Dissertationen zum Thema „Time /Frequency Selective Broadband Channels“
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Bemani, Ali. „Affine Frequency Division Multiplexing (AFDM) for Wireless Communications“. Electronic Thesis or Diss., Sorbonne université, 2023. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2023SORUS610.pdf.
Der volle Inhalt der QuelleIn the realm of next-generation wireless systems (beyond 5G/6G), the vision is clear: to support a broad range of services and applications. This includes ensuring reliable communications in environments marked by high mobility, such as high-speed railway systems and various vehicular communications. Despite the deployment of various multicarrier techniques like orthogonal frequency division multiplexing (OFDM) and single-carrier frequency division multiple access (SC-FDMA) in standardized communication systems, the challenge persists. These techniques, while effective in time-invariant frequency selective channels, face performance degradation in high mobility scenarios due to the destruction of orthogonality among subcarriers caused by significant Doppler frequency shifts. Addressing this, the search for new, robust modulation techniques is paramount. It stands as a key area of investigation aiming to resolve the reliable communications issue for next-generation wireless networks within doubly-selective wireless channels. In this thesis, a novel solution, affine frequency division multiplexing (AFDM), is proposed. This new chirp-based multicarrier waveform is based on the discrete affine Fourier transform (DAFT), a variant of the discrete Fourier transform characterized with two parameters that can be adapted to better cope with doubly dispersive channels. This thesis provides a comprehensive investigation into the principles of AFDM within high mobility communications. It provides insight into the explicit input-output relation in the DAFT domain, unveiling the consequential impact of AFDM parameters. The manuscript details the precise setting of DAFT parameters, ensuring a full delay-Doppler representation of the channel. Through analytical demonstrations, it asserts that AFDM optimally achieves the diversity order in doubly dispersive channels due to its full delay-Doppler representation. The thesis also proposes two low-complexity detection algorithms for AFDM, taking advantage of its inherent channel sparsity. The first is a low complexity MMSE detector based on LDL factorization. The second is a low complexity iterative decision feedback equalizer (DFE) based on weighted maximal ratio combining (MRC) of the channel impaired input symbols received from different paths. Additionally, the thesis presents an embedded channel estimation strategy for AFDM systems, leveraging AFDM's ability to achieve full delay-Doppler representation of the channel. In this approach, an AFDM frame contains a pilot symbol and data symbols, with zero-padded symbols employed as guard intervals to prevent interference. A practical channel estimation algorithm based on an approximate maximum likelihood (ML) approach and compatible with this pilot scheme is also provided. The thesis concludes by delving into the expanded applications of AFDM, specifically in integrated sensing and communication (ISAC) and extremely high frequency (EHF) band communications. It is demonstrated that to identify all delay and Doppler components linked with the propagation medium, one can use either the full AFDM signal or only its pilot part consisting of one DAFT domain symbol and its guard interval. Furthermore, the chirp nature of AFDM allows for unique and simple self-interference cancellation with a single pilot, eliminating the need for costly full-duplex methods. The thesis also highlights AFDM's efficient performance in high-frequency bands (with or without mobility), where the maximal spreading of its signal in time and frequency ensures a coverage gain. Unlike other waveforms, AFDM not only provides maximal time-frequency spreading but also ensures robust and efficient detection, characterized by one-tap equalization and resilience to carrier frequency offset (CFO) and phase noise
Chu, Alice Pin-Chen. „High-Rate Space-Time Block Codes in Frequency-Selective Fading Channels“. Thesis, University of Canterbury. Electrical and Computer Engineering, 2012. http://hdl.handle.net/10092/10360.
Der volle Inhalt der QuelleKatayama, Masaaki. „Keynote: “Power line channels: frequency and time selective” Part 2.-Noise statistics of indoor PLC channels“. IEEE, 2007. http://hdl.handle.net/2237/9424.
Der volle Inhalt der QuelleWavegedara, Kapila Chandika B. „Advanced receivers for space-time block-coded single-carrier transmissions over frequency-selective fading channels“. Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/620.
