Frequency Non-selective Fading Channels Research Articles

PAPR and BER Performances of OFDM System with Novel Tone Reservation Technique Over Frequency Non-Selective Fading Channel

PAPR and BER Performances of OFDM System with Novel Tone Reservation Technique Over Frequency Non-Selective Fading Channel

Performance of nonorthogonal FSK for the Internet of Things

IEEE 802.15.4 is a popular standard for low-rate wireless communications used for the Internet of Things (IoT). This IEEE standard contains a variety of physical layers (such as SUN, TVWS, RCC LMR, and LECIM) that make use of different modulations, such as nonorthogonal frequency-shift keying (FSK) and position-based FSK. This paper proposes simple closed-form expressions to evaluate the bit-error rate (BER) performance of nonorthogonal FSK schemes used for the IoT. Both coherent and noncoherent detection cases are investigated in additive white Gaussian noise (AWGN) and frequency-nonselective fading channels. In case of AWGN channels, the proposed BER expressions are obtained by selecting and modifying two terms of a union bound on the error probability. In case of fading channels, the proposed BER expressions are obtained by integration of the conditional BER over the fading statistics. Simulation results confirm the good accuracy of the proposed analytical BER expressions for different channel models (such as AWGN, Nakagami-m, Rice, lognormal) and for different detection techniques (such as noncoherent, coherent, and coherent with a residual phase error). Experimental results with wireless transmission and reception confirm the accuracy of the proposed approach. In addition, this paper also presents a BER expression for coherent detection of position-based FSK. Simulation results demonstrate that the presented BER expression for position-based FSK is more accurate than the BER expressions proposed in the literature.

Performance of Direct-Oversampling Correlator-Type Receivers in Chaos-Based DS-CDMA Systems Over Frequency Non-selective Fading Channels

In this paper, we present a study on the performance of direct-oversampling correlator-type receivers in chaos-based direct-sequence code division multiple access systems over frequency non-selective fading channels. At the input, the received signal is sampled at a sampling rate higher than the chip rate. This oversampling step is used to precisely determine the delayed-signal components from multipath fading channels, which can be combined together by a correlator for the sake of increasing the SNR at its output. The main advantage of using direct-oversampling correlator-type receivers is not only their low energy consumption due to their simple structure, but also their ability to exploit the non-selective fading characteristic of multipath channels to improve the overall system performance in scenarios with limited data speeds and low energy requirements, such as low-rate wireless personal area networks. Mathematical models in discrete-time domain for the conventional transmitting side with multiple access operation, the generalized non-selective Rayleigh fading channel, and the proposed receiver are provided and described. A rough theoretical bit-error-rate (BER) expression is first derived by means of Gaussian approximation. We then define the main component in the expression and build its probability mass function through numerical computation. The final BER estimation is carried out by integrating the rough expression over possible discrete values of the PFM. In order to validate our findings, PC simulation is performed and simulated performance is compared with the corresponding estimated one. Obtained results show that the system performance get better with the increment of the number of paths in the channel.

Modelling, analysis and performance comparison of two direct sampling DCSK receivers under frequency non‐selective fading channels

Two direct sampling correlator-type receivers for differential chaos shift keying (DCSK) communication systems under frequency non-selective fading channels are proposed. These receivers operate based on the same hardware platform with different architectures. In the first scheme, namely sum-delay-sum (SDS) receiver, the sum of all samples in a chip period is correlated with its delayed version. The correlation value obtained in each bit period is then compared with a fixed threshold to decide the binary value of recovered bit at the output. On the other hand, the second scheme, namely delay-sum-sum (DSS) receiver, calculates the correlation value of all samples with its delayed version in a chip period. The sum of correlation values in each bit period is then compared with the threshold to recover the data. The conventional DCSK transmitter, frequency non-selective Rayleigh fading channel, and two proposed receivers are mathematically modelled in discrete-time domain. The authors evaluated the bit error rate performance of the receivers by means of both theoretical analysis and numerical simulation. The performance comparison shows that the two proposed receivers can perform well under the studied channel, where the performances get better when the number of paths increases and the DSS receiver outperforms the SDS one.

