Conference Record of the Thirty-Ninth Asilomar Conference onSignals, Systems and Computers, 2005.最新文献

{"title":"Multiscale Wireless Communications Using Compactly-Parametrized Wavelets","authors":"G. Mandyam","doi":"10.1109/ACSSC.2005.1599729","DOIUrl":"https://doi.org/10.1109/ACSSC.2005.1599729","url":null,"abstract":"Wireless communications has traditionally involved single-scale modulation, usually involving either time or frequency conditioning of the transmitted signal. In this paper multiscale modulation, wherein time-frequency conditioning of the transmitted signal is used, is considered with respect to typical wireless communications systems. Multipath channels require equalization, which can be complex in the time-frequency domain. In this work, a different approach in which the modulating wavelet is matched to a specific channel condition is proposed. Specifically, compactly supported wavelet bases are employed, and based on their parameterization a wavelet is selected that best characterizes the wireless channel conditions","PeriodicalId":326489,"journal":{"name":"Conference Record of the Thirty-Ninth Asilomar Conference onSignals, Systems and Computers, 2005.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127250971","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Blind Equalization in OFDM Systems Exploiting Guard Interval Redundancy","authors":"F. O. Alayyan, K. Abed-Meraim, A. Zoubir","doi":"10.1109/ACSSC.2005.1599841","DOIUrl":"https://doi.org/10.1109/ACSSC.2005.1599841","url":null,"abstract":"We introduce a new low-complexity equalizer for OFDM systems, which in the presence of a guard interval, utilizes existing redundancy in the time domain to completely eliminate inter-symbol-interference. We prove that the usage of this guard interval redundancy is sufficient to obtain a zero-forcing time domain equalizer of the channel. The main advantage of this approach resides in its simplicity as the equalizer coefficients are estimated using a second-order least square fitting (LSF). In addition, to fully exploit the data information, we propose to use the previous LSF based equalizer in conjunction with a constant modulus algorithm (CMA). This would help to refine the equalizer estimation, especially for short data lengths, and to improve the system performance. Several implementations are proposed and compared through simulation experiments","PeriodicalId":326489,"journal":{"name":"Conference Record of the Thirty-Ninth Asilomar Conference onSignals, Systems and Computers, 2005.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124820152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Multi-user SC-FDE-MIMO System for Frequency-Selective Channels","authors":"Li Guo, Yih-Fang Huang","doi":"10.1109/ACSSC.2005.1600036","DOIUrl":"https://doi.org/10.1109/ACSSC.2005.1600036","url":null,"abstract":"This paper proposes a multi-user multiple input-multiple output (MIMO) system based on a singlecarrier frequency-domain equalization (SC-FDE) technique for frequency-dispersive multipath environments, where the signals are corrupted by both co-channel interference (CCI) and intersymbol interference (ISI). The proposed scheme effectively suppresses both CCI and ISI simultaneously with relatively low complexity. Furthermore, it does not impose any restriction on the number of available antennas. Simulation results show that the proposed scheme offers improved bit error rate and throughput performance and is superior to multi-carrier systems. The proposed scheme will make the multi-user MIMO system for frequency-selective channels more practically feasible.","PeriodicalId":326489,"journal":{"name":"Conference Record of the Thirty-Ninth Asilomar Conference onSignals, Systems and Computers, 2005.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123754711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On Subspace-based Blind Channel Estimation Algorithms for SFBC MC-CDMA systems","authors":"S. N. Nazar, I. Psaromiligkos","doi":"10.1109/ACSSC.2005.1599927","DOIUrl":"https://doi.org/10.1109/ACSSC.2005.1599927","url":null,"abstract":"The issue of blind channel estimation for the downlink of Space-Frequency Block Coded Multi-Carrier Code Division Multiple Access (SFBC MC-CDMA) systems is ad- dressed. Specifically, we consider an intuitive subspace-based channel estimation method and we investigate the corresponding necessary and sufficient conditions under which the channel estimate is unique (within a complex scalar). The derived identifiability conditions are used to highlight two interesting properties of SFBC MC-CDMA systems: (i) there is no antenna order ambiguity even when only one spreading code is assigned to each user, (ii) channel identifiablility is guaranteed, regardless of the channel zeros location. We also establish the unbiasedness of the channel estimates and we derive closed-form expressions for the mean-square-error (MSE) of the estimates as well as the corresponding Cramer-Rao bound (CRB). For the derivation of the CRB, we follow a novel approach which assumes the knowledge of only the spreading code of the desired user and results in a much tighter bound than the CRB derived based on the knowledge of all users' signatures. I. INTRODUCTION Transmit diversity techniques, and particularly Space- Time/Frequency Block Codes (STBC/SFBC) (1), are known to be very effective for combating multipath fading in broad- band wireless communications. These schemes are even more attractive when applied to a robust multiple access technique such as Multi-Carrier Code Division Multiple Access (MC- CDMA). However, the diversity and coding gains that are possible in such systems can only be realized if the underlying channels are accurately acquired at the receiver (4). The issue of blind channel estimation for STBC MC-CDMA systems has been addressed in the past (2), (3); however, to the authors best knowledge, no channel estimation method has been proposed or analyzed for SFBC MC-CDMA. In this work, as a first step in filling that void, we investigate the problem of blind channel estimation for SFBC MC-CDMA systems. We begin by presenting a system model for complex modulation schemes that enables us to treat the links between the multiple transmit antennas and the single receive antenna as a single channel and, thus, reduces the multichannel estima- tion problem to a single-input single-output (SISO) problem. This allows us to develop a simple, intuitive, subspace-based","PeriodicalId":326489,"journal":{"name":"Conference Record of the Thirty-Ninth Asilomar Conference onSignals, Systems and Computers, 2005.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125284755","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Common and Dedicated Pilot-Based Channel Estimates Combining and Kalman Filtering for WCDMA Terminals","authors":"A. Bastug, G. Montalbano, D. Slock","doi":"10.1109/ACSSC.2005.1599713","DOIUrl":"https://doi.org/10.1109/ACSSC.2005.1599713","url":null,"abstract":"We consider a family of user dedicated downlink channel estimation methods in WCDMA receivers which are particularly suited for the presence of dedicated channel transmit beamforming and which assume no a priori knowledge of the path delays and the beamforming parameters. They exploit all the transmitted pilot sequences as well as the structured dynamics of the channel. First we build slot-wise least squares (LS) estimates of the channels associated with dedicated and common pilots. Then we optimally improve the dedicated channel estimate quality by jointly Kalman filtering the two LS estimates or alternatively (suboptimally) Kalman filtering them separately and combining via weighted LS. In the suboptimal case, the order of Kalman filtering and weighted LS combining results in differing performance and complexity in different conditions","PeriodicalId":326489,"journal":{"name":"Conference Record of the Thirty-Ninth Asilomar Conference onSignals, Systems and Computers, 2005.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122662473","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Efficient Demodulation in Cooperative Schemes Using Decode-and-Forward Relays","authors":"Tairan Wang, A. Cano, G. Giannakis","doi":"10.1109/ACSSC.2005.1599919","DOIUrl":"https://doi.org/10.1109/ACSSC.2005.1599919","url":null,"abstract":"Cooperative communication systems using various relay strategies can achieve spatial diversity gains, enhance coverage and potentially increase capacity. For the practically attractive decode-and-forward (DF) relay strategy, we derive an efficient demodulator at the destination in the form of a weighted combiner. The weights are selected adaptively to account for the quality of both source-relay-destination and source-destination links. Analysis proves that the novel demodulator can achieve the maximum possible diversity, regardless of the underlying constellation. Its error performance tightly bounds that of maximumlikelihood (ML) demodulation which provably quantifies the diversity gain of ML detection with DF relaying. Simulations corroborate our theoretical analyses and compare performance of the novel decoder with existing diversity-achieving strategies including analog amplify-and-forward and selective-relaying.","PeriodicalId":326489,"journal":{"name":"Conference Record of the Thirty-Ninth Asilomar Conference onSignals, Systems and Computers, 2005.