Context to understand my need: I moved to an area without good cellular data coverage but with good cellular voice coverage.
I want to send small amounts of digital data over voice. Preferably over Android phones.
I was trying a way to connect my phone acting as a dial-up modem, but actually I don't think that is possible to use Android as Dialup/FAX Modem
Anyway I don't need that because I have my own servers and I can configure a PBX to receive calls and translate "voice" (sounds) to digital data and send something in response.
Could be great to use all TCP-IP through voice in my phone, but my question accepts answers that just translate "voice" to small amounts of ASCII bytes (or less than ASCII) that my server could send to internet in a predefined way.
So my idea is to programming something for both (Android and server), but maybe exists another easier way to do it (with or without a PBX) or somebody knows of a ready-made library that I can base my invention on. I'm open to start from some good point.
Extra: Also this "feature" could be used in emergencies. And also is a good idea to encrypt data through voice (that is something that you can't do because GSM encryption is broken).
I am trying to find a way to send measurements from a digital device (as the blood pressure device) to a mobile application that can analyse these data ..... How to send these measurements wireless efficiently?
Please use a simple language
You need to make sure your digital device has an embedded Bluetooth adapter so that it can broadcast either BLE with standardized payloads for medical industry like. Your other option, if the data is larger, or streaming or secure, is to use standard traditional Bluetooth.
For this scenario your embedded code would create a server socket.
your mobile would create a client socket and a pairing request would occur.
You can either programmatically handle the pairing or allow the user to do it. Once the devices are paired, you can send bytes directly to and from the device to the mobile phone. Parsing these bytes into the object models that represent the data you are displaying or analyzing.
If you need a Bluetooth Manager Class example for Android I can supply that, but your embedded C code for the digital device is not something i have an immediate sample to provide.
Hope that helps. Let me know if you meant something else.
I am looking for the best way to send accelerometer data from my Android Wear device (20 entries per second) to my smartphone. The exchange should be as fast as possible to create a nearly real time XYchart on the smartphone.
What is the best way to send my data? Does MessageAPI provides an exchange which is fast enough?
You need to use either the Message or Data API. SharedPreferences aren't automatically "shared" between devices (such as a watch and a phone).
Also, be realistic about data transfer rates. You'll get accelerometer data on the watch at a much faster rate than you can realistically send it to the phone, and will need to handle that discrepancy. It might be that you want to use the Channel API instead - but that will require repackaging your ArrayList into a Stream.
I want to know if there is any way to communicate users without internet connection to a server.
I thought it might be possible through SMS and machine-readable encoding. However this question confirms that iOS apps allows sending but not reading SMS: iphone app reading sms
I've also read a lot about using USSD but it seems that mobile opened messages aren't possible in iOS (dial USSD code from iphone programatically) and while in Android is possible to call a code programatically there is no USSD API to, nor it's possible to send USSD messages silently.
Is there any way to transfer data between my app and my server with only basic voice-sms signal?
You are correct that SMS could be used to communicate with the server, if the server has access to a GSM modem. For large volumes of SMSes, you'd expect to have an internet connection between your server and an SMS gateway that connects directly to the messaging centre in the mobile network, instead of a modem.
This is the model of the SMS voting servers.
You can send/receive SMS as long as you have a GSM network, and you're right; no IP connection is needed.
The Android platform lets you send and receive SMSes - see here.
Disadvantages are that SMS can be expensive, and has no guaranteed delivery, and no guaranteed delivery time. It's not suitable for real time communication.
USSD is another form of communication between a mobile device and the network that's built directly into the GSM network, but USSD messages are owned or licenced by the network operators, and aren't free for customers to use, as SMS is.
EDIT: USSD isn't a native protocol in CDMA, but various implementations are available from different operators. For example, here's a patent application describing an idea for one such system, which does not appear to require an IP connection. Googling "USSD CDMA" also gives various news items about commercial implementations, technical details unknown. I think you just have to find out what your target operator(s) offer.
I haven't worked directly with WAP, but a glance at the WAP Protocol Stack shows that it can indeed run over CDMA, or GSM without an IP connection. There is also a very useful Wikipedia article. My experience testing MMS is that it usually doesn't work without an IP connection, even though it is supposed to (according to that Wiki article, with WAP/SMS). So I would question how far European operators or mobile devices are supporting or testing WAP. Whether WAP is a practical choice could come down to pricing/availability at the end of the day, rather than technical issues.
Well, there are yet other options, depending on the amount of data you need to transfer back and forth to the server.
Instead of sms, for short amount of data you could try to implement an Asterisk PBX, whith your mobile calling your server and then sending other DTMF digits as your data, which would be interpreted by your Asterisk PBX (like an interactive phone audio menu from your cable company). Asterisk is GPL open-source.
Another option (an expensive one and with heavy work to do), would be to generate an audio signal encoded with your data content, and dial a phone number linked with an attached fax/modem pci board on a server, sending that audio like a call. It would'nt need to be a long call, as you could fit lots of data in a short bursts of audio stream.
Your server could check that data by acessing the content on the receiving end. Simply recording the call from the attached fax/modem pci board, or you could use an Asterisk PBX server on a local computer to save the audio file and then process by your server software.
Anyway, you would need to create a new protocol and data encoding type, like you mentioned "machine-readable encoding".
So, for the data types you could just save a lot of short audio files on your mobile and play them as your datatypes, but it would be easier to just go for the DTMF already mentioned above. Or you could encode like this: get the sound spectrum allowed to use through the voice call (Wideband/Narrowband), and divide it by the amount of single characters or chunks needed (take a look at how to encode in base64, to have some ideas). Then create a function to just encode your data as a short audio stream (read about PCM encoding and also read more about Fast Fourier transforms, if you want to complicate (but speed up) even further.
Create a simple protocol like this: first audio packet is a sequence of tones that makes a request, authenticates, and waits for acknowledgement response from the server (which could be just by not dropping the call 1 second after that). The 2nd audio packet is the size of the first frame of data, then the 3d audio packet onwards is the data itself with the size shown before. And so on. Have a look at the ftp protocol description for simplicity. Then you need to refine it so that the time of every packet above is the least possible while mantaining confiability.
For costs saving on voice calling, you could also explore phone number options, like Google Voice, Skype or any Voip service.
I require a fast reliable method of sending control commands (simple data, possibly only a few dozen possible commands) to a remote system which is using a smartphone* as its onboard computer. I have deemed standard data packages used for mobile internet data transfer as too unreliable of control purposes, however I have noticed that once a voice call is initiated it is much more reliable. Has there been any development into sending data between phones across a connected call, and if not are there any known reasons a modified dialup modem in software form couldn't be used?
Furthermore, could this protocol be robust enough to send back low res video and other simple numeric data?
*Smartphone - A phone with significant processing power and ability to run custom programs (most likely with an Android based OS however am open to suggestions)
Have you tried SMS? while you won't get video data it may work for small chunks of data. Also if the small chunks are from the phone to a server, you may try sending DTMF down the line (however I've yet to see that working.
Other than that it's customised hardware.
Hmmm...this reminds me of those old TV games like Hugo...there you had a voice connection and I think the commands were given by the different tone of the key pressed from 0-9. Maybe you should try something similar.