共查询到20条相似文献,搜索用时 31 毫秒
1.
Hsiao-Chun Wu Xiaozhou Huang Dongxin Xu 《Broadcasting, IEEE Transactions on》2006,52(2):211-218
Intercarrier interference is deemed as one of the crucial problems in the wireless orthogonal frequency division multiplexing (OFDM) systems. The conventional ICI mitigation schemes involve the frequency-domain channel estimation or the additional coding, both of which require the spectral overhead and hence lead to the significant throughput reduction. Besides, the OFDM receivers using the ICI estimation rely on a large-dimensional matrix inverter with high computational complexity especially for many subcarriers such as digital video broadcasting (DVB) systems and wireless metropolitan-area networks (WMAN). To the best of our knowledge, no semi-blind ICI equalization has been addressed in the existing literature. Thus, in this paper, we propose a novel semi-blind ICI equalization scheme using the joint multiple matrix diagonalization (JMMD) algorithm to greatly reduce the intercarrier interference in OFDM. However, the well-known phase and permutation indeterminacies emerge in all blind equalization schemes. Hence we also design a few OFDM pilot blocks and propose an iterative identification method to determine the corresponding phase and permutation variants in our semi-blind scheme. Our semi-blind ICI equalization algorithm integrating the JMMD with the additional pilot-based iterative identification is very promising for the future high-throughput OFDM systems. Through Monte Carlo simulations, the QPSK-OFDM system with our proposed semi-blind ICI equalizer can achieve significantly better performance with symbol error rate reduction in several orders-of-magnitude. For the 16QAM-OFDM system, our scheme can also improve the performance over the plain OFDM system to some extent. 相似文献
2.
《Wireless Communications, IEEE Transactions on》2008,7(10):3791-3798
The intercarrier interference (ICI) due to the Doppler frequency shift, sampling clock offset, time-varying multipath fading and local oscillator frequency offset becomes the major difficulty for the data transmission via the wireless orthogonal frequency division multiplexing (OFDM) systems. The existing ICI mitigation schemes involve the frequency-domain channel estimation/equalization or the additional coding and therefore require the pilot symbols which reduce the throughput. The frequency-domain channel estimation/equalization relies on the huge matrix inversion with high computational complexity especially for the OFDM technologies possessing many subcarriers such as digital video broadcasting (DVB) systems and wireless metropolitan-area networks (WMAN). In our previous work, we proposed a semi-blind ICI equalization scheme using the joint multiple matrix diagonalization (JMMD) algorithm and empirically showed that the proposed method significantly improved the symbol error rates for QPSK- and 16QAM-OFDM systems. In this paper, we discuss the sufficient condition for the theoretical ICI equalizability and also propose an alternative semi-blind ICI equalization method based on the joint approximate diagonalization of eigen-matrices (JADE) algorithm, which is much more computationally efficient than our previous method. 相似文献
3.
《Broadcasting, IEEE Transactions on》2008,54(4):816-820
4.
Rajagopal S. Bhashyam S. Cavallaro J.R. Aazhang B. 《Wireless Communications, IEEE Transactions on》2002,1(3):468-479
This paper presents algorithms and architecture designs that can meet real-time requirements of multiuser channel estimation and detection in future code-division multiple-access-based wireless base-station receivers. Sophisticated algorithms proposed to implement multiuser channel estimation and detection make their real-time implementation difficult on current digital signal processor-based receivers. A maximum-likelihood based multiuser channel estimation scheme requiring matrix inversions is redesigned from an implementation perspective for a reduced complexity, iterative scheme with a simple fixed-point very large scale integration (VLSI) architecture. A reduced-complexity, bit-streaming multiuser detection algorithm that avoids the need for multishot detection is also developed for a simple, pipelined VLSI architecture. Thus, we develop real-time solutions for multiuser channel estimation and detection for third-generation wireless systems by: (1) designing the algorithms from a fixed-point implementation perspective, without significant loss in error rate performance; (2) task partitioning; and (3) designing bit-streaming fixed-point VLSI architectures that explore pipelining, parallelism, and bit-level computations to achieve real-time with minimum area overhead 相似文献
5.
《Vehicular Technology, IEEE Transactions on》2009,58(9):4903-4908
6.
In this work, a sequential estimation algorithm based on branch metric is used as channel equalizer to combat intersymbol
interference in frequency-selective wireless communication channels. The bit error rate (BER) and computational complexity
of the algorithm are compared with those of the maximum likelihood sequence estimation (MLSE), the recursive least squares
(RLS) algorithm, the Fano sequential algorithm, the stack sequential algorithm, list-type MAP equalizer, soft-output sequential
algorithm (SOSA) and maximum-likelihood soft-decision sequential decoding algorithm (MLSDA). The BER results have shown that
whilst the sequential estimation algorithm has a close performance to the MLSE using the Viterbi algorithm, its performance
is better than the other algorithms. Beside, the sequential estimation algorithm is the best in terms of computational complexity
among the algorithms mentioned above, so it performs the channel equalization faster. Especially in M-ary modulated systems, the equalization speed of the algorithm increases exponentially when compared to those of the other
algorithms. 相似文献
7.
Raphael Visoz 《电信纪事》2002,57(3-4):306-306
The classical receiver performs separately three tasks, namely, channel estimation,equalization and decoding. The optimal receiver however would treat them jointly but is often non-tractable due to its tremendous complexity. Throughout this thesis, we identified contexts where this sub-optimality could entail substantial performance loss with the help of the Matched Filter Bound (mfb). Three main contexts were pointed out: wireless LAN with very high data rate and granularity constraints, high data rate cdma with low spreading factor and advanced tdma systems with high order modulation and/or Multiple Input Multiple Output channel. Once these contexts identified, we then tried to alleviate this impairment by suggesting low complexity sub-optimal receivers that perform iteratively/jointly channel estimation,equalization, and decoding (retransmission is seen as a special case of channel coding). In order to tackle the complexity issue while keeping the Maximum A Posteriori criterion, efficient reduced state trellis search techniques mainly based on Per Survivor Processing (psp) are exhaustively described and put into practice for the aforementioned contexts. A generalization of the well known psp technique consisting quite simply in keeping more than one survivor per state was proved to be very robust to error propagation even in the case of non minimum phase channels. This generalization was first introduced for the Generalized Viterbi Algorithm (gva) and the technique itself is refereed as Generalized Per Survivor Processing (gpsp) in this thesis. 相似文献
8.
Yue Chen Letaief K.B. Chuang J.C.-I. 《Selected Areas in Communications, IEEE Journal on》1998,16(9):1679-1690
This paper investigates the use of a maximum a posteriori probability (MAP) algorithm to realize soft-output equalization in a concatenated equalization and trellis-coded modulation (TCM) decoding-based wireless communication system. Specifically, we first begin with a general MAP algorithm and then focus on studying Bahl's (1974) MAP and Lee's (1974) MAP algorithms. We then propose a modified version of Lee's MAP algorithm which is much simpler than the original, in terms of complexity, and is more practical. In particular, a very simple channel estimation method which employs orthogonal training sequences is proposed. In order to improve the system performance, equal-gain combining and selection diversity are also considered. Finally, we compare the performance of the MAP algorithm-based equalization with our previously proposed equalization scheme, which combines decision feedback equalization and TCM 相似文献
9.
Impulse radio ultra wide band (UWB) communications require robust receivers; typically Rake receivers are required to capture a large number of resolvable paths, (even hundred of paths), so large number of correlators are needed; otherwise, adaptive receivers use complex filters and channel estimation algorithms. Therefore, traditional Impulse radio receivers demand non-practical implementation structures. In this paper we propose a novel correlation-adaptive receiver structure with low complexity for indoor high speed ultra wide band systems. This novel structure combines correlation characteristics from Rake receivers with recursive filters from adaptive receivers. The receiver includes a low complexity recursive channel estimation filter capable of estimating hundreds of channel impulse responses, and a single filter-correlation filter used for coherent bit demodulation. Furthermore, we derive by simulations the bit error rate for high density multipath environments for several impulse radio modulations like TH-PPM, DS-BPSK and TH-BPSK and we compare the performance of the proposed structure with typical Rake receivers. 相似文献
10.
