Showing papers on "Quadrature amplitude modulation published in 2004"

OFDM or single-carrier block transmissions?

Abstract: We compare two block transmission systems over frequency-selective fading channels: orthogonal frequency-division multiplexing (OFDM) versus single-carrier modulated blocks with zero padding (ZP). We first compare their peak-to-average power ratio (PAR) and the corresponding power amplifier backoff for phase-shift keying or quadrature amplitude modulation. Then, we study the effects of carrier frequency offset on their performance and throughput. We further compare the performance and complexity of uncoded and coded transmissions over random dispersive channels, including Rayleigh fading channels, as well as practical HIPERLAN/2 indoor and outdoor channels. We establish that unlike OFDM, uncoded block transmissions with ZP enjoy maximum diversity and coding gains within the class of linearly precoded block transmissions. Analysis and computer simulations confirm the considerable edge of ZP-only in terms of PAR, robustness to carrier frequency offset, and uncoded performance, at the price of slightly increased complexity. In the coded case, ZP is preferable when the code rate is high (e.g., 3/4), while coded OFDM is to be preferred in terms of both performance and complexity when the code rate is low (e.g., 1/2) and the error-correcting capability is enhanced. As ZP block transmissions can approximate serial single-carrier systems as well, the scope of the present comparison is broader.

Spectral efficiency limits and modulation/detection techniques for DWDM systems

Abstract: Information-theoretic limits to spectral efficiency in dense wavelength-division-multiplexed (DWDM) transmission systems are reviewed, considering various modulation techniques (unconstrained, constant-intensity, binary), detection techniques (coherent, direct), and propagation regimes (linear, nonlinear). Spontaneous emission from inline optical amplifiers is assumed to be the dominant noise source in all cases. Coherent detection allows use of two degrees of freedom per polarization, and its spectral efficiency limits are several b/s/Hz in typical terrestrial systems, even considering nonlinear effects. Using either constant-intensity modulation or direct detection, only one degree of freedom per polarization can be used, significantly reducing spectral efficiency. Using binary modulation, regardless of detection technique, spectral efficiency cannot exceed 1 b/s/Hz per polarization. When the number of signal and/or noise photons is small, the particle nature of photons must be considered. The quantum-limited spectral efficiency for coherent detection is slightly smaller than the classical capacity, but that for direct detection is 0.3 b/s/Hz higher than its classical counterpart. Various binary and nonbinary modulation techniques, in conjunction with appropriate detection techniques, are compared in terms of their spectral efficiencies and signal-to-noise ratio requirements, assuming amplified spontaneous emission is the dominant noise source. These include a) pulse-amplitude modulation with direct detection, b) differential phase-shift keying with interferometric detection, c) phase-shift keying with coherent detection, and d) quadrature-amplitude modulation with coherent detection.

Quadrature Amplitude Modulation: From Basics to Adaptive Trellis-Coded, Turbo-Equalised and Space-Time Coded OFDM, CDMA and MC-CDMA Systems

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Gain, phase imbalance, and phase noise effects on error vector magnitude

Abstract: The error vector magnitude (EVM) is extensively applied as a measure of communication systems' performance. In this paper, the effects of gain, phase imbalance, and phase noise on EVM are examined. The work is focused on single-carrier, linear, and memoryless modulated signals, such as phase-shift keying and quadrature amplitude modulation (QAM). The EVM is calculated under the assumption that the transmitted signal consists of zero-mean uncorrelated inphase and quadrature components that are corrupted by additive white Gaussian noise. The contributions of this paper are as follows. First, an expression for the EVM is derived using a simple model that accounts for linear transmitter and receiver imperfections, inspired by the works of Cavers and Liao, 1993. Second, a union bound on the symbol error rate (SER) is derived. The root mean square EVM is shown to be independent of the constellation shape. The SER, however, is sensitive to the individual transmitted symbols and, therefore, the constellation shape. The resulting equations are used to examine the relation between EVM, sideband suppression, and phase noise.

