Passive optical network
A passive optical network is a telecommunications technology used to provide fiber to the end consumer, both domestic and commercial. A PON's distinguishing feature is that it implements a point-to-multipoint architecture, in which unpowered fiber optic splitters are used to enable a single optical fiber to serve multiple end-points; the end-points are individual customers, rather than commercial. A PON does not have to provision individual fibers between the customer. Passive optical networks are referred to as the "last mile" between an ISP and customer. A PON consists of an optical line terminal at the service provider's central office and a number of optical network units or optical network terminals, near end users. A PON reduces the amount of fiber and central office equipment required compared with point-to-point architectures. A passive optical network is a form of fiber-optic access network. In most cases, downstream signals are broadcast to all premises sharing multiple fibers. Encryption can prevent eavesdropping.
Upstream signals are combined using a multiple access protocol time division multiple access. Two major standard groups, the Institute of Electrical and Electronics Engineers and the Telecommunication Standardization Sector of the International Telecommunication Union, develop standards along with a number of other industry organizations; the Society of Cable Telecommunications Engineers specified radio frequency over glass for carrying signals over a passive optical network. Starting in 1995, work on fiber to the home architectures was done by the Full Service Access Network working group, formed by major telecommunications service providers and system vendors; the International Telecommunications Union did further work, standardized on two generations of PON. The older ITU-T G.983 standard was based on Asynchronous Transfer Mode, has therefore been referred to as APON. Further improvements to the original APON standard – as well as the gradual falling out of favor of ATM as a protocol – led to the full, final version of ITU-T G.983 being referred to more as broadband PON, or BPON.
A typical APON/BPON provides 622 megabits per second of downstream bandwidth and 155 Mbit/s of upstream traffic, although the standard accommodates higher rates. The ITU-T G.984 Gigabit-capable Passive Optical Networks standard represented an increase, compared to BPON, in both the total bandwidth and bandwidth efficiency through the use of larger, variable-length packets. Again, the standards permit several choices of bit rate, but the industry has converged on 2.488 gigabits per second of downstream bandwidth, 1.244 Gbit/s of upstream bandwidth. GPON Encapsulation Method allows efficient packaging of user traffic with frame segmentation. By mid-2008, Verizon had installed over 800,000 lines. British Telecom, BSNL, Saudi Telecom Company, AT&T were in advanced trials in Britain, Saudi Arabia, the UAE, the US, respectively. GPON networks have now been deployed in numerous networks across the globe, the trends indicate higher growth in GPON than other PON technologies. G.987 defined 10G-PON with 10 Gbit/s downstream and 2.5 Gbit/s upstream – framing is "G-PON like" and designed to coexist with GPON devices on the same network.
Developed in 2009 by Cable Manufacturing Business to meet SIPRNet requirements of the US Air Force, secure passive optical network integrates gigabit passive optical network technology and protective distribution system. Changes to the NSTISSI 7003 requirements for PDS and the mandate by the US federal government for GREEN technologies allowed for the US federal government consideration of the two technologies as an alternative to active Ethernet and encryption deviсes; the chief information officer of the United States Department of the Army issued a directive to adopt the technology by fiscal year 2013. It is marketed to the US military by companies such as Telos Corporation. In 2004, the Ethernet PON standard 802.3ah-2004 was ratified as part of the Ethernet in the first mile project of the IEEE 802.3. EPON is a "short haul" network using ethernet packets, fiber optic cables, single protocol layer. EPON uses standard 802.3 Ethernet frames with symmetric 1 gigabit per second upstream and downstream rates.
