Energy efficiency in short and wide-area IoT technologies—A survey

In the last years, the Internet of Things (IoT) has emerged as a key application context in the design and evolution of technologies in the transition toward a 5G ecosystem. More and more IoT technologies have entered the market and represent important enablers in the deployment of networks of interconnected devices. As network and spatial device densities grow, energy efficiency and consumption are becoming an important aspect in analyzing the performance and suitability of different technologies. In this framework, this survey presents an extensive review of IoT technologies, including both Low-Power Short-Area Networks (LPSANs) and Low-Power Wide-Area Networks (LPWANs), from the perspective of energy efficiency and power consumption. Existing consumption models and energy efficiency mechanisms are categorized, analyzed and discussed, in order to highlight the main trends proposed in literature and standards toward achieving energy-efficient IoT networks. Current limitations and open challenges are also discussed, aiming at highlighting new possible research directions

Location based services with personal area network for community and tourism applications

The Infopoint Explorer is an outdoor wireless personal area network for location-based services that allows users to access locality information interactively using mobile computing devices such as PDAs and smartphones. The Infopoint explorer was used to study the limitations imposed by inexpensive and popular wireless technologies such as Bluetooth for outdoor location-based services. The Infopoint Explorer functioned as a multimedia guidebook that allowed access to location-specific information using wireless Infopoints. The Infopoints detect and attempt to transfer multimedia content to nearby mobile computing devices using Bluetooth connectivity. An adaptive Bluetooth Inquiry Access Code algorithm was developed to reduce the time taken for the Infopoint to detect nearby devices. The Infopoint was deployed for a four-month trial

AN EFFICIENT COMBINED CONGESTION HANDLING=--A--cN-:cD~-­ ROUTE MAINTENANCE PROTOCOL FOR DYNAMIC ENVIRONMENT IN BLUETOOTH NETWORK

Bluetooth IS a widespread technology for small wireless networks that permits Bluetooth devices to construct a multi-hop network called a scatternet. A large number of connections passing through a single master/ bridge device may create the problem of congestion in a Bluetooth scatternet. In addition, routing in a multi-hop dynamic Bluetooth network, where a number of masters and bridges exist, sometimes creates technical hitches in a scatternet. It has been observed that frequent link disconnections and a new route construction consume more system resources that ultimately degrade the performance of the whole network. As, Bluetooth specification has defined piconet configuration, scatternet configuration has still not been standardized. The main objective of this thesis is to provide an efficient combined protocol for scatternet congestion handling and route maintenance. The methodology contains three parts

Energy efficient medium access control for wireless sensor networks

A wireless sensor network designates a system composed of numerous sensor nodes distributed over an area in order to collect information. The sensor nodes communicate wirelessly with each other in order to self-organize into a multi-hop network, collaborate in the sensing activity and forward the acquired information towards one or more users of the information. Applications of sensor networks are numerous, ranging from environmental monitoring, home and building automation to industrial control. Since sensor nodes are expected to be deployed in large numbers, they must be inexpensive. Communication between sensor nodes should be wireless in order to minimize the deployment cost. The lifetime of sensor nodes must be long for minimal maintenance cost. The most important consequence of the low cost and long lifetime requirements is the need for low power consumption. With today's technology, wireless communication hardware consumes so much power that it is not acceptable to keep the wireless communication interface constantly in operation. As a result, it is required to use a communication protocol with which sensor nodes are able to communicate keeping the communication interface turned-off most of the time. The subject of this dissertation is the design of medium access control protocols permitting to reach a very low power consumption when communicating at a low average throughput in multi-hop wireless sensor networks. In a first part, the performance of a scheduled protocol (time division multiple access, TDMA) is compared to the one of a contention protocol (non-persistent carrier sensing multiple access with preamble sampling, NP-CSMA-PS). The preamble sampling technique is a scheme that avoids constant listening to an idle medium. This thesis presents a low power contention protocol obtained through the combination of preamble sampling with non-persistent carrier sensing multiple access. The analysis of the strengths and weaknesses of TDMA and NP-CSMA-PS led us to propose a solution that exploits TDMA for the transport of frequent periodic data traffic and NP-CSMA-PS for the transport of sporadic signalling traffic required to setup the TDMA schedule. The second part of this thesis describes the WiseMAC protocol. This protocol is a further enhancement of CSMA with preamble sampling that proved to provide both a low power consumption in low traffic conditions and a high energy efficiency in high traffic conditions. It is shown that this protocol can provide either a power consumption or a latency several times lower that what is provided by previously proposed protocols. The WiseMAC protocol was initially designed for multi-hop wireless sensor networks. A comparison with power saving protocols designed specifically for the downlink of infrastructure wireless networks shows that it is also of interest in such cases. An implementation of the WiseMAC protocol has permitted to validate experimentally the proposed concepts and the presented analysis

