共查询到20条相似文献,搜索用时 46 毫秒
1.
WCDMA下行链路一种加权的信道估计方法 总被引:1,自引:0,他引:1
本文针对第三代移动通信标准WCDMA(FDD)下行链路的结构,提出了一种新的利用公共导频信道和专用数据信道中的导频符号进行加权的信道估计方法。仿真表明本方案有效地提高了信道参数估计的准确度,使Rake接收机的性能比传统的只利用公共导频信道进行信道估计的方案有了一定的改善,特别是在公共导频信道受到明显衰落时。 相似文献
2.
在二维RAKE接收机中,通常仅用导频信道来估计信道矢量,当导频功率较低时,估计误差较大。本文提出一种新的信道矢量估计算法,该算法采用导频信道与业务信道联合估计技术,通过分集组合两个信道的估计结果,使信道矢量的估计精度得到了提高,仿真结果表明,该算法能有效地降低系统的误码率。 相似文献
3.
4.
Nen-Fu Huang Shiann-Tsong Sheu 《Lightwave Technology, Journal of》1996,14(5):678-692
In a multichannel photonic dual bus network, each of the unidirectional bus contains a number of channels (wavelengths) and the bus headend periodically generates fixed length slots on each of the channels. Generally, one channel called control channel is used to carry signals and the others are data channels. Each station is equipped with one fixed-transmitter and one fixed-receiver which are permanently tuned to the dedicated control channel, and n tunable-transmitters and m tunable-receivers are tunable over the entire wavelength range. For nonoverlapping traffic in network, the maximum network throughput will be achieved by applying the wavelength reusing concept. Given a set of serving traffic, a set of new traffic requests, and c data channels (wavelengths), the wavelength/receiver assignment problem [(n,m,c)-WRAP] is to assign a transmission wavelength and a receiver for each of the request such that the network throughput is maximized and the number of assigned wavelengths is minimized. In this paper, we prove that the (n,m,c)-WRAP is NP-hard. An efficient distributed wavelength reusing/sharing access protocol (DWRAP) is proposed for the (1,m,c)-WRAP. Based on the DWRAP, three different schemes are proposed for assigning the wavelength/receiver. The throughput of the DWRAP is analyzed and the performance of the three proposed schemes on the DWRAP are evaluated and compared by simulation. Simulation results demonstrate that for a limited number of wavelengths and receivers, the proposed schemes substantially improve the network throughput and access delay under general traffic demands 相似文献
5.
A CDMA receiver with enhanced multiple access interference (MAI) suppressionis proposed for a pilot symbols assisted system over multipath channels. Thedesign of the receiver involves the following procedure. First, blind adaptivecorrelators are constructed at different fingers based on the scheme ofgeneralized sidelobe canceller (GSC) to collect the multipath signals andsuppress MAI. A low-complexity partially adaptive (PA) realization of the GSCcorrelators is proposed which incorporates multi-user information for reducedrank processing. By a judiciously designed decorrelating procedure, a new GSCstructure is obtained in which the MAI are decorrelated and suppressedindividually. The next step is then a simple coherent combining of thecorrelator outputs with pilot aided channel estimation. Finally, furtherperformance enhancement is achieved by an iterative scheme in which the signalis reconstructed and subtracted from the GSC correlators input data, leadingto faster convergence of the receiver. The proposed low-complexity PA CDMAmulti-user receiver is shown to be robust to multipath fading and channelerrors, and achieve nearly the same performance of the ideal maximum SINR andMMSE receivers by using a small number of pilot symbols. 相似文献
6.
