Centre for Communication Systems Research

Connected vehicles are promoted with the use of different communication technologies for diverse applications. A host with multiple network devices is referred to as a multi- homed node. Stream Control Transmission Protocol (SCTP) is an IETF standard which supports multi-homing. However, original SCTP multi-homing functionality is only used when the primary address becomes unavailable. This paper presents an analytical model for a modified SCTP with multi-homed hosts, which selects the primary network address using a utility function based on minimum round trip time.

There is an ongoing debate in research and industry communities whether IEEE 802.11p or 3GPP LTE should be used for vehicular communications. In this work, we argue that a hybrid vehicular network combining both technologies can increase the performance of the system. We first propose a mechanism to improve location- based routing in a hybrid vehicular networks architecture, by data and signalling traffic separation on independent wireless networks. We then develop analytical models for calculating the stochastic upper bound of the end-to- end delay for location-based routing in three different networking architecture alternatives based on: (a) short range ad-hoc only, (b) cellular only, and (c) the proposed hybrid ad-hoc/cellular network. The analytical approach in this paper is based on Stochastic Network Calculus theory, which provides a solid and uniform framework for analysis of the upper bound of the end-to-end delay in communication networks. It is demonstrated that the proposed hybrid network provides a lower end-to-end delay compared to the other two alternatives. Comparisons of realistic simulation results, carried out in NS3, and analytical results show that the proposed delay bounds provide relatively tight approximations for the end-to-end delay in the three alternative architectures for vehicular networks investigated in this paper.

This paper introduces a distributed system for next generation multimedia support in dynamically changing pervasive computing environments. The overall goal is to enhance the experience of mobile users by intelligently adapting the way a service is presented, in particular by adapting the way the user receives multimedia content from the service and how he interacts with the service. The system tailors this presentation to the user's context, for instance based on his current activity (e.g., driving or walking) or the characteristics of the devices that surround him (e.g., devices for multimedia rendering and user interaction devices). The system integrates with the (IMS-based) service platforms of "beyond 3G" telecom operators and allows multimedia content to be rendered on multiple devices at the same time. It can also dynamically and seamlessly adapt the way a service is presented while it is being used (e.g., from gesture-based input to voice commands). These changes are triggered by changes in the user's context (e.g., when the user gets into his car). This paper discusses the system's requirements, presents an architecture proposal and describes its current implementation.

Sensor networks are used in various applications in several domains for measuring and determining physical phenomena and natural events. Sensors enable machines to capture and observe characteristics of physical objects and features of natural incidents. Sensor networks generate immense amount of data which requires advanced analytical processing and interpretation by machines. Most of the current efforts on sensor networks are focused on network technologies and service development for various applications, but less on processing the emerging data. Sensor data in a real world application will be an integration of various data obtained from different sensors such as temperature, pressure, and humidity. Processing and interpretation of huge amounts of heterogeneous sensor data and interoperability are important issues in designing a scalable sensor network architecture. This paper describes a semantic model for heterogeneous sensor data representation. We use common standards and logical description frameworks proposed by the Semantic Web community to create a sensor data description model. The work describes a sensor data ontology which is created based on the Sensor Web Enablement (SWE) and SensorML data component models. We describe how the semantic relationship and operational constraints are deployed in a uniform structure to describe the heterogeneous sensor data.

This paper introduces a systematic approach for Digital Signal Processing (DSP) structure optimizations based on the Multirate Signal Flow Graph (MSFG) representation and transformations. With this method, the optimization of dsp algorithms and structures is reduced to a series of MSFG transformations that makes automation of dsp structure optimization possible. To demonstrate the effectiveness of the approach, an efficient Digital Down Converter (DDC) structure is derived through MSFG transformations. This method can be used for optimizations of any linear time-invariant or periodically time-varying system.

This article presents findings from the first large-scale quantitative assessment of Peer-to-Peer (P2P) exchanges of copyrighted material on a college campus based on actual observation. Through passive monitoring and deep packet inspection (DPI), we assess ...

This article presents findings from the first large-scale quantitative assessment of Peer-to-Peer (P2P) exchanges of copyrighted material on a college campus based on actual observation. Through passive monitoring and deep packet inspection (DPI), we assess ...

This paper examines strategies for implementing and operating IP routing effectively within satellite constellation networks, given known constraints on the constellation resulting from satellite mobility, global visibility, routing and addressing.

Here, we examine networking and internetworking issues affecting satellite networking in complex satellite constellation networks, and determine what is needed in order to support services based on the TCP/IP suite well in satellite constellations.

In this paper we present a traffic conditioner able to provide fairness between responsive and unresponsive flows originating from the same customer network, using a Fair Two-Rate Three-Color Marker. Its capability for fairness is based on the use of the FRED fair active buffer algorithm to control the token allocation of the token buckets residing in the traffic conditioner.

The rosette satellite constellation network with intersatellite links (ISLs) presents unique properties, in providing locally separate ascending and descending network surfaces of interconnected satellites with which the ground terminal can communicate. We present a novel approach exploiting this rosette geometry, by use of control of handover and management of satellite diversity, to determine which surface a ground terminal will select for communication.