29-06-2012, 12:50 PM
WIRELESS LAN
WLAN report.docx (Size: 151.42 KB / Downloads: 35)
INTRODUCTION
Wireless technology has helped to simplify networking by enabling multiple computer users to simultaneously share resources in a home or business without additional or intrusive wiring. These resources might include a broadband Internet connection, network printers, data files, and even streaming audio and video. This kind of resource sharing has become more prevalent as computer users have changed their habits from using single, stand-alone computers to working on networks with multiple computers, each with potentially different operating systems and varying peripheral hardware. U.S. Robotics wireless networking products offer a variety of solutions to seamlessly integrate computers, peripherals, and data. Wireless networking enables the same capabilities and comparable speeds of a wired 10BASE-T network without the difficulties associated with laying wire, drilling into walls, or stringing Ethernet cables throughout an office building or home. Laptop users have the freedom to roam anywhere in the office building or home without having to hunt down a connector cable or available jack. Every room in a wireless home or office can be “connected” to the network, so adding more users and growing a network can be as simple as installing a new wireless network adapter.
IEEE Wireless Network Specification
The IEEE (Institute of Electrical and Electronic Engineers) released the 802.11 specifications in June 1999. The initial specification, known as 802.11, used the 2.4 GHz frequency and supported a maximum data rate of 1 to 2 Mbps. In late 1999, two new addenda were released. The 802.11b specification increased the performance to 11 Mbps in the 2.4 GHz range while the 802.11a specification utilized the 5 GHz range and supported up to 54 Mbps. Unfortunately, the two new specifications were incompatible because they used different frequencies. This means that 802.11a network interface cards (NICs) and access points cannot communicate with 802.11b NICs and access points. This incompatibility forced the creation of the new draft standard known as 802.11g. 802.11g supports up to 54 Mbps and is interoperable with 802.11b products on the market today. The concern is that the 802.11g specification is currently in development and products will not be available until a later date. 802.11 Specifications The 802.11 specifications were developed specifically for Wireless Local Area Networks (WLANs) by the IEEE and include four subsets of Ethernet-based protocol standards: 802.11, 802.11a, 802.11b, and 802.11g. 802.11 802.11 operated in the 2.4 GHz range and was the original specification of the 802.11 IEEE standards. This specification delivered 1 to 2 Mbps using a technology known as phase-shift keying (PSK) modulation. This specification is no longer used and has largely been replaced by other forms of the 802.11 standard. 802.11a 802.11a operates in the 5 - 6 GHz range with data rates commonly in the 6 Mbps, 12 Mbps, or 24 Mbps range. Because 802.11a uses the orthogonal frequency division multiplexing (OFDM) standard, data transfer rates can be as high as 54 Mbps. OFDM breaks up fast serial information signals into several slower sub-signals that are transferred at the same time via different frequencies, providing more resistance to radio frequency interference. The 802.11a specification is also known as Wi-Fi5, and though regionally deployed, it is not a global standard like 802.11b. 802.11b the 802.11b standard (also known as Wi-Fi) operates in the 2.4 GHz range with up to 11 Mbps data rates and is backward compatible with the 802.11 standard. 802.11b uses a technology known as complementary code keying (CCK) modulation, which allows for higher data rates with less chance of multi-path propagation interference (duplicate signals bouncing off walls). U.S. Robotics 22 Mbps 802.11b recent developments to 802.11b have seen numerous improvements to this well-established and widely-deployed wireless standard. New U.S. Robotics 22 Mbps products are designed to support Packet Binary Convolution Coding (PBCC) in addition to CCK modulation. This not only increases performance but also maintains complete 802.11b compatibility with both 11 Mbps and 22 Mbps products. The overall benefits include: • Up to twice the data rate of conventional 11 Mbps 802.11b standard products • Greater WLAN coverage: up to 70% greater than standard 11 Mbps 802.11b products • Full interoperability with all 802.11b products: works with 802.11b 11 Mbps, 802.11b 22 Mbps, and upcoming 802.11g products • Improved security over standard 802.11b: 256-bit WEP encryption and MAC address authentication* 802.11g 802.11g is the most recent IEEE 802.11 draft standard and operates in the 2.4 GHz range with data rates as high as 54 Mbps over a limited distance. It is also backward compatible with 802.11b and will work with both 11 and 22 Mbps U.S. Robotics wireless networking products. 802.11g offers the best features of both 802.11 and 802.11b, but as of the publication date of this document, this standard has not yet been certified, and therefore is unavailable. 2 * MAC address authentication available with U.S. Robotics 22 Mbps Wireless Access Point and U.S. Robotics 22 Mbps Wireless Cable/DSLR outer. All four standards are based on the CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) Ethernet protocol for path sharing. The most significant contribution of the 802.11 specification is that it allows for interoperability among different vendors’ equipment. Thanks to the Wireless Ethernet Compatibility Alliance (WECA), 802.11 standard equipment will work together interchangeably, regardless of the manufacturer.
