|Title of Invention||
A DEVICE FOR SIMULTANEOUSLY PROVIDING PERMANENT INTERNET ACCESS AND NORMAL VOICE TELEPHONY TO SUBSCRIBERS
|Abstract||A system for simultaneously providing permanent Internet access and normal voice telephony to subscribers,using a single conventional telephone line per subscriber, consisting of at least One Access Terminal comprising a DSL, DSP and ASIC with telephone interface and Ethetnet interface, and at least one Access Switch comprising a DSP, buffer memory; routing engine connected to an interface module,said Acoess Tetminal and Access Switch being located at user-premises and outside the said premises respectively, characterised in that the output side of said Access Terminal being connected to the input side of the said Access Switch by the known telephone line, while the input side of the said Access Treminal is colnnectable to one or more telephones on the user-premises and also to one or more computers on the said premises, and the output side of the said Access Switch is connectable to the PS1N for voice transmission and to Internet Service provided for computer data transmission.|
|Full Text||THE PATENTS ACT 1970
A DEVICE FOR SIMULTANEOUSLY PROVIDING PERMANENT INTERNET ACCESS AND NORMAL VOICE TELEPHONY TO SUBSCRIBERS USING CONVENTIONAL TELEPHONE LINES
INDIAN INSTITUTE OF TECHNOLOGY, IIT P.O. CHENNAI 600 036, INDIA. AN AUTONOMOUS BODY SET UP BY THE GOVERNMENT OF INDIA UNDER AN ACT OF PARLIAMENT,
THE FOLLOWIN0 Specification PARTICULARLY DESCRIBES AND ASCERTAINS THE NATURE OF THIS INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
This invention relates a device for simultaneously providing permanenet Internet access and normal voice telephony to subscribers using conventional telephone lines.
Presently, a telephone subscriber accesses the Internet by placing a call to an Internet Service Provider (ISP). But this has several disadvantages, namely : the phone line is not available during Internet access; call charges can be quite high if the call is a toll call (even when it is a local call, wherever local calls are metered); congestion in the inter-exchange trunk network due to the much longer duration of Internet calls compared to voice calls ; cost of modems at both the user and ISP nodes ; low data rates (2.4 - 33 Kbps) over the analog local loop, especially outside large cities.
While many users have several computers on a Ethernet LAN (Local Area Network), dial-up access allows only one computer to be connected to the Internet. To connect a LAN requires an expensive Router in addition to the modem.
The circuit-switched call model suits voice conversations well. The line is utilized almost all the time since the caller or receiver is speaking. Internet traffic is, however, "bursty" For instance, an e-mail message of a few lines may take many minutes to compose/read, but only a few seconds to transmit. A farmer's PC could receive a brief weather forecast every few minutes and alert the farmer only in case of impending change. Thus, during a call to an ISP, the line is under-utilized most of the time.
Ideally, what a user would like is a permanent connection to the Internet that does not interfere with voice calls and for which the user has to pay only for actual use during Internet access.
Currently, there are two solutions.
The first solution is to obtain a leased line between the user and the Internet Service Provider, either using cable or by using wireless access. The solution is however very expensive.
The second is to use ISDN (Integrated Services Digital Network) to provide two 64 Kbps channels on one twisted-pair cable. One would be for voice and the other for data. However, this requires ISDN equipment at the user and ISP ends, apart from the fact that the exchanges and network between the two ends must also support ISDN. This again results in high cost. Besides, in both the above options, a circuit between the user and the ISP is occupied for the entire duration of Internet access (often over an hour) resulting in congestion in the telecom network.
This invention, therefore, proposes a device to largely overcome the above drawbacks and provides simultaneously permanent access to the Internet and dial-up access to the PSTN over a single copper twisted pair to a digital local exchange supporting the V5.2 interface or any other interface supported by the exchange.
The device proposed herein enables separation of voice and data from a single user at the kerb (where typically the Access Switch comprised in the device is located as close to the user as possible), thereby enabling the data from a plurality of users to be multiplexed and to proceed to the Internet Service Provider (ISP) on shared lines.
