Showing papers on "Keying published in 2007"

OFDM Visible Light Wireless Communication Based on White LEDs

Abstract: White LEDs are set to penetrate many areas of everyday life. An interesting property of these devices (in addition to their lightening capabilities) is that they can be utilised for data transmission. In the past, primarily OOK (on-off keying) has been used for digital data modulation of such devices. OOK imposes limitations on the achievable data rates. Therefore, in this paper OFDM is considered in combination with higher order modulation schemes. A hardware demonstrator with an entire link chain (transmitter and receiver) is developed and measured BER (bit error ratio) results are reported. The system uses pilot sub-carriers to correct frequency synchronisation errors, training sequences for channel estimation and time synchronisation routines. Forward error correction (FEC) coding is used. It is shown that for COFDM (coded OFDM) with QPSK (quadrature phase shift keying) modulation and a single LED, a BER of 2 times 10-5 is achieved for a distance of 90 cm between transmitter and receiver.

How to do more with numbers : elementary stakes, framing, keying, and the three-dimensional character of numerical signs

Abstract: This paper investigates the various ways in which the use numbers is involved in the ordering of activity in social situations. Drawing on social studies of finance and accounting, elementary stakes within the situated use of numbers are initially considered, listing alongside the utilization of numbers as bearers of information their impact on opportunities of action, the embedding of situations, and the use of numbers as social resources. Subsequently, Erving Goffman’s method of frame analysis is drawn upon to more closely investigate how the utilization of numbers is interactively regulated. The framing of activity differentiates consumptive and reproductive utilizations of numbers, and processes of keying manage transitions between frames of consumption and reproduction. Through framing and keying, numbers acquire a three-dimensional character combining calculative, symptomatic and existential qualities. This is illustrated by a sketch of the kind of social order which unfolds when participants attempt to regulate at a distance activity embedded in networks of circulating numbers. In conclusion, there appear to be general differences between the use of numbers and the use of letters and written narrative which derive from the more immediate bearing of the use of numbers on the ordering of social situations, and particularly its unique power of upkeying.

An Automatic Digital Modulation Classifier for Measurement on Telecommunication Networks

Abstract: This paper presents a method for the automatic classification of digital modulations without a priori knowledge of the signal parameters. This method can recognize classical single- carrier modulations such as M-ary phase-shift keying, M-ary frequency-shift keying, M-ary amplitude-shift keying, and M-ary quadrature amplitude modulation, as well as orthogonal frequency-division multiplexing modulations such as discrete mul- titone that is used for asymmetric digital subscriber line and very high speed digital subscriber line standards and for power-line carrier transmissions. After identification of the modulation type, the method automatically estimates some parameters characterizing the modulation. To evaluate the method performance, several simulations have been carried out in different operating conditions that should be particularly critical by varying the values of signal- to-noise ratio and the main parameters of each identifiable modulation. To assess the advantages, comparison with other classification methods has been given. To validate the assumption that is made, experimental tests have been performed.

LDPC coded OFDM over the atmospheric turbulence channel.

Abstract: Low-density parity-check (LDPC) coded optical orthogonal frequency division multiplexing (OFDM) is shown to significantly outperform LDPC coded on-off keying (OOK) over the atmospheric turbulence channel in terms of both coding gain and spectral efficiency. In the regime of strong turbulence at a bit-error rate of 10-5, the coding gain improvement of the LDPC coded single-side band unclipped-OFDM system with 64 sub-carriers is larger than the coding gain of the LDPC coded OOK system by 20.2dB for quadrature-phase-shift keying (QPSK) and by 23.4dB for binary-phase-shift keying (BPSK).

