Dissertations / Theses: 'Rayleigh fading channel'

1

van, Nobelen Robert. "Coding for the Rayleigh fading channel." Thesis, University of Canterbury. Electrical and Electronic Engineering, 1996. http://hdl.handle.net/10092/6060.

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The problem of effective coding for the Rayleigh fading channel is addressed. A signal transmitted over the Rayleigh fading channel experiences quasi-periodic deep fades in the signal amplitude, and random phase shifts. The fades in signal amplitude are the cause of error events and limit the bit error rate of an uncoded system to about 10-4 at a signal-to-noise ratio of 30 dB. For applications where a lower error rate is desired, more sophisticated methods of transmission and detection are required. We present an extensive generalised analysis of the probability of error of maximum likelihood sequence estimation techniques for the Rayleigh fading channel This analysis provides the criteria for good code design for the Rayleigh fading channel and we extend the recently developed area of geometrically uniform (GU) codes for the AWGN channel, to the Rayleigh fading channel, and present the results of searches for good GU trellis codes. The concept of geometric uniformity is extended to set of points to form geometrically uniform partitions of signal sets. The GU partitions readily allow powerful multi-level codes to be defined with good distance properties. Multi-level codes have the advantage of outperforming trellis codes in terms of decoding complexity at the cost of greater decoding delay. Good multi-level codes over GU partitions are presented and compared with similarly performing trellis codes. Finally a system is presented which combines the techniques of multiple symbol differential detection (MSDD) with multi-level coding to obtain a good probability of error performance without assuming coherent detection, or ideal channel state information.

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2

Hsu, Teh-Hsuan. "Robust concatenated codes for the slow Rayleigh fading channel." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2723.

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3

Sathini, Ramaswamy Vishnu Raghavan. "A comparative study of Rayleigh fading wireless channel simulators." Texas A&M University, 2005. http://hdl.handle.net/1969.1/3046.

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Computer simulation is now increasingly being used for design and performance evaluation of communication systems. When simulating a mobile wireless channel for communication systems, it is usually assumed that the fading process is a random variate with Rayleigh distribution. The random variates of the fading process should also have other properties, like autocorrelation, spectrum, etc. At present, there are a number of methods to generate the Rayleigh fading process, some of them quite recently proposed. Due to the use of different Rayleigh fading generators, different simulations of the same communication system yield different results. Three methods, viz., the Jakes method, the IDFT method and the filtering WGN method, have been studied, simulated and compared based on the Rayleigh fading process' properties. Various communication systems have been simulated using the Rayleigh fading generators and the difference in the results, if any, have been analyzed. The research studies the different Rayleigh fading generators and compares them using the properties of the Rayleigh fading channel. It is found that the IDFT method and the filtering WGN method generate processes that have properties very close to the ideal Rayleigh fading process.

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4

Pan, Li. "Selective multistage detection algorithm in flat Rayleigh fading channel." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26735.

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Selective multistage detection algorithm applied in AWGN channel is first proposed in [1]. It is shown that the BER performance of this detector is slightly better than conventional multistage detector if the threshold level is properly selected. At the same time, the number of computations performed by the receiver is greatly reduced since MAI cancellation is only applied to those decision variables whose magnitudes are less than a threshold value. In this thesis, we will investigate the performance of selective multistage detection algorithm for the frequency nonselective Rayleigh fading channel which is more common in the wireless communications. The performance will be determined by computer simulation. First, we will consider the performance of selective multistage detection and nonselective multistage detection when the receiver perfectly estimates the channel gains of all of the users. Then we will employ pilots based estimation with optimum interpolator to estimate the channel gains. Receiver will make use of the estimated channel gain to detect the data of every user. Finally we will compare the performances of selective and nonselective multistage detectors under the imperfect channel estimation case. We also propose a modified selective multistage algorithm in order to improve the performance of selective multistage detector further without a large increase in the amount of computation. It applies partial MAI cancellation, instead of full cancellation, to those decision variables whose magnitudes are less than a threshold value. By employing the modified selective multistage algorithm, we will achieve the performance that is close to that of conventional multistage with perfect channel estimation.

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5

Manglani, Manish. "Wavelet Modulation in Gaussian and Rayleigh Fading Channels." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/34396.

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Wavelet Modulation (WM)---also referred to as fractal modulation---simultaneously sends data at multiple rates through an unknown channel. This novel multirate diversity strategy offers improved message recovery over conventional modulation techniques: if the message is not received at one rate due to the channel disturbances, it can be received at another rate where the channel is clear. Previous research has demonstrated the performance of wavelet modulation in Gaussian channels. This paper extends the investigation to the performance of wavelet modulation in time varying channels. We show that bit error rate (BER) wavelet demodulation performance in the additive, white, Gaussian noise (AWGN) channel is comparable to theoretical binary phase shift keying. Our results depict the improvement in performance that can be realized for time varying channels by utilizing the various rates of wavelet modulation; BER versus SNR curves for each fading channel show how the message at one rate can be more accurately recovered than at another rate. Furthermore, we also present results indicating the dramatic improvement in wavelet demodulation performance when multiple rates are available and utilized for demodulation. This improvement in performance is highly visible in BER performance for the AWGN and flat fading channels. Finally, a comparison of binary phase shift keying (BPSK) and WM in a frequency selective channel is performed. The BER improvement of WM is shown when demodulation is done at rates which are least corrupted by ISI. We illustrate our new algorithm that: identifies the channel characteristics; determines which rates are maximally corrupted by ISI; and, utilizes only those uncorrupted copies in demodulation.
Master of Science

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6

Teletar, Ä°brahim Emre. "Coding and multiaccess for the energy limited Rayleigh fading channel." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14759.

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7

Zhu, Chao. "Performance Analysis of Minimum Selection GSC with Channel Estimation Errors in Rayleigh Fading Channels." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1250184723.

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8

Jagiello, Kristin, and Charlie Cooper. "Convolutional Versus LDPC and Turbo Codes on the Rayleigh Fading Channel." International Foundation for Telemetering, 2009. http://hdl.handle.net/10150/606117.

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ITC/USA 2009 Conference Proceedings / The Forty-Fifth Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2009 / Riviera Hotel & Convention Center, Las Vegas, Nevada
We consider the performance of low-density parity-check (LDPC) codes, turbo codes and convolutional codes over the binary-input AWGN channel with flat Rayleigh fading. LDPC and turbo codes are capacity-approaching codes for long codewords. For short and medium codewords we seek to determine if they still outperform the industry-standard memory-6, rate-1/2 convolutional code. For a fixed SNR, the probability of error for the codes of interest are plotted as a function of codelength. We find that for very short codewords, the convolutional code performs best.

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9

Vu, Hung Van. "Capacities of Bernoulli-Gaussian Impulsive Noise Channels in Rayleigh Fading." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1407370145.

