Communications system with reliable collision detection method and apparatus

A node in a communications system, comprising:

• a receiving means for receiving data from a communications medium, said receiving means indicating whether data is or is not being received from said medium,
• a transmitting means, responsive to said receiving means indicating data is not being received from said communications medium, for transmitting data on said medium, said transmitting means indicating whether data is or is not being transmitted,
• a first collision detection means, responsive to said receiving means indicating data is being received from said communications medium, and further responsive to said transmitting means indicating data is being transmitted, for detecting a collision when said transmitting means begins indicating data is being transmitted while said receiving means is indicating data is being received, and
• a second collision detection means, responsive to said receiving means and said transmitting means, for detecting a collision when data being transmitted is unequal to data being received.

An apparatus for detecting collisions in a node for a communications system, comprising:

• a receiving means for receiving data from a communications medium, said receiving means indicating whether data is or is not being received from said medium;
• a transmitting means, responsive to said receiving means indicating data is not being received from said communications medium, for transmitting data on said medium, said transmitting means indicating whether data is or is not being transmitted,
• a first collision detection means, responsive to said receiving means indicating data is being received from said communications medium, and further responsive to said transmitting means indicating data is being transmitted, for detecting a collision when said transmitting means begins indicating data is being transmitted while said receiving means is indicating data is being received,
• a second collision detection means, responsive to said receiving means and said transmitting means, for detecting a collision when data being transmitted is unequal to data being received, and
• a unique value, coupled with said transmitting means, consisting of recessive bits and dominant bits, having a recessive bit in a position containing a dominant bit in all other unique values for nodes on said communications system, said unique value included in each transmission from said node onto said communications medium.

A node in a communication system, comprising:

• a receiving means for receiving data from a communications medium, said receiving means indicating whether data is or is not being received from said medium;
• a transmitting means, responsive to said receiving means indicating data is not being received from said communications medium, for transmitting data on said medium, said transmitting means indicating whether data is or is not being transmitted,
• a first collision detection means, responsive to said receiving means indicating data is being received from said communications medium, and further responsive to said transmitting means indicating data is being transmitted, for detecting a collision when said transmitting means begins indicating data is being transmitted while said receiving means is indicating data is being received,
• a second collision detection means, responsive to said receiving means and said transmitting means, for detecting a collision when data being transmitted is unequal to data being received, and
• a unique value, coupled with said transmitting means, consisting of recessive bits and dominant bits, having a recessive bit in a position containing a dominant bit in all other unique values for nodes on said communications system, said unique value included in each transmission from said node onto said communications medium.

A communications system comprising:

• a communications medium using a dominant bit and a recessive bit;
• and
• 20 nodes connected to said medium, each node having:
• a receiving means for receiving data from said medium, and indicating whether data is or is not being received from said medium;
• a transmitting means, responsive to said receiving means indicating data is not being received from said communications medium, for transmitting data on said medium, and indicating whether data is or is not being transmitted;
• a first collision detection means, responsive to said receiving means indicating that data is being received from said communications medium, and further responsive to said transmitting means indicating data is being transmitted, for detecting a collision when said transmitting means begins indicating data is being transmitted while said receiving means indicates that data is being received;
• a second collision detection means, responsive to said receiving means and said transmitting means, for detecting a collision when said transmitted data is unequal to said received data;
• and
• a forty eight bit unique value, included by said transmitting means in every transmission as a source address field, said unique value having recessive bits in two bit positions within said unique value, said two bit positions being one of the following pairs
• 4. 45
• 6, 43
• 8, 41
• 10, 39
• 12, 37
• 14, 35
• 16, 33
• 18, 31
• 20, 29
• 22, 27
• 11, 28
• 9, 30
• 7, 32
• 5, 34
• 3, 36
• 23, 38
• 21, 40
• 19, 42
• 17, 44
• 15, 46,

A method for generating unique values for a communications system, comprising the following steps:

• determining the maximum time shifting possible for concurrent transmissions not detected as collisions by said first collision detection means;
• generating a plurality of unique values where each unique value in said plurality of unique values comprises at least one recessive bit in a position within said unique value, said position containing a dominant bit in all other unique values in said plurality of unique values, said position surrounded by dominant bits in all other unique values in said plurality of unique values, and said unique value having at least one such recessive bit when said unique value is shifted with respect to any other unique value in said plurality of unique values, by any number of bits up to and including said maximum time shifting;
• assigning each one of said plurality of unique values to each one of said plurality of nodes;
• and
• transmitting data within said plurality of nodes.