Showing papers on "Phase-shift keying published in 2001"
TL;DR: A simple closed-form approximation for the distribution of the peak-to-average power ratio (PAPR) in strictly band-limited orthogonal frequency-division multiplexing (OFDM) signals is developed, based on the level-crossing rate analysis.
Abstract: The distribution of the peak-to-average power ratio (PAPR) in strictly band-limited orthogonal frequency-division multiplexing (OFDM) signals is studied. Assuming that the base-band OFDM signal is characterized as a band-limited complex Gaussian process, we first attempt to derive the exact distribution of the PAPR in the band-limited OFDM signals. Since this distribution cannot be expressed in a closed form, we further develop a simple closed-form approximation, based on the level-crossing rate analysis. Comparisons of the proposed distributions with those obtained by computer simulations show good agreement and convergence with an increase in the number of subcarriers.
658 citations
TL;DR: A class of particularly attractive modulations called binary offset carrier (BOC) is described, important characteristics of modulations for radionavigation are presented, several specific BOC designs are introduced, and receiver processing for these modulations are described.
Abstract: Current signaling for GPS employs phase shift keying (PSK) modulation using conventional rectangular (non-return to zero) spreading symbols. Attention has been focused primarily on the design of the spreading code and selection of the keying rates. But better modulation designs are available for next-generation radionavigation systems, offering improved performance and the opportunity for spectrum sharing while retaining implementation simplicity. This paper describes a class of particularly attractive modulations called binary offset carrier (BOC). It presents important characteristics of modulations for radionavigation, introduces several specific BOC designs that satisfy different applications in evolving radionavigation systems, describes receiver processing for these modulations, and provides analytical and numerical results that describe the modulations' performance and demonstrate advantages over comparable conventional PSK modulations with rectangular spreading symbols.
422 citations
TL;DR: It is shown that the instantaneous envelope power function can be transformed into a linear sum of Chebyshev polynomials and the roots of the derivative of EPF can be obtained by solving a polynomial.
Abstract: A procedure for computing the continuous-time peak-to-average power ratio (PAR) of an orthogonal frequency-division multiplexing (OFDM) signal, with binary phase-shift keying (BPSK) subcarriers, is developed. It is shown that the instantaneous envelope power function (EPF) can be transformed into a linear sum of Chebyshev polynomials. Consequently, the roots of the derivative of EPF can be obtained by solving a polynomial. Using the procedure to evaluate the difference between the continuous-time and discrete-time PAR, it is shown that an oversampling factor of four is accurate.
399 citations
TL;DR: A method for coherently detecting and decoding turbo-coded binary phase shift keying signals transmitted over frequency-flat fading channels is discussed and results show the influence of pilot symbol spacing, estimation filter size and type, and fade rate.
Abstract: A method for coherently detecting and decoding turbo-coded binary phase shift keying (BPSK) signals transmitted over frequency-flat fading channels is discussed. Estimates of the complex channel gain and variance of the additive noise are derived first from known pilot symbols and an estimation filter. After each iteration of turbo decoding, the channel estimates are refined using information fed back from the decoder. Both hard-decision and soft-decision feedback are considered and compared with three baseline turbo-coded systems: (1) a BPSK system that has perfect channel estimates; (2) a system that uses differential phase shift keying and hence needs no estimates; and (3) a system that performs channel estimation using pilot symbols but has no feedback path from decoder to estimator. Performance can be further improved by borrowing channel estimates from the previously decoded frame. Simulation results show the influence of pilot symbol spacing, estimation filter size and type, and fade rate. Performance within 0.49 and 1.16 dB of turbo-coded BPSK with perfect coherent detection is observed at a bit-error rate of 10/sup -4/ for normalized fade rates of f/sub d/T/sub s/=0.005 and f/sub d/T/sub s/=0.02, respectively.
307 citations
TL;DR: This letter proposes a precise numerical technique for calculating the effect of the CFO on the BER or symbol error in an OFDM system and uses an infinite series expression for the error function in order to express the average probability of error in terms of the two-dimensional characteristic function of the ICI.
