An enhanced solution provides path protection in addition to dynamic QoS awareness . It was discovered that HQ though being a better option has high computation time as compare to SP. This degrades the overall performance in terms of computation time and the solution becomes expensive. The task is now modified to provide advantages of HQ while maintaining a low computation time. Shortest Path Adaptive Link Weight (SPALW) algorithm provides low computation time and its blocking probability converges to HQ at large network load under dark lit path protection scheme while HQ has better performance in terms of blocking probability over large network load . The SPALW calculates link weight as a linear function of path length, wavelength usage (which is the ratio of used wavelengths to the available wavelengths) and the connection state for each link. The link with the minimum weight is selected for high QoS provisioning. Both HQ and SPALW do not differentiate among predictable and non-predictable traffic. They are both adaptive algorithms and treat all traffic as unpredictable.
RoF consists in transporting the radio signals by means of an optical carrier from the remote site to the head-end node of the cellular network where it is processed [3.16-3.18]. RoF links where an optical carrier is modulated by the wireless signals, known as analog RoF inherently suffer from inter modulation distortions arising from the nonlinearities of both RF and optical components [3.19]. Furthermore, it has been shown that the dynamic range of the analog optical link depend on the optical modulation that is used and optical fiber dispersion. Digitized RoF has been proposed during these last ten years thanks to the increasing speed of electronics. The main objective of digital RoF is to facilitate the usage of distributed antennas and to standardize the various interfaces of the radio equipment according to the common public radio interface (CPRI) or open base station architecture initiative (OBSAI). Such a modulation requires the usage of high-speed analog-to-digital converters (ADCs) at the source and Digital-to-Analog converters (DACs) at the destination. Similarly to analog RoF, it is possible to rebuild directly at destination the pre-modulated radio frequency (RF) signal without the usage of costly RF and intermediate frequency (IF) oscillators, in case of a low bandwidth and a low frequency signal. Meanwhile, in the case of broadband RF signals, the speed of electronics needed for the design of ADC/DAC may become restrictive. In that case, it is possible to digitize only the pre-modulated IF signal instead of the RF signal, an RF oscillator being needed at destination to up-convert the IF signal to the radio carrier frequency [3.20]. Contrary to what happens in analog systems, by employing digitalization of RF signals inoptical
Optical network has been well established as the technology to support the traffic demand in backbones, due to its capacity to support more than a hundred of channels by meaning of WavelengthDivisionMultiplexing (WDM), where each wavelength can transmit 100Gb/s. This technology has permitted the development of different corporative and domestic services, such as, Video on Demand (VoD), Cloud Services, Data Center, etc. The classical configuration problem in WDM opticalnetworks supporting electronic processing is called traffic grooming, routing and wavelengthassignment problem (GRWA). Because of its complexity to generate a good network configuration, this problem is frequently divided in smaller parts where the main goal is the optimization of resources -. The division for GRWA problem is made according these following sub-problems: Virtual Topology Design (VTD); Routing and WavelengthAssignment (RWA); and Traffic Grooming Problem (TGP).
The extensive simulation of PSEMQoS is conducted through ns-2 with the aid of NSF network which contains the topology of 30 nodes and 25 links with Jumpstart JIT signaling protocol as the base protocol. The simulation is carried out by letting the most loaded link of the NSF network to fail for analyzing the role of PSEMQoS in regaining the required QoS.Furthur, PSEMQoS is compared with OBSRWA(Optical Burst Switching reservation and wavelengthassignment approach) and NFRMOBS (Novel Fast Restoration Mechanism for Optical Burst Switched networks ) that reduces the number of required wavelengths to assign a different wavelength to each path in a set of overlapping paths (asynchronous PQP).Furthermore , we analyze the traffic pattern variations for all the schemes considered for measuring the performance of proposed technique through parameters namely Burst loss probability, jitter, Average Goodput and packet delivery ratio. In addition, The assumptions considered for carrying out the simulation are:
As the number of integrated Intellectual Property (IP) cores increases in a single chip, some of the performance aspects of the Network on Chip (NoC) are affected and begin to be limited, such as throughput, data latency, power consumption, etc. Electrical interconnect does not so well in terms of performance scalability and power efficiency  and there is a reliability problem as well . One of the solutions to solve the above mentioned problems is the optical interconnect with lower power dissipation, higher density of bandwidth and higher speed of signal propagation. According to the platform of Silicon-on-Insulator (SOI), there are significant advances for a high number of optical devices that can be used in the NoCs [3-9] and this makes the optical interconnect technology an interesting option. As an outcome, according to according to compatibility the silicon photonics with CMOS technology, various groups of researchers