I am thinking about following idea. I want to design "active" tags for mobile objects (for example cars). I want to detect that tag is inside specific area, size aproximatelly few meters. There will be many "objects" and "areas", objects should be detectable in ANY area, and areas are separated with distance few meters. Objects could have different shape and mechanical properties (like cars has different sizes). I am assuming at the center of areas will be located zigbee routers, but any two zigbee routers should not communicate with each others. Each "tag" will be simple zigbee device, will search for any others components of network.
Is it possible to limit the range of zigbee device, so each tag could communicate ONLY in range of few meters? I see following problems:
1. Probably each "size" of object will require some "tuning", probably is it possible to use some "signal strenght" value from RF module.
2. When tag is arriving to final "area", but was passing near to another area, it may already connect and keep connected to wrong, even if is in range of router with stronger signal
3. When two tags are in adjacent "area", one tag could "extend" that range of areas, this problem probably will be solved when tags will have disabled router capability.
I have also another idea, let the each "area" has different channel or panid, and force devices to search for network with best signal strenght.
What do you think about ideas and scenarios? I could probably use some UHF RFID tags to locate and identify objects, but objects also needs to send some sensor data over zigbee. In this case I could use both technologies, but have a feeling that zigbee will be enoght.