Showing papers on "Quadrature amplitude modulation published in 2010"
TL;DR: In this article, the capacity limit of fiber-optic communication systems (or fiber channels?) is estimated based on information theory and the relationship between the commonly used signal to noise ratio and the optical signal-to-noise ratio is discussed.
Abstract: We describe a method to estimate the capacity limit of fiber-optic communication systems (or ?fiber channels?) based on information theory. This paper is divided into two parts. Part 1 reviews fundamental concepts of digital communications and information theory. We treat digitization and modulation followed by information theory for channels both without and with memory. We provide explicit relationships between the commonly used signal-to-noise ratio and the optical signal-to-noise ratio. We further evaluate the performance of modulation constellations such as quadrature-amplitude modulation, combinations of amplitude-shift keying and phase-shift keying, exotic constellations, and concentric rings for an additive white Gaussian noise channel using coherent detection. Part 2 is devoted specifically to the "fiber channel.'' We review the physical phenomena present in transmission over optical fiber networks, including sources of noise, the need for optical filtering in optically-routed networks, and, most critically, the presence of fiber Kerr nonlinearity. We describe various transmission scenarios and impairment mitigation techniques, and define a fiber channel deemed to be the most relevant for communication over optically-routed networks. We proceed to evaluate a capacity limit estimate for this fiber channel using ring constellations. Several scenarios are considered, including uniform and optimized ring constellations, different fiber dispersion maps, and varying transmission distances. We further present evidences that point to the physical origin of the fiber capacity limitations and provide a comparison of recent record experiments with our capacity limit estimation.
2,135 citations
TL;DR: In this article, a theoretical analysis of the dual-polarization constant modulus algorithm is presented, where the control surfaces several different equalizer algorithms are derived, including the decision-directed, trained, and the radially directed equalizer for both polarization division multiplexed quadriphase shift keyed (PDM-QPSK) and 16 level quadrature amplitude modulation (PDm-16-QAM).
Abstract: Digital coherent receivers have caused a revolution in the design of optical transmission systems, due to the subsystems and algorithms embedded within such a receiver. After giving a high-level overview of the subsystems, the optical front end, the analog-to-digital converter (ADC) and the digital signal processing (DSP) algorithms, which relax the tolerances on these subsystems are discussed. Attention is then turned to the compensation of transmission impairments, both static and dynamic. The discussion of dynamic-channel equalization, which forms a significant part of the paper, includes a theoretical analysis of the dual-polarization constant modulus algorithm, where the control surfaces several different equalizer algorithms are derived, including the constant modulus, decision-directed, trained, and the radially directed equalizer for both polarization division multiplexed quadriphase shift keyed (PDM-QPSK) and 16 level quadrature amplitude modulation (PDM-16-QAM). Synchronization algorithms employed to recover the timing and carrier phase information are then examined, after which the data may be recovered. The paper concludes with a discussion of the challenges for future coherent optical transmission systems.
772 citations
TL;DR: In this paper, the effects of finite analog-to-digital converter resolution, laser frequency offset, laser phase noise, and narrowband optical filtering on the performance of PDPM 16-ary quadrature amplitude modulation (16-QAM) were investigated.
Abstract: We discuss the generation, wavelength-division-multiplexed (WDM) long-haul transmission, and coherent detection of 112-Gb/s polarization-division-multiplexed (PDM) 16-ary quadrature amplitude modulation (16-QAM) at a line rate of 14 Gbaud and spectral efficiencies beyond 4 b/s/Hz. We describe the (off-line) digital signal processing and blind filter adaptation algorithms used in our intradyne receiver and characterize its performance using both simulated and measured 16-QAM waveforms. We measure a required optical signal-to-noise ratio of 20.2 dB (0.1-nm reference bandwidth; 10-3 bit-error ratio), 3.2-dB off the theoretical limit. We study the effects of finite analog-to-digital converter resolution, laser frequency offset, laser phase noise, and narrowband optical filtering. Our experiments on a 25-GHz WDM grid (4.1-b/s/Hz spectral efficiency) reveal a 1-dB penalty after 7 passes though reconfigurable optical add/drop multiplexers (ROADMs) and an achievable transmission reach of 1022 km of uncompensated standard single-mode fiber. At a spectral efficiency of 6.2 b/s/Hz (16.67-GHz WDM channel spacing) a transmission reach of 630 km is attained.
