Dimitris N. Kalofonos

Performance of adaptive MC-CDMA detectors in rapidly fading Rayleigh channels

Multicarrier code-division multiple access (MC-CDMA) combines multicarrier transmission with direct sequence spread spectrum. Different approaches have been adopted which do not assume a perfectly known channel. We examine the forward-link performance of decision-directed adaptive detection schemes, with and without explicit channel estimation, for MC-CDMA systems operating in fast fading channels. We analyze theoretically the impact of channel estimation errors by first considering a simpler system employing a threshold orthogonality restoring combining (TORC) detector with a Kalman channel estimator. We show that the performance deteriorates significantly as the channel fading rate increases and that the fading rate affects the selection of system parameters. We examine the performance of more realistic schemes based on the minimum mean square error (MMSE) criterion using least mean square (LMS) and recursive least square (RLS) adaptation. We present a discussion which compares the decision-directed and pilot-aided approaches and explores the tradeoffs between channel estimation overhead and performance. We find that there is a fading rate range where each method provides a good tradeoff between performance and overhead. We conclude that the MMSE per carrier decision-directed detector with RLS estimation combines good performance in low to moderate fading rates, robustness in parameter variations, and relatively low complexity and overhead. For higher fading rates, however, only pilot-symbol-aided detectors are appropriate.

A P2P SOA enabling group collaboration through service composition

The Service-Oriented Architecture (SOA) paradigm was introduced for exposing business processes as services and enabling their interaction and composition over the Internet. The same computing model can potentially be extended to services of personal devices. As personal devices become network-aware their services can be made available (by their owners) to members of trusted peer groups, thus allowing them to compose new distributed collaborative applications. However, dealing with firewall traversals, NATs, mobility and issues of service-level naming and addressing stand in the way of this vision. In this paper we introduce a P2P SOA middleware architecture that addresses such problems of pervasive connectivity without requiring any intermediaries or changes to the service implementations. We present the basic elements of the architecture and the design of a specific instance of it, which enables the P2P service discovery and execution of composite personal services in distributed OSGi containers over JXTA.

A Framework for End-User Programming of Smart Homes Using Mobile Devices

A crucial challenge to enabling multi-device home networked systems is providing a way for non-expert consumers to combine, configure and control the available functions. Unfortunately, the typical consumers find it difficult to perform tasks using even stand-alone programmable CE devices; programming and controlling smart homes involving a number of connected devices and services represents a significantly bigger challenge. We present our architecture for end-user programming of novel application concepts in smart homes. Our architecture has an end-user layer, a scripting layer, a semantic adaptation layer, a distributed middleware layer and a local system layer. We describe the overall end-users process for creating applications. We discuss a part of our implementation that automatically discovers and composes devices into arrangements that satisfy the users goal.

Intuisec: A Framework for Intuitive User Interaction with Smart Home Security using Mobile Devices

This paper presents IntuiSec, a framework for intuitive user interaction with smart home security using mobile devices. The design approach of IntuiSec is to introduce a level of indirection between the user-level intent and the system-level security infrastructure. This layer of indirection, implemented by a collection of distributed middleware and user-level tools, exposes only concepts and real-world metaphors that are intuitive to non-expert users and translates their intent to the necessary underlying security settings. The IntuiSec framework presents the user with intuitive steps for setting up a secure home network, establishing trusted relationships between devices, and granting temporal, selective access for both home occupants and visitors to devices within the smart home.

A hybrid P2P/Infrastructure platform for personal and social Internet services

While pure Web-based services and P2P technologies are popular for personal and social networking, they both have inherent limitations. A hybrid P2P/Infrastrucutre approach could leverage strengths and address limitations of both paradigms. In this paper we propose such a platform based on MyNet, our P2P personal and social networking system. The new hybrid architecture enhances the properties of pervasive access, security and ease of use found in MyNet through the introduction of infrastructure-hosted MyNet Virtual Devices (MVD). MVDs act as userspsila personal devices, but also host MyNet-aware Internet services (MaIS), proxies for 3rd party Internet services. A proof-of-concept prototype and user results are presented to showcase key system features.

A Network Connectivity Power-Saving Mechanism for Mobile Devices in DLNA Home Networks

Mobile devices are increasingly assuming an important role in “smart home” network environments. Although their computing, storage and networking capabilities have evolved significantly, these devices remain power-constrained and, therefore, need to actively take measures to minimize their power consumption. In this paper, we propose a Network Connectivity Power Saving (NC-PS) mechanism for mobile devices in Digital Living Network Alliance (DLNA) home networks, which allows them to conserve power without compromising their higher-layer functionality. The proposed mechanism introduces a level of indirection that abstracts the low-level low-power support of different wireless bearers and exposes a uniform interface to higher-layer entities, such as applications and Universal–Plugand-Play (UPnP) agents. We define four abstract NC-PS modes and we describe their mapping in the case of Bluetooth, a common wireless bearer for mobile devices, now supported in DLNA.

P2P social networking for the rest of US

The user experience of current P2P Personal and Social networking systems does not meet the usability needs of the technically naive users. This is the motivation behind MyNet, a P2P platform that enables non-expert users to easily organize their resources and share them in their immediate social neighborhood. In this paper, we present our experience following a user-centered approach in designing MyNet: using real-world metaphors in the core system, leveraging NFC-based touch to mirror human behavior models, and involving actual users in the design process. The results of our 50-user usability evaluation are also presented in detail.

Using RFID-based “Touch” for Intuitive User Interaction with Smart Space Security

Home networks and networked consumer electronic devices are increasingly becoming a part of our everyday lives. One of the challenges in designing smart home technology is making these systems secure and, at the same time, easy-to-use for non-expert consumers. We believe that mobile devices equipped with a “touch” network interface and corresponding middleware are ideal for enabling users to intuitively setup and manage the security of their smart homes. In this chapter, we describe such a middleware for mobile phones based on Near Field Communication (NFC) technology. We propose a mobile middleware architecture called iTouchSec based on a higher level User-Interaction with Security (UI-SEC) middleware, called IntuiSec, and a lower level NFC middleware, called iTouch. We present the overall architecture, as well as the detailed design of the necessary NFC records that are exchanged over RF. Finally, we present our experience with an initial implementation of parts of the proposed middleware using actual NFC hardware and Symbian-based mobile phones.

An experimental end-node architecture and communications middleware for dynamic proximity networks

In this paper, we present our experience in implementing an experimental end-node architecture and communications middleware that enables devices to (a) create and maintain ad-hoc connectivity in the absence of infrastructure support, (b) heal IP network partitions and resume active TCP sessions during intermittent connectivity, (c) detect network infrastructure (e.g. access points) when available and use it, and (d) discover devices and services currently attached to the network. In broader terms, our communications middleware includes a connection manager (CM) that provides and maintains the link-level and IP infrastructures and heal network partitions as they occur, arid a session manager (SM), which provides end-to-end active TCP-session support against intermittent connectivity and IP address changes. Finally, we provide some experimental results from a working implementation of our communications middleware on Linux devices and results from its support, of two example distributed applications, namely a distributed file browser and a multiplayer game

A Bluetooth scatternet formation and healing protocol for ad-hoc group collaboration

In this paper, we present a new tree-based Bluetooth (BTH) scatternet formation and healing protocol called GC-tree, Our protocol enables group collaboration, e.g. wireless ad-hoc meetings, where individuals bring piconets with their devices in a scatternet to collaborate. We present experimental performance results from a prototype implementation using uff-the-self BTH v1.1 hardware and Linux-based devices. Finally, we complement our experimental results with a realistic simulation model