arXiv subjects

Chris Blondia

Publications and source records attributed to Chris Blondia.

At least 19 recordsLinked to original sources

arXiv2025

Evaluating UORA-Based Polling Mechanism for Latency-Sensitive Uplink Traffic in Wi-Fi Networks

IEEE 802.11ax (Wi-Fi 6) introduced Orthogonal Frequency Division Multiple Access (OFDMA), which enables simultaneous transmissions through centralized resource allocation. However, effective uplink scheduling requires the Access Point (AP) to identify which stations (STAs) have data to transmit. This typically necessitates polling for buffer status reports, a process that becomes increasingly inefficient and unscalable with growing device density. In this paper, we study how the Uplink OFDMA-based Random Access (UORA) feature improves the scalability and delay experienced by latency-sensitive data streams. We show that UORA enables efficient uplink scheduling while opportunistically identifying buffered traffic from unscheduled STAs, striking a balance between coordination and scalability. Performance evaluation of different polling strategies is done by means of simulation in ns-3. The results indicate that UORA-based polling outperforms alternative schemes in densely deployed network environments with heterogeneous uplink traffic patterns. Furthermore, under highly sparse and sporadic traffic conditions, UORA-based polling yields over 40% delay reduction compared to Scheduled Access (SA) OFDMA.

cs.NI↗

arXiv2024

Dedicated Restricted Target Wake Time for Real-Time Applications in Wi-Fi 7

Real-time applications (RTA) tend to play a crucial role in people's everyday life. Such applications are among the key use cases for the next generations of wireless technologies. RTA applications are characterized by strict guaranteed delay requirements (in the order of a few milliseconds). One of the pillars of enabling RTA in next-generation Wi-Fi standards is Restricted Target Wake Time (R-TWT), which provides Wi-Fi stations exclusive channel access within negotiated service periods (SPs). If each RTA data flow uses dedicated SPs for data transmission, they are completely isolated from each other and do not experience any contention. To ensure the satisfaction of RTA QoS requirements while minimizing the channel airtime consumption, it is important to properly select the R-TWT parameters, namely the duration of SPs and the period between SPs. In this paper, we develop a mathematical model that estimates the delay probability distribution and packet loss probability for a given set of network, traffic and R-TWT parameters. Using this model, the access point can select the optimal R-TWT parameters for the given QoS requirements. The high accuracy of the model is proven by means of simulation.

cs.NI↗

arXiv2024

Battery-Less LoRaWAN Communications using Energy Harvesting: Modeling and Characterization

Billions of IoT devices are deployed worldwide and batteries are their main power source. However, these batteries are bulky, short-lived and full of hazardous chemicals that damage our environment. Relying on batteries is not a sustainable solution for the future IoT. As an alternative, battery-less devices run on long-lived capacitors charged using energy harvesters. The small energy storage capacity of capacitors results in an intermittent on-off behaviour. LoRaWAN is a popular Low Power Wide Area Network technology used in many IoT devices and can be used in these new scenarios. In this work, we present a Markov model to characterize the performance of battery-less LoRaWAN devices for uplink and downlink transmissions and we evaluate their performance in terms of the parameters that define the model (i.e., device configuration, application behaviour and environmental conditions). Results show that LoRaWAN battery-less communications are feasible if choosing the proper configuration (i.e., capacitor size, turn-on voltage threshold) for different application behaviour (i.e., transmission interval, UL/DL packet sizes) and environmental conditions (i.e., energy harvesting rate). Since downlink in the second reception window highly affects the performance, only small DL packet sizes should be considered for these devices. Besides, a 47 mF capacitor can support 1 Byte $SF7$ transmissions every 60 s at an energy harvesting rate of 1 mW. However, if no DL is expected, a 4.7 mF capacitor could support 1 Byte $SF7$ transmissions every 9~s.

