Abstract:
A subscriber distribution network includes a backplane board that has a network switch and a plurality of subscriber line units, the network data, the plurality of subscriber line units being provided between the network switch and subscriber set-tops, providing data from the network switch to a corresponding subscriber set-top, and providing data transmitted from the subscriber set-tops to the network switch. In the subscriber distribution network apparatus, the network switch can be connected in simple fashion to the subscriber line units by connectors.

Description:
CLAIM OF PRIORITY 
   This application claims priority to an application entitled “Subscriber distribution network apparatus and subscriber line unit which can in simple fashion connect with network switch,” filed in the Korean Intellectual Property Office on Sep. 16, 2003 and assigned Ser. No. 2003-64071, the contents of which are hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a convergence system of broadcasting and communication that provides subscribers by converging broadcasting and communication services through optical fiber transmission lines. More particularly, the present invention relates to a connection structure between a network switch (L 2  switch), such as a layer  2  for processing an IP over Ethernet that is a communication service, and a subscriber line unit (SLU) in a subscriber distribution network apparatus of a convergence system of broadcasting and communication. 
   2. Description of the Related Art 
   In general, a communication network using the Ethernet protocol comprises a packet communication network that provides the foundation for most local area networks and Internet communication networks. 
   A 10 Base-T is commonly employed in most of the Ethernet communication networks utilized by subscribers, which is mainly used in local area networks, companies, and schools. Recent improvements in Ethernet technology has led to a metro Ethernet communication network providing subscriber homes with 100 Mbps Internet communication services of 100 Base-T by means of an unshielded twisted pair (hereinafter, referred to as an UTP) cable. 
   A convergence system of broadcasting and communication that utilizes Ethernet communication networks, Ethernet equipment that multiplexes digital broadcasting streams and Ethernet data by a time division multiplexing (TDM), generates new types of digital streams, and distributes the generated digital streams to subscribers. 
     FIG. 1  is a block diagram of a conventional convergence system of broadcasting and communication. As shown in  FIG. 1 , the conventional convergence system that provides broadcasting and communication services includes an optical line terminal (hereinafter, referred to as an OLT)  100 , an optical network unit (hereinafter, referred to as an ONU)  102  comprising a plurality of ONUs numbered from 1 to N, and optical cables that connect plurality of ONUs to the OLT  100 . The OLT  100  receives broadcasting data from broadcasters to provide subscribers with broadcasting services by converting the data into an optical signal containing bundled components that correspond to the data, and then transmitting one tied optical signal. The ONU  102  is a user-side apparatus that send information transmitted from the OLT  100  to subscribers. When broadcasting/communication data sent from broadcasters are subsequently transmitted to the ONU  102  via the OLT  100 , the ONU  102  receives the service requirements of subscribers from a set-top box  104  and then provides corresponding services. 
   In designing the ONU  102  functioning as an optical subscriber distribution network for the users via set-top boxes, which simultaneously provides broadcasting and communication in a convergence system of broadcasting and communication as described above, a commercial L 2  switch must be used as part of the network apparatus in order to process Ethernet-based packet data for communication services. 
     FIG. 2  shows a structure for connecting the commercial L 2  switch. The switch outputs 100 Base-T signals in the ONU providing the convergence system of broadcasting and communication, to a plurality of subscriber line units (hereinafter, referred to as a SLU) for adding broadcasting signals, which are output from broadcasting signal receivers, to Ethernet signals outputted from the L 2  switch  110  (shown in  FIG. 2  ). 
     FIG. 2  shows outside media attachment units (hereinafter, referred to as a MAU)  114  have UTP cable interfaces, as well as media converters (hereinafter, referred to as a MIC)  120  that are additionally provided in the ONU  102 . Further, the L 2  switch  110  is connected to SLUs  130  through the outside MAUs  114  having UTP cable interfaces and the M/Cs  120 . Herein, the M/Cs  120  convert 100 Base-T signals into 100 Base-F signals in order to input the 100 Base-T signals outputted from the L 2  switch  110  to the SLUs  130 . 
   The L 2  switch  110  classifies the packets and controls paths of a commercial network switch outputting the 100 Base-T signals. In general, the L 2  switch  110  includes a PHY  112  (PHY is an abbreviation for physical chip), which is connected to a switch chipset  111 , and MAUs  113 . Each of the MAUs  113  has a connector connection portion that connects each of the MAUs  113  to the PHY  112  through a connector. In addition, each of the MAUs has a UTP cable connection portion to which a UTP cable is connected. Further, each of the MAUs  113  generates power for transmitting signals through the UTP cable. 
