Showing papers on "Continuous phase modulation published in 2006"

Single-channel receiver limitations in Doppler radar measurements of periodic motion

Abstract: Periodic motion, such as that resulting from cardiopulmonary activity can be measured by direct-conversion microwave Doppler radar. In a direct-conversion receiver, motion is measured as phase modulation, and the baseline phase relationship between the received signal and local oscillator signal for a given position has a significant effect on the demodulation sensitivity, resulting in optimum and null case extreme target positions. Presented here is a mathematical analysis of this target-position sensitivity verified with measurements using a custom compact Doppler radar transceiver with separate quadrature outputs. The results indicate that increased error in respiration and heart rate measurements can be expected for null case positions due to significant changes in mathematical conditions as well as reduced sensitivity, and that these limitations can be accommodated using two receiver channels in quadrature.

Spectrally Precoded OFDM

Abstract: By bilinearly transforming the rectangularly pulsed multicarrier basis signals, new basis sets containing full-response continuous basis signals are developed for constructing spectrally efficient orthogonal frequency-division multiplexing (OFDM) signals with or without cyclic prefix (CP) or zero padding (ZP). Both multiple-product and linear-combination formats are presented for these basis sets. In the multiple-product format, the developed full-response basis signals are shown to be zero-valued at interval edges, and thus can be used to construct continuous-phase OFDM signals. It is analytically shown that the constructed continuous-phase OFDM signals exhibit relatively small power spectral sidelobes which fall off as f-4, and can thus provide much higher spectral efficiency than the traditional rectangularly pulsed OFDM signal. In the linear-combination format, the proposed basis signals are shown to be the linear combinations of rectangularly pulsed multicarrier basis signals, and thereby allow for the efficient realization of fast Fourier transform (FFT). Specifically, a spectrally precoded signaling structure is developed in conjunction with inverse FFT and guard insertion to construct continuous-phase OFDM signals with or without CP or ZP. The corresponding spectral decoders are also developed to enable zero-forcing (ZF) demodulation for spectrally precoded OFDM. With the zero-forcing demodulation, the spectrally precoded OFDM schemes are shown to outperform in average error-rate characteristics the conventional rectangularly pulsed and correlatively coded OFDM schemes on various delay-spread channels

Uplink modulation and receiver structures for asymmetric OFDMA systems

Abstract: The present invention centers upon uplink communication protocols for use primarily with orthogonal frequency division multiple access (OFDMA) communication systems. Aspects of the invention relate to narrow band frequency division multiplexed (NBFDM) modulation protocols primarily for uplink usage in asymmetric OFDMA communication systems. In particular, NBFDM uplinks that use quadrature multiplexed continuous phase modulation are detailed and noncoherent detection schemes are developed to process the uplink channel signals without the need to transmit uplink phase reference signals. Other aspects of the invention relate to burst mode uplink communications in OFDMA systems such as those involving opportunistic beamforming.

Serially concatenated continuous phase modulation with convolutional codes over rings

Abstract: In this paper, we investigate serially concatenated continuous phase modulation (SCCPM) with convolutional codes (CC) over rings. The transmitted signals are disturbed by additive white Gaussian noise. The properties for systems with both infinite and finite block lengths are investigated. For an infinite-length system, we check the convergence threshold using the extrinsic information transfer chart. For a finite-length system, we use union-bound techniques to estimate the error floors. In the union-bound analysis, we consider both the order and the position of nonzero permuted symbols. A simple method for determining a CPM error event through the sum of the input symbol sequence is shown. Thus, we can determine if the output symbol sequence of an error event in the ring CC can form an error event in CPM. Two properties concerning the interleaver gain (IG) are investigated. A recursive search algorithm for the maximal IG is shown. Compared with previous SCCPM with a binary CC, the proposed system shows an improvement concerning the convergence threshold or error floors

Optimization of a continuous phase-only sampling for high channel-count fiber Bragg gratings

Abstract: A novel continuous phase-only sampling function capable of producing up to 81-channel FBG with excellent channel uniformity and high in-band energy efficiency is presented and optimized by using the simulated annealing algorithm. In order to fabricate this kind of FBG with a conventional side-writing phase-mask technique, both the diffraction effects and fabrication tolerance of the phase-shifted phase mask have also been addressed. Compared with the numerical results, a 45-channel (spacing 100 GHz) and an 81-channel (spacing of 50 GHz) phase-only sampled linearly chirped FBG are successfully demonstrated.

