FI119271B - Data link management in coaxial media - Google Patents

Description

119271

Data link management in coaxial media

Field of the Invention

The invention relates to an arrangement for transmitting a data signal in a coaxial cable network, and in particular for managing a data link in coaxial media.

Background of the Invention

The increasing use of the Internet is constantly increasing the demand for Internet home connections. Conventional telephone modem subscriptions are relatively slow due to their narrow bandwidth and typically reserve a telephone line for Internet access. Higher transfer rates are available through a variety of 10 xDSL and cable modem interfaces. Especially in areas where the television signal is brought to households via a cable network, the cable network also provides a ready-made transmission path for the transmission of data signals.

In a DOCSIS (Data-Over-Cable Service Interface Specifications) cable television system (CATV, Community Antenna Television), the data signal is modulated to its own frequency (channel) like TV signals so that the signals can be transmitted on the same cable and separated at the receiver. need 20 special cable modems (CM) to establish data connectivity ···. computer. The disadvantage for households is that cable modems • f are quite expensive. The problem for cable network operators: * Y is that the expensive network modem • · · * “used for cable modem connections can provide: ···: 25 only a limited number of connections. In addition, the disadvantage of a cable modem interface is that it is a shared network in which the available transmission · · v: capacity (e.g., transmission capacity of one branch of the CATV network) is shared between all simultaneously available interfaces, whereby. *. ·, The transmission capacity available to one household may be low.

To avoid these drawbacks, a solution has been developed which is described in more detail in EP 1099349. EP 1099349 describes a method and apparatus for bidirectional transmission of an Ethernet signal to a 119271 2 cable network. The bidirectional Ethernet signals transmitted in two separate cables are combined by a splitter into a bidirectional signal in one cable and finally connected by a diplexer filter to the traditional CATV signal. The resulting composite signal 5 can be transmitted on a CATV network subscriber line. Similarly, in the reception of a combined signal (in a household interface), the Ethernet signal and the CATV signal are separated from the combined signal by means of filters. The direction of transmission of the bidirectional Ethernet signal is separated by a branch, and the transmit and receive signals are routed over their own cables 10 to a long computer, typically via a network interface. The CATV signal is normally output to the television.

The purpose of patent application EP 1099349 is to provide low-cost means for using a CATV network to transmit both a CATV signal and an exemplary computer-controlled Ethernet signal without a cable modem. Since transmission of a baseband data signal does not require modulation / demodulation, passive components may be used to combine and separate the CATV signal and the baseband Ethernet signal.

In practice, the above arrangement as such is not useful for transmitting an Ethernet signal, since the overall reflection loss of the proposed network structure remains too weak. This, in turn, results in a strong crosstalk between the transmitted and the received signal: 25. This is particularly detrimental in detecting Ethernet link pulses. • 10BaseT-Ethernet uses full-duplex (FDX) link pulses for two • · ·. ···. link between the two devices. Link pulses of smaller amplitude than the payload are mixed with crosstalk-induced interference, especially when data traffic is strongly unidirectional, resulting in link breakage. In addition to crosstalk, other signals transmitted on the coaxial cable also cause interference, which impedes the correct transmission of the baseband data signal and the link pulses. These signals include, for example, low frequency components of radio and TV broadcasts and EMC interference from various electrical equipment.

• * 119271 3

Brief Description of the Invention

An improved arrangement has now been developed to reduce the above problems. In various aspects of the invention, there is provided a communication system, a data network switching point, and a computer program product which are characterized by what is stated in the independent claims. Preferred embodiments of the invention are claimed in the dependent claims.

The invention is based on the fact that, when transmitting data on a coaxial cable network, the link system pulse negotiation of an Ethernet system is at least partially disabled and replaced by a more suitable link management procedure for the system described above. for transmitting a data signal between said telecommunication system and an external data network or server; a coaxial cable network for transmitting said baseband data signal 20 between said data network switching point and at least one ..... data terminal switching point; and interface means for forwarding said * · * [baseband data signal to at least one da] .. * terminal. The data network switching point comprised by the system is ί * ·: arranged to direct its receiver to a receiving mode for receiving data from said at least one data terminal; and transmitting to said at least one data terminal device periodically blank data to direct the receiver of said at least one data terminal device to a listening mode.

