Search

One of the most significant concerns in serial digital communication is the synchronization of data bits between the transmitter and receiver. Therefore, the preferred coding symbols should contain an inherited clock signal. The cyclic-shift chirp, which is primarily used in long-range systems, employs a single slope in a symbol, which contains few information for synchronization. Hence, two new forms of cyclic-shift chirp symbols are proposed herein. The associated coding schemes are based on the use of a dual slope within one symbol. Synchronization is inherited in the coding symbol using a dual slope. Additionally, both proposed coding schemes utilize the same decoding technique. The decoded chirp symbol is in the form of a pulse width modulation signal, which can be used for synchronization and retrieving data bits from their duty cycle. The simulation results show that the coding and decoding processes of the proposed coding schemes align with those of a theoretical framework. The error performance analysis for the proposed detection scheme is given and the results of error probability analysis are consistent with the simulation results. Moreover, under a Rayleigh fading channel, the proposed coding schemes provide superior performance compared with other comparable coding schemes.

In a range of IoT applications, edge nodes require minimal size, mass, and power/energy use. When node complexity is severely constrained, the burden of detection falls to the receiving system. In this paper we present a method of detection for RF signals motivated by wildlife radio telemetry, where miniature transmitters emit VHF pulses that are used to detect and localize animals in the field. We address the challenges of limited transmit power and large path losses that lead to low received SNR. In addition, the pulse train structure requires joint frequency acquisition, time synchronization, and detection; our approach addresses the key challenge of large uncertainty in signal parameters. Our algorithm explicitly integrates frequency acquisition and time synchronization, using nearly phase-coherent matched filtering followed by non-coherent pulse combining and a multiple hypotheses test to provide near-optimal detection performance in low SNR scenarios. We provide quantitative results showing performance as a function of SNR and signal uncertainty. When compared to the single pulse detection case as used in existing systems, our multipulse combining approach pulses improves detection performance by 4 dB, even under the conditions of temporal and frequency/phase uncertainty resulting from transmitter design and manufacturing. We also describe an efficient real-time signal processing implementation of the algorithm, including signal tracking that supports localization after initial signal detection.

A novel time division duplex massive MIMO technique is proposed based on performing a pilot-less channel estimation in the uplink (UL) utilizing reconstructed differentially encoded data. Spatial multiplexing and differentially encoded data is applied both in the UL and in the downlink (DL). In this system, a reference signal is the first one of the differentially encoded streams in the UL and DL, and the pilots for data estimation are avoided while maintaining spatial multiplexing capabilities. To improve the channel estimation we propose to use a linear Wiener filter and we also propose different symbols placing strategies in an OFDM grid. We also propose a detection improvement of the UL data utilizing the predicted channels. We perform an analysis of the MSE of the blind channel estimation using the differentially encoded data and analyze the symbol-error-rate for both the UL and the DL when channel aging is considered. The analysis is corroborated via numerical results and the proposed scheme is shown to outperform its pilot-based counterpart.

In this letter, the problem of non-coherent direction of arrival (DOA) estimation is investigated exploiting the sign of the measurements in order to resolve the inherent ambiguity of the problem. Although the phase values are inaccurate, the sign of real and imaginary parts of the measurements will most likely remain correct under limited phase errors. Furthermore, a new approach for solving the problem is proposed employing a modified version of the Majorization-Minimization (MM) technique, without any prior information about the number of incident signals. Some theoretical analyses of our proposed algorithm are also provided in the paper. Finally, the simulation results are presented, demonstrating the efficiency of the proposed algorithm in comparison to some state-of-the-art methods in the literature. [ABSTRACT FROM AUTHOR]

Bluetooth is a common wireless technology that is widely used as a connection medium between various consumer electronic devices. The Bluetooth receiver usually adopts a Viterbi algorithm to improve signal-to-noise ratio performance, but requires complex hardware and calculations for continuous search and estimation for the irrational modulation indexes at the transmission. This paper proposes a non-coherent maximum estimation based 8-State Viterbi FSM to solve these complexity problems. The proposed optimal Viterbi FSM can detect Gaussian frequency-shfit keying symbol without any prior information and estimation for the modulation indexes. The HV1/HV2 packets are used for the estimation of the proposed algorithm and the simulation results have shown performance improvements with about 2dB for 10 -3 BER compared to other ideal approaches such as decision direct method. [ABSTRACT FROM AUTHOR]

