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International Workshop for B3G/4G Satellite Communications

International Workshop for B3G/4G Satellite Communications. Nonlinear Mitigation for Two Carrier Transmission. Using Regenerative Satellite Payloads. Craig E Burnet. In Bok Yom. Presentation Overview. Joint research between ITR from University of South Australia and ETRI, South Korea

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International Workshop for B3G/4G Satellite Communications

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  1. International Workshop for B3G/4G Satellite Communications Nonlinear Mitigation for Two Carrier Transmission Using Regenerative Satellite Payloads Craig E Burnet In Bok Yom

  2. Presentation Overview • Joint research between ITR from University of South Australia and ETRI, South Korea • Project description and problem statement • TWTA characterisation • Iterative ISI cancellation process for two carriers • Summary of performance results

  3. Regenerative Satellite Model

  4. Satellite Transmission Model

  5. Transmission Model Summary • Multiple uplink TDMA channels • Regenerative satellite model, including onboard switch • Two high rate TDM downlink carriers per transponder • Mitigation technique has knowledge of both data streams and nonlinear characteristics of the TWTA • Investigate an optimum mitigation technique

  6. Measured TWTA Characteristics AM/AM Characteristic AM/PM Characteristic

  7. TWTA AM/AM and AM/PM Functions • Fit a piecewise polynomial to the characteristics with the following constraints: • Both AM/AM and AM/PM pass through the origin • Extension of the curves past the measured data • No discontinuities at breakpoints and first derivative continuous • AM/AM polynomial contains only odd coefficients • AM/PM polynomial contains only even coefficients

  8. Polynomial Approximations TWTA AM/AM TWTA AM/PM

  9. Simulation Scenarios • Three models for the nonlinearity are considered for comparison purposes: • Original nonlinear characteristics • Clipped nonlinear characteristics • Ideal linearised model Clipped Nonlinear:

  10. Three Simulation Scenarios Ideal Linearised:

  11. Iterative ISI Cancellation for each block of 8196 symbols for each of 10 iterations construct the transmitted two carrier signal simulate the nonlinear distortion for each of the two carriers determine the ISI, , for each received symbol subtract from each transmitted symbol end for end for end for where = 0.1

  12. Total Degradation • Overall performance through the nonlinear amplifier • Output power • Output distortion components • Assume two QPSK carriers of the same bandwidth and same power level • Performance results are for uncoded at a BER of 10-1 which loosely corresponds to error free transmission for rate ½ QPSK turbo coded systems

  13. Performance Results

  14. Conclusions • Mitigation technique for the combined nonlinearity and memory • Iterative predistortion technique using data predistortion • Better results and less complexity than signal predistortion • Can be extended to OFDM systems

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