System and method for equalization of forward and reverse channels of a communication network system

• US 5,608,728 A
• Filed: 04/13/1995
• Issued: 03/04/1997
• Est. Priority Date: 04/13/1995
• Status: Expired due to Term

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: LANcity Corporation (Nortel Networks Corporation)
• Inventors: Ulm, John, Corley, William D., Mazza-Brennan, Cynthia, Grobicki, Christopher
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): Carman, Melissa Kay
• Application Number:
  US08/421,612
• Time in Patent Office: 691 Days
• Field of Search: 370/85.2, 370/85.1, 370/85.3, 370/60, 370/95.1, 370/94.1, 340/825.5, 340/825.51, 340/825.05, 455/6.1, 455/82, 375/354, 375/365, 375/229, 375/232
• US Class Current: 370/488
• CPC Class Codes: H04L 12/2801 Broadband local area networks
• CPC Class Codes: H04L 25/03133 with a non-recursive structure H04L25/03127 takes precedence
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications

Abstract

A system and method for equalization for forward and reverse channels of communicating highway network system having a branching tree topology. The system and method cause the forward channel to be adjusted first for equalization, then the reverse channel is adjusted for equalization. A reference node periodically transmits a frequency-rich signal on the network to the head end, which broadcasts this signal to each of a number of system nodes. Each system node compares the frequency-rich signal with an expected signal, and adjusts its receiver based on this comparison. Next, each system node transmits another frequency-rich signal to the head end, receives a return echo, compares the echo with the transmitted signal, and adjusts its transmitter based on the comparison.

Claims

1. An equalization system for equalizing forward and reverse channels of a network, comprising:

a central node that is capable of receiving and broadcasting signals on the network;

a network bus for transmitting signals to, and receiving signals from, the central node; and

a plurality of network nodes connected to network bus, each of the network nodes being capable of communicating with each of the other network nodes over the network bus via the central node, each network node including at least,

a transmitter capable of transmitting a transmitter equalization signal for adjusting the transmitter to provide a signal of predetermined characteristics to the central node and transmitting receiver equalization signals for adjusting received signals to have a predetermined signal quality,

a receiver that is capable of receiving a receiver equalization signal transmitted by a transmitter of a predetermined network node and receiving a transmitter equalization signal transmitted by the transmitter associated with said receiver, and

processing means for comparing the received receiver equalization signal with a first stored signal and determining an adjustment for the receiver for forward channel equalization, and/or comparing the received transmitter equalization signal with a second stored signal and determining an adjustment for the transmitter for reverse channel equalization.

2. The system of claim 1, wherein the adjustment for a transmitter is for pre-distorting signals to be transmitted therefrom.

3. The system of claim 1, wherein the predetermined network node is a reference node.

4. The system of claim 1, wherein the transmitter includes an output amplifier that connects to the network bus, a D/A converter that has an output connected to the input of the output amplifier, a modulator that provides an input to the D/A converter, an oscillator for providing a signal carrier input to the modulator, and first filter means for providing a data input to the modulator, the output of the modulator being the signal carrier modulated with the data.

5. The system of claim 4, wherein the first filter means is an FIR filter.

6. The system of claim 1, wherein transmitter equalization signal is a frequency-rich signal.

7. The system of claim 1, wherein the receiver equalization signal is a frequency-rich signal.

8. The system of claim 1, wherein the receiver includes an A/D converter for receiving signals from the network bus, a second filter means for receiving the output from the A/D converter, a demodulator for receiving and demodulating signals output from the second filter means, first storage means for storing samples from the A/D converter.

9. The system of claim 8, wherein the second filter means is an FIR filter.

10. The system of claim 1, wherein the processing means includes second storage means for storing predetermined samples as the second stored signal.

11. A method for equalizing transmissions on forward channels of a network having at least a central node, a network bus, and a plurality of network nodes, each network node having at least a transmitter, a receiver, and a processor, the method comprising steps of:

(a) a transmitter of a predetermined network node transmitting a predetermined receiver equalization signal to the central node;

(b) the central node retransmitting the receiver equalization signal on the network to the plurality of network nodes;

(c) the receiver at each network node receiving the receiver equalization signal from the central node; and

(d) the processor adjusting the receiver based on a comparison of the received receiver equalization signal and the predetermined receiver equalization signal to compensate for transmission distortions on the network bus from the central node to the network node.

12. The method of claim 11, wherein the receiver equalization signal is a frequency-rich signal.

13. A method for equalizing transmissions on reverse channels of a network having at least a central node, a network bus, and a plurality of network nodes, each network node having at least a transmitter, a receiver, and a processor, the method comprising the steps of:

(a) the transmitter transmitting a transmitter equalization signal to the central node;

(b) the central node retransmitting the transmitter equalization signal on the network bus;

(c) the receiver associated with the transmitter receiving the transmitter equalization signal retransmitted by the central node; and

(d) the processor adjusting the transmitter based on a comparison of the transmitted and received transmitter equalization signals to compensate for distortions on the network bus from the network node to the central node.

14. The method of claim 13, wherein the transmitter equalization signal is a frequency-rich signal.

15. The method of claim 13, wherein adjusting the transmitter includes adjusting the transmitter to pre-distort transmitted signals based on the comparison.

16. A method for equalizing transmissions on forward and reverse channels of a network having at least a central node, a network bus, and a plurality of network nodes, each network node having at least a transmitter, receiver, and a processor, the method comprising steps of:

(a) a transmitter of a predetermined network node transmitting a predetermined receiver equalization signal to the central node;

(b) the central node retransmitting the receiver equalization signal on the network bus;

(c) each receiver receiving the receiver equalization signal from the central node;

(d) each network node processor adjusting its respective receiver based on a comparison of the received receiver equalization signal and the predetermined receiver equalization signal to compensate for distortions in transmissions on the network bus from the central node to the network node;

(e) for each network node, the transmitter transmitting a transmitter equalization signal to the central node;

(f) the central node retransmitting the transmitter equalization signal on the network bus;

(g) for each network node, the receiver associated with each transmitter receiving the transmitter equalization signal retransmitted by the central node; and

(h) for each network node, the processor adjusting the respective transmitter based on a comparison of the transmitted and received transmitter equalization signals.

17. The method of claim 16, wherein the receiver equalization signal is a frequency-rich signal.

18. The method of claim 16, wherein the transmitter equalization signal is a frequency-rich signal.

19. The method of claim 16, wherein adjusting the transmitter includes adjusting the transmitter to pre-distort transmitted signals based on the comparison.