Satyanarayana Vuppala

On the Performance of Relay Aided Millimeter Wave Networks

In this paper, we investigate the potential benefits of deploying relays in outdoor millimeter-wave (mmWave) networks. We study the coverage probability from sources to a destination for such systems aided by relays. The sources and the relays are modeled as independent homogeneous Poisson point processes (PPPs). We present a relay modeling technique for mmWave networks considering blockages and compute the density of active relays that aid the transmission. Two relay selection techniques are discussed, namely best path selection and best relay selection. For the first technique, we provide a closed form expression for end-to-end signal-to-noise ratio (SNR) and compute the best random relay path in a mmWave network using order statistics. Moreover, the maximum end-to-end SNR of random relay paths is investigated asymptotically by using extreme value theory. For the second technique, we provide a closed form expression for the best relay node having the maximum path gain. Finally, we analyze the coverage probability and transmission capacity of the network and validate them with simulation results. Our results show that deploying relays in mmWave networks can increase the coverage probability and transmission capacity of such systems.

An Analysis on Secure Communication in Millimeter/Micro-Wave Hybrid Networks

The secrecy outage of millimeter wave (mmWave) overlaid micro-wave (μWave) networks under the impact of blockages is analyzed, and closed form as well as integral expressions are provided. Specifically, using a network model that accounts for uncertainties both in node locations and blockages, we characterize the conditional connection outage probability and the secrecy outage probability of hybrid networks with multiple eavesdroppers under basic factors, such as density of eavesdropping nodes, antenna gain, and blockage density. The upper and lower bounds of the conditional secrecy outage probability for both the line-of-sight and non-line-of-sight links are derived. As a desirable side effect, certain factors, such as blockages and reduced antenna gain, can decrease the secrecy outage probability in mmWave networks. This can be considered as a tradeoff between outage capacity and secrecy outage capacity with respect to blockages. Hence, blockages that have been proved to be detrimental to achieving higher data rates in mmWave systems, can be helpful for systems with secrecy constraints. Finally, we have shown the coexistence of mmWave and μWave networks from a secrecy perspective.

Robust Relay Selection for Large-Scale Energy-Harvesting IoT Networks

We consider the relay selection problem in large-scale energy harvesting (EH) networks. It is known that if channel state information (CSI) is available at EH relays, a diversity order equal to the number of relays can be obtained, however, at the penalty of a feedback overhead (necessary to obtain accurate CSI) which is not suitable for energy-limited devices intended, e.g., for Internet-of-Things applications. In this paper, we therefore propose a new EH relay selection scheme which is based on the residual energy at each relay’s battery, and on information on the distribution of the channels between relays and the destination. The method thus minimizes both the outage probability and the feedback cost. Where previous work relay selection based on channel distribution information consider only small-scale fading distribution, we employ a stochastic geometry approach to consider jointly the geometrical distribution (i.e., large-scale fading) and small-scale fading yielding a simple relay selection criterion that furthermore utilizes only rough information on the relay’s location, i.e., an ordinal number from the destination. The outage probability of the proposed relay selection scheme is analytically derived, and the achievable diversity order of the proposed approach is investigated. Computer simulations confirm our theoretical analyses and show that our approach is robust against errors in the estimation of the distances between nodes.

Robust Transceiver Design for Full Duplex Multiuser MIMO Systems

We consider a weighted sum-rate maximization problem for a multiuser multiple-input multiple-output (MIMO) cellular system where a full-duplex (FD) base-station (BS) serves multiple half-duplex (HD) uplink (UL) and downlink (DL) users simultaneously while taking the imperfect channel knowledge into consideration. By exploiting the relationship between weighted sum-rate and weighted minimum-mean-squared-error problems, joint design of transceiver matrices can be obtained through an iterative convergent algorithm. Simulation results confirmed the importance of accurate channel estimation in FD systems.

On the Uplink Secrecy Capacity Analysis in D2D-Enabled Cellular Network

Recent research prove that device-to-device (D2D) communications offer substantial gain through enhancing throughput and spectral efficiency as well as widening coverage area of cellular network. However, from security perspective, performance of such network has not been well investigated. With this motive and inspired by stochastic geometry approach, we provide secrecy rate analysis for D2D-enabled cellular network under Rayleigh fading channels. The minimum distance among mobile users is used to characterize the retention probability and hence, density of D2D nodes. Moreover, a fraction of the total transmitted power from D2D nodes is allocated to radiate artificial noise (AN) to degrade the eavesdroppers channel. Under such conditions, we derive the closed-form expressions for the probability of achieving nonzero secrecy capacity for the uplink channel between user-equipment and cellular base-station in the presence of D2D nodes and eavesdropper(s). Throughout the paper, we consider the following eavesdropping strategies: 1) a single eavesdropper case; 2) multiple eavesdroppers that can cooperatively cancel the interference; 3) multiple cooperative eavesdroppers that can cooperatively cancel both the interference, and AN; and 4) the case of cooperative colluding eavesdroppers. The derived expressions are validated via simulation as a function of antenna gain, eavesdropper density, D2D hard-core distance, and D2D node density.

Secrecy outage analysis of cognitive wireless sensor networks

We examine the secrecy outage of primary links in cognitive wireless sensor networks with interference from secondary users, offering original and highly accurate expressions for the aggregate interference with fading and shadowing. It is found that the presence of shadowing has a significant impact which can swiftly increase secrecy outage. The expressions derived can also be used to obtain other analytical results such as secrecy rate and secrecy transmission capacity.

On the Physical Layer Security Analysis of Hybrid Millimeter Wave Networks

To cope up with the explosive growth of mobile data demand, the fifth-generation mobile network intents to exploit the available spectrum in millimeter-wave (mmWave) band to boost the communication capacity. However, for a potential mmWave communication to happen, challenges, as propagation losses and blockages, have to be dealt with. Abundant literature illustrating techniques to circumvent these challenges and increase the cellular capacity can be found. Among the approaches used to overcome the challenges in mmWave networks, optimal transmit precoding design, spatial reuse of mmWave base stations (BSs), and mmWave-overlaid microwave (

On the security region of best source indices in random wireless networks

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Beamforming Design for Full-Duplex MIMO Interference Channels–QoS and Energy-Efficiency Considerations

Wave) cellular networks are employed. This paper focuses on the performance analysis of mmWave-overlaid microwave cellular networks, from security perspective. We particularly developed a mathematical framework to analyze the connection outage probability, the secrecy outage probability, and the achievable average secrecy rate of the hybrid mmWave network, while taking fading and the impact of blockages into consideration. Moreover, based on the received signal strength, we formulated a scheme for a generic mobile user to be associated with either the mmWave or

An analysis on relay assisted millimeter wave networks

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