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10

Al-Agamy, M. A. A. "Time-efficient error correction coding for the Rayleigh fading mobile communications channel." Thesis, University of Kent, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304148.

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11

Auer, Gunther. "On receiver design for an unknown, rapidly time-varying, Rayleigh fading channel." Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/13684.

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In this thesis receiver architectures for an unknown, time-varying Rayleigh fading channel are investigated. This includes fast fading scenarios, where the channel impulse response (CIR) can change significantly between two adjacent samples. Channel estimation based on the minimum mean squared error criterion (MMSE) applied to smoothing and linear prediction is considered. One of the key objectives in this thesis is the analysis of error propagation effects due to decision feedback. The studied receiver architectures are divided into two main parts: one-shot receivers which detect the received symbol on a symbol-by-symbol basis, and sequence detectors which jointly estimate and detect the entire received signal sequence. Considering one-shot receivers, a decision directed receiver is studied using differential modulation (DPSK). The receiver can significantly improve the fast fading performance of conventional DPSK, through linear predictive channel estimation. It is demonstrated through simulation that the performance of the decision directed receiver is better than that of an idealised reference receiver where channel estimation is not corrupted by decision feedback errors (e.g. by means of employing a pilot signal). Furthermore, a receiver employing coherent modulation is considered. The necessary phase reference is provided by time multiplexed pilot symbols. A receiver which exclusively uses these pilot symbols for channel estimation is the pilot aided receiver. The performance for slow fading is excellent, whereas the performance degrades as the Doppler frequency increases. The degradation is proportional to the spacing of the pilots. The performance of both the decision directed and the pilot aided receiver can be significantly improved by employing a second stage channel estimation filter, using a smoothing type estimation filter.

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12

Mannem, Narender Reddy. "Adaptive Data Rate Multicarrier Direct Sequence Spread Spectrum in Rayleigh Fading Channel." Ohio University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1125782227.

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13

McDougall, Jeffrey Michael. "Low complexity channel models for approximating flat Rayleigh fading in network simulations." Texas A&M University, 2003. http://hdl.handle.net/1969/294.

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14

Menon, Rekha. "Impact of Channel Estimation Errors on Space Time Trellis Codes." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/36490.

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Space Time Trellis Coding (STTC) is a unique technique that combines the use of multiple transmit antennas with channel coding. This scheme provides capacity benefits in fading channels, and helps in improving the data rate and reliability of wireless communication. STTC schemes have been primarily designed assuming perfect channel estimates to be available at the receiver. However, in practical wireless systems, this is never the case. The noisy wireless channel precludes an exact characterization of channel coefficients. Even near-perfect channel estimates can necessitate huge overhead in terms of processing or spectral efficiency. This practical concern motivates the study of the impact of channel estimation errors on the design and performance of STTC.

The design criteria for STTC are validated in the absence of perfect channel estimates at the receiver. Analytical results are presented that model the performance of STTC systems in the presence of channel estimation errors. Training based channel estimation schemes are the most popular choice for STTC systems. The amount of training however, increases with the number of transmit antennas used, the number of multi-path components in the channel and a decrease in the channel coherence time. This dependence is shown to decrease the performance gain obtained when increasing the number of transmit antennas in STTC systems, especially in channels with a large Doppler spread (low channel coherence time). In frequency selective channels, the training overhead associated with increasing the number of antennas can be so large that no benefit is shown to be obtained by using STTC.

The amount of performance degradation due to channel estimation errors is shown to be influenced by system parameters such as the specific STTC code employed and the number of transmit and receive antennas in the system in addition to the magnitude of the estimation error. Hence inappropriate choice of system parameters is shown to significantly alter the performance pattern of STTC.

The viability of STTC in practical wireless systems is thus addressed and it is shown that that channel estimation could offset benefits derived from this scheme.

Master of Science

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15

Ahmed, Sabbir. "Performance of Multi-Channel Medium Access Control Protocol incorporating Opportunistic Cooperative Diversity over Rayleigh Fading Channel." Thesis, Blekinge Tekniska Högskola, Avdelningen för signalbehandling, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-6171.

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This thesis paper proposes a Medium Access Control (MAC) protocol for wireless networks, termed as CD-MMAC that utilizes multiple channels and incorporates opportunistic cooperative diversity dynamically to improve its performance. The IEEE 802.11b standard protocol allows the use of multiple channels available at the physical layer but its MAC protocol is designed only for a single channel. The proposed protocol utilizes multiple channels by using single interface and incorporates opportunistic cooperative diversity by using cross-layer MAC. The new protocol leverages the multi-rate capability of IEEE 802.11b and allows wireless nodes far away from destination node to transmit at a higher rate by using intermediate nodes as a relays. The protocol improves network throughput and packet delivery ratio significantly and reduces packet delay. The performance improvement is further evaluated by simulation and analysis.
sabbir@linuxmail.org

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16

Zhou, Jiahuai. "Iterative map and Apri-SOVA receivers for the frequency-selective Rayleigh fading channel." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0001/MQ32293.pdf.

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17

Shumba, Josiah. "Performance Evaluation of Cognitive Radio Spectrum Sensing Techniques through a Rayleigh Fading Channel." Master's thesis, Faculty of Engineering and the Built Environment, 2021. http://hdl.handle.net/11427/33021.

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In recent years, there has been a steep rise in the demand for bandwidth due to a sharp increase in the number of devices connected to the wireless network. Coupled with the expected commercialization of 5G services and massive adoption of IoT, the upsurge in the number of devices connected to the wireless network will continue to grow exponentially into billions of devices. To accommodate the associated demand for wireless spectrum as we step into this new era of wireless connectivity, traditional methods of spectrum utilization based on fixed and static allocation are no longer adequate. New innovative forms that support dynamic assignment of spectrum space on as-per-need basis are now paramount. Cognitive radio has emerged as one of the most promising techniques that allow flexible usage of the scarce spectrum resource. Cognitive radio allows unlicensed users to opportunistically access spectrum bands assigned to primary users when these spectrum bands are idle. As such, cognitive radio reduces the gap between spectrum scarcity and spectrum underutilization. The most critical function of cognitive radio is spectrum sensing, which establishes the occupation status of a spectrum band, paving the way for a cognitive radio to initiate transmission if the band is idle. The most common and widely used methods for spectrum sensing are energy detection, matched filter detection, cyclostationary feature detection and cooperative based spectrum sensing. This dissertation investigates the performance of these spectrum-sensing techniques through a Rayleigh fading channel. In a wireless environment, a Rayleigh fading channel models the propagation of a wireless signal where there is no dominant line of sight between the transmitter and receiver. Understanding the performance of spectrum sensing techniques in a real world simulation environment is important for both industry and academia, as this allows for the optimal design of cognitive radio systems capable of efficiently executing their function. MATLAB software provides an experimental platform for the fusion of various Rayleigh fading channel parameters that mimic real world wireless channel characteristics. In this project, a MATLAB environment test bed is used to simulate the performance for each spectrum sensing technique across a range of signal-to-noise values, through a Rayleigh fading channel with a given set of parameters for channel delay, channel gain and Doppler shift. Simulation results are presented as plots for probability of detection versus signal-tonoise ratio, receiver operating characteristics (ROC) curves and complementary ROC curves. A detailed performance analysis for each spectrum sensing technique then follows, with comparisons done to determine the technique that offers the best relative performance.

