Inthisarticleabridgebetweentheexpectedcomplexityandperformanceofspheredecoding(SD)isbuilt.TheexpectedcomplexityofSDforinfinitelatticesistheninvestigated,whichnaturallyistheupper-boundofthoseforallthefinitelatticesifgivenbythesamechannelmatrixandsignalnoiseratio(SNR).SuchexpectedcomplexityisanimportantcharacterizationofSDinmulti-antennasystems,becausenomatterwhatmodulationschemeisusedinpractice(generallyithasfiniteconstellationsize)thisupper-boundholds.AbovebridgealsoleadstoanewmethodofdeterminingtheradiusforSD.Thenumericalresultsshowboththerealvalueandupper-boundofaveragesearchednumberofcandidatesinSDfor16-QAMmodulatedsystemusingtheproposedsphereradiusdeterminingmethod.MostimportantofallnewunderstandingsofexpectedcomplexityofSDaregivenbasedonabovementionedtheoreticanalysisandnumericalresults.