have proposed a number of photonic NoC architectural designs. The opticalnetworks have been widely considered as the most promising alternatives for the networks with traditional electrical interconnections as the media for communication among the processor cores of the chip multiprocessors due to their extremely low power consumption, small delay in communication and extremely high bandwidth. A feasible method is provided by wavelengthdivisionmultiplexing (WDM) for realizing the optical interconnection networks. When the bandwidth of an optical fiber is divided into a number of communication channels and their respective wavelengths are their representatives, at the same time, a multiplicity of data streams can be transmitted across the same waveguide. There are two major challenges that the photonic networks confront with. The first one is the buffering impossibility and the lack of processing in
In a WavelengthDivisionMultiplexing (WDM)- based access, the demand for bandwidth has increased in an extremely fast and is a promising solution for data transport in future all-optical wide area networks (Ab- Rahman et al., 2009). At the same time, the cost of transporting information bit per km also needs to be reduced. WDM system in Free Space Optical (FSO) is the way to maximize the bandwidth usage but in low cost. It has been quite mature and applied to optical fiber networks universally. Several FSO WDM transmission system have been demonstrated successfully (Kintaka et al., 2010 and Sinefeld and Marom, 2010). Although FSO is an old topic, due to the availability of advanced technologies and high
In this paper we focus on access networks, the “last mile” of telecommunication networks connecting the central office (CO) to residential and business customers . The access section comprises a large part of the Internet and contains a large number of active elements, where traffic aggregation occurs to a lesser extent compared to the core, becoming a major energy consumer . Here we address the challenge of reducing the energy consumption of fiber–wireless (FiWi) access networks while keeping delay under a threshold. FiWi access networks have been proposed as flexible and cost-effective solutions because fiber is provided as far as possible, from the CO to the end users, and then wireless is used at the front-end where fiber can be difficult to install . At the back-end, a passive optical network (PON) is usually used because of low maintenance, high reliability and low power consumption . PONs consist of point-to-multipoint optical structures where an optical line terminal (OLT) at the CO serves many optical network units (ONUs) near the users. This is a time divisionmultiplexing (TDM) shared optical medium where the downstream signal is broadcasted to all ONUs. For the upstream, the ONUs are kept synchronized in a TDM fashion so that their signals can be joined, ensuring a collision-free medium.
In scheme (1), the first hybrid OCDMA-WDM overlay system has been experimentally demonstrated by Shen and Weiner (2001). The concept of this scheme is that ultra short-pulses are used for spectral encoded/decoded OCDMA. Sub-picoseconed laser pulses that used as short pulses for OCDMA coding make the system more complex technology. The hybrid operation is addressed with high closely spaced WDM users. Focus is at the OCDMA receiver for attenuation of WDM interference for error-free detection. By using a nonlinear fiber thresholder in the decoder, the WDM signals can be filtered and suppressed properly. In (Chang et al., 2005), the same concept was implemented in the optical domain, where OCDMA encoded short pulses spread over time for spectral phase coding. The decoder consists of a Fourier transform for the windowed data signals. The WDMA technique can allow electrical user signals to access the opticalnetworks. Both access approaches in a combined scheme is to achieve high throughputs, resourceful and high-speed access to networks of WAN, greatly faster and further flexible to LANs (Chen, 2005). A matched filter of transmitted pulses includes a conjugate modulator followed by an integrator. Consequently, the signals from both systems can be separated sufficiently based on the perfectly synchronous case for every one of users. Therefore, the effects of thermal noise and adjacent-channel interferences can be neglected. In this hybrid approach,
All the performance parameters were calculated as function of network load, ranging from 10 E to 500 E, with intervals of 10 E, totalizing 50 points per curve. The first results are referred to blocking probability, which are shown in Fig. 5. The contribution of each switching paradigm on blocking probability, calculated by using (7), is shown in Fig. 5(a). The total blocking probability can be seen in this figure with a purple continuous line without markers, calculated by using (8). This figure shows that the major contribution for blocking probability is due to OCS, followed by OBS and OPS. Specifically, the OPS switching paradigm presents a high level of blocking, considering its low relative load. This behavior can be explained by the fact that the network available resources are shared by all the switching paradigms, and clearly OCS and OBS hold the resources for longer periods when compared to OPS. Thus, OPS suffers higher blocking probabilities because resource conversion is not possible and no contention resolution scheme are being used. Furthermore, the decentralized way to reserve resources for OCS makes all the available resources busy in the resource discovering process even if it will use just one of them. Since OPS is the most dynamical switching paradigm among the considered ones, it also suffers blocking probability.
