Empirical evaluation of designing multicasting network with minimum delay variation

Computer supported collaborative applications on overlay networks are gaining popularity among users who are geographically dispersed. Examples of these kinds of applications include video-conferencing, distributed database replication, and online games. This type of application requires a multicasting subnetwork, using which messages should arrive at the destinations within a specified delay bound. These applications also require that destinations receive the message from the source at approximately the same time. The problem of finding a multicasting subnetwork with delay and delay-variation bound has been proved to be an NP complete problem in the literature and heuristics have been proposed for this problem. In this paper, we provide an efficient heuristic to obtain a multicast subnetwork on an overlay network, given a source and a set of destinations that is within a specified maximum delay and a specified maximum variation in the delays from a source to the destinations. The time-complexity of our algorithm is O(|E|+nk log(|E|/n)+m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> k), where n and |E| are the number of nodes and edges in the network, respectively, k is the number of shortest paths determined, and m is the number of destinations. We have shown that our algorithm is significantly better in terms of time-complexity than existing algorithms for the same problem. Our extensive empirical studies indicate that our heuristic uses significantly less runtime in comparison with the best-known heuristics while achieving the tightest delay variation for a given end-to-end delay bound

We consider the scheduling problem in a new slotted optical network called TWIN. The TWIN architecture possesses interesting properties, which may offer solutions for next-generation optical networks. Besides, TWIN has the ability to support quality of service (QoS) by controlling two important parameters: queueing delay and delay variance. However, to the best of our knowledge, the existing scheduling algorithms in TWIN focused mainly on maximizing the throughput and ignored the consideration of QoS. We formulate the scheduling problem into an integer linear programming problem and propose a heuristic--virtual topology-based dynamic scheduling (VTBDS) algorithm to solve it fast and efficiently. Besides, we derive an analytical model for TWIN and investigate the performance of VTBDS in it. By means of simulations, we demonstrate that our model approximates the TWIN network very well, and VTBDS incurs smaller queueing delay and delay variance, which are advantageous for guaranteeing better QoS.

A scheme for enhancing sensor network lifetime is proposed using multiple mobile CHs. The CHs controllably move toward the energy-rich sensors maintaining remaining energy more evenly, eliminating multihop transmission. Collaboration among CHs is considered to maintain their continuous connectivity to the base station (BS) to reduce the delay in communication. Network lifetime is increased by 75% by making CHs always move towards a stable equilibrium point whereas connectivity algorithm provides 40% improvement in transmission delays over existing schemes.

Quality of service (QoS) provisioning generally assumes more than one QoS measure which implies that QoS routing can be categorized as an instance of routing subject to multiple constraints: delay-jitter, bandwidth, cost, etc. We study the problem of constructing multicast trees to meet the QoS requirements of real-time interactive applications where it is necessary to provide bounded delays and bounded delay variation among the source and all destinations while keeping overall cost of the multicast tree low. The main contribution of our work is a new strategy for constructing multiconstrained multicast trees. We first derive mathematically a new Delay-Variation Estimation Scheme and prove its efficiency. Thereafter, we propose a simple and competitive (in terms of system running time) heuristic algorithm, for delay and delay variation constrained routing problem based on the proposed delay-variation estimation scheme and using the Extended Prim-Dijkstra tradeoffs' algorithm. Besides, our algorithm uses cost information only from neighboring nodes as it proceeds which makes it more practical from an implementation point of view. Our contribution also extends previous works in providing some properties and analyses of delay bounded paths satisfying delay variation constraints.

This paper studies an important problem in the IEEE 802.11 distributed coordination function (DCF)-based wireless local area network (WLAN): how well can the network support quality of service (QoS). Specifically, this paper analyzes the network's performance in terms of maximum protocol capacity or throughput, delay, and packet loss rate. Although the performance of the 802.11 protocol, such as throughput or delay, has been extensively studied in the saturated case, it is demonstrated that maximum protocol capacity can only be achieved in the nonsaturated case and is almost independent of the number of active nodes. By analyzing packet delay, consisting of medium access control (MAC) service time and waiting time, accurate estimates were derived for delay and delay variation when the throughput increases from zero to the maximum value. Packet loss rate is also given for the nonsaturated case. Furthermore, it is shown that the channel busyness ratio provides precise and robust information about the current network status, which can be utilized to facilitate QoS provisioning. The authors have conducted a comprehensive simulation study to verify their analytical results and to tune the 802.11 to work at the optimal point with maximum throughput and low delay and packet loss rate. The simulation results show that by controlling the total traffic rate, the original 802.11 protocol can support strict QoS requirements, such as those required by voice over Internet protocol (VoIP) or streaming video, and at the same time achieve high channel utilization.

