Zach Shelby

UWB wireless sensor networks: UWEN - a practical example

The research topic of sensor networks has been around for some time. With improvements in device size, power consumption, communications, and computing technology, sensor networks are becoming more popular for an ever increasing range of applications. Since 2002, there has been an increased in the popularity of commercial applications based on ultra wideband. This, in turn, has ignited interest in the use of this technology for sensor networks and fuelled research in the area. Impulse-radio-based UWB technology has a number of inherent properties that are well suited to sensor network applications. In particular, UWB systems have potentially low complexity and low cost, have noise-like signal, are resistant to severe multipath and jamming, and have very good time domain resolution allowing for location and tracking applications. This article examines one example of a UWB sensor network for outdoor sport and lifestyle applications.

Energy optimization in multihop wireless embedded and sensor networks

This paper provides an analytical model for the study of energy consumption in multihop wireless embedded and sensor networks where nodes are extremely power constrained. Low-power optimization techniques developed for conventional ad hoc networks are not sufficient as they do not properly address particular features of embedded and sensor networks. It is not enough to reduce overall energy consumption, it is also important to maximize the lifetime of the entire network, that is, maintain full network connectivity for as long as possible. This paper considers different multihop scenarios to compute the energy per bit, efficiency and energy consumed by individual nodes and the network as a whole. The analysis uses a detailed model for the energy consumed by the radio at each node. Multihop topologies with equidistant and optimal node spacing are studied. Numerical computations illustrate the effects of packet routing, and explore the effects of coding and medium access control. These results show that always using a simple multihop message relay strategy is not always the best procedure.

Cross-layer Energy Analysis of Multi-hop Wireless Sensor Networks

In this paper, we propose a detailed energy survey of the physical, data link, and network layer by analytical techniques. We also show the impact of regular sleep periods on node energy consumption and present a comparison analysis of single-hop vs. multi-hop communications in the energy realm. A detailed energy expenditure analysis of not only the physical layer but also the link and network layer provides a basis for developing new energy efficient wireless sensor networks. Regular, coordinated sleeping extends the lifetime of sensor nodes, but systems can only benefit from sleeping in terms of transmitted packets if the data arrival rate to the system is low. Energy efficiency is the driving motivation for it can be considered the most important factor for wireless sensor networks because of the power constraints set by battery operation. Radio solutions in the lower ISM bands are attractive because of their relatively easy implementation and low power consumption. However, the data rates of these commercial radios are also relatively low, limiting transmittable frame sizes to a few tens of octets along with strict duty cycle requirements. From the analysis we extract key parameters of selected MAC protocols and show that some traditional mechanisms, such as binary exponential backoff, have some inherent problems. We also argue that single-hop communications has up to 40% lower energy consumption than multihop forwarding within the feasible transmission distances of an ISM radio.

Coding for energy efficient wireless embedded networks

This paper studies the effect of coding on the energy consumption in wireless embedded networks. An analytical model of the radio energy consumption is developed to study how different DC balanced codes affect the energy consumption for the one-hop case. A Rayleigh fading channel is assumed. The analysis is extended to include multihop scenarios in order to study the tradeoff between coding overhead and energy consumption. The numerical results obtained show that energy efficiencies of the codes used in a multihop routing scenario are strongly dependent on the channel conditions and on the number of hops used.

Wireless Internet over LMDS: architecture and experimental implementation

LMDS is currently a promising emerging technology in broadband fixed wireless communications. The cellular structure, high data rates, and flexibility make it perfect for multimedia, digital television, and interactive services. These high-bandwidth multimedia services received most of the research attention until lately. There has been a clear gap when considering UDP/TCP/IP and other data services over LMDS. We examine the ramifications of using standard TCP/IP data communication over a two-layer LMDS system. We argue that the former emphasis only on multimedia and ATM-based communication over LMDS was a mistake. The most exciting prospect for LMDS should be in the role of enabling Internet and data services together with multimedia. We introduce a basic architecture for two-layer IP-LMDS based on a trial network built between 1996 and 2000.

