Where you get squeezed is, output power is limited by regulation (for good reason). And sensitivity is limited by noise which is related to your signal bandwidth. The wider the band, the more noise you capture. There is a signal to noise 'wall/floor' defined by information theory, etc etc. Encoding technologies+ allow you to operate closer to the wall, but it's still here as a hard limit. Once your signal/noise drops below 3-6db game over+.
These new technologies/products try to solve the problem from both ends. Increasing transmit power to the max allowed. Some early Zigbee chips for instance had transmit powers of 0db, big fail. These new radios transmit 10 to 20 db output power. On the receive side reduce bandwidth to increase the sensitivity by 10-30 db, at the expense of data rate.
The cost of all this is very low bandwidth. Not just in bps, but also packets per minute due to duty cycle regulations. This poses some problems if you want encrypt your packets. Add at least 32-64 bytes overhead. Another problem is as the coverage area gets wider so does the number of interfering radio's.
+ Sometimes you hear comments that spread spectrum allows you operate below the noise floor, but that's only for the spread signal. Once the signal is despread at the receiver, same rules apply.
These new technologies/products try to solve the problem from both ends. Increasing transmit power to the max allowed. Some early Zigbee chips for instance had transmit powers of 0db, big fail. These new radios transmit 10 to 20 db output power. On the receive side reduce bandwidth to increase the sensitivity by 10-30 db, at the expense of data rate.
The cost of all this is very low bandwidth. Not just in bps, but also packets per minute due to duty cycle regulations. This poses some problems if you want encrypt your packets. Add at least 32-64 bytes overhead. Another problem is as the coverage area gets wider so does the number of interfering radio's.
+ Sometimes you hear comments that spread spectrum allows you operate below the noise floor, but that's only for the spread signal. Once the signal is despread at the receiver, same rules apply.