Orthogonal code division multiplexing for twisted pair channels

• US 6,711,121 B1
• Filed: 10/06/1999
• Issued: 03/23/2004
• Est. Priority Date: 10/09/1998
• Status: Expired due to Term

• Current Assignee: AT&T Corporation (AT&T, Inc.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Gerakoulis, Diakoumis Parissis, Geraniotis, Evaggelos
• Primary Examiner(s): Olms, Douglas
• Assistant Examiner(s): NGUYEN, VAN KIM T
• Application Number:
  US09/413,162
• Time in Patent Office: 1,630 Days
• Field of Search: 370/479, 370/208, 370/320, 370/327, 370/335, 370/342, 370/441, 370/533, 370/535, 370/536, 370/537, 370/538, 370/539, 370/540, 370/541, 370/465-468, 370/482, 370/485, 370/484, 370/493-495, 375/204-211, 375/146, 375/260, 375/285, 375/296, 375/144, 375/242-254, 341/100, 341/101, 710/71
• US Class Current: 370/205
• CPC Class Codes: H04J 13/004 Orthogonal
• CPC Class Codes: H04J 13/0077 Multicode, e.g. multiple codes assigned to one user

Abstract

A plurality of data signals are separated into parallel bit streams with each parallel stream having a bandwidth characteristic such that the combined cumulative effect of all the individual bandwidths produces a spectral characteristic of the data signals that match the spectral high speed data characteristic of a twisted pair.

Claims

1. A method for developing a signal adapted for transmission over a twisted pair wire comprising the steps of:

forming a plurality of streams from data of one or more sources, and for each stream j of said plurality of streams performing the steps of;

(a) applying to said stream j a M_j-PAM modulator that converts block of k_j bits into symbols having M_j levels, where M_j=2^k_jthereby creating a P_j modulated signal with a bandwidth related to selected integer value of ki;

(b) splitting said signal P_j into N substreams;

(c) spreading each of said substreams with a different spreading code from an orthogonal code set, each of said different spreading codes being at a common rate R_s; and

combining the spread signals to form said signal adapted for transmission.

4. The method of claim 1, wherein said k_j values of said M_j-PAM modulators are chosen create a power spectrum density that when all spread signals are combined, achieves a combined power density characteristic approximating the twisted pair transfer function.

6. The method of claim 1, wherein said combining includes applying a PN cover code to said summed signal to create a signal with a spectrum that approximates white noise.

11. The method of claim 1, wherein said combining comprises the steps of

summing each P_j plurality of spread signals to form a channel signal;

modulating each channel signal with a code;

filtering each modulated channel signal; and

summing the filtered signals.

12. The method of claim 1, wherein numbers of said modulated signals in the P_j plurality of modulated signals, summed over all values of j, equals number of orthogonal codes in said orthogonal code set.

2. A method of facilitating high speed data transit over a twisted pair, comprising the steps of:

demultiplexing an incoming symbol stream having a rate R_s into N parallel symbol streams with rate R_s/N;

applying spreading techniques using orthogonal codes to increase each of the parallel symbol streams to a rate N_s;

summing all the parallel symbol streams and multiplying by a PN code of rate R_s to form a plurality of output pulses; and

shaping said plurality of output pulses so that its cumulative power spectra substantially matches a power transfer function of the twisted pair.

7. The method of claim 2, wherein each of the parallel streams is modulated by a different modulation loading to create a spectrum distribution substantially matching the transfer characteristic of the twisted pair.

8. The method of claim 2, wherein the PN code is orthogonal.

9. The method of claim 2, wherein each parallel stream is loaded to a different order of modulation so that combining the order generates a spectral density similar to the spectral density of the twisted pair.

3. A method of matching a transfer characteristic of a serial stream of data with a power spectrum transfer characteristic of a twisted pair, comprising the steps of:

enhancing said stream with forward error correction information;

performing serial-to-parallel conversion on the enhanced stream, and modulating the converted signal to obtain pulse amplitude modulated signals in each of parallel branches;

splitting the signal of each parallel branch to form substreams;

spreading the signal of each parallel branch by multiplying each substream of the branch by a different code from a set of orthogonal codes;

summing the spread signals of the parallel branches to create a summed signal;

modifying density of the summed signal by overspreading with a PN cover code to form a white noise spectral distribution of energy; and

filtering results of said modifying to alter spectral distribution of an output signal so as to approximate said transform function for the twisted pair.

5. The method of claim 3 where number of said substreams is equal to number of codes in said set of orthogonal codes.

10. The method of claim 3, wherein each signal on parallel branches is modulated to a different loading so that its cumulative power spectra approximated that of the transfer function of the twisted pair.