To deyelop the broadband integrated services digital network (B‐ISDN) service on a national scale and to handle various media in a unified way economically from ‐ an early stage, it will be effective to construct a system combining the satellite link into the terrestrial communication network. the TDMA system is adequate as the transmission system in the satellite link in such a system which can contain efficiently users distributed over a country.When the satellite TDMA link, which is a synchronous system, and the terrestrial network, based on the asynchronous transfer mode (ATM), are to be connected, the deterioration of the ATM transmission quality such as the cell delay variation, is a serious problem. Then there must be a compensation method for the delay variation which can cope with the asynchronous transfer. In such a transformation between ATM and TDMA, it is required that the maximum delay variation should be kept below the specified value, the burstiness of the transferred cell sequence should not be increased, and the satellite link with limited network resources should efficiently be utilized.This paper assumes that the time‐stamp method, which is considered in the ground network, is applied to the satellite link as a method for the delay variation 38 compensation and summarizes the problems in the application. Then the cell‐numbering method is proposed and the performance is evaluated to solve the problems.

Objective: To increase the resource utilization and balance the load in the grid environment. Methods: Memory Constrained Load Shared Minimum Execution Time (MCLSMET) scheduling is proposed to make best use of the resource utilization in a grid environment to reduce makespan. Load balancing is achieved by rescheduling the resources based on memory requirement and execution time of the tasks. This algorithm considers memory as Quality of Service (QoS) factor. Results: The proposed algorithm has been implemented in a simulated environment and the results are compared with the Minimum Execution Time (MET) algorithms. In MCLSMET algorithm, the Maximum Completion Time, Resource Utilization is computed to compare with the existing MET scheduling Algorithm. The MET scheduling algorithm produces the makespan 34 ms whereas the proposed method reduces the makespan to 15 ms for a task. In the existing MET scheduling Algorithm produces severe load imbalance problem. In the proposed method load is shared among the available resource and the resource utilization percentage is increased. Conclusion: The Memory Constrained Load Shared Minimum Execution Time (MCLSMET) scheduling algorithm is suggested that this algorithm produces higher resource utilization, reduces the makespan and load balancing.

Analysis of descriptive epidemiological characteristics of pancreatic cancer in Vojvodina, Serbia. The study covers population of Vojvodina in the period from 2000 to 2009. The method used for data processing was the descriptive. The data, referring to a specified period of time, were analyzed from chronological and demographic aspects and according to histological diagnosis. In the period from 2000 to 2009, there were 2,108 registered cases of pancreatic cancer of which 1,886 had a fatal outcome. Standardized incidence rates varied between 5.7 and 9.1 per 100,000 population in males and between 4.2 and 5.3 in females. Linear incidence trends in males in the specified period of time, based on crude (r=0.7883, p<0.05) and standardized (r=0,6373, p<0,05) incidence rates, demonstrated increase. Annual percent increase in the crude incidence rate was 4.5% in males, and 2.8% in females. Age-standardized mortality rates varied between 5.2 and 7.5 per 100,000 population in males and 3.6 and 4.7 in females. Linear mortality trends in males in the specified period of time, based on crude (r=0.8795, p<0.05) and standardized (r=0.7669, p<0.05) mortality rates, also demonstrated annual percent increase. Data analysis shows unfavorable onco-epidemiological situation related to pancreatic cancer in Vojvodina, in aspects of both incidence and mortality. Absence of primary and secondary prevention does not allow medical institutions to successfully fight against this disease.

This paper presents a synchronization model that implements the presentation of multimedia objects as well as a synchronization scheme that improves media data latency and quality of service (QoS) in mobile environments. The proposed model meets synchronization requirements among multimedia data because it employs an approach to not only adjusting synchronization intervals using the maximum available delay variation or jitter at the base station (BS) but also flexibly dealing with variable latencies due to variations in delay time.

Klout, a famous App, could measure people's social network influence power. Klout score is measured according to the data from past 90 days and an individual who has high Klout score is thought as having high social influence power. Lots of businesses or organizations like to hire high Klout score people to help them to diffuse their brand images. However, Klout score cannot tell us who has high influence power in a specific short time period. For example, it is possible that some of the users might always have high influence power on Monday or on Monday morning. These time-dependent influential users probably have low Klout scores in average but have high influence power in some specific time periods. Businesses should not just know who are the high Klout score users but also they should identify who are the time-dependent influential users because all of them may have some sort of power to influence other users' buying decisions. In this study, a framework based on frequent pattern mining is proposed to find the time-dependent influential users. First of all, the framework will divide a predefined long time period into successive short time segments and then influential transactions that contain Facebook fans' influence power data will be defined in each time segment. From the frequent patterns, the proper time for time-dependent influence users to spread information can be found. A theoretical experiment is given to verify the effectiveness of the proposed framework.

