Abstract
Original language  English 

Qualification  Doctor Degree 
Awarding Institution 

Award date  19 Nov 2026 
Place of Publication  Espoo 
Publisher  
Print ISBNs  9513847918 
Publication status  Published  1995 
MoE publication type  G4 Doctoral dissertation (monograph) 
Fingerprint
Keywords
 electronics
 digital communications
 radio communications
 fading
 receivers
 aircraft communications
 satellite communications
 land mobile communications
 transmitters
 design
 models
 diversity reception
Cite this
}
Diversity receivers in a fast fading multipath channel : Dissertation. / Mämmelä, Aarne.
Espoo : VTT Technical Research Centre of Finland, 1995. 128 p.Research output: Thesis › Dissertation › Monograph
TY  THES
T1  Diversity receivers in a fast fading multipath channel
T2  Dissertation
AU  Mämmelä, Aarne
N1  Project code: E5SU00124
PY  1995
Y1  1995
N2  Some radio channels are fast fading in the sense that they are randomly timevariant and the Doppler spread is in the order of or larger than the symbol rate of the digital signal. Such channels can be found in landmobile, aircraft, and satellite communications, especially when the symbol rate is small, the velocity of the mobile station is large, and the carrier frequency is large. With small symbol rates, a Doppler barrier exists, below which the complexity of the optimal receiver is increased. The Doppler barrier is the timefrequency dual of the ISI barrier with large symbol rates. In the thesis, the history of digital communications in fading multipath channels is first summarized. The ML sequence detector, consisting of a correlator and an estimator, is derived in a WSSUS fast Rayleigh fading channel. In the system model, each symbol is divided into several short segments and ideal symbol synchronization is assumed. Finally, suboptimal receivers based on linear prediction and smoothing are analyzed in a fast fading channel. The authors main contribution is the extension of Kams ideas to the segmented waveform concept, so that the channel may be considered timeinvariant over a segment duration. The system model is very useful, since it allows for a very tidy theoretical development concerning receiver structures; this bridges the gap between the classical oneshot receivers and the modern sequence estimation approach. Of almost equal importance is that the results of the thesis also bridge the gap between receivers for slow and for fast fading channel models. In a fast fading frequencynonselective channel, an unexpected diversity effect was observed. The performance of the receiver is improved since the fading in different parts of a symbol is partially uncorrelated. In addition, the RAKE principle is extended to a fast fading channel, and this gives an additional improvement in performance. To simplify the receiver, data modulation must somehow be avoided or removed before the estimator, and either a predictor or a smoother can be used in the estimator. Performance analysis includes MMSE and bit error probability analysis. Many numerical results are given, and their validity is demonstrated with Monte Carlo simulations. The results can be applied in both conventional narrowband and spreadspectrum (CDMA) systems. An extensive bibliography consisting of some 250 references is included in the thesis.
AB  Some radio channels are fast fading in the sense that they are randomly timevariant and the Doppler spread is in the order of or larger than the symbol rate of the digital signal. Such channels can be found in landmobile, aircraft, and satellite communications, especially when the symbol rate is small, the velocity of the mobile station is large, and the carrier frequency is large. With small symbol rates, a Doppler barrier exists, below which the complexity of the optimal receiver is increased. The Doppler barrier is the timefrequency dual of the ISI barrier with large symbol rates. In the thesis, the history of digital communications in fading multipath channels is first summarized. The ML sequence detector, consisting of a correlator and an estimator, is derived in a WSSUS fast Rayleigh fading channel. In the system model, each symbol is divided into several short segments and ideal symbol synchronization is assumed. Finally, suboptimal receivers based on linear prediction and smoothing are analyzed in a fast fading channel. The authors main contribution is the extension of Kams ideas to the segmented waveform concept, so that the channel may be considered timeinvariant over a segment duration. The system model is very useful, since it allows for a very tidy theoretical development concerning receiver structures; this bridges the gap between the classical oneshot receivers and the modern sequence estimation approach. Of almost equal importance is that the results of the thesis also bridge the gap between receivers for slow and for fast fading channel models. In a fast fading frequencynonselective channel, an unexpected diversity effect was observed. The performance of the receiver is improved since the fading in different parts of a symbol is partially uncorrelated. In addition, the RAKE principle is extended to a fast fading channel, and this gives an additional improvement in performance. To simplify the receiver, data modulation must somehow be avoided or removed before the estimator, and either a predictor or a smoother can be used in the estimator. Performance analysis includes MMSE and bit error probability analysis. Many numerical results are given, and their validity is demonstrated with Monte Carlo simulations. The results can be applied in both conventional narrowband and spreadspectrum (CDMA) systems. An extensive bibliography consisting of some 250 references is included in the thesis.
KW  electronics
KW  digital communications
KW  radio communications
KW  fading
KW  receivers
KW  aircraft communications
KW  satellite communications
KW  land mobile communications
KW  transmitters
KW  design
KW  models
KW  diversity reception
M3  Dissertation
SN  9513847918
T3  VTT Publications
PB  VTT Technical Research Centre of Finland
CY  Espoo
ER 