Showing papers on "Keying published in 1999"

M-PSK and M-QAM BER computation using signal-space concepts

Abstract: In this paper, we introduce a simple geometric approach that is based on signal-space concepts to efficiently evaluate the performance of M-ary phase-shift keying (M-PSK) and M-ary quadrature amplitude modulation (M-QAM) schemes over an additive white Gaussian noise channel. In particular, new bit error rate approximations are derived and shown to be in excellent agreement with Monte Carlo simulation results.

Method and apparatus for secure content delivery over broadband access networks

Abstract: A system for secure delivery of on-demand content over broadband access networks utilizes a pair of servers and security mechanisms to prevent client processes from accessing and executing content without authorization. A plurality of encrypted titles are stored on a content server coupled to the network. An access server also coupled to the network contains the network addresses of the titles and various keying and authorization data necessary to decrypt and execute a title. A client application executing on a user's local computer system is required to retrieve the address, keying and authorization data from the access server before retrieving a title from the content server and enabling execution of the title on a user's local computer system.

Demonstration of return-to-zero signaling in both OOK and DPSK formats to improve receiver sensitivity in an optically preamplified receiver

Abstract: Summary form only given. We demonstrate record receiver sensitivities at 1O Gb/s using RZ signaling and optimization of the optical filter bandwidths (for a Fabry-Perot optical filter and fixed 10 GHz electrical filter bandwidth). Two different modulation formats are considered: on-off keying (OOK) and differential phase shift keying (DPSK). To the best of our knowledge, this is the first demonstration of encoding phase information on RZ optical pulses to be subsequently decoded in a DPSK demodulator, and as such we christen the term RZDPSK to describe this format. Direct comparison with NRZ signaling and constant intensity DPSK reveals an improvement of about 1 dB in receiver sensitivity.

Analysis of hybrid selection/maximal-ratio combining of diversity branches with unequal SNR in Rayleigh fading

Abstract: The performance of a hybrid selection/maximal-ratio combining (H-S/MRC) diversity system in multipath fading environment is analyzed. With H-S/MRC, L out of N diversity branches are selected and combined using maximal-ratio combining (MRC). This technique provides improved performance over L branch MRC when additional diversity is available, without requiring additional resources (i.e., power consumption, RF electronics). In particular, we consider independent Rayleigh fading on each diversity branch without assuming equal signal-to-noise ratio (SNR) averaged over the fading. We analyze this system using a "virtual branch" technique which results in a simple derivation and formula for the mean of the combiner output SNR for any L and N. We further obtain the symbol error probability (SEP) for coherent reception of M-ary phase-shift keying (MPSK) and quadrature amplitude modulation (MQAM).

DS-CDMA chip waveform design for minimal interference under bandwidth, phase, and envelope constraints

Abstract: This paper investigates the effect of chip waveform shaping on the error performance, bandwidth confinement, phase continuity, and envelope uniformity in direct-sequence code-division multiple-access communication systems employing offset quadrature modulation formats. An optimal design methodology is developed for the problem of minimizing the multiple-access interference power under various desirable signal constraints, including limited 99% and 99.9% power bandwidth occupancies, continuous signal phase, and near-constant envelope. The methodology is based on the use of prolate spheroidal wave functions to obtain a reduced-dimension discrete constrained optimization problem formulation. Numerous design examples are discussed to compare the performance achieved by the optimally-designed chip waveforms with other conventional schemes, such as offset quadrature phase-shift keying, minimum-shift keying (MSK), sinusoidal frequency-shift keying (SFSK), and time-domain raised-cosine pulses. In general, it is found that while the optimized chip pulses achieved substantial gains when no envelope constraints were imposed, these gains vanish when a low envelope fluctuation constraint was introduced. In particular, it is also shown that MSK is quasi-optimal with regard to the 99% bandwidth measure, while the raised-cosine pulse is equally good with both the 99% and 99.9% measures, but at the expense of some envelope variation. On the other hand, SFSK is quasi-optimal with regard to the 99.9% bandwidth occupancy, among the class of constant-to-low envelope variation pulses.