Binary adaptive coded pilot symbol assisted modulation over Rayleigh fading channels without feedback 总被引:1,自引:0,他引:1
Pilot symbol assisted modulation (PSAM) is a standard approach for transceiver design for time-varying channels, with channel estimates obtained from pilot symbols being employed for coherent demodulation of the data symbols. In this paper, we show that PSAM schemes can be improved by adapting the coded modulation strategy at the sender to the quality of the channel measurement at the receiver, without requiring any channel feedback from the receiver. We consider performance in terms of achievable rate for binary signaling schemes. The transmitter employs interleaved codes, with data symbols coded according to their distance from the nearest pilot symbols. Symbols far away from pilot symbols encounter poorer channel measurements at the receiver and are therefore coded with lower rate codes, while symbols close to pilot symbols benefit from recent channel measurements and are coded with higher rate codes. The performance benefits from this approach are quantified in the context of binary signaling over time-varying Rayleigh fading channels described by a Gauss-Markov model. The spacing of the pilot symbols is optimized to maximize the mutual information between input and output in this setting. Causal and noncausal channel estimators of varying complexity and delay are considered. It is shown that, by appropriate optimization for the spacing between consecutive pilot symbols, the adaptive coding techniques proposed can improve achievable rate, without any feedback from the receiver to the sender. Moreover, channel estimation based on the two closest pilot symbols is generally close to optimal. 相似文献
7.
Seunghyun Min Kwang Bok Lee 《Electronics letters》1999,35(6):457-459
A channel estimation scheme, based on both pilot and traffic channels, is proposed for next generation DS/CDMA systems. This scheme has no channel estimation delay, and is found to perform significantly better than a scheme based on only the pilot channel 相似文献
8.
9.
10.
11.
Shin-Yuan Wang Chia-Chi Huang 《Vehicular Technology, IEEE Transactions on》2001,50(1):234-243
This paper describes a spread-spectrum downlink RAKE receiver that computes data detection in the frequency domain. We assume a pilot signal is transmitted with data signals for channel sounding. The pilot signal does not degrade the receiver bit error rate (BER) performance because the receiver estimates the pilot signal and subtracts the estimated pilot signal from the received signal before data detection. A spreading code matched filter, a channel matched filter, and a sounding receiver are implemented by fast Fourier transform (FFT)-based matched filtering and integrated in a unified architecture. Monte Carlo simulation is used to evaluate the receiver BER performance in both a static channel and a mobile radio channel. Simulation results show that the RAKE receiver performs well in both kinds of channels 相似文献
12.
A soft iterative multisensor array receiver for coded multiuser wideband code-division multiple-access wireless uplink channels is proposed, such channels are typically both frequency- and time-selective. A new equivalent discrete-time synchronous representation is used to model asynchronous multiuser dispersive channels that employ, in general, random spreading. The proposed scheme suppresses multiuser interference over a wide range of user signal powers, by iteratively exchanging soft information between a minimum mean-square-error (MMSE) multiuser demodulator and a bank of single-user decoders, feeding back the outputs of the latter to aid in soft multiuser multisensor MMSE-RAKE demodulation and subtractive interference cancellation, in the second and subsequent iterations. It displays near-far resistance since it behaves like a successive interference subtracter across iterations. The array responses are obtained via a multipass estimation scheme that uses both (temporal) pilot symbols and soft estimates fed back from the decoders to effectively provide multisymbol pilot signals and thence successively refined estimates with increasing iterations, while seeking neither to rely on the array geometry nor to estimate the directions from which users' signals arrive at the receiver. Simulation studies indicate that this scheme performs close to the single-user case with a two-sensor receiver array, and perfect channel state information, after four iterations; alternatively, it allows significantly increased user capacity compared with conventional receivers, and suffers only a modest loss with estimated array responses 相似文献
13.
This paper develops a maximum likelihood sequence estimation (MLSE) receiver for the frequency-flat, fast-fading channel corrupted by additive Gaussian noise when linear modulations (M-ASK, M-PSK, and M-QAM) are employed. This paper extends Ungerboeck's derivation of the extended MLSE receiver for the purely frequency-selective channel to the time-selective channel. Although the new receiver's structure and metric assume ideal channel state information (CSI) at the receiver, the receiver structure can be used wherever high-quality CSI is available. The receiver is maximum likelihood for a variety of channels, including Ricean, Rayleigh, lognormal, and additive white Gaussian noise (AWGN) channels. Bounds on the receiver's bit error rate (BER) are deduced for ideal and pilot tone CSI for fast Rayleigh fading. A crude lower bound is developed on the BER of predictor-based receivers for the same channel. This paper offers insight into matched filtering and receiver processing for the fast-fading channel and shows how pilot symbols and tones should be exploited 相似文献
14.
