Please cite this article in press as: Siadari TS, Shin SY. Joint Hadamard transform and Alamouti scheme for wireless communication system. Int J Electron Commun (AEÜ) (2014), http://dx.doi.org/10.1016/j.aeue.2014.04.009 ARTICLE IN PRESS G Model AEUE-51195; No. of Pages 3 Int. J. Electron. Commun. (AEÜ) xxx (2014) xxx–xxx Contents lists available at ScienceDirect International Journal of Electronics and Communications (AEÜ) j ourna l h om epage: www.elsevier.com/locate/aeue Joint Hadamard transform and Alamouti scheme for wireless communication system Thomhert Suprapto Siadari, Soo Young Shin ∗ Department of IT Convergence, Kumoh National Institute of Technology, South Korea a r t i c l e i n f o Article history: Received 7 May 2013 Accepted 7 April 2014 Keywords: Hadamard transform Alamouti scheme Bit error rate a b s t r a c t In this letter, the joint of Hadamard transform and Alamouti scheme is proposed. By applying Hadamard transform in the Alamouti scheme, two points of constellation can be merged into one symbol. This symbol is used for input of Alamouti scheme without changing the behavior of Alamouti scheme. System model for joint Hadamard transform and Alamouti scheme is also suggested and formulated. Simulation results show that the bit error rate (BER) performance of the proposed scheme outperforms the original Alamouti scheme. © 2014 Published by Elsevier GmbH. 1. Introduction Alamouti [1] has introduced his orthogonal space time block code (STBC) in 1998 and his approached has received a great attention due to the simplicity of the algorithm’s detection. When the transmitter with two antennas is employed, it may achieve the full-diversity performance with symbol rate of one [2]. The Alamouti – STBC is known as one of the most effective diver- sity methods in multi-input multi-output (MIMO) system used to combat the effect of channel fading in wireless communica- tion. Another well-known code used in communication system is Hadamard transform [3]. It is specially used in mobile communi- cation system (CDMA, UMTS) for orthogonal variable spreading factor (OVSF) codes. Moreover, a research of [4] analyzed a modulation code or multiplexing scheme based on Hadamard transform. The modulation code presents the identical transmit- ter configuration with orthogonal multiplexing schemes where different antipodal data streams are spread by different codes and summed up synchronously over the block length of the code, the receiver uses alternative structures in order to take advantage of the inherent time diversity introduced over fully interleaved fading channels. A space-time block code based on Hadamard transform is described in [5] investigating the STBC using Walsh–Hadamard transform with simple decoupling. The authors described how to develop a diversity technique using Hadamard transform instead of using other technique such as ∗ Corresponding author. Tel.: +82 544787473. E-mail addresses: thomhert@kumoh.ac.kr, siadari.thomhert@gmail.com (T.S. Siadari), wdragon@kumoh.ac.kr (S.Y. Shin). Alamouti scheme. The input of Hadamard transform is the out- put modulation signal of PSK or QAM. Event though our proposed scheme contains Hadamard transform but it has different approach in using the Hadamard transform (HT). In our proposed scheme, the Hadamard transform is used for merging two points of modu- lation’s constellation and the merged point becomes the input of Alamouti scheme. This letter proposes a novel method of joint Hadamard trans- form and Alamouti scheme to enhance the performance of wireless communication. To authors’ best knowledge, the proposed scheme of joint Hadamard transform and Alamouti scheme has never been studied yet. This makes it possible to deliver one symbol that con- tains two points of modulation results at one time slot without changing the common structure of Alamouti scheme. By multi- plying the modulation results into Hadamard transform, the new constellation points can be obtained. The benefit is that it is pos- sible to transmit two points of constellation into one symbol of Alamouti scheme. Furthermore, the Alamouti scheme uses these new constellations as symbols to be transmitted through the wire- less channel. In this case, transmitting two different symbols at one time slot and the conjugate symbol in the next time slot as principle of Alamouti scheme diversity is possible. The combina- tion of two points of constellation could be elaborated in each time slot and antenna. Even though one symbol comprises two points of modulation, the energy symbol is normalized as the same as conventional Alamouti scheme. Hence, the proposed scheme and conventional Alamouti scheme are compared in the same environ- ment. Notations: We notate all equations and symbols in italics form. For readability, the Hadamard transform denotes as H n and channel information as H. http://dx.doi.org/10.1016/j.aeue.2014.04.009 1434-8411/© 2014 Published by Elsevier GmbH.