This paper considers the problem of developing and utilizing side information in a frequency-hopped communication system using phase-shift keying (PSK) and operating in an environment with partial-band jamming. Two aspects of side information are studied. The first deals with estimating the unknown random carrier phase that varies from hop to hop. The second aspect is the detection of jamming signals. We use a serially concatenated convolutional code structure with differential M-ary PSK as the inner code. The iterative receiver uses an expanded trellis in the inner decoder to resolve the phase ambiguity and is augmented by a ratio-threshold test for detecting jammer energy. Performance is compared for different dwell interval lengths and both log-APP and max-log-APP decoding algorithms. This paper also considers the effect of different thresholds on the false alarm and detection probabilities of the ratio-threshold test.

In systems employing power amplifiers with non-linear characteristics, offset quaternary phase-shift keying (OQPSK) is preferred over conventional QPSK due to its reduced degree of instantaneous phase transitions. In addition, when pulse shaping filters are used on the transmitted signal, OQPSK results in lower peak-to-average power ratios than QPSK, and therefore allows for amplifiers to operate closer to saturation. Recently, it was shown for a multiple-bit differential detection of a particular preceding of OQPSK modulated data, the bound on bit error rate is 3 dB away from the corresponding bound on conventional QPSK. This paper refines that bound and extends the results to show that for a different, symbol-wise precoding, performance approaches that of multiple-symbol differential detection of conventional QPSK. In addition, results are presented for non-rectangular pulse-shaped OQPSK and a generalized likelihood ratio test detector. For that scenario, performance is within a fraction of a decibel of coherent performance for reasonable complexity.

We consider a direct sequence (DS-) code division multiple access (CDMA) system with orthogonally multiplexed pilot signals and minimum mean squared error (MMSE) data and channel estimation. Both flat and frequency-selective fading channels are considered. Large system analysis is used to optimize the pilot-to-data power ratio (PDR) and the code rate for a fixed bandwidth expansion. Specifically, the PDR is selected to minimize the probability of error subject to a constraint on transmitted power. When the MMSE filter estimates the channel of the desired user, but averages over the channels of the interferers (corresponding to an adaptive filter in moderate to fast fading), the optimal PDR is less than that for the matched filter (MF). That is, the MMSE filter benefits from allocating more power to the data. When the MMSE filter directly incorporates estimates of all users' channel coefficients, the optimal PDR is greater than that for the MF. System performance as a function of code rate is characterized through both probability of error and cutoff rate. The optimal code rate for the MMSE receiver is generally higher than that for the MF, and increases with load and E/sub b//N/sub 0/. In the presence of fading, and with channel estimation, the optimal code rate approaches zero for both MMSE and MF receivers, but the MMSE filter is more robust with respect to a suboptimal choice of code rate.

We study the forward link of a DS-CDMA system with transmitter diversity, assuming the channel is known at the receiver but not at the transmitter. Space-time coding is compared to orthogonal designs for a block fading channel, including frequency-selective fading. A minimum mean squared error (MMSE) decision-feedback detector (DFD) suppresses multiple-access interference and cancels self-interference from the multiple transmitter antennas. This receiver can be implemented adaptively in the absence of channel estimates. We consider both hard decision-feedback and iterative soft decision-feedback in combination with MAP decoding. Our results show that for the cases considered, the hard and soft DFDs perform close to the receiver with perfect cancellation, which offers significant gain with respect to the orthogonal designs.

We consider a direct sequence (DS-) CDMA system with orthogonally multiplexed pilot signals and minimum mean square error (MMSE) data and channel estimation. Large system analysis is used to optimize the pilot-to-data power ratio (PDR). Specifically, the PDR is selected to minimize the probability of error subject to a transmitted power constraint. Both flat and frequency-selective fading channels are considered. When the MMSE filter averages over the channels of the interferers, the optimal PDR is less than that for the matched filter. That is, the MMSE filter benefits from allocating more power to the data. For the case considered, when the MMSE filter directly incorporates channel estimates, the optimal PDR is greater than that for the matched filter.