KR20030032048A - Provisioning of cable modems with transmission frequency information - Google Patents

Abstract

The present invention relates to a system for providing a cable modem 205 having frequency information for communicating with the CMTS 120 of a cable television facility. In a first embodiment, a virtual channel map of a programming service (eg, a television program) is tested (150, 160) to determine which carrier frequency is not used. This unused frequency is used to form a table of available CMTS frequencies that are sent to the cable modem 205. At this time, the modem should only search a subset of all frequencies to locate the one with the CMTS identification. On the other hand, the modem 205 can be directly informed of the CMTS frequency, so that searching is not required. In another embodiment, multiple CMTSs are used in the signal repeater 300, and the traffic monitor 310 dynamically adjusts the frequencies used by the modem for upstream transmissions to balance the load on the CMTSs.

Description

PROVISIONING OF CABLE MODEMS WITH TRANSMISSION FREQUENCY INFORMATION

Cable modems are devices that allow a personal computer (PC) to transmit and receive data over a cable television network, typically at a data rate that significantly exceeds the telephone modem. In addition to faster data rates, cable modems provide a continuous connection to avoid the need for a telephone line connection.

Moreover, the cable modem may be external to the set top box (eg terminal or integrated receiver-decoder) or PC or integrated together. Cable modems are becoming more and more popular as users can access the Internet at relatively high speeds. An internet browser running on a standalone PC or TV based device may be used.

Typically, the cable modem is attached to a standard 10Base-Tthernet card in a computer.

Moreover, in a user's home or office, various cable modems are connected to a cable TV company coaxial cable or a hybrid fiber coax (HFC) to communicate with the CMTS at a local cable TV company (signal repeater). The cable modem may receive data from the CMTS and transmit data to the CMTS. Moreover, larger cable systems may employ multiple CMTS to handle large amounts of cable modem traffic.

CMTS is typically connected to the Internet using a T1 line (1.544 Mbps) or faster.

DOCSIS (Data Over Cable Service Interface Specification) (and related Euro DOCSIS) has become the primary standard for cable modems. According to this standard, using video data standards such as time division multiplexing (TDM) and MPEG, data is transmitted downstream from the CMTS to the cable modem. Depending on the 64 or 256 Quadrature Amplitude Modulation (QAM) signal, a spectrum of 42-850 MHz is used. For upstream transmission, from the cable modem to the CMTS, time division multiple access is used in the spectrum of 5-42 MHz and in Quadrature Phase-Shift Keying (QPSK) or 16-QAM signals.

Thus, the cable modem must determine the carrier frequency or frequencies at which one or more CMTS in the signal repeater is used to transmit downstream data. This process must be brought about, for example, when a cable modem is installed in the user's home. Typically, the cable modem searches through the frequency range of 80-860 MHz in the trial and error process to identify the signal from the CMTS from which the modem will receive data. However, while the cable modem is not available, this discovery procedure may take more time and may take several minutes.

Accordingly, it is desirable to provide a system for quickly providing a cable modem with carrier frequency information used by the CMTS to transmit data to the cable modem.

The system provides a reduced set of frequencies for the cable modem to search for the CMTS identification signal.

On the other hand, the system must inform the cable modem of the carrier frequency used, for example, by using a CMTS that uses messages outside the band.

It would be further desirable to provide a system that dynamically changes the CMTS (of a multi-CMTS signal repeater) to route upstream cable modem traffic to lightly loaded CMTS to improve system response.

The system is compatible with DOCSIS and other cable modem standards.

The present invention provides a system with these and other advantages.

The present invention relates to a cable modem used in a cable television facility so that a user can access a computer network such as the Internet, and a cable modem termination system (CMTS) used in a headend of a cable television. will be.

1 is a signal repeater for providing a cable modem using a map by directly specifying an available CMTS transmission frequency or frequency in accordance with the present invention;

2 illustrates an apparatus for receiving CMTS transmission frequency information according to the present invention;

3 is a diagram illustrating a signal repeater for dynamically balancing upstream cable modem traffic load between multiple CMTS in accordance with the present invention.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and an object thereof is to provide a cable modem used in a cable television facility and a cable modem termination system (CMTS) so that a user can access a computer network such as the Internet.

