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Efficient Modulation for the Last Symbol in OFDM Systems

OFDM 시스템의 마지막 심볼을 위한 효율적인 변조 방식

  • Yu, Heejung (Department of Information and Communication Engineering, Yeungnam University)
  • Received : 2017.11.05
  • Accepted : 2017.11.23
  • Published : 2018.03.28

Abstract

OFDM modulation has been used for a transmission scheme in 4G LTE (Long Term Evolution) and Wi-Fi systems to mitigate the effects of frequency selective fading channels. An OFDM modulation is a block transmission scheme because an OFDM symbol consists of multiple subcarriers with narrow bandwidth. Therefore, all OFDM symbols in a frame should be filled out with data and padding bits. Depending on the amount of data, more padding bits than information bits can occupy the last OFDM symbol. Such inefficiency causes the loss of throughput. To overcome this problem, an efficiency padding method is proposed by using the property of DFT (Discrete Fourier Transform). In the proposed method, symbol duration of the last symbol is changed depending on the number used data subcarriers in the last symbol. With numerical evaluation, it is examined that throughput enhancement achieved by the proposed method can be about 20% depending a transmission scheme and data length.

Acknowledgement

Supported by : Yeungnam University

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