On the Polar Code Encoding in Fading Channels
  Besides the determined construction of polar codes in BEC channels, different construction techniques have been proposed for AWGN channels. The current state-of-the-art algorithm starts with a design-SNR (or an operating SNR) and then processing is carried out to approximate each individual bit channel. However, as found in this paper, for fading channels, an operating SNR can not be directly used in approximating the bit channels. To achieve a better BER performance, the input SNR for the polar code construction in fadding channels is derived. A selection of the design-SNR for both the AWGN and the fading channels from an information theoretical point of view is studied. Also presented in this paper is the study of sacrificing a small data rate to gain orders of magnitude increase in the BER performance. 
Rui Deng, Liping Li, Yanjun Hu
cs.IT math.IT