A wireless local area network (WLAN) may be a knowledge gear designed to supply location-independent network access between computing devices by victimisation radio waves instead of a cable infrastructure.
In the company enterprise, wireless LANs square measure typically enforced because the final link between the present wired network and a bunch of shopper computers, giving these users wireless access to the complete resources and services of the company network across a building or field setting.
802.11 Standards
802.11 - the first LAN customary
802.11a - High speed LAN customary for 5GHz band, supports up to 54mbps
802.11b - LAN customary for two.4GHz band, supports 11mbps
802.11e - Describes QoS, Quality of Service needs for all IEEE LAN radio interfaces
802.11f - Defines inter-access purpose communications to facilitate multiple vendor-distributed
LAN networks
802.11g - Defines an extra modulation technique for two.4 Ghz band. meant to supply speeds
up to fifty four Mbps.
802.11h - Defines the spectrum management of the five gigacycle band to be used in Europe and in Asia Pacific.
802.11i - Address the present security weaknesses for each authentication and coding protocols.
Compatibility Matrix
802.11a standard
802.11a, is way quicker than 802.11b, with a 54Mbps most rate operates within the 5GHz frequency vary and permits eight synchronal channels.
802.11a uses Orthogonal Frequency Division Multiplexing (OFDM), associate degree secret writing theme that provides edges over unfold spectrum in channel accessibility and rate.
Channel accessibility is important as a result of the additional freelance channels that square measure obtainable, the additional climbable the wireless network becomes. 802.11a uses OFDM to outline a complete of eight non-overlapping twenty Mc channels across the two lower bands. By comparison, 802.11b uses three non-overlapping channels.
All wireless LANs use unlicenced spectrum; so they are at risk of interference and transmission errors. to cut back errors, each styles of 802.11 mechanically cut back the Physical layer rate.
IEEE 802.11b has 3 lower knowledge rates (5.5, 2, and 1Mbit/sec), and 802.11a has seven (48, 36, 24, 18, 12, 9, and 6Mbits/sec). Higher (and more) knowledge rates are not 802.11a's solely advantage. It conjointly uses the next waveband, 5GHz, that is each wider and fewer packed than the two.4GHz band that 802.11b shares with conductor phones, microwave ovens, and Bluetooth devices
802.11b standard
With 802.11b WLANs, mobile users will get LAN levels of performance, throughput, and accessibility.
The basic design, features, and services of 802.11b square measure outlined by the first 802.11 customary. The 802.11b specification affects solely the physical layer, adding higher knowledge rates and additional sturdy property.
The key contribution of the 802.11b addition to the wireless local area network customary was to standardize the physical layer support of 2 new speeds,5.5 Mbps and eleven Mbps.
To accomplish this, DSSS had to be elect because the sole physical layer technique for the quality since, as frequency hopping cannot support the upper speeds while not violating current FCC laws. The implication is that 802.11b systems can interoperate with one Mbps and a couple of Mbps 802.11 DSSS systems, however won't work with one Mbps and a couple of Mbps 802.11 FHSS systems.
The original 802.11 DSSS customary specifies associate degree eleven-bit chipping?called a Barker sequence?to encrypt all knowledge sent over the air. every 11-chip sequence represents one knowledge bit (1 or 0), and is reborn to a wave, known as a logo, that may be sent over the air.
These images square measure transmitted at a one MSps (1 million symbols per second) symbol rate victimisation technique known as Binary section Shift Keying BPSK). within the case of two Mbps, a additional subtle implementation known as construction section Shift Keying (QPSK) is used; it doubles the info rate obtainable in BPSK, via improved potency within the use of the radio information measure. to extend the info rate within the 802.11b customary, advanced cryptography techniques square measure used.
Rather than the 2 11-bit Barker sequences, 802.11b specifies Complementary Code Keying (CCK), that consists of a group of sixty four 8-bit code words. As a set, these code words have distinctive mathematical properties that enable them to be properly distinguished from each other by a receiver even within the presence of considerable noise and multipath interference (e.g., interference caused by receiving multiple radio reflections among a building).
The 5.5 Mbps rate uses CCK to encrypt four bits per carrier, whereas the eleven Mbps rate encodes eight bits per carrier. each speeds use QPSK because the modulation technique and signal at one.375 MSps. this is often however the upper knowledge rates square measure obtained. To support terribly clattering environments in addition as extended vary, 802.11b WLANs use dynamic rate shifting, permitting knowledge rates to be mechanically adjusted to complete the dynamic nature of the radio channel. Ideally, users connect at the complete eleven Mbps rate.
