In this paper, an optimal approach based on B-splines functions is presented for the design of ultra wideband (UWB) pulses which satisfy simultaneously the following 3 criteria : compatibility with the spectral mask authorised in USA or in Europe, spectral efficiency and orthogonality of generated pulses. The first property allows UWB systems to coexist with other applications without disturbing their operation. The second property enables the efficient utilization of power spectrum allowed by mask while third permits to reduce inter-symbol interference. Afterwards, a general architecture of transmitter/receiver adapted to these types of signals is described using TH-PSM (Time Hopping - Pulse Shape Modulation). The performance of proposed UWB structure is firstly assessed in ideal channel i.e. in the presence of additive white Gaussian noise only and then in second step the performance is evaluated in a more realistic channel, i.e. the indoor multipath channel defined by the standard IEEE 802.15.3a.