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A Statistical Model for Indoor Multipath Propagation.
Abstract
The results of indoor multipath propagation measurement using 10-ns, 1. 5-GHz, radarlike pulses are presented for a medium-size office building. The observed channel was very slowly time-varying, with the delay spread extending over a range up to about 200 ns and rms values of up to about 50 ns. The attenuation varied over a 60-dB dynamic range. A simple statistical multipath model of the indoor radio channel that fits the measurements well is presented. More importantly, the model appears to be extendable to other buildings. With this model, the received signal rays arrive in clusters. The rays have independent uniform phases, and independent Rayleigh amplitudes with variances that decay exponentially with cluster and ray delays. The clusters, and the rays within the cluster, form Poisson arrival processes with different, but fixed, rates.
... There are plenty of standard channel models in existence for a wide range of circumstances and environments, often created by standards institutions. Two channel models of interest to us are the typical urban (TU) channel from the European Cooperation in the field of Scientific and Technical Research (COST) Action 207 project (COST-207) [68] which was developed to define a time-dispersive test channel for use with GSM equaliser performance evaluation, and the Saleh-Valenzuela channel [71,72]. ...
... Model. The Saleh-Valenzuela (SV) [71,72] channel model enables us to create a highly-time dispersive and frequency-selective channel, which we may consider to be wideband, and as it is a statistical model we may run the generation algorithm as many times as required to create as many channel realisations as we require. In this respect it is better than the SPIB channels which are single measured samples of a channel. ...
... where Y1,0 [71] v1,0 [71] xo [71] yp,o [71] vp,o [71] xo [71 - ...
p>This thesis is concerned with the application of techniques that find the best broadband MIMO equaliser in terms of MSE or BER performance while keeping the computational cost as realistically low as possible. It examines established adaptive and analytic methods of doing this and then moves on to the application of subband adaptive filtering techniques to perform MIMO channel equalisation and detection, since this technique has been found to give considerable advantages with respect to computational complexity and convergence rate for related SISO applications. For many slow-converging low-cost adaptive algorithms applied to the inversion of channels, the convergence rate can be increased by use of subband processing, where, in independent frequency bands, separate smaller-scale adaptive algorithms are operated at a reduced update rate. We will apply such methods to the identification and inversion of MIMO channels. Fractionally spaced systems also are known to outperform their symbol-spaced counterparts hence these are factored into the subband MIMO systems developed.
Many simulation results demonstrating the benefits of MIMO systems with respect to the channel capacity, the performance of various adaptive and analytic MIMO inversion techniques and the potential complexity and convergence rate improvements of the subband approach in the MIMO context are presented. Adaptation to MIMO systems generally take much longer than for SISO systems. For adaptive identification the time increases by an amount approximately equal to dimensions of the MIMO system.</p
... The proposed model is a model derived from Saleh and Valenzuela (SV) model [17] for indoor channels that Appropriate with the properties of UWB channels. The IEEE 802.15.3a model is a statistical model based on the assumption when the multipath components (MPCs) arrive in clusters, formed by the multiple reflections from the objects in the vicinity of receiver and transmitter [18]. a log-normal distribution is used for the multipath gain magnitude. ...
... The clusters, as well as the path arrival times, may be modeled according to Poisson random variables processes with different rates and have interarrival times that are exponentially distributed. The MPCs amplitudes follow a log-normal distribution, whereas the corresponding phase angles are a uniform random variable over [0,2π].The power decays exponentially with cluster decay likewise as excess delay within a cluster [18]. The UWB system modeling defined four different channel models (CM1 to CM4) each with decay factors and arrival rates selected to match different employment scenarios and to adapt line-of-sight (LOS) and non-line-of-sight (NLOS) cases. ...
An important role performed by Zero Padding (ZP) in multi-band OFDM (MB-OFDM) System.
This role show for low-complexity in résistance against multipath interference by reducing
inter-carrier interference (ICI) and eliminating the inter-symbol interference (ISI) Also, zeropadded
suffix can be used to eliminate ripples in the power spectral density in order to conform
to FCC requirements.
At the receiver of MB-OFDM system needs to use of a technique called as overlap-and-add
(OLA). Which maintain the circular convolution property and take the multipath energy of the
channel.
