Showing papers on "Keying published in 1995"

Unconventional cryptographic keying variable management

Abstract: We present three unconventional approaches to keying variable management. The first approach is based on using a public key cryptosystem (PKC) that is breakable in short, but on average less, time than it takes to set up an ultrawide bandwidth modem that is then used to transport a keying variable for a classical cryptosystem. The second concept proposes using the characteristics of an urban UHF radio channel, determined by mutual sounding, as the cryptovariable. The third concept encourages research into ill-conditioned problems as potentially fruitful ground for PKCs not based on finite field arithmetic. >

Data transmission from an implantable biotelemeter by load-shift keying using circuit configuration modulator

Abstract: Using the reflected impedance property of an inductive couple (transformer), a modulation method, load-shift keying using circuit configuration modulator (LSK-CCM), was developed to perform data transmission from an implantable telemeter. With a very simple circuit, this method utilizes a radio-frequency electromagnetic field induced with a single pair of coils to transmit power into the implant and data out of it. >

Real time video conferencing system and method with multilayer keying of multiple video images

Abstract: A video conferencing system and method that uses a central multimedia bridge to combine multimedia signals from a plurality of conference participants into a single composite signal for each participant. The system gives each conference participant the ability to customize their individual display of other participants, including keying in and out selected portions of the display and overlapping displayed images, and the ability to identify individual images in a composed video stream by click and drag operations or the like. The system uses a chain of video composing modules that can be extended as necessary to combine video signal streams from any number of conference participants in real time. Multimedia association software is provided for associating different media types to enhance display and manipulation capabilities for multimedia uses. The system also allows each user to dynamically change who can receive the information they provide to the conference.

Multi-function control switch for electrically operating devices

Abstract: A multi-function control switch for electrically operating devices, such as a lighting system, is disclosed. The multi-function control switch includes a rocker-type actuating arm for actuating a plurality of momentary switches. When actuated, the momentary switches send signals to an electronic operating module which houses a control logic circuit. The control logic circuit receives input keying sequences from the user, and interprets the input to determines whether the input keying sequence is associated with any of the command logic elements stored in its memory, and whether the system may validly switch from the current operating function to the new operating function. If the transition is valid, the control logic circuit signals the electronic operating module to execute the command logic element associated with the new operating function.

Performance evaluation of baseband OOK for wireless indoor infrared LAN's operating at 100 Mb/s

Abstract: We investigate 100 Mb/s wireless nondirectional infrared communication in the indoor environment using baseband nonreturn-to-zero (NRZ) on-off keying (OOK) modulation. We show that intersymbol interference induced by multipath propagation impairs detection efficiency. Analytical and simulation results on specific channels demonstrate that an adaptive decision-feedback equalizer adapted according to the least-mean-squares algorithm recovers most of the performance degradation. We also evaluate the performance of a timing-recovery phase-locked loop operating independent of the adaptive equalizer; showing that it quickly and accurately determines the sampling phase with negligible performance degradation. We discuss effective methods of mitigating low-frequency noise induced by fluorescent lighting. We present a packet-based communication method and describe its features and performance. Our results support the feasibility of communication at 100 Mb/s over the infrared channel. >

Quick connect coupling

Abstract: A coupling comprising a male and female half (11, 12) that are coupled together in axial alignment. A keying portion (13) is provided at one end of the male half (11) which has at least one keying element (14) with a bearing surface (20). The female half (12) has an opening (17) located on one side with recesses (18) therein shaped for location of the keying element (14). The opening (17) allows the keying portion (14) to engage the opening (17) in a direction that is transverse to the aligned axis. The recess (18) has abutment surfaces (21) against which the bearing surfaces (20) locate when the keying portion (14) is engaged within the recess (18). The bearing (20) and abutment (21) surfaces prevent separation of the coupling when placed under tension along the aligned axis. The invention provides a simplified means for connection of the coupling while at the same time allowing relative rotation between the male and female halves (11, 12).

