Experiences from porting the Contiki operating system to a popular hardware platform

In contrast to original belief, recent work has demonstrated the viability of IPv6-based Wireless Sensor Networks (WSNs). This has led to significant research and standardization efforts with outcomes such as the "IPv6 over Low-Power Wireless Personal Area Networks " (6LoWPAN) specification. The Contiki embedded operating system is an important open source, multi-platform effort to implement 6LoWPAN functionality for constrained devices. Alongside its RFC-compliant TCP/IP stack (uIP), it provides support for 6LoWPAN and many related standards. As part of our work, we have made considerable fixes and enhancements to one of Contiki's ports. In the process, we made significant optimizations and a thorough evaluation of Contiki's memory and code footprint characteristics, focusing on network-related functionality. In this paper we present our experiences from the porting process, we disclose our optimizations and demonstrate their significance. Lastly, we discuss a method of using Contiki to deploy an embedded Internet-to-6LoWPAN router. Our porting work has been made available to the community under the terms of the Contiki license

Experiences from porting the Contiki operating system to a popular hardware platform

In contrast to original belief, recent work has demonstrated the viability of IPv6-based Wireless Sensor Networks (WSNs). This has led to significant research and standardization efforts with outcomes such as the "IPv6 over Low-Power Wireless Personal Area Networks " (6LoWPAN) specification. The Contiki embedded operating system is an important open source, multi-platform effort to implement 6LoWPAN functionality for constrained devices. Alongside its RFC-compliant TCP/IP stack (uIP), it provides support for 6LoWPAN and many related standards. As part of our work, we have made considerable fixes and enhancements to one of Contiki's ports. In the process, we made significant optimizations and a thorough evaluation of Contiki's memory and code footprint characteristics, focusing on network-related functionality. In this paper we present our experiences from the porting process, we disclose our optimizations and demonstrate their significance. Lastly, we discuss a method of using Contiki to deploy an embedded Internet-to-6LoWPAN router. Our porting work has been made available to the community under the terms of the Contiki license

BatNet: a 6LoWPAN-based sensors and actuators network

Improving energy efficiency in buildings is one of the goals of the Smart City initiatives and a challenge for the European Union. This paper presents a 6LoWPAN wireless transducer network (BatNet) as part of an open energy management system. This network has been designed to operate in buildings, to collect environmental information (temperature, humidity, illumination and presence) and electrical consumption in real time (voltage, current and power factor). The system has been implemented and tested in the Energy Efficiency Research Facility at CeDInt-UPM

Open multi-technology building energy management system

Energy Efficiency is one of the goals of the Smart Building initiatives. This paper presents an Open Energy Management System which consists of an ontology-based multi-technology platform and a wireless transducer network using 6LoWPAN communication technology. The system allows the integration of several building automation protocols and eases the development of different kind of services to make use of them. The system has been implemented and tested in the Energy Efficiency Research Facility at CeDInt-UPM

Adaptive and context-aware service discovery for the Internet of Things

The Internet of Things (IoT) vision foresees a future Internet encompassing the realm of smart physical objects, which offer hosted functionality as services. The role of service discovery is crucial when providing application-level, end-to-end integration. In this paper, we propose trendy: a RESTful web services based Service Discovery protocol to tackle the challenges posed by constrained domains while offering the required interoperability. It provides a service selection technique to offer the appropriate service to the user application depending on the available context information of user and services. Furthermore, it employs a demand-based adaptive timer and caching mechanism to reduce the communication overhead and to decrease the service invocation delay. trendy’s grouping technique creates location-based teams of nodes to offer service composition. Our simulation results show that the employed techniques reduce the control packet overhead, service invocation delay and energy consumption. In addition, the grouping technique provides the foundation for group-based service mash-ups and localises control traffic to improve scalability

