2180308
RARE - Resource Aware Routing for mEsh
An important element of any routing protocol used for wireless mesh networks (WMNs) is the link cost function used to represent the radio link characteristic. The majority of the routing protocols for WMNs attempt to accurately characterise the radio link quality by constructing the link cost function from the measurements obtained using active probing techniques, which introduces overhead. In this paper we propose a new approach called resource aware routing for mesh (RARE) which instead employs passive monitoring to gather radio link information. This results in a smaller overhead than the other methods that require active network probing, and is load independent since it does not require an access to the medium. Moreover, we show that our RARE approach performs well in a real radio environment through a number of experiments performed on a static 17 node WLAN mesh testbed.
553221
An Experimental Investigation of Parallel Multimedia Streams Over IEEE 802.11e WLAN Networks Using TXOP
In this paper we perform an experimental investigation of the IEEE 802.11e TXOP facility to enhance the transmission of parallel multimedia streaming sessions through efficient bandwidth reservation and explicitly consider both the audio and video streams. The delay constraints associated with the audio and video streams that comprise a multimedia session pose the greatest challenge since real-time multimedia is particularly sensitive to delay as the packets require a strict bounded end-to-end delay. We show how the TXOPLimit parameter can be efficiently dimensioned to reduce the transmission delay for the video frames. Due to its frame-based nature, video applications are considered to be bursty as each video frame is typically transmitted as a burst of packets. The size of the burst is related to the size of the video frame and the number of packets required to transmit the video frame. The TXOP facility is particularly suited to efficiently deal with this burstiness since it can be used to reserve bandwidth for the duration of the packet burst. Through experimental investigation, we show that there is a significant performance improvement for the video streams by using the TXOPLimit parameter however there is no such improvement for the audio streams. We show that over-dimensioning the TXOPLimit parameter can cause the video stream to seize too much bandwidth which results in a deterioration in performance for the other competing traffic streams. This deterioration becomes more prominent as the number of parallel multimedia streams increases. We show that there is a performance improvement to all traffic streams by providing differentiated service to the constituent I, P, and B video frame types in conjunction with the TXOP facility.
18478829
Gauging VoIP call quality from 802.11 WLAN resource usage
In this paper we experimentally study the relationship between resource utilization in the wireless LAN and the quality of VoIP calls transmitted over the wireless medium. Specifically we evaluate how its overall capacity is shared between three basic MAC bandwidth components (load, access, and free) as the number of VoIP calls increases and how it influences transmission impairments (delay, loss, and jitter) and thus call quality. Resource utilization (under the MAC bandwidth components framework) is calculated by a WLAN probe application that passively "sniffs" packets at the L2/MAC layer of the wireless medium and analyses their headers and temporal characteristics. The quality of VoIP calls is predicted using an extended version of the ITU-T E-model, which estimates user satisfaction from time varying transmission impairments. Through experimentation with various codecs and packetization schemes we found that as the load (number of calls) reaches the available capacity level, packet delays and jitter increase dramatically resulting in the call quality becoming degraded. We show how these MAC bandwidth components maybe used to assess the VoIP call quality on 802.11 WLANs
12221702
The capability of the EDCA mechanism to support voice traffic in a mixed voice/data transmission over 802.11e WLANs - an experimental investigation
In this paper we experimentally evaluate the capability of the EDCA mechanism to support voice traffic in a mixed voice/data transmission over 802.1 le WLANs. In particular we investigate how real-time voice transmission can be supported by tuning four EDCA parameters, namely AIFSN, CWmin , CWmax, and TXOP and how this impacts on background data transmission. The experimental set-up involves fifteen VoIP terminals sending bi-directional traffic between wired and wireless subnets and another station injecting various types of heavy background loads to the wireless subnet. End-to-end voice transmission quality is predicted from time-varying transmission impairments with the use of the latest appendix to the ITU-T E-model. Our experimental results show that the AIFSN parameter more effectively protects voice calls against background data traffic than CWmin. We also demonstrate that tuning of the TXOP parameter does not improve the quality of voice transmission. To the best of our knowledge, this is the first experimental investigation regarding tuning of MAC layer EDCA parameters in a real 802.1 le WLAN network from the perspective of end-to-end voice transmission quality and end user satisfaction.
