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known pilot bits for interference mitigation channel estimation and coherent

BÁO CÁO HÓA HỌC   RESEARCH ARTICLE A NOVEL QUANTIZE AND FORWARD COOPERATIVE SYSTEM  CHANNEL ESTIMATION AND M PSK DETECTION PERFORMANCE  POTX

BÁO CÁO HÓA HỌC RESEARCH ARTICLE A NOVEL QUANTIZE AND FORWARD COOPERATIVE SYSTEM CHANNEL ESTIMATION AND M PSK DETECTION PERFORMANCE POTX

Copyright ' 2010 Iancu Avram et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproductio n in any medium, provided the original work is properly cited. A method to improve the reliability of data transmission between two terminals without using multiple antennas is cooperative communication, where spatial diversity is introduced by the presence of a relay terminal. The Quantize and Forward (QF) protocol is suitable to implement in resource constraint relays, because of its low complexity. In prior studies of the QF protocol, all channel parameters are assumed to be perfectly known at the destination , while in reality these need to be estimated. This paper proposes a novel quantization scheme, in which the relay compensates for the rotation caused by the source-relay channel, before quantizing the phase of the received M-PSK data symbols. In doing so, channel estimation at the destination is greatly simplied, without signicantly increasing the complexity of the relay terminals. Further, the destination applies the expectation maximization (EM) algorithm to improve the estimates of the source-destination and r elay-destination channels. The resulting performance is shown to be close to that of a system with known channel parameters.
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ĐIỆN THOẠI DI ĐỘNG VÔ TUYẾN ĐIỆN   TUYÊN TRUYỀN CHANNEL P1 POT

ĐIỆN THOẠI DI ĐỘNG VÔ TUYẾN ĐIỆN TUYÊN TRUYỀN CHANNEL P1 POT

Nowadays the term `mobile radio' is deemed to embrace almost any situation where the transmitter or receiver is capable of being moved, whether it actually moves or not. It therefore encompasses satellite mobile, aeromobile and maritime mobile, as well as cordless telephones, radio paging, traditional private mobile radio (PMR) and cellular systems. Any book which attempted to cover all these areas would have to be very bulky and the present volume will therefore be concerned principally with the latter categories of use, which are covered by the generic term `land mobile radio'. This, however, is not a book that deals with the systems and techniques that are used in land mobile communications; it is restricted primarily to a discussion of the radio channel ± the transmission medium ± a vital and central feature which places fundamental limitations on the performance of radio systems. The majority of the book is concerned with the way in which the radio channel a€ects the signal that propagates through it, but there are other chapters treating related topics. These have been included to make the book more comprehensive without straying too far from the main theme.
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BÁO CÁO HÓA HỌC:

BÁO CÁO HÓA HỌC: " RESEARCH ARTICLE A TOA-AOA-BASED NLOS ERROR MITIGATION METHOD FOR LOCATION ESTIMATIO" DOCX

This paper proposes a geometric method to locate a mobile station (MS) in a mobile cellular network when both the range and angle measurements are corrupted by non-line-of-sight (NLOS) errors. The MS location is restricted to an enclosed region by geometric constraints from the temporal-spatial characteristics of the radio propagation channel. A closed-form equation of the MS position, time of arrival (TOA), angle of arrival (AOA), and angle spread is provided. The solution space of the equation is very large because the angle spreads are random variables in nature. A constrained objective function is constructed to further limit the MS position. A Lagrange multiplier-based solution and a numerical solution are proposed to resolve the MS position. The estimation quality of the estimator in term of “biased” or “unbiased” is discussed. The scale factors, which may be used to evaluate NLOS propagation level, can be estimated by the proposed method. AOA seen at base stations may be corrected to some degree. The performance comparisons among the proposed method and other hybrid location methods are investigated on different NLOS error models and with two scenarios of cell layout. It is found that the proposed method can deal with NLOS error effectively, and it is attractive for location estimation in cellular networks.
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Chapter 16 – threats to marsh resources and mitigation

Chapter 16 – threats to marsh resources and mitigation

Chapter 16 – threats to marsh resources and mitigation Chapter 16 – threats to marsh resources and mitigation Chapter 16 – threats to marsh resources and mitigation Chapter 16 – threats to marsh resources and mitigation Chapter 16 – threats to marsh resources and mitigation Chapter 16 – threats to marsh resources and mitigation Chapter 16 – threats to marsh resources and mitigation
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BASIC THEORETICAL PHYSICS: A CONCISE OVERVIEW P29 PPTX