Adaptive modulation systems for predicted wireless channels

Abstract: When adaptive modulation is used to counter short-term fading in mobile radio channels, signaling delays create problems with outdated channel state information. The use of channel power prediction will improve the performance of the link adaptation. It is then of interest to take the quality of these predictions into account explicitly when designing an adaptive modulation scheme. We study the optimum design of an adaptive modulation scheme based on uncoded M-quadrature amplitude modulation, assisted by channel prediction for the flat Rayleigh fading channel. The data rate, and in some variants the transmit power, are adapted to maximize the spectral efficiency, subject to average power and bit-error rate constraints. The key issues studied here are how a known prediction error variance will affect the optimized transmission properties, such as the signal-to-noise ratio (SNR) boundaries that determine when to apply different modulation rates, and to what extent it affects the spectral efficiency. This investigation is performed by analytical optimization of the link adaptation, using the statistical properties of a particular, but efficient, channel power predictor. Optimum solutions for the rate and transmit power are derived, based on the predicted SNR and the prediction error variance.

The generalized discontinuous PWM scheme for three-phase voltage source inverters

Abstract: This paper presents analytical techniques for the determination of the expressions for the modulation signals used in the carrier-based sinusoidal and generalized discontinuous pulse-width modulation schemes for two-level, three-phase voltage source inverters. The proposed modulation schemes are applicable to inverters generating balanced or unbalanced phase voltages. Some results presented in this paper analytically generalize the several expressions for the modulation signals already reported in the literature and new ones are set forth for generating unbalanced three-phase voltages. Confirmatory experimental and simulation results are provided to illustrate the analyses.

A magnitude/phase-locked loop system based on estimation of frequency and in-phase/quadrature-phase amplitudes

Abstract: This paper introduces a new phase-locked loop (PLL) system. The proposed system provides the dominant frequency component of the input signal and estimates its frequency. The mechanism of the proposed PLL is based on estimating in-phase and quadrature-phase amplitudes of the desired signal and, hence, has application advantages for communication systems which employ quadrature modulation techniques. The studies demonstrate that the proposed PLL also provides a superior performance for power system applications. Derivation of the mathematical model and theoretical stability analysis of the proposed PLL are carried out using dynamical systems theory. Advantages of the proposed PLL over the conventional PLLs are its capability of providing the fundamental component of the input signal which is not only locked in phase but also in amplitude to the actual signal while providing an estimate of its frequency. Computer simulation is used to evaluate its performance. Evaluations confirm structural robustness of the proposed PLL with respect to noise and distortions.

MIMO systems with adaptive modulation

Abstract: We investigate adaptive modulation (AM) schemes in multiple-input-multiple-output (MIMO) systems with various degrees of freedom (D.F.s), such as the subchannel BER, power and spectral efficiency (SE), to be adapted. The adaptation is considered as a nonlinear constrained nonlinear optimization problem in the spatial domain. We obtained both analytical and numerical solutions for uncoded continuous SE systems and showed that the average spectral efficiency (ASE) achieved is insensitive to the number of adaptable D.F.s and which D.F. is adapted. The discrete SE systems are shown to have some penalty compared with the continuous SE cases, but have similar insensitivity.

Embedding carrier phase recovery into iterative decoding of turbo-coded linear modulations

Abstract: In this paper, we introduce a low-complexity carrier phase estimation algorithm to be integrated into the data decoder of a turbo-coded modem employing a linear modulation. The estimator is based on a pseudo-maximum-likelihood approach and makes iterative use of soft decisions provided by the soft-in/soft-out decoders within the overall turbo-decoding scheme. In doing so, iterative decoding and carrier phase recovery go together iteration after iteration in a "soft decision-directed" mode. This allows performing reliable blind phase estimation and almost ideal coherent detection for values of the signal-to-noise ratio down to a few decibels only, and without the need to resort to narrowband phase-locked loops with large acquisition time. Performance in terms of mean estimated value, root mean-squared estimation error, and overall decoder bit-error rate as derived by simulation are also reported.

