We present a novel power-efficient wireless sensor network for continuously monitoring and analyzing seismic vibrations with sensor nodes and forwarding the retrieved information with low-cost relay nodes to backend applications. The applied vibration sensing algorithms are derived from the DIN 4150-3 standard. All nodes in the network are battery-powered and equipped with an IEEE 802.15.4 compatible radio transceiver. The nodes communicate with each other by executing a novel power-efficient protocol stack, which provides all network functions required by the vibration-sensing application and uses a publish/subscribe messaging protocol for communicating between the network nodes and the backend applications. Results obtained in certification and field tests show that the proposed vibration-sensing solution is standard-compliant, and that the wireless vibration sensor network (WVSN) exhibits excellent performance in terms of packet delivery rate, latency, and power efficiency.

A method is presented for efficiently and reliably routing data packets from a static information source to a mobile sink through a multi-hop wireless sensor network. While the source and all sensor nodes are located at fixed and known positions, the mobile sink estimates and tracks its location, speed, and acceleration with a Kalman filter. To reliably and timely route data packets, the source predicts the location of the mobile sink. The prediction is updated by receiving messages from the mobile sink, containing its current location, speed, and acceleration. These messages are sent only if the Euclidean norm of the error between the predicted state and the state estimated by the Kalman filter exceeds a pre-defined threshold. The control messages and the data packets are forwarded in a multi-hop fashion through the network using geographic routing. Simulation results demonstrate that the proposed scheme outperforms conventional routing protocols in terms of packet transfer reliability, latency, and energy efficiency.

In this paper, we propose a novel dynamic routing strategy called tunnel routing that enables efficient and resilient data forwarding from sensors to a destination in wireless sensor networks. Instead of establishing a single static path, tunnel routing identifies a set of trusted sensor nodes that form a tunnel between the source and the destination. Terminals in the tunnel cooperate with each other to reliably route data and to defend against compromised nodes that may maliciously drop or re-direct packets. To achieve this, not only do sensor terminals forward data, but also they act as support nodes, providing on-demand retransmissions in order to combat channel fading, and initializing multi-path data forwarding towards the destination in case they detect a misbehavior of a forwarding node. Simulation results demonstrate the advantages of the proposed scheme.

Geographic routing is a promising solution for data forwarding in power-constrained ad-hoc networks. Such protocols are especially attractive for wireless sensor networks as they can be operated without a central control and are scalable to an arbitrary number of nodes. In this work, we present a class of geographic routing algorithms that enhance energy-efficiency by means of a cross-layer design that incorporates PHY/MAC functions such as on-demand cooperative relaying and leapfrogging. The performance of these protocols is evaluated by means of OMNET++ simulations. Significant improvements are shown in terms of packet delivery ratio, latency and connectivity for different network topologies.

A novel geographic routing protocol for multi-hop wireless sensor networks is presented. It exploits the broadcast nature of the wireless channel to enable on-demand cooperative relaying and leapfrogging for circumventing weak radio links. In order to achieve energy efficiency, a metric is introduced for next-hop selection that takes into account information on the residual battery energy, the geographical position of the sensor nodes, and the channel quality of the involved radio links when available. Performance results show that the completely decentralized protocol offers significant benefits by reducing the number of (re)transmissions required to reach the destination. This translates into network-wide energy savings that extend the network lifetime.

This paper introduces an opportunistic medium-access control (MAC) scheme for controlling the uplink message transfer from sensor nodes to a central controller in wireless sensor networks (WSN). By equipping the controller with multiple antennas to communicate with single-antenna sensors, we propose a scheme that benefits from diversity reception at the controller and leads to a considerable reduction of battery energy consumption in sensor nodes. The performance of the scheme is illustrated using a Rayleigh fading channel model.

The wireless communication landscape will continue to develop at a rapid pace over the next years. New systems and standards are on the horizon, which enable broadband wireless communication in the office, at home, and "on the move". They will finally bring the information services provided by the Internet and the World-Wide-Web also to the mobile users, together with a variety of multimedia entertainment services. In this paper we give an overview of key developments in wireless communication systems. The emerging 3rd generation cellular systems and the growing importance of wireless local-area and personal-area networks are discussed. The physical and medium-access control (MAC) layer of the new broadband wireless LANs which enable "hot-spot" data and multimedia services in airports, hotel lobbies, and a variety of other "public" places are presented. We give an outlook towards a future 4th-generation wireless communication system, which can be integrated with the IP backbone network and provides Quality of Service (QoS) support for multimedia applications. It supports dynamic scheduling, link adaptation, and frequency selection in addition to full mobility support. Finally, we illuminate some of the underlying technology developments driving the wireless evolution.

The paper describes the methodology used for specifying, analysing, simulating, validating and implementing the radio protocols for a CDMA testbed of the future Universal Mobile Telecommunication System (UMTS). The specification methodology is based on the ITU-T guidelines for the use of the specification and description language (SDL).>

The realization of a digital recording system using partial-response class-IV signaling with maximum-likelihood sequence detection (MLSD) is described. To perform MLSD at the high data rates encountered in recording systems, a simple implementation of the Viterbi detector based on a difference-metric algorithm is developed. Decision-directed schemes for gain control and timing recovery, for tracking variations of the gain and timing phase during data readback, and for fast initial adjustment from a known preamble are presented. The dynamic behavior of the control algorithms was studied by computer simulations. Coding was used to facilitate timing recovery and gain control, to limit the path memory length of the Viterbi detector, and to allow fast and reliable startup of the receiver. The design and properties of rate 8/9 constrained codes are examined. The problem of equalization is addressed, and analog and combined analog/digital filter implementations are developed. A simple adaptive equalizer capable of compensating variations of the recording channel characteristics with track radius and/or head-to-medium distance is described.>