On the Scaling of Feedback Algorithms for Very Large Multicast Groups

Feedback from multicast group members is vital for many multicast protocols. In order to avoid feedback implosion in very large groups feedback algorithms with well behaved scaling-properties must be chosen. In this paper we analyse the performance of three typical feedback algorithms described in the literature. Apart from the basic trade-off between feedback latency and response duplicates we especially focus on the algorithms' sensitivity to the quality of the group size estimation. Based on this analysis we give recommendations for the choice of well behaved feedback algorithms that are suitable for very large groups

Transporte de datos multicast confiable con control de congestión dinámico

La naturaleza de la transmisión multicast hace que sea un mecanismo no orientado a conexión, por lo que la mayoría de los protocolos multicast se desarrollan sobre la capa de transporte UDP y sobre este es necesario construir un esquema de confiabilidad. Para aplicaciones de “streaming” de audio o vídeo, la pérdida ocasional de un segmento es aceptable, pero al transmitir datos críticos (archivos, programas, etc.) es necesario un mecanismo que garantice confiabilidad. Por lo tanto se presenta en esta publicaci´on una propuesta de transmisión multicast confiable con control de congestión, como alternativa a los mecanismos disponibles en la actualidad.XI Workshop Arquitectura, Redes y Sistemas Operativos (WARSO).Red de Universidades con Carreras en Informática (RedUNCI

Transporte de datos multicast confiable con control de congestión dinámico

La naturaleza de la transmisión multicast hace que sea un mecanismo no orientado a conexión, por lo que la mayoría de los protocolos multicast se desarrollan sobre la capa de transporte UDP y sobre este es necesario construir un esquema de confiabilidad. Para aplicaciones de “streaming” de audio o vídeo, la pérdida ocasional de un segmento es aceptable, pero al transmitir datos críticos (archivos, programas, etc.) es necesario un mecanismo que garantice confiabilidad. Por lo tanto se presenta en esta publicaci´on una propuesta de transmisión multicast confiable con control de congestión, como alternativa a los mecanismos disponibles en la actualidad.XI Workshop Arquitectura, Redes y Sistemas Operativos (WARSO).Red de Universidades con Carreras en Informática (RedUNCI

Transporte de datos multicast confiable con control de congestión dinámico

La naturaleza de la transmisión multicast hace que sea un mecanismo no orientado a conexión, por lo que la mayoría de los protocolos multicast se desarrollan sobre la capa de transporte UDP y sobre este es necesario construir un esquema de confiabilidad. Para aplicaciones de “streaming” de audio o vídeo, la pérdida ocasional de un segmento es aceptable, pero al transmitir datos críticos (archivos, programas, etc.) es necesario un mecanismo que garantice confiabilidad. Por lo tanto se presenta en esta publicaci´on una propuesta de transmisión multicast confiable con control de congestión, como alternativa a los mecanismos disponibles en la actualidad.XI Workshop Arquitectura, Redes y Sistemas Operativos (WARSO).Red de Universidades con Carreras en Informática (RedUNCI

A constrained steiner tree approach for reconstructions of multicast trees.

Sun Tong.Thesis (M.Phil.)--Chinese University of Hong Kong, 2004.Includes bibliographical references (leaves 77-81).Abstracts in English and Chinese.Chinese Abstract --- p.IAbstract --- p.IIAcknowledgements --- p.IIIList of Contents --- p.IVList of Figures --- p.VIIChapter Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Multicast Routing Problem --- p.1Chapter 1.2 --- Constrained multicast routing problem and SSRA algorithm --- p.4Chapter 1.3 --- Thesis organization --- p.7Chapter Chapter 2 --- Constrained Multicast Routing Algorithms --- p.8Chapter 2.1 --- Steiner tree heuristic --- p.8Chapter 2.1.1 --- Shortest Paths Heuristic --- p.9Chapter 2.1.2 --- Distance Network Heuristic --- p.10Chapter 2.2 --- Review of existing constrained multicast routing algorithms --- p.10Chapter 2.2.1 --- Static group member --- p.10Chapter 2.2.2 --- Dynamic group member --- p.14Chapter 2.2.2.1 --- Non-rearrangeable --- p.15Chapter 2.2.2.2 --- Rearrangeable --- p.23Chapter Chapter 3 --- Small Scale Rearrangement Algorithm for Multicast Routing --- p.32Chapter 3.1 --- Problem formulation --- p.32Chapter 3.1.1 --- Network Model --- p.32Chapter 3.1.2 --- Problem Specification --- p.33Chapter 3.1.3 --- Definitions and Notations --- p.36Chapter 3.2 --- Local Checking Scheme (LCS) --- p.37Chapter 3.3 --- Small Scale Rearrangement Algorithm (SSRA) for Multicast Routing --- p.41Chapter 3.3.1 --- Static group membership --- p.42Chapter 3.3.2 --- Dynamic group membership --- p.43Chapter 3.3.2.1 --- Node addition --- p.44Chapter 3.3.2.2 --- Node removal --- p.44Chapter 3.3.2.3 --- General steps --- p.45Chapter 3.3.2.4 --- Example --- p.47Chapter Chapter 4 --- Analysis --- p.50Chapter Chapter 5 --- Simulations --- p.54Chapter 5.1 --- Simulation Model --- p.54Chapter 5.2 --- Simulation Parameters Parameter Default Value/Generating Method --- p.56Chapter 5.3 --- Performance Metrics --- p.58Chapter 5.4 --- Discussion of Results --- p.59Chapter 5.4.1 --- Group 1: static group membership --- p.59Chapter 5.4.2 --- Group 2: dynamic group membership --- p.63Chapter 5.4.3 --- Comparison --- p.69Chapter 5.5 --- Implementation Issue --- p.73Chapter Chapter 6 --- Conclusion --- p.75Reference --- p.7

