The hardware rating may be 108 Mbps, a router, NIC card, even cabling. I believe that the math behind getting that 108 Mbps may mean total data rate transmit / receive, and could be a bit misleading.
If the rating is for Full Duplex mode, this is related to the fact that the transceiver (transmitter+receiver), NIC, or media can transmit data @ 54 Mbps while simultaneously receiving data @ 54 Mbps for a total transmit / receive data rate of 108 Mbps. Your hardware would still only be capable of 54 Mbps top speed in either direction, sending or receiving data. But when sending and receiving simultaneously (transmit / receive) at stop speed (54 Mbps), the sum of data rates in both directions is equal to 108 Mbps.
So Full Duplex mode means you are taking the sum of the transmission and reception channels to calculate the data transfer speed rating which is equal to the data transfer rate over all communication / signal channels in both directions. To simplify, the data rate of transmission + the data rate of reception = data transfer rate -> speed rating.
Therefore, your reading of 54 Mbps would be correct for your signal strength at Excellent (for data transfer in either direction). You are able to transmit data @ 54 Mbps with Excellent signal strength; similarly, you are also able to receive data @ 54 Mbps simultaneously. Therefore your hardware's transmit / receive data rate (in Full Duplex mode) is 108 Mbps.
That mode of mathematics when working with networking equipment (as well as the cabling that interconnects in wired networks), is quite common and to the uninitiated it is often misleading.
Edited by Cyb3r_Ninj@, 01 March 2008 - 06:02 PM.