381 citations
TL;DR: In this paper, a quaternary phase-shift-keying (QPSK) partition scheme was proposed for 16-ary quadrature amplitude modulation (16-QAM) coherent optical systems.
Abstract: The laser linewidth tolerance for 16-ary quadrature amplitude modulation (16-QAM) coherent optical systems is investigated using a quaternary phase-shift-keying (QPSK) partition scheme. The different stages needed to partition the square-16-QAM into QPSK constellations for carrier phase estimation are discussed. It is shown that at 1 dB above sensitivity at a bit-error rate of 10-3, a combined linewidths symbol duration product of 1 × 10-4 is tolerable. The performance of the algorithm with different bits resolution in the analog-to-digital converter is also presented.
243 citations
TL;DR: A theoretical analysis of the efficiency of power transfer and phase-shift-keying communications through an inductive link and it is shown that the coplanar geometry approach is better suited for displacement tolerance.
Abstract: Biomedical implants require wireless power and bidirectional data transfer. We pursue our previous work on a novel topology for a multiple carrier inductive link by presenting the fabricated coils. We show that the coplanar geometry approach is better suited for displacement tolerance. We provide a theoretical analysis of the efficiency of power transfer and phase-shift-keying communications through an inductive link. An efficiency of up to 61% has been achieved experimentally for power transfer and a data rate of 4.16 Mb/s with a bit-error rate of less than 2 × 10-6 has been obtained with our fabricated offset quadrature phase-shift keying modules due to the inductive link optimization presented in this paper.
179 citations
TL;DR: It is shown that by introducing multiple cascaded feed-forward carrier recovery stages, the required compute power can be significantly reduced compared to the prior art using the single-stage-based blind phase search method.
Abstract: An improved feed-forward carrier phase recovery method is proposed for coherent receivers using M-ary quadrature amplitude modulation-based modulation formats. It is shown that by introducing multiple cascaded feed-forward carrier recovery stages, the required compute power can be significantly reduced compared to the prior art using the single-stage-based blind phase search method.
166 citations
TL;DR: Compared with the traditional cumulant-based classifiers, the proposed K-S classifiers offer superior classification performance, require less number of signal samples (thus is fast), and is more robust to various channel impairments.
Abstract: A new approach to modulation classification based on the Kolmogorov-Smirnov (K-S) test is proposed. The K-S test is a non-parametric method to measure the goodness of fit. The basic procedure involves computing the empirical cumulative distribution function (ECDF) of some decision statistic derived from the received signal, and comparing it with the CDFs or the ECDFs of the signal under each candidate modulation format. The K-S-based modulation classifiers are developed for various channels, including the AWGN channel, the flat-fading channel, the OFDM channel, and the channel with unknown phase and frequency offsets, as well as the non-Gaussian noise channel, for both QAM and PSK modulations. Extensive simulation results demonstrate that compared with the traditional cumulant-based classifiers, the proposed K-S classifiers offer superior classification performance, require less number of signal samples (thus is fast), and is more robust to various channel impairments.
164 citations
21 Mar 2010
TL;DR: In this paper, the authors demonstrate the record total capacity of 69.1 Tb/s with a spectral efficiency of 6.4 b/s/Hz by employing 21.4-Gbaud 16-QAM modulation, blind digital coherent detection, and 10.8-THz ultra-wideband amplification in the C- and extended L-bands.
Abstract: We demonstrate the record total capacity of 69.1 Tb/s with a spectral efficiency of 6.4 b/s/Hz by employing 21.4-Gbaud 16-QAM modulation, blind digital coherent detection, and 10.8-THz ultra-wideband amplification in the C- and extended L-bands.