In this paper, we proposed a method of performing overlap-and-add length for zero padded
suffixes. Then, we studied the effect of this method, dynamic optimization of overlap-and-add
(OLA) equalization, on the performance of MBOFDM system on Bit Error Rate (BER) with
AWGN channel and Saleh-Valenzuela (S-V) Multipath channel Model.
In the dynamic optimization OLA, the Length of ZP depends on length of channel impulse
response (CIR). These measures, based on SNR, insert the ZP according to the measurement.
Dynamic optimization of length of ZP improves the Performance of MBOFDM system. In fact
we developed a technique to select the length of ZP as function of SNR and CIR
estimate(repetition). In our simulation this technique improve to 3 dB at BER=10-2 with a
multipath channels CM4.
... System simulations are performed on VHDL-AMS simulator under MATLAB scripts. Previously developed UWB Saleh-Valenzuela multipath UWB channel model by [6] is used in the MATLAB environment. Therefore, it is not necessary to construct the channel model using VHDL-AMS modeling environment, which takes additional design time. ...
... In order to keep simulation time on a reasonable level, the step size is selected as 10 ps which correctly represents UWB pulses with 4GHz center frequency. Then, a wireless UWB channel model including multipath CM1 [6] and impulsive noise [7] is applied to the transmitter results with automatically swept noise levels to observe the overall performance. The designer can also select specific noise level for simulation. ...
This paper presents a MATLAB-VHDL-AMS computer
aided design automation flow for the design of an IR-UWB
transceiver. The co-simulation environment helps the user to
create the transceiver system in a top-down design methodology.
The constructed CAD flow enables the user to analyze the
performance of the system with the aid of BER vs EB /N0
figures. The effect of system and circuit level parameters on
the system performance can be analyzed and these parameters
can be determined from the model. The transceiver system
model is based on circuit parameters such as gain, linearity,
and reflection coefficient. The individual system blocks can
be interchanged with actual circuit designs. Therefore, the
performance of these individual blocks in a transceiver system
can also be studied.
... IEEE report [16]. Its large scale fading is given in [17] and small scale fading is given by a Nakagami-m distribution. The equation that describes the channel impulse response (CIR) is as follows: ...
This work outlines important characteristics of hybrid PLC-wireless systems for smart grid applications. Moreover, it discusses the hybrid wireless-PLC systems advantages in comparison to not hybrid systems. These advantages are demonstrated not only in the technical point of view, but also in the infrastructural perspective. Moreover, It addresses the environment influence on wireless and power line communications as well as relevant security aspects for a Smart Grid implementation. Computational simulations based on physical layer of IEEE P1901.2 standard and PLC and wireless channel models show that the hybrid PLC-wireless system offers a gain of signal to noise ratio when compared to only a wireless or PLC system.
... 1) Modelos de canal y propagación: Para caracterizar la propagación indoor de forma adecuada, es importante tener en cuenta que la propagación multi-camino (multi-path) es el efecto dominante debido a la naturaleza del entorno. Además, el tipo de estructuras y los materiales también juegan un papel crucial [64]. Con la aparición de MIMO y la potencial utilización de ondas milimétricas, la investigación acerca de modelos de canal adecuados para interiores se ha intensificado y ha adquirido más relevancia [65][66][67][68][69]. ...
... We used IEEE P802.15-02/368r5 compliant UWB channel model to simulate path loss and multi-path fading effect. This channel model is derived from Saleh-Valenzuela model [20] based on lognormal distribution. Discrete time impulse response for antenna feeding voltage or current signal is given as, in [19], ...
The system architecture of CMOS multi-band Ultra-Wideband (UWB) transceiver based on frequency-hopping orthogonal frequency domain modulation (OFDM) physical layer proposed by IEEE 802.15.3a High-Rate Wireless PAN Task Group is presented. This paper shows that the frequency dependent impedance of dipole antenna can be compensated by single-tap adaptive linear equalizer, facilitating the use of portable small antenna instead of bulky wideband antenna. CMOS implementation issues of this UWB transceiver, including antenna impedance matching, analog frontend linearity and noise
figure requirement, AD conversion precision, frontend filtering, baseband AGC, channel equalizer precision and PHY layer design constraints will be discussed. Simulated UWB transceiver operates with 3.96 GHz center frequency and 528 MHz bandwidth is allocated for PHY band. Simulation results show that
the 320 Mbps throughput is obtained under line-of-sight wireless
fading channel within 4 meters with 2% bit-error rate.