Pilot symbol assisted modulation (PSAM) is widely used to obtain the channel state information (CSI) needed for coherent demodulation. It allows the density of pilot symbols to be dynamically chosen depending on the channel conditions. However, the insertion of pilots reduces the spectral efficiency, more severely when the channel is highly time-variant and/or frequency-selective. In these cases a significant amount of pilots is required to properly track the channel variations in both time and frequency dimensions. Alternatively, non-coherent demodulation does not require any CSI for the demodulation independently of the channel conditions. For the particular case of up-link (UL) based on massive single input - multiple output (SIMO) combined with orthogonal frequency division multiplexing (OFDM), we propose to replace the traditional reference signals of PSAM by a new differentially-encoded data stream that can be non-coherently detected. The latter can be demodulated without the knowledge of the CSI and subsequently used for the channel estimation. We denote our proposal as hybrid demodulation scheme (HDS) because it exploits both the benefits of a coherent demodulation scheme (CDS) and a non-coherent demodulation scheme (NCDS) to increase the spectral efficiency. The mean squared error (MSE) of the channel estimation, bit error rate (BER), achieved throughput and complexity are analyzed to highlight the benefits of this differential data-aided channel estimation as compared to other approaches. We show that the channel estimation is almost as good as PSAM, while the BER performance and throughput are improved for different channel conditions with a very small complexity increase.

In the presence of Weibull clutter, the development of sliding window detection processes, based on scale and power invariant distributions, has been extensively examined. This involves the selection of two functions labeled as scale-invariant and secondary CRP (clutter range profile) functions. However, due to the presence of outliers, existing CFAR (constant false alarm rate) algorithms show remarkable CFAR losses. We resort in this work to the practice of a suitable choice of these two functions in order to have a new decision rule with immunity against interfering targets. To do this, a quadruple-order statistics-based CFAR detection algorithm with different four-order statistics are proposed in the presence of log-normal and Weibull clutter disturbances. Via Monte Carlo simulations, the analysis of the false alarm regulation of the proposed detector is studied showing its robustness with respect to clutter parameters. Moreover, for comparison purposes with existing CFAR algorithms, simulated results indicate that lowest CFAR losses can be obtained by the proposed quadruple-order statistics named WHWH-CFAR (Weber–Haykin-Weber–Haykin) in the presence of strong interfering targets. IPIX real data are also performed to test the validity of the proposed detector. [ABSTRACT FROM AUTHOR]

Sixty years of coherent versus non-coherent tradeoff as well as the twenty years of coherent versus non-coherent tradeoff in Multiple-Input Multiple-Output (MIMO) systems are surveyed. Furthermore, the advantages of adaptivity are discussed. More explicitly, in order to support the diverse communication requirements of different applications in a unified platform, the 5G New Radio (NR) offers unprecendented adaptivity, abeit at the cost of a substantial amount of signalling overhead that consumes both power and the valuable spectral resources. Striking a beneficial coherent versus non-coherent tradeoff is capable of reducing the pilot overheads of channel estimation, whilst relying on low-complexity detectors, especially in high-mobility scenarios. Furthermore, since energy-efficiency is of salient importance both in the operational and future networks, following the powerful Index Modulation (IM) pholosophy, we conceive a holistic adaptive pholosophy striking the most appropriate coherent/non-coherent, single-/multiple-antenna and diversity/multiplexing tradeoffs, where the number of RF chains, the Peak-to-Average Power Ratio (PAPR) of signal transmission and the maximum amount of interference tolerated by signal detection are all taken into account. We demonstrate that this intelligent tripple-fold adaptivity offers significant benefits in next-generation applications of mmWave and Terahertz solutions, in space-air-ground integrated networks, in full-duplex techniques and in other sophisticated channel coding assisted system designs, where powerful machine learning algorithms are expected to make autonomous decisions concerning the best mode of operation with minimal human intervention.

