Showing papers on "Keying published in 2009"

Performance of Dual-Polarization QPSK for Optical Transport Systems

Abstract: The emergence of capable semiconductor processes has allowed digital signal processing to extend the application range of high-capacity optical systems. We report the performance of polarization multiplexed (or dual-polarization) quadrature phase-shift keying at 40 and 100 Gb/s.

Performance comparison of different modulation formats over free-space optical (FSO) turbulence links with space diversity reception technique

Abstract: The transmission performance of a free-space optical (FSO) link could be severely degraded due to atmospheric turbulence, which causes the temporal and spatial fluctuation of light intensity. Both the space diversity reception technique (SDRT) and advanced modulation formats can successfully mitigate the transmission impairments of the atmospheric turbulence. The purpose of this paper is to study and compare the bit-error-rate (BER) performance of several widely used modulation formats under different atmospheric turbulence scenarios with and without SDRT. The modulation formats studied in this paper include on-off keying (OOK), differential phase-shift keying (DPSK), and differential quadrature phase-shift keying (DQPSK). We derive a series-form formula for evaluating the BER performance of the DPSK format in the Gamma-Gamma distributed channel with SDRT. We use both theoretical analysis and simulation to examine the BER performance of OOK, DPSK, and DQPSK formats with and without SDRT. It is found that, in the strongly turbulent scenario, the OOK and DPSK formats can have as large as 19.5 and 20.3 dB of SDRT gains at the BER of 10-3, respectively. Using SDRT, the modulation gains of the DPSK format over the OOK format are 3.2 dB in the strongly turbulent scenario and 4.5 dB in the weakly turbulent scenario, respectively. In addition, in the moderately and strongly turbulent scenarios, it is found that the DPSK and DQPSK formats have almost the same BER performance under the same symbol rate.

Circle Polarization Shift Keying With Direct Detection for Free-Space Optical Communication

Abstract: A binary polarization shift-keying scheme with two circle polarization states, circle polarization shift keying (CPolSK), is proposed and discussed. The propagation of the circle-polarized Gaussian Schell model beam is studied based on the cross-spectral density matrix. The results show that the state of polarization remains unchanged and the degree of polarization slightly increases upon propagation in a turbulent atmosphere. The analysis of the bit-error-rate performance shows that the CPolSK system has about a 3 dB lower requirement in signal-to-noise ratio than the on-off keying system. The modulation scheme will be helpful for practical free-space optical communication systems in the future.

Amplitude Regeneration of RZ-DPSK Signals in Single-Pump Fiber-Optic Parametric Amplifiers

Abstract: The input power tolerance of a single-pump fiber-optic parametric amplifier (FOPA) is experimentally shown to be enhanced for return-to-zero differential phase-shift keying (RZ-DPSK) modulation compared to RZ on-off keying modulation at 40 Gb/s. The improved nonlinear tolerance is exploited to demonstrate amplitude regeneration of a distorted RZ-DPSK signal in a gain-saturated FOPA. An optical signal-to-noise ratio penalty of 3.5 dB after amplitude distortion is shown to be reduced to 0.2 dB after the FOPA, thus clearly demonstrating the regenerative nature of saturated FOPAs for RZ-DPSK modulation.

Digital Coherent Receiver for Phase-Modulated Radio-Over-Fiber Optical Links

Abstract: A novel digital signal processing-based coherent receiver for phase-modulated radio-over-fiber (RoF) optical links is presented and demonstrated experimentally. Error-free demodulation of 50-Mbaud binary phase-shift keying (BPSK) and quadrature phase-shift keying data signal modulated on a 5-GHz radio-frequency (RF) carrier is experimentally demonstrated using the proposed digital coherent receiver. Additionally, a wavelength- division-multiplexing (WDM) phase-modulated RoF optical link is experimentally demonstrated. A 3times50 Mb/s WDM transmission of a BPSK modulated 5-GHz RF carrier is achieved over 25 km for the WDM channel spacing of 12.5 and 25 GHz, respectively.

