Showing papers on "Keying published in 2006"
Posted Content•
TL;DR: In this article, a quasi-orthogonal (QO) space-time block code with minimum decoding complexity (MDC-QO-STBC) was proposed.
Abstract: In this paper, we consider a quasi-orthogonal (QO) space-time block code (STBC) with minimum decoding complexity (MDC-QO-STBC). We formulate its algebraic structure and propose a systematic method for its construction. We show that a maximum-likelihood (ML) decoder for this MDC-QOSTBC, for any number of transmit antennas, only requires the joint detection of two real symbols. Assuming the use of a square or rectangular quadratic-amplitude modulation (QAM) or multiple phase-shift keying (MPSK) modulation for this MDC-QOSTBC, we also obtain the optimum constellation rotation angle, in order to achieve full diversity and optimum coding gain. We show that the maximum achievable code rate of these MDC-QOSTBC is 1 for three and four antennas and 3/4 for five to eight antennas. We also show that the proposed MDC-QOSTBC has several desirable properties, such as a more even power distribution among antennas and better scalability in adjusting the number of transmit antennas, compared with the coordinate interleaved orthogonal design (CIOD) and asymmetric CIOD (ACIOD) codes. For the case of an odd number of transmit antennas, MDC-QO-STBC also has better decoding performance than CIOD.
243 citations
TL;DR: The capacity of multiple-input multiple-output (MIMO) systems using multidimensional phase-shift keying/quadratic-amplitude modulation signal sets is evaluated and it was shown that transmit diversity is capable of narrowing the gap between the capacity of the Rayleigh-fading channel and that of the additive white Gaussian noise channel.
Abstract: In this contribution, the capacity of multiple-input multiple-output (MIMO) systems using multidimensional phase-shift keying/quadratic-amplitude modulation signal sets is evaluated. It was shown that transmit diversity is capable of narrowing the gap between the capacity of the Rayleigh-fading channel and that of the additive white Gaussian noise channel. However, because this gap becomes narrower when the receiver diversity order is increased, for higher order receiver diversity, the performance advantage of transmit diversity diminishes. A MIMO system having full multiplexing gain has a higher achievable throughput than the corresponding MIMO system designed for full diversity gain, although this is attained at the cost of a higher complexity and a higher signal-to-noise ratio. The tradeoffs between diversity gain, multiplexing gain, complexity, and bandwidth are studied.
154 citations
01 Nov 2006
TL;DR: It is shown that ACO- OFDM with 4-QAVI subcarrier modulation has the same bandwidth efficiency but requires 2 dB less energy per bit than on-off keying, andACO-OFDM with larger constellation sizes gives higher bandwidth efficiencies and lower optical power than other modulation schemes.
Abstract: Orthogonal frequency division multiplexing (OFDM) is used in many wired and wireless broadband communication systems because of its resilience in the presence of signal dispersion or multipath distortion. OFDM has not been used in practical optical communication systems because the bipolar waveform cannot be used in intensity-modulated direct detection (IM/DD) systems. A new unipolar form of OFDM, asymmetrically clipped optical OFDM (ACO-OFDM), has recently been developed. For the case of an AWGN channel, we compare ACO- OFDM and other modulation schemes. It is shown that ACO- OFDM with 4-QAVI subcarrier modulation has the same bandwidth efficiency but requires 2 dB less energy per bit than on-off keying. ACO-OFDM with larger constellation sizes gives higher bandwidth efficiencies and lower optical power than other modulation schemes. Unlike existing methods, the performance of ACO-OFDM is limited by the bandwidth of the transmitter and receiver not the dispersion of the channel.
147 citations
Journal Article•
TL;DR: A DSP-based phase-estimation scheme consists of a simple and demultiplexable architecture that allows the system to reach significantly higher performance than conventional optical delay detection and various kinds of postprocessing of the received signal become possible.