New media transmission frameworks are continually being created to address persistently expanding remote correspondence needs. The cutting edge organizations and gadgets are wanted to be accessible, in no time by 2021. Because of huge measure of accessible range millimeter wave (mmWave) correspondence is quite possibly the most encouraging advancements in cutting edge portable organizations. Regardless of the hypothetical capability of a high information rate, there are different specialized difficulties with utilizing mmWave. An important feature of mmWave is utilization of frequencies, propagation and channel modelling. The objective of this paper is to define the channel models for the indoor and outdoor scenario for the next generation systems using mmWave frequency. New requirements are identified and addressed for the channel modelling. Furthermore, the simulations of the widely suggested models Saleh-Valenzuela (SV), Wide-Sense Stationary Uncorrelated Scattering (WSSUS), Log-Distance Path Loss or Log-typical shadowing may give over-hopeful multi-client MIMO (MU-MIMO) execution in an indoor and open air climate at 30 GHz is done. The results in this paper give the choice of channel model for suitable environment in terms of estimated Frame Error Rate versus Signal to-Noise ratio parameter.KeywordsmmWaveChannel modelIndoorOutdoorMIMO
The automatically paired time of arrival (TOA) and direction of arrival (DOA) can be jointly estimated via a high-precision multidimensional spectral peak search- (SPS-) based multiple signal classification (MUSIC) algorithm in the impulse radio ultrawideband (IR-UWB) positioning system, while heavy computational burden is required. To tackle this issue, we propose an improved root-MUSIC algorithm for joint TOA and DOA estimation. After modelling the frequency domain form of the received signal, the algorithm first uses the signal subspace to establish the relationship between the two antennas. Then, the MUSIC spatial spectrum function is reconstructed with this relation, which enables it to offer a spectrum function in regard to the one-dimensional (1D) parameter of time delay. For further reducing the complexity, the TOA estimates of one antenna are obtained via 1D polynomial root finding instead of SPS, and the TOA estimates of the other antenna can be calculated by the established relationship. Finally, the DOA estimation can be achieved with the estimated TOAs. Due to the relationship between two antennas with signal subspace, the parameters estimated by the proposed algorithm are autopaired. Numerical simulations substantiate the superiority of the proposed algorithm.
An electromagnetic wave is the propagation of an electrical disturbance of the matter: a static charge creates an electric field, a charge that moves creates a magnetic field, a disturbance in both creates an electromagnetic field that moves in space (vacuum, air, materials, etc.), that is an electromagnetic wave. Mobile radio propagation, in particular, is a multi‐path propagation. Signals often follow paths of different lengths, travel times and arrive at the receiver in different phases. Low power laser beams involve the transmission of an optical signal (visible or infrared) through the Earth's atmosphere. The Meteorological Optical Range, a parameter used to characterize the transparency of the atmosphere, is defined in this chapter. Different measuring instruments such as the transmissometer and the scatterometer are also described.
The characteristics of multipath components (MPCs) are addressed in an industrial environment at 1.3 GHz by means of measurements with a multidimensional channel sounder. The maximum likelihood estimator, RiMAX, is used to determine the MPCs parameters and takes into account the diffuse scattering. Both line‐of‐sight (LOS) and
obstructed LOS (OLOS) scenarios have been considered, along with the four polarization states. We found that the environment is very rich in multipath, that is on average, about 120 (resp. 70) MPCs in LOS (resp. OLOS) scenario due to the presence of several metallic reflectors. The azimuthal angle implies clustering of the MPCs, and therefore, the estimated MPCs are grouped in clusters using the K‐powers‐means algorithm based on the multipath component distance. In general, one to four clusters are determined with three clusters occurring with the highest probability, regardless of the scenario. Next, the intra‐cluster parameters have been determined, and we show that the root‐mean‐square (rms) delay spread and rms angular spread follow a gamma distribution, regardless of the polarization. The MPC characteristics agree with the results in the literature and can be valuable when deploying a wireless sensor network in industrial environments.
