In 1970 University of Hawaii, under the leadership of Norman Abramson, developed the world’s first computer communication network using low-cost ham-like radios, named ALOHAnet. The bi-directional star topology of the system included seven computers deployed over four islands to communicate with the central computer on the Oahu Island without using phone lines.[1]
"In 1979, F.R. Gfeller and U. Bapst published a paper in the IEEE Proceedings reporting an experimental wireless local area network using diffused infrared communications. Shortly thereafter, in 1980, P. Ferrert reported on an experimental application of a single code spread spectrum radio for wireless terminal communications in the IEEE National Telecommunications Conference. In 1984, a comparison between Infrared and CDMA spread spectrum communications for wireless office information networks was published by Kaveh Pahlavan in IEEE Computer Networking Symposium which appeared later in the IEEE Communication Society Magazine. In May 1985, the efforts of Marcus led the FCC to announce experimental ISM bands for commercial application of spread spectrum technology. Later on, M. Kavehrad reported on an experimental wireless PBX system using code division multiple access. These efforts prompted significant industrial activities in the development of a new generation of wireless local area networks and it updated several old discussions in the portable and mobile radio industry.
The first generation of wireless data modems was developed in the early 1980s by amateur radio operators, who commonly referred to this as packet radio. They added a voice band data communication modem, with data rates below 9600-bit/s, to an existing short distance radio system, typically in the two meter amateur band. The second generation of wireless modems was developed immediately after the FCC announcement in the experimental bands for non-military use of the spread spectrum technology. These modems provided data rates on the order of hundreds of kbit/s. The third generation of wireless modem then aimed at compatibility with the existing LANs with data rates on the order of Mbit/s. Several companies developed the third generation products with data rates above 1 Mbit/s and a couple of products had already been announced by the time of the first IEEE Workshop on Wireless LANs."
Tuesday, May 5, 2009
Wi-Fi
Wi-Fi uses both single carrier direct-sequence spread spectrum radio technology (part of the larger family of spread spectrum systems) and multi-carrier OFDM (Orthogonal Frequency Division Multiplexing) radio technology. The regulations for unlicensed spread spectrum enabled the development of Wi-Fi, its onetime competitor HomeRF, Bluetooth, and many other products such as some types of cordless telephones.
Unlicensed spread spectrum was first made available in the US by the Federal Communications Commission in 1985 and these FCC regulations were later copied with some changes in many other countries enabling use of this technology in all major countries.[1] The FCC action was proposed by Michael Marcus of the FCC staff in 1980 and the subsequent regulatory action took 5 more years. It was part of a broader proposal to allow civil use of spread spectrum technology and was opposed at the time by main stream equipment manufacturers and many radio system operators.[2]
The precursor to Wi-Fi was invented in 1991 by NCR Corporation/AT&T (later Lucent & Agere Systems) in Nieuwegein, the Netherlands. It was initially intended for cashier systems; the first wireless products were brought on the market under the name WaveLAN with speeds of 1 Mbit/s to 2 Mbit/s. Vic Hayes, who held the chair of IEEE 802.11 for 10 years and has been named the 'father of Wi-Fi,' was involved in designing standards such as IEEE 802.11b, and 802.11a.
The original patents behind 802.11 Wi-Fi technology, filed in 1996, are held by the CSIRO, an Australian research body. The patents have been the subject of protracted and ongoing legal battles between the CSIRO and major IT corporations over the non-payment of royalties. In 2009 the CSIRO reached a settlement with 14 companies, including Hewlett-Packard, Intel, Dell, Toshiba, ASUS, Microsoft and Nintendo, on the condition that the CSIRO did not broadcast the resolution.
