Duty-cycled Medium Access Control Research Articles

Empirical Analysis of Extended QX-MAC for IOT-Based WSNS

The Internet of Things (IoT) connects our world in more ways than we imagine. Wireless sensor network (WSN) technology is at the core of implementing IoT architectures. Although WSN applications give us enormous opportunities, their deployment is challenging because of the energy constraint in sensor nodes. The primary design objective of WSNs is therefore to maximize energy efficiency. Enhancing network quality of service (QoS), such as latency, is another crucial factor, particularly for different delay-sensitive applications. Medium access control (MAC) protocols are of paramount importance to achieve these targets. Over the years, several duty-cycled MAC protocols were proposed. Among them, the strobed preamble approach introduced in X-MAC has gained much interest in IoT field because of its several theoretical advantages. However, X-MAC is highly efficient only under light traffic. Under heavy traffic, X-MAC incurs high per-packet overhead and extra delay. In addition, X-MAC has several design flaws that can significantly degrade network performance. In this paper, we point out some specific malfunctions in the original X-MAC design and propose alternatives to reduce their impact. We present an energy-efficient, traffic-adaptive MAC protocol called QX-MAC that addresses the foreseen shortcomings in X-MAC. QX-MAC integrates Q-learning and the more bit scheme to enable the nodes to adapt the active period and duty cycle in accordance with incoming traffic. Finally, the performance of QX-MAC is thoroughly analyzed compared with other reference protocols to validate its efficacy. Our QX-MAC simulation results demonstrate substantial improvements in overall network performance in terms of energy consumption, packet loss, delay, or throughput.

A Scalable and Energy-Efficient MAC Protocol for Linear Sensor Networks

Linear topologies arise naturally in the context of Internet-of-Things (IoT) applications for smart cities, where the infrastructure itself commonly has a linear or semi-linear structure. This is the case of buildings, public transportation systems, road infrastructure, and utility distribution networks. Given the prevalence of this type of topologies, several Medium Access Control (MAC) protocols have been designed to take advantage of their particular properties. Unfortunately, most of them do not scale well as the node density and the distance in hops to the sink increases. The result is that packets generated many hops away from the sink tend to experience unacceptable high end-to-end delay and low delivery probabilities. This paper introduces HP-MAC, a synchronized duty-cycled MAC protocol for Linear Sensor Networks (LSNs) that assigns transmission priorities to nodes to avoid collisions, through the implementation of distributed elections based on hash functions. HP-MAC also implements a packet queuing scheme that acts as a mechanism to control the amount of network resources allocated to data flows generated at different distances to the sink. This way, packets can reach their destination with loss probability and end-to-end delay that do not depend on their distance to the sink. We use a Discrete-Time Markov Chain (DTMC) to model the performance of the proposed protocol. Numerical solutions of this model show that HP-MAC outperforms state-of-the-art representatives in terms of throughput, end-to-end delay, power consumption, and packet loss probability. These results are validated through extensive discrete-event simulations.

A synchronous duty-cycled reservation based MAC protocol for underwater wireless sensor networks

To design an energy-efficient Medium Access Control (MAC) protocol for the Underwater Wireless Sensor Networks (UWSNs) is an urgent research issue since depleted batteries cannot be recharged or replaced in the underwater environment. Moreover, the underwater acoustic channels are affected by hindrances such as long propagation delay and limited bandwidth, which appear in the design of the MAC protocol for the UWSNs. The available MAC protocols for the terrestrial wireless sensor networks exhibit low performance in energy efficiency, throughput and reliability in the UWSNs, and cannot be used in the UWSNs directly because of their unique characteristics. This paper proposes a synchronous duty-cycled reservation-based MAC protocol named Ordered Contention MAC (OCMAC) protocol. The basic mechanism of this protocol is to schedule data transmission by transmitters through the scheduling of Ready To Send (RTS) frames. The protocol eliminates the possible collision during data transmission and improves communication efficiency. The paper analyzes the performance in energy efficiency, throughput and reliability of the protocol by modeling the queuing behavior of OCMAC with a Markov Chain process. Furthermore, the analytical model is validated through a simulation study. The analysis results demonstrated that while providing good throughput and reliability, OCMAC can achieve energy saving.

