JP2007006386A - Cable modem apparatus, repeating apparatus, communication system, and frequency setting apparatus in cable modem apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cable modem apparatus or the like to improve a delay of uplink data transmission. <P>SOLUTION: Uplink transmission condition is determined while the data is transmitted at a prescribed frequency in an uplink to a CMTS 10 which is a communication partner. When it is determined that the communication condition is not good, a UCC-KICK frame is transmitted so as to notice a UCC-REQ frame to the CMTS 10. The CMTS 10 transmits the UCC-REQ frame to a CM 20 which has transmitted the UCC-KICK, by receiving the UCC-KICK if other channel is available. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cable modem device, and more particularly to a cable modem device having an uplink frequency changing means and a frequency setting method in the same.

  In recent years, the use of the Internet has expanded without distinction between individuals and companies (hereinafter sometimes collectively referred to as users). Along with this, the Internet connection method (access method) is diversified by using not only a normal telephone line but also a satellite communication line and a CATV (Cable Television) system (CATV station and related equipment). .

  In particular, a method using a CATV system (CATV Internet) is attracting attention as a promising method because it can realize an Internet environment that can be always connected at high speed. The CATV Internet has a configuration in which a CATV station (center station) and a user are connected by a cable (coaxial cable), and the CATV station and the Internet are connected.

In other words, the user accesses the Internet through a CATV station that also serves as an ISP (Internet Service Provider).

  A schematic configuration for realizing the CATV Internet is provided on the user side with a kind of relay device (having a bridge or router function) called CMTS (Cable Modem Termination System) or headend modem (HM) on the CATV station side. A cable modem (CM) is connected by a cable. A personal computer (PC) operated by a user is connected to the cable modem. On the user side, when a television set (TV) that receives CATV broadcasts is also connected, the TV and CM are normally connected in parallel via a distributor.

  Communication between the CMTS on the CATV station side and the CM on the user side consists of a downlink (downstream) transmitted to the user side and an uplink (upstream) in the reverse direction. Normally, a downlink mainly composed of homepage download (such as WWW browser processing) from the Internet has a higher transmission speed than the uplink. For the frequency band, for example, a range of 90 to 857 MHz is used for the downlink and 10 to 55 MHz is used for the uplink.

  By the way, a plurality of CMs are connected to one uplink, and simultaneous access must be realized. For this reason, the uplink is divided into several channels, and the CM performs data transmission using the channels. However, when a large number of CMs are connected, the probability that the uplink band cannot be allocated immediately on the CMTS side increases, and as a result, problems such as data transmission delay occur in the uplink.

For such a problem, a transmission method that supports two transmission schemes simultaneously for one physical uplink channel has been proposed (see, for example, Patent Document 1).
JP 2001-44956 (Page 15, FIG. 1)

  However, if the technique of Patent Document 1 described above is directly applied to the CM, two transmission methods are supported simultaneously, and the entire apparatus becomes complicated.

  Therefore, the present invention has been made to solve the above-described problem, and when a data transmission delay occurs in the uplink, a request is made to notify the frequency change information of the uplink from the CM side to the CMTS side. It is an object of the present invention to provide a cable modem device and a frequency setting method in the device that can improve the delay of uplink data transmission.

  In order to achieve the above object, the cable modem device of the present invention determines whether or not the uplink transmission state is good when uplink data is transmitted to a communication partner device at a predetermined frequency. A transmission state determination unit that determines the transmission frequency, and a notification requesting the communication partner device to notify the frequency change information of the uplink when the transmission state determination unit determines that the transmission state is not good. When the notification is received by the notification requesting unit, the requesting unit includes a channel changing unit that changes the frequency to the uplink frequency indicated in the notification.

  In addition, the relay device according to the present invention has a transmission means capable of uplink data transmission with a plurality of cable modem devices, and when the cable modem device is requested to notify the frequency change information of the uplink. Change determination means for determining whether or not the change of the frequency is possible, and when the change determination means determines that the change of the frequency is possible, information on the frequency change of the uplink is requested for the notification. And a change information notifying means for notifying the cable modem device that has performed.

