A Direct Geometrical Method for Bounding the Error Exponent for Specific Families of Channel Codes Part II: The Confining Region Lower Bound for Block Codes

The introduction of a confining region that divides the channel output space in two disjoint parts attains the same effect as the Gallager´s exponent, but gives much mope insight into the behaviour of channel codes. Moreover, the bounds obtained are always tight at low code rates (for optimal codes they are always tight).