Medium Access Protocol Research Articles

Resource allocation in heterogeneous cognitive radio sensor networks

Cognitive radio sensor networks offer a promising means of meeting rapidly expanding demand for wireless sensor network applications in new monitoring and objects tracking fields. Several challenges, particularly in terms of quality of service provisioning, arise because of the inherited capability-limitation of end-sensor nodes. In this article, an efficient resource allocation scheme, improved Pliable Cognitive Medium Access Protocol, is proposed to tackle multilevel of heterogeneity in cognitive radio sensor networks. The first level is the network’s application heterogeneity, and the second level is the heterogeneity of the radio environment. The proposed scheme addresses scheduling and radio channel allocation issues. Allocation-decision making is centralized, whereas spectrum sensing is distributed, thereby increasing efficiency and limiting interference. Despite the limited capabilities of the sensor’s networks, the effectiveness of the proposed scheme also includes increasing the opportunity to utilize a wider range of the radio spectrum. improved Pliable Cognitive Medium Access protocol is quite appropriate for critical communications that gain attention in the next 5G of wireless networks. Simulation results and the comparison of the proposed protocol with other protocols indicate the robust performance of the proposed scheme. The results reveal the significant effectiveness, with only a slight trade-off in terms of complexity.

Design and Evaluation of Low-Cost and Energy-Efficient Magneto-Inductive Sensor Nodes for Wireless Sensor Networks

A set of low-cost and energy-efficient sensor nodes are designed and implemented using magnetic induction (MI) communications for wireless sensor networks (WSN), which are especially suited for underwater and underground networks where the conventional mode of communication does not perform well. Hardware features of the sensor nodes include a three-dimensional MI coil antenna and its different configurations for transmit and receive operations, low-power circuits for sleep mode, several types of sensors, data storage, and best transmit/receive circuits selected to achieve the maximum communication range with low-power consumption. The material cost of a sensor node is less than $\$$ 100 USD at the prototyping stage and can be drastically reduced at volume production. Software design utilizes low-power modes of microcontrollers and power supply circuits, state machine implementation of sleep, receive, sensing, and transmit modes, range estimation from received signal strength indicators (RSSIs), and medium access protocols, such as carrier sense multiple access (CSMA). Extensive lab and field tests conducted with the sensor nodes demonstrate promising performance in terms of low-power consumption, communication range, range estimation, and robustness against mismatching of coil orientations, and networking capabilities. The current consumption is as low as 60 $\mu$ A in sleep mode, 0.49 $\text{m}$ A in receive mode, and 253 $\text{m}$ A in transmit mode. The sensor node achieves a maximum of 40-m range with 1 kb/s data rate at 125 kHz carrier frequency.

Energy optimization of sustainable Internet of Things (IoT) systems using an energy harvesting medium access protocol

The process of modelling the energy expenditure for IoT systems is distinct when compared to Wireless Sensor Networks (WSN), due to a number of factors and metrics. Few of such factors to mention are the IoT layers being different from the Open System Interconnection (OSI) with communication protocols like IPv6 Low power Wireless Personal Area Networks (6LoWPAN), Routing for Low Power and Lossy networks (RPL) and Constrained Application Protocol (CoAP). This leads to the demand for designing efficient Medium Access Control (MAC) protocols to serve the purpose of balance between the performance of the system and minimum energy consumption. The challenge of compatibility of MAC protocols for IoT deployment needs to be addressed. The proposed work is aimed at developing energy efficient framework for optimal balance between energy consumed by connected devices (sensor networks) in a complex and time-critical IoT system through performance monitoring of underlying communication technologies. It also focuses to address the trade-off between energy expenditure and performance of the network for the communicating nodes. An Energy Harvesting MAC protocol is designed and developed after modelling of the nodes using Reinforcement Learning (RL) for time critical IoT systems. The results have shown that the energy expenditure of the IoT devices is considerably minimized and the performance is increased by nearly 80% when compared to the state-of-art energy harvesting solutions for sustainable IoT systems. This research also plays a significant role in matching the energy predictions and the experimentations that validate the IoT systems in a real-world scenario.

Throughput Enrichment and Drooping Off Power Ingestion in Ad Hoc Networks by EE-MAC Protocol

The wireless ad hoc networks impel the necessity for power control transmission based on interference aware to increase the throughput of the network and the spatial utilization. Developing an efficient medium access protocol is the significant issue in the wireless network that optimizes the reuse of spectral and hence increases the utilization of the aggregate channel. In such networks, to synchronize the user’s access to the shared medium, the protocol called as distributed medium access control (MAC) plays a major role. This work introduced an energy efficient MAC protocol utilizing a relay selection to minimize the consumption of power of a network. In this optimal power control protocol, the transmission floor area is reduced to improve the efficiency of space–time utilization and reduce collisions. Based on the control packets interchanging, transmission power is optimally allocated to the transmitters to send the data packets to receivers. The time management protocols removes the interference. Simulations prove that this work achieves higher throughput, a reduced amount of energy and extend the lifetime of the network when compared with the ordinary MAC protocol.

