Abstract
We construct a class of linear quasi-orthogonal space-time block codes that achieve full diversity over quasistatic fading channels for any transmit antennas. These codes achieve a normalized rate of one symbol per channel use. Constellation rotation is shown to be necessary for the full-diversity feature of these codes. When the number of transmit antennas is a power of 2, these codes are also delay optimal. The quasi-orthogonal property of the code makes one half of the symbols orthogonal to the other half, and we show that this allows each half to be decoded separately without any loss of performance. We give an iterative construction of these codes with a practical decoding algorithm. Numerical simulations are presented to evaluate the performance of these codes in terms of capacity as well as probability of error versus SNR curves. For some special cases, we compute the pairwise probability of error averaged over all the channel states as a single integral that shows the diversity and coding gain more clearly.
Highlights
Multiple antenna systems have been of great interest in recent times because of their ability to support higher data rates at the same bandwidth and noise conditions; see, for example, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11] and references therein.For two transmit antennas, Alamouti’s orthogonal design gave a full-rate space-time block code with full diversity [6, 12]
For more than two transmit antennas and complex constellations, these codes offered on the average a rate of less than one symbol per channel use, where each symbol time period corresponds to a channel use
The highest theoretical code rate for fulldiversity code when the symbols are constrained to be chosen from the same constellation was shown to be one symbol per channel use
Summary
Alamouti’s orthogonal design gave a full-rate space-time block code with full diversity [6, 12]. For more than two transmit antennas and complex constellations, these codes offered on the average a rate of less than one symbol per channel use, where each symbol time period corresponds to a channel use. (This constraint is relaxed by using rotated constellations and many of the recent papers give space-time codes that offer full diversity for more than one symbols per channel use [16, 17].
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