Propagation models constitute a fundamental building block of wireless communications research. Before we build and operate real systems, we must understand the science of radio propagation, and develop channel models that both reflect the important propagation processes and allow a fair comparison of different systems. In the past five decades, wireless systems have gone through five generations, from supporting voice applications to enhanced mobile broadband. To meet the ever increasing data rate demands of wireless systems, frequency bands covering a wide range from 800 MHz to 100 GHz have been allocated for use. The standardization of these systems started in the early/mid 1980s in Europe by the European Telecommunications Standards Institute with the advent of Global System for Mobile Communications. This motivated the development of the first standardized propagation model by the European Cooperation in Science and Technology (COST) 207 working group. These standardization activities were continued and expanded for the third, fourth, and fifth generations of COST, as well as by the Third Generation Partnership Project, and the International Telecommnunication Union. This paper presents a historical overview of the standardized propagation models covering first to fifth-generation systems. In particular, we discuss the evolution and standardization of pathloss models, as well as large and small-scale fading parameters for single antenna and multiple antenna systems. Furthermore, we present insights into the progress of deterministic modelling across the five generations of systems, as well as discuss more advanced modelling components needed for the detailed simulations of millimeter-wave channels. A comprehensive bibliography at the end of the paper will aid the interested reader to dig deeper.
A comprehensive treatment of wireless underground channel modeling is presented in this chapter. The impacts of the soil on bandwidth and path loss are analyzed. A mechanism for the UG channel sounding and multipath characteristics analysis is discussed. Moreover, novel time-domain impulse response model for WUC is reviewed with the explanation of model parameters and statistics. Furthermore, different types of the through-the-soil wireless communications are surveyed. Finally, the chapter concludes with discussion of the UG wireless statistical model and path loss model for through-the-soil wireless communications in decision agriculture. The model presented in this chapter is also validated with empirical data.
Recent advances in manufacturing industry which paved a way to intelligent Manufacturing in the Context of next generation of industry, referred to as "Industry 4.0". There is relevant information from all related resources which is monitored and synchronized. These units must be as smart as they can collect, act, and behave within a smart environment. Most research and survey have paid more attention to networked machines. So, they can be able to exercise more efficiently, collaboratively and resiliently. However, connected people, who are the key elements of future manufacturing, side by side with intelligent machines for making smarter decision, do not receive much interest in these worldwide movements. This paper focuses on constructing a general architecture by exploring the technical features and beneficial outcomes by incorporating Ultra-Wideband (UWB)-based Wireless Body Area Network (WBAN) sensors into this smart environment. In addition, a comprehensive overview of UWB-based WBANs radiowave communication channel measurements in industrial indoor environment will be presented.
This paper presents an evaluation of multicarrier channel sounding techniques using different random and pseudo-random sequences to modulate the OFDM sounding signal. The Random (Rand), Pseudo-Noise (PN) and Zadoff-Chu (ZC) were tested, both in laboratory simulations and in field measurements. For the laboratory simulations Matlab routines were used to generate OFDM signals modulated with each of the three sounding signals, that were then convoluted with a synthesized transfer function of a test channel with six multipath components and added Gaussian noise and Doppler fading. The resulting signals are then correlated with a copy of the original signal to provide the multipath power delay profiles. The root mean square deviation (RMSD) and the relationship between peak power and mean power (PAPR) were used as metrics for the comparison between the test transfer function and the simulation detected multipath delay profiles, showing slight advantages of the ZC sequence. The three sequences were then used in field measurements to characterize an urban channel at 700 MHz. In the field measurements, the ZC sequence showed the lowest detection threshold, allowing for the detection of a larger number of multipath components.
