Search

Frame coalescing is one of the most efficient techniques to manage the low power idle (LPI) mode supported by Energy Efficient Ethernet (EEE) interfaces. This technique enables EEE interfaces to remain in the LPI mode for a certain amount of time upon the arrival of the first frame (time-based coalescing) or until a predefined amount of traffic accumulates in the transmission buffer (size-based coalescing). This paper provides new insights on the practical efficiency limits of both coalescing techniques. In particular, we derive the fundamental limits on the maximum energy savings considering a target average frame delay. Additionally, we present new open-loop adaptive variants of both time-based and size-based coalescing techniques. These proposals dynamically adjust the length of the sleeping periods in accordance with actual traffic conditions to reduce energy consumption while keeping the average delay near a predefined value simultaneously. Analytical and simulation results show that the energy consumption of both proposals is comparable to the fundamental limits. Consequently, we recommend the usage of the time-based algorithm in most scenarios because of its simplicity as well as its ability to bound the maximum frame delay at the same time., Comment: 10 pages. To be published in IEEE Transactions on Green Communications and Networking

The IEEE has recently released the 802.3bj standard that defines two different low power operating modes for high speed Energy Efficient Ethernet physical interfaces (PHYs) working at 40 and 100 Gb/s. In this paper, we propose the use of the well-known frame coalescing algorithm to manage them and provide an analytical model to evaluate the influence of coalescing parameters and PHY characteristics on their power consumption.

The Discontinuous Reception (DRX) mechanism is commonly employed in current LTE networks to improve energy efficiency of user equipment (UE). DRX allows UEs to monitor the physical downlink control channel (PDCCH) discontinuously when there is no downlink traffic for them, thus reducing their energy consumption. However, DRX power savings are achieved at the expense of some increase in packet delay since downlink traffic transmission must be deferred until the UEs resume listening to the PDCCH. In this paper, we present a promising mechanism that reduces energy consumption of UEs using DRX while simultaneously maintaining average packet delay around a desired target. Furthermore, our proposal is able to achieve significant power savings without either increasing signaling overhead or requiring any changes to deployed wireless protocols.

Receiver-initiated medium access control protocols for wireless sensor networks are theoretically able to adapt to changing network conditions in a distributed manner. However, existing algorithms rely on fixed beacon rates at each receiver. We present a new received initiated MAC protocol that adapts the beacon rate at each receiver to its actual traffic load. Our proposal uses a computationally inexpensive formula for calculating the optimum beacon rate that minimizes network energy consumption and, so, it can be easily adopted by receivers. Simulation results show that our proposal reduces collisions and diminishes delivery time maintaining a low duty cycle., Comment: 4 pages, 6 figures

Network interfaces in most LAN computing devices are usually severely under-utilized, wasting energy while waiting for new packets to arrive. In this paper, we present two algorithms for opportunistically powering down unused network interfaces in order to save some of that wasted energy. We compare our proposals to the best known opportunistic method, and show that they provide much greater power savings inflicting even lower delays to Internet traffic.

Delay-based congestion control algorithms provide higher throughput and stability than traditional loss-based AIMD algorithms, but they are inherently unfair against older connections when the queuing and the propagation delay cannot be measured accurately and independently. This paper presents a novel measurement algorithm whereby fairness between old and new connections is preserved. The algorithm does not modify the dynamics of congestion control, and runs entirely in the server host using locally available information.

Although delay-based congestion control protocols such as FAST promise to deliver better performance than traditional TCP Reno, they have not yet been widely incorporated to the Internet. Several factors have contributed to their lack of deployment. Probably, the main contributing factor is that they are not able to compete fairly against loss-based congestion control protocols. In fact, the transmission rate in equilibrium of delay-based approaches is always less than their fair share when they share the network with traditional TCP-Reno derivatives, that employ packet losses as their congestion signal. There are also other performance impairments caused by the sensitivity to errors in the measurement of the congestion signal (queuing delay) that reduce the efficiency and the intra-protocol fairness of the algorithms. In this paper we report, analyze and discuss some recent proposals in the literature to improve the dynamic behavior of delay-based congestion control algorithms, and FAST in particular. Coexistence of sources reacting differently to congestion, identifying congestion appearance in the reverse path and the persistent congestion problem are the issues specifically addressed.

FAST-TCP achieves better performance than traditional TCP-Reno schemes, but unfortunately it is inherently unfair to older connections due to wrong estimations of the round-trip propagation delay. This paper presents a model for this anomalous behavior of FAST flows, known as the persistent congestion problem. We first develop an elementary analysis for a scenario with just two flows, and then build up the general case with an arbitrary number of flows. The model correctly quantifies how much unfairness shows up among the different connections, confirming experimental observations made by several previous studies. We built on this model to develop an algorithm to obtain a good estimate of the propagation delay for FAST-TCP that enables to achieve fairness between aged and new connections while preserving the high throughput and low buffer occupancy of the original protocol. Furthermore, our proposal only requires a modification of the sender host, avoiding the need to upgrade the intermediate routers in any way.

In this paper, we research the feasibility of adapting the packet coalescing algorithm, used successfully in IEEE 802.3az Ethernet cards, to upstream EPON channels. Our simulation experiments show that, using this algorithm, great power savings are feasible without requiring any changes to the deployed access network infrastructure nor to protocols.