Performance evaluation of direct-sequence spread spectrum multiple-access for indoor wireless communication in a Rician fading channel

Abstract: The bit error probability in a Rician fading channel is evaluated for indoor wireless communications considering direct-sequence spread spectrum multiple access (DS/SSMA) with differential phase shift keying (DPSK) modulation and two types of diversity: selection diversity and maximal ratio combining. The performance of the indoor radio system is also obtained in terms of outage probability and bandwidth efficiency. The analysis is done for a star-connected multiple access radio network. Furthermore the influence of three types of forward error correcting (FEC) codes namely, the (15,7) BCH code, the (7,4) Hamming code and the (23,12) Golay code, on the performance is studied. Computational results are presented for suitable values of Rician parameters in an indoor environment and using Gold codes as spread spectrum codes. >

Diversity combining considerations for incoherent frequency hopping multiple access systems

Abstract: This paper studies the problem of diversity combining for frequency hopped multiple access (FHMA) systems that operate in a mobile satellite environment characterized by frequency-nonselective Rician multipath fading. The modulation scheme considered is the incoherent M-ary frequency-shift keying (MFSK). The optimal diversity combining rule is derived under the assumptions that the number of active users (K) in the system is known, all users are chip (hop)-synchronous, and each user employs a random FH address. We suggest practical implementations that are close approximations of the optimal rule and examine the effects of various system parameters on the resulting receivers. The bit error probability performance is analyzed and numerical examples are provided. The effects of the diversity order (L), the signaling size (M) and unequal received powers are examined and related system design concerns such as system capacity and spectral efficiency are evaluated as well. >

Performance of coherent optical polarization shift keying modulation in the presence of phase noise

Abstract: The performance of optical coherent modulation schemes using the state of polarization of light as the modulating parameter (POLSK, POLarization Shift Keying) is analyzed, in the presence of laser phase noise. First, we compare three different analysis methods to account for the effects of phase noise in the binary case, and choose the one offering the best trade-off in terms of accuracy/complexity. Successively, we derive a tight upper bound to the performance of multilevel POLSK systems with postdetection filtering. Then, we include phase noise using the best method as tested in the binary case and extensively discuss the performance of binary and various multilevel POLSK constellations, optimized with respect to the IF filter bandwidth. The results show that binary POLSK has a very low sensitivity to phase noise and that multilevel POLSK is even less sensitive than the binary scheme. >

Method and apparatus for measuring idle channel quality in an RF frequency sharing environment

Abstract: A method of measuring idle channel quality which includes the steps of performing a first signal quality measurement (200), comparing the measurement to a threshold (202), and keying the channel (204) in response to the comparison (202) when the signal quality measurement exceeds the threshold. An apparatus for measuring idle channel quality comprising an antenna (116), a transmitter (110) coupled to the antenna (116), a receiver (110) in communication with the antenna (116), an idle channel measurement unit (112), and a channel allocator (102) in communication with the receiver and the transmitter (110). The channel allocator (102) receives channel measurements from the channel measurement unit (112) and keys an idle channel in response to a comparison between the channel measurements and a threshold when the signal quality measurement exceeds the threshold. In response to the keying, a CDPD system (14) stops transmitting on the channel.

Speech versus keying in command and control applications

Abstract: Experimental comparisons of speech and competitor input media such as keying have, taken overall, produced equivocal results: this has usually been attributed to "task-specific variables". Thus, it seems that there are some good, and some less good, situations for utilization of speech input. One application generally thought to be a success is small-vocabulary, isolated-word recognition for command and control. In a simulated command and control task, Poock purportedly showed a very significant superiority of speech over keying in terms of higher input speeds and lower error rates. This paper argues that the apparent superiority observed results from a methodological error—specifically that the verbose commands chosen suit the requirements of speech input but make little or no concession to the requirements of keying. We describe experiments modelled on those of Poock, but designed to overcome this putative flaw and to effect a fair comparison of the input media by using terse, abbreviated commands for the keying condition at least. Results of these new experiments reveal that speech input is 10.6% slower (although this difference is not statistically significant) and 360.4% more error-prone than keying, supporting our hypothesis that the methodology of the earlier work was flawed. However, simple extrapolation of our data for terse commands to the situation where keyed commands are entered in full suggests that other differences between our work and Poock's could play a part. Overall, we conclude that a fair comparison of input media requires an experimental design that explicitly attempts to minimize the so-called transaction cycle—the number of user actions necessary to elicit a system response—for each medium.

Video-Rate Z Keying: A New Method for Merging Images

Abstract: : Video-rate z keying is a new image keying method for merging real and synthetic images in real time. In visual media communication and display, it is often necessary to merge video signals from a real camera and a synthetic video produced by computer graphics. A standard technique for such a purpose is chroma keying which is used, for example, in TV weather reports. Chroma keying, however, simply puts real world objects in the foreground of the synthetic image, and cannot deal with situation where real and synthetic objects occlude each other. The z key method we present merges real and virtual world images in a more flexible way. The z key uses pixel-by-pixel depth information in the form of a depth map as a switch. For each pixel, the z key switch compares the pixel depth values of two images, and routes the color value of the foreground image that is nearer to the camera for the merged output image. The result of this pixel-by-pixel switching is that real and virtual objects can occlude each other correctly depending on their geometrical relationships. The critical capability for realizing such video-rate z keying is video-rate pixel-by-pixel depth mapping of a real scene. We have developed a video-rate stereo machine which can produce 200 x 200 depth images at video rate. With this machine, merging a real scene with a synthetic scene by means of z keying in real-time has been demonstrated; a real person walks around in a synthetic room with correct relationships with virtual objects in the room at the rate of 15 frames/sec.

