Frequency-Selective Link Adaptation using Duo-Binary Turbo Codes in OFDM Systems

This paper is devoted to a novel frequency-selective link adaptation (LA) strategy developed in the WINNER Integrated Project, which aims to provide a new radio interface for future 4G wireless communication systems. For a single-user adaptation of modulation and code rate in a coded OFDM system, the presented bit-loading algorithm offers performance results very close to the optimum solution of the well-known Hughes-Hartogs bit and power loading algorithm, which is verified by simulations. Efficient rate-compatible punctured duo-binary turbo codes (DBTC) have been used in evaluations. The adaptation is performed in two steps: first, adaptive QAM mapping is done on subcarrier groups in frequency direction, according to a short-term channel quality information. Then, an average code rate is calculated for the entire set of used subcarriers with heterogeneous modulation alphabets. This method results in moderate system complexity while offering excellent performance.