Generally, a conventional cable broadcasting network is aimed principally at the transmission of cable broadcast signals to the TVs of subscribers. Therefore, the conventional cable broadcasting network is constructed to connect a wired network (for example, a coaxial cable network) to the homes of respective cable television subscribers through an Optical Node Unit (ONU), and to transmit cable broadcast signals over the connected wired network. In a conventional wired network, sectors are obtained by dividing a target area, to which cable broadcast signals are to be transmitted, into several regions, and there is no need to connect the terminals of respective sectors, which are connected to an ONU, to each other. That is, the conventional cable broadcasting network has a structure in which wired networks extend radially around the ONU. Therefore, when Internet services are provided using the conventional cable broadcasting network, respective sectors have independent characteristics therebetween.
FIG. 1 is a diagram conceptually showing a method of assigning frequencies to respective subscriber units in a conventional Hybrid Fiber Coaxial (HFC) network.
Reference numeral 10 denotes an ONU disposed between an optical cable and a coaxial cable. The ONU 10 performs signal conversion between a cable broadcasting company, connected through an optical cable, and subscriber units, connected through a coaxial cable. Of the bandwidth provided from the ONU 10 to the coaxial cable, frequency bands A, B, C, and D, which can be assigned for the Internet, range from approximately 540 MHz to 900 MHz. The ONU 10 provides the assigned frequency bands to a tap-off unit 20. The tap-off unit 20 distributes the assigned frequency bands to respective sectors 1 to 4. That is, the frequency bands A, B, C, and D are assigned to the sectors 1, 2, 3, and 4, respectively. Each of the sectors is a region in which a cable network is assigned to a plurality of subscriber units. In the case of the sector 1, the frequency band A is divided into frequency bands A1, A2, A3 and A4, and the resulting frequency bands A1, A2, A3, and A4 are assigned to subscriber units 1 to 4, respectively. That is, in conventional Internet services provided through a wired network, the bandwidth assigned to each of the subscriber units 1 to 4 decreases in proportion to the number of subscribers connected to a unit sector (for example, sector 1), thus resulting in a decrease in the data transfer rate of each subscriber unit. Further, since the sectors 1 to 4 use frequency bands assigned to and distributed by the ONU 10, there is a problem in that the number of subscriber units that can be covered by the ONU 10 is limited.
FIG. 2 is a diagram showing an example in which a cable network is deployed by a cable broadcasting company.
As shown in the drawing, since the conventional cable network is deployed to provide cable broadcasts to subscribers through a wired connection, it is disposed radially around the ONU 10, and the end terminals of the cable network do not meet each other. A typical network is configured to have a ring topology, in which end terminals of a network meet each other, in order to secure the stability of data transmission, while a cable network is typically configured in a radial topology, in which the end terminals of the cable network are not connected to each other, because the cable network only sends broadcasts from a cable broadcasting station to subscribers. The applicant of the present invention discards the conventional network configuration method of configuring a network in such a manner that the tap-off unit 20 assigns frequency bands, assigned by the ONU 10, to the respective sectors 1 to 4 equally, and proposes an optical network device for generating a multi-channel, in which the same frequency band is assigned to the sectors 1 to 4, so that the same frequency band can be reused, thus increasing the frequency band assignable to respective subscriber units and also increasing the data transfer rate of respective subscriber units.