Abstract: Orthogonal frequency-division multiplexing (OFDM) is sensitive to the carrier frequency offset (CFO), which destroys orthogonality and causes intercarrier interference (ICI), Previously, two methods were available for the analysis of the resultant degradation in performance. Firstly, the statistical average of the ICI could be used as a performance measure. Secondly, the bit error rate (BER) caused by CFO could be approximated by assuming the ICI to be Gaussian. However, a more precise analysis of the performance (i.e., BER or SER) degradation is desirable. In this letter, we propose a precise numerical technique for calculating the effect of the CFO on the BER or symbol error in an OFDM system. The subcarriers can be modulated with binary phase shift keying (BPSK), quaternary phase shift keying (QPSK), or 16-ary quadrature amplitude modulation (16-QAM), used in many OFDM applications. The BPSK case is solved using a series due to Beaulieu (1990). For the QPSK and 16-QAM cases, we use an infinite series expression for the error function in order to express the average probability of error in terms of the two-dimensional characteristic function of the ICI.
289 citations
TL;DR: Analytical expressions for the symbol error probability (SEP) for a hybrid selection/maximal-ratio combining (H-S/MRC) diversity system in multipath-fading wireless environments and presents numerical examples illustrating that H-S-MRC, even with L/spl Lt/N, can achieve a performance close to that of N-branch MRC.
Abstract: We derive analytical expressions for the symbol error probability (SEP) for a hybrid selection/maximal-ratio combining (H-S/MRC) diversity system in multipath-fading wireless environments. With H-S/MRC, L out of N diversity branches are selected and combined using maximal-ratio combining (MRC). We consider coherent detection of M-ary phase-shift keying (MPSK) and quadrature amplitude modulation (MQAM) using H-S/MRC for the case of independent Rayleigh fading with equal signal-to-noise ratio averaged over the fading. The proposed problem is made analytically tractable by transforming the ordered physical diversity branches, which are correlated, into independent and identically distributed (i.i.d.) "virtual branches," which results in a simple derivation of the SEP for arbitrary L and N. We further obtain a canonical structure for the SEP of H-S/MRC as a weighted sum of the elementary SEPs, which are the SEPs using MRC with i.i.d. diversity branches in Rayleigh fading, or equivalently the SEPs of the nondiversity (single-branch) system in Nakagami fading, whose closed-form expressions are well-known. We present numerical examples illustrating that H-S/MRC, even with L/spl Lt/N, can achieve a performance close to that of N-branch MRC.
281 citations
TL;DR: Novel blind channel estimators based on the finite alphabet property of information symbols are derived in this paper for OFDM and related multicarrier code-division multiple access (MC-CDMA) systems to improve symbol recovery at the expense of altering the transmitter and complicating the equalizer.
Abstract: Novel blind channel estimators based on the finite alphabet property of information symbols are derived in this paper for OFDM and related multicarrier code-division multiple access (MC-CDMA) systems. The resulting algorithms are applicable not only to standard OFDM transmitters with cyclic prefix, but also to the zero padded OFDM transmissions that improve symbol recovery at the expense of altering the transmitter and complicating the equalizer. Based on FFT-processed received data, channel identifiability is guaranteed regardless of channel zero locations and various channel estimation algorithms become available by trading on the complexity for performance. Unlike existing blind channel estimators, the proposed alternatives require short data records especially for PSK transmissions. The inherent scalar ambiguity is easily resolved because it has unit amplitude and phase values drawn from a finite set. Decoupling channel from symbol estimation enables a phase-directed operation that improves upon decision-directed schemes that are known to suffer from error propagation. Practical issues are also addressed including the presence of frequency guard intervals, constellation and power loading, various frame designs, coded transmissions as well as semi-blind and online implementations for systems with training sequences. The algorithms are tested with simulations and also compared with existing alternatives in a realistic HIPERLAN/2 setting.
206 citations
TL;DR: Results from shallow water testing in two different scenarios are presented to illustrate the techniques and their performance and two direct-sequence receivers potentially suitable for the underwater channel are presented.
