Дисертації з теми "High Mobility Environments"
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Qu, Ming. "Experimental studies of wireless communication and GNSS kinematic positioning performance in high-mobility vehicle environments." Thesis, Queensland University of Technology, 2012. https://eprints.qut.edu.au/50953/1/Ming_Qu_Thesis.pdf.
Повний текст джерелаEdwards, Michael. "Characterization of Fillite as a Planetary Soil Simulant in Support of Rover Mobility Assessment in High-Sinkage/High-Slip Environments." ScholarWorks @ UVM, 2015. http://scholarworks.uvm.edu/graddis/292.
Повний текст джерелаSavoie, Courtney Beth Young. "Arsenic Mobility and Compositional Variability in High-Silica Ash Flow Tuffs." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/1012.
Повний текст джерелаKim, Samuel H. "Addressing thermal and environmental reliability in GaN based high electron mobility transistors." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52244.
Повний текст джерелаOng, Felicia Li Chin. "Heterogeneous Networking for Beyond 3G system in a High-Speed Train Environment. Investigation of handover procedures in a high-speed train environment and adoption of a pattern classification neural-networks approach for handover management." Thesis, University of Bradford, 2016. http://hdl.handle.net/10454/12341.
Повний текст джерелаUppoor, Sandesh. "Understanding and Exploiting Mobility in Wireless Networks." Phd thesis, INSA de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-00912521.
Повний текст джерелаBenigni, Paolo. "Trapped Ion Mobility Spectrometry coupled to Fourier Transform Ion Cyclotron Resonance Mass Spectrometry for the analysis of Complex Mixtures." FIU Digital Commons, 2017. https://digitalcommons.fiu.edu/etd/3547.
Повний текст джерелаKrämer, Dennis [Verfasser], Michael [Akademischer Betreuer] Bau, Andrea [Akademischer Betreuer] Koschinsky, Gregor [Akademischer Betreuer] Borg, and Thomas [Akademischer Betreuer] Kuhn. "Mobility of High-Technology Metals in Earth’s Surface Environment : A Study on Siderophore-Promoted Mobilization and Implications for the Extractive Hydrometallurgy of some Critical Metals / Dennis Krämer. Betreuer: Michael Bau. Gutachter: Michael Bau ; Andrea Koschinsky ; Gregor Borg ; Thomas Kuhn." Bremen : IRC-Library, Information Resource Center der Jacobs University Bremen, 2015. http://d-nb.info/1095233416/34.
Повний текст джерелаJHANG, LUN-YUAN, and 張掄元. "Reduced-complexity OFDM signal detection under high mobility environments." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/05136578910983662760.
Повний текст джерела南開科技大學
電機與資訊工程研究所
99
In orthogonal frequency division multiplexing (OFDM) system, the intercarrier interference (ICI) causes significant performance degradation. The successive interference cancellation (SIC) has been proved to have an excellent performance for mitigating the ICI in OFDM system. However, since the complexity of SIC is proportional to the number of OFDM subcarrier N, the realization of this detector becomes impractical, especially when large number of subcarrier is considered. In this thesis, a modified successive interference cancellation (SIC) algorithm which is referred to as qSIC is proposed for high mobility OFDM system. The qSIC algorithm not only significantly reduces the computational complexity of SIC algorithm, but its performance also approaches the performance of conventional SIC algorithm. Furthermore, a fast matrix inversion for qSIC was purposed. In qSIC, the pseudo-inverse of the (2j+1)-dimensional matrices are repeatedly calculated and successively padded with zero columns. This means that the taken (2j+1)-square matrices are mostly non-full-rank. Thus this leaves room for improvement in decreasing computational complexity. The presented fast matrix inverse can obtain reliable and accurate approximations in the qSIC simulation cases.
Liu, Ju-Chieh, and 劉如傑. "Channel Tracking Techniques for the High-Mobility Wireless Access in Vehicular Environments." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/89250474019104851485.
Повний текст джерела國立中正大學
通訊工程研究所
95
The industrial standard of Wireless Access Vehicular Environment (WAVE), or called the IEEE 802.11p standard, is an example of the orthogonal frequency division multiplexing (OFDM) technique applied to the high-mobility environment. In addition to the multipath effect, the high-mobility environment introduces severe fading to the received signals. Tracking of the channel state information becomes the critical issue for such high-mobility system. Based one the conventional decision-directed channel tracking (DDCT) algorithm, we proposes a modified decision-directed channel tracking (MDDCT) algorithm. Our proposed algorithm is shown to have approximately equal uncoded bit error rate (BER) to that of the conventional DDCT algorithm, but have significant lower packet error rate than that of the conventional DDCT algorithm under a variety of high-mobility environments. After comparing the error patterns of the uncoded bits that are demodulated by the conventional and our MDDCT algorithms, we observe that our MDDCT algorithm mitigates the burst error; hence, the following error correction decoder works more effectively to improve its packet error rate. Finally, our MDDCT is of very low complexity, and is of practical use.
