CA2324678A1 - Data distribution network and high pass bridging filter or combiner therefor - Google Patents

Abstract

A filter bridge, coupler or combiner coupling dedicated subscriber telephone lines at specified frequencies turns a local network of telephone wires into a connectionless network at the specified frequencies while maintaining a circuit-switched network of dedicated subscriber telephone lines at all other frequencies. Telephone carriers remain isolated to each dedicated subscriber telephone line, while other telecommunications service (e.g.
audio/video) carriers can be distributed over the same local twisted pair network as a connectionless network within a specified range of frequencies. Any range of frequencies can be specified for the connectionless network, for example using a high pass filter or a notch filter. In the case where the redistributor dynamically allocates frequencies for the redistributed signals, a dynamic filter bridge may be used to select a passband corresponding to a frequency allocated by the redistributor for redistributed signals at any particular time.

Description

DATA DISTRIBUTION NETWORK AND
HIGH PASS BRIDGING FILTER OR COMBINER THEREFOR
Field of Invention This invention relates to communications systems. In particular, this invention relates to a bridging filter for a data distribution network in which different types of data are differentially distributed over a plurality of frequencies.
Background of the Invention Today's telecommunications to home and business involves two major facets:
telephone communications, which provides telephony, facsimile and other modulated telecommunications signals on low frequency carriers, transmitted typically over any of various categories of twisted pair telephone wiring; and audio/video telecommunications, providing information and entertainment services such as television, the Internet, video on demand and the like, typically on high frequency analog or digital carriers transmitted over coaxial cable or wireless communications networks. Between these two major telecommunications methods, a virtually unlimited variety of information and entertainment services are accessible practically everywhere throughout the world.
Video compression techniques have recently been developed which allow for the transmission of low resolution, low frame-rate video signals over telephone wires on relatively low frequency modulated carriers. However, high quality video signals have a much higher data density, and as such require a high frequency carrier.
United States Patent No. 6,038,425 issued March 14, 2000 to Jeffery, which is incorporated herein by reference, teaches a system for the delivery of both low frequency telephony and high frequency audio/video signals over a network of twisted pair telephone wires, in an interactive audio/video redistribution system that pools various broadcast and telecommunications services and integrates these services into a single system, redistributing audio and audio/video signals received in different formats to multiple users.
This system does not interfere with normal use of the telephone network, so subscribers can interactively access services provided by the redistribution system and use the telephone at the same time.

