Tree TDMA MAC Algorithm Using Time and Frequency Slot Allocations in Tree-Based WSNs

In this paper, we propose a tree-based time division multiple access (Tree TDMA) media access control (MAC) algorithm based on the IEEE 802.15.4 PHY standard. The method involves the simultaneous use of two algorithms, a time slot allocation algorithm (TSAA) and a frequency slot allocation algorithm (FSAA), at low power consumption to support voice and data communication to solve the problems afflicting prevalent MAC protocols in tree topology networks. The TSAA first generates routing paths through the control channel in a super frame prior to transmitting packets, and allocates time slots for each node to transmit packets. The FSAA then allocates frequencies to each path according to the routing paths generated following its application. The overhearing problem and the funneling effect in TDMA as well as carrier sense multiple access with collision avoidance (CSMA/CA) MACs are resolved by these two algorithms because a given node and its neighbors are orthogonal in terms of time and frequency. The problem of inter-node synchronization is addressed by periodically sending a beacon from higher to lower nodes, and the issue of low power is solved by leaving unsigned time slots in an idle state. To test the effectiveness of the proposed algorithm, we used a MATLAB simulation to compare its performance with that of contention-based CSMA MAC and non-contention-based TreeMAC in terms of network throughput, network delay, energy efficiency, and energy consumption. We also tested the performance of the algorithms for increasing number of nodes and transmission packets in the tree topology network.This work was supported by the ICT R&D Program of MSIP/IITP. [B0126-16-1018, The IoT Platform for Virtual Things, Distributed Autonomous Intellgence and Data Federation/Analysis

TraPy-MAC: Traffic Priority Aware Medium Access Control Protocol for Wireless Body Area Network

Recently, Wireless Body Area Network (WBAN) has witnessed significant attentions in research and product development due to the growing number of sensor-based applications in healthcare domain. Design of efficient and effective Medium Access Control (MAC) protocol is one of the fundamental research themes in WBAN. Static on-demand slot allocation to patient data is the main approach adopted in the design of MAC protocol in literature, without considering the type of patient data specifically the level of severity on patient data. This leads to the degradation of the performance of MAC protocols considering effectiveness and traffic adjustability in realistic medical environments. In this context, this paper proposes a Traffic Priority-Aware MAC (TraPy-MAC) protocol for WBAN. It classifies patient data into emergency and non-emergency categories based on the severity of patient data. The threshold value aided classification considers a number of parameters including type of sensor, body placement location, and data transmission time for allocating dedicated slots patient data. Emergency data are not required to carry out contention and slots are allocated by giving the due importance to threshold value of vital sign data. The contention for slots is made efficient in case of non-emergency data considering threshold value in slot allocation. Moreover, the slot allocation to emergency and non-emergency data are performed parallel resulting in performance gain in channel assignment. Two algorithms namely, Detection of Severity on Vital Sign data (DSVS), and ETS Slots allocation based on the Severity on Vital Sign (ETS-SVS) are developed for calculating threshold value and resolving the conflicts of channel assignment, respectively. Simulations are performed in ns2 and results are compared with the state-of-the-art MAC techniques. Analysis of results attests the benefit of TraPy-MAC in comparison with the state-of-the-art MAC in channel assignment in realistic medical environments

A novel real-time MAC layer protocol for wireless sensor network applications

This paper presents a comparative study of existing real-time MAC layer protocols for wireless sensor networks. Then, a new real-Time MAC protocol is presented that is based on a general purpose MAC protocol, called S-MAC. While medium access strategy in S-MAC is based on contention and back-off schemes, protocol proposed in this paper uses feedback approach as a medium access strategy. As a result of this, it increases consistency in data transmission pattern, which enables it to guarantee end-to-end delay deadlines for soft realtime applications. Proposed protocol works in continuous ON mode of operation at MAC layer and is intended to be used for randomly deployed single stream wireless sensor applications. Finally, a comparative performance analysis of proposed realtime protocol is done with other real-time and general purpose MAC protocols for wireless sensor networks