Capacity bounds for power- and band-limited optical intensity channels corrupted by Gaussian noise

Abstract: We determine upper and lower bounds on the channel capacity of power- and bandwidth-constrained optical intensity channels corrupted by white Gaussian noise. These bounds are shown to converge asymptotically at high optical signal-to-noise ratios (SNRs). Unlike previous investigations on low-intensity Poisson photon counting channels, such as some fiber optic links, this channel model is realistic for indoor free space optical channels corrupted by intense ambient light. An upper bound on the capacity is found through a sphere-packing argument while a lower bound is computed through the maxentropic source distribution. The role of bandwidth is expressed by way of the effective dimension of the set of signals and, together with an average optical power constraint, is used to determine bounds on the spectral efficiency of time-disjoint optical intensity signaling schemes. The bounds show that, at high optical SNRs, pulse sets based on raised-quadrature amplitude modulation (QAM) and prolate spheroidal wave functions have larger achievable maximum spectral efficiencies than traditional rectangular pulse basis sets. This result can be considered as an extension of previous work on photon counting channels which closely model low optical intensity channels with rectangular pulse shapes.

Digital Modulation Techniques

Abstract: First considers the three basic forms of digital modulation: amplitude-shift-keying, frequency-shift keying, and phase-shift keying Compares binary modulation systems, in terms of power efficiency and spectrum efficiency Explains the principle of quadrature modulation used with M-ary PSK Describes three modulation techniques that offer certain advantages for band-limited, nonlinear channels: offset quadrature phase-shift keying, QPSK, and minimum-shift keying Explains how the technique of quadrature partial response increases the bandwidth efficiency of OAM signaling Describes trellis coded modulation as a combination of convolutional coding and digital modulation, and show an example in detail Shows the principles behind orthogonal frequency-division multiplexing (OFDM) Compares digital modulation techniques in terms of error performance, complexity of implementation, and all bandwidth efficiency

Adaptive selection of surviving symbol replica candidates based on maximum reliability in QRM-MLD for OFCDM MIMO multiplexing

Abstract: The paper proposes an adaptive selection algorithm for surviving symbol replica candidates based on the maximum reliability in ML detection with QR decomposition and M-algorithm (QRM-MLD) for OFCDM MIMO multiplexing. In the proposed algorithm, symbol replica candidates newly-added at each stage are ranked for each surviving symbol replica from the previous stage using multiple quadrant detection. Then, branch metrics are calculated only for the limited number of symbol replica candidates with high reliability based on an iterative loop in increasing order of the accumulated branch metrics from the candidate with the minimum one. Simulation results show that the computational complexity of the proposed algorithm from the viewpoint of the number of real multiplications is reduced to approximately 1/6 and 1/1900, respectively, compared to that of the original QRM-MLD and that of the conventional MLD with squared Euclidian distance calculations for all symbol replica candidates, assuming the identical achievable average block error rate (BLER) performance in 4-by-4 MIMO multiplexing with 16QAM data modulation. The results also show that 1-Gbps throughput is achieved at the E/sub b//N/sub 0/ per receiver antenna of approximately 9 dB using the adaptive selection algorithm in QRM-MLD associated with 16QAM modulation and turbo coding with coding rate of 8/9, assuming a 100-MHz bandwidth for a twelve-path Rayleigh fading channel (rms delay spread, 0.26 /spl mu/sec; maximum Doppler frequency, 20 Hz).

