Patent Document

CLAIM OF PRIORITY 
     This application claims priority to an application entitled “FTTH SYSTEM FOR BROADCAST/COMMUNICATION CONVERGENCE USING IEEE 1394”, filed in the Korean Intellectual Property Office on Feb. 3, 2004 and assigned Serial No. 2004-7046, the contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a broadcast/communication convergence system. More particularly, the present invention relates to broadcasting in an FTTH (Fiber To The Home) system. 
     2. Description of the Related Art 
     Current communication/broadcast subscribers have the choice of employing a data service chosen from a plurality of data services, such as a very high-speed Internet service, etc. via an ADSL (Asymmetric Digital Subscriber Line), VDSL (Very High Bit-Rate Digital Subscriber Line), Ethernet LAN (Local Area Network), cable modem, etc., and may also employ broadcast services from at least one of cable and satellite broadcasting based on an HFC (Hybrid Fiber Coaxial) system. In other words, the subscribers have the option to employ different mediums to receive the communication and broadcast services. In cases where there are a combination of protocols, a communication service rate is only several Mbps. 
     In order that high-speed, large-capacity communication/broadcast services can be provided to the subscribers to overcome limitations of older protocols, an FTTH (Fiber To The Home) system for coupling an optical fiber to the subscriber&#39;s premises or home is considered to be the best solution. FTTH systems that provide high-speed, large-capacity communication/broadcast services can be classified into one of a PON (Passive Optical Network) and an AON (Active Optical Network). 
     In order for broadcast/communication convergence to be performed using the FTTH system, there has been proposed an FTTH system for broadcast/communication convergence as shown in  FIG. 1 . The FTTH system for broadcast/communication convergence shown in  FIG. 1  comprises an OLT (Optical Line Terminal)  300 , an ONU (Optical Network Unit)  400  and a gateway  500 . The components for broadcast/communication convergence perform the following operations. 
     First, the OLT  300  receives digital broadcast information  100  and external data communication (VOD (Video On Demand), Internet or etc.) information  200  via an external broadcasting network, electro-optically converges received signals into an optical signal, and transmits the optical signal using optical WDM (Wavelength Division Multiplexing) via a WDM  106 . 
     Moreover, the ONU  400  demultiplexes the WDM optical signal received from the OLT  300  into broadcast and communication signals via WDM  107 , opto-electrically converts the broadcast and communication signals, processes upstream information received from a subscriber, and carries out a TDM (Time Division Multiplexing) operation for the broadcast and communication signals selected user by user, and transmits a TDM signal. 
     The gateway  500  carries out a TDDM (Time Division Demultiplexing) operation for the TDM signal received from the ONU  400  and distributes a result of the TDDM operation service by service. The gateway  500  optically transmits the upstream information from the subscriber to the ONU  400 . 
     Now, the components will be described in detail. The OLT  300  shown in  FIG. 1  includes: a broadcast MUX (Multiplexer)  101  for receiving digital broadcast signals and multiplexing the received digital broadcast signals; an optical transmitter  102  for converting the multiplexed broadcast signals into an optical signal; a communication switch  103  for receiving the Internet/VOD information  200  to carry out a downstream switching operation for the received Internet/VOD information  200  and receiving an upstream communication signal from each subscriber to carry out an upstream switching operation for the received upstream communication signal to a network for the Internet/VOD information  200 ; an optical transmitter (Tx)  104  for converting a downstream communication signal into an optical signal; an optical receiver (Rx)  105  for receiving an upstream optical signal and converting the received upstream optical signal into an electrical signal; and a wavelength division multiplexer  106  for carrying out a WDM (Wavelength Division Multiplexing) operation and transmitting a result of the WDM operation. 
