Showing papers on "Keying published in 2000"

Differential unitary space-time modulation

Abstract: We present a framework for differential modulation with multiple antennas across a continuously fading channel, where neither the transmitter nor the receiver knows the fading coefficients. The framework can be seen as a natural extension of standard differential phase-shift keying commonly used in single-antenna unknown-channel systems. We show how our differential framework links the unknown-channel system with a known-channel system, and we develop performance design criteria. As a special ease, we introduce a class of diagonal signals where only one antenna is active at any time, and demonstrate how these signals may be used to achieve full transmitter diversity and low probability of error.

Digital Modulation Techniques

Abstract: Baseband modulation frequency shift keying phase shift keying minimum shift keying continuous phase modulation multi-H phase shift keying quadrature amplitude modulation other nonconstant envelope modulations multicarrier modulation spread spectrum modulation coded modulation applications in baseband data communications applications in wired telephony applications in wireless mobile communications applications in fixed terrestrial microwave links applications in satellite links.

Sheet fed printer for a hand held terminal

Abstract: A hand held terminal has a display, a keying input, a printer, a processor for receiving information from the keying input and for directing information onto the display and to the printer and a housing for the keying input, display and processor. The printer is directly mechanically connected to the housing and the printer is a sheet fed printer.

Platform and method of creating a secure boot that enforces proper user authentication and enforces hardware configurations

Abstract: In general, a method of securely transmitting data features an operation of authenticating a user of a platform during a Basic Input/Output System (BIOS) boot process. In response to authenticating the user, a first keying material is released from a token communicatively coupled to the platform. The first keying material is combined with a second keying material internally stored within the platform in order to produce a combination key. This combination key is used to decrypt a second BIOS area to recover a second segment of BIOS code.

Comparison of DPSK and MSK bit error rates for K and Rayleigh-lognormal fading distributions

Abstract: The composite Rayleigh-lognormal distribution is mathematically intractable for the analytical evaluation of such a communication system performance metric as bit error rate. The composite K distribution closely approximates the Rayleigh-lognormal and is potentially useful for analytical manipulations. In this contribution we derive the bit error rates of differential phase-shift keying (DPSK) and minimum shift keying (MSK), in manageable closed forms, for the K distribution model of multipath fading and shadow fading, and show, numerically, the close agreement between these results and those based on the Rayleigh-lognormal distribution.

Electrical connector having circuit boards and keying for different types of circuit boards

Abstract: An electrical connector includes a housing ( 12 ) that carries a plurality of circuit boards ( 13 ) in a parallel, spaced-apart array. The circuit boards are of two different types. One type has a keying recess ( 60 ) that is keyed to a land ( 39 ) in the housing, and the other type has a keying recess ( 62 ) that is keyed to a web ( 40 ) in the housing.

Advanced frequency hopping modulation for spread spectrum WLAN

Abstract: A wireless LAN standard developed by IEEE committee P802.11 operates in the unlicensed 2.4 GHz ISM band. This band is a very hostile environment due to many unpredictable interference sources, such as microwave ovens, utilizing the same frequency bands. At the same time the allowed signal power density that can be used is limited in order to minimize the interference to other users in the same band. In order to avoid these interference and keep a low signal power density the standard supports both direct sequence (DS) and frequency hopping (FH) modulation for these applications. The new test beds for multimedia wireless (WLANs) also use FH modulation. We analyze the performance of a modification of the FH multiple frequency shift keying (MFSK) system that includes a multitone multiamplitude MFSK signal, designated as amMFSK modulation. In this case, in order to meet the transmitted power density limits imposed in the ISM band, the signal energy is split into m separate tones. This makes the system more vulnerable to noise and fading, but still the overall flow of useful information will be increased. The results demonstrate that under the large range of the signal, channel and interference parameters this system offers better performance.

Optimal transmission ranges and code rates for frequency-hop packet radio networks

Abstract: We consider a frequency-hopping multihop packet radio network using M-ary frequency-shift keying modulation in a Rayleigh fading environment. Each node transmits packets using an extended (n, k) Reed-Solomon code and the slotted ALOHA channel access protocol. For this network, we determine the optimum transmission range, optimum code rate, and optimum slotted ALOHA transmission probability to be used by each node in the network. Tradeoffs in choosing the transmission range and code rate, and the spectral efficiency of the network are captured in a new performance measure, information efficiency, which is analogous to expected forward progress. Maximizing the information efficiency yields the optimum desired network parameters.