Abstract: Multiuser underwater acoustic communication is one of the enabling technologies for the autonomous ocean-sampling network (AOSN). Multiuser communication allows vehicles, moorings, and bottom instruments to interact without human intervention to perform adaptive sampling tasks. In addition, multiuser communication may be used to send data from many autonomous users to one buoy with RF communications capability, which will then forward the information to shore. The two major signaling techniques for multiuser acoustic communication are phase-shift keying (PSK) direct-sequence spread-spectrum (DSSS) and frequency-shift keying (FSK) frequency-hopped spread-spectrum (FHSS). Selecting between these two techniques requires not only a study of their performance under multiuser conditions, but also an analysis of the impact of the underwater acoustic channel. In the case of DSSS, limitations in temporal coherence of the channel affect the maximum spreading factor, leading to situations that may be better suited to FHSS signals. Conversely, the multipath resolving properties of DSSS minimize the effects of frequency-selective fading that degrade the performance of FSK modulation. Two direct-sequence receivers potentially suitable for the underwater channel are presented. The first utilizes standard despreading followed by decision-directed gain and phase tracking. The second uses chip-rate adaptive filtering and phase tracking prior to despreading. Results from shallow water testing in two different scenarios are presented to illustrate the techniques and their performance.
180 citations
TL;DR: In this article, a new direct-conversion wide-band (23-31 GHz) six-port receiver is proposed suitable for millimeter-wave integrated system design, which is found to be robust, rugged, low cost, and suitable for use in broad-band wireless mass-market QPSK communications.
Abstract: A new direct-conversion wide-band (23-31 GHz) six-port receiver is proposed suitable for millimeter-wave integrated system design. This new hardware receiver is found to be robust, rugged, low cost, and suitable for use in broad-band wireless mass-market QPSK communications. The prototype circuits are fabricated to validate this new concept with our miniaturized hybrid microwave integrated-circuit technology and the proposed receiver topology is also suitable for monolithic-microwave integrated-circuit fabrication. This application-specific integrated receiver is designed on the basis of a wide-band six-port junction and other analogical circuits in the form of a simple multichip module. Bit-error-rate measurements and simulation results are shown and discussed in the presence of noise, adjacent signal interference, local-oscillator (LO) phase shift, and LO phase noise. The maximum bit rate is fundamentally limited by the speed of the video and decoder circuits. Nevertheless, several hundred megabits per second can be achieved at low cost.
177 citations
TL;DR: It is shown that new minimum distance estimator performs close to the QAM bound and provides a large improvement over the power law estimator at moderate to high signal-to-noise ratios.
Abstract: In this paper, we present the true Cramer-Rao lower bounds (CRLBs) for the estimation of phase offset for common quadrature amplitude modulation (QAM), PSK, and PAM signals in AWGN channels. It is shown that the same analysis also applies to the QAM, FSK, and PAM CRLBs for frequency offset estimation. The ratio of the modulated to the unmodulated CRLBs is derived for all QAM, PSK, and PAM signals and calculated for specific cases of interest. This is useful to determine the limiting performance of synchronization circuits for coherent receivers without the need to simulate particular algorithms. The hounds are compared to the existing true CRLBs for an unmodulated carrier wave (CW), BPSK, and QPSK. We investigated new and existing QAM phase estimation algorithms in order to verify the new phase CRLB. This showed that new minimum distance estimator performs close to the QAM bound and provides a large improvement over the power law estimator at moderate to high signal-to-noise ratios.
165 citations
TL;DR: Cramer-Rao lower bounds (CRLBs) are derived for the estimation of signal-to-noise ratio (SNR) of binary phase-shift keying and quaternary phase- shift keying modulated signals.
Abstract: We derive Cramer-Rao lower bounds (CRLBs) for the estimation of signal-to-noise ratio (SNR) of binary phase-shift keying (BPSK) and quaternary phase-shift keying (QPSK) modulated signals. The received signal is corrupted by additive white Gaussian noise (AWGN). The lower bounds are derived for non-data-aided estimation where the transmitted symbols are unknown at the receiver. The bounds are compared to those for data-aided estimations (known symbols at the receiver). It is shown that at low SNR there is a significant difference between the bounds for non-data-aided and data-aided estimations.
TL;DR: A bit-error-rate (BER) analysis for closed-loop transmit diversity in a time-selective Rayleigh fading channel containing feedback delay demonstrates that, for a given transmitted energy and number of transmit antennas, open-loop outperforms closed- loop at sufficiently fast channel fading.