· · · • · ·. ·· *. According to one embodiment, the data network switching point is arranged to monitor the state of the link established from said at least one data terminal to the switching point based on the integrity of the received data.

* • i

• I

119271 4

According to one embodiment, said data network switching point is an Ethernet switch arranged to disable link pulse conferencing according to the Ethernet standard.

According to one embodiment, the data network switching point is arranged to turn on link pulse conferencing according to the Ethernet standard for a period of time to detect new data terminals attempting to establish a link.

According to one embodiment, the data network switching point is arranged to monitor interference on the data link between the switching point and said at least one data terminal; and adjusting the time interval for transmitting the blank data according to the interference conditions.

15

According to one embodiment, the telecommunication system is arranged to transmit a cable television signal as a combined signal with said baseband bidirectional data signal, the telecommunication system further comprising a television signal generator 20 for generating a cable television signal; a connector for filtering the cable television signal and the baseband data signal to its own wavelengths and combining it into a combined signal transmitted in a coaxial cable network; and a separator for filtering the cable television signal and the baseband data signal from the received combined: 25 signal to its own frequencies and separating it into separate signals.

• · «• * m. ···. The invention and its various embodiments provide numerous advantages.

The procedure of the invention can ensure the operation of the link #Vi even in difficult crosstalk situations. By using both downstream and *:!: * 30 upstream data instead of link pulses, the system described above can provide a more reliable indication of link operation,: t: \ * because double amplitude data is considerably less! In addition, by periodically sending 35 data from the switching point to the terminal, the receiver of the terminal is continuously woken up at sufficiently short intervals, sufficient to maintain the link in the downstream direction. A further advantage is that a normal Ethernet pulse negotiation according to the Ethernet standard can be used when crosstalk does not significantly interfere with the pulses of the link and the 5 forced controls described above. it is only when the link pulse counseling is no longer possible due to an increased crosstalk disorder.

In another aspect of the invention, there is provided a data network switching point for transmitting a baseband data signal between at least one data terminal connected to a communication system comprising a coaxial cable network and an external data network or server, comprising switching means for connecting a switching point to said coaxial cable; Said data network switching point is arranged to direct its receiver to a receiving mode for receiving data from said at least one data terminal; and periodically sending blank data to said at least one data terminal to control a receiver of said at least one data terminal with its listening.

In a third aspect of the invention, there is provided a computer program product 20 stored on a computer readable memory medium for controlling a data network switching point described above. Computer Software- ·· * v; the product comprising a computer program code switching point for controlling the receiver · ϊ · * ί to a receiving mode and receiving data from said at least one data terminal; and computer program code for transmitting • 25 blank data to said at least one data terminal device IM ·. . *. periodically, the receiver program of said at least one data terminal device · * ··. to stay in listening mode.

• M *

BRIEF DESCRIPTION OF THE FIGURES • *

The invention will now be described in more detail in connection with the preferred embodiments, with reference to the accompanying drawings, in which: -, -. Fig. 1a shows a prior art network arrangement for transmitting a CATV signal and a baseband bidirectional data signal; 35 119271 6

Figure 1b illustrates data transmission in the network arrangement of Figure 1a; and

Fig. 2 is a flowchart showing some embodiments of the invention.

5

Detailed Description of Embodiments

Fig. 1a is a simplified block diagram of a prior art CATV network arrangement for transmitting a CATV signal and a baseband bidirectional data signal as described in EP 1099349. The arrangement of Fig. 1a illustrates a CATV network arrangement in the immediate vicinity of household connections where the TV signal is supplied to a distribution point DP as a broadband connection, typically over an optical fiber or coaxial cable. From the distribution point DP onwards, the network is implemented as a coaxial cable network 15 all the way to the household access point. This part of the coaxial cable network is often referred to as '' the last 100 meters '' or 'last mile'.

