Multidimensional orthogonal design for ultra-wideband downlink

In a traditional time-hopping multiple access ultra-wideband communication system, the orthogonal time-hopping sequence can be designed to improve system performance. However, system capacity is restrictive. We propose a new multiple access system model for a UWB downlink and deploy orthogonal design in three dimensions: time-hopping code, multiuser code, and pulse waveform, or equivalently the position, polarity, and shape of a basic pulse. Such a system provides more freedoms than a traditional time-hopping system. Thus, it is more robust to multiple access interference and can support more users. Performance of the system is analyzed and verified by simulations.