Clear Channel Assessment (CCA) with multiplexed preamble symbols for impulse Ultra-wideband (UWB) communications

Because of the low radiation power density and the sparse and transient nature of impulse UWB radio, the conventional clear channel assessment (CCA) technique, which is to detect the energy of carrier waveforms, cannot be applied. In this paper, we propose a simple packet structure with multiplexed preamble symbols to enable the CCA of impulse UWB radio, where CCA is to detect the presence of a preamble symbol. We introduce two types of multiplexed preamble symbols, i.e., the CDMA (code division multiple access) type and the TDMA (time division multiple access) type. We devise a corresponding CCA scheme, where the processing gain is enhanced by exploiting the spreading code and repetition of a preamble symbol. Simulation results show the effectiveness of our approach. Our proposed TDMA type multiplexed preamble structure and related CCA parameter specifications have been accepted by the IEEE 802.15.4a standard to support the CCA function for UWB frequency bands