Receiving and treating multiple signals

Hi,

I have used in the past RX - TX chips (433Mhz) receiving one signal using Manchester encoding works fine. In my next project, I would like to include multiple TX chips ... lets say 20 and one receiving chip to get GPS information. I am kinda confused on how the receiving end will make a difference between all the signals. The information I quiet long maybe 64bits or even 128 bits, my worry is how to differentiate the information from one signal to another in the middle of the transmission.
I can use a unique code in the beginning of the "string", but when it come to the 32rd bit or 64 bit, other bits from 19 other signals are pouring in. Can someone illuminate me on this, and if it is feasible?
I think it is, with all the communication between cell phone and towers..
thanks
Ken

Hi Ken,
Are you saying that you will have 20 transmitters randomly transmitting data on the same channel/frequency?
I don't know much about modern radio tecniques but to me that sound sort of impossible. I mean if two or more nodes are transmitting at the same time, on the same channel/frequency you're going to get the equivalent of bus contention. If they are not transmitting on the same channel/frequency then how's the receiver going to "tune" to multiple carriers at once?

Do you have a link to the radios you intend to use?

My guess is that the easiset way is to use tranceivers in all nodes and a master/slave type network. Ie. the slaves never sends unless specifically asked to by the master.

Again, I don't that much about the details of modern radios so if someone else is of another opinion, please enlighten me!

/Henrik.

EDIT: Depending on the radio modules it might be possible to do something similar to what CAN does to prevent bus contention.

HI,

this is one module i am going to try, all of these have the same frequency. ..
Arduino 433MHz LoRa SX1278 long range RF

ken

You realy should look at nRF24L01+, that level of protocol all implemented in silicon, ACK, node address, retry, multicast, ACK with payload, automatic packet assembly (CRC, preamble, address), dynamic payload length, pipes, the list is endless, and all for practically no money $1.50/£1 per module on ebay. Several different modules are available, PCB, ceramic or exteral antenna, some with PA/LNA some without.

George