Encoding and decoding algorithm for convolutional Turbo code in IEEE802.16e

In order to analyze the impact of different coding parameters on CTC performance and compare the performance of CTC with that of convolutional codes both supported by IEEE802.16e, a coding scheme of CTC used in IEEE802.16e is introduced and the derivation for determination of circular state in encoding process is presented. Then the iterative decoding structure and decoding algorithm of CTC are analyzed and the performance of CTC is simulated. Results show that, at the same code rate and with the same modulation mode, CTC has a larger coding gain than convolutional codes. Therefore, under conditions of low code rate, good channel condition and strict real-time requirement, convolutional codes can be used to reduce the complexity of channel coding. While under conditions of high code rate, poor channel condition and strict BER requirement, CTC encoding scheme should be used to ensure the reliability of communication.