Wireless Sensor Networking in Challenging Environments

Recent years have witnessed growing interest in deploying wireless sensing applications in real-world environments. For example, home automation systems provide fine-grained metering and control of home appliances in residential settings. Similarly, assisted living applications employ wireless sensors to provide continuous health and wellness monitoring in homes. However, real deployments of Wireless Sensor Networks (WSNs) pose significant challenges due to their low-power radios and uncontrolled ambient environments. Our empirical study in over 15 real-world apartments shows that low-power WSNs based on the IEEE 802.15.4 standard are highly susceptible to external interference beyond user control, such as Wi-Fi access points, Bluetooth peripherals, cordless phones, and numerous other devices prevalent in residential environments that share the unlicensed 2.4 GHz ISM band with IEEE 802.15.4 radios. To address these real-world challenges, we developed two practical wireless network protocols including the Adaptive and Robust Channel Hopping (ARCH) protocol and the Adaptive Energy Detection Protocol (AEDP). ARCH enhances network reliability through opportunistically changing radio\u27s frequency to avoid interference and environmental noise and AEDP reduces false wakeups in noisy wireless environments by dynamically adjusting the wakeup threshold of low-power radios. Another major trend in WSNs is the convergence with smart phones. To deal with the dynamic wireless conditions and varying application requirements of mobile users, we developed the Self-Adapting MAC Layer (SAML) to support adaptive communication between smart phones and wireless sensors. SAML dynamically selects and switches Medium Access Control protocols to accommodate changes in ambient conditions and application requirements. Compared with the residential and personal wireless systems, industrial applications pose unique challenges due to their critical demands on reliability and real-time performance. We developed an experimental testbed by realizing key network mechanisms of industrial Wireless Sensor and Actuator Networks (WSANs) and conducted an empirical study that revealed the limitations and potential enhancements of those mechanisms. Our study shows that graph routing is more resilient to interference and its backup routes may be heavily used in noisy environments, which demonstrate the necessity of path diversity for reliable WSANs. Our study also suggests that combining channel diversity with retransmission may effectively reduce the burstiness of transmission failures and judicious allocation of multiple transmissions in a shared slot can effectively improve network capacity without significantly impacting reliability

Link Scheduling Algorithms For In-Band Full-Duplex Wireless Networks

In the last two decades, wireless networks and their corresponding data traffic have grown significantly. This is because wireless networks have become an indispens- able and critical communication infrastructure in a modern society. An on-going challenge in communication systems is meeting the continuous increase in traffic de- mands. This is driven by the proliferation of electronic devices such as smartphones with a WiFi interface along with their bandwidth intensive applications. Moreover, in the near future, sensor devices that form the Internet of Things (IoTs) ecosystem will also add to future traffic growth. One promising approach to meet growing traffic demands is to equip nodes with an In-band-Full-Duplex (IBFD) radio. This radio thus allows nodes to transmit and receive data concurrently over the same frequency band. Another approach to in- crease network or link capacity is to exploit the benefits of Multiple-Input-Multiple- Output (MIMO) technologies; namely, (i) spatial diversity gain, which improves Signal-to-Noise Ratio (SNR) and thus has a direct impact on the data rate used by nodes, and (ii) spatial multiplexing gain, whereby nodes are able to form concurrent links to neighbors

SDA-SM: An Efficient Secure Data Aggregation Scheme using Separate MAC across Wireless Sensor Networks

Securing the aggregated data of the wireless sensor networks (WSNs) is a vital issue to minimize energy consumption and face potential attacks. This paper presents a novel end to end encryption scheme defined as Aggregating Secure Data -Separate MAC (SDA-SM). The importance of the SDA-SM is twofold. First, it separates the secured aggregated data and the message authentication codes (MAC) into two different packets. Second, it transmits these packets in a random separate time-slot according to the scheduling of the TDMA. Moreover, the TDMA applied in the LEACH protocol is modified to adequate to the proposed SDA-SM scheme. The SDA-SM uses MACs to verify the integrity of the aggregated data and uses a sensor protected identifier to authenticate the source of data. The simulation results of the experiments assure the SDA-SM objectives can be achieved with less computation of the communication overheads than earlier techniques. Besides, SDA-SM will be able to accomplish the integrity and confidentiality of accurate aggregated data while saving the energy to prolong the network lifetime

