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Abstract Wireless sensor networks (WSNs) offer us a potential for greater awareness of our surroundings, collecting, measuring, and aggregating parameters beyond our current abilities, and provide an opportunity to enrich our experience through context-awareness. As a typical sensor node is small with limited processing power, memory, and energy resources, in particular, these WSNs must be very energy-efficient for practical deployment. Medium access control (MAC) protocols are central to the energy-efficiency objective of WSNs, as they directly control the most energy consuming part of a sensor node: communications over the shared medium. This thesis focuses on evaluating MAC protocols within the WSN domain by, firstly, surveying a representative number of MAC protocols and their features. Secondly, three novel MAC protocols are proposed, one for layered contention-based access, one for layered scheduled access, and one for cross-layer contention-based access. Thirdly, a novel energy consumption model is proposed, and fourthly, a holistic MAC protocol evaluation model is proposed that takes into account application emphasis on performance metrics. The MAC protocols are evaluated analytically. In addition, the layered contention-based MAC protocol has been implemented and measured, and the cross-layer contention-based protocol operating over an impulse radio-ultra wideband (IR-UWB) physical layer has been verified by simulations with relevant physical layer characteristics. The energy consumption evaluation model proposed is straightforward to modify for evaluating delay, and it can reuse state transition probabilities derived from throughput analysis. The holistic application-driven MAC protocol evaluation model uses a novel single compound metric that represents a MAC protocol’s relative performance in a given application scenario. The evaluations have revealed several significant flaws in sensor MAC protocols that are adapted to sensor networking from ad hoc networks. Furthermore, it has been shown that, when taking sufficient details into account, single hop communications can outperform multi-hop communications in the energy perspective within the feasible transmission ranges provided by sensor nodes. The impulse radio physical layer introduces characteristics to MAC protocols that invalidate traditional techniques which model the physical layer in terms of simple collisions. Hence, these physical layer characteristics have been modelled and included in the analysis, which improves the level of agreements with simulated results.
Abstract LTE network is a good choice for delivering smart grid demand response (DR) traffic. However, LTE connectivity is not pervasively available due to smart meter improper positioning, limited of coverage, or base station software or hardware failures. In this paper, a solution is introduced to overcome issues relating to lack of LTE base station connectivity for user equipment (UE) considered as remote terminal units, i.e. communication interfaces connected to smart meters. The solution is an ad hoc mode for the LTE-Advanced UE. The ad hoc mode is applied to reach a relay node that is the nearest UE with base station connection. DR traffic is delivered between clusters of UEs and a relay node using multi-hop communications. Analytical Markov chain models and a Riverbed Modeler network simulation model are implemented to illustrate the functionalities and the performance when DR traffic is delivered with varying transmission power levels. A detailed physical layer propagation model for device-to-device communications, a static resource allocation in time domain, hybrid automatic repeat request retransmissions, and a capability for a UE to receive uplink transmissions are modeled both analytically and in the simulator. Both the disjoint analysis and simulations show that all packets are successfully transmitted at most with the fourth transmission attempt and the average network delay is low enough to support most of the smart grid DR applications (139.2–546.6 ms).
Abstract Smart grid (SG) demand response (DR) programs and their management attain higher importance as distributed energy generation becomes more popular in households due to reducing prices of small-scale renewable energy generation equipment. The use of public telecommunications infrastructure is a good candidate for enabling DR communications over SGs, but the LTE networks become excessively congested during peak hours and the SG DR traffic delivery can be degraded. The network simulations evaluate traffic volumes, delivery ratios, and delays of various traffic types, including SG DR communications, when an LTE macrocell network capacity is exceeded by an increased amount of typical traffic types (Skype video call, FTP, Yotube video stream, and HTTP). The results show that the SG DR traffic can be delivered, maintaining satisfactory communications performance also in a highly loaded network conditions. The QoS class of SG DR traffic transmitted in downlink direction can even be considered to be lowered below the QoS of typical traffic types.
Abstract This paper investigates the possibility of delivering distinct smart grid (SG) demand response (DR) applications in a highly loaded LTE network. In a shared LTE network, the proportion of SG DR traffic is relatively low when compared to typical traffics such as voice over IP, Skype video call, FTP, Youtube video stream, and HTTP. The quality of service (QoS) requirements for the SG DR traffics have to be fulfilled by maintaining the network delays and the packet delivery ratios within certain limits, while not causing significant hindrance to the typical traffics. The Riverbed Modeler network simulations are performed using detailed physical layer propagation models, detailed LTE functionality, and a suburban topology. In the simulation scenarios, three distinct DR applications generate varying amounts of SG DR traffic to the LTE network while the LTE capacity is exceeded by the typical traffics. The results illustrate that satisfactory performance for the SG DR traffics can be maintained due to the constant traffic characteristics and relatively low traffic amount that facilitates the scheduling of channel resources. Typically, the more a DR application generates traffic the higher hindrance it causes for the typical traffics other than the voice over IP that applies the QoS class of highest priority.
Abstract A novel neighbour network discovery mechanism targeted especially for wireless body area networks (WBANs) is defined and analysed in this paper. The Institute of Electrical and Electronics Engineers (IEEE) standard 802.15.6 and the European Telecommunications Standards Institute (ETSI) technical committee SmartBAN define physical (PHY) and medium access control (MAC) specifications for packet-based short-range communications in WBANs. Neither the aforementioned standards provides a solution for discovery of operating WBAN networks by another operating WBAN using the same standard specifications in near vicinity. The proposed method provides a SmartBAN-compliant mechanism to discover other neighbouring SmartBAN networks while maintaining uninterrupted operations of both the wireless network carrying out the discovery and the wireless networks to be discovered. A SmartBAN network operates in two physical channels: a control channel (CCH) and a data channel (DCH). The key feature of the mechanism is the utilisation of the Inactive Periods of the discovering SmartBAN’s DCH by alternating the Inactive Period durations for scanning CCH beacons of the target SmartBAN. Based on the analysis, it can be concluded that the proposed mechanism outperforms a mechanism in which the scan is performed in a fixed cyclical mode in terms of probability of discovery and discovery time. Currently, the discovery mechanism is under consideration for the revision of MAC specifications in TC SmartBAN.
Abstract The paper introduces a LoRaWAN simulation model implemented for the Riverbed Modeler (former OPNET modeler suite). First, the key components of the developed simulator solution are detailed. Then, the results of the simulator’s validation for several test scenarios are presented. The developed simulator is used to investigate the effect of collision models on the results of LoRaWAN performance simulation. Specifically, the three models are studied: a baseline — implying loss off all colliding packets, an intra spreading factor (SF) with capture effect, and intra/inter SF with capture effect. The simulations verify that the results of the baseline model are in line with that for pure Aloha, while the two other demonstrate up to two-three fold higher delivery ratio. The obtained results illustrate the substantial impact of the collision model on the accuracy of simulations and motivate the need for further practical studies for the collision and interference mechanisms within a LoRaWAN network. Based on the results obtained through simulations, several drawbacks related to the use of strictly periodic traffic in LoRaWAN networks are noted.
Abstract This paper presents an updated survey on research related to ultra wideband (UWB) communications, particularly that of impulse radio (IR) technology. In addition to the research, we survey UWB physical layer specifications of the two existing standards-the IEEE 802.15.6-2012 and the IEEE 802.15.4-2015-as well as the leading global UWB spectrum regulatory limitations which have been updated recently. The latter standard including the UWB specifications was first published in 2007 and the latest revision dates to 2015. The focus in this paper is the period from 2007 to 2015. Our purpose is to provide an in-depth survey with a clearly specified topic together with the standard specifications and the related regulatory restrictions. Additionally, the last part of this paper discusses the possibilities of increasing the current IR-UWB data rates to meet increasing future demands.
