Resource Allocation for the Internet of Everything: From Energy Harvesting Tags to Cellular Networks

In the near future, objects equipped with heterogeneous devices such as sensors, actuators, and tags, will be able to interact with each other and cooperate to achieve common goals. These networks are termed the Internet of Things (IoT) and have applications in healthcare, smart buildings, assisted living, manufacturing, supply chain management, and intelligent transportation. The IoT vision is enabled by ubiquitous wireless communications and there are numerous resource allocation challenges to efficiently connect each device to the network. In this thesis, we study wireless resource allocation problems that arise in the IoT, namely in the areas of the energy harvesting tags, termed the Internet of Tags (IoTags), and in cellular networks (mobile and cognitive). First, we present our experience designing and developing Energy Harvesting Active Networked Tags (EnHANTs). The prototypes harvest indoor light energy using custom organic solar cells, communicate and form multihop networks using ultra-low-power Ultra- Wideband Impulse Radio (UWB-IR) transceivers, and dynamically adapt their communications and networking patterns to the energy harvesting and battery states. Using our custom designed small scale testbed, we evaluate energy-adaptive networking algorithms spanning the protocol stack (link, network, and flow control). Throughout the evaluation of experiments, we highlight numerous phenomena which are typically difficult to capture in simulations and nearly impossible to model in analytical work. We believe that these lessons would be useful for the designers of many different types of energy harvesters and energy harvesting adaptive networks. Based on the lessons learned from EnHANTs, we present Power Aware Neighbor Discovery Asynchronously (Panda), a Neighbor Discovery (ND) protocol optimized for networks of energy harvesting nodes. To enable object tracking and monitoring applications for IoTags, Panda is designed to efficiently identify nodes which are within wireless communication range of one another. By accounting for numerous hardware constraints which are typically ignored (i.e., energy costs for transmission/reception, and transceiver state switching times/costs), we formulate a power budget to guarantee perpetual ND. Finally, via testbed evaluation utilizing Commercial Off-The-Shelf (COTS) energy harvesting nodes, we demonstrate experimentally that Panda outperforms existing protocols by a factor of 2-3x. We then consider Proportional Fair (PF) cellular scheduling algorithms for mobile users, These users experience slow-fading wireless channels while traversing roads, train tracks, bus routes, etc. We leverage the predicable mobility on these routes and present the Predictive Finite-horizon PF Scheduling ((PF)2S) Framework. We collect extensive channel measurement results from a 3G network and characterize mobility-induced channel state trends. We show that a user’s channel state is highly reproducible and leverage that to develop a data rate prediction mechanism. Our trace-based simulations of the (PF)2S Framework indicate that the framework can increase the throughput by 15%–55% compared to traditional PF schedulers, while improving fairness. Finally, we study fragmentation within a probability model of combinatorial structures. Our model does not refer to any particular application. Yet, it is applicable to dynamic spectrum access networks which can be used as the wireless access technology for numerous IoT applications. In dynamic spectrum access networks, users share the wireless resource and compete to transmit and receive data, and accordingly have specific bandwidth and residence-time requirements. We prove that the spectrum tends towards states of complete fragmentation. That is, for every request for j > 1 sub-channels, nearly all size-j requests are allocated j mutually disjoint sub-channels. In a suite of four theorems, we show how this result specializes for certain classes of request-size distributions. We also show that the delays in reaching the inefficient states of complete fragmentation can be surprisingly long. The results of this chapter provide insights into the fragmentation process and, in turn, into those circumstances where defragmentation is worth the cost it incurs

Diseños de capa cruzada para redes inalámbricas de área corporal energéticamente eficientes: una revisión

RESUMEN: El diseño de capa cruzada se considera una poderosa alternativa para dar solución a las complejidades introducidas por las comunicaciones inalámbricas en redes de área corporal (WBAN), donde el modelo clásico de comunicaciones no ha exhibido un desempeño adecuado. Respecto al problema puntual de consumo de energía, hemos preparado la presente revisión de las publicaciones más relevantes que tratan la eficiencia energética para WBAN usando diseño de capa cruzada. En este artículo se proporciona una revisión exhaustiva de los avances en aproximaciones, protocolos y optimizaciones de capa cruzada cuyo objetivo es incrementar el tiempo de vida de las redes WBAN mediante el ahorro de energía. Luego, se discute los aspectos relevantes y deficiencias de las técnicas de capa cruzada energéticamente eficientes. Además, se introducen aspectos de investigación abiertos y retos en el diseño de capa cruzada para WBAN. En esta revisión proponemos una taxonomía de las aproximaciones de capa cruzada, de modo que las técnicas revisadas se ajustan en categorías de acuerdo a los protocolos involucrados en el diseño. Una clasificación novedosa se incluye para hacer claridad en los conceptos teóricos involucrados en cada esquema de capa cruzada y para luego agrupar aproximaciones similares evidenciando las diferencias con otras técnicas entre sí. Nuestras conclusiones consideran los aspectos de movilidad y modelamiento del canal en escenarios de WBAN como las direcciones para futura investigación en WBAN y en aplicaciones de telemedicina.ABSTRACT: Cross-layer design is considered a powerful alternative to solve the complexities of wireless communication in wireless body area networks (WBAN), where the classical communication model has been shown to be inaccurate. Regarding the energy consumption problem, we have prepared a current survey of the most relevant scientific publications on energy-efficient cross-layer design for WBAN. In this paper, we provide a comprehensive review of the advances in cross-layer approaches, protocols and optimizations aimed at increasing the network lifetime by saving energy in WBANs. Subsequently, we discuss the relevant aspects and shortcomings of these energy-efficient cross-layer techniques and point out the open research issues and challenges in WBAN cross-layer design. In this survey, we propose a taxonomy for cross-layer approaches to fit them into categories based on the protocols involved in the cross-layer scheme. A novel classification is included to clarify the theoretical concepts behind each cross-layer scheme; and to group similar approaches by establishing their differences from the other strategies reviewed. Our conclusion considers the aspects of mobility and channel modeling in WBAN scenarios as the directions of future cross-layer research for WBAN and telemedicine applications

