8.4 Spread spectrum communication systems Let P be the power of the signal.We have,. EP_里×”-xL J。P/WPR J The SNR (E/J)is L times of the signal-to-interference ratio (SIR).So we call L the processing gain.. More, dB J B Specifying a required SNR(E/J)for a desired level of reliability, (P/P)tells that how large an interference the system may tolerant.So,(P/P)is called the interference margin.. UESTC-Wireless communicatons Prof李晓峰 14