Performance of Predistorted APK Modulation for One- and Two-Link Nonlinear Power Amplifier Satellite Communication Channels
Bibliographic record
Abstract
Digital satellite communications has been restricted to date to digital modulations having an efficiency of 2 bps/Hz; that is, filtered-quadrature phase-shift keying (QPSK) with close to a constant envelope. The main limitation to higher order digital modulations is the need for linearity of a high power amplifier both in the satellite and a terminal. Many years ago, Thomas et al. conducted a complete study of the use of higher order linear modulations on nonlinear satellite channels. However, pulse-shaping and predistortion were not treated. We consider these items for 16-point amplitude phase-shift keying (APK) modulation; that is, signal points assigned on concentric circles. A simple predistortion algorithm is given for APK modulations and symbol error-rate performance is determined for both one- and two-link nonlinear channels. Our best result is for an one-link channel and (5, 11) APK-5 points on an inner circle and 11 on the other, which, for predistortion on the nonlinear channel, loses only about 1 dB to 16-point quadrature amplitude modulation transmission on the linear channel.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".