Der volle Inhalt der QuelleKosa, Irfan. „Performance of IEEE 802.11a wireless LAN standard over frequency-selective, slowly fading Nakagami channels in a pulsed jamming environment“. Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02Dec%5FKosa.pdf.
Der volle Inhalt der QuelleThesis advisor(s): R. Clark Robertson, Tri Ha. Includes bibliographical references (p. 107-108). Also available online.
Gong, Yi. „Space-time coding for high data-rate wireless communications over space and frequency selective fading channels /“. View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202002%20GONG.
Der volle Inhalt der QuelleIncludes bibliographical references (leaves 105-114). Also available in electronic version. Access restricted to campus users.
Siyau, Ming Fei. „A novel training-based MIMO channel estimation scheme for layered space-time systems in frequency selective wireless channels“. Thesis, Cranfield University, 2009. http://dspace.lib.cranfield.ac.uk/handle/1826/3464.
Der volle Inhalt der QuelleSiyau, M. F. „A Novel training-based MIMO channel estimation scheme for layered space-time systems in frequency selective wireless channels“. Thesis, Department of Aerospace, Power & Sensors, 2009. http://hdl.handle.net/1826/3464.
Der volle Inhalt der QuelleChi, 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.
Der volle Inhalt der QuelleBoth 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
Chayot, Romain. „Synchronisation, détection et égalisation de modulation à phase continue dans des canaux sélectifs en temps et en fréquence“. Thesis, Toulouse, INPT, 2019. http://oatao.univ-toulouse.fr/24188/1/Chayot_Romain.pdf.
Der volle Inhalt der QuelleChen, Harry Zhi Bing. „Space-time coding for frequency-selective fading channels“. Thesis, 2003. http://hdl.handle.net/2429/15161.
Der volle Inhalt der QuelleVijaya, Krishna A. „A Filterbank Precoding Framework For MIMO Frequency Selective Channels“. Thesis, 2006. https://etd.iisc.ac.in/handle/2005/1084.
Der volle Inhalt der QuelleVijaya, Krishna A. „A Filterbank Precoding Framework For MIMO Frequency Selective Channels“. Thesis, 2006. http://hdl.handle.net/2005/1084.
Der volle Inhalt der QuelleHu, Tsung Wen, und 胡聰文. „Study on complex-field space time trellis codes over frequency selective channels“. Thesis, 2008. http://ndltd.ncl.edu.tw/handle/70354262879016753382.
Der volle Inhalt der Quelle國立交通大學
電子工程系所
96
In this thesis, we propose a novel complex-field Space Time Trellis Codes (STTC) and derive performance upper bounds for this code over frequency selective channels. The novel STTC can directly combine the coding trellis and the channel effect to enable the full diversity order be achieved by joint decoding based on MLSE (Maximum Likelihood Sequence Estimator). Then we discuss the characteristics of the complex-field STTC. In order to simplify the performance analysis of this code, we assume that error probability is dominated by the minimum distance of the first error event in the combined trellis. We use the Rayleigh sum distribution and density to derive an upper bound for this code and show this new code can achieve diversity order as we expect by simulation results.
Li, Chi-Ming, und 李啟銘. „Space-Time Code Design for Linear Modulation over Frequency-Selective Fading Channels“. Thesis, 2017. http://ndltd.ncl.edu.tw/handle/3n9t57.
Der volle Inhalt der Quelle國立清華大學
電機工程學系所
105
In this thesis, we derived the rank design criterion of a space-time code scheme for linear modulation over frequency-selective fast fading channels with oversampling technique. With an optimal convolutional temporal encoder and an optimal spatial encoder achieving the full transmit spatial diversity, the overall diversity gain is at least Lr(L*ECL*L) if L<=l and Lr(Lt*ECL*l+L-l) if L >l, where Lr is the number of receive antennas, Lt the number of transmit antennas, ECL the effective code length of the convolutional encoder, l the oversampling factor and L the number of taps in the equivalent tapped-delay-line channel model. We have devised an finite-state machine for a Viterbi decoder which implements the maximum likelihood sequential detection of the received signal.Simulation results have confirmed that this coding scheme is very effective.
