JP4913156B2 - Data link management in coaxial media - Google Patents

Description

Detailed Description of the Invention

The present invention relates to data signal transmission devices in coaxial cable networks, and more particularly to data link management in coaxial media.

BACKGROUND OF THE INVENTION As the use of the Internet becomes more prevalent, the demand for home Internet connectivity is constantly increasing. Conventional telephone modem connections are relatively slow due to their narrow bandwidth, and usually tie up the telephone line during the internet connection time. Higher transfer rates are available with various xDSL and cable modem subscriber lines. In particular, in areas where television signals are routed to the home via a cable network, the cable network also provides an existing transmission path for transmitting data signals.

  In a DOCSIS (Data-Over-Cable Service Interface Specifications) type cable television system (CATV, joint antenna television), a data signal is modulated to a specific frequency (channel) in the same manner as a TV signal. Can be transmitted in the same cable and separated from each other at the receiver. At home, a specific cable modem (CM) is required to set up a data connection with a computer. The disadvantage for the home is that cable modems are relatively expensive. Cable network operators have a problem that an expensive network device CMTS (Cable Modem Termination System) used for cable modem connection can provide only a limited number of connections. In addition, a cable modem connection is a trunk network that divides the transmission capability (e.g., a branch of CATV network transmission capability) available between all subscriber lines used at the same time, and can be used in one home. There is a disadvantage that the transmission capability is reduced.

  A solution which avoids these disadvantages has been developed and is described in detail in EP 1 099 349. EP 1 099 349 describes a method and apparatus for transmitting an Ethernet signal to a subscriber line of a cable network in a bidirectional manner. The Ethernet signals transmitted in two directions on two separate cables are combined by a combiner to form a signal transferred in two directions on one cable, and finally the Ethernet signal is converted into a conventional CATV signal by a diplexer. Join. The combined signal formed can be transmitted in the subscriber line of the CATV network. At the receiving end of the combined signal (at home connection), the Ethernet signal and the CATV signal are separated from the combined signal by a filter, respectively. The transmission direction of the duplex Ethernet signal is separated by a splitter, and the transmitted signal and the received signal are transmitted to the computer by separate cables, usually via a network adapter connection. The CATV signal is directed to the television in the normal manner.

  The purpose of EP 1 099 349 is to provide an inexpensive means of using a CATV network for the transmission of both CATV signals and, for example, Ethernet signals that are routed to a computer without a cable modem. That is. Since transmission of baseband data signals does not require modulation / demodulation, passive components can be used to combine and separate CATV signals and baseband Ethernet signals.

  In practice, the above arrangement cannot be used for transmission of Ethernet signals or the like. This is because the total reflection attenuation of the proposed network structure remains too weak. This in turn results in strong crosstalk between the transmitted signal and the received signal. This is particularly harmful for detecting Ethernet link pulses. 10BaseT-Ethernet uses full duplex (FDX) link pulses to examine the operation of the link between the two devices. Especially when the data traffic is strongly unidirectional, link pulses that are smaller in amplitude than the payload data are mixed with interference caused by crosstalk and the link is lost. In addition to crosstalk, other signals that are relayed in the coaxial cable also cause interference that makes complete transmission of baseband data signals and link pulses difficult. These signals include, for example, low frequency components of radio and TV transmissions, as well as EMC interference caused by different electrical devices.

BRIEF DESCRIPTION OF THE INVENTION An improved arrangement has now been developed to reduce the aforementioned problems. As different aspects of the invention, the inventors have presented communication systems, data network nodes, and computer software products, which are characterized in what is presented in the independent claims. The dependent claims disclose advantageous embodiments of the invention.

  The invention is based on the idea that when data is transmitted in a coaxial cable network, the link pulse negotiation of the Ethernet system is at least partly removed from use and replaced with a link management procedure more suitable for the aforementioned system. Based.

