Direct Sequence and Time-Hopping Sequence Designs for Narrowband Interference Mitigation in Impulse Radio UWB Systems

Direct sequence and time-hopping sequence designs are proposed for impulse radio ultra-wide bandwidth systems to suppress the mutual interference between ultra-wide bandwidth wireless and coexisting narrowband services. Notch frequencies are created in the ultra-wide bandwidth signal spectrum at bands where narrowband services operate. The direct sequence and the time-hopping sequence designs have low computational complexities and can be easily implemented in practical systems. When combined with the cognitive radio technique, these designs can adapt to channel conditions according to the spectral occupancy information provided by cognitive radio. Numerical results are provided to show that these designs can significantly suppress the mutual interference between ultra-wide bandwidth and narrowband services. Therefore, the integrity of both ultra-wide bandwidth and narrowband systems can be highly enhanced.