Apparatus and method for a high throughput fiber-optic access network using code division multiple access

Abstract: A method and apparatus for implementation of a code division multiple access encoding scheme in a fiber-optic network. One preferred embodiment of the present invention provides an encoder and decoder for each terminal in the communications network, for example SONET OC-3, and allows each terminal to transmit their signals into the fiber-optic network at random. Because no time slot management is used, signals from all terminals interfere with one another. A coding technique is used by each decoder to sort its own signal out of this interference. The encoded data from each terminal is modulated with a technique known as MFSK (multiple frequency shift keying). The modulated signal is further used to intensity-modulate a semiconductor laser diode which may or may not be a single wavelength laser. At the receiver, the combined interference signal is first detected by a optical intensity detector and then sent to a frequency tone detectors which demodulate the MFSK signal. The output of the MFSK demodulator is then sent to a decoder where the original data bits are recovered. The network employs an optimum spread spectrum multiple access coding and modulation method that hops the subcarrier of a semiconductor laser diode over the entire range of DC -30 Ghz. Powerful concatenated Reed-Solomon outer, dual-K convolutional inner codes are used to minimize errors caused by mutual interference.

Channel-adaptive modulation

Abstract: Packet reservation multiple access (PRMA) assisted adaptive modulation using 1, 2 and 4 bit/symbol transmissions is proposed as an alternative to dynamic channel allocation (DCA) in order to maximise the number of users supported in a traffic cell. The cell is divided in three concentric rings and in the central high signal-to-noise ratio (SNR) region 16-level star quadrature amplitude modulation (16-StQAM) is used, in the first ring differential quaternary phase shift keying (DQPSK) is invoked, while in the outer ring differential phase shift keying (DPSK) is utilised. A channel SNR of about 7, 10 and 20 dB, respectively, was required in order to maintain a bit error ratio (BER) of about 1%, which can then be rendered error-free by the binary BCH error correction codes used. A 4.7 kbps algebraic code excited linear predictive (ACELP) speech codec is favoured, which is protected by a quad-class source-sensitivity matched BCH coding scheme, yielding a total bit rate of 8.4 kbps. A GSM-like voice activity detector (VAD) controls the PRMA-assisted adaptive system, which ensures a capacity improvement of a factor of 1.78 over PRMA-aided binary schemes.

Hybrid ppm‐cdma systems utilizing optical orthogonal codes for indoor wireless infrared communication

Abstract: An original hybrid pulse position modulation code division multiple access (PPM-CDMA) scheme is proposed and studied in the context of the indoor infrared communication network. The use of optical orthogonal codes (OOC) is proposed and original results are presented illustrating the improvement in bit rate achieved by utilizing PPM-CDMA rather than on/off keying (OOK) CDMA. Results are presented for the maximum number of users that can communicate over the network at a given bit rate and it is shown that there exists an optimum PPM order, at a given number of users, that maximizes the achievable bit rate. Original results are presented for the false-alarm errors due to the OOC cross correlations, and the optimum system operating parameters that minimize these errors are specified.

Information transmission by chaotizing

Abstract: The paper deals with the keying of information in spread spectrum signals by the use of chaotic systems. The chaotizer-dechaotizer concept (Bohme and Schwarz 1995) for continuous and discrete time systems is presented and investigated from a common point of view with respect to working conditions.

Method and apparatus for using Walsh shift keying in a spread spectrum communication system

Abstract: Method and apparatus for generating orthogonally encoded communication signals for communication system subscribers using multiple orthogonal functions for each orthogonal communication channel. Digital data symbols for signal recipients are M-ary modulated using at least two n-length orthogonal modulation symbols, which are generally Walsh functions normally used within the communication system. These symbols are provided by a modulation symbol selector (124) typically from one or more code generators (126, 128), and the modulation is such that M equals a product of a total number of orthogonal functions and the number used to generate individual modulation symbols. Each group of log M encoded data symbols from data processing elements (100, 102) are mapped into one modulation symbol using the modulation symbol selection element (124) according to their binary values. In some embodiments, a fast Hadamard transformer is used for symbol mapping. The resulting communication signals are demodulated by correlating them with the preselected number of orthogonal functions, in parallel, and demodulating the results into M energy values representing each orthogonal modulation symbol. The energy values are mapped into energy metric data using a dual maximum metric generation process. The correlation and demodulation can be accomplished using at least two sets of N correlators (142), N being the number of functions used, and applying correlated signals to one demodulator for each set of correlators (144). Each demodulator outputs M energy values representing each of the M mutually orthogonal modulation symbols, which are then combined into a single set of M energy values. In further configurations, coherent demodulators (172, 174) can be used to produce amplitude values for received signals which are then combined (178) with dual maximum metric results (170) to produce composite metric values for data symbols (178).