Luschi C. Sandell M. Strauch P. Jian-Jun Wu Ilas C. Ping-Wen Ong Baeriswyl R. Battaglia F. Karageorgis S. Ran-Hong Yan 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2000,88(10):1633-1650
Substantial progress has been made in the receiver signal-processing algorithms for wireless communications to minimize the requirements on signal-to-noise (and/or interference) power ratio and computational complexities for the same quality of service. In cellular infrastructure systems, one of the key system design objectives in the base stations is to maximize the receiver sensitivity, so that the required signal level from the mobile stations can be minimized. The use of advance signal-processing algorithms, based on maximum a posteriori (MAP) estimation, iterative (turbo) channel estimation, equalization, and decoding, allows for a reduction of the required transmitter power by one-third to one-half. Lower computational complexities in the terminals, which implies a reduced power drain on the digital circuits, can be achieved by using techniques that adapt the state complexity of the receiver to the propagation channel. We give an in-depth review of these algorithms, and discuss their performance and implementation requirements 相似文献
11.
Traditional equalizers are very sensitive to carrier frequency offsets between the transmitter and receiver. Coherent receivers with frequency estimation algorithms can remove the offset to prevent the equalizer breakdown, but with a penalty in receiver complexity. On the other hand, noncoherent receivers such as differential detectors are inherently robust to the frequency offsets but cannot employ standard equalization techniques due to their nonlinear front-end. We introduce a simple noncoherent equalizer receiver structure for fading channel environments with short memory (up to two-bit intervals). The receiver consists of a whitened matched filter followed by a differential detector and a maximum likelihood sequence estimation (MLSE) equalizer. We examine the performance of this noncoherent equalizer by both analysis and simulation. It is shown that despite the simplicity, this receiver structure is capable of significant performance improvement as compared to an ordinary differential detector while operating with receiver frequency offsets two orders of magnitude greater than a traditional MLSE equalizer. This structure offers an attractive solution for high-bit-rate cordless transmission systems such as Digital Enhanced Cordless Telecommunications (DECT) that use simple noncoherent receivers whose performance can be constrained by channel dispersion. Using DECT as a case study, we show that the equalizer's performance limits are caused by the receiver nonlinearity and can be improved by adaptation of this nonlinearity to channel conditions. 相似文献
12.
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14.
Blind channel estimation and equalization in wireless sensor networks based on correlations among sensors 总被引:2,自引:0,他引:2
Xiaohua Li 《Signal Processing, IEEE Transactions on》2005,53(4):1511-1519
In densely deployed wireless sensor networks, signals of adjacent sensors can be highly cross-correlated. This paper proposes to utilize such a property to develop efficient and robust blind channel identification and equalization algorithms. Blind equalization can be performed with complexity as low as O(N/spl tilde/), where N/spl tilde/ is the length of equalizers. Transmissions can be more power and bandwidth efficient in multipath propagation environment, which is especially important for wideband sensor networks such as those for acoustic location or video surveillance. The cross-correlation property of sensor signals and the finite sample effect are analyzed quantitatively to guide the design of low duty-cycle sensor networks. Simulations demonstrate the superior performance of the proposed method. 相似文献
15.
DRM(Digital Radio Mondial)规定了一种应用于30MHz以下地面广播的数字声音广播系统,能够高质量地传输声音、数据及静止图片等。DRM系统采用正交频分复用和多电平调制技术,为保证接收信号质量,在接收机中需要进行信道均衡。根据DRM系统发射信号的特点,设计了一种信道估计算法,兼顾了复杂程度和均衡精度,并且对载波频偏不敏感。 相似文献
16.
In the last few years, ultra-wideband (UWB) systems became an appealing technology for wireless communication applications. Unfortunately, when the transmission channel is affected by intersymbol interference (ISI), system performance of UWB systems equipped with receivers based on conventional matched filters presents error-floor phenomena. Aimed by these considerations, in this letter, we present a novel transmit-receive scheme allowing blind channel estimation and minimum mean-square error linear channel equalization. Essentially, the proposed scheme exploits a very short duration of the UWB pulse for achieving reliable blind deconvolution of the received signal. A nice feature of the resulting system is that blind deconvolution of the received signal is achieved without power and throughput losses. Simulation results support the effectiveness of the proposed scheme, and show that it is able to gain about 8 dB over current UWB receivers based on matched filtering on several test channels impaired by ISI. 相似文献
17.
Vyacheslav Tuzlukov 《Circuits, Systems, and Signal Processing》2011,30(6):1197-1230
The generalized receiver (GR) based on a generalized approach to signal processing (GASP) in noise is investigated in a direct-sequence
code-division multiple access (DS-CDMA) wireless communication system with frequency-selective channels. We consider four
avenues: linear equalization with finite impulse response (FIR) beamforming filters; channel estimation and spatially correlation;
optimal combining; and partial cancellation. We investigate the GR with simple linear equalization and FIR beamforming filters.
