Current Issue : October - December Volume : 2014 Issue Number : 4 Articles : 6 Articles
Nowadays, VoIP is a technology with a great demand and wireless networks are increasingly deployed. Each of these has its own\ntechnology constraints. For VoIP, it is very important to take into consideration the need to provide a high quality service according\nto well-defined standard transmission (jitter, end-to-end delay, MOS, and packet loss). However, wireless networks (IEEE 802.11)\nare based on radio which undergoes a number of technical constraints to achieve theoretical transmission rates; among these\nconstraints the number of users of the networks, the distance between the client and the access, and the amount of data transmitted\npoint are included. In this term, a study is made by simulating wireless network in OPNET Modeler with a fairly large number of\nVoIPs (15 users) whose signaling is handled via a new node that was created specifically to manage the signaling tasks under SIP\nand H.323 in order to minimize the number of nodes in the network and avoid the congestion. In this paper, two scenarios are\ncompared; the first contains a number of VoIP users with SIP and H.323 signaling handled by the new created device; the second\nscenario is similar to the first except that the distance between the stations is remarkably lower....
With the development of multi-processor system-on-Chip (MPSoC) in recent years, the intra-chip communication is becoming the bottleneck of the whole system. Current electronic network on-chip (NoC) designs face serious challenges, such as bandwidth, latency and power consumption. Networks-on-chip (NoCs) can improve the communication bandwidth and power efficiency of multiprocessor systems-on-chip (MPSoC). However, traditional metallic interconnects consume significant amount of power to deliver even higher communication bandwidth required in the near future. Optical interconnection networks are a promising technology to overcome these problems. In this paper, we study the routing problem in optical NoCs with arbitrary network topologies. Traditionally, a minimum hop count routing policy is employed for electronic NoCs, as it minimizes both power consumption and latency. However, due to the special architecture of current optical NoC routers, such a minimum-hop path may not be energy-wise optimal. Using a detailed model of optical routers we reduce the energy-aware routing problem into a shortest-path problem, which can then be solved using one of the many well known techniques. By applying our approach to different popular topologies, we show that the energy consumed in data communication in an optical NoC can be significantly reduced. We also propose the use of optical burst switching (OBS) in optical NoCs to reduce control overhead, as well as an adaptive routing mechanism to reduce energy consumption without introducing extra latency. Our simulation results demonstrate the effectiveness of the proposed algorithms....
In Long Term Evolution-Advanced (LTE-A), the signal quality in a wireless channel is estimated based on the channel quality\nmeasurements.Themeasurement results are used to select suitablemodulation and coding scheme for each transmission, feedback,\nand processing delay, which can cause amismatch between channel quality information (CQI) and current channel state at the base\nstation. However, prospect delays in the reception of such CQI may lead to a system performance degradation. This study analyzes\nthe impact of CQI feedback delay on joint user scheduling (JUS) scheme and separated random user scheduling (SRUS) scheme\nin LTE-A system over carrier aggregation. The analysis will be compared with the system having delayed channel and perfect\nknowledge at different deployment scenario.We will study the throughput performance of both scheduling schemes with different\ndeployment scenario, and then recommend the suitable deployment scenario to keep the desired QoS for a specific number of\nusers. Results show that, in main beamdirected at sector boundaries and diverse coverage, JUS scheme performs better than SRUS,\nwhich can justify the intensive use of user equipment power and extra control signaling overhead....
There have been researchers working on the design of coding-aware routing protocols to exploit the power of network coding in\nstatic wireless ad hoc networks.However, most of them have overlooked the fact that routing decisions formultiple flows need to be\ncoordinated in order to achieve maximum throughput. Amechanism to alter prior routing decisions is mandatory for this purpose.\nIn this paper, we propose Self-recommendation coding-aware routing (SCAR), to provide such a mechanism. With intermediate\nnodes sensing the arrival of new flows, they can send self-recommendations to source nodes, triggering a route-change procedure.\nIn the route-change procedure, adjustments are applied to the route metrics so that the newly recommended route can be fairly\nweighed without bias. A thorough analysis of coding structures is carried out, and a series of indicators are devised to predict\nhow much throughput benefits we can gain from the mere knowledge of the topology. The rationale behind the protocol design\nand the effectiveness of the indicators are further justified by a series of simulations. Results show that SCAR can exploit coding\nopportunities better and provide higher throughput than other coding-aware routing protocols. It is also shown that the opportunity\nof throughput gain is ubiquitous and it is tested on many typical topologies....
In modeling communication networks for simulation of survivability schemes, one goal is often to implement these schemes across\nvarying degrees of nodal connectivity to get unbiased performance results. Abstractions of real networks, simple randomnetworks,\nand families of networks are the most common categories of these sample networks. This paper looks at how using the network\nfamily concept provides a solid unbiased foundation to compare different network protectionmodels. The network family provides\nan advantage over randomnetworks by requiring one solution per average nodal degree, as opposed to having to solvemany, which\ncould take a significant amount of time. Also, because the network family looks at a protection scheme across a variety of average\nnodal connectivities, a clearer picture of the scheme�s performance is gained compared to just running the simulation on a single\nnetwork or select few networks....
We propose a new architecture of dynamic time-wavelength division multiplexing-passive optical network (TWDM-PON) system\nthat employs integrated all-optical packet routing (AOPR) module using 4? Ã?â?? 10Gbps downstream signal to support 20 km fiber\ntransmission. This module has been designed to support high speed L2 aggregation and routing in the physical layer PON system\nby using multicasting cross-gain modulation (XGM) to route packet from any PON port to multiple PON links. Meanwhile, the\nfixed wavelength optical line terminal (OLT) transmitter with wavelength tuning free features has been designed to integrate with\nthe semiconductor optical amplifier (SOA) and passive arrayed waveguide grating (AWG). By implementing hybrid multicasting\nand multiplexing, the system has been able to support a PON system with full flexibility function for managing highly efficient\ndynamic bandwidth allocation to support the 4????Ã?â??10 Gb/s TWDM-PON system used to connect 4 different PON links using fixed\nwavelength OLT transceivers with maximum 38 dB link loss....
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