Golden codeword–based modulation schemes for single‐input multiple‐output systems

The Golden code has full rate and full diversity. The Golden codeword matrix contains two pairs of super symbols. Based on one pair of super symbols, two modulation schemes, Golden codeword–based M‐ary quadrature amplitude modulation (GC‐MQAM) and component‐interleaved GC‐MQAM (CI‐GC‐MQAM), are proposed for single‐input multiple‐output (SIMO) systems. Since the complexities of the maximum likelihood detection for the proposed GC‐MQAM and CI‐GC‐MQAM are proportional to O(M²) and O(M⁴), respectively, low complexity detection schemes for the proposed GC‐MQAM and CI‐GC‐MQAM are further proposed. In addition, the theoretical average bit error probabilities (ABEPs) for the proposed GC‐MQAM and CI‐GC‐MQAM are derived. The derived ABEPs are validated through Monte Carlo simulations. Simulation and theoretical results show that the proposed GC‐MQAM can achieve the error performance of signal space diversity. Simulation and theoretical results further show that the proposed CI‐GC‐16QAM, ‐64QAM, and ‐256QAM with three receive antennas can achieve approximately 2.2, 2.0, and 2.1 dB gain at a bit error rate of 4 × 10^?6 compared with GC‐16QAM, ‐64QAM, and ‐256QAM, respectively.     

Bandwidth Compressive 16-State SQAM Modems Through Saturated Amplifiers

The performance of new bandwidth compressive 16 SQAM (Superposed-QAM) modems, operating in a highly power-efficient saturation mode, is analyzed. Nonlinearly amplified 16 SQAM retains the out-of-band energy much lower than 4-level rectangular (i.e., 16 QAM) or sinusoidal shaped (i.e., MAMSK) QAM, and operates within 0.7 dB of theoretical (i.e., 16 QAM in Nyquist linear channel) performance atP(e) = 10^{-6}using simple 4th-order Butterworth LPF's. Effects of baseband pulse shaping, receive filter BTs, power level variations and propagation time difference (or static phase shift) of transmit HPA's are analyzed in terms of BER.     

A <Emphasis Type="Italic">N</Emphasis>-Radon Based OFDM Trasceivers Design and Performance Simulation Over Different Channel Models

In this paper a new method is proposed to perform the N-Radon orthogonal frequency division multiplexing (OFDM), which are equivalent to 4-quadrature amplitude modulation (QAM), 16-QAM, 64-QAM, 256-QAM, ... etc. in spectral efficiency. This non conventional method is proposed in order to reduce the constellation energy and increase spectral efficiency. The proposed method gives a significant improvement in Bit Error Rate performance, and keeps bandwidth efficiency and spectrum shape as good as conventional Fast Fourier Transform based OFDM. The new structure was tested and compared with conventional OFDM for Additive White Gaussian Noise, flat, and multi-path selective fading channels. Simulation tests were generated for different channels parameters values including multi-path gains vector, multi-path delay time vector, and maximum Doppler shift.     

Analysis of different sub-carrier allocation of M-ary QAM-OFDM downlink in RoF system

In this paper, the performance of a 60 GHz radio over fiber (RoF) system with 4/16/64 quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) downstream signals is studied. Delivery of 10 Gbit/s M-ary QAM (MQAM) OFDM signals through the 20-km-long single-mode fiber (SMF) is complicated in terms of intensity modulation and direct detection (IM/DD). Using self-homodyne method, the beating of two independent light waves generating the millimeter-wave at the photodetector can be down-converted to baseband in the electrical domain. Meanwhile, three kinds of sub-carrier arrangement schemes are compared and discussed, and the simulation results show that lower peak-to-average power ratio (PAPR) can be obtained adopting the adjacent scheme. At bit error rate (BER) of 10-3, the receiver sensitivity using 4QAM-OFDM sub-carrier signal is almost enhanced by 4 dB and 9 dB compared with those of 16QAM-OFDM signal and 64QAM-OFDM signal.     

