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Space time block codes (STBCs) have been studied to exploit the spatial and temporal diversities in wireless systems. Orthogonal space time polarization block codes (OSTPBCs) designed using the quaternion algebra promise gains in terms of higher data rates, diversity and spectral efficiency. In this context, quaternion modulation has been proposed using the dual-polarized antennas to generate efficient selection of the polarization and optimal decoding at the receiver end. In this paper, the quaternion modulation technique has been evaluated considering the quaternionic channel using the dual-polarized antennas. The results show promising diversity gains with benefits in terms of spectral efficiency and data rates. An extension of this scheme for higher number of symbols and higher dual-polarized antenna dimensions has also been presented. The proposal includes linear decoupled decoding of the quaternion orthogonal codes (QODs) at the receiver end where the complexity stays independent of the number of transmitted symbols. The design of the quaternion modulation using the quaternionic channel fully exploits the polarization diversity in addition to unfolding its applicability for future massive multiple-input multiple-output (MIMO) wireless systems.

Over the past few decades, wireless communication aims to support high data rates and reliability and thus several techniques exploiting space, time, and polarization diversities have been used to achieve large diversity gains. Orthogonal space time block codes (OSTBC) in combination with polarization diversity promise optimal diversity gains. For dual-polarized antennas, we propose a new system model based on the quaternionic structure of the channel, which offers a way to exploit polarization diversity quite independently of other forms of diversities. Moreover, such OSTPBC achieve better throughput and provide a linear decoupled decoding solution at the receiver, which significantly reduces computational complexity.

This paper describes the indigenous development of a secure, inter-department Bulk Encryption Unit in enterprise network systems, which is a special purpose device for securing the data communication between two parties in a VPN/ enterprise network. It is a hardware which will help organizations, institutes and enterprises to protect data against eaves-droppers and will protect sensitive information against unauthorized access. The services provided by encryption equipment can be summarized as data security, traffic flow security and authentication. The equipment provides information and communication security by encrypting/decrypting data over E1 links in the tactical area. It operates in duplex traffic working mode at transmission rates over 2 Mbps. It is a very flexible encryption unit that supports direct key loading via Key Gun device. Key management and authentication is controlled by the configuration module which allows only authorized users to program the device and change keys.