EPON is applicable for data-centric networks, as well as full-service voice and video networks. 10 Gbit/s EPON or 10G-EPON was ratified as an amendment IEEE 802.3av to IEEE 802.3. 10G-EPON supports 10/1 Gbit/s. The downstream wavelength plan support simultaneous operation of 10 Gbit/s on one wavelength and 1 Gbit/s on a separate wavelength for the operation of IEEE 802.3av and IEEE 802.3ah on the same PON concurrently. The upstream channel can support simultaneous operation of IEEE 802.3av and 1 Gbit/s 802.3ah on a single shared channel. In 2014, there were over 40 million installed EPON ports, making it the most deployed PON technology globally. EPON is the foundation for cable operators’ business services as part of the DOCSIS Provisioning of EPON specifications. 10G EPON is compatible with other Ethernet standards and requires no conversion or encapsulation to connect to Ethernet-based networks on either the upstream or downstream end. This technology connects seamlessly with any type of IP-based or packetized communications, thanks to the ubiquity of Ethernet installations in homes and elsewhere, EPON is very inexpensive to implement.
A PON takes advantage of wavelength division multiplexing, using one wavelength for downstream traffic and another for upstream traffic on a single mode fiber. BPO
In telecommunication and radio communication, spread-spectrum techniques are methods by which a signal generated with a particular bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth. These techniques are used for a variety of reasons, including the establishment of secure communications, increasing resistance to natural interference and jamming, to prevent detection, to limit power flux density; this is a technique in which a telecommunication signal is transmitted on a bandwidth larger than the frequency content of the original information. Frequency hopping is a basic modulation technique used in spread spectrum signal transmission. Spread-spectrum telecommunications is a signal structuring technique that employs direct sequence, frequency hopping, or a hybrid of these, which can be used for multiple access and/or multiple functions; this technique decreases the potential interference to other receivers. Spread spectrum makes use of a sequential noise-like signal structure to spread the narrowband information signal over a wideband band of frequencies.
The receiver correlates the received signals to retrieve the original information signal. There were two motivations: either to resist enemy efforts to jam the communications, or to hide the fact that communication was taking place, sometimes called low probability of intercept. Frequency-hopping spread spectrum, direct-sequence spread spectrum, time-hopping spread spectrum, chirp spread spectrum, combinations of these techniques are forms of spread spectrum; the first two of these techniques employ pseudorandom number sequences—created using pseudorandom number generators—to determine and control the spreading pattern of the signal across the allocated bandwidth. Wireless standard IEEE 802.11 uses either DSSS in its radio interface. Techniques known since the 1940s and used in military communication systems since the 1950s "spread" a radio signal over a wide frequency range several magnitudes higher than minimum requirement; the core principle of spread spectrum is the use of noise-like carrier waves, and, as the name implies, bandwidths much wider than that required for simple point-to-point communication at the same data rate.
Resistance to jamming. DS is good at resisting continuous-time narrowband jamming, while FH is better at resisting pulse jamming. In DS systems, narrowband jamming affects detection performance about as much as if the amount of jamming power is spread over the whole signal bandwidth, when it will not be much stronger than background noise. By contrast, in narrowband systems where the signal bandwidth is low, the received signal quality will be lowered if the jamming power happens to be concentrated on the signal bandwidth. Resistance to eavesdropping; the spreading code or the frequency-hopping pattern is unknown by anyone for whom the signal is unintended, in which case it obscures the signal and reduces the chance of an adversary making sense of it. Moreover, for a given noise power spectral density, spread-spectrum systems require the same amount of energy per bit before spreading as narrowband systems and therefore the same amount of power if the bitrate before spreading is the same, but since the signal power is spread over a large bandwidth, the signal PSD is much lower — significantly lower than the noise PSD — so that the adversary may be unable to determine whether the signal exists at all.
However, for mission-critical applications those employing commercially available radios, spread-spectrum radios do not intrinsically provide adequate security. Resistance to fading; the high bandwidth occupied by spread-spectrum signals offer some frequency diversity, i.e. it is unlikely that the signal will encounter severe multipath fading over its whole bandwidth, in other cases the signal can be detected using e.g. a rake receiver. Multiple access capability, known as code-division multiple access or code-division multiplexing. Multiple users can transmit in the same frequency band as long as they use different k codes. Frequency-hopping may date back to radio pioneer Jonathan Zenneck's 1908 German book Wireless Telegraphy although he states that Telefunken was using it previously, it saw limited use by the German military in World War I, was put forward by Polish engineer Leonard Danilewicz in 1929, showed up in a patent in the 1930s by Willem Broertjes, in the top-secret US Army Signal Corps World War II communications system named SIGSALY.
