From: Mark Webb-Johnson <mark@webb-johnson.net>
Message-Id: <2D6B1263-282D-4C24-AECD-A05AB4B28BAF@webb-johnson.net>
Date: Tue, 20 Aug 2013 21:04:06 +0800
To: OVMS Developers <ovmsdev@lists.teslaclub.hk>
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Subject: [Ovmsdev] USSD Signaling
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I've had a proposal from a M2M provider that is interesting, so thought =
I'd distribute it here, and get feedback.

A very low-level protocol in the GSM standard is called USSD. It =
involves the transmission of a single alpha-numeric message of up to =
about 120 characters. Our protocol messages would fit perfectly into it. =
The USSD protocol is routed at a very low level, and is a datagram-syle =
protocol (it may be discarded by the network if there is no cellular =
connectivity, kind of like UDP). The protocol is supposedly better able =
to make it through congested and low-signal areas than even SMS, and =
certainly much better than GPRS. Message transit times are faster than =
SMS at around 1 second (of course, depending on cellular coverage).

The interesting things about the protocol are than (a) it is free (or =
flat-rate, at least), and (b) it supports roaming. One SIM, flat rate, =
globally.

The M2M provider suggests that we buy SIMs from them with unlimited USSD =
plans. Once activated, the SIMs would work globally on hundreds of =
partner carriers, and would only support USSD (not SMS or GPRS data). =
The way it would work for OVMS would  be:

Every OVMS module would be provided with a USSD SIM already onboard. It =
would work globally.
The owner would go to the www.openvehicles.com website and create a =
vehicle record as normal, but also enter the serial number of the SIM.
When the OVMS module powers on, it would read the serial number from the =
SIM then send a single USSD message to us to request provisioning =
(vehicleid, server password, etc).
The OVMS server would send back a USSD message to provision the module =
in the car.
=46rom then onwards, USSD messages would be used to encapsulate our =
current OVMS protocol messages.
The USSD messages are bi-directionally gatewayed to the OVMS server via =
the M2M provider, over the Internet.
There would need to be some small changes to the encryption protocol we =
use.
The OVMS firmware could support this as a special operation mode - based =
on the prefix of the SIM inserted. So, it could work in normal SMS/GPRS =
mode as well as USSD mode (switched by the SIM in the module).

Cost wise, this would increase the cost of the module by less than US$10 =
(price of the SIM). A monthly flat-rate "unlimited" USSD plan would be =
around US$8-US$10 per month.

What do people think?

Regards, Mark


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<html><head><meta http-equiv=3D"Content-Type" content=3D"text/html =
charset=3Dus-ascii"></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: after-white-space; =
"><div><br></div><div>I've had a proposal from a M2M provider that is =
interesting, so thought I'd distribute it here, and get =
feedback.</div><div><br></div><div>A very low-level protocol in the GSM =
standard is called USSD. It involves the transmission of a single =
alpha-numeric message of up to about 120 characters. Our protocol =
messages would fit perfectly into it. The USSD protocol is routed at a =
very low level, and is a datagram-syle protocol (it may be discarded by =
the network if there is no cellular connectivity, kind of like =
UDP).&nbsp;The protocol is supposedly better able to make it through =
congested and low-signal areas than even SMS, and certainly much better =
than GPRS. Message transit times are faster than SMS at around 1 second =
(of course, depending on cellular =
coverage).</div><div><br></div><div>The interesting things about the =
protocol are than (a) it is free (or flat-rate, at least), and (b) it =
supports roaming. One SIM, flat rate, =
globally.</div><div><br></div><div>The M2M provider suggests that we buy =
SIMs from them with unlimited USSD plans. Once activated, the SIMs would =
work globally on hundreds of partner carriers, and would only support =
USSD (not SMS or GPRS data). The way it would work for OVMS would =
&nbsp;be:</div><div><br></div><div><ol class=3D"MailOutline"><li>Every =
OVMS module would be provided with a USSD SIM already onboard. It would =
work globally.</li><li>The owner would go to the <a =
href=3D"http://www.openvehicles.com">www.openvehicles.com</a> website =
and create a vehicle record as normal, but also enter the serial number =
of the SIM.</li><li>When the OVMS module powers on, it would read the =
serial number from the SIM then send a single USSD message to us to =
request provisioning (vehicleid, server password, etc).</li><li>The OVMS =
server would send back a USSD message to provision the module in the =
car.</li><li>=46rom then onwards, USSD messages would be used to =
encapsulate our current OVMS protocol messages.</li><li>The USSD =
messages are bi-directionally gatewayed to the OVMS server via the M2M =
provider, over the Internet.</li><li>There would need to be some small =
changes to the encryption protocol we use.</li><li>The OVMS firmware =
could support this as a special operation mode - based on the prefix of =
the SIM inserted. So, it could work in normal SMS/GPRS mode as well as =
USSD mode (switched by the SIM in the =
module).</li></ol></div><div><br></div><div>Cost wise, this would =
increase the cost of the module by less than US$10 (price of the SIM). A =
monthly flat-rate "unlimited" USSD plan would be around US$8-US$10 per =
month.</div><div><br></div><div>What do people =
think?</div><div><br></div><div>Regards, =
Mark</div><div><br></div></body></html>=

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