173 research outputs found
On Amplify-and-Forward Relaying Over Hyper-Rayleigh Fading Channels
Relayed transmission holds promise for the next generation of wireless communication systems due to the performance gains it can provide over non-cooperative systems. Recently hyper-Rayleigh fading, which represents fading conditions more severe than Rayleigh fading, has received attention in the context of many practical communication scenarios. Though power allocation for Amplify-and-Forward (AF) relaying networks has been studied in the literature, a theoretical analysis of the power allocation problem for hyper-Rayleigh fading channels is a novel contribution of this work. We develop an optimal power allocation (OPA) strategy for a dual-hop AF relaying network in which the relay-destination link experiences hyper-Rayleigh fading. A new closed-form expression for the average signal-to-noise ratio (SNR) at destination is derived and it is shown to provide a new upper-bound on the average SNR at destination, which outperforms a previously proposed upper-bound based on the well-known harmonic-geometric mean inequality. An OPA across the source and relay nodes, subject to a sum-power constraint, is proposed and it is shown to provide measurable performance gains in average SNR and SNR outage at the destination relative to the case of equal power allocation
Secure Communications in Millimeter Wave Ad Hoc Networks
Wireless networks with directional antennas, like millimeter wave (mmWave)
networks, have enhanced security. For a large-scale mmWave ad hoc network in
which eavesdroppers are randomly located, however, eavesdroppers can still
intercept the confidential messages, since they may reside in the signal beam.
This paper explores the potential of physical layer security in mmWave ad hoc
networks. Specifically, we characterize the impact of mmWave channel
characteristics, random blockages, and antenna gains on the secrecy
performance. For the special case of uniform linear array (ULA), a tractable
approach is proposed to evaluate the average achievable secrecy rate. We also
characterize the impact of artificial noise in such networks. Our results
reveal that in the low transmit powerregime, the use of low mmWave frequency
achieves better secrecy performance, and when increasing transmit power, a
transition from low mmWave frequency to high mmWave frequency is demanded for
obtaining a higher secrecy rate. More antennas at the transmitting nodes are
needed to decrease the antenna gain obtained by the eavesdroppers when using
ULA. Eavesdroppers can intercept more information by using a wide beam pattern.
Furthermore, the use of artificial noise may be ineffective for enhancing the
secrecy rate.Comment: Accepted by IEEE Transactions on Wireless Communication
Opportunistic Relay Selection over Generalized Fading and Inverse Gamma Composite Fading Mixed Multicast Channels : A Secrecy Tradeoff
This work was supported in part by the National Research Foundation of Korea funded by the Korean Government, Ministry of Science and ICT, under Grant ICT-NRF-2020R1A2B5B02002478; and in part by Sejong University through its Faculty Research Program under Grant 20212023.Peer reviewedPublisher PD
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