Chase decoding of linear ℤ4 codes at low to moderate rates

Abstract

A free ℤ4 code C may be decoded by decoding its canonical image C̄ over ℤ2 twice in succession. Hence, a Chase decoder for C could employ as its hard-decision (HD) decoder, a two-stage decoder which performs HD decoding on C̄ in each stage. Alternatively, one could have a two-stage soft-decision decoder by employing a Chase decoder for C̄ in each stage. We demonstrate that the latter approach can offer a significant reduction in complexity over the other, with little or no price to pay in terms of word error rate performance, particularly at low to moderate code rates. © 2007 IEEE.