The Journal of Korean Institute of Communications and Information Sciences (한국통신학회논문지)

The Korean Institute of Commucations and Information Sciences (한국통신학회)
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Allowing a Large Access Timing Offset in OFDM-CDMA Using ZCZ Code and Block Spreading

ZCZ 부호와 블록 확산을 이용한 사용자 동기화 경감 OFDM-CDMA

  • Na, Donj-jun (Yeungnam University Dept. of Information Communications Engineering) ;
  • Choi, Kwonhue (Yeungnam University Dept. of Information Communications Engineering)
  • Received : 2015.09.16
  • Accepted : 2015.12.21
  • Published : 2016.01.31
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Abstract

We propose a new type of OFDM-CDMA scheme which allows large inter-user timing offset using zero correlation zone(ZCZ) code in conjunction with block spreading technique. Moreover to maximize spectral efficiency, the proposed OFDMA does not have guard time(GT). This is opposite to the trends in the conventional schemes where GT are supposed to be larger to allow larger inter-user timing offset. It is remarkable that the proposed GT-free OFDM-CDMA scheme completely cancels inter-user interference in the multipath fading simply by despreading process. This inter-user interference-free feature still remains even there exist inter-user timing offsets as large as multiple OFDM symbols. Although the self-user interference exists due to no GT, it can be effectively suppressed by simple successive interference cancellation(SIC) from the first symbol in spread block as it is free from inter symbol interference(ISI).

본 논문에서 제안하는 새로운 유형의 상향링크 OFDM-CDMA 기법은 ZCZ(Zero Correlation Zone) 부호와 블록 확산 기법을 함께 이용하여 사용자간의 넓은 접속시간 동기오차 허용범위를 가진다. 또한, 제안하는 기법은 OFDM 신호에 보호구간을 삽입하지 않아 주파수 효율을 최대화 한다. 넓은 사용자간 접속시간 동기오차 허용범위를 가지려면 보호구간의 길이를 늘여야 하는 기존 기법과 달리, 본 논문에서 제안하는 기법은 보호구간을 삽입하지 않아도 아주 넓은 사용자간 접속시간 동기오차 허용범위를 가진다. 제안하는 보호구간이 없는 상향링크 OFDM-CDMA 기법은 다중경로 페이딩 환경에서 수신단의 역확산 과정을 통해 모든 사용자간 간섭이 사라지는 특성을 가진다. 더욱이, 제안하는 기법은 복수개의 OFDM 심볼 길이만큼의 사용자간 동기오차 환경에서도 모든 사용자간 간섭이 없다. 보호구간이 없기 때문에 자기 신호의 부반송파간 간섭은 존재하지만, 제안하는 블록 확산 방식으로 인한 블록의 첫 번째 심볼이 ISI(Inter Symbol Interference)가 없는 특성을 이용하여 간단한 SIC(Successive Interference Cancellation)를 통해 첫 번째 이후 심볼의 간섭도 효과적으로 억제할 수 있다.

Keywords

References

  1. K. Kim, K. Choi, and K. Kim, "DFT-based channel estimation scheme for the uplink of LTE-A systems," J. KICS, vol. 40, no. 2, pp. 307-309, Feb. 2015. https://doi.org/10.7840/kics.2015.40.2.307
  2. K. Kim, K. Choi, J. Lee, and K. Kim, "Adaptive multi-antenna channel estimation scheme for uplink multiuser environments," J. KICS, vol. 40, no. 7, pp. 1293-1295, Jul. 2015. https://doi.org/10.7840/kics.2015.40.7.1293
  3. M. Irfan, J. Kim, and S. Shin, "Spectral and energy efficient spatially modulated nonorthogonal multiple access (NOMA) for 5G," J. KICS, vol. 40, no. 8, pp. 1507-1514, Aug. 2015. https://doi.org/10.7840/kics.2015.40.8.1507
  4. IEEE LAN/MAN Standards Committee, broadband Wireless Access: IEEE MAN standard, IEEE 802.16.-2004, 2003.
  5. S. H. Tsai, Y. P. Lin, and C.-C. J. Kuo, "Precoded multiuser OFDM transceiver in time asynchronous environment," IEEE Trans. Commun., vol. 55, No. 10, pp. 1863-1866, Oct. 2007. https://doi.org/10.1109/TCOMM.2007.906388
  6. H. Wei, L. Yang, and L. Hanzo, "Time-andfrequency-domain spreading assisted MC DSCDMAusing interference rejection spreadingcodes for quasi-synchronous communications,"in Proc. IEEE VTC2004-Fall., vol. 1, pp. 389-393, Sept. 2004.
  7. M. Rim, "A random access scheme robust to timing offsets for uplink OFDMA systems," IEICE Trans. Commun., vol. E92-B, no. 10, pp. 3274-3276, Oct. 2009. https://doi.org/10.1587/transcom.E92.B.3274
  8. B. Kim and K. Choi, "Uplink OFDMA schemes for loose multi-user synchronization," ICTC, pp. 417-421, Sept. 2011.
  9. B. Kim and K. Choi, "Inter-user quasisynchronous OFDMA for cooperative base stations systems," The Korea Soc. Space Technol., vol. 9, no. 1, pp. 97-101, Mar. 2014.
  10. J. Ahn and P. Song, "Prospect of 5G mobile communication development based on 3GPP," KICS Inf. and Commun. Mag., vol. 30, no. 12, pp. 37-50, Nov. 2013.
  11. G. Kim and H. Park, "R&D issues and progress direction of mobile communication," KICS Inf. and Commun. Mag., vol. 32, no. 1, pp. 28-32, Dec. 2014.
  12. K. Koo, K. Oh, and H. Youn, "A study on trend of research and development for 5G," in Proc. KICS Fall Conf., pp. 266-267, Daejeon, Korea, Nov. 2014.
  13. Z. Shengli, G. B. Giannakis, and C. Le Martret, "Chip-interleaved block-spread code division multiple access," IEEE Trans. Commun., vol. 50, no. 2, pp. 235-248, Aug. 2002. https://doi.org/10.1109/26.983320
  14. K. Choi and H. Liu, "Quasi-synchronous CDMA using properly scrambled walsh codes as user spreading sequences," IEEE Trans. Veh. Technol., vol. 59, no. 7, pp. 3609-3617, Sept. 2010. https://doi.org/10.1109/TVT.2010.2050916
  15. M. Park, K. Ko, B. Park, and D. Hong, "Effects of asynchronous MAI on average SEP performance of OFDMA uplink systems over frequency-selective rayleigh fading channels," IEEE Trans. Commun., vol. 58, no. 2, pp. 586-599, Feb. 2010. https://doi.org/10.1109/TCOMM.2010.02.050324
  16. M. Tuchler, A. C. Singer, and R. Koetter, "Minimum mean squared error equalization using a priori information," IEEE Trans. Signal Process., vol. 50, no. 3, pp. 673-683, Mar. 2002. https://doi.org/10.1109/78.984761
  17. Technologies Agilent, Advanced design system - LTE channel model - R4-070872 3GPP TR 36.803 v0.3.0., 2008.