Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
2001-03-12
2004-07-13
Hsu, Alpus H. (Department: 2665)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S466000, C370S474000, C398S058000, C398S074000, C725S109000, C725S119000
Reexamination Certificate
active
06763025
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to information delivery and distribution, and more particularly, to a time division multiplexing over broadband modulation method and apparatus that enables the delivery of allocated, unshared and deterministic bandwidth to subscribers in a network.
DESCRIPTION OF RELATED ART
The demand for broadband content by business and residential subscribers is continually increasing. Broadband content includes multiple types of entertainment programming, communications and data, such as broadcast television channels, video on demand, streaming video, multimedia data, internet access, voice-over-IP, etc. To meet the increasing demand, it is necessary to increase bandwidth to each subscriber and to improve quality of service. Current delivery technologies include several variations of DSL (digital subscriber line) technology, such as ADSL (asymmetrical DSL) and the like, which uses telephony technology, cable modem systems using television technology and HFC (hybrid fiber coax) distribution networks, 2-way wireless local loop (WLL), including 2-way satellite, etc. The existing legacy technology for providing broadband content is becoming increasingly inadequate to meet the demand.
DSL technology is a method of delivering data over a twisted pair of copper wires or twisted pair cables, and typically uses the Public Switched Telephone Networks (PSTN). There are several major problems with provisioning video services over the existing PSTN and twisted pair cables (network plant). The existing network plant is not uniform and most of the plant is old with poor copper conditions that cause signal loss and line noise. In fact, ADSL cannot be provisioned for a large portion of the population over the existing plant because of significant distances to the closest DSL Access Multiplexor (DSLAM) and poor conditions of the existing plants. In addition, ADSL currently has a limited downstream bandwidth, and inherently provides a very limited return bandwidth. ADSL is not adequate for many types of content originating at a subscriber destination, such as video conferencing and the like because of its bandwidth limitations and characteristics.
Cable modem systems for delivery of data services using Data-Over-Cable Service Interface Specifications (DOCSIS) utilize the television broadcast spectrum and television technology to broadcast so-called broadband data to subscribers. One problem with delivery of broadband data (video on demand, streaming video, etc.) using existing HFC networks is the limitation on available delivery spectrum. The television data delivery systems have been established to deliver data to subscribers over a television broadcast spectrum extending from approximately 15 Megahertz (MHz) to approximately 860 MHz. Delivery of analog television downstream to the subscriber occupies the spectrum between approximately 54 MHz to 550 MHz, which leaves a relatively small range of spectrum for the delivery of digital information over HFC cable modem systems. The diplex filter separating the downstream from the upstream is located within the frequency range of approximately 42 to 54 MHz in an extended sub-split frequency plan, which is common for most consumer-based HFC systems. Therefore, the two effective delivery frequency ranges using typical consumer-based HFC systems are those between approximately 15-42 MHz (upstream) and those between approximately 5 50-860 MHz (downstream).
Data-Over-Cable Service Interface Specifications (DOCSIS) is a standard that specifies the methodology for delivering data services over an HFC plant. DOCSIS defines a Cable Modem Termination System (CMTS), which is an entity used to deliver data services over an HFC network from a central distribution point. These legacy systems use a shared frequency channel to broadcast all data to every downstream subscriber. The shared channel is generally 6 MHz wide providing a total data bandwidth of approximately 27-38 megabits per second (Mbps) for digital information. The channel, however, is shared among many subscribers, so that the data rate varies dramatically depending upon the time of use and the number of subscribers simultaneously logged on. The quality of service is particularly low during popular usage time periods. An exemplary legacy system might distribute the shared channel among 4 separate nodes, each serving approximately 500 subscribers or more, so that resulting downstream data rate is often relatively low. The upstream shared channel is usually smaller, such as 3.2 MHz or less, and a “poll and grant” system is employed to identify data for upstream transmission. The resulting upstream performance is often no higher (and sometimes less) than a standard 56 Kbps modem.
It is desired to provide a system and method for distributing information via existing and future communication networks that meets the increasing demand for broadband content.
SUMMARY OF THE INVENTION
A packet switch router according to embodiments of the present invention processes downstream digital information at a point of distribution to provide dedicated bandwidth for each of a plurality of subscriber destinations in a hybrid fiber coax (HFC) network. The packet switch router includes a network interface module that terminates a network connection, a switch that forwards packetized data from the network interface module, and at least one channel module. The channel module includes a switch interface, a cell processing engine, one or more modulators, and a radio frequency (RF) transmitter network. The switch interface receives and forwards packetized data from the switch to the cell processing engine. The cell processing engine forwards the packetized data into multiple data streams, encapsulates the packetized data in each data stream into data cells, and multiplexes the data cells of each the data streams into a multiplexed stream of data cells. Each modulator is configured to modulate a corresponding multiplexed stream of data cells into an analog signal. The RF transmitter network upconverts and combines a plurality of analog signals into a combined electrical signal for transmission.
A channel module in accordance with embodiments of the present invention includes an interface that receives packetized data, a cell processing engine, a modulator, and an RF transmitter network. The cell processing engine includes a switch that forwards the packetized data into one or more data streams, an encapsulator that encapsulates the packetized data in each data stream into data cells, and a channelizer that multiplexes the data cells of each data streams into a multiplexed stream of data cells. In one embodiment, the cell processing engine includes a frame processor that decapsulates the packetized data in one format and re-assembles packets into a different format. For example, the packetized data may be re-assembled back into IP packets. The cell processing engine may further include a packet adaptation procedure (PAP) processor that frames the re-assembled packets in each data stream with a frame header including a length value indicative of the size of each packet. The encapsulator may further include a cell convergence procedure (CCP) processor that generates the data cells by segmenting framed packets and encapsulating each segment with a CCP header. The CCP header includes a pointer value indicative of the location of a next frame header in a stream of data cells. In a particular embodiment, the CCP processor adds a synchronization value in accordance with MPEG-2 to spoof an MPEG data stream. The CCP processor may be configured to pad partial segments with at least one null value to create equal-sized data cells. The CCP processor may further be configured to generate null data cells if input packetized data is not available to maintain a continuous synchronous data stream.
In more particular embodiments, the channelizer operates to organize the multiplexed stream of data cells into cell groups, where each cell group includes multiple time slots. The channelizer inserts data cells
Johnson Robert Edward Lee
Leatherbury Ryan M.
Advent Networks, Inc.
Dillon & Yudell LLP
Hsu Alpus H.
Yudell Craig J.
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