Abstract
Original language  English 

Qualification  Licentiate Degree 
Awarding Institution 

Place of Publication  Oulu 
Publisher  
Publication status  Published  2005 
MoE publication type  G3 Licentiate thesis 
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Keywords
 Nonideal frequency synthesiser
 multicarrier modulation
 performance analysis
 timing offset
 phase memory
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Carrier frequency offset estimation in a frequencyhopping ultrawideband OFDM system : Licenciate thesis. / Anttonen, Antti.
Oulu : University of Oulu, 2005.Research output: Thesis › Licenciate › Theses
TY  THES
T1  Carrier frequency offset estimation in a frequencyhopping ultrawideband OFDM system
T2  Licenciate thesis
AU  Anttonen, Antti
N1  ELE University of Oulu, Department of Electrical and Information Engineering
PY  2005
Y1  2005
N2  In this thesis the performance of selected carrier frequency offset (CFO) estimators is studied in an ultrawideband (UWB) slow frequencyhopping orthogonal frequency division multiplexing (FHOFDM) system. A challenge in a very high data rate FHOFDM system is to minimize self interference such as intercarrier interference (ICI) and constellation rotation due to the CFO under several nonidealities. Various transmission techniques are first represented emphasising UWB transmission, orthogonal frequency division multiplexing (OFDM), frequencyhopping spread spectrum (FHSS) and the combination of these schemes. The synchronization requirements in wireless communications are considered next, followed by the review of the existing CFO estimation methods. After presenting the characteristics of the target system model the simulation results are shown with the appropriate analysis. First, the basic algorithms from each defined estimation category are compared in additive white Gaussian noise (AWGN) channel. The effects of nonidealities in despreading the frequencyhopped signal are considered next in a frequencyselective fading channel. The nonidealities may introduce a residual frequencyhopping timing offset (FHO) and phase offset (PHO) due to the nonideal hoptiming estimator, frequencyhopping synthesiser and frequencyselective channel. The main class of the studied CFO estimators is based on the autocorrelation of the received samples. The algorithms have two parameters to adjust for mitigating the noise. These include an averaging length and a distance between correlative samples. The simulation results indicate the kind of hop timing estimator, preamble structure, frequencyhopping synthesiser and signaltonoise ratio (SNR) operation point that are required before the CFO estimation can be performed with the given estimators. Simulations show that Lank’s CFO estimator is suitable for the target scenario and requirements when using relatively high SNR. For the lower SNR operation points Fitz’s, Luise’s or Mengali’s algorithms give better performance at the cost of increased complexity or reduced estimation range. Furthermore, the CFO estimators are quite robust to the FHO less than half the hopping duration, which causes a slight increase in standard deviation. It is shown that this degradation can be compensated using the CFO algorithm itself and utilizing the available preamble. The estimators are, however, sensitive to the PHO caused by the possible lack of phase memory in the frequencyhopping synthesizer or frequencyselective channel, resulting in a significant bias to the CFO estimate.
AB  In this thesis the performance of selected carrier frequency offset (CFO) estimators is studied in an ultrawideband (UWB) slow frequencyhopping orthogonal frequency division multiplexing (FHOFDM) system. A challenge in a very high data rate FHOFDM system is to minimize self interference such as intercarrier interference (ICI) and constellation rotation due to the CFO under several nonidealities. Various transmission techniques are first represented emphasising UWB transmission, orthogonal frequency division multiplexing (OFDM), frequencyhopping spread spectrum (FHSS) and the combination of these schemes. The synchronization requirements in wireless communications are considered next, followed by the review of the existing CFO estimation methods. After presenting the characteristics of the target system model the simulation results are shown with the appropriate analysis. First, the basic algorithms from each defined estimation category are compared in additive white Gaussian noise (AWGN) channel. The effects of nonidealities in despreading the frequencyhopped signal are considered next in a frequencyselective fading channel. The nonidealities may introduce a residual frequencyhopping timing offset (FHO) and phase offset (PHO) due to the nonideal hoptiming estimator, frequencyhopping synthesiser and frequencyselective channel. The main class of the studied CFO estimators is based on the autocorrelation of the received samples. The algorithms have two parameters to adjust for mitigating the noise. These include an averaging length and a distance between correlative samples. The simulation results indicate the kind of hop timing estimator, preamble structure, frequencyhopping synthesiser and signaltonoise ratio (SNR) operation point that are required before the CFO estimation can be performed with the given estimators. Simulations show that Lank’s CFO estimator is suitable for the target scenario and requirements when using relatively high SNR. For the lower SNR operation points Fitz’s, Luise’s or Mengali’s algorithms give better performance at the cost of increased complexity or reduced estimation range. Furthermore, the CFO estimators are quite robust to the FHO less than half the hopping duration, which causes a slight increase in standard deviation. It is shown that this degradation can be compensated using the CFO algorithm itself and utilizing the available preamble. The estimators are, however, sensitive to the PHO caused by the possible lack of phase memory in the frequencyhopping synthesizer or frequencyselective channel, resulting in a significant bias to the CFO estimate.
KW  Nonideal frequency synthesiser
KW  multicarrier modulation
KW  performance analysis
KW  timing offset
KW  phase memory
M3  Licenciate
PB  University of Oulu
CY  Oulu
ER 