The beginning of studying argumentation stems from the time of Old Greece and the development of rhetoric as discipline. Contemporary argumentation theory is based on Aristotle's rhetoric. The development of linguistics and discourse analysis has also brought new perspectives on argumentation. Today's theory looks at argumentation, arguments (as parts of it), assumptions, etc. from the position of pragma-dialectic. In the paper we present the basic characteristics of argumentation, which are supported by examples from our debate practice. We are talking about the basic concepts operated by contemporary argumentation. In this paper we also analyze some of the features of the macrostructure of the debate, the relationship between arguments and the structure of argumentation. Identified elements of argumentation, manifestations, structure, linguistic elements are also empirically substantiated through their existence in concrete discourse.

Orthogonal frequency division multiplexing (OFDM) and multiple-input multiple-output (MIMO) are wireless radio technologies adopted by the new Fifth Generation (5G) of mobile communications. A very large number of antennas (massive MIMO) is used to perform the beam-forming of the transmitted signal, either to reduce the multi-user interference (MUI), when spatially multiplexing several users, or to compensate the path-loss when higher frequencies than microwave are used, such as the millimeter-waves (mm-Waves). Usually, a coherent demodulation scheme (CDS) is used in order to exploit MIMO-OFDM, where the channel estimation and the pre/post-equalization processes are complex and time consuming operations, which require a considerable pilot overhead and also increase the latency of the system. As an alternative, non-coherent techniques based on a differential modulation scheme have been proposed for the up-link (UL). However, it is not straightforward to extend these proposals to the down-link (DL) due to the (usually) reduced number of antennas at the receiver side. In this paper we overcome this problem, and assuming that each user equipment (UE) is only equipped with one single antenna, we propose the combination of beam-forming with a differential modulation scheme for the DL, enhanced by the frequency diversity. The new transmission and reception schemes are described, and the signal-to-interference-plus-noise ratio (SINR) and the complexity are analysed. The numerical results verify the accuracy of the analysis and show that our proposal outperforms the existing CDS with a significant lower complexity. [ABSTRACT FROM AUTHOR]

This paper introduces the structure of a Q-ary pulse position modulation (PPM) signal and presents a noncoherent suboptimal receiver and a noncoherent optimal receiver. Aiming at addressing the lack of an accurate theoretical formula of the bit error rate (BER) of a Q-ary PPM receiver in the additive white Gaussian noise (AWGN) channel in the existing literature, the theoretical formulas of the BER of a noncoherent suboptimal receiver and noncoherent optimal receiver are derived, respectively. The simulation results verify the correctness of the theoretical formulas. The theoretical formulas can be applied to a Q-ary PPM system including binary PPM. In addition, the analysis shows that the larger the Q, the better the error performance of the receiver and that the error performance of the optimal receiver is about 2 dB better than that of the suboptimal receiver. The relationship between the threshold coefficient of the suboptimal receiver and the error performance is also given.

We introduce a novel blind (noncoherent) communication scheme, called modulation on conjugate-reciprocal zeros (MOCZ), pronounced as “Moxie,” to reliably transmit sporadic short-packets over unknown wireless multipath channels. In MOCZ, the information is modulated onto the zeros of the transmitted discrete-time baseband signal’s $z-$ transform, which yields to a codebook of non-orthogonal signals. In the absence of additive noise, the zero structure of the signal is perfectly preserved at the receiver, no matter what the channel impulse response (CIR) is. Furthermore, by a proper selection of the zeros, we show that MOCZ is not only invariant to the CIR but also robust against additive noise. Starting with the maximum-likelihood estimator, we define a low complexity and reliable decoder and compare it to various state-of-the-art noncoherent multipath schemes, such as OFDM index-modulation (IM), OFDM pilot-aided, OFDM differential-modulation, and pulse-position-modulation. Our scheme outperforms all schemes and maintains its performance even if the length becomes shorter than the CIR. [ABSTRACT FROM AUTHOR]

This paper presents a novel implementation of the saddle-point technique for calculating the non-coherent detection probability of targets by airborne surveillance radar in the presence of pulse-to-pulse correlation. It is based on the inverse Laplace transform of the moment generating function for the returned power distribution by means of integration along the path of steepest descent. To illustrate the methodology, the problem of non-coherent pulse integration for a target with gamma-fluctuating partially correlated radar cross-section embedded within compound surface clutter with uncorrelated speckle is revisited. This situation arises for maritime or overland surveillance radar with sufficient frequency agility to fully decorrelate the clutter speckle but not the fluctuations of the target radar cross-section. An exact method and a hierarchy of approximations are described, all of which perform well for this problem. Monte Carlo simulation at the quadrature component level is used to verify the results. [ABSTRACT FROM AUTHOR]

