I am currently trying to meet the EN 300-220-1 regulations with a C1121 design. I need the maximum bit rate in a 100Khz channel that will meet both the receiver sensitivity requirements of modulation bandwidth EN 300-220-1 clause 7.7.3 that the power at the edge of the band will not exceed 30dBm. Given that I need at least 10dBm transmit power this effectively means 40 dB reduction at 50kHz from centre of band.
Because I am also using LBT to get around the duty cycle I also need to ensure that I get a required receiver sensitivity of 100dBm according to EN 300-220-1 clause 8.1.4
I cannot change to a wider bandwidth because I want to use FHSS with LBT and the EN regualtions specify a maximum channel bandwidth of 100 kHz in this case. Also I require it to fit into the 868-870 band where 100kHz is the only effective channel size that fits efficiently into all the available bands
The best rate that fits into the spectrum requirements so far is 80kb/s using 4-GFSK with 20Khz deviation. This is close to the edge of the mask. The problem is I am having difficulty in measuring the receiver sensitivity without approaching a test house. I would like to do preliminary testing to make sure that the design has a chance of succeeding. Most of the test houses that will deal with these regulations are oversea and therefore not easy to access during preliminary investigations. Using the RSSI measurement from RF studio it seems to fail. (96-98dBm for 10% packet rate.)
I also tried 4-GMSK (4-GFSK with deviation of 0.25) i.e 90 kbits with 11 Khz deviation but this seems to have a RSSI value of about 94 dBm before the bit error rate climbs.
In theory the chip supports MSK and GMSK in the data sheet and with GMSK I should be able to reach a bandwidth of about 1.15 of the symbol rate before things start falling apart but I don't seem to be able to get close.
What would people recommend as the setting for the highest throughput that meets the EN Regulations of both modulation bandwidth and receiver sensitivity on a 100kHz channel ?