Different WLAN Technologies
As various wireless networking technologies have advanced over time, several WLAN technologies have emerged, including: narrowband, spread spectrum, frequency hopping spread spectrum, and direct sequence spread spectrum. Narrowband As the name suggests, narrowband technology uses a specific radio frequency (in the range of 50 cps to 64 Kbps) for data transmission. Spread Spectrum Originally developed for military use, spread spectrum technology allows for greater bandwidth by continually altering the frequency of the transmitted signal, thus spreading the transmission across multiple frequencies. Spread spectrum uses more bandwidth than narrowband, but the transmission is more secure, reliable, and easier to detect.
Frequency Hopping Spread Spectrum (FHSS)
Frequency hopping spread spectrum (FHSS) technology synchronizes the changing frequency of both the transmitter and receiver (using a narrowband carrier) to, in effect, produce a single transmission signal. This frequency “hopping” can occur as often as several times a second; it is constantly changing from one frequency to another, transmitting data for a certain period of time before changing frequency again. Like spread spectrum technology, FHSS technology consumes additional bandwidth, however, this is over the course of multiple carrier frequencies.
Direct Sequence Spread Spectrum (DSSS)
Direct sequence spread spectrum (DSSS) technology breaks down the transmitted stream of data into small pieces across a frequency channel. A redundant bit pattern (known as a chipping code) is generated for each bit transmitted. Generally, the longer the chipping code, the more likely it is that the original transmitted data will be properly received. DSSS technology uses more bandwidth than FHSS, but DSSS is considered more reliable and resists interference. Because of the chipping code, data can still be recovered without retransmission of the signal, even in the case of damaged data bits. U.S. Robotics wireless networking products utilize DSSS technology. Wireless LAN Frequency Usage The 802.11b standard defines 14 frequency channels for use with this technology. Depending on the country a user lives in and where he or she will be installing a WLAN, there are certain governmental restrictions for companies offering these products and consumers or businesses deploying these products. In North America, the FCC (Federal Communications Commission) and IC (Industry Canada) allow manufacturers and users to use channels 1 through 11, per ETSI approval (European Telecommunications Standards Institute); most of Europe can use channels 1 through 13, while in Japan, users have all 14 channels available.
Ad Hoc (Peer-to-Peer) Mode vs. Infrastructure Mode
The 802.11 specification defines two types of operational modes: ad hoc (peer-to-peer) mode and infrastructure mode. In ad hoc mode, the wireless network is relatively simple and consists of 802.11 network interface cards (NICs). The networked computers communicate directly with one another without the use of an access point. In infrastructure mode, the wireless network is composed of a wireless access point(s) and 802.11 network interface cards (NICs). The access point acts as a base station in an 802.11 network and all communications from all of the wireless clients go through the access point. The access point also provides for increased wireless range, growth of the number of wireless users, and additional network security.