The application of forward error correction techniques in wireless ATM

Bibliography: pages 116-121.The possibility of providing wireless access to an ATM network promises nomadic users a communication tool of unparalleled power and flexibility. Unfortunately, the physical realization of a wireless A TM system is fraught with technical difficulties, not the least of which is the problem of supporting a traditional ATM protocol over a non-benign wireless link. The objective of this thesis, titled "The Application of Forward Error Correction Techniques in Wireless ATM' is to examine the feasibility of using forward error correction techniques to improve the perceived channel characteristics to the extent that the channel becomes transparent to the higher layers and allows the use of an unmodified A TM protocol over the channel. In the course of the investigation that this dissertation describes, three possible error control strategies were suggested for implementation in a generic wireless channel. These schemes used a combination of forward error correction coding schemes, automatic repeat request schemes and interleavers to combat the impact of bit errors on the performance of the link. The following error control strategies were considered : 1. A stand alone fixed rate Reed-Solomon encoder/decoder with automatic repeat request. 2. A concatenated Reed-Solomon, convolution encoder/decoder with automatic request and convolution interleaving for the convolution codec. 3. A dynamic rate encoder/decoder using either a concatenated Reed-Solomon, convolution scheme or a Reed-Solomon only scheme with variable length Reed-Solomon words

Improving Multicast Communications Over Wireless Mesh Networks

In wireless mesh networks (WMNs) the traditional approach to shortest path tree based multicasting is to cater for the needs of the poorest performingnode i.e. the maximum permitted multicast line rate is limited to the lowest line rate used by the individual Child nodes on a branch. In general, this meansfixing the line rate to its minimum value and fixing the transmit power to its maximum permitted value. This simplistic approach of applying a single multicast rate for all nodes in the multicast group results in a sub-optimal trade-off between the mean network throughput and coverage area that does not allow for high bandwidth multimedia applications to be supported. By relaxing this constraint and allowing multiple line rates to be used, the mean network throughput can be improved. This thesis presents two methods that aim to increase the mean network throughput through the use of multiple line rates by the forwarding nodes. This is achieved by identifying the Child nodes responsible for reducing the multicast group rate. The first method identifies specific locations for the placement of relay nodes which allows for higher multicast branch line rates to be used. The second method uses a power control algorithm to tune the transmit power to allow for higher multicast branch line rates. The use of power control also helps to reduce the interference caused to neighbouring nodes.Through extensive computer simulation it can be shown that these two methods can lead to a four-fold gain in the mean network throughput undertypical WMN operating conditions compared with the single line rate case

Service-based Requirements for Future Mobile Networks

The mobile phone has, as a device, taken the world by storm in the past decade; from only 136 million phones globally in 1996, it is now estimated that by the end of 2008 roughly half of the worlds population will own a mobile phone. Over the years, the capabilities of the phones as well as the networks have increased tremendously, reaching the point where the devices are better called miniature computers rather than simply mobile phones. The mobile industry is currently undertaking several initiatives of developing new generations of mobile network technologies; technologies that to a large extent focus at offering ever-increasing data rates. This thesis seeks to answer the question of whether the future mobile networks in development and the future mobile services are in sync; taking a forward-looking timeframe of five to eight years into the future, will there be services that will need the high-performance new networks being planned? The question is seen to be especially pertinent in light of slower-than-expected takeoff of 3G data services. Current and future mobile services are analyzed from two viewpoints; first, looking at the gradual, evolutionary development of the services and second, through seeking to identify potential revolutionary new mobile services. With information on both current and future mobile networks as well as services, a network capability - service requirements mapping is performed to identify which services will work in which networks. Based on the analysis, it is far from certain whether the new mobile networks, especially those planned for deployment after HSPA, will be needed as soon as they are being currently roadmapped. The true service-based demand for the 'beyond HSPA' technologies may be many years into the future - or, indeed, may never materialize thanks to the increasing deployment of local area wireless broadband technologies

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