Contributions to Improve Cognitive Strategies with Respect to Wireless Coexistence

Cognitive radio (CR) can identify temporarily available opportunities in a shared radio environment to improve spectral efficiency and coexistence behavior of radio systems. It operates as a secondary user (SU) and accommodates itself in detected opportunities with an intention to avoid harmful collisions with coexisting primary user (PU) systems. Such opportunistic operation of a CR system requires efficient situational awareness and reliable decision making for radio resource allocation. Situational awareness includes sensing the environment followed by a hypothesis testing for detection of available opportunities in the coexisting environment. This process is often known as spectral hole detection. Situational knowledge can be further enriched by forecasting the primary activities in the radio environment using predictive modeling based approaches. Improved knowledge about the coexisting environment essentially means better decision making for secondary resource allocation. This dissertation identifies limitations of existing predictive modeling and spectral hole detection based resource allocation strategies and suggest improvements. Firstly, accurate and efficient estimation of statistical parameters of the radio environment is identified as a fundamental challenge to realize predictive modeling based cognitive approaches. Lots of useful training data which are essential to learn the system parameters are not available either because of environmental effects such as noise, interference and fading or because of limited system resources particularly sensor bandwidth. While handling environmental effects to improve signal reception in radio systems has already gained much attention, this dissertation addresses the problem of data losses caused by limited sensor bandwidth as it is totally ignored so far and presents bandwidth independent parameter estimation methods. Where, bandwidth independent means achieving the same level of estimation accuracy for any sensor bandwidth. Secondly, this dissertation argues that the existing hole detection strategies are dumb because they provide very little information about the coexisting environment. Decision making for resource allocation based on this dumb hole detection approach cannot optimally exploit the opportunities available in the coexisting environment. As a solution, an intelligent hole detection scheme is proposed which suggests classifying the primary systems and using the documented knowledge of identified radio technologies to fully understand their coexistence behavior. Finally, this dissertation presents a neuro-fuzzy signal classifier (NFSC) that uses bandwidth, operating frequency, pulse shape, hopping behavior and time behavior of signals as distinct features in order to xii identify the PU signals in coexisting environments. This classifier provides the foundation for bandwidth independent parameter estimation and intelligent hole detection. MATLAB/Simulink based simulations are used to support the arguments throughout in this dissertation. A proof-of-concept demonstrator using microcontroller and hardware defined radio (HDR) based transceiver is also presented at the end.</p