     FIG. 3  shows that each of the SLUs  130  includes a first PHY  131 , a time division multiplexing (hereinafter, referred to as a TDM)  132 , a plurality of transceiving modules  133 , a second PHY  134  provided between each of the transceiving modules  133  and the first PHY  131 , and a voltage signal conversion unit  135 . The first PHY  131  converts parallel signals having a type of a media independent interface (hereinafter, referred to as a MII) into 100 Base-F signals, or which converts 100 Base-F signals into MII signals. The TDM  132  multiplexes Ethernet signals having a MII type and broadcasting signals. The voltage signal conversion unit  135  converts the multiplexed signal outputted from the TDM  132  into a differential positive emitter coupled logic (PECL) signal, which is a voltage signal having a predetermined level, and then the voltage signal conversion unit provides the PECL signal to the transceiving modules  133 . The second PHY  134  converts the PECL signals provided from the transceiving modules  133  into MII signals and then provides the MII signals to the first PHY  131 . 
   In designing the ONU  102  by means of the L 2  switch to process Ethernet-based packet data for communication services, the ONU  102 , which is an optical subscriber distribution network apparatus for simultaneously providing broadcasting and communication, must include a MAU  114  and a M/C  120  in order to connect the L 2  switch with the SLUs  130 . The MAU  114  has an UTP cable connection portion and an RJ-45 connector connection portion, and the M/C  120  is used for converting 100 Base-T signals into 100 Base-F signals. 
   As described above, the commercial L 2  switch has an UTP cable interface. Therefore, when the commercial L 2  switch is used, it is necessary to provide separate apparatuses for the UTP cable interface between the commercial L 2  switch and the SLUs. Further, when one subscriber distribution network comprises a system for providing services to several hundred subscriber (400˜500 subscribers), a plurality of UTP cables are used for connecting the L 2  switch to the plurality of SLUs. Therefore, the structure of the system becomes more complicated and the volume of the system increases, thereby having difficulties in providing an efficient subscriber distribution network. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention has been made to solve the above-mentioned problems. The present invention provides a subscriber distribution network apparatus that can in simple fashion connect subscriber line units (SLUs) to a network switch. 
   In order to accomplish the aforementioned objects, according to an aspect of the present invention, there is provided a subscriber distribution network apparatus having a backplane board, which includes a network switch and a plurality of subscriber line units, the network switch switching Ethernet data and broadcasting data, the plurality of subscriber line units being provided between the network switch and subscriber set-tops, providing data from the network switch to a corresponding subscriber set-top box, and providing data transmitted from the subscriber set-tops to the network switch, wherein, the network switch includes a switch chipset and a first differential driver that converts serial signals of Ethernet data and broadcasting data outputted from the switch chipset into differential signals. According to the present invention, each of the subscriber line units includes a second differential driver, a signal converter, a time division multiplexing processing unit, and an optical transceiving module. The second differential driver is connected to the first differential driver through a connector and restores the differential signals into serial signals. The signal converter converts the serial signals output from the second differential driver into parallel signals. The time division multiplexing processing unit multiplexes the Ethernet signal and broadcast signal output in parallel to each other from the signal converter, and converts the multiplexed signal into a voltage signal having a predetermined level. Finally, the optical transceiving module converts the voltage signal into an optical signal, outputs the optical signal to the subscriber set-tops, and provides the second differential driver with signals transmitted from the subscriber set-tops. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a block diagram of a conventional convergence system of broadcasting and communication; 
       FIG. 2  is a block diagram showing a structure for connecting a L 2  switch to subscriber line units (SLUs) in a subscriber distribution network apparatus of a conventional convergence system of broadcasting and communication; 
       FIG. 3  is a block diagram of each of the SLUs in  FIG. 2 ; 
       FIG. 4  is a block diagram showing a structure for connecting a L 2  switch to subscriber line units (SLUs) in a subscriber distribution network apparatus according to the present invention; and 
       FIG. 5  is a block diagram of each of the SLUs in  FIG. 4 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Hereinafter, one or more preferred aspects of the present invention will be described with reference to the accompanying drawings. The same reference numerals are used to designate the same elements as those shown in other drawings. In the description below, there are many particular items, such as detailed elements of circuit, are shown, but these are provided for helping the general understanding of the present invention. It is to be understood by those skilled in the art that the present invention can be embodied without such particular items. In the following description of the present invention, there are instances when a detailed description of known functions and configuration incorporated herein will be omitted when it may possible obscure the subject matter of the present invention  FIG. 4  is a block diagram of a subscriber distribution network apparatus according to the present invention. As shown in  FIG. 4 , a network switch  20  is connected to SLUs  30  through connectors and provided in the same backplane board  10 . 