Li, Ying-Hao, and 李英豪. "A Study on WCDMA Power Control Algorithms under Very High Mobility Environments." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/82908467543040163001.
Повний текст джерелаWu, Chong-Wei, and 吳崇瑋. "Code-Decision Directed Iterative ICI Mitigation Techniques for OFDM System in High Mobility Environments." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/03178160436623977944.
Повний текст джерела國立中央大學
通訊工程研究所
99
Orthogonal frequency-division multiplexing (OFDM) is a technique well suited for wireless broad-band communications.A drawback of OFDM is its sensitivity to time-varying channel effect in a mobile receiving environment with significant Doppler spread. In this scenario, the orthogonality between subcarriers is destroyed and the inter-carrier interference (ICI) is thus arised.In this thesis, we propose a modified iterative ICI mitigation method, which incorporates code-decision direct and an approximate maximum-likelihood detection, to improve the performance of a OFDM receiver in high-mobility environemt .
Surabhi, G. D. "On Orthogonal Time Frequency Space Modulation for Wireless Communications." Thesis, 2020. https://etd.iisc.ac.in/handle/2005/4461.
Повний текст джерелаLin, Wei-cheng, and 林韋丞. "Synchronization for DVB-T in High-mobility Environment." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/24722855096619877379.
Повний текст джерела國立中央大學
通訊工程研究所
96
OFDM technique is adopted in many standards, including DVB-T, since it exhibits outstanding characteristics in terms of efficiency in spectral utilization, simplicity in equalization and immunity in Inter-Symbol-Interference (ISI). However OFDM system performance is sensitive to synchronization errors including symbol timing offset, carrier frequency offset and sampling clock frequency offset. Typical methods exploiting the correlation of cyclic-prefix in time domain and the correlation of continual pilots in frequency domain have been proposed for estimating and correcting the synchronization errors for OFDM systems. In these methods the channel model is generally assumed to be static, i.e., the transmitter and receiver are in stationary positions and the channel impulse response is time invariant. This assumption is violated especially when the receiver and/or transmitter are in high-mobility environment, i.e., the channel impulse response becomes time varying significantly. In this thesis, we focus on studying on the synchronization problems of DVB-T system when the receiver is in mobility as high as to 300 km/hr. In this scenario, significant time-varying channel impulse response due to large Doppler spread is noticed which causes the loss of subcarrier orthogonality and signal correlation, and the performance of typical synchronization algorithms is evaluated. Finally, a synchronization method, which is more suitable to high-mobility reception, is designed for DVB-T receiver. The implementation of synchronization systems is verified with Modelsim tool and real-time implementation on FPGA hardware.
Chang, Wei-Hsuan, and 張維軒. "A WiMAX Baseband Transceiver for High Mobility Environment." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/50898248259799112299.
Повний текст джерела國立清華大學
電機工程學系
96
This thesis is focus on a MIMO-OFDM system, which uses space frequency block coding algorithm for high mobility environment. An inner transmitter and receiver for IEEE 802.16e uplink specification is designed to implement this algorithm. In order to model a high mobility environment, ITU-VA channel model, which is constituted by 3GPP, is used for the simulation. Additionally, Jakes model is added to simulate the high mobility environment. Compare with space time block code and space frequency block code, space frequency block code has better performance in outdoor environment with high mobility. Thus, this thesis propose a SFBC decoding algorithm to against Doppler effect. An 2x2 SFBC-OFDM is defined in IEEE 802.16e standard. The simulation result shows that Doppler effect can be alleviated through this algorithm. In general SFBC system, the adjacent channel responses are assumed constant. However, channel responses are not constant in real communication systems, especially in high mobility environment. The variation between adjacent channel responses causes interference while decoding, so the error will occur in high SNR. Thus, an interference cancellation method is needed to solve this problem. The demapping result is sent back to the SFBC decoder for the interference cancellation. The simulation result shows that this cancellation can prevent error floor in high SNR region. In order to implement this system, we designed an inner transmitter platform for high speed emulation. This platform consist hardware part and software part. Some complicated operations can be implement in hardware, so the emulation time can be reduced. Furthermore, the receiver is designed in software, so the user can change or replace the receiving method easily. If designer want to develop a new receiving algorithm, it can save the development time. Additionally, this platform is built on the webpage, so everyone can use this platform from anywhere through the internet.