  Further, the communication system of the present invention is a communication system having a relay device and a cable modem device, wherein the relay device includes a plurality of cable modem devices and transmission means capable of uplink data transmission, and the cable modem device from the cable modem device. When a notification of uplink frequency change information is requested, it is determined whether or not the frequency can be changed, and the change determining means determines that the frequency can be changed. A change information notifying unit for notifying the cable modem apparatus that has requested the notification of information on the frequency change of the uplink, and the cable modem apparatus is configured to communicate with a communication partner apparatus at a predetermined frequency. Transmission state determination means for determining whether or not the uplink transmission state is good and the transmission state determination means when transmitting uplink data If it is determined that the transmission state is not good, the notification is received by the notification request means for requesting notification of the uplink frequency change information to the communication partner apparatus, and the notification request means. In this case, it has a channel changing means for changing to the uplink frequency indicated in the notification.

  Further, according to the frequency setting method of the cable modem device of the present invention, when uplink data is transmitted to a communication partner device at a predetermined frequency, it is determined whether or not the uplink transmission state is good. And a notification requesting step for requesting the communication partner apparatus to notify the frequency change information of the uplink when it is determined that the transmission condition is not good. And a channel change step of changing to the uplink frequency indicated in the notification when the notification is received in the notification requesting step.

  The delay in uplink data transmission can be improved.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a system for constructing a CATV Internet according to this embodiment.

  In the present embodiment, as shown in FIG. 1, the system 1 on the CATV station side and the system 2 on the user side are also referred to as coaxial cables (also referred to as “RF cables”, hereinafter simply referred to as “cables”) 3. A connected system.

  The CATV station system 1 includes a CMTS 10 and a server 12 connected to a LAN (Local Area Network) cable 11. The server 12 realizes an ISP (Internet Service Provider) function for managing data communication between the users 2 via the Internet 30 and the CMTS 10 connected via the LAN cable 11. That is, the server 12 plays the role of at least a DHCP (Dynamic Host Configuration Protocol) server, a TFTP (Trivial File Transfer Protocol) server, and a TOD (Time of Day) server.

  As described above, the CMTS 10 is a kind of relay device also called a head-end modem (HM), and has functions of a bridge and a router.

  The system 2 on the user side is connected to the CM 20 via a cable modem (CM) 20 connected to the CMTS 10 on the CATV station side via a cable 3 and a home LAN cable (hereinafter also referred to as “LAN cable”) 22. A personal computer (PC) 21 connected thereto;

  Further, in the user-side system 2, a plurality of CMs 20 (and PCs 21) can be connected to the CMTS 10. In FIG. 1, the user-side system 2 shows two CMs (CM20a, CM20b) and two PCs (PC21a, PC21b).

  Note that, as the user-side system 2, a television device (TV) that is connected to the cable 3 and receives a CATV broadcast, a distributor for distributing signals to the CM 20, and the like are omitted.

  Next, the configuration of the cable modem will be described with reference to FIG. FIG. 2 is a block diagram showing a main part of the cable modem (CM).

  As shown in FIG. 2, the CM 20 of this embodiment includes an RF interface 200, a flash memory 201, a main memory 202, a CPU (Central Processing Unit) 203, and a LAN interface 204. Each element is connected by a bus B.

  The RF interface 200 has a function of transmitting / receiving a data signal (analog signal) transmitted through the cable 3, an A / D conversion function of converting the received data signal into a digital signal, and a data signal to be transmitted as an analog signal. It has a D / A conversion function for conversion. Here, the RF interface 200 receives a UCC-REQ frame, which will be described later, from the CMTS 10, so that various parameters are set according to frequency information instructed by the CPU 203 and the channel is changed to a designated frequency.

  The flash memory 201 stores a program necessary for the operation of the CPU 203.

  The main memory 202 is accessed by the CPU 203 and holds various data used while the CM 20 is executing.

  The CPU 203 controls the entire CM 20 device. In particular, in the present embodiment, when uplink data is transmitted to the CMTS 10 at a predetermined frequency, it is determined whether or not the uplink transmission state is good. The CMTS 10 is requested to notify uplink frequency change information (UCC-REQ) (UCC-KICK).

