Dept. of Systems and Computer Engineering
Broadband Wireless Solutions
IEEE 802.16 Session #11
Monday 22 January 2001
Presentation Slides and Notes
Presentation Slides and Notes available here
Broadband wireless systems deployed in outdoor non-line of sight environments may encounter delay spreads of over 5 to 10 _s - which can cause potential intersymbol interference over 50 or more data symbol intervals. OFDM (orthogonal frequency division multiplexing) has been suggested to combat this ISI problem with reasonable complexity. However OFDM systems generate high transmitted peak-to-average ratios and are sensitive to phase noise; this can increase RF subsystem cost and complexity.
In this tutorial we survey recent advances in frequency domain equalization (FDE) for single carrier (SC) systems. SC modulation systems have lower peak-to average-ratios than OFDM, and when combined with FDE, their performance is at least as good as OFDM systems (in some cases better); furthermore, they have the same reduced signal processing complexity enjoyed by OFDM systems.
We introduce linear and decision feedback equalization versions of SC-FDE, and present some comparative performance results. We briefly explore the possible interoperability of OFDM and SC-FDE systems, and also present a proposal for reducing subscriber unit cost and complexity by employing OFDM in the downlink and SC-FDE in the uplink.
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