WLAN report.docx (Size: 151.42 KB / Downloads: 35)
INTRODUCTION
Wireless technology has helped to simplify networking by enabling multiple computer users to simultaneously share resources in a home or business without additional or intrusive wiring. These resources might include a broadband Internet connection, network printers, data files, and even streaming audio and video. This kind of resource sharing has become more prevalent as computer users have changed their habits from using single, stand-alone computers to working on networks with multiple computers, each with potentially different operating systems and varying peripheral hardware. U.S. Robotics wireless networking products offer a variety of solutions to seamlessly integrate computers, peripherals, and data. Wireless networking enables the same capabilities and comparable speeds of a wired 10BASE-T network without the difficulties associated with laying wire, drilling into walls, or stringing Ethernet cables throughout an office building or home. Laptop users have the freedom to roam anywhere in the office building or home without having to hunt down a connector cable or available jack. Every room in a wireless home or office can be “connected” to the network, so adding more users and growing a network can be as simple as installing a new wireless network adapter.
IEEE Wireless Network Specification
The IEEE (Institute of Electrical and Electronic Engineers) released the 802.11 specifications in June 1999. The initial specification, known as 802.11, used the 2.4 GHz frequency and supported a maximum data rate of 1 to 2 Mbps. In late 1999, two new addenda were released. The 802.11b specification increased the performance to 11 Mbps in the 2.4 GHz range while the 802.11a specification utilized the 5 GHz range and supported up to 54 Mbps. Unfortunately, the two new specifications were incompatible because they used different frequencies. This means that 802.11a network interface cards (NICs) and access points cannot communicate with 802.11b NICs and access points. This incompatibility forced the creation of the new draft standard known as 802.11g. 802.11g supports up to 54 Mbps and is interoperable with 802.11b products on the market today. The concern is that the 802.11g specification is currently in development and products will not be available until a later date. 802.11 Specifications The 802.11 specifications were developed specifically for Wireless Local Area Networks (WLANs) by the IEEE and include four subsets of Ethernet-based protocol standards: 802.11, 802.11a, 802.11b, and 802.11g. 802.11 802.11 operated in the 2.4 GHz range and was the original specification of the 802.11 IEEE standards. This specification delivered 1 to 2 Mbps using a technology known as phase-shift keying (PSK) modulation. This specification is no longer used and has largely been replaced by other forms of the 802.11 standard. 802.11a 802.11a operates in the 5 - 6 GHz range with data rates commonly in the 6 Mbps, 12 Mbps, or 24 Mbps range. Because 802.11a uses the orthogonal frequency division multiplexing (OFDM) standard, data transfer rates can be as high as 54 Mbps. OFDM breaks up fast serial information signals into several slower sub-signals that are transferred at the same time via different frequencies, providing more resistance to radio frequency interference. The 802.11a specification is also known as Wi-Fi5, and though regionally deployed, it is not a global standard like 802.11b. 802.11b the 802.11b standard (also known as Wi-Fi) operates in the 2.4 GHz range with up to 11 Mbps data rates and is backward compatible with the 802.11 standard. 802.11b uses a technology known as complementary code keying (CCK) modulation, which allows for higher data rates with less chance of multi-path propagation interference (duplicate signals bouncing off walls). U.S. Robotics 22 Mbps 802.11b recent developments to 802.11b have seen numerous improvements to this well-established and widely-deployed wireless standard. New U.S. Robotics 22 Mbps products are designed to support Packet Binary Convolution Coding (PBCC) in addition to CCK modulation. This not only increases performance but also maintains complete 802.11b compatibility with both 11 Mbps and 22 Mbps products. The overall benefits include: • Up to twice the data rate of conventional 11 Mbps 802.11b standard products • Greater WLAN coverage: up to 70% greater than standard 11 Mbps 802.11b products • Full interoperability with all 802.11b products: works with 802.11b 11 Mbps, 802.11b 22 Mbps, and upcoming 802.11g products • Improved security over standard 802.11b: 256-bit WEP encryption and MAC address authentication* 802.11g 802.11g is the most recent IEEE 802.11 draft standard and operates in the 2.4 GHz range with data rates as high as 54 Mbps over a limited distance. It is also backward compatible with 802.11b and will work with both 11 and 22 Mbps U.S. Robotics wireless networking products. 802.11g offers the best features of both 802.11 and 802.11b, but as of the publication date of this document, this standard has not yet been certified, and therefore is unavailable. 2 * MAC address authentication available with U.S. Robotics 22 Mbps Wireless Access Point and U.S. Robotics 22 Mbps Wireless Cable/DSLR outer. All four standards are based on the CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) Ethernet protocol for path sharing. The most significant contribution of the 802.11 specification is that it allows for interoperability among different vendors’ equipment. Thanks to the Wireless Ethernet Compatibility Alliance (WECA), 802.11 standard equipment will work together interchangeably, regardless of the manufacturer.
