Smart spaces such as smart homes deliver digital services to optimize space use and enhance user experience. They are composed of an Internet of Things (IoT), people, and physical content. They differ from traditional computer systems in that their cyber-physical nature ties intimately with the users and the built environment. The impact of ill-programmed applications in such spaces goes beyond loss of data or a computer crash, risking potentially physical harm to the space and its users. Ensuring smart space safety is therefore critically important to successfully deliver intimate and convenient services surrounding our daily lives. By modeling smart space as a highly dynamic database, we present IoT Transactions, an analogy to database transactions, as an abstraction for programming and executing the services as the handling of the devices in smart space. Unlike traditional database management systems that take a “clear room approach,” smart spaces take a “dirty room approach” where imperfection and unattainability of full control and guarantees are the new normal. We identify Atomicity, Isolation, Integrity and Durability (AI 2 D) as the set of properties necessary to define the safe runtime behavior for IoT transactions for maintaining “permissible device settings” of execution and to avoid or detect and resolve “impermissible settings.” Furthermore, we introduce a lock protocol, utilizing variations of lock concepts, that enforces AI 2 D safety properties during transaction processing. We show a brief proof of the protocol correctness and a detailed analytical model to evaluate its performance.

The first cohort of “baby boomers” are now 65 years or older, presaging a massive wave of aging “boomers” that could degrade health care and elder care over the next quarter-century. Cost-effective, high-impact technologies for aging, disabilities and independent living are urgently needed. In this paper, we present our experience in building “assistive environments” for older adults-the Gator Tech Smart House (GTSH) project. Numerous R&D efforts similar to ours are either underway or have recently been conducted. In most of these projects, prototypes have been built to achieve independence, well being, and in general, good quality of life. But prototyping a technology is one thing; commercial proliferation and creating a vibrant industry around such technology is an altogether different proposition. From the lessons learned in the GTSH, we analyze the impediments hindering the emergence of products and services for assistive environments, and present the blueprints of an ecosystem based on requirements drawn from the lessons learned. We believe the proposed ecosystem is an important beginning to providing better conditions for an accelerated proliferation of next-generation smart homes and assistive environments.

In ad hoc networks with Internet connectivity, an Internet gateway (IG) is used to connect ad hoc mobile nodes to the Internet. Multiple Internet gateways may be deployed in order to provide more scalable and robust ubiquitous coverage. In this case, we need to solve the Internet gateway selection problem in order for successful integration of the Internet with mobile ad hoc networks. An ad hoc mobile node first discovers available Internet gateways, and then the node selects a serving gateway among those candidates for optimal performance. In this paper, we propose an adaptive Internet gateway selection scheme using redirecting selection method which is based on QoS attributes such as hop-count and residual capacity. Our objective is to design a selection method for providing enhanced performance. Simulation results show that our adaptive Internet gateway selection scheme achieves better performance as well as better load balancing than existing selection schemes.

This paper proposes an adaptive and dynamic localized scheme unique to hierarchical clustering in RFID networks, while reducing the overlapping areas of clusters and consequently reducing collisions among RFID readers. Drew on our LLC scheme that adjusts cluster coverage to minimize energy consumption, low-energy localized clustering for RFID networks (LLCR) addresses RFID reader anti-collision problem in this paper. LLCR is a RFID reader anti-collision algorithm that minimizes collisions by minimizing overlapping areas of clusters that each RFID reader covers. LLCR takes into account each RFID reader's energy state as well as RFID reader collisions. For the energy state factor, we distinguish homogeneous RFID networks from heterogeneous ones according to computing power of each RFID reader. Therefore, we have designed efficient homo-LLCR and hetero-LLCR schemes for each case. Our simulation-based performance evaluation shows that LLCR minimizes energy consumption and overlapping areas of clusters of RFID readers.

The Pervasive Computing Laboratory at the University of Florida is dedicated to creating smart environments and assistants to enable elderly persons to live a longer and a more independent life at home. By achieving this goal, technology will increase the chances of successful aging despite an ailing health care system (e.g. Medicaid). One of the essential services required to maximize the intelligence of a smart environment is an indoor precision tracking system. Such system allows the smart home to make proactive decisions to better serve its occupants by enabling context-awareness instead of being solely reactive to their commands. This paper presents our hands-on experience and lessons learnt from our first phase work to build up a smart home infrastructure for the elderly. We review location tracking technology and describe the rationale behind our choice of the emerging ultrasonic sensor technology. We give an overview of the House of Matilda (an in-laboratory mock up house) and describe our design of a precision in-door tracking system. We also describe an OSGi-based robust framework that abstracts the ultrasonic technology into a standard service to enable the creation of tracking based applications by third party, and to facilitate the collaboration among various devices and other OSGi services. Finally, we describe three pervasive computing applications that use the location-tracking system which we have implemented in Matilda's house.

