Patent Application
20080175361
The invention is related to the field of telecommunication devices and services and more specifically, the invention is directed to an apparatus for enabling Voice over IP (VoIP) services on existing subscriber location Plain Old Telephone Service (POTS) wiring/networks.
Present day telephony voice networks were built around circuit switches, end offices, a toll network, tandem switches, and twisted pair wires. These voice networks are referred to as a Public Switched Telephone Network (PSTN) or Plain Old Telephone Service (POTS). Due to bandwidth limitations of POTS, there is an inherent inability to efficiently integrate multiple types of media such as telephony, data communications (including video) for Personal Computers (PC), and Television (TV) broadcasts. As such, broadband technology and architectures were developed that could be adapted to the POTS infrastructure. This technology included Asymmetrical Digital Subscriber Line (ADSL) communication networks where voice signals were transmitted in a lower frequency range of the POTS frequency baseband and data signals were transmitted in a higher frequency range.
Voice over IP (VoIP) is a recent technological development in the field of telecommunications that is utilized to transmit voice over a data network using the Internet Protocol (IP). IP is a part of the Transmission Control Protocol/Internet Protocol (TCP/IP) family of protocols described in software that tracks the Internet address of nodes, routes outgoing messages, and recognizes incoming messages. Such a data network may be the Internet or a corporate intranet, or any other TCP/IP network. Subscribers (either businesses or individuals) use VoIP over DSL (i.e., over the old POTS lines) by purchasing and installing the necessary equipment to access a VoIP service provider at their DSL-equipped location. Such VoIP equipment would include, in one example, an adapter connected between the subscriber's PSTN phone and a DSL modem to convert voice data to/from analog/digital format. Voice data is subsequently passed from the DSL modem to an IP network via a PSTN gateway.
Based on this description, it is understandable that when a new VoIP subscriber establishes service, some manner of rewiring must be performed in order to connect the VoIP equipment to the DSL service. For example, new/additional lines 116 would have to be run from the location of the modem 110/adapter 114 to any and all telephones that the customer would want to have for VoIP service. In the alternative, the subscriber would have to pay for cordless equipment in each instance where the VoIP service was preferred throughout the location. One solution to this rewiring problem and the attendant expense is to use the existing telephone wiring/network at the subscriber's location. However, this solution requires the subscriber to access the NIU and perform a number of rewiring operations that may confuse someone who is not familiar with basic telephone wiring. One such rewiring operation requires the use of a second pair of telephone wiring be connected between the POTS/DSL service and the DSL modem to take advantage of the previously wired “network” existing in the residence. If the rewiring operations are not correctly performed, permanent damage can occur to the VoIP equipment. If such rewiring operations were correctly performed, the rewiring operation could accidentally be reversed by others who have access to the NIU (e.g., a technician of the local POTS service).
Therefore, there is a need in the art for an apparatus and method for enabling simultaneous operation of VoIP and DSL services on existing telephone wiring/networks at a subscriber location that mitigates the aforementioned problems of additional equipment/wiring costs and/or rewiring errors.
The present invention generally relates to an apparatus for converting a local POTS network to VoIP capability. The apparatus includes a signal controller that is adapted for connection between a broadband-enhanced POTS service point and the local network for reducing POTS signaling. In one embodiment of the invention, the apparatus is a high pass filter. Such high pass filter includes a first port for receiving broadband-enhanced POTS service and a second port for sending DSL signals to the local network. The high pass filter is connected to broadband-enhanced POTS service at a Network Interface Unit of a DSL subscriber location. Preferably, the high pass filter has a frequency response of approximately 15 KHz-5 MHz or other such frequency response ranges that are capable of greatly reducing or eliminating a POTS service loop voltage and/or baseband voice signals on the local network and isolating the service loop from the local VoIP telephony voltages and signals.
So that the manner in which the above recited features of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings.
It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.
To achieve the desired objectives, the subject invention provides for an apparatus that provides for the coextensive operation of different broadband services or features on the same physical medium that makes up a local network. This apparatus avoids the need to perform complex or additional wiring operations by taking advantage of the existing physical wiring of which the local network is comprised. In a preferred embodiment of the invention, shown in
The apparatus and overall system described above provides VoIP service to any and all second local network end-user devices (e.g., telephones) that the customer would want by connecting an interface line 202 of the adapter 114 to the existing local network 100 (i.e., the existing twisted pair telephone wiring) at the distribution line 104. In greater detail, the signal controller 200 reduces or completely eliminates the DC loop voltage and baseband voice signals that comprise the POTS portion of the POTS/DSL service provided to the local network 100. As such, the second local network end-user devices 106 are essentially cut off from the existing POTS signaling and network (the characteristics and frequency response of the controller 200 are explained in greater detail below). Since the adapter 114 converts digital signals (e.g., from the DSL service carrying Internet Protocol (IP) signaling) to/from analog signals that drive ordinary POTS type telephones, the second local network end-user devices 106 can now only “see” signaling from the adapter 114 which becomes a new foreign exchange station for the second local network end-user devices 106. That is, the analog signals from the second local network end-user devices 106 travel along the existing network distribution line 104 to interface line 202 and back to the adapter 114 and vice versa. The adapter 114 then passes digital signals back to the DSL service (and an external network, not shown) via the modem 110. Accordingly, multiple broadband services (DSL and VoIP in the discussed example) are sharing a portion of the same physical medium (distribution line 104).
Only the high frequency DSL component of the originally inputted signal is seen at an output port 304 of the controller and on the distribution line 104. As a result, the original subscriber POTS equipment 106 is effectively disconnected from the POTS network and service without having to physically disconnect the actual distribution line 104 that previously provided the POTS service. The benefit realized is that all of the existing phone lines in the residence now can be used for VoIP service without the need for rewiring the NIU or internal residential telephone lines or adding new lines downstream of the VoIP adapter 114. These same lines also still carry the DSL signals; therefore, multiple broadband services can exist on the subscriber's POTS network. A further advantage is recognized by virtue of the characteristics of the signal controller 200. Specifically, high impedance characteristics are present at both the input port 302 and the output port 304 for DC and low frequency telephony signals. As such, the adapter 114 does not “electrically see” the impedance load inherent in the service loop 118 running from the NIU 102 to the Central Office (or switch therebetween); therefore, there are no power losses or loading in the network caused by trying to drive such a long conductor from a relatively small power supply (adapter 114).
As a precautionary measure, the controller 200 is equipped with a voltage detection/alarm feature 204 (see
In greater detail with regard to one embodiment of the subject invention, it is well known that typical POTS processes voice signals in a bandwidth of approximately 400-3,400 Hz. All frequencies below 400 Hz (including the DC loop voltage that energizes a basic telephone circuit) and above 3,400 hertz are attenuated.
While foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof.
