Showing papers on "Continuous phase modulation published in 1983"

QPSK, Staggered QPSK, and MSK--A Comparative Evaluation

Abstract: Bandwidth- and power-efficient quadrature carrier modulation techniques are identified, evaluated, and compared. The modulation techniques include quadrature phase shift keying (QPSK), staggered QPSK (SQPSK), and minimum (frequency) shift keying (MSK). High quality QPSK, SQPSK, and MSK transmitters and receivers were used in the evaluation, along with a computer simulation program which modeled the hardware. Both linear and nonlinear channels were included in the comparative investigation. The agreement between simulated and measured results is shown to be excellent. In the comparison of modulation techniques, the effects of channel filtering (band limiting), nonlinearities, detection techniques, and phase equalization are addressed. The application-oriented results are intended to be an aid in selecting modulation and detection implementations, and in predicting the performance of linear and nonlinear communication systems. For systems with imperfections, data are presented for determination of passive detection filters which can outperform "matched" integrate and dump (I&D) filters.

On continuous phase modulation in cellular digital mobile radio systems

Abstract: This paper considers the application of constant-amplitude, partial-response, continuous-phase modulation with simple near-optimum receivers to cellular digital mobile radio systems. These smoothed modulation schemes have low spectral sidelobes and narrow main lobes. A combiner for time-division retransmission systems with space diversity is given for continuous-phase modulation. Cochannel interference and adjacent-channel interference are calculated for continuous-phase modulation in cellular systems with frequency reuse. The efficiency of 3RC and 4RC modulations with space diversity is evaluated for conventional cellular systems.

Passive Arm Filters in I and Q Receivers for MSK-Type Continuous Phase Modulations

Abstract: The use of Butterworth and Chebyshev low-pass filters in suboptimum in-phase ( I ) and quadrature phase ( Q ) receivers is considered for several bandwidth efficient modulations. These modulations are: minimum shift keying (MSK), tamed frequency modulation with rectangular pulse shaping (TFMREC), and MSK with duobinary encoding of the source bits (DMSK). The sensitivity of the modulations with their I and Q receivers to a noisy phase reference and to timing errors is also investigated. It was found that standard, passive low-pass filter receive filters performed quite well when compared to other nonstandard filters. The use of standard filters should thus be considered in any system design. The modulations, with their simple receivers, can be ranked in order of increasing sensitivity to timing errors as follows: MSK, DMSK, TFMREC. This ranking is the reverse to the one obtained when it is done in order of best bandwidth efficiency.

Asymptotic receiver operating characteristics for envelope detection of a phase modulated sinusoid (Corresp.)

Abstract: The effect of a Gaussian-distributed phase modulation on the envelope detection of a sinusoid is investigated. Asymptotic receiver operating characteristics are obtained for Gaussian-distributed phase modulation processes that satisfy a central limit theorem due to Sun. Numerical results are presented for a first-order Butterworth phase modulation spectrum.

A method of coding for narrow-band CPFSK

Abstract: Although the continuous phase FSK (CPFSK) scheme has been used for narrow-band data transmission, its error rate performance is rather poor. This paper describes a coding method for improving the error rate performance of the narrow-band CPFSK scheme with modulation indices of 1/3 and 1/4. the proposed method examines the structure of the signal space for the given modulation scheme and avoids using the signal metric of small value in the coding. Hence, the objective of this method is not error correction, but maximization of the minimum signal metric. the application of this method in narrow-band CPFSK system yields better performance than the MSK scheme in terms of both bandwidth and error rate.