BASIC THEORETICAL PHYSICS: A CONCISE OVERVIEW P29 PPTX

The totality of these statements is the so-called Copenhagen interpretation of quantum mechanics. After the objections of Einstein, Podolski and Rosen in their paper of 1935 were disproved by Bell experiments, it has now been accepted without controversy for several decades. The Copenhagen interpre- tation is also in agreement with non-local behavior, e.g., Aharonov-Bohm experiments. According to these experiments, the ψ -function, in contrast to the classical particle, does not “see” the local magnetic field and the Lorentz forces exerted by it, cf. Part II (so-called “local action”), but instead it “sees”, through the vector potential, its non-local flux (“remote action”). Other con- sequences of the interpretation based, e.g., on entanglement , coherence and
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Chapter 6 – storm surge warning, mitigation and adaptation

Chapter 6 – storm surge warning, mitigation and adaptation

Chapter 6 – storm surge warning, mitigation, and adaptation Chapter 6 – storm surge warning, mitigation, and adaptation Chapter 6 – storm surge warning, mitigation, and adaptation Chapter 6 – storm surge warning, mitigation, and adaptation Chapter 6 – storm surge warning, mitigation, and adaptation Chapter 6 – storm surge warning, mitigation, and adaptation
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Chapter 2 – tsunami dynamics, forecasting, and mitigation

Chapter 2 – tsunami dynamics, forecasting, and mitigation

Chapter 2 – tsunami dynamics, forecasting, and mitigation Chapter 2 – tsunami dynamics, forecasting, and mitigation Chapter 2 – tsunami dynamics, forecasting, and mitigation Chapter 2 – tsunami dynamics, forecasting, and mitigation Chapter 2 – tsunami dynamics, forecasting, and mitigation Chapter 2 – tsunami dynamics, forecasting, and mitigation Chapter 2 – tsunami dynamics, forecasting, and mitigation
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BÁO CÁO HÓA HỌC:

BÁO CÁO HÓA HỌC: " RESEARCH ARTICLE DISTRIBUTED ITERATIVE MULTIUSER DETECTION THROUGH BASE STATION COOPERATION" POT

4.3. DID with unconstrained backhaul In this version of decentralized detection, all estimates of the received data streams are detected at each BS, and all available soft LLR values are exchanged. This approach uses multiple exchanges of extrinsic information between the BSs and is similar to message passing (although we may use an ML detector during the first information pass). Since all detected input streams are exchanged, both diversity and array gain are obtained. In addition, the algorithm converges more quickly than the ones with constrained backhaul. While the simultaneous detection of multiple data streams through SAIC during initial iteration can further speed up convergence, low-complexity SUD detection during the first iteration is normally su ffi cient and results in only marginal degradation in performance. The amount of backhaul per iteration for a fully coupled system ( m l = M ), however, grows cubically in the cooperating setup size, that is, backhaul ∝ MN ( M − 1), making this scheme impractical even for a few BSs in cooperation.
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BÁO CÁO SINH HỌC    RESEARCH ARTICLE TIME FREQUENCY BASED CHANNEL ESTIMATION FOR HIGH MOBILITY OFDM SYSTEMS—PART II  COOPERATIVE RELAYING CASE  PPTX

BÁO CÁO SINH HỌC RESEARCH ARTICLE TIME FREQUENCY BASED CHANNEL ESTIMATION FOR HIGH MOBILITY OFDM SYSTEMS—PART II COOPERATIVE RELAYING CASE PPTX

Academic Editor: Lutfiye Durak Copyright © 2010 Erol ¨ Onen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We consider the estimation of time-varying channels for Cooperative Orthogonal Frequency Division Multiplexing (CO-OFDM) systems. In the next generation mobile wireless communication systems, significant Doppler frequency shifts are expected the channel frequency response to vary in time. A time-invariant channel is assumed during the transmission of a symbol in the previous studies on CO-OFDM systems, which is not valid in high mobility cases. Estimation of channel parameters is required at the receiver to improve the performance of the system. We estimate the model parameters of the channel from a time-frequency representation of the received signal. We present two approaches for the CO-OFDM channel estimation problem where in the first approach, individual channels are estimated at the relay and destination whereas in the second one, the cascaded source-relay- destination channel is estimated at the destination. Simulation results show that the individual channel estimation approach has better performance in terms of MSE and BER; however it has higher computational cost compared to the cascaded approach.
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experimental approach cdma & interference(from architecture through vlsi)

experimental approach cdma & interference(from architecture through vlsi)

