With the increasingly complex distribution network topology and electromagnetic environment, in order to improve the reliability of the grid information-aware communication, in this paper, the wireless channel transmission model is studied, and for the Rayleigh and Ricean distribution of the signal and noise model, a numerical lookup table of probability distribution under the given false alarm rate is designed by using the curve fitting algorithm, which can greatly reduce the complexity of the signal detection algorithm implemented by the receiver baseband ASIC. On this basis, the calculation method of the carrier noise ratio of the receiver is given. The Monte Carlo simulation results show that this method has good signal detection performance at low complexity, which has good guideline significance for the design of baseband ASIC for wireless spread spectrum signal receiver.