Highlights • The elements squared of array covariance are exploited for non-coherent DOA estimation. • The nonlinear model is approximately cast as a linear model under a high-power reference source. • A simple but effective strategy is designed to avoid ambiguities. • The nested CADiS is adopted to enhance the number of DOFs greatly. • The algorithm performs independent of phase errors and can provide improved performance. Abstract This fast communication presents a non-coherent direction of arrival (DOA) estimation algorithm utilizing the elements squared of the array covariance. Very different from previous non-coherent DOA estimation algorithms, the nonlinear model produced by the squared operation is approximately cast as a linear model, under a high-power reference source. And then, the DOA estimation is efficiently obtained via the mature ℓ 1 -norm minimization. The proposed algorithm can be applied to arbitrary arrays. Focused on the estimation accuracy, the nested coprime array with displaced subarrays (CADiS) is exploited. To resolve the ambiguity problems in the scenario that the sources impinging on the array from the range [ − 90 ∘ , 90 ∘ ] , a simple but effective strategy is introduced. The proposed algorithm performs independent of the phase errors and can provide improved DOA estimation accuracy with reduced computational complexity in large snapshot case. Simulation results demonstrate the effectiveness and superiority of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Massive MIMO is one of the salient techniques for achieving high spectral efficiency in the next-generation wireless networks. Recently, a combined strategy of the massive MIMO and the artificial noise (AN), namely, AN assisted massive (ANAM) MIMO has been investigated for security enhancement. However, most of the recent studies have been built upon the assumption of perfect channel state information (CSI) at the eavesdropper (ED), the results of which may be too pessimistic in terms of security because there exists no ED-friendly downlink training from the base station in the practical ANAM systems. In this paper, we provide more sophisticated analysis on the secrecy performance of the ANAM systems assuming that the CSI of the ED channels are unknown to both the base station and the ED or partially known to the ED. We measure the secrecy in terms of the leakage rate to the ED (or the secrecy rate to the legitimate users) and characterize their upper and lower bounds in the high signal-to-noise ratio regime. Our analytical result is represented by a single compact expression as a function of the number of ED antennas, the dimensionality of signal space, and the channel coherence time, and thus offers useful insights that help us fully exploit the secrecy potential of the ANAM systems. Finally, several useful observations are made from the numerical examples. [ABSTRACT FROM AUTHOR]

Composite spectrum (CS) is a data-fusion technique that reduces the number of spectra to be analyzed, simplifying the analysis process for machine monitoring and fault detection. In this work, vibration signals from five components of a combine harvester (thresher, chopper, straw walkers, sieve box, and engine) are obtained by placing four accelerometers along the combine-harvester chassis in non-optimal locations. Four individual spectra (one from each accelerometer) and three CS (non-coherent, coherent and poly-coherent spectra) from 18 cases are analyzed. The different cases result from the combination of three working conditions of the components—deactivated (off), balanced (healthy), and unbalanced (faulty)—and two speeds—idle and maximum revolutions per minute (RPM). The results showed that (i) the peaks can be identified in the four individual spectra that correspond to the rotational speeds of the five components in the analysis; (ii) the three formulations of the CS retain the relevant information from the individual spectra, thereby reducing the number of spectra required for monitoring and detecting rotating unbalances within a combine harvester; and, (iii) data noise reduction is observed in coherent and poly-coherent CS with respect to the non-coherent CS and the individual spectra. This study demonstrates that the rotating unbalances of various components within agricultural machines, can be detected with a reduced number of accelerometers located in non-optimal positions, and that it is feasible to simplify the monitoring with CS. Overall, the coherent CS may be the best composite spectra formulation in order to monitor and detect rotating unbalances in agricultural machines.