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Al-Askary, Omar. "Coding and Iterative Decoding of Concentrated Multi-level Codes for the Rayleigh Fading Channel." Doctoral thesis, KTH, Kommunikationssystem, CoS, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4011.

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In this thesis we present the concept of concatenated multilevel codes. These codes are a combination of generalized concatenated codes with multilevel coding. The structure of these codes is simple and relies on the concatenation of two or more codes of shorter length. These codes can be designed to have large diversity which makes them attractive for use in fading channels. We also present an iterative decoding algorithm taylored to fit the properties of the proposed codes. The iterative decoding algorithm we present has a complexity comparable to the complexity of GMD decoding of the same codes. However, The gain obtained by using the iterative decoder as compared to GMD decdoing of these codes is quite high for Rayleigh fading channels at bit error rates of interest. Some bounds on the performance of these codes are given in this thesis. Some of the bounds are information theoretic bounds which can be used regardless of the code under study. Other bounds are on the error probability of concatenated multilevel codes. Finally we give examples on the implementation of these codes in adaptive coding of OFDM channels and MIMO channels.
QC 20100629

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Al-Askary, Omar. "Coding and iterative decoding of concatenated multi-level codes for the Rayleigh fading channel /." Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1615.

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20

Zhen, Haobo. "Performance Evaluation of 2-D Pilot Aided OFDM System under Hyper-Rayleigh Fading Channel." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1310071803.

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21

Hloušek, Tomáš. "Rušení v bezdrátových sítích a jejich modelování (AWGN, Rayleigh, Rice fading channels)." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-217537.

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This thesis describes and models wirelesss transmission intereferences in real communication channels. A signal received on a fading channel is subjected to a multiplicative distortion and to the usual additive noise. Real channel adds to the signal noise and fadings. Gaussian noise is a result of channel awgn. Fadings is implicated by multipath propagation of signal in Rayleigh and Rician channels. Main goal of this project is to program BERsolve, which is created in tool GUIDE in Matlab. User program BERsolve makes it possible to analyse bit error rate and symbol error rate for some types of channel models, which are defined by standard COST207. BERsolve offers some other functions i.e. display time behaviour, constellation diagram and spectrum. This program provides us with an overview representation of problem by multipath interferences in communication channels.

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Mwangi, Patricia A. W., Amr Haj-Omar, and Kishan Montaque. "SIMULATION OF THE AERONAUTICAL RADIO CHANNEL FOR TELEMETRY APPLICATIONS." International Foundation for Telemetering, 2006. http://hdl.handle.net/10150/604033.

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ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California
The aeronautical channel is an air to ground channel characterized by multipath, high doppler shifts, Rayleigh fading and noise. Use of a channel sounder ensures proper estimation of the parameters associated with the impulse response of the channel. These estimates help us to characterize the radio channels associated with aeronautical telemetry. In order to have a satisfactory channel characterization, the amplitudes, phase shifts and delays associated with each multipath component in the channel model must be determined.

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23

Ng, Jimmy Hon-yuen. "Estimation of error rates and fade distributions on a Rayleigh fading channel with additive white Gaussian noise." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26318.

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Several characteristics of the Rayleigh fading channel are examined. A digital Rayleigh fading simulator is used to generate the (fading) signal envelope from which various statistics are derived. Based on the simulation results, a simple model is proposed in order to estimate the block error rate of a block of N data bits transmitted over the Rayleigh fading channel in the presence of additive white Gaussian noise. This model gives an average estimation error of about 4 % over the range of blocksizes N = 63, 127, 255, 511, 1023, 2047 (bits), average signal-to-noise ratios 70 = 5 to 35 (dB) and fading frequencies f[sub D] = 10 to 90 (Hz) corresponding to vehicle speeds of 8 to 71 MPH at a radio carrier frequency of 850 MHz. A second somewhat more complex model for estimating the block error rate is found to yield a lower average estimation error of 2.4 % over the same set of simulated data. The probability distributions of the fade rate and the fade duration are also examined. Empirical models are derived for the estimation of the probability mass function of the fade rate and the probability density function of the fade duration. These empirical models allow fairly accurate estimates without the need for cosdy and time-consuming simulations. The probability of m-bit errors in an N-bit block is an important parameter in the design of error-correcting codes for use on the mobile radio channel. However, such probabilities are difficult to determine without performing extensive simulation or field trials. An approach to estimate them empirically is proposed.
Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate

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24

Tsai, Chiou-Wei, Richard E. Cagley, and Ronald A. Iltis. "JOINT INTERFERENCE SUPPRESSION AND QRD-M DETECTION FOR SPATIAL MULTIPLEXING MIMO SYSTEMS IN A RAYLEIGH FADING CHANNEL." International Foundation for Telemetering, 2006. http://hdl.handle.net/10150/604390.

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ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California
Spatial multiplexing (SM) systems have received significant attention because the architecture offers high spectral efficiency. However, relatively little research exists on optimization of SM systems in the presence of jamming. In a spatially uncoded SM system, such as V-BLAST, the channel state information is assumed to be unavailable a priori at both transmitter and receiver. Here, Kalman filtering is used to estimate the Rayleigh fading channel at the receiver. The spatial correlation of the jammer plus noise is also estimated, and spatial whitening to reject the jammers is employed in both the Kalman channel estimator and detector. To avoid the exponential complexity of maximum-likelihood (ML) detection, the QRD-M algorithm is employed. In contrast to sphere decoding, QRD-M has fixed decoding complexity of order O(M), and is thus attractive for hardware implementation. The performance of the joint Kalman filter channel estimator, spatial whitener and QRD-M detector is verfied by simulations.

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25

Spilchen, Elizabeth Donna Carleton University Dissertation Engineering Systems and Computer. "Diversity combining for M-ary fast frequency hopping in a multiple- access AWGN and Rayleigh fading channel." Ottawa, 1996.

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26

Hanafi, Effariza binti. "Quickest spectrum sensing with multiple antennas: performance analysis in various fading channels." Thesis, University of Canterbury. Electrical and Computer Engineering, 2014. http://hdl.handle.net/10092/9642.

