I was trying to send data from two Xbee-RF modules(S1) to one Xbee-RF. However, it makes the timing of data reception extremely unstable. The following figures shows the comparison. The Sampling Rate is 20 ms and baud is 9600.

One solution might be using two Xbee modules as receivers, employing different two channels to data but it occupies two USB port and require two modules. may be i could use an arduino as a hub… but anyways, this is disappointing.

Randomized timing

There is a way to randomize the timing of transfer in order to avoid collisions (below), using AT command RN but this does not solve the problem dramatically.