Coherent DLL code tracking and BER effect on QPSK demodulation in wideband DS-CDMA reverse link

In this paper, a novel coherent code tracking scheme called as pilot-aided delay locked loop (PADLL) for QPSK demodulation in wideband DS-CDMA reverse link is proposed. When noncoherent DLL is applied, it suffers from the timing zitter degradation due to squaring loss. The timing zitter formula for PADLL in AWGN is derived and compared with the noncoherent DLL tracking scheme. The analysis shows that the proposed PADLL scheme with the accumulation period of 4 symbols improves the performance of QPSK demodulation by 0.6 dB over the noncoherent code tracking.