145 citations
TL;DR: It is shown that high-speed QPSK, 8PSK.
Abstract: We review and summarize several 100G per channel high-capacity transmission systems enabled by advanced technologies such as multilevel modulation format, new low-loss and large effective area fiber, hybrid EDFA/Raman amplification, and digital coherent detection technologies. We show that high-speed QPSK, 8PSK, 8QAM, and 16QAM can all be generated using commercially available optical modulators using only binary electrical drive signals through novel synthesis methods, and that all of these modulation formats can be detected using digital coherent detection. We also show our latest research results on 400 Gb/s and 1 Tb/s per channel by using orthogonal DWDM transmission technologies.
144 citations
Patent•
14 Jul 2010
TL;DR: In this paper, a presswork encryption security printing technology based on multi-system quadrature amplitude modulation (QAM) has been proposed, which can effectively resist piracy behavior based on cameras, scanners, electronic documents and the like.
Abstract: The invention discloses a presswork encryption security printing technology based on multi-system quadrature amplitude modulation By adopting the security printing technology, a paseudorandom modulating signal can be generated from anti-counterfeiting information through spread spectrum, encryption and channel coding, the anti-counterfeiting information can be embedded into a whole page through a multi-system quadrature amplitude modulation (QAM) mode, and the anti-counterfeiting information can be identified from any fragment in presswork identification The invention has very strong smash-resistance, can effectively resist piracy behaviour based on cameras, scanners, electronic documents and the like, and can be widely applied to the field of presswork anti-counterfeit
143 citations
TL;DR: The performance of the receiver using a digital backpropagation algorithm with varying nonlinear step size is characterized to determine an upper bound on the suppression of intrachannel nonlinearities in a single-channel system.
Abstract: Coherent detection with receiver-based DSP has recently enabled the mitigation of fiber nonlinear effects. We investigate the performance benefits available from the backpropagation algorithm for polarization division multiplexed quadrature amplitude phase-shift keying (PDM-QPSK) and 16-state quadrature amplitude modulation (PDM-QAM16). The performance of the receiver using a digital backpropagation algorithm with varying nonlinear step size is characterized to determine an upper bound on the suppression of intrachannel nonlinearities in a single-channel system. The results show that for the system under investigation PDM-QPSK and PDM-QAM16 have maximum step sizes for optimal performance of 160 and 80 km, respectively. Whilst the optimal launch power is increased by 2 and 2.5 dB for PDM-QPSK and PDM-QAM16, respectively, the Q-factor is correspondingly increased by 1.6 and 1 dB, highlighting the importance of studying nonlinear compensation for higher level modulation formats.
TL;DR: A comparative analysis of three popular digital filters for chromatic dispersion compensation: a time-domain least mean square adaptive filter, aTime-domain fiber dispersion finite impulse response filter, and a frequency-domain blind look-up filter.
Abstract: We present a comparative analysis of three popular digital filters for chromatic dispersion compensation: a time-domain least mean square adaptive filter, a time-domain fiber dispersion finite impulse response filter, and a frequency-domain blind look-up filter. The filters are applied to equalize the chromatic dispersion in a 112-Gbit/s non-return-to-zero polarization division multiplexed quadrature phase shift keying transmission system. The characteristics of these filters are compared by evaluating their applicability for different fiber lengths, their usability for dispersion perturbations, and their computational complexity. In addition, the phase noise tolerance of these filters is also analyzed.
TL;DR: A software-defined real-time optical multiformat transmitter enabling format switching in the nanosecond regime without changing the transmitter hardware is demonstrated.
Abstract: We demonstrate a software-defined real-time optical multiformat transmitter. Here, eight different modulation formats are shown. Data rate and modulation formats are defined through software accessible look-up tables enabling format switching in the nanosecond regime without changing the transmitter hardware. No data are lost during the switching process. SP-64 quadrature amplitude modulation at 28 Gbd has been generated and tested. This allows us to generate a 336-Gb/s real-time pseudorandom bit sequence in a dual polarization setup.
