Multiplex communications – Diagnostic testing – Path check
Reexamination Certificate
2000-02-23
2004-03-09
Jung, Min (Department: 2663)
Multiplex communications
Diagnostic testing
Path check
C370S255000
Reexamination Certificate
active
06704288
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a hybrid fiber/coax (HFC) access communication network and, more particularly, to an arrangement for automatically discovering and constantly updating the network topology of an HFC access communication network.
BACKGROUND OF THE INVENTION
Modern cable systems utilize a hybrid fiber/coax (HFC) architecture in which signals are distributed via a fiber optic connection to a node that converts the optical signal to an electrical signal, then distributes the signals to residences via a tree and branch coaxial cable distribution network. The distribution network comprises network elements such as coaxial cable, amplifiers, line extenders and taps. At the subscriber side, terminal equipment supports the delivery of cable services to subscribers. Cable services have evolved from video services to data and voice services, introducing at the same time new terminal equipment. The set-top box (STB) terminal equipment supports video services which include broadcast TV and interactive services such as video-on-demand (VOD) and “near” video-on-demand (NVOD).
Data and voice services are supported by cable modems and communication gateways, respectively, which also require the use of an upstream signal path. The network is provisioned as a bi-directional network by using a fiber optic return signal path from the node to the headend. A return band, typically designated at 5-42 MHz, is used to support transmissions from devices in the home (or located on the side of the home) back to the headend. Additional network elements may be placed inside the cable network to support service delivery or to monitor service quality. The cable modem is a network interface element for providing data services such as Internet access and other related services to the subscriber. A cable modem generally uses standardized communication methods based on Cable Labs' Data Over Cable System Interface Specification (DOCSIS) to access data services through the cable network. A cable modem termination system (CMTS) located at the HFC access network head end side provides an interface to the data network, as well as an interface to the cable modems. In particular, cable modems can be identified by one or more unique addresses including, but not limited to, a Media Access Control (MAC) address or an IP address.
A television set-top box supports video and data services that may be accessed through the television interface. Set-top functionality can also be extended to support telecommunications services including voice and video telephony. In a particular embodiment, an exemplary set-top box receives analog and digital signals on the downstream through the HFC cable plant, and can use a variety of communications techniques for return path communications, including telephone plant return, response to polling from the headend, or cable modem communications, including the use of DOCSIS-compliant or other cable modem technology. Set-tops are typically identified by a unique address which can be, as mentioned above, a MAC address. Another network element which can be monitored and managed is defined as a “communication gateway”, where the communication gateway is located at or near the subscriber residence and functions to support a variety of voice and data services. An exemplary communication gateway comprises a cable modem along with a microprocessor, digital signal processing (DSP) unit, and other hardware required to support IP telephony services. Along with its IP telephony services support feature, a communication gateway can also perform ingress monitoring operations. The communication gateway may be located outside the residence, typically on the side of the house, or can be inside the home in a central location, such as a basement or attic. Alternatively, the communication gateway functionality can be incorporated into a television set-top.
A telephony test point (TTP) is a monitoring element placed at a specific point inside the cable plant and used to perform certain operations autonomously, or under the control of a network management system. The basic functions of the TTP are to monitor and control ingress, discover the topology of the cable network, and identify the ingress sources. The TTP is based on a communication gateway, without the telephony interfaces. In one embodiment, the TTP is equipped with a tunable spectrum analyzer to monitor ingress.
Although these various components are capable of autonomous operation in an HFC access network, the impact of ingress at a particular network element can result in affecting the performance of other network elements, eventually resulting in system failures within portions of the network. The source and extent of ingress may be difficult to identify and, as a result, time-consuming to locate and remediate.
A need remains, therefore, for an arrangement capable of “discovering” and thereafter monitoring the network topology as elements are added to and deleted from the network in a manner whereby faults in the network can be quickly and efficiently located and corrected.
SUMMARY OF THE INVENTION
These and other needs remaining in the prior art are addressed by the present invention, which relates to a hybrid fiber/coax (HFC) access communication network and, more particularly, to an arrangement for automatically discovering and constantly updating the network topology of an HFC access communication network.
In accordance with the present invention, a plurality of telephony test points are distributed through out the HFC access network and, upon request, polled to determine the identity and location of various network elements located “downstream” of each polled telephony test point.
In one embodiment of the present invention, the telephony test points are used to receive packets transmitted by terminal equipment and detect the logical address associated with each piece of such equipment. The logical address information can then be forwarded to a topology manager at the head end of the access network, where the topology manager uses the information received from all of the telephony test points to build a logical network using the address information.
In an alternative embodiment, a directed discovery method is controlled by the head end topology manager, which instructs the telephony test points to “discover” network elements by polling the elements on a vacant channel in the TDMA communication system.
Other and further embodiments of the present invention will become apparent during the course of the following discussion and by reference to the accompanying drawings.
REFERENCES:
patent: 6272150 (2001-08-01), Hrastar et al.
patent: 6400863 (2002-06-01), Weinstock et al.
patent: 6452925 (2002-09-01), Sistanizadeh et al.
patent: 6484317 (2002-11-01), Wright
patent: 6570880 (2003-05-01), Coden
Dziekan Richard R.
Lee Nicholas D.
Sylla M. Lamine
Weinstock Jonathan A.
Coker Caroline
General Instrument Corporation
Jung Min
Koba Wendy
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