Abstract: Random access represents possibly the simplest and yet one of the best known approaches for sharing a channel among several users. Since their introduction in the 1970s, random access schemes have been thoroughly studied and small variations of the pioneering Aloha protocol have since then become a key component of many communications standards, ranging from satellite networks to ad hoc and cellular scenarios. A fundamental step forward for this old paradigm has been witnessed in the past few years, with the development of new solutions, mainly based on the principles of successive interference cancellation, which made it possible to embrace constructively collisions among packets rather enduring them as a waste of resources. These new lines of research have rendered the performance of modern random access protocols competitive to that of their coordinated counterparts, paving the road for a multitude of new applications.This monograph explores the main ideas and design principles that are behind some of such novel schemes, and aims at offering to the reader an introduction to the analytical tools that can be used to model their performance. After reviewing some relevant results for the random access channel, the volume focuses on slotted solutions that combine the approach of diversity Aloha with successive interference cancellation, and discusses their optimisation based on an analogy with the theory of codes on graphs. The potential of modern random access is then further explored considering two families of schemes: the former based on physical layer network coding to resolve collisions among users, and the latter leaning on the concept of receiver diversity. Finally, the opportunities and the challenges encountered by random access solutions recently devised to operate in asynchronous, i.e., unslotted, scenarios are reviewed and discussedSuggested CitationMatteo Berioli, Giuseppe Cocco, Gianluigi Liva and Andrea Munari (2016), "Modern Random Access Protocols", Foundations and Trends® in Networking: Vol. 10: No. 4, pp 317-446. http://dx.doi.org/10.1561/1300000047 PubDate: Thu, 17 Nov 2016 00:00:00 +010

Abstract: Wireless multi-hop networks have become an important part of many modern communication systems. Opportunistic routing aims to overcome the deficiencies of conventional routing on wireless multi-hop networks, by specifically utilizing wireless broadcast opportunities and receiver diversity. Opportunistic routing algorithms, which are specifically optimized to incorporate into the routing decisions a model of wireless transmission, take advantage of scheduling, multi-user, andreceiver diversity gains and result in significant reduction in the expected cost of routing per packet. The ability of the algorithm to take advantage of the aspects of wireless transmission, however, depends on the scalability and the additional overhead associated with the opportunistic routing as well as the availability of side information regarding wireless channel statistics, topology, etc. This monograph sheds light on the performance gains associated with incorporating into the routing strategy the nature of wireless transmission.This monograph first provides an overview of various opportunistic distance-vector algorithms that have been developed to incorporate wireless transmission and routing opportunities. Furthermore, an optimal opportunistic distance metric is proposed whose performance is examined against the performance of several routing algorithms from the literature. The performance is examined first in analytical examples, then via simulation to identify the strengths of the optimal opportunist routing algorithm. To allow for a scalable and distributed solution, the distributed computation of this optimal distance-metric is provided. The performance of a distributed implementation of the optimal opportunistic routing algorithm is also examined via simulation. In addition to the construction of the opportunistic schemes in centralized and distributed fashions, this monograph also addresses how learning the wireless medium can be efficiently incorporated in the structure of routing algorithm. Finally, this monograph examines the dynamic congestion-based distance metric and its performance against other congestion aware solutions in the literature.Suggested CitationTara Javidi and Eric Van Buhler (2016), "Opportunistic Routing in Wireless Networks", Foundations and Trends® in Networking: Vol. 10: No. 4. http://dx.doi.org/10.1561/1300000021 PubDate: Wed, 31 Aug 2016 00:00:00 +020

Abstract: The smart energy grid has evolved into a complex ecosystem, with new entering actors such as aggregators, and traditional ones like consumers, operators and generators having fundamentally different, active roles in the system. In addition, advances in key technologies such as renewables, energy storage, communication and control have paved the way to new research directions and problems. In this work we attempt to give some structure to the complex ecosystem above, and we present key research problems that shape the area. The emphasis is on the control and optimization methodology toward approaching these problems. The first thread we consider is demand-response where the central theme is to optimize the demand load of consumers. The basic problem is the scheduling of demand load of consumers with the aim to minimize a cost function from the point of view of the utility operator or the consumer. Next, we review fundamental problems in energy storage management. The basic energy storage management problem amounts to deciding when and how much to charge and discharge the battery in order to achieve a certain optimization objective, either in terms of a generation cost or a mismatch between energy demand and supply, which again may capture the goals of the consumer or the utility. We also discuss the market interactions of various entities in the smart grid ecosystem and the impact of their strategic decisions on the market structure. Finally, we study key aspects of consumer behavior such as response to gamification models, and uncertainty due to consumer decisions that influence the system, and we discuss the role of data in building data-driven models for predicting consumer behavior. For each problem instance above, we provide an exposition that places emphasis on the related model and on key aspects of the analysis.Suggested CitationIordanis Koutsopoulos, Thanasis G. Papaioannou and Vasiliki Hatzi (2016), "Modeling and Optimization of the Smart Grid Ecosystem", Foundations and Trends® in Networking: Vol. 10: No. 2-3, pp 115-316. http://dx.doi.org/10.1561/1300000042 PubDate: Wed, 22 Jun 2016 00:00:00 +020