     Moreover, the ONU  400  shown in  FIG. 1  includes: a wavelength division demultiplexer  107  for separating an optical signal received from the OLT  300  into broadcast and communication signals; a broadcast DEMUX (Demultiplexer)  108  for separating the broadcast signals received from the wavelength division demultiplexer  107  on a broadcast channel-by-channel basis; a broadcast switch  109  for switching the broadcast signals separated channel by channel according to the subscriber&#39;s selection operation; a communication switch  112  for switching a downstream communication signal separated from the wavelength division demultiplexer  107  subscriber by subscriber and switching an upstream communication signal received from the subscriber to the OLT  300 ; time division multiplexers  110 - 1  to  110 -n for carrying out a TDM operation for the broadcast and communication signals subscriber by subscriber; and optical transceiver (Tx/Rx)  111 - 1  to  111 -n for transmitting the broadcast and communication signals multiplexed by the time division multiplexers  110 - 1  to  110 -n to respective subscribers (or gateways) and transmitting upstream signals from the subscribers to the communication switch  112  via the time division multiplexers  110 - 1  to  110 -n. 
     Moreover, each gateway  500 , as shown in the exploded view in  FIG. 1 , includes: a transceiver (Tx/Rx)  113  for receiving a downstream signal from the ONU  400  and transmitting an upstream signal to the ONU  400 ; a time division demultiplexer  114  for separating the broadcast and communication signals multiplexed by the TDM operation; and a communication switch  115  for receiving the communication signal from the time division demultiplexer  114  to transmit the received communication signal to a communication unit such as an Internet/PC (Personal Computer)  118  of the subscriber, etc., and receiving an upstream signal from the communication unit (such as the Internet/PC  118 , etc.) to transmit the received upstream signal to the ONU  400 . 
     After receiving the broadcast signals transferred from the time division demultiplexer  114 , the subscriber decodes the broadcast signals through an STB (Set-Top Box)  116 , views the broadcast on a digital TV (Television)  117 , and can access the network by transmitting and receiving the communication signals sent through the Internet/PC  118 . 
     The conventional FTTH system for broadcast/communication convergence carries out a TDM operation for the broadcast and communication signals to transmit a result of the TDM operation according to a connection between the ONU  400  and the gateway  500 , and subsequently carries out a TDDM operation. However, the conventional FTTH system has problems when accommodating items such as a multi-channel broadcast signal or a broadband communication signal. 
     The reason that the conventional FTTH system for broadcast/communication convergence has problems accommodating multi-channel broadcast signals or broadband communication signals is that the FTTH system employs a TDM operation for multiplexing a communication signal (e.g., Ethernet data) between the ONU  400  and the gateway  500  at a subscriber side and broadcast signals selected by the subscriber into one time frame, followed by transmitting a result of the multiplexing. Here, the time frame is generated through an FPGA (Field Programmable Gate Array). In this case, the FPGA can accommodate only a 100-Mbps Ethernet signal and a maximum of two HD (High Definition) channels because of the limitations of its processing rate. In particular, the FPGA is designed so that it can accommodate only fixed-length broadcast signals. For this reason, the conventional FTTH system for broadcast/communication convergence is not capable of accommodating broadcast signals based on various standards (e.g., broadcast signals of various wavelengths), and cannot accommodate three-channel broadcast signals. 
     SUMMARY OF THE INVENTION 
     The present invention provides an FTTH (Fiber To The Home) system for broadcast/communication convergence using IEEE (Institute of Electrical and Electronics Engineers) 1394 that can accommodate broadcast signals of various channels and variable band signals by converging broadcast and communication signals and transmitting the converged broadcast and communication signals using an IEEE 1394 transmission method serving as a standard interface in the FTTH system for broadcast/communication convergence. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a block diagram illustrating an FTTH (Fiber To The Home) system for broadcast/communication convergence as has been previously proposed; 
         FIG. 2  is a block diagram illustrating an FTTH (Fiber To The Home) system for broadcast/communication convergence using IEEE (Institute of Electrical and Electronics Engineers) 1394 in accordance with an aspect of the present invention; 
         FIG. 3  is a block diagram illustrating an ONU (Optical Network Unit) included in the FTTH system for broadcast/communication convergence using IEEE 1394 in accordance with an aspect of the present invention; and 
         FIG. 4  shows an example of a data transmission cycle used in the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Now, several aspects of the present invention will be described in detail with reference to the annexed drawings. In the drawings, the same or similar elements are denoted by the same reference numerals even though they are depicted in different drawings. For the purposes of clarity and simplicity, a detailed description of known functions and configurations incorporated herein will be omitted as it may obscure the subject matter of the present. 