However, this system requires a network that is circuit-switched at all frequencies, and utilizes a matrix switcher to isolate each subscriber-selected service. This requires a separate modem to demodulate the redistributor output at each dedicated telephone line, in order to distribute the selected signal to each subscriber's premises without interfering with telecommunications services to surrounding subscribers and without providing unwanted or free services to other subscribers serviced by the same local telephone network.
Summary of the Invention The present invention overcomes this disadvantage by providing a mufti-service redistribution system for distributing various telecommunications services over subscriber telephone lines in a single local network, for example in a mufti-unit residential or office building or complex, or within a mufti-user office or other premises, which distributes telecommunications services through a single modem that demodulates the redistributor output while allowing the concurrent distribution of telephone services to individual subscribers without cross-talk or interference between dedicated subscriber telephone lines.
The invention accomplishes this by providing a filter bridge or combiner coupling all subscriber telephone lines at specified frequencies, thus turning the local network into a connectionless network at the specified frequencies while maintaining a circuit-switched network of dedicated subscriber telephone lines at all other frequencies, for example those conventionally used for telephone communications. Thus, while telephone Garners remain isolated to each dedicated subscriber telephone line, other telecommunications service (e.g.
audio/video) carriers can be distributed over the same local twisted pair network as a connectionless network for a specified range of frequencies, preferably via a suitable Transmission Control Protocol such as TCP/IP, to all subscribers in the local network.
The invention thus distributes selected services by connectionless communication, for example conventional packet switching techniques in which each data packet comprises a header containing an address associated with the redistribution subscriber, and a communications interface in each subscriber premises is programmed to accept only data packets having the specified address. Alternatively, the data packets may comprise a unique identifier corresponding to the service signal selected by a particular redistribution subscriber, and the redistribution subscriber's communications interface is programmed to receive only data having the unique identifier associated with the selected signal.
Thus, according to the invention, while all redistribution Garners are distributed over the entire local twisted pair network, only those services requested by each redistribution subscriber can actually be received by the redistribution subscriber. At the same time, because the local network is bridged by a filter coupler or combiner which blocks frequencies outside of the frequencies used for redistribution subscribers, the local network is connectionless only at the redistribution frequencies and each dedicated subscriber telephone line remains isolated at carrier frequencies which provide telephone services to telephone subscribers, so there is no crosstalk or other interference between dedicated subscriber telephone lines.
Any range of frequencies can be specified for the connectionless network, for example using a high pass filter to pass only high frequency Garners between subscriber telephone lines, or a notch filter to pass a limited range of high frequency Garners between subscriber telephone lines. In one preferred embodiment in which the redistributor dynamically selects and allocates a redistribution frequency most suitable for the signal selected by each user, having regard to a number of variable factors, a dynamic filter bridge or coupler/combiner is used to select a passband corresponding to the frequency allocated by the redistributor for redistributed signals at any particular time.
The present invention thus provides a bandpass filter bridge for a local network of dedicated twisted pair telephone lines each comprising a twisted pair of telephone wires, the filter bridge comprising at least one bandpass filter coupling at least two telephone lines within the local network, wherein signals outside of the passband of the filter remain isolated to each dedicated telephone line while signals within the passband of the filter are transmitted across all telephone lines coupled by the filter bridge.
In further aspects of the filter bridge of the invention: the filter bridge comprises a plurality of bandpass filters coupling a plurality of telephone lines; the bandpass filters have a fixed passband; the bandpass filters are high pass filters; the bandpass filters have a variable passband; the bandpass filters are notch filters; and/or the filter bridge comprises a controller which dynamically allocates a variable passband frequency to the bandpass filters.