Abstract: This paper describes a phase-diversity homodyne receiver that which can cope with multilevel modulation formats. The carrier phase drift is estimated with digital signal processing (DSP) on the homodyne-detected signal, entirely restoring the complex amplitude of the incoming signal. Our DSP-based phase-estimation scheme consists of a simple and demultiplexable architecture that allows the system to reach significantly higher performance than conventional optical delay detection. Since the whole optical signal information is preserved with our receiver, various kinds of postprocessing of the received signal become possible. For example, we can demultiplex wavelength-division/optical time-division multiplexed channels and compensate for group velocity dispersion of fibers as well as the nonlinear phase noise in the electrical domain. We also experimentally evaluate the performance of our receiver. Our offline bit-error rate experiments show the feasibility of transmitting polarization-multiplexed 40-Gb/s quadrature phase-shift keying signals over 200 km with channel spacing of 16 GHz, leading to spectral efficiency of 2.5 b/s/Hz
145 citations
Patent•
20 Jun 2006
TL;DR: In this article, an iterative method of removing keying ambiguity from a keyboard comprising an array of capacitive keys is presented, which involves measuring a signal strength associated with each key in the array, comparing the measured signal strengths to find a maximum, determining that the key having the maximum signal strength is the unique user-selected key, and maintaining that selection until either the initially selected key's signal strength drops below some threshold level or a second key's scale exceeds the first key's.
Abstract: Keyboards, keypads and other data entry devices can suffer from a keying ambiguity problem. In a small keyboard, for example, a user's finger is likely to overlap from a desired key to onto adjacent ones. An iterative method of removing keying ambiguity from a keyboard comprising an array of capacitive keys involves measuring a signal strength associated with each key in the array, comparing the measured signal strengths to find a maximum, determining that the key having the maximum signal strength is the unique user-selected key, and maintaining that selection until either the initially selected key's signal strength drops below some threshold level or a second key's signal strength exceeds the first key's signal strength.
120 citations
TL;DR: In this article, a modulation format conversion from non-return-to-zero on-off keying (NRZ-OOK) to return-tozero binary phase-shift keying was proposed.
Abstract: A novel all-optical modulation-format conversion from nonreturn-to-zero on-off keying (NRZ-OOK) to return-to-zero binary phase-shift keying (RZ-BPSK) is proposed. A Mach-Zehnder interferometric (MZI) wavelength converter consisting of integrated semiconductor optical amplifiers (SOAs) is utilized to implement the proposed format conversion. Error-free operation at a bit rate of 10.7 Gb/s is experimentally demonstrated in order to show the feasibility of the proposed scheme. The received sensitivity of the converted signal is improved by 2.9 dB compared with a back-to-back NRZ-OOK signal at BER=10 -9. In addition, a reasonable dispersion tolerance of the converted signal up to plusmn500 ps/nm is observed. The numerical simulation based upon the carrier-rate equation verifies the experimental results
105 citations
TL;DR: The new proposed scheme is spectrally more efficient for data transmission, while keeping the same outage probability for voice and data (both classes) as the scheme employing BPSK/M-AM, and provides, as a by-product, aSpectrally efficient way of transmitting voice and a single-class data.
Abstract: In this paper, a new technique for simultaneous voice and multiclass data transmission over fading channels using adaptive hierarchical modulation is proposed. According to the link quality, the proposed scheme changes the constellation size as well as the priority parameters of the hierarchical signal constellations and assigns available subchannels (i.e., different bit positions) to different kinds of bits. Specifically, for very bad channel conditions, it only transmits voice with binary phase-shift keying (BPSK). As the channel condition improves, a variable-rate adaptive hierarchical M-ary quadrature amplitude modulation (M-QAM) is used to increase the data throughput. The voice bits are always transmitted in the lowest priority subchannel (i.e., the least significant bit (LSB) position) of the quadrature (Q) channel of the hierarchical M-QAM. The remaining (log2M-1) subchannels, called data subchannels, are assigned to two different classes of data according to the selected priority parameters. Closed-form expressions as well as numerical results for outage probability, achievable spectral efficiency, and average bit error rate (BER) for voice and data transmission over Nakagami-m fading channels are presented. The adaptive techniques employing hybrid binary shift keying (BPSK)/M-ary AM (M-AM) and uniform M-QAM for simultaneous voice and two different classes of data transmission are also extended. Compared to the extended schemes, the new proposed scheme is spectrally more efficient for data transmission, while keeping the same outage probability for voice and data (both classes) as the scheme employing BPSK/M-AM. The new scheme also provides, as a by-product, a spectrally efficient way of transmitting voice and a single-class data
97 citations
TL;DR: In this article, the authors present experimental results of coherent time reversal communications (binary phase-shift keying, quaternary phase shift keying and 8-quadratic-amplitude modulation) at 3.5 kHz with a 1-kHz bandwidth where different messages were sent simultaneously to either two or three different depths at an 8.6-km range in a 105m-deep water.