       FIG. 2  is a block diagram illustrating an FTTH (Fiber To The Home) system for broadcast/communication convergence using IEEE (Institute of Electrical and Electronics Engineers) 1394 in accordance with an aspect of the present invention. 
     As shown in  FIG. 2 , the FTTH system for broadcast/communication convergence using IEEE 1394 in accordance with the present invention includes the components of the OLT  300  and the connection between the OLT  300  and the ONU  400  as in the conventional FTTH system for broadcast/communication convergence shown in  FIG. 1 . Therefore, a description of the identical components and connection structures will be omitted. 
     Before a detailed description is given of a constitution of the present invention, a description will be given of IEEE 1394. 
     IEEE 1394 is called “Firewire” as a standard of a serial bus interface jointly created by Apple Computer, Inc. and Texas Instruments, Inc. IEEE 1394 was conceived in 1986 and was standardized on December 1995 by IEEE. 
     IEEE 1394 serves as a serial bus interface that enables a maximum of 63 nodes to be coupled to each bus. Due to the fact that IEEE 1394 gives a priority to isochronous data in processing isochronous data/AV (Audio Visual) stream data mainly used for transmitting multimedia information, and asynchronous data/control and packet data used for transmitting communication or control information, there is an advantage in that QoS (Quality of Service) for multimedia data can be ensured in a home network. Moreover, IEEE 1394a defines S 100 , S 200  and S 400  bit rates, and IEEE 1394b defines optical mediums such as POFs (Plastic Optical Fibers), SMFs (Single Mode Fibers), MMFs (Multi-Mode Fibers), etc., such that a high bit rate of 3.2 Gbps can be ensured and hence it is predicted that an effective solution for the home network and remote data communication will be provided. 
     The FTTH system in accordance with the aspect of the present invention employs the MMF or SMF as the transfer medium according to the IEEE 1394b standard. The present invention shows an example of the design of a low-priced light source. 
     Here, the low-priced light source can be selected according to a transmission distance, transmission rate, price, etc. A typical example of the low-priced light source used in the conventional FTTH system is an SFP (Small Form-factor Pluggable). Where the MMF is employed as the transfer medium in the SFP of an output wavelength of 850 nm, an optical signal can be transmitted up to a maximum of 3 Km at 1.25 Gbps. Accordingly, the FTTH system using IEEE 1394 employs the SFP as the light source, because the ONU  400  and the subscriber (or gateway  500 ) can be designed within approximately 1˜2 Km. 
     The currently commercialized IEEE 1394b supports a maximum transmission rate of 800 Mbps. The IEEE 1394b standard defines a transmission rate of up to 3.2 Gbps. For this reason, transmission capacity of the FTTH system will be able to be improved using IEEE 1394 in the future as taught by the present invention. 
       FIG. 4  shows an example of a data transmission cycle used in the present invention. 
     IEEE 1394 basically defines 125 us as one cycle  41 ,  42  or  43 , and defines a transfer layer with a data rate of S 100 , S 200 , S 400 , S 800 , S 1600  or S 3200 . According to IEEE 1394, isochronous data units  404 ,  405 ,  406  and  412  can occupy a maximum of 80% of one cycle, while asynchronous data units  401 ,  402 ,  407 ,  408 ,  409  and  410  can occupy a total of 20% of one cycle. In the beginning of each cycle  41 ,  42  or  43 , a cycle start packet  403  or  411  is used to indicate that a new cycle starts. 
     Because a transmission timing of the isochronous data is first taken into account and the isochronous data is transmitted in a transmission form appropriate for transmitting multimedia data, the isochronous data is transmitted prior to the asynchronous data. On the other hand, the asynchronous data can employ 20% of one cycle, and is transmitted taking into account its transmission quality. 