A dispersion flattened fiber front-haul transmission system with high bitrate signal at low input optical power

We propose a dispersion flattened fiber (DFF) front-haul transmission system with high bitrate, polarization multiplexing (PM) and quadrature amplitude modulation (QAM) signal at low input optical power. The modulation format of the system is PM-16QAM, and the bitrate is 256 Gbit/s. The transmission characteristics over DFF link system are experimentally studied, which are compared with those over non-zero dispersion shifted fiber (NZDSF) link and standard single mode fiber (SSMF) link. The experimental results show that the error vector magnitude (EVM) of 256 Gbit/s and PM-16QAM signal over 25 km DFF link is 0.75% better than that over 25 km NZDSF link at least, and the bit error rate (BER) and Q-factor are much better than those of NZDSF. Their EVM and BER are both decreased with the increase of input optical power, and the Q-factor is increased. Those characteristics over 25 km SSMF are the worst at the same case. The larger the dispersion is, the more the constellation points are deviated from their respective centers and the worse the constellation characteristics are. The greater the attenuation of the DFF is, the smaller the input power of the DFF is, the more the constellation points are deviated from their centers and the worse the constellation characteristics are. This study provides a new idea and experimental support for long span front-haul propagation in mobile communication.     

An Easy Rake Receiver for TD-SCDMA Smart Antenna

The application research on smart antenna (SA) for CDMA system is consists of two parts in general. One part is the research on mathematical methods in SA technology, i.e., how to isolate the array manifold parameter e^ja_m {e^{ja_m }} and then to get the weighting coefficient w _m for the SA receiving signal S(t)e^ja_m {S(t)e^{ja_m }} . The estimation of DOA is included in the above handling process. The other is how to extract the signal S(t)e^ja_m {S(t)e^{ja_m }} from SA receiver, which should be the focus of the research of SA application. Utilizing the feature of mid-amble sequence of TD-SCDMA system, a novel DOA estimation method based on mid-amble sequence (MDOA) is presented in this paper, by which the array manifold e^ja_m {e^{ja_m }} can be extracted directly from the SA receiving signal. Making use of the array manifold parameter e^ja_m {e^{ja_m }} obtained by the MDOA method, the simulation of downlink beam-forming shows that the proposed MDOA method is feasible. This method will result in the research of mathematical methods used in SA being completely abandoned. Also, a usable SA receiver for TD-SCDMA with beam-forming by amplitude weighting in base-band is given as well as the correctness proof by using spectrum searching method in base-band.     

Radiation emitted by quantum-well InGaAs structures I. Spontaneous emission spectra

The spontaneous emission spectra of strained InGaAs quantum wells in the spectral range 1.2–1.5 eV were studied experimentally at 4.2–286 K with pump currents up to ∼9.2 kA· cm⁻². An interpretation of the observed bands is given. The transition 1e–1hh (TE polarization) dominates the spectrum. The position of the peak for this transition is virtually current-independent. No indications of a “red” shift, expected at a high carrier density, were observed. The weak forbidden transitions (1e–2hh) were identified. The longwavelength edge of the band drops off exponentially, by analogy with the well-known Urbach rule for the absorption edge. Fiz. Tekh. Poluprovodn. 32, 472–477 (April 1998)     

Note on Generalized Linear-Phase Property of Discrete-Time Finite Impulse Response Systems

A discrete-time linear time-invariant system is said to have generalized linear phase if its frequency response takes the form: H(e ^jω )=A(e ^jω )e ^−jαω+jβ , |ω|<π, where α and β are real constants and A(e ^jω ) is real-valued. By a simple analyticity argument, we show that for finite impulse response systems to have generalized linear phase, the group delay α must be integer or half integer, a crucial step to complete characterization of such systems.     