Continuous-phase frequency-shift keying with external modulation

Abstract: A high-speed external modulation scheme for optical continuous-phase frequency-shift keying (CPFSK) is presented. In external frequency-shift keying (FSK) modulation using single-sideband modulation technology, an optical upper/lower sideband (USB/LSB) component with respect to a carrier frequency is selectively generated. However, the FSK-modulated signal has phase discontinuities at the timings of frequency shifts. To overcome the problem, we propose a synchronous control technique that enables continuous phase modulation. In the external CPFSK modulation, the USB/LSB is allowed to shift to the other state when their phases coincide with each other. It is shown that CPFSK with a zero-to-peak frequency deviation of 0.5times(bit rate) is achieved with this synchronous control. Occupant bandwidth is less than half that of the externally modulated incoherent FSK with phase discontinuities. At a modulation speed of 10 Gb/s, higher order sidelobes are highly suppressed by more than 20 dB at the 20-GHz offset, comparing to a conventional binary phase-shift keying (BPSK). By the use of a Mach-Zehnder interferometer with balanced photodetection, receiver sensitivity is 3-dB greater than that of an on-off keying, as well as a BPSK. In this paper, we report on the experimental demonstration of CPFSK modulation/demodulation. A six-channel wavelength-division-multiplexed, 10-Gb/s CPFSK modulation/demodulation was successfully demonstrated

Innovations-based MAP estimation with application to phase synchronization for serially concatenated CPM

Abstract: A novel adaptive soft-input soft-output (A-SISO) module is developed for maximum a posteriori (MAP) symbol detection with parameter uncertainty. In contrast to the existing A-SISO algorithms that use linear prediction, the parameter estimation in the proposed structure is operated in a more general least-squares sense. Based on this scheme, a family of fixed-interval A-SISO (FI-A-SISO) algorithms is utilized to implement blind iterative phase synchronization for serially concatenated continuous phase modulation (SCCPM). For SCCPM systems, the forward-only FI-A-SISO algorithms are shown to be much more robust than the forward-backward FI-A-SISO algorithms in acquiring and tracking a time-varying carrier phase. The reason has to do with rotational invariance of CPM signals. This result can be extended to any rotationally invariant convolutional coded system with an unknown carrier phase.

Robust time and phase synchronization for continuous phase modulation

Abstract: A novel joint timing and phase-recovery technique is proposed for continuous phase modulation (CPM) systems based on Kalman filtering and an approximate representation of CPM signals with nonorthogonal exponential expansions (nOEE). Compared with existing techniques, the proposed synchronizer requires a less complex front-end processor, and can achieve reliable acquisition performance with a shorter preamble. The asymptotic stability and convergence of the proposed synchronizer is analyzed, including the effect of statistical channel-modeling errors on the convergence characteristics. The selection of suboptimal nOEEs and the design of triple-initialized Kalman filters are also discussed. Both theoretical and simulation results show that the proposed synchronizer is robust in acquiring and tracking both the time shift and the phase offset on either time-invariant or time-variant channels

Spectrally Efficient CPM Waveforms for Narrowband Tactical Communications in Frequency Hopped Networks

Abstract: A family of spectrally efficient waveforms for serial concatenated continuous phase modulation in frequency hopping systems is presented, for the challenging case where there are multiple hops per interleaver duration. The proposed waveforms are designed for narrowband tactical communication systems and are shown to meet stringent spectral emission masks of -40 dBc at the band edges for terrestrial communications below 100 MHz whilst maintaining data rates up to 64 kbit/sec in a standard 25 kHz bandwidth. In addition, a design approach is outlined enabling near-constant envelope waveforms for a variety of user defined information rates. This ensures efficient use of energy by the transmitter power amplifier, and achieves good performance and spectral efficiency for both tactical data and low latency voice communications. Furthermore, simulation results based on channel measurements in the tactical VHF band allow for the evaluation of the overall system performance in typical multipath environments