Towards an Improved Energy Efficient and End-to-End Secure Protocol for IoT Healthcare Applications

In this paper, we proposed LCX-MAC (local coordination X-MAC) as an extension of X-MAC. X-MAC is an asynchronous duty cycle medium access control (MAC) protocol. X-MAC used one important technique of short preamble which is to allow sender nodes to quickly send their actual data when the corresponding receivers wake up. X-MAC node keeps sending short preamble to wake up its receiver node, which causes energy, increases transmission delay, and makes the channel busy since a lot of short preambles are discarded, as these days Internet of Things (IoT) healthcare with different sensor nodes for the healthcare is time-critical applications and needs a quick response. A possible improvement over X-MAC is that local information of each node will share with its neighbour node. This local information exchanged will cause much less overhead than in the nodes which are synchronized. To calculate the effect of this the local coordination on X-MAC in this paper, we built an analytical model of LCX-MAC that incorporates the local coordination in X-MAC. The analytical results show that LCX-MAC outperformed X-MAC and X-MAC/BEB in terms of throughput, delay, and energy.

A Survey on the Evolution of Opportunistic Routing with Asynchronous Duty-Cycled MAC in Wireless Sensor Networks.

Wireless sensor networks (WSNs) have been used for environmental monitoring and reporting for many decades. Energy consumption is a significant research topic because wireless sensor nodes are battery-operated to be highly energy-constrained. Several strategies have been introduced in routing and MAC (Medium Access Control) layer protocols to facilitate energy saving. At the routing layer, an energy-efficient routing protocol, known as opportunistic routing (OR), has been designed to improve efficiency. OR achieves energy efficiency via load-balancing, which forwards packets along multiple routes over WSNs. At the MAC layer, an energy-efficient MAC protocol known as the asynchronous duty-cycled MAC (ADCM) protocol achieves energy saving by turning on and off a sensor node’s transmitter and receiver to eliminate unnecessary energy wastage. These protocols each have their own advantages and disadvantages. OR achieves energy efficiency at the routing layer but it raises an issue at the MAC layer. ADCM achieves energy efficiency at the MAC layer, but it hinders the packet forwarding efficiency of the OR. To attain better energy efficiency, a combination of these two ideas led to the development of OR with asynchronous duty-cycled MAC (OR-ADCM). However, even with better energy efficiency, limitations still exist in combining load-balancing and duty-cycling due to conflicts in the inherent properties of OR and ADCM. In this paper, we present a survey of the evolution of OR-ADCM over WSNs to help the reader better understand and appreciate the details of this tradeoff, which we hope will lead to the development of better protocol designs.

Intelligent Sharing for LTE and WiFi Systems in Unlicensed Bands: A Deep Reinforcement Learning Approach

Operating LTE networks in unlicensed bands together with legacy WiFi systems is deemed as a promising technique to support explosively growing mobile traffic. In conventional LTE/WiFi spectrum sharing schemes, LTE systems need to know WiFi traffic demands for optimizing system parameters to protect WiFi systems, for which the two systems are required to cooperate with each other via signallings exchanges. However, it is difficult to establish a dedicated channel among the two independent systems for exchanging signallings. Hence, in this paper, we propose an intelligent duty-cycle medium access control protocol to realize the effective and fair spectrum sharing between LTE and WiFi systems without requiring signalling exchanges. Specifically, we first design a duty-cycle spectrum sharing framework, which allows an LTE system to share the spectrum with a WiFi system by using time sharing. After that, we develop deep reinforcement learning (DRL)-based algorithms to learn WiFi traffic demands by analyzing WiFi channel activity, e.g., the idleness/business of WiFi channels, which can be observed by the LTE system via monitoring WiFi channels. Based on the learnt knowledge, the LTE system can adaptively optimize LTE transmission time to maximize its own throughput and meanwhile to provide sufficient protection to the WiFi system. Simulation results show that, in terms of LTE throughput and WiFi protection, the performance of the proposed intelligent scheme can approach that of the genie-aided exhaustive search algorithm, which needs the perfect knowledge of WiFi traffic demands through massive signalling exchanges and is of high computational complexity.

