Abstract: This paper presents the trellis decoding scheme of uncoded DUSTM system in the situation where its constellations form a group under the matrix multiplication.The system structure of DUSTM can be considered as a trellis structure which has full transition branches with the cardinality of the constellation as the number of the trellis states.Thus the soft Viterbi decoding algorithm can be performed.It is shown that more coding advantages can be gotten compared with the traditional uncoded DUSTM which is decoded by maximum likelyhood decoding based on single symbol.Since no constellation expansion，the scheme has higher spectral efficiency against the combined DUSTM at the expense of some performance.

摘要： 提出了未编码DUSTM系统的网格译码。将DUSTM系统视为具有全状态转移的网格结构，采用维特比软译码算法进行信号解调。仿真结果表明该方案相比传统的基于单符号最大似然解调的DUSTM系统性能有大幅提升，且比编码DUSTM系统具有更高的频谱利用率。