In recent years, Internet of Things (IoT) has attracted great attention from academia, industry, and government. IoT is considered to be a networking infrastructure that can connect enormous physical objects and has great potential to extend mankind's capabilities in monitoring, analyzing, and controlling the physical space using cyber technologies. Extensive studies on IoT have been carried out and many IoT prototype systems have been built. However, most of these systems are usually suitable for domain-specific applications and operate in a local region. They are really “Nets of Things (NoT)” as they miss mechanisms for large-scale interconnection. As such, how to build a globally interconnected IoT is still an open problem. In this article, by reviewing the development of the Internet, we derive a pathway that may lead to successful development and deployment of a global IoT. We propose and examine a novel IoT architecture, namely, WInternet, which aims at interconnecting small-scale domain-specific NoTs into a globally connected IoT.

In real-time systems, utilization-based schedulability test is a common approach to determine whether or not tasks can be admitted without violating deadline requirements. The test is extremely simple, since it only needs to compare the utilization of the tasks with a predetermined bound. As such, utilization-based schedulability tests are suitable for online use. The challenge is how to derive a reasonable utilization bound for a given system. Most existing results are obtained on a case-by-case basis because of their analytical complexity. In this paper, we develop a flexible and unified representation framework of real-time systems (i.e., tasks and schedulers) based on network calculus techniques. Our representation framework, together with the proposed bound derivation method, leads to a general bound result, which is applicable to a large family of real-time systems.

Schedulability analysis is a cornerstone of modern real-time scheduling theory development. Utilization- bound based schedulability test is considered one of most efficient and effective schedulability tests, because of its extremely low runtime overhead. Deriving the utilization bound for a given real-time system has, nevertheless, been a challenging task as it usually requires comprehensive modeling and understanding of the system and payload tasks. This paper is focused on deriving utilization bounds for weighted round robin schedulers. We demonstrate how to establish a unified modeling framework and then use it to derive utilization bounds. We obtain the optimal parameter selection that maximizes the utilization bound, then compare the new bound with those of fixed priority schedulers, and timed token ring schedulers. The new bound is further extended to systems with sporadic job requests. We argue that our modeling framework is highly versatile, and hence, can be easily tailored for analysis of other types of real-time systems.

While utilization bound based schedulability test is simple and effective, it is often difficult to derive the bound itself. For its analytical complexity, utilization bound results are usually obtained on a case-by-case basis. In this paper, we develop a general framework that allows one to effectively derive schedulability bounds for a wide range of real-time systems with different workload patterns and schedulers. Our analytical model is capable of describing a wide range of tasks and schedulers' behaviors. We propose a new definition of utilization, called workload rate. While similar to utilization, workload rate enables flexible representation of different scheduling and workload scenarios and leads to uniform derivation of schedulability bounds. We derive a parameterized schedulability bound for static priority schedulers with arbitrary priority assignment. Existing utilization bounds for different priority assignments and task releasing patterns can be derived from our closed-form formula by simple assignments of proper parameters.