Recent studies have shown that to achieve an acceptable performance for a practical FSO link, it requires to overcome some major challenges. The challenges are: determination of modulation techniques, suitable light sources, source power, transmitter-receiver alignment and transmitting wavelengths. Moreover, the types of detectors, various sources of noise and error correction techniques are also the factors that should be considered in the installation of practical FSO link . However, the quality of FSO link is strongly dependent on the performance of FSO channel (free space) . There are several challenges facing the channel performance, from which the effect of weather variations on channel is one of them. Moreover, visibility is one of the most important weather factors affecting the channel performance. With the change in weather conditions, visibility changes, which consequently changes the atmospheric attenuation experienced by the FSO channel . The change in operating wavelength is another factor which also affects the atmospheric attenuation of the channel . The change in attenuation changes the link performance [5, 6]. Hence, it is important to consider the effect of visibility for different weather conditions as well as operating wavelength on FSO communication channel before installing any FSO link.
The Multi-Band Orthogonal Frequency DivisionMultiplexing (MB-OFDM) has been proposed as a promising technology by IEEE and European Computer Manufacturers Association (ECMA) working groups for short range high data rate UWB communication applications (Saeed et al., 2005; Batra et al., 2004) IEEE Std, 2005. In MB-OFDM based UWB system, the allocated spectrum of 3.1-10.6 GHz by Federal Communication Commission (FCC) is divided into fourteen 528 MHz sub bands. In each sub band data is transmitted using OFDM. The distinct feature of MB- OFDM is the use of Zero Padding (ZP) instead of Cyclic Prefix (CP). In a CP based OFDM, there exists a correlation between CP and OFDM signal. This manifests in the form of ripples in the Power Spectral Density (PSD) of the transmitted signal and hence results in additional power back-off. It has been reported that the use of ZP has reduced the ripples in PSD to zero (Saeed et al., 2005). In MB-OFDM, the availability of varying channel responses across different sub bands provide diversity gain. However,
Abstract — Gigabit-Capable Passive Optical Network (GPON) and Long Term Evolution (LTE) are two promising broadband access technologies with high-capacity and QoS services for wired access networks and wireless access networks, respectively. A convergence of GPON and LTE networks is proposed to take the bandwidth advantage of opticalnetworks and the mobility feature of wireless communications in this paper. First, GPON-LTE Converged Network Architecture (GLCNA) is presented and especially the concept of Optical Network Unit-evolved NodeB (ONU-eNB). Second, the QoS mapping strategy is defined for GPON-LTE converged networks. Third, a Synchronous Interleaved Dynamic Bandwidth Assignment (SIDBA) scheme is proposed to alleviate the asynchrony problem in upstream bandwidth allocation due to the cycle time of GPON (usually is between 1ms and 2ms) and the frame size of LTE (usually is 5ms or 10ms) are mismatched. The simulation results show that the proposed SIDBA scheme can effectively enhance the system performance for different polling cycle time/frame size pairs in terms of network throughput and packet delay, especially the polling cycle time/frame size pair is 2ms/5ms performs the best.
It is well recognized that the choice of suitable host ma- terials is crucial to the development of novel and more effi- cient optical devices. 1 Tellurite and chalcogenide glasses are attractive as hosts due to their high refractive index, low phonon energy, and wide transparency window ranging from the visible to the mid-IR. 2,3 The high refractive index corre- lates with large emission cross sections, and the low phonon energy with reduced nonradiative rates, leading to high quan- tum efficiencies of radiative transitions. Furthermore, these glasses can accept in their network large amounts of rare earth ions, which opens up the possibility of efficient upcon- version lasers. 4 In addition, the high solubility of rare earth makes chalcogenides and tellurites promising candidates for the development of high density optical data storage and displays. 2 The low glass transition temperature of these glasses represents a potential advantage for photonic applications. 5 Chalcogenides, in particular, exhibit amor- phous semiconductor behavior, in that they have band gap energies ranging from 1 to 3 eV. They also exhibit strong photorefractive effects, such as photodarkening, reversible photostructural changes, and photoinduced phase changes, which have been explored for the fabrication of photonic
242 particular,  solves the joint routing and channel assignment problem which intends to optimize the overall network throughput subject to the fairness constraint. In general, most work on both Optical-wireless networks and WMNs focus on the traffic destined to gateways for the Internet access. As introduced in the previous section, Optical-wireless network provides an attractive alternative routing for peer-to-peer communications, which can utilize the high bandwidth provided by the PON sub network and alleviate interferences in wireless sub network, thus increasing the network throughput. Therefore, our focus is on the network throughput gain brought by the new structural features inOptical-wireless networks compared with traditional WMNs when peer-to-peer communications is the traffic load.