During World War II, Golden Age of Hollywood actress Hedy Lamarr and avant-garde composer George Antheil developed an intended jamming-resistant radio guidance system for use in Allied torpedoes, patenting the device under US Patent 2,292,387 "Secret Communications System" on August 11, 1942. Their approach was unique in that frequency coordination was done with paper player piano rolls - a novel approach, never put into practice. Spread-spectrum clock generation is used in some synchronous digital systems those containing microprocessors, to reduce the spectral density of the electromagnetic interference that these systems generate. A synchronous digital system is one, driven by a clock signal and, because of its periodic nature, has an unavoidably narrow frequency spectrum. In fact, a perfect clock signal would have all its
Fiber to the x
Fiber to the x or fiber in the loop is a generic term for any broadband network architecture using optical fiber to provide all or part of the local loop used for last mile telecommunications. As fiber optic cables are able to carry much more data than copper cables over long distances, copper telephone networks built in the 20th century are being replaced by fiber. FTTX is a generalization for several configurations of fiber deployment, arranged into two groups: FTTP/FTTH/FTTB and FTTC/N. Residential areas served by balanced pair distribution plant call for a trade-off between cost and capacity; the closer the fiber head, the higher the cost of construction and the higher the channel capacity. In places not served by metallic facilities, little cost is saved by not running fiber to the home. Fiber to the x is the key method used to drive next-generation access, which describes a significant upgrade to the Broadband available by making a step change in speed and quality of the service; this is thought of as asymmetrical with a download speed of 24 Mbit/s plus and a fast upload speed.
The Definition of UK Superfast Next Generation Broadband OFCOM have defined NGA as in "Ofcom's March 2010'Review of the wholesale local access market" "Super-fast broadband is taken to mean broadband products that provide a maximum download speed, greater than 24 Mbit/s. This threshold is considered to be the maximum speed that can be supported on current generation networks." A similar network called a hybrid fiber-coaxial network is used by cable television operators but is not synonymous with "fiber In the loop", although similar advanced services are provided by the HFC networks. Fixed wireless and mobile wireless technologies such as Wi-Fi, WiMAX and 3GPP Long Term Evolution are an alternative for providing Internet access; the telecommunications industry differentiates between several distinct FTTX configurations. The terms in most widespread use today are: FTTP: This term is used either as a blanket term for both FTTH and FTTB, or where the fiber network includes both homes and small businesses FTTH: Fiber reaches the boundary of the living space, such as a box on the outside wall of a home.
Passive optical networks and point-to-point Ethernet are architectures that are capable of delivering triple-play services over FTTH networks directly from an operator's central office. FTTB: Fiber reaches the boundary of the building, such as the basement in a multi-dwelling unit, with the final connection to the individual living space being made via alternative means, similar to the curb or pole technologies FTTD: Fiber connection is installed from the main computer room to a terminal or fiber media converter near the user's desk FTTR: Fiber connection is installed from the router to the ISP's fiber network FTTO: Fiber connection is installed from the main computer room/core switch to a special mini-switch located at the user's workstation or service points; this mini-switch provides Ethernet services to end user devices via standard twisted pair patch cords. The switches are located decentrally all over the building, but managed from one central point FTTF: This is similar to FTTB. In a fiber to the front yard scenario, each fiber node serves a single subscriber.