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Traditional wireless networks are regulated by a fixed spectrum assignment policy. This results in situations where most of the allocated radio spectrum is not utilized. In order to address this spectrum underutilization, cognitive radio (CR) has emerged as a promising solution. Spectrum sensing is an essential component in CR networks to discover spectrum opportunities. The most common spectrum sensing techniques are energy detection, matched filtering or cyclostationary feature detection, which aim to maximize the probability of detection subject to a certain false alarm rate. Besides probability of detection, detection delay is also a crucial criterion in spectrum sensing. In an interweave CR network, quick detection of the absence of primary user (PU), which is the owner of the licensed spectrum, allows good utilization of unused spectrum, while quick detection of PU transmission is important to avoid any harmful interference. This thesis consider quickest spectrum sensing, where the aim is to detect the PU with minimal detection delay subject to a certain false alarm rate. In the earlier chapters of this thesis, a single antenna cognitive user (CU) is considered and we study quickest spectrum sensing performance in Gaussian channel and classical fading channel models, including Rayleigh, Rician, Nakagami-m and a long-tailed channel. We prove that the power of the complex received signal is a sufficient statistic and derive the probability density function (pdf) of the received signal amplitude for all of the fading cases. The novel derivation of the pdfs of the amplitude of the received signal for the Rayleigh, Rician and Nakagami-m channels uses an approach which avoids numerical integration. We also consider the event of a mis-matched channel, where the cumulative sum (CUSUM) detector is designed for a specific channel, but a different channel is experienced. This scenario could occur in CR network as the channel may not be known and hence the CUSUM detector may be experiencing a different channel. Simulations results illustrate that the average detection delay depends greatly on the channel but very little on the nature of the detector. Hence, the simplest time-invariant detector can be employed with minimal performance loss. Theoretical expressions for the distribution of detection delay for the time-invariant CUSUM detector, with single antenna CU are developed. These are useful for a more detailed analysis of the quickest spectrum sensing performance. We present several techniques to approximate the distribution of detection delay, including deriving a novel closed-form expression for the detection delay distribution when the received signal experiences a Gaussian channel. We also derive novel approximations for the distribution of detection delay for the general case due to the absence of a general framework. Most of the techniques are general and can be applied to any independent and identically distributed (i.i.d) channel. Results show that different signal-to-noise ratio (SNR) and detection delay conditions require different methods in order to achieve good approximations of the detection delay distributions. The remarkably simple Brownian motion approach gives the best approximation for longer detection delays. In addition, results show that the type of fading channel has very little impact on long detection delays. In later chapters of this thesis, we employ multiple receive antennas at the CU. In particular, we study the performance of multi-antenna quickest spectrum sensing when the received signal experiences Gaussian, independent and correlated Rayleigh and Rician channels. The pdfs of the received signals required to form the CUSUM detector are derived for each of the scenarios. The extension into multiple antennas allows us to gain some insight into the reduction in detection delay that multiple antennas can provide. Results show that the sensing performance increases with an increasing Rician K-factor. In addition, channel correlation has little impact on the sensing performance at high SNR, whereas at low SNR, increasing correlation between channels improves the quickest spectrum sensing performance. We also consider mis-matched channel conditions and show that the quickest spectrum sensing performance at a particular correlation coefficient or Rician K-factor depends heavily on the true channel irrespective of the number of antennas at the CU and is relatively insensitive to the channel used to design the CUSUM detector. Hence, a simple multi-antenna time-invariant detector can be employed. Based on the results obtained in the earlier chapters, we derive theoretical expressions for the detection delay distribution when multiple receive antennas are employed at the CU. In particular, the approximation of the detection delay distribution is based on the Brownian motion approach.

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Chi, Xuan. "The Impact of Channel Estimation Error on Space-Time Block and Trellis Codes in Flat and Frequency Selective Channels." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/33963.

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Recently multiple antenna systems have received significant attention from researchers as a means to improve the energy and spectral efficiency of wireless systems. Among many classes of schemes, Space-Time Block codes (STBC) and Space-Time Trellis codes (STTC) have been the subject of many investigations.

Both techniques provide a means for combatting the effects of multipath fading without adding much complexity to the receiver. This is especially useful in the downlink of wireless systems. In this thesis we investigate the impact of channel estimation error on the performance of both STBC and STTC.

Channel estimation is especially important to consider in multiple antenna systems since (A) for coherent systems there are more channels to estimate due to multiple antennas and (B) the decoupling of data streams relies on correct channel estimation. The latter effect is due to the intentional cross-talk introduced into STBC.
Master of Science

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28

Conka, Tahir. "Performance analysis of noncoherent differential phase shift keying using Post-Detection Selection Combining over a Rayleigh fading channel." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA346398.

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Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, June 1998.
Thesis advisor(s): Tri T. Ha, Ralph D. Hippenstiel. "June 1998." Includes bibliographical references (p. 77). Also available online.

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Dietze, Kai. "Analysis of a Two-Branch Maximal Ratio and Selection Diversity System with Unequal Branch Powers and Correlated Inputs for a Rayleigh Fading Channel." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/32412.

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This report, presents an analytical framework for analyzing two-branch diversity systems for a Rayleigh fading channel. In many cases the fading received at both branches (i.e. a two-antenna element system) is correlated because of the proximity of the antenna elements to each other. It is also not uncommon for a diversity system to use antennas with different patterns or polarizations, this usually results in differences in average signal-to-noise ratios at both branches depending on which element is better matched to the signal environment. As will be shown, the performance of a diversity system depends greatly on the envelope correlation, average power imbalance and the combining scheme used on both branches. An analytical expression for the probability density function of the signal-to-noise ratio at the output of a two-branch maximal ratio and selection diversity system is developed in this report. The two branches are assumed to be Rayleigh fading, correlated, as well as of unequal signal-to-noise ratios. Measurements were made in Rayleigh fading channels and compared to the analytical results. The analytical cumulative distribution functions (derived using probability distributions) were found to be within 1 dB of the measured results (statistics obtained from time combining) for both maximal ratio and selection diversity attesting to the validity of the analytic results. Also developed in this report are the exact analytical average probabilities of symbol error for coherent BPSK and coherent QPSK before and after maximal ratio combining for this environment. The diversity gain for selection, maximal ratio, and equal gain combining for the 10% probability level is presented as a function of power imbalance and correlation between branches for a two-branch Rayleigh diversity system
Master of Science

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30

Huang, Kaiyu. "High Security Cognitive Radio Network via Instantaneous Channel Information." Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1558574722164809.

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31

R, V. Krishnam Raju Kunadha Raju. "Perceptual Image Quality Prediction Using Region of Interest Based Reduced Reference Metrics Over Wireless Channel." Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13631.