Yeh, Kao-Fa, and 葉高發. "Optimizing UMTS Performance in High Speed Mobility Environment." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/7t6k62.
Повний текст джерела國立臺北科技大學
電腦與通訊研究所
97
Third Generation Mobile communication system using wideband code division multiple access (WCDMA) technology. Netork providers served one after another. We usually name for 3rd Generation Mobile communication. Netork operators enable voice、data、high speed downlink access services(HSDPA). According variety of serves incress. The subscribe request rigorous handover algorithm.Therefor those Handover algorithm are currently being standardized in 3GPP for Release 99 and R5.This article introduced “Handover Algorithm difference”and proposed “Apposite Handover Algorithm” for High Speed rail environment. Finally, we provided internal real mobile network measured data result in high speed rail environment for research and conclusion.
Lin, Hong-Yi, and 林弘毅. "A MIMO-OFDM Baseband Engine for High Mobility Environment." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/82800494641140257700.
Повний текст джерела國立清華大學
電機工程學系
97
In this thesis, a MIMO-OFDM system which is designed for high mobility environment is proposed. In order to fight with the time varying channel, the system uses space frequency block coding (SFBC) algorithm to obtain additional diversity gain without any extra communication resource. Furthermore, a flexible and low complexity intercarrier interference (ICI) mitigation module is also proposed in the thesis. Doppler Effect causes ICI in high mobility environment. The ICI destroys orthogonality between subcarriers and degrades the system performance. In other words, the channel matrix is not a diagonal matrix anymore, non diagonal elements are the equivalent ICI factors and need to be eliminated. The channel matrix estimation uses a linear approximation algorithm. In order to adapt the module to MIMO systems, the proposed method substitutes for ZF ICI compensation algorithm to mitigate the ICI. So as to avoid calculating the inverse matrix, we take subtraction instead of inversion computation. The computational complexity can be reduced from O(N3) to O(N). The module can be applied not only in SISO systems but also in MIMO systems flexibly. The proposed SFBC-OFDM baseband transceiver is constructed by SystemC language. The receiver includes a timing synchronization module, a carrier frequency offset estimation and compensation module, a channel estimation module, a SFBC decoder with soft output, and a flexible and low complexity ICI mitigation module. In order to model a high mobility environment, ITU-VA channel model, which is constituted by 3GPP, is employed for the simulation. Also, Jakes’ model is added to simulate the high mobility environment. According to the simulation result, the proposed SFBC-OFDM system with ICI mitigation obtains about 3dB gain after ICI compensation in the high mobility environment.
Basnet, Modick Bahadur, and 莫迪. "Self-optimizing algorithms for LTE system in high mobility environment." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/527sy6.
Повний текст джерела元智大學
通訊工程學系
104
This dissertation is concerned with three self-optimizing algorithms all of which pertain to improve the performance of LTE system in high mobility environment. These algorithms include: a self-optimizing power control and receive antenna number selection (SOPCRAS) algorithm for high mobility MIMO-SC-FDMA transceiver and a self-optimizing beamforming null control (SOBNC) algorithm to improve the signal-to-interference-plus-noise ratio (SINR) for LTE uplink transceiver. LTE standard requires adequate performance for UE velocities up to 350 km/h, however, even with a good channel estimation method LTE performance in velocities above 100 km/h suffers with intense fading channel dispersion. LTE data rate performance depends on channel quality index (CQI) value which can be supported by maintaining certain SINR threshold to keep BLER<10-1. This dissertation proposes SOPCRAS algorithm to minimize the uplink power and inter-cell interference (ICI) of LTE uplink MIMO-SC-FDMA transceivers in high-mobility environments. In SOPCRAS algorithm, an MIMO-based self-optimization power controller is used to adjust the transmit power adaptively to minimize the UE transmit power and select minimum number of receiver antenna at eNB to satisfy BLER < 10-1 in extended vehicular A (EVA) channel for velocities in the range of 0~300 km/h. The throughput and power consumption of the SOPCRAS algorithm are compared numerically with open loop power control (OLPC) method in which the UE transmit power is adjusted in accordance with AWGN performance. Co-channel interference (CCI) has tremendous impact on the performance of heterogeneous networks (HetNets). The proposed SOPCRAS algorithm will increase the transmit power of transceivers with the interference power adaptively to maintain the BLER less than 10-1 if the transmit power is less than the upper bound of transmitter. A novel SOBNC algorithm based on the estimation of the SINR and angular spread is proposed in this dissertation which adapts the null width and depth of uniform linear array (ULA) to the changing environments. The SOBNC algorithm is initiated to reject the interference if the transmit power reaches the upper bound of transmitter. Finally, it has shown that the SOBNC can maintain the SINR level of eNB receiver at required threshold as per changing environments and its performance is superior to the conventional fixed null scheme.