Hybrid DS/FH-CDMA system employing MT-FSK modulation for mobile radio

Abstract: This paper presents an analytical evaluation of a direct-sequence/frequency-hopped code division multiple access (DS/FH-CDMA) system employing non-coherent multiple tone frequency shift keying (MT-FSK) modulation in a Rayleigh fading environment. Multiple-tones per symbol rather than single tone per symbol (as in conventional MFSK) is used to provide diversity in a frequency selective channel. In the performance evaluations, multiple access interference (MAI) has been taken into account and the capacity for uncoded as well as convolutionally coded systems have been calculated.

Chromakey method and associated circuit arrangement

Abstract: A chromakey method and an associated circuit arrangement are intended for treating transition colors in color keying in which transition colors occur in video pictures, for example at the edges between foreground objects and the key color of the background of these objects. For the proposed treatment of the transition colors, inter alia the keying function (k) plays a decisive role. It indicates the key color component for each transition color. To define this keying function (k), parameters are applied to a computer (C), which parameters fix a key color (|KC|,θ,Φ), a transition color (Cb, Cr, Y) and a boundary region (α,β). In the color space, the boundary region separates the color of the foreground of a video picture from all other colors which may occur in the video picture. The keying function (k) is determined by way of the equation for the boundary.

The effect of pulse shaping and transmitter filter on the performance of FSK-DPD and CPM-DPD in satellite mobile channel

Abstract: This paper investigates how a bandlimiting transmitter filter and the shape of the frequency pulse effect the bit-error probability of frequency shift keying with differential phase detection in satellite mobile channel. Numerical results are presented for the case when the transmitter and receiver filters are Butterworth filters of order N/sub T/=4 and N/sub R/=3, respectively, and the frequency shaping pulse is rectangular or raised cosine. It is shown that in all cases of practical interest, continuous phase modulation (with raised cosine pulse shaping) gives a lower bit-error probability and requires less bandwidth than frequency-shift keying (with rectangular pulse shaping) when all other parameters (number of symbols, Rician factor of the channel, order of filters, etc.) are the same. >

Method of controlling the power of an induction motor

Abstract: To control the output from an induction motor with a main winding and an auxiliary winding with multiple taps, varying output stages of the motor are adjusted by the activation of the auxiliary winding or one of its part-windings. According to the invention, the coarse adjustment of the power to be output by the motor is effected by the selection of a certain output stage and a repeating digital m-bit keying pattern generated simultaneously for the purpose of fine adjustment, so that the motor is driven alternately at the set output stage and the next higher or next lower output stage as a function of the sequential logic values of the keying pattern. By means of the process complying with the invention, precise power control is possible which can be used to advantage for the adjustment of output. In addition, a device is described to carry out the process complying with the invention, according to which a microprocessor undertakes the coarse adjustment by way of a control circuit while simultaneously generating the m-bit keying pattern, which is stored in a ring counter, which itself directs the logic values of the keying pattern to the control circuit in succession.

Improved chromakeying system

Abstract: A chromakeying panel (20) for use in conjunction with a chromakeying system (10, 14, 50, 60) is disclosed (see figure). The panel (20) comprises a color pattern (40) having plurality of first locations bearing a first color within the color keying spectrum and a plurality of second locations bearing a second color within the color keying spectrum.

Method and apparatus for using on-off-keying using laser relaxation oscillation

Abstract: An optical communications system for transmission of optical signals using relaxation oscillation subcarrier, on-off keying modulation of the optical signals. Relaxation oscillation subcarrier on-off keying improves the signal-to-noise ratio of a receiver receiving the modulated optical signals and the data rate of the optical signal. A modulation device generates relaxation oscillations by pulsing a driving current for a transmitter between a first level below a threshold current and a second level above the threshold current. The optical communication system can further include a fiber optic link between the transmitter and the receiver. The optical communications system can further incorporate multiple frequency shift keying. The modulation device and modulation scheme can be used in all digital optical communications systems using a pulsed laser diode.