Trellis-based detector is an effective method to demodulate non-coherent continuous-phase modulated sequences. Most of them have been derived for the maximum likelihood sequence estimation setting, while only few contributions have been proposed for the maximum a posteriori (MAP) symbol detection, required when soft information is needed for iterative detection and decoding. In this letter, we derive a new symbol MAP non-coherent receiver with reduced state space representation compared with the existing extended state-space-based approaches. While having the same performance, it enables a lower complexity. [ABSTRACT FROM AUTHOR]

A non-coherent spatial modulation scheme assuming no channel state information (CSI) at the receiver is proposed in this letter. Different from the differential spatial modulation, in which the difference between the previous information block and the current information block is employed, the proposed scheme only utilizes the estimation of the previous transmission block to eliminate the restriction of CSI. Moreover, a generalized multi-ring amplitude phase shift keying (APSK) constellation with arbitrary modulation order of PSK on each circle is used in the scheme, and the optimal one is found through the design method proposed in this letter. Simulation results show that, at the same spectral efficiency, the proposed scheme with optimal constellation outperforms the scheme with traditional PSK, QAM, and existing APSK in Rayleigh fading channel. [ABSTRACT FROM PUBLISHER]

A novel method based on clustered point process was proposed to calculate average bit error probability（ABEP） of UWB non-coherent system on IEEE 802.15.3a channel.In particular,the expectation and variance of the sig-nal to noise ratio（SNR） in the detection window were derived in closed form.Moreover,lognormal and normal variants were employed and compared to approximate the SNR in receiver window with respects to several characteristics.The results show that lognormal approximation is more feasible than normal approximation.In term of performance with PPM and OOK modulations,the efficiency of lognormal approximation is respectively much better than that of normal approximation.

In this paper, we introduce self-coherent orthogonal frequency-division multiplexing (OFDM), a well-known non-coherent technique in optical communications, for wireless radio frequency communications. Self-coherent OFDM provides complete immunity against phase noise (PN) using a non-coherent receiver and a significantly higher spectral efficiency than self-heterodyne (self-het) OFDM, which utilizes at most 50% of the available spectrum for communications. We present the performance analysis of self-coherent OFDM over additive white Gaussian noise and frequency selective fading channels, and show by simulations that self-coherent OFDM provides both higher spectral efficiency and better bit error rate performance than self-het OFDM. Considering that filter realization in high-frequency bands is challenging, we adopt the undersampling downconversion technique in conjunction with self-coherent OFDM. We show that with the self-coherent demodulation, the additional PN introduced by undersampling downconversion can be significantly reduced. We compare analytically the system performance of self-coherent OFDM using undersampling downconversion with two other conventional OFDM systems: one with super-heterodyne receiver and the other with undersampling downconversion. We show theoretically and by simulations that both in AWGN and frequency selective fading channels, self-coherent OFDM with undersampling downconversion outperforms the two conventional OFDM systems even when intercarrier interference compensation schemes are applied. [ABSTRACT FROM PUBLISHER]

This paper presents the detector design and symbol error rate (SER) analysis of $M$ -ary amplitude shift keying over multipath fading channels using amplitude-coherent detection (ACD). The optimum detector is derived using the maximum likelihood criterion, and then it is used to derive two efficient low-complexity suboptimal detectors. The probability distribution function of the decision variables and the SER of the two suboptimal detectors are expressed using simple closed-form analytical formulas when single receiving antenna is used. The SER with receiver diversity is obtained using Monte Carlo simulation. The obtained analytical and simulation results reveal that ACD can provide reliable SER as compared with noncoherent detection. Moreover, we present an efficient blind channel estimation algorithm using ACD and hybrid modulation frame structures. [ABSTRACT FROM PUBLISHER]

Discrete signaling schemes are proposed for non-coherent, single-antenna, Rayleigh block-fading channels (RBFCs). The schemes are inspired by the capacity-achieving distribution. A nested Monte-Carlo method is developed to compute the mutual information across the RBFC. Mutual information curves are presented and compared with other signaling schemes proposed in the literature. [ABSTRACT FROM PUBLISHER]

