Patent Publication Number: US-2007116042-A1

Title: Power extension apparatus having local area network switching function

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a local area network using existing power line wiring, in particular to a power extension apparatus having a network switching function for the power-line based local area network.  
      2. The Related Art  
      Riding on the tremendous growth of PCs, many computer users have second computer and more than one peripheral device back at home for creating a home network or local area network. For example, a desktop computer, a notebook computer, a scanner, and a printer are all connected by some means to exchange data and share a common router to the Internet.  
      The more common local area networks are Ethernet and wireless LAN (802.11x). However, after a decade of development, there are other options available, such as HomePNA, HomePlug, etc.  
      HomePNA is a networking standard basing on the existing telephone lines, while HomePlug is another networking standard that utilizes the existing power line wiring to connect to multiple home PCs as shown in  FIG. 1 .  
      The power line network has a number of advantages. First, there is no need to lay down a separate network. Second, the power line network is not as easily affected by interference as in a wireless network. Third, as the power line network is separated from the outside wiring by the household&#39;s wattage meter and there is therefore no data security concern.  
      Homeplug, a trademark of the HomePlug Powerline Alliance, is an industry-standard method for transmitting and receiving data via the power line, which can be audio, video, text, control signals, etc.  
      Referring to  FIG. 1 , showing a typical architecture of the HomePlug network, where the computing devices  10 ,  11  are connected to the power line wiring  30  through special adaptors  20  and wall outlets  31 . Each special adaptor  20  has a conventional power plug on one end for plugging into the wall outlet  31  or an ordinary power extension cord  32 , and the cable connection between a computing device  10 / 11  and an adaptor  20  is either an universal serial bus (USB) cable or a RJ-45 cable. The computing devices  10 ,  11  being connected through the power line wiring  30  form a HomePlug local area network as such.  
      Each special adaptor  20  is built in with a HomePlug module for connecting computing devices to the HomePlug network. The HomePlug network could be further linked with other local area networks (such as the Ethernet  40 ), and could be connected to the Internet  60  via ADSL/cable modems  50 .  
      However, there are several limitations for using the special adaptors  20 . For example, the bulky size and shape of the special adaptor  20  would have trouble in plugging into or unplugging from one of the power sockets adjacent to each other and crowded with various cables.  
      Each special adaptor  20  usually provides only one network interface port. When more than one computing devices are to be linked to create a HomePlug network, several special adaptors are needed to fulfill the purpose, but then there might not be enough wall outlets. The alternative is to connect these PCs through a network hub or switch  70 .  
      In these aspects, the power extension apparatus for HomePlug networking according to the present invention substantially reduces or obviates the limitations and disadvantages of the prior art.  
     SUMMARY OF THE INVENTION  
      The primary object of the invention is to provide a power extension apparatus for a power-line based local area network that acts as a network hub or switch.  
      The secondary object of the invention is to provide a power extension apparatus that supports the HomePlug standard or other similar communication standards using existing power line wiring.  
      To achieve the above-mentioned objects, the present invention provides a power extension apparatus that physically resembles a power extension cord, having an extension cable of appropriate length with a power plug on one end, and a casing on the other end, through which two or more computing devices are connected to form a power-line network.  
      In accordance with the present invention, there is an array of power sockets and network interface ports on the surface panel of the casing. This power extension apparatus serves dual functions: one is to provide power distribution to one or more computing devices connected to the power sockets, and another one is to provide data communications among the computing devices being connected to network interface ports.  
      In accordance with the present invention, the power extension apparatus built in with the HomePlug module allows two or more computing devices being connected to an existing power line wiring in a building to form a local area netvork in compliance with an appropriate data communication protocol.  
      In accordance with the present invention, the power extension apparatus built in with the HomePlug module allows a local area network to be linked to other computing devices over the existing power line wiring in compliance with an appropriate data communication protocol.  
      These along with other features of novelty which characterize the invention, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, the operating advantages and the specific objectives attained by its uses, references should be made to the accompanying drawings and descriptive matter illustrated in preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a diagram of a network architecture basing on the HomePlug technology;  
       FIG. 2  is a top view of the structure of the power extension apparatus in accordance with one preferred embodiment of the invention;  
       FIG. 3  is a block diagram of the hardware architecture of the power extension apparatus. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      The power extension apparatus  100  as shown in  FIG. 2  has an extension cable  110  of appropriate length, one end of which has a power plug  112  for plugging into a wall outlet or a power socket of other power source.  
      One end of the extension cable  110  is connected with a casing  120 , which has an array of power sockets  122  on one side and an array of network interface ports  124  on the other side. The power sockets  122  provide power distribution to one or more computing devices being connected thereon. The network interface port  124  is a standard RJ-45 connector, which is to be connected to a computing device using the standard RJ-45 Ethernet cable.  
