6.3 Wireless networks


6.3 Wireless networks

Wireless networks are used to transmit data between mobile devices or personal computers using wireless adapters without the use of a physical cable or wire. Depending on the coverage range, these networks could be classified as:

  • PAN (Personal Area Network)

  • WLAN (Wireless Local Area Network)

  • WWAN (Wireless Wide Area Network)

6.3.1 PAN (Personal Area Network)

A PAN has a very short range, usually up to 10 “20 feet. The main objective of this network is to interconnect personal devices, for example a cell phone to a PDA or keyboard to a desktop computer. It is also used to connect these with other available devices in the environment, for example a cell phone with vending machines. Several technologies could be used to implement a PAN, such as Infrared and Bluetooth.

Infrared technology

Infrared is an invisible band of radiation at the lower end of the electromagnetic spectrum; it starts in the middle of the microwave spectrum and goes up to the beginning of visible light. Infrared transmission requires an unobstructed line of sight between transmitter and receiver. It is used for short range point-to-point wireless transmission between computer devices, as well as many handheld remotes for TVs and video and stereo equipment.

The Infrared technology standards are controlled by IrDA, Infrared Technology Data Association, to ensure interoperability between devices of all types. For more information, you can visit the official IrDA Web site at:

  • http://www.irda.org

Bluetooth

Bluetooth is an open technology specification created for short-range (up to 10 meters ) wireless connection using low-cost transceiver chips to be embedded in mobile PCs, smart phones, and other portable devices. It provides three voice and data channels via a one-to-one connection with built-in encryption and verification. The objective is to connect devices and establish ad-hoc connections in a peer-to-peer mode, using the unlicensed 2.4GHz frequency. This technology can transfer data at up to 1 Mb per second. The Bluetooth technology signals are omni-directional , thus eliminating the need for line-of-sight.

The Bluetooth technology is governed by the Bluetooth Special Interest Group (SIG) which includes promoter group companies 3Com, Agere, Ericsson, IBM, Intel , Microsoft, Motorola, Nokia and Toshiba, and more than 2000 Associate and Adopter member companies representing a broad spread of industry interest.

The Bluetooth Special Interest Group is working together with the IEEE, Institute of Electrical and Electronics Engineers, focused on the development of consensus standards for PAN. It is also working on recommended practices and guidelines to handle, among other issues, manufacturer interoperability. The IEEE 802.15.1 standard is an additional resource for those who implement Bluetooth devices.

For more information, you can visit the official Bluetooth Web site at:

  • http://www.bluetooth.com

or the IEEE Web site at:

  • http://www.ieee.org

If you want to understand the IBM's perspective regarding the synergies between the Bluetooth technology and the pervasive computing, you can read our white paper at:

  • http://www.ibm.com/industries/telecom/doc/content/bin/Bluetooth.pdf .

6.3.2 WLAN (Wireless Local Area Network)

A Wireless LAN is a local area network that uses wireless technologies to connect devices and transmits data. To work properly, a WLAN requires an antenna connected to the network and a client with a wireless card. The antenna is known as an access point and the wireless card is usually a PCMCIA card. The widespread technology is the IEEE 802.11b which uses an unlicensed 2.4GHz frequency and can transfer data at up to 11MB per second. The current speed is dependent on the distance between the access point and the client. The closer the client is to the access point, the higher the speed it will achieve.

The IEEE (Institute of Electrical and Electronics Engineers) is responsible for the IEEE 802.11b standard. There are some other WLAN standards that are starting to have commercial products like IEEE 802.11a, which uses the 5GHz frequency and can transfer data at up to 54MB per second. The IEEE is continuously developing other standards like 802.11g (for WLANS operating in the 2.4 GHz frequency but with a bandwidth of 54 MBps), 802.11i (enhanced security), 802.11h (spectrum and power control management) and 802.11e (quality of service).