This allows for multi-gigabit speeds using XG-fast technology. The fiber node may be reverse-powered by the subscriber modem FTTE / FTTZ: is a form of structured cabling used in enterprise local area networks, where fiber is used to link the main computer equipment room to an enclosure close to the desk or workstation. FTTE and FTTZ are not considered part of the FTTX group of technologies, despite the similarity in name. FTTdp: This is similar to FTTC / FTTN but is one-step closer again moving the end of the fiber to within meters of the boundary of the customers premises in last junction possible junction box known as the "distribution point" this allows for near-gigabit speeds FTTN / FTTLA: Fiber is terminated in a street cabinet miles away from the customer premises, with the final connections being copper. FTTN is an interim step toward full FTTH and is used to deliver'advanced' triple-play telecommunications services FTTC / FTTK: This is similar to FTTN, but the street cabinet or pole is closer to the user's premises within 1,000 feet, within range for high-bandwidth copper technologies such as wired ethernet or IEEE 1901 power line networking and wireless Wi-Fi technology.
FTTC is ambiguously called FTTP, leading to confusion with the distinct fiber-to-the-premises systemTo promote consistency when comparing FTTH penetration rates between countries, the three FTTH Councils of Europe, North America, Asia-Pacific agreed upon definitions for FTTH and FTTB in 2006, with an update in 2009, 2011 and another in 2015. The FTTH Councils do not have formal definitions for FTTC and FTTN. While fiber optic cables can carry data at high speeds over long distances, copper cables used in traditional telephone lines and ADSL cannot. For example, the common form of Gigabit Ethernet runs over economical category 5e, category 6 or augmented category 6 un
HomePlug is the family name for various power line communications specifications under the HomePlug designation, with each offering unique performance capabilities and coexistence or compatibility with other HomePlug specifications. Some HomePlug specifications target broadband applications such as in-home distribution of low data rate IPTV, Internet content, while others focus on low-power, low throughput, extended operating temperatures for applications such as smart power meters and in-home communications between electric systems and appliances. All of the HomePlug specifications were developed by the HomePlug Powerline Alliance, which owns the HomePlug trademark. On 18 October 2016, the HomePlug Alliance announced that all of its specifications would be put into the public domain and that other organizations would be taking on future activities relating to deployment of the existing technologies. There was no mention in the announcement of any further technology development within the HomePlug community.
The HomePlug Powerline Alliance was formed to develop standards and technology for enabling devices to communicate with each other, the Internet, over existing home electrical wiring. One of the greatest technical challenges was finding a way to reduce sensitivity to the electrical noise present on power lines. HomePlug solved this problem by increasing the communication carrier frequencies so that the signal is conveyed by the neutral conductor, common to all phases; the first HomePlug specification, HomePlug 1.0, was released in June 2001. The HomePlug AV specification, released in 2005, increased physical layer peak data rates from 13.0 Mbit/s to 200 Mbit/s. The HomePlug Green PHY specification was released in June 2010 and targets Smart Energy and Smart Grid applications as an interoperable "sibling" to HomePlug AV with lower cost, lower power consumption and decreased throughput. In 2010, the IEEE 1901 was approved and HomePlug AV, as baseline technology for the FFT-OFDM PHY within the standard, was now an international standard.
The HomePlug Powerline Alliance is a certifying body for IEEE 1901 products. The three major specifications published by HomePlug are compliant; as of 2017, there are at least six chip vendors shipping HomePlug AV chipsets with IEEE 1901 support: Broadcom, Qualcomm Atheros, Sigma Designs, Intellon, SPiDCOM, MStar. In 2011, the HomePlug Green PHY specification was adopted by Ford, General Motors, Audi, BMW, Daimler and Volkswagen, as a connectivity standard for Plug-In Electrical Vehicle. Newer versions of HomePlug support the use of Ethernet in bus topology via OFDM modulation that enables several distinct data carriers to coexist in the same wire. HomePlug's OFDM technology can turn off any sub-carriers that overlap allocated radio spectrum in a given geographic region, thus preventing interference. In North America, for instance, HomePlug AV only uses 917 of 1155 sub-carriers. Powerline networking in general means a network can be set up using a building's existing electrical wiring. For electric vehicle charging, the SAE J1772 standard plug-in electric vehicle charger requires HomePlug Green PHY to establish communications over a powerline before the vehicle can begin to draw any charging power.
