Title :
Quasi-coherent delay-locked loops for fading channels
Author :
Latva-aho, Matti ; Vallström, Jari
Author_Institution :
Telecommun. Lab., Oulu Univ., Finland
Abstract :
The most widely used delay estimators in DS-CDMA receivers are based on the delay-locked loops (DLL). In a coherent RAKE receiver the complex channel coefficient estimate can be used to attain the phase coherency in DLL and the effect of data modulation can be removed via decision feedback. The resulting algorithms are called quasi-coherent delay-locked loops (QCDLL). The performance of four variations for QCDLLs based on lead-lag phase-locked loops has been analyzed by computer simulations. All the loops performed satisfactorily in a fading channel, but the quasi-coherent sample-correlate-choose-largest (QCSCCL) loop had 5-6 dB better performance than the other schemes
Keywords :
adaptive control; circuit feedback; correlation methods; delay circuits; fading; pseudonoise codes; radio receivers; signal sampling; spread spectrum communication; telecommunication control; DLL; adaptive loop gain control algorithms; coherent RAKE receiver; complex channel coefficient estimate; computer simulations; data modulation; decision feedback; fading channel; fading channels; lead-lag phase-locked loops; performance; phase coherency; quasicoherent delay-locked loops; quasicoherent sample-correlate-choose-largest loop; Delay estimation; Fading; Feedback; Multiaccess communication; Multipath channels; Performance analysis; Phase estimation; Phase locked loops; Phase modulation; RAKE receivers;
Conference_Titel :
Spread Spectrum Techniques and Applications Proceedings, 1996., IEEE 4th International Symposium on
Conference_Location :
Mainz
Print_ISBN :
0-7803-3567-8
DOI :
10.1109/ISSSTA.1996.563818