The present invention provides a virtual channel table / map (VCM / VCT; virtual) that provides information about video and data channels typically configured on a cable facility (e.g., channel name, frequency, channel type, modulation mode) for the cable modem space. channel table / map). A new virtual channel type is added that specifies the cable modem type.

The operator creates a virtual channel table by including the cable modem type, the source name for the CMTS, and the channel for the cable modem path that identifies the frequency. Upon initialization, the cable modem code queries the virtual channel table for the channel type of the "cable modem" and specifies the source name if possible. The query returns the frequency used by the cable modem to communicate with the CMTS.

If the cable modem channel is changed, then the existing virtual channel table update mechanism is adopted so that the cable modem software can receive notification of the change and update itself as required.

By using the virtual channel table configuration, the cable modem can react to asynchronous changes in the CMTS frequency through standard update mechanisms.

In a first embodiment, the cable modem is provided with a table of available CMTS frequencies to reduce the required number of carrier frequencies for the search. This table is obtained by determining which frequency is not used in the virtual channel table for the programming service.

In a second embodiment, the cable modem directly announces the frequency used to receive data from a particular frequency or CMTS.

In a third embodiment, the load balancing of multiple CMTSs in a signal repeater monitors upstream traffic at each CMTS and dynamically monitors the frequencies monitored by each CMTS according to shift traffic for upstream or less loaded CMTS. It is achieved by making a change.

Corresponding methods and apparatus exist.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

TECHNICAL FIELD The present invention relates to a cable modem used in a cable television facility and to a CMTS so that a user can access a computer network such as the Internet.

1 is a diagram illustrating a signal repeater for providing a cable modem using a map by directly specifying an available CMTS transmission frequency or frequency in accordance with the present invention.

Signal repeater 100 (headend) includes an interface 110 for transmitting data to and receiving data from a computer network, such as the Internet 115. For example, the received data may include web pages, e-mails, and the like. The transmitted data may include a request for a web page, such as, for example, a Uniform Resource Locator (URL).

Although one or more may be provided, the CMTS 120 is shown by way of example. Modulator / demodulator bank 130 modulates data transmitted from CMTS to downstream cable modem at carrier frequency f _downstream and typically demodulates data received from downstream cable modem at another carrier frequency f _upstream . Is provided for.

Modulator / demodulator bank 130 includes a modulator for modulating programming service data at a number of different carrier frequencies. This data is shown to be provided by the program service processing function 140. For example, the processing may include transcoding for the received compressed bitstream, or encoding for uncompressed source code.

The virtual channel map decode function 150 decodes the virtual channel map data from a received programming service signal, for example, which may be provided according to the MPEG video standard. A virtual channel map or table is a data structure that provides information related to video and data services (channels) configured on a cable television facility.

An example of a simple virtual channel map is shown in Table 1.

Table 1-Virtual Channel Map

Channel name Carrier frequency Channel type Modulation mode HBO f1 satellite QAM Available f2 ABC f3 satellite QAM Showtime f4 satellite QAM Available f5 NBC f6 satellite QAM Available f7 CNN f8 satellite QAM ESPN f9 satellite QAM

The CMTS frequency function unit 16 includes a table forming function unit 162 for forming a table of usable CMTS frequencies from the virtual channel map, or a frequency specifying function unit 162 for directly specifying a CMTS frequency to be used. do. For example, the functional unit 162 may form the usable frequency table shown in Table 2 from the example of the virtual channel map of Table 1.

Table 2-Available Frequency Table

frequency f2 f5 f7

The usable frequency table represents the downstream carrier frequencies that may be used as much as possible by one or more CMTS in the signal repeater. This information is provided to the modulator / demodulator bank 130 for communication over the cable television facility 170 for modulating at any available modulation carrier frequency and for one or more cable modems.

In addition, available frequency information is provided from the functional unit 162 to the CMTS 120 to enable the CMTS to select a frequency for transmitting corresponding data, such as Internet data, for the cable modem.