6738991
An Experimental Investigation of IEEE 802.11e TXOP Facility for Real-Time Video Streaming
Real-time multimedia streaming applications require a strict bounded end-to-end delay and are considered to be bursty as each video frame is typically transmitted as a burst of packets. In this paper we show how the distribution of video frame sizes can be used to efficiently dimension the IEEE 802.lie TXOP limit parameter to efficiently deal with this burstiness in order to enhance the transmission of real-time video streaming services. Through experimental investigation, we show that by using the mean video frame size to dimension the TXOP limit parameter, the transmission delay for the video frame is reduced by 67% under heavily loaded conditions. Other techniques investigated in this paper include applying the TXOP facility separately to each of the constituent I, P, and B video frame types.
571649
An Evaluation of a Conservative Transmit Power Control Mechanism on an Indoor 802.11 Wireless Mesh Testbed
Power control techniques for IEEE 802.11 wireless networks have already gained considerable attention. Such techniques are particularly attractive because they can improve various aspects of wireless network operation such as interference mitigation, spatial reuse in dense wireless deployments, topology control, and link quality enhancement. In this paper we propose a novel delivery ratio based Conservative Transmit Power Control (ConTPC) mechanism. Our implementation is conservative when it comes to deciding if the transmit power should be reduced for a given link. This is because we do not want poor quality wireless links to further reduce their quality and be overwhelmed by other links transmitting at maximum power. We have experimentally evaluated the benefit of the proposed power control scheme when compared with fixed power level systems. We show that our ConTPC mechanism can increase the throughput, however the magnitude of this enhancement largely depends on the topology of the wireless network.
215753551
The Unicode Standard, Version 3.0
Disclaimer These charts are provided as the online reference to the character contents of the Unicode Standard, Version 8.0 but do not provide all the information needed to fully support individual scripts using the Unicode Standard. For a complete understanding of the use of the characters contained in this file, please consult the appropriate sections of The Unicode Standard, Version 8.0, online at http://www.unicode.org/versions/Unicode8.0.0/, as well as Unicode Standard Annexes #9, #11, #14, #15, #24, #29, #31, #34, #38, #41, #42, #44, and #45, the other Unicode Technical Reports and Standards, and the Unicode Character Database, which are available online.
41330468
Detecting Data Concealment Programs Using File System Analysis
An improved closure and nozzle system for containers for air-curable materials such as cartridges for sealant and caulking compounds is disclosed. A container such as a caulking cartridge is provided with a threaded neck for attachment of a correspondingly threaded nozzle having a tapered tip portion designed to be cut off to provide a desired orifice size. A cap having a snap-fit ring is designed to mate with a corresponding snap-fit ring on the nozzle short of the tip and also having a threaded external portion designed to mate with the container neck so that the cartridge can be resealed after opening.
5625582
Experimental evaluation of the Hewlett-Parkard exemplar file system
This article presents results from an experimental evaluation study of the HP Exemplar file system. Our experiments consist of simple micro-benchmarks that study the impact of various factors on the file system performance. These factors include I/O request/buffer sizes, vectored/non-vectored access patterns, read-ahead policies, multi-threaded (temporally irregular) requests, and architectural issues (cache parameters, NUMA behavior, etc.). Experimental results indicate that the Exemplar file system provides high I/O bandwidth, both for single- and multi-threaded applications. The buffer cache, with prioritized buffer management and large buffer sizes, is effective in exploiting temporal and spatial access localities. The performance of non-contiguous accesses can be improved by either using vectored I/O interfaces or tuning the read-ahead facilities. The file system performance depends on the relative locations of the computing threads and the file system, and also on various Exemplar design parameters such as the NUMA architecture, TLB/data cache management and paging policies.
45315809
Forensic Analysis of BIOS Chips
Data can be hidden in BIOS chips without hindering computer performance. This feature has been exploited by virus writers and computer game enthusiasts. Unused BIOS storage can also be used by criminals, terrorists and intelligence agents to conceal secrets. However, BIOS chips are largely ignored in digital forensic investigations. Few techniques exist for imaging BIOS chips and no tools are available specifically for analyzing BIOS data.
34331062
A Noice Whitening approach to Multiple-Access Noise Rejection - Part II: Implementation Issues
Several practical methods are proposed for the implementation of linear filters that reject multiple-access noise in direct sequence code-division multiple-access (DS-CDMA) receivers. These methods rely on taking advantage of variations in the received chip spectrum, and do not require locking and despreading multiple signals. The resulting structures are simple, and some can operate at a high chip rate. Adaptive structures are also proposed. It is shown that a close relationship exists between noise whitening and chip-equalization for a DS-CDMA receiver. System issues affecting the choice of the chip spectrum, and thus the applicability of these methods, are described.