Ageliki Tsioliaridou

CORONA: A Coordinate and Routing system for Nanonetworks

The present paper introduces a joint coordinate and routing system (CORONA) which can be deployed dynamically on a 2D ad-hoc nanonetwork. User-selected nodes are used as anchor-points at the setup phase. All nodes then measure their distances, in number of hops, from these anchors, obtaining a sense of geolocation. At operation phase, the routing employs the appropriate subset of anchors, selected by the sender of a packet. CORONA requires minimal setup overhead and simple integer-based calculations only, imposing limited requirements for trustworthy operation. Once deployed, it operates efficiently, yielding a very low packet retransmission and packet loss rate, promoting energy-efficiency and medium multiplexity.

Lightweight, self-tuning data dissemination for dense nanonetworks

Abstract A nanonetwork comprises a high number of autonomous nodes with wireless connectivity, assembled at micro-to-nanoscale. In general, manufacturing and cost considerations imply that nanonetworking approaches should have minimal complexity, ideally without sacrifices in network coverage. The present paper studies a networking approach fit for static, dense topologies comprising numerous, identical, computationally-constrained nodes. These attributes are especially important in the context of recently proposed applications of nanonetworks. The presented networking approach assumes that each node is equipped with 10 bits of reclaimable storage to accommodate four integer counters, and a trivial set of integer operations on them. These modest resources are used for logging packet reception statistics. Nanonodes with good reception serve as retransmitters within the network. This classification process is based on the Misra–Gries algorithm, used for detecting frequent items into sequential streams. Evaluation via extensive simulations in various 2D and 3D topologies yields high network coverage, achieved with less resources than related approaches.

Packet routing in 3D nanonetworks: A lightweight, linear-path scheme

Packet routing in nanonetworks requires novel approaches, which can cope with the extreme limitations posed by the nano-scale. Highly lossy wireless channels, extremely limited hardware capabilities and non-unique node identifiers are among the restrictions. The present work offers an addressing and routing solution for static 3D nanonetworks that find applications in material monitoring and programmatic property tuning. The addressing process relies on virtual coordinates from multiple, alternative anchor point sets that act as \emph{viewports}. Each viewport offers different address granularity within the network space, and its selection is optimized by a packet sending node using a novel heuristic. Regarding routing, each node can deduce whether it is located on the linear segment connecting the sender to the recipient node. This deduction is made using integer calculations, node-local information and in a stateless manner, minimizing the computational and storage overhead of the proposed scheme. Most importantly, the nodes can regulate the width of the linear path, thus trading energy efficiency (redundant transmissions) for increased path diversity. This trait can enable future adaptive routing schemes. Extensive evaluation via simulations highlights the advantages of the novel scheme over related approaches.

Computing and Communications for the Software-Defined Metamaterial Paradigm: A Context Analysis

Metamaterials are artificial structures that have recently enabled the realization of novel electromagnetic components with engineered and even unnatural functionalities. Existing metamaterials are specifically designed for a single application working under preset conditions (e.g., electromagnetic cloaking for a fixed angle of incidence) and cannot be reused. Software-defined metamaterials (SDMs) are a much sought-after paradigm shift, exhibiting electromagnetic properties that can be reconfigured at runtime using a set of software primitives. To enable this new technology, SDMs require the integration of a network of controllers within the structure of the metamaterial, where each controller interacts locally and communicates globally to obtain the programmed behavior. The design approach for such controllers and the interconnection network, however, remains unclear due to the unique combination of constraints and requirements of the scenario. To bridge this gap, this paper aims to provide a context analysis from the computation and communication perspectives. Then, analogies are drawn between the SDM scenario and other applications both at the micro and nano scales, identifying possible candidates for the implementation of the controllers and the intra-SDM network. Finally, the main challenges of SDMs related to computing and communications are outlined.

N3: Addressing and routing in 3D nanonetworks

Wireless communication at nanoscale faces unique challenges stemming from low hardware capabilities, limited power supply and unreliable channel conditions. The present paper proposes a networking scheme that can operate efficiently under such physical restrictions. Studying 3D multi-hop networks, the novel scheme offers scalable, trilateration-based node addressing and low-complexity packet routing mechanisms. Analysis is employed to design a routing process that balances path multiplicity for robust data delivery, and minimization of redundant transmissions. Extensive simulations yield increased resilience to challenging network conditions.

