Gezici, SinanCelebi, H.Arslan, H.Poor, H. V.2016-02-082016-02-082008-09http://hdl.handle.net/11693/26798Date of Conference: 10-12 Sept. 2008Conference name: 2008 IEEE International Conference on Ultra-WidebandIn this paper, theoretical limits on time delay estimation are studied for ultra-wideband (UWB) cognitive radio systems. For a generic UWB spectrum with dispersed bands, the Cramer-Rao lower bound (CRLB) is derived for unknown channel coefficients and carrier-frequency offsets (CFOs). Then, the effects of unknown channel coefficients and CFOs are investigated for linearly and non-linearly modulated training signals by obtaining specific CRLB expressions. It is shown that for linear modulations with a constant envelope, the effects of the unknown parameters can be mitigated. Finally, numerical results, which support the theoretical analysis, are presented. © 2008 IEEE.EnglishCarrier frequency offset (CFO)Cramer-rao lower bound (CRLB)Dispersed spectrum utilizationTime delay estimationUltra-wideband (UWB) cognitive radioCivil aviationCognitive systemsCommunication channels (information theory)Control theoryCramer-Rao boundsElectric network analysisFrequency allocationFrequency bandsFrequency estimationModulationRadioRadio systemsSensor networksTelecommunication systemsTime delayWireless telecommunication systemsConference Paper10.1109/ICUWB.2008.4653380