The cable modem uses the received usable frequency table to retrieve the corresponding carrier frequency to locate the one used by the CMTS. The frequency of the CMTS can typically be located by means of a predefined CMTS identification signal which can basically be agreed upon according to the signal sequence. Usefully, since the number of available frequencies is typically a small subset of the total number of frequencies in the virtual channel map, the cable modem may be able to search the CMTS frequencies faster if it has to search all frequencies in the virtual channel map until a CMTS identification signal is found. It can be placed.

Functional unit 164, on the other hand, modulators / demodulator banks for modulation across a predetermined usable modulation carrier frequency (such as frequencies outside the band) and for communication across cable television facility 170 for one or more cable modems. It can be used to specify the CMTS frequency that is encoded and transmitted for 130. In particular, this frequency data can be transmitted to all cable modems in the network when only one CMTS is used.

If multiple CMTSs are used, frequency data may be targeted for transmission to a specified cable modem or group of modems using the identifier of the modem or set-top. For example, well-known set-top addressing techniques can be used for this purpose. The function unit 164 may include a memory for storing the frequency allocation of the modem. The specified frequency information may be provided from functional unit 164 to CMTS 120 such that the frequency instructs the CMTS to be used to transmit the data to the cable modem.

According to this embodiment, the cable modem uses the received frequency information to immediately locate the carrier frequency used by the CMTS. Usefully, this avoids the need for a modem to "hunt" by testing each frequency in the trial and error process until a CMTS identification signal is found.

2 is a diagram illustrating an apparatus for receiving CMTS transmission frequency information according to the present invention.

Device 200 may be configured in a variety of ways. For example, a single device may include a cable modem portion 205, a video / audio receiver portion 260, and a PC portion 265. Alternatively, these parts may be provided separately to the device or may be combined in other ways. For example, the cable modem section 205 and the video / audio receiver section 260 may be combined while the PC section may remain separate. The output device 280 may be combined with other units or may be separated.

For example, the cable modem 205 demodulates data received from the CMTS via a cable facility at the downstream carrier frequency, and modulates / demodulates the function 210 to modulate data transmitting upstream to the CMTS at the upstream carrier frequency. ).

For example, the browser 270 of the PC unit 265 sends a request to the modulation / demodulation function unit 210 via the interface 25, modulates the request, and transmits the request to the CMTS. In turn, the CMTS can send the request to the Internet.

In one embodiment, the modulation / demodulation function 210 demodulates the table of usable frequencies provided as described in connection with the function 162 of FIG. The table is recovered (eg, decoded) and conditionally stored in the functional unit 220. Preferably, as the functional unit 220 uses a nonvolatile memory, the stored information may be restored whenever power is applied to the device 200. Moreover, the available frequencies or specified frequency tables may be provided to the apparatus 200 via the modulation / demodulation function 210 used for CMTS data, or the demodulation function 262 used for programming service data. Note that you can.

A frequency table now available is used by the CMTS identification location function 240 to locate the CMTS identification by searching the carrier frequency in the table. To accomplish this, function 240 causes demodulator 201 (function) to test each carrier frequency in the table. When the CMTS identification signal is located, the functional unit 240 records the corresponding carrier frequency and stores it in the functional unit 220 (memory). The demodulator 210 (function unit) then remains tuned to the CMTS carrier frequency where it is detected to continuously receive data from the CMTS, such as a web page requested from the Internet.

As noted above, this embodiment allows the modem portion 205 to locate the CMTS carrier frequency relatively quickly without testing all possible frequencies.

In the conditional embodiment, the functional unit 210 demodulates the specified frequency information provided as discussed in connection with the functional unit 164 of FIG. 1. The specified frequency information is recovered (eg, decoded) and conditionally stored in the functional unit 220. The specified frequency information is used by the demodulator 210 (function unit) to immediately tune to the CMTS carrier frequency designated to receive data from the CMTS.

As noted above, this embodiment allows the modem unit 205 to immediately locate the CMTS carrier frequency. The drate-off according to this embodiment is for a signal repeater employing multiple CMTS, which CMTS are sent to which cable modem or group of modems, and at the frequencies used by a given CMTS or modem associated with a given CMTS. And possible needs for the purpose of transmitting the specified frequency information for a particular modem or group of modems, for example, based on some form of modem or group identifier.

