scispace - formally typeset
Search or ask a question

Showing papers on "Continuous phase modulation published in 2013"


Journal ArticleDOI
TL;DR: A complete synchronization algorithm for continuous phase modulation (CPM) signals in burst-mode transmission over additive white Gaussian noise (AWGN) channels is proposed through a data-aided maximum likelihood algorithm, which jointly estimates symbol timing, carrier phase, and frequency offsets based on an optimized synchronization preamble.
Abstract: In this paper, we propose a complete synchronization algorithm for continuous phase modulation (CPM) signals in burst-mode transmission over additive white Gaussian noise (AWGN) channels. The timing and carrier recovery are performed through a data-aided (DA) maximum likelihood algorithm, which jointly estimates symbol timing, carrier phase, and frequency offsets based on an optimized synchronization preamble. Our algorithm estimates the frequency offset via a one-dimensional grid search, after which symbol timing and carrier phase are computed via simple closed-form expressions. The mean-square error (MSE) of the algorithm's estimates reveals that it performs very close to the theoretical Cramer-Rao bound (CRB) for various CPMs at signal-to-noise ratios (SNRs) as low as 0 dB. Furthermore, we present a frame synchronization algorithm that detects the arrival of bursts and estimates the start-of-signal. We simulate the performance of the frame synchronization algorithm along with the timing and carrier recovery algorithm. The bit error rate results demonstrate near ideal synchronization performance for low SNRs and short preambles.

57 citations


Proceedings ArticleDOI
01 Dec 2013
TL;DR: The BER performance under BPSK modulation is better compared to OOK, RZ-OOK, PAM, 2-P PM, 4-PPM, DPSK, and QPSKModulation techniques, and for FSO communication systems, although the power efficiency is inferior to PPM.
Abstract: In this paper, we are interested in more efficient modulation techniques that achieve a good Bit Error Rate (BER) performance, bandwidth and power efficiencies for Free Space Optics (FSO) Communication Systems. The theoretical expressions of the BER versus the Signal-to-Noise Ratio (SNR), the bandwidth efficiency, and the normalized power requirements for NRZ-OOK, RZ-OOK, PPM, PAM, DPSK, BPSK, and QPSK modulation schemes for FSO communication systems are introduced, and a comparison between these modulation techniques is presented. The comparative study of the PPM and PAM schemes is also discussed and showed that for similar SNR, PPM offered improved BER performance. In addition, the BER performance under BPSK modulation is better compared to OOK, RZ-OOK, PAM, 2-PPM, 4-PPM, DPSK, and QPSK modulation techniques. And for FSO communication systems, although the power efficiency is inferior to PPM, OOK is more commonly used due to its efficient bandwidth usage, but PAM scheme is the bandwidth efficient modulation scheme in this research for more than two bits of information sent, while the PPM scheme is the power efficient modulation scheme for more than two bits of information sent.

51 citations


Journal ArticleDOI
TL;DR: In this paper, three linewidth-tolerant, low-complexity, two-stage carrier phase estimation algorithms are introduced for dual-polarization 16-ary quadrature amplitude modulation (DP 16-QAM) with coherent detection.
Abstract: Three novel linewidth-tolerant, low-complexity, two-stage feed-forward carrier phase estimation algorithms are introduced for dual-polarization 16-ary quadrature amplitude modulation (DP 16-QAM) with coherent detection. The first stage employs either the quadrature phase-shift keying (QPSK) partitioning algorithm, simplified QPSK partitioning algorithm, or blind phase search (BPS) algorithm. The second stage employs a novel modified QPSK partitioning algorithm. Based on experimental data, all three algorithms achieve comparable performance for DP 16-QAM back to back and transmission systems. The linewidth tolerance for the three algorithms is numerically studied. A linewidth symbol duration product of 1.3×10-4 is demonstrated for a 1 dB optical signal-to-noise-ratio penalty at a bit error ratio 10-3 of for all the proposed algorithms, which is comparable to the single-stage BPS algorithm with a large number of test phases. Reductions in the hardware complexity by factors of about 1.7-5.3 are achieved in comparison to the single-stage BPS algorithm.