Modified chroma keyed technique for simple shape coding for digital video

Abstract: An efficient chroma key-based coding technique for digital video with an optimized switching threshold. An optimized binary keying threshold (T) is provided for switching between a first image region (such as a background region) (B) and second image region (such as a foreground object) (A) video picture. The threshold optimizes a PSNR of a quantization error Q of a key color K. A chroma key technique is also provided for representing the shape of a video object, where the shape information (alpha plane) of a foreground object is embedded in the keyed output, so there is no need to carry an explicit alpha plane, or use alpha plane coding. The chroma key shape representation technique provides a smooth transition at the boundary (500, 505) between objects without the need for special switching patterns, such as a general gray scale shape coding tool, or post-processing, e.g., using feathering filters.

Quantum detection and mutual information for QAM and PSK signals

Abstract: We analyze the performance of the error probability and the mutual information for quadrature amplitude modulation (QAM) and phase-shift keying systems based on quantum detection theory. It is shown that the quantum receiver called square root measurement gives about 5.7 dB improvement in power in comparison with the classical one. Furthermore, we show that the quantum QAM system can achieve the same reliability as the conventional intensity modulation-direct detection (IM-DD) system with almost equal power, compressing the required bandwidth, while the reliability is degraded in general.

Distributed detection for diversity reception of fading signals in noise

Abstract: A multiple-antenna diversity scheme is investigated for digital communications. Antenna observations are immediately quantized and sent to a fusion center. At the fusion center, the quantized observations are combined to form a final decision on which symbol was transmitted. The optimum reception scheme is described for the case where frequency-shift keying is employed and where slow Rayleigh fading and Gaussian additive noise are present. Two cases are studied. In the first case, an accurate estimate of the signal-to-noise ratio is available at each receiver. In the second case, estimates are not available. Results indicate that two- or three-bit quantizations may be most appropriate. Further, if binary decisions are made at each antenna, the performance may not improve if an estimate of the signal-to-noise ratio is available at each antenna or if two antennas are used instead of one.

Bit rate agile third-generation wireless CDMA, GSM, TDMA and OFDM system

Abstract: Systems, apparatus, and methods for new generations of wireless systems, including multiple standard, interoperable Third-Generation (3G) and Second-Generation (2G), Spread Spectrum CDMA, WCDMA, GSM, Enhanced GSM systems and CSMA, TDMA and OFDM. Bit Rate Agile (BRA), Modulation and Code Selectable processing techniques of Gaussian Minimum Shiftl Keying (GMSK), Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (QAM), and of Mis-Matched demodulator filters in which the demodulator filter set is mis-matched to the filter set of the signal modulator.

Real-time control of a servosystem using the inverter-fed power lines to communicate sensor feedback

Abstract: It is shown that the pulsewidth modulation inverter-fed power line is a feasible medium for the transmission of modulated digital information at data rates of over 40 kb/s and that this transmission path provides a suitable alternative to the sensor cabling between the actuator and the controller of an encoder-based servosystem. The encoder data is modulated and transmitted from the actuator to the controller, over the inverter-fed power cable. The data is modulated using frequency-shift keying, based on a center frequency of 5 MHz. Specialized magnetics design techniques are outlined for the coupling and decoupling circuits which transfer the modulated digital information to and from the power lines. A software observer is employed to improve the velocity derived from the received position information, and this velocity is used in the motion control algorithm to generate a reference torque signal for the controller.

On the effect of cochannel interference on average error rates in Nakagami-fading channels

Abstract: The effect of cochannel interference on the performance of digital mobile radio systems in a Nakagami-fading channel is studied. Closed-form expressions are derived for the average probability of error of both coherent and noncoherent (differentially coherent) binary frequency shift keying and phase-shift keying schemes in an interference-limited system. The analysis assumes an arbitrary number of independent and identically distributed Nakagami interferers. The effect of maximal ratio combining diversity is also examined.