Lan, Yi-Yao, and 藍義堯. "Frequency Synchronization for OFDM System in Very High Mobility Environment." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/41333352586889337624.
Повний текст джерела國立臺灣大學
電信工程學研究所
96
This thesis emphasize on frequency synchronization for OFDM in very high mobility environment. The very high mobility environment for TAIWAN HIGH SPEED RAIL (300km/hr) leads to critical doppler effect, so the channel will cause fast fading and multipath interference (doubly selective channel).The mismatch between transmitter and receiver and doppler effect will bring about carrier frequency offset. In order to working OFDM technique in very high mobility environment, we propose multiple sections training symbol method、weighting method and prediction mode method to resist time-variant channel and then do carrier frequency offset estimation。After we finish carrier frequency offset estimation, we do frequency compensation to reach whole frequency synchronization.
LEE, CHIN-CHUN, and 李靖群. "Channel Identification of OFDM System in Very High Mobility Environment." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/33496862415888669817.
Повний текст джерела國立暨南國際大學
通訊工程研究所
96
This thesis probes for the very high mobility environment mainly. In medium or low mobility environment,we usually assume that the channel is time-invariant during each OFDM symbol which we transmit and demodulate. Because the very high mobility environment for TAIWAN HIGH SPEED RAIL (300km/hr) leads to critical doppler effect,the system suffers from the fast fading effect severely. In OFDM used large FFT points transmission architecture,the channel will change during each OFDM symbol.The bit error rate of conventional transmission and demodulation for time-variant channel will increase substantially ,so the major issues that how to transmit pilots and demodulate in receiver to decrease the bit error rate. This thesis uses ML channel estimation to estimate channel value and do interpolation in time domain to modify the channel situation. Finally ,we Use linear minimum mean square error equalizer to resist ICI effect. Besides , the channel is impossible to be known in real environment,so using power detection to distinguish the longest channel impulse length and noise location is the other major issue.
Chang, Ya-Fen, and 張雅芬. "Cellular IP-based mobility management in very high speed railway environment." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/70097750689455964140.
Повний текст джерела國立暨南國際大學
電機工程學系
94
In this thesis, we analyzed the signaling cost for Cellular IP operating in either non-grouping or grouping case. We have both considered the Routing Update procedure for Active users and Location Update procedure for Idle users. We can easily know that grouping management for users in high speed train would be beneficial in Cellular IP network. It is because all passengers have the same mobility behavior and when grouping them together a lot of signaling could be saved. Moreover, we also consider the cost associated with group management, which includes the signaling sent for user to join and leave the group. We have provided a general mathematical model and method for the evaluation process.
Chen, Shu-Yu, and 陳書妤. "Inter-Carrier Interference Cancellation for DVB-T in High-Mobility Environment." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/54419272123123653256.
Повний текст джерела國立中央大學
通訊工程研究所
97
OFDM is a nucleus system of DVB-T. This system successfully eliminated the ISI effect and multi-path interference by using multi-carriers and inserting cyclic-prefix. In high-mobility environment, DVB-T signals pass the time-varying channel, and a loss of sub-carrier orthogonality due to Doppler spread of received signals leads to inter-carrier interference (ICI).This ICI effect degrades the maximum allowed velocity of reception. For eliminating this ICI effect due to high-mobility reception, this thesis modifies other’s methods and introduces a method about channel estimation and equalization, which is suitable high-mobility reception. This thesis refers to the DVB-T standard, and further makes it suitability for high mobility environment. By using ICI cancellation, and comparing three different scheme (Traditional, iterative ICI cancellation, and Taylor series-like) for channel and ICI estimation. In addition, we aim at low SIR ratio part which is influenced by ICI to add ML detection, which can improve the performance and reduce bit error rate.
Chih-Hua, Hsu, and 徐志華. "A Study of Adaptive Modulation with OFDM In High Mobility Environment." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/83772941712345144430.
