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Frequency synchronization plays a critical role in acquiring cooperative diversity for cooperative OFDM systems. However, the superposition of different carrier frequency offsets (CFOs) among each relay and destination makes the estimation difficult. In this paper, a novel multiple CFOs estimation algorithm is proposed. With this algorithm, the CFO corresponding to each relay can be accurately estimated...
We propose a dual diagonal linear-minimum-mean-square-error (DD-LMMSE) channel estimation algorithm for orthogonal frequency division multiplexing (OFDM) systems involving joint channel estimation and signal detection. Computational complexity and mean-square-error (MSE) analysis are presented to evaluate the efficiency of the proposed algorithm. Compared with the optimal LMMSE method, the proposed...
Abstract - A new inter-cell interference aware channel estimation technique for OFDM systems is presented. In the proposed algorithm, user equipment (UE) jointly detects the channel weights of the communication links associated with the serving and the interfering cells. Performance benefits of the proposed method are demonstrated by considering the OFDMA downlink as defined in 3GPP Long Term Evolution...
In this paper, based on mutually orthogonal (MO) ZCZ polyphase sequence (PS) sets proposed by Ref. [11], a method for improving the family size of ZCZ sequences in each set mentioned above is presented. As compared with Ref. [11], the resulting ZCZ sequences in each set can arrive to their theoretical bound due to expansion of their family size, whereas the length and width of ZCZ of ZCZ sequences...
The paper studies channel estimation methods with DRS in an OFDM system. As the DRS may only locate on part of the bandwidth, conventional methods, such as 2D Wiener filter and DFT based time domain estimation, cannot function well. A weighted averaging channel estimation method is proposed by which the channel responses estimated by LS estimation is averaged using Lagrange method. To verify the efficiency...
Various terrestrial digital television broadcasting standards have been developed in the last two decades for both fixed residential and mobile receivers. Since personal mobile terminal integrated with multiple functionalities is becoming more popular, it is highly desirable to come up with a universal platform for mobile TV reception which can detect the system parameters of DTV signals automatically...
In broadband orthogonal frequency division multiplexing (OFDM) systems, accurate channel state information (CSI) is required to support coherent detection and diversity combining. However, it is indeed challenging for channel estimation in real systems since some tones are nulled to ease the implementation of spectral masking filters. We propose a novel channel estimation scheme which can solve the...
Existing works on joint carrier frequency offset (CFO) and channel estimation in two-way relay networks (TWRN) only deal with the composite channel parameters and the mixed CFO values. In this paper, we design a superimposed pilot based training strategy such that the individual frequency and channel parameters can be obtained at the source terminals. We consider the amplify-and-forward (AF) relaying...
A novel timing offset estimation scheme for orthogonal frequency division multiplex (OFDM) systems is proposed in this paper, which can eliminate the ambiguity of the first arriving path estimation in multipath channels. The timing of the first arriving path is determined by detecting the first falling edge of the sliding window of the correlation result. A predefined threshold is adopted to validate...
Applying multiple-input multiple-output (MIMO) techniques to orthogonal frequency division multiplexing (OFDM) systems promise to achieve high spectral efficiency. However, similar to single antenna OFDM systems, phase noise drastically degrades the performance of such systems. In this paper, we investigate the influence of phase noise in MIMO-OFDM wireless systems and propose a new algorithm for...
To meet the evolution goals such as high peak rates, larger system capacity. LTE downlink adopts MIMO- OFDM technology. In this paper, we focus on channel estimation, which is one of the core technologies of the LTE downlink. First we establish the system framework .On this basis, we implement the channel estimation with two transmitting antennas and two receiving antennas. LS (Least Square) and LMMSE...
This paper deals with the problem of channel estimation for multiple-input multiple-output/orthogonal frequency-division multiplexing (MIMO/OFDM) systems based on superimposed training (ST). Channel coefficients are firstly estimated by judicious designing superimposed pilot sequences across different users. Then, we analyze the channel estimation performance and derive a closed-form expression for...
In Orthogonal Frequency Division Multiplexing (OFDM), multiple pilot subcarriers are dispersed for propagation channel estimation. Our study suggests a method to reduce the number of pilot subcarriers to 1/15 while maintaining fading tolerance. This can be realized by estimating the propagation channel parameters with combined implementation of sequential feedback estimation for the time direction...
In this paper, an OFDM-based high resolution, channel sounding (CS) method is proposed under T/2-spaced sampling. The proposed CS method consists of three iterative steps. In each iteration, it attempts to catch a new path with accurate fractional delay. Besides, it is equipped with EDC criterion for path order determination. The CFR-MSE performance can be greatly improved over the conventional LS...
In this study, it is investigated the validity of applying nonlinear device model to estimate distorted spectrum shapes of the OFDM signals for spectrum sharing studies. We used an LNA and two LNBs, which are off-the-shelf devices and the spectrum shape of OFDM signal distorted by the nonlinear devices, are evaluated by the means of model-based estimation and indoor experiment. As the results, the...
In this paper, by combining CS and TDKF, we propose a novel channel estimation scheme for OFDM time-variant channels. Compared with conventional TDKF method, our scheme is more practical as it need not to know the delays of multipath previously. Numerical results proved that compared with LS method, both the MSE and the BER performance are improved in our scheme.
In this paper, a simple and effective synchronization scheme for NC-OFDM systems is proposed. To keep the autocorrelation in the scenario of subcarriers deficiency, the preamble is consists of two identical pseudo-noise (PN) sequences instead of ZC sequences. Coarse timing estimation and fractional CFO(carrier frequency offset) estimation are completed according to the correlation between the received...
On the basis of analysis to MIMO-OFDM system, the paper use the characteristic of the time domain channel energy concentrated on relatively small number of sampling points to improve the estimation algorithm, and use singular value decomposition (SVD) to give a low-level channel estimation algorithm. Simulation results show that the improved algorithm has better estimation performance and low computational...
This paper discussed the channel estimation method of OFDM for DVB-T systems, and presents a two-dimensional time-frequency interpolation channel estimation scheme. This scheme, which uses Linear interpolation algorithm and Laplace interpolation algorithm, is based on the distribution of discrete pilot frequency of DVB-T. Results from computer simulations of OFDM transmission for DVB-T systems employing...
Since the received MIMO-OFDM signal is usually corrupted in the time-domain due to some adverse factors such as frequency offset and large peak-to-average power ratio (PAPR) etc., a high-quality signal may only be obtained in the frequency domain. However, the second-order statistics of the time-domain signal are very often used in a blind or semi-blind channel estimation, which means that an IFFT...
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