A Low-Power CoAP for Contiki

Internet of Things devices will by and large be battery-operated, but existing application protocols have typically not been designed with power-efficiency in mind. In low-power wireless systems, power-efficiency is determined by the ability to maintain a low radio duty cycle: keeping the radio off as much as possible. We present an implementation of the IETF Constrained Application Protocol (CoAP) for the Contiki operating system that leverages the ContikiMAC low-power duty cycling mechanism to provide power efficiency. We experimentally evaluate our low-power CoAP, demonstrating that an existing application layer protocol can be made power-efficient through a generic radio duty cycling mechanism. To the best of our knowledge, our CoAP implementation is the first to provide power-efficient operation through radio duty cycling. Our results question the need for specialized low-power mechanisms at the application layer, instead providing low-power operation only at the radio duty cycling layer

Practical semantics for the Internet of Things: Physical states, device mashups, and open questions

Abstract—The Internet of Things (IoT) envisions cross-domain applications that combine digital services with services provided by resource-constrained embedded devices that connect to the physical world. Such smart environments can comprise a large number of devices from various different vendors. This requires a high degree of decoupling and neither devices nor user agents can rely on a priori knowledge of service APIs. Semantic service descriptions are applicable to heterogeneous application domains due to their high level of abstraction and can enable auto-matic service composition. This paper shows how the RESTdesc description format and semantic reasoning can be applied to create Web-like mashups in smart environments. Our approach supports highly dynamic environments with resource-constrained IoT devices where services can become unavailable due to device mobility, limited energy, or network disruptions. The concepts are backed by a concrete system architecture whose implementation is publicly available. It is used to evaluate the semantics-based approach in a realistic IoT-related scenario. The results show that current reasoners are able to produce medium-sized IoT mashups, but struggle with state space explosion when physical states become part of the proofing process. I

Firm Firmware and Apps for the Internet of Things

Among the challenges for the Internet of Things, two stand out: a scalable application layer with wide interoperability and a common, reliable programming model. We propose to strip all application logic from the firmware and only provide a RESTful interface to the hardware functionality. Critical parts such as the network stack remain in the immutable firmware that is maintained by experts. Applications are developed atop the resource abstraction and run in the cloud. Leaving the embedded domain, application development is eased while sharing and customizing applications helps to cope with the vast number of diversified device types. Categories and Subject Descriptor

Embedding Internet Technology for Home Automation

As more and more digital appliances populate our homes, networking them to form a home automation (HA) system not only becomes an option, but almost a necessity. While comfort, security, and energy efficiency can be provided by many existing systems, they all remain complex islands that are difficult to expand and customize. We propose Internet technology to remedy the situation and to become the future solution for HA. For this, we analyze the feasibility of today’s Internet technology with regard to traditional HA solutions. Furthermore, we present two case studies that substantiate the benefits of our proposal. As we will show, with IPv6 and 6LoWPAN, a single network serves the classical as well as emerging aspects of HA while concepts from the Web provide benefits for both, developers and users.

Actinium: A RESTful Runtime Container for Scriptable Internet of Things Applications

Programming Internet of Things (IoT) applications is challenging because developers have to be knowledgeable in various technical domains, from low-power networking, over embedded operating systems, to distributed algorithms. Hence, it will be challenging to find enough experts to provide software for the vast number of expected devices, which must also be scalable and particularly safe due to the connection to the physical world. To remedy this situation, we propose an architecture that provides Web-like scripting for low-end devices through Cloud-based application servers and a consistent, RESTful programming model. Our novel runtime container Actinium (Ac) exposes scripts, their configuration, and their lifecycle management through a fully RESTful programming interface using the Constrained Application Protocol (CoAP). We endow the JavaScript language with an API for direct interaction with mote-class IoT devices, the CoapRequest object, and means to export script data as Web resources. With Actinium, applications can be created by simply mashing up resources provided by CoAP servers on devices, other scripts, and classic Web services. We also discuss security considerations and show the suitability of this architecture in terms of performance with our publicly available implementation.PromosCONE