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122949186","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"FPGA Implementation of Viterbi Decoders for MIMO-BICM","authors":"S. Haene, A. Burg, D. Perels, P. Luethi, N. Felber, W. Fichtner","doi":"10.1109/ACSSC.2005.1599849","DOIUrl":"https://doi.org/10.1109/ACSSC.2005.1599849","url":null,"abstract":"The FPGA implementation of Viterbi decoders for multiple-input multiple-output (MIMO) wireless communication systems with bit-interleaved coded modulation (BICM) and per-antenna coding is considered. The paper describes how the recursive add-compare-select (ACS) unit, which constitutes the performance bottleneck of the circuit, can be pipelined to increase the throughput. As opposed to employing multiple parallel decoders, silicon area (resource utilization on the FPGA) is significantly reduced. The proposed optimizations lead to an implementation that achieves a throughput of 216 Mbps in a 4 times 4 MIMO-WLAN system prototype based on IEEE 802.11a","PeriodicalId":326489,"journal":{"name":"Conference Record of the Thirty-Ninth Asilomar Conference onSignals, Systems and Computers, 2005.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114184966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Representation of unit range numbers","authors":"T. Lang, J. Bruguera","doi":"10.1109/ACSSC.2005.1599943","DOIUrl":"https://doi.org/10.1109/ACSSC.2005.1599943","url":null,"abstract":"Floating–point representation has a large dynamic range but can be inefficient for computations with values that have a limited range. This issue is explored here for values in the range −1 to 1, which, for instance, is the range of some trigonometric functions and exponentials. Examples are shown in which the results are inaccurate, because of the small density of the representation close to 1. Although a fractional fixedpoint representation seems suitable for these computations, its uniform density does not allow the representation of values close to zero and close to one, resulting in similar inaccuracies. To improve the accuracy, we propose a more suitable representation, that we call unity representation. This representation is able to represent very small values with high accuracy, as in floating point, as well as values very close to 1. We show the advantages of this representation providing several computation examples. Moreover, we list the architectural support that is needed to use this representation in a floating-point processor.","PeriodicalId":326489,"journal":{"name":"Conference Record of the Thirty-Ninth Asilomar Conference onSignals, Systems and Computers, 2005.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114577238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rao-Blackwellized Gauss-Hermite Filter for Joint Frequency Offset and Channel Estimation for the MIMO-OFDM System","authors":"Kyeong Jin Kim, R. Iltis","doi":"10.1109/ACSSC.2005.1599870","DOIUrl":"https://doi.org/10.1109/ACSSC.2005.1599870","url":null,"abstract":"We propose a new frequency offset and channel estimation algorithm for a MIMO-OFDM system. To estimate offset parameters which enter the observation function in a nonlinear manner, we propose a Gauss-Hermite Filter which incorporates the Kalman filter (KF) conditioned on a random offset sample. To reduce the complexity, the Rao-Blackwellization is employed. In the MIMO-OFDM system, the initial estimate for the offsets and channels are obtained using one training symbol. In the remaining OFDM symbol intervals, the MIMO data detector is employed to detect the transmitted data symbols. The used data detector and Gauss-Hermite filter based channel/offset estimator are finally combined in a joint decision-directed algorithm","PeriodicalId":326489,"journal":{"name":"Conference Record of the Thirty-Ninth Asilomar Conference onSignals, Systems and Computers, 2005.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128237784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hidden Markov Modeling of Noise Periodograms Using Rayleigh Mixture Models","authors":"K. Sørensen, S. Andersen","doi":"10.1109/ACSSC.2005.1600052","DOIUrl":"https://doi.org/10.1109/ACSSC.2005.1600052","url":null,"abstract":"In this paper, we derive an Expectation-Maximization algorithm for hidden Markov models (HMMs) with a multivariate Rayleigh mixture model (RMM) in each state. We compare the use of multivariate RMMs to multivariate Gaussian mixture models in the general case where the HMM is a dynamic model and for the special case where it has a single state and reduces to a static model. We evaluate the proposed method when used to model probability density of periodpgrams from real-life noise sources and white Gaussian noise, which we include for reference purposes.","PeriodicalId":326489,"journal":{"name":"Conference Record of the Thirty-Ninth Asilomar Conference onSignals, Systems and Computers, 2005.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128572853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}