国家重点实验室 Channel polarization o When N-→∞ >the fraction of indices i for C(W)(1-,1]>C(W) >the fraction of indices i for c(W()[0,)1-C(W) Theorem(Polarization,A.2007) Under the above polarization scheme,almost all channels become either perfect or completely useless as the construction size grows. For anyδ∈(0,1)，as the construction size N grows, [fraction of(good)channels with C(W)>(1-δ)]→C(W)） and [fraction of (bad)channels with C(Wi)<](1-C(W)) Theorem(Rate of polarization,A.and Telatar(2008)) Above theorem holds with2-N 21 Channel polarization When  the fraction of indices i for  the fraction of indices i for 21 N → ∞ ( ) ( ) (1 ,1] ( ) i CW CW N ∈− → δ ( ) ( ) [0, ) 1 ( ) i CW CW N ∈ →− δ