Abstract: A recent time reversal (TR) experiment demonstrated that multiple foci can be projected from an array of sources to the same range but at different depths. This multiple input/multiple output process can potentially increase the information data rate. This paper presents experimental results of coherent TR communications (binary phase-shift keying, quaternary phase-shift keying, and 8-quadratic-amplitude modulation) at 3.5 kHz with a 1-kHz bandwidth where different messages were sent simultaneously to either two or three different depths at an 8.6-km range in a 105-m-deep water
96 citations
TL;DR: In this paper, the application of differential phase-shift keying data format in coherent optical code-division multiple access (DPSK-OCDMA) has been proposed and investigated theoretically and experimentally to combat noise in the OCDMA system.
Abstract: In this letter, the application of differential phase-shift keying data format in coherent optical code-division multiple-access (DPSK-OCDMA) has been proposed and investigated theoretically and experimentally to combat noise in the OCDMA system. The DPSK-OCDMA can also ease the receiver's threshold level setting and enhance the system confidentiality.
76 citations
TL;DR: In this paper, the power spectra of return-to-zero (RZ) optical signals generated by Mach-Zehnder (MZ) modulators are derived.
Abstract: Analytical formulas for the power spectra of return-to-zero (RZ) optical signals generated by Mach-Zehnder (MZ) modulators are derived. Pulse duty cycles of 33%, 50%, and 67%, in conjunction with several modulation techniques, including binary ON-OFF keying (OOK), duobinary OOK, and M-ary differential phase-shift keying (DPSK), phase-shift keying (PSK), and quadrature-amplitude modulation (QAM), are considered. Spectral characteristics and bandwidth requirements of these different schemes are compared
73 citations
TL;DR: For the first time, synchronous quadrature phase-shift keying data is recovered in real-time after transmission with standard distributed feedback lasers using a digital inphase and quadratures receiver.
Abstract: For the first time, synchronous quadrature phase-shift keying data is recovered in real-time after transmission with standard distributed feedback lasers using a digital inphase and quadrature receiver. Forward-error-correction-compatible performance is reached at 800 Mb/s after 63 km of fiber. Self-homodyne operation with an external cavity laser is error-free
TL;DR: This paper studies the design of signaling waveforms for time-hopping impulse radio with limits on the power spectral density, and proposes the use of polarity randomization, which eliminates the spectral lines and also leads to a smoothing of the continuous part of the spectrum.
Abstract: This paper studies the design of signaling waveforms for time-hopping impulse radio (TH-IR) with limits on the power spectral density. Such restrictions are imposed by the spectral mask prescribed by frequency regulators for ultra-wideband (UWB) signals. The "conventional" TH-IR system with pulse-position modulation and time-hopping multiple access gives rise to spectral lines that either violate the regulations, or require a significant power backoff. To remedy this situation, we propose the use of polarity randomization, which eliminates the spectral lines and also leads to a smoothing of the continuous part of the spectrum. We analyze different variants of the polarity randomization, considering short and long randomization sequences, as well as symbol-based or pulse-based randomization. We analyze the effect of this technique on both pulse position modulation and binary phase-shift keying modulation.
Patent•
10 Apr 2006TL;DR: In this article, a system for sharing secure keying information with a new device not of a secure wireless network was proposed, where the keying is used for encryption and provided to the new device in a manner which is not susceptible to exposure outside of the secure network.