The invention fiuther provides a system for distributing a plurality of signals having different frequencies to a plurality of communications interfaces over a local network of dedicated telephone lines, each telephone line comprising a twisted pair of telephone wires, comprising a redistributor comprising a server, for receiving a plurality of input signals and redistributing subscriber-selected signals of the plurality of input signals to the communications interfaces, the redistributed signals being distributed over the local network as data packets each having unique identifier information relating each data packet to a particular communications interface or to a particular redistributed signal, the local network comprising at least one bandpass filter coupling at least two dedicated telephone lines, to thereby transmit signals within a passband of the filter across all connected subscriber lines, wherein signals outside of the passband of the filter remain isolated to each dedicated telephone line while redistributed signals within the passband of the filter are transmitted to all communications interfaces in the local network and each communications interface selectively processes only data packets having unique identifier information associated with the communications interface or associated with the subscriber-selected signal.
The invention fiwther provides a method of distributing a plurality of signals having different frequencies to a plurality of communications interfaces over a local network of dedicated telephone lines, each telephone line comprising a twisted pair of telephone wires, comprising the steps of a. redistributing subscriber-selected signals of a plurality of input signals to the communications interfaces as data packets each having unique identifier information relating each data packet to a particular communications interface or to a particular redistributed signal, b. coupling at least two dedicated telephone lines with a bandpass filter, to thereby allow signals within a passband of the filter to pass between the connected subscriber lines, and c. distributing other signals outside of the passband of the filter, wherein the signals outside of the passband of the filter remain isolated to each dedicated telephone line while redistributed signals are transmitted to all communications interfaces in the local network and each communications interface selectively processes only data packets having unique identifier information associated with the communications interface or associated with the subscriber-selected signal.
In further aspects of the system and method of the invention: a plurality of bandpass filters couple a plurality of telephone lines; the bandpass filters have a fixed passband; the -S-bandpass filters are high pass filters; the bandpass filters have a variable passband; the bandpass filters are notch filters; a controller dynamically allocates a variable passband frequency to the bandpass filters; the controller dynamically allocates a variable passband frequency to the bandpass filters responsive to an allocation of a redistribution frequency by the redistributor; the unique identifier information comprises an address associated with a subscriber's communications interface; and/or the unique identifier information is uniquely associated with a subscriber-selected one of the input signals.
Brief Description of the Drawings In drawings which illustrate by way of example only a preferred embodiment of the invention, Figure 1 is a schematic view of a preferred embodiment of the invention utilizing a passive filter bridge, and Figure 2 is a schematic view of a fiu-ther preferred embodiment of the invention utilizing a dynamic filter coupler/combiner.
Detailed Description of the Invention Figure 1 illustrates a conventional local network 10 of telephone lines 12 comprising twisted pair telephone wires, for example as may be found in a mufti-user site such as a commercial or residential building or complex. The local network 10 may be a PBX
telephone system, a local loop served by a telephone switching station, or any other network of telephone wires which distribute signals from a common switch point.
Telephone signals are distributed, typically at a earner of a frequency around 7 kHz, from the common distribution point 14, which may be a switch or distribution panel 14, for example a PSTN
splice block in a telephone room, local telephone company switching terminal, PBX
telephone system panel etc., to telephones 2 of subscribers in the various units serviced by the local network 10.
Each telephone line 12 is dedicated to a single subscriber unit, such that the local network forms a circuit-switched network wherein telephone signals received at the common distribution point 14 from a local telephone utility (not shown) are isolated to the telephone line 12 associated with the destination subscriber. This ensures telephone subscriber privacy and prevents crosstalk or interference between dedicated telephone lines 12.
As in United States Patent No. 6,038,425 issued March 14, 2000 to Jeffery, which is incorporated herein by reference, a redistributor 20 serves as a telecommunications signal receiver and router/distributor, receiving a plurality of audio/video input signals and redistributing subscriber-selected signals to multiple subscribers from the common distribution point 14 of the telephone wiring at the multi-user site, for example a PSTN splice block, through modem 22. A communications interface located in each subscriber's unit comprises a modem 30 which modulates and delivers the input signal selected by the subscriber in that unit from the redistributor to a receiving device (not shown), for example a conventional television receiver or computer, and receives control signals input by the user for transmission to the redistributor 20 to select the input signal and communicate interactively where the selected input signal permits.
