One problem with Basic Bit-Map Protocol is that the overhead is 1 bit per frame per station. We can do better by using binary station addresses.
- A station wanting to use the channel now broadcasts its address as a binary bit string in serial fashion.
- As soon as a station sees that a high-order bit position that is 0 in its address has been overwritten by a 1, it gives up (meaning some high order station wants to transmit).
- The remaining stations keep sending their addresses on the network, until a winner merges.
- The wining station sends out the frame. The bidding process repeats.
For example, if stations 0010, 0100, 1001, and 1010 are all trying to get the channel, in the first bit time the four stations transmit 0, 0, 1, and 1, respectively. These are ORed together resulting in a 1. Stations 0010 and 0100 see the 1 and know that a higher-numbered station is competing for the channel, so they give up for the current round. Stations 1001 and 1010 continue. The next bit sent from both stations is 0, both continues. The next bit is 1, so station 1001 gives up. The winner is 1010. This station transmits its frame. Then a new bidding process begins. The channel efficiency is now d/(d + ln N)