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MaxNet is a distributed congestion control architecture in which only the most severely bottlenecked link on the end-to-end path controls the source rate. This paper shows that the small-signal convergence speed of MaxNet is higher than that of conventional architectures, such as the current Internet or REM. It also shows that MaxNet decouples the control, so that each pole position depends only on...
Eventually, society will need to be powered almost entirely by renewable energy sources. This will require very large scale storage for long time periods, such as between seasons or even between years. On these timescales, issues such as gradual leakage of energy and price rises must be considered. This paper considers optimal storage management schedules on these long time scales, from the point...
Under dynamic pricing, organizations can reduce their electricity cost by varying their load with price. When the end load is inflexible, storage can match the energy draw from the grid to the price. In this paper we present a general model for power cost management by shifting demand for high power away from high electricity price periods through imperfect energy storages. Using Lyapunov optimization,...
To achieve high system efficiency with increasing speeds, recent WiFi standards, such as IEEE 802.11e/n, allow burst transmissions with block acknowledgements, provided the initial packet is successfully received. Consequently, a user can sometimes improve its throughput by sending the initial packet at a lower rate than other users. We model such a system as a game. Our results show that the socially...
As of April 2013 almost 95% of the IPv4 address space has been allocated. Yet, the transition to IPv6 is still relatively slow. One reason could be existing “IPv4 reserves” - allocated but unused IPv4 addresses. Knowing how many addresses are actively used is important to predict a potential IPv4 address market, predict the IPv6 deployment time frame, and measure progressive exhaustion after the IPv4...
We investigate three ways WLANs can use two channels to carry TCP traffic. Using simulation and a simple model, we show that load balancing over both channels outperforms the others while using a single double-width channel is the worst.
Energy storage is becoming increasingly important, both to mitigate intermittency in renewable generation and to reduce peak demand. However, storage remains expensive and so must be managed optimally. This paper considers the optimal management of storage that is subject to inefficiency in charging/discharging and to self-discharge, with the objective of minimizing energy costs. Notably, it shows...
It has recently been proposed that Internet energy costs, both monetary and environmental, can be reduced by exploiting temporal variations and shifting processing to data centers located in regions where energy currently has low cost. Lightly loaded data centers can then turn off surplus servers. This paper studies online algorithms for determining the number of servers to leave on in each data center,...
Data centre power consumption can be reduced by switching off servers during low load. However, excess switching is wasteful. This paper reviews online algorithms for optimizing this tradeoff, including the benefits of shifting load between geographically distant data centres. These algorithms can also adjust a link's number of parallel lightpaths.
Wireless LANs carry a mixture of traffic, with different delay and throughput requirements. The usual way to provide low-delay services is to give priority to such traffic. However this creates an incentive for throughput sensitive traffic also to use this service, which degrades overall network performance. We propose to allow applications to trade off delay for throughput, without giving preference...
Network induced energy consumption is a significant fraction of all ICT energy consumption. This paper investigates the most energy efficient way to distribute a file to a large number of recipients. It is shown that using peer-to-peer and naively minimizing the transfer time results in energy consumption that is an order of magnitude larger than simply distributing directly from a server, but that...
Power consumption imposes a significant cost for implementing cloud services, yet much of that power is used to maintain excess service capacity during periods of low load. In this work, we study how to avoid such waste via an online dynamic capacity provisioning. We overview recent results showing that the optimal offline algorithm for dynamic capacity provisioning has a simple structure when viewed...
Power consumption imposes a significant cost for data centers implementing cloud services, yet much of that power is used to maintain excess service capacity during periods of predictably low load. This paper investigates how much can be saved by dynamically ‘right-sizing’ the data center by turning off servers during such periods, and how to achieve that saving via an online algorithm. We prove that...
Wireless local area networks (WLANs) support a wide range of applications, with various packet sizes. This diversity is set to increase in 802.11e WLANs which effectively allow very large packets controlled by a transmission opportunity (TxOP) parameter. This paper demonstrates a new phenomenon which occurs as a result of this diversity: When a network carries some large packets and many small packets,...
It has been recently discovered that heavy-tailed file completion time can result from protocol interaction even when file sizes are light-tailed. A key to this phenomenon is the RESTART feature where if a file transfer is interrupted before it is completed, the transfer needs to restart from the beginning. In this paper, we show that independent or bounded fragmentation produces light-tailed file...
This paper presents an optimal strategy for utilizing superimposed pilots for OFDM channel estimation using Wiener filtering. An algorithm is formulated to determine the optimal rectangular set of time-frequency samples for channel estimation for a given complexity. The proposed scheme shows an improved performance at high Doppler frequencies. Moreover, the separable implementation of the 2D Wiener...
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