  Polar codes are designed for parallel binary-input additive white Gaussian
noise (BiAWGN) channels with an average power constraint. The two main design
choices are: the mapping between codeword bits and channels of different
quality, and the power allocation under the average power constraint.
Information theory suggests to allocate power such that the sum of mutual
information (MI) terms is maximized. However, a power allocation specific to
polar codes shows significant gains.