  The details of the part related to frequency change (channel change) such as UCC-REQ and UCC-KICK will be described later.

  The LAN interface 204 is an interface that connects the CM 20 and the PC 21 via the LAN cable 22.

  Next, an outline of channel change between CM and CMTS will be described with reference to FIG. FIG. 3 is a diagram showing an outline of channel change between the CM and the CMTS.

  In FIG. 3, the CMTS 10 is assumed to have two CMs (CM 20a, CM 20b) connected via the coaxial cable 3, and both the CM 20a and the CM 20b are transmitted to one channel (US # 1) in the uplink. It is assumed that PDU which is data is transmitted (state A).

  The present invention transits from the state A to the state B through the steps of (1) UCC-KICK, (2) UCC-REQ, and (3) UCC-RSP. That is, the CM 20a changes the frequency (channel change) to another channel (US # 2).

  Here, the UCC-KICK is a frame that the CM 20 transmits to the CMTS 10, and is not a frame that conforms to the existing DOCSIS (Data Over Cable Service Specifications) such as UCC-REQ and UCC-RSP. This is a newly provided frame. That is, when the CM 20 transmits data on the uplink to the CMTS 10 that is a communication partner at a predetermined frequency, it is determined whether the uplink transmission state is good, and the transmission state is not good. If it is determined, it is a frame that requests the CMTS 10 to notify the UCC-REQ. A method for determining whether the uplink transmission state is good will be described later.

  Here, the UCC-REQ is a DOCSIS-compliant frame transmitted from the CMTS 10 to the CM 20, and is a frame for notifying information on uplink frequency change. In the case of DOCSIS compliance, the UCC-REQ is notified to the CM 20 regardless of the CM 20 only by the determination of the CMTS 10 side. However, in this embodiment, the CMTS 10 receives the UCC-KICK from the CM 20 side. In addition, it has a function of notifying the CM 20 of UCC-REQ.

  The UCC-RSP is a DOCSIS-compliant frame transmitted from the CM 20 to the CMTS 10, receives a UCC-REQ frame from the CMTS 10 side, and notifies that the channel change to the frequency designated on the CM 20 side is completed. is there.

(Processing on the CM20 side)
Next, the processing in the CM 20 accompanying the channel change will be described with reference to FIG. FIG. 4 is a flowchart showing processing on the CM 20 side according to the embodiment of the present invention. This flowchart is a case where communication between the CM 20 and the CMTS 10 has already been established, and the CMTS 10 has established communication with the CM 20a and CM 20b as shown in FIG. It is described assuming state A). In the present embodiment, since the CM 20a changes from the state A to the state B in accordance with FIG. 3, the operation of the CM 20 in FIG. 4 means the operation of the CM 20a shown in FIG.

  First, the CM 20 initializes a pending number N and a polling time T, which will be described later (step S201).

  Next, the CM 20 starts measuring the polling time T (step S202).

  Next, the CM 20 determines whether or not the own device is in a pending state (step S203). Here, the pending state means a case where a band of “0” is allocated in the frequency allocation from the CMTS 10.

  That is, when a plurality of CMs 20 are connected, data is transmitted to the uplink in accordance with DCOSIS in the following procedure. First, a request message is transmitted from the CM 20 to the CMTS 10 in order to request a necessary uplink band (slot). When the CMTS 10 receives a request message from the CM 20, the CMTS 10 performs a procedure of allocating a band in the MAP message.

  However, if it is impossible to immediately allocate bandwidth in this allocation, “0” is allocated. The state assigned “0” is the pending state.

  Therefore, when it is determined that the CM 20 is not in the pending state (No in step S203), the processing of the CM 20 is terminated because the transmission state is good.

  On the other hand, when it is determined that the CM 20 is in the pending state (Yes in step S203), the CM 20 increases the number of pending times N by one (step S204).

  Next, the CM 20 determines whether or not a polling time T that is a time for counting the pending state exceeds a threshold value α that is a predetermined time stored in the CM 20 in advance (step S205).

  As a result, when the CM 20 determines that the polling time T does not exceed the threshold value α (No in Step S205), the CM 20 returns to Step S203 and determines whether or not it is in the pending state.