Unlicensed spread spectrum was first made available in the US by the Federal Communications Commission in 1985 and these FCC regulations were later copied with some changes in many other countries enabling use of this technology in all major countries.[1] The FCC action was proposed by Michael Marcus of the FCC staff in 1980 and the subsequent regulatory action took 5 more years. It was part of a broader proposal to allow civil use of spread spectrum technology and was opposed at the time by main stream equipment manufacturers and many radio system operators.[2]
The precursor to Wi-Fi was invented in 1991 by NCR Corporation/AT&T (later Lucent & Agere Systems) in Nieuwegein, the Netherlands. It was initially intended for cashier systems; the first wireless products were brought on the market under the name WaveLAN with speeds of 1 Mbit/s to 2 Mbit/s. Vic Hayes, who held the chair of IEEE 802.11 for 10 years and has been named the 'father of Wi-Fi,' was involved in designing standards such as IEEE 802.11b, and 802.11a.
The original patents behind 802.11 Wi-Fi technology, filed in 1996, are held by the CSIRO, an Australian research body. The patents have been the subject of protracted and ongoing legal battles between the CSIRO and major IT corporations over the non-payment of royalties. In 2009 the CSIRO reached a settlement with 14 companies, including Hewlett-Packard, Intel, Dell, Toshiba, ASUS, Microsoft and Nintendo, on the condition that the CSIRO did not broadcast the resolution.
Wireless Internet service provider
WISPs often offer additional services like location based content, Virtual Private Networking and Voice over IP. Isolated municipal ISPs and larger state-wide initiatives alike are tightly focused on wireless networking.
WISP's are predominantly in rural environments where cable and digital subscriber lines are not available. WiMax is expected to become mainstream in the near future, bringing with it dramatic changes to the marketplace by increasing the number of interoperable equipment on the market and making mobile data transmission feasible, increasing the utility of such networks in rural environments. However, high-bandwidth wireless backhauls are already common in major cities[citation needed], providing levels of bandwidth previously only available through expensive fiber optic connections.
Typically, the way that a WISP operates is to pull a large and usually expensive point to point connection to the center of the area they wish to service. From here, they will need to find some sort of elevated point in the region, such as a radio or water tower, on which to mount their equipment. On the consumers side, they will mount a small dish or antenna to the roof of their home and point it back to the WISP's nearest antenna site. When operating over the tightly limited range of the heavily populated 2.4 GHz band, as nearly all 802.11-based WiFi providers do, it is not uncommon to also see access points mounted on light posts and customer buildings.
Since it is difficult for a single service provider to build an infrastructure that offers global access to its subscribers, roaming between service providers is encouraged by the Wi-Fi Alliance with the WISPr protocol. WISPr is a set of recommendations approved by the alliance which facilitate inter-network and inter-operator roaming of Wi-Fi users. Modern wireless technology has comparable latency to other terrestrial broadband networks.
WISP's are predominantly in rural environments where cable and digital subscriber lines are not available. WiMax is expected to become mainstream in the near future, bringing with it dramatic changes to the marketplace by increasing the number of interoperable equipment on the market and making mobile data transmission feasible, increasing the utility of such networks in rural environments. However, high-bandwidth wireless backhauls are already common in major cities[citation needed], providing levels of bandwidth previously only available through expensive fiber optic connections.
Typically, the way that a WISP operates is to pull a large and usually expensive point to point connection to the center of the area they wish to service. From here, they will need to find some sort of elevated point in the region, such as a radio or water tower, on which to mount their equipment. On the consumers side, they will mount a small dish or antenna to the roof of their home and point it back to the WISP's nearest antenna site. When operating over the tightly limited range of the heavily populated 2.4 GHz band, as nearly all 802.11-based WiFi providers do, it is not uncommon to also see access points mounted on light posts and customer buildings.
Since it is difficult for a single service provider to build an infrastructure that offers global access to its subscribers, roaming between service providers is encouraged by the Wi-Fi Alliance with the WISPr protocol. WISPr is a set of recommendations approved by the alliance which facilitate inter-network and inter-operator roaming of Wi-Fi users. Modern wireless technology has comparable latency to other terrestrial broadband networks.