Continuous Phase Modulated Halftones and Their Application to Halftone Data Embedding

Abstract: We propose a generalization of periodic clustered-dot halftones, wherein the phase of the halftones is modulated using a secondary signal. The process is accomplished using an analytic halftone threshold function and allows halftones to be generated with different phase variation in different regions of the printed page. We demonstrate that ensuring continuity of the phase assures that the resulting halftone images are free from visible artifacts despite the modulation in phase. We present, applications of the proposed method to halftone data embedding, wherein the changes in phase or in frequency encode the embedded information. For the frequency embedding, using continuous phase modulation, we also consider the limitations on signals that are embedded within our framework. For both applications, we demonstrate how the embedded signals may be recovered from the printed halftones either using the image as a self-reference which reveals the watermark when it is shifted and overlaid with itself or by employing a separate transparency mask.

Optimum and reduced complexity multiuser detectors for asynchronous CPM signaling

Abstract: Maximum likelihood detector algorithms are developed for the matrix of transmitted symbols in a multiuser system in which the received signal is the sum of K cochannel continuous phase modulated (CPM) signals and additive white Gaussian noise. We illustrate that the maximum likelihood matrix detector, which provides optimum detector performance, consists of K sets of front-end matched filters followed by a Viterbi algorithm. We also derive two reduced complexity receivers, demonstrating through simulation that they perform within 1-2 dB of the optimal while substantially reducing complexity. The paper demonstrates how performance can be traded off against complexity, giving particular attention to cochannel Gaussian minimum shift keyed (GMSK) signals

Method, system and apparatus for optical phase modulation based on frequency shift

Abstract: The present invention provides an optical phase modulation method using optical frequency shift devices. By accurately controlling the frequency shift, the phase delay experienced by the light signal through an optical medium (fibre, free space, vacuum, or other) can be controlled with high resolution. Hence, phase change can be achieved through frequency change. This technique can be applied to a wide range of applications whenever phase modulation is needed, such as in various phase-shifted keying techniques in optical communications, and in optical metrology. The disclosed phase modulation method can also be used as a phase encoding technique in quantum key distribution.

A Unified Approach to Optimum Frame Synchronization

Abstract: In this paper, we present a unified approach for optimum frame synchronization where the observed symbols are modeled as the output of a Markov chain corrupted by additive white Gaussian noise (AWGN). This model encompasses many different frame synchronization situations e.g., convolutionally coded transmissions and nonlinear modulations with memory, such as continuous-phase modulation. The proposed frame synchronizer is implemented with trellis path search used for Markov chain decoding and provides better performance than conventional synchronizers because it is able to exploit coding gain. The proposed synchronizer includes many previously proposed synchronizers either as special cases or as suboptimal approximations. The numerical results show the performance gain of the proposed frame synchronizer for convolutional codes with linear modulation, transmission over known intersymbol-interference channels, and nonlinear continuous-phase modulation signals. The proposed frame synchronizer is derived for the case of continuous transmission but may also be applied to certain packet transmission scenarios

An algebraic receiver for full response CPM demodulation

Abstract: This paper proposes a new algebraic demodulation method for full response CPM signals in AWGN channel The method is based in a new estimation/identification theory that has also already been used for channel identification and signal deconvolution The signals and noise are considered to be deterministic and we find an explicit formula for the recovery of the transmitted symbols Based on this formula, the symbols are recovered blindly, needing only the knowledge of the modulation index The method is not only simple and robust to noise, but also very fast, what enables its implementation on-line It can also be equally used for coherent or non-coherent demodulations The method is applied to the CPFSK and LRC families of signals showing good results

System and method for power line communication

Abstract: A communication system for a power line is described. A transmission system of the communication system divides the time axis into a number of time slots synchronized such that one time slot can start about a zero crossing of the power line signal. These time slots are referred to as channels and are numbered from 1 to n. A modulation method is described to is narrow band continuous phase FSK, where a number m of modulating frequencies are used, arranged such that an integral number of full cycles fit into each channel time slot for all m frequencies. The system transmits during only a subset of the available time slots (channels) concentrated near the zero crossing of the power line waveform where the noise is typically minimal.