Abstract: In this paper, a bit-error-rate (BER) analysis for closed-loop transmit diversity in a time-selective Rayleigh fading channel containing feedback delay is presented. In the absence of feedback delay, closed-loop transmit diversity always outperforms open-loop transmit for a given transmitted signal energy. This is no longer true in the presence of feedback delay. We derive closed-form expressions of the average BER for this case assuming QPSK and BPSK signaling. The results of the analysis are instrumental for comparing closed-loop with open-loop schemes under given operating conditions. In particular, we demonstrate that, for a given transmitted energy and number of transmit antennas, open-loop outperforms closed-loop at sufficiently fast channel fading. We also show that, for a given transmitted signal energy and fading rate, closed-loop outperforms open-loop for sufficiently large numbers of transmit antennas while the total average transmitted signal energy is kept constant. For some special cases, closed-form expressions for the fading rate at which the performance of open-loop is equal to closed-loop are obtained.
TL;DR: A suitable Markov model with a finite number of states is introduced, designed to approximate both the values and the statistical properties of the correlated flat fading channel phase, which poses a more severe challenge to PSK transmission than amplitude hiding.
Abstract: This paper addresses the design and performance evaluation with respect to capacity of M-PSK turbo-coded systems operating in frequency-flat time-selective Rayleigh fading. The receiver jointly performs channel estimation and turbo decoding, allowing the two processes to benefit from each other. To this end, we introduce a suitable Markov model with a finite number of states, designed to approximate both the values and the statistical properties of the correlated flat fading channel phase, which poses a more severe challenge to PSK transmission than amplitude hiding. Then, the forward-backward algorithm determines both the maximum a posteriori probability (MAP) value for each symbol in the data sequence and the MAP channel phase in each iteration. Simulations show good performance in standard correlated Rayleigh fading channels. A sequence of progressively tighter upper bounds to the capacity of a simplified Markov-phase channel is derived, and performance of a turbo code with joint iterative channel estimation and decoding is demonstrated to approach these capacity bounds.
TL;DR: In this article, a method to perform a predictive search for a given amplitude and phase modulation response in twisted nematic liquid crystal displays is presented, based on a simple physical model that considers the effect of liquid-crystal layers located in the vicinity of the edges, which are not able to tilt.
Abstract: A method to perform a predictive search for a given amplitude and phase modulation response in twisted nematic liquid crystal displays is presented. The algorithm is based on a simple physical model that we recently proposed and that considers the effect of liquid-crystal layers located in the vicinity of the edges, which are not able to tilt. This model was demonstrated to explain accurately the experimental transmittance modulation curves. Here the model is applied to perform a predictive search for an optimized modulation by changing the input and output polarization configurations. A generalized configuration to generate and detect elliptically polarized light is proposed. The method is applied for seeking two different configurations useful for optical image processors: phase-only modulation and amplitude-only modulation. The excellent agreement with the experimental measurements validates the potential of the proposed method.
TL;DR: Simulation results and parameter comparison show that these STTC with a feedforward structure offer a better performance on fast fading channels than other known codes while maintaining a comparable performance on slow fading channels.
Abstract: New space-time trellis-coded modulation (STTC) which best satisfies the design criteria proposed by Tarokh, et al. (see IEEE Trans. Inform. Theory, vol.44, p.746-65, 1998) over fast fading channels are presented. STTC with a feedforward structure have been constructed by a systematic and exhaustive search. Simulation results and parameter comparison show that these codes offer a better performance on fast fading channels than other known codes while maintaining a comparable performance on slow fading channels.
TL;DR: The effect of cochannel interference on the performance of digital mobile radio systems in a Nakagami (1960) fading channel and maximal ratio combining (MRC) diversity is analyzed in the presence of multiple equal-power cochannel interferers and additive white Gaussian noise.
Abstract: The effect of cochannel interference on the performance of digital mobile radio systems in a Nakagami (1960) fading channel is studied. The performance of maximal ratio combining (MRC) diversity is analyzed in the presence of multiple equal-power cochannel interferers and additive white Gaussian noise. Closed-form expressions are derived for the average probability of error as well as outage probability of both coherent and noncoherent (differentially coherent) binary frequency-shift keying and binary phase-shift keying schemes in an environment with cochannel interference and noise. The results are expressed in terms of the confluent hypergeometric function of the second kind, a function that can be easily evaluated numerically. The analysis assumes an arbitrary number of independent and identically distributed Nakagami interferers.