Abstract: A system for sharing secure keying information with a new device not of a secure wireless network. The keying information may be used for encryption and provided to the new device in a manner which is not susceptible to exposure outside of the secure network. The keying information shared with the new device may be regarded as a birth key. Upon appropriate provision of the birth key, the new device may request with a birth key encrypted message via a communication mode exposed to potential adversaries to be added to the secure network.
TL;DR: The proposed WL receiver is shown to outperform the classical strictly linear (SL) receiver when the interfering users are (quasi-)synchronous with respect to the user of interest, and it is shown that the proposed structure is capable of delivering the maximum signal-to-noise ratio predicted by theory.
Abstract: This paper studies an enhanced widely linear (WL) receiver for direct-sequence code-division multiple-access (DS-CDMA) systems that employ aperiodic spreading sequences with offset quadrature phase-shift keying (OQPSK) modulation. The modulation scheme generates improper complex multiple-access interference (MAI) and necessitates the use of WL receivers. Focus is on bandlimited pulse shapes and the inherent cyclostationarity (CS) of the uncoded received signal. The enhanced WL receiver replaces the conventional chip-matched filter with new filters that exploit the CS of the received signal through frequency shifting. The proposed WL receiver is shown to outperform the classical strictly linear (SL) receiver when the interfering users are (quasi-)synchronous with respect to the user of interest. High-powered interfering users, that may exist to support high data rates, increase the performance improvement delivered by the WL receiver. Moreover, it is shown that MAI can become proper, either identically or asymptotically, when users are asynchronous and equally powered. This is despite the fact that individual interfering signals are improper. Numerical results demonstrate that the WL receiver can outperform the SL receiver by 1-3 dB under the examined scenarios with current CDMA standards settings. In asynchronous or quasi-synchronous transmission modes, performance gain of the WL receiver degrades unless the number of high-powered active users remains small. An example for implementation of the WL receiver is proposed and compared with that of the SL receiver when minimum-shift keying modulation, a special case of OQPSK, is used. The implementation is based on a fractionally spaced equalizer whose taps are updated by an adaptive algorithm. It is shown that the proposed structure is capable of delivering the maximum signal-to-noise ratio predicted by theory.
05 Mar 2006
TL;DR: In this article, a phase-diversity optical homodyne receiver for demodulating M-array phase-shift keying (PSK) signals is proposed, which is based on digital carrier-phase estimation.
Abstract: We describe a phase-diversity optical homodyne receiver for demodulating M-array phase-shift keying (PSK) signals, which is based on digital carrier-phase estimation. Bit-error rate measurements in 2-, 4- and 8-PSK systems are demonstrated with such receiver.
TL;DR: In this article, the authors investigated the capacity of M-ary on-off frequency-shift keying (OOFSK) in the context of wideband fading channels, where the receiver uses energy detection for the reception of OOFSK signals.
Abstract: M-ary on-off frequency-shift keying (OOFSK) is a digital modulation format in which M-ary FSK signaling is overlaid on on/off keying. This paper investigates the potential of this modulation format in the context of wideband fading channels. First, it is assumed that the receiver uses energy detection for the reception of OOFSK signals. Capacity expressions are obtained for the cases in which the receiver has perfect and imperfect fading side information. Power efficiency is investigated when the transmitter is subject to a peak-to-average power ratio (PAR) limitation or a peak power limitation. It is shown that under a PAR limitation, it is extremely power inefficient to operate in the very-low-SNR regime. On the other hand, if there is only a peak power limitation, it is demonstrated that power efficiency improves as one operates with smaller SNR and vanishing duty factor. Also studied are the capacity improvements that accrue when the receiver can track phase shifts in the channel or if the received signal has a specular component. To take advantage of those features, the phase of the modulation is also allowed to carry information.
TL;DR: In this article, a software-defined radio (SDR) receiver platform based on a new substrate integrated waveguide six-port structure is proposed for high bit-rate SDR applications.
