Slow Fade to Blackout

We propose the Optimum Power Allocation (OPA) scheme for Distributed Antenna Systems(DAS) in the time-varying Rayleigh fading channel. Recently, the OPA schemes which uses the Channel State Information (CSI) including a small scale (fast) fading have been proposed. However, the channel is changing vary fast over time due to small scale fading, therefore Bit Error Rate (BER) increases. Because of this reason, we derive the OPA for minimizing BER in DAS, which only uses a large scale fading to CSI and excepts a small scale fading. The simulation results show that the proposed OPA achieves better BER performance than conventional OPA considering a small scale fading in time-varying Rayleigh fading channel, and also has similar performance in Rayleigh flat-fading environment. The BER performance of proposed OPA which derived in Rayleigh fading channel is similar to minimum BER of Ricean fading channel which has small Line-of-Sight (LOS).

The probability of packet error for Multi-Carrier CDMA system with maximum ratio combining diversity is evaluated and compared in the slow and fast correlated Nakagami fading plus multiple access interference channel. From the results, the probability of packet error in fast fading is higher than that in slow fading, and the difference of packet error probability between the fast fading and slow fading diminishes with Nakagami fading parameter approaching infinity. When the error correction coding technique is used, it is observed that coding technique for Multi-Carrier CDMA system is more effective in the fast fading case than that in the slow fading case.KeywordsFading ChannelDiversity BranchNakagami Fading ChannelFading CaseCorrelate FadingThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Analysis of the time series data collected from a stationary location in the continental shelf of the southeastern Arabian Sea during different month indicated prominent internal wave (IW) activity. Time evolution of temperature, resolved using Morlet wavelet technique, revealed that maximum energy was concentrated in the diurnal band at the density interface, whereas within the interior of thermocline, the dominant energy concentration shifted to semi-diurnal band. Both these harmonics have maximum amplitude (>15 m) during the pre-monsoon and monsoon season when the water column was highly stratified (>0.05 kg/m4), but they were not discernable in the temperature record when the stratification was weak (i.e., especially during winter). An acoustic propagation model based on ray theory, Bellhop (http:/oalib.hlsresearch.com/modes/acoustictoolbox/at.zip) was utilized to compute the transmission loss (TL) associated with the passage of low-frequency IWs. The TL was computed using the model considering (1) range-dependent and range-independent environmental scenario and (2) for different source and receiver depth configurations. Intermittent fading of acoustic signals was observed in the presence of IW. It was also observed that fading of signals very much depends on the source–receiver configuration.

This paper shows the study of Bit Error Rate (BER) using differential dual hop relaying system over Alpha-mu fading channel, Generalized- Gamma fading channeland Rician fading channel between Source to Relay/Relay to Destination i.e. (S-R)/(R-D). Here, two modulation techniques; DQPSK and DBPSK are used along with three channel schemes; SR - Slow Fading and RD - Slow Fading, SR- Fast Fading and RD- Slow Fading and SR - Fast Fading and RD - Fast Fading for the analysis of BER. Firstly, the BER is simulated over the combination of Alpha-mu fading channel andRician fading channel. Also, similar analysis has been achieved over the combination of Generalized Gamma fading channel and Rician fading channel. Finally, the results have been verified through the numerical analysis.

This paper presents a mathematical model for communication subject to both interference and noise. The spatial distribution of the interfering nodes is accounted for by resorting to a Poisson point process in the two-dimensional plane. We consider a realistic scenario of slowly-moving, asynchronous nodes in a wireless environment subject to both log-normal shadowing and fast Rayleigh fading. Under this scenario, we determine the statistical distribution of the cumulative interference at the output of a linear receiver, located anywhere in the two-dimensional plane. Furthermore, we provide the corresponding error performance analysis, which is valid for any linear modulation scheme. The proposed model captures all the essential physical parameters that impact network interference, but is simple enough to allow a tractable analysis and provide fundamental insights. Furthermore, our work generalizes the conventional analysis of linear detection in the presence of additive white gaussian noise (AWGN) and fast fading, allowing the traditional results to be extended in a simple way to include the effect of interference.