47 citations


Journal ArticleDOI
TL;DR: This method allows direct recovery of continuous phase information encoded in digital holography without cumbersome physical or digital compensation procedure and provides a new way to eliminate the tilt and quadratic phase aberration inherent in digital HoloLens.

37 citations


Journal ArticleDOI
TL;DR: The performance of a differential carrier phase recovery algorithm is investigated for the quadrature phase shift keying (QPSK) modulation format with an integrated tunable laser.
Abstract: The performance of a differential carrier phase recovery algorithm is investigated for the quadrature phase shift keying (QPSK) modulation format with an integrated tunable laser. The phase noise of the widely-tunable laser measured using a digital coherent receiver is shown to exhibit significant drift compared to a standard distributed feedback (DFB) laser due to enhanced low frequency noise component. The simulated performance of the differential algorithm is compared to the Viterbi-Viterbi phase estimation at different baud rates using the measured phase noise for the integrated tunable laser.

33 citations


Journal ArticleDOI
TL;DR: This paper studies the Cramer-Rao bound (CRB) for continuous phase modulation (CPM) signals where frequency offset, carrier phase, and symbol timing are jointly estimated when transmitted over an additive white Gaussian noise (AWGN) channel and proposes the optimum training sequence for which the CRB is minimized.
Abstract: In this paper, we study the Cramer-Rao bound (CRB) for continuous phase modulation (CPM) signals where frequency offset, carrier phase, and symbol timing are jointly estimated when transmitted over an additive white Gaussian noise (AWGN) channel. We consider a data-aided (DA) estimation scenario in which the estimator takes advantage of a known training sequence at the start of each burst. Thus, we first derive the joint CRBs as functions of a known training sequence and CPM parameters. By analyzing the CRB expressions, we propose the optimum training sequence for which the CRB is minimized. We show that the same training sequence is optimum for all three estimation parameters. Additionally, we compare the performance of the optimum training sequence with a random one by providing a closed-form expression for the unconditional CRB (UCRB) for symbol timing estimation of CPM signals. Comparing the UCRB and the CRB for the optimum training sequence reveals that a DA estimator with the optimum training sequence leads to significant gains in terms of the mean-square error of the estimation parameter when the underlying CPM scheme is non-binary and/or partial response.

26 citations


Journal ArticleDOI
TL;DR: In this paper, a trellis-based demodulation scheme is proposed to deal with the memory of phase noise in high-order modulations with 4-ary quadrature amplitude modulation (4QAM) and 16-QAM.
Abstract: In optical transmission systems based on high-order modulations, the impact on system performance of Wiener phase noise affecting the received carrier phase can be relevant. To make less severe phase noise effects, solutions based on the use of known pilot symbols, that aid carrier phase recovery, have been recently introduced. This letter proposes a pilot-aided demodulation scheme where the memory of phase noise is dealt with by a trellis-based demodulation algorithm. The benefits in terms of achievable information rate and bit error rate compared to adversary schemes are demonstrated by computer simulations for strong phase noise with 4-ary quadrature amplitude modulation (4-QAM) and 16-QAM.

23 citations


Proceedings ArticleDOI
09 Sep 2013
TL;DR: In this article, a method is developed to design OFDM-based radar emissions with low range sidelobes in the presence of transmitter-induced distortion, which may potentially provide a feasible alternative waveform design scheme.
Abstract: The inherent amplitude modulation of orthogonal frequency division multiplexing (OFDM) has limited its use in radar due to transmitter-induced distortion. Specifically, there is a necessary trade-off between reduced SNR caused by power back-off to accommodate these AM effects and the waveform distortion that occurs when driving the amplifier closer to saturation. Here a method is developed to design OFDM-based radar emissions with low range sidelobes in the presence of transmitter-induced distortion. This work builds upon previous results for hardware-in-the-loop optimization of continuous phase modulation (CPM) waveforms to demonstrate how saturated OFDM emissions may potentially provide a feasible alternative waveform design scheme.

