Analytic Bounds for Quasioptimal Block Code Reception Methods in the Large

The article investigates the so-called Chase's second algorithm, which has achieved some renown and is a quasioptimal version of reception “in the large” of block codes with a complexity proportional to $2^{d/2}$. A new lower bound for the noise stability of this method is derived; it is more exact for large $n$ than the one proposed by Chase. Computer calculations for this bound are compared with data of statistical experiments (the authors' own and experiments analogous to the numerical experiments of Baumert and McEliece).