Block-coded M-PSK modulation over GF(M)

Channel codes where the redundancy is obtained not from parity symbols, but from expanding the channel signal-set, are addressed. They were initially proposed by G. Ungerboeck (1982) using a convolutional code. Here, a block coding approach is given. Rate m/(m+1) coded 2^m+1-ary phase-shift keying (PSK) is considered. The expanded signal-set is given the structure of a finite field. The code is defined by a square nonsingular circulant generator matrix over the field. Binary data are mapped on a dataword, of the same length as the codewords, over an additive subgroup of the field. The codes using trellises are described, and then the Viterbi algorithm for decoding is applied. The asymptotic coding gain ranges from 1.8 to 6.0 dB for QPSK going from blocklength 3 to 12. For 8-PSK, the gain is from 0.7 to 3.0 dB with blocklength 4 to 8. With only four states in the trellis, codes of any length for QPSK and 8-PSK are constructed, each having an asymptotic coding gain of 3.0 dB. Simulation results are presented. It is found that the bit-error rate performance at moderate signal-to-noise ratios is sensitive to the number of nearest and next-nearest neighbors     

Fully digital M-ary PSK and M-ary QAMdemodulators for land mobile satellite communications

A fully digital implementation of digital modems is the preferred option of system designers because high performance can be achieved at reasonable cost. The author explains the beneficial features inherent in fully digital demodulator implementations. Other features which are required for land mobile satellite communication systems are also discussed. Recently reported techniques for the synchronisation and detection of M-ary PSK and M-ary QAM modulation schemes are reviewed with emphasis placed on those which are well suited to digital implementation     

DC-20 GHz N×M passive switches

High-order, bidirectional, DC-20-GHz switch networks are discussed. Single-chip 1×2, 1×4, and 2×2 switch MMICs have been demonstrated. Multiple chips have been used to demonstrate 4×4 and 1×16 switches. The switches all use a combination of series and shunt passive FET switching elements. The 1×4 switch is made of a single stage of switching elements, rather than the usual two stages of 1×2 switches. The 2×2 switch is comprised of two stages of 1×2 switches. The multiple-chip 4×4 switch is made of four stages of 1×2 switches (using the 2×2 switch MMICs). Two stages of 1×4 switches are used to make the 1×16 switch     

Rotationally invariant trellis-coded modulations withmultidimensional M-PSK

Using a multidimensional approach, the author discovers a large family of rotationally invariant trellis-coded M-PSK (M-ary shift keying) schemes, M⩾8, with nominal coding gains ranging from 3 to 5 dB and with bandwidth requirements the same as, or even less than, those of uncoded M/2-PSK schemes at the same information bit rate. The rotationally invariant schemes have performance and complexities comparable to the best known nonrotationally-invariant trellis-coded two-dimensional M-PSK schemes. Computer simulation results for these schemes, assuming an additive white-Gaussian-noise (AWGN) channel, are reported     

M×N Booth encoded multiplier generatorusing optimized Wallace trees

The architecture of a design method for an M-bit by N -bit Booth encoded parallel multiplier generator are discussed. An algorithm for reducing the delay inside the branches of the Wallace tree section is explained. The final step of adding two N±M-1-bit numbers is done by an optimal carry select adder stage. The algorithm for optimal partitioning of the N ±M-1-bit adder is also presented     

M-ary orthogonal signaling in the presence of Doppler

The performance degradation of an M-ary orthogonal keying (MOK) system due to relative motion between its transmitter and receiver can be minimized by selecting good signaling sets. A formulation for evaluating good signaling sets, or code sets, is developed for Walsh function data modulations. A union bound performance measure which closely approximates the exact probability of a demodulation error, is devised to allow for convenient evaluation of Walsh function codesets. The best Walsh function codesets for codevectors up to length 10 and for M=2, 4, 8 and 16, found by exhaustive search, are presented, along with their performance. In addition, codesets based on error-correcting codes are presented, along with a performance bound expressed in terms of the code's minimum distance     

Extended M-sequence codes for SAC FO-CDMA PONS applications

A new code structure, namely extended M-sequence (EMS) codes, is presented suitable for passive optical networks (PON). Based on these codes, a spectral-amplitude-coding (SAC) fibre-optic code-division multiple-access system (FO-CDMA) is designed with shared optical line terminal (OLT) and flexible optical network units (ONUs) for PON applications. The results shows the proposed system has excellent performance.     

Phase noise effects on M-ary PSK trellis codes

The performance of M-ary phase-shift keying (PSK) coded systems in the presence of added white Gaussian noise (AWGN), with a noisy carrier reference in the receiver, is examined. The results are obtained by combining the Chernoff bound technique with the generating function approach. The bit error probability analysis is carried out for 8- and 16-PSK with code rates of 2/3 and 3/4, respectively. The numerical results obtained demonstrate the error performance degradation due to a Tikhonov phase noise process with parameter α     

A nonsorting VLSI structure for implementing the (M, L) algorithm

A nonsorting structure for implementing the (M, L) algorithm is presented. The processing is based on a survivor selection operation that incorporates parallelism and has an execution time proportional to the product of the logarithm of bM (the number of contender paths), and k (the number of bits used for path metrics). Aside from the path extender(s), the processor area is only a small fraction of the total chip area; most is simply for required storage of path histories and metrics. This means that the structure can support a large M on a single chip. In addition, the structure can be extended to larger M by stacking rows of a few different types of custom chips     

