Mesh/a x b : c notation

802.11n routers can have up to four antennas and the ability to send and receive on between one and four of those at the same time.

The a x b : c notation is a way of specifying:

• a: The number of transmit antennas
• b: The number of receive antennas
• c: How many antennas can be used at the same time (number of spatial streams)

Note that a router with 1 antenna used for both receive and transmit would be 1 x 1 : 1.

See also the description on wikipedia, and how encoding and the number of spatial streams affect available bandwidth [1].