21 citations


Posted Content
TL;DR: Techniques described include quadratures phase shift keying (QPSK) and quadrature amplitude modulation (QAM) and how these techniques can be used to increase the capacity and speed of a wireless network.
Abstract: In this paper, introduced below are the concepts of digital modulation used in many communication systems today. Techniques described include quadrature phase shift keying (QPSK) and quadrature amplitude modulation (QAM) and how these techniques can be used to increase the capacity and speed of a wireless network. These modulation techniques are the basis of communications for systems like cable modems, DSL modems, CDMA, 3G, Wi-Fi* (IEEE 802.11) and WiMAX* (IEEE 802.16).

21 citations


Journal ArticleDOI
TL;DR: The corporation of pseudo-range capability and carrier phase in single-frequency GPS receivers will be discussed which makes a substitute for the pure pseudo- range observations and provides a high level of positioning accuracy to achieve this aim.
Abstract: Today Global Positioning System (GPS) is the most important system of positioning in the world and is used in different industries. Basic positioning methods in GPS receivers are based on pseudo-range and carrier phase measurements types whilst each of which has its own advantages and disadvantages. Pseudo-range method is not very much accurate. Carrier phase has a substantial accuracy, but its main problem is that it is an indirect measurement which only computes the displacement. Carrier phase measurement can include some whole cycles plus a fraction of carrier phase. The number of whole cycles may change through time however this change is unknown for us. Code measurements (based on pseudo-range) and carrier phase are corrupted with the same error sources, but with main differences. Basically, code tracking with low accuracy makes unambiguous pseudo-ranges. Carrier phase measurements are highly accurate, but get limited with integer ambiguity. Integer is fixed until the time that carrier tracking loop is saved. Every kind of gap in tracking, no matter how short it is, changes the amount of integer which is the biggest problem in carrier phase utilization. In this paper, the corporation of pseudo-range capability and carrier phase in single-frequency GPS receivers will be discussed which makes a substitute for the pure pseudo-range observations and provides a high level of positioning accuracy. To achieve this aim, Kalman filter will be used.

19 citations


Proceedings ArticleDOI
09 Jun 2013
TL;DR: Simulation under the same symbol error rate and channel state shows the JPAPM can improve the PA energy efficiency significantly compared with the traditional quadrature amplitude modulation.
Abstract: A Joint Polarization-Amplitude-Phase Modulation (JPAPM) scheme in wireless communication is proposed to improve the Power Amplifier (PA) energy efficiency. The proposed scheme introduces the signal's Polarization State (PS), amplitude and phase as the information-bearing parameters. Thus, the data rate can be further enhanced on the basis of the traditional amplitude-phase modulation. Also, since the transmitted signal's PS completely manipulated by orthogonally dual-polarized antennas is unaffected by the PA, JPAPM can let PA work in its nonlinear region to acquire high PA conversion efficiency. Furthermore, to mitigate the polarization-based impairment to JPAPM caused by the wireless channel's polarization dependent loss effect, the optimal pre-compensation algorithm is also presented. Simulation under the same symbol error rate and channel state shows the JPAPM can improve the PA energy efficiency significantly compared with the traditional quadrature amplitude modulation.

Journal ArticleDOI
TL;DR: The results show that the use of chaotic interleaving with CPM-OFDM andCPM-SC-FDE systems provides a good trade-off between system performance and bandwidth efficiency.
Abstract: In this paper, we present a chaotic interleaving scheme for both the Continuous Phase Modulation (CPM) based Orthogonal Frequency Division Multiplexing (CPM-OFDM) and CPM-based Single-Carrier Frequency-Domain Equalization (CPM-SC-FDE) systems. Chaotic interleaving is used to generate permuted versions from the sample sequences to be transmitted with low correlation among their samples, and hence a better Bit Error Rate (BER) performance can be achieved. The proposed CPM-OFDM and CPM-SC-FDE systems with chaotic interleaving combine the advantages of the frequency diversity and the high power efficiency of the CPM-based systems and the performance improvements due to chaotic interleaving. The BER performance of the both systems with and without chaotic interleaving is evaluated by computer simulations. Also, a comparison between chaotic interleaving and block interleaving is performed. Simulation results show that, the proposed chaotic interleaving scheme can greatly improve the performance of the CPM-OFDM system and the CPM-SC-FDE system. Furthermore, the results show that the chaotic interleaving scheme outperforms the traditional block interleaving scheme in both systems. The results also show that the use of chaotic interleaving with CPM-OFDM and CPM-SC-FDE systems provides a good trade-off between system performance and bandwidth efficiency.