Abstract: With recent advances in semiconductor processing technology and the development of reconfigurable devices, high bit-rate software-defined radio (SDR) has become practical for commercial applications. This paper proposes an SDR receiver platform based on a new substrate integrated waveguide six-port structure. This SDR receiver platform operates from 22 to 26 GHz and it is designed to be robust, low cost, and suitable for different communication schemes. In this study, the receiver is demonstrated to support quadrature phase-shift keying and 16 quadrature amplitude modulation schemes. System-level simulation is made and prototype circuits are fabricated to evaluate the system performance. It is found that the combination of SDR and six-port technology can provide a great flexibility in system configuration, a significant reduction in system development cost, and also a high potential for software reuse. The proposed receiver shows a possible application of universal direct demodulator for future SDR terminals in various wireless communication systems.
08 Jun 2006
TL;DR: A comprehensive system design for cognitive radio is presented and it is proposed to transmit the spectrum sensing related information via on-off keying (OOK) modulated ultrawideband (UWB) and a processing gain based approach that leads to an increased range for cognitive networks.
Abstract: The rising number and capacity requirements of radio systems bring about an increasing demand for frequency spectrum. Cognitive radio offers a tempting solution to this problem by proposing opportunistic usage of frequency bands that are not occupied by their licensed users. Since it is a rather new concept, there is no consensus on the practical implementation of cognitive radio communications. In this paper, a comprehensive system design for cognitive radio is presented. The details of spectrum sensing and dynamic spectrum shaping, which constitute the basics of opportunistic spectrum usage, are given. It is proposed to transmit the spectrum sensing related information via on-off keying (OOK) modulated ultrawideband (UWB). The limits on the range of one-to-one cognitive communications are discussed. A processing gain based approach that leads to an increased range for cognitive networks is proposed. Different signaling options for the real data communications are given, and among these options an impulse radio that employs raised cosine filters is investigated in detail.
TL;DR: It is shown that 100-Gb/s transmission over 3840 km can be achieved using single-sideband quadrature-phase-shift keying OFDM transmission and low-density parity-check codes.
Abstract: The possibility of 100-Gb/s transmission over 25-GHz bandwidth using orthogonal frequency-division multiplexing (OFDM) is demonstrated It is shown that 100-Gb/s transmission over 3840 km can be achieved using single-sideband quadrature-phase-shift keying OFDM transmission and low-density parity-check codes
TL;DR: In this article, a theoretical analysis and an experimental demonstration of semiconductor optical amplifier (SOA)-based regenerative amplification (SORA) of phase noise (PN)-degraded return-to-zero (RZ) differential phase-shift keying (DPSK) signals are presented.
Abstract: A theoretical analysis and an experimental demonstration of semiconductor optical amplifier (SOA)-based regenerative amplification (SORA) of phase noise (PN)-degraded return-to-zero (RZ) differential phase-shift keying (DPSK) signals are presented. The Q-factor improvement is 1.6 dB in single-channel and about 0.8 dB in two non-demultiplexed-channel regimes. The key physical mechanism that enables regeneration by the SORA is the discriminative gain provided by the SOA for the logical 0s versus the logical 1s when two mutually antisymmetric ON-OFF keying (OOK) data trains, created by the DPSK signal, collide in the SOA. The modeling results agree with the experiment.
TL;DR: In this article, an analysis of two methods for enhancing the performance of two-dimensional time-wavelength optical code-division multiple access systems by mitigating the effects of beat noise is presented.
Abstract: This paper presents an analysis of two methods for enhancing the performance of two-dimensional time-wavelength Optical code-division multiple-access systems by mitigating the effects of beat noise. The first methodology makes use of an optical hard limiter (OHL) in the receiver prior to the optical correlator; a general formula for the error probability as a function of crosstalk level for systems adopting OHLs is given, and the implications of the OHL's nonideal transfer characteristics are then examined. The second approach adopts pulse position modulation, and system performance is estimated and compared to that associated with on-off keying
Patent•
11 Jul 2006TL;DR: In this article, a method of delivering an application key or keys to an application server for use in securing data exchanged between the application server and a user equipment, the user equipment accessing a communications network via an access domain.
