Google Android Mesh Network for Disaster Communications

Paul Gardner-Stephen has founded The Serval Project at Flinders University to provide a way for mobile phones to be used for disaster communications without a cell tower. The phones would cooperate in a mesh network, to relay signals from phone to phone. Initial implementation is with Google Android smart phones. The work is assisted with a $1,000 grant from the Awesome Foundation for the Arts and Sciences.

On the face of it using mobile phones for disaster communications does not seem a good idea. Most mobile phones are designed for city use, have very small antennas giving them a short range and rely on there being a high cell tower to relay signals. Walkie talkie CB radios are available for less than $100 which are designed to work on their own or with a low cost repeater for longer range communications. These can be set up quickly for use in a disaster area. Emergency workers can also be issued with more sophisticated "trunked radio" which has similar features to cell phones but are also designed to operate in more primitive conditions.

However, not all workers can be issued with a radio in a disaster zone and new communications procedures are needed to use them. Also low cost two way radios do not provide text messaging or computer interfaces. It would be much easier if workers could use their existing cell phone, with SMS as also access to the web.

It is a little misleading to describe the Serval project as making use of cell phones as it is the WiFi radio function of the smart phones being used, not the cell phone radio. The technique used is the same as used by OLPC computers which have a mesh network installed. In effect the service provides data transmission and then voice calls can be carried over that network. In a disaster it is likely that bandwidth will be limited and the system will mostly be sued for SMS and data transmission. The bandwidth needed for one voice call would service hundreds of SMS users..

What might make the system more practical would be use of external antennas on the smart phones to extend their range. This could be combined with a rugged case to protect the phone. While these would not look fashionable, there might be some kudos for volunteer emergency workers to have a bright yellow rubber covered phone with a whip antenna to show they are ready to help the community.

Also while the current project is concentrating on Andropid Phones, there is no reason why Apple iPhones, iPads, laptops netbook computers could not use the same system.

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): 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...

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).