Interference Mitigation Using Improved Spectrum Shaping TH Codes to Address Coexistence Issue in UWB Systems
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 authorsprovidesalgorithms 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 paperprovides a novel and general mathematical model for improving correlation properties of spectrum shapingcode 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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