Abstract:
A method of, and an apparatus for, providing broadband services to multiple remote units located at a client premise via a single communication line are provided. Authorization data is communicated from distribution equipment to the remote units and the authorization data authorizes one of the remote units to transmit data to the distribution equipment. The authorization data is included in a DSL frame and is sequentially changed thereby sequentially to authorize each remote unit one at a time to transmit data. The distribution equipment provides the authorization data in a control word of a frame header of a VDSL frame.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to the field of broadband communication and, more specifically, to a system for, and a method of, communicating broadband content to a plurality of remote units. It also relates to a remote unit and distribution equipment. 
     BACKGROUND OF THE INVENTION 
     Service providers use various types of communication lines to provide broadband content to users. In order to utilize conventional telephone networks, various technologies have been developed. An example of such a technology is digital subscriber line or DSL technology. Examples of DSL technology include asymmetrical DSL (ADSL), symmetrical DSL (SDSL), very-high-bit-rate DSL (VDSL) or the like. Due to the various different types of DSL, reference is often generically made to xDSL. The xDSL technology allows broadband content (including voice, data and video) to be communicated over existing, relatively rudimentary, communication networks such a conventional copper wires forming part of a plain old telephone service (POTS). For the purposes of this specification, the application of the invention to xDSL technology should be predominantly, but not exclusively, borne in mind. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention, there is provided a method of providing broadband services to a plurality of remote units located at a client premise via a single communication line, the method including communicating authorization data from distribution equipment to the remote units, the authorization data authorizing one of the remote units to transmit data to the distribution equipment. 
     Further in accordance with the invention, there is provided a system for providing broadband services, the system including:
         distribution equipment connected to at least one content provider and configured to provide the broadband services via a plurality of subscriber communication lines; and       

     a plurality of remote units connectable to each subscriber communication line, the distribution equipment being configured to communicate authorization data to the remote units that authorizes the remote units to transmit data to the distribution equipment one at a time. 
     Still further in accordance with the invention, there is provided a remote unit for receiving broadband services via a communication line, the remote unit including:
         interface circuitry to interface the remote unit to a user device;   a receiver connected to the interface circuitry for receiving downstream data from distribution equipment; and   a transmitter connected to the interface circuitry, the transmitter transmitting upstream data to the distribution equipment upon authorization by the distribution equipment.       

     In accordance with a yet further aspect of the invention, there is provided distribution equipment which includes:
         a network interface to interface the distribution equipment to at least one broadband content provider; and   a communication interface to interface the distribution equipment to a communication line to which a plurality of remote units are connectable, the distribution equipment being operable to control upstream transmission of data by each remote unit.       

     Other features of the present invention will be apparent from the accompanying drawings and from the detailed description which follows. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The invention is now described, by way of non-limiting example, with reference to the accompanying diagrammatic drawings. 
       In the drawings, 
         FIG. 1  shows a schematic block diagram of a prior art system for distributing broadband content to a plurality of subscribers in a point-to-point fashion; 
         FIG. 2  shows a schematic block diagram of a system, in accordance to the invention, for distributing broadband content to a plurality of users in a multi-drop fashion; 
         FIG. 3  shows a more detailed schematic block diagram of distribution equipment and a remote unit, both in accordance with the invention, of the system of  FIG. 2 ; 
         FIG. 4  shows a more detailed schematic block diagram of the remote unit; 
         FIG. 5  shows a schematic diagram of a various functional layers of the remote unit of  FIG. 4 ; 
         FIG. 6  shows a schematic flow diagram of functional interaction between the distribution equipment and each remote unit; 
         FIG. 7  shows a schematic representation of a VDSL frame including authorization data that controls operation of the remote units connected directly to a DSL communication line; and 
         FIG. 8  shows a schematic block diagram of a computer system which may be used in the system. 
     
    
    
     DETAILED DESCRIPTION 
     A method and system, with their associated components, is described. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be evident, however, to one skilled in the art that the present invention may be practiced without these specific details. 