In Fig. 1a, for distribution purposes, the distribution point 100 is shown as one logical entity 20, but in practice the ··· v: components included in the distribution point are separate and can be located quite far apart.

The distribution point 100 comprises an analog and / or digital TV signal modulator 102 which converts the picture and audio signals into a coaxial cable network. In particular, the TV I ·· · 25 signal modulator 102 may be located up to kilometers away from a distribution point * ··. I make other components. The network arrangement further comprises a server 104, which may be located, for example, in the main cable of the coaxial cable network. . in the sensor where the Ethemet data signal is transmitted over the broadband! - • · · connection 106a, such as a 100BaseT paired cable connection.

The server 104 transmits the data signal to suitable hardware and transmission media: 106b to the Ethemet switch 108, which comprises a plurality of *** ports 110 (so-called Ethernet multitap) to which the data signal is adapted. for a coaxial cable network, the distribution point mainly comprises filters implemented *: 35 connector 114 (practically a diplexer filter), which filters the baseband Ethernet data signal with its own low pass filter 119271 7 116 and CATV signal respectively. combining to form a combined signal to be transmitted in a coaxial cable network 122. In addition, the paired game connector 120 has a splitter arrangement for separating upstream and 5 downstream Ethernet signals for the paired cable connection 112.

Correspondingly, in connection with the house interface 124, a ground separator 126 is located which filters out the lowest interference frequencies from the combined signal. The combined signal is further provided by a coaxial cable connection 128 to a household wall socket 130 ("socket") comprising a disconnector to perform the opposite action to the connector 114: separating the low-pass and high-pass filters 132 and 134 (corresponding to filters 116 and 118) Further, in order to separate upstream and downstream Ethernet signals, the twisted pair connector 136, used as a wall connector, employs a branching arrangement similar to the distribution point 100. Thus, the Ethernet signal is supplied through the twisted-pair connector 136 and the twisted-pair connection 138 to the computer the signal passes through the same connection in the opposite direction, and the CATV signal is further supplied through the wall connector 142 and the · · · v | coaxial cable 144 to the television 146.

Fig. 1b illustrates the same CATV network arrangement in a special way: *: 25 times for data transmission using, where applicable, the same reference numeral as in Fig. 1a. The data in and out of the network arrangement shown passes through a data cable 106b, which preferably comprises a · # · paired cable connection, where separate wires are reserved for the data going in different directions. The data signal directed to the coaxial cable network is supplied to an Ethernet Multi-Pin (EMT) Ethernet Switch 108, which in Fig. T * 1b is further subdivided into a data packet processor 108a, a transmitter 108b ί.ί and a receiver 108c. The output data signal of transmitter 108b (mm.

:] "t the payload, control signals, link pulses) are illustrated in Fig. 1b ..I .: with reference S1 and the input signal of receiver 108c with reference S2.

Thus, these signals S1 and S2 are transmitted in the paired cable media 112 between the Ethernet switch 108 and the connector / disconnector 114. The coaxial cable 122 transmits a combined data and CATV signal S3, which thus comprises 119271 8 data direction components S3a and S3b. In the connector / separator connected to the Ethernet socket 130 of the household interface, the baseband Ethernet data signal and the CATV signal are separated and the Ethemet signals S4 and S5 5 in different directions are separated for the paired cable connection 138. More specifically, the computer network card 140 of the computer cable connected to the paired cable 138, such as a computer, is illustrated in Figure 1b into three blocks like an Ethernet switch 108: a data packet processor 140a, a transmitter 140b and a receiver 140c.

10

However, a closer look at the operation of such a network arrangement for transmitting an Ether-net signal reveals serious problems. 10BaseT Ethernet is designed for a dual-cable transmission with separate transmission channels for transmission and reception. When transmitting 15 data signals on a coaxial cable network, transmission and reception share common coaxial cable media. The non-idealities of the presented system cause too low total reflection loss, which causes a strong crosstalk between transmission and reception.

