user21409: I have a GSM shield for my arduino and am wondering the most efficient way to receive and send data to the cloud. 
The specific project I am looking to accomplish is starting my car from a web browser (or custom built ionic mobile app) that will send data to my GSM shielded arduino and the arduino then "press the button" of an already installed remote car starter (which is all probably in the car's trunk). 
What is more power efficient, sending and receiving a SMS (text message) or sending and receiving data via GPRS?
What is best when considering strategies like sleep, or deep sleep cycles?

user4143: Looking at it logically SMS is probably the most power efficient method.
The thinking is this:
With SMS:

The shield sits there connected to the mobile network doing nothing much
An SMS is sent by you which travels through the mobile network
The SMS is sent from the mobile network to your GSM shield which then wakes up and does things with it
The shield sits there connected to the mobile network doing nothing much

With GPRS:

The shield queries an on-line service to see if a request is available
The shield queries an on-line service to see if a request is available
The shield queries an on-line service to see if a request is available
The shield queries an on-line service to see if a request is available
The shield queries an on-line service to see if a request is available
The shield queries an on-line service to see if a request is available
The shield queries an on-line service and sees a request is available
The shield downloads the request
The shield acts on the request
The shield goes back to querying the on-line service
The shield queries an on-line service to see if a request is available
The shield queries an on-line service to see if a request is available
The shield queries an on-line service to see if a request is available
... etc ad nausium ...

As you can see with SMS the onus is on the mobile network to send the data to the shield, whereas with GPRS the onus is on the shield to keep querying an on-line service to see if there is any requests to handle. There is no way of you sending data to the shield directly (indeed, most GPRS services include at least one layer of NAT gatewaying). So your shield has to be active all the time and constantly looking at something online - not only power hungry, but potentially financially expensive too. 

user52028: You could theoretically use a SIP Server in the middle to keep the session alive over GPRS or higher. And there are techniques you can use to make it as power efficient as can be, depending on your application (which is a rather simple one I assume with little data throughput).
However, as @Majenko stated above, it may not be as power efficient as SMS.
That said, there may be other considerations, such as cost of sending/receiving SMS messages that may matter as you weigh the totality of requirements for your application.
I haven't worked personally on a Particle board (particle.io) but they do have a MCU/3G board that provides a certain amount of free (as in no $) bandwidth per month that might be a reasonable solution to consider for your application.
Please keep us posted. I'm considering something similar myself.

21409: <p>I have a GSM shield for my arduino and am wondering the most efficient way to receive and send data to the cloud. </p>

<p>The specific project I am looking to accomplish is starting my car from a web browser (or custom built ionic mobile app) that will send data to my GSM shielded arduino and the arduino then "press the button" of an already installed remote car starter (which is all probably in the car's trunk). </p>

<p>What is more power efficient, sending and receiving a SMS (text message) or sending and receiving data via GPRS?</p>

<p>What is best when considering strategies like sleep, or deep sleep cycles?</p>
 4143: <p>Looking at it logically SMS is probably the most power efficient method.</p>

<p>The thinking is this:</p>

<p><strong>With SMS:</strong></p>

<ul>
<li>The shield sits there connected to the mobile network doing nothing much</li>
<li>An SMS is sent by you which travels through the mobile network</li>
<li>The SMS is sent from the mobile network to your GSM shield which then wakes up and does things with it</li>
<li>The shield sits there connected to the mobile network doing nothing much</li>
</ul>

<p><strong>With GPRS:</strong></p>

<ul>
<li>The shield queries an on-line service to see if a request is available</li>
<li>The shield queries an on-line service to see if a request is available</li>
<li>The shield queries an on-line service to see if a request is available</li>
<li>The shield queries an on-line service to see if a request is available</li>
<li>The shield queries an on-line service to see if a request is available</li>
<li>The shield queries an on-line service to see if a request is available</li>
<li>The shield queries an on-line service and sees a request is available</li>
<li>The shield downloads the request</li>
<li>The shield acts on the request</li>
<li>The shield goes back to querying the on-line service</li>
<li>The shield queries an on-line service to see if a request is available</li>
<li>The shield queries an on-line service to see if a request is available</li>
<li>The shield queries an on-line service to see if a request is available</li>
<li>... etc ad nausium ...</li>
</ul>

<p>As you can see with SMS the onus is on the mobile network to send the data to the shield, whereas with GPRS the onus is on the shield to keep querying an on-line service to see if there is any requests to handle. There is no way of you sending data to the shield directly (indeed, most GPRS services include at least one layer of NAT gatewaying). So your shield has to be active all the time and constantly looking at something online - not only power hungry, but potentially financially expensive too. </p>
 52028: <p>You could theoretically use a SIP Server in the middle to keep the session alive over GPRS or higher. And there are techniques you can use to make it as power efficient as can be, depending on your application (which is a rather simple one I assume with little data throughput).</p>

<p>However, as @Majenko stated above, it may not be as power efficient as SMS.</p>

<p>That said, there may be other considerations, such as cost of sending/receiving SMS messages that may matter as you weigh the totality of requirements for your application.</p>

<p>I haven't worked personally on a Particle board (particle.io) but they do have a MCU/3G board that provides a certain amount of free (as in no $) bandwidth per month that might be a reasonable solution to consider for your application.</p>

<p>Please keep us posted. I'm considering something similar myself.</p>