Energy optimal codes for wireless communications

Abstract: Source coding and channel coding algorithms minimizing the battery power needed for RF transmission are presented. Digital RF transmitters in portable devices using on/off keying modulation consume energy only when high bits are sent and virtually no energy is consumed when low bits are sent. Therefore, energy consumption can be minimized by devising codes that minimize the occurrence of high bits in transmitting information. In this paper, we first formulate the minimum energy coding problem for RF transmission. We then derive the energy optimal source coding algorithm from the source statistics. Finally, we combine this energy optimal source coding algorithm with Hamming codes for energy efficient error recovery. Overall, we take a first step towards a novel energy saving wireless communication protocol.

Performance Evaluation and Interpretation of Unfiltered Feher-Patented Quadrature-Phase-Shift Keying (FQPSK)

Abstract: A new interpretation of unfiltered Feher-patented quadrature-phase-shift keying (FQPSK) is presented that readily identifies a means for spectral enhancement of the transmitted waveform as well as an improved method of reception. The key to these successes is the replacement of the half-symbol-by-half-symbol mapping originally used to describe FQPSK by a symbol-by-symbol mapping operation combined with memory. The advantages of such an interpretation are twofold. In particular, the original FQPSK scheme can be modified such that the potential of a waveform slope discontinuity at the boundary between half symbols is avoided without sacrificing the “constant” envelope property of the transmitted waveform, and, furthermore, a memory receiver can be employed to improve error-probability performance relative to previously proposed symbol-by-symbol detection methods. The analysis presented in this article does not include other versions of FQPSK such as FQPSK-B, which currently is being considered for military application.

Software chroma keying in an immersive virtual environment

Abstract: This paper presents a very fast software chroma keying algorithm, requiring at most five integer operations per pixel. An improvement of more than 300% in performance over HLS based algorithms was achieved. The algorithm has been developed for use in an immersive virtual environment, which is also described here.

Optical wireless communication using digital pulse interval modulation

Abstract: This paper presents a study of digital pulse interval modulation (DPIM) as a candidate modulation scheme for optical wireless communications. DPIM code characteristics are discussed and the theoretical error probability performance of DPIM is analyzed in terms of the packet error rate. Performance comparisons are made with the more established techniques of on-off keying and pulse position modulation (PPM). We show that, for a simple threshold detector based receiver, DPIM can out perform PPM in terms of bandwidth efficiency and power efficiency, by taking advantage of its inherent variable symbol duration. Practical results are given for an experimental system in the form of eye diagrams. The use of a coding scheme with a non-uniform symbol duration does have implications for system design, which are discussed in the paper.

Random access in a mobile telecommunications system

Abstract: For one embodiment, a Random Access Channel (RACH) preamble modulation method and apparatus are disclosed in which the real and imaginary components of a complex RACH preamble are filtered in corresponding pulse shaping filters. Consequently, the phase transitions in the resulting signal are limited at all chip positions, and the resulting quadriphase codes produce transmitted signals with lower Peak-to-Average Power Ratios (PAPRs) than those that result using conventional Hybrid Phase-Shift Keying (HPSK) modulation schemes. On the other side, the resulting quadriphase synchronization code retains the same aperiodic autocorrelation magnitude as the original binary code, optimized to produce the minimum probability of incorrect synchronization.

Differential binary phase-shift keying transmission using cascaded semiconductor optical amplifiers

Abstract: Recently the performance of Semiconductor Optical Amplifiers (SOA) in 1.3/spl mu/n fiber communication systems has been intensively studied and a 10 Gbit/s RZ - transmission over 500 km has been demonstrated in the field and over 1500 km in a re-circulating fiber loop set up using MQW-SOA. It turned out that the performance of such systems is primarily limited by three factors: the fast growth of Amplified Spontaneous Emission (ASE), the pattern effect and the nonlinear impulse-phase distortions in SOA which are caused by the low saturation energy of SOA, the gain recovery time comparable with the bit period and by the strong nonlinearity of SOA. The effects are also important in other systems where cascaded SOA are used, for example, as optical gates. With increasing bit rate in TDM systems and with number of channels in WDM, the effects became stronger and the maximum propagation distances decrease. So in the case of a 4/spl times/10 Gbit/s WDM system a 80 km transmission has been experimentally demonstrated and up to 200 km predicted from numerical simulations. The limiting effects and consequently the performance are similar in systems with both NRZ or RZ modulation formats. But using other modulation formats like Phase Shift Keying (PSK) or Frequency-Shift Keying (FSK), where the signal power is constant, it would be possible to avoid these specific for SOA, harmful effects and to approach the performance in the 1.5 /spl mu/m window. In this paper we present the results on a single channel 10 Gbit/s Differential Binary PSK - Direct Detection (DBPSK-DD) transmission in a 1.3 /spl mu/m system with in-line MQW-SOA amplifiers. The format has been chosen because of simplicity of the transmitter and receiver designs.

