Performance of multiple-input and multiple-output orthogonal frequency and code division multiplexing systems in fading channels
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Bibliographic record
Abstract
In broadband downlink transmission, orthogonal frequency-division multiplexing (OFDM) combined with code-division multiple access (CDMA) is a prospective technique for high-data rate transmission in future wireless communication systems. By adding spatial diversity, multiple-input and multiple-output orthogonal frequency and code division multiplexing (MIMO-OFCDM) offers superior performance relative to both traditional OFDM systems and single-input and single-output OFCDM (SISO-OFCDM) systems. In this study, the authors present an analytical study and investigation of a MIMO-OFCDM downlink system that hires orthogonal variable spreading factor codes to spread each transmitted symbol in both time and frequency domains. Different gain combining schemes are employed in the frequency domain to recover the data symbols of the desired code channels, and space–time block coding is used to achieve spatial diversity. The more general Ricean fading channel is used to model the MIMO channel. The OFCDM system employs Alamouti transmit diversity scheme with multiple receive antennas. For systems without multi-code interference (MCI), analytical bit-error rate results are obtained and compared with simulation results. The authors also investigate the effect of correlation in frequency domain, where we verify that minimum mean-square error frequency combining is more robust to MCI than equal-gain combining.
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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 | 0.000 | 0.001 |
| Open science | 0.003 | 0.003 |
| Research integrity | 0.000 | 0.001 |
| 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 it