emulating ASICs in a realistic system environment. Indeed, wireless systems often have very stringent Bit Error Rate (BER) requirements. For example, the typical BER requirement for a 2G system is approximately 10 -2 (voice communications), whereas it may be as low as 10 -6 (multimedia) for a 3G system. In general, the lower the BER requirements, the longer must be the bitstream to be simulated to achieve statistically valid results 4 . As a rule of the thumb we can assume that, in the case of randomly distributed errors, a reliable estimate of the BER with the error counting technique can be ob- tained by observing about 100 error events. It follows that in order to relia- bly measure a BER of 10 -2 , about 10 4 symbols must be simulated, while a BER of 10 -6 requires about 10 8 symbols. This can be unfeasible especially for verification at the lowest level of abstraction. Many rapid prototyping environment are available on the market for system emulation (such as Cadence [Smi97], Aptix [aptix], FlexBench [Pav02], Nallatech [nalla] and Celoxica [celox]). Alternatively, a prototyping environment can be devel- oped in house, exploiting FPGA technology, possibly with downgrading of speed performance with respect to an ASIC solution, but still validating the logic functioning and hardware/software interfaces. Basing the FPGA proto- type development exclusively on ASIC design rules, makes FPGA to ASIC technology conversion unnecessary, and lets the design version verified in the prototype ready for ASIC SoC implementation.
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EURASIP JOURNAL ON APPLIED SIGNAL PROCESSING 2003:13, 1268–1278 C 2003 HINDAWI PUBLISHING PPT

EURASIP JOURNAL ON APPLIED SIGNAL PROCESSING 2003:13, 1268–1278 C 2003 HINDAWI PUBLISHING PPT

Many techniques were presented to cope with closely spaced multipath propagations, such as subspace-based methods [ 8 ] or least square (LS) approaches [ 9 , 10 ]. These techniques can provide rather accurate estimation of the multipath delays, but they su ff er from the high complex- ity for the implementation in WCDMA systems in tracking mode. Few authors have studied the problem of joint param- eters estimation using Kalman filtering in multipath fading and multiuser environment. In [ 11 ], Iltis has developed a new technique for jointly estimating the channel coe ffi cients and the first-path delay in frequency selective channel based on Kalman filtering in a single user system. Recently, the idea has been extended to multiuser scenario [ 12 ]. In order to solve the closely spaced multipaths, we propose here an EKF-based solution with IC scheme. EKF algorithm jointly estimates the delays and complex coe ffi cients of all the paths from all the participating BSs and it is combined with a new IC scheme to enhance the estimation of the channel from the desired BS (serving BS). The obtained estimates are used to detect whether the LOS component is present or not. The detection procedure exploits the distribution of the first ar- riving path. If the distribution is Rician with strong Rician factor, then LOS component is likely to be present. If the dis- tribution is Rayleigh, it is more likely that LOS component is absent. We point out that the proposed algorithm is not limited to a WCDMA system and it can be easily extended to other mobile positioning systems.
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TÀI LIỆU NHIỀU GIAO THỨC TRUY CẬP ĐỐI VỚI TRUYỀN THÔNG DI ĐỘNG P10 DOC

TÀI LIỆU NHIỀU GIAO THỨC TRUY CẬP ĐỐI VỚI TRUYỀN THÔNG DI ĐỘNG P10 DOC

10.4.5.1 Uplink Shared Channel Operation USCH operation resembles very much the GPRS fixed allocation scheme. The selection of the mobile terminal allowed to transmit on the USCH for a certain period of time is performed by higher layer signalling. There are currently no means similar to the uplink state flag in GPRS which would allow terminal selection to be performed on a frame-by-frame basis (or rather, on a TTI basis). Terminals request USCH capacity by sending capacity request messages on the SHCCH, which is either mapped onto currently allocated USCH resources, thus corresponding to ‘reservation mode’ according to terminology used in earlier chapters, or onto the RACH, in which case these requests would be sent in ‘contention mode’. If a capacity request is sent on the RACH, a 16- bit C-RNTI is included in the message, which is a unique MS entity in the relevant cell, so that contention resolution issues known from GPRS are avoided. In terms of the R-ALOHA protocol classification made in Chapter 3, sending capacity requests on the USCH would correspond to some kind of piggybacking scheme for capacity requests. If the network wants to allocate capacity on a suitable USCH, it sends a physical shared channel allocation message on the SHCCH, which is either mapped onto a DSCH, if one is already assigned to the requesting user, or on the FACH. This message specifies the physical resources to be used and the period of time (also referred to as allocation period ) during which the terminal can use the USCH for data transfer. The allocation period can be selected from 1 to 256 radio frames.
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Báo cáo hóa học:

Báo cáo hóa học: " Asymmetric Joint Source-Channel Coding for Correlated Sources with Blind HMM Estimation at the Receiver" doc