Interference management in impulse-radio ultra-wide band networks

We consider networks of impulse-radio ultra-wide band (IR-UWB) devices. We are interested in the architecture, design, and performance evaluation of these networks in a low data-rate, self-organized, and multi-hop setting. IR-UWB is a potential physical layer for sensor networks and emerging pervasive wireless networks. These networks are likely to have no particular infrastructure, might have nodes embedded in everyday life objects and have a size ranging from a few dozen nodes to large-scale networks composed of hundreds of nodes. Their average data-rate is low, on the order of a few megabits per second. IR-UWB physical layers are attractive for these networks because they potentially combine low-power consumption, robustness to multipath fading and to interference, and location/ranging capability. The features of an IR-UWB physical layer greatly differ from the features of the narrow-band physical layers used in existing wireless networks. First, the bandwidth of an IR-UWB physical layer is at least 500 MHz, which is easily two orders of magnitude larger than the bandwidth used by a typical narrow-band physical layer. Second, this large bandwidth implies stringent radio spectrum regulations because UWB systems might occupy a portion of the spectrum that is already in use. Consequently, UWB systems exhibit extremely low power spectral densities. Finally IR-UWB physical layers offer multi-channel capabilities for multiple and concurrent access to the physical layer. Hence, the architecture and design of IR-UWB networks are likely to differ significantly from narrow-band wireless networks. For the network to operate efficiently, it must be designed and implemented to take into account the features of IR-UWB and to take advantage of them. In this thesis, we focus on both the medium access control (MAC) layer and the physical layer. Our main objectives are to understand and determine (1) the architecture and design principles of IR-UWB networks, and (2) how to implement them in practical schemes. In the first part of this thesis, we explore the design space of IR-UWB networks and analyze the fundamental design choices. We show that interference from concurrent transmissions should not be prevented as in protocols that use mutual exclusion (for instance, IEEE 802.11). Instead, interference must be managed with rate adaptation, and an interference mitigation scheme should be used at the physical layer. Power control is useless. Based on these findings, we develop a practical PHY-aware MAC protocol that takes into account the specific nature of IR-UWB and that is able to adapt its rate to interference. We evaluate the performance obtained with this design: It clearly outperforms traditional designs that, instead, use mutual exclusion or power control. One crucial aspect of IR-UWB networks is packet detection and timing acquisition. In this context, a network design choice is whether to use a common or private acquisition preamble for timing acquisition. Therefore, we evaluate how this network design issue affects the network throughput. Our analysis shows that a private acquisition preamble yields a tremendous increase in throughput, compared with a common acquisition preamble. In addition, simulations on multi-hop topologies with TCP flows demonstrate that a network using private acquisition preambles has a stable throughput. On the contrary, using a common acquisition preamble exhibits an effect similar to exposed terminal issues in 802.11 networks: the throughput is severely degraded and flow starvation might occur. In the second part of this thesis, we are interested in IEEE 802.15.4a, a standard for low data-rate, low complexity networks that employs an IR-UWB physical layer. Due to its low complexity, energy detection is appealing for the implementation of practical receivers. But it is less robust to multi-user interference (MUI) than a coherent receiver. Hence, we evaluate the performance of an IEEE 802.15.4a physical layer with an energy detection receiver to find out whether a satisfactory performance is still obtained. Our results show that MUI severely degrades the performance in this case. The energy detection receiver significantly diminishes one of the most appealing benefits of UWB, specifically its robustness to MUI and thus the possibility of allowing for parallel transmissions. This performance analysis leads to the development of an IR-UWB receiver architecture, based on energy detection, that is robust to MUI and adapted to the peculiarities of IEEE 802.15.4a. This architecture greatly improves the performance and entails only a moderate increase in complexity. Finally, we present the architecture of an IR-UWB physical layer implementation in ns-2, a well-known network simulator. This architecture is generic and allows for the simulation of several multiple-access physical layers. In addition, it comprises a model of packet detection and timing acquisition. Network simulators also need to have efficient algorithms to accurately compute bit or packet error rates. Hence, we present a fast algorithm to compute the bit error rate of an IR-UWB physical layer in a network setting with MUI. It is based on a novel combination of large deviation theory and importance sampling

Advanced Trends in Wireless Communications

Physical limitations on wireless communication channels impose huge challenges to reliable communication. Bandwidth limitations, propagation loss, noise and interference make the wireless channel a narrow pipe that does not readily accommodate rapid flow of data. Thus, researches aim to design systems that are suitable to operate in such channels, in order to have high performance quality of service. Also, the mobility of the communication systems requires further investigations to reduce the complexity and the power consumption of the receiver. This book aims to provide highlights of the current research in the field of wireless communications. The subjects discussed are very valuable to communication researchers rather than researchers in the wireless related areas. The book chapters cover a wide range of wireless communication topics