Dissimilar Channels Research Articles

Performance of a Direct-Detection Spot Mode Division Multiplexing in Multimode Fiber

AbstractMultimode fiber (MMF) regarded as an excellent choice for providing large capacity and high-speed for applications such as data centers due to its adaptability and unwavering quality. The ceaseless development and the increase of Internet users that emphasis on increasing data capacity have promoted mode division multiplexing (MDM) as a promising contender for providing further level of multiplexing freedom by propagating several and dissimilar channels in different mode stream. This paper investigates and analyzes the effects of launching MDM spot mode with various vortex order using vertical-cavity surface-emitting laser array in conjunction with equalization scheme. A capacity of 40 Gbit/s transmitted over MMF long distance of 1500 m has been achieved at a wavelength of 1550.12 nm.

On the Performance of Power Splitting Energy Harvested Wireless Full-Duplex Relaying Network with Imperfect CSI over Dissimilar Channels

The energy harvesting amplify-and-forward full-duplex relaying network over the dissimilar fading environments in imperfect CSI condition is investigated. In this system model, the energy, and information are transferred from the source to the relay nodes by the power splitting protocol with helping of the full-duplex relay node. Firstly, the outage probability, achievable throughput, and the optimal power splitting factor in terms of the analytical mathematical expressions were proposed, analyzed, and demonstrated. Furthermore, the system performance of the proposed model on the connection with all system parameters is rigorously studied. Finally, the numerical results demonstrated and convinced one that the analytical and the simulation results are matched well with each other for all system parameter values using Monte-Carlo simulation. The results show that the system performance degrades significantly but is still in a permissible interval while the channel estimation error increases and the system performance of the mixing scenarios is better in comparison with the Rayleigh-Rayleigh scenario.

Performance of Amplify-and-Forward Relaying with Wireless Power Transfer over Dissimilar Channels

Relaying transmission is a promising approach for enhancing the performance of wireless networks, meanwhile wireless power transfer is an emerging solution for prolonging the lifetime of energy constrained relay nodes. In this framework, the amplify-and-forward (AF) relay network consisting of a power transfer and information source, an energy constrained relay and a destination over dissimilar fading channels is taken into account. First, the relay employs the time switching-based relaying (TSR) protocol to harvest energy from the source. Accordingly, the relay supports the source transmits information to the destination. By utilizing the statistical characteristics of signal-to-noise ratio (SNR), the closed-form expressions of outage probability (OP) and average symbol error probability (ASEP) are derived. By means of the obtained result of OP, we also investigate throughput of the system for delay-limited transmission mode. Moreover, we accordingly evaluate the analysis in details and assess the performance of the considered system in various system parameters, such as energy harvesting time, energy harvesting efficiency, and relay location. Finally, Monte-Carlo simulation is also contributed to confirm the correctness of the analytical results. DOI: http://dx.doi.org/10.5755/j01.eee.21.5.13331

Performance of Amplify-and-Forward Relaying with Wireless Power Transfer over Dissimilar Channels

Performance of Amplify-and-Forward Relaying with Wireless Power Transfer over Dissimilar Channels

Scaled Selection Combining for Adaptive Decode-and-Forward Relaying in Dissimilar Rayleigh Fading Channels

This paper enhances the conventional scaled selection combiner (SSC) for decode-and-forward (DF) relay networks using adaptive M-ary quadrature amplitude modulation (M-QAM) to improve the spectral efficiency. Compared with the conventional SSC designed for the combining of identically distributed diversity branches using the same modulation level, the improved SSC allows all diversity branches to choose different modulation levels according to the dissimilar channel conditions. Different scale factors are used for all diversity branches to reflect not only the performance degradation caused by possible erroneous relaying but also different error-resistance abilities of different levels QAM. We derive the bit-error-rate (BER) expressions for DF relay networks using SSC in a recursive way, with all channels conforming to independently and non-identically distributed (i.ni.d.) Rayleigh fading. Newton’s method is employed to obtain the numerical solutions of the optimal scale factors minimizing the BER, and the approximations of the optimal scale factors are derived in closed form for high SNRs. Theoretical analysis and simulation results show that the improved SSC can effectively combine diversity branches with different modulation levels, and for a DF cooperative network with N relay nodes, SSC achieves the full diversity gain of N+1 if for each branch its source-to-relay SNR is proportional to the (N+1)th power of its relay-to-destination SNR.