Proceedings ArticleDOI
Han Sun, R. Egorov1, B. Basch1, John D. McNicol, Kuang-Tsan Wu 
28 Oct 2013
TL;DR: In this article, two modulation formats at spectral efficiency of 5 bits/dual-pol symbol are compared and Linewidth tolerances and feed-forward carrier recovery methods are discussed.
Abstract: Two modulation formats at spectral efficiency of 5 bits/dual-pol symbol are compared. Linewidth tolerances and feed-forward carrier recovery methods are discussed. Performances over uncompensated SMF and LEAF fibers are shown. The 4-D optimized format is found to be modestly better than a hybrid combination better th of PM-QPSK and PM-8QAM.

Journal ArticleDOI
TL;DR: Simulation results show that this algorithm with an appropriate memory length has better performance at low signal-to-noise ratio (SNR) than other estimators applicable to partial-response CPM in the literature, and that the performance losses of this algorithm caused by residual carrier frequency offset (CFO) and timing offset are acceptable in practice.
Abstract: Based on Laurent's representation of continuous-phase modulated (CPM) signals, a channel shaping prefiltering method is exploited to transform the overall channel impulse response (CIR) into one that approximates a two-path desired impulse response (DIR). By utilizing this property of the overall CIR, a differential algorithm for the estimation of the modulation index of partial-response CPM is derived as an approximation to a quasi-maximum likelihood estimator. In this algorithm, the tradeoff between the robustness to time-varying phase and performance can be controlled by a memory length parameter. Also, in this algorithm, an error compensation technique is proposed to reduce the estimation error resulting from the high-order components of Laurent's decomposition. Simulation results show that this algorithm with an appropriate memory length has better performance at low signal-to-noise ratio (SNR) than other estimators applicable to partial-response CPM in the literature, and that the performance losses of this algorithm caused by residual carrier frequency offset (CFO) and timing offset are acceptable in practice. Owing to its high convergence rate, this algorithm is appropriate for short-packet applications.

Journal ArticleDOI
TL;DR: A novel system to stabilize the phase of the optical carrier signals for wireless communications is introduced, and error-free transmission is successfully achieved up to a bit rate of 8.5 Gbit/s at 100 GHz.
Abstract: In this paper, we present a photonic approach for generating highly stable coherent sub-terahertz (THz) signals for wireless communications. As proof-of-concept we transmit data at 100 GHz carrier frequency using on-off keying modulation and heterodyne detection. The sub-THz carrier signals are generated by photo-mixing two optical carrier signals at different frequencies, extracted from an optical frequency comb. We introduce a novel system to stabilize the phase of the optical carrier signals. Error-free transmission is successfully achieved up to a bit rate of 8.5 Gbit/s at 100 GHz.

Proceedings ArticleDOI
28 Oct 2013
TL;DR: In this paper, a three-stage digital feed-forward carrier recovery algorithm based on the transformation of 64-QAM constellation into QPSK is proposed, which can tolerate a linewidth-times-symbol-rate product of 4.5·10-5.
Abstract: A novel three-stage digital feed-forward carrier recovery algorithm based on the transformation of 64-QAM constellation into QPSK is proposed. For 1 dB penalty at BER=10-2, it can tolerate a linewidth-times-symbol-rate product of 4.5·10-5, making it possible to operate 32-Gbaud optical 64-QAM systems with current commercial tunable lasers.

Patent
23 Dec 2013
TL;DR: In this paper, a modulation method and an apparatus with consideration of adaptive HARQ in a wireless communication system are provided, where the method of a transmission end supporting a hybrid modulation technique in which different types of modulation schemes are mixed, information of a channel state with a reception end is collected.
Abstract: A modulation method and an apparatus with consideration of adaptive Hybrid Automatic Repeat reQuest (HARQ) in a wireless communication system are provided. The method of a transmission end supporting a hybrid modulation technique in which different types of modulation schemes are mixed, information of a channel state with a reception end is collected. A modulation order of a first type of a modulation scheme and a modulation order of a second type of a modulation scheme are determined. The modulation order of a first type of a modulation scheme and a modulation order of a second type of a modulation scheme form the hybrid modulation technique.

