Is this wired or wireless?
How far away are the transmitters from the receiver?
For close, wired, connections, using the UART on a master device and just daisy-chaining the remote devices (with diodes to OR the TXD) can do fine. Or use I2C; it's great for multi-device communication under, say, a meter.
For far, wired, connections, you probably want to use the UART with a RS-485 conversion chip, and run it in half duplex.
For wireless connections, look at the XBee series of wireless modules; they have a variety of options available.