Wireless Data Networks

Current wireless networks use standards developed by the IEEE:

LAN/MAN Standards Committee (aka IEEE 802).

802.11: Wireless Local-Area Networks (Wi-Fi)

802.11b: 11Mbps (6.5Mbps typ) @ 2.4GHz, 100m

802.11a: 54Mbps (25Mbps typ) @ 5GHz, 50m

802.11g: 54Mbps (11Mbps typ) @ 2.4GHz, 100m

802.11n: 540Mbps (200Mbps typ) @ 2.4GHz or 5GHz, 250m

802.15: Wireless Personal-Area Networks

802.15.1: (Bluetooth) 1-3Mbps @ 2.4GHz, 1:10:100m

802.15.3: (UWB) 100-500Mbps @ 3.1-10.6GHz, 1-3m

802.15.4: (ZigBee) 40kbps

@ 915MHz, 250kbps @2.4GHz, 10-75m

802.16: Broadband Wireless Access (WiMAX)

up to 70Mbps and up to 100km

(but not at the same time!)

@ 1-10GHz, or @ 10-66GHz

802.11a:

12 channels in 5GHz band

•

20MHz bandwidth (16.6MHz occupied)

–

Orthogonal Frequency Divi

sion Multiplexing (OFDM)

–

52 subcarriers (48 data, 4 pilot) 

802.11a Transmitter:

See Here

802.11a Receiver:

see Here

802.11a Packet Structure:

see Here

802.11a Virtual CSMA/CA :

Full Collision Detect would require full duplex radio ($$$)

•

Transmitter sends Request-To-Send packet specifying

source, destination and duration (cts+pkt+ack)

•

Receiver sends Clear-To-Send packet with duration (pkt+ack)

•

Everyone receiving RTS or CTS will mark channel as busy for

given duration

•

Transmitter sends Data packet, receiver checks CRC and

replies with ACK packet.