Design and Development of HiperLAN/2 Physical Layer Model Based Wavelet Signals

HiperLAN (High Performance Radio LAN) is a Wireless LAN standard. It is defined by the European Telecommunications Standards Institute (ETSI). In ETSI the standards are defined by the BRAN project (Broadband Radio Access Networks). In this paper, we improve HIPERLAN/2 based Orthogonal Frequency-Division Multiplexing OFDM, based wavelet signals execution via a MATLAB/ Simulink simulation .These systems provide channel adaptive data rates up to 54 Mb/s (in a 20 MHz channel spacing) in the 5 GHz radio band. For dissimilar channels. MATLAB/ Simulink modeling proved that the performance of wavelet OFDM has a significant degradation in the packet (PDU or PSDU) error rate (PER) compared to based OFDM on Fast Fourier transform (FFT) due to the considerable channel models. With HiperLAN/2 based DWT-OFDM, Carrier-to-Noise Ratio (C/N) development compared to conventional HiperLAN/2 based FFT-OFDM is accomplished. Keywords: HiperLAN/2, OFDM, DWT, IDWT.

Outage Performance of Relaying with Directional Antennas in the Presence of Co-Channel Interferences at Relays

Relaying with directional antennas helps enhance the link reliability and extend the communication range for millimeter wave 60GHz communication system, particularly in the presence of multiple co-channel interferences (CCIs). In this letter, the outage performance of decode-and-forward (DnF) and amplify-and-forward (AnF) relaying schemes with directional antennas are analyzed and compared. Our derived exact and closed-form expressions using Moschopoulos's gamma series in the presence of multiple CCIs with dissimilar Nakagami fading channels at relays offer more accurate analytic result with practically computational efficiency. Numerical results show that relaying with directional antennas, in the forms of uniformly spaced linear antenna arrays, helps improve the system performance significantly in the presence of CCIs.

On the Performance of an Automatic Frequency Control Loop in Dissimilar Fading Channels in the Presence of Interference

Two effects of a single interference on the performance of an automatic frequency control (AFC) loop are explained, and two measures, average switching rate and mean time to loss of lock, are presented to capture the impact of each effect. These measures are derived in closed-form expressions and single integral formulas in dissimilar fading channels with Rayleigh, Rician, and Nakagami-m distributions. The general case of modulated carriers as well as different special cases are considered. Numerical examples are provided to illustrate the effects of different fading scenarios on the performance of an AFC. The effect of maximum Doppler frequency on the performance of the AFC is also investigated.

Analytical performance evaluation of dual-hop cooperative communication under fading environments

This paper mainly investigates the performance of cooperative communication systems over dissimilar Nakagami-q (Hoyt) and Nakagami-m fading channels. Its relaying protocol selects these relays successfully regenerating the received signals to cooperatively forward the signals through orthogonal channels. The destination finally demodulates the messaged received in both phases exploiting Maximal-Ratio Combining (MRC) technique. Closed-form Symbol Error Rate (SER) expressions for repetition-based relaying protocol and space-time-code-based protocol are elaborated, respectively. Numerical result comparisons between the repetition-based protocol and the space-time-code-based protocol evidently indicate that, given the same spectral efficiency, the latter can provide better performance in terms of SER.

Closed-form symbol error rate expression of decode-and-forward relaying using orthogonal space–time block coding

The authors investigate the symbol error rate (SER) performance of the cooperative decode-and-forward (DF) relaying strategy with orthogonal space–time block coding (OSTBC) applied at all links of source-relay, source-destination and relay-destination. Only when one relay node is able to correctly decode the OSTBC codeword of the source, it will forward source information to the destination with the same OSTBC codeword. The exact SER expressions of DF relaying with OSTBC are presented for M-PSK and M-QAM modulations, respectively, over dissimilar Rayleigh fading channels. By virtue of the multinomial theorem and the law of total probability, the derived expressions are further deduced in closed form. Simulations demonstrate the proposed closed-form analytical results. It is pointed out that such results have seldom appeared in literatures before.

