A wireless receiver and method of wireless communication determines levels of noise, including interference, in communication channels without need of calibration. A digital test signal is digitally added to digitized noise, and a signal-to-noise-and-interference (SNIR) value is determined from a resulting bit error rate and/or message error rate. The level of noise is then determined from the SNIR. The amplitude of the digital test signal is adjusted to cause the SNIR to be sensitive to the noise level, which can require an SNIR between 1 dB and 10 dB. The system can include a digital test signal generator, or the digital test signal can be stored in a memory. The system can further include a channelizer, demodulator, data correlator, decryptor, and message assembler. Noise and interference level determinations can be used to select an optimal communication channel, and to adjust a transmission power and/or rate to suitable values.