Despite the lure of a considerable increase in spectrum usage efficiency, the practical implementation of cognitive radio (CR) systems is being obstructed by the need for efficient and reliable protection mechanisms that can safeguard the quality of service (QoS) requirements of licensed users. This need becomes particularly apparent in dynamic wireless networks where channel conditions may var...

Cognitive Radio (CR) is an intelligent radio that can dynamically access the radio spectrum. Secondary users in Cognitive Radio Network (CRN) can access the licensed spectrum without causing harmful interference to primary users. The performance of cognitive radio networking functionalities depends on the properties of the spectrum band in use. This necessitates a crosslayer design in the entir...

For this purpose, a technical approach for all.and improve the spectrum utilization, cognitive radio concept has been evolved. Cognitive radios are the radio systems that autonomously coordinate the. Levels for the cognitive radio system. We have studied intelligent channel selection for transmission of data and control information based on.Fundamental Design Tradeoffs in Cognitive Radio System...

Motivated by recent developments in wireless communication, this thesis aims to characterize the secrecy performance in several types of typical wireless networks. Advanced techniques are designed and evaluated to enhance physical layer security in these networks with realistic assumptions, such as signal propagation loss, random node distribution and non-instantaneous channel state information...

Current models of causal induction are seriously compromised because they cannot represent variations in cause-effect timing. Theoretical considerations and empirical evidence converge, suggesting that cause-effect timing influences induction beyond mere interference, in line with predictions of psychophysical models of rate comparison. Rather than accepting two distinct cognitive processes for...

Communication in the presence of a priori known interference at the encoder has gained great interest because of its many practical applications. In this paper, additive exponential noise channel with additive exponential interference (AENC-AEI) known non-causally at the transmitter is introduced as a new variant of such communication scenarios‎. First, it is shown that the additive Gaussian ch...

Cognitive radio is one of the technologies promoting flexible and efficient use of radio frequency spectrum, thus solving spectrum scarcity problem. Frequency assignment is an integral part of the cognitive radio spectrum management and a critical point of success or failure of the cognitive radio concept. In this paper, cognitive radio frequency assignment with a novel interference weighting a...

In this work, we derive achievable rate regions for the three-user interference channels with asymmetric transmitter cooperation and various decoding capabilities at the receivers. The three-user channel facilitates different ways of message sharing between the transmitters. We introduce two natural ways of extending the concept of unidirectional message sharing from two users to three users (i...

The secrecy problem in the state-dependent cognitive interference channel is considered in this paper. In our model, there are a primary and a secondary (cognitive) transmitter-receiver pairs, in which the cognitive transmitter has the message of the primary one as side information. In addition, the channel is affected by a channel state sequence which is estimated partially at the cognitive tr...