Referring to Figure 1b, crosstalk occurs particularly between signals S1 and ... S2 and between signals S3a and S3b, respectively. In addition, the non-idealities of the Ethernet switch 108, the connector / disconnector 114, the coaxial cable 122, the connector / disconnector in the socket 130, the paired cable 138, and the data processing device 140 cause crosstalk of the signals j. : '; 25 between. Further, interference with signals S3a and S3b, in particular, is caused by l i /. low-frequency components for radio and TV transmissions in coaxial cable: *** · set. In addition, especially coaxial cable 122 and twin cable ··· 138 are exposed to various EMC interferences.

30 As a result of the crosstalk T * caused by poor total reflection attenuation, especially the link segment monitors and controls the operation of the link pulses of smaller amplitude than the useful data, and the link function may not be confirmed but the link may fall off. · Off, so that the data can no longer be sent via the link.

• t

The present invention provides a solution to this problem. The invention is based on the fact that because the system cannot guarantee the transmission of the link pulses according to the Ethernet standard, the link pulse negotiation of the Ethernet system in the network arrangement according to the invention is at least partially disabled and replaced by a better link management procedure.

5

According to one embodiment, the Ethernet switch 108 maintains the system-connected data terminals 140 in the listening mode by periodically transmitting idle data that directs the system-connected terminals 140c to the listening mode if they have not already received the data and are thus ready to enter the listening mode. Because the terminal receiver is constantly awake, this is sufficient to maintain the link downstream (from the Ethernet switch to the terminals). According to one embodiment, the Ethemet switch 108 comprises means for adjusting the time interval for transmitting blank data according to conditions to achieve optimal operation in different environments.

However, the data terminals 140 connected to the system operate according to the Ether-net standard using, for example, network cards according to the Ethernet standard 20. Thus, the data terminals 140 transmit link pulses according to the Ethernet standard.

• · · • · t *

According to one embodiment, in the link management procedure, the receiver 108c of the Ethernet-C: switch 108 is forced to remain switched on substantially continuously, so that when forced into the receive mode, the receiver does not • even seek to interpret link pulses or interfere with received. disturbed link pulses. The receiver 108c is arranged to receive upstream data from the terminal, whereby the receiver checks the integrity of the data and inferred the link operation status from the data integrity. In the system described above, this guarantees '·; · * a more reliable indication of link behavior because in the system!. ·'? the data is significantly less sensitive to crosstalk interference than the link pulses because the amplitude of the data is twice that of the link pulses.

• · 35 Practice has shown that the above-described overheating disorder is significant, especially when a large amount of data is transmitted downstream. Thus, according to one embodiment, a normal Ethernet pulse link pulse negotiation can be used in the system when crosstalk does not significantly interfere with the link pulses (e.g., downstream traffic is silent) and the above-described packet-5 co-control is only transitioned to can no longer succeed due to increased crosstalk. Similarly, if the over-hearing interference decreases, one can switch back to normal link pulse conferencing.

10 According to one embodiment, the opening of a new link, i.e. the connection between the new terminal and the Ethernet switch seeking to connect to the network arrangement is preferably accomplished by means of a link pulse negotiation according to a standard Ethernet standard. This is because, when forced to receive mode, the Ethernet switch 15,108 does not receive the information that a new link should be opened, so that it cannot open the port required for the connection. Thus, the receiver 108c forced into the receive state by the Ethemet switch 108 is periodically removed from the receive state and briefly set to listen mode to listen for possible link pulses from the 20 new terminals attempting to enter the network arrangement. Such instant setting of the receiver 108c of the Ethernet switch 108 into the listening mode of the link pulses does not substantially interfere with the maintenance of the link, since returning to the receiving mode is quick. Furthermore, it should be noted that the interruption of the link pulses is not continuous but intermittent, whereby the opening of the new link may be performed in a situation where the crosstalk interference is small, for example in the situation described above with downstream traffic. · '··. quiet.

