Papers by Dr.mohammed Ghanbari
... 5. SCALABLE POLYGONAL APPROXIMATION ENCODING For the coarser polygonal approximation encoding... more ... 5. SCALABLE POLYGONAL APPROXIMATION ENCODING For the coarser polygonal approximation encoding DPCM coding of the vertices is used. The difference between the vertices co-ordinates, AB and Az are encoded using an arithmetic encoder [9]. I - 166 Page 3. ...
The intrinsic scalability limitations of traditional centralised Network Management (NM) become s... more The intrinsic scalability limitations of traditional centralised Network Management (NM) become significantly more pronounced when transfers of bulk network monitoring data are considered. This fact has encouraged a trend towards distributed management intelligence, which promises more flexible and scalable solutions. However, distributed Mobile Agent (MA) based NM architectures reported in the literature do not adequately address scalability problems when considering data intensive NM applications. In this paper, we present three novel applications in which MAs are used to perform management data aggregation, acquire SNMP table snapshots and filter SNMP table contents subject to filtering expressions. Both real-time and off-line NM data acquisition is considered. The applications, supported by a lightweight management framework described in previous work, are shown to outperform SNMP-based polling in terms of bandwidth consumption.
Existing congestion controllers have been designed with TCP traffic in mind. Changing traffic pat... more Existing congestion controllers have been designed with TCP traffic in mind. Changing traffic patterns on the Internet imply that on some tight links all UDP video streams will occur. Three different congestion controllers (RAP, TFRC, and fuzzy-logic based), already successful in avoiding instability in current TCPdominated internets, were tested across a tight link in which video traffic dominated. Congestion control is either achieved by modulating the sending rate in response to feedback of packet loss rates and/or round-trip delays (RAP/TFRC) or a congestion level based on packet dispersion across a network path (fuzzy controller). The controllers were found to differ in the smoothness of resulting video clip streams, with the fuzzy and TFRC controllers, in that order, producing the smoothest received video. Tests also demonstrated that, when controlled flows of different types compete across a tight link, it is possible for the sending rate of TFRC to exceed the available bandwidth, resulting in excess packet loss and implying quite poor video quality at the receiver. The results show that fuzzy-logic control is more flexible when video streams dominate.
Intelligent Environments (Workshops), 2011
It has become standard practice to use the traditional information technologies such as web and e... more It has become standard practice to use the traditional information technologies such as web and email in education. But as the University campus becomes increasingly deployed with interconnected computing technology, we begin to ask how the resulting "iCampus" resource can be used in new and novel ways. This paper builds upon our previous work in the area of intelligent environments and goes beyond the typical use of computing technology within education. We report on our current research that aims to apply mixed reality and ubiquitous computing paradigms to enrich the teaching and learning experience and describe our deployments and innovations across the University of Essex campus.
International journal of networks and communications, Mar 1, 2014
Currently, data communication during heavy traffic transmission on the network suffers from node ... more Currently, data communication during heavy traffic transmission on the network suffers from node failures. A failure in the network is required to be restored by the routing protocols in the networks. Traditional routing protocols schemes normally compute a routing table which contains all paths between all nodes on the network. Hence, the data packets will be passed via the single shortest path which is the best path between each source and destination. In this paper, a pre-computed alternate path is introduced to assist the congested networks to continue passing the data packets from its source to the final destination once failure occurs. The proposed alternative routing table (ART) algorithm aims to re-route the traffic through a backup route when the primary path has failed. We have evaluated the performance of the proposed scheme with OSPF routing protocol through NS2 simulator. The results show that packet losses, rerouting and end to end delay times of the proposed methods are substantially improved.
IET Communications, 2019
Vehicular ad-hoc networks (VANETs) despite their potential benefits, especially for intelligent t... more Vehicular ad-hoc networks (VANETs) despite their potential benefits, especially for intelligent transportation and safety systems face some important challenges. The main challenges are caused by high mobility of vehicles and dynamic environment. In addition, VANET channel is wireless and is extremely error prone. To overcome these problems, several routing strategies have been proposed in order to find paths with high reliability and low delay. One of these strategies is the opportunistic routing (OR) paradigm where its performance can be significantly affected by the method applied for prioritised transmission to the nodes within the relays set. The OR protocol proposed in this study is based on the Dempster-Shafer evidence theory. In this method, the source vehicle employs the packet advancement, vehicle density, and packet delivery probability as parameters for determining the appropriate vehicle as to the next hop. The number of vehicles participating in forwarding the packets is optimised using trust-based calculations. In addition, the source vehicle can schedule a set of relay nodes based on their degree of trust. Highway environment simulations suggest that compared to other published methods in the literature, the proposed method can improve routing performance in terms of all quality-of-service metrics.
