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Apparatus and method for symbol alignment in a multi-point OFDM/DMT digital communications system

a digital communication system and multi-point technology, applied in the direction of orthogonal multiplex, multiplex communication, duplex signal operation, etc., can solve the problems of increasing the use of cable telephony system, and affecting the operation of the cable telephony system

Inactive Publication Date: 2006-02-16
MARCHOK DANIEL J +3
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009] In accordance with a further aspect of the present invention, the receivers apply a predetermined incremental phase shift to received samples corresponding to the received OFDM / DMT symbols to thereby compensate for phase shifts resulting from the cyclic prefix.

Problems solved by technology

As the number of cable telephony subscribers increases over time, the increased use will strain the limited bandwidth allocated to the cable telephony system.
It is often impractical to increase the bandwidth allocated to the cable telephony system given the competition between services for the total bandwidth available to the cable service provider.
Such systems, however, present a number of technical problems.
One such problem is the determination of how a newly added receiver is to attain symbol alignment without disrupting communications to the other receivers that are already in communication with a primary transmitter at a central site.

Method used

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  • Apparatus and method for symbol alignment in a multi-point OFDM/DMT digital communications system
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  • Apparatus and method for symbol alignment in a multi-point OFDM/DMT digital communications system

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Embodiment Construction

[0020]FIG. 1 is a block diagram of a multi-point communications system which may use a remote service unit having the improved receiver and transmitter architectures disclosed herein. As illustrated, the communications system, shown generally at 20 includes a head end unit (HE) 25 disposed at a primary site. The head end unit communicates with a plurality of remote service units (RSUs) 30 respectively disposed at a plurality of secondary sites, over a transmission medium 35 such as a coaxial cable.

[0021] The digital communications system 20 may, for example, be a cable telephony system. In such an application, the head end unit 25 is disposed at a cable television transmission facility while the remote service units 30 are disposed at individual customer locations, such as individual customer homes. The transmission medium 35 would be the new or existing transmission cable used to transmit the cable television services. The head end unit 25 in a cable telephony network is responsib...

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Abstract

A multi-point communications system that is set forth herein. The communication system comprises a head end unit disposed at a primary site and a plurality of receivers disposed at remote sites. The head end unit includes a transmitter for transmitting OFDM / DMT symbols over a predetermined number of bins across a transmission medium. The OFDM / DMT symbols are transmitted in periodically occurring formatted symbol frames. The cyclic prefix includes a predetermined periodic signal superimposed thereon. The receivers receive the OFDM / DMT symbols over a subset of the predetermined number of bins from the transmission medium and use the superimposed signals to attain symbol alignment.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] The present application is a continuation of U.S. patent application Ser. No. 09 / 912,990, filed Jul. 25, 2001 which is a continuation-in-part application of U.S. Ser. No. 08 / 700,779, filed Aug. 22, 1996 and a continuation of application Ser. No. 08 / 845,544, filed Apr. 24, 1997.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0002] Not applicable. BACKGROUND OF THE INVENTION [0003] The present invention is directed to an OFDM / DMT digital communications system. More particularly, the present invention is directed to an apparatus and method for attaining symbol alignment in a multi-point, OFDM / DMT digital communications system. [0004] Multi-point communications systems having a primary site that is coupled for communication with a plurality of secondary sites are known. One such communications system type is a cable telephony system. Cable telephony systems transmit and receive telephone call communications over the same ca...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H04J11/00H04L5/02H04L5/14H04L27/26
CPCH04L5/023H04L5/1453H04L27/2602H04L27/2662H04L27/2657
Inventor MARCHOK, DANIEL J.YOUNCE, RICHARD C.KAPOOR, SAMIRMELSA, PETER J.W.
Owner MARCHOK DANIEL J
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