An efficient self-recovering adaptive algorithm for BPSK signals transmitted through underwater acoustic channels

Abstract: Proposes a receiver which performs fast self-recovering adaptive identification and equalization based on decision feedback equalization and reduced maximum likelihood sequence estimation. It runs on binary-phase-shift keying signals through underwater acoustic channels. Considerations for its implementation are discussed. Its performance is demonstrated both on experimental data from a long-range deep water channel and on simulated data from two discrete-time channels with severe amplitude distortion and additive white Gaussian noise.

Method for deciding simultaneous input of plural keys, and key input device

Abstract: PURPOSE: To improve operabilty and enables fast input by deciding each key, whose keying and time is later than the least keying start time, as a simultaneously pressed key, and then surely recognizing the keys when the keys are pressed at the same time. CONSTITUTION: General keys are composed of 15 keys 101-115 in a main key area 3A and special keys are composed of four keys 116-119 in a control key area 3B and three keys 120-122 in a subordinate key area 3C. When plural keys are pressed, the keying start time when each key is pressed and the keying end time when the key is released are detected and each key whose keying end time is later than the keying start time of the key which is pressed most lately is decided as a key which is pressed at the same time. Consequently, if one of plural keys is mispressed, a correct key is pressed after only the wrong key is released, and then the key is not decided as a simultaneously inputted key, thereby easily correcting the key input.

Multidimensional frame synchronisation strategy for 4D-Q2PSK

Abstract: A novel multidimensional double complex correlation frame synchronisation strategy is proposed for the four-dimensional quadrature-quadrature phase-shift keying modulation technique. The synchronisation method is intended for application in high speed spectrally efficient burst mode mobile digital communications.

A performance analysis of coherently demodulated PSK using a digital phase estimate in frequency hopped systems

Abstract: Most existing frequency hopping AJ systems utilize a non-coherent waveform such as differential phase shift keying (DPSK) or frequency shift keying (FSK). This choice is based on a trade-off between the efficiency of the waveform and the difficulties entailed in reestablishing a phase reference at the beginning of every hop. An alternative technique that is being explored for several planned systems is the use of reference symbols combined with coherent demodulation. If several reference symbols of known phase are sent during each hop then the receiver can establish the absolute carrier phase and perform coherent demodulation. This paper explores the performance of frequency hopped systems utilizing reference symbols with a PSK waveform in both a benign and stressed environment. The results indicate that if as few as 10 reference symbols/hop are used that near coherent performance is obtained. Furthermore, the use of reference symbols yielded performance better than that obtained by differential encoding and non-coherent detection for all cases considered.

Double electronic game machine

Abstract: PURPOSE:To provide a device which helps a player enjoy a game on a large screen even if the game machine is small CONSTITUTION:A game program stored in a sub memory 13 of a small game machine 6 is run by operating a key 7 and the process thereof is displayed by LCD8 The game program stored in the sub memory 13 is stored in a main memory of a double game machine through buffers 12, 11 and run by keying operation of a keyboard 2 and the process of the game is displayed on a large screen like CRT3

Multi-key pressing high-speed Chinese character input method and keyboard

Abstract: A kind of multi-key keying simultaneously high speed Chinese character input method and the keyboard thereof are that on the 24-key key board there are symmetrically located 12 keys on left and right sides separately to represent the key of initial constant (or key combination) and vovel (or key combination) of the Chinese syllable of the Chinese phonetic Alphabet. By multi-key keying simultaneously the initial constant key and volvel key (or key combination) to translate the character by one hand then said Chinese character input is implemented. Once double hands multikey keying simultaneously can input two Chinese characters syllables, so the input time is greatly shortened and input speed is double the speed of existent input method.

Differential phase shift keying modulation and demodulation device

Abstract: PURPOSE:To accurately demodulate data by eliminating a phase error due to an intermediate frequency component in the differential phase shift keying modulation and demodulation device. CONSTITUTION:A transmitter S uses a differential coder 2a to apply differential coding to a 1st data series 1 to be sent to generate a 2nd data series, a differential coder 2b applies differential coding to the 2nd data series, applies BPSK modulation to a 3rd data series, executes frequency conversion and power amplification and the result is sent from a transmission antenna 7. A receiver S applies power amplification and frequency conversion to the signal received by a reception antenna 8 and a differential decoding section 11a applies differential decoding to the signal to generate a 4th data series and a differential decoding section 11b applies differential decoding again to the 4th data series. Thus, a phase error due to intermediate frequency component included in the 4th data series is cancelled to obtain the 1st data series.