Continuous phase modulation

About: Continuous phase modulation is a research topic. Over the lifetime, 3199 publications have been published within this topic receiving 37245 citations. The topic is also known as: CPM.

On noncoherent sequence detection of continuous phase modulations

Abstract: Based on Laurent (1986) decomposition of a multilevel continuous phase modulation (CPM) as a sum of linearly modulated components, we derive new noncoherent sequence detection algorithms for M-ary CPM signals transmitted over additive white Gaussian noise (AWGN) channels. Noncoherent sequence detection based on the Viterbi algorithm (.) has been proposed for linearly modulated signals. These schemes are attractive because they closely approach the performance of coherent receivers with acceptable complexity. This paper extends previous results and proposes a general structure for noncoherent sequence detection of CPM signals. The robustness of noncoherent sequence detection schemes to phase noise and frequency offset is also demonstrated.

Method and apparatus for correlating a continuous phase modulated spread spectrum signal

Abstract: A technique for modulating and demodulating continuous phase modulation (CPM) spread spectrum signals and variations thereof. A transmitter encodes M data bits using a selected spread spectrum code, divides the spread spectrum code into a plurality of chip codes (such as even chips and odd chips), independently modulates the even and odd chips with orthogonal carrier signals using CPM or a related technique, and superposes the plurality of resultants for transmission. A receiver receives the superposed spread spectrum signal, divides the spread spectrum signal into duplicate signals, separately demodulates the duplicate signals into an odd chip signal and an even chip signal, simultaneously attempts to correlate the odd chip signal with a locally generated odd chip sequence and the even chip signal with a locally generated even chip sequence, and interleaves the correlation signals into a unified correlation signal. The unified correlation signal may be compared against other correlation signals to determine the content of the transmitted data.

Non-coherent demodulation for orthogonal space-time coded CPM

Abstract: In this paper non-coherent receivers for orthogonal space-time coded continuous phase modulated signals transmitted over additive white Gaussian noise and quasi-static fading channels are presented. The receivers are found to perform less than 1-dB away from the corresponding coherent detectors.

QM-CPM modems with higher order signaling

Abstract: A quadrature-multiplexed continuous phase modulation (QM-CPM) signal is made up of the real parts of two underlying CPM signals whose information content can be recovered from just their real parts. The real parts of two such signals are I/Q multiplexed and transmitted onto a single channel to approximately double the bits/Hz of the underlying CPM signals, while maintaining the same or similar minimum distance. A class of QM-CPFSK (QM-continuous phase frequency shift keyed) signals are presented that use binary signaling but more phase states, and M 2 -ary QM-CPFSK signals are derived from constant envelope M-ary CPFSK signals. M 2 -ary multi-amplitude CPFSK signaling schemes are constructed that maintain the same distance as known multi-amplitude CPFSK schemes, but more than double the bandwidth efficiency in bits/Hz. In addition to these CPFSK based embodiments, embodiments are provided that more generally use CPM, non-continuous phase modulated signals, and even trellis-based PAM based signals.

A soft output GMSK demodulator using a 4-filter MLSE for small BT product

Abstract: We consider GMSK for use in frequency division multiple access (FDMA) satellite communication systems where only limited system bandwidth is available. The demodulator employs maximum likelihood sequence estimation (MLSE) of the GMSK signal using a simplified Viterbi processor. For the case of GMSK having a time-bandwidth product of BT=1/4, a two matched filter approximation gives very good performance, while, for BT=1/6, a two filter approximation is very similar to a four filter approximation. For a convolutional code with rate 1/2 and constraint length 7, simulation shows that soft output Viterbi algorithm (SOVA) decoding using a four-filter demodulator for BT=1/6 and BT=1/8, results in a performance improvement of 2.1 dB and 2.3 dB, respectively, in signal-to-noise ratio (SNR), compared to hard decision Viterbi algorithm (HOVA) decoding, at a bit error probability (BEP) of 10/sup -5/. When compared to a BPSK system that employs a similar soft decision decoder, the BEP power penalty for these schemes is 2.3 dB and 4.1 dB respectively. The spectral efficiency, relative the 95% RF power containment bandwidth, is 1.88 bits per sec per Hz (bps/Hz) and 2.1 bps/Hz of bandwidth for BT=1/6 and 1/8 GMSK respectively, and only 0.35 bps/Hz for BPSK. As ratios, the spectral efficiency improvement factor is 5.37 and 6.0 respectively.