SER Performance Analysis for Physical Layer Network Coding over AWGN Channels

Abstract: While original network coding is proposed over the data link layer, recent work suggests that it can also be implemented on the physical layer. In fact it is more natural for wireless networks because of its omnidirectional transmission. In this paper, we investigate the symbol-error-rate (SER) for binary phase-shift keying (BPSK) and quadrature phase-shift keying (QPSK), but the approaches can be generalized to other constellation schemes. The closed-form SER results are derived for physical layer network coding over AWGN channels. The theoretical analysis is also validated by numerical simulation.

Modulation-format agile, reconfigurable Tb/s transmitter based on optical arbitrary waveform generation

Abstract: This paper presents the concept of an optical transmitter based on optical arbitrary waveform generation (OAWG) capable of synthesizing Tb/s optical signals of arbitrary modulation format. Experimental and theoretical demonstrations in this paper include generation of data packet waveforms focusing on (a) achieving high spectral efficiencies in quadrature phase-shift keying (QPSK) and 16 quadrature amplitude modulation (16QAM) modulation formats, (b) generation of complex data waveform packets used for optical-label switching (OLS) consisting of a data payload and label on a carrier and subcarrier, and (c) repeatability and accuracy of duobinary (DB) data packet waveforms with BER measurements. These initial demonstrations are based on static OAWG, or line-by-line pulse shaping, to generate repeated waveforms of arbitrary shape. In addition to experimental and theoretical demonstrations of static OAWG, simulated results show dynamic OAWG, which involves encoding continuous data streams of arbitrary symbol sequence on data packet waveforms of arbitrary length.

Investigation of Transparency of FWM in SOA to Advanced Modulation Formats Involving Intensity, Phase, and Polarization Multiplexing

Abstract: We experimentally investigate the real transparency of four-wave mixing (FWM) in semiconductor optical amplifiers to modulation formats involving intensity, phase, and polarization multiplexing. We exploit two different FWM polarization-independent schemes (that make use of two pumps) to wavelength-convert 40 Gb/s single-polarization and 80 Gb/s polarization-multiplexed signals in case of both nonreturn-to-zero ON -OFF keying (NRZ-OOK) and NRZ differential phase-shift keying modulation formats. We found that, although FWM conversion is transparent to modulation formats employing phase and intensity, polarization-multiplexed signals pose serious limitations to all-optical processing transparency.

Light with keying arrangement mountable on a mounting rail

Abstract: A keyed mounting arrangement for a light or other object mountable on a mounting rail having a keying feature may comprise a body containing operating elements; a clamping arrangement including clamp members on the body for clamping and releasing the mounting rail; and a keying member removably disposed in a recess located on the body in a predetermined location and having a keying feature that engages the keying feature of the mounting rail when the body is clamped to the mounting rail. Where the object is mountable on mounting rails having keying features of different sizes and shapes, the keying member may be selected from a set of keying members for having a keying feature of a size and shape that corresponds to the size and shape of the keying feature of the mounting rail.

111-Gb/s Transmission Over 1040-km Field-Deployed Fiber With 10G/40G Neighbors

Abstract: We demonstrate transmission of a 111-Gb/s coherent polarization-multiplexed return-to-zero differential quadrature phase-shift keying signal over 1040-km field-deployed fiber together with different types of neighboring channels, and with a cascade of 50-GHz reconfigerable optical add-drop multiplexers. Our transmission experiment proves the feasibility of transmitting a 111-Gb/s phase-modulated channel with 10 times 10.7-Gb/s on-off keying neighboring channels on a 50-GHz grid, despite the presence of strong cross-phase modulation.