Abstract In this paper we advocate the use of device-to-device (D2D) communications in a LoRaWAN Low Power Wide Area Network (LPWAN). After overviewing the critical features of the LoRaWAN technology, we discuss the pros and cons of enabling the D2D communications for it. Subsequently we propose a network-assisted D2D communications protocol and show its feasibility by implementing it on top of a LoRaWAN-certified commercial transceiver. The conducted experiments show the performance of the proposed D2D communications protocol and enable us to assess its performance. More precisely, we show that the D2D communications can reduce the time and energy for data transfer by 6 to 20 times compared to conventional LoRaWAN data transfer mechanisms. In addition, the use of D2D communications may have a positive effect on the network by enabling spatial re-use of the frequency resources. The proposed LoRaWAN D2D communications can be used for a wide variety of applications requiring high coverage, e.g. use cases in distributed smart grid deployments for management and trading.
Abstract Vehicle-to-vehicle (V2V) communication plays a pivotal role in intelligent transport systems (ITS) with cellular-vehicle to everything (C-V2X) and IEEE 802.11p being the two competing enabling technologies. This paper presents multi-dimensional discrete-time Markov chain (DTMC) based models to study the medium access control (MAC) layer performance of the IEEE 802.11p standard and C-V2X Mode 4, considering periodic cooperative awareness messages (CAMs) and event-driven decentralized environmental notification messages (DENMs). Closed-form solutions for the models’ steady-state probabilities are obtained, which are then utilized to derive expressions for several key performance metrics. Numerical results are provided to draw insights on the performance. In particular, a performance comparison between IEEE 802.11p and C-V2X Mode 4 in terms of the average delay, the collision probability, and the channel utilization is presented. The results show that IEEE 802.11p is superior in terms of average delay, whereas C-V2X Mode 4 excels in collision resolution. The paper also includes design insights on possible future MAC layer performance enhancements of both standards.
Abstract The enhanced distributed channel access (EDCA) mechanism enables IEEE 802.11p to accommodate differential quality of service (QoS) levels in vehicle-to-vehicle (V2V) communications, through four access categories (ACs). This paper presents multi-dimensional discrete-time Markov chain (DTMC) based model to study the effect of parallel operation of the ACs on the medium access control (MAC) layer performance of ITS-G5 IEEE 802.11p. The overall model consists of four queue models with their respective traffic generators, which are appropriately linked with the DTMCs modeling the operation of each AC. Closed-form solutions for the steady-state probabilities of the models are obtained, which are then utilized to derive expressions for key performance indicators at the MAC layer. An application for a highway scenario is presented to draw insights on the performance. The results show how the performance measures vary among ACs according to their priority levels, and emphasize the importance of analytical modeling of the parallel operation of all four ACs.
Abstract Supporting parallel multi-priority data streams is vital for maintaining the quality of service (QoS) in vehicle-to-everything (V2X) communication. Hence, the European telecommunications standard institute (ETSI) has defined four packet types, with varying priority levels, to be used as broadcast packets in such communication. This paper studies the medium access control (MAC) layer performance of IEEE 802.11p and cellular-V2X (C-V2X) Mode 4 using discrete-time Markov chain (DTMC) based models, while considering parallel multi-priority data streams. The overall model consists of four queue models with their respective traffic generators, which are appropriately linked with the DTMCs modeling the MAC layer operations of IEEE 802.11p and C-V2X Mode 4. Closed-form solutions for the steady-state probabilities of the models are obtained, which are then utilized to derive expressions for key performance indicators at the MAC layer. Numerical results are provided to draw insights on the MAC layer performance of the two technologies. IEEE 802.11p is comparatively superior in average delay, and at maintaining fairness among multi-priority data streams, whereas C-V2X Mode 4 exhibits better collision resolution, which leads to its higher throughput. The paper also includes design insights on possible performance enhancements for future releases.