SEP performance of triangular QAM with MRC spatial diversity over fading channels

This paper presents the mathematical model for symbol error probability of triangular quadrature amplitude modulation in a single-input multi-output environment. The symbol error probability performance is evaluated over fading channels namely Rayleigh, Nakagami-m, Nakagami-n, and Nakagami-q. The maximal-ratio combining technique is considered as spatial diversity algorithm and unified moment-generating-function-based approach is applied to derive the results. The multiple channels considered are independent but not necessarily identically distributed. The results presented are valid for slow and frequency non-selective fading channels only. The symbol error probability expressions obtained contain single integrals with finite limits and integrand composed of elementary functions which help us evaluate our analytical expressions numerically. We also compare these expressions with the error performances obtained through computer simulation, which show excellent agreement. In addition, an example has been simulated to validate our derived mathematical expressions.

A Novel Prediction Model for WBAN Frequency Nonselective Fading Channel

The prediction of the frequency non-selective WBAN fading channel behaviors is investigated. An novel WBAN prediction channel model is implemented based on Suzuki fading channel and Rice method and the parameters of the proposed model has been adjusted through MEA, MEDS, Jakes and Monte Carlo multipath simulation method. The performance evaluation for the adaptive WBAN channel model based on simulations is given. The validity of the proposed prediction model is confirmed by comparison of the first order statistics of the measured data.

INVESTIGATION OF CAPACITY GAINS IN MIMO CORRELATED RICIAN FADING CHANNELS SYSTEMS

This paper investigate the effect of Rician fading and correlation on the capacity and diversity of MIMO channels. The use of antenna arrays at both sides of the wireless communication link (MIMO systems) can increase channel capacity provided the propagation medium is rich scattering or Rayleigh fading and the antenna arrays at both sides are uncorrelated. However, the presence of line-of-sight (LOS) component and correlation of real world wireless channels may affect the system performance. Along with that we also investigate power distribution methods for higher capacity gains and effect of CSI at the transmitter on the capacity for range of SNR. Our investigation follows capacity gain as function of number of antennas and signal-to-noise (SNR) power ratio Block and frequency nonselective Rician fading channel is assumed, and the effect of Rician factor (L) and the correlation parameter (ρ) on the capacity and diversity gains of MIMO channels are found. Index.

Improved Pilot-Aided Channel Estimation for MIMO-OFDM Fading Channels

An improved pilot-aided channel estimation scheme is proposed to enhance the channel estimation accuracy of multiple-input multiple-output-orthogonal frequency division multiplexing (MIMO-OFDM) fading channels. Based on the adaptive path number selection mechanism, the number of paths can be scalable and adaptively changed with the characteristics of MIMO-OFDM fading channels. The fine channel estimation formulas for all data subcarriers are derived. The space-frequency block code-OFDM (SFBC-OFDM) system and a six-path fading channel model are considered as an example of the high mobility MIMO-OFDM wireless communications system. Through simulations it is shown that SFBC-OFDM system using the proposed approach can satisfy the performance requirements over frequency selective and frequency nonselective fast fading channels.

비선택성 레일리 페이딩 채널 환경에서 디지털 M/W 전송 시스템의 전력 스펙트럼 성능 분석

본 논문에서는 디지털 M/W 전송 채널을 비선택성 레일리 페이딩 채널로 모델링하고 직교 주파수 분할 다중화(OFDM ; Orthogonal Frequency Division Multiplexing) 기법을 적용한 디지털 M/W 전송 시스템의 전력 스펙트럼 크기를 시뮬레이션을 통해 분석하였다. 성능 분석 결과, AWGN 환경에서는 고정된 대역폭 내에서 전력 스펙트럼 크기에 큰 널링(ing)이 발생하지 않음을 알 수 있었다. 그리고 비선택성 레일리 페이딩 채널 환경에서는 AWGN 환경보다 전력 스펙트럼 크기가 상대적으로 작아짐을 알 수 있었고, 게다가 반송파 주파수와 이동 차량 속도가 높아지면(도플러 주파수가 커지면) 전력 스펙트럼 크기가 더욱 더 작아짐을 알 수 있었다. In this paper, we modeled digital M/W transmission channel by frequency non-selective fading channel and analyzed the power spectrum magnitude of digital M/W transmission systems adopting OFDM modulation scheme through simulation. From the simulation results, it was found that deep does not appear in the specified fixed bandwidth under the AWGN environment. Also, lower power spectrum magnitude was shown in frequency non-selective fading channel than that in AWGN channel. Futhermore, the power spectrum magnitude value became more lowered when carrier frequency and vehicle speed became higher.

