• ETRI Journal
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• v.33 no.1
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• pp.1-5
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• 2011

Downlink transmit power allocation schemes are proposed for soft fractional frequency reuse (FFR) in loose and tightly coordinated systems. The transmit powers are allocated so that the loss of spectral efficiency from the soft FFR is minimized, and the required cell edge user throughput is guaranteed. The effect of the soft FFR on spectral efficiency is evaluated depending on the power allocation schemes and the number of subbands. Results show that the loss of spectral efficiency from the soft FFR can be reduced by configuring an appropriate number of subbands in the loosely coordinated systems. In tightly coordinated systems, results show that the loss of spectral efficiency can be minimized regardless of the number of subbands due to its fast coordination.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11C
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• pp.1108-1115
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• 2005

In this paper, we propose a practical iterative channel estimation and decoding method for an LDPC-coded frequency hopping OFDMA system in the uplink of a packet-based cellular system. In the method, the channel gain and noise variance are iteratively estimated with both pilot symbols and LDPC decoder outputs to provide more reliable decoding metrics in intercell interference (ICI) environments. In addition, the channel correlation coefficient is also estimated to select proper filter coefficients according to the channel variation rate. Through simulations under the various channel conditions and different receiver configurations, it is shown that the proposed iterative receiver improves the performance without boosting the pilot power and mitigates the adverse effects of the non-uniform ICI.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.10
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• pp.1986-1993
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• 2015

We investigate the optimal resource and power allocation for device-to-device (D2D) communications in a multicell environment. When D2D links reuse the cellular radio resources, each D2D user will interfere with a cellular link and other D2D links, in its own cell as well as in adjacent cells. Under such situation, we propose a coordinated resource allocation scheme that can handle the intercell interferences as well as the intracell interference. For a given resource allocation, we also formulate a power optimization problem and present an algorithm for finding the optimal solution. The resource and power allocation algorithms are designed to maximize the achievable rate of the D2D link, while limiting the generated interference to the cellular link. The performance of the proposed algorithms is evaluated through simulations in a multicell environment. Numerical results are presented to verify the coordination gain in the resource and power allocation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.11
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• pp.1256-1263
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• 2012

Assigning different frequency resources among adjacent cells, namely the frequency reuse technique can be utilized to mitigate intercell interference, which is a major cause of performance degradation in cellular systems. Since most of conventional frequency reuse patterns are limited to the two-dimensional environment, the research for the three-dimensional frequency reuse would be beneficial especially for the implementation of femto cells in downtown office buildings. We propose frequency reuse patterns in three-dimensional space and evaluate their performance of each pattern in terms of channel capacity. In particular, we show that the proposed three-dimensional frequency reuse patterns can be applied for carrier-aggregated transmission of LTE-Advanced systems. The performance of the proposed patterns is evaluated using computer simulation.