Assuming there are no new frequency tables or specified frequencies received from the signal repeater, the demodulator 210 (function unit) can automatically return to the identified CMTS carrier frequency each time power is applied. When a new CMTS carrier frequency table is received from the signal repeater, if the associated carrier frequency changes, the CMTS identification signal is re-identified for viewing. Otherwise, the new specified frequency is tuned.

The video / audio receiver portion 260 is shown to be used with a cable modem. However, this is not required. In some cases, data from the Internet or other network may be accessed by cable modem 205 and displayed on output device 280 associated with a programming service (eg, a television program). In other cases, a user can use a cable modem without accessing programming services. The video / audio receiver unit 260 receives a programming service from a signal repeater and demodulates it in a demodulator 262 (demodulation function unit). Subsequently, data is decoded in the decode / processing section 264, and other necessary processing is performed to provide a signal to an output device 280 such as a television.

Note that browser 270 is also shown to provide a signal to output device 280. Conditionally, or additionally, browser 270 may have its own designated output, such as a PC monitor. However, the configuration shown is expected to be more common with the integration of television and internet systems.

3 is a diagram illustrating a signal repeater for dynamically balancing upstream cable modem traffic load between multiple CMTS in accordance with the present invention.

The same reference numerals correspond to each other in the drawings.

Larger cable television networks have multiple instances, such as CMTS (120, ---, 122), with n Internet interfaces (110, ---, 112) to handle larger amounts of cable modem and Internet traffic. Use CMTS. For example, each CMTS may be able to establish its own connection to the Internet, for example via a corresponding T1 line.

Here, traffic monitor 310 monitors the amount of upstream cable modem received at each CMTS 120,-,-122. For example, traffic monitor 310 monitors the pure amount of data received, for example using a bit counter, otherwise some other measure of traffic may be used, such as the number of messages received by a given CMTS, and The amount or portion of time by the CMTS is a congested received upstream message or the like.

To balance the load between the CMTSs, traffic monitor 310 directs the CMTS to receive upstream cable modem data at different frequencies (eg, from other demodulators of bank 130). The traffic monitor may also be able to communicate with the enabled / specified frequency function 320 to cause the cable modem to use a different upstream frequency. This can be achieved directly, for example by assigning a modem to the desired frequency.

It should be noted that the cable modem may transmit its upstream data to another CMTS rather than from the modem receiving the downstream data to the CMTS.

The enabled / specified frequency function 320 may, for example, function of the CMTS frequency function 160 of FIG. 1 to inform the cable modem of the available or assigned downstream frequencies with the CMTS 120, ---, 122. Can be integrated.

Accordingly, signal repeater 300 may conditionally cable to change the carrier frequency for upstream communication, such as DOSIS data, and to enable cabling to dynamically route upstream traffic for relatively lightly loaded CMTS. By notifying the modem, system response is improved.

Accordingly, it can be seen that the present invention provides a system for enabling a cable modem to efficiently locate downstream frequencies for recovering data from a CMTS. The cable modem is provided with a table of available CMTS frequencies to reduce the required number of carrier frequencies for searching to locate the CMTS identification signal, or the modem may directly select specific frequencies or frequencies to avoid the need for searching. You will be notified.

In addition, load balancing of multiple CMTS in a signal repeater can be achieved by monitoring upstream traffic at each CMTS and dynamically changing the upstream frequency monitored by each CMTS as the traffic shifts for the less loaded CMTS. Can be.

In addition, this invention is not limited to the above-mentioned embodiment, Of course, it can change and implement variously within the range which does not deviate from the summary of this invention.

Claims (20)

