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Distributed Opportunistic Scheduling: A Control Theoretic Approach
Get PDFDistributed Opportunistic Scheduling (DOS) techniques
have been recently proposed to improve the throughput
performance of wireless networks. With DOS, each station
contends for the channel with a certain access probability. If a contention is successful, the station measures the channel conditions and transmits in case the channel quality is above a certain threshold. Otherwise, the station does not use the transmission opportunity, allowing all stations to recontend. A key challenge with DOS is to design a distributed algorithm that optimally adjusts the access probability and the threshold of each station. To address this challenge, in this paper we first compute
the configuration of these two parameters that jointly optimizes throughput performance in terms of proportional fairness. Then, we propose an adaptive algorithm based on control theory that converges to the desired point of operation. Finally, we conduct a control theoretic analysis of the algorithm to find a setting for its parameters that provides a good tradeoff between stability and speed of convergence. Simulation results validate the design of
the proposed algorithm and confirm its advantages over previous proposals.TRUEpu
Adaptive Modulation for Finite Horizon Multicasting of Erasure-coded Data
Get PDFWe design an adaptive modulation scheme to support opportunistic multicast scheduling in wireless networks. Whereas prior work optimizes capacity, we investigate the finite horizon problem where (once or repeatedly) a fixed number of packets has to be transmitted to a set of wireless receivers in the shortest amount of time – a common problem, e.g., for software updates or video multicast. In the finite horizon problem, the optimum coding and modulation schemes critically depend on the recent reception history of the receivers and requires a fine balance between maximizing overall throughput and equalizing individual receiver throughput. We formulate
a dynamic programming algorithm that optimally solves this scheduling problem. We then develop two low complexity heuristics that perform very close to the optimal solution and are suitable for practical online scheduling in base stations. We further analyze the performance of our algorithms by means of simulation in a wide range of wireless scenarios. They substantially outperform existing solutions based on throughput maximization or favoring
the user with the worst channel, and we obtain a 25% performance improvement over the former and a 40% improvement over the latter in a scenario with Rayleigh fading.Joerg WidmerTelematics EngineeringUniversidad Carlos III de Madrid, Spainpu
Transactions on Petri Nets and Other Models of Concurrency VI: Aims and Scope (Editorial)
No full textThe sixth volume of ToPNoC includes revised versions of selected papers from workshops and tutorials held at the 32nd International Conference on Application and Theory of Petri Nets and Concurrency. It also contains a special section on Networks, Protocols, and Services, as well as a contributed paper submitted through the regular submission track of ToPNoC. The 14 papers cover a diverse range of topics including model checking and system verification, synthesis, foundational work on specific classes of Petri nets, and innovative applications of Petri nets and other models of concurrency. Thus this volume gives a good view of ongoing concurrent systems and Petri nets research.The sixth volume of ToPNoC includes revised versions of selected papers from workshops and tutorials held at the 32nd International Conference on Application and Theory of Petri Nets and Concurrency. It also contains a special section on Networks, Protocols, and Services, as well as a contributed paper submitted through the regular submission track of ToPNoC. The 14 papers cover a diverse range of topics including model checking and system verification, synthesis, foundational work on specific classes of Petri nets, and innovative applications of Petri nets and other models of concurrency. Thus this volume gives a good view of ongoing concurrent systems and Petri nets research.TRUEpu
SLBN: A Scalable Max-min Fair Algorithm for Rate-Based Explicit Congestion Control
Get PDFAlso in: XX Jornadas de Concurrencia y Sistemas Distribuidos, JCSD 2012, 13-15 June 2012, Pamplona, Spain.The growth of the Internet has increased the need
for scalable congestion control mechanisms in high speed networks. In this context, we propose a rate-based explicit congestion control mechanism with which the sources are provided with the rate at which they can transmit. These rates are computed with a distributed max-min fair algorithm, SLBN. The novelty of SLBN is that it combines two interesting features not simultaneously present in existing proposals: scalability and fast convergence to
the max-min fair rates, even under high session churn. SLBN
is scalable because routers only maintain a constant amount of state information (only three integer variables per link) and only incur a constant amount of computation per protocol packet, independently of the number of sessions that cross the router. Additionally, SLBN does not require processing any data packet, and it converges independently of sessions’ RTT. Finally, by design, the protocol is conservative when assigning rates, even in the presence of high churn, which helps preventing link overshoots in transient periods. We claim that, with all these features, our mechanism is a good candidate to be used in real deployments.TRUEpu
Recouping Opportunistic Gain in Dense Base Station Layouts Through Energy-Aware User Cooperation
No full textTo meet the increasing demand for wireless capacity, future networks are likely to consist of dense layouts of small cells. Thus, the number of concurrent users served by each base station is likely to be small resulting in diminished gains from opportunistic scheduling, particularly under dynamic traffic loads. We propose user-initiated traffic spreading, that is transparent to base stations, in order to extract higher opportunistic gain and improve downlink performance. For a specified tradeoff between energy consumption and performance, we characterize the optimal policy by modelling the system as a Markov decision process and also present a tractable heuristic that yields significant performance gains even in multi-user scenarios. Our simulations show that, in the performance-centric case, average delays can be lowered by up to 25% even in homogeneous scenarios where users have identical channel distribution, and up to 51% with heterogeneous users. Further, we show that the bulk of the performance improvement can be achieved with very small increase in energy consumption, e.g., in an energy-sensitive scenario, up to 73% of the performance improvement can typically be achieved at 14% of the energy cost of the performance-centric case.pu
VANET-Based optimization of infotainment and traffic efficiency vehicular services
Get PDFThe design, standardization and future deployment of vehicular communications systems have been driven so far by safety applications. There are two more aspects of the vehicular networking that have increased their importance in the last years: infotainment and traffic efficiency,
as they can improve drivers' experience, making vehicular communications systems more attractive to end-users. In this thesis we propose optimization mechanisms for both types of vehicular services.