Likelihood function for QRM-MLD suitable for soft-decision turbo decoding and its performance for OFCDM MIMO multiplexing in multipath fading channel

Abstract: This paper proposes likelihood function generation of complexity-reduced maximum likelihood detection with QR decomposition and M-algorithm (QRM-MLD) suitable for soft-decision turbo decoding and investigates the throughput performance using QRM-MLD with the proposed likelihood function in multipath Rayleigh fading channels for orthogonal frequency and code division multiplexing (OFCDM) with multiple-input multiple-output (MIMO) multiplexing Simulation results show that by using the proposed likelihood function generation scheme for soft-decision turbo decoding following QRM-MLD in 4-by-4 MIMO multiplexing, the required average received signal energy per bit-to-noise power spectrum density ratio (E/sub b//N/sub o/) at the average block error rate (BLER) of 10/sup -2/ at a 1-Gbps data rate is significantly reduced compared to that using hard-decision decoding in OFCDM access with 16 QAM modulation, the coding rate of 8/9, and 8-code multiplexing with a spreading factor of 8 assuming a 100-MHz bandwidth Furthermore, we show that by employing QRM-MLD associated with soft-decision turbo decoding for 4-by-4 MIMO multiplexing, the throughput values of 500 Mbps and 1 Gbps are achieved at the average received E/sub b//N/sub o/ of approximately 45 and 93 dB by QPSK with the coding rate of R = 8/9 and 16 QAM with R = 8/9, respectively, for OFCDM access assuming a 100-MHz bandwidth in a twelve-path Rayleigh fading channel

Constellation shaping for pragmatic turbo-coded modulation with high spectral efficiency

Abstract: We propose a new turbo-encoding scheme for high spectral efficiency with performance close to the Gaussian channel capacity. The scheme combines nonuniform signaling on a Gaussian channel with pragmatic turbo-coded modulation (TCM) for simple and flexible implementation. A variable-rate turbo code is followed by a Huffmann code mapping onto nonequiprobable points in a quadrature amplitude modulation constellation. The rate of the turbo code is matched to the Huffmann code by variable puncturing, such that both the input bit rate and the output symbol rate are constant. It is shown that the new scheme provides shaping gains of 0.6 and 0.9 dB, at rates 2 and 3 b/dimension, respectively, compared with the equiprobable pragmatic TCM, and reach about 1 dB from the continuous input Gaussian channel capacity.

Analysis of decision feedback detection for MIMO Rayleigh-fading channels and the optimization of power and rate allocations

Abstract: For an uncoded, K-transmit, N-receive antenna coherent narrow-band communication system employing a decorrelating decision feedback detector (D-DFD), the exact average (over channel realizations) joint error probability (JEP) as well as the average per-symbol error probabilities (SEPs) are derived without making any simplifying assumptions on error propagation. It is proved that the diversity orders of the JEP and the SEP (of every symbol) is limited by error propagation to N-K+1. Based on our exact error probability analysis, however, we suggest an optimization of JEP over nonnegative quadrature amplitude modulation (QAM) constellation sizes (rates) and average powers across transmitters which yield significant improvements over the usual equal power and equal rate assignment. In fact, the JEP of such an optimized design has the much improved diversity order of N (which is also the diversity order obtained through the optimum maximum-likelihood (ML) detector). Moreover, it is seen that these simple optimized designs can achieve a significant fraction of the /spl epsi/-outage capacity even without outer codes. It is also known-but only through simulations-that when the symbols are detected in certain channel realization-dependent orders it is possible to improve substantially over fixed-order detection in the case of the equal rate and equal power assignment. We provide an analysis for a recently proposed channel-dependent ordering rule and show that it does not provide an improvement of the diversity order of the JEP beyond N-K+1. Another ordering rule that was proposed earlier to maximize the worst case post-detection signal-to-noise ratio (SNR) under the perfect feedback assumption is shown to be optimal under a more compelling criterion that does not involve that simplifying assumption. While efficiently computable, this ordering rule is seen to perform almost as well as the optimal channel-dependent ordering rule that minimizes the conditional JEP (and hence the JEP). Nevertheless, a multiple-input multiple-output (MIMO) system with an optimized rate and power allocation and a fixed order of detection is not only less complex but also has a significantly lower JEP than that of the equal-power, equal-rate system, where transmitters are detected in a channel-dependent order, optimal or otherwise.

Wide-band QAM-over-fiber using phase modulation and interferometric demodulation

Abstract: Transmission of microwave quadrature amplitude modulation over an all-Raman 105-km fiber-optic link is demonstrated. The link employs optical phase modulation and single-port interferometric demodulation to deliver up to 6 Gb/s in a single channel.

