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A FAST SELECTIVE-DIRECTION MMSE TIMING RECOVERY ALGORITHM FOR SPATIAL-TEMPORAL EQUALIZATION IN EDGE

A FAST SELECTIVE-DIRECTION MMSE TIMING RECOVERY ALGORITHM FOR SPATIAL-TEMPORAL EQUALIZATION IN EDGE . Hanks H. Zeng Ye Li Jack H. Winters. AT&T Labs - Research Red Bank, NJ 07701-7033 jhw@research.att.com September 27, 2000. OUTLINE. EDGE Spatial-Temporal equalization

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A FAST SELECTIVE-DIRECTION MMSE TIMING RECOVERY ALGORITHM FOR SPATIAL-TEMPORAL EQUALIZATION IN EDGE

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  1. A FAST SELECTIVE-DIRECTION MMSE TIMING RECOVERY ALGORITHM FOR SPATIAL-TEMPORAL EQUALIZATION IN EDGE Hanks H. Zeng Ye Li Jack H. Winters AT&T Labs - Research Red Bank, NJ 07701-7033 jhw@research.att.com September 27, 2000

  2. OUTLINE • EDGE • Spatial-Temporal equalization • Selective-direction timing recovery • Results • Conclusions

  3. THIRD GENERATION TDMA SYSTEM: EDGE • EDGE: Enhanced Data Rates for Global Evolution • High data rate (384 kbps) service based on GSM, evolution of IS-136 and GSM • 8PSK at 270.833 ksps • 26 symbol training sequence • 1/3, 3/9 or 4/12 reuse • Both ISI and CCI 58 3 8.25 3 26 58 576.92 s

  4. SMART ANTENNAS IN TDMA SYSTEMS • Currently, 2 receive antennas at base stations with IS-136 • Combining changed from maximal ratio to MMSE combining in 1999 => 3-4 dB SINR gain • Planned upgrade to 4 antennas for further improvement • Spatial processing (track channel across time slot) • Want to use smart antenna techniques in EDGE • Spatial-Temporal processing (constant weights across time slot)

  5. SMART ANTENNAS IN EDGE • Spatial-Temporal processing using DDFSE for interference suppression • 5 feedforward taps, 5 feedback taps, 8-state Viterbi Equalizer • Degradation due to shortened equalizer => timing critical

  6. WEIGHT ESTIMATION AND TIMING RECOVERY Previous technique: Weight estimation: Train as MMSE-DFE Timing: MPE - Minimize ratio of precursor to cursor energy Issue: Much poorer performance with strong precursor versus postcursor ISI

  7. WEIGHT ESTIMATION AND TIMING RECOVERY Solution: Selective-direction equalization Since time slot is processed as a block, select either the forward or reverse direction for processing, with timing that minimizes the MMSE (trained as MMSE- DFE).

  8. WEIGHT ESTIMATION AND TIMING RECOVERY Issue: Computational complexity of training is doubled (with two directions) - important since inverse of large matrix is required, which is computationally intensive Solution: As shown in paper, the training algorithm can be modified so that the same matrix inverse is used for both directions => minimal computational-complexity increase with our technique

  9. BER with 2 antennas, HT profile, and single interferer

  10. BLER with single interferer (MCS-5)

  11. CONCLUSIONS Proposed a selective-direction MMSE timing recovery algorithm for ST processing: Improves performance with minimal increase in computational complexity Applied algorithm to EDGE: 3 dB lower SIR for 1% raw BER with 2 antennas as compared to previous technique Up to 25 dB interference suppression at 10% BLER with two antenna versus single antenna receiver

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