Overview of 802.11 Power Saving Mechanisms

This paper presents overview of 802.11 power saving mechanisms with priority to Distributed Coordination Function (DCF). In the 802.11 power saving mechanism, time is divided into beacon intervals. When each beacon interval starts, each node periodically wakes up for a time period called ATIM window. Synchronization is required between nodes so that they remain active at the same time. During ATIM window, nodes exchange control packets to determine whether they need to remain active for the rest of the beacon interval. The size of the ATIM window has a major marked effect on energy savings and throughput achieved by nodes. In the mechanism, the nodes that are involved in the data communication remain active and other nodes go into doze mode

Link Layer Support For Unified Radio Power Management in Wireless Sensor Networks, Master\u27s Thesis, May 2007

Radio power management is of paramount concern in wireless sensor networks that must achieve long lifetimes on scarce amounts of energy. While a multitude of power management protocols have been proposed in the past, the lack of system support for flexibly integrating them with a diverse set of applications and network platforms has made them difficult to use. Instead of proposing yet another power management protocol, this thesis focuses on providing link layer support towards realizing a Unified Power Management Architecture (UPMA) for flexible radio power management in wireless sensor networks. In contrast to the monolithic approaches adopted by existing power management solutions, we provide (1) a set of standard interfaces that allow different power management protocols existing at the link layer to be easily implemented on top of common MAC level functionality, (2) an architectural framework for enabling these protocols to be easily swapped in and out depending on the needs of the applications that require them, and (3) a mechanism for coordinating the existence of multiple applications, each of which may have different requirements for the same underlying power management protocol. We have implemented these features on the Mica2 and Telosb radio stacks in TinyOS-2.0. Microbenchmark results demonstrate that the separation of power management from MAC level functionality incurs a negligible decrease in performance when compared to existing monolithic implementations. Two case studies show that the power management requirements of multiple applications can be easily coordinated, sometimes even resulting in better power savings than any one of them can achieve individually

Performance of MAC- IEEE802.11n-Over-Fiber Network in Presence of Errors in the Transmitting Channel

An analytical model is presented to evaluate the MAC-protocol performance of the IEEE802.11n-over–fiber network with taking into account probability of error occurring in the transmitting channel. The results show that the data throughput with using RTS/CTS or basic access mechanism is suppressed with increasing amount of errors in the transmitting channel over all the range of fiber delay as well as it is very sensitive to the number of stations and packet length. And utilizing the RTS/CTS mechanism shows higher immunity than basic access mechanism when the network is utilized by high number of users and errors in transmission channel is relatively high

Modelling revenue generation in a dynamically priced mobile telephony service

Dynamic pricing has been used extensively in specific markets for many years but recent years have seen an interest in the utilization of this approach for the deployment of novel and attractive tariff structures for mobile communication services. This paper describes the development and operation of an agent based model (ABM) for subscriber behavior in a dynamically priced mobile telephony network. The design of the ABM was based on an analysis of real call detail records recorded in a Uganda mobile telephony network in which dynamic pricing was deployed. The ABM includes components which simulate subscriber calling behavior, mobility within the network and social linkages. Using this model, this paper reports on an investigation of a number of alternative strategies for the dynamic pricing algorithm which indicate that the network operator will likely experience revenue losses ranging from a 5 %, when the pricing algorithm is based on offering high value subscriber cohort enhanced random discounts compared to a lower value subscriber cohort, to 30 %, when the priding algorithm results in the discount on offer in a cell being inversely proportional to the contemporary cell load. Additionally, the model appears to suggest that the use of optimization algorithms to control the level of discount offered in cells would likely result in discount simply converging to a “no-discount” scenario. Finally, commentary is offered on additional factors which need to be considered when interpreting the results of this work such as the impact of subscriber churn on the size of the subscriber base and the technical and marketing challenges of deploying the various dynamic pricing algorithms which have been investigated

Walizka Tuwima. Rzecz o Tuwimie i o Liberaturze

The article explores the connection between Julian Tuwim\u2019s oeuvre and the concept of liberature. Coined by Zenon Fajfer in the 1990s, the term liberature accentuates the visual and spatial aspects of a literary text and highlights the fact that the meaning of a text depends on its material form. The author reconstructs Tuwim\u2019s approach to formal experimentation related to the spatial and visual aspects of a text. To this aim, he analyses Pegaz d\u119ba (written before 1939, first published in 1950, and republished in 2008), whose manuscript survived the war in a suitcase buried close to Tuwim\u2019s house. The book is a collection and study of various genres and other forms of artistic expression which showed liberary features long before the term was coined. Ranocchi argues that although Tuwim treated what is now called liberature as an insignificant and marginal curiosity, he nevertheless defined it as an area of interest for both literary historians and writers. Thus, Pegaz d\u119ba can be seen as the first Polish attempt to systematize the literary works that have more recently been labelled as liberature and as such won critical acclaim