Maa, Ching-Shyang, und 馬清祥. „Structured Design and Analysis of Space-Time Codes in Frequency-Selective Wireless Channels“. Thesis, 2004. http://ndltd.ncl.edu.tw/handle/67120193517783610255.
Der volle Inhalt der Quelle國立清華大學
通訊工程研究所
92
In a wireless system with multipath MIMO (multiple input multiple output) channels using antenna arrays, the delay spread of multipaths results in intersymbol interference (ISI) and channel frequency selectivity. Similar to the channel frequency selectivity, spatial gains at the multipath angles also naturally result in channel angle selectivity. Based on the channel selectivity structures characterized by the path delays and the path directions-of-departure/arrival (DODs/DOAs), in this thesis, we first seek new insights into the matching of space-time codes and multipath MIMO channels in their angle-frequency (AF) structures. Next, by exploiting the wireless MIMO channel structure, new space-time code design criteria are derived. New structure-based space-time codes are identified through computer searches to justify the new criteria. Simulation results show that these codes have superior performance over the existing codes in the corresponding frequency-selective channels. Based on the new design criteria, we propose two low-complexity channel-adapted space-time (CAST) coding schemes, where trade-offs among codeword error rate, data throughput and computational complexity are very flexible. Simulation results confirm that, in the frequency-selective MIMO channels, the CAST coding schemes can perform significantly better than the existing space-time codes, e.g., Alamouti space-time orthogonal code. In addition, recent advances in information theory show that employing multiple antennas at both sides of a wireless link promises enormous capacity potential. With knowledge of channel state information (CSI) at the transmitter, space-time eigen-beamforming is the optimum coding scheme to exploit this potential. However, in non-stationary wireless environments, high complexity on MIMO channel tracking and large amounts of CSI feedback render such an approach impractical. By exploiting the wireless multipath channel structure, a space-time coding scheme involving a novel structure-based water-filling algorithm is proposed. Outage capacities evaluated through Monte Carlo simulations confirm the performance advantage of the proposed space-time coding scheme. For more efficient usage of bandwidth, blind detection schemes attract more and more attention. In a noncoherent system, a differential phase coding scheme is an attractive technique as it obviates the need for phase synchronization. However, its performance degrades considerably when channels vary rapidly. To establish a reliable communication link, we propose a wireless system with a blind receiver which jointly performs noncoherent channel estimation and serially-concatenated turbo code decoding over fast time-varying Rayleigh-fading channels. The low complexity blind receiver consists of two parts: 1) a Kalman filter as its channel estimation part and 2) two decoders, including a differential decoder and a convolutional decoder, as its signal decoding part. With various soft information, calculated in the maximum likelihood sense, iteratively passed around between the channel estimator and the signal decoder, the system is expected to hopefully approach the optimal performance. Note that, with no training data in the proposed system, it is impossible for the Kalman filter to avoid the CSI phase ambiguity problem, which can be perfectly taken care of by the differential decoder. Computer simulations confirm that the proposed system exhibits robustness against fast time-variation of Rayleigh-fading channels.
Li, Yu-chen, und 李昱蓁. „Coherent and Noncoherent Space-Time Modulation for Single-Carrier Block Transmission over Frequency-Selective Channels“. Thesis, 2008. http://ndltd.ncl.edu.tw/handle/20556569555351308304.