Повний текст джерела國立臺灣大學
電信工程學研究所
95
The fundamental technology of adaptive modulation is to advance data throughput。The principle is receiver adjusts modulation level for next transmission depend on channel condition,i.e. when the channel condition is appropriate,it use high modulation level; when the channel is unfavorable,it use low modulation level,For example QPSK or BPSK。 OFDM (Orthogonal Frequency Division Multiplexing) can improve data throughput in the limited bandwidth。It transmits orthogonal sub-carriers in the limited bandwidth。OFDM can resist multi-path,ISI etc.. If we combine adaptive modulation and OFDM technology,we can get higher data throughput than single technology. Traditional adaptive modulation with OFDM have single transmission direction only and many assumptive conditions。For example,there is a perfect channel between transmitter and receiver。Another is modulation level in the modulated frame mustn''t affect by channel,i.e. the receiver can demodulate the level of modulation accurately. However these assumptive conditions were not true in the real world。 We propose a new algorithm for adaptive modulation with OFDM。We calculate pilot''s BER to adjust modulation level for next transmission,and decide which modulation level we use to demodulate it。 Other topic is to separate many blocks in a OFDM symbol。Each block has different modulation level then we can get maximum data throughput。
Roni, Harmoko Habibi, and 林忠良. "Low Complexity Detection Algorithms for OFDM System under High Mobility Environment." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/35743906264403919203.
Повний текст джерела國立暨南國際大學
通訊工程研究所
97
In orthogonal frequency division multiplexing (OFDM) system, the intercarrier interference (ICI) causes significant performance degradation. A well-known interference cancellation technique called successive interference cancellation (SIC) has been proved to have an excellent performance for mitigating the ICI in OFDM system. However, since the complexity of SIC is proportional to the number of OFDM subcarrier N, the realization of this detector becomes impractical, especially when large number of subcarrier is considered. In this thesis, a modified successive interference cancellation (SIC) algorithm which is referred to as qSIC is proposed for high mobility OFDM system. The proposed low complexity qSIC algorithm only requires the computational complexity of order O(N(q+1)2.376), where N is the number of subcarrier and q is the number of neighborhood subcarrier. The qSIC algorithm not only significantly reduces the computational complexity of SIC algorithm, but its performance also approaches the performance of conventional SIC algorithm. Furthermore, the lattice reduction aided zero forcing (LR-ZF) and lattice reduction aided minimum mean square error (LR-MMSE) algorithm that were purposed for MIMO system are also studied. Using computer simulations, we also verify that lattice reduction algorithm not only significantly increases the performance of the conventional ZF and MMSE equalizer but its performance also approaches the performance of the optimal maximum likelihood (ML) detector. For this reason, we adopt the LR-ZF to the OFDM system and in order to decrease the computational complexity of LR-ZF, we also present the modified LR-ZF that excludes the swap operation of LLL algorithm.
Shih, Pao-chen, and 施寶鎮. "Channel Estimation and Equalization for DVB-T in High-mobility Environment." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/62842899722177665736.
Повний текст джерела國立中央大學
通訊工程研究所
95
DVB-T is an OFDM system, which exhibits outstanding characteristics in terms of simplicity in combating multi-path transmission and efficiency in spectral utilization. The ISI effect results from the multi-path interference could be successfully eliminated by the insertion of cyclic-prefix and the use of multi-carriers. In high-mobility environment, DVB-T signals pass the time-varying channel, and a loss of sub-carrier orthogonality due to Doppler spread of received signals leads to inter-carrier interference (ICI).This ICI effect degrades the maximum allowed velocity of reception. For eliminating this ICI effect due to high-mobility reception, this thesis modifies other’s methods and introduces a method about channel estimation and equalization, which is suitable high-mobility reception. Some ICI estimation schemes, which using first order linear model to approximate the channel variations, have been developed. This thesis compares three different schemes of ICI estimation, which two is first order model and the other is second order model, and iteratively repeats ICI cancellation to improve the maximum allowed velocity of reception. This modified method improves the normalized Doppler frequency from 8.6% to 13% for DVB-T signals in 8K mode、16QAM、code-rate=1/2.
Hsu, Hua-Lin, and 徐華璘. "Channel Estimation and Equalization for multiple antennas OFDM System in High-mobility Environment." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/40862646414350085067.