A method for using a signal repeater in a cable television network to provide frequency information to at least one cable modem in a network to allow communication with the signal repeater. Receiving channel map information at a signal repeater indicating an unusable carrier frequency used for communicating a programming service and at least one available carrier frequency not used for communicating a programming service; Providing a signal from the signal repeater to the at least one cable modem to inform the cable modem of at least one available carrier frequency; And configuring at least one cable modem termination system at the signal repeater to use at least one available carrier frequency to provide data to at least one cable modem. The method of claim 1, wherein the at least one cable modem termination system is configured to transmit an identification signal on at least one available carrier frequency for detection by the at least one cable modem. The method of claim 1, wherein the signal specifies that the at least one cable modem uses at least one available carrier frequency for receiving data from the at least one cable modem termination system. The method of claim 1, wherein the signal specifies that the at least one cable modem uses at least one available carrier frequency for providing data to the at least one cable modem termination system. 2. The method of claim 1, wherein the channel map information received at the signal repeater indicates a number of available carrier frequencies that are not used for communicating programming services. 6. The system of claim 5, wherein at least one cable modem provides the plurality of usable carrier frequencies provided therein to locate a particular frequency used by at least one cable modem termination system to provide data to at least one cable modem. And adapted to search. 7. The method of claim 6, wherein at least one cable modem locates the particular frequency by detecting a cable modem termination system-identification carrier. A signal repeater device in a cable television network for providing frequency information to at least one cable modem in a network to allow communication with a signal repeater. Means for receiving channel map information at a signal repeater indicating an unusable carrier frequency used for communicating a programming service and at least one available carrier frequency not used for communicating a programming service; Means for providing a signal from the signal repeater to the at least one cable modem to inform the cable modem of at least one available carrier frequency; And means for configuring at least one cable modem termination system at the signal repeater to use at least one available carrier frequency to provide data to the at least one cable modem. A method for enabling at least one cable modem to provide itself with frequency information of a cable television network to allow communication with a signal repeater of a network, the method comprising: Receiving a signal from a signal repeater that identifies a number of available carrier frequencies that are not used to communicate a programming service; Retrieving the plurality of available carrier frequencies provided thereon to locate a particular frequency used by at least one cable modem termination system in the signal repeater to provide data to the cable modem. Way. 10. The system of claim 9, wherein the usable carrier frequency is extracted from received channel map information at a signal repeater, the channel map information being used to communicate a programming service, and the usable carrier frequency. Method comprising a. 10. The method of claim 9, wherein the cable modem is adapted to use a particular frequency to provide data to the cable modem termination system. 10. The method of claim 9, wherein a cable modem locates the specific frequency by detecting an identification signal of the cable modem termination system. A cable modem device for providing frequency information of a cable television network to itself to allow communication with a signal repeater of a network, Means for receiving a signal from a signal repeater that establishes a number of available carrier frequencies that are not used to communicate a programming service; And means for retrieving said plurality of usable carrier frequencies provided thereon to locate a particular frequency used by at least one cable modem termination system in the signal repeater for providing data to a cable modem. Device. A method for enabling at least one cable modem to provide itself with frequency information of a cable television network to allow communication with a signal repeater of a network, the method comprising: Receiving a signal from a signal repeater specifying at least one available carrier frequency for receiving data from at least one cable modem termination system in the signal repeater; At least one available carrier frequency is not used to communicate a programming service. 15. The system of claim 14, wherein the at least one available carrier frequency is extracted from received channel map information at a signal repeater, the channel map information being used to communicate a programming service, and the at least one And both carrier frequencies available. A cable modem device for providing frequency information of a cable television network to itself to allow communication with a signal repeater of a network, Means for receiving a signal from the signal repeater specifying at least one available carrier frequency for receiving data from at least one cable modem termination system in the signal repeater; At least one available carrier frequency is not used to communicate a programming service. A method for using a signal repeater in a cable television network to receive upstream data from a plurality of cable modems in a network, the method comprising: Providing a plurality of cable modem termination systems to the signal relay for receiving upstream data, each cable modem termination system being assigned to at least one associated upstream carrier frequency to receive a portion of the upstream; Monitoring the amount of upstream data received by each cable modem end system; Balancing the load of upstream data between cable modem end systems in response to said monitoring step. 18. The method of claim 17, wherein said balancing comprises dynamically varying at least one upstream carrier frequency to which at least one cable modem termination system is assigned. 18. The method of claim 17, wherein the balancing step comprises communicating data for at least one cable modem to use a different upstream carrier frequency. A signal repeater device in a cable television network for receiving upstream data from a plurality of cable modems in a network, wherein A plurality of cable modem termination systems for receiving upstream data, assigned to at least one associated upstream carrier frequency for receiving a portion of the upstream; Means for monitoring the amount of upstream data received by each cable modem termination system; Means for balancing the load of upstream data between cable modem end systems in response to said monitoring means.