Fast and efficient construction of an unbiased random sequence

The problem of converting a sequence of symbols generated by a Bernoulli source into an unbiased random sequence is well-known in information theory. The proposed method is based on Elias' (1972) algorithm in which the sequence of symbols is divided into blocks of length N,N/spl ges/1. We suggest a new method of constructing an unbiased random sequence which uses O(Nlog/sup 2/N) bits of memory and takes O(log/sup 8/Nloglog(N)) bit operations per letter.