TELECOMMUNICATIONS AND RADIO ENGINEERING - 2010 Vol. 69,
No 7 		 

 

 

 

Interference Cancellation Based MMSE DFE with Multiple Antennas for Wideband CDMA (WCDMA)


S.K. Sharma
Department of Electronics and Communication Engg.,
Krishna Institute of Engg. And Technology, Ghaziabad, India
Address all correspondence to S.K. Sharma E-mail: sanjaysharma1515@yahoo.co.in

S.N. Ahmad
Department of Electronics and Communication Engg.,
Jamia Millia Islamia, New Delhi, India

Abstract
In recent times, there has been a lot of interest in integration of voice, data and video traffic in wireless mobile communication networks. With these growing interests, wideband code division multiple access (WCDMA) has immerged as an attractive and efficient access technique. The performance of WCDMA system is deteriorated in presence of multipath fading environment. In WCDMA, the frequency selective fading destroys the orthogonility and produces multiple access interference (MAI). A Rake receiver is a usual solution in the WCDMA downlink channel. In essence, because of path diversity, a rake receiver yields reasonable system performance. However, it does not restore the orthogonality. For this, we can adopt an equalizer to restore orthogonality without significantly increasing the system complexity. The linear adaptive equalizers have proven to be the most promising method to enhance the performance of WCDMA downlink receivers. They provide an acceptable balance between system performance and system complexity and yield simple adaptive implementations and exhibit reasonable robustness with respect to the underlying assumptions. However, the adaptive equalizers do not perform well on channels having spectral nulls in the pass band. As a more attractive and efficient receiver structure, we prefer a decision feedback equalizer (DFE). A DFE exhibits better immunity against the spectral channel characteristics. The paper presents an interference cancellation based minimum mean square error (MMSE) Decision Feedback Equalizer (DFE) for wideband code division multiple access (WCDMA) in a frequency selective channel. The filter coefficients in MMSE DFE are optimized to suppress noise, intersymbol interference (ISI), and multiple access interference (MAI) with reasonable system complexity. The work includes the design of the DFE when the transmit diversity in the form of Alamouti approach is employed at the transmitter. For the above structure, we have presented the estimation of Bit Error Rate (BER) for a MMSE DFE using computer simulation experiments. The simulation process takes into consideration   the effects of interference which includes additive white Gaussian noise, multipath fading, intersymbol interference (ISI) and multiple access interference (MAI). Furthermore, the performance is compared with standard adaptive linear equalizer (LE) and RAKE receiver. Numerical and simulation results show that the MMSE DFE exhibits significant performance improvement over the standard adaptive linear equalizer (LE) and RAKE receiver

KEY WORDS: code division, equalized, error, receiver



References
  1. Milstein, L.B., (2000), Wideband code division multiple access, IEEE, J.Select. Areas Commun. 18:1344-1354.
  2. Griffin, E.A., (1997), A first look at communication theory, McGraw-Hill, New York.
  3. Haykin, S., (2002), Adaptive Filter Theory, Prentice Hall.
  4. Shannon, C.E., (1948), A mathematical theory of communication, Bell system Technical Journal, 27.
  5. John, G. and Proakis, (2001), Digital Communication, 4th ed., McGraw-Hill, New York.
  6. Siebert, W.M., (1986), Circuits, Signals, and Systems, Cambridge, MA, MIT Press.
  7. Rappaport, T.S., (1996), Wireless communications, Chapter 3 and 4, Prentice Hall, New Jersey.
  8. Coon, J., Armour, S., Beach, M., and Mcgeehan, J., (2005), Adaptive frequency-domain equalization for single-carrier multiple input-multiple-output wireless transmissions, IEEE Trans. Signal Processing, 53(8):3247-3256.
  9. Bottomed, G.E., Ottosson, T., and Wang, Y.E., (2000), A generalized RAKE receiver for interference suppression. IEEE J. Select. Areas Commun., 18(8):1536-1545.
  10. Proakis, J., (1991), Adaptive equalization for TDMA Digital Mobile Radio, IEEE Transactions on Vehicular Technology, 40(2):333-341.
  11. Ts 25.213 3GPP TSG RAN, V. 5.2.0, Spreading and Modulation (FDD), 2002.
  12. Lee, Yu. and Donald, C., (1998), Cox, MAP selection Diversity DFE and Indoor Wireless Data Communication, IEEE Journal on selected Areas in communication, 16(8).
  13. Brady, D.M., (1970), An Adaptive Coherent Diversity Receiver for Data Transmission through Dispersive Media, Proceeding of IEEE International Conference on Communications, pp.21-35.
  14. Monsen, P., (1984), MMSE Equalization of interference on fading diversity channels, IEEE Trans. Commun. COM-32:5-12.
  15. Abdulrahman, M., Sheikh, A.U.H., and Falconer, D.D., (1994), Decision feedback equalization for CDMA in indoor wireless communications, IEEE J. Select. Areas Commun. 12:698-706.
  16. Madhow, U. and Honig, M.L., (1994), MMSE interference suppression for direct sequence spread spectrum CDMA, IEEE Trans. Commun. 42:3178-3188.
  17. Hochwald, B., Marzetta, T.L., and Papadias, C.B., (2001), A transmitter diversity scheme for wideband CDMA systems based on space-time spreading, IEEE J. Select. Areas Commun., 19:48-60.
  18. Al-Dhahir N. and Cioffi, J.M., (1995), MMSE Decision feedback sequence estimation, IEEE Tran. Inform. Theory, 41:961-975.
  19. Smee, J.E. and Schwartz, S.C., (2000), Adaptive feed forward feedback architectures for multiuser detection in high data rate wireless CDMA networks, IEEE Tran. Commn., 48:996-1011.
  20. Robler, J.F., Lampe, L.H.J., Gerstacker, W.H., and Huber, J.B., (2002), Decision feedback equalization for CDMA downlink, Int. Vehicular Technology Conf., l2:816-820.
  21. Tarokh, V., Seshadri, N., and Calderbank, A.R., (1998), Space-time codes for high data rate wireless communication: Performance criterion and code construction, IEEE Trans. Inform. Theory, 44:765-774.
  22. Alamouti, S.M., (1998), A Simple transmit diversity technique for wireless communication, IEEE J. Select. Areas Commun., 16(8):1451-1458.
  23. Aljerjawi, M. and Hamouda, W., (2005), Performance of space-time  spreading in multiuser DS-CDMA systems over fast fading channels, Proc. IEEE Global Telecommunications Conference, 3:1525-1529.


pages 639-652

Back