In　this　paper,　we　develop　a　non-coherent　differential　chaos　shift　keying　based　index　modulation　by　using　initial　value　index　(IVI-DCSK)　to　convey　additional　information　for　wireless　communications.　In　the　proposed　scheme,　mc　mapped　bits　are　carried　by　2mc　chaotic　sequences　by　exploiting　the　quasi-orthogonality　of　different　chaotic　signals,　while　the　modulated　bit　is　carried　by　DCSK.　To　diminish　the　multiuser　interference,　the　references　allocated　to　different　users　are　sent　in　individual　time　slots,　while　the　information-bearing　sequences　for　the　mapped　bits　of　users　are　sent　simultaneously.　We　then　derive　the　bit　error　rate　(BER)　expression　of　multi-user　IVI-DCSK　over　multipath　Rayleigh　fading　channels.　The　theoretical　and　consistent　simulation　results　show　that　the　proposed　IVI-DCSK　achieves　significant　gains　over　the　conventional　chaotic-based　index　modulations,　i.e.,　permutation　index　DCSK　(PI-DCSK)　and　code　index　modulation　DCSK　(CIM-DCSK).　This　gain　can　be　more　than　4　dB　in　fading　channels　with　high　multipath　delay.　In　addition,　it　achieves　higher　energy　and　spectral　efficiencies　over　the　latter　ones.　The　superiority　of　the　proposed　scheme　is　further　verified　in　practical　ultra-wideband　(UWB)　communications.　Thus,　this　proposed　scheme　is　efficient　and　promising　for　chaotic-based　low-complexity　communications,　such　as　in　wireless　local　area　network　(WLAN)　and　indoor　applications.　IEEE