Abstract: To reduce the computation complexity of quadrature index modulation multiple access(QIMMA) detection, two low-complexity detection schemes based on receiver sphere decoding and sorting-based sphere decoding are presented. By weighting the combination of time slots, the detection accuracy is enhanced, the number of searches is reduced, and the effect of reducing complexity is achieved. Compared with the maximum likelihood detector, the new scheme can reduce the detection complexity by more than one-third without any performance loss. In addition, analysis of the average bit error rate is derived according to the characteristics of QIMMA system. It ids shown that it coincides very well with their theoretical counterparts in the range of middle and high signal-to-noise ratio.

Key words: index modulation, uplink transmission, multiple access system, low complexity detection algorithm