Abstract: Future vehicles will require massive sensing capability. Leveraging only onboard sensors, though, is challenging in crowded environments where the sensing field-of-view is obstructed. One potential solution is to share sensor data among the vehicles and infrastructure. This has the benefits of providing vehicles with an enhanced field-of-view and also additional redundancy to provide more reliability in the sensor data. A main challenge in sharing sensor data is providing the high data rates required to exchange raw sensor data. The large spectral channels at millimeter wave (mmWave) frequencies provide a means of achieving much higher data rates. This monograph provides an overview of mmWave vehicular communication with an emphasis on results on channel measurements, the physical (PHY) layer, and the medium access control (MAC) layer. The main objective is to summarize key findings in each area, with special attention paid to identifying important topics of future research. In addition to surveying existing work, some new simulation results are also presented to give insights on the effect of directionality and blockage, which are the two distinguishing features of mmWave vehicular channels. A main conclusion of this monograph is that given the renewed interest in high rate vehicle connectivity, many challenges remain in the design of a mmWave vehicular network.Suggested CitationVutha Va, Takayuki Shimizu, Gaurav Bansal and Robert W. Heath Jr. (2016), "Millimeter Wave Vehicular Communications: A Survey", Foundations and Trends® in Networking: Vol. 10: No. 1, pp 1-113. http://dx.doi.org/10.1561/1300000054 PubDate: Wed, 22 Jun 2016 00:00:00 +020

Abstract: Distributed storage has been an active research area for decades. With the proliferation of cloud computing, there has been a rejuvenated interest in two perspectives. The first perspective is seen through the lenses of the cloud providers: how should we build global storage services for cloud hosted services and applications at scale with high reliability and availability guarantees, but also in a cost effective way' The second perspective is seen through the lenses of the service providers that utilize public clouds: how can we achieve high I/O performance over cloud storage within a cost budget' In this manuscript, we first present various kinds of distributed storage systems, their operational characteristics and the key techniques to improve their performance. We then focus on cloud storage, exclusively. Cloud storage has massive scales with the promise to provide as much storage capacity as their tenants demand. Cloud providers also promise very high durability, availability, and I/O performance. In this context, we cover the fundamental tradeoffs between storage efficiency and network bandwidth as well as I/O throughput and latency. Erasure codes play an essential role in these tradeoffs and, thus, we also present their design and usage in the context of cloud storage broadly. We pay particular attention on various queuing models and the corresponding performance analysis in the presence of coded storage. We provide exact and approximate solutions under various settings and assumptions. We describe optimal or near-optimal scheduling and coding strategies that are established based on these analyses.Suggested CitationUlas C. Kozat and Guanfeng Liang (2015), "Building Reliable Storage Clouds: Models, Fundamental Tradeoffs, and Solutions", Foundations and Trends® in Networking: Vol. 9: No. 4, pp 219-3115. http://dx.doi.org/10.1561/1300000051 PubDate: Thu, 17 Dec 2015 00:00:00 +010