Wireless broadband
Few WISPs provide download speeds of over 100 Mbit/s; most broadband wireless access services are estimated to have a range of 50 km (30 miles) from a tower.[1] Technologies used include LMDS and MMDS, as well as heavy use of the ISM bands and one particular access technology is being standardized by IEEE 802.16, also known as WiMAX. WiMAX is highly popular in Europe but has not met full acceptance in the United States because cost of deployment does not meet return on investment figures. In 2005 the Federal Communications Commission adopted a Report and Order that revised the FCC’s rules to open the 3650 MHz band for terrestrial wireless broadband operations.[2] On November 14, 2007 the Commission released Public Notice DA 07-4605 in which the Wireless Telecommunications Bureau announced the start date for licensing and registration process for the 3650-3700 MHz band.[3]
Initially, Wireless Internet Service Providers (WISPs) were only found in rural areas not covered by cable or DSL.[4] These early WISPs would employ a high-capacity T-carrier, such as a T1 or DS3 connection, and then broadcast the signal from a high elevation, such as at the top of a water tower. To receive this type of Internet connection, consumers mount a small dish to the roof of their home or office and point it to the transmitter. Line of sight is usually necessary for WISPs operating in the 2.4 and 5GHz bands with 900MHz offering better NLOS performance.
Initially, Wireless Internet Service Providers (WISPs) were only found in rural areas not covered by cable or DSL.[4] These early WISPs would employ a high-capacity T-carrier, such as a T1 or DS3 connection, and then broadcast the signal from a high elevation, such as at the top of a water tower. To receive this type of Internet connection, consumers mount a small dish to the roof of their home or office and point it to the transmitter. Line of sight is usually necessary for WISPs operating in the 2.4 and 5GHz bands with 900MHz offering better NLOS performance.
WiMAX
The current WiMAX incarnation, Mobile WiMAX, is based upon IEEE Std 802.16e-2005,[27] approved in December 2005. It is a supplement to the IEEE Std 802.16-2004,[28] and so the actual standard is 802.16-2004 as amended by 802.16e-2005 — the specifications need to be read together to understand them.
IEEE Std 802.16-2004 addresses only fixed systems. It replaced IEEE Standards 802.16-2001, 802.16c-2002, and 802.16a-2003.
IEEE 802.16e-2005 improves upon IEEE 802.16-2004 by:
* Adding support for mobility (soft and hard handover between base stations). This is seen as one of the most important aspects of 802.16e-2005, and is the very basis of 'Mobile WiMAX' (though this has yet to be demonstrated in any installed systems).
* Scaling of the Fast Fourier transform (FFT) to the channel bandwidth in order to keep the carrier spacing constant across different channel bandwidths (typically 1.25 MHz, 5 MHz, 10 MHz or 20 MHz). Constant carrier spacing results in a higher spectrum efficiency in wide channels, and a cost reduction in narrow channels. Also known as Scalable OFDMA (SOFDMA). Other bands not multiples of 1.25 MHz are defined in the standard, but because the allowed FFT subcarrier numbers are only 128, 512, 1024 and 2048, other frequency bands will not have exactly the same carrier spacing, which might not be optimal for implementations.
* Advanced antenna diversity schemes, and hybrid automatic repeat-request (HARQ)
* Adaptive Antenna Systems (AAS) and MIMO technology
* Denser sub-channelization, thereby improving indoor penetration
* Introducing Turbo Coding and Low-Density Parity Check (LDPC)
* Introducing downlink sub-channelization, allowing administrators to trade coverage for capacity or vice versa
* Fast Fourier transform algorithm
* Adding an extra QoS class for VoIP applications.
802.16d vendors point out that fixed WiMAX offers the benefit of available commercial products and implementations optimized for fixed access. It is a popular standard among alternative service providers and operators in developing areas due to its low cost of deployment and advanced performance in a fixed environment. Fixed WiMAX is also seen as a potential standard for backhaul of wireless base stations such as cellular, or Wi-Fi.
SOFDMA (used in 802.16e-2005) and OFDM256 (802.16d) are not compatible thus most equipment will have to be replaced if an operator wants or needs to move to the later standard. However, some manufacturers are planning to provide a migration path for older equipment to SOFDMA compatibility which would ease the transition for those networks which have already made the OFDM256 investment. Intel provides a dual-mode 802.16-2004 802.16-2005 chipset for subscriber units.
IEEE Std 802.16-2004 addresses only fixed systems. It replaced IEEE Standards 802.16-2001, 802.16c-2002, and 802.16a-2003.
