Abstract-We investigate the physical layer (PHY) security of a system with a base-station (BS), a legitimate user, and an eavesdropper, whose exact location is unknown but within a ring-shaped area around the BS. To this end, we present novel closed-form expressions for the secrecy outage probability, which take into consideration both the impact of fading, as well as the eavesdropper's location uncertainty. The derived expressions are validated through simulations, which reveal that the level of uncertainty should be seriously taken into account in the design and deployment of a wireless system with PHY security.

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We evaluate and quantify the joint effect of fading and multiple interferers on the physical-layer (PHY) security of a system consisted of a base-station (BS), a legitimate user, and an eavesdropper. To this end, we present a novel closed-form expression for the secrecy outage probability, which takes into account the fading characteristics of the wireless environment, the location and the number of interferers, as well as the transmission power of the BS and the interference. The results reveal that the impact of interference should be seriously taken into account in the design and deployment of a wireless system with PHY security.Index Terms-Interference, Secrecy Outage Probability, Physical layer security.

Polar codes have recently been proven to be capacity achieving for the physically degraded relay channel and relevant coding schemes have been proposed in the literature. In this paper, we deal with the design of polar codes in decode-andforward relaying and prove that the selective transmission of the relay to the destination, based on the decision of a detector of erroneous decoding -a method which we call "smart" relaying -can significantly improve the error probability performance. Furthermore, we propose a design for the aforementioned detector, that can be applied on the successive cancellation decoding of polar codes. Simulation results are presented to illustrate the efficiency of the proposed method.

This paper deals with the performance assessment of the Long Term Evolution (LTE)-Advanced Release 12 physical downlink channel, emphasizing on the Carrier Aggregation (CA) technology and its recent advances, such as the challenging interband non-contiguous solution. By processing the LTE-Advanced waveforms in the time domain (instead of the more common baseband), we describe the underlying system model and the associated simulation setup in detail. The error performance of the system is evaluated under different physical layer parameters and CA scenarios, according to the latest updates of the Third Generation Partnership Project (3GPP) technical specifications. Our analysis reveals that the Heterogeneous Band (HetBand) non-contiguous CA technology can be efficiently applied to the design of next generation mobile broadband networks, given that the exploitation of both unlicensed and frequency dispersed bands might be a promising solution against the spectrum scarcity.