The high Peak to Average Power Ratio (PAPR) of Orthogonal Frequency Division Multiplexing (OFDM) and MIMO-OFDM systems reduces the system efficiency. In this paper, an extension of Tone Reservation (TR) method is introduced for PAPR reduction in Space Frequency Block CODEd OFDM (SFBC-OFDM) systems. The proposed algorithm is based on a time domain kernel which is added to the signal of the antenna with maximum PAPR to reduce its peak power. The time domain kernel has been designed such that the location of the reserved tones is compatible with the structure of the space frequency CODE. Simulation results show that the proposed method has a very close PAPR reduction performance to that of the well-known RC-PII (Reduced Complexity-Polyphase Interleaving and Inversion) method, but its complexity is much less than of RC-PII.

In this paper, a new method for enhancing the physical layer security of an extended ALAMOUTI space-time coding systems is presented. In this method, the transmitted signals from each antenna are designed in such way to be related to the corresponding channel of the intended receiver, assuming that the transmitter has the knowledge of that channel. Furthermore, the transmitter uses artificial noise and more than two antennas to obtain an additional security. Theoretical mathematical formulas are derived for one-branch, two-branch, and artificial noise aided multi-branch scenarios. Simulation results show the ability of proposed method in enhancing physical layer security compared with other existing methods.

The goal of the future terrestrial digital video broadcasting (DVB-T) standard is to employ diversity and spatial multiplexing in order to achieve the fully multiple-input multiple-output (MIMO) channel capacity. The DVB-T2 standard targets an improved system performance throughput by at least 30% over the DVB-T. The DVB-T2 enhances the performance using improved coding methods, modulation techniques and multiple antenna technologies. After a brief presentation of the antenna diversity technique and its properties, we introduce the fact of the well-known ALAMOUTI decoding scheme cannot be simply used over the frequency selective channels. In other words, the ALAMOUTI Space-Frequency coding in DVB-T2 provides additional diversity. However, the performance degrades in highly frequency-selective channels, because the channel frequency response is not necessarily flat over the entire ALAMOUTI block CODE. The objective of this work is to present an enhanced ALAMOUTI space frequency block decoding scheme for MIMO and orthogonal frequency-division multiplexing (OFDM) systems using the delay diversity techniques over highly frequency selective channels. Also, we investigate the properties of the proposed scheme over different channels. Specifically, we show that the ALAMOUTI scheme with using Cyclic Delay Diversity (CDD) over some particular channels has the better performance. Then, we exemplarity implement this scheme to the DVB-T2 system. Simulation results confirm that the proposed scheme has lower bit error rate (BER), especially for high SNRs, with respect to the standard ALAMOUTI deCODEr over highly frequency-selective channels such as single frequency networks (SFN). Furthermore, the new scheme allows a high reliability and tolerability. The other advantages of the proposed method are its simplicity, flexibility and standard compatibility with respect to the conventional methods.

Interference Alignment (IA) with ALAMOUTI coding is an innovative method to increase the multiplexing gain and the diversity gain, simultaneously, in wireless Multiple-Input Multiple-Output (MIMO) systems. The main limitation of this method is requiring Perfect Channel State Information (CSI) to perform the beamforming on transmitters and receivers signals. Contrary to the acceptable performance of ALAMOUTI coding in perfect CSI conditions, its efficiency is severely reduced in imperfect CSI conditions. In order to overcome this shortcoming, this paper discusses about the effect of imperfect CSI on a two user MIMO X-channel which uses interference alignment together with ALAMOUTI coding. Also, a closed form solution is extracted for the received signal in an imperfect CSI scenario. Our analysis shows that when the variance of the CSI error is increased, the Bit Error Rate (BER) of system increases linearly. Also, we propose a joint Power Allocation (PA) and constellation rotation algorithm to improve the performance of system in an imperfect CSI scenario. Computer simulations show a desirable improvement in BER by using PA, constellation rotation and joint of them.

Terrorism is a phenomenon which considerable attention has been focused on in recent years. In this respect, the criminal CODE is one of mechanisms has been regarded to combat terrorism. Although the penal CODE is a tool to response the crimes of punishments of offenders, political entity of terrorism can separate the criminal CODE from its basic principles in order to combat terrorism procedures and establishing Tool-using for politicians. Notwithstanding this danger (risk), the criminal CODE has many privileges to the non-legal alternatives which based on the criminal CODE; it can be preferred to other methods like war. Still, the suggested method is creating a comprehensive method to combat terrorism entities which it is to employ every of these methods besides the others.