Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:LLL based LR has been used for ZF decoding [1 1], [12], MMSE decoding [13], and ZF precoding [12], [14], which are often called lattice reduction aided (LRA) decoding/precoding.
Category: