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- 저자 : SeongKeunOh (검색결과 3 건)
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A New OFDM Transmission Scheme Using DFT Code Multiplexing
SeongKeunOh,KiSeubLee,Myung Hoon Sunwoo 에스케이텔레콤 (주) 2002 Telecommunications Review Vol.12 No.4
We propose a new orthogonal frequency division multiplexing transmission scheme using orthogonal code multiplexing. This scheme makes all modulation symbols have the same reliability even in a frequency selective fading channel, through a distributed transmission of each symbol over the whole effective subcarriers using a distinct orthogonal code. As an appropriate set of orthogonal multiplexing codes, we use the set of discrete Fourier transform code sequences that hold the orthogonality irrespective of the length. Using this set, we also can greatly reduce the peak-to-average-power ratio (PAR) of the resulting signal. Simulation results show that the proposed scheme can significantly reduce the required signal-to-noise ratio at a given bit error rate over the existing schemes. The scheme can maintain the PAR within a reasonable range of about 6dB even up to 512 subcarriers and works well even with PAR clipping of 1.5dB.
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A Class of MIMO Systems Using Transmit Diversity Pre-combining Scheme and Space-Time Trellis Codes
SeongKeunOh,SuHwanLim 에스케이텔레콤 (주) 2002 Telecommunications Review Vol.12 No.2
In this paper, we propose a class of multiple input multiple output (MIMO) systems using transmit diversity precombining (TDPC) scheme, assuming perfect channel state information (CSI) at a transmitter. In such a class of systems, each transmitter antenna is weighted independently according to the channel condition in order to combat the fading impairment through pre-compensation and/or to utilize effectively the fading information through selective transmission. We also introduce a novel space-time trellis code (STTC) that is a quite effective for the proposed class of MIMO systems. It can maximize the minimum Euclidean distance between code words, irrespective of the number of transmitter antennas. Incorporating both the TDPC scheme and the proposed STTC into MIMO systems can improve greatly the performance of such systems as compared with that of conventional STTC-MIMO systems. Computer simulations are performed to evaluate the frame error rate (FER) performance of the proposed systems.
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A DSP Architecture for High-Speed FFT in OFDM Systems
JaesungLee,JeonghooLee,MyungH.Sunwoo,SangmanMoh,SeongKeunOh 한국전자통신연구원 2002 ETRI Journal Vol.24 No.5
This paper presents digital signal processor (DSP) instructions and their data processing unit (DPU) architecture for high-speed fast Fourier transforms (FFTs) in orthogonal frequency division multiplexing (OFDM) systems. The proposed instructions jointly perform new operation flows that are more efficient than the operation flow of the multiply and accumulate (MAC) instruction on which existing DSP chips heavily depend. We further propose a DPU architecture that fully supports the instructions and show that the architecture is two times faster than existing DSP chips for FFTs. We simulated the proposed model with a Verilog HDL, performed a logic synthesis using the 0.35 mm standard cell library, and then verified the functions thoroughly.
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