Real time multimedia application is a challenging issue in the mobile networks, due to high compr... more Real time multimedia application is a challenging issue in the mobile networks, due to high compression requirements and limited and varying channel bandwidth. H.264/AVC addresses these issues with its excellent coding efficiency, error resiliency features and provision of bit rate adaptivity, using switching (SP-) frames. To reduce the quantization errors due to multiple quantization, SP-frames are usually coded with finer quantization parameters (QP) than the rest of the sequence, resulting in an increased bit rate, sometimes exceeding to that of intra (I-) frames. This limits the basic advantages of SP-frames over I-frames and that is better coding efficiency, leading to poor utilization of the resources like bandwidth. Thus the question is "what is the safe range of QP such that the bit rate of the switching frames does not exceed that of the I-frames"? The aim of this paper to suggest a solution to this problem by analyzing characteristics of SP-frames and to suggest a safe range of QP for switching frames ensuring that its bit rate remains lower than that of I-frames.
Recent patents on telecommunications, Jun 1, 2012
Recent Patents on Signal Processing, Dec 21, 2011
Router buffer overflow and random bit errors have always been a problem in the Internet. The grow... more Router buffer overflow and random bit errors have always been a problem in the Internet. The growth in multimedia applications in mobile extensions of the Internet has increased the threat from error bursts, random errors, and packet erasures that are a manifestation of wireless channels. Source-coded error resilience has come to prominence in the H.264/AVC codec standard, and this paper reviews such innovations surrounding this codec. Some innovations are new variants of an existing technique such as datapartitioning and some are entirely new such as the powerful dispersed-mode flexible macroblock ordering. Other techniques, such as reversible variable length coding, were not be transferred to H.264 from earlier codecs and, hence, innovations are proposed to still provide robust entropy coding. Other variants such as adaptive intra-refresh are still being experimented with. When error resilience or other protection methods fail to present an adequate video frame then error concealment can be brought to bear. This paper reviews error concealment which is important to commercial companies as they are able to distinguish their codec from others. The paper considers spatial, temporal and hybrid error concealment methods. Though this paper contains over one hundred references it can only provide a slice through this rich field.
Recent Patents on Signal Processing, Nov 24, 2014
Intra-coding is the application of spatial prediction coding to video data either on a whole fram... more Intra-coding is the application of spatial prediction coding to video data either on a whole frame basis or on individual macroblocks. This paper outlines the growing sophistication in intra-coding within recent standard codecs, the topic which is primarily relevant to compression for data storage. It then specializes to intra-coding for error resilience and intra-refresh, the topic which is relevant to video streaming applications. Efficient intra coding is becoming important for real-time high-resolution video, due to the computational cost of inter-coding, as the paper will consider for recent codecs. The paper will compare error-resilience performance across a variety of schemes. There are choices, which the paper analyses, as to whether to protect: on a whole frame basis; by intra-coding selected macro-blocks; and whether to use an isolated region; a cyclic intra-refresh line; or randomized insertion of macroblocks. The paper contains over 100 references, including recent patents in this field.
Mobile, broadband wireless access is increasingly being used for video streaming. This paper is a... more Mobile, broadband wireless access is increasingly being used for video streaming. This paper is a study of the impact of intra-refresh provision upon a robust video streaming scheme intended for WiMAX. The paper demonstrates the use of intrarefresh macroblocks within inter-coded video frames as an alternative to periodic intra-refresh video frames. In fact, the proposed scheme combines intra-refresh macroblocks with data-partitioned video compression, both error resilience tools from the H.264 video codec. Redundant video packets along with adaptive channel coding are also used to protect video streams. In harsh wireless channel conditions, it is found that all the proposed measures are necessary. This is because error bursts, arising from both slow and fast fading, as well as other channel impairments, are possible. The main conclusions from a detailed analysis are that: because of the effect on packet size it is important to select a moderate quantization parameter; and because of the higher overhead from cyclic intra macroblock line update it is better to select a low percentage per frame of intra-refresh macroblocks. The proposed video streaming scheme will be applicable to other 4G wireless technologies such as LTE.
