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Strengthen the last line in the previous description of Q-STBCs and connecting the technical contents of Q-STBCs to Alamouti code detection and taking care not to paraphrase from other sources Tag: Reverted |
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The orthogonality criterion only holds for columns (1 and 2), (1 and 3), (2 and 4) and (3 and 4). Crucially, however, the code is full-rate and still only requires linear processing at the receiver, although decoding is slightly more complex than for orthogonal STBCs. Results show that this Q-STBC outperforms (in a bit-error rate sense) the fully orthogonal 4-antenna STBC over a good range of [[signal-to-noise ratio]]s (SNRs). At high SNRs, though (above about 22 dB in this particular case), the increased diversity offered by orthogonal STBCs yields a better BER. Beyond this point, the relative merits of the schemes have to be considered in terms of useful data throughput.
Q-STBCs have also been developed considerably from the basic example shown. With some algebraic manipulation, it can be shown that the MIMO detection problem using <math>C_{4,1}</math> decomposes into a [[multiuser detection]] problem consisting of two virtual users using the Alamouti code, <math>C_2</math>, which permits the development of adaptive technique like [[code diversity]] that uses feedback to improve the performance of open-loop transmit diversity scheme.<ref>{{Cite journal|author1=C. W. Tan |author2=A. Robert Calderbank |name-list-style=amp |title=Multiuser Detection of Alamouti Signals|journal= IEEE Transactions on Communications|volume= 57|issue= 7|pages= 2080–2089|date=Jul 2009|doi= 10.1109/TCOMM.2009.07.070592 }}</ref>
==See also==
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