Broadcasting huge number of signals simultaneously

[ahmadicabara]

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,

 

[rohitkhanna]

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!

 

[ahmadicabara]

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?

 

[rohitkhanna]

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!

 

[ahmadicabara]

I checked this **broken link removed**
but I could not understand how it is related to my needs?

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

 

[rohitkhanna]

I checked this **broken link removed**
but I could not understand how it is related to my needs?

However, CSMA/CD seems good (https://www.ethermanage.com/ethernet/10quickref/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.

 

[jossion]

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.