Experimental on Hierarchical Transmission Scheme for Visible Light Communication using LED Traffic Light and High-Speed Camera

Abstract: LEDs are expected as lighting sources for next generation, and data transmission system using LEDs attract attention. In this paper, we present hierarchical coding scheme using LED traffic lights and high-speed camera for intelligent transport systems (ITS) application. Further, if each of LEDs in traffic lights is individually modulated, parallel data transmissions are possible using a camera as a reception device. Such parallel LED-camera channel can be modeled as spatial low-pass filtered channel of which the cut-off frequency varies according to the distance. To overcome, we propose hierarchical coding scheme based on 2D fast Haar wavelet transform. As results, the proposed hierarchical transmission schemes outperform the conventional on-off keying and the reception of high priority data is guaranteed even LED-camera distance is further.

Multiuser Communications Using Passive Time Reversal

Abstract: A recent paper (Song , IEEE Journal of Oceanic Engineering, vol. 31, no. 2, pp. 170-178, 2006) demonstrated multiple-input-multiple-output (MIMO) communications in shallow water using active time reversal where the time reversal array (i.e., base station) sent different messages to multiple users simultaneously over a common bandwidth channel. Passive time reversal essentially is equivalent to active time reversal with the communications link being in the opposite direction. This paper describes passive time reversal communications which enables multiple users to send information simultaneously to the time reversal array. Experimental results at 3.5 kHz with a 1-kHz bandwidth demonstrate that as many as six users can transmit information over a 4-km range in a 120-m-deep water using quaternary phase-shift keying (QPSK) modulation, achieving an aggregate data rate of 6 kb/s. Moreover, the same data rate has been achieved at 20-km range by three users using 16 quadrature amplitude modulation (16-QAM).

Dynamic Adaptation of Projected Imperceptible Codes

Abstract: In this paper we present an innovative adaptive imperceptible pattern projection technique that takes into account parameters of human visual perception. A coded image is temporally integrated into the projected image, which is invisible to the human eye but can be reconstructed by a synchronized camera. The embedded code is dynamically adjusted on the fly to guarantee its imperceptibility and to adapt it to the current camera pose. Linked with real-time flash keying, for instance, this enables in-shot optical tracking using a dynamic multi-resolution marker technique. A sample prototype has been realized that demonstrates the application of our method in the context of augmentations in television studios.

Sixth-Order Statistics-Based Non-Data-Aided SNR Estimation

Abstract: Signal-to-noise ratio (SNR) estimation is an important task in many digital communication systems. With nonconstant modulus constellations, the performance of the classical second- and fourth-order moments estimate is known to degrade with increasing SNR. A new non-data-aided estimate is proposed, which makes use of the sixth-order moment of the received data, and which can be tuned for a particular constellation in order to extend the usable range of SNR values. The advantage of the new method is especially significant for constellations with two different amplitude levels, e.g. 16-amplitude-and-phase-shift keying (16-APSK)

Optical Systems With High-Order DPSK and Star QAM Modulation Based on Interferometric Direct Detection

Abstract: Increased interest in novel modulation formats for optical transmission has come up in recent years. Receivers with interferometric direct detection can be used to detect arbitrary modulation formats with differentially encoded phases as differential phase-shift keying (DPSK) and differentially phase-encoded star-shaped quadrature amplitude modulation (Star QAM). In this paper, two novel 16-ary modulation formats, which are the 16 DPSK and the Star 16 QAM (ASK-8 DPSK), are characterized for optical transmission for the first time. To be able to identify clear performance tendencies for high-order optical modulation, the novel formats are compared to a wide range of already investigated formats by conducting comprehensive calculations in a uniform simulation environment. The influence of different transmitter structures and decision schemes is considered, and all the systems are characterized with respect to the optical signal-to-noise ratio requirements, dispersion tolerance, and self-phase-modulation (SPM) performance for nonreturn-to-zero (NRZ) and RZ pulse shapes. Moreover, an inherent problem of Star QAM transmission concerning SPM is illustrated, and compensation techniques are examined. The results give a substantial insight into the properties of high-order optical modulation formats.

