This study presents a simple technique, which is used to estimate both channel state and carrier frequency offset (CFO) in decode-and-forward relay systems, where coded orthogonal frequency division multiplexing is em...
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This study presents a simple technique, which is used to estimate both channel state and carrier frequency offset (CFO) in decode-and-forward relay systems, where coded orthogonal frequency division multiplexing is employed without cyclic prefix. On the basis of the least-square criterion, we derive the estimate of CFO and channel with the aids of consecutive blocks of pilot symbols. The initially proposed estimation technique achieves a distinguished performance by using a two-dimensional complete search approach;however, the computation becomes more and more intensive when the search granularity becomes finer and finer. For this reason, we further present an iterative approach as an alternative solution, which provides a performance comparable with that of the complete search method, while greatly reducing the implementation complexity. Besides, we also derive a closed-form expression of the CFO estimate for the considered system, which allows us to avoid the exhaustive search during the estimation processing. Computer simulations have been conducted to verify the efficiency of the proposed schemes.
Due to a dramatic increase in the number of mobile users, operators are forced to expand their networks accordingly. Cloud Radio Access Network (C-RAN) was introduced to tackle the problems of the current generation o...
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Due to a dramatic increase in the number of mobile users, operators are forced to expand their networks accordingly. Cloud Radio Access Network (C-RAN) was introduced to tackle the problems of the current generation of mobile networks and to support future SG networks. However, many challenges have arisen through the centralised structure of C-RAN. The accuracy of the channel state information acquisition in the C-RAN for large numbers of remote radio heads and user equipment is one of the main challenges in this architecture. In order to minimize the time required to acquire the channel information in C-RAN and to reduce the end-to-end latency, in this paper a dynamic channel estimator selection algorithm is proposed. The idea is to assign different channel estimation algorithms to the users of mobile networks based on their link status (particularly the SNR threshold). For the purpose of automatic and adaptive selection to channel estimators, a fuzzy logic algorithm is employed as a decision maker to select the best SNR threshold by utilising the bit error rate measurements. The results demonstrate a reduction in the estimation time with low loss in data throughput. It is also observed that the outcome of the proposed algorithm increases at high SNR values. (C) 2018 Elsevier B.V. All rights reserved.
Calibration of the rf branches of the arrays at the two sides of the link is a necessary procedure for the channel estimation algorithms of smart antenna based wireless communication systems. Reciprocity calibration i...
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ISBN:
(纸本)9781424449682
Calibration of the rf branches of the arrays at the two sides of the link is a necessary procedure for the channel estimation algorithms of smart antenna based wireless communication systems. Reciprocity calibration is a procedure adopted by Time Domain Duplex (TDD) systems such as WiMAX. This paper discusses the reciprocity calibration of an MxN TDD wireless system and uses a termination based formulation to identify a new design constraint. An integral part of the operation of TDD systems employing smart antennas is the process of estimating the downlink (DL) channel. This channelestimation has to be done efficiently so that valuable ""over the air resources"" are not wasted in the process. Typically, great attention is being paid to designing a wireless system so that the Signal to Noise Ratio (SNR) is maximized thus resulting in the best throughput from one side of the link to the other. Termination based formulations of the general MxN communication system problem have appeared in several recent works. In the present paper, we discuss the design constraints necessary for the implementation of a reciprocity based calibration and channelestimation. Ramifications of not meeting these design constraints will be studied and reported in the future.
In this paper, the general channel estimator for MIMO OFDM is derived and MM algorithms are used to reduce computational complexity. The first M of MM stands for majorization(minorization) and the second M stands for ...
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ISBN:
(纸本)078039335X
In this paper, the general channel estimator for MIMO OFDM is derived and MM algorithms are used to reduce computational complexity. The first M of MM stands for majorization(minorization) and the second M stands for minimization(maximization). It's well known that EM algorithms are powerful tools for channelestimation using iterative calculation. Indeed, every EM-type algorithm is a special case of the more general class of MM algorithms. To construct an EM-type algorithm is skillful and complicated. In contrast, the MM algorithms are easier to be understood and applied. In addition to constructing channel estimation algorithms based on the MM principle we also analyze the convergence property of the MM-type algorithms. Finally, the simulation results demonstrate the performance of MM-type channel estimation algorithms.
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