Advances in multimedia and interactive technologies book series, 2012
Mobile WiMAX is suitable for video-on-demand as well as broadcast TV services. Delivery of video ... more Mobile WiMAX is suitable for video-on-demand as well as broadcast TV services. Delivery of video streams over an IP packet-switched network, which includes broadband wireless access, requires rate or congestion control along with methods to protect the compressed stream from the impact of channel conditions. The Chapter considers possible solutions for both these requirements: multi-connection streaming overcomes the risk of poor channel utilization when restraining rates due to detected packet loss, while data-partitioning is a form of error resilience which includes the possible of graceful quality degradation. In the Chapter, ratelesschannel coding is adaptively employed along with error control. The Chapter also surveys the WiMAX option, acknowledging demerits as well as merits of this technology, and considering what other investigations have taken place to deliver multimedia services over broadband wireless.
Advances in multimedia and interactive technologies book series, 2012
This Chapter proposes the concept of resilient multi-source streaming using a peer-to-peer overla... more This Chapter proposes the concept of resilient multi-source streaming using a peer-to-peer overlay network over an urban vehicular ad-hoc network. Peer-to-peer overlay networks with multiple sources have proven to be robust, distributed solutions to multimedia transport, including streaming. To achieve video streaming over a vehicular ad-hoc network overlay, the Chapter introduces spatial partitioning of a video stream based on flexible macroblock ordering. Flexible macroblock ordering is an error resilient feature of an H.264 video codec in which macroblocks can be assigned to slices in non-raster scan order. Furthermore, the Chapter examines the impact of differing traffic densities and road layouts upon a peer-to-peer overlay network's performance when streaming video. The research demonstrates that the vehicles' mobility pattern and their drivers' behaviors need to be carefully modeled to determine signal reception. The Chapter also considers the impact of the wireless channel, which also should be more realistically modeled, compared to the usual two-ray path loss model.
International Journal of Handheld Computing Research, Jul 1, 2013
IPTV video services are increasingly being considered for delivery to mobile devices over broadba... more IPTV video services are increasingly being considered for delivery to mobile devices over broadband wireless access networks. The IPTV streams or channels are multiplexed together for transport across an IP core network prior to distribution across the access network. According to the type of access network, prior bandwidth constraints exist that restrict the multiplex data-rate. This paper presents a bandwidth allocation scheme based on content complexity to equalize the overall video quality of the IPTV sub-streams, in effect a form of statistical multiplexing. Bandwidth adaptation is achieved through a bank of bit-rate transcoders. Complexity metrics serve to estimate the appropriate bandwidth share for each stream, prior to distribution over a wireless or ADSL access network. These metrics are derived after entropy decoding of the input compressed bit-streams, without the delay resulting from a full decode. Fuzzy-logic control serves to adjust the balance between spatial and temporal coding complexity. The paper examines constant and varying bandwidth scenarios. Experimental results show a significant overall gain in video quality in comparison to a fixed bandwidth allocation.
International Conference on Systems, Signals and Image Processing, Jun 16, 2011
The proposed scheme in this paper combines adaptive channel coding with additional duplicate pack... more The proposed scheme in this paper combines adaptive channel coding with additional duplicate packets. Adaptive channel coding takes place by: varying the amount of redundancy according to channel conditions; and by retransmission of extra redundant data to reconstruct corrupted packets. In video streaming, greater bandwidth efficiency occurs by transmitting the same video quality at a reduced bitrate. This paper shows that the proposed protection scheme for data- partitioned video achieves that objective when streaming over an IEEE 802.16e (mobile WiMAX) channel.
Advances in multimedia and interactive technologies book series, May 24, 2011
Abstract-Este articulo presenta un estudio comparativo de tres simuladores híbridos de red: Model... more Abstract-Este articulo presenta un estudio comparativo de tres simuladores híbridos de red: Modeler de OPNET y Ns-2, así como NCTUns. Se comparan los resultados obtenidos desde una red de prueba real con una metodología de análisis a nivel paquete. Utilizando una ...
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Papers by Dr.mohammed Ghanbari