Power-efficient Irregular Repeat-Accumulate Encoded BICM-ID for 16-ary Signal Constellations

The design of power-efficient forward error correction techniques over additive white Gaussian noise (AWGN) and frequency non-selective fading channels is considered in this work. The aim of this paper is to investigate the application of BICM with iterative demodulation and decoding (BICM-ID) system with irregular repeat-accumulate (IRA) codes to minimize the bit error rate (BER) and determine the most suitable constellation and mapping pairs for designing power-efficient BICM-ID systems over AWGN and Rayleigh fading channels using the concept of channel capacity limit. Simulation results have confirmed that a remarkable BER improvement can be achieved using the proposed design criterion. Based on the IRA-encoded BICM-ID technique considered, the BER improvement gained is exhibited either as an additional coding gain, error floor elimination, or both. The code components include the IRA codes, irregular low-density parity-check (ILDPC) codes and convolutional codes (CC). The modulation technique considered is the widely-used 16-ary constellations with various bit mappings .

Exact symbol and bit error probabilities of linearly modulated signals with maximum ratio combining diversity in frequency non-selective Rician and Rayleigh fading channels

The exact symbol and bit error probabilities of linearly modulated signals in frequency non-selective Rician fading channels with Lth diversity branches are derived, where coherent detection with maximum ratio combining (MRC) is used at the receiver. For performance evaluation, the multiplicative distortion is combined with the additive Gaussian noise and form an additive noise is formed. This method allows computing the exact symbol and bit error probabilities of M-ary phase shift keying (M-PSK), M-ary quadrature amplitude modulation (M-QAM), M-ary amplitude modulation (M-AM) and M-ary amplitude modulation phase modulation (M-AMPM) for any arbitrary bit mappings. The results contain several versions of one simple integral. The error probabilities are also obtained for Rayleigh channel, which is a special case of Rice channel. Further, the results for Nakagami-m channel with the integer parameter are found. The results quite match with the previous ones while having simple forms. Also, for some unsolved cases, the exact error probabilities are presented. Simulations are carried out to verify the analytical evaluations.

A Simple Multiphase Coding Technique for Transmit Diversity in Continuous Fading Channels

We propose a simple constellation-precoding technique for coherent phase-shift keying (PSK) modulation. The constellation of coded symbols is designed for a multiple-input-multiple-output (MIMO) system in frequency-nonselective Nakagami-m fading channels. Such a signaling mechanism, which is composed of the precoding technique and orthogonal pulse shaping, is shown to provide error performance and bandwidth efficiency comparable with those of the conventional space-time block codes (STBCs). We present a low-complexity coherent receiver, error bounds, and a code-search criterion for the considered system, which can alternatively operate with or without full channel-state information (CSI). Numerical and simulation results are provided to verify the significant performance improvement obtained by the proposed diversity scheme over Nakagami-m fading. The proposed approach is shown to be more robust against the decrease of adjacent fading sample correlation than the conventional STBCs while continuous fading is considered. For certain wireless environment limitations such as full CSI absence and fast fading, the scheme provides an alternative solution to mitigate the fading effects at the cost of low implementation complexities.

