Saturday, October 31, 2009

Mesh network for Victorian smart meters

Responding to my post on WiMax smart meters, Robin Whittle responded with
"electricity meters use Zigbee and 915-928 MHz mesh", Fri Oct 30 17:56:59 EST 2009:
Two Victorian distributors - Jemena and United Energy, are going to use meters from PRI in the UK with a Silver Spring radio card (NIC):

The Jemena information shows a particular meter:

This looks the same as a particular meter shown here, a PRI meter with a Silver Spring NIC (radio card):

The meter is from PRI in the UK:

The radio interface (NIC), with a 1 watt transmitter: "dynamically discovers and self-heals its Neighborhood Area Network (NAN), notifies the Smart Energy Network of outages and restorations."

The datasheet: shows that while the meter uses Zigbee to communicate with devices in the home, it uses some unspecified protocol for its connection to the outside world.

"High data rate communications between the back office and the Meter, allow for thousands of meters to be read in minutes."

Two-way 915-928 MHz FHSS (Frequency Hopping Spread Spectrum) communications
Dynamic network discovery and self-healing
Supports scheduled and on-demand meter reads
Supports "over-the-air" firmware upgrades, meter programming and tariff changes
Optional GSM / GPRS modem (in ETBC)
Data rate 100 kbps
Spread Spectrum Technology FHSS
Channels 43
Modulation Binary FSK
All the type approvals are for Australia.

The diagram shows a mesh between the meters, presumably using the 915-928 MHz FHSS system, and part of the mesh is "access points" which may be connected back to base via GSM-GPRS, Ethernet or CDMA. I guess they could use 3G too.

So from this, it seems they will plonk access points around the place and talk to them via GSM/3G, and each one of these will communicate directly or indirectly with a large number of meters. This sounds like a good arrangement to me.

I think that in country areas there may be such isolated meters that there would be a single access point, presumably linked back to base by GSM-GPRS. In principle it may be possible to put a GSM modem in the meter, but perhaps it would be simpler to keep all the meters much the same, and dedicate an access point on the nearby power pole for each isolated home.

I hope they won't turn on the ZigBee system by default. That would be another 2.4GHz transmitter in every house - in an already widely used frequency band.

We should have a Jemena meter installed in the next few months. Does anyone near here (north-eastern suburbs of Melbourne) have a 2.4 GHz scanner to see if it is emitting anything?

According to: the 915 to 928 MHz band is "Radiolocation" and most of it, 915 to 926 MHz, is an ISM (Industrial Scientific and Medical) applications band. I understand this is used for RFID. Does anyone know more about this part of the spectrum?

Tom Worthington has a page discussing another distributor's plans to use WiMax to the "smart" meters...

This will involve "Motorola WiMAX WAP 650 base stations on 2.3GHz connected by a microwave system". This looks a lot more expensive and presumably involves licensed spectrum and expensive microwave or fibre links.

Since almost all of the locations where there are electricity meters are covered by GSM or a 3G network already, I think the GSM/3G access point, with 915 MHz ISM band mesh network approach looks technically and economically the most attractive. However, the system relies on unlicensed spectrum.
Yes, SP AusNet plans to use spectrum licensed to Unwired. WiMax can use a mesh architecture, so they could reduce the number of base stations to lower the cost a bit, but this will cost more than the Jemena and United Energy approach.

But I suspect SP AusNet plans to create a wireless network suitable for selling broadband services, not just smart meters. As an example, if they put a WiFi chip in the smart meter, then they can offer a wireless broadband service to the household and to the street. Assuming that every second house in the street has such a meter, that would provide
complete wireless coverage of a suburb. Apart from data services, this could provide telephony (there would not be enough bandwidth for TV).

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