Повний текст джерела國立中央大學
通訊工程研究所
96
DVB-T is an OFDM system, which exhibits outstanding characteristics in terms of simplicity in combating multi-path transmission and efficiency in spectral utilization. The ISI effect results from the multi-path interference could be successfully eliminated by the insertion of cyclic-prefix and the use of multi-carriers. In high-mobility environment, DVB-T signals pass the time-varying channel, and a loss of sub-carrier orthogonality due to Doppler spread of received signals leads to inter-carrier interference (ICI).This ICI effect degrades the maximum allowed velocity of reception. For eliminating this ICI effect due to high-mobility reception, this thesis modifies other’s methods and introduces a method about channel estimation and equalization, which is suitable high-mobility reception. In this thesis, we refer to the DVB-T standard, and further make it suitability for high mobility environment.We use multiple antennas technique and ICI cancellation,compares three different scheme for channel and ICI estimation. This thesis proposed method improve the maximum allowed velocity as high as 250km/h for DVB-T receiver with SISO in 8K mode、16QAM、code-rate=1/2,and multiple antennas DVB-T reception improve the maximum allowed velocity more then 300km/h.Finally, reception use group pilot estimation technique SISO-DVB-T-like can work as 300km/h.
Chuang, Ming-Dao, and 莊明道. "Performance Evaluation on Orthogonal Frequency Division Multiplexing System in Very High Mobility Environment." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/87156629519673657864.
Повний текст джерела國立臺灣大學
電信工程學研究所
95
In very high mobility environments, it is easy for the receiver to have large Doppler effects. The influence on the system caused by fast fading is very large. The traditional non-time-varying channels may increase bit error rate. According to fast fading channels, we use decoding methods aim at time-varying channels at receiver ( ML channel estimation or MMSE channel estimation + time-domain interpolation refinement + LMMSE equalizer ) to do performance evaluation. Pilot symbols at transmitter use comb type and block type to transmit. We compute overall pilot symbol ratios at least to transmit for tolerable bit error rate, and compare to traditional receiver which doesn’t consider time-varying channels. In high-speed trains environment, we can use partial known information, for example, predictability of progress routes of train, every multipath delay spread of channel impulse response known characteristics for the complexity reduction and the performance advance. Besides these, we also discuss channel impulse response longest delay spread grid of ML and MMSE channel estimation which sets inaccuracy to see the influence.
Wang, Yi-Yuan, and 王易垣. "The Improved ICI Self-Cancellation Method in OFDM Systems for High Mobility Environment." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/8753wc.
Повний текст джерела國立臺北科技大學
電機工程系研究所
97
This thesis is to investigate the solutions for inter-carrier interference (ICI) cancellation due to Doppler shifts caused by time-variant highly mobile channel in the OFDM system. In conventional OFDM receiver, the energy of each subcarrier will leak to adjacent subcarriers which destroys the orthogonality between subcarriers in time-variant channel. This will result in the increased bit-error rate (BER) and raised error floor as well. The approaches for ICI cancellation can be categorized into three types including frequency-domain equalizer, time-domain window algorithm, and self-cancellation. The pre-mapping algorithm is an improved ICI self-cancellation method with low complexity without loss of bandwidth efficiency. An ICI self-cancellation method based on pre-mapping algorithm was proposed in this thesis. By using new pre-mapping matrix, the proposed method can improve the system performance without increasing much system complexity. Computer simulation results show that the proposed method is good in system performance, complexity and bandwidth efficiency.
Lin, Chien-Yang, and 林見陽. "A Study on Turbo Equalizer Combined with OFDM System in Very High Mobility Environment." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/00249150746128543502.
Повний текст джерела國立臺灣大學
電信工程學研究所
95
Turbo equalization is a new method which combines channel equalization and channel coding .It is different from traditional equalization. The performance of turbo equalizer (TE) with single carrier system in very high mobility environment is excellent. So we try to use TE combined with multicarrier system ,such as Orthogonal Frequency Division Multiplexing (OFDM), in very high mobility environment. OFDM system would suffer gravely from Intercarrier Interference effect (ICI) in very high mobility environment, so we hope that TE could help OFDM system lower its Bit Error Rate (BER). At first, we simulate TE combined with OFDM system with small FFT (Fast Fourier Transform) size in very high mobility environment to make sure about its feasibility. Then we substitute the low FFT size for higher FFT size. Secondly, we use the high speed rail’s characterization of the fixed path to demonstrate two kinds of channel information for channel estimation. In the end, we change the ratio of data symbols and training segments in frame format in order to improve our system useful data rate.
Wu, Yi-Lin, and 吳宜霖. "A Study on Slot Synchronization of W-CDMA System in Very High Mobility Environment." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/13034695058344783658.