A Wake-Up Radio-Based MAC Protocol for Autonomous Wireless Sensor Networks

Wireless sensor networks (WSNs) with energy harvesting capabilities have drawn increasing attention in the last few years, as they enable long-term monitoring applications. However, the level of power harvested is usually limited to few mW. To improve the energy efficiency of WSNs, many power management techniques have been proposed to adjust the quality of service according to the harvested energy fluctuations. As wireless communications consume a major fraction of the available energy, numerous medium access control (MAC) protocols have been proposed to minimize energy consumption, latency, and data collisions. In this paper, we present an innovative MAC protocol for energy-harvesting based WSNs exploiting ultralow-power wake-up radios. To overcome the limited range typical of wake-up radios, a multi-hop wake-up scheme based on a dual radio system is proposed enabling asynchronous communications between a base station and any node of the network while maintaining a low latency and a high energy efficiency. To reduce energy consumption, wake-up calls and data packets are transmitted using two distinct data rates. Combined with destination address decoding, using a higher data rate for data transmission also minimizes the risk of collisions. Our approach has been applied to monitoring applications composed of autonomous sensor nodes powered by indoor light energy. OMNeT++ simulation results demonstrate the benefits of our wake-up radio-based approach in terms of energy, latency, and collisions when compared with the state-of-the-art duty-cycled MAC protocols. Experiments performed with real WSN platforms equipped with a wake-up radio prototype confirm the efficiency of our approach.

Sleepy Devices Versus Radio Duty Cycling: The Case of Lightweight M2M

Standard protocols for wireless Internet of Things (IoT) communication must be energy-efficient in order to prolong the lifetimes of IoT devices. Two energy-saving strategies for wireless communication are prevalent within the IoT domain: 1) sleepy devices and 2) radio duty cycling. In this paper, we conduct a comprehensive evaluation as to what types of application scenarios benefit the most from either type of energy-saving strategy. We select the lightweight machine to machine (LwM2M) protocol for this purpose because it operates atop the standard constrained application protocol, and has support for sleepy devices through its Queue Mode. We implement the Queue Mode at both the server side and client side, and design enhancements of Queue Mode to further improve the performance. In our experimental evaluation, we compare the performance and characteristics of Queue Mode with that of running LwM2M in a network stack with the standard time-slotted channel hopping as the duty cycling medium access control protocol. By analyzing the results with the support of an empirical model, we find that each energy-saving strategy has different advantages and disadvantages depending on the scenario and traffic pattern. Hence, we also produce guidelines that can help developers to select the appropriate energy-saving strategy based on the application scenario.

Comparative analysis of contention based and TDMA based MAC protocols for wireless sensor networks

Wireless sensor networks have been widely considered as one of the most important technologies that promises wide range of applications in the field of medical, military, environment, home, agriculture, etc. A variety of Medium Access Control (MAC) protocols have been proposed for wireless sensor networks. This paper presents the comparative analysis of two MAC protocols–RI-MAC, receiver initiated asynchronous duty cycle MAC protocol which is a contention based protocol and ATMA, advertisement-based TDMA MAC protocol. The two MAC protocols are analyzed using four performance parameters such as end to end delay, throughput, packet delivery ratio and energy consumption.

Performance of frame transmissions and event-triggered sleeping in duty-cycled WSNs with error-prone wireless links

Two types of packet transmission schemes are prevalent in duty-cycled wireless sensor networks, i.e., single packet transmission and aggregated packet transmission which integrates multiple packets in one frame. While most existing models are developed based on an error-free channel assumption, this paper evaluates the performance of both transmission schemes under error-prone channel conditions. We develop a four-dimensional discrete-time Markov chain model to investigate the impact of channel impairments on the performance of frame transmissions. Together with tracking the number of packets in the queue, number of retransmissions and number of active nodes, the fourth dimension of the model is able to capture the channel behavior at the frame-level. Based on the developed model, we analyze packet loss probability, packet delay, throughput, node energy consumption, and energy efficiency under various channel conditions. To further reduce energy consumption, we propose an event-triggered sleeping (ETS) energy mode for synchronous duty-cycling medium access control protocols. Numerical results reveal to which extent channel impairments may deteriorate the network performance, as well as the advantage of adopting aggregated packet transmission. The benefit brought by the ETS energy mode is also demonstrated showing that the network lifetime is considerably extended, particularly in low traffic load scenarios.

Multiple Packet Transmissions in Duty Cycling WSNs: A DTMC-Based Throughput Analysis

Multiple packet transmissions (MPTs) improve performance by transmitting multiple packets in a single operational cycle. Asynchronous duty cycling medium access control (MAC) protocols such as receiver initiated MAC protocol (RI-MAC) transmit multiple packets in one cycle. In this letter, we develop two associated discrete time Markov chain (DTMC) models to model MPT that can be achieved via multiple node competitions. Furthermore, we present the way of incorporating those developed models with each other for evaluating performance of RI-MAC with MPT. Using the solution of DTMC models, network throughput of MPT is calculated and compared with the one achieved by single packet transmission MAC (e.g., S-MAC) protocol. Validation of analytical results through discrete-event simulations confirms the accuracy of modeling and discloses the operation of MPT in RI-MAC protocol.

