Multiple Cell Phones 1

[itsmoked]

Is there a way to have a large constellation of independant cell phones?

Example: You have a hundred sites that you want to gather information at certain times and email it in, but you don't want 100 monthly accounts. They could all have the same phone number. They would only call in.

What happens when someone inevitably, wrong number, dials that phone number?

What would happen if more then one phone emailed(called) in at the same same time.

 

[Higgler]

I don't think you could do that on your own. Each phone has a serial number and is uniquely identified.
The phone company may be able to give you a reduced rate if you're involved in a worthy cause.

I assume you'd send simple text data that doesn't clog the phone system much.

Many cell providers have $10 per extra phone per month feature for up to 4 extra phones, so at a minimum, maybe it ends up being $15 per phone, or $1500 per month cost.

kch

 

[rmw]

On what type of system is the information that you want telephoned to you? I know of something that does this type of thing, but don't know if it would be adaptable to the way you have presented it.

rmw

 

[itsmoked]

Thanks for the input guys.

A data system like for monitoring sewage levels around a town. You might need 50 or 60 but requiring 50 or 60 cell accounts would be a total show stopper.

rmw the type of info would be minimal in this example; identifier, time, depth. Five to 15 bytes. These would be sent to a standard email account for easy handling.

 

[Higgler]

That's such a narrow data bandwidth, you could possibly make your own transmitters legally per FCC rules using very low power legally. Using a very narrow band receiver and communicate several miles.

Sounds like something that if available commercially could be around $40 per transmitter and a $1k receiver.

Doesn't sound off the shelf though.

kch

 

[IRstuff]

It wouldn't have to be separate accounts necessarily. Most multiple phone family plans are actually on the same account, since they share all the minutes, even though they have separate phone numbers.

Another choice is:

http://www.awprofessional.com/articles/article.asp?p=24919&seqNum=3&rl=1#pager

The blurb refers to "uplink pagers," but I couldn't much detail beyond that.

TTFN

 

[IRstuff]

Oh, here we go:

http://www.apollowireless.com/shtml/item/FullPath/2;541;557/id/541/ipid/557.html

http://www.villagesoft.com/wisk/technology.htm

TTFN

 

[jraef]

itsmoked,
I have seen a system using a Tixi modem Link to Tixi, and was told that T-Mobile has an SMS only account program where you can buy small amounts of SMS messaging very cheaply for SCADA systems like this. The Tixi modem can convert inputs to SMS messages. There are undoubtedly other systems like it available, this is just the only one I have seen.

"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more."
Nikola Tesla

 

[itsmoked]

Higgler; after being involved in exactly those kind of networks several times is why I want to leverage cheap cell phones. :~/ The entire licensing migraine is avoided if I can use standard cell phones.

Further the example I gave while it does, I agree, fit the "relatively close together" discription. It is addressable by lots of off the shelf SCADA systems.

IRstuff; Thanks for the links I'll look into the RIM but I'm afraid that they will want $25/ month for a backwards capable pager.

The Apollo deally is again a local transmitter requiring me to put up and maintain an RF network. gaah!

Wisk is interesting but way too expensive. You can get cell phones at half the price. Then under pricing they say
besides software licensing fees you need wireless service fees. Which I realize must be paid but I'm trying to figure out how to reduce this to something reasonable for the scrawny amount of data I'm looking to pass.

jraef those Tixi are neat! But profoundly expensive.

Here's what I'm talking about.

http://www.riccibitti.com/tinyplanet/tiny_article.htm

I want to do this, but add several features making the unit that plugs *into* the cellphone. But if each phone costs $20/month for an account and then $0.10/message a huge number of applications evaporate.

