The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Efficient and accurate spectrum sensing is a necessary part in cognitive radio networks. A simple and efficient spectrum sensing technique is proposed to solve the bad performance of spectrum sensing in non synchronous OFDM signals with low SNR regimes. Through the decomposition of the traditional OFDM signal spectrum sensing technology based on cyclostationarity, the real part and the imaginary part...
This paper deals with carrier frequency offset (CFO) estimation for interleaved orthogonal frequency division multiple access (OFDMA) uplink systems. Firstly, gravitational search algorithm (GSA) with center-symmetric trimmed correlation matrix and multiple signal classification criterion is presented for the purpose of efficient estimation. It has been shown that the estimate accuracy of the searching-based...
In this paper, we present the simulation results of FFO(fractional frequency offset) influences on PLC preamble correlation based PLC synchronization in DOCSIS 3.1 Downstream. FFO makes inter-carrier interferences and breaks orthogonality in OFDM based transmission system. It degrades the performance of OFDM by reducing SNR(signal to noise ratio). The performance of PLC synchronization is influenced...
The reliability of spectrum sensing is a challenging issue in cognitive radio (CR) systems. In this paper, we validate the reliability of two spectrum sensing algorithms for pilot-added OFDM signals: time-domain symbol cross-correlation (TDSC) and periodical peaks of autocorrelation (PPA) with a real system in real environments. To validate, these two algorithms carry out detection function for real...
For the spatially correlated multiuser MIMO-OFDM channels, the conventional iterative MMSE-SIC detection suffers from a considerable performance loss. In this paper, we use the factor graph framework to design robust detection algorithms by clustering a group of symbols to combat the spatial correlation and using the principle of expectation propagation to improve message passing. Furthermore, as...
In this paper, a new carrier frequency offset (CFO) estimation algorithm is proposed for MIMO-OFDM based wireless local area network (WLAN) systems, IEEE 802.11ad. The existing hardware-efficient auto-correlation scheme which subsamples the short train symbol can be used for low-complexity. However this method has a limitation of performance degradation. Therefore, we combine the subsampled auto-correlation...
Initial cell search synchronization in the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) system includes the time synchronization, the frequency synchronization of frames and the acquisition of cell identity (Cell ID). How to efficiently compensate initial frequency offset, combat uplink interference and adjust the automatic gain control (AGC) in initial cell search procedure...
This paper presents a semi-blind channel estimation approach for MIMO-OFDM Systems. The proposed method is a combination of methods based on Independent Component Analysis(ICA) and methods based on Pilot Carriers. Firstly, the Pilot Carriers are used for pre-estimation of the channel, and then the pre-estimated values are exploited as a kind of piroir information in the algorithm of ICA. Secondly,...
In-band pilot and cyclic prefix (CP)-based sensing, exploiting OFDM signal characteristics in the frequency domain and time domain respectively, are two effective techniques for low SNR spectrum sensing in cognitive radio communications. This paper seeks the theoretical performance improvement and optimal solution on the combination of these two techniques. The principles and performances of these...
In this paper, we consider the symbol-wise beamforming with limited feedback for MIMO-OFDM systems in the presence of co-channel interference. We propose a non-iterative algorithm for the symbol-wise beamforming with limited feedback, which provides the considerable performance with low computational complexity. We also propose the codebook for the symbol-wise beamforming with limited feedback under...
A cross-correlation function (CCF) based timing synchronization algorithm of low complexity, applicable for single-band transmission is presented. Novelty of the synchronizer lies in utilization of specific preamble structure of the Multi-band OFDM frame format. This threshold based algorithm also takes care of the fact that stronger multipath components frequently appear on the later clusters. Performance...
This paper deals with design and VLSI implementation of autocorrelator and CORDIC algorithm for OFDM based WLAN using ASIC technology. The autocorrelator is used for frame detection and carrier frequency offset estimation. The CORDIC is used to estimate the frequency offset and to calculate division operation in the channel estimation algorithm. A fast pipelined CORDIC architecture and autocorrelator...
This paper proposes a minimum mean square error (MMSE)-based algorithm for semi-blind estimation of a complex fading channel matrix. By approximating the channel product matrices to channel autocorrelation matrix, which is gained from the covariance matrix of the received data, a novel semi-blind algorithm named MMVE (MMSE to EVD technique) is rebuilt. The eigenvalue-eigenvector decomposition (EVD)...
A novel channel estimation algorithm for sounding reference signal in DFT-spread OFDM (DFT-S OFDM) system is proposed, which can estimate the channel response with high efficiency. According to the MSE metric between the estimated channel response and the real one, the simulation result shows that the intra-cell interference is neglectable while the effect of the inter-cell interference is so serious...
Carrier frequency offset (CFO) may cause multiple access interference (MAI) among users in multi-carrier code division multiple access (MC-CDMA) system. In the paper the code sensitivity of spreading codes and its correlative to the CFO is observed. An interesting property of orthogonality invariant for spreading codes under CFO has been presented. Based on the properties of code sensitivity, several...
This paper studies an algorithm on frame and symbol timing synchronization in burst OFDM communication based on IEEE802.11a, and analyzes the effect of symbol timing synchronization error. Itpsilas not perfect in many algorithms on timing synchronization at present, such as high complexity, floated threshold along with the signal energy. Therefore, it's necessary to propose an algorithm on symbol...
The existing algorithm to reduce peak-to-average power ratio (PAPR) about orthogonal frequency division multiplexing (OFDM) system will be discussed in this paper. A new algorithm is proposed for the particularity of complicated low-voltage power line network communication channel. The algorithm makes original sequence disordered through pseudo-random sequence matrix, and the disordered sequence is...
In this paper, a joint maximum a posteriori (MAP) detection algorithm is proposed for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO- OFDM) systems. Without the need of estimating the channel state information (CSI), it can directly compute the a posteriori probability (APP) of the transmitted data and generate the detection results under the MAP criterion by efficient...
This paper presents a symbol synchronization algorithm in the multi-mode orthogonal frequency division multiplexing (OFDM) systems. Efficient system reconfiguration algorithm applying to the adaptive modulation and coding (AMC) method is also presented. The algorithm for the symbol synchronization uses the shorter repetition period for computing correlation values than existing methods. It can reduce...
In this paper, a low complexity cell search algorithm (ML-ACL algorithm) for mobile OFDMA systems is proposed, with IEEE 802.16e as the example. The main problem on cell search is the huge computational complexity due to the long pseudo-noise (PN) series. Based on the maximum-likelihood (ML) detection theory, the ML-ACL algorithm uses an adaptive correlation length (ACL) to greatly reduce computational...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.