. . Breaking an existing link is interpreted as a Y.f 30 disconnected terminal. The Ethernet switch 108 preferably monitors upstream data from the terminal by means of a timer, whereby if the terminal does not transmit data for a predetermined time, the Ethernet switch 108 breaks the link and enters the listening mode. If again ββ * β. in listening mode, the Ethernet switch detects link pulses in the network system! 35 terminals, either from the same or new terminals, seeking to connect to the port, open the required port on the connection and establish a new link. The link break can also be detected with the Ethernet switch 119271 11 if the terminal has disconnected and closed its own port, whereupon the Ethernet switch in question. the data transmitted to the terminal is reflected back to the Ethernet switch. The Ethemet switch will then see its own transmission from its receiving port.

5

The operation of the Ethemet switch with respect to the above-described embodiments may be illustrated by the flow chart of Figure 2. Initially, no data terminal is connected and the receiver of the Ethernet switch listens (200) the link pulses. When the link pulses transmitted by the data terminal are detected from the connection 10, a link pulse negotiation according to the Ethernet standard (202) is initiated, which results in the establishment of an (204) Ethernet communication link between the Ethernet switch and the at least one data terminal.

When a communication link is established between the Ethernet switch and at least one data terminal, the Ethernet switch enters a forced control mode (206), wherein the Ethernet switch transmitter is controlled to transmit idle data to the link data terminals at regular intervals and the Ethernet switch receiver is set to receive. The -20 pulses are not listened to, but the state of the link is deduced from the integrity of the data.

After this, the Ethernet switch can advantageously continue in forced control mode while observing the established links, i.e. send -j: *: 25k terminal data to Ethernet switch at predefined time or. j'j whether the Ethernet transmission's own transmission reflects the closure of the data terminal ···. from the receiving port back (208). If the timer after the last data transmission of the terminal has expired, or if the Ethernet TV switch sees its own transmission, the Ethernet switch receiver enters 30 normal link pulse listening mode (200). If, on the other hand, the • · * ·; · * link appears intact, i.e. receiving data from the terminal within a predetermined time interval, then the Ethernet switch continues to operate in forced control mode (206).

Obviously, the operation of the Ethernet switch of Fig. 2 comprises some preferred embodiments which are not necessary to realize the basic idea of the invention, but which, when implemented, provide certain advantages in terms of system operation. However, one of ordinary skill in the art will understand from the above description that, at its simplest, the invention may be implemented such that after the link is established between the Ethernet switch and the at least one data terminal 5, the Ethernet switch is forced into control mode.

Thus, it is also clear that the implementation of the basic idea of the invention does not require a network arrangement in which the television signal is combined with a data signal 10 for coaxial cable transmission. Thus, although the invention has been described above by way of example in a CATV network arrangement according to patent application EP 1099349, the basic idea of the invention can be simplified as a coaxial cable network arrangement which transmits only baseband bidirectional data signals. Of course, the invention is most obviously applicable to existing CATV networks, whereby it can also be used to eliminate some of the disadvantages of the CATV network arrangement according to patent application EP 1099349.

Most preferably, the above-described embodiments of the invention are implemented as a computer program SW, which is downloadable into memory MEM operated by an Ethernet switch and executed by a processor comprising the Ethernet switch to provide the Ethernet switch to perform the operations of the invention. . Computer Program SW Functions: 25 can be divided into several separate and communicating ♦ ·· ·. . ·. software components. The computer program may be stored for some time ···. hans memory media, such as a PC hard disk or a CD-ROM, from where it can be loaded into the memory of the Ethernet switch MEM. The computer program can also be downloaded over the network using, for example, the TCP / IP-30 protocol stack. It is also possible to use march solutions or a combination of hard and software solutions to implement the inventive tools.

·· «• · • ··· |. It will be obvious to one skilled in the art that the basic idea of the invention can be implemented in many different ways, so that the invention and its embodiments are not limited to the examples described above, but may vary within the scope of the appended claims.

