Missed call communication protocol

wim delvaux wim.delvaux at adaptiveplanet.com
Wed Feb 7 12:26:17 CET 2007

On Wednesday 07 February 2007 12:16:33 Richard Bennett wrote:
> Hi all,
> In keeping with moving the control advantage away from the network
> operators, and to the users, I wonder what you think of this suggestion:
> When you use a SIP server, like Openser.org , you can set the CLI (Calling
> line identifier) to any value you like when you send the call on to a PSTN
> gateway.
> That means the 'from' number you see on your mobile screen when I call you
> from a SIP proxy can be any numeric value I like. (most PSTN termination
> gateways will require a valid e164 number
> http://www.answers.com/topic/e-164).
> So I can send a call to my openmoko number, using a CLI set to +10 followed
> by 13 arbitrary numbers, which should satisfy the e164 requirement .
> No real phone numbers start with +10 , so I could program my openmoko to
> reject any calls arriving with a CLI starting with +10, and to process the
> next 13 numbers of the CLI as a message, hiding this call from the missed
> calls list.
> As far as I know there is no networks charge for a rejected call from a
> mobile, and initiating a call from the openmoko to a number that always
> returns a 'busy' would also be free of charge.
> This gives us a free up/down communication channel that can take a payload
> of 13 numbers in each packet.
> This could be used for:
> * Push email notification.
> * Presence. Like the 'online' indicator in a chat app that shows your
> status. This is the next big area carriers are looking to charge us for,
> with their new IM platforms. It can also be used in the routing logic of
> your own SIP proxy/PBX, for instance: "Forward calls to mobile unless GSM
> presence is 'meeting' in that case send calling number by SMS, if SMS
> presence is 'available', and forward calls to secretary".
> * Ultra Short Message Service (SMSes that use a phrase-book on both sender
> and receiver, so you send the number that identifies a pre-formatted
> message i.e.: 112='Please call home when you're free').
> * Trigger predefined macros (shell scripts) on the phone, like "Send GPS
> coords by SMS".
> * Sync applications, like 'mark meeting14 as postponed', or "New updates
> available, do you want to sync now?"
> etc
> Unless our list lawyers shoot this idea down from the start, we could start
> thinking about the best way to define a missed-call protocol.
> I'm thinking of using 4 of the numbers as a identifying pincode, then a 3
> digit action identifier, and use the next 6 digits as payload depending on
> what action was selected .
> For instance update our presence info from the Openmoko to a server:
>  Call server: +122334455
>  send CLI +101234999100100
> That is:
> +1	=	Required valid international code
> 0	=	protocol identifier that never occurs in real calls.
> 1234=	pincode to identify the caller, and assign access rights. (Many
> different servers could send MCP (missed call protocol) messages to the
> same phone, a bit like the bluetooth pincode/identifier)
> 999	=	matches 'update presence information'
> 1	=	GSM available.
> 0	=	GPRS offline
> 0	=	Bluetooth offline
> 1	=	SMS available
> 0	=	reserved
> 0	=	reserved.
> What do you think?

If this works I vote for it (for as long as it will work ...)  However 
receiving SMS is also free no ? couldn't you use that ?

> Richard.
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