MPMAC: Clustering Based MAC Protocol for VANETs

Vehicular safety messaging is warranted mostly in turbulent traffic situations in which even cluster based MAC protocols are beset by problems of cluster rupture, which leads to non-availability of channels to vehicles even when channels are idle. To solve this, motion parameters based cluster medium access (MPMAC) protocol is presented in this paper. The vehicles organize themselves into headless clusters without any messaging. The members of a cluster are not spatially bunched and may belong to different lanes. Each cluster has channels earmarked with the flexibility of utilizing idle channels belonging to other clusters. Safety messages are accorded higher priority with one channel dedicated exclusively for these messages. To enhance channel utilization and avoid the hidden station problem, the RSU monitors the channels and periodically advertises the channel usage map. The MPMAC protocol increases the system’s throughput by enhancing channel utilization and facilitates the availability of channels during traffic conditions like phantom jams, lane changing and congestion. The delivery of safety messages to intended vehicles is ensured make provisions for flexible and prioritized channel access in addition to an earmarked channel. Simulation results show that the proposed MPMAC protocol is able to provide sufficient channels for dissemination of safety and other messages with enhanced throughput, fair access, and increased channel utilization while minimizing cluster formation overheads.

A Study on the Impact of Packet Length on Communication in Low Power Wireless Sensor Networks Under Interference

Reliability is nowadays considered a key requirement in wireless sensor networks for their increasing diffusion in various Internet of Things applications. However, radio interference from various sources may heavily affect the performance of wirelessly connected embedded devices, resulting into increased packet collisions and congestions. There is therefore a widely recognized need of both theoretical and practical investigations capable of shedding light on the factors affecting the operativeness of sensor networks subject to interference. In this paper, we investigate the role of packet length into the reliability and energy efficiency of low-power medium access protocols. Specifically, we propose a mathematical model to explore the functional dependence of the reliability of a pair of sensor nodes under interference from packet length. We also present a wide range of experimental evaluations aimed at validating the model and at providing novel insights on dependability issues. In particular, we assess the performance of Contiki's default medium access control layer (together with that of an always listening receiver, as a baseline) in terms of packet loss rate and energy efficiency for varying payload lengths. Experimental results highlight the interplay between packet size and interference and in particular the tradeoff between the robustness against interference and the overhead imposed to communication as a function of the length of data packets. The Pareto curve describing the energy efficiency as a function of the packet loss rate, demonstrates the existence of intermediate packet size representing an optimal choice for balancing energy consumption and communication reliability, enabling adequate system dimensioning at design-level.

Adaptive Medium Access Control for Distributed Processing in Wireless Sensor Networks

Signal and information processing tasks over Wireless Sensor Networks can be successfully accomplished by means of a distributed implementation among the nodes. Existing distributed schemes are commonly based on iterative strategies that imply a huge demand of one-hop transmissions, which must be efficiently processed by the lower layers of the nodes. At the link layer, general purpose medium access (MAC) policies for wireless communications usually focus on avoiding collisions. These existing approaches result in a reduction of the number of simultaneous transmissions, and an underutilization of the channel as a consequence. This leads to a decrease in the performance of the distributed tasks, since an efficient channel occupation is not generally accomplished. In this paper, we propose a new MAC protocol that, besides focusing on the reliability of the communications, provides an efficient channel occupation. While the former has a direct impact on the energy consumption of usually battery powered devices, the latter affects the performance of the distributed task executed. We include both aspects in a global utility function that the nodes, relying just on local available information, aim to increase at every communication step. Furthermore, our proposal combines in a unique framework both unicast and broadcast scenarios. Through several simulation results, we show that our adaptive protocol outperforms the related literature.

