433 MHz indoor propagation

433 mhz propagation

Hi guys,

I am developing a 418 (US) and 433 MHz (EU) transmitter / receiver with FSK for fairly low data rate (<10 kbit/sec) for remote control purposes inside a home. It is not a trcvr but a single TX and RX and the devices should be low $.

Now for indoor propagation one has always the big problem of multipath "dips" when walking around in a room or when some person is moving in that room.
I learned from the book from "Theodore Rappaport" that the dips can be quite deep.... up to > 30dB surplus attenuation. They depend upon the actual room and reflection of the walls ,ceiling etc.
I have no data though as how long these dips are to be expected when normally moving into a room. I have read some figures of "in the order of 10mS" but these figures were given for 900MHz and 2.4G. I expect it to be lower for 433 MHz because multipath fading improves with lower operating freq.

With these long times I wonder if this can be adequately solved by introducing some FEC (adding bits) and do some interleaving.
Anayone has some practical experience if things improve actually by this technique ? Or some tips to literature on the subject ?
The one other thing I consider is to have a RX antenna with multiple polarisation capabilities (adding a horiz pol and vertical polarised antenna together) Is not really diversity but this might help also. Real diversity I think is difficult and takes more time without having a trcvr function.

Thanks in advance

Mike

Is your TX stationary? If it is, you may try transmit diversity. Thw two antennas should be many lambda separation. Hence, it will use more space. The big problem is low $