Why use GPRS for this scenario

Sorry for this being so vague but I'm trying to understand the use of GPRS in the following context:

Small amounts of data to send e.g. could all fit in one SMS
Restrictive power consumption requirement
Possible need to contact the GPRS enabled unit remotely

So the question is, why bother with GPRS when SMS would do the job nicely and save on power. Also, to force a connection to the GPRS unit, surely you would need to program it with a specific date/time to wake up or, alternatively, send an SMS to make it dial out and create the connection.... or am I missing something?!


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drelectroConnect With a Mentor Commented:
For 1 message a day SMS is almost certainly the way to go, unless of course the number of field devices is VERY large.

But for example of an app where GPRS makes sense lets say you had 3000 (or even 300) field devices and required 15 minute integrity polls (to each of the 3000 devices) ?
SMS, Dial Up or pretty much any other bearer just doesn't stack up like GPRS (or 1xRTT).

1/ Here in Australia SMS costs (retail) 25c for up to 160 characters so a send plus acknowledgement could cost up to 50c , GPRS costs about 1c KB or about 0.15c for 160 characters. Commercial rates for either are cheaper.
Also connecting to GPRS is easy at the server end, its standard IP and does not require anything more than an internet connection, connecting to an SMSC is relativly difficult, connecting to an SMS service provider is not cheap, simply using another mobile at the server end to send/receive SMSs will not scale very well.

2/ An idle GPRS session uses no more power than an idle phone waiting for an SMS

3/ Leave the GPRS session up permanantly, make a TCP connection or send UDP packets to the device when you want to talk to it, this can be tricky due to NAT on most public GPRS networks but most carriers support private network configurations for commercial GPRS applications that remove this problem and increase application security.

J_SeamanAuthor Commented:

Thanks for the response:

1. Cost isn't an issue because we have contracts which allow us to send SMS cheaper than GPRS would be. I agree with the connection being simpler over IP (That was one of the few reasons I could come up with for using GPRS) although we already have an SMS data collection system.

2. The session won't be in idle mode for either SMS or GPRS. The unit will be 'off' most of the time then wake up at regular intervals to send data one way or the other.

3. If you try and maintain a TCP connection and don't send data will you get kicked off the network? Any links on the private network stuff, I don't know if it's what we want but might make some interesting reading.

So far I'm not convinced but GPRS is taking off in a big way in our market - just can't understand why. Maybe it's just buzz word of the moment.

Any more opinions please??
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J_SeamanAuthor Commented:

Will some more points draw any interest?
That's great, at the end of the day if the data gets from point a to point b there's really only 3 factors to consider Speed of delivery, Reliability and Cost.
Assuming that there's some sort of business objective behind this who really cares how the data is transported assuming it arives reliably in a timely fasion and at a cost that fits the application.
Theres always 2 solutions to a problem, eg if SMS is more expensive than say GPRS you could either move to GRPS or make SMS cheaper.
For most people though GPRS is cheaper and enables a number of applications that are not possible using SMS (with traditional SMS pricing).

2 and 3/
If you're going to turn the phone fully off then SMS may appear attractive since the SMSC SHOULD forward any SMSs that were sent whilst thw mobile was off to the mobile wehn it is turned on.
The problem with this is that most SMSC's don't actually send queued SMSs the moment the mobile is turned on so you may have too keep the mobile on for some considerable (and unpredictable) period of time. I say unpredictable beacuse although it may work as you expect today on carrier X things may change if you change carrier or your existing carrier changes thier SMSC configuration (which they'l do without telling you).

The advantage with GRPS here is that the mobile can make a positive connection to the host as soon as it powers up check for messages and go straight back to sleep.
The host can detect and log that the mobile has polled for messages and the mobile can implement a retry strategy if it cannot connect to the host.

Re private network configurations, What country are you in ?
MeffConnect With a Mentor Commented:
> So the question is, why bother with GPRS when SMS would do the job nicely and save on power.
- Nobody can tell when your SMS will be forwarded. It is from seconds, to hours to never.
- GPRS is may cheaper. Depends how you would like to send a message
- GPRS is more secure
- GPRS gives you the option to send a still alive message for very low money

How often you have to send?
Standby time of your application without charging of battery?
How important it is to receive the message in real time?

A few more notes:
What kind antenna you would like to use? Take care on gain and low VSWR, because with wrong antenna or bad ground plane your power consumption will higher.

P.S. My daily job is the design in of GSM modules and the making of hardware concepts for GSM based applications
J_SeamanAuthor Commented:

Thanks guys, good to have the input - in response :

drelectro -

1. Very true - speed should be pretty similar (SMS will probably be faster in this case), reliability is very slightly in favour of GPRS but negligible and cost is again negligible. The only problem is that so many people are advertising 'GPRS enabled' etc that customers wonder why we don't.

2. Store and forward is attractive but we would have SMS receive capabaility on the GPRS alternative. Tell me about it - SMSCs are a right pain!

I'm in England.

Meff -

It's not time critical as such so delays forwarding SMS to our collection system isn't a problem but fair point
Depends 'how' we would like to send a message? Don't see quite what you mean there
Security is not a huge factor for us but worth considering
By still alive I presume you mean send a message and stay connected for a response?

We will be sending daily
The charging system is a whole can of worms I won't get into
Not important to receive messages in real time although it could sometimes be important to send them in real time and also to make unsolicited calls to the device for which GPRS would come into its own.

