Why Does Flow Director Cause Packet Reordering?

Intel Ethernet Flow Director is an advanced network interface card (NIC) technology. It provides the benefits of parallel receive processing in multiprocessing environments and can automatically steer incoming network data to the same core on which its application process resides. However, our analysis and experiments show that Flow Director cannot guarantee in-order packet delivery in multiprocessing environments. Packet reordering causes various negative impacts. E.g., TCP performs poorly with severe packet reordering. In this paper, we use a simplified model to analyze why Flow Director can cause packet reordering. Our experiments verify our analysis

Performance Optimization in Video Transmission over ZigBee using Particle Swarm Optimization

IEEE 802.15.4 - ZigBee is a wireless sensor targeted at applications that require low data rate, low power and inexpensive. IEEE 802.15.4 is limited to a throughput of 250kbps and is designed to provide highly efficient connec-tivity. Hence, IEEE 802.15.4 is not designed to transfer large amounts of da-ta or MPEG-4 as its bandwidth is too low. In engineering and computer sci-ence often use optimization techniques, as do real environment applications in order to overcome complex issues and now this paper a solution has been accomplished by applying Particle Swarm Optimization (PSO) to improve the quality of transmitted MPEG-4 over IEEE 802.15.4. The proposed intelligent system should minimize data loss and distortion. The computer simulation results confirm that applying PSO in video transmission improve the quality of picture and reduce data loss when compared with the conventional MPEG video transmission in ZigBee

An intelligent approach to quality of service for MPEG-4 video transmission in IEEE 802.15.1

Nowadays, wireless connectivity is becoming ubiquitous spreading to companies and in domestic areas. IEEE 802.15.1 commonly known as Bluetooth is high-quality, high-security, high-speed and low-cost radio signal technology. This wireless technology allows a maximum access range of 100 meters yet needs power as low as 1mW. Regrettably, IEEE 802.15.1 has a very limited bandwidth. This limitation can become a real problem If the user wishes to transmit a large amount of data in a very short time. The version 1.2 which is used in this project could only carry a maximum download rate of 724Kbps and an upload rate of 54Kbps In its asynchronous mode. But video needs a very large bandwidth to be transmitted with a sufficient level of quality. Video transmission over IEEE 802.15.1 networks would therefore be difficult to achieve, due to the limited bandwidth. Hence, a solution to transmit digital video with a sufficient quality of picture to arrive at the receiving end is required. A hybrid scheme has been developed in this thesis, comprises of a fuzzy logic set of rules and an artificial neural network algorithms. MPEG-4 video compression has been used in this work to optimise the transmission. This research further utilises an ‘added-buffer’ to prevent excessive data loss of MPEG-4 video over IEEE 802.15.1transmission and subsequently increase picture quality. The neural-fuzzy scheme regulates the output rate of the added-buffer to ensure that MPEG-4 video stream conforms to the traffic conditions of the IEEE 802.15.1 channel during the transmission period, that is to send more data when the bandwidth is not fully used and keep the data in the buffers if the bandwidth is overused. Computer simulation results confirm that intelligence techniques and added-buffer do improve quality of picture, reduce data loss and communication delay, as compared with conventional MPEG video transmission over IEEE 802.15.1

Performance Analysis of Wireless Networks with QoS Adaptations

The explosive demand for multimedia and fast transmission of continuous media on wireless networks means the simultaneous existence of traffic requiring different qualities of service (QoS). In this thesis, several efficient algorithms have been developed which offer several QoS to the end-user. We first look at a request TDMA/CDMA protocol for supporting wireless multimedia traffic, where CDMA is laid over TDMA. Then we look at a hybrid push-pull algorithm for wireless networks, and present a generalized performance analysis of the proposed protocol. Some of the QoS factors considered include customer retrial rates due to user impatience and system timeouts and different levels of priority and weights for mobile hosts. We have also looked at how customer impatience and system timeouts affect the QoS provided by several queuing and scheduling schemes such as FIFO, priority, weighted fair queuing, and the application of the stretch-optimal algorithm to scheduling

Time keeping in myriad networks : theories, solutions and applications

Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2001.Includes bibliographical references (leaves 70-72).Distributed sensor networks make extensive use of a common time reference. In this work we address the problem of time dissemination in a packet switched network when the nodes are NOT generally all connected to an accurate, external time reference source. We thoroughly analyze Network Time Protocol - version 3 and identify its oversimplified clock modeling and its neglect of network delay variance (network jitter) as the primal causes for its inaccuracy. We explicitly address frequency skew in our clock model and propose a novel Kalman filtering technique for de-noising (remove of network jitter) during the NTP time synchronization process. The parameters of the Kalman linear estimator are optimal and they are computed online from the network environment, with a well-defined procedure. Our End-to-End technique decreases NTP rms error by two orders of magnitude and is compared with a software phased lock loop and a linear programming technique, with cross traffic exhibiting long-range dependence (fractional Brownian motion cross-traffic) or no dependence at all (white Gaussian case). We conclude with applications over packet switched networks that require time synchronization, like spatial filtering (beam-forming). The suite of algorithms and applications define a new class of packet switched networks, called Myriad Networks.by Aggelos Anastasiou Bletsas.S.M