  Therefore, as a first aspect of the present invention, the inventors have presented a communication system for transmitting baseband duplex data signals in a coaxial cable network, the communication system comprising the communication system and an external data network. Or a node of a data network for transmitting a baseband data signal to / from a server, and a coaxial cable for transmitting the baseband data signal between the node of the data network and at least one node of a data terminal A network and connection means for transmitting the baseband data signal to at least one data terminal. A node of the data network included in the system controls the receiver to receive mode to receive data from the at least one data terminal and periodically transmits idle data to the at least one data terminal. The at least one data terminal is arranged to control the listening mode.

  According to one embodiment, the nodes of the data network are arranged to monitor the status of the link formed from the at least one data terminal to the node based on the integrity of the received data.

  According to one embodiment, the node of the data network is an Ethernet switch arranged to switch off link pulse negotiation according to the Ethernet standard.

  According to one embodiment, the nodes of the data network are arranged to switch on link pulse negotiation according to the Ethernet standard for a period of time in order to detect new data terminals that are to be linked.

  According to one embodiment, the nodes of the data network optimize the idle data transmission time range so as to monitor interference in the data transmission connection between the node and the at least one data terminal and according to the interference conditions. Arranged to adjust.

  According to one embodiment, a cable television signal is arranged in the communication system to be transmitted as a combined signal with the baseband duplex data signal, in which case the communication system further transmits the cable television signal. To filter the television signal generator to be formed, the cable television signal and the baseband data signal to separate frequencies, and combine them into a combined signal for transmission in a coaxial cable network And a separator for filtering the reception television signal and the baseband data signal to separate frequencies and separating them into separate signals.

  Various advantages can be obtained by the present invention and its various embodiments. With the arrangement according to the invention it is possible to ensure the operation of the link even in difficult crosstalk situations. By using both downstream and upstream data instead of link pulses, a more reliable indication of link operation can be ensured in the aforementioned system. This is because data with twice the amplitude is significantly less sensitive than interference to interference caused by crosstalk. In addition, by periodically transmitting idle data from the node to the terminal, the terminal receiver is woken up continuously at short but sufficient intervals, which is sufficient to maintain the downstream link. . Further, since the node receiver determines the mode of operation of the link based on data integrity, further confirmation regarding the operation of the link is received. A further advantage is that if the crosstalk does not significantly interfere with the link pulse, normal link pulse negotiation according to the Ethernet standard can be used, and the forced control described above only in situations where link pulse negotiation is no longer successful due to increased crosstalk interference. Is used.

  Another aspect of the present invention is a data network node for transmitting baseband data signals between at least one data terminal connected to a communication system having a coaxial cable network and an external data network or server. And the node has connecting means for connecting the node to the coaxial cable network. The node of the data network controls the receiver to receive mode to receive data from the at least one data terminal and periodically transmits idle data to the at least one data terminal to It arrange | positions so that one data terminal may be controlled to listening mode.

  As a third aspect of the present invention, the inventors present a computer software product stored in computer readable memory means for controlling the aforementioned nodes of the data network. The computer software product controls the node receiver to receive mode and periodically transmits idle software to the at least one data terminal and computer software code for receiving data from the at least one data terminal, Computer software code for controlling a receiver of the at least one data terminal to a listening mode.

  The invention will be described in more detail in connection with preferred embodiments with reference to the accompanying drawings.

Detailed Description of Embodiments FIG. 1a shows a prior art CATV network deployment for the transmission of CATV signals and baseband duplex data signals, as described in EP 1 099 349. It is a simple block chart. The arrangement of FIG. 1a illustrates a CATV network arrangement very close to the home subscriber line, where the TV signal is routed to the distribution point DP, usually as a baseband connection, via fiber optic or coaxial cable. The network is implemented as a coaxial cable network from the distribution point DP on the network to the home connection point. The coaxial cable portion of this network is often referred to as “last 100 meters” or “last mile”.