Design And Hardware Implementation Of A Novel Scrambling Security Algorithm For Robust Wireless Local Area Networks

The IEEE802.11 standard for wireless networks includes a Wired Equivalent Privacy (WEP) protocol, which is a popular wireless secure communication stream cipher protocol approach to network security used to protect link-layer communications from eavesdropping and other attacks. It allows user to communicate with the user; sharing the public key over a network. It provides authentication and encrypted communications over unsecured channels. However, WEP protocol has an inherent security flaw. It is vulnerable to the various attacks, various experiments has proved that WEP fails to achieve its security goals. This thesis entails designing, evaluating and prototyping a wireless security infrastructure that can be used with the WEP protocol optionally, thus reducing the security vulnerabilities. We have studied the flaws of WEP and the reasons for their occurrence, and we provide the design and implementation of a novel scheme in Matlab and VHDL to improve the security of WEP in all aspects by a degree of 1000. The architecture was designed with a consideration for least increment in hardware, thus achieving power and cost efficiency. It also provides flexibility for optional implementation with the available technology by being able to be bypassed by the technology, which allows for non-replacement of existing hardware, common on both, the WEP and the proposed protocols, on the fly

Run-time transmission power reconfiguration and adaptive packet relocation in wireless network-on-chip

Network-on-chip (NoC) is an on-chip communication network that allows parallel communication between all cores to improve inter-core performance. Wireless NoC (WiNoC) introduces long-range and high bandwidth radio frequency (RF) interconnects that can possibly reduce the multi-hop communication of the planar metal interconnects in conventional NoC platforms. In WiNoC, RF transceivers account for a significant power consumption, particularly its transmitter, out of its total communication energy. CurrentWiNoC architectures employ constant maximum transmitting power for communicating radio hubs regardless of physical location of the receiver radio hubs. Besides, high transmission power consumption in WiNoC with constant maximum power suffers from significant energy and load imbalance among RF transceivers which lead to hotspot formation, thus affecting the reliability of the onchip network system. There are two main objectives covered by this thesis. Firstly, this work proposes a reconfigurable transmitting power control scheme that, by using bit error rate (BER) estimation obtained at the receiver’s side, dynamically calibrates the transmitting power level needed for communication between the source and destination radio hubs. The proposed scheme achieves significant total system energy reduction by about 40% with an average performance degradation of 3% and with no impact on throughput. The proposed design utilizes a small fraction of both area and power overheads (about 0.1%) out of total transceiver properties. The proposed technique is generic and can be applied to any WiNoC architecture for improving its energy efficiency with a negligible overhead in terms of silicon area. Secondly, an energyaware adaptive packet relocator scheme has been proposed. Based on transmission energy consumption and predefined energy threshold, packets are routed to adjacent transmitter for communication with receiver radio hub, with an aim to balance energy distribution in WiNoC. The proposed strategy alone achieves total communication energy savings of about 8%. A joint scheme of the reconfigurable transmitting power management and energy-aware adaptive packet relocator is also introduced. The scheme consistently results in an energy savings of 30% with minimal performance degradation

Corl8: A System for Analyzing Diagnostic Measures in Wireless Sensor Networks

Due to an increasing demand to monitor the physical world, researchers are deploying wireless sensor networks more than ever before. These networks comprise a large number of sensors integrated with small, low-power wireless transceivers used to transmit data to a central processing and storage location. These devices are often deployed in harsh, volatile locations, which increases their failure rate and decreases the rate at which packets can be successfully transmitted. Existing sensor debugging tools, such as Sympathy and EmStar, rely on add-in network protocols to report status information, and to collectively diagnose network problems. Some protocols rely on a central node to initiate the diagnosis sequence. These methods can congest network channels and consume scarce resources, including battery power. In this thesis, we present Corl8, a system for analyzing diagnostic traces in wireless sensor networks. Our method relies on diagnostic data that is periodically transmitted to a network sink as a part of the standard sensor payload to enable fault diagnosis. Corl8 does not require any specific data to be present in the system, making it flexible. Our system provides an interactive environment for exploring correlated changes across different diagnostic measures within an individual node. It also supports processing on a batch level to automatically flag interesting correlations. The system\u27s flexibility makes it applicable for use in any wireless sensor network that transmits diagnostic measures. The analysis methods are user-configurable, but we suggest settings and analyze their performance. For our evaluation, we use data from five real-world deployments from the Intelligent River(R) project consisting of 36 sensor nodes