Повний текст джерелаYuan, Wen-Hao, and 袁文浩. "A Study on Channel Estimation Algorithms for WCDMA System in Very High Mobility Environment." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/01774728996074187961.
Повний текст джерелаLee, Yi-Hua, and 李怡樺. "Improvement of Inter-Carrier Interference Mitigation Technology for OFDM System in High-mobility Environment." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/95221031095694753288.
Повний текст джерела國立中央大學
通訊工程研究所
98
The core of DVB-T is OFDM system. By using multi-carriers and inserting cyclic prefix, this technology successfully eliminated the ISI effect and multi-path interference. In high-mobility environment, when DVB-T signals pass through the time-varying channel, the receive signals will have Doppler spread that can loss of sub-carrier orthogonality and cause the ICI. This ICI effect degrades the maximum allowed velocity of reception. To overcome the ICI which caused by the high-mobility, this thesis modifies other’s methods and introduces a method about the channel estimation and elimination of ICI which is suitable for high mobility reception. This thesis refers to the DVB-T standard, and further modifies it to suit in high-mobility environment. In high-mobility environment, the performance of wireless OFDM communication systems is degraded and limited by inter-carrier-interference (ICI) phenomenon. In this paper we proposed an algorithm based on maximum-likelihood criterion with improved performance in mitigation of ICI.
Huang, Xiang-yuan, and 黃祥原. "Practical Channel Tracking and Signal Recovery for the OFDM System Under High-Mobility Environment." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/16209554312044403159.
Повний текст джерела國立中正大學
通訊工程研究所
96
WAVE (IEEE802.11p) standard is proposed to use in high-mobility environment and used OFDM as the modulation scheme. Because of the high-mobility, the received signal is interfered by the multipath and Doppler. The time-variant fading channel model is considered. In this paper, a channel tracking and recovery technique is proposed for high-mobility environment. With an initial channel estimation based on preamble by Least Square (LS) algorithm, the channel frequency response is tracked by adaptive filters. We can find some conclusions after analyzing simulations. The first, Recursive Least Square (RLS) algorithm, robust Recursive Least Square (rRLS) algorithm, and Adaptive forgetting factor Recursive Least Square (AFRLS) algorithm can efficiently slow down the phenomenon of error floor than Least Mean Square(LMS) algorithm, Normalized Least Mean Square(NLMS) algorithm, and Adaptive step size Least Mean Square(ASLMS) algorithm. The second, rRLS, RLS, and AFRLS have better performance when under the environment of accelerating the speed of vehicle or increasing the packet length. The third, After a comparison of robust Recursive Least Square (rRLS) algorithm, Recursive Least Square (RLS) algorithm, and Adaptive forgetting factor Recursive Least Square (AFRLS) algorithm can find that rRLS have better performance than RLS and rRLS have lower computation complexity than AFRLS. Finally, we can find the best value of forgetting factor of RLS by [5] under the time-variant fading channel model.
Liao, Keng-te, and 廖耕德. "Improvment of Channel Estimation and Equalization for MISO OFDM System in High Mobility Environment." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/23018288731098586695.
Повний текст джерела國立中央大學
通訊工程研究所
99
OFDM systems exhibit advantageous characteristics in combating multi-path transmission and spectral efficiency, which use cyclic-prefix to overcome the inter-symbol interference (ISI) effect caused in multi-path transmission and multi-carriers with orthogonality to achieve high spectral efficiency. In high mobility environment, when the orthogonal multi-carrier signal passes through time-varying channel, inter-carrier interference (ICI) is resulted due to the loss of orthogonality of subcarriers. The degradation of the system performance due ICI is proportional to the Doppler spread, and thus a limitation in the velocity of the mobile receiver is inferred in OFDM systems. In this thesis we study on using transmitter diversity to improve the performance of OFDM systems in high mobility environment. We propose a modification of the transmitter diversity technique in DVB-T2 standard, which is designed originally for fixed reception, to make it more suitable for high mobility reception. vi
Cheng, Chia-Chen, and 鄭佳臻. "Channel Tracking and Signal Recovery of the MIMO-OFDM System Under High-Mobility Environment." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/39190176809544785575.