  In FIG. 1a, the distribution point 100 is shown as a signal logic unit for illustration, but in practice the components of the distribution point are separate and can be arranged at relatively long distances from each other. Distribution point 100 has an analog and / or digital TV signal modulator 102 that modulates video and audio signals into a state suitable for a coaxial cable network. In particular, the TV signal modulator 102 can be placed at a distance of several kilometers from the other components of the distribution point. In addition, the network deployment includes a server 104 that can be deployed in connection with, for example, the head end of a coaxial cable network that introduces Ethernet data signals over a broadband connection 106a, such as a 100BaseT to cable connection. Using appropriate equipment and transmission media 106b, the server 104 transmits further data signals to an Ethernet switch 108 (so-called Ethernet multi-tap) having a number of ports 110 through which the data signals are generally 10BaseT to cable. Fits connection 112. For a coaxial cable network, the distribution point has a combiner 114 that is implemented primarily by a filter (actually a diplexer) to filter baseband Ethernet data signals and CATV signals by a specific low-pass filter 116 and high-pass filter 118, respectively. Call. These filtered signals are combined to form a combined signal that is transmitted into the coaxial cable network 122. In addition, there is a branch circuit arrangement for connecting to the pair cable connection 120 to separate the upstream and downstream Ethernet signals of the pair cable connection 112.

  Similarly, home subscriber line 124 includes a ground isolator 126 for filtering off the lowest interference frequency from the combined signal. In addition, the combined signal is routed through a coaxial cable connection 128 to a home subscriber line wall connection 130 (“wall socket”), which has a separator that performs the reverse operation of that of the combiner 114. A low pass filter 132 and a high pass filter 134 (corresponding to filters 116 and 118) are used to separate the baseband Ethernet data signal and the CATV signal from each other. In addition, to cable connector 136 operating as a wall connection to separate upstream and downstream Ethernet signals has a branch circuit arrangement similar to that of distribution point 100. Therefore, the Ethernet signal is input to the computer 140 via the pair cable connector 136 and the pair cable connection 138. Upstream Ethernet signals are routed through the same connections in opposite directions. Further, the CATV signal is input to the television set 146 via the wall connection 142 and the coaxial cable 144.

  In FIG. 1b, a similar CATV network arrangement is illustrated using the same reference signs as in FIG. 1a where applicable, particularly from a data transfer perspective. Incoming data to the network arrangement and transmission data from the network arrangement travel via the data cable 106b, which has a cable connection with separate conductors for data traveling in different directions. It is advantageous. Data signals destined for the coaxial cable network are carried to an Ethernet multi-tap Ethernet switch 108, which is further defined in FIG. 1b as being divided into a data packet handler 108a, a transmitter 108b and a receiver 108c. The output data signal of the transmitter 108b (eg, payload data, control signal, link pulse) is shown in FIG. 1b as S1, and the input signal of the receiver 108c is shown as S2. Therefore, these signals S1 and S2 travel in the pair cable media 112 between the Ethernet switch 108 and the connector / separator 114. In the coaxial cable 122, there is a CATV signal S3 including coupled data and data signal components S3a and S3b moving in different directions. In the connector / separator that connects to the Ethernet wall socket of the home subscriber line, the baseband Ethernet data signal and the CATV signal are separated from each other, and the Ethernet signals S4 and S5 traveling in different directions are for the pair cable connection 138. Separated from each other. The data processing device 140 connected to the pair cable 138 is a computer, more precisely a network adapter of the computer, etc., and for simplicity, like the Ethernet switch 108, in FIG. The receiver 140c is divided into three blocks.

  However, a more detailed investigation of the operation of such network deployment in the transmission of Ethernet signals finds significant problems. 10BaseT-Ethernet is designed for cable-to-cable transmission lines with separate transmission channels for transmission and reception. When transferring data signals within a coaxial cable network, transmission and reception share a common coaxial cable medium. The aforementioned non-idealities cause total reflection attenuation that is too weak, which causes strong crosstalk between transmission and reception.