     Referring to the drawings, reference numeral  10  generally indicates a prior art system for communicating broadband content to a plurality of client premises or subscriber locations  16 - 22 . The system  10  includes central office equipment  12  which receives broadband content via a communication line  14  and selectively distributes the content to the subscriber locations  16 - 22  via a DSL Access Multiplexer (DSLAM)  24 . Accordingly, the DSLAM  24  includes a plurality of subscriber ports or central office transmitter units (TU-C)  26 . 1 - 26 . n  that are connected to electronic apparatus at the subscriber location  22  via communication line  28 . The communication line  28  is typically a twisted pair of copper wires that telephone companies install to provide telephone services to the subscriber locations  16 - 22 . 
     As mentioned above, the communication line  28  is typically standard telephone wiring that terminates in a telephone wiring installation  30  in a dwelling at the subscriber location  22 . In these circumstances, a plurality of telephone access points  32 - 42  is typically provided throughout the dwelling and, at each of these access points  32 - 42 , electronic apparatus or devices may be connected. For example, a telephone  44  may be connected at the access point  32 , a fax machine  46  may be connected at the access point  34 , and a further telephone  48  may be connected at the access point  40 . Each of the aforementioned apparatus  44 - 48  is connected via a filter  50  in a conventional fashion. However, in order to provide broadband content to suitable electronic apparatus, a gateway in the form of a prior art DSL modem  52  is connected to one of the access points  32 - 42 , for example the access point  36 , and distributes broadband content to customer specific apparatus such as a plurality of personal computers (PCs)  54 , a set top box (STB)  56 , or the like. It is to be noted that in the prior art configuration, the STB  56  and the PCs  54  are not directly connected to the telephone wiring installation  30  in that they require a gateway such as the DSL modem  52  to request and receive broadband content. If the customer specific apparatus is located remote from the gateway, a separate independent wiring network  58  is required in addition to the telephone wiring installation  30 . Despite the inconvenience of setting up this independent wiring network  58 , it also results in additional costs. 
     Referring in particular to  FIG. 2  of the drawings, reference numeral  100  generally indicates a system, in accordance to the invention, for distributing broadband content to a plurality of subscriber locations  16 - 22  in a multi-drop fashion. Unlike the prior art system  10 , the system  100  is arranged in a multi-drop fashion in which a plurality of remote units  102  are connected directly to the telephone wiring installation  30  provided, for example, in a house, apartment, office or the like. The wiring installation  30  is connected to the communication line  28 . Accordingly, broadband communicated via the distribution equipment  106  may be tapped off from a communication line at any one of the telephone access points  32 - 42  provided within the dwelling. Thus, no gateway in the form of a modem  52  is required in addition to further dedicated wiring  58  as in the case of the prior art (see  FIG. 1 ). As described in more detail below, the system  100  includes a master transmitter controller  104  included at the distribution equipment  106 , also in accordance with the invention. The master transmitter controller  104  controls operation of each remote unit  102  so that only a single remote unit  102  communicates or transmits upstream data at any given time as described in more detail below. The distribution equipment  106  and remote units  102  are configured communicate very-high-bit rate DSL (VDSL) via the communication line  28 . It is however important to appreciate that the invention can be applied to any other type of DSL (xDSL). 
     Referring in particular to  FIG. 3  of the drawings, the distribution equipment  106  includes application specific processing components  108  which interface the distribution equipment  106  to an exchange via which broadband content is provided. The distribution equipment  106  may thus define a transmitter unit (TU-O) at an optical network unit (ONU), which converts digital data to and from continuous-time physical-layer VDSL signals communicated via the communication line  28 . The distribution equipment  106  may be located at a central office when VDSL is deployed from the exchange, or located in a cabinet when VDSL is deployed from a midloop location different from the central office. It is however to be appreciated that the distribution equipment  106  may be located at any other suitable point in a communication network. 