     Therefore, in accordance with the present invention, a broadcast signal is assigned to the isochronous data, while a communication signal (e.g., a zapping signal or a signal from an NMS/EMS (Network Management System/Element Management System) or etc. is assigned to the asynchronous data. Accordingly, the present invention can perform a transmission operation based on broadcast/communication convergence as in TDM (Time Division Multiplexing) of the conventional FTTH system. 
     Moreover, a plurality of isochronous channels  404 ,  405  and  406  can be accommodated within a transmission cycle of 125 us in IEEE 1394. Where the maximum transmission capacity is designed at 400 Mbps, the isochronous channels can consist of channels of various lengths at a maximum of 300 Mbps if asynchronous data transmission at 100 Mbps is assigned for use in the Ethernet. 
     For example, a maximum of 6 fixed-length broadcast channels at 50 Mbps can be supported. In case of 27-Mbps broadcast channels, 11 channels can be transmitted to a single subscriber. Moreover, as the length of each isochronous packet varies, data can be transmitted according to various broadcast formats. Theoretically, a maximum of 64 isochronous channels can be supported. 
     Thus, the FTTH system according to the present invention provides a transmission technology or operation between the ONU  400  and the gateway  500  that is implemented using the IEEE 1394 transmission method in the inventive FTTH system, rather than an implementation TDM through the FPGA as known heretofore. 
     As shown in  FIG. 2 , the ONU  400  includes: a wavelength division demultiplexer  201  for separating an optical signal received from the OLT  300  into broadcast and communication signals; a broadcast DEMUX (Demultiplexer)  202  for separating the broadcast signals received from the wavelength division demultiplexer  201  on a broadcast channel-by-channel basis; a broadcast switch  203  for switching the broadcast signals separated channel by channel according to a subscriber&#39;s selection operation; a communication switch  208  for switching a downstream communication signal separated from the wavelength division demultiplexer  201  subscriber by subscriber, and for transmitting an upstream communication signal received from the subscriber to the OLT  300 ; LLCs (Link Layer Controllers)  204 - 1  to  204 -n for converting the broadcast and communication signals switched subscriber by subscriber into IEEE 1394 data; IEEE 1394 PHYs (PHYsical layer controllers)  205 - 1  to  205 -n responsible for IEEE 1394 interfacing; low-priced optical transceiver (Tx/Rx)  206 - 1  to  206 -n for transmitting the IEEE 1394 data to the gateway  500 ; and a microprocessor  207  coupled to the LLCs  204 - 1  to  204 -n for controlling flow of the broadcast signals to provide a path for the communication signal and processing of a control signal (e.g., channel zapping). 
     Moreover, each gateway  500  comprises: an optical transceiver (Tx/Rx)  209  for optically transmitting and receiving light based on IEEE 1394; a PHY (PHYsical layer controller)  210  for receiving IEEE 1394 data transferred through the low-priced optical transceiver  209 ; an LLC (Link Layer Controller)  211  for converting the IEEE 1394 data into the broadcast and communication signals; a decoder  212  for receiving and decoding the broadcast signals from the LLC  211  and providing the decoded broadcast signals to a digital TV (Television); a communication switch  213  for receiving the communication signal from the LLC  211  to transfer the received communication signal to the subscriber and receiving an upstream communication signal from the subscriber to transfer the received upstream communication signal to the LLC  211 ; and a microprocessor  214  coupled to the LLC  211  for controlling flow of the broadcast signals, providing a path for the communication signal, and for processing a control signal (e.g., channel zapping). 
     Moreover, each subscriber is directly coupled to the LLC  211  using the STB supporting the IEEE 1394 standard to use the digital TV. Where IEEE 1394 is not supported, the digital TV is used through the decoder  212 . Data service is received through the communication switch  213  using the Internet/PC (Personal Computer). 
