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In broadcast communications, a diversity scheme refers to a technique for enhancing the reliability of a message signal by utilizing at least two correspondence channels with various attributes. In this paper we consider all four possible scenarios: Multiple-input and multiple output (MIMO), multiple-input and single-output (MISO), single input and multi-output (SIMO), and single-input and single-output (SISO) systems. We derive the closed form expressions of channel capacity, and reformulate them irrelevant to the channel of the eavesdropper. This makes our scheme valid when the transmitter does not know any information about the eavesdropper. We investigate the solution for the capacity problem in SISO scenario at first, which can be extended to SIMO, MISO, and MIMO systems. We also analyze the channel capacity of all four types of scenarios. The comparative studies show that the channel capacity of MIMO system is higher.
Future generation of cellular communication require higher data rates and a more reliable transmission link. The information rates can be enhanced by expanding the transmission data transmission and utilizing higher transmission control. Wireless communication channels suffer from various factors such as fading problems. A diversity technique is used to improve the performance of these fading channels. In diversity techniques communication channels are supplied with multiple transmitting and receiving antennas. The signal is transmitted and received through different ways. As a result, the probabilities that all replicas of signals will fade simultaneously is reduced considerably. Concerns on wireless communication security grow rapidly with the wide application and popularity of wireless communication because it is easy to overhear communication over wireless medium. An eavesdropper can receive the radio signal from a transmitter to its intended receiver for the broadcast nature of wireless medium. Consequently, eavesdroppers can acquire the channel state information (CSI) between the transmitter and the receiver. On the contrary, the transmitter usually knows nothing about the eavesdropper, such as its location, its CSI, even its presence. Physical layer security technology aims to change the adverse situation and provide secure communication in physical layer. In the study of physical layer secrecy, it is assumed that the transmitter knows nothing about the eavesdropper, but the eavesdropper has acquired what are needed for the communication. This situation makes more difficult to realize secure communication.
This paper gives the significant highlights innovations and execution of MIMO connects and in addition SISO and MIMO limit correlation for cutting edge remote system frameworks. High information rates and execution of the framework is accomplished by appropriate framework outline of MIMO framework. It is cleared that the accomplishment of MIMO framework joining into business models, for example, 3G, 4G, WiMAX, WLAN, LTE and so forth. Along these lines, at high SNR, the limit increments directly with the quantity of receiving wires at both transmitter and beneficiary side of the MIMO framework. We have examined the conduct of MIMO frameworks that select a subset of accessible radio wires at one connection end. Important applications for such frameworks are cell frameworks with MIMO capacity. The need of choosing reception apparatuses at one connection end (rather than utilizing every one of them) stems either from many-sided quality or cost considerations.
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