Recently the Homeplug AV specification as part of the IEEE P1901 power line modem specification has been updated for Green applications. The Homeplug.org group has released a new Green PHY spec that is targeted for smart grid & smart meter/appliance applications under a 1Mb/s data rate, rather than the typical 200Mb/s data rate that is for video and IPTV applications.

The recent advances were started about 3 years ago as an alternative to Zigbee wireless to help get data to the meters from inside the hous, without the overhead of the mesh network. The application was initially developed for the PCT (Programmable Control Thermostat) which is a 24V appliance that connects only to the power grid and the furnace. The thermostat is one of the iconic devices that represents the home smart control movement. In conjunction with major appliances (TV, refrigerator, freezer, dish washer, washer, dryer) these make up the bulk of the currently “dumb” items that do not report their status or get managed for optimal peak power use. The Green PHY spec addresses this market by providing both chipsets for inclusion in new models of the white goods, and in new smart plug control modules that can monitor and help regulate power use of these appliances. The use of the power line networks is key for these appliances, as they are generally located in places where traditional networking is not accessible either requiring custom wiring to be put in to connect them or having to try and extend WiFi access beyond the normal living areas.

One of the challenges for power line networks is the connection loop through and around the power panels. Most single family residences in North America and Europe, have a main panel at the side of the building, and then a single sub-panel with fuses/circuit breakers in-side. In this environment, the powerline networks have traditionally works, with the exception of having data interruption from large spikes of appliances turning on and off. The challenge has been for systems with multiple sub-panels (multi-tenant dwellings) and structures that have a break in the power loop to support solar power/alternate energy feeds.

Recently Atheros has introduced a new controller that is compatible with the multi-panel arrangements with a main panel, and then having it subdivided into a feed from a Solar inverter, and more than one sub-panel. This environment (two distributed subpanels at 200A each, with a Fronius inverter tied in to a single 400A main planel) was tested with the Monster Cable PowerNet 200 & 300 products using the Atheros 5500 & 6400 Home AV chips.

atheros powerline chips

The system was tested at multiple points in the loop, on the same sub branches and on separate sub-branches and it was sucessful at connecting the network. Near the inverter, the system did need another PowerNet product to link that subnet, but at it is a drop loop that only goes to the Solar metering system, the reality of the sub-loop being isolated is not an impact on the rest of the system operation. This left a single connection to the main broadband connection and access at 100Mb/s in over 20 rooms/areas with only the powerline connection which has been able to operate for over 10days without a line drop. The system automatically came back up and connected when the broadband was reset and did not interfere with the syncing process. Two years ago when this same test was performed, only two groups of the 4 rooms were able to connect at an average disconnect and dropped line time of 2 minutes. These two loops were not able to communicate across the main panel due to noise constraints on the line. The new designs worked properly, primarily due to the new noise compensation scheme. In order to compensate for the high noise condition the Atheros product has a “robo mode” with uses a combination of OFDM (Orthogonal frequency-division multiplexing) and QPSK (Quadrature Phase Shift Keying) in a 2-5 time testing feature that resends each signal to make sure it get interpreted correctly.

powerline modems - Monster Cable

 

To be able to support the Home AV system requirements of streaming video and high level data transfer, the data is priortized. In this manner, the smart grid/Green control is scheduled to a lower priority as a device to insure it does not utilize more than 7% of the available traffic bandwidth. These solutions are currently in production and available in both the compont form and as also as full powerline modem sets.

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