Author: Xiaohui Liu (whulxh@gmail.com)
Created: 12/30/2011

Description:
-SignalMap: implementation of signal map
-TestSMC:	an example demonstrating how to use SignalMap

Known bugs/limitations:
1) Transmission power level must be legitimate, i.e., one of the levels specified by CC2420 datasheet.
2) May not work under extremely heavy traffic because concurrent tx interfere with RSSI sampling