Segmentation with invisible keying signal

Abstract: Chroma keying is the process of segmenting objects from images and video using color cues. A blue (or green) screen placed behind an object during recording is used in special effects and in virtual studios. The blue color is later replaced by a different background. A new method for automatic keying using invisible signal is presented. The advantages of the new approach over conventional chroma keying include: (i) Unlimited color range for foreground objects. (ii) No foreground contamination by background color. (iii) Better performance in non uniform illumination. (iv) Features for generating refraction and reflection of dynamic objects. The method can be used in real-time and no user assistance is required. New design of Catadioptric camera and a single chip sensor for keying is also presented.

Frequency-hopped multiple-access communications with multicarrier on-off keying in Rayleigh fading channels

Abstract: We propose the multicarrier on-off keying (MC-OOK) as a bandwidth-efficient modulation method for frequency-hopped multiple-access (FHMA) communications The motivation for using MC-OOK is that a more bandwidth-efficient modulation scheme allows a larger number of frequency slots, and thus provides a higher immunity against multiple-access interference in FHMA systems We analyze the average bit-error probability in slow frequency-nonselective Rayleigh fading channels with background noise We find that the capacity gain that MC-OOK/FHMA system provides over the MFSK/FHMA system in an interference-limited region is more than 25 when the modulation alphabet size M is 8, and even a higher capacity gain can be obtained with a larger M

Optimal detection of differential chaos shift keying

Abstract: Recent advances in the development of communication schemes based on chaos suggest that differential chaos shift keying (DCSK) is one of the most promising candidates for a feasible implementation. Traditionally, the demodulation-decoding of DCSK has been achieved by means of a noncoherent approach based on a correlation detector This approach in general works fur any differential noise shift keying out of which DCSK is a subclass, i.e., it does not exploit the chaotic dynamics involved. In this paper it is shown that the simple correlation detector can be augmented by information based on the chaotic dynamics to improve the performance, yielding a statistically optimal detection. Introducing a rigorous probabilistic framework, the optimal receiver for additive white Gaussian noise is derived, and it is shown that it decomposes into a part based an correlation and a part based on the chaotic dynamics.

Digital pulse interval modulation for IR communication systems a review

Abstract: This paper presents a brief review of infrared communications systems, modulation techniques and in particular, a digital pulse modulation scheme known as digital pulse interval modulation (DPIM) for infrared (IR) communication systems employing intensity modulation with direct detection (IM/DD). DPIM code characteristics, power spectral density and error probability in terms of the packet error rate are discussed. Performance comparison is made with that of on–off keying (OOK) and pulse position modulation (PPM). For comparison, relevant expressions for both OOK and PPM are also presented. Using a threshold-detector-based receiver, we show that DPIM outperforms both OOK and PPM in terms of power efficiency and PPM in terms of bandwidth efficiency, by taking advantage of its inherent variable symbol duration. However, using a maximum-a posteriori (MAP) detector it provides marginally inferior error rate performance compared with PPM.

Decision directed phase locked loop (DD-PLL) for use with short block codes in digital communication systems

Abstract: An improved digital decision directed phase locked loop (DD-PLL) for use with short block codes using phase shifting keying (PSK) modulation. The improvement involves a conventional digital phase lock loop which is modified to base its loop corrections on the results obtained by decoding the short block code rather than on a symbol by symbol basis as is customary in conventional DD-PLLs. The improved method of loop corrections involves retaining the symbol data pending the decoder's decision, derotating the retained data in accordance with the decoded result, and integrating the derotated data to form a composite estimator upon which to base the loop correction. In its preferred embodiment, the invention uses an (8, 4) biorthogonal code with quatenary PSK.

Further analytical results on the joint detection of cochannel signals using diversity arrays

Abstract: We derive a fully analytical expression for the union bound on symbol-error rate for the joint detection of several cochannel fading signals using a diversity antenna array, putting numerical results previously published on a firm analytical base. We prove that with pilot-based multiuser channel estimation, any number of users can enjoy diversity order equal to the number of antennas, and we quantify the performance penalty relative to single-user binary phase-shift keying as a function of number of users, constellation density, and number of antennas. We also demonstrate the interdependence of all users participating in the detection process.

Frequency-Hopped Multiple-Access Communications with Multicarrier On-Off Keying in

Abstract: We propose the multicarrier on-off keying (MC-OOK) as a bandwidth-efficient modulation method for frequency-hopped multiple-access (FHMA) communications. The motivation for using MC-OOK is that a more bandwidth-efficient modulation scheme allows a larger number of frequency slots, and thus provides a higher immunity against multiple-access interference in FHMA systems. We analyze the average bit-error probability in slow frequency-nonselective Rayleigh fading chan- nels with background noise. We find that the capacity gain that MC-OOK/FHMA system provides over MFSK/FHMA system in an interference-limited region is more than 2.5 when the modulation alphabet size is 8, and even a higher capacity gain can be obtained with a larger .

