Enabling opportunistic communication in sensors for better power conservation

Imagine that you have temperature or pollution sensors sprayed along river beds or ponds, and you fly a plane overhead or row past in a boat to pick up information from these sensors. You need opportunistic communication here so that the sensors can somehow detect that an information aggregation resource is close by, wake up, send the data, and then again go off to sleep. This will be more power efficient than to have sensors wake up every now and then to detect a wireless signal.

The Rf-Id wakeup idea becomes applicable here. You just have to transmit energy from the plane to wake up the devices. And not just that, but optimizations can also be made in the way such sensors are designed. Consider this:

1. The radio wakes up through a RFID like circuitry on detecting a flood of wireless energy in the medium
2. Sets up the connection
3. Wakes up the processor and boots a small OS from a flash memory or ROM
4. Receives or transmits whatever data it needs to
5. Again powers down the processor
6. Periodically wakes up the processor and boots the full fledged OS to do whatever local processing it needs to

I am not aware of the state-of-the-art in sensor research, and it is likely that such work for design of sensors might have been done already. But there are some MAC layer problems for Rf-Id wakeup in such cases. A flood of energy is not just going to wake up one sensor, but many sensors. If all start transmitting at the same time, there is bound to be interference. Maybe, just an initial random backoff might suffice in this case.