Claims (13)

119271 A communication system for transmitting a baseband bidirectional data signal in a coaxial cable network, the communication system comprising a data network switching point (108) for transmitting a baseband data signal between said communication system and an external data network (106a, 106b) or server (104); a coaxial cable network (122) for transmitting said baseband data signal between said data network switching point (108) and said at least one data terminal switching point (130); interface means (136) for further transmitting said baseband data signal to at least one data terminal (140), characterized in that said data network switching point (108) is arranged to direct (200) its receiver to a receiving state for receiving data from said at least one data terminal; and transmitting (206) periodically blank data to said at least one data terminal for controlling the receiver of said at least one data terminal to a listening mode. A communication system according to claim 1, v * characterized in that said data network switching point (108) is arranged to accurately switch from at least one of the data terminals (140) a switch state: * · 25 the integrity of the received data on a p-: i *: basis. · * · * · * · · · · The communication system according to claim 1 or 2. characterized in that said data network access point (108) is an Ethernet switch arranged to disable link pulse conferencing according to the Ethernet standard. ··· • · ··· A communication system according to claim 3, characterized in that said data network switching point (108) is configured to turn on an Ethernet standard link pulse negotiation (202) for a period of time in order to detect new data terminals attempting to establish a link. 5 Communication system according to any one of the preceding claims, characterized in that said data network switching point (108) is arranged to monitor interference on the communication link between the switching point and said at least one data terminal (140); and adjusting the time interval for transmitting the blank data according to the interference conditions. The telecommunications system according to any one of the preceding claims, characterized in that the telecommunications system is arranged to transmit a cable television signal combined with said baseband bidirectional data signal, the communication system further comprising a television signal generator (102) for forming a cable television signal; a connector (114) for filtering the cable television signal and the baseband: data signal to its own frequencies and combining it: *: * · * for a combined signal to be transmitted in a coaxial cable network (122); • · · and: •: 25 filters (132, 134) to filter the cable TV signal and the baseband data signal from the received combined signal to its • own frequencies and to separate them into separate signals. Itt A data network switching point (108) for transmitting a baseband data signal between at least one data terminal (140) connected to a communication system comprising a coaxial cable network (122) and an external data network (106a, 106b) or server (104), which switch -: [[[: the field point comprises connection means (110, 112, 114) for connecting the switch point * 35 to said coaxial cable network; characterized in that said da network switching point is configured 119271 to control (200) its receiver in a receiving mode for receiving data from said at least one data terminal (140); and transmitting (206) periodically blank data to said at least one data terminal for controlling the receiver of said at least one data terminal to listen. The data network switching point according to claim 7, characterized in that the data network switching point 10 is arranged to monitor the state of the link established from said at least one data terminal to the switching point based on the integrity of the received data. The data network switching point according to claim 7 or 8, characterized in that the data network switching point is an Ethemet switch arranged to disable the link pulse negotiation according to the Ethernet standard. The data network switching point according to claim 9, characterized in that: · **: the data network switching point is arranged to turn on the Ethernet standard link pulse negotiation (202) for a fixed period of time • · * to detect new data terminal devices attempting to establish a link. • · · • · · · · · 11. The data network switching point according to any one of claims 7 to 10, characterized in that the data network switching point is arranged in a «« l · '.' 30 to monitor for interference in the communication link between the switching point and said at least * ': ** one data terminal; and adjusting the time interval for transmitting the blank data according to the interference conditions. • « The data network switching point according to any one of claims 7 to 11, characterized in that said connection means are connected to a 119271 filter unit (114) comprising a filter TV signal to be transmitted by the filter means (116, 118) and at least one data terminal 140 from said data network switching point. filtering the transmitted baseband data signal 5 to its own frequencies and combining it into a combined signal to be transmitted in the coaxial cable network (122) and filtering the baseband data signal received from said at least one data terminal from the received combined signal to its own frequency. 10 A computer program product stored on a computer-readable memory medium for controlling a data network switching point (108) adapted to transmit a baseband data signal from at least one data terminal (106) connected to a telecommunication system 106 and a ) or between a server (104), the connection point comprising connection means (110, 112, 114) for connecting the connection point to said coaxial cable network (122); characterized in that the computer program product comprises 20 computer program code switching points for controlling the receiver ... in a receiving mode (200) and for receiving data in said • · · * · * | fire from at least one data terminal; and a computer program code for transmitting (206) blank data to said at least one data terminal to periodically control a receiver of said at least one data terminal to a listening mode. ··· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Reg · · · · · · · · · · · · Φ φ Φ 119271