Bandwidth Efficiency Enhancement for OFDM System Using Hybrid Equalization Techniques
Engineering and Technology Journal,
2009, Volume 27, Issue 8, Pages 1508-1518
AbstractThe Cyclic prefixed OFDM systems are very robust to multipath, provided that the delay spread of the transmission channel is less than the length of the CP inserted between transmitted symbols. Moreover, appending CP to each OFDM symbol decreases the bandwidth efficiency of the OFDM system, since the CP does not carry useful information.
To maintain bandwidth efficiency, a time-domain equalizer (TEQ) and frequency-domain equalizer (FEQ) is used in the OFDM system to mitigate ISI and ICI when the CIR interval is larger than the CP interval. However, the performances of these two equalizers are
degraded under severe channel condition. So a proposed hybrid equalizer structure is suggested in this paper. The hybrid equalizer gives about 10dB, 5dB and 3dB advantages at 10-4 BER compared with OT-FEQ, TEQ and PTEQ respectively. This comparison at fd=50Hz with sufficient length of CP. Also, for this case but with an insufficient length of
CP, the hybrid equalizer gives about 8dB and 7dB advantage compared with both TEQ and PTEQ respectively. Moreover, at fd=100Hz with sufficient CP length, the hybrid equalizer gives about 6dB, 3.5dB and 3dB advantage at 10-4 BER compared with OT-FEQ, TEQ and
PTEQ respectively. Also, for this case but with an insufficient length of CP, the hybrid equalizer gives about 6dB and 4dB advantage compared with both TEQ and PTEQ respectively.
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