Automatic transfer and identification of monitored data with hierarchical key management infrastructure

Abstract: A measurement device (14) includes a measuring unit (42) for obtaining health related parameters of a patient (12), and a body-coupled communication unit (40) for sending at least measurement results. An identification device (20), associated with the patient, includes a body-coupled communication unit (26) for receiving and sending out the measurement results. A gateway device (72) includes a body-coupled communication unit (78) for receiving patient's measurement results. Additionally, a hierarchical relational deployment model (100) facilitates grouping wireless devices in a healthcare environment into subgroups based on relationships between the devices, and a hierarchical key pre-distribution scheme (110) permits distribution of unique keying material for security domains of respective groups of devices, prior to deploying the devices in a healthcare network. Devices can then execute a handshake protocol by which they identify their deepest common node in the deployment model (100), and employ keying material assigned to that nodes group in the pre-distribution scheme (110) to facilitate granular communication security.

Back-to-back receptacle

Abstract: A back-to-back receptacle and system for providing selective interconnection between a pair of optic fibres. The system comprises a receptacle comprising a pair of back-to-back receptacle sockets, with at least a first of the sockets configured to one of a plurality of predefined receptacle keying geometries, a first connector plug terminating the first optic fibre, the plug adapted for insertion into the first receptacle socket, the plug configured to one of a plurality of predefined connector keying geometries and a second connector plug terminating the second optic fibre, the plug adapted for insertion into a second of the back-to-back receptacle sockets. At least one of the predefined connector keying geometries matches at least one of the predefined receptacle keying geometries. When the receptacle keying geometry of the first receptacle socket corresponds to the connector keying geometry of the first plug and optionally the receptacle geometry of the second of the back-to-back receptacle sockets corresponds to the connector keying geometry of the second plug, the first plug can be inserted in the first socket and the second plug can be inserted in the second socket bringing the first optic fibre into axial alignment with the second optic fibre.

Real-time Stereo Vision FPGA Chip with Low Error Rate

Abstract: As a step towards real-time stereo, we will present a fast and efficient VLSI architecture and implementation of a stereo matching algorithm which has a low error rate. The architecture has the form of linear systolic array using simple processing element (PE)s that are connected with neighboring PEs. Due to this simple full parallel structure, it is smaller in the time complexity load than other methods. Thus our structure is more adequate for high resolution and real-time applications like the 3D video conference, the Z- keying,and the virtual reality. Our chip can process 320 by 240 images of 128 levels at 30 frames/s.

Orthogonal Wavelength-Division Multiplexing Using Coherent Detection

Abstract: Optical wavelength-division multiplexing (WDM) with channel spacing equal to the symbol rate is demonstrated. Coherent detection with subsequent digital signal processing is used for demultiplexing and demodulation. Experimental results for a 6-Gbaud binary phase-shift keying WDM transmission with a 6-GHz channel spacing achieve a Q-factor penalty of 2.8 dB compared to a single-channel transmission.

Coherent Digital Polarization Diversity Receiver for Real-Time Polarization-Multiplexed QPSK Transmission at 2.8 Gb/s

Abstract: This letter presents a coherent digital polarization diversity receiver for real-time polarization-multiplexed synchronous quadrature phase-shift keying transmission with distributed feedback lasers at a data rate of 2.8 Gb/s. The tolerance against fast polarization changes and polarization-dependent loss is evaluated for different filter widths in the carrier recovery circuit. The minimum achieved bit-error rate is 3.4 times 10-7.

A Dual Band Wireless Power and FSK Data Telemetry for Biomedical Implants

Abstract: A dual-link coil arrangement and a novel digital frequency-shift keying (FSK) demodulator are presented. The primary application of this system is for inductively powered biomedical implants. The implant is provided with data and power via two separate links. Two sets of coils are used in an arrangement such that the magnetic interference between the two pairs is minimized. The demodulator circuitry presented relies solely on delaying elements, utilizing a delayed digital FSK signal to sample the original digital FSK signal. A synchronized clock can be derived from the FSK signals alone, however, by utilizing the power signal to obtain a synchronized clock, a higher data rate and a decrease in complexity of the receiver circuitry can be achieved. The system was implemented on the bench and experimentally tested at a data rate of 2.083 Mbps with zero bit error rate while receiving a 4.17/6.25 MHz FSK carrier signal synchronized with 2.083 MHz clock derived from the power carrier. The power link was set to provide 58 mW.

