application Protocol

The Wireless Application Protocol (WAP) Forum, an industry association with over 100 members, is working to develop a specification for communications between wireless networks and hand-held wireless mobile devices such as telephones, pagers, two-way radios, PDAs, smart phones, and so on. The primary goals of the forum are to ensure interoperability between wireless devices and promote wireless industry growth.

The WAP specification supports most wireless network services and protocols, including GSM, PDC, TDMA, CDMA, and CDPD, and is specifically devised for small-screen devices intended for one-hand navigation without a keyboard.

One of the primary purposes of the WAP specification is to permit hand-held devices to link with and communicate with wireless networks regardless of the operating systems and protocols used in the networks. WAP uses an eXtensible Markup Language (XML)-compliant markup language called Wireless Markup Language (WML) to permit interoperability between hand-held wireless devices. WML's user interface is a microbrowser that works well with small displays such as those on cellular telephones. With WAP and WML, content can be pulled from the Internet and formatted for use on the small display of a hand-held device.

At this time, WAP is not a formal standard, but is widely accepted and is likely to become a de facto standard. The WAP forum has released version 1 of their specification and plans to release version 1.1 in mid-1999.

Wireless Home Networks

Wireless home networks are becoming popular with telecommuters and mobile workers. HomeRF as well as the 802.11 and Bluetooth wireless technologies used in corporate office environments are all well suited for use in home networks. Having the same wireless technology at home and in the corporate office lets a mobile worker quickly resume work at home without having to worry about a docking station or a physical connection to the network. And, with a wireless home network, an individual can choose where to work.

A wireless home office can provide wireless connections between devices in the home, as well as having a residential gateway connected to a broadband pipe that provides high-speed access to a corporate network, the Internet, video, and voice services. The broadband pipe can be wireline or wireless, using one of many available services such as Integrated Services Digital Network (ISDN), cable modems, digital subscriber line (DSL), or satellite services such as DirectPC.

Software Support for Wireless

Microsoft® Windows® operating systems with Network Driver Interface Specification (NDIS)4 and NDIS5 support 802.11, HiperLAN, and HomeRF wireless devices. After the user loads the drivers supplied with the wireless device, the wireless device appears to the operating system as a standard Ethernet network adapter.

The appropriate versions of NDIS are included in the Microsoft Windows 95 operating system release 2 (OS/R2), Windows 98, Windows NT® 4, and Windows 2000. Earlier Microsoft operating systems with NDIS3 do not support wireless devices.

The Bluetooth technology is implemented in a way that does not conform to the OSI model. Thus, Bluetooth devices are not compatible with the NDIS specifications, and do not work with Windows operating systems. However, there are other operating systems that support Bluetooth devices. One example is Symbian's 32-bit EPOC operating system that is optimized for wireless devices such as those in which Bluetooth technology can be used. The EPOC product family includes a multithreaded operating system, application framework, and application programs. A developer's kit is available for developing programs in several languages. The URL for the Symbian Web site is included at the end of this paper.

Dell's Wireless Strategy

Dell views wireless as a key enabler for the future, and is pursuing a three-fold wireless strategy:

  • Enable anytime/anywhere computing

  • Provide a better user experience by reducing or eliminating the need for interconnecting cables

  • Reduce the customer's total cost of ownership (TCO) by providing an alternative to fixed wiring and installation expenses

Dell intends to actively engage in development of strategic emerging wireless standards to ensure that it offers customers these technologies as early as possible. Dell is a founding member of several wireless initiatives, and is participating in the review of the Bluetooth standard, the HomeRF standard, and revisions to the IEEE 802.11 standard. Dell also plans to work with its business partners to offer its customers (through DellPlus) complete wireless solutions for seamless connections between WANs, LANs, and PANs.

Dell plans to work closely with Microsoft and other software vendors to ensure that operating systems and application programs include support for wireless applications. Management and security issues are of special concern to most organizations who intend to incorporate wireless devices in their networks. Although the security offered by spread spectrum technologies will be adequate for many users, Dell will work with its development partners and third-party vendors to provide additional security for customers with special requirements.

Dell's initial offerings of wireless products will be 802.11-compliant PC Card and PCI card-based wireless devices packaged with the necessary software and tested by DellPlus to ensure proper operation. Embedded wireless solutions and higher-speed devices are expected to follow in the first half of 2000.

Conclusion

PC Magazine Online (July 20, 1999) features an article titled "Connect Anywhere," which provides a thorough review and comparison of currently available wireless devices and data services. The URL for the online version of the article is listed at the end of this white paper.

Emerging wireless technologies offer network users unprecedented mobility. With wireless devices that conform to the emerging standards discussed in this paper, a network user no longer needs a physical link to a network to take advantage of all the services offered by a wired LAN. Access to the Internet or remote data from almost any location is possible with the appropriate wireless equipment. This new freedom from cables permits users of portable computers and hand-held digital devices to access network resources in environments where it was difficult or impossible until recently.

One of the best features these new wireless technologies offer is a data transfer rate that permits voice and data services to be combined over a shared wireless connection. And, as QoS becomes available in the future, wireless voice service is likely to be part of a combined package in which Internet service providers (ISPs) offer voice, data, and Internet service all in one package.

With data rates approaching those of wired LANS and much higher rates on the horizon, wireless devices are expected to see a dramatic increase in use in the coming months. Along with the increased use, prices for wireless solutions are expected to become competitive with wired network connections in the future.

For More Information

For more information on the wireless technologies discussed in this white paper, see the following Web sites:


Information in this document is subject to change without notice.
© 1999 Dell Computer Corporation. All rights reserved.

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