Collision detection system for multiple stations in discrete multi-tone

Abstract

A novel collision detecting method is provided at the physical layer for use in a multi-point DMT communication network having stations transmitting over common media. The method includes generating a collision code corresponding to ID information of a station. A collision symbol representing the collision code is transmitted at the beginning of a portion of a random access data communication. A station in the network receives the collision symbol and decodes a collision signal carried by the collision symbol. A collision event is detected if the collision signal does not satisfy pre-set requirements. For example, energy of each component of the collision signal may be compared with a predetermined minimum energy level to generate a code element for each component having energy exceeding the predetermined minimum energy level. Validity of the code having the generated code elements is determined based on a predetermined validity criterion. Also, the distance in frequency domain between components of the collision signal corresponding to the generated code elements is compared with a predetermined minimum distance in frequency domain, to confirm validity of the detected code.