Error probability of binary NFSK and DPSK with postdetection combining over correlated Rician channels

Abstract: For binary noncoherent orthogonal frequency-shift keying and binary differential phase-shift keying over slow nonselective Rician fading channels having arbitrarily correlated branches and unequal branch powers, a closed-form expression for the symbol-error probability in the case of postdetection equal-gain combining is obtained directly from the characteristic function of the decision variable.

Full-duplex optical communication system

Abstract: A method of full-duplex electromagnetic communication wherein a pair of data modulation formats are selected for the forward and return data links respectively such that the forward data electro-magnetic beam serves as a carrier for the return data. A method of encoding optical information is used wherein right-hand and left-hand circular polarizations are assigned to optical information to represent binary states. An application for an earth to low earth orbit optical communications system is presented which implements the full-duplex communication and circular polarization keying modulation format.

Low-complexity carrier-phase estimator suited to on-board implementation

Abstract: In this paper, we describe and analyze a new feedforward carrier-phase algorithm suited to on-board digital implementation. The algorithm studied here (for phase recovery of M-ary phase-shift keying signals) has the particularity to perform all calculations in polar coordinates in order to reduce the implementation complexity. The defined phase estimator is operating at very low signal-to-noise ratio with small frequency offsets. Its performance is close to those of the Viterbi and Viterbi algorithm.

Portable certification device with acoustic coupling

Abstract: A portable certification device comprises a compact housing provided with: data storage means for storage of at least one cryptographic key and/or smart card interface; processing means for computer processing; at least one acoustic interface for wireless exchange of information with the device, by means of at least an acoustic signal generated using a modulation technique selected from the group consisting of: frequency-shift keying, phase-shift keying, amplitude-shift keying and any combination thereof; means for supplying power to the acoustic interface, processing means, storage means and/or smart card interface.

Performance of a digital symbol synchronizer in cochannel interference and noise

Abstract: The performance of a binary-quantized data-transition tracking loop symbol synchronizer operating in cochannel interference (CCI) and noise is examined for both binary phase-shift keying and quaternary phase-shift keying modulations. The CCI can be included in a previously known Markov chain model without increasing the number of states in the chain, but the cost of computing the transition probabilities increases exponentially with the number of interferers. It is shown that a first-order Markov model and simulation are in close agreement for some important applications. The effect of interferer epoch on the degradation caused by the interference is investigated and the degradations in performance caused by CCI and by Gaussian noise are compared.

Power line communication system and method

Abstract: A system for communicating digital information over wires having a great deal of harmonic distortion, attenuation and noise, such as a power line, employs a transmitter which generates a signal representing a symbol of data. Some form of signal modulation such as Differential Phase Shift Keying (DPSK) or Frequency Shift Keying (FSK) is used to encode the data. The transmitter will continuously transmit or retransmit each data symbol until an acknowledgment is received from a receiving device. At the receiving device, the received signal is sampled and multiple repetitions of the same symbol are averaged to reduce noise. The averaged samples are then analyzed to demodulate the data. Both transmitting and receiving devices are clocked at the same frequency which is derived in both from the fundamental power line frequency. As such, the generation and detection of the data signals is coherent, making it possible to average out the effect of noise over multiple frames thereby ensuring communication even over highly noisy transmission media.

Electrical connector with programmable keying

Abstract: An electrical connector ( 22 ) having an array of terminals ( 50 ) disposed in respective terminal receiving passageways ( 30 ) therein and a programmable keying member ( 60 ) disposed into a key receiving opening ( 32 ) extending into the mating face ( 26 ) among the array of terminal receiving passageways ( 30 ). The key receiving opening ( 32 ) is configured to receive the keying member ( 60 ) in any of a plurality of orientations. The keying member ( 60 ) further may include other terminals ( 82, 84 ) disposed in terminals receiving passageways ( 78, 80 ) of the keying member ( 60 ).

Frequency-domain echo cancellation in digital multicarrier modulation systems

Abstract: The data driven frequency-domain echo canceller (EC) for a multicarrier modulation system is considered. An EC in such a system has to deal with both the interchannel and intersymbol interference occurring in the echo signal. For this reason, the main disadvantage of the data driven EC structure is the large computational complexity. Here, the solution of the computational complexity problem is presented. It is based on assumption that in practice, interchannel interference has a limited range. The number of operations per symbol as a measure of the EC computational complexity is given. Simulation results present echo attenuation in the frequency-domain EC, operating in the orthogonally multiplexed quadrature amplitude-shift keying system. Modifications of the proposed EC structure and its computational complexity in the systems with pulse shaping are discussed.