A new estimator for sparse time dispersive channels in pilot aided Orthogonal Frequency Division Multiplexing (OFDM) systems is developed by considering prior knowledge on channel time dispersions. We propose a Weighted Atomic Norm Minimization (WANM) in order to incorporate the prior information into the estimator. The dual of the WANM is then converted to a tractable semidefinite programming using Positive Tirgonometirc Polynomial (PTP) theory. After solving the dual problem, the channel response is identified by solving a Least Squares (LS) approach. In this work, we assume that time dispersions' associated delays can take any value with a mild minimum separation condition on the normalized interval [0, 1). The performance of the new estimator is compared with conventional approaches. With respect to the pilot number and Signal to Noise Ratio (SNR), simulation results reveal that the proposed estimator performs superior to that of traditional methods. It is shown that both a lower SNR and number of pilots are required to achieve the same Mean Square Error (MSE) reported in previous works.
We explore the potential of mathematically modelling the ultra‐wideband (3.1–6.3 GHz) off‐body radio channel using the same statistical distribution for corridor environments. Radio channel descriptive parameters of received signal strength, mean excess delay (τmean) and root mean square (RMS) delay spread (τRMS) are presented, modelled and compared for five indoor corridor environments. Statistical distributions for these corridors exhibit strong similarities despite each possessing starkly different geometrical and physical characteristics, and test arrangements. Each of the corridor environments was best modelled by the Rician distribution for the line‐of‐sight (LOS) received power and the Lognormal distribution for the non‐LOS (NLOS) received power. Distribution of tmean was best modelled by the normal distribution for both LOS and NLOS scenarios. The distribution of τRMS was likewise best modelled by the normal distribution for both LOS and NLOS arrangements. For corridors 1 and 2 (considered to exhibit the greatest differences), a finite element study was conducted to substantiate that the results cannot be dismissed as statistical anomalies created by the averaging effect over long journey paths. This work is relevant for the mathematical modelling of UWB off‐body channel sounding in interior corridors and may reduce efforts required to model future indoor corridor variants.
Multidimensional characterization of outdoor urban macrocellular propagation channels is essential for the analysis and design of next-generation (5G and beyond) cellular massive MIMO (multiple-input-multiple-output) systems. Since most massive MIMO arrays will extend in two or three dimensions, an understanding of 3-D parameters (i.e., azimuth and elevation) of the multipath components (MPCs) is required. This paper presents an extensive measurement campaign for 3-D outdoor propagation channels in an urban macrocellular environment. Measurements were performed with a 20 MHz wideband polarimetric MIMO channel sounder centered at 2.53 GHz and MPCs were extracted using RIMAX—an iterative maximum likelihood algorithm. The physical propagation mechanisms of the observed discrete MPCs are explained in terms of waveguiding, over-the-rooftop propagation, and scattering by far-away objects. MPCs exhibit clustering in the temporal and spatial domains; both
intra-
and
inter-
cluster parameters and their relevant statistics are provided. We also extract diffuse MPCs, show that they can comprise a moderate portion of the overall energy, and provide a statistical characterization.
We propose a novel soft-input soft-output equalizer for single-carrier transmissions over unknown frequency-selective block-fading channels. Our equalizer leverages the recently proposed parametric bilinear generalized approximate message passing (PBiGAMP) algorithm for joint channel-estimation and symbol-detection, and exploits fast Fourier transform (FFT)-processing to achieve a per-symbol complexity that grows only logarithmically in the channel delay-spread. Furthermore, it supports the use of Gaussian mixture models to support the approximately sparse nature of wideband wireless channel responses. Numerical experiments, conducted using physically motivated Saleh-Valenzuela channel models, show that the proposed approach achieves channel normalized mean square error (NMSE) and bit error rate (BER) that are significant improved over existing turbo frequency-domain equalization approaches for unknown channels. Additional experiments show that the proposed scheme facilitates much higher spectral efficiencies than sparse deconvolution methods based on convex relaxation.
In this paper, we present a technique for indoor localization that uses the results of the Trilateration method and RSSI signal strength to know what is expected in specific locations. Indoor positioning in systems confronts particular problems of precision. This study aims to implement a technical solution that can precisely and efficiently give the position of a target and facilitate the localization of mobile nodes deployed in a given zone. The main objective of this work is to estimate the position of the node with precision. This work was conducted on the basis of the combination of two concepts: trilateration method and RSSI measurement in different positions. The study of a set of simulations indicates that the estimation of the node position; using RSSI level; does not differ from mathematical calculations used by trilateration method. Besides; the network performance is not affected significantly. This is the major concern of our work; mainly in emergency situations; as it gives the right position of individuals to the rescuers.