When one of the channels is noisy, the authors in [ 11 ] (for a binary symmetric channel, BSC) and in [ 12 ] (for a BSC, AWGN and Rayleigh channel) have proposed a joint source-channel coding scheme based on turbo and irregular repeat accumulate (IRA) codes, respectively. In both cases, the correlation among the sources is again as- sumed to be memoryless and known at the receiver. Un- der the same correlation assumptions, the case of symmetric joint source-channel coding when both channels are noisy (AWGN) has been studied using turbo [ 13 ] and low-density generator-matrix (LDGM) [ 14 ] codes. Both assume that the memoryless correlation probability is known at the decoder. In this paper, we take a further step and consider that the correlation between the sources follows a hidden Markov model like the correlation proposed in [ 9 ] for distributed source compression. However, unlike what is assumed in [ 9 ], our proposed scheme does not require any previous knowledge of the HMM parameters. It is based on an itera- tive scheme that jointly estimates, within the turbo-decoding process, the parameters of the HMM correlation model. It is an extension of the estimation method presented by Garcia- Frias and Villasenor [ 15 ] (for point-to-point data transmis- sion over an AWGN of a single HMM source) to the men- tioned distributed joint source-channel coding scenario. As we show in the simulation results, the loss in BER perfor- mance that results from the blind estimation of the HMM parameters when compared to their perfect knowledge is negligible.
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BÁO CÁO SINH HỌC    EDITORIAL FILTER BANKS FOR NEXT GENERATION MULTICARRIER WIRELESS COMMUNICATIONS  POTX

BÁO CÁO SINH HỌC EDITORIAL FILTER BANKS FOR NEXT GENERATION MULTICARRIER WIRELESS COMMUNICATIONS POTX

On the other hand, digital filter banks find various good applications in communications signal processing. In general, they can be used to obtain very sharp frequency selectivity to isolate di ff erent communications frequency channels from each other and from interfering spectral components. This can be done in a very flexible and dynamic manner. Thus filter banks constitute a very powerful generic tool for software-defined radios and spectrally agile communication systems.
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Báo cáo toán học:

Báo cáo toán học: " A practical two-stage MMSE based MIMO detector for interference mitigation with noncooperative interferers" docx

Anish Shah * and Babak Daneshrad Abstract Wireless Multiple Input Multiple Output systems provide system designers with additional degrees of freedom. These can be used to increase throughput, reliability, or even combat spatial interference. The classical Minimum Mean Squared Error (MMSE) solution is the optimal linear estimator for these systems. Its primary drawback is that it requires an estimate of the channel response. This is generally not an issue when interference is absent. However, in environments where interference power is stronger than the desired signal power, this can become difficult to estimate. The problem is even worse in packet-based systems, which rely on training data to estimate the channel before estimating the signal. A strong interference will hinder the receiver ’ s ability to detect the presence of the packet. This makes it impossible to estimate the channel, a critical component for the classical MMSE estimator. For this reason, the classical solution is infeasible in real environments with stronger interferences. We propose a two-stage system that uses practically obtainable channel state information. We will show how this approach significantly improves packet detection, and how the overall solution approaches the performance of the classical MMSE estimator.
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HANDBOOK OF ECONOMETRICS VOLS1 5   CHAPTER 28 PPSX

HANDBOOK OF ECONOMETRICS VOLS1 5 CHAPTER 28 PPSX

During recent years there have been many applications involving multiple criteria of selectivity. Abowd and Farber (1982) consider a model with two decisions: the decision of individuals to join a queue for union jobs and the decision of employers to draw from the queue. Poirier (1980) discusses a model where the two decisions are those of the employee to continue with the sponsoring agency after training and the decisions of the employer to make a job offer after training. Fishe et al. (1981) consider a two-decision model: whether to go to college or not and whether to join the labor force or not. Ham (1982) examines the labor supply problem by classifying individuals into four categories according to their unemployment and under-employment status. Catsiapis and Robinson (1982) study the demand for higher education and the receipt of student aid grants. Tunali (1983) studies migration decisions involving single and multiple moves. Danzon and Lillard (1982) analyze a sequential process of settlement of malpractice suits. Venti and Wise (1982) estimate a model combining student preferences for colleges and the decision of the university to admit the student. All these problems can be classified into different categories depending on whether the decision rules are joint or sequential. This distinction, however, is not made clear in the literature and the studies all use the multivariate normal distribution to specify the joint probabilities.
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BÁO CÁO HÓA HỌC    ADAPTIVE LOW RANK CHANNEL ESTIMATION FOR MULTIBAND OFDM ULTRA WIDEBAND COMMUNICATIONS  DOCX

BÁO CÁO HÓA HỌC ADAPTIVE LOW RANK CHANNEL ESTIMATION FOR MULTIBAND OFDM ULTRA WIDEBAND COMMUNICATIONS DOCX

2. MB-OFDM UWB SYSTEM MODEL In an MB-OFDM UWB system, the spectrum from 3.1 GHz to 10.6 GHz is divided into 14 sub-bands with a bandwidth of 528 MHz each, and the data are trans- mitted across these sub-bands using a specific TFC [3]. The system operates in one sub-band and then switches to another sub-band after a short time. In each sub- band, the OFDM modulation scheme is used to transmit data symbols. The transmitted symbols are time-inter- leaved across the sub-bands to utilize the spectral diver- sity in order to improve the transmission reliability. Additionally, it is important to note that depending on the selected TFC, the MB-OFDM system is equipped with the frequency-hopping (FH) control mechanism. The feature of the FH pattern controlled by the TFCs enables multiple simultaneously operating piconets (SOPs) at the same band group. However, this is of little impact on the channel estimation since it is assumed that each sub-band is estimated independently. The
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BÁO CÁO HÓA HỌC    ADAPTIVE LOW RANK CHANNEL ESTIMATION FOR MULTIBAND OFDM ULTRA WIDEBAND COMMUNICATIONS  PPTX