Abstract: A basic question in wireless networking is how to optimize the wireless network resource allocation for utility maximization and interference management. How can we overcome interference to efficiently optimize fair wireless resource allocation, under various stochastic constraints on quality of service demands' Network designs are traditionally divided into layers. How does fairness permeate through layers' Can physical layer innovation be jointly optimized with network layer routing control' How should large complex wireless networks be analyzed and designed with clearly-defined fairness using beamforming' This monograph provides a comprehensive survey of the models, algorithms, analysis, and methodologies using a Perron-Frobenius theoretic framework to solve wireless utility maximization problems. This approach overcomes the notorious non-convexity barriers in these problems, and the optimal value and solution of the optimization problems can be analytically characterized by the spectral property of matrices induced by nonlinear positive mappings. It also provides a systematic way to derive distributed and fast-convergent algorithms and to evaluate the fairness of resource allocation. This approach can even solve several previously open problems in the wireless networking literature. More generally, this approach links fundamental results in nonnegative matrix theory and (linear and nonlinear) Perron-Frobenius theory with the solvability of non-convex problems. In particular, for seemingly nonconvex problems, e.g., max-min wireless fairness problems, it can solve them optimally; for truly nonconvex problems, e.g., sum rate maximization, it can even be used to identify polynomial-time solvable special cases or to enable convex relaxation for global optimization.To highlight the key aspects, we also list several case studies of using the nonlinear Perron-Frobenius theoretic framework for applications in MIMO wireless cellular, heterogeneous small-cell and cognitive radio networks. Key implications arising from these work along with severalopen issues are discussed in this monograph.Suggested CitationChee Wei Tan (2015), "Wireless Network Optimization by Perron-Frobenius Theory", Foundations and Trends® in Networking: Vol. 9: No. 2-3, pp 107-218. http://dx.doi.org/10.1561/1300000048 PubDate: Thu, 03 Dec 2015 00:00:00 +010

Abstract: The current process of designing secure protocols is tantamount to an arms race between attacks and “patches”. We introduce a system theoretic approach to secure protocol design with provable security guarantees against all attacks that fall within the system model. In this approach, we frame the secure protocol design problem as a max-min optimization of a specific payoff function, where the adversarial nodes with a priori knowledge of the protocol choose a strategy that minimizes the payoff, and the protocol seeks to maximize this worst-case payoff. We make the following three contributions. First, we solve the optimization problem. That is, we describe a protocol and show that is max-min optimal. Second, we show that the protocol is actually min-max optimal which is generally higher than max-min optimality. Finally, we show that the adversarial nodes are effectively limited to one of two modes: either jamming or conforming with the protocol.Suggested CitationJonathan Ponniah, Yih-Chun Hu and P. R. Kumar (2015), "A Clean Slate Approach to Secure Wireless Networking", Foundations and Trends® in Networking: Vol. 9: No. 1, pp 1-105. http://dx.doi.org/10.1561/1300000037 PubDate: Mon, 24 Aug 2015 00:00:00 +020

Abstract: In this monograph we provided a tutorial on a family of sequential learning and decision problems known as the multi-armed bandit problems. We introduced a wide range of application scenarios for this learning framework, as well as its many different variants. The more detailed discussion has focused more on the stochastic bandit problems, with rewards driven by either an IID or a Markovian process, and when the environment consists of a single or multiple simultaneous users. We also presented literature on learning of MDPs, which captures coupling among the evolution of different options that a classical MAB problem does not.Suggested CitationCem Tekin and Mingyan Liu (2015), "Online Learning Methods for Networking", Foundations and Trends® in Networking: Vol. 8: No. 4, pp 281-409. http://dx.doi.org/10.1561/1300000050 PubDate: Mon, 19 Jan 2015 00:00:00 +010

