Inter-carrier interference self-cancellation in synchronous downlink MC-CDMA system

ABSTRACT

MC-CDMA (multiple carrier code division multiple access) has been considered a strong candidate for cognitive radio and dynamic spectrum access network, due to its high spectral efficiency, easy implementation and the capability of operating over non-contiguous frequency bands. However, like other multi-carrier transmission technologies such as OFDM (orthogonal frequency division multiplexing), the orthogonality among subcarriers in MC-CDMA system is lost in a mobile environment, leading to inter-carrier interference (ICI) and performance degradation. In this paper, we apply the ICI self-cancellation scheme previously proposed for OFDM system to orthogonal MC-CDMA system with Hadamard-Walsh codes to diminish ICI and improve BER performance. We show that the ICI self-cancellation scheme for MC-CDMA is equivalent to employing a subset of the Hadamard code matrix. As a direct result, the proposed ICI self cancellation method does not increase the complexity at both transmitter and receiver. To compensate for the network capacity (in terms of the number of users) loss in the proposed ICI self-cancellation method, a second set of orthogonal Hadamard-Walsh codes on the quadrature subcarriers are introduced. The proposed system offers significant BER performance gain than original MC-CDMA with the presence of ICI and same network capacity when BPSK modulation is employed. Simulation results over multi-path fading channel confirm the effectiveness of the proposed scheme, without increasing any complexity.

REFERENCES

• 1: N. Yee and J-P Linnartz and G. Fettweis, "Multi-carrier cdma in indoor wireless radio networks," PIMRC'93, pp. 109--113, 1993.
• 2: S. Hara and R. Prasad, "Design and perfromance of multicarrier cdma system in frequency-selective rayleigh fading channels," IEEE Transactions on Vehicular Technology, vol. 48, pp. 1584--1595, September 1999.
• 3: W. M. Jang, L. Nguyen, and P. Bidarkar, "Mai and ici of synchronous downlink mc-cdma with frequency offset," IEEE Transactions on Wireless Communications, vol. 5, pp. 693--703, March 2006.
• 4: Y. Zhao and S. Haggman, "Intercarrier interference self-cancellation scheme for ofdm mobile communication systems," IEEE Transactions on Wireless Communications, vol. 49, pp. 1185--1191, July 2001.
• 5: Y. Zhao and S. Haggman, "Intercarrier interference compression in ofdm communication systems by using correlative coding," IEEE Commun. Lett., vol. 2, pp. 214--216, August 1998.
• 6: K. Sathananthan and C. Tarambulla, "Forward error correction codes to reduce intercarrier interference in ofdm," vol. 4, pp. 566--569, May 2001.

INDEX TERMS

Primary Classification:
  H. Information Systems
  H.4 INFORMATION SYSTEMS APPLICATIONS

Keywords:
MC-CDMA, communication, inter-carrier interference, self-cancellation