cs.NI↗

arXiv2019

Token Bucket-based Throughput Constraining in Cross-layer Schedulers

In this paper we consider upper and lower constraining users' service rates in a slotted, cross-layer scheduler context. Such schedulers often cannot guarantee these bounds, despite the usefulness in adhering to Quality of Service (QoS) requirements, aiding the admission control system or providing different levels of service to users. We approach this problem with a low-complexity algorithm that is easily integrated in any utility function-based cross-layer scheduler. The algorithm modifies the weights of the associated Network Utility Maximization problem, rather than for example applying a token bucket to the scheduler's output or adding constraints in the physical layer. We study the efficacy of the algorithm through simulations with various schedulers from literature and mixes of traffic. The metrics we consider show that we can bound the average service rate within about five slots, for most schedulers. Schedulers whose weight is very volatile are more difficult to constrain.

cs.NI↗

arXiv2019

Trading off Complexity for Expressiveness in Programming Languages: Visions and Preliminary Experiences

When programming resource-scarce embedded smart devices, the designer often requires both the low-level system programming features of a language such as C and higher level capability typical of a language like Java. The choice of a particular language typically implies trade offs between conflicting design goals such as performance, costs, and overheads. The large variety of languages, virtual machines, and translators provides the designer with a dense trade off space, ranging from minimalistic to rich full-fledged approaches, but once a choice is made it is often difficult for the designer to revise it. In this work we propose a system of light-weighted and modular extensions as a method to flexibly reshape the target programming language as needed, adding only those application layer features that match the current design goals. In so doing complexity is made transparent, but not hidden: While the programmer can benefit of higher level constructs, the designer can deal with modular building blocks each characterized by a certain algorithmic complexity and therefore each accountable for a given share of the overhead. As a result the designer is given a finer control on the amount of resources that are consumed by the run-time executive of the chosen programming language.

cs.PL↗

arXiv2017

Towards a Smarter organization for a Self-servicing Society

Traditional social organizations such as those for the management of healthcare are the result of designs that matched well with an operational context considerably different from the one we are experiencing today. The new context reveals all the fragility of our societies. In this paper, a platform is introduced by combining social-oriented communities and complex-event processing concepts: SELFSERV. Its aim is to complement the "old recipes" with smarter forms of social organization based on the self-service paradigm and by exploring culture-specific aspects and technological challenges.

cs.CY↗

arXiv2016

A Design Tool to Reason about Ambient Assisted Living Systems

This paper proposes a design tool to investigate the properties and emergent behaviours of a special class of Ambient Assisted Living systems, namely mutual assistance communities where the dwellers contribute to each other's well being. Purpose of our system is to understand how mutual assistance communities work, what consequences a design decision could ultimately bring about, and how to construct care communities providing timely and cost-effective service for elderly and disabled people. We prove that mutual assistance between dwellers can provide care in time, and decrease the requirement for professional medical service. The simulation results show that with the existing rules most of the requirements for help can be solved or promptly initiated inside the community before their members resort to external professionals.

cs.CY↗

arXiv2015

A framework for adaptive real-time applications: the declarative real-time OSGi component model

Nowadays, more and more applications require OSGi to have some form of real-time support, which is currently very limited. The resulting closed-system solutions lack of a standard management scheme which forbids standard, system-wide policies for real-time system's deployment, adaptation, and reconfiguration. In order to tackle this problem, this paper proposes a declarative real-time component model. In this model, the distinguishing real-time contract of each component is declaratively described, and a general component real-time management interface is designed. They are used to maintain an accurate view of existing real-time components' promised contracts. A real-time component runtime service is designed to control the whole lifecycle of the components. By using global information and general control interface, it can adjust the system continue to operate without impairing the deployed components' real-time contracts in the face of run-time changes. This system allows itself to be easily extended with other constraint resolving policies to fit different context. The prototype has been tested into a simulated control system. The result shows this framework can provide good real time performance while still provides real-time component dynamicity support as well. To the best of our knowledge, this is the first comprehensive solution providing explicit real-time support from design to execution in OSGi framework.