   According to the present invention, the network switch  20 , is newly constituted, and includes a switch chipset  21  and a differential driver  22 . The differential driver  22  is connected to the SLUs  30  through connectors. The switch chipset  21  in the network switch  20  switches Ethernet signals transmitted from an OLT and provides the switched signals to corresponding SLUs. 
   Further, the switch chipset  21  outputs signals that have a type of a serial media independent interface (hereinafter, referred to as a SMII) or a source synchronous SMII (hereinafter, referred to as a SSSMII), to the differential driver  22 . Further, the differential driver  22  converts the SMII signals or SSSMII signals into differential SMII signals or differential SSSMII signals and then outputs the converted signals to the SLUs  30 . 
     FIG. 5  is a block diagram of each of the SLUs shown in  FIG. 4 . As shown in  FIG. 5 , each of the SLUs  30  includes a differential driver  31 , a signal converter  32 , a time division multiplexor (hereinafter, referred to as a TDM)  33 , a voltage signal conversion unit  36 , a plurality of optical transceiving modules  34 , and a PHY  35 . The differential driver  31  is connected to the network switch  20  through a connector. The signal converter  32  is connected to one side of the differential driver  31 . The TDM  33  is connected to an output side of the signal converter  32 . The voltage signal conversion unit  36  is connected to an output side of the TDM  33 . The plurality of optical transceiving modules  34  are connected to an output side of the voltage signal conversion unit  36 . The PHY  35  is provided between the differential driver  31  and the optical transceiving modules  34  and converts optical signals output from the optical transceiving modules  34  into SMII signals. 
   The differential driver  31  converts differential SMII signals or SSSMII signals provided from the network switch  20  into SMII signals and then provides the SMII signals to the signal converter  32 . The signal converter  32  converts the SMII signals into MII signals and then provides the MII signals to the TDM  33 . The TDM  33  multiplexes Ethernet signals having a MII type and broadcasting signals and then provides the multiplexed signal to the voltage signal conversion unit  36 . The voltage signal conversion unit  36  converts the multiplexed signal into a differential positive emitter coupled logic (hereinafter, referred to as a PECL) signal and then provides the differential PECL signal to the optical transceiving modules  34 . The optical transceiving modules  34  generate optical signals according to the differential PECL signal and then transmit the optical signals to the subscriber set-top boxes (not shown). 
   Further, the optical transceiving modules  34  convert optical signals transmitted from the subscriber set-top boxes into differential PECL signals and then outputs the differential PECL signals to the PHY  35 . The PHY  35  converts the received differential PECL signals into SMII signals and then outputs the SMII signals to the differential driver  31 . The differential driver  31  subsequently converts the SMII signals into differential SMII signals and then provides the differential SMII signals to the network switch  20 . 
   According to the present invention, each of the SLUs  30  receives the differential SMII signals, which are outputted from the network switch  20 , through the differential driver  31  and the signal converter  32 . Further, each of the SLUs  30  multiplexes the MII signals outputted from the signal converter  32  by the TDM  33 , converts the multiplexed signal into a voltage signal by the PHY  35 , converts the voltage signal into an optical signal by each of the optical transceiving modules  34 , and then outputs the optical signal. 
   As described above, the network switch has a differential driver employing a connector as an interface, and the SLUs connected to the network switch are constructed to process the signals of the differential driver, so that the network switch can be connected to the SLUs by the connectors. Therefore, the data can be transmitted through the connectors between the SLUs and the network switch differently from the commercial L 2  switch, which requires UTP cables for connection with the SLUs. That is, the switch chipset  21  of the network switch can be directly connected to the SLUs  30  connected to the network switch. As a result, the network switch and the SLUs  30  can be mounted in the same backplane board, and 10/100 M Ethernet data having a SMII type of the network switch can be transmitted to the SLUs  30  through the connectors instead of UTP cables. 
   While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.