However once devices move on the far side the optimum vary for eleven Mbps operation, or if substantial interference is gift, 802.11b devices can transmit at lower speeds, falling back to five.5, 2, and 1 Mbps. Likewise, if the device moves back among the vary of a higher-speed transmission, the affiliation can mechanically speed up once more. Rate shifting may be a physical layer mechanism clear to the user and therefore the higher layers of the protocol stack.
One of the additional important disadvantages of 802.11b is that the waveband is packed, and subject to interference from alternative networking technologies, microwave ovens, 2.4GHz conductor phones (a vast market), and Bluetooth [ Wireless Standards Up within the Air]. There square measure drawbacks to 802.11b, together with lack of ability with voice devices, and no QoS provisions for multimedia system content. Interference and alternative limitations aside, 802.11b is that the clear leader in business and institutional wireless networking and is gaining share for home applications in addition
802.11g standard
Though 5GHz has several blessings, it conjointly has issues. the foremost vital of those is compatibility:
The different frequencies mean that 802.11a product are not practical with the 802.11b base. to urge around this, the IEEE developed 802.11g, that ought to extend the speed and vary of 802.11b in order that it's absolutely compatible with the older systems.
The standard operates entirely within the a pair of.4GHz frequency, however uses a minimum of 2 modes (both mandatory) with 2 ex gratia modes [ Wireless Standards Up within the Air]. The necessary modulation/access modes square measure constant CCK (Complementary Code Keying) mode utilized by 802.11b (hence the compatibility) and therefore the OFDM (Orthogonal Frequency Division Multiplexing) mode utilized by 802.11a (but during this case within the a pair of.4GHz frequency band). The necessary CCK mode supports 11Mbps and therefore the OFDM mode encompasses a most of 54Mbps. There also are 2 modes that use totally different ways to realize a 22Mbps knowledge rate--PBCC-22 (Packet Binary Convolutional cryptography, rated for six to 54Mbps) and CCK-OFDM mode (with a rated soap of 33Mbps).
The obvious advantage of 802.11g is that it maintains compatibility with 802.11b (and 802.11b's worldwide acceptance) and conjointly offers quicker knowledge rates comparable 802.11a. the amount of channels obtainable, however, isn't magnified, since channels square measure a operate of information measure, not radio wave modulation - and thereon score, 802.11a wins with its eight channels, compared to the 3 channels obtainable with either 802.11b or 802.11g. Another disadvantage of 802.11g is that it conjointly works within the a pair of.4 gigacycle band so as a result of interference it'll ne'er be as quick as 802.11a.
In the company enterprise, wireless LANs square measure typically enforced because the final link between the present wired network and a bunch of shopper computers, giving these users wireless access to the complete resources and services of the company network across a building or field setting.
802.11 Standards
802.11 - the first LAN customary
802.11a - High speed LAN customary for 5GHz band, supports up to 54mbps
802.11b - LAN customary for two.4GHz band, supports 11mbps
802.11e - Describes QoS, Quality of Service needs for all IEEE LAN radio interfaces
802.11f - Defines inter-access purpose communications to facilitate multiple vendor-distributed
LAN networks
802.11g - Defines an extra modulation technique for two.4 Ghz band. meant to supply speeds
up to fifty four Mbps.
802.11h - Defines the spectrum management of the five gigacycle band to be used in Europe and in Asia Pacific.
802.11i - Address the present security weaknesses for each authentication and coding protocols.
Compatibility Matrix
802.11a standard
802.11a, is way quicker than 802.11b, with a 54Mbps most rate operates within the 5GHz frequency vary and permits eight synchronal channels.
802.11a uses Orthogonal Frequency Division Multiplexing (OFDM), associate degree secret writing theme that provides edges over unfold spectrum in channel accessibility and rate.
Channel accessibility is important as a result of the additional freelance channels that square measure obtainable, the additional climbable the wireless network becomes. 802.11a uses OFDM to outline a complete of eight non-overlapping twenty Mc channels across the two lower bands. By comparison, 802.11b uses three non-overlapping channels.
All wireless LANs use unlicenced spectrum; so they are at risk of interference and transmission errors. to cut back errors, each styles of 802.11 mechanically cut back the Physical layer rate.
IEEE 802.11b has 3 lower knowledge rates (5.5, 2, and 1Mbit/sec), and 802.11a has seven (48, 36, 24, 18, 12, 9, and 6Mbits/sec). Higher (and more) knowledge rates are not 802.11a's solely advantage. It conjointly uses the next waveband, 5GHz, that is each wider and fewer packed than the two.4GHz band that 802.11b shares with conductor phones, microwave ovens, and Bluetooth devices
802.11b standard
With 802.11b WLANs, mobile users will get LAN levels of performance, throughput, and accessibility.
