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SpaceTimeFrequency Block Codes over Frequency Selective Fading Channels
Kenji SUTO Tomoaki OHTSUKI
Publication
IEICE TRANSACTIONS on Communications
Vol.E87B
No.7
pp.19391945 Publication Date: 2004/07/01
Online ISSN:
DOI:
Print ISSN: 09168516 Type of Manuscript: PAPER Category: Wireless Communication Technology Keyword: STBC, STOFDM, SFOFDM, STFOFDM,
Full Text: PDF>>
Summary:
Spacetime block coded orthogonal frequency division multiplexing (STOFDM) has been proposed as an attractive solution for a high bit rate data transmission in a multipath fading environment. Spacefrequency block coded OFDM (SFOFDM) has been also proposed as another solution. These two systems utilize STBC with a 22 transmission matrix, using two transmit antennas. In STOFDM the block codes are formed over the spacetime domains. In SFOFDM the block codes are formed over the spacefrequency domains. If we apply STBC with a 44 transmission matrix to OFDM, using four transmit antennas, we can expect the performance improvement. However, when the block codes are formed over spacetime (frequency) domains with four transmit antennas, the conditions of the orthogonality become more strict. We can expect that if the block codes are formed over spacetimefrequency domains with four transmit antennas, that is, if we implement spacetimefrequency block coded OFDM (STFOFDM), the condition of the orthogonality is more relaxed. In this paper, we apply STBC with a 44 transmission matrix to OFDM and propose STFOFDM. We evaluate the performance of the three types of systems (STOFDM, SFOFDM, STFOFDM). We show that the best system with respect to the error rate performance differs in the different channel conditions. When the effect of the Doppler spread is large and the effect of the delay spread is small, SFOFDM has the best error rate performance, and STFOFDM and STOFDM follow in order. When the effect of the delay spread is large and the effect of the Doppler spread is small, STOFDM has the best error rate performance, and STFOFDM and SFOFDM follow in order. We also show that STFOFDM is attractive in wireless communications. STFOFDM is more tolerant than STOFDM with respect to the Doppler spread and SFOFDM with respect to the delay spread, respectively.