TL;DR: A novel method of adding extended active interference cancellation signals to suppress sidelobes and to shape the spectrum of the CR-OFDM signal with a cyclic prefix (CP), which can achieve high spectrum efficiency with low implementation complexity.
Abstract: The sidelobe of noncontiguous orthogonal frequency-division multiplexing (OFDM) signals is required to be deeply suppressed in the licensed user's band in cognitive radio (CR) systems. To this end, we propose a novel method of adding extended active interference cancellation (EAIC) signals to suppress sidelobes and to shape the spectrum of the CR-OFDM signal with a cyclic prefix (CP). For simplicity, we called the proposed scheme EAIC-CP. The key idea of the proposed EAIC-CP is to employ some cancellation signals consisting of tones spaced closer than the interval of OFDM subcarriers to cancel the sidelobes of OFDM signals. Moreover, we derive the optimal cancellation signals to minimize the total sidelobe power subject to a self-interference constraint. Numerical results show that, when the guard bandwidth is equal to one OFDM subcarrier interval, the EAIC-CP scheme offers more than a 45.0-dB sidelobe suppression with unnoticeable signal-to-noise ratio (SNR) loss at a symbol error rate (SER) from 10-2 to 10-3 for 64 quadratic-amplitude modulation (64QAM). Moreover, the EAIC-CP scheme can achieve high spectrum efficiency with low implementation complexity.
TL;DR: This paper investigates the capacity gains offered by cognitive radio in a spectrum-sharing system where the transmit power and rate of thesecondary user are adjusted based on the channel variations of the secondary link and spectrum-sensing information pertaining to the activity of the licensed user.
Abstract: In this paper, we investigate the capacity gains offered by cognitive radio in a spectrum-sharing system where the transmit power and rate of the secondary user are adjusted based on the channel variations of the secondary link and spectrum-sensing information pertaining to the activity of the licensed user. We assume a primary/secondary spectrum-sharing system where the secondary users may have access to the spectrum band originally assigned to the primary (licensed) user, as long as the interference power inflicted on the primary receiver is considered unharmful. In this context, considering joint average interference-power and peak transmit-power constraints, we first obtain the optimal power allocation scheme, namely variable power, for maximizing the achievable capacity of the secondary user over fading channels. Thereafter, we look into the variable rate and power adaptation policy by maximizing the achievable capacity under said power constraints and bit error rate requirements in multilevel quadrature amplitude modulation (M-QAM). Finally, the benefits of using soft-sensing information about the primary user's activity on the power and rate adaptation strategies are assessed, and numerical results and comparisons illustrating the performance of our spectrum-sharing system in different operating scenarios are provided.
TL;DR: In this article, a mathematical model for communication subject to both network interference and noise is presented, where the interferers are scattered according to a spatial Poisson process, and are operating asynchronously in a wireless environment subject to path loss, shadowing, and multipath fading.
Abstract: We present a mathematical model for communication subject to both network interference and noise. We introduce a framework where the interferers are scattered according to a spatial Poisson process, and are operating asynchronously in a wireless environment subject to path loss, shadowing, and multipath fading. We consider both cases of slow and fast-varying interferer positions. The paper is comprised of two separate parts. In Part I, we determine the distribution of the aggregate network interference at the output of a linear receiver. We characterize the error performance of the link, in terms of average and outage probabilities. The proposed model is valid for any linear modulation scheme (e.g., M-ary phase shift keying or M-ary quadrature amplitude modulation), and captures all the essential physical parameters that affect network interference. Our work generalizes the conventional analysis of communication in the presence of additive white Gaussian noise and fast fading, allowing such results to account for the effect of network interference. In Part II of the paper, we derive the capacity of the link when subject to network interference and noise, and characterize the spectrum of the aggregate interference.
TL;DR: Using an accurate exponential bound for the Gaussian Q-function, the authors derived simple approximate closed-form expressions for the average symbol error probability (ASEP) of a free-space optical communication link using subcarrier intensity modulation (SIM) with general-order rectangular quadrature amplitude modulation (QAM) over atmospheric turbulence channels.