05 Nov 2001
TL;DR: In this paper, a probe source pulse is transmitted and a complicated multipath signal is measured by an array of source/receiver elements. The signal is time reversed and retransmitted into the ocean.
Abstract: Time reversal, or phase-conjugation, refocuses energy back to a probe source location despite the complexity of the propagation channel. A probe source pulse is transmitted and a complicated multipath signal is measured by an array of source/receiver elements. The signal is time reversed and retransmitted into the ocean. The time-reversal process recombines this temporal multipath at the original probe source range and depth. The ability of time reversal to reduce dispersion and its simplicity of implementation makes it ideal for underwater acoustic communications, which must mitigate the inter-symbol interference caused by the time-varying multipath dispersion. Furthermore, time reversal focuses energy at the desired depth, thus mitigating the effects of channel fading. An experiment was conducted in June 2000 demonstrating that the time-reversal process recombined the temporal multipath resulting in reduced bit errors for communication. Communication sequences were transmitted over a distance of 10 km both in range independent and range dependent environments north of Elba Island, Italy. The range independent transmissions were made in 110-m deep water and the range dependent transmissions were made upslope from 110-m deep water into 40-m deep water. Single source transmissions were also measured in the same channels. Quantitative bit error results are shown for BPSK (binary phase shift keying) and QPSK (quadrature phase shift keying).
11 Jun 2001
TL;DR: It is shown that when STTCM is used in systems with a large product of the numbers of the transmit and the receive antennas, the multiple fading subchannels between individual transmit and receive antenna pairs converge to an additive white Gaussian noise (AWGN) channel and the design of codes with maximum coding gain is governed by the minimum trace of the distance matrices.
Abstract: It has been established that the appropriate criteria for space-time trellis coded modulation (STTCM) design on slow Rayleigh fading channels are maximization of the minimum rank and the minimum determinant of the distance matrices. We show here that when STTCM is used in systems with a large product of the numbers of the transmit and the receive antennas (>3), the multiple fading subchannels between individual transmit and receive antenna pairs converge to an additive white Gaussian noise (AWGN) channel and the design of codes with maximum coding gain is governed by the minimum trace of the distance matrices, or the minimum Euclidean distance between any two codewords over all transmit antennas. A number of new 4 and 8-PSK codes based on the proposed design criterion were constructed and shown to be superior to other known codes.
TL;DR: In attempting to find a spectrally and power efficient channel code which is able to exploit maximum diversity from a wireless channel whenever available, this work investigates the possibility of constructing a full antenna diversity space-time turbo code.
Abstract: In attempting to find a spectrally and power efficient channel code which is able to exploit maximum diversity from a wireless channel whenever available, we investigate the possibility of constructing a full antenna diversity space-time turbo code. As a result, both three-antenna and two-antenna (punctured) constructions are shown to be possible and very easy to find. To check the decodability and performance of the proposed codes, we derive non-binary soft-decoding algorithms. The performance of these codes are then simulated and compared with two existing space-time convolutional codes (one has minimum worst-case symbol-error probability; the other has maximal minimum free distance) having similar decoding complexity. As the simulation results show, the proposed space-time turbo codes give similar or slightly better performance than the convolutional codes under extremely slow fading. When fading is fast, the better distance spectra of the turbo codes help seize the temporal diversity. Thus, the performance advantage of the turbo codes becomes evident. In particular, 10/sup -5/ bit-error rate and 10/sup -3/ frame-error rate can be achieved at less than 6-dB E/sub b//N/sub 0/ with 1 b/s/Hz and binary phase-shift keying modulation. The practical issue of obtaining the critical channel state information (CSI) is also considered by applying an iteratively filtered pilot symbol-assisted modulation technique. The penalty when the CSI is not given a priori is about 2-3 dB.
TL;DR: A general approach for analyzing the performance of digital signaling with multichannel reception on correlated fading channels is presented, exploiting the complex Gaussian model for the joint distribution of the fading on the multiple channels and applying recent results on the unified performance analysis.
