Low Bandwidth Application

[GARL]

Hi everyone,

I am doing a trade study on replacing the wires on the sensor network for a wireless sensor network.

These sensors for example would measure pressure or temperature. I do not need a high-bandwidth standard. What do you recommend for my application.

So far I have done some research in Bluetooth, but it seems like its a high data rate transfer, and has a time slot of 625uS. Which is a lot faster than what I need.

Can this time slot be modified? I only need to send and receive once every 10 seconds or so. And my the amount of data I must send tops out at 3 Bytes. As from before these signals are only used to take readings from sensors.

Any input would be helpful. I was thinking of may be taking some of the standards and modifying it a little bit so I can get maximum battery life out.

Thanks!,

Garl

 

[johnwiss]

Look at ZigBee--I think Philips makes chips to do this standard. Bluetooth at a lower data rate would be OK. It has a constant envelope which means you can transmit at a level that will be near saturation making the modulation efficient. The demodulation is pretty simple if you can take a loss -- most BT receivers are limiter/discriminator types (with good analog filterws) or use a Delta-Sigma ADC-type front end (with relaxed analog filtering requirements since you can do it digitally).

Direct-sequence Spread Spectrum (DSSS) is another good choice. I would recommend a spreading gain of 16 dB or more and use BPSK or maybe pi/2 Differential BPSK.

The RF frequency is also important--you need to pick one that you are allowed to operate in (900 MHz, 2.4 GHz range) if you want to use unlicensed--typically lower is better.

Search Google to get some ideas.