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As there is a rapid growth in the field of wireless communications, the demand for various multimedia services is also increasing. The data that is being transmitted suffers from distortions through source encoding and transmission over errorprone channels. Due to these errors, the quality of the content is degraded. There is a need for service providers to provide certain Quality of Experience (QoE) to the end user. Several methods are being developed by network providers for better QoE.The human tendency mainly focuses on distortions in the Region of Interest(ROI) which are perceived to be more annoying compared to the Background(BG). With this as a base, the main aim of this thesis is to get an accurate prediction quality metric to measure the quality of the image over ROI and the BG independently. Reduced Reference Image Quality Assessment (RRIQA), a reduced reference image quality assessment metric, is chosen for this purpose. In this method, only partial information about the reference image is available to assess the quality. The quality metric is measured independently over ROI and BG. Finally the metric estimated over ROI and BG are pooled together to get aROI aware metric to predict the Mean Opinion Score (MOS) of the image.In this thesis, an ROI aware quality metric is used to measure the quality of distorted images that are generated using a wireless channel. The MOS of distorted images are obtained. Finally, the obtained MOS are validated with the MOS obtained from a database [1].It is observed that the proposed image quality assessment method provides better results compared to the traditional approach. It also gives a better performance over a wide variety of distortions. The obtained results show that the impairments in ROI are perceived to be more annoying when compared to the BG.

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Chan, Raymond. "Channel Prediction for Adaptive Modulation in Wireless Communications." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/34118.

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This thesis examines the benefits of using adaptive modulation and coding in terms of spectral efficiency and probability of bit error. Specifically, we examine the performance enhancement made possible by using linear prediction along with channel estimation in conjunction with adaptive modulation. We begin this manuscript with basic fundamentals of our study, followed by a detailed view of simulations, their results, and our conclusions from them. The study includes simulations in slow and moderately fast flat fading Rayleigh channels. We present our findings regarding the advantages of using predictive measures to foresee the state of the channel and make adjustments to transmissions accordingly. In addition to finding the general advantages of channel prediction in adaptive modulation, we explore various ways to adjust the prediction algorithm when we are faced with high Doppler rates and fast fading. By the end of this work, we should have a better understanding of when channel prediction is most valuable to adaptive modulation and when it is weakest, and how we can alleviate the problems that prediction will have in harsh environments.
Master of Science

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Krause, Michael. "Signal Detection for Overloaded Receivers." Thesis, University of Canterbury. Department of Electrical and Computer Engineering, 2009. http://hdl.handle.net/10092/2959.

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In this work wireless communication systems with multiple co-channel signals present at the receiver are considered. One of the major challenges in the development of such systems is the computational complexity required for the detection of the transmitted signals. This thesis addresses this problem and develops reduced complexity algorithms for the detection of multiple co-channel signals in receivers with multiple antennas. The signals are transmitted from either a single user employing multiple transmit antennas, from multiple users or in the most general case by a mixture of the two. The receiver is assumed to be overloaded in that the number of transmitted signals exceeds the number of receive antennas. Joint Maximum Likelihood (JML) is the optimum detection algorithm which has exponential complexity in the number of signals. As a result, detection of the signals of interest at the receiver is challenging and infeasible in most practical systems. The thesis presents a framework for the detection of multiple co-channel signals in overloaded receivers. It proposes receiver structures and two list-based signal detection algorithms that allow for complexity reduction compared to the optimum detector while being able to maintain near optimum performance. Complexity savings are achieved by first employing a linear preprocessor at the receiver to reduce the effect of Co-Channel Interference (CCI) and second, by using a detection algorithm that searches only over a subspace of the transmitted symbols. Both algorithms use iterative processing to extract ordered lists of the most likely transmit symbols. Soft information can be obtained from the detector output list and can then be used by error control decoders. The first algorithm named Parallel Detection with Interference Estimation (PD-IE) considers the Additive White Gaussian Noise (AWGN) channel. It relies on a spatially reduced search over subsets of the transmitted symbols in combination with CCI estimation. Computational complexity under overload is lower than that of JML. Performance results show that PD-IE achieves near optimum performance in receivers with Uniform Circular Array (UCA) and Uniform Linear Array (ULA) antenna geometries. The second algorithm is referred to as List Group Search (LGS) detection. It is applied to overloaded receivers that operate in frequency-flat multipath fading channels. The List Group Search (LGS) detection algorithm forms multiple groups of the transmitted symbols over which an exhaustive search is performed. Simulation results show that LGS detection provides good complexity-performance tradeoffs under overload. A union bound for group-wise and list-based group-wise symbol detectors is also derived. It provides an approximation to the error performance of such detectors without the need for simulation. Moreover, the bound can be used to determine some detection parameters and tradeoffs. Results show that the bound is tight in the high Signal to Interference and Noise Ratio (SINR) region.

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Jain, Payal. "On the Impact of Channel and Channel Quality Estimation on Adaptive Modulation." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/36072.

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The rapid growth in wireless communications has given rise to an increasing demand for channel capacity using limited bandwidth. Wireless channels vary over time due to fading and changing interference conditions. Typical wireless systems are designed by choosing a modulation scheme to meet worst case conditions and thus rely on power control to adapt to changing channel conditions. Adaptive modulation, however, exploits these channel variations to improve the spectral efficiency of wireless communications by intelligently changing the modulation scheme based on channel conditions. Necessarily, among the modulation schemes used are spectrally efficient modulation schemes such as quadrature amplitude modulation (QAM) techniques. QAM yields the high spectral efficiency due to its use of amplitude as well as phase modulation and therefore is an effective technique for achieving high channel capacity. The main drawbacks of QAM modulation are its reduced energy efficiency (as compared to standard QPSK) and its sensitivity to channel amplitude variations. Adaptive modulation attempts to address the first drawback by using more energy efficient schemes in low SNR conditions are reserving the use of QAM for high SNR conditions. The second drawback leads to a requirement of high quality channel estimation. Many researchers have studied pilot symbol assisted modulation for compensating the effects of fading at the receiver. A main contribution of this thesis is the investigation of different channel estimation techniques (along with the effect of pilot symbol spacing and Doppler spread) on the performance of adaptive modulation. Another important parameter affecting adaptive modulation is the signal-to-noise ratio. In order to adapt modulation efficiently, it is essential to have accurate knowledge of the channel signal-to-noise ratio. The performance of adaptive modulation depends directly on how well the channel SNR is estimated. The more accurate the estimation of the channel SNR is, the better the choice of modulation scheme becomes, and the better the ability to exploit the variations in the wireless channel is. The second main contribution of this thesis is the investigation of the impact of SNR estimation techniques on the performance and spectral efficiency of adaptive modulation. Further, we investigate the impact of various channel conditions on SNR estimation and the resulting impact on the performance of adaptive modulation. Finally, we investigate long term SNR estimation, its use in adaptive modulation and present a comparison between the two approaches
Master of Science

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Minh, Vu Nhat. "Optimal Signaling Schemes and Capacities of Non-Coherent Correlated MISO Channels under Per-Antenna Power Constraints." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1533115867950851.

