Space-Time Spreading for MIMO CDMA-Based Systems over Fast-Fading Channels
Bibliographic record
Abstract
In this paper, a transmit diversity scheme based on space-time spreading for code-division multiple-access (CDMA) systems in fast-fading channels is introduced. The proposed transmit diversity scheme employs orthogonal Walsh spreading codes to exploit the time diversity introduced by the channel, and hence achieves two-fold of the diversity order obtained using conventional space-time spreading schemes. A generalization of the proposed coding scheme to systems with different antenna configurations is also discussed. For slowly-fading channels, we show that the proposed transmit diversity scheme reduces to that of conventional transmit diversity schemes with no performance degradation. For nonorthogonal spreading codes, we propose a receiver structure that employs an interference cancellation scheme to compensate for signal interference. Our results show a large performance improvement when using such an interference cancellation scheme relative to the conventional matched filter receiver.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 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".