Volker Hespelt

A new pattern jitter free frequency error detector

One method to enable fast acquisition of a phase-locked loop (PLL) in spite of large frequency offsets and small PLL bandwidths is to use an additional AFC (automatic frequency control) loop. A suitable frequency error detector (FED) for large frequency offsets is the well-known balanced quadricorrelator. This FED is shown to produce great pattern jitter if it is to work with digital modulated MQAM and MPSK signals (M>2) and random data. The authors describe how this pattern jitter for MQAM and MPSK signals can be overcome completely. Another understanding of the balance quadricorrelator is also given. >

On the detection of bandlimited direct-sequence spread-spectrum signals transmitted via fading multipath channels

Recent investigations suggest bandlimited direct-sequence spread-spectrum transmission for use in CDMA mobile radio systems. In this paper, transmission systems with signal bandwidths not exceeding the chip rate are considered. First, the optimum noncoherent single-user receiver and various suboptimum approximations thereof are derived. These receivers utilize the fact that the received signals can be sampled at chip rate. This results in receiver concepts, which are well suited for fully digital implementations. Then, it is shown that the main result on the structure of the optimum single-user receiver is directly applicable to optimum noncoherent multiuser joint detection and interference cancellation. In this paper, noncoherent detection is considered. By this, we mean that only the channel statistics and not the channel itself is known to the receiver. It is shown that due to this less restrictive assumption, more powerful channel coding and interleaving schemes can be employed. >