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Solutions for PLC Systems


Library Development is Underway with a Focus on Low-speed PLC Networks, and a Large Field Test Has Verified Stable Network Operation

The Renesas-developed network-layer library software simplifies the implementation of repeater and router functions, particularly those required for automatic meter reading applications

Power Line Communication (PLC) networking technology uses existing electric power lines as its communication medium, eliminating the need to install new wires in order to implement connectivity between products plugged into the AC mains. The benefits of PLC technology are expected to lead to its widespread use in networks in homes and buildings, as well as in applications such as automatic meter reading (AMR) systems and streetlight control. Renesas has placed a particular emphasis on the medium-speed and low-speed types of PLC that are suitable for control applications. We have achieved good results from a large-scale field test of an AMR system in Europe. Microcomputers in the M16C/6S group of incorporate the IT800 power-line modem.

Meeting the accelerating demand for low-speed PLC for applications such as AMR and streetlight control, particularly overseas

The PLC (Power Line Communication) standard for networking via electric power lines comes in three different types: low speed, medium speed, and high speed. Renesas is focusing on the 400kbps medium-speed types and the 7.5kbps low-speed versions, which are described below:

  • Medium-speed PLC uses a frequency band of 2MHz to 9MHz and is intended solely for indoor use. Potential applications include appliance control in the home, and air-conditioning and lighting system control in apartment blocks and other buildings. Communication speed is limited to only a few hundred kbps, but the design advantages of medium-speed PLC include small circuit size and lower cost than high-speed PLC implementations.
  • Low-speed PLC uses the 10kHz to 450kHz band and is authorized by law for use both internally within structures and externally. Currently, demand is being led by external applications overseas. There are substantial requirements for low-speed PLC in external applications such as automatic electric power metering (AMR: Automatic Meter Reading) and control of street lighting. Europe and Asia, in particular, are taking the lead in using PLC for AMR, and this application also is gaining popularity in North America. Lighting control is attracting most attention in Asia, followed by Europe and North America.
    Growth of low-speed PLC for internal applications has not yet begun to accelerate, perhaps due to the need for protocol standardization. Renesas plans to comply with the command-and-control specification in the HomePlug protocol for in-home networks that's being formulated into an international standard by the HomePlug Powerline Alliance.
    • Achieving good results from a European field test that has boosted prospects for wider PLC adoption

    To succeed as a major supplier of semiconductor solutions for global PLC markets, Renesas is focusing in particular on AMR applications in Europe. The infrastructure for AMR is already in place in Italy and work is also underway to implement it widely in Norway, Sweden, and Denmark. Numerous countries are planning or developing ways to deploy AMR, and more field-tests are being conducted every year. This progress is taking place against a background of restructuring and increased competition as the liberalization of the European electricity market drives changes such as industry privatization.

    Four main requirements characterize PLC implementations for AMR systems in Europe:

  • Designs must be able to collect data from all nodes
  • Systems must offer support for more than 1000 electronic meter nodes
  • Systems must incorporate repeater and routing functions
  • Designs must have at least a 2km concentrator-to-node range and a 500m node-to-node range.

    • A solution that Renesas has developed for this application is the "Renesas Ubiquitous Network for Metering" network-layer library software. It simplifies the implementation of the repeater and router functions required for AMR. This library runs on top of the D2DL data-link layer library, which can support any protocol and was also developed by Renesas. Also, the library incorporates a repeater function with 7 levels and 255 nodes per level. Other features of the library software include an abnormal-node detection function, automatic rerouting, and a plug&play recognition function.

    A successful large-scale AMR field test has already been completed in Europe. The test took place in an area containing a number of typical housing complexes containing a total of 572 single-phase meters, 21 three-phase meters, and 3 concentrators, arranged as shown in Figure 1. Factors evaluated in the test included the telecommunication performance of the PLC physical layer, as well as the operation of the data link layer and network layer software libraries. Due to the success of the test, full-scale operation of the system has commenced. A similar field test is now planned in Asia.

    Figure 1: Outline model of PLC network used in large-scale field test in Europe.
    Offering chips optimized for PLC use

    The low-speed PLC devices used for the trial were Renesas M16C/6S group microcomputers with integrated IT800 power-line modems developed by Yitran Communications, Ltd. of Israel. In Japan, these devices can operate in the 100kHz to 400kHz band and have a maximum communication speed of 7.5kbps. A next-generation chip with a compact design, additional peripheral functions, and an eightfold (8x) speed increase is under development.

    For medium-speed PLC applications, Renesas is producing the R5L08000DFP special-purpose LSI. This chip uses a power line modem of our own circuit design.

    Development tools are available to facilitate system design. For low-speed PLC applications, one of these tools is a PLC evaluation board with a M16C/6S group microcomputer (see Photograph 1). Others include an integrated development environment, C compiler, on-chip emulator, and data-link layer library. For medium-speed PLC systems, an evaluation kit is available with a board that mounts the special-purpose LSI (see Photograph 2). This kit also provides a power supply board in a box housing.

    Renesas plans to continue developing PLC solutions that are tailored for control uses, maintaining the emphasis on low and medium-speed applications.

    For more information on M16C/6S group microcomputers for low-speed PLC applications, click here.

    Photograph 1: Low-speed PLC evaluation board.
    This board uses a microcomputer from the M16C/6S group.

    Photograph 2: PLC circuit on medium-speed PLC evaluation board.
    The Renesas-developed R5L08000DFP special-purpose LSI chip is mounted on this board.

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