In this thesis, we cope with the fundamental mathematical and physical problems of the space-time-Doppler UWB system design for fading channels: multi-input multi-output (MIMO) wireless communication with adaptive filtering. The estimation algorithm from equalizer providing an accurate parameters estimate is investigated. UWB radio is a fast emerging technology with uniquely attractively features inviting major advances in wireless communications, networking, radar, imaging, and positioning systems. By its rule-making proposal in 2002, the Federal Communications Commission (FCC) in the United States essentially unleashed huge new bandwidth (3.6-10.6 GHz) at the noise floor, where UWB radios overlaying coexistence RF systems cerate using low-power ultra-short information bearing pulses. Right now, there are three basic types of UWB: multiband OFDM UWB (MB-OFDM UWB), impulse-UWB (I-UWB), and direct sequence UWB (DS-UWB). We focus on I-UWB and MB-OFDM-UWB, and compare their performance. A simple means for spreading the spectrum of low duty cycle pulse trains is time hopping (TH), with pulse position modulation (PPM) for data modulation at the rate of many pulses per data bit. The main contribution of this thesis for I-UWB is the design of leading edge detectors, coherent correlation detector (CCD), and pilot performance enhancement compared with different Rayleigh and Ricean fading conditions. For MB-OFDM UWB, we have considered the performance analysis and design criteria of MIMO OFDM UWB systems for high data-rate wireless transmission. The signal processing of frame detection, time synchronization, frequency synchronization, channel estimation, synchronization tracking using pilot subcarriers and 2-D MIMO detection algorithms is discussed. The main contributions of this thesis are 1) Compared with receiver employing the Maximum Likelihood (ML) detector, the receiver employing a low-complexity linear Minimum Mean Square Error (MMSE) demodulator can perform a limited performance loss in spatially uncorrelated channels. 2) Due to the operations of spreading and dispreading combined with MMSE-based frequency domain equalization, the adverse effects of the low-SNR subcarriers on the average BER performance are potentially improved. This is a direct consequence of spreading, because even if the signal corresponding to a specific chip is obliterated by a deep frequency domain channel fade, after dispreading these effects are spread over the Walsh-Hadamard Transform (WHT) length. Hence there is a high chance of still recovering all the partially affected subcarrier symbols without errors. 3) As a test case, the OFDM-based 200 Mb/s MB-UWB network (IEEE 802.15.3a) are considered, but the simulation results are shown above section. 4) The simulation channel can be easily applied to NOS and NLOS situation with WHT transformation from Simulink model. The fading channels of UWB with low/high signal to noise ratio (SNR), multipath effects, and multiuser interference may introduce large errors in location. The location engine performs the following tasks: █ Data fusion techniques: Different data fusion techniques are implemented using Time Of Arrival (TOA), Angle Of Arrival (AOA), or a combination of both. █ Channel modeling: A multipath, multiuser channel environment is created that models path loss, shadowing, Rayleigh fading, and Doppler frequency effects. █ Parameter estimation: TOA and AOA estimation algorithms are implemented as part of the location finding engine. Different variations of algorithms are implemented for performance and comparison purposes. █ Configuring the physical layer for different wireless networks. Among the programmable parameters are spreading factor, packet size, training length, constellation type, modulation technique, carrier frequency, level of transmitted signal power, and the number of antennas at the transmitter for both sides. █ Configuring the mobile user conditions. The wireless channel models depend on the Doppler frequencies present in the environment. The Doppler frequency depends on the mobile speed and carrier frequencies as input and generates a Rayleigh fading channel with the U-shape Doppler spectrum. █ Configuring the environmental parameters and network geographical structure. One of the factors affecting the performance of the wireless location system is the environment type (e.g., bad urban, urban, suburban, or rural area). For example, in a bad urban area with many blocking objects and buildings, non-line of sight (NLOS) effects plays an important role in the estimation accuracy.

Prior work has developed a variation of MCCDMA, block-spread OFDM (BSOFDM), providing good error performance over stationary channels with low detection cost and allowing parallel computation to reduce the receiver latency. The previous detection algorithms developed for BSOFDM are not robust to fast fading. In this paper, it is demonstrated through the use of performance bounds that the performance degradation under fast fading is caused by limitations of the previous decoding algorithms, and is not an inherent limitation of BSOFDM. A novel iterative detection algorithm is introduced with intrinsic data-level parallelism for detecting BSOFDM in the presence of fast fading. Detection is first performed independently on subblocks of the received block vector. Information is exchanged between these parallel detectors in an iterative manner by estimating the interference between the blocks and removing it from the signal vector. It is shown that the computational complexity of this algorithm is not significantly higher than the prior detection algorithms for BSOFDM, and achieves excellent BER for fast fading with fixed-point arithmetic, making it suitable for use on embedded systems. In addition the inherent parallelism of this algorithm means multiple computational units can be exploited, if available, to reduce receiver latency.