Proposal for Beyond 100-Gb/s Optical Transmission Based on Bit-Interleaved LDPC-Coded Modulation

Abstract: An iterative bandwidth-efficient coded modulation scheme based on bit-interleaving low-density parity-check (LDPC) codes, and M-ary differential phase-shift keying is proposed. A bit-interleaved LDPC-coded scheme, carrying 3 bits/symbol, provides the coding gain of 8.3 dB at a bit-error rate (BER) of 10-7. The expected coding gain at BER of 10-12 is 12.8 dB. Possible applications include 100G Ethernet, and high-speed (>100 Gb/s) long-haul transmission

Intersymbol Interference (ISI) Suppression Technique for Optical Binary and Multilevel Signal Generation

Abstract: An intersymbol interference (ISI)-suppressed optical multilevel modulation technique that is applicable to a wide range of binary and multilevel signaling is proposed. It employs binary phase-shift keying modulations that are generated by Mach-Zehnder intensity modulators as basic building blocks, and complex multilevel modulations are synthesized using interferometric addition and tandem modulations. Its feasibility and ISI suppression effect are verified in various binary and multilevel signal synthesis schemes using numerical simulations. Furthermore, the generation of ISI-suppressed zero-chirp binary and quaternary amplitude-shift keying modulations is experimentally demonstrated. Finally, its applicability to complex optical multilevel signaling is shown in the generation of a 40-Gb/s 16-level amplitude- and phase-shift keying signal, which results in 3-dB sensitivity improvement compared with the one using a conventional four-level electrical driving signal.

Bidirectional ROF Links Using Optically Up-Converted DPSK for Downstream and Remodulated OOK for Upstream

Abstract: We propose a novel radio-over-fiber system to provide full-duplex services by using optical differential phase-shift keying modulation format at the central station for downstream and on-off keying remodulation of the downlink carrier at the base station (BS) for upstream. The optical carrier suppression modulation scheme is employed to simultaneously generate and up-convert 40-GHz optical millimeter wave. As the same optical carrier is used for both uplink and downlink, no additional light source is required at the BS, which greatly reduces the cost and simplifies the overall system. Simulations and experimental results show that the bidirectional 2.5-Gb/s data is successfully transmitted over 40-km single-mode fiber (SMF-28) with less than 2-dB power penalty

A synopsis of modulation techniques for wireless infrared communication

Abstract: A number of modulation techniques have been proposed and thoroughly analysed in literature for optical wireless communication systems. Each modulation technique has its unique attractive features as well as its challenges. Some are very simple to implement and bandwidth efficient like the on-off keying (OOK). Pulse interval modulation (PIM) techniques are reputed for their inherent synchronisation pulse, subcarrier modulation offers increased throughput, resilience to the inter-symbol interference (ISI) and immunity against the fluorescent-light noise near DC, while pulse position modulation (PPM) provides the unparalleled power efficiency in line of sight (LOS) links but the performance degrades severely in dispersed communication channel. There has been an enormous work on the analysis of these and many more modulation techniques under different channel and environmental conditions; we however present here a concise synopsis of the mostly reported wireless infrared modulation techniques.

Phase-shift-keying and on-off-keying with improved performances using electroabsorption modulators with interferometric effects

Abstract: We present methods of optical modulation employing electroabsorption in an interferometric structure. The interferometric operation enables electroabsorption modulators for phase-shift keying and allows generation of on-off-keying signals with much improved extinction ratios. We demonstrate 40-Gb/s phase-shift-keying modulation, and up to 8.7 dB improvement in extinction ratio in 40-Gb/s on-off-keying modulation with 0.8V driving voltage using a commercial electroabsorption modulator. Methods of applying electroabsorption modulators for high spectral-efficiency formats generation are also proposed.

