Patent ID: 6295272
Filing Date: 2001-09-25
Classification: H04L

Abstract:
A system comprising:a copper or fiber optic shared transmission media;a high speed data transmitter having a data input for coupling to a source of date to be transmitted, for encoding data received at said high speed data input using a DC balanced data encoding scheme and outputting said encoded data in NRZ format at an output, said encoding being such that low frequency components in the Fourier spectrum of said encoded high speed data are heavily suppressed, said encoding scheme having a bounded transition density;a summing junction coupled to receive the encoded NRZ format data signal output by said high speed data transmitter;a subchannel transmitter for generating a subchannel carrier signal modulated with subchannel data and having an output coupled to said summing junction so as to generate a combined signal comprising the sum of said high speed data signal and said subchannel carrier signal, said subchannel transmitter having a data input for receiving subchannel data to be transmitted over said shared transmission media and using said subchannel data to modulate said subchannel data onto a subchannel carrier by frequency shift keying, said subchannel carrier having a frequency in the range of low frequencies that are heavily suppressed in the Fourier spectrum of said high speed data, said subchannel transmitter including means for controlling the injection current into said summing junction generated by said subchannel transmitter so as to generate an subchannel component in said combined signal which is strong enough to be detected but which is not so strong as to cause excessive jitter in any conventional high speed data receiver to which said combined signal is coupled;a media interface driver means which is designed to drive the particular type of shared transmission media present and having an input coupled to said summing junction and having an output coupled to said shared transmission media, for driving the combined signal generated at said summing junction onto said shared transmission media;a media interface converter means having an input coupled to said shared transmission media and having an output, for converting the combined signal on said shared transmission media into a signal at said output which can be coupled to the input of a conventional high speed data receiver;a high speed data receiver having an input coupled to said media interface converter, for recovering said high speed data; anda low pass filter having an input coupled to said media interface converter output and having an output and having a passband which includes said subchannel carrier and which has a rolloff frequency set so as to heavily attenuate the high frequency Fourier components of the combined signal output by said media interface converter during passage through said low pass filter; anda subchannel receiver having an input coupled to said output of said low pass filter, for converting the frequency shifts in said subchannel carrier to logic levels so as to recreate said subchannel data.