  Referring to FIG. 1b, crosstalk occurs particularly between signal S1 and signal S2, and also between signal S3a and signal S3b. In addition, the non-idealities of the Ethernet switch 108, connector / separator 114, coaxial cable 122, wall socket 130 connector / separator, pair cable 138 and data processing device cause crosstalk between signals. In addition, the low frequency components of radio and TV transmissions transferred in the coaxial cable cause interference to the signals S3a and S3b in particular. In addition, especially the coaxial cable 122 and the pair cable 138 are exposed to different EMC interference.

  As a result of crosstalk caused by weak total reflection attenuation, link pulses that monitor and control link segment operation and whose amplitude is smaller than the payload data can be specifically interfered to ensure link operation. And the link may be broken, in which case data can no longer be transmitted over the link.

  The present invention provides a solution to this problem. In the network arrangement according to the present invention, the link management scheme more suitable for the aforementioned system, at least partly out of link pulse negotiation of the Ethernet system, because the system cannot ensure the transmission of link pulses according to the Ethernet standard. The present invention is based on the idea of replacing

  According to one embodiment, the Ethernet switch 108 keeps the data terminal 140 connected to the system in the listening mode by periodically transmitting idle data. If the data terminal 140 has not yet received data and is therefore not yet in listening mode, the idle data controls the receiver 140c of the terminal connected to the system to enter listening mode. This is sufficient to maintain a downstream link (from the Ethernet switch to the terminal) since the terminal receiver is continuously active. According to one embodiment, the Ethernet switch 108 has idle data transmission means for controlling the time range according to the state, so that optimum operation is provided even in different environments.

  However, the data terminal 140 connected to the system operates according to the Ethernet standard by using, for example, a network adapter according to the Ethernet standard. Therefore, the data terminal 140 transmits a link pulse according to the Ethernet standard.

  According to one embodiment, in a link management arrangement, the Ethernet switch receiver 108c is forced to remain substantially continuous, and in this situation, the receiver attempts to interpret the link pulse even when in receive mode. Neither is it disturbed nor is it interfered by the received interfering link pulse. The receiver 108c is arranged to receive upstream data coming from the terminal. In this situation, the receiver checks the data integrity and determines the link operating mode according to the data integrity. In the system described above, this ensures a more reliable indication of link operation. This is because in the system, the amplitude of the data is twice that of the link pulse, so the data is significantly less sensitive than the link pulse to interference caused by crosstalk.

  Practice has shown that the aforementioned crosstalk interference is particularly noticeable when large amounts of data are transmitted downstream. Thus, according to one embodiment, normal link pulse negotiation according to the Ethernet standard can be used when crosstalk does not significantly interfere with the link pulse (eg, when the traffic in the downstream direction is mild) Control is only used in situations where link pulse negotiation is no longer successful due to increased crosstalk interference. Similarly, if crosstalk interference is reduced, normal link pulse negotiation can be restored.

  According to one embodiment, the establishment of a new link, i.e. the formation of a connection between a new terminal and an Ethernet switch intended for connection with a network arrangement is advantageously performed by link pulse negotiation according to the normal Ethernet standard. The This is because once the reception mode is entered, the Ethernet switch 108 does not receive information that a new link should be opened, and in this situation it is not possible to open a port that is essential for the connection. . Therefore, the receiver 108c of the Ethernet switch 108 that has entered the reception mode is periodically removed from the reception mode, instantaneously set to the listening mode, and from a new terminal intended to be connected to the network arrangement. Try to hear possible link pulses. This type of instantaneous setting of the receiver 108c of the Ethernet switch 108 to the link pulse listening mode does not substantially interfere with the maintenance of the link because the recovery to the receiving mode is made quickly. In addition, link pulse interference is accidental rather than continuous, and the opening of a new link in this situation is a situation where the crosstalk interference is low, such as in the situation described above where the traffic in the downstream direction is moderate. It should be noted that can be performed in

  An existing link break is interpreted as a terminal switched off from the network deployment. The Ethernet switch 108 advantageously monitors the upstream data coming from the terminal with a timer, and in this situation, if the terminal does not transmit data within a predetermined time, the Ethernet switch 108 switches off the link and listens to the listening mode. Move on. In the listening mode, if the Ethernet switch detects a link pulse from the same or new terminal that is intended to connect to the network configuration, a port necessary for connection is opened and a new link is established. Is formed. Link switch off can also be done by an Ethernet switch when the terminal switches off the connection and closes its port, and data sent from the Ethernet switch to the problem terminal is reflected back to the Ethernet switch. Can be detected. Thus, the Ethernet switch sees its transmission from its receiving port.