Повний текст джерела國立中正大學
通訊工程學系
98
The multiple antennas and OFDM technologies are being considered as a possible solution to provide high data rate for the high-throughput wireless local area network (WLAN). Channel model is time-variant fading channel due to the multipath and doppler effects in high-mobility wireless environment. Based on the spatial channel model, several channel tracking and signal recovery techniques are compared in this thesis. Initially, least squared (LS) criterion is exploited to the received long training sequences in the preamble of IEEE 802.11n frame. Several adaptive channel tracking algorithms follow to track the variation of the channel/weight frequency responses. Our simulation results show that using recursive least square algorithm to track the variation of the channel frequency responses is yield better performance than to track the variation of the weight frequency responses. The ordered successive interference cancellation algorithm can be utilized to improve performance at the cost of higher computational complexity.
Chen, Hsuan-Yu, and 陳鏇羽. "Study of self-optimization power control algorithms for MIMO downlink transceiver in high mobility environment." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/kqdzx2.
Повний текст джерела元智大學
通訊工程學系
104
The study of self-optimizing power control (SOPC) algorithm for high mobility MIMO-OFDM transceiver is the main purpose of the research report. The objective of SOPC is to make the downlink MIMO-OFDM transceiver to minimize transmit power and optimize average throughput under different channel quality indicator (CQI), user speed and antenna mode autonomously. The major research items of the project include the design of SOPC mechanism for downlink MIMO-OFDM transceiver; generation of the training data for adaptive network fuzzy inference system (ANFIS) controller through the simulations of blocking error rate (BLER) of downlink MIMO-OFDM transceiver over high mobility extended vehicular channel A (EVA) channel; the performance of the high mobility MIMO-OFDM transceiver using SOPC is compared with the traditional CQI-based method. Simulation results show the proposed algorithm can provide the better average throughput under high mobility environments.
Ting, Hao-Hsuan, and 丁浩軒. "A Study of Turbo Equalization on WCDMA and OFDM Systems in Very High Mobility Environment." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/48393607614248676573.
Повний текст джерелаChen, Po-Hong, and 陳伯紘. "A Study on Timing Synchronization in Frame for OFDM Systems in Very-High Mobility Environment." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/61035439709680966891.
Повний текст джерелаWu, Wei-Li, and 吳偉立. "Feasible Study of Using STC Algorithms in MIMO Wireless Communications in Very High Mobility Environment." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/39736558623570595518.
Повний текст джерелаLopes, Inês Mariana Lemos. "Software-defined connectivity in a mobile environment." Master's thesis, 2020. http://hdl.handle.net/10773/29545.
Повний текст джерелаO acesso à Internet de banda larga em comboios tornou-se num serviço esperado por parte dos passageiros e o aumento na exigência de qualidade tem constituído um desafio para os prestadores de serviços. Existem soluções de acesso à Internet em comboios que carecem da flexibilidade e redundância necessárias para uma melhor qualidade de serviço na rede. Assim, esta dissertação estuda duas novas soluções de balanceamento de carga, uma distribuída e outra centralizada. Numa rede de comboio emulada, routers de cada carruagem comunicam as suas estatísticas de rede para outros nós da rede, para posteriormente serem tomadas decisões de balanceamento de carga. Na solução distribuída, cada router tem capacidade de tomar decisões de balanceamento de carga, enquanto que na solução centralizada, um controlador dentro do comboio toma essas decisões. Esta última solução baseiase num balanceamento de carga em ambiente SDN. Neste sistema, uma entidade remota agrega o tráfego dos passageiros e encaminha-o para uma rede externa, ou para a Internet. Os sistemas devem proporcionar uma qualidade de experiência melhorada aos passageiros do comboio e a largura de banda total disponível deve ser distribuída mais uniformememente por todas as carruagens. Requisitos foram estabelecidos para os sistemas, que foram desenvolvidos após uma análise aprofundada das soluções de acesso à Internet em comboios encontradas na literatura. Após a obtenção dos resultados dos testes de desempenho, concluiu-se que as duas soluções melhoram o QoE dos passageiros, desde que as condições da rede sejam aproximadamente constantes durante um certo período.
Mestrado em Engenharia de Computadores e Telemática
Huang, Wen-Yu, and 黃文昱. "Design and FPGA Implementation of An Improved Inter-Carrier Interference Mitigation Scheme for OFDM Systems in High-Mobility Environment." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/54186969516007197659.
Повний текст джерела國立中央大學
通訊工程研究所
98
In high-mobility environment, the performance of wireless OFDM communication systems is limited by inter-carrier-interference (ICI) phenomenon and ICI effect is more serious with higher velocity of receiver. To overcome ICI which is caused by the high mobility, in this thesis we present an improved ICI mitigation scheme based on maximum-likelihood criterion. We take DVB-T system for example and finally implement the algorithm we propose with FPGA.