(22) (PDF) Positioning system for emergency situation based on RSSI measurements for WSN. Available from: https://www.researchgate.net/publication/323645985_Positioning_system_for_emergency_situation_based_on_RSSI_measurements_for_WSN [accessed May 09 2020].
This paper presents an investigation of the wideband Self-Interference (SI) channel characteristics of a 2×2 MIMO full-duplex transceiver using dual-polarized antennas. The measured SI-channel power delay profiles at 2.45 GHz with 500 MHz span in various environments: anechoic chamber, laboratory room, and corridor, reveal that the SI-channel can be represented by a multipath model consisting of two components: a quasi-static internal SI-sub-channel due to the specific Tx/Rx antenna structure and a time-varying external SI-sub-channel due to possible reflections from the surrounding environment. The quasi-static internal SI-sub-channel parameters can be derived from the Tx/Rx antenna structure specifications. The time-varying external SI-channel exhibits cluster arrival features and can be represented by a modified Saleh-Valenzuela (S-V) model with lognormal-distributed taps, and the cluster power exponentially decays with cluster arrival delay. However, the path power-versus-arrival-delay decay is exponential in a laboratory-room environment while it follows the power law in a corridor environment. The SI-channel coherence bandwidth and delay spread in all three measurement environments follow normal and lognormal distributions, respectively.
In communication systems that use a linear modulation scheme for transmission, the fractionally-spaced (FS) samples of the received signal constitute a wide-sense cyclostationary (WSCS) time series. Hence, standard Fourier transform techniques cannot be used to study the spectral characteristics of the received FS samples or to derive the transfer function (TF) of the corresponding digital minimum mean-square error (MMSE) receiver. In this paper, an analytical expression for the TF of the FS MMSE equalizer is derived which includes the effects of the continuous-time to discrete-time (C/D) converter used at the receiver front end. Using this TF, the sources of instability of the FS least-mean-square (LMS) algorithm and the effects of the equalizer length and sampling phase on convergence of the LMS algorithm are explained. For stabilization of the FS LMS algorithm, conditions on the front-end C/D converter are provided such that when satisfied the LMS algorithm becomes more stable. The learning characteristics of the modified receiver are better than the leaky-FS LMS algorithm. Theoretical results are corroborated by simulations.
A novel unified framework of geometry-based stochastic models (GBSMs) for the fifth generation (5G) wireless communication systems is proposed in this paper. The proposed general 5G channel model aims at capturing small-scale fading channel characteristics of key 5G communication scenarios, such as massive multiple-input multiple-output (MIMO), high-speed train (HST), vehicle-to-vehicle (V2V), and millimeter wave (mmWave) communication scenarios. It is a three-dimensional (3D) non-stationary channel model based on the WINNER II and Saleh-Valenzuela (SV) channel models considering array-time cluster evolution. Moreover, it can easily be reduced to various simplified channel models by properly adjusting model parameters. Statistical properties of the proposed general 5G small-scale fading channel model are investigated to demonstrate its capability of capturing channel characteristics of various scenarios, with excellent fitting to some corresponding channel measurements.
In the Internet of Things (IoT), wireless devices need more easily accessible energy resources, which motivates the development of wireless power transfer (WPT) using radio frequency (RF) signals. Beamforming technique has been widely adopted by using multiple transmit antennas to form a sharp energy beam toward an intended receiver. However, few of them have considered the potential gain of multipath propagation. In this paper, we propose a joint power waveforming and beamfoming in the time domain for WPT, in which the waveforms on multiple transmit antennas driven by a common reference signal are designed to maximize the gain of energy delivery efficiency. We consider both non-periodic and periodic reference signals and propose low-complexity waveforms that can achieve near-optimal performance. It is found that the energy delivery efficiency gain of the proposed approach increases with the waveform length until saturation. We theoretically analyze the outage probability of the proposed approach under a uniform power delay (UPD) channel profile, which quantifies the impact of the number of antennas and multipaths. Simulations are performed to validate the theoretic analysis and the effectiveness of the proposed joint power waveforming and beamforming approach.