Abstract: A method of delivering an application key or keys to an application server for use in securing data exchanged between the application server and a user equipment, the user equipment accessing a communications network via an access domain. The method comprises running an Authentication and Key Agreement procedure between the user equipment and a home domain in order to make keying material available to the user equipment and to an access enforcement point. At least a part of said keying material is used to secure a communication tunnel between the user equipment and the access enforcement point, and one or more application keys are derived within the home domain using at least part of said keying material. Said application key(s) is(are) provided to said application server, and the same application key(s) derived at the user equipment, wherein said access enforcement point is unable to derive or have access to said application key(s).
01 Sep 2006
TL;DR: The acoustic link performances was evaluated and shown its robustness for transmission in a strongly disturbed channel and GESMA also wants to increase the link reliability and provides strongly protected low bit rate speech (MELP, 2400 bps) transmission.
Abstract: GESMA (Groupe d'Etudes Sous-Marines de l'Atlantique) objective is to develop a sufficiently robust acoustic link allowing the transmission of different information (text, images...). A real-time platform named TRIDENT (TRansmission d'Images et de Donnes EN Temps reel) was designed at ENST Bretagne. A blind spatio-temporal equalizer is used to reduce the various perturbations brought by the underwater acoustic channel (UWA). The acoustic link performances was evaluated and shown its robustness for transmission in a strongly disturbed channel. GESMA also wants to increase the link reliability and provides strongly protected low bit rate speech (MELP, 2400 bps) transmission. In order to do so, a channel coding will be added to the system. Different kinds of error correcting scheme will be tested including Convolutional Codes (CC) and Reed Solomon (RS) block code. A Differential Phase-Shift Keying (DPSK) is used to solve phase ambiguities in case of CC coding and Viterbi decoding utilization.
TL;DR: In this paper, the authors investigated 20 channels at 10Gb/s wavelength division multiplexing (WDM) transmission over 1190 km single mode fiber and dispersion compensating fiber using cascaded inline semiconductor optical amplifier at a span of 70 km for RZ-DPSK (return zero differential phase-shift keying) modulation format by using same channel spacing, i.e. 100 GHz.
12 Jun 2006
TL;DR: In this paper, the performance of 10 Gbit/s 4-ary amplitude shift keying (ASK) systems in dispersive environments at 1550 nm was investigated and compared to on-off keying.
Abstract: The authors model and characterise the performance of 10 Gbit/s 4-ary amplitude shift keying (ASK) systems in dispersive environments at 1550 nm. Both non-return-to-zero (NRZ) and return-to-zero (RZ) formats are examined, with comparisons to on-off keying (OOK) in each case. Both single amplified links and cascaded fibre-amplifier links are modelled. While 4-ary ASK systems suffer a back-to-back sensitivity penalty of up to 7 dB with respect to OOK, they offer a significantly reduced dispersion sensitivity, particularly for RZ formats. This suggests advantages for M-ary coding in future systems employing optical time division multiplexing. Optimal level spacing for ASK is analysed and approximations for different noise regimes are shown to fit well to detailed calculations. Sensitivity to extinction ratio is examined; RZ systems are shown to have higher sensitivity than NRZ for both 4-ary and OOK. Finally, the authors show that frequency drift, or equivalently, a de-tuning in the centre frequency of the optical filter, is more severe for OOK than for 4-ary ASK, especially in the case of non-fully dispersion uncompensated systems.
TL;DR: Although the conventional bit error rate estimation method based on the eye Q-factor with Gaussian approximation is not accurate enough for DPSK and DQPSK, it is found to be reasonably accurate for M-DPSK with M>8 and in M-DPolPSK.
