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Wireless Network Standards
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1. What does the Institute for Electrical & Electronics Engineers (IEEE) 802.11 standards - also known as Wi-Fi - describe?
How wireless networking functions at the Physical and Data Link layers of the OSI model.
The wireless standards differ in transmission speeds and network range. Different standards are suitable for different types of WLAN.
The original 802.11 standard was published in 1997 but is no longer used today. It had a throughput of 1 or 2 Mbps on the 2.4 GHz range. It was replaced with 802.11b, which in turn was replaced with 802.11g.
802.11b was published in 1999. It was started after 802.11a was started but work on it was finished before 802.11a was released. It was the first widely implemented 802.11 standard.
An 802.11b wireless network has a theoretical maximum transmission speed of 11 Mbps, with an effective throughput of 5 Mbps and a transmission range of about 100 meters, or 330 feet. It operates on the 2.4 GHz band using 22 MHz channels.
802.11b uses the direct-sequence spread spectrum, or DSSS, modulation technique to spread its signal over the full available bandwidth.
The 802.11b standard is being replaced with 802.11g, which is backwards compatible with it and is much faster.
The 802.11a standard was ratified in 1999. An 802.11a wireless network has a theoretical maximum transmission speed of 54 Mbps with an effective transmission speed of 11 to 18 Mbps and a range of about 20 meters, or 65 feet.
It uses the 5 GHz frequency, which is less susceptible to interference from microwave ovens, cordless phones, and electric motors than the frequency used by 802.11b. However, the 5 GHz frequency suffers from a lower range and requires more power to transmit than 2.4 GHz. This made the hardware more expensive than similar 2.4 GHz hardware.
Furthermore, 802.11a isn't backwards compatible with 802.11b because it uses a different frequency.
The shortened range of each transmitter also means that more access points are required, which can further push up the price. The 802.11a standard is the least popular of the standards despite the benefits of using the 5 GHz band.
802.11a uses the orthogonal frequency-division multiplexing, or OFDM, modulation technique to split data over a number of channels.
802.11g was ratified in 2003 and has a theoretical maximum transmission speed of 54 Mbps, with an effective transmission speed of 20 to 25 Mbps and a range of about 100 meters, or 330 feet. It uses the same 2.4 GHz frequency as the 802.11b standard but achieves faster throughput by using the OFDM data modulation technique developed by 802.11a, in addition to DSSS.
802.11g is backwards compatible with 802.11b so networks with existing 802.11b infrastructure could be upgraded incrementally to 802.11g.
802.11g devices also became as affordable as 802.11b devices. As a result, the 802.11g standard is more popular than 802.11a and remains the most widely used.
802.11n was ratified in 2009 and has a theoretical maximum transmission speed of 600 Mbps. Its effective transmission speed depends on the innovations used, and ranges from 65 to 600 Mbps. The range of 802.11n is about 53 meters or 175 feet. It uses both the 2.4 GHz and the 5 GHz frequencies.
802.11n is backwards compatible with 802.11b, a, and g.
It uses four technologies to achieve its transmission speeds and range. These are multiple input-multiple output - or MIMO - channel bonding, modulation rates, and frame aggregation.
MIMO increases signal strength by using multiple antennas on each transceiver to send multipath signals. The aggregation of signals from the antennas provides a stronger signal.
7. How many channels can 802.11n bond?
802.11n can bond two 20 MHz channels, effectively creating a 40 MHz channel - and it makes the buffer frequency that would be required between the two channels available for transmitting data. Channel bonding is usually performed on the 5 GHz frequency because it has more channels and is less prone to interference.
8. What does 802.11n use to achieve fast input?
802.11n uses OFDM to achieve fast throughput like 802.11g. However, it has higher modulation rates than 802.11g because it can choose between multiple encoding modes, uses more efficient channel bonding, and requires less wait time between each transmitted bit.
9. Frame aggregation
Frame aggregation involves increasing the size of each frame that's transmitted, which lowers the overhead for each transmission. However, errors are more likely to occur when large frames are transmitted.
10. 802.11n Frames
802.11n can transmit frames of up to 64 KB - as opposed to the usual frame size of 4 KB with the 802.11g standard.
The 802.11ac standard is currently being developed. It will use the 5 GHz range with a wider band to transfer data at up to 1 Gbps.
This set is often in folders with...
Twisted Pair & Coaxial Cabling
Wiring Distribution Infrastructure
Fiber Network Media
Basic Operations of Wireless Networks
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