Method and apparatus for detecting a set up signal used for data communication over a communication network

A method of detecting phase reversals in a set up signal used for data transmissions over a communication network, the set up signal having a predetermined frequency and including predetermined phase reversals at predetermined intervals, comprising:

• filtering a received signal by a filter having a passband including the predetermined frequency, wherein the filtered received signal comprises a plurality of frames, with each frame comprising N frame portions;
• determining the energy level of the filtered received signal over different sets of a predetermined number of consecutive frame portions of the filtered received signal;
• processing the determined energy levels;
• and
• detecting the predetermined phase reversals in the set up signal when the determined energy levels correspond to a predetermined pattern.

A method of detecting a set up signal used for data transmissions over a communication network, the set up signal having a predetermined frequency and including predetermined phase reversals at predetermined intervals, comprising:

• determining an energy level of a received signal at substantially the predetermined frequency;
• comparing the determined energy level with a predetermined value and providing a detect signal when the determined energy level is greater than the predetermined value;
• filtering the received signal by a filter having a passband including the predetermined frequency, wherein the filtered received signal comprises a plurality of frames, with each frame comprising N frame portions;
• determining the energy level of the filtered received signal over different sets of a predetermined number of consecutive frame portions of the filtered received signal;
• processing the determined energy levels;
• detecting the predetermined phase reversals in the set up signal when the determined energy levels correspond to a predetermined pattern;
• and
• detecting the set up signal in the received signal in response to the detect signal or in response to detecting the predetermined phase reversals in the set up signal.

A computer readable medium including instructions that when executed by a processor perform the method of detecting a set up signal used for data transmissions over a communication network, the set up signal having a predetermined frequency, the method comprising:

• filtering a received signal by a filter having a passband including the predetermined frequency, determining an energy level of the filtered received signal and comparing the determined energy level of the filtered received signal with a first predetermined value and providing a first detect signal when the determined energy level is greater than the first predetermined value;
• identifying a component of the received signal at the predetermined frequency and determining an energy level of the identified component, comparing the determined energy level of the identified component with a second predetermined value and providing a second detect signal when the determined energy level is greater than the second predetermined value;
• performing an autocorrelation function on the received signal to discriminate between the set up signal and other signals in the received signal and providing a check signal when the autocorrelation function identifies the set up signal;
• and
• detecting the set up signal in the received signal in response to the first and the second detect signals and the check signal.