Abstract This paper proposes a multi-dimensional Markov model to evaluate the medium access control (MAC) layer performance of 3GPP cellular vehicle to everything (V2X) Mode 4. The Mode 4 specifications enable quality of service guarantees in a decentralized manner, without the connectivity of a cellular base station, and therefore, ideal for V2X messaging in intelligent transportation systems (ITS). To this end, periodic cooperative aware messages (CAMs) and event triggered decentralized environmental notification messages (DENMs) are considered in the paper. The discrete time Markov model consists of a node model, a queue model, and traffic generators for CAM and DENM packets that are dependent and solved in closed form and iteratively. The model is applied to a highway scenario to provide insights on the average delay, the collision probability, and the channel utilization in Mode 4. The results show that Mode 4 has been partially over-specified for ITS applications and able to serve CAMs and DENMs conveniently. However, there exists locally optimal combinations of CAM and DENM intervals that can lead to lower average delay.
Abstract In this paper, a throughput- and channel-aware (TCA) medium access control (MAC) scheduling scheme is presented and evaluated for smart body area network (SmartBAN) standard, developed by the European Telecommunication Standard Institute (ETSI). The presented algorithm utilizes the radio link signal-to-noise ratio (SNR) to select the candidate nodes for a given time slot in the first phase, while, in the second phase, the slot is assigned to one of the chosen nodes based on their priority level and data packet availability. The algorithm uses an m-periodic scheduling technique, in which the nodes are considered for slot assignment according to their data packet generation rates during the second phase. Subsequently, a comprehensive explanation of the TCA algorithm execution through the slot reassignment method in SmartBAN is provided. For performance comparison, we use four key performance indicators (KPIs), which include packet reception rate (PRR), latency, energy consumption per successful transmission, and throughput. The simulation results indicate a significant performance gain of the SmartBAN-complaint TCA algorithm in terms of PRR and energy efficiency over the reference SmartBAN MAC scheduling with and without repetition. The average improvement in the PRR results is approximately 40%, whereas a maximum enhancement of 66% is observed in terms of energy efficiency while satisfying the throughput and latency requirements of the use case considered during simulations. Furthermore, we introduce some enhancements in the primary TCA to decrease the frequency of TCA execution via slot re-assignment frames transmission for reducing energy consumption, which results in a slight improvement of energy efficiency.
Abstract Scheduling fast uplink grant transmissions for machine type communications (MTCs) is one of the main challenges of future wireless systems. In this paper, a novel fast uplink grant scheduling method based on the theory of multi-armed bandits (MABs) is proposed. First, a single quality-of-service metric is defined as a combination of the value of data packets, maximum tolerable access delay, and data rate. Since full knowledge of these metrics for all machine type devices (MTDs) cannot be known in advance at the base station (BS) and the set of active MTDs changes over time, the problem is modeled as a sleeping MAB with stochastic availability and a stochastic reward function. In particular, given that, at each time step, the knowledge on the set of active MTDs is probabilistic, a novel probabilistic sleeping MAB algorithm is proposed to maximize the defined metric. Analysis of the regret is presented and the effect of the prediction error of the source traffic prediction algorithm on the performance of the proposed sleeping MAB algorithm is investigated. Moreover, to enable fast uplink allocation for multiple MTDs at each time, a novel method is proposed based on the concept of best arms ordering in the MAB setting. Simulation results show that the proposed framework yields a three-fold reduction in latency compared to a maximum probability scheduling policy since it prioritizes the scheduling of MTDs that have stricter latency requirements. Moreover, by properly balancing the exploration versus exploitation tradeoff, the proposed algorithm selects the most important MTDs more often by exploitation. During exploration, the sub-optimal MTDs will be selected, which increases the fairness in the system, and, also provides a better estimate of the reward of the sub-optimal MTD.