  On the other hand, if the CM 20 determines that the polling time T has exceeded the threshold value α (Yes in step S205), then the CM 20 has determined whether the pending number N has exceeded the threshold value β, which is a predetermined number stored in the CM 20. It is determined whether or not (step S206).

  As a result, when the CM 20 determines that the pending count N does not exceed the threshold value β (No in step S206), the CM 20 ends the processing with a good transmission state.

  On the other hand, when the CM 20 determines that the pending number N has exceeded the threshold β (Yes in step S206), the CM 20 determines that the transmission state is not good and transmits a UCC-REQ transmission request (UCC-KICK request) to the CMTS 10. Transmission) is performed (step S207).

  Next, the CM 20 measures a UCC-REQ waiting time WT, which is a waiting time for receiving the UCC-REQ from the CMTS 10 side (step S208).

  Next, the CM 20 determines whether or not a UCC-REQ is received from the CMTS 10 (Step S209).

  As a result, when the CM 20 has not received the UCC-REQ (No in step S209), the UCC-REQ waiting time WT measured next by the CM 20 is a predetermined time stored in the CM 20. It is determined whether or not the threshold value γ is exceeded (step S211).

  As a result, when the UCC-REQ waiting time WT does not exceed the threshold γ (No in step S211), the process returns to step S208, and the measurement of the UCC-REQ waiting time WT is continued.

  On the other hand, when the UCC-REQ waiting time WT exceeds the threshold γ (Yes in step S211), the process returns to step S201, and the polling time T of the pending count N is initialized.

  On the other hand, when the CM 20 receives the UCC-REQ in Step S209 (Yes in Step S209), the UCC process is performed according to the DOCSIS rules (Step S210).

  That is, when the CM 20 receives a UCC-REQ frame from the CMTS 10 side due to the transmission of the UCC-KICK, the CM 20 changes the channel to the frequency instructed by the CMTS 10, and the processing is completed after this processing is completed. The UCC-RSP frame that is the frame shown is transmitted.

(Processing on the CMTS10 side)
Next, processing in the CMTS 10 accompanying the channel change will be described with reference to FIG. FIG. 5 is a flowchart showing processing on the CMTS 10 side according to the embodiment of the present invention. This flowchart is a case where communication between the CM 20 and the CMTS 10 has already been established, as in FIG. 4. The CMTS 10 can communicate with the CM 20a and the CM 20b as shown in FIG. 3, for example. It is described assuming an established state (state A). Also, the CMTS 10 in this flowchart is based on the premise that the CMTS supports a UCC-KICK frame.

  First, the CMTS 10 receives the UCC-KICK frame and starts subsequent processing (step S101).

  That is, when the UCC-KICK has not been received (No in Step S101), the processes after Step S102 are not performed until the UCC-KICK is received.

  On the other hand, when the CMTS 10 receives the UCC-KICK (Yes in step S101), it is possible to change the CM 20 that transmitted the UCC-KICK (in this case, the CM 20a) to another uplink channel. Whether or not (step S102).

  As a result, when it is determined that it is not possible to change to another channel (No in step S102), the received UCC-KICK is discarded (step S105), and this process ends.

  On the other hand, if the CMTS 10 determines that the channel can be changed to another channel (Yes in step S102), the CMTS 10 transmits a UCC-REQ frame to the CM 20a that is the CM that transmitted the UCC-KICK (step S102). Then, UCC processing is performed in accordance with DOCSIS rules (step S104).

  As described above, the result shown in FIG. 3 is obtained by performing the processing shown in FIG. 4 on the CM 20 side and the processing shown in FIG. 5 on the CMTS 10 side.

  That is, as shown in FIG. 3, the CM 20a shown in the state A has transmitted uplink data to the channel US # 1, but when the above processing is performed, the CM 20 frequently generates pending status. As shown in B, the CM 20a performs uplink data transmission on the channel US # 2, thereby improving the delay of uplink data transmission.

