Large code set for PAPR reduction of OFDM signals and capacity increasing in MC-CDMA system

ABSTRACT

An interest to increase the capacity of multicarrier system such as multi-carrier code division multiple access (MC-CDMA) is attracting many studies to develop spreading code for a higher user capacity. In this paper, we proposes a new large spreading code set that is capable of increasing the capacity of MC-CDMA more than twice, offering better performance due to its uniform low cross correlations and high autocorrelation properties and has an additional advantage to reduce peak power of the orthogonal frequency division multiplexing (OFDM) transmit signals. By the proposed code, peak-to-average power ratio (PAPR) of OFDM system can be reduced up to the PAPR level of single carrier system (for some roll-of-factor values). Our proposed code with code length of N, has large code number of K=2N+1 for supporting 2N+1 users, while the conventional spreading codes is up to K=N+M, where M≥N. The capacity of 2N+1 means that 2N+1 users or data symbols are able to be transmitted over only N subcarriers. Our results confirms that the proposed code outperforms current famous pseudo-orthogonal carrier interferometry (POCI) code with gain of 3dB at bit-error-rate (BER) level of 10⁻⁶ in additive white Gaussian noise (AWGN) channel and gain of more than 4dB in multipath fading channel.

REFERENCES

• 1: Richard van Nee , Ramjee Prasad, OFDM for Wireless Multimedia Communications, Artech House, Inc., Norwood, MA, 2000
• 2: S. Hara and R. Prasad: Overview of multicarrier CDMA", IEEE Commun. Mag., pp. 126--131, Dec. 1997.
• 3: M. Debbah, P. Loubaton and M. de Courville: Spread OFDM performance with MMSE equalization. IEEE ICASSP 2001. Volume: 4, 2001 pp. 2385--2388.
• 4: N. Yee, P. Linnartz and G. Fettweis: Multi-carrier CDMA in indoor wireless networks. IEICE Tans. On Communications, Japan, Vol. E77-B, No.7, pp. 900--904, July 1994.
• 5: A. Bury, J. Eagle, and J. Lindner: Diversity comparison of spreading transforms for multicarrier spread spectrum transmission. IEEE Trans. Commun., Vol. 51, No. 5, pp. 774--781, May 2003.
• 6: D. A. Wiegandt, C. R. Nassar and Z. Wu: Overcoming peak-to-average power ratio issues in OFDM via Carrier Interferometry Codes. IEEE Vehicular Tech. Conf. (VTC2001), Atlantic City, NJ, pp. 660--663, 2001.
• 7: K. Anwar, M. Saito, T. Hara, M. Okada and H. Yamamoto: Simplified realization of carrier interferometry OFDM by FFT algorithm. IEEE VTS APWCS 2005, pp. 199--203, August 2005.
• 8: K. Anwar, M. Saito, T, Hara, M. Okada and H. Yamamoto: Simplified realization of pseudo-orthogonal carrier interferometry OFDM by FFT algorithm. IEEE Multi-Carrier Spread Spectrum (MC-SS 2005), Oberpfaffenhofen, September 14--16, 2005.
• 9: K. Anwar and H. Yamamoto: A new design of carrier interferometry OFDM with FFT as spreading codes. IEEE Radio and Wireless Symposium (RWS 2006), San Diego, CA, January 14--19, 2006.
• 10: K. Anwar, M. Saito, T. Hara and H. Yamamoto: On the PAPR reduction of wavelet-based multicarrier modulations system", IASTED CCN2004, pp. 138--143, USA, Nov. 2004.
• 11: F. Vanhaverbeke, M. Moeneclay, H. Sari: DS-CDMA with two sets of orthogonal spreading sequences and iterative detection. IEEE Comm. Letter, Vol. 4, No. 9, 2000.
• 12: B. M. Popovic, N. Suehiro and P. Z. Fan: Orthogonal sets of quadriphase sequences with good cross correlation properties. IEEE Trans. Inf. Theory, Vol. 48, pp. 956-959, April 2002.
• 13: B. Natarajan, C. R. Nassar, S. Shattil, M. Michelini, and Z. Wu: High-performance MC-CDMA via carrier interferometry codes. IEEE Trans. Vehicular Techs., Vol. 50, pp. 1344--1353, Nov 2001.
• 14: B. Natarajan, Z. Wu, C. R. Nassar, and S. Shatill: Large set of CI spreading codes for high capacity MC-CDMA. IEEE Trans Communications Vol. 52, No. 11, Nov. 2004.
• 15: D. A. Wiegandt, Z. Wu, C. R. Nassar: High-throughput, high-performance OFDM via pseudo-orthogonal carrier interferometry spreading codes. IEEE Trans. on Comm., Vol. 51, No.7, July 2003.
• 16: M. Akhavan-Bahabdi and M. Shiva: Double orthogonal codes for increasing capacity in MC-CDMA systems. IFIP WOCN 2005, Dubai, UAE, March 2005.
• 17: G. Chandran and J. S. Jaffe: Signal set design with constrained amplitude spectrum and specified time-bandwidth product. IEEE Trans. Comm. Vol. 44, No. 6, June 1996.
• 18: Matthias Patzold, Mobile Fading Channels, John Wiley & Sons, Inc., New York, NY, 2003

INDEX TERMS

Primary Classification:
  C. Computer Systems Organization
  C.2 COMPUTER-COMMUNICATION NETWORKS
      C.2.1 Network Architecture and Design
          Subjects: Wireless communication

General Terms:
Algorithms, Design, Measurement, Performance, Verification

Keywords:
MC-CDMA, OFDM, peak-to-average power ratio (PAPR), pseudo-orthogonal carrier interferometry, spreading code