Why do we see what is not there? Fading of a target on a uniform background and perceptual filling-in from the edge are examples of the failure of the visual system to provide sustained vision under conditions of prolonged fixation. Another phenomenon that falls into this category is motion-induced blindness. The relationship between these three phenomena is not entirely clear, but the preference for small, peripheral, and low-contrast targets suggests that the mechanism underlying these effects may be similar. It has lately been shown that in addition to the above stimulus attributes, salience of the stimulus and perceptual grouping may also affect fading and filling-in. Furthermore, stereodepth and monocular depth cues have been proposed as relevant factors. These findings imply that in addition to bottom-up mechanisms top-down mechanisms are responsible for the perceptual disappearance of a fixated target by fading and filling-in. The following four articles in this special issue will summarize the phenomenological and psychophysical findings for fading and filling-in of brightness, color, and texture and correlate these observations with the presumed neurophysiological mechanisms.

This thesis describes the analytical design and the performance analysis of optimum receivers for Multiple Input - Multiple Output (MIMO) fading channels. In particular, a novel Optimum Receiver for separately-correlated MIMO channels is proposed. This novel pilot-aided receiver is able to process jointly the pilot symbols, transmitted within each time frame as a preamble, and the information symbols and to decode the transmitted data in a single step, avoiding the explicit estimation of the channel matrix. The optimum receiver is designed for the following two scenarios, corresponding to different transmission schemes and channel models: 1) Narrowband Rician fading MIMO channel with spatial separate correlation; 2) MIMO-OFDM Rician fading channel with space and frequency separate correlation. For each system the performance of the optimum receiver is studied in detail under different channel conditions. The optimum receiver is compared with: - the ideal Genie Receiver, knowing perfectly the Channel State Information (CSI) at no cost; - the standard Mismatched Receiver, estimating the CSI in a first step, then using this imperfect estimate in the ideal channel metric. Since the optimum receiver requires the knowledge of the channel parameters for the decoding process, an estimation algorithm is proposed and tested. Moreover, a complexity analysis is carried out and methods for complexity reduction are proposed. Furthermore, the narrowband receiver is tested in realistic conditions using measured channel samples. Finally, a blind version of the receiver is proposed

Objective To investigate the effect of Maxing-Shigan decoction on inflammatory factors and immune function of mycoplasma pneumonia (MPP). Methods According to the random table method, 123 children with MPP who met the inclusion criteria were divided into control group (61 cases) and treatment group (62 cases). The control group was treated with azithromycin, while the treatment group was treated with Maxing-Shigan decoction on the basis of the control group. The treatment course was two weeks in two groups. The level of IL-2, IL-4, IL-6, TNF-α, CRP and CD3+, CD4+, CD8+ and CD4+/CD8+ was detected by ELISA. The recovery time of body temperature, the fading time of coughing, the fading time of crackles and rale and the time of hospitalization was observed, TCM symptoms and signs was also scored, and the clinical efficacy was evaluated. Results The total effective rate was 90.3% (56/62) in the treatment group and 73.8% (45/61) in the control group. There was significant difference between the two groups (χ2=5.736, P=0.017). The recovery time of body temperature, the fading time of coughing, the fading time of crackles and rale and the time of hospitalization in the treatment group was significantly lower than those in the control group (t=-6.969, -5.700, -8.226, -7.034, P<0.01). Compared with the control group after treatment, the serum level of IL-2 significantly increased, IL-4, IL-6, TNF-α and CRP significantly decreased in the treatment group (t=12.729, -6.373, -6.416, -14.482, -20.071, P<0.01), while the serum level of CD3+, CD4+, CD4+/CD8+ significantly increased and CD8+ significantly decreased in the treatment group (t=2.314, 2.556, -3.866, 11.226, P<0.05). Conclusions The Maxing-Shigan decoction treats MPP by improving inflammatory factors and immune function, which not only improve the clinical symptoms, but also has high safety. It is worth promoting the application in clinic. Key words: Ma Xing Shi Gan Tang; Pneumonia, mycoplasma; Immunity; Inflammatory factors