Spectral shaping and digital synthesis of an M-ary timeseries

The use of pulse shaping to control transmitted spectral density precisely is examined. A digital filter architecture is described that not only mitigates the traditional problems of lengthy development intervals and cost manufacturing methods, but offers the additional features of intrinsically coding high-speed binary (M=2) data into M-ary symbols while ensuring highly reproducible, baud-normalized, transmitter pulse shaping. A conceptual basis for the digital synthesis method is first described, including a functional circuit appropriate to the simplest filter realizations. Spectral effects internal to the filter are considered, and a simple method to obtain desired transmitted spectra is outlined. It is shown that even relatively short pulses used in high-level modulation systems lead to impractical memory storage demands; however, the simple expedient of segmenting the finite impulse function greatly reduced the individual memory requirements, though it necessitates intermediate adding operations. Experimental examples illustrate the design methodology for quaternary (M=4) data signals in a Nyquist communication channel and serve as points of reference for addressing performance and design flexibility     

Asymptotic performance of M-ary orthogonal modulation ingeneralized fading channels

The asymptotic (M→∞) probability of symbol error P_e,_m for M-ary orthogonal modulation in a Nakagami-m fading channel is given by the incomplete gamma function P(m, mx) where x=In 2/(E_b/N₀) and E_b is the average energy per bit. For large signal-to-noise ratio this leads to a channel where the probability of symbol error varies as the inverse mth power of E_b/N₀. These channels exist for all m⩾1/2. The special case of m=1 corresponds to Rayleigh fading, an inverse linear channel     

Performance evaluation of M-ary QPRS schemes in severeimpulsive noise environments

The performance of multilevel quadrature partial-response systems (QPRS) in the presence of an additive combination of Gaussian and impulsive noise is analytically evaluated by means of the Fourier-Bessel series expansion method. The model of the impulsive noise used, which closely models atmospheric and/or man-made electromagnetic interference, consists of a stream of Poisson impulses with areas distributed according to a power Rayleigh probability density function. Analytical performance evaluation results are presented for 9, 49, and 225 QPR systems. The results indicate severe system performance degradation, especially for highly bandwidth-efficient systems (e.g. 225 QPRS), mostly due to the long error bursts caused by the impulsive noise tails. However, a qualitative comparison between these results and the corresponding performance results of equivalent QAM schemes demonstrates that 49 QPRS could be a suitable choice for microwave radio or HDTV satellite links operating in pure impulsive noise environments     

Probability of error of M-ary PSK and DPSK on a Rayleighfading channel

M-ary phase-shift keying and differential phase-shift keying (DPSK) on a slow fading Rayleigh channel without diversity is investigated. Expressions for the distribution of the phase angle between a vector with Rayleigh amplitude distribution and a noiseless reference, and between two vectors both with Rayleigh amplitude distribution perturbed by Gaussian noise are obtained     

Measurement of mode partition characteristics of laser diodesmodulated by M-sequences

A method which permits the determination of k-values of laser diodes modulated by M-sequences is described. With this method, the mode partition characteristics of laser diodes in actual operating conditions can be measured. Measurements at frequencies which are lower by two orders of magnitude compared with conventional methods are possible     

Baseband pulse shaping to improve M-ary FSK in satellitemobile systems

Baseband pulse shaping is proposed to improve the performance of M-ary FSK with limiter discriminator integrator detection in a satellite mobile channel. Numerical results obtained for binary, quaternary, and octonary signaling with a Gaussian and a third-order Butterworth IF filter indicate that pulse shaped signals perform significantly better than frequency shift keying (FSK) signals. The error rate floor in the presence of a Doppler shift is also analyzed. Numerical results indicate that the error rate floor of pulse-shaped signals is significantly lower than that of FSK signals     

Optimum control of N-input K-output matrixconverters

Significant developments of the general optimum control theory presented in a previous paper by the authors (1988) are discussed for the specific case of multiphase matrix converters. Results hold, regardless of system configuration, input and output voltage waveforms, and loads. Applications to the most practical converter structures are illustrated, and implementation criteria of the optimum control method are derived. Simulated results confirm the flexibility and effectiveness of the approach     

Performance of convolutionally coded optical M-PPM systemswith imperfect slot synchronization

Performance of convolutionally coded M-ary pulse position modulation (M-PPM) systems in the presence of slot synchronization errors is evaluated for the shot-noise-limited photon-counting receiver and the avalanche photodetection receiver. Both hard and soft (δ-max) demodulation results are given, and two soft-decision metrics are investigated     

Symbol error rate curves for M-QAM signals with multiplecochannel interferers

A recursive algorithm for determining the probability of symbol error in an M-QAM system, subject to multiple-cochannel interferers, is presented. In particular, a recursive formula is derived for determining the symbol-error-rate (SER) of an M-QAM system subject to both multiple-sinusoidal and similar, independent QAM interferers. The result is expected to prove useful in the analysis of such systems exposed to ever-increasing interference