802.11 a/b/g/n Explained
Frequency Modulation Bandwidth Data Rates
a 5 GHz OFDM 20 MHz 6, 9, 12, 18, 24, 36, 48, 54 1 High frequency reduces effective range.
b 2.4 GHz DSSS 20 MHz 1, 2, 5.5, 11 1 Many IT departments are turning off "b" access points.
g 2.4 GHz OFDM
20 MHz 6, 9, 12, 18, 24, 36, 48, 54 1 Only universal module scheme.
Access points auto-adjust rate to minimize the packet error rate.
n 2.4 GHz
5 GHz
40 MHz
7.2, 14.4, 21.7, 28.9, 43.3, 57.8, 65, 72.2 (per stream) 4 Must implement MIMO and 40 MHz bandwidth to get maximum data rates (600 Mb/s).

802.11 uses latency and rate reduction as a means of addressing increasing packet error rates and increasing range. Thus, the ability to step down through rates is part of the specification to create robust, high range networks.

802.11a is used to isolate networks and avoid crowded 2.4 GHz spectrums.

  • For example – hospitals and patient records

802.11g is an energy efficient radio that is fully compatible with basic 802.11n networks.

  • Same modulation technique

802.11n is useful for high data throughput applications.

In order to preserve battery life, most embedded 802.11n device clients (ATWINC1500) are single-stream (1x1) devices (i.e. having a single radio chain).

802.11a/b/g vs 802.11n AP Performance:

As with any wireless technology, as you move farther from the AP, the data rate decreases.
802.11n routers use MIMO reception to increase the range at which the client can transmit at its highest data rates, i.e. 802.11n access points providing service for older 802.11g clients provide "better g than g."

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