Equalization strategy for dual-polarization optical transport system

Abstract: A method is provided for an equalization strategy for compensating channel distortions in a dual-polarization optical transport system wherein the received signal includes a complex signal of a first transmitted polarization component and a complex signal of a second transmitted polarization component. In a first step, a blind self-recovery mode used a blind adaptation algorithm in calculating and modifying multiple complex equalizer transfer function coefficients to enable recovery of only the complex signal of the first transmitted polarization component. By recovering only a single polarization component in the first step the degenerate case of recovering only a single transmitted signal at both polarization component outputs of an equalizer is prevented. In a second step, equalization is performed in a training mode for calculating and modifying the multiple complex equalizer transfer function coefficients to enable recovery of the complex signals of the first and second transmitted polarization components. In a third step, equalization is performed in a data directed mode for continuing to calculate and modify the multiple complex equalizer transfer function coefficients to ensure continued recovery of the complex signals of the first and second transmitted polarization components. The method is suited for a digital signal processing implementation in a coherent receiver when a modulation scheme used on a transmitted signal is quadriphase-shift keying (QPSK). In other embodiments, the method can be used with modulation schemes such as binary PSK, M-ary PSK where M>4, or Quadrature Amplitude Modulation (QAM).

Robust QAM modulation classification algorithm using cyclic cumulants

Abstract: In this paper we develop an algorithm based on higher-order cyclic cumulants for the automatic recognition of QAM signals. The method is robust to the presence of carrier phase and frequency offsets. Theoretical arguments are verified with simulations performed for 4-QAM and 16-QAM signals.

Adaptive receivers for bit rate agile (BRA) and modulation demodulation (modem) format selectable (MFS) signals

Abstract: Systems, apparatus, and methods for new generations of wireless systems, including multiple standard, interoperable Third-Generation (3G) and Second-Generation (2G), Spread Spectrum CDMA, WCDMA, GSM, Enhanced GSM systems and CSMA, TDMA and OFDM. Bit Rate Agile (BRA), Modulation and Code Selectable processing techniques of Gaussian Minimum Shift Keying (GMSK), Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (QAM), and of Mis-Matched demodulator filters in which the demodulator filter set is mismatched to the filter set of the signal modulator.

A hybrid adaptive blind equalization algorithm for QAM signals in wireless communications

Abstract: A hybrid adaptive channel equalization technique for quadrature amplitude modulation (QAM) signals is proposed. The proposed algorithm, which is referred to as the modified constant modulus algorithm (MCMA), minimizes an error cost function that includes both amplitude and phase of the equalizer output. In addition to the amplitude-dependent term that is provided by the conventional constant modulus algorithm (CMA), the cost function includes an additive signal constellation matched error (CME) term. This term can be designed to satisfy a set of desirable properties. The MCMA is compared with the CMA for blind equalization. The performance is measured for wireless channels using both transient and steady-state behavior of the mean square error (MSE). It is shown that MCMA is superior and more robust in low signal-to-noise ratio (SNR) environments. Simulation results demonstrate that using MCMA improves adaptive channel equalization by increasing the convergence rate and decreasing the steady-state mean square error.

Exact error-rate analysis of diversity 16-QAM with channel estimation error

Abstract: The bit-error rate (BER) performance of multilevel quadrature amplitude modulation with pilot-symbol-assisted modulation channel estimation in static and Rayleigh fading channels is derived, both for single branch reception and maximal ratio combining diversity receiver systems. The effects of noise and estimator decorrelation on the received BER are examined. The high sensitivity of diversity systems to channel estimation error is investigated and quantified. The influence of the pilot-symbol interpolation filter windowing is also considered.