Demand-assigned multiple access (DAMA) communication device and associated acquisition methods

Abstract: The communications terminal and acquisition method is for use with Continuous Phase Modulation (CPM) and Phase Shift Keying (PSK) modulation-type signals, each modulation-type signal having a respective preamble phasing sequence. The communications terminal may include a wireless communications device to receive a modulated signal having one of the CPM and PSK modulation types, and having a symbol rate. A controller may be included to cooperate with the wireless communications device to perform a transform process, such as a Fourier Transform (FT) process, on the received modulated signal to detect the modulation type and the symbol rate of the received modulated signal based upon the preamble phasing sequence. Carrier phase and frequency of the received modulated signal may be estimated based upon bin amplitudes. Also, symbol timing may be estimated based upon a phase difference between tones associated with the preamble phasing sequence.

System and method for power line communications

Abstract: A communication system for a power line is described. A transmission system of the communication system divides the time axis into a number of time slots synchronized such that one time slot can start about a zero crossing of the power line signal. These time slots are referred to as channels and are numbered from 1 to n. A modulation method is described to is narrow band continuous phase FSK, where a number m of modulating frequencies are used, arranged such that an integral number of full cycles fit into each channel time slot for all m frequencies. The system transmits during only a subset of the available time slots (channels) concentrated near the zero crossing of the power line waveform where the noise is typically minimal.

Boundless-range optical phase modulator for high-speed frequency-shift and heterodyne applications

Abstract: Optical phase modulators are used for many applications in optical communication systems and signal processing, but they are fundamentally limited in the amount of a monotonic phase change that can be induced due to practical physical limits on the drive-signal magnitude In this paper, the necessary drive conditions are derived to achieve a boundless monotonic phase change on the output while keeping the drive inputs within practical physical bounds, ie, comparable to an amplitude modulator A simulation of a three-section modulator with two distinct drive signals is provided whereby a continuous phase change on the output is achieved with only a maximum phase shift of /spl pi//2 created in any individual section The architecture has two outputs, therefore a design tradeoff can be made in choosing the power splitting ratio between the outputs The amplitudes are kept constant as the phase is modulated The other output is not frequency shifted and may provide a convenient heterodyne signal for subsequent coherent processing

A New PAM Decomposition for Continuous Phase Modulation

Abstract: The Laurent decomposition expresses any binary single-h continuous phase modulated signal as the finite summation of pulse amplitude modulated (PAM) waveforms, and the resulting signal space is so constructed that the CPM signal can usually be synthesized with a reasonable degree of accuracy by using only the "main" PAM component pulse. This derivation has been very useful for reduced complexity demodulation of binary CPM signals. Subsequent to Laurent's work, it was shown that commensurate expressions could be obtained for multilevel and multi-h CPM, but with an exponential increase in the total number of PAM component pulses in the signal representation. In this paper, we derive a generalization of Laurent's result which can be universally applied to all variants of CPM. Most notably, the component pulses are naturally ranked in order of decreasing signal energy, so that over each symbol interval there is a single "main pulse" that can be used in a good first-order PAM approximation of the CPM signal.

Minimum entropy approach for carrier frequency recovery

Abstract: This paper introduces a new carrier frequency recovery approach. It can be applied before modulation classification and/or demodulation of the M-ary PSK signals. It relies on the entropy of the instantaneous phase probability density function, and uses the fact that it reaches minimum when the receiver is fine-tuned to the unknown carrier frequency. This estimator is applicable to algorithms requiring high accuracy without any a priori knowledge concerning modulation scheme, signal contents (bit-stream), or its timing parameters. Simulation results have proved the robustness of the algorithm: for low carrier to noise ratios (CNR), corresponding variances are proportional and close to Cramer-Rao lower bounds (CRLB). For CNR greater than 20 dB, they are constant and limited by the resolution of the algorithm.