Journal ArticleDOI
TL;DR: The dual-loop PLL-based coherent-source array in this paper offers considerable practical advantages when implementing beamforming, as compared to other beamforming techniques.
Abstract: In this paper, a novel array of coherent sources based on dual-loop phase-locked loop (PLL) is proposed. An advanced low-cost frequency and phase control technique for a group of PLLs is presented. A novel dual-loop PLL infrastructure consists of a conventional PLL loop and a microcontroller-unit-controlled phase-detector-array loop, which achieves real-time calibration on both frequency and phase by reducing the effect of component aging and environmental issues. This technique has its advantages of building a phased transmitter array. For the purpose of demonstration, a four-element phased array has been designed and implemented by using commercially available components at S-band. Near-perfect local oscillator (LO) beamforming performance and array pattern self-compensation realization are presented and analyzed. Due to analog continuous phase control and individual programmable transmit frequency, the dual-loop PLL-based coherent-source array in this paper offers considerable practical advantages when implementing beamforming, as compared to other beamforming techniques.

Proceedings ArticleDOI
23 Jun 2013
TL;DR: In this paper, a modified QPSK partitioning algorithm is proposed for carrier phase estimation of 16-ary quadrature amplitude modulation (16-QAM) formats, which can tolerate a linewidth times symbol duration product (Δv · Ts) of the order of 10-4, with 1 dB penalty at a bit error rate (BER) of 10 − 3.
Abstract: Coherent optical communications based on higher order modulation formats are severely affected by the phase noise of transmitter and receiver lasers. In this work, a novel yet simple scheme is presented for carrier phase estimation (CPE) of 16-ary Quadrature Amplitude Modulation (16- QAM) formats, based on a modified QPSK-partitioning algorithm. The proposed algorithm can tolerate a linewidth times symbol duration product (Δv · Ts) of the order of 10-4, with 1 dB penalty at a bit error rate (BER) of 10-3. Tolerance can be further improved by introducing a maximum likelihood estimation (MLE) stage (Δv · Ts ≈ 1.432×10-4). Comparison of the scheme with other proposed algorithms is shown. The obtained results indicate that the presented approach can be used with the commercially available state of the art lasers for 16-ary Quadrature Amplitude Modulation (16- QAM) transmission at 100 Gbps.


Journal ArticleDOI
TL;DR: It will be shown that the proposed CPM-based spread spectrum system achieves an overall spectral efficiency larger than that of a single-user single-h CPM transmission even when asingle-user detector is employed at the receiver.
Abstract: We propose a new spread spectrum (SS) system based on continuous-phase modulations (CPMs). The main idea is to exploit the sequence of modulation indices of a multi-h CPM as a frequency-hopping (FH) sequence. Spectral spreading, flatness and smoothness can be easily achieved by an appropriate choice of the maximum value of the modulation index and of the length of the index sequence. We will show that the proposed CPM-based spread spectrum system achieves an overall spectral efficiency larger than that of a single-user single-h CPM transmission even when a single-user detector is employed at the receiver. It also outperforms other solutions in the literature. In addition, we will also derive some suboptimal multi-user detectors.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a low-latency parallel digital phase lock loop in combination with common feed-forward carrier phase recovery algorithms to compensate both the phase noise and laser frequency fluctuation effects on 16-quadrature amplitude modulation receivers.
Abstract: Frequency fluctuations caused by mechanical vibrations, power supply noise, and other mechanisms are detrimental to the phase estimator performance in high speed intradyne coherent optical receivers. In this letter, we propose the use of a low-latency parallel digital phase lock loop in combination with common feed-forward carrier phase recovery algorithms in order to compensate both the phase noise and laser frequency fluctuation effects on 16-quadrature amplitude modulation receivers. Numerical results demonstrate the excellent behavior of the proposed two-stage carrier recovery scheme.