Abstract: Multi-hop communication paradigms are expected to play a central role in future wireless networks by enabling a higher spatial reuse of the spectrum. A major challenge in multi-hop multi-user (or multi-flow) wireless networks is that "interference management" and "relaying" are coupled with each other. In other words, wireless relay nodes must play a dual role: they serve as intermediate steps for multi-hop communication and as part of the mechanism that allows interference management schemes. Nonetheless, in the communications, networking and information theory literature, these two tasks have traditionally been addressed separately, and the fundamental principles of the "wireless networks of the future" are currently not well understood. In this monograph, we take a unified approach to relaying and interference management, and seek to develop tools to study the fundamentals of multi-hop multi-flowwireless networks. We first consider multi-hop two-flow – or two-unicast – wireless networks. In order to handle networks with an arbitrary number of hops and arbitrary interference patterns, we introduce the idea of network condensation, by which a network with an arbitrary number of layers is effectively reduced to a network with at most four layers. This is done by identifying key layers and letting the nodes in all other layers apply random linear coding to relay the messages. Only the nodes in the remaining key layers need to be "smart" and perform coupled relaying and interference management operations. In addition, we introduce the new notion of paths with manageable interference, which represents a first attempt at finding flow-like structures in multi-user wireless networks, and develop novel outer bounds that capture the interference structure of a given topology. These techniques yield a complete characterization of the degrees of freedom of two-unicast layered networks as a function of the network graph. Extending these results for general K-unicast networks is quite challenging. To make progress on this front, we focus on the K x K x K wireless network, a two-hop network consisting of K sources, K relays, and K destinations. This network represents a canonical example of a multi-hop multi-flow wireless network for which previously there was a large gap between known inner and outer bounds, even from a degrees-of-freedom perspective. We introduce a coding scheme called Aligned Network Diagonalization (AND) that couples relaying and interference management in a way that all interference experienced by the destinations is simultaneously neutralized. This proves that K x K x K wireless networks have K sum degrees of freedom and demonstrates the significant gains that can be obtained with a unified approach to relaying and interference management. Moreover, this automotically yields the optimal scheme and degrees-of-freedom characterization for layered K unicast networks with fully connected hops. We then describe ideas and preliminary results for K-unicast networks with general topologies. Besides discussing how the tools developed for two-unicast networks and for K x K x K networks can be extended to this general setting, we present a novel outer-bounding technique, which improves over the cut-set bound and can capture limitations imposed by the interference between different users. The new bound can be understood as computing the flow across multiple "nested cuts", as opposed to a single cut, as is the case in the classical cut-set bound. This technique allows us to establish a graph-theoretic notion of manageable interference in K x K x K wireless networks with arbitrary connectivity. Throughout the monograph, many extensions and future directions are addressed. At the end of each chapter, related work is also described and several open problems are presented. Important research directions such as accounting for the lack of global channel state information in large networks and reducing the complexity of relaying operations are discussed, and recent results along these lines are described.Suggested CitationIlan Shomorony and Salman Avestimehr (2014), "Multihop Wireless Networks: A Unified Approach to Relaying and Interference Management", Foundations and Trends® in Networking: Vol. 8: No. 3, pp 149-280. http://dx.doi.org/10.1561/1300000044 PubDate: Wed, 03 Dec 2014 00:00:00 +010

Abstract: Molecular communication (MC) is a promising bio-inspired paradigm for the interconnection of autonomous nanotechnology-enabled devices, or nanomachines, into nanonetworks. MC realizes the exchange of information through the transmission, propagation, and reception of molecules, and it is proposed as a feasible solution for nanonetworks. This idea is motivated by the observation of nature, where MC is successfully adopted by cells for intracellular and intercellular communication. MC-based nanonetworks have the potential to be the enabling technology for a wide range of applications, mostly in the biomedical, but also in the industrial and surveillance fields. The focus of this article is on the most fundamental type of MC, i.e., diffusion-based MC, where the propagation of information-bearing molecules between a transmitter and a receiver is realized through free diffusion in a fluid. The objectives of the research presented in this article are to analyze an MC link from the point of view of communication engineering and information theory, and to provide solutions to the modeling and design of MC-based nanonetworks. First, a deterministic model is realized to study each component, as well as the overall diffusion-based- MC link, in terms of gain and delay. Second, the noise sources affecting a diffusion-based-MC link are identified and statistically modeled. Third, upper/lower bounds to the capacity are derived to evaluate the information-theoretic performance of diffusion-based MC. Fourth, an analysis of the interference produced by multiple diffusion-based MC links in a nanonetwork is provided. This research provides fundamental results that establish a basis for the modeling, design, and realization of future MC-based nanonetworks, as novel technologies and tools are being developed.Suggested CitationMassimiliano Pierobon and Ian F. Akyildiz (2014), "Fundamentals of Diffusion-Based Molecular Communication in Nanonetworks", Foundations and Trends® in Networking: Vol. 8: No. 1-2, pp 1-147. http://dx.doi.org/10.1561/1300000033 PubDate: Wed, 23 Apr 2014 00:00:00 +020

Abstract: We present a review of the notion of stability and of stable throughput regions in wireless networks, with emphasis on network layer cooperation between interacting users. After a brief introduction, we examine in detail specific instances of the stability issue. These instances differ from each other in terms of the network, channel and traffic models they use. What they share is the notion of how stability is affected by node cooperation, as well as the notion of "interacting queues" that makes the stable throughput analysis difficult and often intractable. This review is intended to provide a reference point for the rich set of network control problems that arise in the context of queue stability in modern and future networks.Suggested CitationSastry Kompella and Anthony Ephremides (2014), "Stable Throughput Regions in Wireless Networks", Foundations and Trends® in Networking: Vol. 7: No. 4, pp 235-338. http://dx.doi.org/10.1561/1300000039 PubDate: Thu, 13 Mar 2014 00:00:00 +010