Space and frequency diversity measurements of the 1.7 GHz indoor radio channel for wireless personal communications
Bibliographic record
Abstract
The authors empirically evaluate three diversity schemes for indoor wireless personal communications. Measurements at 1.75 GHz, using a four-branch diversity receiver and selection combining (SC), are analyzed to determine the effects of physical parameters, signal fading statistics and a switched combiner on diversity performance. Results are obtained from numerous locations and over 800 measurements. These indicate that antenna separations of as small as a quarter wavelength provide significant diversity gains. For similar performance, frequency diversity requires separations of at least 5 MHz. A 4-branch combination of these schemes (hybrid diversity) yields on average a 16 dB improvement at 99% signal availability. The local mean variations between branches in these measurements is +or-3 dB but this has a negligible effect on average diversity performance using ideal SC. The diversity gains are shown to have a variability of +or-2.5 dB. Switch and stay combining (SAS), a form of SC, is sensitive to the input fading statistics and to switch delay. These variations in diversity performance should be considered for a worst case link design.>
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 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) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".