The block diagram which shows the structure of the system for constructing | assembling the CATV internet regarding this embodiment. The block diagram which shows the principal part of a cable modem (CM). The figure which showed the outline | summary of the channel change between CM and CMTS. The flowchart which shows the process by CM20 side which concerns on embodiment of this invention. The flowchart which shows the process by the side of CMTS10 which concerns on embodiment of this invention.

Explanation of symbols

1 CATV station side system 2 User side system 3 Coaxial cable 10 CMTS (head end modem)
11 LAN cable 12 Server 20 Cable modem (CM)
21 Personal computer (PC)
22 LAN cable 30 Internet 200 RF interface 201 Flash memory 202 Main memory 203 Microprocessor (CPU)
204 LAN interface N Pending times T Polling time WT UCC-REQ waiting time α, β, γ Threshold

Claims (13)

Transmission state determining means for determining whether or not the uplink transmission state is good when transmitting uplink data to a communication partner apparatus at a predetermined frequency;
When the transmission state determination unit determines that the transmission state is not good, a notification request unit that requests notification of the uplink frequency change information to the communication partner device, and the notification request unit Channel changing means for changing to the uplink frequency indicated in the notification when the notification is received;
A cable modem device comprising:   The transmission state determining means counts the number of times that the uplink frequency allocated by the communication partner apparatus is zero, and determines that the transmission state is not good when the number of times exceeds a predetermined threshold. The cable modem device according to claim 1.   2. The cable modem according to claim 1, further comprising a change completion notifying unit that notifies the communication counterpart apparatus that the uplink frequency change has been completed after the channel changing unit is completed. apparatus.   The cable modem apparatus according to claim 1, wherein the cable modem apparatus conforms to DOCSIS.   The notification of the uplink frequency change information in the notification request unit is a DOCSIS-compliant UCC-REQ frame, and the change completion notification unit is a DOCSIS-compliant UCC-RSP frame. Item 4. The cable modem device according to Item 3. A plurality of cable modem devices and transmission means capable of uplink data transmission;
A change determination means for determining whether or not the frequency can be changed when a request for notification of the frequency change of the uplink is requested from the cable modem device;
If it is determined by the change determining means that the frequency can be changed, a change information notifying means for notifying the cable modem device that has requested the notification of information on the uplink frequency change;
A relay apparatus comprising:   The relay apparatus according to claim 6, wherein the relay apparatus is DOCSIS compliant. In a communication system having a relay device and a cable modem device,
The relay device
A plurality of cable modem devices and transmission means capable of uplink data transmission;
A change determination means for determining whether or not the frequency can be changed when a request for notification of the frequency change of the uplink is requested from the cable modem device;
If it is determined that the change of the frequency is possible by the change determination means, it has a change information notification means for notifying the cable modem device that requested the notification of the information on the frequency change of the uplink,
The cable modem device is
Transmission state determining means for determining whether or not the uplink transmission state is good when transmitting uplink data to a communication partner apparatus at a predetermined frequency;
If it is determined by the transmission state determination means that the transmission state is not good, notification request means for requesting notification of information on the frequency change of the uplink to the communication partner device;
Channel changing means for changing to the uplink frequency indicated in the notification when the notification is received by the notification request means;
A communication system comprising:   The communication system according to claim 8, wherein the relay device and the cable modem device are DOCSIS compliant. A transmission state determination step for determining whether or not the uplink transmission state is good when transmitting uplink data to a communication partner apparatus at a predetermined frequency;
If it is determined in the transmission state determination step that the transmission state is not good, a notification request step for requesting notification of information on the frequency change of the uplink to the communication partner device;
A channel changing step for changing to the uplink frequency indicated in the notification when the notification is received by the notification requesting step;
A frequency setting method for a cable modem device, comprising:   The transmission state determination step counts the number of times that the uplink frequency allocated by the communication partner apparatus is zero, and determines that the transmission state is not good when this number exceeds a predetermined threshold. The frequency setting method for a cable modem device according to claim 1.   2. The cable modem according to claim 1, further comprising a change completion notifying step of notifying the communication partner apparatus that the uplink frequency change is completed after the channel changing step is completed. How to set the frequency of the device.   The frequency setting method for a cable modem device according to claim 9, wherein the cable modem device is compliant with DOCSIS.

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