|
Wireless Local Area Networks
Pdf ko'rish
|
| bet | 33/55 | | Sana | 24.05.2024 | | Hajmi | 343,31 Kb. | | #252539 |
Bog'liq garg200721.10 IEEE
802.11n
In response to growing market demand for higher-performance WLANs, the
IEEE formed the task group 802.11n. The scope of this task group is to defi ne
modifi cations to the physical and MAC layer to deliver a minimum of 100 Mbps
throughput at the MAC service access point (SAP).
802.11n employs an evolutionary philosophy reusing existing technologies
where practical, while introducing new technologies where they provide effective
performance improvements to meet the needs of evolving applications. Reuse of
legacy technologies such as OFDM, forward error correction coding, interleaving,
and quadrature amplitude modulation mapping have been maintained to keep
costs down and ease backward compatibility.
There are three key areas that need to be considered when addressing
increases in WLAN performance. First, improvements in radio technology are
needed to increase the physical transfer rate. Second, new mechanisms imple-
menting the effective management of enhanced physical layer performance modes
must be developed. Third, improvements in data transfer effi ciency are needed to
reduce the improvements achieved with an increase in physical transfer rate.
The emerging 802.11n specifi cation differs from its predecessors in that it
provides for a variety of optional modes and confi gurations that dictate different
maximum raw data rates. This enables the standard to provide baseline performance
parameters for all 802.11n devices, while allowing manufacturers to enhance or tune
capabilities to accommodate different applications and price points. WLAN hard-
ware does not need to support every option to be compliant with the standard.
The fi rst requirement is to support an OFDM implementation that improves
upon the one employed in 802.11a/g standards, using a higher maximum code
rate and slightly wider bandwidth. This change improves the highest attainable
raw data rate to 65 Mbps from 54 Mbps in the existing standards.
|
| |