A study in grid simulation and scheduling

Grid computing is emerging as an essential tool for large scale analysis and problem solving in scientific and business domains. Whilst the idea of stealing unused processor cycles is as old as the Internet, we are still far from reaching a position where many distributed resources can be seamlessly utilised on demand. One major issue preventing this vision is deciding how to effectively manage the remote resources and how to schedule the tasks amongst these resources. This thesis describes an investigation into Grid computing, specifically the problem of Grid scheduling. This complex problem has many unique features making it particularly difficult to solve and as a result many current Grid systems employ simplistic, inefficient solutions. This work describes the development of a simulation tool, G-Sim, which can be used to test the effectiveness of potential Grid scheduling algorithms under realistic operating conditions. This tool is used to analyse the effectiveness of a simple, novel scheduling technique in numerous scenarios. The results are positive and show that it could be applied to current procedures to enhance performance and decrease the negative effect of resource failure. Finally a conversion between the Grid scheduling problem and the classic computing problem SAT is provided. Such a conversion allows for the possibility of applying sophisticated SAT solving procedures to Grid scheduling providing potentially effective solutions

Base Station controlled load balancing with handovers in Mobile WiMAX

Tämän diplomityön päätavoitteena on tutkia, kuinka kuorman tasaus voidaan suorittaa tukiaseman aloitteesta yhteysvastuun vaihdoilla mobiili WiMAX:ssa ja selvittää menetelmän potentiaalia edistää resurssien käyttöä sekä palvelun laatua koko systeemissä. Tavoitteena on myös tutkia alustavasti sitä, miten turvakaistoja voitaisiin varata ns. pelastavalle yhteysvastuun vaihdolle mobiili WiMAX:ssa, kuinka tämä vaikuttaisi kuorman tasaukseen ja kuinka nämä lähestymistavat voitaisiin yhdistää. Diplomityö sisältää koosteen IEEE 802.16e radiorajapintateknologian ja WiMAX Forum liityntäverkkoarkkitehtuurin tärkeimmistä elementeistä kuorman tasauksen ja yhteysvastuun vaihdon suhteen sekä kirjallisuuskatsauksen kuorman tasauksesta, sekä pelastavan yhteysvastuun vaihdon ja liikenteen priorisoinnista. Näiden perusteella suunniteltiin mobiili WiMAX:lle räätälöity resurssien käyttöön perustuva peruskuormantasausalgoritmi. Tämän lisäksi tehtiin muutama alustava ehdotus perusalgoritmia edistävistä menetelmistä. Näihin kuuluivat esimerkiksi kuorman tasauksen laukaisuun tarkoitetun kynnyksen automaattinen säätäminen, useiden kynnysten käyttäminen sekä resurssien varaukseen perustuva laukaisu, missä kuorman tasaus voidaan laukaista turvakaistojen suhteen. Lopuksi perusalgoritmi evaluoitiin staattisessa ympäristössä. Vaikka suoritetut simulaatiot eivät olleet laajamittaisia, perusalgoritmin parametreista ja yleisestä suorituskyvystä saatiin hyödyllistä informaatiota. Vaikka algoritmi suoriutui hyvin simuloidussa ympäristössä, aikaisemmin suunnitelluille edistäville menetelmille todettiin yleisesti ottaen selvä tarve. Tämän diplomityön pitäisi luoda hyvä pohja yhteysvastuun vaihtoon perustuvan kuorman tasauksen edelleen kehittämiselle ja evaluoinnille mobiili WiMAX:ssa. Tutkimuksen perusteella päädyttiin siihen johtopäätökseen, että kuorman tasaus yhteysvastuun vaihdolla voi olla todella tehokas tapa vapauttaa resursseja suurimmassa osassa ympäristöistä, mutta että turvakaistojen käyttöä tulisi silti harkita.The purpose of this thesis is to examine how load balancing with Base Station initiated directed handovers could be conducted in Mobile WiMAX and the potential it has to enhance Resource Utilization and QoS system wide. An additional goal of the thesis is also to conduct preliminary research on how guard bands for rescue handovers could be used in Mobile WiMAX, how this would affect load balancing and how these two approaches could be combined. The thesis includes a background study on the key system aspects of the IEEE 802.16e radio interface technology and WiMAX Forum Access Network Architecture in terms of load balancing and handovers and a literary review on load balancing, and system wide handover and traffic prioritization. Based on the gained knowledge a basic Resource Utilization based load balancing algorithm tailored for Mobile WiMAX is designed. Few preliminary enhancement proposals are also made in terms of e.g. automatic tuning of the triggering threshold, multiple threshold based triggering and Resource Reservation based triggering where load balancing can be triggered in relations to the reserved guard for rescue handovers and higher priority traffic. Finally preliminary evaluation of the basic algorithm in a static environment is conducted. Although the simulations are not extensive, beneficial information is obtained of the basic parameters of the algorithm and of the overall performance of the algorithm. Even though the basic algorithm performed well in the simulated environment, a clear need was recognized for the enhancements introduced earlier. All in all this thesis should form a very good basis for the further development and evaluation of handover based load balancing in Mobile WiMAX. Based on the study it was concluded that load balancing with directed handovers can be a very efficient way to release resources in most cases but the use of rescue handover guard bands should still be considered