       FIG. 3  is a block diagram illustrating the ONU  400  included in the FTTH system for broadcast/communication convergence using IEEE 1394 in accordance with another aspect of the present invention. 
     As shown in  FIG. 3 , the ONU  400  in accordance with the present invention comprises: a receiving/demultiplexing unit  31  for receiving a signal from the OLT; a broadcast/communication data switching unit  32  for switching the broadcast and communication signals; and an IEEE 1394 data controlling and transmitting/receiving unit  33  for transmitting and receiving IEEE 1394 data. It should be noted that units  31  and  32  could be arranged somewhat differently than as shown in  FIG. 3 , as the illustration is provided for explanatory purposes, and is not intended to limit the invention to the arrangement shown. 
     According to this aspect of the present invention, the IEEE 1394 data controlling and transmitting/receiving unit  33  converts data output from the broadcast switch  203  into an IEEE 1394 transmission frame and transmits the IEEE 1394 transmission frame to the gateway  500  subscriber by subscriber. In order to perform such functions, the ONU according to the present invention includes the IEEE 1394 data controlling and transmitting/receiving unit  33  having IEEE 1394 LLCs  204 - 1  to  204 -n, IEEE 1394 PHYs  205 - 1  to  205 -n, SFPs  206 - 1  to  206 -n, and a microprocessor  207 . 
     Here, the LLCs  204 - 1  to  204 -n include a predetermined number of buffers adapted for being controlled and having a predetermined number of data interfaces. Since each of the buffers included in the LLCs  204 - 1  to  204 -n is assigned to a single broadcast channel (or MPTS (Multi-Program Transport Stream)), the number of buffers corresponds to the number of acceptable broadcast channels (or MPTSs). 
     Moreover, the microprocessor  207  coupled to the LLCs  204 - 1  to  204 -n controls a flow of the broadcast signals, provides a path of the communication signal and processes a control signal (e.g., channel-zapping, etc.). The operation of the microprocessor  207  typically conforms to a specification of the IEEE 1394 standard. 
     The PHYs  205 - 1  to  205 -n enabling a beta output based on the IEEE 1394a standard can directly drive light sources for various subscribers such as a UTP (Unshielded Twisted Pair), a POF (Plastic Optical Fiber), an SFP (Small Form-factor Pluggable), etc. Preferably, the SFPs  206 - 1  to  206 -n are used to ensure a transmission distance between the ONU and the subscriber within 2 Km and a transmission bandwidth of a 400-Mbps class. The system can be configured using various light sources such as an SFF (Small Form Factor), a bidirectional transceiver, multiple sources, etc. The optical transceiver (Tx/Rx)  206 - 1  to  206 -n shown in  FIG. 2  use the SFPs  206 - 1  to  206 -n shown in  FIG. 3 . 
     The subscriber gateway  500  employs an IEEE 1394 transmitting/receiving unit (e.g., the above-described low-priced light source, etc.) as in the configuration of the ONU  400 . The gateway  500  is symmetric to the IEEE 1394 controlling and transmitting/receiving unit of the ONU  400 . This has been described with reference to  FIG. 2 . Transceivers for IEEE 1394 data are independently implemented subscriber by subscriber. In other words, when an IEEE 1394 device is attached or removed where a network for multiple channels using IEEE 1394 is implemented, an operation for resetting a system is independently carried out in each subscriber, such that no interference occurs. According to the implementation of an independent IEEE 1394 transmission network, the IEEE 1394 transmission network can provide a sufficient communication bandwidth and a plurality of high-quality broadcast channels. 
     As apparent from the above description, the present invention can accommodate broadcast signals of various channels by converging broadcast and communication signals and transmitting the converged broadcast and communication signals using an IEEE (Institute of Electrical and Electronics Engineers) 1394 transmission method serving as a standard interface in an FTTH (Fiber To The Home) system for broadcast/communication convergence. 
     Moreover, the present invention can accommodate variable band signals by transmitting data through IEEE 1394. 
     Although the preferred aspects of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the spirit of the invention or the scope of the appended claims.

Technology Category: 5