BÁO CÁO HÓA HỌC ADAPTIVE LOW RANK CHANNEL ESTIMATION FOR MULTIBAND OFDM ULTRA WIDEBAND COMMUNICATIONS PPTX

to obtain international standardization. This promising wireless-connectivity technique increases successfully both the traffic capacity and the frequency diversity. In MB-OFDM UWB wireless systems, by utilizing several types of time-frequency codes (TFCs) in the preamble part, multiple users are allowed to use the same fre- quency-band group simultaneously to provide frequency diversity as well as channelization and multiple-access capability among different piconets. That is the primary reason why the preamble symbols gain a high probabil- ity of being corrupted by multiple-access interference (MAI). To enhance the system performance, pilot- assisted channel estimation schemes are commonly employed for the MB-OFDM UWB systems. In particu- lar, the performance of channel estimation in a pilot- aided MB-OFDM UWB system has been investigated based on the least-squares (LS) algorithm [5], the maxi- mum likelihood estimator (MLE) [6], and the minimum mean-square error (MMSE) estimator [5,7]. The channel estimation with the use of the MLE obviates the neces- sity of the information of either the channel statistics or the operating signal-to-noise ratio (SNR). However, it is already known that the computational costs for these estimators are very expensive and thus lead to a limited usage in practice. This requirement is, in general, prohi- bitive for low-power and cost-effective wireless UWB devices.
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BÁO CÁO HÓA HỌC:

BÁO CÁO HÓA HỌC: " TWO-STAGE MAXIMUM LIKELIHOOD ESTIMATION (TSMLE) FOR MT-CDMA SIGNALS IN THE INDOOR ENVIRONMENT" DOC

Keywords and phrases: code division multiple access, indoor fading channel, OFDM, maximum likelihood estimation. 1. INTRODUCTION High-data-rate multimedia communications is one of the challenges currently being addressed in the research do- main for the upcoming next generation wireless sys- tems [ 1 , 2 ]. Although the third generation (3G) systems ( www.3gtoday.com ) are supporting a maximum data rate of 153 kbps (CDMA2000) and 384 kbps (WCDMA) for voice and data applications, and 2.4 Mbps for data-only (CDMA 2000 1xEV-DO) applications, transmission rate for com- bined voice and data applications for the future generation systems is expected, and needed to be much higher. Conse- quently, researchers are exploring di ff erent schemes for high- data-rate applications. In this regard, multicarrier modula- tion schemes [ 3 ] such as multitone code division multiple ac- cess (MT-CDMA) system [ 4 ] are getting special attention [ 5 ]. MT-CDMA, a combination of orthogonal frequency division multiplexing (OFDM) and direct-sequence spread-spectrum (DS-SS) modulation, provides both high-data-rate transmis- sion and multiple-access capabilities. Several research stud- ies have developed MT-CDMA-based efficient schemes to combat different adverse effects, such as multiple-access in-
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BÁO CÁO HÓA HỌC:

BÁO CÁO HÓA HỌC: " ADAPTIVE MOBILE POSITIONING IN WCDMA NETWORKS" PDF

Department of Electrical Engineering, Columbia University, New York, NY 10027-4712, USA Email: wangx@ee.columbia.edu Received 6 November 2004; Revised 14 March 2005 We propose a new technique for mobile tracking in wideband code-division multiple-access (WCDMA) systems employing multi- ple receive antennas. To achieve a high estimation accuracy, the algorithm utilizes the time difference of arrival (TDOA) measure- ments in the forward link pilot channel, the angle of arrival (AOA) measurements in the reverse-link pilot channel, as well as the received signal strength. The mobility dynamic is modelled by a first-order autoregressive (AR) vector process with an additional discrete state variable as the motion offset, which evolves according to a discrete-time Markov chain. It is assumed that the param- eters in this model are unknown and must be jointly estimated by the tracking algorithm. By viewing a nonlinear dynamic system such as a jump-Markov model, we develop an efficient auxiliary particle filtering algorithm to track both the discrete and contin- uous state variables of this system as well as the associated system parameters. Simulation results are provided to demonstrate the excellent performance of the proposed adaptive mobile positioning algorithm in WCDMA networks.
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BÁO CÁO HÓA HỌC    RESEARCH ARTICLE AN ML BASED ESTIMATE AND THE CRAMER RAO BOUND FOR DATA AIDED CHANNEL ESTIMATION IN KSP OFDM  PDF

