Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
2000-06-20
2004-10-19
Chin, Wellington (Department: 2664)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S280000, C370S326000, C370S478000, C370S346000
Reexamination Certificate
active
06807193
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to communications and computer local area and wide area networks. More specifically, the invention relates to a modem such as a cable modem as well as a method and system for transmitting computer network data and voice data over a medium, such as a broadband medium, particularly a cable TV network.
BACKGROUND OF THE INVENTION
Many residential communities have been wired with coaxial cable for delivery of TV signals from a cable TV station. Cable television networks provide cable television services to a large number of subscribers over a large geographical area. The cable television networks typically are interconnected by cables such as coaxial cables or a Hybrid Fiber/Coaxial (“HFC”) cable system which have data rates of about 10 Mega-bits-per-second (“Mbps”) to 30+ Mbps. The Internet, a world-wide-network of interconnected computers, provides multi-media content including audio, video, graphics and text that typically requires a large bandwidth for downloading and viewing. The cable TV station is able to transmit a large number of cable TV channels through the coaxial cable to the homes connected to the coaxial cable. The cable TV cable has a large amount of bandwidth, and very often the cable TV station does not use all of the bandwidth of the cable to transmit the cable TV signals. Cable TV networks therefore often have excess or unused capacity on their cable TV cables. Cable modems, such as those provided by 3Com Corporation of Santa Clara, Calif., and others offer customers higher-speed connectivity to the Internet and other wide area Networks (WANs), an intranet, Local Area Networks (LANs) and other computer networks via the cable television network.
Cable TV companies have taken advantage of the extra capacity of their cable networks and have modified their cable systems to connect individual residential users to the Internet through their cable system. A description of a cable TV system which can also provide Internet, WAN, intranet, LAN and other computer network interconnection via the cable television network is described in the publication Data-Over-Cable-Service-Interface-Specifications (DOCSIS) which is hereby incorporated by reference.
Apart from passing network data there exists an interest in using the Internet and other computer networks to conduct real time voice conversations between two or more separate parties. These voice conversations would be handled much like telephone calls handled by the existing telephone companies. However existing telephone systems and the Internet operate very differently. Traditional telephone systems (voice and video telephony) provide a dedicated connection between two persons during a voice call. When the voice call is initiated, the dedicated connection is created, and after the voice call has been terminated, the connection is also terminated. The Internet on the other hand, divides information into packets or cells. Various computer networks exist capable of transporting variable length (VL) information, such as Internet Protocol (IP) or IEEE 802.3 frames (packets); and fixed length information such as asynchronous transfer mode (ATM) cells. These packets or cells are individually sent out onto the network, mixed with other packets or cells and then individually switched from one path to another by switches in the network until the packet reaches its final destination. A voice call over the Internet, creates a large number of packets which must be delivered very quickly and very accurately. This places a high burden on the computer network.
SUMMARY AND OBJECTS OF THE INVENTION
It is a primary object of the present invention to provide a modem, system and method to carry data units between the modem and a termination system that facilitates real time service flows that generate fixed size data packets on a periodic basis, such as voice over IP, and also allows efficient data traffic including allocation to other users connected to the termination system.
According to the invention, A modem, communications system and method are provided with a transmitter connected to a modem termination system by a medium and with a receiver connected to the modem termination system by the medium. The modem has a memory forming a transmit queue as well as an input/output supplying generated data units, including (at times) voice communications data units. The modem has a data unit controller for sending data units to the input/output from the receive queue and for transmitting data units to the modem termination system such as a cable modem termination system (CMTS). The modem requests unsolicited grant service (UGS) from the CMTS when the modem frame controller detects voice communications data units or another periodic stream, providing fixed data grants of bandwidth time slots, on a real time basis (particularly used for voice communications data units). The controller uses the unsolicited data grants for transmission to the modem termination system. Upon detecting an accumulation of data units in the receive queue, the controller asserts a queue indicator, in a transmission to the modem termination system. The Modem receives in response an occasional extra grant per interval and uses these data grants until the queue indicator is not asserted. According to another feature of the modem, system and method, upon requesting unsolicited grant service (UGS) from the CMTS, the CMTS allocates at least an extra grant to form a talk spurt grant burst in the initial response to the UGS request.
The system and method of the invention are based on the CM and CMTS and a telephone including an audio input, a packet generator and a packet output connected to the input of the CM. Data units supplied by the telephone being are sent to a transmit queue before transmission to the CMTS. Unsolicited grant service (UGS) is established, requested by the CM to the CMTS during a transmission. This provides fixed unsolicited data grants of bandwidth time slots, on a real time basis. Transmissions form the CM to the CMTS use the unsolicited data grants for data units. The CM asserts a queue Indicator, in a transmission to the CMTS upon detecting data units accumulating in the transmission queue. The CMTS allocates an occasional extra grant until the queue indicator is not asserted.
A preferred embodiment of the invention uses the data packet carrying ability of cable TV networks as described in DOCSIS to accurately and quickly transmit a voice call from a cable user to another user over a cable TV cable. However, the invention may also be applied to a wireless system with a packetizing data/audio/video device which sends packets or cells of data to a termination system via radio waves, infrared or other media.
A preferred system is based on a subscriber using a cable modem (CM) connected to a cable modem termination system (CMTS) via a cable. Other media could be used to practice the invention. The system allows for various uses ofthe entire cable bandwidth. The subscriber can have customer premises equipment (CPE) of various types (a television set may be connected to the cable but this is not required for the invention). The CPE particularly includes a voice signal packet generating device (hereinafter “telephone”) connected to the cable modem. This may be a microphone with digital signal processor (DSP) either connected to a personal computer (PC), or as a stand alone unit connected directly to the CM or connected to the CM via a LAN or via a PC. The telephone has a sound input, a CODEC (coder/decoder), to convert the analog signal to digital, and a packetizer to packetize data units based on the audio signal(or other real time signals that generate fixed size data packets on a periodic basis, e.g., a video signal). The terms “packets” and “cells” are used interchangeably in this specification and represent any data unit that is sent between the cable modem and the CMTS. That is, frames sent between the CM and the CMTS may include protocol data units (PDUs) that are packets or cells. The preferred
3COM Corporation
Chin Wellington
Fox Jamal A.
McGlew and Tuttle PC
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