cs.SE↗

arXiv2015

Promises and Challenges of Ambient Assisted Living Systems

The population of elderly people keeps increasing rapidly, which becomes a predominant aspect of our societies. As such, solutions both efficacious and cost-effective need to be sought. Ambient Assisted Living (AAL) is a new approach which promises to address the needs from elderly people. Ambient Intelligence technologies are widely developed in this domain aiming to construct safe environments around assisted peoples and help them maintain independent living. However, there are still many fundamental issues in AAL that remain open. Most of the current efforts still do not fully express the power of human being, and the importance of social connections and social activities is less noticed. Our conjecture is that such features are fundamental prerequisites towards truly effective AAL services. This paper reviews the current status of researches on AAL, discusses the promises and possible advantages of AAL, and also indicates the challenges we must meet in order to develop practical and efficient AAL systems for elderly people. In this paper, we also propose an approach to construct effective home-care system for the elderly people.

cs.CY↗

arXiv2015

Robust and Tuneable Family of Gossiping Algorithms

We present a family of gossiping algorithms whose members share the same structure though they vary their performance in function of a combinatorial parameter. We show that such parameter may be considered as a "knob" controlling the amount of communication parallelism characterizing the algorithms. After this we introduce procedures to operate the knob and choose parameters matching the amount of communication channels currently provided by the available communication system(s). In so doing we provide a robust mechanism to tune the production of requests for communication after the current operational conditions of the consumers of such requests. This can be used to achieve high performance and programmatic avoidance of undesirable events such as message collisions.

cs.DC↗

arXiv2015

A System Structure for Adaptive Mobile Applications

A system structure for adaptive mobile applications is introduced and discussed, together with a compliant architecture and a prototypic implementation. A methodology is also introduced, which exploits our structure to decompose the behavior of non stable systems into a set of quasi-stable scenarios. Within each of these scenarios we can exploit the knowledge of the available QoS figures to express simpler and better adaptation strategies.

cs.SE↗

arXiv2015

On the Requirements of New Software Development

Changes, they use to say, are the only constant in life. Everything changes rapidly around us, and more and more key to survival is the ability to rapidly adapt to changes. This consideration applies to many aspects of our lives. Strangely enough, this nearly self-evident truth is not always considered by software engineers with the seriousness that it calls for: The assumptions we draw for our systems often do not take into due account that e.g., the run-time environments, the operational conditions, or the available resources will vary. Software is especially vulnerable to this threat, and with today's software-dominated systems controlling crucial services in nuclear plants, airborne equipments, health care systems and so forth, it becomes clear how this situation may potentially lead to catastrophes. This paper discusses this problem and defines some of the requirements towards its effective solution, which we call "New Software Development" as a software equivalent of the well-known concept of New Product Development. The paper also introduces and discusses a practical example of a software tool designed taking those requirements into account --- an adaptive data integrity provision in which the degree of redundancy is not fixed once and for all at design time, but rather it changes dynamically with respect to the disturbances experienced during the run time.

cs.SE↗

arXiv2015

Safety enhancement through situation-aware user interfaces

Due to their privileged position halfway between the physical and the cyber universes, user interfaces may play an important role in preventing, tolerating, and learning from scenarios potentially affecting mission safety and the user's quality of experience. This vision is embodied here in the main ideas and a proof-of-concepts implementation of user interfaces that combine dynamic profiling with context- and situation-awareness and autonomic software adaptation.

cs.HC↗

arXiv2015

Design Tool To Express Failure Detection Protocols

Failure detection protocols---a fundamental building block for crafting fault-tolerant distributed systems---are in many cases described by their authors making use of informal pseudo-codes of their conception. Often these pseudo-codes use syntactical constructs that are not available in COTS programming languages such as C or C++. This translates into informal descriptions that call for ad hoc interpretations and implementations. Being informal, these descriptions cannot be tested by their authors, which may translate into insufficiently detailed or even faulty specifications. This paper tackles this problem introducing a formal syntax for those constructs and a C library that implements them---a tool-set to express and reason about failure detection protocols. The resulting specifications are longer but non ambiguous, and eligible for becoming a standard form.

