Browse > Article
http://dx.doi.org/10.6109/jkiice.2018.22.3.513

Efficient Modulation for the Last Symbol in OFDM Systems  

Yu, Heejung (Department of Information and Communication Engineering, Yeungnam University)
Publication Information
Journal of the Korea Institute of Information and Communication Engineering / v.22, no.3, 2018 , pp. 513-519 More about this Journal
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.
Keywords
OFDM; padding; (I)DFT; throughput;
Citations & Related Records
연도 인용수 순위
  • Reference
1 IEEE Std 802.11ac, Wireless LAN Medium Access ControlMAC) and Physical Layer (PHY) Specifications Amendment 4: Enhancements for Very High Throughput for Operation in Bands below 6 GHz, IEEE, Piscataway, N.J., 2013.
2 H. Yu, D. Lee, S. Moon, Y. Noh, and M. Cheong, "Inefficiency of 256-FFT per 20MHz," IEEE 802.11 Technical contribution 11/15/0572r1, 2015.
3 K. Waqas and H. Yu, "An efficient padding method in the last symbol for OFDM systems," in Proceedings of the Korean Institute of Communications and Information Science Summer Conference, Jeju, Korea, pp. 392-393, 2017.
4 S. G. Kang, "A mathematical implementation of OFDM system with orthogonal basis matrix," Journal of the Korea Institute of Information and Communication Engineering, vol. 13, no. 12, pp. 2731-2736, Dec. 2009.
5 T. Adame, A. Bel, B. Bellalta, J. Barcelo and M. Oliver, "IEEE 802.11AH: the WiFi approach for M2M communications," IEEE Wireless Communications, vol. 21, no. 6, pp. 144-152, Dec. 2014.   DOI
6 S. Verma, G. S. Tomar, "Call admission control and handoff techniques for 3-G and beyond mobile networks," Asia-Pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology, vol. 1, no.1, pp.29-40, Jun. 2011.
7 IEEE 802.11ax/D2.0, Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment 6: Enhancements for High Efficiency WLAN, IEEE, Piscataway, N.J., 2017.
8 IEEE Std 802.11a, Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment 1: High-speed Physical Layer in the 5 GHz Band (Amendment 1), IEEE, Piscataway, N.J., 1999.
9 IEEE Std 802.11n, Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment 5: Enhancements for Higher Throughput, IEEE, 2009.