Orthogonal variable spreading factor codes with zero-correlation zone for TS-UWB

We propose an algorithm for the construction of ternary orthogonal variable-spreading-factor (OVSF) codes with zero-correlation zone (ZCZ); this is of particular interest for ternary sequence based UWB (TS-UWB) systems. The conventional approach is to design OVSF codes based on Walsh codes and, in this case, the orthogonality of the corresponding OVSF codes is easily lost when synchronism is lacking or in a multipath scenario. 2D OVSF codes possess ideal correlation properties which significantly improve the interference-rejection capability of multicarrier DS-CDMA systems. However, 2D OVSF code schemes, applied over multiple orthogonal channels, suffer from the disadvantages of a high peak-to-average power ratio (PAPR) and high complexities on transceiver design. The proposed OVSF codes, derived from two-dimensional (2D) OVSF codes, present a ZCZ which allows for significant suppression of multipath and multiuser interference and keeps the transceiver of an impulse based UWB system simple.