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Huynh, Jack, and Mattias Gylin. "Modelering av Wideband : Code Division Multiple Access." Thesis, Linköping University, Department of Electrical Engineering, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2845.

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Today wireless transmission of data is becoming more and more popular and the need for faster transmission rates is increasing. Since the bandwidth is limited it is important to try to use it to the fullest. CDMA is a technology that allows multiple accesses on the same frequency and time thus making it very bandwidth efficient. The CDMA technology was first introduced in the second generation’s cellular systems but has since then been improved and is reused in today’s 3G systems as Wideband CDMA. ISY is interested in getting a behavioural model of a W-CDMA system since they had developed a DSP processor called BBP1 and were thinking about adding W-CDMA support for it. Even though our system is not implemented on the BBP1 it should provide a good base for future implementations. This thesis project will describe the construction of a behavioural model of a W-CDMA system following the standard specified by 3GPP. The system simulates W-CDMA transmission and reception and has an optional channel used to simulate real world interference. The receiver uses a rake combiner to improve the performance of the system.

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Kučera, Jan. "Modelování přenosových kanálů pro příjem digitální televize DVB-T/H." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218612.

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This thesis focuses on analysis, classification, simulation and assessment of the signal fading in the scope of terrestrial digital television reception. This is a phenomenon associated with signal multipath propagation caused by the reflection, dispersion and diffraction of electromagnetic waves in interaction with relief and artificial obstacles. Wave propagation issues in a specific landscape are not the central theme of this project. Signal transmission between the transmitter and receiver is defined by channel profile models. Attention is directed not only to static reception but also to portable and mobile reception. Simulation of this phenomenon takes place in the software environment of MATLAB. In the framework of this project program fundament was created which allows simulate the signal processing across the entire communication chain of television broadcasting, including its transmitting and receiving parts.

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Kančo, Vít. "Simulace MIMO systémů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218624.

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MIMO systems are mainly used in application for wireless communication. Their principle is to use a large number of antennas for transmition and the reception of a signal. The core of these systems is to use space-time coding and either block or trellis space-time code. In the future, it is assumed enormous enlargement MIMO systems in many applications

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Silva, Vanderlei Aparecido da. "Modelagem computacional de canais de comunicação móvel." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/3/3142/tde-19112004-172238/.

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A modelagem computacional tem se tornado uma poderosa ferramenta utilizada mundialmente em pesquisas sobre sistemas de comunicação móvel. Em tais sistemas, a modelagem do canal é fator indispensável, pois as características de mobilidade e propagação presentes nesse tipo de sistema são responsáveis por distorções ocorridas sobre o sinal transmitido. O presente trabalho reúne os principais modelos matemáticos e computacionais de canal de comunicação móvel. Realiza-se uma abordagem histórica sobre o assunto, apresentado a natureza do problema do desvanecimento e a forma como foi modelado inicialmente. Por outro lado, apresentam-se modelos recentes, considerados eficazes do ponto de vista matemático e eficientes do ponto de vista computacional. O trabalho traz como contribuição a proposta de um novo modelo de canal com desvanecimento. Os modelos apresentados foram analisados do ponto de vista matemático por meio de suas propriedades estatísticas. Do ponto de vista numérico e computacional a análise se deu por meio de simulações. A principal conclusão obtida mostra que dois modelos com filtragem no domínio da freqüência, sendo um deles o novo modelo proposto, são os mais indicados para simular formas de onda que representem um canal com desvanecimento Rayleigh. Este trabalho tem a pretensão de ser útil para pesquisadores atuantes na área de modelagem e simulação de sistemas atuais de comunicação móvel.
Computational modelling is a powerful and widely used tool for research in mobile communication systems. In such systems, the communication channel modelling is an indispensable factor, because its mobility and propagation characteristics can cause distortion over the transmitted waveform. This work contains the main mathematical and computing communication channel models. A historical cover is provided, which presents the nature of the problem and the initial modelling of the fading phenomenon. On the other hand, recent models are presented, which are mathematically effective and computationally efficient. One contribution of this work is the proposal of a new fading channel computational model, which was suitably tested and validated. The presented models were mathematically analyzed through its statistical properties. From numerical and computational point of view, the models were analyzed through several simulations. The main conclusion, from analytical and simulated results, shows that two models using frequency filtering are the best choice for the generation of multiple uncorrelated Rayleigh fading waveforms, where one of them is the new proposed model. This work can help mobile communications researchers to suitably model the communication channel in a computer simulation.

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Usman, Muhammad. "Investigation, Design and Implementation of MIMO Antennas for Mobile Phones. Simulation and Measurement of MIMO Antennas for Mobile Handsets and Investigations of Channel Capacity of the Radiating Elements Using Spatial and Polarisation Diversity Strategies." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4279.

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The objectives of this work were to investigate, design and implement Multiple-Input Multiple-Output (MIMO) antenna arrays for mobile phones. Several MIMO antennas were developed and tested over various wireless-communication frequency bands. The radiation performance and channel capacity of these antennas were computed and measured: the results are discussed in the context of the frequency bands of interest. A comprehensive study of MIMO antenna configurations such as 2 × 1, 3 × 1, 2 × 2 and 3 × 3, using polarisation diversity as proposed for future mobile handsets, is presented. The channel capacity is investigated and discussed, as applying to Rayleigh fading channels with different power spectrum distributions with respect to azimuth and zenith angles. The channel capacity of 2 × 2 and 3 × 3 MIMO systems using spatial polarisation diversity is presented for different antenna designs. The presented results show that the maximum channel capacity for an antenna contained within a small volume can be reached with careful selection of the orthogonal spatial fields. The results are also compared against planar array MIMO antenna systems, in which the antenna size considered was much larger. A 50% antenna size reduction method is explored by applying magnetic wall concept on the symmetry reference of the antenna structure. Using this method, a triple dual-band inverted-F antenna system is presented and considered for MIMO application. Means of achieving minimum coupling between the three antennas are investigated over the 2.45 GHz and 5.2 GHz bands. A new 2 2 MIMO dual-band balanced antenna handset, intended to minimise the coupling with the handset and human body was proposed, developed and tested. The antenna coupling with the handset and human hand is reported in terms the radiation performance and the available channel capacity. In addition, a dual-polarisation dipole antenna is proposed, intended for use as one of three collocated orthogonal antennas in a polarisation-diversity MIMO communication system. The antenna actually consists of two overlaid electric and magnetic dipoles, such that their radiation patterns are nominally identical but they are cross-polarised and hence only interact minimally.

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Ghosh, Kaushik. "Downlink W-CDMA performance analysis and receiver implmentation on SC140 Motorola DSP." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969/169.

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ʿUs̲mān, Muḥammad. "Investigation, design and implementation of MIMO antennas for mobile phones : simulation and measurement of MIMO antennas for mobile handsets and investigations of channel capacity of the radiating elements using spatial and polarisation diversity strategies." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4279.

