Coding technique for out-of-band power reduction of multicarrier CDMA and OFDM systems

: pp. 17-24
Ukrainian State Centre of Radio Frequencies

In this paper, we introduce a method for out-of-band power reduction of multicarrier (MC) communication systems. Recent years MC systems possess a dominated role in wireless access owing to the ability to achieve high data rates and simultaneously high robustness to multipath and fading. Despite all advantages, MC transmission produces an essential out-of-band (OOB) interference. The OOB radiation leads to the wastage of scarce spectral resources and severe threats to adjacent wireless channels. We propose a novel technique for reducing OOB radiations in Orthogonal Frequency Division Multiplexing (OFDM) and MC Code Division Multiple Access (MC-CDMA) systems. To reduce the OOB emissions in the MC-CDMA system, we propose an analytical criterion for spectrum efficiency estimation as well as a low complexity algebraic algorithm for the proper waveform selection. The structure of selected waveform provides suppression for radiation outside the signal necessary bandwidth. Being implemented in the OFDM system, the proposed algorithm is used for the calculation of phases of cancellation carriers suppressing most powerful OOB sidelobes in a transmitted signal. In the final part of the article we consider an example of a simple precoding procedure for OFDM systems reducing the OOB power by 10 dB or more at the cost of the insignificant decrease of the information data rate.

  1. L. Hanzo, M. Munster, T. Keller, and B-J. Choi, OFDM and MC-CDMA for Broadband Multi-User Communications, WLANs and Broadcasting, John-Wiley and IEEE Press, 2003.
  2. Z. Yuan, S. Pagadarai, and A. Wyglinski, “Sidelobe suppression of OFDM transmissions using genetic algorithm optimization,” in Proc. IEEE Military Commun. Conf., vol. 4, pp. 1–5, 2008.
  3. IEEE Std 802.20 for Local and metropolitan area networks, Part 20: “Air Interface for Mobile Broadband Wireless Access Systems Supporting Vehicular Mobility Specification: Physical and Media Access Control Layer,” IEEE, 2008.
  4. A. Hisham A. Mahmoud, and Hüseyin Arslan, “Sidelobe suppression in OFDM-based spectrum sharing systems using adaptive symbol transition,” IEEE Commun. Lett., vol. 12, no. 2, pp. 133–135, Feb. 2008.
  5. T. Magesacher, “Spectral compensation for multicarrier communicati-on”, IEEE Trans. Signal Proc., vol. 55, no. 7, pp. 3366-3379, July 2007.
  6. I. Cosovic, S. Brandes, and M. Schnell, “Subcarrier weighting: a method for sidelobe suppression in OFDM systems,” IEEE Commun. Lett., vol. 10, no. 6, pp. 444–446, June 2006.
  7. S. Brandes, I. Cosovic, and M. Schnell, “Reduction of out-of-band radiation in OFDM systems by insertion of cancellation carriers,” IEEE Commun. Lett., vol. 10, no. 6, pp. 420–422, June 2006.
  8. I. Cosovic and T. Mazzoni, “Suppression of sidelobes in OFDM systems by multiple-choice sequences,” Eur. Trans. Telecomms., vol. 17, pp. 623–630, June 2006.
  9. T.F. Ho and V.K. Wei, “Construction of Spectrally Efficient Low-Crest Waveforms for Multicarrier CDMA System”, in Proc. 4th IEEE Int. Conf. on Universal Personal Communications Record, vol. 4, Nov. 2006, pp. 522–526.Tokyo, 1995
  10. I.S. Gradshteyn and I.M. Ryzhik, Table of Integrals, Series, and Products, translated from Russian, Elsevier Academic Press, USA, 2007.