Abstract: A general approach is presented for analyzing the performance of digital signaling with multichannel reception on correlated fading channels. The approach is based on: (i) exploiting the complex Gaussian model for the joint distribution of the fading on the multiple channels; and (ii) applying recent results on the unified performance analysis of digital signaling on fading channels using alternative representations of the Q(/spl middot/) and related functions. Numerical results that illustrate the effect of correlation on the diversity gain from multichannel reception are also presented.
TL;DR: A new fractionally-spaced maximum a posteriori (MAP) equalizer for data transmission over frequency-selective fading channels and is presented in an iterative (turbo) receiver structure.
Abstract: This paper presents a new fractionally-spaced maximum a posteriori (MAP) equalizer for data transmission over frequency-selective fading channels. The technique is applicable to any standard modulation technique. The MAP equalizer uses an expanded hypothesis trellis for the purpose of joint channel estimation and equalization. The fading channel is estimated by coupling minimum mean square error techniques with the (fixed size) expanded trellis. The new MAP equalizer is also presented in an iterative (turbo) receiver structure. Both uncoded and conventionally coded systems (including iterative processing) are studied. Even on frequency-flat fading channels, the proposed receiver outperforms conventional techniques. Simulations demonstrate the performance of the proposed equalizer.
Patent•
07 Mar 2001TL;DR: In this article, the log-likelihood ratio (LLR) metrics on code symbols are estimated as products of various constant values and various combinations of the in-phase and quadrature components of a demodulated soft decision.
Abstract: A method and apparatus for computing soft decision input metrics to a turbo decoder includes circuits associated with eight-ary phase shift keyed (8PSK) modulation and sixteen-ary quadrature amplitude modulation (16QAM). In both implementations log-likelihood ratio (LLR) metrics on code symbols are estimated as products of various constant values and various combinations of the in-phase and quadrature components of a demodulated soft decision. In the implementation associated with the 16QAM modulation scheme, an estimate of the carrier-signal-to-interference (C/I) ratio is also used to estimate some of the LLR metrics. Estimates of the LLR metrics may also be obtained in association with generalized square QAM and M-ary PSK modulation schemes including, e.g., 64QAM, 256QAM, and 16PSK.
TL;DR: This work deals with interference suppression in asynchronous direct-sequence code-division multiple-access (CDMA) systems employing binary phase-shift keying modulation and derives a new family of minimum mean-square-error detectors, which differ from their conventional counterparts in that they minimize a modified cost function.
Abstract: We deal with interference suppression in asynchronous direct-sequence code-division multiple-access (CDMA) systems employing binary phase-shift keying modulation. Such an interference may arise from other users of the network, from external low-rate systems, as well as from a CDMA network coexisting with the primary network to form a dual-rate network. We derive, for all of these cases, a new family of minimum mean-square-error detectors, which differ from their conventional counterparts in that they minimize a modified cost function. Since the resulting structure is not implementable with acceptable complexity, we also propose some suboptimum systems. The statistical analysis reveals that both the optimum and the suboptimum receivers are near-far resistant, not only with respect to the other users, but also with respect to the external interference. We also present a blind and a recursive least squares-based, decision-directed implementation of the receivers wherein only the signature and the timing of the user to be decoded and the signaling time and the frequency offset of the external interferer are assumed known. Finally, computer simulations show that the proposed adaptive algorithm outperforms the classical decision-directed RLS algorithm.
25 Nov 2001
TL;DR: A new differential modulation scheme for multiple-antenna systems based on square space-time block codes (STBC) when neither the transmitter nor the receiver knows channel state information is proposed, which potentially allows the spectral efficiency to be increased by carrying information not only on orientations but also on amplitudes.
Abstract: We propose a new differential modulation scheme for multiple-antenna systems based on square space-time block codes (STBC) when neither the transmitter nor the receiver knows channel state information. Compared with the known differential unitary space-time modulation (DUSTM), the proposed constellations generally have multiple amplitudes and do not have group properties. This generalization potentially allows the spectral efficiency to be increased by carrying information not only on orientations (or phases) but also on amplitudes. Two non-coherent decoders, optimal differential decoder (DD) and near-optimal DD, are derived for flat Rayleigh fading channels. Particularly, the near-optimal DD inherits the decomposition decoding property retained by STBC with coherent receiver and thus has linear complexity. Compared with the best-known cyclic group constellations designed for DUSTM, our proposed constellations with the near-optimal DD have significantly lower probability of error and lower decoding complexity.