The Performance of Network Coding at the Physical Layer with Imperfect Self-Information Removal

Network capacity for bidirectional communication between pairs of wireless end users assisted by a relay terminal can be improved by network coding at the physical layer (PNC). Narrowband analog network coding (ANC) was introduced as a simpler implementation of PNC in a flat (i.e., frequency-nonselective fading) channel. Recently, broadband ANC has been studied for communication over a frequency-selective fading channel. In ANC, the end user removes its own information from the received signal before detecting the data of the other user. Clearly, the network performance of ANC scheme depends on the self-information removal at the destination terminal. In this paper, we discuss the impact of imperfect self-information removal on the performance of broadband ANC in terms of the bit error rate (BER) and achievable throughput in a frequency-selective fading channel. The theoretical minimum mean square error (MMSE) equalization weight for ANC based on single carrier with frequency domain equalization (SC-FDE) radio access is derived by taking into account the self-interference. We have used analysis and computer simulation to evaluate how the imperfect removal of self-information influences the achievable BER and throughput.

Improving the Performance of Chaos-Based Modulations Via Serial Concatenation

This paper proposes a serially concatenated system with an outer convolutional channel encoder and an inner chaos-based coded modulator. With the help of the principles of symbolic dynamics, the chaotic modulation can be described in terms of a trellis. Owing to this, we show that the resulting system can be designed and analyzed following developments made for serially concatenated channel codes (SCCCs) or bit-interleaved coded-modulation systems. We show how the iterative decoding algorithm used in this concatenated framework can be analyzed through the well-known extrinsic information transfer chart device and how the bit error rate can be bounded using the transfer function of the convolutional channel encoder. Comparison with a related SCCC system in both additive white Gaussian noise and frequency-nonselective fading channels shows that this kind of chaos-based systems keeps the potential advantages of coded-modulation-based systems. We are thus confident that the principles shown here can lead to the design of competitive chaotic discrete communication systems.

The Weibull–Lognormal Fading Channel: Analysis, Simulation, and Validation

In frequency-nonselective fading channels, the partial waves arriving at the mobile receiver cannot explicitly be of homogeneous nature due to nonuniform scattering caused by objects of specific reflective nature. Moreover, shadowing influences the received signal level by causing slow variations to its local mean. In this paper, we investigate a mixture stochastic process accounting for both inhomogeneous scattering and shadow fading by multiplying a Weibull process with a lognormal process. The first process models the possible scattering nonuniformities of the channel, whereas the second process accounts for the slow-term variations of the local mean due to shadowing. An exact solution for the composite probability density function (pdf) will be given, together with approximate solutions for the second-order statistics, i.e., the level crossing rate (LCR) and the average duration of fades (ADF). The approximate solutions come from the assumption of a slowly time-varying lognormal process compared with the Weibull process, the validity of which will be tested via an efficient deterministic simulation scheme that implements the analytical model on a digital computer. Finally, a curve fitting of the LCR to real-world data drawn from channel measurements will demonstrate the flexibility and usefulness of the proposed model.

Performance of Single and Multichannel Coherent Reception under Rician Fading

In the present work, simple closed-form series solutions for the average error rate of several coherent modulation schemes such as, binary phase shift keying (BPSK), binary frequency shift keying (BFSK), differential binary phase shift keying (DBPSK), quadrature phase shift keying (QPSK), offset-QPSK, minimum shift keying (MSK), and square M-ary quadrature amplitude modulation (M-QAM), operating over frequency non-selective slow Rician fading channel and corrupted by additive white Gaussian noise (AWGN) are derived. Further, to improve the link quality, receiver antenna space diversity is considered, where multiple independent and identically distributed (i.i.d.) as well as uncorrelated signal replicas are combined before successive demodulation. The proposed linear predetection combiner follows optimum maximal ratio combining (MRC) algorithm. Starting from a novel unified expression of conditional error probability the error rates are analysed using probability density function (pdf) based approach. The derived end expressions, consisting of rapidly converging infinite series summations of Gauss hypergeometric function, are accurate, free from any numerical integration and general enough, as it encompasses as special situations, some cases of non-diversity, non-fading AWGN and Rayleigh fading. Symbol or, bit error probabilities (SEP/BEP) are graphically displayed against signal to noise ratio (SNR) per bit per channel for all the digital modulation schemes stated above with different values of diversity order L and varying values of the channel specular-to-scatter ratio or, the Rician parameter K, as found from the measured statistics of mobile and indoor wireless channels. In addition, to examine the dependence of error rate performance of M-QAM on the constellation size M, numerical results are plotted for various values of M. Selected simulation results are also provided to verify the analytical deductions. The series solutions presented in current text realize a trade-off between precision and complexity and offers valuable insight into the performance evaluation over a fading channel in a unified manner.