 

[VisiGoth]

IRstuff. There is a large industry in Europe using headless GSM phones in vending machines and the like (telematics and telemetry would be key words for this). For exactly the reasons you mentioned. I believe there is fleet cost for these systems that is unrelated to what a typical cell phone user would experience. The major vendors have division that service special customers. I do not think SMS is typically used. I think short scheduled bursts of GPRS is more cost effective.

jsolar

 

[Comcokid]

There are proprietary cellular data collection systems used by utilites to remotly read meters. They have big established base and can make the contracts directly with the cellular providers. Then there are the other data collection systems used by home security, vehicle tracking, and remote process companies.

These other systems use a cellular data modem module built by companies such as Advantra, Conxtra, or Skybility, and a service provider such as Aeris. A company builds their product around the cellular modem module and contracts with Aeris, who in term has established contracts with all of the cellular providers for data collection and forwarding.

You don't have to "roll your own" One example of a system made for remote fluid level measurement is as follows:

http://wirelessmonitoring.centeron.net/fuels/monitors_quicksilver.html

 

[hrc]

Another choice for this is if the remote units are within 40 miles or so, use a wireless modem such as the Xtend from Maxstream (

http://www.maxstream.net).

I am curently using these in a project.

 

[hrc]

Let me ask another question...since I just got a call from a client on this. And its a pretty general question since I'm not an expert at CDMA and the like...

Is SMS the text messaging protocol? So, if I have a remote system, and use one of these cell modem modules where the interface is simply serial, do the text messages just transfer to and from via using the port? For example (im not all up on texting...my kids use it I dont) if I text a phone number 555-5555 and send the message "OPEN VALVE #3" I assume the network sends the text message to the phone number where the cell modem answers..does it just pass the serial text data to the port where my micro can then read and act...plus ack the message? I guess on the ack....is the phone number that sent the message embedded into the message itself..so that the micro could call it back sending a message as well.

 

[hrc]

I should have added this to the last post as well. It falls in line with the same thing in that....if I want to text a message not to another phone but to a computer OR weblink..ie...pass the text to some software program and have the PC do something with the intrepreted text...is that available off the shelf?

I hope this hasn't deviated too much from the original subject

 

[itsmoked]

Thanks for that info Comcokid.

hrc did you look at that last link "tinyplanet"? It is sort of a tutorial on the subject.

 

[VEBill]

Many of the various underground infrastructure in this municipality have masts sticking out of the concrete lids with horizontally polarized yagi antennas (about 800 or 900 MHz).

When the power grid was knocked off line for a week or more by Hurricane Juan in 2003, they sent around sludge trucks to pump out the pits before they overflowed onto the street. I assume that the pits 'phoned home' using backup batteries.

It seems to be a low power packet radio network. I'm guessing it is low power due to the very nice high gain antennas. If it was (for example) ten watts, then I assume that they could've just used simple whips.

 

[itsmoked]

VE1BLL; For some fixed position licensed systems I believe the FCC prefers the licensee not spray the signal in 359 other directions. I'm sure the Yagis increase signal to noise a bunch too. They were probably more like 1 watt. They wouldn't be phoning home long on 10W

 

[VEBill]

The transmit duty cycle must be fairly low - I don't think that these pits are extremely busy places and I assume that the data packet is relatively tiny. Maybe a single, short packet burst every 10 or 15 minutes... ?

 

[VisiGoth]

hrc The SMS is not done by a phone call. It works out that your cell phone is actually in constant (except for very brief sleep times) communication with perhaps up to 8 cell towers at a time. This is known as the control channel. When you want to call or receive a call, a data channel is opened up. There happens to be a little bit of bandwidth available on the control channel, and that is what is generically called the SMS. A phone company could make this a billable service or give it away. Since there is almost no cost, it is a great way to move small amounts of data that live with a large latency. So, for the problem above, no phone call have to be made. However, if this limited bandwidth is made available to too many users in one area the QOS or quality of service could suffer and there could be a large backlog. So for reliable data transfer GPRS (or the CDMA equivalent) is used; which makes an actual phone call on a traffic channel.

 

[skalybur]

Do you know an Ad Hoc Network?. It's an independent mobile network.