In　this　paper,　we　valign=＇-60pt　propose　a　joint　differential　pulse　position　modulation　and　differential　chaos　shift　key　modulation　(DPPM-DCSK),　where　one　bit　modulates　the　reference　PPM　signal　by　chaotic　signal,　and　the　other　mc　bits　are　mapped　by　the　position　index　of　this　chaotic　pulse　in　the　information　signal.　In　particular,　in　the　DPPM-DCSK,　the　information-carrying　PPM　signal　for　the　current　symbol　also　serves　as　the　reference　for　the　next　symbol.　It　can　avoid　the　energy　and　rate　wastes　in　the　conventional　PPM-DCSK.　Moreover,　we　redesign　the　differential　Walsh　codes　(WC)　for　DPPM-DCSK　to　enable　multi-user　communications.　The　numerical　bit-error-rate　(BER)　performance　of　the　proposed　DPPM-DCSK-WC　over　multipath　Rayleigh　fading　channels　are　derived　and　then　verified　by　simulations.　The　results　demonstrate　that　the　DPPM-DCSK-WC　can　achieve　performance　gains　of　more　than　2　dB　over　the　conventional　PPM-DCSK　and　DDCSK-WC　for　multi-user　scenarios,　and　this　gain　can　be　up　to　5　dB　in　the　high-delay　channels　at　a　BER　of　10-4.　In　addition,　the　superior　performance　of　the　proposed　scheme　is　proved　over　ultra-wideband　(UWB)　wireless　channels,　which　indicates　its　great　potential　for　chaotic-based　wireless　applications.　©　1967-2012　IEEE.