Component importance measures have been defined and applied so far mostly for coherent systems. This paper develops and compares possible extensions of the traditional measures to non-coherent systems. The focus is on Birnbaum- and Criticality-type importances, both with respect to system unavailability and system failure intensity. Several versions are suggested for both measure types, each with different interpretation and potential applications. The measures are presented in terms of Boolean system logic functions so that they can be quantified with usual fault tree techniques even for large systems without manually solving and derivation of lengthy analytical functions. Examples demonstrate the method and discover some potential problems in system design if a component can initiate an accident while it is also part of a safety function to prevent an accident. Results are compared to earlier published results obtained with different algorithms. [ABSTRACT FROM AUTHOR]

This paper focuses on analytically modeling the multipath error effects in the code tracking Delay-Locked-Loop (DLL) with standard and narrow early-late correlators of Global Navigation Satellite System (GNSS) for Cosine Binary Offset Carrier (CosBOC) modulated signal. The latter one will be part of the modernized American Global Positioning System (GPS), the Russian GLONASS (GLObal NAvigation Satellite System in English), the new European Galileo and the Chinese Compass/BeiDou systems, signal plan. The mathematical formalism of the analytical model of the Correlation Function is proposed for any CosBOC modulated signal. Also derived, are the models of the DLL Discriminator Functions and the Multipath Error Envelopes for both coherent and non-coherent configurations. The computer implementations have shown that all the proposed models match closely the numerical ones. [ABSTRACT FROM AUTHOR]

Localization of a non-cooperative target with binary detectors is considered. A general expression for the Fisher information for estimation of target location and power is developed. This general expression is then used to derive closed-form approximations for the Cramér-Rao bound for the case of non-coherent detectors. Simulations show that the approximations are quite consistent with the exact bounds. [ABSTRACT FROM AUTHOR]

This article aims to investigate synchronization of UWB signals between transmitter and receiver in communication networks. In Ultra wideband technology, synchronization consists of two sections. In the former section coarse synchronization has been accomplished which leads to fine one at the end. In first section of coarse synchronization, maximum detection was utilized. In order to improve the performance of the synchronization algorithm and decreasing the complexity of calculation, in second section of coarse synchronization search back algorithm was presented. Synchronizations were performed in MATLAB and the results were the indication of a decrease in calculation and improvement in synchronization performance. To evaluate the performance of synchronization algorithms MAE, RMSE were utilized as two criteria and the results obtained explains the fact that RMSE criterion in search back algorithm has better performance for lower SNR. [ABSTRACT FROM AUTHOR]

Self-heterodyne OFDM (self-het OFDM) is known to provide complete immunity against frequency-offset and phase noise, with a much lower RF frontend complexity, when compared to conventional OFDM techniques. Self-het OFDM is considered to be a promising physical layer technology for millimeter-wave RF communications, where the implementation of low complexity stable oscillators is technically difficult. Although self-het OFDM has great potential, it has only been studied for additive white Gaussian noise and two-ray channel models. In this paper, we analyze the performance of self-het OFDM for general frequency selective channels and show that the standard self-het OFDM undergoes an outage if the RF carrier is affected by deep fading. In order to avoid this, we introduce a new technique called smart carrier positioning. We show both analytically and by simulation that the smart carrier positioning can improve the diversity order and the performance of standard self-het OFDM by approximately 4dB at bit error rate of 10^-2. In addition, we investigate the optimum power allocation between the carrier and the OFDM subcarriers under frequency selective conditions. [ABSTRACT FROM AUTHOR]

Abstract: Historically, fault trees are extensively used in Probabilistic Safety Assessment (PSA) to model and evaluate the probability and consequence of failures of complex engineering systems, such as nuclear power plants. Scenarios of hypothetical accidents resulting in severe core damage can be developed. Petri net is another modeling technique that offers many advantages when comparing with fault trees, such as is ability to represent the time sequence of the events along with their duration. In this research, Petri net theory is extended to model system failures. The transformations required to model logic gates by Petri nets are explored and examples provided. Methods for qualitative analysis for Petri nets are presented. The application of Petri net in the airlock system of a Canada Deuterium Uranium (CANDU) reactor is explored. It is further demonstrated that Petri net can be used in both coherent and non-coherent systems. [Copyright &y& Elsevier]