Self managed Access Scheme for Demand Request in TDM TDMA Star Topology Network

In demand assignment protocol, resources are granted on the basis of demand, governing some rules, policies in resource assignment and after the completion of need, resources are released back to the central pool for further requests. In star topology TDM/TDMA network of VSATs, large number of participating terminals generate signaling packet on common demand request channel. It is desired that these signaling terminals to have higher chances of successful access to the media and at the same time with minimal number of collision over the shared channel. Under these circumstances, performance of media access protocol is really crucial. Aloha is the simplistic technique to access the shared channel but suffers from extremely low throughput. Its immediate successor slotted Aloha improves the throughput by cutting down the vulnerable period to half by agreeing on transmission at slot boundaries. This improvement is also not adequate to provide the better chances of packets getting through when multiple nodes are participating. The large latency network where one hop delay is of the order of 270ms, feedback time and timeouts are also of high order this further worsen the problem. In this paper, we propose self-managed access scheme for demand request that tries to reduce the collision by managing the multiple requests and distributing them over different slots.

Wireless Multimedia Sensor Networks based Quality of Service Sentient Routing Protocols: A Survey

Improvements in nanotechnology have introduced contemporary sensory devices that are capable of gathering multimedia data in form of images, audio and video. Wireless multimedia sensor networks are designed to handle such type of heterogeneous traffic. The ability to handle scalar and non-scalar data has led to the development of various real-time applications such as security surveillance, traffic monitoring and health systems. Since, these networks are an emergent of wireless sensor networks; they inherit constraints that exist in these traditional networks. Particularly, these networks suffer from quality of service and energy efficiency due to the nature of traffic. This paper presents the characteristics and requirements of wireless multimedia sensor networks and approaches to mitigate existing challenges. Furthermore, a review of recent research on multipath routing protocols and multi-channel media access protocols that have quality of service assurances and energy efficiency in handling multimedia data have included.

A Physical-Layer Scheduling Approach in Large-Scale Cooperative Networks

In a sensor, mesh, or ad hoc network, different transmissions take place between multiple source-destination pairs, which is referred to as data flows. In this paper, each data flow is associated with a certain duty cycle schedule to avoid collisions of multiple flows in an energy-efficient manner. Cooperative routes in the network are assumed to be linear and strip-shaped, where each hop or a level contains multiple nodes, and the distance between the nodes is kept constant. We assume all nodes in a cooperative route, which corresponds to one source-destination pair, follow the same duty cycle schedule, while schedules of different routes are orthogonal in time to avoid interference between routes. Therefore, when a new route is formed, it is important to select a duty cycle schedule that is not already in use by the nodes participating in the new route. As part of route set-up, an orthogonal frequency division multiplexing packet travels from the source to the destination, identifying the schedules in use by the nodes along the path. Our objective in this paper is to analyze the probabilities of detection for this method of detecting schedules, which is useful to gain insights into duty cycling-based medium access protocol design in the presence of multiple data flows. To this end, the successive transmissions in a linear network are modeled using an irreducible discrete time Markov chain. Also, three different approaches to detect a certain schedule are investigated, which are distinguished by the binary integration process with multiple sub-carriers corresponding to the schedule. We derive the probability transition matrix for the Markov chain based on different distributions of the received signal energy, the left eigenvector of which yields the probability of detection.

Reinforcement Learning Based MAC Protocol (UW-ALOHA-Q) for Underwater Acoustic Sensor Networks

The demand for regular monitoring of the marine environment and ocean exploration is rapidly increasing, yet the limited bandwidth and slow propagation speed of acoustic signals leads to low data throughput for underwater networks used for such purposes. This study describes a novel approach to medium access control that engenders efficient use of an acoustic channel. ALOHA-Q is a medium access protocol designed for terrestrial radio sensor networks and reinforcement learning is incorporated into the protocol to provide efficient channel access. In principle, it potentially offers opportunities for underwater network design, due to its adaptive capability and its responsiveness to environmental changes. However, preliminary work has shown that the achievable channel utilisation is much lower in underwater environments compared with the terrestrial environment. Three improvements are proposed in this paper to address key limitations and establish a new protocol (UW-ALOHA-Q). The new protocol includes asynchronous operation to eliminate the challenges associated with time synchronisation under water, offer an increase in channel utilisation through a reduction in the number of slots per frame, and achieve collision free scheduling by incorporating a new random back-off scheme. Simulations demonstrate that UW-ALOHA-Q provides considerable benefits in terms of achievable channel utilisation, particularly when used in large scale distributed networks.