This paper addresses the problem of efficient multicast communication in wavelength-division multiplexed optical networks. In particular, we consider all-optical networks in which each transmitting node may deliver its message to some fixed number of destination nodes on a light path. The number of destination nodes that may receive the message using a single path depends on the power budget of the transmitting node. We study the wavelength requirements for multicast communication under this model.

Real-time applications such as VoIP, video-conference or online games are delay-sensitive multimedia applications and require relatively small delay and small delay variation. Recently, IEEE 802.11 WLANs have reached an important stage and have become a common technology for wireless access due to its low cost, ease of deployment and mobility support. Its new standard, EDCA, has the ability to accommodate real-time traffic and provide relatively small delay. However, it cannot achieve small delay variation due to the burst feature of its backoff mechanism after a collision or a frame error. Since the real-time services such as Voice over IP (VoIP) has a delay constraint to guarantee a QoS, a fast retransmission scheme for corrupted frames is required. In this paper, we propose a new fast retransmission mechanism for VoIP frames to reduce the delay and delay variation. Then, we integrate our scheme with an Adaptive Jitter Buffer (AJB) algorithm to optimize end-to-end QoS performance. Simulation results indicate that proposed fast retransmission scheme reduces not only delay, delay variation and dropping probability of frames, but it also helps the AJB to support QoS maintaining voice quality at high level on EDCA-based WLANs.

Voice over IP (VoIP) is nowadays a common component of multimedia converged networks. In this paper, Quality of Service (QoS) analysis of VoIP traffic is presented in a multimedia network having other types of network traffic also deployed i.e. video, database and web. In such traffic occupied network, VoIP is configured with different codecs and frame counts per packet to observe the effect of these variations on the QoS of VoIP in terms of queuing delay, jitter, packet end-to-end delay and packet delay variation (end-to-end jitter) metrics. The significance of this paper is the emphasis on QoS evaluations in a VoIP deployment while observing the effects of variations in voice codecs and packet lengths. Many previous research papers focus on the perceived speech quality and packet losses; whereas queuing delays and end-to-end latency are usually not considered when analysis is done for different codecs and packet lengths at a time. We consider three main voice codecs (G.711, G.729 and G.723.1) and three frame counts per packet values (10, 25 and 50 voice frames per packet) under each codec. The simulation results show that G.723.1 voice encoding experiences higher queuing delays and queue delay variations (jitter) for higher numbers of frames per packet. However, the least packet end-to-end delay is observed in voice packets encoded with G.729 codec for all configured values of frames per packet.

This paper describes and evaluates experimentally two versions of Si3N4 photonic integrated devices based on optical ring resonators (ORRs) and multi-core fiber (MCF) that enable radio beamsteering for operating 5G and beyond in the K-band. The RF beamsteerer depends on the optical delay induced by the ORRs that can be modified by heater tuning (slow switching) or by wavelength shift (fast switching). The first version of the beamforming chip permits multi-wavelength operation by keeping the heaters’ configuration and changing the wavelength. The second version of the chip includes independent dual-wavelength operation with dedicated heaters’ configurations for each wavelength. The experimental evaluations are performed for both short-reach and long-reach applications with the transmission of the photonic TTD over 150-m of 4-core MCF and over 1-km of 7-core MCF for the first and second version of the chip, respectively. In addition, the stability and delay variation were measured experimentally over 1-hour run time for different heater configurations. A maximum delay variation of 4 ps was measured, which translates to a 9° steering angle resolution at 19 GHz RF. The impact of the delay variation applied to one of the antenna elements in the resulting beam steering is analyzed in more detail in this work, confirming the suitability of the proposed technique.

Recently, the high-performance computing community has realized that power is a performance-limiting factor. One reason for this is that supercomputing centers have limited power capacity and machines are starting to hit that limit. In addition, the cost of energy has become increasingly significant, and the heat produced by higher-energy components tends to reduce their reliability. One way to reduce power (and therefore energy) requirements is to use high-performance cluster nodes that are frequency- and voltage-scalable (e.g., AMD-64 processors).The problem we address in this paper is: given a target program, a power-scalable cluster, and an upper limit for energy consumption, choose a schedule (number of nodes and CPU frequency) that simultaneously (1) satisfies an external upper limit for energy consumption and (2) minimizes execution time. There are too many schedules for an exhaustive search. Therefore, we find a schedule through a novel combination of performance modeling, performance prediction, and program execution. Using our technique, we are able to find a near-optimal schedule for all of our benchmarks in just a handful of partial program executions.