In this contribution we study the challenging issue of WiMedia solution which the ability to support high data rate applications but is limited to three piconets simultaneously communicating in the same area. For this reason we analyze the suitability of Channel Division Multiple Access (ChDMA) approach for Multiband Orthogonal Frequency Division Multiplexing (MBOFDM) Ultra Wide Band (UWB) (MB-UWB) system over IEEE 802.15.3a (UWB) channel model. ChDMA approach exploits the characteristics of MB-UWB system to separate the piconets. Each piconet employs its own Channel Frequency Response (CFR) as a signature code which introduces diversity. We have presented analytical analysis in terms of spectral efficiency (bits/s/Hz) assuming that the receiver knows the channel. Numerical analysis is run over IEEE 802.15.3a high data rate channel justified the importance of ChDMA solution to improve the spectral efficiency of MB-UWB system. Then, performance evaluation is investigated when minimum mean square error (MMSE) and matched filter (MF) receiver is applied. Simulations results show the importance of MMSE receiver to improve the performance of MB-UWB ChDMA system.