The default basebandrate of baseband service is 12000 samples/s , but it's a little low for me. How can I change the basebandrate of the baseband service?
The baseband rate for UnetStack depends on the settings of the modem.
If you are using a simulator, you can set the carrier frequency and baseband rate as desired using modem model parameters modem.carrierFrequency and modem.basebandRate in your simulation script.
If you are using unet audio, that uses the laptop soundcard and so the carrier frequency needs to be within the supported range for the soundcard. The default is 12 kHz carrier and 12 kHz bandwidth, with an effective band of 6-18 kHz. You can't go much higher with most standard soundcards.
If you are working with a modem, the carrier frequency and bandwidth is determined by the modem manufacturer and cannot be changed.