|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|
|20 MHz||6, 9, 12, 18, 24, 36, 48, 54||1||Only universal module scheme.
Access points auto-adjust rate to minimize packet error rate.
|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 (600Mb/s)|
802.11 uses latency and rate reduction as a means of addressing increasing packet error rate 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 2.4GHz spectrum
- For example – hospitals and patient records
802.11g are energy efficient radios and fully compatible with basic 802.11n networks.
- Same modulation technique
802.11n is useful for high data throughput applications
- High definition video, moving Mbytes of data
- Must implement bonding and Multiple Input Multiple Output (MIMO), to achieve higher rates
Most embedded 802.11n device clients (MRF24WN0MA) are Single-Stream (1x1) devices (i.e. having a single radio chain) in order to preserve battery life.
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"