Dense clustered multi-channel wireless sensor cloud

Dense Wireless Sensor Network Clouds have an inherent issue of latency and packet drops with regards to data collection. Though there is extensive literature that tries to address these issues through either scheduling, channel contention or a combination of the two, the problem still largely exists. In this paper, a Clustered Multi-Channel Scheduling Protocol (CMSP) is designed that creates a Voronoi partition of a dense network. Each partition is assigned a channel, and a scheduling scheme is adopted to collect data within the Voronoi partitions. This scheme collects data from the partitions concurrently and then passes it to the base station. CMSP is compared using simulation with other multi-channel protocols like Tree-based Multi-Channel, Multi-Channel MAC and Multi-frequency Media Access Control for wireless sensor networks. Results indicate CMSP has higher throughput and data delivery ratio at a lower power consumption due to network partitioning and hierarchical scheduling that minimizes load on the network

Analysis of the impact of wireless mobile devices in critical industrial applications

The main objective of the thesis is to study the impact of mobile nodes in industrial applications with strict reliability and time constraints in both centralized and decentralized topologies. Considering the harsh wireless channel conditions of industrial environments, that goal implies a considerable challenge. In order not to compromise the performance of the system, a deterministic Real-Time (RT) communication protocol is needed, along with a mechanism to deal with changes in the topology due to the movements of the wireless devices. The existing wireless standard technologies do not satisfy the requirements demanded by the most critical industrial applications such as Distributed Control Systems (DCS) and, thus, wired communication cannot be directly replaced by wireless solutions. Nevertheless, the adoption of wireless communications can be seen as an extension to the existing wired networks to create hybrid networks with mobility requirements. The design of a proper communication solution depends mainly on the choice of the Medium Access Control (MAC) protocol, which is responsible for controlling access to the medium and thereby plays a vital role in decreasing latency and packet errors. Furthermore, the changes in the topology due to the movement of the wireless devices must be managed correctly in order not to affect the performance of the entire network. In this doctoral thesis, a hybrid centralized architecture designed for industrial applications with strict requirements in terms of robustness, determinism and RT is proposed and evaluated. For that, a wireless RT MAC scheme based on the IEEE 802.11 physical layer is proposed along with a Real-Time Ethernet (RTE) MAC scheme. This hybrid system ensures seamless communication between both media. With the aim of including mobile devices in the proposed architecture, a soft-handover algorithm is designed and evaluated. This algorithm guarantees an uninterrupted communication during the handover process without the need for a second radio interface and with a reduced growth in network overhead. Finally, the impact of mobile nodes in a decentralized wireless topology is analysed. For that, the Self-Organizing Time Division Multiple Access (STDMA) protocol is evaluated to analyse its viability as an alternative to carrying out a handover in industrial applications without centralized systems.El objetivo principal de la tesis es estudiar el impacto de los nodos móviles en las aplicaciones inalámbricas industriales con requisitos estrictos de tiempo y robustez tanto para topologías centralizadas como descentralizadas. Este objetivo supone un gran desafío dadas las adversas condiciones del canal inalámbrico en los entornos industriales. Para no comprometer el rendimiento del sistema, es necesario un protocolo de comunicación determinista y con garantías de tiempo real, junto con un mecanismo para hacer frente a los cambios en la topología debido al movimiento de los dispositivos inalámbricos. Las tecnologías estándar inalámbricas existentes no satisfacen los requisitos exigidos por las aplicaciones industriales más críticas, como los Sistemas de Control Distribuido (DCS - Distributed Control