Outage Performance of Cooperative Communication Systems Using Opportunistic Relaying and Selection Combining Receiver

We analyze the performance of cooperative communication systems with opportunistic decode-and-forward for relaying and selection combining receiver at the destination. We derive an exact closed-form expression for the outage of the system over dissimilar Nakagami fading channels. Also, we study its asymptotic outage performance, based on which the optimum power allocations for the source and the relays are determined. Finally, we verify the theoretical results by simulations.

Error rate and diversity order of multinode cooperative communications in dissimilar Nakagami fading channels

Cooperative communications has been recognised as an effective technique to combat multi-path fading impairment and to provide additional diversity advantage for small-size and low-power-consumption mobile terminals. A class of decode-and-forward (DF) relaying serial cooperative communications, in which each node is assumed to be able to determine whether the received signals can be successfully decoded or not, has recently been proposed and analysed over Rayleigh fading channels. Since the Nakagami fading channels represent a wide variety of realistic channels, such serial cooperative networks should be investigated over such channels before putting into real applications. In this paper, we analyse the performance of such serial cooperative transmission systems thoroughly over dissimilar Nakagami fading channels. We derive a closed-form symbol-error-rate expression for the case of M-ary phase shift keying (PSK) modulation. Moreover, we evaluate the system diversity property and investigate the achievable diversity order under two specific channel conditions. Finally, we perform simulations to verify the theoretical findings.

Multi-dialect speech recognition method and apparatus

Apparatus and method for improving the speed an accuracy of recognition of speech dialects, or speech tansferred via dissimilar channels is described. The invention provides multiple models tailored to specific segments or dialects, and/or speech channels, of the population. However, there is not a proportional increase in recognition time or computing power or computing resources needed. Probability density functions for the acoustic descriptors are provided which are shared among the various models. Since there is a common pool of probability density functions which are mapped or pointed to for the different acoustic descriptors for each different dialect or speech channel model, the memory requirements for the speech recognition apparatus and method are significantly reduced. Each model is comprised of triphonemes which are modelled by discrete probability distribution functions forming hidden Markov models or statistical word models. Any one probability density function is assigned or mapped to many different triphonemes in many different dialects or different models. The invention provides for an automatic selection of the best model in real time wherein the best fit is determined by a voting process.

Error probability performance of L-branch diversity reception of MQAM in Rayleigh fading

New exact expressions involving hypergeometric functions are derived for the symbol-error rate (SER) of M-ary quadrature amplitude modulation (MQAM) for L branch diversity reception in Rayleigh fading and additive white Gaussian noise (AWGN). The diversity combining techniques considered are maximum ratio combining (MRC) and selection combining (SC). MRC with identical channels and dissimilar channels are analyzed.

Error rates for Rayleigh fading multichannel reception of MPSK signals

This paper provides a new closed form expression for calculating the probability that an MPSK signal will lie in a particular decision region when received over N independent and identically distributed Rayleigh fading channels corrupted by additive white Gaussian noise. This expression is applied to provide a unified method to derive the exact symbol error rate and bit error rate for MPSK signals considering N channel diversity reception. The N channel diversity reception techniques considered are maximal ratio combining (MRC) and selection combining. MRC with identical channels and dissimilar channels is considered. The results for MRC can be extended to provide an approximation for the error rates of MPSK under equal gain combining.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Control of cardiac output by regional blood flow distribution

Most data indicate that cardiac output is normally controlled by the systemic circulation rather than by the heart. This manuscript extends that concept by analyzing the systemic circulation with a mathematical model comprised of two dissimilar blood flow channels. The concept and the model are not new and have, in fact, a strong anatomical and historical basis. However, re-examination using a quantitative, computerized analysis scaled to human dimensions is made in the face of new experimental data.