asynchronous transceiver for wireless sensor networks

I was reading a paper abt async transceiver for WSN.... can some one please explain me what is difference between syn and async transceiver... I know asyn transmission involves sending start bit data and stop bit but how is it useful in reducing power consumption of WSN... and syn transmission too sends data so wats the difference... also I read for asyn transmission eg was given to be talking in phone wer both persons can talk randomly I mean at the same time... so if this is the case wont der be collision of data in asyn mode? somebody pls help

in asynchronous transmission your data is sending like each bit of data one by one following on each time pulse
in asynchronous all bit are sending on one pulse

More fundamentally, asynchronous has no reference clock, it carries the information needed to frame the data in the stream itself. This is normally a start and stop bit and to recover the data between them the transmitting and receiving systems have to work at (or close to) the same speed.

Synchronous implies the data is synchronized with a timing reference. In wired system the transmit reference clock is sent along a wire so the receiver can use it to 'clock in' the data bits. That makes it a bit more complicated in wireless links where typcally only one channel exists.

I think you are confusing the phone link with something else - half duplex and full duplex. Half duplex can send OR receive but not both simultaneously, Full duplex is like the phone line, it carries data both ways at the same time.

Brian.