FIG. 1 depicts a schematic diagram of a portion of wireless local area network 100 in the prior art. Local area network 100 comprises legacy stations 101-1 through 101-K, wherein K is a positive integer, and enhanced stations 102-1 through 102-L, wherein L is a positive integer. Legacy stations 101-1 through 101-K and enhanced stations 102-1 through 102-L use shared-communications medium 103 to communicate among themselves. Shared-communications medium 103 comprises multiple shared-communications channels. Only one of the stations can transmit into a given channel at a time, although one of the stations can transmit into a first channel while another station transmits into a second channel.
When two stations transmit into a given channel at the same time, the result is a cacophony and both transmissions are garbled. Prior art techniques, such as Carrier Sense Multiple Access, are used by the stations to coordinate when each of them transmits over a single shared-communications channel.
Legacy stations 101-1 through 101-K can transmit and receive using:    i. a modulation scheme that uses one shared-communications channel at a time (i.e., a single-channel modulation scheme).In contrast, enhanced stations 102-1 through 102-L can transmit and receive using:    i. a modulation scheme that uses one shared-communications channel at a time (i.e., a single-channel modulation scheme), and    ii. a modulation scheme that uses multiple shared-communications channels simultaneously (i.e., a multi-channel modulation scheme).
Any two stations that need to communicate must do so in accordance with a modulation scheme that is available to both of them. Therefore, two enhanced stations can communicate with each other by using a multi-channel modulation scheme, but any communication involving a legacy station must use a single-channel modulation scheme.
Enhanced stations 102-1 and 102-2, for example, communicate with each other by using the multi-channel modulation scheme when possible because it enhances communication throughput in comparison to the single-channel modulation scheme. One effect of using the multi-channel modulation scheme, however, is that legacy station 101-1, for example, cannot detect when enhanced stations 102-1 and 102-2 are communicating (i.e., enhanced stations 102-1 and 102-2 are essentially undetectable by legacy station 101-1 when enhanced stations 102-1 and 102-2 are communicating by using the multi-channel modulation scheme). This can cause legacy station 101-1 to transmit when enhanced stations 102-1 and 102-2 are communicating, which causes all of the transmissions to be garbled.
Even if enhanced station 102-1 successfully transmits the data block to enhanced station 102-2, enhanced station 102-2 might subsequently have difficulty transmitting an acknowledgment of the data block back to enhanced station 102-1. The difficulty in transmitting the acknowledgment is attributed to the same reason of enhanced nodes being undetectable that was described earlier. In the event of an unsuccessful acknowledgment transmission, enhanced station 102-1 has to re-transmit the data block in its entirety.
What is needed is a way to improve data transmission over multiple shared-communications channels without some of the performance disadvantages in the prior art.