Numerical results and simulation show that the GR with FIR beamforming filters surpasses in performance the optimum infinite
impulse response beamforming filters with conventional receivers, and can closely approach the performance of GR with infinite
impulse response beamforming filters. Channel estimation errors are taken into consideration so that DS-CDMA wireless communication
system performance will not be degraded under practical channel estimation. GR takes an estimation error of a maximum likelihood
(ML) multiple-input multiple-output (MIMO) channel estimation and GR spatially correlation into account in computation of
minimum mean square error (MMSE) and log-likelihood ratio (LLR) of each coded bit. The symbol error rate (SER) performance
of DS-CDMA employing GR with a quadrature sub-branch hybrid selection/maximal-ratio combining (HS/MRC) scheme for 1-D modulations
in Rayleigh fading is obtained and compared with that of conventional HS/MRC receivers. Procedure of selecting a partial cancelation
factor (PCF) for the first stage of a hard-decision partial parallel interference cancellation (PPIC) of the GR employed in
DS-CDMA wireless communication system is proposed. A range of optimal PCFs is derived based on the Price’s theorem. Computer
simulation results show superiority in bit error rate (BER) performance that is very close to that potentially achieved and
surpasses the BER performance of the real PCF for DS-CDMA systems discussed in literature. 相似文献
18.
Sridhar Rajagopal Srikrishna Bhashyam Joseph R. Cavallaro Behnaam Aazhang 《The Journal of VLSI Signal Processing》2002,31(2):143-156
This paper presents a reduced-complexity, fixed-point algorithm and efficient real-time VLSI architectures for multiuser channel estimation, one of the core baseband processing operations in wireless base-station receivers for CDMA. Future wireless base-station receivers will need to use sophisticated algorithms to support extremely high data rates and multimedia. Current DSP implementations of these algorithms are unable to meet real-time requirements. However, there exists massive parallelism and bit level arithmetic present in these algorithms than can be revealed and efficiently implemented in a VLSI architecture. We re-design an existing channel estimation algorithm from an implementation perspective for a reduced complexity, fixed-point hardware implementation. Fixed point simulations are presented to evaluate the precision requirements of the algorithm. A dependence graph of the algorithm is presented and area-time trade-offs are developed. An area-constrained architecture achieves low data rates with minimum hardware, which may be used in pico-cell base-stations. A time-constrained solution exploits the entire available parallelism and determines the maximum theoretical data processing rates. An area-time efficient architecture meets real-time requirements with minimum area overhead. 相似文献
19.
单载波频域均衡(SC-FDE)技术具有发送信号低峰均功率比的优势,是新一代通信3GPP-LTE/LTE-Advanced上行链路的关键技术之一。针对非理想信道估计,基于信道估计误差的统计模型,提出了一种联合频域均衡和时域判决反馈的鲁棒接收均衡器。以最小化均方误差(MSE)为最优准则,推导了均衡器的系数和均方误差的表达式。仿真结果表明,这种鲁棒的混合均衡器在非理想信道估计下较传统均衡器具有显著的性能提升。 相似文献
20.
《Selected Areas in Communications, IEEE Journal on》2006,24(8):1560-1570
Traditional multiuser receiver algorithms developed for multiple-input–multiple-output (MIMO) wireless systems are based on the assumption that the channel state information (CSI) is precisely known at the receiver. However, in practical situations, the exact CSI may be unavailable because of channel estimation errors and/or outdated training. In this paper, we address the problem of robustness of multiuser MIMO receivers against imperfect CSI and propose a new linear technique that guarantees the robustness against CSI errors with a certain selected probability. The proposed receivers are formulated as probabilistically constrained stochastic optimization problems. Provided that the CSI mismatch is Gaussian, each of these problems is shown to be convex and to have a unique solution. The fact that the CSI mismatch is Gaussian also enables to convert the original stochastic problems to a more tractable deterministic form and to solve them using the second-order cone programming approach. Numerical simulations illustrate an improved robustness of the proposed receivers against CSI errors and validate their better flexibility as compared with the robust multiuser MIMO receivers based on the worst case designs. 相似文献