IPv6 multicast forwarding in RPL-based wireless sensor networks

In wireless sensor deployments, network layer multicast can be used to improve the bandwidth and energy efficiency for a variety of applications, such as service discovery or network management. However, despite efforts to adopt IPv6 in networks of constrained devices, multicast has been somewhat overlooked. The Multicast Forwarding Using Trickle (Trickle Multicast) internet draft is one of the most noteworthy efforts. The specification of the IPv6 routing protocol for low power and lossy networks (RPL) also attempts to address the area but leaves many questions unanswered. In this paper we highlight our concerns about both these approaches. Subsequently, we present our alternative mechanism, called stateless multicast RPL forwarding algorithm (SMRF), which addresses the aforementioned drawbacks. Having extended the TCP/IP engine of the Contiki embedded operating system to support both trickle multicast (TM) and SMRF, we present an in-depth comparison, backed by simulated evaluation as well as by experiments conducted on a multi-hop hardware testbed. Results demonstrate that SMRF achieves significant delay and energy efficiency improvements at the cost of a small increase in packet loss. The outcome of our hardware experiments show that simulation results were realistic. Lastly, we evaluate both algorithms in terms of code size and memory requirements, highlighting SMRF's low implementation complexity. Both implementations have been made available to the community for adoption

Overlay virtualized wireless sensor networks for application in industrial internet of things : a review

Abstract: In recent times, Wireless Sensor Networks (WSNs) are broadly applied in the Industrial Internet of Things (IIoT) in order to enhance the productivity and efficiency of existing and prospective manufacturing industries. In particular, an area of interest that concerns the use of WSNs in IIoT is the concept of sensor network virtualization and overlay networks. Both network virtualization and overlay networks are considered contemporary because they provide the capacity to create services and applications at the edge of existing virtual networks without changing the underlying infrastructure. This capability makes both network virtualization and overlay network services highly beneficial, particularly for the dynamic needs of IIoT based applications such as in smart industry applications, smart city, and smart home applications. Consequently, the study of both WSN virtualization and overlay networks has become highly patronized in the literature, leading to the growth and maturity of the research area. In line with this growth, this paper provides a review of the development made thus far concerning virtualized sensor networks, with emphasis on the application of overlay networks in IIoT. Principally, the process of virtualization in WSN is discussed along with its importance in IIoT applications. Different challenges in WSN are also presented along with possible solutions given by the use of virtualized WSNs. Further details are also presented concerning the use of overlay networks as the next step to supporting virtualization in shared sensor networks. Our discussion closes with an exposition of the existing challenges in the use of virtualized WSN for IIoT applications. In general, because overlay networks will be contributory to the future development and advancement of smart industrial and smart city applications, this review may be considered by researchers as a reference point for those particularly interested in the study of this growing field

IPv6 Multicast Forwarding in RPL-Based Wireless Sensor Networks

This article was published in the journal, Wireless Personal Communications [© Springer Science+Business Media] and the definitive version is available at: http://dx.doi.org/10.1007/s11277-013-1250-5In wireless sensor deployments, network layer multicast can be used to improve the bandwidth and energy efficiency for a variety of applications, such as service discovery or network management. However, despite efforts to adopt IPv6 in networks of constrained devices, multicast has been somewhat overlooked. The Multicast Forwarding Using Trickle (Trickle Multicast) internet draft is one of the most noteworthy efforts. The specification of the IPv6 routing protocol for low power and lossy networks (RPL) also attempts to address the area but leaves many questions unanswered. In this paper we highlight our concerns about both these approaches. Subsequently, we present our alternative mechanism, called stateless multicast RPL forwarding algorithm (SMRF), which addresses the aforementioned drawbacks. Having extended the TCP/IP engine of the Contiki embedded operating system to support both trickle multicast (TM) and SMRF, we present an in-depth comparison, backed by simulated evaluation as well as by experiments conducted on a multi-hop hardware testbed. Results demonstrate that SMRF achieves significant delay and energy efficiency improvements at the cost of a small increase in packet loss. The outcome of our hardware experiments show that simulation results were realistic. Lastly, we evaluate both algorithms in terms of code size and memory requirements, highlighting SMRF's low implementation complexity. Both implementations have been made available to the community for adoption