  The operation of the Ethernet switch in relation to the parts of the previous embodiment can be described in the flowchart according to FIG. Initially, no connection is made to any data terminal and the receiver of the Ethernet switch listens for link pulses (200). When a link pulse transmitted by any data terminal is detected from the connection, link pulse negotiation according to the Ethernet standard is initiated (202) so that the data transmission link according to the Ethernet standard is connected to the Ethernet switch and at least one It is formed between the data terminals (204).

  When the data transfer link is formed between the Ethernet switch and the at least one data terminal, the Ethernet switch moves to forced control mode (206), where the Ethernet switch transmitter periodically transmits idle data to the link. Controlled to transmit to the formed data terminal, the receiver of the Ethernet switch is set to receive, where no link pulse is heard, but the link operating mode is determined based on data integrity.

  After this, the Ethernet switch can advantageously continue in the forced control mode and at the same time monitor the formed link. That is, it monitors whether the terminal is transmitting data to the Ethernet switch within a predetermined time, or whether its own transmission is reflected back from the closed reception port of the data terminal (208). If the timer that measures the time after the terminal's previous data transmission expires or if its own transmission is seen on the Ethernet switch, the receiver of the Ethernet switch moves to the normal link pulse listening mode (200). Also, if the formed link looks perfect, ie if data is received from the terminal within the set time, the Ethernet switch continues its operation in forced control mode (206).

  The operation of the Ethernet switch according to FIG. 2 includes several advantageous embodiments, which are not essential for carrying out the basic idea of the invention, but provide certain advantages over the operation of the system when carried out. It is clear. However, in its simplest form, the present invention is such that after a link is formed between the Ethernet switch and at least one terminal, the Ethernet switch is directed to forced control mode, thereby managing the link. Those skilled in the art will understand based on the foregoing description that it can be implemented.

  It is therefore clear that the implementation of the basic idea of the invention does not require a network arrangement, in which case the television signal is combined with the data signal for coaxial cable transmission. Thus, despite the fact that the above-described invention has been described as an example of a CATV network arrangement according to EP 1 099 349, the basic idea of the present invention is that only baseband duplex data signals are transmitted. Can be implemented in a simple manner, such as a coaxial cable network deployment. The invention can be used with certainty in existing CATV networks, in which case it can also be used to eliminate some of the disadvantages of CATV network deployments according to EP 1 099 349.

  The aforementioned embodiments of the present invention can be most advantageously implemented as computer software SW, which can be installed in a memory MEM included by an Ethernet switch, and the computer software SW is the processor CPU of the Ethernet switch. Causes the Ethernet switch to perform the task according to the present invention. The functionality of the computer software SW can be distributed among various different software components that communicate with each other. The computer software can be stored in any memory means such as a PC hard drive or a CD-ROM disk, from which the computer software can be loaded into the Ethernet switch memory MEM. The computer program can also be loaded through a network, for example by using a TCP / IP protocol stack. It is also possible to use a hardware solution or a combination of hardware and software solutions to implement the means of the present invention.

  It will be apparent to those skilled in the art that the basic principles of the present invention can be implemented in various ways, and that the present invention and its embodiments are not limited to the foregoing examples, but can be modified within the scope of the appended claims. is there.

FIG. 2 shows a prior art network arrangement for transmission of CATV signals and baseband duplex data signals. FIG. 1b shows in more detail the data transfer in the network arrangement according to FIG. 1a. FIG. 2 is a flowchart illustrating some embodiments of the present invention.