Due to the receiver complexity introduced by interleaving, the implementation of maximum likelihood (IML) decoding of interleaved coded signals transmitted over frequency nonselective Rayleigh fading channels has been shown to be practically impossible. As an alternative, a two-stage receiver structure has been proposed, where the channel estimation and sequence decoding are done separately. The channel estimation issue in a two-stage receiver is examined in detail in this paper. It is shown that although an optimum (maximum a posteriori (MAP)) channel estimation is not possible in practice, it can be approached asymptotically by joint MAP estimation of the channel and the coded data sequence. The implementation of the joint MAP estimation is shown to be an ML sequence estimator followed by an minimum mean-square error (MMSE) channel estimator. Approximate fill sequence estimation using pilot symbol interpolation is also studied, and through computer simulations, its performance is compared to receivers using hit sequence estimation. The effect of decision delay (DD), prediction order, and pilot insertion rate (PIR) on the reduced complexity ML sequence estimation is investigated as well. Finally, a practical receiver is proposed that makes the best compromise among the error performance, receiver complexity, DD, and power (or bandwidth) expansion due to pilot insertion 相似文献
15.
Nuno Pratas Nicola Marchetti Neeli Rashmi Prasad António Rodrigues Ramjee Prasad 《Wireless Personal Communications》2012,62(1):93-106
We propose in this paper a dual-antenna-array (with transmitter antenna array and receiver antenna array) architecture, where
the antenna elements are divided into several antenna element sets and each traffic channel is transmitted over an antenna
element set, to realize the multiple traffic channels set up by a user. A SINR feedback based algorithm, which can regulate
the transmission rate by iteratively adjusting the power on each traffic channel, is proposed to execute the rate control
for the proposed dual-antenna-array architecture under cochannel interference. It is shown that the proposed algorithm can
make the throughput meet the throughput requirement or achieve the weighted bandwidth sharing for certain fairness. In addition,
we further propose a traffic channel configuration algorithm to help the SINR feedback based algorithm find the optimal traffic
channel configuration that can meet the throughput requirement for each traffic channel or results in the maximal total throughput
for each user. 相似文献
16.
Rong Chen Xiaodong Wang Liu J.S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2000,46(6):2079-2094
A novel adaptive Bayesian receiver for signal detection and decoding in fading channels with known channel statistics is developed; it is based on the sequential Monte Carlo methodology that has emerged in the field of statistics. The basic idea is to treat the transmitted signals as “missing data” and to sequentially impute multiple samples of them based on the observed signals. The imputed signal sequences, together with their importance weights, provide a way to approximate the Bayesian estimate of the transmitted signals and the channel states. Adaptive receiver algorithms for both uncoded and convolutionally coded systems are developed. The proposed techniques can easily handle the non-Gaussian ambient channel noise. It is shown through simulations that the proposed sequential Monte Carlo receivers achieve near-bound performance in fading channels for both uncoded and coded systems, without the use of any training/pilot symbols or decision feedback. Moreover, the proposed receiver structure exhibits massive parallelism and is ideally suited for high-speed parallel implementation using the very large scale integration (VLSI) systolic array technology 相似文献
17.