A wireless LAN does not require lining up devices for line-of-sight transmission such as IrDA. The wireless access points (base stations ) are connected to an Ethernet network or server and transmit a radio frequency over an area of several hundred to a thousand feet. This frequency can penetrate walls and other non-metal barriers. Roaming users can be handed off from one access point to another as in a cellular phone system. Laptops usually use PCMCIA cards to connect to a wireless access point and desktops and servers use plug-in cards.

Wi-Fi Alliance

The Wi-Fi Alliance is an important member of the IEEE 802.11 ecosystem. They are a nonprofit trade organization that promotes the use of standardized 802.11 technologies and certify Wi-Fi product interoperability.

For more information, you can visit the official IEEE Web site at:

  • http://www.ieee.org

or the Wi-Fi Alliance Web site at:

  • http://www.weca.net

6.3.3 WWAN (Wireless Wide Area Network)

Wireless WANs use the cellular networks to provide access. The cellular technology is in constant evolution. Each major advance is often referred to as a generation with its acronyms: 1G (first generation), 2G (second generation) and so on.

1G

The First-generation (1G) was the first analogic circuit-switching cellular technology appropriated to mobile voice communication.

2G

The Second-generation (2G) systems represented the digital evolution and were introduced in the 1990s. Some of the technologies implemented included TDMA, CDMA, and GSM. 2G systems were used primarily for voice. They have basic data capabilities but with a slow data transfer speed, between 9.6KBps and 14.4KBps. These protocols support high bit rate voice and limited data communications. They offer auxiliary services such as data, fax and SMS.

2.5G

The 2.5G represents a major step towards the convergence between telecommunication and the Internet. It brings packet-switching technology to data transfer. Some 2.5G systems have been implemented recently, such GPRS and CDMA 1xRTT. Both can be considered a packet-based extension of GSM and CDMA networks, respectively, and provide higher data throughput and always-on connectivity. They also provide new business models such as the pay per packet model.

Under the wireless solution perspective, we should focus on the 2.5G which brings higher packet data transfer speed, allowing the development of a huge spectrum of new applications.

3G

Third-generation (3G) systems are starting to be implemented and will be called IMT-2000 (International Mobile Telecommunications-2000). IMT-2000 is the ITU (International Telecommunication Union) globally coordinated definition of 3G, covering key issues such as frequency spectrum use and technical standards. 3G networks provide higher-speed transmission to support high-quality audio and video, as well as global roaming capability. 3G will support bandwidth-hungry applications such as full-motion video, video-conferencing and full Internet access. For more information, you can visit the ITU Official Web site at:

  • http://www.itu.int

UMTS

The Universal Mobile Telecommunications System (UMTS) is the European implementation of the 3G wireless phone system supported by the European Telecommunications Standard Institute (ETSI). UMTS, which is part of IMT-2000, offers global roaming and personalized features. UMTS was designed as an evolutionary system for GSM network operators. UMTS uses the W-CDMA technology. GPRS and EDGE are interim steps that will speed up wireless data for GSM. For more information you can visit the UMTS Forum Web site at:

  • http://www.umts-forum.org

or the ETSI Web site at:

  • http://www.etsi.org .

WCDMA

The Wideband Code Division Multiple Access (WCDMA) radio access technology is part of UMTS and is supported by several manufacturers such as Ericsson (Sweden) and Nokia (Finland). This technology will be used mainly in Europe and Japan. The data translation rate is 64 kbps for upstream and 384 kbps for downstream.

CDMA2000

CDMA2000 is a specification developed by the Third Generation Partnership Project 2 (3GPP2). It is an evolution from CDMA technology. The first phase of CDMA2000 is known as CDMA2000 1X and will provide bandwidth of 144 kbps. The second phase is labeled CDMA2000 1xEV and will provide for bandwidth in the 2Mbps range. For more information you can visit the 3GPP Web site at:

  • http://www.3gpp2.org




Patterns. Pervasive Portals
Patterns: Pervasive Portals Patterns for E-Business Series
ISBN: 0738427772
EAN: 2147483647
Year: 2002
Pages: 83
Authors: IBM Redbooks

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