Abstract: Sensitivities of several direct-detection multilevel modulation formats, including M-ary differential phase-shift keying (M-DPSK), M-ary differential amplitude-phase-shift keying (M-DAPSK), and M-ary differential polarization-phase-shift keying (M-DPolPSK) are systematically calculated. The theory is based on a unified mathematical framework for direct-detection receivers using optical delay interferometers and balanced detectors. Results quantitatively elucidate the tradeoffs between these direct-detection multilevel modulation formats as well as the classic multilevel modulation format, M-ary amplitude-shift keying (M-ASK). Although the conventional bit error rate estimation method based on the eye Q-factor with Gaussian approximation is not accurate enough for DPSK and DQPSK, it is found to be reasonably accurate for M-DPSK with M>8 and in M-DPolPSK
TL;DR: It is demonstrated that pre-encoding the data with a Raptor code allows for simple reconstruction of the message, regardless of the erasure pattern introduced from the nondemodulated bits.
Abstract: We introduce a rate-adaptive system in which the receiver demodulates only those bits that have a high probability of being correct, treating nondemodulated bits as erasures. Several sets of decision regions, derived using composite hypothesis testing, are proposed for 16-QAM and 16-phase-shift keying, which allow for the simple implementation of this demodulation strategy. We demonstrate that pre-encoding the data with a Raptor code allows for simple reconstruction of the message, regardless of the erasure pattern introduced from the nondemodulated bits. We prove the optimality of the proposed decision regions in selecting the most likely subset of bits from any received symbol in moderate-to-high signal-to-noise ratios, and we analyze the performance of demodulating with these decision regions over an additive white Gaussian noise channel. Also demonstrated is the strong performance of 16-QAM for this application, compared with other power-efficient constellations and the near-optimality of using Gray mapping, even under the proposed alternate sets of decision regions
TL;DR: This paper will review long-haul transmission results using RZ-DPSK and will compare the transmission properties of RZ to zero on-off shift keying signals versus Rz-OOK signals, finding that due to superior receiver sensitivity, the R Z-D PSK modulation format can be an enabling technology for 40-Gb/s per channel transoceanic transmission.
Abstract: This paper reviews technologies and techniques that have been used in deployed long-haul wavelength division multiplexing (WDM) systems and emerging technologies that could be used for the next generation of cost-reduced systems. The overview of current generation technologies starts with a discussion of modulation formats, focusing on the superior properties of the chirped return to zero on-off shift keying (CRZ-OOK) modulation format. The use of 10-Gb/s CRZ-OOK modulation format together with advanced fiber types, more powerful forward error correction (FEC), and broadband erbium-doped fiber amplifiers resulted in the deployment of dense WDM systems with capacities per fiber in terabits per second range and trans-Pacific reach. Demand for the systems with large design capacity led to further development of broadband optical amplifiers. Laboratory demonstrations successfully expanded transmission into the full C-band and later in the C and L transmission bands. The current market conditions dictate the need for reducing the first cost of an installed system rather than reaching record capacity per fiber. Reducing first cost can be achieved by reducing the amount of optical amplifiers in the cable by utilizing an excess performance margin provided by available RZ-OOK technology. Further improvements would be possible if more powerful FEC and modulation formats with better receiver sensitivity are used. For example, the RZ differential phase-shift keying (RZ-DPSK) modulation format with 3-dB better receiver sensitivity and better nonlinear tolerance to large amounts of accumulated dispersion is a very promising technology. This paper will review long-haul transmission results using RZ-DPSK and will compare the transmission properties of RZ-DPSK signals versus RZ-OOK signals. Due to superior receiver sensitivity, the RZ-DPSK modulation format can be an enabling technology for 40-Gb/s per channel transoceanic transmission
TL;DR: A discrete-time mixed-signal Gaussian frequency-shift keying demodulator designed for a low intermediate frequency Bluetooth receiver performs FSK demodulation.
Abstract: A discrete-time mixed-signal Gaussian frequency-shift keying demodulator designed for a low intermediate frequency Bluetooth receiver performs FSK demodulation. Employing passive sampling and time-domain differentiation techniques, the demodulator performs quadrature demodulation while tolerating up to 200-kHz frequency offset. A distributed array of interleaved sampling circuits and a low-voltage multiplier allow both low-voltage operation and low power dissipation. Fabricated in a CMOS 0.25-/spl mu/m technology, the demodulator only dissipates 6 mW from a 2-V power supply.