A Novel Impulse Radio DS-UWB Transmission Scheme Using Variable Length Spreading Sequence

In this paper an adaptive impulse radio direct sequence ultra-wideband (DS-UWB) transmission scheme using variable-length spreading sequence (VLSS) is proposed in an in-car wireless communication environment. In contrast to the conventional DS-UWB system which employs a fixed length spreading code, the proposed system changes the length of spreading code according to the system load adaptively, which is proven to be able to reduce the inter-chip interference (ICI), intersymbol interference (ISI) and multiple access interference (MAI) and thus improve the system performance in terms of bit error rate (BER). The proposed system is simulated in multipath channels with a high level of multipath fragments, modelled by the standard IEEE 802.15.3a indoor channel model 1 (CM1) and channel model 2 (CM2). Numerical results demonstrate that when Rake receivers are employed, the proposed VLSS DS-UWB system significantly outperforms the conventional system by appropriately allocating the spreading sequences.