Papers by Maricica Nistor
IEEE Transactions on Smart Grid, 2018
Hardware Abstraction and Protocol Optimization for Coded Sensor Networks
IEEE ACM Transactions on Networking, Jun 1, 2015
ABSTRACT The design of the communication protocols in wireless sensor networks (WSNs) often negle... more ABSTRACT The design of the communication protocols in wireless sensor networks (WSNs) often neglects several key characteristics of the sensor’s hardware, while assuming that the number of transmitted bits is the dominating factor behind the system’s energy consumption. A closer look at the hardware specifications of common sensors reveals, however, that other equally important culprits exist, such as the reception and processing energy. Hence, there is a need for a more complete hardware abstraction of a sensor node to reduce effectively the total energy consumption of the network by designing energy-efficient protocols that use such an abstraction, as well as mechanisms to optimize a communication protocol in terms of energy consumption. The problem is modeled for different feedback-based techniques, where sensors are connected to a base station, either directly or through relays. We show that for four example platforms, the use of relays may decrease up to 4.5 times the total energy consumption when the protocol and the hardware are carefully matched. We conclude that: 1) the energy budget for a communication protocol varies significantly on different sensor platforms; and 2) the protocols can be judiciously adapted to the underlying hardware. The results are cross-validated using real-life measurements.
Network coding is a technique that proposes a different approach for the protocol design in data ... more Network coding is a technique that proposes a different approach for the protocol design in data communication networks. Thus, the nodes in the network are allowed not only to store and forward data packets, but also to process and mix different packets in a single coded packet. By using this technique, the throughput and robustness of the network can be significantly improved. However, the transmission delay of network coding is still not well understood. In real-time communication systems with stringent delay constraints, understanding the transmission delay distribution is at the core of implementing network coding in practical scenarios. Moreover, the benefits of network coding for broadcast scenarios have been proven, but the use of this technique in data gathering applications is limited. Unlike broadcast applications, where the main objective is to minimize the transmission delay, in data gathering applications the challenge is to reduce the data collection time, called the c...
International Journal of Transport Development and Integration, 2019
Bike sharing systems are fundamental sources of data for creating applications of monitoring the ... more Bike sharing systems are fundamental sources of data for creating applications of monitoring the city and guiding the user's choice for bike usage. Although many related works analyse the generated data by these urban bike systems with the scope of finding bike usage patterns, the variety of the cities and the lack of impact factors require further deeper investigations. We propose a simple, but efficient mathematical approach based on a Markovian model to predict the bike distribution for an urban sharing bike system considering the weather and event impacts. The model is applied for data collected from the New York city bike system. The main findings are relevant for the urban applications and are summarized as follows: (a) the model results substantially address the city's characteristics, i.e., for the New York city, in terms of weather, only the temperature influences the bike usage, while regarding the events, the impact is insignificant, (b) the hourly bike distribution is predicted 1 day-ahead that is of particular interest to the city manager and (c) to the user who is able to know 1 day in advance the probability of finding an available bike or a free parking space at a specific station. Further city comparison analysis in terms of traffic, vehicle utilization and population density is provided for future purposes. Finding the precise station's capacity is a forthcoming feature of the proposed model.
2010 IEEE International Symposium on Network Coding (NetCod), 2010
asymptotic analysis: infinite block lengths non-asymptotic analysis: finite block lengths average... more asymptotic analysis: infinite block lengths non-asymptotic analysis: finite block lengths average analysis complete probability distribution (average and worst-case analysis) Receiver 1 Source Receiver 2 e n e 2 e 1
Network Coding Protocols for Data Gathering Applications
IEEE Communications Letters, 2015
A total energy approach to protocol design in coded wireless sensor networks
2012 International Symposium on Network Coding (NetCod), 2012
ABSTRACT The development of hardware platforms for sensing applications and the design of energy-... more ABSTRACT The development of hardware platforms for sensing applications and the design of energy-efficient protocols for data gathering are typically viewed as separate tasks. In many cases, communication engineers decide on the protocol specification based on high-level hardware abstractions, which assume that the radio transmission block is the top spender of electrical power. However, a closer inspection of the existing technology immediately reveals that this assumption does not hold for the majority of sensor platforms currently available in the market. To help close this gap, we propose a new hardware abstraction for protocol design that takes into consideration all of the main energy spending operations. Our preliminary results confirm that (a) the same protocol can have very different energy consumption profiles over different sensor platforms and (b) slight changes to the protocols using the proposed hardware abstraction can lead to significant energy gains over a wider range of sensor platforms. The latter findings are supported by real-life measurements, where network coding is implemented using common sensor motes.