The basic design, features, and services of 802.11b square measure outlined by the first 802.11 customary. The 802.11b specification affects solely the physical layer, adding higher knowledge rates and additional sturdy property.
The key contribution of the 802.11b addition to the wireless local area network customary was to standardize the physical layer support of 2 new speeds,5.5 Mbps and eleven Mbps.
To accomplish this, DSSS had to be elect because the sole physical layer technique for the quality since, as frequency hopping cannot support the upper speeds while not violating current FCC laws. The implication is that 802.11b systems can interoperate with one Mbps and a couple of Mbps 802.11 DSSS systems, however won't work with one Mbps and a couple of Mbps 802.11 FHSS systems.
The original 802.11 DSSS customary specifies associate degree eleven-bit chipping?called a Barker sequence?to encrypt all knowledge sent over the air. every 11-chip sequence represents one knowledge bit (1 or 0), and is reborn to a wave, known as a logo, that may be sent over the air.
These images square measure transmitted at a one MSps (1 million symbols per second) symbol rate victimisation technique known as Binary section Shift Keying BPSK). within the case of two Mbps, a additional subtle implementation known as construction section Shift Keying (QPSK) is used; it doubles the info rate obtainable in BPSK, via improved potency within the use of the radio information measure. to extend the info rate within the 802.11b customary, advanced cryptography techniques square measure used.
Rather than the 2 11-bit Barker sequences, 802.11b specifies Complementary Code Keying (CCK), that consists of a group of sixty four 8-bit code words. As a set, these code words have distinctive mathematical properties that enable them to be properly distinguished from each other by a receiver even within the presence of considerable noise and multipath interference (e.g., interference caused by receiving multiple radio reflections among a building).
The 5.5 Mbps rate uses CCK to encrypt four bits per carrier, whereas the eleven Mbps rate encodes eight bits per carrier. each speeds use QPSK because the modulation technique and signal at one.375 MSps. this is often however the upper knowledge rates square measure obtained. To support terribly clattering environments in addition as extended vary, 802.11b WLANs use dynamic rate shifting, permitting knowledge rates to be mechanically adjusted to complete the dynamic nature of the radio channel. Ideally, users connect at the complete eleven Mbps rate.
However once devices move on the far side the optimum vary for eleven Mbps operation, or if substantial interference is gift, 802.11b devices can transmit at lower speeds, falling back to five.5, 2, and 1 Mbps. Likewise, if the device moves back among the vary of a higher-speed transmission, the affiliation can mechanically speed up once more. Rate shifting may be a physical layer mechanism clear to the user and therefore the higher layers of the protocol stack.
One of the additional important disadvantages of 802.11b is that the waveband is packed, and subject to interference from alternative networking technologies, microwave ovens, 2.4GHz conductor phones (a vast market), and Bluetooth [ Wireless Standards Up within the Air]. There square measure drawbacks to 802.11b, together with lack of ability with voice devices, and no QoS provisions for multimedia system content. Interference and alternative limitations aside, 802.11b is that the clear leader in business and institutional wireless networking and is gaining share for home applications in addition
802.11g standard
Though 5GHz has several blessings, it conjointly has issues. the foremost vital of those is compatibility:
The different frequencies mean that 802.11a product are not practical with the 802.11b base. to urge around this, the IEEE developed 802.11g, that ought to extend the speed and vary of 802.11b in order that it's absolutely compatible with the older systems.
The standard operates entirely within the a pair of.4GHz frequency, however uses a minimum of 2 modes (both mandatory) with 2 ex gratia modes [ Wireless Standards Up within the Air]. The necessary modulation/access modes square measure constant CCK (Complementary Code Keying) mode utilized by 802.11b (hence the compatibility) and therefore the OFDM (Orthogonal Frequency Division Multiplexing) mode utilized by 802.11a (but during this case within the a pair of.4GHz frequency band). The necessary CCK mode supports 11Mbps and therefore the OFDM mode encompasses a most of 54Mbps. There also are 2 modes that use totally different ways to realize a 22Mbps knowledge rate--PBCC-22 (Packet Binary Convolutional cryptography, rated for six to 54Mbps) and CCK-OFDM mode (with a rated soap of 33Mbps).
The obvious advantage of 802.11g is that it maintains compatibility with 802.11b (and 802.11b's worldwide acceptance) and conjointly offers quicker knowledge rates comparable 802.11a. the amount of channels obtainable, however, isn't magnified, since channels square measure a operate of information measure, not radio wave modulation - and thereon score, 802.11a wins with its eight channels, compared to the 3 channels obtainable with either 802.11b or 802.11g. Another disadvantage of 802.11g is that it conjointly works within the a pair of.4 gigacycle band so as a result of interference it'll ne'er be as quick as 802.11a.
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