Different WLAN Technologies
As various wireless networking technologies have advanced over time, several WLAN technologies have emerged, including: narrowband, spread spectrum, frequency hopping spread spectrum, and direct sequence spread spectrum. Narrowband As the name suggests, narrowband technology uses a specific radio frequency (in the range of 50 cps to 64 Kbps) for data transmission. Spread Spectrum Originally developed for military use, spread spectrum technology allows for greater bandwidth by continually altering the frequency of the transmitted signal, thus spreading the transmission across multiple frequencies. Spread spectrum uses more bandwidth than narrowband, but the transmission is more secure, reliable, and easier to detect.
Frequency Hopping Spread Spectrum (FHSS)
Frequency hopping spread spectrum (FHSS) technology synchronizes the changing frequency of both the transmitter and receiver (using a narrowband carrier) to, in effect, produce a single transmission signal. This frequency “hopping” can occur as often as several times a second; it is constantly changing from one frequency to another, transmitting data for a certain period of time before changing frequency again. Like spread spectrum technology, FHSS technology consumes additional bandwidth, however, this is over the course of multiple carrier frequencies.
Direct Sequence Spread Spectrum (DSSS)
Direct sequence spread spectrum (DSSS) technology breaks down the transmitted stream of data into small pieces across a frequency channel. A redundant bit pattern (known as a chipping code) is generated for each bit transmitted. Generally, the longer the chipping code, the more likely it is that the original transmitted data will be properly received. DSSS technology uses more bandwidth than FHSS, but DSSS is considered more reliable and resists interference. Because of the chipping code, data can still be recovered without retransmission of the signal, even in the case of damaged data bits. U.S. Robotics wireless networking products utilize DSSS technology. Wireless LAN Frequency Usage The 802.11b standard defines 14 frequency channels for use with this technology. Depending on the country a user lives in and where he or she will be installing a WLAN, there are certain governmental restrictions for companies offering these products and consumers or businesses deploying these products. In North America, the FCC (Federal Communications Commission) and IC (Industry Canada) allow manufacturers and users to use channels 1 through 11, per ETSI approval (European Telecommunications Standards Institute); most of Europe can use channels 1 through 13, while in Japan, users have all 14 channels available.
Ad Hoc (Peer-to-Peer) Mode vs. Infrastructure Mode
The 802.11 specification defines two types of operational modes: ad hoc (peer-to-peer) mode and infrastructure mode. In ad hoc mode, the wireless network is relatively simple and consists of 802.11 network interface cards (NICs). The networked computers communicate directly with one another without the use of an access point. In infrastructure mode, the wireless network is composed of a wireless access point(s) and 802.11 network interface cards (NICs). The access point acts as a base station in an 802.11 network and all communications from all of the wireless clients go through the access point. The access point also provides for increased wireless range, growth of the number of wireless users, and additional network security.