802.11 the Wi-Fi standard
| Posted in Networks | Posted on 28-12-2009
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Pointout team asked:
IEEE(Institute of Electrical and Electronics Engineers) 802.11 standards of communication between wireless devices are set in 2.4 and 5 GHz frequency band. IEEE 802.11 communication architecture is the one building many of todays wireless local networks called wlans.This standard has it’s another popular name “ Wi-Fi “ which is used with the real name interchangeably depending on the market demands. Devices operating with this standard should have a Wi-FI sticker on them meaning they are certified 802.11 products.
The frequency used in 802.11 is either 2.4 GHz or 5GHz depending mostly on where you live. 802.11a is mostly used in United States while 802.11b and 802.11g cover the Wi-Fi communication in Europe and so. There are advantages and disadvantages to using both standards. 802.11 operate at higher frequency meaning all the home devices like microwave oven , tv etc. doesn’t have much effect on quality of communication and signal. But in other hand solid metal parts of houses in the walls are getting in the way for 802.11a higher frequencies. Also with higher frequency band we cannot establish connection with very distant devices. Maximal distance can be 10-15m in circle.802.11b and g standards offer communication on lower frequencies allowing us to connect at greater distances like 25-30 meters but the biggest disadvantage of them is that they are affected by microwaves from oven , tv signals etc.
802.11 have similar problems like Ethernet network consisted of hubs connecting PC’s. Because hubs just forward packet that arrives to one port to all other ports and the communication is half duplex packets can collide and make errors.In this case Ethernet uses CSMA/CD (Carier Sense Multiple Access/Collision Detection) to help avoid data packet collisions and react in case they happen.
For more information about wireless networks,standards and protocols visit www.pointout.org your web resource for computer and network technology.
With 802.11 problem is similar, every device transmits its data over air so packets would be constantly colliding without CMSA/CA (Carier Sense Multiple Access/Collision Avoidance) protocol implemented. This protocol sets the rule of communication in this environment.Every host(node) before transmiting a data packet must first tell the other devices using the network that it’s going to send now and use a channel. Than device is permitted to send his data. The well known problem with this system is called “the missing node” which occurs when two nodes(end hosts) are to far away one from each other to see the signal of other and missing the signal from other node before it starts to send packets, so this can lead to packet collisions.
Another Wi-Fi standard yet in draft form is 802.11n and is being developed pretty fast in the last few years. It should work with a number of antennas and use them simultaneously for data transfers allowing much higher bandwidth in networks like these. For now bandwidth for 802.11a standard is 54Mb/s max. and for 802.11b 11Mb/s , 802.11g 54Mb/s.
IEEE(Institute of Electrical and Electronics Engineers) 802.11 standards of communication between wireless devices are set in 2.4 and 5 GHz frequency band. IEEE 802.11 communication architecture is the one building many of todays wireless local networks called wlans.This standard has it’s another popular name “ Wi-Fi “ which is used with the real name interchangeably depending on the market demands. Devices operating with this standard should have a Wi-FI sticker on them meaning they are certified 802.11 products.
The frequency used in 802.11 is either 2.4 GHz or 5GHz depending mostly on where you live. 802.11a is mostly used in United States while 802.11b and 802.11g cover the Wi-Fi communication in Europe and so. There are advantages and disadvantages to using both standards. 802.11 operate at higher frequency meaning all the home devices like microwave oven , tv etc. doesn’t have much effect on quality of communication and signal. But in other hand solid metal parts of houses in the walls are getting in the way for 802.11a higher frequencies. Also with higher frequency band we cannot establish connection with very distant devices. Maximal distance can be 10-15m in circle.802.11b and g standards offer communication on lower frequencies allowing us to connect at greater distances like 25-30 meters but the biggest disadvantage of them is that they are affected by microwaves from oven , tv signals etc.
802.11 have similar problems like Ethernet network consisted of hubs connecting PC’s. Because hubs just forward packet that arrives to one port to all other ports and the communication is half duplex packets can collide and make errors.In this case Ethernet uses CSMA/CD (Carier Sense Multiple Access/Collision Detection) to help avoid data packet collisions and react in case they happen.
For more information about wireless networks,standards and protocols visit www.pointout.org your web resource for computer and network technology.
With 802.11 problem is similar, every device transmits its data over air so packets would be constantly colliding without CMSA/CA (Carier Sense Multiple Access/Collision Avoidance) protocol implemented. This protocol sets the rule of communication in this environment.Every host(node) before transmiting a data packet must first tell the other devices using the network that it’s going to send now and use a channel. Than device is permitted to send his data. The well known problem with this system is called “the missing node” which occurs when two nodes(end hosts) are to far away one from each other to see the signal of other and missing the signal from other node before it starts to send packets, so this can lead to packet collisions.
Another Wi-Fi standard yet in draft form is 802.11n and is being developed pretty fast in the last few years. It should work with a number of antennas and use them simultaneously for data transfers allowing much higher bandwidth in networks like these. For now bandwidth for 802.11a standard is 54Mb/s max. and for 802.11b 11Mb/s , 802.11g 54Mb/s.