Channel coding and carrier recovery for adaptive modulation microwave radio links

This paper deals with channel coding and carrier recovery design for high-speed adaptive modulation microwave radio transmission sytems. The challenges posed by the microwave channel are discussed and the design trade-offs are analyzed. The proposed flexible adaptive modulation solution employs M-QAM modulations from 4 QAM up to 512 QAM and a high rate LDPC code. The code-rate flexible LDPC code performs within 1 dB away from the pragmatic capacity in AWGN channel. Particular attention is paid to the design of the carrier synchronization algorithm working at the low SNR conditions imposed by the code and the relatively poor local oscillator behavior.