This is slightly hard to look at but I'll try to break it down.
On "Sheet1" cell B2 put the following:
=SUM(IF(speed!B$1:speed!B$24508=A2,IF(speed!C$1:speed!C$24508=MAX(IF(speed!B$1:speed!B$24508=A2,speed!C$1:speed!C$24508,0)),1,0),0))
you will need to enter this as an array formula by pressing ctrl+shift+enter
I'm going to color code this so its easier to explain how it works.
=SUM(IF(speed!B$1:speed!B$24508=A2,IF(speed!C$1:speed!C$24508=MAX(IF(speed!B$1:speed!B$24508=A2,speed!C$1:speed!C$24508,0)),1,0),0))
The Red portion is there for us to only look at the data that pertains to the ssid in A2.
The Blue portion, then checks to see if the value in column C is equal to the max for the ssid, if it is it adds 1 to the count
The Green portion helps us find the max speed for our given value in this case cell A2 = Ant.