The Performance of Staggered Quadrature Amplitude Modulation in the Presence of Phase Jitter

We report on the performance of band-limited staggered quadrature amplitude modulation (SQAM) in the presence of phase jitter and additive Gaussion noise. It is demonstrated that offsetting, or staggering, the in-phase and quadrature data streams by a fraction of a symbol interval improves the phase-jitter immunity of a conventional QAM data transmission system. For example, with a raised cosine pulse having unity rolloff, staggering can reduce the effective jitter variance by a factor of two. Under the constraint of no intersymbol interference, the optimum staggering epoch is shown to be half a symbol interval, and since the resulting system is equivalent to a form of vestigial sideband modulation (VSB)VSB is superior to QAM with respect to phase-jitter immunity. Using both optimum pulse design and data staggering, it is shown that the improvement over conventional QAM is proportional to the excess bandwidth. Consequently, SQAM may be warranted whenever a high-quality phase-locked loop is not used to track phase jitter. While the SQAM technique is not new, it has heretofore not been recognized as possessing the above-mentioned advantages.     

Generation of vertex connected subgraphs for multi-input multi-output reliability networks

In this paper, the problem of evaluation of reliability (probability of success) of a network consisting of several inputs and outputs is studied. Edges are assumed to be perfect and vertices are assigned the probabilities of success. A new concept called “vertex connected subgraph” is introduced for this purpose. This concept is useful even for dense graphs because they are of the order of 2^(v-k-1) which is independent of e, where ν(e) is the number of vertices (edges) and k is the number of outputs of a graph.     

SQAM: A New Superposed QAM Modem Technique

A spectral and power efficient modulation techniquesuperposed quadrature amplitude modulation (SQAM-is introduced. In SQAM, the premodulation baseband signal is a double-interval (2T_{s}) raised-cosine pulse superposed with weighted single-interval (Ts) raisedcosine pulses. Our results indicate that SQAM has spectral advantages over OQPSK, QBL, and MSK, and betterP(e)performance than MSK, IJF-OQPSK (or SQORC), and TFM.     

Envelope-Derived Timing Recovery in QAM and SQAM Systems

The problem of continuously recovering timing phase and frequency in a high-rate carrier-modulated data communication device is addressed. The communication link is assumed narrowband with respect to the baud rate of the device, thus necessitating the use of some type of equalization in the receiver. The receiver demodulator is assumed coherent in nature. A timing recovery technique based on narrow-band filtering and squaring of the received demodulated waveform(s) is examined. Analysis of the first moment of the waveforms so generated reveals a convenient indicator of sampling instants. If the timing recovery filters are properly designed, then these sampling instants exactly satisfy a requirement previously derived, ensuring efficient operation of the equalizer. Design criteria for the filters are given. Two principal types of linear modulation techniques are considered. These are quardrature-carrier amplitude modulation (QAM) and staggered QAM (SQAM). A set of experimental waveforms observed in a QAM modem signaling at 2400 Bd is included for illustration. Several conclusions are drawn as a result of the study. First, the mean timing waveforms in QAM and SQAM systems bear fixed time relationships to suitable receiver sampling instants. Second, adequate timing filter design is attained with very narrowband filters centered on frequencies equal to half the baud rate and the full baud rate. Third, recovery circuits used in QAM systems may be designed so as to have negligible timing jitter. In SQAM systems and, consequently, in vestigial sideband-amplitude modulation (VSB-AM) systems, this advantage is generally not found.     