A wireless internet access method and system

Abstract: A wireless Internet access system (100) and method supports the transmission and reception of multiple types of traffic between mobile subscriber units (105, 106) and existing networks (120). A frame structure is used that can support the transmission of multiple types of traffic and adapt to changes in the traffic types needed and the amount of data for a particular traffic type. In addition, data transmission is performed using orthogonal frequency division multiplexing and differential phase shift keying to avoid inter-symbol interference. Receiving units in the mobile subscriber units (105, 106) and existing networks (120) include antenna arrays to provide a multipath transmission.

An FPGA receiver for CPSK spread spectrum signaling

Abstract: In this paper, we present the design, implementation and testing of an M-ary direct sequence spread spectrum receiver suitable for wireless home networking applications. The receiver employs a novel code-phase-shift keying (CPSK) signaling scheme, in which each of the M signaling waveforms is derived from a different phase shift of a single pseudonoise code sequence. The receiver consists of an IF demodulator and a CPSK baseband decoder, implemented using discrete components and an FPGA (field programmable gate array) chip, respectively. A modified double-dwell serial search scheme is used for code acquisition and tracking, and the carrier-phase synchronization is solved by a Costas loop in the IF demodulator and a double threshold detection scheme in the CPSK decoder. Measurements of receiver performance are presented and compared with theoretical calculations.

Unequal power allocation to the turbo-encoder output bits with application to CDMA systems

Abstract: Traditional turbo-codes with binary phase-shift keying modulation assign equal noise margins to the turbo-encoder output bits. It is shown that by using unequal power allocation (UPA) among the encoder output streams, one can improve the code performance especially for large block lengths. On the other hand, there has been a growing interest in the application of turbo-codes for signaling over a code-division multiple-access (CDMA) channel. A usual practice in CDMA systems for matching of rate is based on repeating the encoder output bits. This feature can be used to provide UPA with a negligible increase in the complexity. Simulation results are presented showing a noticeable improvement in the bit error rate performance.

Miter joint keying system

Abstract: A keying system for a miter joint with a work holder for engaging the outer surfaces of the boards when assembled. A flat planar tool guide is fixed to the work holder and has a slot that receives and guides a router tool to cut a slot through both boards triangularly shaped in its longitudinal direction and shaped in cross section as the cutting tool. Keys having a shape complementary to the slots in both directions are fixed in the slots to both decorate and support the joint.

A method for executing an application without being installed

Abstract: not available for EP1131934Abstract of corresponding document: WO0030323A system for secure delivery of on-demand content over broadband access networks utilizes a pair of servers and security mechanisms to prevent client processes from accessing and executing content without authorization. A plurality of encrypted titles are stored on a content server coupled to the network. An access server also coupled to the network contains the network addresses of the titles and various keying and authorization data necessary to decrypt and execute a title. A client application executing on a user's local computer system is required to retrieve the address, keying and authorization data from the access server before retrieving a title from the content server and enabling execution of the title on a user's local computer system.