The growth of the wireless Internet has led to the optimization of network protocols to provide for a better performance. Most of the Internet traffic uses TCP, the de facto transport layer protocol. Unfortunately, TCP performance degrades in the mobile and wireless environments. A good amount of research has been attempted to improve its performance in the unpredictable mobile and wireless environments where link disconnections, packets losses and delays are common. Most of these proposed solutions target the case where the mobile host acts as a TCP receiver. For various reasons, almost none of the solutions have reached the stage of deployment. In this paper, we propose an interlayer collaboration model for TCP performance improvement in mobile and wireless environments. We specifically target the case where a mobile acts as a TCP sender. ILC-TCP is an end-to-end approach and does not need any special support from the base station infrastructure. ILC-TCP is evaluated against the normal TCP in various scenarios. Performance results suggest that ILC-TCP performs better than the normal TCP in many scenarios involving long disconnections, frequent disconnections and in the scenarios where a mobile host moves at considerable speeds.

The proliferation of mobile devices and the pervasiveness of wireless technology have provided a major impetus to replicate the network-based service discovery technologies in wireless and mobile networks. However, existing service discovery protocols and delivery mechanisms fall short of accommodating the complexities of the ad-hoc environment. They also place emphasis on device capabilities as services rather than device independent software services, making them unsuitable for m-commerce oriented scenarios. Konark is a service discovery and delivery protocol designed specifically for ad-hoc, peer-to-peer networks, and targeted towards device independent services in particular. It has two major aspects - service discovery and service delivery. For discovery, Konark uses a completely distributed, peer-to-peer mechanism that provides each device the ability to advertise and discover services in the network. The approach towards service description is XML based. It includes a description template that allows services to be described in a human and software understandable forms. A micro-HTTP server present on each device handles service delivery, which is based on SOAP. Konark provides a framework for connecting isolated services offered by proximal pervasive devices over a wireless medium.

In this paper, we address the problem of cache invalidation in mobile and wireless client/server environments. We present cache invalidation techniques that can scale not only to a large number of mobile clients, but also to a large number of data items that can be cached in the mobile clients. We propose two scalable algorithms: the Multidimensional Bit-Sequence (MD-BS) algorithm and the Multilevel Bit-Sequence (ML-BS) algorithm. Both algorithms are based on our prior work on the Basic Bit-Sequences (BS) algorithm. Our study shows that the proposed algorithms are effective for a large number of cached data items with low update rates. The study also illustrates that the algorithms ran be used with other complementary techniques to address the problem of cache invalidation for data items with varied update and access rates.

The proliferation of mobile devices and the pervasiveness of wireless technology have provided a major impetus to replicate the network-based service discovery technologies in wireless and mobile networks. However, existing service discovery protocols and delivery mechanisms designed for traditional infrastructure-based networks fall short of accommodating the complexities of the ad hoc environment. Konark is a service discovery and delivery protocol designed specifically for ad hoc, peer-to-peer networks, and targeted toward device-independent services in general and m-commerce oriented software services in particular. It has two major aspects-service discovery and service delivery. For discovery, Konark uses a novel decentralized, peer-to-peer mechanism that provides each device the ability to advertise and discover services in an efficient way. The approach toward service description is XML-based. It includes a description template that allows services to be described in a human and software understandable forms. A micro-HTTP server present on each device handles service delivery, which is based on SOAP. Konark provides a framework for connecting isolated services offered by proximal pervasive devices over a wireless medium.

We present a Bluetooth LAN access point (LAP) simulator that we have developed to study pervasive application behavior under Bluetooth local connectivity. Our goal is to explore the impact on IP applications caused by the underlying Bluetooth protocol. Our simulator implements detailed processing of upper layers of the Bluetooth LAP stack, including PPP, RFCOMM, and L2CAP. For lower layers, it tries to capture major characteristics by performing macro-simulation. We present simulation results of a simple network configuration in Bluelooth LAP environments. Our simulator is based on the popular Network Simulator (ns) and its components.

To allow a seamless integration between wireless LANs and wireless WANs, we developed a full stack adaptation model and a simple subnet architecture that superimposes Mobile-IP on cellular-type wireless LANs. The idea is to use Mobile IP as an integrative layer atop different LAN/WAN networks. While Mobile-IP is widely used in wireless WANs, it is not known how well it performs under a wireless LAN environment, against native MAC-level handoff. Through experimentation using the 802.11 W-LAN, we found that under practical values of handoff frequencies, the performance of Mobile IP based W-LAN handoff is almost identical to the performance of W-LAN handoff. Further performance studies show the suitability of Mobile-IP as an integrative layer in this architecture.