     The distribution equipment  106  further includes physical medium specific transmission convergence (PMS-TC) components and physical medium dependent (PMD) components  110 , which interface the application specific components  108  to the communication line  28 . The components  108  and  110  may be similar to conventional components currently used in a VDSL network. However, unlike the prior art system  10 , the distribution equipment  106  includes the master transmitter controller  104  which inserts control bits into VDSL frames communicated to each remote unit  102  which, in response thereto, enters a different mode of operation as described in more detail below. In a similar fashion to a conventional VDSL network, the system  100  includes a service splitter  112  for extracting voice data communicated by a public switched telephone network (PSTN) or integrated services digital network (ISDN) line. The service splitter  112 , in a conventional fashion, allows PSTN signals to occupy the same physical medium as the VDSL signal. 
     The remote unit  102  defines a VDSL transmitter unit at client premises or subscriber location  16 - 22 , which converts digital data to or from continuous-time physical-layer VDSL signals for communication via the communication line  28 . In particular, the remote unit  102  includes physical medium-specific transmission convergence (PMS-TC) and physical medium-dependent (PMD) components  114 . The components  114  interface the remote unit  102  to the communication line  28  and are configured to communicate VDSL frames to the distribution equipment  106 . Further, the remote unit  102  includes at least one application specific (customer/subscriber device or apparatus) interface  116  which interfaces the remote unit  102  via a communication line  118  to the STABS  56 , the PCs  54 , or the like. Accordingly, each remote unit  102  may have one or more application specific interfaces  116  configured to supply broadband content to one or more user devices or apparatus. In less sophisticated embodiments, the application specific interface  116  is configured to supply only data thereby to render the remote unit  102  suitable for interfacing the PC  54  to the Internet using VDSL technology. In other embodiments, the application specific interface  116  is configured to have a co-axial output so that it can interface with the STB  56  and thereby provide video content. It is however to be appreciated that one or more application specific interfaces  116  may be included in each remote unit  102  so that it may drive different user devices. 
     The components  114  and  116  may resemble conventional components, however, unlike the prior art components, the remote unit  102  includes a slave transmitter controller  120  which, in response to authorization data provided by the distribution equipment  106  in the VDSL frame, controls operation of the remote unit  102  so that only one remote unit  102  communicates upstream data at any given time. It is to be appreciated that the master transmitter controller  104  and slave transmitter controller  120  may be implemented by software modules that control operation of the distribution equipment  106  and remote unit  102  respectively. 
     A more detail block diagram of the remote unit  102  is shown in  FIG. 4 . From a functional point of view, the remote unit  102  includes a physical medium-dependent (PMD) layer  122 , a transmission convergence (TC) layer  124 , a transport layer  126 , and application specific customer interface (ASCII) layer  128 . These layers correspond to the components  114  and  116  of  FIG. 6 . The PMD layer  122  includes a demodulator or receiver  130 , a modulator or transmitter  132 , and the slave transmitter controller  120  which, as mentioned above, is typically in the form of a software module operable to enable and disable the transmitter  132  in response to the authorization data. In the embodiment depicted in  FIG. 4 , the ASCII  116  includes a data interface  134  for driving the PC  54  or local area network (LAN), and a video interface for driving the STB  56 . Further ASCII  138  may be provided for various other electronic devices for receiving and transmitting broadband content. The remote unit  102  includes a control component  140  that controls operation of its various modules and components. 
     As mentioned above, the distribution equipment  106  and remote unit  102  are configured to communicate broadband content by VDSL signals. The content is typically included in VDSL frames  142  (see  FIGS. 5 and 8 ). Each VDSL frame  142  includes, inter alia, syncword octets  144 , three control octets  146 , and a payload portion  148 . In terms of standard VDSL conventions, such as those provided by Committee T1—Telecommunications, Working Group T1E1.4(DSL Access), T1E1.4/2001-009R4 and T1E1.4/4/2001-011, four bits of a control  3  octet are reserved for proprietary applications (see  FIG. 7 ). The four bits reserved for proprietary applications define the authorization data  150  that includes two bits defining identification data  152 , and two bits defining status data  154 . As the identification data  152  has two bits available, it can identify up to four remote units  102  and, the two bits of the status data  154  can define up to four different modes of operation of the particular remote unit  102  identified by the identification data  152 . In the embodiment depicted in the drawings, the following four modes of operation are defined. A “Train” mode during which the distribution equipment issues Train commands to train the remote unit  102  in a similar fashion to that conventionally done with VDSL devices, an “Acquire” synchronization mode in which the particular remote unit  102  in response to an Acquire command transmits data in order to establish synchronization with the distribution equipment  106 , a “Data” transmission mode in which the particular remote unit  102  is commanded or authorized to include data in the payload portion  148  of the VDSL frame  142  for communication to the distribution equipment  106 , and a “Finish” mode in which the distribution equipment  106  issues a Finish command that instructs the particular remote unit  102  to terminate communication of data. 