Evaluation of a duty-cycled asynchronous X-MAC protocol for vehicular sensor networks

An asynchronous medium access control (MAC) duty-cycled protocols have higher energy efficiency and lower packet latency than synchronized ones due to reduced idle listening. Moreover, they provide efficient utilization of energy supplied to mobile sensors. They are considered very important in MAC protocols due to the adverse effects of hidden terminals which causes energy consumption in sensor networks. Therefore, in this paper, the impact of hidden terminals on the performance of an asynchronous duty-cycled MAC protocol X-MAC for vehicle-base sensor is investigated via analysis and simulations. We propose a Markov model to analyze the quality-of-service (QoS) parameters in terms of energy consumption, delay, and throughput. Our analytical model provides QoS parameter values that closely match the simulation results under various network conditions. Our model is more computationally efficient and provides accurate results quickly compared with simulations. More importantly, our model enables the designers to obtain a better understanding of the effects of different numbers of mobile sensor nodes and data arrival rates on the performance of an asynchronous MAC duty-cycled protocol.

Low Duty-Cycling MAC Protocol for Low Data-Rate Medical Wireless Body Area Networks.

Wireless body area networks (WBANs) are severely energy constrained, and how to improve the energy efficiency so as to prolong the network lifetime as long as possible is one of the most important goals of WBAN research. Low data-rate WBANs are promising to cut down the energy consumption and extend the network lifetime. Considering the characteristics and demands of low data-rate WBANs, a low duty-cycling medium access control (MAC) protocol is specially designed for this kind of WBAN in this paper. Longer superframes are exploited to cut down the energy consumed on the transmissions and receptions of redundant beacon frames. Insertion time slots are embedded into the inactive part of a superframe to deliver the frames and satisfy the quality of service (QoS) requirements. The number of the data subsections in an insertion time slot can be adaptively adjusted so as to accommodate low data-rate WBANs with different traffic. Simulation results show that the proposed MAC protocol performs well under the condition of low data-rate monitoring traffic.

Performance evaluation of X-MAC/BEB protocol for wireless sensor networks

This paper proposes an X-MAC/BEB protocol that runs a binary exponential backoff (BEB) algorithm on top of an X-MAC protocol to save more energy by reducing collision, especially in densely populated wireless sensor networks (WSNs). X-MAC, a lightweight asynchronous duty cycle medium access control (MAC) protocol, was introduced for spending less energy than its predecessor, B-MAC. One of X-MAC 's conspicuous technique is a mechanism to allow senders to promptly send their data when their receivers wake up. X-MAC, however, has no mechanism to deal with sudden traffic fluctuations that often occur whenever closely located nodes simultaneously diffuse their sense data. To precisely evaluate the impact of the BEB algorithm on X-MAC, this paper builds an analytical model of X-MAC/BEB that integrates the BEB model with the X-MAC model. The analytical and simulation results confirmed that X-MAC/BEB outperformed X-MAC in terms of throughput, delay, and energy consumption, especially in congested WSNs.

Modeling and Analyzing Duty-Cycling Pipelined-Scheduling MAC for Linear Sensor Networks

Linear sensor networks (LSNs) have recently attracted increasing attention due to the vast requirements on the monitoring and surveillance of a structure or an area with a linear topology. However, there is not a lot of work on network modeling and analysis based on a duty-cycling medium access control (MAC) protocol for LSNs. In this paper, we model a duty-cycling MAC with a pipelined-scheduling feature for an LSN, where each node is responsible for monitoring a certain area and can generate packets according to its sensed results. Based on the model, we analyze the network performance in terms of system throughput, active time ratio per cycle of each node, and packet delivery latency. Through extensive OPNET-based simulations, we validate the model and reveal the dependence of the network performance on various system parameters. Apart from enabling the effective estimation of the protocol performance by using our model, we believe that our model and analysis could provide an insightful understanding on the behavior of a duty-cycling MAC protocol and aid in its design and optimization for a multihop LSN.

Has Time Come to Switch From Duty-Cycled MAC Protocols to Wake-Up Radio for Wireless Sensor Networks?

