This book refers for Error Correcting Codes . In Wireless communication due to noisy channel lot of errors are introduce at the time of transmission. To Overcome these errors, Error Correcting Codes are used for efficient and reliable digital data transmission. The convolutional codes and turbo codes are used as error correcting codes and able to come very close to theoretical limit, the Shannon limit. Performance of turbo decoder is analysis on the basis of BER, E_b?N_o , different code rate, constraint length, iteration and frame size using MATLAB.