Abstract: Using an accurate exponential bound for the Gaussian Q-function, we derive simple approximate closed-form expressions for the average symbol error probability (ASEP) of a free-space optical communication link using subcarrier intensity modulation (SIM) with general-order rectangular quadrature amplitude modulation (QAM) over atmospheric turbulence channels. To model the atmospheric turbulence conditions, the log-normal and the gamma-gamma distribution are used. Extensive numerical and computer simulation results are presented in order to verify the accuracy of the proposed mathematical analysis.
TL;DR: In this paper, the authors proposed a highly linear radio-over-fiber system with low intermodulation distortion using a single-drive dual-parallel Mach-Zehnder modulator (SD-DPMZM).
Abstract: We propose a highly linear radio-over-fiber system with low intermodulation distortion (IMD) using a single-drive dual-parallel Mach-Zehnder modulator (SD-DPMZM). The optical carrier is modulated in one of the two parallel modulators, while remaining unmodulated in the other one. There exists optimal working points for SD-DPMZM that makes its two kinds of origins of third-order IMD (IMD3) have opposite phase and equal intensity, and cancel each other; hence the output IMD3 is suppressed dramatically. Experimental results show that the proposed scheme can achieve a spurious-free dynamic range of up to 122.9 dB · Hz2/3, which is in agreement with the theoretical analysis. It is about 20 dB more than a conventional MZM. The error vector magnitude of the proposed scheme, for a 16-QAM 10-MSym/s signal centered at 4 GHz, is 1.94%.
TL;DR: In this article, an adaptive decision-aided (DA) receiver that does not require knowledge of the statistical characteristics of the carrier phase, or any parameter to be preset, is proposed.
Abstract: We analytically studied the block length effect (BLE) of decision-aided maximum likelihood (DA ML) carrier phase estimation in coherent optical phase-modulated systems. The results agree well with the trends found using extensive Monte Carlo simulations. In order to eliminate the BLE and accurately recover the carrier phase, an adaptive decision-aided (DA) receiver is proposed that does not require knowledge of the statistical characteristics of the carrier phase, or any parameter to be preset. The simulation results show that using the adaptive DA receiver, the maximum tolerance ratio of the linewidth per laser to symbol rate (?vT) at a bit error rate (BER) = 10-4 has been increased to 2.5 × 10-4, 4.1 × 10-5, and 9.5 × 10-6, respectively, for quadrature-, 8- and 16-phase-shift keying formats. The ratio (?vT) of the adaptive DA receiver in 16 quadrature amplitude modulation (QAM) is decreased to 2 × 10-5 due to the constellation penalty from 2.5 × 10-5 by using DA ML with optimum memory length, though it consistently performs well without optimizing any parameters as in DA ML. The phase error variance of the adaptive DA receiver is also analytically investigated. In addition, an analog-to-digital converter with bit resolution higher than 4 bits is shown to be sufficient to implement our adaptive DA receiver.
TL;DR: In this article, the authors proposed an optical orthogonal frequency division multiplexing (O-OFDM) scheme, suitable for intensity-modulated direct-detection systems, where the modulation/demodulation processing takes advantage of the fast Hartley transform algorithm.
Abstract: We present a novel optical orthogonal frequency division multiplexing (O-OFDM) scheme, suitable for intensity-modulated direct-detection systems, where the modulation/demodulation processing takes advantage of the fast Hartley transform algorithm. Due to the properties of the discrete Hartley transform (DHT), the conventional transmission scheme can be streamlined. We demonstrate that asymmetrically clipping (AC) technique can also be applied to DHT-based OFDM; the signal can be transmitted without the need of a DC bias, resulting in a power-efficient system, not affected by clipping noise. Hermitian symmetry is not required for the input signal. Therefore, this technique supports the double of input symbols compared to both AC and DC-biased O-OFDM, based on standard Fourier processing. The analysis in an additive white Gaussian noise channel shows that the same performance can be achieved by replacing 4, 16, and 64 QAM (quadrature-amplitude modulation) AC optical-OFDM with a simpler system based on DHT, using binary phase-shift keying (BPSK), 4 and 8 PAM (pulse-amplitude modulation), respectively.
