Broadcasting huge number of signals simultaneously

Hi,

Is it practically possible to have 10 thousand users on the same RF channel simultaneously receiving and sending broadcasted msgs from the other users?
-Can this scenario be achieved by low power equipment like the Xbee?

Regards,

Yes its possible. Checkout ALOHA protocols & similar. Whether its "practical" or not depends on what you want to achieve. If I remember correctly, the channel should be NOT MORE than 10% loaded to get a reasonable thruput/ response-time. And various other parameters - lots of info available depending on what particular scheme you use....

cheers!

Thanks for your reply. If I want each user to broadcast msg with 100 char every 5 sec, will he be able to process similar msgs coming from the other 10K users? What other parameters do I need to know?
How to calculate the 10%, I mean how to know the max?

Admit it.... you didn't even TRY to checkout ALOHA, or any of the other material on CSMA/CD type of protocols. Be truthful now.

cheers!

I checked this http://www.laynetworks.com/ALOHA%20PROTOCOL.htm
but I could not understand how it is related to my needs?

However, CSMA/CD seems good (http://www.ethermanage.com/ethernet/...f/ch1qr_7.html) but I fail to understand how it wil be able to handle 10K users sending signals at 5 sec intervals?

How is it related ?!?!?!?!? Crikey.

These are EXACTLY what you need to answer your question.

So lets do some calculation.
100 characters sum to 100*8=800bits
Time - 5 sec
So bit rate is 800/5=160bps.
Now one user needs 160bps of data rate.
We will take the case of a time slotted network like GSM but the use case will be 1 slot per user to transmit. I am not considering any overhead right now.
For 10,000 users the total time slot will be 5 secs.
Per user 500us.
In 500us you need to send 800bits.
So data rate will be 1.6Mbps. Now adding overheads will still increase the data rate to roughly 2Mbps. So with a modem of 2Mbps you will be able to do your job with suitable time slotting protocol.
Xbee is only having a rated throughput of around 250kbps. You will have to reduce the users if you use Xbee.