I have a problem where BPSK modulation has packet loss due to interference greater than QAM16 at good RSSI levels.

I am using tons of DSSS all around the troubled OFDM link. (16 PtMP links totalled from two cells, 2 miles apart). And my DSSS links most likely are the culprits causing some self interference with the OFDM PtP link. So is there anything about BPSK modulation that would make it more prone to interferrence from DSSS radios apposed to QAM16?

RSSI at -65 when this occured most obviously.

QPSK had similar characteristic/loss as BPSK, when comparing to QAM16.

At -55 QAM modulations got worse/unusable, possibly because overloaded by self noise. At -75 QAM modulations got worse/unusable, possibly because to close to noise floor (-80). Testing at -65 was the sweet spot that QAM worked well, much better than BPSK and QPSK. QOS loss was relatively consistent for BPSK/QPSK at -55,-65, rssi, with a little more degregation at -75 for QPSK as getting close to noise.

Note: 10 mile link. Rssi adjustments accomplished by reducing radio TX power on both ends, Antenna type remained constant. For the purpose of this discussion, I'm looking for theory pertaining to all radios, not a specific brand.

Tom DeReggi
RapidDSL & Wireless, Inc
IntAirNet- Fixed Wireless Broadband
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