TL;DR: A new algorithm is proposed which attains the ML performance with significantly reduced complexity based on the minimum mean square error (MMSE) criterion and an efficient way of generating the log likelihood ratio (LLR) values which can be used for coded systems.
Abstract: For multiple-input multiple-output (MIMO) systems, the optimum maximum likelihood (ML) detection requires tremendous complexity as the number of antennas or modulation level increases. This paper proposes a new algorithm which attains the ML performance with significantly reduced complexity. Based on the minimum mean square error (MMSE) criterion, the proposed scheme reduces the search space by excluding unreliable candidate symbols in data streams. Utilizing the probability metric which evaluates the reliability with the normalized likelihood functions of each symbol candidate, near optimal ML detection is made possible. Also we derive the performance analysis which supports the validity of our proposed method. A threshold parameter is introduced to balance a tradeoff between complexity and performance. Besides, we propose an efficient way of generating the log likelihood ratio (LLR) values which can be used for coded systems. Simulation results show that the proposed scheme achieves almost the same performance as the ML detection at a bit error rate (BER) of 10-4 with 28% and 15% of real multiplications compared to the conventional QR decomposition with M-algorithm (QRD-M) in 4-QAM and 16- QAM, respectively. Also we confirm that the proposed scheme achieves the near-optimal performance for all ranges of code rates with much reduced complexity. For instance, our scheme exhibits 74% and 46% multiplication reduction in 4-QAM and 16-QAM, respectively, compared to the sphere decoding based soft-output scheme with rate-1/2 convolutional code.
18 Mar 2010
TL;DR: A158-to-165GHz TX and RX chipset supporting QAM modulation schemes is implemented in SiGe with double-balanced l/Q mixers used for direct up-/down-conversion.
Abstract: A chipset for emerging high-frequency applications at 158 to 165GHz is presented. The two chips (RX and TX) are implemented in a European (DotFive) SiGe BiCMOS technology with f T =260GHz and f MAX =380GHz [1]. Envisioned applications include broadband wireless communication, ranging, and imaging using quadrature modulation schemes. Highly integrated mm-Wave SiGe transceivers have been previously demonstrated for communication at 60GHz [2] and 77GHz [3], and more recently for the 110-to-180GHz range [4]. This transmitter and receiver chipset is the first one with zero-IF quadrature mixing covering the 158-to-165GHz band with up to 5dBm output power.
TL;DR: The Generalized Case IV and Generalizedcase V constructions for 4q-QAM (q > =3) GCSs are proposed using selected Gaussian integer pairs, each of which contains two distinct Gaussian integers with identical magnitude and which are not conjugate with each other.
Abstract: A construction of general quadrature amplitude modulation (QAM) Golay complementary sequences based on quadrature phase shift keying Golay-Davis-Jedwab sequences (GDJ sequences) is described. Existing constructions of 16- and 64-QAM Golay sequences are extended to 4q-QAM sequences of length 2m, for q ≥ 1, m ≥ 2. This construction gives [(m + 1)42(q - 1) - (m + 1)4(q - 1) + 2q - 1](m! / 2)4(m + 1) Golay complementary sequences. A previous offset pair enumeration conjecture for 64-QAM Golay sequences is proved as a special case of the enumeration for 4q-QAM Golay sequences. When used for orthogonal frequency-division multiplexing signals, the peak-to-mean envelope power ratio upper bound is shown to be 6(2q - 1)/ (2q + 1), approaching 6 as the QAM constellation size increases.
TL;DR: It is shown that the constellation-based compensation method can efficiently mitigate the effect of HPANonlinearity with low complexity and that the SMC-based detection scheme is efficient to compensate for HPA nonlinearity in the case without knowledge of the HPA parameters.
