Internet of Things-aided Smart Grid: Technologies, Architectures, Applications, Prototypes, and Future Research Directions

Traditional power grids are being transformed into Smart Grids (SGs) to address the issues in existing power system due to uni-directional information flow, energy wastage, growing energy demand, reliability and security. SGs offer bi-directional energy flow between service providers and consumers, involving power generation, transmission, distribution and utilization systems. SGs employ various devices for the monitoring, analysis and control of the grid, deployed at power plants, distribution centers and in consumers' premises in a very large number. Hence, an SG requires connectivity, automation and the tracking of such devices. This is achieved with the help of Internet of Things (IoT). IoT helps SG systems to support various network functions throughout the generation, transmission, distribution and consumption of energy by incorporating IoT devices (such as sensors, actuators and smart meters), as well as by providing the connectivity, automation and tracking for such devices. In this paper, we provide a comprehensive survey on IoT-aided SG systems, which includes the existing architectures, applications and prototypes of IoT-aided SG systems. This survey also highlights the open issues, challenges and future research directions for IoT-aided SG systems

Baseband Radio over Fiber Aided Millimeter-Wave Distributed Antenna for Optical/Wireless Integration

A Baseband Radio Over Fiber (BROF) architecture is proposed, where upto four Radio Frequency (RF) carriers can be generated, while using the heterodyne photo-detection of only two optical signals. This proposed BROF architecture has a star-like structure and it is composed of six Radio Access Units (RAUs), where data is transmitted from the Central Unit (CU) to the Base Station (BS) and from the BS to the RAU over a distance of 20 Km and 0.3 Km, respectively, at a rate of 768 Mbps. The performance of the system supporting four carrier frequencies drops by at most 1dB, at a BER of 10-9, compared to conventional heterodyne photo-detection

Boosting Fronthaul Capacity: Global Optimization of Power Sharing for Centralized Radio Access Network

The limited fronthaul capacity imposes a challenge on the uplink of centralized radio access network (C-RAN). We propose to boost the fronthaul capacity of massive multiple-input multiple-output (MIMO) aided C-RAN by globally optimizing the power sharing between channel estimation and data transmission both for the user devices (UDs) and the remote radio units (RRUs). Intuitively, allocating more power to the channel estimation will result in more accurate channel estimates, which increases the achievable throughput. However, increasing the power allocated to the pilot training will reduce the power assigned to data transmission, which reduces the achievable throughput. In order to optimize the powers allocated to the pilot training and to the data transmission of both the UDs and the RRUs, we assign an individual power sharing factor to each of them and derive an asymptotic closed-form expression of the signal-to-interference-plus-noise for the massive MIMO aided C-RAN consisting of both the UD-to-RRU links and the RRU-to-baseband unit (BBU) links. We then exploit the C-RAN architecture's central computing and control capability for jointly optimizing the UDs' power sharing factors and the RRUs' power sharing factors aiming for maximizing the fronthaul capacity. Our simulation results show that the fronthaul capacity is significantly boosted by the proposed global optimization of the power allocation between channel estimation and data transmission both for the UDs and for their host RRUs. As a specific example of 32 receive antennas (RAs) deployed by RRU and 128 RAs deployed by BBU, the sum-rate of 10 UDs achieved with the optimal power sharing factors improves 33\% compared with the one attained without optimizing power sharing factors

A Full-Duplex Diversity-Assisted Hybrid Analogue/Digitized Radio Over Fibre for Optical/Wireless Integration

A duplex Radio Over Fibre (ROF) ring architecture is proposed taking into account the constraints imposed by the cost of fibre laying and of the optical/electronic components, as well as the spectral efficiency and the duplex link performance. It has been shown that relying on Analogue ROF (AROF) and state-of-the-art Digitized ROF (DROF) architectures for downlink and uplink transmission, respectively, attains a high-integrity duplex performance. A sophisticated amalgam of Optical Carrier Suppression (OCS), Code Division Multiplexing (CDM), optical frequency multiplexing, Optical Carrier Reuse (OCR) and distributed antennas is conceived

Imperfect Digital Fibre Optic Link Based Cooperative Distributed Antennas with Fractional Frequency Reuse in Multicell Multiuser Networks

The achievable throughput of the entire cellular area is investigated, when employing fractional frequency reuse techniques in conjunction with realistically modelled imperfect optical fibre aided distributed antenna systems (DAS) operating in a multicell multiuser scenario. Given a fixed total transmit power, a substantial improvement of the cell-edge area's throughput can be achieved without reducing the cell-centre's throughput. The cell-edge's throughput supported in the worst-case direction is significantly enhanced by the cooperative linear transmit processing technique advocated. Explicitly, a cell-edge throughput of $\eta=5$ bits/s/Hz may be maintained for an imperfect optical fibre model, regardless of the specific geographic distribution of the users

Sum-Rate Analysis for High Altitude Platform (HAP) Drones with Tethered Balloon Relay

High altitude platform (HAP) drones can provide broadband wireless connectivity to ground users in rural areas by establishing line-of-sight (LoS) links and exploiting effective beamforming techniques. However, at high altitudes, acquiring the channel state information (CSI) for HAPs, which is a key component to perform beamforming, is challenging. In this paper, by exploiting an interference alignment (IA) technique, a novel method for achieving the maximum sum-rate in HAP-based communications without CSI is proposed. In particular, to realize IA, a multiple-antenna tethered balloon is used as a relay between multiple HAP drones and ground stations (GSs). Here, a multiple-input multiple-output X network system is considered. The capacity of the considered M*N X network with a tethered balloon relay is derived in closed-form. Simulation results corroborate the theoretical findings and show that the proposed approach yields the maximum sum-rate in multiple HAPs-GSs communications in absence of CSI. The results also show the existence of an optimal balloon's altitude for which the sum-rate is maximized.Comment: Accepted in IEEE Communications Letter