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Improving Spectral Efficiency of NonOrthogonal Space Time Block CodedContinuous Phase Modulation
Kazuyuki MORIOKA Satoshi YAMAZAKI David ASANO
Publication
IEICE TRANSACTIONS on Communications
Vol.E101B
No.9
pp.20242032 Publication Date: 2018/09/01
Online ISSN: 17451345
DOI: 10.1587/transcom.2018EBP3018
Type of Manuscript: PAPER Category: Wireless Communication Technologies Keyword: continuous phase modulation, space time block code, quasi orthogonalspace time block code, group orthogonal toeplitz code,
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Summary:
We consider space time block codedcontinuous phase modulation (STBCCPM), which has the advantages of both STBC and CPM at the same time. A weak point of STBCCPM is that the normalized spectral efficiency (NSE) is limited by the orthogonality of the STBC and CPM parameters. The purpose of this study is to improve the NSE of STBCCPM. The NSE depends on the transmission rate (TR), the bit error rate (BER) and the occupied bandwidth (OBW). First, to improve the TR, we adapt quasi orthogonalSTBC (QOSTBC) for four transmit antennas and quasigroup orthogonal Toeplitz code (QGOTC) for eight transmit antennas, at the expense of the orthogonality. Second, to evaluate the BER, we derive a BER approximation of STBCCPM with nonorthogonal STBC (NOSTBC). The theoretical analysis and simulation results show that the NSE can be improved by using QOSTBC and QGOTC. Third, the OBW depends on CPM parameters, therefore, the tradeoff between the NSE and the CPM parameters is considered. A computer simulation provides a candidate set of CPM parameters which have better NSE. Finally, the adaptation of nonorthogonal STBC to STBCCPM can be viewed as a generalization of the study by Silvester et al., because orthogonal STBC can be thought of as a special case of nonorthogonal STBC. Also, the adaptation of QGOTC to CPM can be viewed as a generalization of our previous letter, because linear modulation scheme can be thought of as a special case of nonlinear modulation.