The redistributor 20 receives signals in multiple formats, processes the signals and, based on commands transmitted through a subscriber's communications interface, redistributes the selected signal to the subscriber, in the preferred embodiment over the same twisted pair telephone wire 12 carrying telephone services to the unit. The redistributor 20 is installed at the multi-user site, which may for example be an apartment or condominium, commercial high rise, hospital, school, a local loop in a neighborhood telephone system, or any other site or network which provides a common distribution point 14 for twisted-pair telephone wire (including PSTN, network category five copper cable or any other local area network cabling) distributed to telephone subscribers within the local network 10.
The local network 10 thus connects the redistributor 20 with the communications interfaces comprising modems 30. Each redistributor input may comprise a demodulator and processor suitable for the particular format of the input signal, as described in United States Patent No. 6,038,425, so that the redistributor 20 receives and processes a plurality of input signals for redistribution of a subscriber-selected one of the plurality of input signals to the selecting subscriber's communications interface.
According to the present invention the redistributor 20 distributes the subscriber-selected signals as data packets, preferably on a high frequency Garner, for example in the _7_ range of 7 to 10 MHz, to maximize bandwidth. The redistributor 20 can distribute signals using any desired modulation technique via modem 22, including but not limited to frequency division multiplexing, orthogonal frequency division multiplexing, QAM, FSK, PSK, QPSK
etc. The data packets are encoded with a unique identifier, which ensures that each data packet is routed to the destination subscriber and which governs the reconstruction of the original input signal from the discrete data packets according to conventional packet switching techniques. For example, in packet switching techniques operating over a Transmission Control Protocol such as TCP/g', each data packet has a header containing an address which is processed to route the data packet to the requesting subscriber's destination, and each subscriber's modem 30 processes only data packets having the routing address associated with the destination subscriber.
Those skilled in the art will appreciate that it is equally possible to instead (or in addition) embed or encode in each data packet a unique identifier associated with the input signal, rather than the subscriber destination, and the subscriber's communications interface would be programmed to process only data packets having the unique identifier corresponding to the specific signal selected by the subscriber.
The redistributor 20 is connected to the local network 10, preferably at an intermediate point between the common distribution point 14 and the subscribers' communications interfaces, so that redistributed signals can be transmitted along all or selected dedicated telephone lines 12. According to a preferred embodiment of the invention, a bandpass filter bridge 40 is coupled to the local network 10 between the redistributor 20 and the communications interfaces. The filter bridge 40 comprises at least one bandpass filter coupling at least two of the dedicated telephone lines 12, and in the preferred embodiment couples all telephone lines 12 dedicated to redistribution subscribers. The bandpass filter bridge 40 thus interconnects the dedicated telephone lines 12 to create a connectionless network at all passband frequencies, turning the local network 10 into a connectionless network only at frequencies passed by the coupler 40.
The bandpass filter bridge 40 may comprise high pass filters 42 as shown in Figure l, distributing all carriers above a selected cutoff frequency amongst the dedicated subscriber telephone lines 12, or notch filters 44 as shown in Figure 2, allowing for the selection of any _g_ desired passband for the connectionless distribution of signals across the network 10 between two selected cutoff frequencies. This allows for the redistributor to distribute signals using any desired frequency, which allows the system to redistribute signals over conventional telephone signal Garner frequencies (e.g. at 0 to 7 kHz) and around high speed telephone service Garners (e.g. in the order of 1 MHz). The bandpass filter bridge 40 may comprise low pass filters (not shown), distributing across the local network 10 all Garners below a selected cutoff frequency, however it is anticipated that this embodiment would have limited application as the redistributed services would typically require high frequency Garners, and telephone signals which have to be blocked by the filter bridge 40 are typically carned at lower frequencies.
Thus, while the local network 10 remains a circuit-switched network at frequencies below and/or above the cutoff frequencies of the filter bridge 40, so that the telephone lines 12 remain dedicated and isolated to each telephone subscriber at frequencies outside of the passband, at frequencies within the passband of the filter bridge 40 the local network 10 becomes a connectionless network. The redistributor 20 redistributes each input signal selected by a subscriber at a frequency within the passband of the high pass filter bridge 40, such that each selected redistributed signal is distributed to all redistribution subscribers, but each redistribution subscriber's modem 30 selectively processes only data packets having the unique identifier associated with the subscriber's request (i.e. a routing address specifying the destination subscriber's communications interface or a unique identifier corresponding to the subscriber-selected signal). Thus, only the input signal selected by each subscriber is processed for transmission to the receiving unit 2 connected to the selecting subscriber's communications interface.