A systematic approach to the design and analysis of optimum DPSK receivers for generalized diversity communications over Rayleigh fading channels

Abstract: A generalized diversity channel is introduced that models a variety of wireless communication systems that use time, frequency, multipath, and/or antenna diversity with various interbranch correlations between signaling waveforms and the fading and additive noise processes. In the context of this general model, a systematic approach to the design and analysis of optimum noncoherent differential phase-shift keying (DPSK) receivers is introduced. In particular, it is shown how the minimum error probability (MEP) and the generalized likelihood ratio tests (GLRT) can be applied to obtain optimal noncoherent combining rules. A comparative error-rate analysis of the GLRT and MEP detectors and an ad hoc equal-gain combiner is provided for binary signaling, and the suitability of the three schemes is determined as a function of fading characteristics. The asymptotic bit-error-rate analysis is undertaken for the MEP detector for slow and fast fading channels. An estimator-detector decomposition of the noncoherent MEP rule is obtained which allows an insightful comparative study of the fundamental limits of binary phase-shift keying and DPSK modulation-detection methods for both slow and fast fading. The results of this paper are also applicable to postdecorrelative receivers in multiuser channels.

Construct‐oriented Biodata Development for Selection to a Differentiated Performance Domain

Abstract: This study describes the development of a multidimensional biodata form which used explicit constructs to guide item generation and rational scale development, construct validation, criterion measurement and empirical keying. These constructs were goal-orientation, teamwork, customer service, resourcefulness, learning ability and leadership. Exploratory and confirmatory factor analyses in both applicant and incumbent samples were used to identify and test the model which included the thirteen, more differentiated rational scales relating to these six, broader constructs. Empirical keying of the rationally developed scales was conducted against criterion construct scales conceptually related to each predictor construct. Empirical keying at the item level was found to result in higher validities and cross-validities than either empirical keying at the scale level, or rational keying. The item keyed instrument also demonstrated incremental validity over a test of cognitive ability for specific work performance domains as well as overall work performance.

Device and method for generating spreading code and spreading channel signals using spreading code in cdma communication system

Abstract: A spreading code generating device for a Code Division Multiple Access (CDMA) communication system is disclosed. The device comprises a PN (Pseudo-random Noise) code sequence generator for generating PNi and PNq sequences; an orthogonal code generator for generating first and second orthogonal codes (OC1, OC2) which perform Differential Phase Shift Keying (DPSK) state transitions at intervals of at least two chips; and a spreading code generator for generating spreading codes Ci and Cq by mixing the PNi and PNq code sequences with the first and second orthogonal codes (OC1, OC2) such that a present phase of the spreading codes Ci and Cq alternately makes Quadrature Phase Shift Keying (QPSK) and DPSK state transitions with respect to a previous phase of the spreading codes Ci and Cq.

Reduction of backscattering-induced noise by ternary phase shift keying in resonator micro-optic gyro integrated on silica planar lightwave circuit

Abstract: The authors propose a method that uses ternary phase shift keying modulation to eliminate backscattering-induced noise in a resonator micro-optic gyro (R-MOG) integrated onto a silica planar lightwave circuit (PLC). Ternary modulation overcomes limitations on the degree of elimination possible caused by the narrow bandwidth of the thermo-optic phase modulator on PLC, the bandwidth of which is limited to 1 kHz.

RZ-Gaussian pulses reduce the receiver complexity in wireless infrared links at high bit rates

Abstract: The authors conclude that the on-off keying (OOK) format with return-to-zero Gaussian (RZ-Gaussian) pulses provides better performance than other signalling formats, more frequently proposed in reported works, allowing the adoption of a low-complexity receiver, and obviating the need for baseline restoration and equaliser filters. The above conclusion is validated by the corresponding bit error rate (BER) computation.

Wavelength shift keying technique to reduce four-wave mixing crosstalk in WDM

Abstract: In low dispersion fibers, FWM spectrum is symmetric around the zero dispersion point Wavelength shift keying technique using symmetric wavelengths and balanced detection can cancel FWM crosstalk to first order

Secure digital communications by means of stochastic process shift keying

Abstract: A digital communications keying concept that applies stochastic processes rather than deterministic waveforms is introduced and demonstrated. The technique implies a higher degree of security that conventional digital communications systems, reducing the risk of eavesdropping. The resulting receivers are non-coherent, and simpler than those of spread spectrum and chaotic encoders.