An efficient blind turbo equalizer for compensating Doppler effects

The performance of single-carrier communication systems is seriously degraded by ISI (inter-symbol interference). In order to overcome the ISI Turbo equalization technique was proposed to maximize system performance. Furthermore, Doppler effects are affected to system performance. Turbo equalizer can achieve impressive performance gains over ISI and Doppler channel. In general, Turbo equalizer performs iterative feedback from decoder to equalizer in receiver. Because of iterative feedback, turbo equalizer gets better system performance according to the iteration number. In this paper, we propose a novel turbo equalizer, which is called as blind turbo equalizer for compensating ISI and Doppler effects. Proposed blind turbo equalizer is included with feed-forward filter and feed-back filter. We adopt 2 kinds of blind algorithms at feed-forward filter. One is normal CMA (constant modulus algorithm), another is SAGMCMA (stop-and-go modified constant modulus algorithm). Also, we adopt linear SISO-MMSE (soft-input soft-output minimum mean square error) equalizer at feed-back filter. Therefore, we improve the BER performance through proposed blind turbo equalizer.