Abstract: The nonlinearity of high-power amplifiers (HPAs) has a crucial effect on the performance of multiple-input-multiple-output (MIMO) systems. In this paper, we investigate the performance of MIMO orthogonal space-time block coding (OSTBC) systems in the presence of nonlinear HPAs. Specifically, we propose a constellation-based compensation method for HPA nonlinearity in the case with knowledge of the HPA parameters at the transmitter and receiver, where the constellation and decision regions of the distorted transmitted signal are derived in advance. Furthermore, in the scenario without knowledge of the HPA parameters, a sequential Monte Carlo (SMC)-based compensation method for the HPA nonlinearity is proposed, which first estimates the channel-gain matrix by means of the SMC method and then uses the SMC-based algorithm to detect the desired signal. The performance of the MIMO-OSTBC system under study is evaluated in terms of average symbol error probability (SEP), total degradation (TD) and system capacity, in uncorrelated Nakagami-m fading channels. Numerical and simulation results are provided and show the effects on performance of several system parameters, such as the parameters of the HPA model, output back-off (OBO) of nonlinear HPA, numbers of transmit and receive antennas, modulation order of quadrature amplitude modulation (QAM), and number of SMC samples. In particular, it is shown that the constellation-based compensation method can efficiently mitigate the effect of HPA nonlinearity with low complexity and that the SMC-based detection scheme is efficient to compensate for HPA nonlinearity in the case without knowledge of the HPA parameters.
14 Apr 2010
TL;DR: In this article, the authors proposed a QAM backscatter method using no on-chip inductors that is compatible with a single-chip CMOS tag implementation, which allows tags to transmit more than one data bit per symbol period, permitting tag designers to employ a lower power onchip oscillator operating at a frequency equal to the (lower) symbol rate.
Abstract: Traditional passive UHF RFID tags employ either ASK or PSK backscatter modulation to communicate data from memory or sensors on the tag to a remotely-located reader These simple modulation schemes transfer data at a rate of one bit per symbol period, which for an integrated CMOS tag IC requires an on-chip oscillator with a frequency at least equal to the bit rate Motivated by the fact that most modern UHF RFID readers already employ I/Q demodulation of the backscattered signal to account for backscatter phase rotation as the tag moves with respect to the reader, we propose a QAM backscatter method using no on-chip inductors that is compatible with a single-chip CMOS tag implementationWith QAM backscatter, tags transmit more than one data bit per symbol period, permitting tag designers to employ a lower power on-chip oscillator operating at a frequency equal to the (lower) symbol rate while maintaining the same data throughput as ASK or PSK, or alternatively to send data at a higher rate for a given on-chip oscillator frequency We present the fundamental design equations required for arbitrary QAM backscatter modulators and present simulated bit error rate (BER) and error vector magnitude (EVM) curves for the operation of an inductor-free 4-QAM and 8-QAM modulator centered at 915MHz and evaluated over the 860MHz–950MHz worldwide UHF band
TL;DR: In this article, a 4-Gsymbol/s 256 quadrature amplitude modulation (QAM) coherent optical transmission over 160 km was reported, and a 64-Gb/s data signal was successfully transmitted with an optical bandwidth of 5.4 GHz.
Abstract: We report a polarization-multiplexed (Pol-Mux) 4-Gsymbol/s 256 quadrature amplitude modulation (QAM) coherent optical transmission over 160 km. A 64-Gb/s data signal was successfully transmitted with an optical bandwidth of 5.4 GHz. We also describe a Pol-Mux, 10-Gsymbol/s, 128- and 64-QAM (140 and 120 Gb/s) transmission over 150 km.
01 Jan 2010
TL;DR: In this paper, the authors describe the principle of operation of coherent detection, the concept of the digital coherent receiver, and its performance evaluation, and the challenges for the future are summarized.
