Novel OFDM System Using Orthogonal Pilot Symbols with Subcarrier Index Modulation

In this work, two new transmission schemes are proposed to increase the spectral efficiency of orthogonal frequency division multiplexing (OFDM). In practical OFDM systems, channel estimation is usually performed by employing pilot symbols which is based on inserting known symbols in the time-frequency domain. However, pilot symbol designing is one of the bottlenecks of OFDM systems limiting the increase of spectral efficiency. We apply new pilot design structures, which are use orthogonal Walsh-Hadamard codes. To increase the spectral efficiency of OFDM systems, we assign the extra bits to the index of the each orthogonal Walsh-Hadamard codes. Simulation and theoretical results show that proposed methods have better performance than conventional OFDM with higher spectral efficiency. Moreover, no more energy is spent for additional information carried in the indices compared to classical OFDM systems. As a result, proposed methods provide both spectral efficiency and energy efficiency.

PDF

___

R. Nee, P. Ramjee, “OFDM for wireless multimedia communications,” Artech House, Inc., 2000.
K. Fazel, S. Kaiser. Multi-carrier and spread spectrum systems: from OFDM and MC-CDMA to LTE and WiMAX. John Wiley & Sons, 2008.
M. Ergen, Mobile broadband: including WiMAX and LTE. Springer Science & Business Media, 2009.
B. Kamislioglu and A.Akbal, “Effect of doubly selective channels about bit error probability in OFDM and FBMC,” European Journal of Technique, Vol. 7 No.2, 2017, pp. 96-101.
M. C. Necker and G. L. Stuber, ‘‘Totally blind channel estimation for ofdm on fast varying mobile radio channels,’’ IEEE Trans. Wireless Comm., Vol.3, No.5, 2004, pp. 1514-1525.
Y. Acar, H . Dogan, E. Basar, and E. Panayirci, ‘‘Interpolation based pilot aided channel estimation for stbc spatial modulation and performance analysis under imperfect CSI,’’ IET Comm., Vol.10, No.14, 2016, pp. 1820-1828.
Y. Acar, H. Dogan, and E. Panayirci, ‘‘Pilot symbol aided channel estimation for spatial modulation-OFDM systems and its performance analysis with different types of interpolations’’, Wireless Personal Communications, Vol.94, No.3, 2017, pp. 1387-1404.
Y. Acar, S. Aldırmaz and E. Başar, ‘‘Channel estimation for OFDM-IM systems,’’ Turkish Journal of Electrical Engineering & Computer Sciences, 2019, 27.3: 1908-1921.
B. Özbek, R. Yılmaz . "The Adaptive Channel Estimation For STBC-OFDM Systems". IU-Journal of Electrical & Electronics Engineering 5 (2011): 1333-1340.
B. Kamişlioğlu, A. AKBAL, "LSE Channel Estimation and Performance Analysis of OFDM Systems". Fırat University Turkish Journal of Science and Technology 12 (2017 ): 53-57
Y. Liu, et al. ‘‘Channel estimation for OFDM. IEEE Communications Surveys & Tutorials, 2014, 16.4: 1891-1908.
R. Mesleh, H. Haas, C.W. Ahn,, and S. Yun, “Spatial modulation-a new low complexity spectral efficiency enhancing technique”, 2006 First International Conference on Communications and Networking, China (pp. 1-5). IEEE., October 2006.
Y. Acar, ‘‘Subblock Aided OFDM with Index Modulation,” Balkan Journal of Electrical and Computer Engineering, 7 (2) , 156-161, (2019). DOI: 10.17694/bajece.514324
S. Aldırmaz, Y. Acar, and E. Basar. "Adaptive dual-mode OFDM with index modulation." Physical Communication 30 (2018): 15-25.
Y. Acar, and T. Cooklev. "High performance OFDM with index modulation." Physical Communication 32 (2019): 192-199.
E. Basar, M. Wen, R. Mesleh, M. Di Renzo, Y. Xiao, and H. Haas, ‘‘Index modulation techniques for next-generation wireless networks,’’ IEEE Access, Vol.5, 2017, pp. 16693-16746.
Q. Wang, G. Dou, X. He, R. Deng, J. Gao, “Novel OFDM System Using Data-Nulling Superimposed Pilots With Subcarrier Index Modulation”, IEEE Communications Letters, Vol. 22, No.10, 2018, pp. 2164-2167.
D. A. Bell, ‘‘Walsh functions and Hadamard matrixes,’’ IET Electronics Letter, Vol.2, No.9, 1966, pp. 340-341.