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The objectives of this work were to investigate, design and implement Multiple-Input Multiple-Output (MIMO) antenna arrays for mobile phones. Several MIMO antennas were developed and tested over various wireless-communication frequency bands. The radiation performance and channel capacity of these antennas were computed and measured: the results are discussed in the context of the frequency bands of interest. A comprehensive study of MIMO antenna configurations such as 2 × 1, 3 × 1, 2 × 2 and 3 × 3, using polarisation diversity as proposed for future mobile handsets, is presented. The channel capacity is investigated and discussed, as applying to Rayleigh fading channels with different power spectrum distributions with respect to azimuth and zenith angles. The channel capacity of 2 × 2 and 3 × 3 MIMO systems using spatial polarisation diversity is presented for different antenna designs. The presented results show that the maximum channel capacity for an antenna contained within a small volume can be reached with careful selection of the orthogonal spatial fields. The results are also compared against planar array MIMO antenna systems, in which the antenna size considered was much larger. A 50% antenna size reduction method is explored by applying magnetic wall concept on the symmetry reference of the antenna structure. Using this method, a triple dual-band inverted-F antenna system is presented and considered for MIMO application. Means of achieving minimum coupling between the three antennas are investigated over the 2.45 GHz and 5.2 GHz bands. A new 2 2 MIMO dual-band balanced antenna handset, intended to minimise the coupling with the handset and human body was proposed, developed and tested. The antenna coupling with the handset and human hand is reported in terms the radiation performance and the available channel capacity. In addition, a dual-polarisation dipole antenna is proposed, intended for use as one of three collocated orthogonal antennas in a polarisation-diversity MIMO communication system. The antenna actually consists of two overlaid electric and magnetic dipoles, such that their radiation patterns are nominally identical but they are cross-polarised and hence only interact minimally.

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Baas, Nicholas J. "Decomposition of Rayleigh Fading dispersive channels." Thesis, University of Canterbury. Electrical and Electronic Engineering, 2001. http://hdl.handle.net/10092/5448.

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This thesis identifies, develops and applies methods for the decomposition of fading dispersive channels. Such channels arise in wireless communication as a result of multipath and relative motion of the transmitter, scatterers and receiver. The decompositions considered are the f-power series and Karhunen-Loève (KL) expansions. For the KL expansion generalisations to rapid time variation are possible with the separate options of single spread and double spread decomposition. The single spread decomposition involves a model of the instantaneous channel transfer function with time variation supported by sample spaced coefficients. The double spread decomposition employs a model of each received pulse and requires symbol spaced coefficients. The decompositions are applied to pulse shaping, channel modelling for equalisation and the determination of performance limits for linear modulation over fading dispersive channels. The results on pulse shaping show that, with moderate bandwidth expansion and appropriate design, it is possible to significantly lower the complexity of a mobile receiver. The approach suggests a way to move complexity and power consumption away from the mobile unit and into the base station. The effects of diversity on performance are investigated by assuming a single pulse from a linear modulation format. This removes the need to consider intersymbol interference and allows conclusions about the impact of fading and dispersion on the probability of error and the average mutual information.

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Abou, Faycal Ibrahim C. (Ibrahim Chafik). "Reliable communication over Rayleigh fading channels." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10648.

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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.
Includes bibliographical references (p. 73-74).
by Ibrahim C. Abou Faycal.
M.S.

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Basharati, Sarhad. "MIMO and Relay Systems Based on Multi-Amplitude Minimum Shift Keying." Thesis, University of Canterbury. Electrical and Computer Engineering, 2013. http://hdl.handle.net/10092/8491.

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This thesis describes the use of a multi-amplitude minimum shift keying (MAMSK) signal in various types of wireless communication system. A MAMSK signal is a bandwidth efficient modulation scheme obtained by superimposing ℳ minimum shift keying (MSK) signals with unequal amplitudes. The overall phase of a MAMSK signal is controlled by the phase of the largest component MSK signal which allows the use of a low-complexity differential detector. A closed form expression for the average bit error rate (BER) for coherent detection of an MAMSK in AWGN is derived and is shown to achieve the same BER as that of square constellation quadrature amplitude modulation (QAM) with the same average transmit power. We describe the design and implementation of a STBC-based MIMO radio system in conjunction with MAMSK modulation. The proposed system provides high capacity data transmission by carrying information not only in the phases but also in the amplitude. Despite using a simple MAMSK differential receiver the system achieves performance within 1 dB of coherent detection. The existing MSK modems in conjunction with STBC could easily be modified to construct the proposed system. The MAMSK modulation scheme is extended to a multiuser relaying network where two nodes cooperate in a half-duplex environment to achieve diversity gain. The cooperative scheme is based on superposition modulation using a decode-and-forward (DF) strategy. In the proposed scheme, each node simultaneously transmits its own and the relayed signals by superimposing one on the other. A MAMSK signal is an excellent choice for this type of cooperative communication due its being obtained by a superposition technique. The proposed system exploits the overall phase of a MAMSK signal which allows differential detection and as a result it provides the lowest decoding complexity and memory requirements among the existing superposition based cooperation schemes. The performance of the system is evaluated by simulation, where it is shown that the MAMSK cooperative system outperforms a conventional DF scheme in terms of both power and bandwidth efficiency.

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Sng, Sin Hie. "Radio channel modeling for mobile ad hoc wireless networks." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FSng.pdf.

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Thesis (M.S. in Engineering Science (Electrical Engineering))--Naval Postgraduate School, June 2004.
Thesis advisor(s): Murali Tummala, Roberto Cristi. Includes bibliographical references (p. 71). Also available online.

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Vigato, Alberto. "Advanced Coding and Modulation for Digital Terrestrial Broadcasting and Cellular Systems." Doctoral thesis, Università degli studi di Padova, 2010. http://hdl.handle.net/11577/3421884.

