Browsing by Author "Lin, Kuhn-Chang"

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A Linear Programming Approach for PAPR Reduction in OFDM Systems
(2009)
Tung, Yuan-Hao
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Lin, Kuhn-Chang
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Su, Yu T.
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電信工程研究所
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Institute of Communications Engineering
Peak-to-average-power ratio (PAPR) is a key design concern of an OFDM system as it determines the system's power efficiency. Clipping is a simple and efficient way of reducing PAPR. A suboptimal recursive clipping and filtering (RCF) method was proposed in [5] to reduce PAPR. This paper presents an alternate RCF approach which selects an error (clipping) vector that minimizes the peaks in both I-and Q-channels while satisfying some time and frequency domain distortion bounds. We formulate the design problem as a constrained linear programming (CLP) problem and extend it to include the tone-reservation option. Like the RCF method, our approach does not need side information and incurs no data rate loss. Since the error vector used in RCF has not been optimized, our approach offers improved PAPR reduction. It also provide tradeoff between PAPR reduction and bit error rate (BER) degradation.
Energy-Efficient Scheduling for Wireless Communication System
(2012)
Lin, Kuhn-Chang
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Lai, Jiun-You
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Su, Yu Ted
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交大名義發表
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National Chiao Tung University
Energy-efficient scheduling problem in wireless communication system is investigated in this paper. We propose two near-optimal schedulers which have simple structures for the general hard delay constraint scenario. Both single-user and multiuser cases are considered. The first scheduler invokes Gaussian approximation while the second one is inspired by the inverse water-filling (IWF) approach. The scheduling policies consist of a channel-awareness term and a delay-awareness term. Numerical results show that the proposed policies achieve near optimal performance when the total required transmit bits, R, is large. For the multiuser scenario, our scheduling strategy consists of an initial resource (number of time slots) allocation and a slot-by-slot user selection and bit loading algorithm. The former depends on the rate requirement and a priori knowledge of user-dependent channel statistic while the latter use an order statistic based approach designed to minimize the expected total energy consumption.
Initial Synchronization for Multi-Cell OFDMA Systems
(2009)
Liu, Yen-Cheng
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Lin, Kuhn-Chang
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Su, Yu T.
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電信工程研究所
;
Institute of Communications Engineering
In this paper, a complete solution to the initial synchronization for multi-cell OFDMA (orthogonal frequency division multiple access) systems is proposed. The proposed method consists of the following operations: timing synchronization, fractional carrier frequency offset (CFO) estimation, fractional CFO compensation, and joint integer CFO and preamble index estimation. To estimate multiple fractional CFOs with pseudo-periodic preamble, we suggest an over-sampling approach. An ill-condition detection and noise suppression algorithm is also presented. For joint integer CFO and preamble index estimation, we use a differential detection based cross-correlation method. Simulation results have shown that the proposed method gives satisfactory performance for a wide SNR range even when the mobile station (MS) is on the cell boundaries.
Ranging Sequences Design for OFDMA Systems
(2010)
Lin, Kuhn-Chang
;
Su, Yu T.
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傳播研究所
;
Institute of Communication Studies
We present a novel BCH code based sequences design method for generating large families of ranging sequences. The sequences can be used in an OFDMA network to offer sufficient ranging opportunities and guarantee low probability of false detection. Each derived sequence has low peak to average power ratio (PAPR) and cross-correlations with other sequences. These properties enable a mobile receiver to easily detect multiple ranging sequences and estimate the corresponding time offsets. Our approach leads to improved performance and enhanced robustness against multi-user interference and multi-path fading. Numerical results verify the effectiveness of the proposed method and its advantages over the class of pseudo-random binary sequences (PRBS) [2].