John M Ritchie

US Patent:

20030053493, Mar 20, 2003

Filed:

Sep 17, 2002

Appl. No.:

10/245054

Inventors:

Joseph Graham Mobley - Dunwoody GA, US
Jiening Ao - Suwanee GA, US
John Ritchie - Duluth GA, US
Donald Sorenson - Lawrenceville GA, US
Lamar West - Maysville GA, US

International Classification:

H04J003/02

US Classification:

370/538000

Abstract:

An architecture for providing high-speed access over frequency-division multiplexed (FDM) channels allows transmission of ethernet frames and/or other data across a cable transmission network or other form of FDM transport. The architecture involves downstream and upstream FDM multiplexing techniques to allow contemporaneous, parallel communications across a plurality of frequency channels. Also, the modulation indices of various upstream frequency channels may be different, but a plurality of upstream channels may be used to carry a single data flow generally in parallel. The upstream data flow is fragmented into blocks and formed into superframes to allow transmission over at least one upstream frequency channel. When a plurality of upstream frequency channels are utilized, the superframes facilitate the possibility of having different modulation indices on the plurality of frequency channels. The upstream frequency channels or tones generally use a smaller amount of frequency bandwidth than the amount of frequency bandwidth commonly used to carry television channels on a cable transmission network. The smaller frequency bandwidth generally allows a plurality of the smaller frequency channels to be frequency-division multiplexed into a larger frequency channel capable of carrying television channels on a cable transmission network. Smaller frequency bandwidth channels allow a more efficient allocation of bandwidth to a client device and allows more accurate control over transmission characteristics (such as but not limited to group delay) of the frequency bandwidth. The smaller frequency channels generally can each be assigned to a different client device. Thus, client devices may share one of the large frequency bandwidth channels using frequency-division multiplexing of the smaller frequency bandwidth channels.

US Patent:

55947263, Jan 14, 1997

Filed:

Mar 30, 1994

Appl. No.:

8/219848

Inventors:

Leo J. Thompson - Lilburn GA
Gregory T. Dubberly - Atlanta GA
John A. Ritchie - Duluth GA

Assignee:

Scientific-Atlanta, Inc. - Atlanta GA

International Classification:

H04J 100

US Classification:

370485

Abstract:

A broadband communications system for coupling telephony or other digital networks to a CATV network. The system transmits a multiplex of telephony signals in the forward band of the CATV network. Each forward channel is QPR modulated on a carrier and contains multiple subscriber telephony signals. The forward telephony channels are demodulated and demultiplexed by a plurality of subscriber terminals into the individual telephony signals directed to an addressed subscriber. Audio and control signals returning from the subscriber are digitized into standard telephony signals and QPSK modulated on a carrier onto the reverse band of the CATV network. The multiplicity of reverse band telephony channels are demodulated and multiplexed into a standard telephony signal which is directly interfaced to the telephony network. The reverse band modulators are frequency agile and modulate telephony signals from a subscriber in a selected one or more frequency subbands in the reverse band of the subscription network, so as to provide selectably changeable frequencies and selectably variable bandwidth in the reverse band commensurate with a selected subscriber communication feature. e. g. a single voice line, multiple voice lines, ISDN service, data communications services, security monitoring services, etc.

US Patent:

54992419, Mar 12, 1996

Filed:

Sep 17, 1993

Appl. No.:

8/123363

Inventors:

Leo J. Thompson - Lilburn GA
Gregory T. Dubberly - Atlanta GA
John A. Ritchie - Duluth GA
David M. Fellows - Beverly MA

Assignee:

Scientific-Atlanta, Inc. - Norcross GA

International Classification:

H04H 108

US Classification:

370 73

Abstract:

A broadband communications system for coupling telephony or other digital networks to a CTV network. The system includes transmitting a multiplex of telephony signals in 3 MHz channels in the forward band of the CTV network. Each 3 MHz channel is QPR modulated on a carrier and contains multiple subscriber telephony signals. The forward telephony channels are demodulated and demultiplexed by a plurality of subscriber terminals into the individual telephony signals directed to an addressed subscriber. The individually addressed telephony signal is then applied to a line card which connects the subscriber telephone equipment to the system. Audio and control signals returning from the subscriber are digitized into standard telephony signals and modulated on a carrier in 50 kHz reserved telephony channels onto the reverse band of the CTV network. The multiplicity of reverse band telephony channels are demodulated and multiplexed into a standard telephony signal which can be directly interfaced to the telephony network. In the illustrated embodiment, the CTV network has a fiber to the serving area architecture that can be used to increase the number of reverse band channels which are available to the broadband communications system.

US Patent:

57905231, Aug 4, 1998

Filed:

Jul 31, 1996

Appl. No.:

8/690628

Inventors:

John A. Ritchie - Duluth GA
Steve Idler - Bolingbrook IL
Gregory T. Dubberly - Atlanta GA

Assignee:

Scientific-Atlanta, Inc. - Norcross GA

International Classification:

H04J 116

US Classification:

370241

Abstract:

A test system for evaluating the operating state of a headend of a broadband communications network for communicating telephony signals between a telephony system and subscribers of communications services. Modulators at the headend transmit telephony signals in the forward band of the broadband communications network. The forward telephony channels are demodulated and demultiplexed by a plurality of subscriber terminals into individual telephony signals directed to an addressed subscriber. Signals returning from subscribers are digitized into standard telephony signals onto the reverse band of the broadband communications network, and demodulated by demodulators of the headend into a standard telephony signal that is interfaced to the telephony network. The test system evaluates the operating state of a selected demodulator of the headend by modulating a carrier with a predetermined data pattern to generate a upstream test signal. The upstream test signal is transmitted to the selected demodulator, which responds by outputting a detected upstream test signal.