Multihop medium access control for WSNs: an energy analysis model

We present an energy analysis technique applicable to medium access control (MAC) and multihop communications. Furthermore, the techniques application gives insight on using multihop forwarding instead of single-hop communications. Using the technique, we perform an energy analysis of carrier-sense-multiple-access (CSMA-) based MAC protocols with sleeping schemes. Power constraints set by battery operation raise energy efficiency as the prime factor for wireless sensor networks. A detailed energy expenditure analysis of the physical, the link, and the network layers together can provide a basis for developing new energy-efficient wireless sensor networks. The presented technique provides a set of analytical tools for accomplishing this. With those tools, the energy impact of radio, MAC, and topology parameters on the network can be investigated. From the analysis, we extract key parameters of selected MAC protocols and show that some traditional mechanisms, such as binary exponential backoff, have inherent problems.

NanoIP: the zen of embedded networking

This paper reports on the development of an embedded networking protocol stack, which is for pervasive embedded devices. Taking into account requirements for sensors and low-price consumer devices. Instead of applying TCP/IP (designed to support routing and end-to-end connectivity) to embedded networking, our boundary conditions are quite different. The protocols presented here specifically provide embedded networking within local subnets. No routing is performed; instead a gateway can make the embedded devices visible to the global Internet. This configuration provides better scalability, RAM/ROM utilization, and lower power consumption. The developed single subnet architecture and additional protocols supporting pervasive applications are presented and shortly analyzed.

Advanced Wireless ICT Healthcare Research

Recently, the methods to improve general hospital logistics and processes have been under heavy investigation all over the world. Especially in the public healthcare and welfare sectors, the improved process practices can save a lot of time from supporting tasks which could be redirected to personal, patient care duties. Changes in processes directly affect overall healthcare costs. How to shift work load from supporting activities to patient-centric care, and make the patient passage through hospital processes more convenient using wireless technology are discussed in this paper. Some examples on hardware implementation related to the topic are also discussed.

Performance Evaluation of Optimized Medium Access Control Schemes Based on Ultra Wideband Technology

In this paper we evaluate the energy, event delivery, and delay performance of a number of medium access control protocols suitable for ultra-wideband (UWB) physical layer. While ultra-wideband is a promising technology, it creates unique challenges in MAC protocol design. Firstly, we analytically inspect the energy consumption of three UWB suitable MAC protocols and secondly concentrate on simulation of the IEEE 802.15.4 MAC and its UWB version. Comparison between UWB and direct sequence radios with the 802.15.4 MAC protocol clearly show the superior performance of UWB technology

Two‐layer LMDS system architecture: DAVIC‐based approach and analysis

Despite the growing interest for LMDS systems there have been only a few commercial implementations un- til now especially outside of the U.S.A. The use of hierar- chial structure through two-layer networking has been even rarer. In many cases LMDS systems have strong advantages against its competitors to cover the last mile. In this article, we review and analyze the standards currently available and describe the European two-layer trial system developed in 1996-2000. We show why further development towards IP based LMDS is useful in the future. Most of our recom- mendations are based on results derived from the European Union supported research project CABSINET. It had the aim of demonstrating the viability of a 40 GHz cellular dig- ital television system with a return channel to oer interac- tive services. Two systems were tested: A line of sight link using QPSK that is known as MVDS, and a non-line of sight with COFDM modulation scheme. In the RF-subsystems, the greatest diculty of any viable LMDS system is to ob- tain a moderately low price for the user receiver, while fulfilling the hard OFDM requirements in terms of phase noise, stability, and spectrum restrictions. Several options have been studied in order to design the subsystems with the smallest cost. This paper will present the architectures of the transmitters, nomadic terminals, and the design of the IF/RF subsystems for both types of modulations. The discussion is focused on system engineering and selections required in order to build a full two-layer LMDS system. Keywords—LMDS, Wireless Broadband Communications,