Figure 1 illustrates a passive filter bridge embodiment of the invention, utilizing a high pass filter bridge 40 comprising capacitors 42 having a capacitance selected according to the desired passband of the high pass filter bridge 40. For example, with redistribution services being distributed in Garners ranging between 7 and 10 MHz, analog telephone service at 7 kHz and digital or high-speed telephone service (such as DSL) at 1 MHz can be effectively isolated by selection of a suitable capacitance N, creating a passband at all frequencies over 4 MHz. Control signals for subscriber service selection, which may for example be sent from the communications interfaces to the redistributor 20 in a carrier having a frequency around 180 kHz, as described in copending United States Patent Application No.
09/522,940 to Jeffery filed March 10, 2000 which is incorporated herein by reference, are well below the cutoff frequency of the filter bridge 40 and thus are also isolated to each dedicated subscriber telephone line 12. This is advantageous as it allows all control signals from different subscribers to be carned at the same frequency. If desired, control signals could be transmitted at a frequency within the passband of the filter bridge 40, but in this situation control signals from different redistribution subscribers would interfere with one another so each subscriber would have to be assigned a different frequency for the transmission of control signals.
The filter bridge 40 is coupled only to the dedicated telephone lines 12 servicing redistribution service subscribers. The dedicated telephone lines 12 leading to any telephone subscribers that are not also redistribution subscribers are not connected to the filter bridge 40, and as such remain dedicated and isolated at all frequencies, so non-paying subscribers cannot obtain free redistribution services by clandestinely installing a counterfeit communications interface. It will also be appreciated that a plurality of high pass filters 42 having different passbands may be selectively installed in the local network 10, to exclude certain services from some redistribution service subscribers and thus facilitate a mufti-tiered redistribution service, wherein for example basic and premium subscribers have access to different levels of redistribution services.
Figure 2 illustrates a dynamic filter bridge embodiment of the invention. In this embodiment a microprocessor-controlled filter controller 46 dynamically controls the passband of notch filters 44 to selectively pass signals within any desired frequency range, for example below or above a selected cutoff frequency or within a notch between two cutoff frequencies. The notch filters 44 may for example each comprise a resistor-capacitance circuit controlled by a standard operational amplifier, or any other suitable variable-passband filter.
In this embodiment the controller 46 can thus change the passband to dynamically allocate passband frequencies to the filter bridge 40 responsive to the dynamic allocation of redistribution frequencies by the redistributor 20.
For example, to avoid interference and cross-talk in the system described in copending United States Patent Application No. 09/522,940 to Jeffery, the redistributor dynamically selects and allocates a redistribution frequency most suitable for the signal selected by each user. Frequency allocation can be based on conditions such as attenuation due to interference from other sources or cable length, signal loss, signal-to-noise ratio, data density of the output signal and signal sharing with output signals being distributed to other subscribers, and redistribution frequencies will accordingly vary over time. Thus, according to the present invention the dynamic filter controller 46 can dynamically establish the passband of the connectionless network responsive to the allocation of frequencies by the redistributor 20 for redistributed signals. In this manner, the flexibility of the redistributor 20 to allocate optimum frequencies is maintained.
It can thus be seen that the filter bridge or coupler/combiner 40 of the invention effectively creates a frequency-dependent hybrid circuit-switched/connectionless network.
Such a network allows for the differential distribution, over a local network 10 of dedicated telephone lines 12, of at least one signal in the form of data packets having identifier information on a earner within the filter passband of the filter bridge 40, and at least one signal on a earner outside of the filter passband which remains isolated to each dedicated subscriber telephone line 12.
It will be appreciated that the system and method of the invention is suitable for use in cable modem applications, which utilize packet switching techniques under the DOCSIS
(Data Over Cable Service Interface Specifications) standard to deliver data to individual subscribers over a shared coaxial cable network.
A preferred embodiment of the invention having been thus described by way of example only, it will be apparent to those skilled in the art that certain modifications and adaptations may be made without departing from the scope of the invention, as set out in the appended claims.