《Vehicular Technology, IEEE Transactions on》2006,55(5):1671-1677
The problem of pilot and data channel mismatch in a steered space-time spreading (SSTS) system is addressed by means of advanced signal processing at the mobile receiver. The main idea is to apply the SSTS antenna array architecture and transmission algorithm and involve both the pilot and traffic signals in channel estimation at the receiver. Two semiblind algorithms are compared with the conventional pilot-based receiver in a CDMA2000-1X RC3 environment by means of simulations with variable speed and spatial angular spread, taking into account main imperfections such as estimation error for the correlation coefficient at the reverse link, calibration error, and different pilot powers for diversity antennas. It is demonstrated that the semiblind algorithms outperform the conventional receiver in the low- and medium-speed area. 相似文献
18.
Generalized frequency-division multiplexing (GFDM) is a candidate waveform for the fifth generation (5G) wireless communication systems. However, the carrier frequency offset (CFO) causing synchronization problem is very important for GFDM system. In this paper, we propose a turbo receiver with channel estimation, equalization and CFO compensation for MIMO (multiple input multiple output) GFDM system with index modulation (IM). So far, no related researches exist. This paper proposes a novel receiver to solve CFO compensation with two-path transmission and proposes a modified phase rotated conjugate cancellation (PRCC) algorithm for the receiver. On the other hand, GFDM with index modulation (GFDM-IM) can achieve better performance and lower peak-to-average power ratio (PAPR) than those of GFDM by using active index subcarrier. To reduce the system complexity, the log-likelihood ratio (LLR) criteria is also employed to search which subcarrier is active. Moreover, the Kalman filter is employed to trace the time-varying channels. The initial channel estimation is performed by the sparse pilot signals. In the simulations, we compare the proposed receiver with several existing schemes in different time-varying channels and modulations. The proposed scheme outperforms the existing schemes. 相似文献
19.
Ming-Xian Chang Tsung-Da Hsieh 《Vehicular Technology, IEEE Transactions on》2008,57(2):859-872
In fast-varying channels, an orthogonal frequency-division multiplexing system needs to insert denser pilot symbols among transmitted symbols in tracking the variation of a channel. However, using denser pilot symbols reduces transmission throughput. In this paper, we propose a pseudopilot algorithm for data detection in fast-varying channels without increasing the pilot density. Our algorithm is based on a regressional model-based least-squares-fitting approach. Within a block of received symbols, we select some data symbols and regard them as pseudopilot symbols. The receiver considers all the possible patterns of the pseudopilots and associates each of them with a data sequence and a corresponding metric. The associated data sequence, whose metric is minimum, is selected as the detected data sequence. Our algorithm is not based on a decision-directed or decision-feedback architecture because the pseudopilots do not come from any detected symbols. The proposed algorithm needs to search all the possible patterns of the pseudopilots, and the complexity may increase with the number of pseudopilots and constellation size. To reduce the number of search, we further propose two modified approaches. The simulation results show that the performance of the proposed algorithms could approach a bit-error probability lower bound that is obtained by letting the receiver know the true values of the pseudopilots. Compared with the linear interpolation method, the proposed algorithm shows obvious improvement in fast-varying channels. The proposed modified approaches could also effectively reduce the number of search while maintaining the performance. We also give the complexity analysis of the proposed algorithm and an approach to determine the degree of the regression polynomial. 相似文献
20.
Jiang Bofeng Zhang Jianguo Yin Qinye 《电子科学学刊(英文版)》2001,18(2):127-134
2-D RAKE receiver is an efficient way to realize the space-time processing for CDMA systems with aperiodic spreading codes. The Direction Of Arrival (DOA) and the relative time delay of every user's multipath must be known to realize the 2-D RAKE receiver. In the third generation CDMA mobile communication system, auxiliary pilot channel is used in the uplink channels. The different user's Vector Channel Impulse Response (VCIR) can be estimated from the pilot channel easily. The VCIR contains spatial and temporal information. In this paper, by utilizing the known pulse shape function, a parameter matrix method used to estimate the Spatial Signature Vector (SSV) and the relative time delay is proposed in frequency domain. The DOA can be estimated from the SSV. By reconstructing the SSV and utilizing approximate Capon space filter, the performance of the 2-D RAKE receiver with uniform circular array can be improved with a little additional computation work. 相似文献