All commercial HomePlug implementations meet the AES-128 encryption standard specified for advanced metering infrastructure by the US FERC. Accordingly, these devices are suitable to deploy as utility grade meters off the shelf with appropriate software; as of late 2012, the most deployed HomePlug devices are "adapters", which are standalone modules that plug into wall outlets and provide one or more Ethernet ports. In a simple home network, the Internet gateway router connects via Ethernet cable to a powerline adapter, which in turn plugs into a nearby power outlet. A second adapter, plugged into any other outlet in the home, connects via Ethernet cable to any Ethernet device. Communications between the router and Ethernet devices are conveyed over existing home electrical wiring. More complex networks can be implemented by plugging in additional adapters as needed. A powerline adapter may be plugged into a hub or switch so that it supports multiple Ethernet devices residing in a common room.
The functionality found in standalone adapters is being built into end devices such as power control centers, digital media adapters, Internet security cameras. It is anticipated that powerline networking functionality will be embedded in TVs, set-top boxes, DVRs, other consumer electronics with the emergence of global powerline networking standards such as the IEEE 1901 standard, ratified in September 2010. Several manufacturers sell devices that include 802.11n, HomePlug and four ports of gigabit ethernet connectivity for under US$100. Several are announced for early 2013 that include 802.11ac connectivity, the combination of which with HomePlug is sold by Qualcomm Atheros as its Hy-Fi hybrid networking technology, an implementation of IEEE P1905. This permits a device to use wired ethernet, powerline or wireless communication as available to provide a redundant and reliable failover – thought to be important in consumer applications where there is no onsite expertise available to debug connections.
The first HomePlug specification, HomePlug 1.0, provides a peak PHY-rate of 14 Mbit/s. It was first introduced in June, 2001 and has since been replaced by HomePlug AV. On May 28, 2008 Telecommunications Industry Association incorporated HomePlug 1.0 powerline technology into the newly publishe
A home network or home area network is a type of computer network that facilitates communication among devices within the close vicinity of a home. Devices capable of participating in this network, for example, smart devices such as network printers and handheld mobile computers gain enhanced emergent capabilities through their ability to interact; these additional capabilities can be used to increase the quality of life inside the home in a variety of ways, such as automation of repetitive tasks, increased personal productivity, enhanced home security, easier access to entertainment. Establishing this kind of network is necessary for sharing residential Internet access to all networked devices. Based on techniques to mitigate IPv4 address exhaustion, most Internet service providers provide only a single wide area network-facing IP address for each residential customer. Therefore, such networks require network address translation in the network router. A home network relies on one or more of the following equipment to establish physical layer, data link layer, network layer connectivity among internal devices known as the LAN, external devices outside the LAN networks or the WAN.
The following are examples of typical LAN devices: A modem exposes an Ethernet interface to a service provider's native telecommunications infrastructure. In homes these come in the form of a DSL modem or cable modem. A router manages network layer connectivity between a WAN and the HAN, it performs the key function of network address translation enabling multiple devices to share the home's single WAN address. Most home networks feature a particular class of small, passively cooled, table-top device with an integrated wireless access point and 4 port Ethernet switch; these devices aim to make the installation and management of a home network as automated, user friendly, "plug-and-play" as possible. A network switch is used to allow devices on the home network to talk to one another via Ethernet. While the needs of most home networks are satisfied with the built-in wireless and/or switching capabilities of their router, some situations require the addition of a separate switch with advanced capabilities.