Proceedings of the 5th International Conference on Vehicle Technology and Intelligent Transport Systems, 2019
Bike sharing systems offer a convenient, ecologic, and economic transport mode that has been incr... more Bike sharing systems offer a convenient, ecologic, and economic transport mode that has been increasingly adopted. However, the distribution of bikes is often unbalanced, which decreases user satisfaction and potential revenues. Moreover, bike sharing literature is mostly focused on the prediction of demand on large scale systems and uses simulations for the assessment of relocation operations to increase the number of utilizations. We propose prediction models based on machine learning approaches to improve the bike sharing re-balancing in a small city of Portugal. The algorithm aims to improve three metrics, namely (1) increase the number of utilizations, (2) reduce the number of stations without bikes, (3) reduce the time without available bikes in the stations. The relocation operations are validated using real data. Our findings show that (a) the estimated number of utilizations created by this system is substantially higher than the current system by 223%, (b) our model allows the correct identification of more 70%, 165%, 249% empty stations with the same or substantially higher precision than the existing approach, (c) the total time of bike unavailability reduced by the predictive model is 283% higher than the time reduced by current approach (1,394,454 vs 363,971 minutes).
2010 Information Theory and Applications Workshop (ITA), 2010
Understanding the delay behavior of network coding with a fixed number of receivers, small field ... more Understanding the delay behavior of network coding with a fixed number of receivers, small field sizes and a limited number of encoded symbols is a key step towards its applicability in real-time communication systems with stringent delay constraints. Previous results are typically asymptotic in nature and focus mainly on the average delay performance. Seeking to characterize the complete delay distribution of random linear network coding, we present a brute-force methodology that is feasible for up to four receivers, limited field and generation sizes. The key idea is to fix the pattern of packet erasures and to try out all possible encodings for various system and channel parameters. Our findings, which are valid for both decoding delay and ordered-delivery delay, can be used to optimize network coding protocols with respect not only to their average but also to their worst-case performance.
Soft Computing Applications for Renewable Energy and Energy Efficiency, 2015
The gradual transformation of electricity distribution networks to smart grids is expected to pro... more The gradual transformation of electricity distribution networks to smart grids is expected to provide the technological infrastructure allowing demand to be treated as a responsive resource, enabling end-users to make optimized decisions concerning the integrated use of domestic energy resources (i.e. manageable loads, storage, and local generation systems). The support to this active use of demand asks for the development of optimization models of combinatorial nature, given the diversity of comfort requirements, technical constraints, appliances to be scheduled, etc. in a near real-time framework. Evolutionary algorithms have been used to cope with the combinatorial characteristics of models, large and irregular search spaces, and also multiple objectives of economic, environmental, quality of service, and technical nature. This chapter makes a review of the use of evolutionary algorithms to optimize the use of domestic energy resources, identifying the main characteristics of the approach, including decision variables, sets of constraints and objective functions, as well as the main algorithmic features to obtain usable solutions.
IEEE Transactions on Smart Grid, 2000
We propose a robust network coding protocol for enhancing the reliability and speed of data gathe... more We propose a robust network coding protocol for enhancing the reliability and speed of data gathering in smart grids. At the heart of our protocol lies the idea of tunable sparse network coding, which adopts the transmission of sparsely coded packets at the beginning of the transmission process but then switches to a denser coding structure towards the end. Our systematic mechanism maintains the sparse structure during the recombination of packets at the intermediate nodes. The performance of our protocol is compared by means of simulations of IEEE reference grids against standard master-slave protocols used in real systems. Our results show that network coding achieves 100% reliability, even for hostile network conditions, while gathering data 10 times faster than standard master-slave schemes.
On the Delay Distribution of Random Linear Network Coding
IEEE Journal on Selected Areas in Communications - JSAC, 2011
A fundamental understanding of the delay behavior of network coding is key towards its successful... more A fundamental understanding of the delay behavior of network coding is key towards its successful application in real-time applications with strict message deadlines. Previous contributions focused mostly on the average decoding delay, which although useful in various scenarios of interest is not sufficient for providing worst-case delay guarantees. To overcome this challenge, we investigate the entire delay distribution of random linear network coding for any field size and arbitrary number of encoded symbols (or generation size). By introducing a Markov chain model we are able to obtain a complete solution for the erasure broadcast channel with two receivers. A comparison with Automatic Repeat reQuest (ARQ) with perfect feedback, round robin scheduling and a class of fountain codes reveals that network coding on GF(2 4 ) offers the best delay performance for two receivers. We also conclude that GF(2) induces a heavy tail in the delay distribution, which implies that network coding...
Uploads
Papers by Maricica Nistor