Hierarchical modulation for client-driven selective streaming of multi-view video over AWGN channels

We consider a client-driven selective streaming system for multi-view video, which is supported by scalable multi-view video coding (SMVC). The system is used to reduce bit-rates for efficient transmission of multi-view video. The transmit source is partitioned into three layers: a base and two enhancement layers. The base layer contains all views encoded by MVC at a low-quality, while each enhancement layer contains high-quality part of the selected left and right views, respectively. The base layer is more important than the enhancement layers to create 3D perception, albeit of low-quality, and should be more protected than the enhancement layers. In this paper, two-level and three-level hierarchical 64QAM are used to provide unequal error protection (UEP) for the client-driven selective streaming system. First we find the suitable hierarchical values, which is the ratio of the distances in hierarchical 64QAM, for the client-driven selective streaming system. Furthermore, we analyze numerically how the hierarchical 64QAM impacts peak signal-to-noise ratio (PSNR) performance of fast and slow-motion sequences. Simulation results show that the three-level hierarchical 64QAM outperforms both conventional 64QAM with Gray mapping and the two-level hierarchical 64QAM in terms of achieving the target average PSNR performance at a low SNR environment.     

Sliding window adaptive SVD using the unsymmetric householder partial compressor

A fast algorithm for tracking the rank-r SVD-approximant Q(t)P(t)U^T(t) of a sliding window data matrix X(t) of dimension L×N is introduced, where P(t) is a square-root power matrix of dimension r×r with r<min{L,N}. This algorithm is based on the unsymmetric Householder partial compressor and uses a reorthonormalizing Householder transformation for downdating. The concept is numerically self-stabilizing and requires no leakage. The dominant complexity is 4Lr+3Nr multiplications per time update which is the lower bound in complexity for an algorithm of this kind. Applications occur in the area of adaptive array processing and other forms of adaptive processing in finite duration subspaces. A complete algorithm summary is provided. Computer simulations illustrate the operation of the algorithm.     

High-Energy-Density All-Organic Dielectric Film via a Continuous Preparation Processing

Dielectric polymers with high power density and breakdown strength (E_b) are indispensably used in electrostatic energy-storing systems and devices. However, the discharged energy density (U_e) of dielectric polymers is severely limited due to the relatively low dielectric constant (K). Although current polymer composites improve K, this approach usually faces challenges in enhancing U_e due to the trade-off relation between K and E_b and difficulties in scalable production of dielectric films. Here, a fully melt-extrudable, meter-scale, and high-U_e ferroelectric polymer-based all organic composite film comprising a poly(p-phenylene terephthalamide)-based fluxible polymer (denoted as f-PPTA) is reported. The polymer composite with only 2 wt% of f-PPTA presents a productivity of 12 m² h⁻¹ and an ultrahigh U_e of 20.7 J cm⁻³, which outperforms other extruded dielectric polymers reported in the literatures. Such enhancements of dielectric and capacitive properties have been comprehensively investigated and attributed to the crystallization behavior modulations and conformation changes induced by f-PPTA. As a demonstration of real applications, the dielectric capacitors established based on the extruded films enable tens of times higher efficacy on powering electronic devices than biaxially oriented polypropylene capacitors, in addition to long-term cyclic stability. This study opens up new avenue for the design and fabrication of high-U_e polymer dielectrics that are totally compatible with industrial production.     

Robust pole placement in discrete-time systems

The problem of robust pole placement via a state-space feedback is discussed for discrete-time systems. It is assumed that a discrete-time system is described in terms of the state-space equation x(k+1)=Ax(k)+bu(k),y(k)=c^Tx(k)+eu(k) with uncertain entries of matrices (c, A, b,e). A feedback matrix f is calculated such that the real stability radius of the characteristic polynomial of the closed-loop system is possibly maximal.     

不同调制格式对400 Gb/s通信系统传输容量和距离的影响

单载波400 Gb/s传输是下一代通信系统的主要应用速率,为提高此速率通信在实际工程应用中的传输效率,理论分析了高速通信系统中不同调制方式与传输谱宽的关系,基于16阶正交幅度调制(16QAM)、16QAM/32QAM混传、32QAM、32QAM/64QAM混传和64QAM 5种不同调制格式,对400 Gb/s传输系统的...     