     When the system  100  is in its “Train” mode of operation, three communication link-training types are typically performed. In particular, a cold start of the distribution equipment  106  or TU-O, a cold start of the remote unit  102 , and a warm start of the remote unit  102  may be performed. When the distribution equipment  106  performs a cold start, typically all remote units  102  or TU-R links are brought down and then brought up one by one. Accordingly, this typically results in a complete service interruption and is thus only done when absolutely necessary. For example, such a cold start may be preformed after the installation of any additional remote units  102 , after any maintenance or re-provisioning work is carried out, or in the event of one or more of the remote units  102  being unable to maintain or restore satisfactory operation using its start procedures. It is important to appreciate that conventional prior art training procedures may be included in the training procedures of the system  100 . 
     During the cold start at the distribution equipment  106 , the distribution equipment  106  executes conventional VDSL link-training commands to each particular remote unit  102  that is identified and controlled by the authorization data  150 . The identification data  152  of the authorization data  150  may be pre-assigned to each particular remote unit  102  or assigned during the link-training mode of operation. When the identification data  152 , which uniquely identifies the particular remote unit  102 , is pre-assigned, each remote unit  102  is then configured to wait unit it recognizes its identification data (as described in more detail below) before it transmits a response to the distribution equipment  106 . However, when the identification data  152  is assigned during the link training procedure, some form of collision resolution, such as random back-off, is typically initiated by the distribution equipment  106  so as to cause only one of the remote units  102  to train at a time. During this process, unique identification data is stored at the remote unit uniquely to identify the particular remote unit  102 . For example, a first remote unit  102  at the particular subscriber location  16 - 22  may be identified by “00”, a second remote unit  102  at the particular subscriber location  16 - 22  may be identified by “01”, and so on. Once all the remote units  102  directly connected to the communication line  28  at the particular subscriber location  16 - 22  have been trained, the distribution equipment  106  then determines which transmission profiles can be used and then commands each remote unit  102  to switch to the particular profile. 
     A cold start of the remote unit  102  is typically initiated when the remote unit  102  has not been previously trained and is then brought into service, or when the remote unit  102  has had a warm start that has failed. Typically, the warm start is a default for any remote unit  102  that is brought back into service. Upstream communications between the remote units  102  at a particular subscriber location are performed in a time division multiplexed fashion. Accordingly, both cold and warm start training of each remote unit  102  is preformed only during the time slots assigned to that particular remote unit  102 . Accordingly, service to other remote units  102  is not interrupted when training on any particular remote unit  102  is performed. The downstream VDSL signal received by the remote unit  102  is checked for satisfactory service and if this is not obtained, a cold start of distribution equipment  106  may be necessary. 
     During a warm start, the distribution equipment  106  checks the quality of the signal received from the remote unit  102  using previously assigned profiles and, if a suitable connection cannot be established, it will command a cold start of the particular remote unit  102 . If a satisfactory connection cannot be established after the cold start, a cold start of the distribution equipment  106  is then performed. 