BÁO CÁO HÓA HỌC RESEARCH ARTICLE AN ML BASED ESTIMATE AND THE CRAMER RAO BOUND FOR DATA AIDED CHANNEL ESTIMATION IN KSP OFDM PDF

In this paper, we derive an approximative analytical ex- pression for the Gaussian Cramer-Rao bound (GCRB) for channel estimation when the pilot symbols are distributed over the guard interval and pilot carriers. The paper is or- ganized as follows. In Section 2 , we describe the system and determine the GCRB. Further, we derive a low complexity ML-based estimate for the channel in Section 3 . Numerical results are given in Section 4 and the conclusions are drawn in Section 5 .
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BÁO CÁO HÓA HỌC:

BÁO CÁO HÓA HỌC: " RESEARCH ARTICLE AN EVALUATION OF INTERFERENCE MITIGATION SCHEMES FOR HAPS SYSTEMS" PPT

Correspondence should be addressed to Bon-Jun Ku, bjkoo@etri.re.kr Received 28 September 2007; Revised 25 February 2008; Accepted 23 May 2008 Recommended by Abbas Mohammed The International Telecommunication Union-Radiocommunication sector (ITU-R) has conducted frequency sharing studies between fixed services (FSs) using a high altitude platform station (HAPS) and fixed-satellite services (FSSs). In particular, ITU-R has investigated the power limitations related to HAPS user terminals (HUTs) to facilitate frequency sharing with space station receivers. To reduce the level of interference from the HUTs that can harm a geostationary earth orbit (GEO) satellite receiver in a space station, previous studies have taken two approaches: frequency sharing using a separated distance (FSSD) and frequency sharing using power control (FSPC). In this paper, various performance evaluation results of interference mitigation schemes are presented. The results include performance evaluations using a new interference mitigation approach as well as conventional approaches. An adaptive beamforming scheme (ABS) is introduced as a new scheme for efficient frequency sharing, and the interference mitigation effect on the ABS is examined considering pointing mismatch errors. The results confirm that the application of ABS enables frequency sharing between two systems with a smaller power reduction of HUTs in a cocoverage area compared to this reduction when conventional schemes are utilized. In addition, the analysis results provide the proper amount of modification at the transmitting power level of the HUT required for the suitable frequency sharing.
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BÁO CÁO HÓA HỌC:

BÁO CÁO HÓA HỌC: " CHANNEL ESTIMATION AND DATA DETECTION FOR MIMO SYSTEMS UNDER SPATIALLY AND TEMPORALLY COLORED INTERFERENCE" POTX

Received 20 December 2002; Revised 6 November 2003 The impact of interference on multiple-input multiple-output (MIMO) systems has recently attracted interest. Most studies of channel estimation and data detection for MIMO systems consider spatially and temporally white interference at the receiver. In this paper, we address channel estimation, interference correlation estimation, and data detection for MIMO systems under both spatially and temporally colored interference. We examine the case of one dominant interferer in which the data rate of the desired user could be the same as or a multiple of that of the interferer. Assuming known temporal interference correlation as a benchmark, we derive maximum likelihood (ML) estimates of the channel matrix and spatial interference correlation matrix, and apply these estimates to a generalized version of the Bell Labs Layered Space-Time (BLAST) ordered data detection algorithm. We then investigate the performance loss by not exploiting interference correlation. For a (5, 5) MIMO system undergoing indepen- dent Rayleigh fading, we observe that exploiting both spatial and temporal interference correlation in channel estimation and data detection results in potential gains of 1.5 dB and 4 dB for an interferer operating at the same data rate and at half the data rate, respectively. Ignoring temporal correlation, it is found that spatial correlation accounts for about 1 dB of this gain.
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Comparative analysis of LDPC and BCH codes error-correcting capabilities

Comparative analysis of LDPC and BCH codes error-correcting capabilities

The error-correcting capabilities of regular LDPC (Low Density Parity Check) codes and BCH (Bose-ChaudhuriHocquenguem) codes are examined. The qualitative analysis and the quantitative assessment of error-correcting abilities are performed for LDPC codes with code word length n=1000 bits and BCH codes with code word length n=1023 bits. The code rates of LDPC and BCH codes are determined for a known signal to noise ratio in the gaussian channel; detected code rates are optimal for predefined modulation type and required information reliability on the receiver side.
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DẠY CON HỌC THẾ NÀO ĐỂ ĐẠT KẾT QUẢ TỐT NHẤT  PPS