01 Jan 2001
TL;DR: The channel capacity of M-ary pulse position modulation (PPM) ultra-wideband (UWB) communications over the additive white Gaussian noise channel is computed demonstrating a fundamental trade-off in UWB system design.
Abstract: We compute the channel capacity of M-ary pulse position modulation (PPM) ultra-wideband (UWB) communications over the additive white Gaussian noise channel. The computation extends the known capacity of PPM orthogonal signals to incorporate UWB-specific constraints. The constraints are the power spectrum density limitation under FCC Part 15 rules and a specified spreading ratio. The UWB capacity is expressed as a function of range demonstrating a fundamental trade-off in UWB system design. UWB capacity is also compared to the capacity of M-ary phase shift keying (PSK) direct sequence spread spectrum (DS-SS). It is shown that for the same power constraint,. both systems have similar capacity at high signal to noise ratio (SNR). At low SNR, UWB has a significant advantage for multilevel modulations with M>4, while for M=2,4, DS-SS has a slight advantage.
30 Sep 2001
TL;DR: In this paper, the authors show theoretically and experimentally that the complicated Mach-Zehnder modulator used at the receiver side can be replaced by a standard narrow optical filter.
Abstract: Optical differential phase shift keying (DPSK) may be considered as a duobinary signal. Considering duobinary coding properties, we show theoretically and experimentally that the complicated Mach-Zehnder modulator used at the receiver side can be replaced by a standard narrow optical filter.
07 Oct 2001
TL;DR: The ability of a simple statistically based physical model to accurately represent the channel behavior is demonstrated and the results of this model are compared to more conventional models that assume complex normal distributions of the channel matrix elements.
Abstract: This paper presents measured data from a narrowband multiple-input multiple-output (MIMO) channel probe in an indoor office/laboratory environment. The system employs ten transmit and ten receive antennas and computes the 10 /spl times/ 10 narrowband channel matrix at 2.45 GHz every 80 milliseconds. We use the data to study the statistical behavior of the channel coefficients and the resulting channel capacity. We also demonstrate the ability of a simple statistically based physical model to accurately represent the channel behavior. The results of this model are compared to more conventional models that assume complex normal distributions of the channel matrix elements.
TL;DR: A space-time block-coded orthogonal frequency-division multiplexing (STBC-OFDM) selective fading channels which does not require channel knowledge either at the transmitter or at the receiver is introduced.
Abstract: We introduce a space-time block-coded orthogonal frequency-division multiplexing (STBC-OFDM) selective fading channels which does not require channel knowledge either at the transmitter or at the receiver. The decoding algorithm is based on generalized maximum-likelihood sequence estimation. We investigate the performance of the proposed scheme over two-tap Rayleigh fading channels. Simulation results show the performance to be near optimum.
TL;DR: In this article, a novel technique for increasing the spectral efficiency of millimetre-wave fiber-radio systems by employing wavelength interleaving in conjunction with optical single sideband modulation, is proposed and demonstrated.
Abstract: A novel technique for increasing the spectral efficiency of millimetre-wave fibre-radio systems by employing wavelength interleaving in conjunction with optical single sideband modulation, is proposed and demonstrated. The technique has been demonstrated experimentally by employing a wavelength interleaved optical add-drop multiplexer and transmission of a 155 Mbit/s BPSK signal at 36 GHz over 20 km of fibre.
TL;DR: A new class of linear multiuser detectors, which can be applied when the users employ BPSK modulation and the fading coefficients of the active users are known at the receiver, and sensible approximations are proposed to facilitate their use in CDMA systems that employ long codes.
Abstract: In this paper, we design and analyze a new class of linear multiuser detectors, which can be applied when the users employ BPSK modulation and the fading coefficients of the active users are known at the receiver (such as base-station demodulation). The tools of asymptotic distribution of the spectrum of large random matrices are used to show that relative to the classical minimum mean-square-error (MMSE) receiver, the output signal-to-noise ratio (SNR) improves by halving the number of effective interferers and adding 3 dB to the input SNR. We also propose sensible approximations to the proposed linear receivers so as to facilitate their use in CDMA systems that employ long codes.