Re: [Discuss-gnuradio] How to detect collision when two packets are transmitted simultaneously from two transmitters.

[Sumedha Goyal]

Hello Aditya,

1. I tried checking for the average power but that doesn't work. Even with two transmitters transmitting at the same time the energy detected by the receiver doesn't change much. It remains in the same order.

2. Is there any other simpler way of detecting collisions other than the mentioned paper?

Regards,

Sumedha

On Fri, Nov 8, 2013 at 8:32 PM, Aditya Dhananjay <address@hidden> wrote:

Hi Sumedha,

1. You could perhaps look at the average power received over that time slot. If there is a collision, the receive power would ostensibly be higher.

2. Traditionally, a collision implied that nothing could be done, and the data was lost (unless one transmitter overwhelmed the other transmitter's signal, leading to the capture effect). However over the past couple of years, there have been techniques developed to recover packets from collisions. You could read the "Zig-Zag decoding" paper by Shyamnath Gollakota and Dina Katabi from SIGCOMM 2008.

http://groups.csail.mit.edu/netmit/wordpress/wp-content/themes/netmit/papers/ZigZag.pdf

Aditya

On Fri, Nov 8, 2013 at 8:44 AM, Sumedha Goyal <address@hidden> wrote:

I have a setup of one receiver and two transmitters. I am implementing a TDMA structure (using USRPs and GNURADIO) where only one packet is sent in each slot. When both transmitters try to transmit in the same slot, collision occurs. I would like to know

1. How can the receiver detect whether a collision has occurred or not?

2. What happens to the collided packets?

Regards,

Sumedha

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