Communication Systems Group

The requirement for increased exibility in order to support the many di erent services in wireless communication has motivated the search for new, improved convolutional codes with a large number of di erent code rates. A new design criterion is introduced which results in codes with better performance on both AWGN channels and Rayleigh fading channels. These codes, called Optimum Distance Spectrum (ODS) convolutional codes, are tabulated for code rate 1/2, 1/3 and 1/4, for di erent constraint lengths. The ODS codes are used as a basis for deriving a large number of codes with di erent rates. Optimum puncturing patterns and spectra are shown for puncturing periods between 2 and 8, parent code rates 1/2, 1/3, and 1/4 and constraint lengths between 3 and 15. A large set of rate-compatible punctured codes are also presented, as well as a detailed evaluation on RCPC puncturing pattern search. Finally the ODS codes are used as starting codes for searching additional generator polynomials (nested code search) to produce very low-rate codes. Maximum free distance codes with rates ranging from 1/4 to 1/512 and constraint lengths between 3 and