We present a method to compute, quickly and efficiently, the mutual information achieved by an independent identically distributed (IID) complex Gaussian signal on a block Rayleigh-faded channel without side information at the receiver. The method accommodates both scalar and multiple-input multiple-output (MIMO) settings. Operationally, this mutual information represents the highest spectral efficiency that can be attained using Gaussian codebooks. Examples are provided that illustrate the loss in spectral efficiency caused by fast fading and how that loss is amplified when multiple transmit antennas are used. These examples are further enriched by comparisons with the channel capacity under perfect channel-state information at the receiver, and with the spectral efficiency attained by pilot-based transmission. [ABSTRACT FROM PUBLISHER]

An ultrawideband transceiver employing chirp pulse modulation is proposed for LDR communication. In contrast to the Gaussian pulse, a transmitted pulse modulated with different chirps can maximize the transmitted energy under low supply voltage and is thus amenable to the voltage scalability of the advanced CMOS technologies. The binary data is encoded with different chirp frequencies and two identical pulses are sent per data bit to enable non-coherent demodulation which simplifies the receiver architecture. A demodulation calibration loop is also incorporated to optimize the SIR performance. In-band/out-of-band SIR as low as -21~dB/-59~dB can be tolerated in order to achieve BER better than 10 ^-3. Implemented in 0.18 \mum CMOS, the transceiver can sustain data rates up to 20 Mbps, and achieve energy efficiency of 0.77 nJ/bit for transmitting and 2.7 nJ/bit for receiving under 1.8 V supply. [ABSTRACT FROM PUBLISHER]

This paper describes a digital baseband designed for use in a non-coherent IR-UWB system. Owing to the nonlinear statistics introduced by the energy-sampling RF front-end, the baseband employs a new quadratic correlation technique that achieves comparable performance to a matched filter classifier, with the added benefit of being robust to SNR estimation errors. Additionally, "alias-free codes" are introduced that allow for pulse-level synchronization accuracy without requiring any increase in front-end complexity. Fabricated in a 90 nm CMOS process, the digital baseband utilizes significant parallelism in addition to clock and data gating to achieve low-power operation, with supply voltages as low as 0.55 V. At a clock frequency of 32 MHz, the baseband requires 14-to-79 µs to process a preamble during which it consumes an average power of 1.6 mW, while payload demodulation requires 12 pJ/bit. [ABSTRACT FROM AUTHOR]

Non-coherent ultra-wideband (UWB) receivers offer an attractive low-complexity solution to ranging with UWB radios. They use a simple receiver architecture that can operate at very low sampling rates compared to the Nyquist rate. In this paper, time-of-arrival (TOA) estimation performances of two different searchback algorithms for non-coherent impulse radio UWB systems are analyzed: jump back and search forward (JBSF) and serial backward search (SBS). Average ranging errors for both algorithms are formulated using noise-based ranging thresholds and at sub-Nyquist sampling rates. For JBSF, a lower bound on the average ranging error is obtained using an error-minimizing threshold. Also, a semi-analytic technique for the selection of the searchback window length is presented. For SBS, noise-based threshold selection for both single-cluster and multi-cluster channels are introduced. Computer simulations in IEEE 802.15.4a channels provide insights on the selection of some of the critical parameters for accurate ranging. The simulation results show that JBSF typically performs better than SBS if the inter-cluster delay parameter ( K) is not selected appropriately for SBS. In both cases, it is shown that even at sampling rates much smaller than the Nyquist rate, ranging accuracies on the order of 33 cm can be obtained using a non-coherent UWB receiver. [ABSTRACT FROM AUTHOR]

A dual-band telemetry, which has different carrier frequencies for power and data signals, is used to maximize both power transfer efficiency and data rate for transcutaneous implants. However, in such a system, the power signal interferes with the data transmission due to the multiple magnetic couplings paths within the inductive coils. Since the power level of the transmitted power signal is significantly larger than that of the data signal, it usually requires a high-order filter to suppress the interference. This paper presents a non-coherent DPSK receiver without a high-order filter that is robust to the interference caused by the power carrier signal. The proposed scheme uses differential demodulation in the analog domain to cancel the interference signal for a dual-band configuration. The data demodulation also uses subsampling to avoid carrier synchronization circuits such as PLLs. The experimental results show that the demodulator can recover 1 and 2 Mb/s data rates at a 20 MHz carrier frequency, and it is able to cancel an interference signal that is 12 dB larger than the data signal without using complex filters. The demodulator is fabricated in a 0.35 µm CMOS process, with a power consumption of 6.2 mW and an active die area of 2.6 × 1.7 mm². [ABSTRACT FROM AUTHOR]