Transparent performance monitoring of RZ-DQPSK systems employing delay-tap sampling

Abstract: Feature Issue on Transmission in Optically Transparent Core NetworksThe emerging transparent optical networks, employing spectrally efficient modulation formats, require new methods for supervision of signal quality in order to maintain control over the transmission in all-optical domains. Optical performance monitoring of optical signal-to-noise ratio, chromatic dispersion, and polarization-mode dispersion in return-to-zero differential quadrature phase-shift keying signals is demonstrated using asynchronous delay-tap sampling and pattern recognition algorithms. Precise estimation of parameters over a broad range of impairment levels and good degradation isolation is shown by means of numerical simulation.

An EER Transmitter Architecture with Burst-Width Envelope Modulation based on Triangle-Wave Comparison PWM

Abstract: High efficiency transmitter architecture based on Kahn envelope elimination and restoration using PWM envelope modulation schemes is studied. At the final stage, it modulates a constant envelope radio frequency signal by on-off keying or "burst width modulation" directly with the PWM or delta-sigma modulated envelope signal without a lowpass filter. This paper shows that it is suitable to use a triangle-wave comparison PWM which has coherent spectrum peaks of spurious due to switching. It is derived from theoretical analysis that the minimum switching/sampling rate is required as five times high as the baseband bandwidth that is much less than that for the delta-sigma modulation. Simulation results show good modulation quality with the EVM less than 1 percent for raised cosine roll-off filtered 64 QAM.

Demonstration and Scalability Analysis of All-Optical Virtual Private Network in Multiple Passive Optical Networks Using ASK/FSK Format

Abstract: We present a scalable all-optical virtual private network (VPN) in a two-stage passive optical network (PON) architecture to connect optical network units (ONUs) in different sub-PONs. It provides efficient access and VPN service covering a wider area. The scheme employs amplitude-shift keying/frequency-shift keying (FSK) orthogonal modulation formats, which are used for the VPN and upstream traffic at 625 Mb/s and 5 Gb/s, respectively. At the optical line terminal side, a fiber Bragg grating reflects one of the two frequency components in the FSK signal back to the ONUs in a same VPN. Using a bidirectional amplifier, the power budget and the scalability of the network are significantly improved, as evidenced by numerical analysis using the parameters in the experiment.

Multi-channel differentially encoded phase shift keyed receivers

Abstract: An optical, multi-channel, Differential Phase Shift Keying (DPSK) receiver demodulates multiple Wavelength Division Multiplexed (WDM) channels using at least one interferometer This distributes expense of the interferometer(s) over all channels of an optical signal, allowing for deployment of cost-effective, scalable, wideband, WDM DPSK systems For example, for an 80 channel WDM link, the receiver uses a single interferometer instead of eighty interferometers and associated stabilization hardware, dramatically reducing size, weight, power, and cost The receiver is architecturally compatible with existing interferometer technologies so previous development and qualification efforts can be leveraged This allows for expedited technology insertion into existing optical communications networks, including terrestrial and space-based optical networks

Phase-Tunable Low-Loss, $S$ -, $C$ -, and $L$ -Band DPSK and DQPSK Demodulator

Abstract: Differential phase-shift keying (DPSK) and differential quadrature phase-shift keying (DQPSK) are touted as performers and reliable advanced modulation formats for next-generation optical transmission systems. One key device enabling such systems is the delay interferometer, converting the signal phase information into intensity modulation to be detected by the photodiodes. We developed an all-fiber delay-line interferometer for DPSK and DQPSK demodulation in the S-, C-, and L-band with low insertion loss, low-birefringence, and greater than 30 dB of extinction ratio over 100 nm and 20 dB from 1460 to 1640 nm in a single device. The device also features insensitivity to mechanical vibration, very low port imbalance (0.1 dB), and very low time delay between all outputs (0.1 ps). The device is highly reliable with a demonstrated failure-in-time rate of less than 100.