This paper presents a clustering and tracking method that exploits the geometry of the scattering points (SPs) obtained from the measurement-based ray tracer. The multipath components (MPCs) were categorized into clusters by applying the KPowerMeans (KPM) framework to those SPs. The clusters were tracked by comparing the cluster-centroid SPs of the adjacent snapshots. The clusters were estimated based on the indoor environment geometry at 11 GHz, and their physical mechanisms were interpreted. The complexity and performance of this method was assessed and compared with that of conventional KPM by comparing the number of flops and the channel eigenvalues obtained from the reconstructed channel matrices, which were calculated by superposing the MPCs randomly generated from intra-cluster parameters. The verification of this method showed that most clusters were estimated and tracked according to the physical location of the scatterers in the environment with acceptable error. Moreover, the eigenvalues reconstructed from the proposed method were closer to the measured ones with less number of flops, which indicates both accuracy and complexity improvement. The results also imply that multiple-input multiple-output (MIMO) performance is highly dependent on the radio propagation channel; therefore, it is imperative that clusters in the channel be determined accurately.
As an attractive interference cancellation (IC) technique, Tomlinson-Harashima precoding (THP) has been investigated thoroughly in theory. Several high performance THP variants have been proposed, e.g., sorted QR decomposition (SQRD), Cholesky decomposition, vertical Bell Laboratories space time (V-BLAST) and lattice reduction aided THPs. From a practical perspective, however, limited hardware implementations have been reported in the literature so far. To bridge the progress gap between the theory and the practice, we present a comprehensive analysis of these THP variants in terms of performance and implementation efficiency in this paper. We first evaluate their bit-error rate (BER) performance under perfect and imperfect channel state information (CSI) scenarios. Subsequently, the emphasis is put on their implementation efficiency, including the computational complexity, the numerical precision requirement and the parallelism potential. Our analysis shows a wide trade-off space exists between the performance and the implementation efficiency in different THP variants, which is especially valuable for hardware designers to implement cost-efficient architectures biased towards practical systems.
Wireless Sensor Network (WSN) is a collection of small sensor nodes with aptitude to sense, compute and transmit data that are deployed to observe a physical environment. The sensor node has limited capabilities, especially for energy reserve and memory storage, that is why topology and routing protocols should be defined for a good network's performances. In this paper, we focus on Zigbee sensor networks based on IEEE 802.15.4 standard for which we improve the topology control by proposing an efficient clustering topology based on Minimum Spanning Tree (MST). In fact, our proposed algorithm tend to propose a topology where the cost of total transmissions into the network should be minimal. Our topology takes also into consideration the indoor environment by proposing a metric that deal with the path loss and signal attenuation due to walls and obstacles to compute the weight of connections between nodes. Finally, our topology showed better results than typical Cluster-tree and mesh topology generally used in Zigbee sensor networks in terms of energy consumption and network's lifetime.
In this chapter, we examined some theoretical aspects of probability density functions and distributions encountered in the study of fading and shadowing in wireless channels. We started with the basic definition of probability, then discussed density functions and properties relating to the analysis of fading and shadowing. We also examined the transformations of random variables in conjunction with relationships of different types of random variables. This is important in the study of diversity and modeling of specific statistical behavior of the wireless channels. The density functions of some of the functions of two or more random variables were derived. We examined order statistics, placing emphasis on the density functions of interest in diversity analysis. Concepts of stochastic processes and their properties were outlined. Similarly, the characteristics of noise were delineated within the context of signal detection. In addition, this study included an exploration of ways of expressing some of the densities in more compact forms using the hypergeometric functions and MeijerG functions.
In this paper, the performance of quasi-coherent combining (QCC) of signals from an antenna array with closely spaced elements, is evaluated for the Rician fading indoor multipath channel at microwave frequencies. The channel model is based on statistical measurement results on channel variation for small antenna displacements at 2.4, 4.75 and 11.5 GHz. Computational BER results for QCC and coherent BPSK modulation are presented and compared to the results for existing diversity techniques.
Measurements of time delay spread of wideband 850 MHz digital radio signals due to multipath propagation within a large building are described. These measurements show a median RMS time delay spread of 125 ns and a worst case of 250 ns. Consequently, signalling rates above 400 kHz may not be feasible.