The objective of all the braking systems fitted in vehicles isto reduce the speed, as well as to keep them at a standstill. Inorder to increase the active road traffic safety, the experts inthe leading vehicle manufacturer companies are trying from day to day to find a more efficient solution of the highest possiblequality. Braking problems, i.e. problems of stopping the vehiclesare closely related to time, forces, momentum, mass andother physical quantities. This is best seen in the braking ofheavy duty vehicles, trucks, buses, where the braking efficacyis questionable due to high inertia forces caused by heavyweight and more recently relatively high speeds. Such vehiclesare fitted with system of brakes that operate on compressed airor combination of pneumatics and hydraulics, since the driverhas not got enough power to achieve appropriate braking effect.However, the biggest problems occur by trucks runningdownhill, when the braking system is operated continuously fora longer period of time. This causes heating and overheating ofthe system elements ('fading'), thus reducing the braking effect.In extreme cases, particularly if the system is poorly maintained,it can eventually fail completely.Because of the mentioned reasons for difficulties in brakingof trucks, such vehicles have been recently fitted with anauxiliary slow-down system. This system is completely independentfromthe main one on the wheels and is used exclusivelyfor slowing down or for maintaining of speed.

In this paper, we propose an analysis of the joint impact of path-loss, shadowing and fast fading on cellular networks. Two analytical methods are developed to express the outage probability. The first one based on the Fenton-Wilkinson approach, approximates a sum of log-normal random variables by a log-normal random variable and approximates fast fading coefficients in interference terms by their average value. We denote it FWBM for Fenton-Wilkinson based method. The second one is based on the central limit theorem for causal functions. It allows to approximate a sum of positive random variables by a Gamma distribution. We denote it CLCFM for central limit theorem for causal functions method. Each method allows to establish a simple and easily computable outage probability formula, which jointly takes into account path-loss, shadowing and fast fading. We compute the outage probability, for mobile stations located at any distance from their serving BS, by using a fluid model network that considers the cellular network as a continuum of BS. We validate our approach by comparing all results to extensive Monte Carlo simulations performed in a traditional hexagonal network and we provide the limits of the two methods in terms of system parameters. The proposed framework is a powerful tool to study performances of cellular networks, e.g., OFDMA systems (WiMAX, LTE).

The quality of mobile communications is limited by the fading phenomena: fast fading and slow fading. Slow fading results from the shadowing of the propagating wave by large obstacles. A model for the stochastical behavior of slow fading is developed. It generates the proper correlated process by means of an uncorrelated stationary process that is given by the log-normal statistics. The basic idea is the Markovian interpretation of the spatial relation between the measured signal powers at different locations. This enables not only a feasible simulation but also a more detailed physical explanation of slow fading.

Mobile Ad-Hoc networks (MANET) has been getting the spotlight in the area of the wireless networks because of its flexibility and salability, and developing of many applications with it. As a consequence, MANETs are required to process not only simple data traffics, but also multimedia traffics, which has some constraints on the performances. However, unlike wired-networks, the wireless networks have frequent route-disconnections due to some reasons such as channel errors and mobility. Such frequent link disconnections makes the delivery of multimedia traffics difficult. Even though there many researches on multimedia transmissions on various environments, the performances of multimedia transmissions over fading channel and mobility even using various routing protocols have not been evaluated. Therefore, this paper extensively simulates the MPEG-4 video transmission over fading channel environment with node's mobility. In addition, the performances with two routing protocols such as AODV and DSR are compared. Finally, the simulation results shows that DSR protocol has the better performances to deliver MPEG-4 traffic.

Distributed multiple-input multiple-output (MIMO) system is a new architecture for next generation wireless communication systems with distributed multiple antennas. In this paper, an uplink model for multiuser distributed MIMO systems with wideband code-division multiple-access (CDMA) technology is presented. We focus on the case where there is no channel state information at the transmitter, but channel state information is assumed at the receiver. The spectral efficiency of the uplink system with single-user detectors at the base stations under multipath fading channels is investigated carefully. Two cases with different assumptions of interference knowledge are studied in detail. The spreading sequences of the CDMA systems are assumed to employ loosely synchronized (LS) spreading sequences and random spreading sequences respectively. LS spreading sequences exhibit a so-called interference free window (IFW), where both the auto-correlation and cross-correlation of the codes become zero. Therefore LS sequences have the promise of mitigating the effects of inter symbol interference (ISI) and multiple access interference (MAI) in multipath fading channels. It is shown by numerical results that the uplink spectral efficiency of the distributed MIMO-CDMA system using LS sequences can significantly outperform that of the system using random spreading sequences. Copyright © 2005 John Wiley & Sons, Ltd.