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.

Massive Multiple-Input-Multiple-Output (MIMO) systems deploying a large number of antennas at the base station (BS) have been shown to produce high spectral and energy efficiency (EE) under the assumptions of increasing BS physical space and critical antenna spacing. We examine the deployment of massive MIMO systems and resulting EE with a more realistic scenario considering a 2D rectangular array with increasing antenna elements within a fixed physical space. Mutual coupling and correlation among the BS antennas are incorporated by deriving a practical mutual coupling matrix which considers coupling among all antenna elements within a BS. We also provide a realistic analysis of the energy consumption using a model, which takes into account the circuit power consumptions as a function of the number of BS antennas and then present a performance analysis of two practical low complexity detectors/receivers keeping EE into consideration. The simulation results obtained show that EE does not monotonically increase with the number of BS antennas. On the contrary, it is a decreasing concave or quasi-concave function of the number of BS antennas depending on the detection technique used at the receiver. We also show that with decreasing spacing between the antennas, mutual coupling increases, contributing towards reduction in EE. Our analysis thus shows that EE does not increase infinitely in a massive MIMO system when the increasing number of antennas are to be accommodated within a fixed physical space and the total power consumed is considered to be a function of the antennas. Accordingly, closed-form expressions for the optimum number of antennas to attain maximum EE for zero forcing (ZF) are obtained.

In this work, the feasibility of spectrum sharing between a multiple-input multiple-output (MIMO) radar system (RS) and a MIMO cellular system (CS), comprising of a full duplex (FD) base station (BS) serving multiple downlink and uplink users at the same time and frequency is investigated. While a joint transceiver design technique at the CS's BS and users is proposed to maximise the probability of detection (PoD) of the MIMO RS, subject to constraints of quality of service (QoS) of users and transmit power at the CS, null-space based waveform projection is used to mitigate the interference from RS towards CS. In particular, the proposed technique optimises the performance of PoD of RS by maximising its lower bound, which is obtained by exploiting the monotonically increasing relationship of PoD and its non-centrality parameter. Numerical results show the utility of the proposed spectrum sharing framework, but with certain trade-offs in performance corresponding to RS's transmit power, RS's PoD, CS's residual self interference power at the FD BS and QoS of users.Index Terms-Multiple-input multiple-output (MIMO), fullduplex (FD), spectrum sharing, MIMO radar, quality-of-service (QoS), transceiver design, convex optimization.

We conducted a search for technosignatures in 2018 and 2019 April with the L-band receiver (1.15–1.73 GHz) of the 100 m diameter Green Bank Telescope. These observations focused on regions surrounding 31 Sun-like stars near the plane of the Galaxy. We present the results of our search for narrowband signals in this data set, as well as improvements to our data processing pipeline. Specifically, we applied an improved candidate signal detection procedure that relies on the topographic prominence of the signal power, which nearly doubles the signal detection count of some previously analyzed data sets. We also improved the direction-of-origin filters that remove most radio frequency interference (RFI) to ensure that they uniquely link signals observed in separate scans. We performed a preliminary signal injection and recovery analysis to test the performance of our pipeline. We found that our pipeline recovers 93% of the injected signals over the usable frequency range of the receiver and 98% if we exclude regions with dense RFI. In this analysis, 99.73% of the recovered signals were correctly classified as technosignature candidates. Our improved data processing pipeline classified over 99.84% of the ∼26 million signals detected in our data as RFI. Of the remaining candidates, 4539 were detected outside of known RFI frequency regions. The remaining candidates were visually inspected and verified to be of anthropogenic nature. Our search compares favorably to other recent searches in terms of end-to-end sensitivity, frequency drift rate coverage, and signal detection count per unit bandwidth per unit integration time.

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. Upper and lower bounds of the conditional secrecy outage probability for both 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 which have been proved to be detrimental for 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. Index Terms-Secrecy outage, random networks, blockages, millimeter wave I. INTRODUCTION In recent years, the explosive growth of mobile data traffic has led to an ever-growing demand for much higher capacity and lower latency in wireless networks. It has culminated in the development of the fifth generation (5G) wireless communication systems, expected to be deployed by the year 2020, with key goals of data rates in the range of Gbps, billions of connected devices, lower latency, improved coverage and reliability, and low-cost, energy efficient and environmentfriendly operation. To meet the ever-increasing demands, and keeping in mind that the current wireless spectrum is almost saturated, it is imperative to shift the paradigm of cellular spectrum to a new range of frequencies. In this regard, millimeter wave (mmWave) bands with significant amounts of unused or lightly used bandwidths appear to be a viable way to move forward. With bands of 20-100 GHz available for communication, mmWave can be the cornerstone in the design of 5G networks. MmWave bands are weak and cannot penetrate through obstacles like buildings, concrete walls, vehicles, trees etc. Due to these limitations, such bands were not considered

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We consider a K link multiple-input multiple-output (MIMO) interference channel where each link consists of two full-duplex (FD) nodes. Two transmit beamforming design problems are solved, i) sum-power minimization problem subject to rate constraints, and ii) energy-efficiency maximization problem subject to individual power constraints. To tackle the sumpower minimization problem, we first generalize the well-known relationship between weighted-sum-rate (WSR) and weighted minimum-mean-squared-error (WMMSE) problems, originally used to solve the sum-rate maximization problems, and then propose a low complexity centralized algorithm which converges to a stationary point. To decrease the exchange of a huge amount of data and excessive signaling traffic among the nodes, a distributed algorithm is also proposed. For the energy-efficiency maximization problem, the original fractional form optimization problem is first transformed into an equivalent subtractiveform optimization problem by exploiting the properties of fractional programming, and then perform a dual-layer optimization scheme. In the outer layer, the energy-efficiency parameter is searched using a simple one-dimensional search, and in the inner layer, the relationship between WSR and WMMSE is exploited to solve the subtractive form optimization problem. Since the proposed algorithms require perfect channel-state-information (CSI), which is difficult to acquire in practice, we also propose a robust design, by taking the imperfect channel knowledge into consideration. It is shown in the simulations that the sum-power achieved in FD mode depends heavily on the transmitter/receiver distortion. Also the energy-efficiency of FD systems is lower than that of half-duplex (HD) systems, as FD nodes need to overcome self-interference and increased inter-user interference which leads to high power consumption.

In this paper, we investigate a full duplex (FD) multiuser non-orthogonal multiple access (NoMA) communication system, based on the optimization of received signalto-interference-plus-noise ratio (SINR) per unit power. Since the communication system operates in FD mode, co-channel interference (CCI) and self-interference (SI) dominate the system's performance. Accordingly, to combat the CCI, we adopt a gametheoretic approach and propose users clustering algorithms and to suppress the SI, we formulate an optimization problem to maximize the power-normalized SINR (PN-SINR). While the user clustering optimization problem is constrained by i) the successive interference cancellation (SIC) constraint and ii) two binary constraints for the allocations of UL and DL users, the PN-SINR problem is constrained by i) total transmit power budget at the base station and uplink (UL) users, ii) the fundamental condition for the implementation of successive interference cancellation in NoMA, and iii) the minimum fairness condition for UL users. The original PN-SINR problem is non-convex and hence is converted into an equivalent subtractive-form problem, after which we propose an iterative algorithm to find the optimal power allocation policy. Properties of all the proposed algorithms are thoroughly investigated and numerical results are provided. Based on the channel conditions and suppression level of SI and CCI, the superiority of the proposed FD-NoMA system over half duplex NoMA and FD orthogonal multiple access systems is verified.