As both radar and optical observations are conducted reg- ularly (the latter each year during the NLC season), one can hope to register several occasions of the presence of grav- ity waves in the NLC area and therefore to obtain statis- tical information on typical wave characteristics in the up- per mesosphere-mesopause system above a given region of the Earth’s surface. Based on the knowledge of typical wave parameters and wave orientations we can attempt to define a possible source for these waves (such as likely an orographic source represented by the Scandinavian ridge). Relating sources to conditions in the troposphere will con- tribute to a better understanding of the mechanisms of grav- ity wave forcing in the summer mesosphere. A comprehen- sive characterization of the sources of gravity waves, with paths traced to the mesopause altitudes, would require mul- tipoint ground-based radar measurements accompanied by simultaneous sounding rocket experiments, as well as stan- dard global meteorological assimilations. However, some progress can likely be made on the basis of the radar used here, together with meteorological assimilations when local sources dominate.
The main idea of the routing-enabled QoS control mechanism of QoS-RRC consists in bootstrapping a routing table with shortest QoS-aware path information, including the IP address of each router along the path and correspondent bottleneck's QoS capabilities (per-class available bandwidth and rates of delay, jitter and loss). For such, each ingress node loods the network, and each visited node initializes per-class over-reservations (taking into account an assigned factor, such as , or . of the local link capacity), adds its IP and current QoS conditions to the message, and forwards it downstream. Ater the operations described above succeed, the egress node signals the ingress one. In order to avoid ininite looping and redundant information storage in looding, each node must only inspect messages once and a limited number of hops (as in TTL) can be assigned to avoid long paths. This looding cycle provides information about unicast paths, composed by one ingress router, a set of core routers and one egress router. Ater inishing the looding cycle, each ingress router implements an algorithm that takes unicast paths to generate all possible QoS-aware multicast trees (matching it and available egress nodes). QoS-RRC ilters the information, keeping only best multicast trees for avoiding excessive matching'S. For instance, trees with ingress routers in the middle are discarded for keeping only downstream transport. Aterwards, QoS-RRC signals each path to setup multicast state accordingly.
Figure 11. Time series of retrieved cloud properties determined by 3 different transmittance based retrieval methods; case A (left) for liquid cloud, case B (center) for mixed-phase cloud, and case C (right) for ice cloud. The mixed-phase cloud case represents a cloud sampled during a time where both ice and liquid water cloud particles are expected to have been present. Colors represent three different cloud retrieval methods: this work (black), the slope method (blue) and the 2-wavelength method (red). For each case study, the top-most panel presents the retrieved optical thickness, τ, the panel directly below shows the effective radius, r e , the panel directly
A lot of research is been carried out in the field of signal and biomedical optical image processing so as to improve the existing medical techniques. As a result of this, spectral domain optical coherence tomography (SD-OCT) was been proposed in early 2000s which could be used to image various aspects of biological tissues. Some of these include structural information, blood flow, polarization sensitivity, elastography, spectroscopy etc . Any combination of above imaging modes can be used to bring out specific features of biological tissues as desired . OCT is based on Michelson interferometry principle. The Michelson interferometer setup consists of a broadband source, which is split by the 50:50 or 90:10 beam splitter along the reference arm and the sample arm. The reference arm consists of mirror and the sample arm consists of sample to be scanned for imaging.
In this work, we show how we can design a routing protocol for wireless sensor networks (WSNs) to support an information-fusion application. Regarding the application, we con- sider that WSNs apply information fusion techniques to detect events in the sensor field. Particularly, in event-driven scenarios there might be long intervals of inactivity. However, at a given instant, multiple sensor nodes might detect one or more events, resulting in high traffic. To save energy, the network should be able to remain in a latent state until an event occurs, then the network should organize itself to properly detect and notify the event. Based on the premise that we have an information-fusion application for event detection, we propose a role assignment algorithm, called Information-Fusion-based Role Assignment (InFRA), to organize the network by assigning roles to nodes only when events are detected. The InFRA algorithm is a distributed heuristic to the minimal Steiner tree, and it is suitable for networks with severe resource constraints, such as WSNs. Theoretical anal- ysis shows that, in some cases, our algorithm has a Oð1Þ-approximation ratio. Simulation results show that the InFRA algorithm can use only 70% of the communication resources spent by a reactive version of the Centered-at-Nearest-Source algorithm.
Viscosity and density of the solution are considered the significant and effective parameters in producing a thin film which the prepared solution should have the molar ratio of Zn/ MEA. Thus, utilizing the sol-gel process, the solution consisting of 86% ml of Mono Ethanol Amine, 1/3 g of Zn (CH3COO) 2.2H2O, 15 ml of Isopropanol in 0.1 ml of water has been prepared. Considering the particular physical properties of this n-type semiconductor with the boiling point of 2360ºC, the melting point of 1975ºC, direct band gap of 3.38 eV, it has a gain and its hexagonal structure is the most stable one in these conditions. The compound is heated with a magnetic stirrer for 50 minutes in order for the transparent, uniform, and almost thick solution to be made. The solution is kept at the room temperature for 24 hours to make sure that there is no sediment.