In this paper, we present analytical bit error probability results for M-ary modulation concatenated with Reed Solomon (RS) codes. The analysis of bit error probability is nontrivial as the number of bits per symbol for the RS codes may not be an integer multiple of the number of bits per symbol for a modulation symbol. We propose a Markov chain technique which allows analytical evaluation of the bit error probability for such cases. The performance of RS coding with coherent biorthogonal, coherent/non-coherent orthogonal modulation over an additive white Gaussian noise (AWGN) channel is evaluated. Simulation of the bit error probability of RS code concatenated with a Nordstrom Robinson (NR) code as an inner code is performed and compared with the case of biorthogonal modulation. From the results, we notice that a stronger inner code gives better bit error probability. In addition, the throughput of the coded system with biorthogonal modulation over an AWGN channel is discussed. For a Rayleigh flat fading and block fading channel, we analyze the bit error probability of RS codes concatenated with biorthogonal modulation. From the result, we notice that a stronger outer code gives a better bit error probability for the case of Rayleigh flat fading channel. [ABSTRACT FROM AUTHOR]

Non-coherent receivers are attractive for pulsed Ultra-WideBand (UWB) systems due to the implementation simplicity. However, they have to face the shortage of performance degradation. Several techniques were proposed to alleviate the noise effect and promote the receiver performance, among which is the weighted combining of multiple integration sub-intervals. In this paper, the performance of the weighted non-coherent receiver for UWB On-Off Keying (UWB-OOK) signal in multipath channels is analyzed, in terms of bit-error-rate. In addition, a closed-form expression of the approximately near-optimal weighting coefficient set is derived, and two simple weighting coefficient sets are proposed as well. Finally, the analytic results are verified via the computer simulations, which reveal obvious performance improvements to the conventional energy detector. [ABSTRACT FROM AUTHOR]

Mainly due to its implementation simplicity, the non-coherent Ultra-Wide Band (UWB) receiver is attractive for lower data rate applications, which gains much attention again in recent years. In this paper, a General Likelihood Ratio Test (GLRT) based non-coherent receiver on UWB Pulse-Position-Modulation (PPM) signal in multipath channels is derived, and a novel structure is proposed as well. Subsequently, the closed-form expressions of asymptotic error-rate performance related to the non-coherent receiver are also derived and verified. [ABSTRACT FROM AUTHOR]

For any earthquake, the slipping fault and the source of high-frequency seismic waves, by and large, coincide. On a more local scale, however, the areas of high seismic slip rate and of increased high-frequency radiation output (seismic luminosity) need not match. To study in some detail how slip rate and seismic luminosity are interrelated, a systematic study is performed that uses 251 records of teleseismic P waves from 23 intermediate-depth earthquakes of magnitude 6.8 and above. From a broadband trace we extract two time histories: (1) displacement and (2) 0.5–2.5 Hz band-passed and squared velocity, or ``HF power'', and calculate correlation coefficient, ρ between the two. To reduce the bias related to formation of P coda, a special procedure is applied to data. We estimated the average value ρ = 0.52 (range of event averages 0.35 to 0.65) for the correlation coefficient between the radiated time histories for displacement and ``HF power'', which is considerably below the ``ideal'' value of unity. We argue that the same or even lower value characterizes the degree of slip rate - seismic luminosity correlation at the fault. Two factors may contribute to the revealed decorrelation: (1) random fluctuations of observed HF power (inevitable for a signal with a limited bandwidth), and (2) the genuine mismatch of slip rate and mean luminosity. We show that these factors, acting separately, would result in the ρ values equal to, correspondingly, 0.72 and 0.80. We also show that genuine decorrelation is statistically significant. We conclude that the observed values of ρ indicate genuine differences between the distributions of the slip rate and the seismic luminosity over the fault area. These results provide important constraints both for the accurate wide-band simulation of strong ground motion and for theoretical dynamic source models. [ABSTRACT FROM AUTHOR]