Carrier phase tracking at low signal-to-noise ratio: a performance comparison of a parity-code-aided and a pilot-symbol-assisted approach

The last decade has seen the development of powerful channel codes such as turbo codes and low-density parity-check (LDPC) codes. The impressive bit error rate (BER) performance of the associated decoding processes implicitly assumes coherent detection, meaning that the carrier phase must be recovered accurately before the data is decoded. However, since the receiver usually operates at extremely low signal-to-noise ratio (SNR) values, conventional carrier synchronizers often fail to provide sufficiently accurate phase estimates. Numerous efforts to improve the carrier synchronization at low SNR have resulted in a myriad of different transceiver schemes; all based on the exploitation of some form of a priori information regarding the conveyed data during the phase estimation process. The resulting synchronization algorithms may be distinguished into two categories: category-I and category-II.