How can I estimate Bhattacharyya parameter for BSC channel, used for Polar codes
I do not think you can use formula (14) on page 5 of 'How to construct polar codes'. I think you want to compute Bhattacharyya parameters after channel polarization. Hence, you need to compute transition probabilities of synthesized channels firstly, and then compute Bhattacharyya parameters using formula (14) on page 5 of 'How to construct polar codes'. The formula of transition probabilities of synthesized channels is give by Arikan in his TIT paper, but it is not easy to implement it.