Fast convergence to network fairness

Most AQM algorithms, such as RED, assure fairness through randomness in congestion notification. However, randomness results in fair allocation of network resources only when time limitations are not considered. This is not compatible with the current Internet, where traffic oscillations are frequent and the demand for fair treatment is rather urgent, due to short duration of most applications. Given the short duration of most modern Internet applications, fast convergence to fairness is necessitated. In this paper, we use fairness as the major criterion to adjust traffic and present a corresponding algorithm of active queue management, which is called Explicit Global Congestion Notifier (EGCN). EGCN notifies flows almost simultaneously about incipient congestion by marking packets arriving at the routers queue, when the load in the network increases and buffer overflow is expected. This is a new approach compared with the random notification policy of RED or ECN. EGCN distributes the burden to adjust backward to more flows and consequently allows for smoother window adjustments. We elaborate on the properties of system-wide response in terms of fairness, smoothness and efficiency. Simulation results demonstrate a clear-cut advantage of the proposed scheme.

A deployable routing system for nanonetworks

Nanonetworks comprise numerous wireless nodes, assembled at micro-to-nano scale. The unique manufacturing challenges and cost considerations of these networks make for minimal complexity solutions at all network layers. From a networking aspect, packet retransmissions should be kept minimal, while ensuring communication between any two nanonodes. In addition, assigning unique addresses to nanonodes is not straightforward, since it can entail a prohibitively high number of packet exchanges. Thus, efficient data routing is considered an open issue in nanonetworking. The present paper proposes a routing system which can be dynamically deployed within a nanonetwork. Static, dense topologies with numerous, identical nodes are examined. These attributes are especially important in the context of recently proposed applications of nanonetworks. The proposed scheme incurs a trivial setup overhead and requires integer processing capabilities only. Once deployed, it operates efficiently, inducing lower packet retransmission rates than related schemes.

On the Properties of System-Wide Responsive Behavior

High contention of flows is associated with unstable network behavior and unmanageable resource administration, i.e., convergence to equilibrium becomes a difficult task. In this paper, we propose a new approach to control congestion. In this context, we present an algorithm for active queue management, to notify simultaneously all competing flows about incipient congestion. Typically, AQM schemes notify only a small portion of participating flows about congestion events. Our notification scheme, called global notifier (GN), allows for an immediate and less aggressive adjustment of transmission windows with three consequent properties: (i) fairness is improved, (ii) smoothness of responsive flows is improved and (iii) system utilization is better regulated between the knee and the cliff. We detail our algorithm and the corresponding responsive behavior of participating flows, and we highlight significant performance results gathered by simulations.

Service Ratio-Optimal, Content Coherence-Aware Data Push Systems

Advertising new information to users via push is the trigger of operation for many contemporary information systems. Furthermore, passive optical networks are expected to extend the reachability of high-quality push services to thousands of clients. The efficiency of a push service is the ratio of successfully informed users. However, pushing only data of high popularity can degrade the thematic coherency of the content. The present work offers a novel, analysis-derived, tunable way for selecting data for push services. The proposed scheme can maximize the service ratio of a push system with regard to data coherence constraints. Extensive simulations demonstrate the efficiency of the scheme compared to alternative solutions. The proposed scheme is the first to tackle the problem of data coherence-aware, service ratio optimization of push services.

Minimal Wireless Broadcast Schedules for Multiobjective Pursuits

Mobile wireless devices can now act as push-based data broadcasters, disseminating information in crowded places. While assuming this role, a device must take into account various factors such as the mean service time, energy expenditure, or copyright costs. Apart from adhering to multiobjective optimality, a broadcast schedule must also be as small as possible in size to be producible and cacheable on a mobile device. This paper analytically proves the existence of optimal schedules that are finite and minimal in size. Furthermore, the optimality of the schedule is allowed to refer to an unlimited number of criteria. The analysis shows that multiobjective optimality can be met precisely by extremely small schedules, enabling their use in mobile devices. Simulations indicate perfect efficiency of the minimal schedules in realistic application scenarios.