Automatic modulation recognition using wavelet transform and neural network

Abstract: Modulation type is one of the most important characteristics used in signal waveform identification An algorithm for automatic modulation recognition has been developed and presented in this study The suggested algorithm is verified using higher order statistical moments of wavelet transform as a features set A multi-layer neural network with resilient backpropagation learning algorithm is proposed as a classifier The purpose is to discriminate different M-ary shift keying modulation types and modulation order without any priori signal information Pre-processing and features subset selection using principal component analysis will reduce the network complexity and increase the recognizer performance

Performance Analysis of Cooperative Communication Systems with Imperfect Channel Estimation

Abstract: This paper investigates the effects of channel estimation errors on the symbol-error-rate (SER) performance of a cooperative communication system operating in an amplify-and-forward (AF) mode. A pilot symbol assisted modulation scheme with linear minimum mean square estimation (LMMSE) is used for the channel estimation. An accurate and easy-to-evaluate SER expression is presented for uncoded cooperative communication systems with quadrature amplitude modulation (QAM) and phase-shift keying (PSK) constellations. Numerical simulations are conducted to verify the correctness of the proposed analytical formulation. It is shown that the performance loss caused by channel estimation errors increases mainly with the normalized maximum Doppler frequency.

Performance analyses of selection combining diversity receiver over α-μ fading channels in the presence of co-channel interference

Abstract: An approach to the performance analyses of dual selection combining (SC) diversity receiver over correlated alpha - mu fading channels with the arbitrary parameters is presented. Fading between the diversity branches and interferers is correlated and distributed with alpha - mu distribution. Infinite series expressions are obtained for the output SIR's probability density function (PDF), cumulative distribution function (CDF) and an important measure of the system's performances, the outage probability (OP). An average error probability is efficiently evaluated for coherent and non-coherent modulation schemes such as coherent frequency-shift keying (CFSK), coherent phase-shift keying (CPSK), binary frequency-shift keying (BFSK) and binary differentially phase-shift keying (BDPSK). Numerical results are presented to show the effects of various parameters such as fading severity, input SIR unbalance and the level of correlation between received desired signals and interferences on system's performances.

A 200-pJ/b MUX-Based RF Transmitter for Implantable Multichannel Neural Recording

Abstract: This paper presents a 400-MHz energy-efficient offset quadrature phase-shift keying (O-QPSK) transmitter for implantable multichannel neural recording applications. Transmitters for these applications must operate at low power while delivering a high data rate. The proposed transmitter incorporates a phase MUX, which directly implements the phase-shift keying operation. The O-QPSK modulation signal is generated by selecting one of the four quadrature phases based on the baseband data via the phase MUX. The power amplifier adopts the inverter-type topology for it is compatible with the quasi-constant-envelope nature of the O-QPSK signal. Implemented in a 0.18- mum CMOS process, the whole transmitter dissipates 2.9 mA from a 1.2-V supply. With a maximum data rate of 17.5 Mb/s, the proposed transmitter achieves an energy efficiency of 200 pJ/bit and is capable of delivering an output power up to -8 dBm.

Optical phase erasure based on FWM in HNLF enabling format conversion from 320-Gb/s RZDQPSK to 160-Gb/s RZ-DPSK.

Abstract: Through four-wave mixing (FWM) process in highly-nonlinear fiber (HNLF) or semiconductor device, the phase-modulation depth of one converted FWM component could be doubled compared with that of the original input signal Therefore, with a multilevel phase-modulated signal and a CW light as inputs, after FWM process in a nonlinear media, phase pattern (0, π) carried in the input multilevel phase-modulated signal will not be transferred to one converted FWM component, which could be referred to as an optical phase erasure process We experimentally demonstrated format conversion from 320-Gb/s return-to-zero differential quadrature phase-shift keying (RZ-DQPSK) to 160-Gb/s return-to-zero differential phase-shift keying (RZ-DPSK) through the proposed all-optical phase erasure scheme The phase information carried in the converted binary RZ-DPSK is logically equal to the input Q-component, or a logical XOR operation result between I and Q components of the input RZ-DQPSK, which correspond to a serial or parallel DQPSK transmitter for the input RZ-DQPSK signal It can be applied to erase a binary tributary from a multilevel modulation format

Phase-Silence-Shift-Keying for Power-Efficient Modulator

Abstract: We propose a new modulation, phase-silence-shift-keying (PSSK), whose symbol error rate (SER) performance is improved by 6dB compared with phase-shift-keying (PSK). To prove this, theoretical analysis of probability of error is provided and simulation results are presented.