Again, the antenna is a massive topic in itself sop I won't get into that - suffice to say a lot of thought's gone into that aspect too.

It seems there is no black and white solution but I'm swaying away from GPRS at the moment. Keep 'em coming ;o)
For my application we went for SMS for the following reasons.

It is easily scallable, the receiving PC can handle hundreds of SMS messages per hour from machines at different locations. SMS allows us to take advantage of PAYG SIMs (Vodafone for instance have a 30-day top-up for £10 that gives us an SMS every 2-hours). If the machine is not on site it doesn't cost anything. If the receiving PC is switched off the SMS messages will be received when it is switched back-on (up to 3-days worth, not 100% reliable but you get most), the same system can be used to SMS engineers on their mobile phones when problems occur.
J_SeamanAuthor Commented:

snerkel - I agree with all that, I think SMS is the way to go. Only thing I can't get is why so many others would adopt GPRS, thought there might be something I was missing but apparently not. Some good points about security and real time advantages but generally speaking I'm not convinced it's the most appropriate way to go - especially having the SMS collection in place already
You can't compare SMS and GPRS, there are different "objects". GPRS - General Packet Radio Service is a protocol of accessing mobile radio tranceiver. SMS is a technology for Short Message Service, and exists in GPRS networks too.
J_SeamanAuthor Commented:

drelectro - The number of devices is potentially going to be VERY large. Certainly tens of thousands. However, integrity poll will never be required, the devices will do the calling in under normal circumstances and it's rare when the server side needs to be establishing the call.

crissand - Err, yes you can for all the reasons we have been discussing. Agreed GPRS is using the GSM network but they are very different entities with different pros and cons as we have been discussing. Just because you can send SMS using a GPRS enabled device doesn't mean you will be. The question here is which is best and why for this situation.

This is proving to be very helpful, any more comments are welcome
I don't know how to explain. SMS is a message service and can be implemented over CDS, GPRS, CDMA, EDGE.

For me, as technician, the two concepts, SMS and GPRS are at different levels and cannot be compared. It's like comparing Ethernet protocol with the content of a Internet site.

Maybe you want to compare sms with mms, or gprs with umts.
imarshadConnect With a Mentor Commented:
>>Only thing I can't get is why so many others would adopt GPRS, thought there might be something I was missing but
>>apparently not

Other people adopt GPRS because they donot have a contract which will give them SMS cheaper then GPRS......In fact GPRS is much more cheaper then SMS.....In our project we have contacted our GSM/GPRS provider and they have given us the following package..... roughly 10 $ per (500 SMS) per month...... Total data that we can transmit is 500*140= 70kB .....
 While using GPRS we can transmit 40 MB per  10 $  per month (US dollar).......Can you see the difference ? 70 kB vrs. 40 MB....So if you require less data transfer then you should go for SMS based system but if data transfer is large then you should go for GPRS.....No matter what your GSM/GPRS provider is offering you SMS can never be cheaper then GPRS for large chunks of data.....

J_SeamanAuthor Commented:

crissand - Don't worry, I know what SMS and GPRS are - that isn't the question. I don't think your analogy really fits to be honest - SMS and GPRS are competing technologies in the market I am in so I don't have a choice of comparing anything else.

Imran - I realise that our SMS contract is a major factor now, we currently pay exactly the same for SMS as we would for GPRS. I tend to agree, sheer volume of data appears to be the only thing that would make GPRS worthwhile.

Are running out of steam here or are there any other comments?
snerkelConnect With a Mentor Commented:
From my understanding of GPRS the power requirements will be greater (While ever the GPRS connection is open the transmitter will be operational), you will need to talk to the provider if they can give you fixed IP addresses so that you may contact the device if required. , GPRS will require a more intelligent device connected.

Both SMS and GPRS have valid plus and minus points, if you have no need for GPRS data rates, and the cost is about the same based on your projected use then SMS is a simpler system, the power draw in standby is minimal, sending SMS messages to the device is as easy as receiving them.

SMS is virtually available on a global scale GPRS isn't

Only you can decide what is right for your system, don't be bullied into making the wrong decision just because everybody else seems to be using GPRS, their applications may need the bandwidth/data rates, if yours don't then ....

If you are selling a product to clients then having GPRS available as an option would be a smart move if it isn't too costly to engineer.

Best advice is KISS
J_SeamanAuthor Commented:

Power requirement shouldn't cause a problem in this app though due to the fact we will wake up, do the sending, then shut down. ie whether it is gprs or sms it'll only occur for a short period of time. If you are idle with a GPRS connection open I expected the current consumption to be comparable to a normal GSM connection, is it not? No way we can get fixed IPs for thousands of products for thousand of customers over GPRS

You calling me stupid? :o) I think that sums it up nicely snerkel, I'll make a stand against thge GPRS revolution!

I think that's a good note to end this on so time to dish out points. This was more a doscussion than a question so I've simply split the points between those who contributed. I thank you all for your time and input.

one note, SMS can be implemented by the mobile network on top of GPRS, in which case using SMS would actually use the GPRS network :-)
As I wrote, sms works on all gsm protocols.
sorry, crissand, missed your statements... although, I'd say its more like comparing IP and HTML, rather than Website content... SMS is also used as a "bearer" somewhat (Voicemail/MMS Service notifications, shortcode services, possibly even OTA SIM applet provisioning, etc...)

I tried to make a point, exagerating. But, since the question is closed....
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