Energy Efficient Uplink MAC Protocol for M2M Devices

To enable connectivity between a massive number of devices on the Internet of Things (IoT) paradigm, machine-to-machine (M2M) communication is implied. The key feature of emerging and ad hoc networks, such as M2M communication, is a low-complexity medium access protocol. In this paper, an uplink centric simple approach is proposed that aims to improve the energy efficiency of the devices of M2M communication. To facilitate the requirements of these networks with a massive number of ubiquitous devices, the current version of slotted aloha is optimized specifically for M2M architecture. To reduce complexity, this paper does not change the architecture but, additionally, add a simplified approach to gain efficiency. Previous slotted aloha protocols work well under less traffic but in the case of M2M architecture, it may become a bottleneck. The proposed power adaptive technique adjusts the delay time for transmission slots mainly for small sensor devices used in M2M applications, such as health care, weather trackers, and other delays sensitive M2M applications. An improvement in energy efficiency was achieved by increasing the energy efficiency at 60% rate compared with other techniques and lifetime to 45% while keeping the throughput steady and reducing the time and space complexity. The results are simulated in MATLAB. Better message delivery was achieved by considering the power profiles of M2M devices.

P-AUV: Position aware routing and medium access for ad hoc AUV networks

Autonomous underwater vehicle (AUV) networks are used for coordinated missions such as area mapping and remote surveillance. AUVs are typically deployed by a central platform such as a ship or a submarine, and they operate in an unattended environment. Although there is no need for continuous monitoring of AUV nodes, the central platform may occasionally need to send messages, route updates, or mission commands to the AUV fleet. Nodes in an AUV network are mobile and self-powered. Moreover, periodic exchange of neighborhood messages is not practical due to large propagation delays. Therefore, reliable, low-latency, and energy-efficient solutions are needed to meet the performance requirements of ad hoc AUV networks. We propose P-AUV as a routing and medium access protocol, which depends on location estimation at each node. Data required for packet relaying decision is carried in the header of each data packet. Loop-free routes are generated, where relay candidates closer to the sink nodes are prioritized. In order to control medium access and to avoid collisions, each node selects a backoff interval according to its own position. We analyze the performance of our solution and we compare P-AUV with probabilistic broadcast in terms of several network parameters. Our results indicate that P-AUV improves packet delivery ratio and end-to-end delay along with lifetime of AUV networks.

Supporting Deterministic Wireless Communications in Industrial IoT

Wireless communication technologies have become widely adopted, appearing in heterogeneous applications ranging from tracking victims, responders, and equipment in disaster scenarios to machine health monitoring in networked manufacturing industries. These systems are said to have real-time timeliness requirements since data communication must be conducted within predefined temporal bounds, whose unfulfillment may compromise the correct behavior of the system and cause economic losses or endanger human lives. The support of real-time communications over license-free bands in open environments is a challenging task since real-time medium access is only achieved by a strict timing control of all communicating stations (real and nonreal-time). However, in open communication environments, the traffic generated by uncontrolled stations cannot be avoided by existing medium access protocols. In this paper, the definition, implementation, and assessment of a novel MAC technique named bandjacking is performed. Results demonstrate that the support of low-power deterministic communications is possible in open environments by using bandjacking .

Bidirectional LiFi Attocell Access Point Slicing Scheme

LiFi attocell access networks will be deployed everywhere to support diverse applications and service provisioning to various end-users. The LiFi infrastructure providers will need to offer LiFi access points (APs) resources as a service. This, however, requires a research challenge to be solved to dynamically and effectively allocate resources among service providers (SPs) while guaranteeing performance isolation among them and their respective users. This paper introduces an autonomic resource slicing (virtualization) scheme, which realizes autonomic management and configuration of virtual APs, in a LiFi attocell access network, based on SPs and their users service requirements. The developed scheme comprises of traffic analysis and classification, a local AP controller, downlink and uplink slice resources manager, traffic measurement, and information collection modules. It also contains a hybrid medium access protocol and an extended token bucket fair queueing algorithm to support uplink access virtualization and spectrum slicing. The proposed resource slicing scheme collects and analyzes the traffic statistics of the different applications supported on the slices defined in each LiFi AP and distributes the available resources fairly and proportionally among them. It uses a control algorithm to adjust the minimum contention window of user devices to achieve the target throughput and ensure airtime fairness among SPs and their users. The developed scheme has been extensively evaluated using OMNeT++. The obtained results show various resource slicing capabilities to support differentiated services and performance isolation.

Robust state estimation for discrete time systems with colored noises and communication constraints

This paper investigates the state estimation problem for networked systems with colored noises and communication constraints. The colored noises are considered to be correlated to itself at other time steps, and communication constraints include two parts: (1) the information is quantized by a logarithmic quantizer before transmission, (2) only one node can access the network channel at each instant based on a specified media access protocol. A robust recursive estimator is designed under the condition of colored noises, quantization error and partially available measurements. The upper bound of the covariance of the estimation error is then derived and minimized by properly designing estimator gains. An illustrative example is finally given to demonstrate the effectiveness of the developed estimator.