Duty-cycled Medium Access Control (MAC) protocols certainly improve the energy efficiency of wireless networks. However, most of these protocols still suffer from severe degrees of overhearing and idle listening. These two issues prevent optimum energy usage, a crucial aspect in energy-constrained wireless networks such as wireless sensor networks (WSNs). Wake-up radio (WuR) systems drastically reduce these problems by completely switching off the nodes' microcontroller unit (MCU) and main radio transceiver until a secondary, extremely low-power receiver is triggered by a particular wireless transmission, the so called wake-up call. Unfortunately, most WuR studies focus on theoretical platforms and/or custom-built simulators. Both these factors reduce the associated usefulness of the obtained results. In this paper, we model and simulate a real, recent, and promising WuR hardware platform developed by the authors. The simulation model uses time and energy consumption values obtained in the laboratory and does not rely on custom-built simulation engines, but rather on the OMNET++ simulator. The performance of the WuR platform is compared to four of the most well-known and widely employed MAC protocols for WSN under three real-world network deployments. The paper demonstrates how the use of our WuR platform presents numerous benefits in several areas, from energy efficiency and latency to packet delivery ratio and applicability, and provides the essential information for serious consideration of switching duty-cycled MAC-based networks to WuR.

An Energy-Efficient Duty-Cycled Wake-Up Radio Protocol for Avoiding Overhearing in Wireless Sensor Networks

Wake-up radio (WuR) system is often presented as the best candidate for replacing traditional duty cycled Medium Access Control (MAC) protocols in Wireless Sensor Networks (WSNs). The Double Radio (DoRa) protocol is a new MAC protocol for in-band WuR system with addressing capabilities. While the DoRa protocol improves the WSNs energy efficiency, it still suffers from an overhearing problem when the WuR system is very often requested. The WuR wastes a noticeable amount of energy when overhearing to wake-up demand intended to other nodes, but it is neither measured nor solved in other works. In this paper, an adaptive duty-cycled DoRa (DC-DoRa) is then proposed to solve the overhearing problem. The primary concept of the work is to enable the WuR functionality before the node is addressed and to disable the WuR after the node sent data. Extensive simulations under OMNeT++ using real input parameters are then performed to show the significant energy-savings through the two protocols and the nearly suppression of overhearing with DC-DoRa. In fact, the mean power consumption is three-order below using the DoRa protocol compared to traditional MAC protocols. While overhearing can represent up to 93% of the WuR energy consumption with the DoRa protocol, it is reduced to only 1% with the DC-DoRa protocol.

A Survey on MAC Protocols for Duty-cycled Wireless Sensor Networks

After more than two decades of their introduction, Wireless Sensor Networks (WSNs) remain an active research topic due to their wide range applications in areas such as healthcare, military, monitoring and surveillance systems. In most applications, sensor nodes are constrained in energy supply and communication bandwidth. Therefore, novel techniques to reduce energy inefficiencies and for efficient use of the limited bandwidth resources are essential. Such constraints combined with dense network deployment pose several challenges to the design and management of WSNs and require energy-awareness at all layers of the networking protocol stack. For instance, at the Data-Link layer, low duty cycle Medium Access Control (MAC) protocols trade off latency for energy efficient operation. In this paper, we present a survey of state-of-the-art low duty cycle MAC protocols. We first outline the design challenges for MAC protocols in WSNs. Then, we present a comprehensive survey of the most prominent and recent MAC protocols. These protocols are classified into synchronous and asynchronous based on their mode of operation. Finally, the paper highlight open research problems in MAC layer for WSNs.

WBAN Energy Efficiency and Dependability Improvement Utilizing Wake-Up Receiver

This paper discusses the perspectives of using a wake-up receiver (WUR) in wireless body area network (WBAN) applications with event-driven data transfers. First we compare energy efficiency between the WUR-based and the duty-cycled medium access control protocol -based IEEE 802.15.6 compliant WBAN. Then, we review the architectures of state-of-the-art WURs and discuss their suitability for WBANs. The presented results clearly show that the radio frequency envelope detection based architecture features the lowest power consumption at a cost of sensitivity. The other architectures are capable of providing better sensitivity, but consume more power. Finally, we propose the design modification that enables using a WUR to receive the control commands beside the wake-up signals. The presented results reveal that use of this feature does not require complex modifications of the current architectures, but enables to improve energy efficiency and latency for small data blocks transfers.

Opportunistic routing with in-network aggregation for duty-cycled WSNs with delay requirements

This paper proposes an opportunistic routing protocol for wireless sensor networks that works on top of an asynchronous duty-cycling medium access control (MAC) protocol. The proposed protocol is designed for applications that are not real-time but still have some requirements on packet delay. The main idea is that if a packet has time to spare, it can wait on a node hoping that it can be aggregated with other packets, resulting in reduced number of transmissions. The forwarders and the packet hold time depend on the energy status of nodes in the network. The simulation results show that the proposed protocol achieves longer network lifetime compared to the other state-of-the-art protocols, while satisfying application delay requirements.