The device has a user access unit with telephone interface and integral Ethernet interface.
The user access unit has a built-in Internet Protocol (IP) routing functionality.
The device has Digital Signal Processor (DSP) based soft-switching in which the voice and the data signals pass through the DSP permitting considerable flexibility and customizability.
The device also enables the provision of a split IP router with the two parts separated by a link several kilometers long.
Various other features of the device proposed herein will be apparent from the following further description thereof
The device proposed herein will now be described with reference to the accompanying drawings, which illustrate, by way of example, one of various possible embodiments of this invention, and wherein :
Fig. 1 illustrates the general layout of the system
Fig.2 illustrates the Access Terminal connections, and
Fig.3 illustrated the Access Switch connections.
As already stated, the device proposed herein provides permanent Internet access and normal voice telephony to a large number of users, each of whom is connected by a single copper twisted pair local loop (marked as 1) Each subscriber may have one or more telephones (marked 2) and one or more computers (marked 3) on an Ethernet LAN.
On the Public Switched Telephone Network (PSTN) side an Access Switch AS is connected to a bundle of El/TI lines running access protocol e.g. the V5.2 (reference ETSI) access protocol (Fig. 1). Such lines are typically provided by most modem telephone exchanges. AS is also connected to ISP using El/Tl lines.
The Access Terminal AT which is located at the user premises, incorporates the functions of an exchange line card for each telephone. The various events e.g. on-hook, off-hook, dialled digits and the digitized voice are encoded and transmitted over the local loop along with Internet data using standard or non-standard Digital Subscriber Loop (DSL) techniques, to the Access Switch AS,
The Access Switch could be located at the exchange side, several kilometers from user premises, but it is advantageous to locate AS on the kerb side, say, a few hundred meters from users. At this point optical fibre with drop and insert could be used to connect it to the exchange.
The AT also incorporates an Ethernet interface with part of the IP routing functionality. Based on this routing, selected IP packets from the Ethernet are transmitted to the local loop to the AS. The voice and data are multiplexed on the local loop and carried using DSL techniques
including n-isdn, HDSL, ADSL or any other digital subscriber loop technique, the choice depending on the number of telephones and the maximum data rate to be supported.
At the AS the voice signals from all subscribers are passed on to the PSTN local exchange (LE) via the V5.2 interface or any other interface supported by the local exchange. The IP packets are separated from the voice signals and the IP packets from all subscribers are passed on to an integral routing engine (located inside the AS). This routes the IP packets to one of several ISPs over 64 kbps dial-up or 64 kbps / 1.544 Mbps / 2 Mbps leased connections. IP packets from many users share these data links to the ISPs. The dial-up leased connections are also made via the V5.2 interface or other equivalent exchange interface.
Thus, voice and Internet traffic are combined on the single dedicated local loop to each subscriber and the voice and data are subsequently seperated before entering the PSTN, and relying on statistical multiplexing computer data efficiently share a few links to the ISPs (which also go through the PSTN).
USE OF DSP IN AT IMPLEMENTATION
While the AT can use off the shelf custom components, a novel use of DSP along with a Application Specific Integration Chip (ASIC) enables realisation of the device at low cost (Fig.2). Analog functions such as driving the telephone speaker, and collision detection on Ethernet are performed in hardware. Time critical functions such as maintaining the 9.6 μs inter-frame gap in Ethernet are done in hardware. All other protocol processing is done in software, leading to lower cost and greater flexibility. This is facilitated by the use of a DSP, traditionally used for signal processing, in a non-traditional manner. The excellent I/O capabilities of the DSP make it well suited for the purpose.
The signals from both Ethernet and the telephones pass through the DSP Hence diverse processing of the data can be done. In particular, the DSP includes certain routing functions such as ARP processing and filtering of local packets. It is only due to these that the IP packets from the 10 Mbps Ethernet can be accommodated on the lower bit rate Digital Subscriber Loop (DSL) without unacceptable congestion and delays.
