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I'm thinking of a system that would take multiple data streams in, encode them into one signal, and then broadcast it out to multiple stations that could then decode the information in the signal for the one stream that station wants. I apologize for the roundabout description of the problem as I don't know what this set up is technically called; as best as I can think of it, like a reverse of CDMA.

schematic

simulate this circuit – Schematic created using CircuitLab

My question then is, is this possible, and if so, does a standard already exist?

Jon.H
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  • IMO this is so simple that nobody bothers to make a general standard for it. Depending on yoyr requirements you could send messages with a target address, or bytes with each bit destined for a different target, etc. – Wouter van Ooijen Dec 08 '14 at 22:03
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    Packet Radio anyone? – Majenko Dec 08 '14 at 22:07
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    this is not the reverse of CDMA, what you are describing is actually CDMA and it can be used to send from many to one, from one to many or from many to many – Fahad Alduraibi Dec 08 '14 at 22:21

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Any *DMA could be used for this - CDMA, TDMA, FDMA, etc. There are many standards that can do this sort of thing, but it is not possible to recommend a specific one without more information about these 'data streams' that you are dealing with.

Edit: Seems like you want to work with either analog or raw samples. With analog, you would need to transmit with N carriers, one per channel, then tune to the carrier that corresponds to the channel that you're interested in.

For digital, generally 48 kHz @ 16 bits is a good format for audio data. If you want to get crazy, you can do 192 kHz @ 24 bits. 48 kHz @ 16 bits is 768 kbps per audio channel. For four channels, you would need at least 3.072 Mbit/sec. I would recommend interleaving the channel samples and combining them into packets of some sort, then picking which samples to play at the receiver. This could be considered sub-packet TDMA, though all of the receivers will actually have to deal with every packet. There will be a tradeoff between packet size, latency, and overhead (due to packet headers and other synchronization necessities).

One decent option might be wifi + some sort of audio over ethernet standard. Take a look at Sending audio over ethernet and https://en.wikipedia.org/wiki/Audio_over_Ethernet . Otherwise, you may find yourself building your own radios, which is a rather tall order, especially since you will need several megabits per second.

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alex.forencich
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  • Thanks for the answer. As hobbyist learning project for wireless stuff that I can use around the house, I was thinking of taking, for instance, multiple MP3 inputs and then being able to select on the speaker which channel play from. Do you have a recommendation for audio transmission like this? – Jon.H Dec 09 '14 at 00:10
  • Where are the "MP3" inputs coming from? – alex.forencich Dec 09 '14 at 00:17
  • The line out on MP3 players or any other audio out conceivably. I thought about Wifi, but I'd rather not go through a network right now. Really this is more of a project I have a specific application for that would give me a good reason to learn about handling wireless transmissions with embedded systems since it's something I've wanted to learn about for a while. – Jon.H Dec 09 '14 at 00:22
  • Seems like you want to either do this in analog or you want to work with raw PCM samples. See edit. – alex.forencich Dec 09 '14 at 00:41