For example: A typical home router has 4 to 6 Ethernet LAN ports, so a router's switching capacity could be exceeded. A network device might require a non-standard port feature such as power over Ethernet. A wireless access point is required for connecting wireless devices to a network. Most home networks rely on a wireless router, which has a built in wireless access point, to fill this role. A home automation controller enables low-power wireless communications with simple, non-data-intensive devices such as smart light bulbs and smart locks. A network bridge connects two networks in order to grant a wired-only device, e.g. Xbox, access to a wireless network medium. A service provider's triple play solution features a rented modem/wireless router combination device, such as an Arris SURFboard SBG6580, that only requires the setting of a password to complete the installation and configuration. In most situations, there is no longer a need to acquire additional infrastructure devices or for the user to possess advanced technical knowledge to distribute internet access throughout the home.
Home networks can use either wireless technologies to connect endpoints. Wireless is the predominant option in homes due to the ease of installation, lack of unsightly cables, network performance characteristics sufficient for residential activities. One of the most common ways of creating a home network is by using wireless radio signal technology. Most wireless-capable residential devices operate at a frequency of 2.4 GHz under 802.11b and 802.11g or 5 GHz under 802.11a. Some home networking devices operate in both radio-band signals and fall within the 802.11n or 802.11ac standards. Wi-Fi is a compliance certification for IEEE 802.11 technologies. The Wi-Fi Alliance has tested compliant products, certifies them for interoperability. Low power, close range communication based on IEEE 802.15 standards has a strong presence in homes. Bluetooth continues to be the technology of choice for most wireless accessories such as keyboards, mice and game controllers; these connections are established in a transient, ad-hoc manner and are not thought of as permanent residents of a home network.
A "low-rate" version of the original WPAN protocol was used as the basis of ZigBee. Despite being conceived as a standard for low power machine-to-machine communication in industrial environments, the technology has been found to be well suited for integration into embedded "Smart Home" offerings that are expected to run on battery for extended periods of time. ZigBee utilizes mesh networking to overcome the distance limitations associated with traditional WPAN in order to establish a single network of addressable devices spread across the entire building. Z-Wave is an additional standard built on 802.15.4, developed with the needs of home automation device makers in mind. Most wired network infrastructures found in homes utilize Category 5 or Category 6 twisted pair cabling with RJ45 compatible terminations; this medium provides physical connectivity between the Ethernet interfaces present on a large number of residential IP-aware devices. Depending on the grade of cable and quality of installation, speeds of up to 10 Mbit/s, 100 Mbit/s, 1 Gbit/s, or 10Gbit/s are supported.
Newer upscale neighborhoods can feature fiber optic cables running directly into the homes. This enables service providers to offer internet services with much higher bandwidth and/or lower
IEEE 802.11 is part of the IEEE 802 set of LAN protocols, specifies the set of media access control and physical layer protocols for implementing wireless local area network Wi-Fi computer communication in various frequencies, including but not limited to 2.4, 5, 60 GHz frequency bands. They are the world's most used wireless computer networking standards, used in most home and office networks to allow laptops and smartphones to talk to each other and access the Internet without connecting wires, they are created and maintained by the Institute of Electrical and Electronics Engineers LAN/MAN Standards Committee. The base version of the standard was released in 1997, has had subsequent amendments; the standard and amendments provide the basis for wireless network products using the Wi-Fi brand. While each amendment is revoked when it is incorporated in the latest version of the standard, the corporate world tends to market to the revisions because they concisely denote capabilities of their products.
As a result, in the marketplace, each revision tends to become its own standard. The protocols are used in conjunction with IEEE 802.2, are designed to interwork seamlessly with Ethernet, are often used to carry Internet Protocol traffic. Although IEEE 802.11 specifications list channels that might be used, the radio frequency spectrum availability allowed varies by regulatory domain. The 802.11 family consists of a series of half-duplex over-the-air modulation techniques that use the same basic protocol. The 802.11 protocol family employ carrier-sense multiple access with collision avoidance whereby equipment listens to a channel for other users before transmitting each packet. 802.11-1997 was the first wireless networking standard in the family, but 802.11b was the first accepted one, followed by 802.11a, 802.11g, 802.11n, 802.11ac. Other standards in the family are service amendments that are used to extend the current scope of the existing standard, which may include corrections to a previous specification.802.11b and 802.11g use the 2.4 GHz ISM band, operating in the United States under Part 15 of the U.