     Referring in particular to  FIG. 6 , reference numeral  156  shows an example of a sequence of communications between the distribution equipment  106  and a remote unit  102  once it has been trained. As shown at  158 , the distribution equipment  106  initially transmits a VDSL frame  142  (see  FIG. 7 ) including identification data  152  that uniquely identifies the particular remote unit  102  with which it requires communication. The remote unit  102  then turns on its transmitter  132  and communicates an idle signal in its payload to the distribution equipment  106  thereby to establish synchronization. Once synchronization has been established, the authorization data  150  instructs the remote unit  102  to enter into the Data transmission mode of operation (generally indicated by reference numeral  160  in  FIG. 6 ) by including an appropriate value in the status data  154 . The remote unit  102  then adds its data to the payload portion  148  of the VDSL frame  142  and communicates it via the communication line  28  to the distribution equipment  106 . As mentioned above, upstream data is communicated in VDSL frames in a time division multiplexed fashion and, accordingly, the distribution equipment  106  may limit the amount of bandwidth allocated to each particular remote unit  102  dependent upon the type of electronic device(s) or apparatus which it is configured to interface with. For example, greater bandwidth may be given to internet data streams than to video channel change control messages. Once the particular remote unit  102  has communicated its data, the distribution equipment  106  then instructs the remote unit  102  to terminate transmission by sending the Finish command code in the status data  154 . If the remote unit  102  that is authorized to transmit, has no data to transmit, then it may immediately transmit an abort signal, as shown by arrow  164 . The above-mentioned procedure is then repeated for each of the remaining remote units  102  connected to the communication line  28 . 
     The payload portion  148  of an upstream VDSL frame can contain information corresponding to the current status or mode of operation of the particular remote unit  102 . This typically occurs during the Train mode of operation, during an idle pattern in the Acquire mode of operation, either idle or PDU during data an abort pattern during Finish. The actual pattern of the payload signals included in the payload portion  148  will be dependent upon the particular data encapsulation code that is used in this system  100 . 
     In a downstream direction, when a remote unit  102  recognizes its unique identification bits from the identification data  152 , it enables its transmitter  132  and maintains transmission until the received identification data  152  changes. When the particular remote unit  102  is no longer authorized to transmit, the distribution unit  106  changes the identification data  152  to identify another remote unit  102  that then, in a similar fashion, enables its transmitter  132 . In an upstream direction in which the transmitter  132  of an identified remote unit  102  transmits VDSL frames  142  to the distribution equipment  106 , the data included in the identification data  152 , of the control word  146  of the VDSL frame  142 , is the unique identification of the particular remote unit  102 . Thus, the distribution equipment  106  may confirm that the particular remote unit  102  which it has authorized to transmit is in fact transmitting. VDSL frames are transmitted in both upstream and downstream directions. 
     A description of the various modes of operation of a specific embodiment of a remote unit  102  is provided below: 
     1. To bring up a link to a particular remote unit  102 , the distribution equipment  106  communicates a Train command via the status data  154  and uses the Operations Channel of a VDSL system in the normal manner. The remote unit  102  then enters the Train mode of operation, echoes the Train command, and responds to the Operations Channel commands. When the training procedures have been completed and, accordingly, the remote unit  102  connected to the communication line  28  has been trained, or a further remote unit  102  which has been connected has been trained, the distribution equipment  106  proceeds to a normal mode of operation. 
     2. In the normal mode of operation, the distribution equipment  106  selects a particular remote unit  102  that is authorized to transmit and communicates the Acquire command in the status data  154  of the VDSL frame  152 . The selected remote unit  102  responds by echoing the Acquire command and places Idle data in its payload. The distribution equipment  106  typically maintains this state until it has synchronized to the VDSL carrier(s), framing and Idle data. 
     3. When the distribution equipment  106  has synchronized to the received signal, it changes the status data from the Acquire to indicate the Data mode of operation. The remote unit  102  responds by echoing the Data status and places transmit data traffic into the payload portion  148 . The distribution equipment  106  maintains this state of operation until either the slot time expires, or the remote unit  102  indicates it has no more data that it wishes to transmit. 
     4. To terminate transmission, the distribution equipment  106  indicates Finish command in the status data  154 . Upon receiving this command, the remote unit  102  echoes this status and terminates the placement of any more data into the payload portion  148 . When the last payload data unit has been sent, the remote unit  102  places Abort data in its payload portion  148 . 
     5. When the distribution equipment  106  has received the Finish confirmation command and observed Abort data in the payload, it changes the identification data  152  and status data  154  to acquire the next remote unit  102 . The current remote unit  102  maintains its transmission until it detects that its unique identification is no longer present in the identification data  152  that it receives. 