cs.DC↗

arXiv2015

A Survey of Linguistic Structures for Application-level Fault-Tolerance

The structures for the expression of fault-tolerance provisions into the application software are the central topic of this paper. Structuring techniques answer the questions "How to incorporate fault-tolerance in the application layer of a computer program" and "How to manage the fault-tolerant code". As such, they provide means to control complexity, the latter being a relevant factor for the introduction of design faults. This fact and the ever increasing complexity of today's distributed software justify the need for simple, coherent, and effective structures for the expression of fault-tolerance in the application software. In this text we first define a "base" of structural attributes with which application-level fault-tolerance structures can be qualitatively assessed and compared with each other and with respect to the above mentioned needs. This result is then used to provide an elaborated survey of the state-of-the-art of application-level fault-tolerance structures.

cs.SE↗

arXiv2015

The Algorithm of Pipelined Gossiping

A family of gossiping algorithms depending on a parameter permutation is introduced, formalized, and discussed. Several of its members are analyzed and their asymptotic behaviour is revealed, including a member whose model and performance closely follows the one of hardware pipelined processors. This similarity is exposed. An optimizing algorithm is finally proposed and discussed as a general strategy to increase the performance of the base algorithms.

cs.DC↗

arXiv2014

Reflective and Refractive Variables: A Model for Effective and Maintainable Adaptive-and-Dependable Software

We propose a simple and effective tool for the expression of tasks such as cross-layer optimization strategies or sensors-related applications. The approach is based on what we refer to as "reflective and refractive variables". Both types of variables are associated with external entities, e.g. sensors or actuators. A reflective variable is a volatile variable, that is, a variable that might be concurrently modified by multiple threads. A library of threads is made available, each of which interfaces a set of sensors and continuously update the value of a corresponding set of sensors. One such thread is "cpu", which exports the current level of usage of the local CPU as an integer between 0 and 100. This integer is reflected into the integer reflective variable cpu. A refractive variable is a reflective variable that can be modified. Each modification is caught and interpreted as a request to change the value of an actuator. For instance, setting variable "tcp_sendrate" would request a cross-layer adjustment to the thread interfacing the local TCP layer entity. This allows express in an easy way complex operations in the application layer of any programming language, e.g. plain old C. We describe our translator and the work we are carrying out within PATS to build simple and powerful libraries of scripts based on reflective and refractive variables, including robotics applications and RFID tags processing.

cs.SE↗

arXiv2014

Service-oriented Communities: Visions and Contributions towards Social Organizations

With the increase of the populations, resources are becoming scarcer, and a smarter way to make use of them becomes a vital necessity of our societies. On the other hand, resource management is traditionally carried out through well established organizations, policies, and regulations that are often considered as impossible to restructure. Our position is that merely expanding the traditional approaches might not be enough. Systems must be radically rethought in order to achieve a truly effective and rational use of the available resources. Classical concepts such as demand and supply need to be rethought as well, as they operate artificial classifications that limit the true potential of systems and organizations. In what follows we propose our vision to future, "smarter" systems able to overcome the limitations of the status quo. Such systems require what Boulding called "gestalts," namely concepts able to "directing research towards the gaps which they reveal". In this paper we elaborate on this and show how such gestalts can pave the way towards novel reformulations of traditional services able to reach a better and more sensible management of the available resources and cope with their scarcity. Our vision of a Service-oriented Community is also introduced. We believe that such communities---in heterarchical coexistence with traditional systems---provide the necessary diversity and innovation orientation to prevent societal lock-ins such as the ones we are experiencing in assisting our elderly ones.

cs.CY↗