Improved Complementary Sequence Keying for Wireless Infrared Communications
Hao Li · Journal of the China Railway Society · 2010
Since the unitary spreading sequence which possesses perfect auto-correlation property does not exist,infrared wireless communication systems based on direct sequence spread spectrum suffer severe multipath interference in multipath channels.CSK is proposed as a new modulation scheme,in which BCP is employed as spreading sequences.Because of the perfect auto-correlation property of BCP,CSK can significantly reduce multipath interference.However,CSK does not make full use of the perfect correlation property of BCP,furthermore,selection of appropriate BCP for CSK involves lots of computation when the length of the spreading sequence is relatively long.We propose an improved CSK,in which data streams after spreading by two element sequence of BCP are transmitted via two different subcarriers.The improved CSK can completely eliminate multipath interference and provide simplicity and flexibility to the selection of appropriate BCP.System performance can be enhanced by employing improved CSK.Our conclusions are verified by theoretical analysis and simulation results.