Patent
01 Aug 2013
TL;DR: In this article, an optical multi-carrier signal has a modulation format and has many individual carrier signals, and parameters of the signal are controlled by receiving an indication of individual carrier transmission performance of the individual carrier signal, and selecting (110) parameter values comprising both a carrier FEC overhead and a carrier bandwidth for the modulation format.
Abstract: An optical multi carrier signal has a modulation format and has many individual carrier signals. Parameters of the signal are controlled by receiving (100) an indication of individual carrier transmission performance of the individual carrier signals, and selecting (110) parameter values for the individual carrier signals, the parameter values comprising both a carrier FEC overhead and a carrier bandwidth for the modulation format. Selection is made according to the indicated individual carrier transmission performance and according to an overall spectral efficiency of the multi carrier signal. The selected parameter values are output (120, 124, 125, 126, 127) for control of the optical multi carrier signal. By selecting values for both parameters rather than either one, better optimisation can be obtained since they are interdependent. The control can have better granularity than changing modulation format, and can make better use of bandwidth or improve the overall capacity.

Journal ArticleDOI
TL;DR: A novel, soft-decision-aided, maximum likelihood (SDA-ML) phase estimator is derived for carrier phase estimation in coherent optical communication and outperform the Mth power and DA-ML in the presence of strong linear laser phase noise.
Abstract: A novel, soft-decision-aided, maximum likelihood (SDA-ML) phase estimator is derived for carrier phase estimation in coherent optical communication. For estimating the carrier phase of the current symbol, SDA-ML uses both the feedback of earlier soft data decisions and the feedforward of later soft data decisions. The estimator is applicable to arbitrary 2-D modulations, where the symbols can have unequal energies and unequal a priori probabilities, and the constellation can be asymmetrical. An iterative SDA-ML algorithm and a simplified DA-SDA-ML algorithm with a reduced computational complexity are proposed. Both algorithms have no phase ambiguity. The data detector does not require to estimate the phase explicitly. Simulations show that SDA-ML and DA-SDA-ML outperform the Mth power and DA-ML in the presence of strong linear laser phase noise.

Journal ArticleDOI
TL;DR: This paper focuses on a dc-ac resonant power converter using a special sine-wave amplitude-modulation concept with the objective of achieving a linear input-output behavior, low harmonic content at the output, and reduced stages number.
Abstract: This paper focuses on a dc-ac resonant power converter using a special sine-wave amplitude-modulation concept with the objective of achieving a linear input-output behavior, low harmonic content at the output, and reduced stages number. This technique can be applied to a wide range of resonant converters' applications. Sine-wave generation techniques and phase-modulation method limitations are analyzed. Alternative solutions, such as a new predistorted phase modulator, are developed. A prototype was designed and implemented. Presented experimental results demonstrate the effectiveness of the presented principle.

Journal ArticleDOI
TL;DR: In this article, the authors demonstrate the power budget improvement of a 10-Gb/s vertical-cavity surface-emitting laser (VCSEL) link by utilizing continuous-phase frequency-shift keying (CPFSK)/amplitude-shift-keying (ASK) modulation format.
Abstract: We experimentally demonstrate the power budget improvement of a 10-Gb/s vertical-cavity surface-emitting laser (VCSEL) link by utilizing continuous-phase frequency-shift keying (CPFSK)/amplitude-shift keying (ASK) modulation format. We first measure the frequency modulation (FM) response of the VCSEL from 10 kHz to 10 GHz and then exploit dc-balanced line coding to utilize the flat region of the FM response. The CPFSK/ASK signals are generated by directly modulating the VCSEL and utilizing a delay interferometer (DI) for FSK-to-ASK conversion. We successfully transmit the signals over a 50-km dispersion-uncompensated link by optimizing the free-spectral range of the DI. Using the proposed scheme, we achieve > 5-dB improvement in the power budget compared with a conventional VCSEL link.