THE DSL (DIGITAL SUBSCRIBER LOOP OR LINE)
The function of the DSL is to transmit a bit stream at speeds ranging from 144 Kbps to several Mbps over the standard twisted-pair local loop between a subscriber and the local exchange.
THE DSP (DIGITAL SIGNAL PROCESSOR)
The function of the DSP is ethernet protocol processing, IP routing functions, multiplexing and demultiplexing, packetization of voice samples, device management and other computation.
THE ASIC (APPLICATION SPECIFIC IC)
The function of the ASIC is to interface between the DSP and the Ethernet LAN and the telephone, and to implement time-critical parts of the Ethernet protocol.
USE OF DSP IN AS IMPLEMENTATION
The Access Switch can be implemented using off the shelf components. However, use of DSP enables a low-cost realisation. The Access Switch AS accepts voice and data streams from N active users through a number of DSP-based interface modules (Fig.3). Each such module
separates the voice streams from the subscribers and sends them to the V5.2 AN protocol (or any protocol used by an exchange with similar functions) in the routing engine and, thereafter, to the local exchange via the El/Tl lines. Likewise, IP packets are put into the buffer memory. As the packet passes through the interface module DSP, it attempts to route it based on certain criteria. If this succeeds, the packet is passed to the appropriate output DSP. If not, the routing engine performs full IP routing to determine the output DSP.
The functions of the DSP is IP routing, V5.2 protocol processing, separation of data and voice, dynamic allocation of lines to ISPs, network management and other computation.
The fiinction of the buffer memory is to temporarily accumulate data packets from subscribers in order to efficiently utilize the lines to the ISPs and to avoid congestion on the said lines.
The function of the routing engine is to separate data packets based on their addresses and to transmit them in various outgoing links. This is based on the IP standards.
THE INTERFACE MODULE
This consists of a DSP and ICs for DSL interface The fiinctionsof these are separation of voice and data, DSL related processing and routing of data packets The data path connecting the access terminals to the Access switch is internal to the device. Hence, it could use any convenient signalling and protocols. However, the twisted pair local loop used for this data path may be a part of a bundle of such cables, some of which may be used for other purposes such as traditional voice telephony. Hence, we choose any of the standard digital subscriber loop physical layers accepted by telecom bodies. These include ISDN at 144 Kbps, HDSL at 1 Mbps, 2 Mbps, ADSL at 6 Mbps and others.
The terms and expressions in this specification are of description and not of limitation and it is understood that various other embodiments of the device proposed herein are possible without departing from the scope and ambit of this invention.
1. A device for simultaneously providing permanent Internet access and normal voice telephony to subscribers, using a single conventional telephone line per subscriber, comprising at least one Access Terminal for being located at user-premises and at least one Access Switch for being located outside the said premises, the output side of said Access Terminal being connectable to the input side of the said Access Switch by the known telephone line, while the input side of the said Access Terminal is connectable to one or more telephones on the user-premises and also to one or more computers on the said premises, and the output side of the said Access Switch is connectable to the PSTN for voice transmission and to Internet Service provided for computer data transmission.
2. A device as claimed in Claim I and Claim 2 wherein the Access Terminal comprises a DSL, DSP and ASIC with telephone interface and Ethernet interface.
3. A device as claimed in Claim 1 and Claim 2 wherein the Access Switch comprises a DSP, '
buffer memory; routing engine connected to an interface module.
4. A device for simultaneously providing permanent Internet access and normal voice
telephony to subscribers using conventional telephone lines substantially as herein
described with reference to, and as illustrated in, the accompanying drawings.
|Indian Patent Application Number||1878/MAS/1998|
|PG Journal Number||26/2007|
|Date of Filing||19-Aug-1998|
|Name of Patentee||INDIAN INSTITUTE OF TECHNOLOGY|
|Applicant Address||IIT P.O, CHENNAI,600 036|
|PCT International Classification Number||H04L12/00|
|PCT International Application Number||N/A|
|PCT International Filing date|