An orthogonal space-time coded CPM system with fast decoding for two transmit antennas

Abstract: Trellis-coded space-time (TC-ST) coding for continuous-phase modulation (TC-ST-CPM) was recently proposed by Zhang and Fitz. In this paper, we propose an orthogonal space-time coding for CPM (OST-CPM) systems and two transmit antennas. In the proposed OST-CPM, signals from two transmit antennas at any time t are orthogonal while both of them have continuous phases. Similar to Alamouti's OST coding for phase-shift keying (PSK) and quadrature amplitude modulation (QAM) systems, the newly proposed OST-CPM has a fast decoding algorithm.

Design and Analysis of a High-Rate Acoustic Link for Underwater Video Transmission

Abstract: A high bit rate acoustic link for underwater video transmission is examined. Currently, encoding standards support video transmission at bit rates as low as 64 kbps. While this rate is still above the limit of commercially available acoustic modems, prototype acoustic modems based on phase coherent modulation/detection have demonstrated successful transmission at 30 kbps over a deep water channel. The key to bridging the remaining gap between the bit-rate needed for video transmission and that supported by the acoustic channel lies in two approaches: use of efficient image/video compression algorithms and use of high-level bandwidth-efficient modulation methods. An experimental system, based on discrete cosine transform (DCT) and Huffman entropy coding for image compression, and variable rate M-ary quadrature amplitude modulation (QAM) was implemented. Phase-coherent equalization is accomplished by joint operation of a decision feedback equalizer (DFE) and a second order phase locked loop (PLL). System performance is demonstrated experimentally, using transmission rate of 25000 symbols/sec at a carrier frequency of 75 kHz over a 10 m vertical path. Excellent results were obtained, thus demonstrating bit rates as high as 150 kbps, which are sufficient for real-time transmission of compressed video. As an alternative to conventional QAM signaling, whose high-level constellations are sensitive to phase distortions induced by the channel, M-ary differential amplitude and phase shift keying (DAPSK) was used. DAPSK does not require explicit carrier phase synchronization at the receiver, but instead relies on simple differentially coherent detection. Receiver processing includes a linear equalizer whose coefficients are adjusted using a modified linear least square (LMS) algorithm. Simulation results confirm good performance of the differentially coherent equalization scheme employed. Thesis Supervisor: Milica Stojanovic Title: Principal Scientist, MIT Sea Grant College Program

EER architecture specifications for OFDM transmitter using a class E amplifier

Abstract: This letter presents envelope elimination and restoration (EER) architecture specifications in the case of orthogonal frequency division multiplex C band transmission. A key point is the recombination of envelope and phase information by supply modulation of the power amplifier (PA). Imperfections, such as time mismatch and phase noise can reduce the performances of the transmission. Compression and conversion effects when supply modulating the PA are introduced in this letter with the simulation of a class E power amplifier. This amplifier was designed under HP-ADS using a nonlinear MESFET model. Results are reported in terms of error vector measurement and spectrum for two different numbers of sub-carriers 32 and 128 in 16-QAM and 64-QAM cases.

A spectrally clean transmitting system for solid-state phased-array radars

Abstract: Navy radar operations are being curtailed in a littoral environment. This is due to two factors: the encroachment of cell phone systems into the naval radar bands; in-band interference from other radars. The spectral width of most pulsed radars is significantly wider than necessary with present modulation schemes. Most radars utilize some form of constant envelope pulse with phase or frequency modulation. This causes the spectrum to broaden to several times the information bandwidth. If both the amplitude and phase of the transmitted signal are allowed to change, a significantly narrower bandwidth can be achieved. The paper presents a method to create waveforms with instantaneous bandwidths of 20 MHz confined within -100 dB. The theoretical spectral results of three popular phase modulation schemes (phase shift keying, minimum phase shift keying and derivative phase shift keying) are compared with the spectrally clean results. In addition, the Chireix out-phasing method is presented as an alternative to generating amplitude and phase modulated waveforms. The Chireix method provides a way of improving the efficiency compared to the conventional class A power amplifier. Preliminary results are shown for a spectrally clean waveform.