IEEE 802.16e-2005 improves upon IEEE 802.16-2004 by:
* Adding support for mobility (soft and hard handover between base stations). This is seen as one of the most important aspects of 802.16e-2005, and is the very basis of 'Mobile WiMAX' (though this has yet to be demonstrated in any installed systems).
* Scaling of the Fast Fourier transform (FFT) to the channel bandwidth in order to keep the carrier spacing constant across different channel bandwidths (typically 1.25 MHz, 5 MHz, 10 MHz or 20 MHz). Constant carrier spacing results in a higher spectrum efficiency in wide channels, and a cost reduction in narrow channels. Also known as Scalable OFDMA (SOFDMA). Other bands not multiples of 1.25 MHz are defined in the standard, but because the allowed FFT subcarrier numbers are only 128, 512, 1024 and 2048, other frequency bands will not have exactly the same carrier spacing, which might not be optimal for implementations.
* Advanced antenna diversity schemes, and hybrid automatic repeat-request (HARQ)
* Adaptive Antenna Systems (AAS) and MIMO technology
* Denser sub-channelization, thereby improving indoor penetration
* Introducing Turbo Coding and Low-Density Parity Check (LDPC)
* Introducing downlink sub-channelization, allowing administrators to trade coverage for capacity or vice versa
* Fast Fourier transform algorithm
* Adding an extra QoS class for VoIP applications.
802.16d vendors point out that fixed WiMAX offers the benefit of available commercial products and implementations optimized for fixed access. It is a popular standard among alternative service providers and operators in developing areas due to its low cost of deployment and advanced performance in a fixed environment. Fixed WiMAX is also seen as a potential standard for backhaul of wireless base stations such as cellular, or Wi-Fi.
SOFDMA (used in 802.16e-2005) and OFDM256 (802.16d) are not compatible thus most equipment will have to be replaced if an operator wants or needs to move to the later standard. However, some manufacturers are planning to provide a migration path for older equipment to SOFDMA compatibility which would ease the transition for those networks which have already made the OFDM256 investment. Intel provides a dual-mode 802.16-2004 802.16-2005 chipset for subscriber units.
Wireless Wide Area Network
A WWAN differs from a WLAN (wireless LAN) in that it uses Mobile telecommunication cellular network technologies such as WIMAX (though it's better applicated into WMAN Networks), UMTS, GPRS, CDMA2000, GSM, CDPD, Mobitex, HSDPA or 3G to transfer data. It can use also LMDS and Wi-Fi to connect to the Internet. These cellular technologies are offered regionally, nationwide, or even globally and are provided by a wireless service provider, typically on paid basis.[1] WWAN connectivity allows a user with a laptop and a WWAN card to surf the web, check email, or connect to a Virtual Private Network (VPN) from anywhere within the regional boundaries of cellular service. Various computers now have integrated WWAN capabilities (Such as HSDPA in Centrino). This means that the system has a cellular radio (GSM/CDMA) built in, which allows the user to send and receive data. There are two basic means that a mobile network may use to transfer data:
* Packet-switched Data Networks (GPRS/CDPD)
* Circuit-switched dial-up connections
Since radio communications systems do not provide a physically secure connection path, WWANs typically incorporate encryption and authentication methods to make them more secure. Unfortunately some of the early GSM encryption techniques were flawed, and security experts have issued warnings that cellular communication, including WWANs, is no longer secure.[2] UMTS(3G) encryption was developed later and has yet to be broken.
Examples of providers for WWAN include Sprint Nextel, Verizon, and AT&T.
* Packet-switched Data Networks (GPRS/CDPD)
* Circuit-switched dial-up connections
Since radio communications systems do not provide a physically secure connection path, WWANs typically incorporate encryption and authentication methods to make them more secure. Unfortunately some of the early GSM encryption techniques were flawed, and security experts have issued warnings that cellular communication, including WWANs, is no longer secure.[2] UMTS(3G) encryption was developed later and has yet to be broken.
Examples of providers for WWAN include Sprint Nextel, Verizon, and AT&T.
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