Abstract: Coherent optical fiber communications were studied extensively in the 1980s mainly because high sensitivity of coherent receivers could elongate the unrepeated transmission distance; however, their research and development have been interrupted for nearly 20 years behind the rapid progress in high-capacity wavelength-division multiplexed (WDM) systems using erbium-doped fiber amplifiers (EDFAs). In 2005, the demonstration of digital carrier phase estimation in coherent receivers has stimulated a widespread interest in coherent optical communications again. This is due to the fact that the digital coherent receiver enables us to employ a variety of spectrally efficient modulation formats such as M-ary phase-shift keying (PSK) and quadrature amplitude modulation (QAM) without relying upon a rather complicated optical phase-locked loop. In addition, since the phase information is preserved after detection, we can realize electrical post-processing functions such as compensation for chromatic dispersion and polarization-mode dispersion in the digital domain. These advantages of the born-again coherent receiver have enormous potential for innovating existing optical communication systems. In this chapter, after reviewing the 20-year history of coherent optical communication systems, we describe the principle of operation of coherent detection, the concept of the digital coherent receiver, and its performance evaluation. Finally, challenges for the future are summarized.
TL;DR: The proposed chip can support up to 8 × 8 64-QAM spatial multiplexing MIMO communications, which surpasses all reported MIMo detector ICs in antenna number and modulation order, and adopts a novel sphere decoding algorithm with high decoding efficiency and superior error rate performance.
Abstract: In this paper, VLSI implementation of a configurable, soft-output MIMO detector is presented. The proposed chip can support up to 8 × 8 64-QAM spatial multiplexing MIMO communications, which surpasses all reported MIMO detector ICs in antenna number and modulation order. Moreover, this chip provides configurable antenna number from 2 × 2 up to 8 × 8 and modulation order from QPSK to 64-QAM. Its outputs include bit-wise log likelihood ratios (LLRs) and a candidate list, making it compatible with powerful soft-input channel decoders and iterative decoding system. The MIMO detector adopts a novel sphere decoding algorithm with high decoding efficiency and superior error rate performance, called modified best-first with fast descent (MBF-FD). Moreover, a low-power pipelined quad-dual-heap (quad-DEAP) circuit for efficient node pool management and several circuit techniques are implemented in this chip. When this chip is configured as 4 × 4 64-QAM and 8 × 8 64-QAM soft-output MIMO detectors, it achieves average throughputs of 431.8 Mbps and 428.8 Mbps with only 58.2 mW and 74.8 mW respective power consumption and reaches 10-5 coded bit error rate (BER) at signal-to-noise ratio (SNR) of 24.2 dB and 22.6 dB, respectively.
21 Mar 2010
TL;DR: A concept of spectrally-efficient optical networking with distance-adaptive spectral allocation by adjusting the number of modulation levels is presented and demonstrated by routing 40 Gb/s optical paths using short-reach, narrow-spectrum 16APSK and long-reach QPSK.
Abstract: We present a concept of spectrally-efficient optical networking with distance-adaptive spectral allocation by adjusting the number of modulation levels. We demonstrate it by routing 40 Gb/s optical paths using short-reach, narrow-spectrum 16APSK and long-reach QPSK.
TL;DR: Preamble-based least squares (LS) channel estimation in orthogonal frequency division multiplexing (OFDM) systems of the QAM and offset QAM (OQAM) types is considered and a sparse preamble consisting of equipowered and equispaced pilots embedded in zeros is investigated.
Abstract: In this correspondence, preamble-based least squares (LS) channel estimation in orthogonal frequency division multiplexing (OFDM) systems of the QAM and offset QAM (OQAM) types is considered. The construction of optimal (in the mean squared error (MSE) sense) preambles is investigated, for sparse (a subset of pilot tones, surrounded by nulls) preambles. The two OFDM systems are compared for the same transmit power, which, for cyclic prefix (CP) based OFDM/QAM, also includes the power spent for CP transmission. OFDM/OQAM, with a sparse preamble consisting of equipowered and equispaced pilots embedded in zeros, turns out to perform at least as well as CP-OFDM. Simulations results are presented that verify the analysis.