Reduced complexity Schnorr-Euchner decoding algorithms for MIMO systems

Abstract: A new reduced-complexity Schnorr-Euchner decoding algorithm is proposed in this letter for uncoded multi-input multi-output systems with q-QAM (q=4,16,...) modulation. Furthermore, a Fano-like metric bias is introduced to the algorithm from the perspective of sequential decoding, as well as an early termination technique. Simulation results show that these modifications reduce the algorithm complexity efficiently, with only a small degradation in bit error rate at high signal to noise ratios.

A closed-form expression for the exact BER of generalized PAM and QAM constellations

Abstract: We derive an explicit closed-form expression for the exact bit-error rate (BER) computation of generalized hierarchical M-ary pulse amplitude modulations over additive white Gaussian noise (AWGN) and fading channels. This expression can also be used to obtain the exact BER of generalized hierarchical quadrature amplitude modulations (square and rectangular). For the AWGN case, these expressions are in the form of a weighted sum of complementary error functions, and are solely dependent on the constellation size M, the carrier-to-noise ratio, and a constellation parameter which controls the relative message importance.

Contemporary communication systems using MATLAB and Simulink

Abstract: 1. SIGNALS AND LINEAR SYSTEMS. Preview. Fourier Series. Fourier Transforms. Power and Energy. Lowpass Equivalent of Bandpass Signals. 2. RANDOM PROCESSES. Preview. Generation of Random Variables. Gaussian and Gauss-Markov Processes. Power Spectrum of Random Processes and White Processes. Linear Filtering of Random Processes. Lowpass and Bandpass Processes. 3. ANALOG MODULATION. Preview. Amplitude Modulation (AM). Demodulation of AM Signals. Angle Modulation. 4. ANALOG-TO-DIGITAL CONVERSION. Preview. Measure of Information. Quantization. Pulse-Code Modulation. 5. BASEBAND DIGITAL TRANSMISSION. Preview. Binary Signal Transmission. Multiamplitude Signal Transmission. Multidimensional Signals. 6. DIGITAL TRANSMISSION THROUGH BANDLIMITED CHANNELS. Preview. The Power Spectrum of a Digital PAM Signal. Characterization of Bandlimited Channels and Channel Distortion. Characterization of Intersymbol Interference. Communication System Design for Bandlimited Channels. Linear Equalizers. Nonlinear Equalizers. 7. DIGITAL TRANSMISSION VIA CARRIER MODULATION. Preview. Carrier-Amplitude Modulation. Carrier-Phase Modulation. Quadrature Amplitude Modulation. Carrier-Frequency Modulation. Synchronization in Communication Systems. 8. CHANNEL CAPACITY AND CODING. Preview. Channel Model and Channel Capacity. Channel Coding. 9. SPREAD SPECTRUM COMMUNICATION SYSTEMS. Preview. Direct-Sequence Spread Spectrum Systems. Generation of PN Sequences. Frequency-Hopped Spread Spectrum.

Comparison of modulation formats for 42.7-gb/s single-channel transmission through 1980 km of SSMF

Abstract: We experimentally compare nonreturn-to-zero and return-to-zero on-off keying with a number of recently proposed modulation formats for 1980-km 42.7-Gb/s single-channel transmission over standard single-mode fiber. Substantial performance improvements are obtained with the new formats.

Low complexity receiver design for MIMO bit-interleaved coded modulation

Abstract: This paper considers multiple-input multiple-output (MIMO) systems with bit-interleaved coded modulation (BICM). Two receiver structures are considered, one based on zero-forcing, the other on minimum mean square error (MMSE). An approximate log-likelihood (ALL) decoding approach is examined in each case, for PSK and QAM. The resulting receivers are significantly lower complexity compared to the maximum likelihood (ML) receiver. We expand on previous results which showed that for the ZF-ALL receiver the performance gap, compared to ML, reduces when either the number of receive antennas or the modulation order is increased. We demonstrate that the ALL metric with BICM counteracts any noise enhancement from the linear receivers. We also show that the linear BICM schemes outperform the corresponding BLAST approaches.