DẠY CON HỌC THẾ NÀO ĐỂ ĐẠT KẾT QUẢ TỐT NHẤT PPS

5. Conclusions In this paper, a novel Quantize and Forward protocol has been introduced, which involves the relay making a coarse estimate of the source-relay channel, using only the received pilot symbols. Doing so, it is shown that quantization with only log 2 bits is su cient to approach the performance of an AF system, while respecting the half-duplex constraint at the relay terminals. Furthermore, one aspect of the relay terminal becomes less complicated, in comparison to [ 6 ], because no overhead is needed in order to allow the destination to make an estimate of the source-relay channel. This makes the proposed QF protocol suitable for the use in sensor networks where a low complexity at the relay terminals is mandatory.
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BÁO CÁO HÓA HỌC:

BÁO CÁO HÓA HỌC: " SERGIO BARBAROSSA DEPARTMENT OF INFORMATION AND COMMUNICATION," PDF

Sergio Barbarossa graduated in 1984 and received his Ph.D. de- gree in 1989 from the University of Rome “La Sapienza,” Italy. From 1984 to 1986, he was a Radar System Engineer at Selenia. In 1988, he was at the Environmental Research Institute of Michi- gan (ERIM), Ann Arbor, USA. From 1989 to 1991, he was with the University of Perugia and in 1991, he joined the University of Rome “La Sapienza,” where he is now a Full Professor. Since 1997, he is a Member of the IEEE Signal Processing for Communications Tech- nical Committee. From 1998 to 2000, he served as an Associate Ed- itor for the IEEE Transactions on Signal Processing. He coauthored a paper that received the 2000 IEEE Best Paper Award in the Sig- nal Processing for Communications area. He has been the General Chairman of the SPAWC 2003 (Rome, 2003). He has held visiting positions at the University of Virginia in 1995 and 1997, Univer- sity of Minnesota in 1999, and Polytechnic University of Catalunya, Spain, in 2002. He is the author of a research monograph on Mul- tiple Antenna Systems (Artech House, 2004). He is the scientific responsible, for his University, of two IST European projects on space-time coding and multihop networks. His current research in- terests lie in the area of self-organizing networks, random graphs, and distributed space-time coding.
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Báo cáo hóa học:

Báo cáo hóa học: " Maximum Likelihood Turbo Iterative Channel Estimation for Space-Time Coded Systems and Its Application to Radio Transmission in Subway Tunnels" potx

modulation scheme. This technique exploits the fact that ISI can be viewed as a form of rate-1, nonrecursive coding. So, whatever coding scheme is used, if an interleaver is located prior to the channel, the overall e ff ect of coding and ISI can be treated as a concatenated code and therefore, itera- tive MAP decoding can be applied. Luschi et al. [6] present an in-depth review of this technique and further improve- ments can be found in [7, 8, 9, 10]. In general, iterative MAP processing can be applied to a variety of situations where the overall system can be viewed as a concatenation of modules whose input/output relationship can be described as a (hid- den) Markov chain. Several works have appeared in the last years exploiting this idea. For instance, G¨ortz [11], Garcia- Frias and Villasenor [12], and Guyader et al. [13] worked on the problem of joint source-channel decoding and Zhang and Burr [14] addressed the problem of symbol timing re- covery.
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BÁO CÁO HÓA HỌC    RESEARCH ARTICLE INTERFERENCE MITIGATION TECHNIQUE FOR COEXISTENCE OF PULSE BASED UWB AND OFDM  DOC

BÁO CÁO HÓA HỌC RESEARCH ARTICLE INTERFERENCE MITIGATION TECHNIQUE FOR COEXISTENCE OF PULSE BASED UWB AND OFDM DOC

Figure 3: BER performance of OFDM interfered with by p-UWB ( E b /N 0 = 20 dB). In Figure 4 , BER performance is evaluated for a multi- path channel. The channel model adopted is CM3 as set out by the IEEE802.15.4a working group [ 18 ]. IEEE802.15.4a is a standard for low-duty cycle PAN systems. Interference prob- lems often occur when the victim transmitter is very close to the UWB transmitter. In most of cases, their positions are in line of sight (LOS). CM3 is designed for o ffi ce LOS environments. It is assumed that OFDM receiver channel estimation and multipath compensation are perfect for the desired signal. The BER performance improves as the pulse repetition interval is set as per the proposal. The e ff ectiveness
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FIBER OPTIC TELECOMMUNICATION PHẦN 3 PPTX

FIBER OPTIC TELECOMMUNICATION PHẦN 3 PPTX

Indoor Cables • Simplex cable —contains a single fiber for one-way communication • Duplex cable —contains two fibers for two-way communication • Multifiber cable —contains more than two fibers. Fibers are usually in pairs for duplex operation. A ten-fiber cable permits five duplex circuits.
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BÁO CÁO HÓA HỌC:

BÁO CÁO HÓA HỌC: " AUTOMATIC IMAGE ENHANCEMENT BY CONTENT DEPENDENT EXPOSURE CORRECTION" DOC

Keywords and phrases: Bayer pattern, skin recognition, features extraction, contrast, focus, exposure correction. 1. INTRODUCTION Reduction of processing time and quality enhancement of ac- quired images is becoming much more significant. The use of sensors with greater resolution combined with advanced solutions [ 1 , 2 , 3 , 4 ] aims to improve the quality of result- ing images. One of the main problems a ff ecting image qual- ity, leading to unpleasant pictures, comes from improper ex- posure to light. Beside the sophisticated features incorpo- rated in today’s cameras (i.e., automatic gain control algo- rithms), failures are not unlikely to occur. Some techniques are completely automatic, cases in point being represented by those based on “average/automatic exposure metering” or the more complex “matrix/intelligent exposure metering.” Others, again, accord the photographer a certain control over the selection of the exposure, thus allowing space for per- sonal taste or enabling him to satisfy particular needs.
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BÁO CÁO HÓA HỌC   STATISTICAL ANALYSIS OF LINEAR SPATIAL HOLES ESTIMATORS IN COGNITIVE RADIO  PPT

BÁO CÁO HÓA HỌC STATISTICAL ANALYSIS OF LINEAR SPATIAL HOLES ESTIMATORS IN COGNITIVE RADIO PPT

In this article, it is assumed that there is no cooperation or known signaling between secondary and primary users. Hence, algorithms which need cooperation between primary and secondary networks cannot be used. For example, because of the need of synchronization between primary and secondary networks, time-based algorithms like time of arrival (TOA) algorithm cannot be used in the CR case. The problem which appears in angle of arrival (AOA) algorithms is that although they have no problem estimating the locations of the primary users, they are unable to estimate their transmission powers. Hence among all of the common location estimation algorithms only the received signal strength (RSS) algorithms can be used for simultaneous estimation of locations and powers of the primary users in a CR network. To estimate the location of the primary user, RSS algorithms measure and process the received power of the primary user’s signal at the secondary users’ receivers.
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BÁO CÁO HÓA HỌC:

BÁO CÁO HÓA HỌC: "RESEARCH ARTICLE A 2-BIT ADAPTIVE DELTA MODULATION SYSTEM WITH IMPROVED PERFORMANCE" PPT

A 2-bit adaptive delta modulation system with improved performance is proposed in this paper. Its main characteristic is a new adaptation algorithm that incorporates both memory and look-ahead instantaneous step-size estimation and leads the modulator into generating a 2-bit output codeword. As shown by computer simulation results, the proposed system offers reduced overshoot and fast response to signal variations in comparison to other similar systems.
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BÁO CÁO HÓA HỌC    RESEARCH ARTICLE ANALYSIS OF CODED FHSS SYSTEMS WITH MULTIPLE ACCESS INTERFERENCE OVER GENERALIZED FADING CHANNELS  PPT

BÁO CÁO HÓA HỌC RESEARCH ARTICLE ANALYSIS OF CODED FHSS SYSTEMS WITH MULTIPLE ACCESS INTERFERENCE OVER GENERALIZED FADING CHANNELS PPT

[ 9 ]. Then, the pairwise error probability (PEP) is derived by conditioning over the number of interfering users in the network and then by averaging over this number. In modelling the MAI, we consider the exact statistics in the case of perfect channel state information (CSI) and Nakagami fading, as well as the Gaussian approximation in the case of imperfect CSI and Rician fading. We investigate that the tradeo ff between channel estimation and diversity in FHSS systems is studied in order to approximate the optimal hopping rate in FHSS systems with MAI, defined as the hope rate at which the performance of the FHSS system is the best compared to its performance using di ff erent hopping rates.
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BÁO CÁO HÓA HỌC:

BÁO CÁO HÓA HỌC: " PARTICLE SWARM OPTIMIZATION FOR PILOT TONES DESIGN IN MIMO-OFDM SYSTEMS" POT

using tracking features of PSO. In [13], continuous and discrete PSO has been used for joint channel and data esti- mation based on maximum likelihood principle. In [14], to decrease the effect of noise, angle domain PSO-LS algo- rithm which exploits most significant taps technique using a suitable threshold for MIMO-OFDM systems has been presented. In [15], genetic algorithm (GA) and PSO-based adaptive channel estimation methodology in space time block coded (STBC) OFDM system are investigated to get optimal solution of MMSE algorithm. In this article, LS channel estimation algorithm for MIMO-OFDM systems based on comb-type pilot tones is described briefly. Then optimization of these pilot tones whose design is very cru- cial for LS channel estimation performance is proposed using PSO. And by optimizing both placement and power of pilot tones, the performance of LS channel estimation algorithm is increased.
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