Shahrudin Awang Nor

Evalvid-RASV: Shaped VBR rate adaptation stored video system

Video traffic is a variable bit rates (VBR) data source in nature and it generates highly bursty traffic. Recent implementations mostly buffer the media source in order to regenerate it in the form of constant bit rates (CBR). Consequently, it will add more delays to the system and thus unable to support the original nature of the video data. Inspired by the works of Hamdi et al. [1] and Lie and Klaue [2], we developed Evalvid-RASV. This system is working on the VBR concept (open-loop video coding), but it is “shaped” so that it will not produce uncompromised bursty traffic without additional delay. With the knowledge of video characteristics in advance, Evalvid-RASV was developed to utilize the information resulting a better algorithm. In addition, we implemented the system in Evalvid-RA environment. It is an environment which is able to perform rate adaptation to the media data source and has an integrated video performance evaluation tools, especially user-perceived video quality. Our experiments have shown that Evalvid-RASV outperforms open-loop VBR in term Peak Signal Noise Ratio (PSNR) value and acceptable delay time.

Friendliness of DCCP towards TCP over large delay link networks

The need for TCP friendly transport protocol is vital for the future Internet. With this motivation, IETF has defined a new transport protocol, DCCP, to be a friendly transport protocol when coexist with other congestion-controlled transport protocol such as TCP. DCCP is an unreliable transport protocol which is designed to be able to carry unreliable time sensitive data traffic such as audio or video streaming with built-in congestion control. Therefore, DCCP can carry streaming data same as UDP but this new transport protocol can adjust the transmission data rate according to the condition of the network. In case of congestion, the sending data rate will be slowed down for the network to function well so that other transport protocol data can have the chance to utilize the network bandwidth simultaneously. In this paper, we investigate the friendliness of DCCP towards another transport protocol TCP over large delay link networks when carrying constant bit rate data. The result showed that DCCP is TCP friendly and it can coexist with TCP harmonically over large delay link networks.

Enhancing DCCP congestion control mechanism for long delay link

Most of the multimedia applications use the User Datagram Protocol (UDP) as a transport layer protocol because it is suitable for the delivery of multimedia data over the Internet. However, the use of UDP could endanger the stability of the network because there is no congestion control applied. To a certain extent, the network can collapse if too many applications deliberately use this protocol. Subsequently, instead of using the UDP, the applications have choices to use the Datagram Congestion Control Protocol (DCCP), which has a built-in congestion control that can provide a better network. Nevertheless, the congestion control mechanism in the Congestion Control Identifier (CCID)-2 TCP-like can cause problems when delivering multimedia data over a long delay link. To alleviate the problems, such as longer time taken for achieving maximum throughput, and throughput fluctuation during a congestion avoidance phase, two approaches have been used, i.e. setting of an appropriate slow-start threshold value and adjusting congestion window during a congestion avoidance phase. “TCP-like Threshold Window (TCP-like TW)” has been developed and modeled in the Network Simulator 2 (ns-2). For a long delay link, the TCP-like TW congestion control mechanism is able to minimize the time taken to achieve the maximum throughput. It also can smooth the fluctuation of throughput after achieving the maximum throughput.

The Relationship of TFRC Congestion Control to Video Rate Control Optimization

Rate control plays an important role in delivering video traffic over the Internet due to highly bursty nature of the video data and variability of the network bandwidth. The researchers in this area are either controlling the video rate coding or optimizing the congestion control to support the video traffic transmission. As a consequence of layering principle of the network architecture, the algorithm in each layer works independently. Thus, any optimization at video coding rate does not necessarily improve the video data transmission effectively. In this paper, we investigated the above-mentioned premise. We found that TFRC works independently from the video coding rate. Consequently, any effort to optimize the video traffic Internet transmission needs to consider employing rate control schemes both at video coding rate and congestion control algorithm.

DCBRP: a deterministic chain-based routing protocol for wireless sensor networks

Background Wireless sensor networks (WSNs) are a promising area for both researchers and industry because of their various applications The sensor node expends the majority of its energy on communication with other nodes. Therefore, the routing protocol plays an important role in delivering network data while minimizing energy consumption as much as possible. The chain-based routing approach is superior to other approaches. However, chain-based routing protocols still expend substantial energy in the Chain Head (CH) node. In addition, these protocols also have the bottleneck issues.Methods A novel routing protocol which is Deterministic Chain-Based Routing Protocol (DCBRP). DCBRP consists of three mechanisms: Backbone Construction Mechanism, Chain Head Selection (CHS), and the Next Hop Connection Mechanism. The CHS mechanism is presented in detail, and it is evaluated through comparison with the CCM and TSCP using an ns-3 simulator.ResultsIt show that DCBRP outperforms both CCM and TSCP in terms of end-to-end delay by 19.3 and 65%, respectively, CH energy consumption by 18.3 and 23.0%, respectively, overall energy consumption by 23.7 and 31.4%, respectively, network lifetime by 22 and 38%, respectively, and the energy*delay metric by 44.85 and 77.54%, respectively.ConclusionDCBRP can be used in any deterministic node deployment applications, such as smart cities or smart agriculture, to reduce energy depletion and prolong the lifetimes of WSNs.