Ultra Low Power Communication Protocols for UWB Impulse Radio Wireless Sensor Networks

This thesis evaluates the potential of Ultra Wideband Impulse Radio for wireless sensor network applications. Wireless sensor networks are collections of small electronic devices composed of one or more sensors to acquire information on their environment, an energy source (typically a battery), a microcontroller to control the measurements, process the information and communicate with its peers, and a radio transceiver to enable these communications. They are used to regularly collect information within their deployment area, often for very long periods of time (up to several years). The large number of devices often considered, as well as the long deployment durations, makes any manual intervention complex and costly. Therefore, these networks must self-configure, and automatically adapt to changes in their electromagnetic environment (channel variations, interferers) and network topology modifications: some nodes may run out of energy, or suffer from a hardware failure. Ultra Wideband Impulse Radio is a novel wireless technology that, thanks to its extremely large bandwidth, is more robust to frequency dependent propagation effects. Its impulsional nature makes it robust to multipath fading, as the short duration of the pulses leads most multipath components to arrive isolated. This technology should also enable high precision ranging through time of flight measurements, and operate at ultra low power levels. The main challenge is to design a system that reaches the same or higher degree of energy savings as existing narrowband systems considering all the protocol layers. As these radios are not yet widely available, the first part of this thesis presents Maximum Pulse Amplitude Estimation, a novel approach to symbol-level modeling of UWB-IR systems that enabled us to implement the first network simulator of devices compatible with the UWB physical layer of the IEEE 802.15.4A standard for wireless sensor networks. In the second part of this thesis, WideMac, a novel ultra low power MAC protocol specifically designed for UWB-IR devices is presented. It uses asynchronous duty cycling of the radio transceiver to minimize the power consumption, combined with periodic beacon emissions so that devices can learn each other's wake-up patterns and exchange packets. After an analytical study of the protocol, the network simulation tool presented in the first part of the thesis is used to evaluate the performance of WideMac in a medical body area network application. It is compared to two narrowband and an FM-UWB solutions. The protocol stack parameters are optimized for each solution, and it is observed that WideMac combined to UWB-IR is a credible technology for such applications. Similar simulations, considering this time a static multi-hop network are performed. It is found that WideMac and UWB-IR perform as well as a mature and highly optimized narrowband solution (based on the WiseMAC ULP MAC protocol), despite the lack of clear channel assessment functionality on the UWB radio. The last part of this thesis studies analytically a dual mode MAC protocol named WideMac-High Availability. It combines the Ultra Low PowerWideMac with the higher performance Aloha protocol, so that ultra low power consumption and hence long deployment times can be combined with high performance low latency communications when required by the application. The potential of this scheme is quantified, and it is proposed to adapt it to narrowband radio transceivers by combining WiseMAC and CSMA under the name WiseMAC-HA

A taxonomy and evaluation for developing 802.11‐based wireless mesh network testbeds

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92433/1/dac1299.pd

Performance evaluation of wake-up radio based wireless body area network

Abstract. The last decade has been really ambitious in new research and development techniques to reduce energy consumption especially in wireless sensor networks (WSNs). Sensor nodes are usually battery-powered and thus have very limited lifetime. Energy efficiency has been the most important aspect to discuss when talking about wireless body area network (WBAN) in particular, since it is the bottleneck of these networks. Medium access control (MAC) protocols hold the vital position to determine the energy efficiency of a WBAN, which is a key design issue for battery operated sensor nodes. The wake-up radio (WUR) based MAC and physical layer (PHY) have been evaluated in this research work in order to contribute to the energy efficient solutions development. WUR is an on-demand approach in which the node is woken up by the wake-up signal (WUS). A WUS switches a node from sleep mode to wake up mode to start signal transmission and reception. The WUS is transmitted or received by a secondary radio transceiver, which operates on very low power. The energy benefit of using WUR is compared with conventional duty-cycling approach. As the protocol defines the nodes in WUR based network do not waste energy on idle listening and are only awakened when there is a request for communication, therefore, energy consumption is extremely low. The performance of WUR based MAC protocol has been evaluated for both physical layer (PHY) and MAC for transmission of WUS and data. The probabilities of miss detection, false alarm and detection error rates are calculated for PHY and the probabilities of collision and successful data transmission for channel access method Aloha is evaluated. The results are obtained to compute and compare the total energy consumption of WUR based network with duty cycling. The results prove that the WUR based networks have significant potential to improve energy efficiency, in comparison to conventional duty cycling approach especially, in the case of low data-reporting rate applications. The duty cycle approach is better than WUR approach when sufficiently low duty cycle is combined with highly frequent communication between the network nodes