Der volle Inhalt der Quelle國立臺灣科技大學
電機工程系
97
This dissertation includes two parts. The first part deals with time-reversal single carrier orthogonal space-time blocked technique employed in a multi-access CDMA uplink system over a quasi-static frequency selective fading channel. To avert the rate loss problem normally encounter in convolutionally coded space-time block modulation, we assign each user multiple spreading sequences so as to expand constellation size of orthogonal space-time codes. At receiver,one approaches, namely single-user detectors based on minimum mean-square error (MMSE) sense. Indeed, in computer simulations this receivers in terms of bit error rate (BER) indicates that the computational complexity was traded for performance gain. We, rather than assume channel state information (CSI) known to both transmitter and receiver, consider noncoherent space-time modulation in single-carrier block system over quasi-static frequency-selective fading channel. Indeed, capitalizing on multi-channel input-output relation in time domain, we construct space-time codes of constant signaling amplitude by means of complex orthogonal sequences to achieve maximal diversity gain along with coding advantage. Numerical result indicates that SC block system can outperform the orthogonal frequency division multiplexing (OFDM) counterpart, which additionally suffers from higher peak-to-average power ratio (PAPR), in terms of block error rate (BLER) under the same scenario conducted in simulations
Lin, Yu-Teng, und 林郁登. „On the Study and Performance Evaluation of the STBC MIMO-OFDM Wireless Broadband Communication System over Frequency Selective Fading Channels“. Thesis, 2006. http://ndltd.ncl.edu.tw/handle/12919638056303631298.
Der volle Inhalt der Quelle龍華科技大學
電子系碩士班
94
Multiple-Input Multiple-Output (MIMO) system is a reliable communication system which applies multi-antenna at both transmitter and receiver sides. The MIMO system can be configured and used as the spatial multiplexing mechanism to increase the data rate or used as the diversity technology to improved data Link reliable. On the other hand, the Orthogonal Frequency Division Multiplexing (OFDM) modulation scheme using a cyclic prefix (CP) technique also exhibits the desired property of strong resistance to the propagation channel fading caused by the channel multipath delay spread. Thus, the use of MIMO system in conjunction with OFDM modulation (MIMO-OFDM) technique has demonstrated its great potential for high quality wireless wideband data communication. However, in most practical situation, the channel knowledge is unknown at transmitter, the use of space-time coding scheme is then required to be introduced into the MIMO-OFDM system to consolidate the system performance by exploiting the benefits of the triple diversities in space, time and frequency domains. It is therefore, the kernel purposes of this paper are to study the MIMO-OFDM system infrastructure using the space-time block coding (STBC) scheme, and to evaluate the system performance over the propagation channel having frequency selective fading. The results can be useful to get insight into the robustness and the capabilities associated with this new noteworthy prospect of the wireless broadband communication system
Yang, Chieh-Chih, und 楊傑智. „On Frequency-Domain Equalization with Training-Based Channel Estimation for Orthogonal Space-Time Block Coded System via MIMO Frequency-Selective Fading Channels“. Thesis, 2007. http://ndltd.ncl.edu.tw/handle/02950626224237711536.
Der volle Inhalt der Quelle國立交通大學
電機與控制工程系所
95
We propose an instructive derivation for the generalized block-level orthogonal space-time block encoder, capable of achieving full spatial diversity via frequency- selective fading environment provided that channel order is known. Instead of dealing with special case and then extending the results intuitively, we provide an alternative by starting with the general signal model with multiple transmit and multiple receive antennas, from which a general form of block-level orthogonality is established. In particular, transmit diversity with more than two transmit antennas can be achieved without compromise by means of frequency-domain equalization, in contrast to the QO-STBC-based approach. Pairwise error probability analysis is derived, under certain assumption which is numerically supported by simulation results, for analytical verifications of our claim on full diversity, inclusive of transmit-receive diversity and the multipath one. Moreover, the encoder structure enables us to generalize a training-based channel estimation technique, originally proposed for flat-fading scenario, to the frequency-selective fading scenario. Surprisingly we even obtain similar optimality criteria for optimal training block design which in our case, the signal block are fixed as OSTBC-based and the design derivation reduces to derive optimal power constraint over the training blocks. The optimality criteria for the training blocks are easy to satisfy when randomness of signal constellation is not a concern. Simulation results validate our discussion of the behaviors of the least-squares and linear MMSE channel estimates.
