Cubic interactions for arbitrary spin N -extended massless supermultiplets in 4d flat space

N -extended massless arbitrary integer and half-integer spin supermultiplets in four dimensional flat space are studied in the framework of light-cone gauge formalism. For such multiplets, by using light-cone momentum superspace, we build unconstrained light-cone gauge superfield formulation. The superfield formulation is used to develop a superspace representation for all cubic interactions vertices of the N -extended massless supermultiplets. Our suitable treatment of the light-cone gauge superfields allows us to obtain attractively simple superspace representation for the cubic interaction vertices. Su- perspace realization of relativistic symmetries of the N -extended Poincare superalgebra on space of interacting fields is also obtained.