Method and system for identifying an industrial personal computer in a rack

Abstract: A system and method for identifying a match between an industrial PC to a slot in a rack which uses a blind mating keying and locking plates, so that when the mechanical keying plate and locking plate do match, then full insertion of the PC into the slot is permitted. When a mis-match occurs, then full insertion is prohibited.

Method and apparatus for re-synchronization of a stream cipher during handoff

Abstract: A method and apparatus for re-synchronizing a stream cipher during soft handoff. Transmitted quasi-secret keying information is used with a secret key to reinitialize a stream cipher generator located in a base station and a stream cipher generator located in a travelling mobile station. Since the quasi-secret keying information is uniquely determined according to each base station in the wireless telephone system, a base station's quasi-secret keying information and a shared secret key can also be used to create a new key. Thus, as the mobile station travels from one base station to another base station, a unique new key is generated for each base station.

Suboptimal maximum-likelihood multiuser detection of synchronous CDMA on frequency-selective multipath channels

Abstract: We propose a signal processing technique, based on the estimate-maximize algorithm, in order to perform multiuser code-division multiple-access (CDMA) detection. This algorithm iteratively seeks for the maximum-likelihood solution. The resulting structure is a successive interference cancellation scheme which can be applied to both synchronous and asynchronous CDMA. Higher performance than similar methods is obtained from using deterministic annealing and multiple stages. A soft output is defined, and the signal-to-noise ratio in the soft output of the detector is measured for predicting performance with an outer code with soft input decoder. The new receiver is applied to the problem whereby in a synchronous CDMA system the orthogonality of the codes is destroyed by a frequency-selective channel, caused by multipath fading. This nonlinear technique is shown to perform much better than the minimum mean-square-error linear solution and several other algorithms. The algorithm lends itself to an efficient DSP or VLSI implementation. We evaluate the performance by simulations with coherent quadrature phase-shift keying modulation, known channel and long random Rayleigh multipath. In most cases, we set the number of users equal to the processing gain for maximal throughput. The results are also presented in the form of outage probabilities for random Rayleigh multipath against required fading margin.

Printer ink supply system

Abstract: A printer ink supply system that includes a docking station having a pair of separated keying members and another docking station having another pair of separated keying members, wherein the docking station and the other docking station can be arranged in a stacked relationship when one of the keying members on the docking station is interlocked with a keying member on the other docking station The keying members are distributed on the top, bottom and side walls of both docking stations thereby enabling the two to be interlocked in top to bottom or side to side relationships The docking stations are interchangeable and any number can be joined in vertical or horizontal relationships, or in combinations of vertical and horizontal relationships

Method and apparatus for rotating the phase of a complex psk signal

Abstract: In applications employing phase-shift keying modulation, a phase rotator (200, 202) as disclosed herein is used to rotate the constellation of signal vectors before carrier modulation in order to maximize modulator output power. Such a rotator (200, 202) may be applied in the digital domain (to complex signals having either binary-valued or multi-valued components) or in the analog domain.

Path diversity performance of DS-CDMA systems in a mobile satellite channel

Abstract: We derive easy to compute semianalytical expressions for the bit error rate performance of coherent and differentially coherent binary phase-shift keying direct-sequence code-division multiple-access systems operating in a mobile satellite channel. The channel is modeled as frequency nonselective with diversity gain obtained through path diversity. This is the scenario when a signal is transmitted to all satellites in view, and the received replicas are independently demodulated and combined at the receiving side. Our analysis extends previous results to the case of unequal mean powers and Rice factors in the combined signals: a valid assumption if we consider that the satellites are in view with different elevation angles. Furthermore, the effect of independent shadowing on each diversity branch is also considered.

Pulse-diverse radar waveform design for accurate joint estimation of time delay and Doppler shift

Abstract: A pulse train of diversely compressed pulses may produce better Doppler-delay resolution than a similar pulse train of identically compressed pulses by reducing the total ambiguity and being more flexible in distributing that reduced ambiguity. This work investigates the design of such a pulse-diverse waveform under a design criterion constraining the allowable sidelobe height in the composite ambiguity function. A genetic algorithm is used to design the pulse modulation parameters for frequency shift keying (FSK) pulse modulation and joint frequency-phase shift keying (FSK-PSK) pulse modulation. Simulation studies verify the superior Doppler-delay resolution and interference rejection capability of these pulse-diverse modulation schemes.