Systems) y, por lo tanto, las comunicaciones cableadas no pueden ser reemplazadas directamente por soluciones inalámbricas. Sin embargo, la adopción de las comunicaciones inalámbricas puede verse como una extensión de las redes cableadas existentes con el objetivo de crear redes híbridas con requisitos de movilidad. El diseño de una solución de comunicación adecuada depende principalmente de la elección del protocolo de control de acceso al medio (MAC - Medium Access Control), el cual, desempeña un papel vital en la disminución de la latencia y del número de paquetes erróneos. Además, los cambios en la topología debidos al movimiento de los dispositivos inalámbricos deben gestionarse correctamente para que el rendimiento de toda la red no se vea afectado. En esta tesis doctoral se propone y se evalúa una arquitectura híbrida centralizada diseñada para aplicaciones industriales con requisitos estrictos de robustez, determinismo y tiempo real. Para ello, se propone un esquema MAC inalámbrico con garantías de tiempo real basado en la capa física IEEE 802.11 junto con un esquema MAC basado en Ethernet en tiempo real (RTE - Real-Time Ethernet). Este esquema híbrido garantiza una comunicación continua entre ambos medios de comunicación. Con el objetivo de incluir dispositivos móviles en la arquitectura propuesta, se propone y evalúa un algoritmo de soft-handover. Este algoritmo garantiza una comunicación ininterrumpida durante el proceso de handover sin la necesidad de una segunda interfaz de radio y con un aumento reducido de la sobrecarga de la red. Finalmente, se analiza el impacto de los nodos móviles en una topología inalámbrica descentralizada. Para ello, se evalúa el protocolo del estado del arte Self-Organizing Time Division Multiple Access (STDMA) con el objetivo de analizar su viabilidad como alternativa para realizar un handover en las aplicaciones industriales sin sistemas centralizados.Tesi honen helburu nagusia, nodo mugikorrek fidagarritasun eta denboraren aldetik baldintza ugari eskatzen duten aplikazio industrial zentralizatu eta deszentralizatuetan duten eragina aztertzea da. Eremu industrialetako haririk gabeko kanaletan ematen diren komunikazioetarako baldintza bereziki aurkakoak direla medio, helburu honek erronka handia sortzen du. Sarearen errendimendua arriskuan ez jartzeko, determinista eta denbora errealeko komunikazio protokolo bat beharrezkoa da, haririk gabeko nodoen mugimenduaren ondorioz topologiaren aldaketei aurre egiteko mekanismo batekin batera. Haririk gabeko teknologia estandarrek ez dute aplikazio industrial kritikoenek dituzten baldintzak betetzen eta, beraz, kable bidezko komunikazioak ezin dira haririk gabeko sistemekin ordezkatu. Hala ere, haririk gabeko komunikazioen erabilpena jadanik existitzen diren kable bidezko komunikazioen hedadura bezala kontsidera daiteke, mobilitate baldintzak dituzten sare hibridoak sortuz. Komunikazio sistemaren diseinu egokia Medium Access Control (MAC) protokoloaren hautaketa zuzenean oinarritzen da gehien bat, sarbidea kontrolatzeaz arduratzen baita, honela ezinbesteko papera izanik latentzian eta pakete erroreen murrizketan. Horretaz aparte, bai sare zentralizatu eta deszentralizatuen kasuan, haririk gabeko nodoen mugimenduek sortutako tipologia aldaketak azkar eta zuzen kudeatu behar dira sare osoko errendimenduak kalterik ez jasateko. Doktore tesi honetan, fidagarritasun zorrotz, determinismo eta denbora-errealeko baldintzak dituzten industria aplikazioetarako arkitektura hibrido zentralizatu bat proposatu eta ebaluatu da. Horretarako, IEEE 802.11 maila fisikoan oinarritutako haririk gabeko MAC eskema bat proposatu da, Real-Time Ethernet-en (RTE) oinarritutako MAC eskema batekin batera. Eskema hibrido honek bi komunikabideen artean etengabeko komunikazioa bermatzen du. Proposatutako arkitekturan nodo mugikorrak kontuan hartu ahal izateko, soft-handover algoritmo bat proposatu eta ebaluatu da. Algoritmo honek etenik gabeko komunikazioa bermatzen du handover prozesuan zehar bigarren irrati interfaze baten beharrik gabe eta sareko gainkarga oso gutxi handituz. Azkenik, nodo mugikorrek duten eragina haririk gabeko topologia deszentralizatuetan aztertu da. Horretako, bibliografiako Self-Organizing Time Division Multiple Access (STDMA) protokoloa ebaluatu da industrial aplikazioetako sistema zentralizatuen handover mekanismoaren alternatiba gisa