All-Optical NRZ-OOK to BPSK Format Conversion in an SOA-Based Nonlinear Polarization Switch

Abstract: All-optical format conversion from nonreturn-to-zero on-off keying to binary phase-shift keying is demonstrated in a semiconductor optical amplifier-based nonlinear polarization switch. This conversion is realized by cross-phase modulation effect for phase encoding and nonlinear polarization rotation effect for amplitude equalization. In the experiment, error-free operation at 10 Gb/s is achieved with a receiver sensitivity penalty of 1.3 dB after single-ended detection.

Digital over-the-air keying system

Abstract: A system for providing operational access to equipment or vehicles is disclosed wherein digital access codes are assigned and transported over-the-air governing a vehicle's or equipment's use. The access codes can be generated in connection with comparison of entered and stored biometric data and/or entered code from a keypad. Various security protocols can be used to ensure the secure dispatch and delivery of code information.

Differential Phase-Shift Keying Receiver Design Applied to Strong Optical Filtering

Abstract: We study, via simulation and experiments, the influence of the differential phase-shift keying decoder free spectral range (FSR) when strong optical filtering is considered for the nonreturn-to-zero and return-to-zero modulation formats and show that larger FSR can improve performance.

Optical differential phase shift keying receivers with multi-symbol decision feedback-based electro-optic front-end processing

Abstract: Novel differential-phase shift keying optical receivers are taught based on multi-symbol differential phase shift keying detection (DPSK) aided by decision feedback (DF) from the decision bits in earlier symbol intervals. In accordance with the invention, the DF is directed to an optical front-end comprising multiple Delay Interferometers (DIs) with multiple delays T, 2T, . . . , where T is the DPSK symbol duration. In one embodiment, the DF bitstream is applied to electronically switch the polarity of DI outputs prior to additive combination and hard detection. In other embodiments the DF is applied to active phase-shifting electrodes incorporated in the DIs. In additional embodiments the DF is applied to modified DI devices which not of the conventional Mach-Zehnder asymmetric two-arms type, but rather comprise either three or more arms with appropriate couplings, or two arms, one of which comprises a recirculating delay line with delay T. These embodiments comprise pairs of active phase-shifting electrodes to be activated by the DF. In other embodiments the teachings of this invention for DPSK with DF are combined with the amplitude-shift keying (ASK) modulation format, yielding improved Differential Phase Amplitude Shift Keying (DPASK) systems with decision feedback. The resulting receiver structures exhibit improved performance trade-offs between error-rate, transmission distance and bitrate, compared with conventional DPSK systems, yet are simpler to realize than prior art multi-symbol and/or DF-aided optical DPSK systems.

A Microtransceiver for UHF Proximity Links Including Mars Surface-to-Orbit Applications

Abstract: A low-volume low-mass low-power ultra-high-frequency radio transceiver for future planetary missions is described. The project targets a volume of less than 10 , mass of less than 50 grams, and power consumption of 50 mW on receive and 100 mW, 300 mW, or 3 W on transmit (for 10 mW, 100 mW, and 1 W output options). The transmitter design supports convolutionally coded binary phase-shift keying (BPSK), RC-BPSK, and quadrature phase-shift keying transmission from 1 to 256 kbps. Command/control instructions can be received at 2 or 8 kbps, with a sensitivity of better than 120 dBm. In addition to its low volume/mass/power features, temperature compensation to 100 C and radiation tolerance to 100 krad allow operation outside of thermally controlled, shielded enclosures, further reducing the mass and complexity of exploration vehicles. The design is described in a top-down format, beginning with system requirements and proceeding through digital modem algorithm development, discussion of the silicon-on-sapphire CMOS process used and elaboration of key blocks in the radio-frequency (RF) integrated circuit design. Techniques to address coupling between high-sensitivity RF and on-chip digital circuits are also presented, and test results are given for prototypes of all major functions. Although designed for the Martian environment, the transceiver is expected to be useful in other proximity links where a small low-power radio compatible with Prox-1 space-link protocols is desired.