The fundamental theory of Over-Saturated Wavelet Packet Multiple Access (OWPMA) in mobile communication is briefly introduced in this paper. By properly selecting over-saturated codes, two OWPMA codes sets (more users than dimensions) are constructed: Lowest Scale OWPMA code set and Orthogonal Lowest Scale OWPMA code set. For Lowest Scale OWPMA code set, the optimal joint detection for tree-structured multiple access system is used as multi-user detector. For Orthogonal Lowest Scale OWPMA code set, the selected over-saturated codes are orthogonal to each other, and a novel multiuser detector, Packet Successive Interference Cancellation (PSIC), is proposed. Computer simulation results in AWGN channel and single path Rayleigh fading channel demonstrate that PSIC-MUD has the performance weakly inferior to the optimal joint detector and reduces the complexity from a low-order polynomial in the number of users to linear with the number of users. Both of the code sets provide more codes than orthogonal code set and the performance of respective MUD is acceptable.