Performance Enhancement of DCCP TCP-like over Long Delay Link Networks

The performance of DCCP TCP-like degrades significantly over long delay link networks. Despite the TCP-like congestion control mechanism follows the TCP SACK, the performance is really affected by the congestion window growth algorithms as employed by Jacobson based TCP variants. In this paper, all the experiments are done using Network Simulator ns-2, and we manipulated the congestion window size drop during congestion avoidance phase to enhance the performance of DCCP TCP-like over long delay link networks. Instead of halving the current congestion window when congestion events are detected, the reduction of current congestion window drop has been shown to improve the DCCP TCP-like throughput with minimal drop packet percentage.

SVD-Based Signal Detector for Cognitive Radio Networks

This paper examines the implementation of the Singular Value Decomposition (SVD) method to detect the presence of wireless signal. The method is used to find the maximum and minimum eigenvalues. We simulated the algorithm using common digital signal in wireless communication namely rectangular pulse shape, raised cosine and root-raised cosine to test the performance of the signal detector. The SVD-based signal detector was found to be more efficient in sensing signal without knowing the properties of the transmitted signal. The execution time is acceptable compared to the favorable energy detection. The computational complexity of SVD-based detector is medium compared to the energy detector. The algorithm is suitable for blind spectrum sensing where the properties of the signal to be detected are unknown. This is also the advantage of the algorithm since any signal would interfere and subsequently affect the quality of service (QoS) of the IEEE 802.22 connection. Furthermore, the algorithm performed better in the low signal-to-noise ratio (SNR) environment.

On the Performance of TCP Pacing with DCCP

Packet pacing in TCP has been introduced as one of the solutions to alleviate bursty traffic in TCP. In this paper, we investigate the performance of paced and standard (unpaced) TCP when coexist with DCCP over short and long delay link networks. We found that paced TCP for the entire TCP connection performs better in long delay link, with smoother throughput and better jitter, whereas in short delay link, there is not much positive effect of using pacing for TCP. The existence of DCCP together with TCP flows does not much affect the performance of paced TCP. However, the performance of paced TCP is slightly better when coexisting with DCCP TCP-like and DCCP TFRC in comparison to standard TCP. Based on the result, it can be used as a fundamental in implementing packet pacing in DCCP TCP-like.

The effect of initial slow-start threshold size in DCCP over large delay link networks

As an alternative to UDP, DCCP is gaining popularity as a new transport protocol for sending streaming multimedia contents in the Internet nowadays. DCCP is a new unreliable transport protocol which has built-in congestion control unlike UDP. With this feature, DCCP ensures that there is no bandwidth monopoly by certain transport protocol like UDP did for years. UDP has been proven that can eat up all the available bandwidth in the Internet while competing with other transport protocols such as TCP in carrying streaming audio and multimedia traffic in many situations. In this paper, we show that initial slow-start threshold (ssthresh) size has a significant effect to the performance of DCCP carrying VoIP traffic over large delay link. Slow-start threshold is used by congestion control implemented in DCCPs TCP-like congestion control (CCID2) where all TCP congestion control implementations are required to support it. From our experiments, we found out that too small initial slow-start threshold value for large delay link makes the traffic throughput sent using DCCP requires longer time to become stable. The selection of suitable value of initial slow-start threshold is then vital to the stability of the network carrying streaming audio data over DCCP.

Scheduling Jobs through Gap Filling and Optimization Techniques in Computational Grid

Due to the heterogeneity and complexity in grid computing, classical algorithms may not be able to deal with dynamic jobs properly. In the dynamic mode, incoming jobs reach the scheduler arbitrary. Therefore, scheduling the jobs using simple policy alone deteriorates the performance of the scheduler. Thus, a policy that can handle the dynamicity efficiently is indispensable. This paper presents the Swift Gap mechanism (SG), which is a hybridization of the Best Gap mechanism, alongside with Tabu search (BGT). In addition, a new decision rule based on completion time is included into the outcome mechanism. The new decision rule based on completion time has shown a significant improvement in the Quality of Service (QoS), especially for a slowdown, tardiness, waiting time and response time. Moreover, an evaluation of the new proposed mechanism Swift Gap is provided. From the evaluation, Swift Gap outperforms BGT, Conservative Backfilling (CONS) and Extensible Argonne Scheduling System (EASY).