Coexistence of OFDM‐Based IMT‐Advanced and FM Broadcasting Systems

Coexistence analysis is extremely important in examining the possibility for spectrum sharing between orthogonal frequency‐division multiplexing (OFDM)‐based international mobile telecommunications (IMT)‐Advanced and other wireless services. In this letter, a new closed form method is derived based on power spectral density analysis in order to analyze the coexistence of OFDM‐based IMT‐Advanced systems and broadcasting frequency modulation (FM) systems. The proposed method evaluates more exact interference power of IMT‐Advanced systems in FM broadcasting systems than the advanced minimum coupling loss (A‐MCL) method. Numerical results show that the interference power is 1.3 dB and 3 dB less than that obtained using the A‐MCL method at cochannel and adjacent channel, respectively. This reduces the minimum separation distance between the two systems, which eventually saves spectrum resources.     

Performance of optimum wavelet waveform for DS‐CDMA chip waveform over QS‐AWGN channel

In this paper, we search for a better chip waveform based on orthogonal wavelets for direct sequence‐code division multiple access (DS‐CDMA) signals to improve the probability of error (P_e) performance with minimal signal bandwidth variations. First, we derive the P_e expression over a quasi‐synchronous additive white Gaussian noise channel for DS‐CDMA signals, which use various pulse shaping waveforms including orthogonal wavelets as chip waveforms. It is observed that this expression depends on the chip waveform. Then, we design an optimum wavelet by using the relationship between wavelets and filter coefficients to reduce the probability of error. The DS‐CDMA system using the optimum wavelet waveform results in a lower probability of error than those using the conventional chip waveforms such as raised cosine, half‐sine and rectangular waveforms. Especially, the P_e of the optimum wavelet‐based scheme becomes significantly better than those of the conventional chip waveforms‐based schemes under the heavy loading that is the case for commercial wireless systems. When the systems work with full load (i.e. the number of users equals the processing gain), the optimum wavelet‐based system results in 0.5, 2.1 and 4 dB better SNR values than those of the raised cosine, half‐sine and rectangular‐based systems, respectively, for a P_e value of 10^?3. Copyright © 2005 John Wiley & Sons, Ltd.     

Channel characterization of EM waves propagation at MHz frequency through seawater

Electromagnetic (EM) communication is considered as a suitable physical layer choice for SeaWater. SeaWater EM communication presents advantages over acoustic and optical in shallow water and deep oceans.Theoretical analysis of EM wave propagation in SeaWater helps us to estimate maximum distance covered in SeaWater at multiple depth points up to 5500 m. Mathematics of EM propagation in SeaWater (conducting medium) shows dependence on f (Hz), ? (F/m), and σ(S/m) of transmission medium. This paper presents channel characteristics of EM waves propagation at 1 to 20 MHz frequency through SeaWater based on real time data of SeaWater T (C°) and S(ppt) for averaged decades from 1955 to 2012 up to 5500 m.We estimated SeaWater σ (S/m), ?_r (F/m) (using Stogryns model), α (Np/m) (using Helmholtz model), Z(ohms), f_T(Hz), v_p(m/second), τ(second), and P_r(dBm) (using Maxwell equations and Friis law). Analysis of these parameters against multiple depths of SeaWater and frequencies shows that we can not assume constant σ (S/m) (4), ?_r (F/m) (81), f_T (Hz) (888 MHz),v_p(m/second) (3.33?10⁷), and τ (second) (8.2?10^?12) for SeaWater. Estimated P_r(dBm) helped us to analyze that for lower transmission frequencies (means higher ) and for lower σ(S/m), P_r(dBm) decays linearly. While for higher frequencies (means lower ) and for higher σ(S/m), P_r(dBm) faces sudden exponential decay. That negates sudden exponential delay (in general) of P_r(dBm) in SeaWater; it was only possible by assuming constant SeaWater ?_r (F/m) and σ(S/m). Our paper illustrates radio frequency communication for SeaWater in 1 to 20 MHz range and also provides comprehensive performance analysis using MATLAB simulation tool.