Interference Mitigation Using Improved Spectrum Shaping TH Codes to Address Coexistence Issue in UWB Systems
Keywords:Ultra Wide Band (UWB) System, Time Hopping (TH) Codes, Frequency Hopping (FH) Codes
The power spectrum of UWB systems can be controlled by proper selection of any of the three entities pulse,
modulation scheme and Time Hopping (TH) codes, or their combinations. This paper proposes algorithms to
improve the correlation properties of these TH codes without changing their spectrum shaping property, so that
system performance is not comprised. The earlier work of the authors provides algorithms to design TH codes
with good correlation properties for spectrum shaping to create Null at a selected frequency, of multiuser UWB
signals, to avoid interference to existing narrow band systems. These algorithms are presented in the form of
three methods (Method I, Method II and Method III) to show correlation improvement in synchronous system
first. The paper provides a novel and general mathematical model for improving correlation properties of
spectrum shaping code using basic code construction of known FH code family, which can be used for both
synchronous as well as asynchronous systems.
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