MGR: Multi-parameter Green Reliable communication for Internet of Things in 5G network

Internet of Things (IoT) plays a major role in connecting the physical world with the cyber world through new services and seamless interconnection between heterogeneous devices. However, exploiting green schemes for IoT is still a challenge because as IoT attains a large scale and becomes more multifaceted, the current trends are not directly applicable to it. Similarly, achieving green communication through the use of 5G also poses new challenges when it comes to transferring huge volume of data efficiently. To address the challenges above, this paper presents a scheme for green IoT in 5G network. Grouping mobile nodes achieve green IoT in a cluster. Also, a mobility management model is designed that helps in triggering efficient handover and selecting optimal networks based on multicriteria decision modeling. Afterwards, we develop a system architecture which integrates green IoT with 5G network. It also helps them in communicating with other heterogeneous networks efficiently with minimum energy requirements. Moreover, the 5G network architecture is supported by the proposed protocol stack, which maps Internet Protocol (IP), Medium Access Protocol (MAC), and Location Identifiers (LOC). The proposed scheme is implemented using C programming language, and extensive mathematical and statistical analysis is carried out regarding cost, energy, and Quality of Service.

Secure Blockchains for Dynamic Spectrum Access: A Decentralized Database in Moving Cognitive Radio Networks Enhances Security and User Access

In this article, we propose a blockchain verification protocol as a method for enabling and securing spectrum sharing in moving cognitive radio (CR) networks. The spectrum-sharing mechanism is used as a medium-access protocol for accessing wireless bandwidth among competing CRs. We introduce a virtual currency, called Specoins, for payment to access the spectrum. An auction mechanism based on a first-come-first-served queue is used, with the price for the spectrum advertised by each primary user in a decentralized fashion. The blockchain protocol facilitates the transactions between primary and secondary users and is used to validate and save each user's virtual wallet. Also important for mobile networks, the blockchain serves as a distributed database that is visible by all participating parties, and any node can volunteer to update the blockchain. The volunteer nodes are called miners, and they are awarded with Specoins. We propose diverse methods to exchange the Specoins to make leasing possible even by CRs that are not miners. We show the improvement of the proposed algorithm compared with the conventional Aloha medium-access protocol in terms of spectrum usage. This difference is investigated using small-scale fading variation in the wireless channel to compare the performance of our secure method with the conventional medium access used in vehicular communications. The secure blockchain verification protocol is not only secure but also outperforms the conventional system in moderate cases of small-scale fading. In the case of severe small-scale fading, the blockchain protocol will outperform the conventional system if multipath diversity is not used.

Wireless Full-Duplex Medium Access Control for Enhancing Energy Efficiency

Recent years have witnessed a proliferation of battery-powered mobile devices, e.g., smartphones, tablets, sensors, and laptops, which leads a significant demand for high capacity wireless communication with high energy efficiency. Among technologies to provide the efficiency is full-duplex wireless communication. Full-duplex wireless enhances capacity by simultaneously transmitting uplink and downlink data with limited frequency resources. Previous studies on full-duplex wireless mostly focuses on doubling the network capacity, whereas in this paper we discuss that full-duplex wireless can also provide higher energy efficiency. We propose low power communication by wireless full-duplexing (LPFD), focusing on the fact that the full-duplex communication duration becomes half of the halfduplex communication duration. In the LPFD, by using the sleep state in which the transceiver provided in the wireless communication terminal is turned off, power consumption of the wireless communication terminal is reduced and energy efficiency in wireless full duplex is improved. Simulation results show that the energy efficiency achieved by LPFD is up to approximately 17.3 times higher than the energy efficiency achieved by existing full-duplex medium access protocol. Further, it is up to approximately 27.5 times higher than the energy efficiency using power saving mode of half-duplex communication.

Reliable wireless MAC layer for industrial internet of things using polarisation diversity

Industrial internet of things (IIoT) requires superior reliability from underlying communication technology that consumer wireless technologies often fail to meet. Utilising polarisation diversity techniques through rotating polarisation waves (RPWs) have been recently proposed to improve the coverage and reliability of IIoT network. However, the design of medium access (MAC) layer that optimally utilises the key features of the underlying physical layer is a key challenge especially when considering multihop networks. Adopting conventional MAC protocols based on carrier sensing or time division alone would not utilise the physical layer in its optimal manner leading to lower throughput and higher end-to-end latency. In this paper, novel medium access techniques to improve the reliability in the RPW wireless communication have been described. We also consider extensions to the MAC layer to support multihop network using the tree topology. An overview of MAC layer methods and comparative mathematical analysis is provided that clearly show the benefits of multi-hop RPW over conventional networks.