On uncoordinated wireless ad-hoc networks:data dissemination over WIFI and cross-layer optimization for ultra wide band impulse radio

Emerging pervasive wireless networks, pocket switched networks, Internet of things, vehicular networks and even sensor networks present very challenging communication circumstances. They might involve up to several hundreds of wireless devices with mobility and intermittent connectivity. Centralized coordination in such networks is practically unfeasible. We deal with these challenge using two potential technologies: WIFI and Ultra Wide Band (UWB) Impulse Radio (IR) for medium and short communication range, respectively. Our main goal is to improve the communication performance and to make these networks sustainable in the absence of a centralized coordination. With WIFI, the goal is to design an environment-oblivious data dissemination protocol that holds in highly dynamic unpredictable wireless ad-hoc networks. To this end, we propose a complete design for a scope limited, multi-hop broadcast middleware, which is adapted to the variability of the ad-hoc environment and works in unlimited ad-hoc networks such as a crowd in a city, or car passengers in a busy highway system. We address practical problems posed by: the impossibility of setting the TTL correctly at all times, the poor performance of multiple access protocols in broadcast mode, flow control when there is no acknowledgment and scheduling of multiple concurrent broadcasts. Our design, called "Self Limiting Epidemic Forwarding" (SLEF), automatically adapts its behavior from single hop MAC layer broadcast to epidemic forwarding when the environment changes from being extremely dense to sparse, sporadically connected. A main feature of SLEF is a non-classical manipulation of the TTL field, which combines the usual decrement-when-sending to many very small decrements when receiving. Then, we identify vulnerabilities that are specific to epidemic forwarding. We address broadcast applications over wireless ad-hoc networks. Epidemic forwarding employs several mechanisms such as forwarding factor control and spread control, and each of them can be implemented using alternative methods. Thus, the existence of vulnerabilities is highly dependent on the methods used. We examine the links between them. We classify vulnerabilities into two categories: malicious and rational. We examine the effect of the attacks according to the number of attackers and the different network settings such as density, mobility and congestion. We show that malicious attacks are hard to achieve and their effects are scenario-dependent. In contrast, rational attackers always obtain a significant benefit. The evaluation is carried out using detailed realistic simulations over networks with up to 1000 nodes. We consider static scenarios, as well as vehicular networks. In order to validate our simulation results, we build a solid and widely adaptable experimental testbed for wireless networks. It is composed of 57 mobile wireless nodes equipped with WIFI interface. The adopted platform is OpenWrt, a Linux-like firmware, which makes the testbed robust and easily configurable. With UWB IR, the main problem we deal with is the presence of uncontrolled interference. Indeed, similarly to Code Division Multiple Access (CDMA) systems, signal acquisition with UWB IR signaling requires power control in the presence of interferers, which is very expensive in an uncoordinated system. We solve this problem through a cross-layer optimization: We propose a new signal acquisition method that is independent of the received signal power and we adapt the MAC layer accordingly. Our signal acquisition method is designed to solve the IUI (Inter-User Interference) that occurs in some ad-hoc networks where concurrent transmissions are allowed with heterogeneous power levels. In such scenarios, the conventional detection method, which is based on correlating the received IR signal with a Template Pulse Train (TPT), does not always perform well. The complexity of our proposal is similar to that of the conventional method. We evaluate its performance with the Line Of Sight (LOS) and the Non-LOS (NLOS) office indoor-channel models proposed by the IEEE P802.15.4a study group and find that the improvement is significant. We also investigate the particular case where the concurrent transmissions have the same time-hopping code, and we show that it does not result in collision, such scenarios appear in ad-hoc networks that employ a common code for control or broadcast purposes. At the MAC level, we focus only on one component of a MAC layer, which is the sleeping mode that could be added to any MAC layer proposal adequate to UWB IR. We are motivated by the low power consumption constraint required by the potential applications. We identify the design elements that should be taken into account for an optimal design for a sleeping protocol for UWB-IR such as the possibility of transmitting concurrently without collision and the power consumption model of the hardware behind which is completely different than with the narrow-band signaling. Then, we design two sleeping protocols for centralized and decentralized ad-hoc networks, respectively. We evaluate their performance analytically with the adopted metric being the average life-time of the wireless nodes