Abstract Ensuring an effective coexistence of conventional broadband cellular users with machine type communications (MTCs) is challenging due to the interference from MTCs to cellular users. This interference challenge stems from the fact that the acquisition of channel state information (CSI) from machine type devices (MTD) to cellular base stations (BS) is infeasible due to the small packet nature of MTC traffic. In this paper, a novel approach based on the concept of opportunistic spatial orthogonalization (OSO) is proposed for interference management between MTC and conventional cellular communications. In particular, a cellular system is considered with a multi-antenna BS in which a receive beamformer is designed to maximize the rate of a cellular user, and, a machine type aggregator (MTA) that receives data from a large set of MTDs. The BS and MTA share the same uplink resources, and, therefore, MTD transmissions create interference on the BS. However, if there is a large number of MTDs to chose from for transmission at each given time for each beamformer, one MTD can be selected such that it causes almost no interference on the BS. A comprehensive analytical study of the characteristics of such an interference from several MTDs on the same beamformer is carried out. It is proven that, for each beamformer, an MTD exists such that the interference on the BS is negligible. To further investigate such interference, the distribution of the signal-to-interference-plus-noise ratio (SINR) of the cellular user is derived, and, subsequently, the distribution of the outage probability is presented. However, the optimal implementation of OSO requires the CSI of all the links in the BS, which is not practical for MTC. To solve this problem, an online learning method based on the concept of contextual multi-armed bandits (MAB) learning is proposed. The receive beamformer is used as the context of the contextual MAB setting and Thompson sampling: a well-known method of solving contextual MAB problems is proposed. Since the number of contexts in this setting can be unlimited, approximating the posterior distributions of Thompson sampling is required. Two function approximation methods, a) linear full posterior sampling, and, b) neural networks are proposed for optimal selection of MTD for transmission for the given beamformer. Simulation results show that is possible to implement OSO with no CSI from MTDs to the BS. Linear full posterior sampling achieves almost 90% of the optimal allocation when the CSI from all the MTDs to the BS is known.
Abstract This paper presents experimental validation of a distributed optimization-based voltage control system. The dual-decomposition method is used in this paper to solve the voltage optimization problem in a fully distributed way. Device-to-device communication is implemented to enable peer-to-peer data exchange between agents of the proposed voltage control system. The paper presents the design, development and hardware setup of a laboratory-based testbed used to validate the performance of the proposed dual-decomposition-based peer-to-peer voltage control. The architecture of the setup consists of four layers: microgrid, control, communication, and monitoring. The key question motivating this research was whether distributed voltage control systems are a technically effective alternative to centralized ones. The results discussed in this paper show that distributed voltage control systems can indeed provide satisfactory regulation of the voltage profiles.
Abstract Selection of the most appropriate communications technology for a smart grid (SG) application is far from trivial. We propose such a feasibility assessment starting from identification of key performance indicators (KPIs) required for peer-to-peer (P2P) energy trading and grid control operations from a communications perspective. A set of cross-disciplinary KPIs, both quantitative and qualitative, are considered from communications, power, business, actor involvement, financial, and demand side management categories. They serve as a general baseline for use cases, as there have been few previous works attempting to capture the essential features of P2P SG operations. The KPIs are briefly identified along with their relations to P2P energy trading and grid control. A straightforward comparison of the quantitative and qualitative KPIs’ impact on technology selection is not feasible. This paper addresses the comparison with: 1) a prioritization of the KPIs using the analytic hierarchy process; 2) a comparison of technology solutions evaluated in our previous works against the KPIs’ requirements; and 3) a total feasibility evaluation of the solutions against selected KPIs. The prioritization shows latency, reliability, security, scalability, robustness, costs of information and communication technologies (ICT) devices, and costs of ICT deployment are the most important KPIs in enabling P2P energy trading and grid control. Further, the technology feasibility assessment enables identification of the most suitable candidates for an SG application.
Abstract This paper provides a view to Peer-to-Peer (P2P) approach for smart grid operation adopted in P2P-SmarTest project. It provides an overview on solutions proposed for distributed P2P energy trading, P2P grid control and wireless communication enabling the proposed P2P operation. The paper proposes some business models that can be adopted in a P2P setting. We also outline the barriers and enablers against and for adopting local or regional P2P based electricity operations.