[LINK] "Smart" electricity meters use Zigbee and 915-928 MHz mesh

Robin Whittle rw at firstpr.com.au
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):

  http://www.metering.com/node/15074

The Jemena information shows a particular meter:

  http://www.jemena.com.au/smartMetering/default.aspx

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

http://silverspringnetworks.com/products/intelligent_endpoints_pri.html

The meter is from PRI in the UK:

http://www.pri.co.uk/PressRelease/PRI-Australasia-to-supply-Smart-Meters-for-the-Victoria-roll-out.aspx

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:

  http://silverspringnetworks.com/pdfs/SSN-DS-PRI.pdf

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:

http://www.acma.gov.au/webwr/aca_home/legislation/radcomm/band_plans/900mhz.pdf

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:

http://www.tomw.net.au/blog/2009/10/smart-electricity-meters-may-displace.html

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.

  - Robin






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