Multiplier-Free Real-Time Phase Tracking for Coherent QPSK Receivers

Abstract: This letter presents a hardware-efficient phase estimation algorithm that can replace the common complex estimators for a coherent quadrature phase-shift keying transmission system.

Digital modulator for a GSM/GPRS/EDGE wireless polar RF transmitter

Abstract: A digital modulator in a radio transmitter includes circuitry for switching between Gaussian Minimum Shift Keying (GMSK) and Phase-Shift Keying (PSK) while maintaining spectral mask requirements. The digital modulator of the present invention includes both GMSK and PSK symbol mappers that produce PSK in-phase and quadrature symbols and GMSK symbols, respectively, to a pulse shaping block. Based on opposite phases of a modulation control signal, the symbol mappers produce either modulated data or a steam of logic zeros to the pulse shaping block. The pulse shaping block filters the received data and multiplexes the data so that each modulated data stream receives non-zero data during a guard time to avoid abrupt changes in the modulated signal that would violate the spectral mask requirements.

A method for operating a network, a system management device, a network and a computer program therefor

Abstract: The present invention relates to a method for operating a network comprising communicating devices representing nodes of the network. More precisely, the invention relates to a method for operating a network (1), comprising a node (D1) and a system management device (3), the system management device comprising a root keying material being a set of alpha-secure functions having a degree of complexity of,and the node being provided with a node keying material share of degree of complexity α derived from the root keying material. The method comprises the following steps, upon receipt at the system management device of a request for an external user (4) to gain access to the node (D1): the system management device generates an external user keying material share of degree of complexity α from the root keying material and an access identifier, the system management device generates an access keying material of degree of complexity less than α, from the external user keying material share and an identifier of the node, the system management device provides the external user with the access keying material share and the access identifier, the external user derives a key from the access keying material share, and transmitting this key and the access certificate to the node, the node computes a key from the access identifier and the node keying material share, and the node compares the key transmitted by the external user and the key computed by the node, so as to authenticate the external user.

Noncoherent physical-layer network coding using binary CPFSK modulation

Abstract: Physical-layer network coding is a high-throughput technique for communicating over the two-way relay channel, which consists of two terminals that communicate exclusively via an intermediate relay. An exchange of messages begins with both terminals transmitting binary data sequences simultaneously to the relay. The relay determines the modulo-2 sum of the sequences, which it modulates and broadcasts to the terminals. Since each terminal knows the information it transmitted, it can determine the information transmitted by the other terminal by subtracting its own information from the broadcast signal. Prior work on the topic of physical-layer network coding has assumed that the signals transmitted by the two terminals arrive at the relay with perfectly aligned phases, permitting coherent reception. In this paper, we relax the assumption of aligned phases and consider noncoherent reception of binary continuous-phase frequency-shift keying signals. A derivation of the relay receiver is given for varying amounts of channel state information, and results are provided showing the error performance of the proposed system without an outer error-correcting code and with an outer turbo code.

Space-Frequency and Space-Time-Frequency M3FSK for Indoor Multiwire Communications

Abstract: This paper investigates the multiple emitting multiple receiving points diversity technique as one of the ways of meeting the tripartite conditions of high data rate, less transmit power, and low unwanted electromagnetic radiations of the frequency-selective power-line channels. To be resilient to the intersymbol interference present in frequency-selective fading, the diversity technique must be used in conjunction with wideband multicarrier modulation. We propose an efficient space-frequency and space-time-frequency (STF)-coded multitone M-ary multilevel frequency-shift keying (M3FSK) for high-rate indoor communications over the multiwire power-line channels. We show that coding by using three dimensions of space, frequency, and time, the STF system is capable of achieving up to 8-dB diversity gain. Simulation results are provided to demonstrate the performance improvement of the STF over other diversity schemes as well as over single-wire M3FSK systems in a highly impulsive power line.

Signal Transmission with Unequal Error Protection in Wireless Relay Networks

Abstract: This paper studies a relaying technique in cooperative networks using hierarchical modulation. Hierarchical modulation is useful in applications that require different protection classes of the information. In particular, a cooperative network with one source, one relay, and one destination is considered. Two different protection classes are modulated by a hierarchical 2/4-amplitude shift keying (ASK) constellation at the source. Based on the instantaneous received signal-to-noise ratio (SNR) at the relay, the relay decides to retransmit both classes by using a hierarchical 2/4-ASK constellation, or the more protection class by using a 2-ASK constellation, or remains silent. Optimal thresholds are chosen to minimize the bit-error-rate (BER) of the less protection class while the BER of the more protection class meets a given requirement. Numerical and simulation results are provided to verify the analysis. The results show that the optimal thresholds improve the performance significantly.

A polarization shift-keying system for underwater optical communications

Abstract: A compact and simple setup for testing polarization modulation in the underwater channel is demonstrated. The results from this system compare favorably to a non-polarization modulation system utilizing on-off keying modulation. This system will allow future work to explore using polarization in optical communication systems underwater. The advantages of such systems include ability to monitor the water quality of the channel during transmission and reduction of receiver shot noise.

System, method, and computer program for superposition coded multicast with a single modulation scheme

Abstract: A cross-layer design architecture is provided for logical superposition coded (SPC) modulation for last-hop wireless data, aiming to overcome the effects of multi-user channel diversity in wireless video multicast. The proposed approach generates a logical SPC modulated signal by mapping successively refined information bits onto layered modulation through dynamic energy allocation and phase keying assignment, which mimics the superposition process for multiple modulated signals in convention hardware-based SPC modulation. At the receiver end, the received logical SPC signal is decoded by implementing a software-based approach on common demodulators without going through the signal-interference cancellation (SIC) process that is necessary in the conventional approach. The approach presented provides comparable or even better overall system throughput than by using the conventional hardware and SIC-based SPC modulation under various scenarios of different histograms of user channel conditions and power allocations for base and enhancement layer information.

Keying of plate anchors in NC clay under inclined loading

Abstract: Plate anchors are commonly used in the offshore industry to anchor floating facilities. They are installed vertically using a follower and subsequently rotated, through a process called keying, to exhibit their maximum area normal to the loading direction. This paper describes a series of centrifuge tests performed in order to investigate the influence of the keying on the overall performance of the anchor. Tests were conducted against a Perspex window in plane strain chambers containing normally consolidated clay. Particle Image Velocimetry (PIV) provided insights into the different failure mechanisms generated during keying, and information about the load inclination and load eccentricity minimising the loss of embedment and hence maximising the anchor performance. The loss of embedment after keying for different load inclinations and different load eccentricities was also quantified.

Method for secure communication in a network, a communication device, a network and a computer program therefor

Abstract: A method for securing communications between a first node (N1) and a second node (N2) in a network (1) further comprising a management device (2) provided with root keying materials, the method comprising the following steps: the management device generating, based on root keying materials, a first node keying material shares comprising a number of sub-elements and the first node keying material shares being arranged for generating a first complete key, the management device selecting a subset of sub-elements of the first keying material shares, the number of sub-elements selected being less or equal than the total number of sub-elements of the first keying material shares, and the selected sub-elements forming a first node partial keying material shares or symmetric-key generation engine, the first node generating, based on the first node symmetric-key generation engine and on an identifier of the second node, a first key, used for securing communications with the second node.

Maximum-Likelihood Sequence Estimation for Optical Phase-Shift Keyed Modulation Formats

Abstract: Electronic chromatic dispersion compensation employing maximum-likelihood sequence estimation (MLSE) has recently been the topic of extensive research and a range of commercial products. It is well known that MLSE provides a considerable benefit for amplitude modulated modulation formats such as on-off keying (OOK) and optical duobinary. However, when applied to optical phase modulation formats, such as differential phase-shift keying (DPSK) and differential quadrature phase-shift keying (DQPSK), it has been shown that the benefit is only marginal. This paper investigates joint-decision MLSE (JD-MLSE) detection applied to 10.7-Gb/s DPSK. It demonstrates that a JD-MLSE using the constructive and destructive components preserves the 3-dB optical signal-to-noise ratio (OSNR) advantage of DPSK over OOK in dispersion-limited optical systems. Furthermore, we demonstrate that the use of a shortened MZDI with MLSE for the 10.7-Gb/s DPSK modulation can equalize an accumulated chromatic dispersion of 4000 ps/nm. In addition, we discuss in this paper different MLSE schemes applied to 2 times 10.7-Gb/s DQPSK modulation. It is shown that a joint-symbol MLSE (JS-MLSE) on the balanced outputs of the in-phase and quadrature components gives the best performance.

360-Gb/s Optical Transmitter With Arbitrary Modulation Format and Dispersion Precompensation

Abstract: This letter introduces a versatile data-rate and modulation format transparent optical transmitter for 360-Gb/s transmission based on optical arbitrary waveform generation (OAWG) techniques. An experimental implementation of static OAWG, or line-by-line pulse shaping, with a silica arrayed-waveguide-grating pair waveform shaper, demonstrates creation of repetitive time-domain waveforms representing data packets in on-off keying and differential phase-shift-keying modulation formats with optional precompensation for fiber chromatic dispersion (CD). Transmission of repeated 9-bit 360-Gb/s data packets occupying 680 GHz of total optical bandwidth, with CD precompensation over a 10-km single-mode fiber link, indicates the potential for terabit-per-second operation. These data packets have a spectral efficiency of 0.53 b/s/Hz.

Hybrid Access Network Integrated With Wireless Multilevel Vector and Wired Baseband Signals Using Frequency Doubling and No Optical Filtering

Abstract: This letter experimentally demonstrated a hybrid access network which supports both radio-over-fiber and fiber-to-the-x systems. A 20-GHz radio-frequency (RF) 312.5-MSymbol/s M-ary phase-shift keying (PSK) signal and a baseband (BB) 1.25-Gb/s on-off keying signal are simultaneously generated and transmitted over an identical distributed infrastructure. The wired BB signal is compatible with the existing passive optical network (PON) system, and the wireless RF PSK signal can also share the same distributed infrastructure. The proposed system has no RF fading issue, no narrowband optical filter at remote node to separate the RF and BB signals, and can carry vector signals. Moreover, a frequency doubling for optical RF signal generation is achieved to reduce the bandwidth requirement of the transmitter. After transmission over 25-km standard signal-mode fiber, the receiver sensitivity penalties are less than 0.5 dB for both the RF and BB channels.

Electronic Pre-Compensation of Narrow Optical Filtering for OOK, DPSK and DQPSK Modulation Formats

Abstract: It is shown that electronic pre-compensation effectively reduces the degradation in system performance caused by narrow filtering that arises from the cascading of optical filters in spectrally efficient, wavelength division multiplexed systems. The pre-compensation is based on generating the appropriate electrical drive signals for an optical modulator such that the transmitted optical signal takes into consideration the subsequent optical filtering. Three modulation formats (on-off keying, differential-phase-shift keying and differential-quadrature-phase-shift keying) and two types of optical modulators (dual-drive Mach-Zehnder modulator and dual-parallel Mach-Zehnder modulator) are considered.