Thank you, very very much for your reply sirs. Actually, i would like to implement wireless sensor nodes using PIC16f877 place on each nodes. Each node will also have a TX/RX ultrasonic and RF. The sequence will follow [ i hope this is correct]:
1. A single node [ NODE A ] will be attached to the PC via RS232.
2. When the other nodes are placed along with NODE A, it will give a real time simulation to the PC, showing the localization of all the nodes present.
But i planned, not to have a predefined location of all the nodes such that these nodes can locate themselves using TDOA or TOA theory.
I have seen it at MIT using Cricket that is really working. But I like to implement it using PIC.
i hope you can help out...