Performance of constrained wireless devices in the Internet of Things

The Internet of Things is an emerging concept where every device, regardless of size, have their own connection to the Internet. This thesis examines what possible limitations are imposed on the functionality of resource constrained, wireless devices. Several different technologies are evaluated and compared, before a set of them is chosen for inclusion in an implementation, for example: IEEE 802.15.4, 6LoWPAN and CoAP. The implementation uses the Contiki operating system, and runs on a Texas Instruments CC2530 SoC. We then examine several different performance aspects of our implementation: the amount of data sent, memory usage and energy consumption. The results are discussed together with security aspects applicable to the Internet of things. The memory usage and power consumption were found to be severe issues. Due to the small amount of memory on the chip, all features could not be used at the same time. In addition, the power consumption was found to be too high for battery-powered usage, giving a lifetime of only 27 hours using a button cell battery. The conclusion is that hardware with more memory, and lower power consumption is required. New protocols for radio power-saving should also be developed and implemented in software.Internet of Things – sakernas internet – är ett framväxande koncept där varje enhet, oavsett storlek, har en anslutning till Internet. Detta examensarbete undersöker vilka möjliga begränsningar i funktionalitet detta får på trådlösa enheter med begränsade resurser. Flera olika teknologier undersöks och jämförs, innan ett antal väljs ut för att ingå i en implementation, till exempel: IEEE 802.15.4, 6LoWPAN och CoAP. Implementationen använder operativsystemet Contiki och körs på ett Texas Instruments CC2530 SoC. Flera prestandaaspekter undersöks: mängden skickad data, minnesanvändning och energiförbrukning. Resultaten diskuteras tillsammans med säkerhetsaspekter att ta hänsyn till i Internet of Things. Minnesanvändningen och energiförbrukningen är de mest problematiska områdena. På grund av chippets begränsade mängd minne kan inte all funktionalitet användas samtidigt. Dessutom är energiförbrukningen för hög för längre tids strömförsörjning med batteri, vilket ger en livslängd på enbart 27 timmar med ett knappcellsbatteri. Slutsatsen är att hårdvara med mer minne och lägre energiförbrukning behövs. Nya protokoll för energibesparande radioanvändning behöver också utvecklas och implementeras i mjukvara

Lightweight Event-driven Real-time Operating System for Resource Constrained Connectivity

Wirepas Connectivity (WPC) is a complex protocol stack for large scale mesh-based Internet of Things (IoT) networks. The communication units in a WPC network are called nodes and these are designed to be cheap, resource constrained and battery operated. In contrast, each node requires several levels of parallel and real-time processing, which is best provided by a Real-Time Operating System (RTOS). The resource constraint aspect places requirements for the RTOS design. The RTOS kernel should take less than 10 kB of program memory and under 1 kB of data memory. It must be energy efficient for battery operation and for this reason its scheduling must be tickless (as opposed to time-sharing). Furthermore, the WPC protocol stack requires deterministic real-time timings with microsecond accuracy from the RTOS. This thesis studies the feasibility of related RTOSs Contiki, TinyOS, µC/OS and FreeRTOS for WPC use. The study shows that none of the related RTOSs are feasible without major modification. Contiki and TinyOS would complicate software development. µC/OS is commercially licensed and would increase per node cost. FreeRTOS lacks sufficient real-time operation for WPC. Furthermore, these RTOSs are designed to be general purpose and thus they are wasteful with precious memory and energy resources. To better deal with these challenges, a more specific approach is required. As a solution, this thesis presents a completely new RTOS called WPC-OS, designed specifically for WPC. The RTOS design targets to timing determinism and energy efficiency in all its functions. The WPC-OS scheduler provides a novel and lightweight timetabled scheduling approach, which uses task durations to determine the next task. Event-driven operation is provided on top of this to achieve reactiveness to concurrent events. For evaluation and measuring WPC-OS design efficiency, it was implemented on an nRF52832 platform. The measurement results show that the WPC-OS kernel achieved a small memory footprint. With the typical WPC node configuration, it uses only 5 kB of program memory and 350 B of data memory. It can handle the WPC timing requirements with its real-time event service, which guarantees 1 us timing accuracy. It provides lightweight multitasking capability for applications, while being energy efficient. WPC-OS solves all design requirements WPC imposes on RTOS design, and is suitable for mass production. As future work, coroutine and hybrid scheduling options for WPC-OS should be investigated