Photonic MSK transmitter models using linear and nonlinear phase shaping for noncoherent long-haul optical transmission

Abstract: We propose two novel transmitter configurations for generation of linear and non-linear phase modulated optical minimum shift keying (MSK) signals based on approaches of continuous phase frequency shift keying (CPFSK) and I-Q component structure of offset/staggered DQPSK formats. The precoder for I-Q optical MSK structure is derived. The direct detection of optical ligtwave is utilized with implementation of the well-known differential non-coherent balanced receivers. Simulated spectral characteristics and dispersion tolerance to 40 Gb/s transmission are presented and compared to those of ASK and DPSK counterparts.

CTH10-6: Diagonal Block Space-Time Code Design for Continuous-Phase Modulation

Abstract: The combination of space-time (ST) coding and continuous-phase modulation (CPM) is attractive for power-efficient transmission over fading channels. In this paper, we propose a diagonal block based ST-CPM (DBST-CPM) scheme, which in addition to high power efficiency facilitates detection without channel state information at the receiver. DBST-CPM can be regarded as a non-trivial extension of well-known differential ST modulation (DSTM) with diagonal signal matrices for linear modulation formats. We derive an upper bound on the frame- error rate of DBST-CPM and we present an efficient algorithm for optimization of the code parameters of DBST-CPM. Numerical and simulation results show that the upper bound accurately predicts the performance of DBST-CPM and that the proposed code optimization yields highly power-efficient designs.

Turbo Synchronization for Serially Concatenated CPM

Abstract: By approximating continuous phase modulated (CPM) signals with a small set of nonsymmetric nonorthogonal exponential functions, we have previously proposed a data-aided time and phase synchronizer that works well for all CPM schemes [1]. This paper extends this non-iterative data-aided synchronizer to its iterative decision-directed counterpart, for serially concatenated CPM systems. To prevent false locks in synchronization process, a preamble and pilot symbols are used in combination with the decision-directed technique. Simulation results show that the proposed turbo synchronizer is robust in acquiring and tracking both time-invariant and time-variant timing and phase errors at low signal-to-noise-ratios.

Multi-symbol noncoherent CPM detector

Abstract: Three receivers are presented for the general case of noncoherent detection of multi-h continuous phase modulation. All three receivers yield performance gains using multi-symbol observations. The first is an existing receiver which has previously been applied to PCM/FM and is now applied to the Advanced Range Telemetry Tier II waveform. The second and third receivers are presented for the first time in this paper. The existing noncoherent receiver is found to perform poorly (and with high complexity) for the Advanced Range Telemetry Tier II case. For single-symbol observations, the new receivers outperform conventional FM demodulation for both telemetry waveforms, and for multi-symbol observation lengths their performance approaches that of the optimal coherent receiver. The performance is evaluated using computer simulations. Receiver performance is also evaluated using a simple channel model with varying carrier phase. The traditional FM demodulator approach is found to outperform all three receivers as channel conditions worsen.

Space-time trellis code design with binary CPM

Abstract: Binary continuous phase modulation (CPM) is considered with space-time trellis codes (STTCs) for multiple-input multiple-output systems. Single-h CPM with rectangular, raised cosine and half cycle sinusoid is considered. The upper bound on the minimum product distance of this signalling scheme is determined over a quasi-static Rayleigh fading channel. Based on the rank and determinant criterion, best STTC/CPM combinations are identified for two transmit and an arbitrary number of receive antennas.

Polar transmitter for increasing modulation rate using multi-phase generator

Abstract: Provided is a polar transmitter which increases a modulation rate using a multi-phase generator and includes: a data processor which processes and separates incoming data to an amplitude component and a phase component; a multi-phase generator which generates a plurality of carriers having a plurality of phase components by processing a carrier having a certain frequency; a selection output part which selects and outputs a carrier having a phase substantially equal to the phase component; and a carrier output part which synthesizes the output carrier with the amplitude component and outputs a carrier. Accordingly, the modulation rate of the carrier can be increased and the bandwidth can be extended with the related art polar transmitter. Therefore, the polar transmitter is applicable to the wideband communications, the multi-mode, and the multi-band.

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.