Proceedings ArticleDOI
03 May 2013
TL;DR: In this article, the authors proposed a receiver architecture which is composed of a common channel equalizer for all carrier modulation schemes and investigated the feasibility of using a well-studied time domain equalizer designed for single carrier modulation, i.e., the sliding window-frequency domain Equalizer (SW-FDE) for general multicarrier modulation (MCM) receivers.
Abstract: Future wireless communications should be designed efficiently to support multi-mode operations for different types of applications, such as machine-to-machine, video streaming, web browsing and voice. In the physical layer multi-mode operation could include the coexistence of single carrier and multicarrier modulations. To reduce overall complexity and power consumption, it is highly desirable to design the receiver such that some of the components are shared or reused by multiple modulation schemes. In this paper we propose a receiver architecture which is composed of a common channel equalizer for all carrier modulation schemes. Furthermore, we investigate the feasibility of using a well-studied time domain equalizer designed for single carrier modulation, i.e., the sliding window-frequency domain equalizer (SW-FDE) for general multicarrier modulation (MCM) receivers. As a specific illustration of the concept, we present the application of this equalizer to an OFDM-offset QAM system.

Proceedings Article
01 Sep 2013
TL;DR: It is shown that the proposed approach to discrete phase only beamformer design is very effective and the number of quantization bits can be increased to obtain results close to optimum continuous phase beamformers.
Abstract: Transmit beamformer design usually results suboptimum beamformers in multicast scenario. In this paper, discrete phase only beamformer design is considered. The design problem is cast in such a form that the solution is always feasible and optimum beamformer can be found using the branch and cut algorithm. Beamformer phase terms and their interrelations are expressed with a set of cosine vectors which lead to linear set of constraint equations that can be solved with mixed integer linear programming. It is shown that the proposed approach is very effective and the number of quantization bits can be increased to obtain results close to optimum continuous phase beamformers.

Proceedings ArticleDOI
Wei Zhou1, Zhiqi Li1, Lina Bai1, Song Huimin1, Qianqian Du1, Na Li1, Wanying Li1, Ying Zhang1 
21 Jul 2013
TL;DR: Through updating concepts, phase comparison and processing beyond identical frequency signals and extend to arbitrary frequency signals are moved and some difficult research problems have been solved.
Abstract: Traditional phase measurement is limited by the identical nominal frequencies of two compared signals. In a lot of applications, there are higher requirements not only on measurement accuracy, but also on the frequency range of compared signals. After years of exploration and efforts, we have discovered some concepts and characteristics which can reflect mutual phase relationship among different frequency signals, such as Least Common Multiple Period, Phase Difference Quantization Step, Equivalent Phase Comparison Frequency, and the continuous phase group characteristics with the least common multiple period (as the time interval and the quantization step phenomenon that the phase difference of the two different frequency signals will change according to a specific value in one least common multiple period). In the process of experiments, we have discovered ambiguity zone edge effects and measurement method of periodic signal parameter quantization error elimination. We achieved precise frequency source synchronization and link, phase processing and measurement between completely different frequency signals with complex relationship. Through updating concepts, we move phase comparison and processing beyond identical frequency signals and extend to arbitrary frequency signals. Major applications include measurement of transient stability, phase noise measurement, edge effects for accurate frequency measurement method of Serial and Parallel. These breakthroughs promote rapid development in the area of measurement and instrument, and some difficult research problems have been solved.

Journal ArticleDOI
TL;DR: This work describes a framework for computing the information rate (IR) and the SE of such systems, and uses it for optimizing the channel spacing between adjacent users and the CPM phase response, and considers practical schemes, where CPMs are serially concatenated with an outer code.
Abstract: We consider a frequency division multiplexed system where each user adopts a continuous phase modulation (CPM) and multiuser detection is employed at the receiver side. The spectral efficiency (SE) is used as a performance measure to compare, from an information-theoretic point of view, different modulation formats. More precisely, we consider the new CPM formats recently included in the DVB-RCS2 standard. We describe a framework for computing the information rate (IR) and the SE of such systems, and use it for optimizing the channel spacing between adjacent users and the CPM phase response. Our analysis reveals that modulation formats adopted in the DVB-RCS2 standard are suboptimal in terms of SE, while if we allow multiuser detection excellent performance can be achieved by using simple binary formats and highly frequency packed signals. Furthermore, we consider practical schemes, where CPMs are serially concatenated with an outer code, and a low-complexity multiuser receiver is employed, showing that the theoretical limits predicted by the IR analysis can be approached.