Claims (13)

A communication system for transmitting baseband duplex data signals in a coaxial cable network,
A data network node for transmitting baseband data signals between the communication system and an external data network or server;
A coaxial cable network for transmitting the baseband data signal between the node of the data network and at least one node of the data terminal;
In a communication system further comprising connector means for transmitting the baseband data signal to at least one terminal, the node of the data network comprises:
Controlling the receiver at the node to receive mode to receive data from the at least one data terminal, and periodically transmitting idle data to the at least one data terminal to A communication system, wherein the communication system is arranged to control the receiver in a listening mode.   2. The node of the data network is arranged to monitor a mode of a link formed from the at least one data terminal to a node based on the integrity of received data. Communications system.   3. The communication system according to claim 1, wherein the node of the data network is an Ethernet switch arranged to switch off link pulse negotiation according to the Ethernet standard.   4. The node of the data network is arranged to switch on link pulse negotiation according to the Ethernet standard for a period of time in order to detect a new data terminal to be linked. Communication system. The node of the data network is arranged to monitor interference in a data transmission connection between the node and the at least one data terminal and to optimally adjust the transmission time range of idle data according to the interference condition The communication system according to any one of claims 1 to 4, wherein: In a communication system, a cable television signal is arranged to be transmitted as a combined signal with the baseband duplex data signal, in which case the communication system further comprises:
A television signal generator for forming a cable television signal;
A combiner for filtering a cable television signal and a baseband data signal to separate frequencies and combining the cable television signal and the baseband data signal into a combined signal transmitted in a coaxial data network;
6. A separator as claimed in claim 1 further comprising a separator for filtering the received combined signal of the cable television signal and the baseband data signal into their separate frequencies and separating them into separate signals. The communication system according to any one of the above. A node of a data network for transmitting a baseband data signal between at least one data terminal connected to a communication system having a coaxial network and an external data network or a server, the node being the coaxial cable network In a node having connecting means for connecting to
The node of the data network controls its receiver to receive mode for receiving data from the at least one data terminal;
Arranged to control the receiver of the receiver to listening mode so as to periodically transmit idle data to the at least one data terminal for controlling the receiver of the at least one data terminal to listening mode A data network node characterized by   8. Data according to claim 7, characterized in that a node of the data network is arranged to monitor the mode of the link formed from the at least one data terminal to the node based on the integrity of the received data. Network node.   9. A data network node according to claim 7 or 8, characterized in that the data network node is an Ethernet switch arranged to switch off link pulse negotiation according to the Ethernet standard.   10. The node of the data network is arranged to switch on link pulse negotiation according to the Ethernet standard for a period of time in order to detect a new data terminal that is to form a link. Data network node. A node of the data network is arranged to monitor interference in a data transmission connection between the node and the at least one data terminal and to optimally adjust the transmission time range of idle data according to the interference condition The node of the data network according to claim 7, wherein the node is a data network node. The connecting means comprises:
Filtering the transmitted cable television signal and the baseband data signal from the node of the data network transmitted to the at least one data terminal to separate frequencies, and the cable television signal and the baseband data signal To the combined signal transmitted in the coaxial cable network, and the baseband data signal received from the at least one data terminal is filtered to obtain the own frequency of the baseband data signal from the received combined signal 12. A node of a data network according to any one of claims 7 to 11, characterized in that it is connected to a filter unit having filtering means for separating and separate signals. A computer-readable memory means including a computer program for controlling a node of a data network, said node comprises at least one data terminal connected to a communication system comprising a coaxial cable network, the external data network Or a computer readable memory means arranged to transmit a baseband data signal to or from a server, wherein the node comprises connection means for connecting the node to the coaxial cable network;
The computer program is
Computer software code for controlling a nodal receiver to receive mode and operating a computer to receive data from said at least one data terminal;
And computer software code for operating the computer to periodically transmit idle data to the at least one data terminal and to connect a receiver of the at least one data terminal to a listening mode. A readable memory means .

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