     6. The selected remote unit  102  may indicate the Finish state at any time to indicate that it has no more payload data to send. In this situation, it places IDLE data into the payload portion  148  if the distribution equipment  106  is authorizing it to transmit data and providing it with an Acquire command. If the distribution equipment  106  is providing Data or Finish commands, and the remote unit  102  has no more data to transmit, it includes Abort data in the payload portion  148 . 
     7. In the event that a remote unit  102  does not respond to its slot for a particular time-out period, the distribution equipment  106  reverts to communicating a Train command in subsequent VDSL slots, until communication with the remote unit  102  is once again re-gained. 
     In a downstream direction in which the distribution equipment  106  communicates broadband content to a particular remote unit  102 , the VDSL signal is received (see  FIG. 5 ) by the remote units  102  and each remote unit  102  demodulates the VDSL signal by means of its receiver or demodulator  130  to extract the relevant frame information from the VDSL frame  142  in the transmission convergence layer  124 . From the data in the payload portion  148  of the VDSL frame  142 , each remote unit  102  identifies it is being addressed and, accordingly, the data included in the payload portion  148  is destined for the particular remote unit  102 . When the particular remote unit  102  is being addressed, the data is conveyed via the transport layer  126  to the application layer  128  for communication to the user device or apparatus. In addition to analyzing the payload portion  148  to ascertain whether or not the data included in the VDSL frame  142  is for the particular remote unit  102 , each remote unit  102  also extracts control word data  146  to obtain the identification data  152  and status data  154  from the authorization data  150 . In response to the authorization data  150 , the slave transmitter controller  120  selectively enables the transmitter or modulator  132  of the particular remote unit  102 . In particular, when the remote unit  102  identifies its particular identification value is included in the control word  146 , the slave transmitter controller  120  by means of a software switch enables the transmitter  132 . When the transmitter  132  is enabled, the remote unit  102  includes its payload in the VDSL frame  142  which is then communicated via the communication line  28  to the distribution equipment  106 . Upstream data that the remote unit  102  transmits is obtained from the user apparatus or device via the application specific layer  128  and the transport layer  126  and the transmission convergence layer  124 . In the receive direction, the payload is extracted as shown at  160  whereafter the address to which the downstream payload is destined is filtered from the payload by discarding payload data units which do not have an address assigned to the particular remote unit  102  (see block  162 ). Thereafter, as shown at block  164 , protocol data units are built from the payload data units for the particular remote unit  102 . 
       FIG. 8  shows a diagrammatic representation of machine in the exemplary form of a computer system  200  within which a set of instructions, for causing the machine to perform any one of the methodologies discussed above, may be executed. In alternative embodiments, the machine may comprise a network router, a network switch, a network bridge, or any machine capable of executing a sequence of instructions that specify actions to be taken by that machine. 
     The computer system  200  includes a processor  202 , a main memory  204  and a static memory  206 , which communicate with each other via a bus  208 . The computer system  200  may further include a video display unit  210  (e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT)). The computer system  200  may also include an alpha-numeric input device  212  (e.g., a keyboard), a cursor control device  214  (e.g., a mouse), a disk drive unit  216 , a signal generation device  218  (e.g., a speaker) and a network interface device  220 . 
     The disk drive unit  216  includes a machine-readable medium  222  on which is stored a set of instructions (software)  224  embodying any one, or all, of the methodologies described above. The software  224  is also shown to reside, completely or at least partially, within the main memory  204  and/or within the processor  202 . The software  224  may further be transmitted or received via the network interface device  220 . For the purposes of this specification, the term “machine-readable medium” shall be taken to include any medium that is capable of storing or encoding a sequence of instructions for execution by the machine and that cause the machine to perform any one of the methodologies of the present invention. The term “machine-readable medium” shall accordingly be taken to included, but not be limited to, solid-state memories, optical and magnetic disks, and carrier wave signals. 
     Thus, a method and system, including their various components, have been described. Although the present invention has been described with reference to specific exemplary embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the invention. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense