Showing papers on "Keying published in 2014"

Design and Implementation of Color-Shift Keying for Visible Light Communications

Abstract: Color-shift keying (CSK) is a visible light communication intensity modulation scheme, outlined in IEEE 802.15.7, that transmits data imperceptibly through the variation of the color emitted by red, green, and blue light emitting diodes. An advantage of CSK is that the power envelope of the transmitted signal is fixed; therefore, CSK reduces the potential for human health complications related to fluctuations in light intensity. In this work, a rigorous design framework for high order CSK constellations is presented. A key benefit of the frame work is that it optimizes constellations while accounting for crosstalk between the color communication channels. In addition, and unlike previous approaches, the method is capable of optimizing 3-D constellations. Furthermore, a prototype CSK communication system is presented to validate the performance of the optimized constellations, which provide gains of 1–3 dB over standard 805.15.7 constellations.

Color-Shift Keying and Code-Division Multiple-Access Transmission for RGB-LED Visible Light Communications Using Mobile Phone Camera

Abstract: Light-emitting diodes (LEDs) have been deployed for various applications in our daily lives. Similarly, image sensors or cameras integrated into mobile phones have become common. Hence, visible light communication (VLC) using LED and mobile phone cameras is attractive and provides low-cost wireless communication. In this paper, we propose and demonstrate a VLC system using color-shift-keying (CSK) modulation and code-division multiple-access (CDMA) technology simultaneously for the first time; a mobile phone camera is used as the receiver (Rx). CSK is used to enhance the VLC system capacity and to mitigate the single color light interference, whereas CDMA allows multiple users to access the network. The system design and operation mechanism of the proposed CSK–CDMA VLC system are discussed. A proof-of-concept demonstration is performed, and error-free transmission is achieved for multiple-access users. A 3-dB transmission gain is also obtained in each user when compared with the traditional on–off keying (OOK) modulation.

Undersampled Phase Shift ON-OFF Keying for Camera Communication

Abstract: In this paper, an optical camera communication system utilizing the under-sampled phase shift ON-OFF keying modulation is proposed to support non-flickering visible light communication. This system sends three types of light symbols through light emitting diode (LED) lamps, which are recorded by a camera. By employing a dual LED lamp with a designated mapping and framing method, the data rate can reach up to 3 times of the camera's frame rate. The experiment results show that the proposed camera communication system can achieve 150 bps error-free communications for a range up to 12 m.

A Tight Upper Bound on Bit Error Rate of Joint OFDM and Multi-Carrier Index Keying

Abstract: This letter investigates performance enhancement by the concept of multi-carrier index keying in orthogonal frequency division multiplexing (OFDM) systems. For the performance evaluation, a tight closed-form approximation of the bit error rate (BER) is derived introducing the expression for the number of bit errors occurring in both the index domain and the complex domain, in the presence of both imperfect and perfect detection of active multi-carrier indices. The accuracy of the derived BER results for various cases are validated using simulations, which can provide accuracy within 1 dB at favorable channels.

Augmented reality simulator

Abstract: An augmented reality system in which video imagery of a physical environment is combined with video images output by a game engine by the use of a traveling matte which identifies portions of the visible physical environment by techniques such as Computer vision or chroma keying and replaces them with the video images output by the video game engine. The composited imagery of the physical environment and the video game imagery is supplied to a trainee through a headmounted display screen. Additionally, peripheral vision is preserved either by providing complete binocular display to the limits of peripheral vision, or by providing a visual path to the peripheral vision which is matched in luminance to higher resolution augmented reality images provided by the binocular displays. A software/hardware element comprised of a server control station and a controller onboard the trainee performs the modeling, scenario generation, communications, tracking, and metric generation.

System and method for enhanced security of storage devices

Abstract: A storage device features a processor and a random number generation which are communicatively coupled to a memory. The memory comprises an access control logic that is configured to (i) transmit a first message that comprises information associated with a random number generated by the random number generator and a first keying material, (ii) receive a second message in response to the first message, the second message comprises information generated using at least the random number, (iii) recover information from the second message, the recovered information comprises information generated using at least pre-stored keying material and a return value being based on the random number, (iv) compare the return value from the recovered information with the random number, and (v) alter an operating state of the storage device from a locked state to an unlocked state upon the return value matching the random number, the unlocked state allows one or more devices to control storage device including accessing stored content within the storage device.

Unified Differential Spatial Modulation

Abstract: This letter proposes a unified differential spatial modulation (DSM) architecture, where a flexible rate-diversity tradeoff is achieved, while enabling a simple single-RF transmitter structure along with non-coherent detection that dispenses with channel estimation at the receiver. In our proposed scheme, by assigning a set of sparse complex-valued antenna-index matrices, only one transmit antenna element is activated during each symbol interval and then a phase-shift keying (PSK) symbol is transmitted from the activated antenna element. The explicit benefit of the proposed scheme's universal DSM framework is ability to strike a balance between previous DSM schemes, such as the symbol-based and the block-based DSM schemes. Moreover, to attain a useful attainable diversity gain, we further extend the proposed DSM scheme in a manner that permits flexible planning of the number of symbols employed per antenna-index block.

Use of SSK Modulation in Two-Way Amplify-and-Forward Relaying

Abstract: Space-shift keying (SSK) modulation is a novel multiple-input-multiple-output (MIMO) technique, which activates only a single antenna for transmission at any time instant and uses the index of this active antenna to implicitly convey information. In this paper, a pragmatic communication strategy for the use of SSK modulation in two-way amplify-and-forward (AF) relaying is proposed. Specifically, the transceiver sends the signal by employing SSK modulation and detects the signal based on the maximal-ratio combining principle. By considering a Nakagami- m fading environment, upper bounded and asymptotic bit error probabilities (BEPs) are both derived in closed form. The optimal power allocation problem in the minimization of the average BEP is also addressed. Finally, Monte Carlo simulations are conducted to verify the accuracy of the analysis.

Direct Phase Modulation DFBs for Cost-Effective ONU Transmitter in udWDM PONs

Abstract: A technique for direct phase modulating a low-cost distributed feedback laser is presented for user transmitter in ultra dense wavelength division multiplexing passive optical networks. It consists of a simple RC network, which equalizes the phase response. The method is tested with differential phase-shift keying modulation and heterodyne coherent detection at 1.25 and 2.5 Gb/s showing a penalty <;1 dB at BER = 10-3 compared with external phase modulation.

Constellation Design for Channel Precompensation in Multi-Wavelength Visible Light Communications

Abstract: The predicted ubiquity of light-emitting diodes (LEDs) suggests great potential for dual-use systems with visible light communications (VLC) capabilities One class of LEDs employs multiple emitters at different wavelengths, making them appropriate for applications requiring colored output and providing multiple channels for communication We present a design framework for optimizing the signaling constellation of VLC systems employing an arbitrary number of such LEDs, each with an arbitrary number of emitters In particular, by considering the design of constellation-symbol locations jointly across LED emitters, the framework provides for the precompensation of linear channel distortions arising from, for example, cross-channel leakage, noise correlation, or wavelength-dependent received-signal and/or noise power, as well as the incorporation of design constraints for color-shift keying, dimming, and/or perceived color Simulation results demonstrate the design approach and the potential performance enhancement that can be achieved for particular system scenarios Experimental measurements using a prototype VLC system confirm such performance enhancements, providing real-world evidence of the benefit of applying the proposed framework to VLC channel precompensation

Photonic microwave-signal-mixing technique using phase-coherent orthogonal optical carriers for radio-over-fiber application

Abstract: An optical-assisted microwave-mixing technique based on orthogonal and phase-coherent optical carriers is proposed and demonstrated. High-quality binary-phase-shift keying, amplitude-shift keying, and on-off keying microwave modulation at 20 GHz implemented in the optical domain have been tested. The ultra-high-bandwidth response of the proposed mixing device is also analyzed and compared. The phase stability of the photonic microwave signal in the radio-over-fiber system is improved by the proposed signal mixing technique.

Packet error rate analysis of OOK, DPIM, and PPM modulation schemes for ground-to-satellite laser uplink communications

Abstract: Performance of on-off keying (OOK), digital pulse interval modulation (DPIM), and pulse position modulation (PPM) schemes are researched for ground-to-satellite laser uplink communications. Packet error rates of these modulation systems are compared, with consideration of the combined effect of intensity fluctuation and beam wander. Based on the numerical results, performances of different modulation systems are discussed. Optimum divergence angle and transmitted beam radius of different modulation systems are indicated and the relations of the transmitted laser power to them are analyzed. This work can be helpful for modulation scheme selection and system design in ground-to-satellite laser uplink communications.

Improving Plate Anchor Design with a Keying Flap

Abstract: Suction embedded plate anchors have been increasingly applied in deepwater projects because of their efficiency and limited cost. Current industry practice equips the fluke of the anchor with an outwardly rotating keying flap aiming at a reduction of the loss of embedment during keying. However, recent experimental and numerical research has questioned the efficiency of the keying flap currently used in practice because it has demonstrated that the flap does not open during keying as was intended. This paper presents a two-dimensional plain strain large deformation finite-element analysis by assuming the soil as homogenous to investigate the performance of plate anchors equipped with various keying flap designs. The results of the paper agree with previous centrifuge and finite-element analysis that the outwardly keying flap has no effect on the loss of embedment and results in a reduction of the bearing capacity postkeying. The performance of an alternative keying flap design where the flap is rotating inward is also discussed. The new design effectively reduces the loss of embedment during keying and exhibits a bearing capacity higher than the current design.

A 100-Gb/s noncoherent silicon receiver for PDM-DBPSK/DQPSK signals.

Abstract: An integrated noncoherent silicon receiver for demodulation of 100-Gb/s polarization-division multiplexed differential quadrature phase-shift keying and polarization-division multiplexed differential binary phase-shift keying signals is demonstrated. The receiver consists of a 2D surface grating coupler, four Mach-Zehnder delay interferometers and four germanium balanced photodetectors.

Quadrature demultiplexing using a degenerate vector parametric amplifier.

Abstract: We report on quadrature demultiplexing of a quadrature phase-shift keying (QPSK) signal into two cross-polarized binary phase-shift keying (BPSK) signals with negligible penalty at bit-error rate (BER) equal to 10−9. The all-optical quadrature demultiplexing is achieved using a degenerate vector parametric amplifier operating in phase-insensitive mode. We also propose and demonstrate the use of a novel and simple phase-locked loop (PLL) scheme based on detecting the envelope of one of the signals after demultiplexing in order to achieve stable quadrature decomposition.

On code design for simultaneous energy and information transfer

Abstract: We consider the problem of binary code design for simultaneous energy and information transfer where the receiver completely relies on the received signal for fulfilling its real-time power requirements. The receiver, in this scenario, would need a certain amount of energy (derived from the received signal) within a sliding time window for its continuous operation. In order to meet this energy requirement at the receiver, the transmitter should use only those codewords which carry sufficient energy. In this paper, we assume that the transmitter uses on-off keying where bit one corresponds to transmission of a high energy signal. The transmitter uses only those codewords which have at least d ones in a sliding window of W = d + 1 bits. We show that with this constraint, the noiseless code capacity is achieved by sequences generated from a finite state Markov machine. We also investigate achievable rates when such constrained codes are used on noisy communication channels. Although a few of these results are well known for run-length limited codes used for data storage, they do not seem to appear in literature in the form presented here.

Photonic generation of microwave frequency shift keying signal using a single-drive Mach–Zehnder modulator

Abstract: We propose and experimentally demonstrate a new scheme for photonic generation of microwave frequency shift keying (FSK) signal by employing one single-drive Mach-Zehnder modulator (MZM) In the proposed method, an electrical signal with different radio frequency (RF) amplitudes and direct current (DC) components for bit '0' and bit '1' is generated After amplification, the signal is fed into a single-drive MZM which is biased at the quadrature and null points of its transmission curve for bit '0' and bit '1', respectively Due to the different RF amplitudes, a microwave FSK signal can be obtained after photodetection, where the space frequency is the same as the RF frequency and the mark frequency is twice as large as the RF frequency The feasibility of the proposed scheme is verified by a proof-of-concept experiment 5/10-GHz and 10/20-GHz microwave FSK signals with different bit rates are successfully demonstrated

Multi-rate DPSK optical transceivers for free-space applications

Abstract: We describe a flexible high-sensitivity laser communication transceiver design that can significantly benefit performance and cost of NASA's satellite-based Laser Communications Relay Demonstration Optical communications using differential phase shift keying, widely deployed for use in long-haul fiber-optic networks, is well known for its superior sensitivity and link performance over on-off keying, while maintaining a relatively straightforward design However, unlike fiber-optic links, free-space applications often require operation over a wide dynamic range of power due to variations in link distance and channel conditions, which can include rapid kHz-class fading when operating through the turbulent atmosphere Here we discuss the implementation of a robust, near-quantum-limited multi-rate DPSK transceiver, co-located transmitter and receiver subsystems that can operate efficiently over the highly-variable free-space channel Key performance features will be presented on the master oscillator power amplifier (MOPA) based TX, including a wavelength-stabilized master laser, high-extinction-ratio burst-mode modulator, and 05 W single polarization power amplifier, as well as low-noise optically preamplified DSPK receiver and built-in test capabilities

A high-sensitivity fully passive wake-up radio front-end for wireless sensor nodes

Abstract: A high-sensitivity fully passive 868-MHz wake-up radio (WUR) front-end for wireless sensor network nodes is presented. The front-end does not have an external power source and extracts the entire energy from the radio-frequency (RF) signal received at the antenna. A high-efficiency differential RF-to-DC converter rectifies the incident RF signal and drives the circuit blocks including a low-power comparator and reference generators; and at the same time detects the envelope of the on-off keying (OOK) wake-up signal. The front-end is designed and simulated 0.13μm CMOS and achieves a sensitivity of -33 dBm for a 100 kbps wake-up signal.

Low-complexity SOCPBFSK-OOK interface between PLC and VLC channels for low data rate transmission applications

Abstract: This paper studies and proposes a low cost low complexity interface between power line communications (PLC) and visible light communications (VLC) for low data rate transmission applications. The discussion presents the performance of a spread orthogonal continuous phase binary frequency shift keying (SOCPBFSK) receiver combined with an on-off keying (OOK) modulator to relay low data transmission between PLC and VLC channels. The characteristics of the interface are presented. The results of an experimental test using the proposed interface over the European Committee for Electrotechnical Standardization (CENELEC) bands C and D are presented. The eye diagrams of the combined error are presented as well.

Benefits and Limits of Modulation Formats for Optical Communications

Abstract: This paper is focused on benefits and lim- its of intensity and phase modulation formats used in optical communications. The simulation results are ob- tained using OptSim software environment, employing Time Domain Split Step method. Non-Return to Zero, Return to Zero, Chirped Return to Zero and Carrier- Suppressed Return to Zero formats are compared in terms of Bit Error Rate and spectral eciency to find the limits for selected transmission network topologies. It is shown that phase modulation formats oer many advantages compared to intensity formats. Dierential Phase-Shift Keying and mainly Dierential Quadrature Phase-Shift Keying improve the Bit Error Rate and transmission reach, among others. A promising solu- tion is the application of Polarization Division Multi- plexing Quadrature Phase-Shift Keying, which primar- ily benefits in spectral eciency, estimated reach, opti- cal signal to noise ratio and chromatic dispersion tol- erances.

Coherent UDWDM PON with joint subcarrier reception at OLT

Abstract: In this contribution, we report on the experimental investigation of an ultra-dense wavelength-division multiplexing (UDWDM) upstream link with up to 700 × 2.488 Gb/s polarization-division multiplexing differential quadrature phase-shift keying parallel upstream user channels transmitted over 80 km of standard single-mode fiber. We discuss challenges of the digital signal processing in the optical line terminal arising from the joint reception of several upstream user channels. We present solutions for resource and cost-efficient realization of the required channel separation, matched filtering, down-conversion and decimation as well as realization of the clock recovery and polarization demultiplexing for each individual channel.

Practical space shift keying VLC system

Abstract: This paper presents results of a practical implementation of a spatial shift keying (SSK) visible light communication (VLC) system. This is the first practical proof-of-concept realtime implementation of SSK to the best knowledge of the authors. The system uses four transmitter light emitting diodes (LEDs) to encode information, and four receiver photo diodes (PDs) to decode the spatial signatures and decode the incoming data signal. The achieved bit error ratio (BER) of less than 2× 10 allows for error-free communication if forward error correction (FEC) is to be applied. The main challenge with practical implementations of SSK in VLC is identified, namely maintaining symbol separation in the received constellation, and solutions are proposed.

Coherent Versus Non-Coherent Reconfigurable Antenna Aided Virtual MIMO Systems

Abstract: In this letter, motivated by the recent universal encoding concept of space-time shift keying (STSK), we propose a novel single radio-frequency (RF) based virtual multiple-input multiple-output (VMIMO) architecture, employing a pattern reconfigurable antenna at a transmitter More specifically, the proposed scheme is based on the concept of pattern-time dispersion matrix activation, which is capable of striking a flexible balance between the transmission rate and the diversity gain, while enabling symbol-based low-complexity detection Furthermore, we conceive its non-coherently detected counterpart in order to dispense with any channel estimation as well as additional pilot overhead, hence having the potential of outperforming the conventional coherently-detected VMIMO schemes in many practical scenarios

Evidence for graded central processing resources in a sequential movement task

Abstract: In the present experiment, we examined slowing of the individual key presses of a familiar keying sequence by four different versions of a concurrent tone counting task. This was done to determine whether the same cognitive processor that has previously been assumed by the dual processor model (DPM) to initiate familiar keying sequences and assist in their execution, is involved also in the central processes of a very different task (viz. identifying tones and counting target tones). The present results confirm this hypothesis. They also suggest that in this particular situation the central processing resources underlying the cognitive processor can be distributed across the central processes of different tasks in a graded manner, rather than that they continue to behave like a single, central processor that serially switches between the central processes of the concurrently performed tasks. We argue that the production of highly practiced movement sequences can be considered automatic in the sense that execution of familiar movement sequences can continue without cognitive control once they have been initiated.

Blind transmission and detection designs with unique identification and full diversity for noncoherent two-way relay networks

Abstract: This paper considers blind detection for a two-way relay system in which two source nodes exchange information with each other via a relay node using an amplify-and-forward (AF) protocol. The channel coefficients are assumed to be nonreciprocal, i.e., the channel gain between two nodes is not identical to that in the reverse link between the same nodes. An effective signaling and transmitting scheme using four M-ary phase-shift keying (M-PSK) constellation sets is proposed to achieve a unique identification of the transmitted symbols and the channel coefficients in a noise-free transmission. Blind receivers with full diversity are derived for Rayleigh fading channels with Gaussian noise by the generalized likelihood ratio test (GLRT) and least squares error (LSE) criteria. Constellation selections are investigated for the source nodes to transmit at a uniform bit rate in each time slot. Power-allocation schemes are discussed to improve further the average error probability of the source nodes in the blind detection. Simulation results are provided to validate the proposed designs.

Polarization-Dependent Loss Impact on Coherent Optical Systems in Presence of Fiber Nonlinearity

Abstract: We investigate the interaction of polarization-dependent loss (PDL) with Kerr nonlinearities by decoupling single- and cross-channel nonlinear distortions in a homogeneous 100-G polarization division multiplexing quadrature phase shift keying (PDM-QPSK) and a hybrid 100-G PDM-QPSK/10-G on/off keying system. Because of the decoupling method, we provide reasons for the interaction, using basic comprehensive examples. Both average Q-factor and its distribution are investigated in both dispersion-managed and dispersion-unmanaged links, showing that realistic PDL values affect outage probabilities notwithstanding a negligible average penalty.

Binary phase-shift keying by coupling modulation of microrings.

Abstract: We propose a coupling-modulated microring in an add-drop configuration for binary phase-shift keying (BPSK), where data is encoded as 0 and π radian phase-shifts on the optical carrier. The device uses the π radian phase-flip across the zero coupling point in a 2 × 2 Mach-Zehnder interferometer coupler to produce the modulation. The coupling-modulated microring combines the drive power reduction of resonant modulators with the digital phase response of Mach-Zehnder BPSK modulators. A proof-of-concept device was demonstrated in silicon-on-insulator, showing differential binary phase-shift keying operation at 5 and 10 Gb/s.