S. Federal Communications Commission Rules and Regulations; because of this choice of frequency band, 802.11b/g/n equipment may suffer interference in the 2.4 GHz band from microwave ovens, cordless telephones, Bluetooth devices etc. 802.11b and 802.11g control their interference and susceptibility to interference by using direct-sequence spread spectrum and orthogonal frequency-division multiplexing signaling methods, respectively. 802.11a uses the 5 GHz U-NII band, for much of the world, offers at least 23 non-overlapping 20 MHz-wide channels rather than the 2.4 GHz ISM frequency band offering only three non-overlapping 20 MHz-wide channels, where other adjacent channels overlap—see list of WLAN channels. Better or worse performance with higher or lower frequencies may be realized, depending on the environment. 802.11 n can use either the 5 GHz band. The segment of the radio frequency spectrum used by 802.11 varies between countries. In the US, 802.11a and 802.11g devices may be operated without a license, as allowed in Part 15 of the FCC Rules and Regulations.
Frequencies used by channels one through six of 802.11b and 802.11g fall within the 2.4 GHz amateur radio band. Licensed amateur radio operators may operate 802.11b/g devices under Part 97 of the FCC Rules and Regulations, allowing increased power output but not commercial content or encryption. 802.11 technology has its origins in a 1985 ruling by the U. S. Federal Communications Commission that released the ISM band for unlicensed use. In 1991 NCR Corporation/AT & T invented a precursor to 802.11 in the Netherlands. The inventors intended to use the technology for cashier systems; the first wireless products were brought to the market under the name WaveLAN with raw data rates of 1 Mbit/s and 2 Mbit/s. Vic Hayes, who held the chair of IEEE 802.11 for 10 years, has been called the "father of Wi-Fi", was involved in designing the initial 802.11b and 802.11a standards within the IEEE. In 1999, the Wi-Fi Alliance was formed as a trade association to hold the Wi-Fi trademark under which most products are sold.
The major commercial breakthrough came with Apple Inc. adopting Wi-Fi for their iBook series of laptops in 1999. It was the first mass consumer product to offer Wi-Fi network connectivity, branded by Apple as AirPort. One year IBM followed with its ThinkPad 1300 series in 2000; the original version of the standard IEEE 802.11 was released in 1997 and clarified in 1999, but is now obsolete. It specified two net bit rates of 2 megabits per second, plus forward error correction code, it specified three alternative physical layer technologies: diffuse infrared operating at 1 Mbit/s. The latter two radio technologies used microwave transmission over the Industrial Scientific Medical frequency band at 2.4 GHz. Some earlier WLAN technologies used lower frequencies, such as the U. S. 900 MHz ISM band. Legacy 802.11 with direct-sequence spread spectrum was supplanted and popularized by 802.11b. 802.11a, published in 1999, uses the same data link layer protocol and frame format as the original standard, but an OFDM based air interface.
It operates in the 5 GHz band with a maximum net data rate of 54 Mbit/s, plus error correction code, which yields realistic net achievable throughput in the mid-20
A wireless network is a computer network that uses wireless data connections between network nodes. Wireless networking is a method by which homes, telecommunications networks and business installations avoid the costly process of introducing cables into a building, or as a connection between various equipment locations. Wireless telecommunications networks are implemented and administered using radio communication; this implementation takes place at the physical level of the OSI model network structure. Examples of wireless networks include cell phone networks, wireless local area networks, wireless sensor networks, satellite communication networks, terrestrial microwave networks; the first professional wireless network was developed under the brand ALOHAnet in 1969 at the University of Hawaii and became operational in June 1971. The first commercial wireless network was the WaveLAN product family, developed by NCR in 1986. 1991 2G cell phone network June 1997 802.11 "Wi-Fi" protocol first release 1999 803.11 VoIP integration Terrestrial microwave – Terrestrial microwave communication uses Earth-based transmitters and receivers resembling satellite dishes.