Infotainment services are related to the provision of classic IP applications, like browsing, reading e-mail or using social networks. Traffic efficiency services
are those accessing new capabilities to the car-navigation systems, aiming at optimizing the usage of road infrastructures, reducing travel times and therefore minimizing the ecological footprint.
Bringing infotainment services to the vehicular environment requires to comply with standard protocols and mechanisms that allow heterogeneous networks to be interconnected in the Internet. There are three main functionalities that have to be provided: i) address autoconfiguration, ii) efficient routing and iii) mobility management.
Regarding infotainment services, this thesis proposes mechanisms tackling the above-named aspects: an overhearing technique to improve an already standardized address autoconfiguration protocol; a tree-based routing algorithm especially tailored for vehicle-to-Internet communications and an optimized mobility management approach for vehicular environments.
Regarding traffic efficiency, this thesis proposes two
algorithms that make use of vehicular communication techniques to monitor and forecast short-term traffic conditions. We first improved our knowledge on drivers' behavior by analyzing real vehicular data traces, and proposes a mixture model for the vehicles interarrival time. This outcome was used for validating the proposed
infotainment optimization as well. All the algorithms and analytical models described in this thesis have been validated by simulations and/or implementations using standard hardware.Telematics EngineeringUniversidad Carlos III de Madrid, Spainpu
On Weather and Internet Traffic Demand - Technical Report
Get PDFThe weather is known to have a major impact on demand of utilities such as electricity or gas. Given that the Internet usage is strongly tied with human activity, one could guess the existence of similar correlation between its traffic demand and the weather conditions. In this paper, empirical in nature, we demonstrate and quantify such correlation between weather conditions and the Internet traffic demand on different time-scales (from hourly to yearly). For that purpose we collect and use the data from 8 Internet eXchange Points (IXP), geographically spread on 5 different continents, as indicators of the Internet demand in those particular areas. We observe that the seasonal traffic demand variability exists in the locations with large yearly variations in temperature, while the traffic demand in locations close to the equator (with low variability of temperature) is season independent. Using a fine-grain dataset, from three European IXPs, we show that precipitation increases the traffic demand for up to 6%, and somewhat surprisingly that in regards to the impact of precipitation on the demand all major types of ISPs (mobile, residential, content, etc.) observe very similar behavior. One of the implications of the observed time-of-the-day dependent impact of the precipitation is that precipitation has a mild impact on the IP transit costs. Finally, we hint on the possible benefits of the seasonal variations on the energy-proportional computing and scheduling large-scale software releases.pu
Recouping Opportunistic Gain in Dense Base Station Layouts Through Energy-Aware User Cooperation
Get PDFTo meet the increasing demand for wireless capacity, future networks are likely to consist of dense layouts of small cells. Thus, the number of concurrent users served by each base station is likely to be small resulting in diminished
gains from opportunistic scheduling, particularly under dynamic traffic loads. We propose user-initiated traffic spreading, that is transparent to base stations, in order to extract higher opportunistic gain and improve downlink performance. For a specified tradeoff between energy consumption and performance, we characterize the optimal policy by modelling the system as a Markov decision process and also present a tractable heuristic that yields significant performance gains even in multi-user scenarios. Our simulations show that, in the performance-centric case, average delays can be lowered by up to 25% even in homogeneous scenarios where users have identical channel distribution, and up to 51% with heterogeneous users. Further, we show that the bulk of the performance improvement can be achieved with very small increase in energy consumption, e.g., in an energy-sensitive scenario, up to 73% of the performance improvement can typically be achieved at 14% of the energy cost of the performance-centric case.Telematics EngineeringUniversidad Carlos III de Madrid, Spainpu
TREND: The FP7 Network of Excellence on Green Networking
Get PDFTREND is to establish the integration of the EU research community in green networking, with a long term perspective to consolidate the European leadership in the field. Network energy consumption can be saved in cellular networks with BS sleep modes.TRUEpu