Rakshith, M. R. „Algorithms For Spatial Modulation Systems“. Thesis, 2013. http://etd.iisc.ac.in/handle/2005/3905.
Der volle Inhalt der QuelleRakshith, M. R. „Algorithms For Spatial Modulation Systems“. Thesis, 2013. http://etd.iisc.ernet.in/2005/3905.
Der volle Inhalt der QuelleΛάλος, Αριστείδης. „Αποδοτικές τεχνικές εκτίμησης – ισοστάθμισης γενικευμένων ασύρματων καναλιών πολλαπλών εισόδων – πολλαπλών εξόδων“. Thesis, 2009. http://nemertes.lis.upatras.gr/jspui/handle/10889/4068.
Der volle Inhalt der QuelleSystems employing multiple antennas at the transmitter and the receiver, known as MIMO (multiinput multioutput) systems, as well as space time coding techniques developed for such systems, are two of the main technologies employed for the evolution of wireless communications. However, the application of MIMO technology to mobile networks, often faces the practical implementation problem of having too many antennas on a small mobile terminal. In an attempt to overcome such a severe limitation, cooperative communication schemes have been proposed. This PhD dissertation, described our work on the design and analysis of signal processing algorithms for the two aforementioned systems, as is described in detail next. Concerning MIMO systems, the pioneering work performed at Bell Labs in the middle of the nineties, proved that the use of multiple antennas can lead to a significant increase in wireless systems capacity. To exploit this potential, sophisticated MIMO receivers should be designed. To this end, a large amount of channel equalizers and, more specifically, decision feedback equalizers has been proposed. Because these assumptions are difficult to meet in high rate single carrier systems, we have focused our attention on decision feedback equalizers. . Our main goal is to derive algorithms for updating the MIMO DFE filters with the following characteristics: 1) convergence properties similar to these of the RLS 2) more computationally efficient than RLS and 3) numerically stable. It is known that adaptive algorithms based on the CG (conjugate gradient) have the above characteristics We initially studied this method as an iterative method for solving linear equations and we pointed out the main differences with the steepest descent method, on which the LMS algorithm is based. An extended search of adaptive DFE algorithms, based on the CG method was carried out. More specifically, a new block adaptive CG algorithm was developed. In the resulting algorithm, one CG iteration per block update is executed. In order to reduce even more the complexity, the algorithm was implemented in the Frequency Domain. The proposed equalizer offers a good performance - complexity trade off. Three new adaptive equalization algorithms for wireless systems operating over frequency selective MIMO channels, based on the CG method and the Galerkin projection method, are proposed. The problem of MIMO decision feedback equalizer (DFE) design is formulated as a set of linear equations with multiple righthand sides (RHSs) evolving in time. These schemes provide a flexible framework in MIMO adaptive equalization design to implement schemes with convergence properties comparable to the RLS, but of lower computational cost. Furthermore, we worked on channel estimation for cooperative communication networks, where the nodes either simply amplify and forward the received signal, or they decode and transmit the signal (DF). We first propose efficient channel estimation techniques for relay networks with N relays. The new methods are implemented in the frequency domain (FD). Initially, training based techniques are presented, where the training pilots are multiplexed with the data in the frequency domain. It is then shown that all the channels in the network can be estimated blindly provided that we know the phases of the frequency response of the (Source → Destination) channel. Thus, by making use of a small number of pilots in only one link (the sourcetodestination link) we can estimate all the other channels (Source→Relay i→Destination) in the network. A theoretical performance study of the proposed algorithms is presented and closed form expressions for the mean squared channel estimation error are provided. The presented theoretical analysis is verified by extensive Monte Carlo simulations. The application of the derived schemes to the DF case, and the impact of erroneous detection to their performance are also studied. Finally, we investigated experimentally four cooperative relaying schemes: amplify and forward (AF), detect and forward (DF), cooperative maximum ratio combining (CMRC) and distributed spacetime coding (DSTC), and one novel selection relaying (SR) scheme on a realtime DSP based testbed. The experimental results are fairly close to the ones predicted by theory