Interference Canceller Based on Cycle-and-Add Property for Single User Detection in DS-CDMA

In this paper, performance of a novel interference cancellation technique for the single user detection in a direct-sequence code-division multiple access (DS-CDMA) system has been investigated. This new algorithm is based on the Cycle-and-Add property of PN (Pseudorandom Noise) sequences and can be applied for both synchronous and asynchronous systems. The proposed strategy provides a simple method that can delete interference signals one by one in spite of the power levels of interferences. Therefore, it is possible to overcome the near-far problem (NFP) in a successive manner without using transmit power control (TPC) techniques. The validity of the proposed procedure is corroborated by computer simulations in additive white Gaussian noise (AWGN) and frequency-nonselective fading channels. Performance results indicate that the proposed receiver outperforms the conventional receiver and, in many cases, it does so with a considerable gain.

Accurate Bit-Error-Rate Analysis of Bandlimited Cooperative OSTBC Networks Under Timing Synchronization Errors

The distributed multiple-input-multiple-output (MIMO) system (e.g., intercluster communication via cooperating nodes in a wireless sensor network) is a topic of emerging interest. Many previous studies have assumed perfect synchronization among cooperating nodes and identically distributed communication links. Such assumptions are rarely valid in practical operating scenarios. This paper develops an analytical framework for computing the average bit error rate (ABER) of a distributed multiple-input-single-output (MISO) space-time-coded system with binary phase shift keying (BPSK) modulation affected by timing synchronization errors. The cooperating nodes use data pulse-shaping filters for transmission over generalized frequency-nonselective fading channels. As an illustrative example, the performance evaluation of a 2 times 1 MISO system that uses distributed orthogonal space-time block coding (OSTBC) is presented, although this approach can be readily extended to analyze distributed transmit diversity with a larger number of cooperating nodes. We show that under certain conditions, a distributed MISO system with time synchronization errors can still outperform a perfectly synchronized single-input-single-output (SISO) system.

Outage performance of MIMO relay channels with maximal ratio transmission

The outage performance of a multiple-input multiple-output (MIMO) relay system over slow frequency-nonselective fading channels, where maximal ratio transmission is adopted at both the source and relay transmitters whereas maximal ratio combining is used at relay and destination receivers, is investigated. A closed-form expression for the outage probability is presented. Numerical results are presented to verify the analysis.

Distributed Space-Time Continuous Phase Modulation Code Design

In this paper, distributed space-time (ST) codes for continuous-phase modulation (CPM) are introduced. The distributed ST codes are designed to operate in wireless networks containing a large set of nodes N, of which only a small a priori unknown subset S sub N will be active at any time. Under the proposed scheme, a relay node transmits a signal which is the product of a diagonal block-based ST code (optimized specifically for ST-CPM transmission) and a signature vector of length N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> uniquely assigned to each node in the network. An efficient method is presented for the design and optimization of appropriate signature vector sets, assuming a quasi-static, frequency nonselective fading channel model. If a properly designed signature vector set is employed it is shown that a diversity order of d = min{N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ,N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> } can be achieved, where N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> is the number of active relay nodes. The decoding complexity of the proposed scheme is shown to be independent of the number of active relay nodes, and non-coherent receiver implementations, which do not require channel estimation, are applicable. Compared to distributed ST transmission with linear modulation, distributed ST-CPM can considerably reduce the energy consumption at the transmitter due to the constant envelope of the transmit signal. At the same time, the additional energy consumption due to more complex receiver processing can be kept low. Therefore, the proposed distributed ST-CPM scheme is particularly apt for energy-efficient cooperative transmission in wireless networks.