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A new platform for HDTV transmissions, in the form of a new generation terrestrial digital video broadcasting standard (DVB-T2), has been developed by the DVB Project. A number of technical innovations have been included in DVB-T2 to boost throughput and ruggedness, enhance single-frequency network coverage, and ease both transmitter and receiver implementation. Several strategies have been investigated during the standard definition. This thesis present a research branch of this investigation starting from a multi-antenna overview: a new soft detector for space-time block codes (STBCs) is proposed, which is claim to be more efficient than the state of art techniques. Commercial and technical reasons have suggested the adoption of orthogonal frequency division multiplexing (OFDM). As multiple-antennas techniques are not backward compatible with DVB-T constellations, new modulation methods and iterative demapping schemes, suitable for OFDM in the presence of Rayleigh fading channels, are assessed in terms of diversity gain without spectral or power inefficiencies. A very important role is played by LDPC codes which are one of the principal innovation of the new digital terrestrial standard. We show how all these scenarios change once an LDPC encoding is applied to the systems. We also evaluate the performance of the coded decision directed demodulation (CD3) technique for channel estimation in DVB-T2. Since the insertion of pilot tones in the OFDM signal affects the spectral efficiency, CD3 is able to provide an accurate channel estimation with very few pilots, even in the presence of highly frequency dispersive and time-variant channels, increasing the spectrum efficiency. We give a comparison in terms of achievable throughput between DVB-T2 with CD3, even with multiple antennas, and current DVB-T. A second part is related to a cellular network scenario. Assume a set of nodes drawn uniformly at random on a finite surface having a time slot where each node broadcasts its identifier. This problem becomes of practical and theoretical interest in a dense scenario where the number of available physical resources is much smaller than the total number of nodes in the system. Here we address link level strategies for single-hop peer discovery assuming that peer identifiers are broadcasted via coded transmission and we are interested on simultaneous detection of peers which share the same physical resource then cause reciprocal interference. Several strategies are investigated through system simulations: it is shown that, in general, joint iterative decoding achieves impressive gains compared with interference cancellation even preserving almost the same complexity. Elementary modifications of broadcasted signals such as symbol permutations permit to further improve the system performance. Finally, in order to extend this work, we introduce some channel estimation procedures for primary channel models which suit with multiple detection goal.
Nel progetto DVB è stato recentemente sviluppato uno standard di nuova generazione per la trasmissione terrestre del segnale video, conosciuto come DVB-T2. Sostanzialmente si tratta di una nuova piattaforma per la trasmissione della televisione digitale ad alta dezione. Il DVB-T2 include una serie di novità tecniche per migliorarne il throughput e la robustezza, estendere la copertura delle reti a singola frequenza, e semplicare la realizzazione del trasmettitore e del ricevitore. Per questa ragione, molteplici strategie sono state studiate nella fase di definizione e stesura dei protocolli del nuovo standard. In questa tesi è presentato un lavoro di ricerca inserito in questo contesto, partendo da una prima indagine sulle trasmissioni multiantenna: a tal fine è stato proposto un decodicatore `soft' per i codici a blocco che operano nello spazio-tempo (codici STBC). Viene illustrato come sia maggiormente efficiente rispetto alle procedure presentate no ad oggi. Le strategie commerciali e tecnologiche hanno favorito l'utilizzo della modulazione OFDM. Considerando la non retrocompatibilità dei sistemi ad antenna multipla con le attuali modulazioni del sistema corrente DVB-T, nuovi schemi di modulazione e demappatura iterativa, specifici per gli schemi OFDM in presenza di canali Rayleigh fading, sono stati valutati in termini di guadagno di diversità senza inefficienze spettrali o di potenza. Un ruolo fondamentale è attribuito ai codici LDPC che sono tra le principali innovazioni del nuovo standard per il digitale terrestre. Mostreremo come cambiano le performance di tutti gli scenari analizzati quando ad essi viene accostata una codica LDPC. Inoltre daremo una valutazione del comportamento della tecnica CD3 per la stima di canale, anch'essa adottata nel DVB-T2. Poiché l'inserimento di toni pilota nel segnale OFDM indebolisce l'efficienza spettrale, il CD3 è in grado di garantire una stima di canale molto accura facendo ricorso ad un numero molto esiguo di toni pilota favorendo una maggiore efficienza dello spettro. Anche in presenza di canali tempo-varianti e altamente dispersivi in frequenza, il CD3 offre prestazioni ragguardevoli. Presenteremo un confronto tra DVB-T2 con stima di canale CD3 in singola e multipla antenna e l'attuale DVB-T in termini di throughput raggiungibile. La seconda parte riguarda uno scenario relativo alle reti cellulari. Consideriamo un insieme di nodi sparsi uniformemente a caso su di un area geografica e ipotiziamo che debbano trasmettere il loro indirizzo identificativo. Il problema assume interesse sia teorico che pratico in uno scenario ad alta densità dove il numero di risorse fisiche è di molto inferiore al numero totale di dispositivi presenti nel sistema. In questa sede vengono proposte strategie a livello di collegamento per il riconoscimento diretto dei dispositivi assumendo che l'indirizzo identificativo sia trasmesso protetto da codica e lo scopo sia di rilevare simultaneamente tutti i dispositivi che condividono la stessa risorsa fisica causando reciproca interferenza. Molteplici strategie sono state analizzate mediante simulazioni del sistema: si darà prova che, in generale, una decodica iterativa congiunta comporta un guadagno rilevante confrontanto con la tecnica classica della cancellazione di interferenza, pur mantenedo una complessità computazionale pressoché simile. Ulteriori semplici modifiche sui segnali trasmessi come la permutazione dei simboli permettono un ulteriore miglioramento delle prestazioni di sistema. Come ultimo passo, per dare un estensione pratica al lavoro, vengono introdotte alcune procedure di stima di canale per modelli di canale elementari che si adattino alla filosofia del rilevamento multiplo.

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Omidi, Mohammad Javad. "Structures for Kalman-based detection over Rayleigh fading channels." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0020/NQ53898.pdf.

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Baghaie, Abchuyeh Marjan. "Multilevel Space-Time Trellis Codes for Rayleigh Fading Channels." Thesis, University of Canterbury. Electrical and Computer Engineering, 2008. http://hdl.handle.net/10092/2101.

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Demand for capacity in wireless communication systems has been rapidly growing world- wide. This has been driven by increasing data rate requirements of cellular mobile systems, and demand for wireless Internet and multimedia services. As the available radio spec- trum is limited, higher data rates can only be achieved by designing more efficient signaling techniques. In this thesis, we propose a new transmission scheme, which benefits from the advantages of conventional space-time trellis codes (CSTTCs) but does not have the disadvantages, especially for larger signal constellations. We achieve this by developing a new class of codes, called Multilevel Space-Time Trellis Codes (IMLSTTC). The new scheme provides a scalable and promising alternative to CSTTCs, by providing the system designer with the flexibility to choose any desired balance between code performance, complexity and throughput. The proposed scheme outperforms layered schemes at high SNRs, using a smaller number of antennas.

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Polák, Ladislav. "Simulace vícecestného šíření vícestavových modulací." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-218043.

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The diploma thesis Simulation of Multipath Propagation of Multistate Modulations is focused on the development of an appropriate algorithm in MATLAB environment, which is capable to simulate the impact of the multipath propagation on received signal (error rate) on the basis of given parameters of the transmission channels. Mechanisms and characteristics of the wave propagation in communication environment, types of digital modulations and their most important parameters are described in the first part of this thesis. The second part is focused on the simulation itself. Created GUI (Graphical User Interface) is able to display constellation diagrams of transmitted and received signals, as well as their bit error rate. It is also possible to compare these data with the data of signal, which is passed by a non-fading channel.

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Dissertations / Theses on the topic 'Rayleigh fading channel'

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