      The power extension apparatus  100  is able to support different power distribution specifications depending on the local requirements. In the present example, the power extension apparatus  100  is connected to power lines having 110V AC/60 Hz, but this could be 220V/60 Hz instead. In some cases, the power extension apparatus  100  could support multiple power distribution specifications. Each power extension apparatus  100  could further contain a fuse and a circuit breaker for surge protection. It shall be noted that the focus of the present invention is not on the electricity distribution specifications nor the power protection, but the capability to create a power-line based local area network using the existing power line wiring, replacing the conventional network hub and a large number of network cables.  
      It shall be noted that the physical layer (PHY) is not limited to a specific specification such as RJ-45, or a specific transmission speed. Any appropriate cable connection specification such as fiber optics, or any appropriate transmission speed such as 10, 100, or 1000 Mbps could all be supported.  
      The network interface ports  124  on the same power extension apparatus  100  need not be the same type, for example, some use RJ-45 Ethernet cable connectors, while others may be fiber optic cable connectors.  
      All network interface ports  124  are connected to a network module  130  embedded in the casing  120 , whose functions and technical specifications are similar to that of a conventional network hub or switch.  
      The network module  130  is able to support general network functions such as auto sensing, flow control, full/half duplex etc, and more advanced functions such as virtual LAN (VLAN), and load-balancing.  
      Since the techniques involved in a network hub or switch have already been quite well known to people in the related art, the details about the network module  130  is omitted here for simplicity sake.  
      Through the function of the network module  130 , all computing devices being connected to the same power extension apparatus  100  or separate power extension apparatuses, as individual nodes, can transmitted video, audio, text, and control signals among the nodes of the power-line network.  
      Referring to  FIG. 3 , the architecture of the casing  120  of the power extension apparatus  100  also includes a power module  140 , whose function is to convert the input AC to +1.8V/3.3V/12V DC for driving the network module  130  and the conversion module  150 .  
      The architecture of the conversion module  150  is similar to a conventional power-line adaptor such as a HomePlug adaptor. The conversion module  150  is simultaneously connected to the network module  130  and extension cable  110 , through which data packets are first received from the network cable and modulated onto the AC waveform and then transmitted over the extension cable  110  compliant with an appropriate power-line communication protocol, and also vice versa.  
      A number of chipsets for implementing the conversion module  150  are currently available from various vendors. For example, the conversion module  150  could be formed by an INT5500 baseband IC and an INT1200 analog front-end IC, both by Intellon, and a line driver and a driver/coupler, as shown in  FIG. 3 . The conversion module  150  so created can support HomePlug 1.0 Turbo mode whose speed is up to 85 Mbps.  
      The details of these chipsets and how they are integrated could be obtained from the technical documentation publicly published by relevant vendors. They are therefore omitted here.  
      The main focus of the present invention is not in the implementation details of the network module  130  or the conversion module  150 . It lies in the integration of commonly known technologies in a novel manner so as to achieve unexpected function from an ordinary power extension cable  
      The power extension apparatus  100  is also a regular power extension cord for distributing power to multiple computing devices being connected thereon.  
      Depending on how the conversion module  150  is implemented, the conversion module  150  in accordance with the present embodiment is able to support different versions of HomePlug standards, such as HomePlug 1.0 Standard, HomePlug 1.0 Turbo mode, and HomePlug AV.  
      HomePlug 1.0 Standard provides 14 Mbps transmission rate, while HomePlug AV is an enhanced version that is able to provide 200 Mbps transmission rate for real time audio and video.  
      The power extension apparatus  100  could further contain indicator lights  126  that reflect the line status, network connectivity, and data flow activities.  
      The power extension apparatus  100  could contain an optional testing function to detect the presence of other computing devices also connected to the power line wiring and cable of data communications with the present embodiment. The power extension apparatus  100  has a triggering device, such as a press button  128 , on the surface panel of the casing  120  connected to the conversion module. When depressed, the conversion module  150  is triggered to conduct the line testing function, and the results are reflected on the indicator lights  126  accordingly. This function allows a user to check the network connectivity and search for other compliant computing devices, even without using any special tools.  
      In accordance with the present invention, the power extension apparatus  100  is not only compatible with all current versions of the HomePlug standard, but would also could support future specifications of the HomePlug standard.  
      The compatibility of the present invention is not limited to the HomePlug standards. In accordance with the present invention, the spirit of the present invention shall be extended to other power line communication protocols and network media that use the AC power waveform as carrier and the power lines to transmit data signals.  
      Although the present invention has been described with reference to the preferred embodiments thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made with regard to different forms and shapes without departing from the spirit and scope of the present invention which is intended to be defined by the appended claims.