Terrestrial microwaves are in the low gigahertz range, which limits all communications to line-of-sight. Relay stations are spaced 48 km apart. Communications satellites – Satellites communicate via microwave radio waves, which are not deflected by the Earth's atmosphere; the satellites are stationed in space in geosynchronous orbit 35,400 km above the equator. These Earth-orbiting systems are capable of receiving and relaying voice, TV signals. Cellular and PCS systems use several radio communications technologies; the systems divide the region covered into multiple geographic areas. Each area has a low-power transmitter or radio relay antenna device to relay calls from one area to the next area. Radio and spread spectrum technologies – Wireless local area networks use a high-frequency radio technology similar to digital cellular and a low-frequency radio technology. Wireless LANs use spread spectrum technology to enable communication between multiple devices in a limited area. IEEE 802.11 defines a common flavor of open-standards wireless radio-wave technology known as.
Free-space optical communication uses invisible light for communications. In most cases, line-of-sight propagation is used, which limits the physical positioning of communicating devices. Wireless personal area networks connect devices within a small area, within a person's reach. For example, both Bluetooth radio and invisible infrared light provides a WPAN for interconnecting a headset to a laptop. ZigBee supports WPAN applications. Wi-Fi PANs are becoming commonplace as equipment designers start to integrate Wi-Fi into a variety of consumer electronic devices. Intel "My WiFi" and Windows 7 "virtual Wi-Fi" capabilities have made Wi-Fi PANs simpler and easier to set up and configure. A wireless local area network links two or more devices over a short distance using a wireless distribution method providing a connection through an access point for internet access; the use of spread-spectrum or OFDM technologies may allow users to move around within a local coverage area, still remain connected to the network.
Products using the IEEE 802.11 WLAN standards are marketed under the Wi-Fi brand name. Fixed wireless technology implements point-to-point links between computers or networks at two distant locations using dedicated microwave or modulated laser light beams over line of sight paths, it is used in cities to connect networks in two or more buildings without installing a wired link. To connect to Wi-Fi, sometimes are used devices like a router or connecting HotSpot using mobile smartphones. A wireless ad hoc network known as a wireless mesh network or mobile ad hoc network, is a wireless network made up of radio nodes organized in a mesh topology; each node forwards messages on behalf of the other nodes and each node performs routing. Ad hoc networks can "self-heal", automatically re-routing around a node. Various network layer protocols are needed to realize ad hoc mobile networks, such as Distance Sequenced Distance Vector routing, Associativity-Based Routing, Ad hoc on-demand Distance Vector routing, Dynamic source routing.
Wireless metropolitan area networks are a type of wireless network that connects several wireless LANs. WiMAX is described by the IEEE 802.16 standard. Wireless wide area networks are wireless networks that cover large areas, such as between neighbouring towns and cities, or city and suburb; these networks can be used to connect branch offices of business or as a public Internet access system. The wireless connections between access points are point to point microwave links using parabolic dishes on the 2.4 GHz and 5.8Ghz band, rather than omnidirectional antennas used with smaller networks. A typical system contains access points and wireless bridging relays. Other configurations are mesh systems; when combined with renewable energy systems such as photovoltaic solar panels or wind systems they can be stand alone systems. A cellular network or mobile network is a radio network distributed over land areas called cells, each served by at least one fixed-location transceiver, known as a cell site or base station.
In a cellular network, each cell characteristically uses a different set of radio frequencies from all their immediate neighbouring cells to avoid any interference. When joined together these cells provide radio coverage over a wide geographic area; this enables a large number of portable transceivers (e.g. mo