Browsing by Author "Ma, Chun-Ying"

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A Simple ICI Suppression Method Utilizing Cyclic Prefix for OFDM Systems in the Presence of Phase Noise
(2013-11-01)
Ma, Chun-Ying
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Wu, Chun-Yen
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Huang, Chia-Chi
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傳播研究所
;
Institute of Communication Studies
An extremely low-complexity inter-carrier interference (ICI) suppression method for OFDM systems in the presence of phase noise is proposed in this paper. The core idea is to utilize the ISI-free part of cyclic prefix (CP), which is simply ignored in traditional methods. We linearly combine the ISI-free samples in CP with the corresponding samples in the OFDM symbol to suppress ICI, and this scheme is called 'CP combining' throughout this paper. In addition, the optimum combining coefficients, in the sense of ICI power minimization, are derived, and a set of near-optimum coefficients are proposed to reduce the complexity. Simulation results show that the proposed CP combining method improves the system performance by 0.5 - 1.5dB. Furthermore, the proposed method can be incorporated with other phase noise mitigation methods to further improve the system performance.
Chunk-based Resource Allocation Under User Rate Constraints in Multiuser MIMO-OFDM Systems
(2012-01-01)
Chou, Po-Chien
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Ma, Chun-Ying
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Huang, Chia-Chi
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電信工程研究所
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Institute of Communications Engineering
In multiuser multiple-input multiple-output orthogonal frequency division multiplexing (MU MIMO-OFDM) systems, the communication resource needs to be efficiently allocated on subcarriers such that the quality-of-service (QoS) of each user can be satisfied. A low complexity chunk-based resource allocation algorithm with low signaling overhead is proposed to minimize the total transmit power under the constraint of each user's data rate. The channel estimation error is considered in the resource allocation problem. Simulation results show that the performance degradation with respect to subcarrier-based water-filling method is small and the effect of channel estimation error is negligible. Meanwhile, computation complexity is nearly in the same order and signaling overhead is reduced.
Energy-Efficient Power Loading Algorithms for Uniform-Rate OFDM Systems
(2014)
Ma, Chun-Ying
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Huang, Chia-Chi
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電信工程研究所
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Institute of Communications Engineering
In recent years, energy-efficiency has become one of the most critical issues in wireless communications. Although it is important and practical to design an energy-efficient power loading algorithms for uniform-rate orthogonal frequency division multiplexing (OFDM) systems, the problem has not been explored in literature. The terminology uniform-rate in this paper means that each subcarrier adopts the same modulation scheme. To this end, we propose an adaptive power-loading algorithm to maximize the energy-efficiency for a uniform-rate OFDM system in this paper. To reduce the complexity, a sub-optimum solution is proposed. The numerical results show that the sub-optimum solution is close to the optimum solution. We also show that by carefully determining the modulation scheme, energy efficiency can be extensively improved.
Low-Complexity ICI Suppression Methods Utilizing Cyclic Prefix for OFDM Systems in High-Mobility Fading Channels
(2014-02-01)
Ma, Chun-Ying
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Liu, Sheng-Wen
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Huang, Chia-Chi
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電機資訊學士班
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Undergraduate Honors Program of Electrical Engineering and Computer Science
This paper focuses on a simple intercarrier interference (ICI) suppression scheme that linearly combines the inter-symbol interference (ISI)-free part of a cyclic prefix (CP) and its corresponding part in an orthogonal frequency-division multiplexing (OFDM) signal to soothe the ICI effect caused by a time-varying channel. In contrast with existing heuristic combining weights in the literature for ICI suppression, we derived three sets of optimum combining weights in different aspects. Through simulations, we show that the proposed combining weights outperform other existing heuristic combining weights. In addition, a simplified implementation is introduced to reduce the computational complexity of combining. Furthermore, the proposed methods can be incorporated with other ICI mitigation methods to further improve the system performance.
On Optimum Segment Combining Weight for ICI Self-Cancellation in OFDM Systems under Doubly Selective Fading Channels
(2012)
Ma, Chun-Ying
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Liu, Sheng-Wen
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Huang, Chia-Chi
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電信工程研究所
;
Institute of Communications Engineering
ICI self-cancellation algorithms are promising techniques to mitigate the ICI effect in OFDM systems caused by high mobility. In the area of ICI self-cancellation, the calculation of optimum combining weight is still an open question. In this paper, the problem of finding optimum combining weight to minimize the ICI-plus-noise power is formulated. We then derived a non-iterative algorithm to find the optimum solution. We also compare the performance of the optimum combining weight with other existing combining weight methods.