Claims (27)

1. A bandpass filter bridge for a local network of dedicated twisted pair telephone lines each comprising a twisted pair of telephone wires, the filter bridge comprising at least one bandpass filter coupling at least two telephone lines within the local network, wherein signals outside of the passband of the filter remain isolated to each dedicated telephone line while signals within the passband of the filter are transmitted to all telephone lines coupled by the filter bridge.

2. The filter bridge of claim 1 comprising a plurality of bandpass filters coupling a plurality of telephone lines.

3. The filter bridge of claim 2 wherein the bandpass filters have a fixed passband.

4. The filter bridge of claim 3 wherein the bandpass filters are high pass filters.

5. The filter bridge of claim 2 wherein the bandpass filters have a variable passband.

6. The filter bridge of claim 5 wherein the bandpass filters are notch filters.

7. The filter bridge of claim 5 comprising a controller which dynamically allocates a variable passband frequency to the bandpass filters.

8. A system for distributing a plurality of signals having different frequencies to a plurality of communications interfaces over a local network of dedicated telephone lines, each telephone line comprising a twisted pair of telephone wires, comprising a redistributor comprising a server, for receiving a plurality of input signals and redistributing subscriber-selected signals of the plurality of input signals to the communications interfaces, the redistributed signals being distributed over the local network as data packets each having unique identifier information relating each data packet to a particular communications interface or to a particular redistributed signal, the local network comprising at least one bandpass filter coupling at least two dedicated telephone lines, to thereby allow signals within a passband of the filter to pass between the coupled subscriber lines, wherein signals outside of the passband of the filter remain isolated to each dedicated telephone line while redistributed signals within the passband of the filter are transmitted to all communications interfaces in the local network and each communications interface selectively processes only data packets having unique identifier information associated with the communications interface or associated with the subscriber-selected signal.

9. The system of claim 8 comprising a plurality of bandpass filters coupling a plurality of telephone lines.

10. The system of claim 9 wherein the bandpass filters have a fixed passband.

11. The system of claim 10 wherein the bandpass filters are high pass filters.

12. The system of claim 9 wherein the bandpass filters have a variable passband.

13. The system of claim 12 wherein the bandpass filters are notch filters.

14. The system of claim 12 comprising a controller which dynamically allocates a variable passband frequency to the bandpass filters.

15. The system of claim 14 wherein the controller dynamically allocates a variable passband frequency to the bandpass filters responsive to an allocation of a redistribution frequency by the redistributor.

16. The system of claim 9 wherein the unique identifier information comprises an address associated with a subscriber's communications interface.

17. The system of claim 9 wherein the unique identifier information is uniquely associated with a subscriber-selected one of the input signals.

18. A method of distributing a plurality of signals having different frequencies to a plurality of communications interfaces over a local network of dedicated telephone lines, each telephone line comprising a twisted pair of telephone wires, comprising the steps of a. redistributing subscriber-selected signals of a plurality of input signals to the communications interfaces as data packets each having unique identifier information relating each data packet to a particular communications interface or to a particular redistributed signal, b. coupling at least two dedicated telephone lines with a bandpass filter, to thereby transmit signals within a passband of the filter across all coupled subscriber lines, and c. distributing other signals outside of the passband of the filter, wherein the signals outside of the passband of the filter remain isolated to each dedicated telephone line while redistributed signals are transmitted to all communications interfaces in the local network and each communications interface selectively processes only data packets having unique identifier information associated with the communications interface or associated with the subscriber-selected signal.

19. The method of claim 18 comprising the step of coupling a plurality of telephone lines with a plurality of bandpass filters.

20. The method of claim 19 wherein the bandpass filters have a fixed passband.

21. The method of claim 20 wherein the bandpass filters are high pass filters.

22. The method of claim 19 wherein the bandpass filters have a variable passband.

23. The method of claim 22 wherein the bandpass filters are notch filters.

24. The method of claim 22 including the step of dynamically allocating a variable passband frequency to the bandpass filters.

25. The method of claim 24 including the step of dynamically allocating a variable passband frequency to the bandpass filters responsive to an allocation of a redistribution frequency by the redistributor.

26. The method of claim 19 wherein the unique identifier information comprises an address associated with a subscriber's communications interface.

27. The method of claim 19 wherein the unique identifier information is uniquely associated with a subscriber-selected one of the input signals.