Space-time codes in wireless communications
Bibliographic record
Abstract
The need to provide reliable high data rate communication over the wireless channel has led to the development of efficient modulation and coding schemes. Diversity (time, frequency, space, polarization, angle) is an effective method to combat fading and improve the link reliability of the wireless channel. Time and frequency diversity lead to loss in bandwidth efficiency. However, by employing multiple antennas at the transmitter and/or at the receiver, spatial diversity mitigates fading without sacrificing the precious bandwidth resource. It is difficult to implement receive diversity in the downlink because of size and power limitations on the portable/mobile terminal. This has motivated the use of transmit diversity schemes wherein multiple antennas are used at the transmitter for the downlink transmission from the base station to the portable terminal. In space-time coding, intelligent coding of symbols across space and time can be done to reap the advantages due to coding and diversity. The coding in space is obtained by using multiple antennas at the transmitter. The article discusses aspects of space-time coding. This is an important research topic in the design of emerging wireless systems. Deployment of wireless systems using space-time codes is expected in the near future.
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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 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.002 | 0.004 |
| Science and technology studies | 0.001 | 0.003 |
| Scholarly communication | 0.002 | 0.003 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.003 | 0.003 |
| Insufficient payload (model declined to judge) | 0.005 | 0.003 |
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".