A new TH/DS-CDMA scheme for UWB communication systems and its performance analysis

We propose a new multiple access technique for ultra wide-band (UWB) systems based on time-hopping (TH) and direct sequence (DS) spread spectrum techniques. In this method, the duration of each bit is divided into N_s frames each one consisting of N_h chips. The outputs of a super-orthogonal encoder and a PN sequence specify the frame number, in which the data is transmitted in DS spread-spectrum form using the second PN sequence. We consider hard decision with threshold and soft decision before Viterbi decoding at the receiver. We evaluate the performance of the proposed method and compare it with the conventional DS-CDMA system. The results show that the proposed method has the best performance while it has the same bandwidth as the conventional DS-CDMA system.