Log-likelihood Ratio Optimal Quantizer for Cooperative Spectrum Sensing in Cognitive Radio

In order to reduce the bandwidth requirement for reporting channel, the quantization of sensing data´s log-likelihood ratio (LLR) in cooperative spectrum sensing is considered. A well-preserved quantizer which minimizes mean square error of the sensing data´s LLR at quantizer output is achieved by applying the well-known Lloyd-Max quantization algorithm. The probability density function of the LLR of the sensing information is also formulated for designing the quantizer. Simulation results reveal that the proposed quantizer provides the same sensing performance of the original LLR test with only few quantization bits.