1. A method for detecting a symbol encoded in one or more received signals, wherein the detected symbol corresponds to a combination of values of n components, n>1, the method comprising: (a) for each of a plurality of different combinations of values of the n components, generating a set of two or more sub-metric values based on the one or more received signals, wherein: each sub-metric is a function of one or more of the n components; and at least one sub-metric is a function of fewer than all n components; and (b) detecting the symbol based on the sets of sub-metric values.