Upstream Links Research Articles

Traffic Signal Optimization for Oversaturated Urban Networks: Queue Growth Equalization

This paper develops a signal optimization algorithm that aims to equalize queue growth rates across links in oversaturated urban roadway networks and thus postpones queue spillbacks that form at the localized sections of networks. The performance of this algorithm is evaluated by simulating traffic conditions with optimized signal settings on an idealized 3 by 3 roadway network under various oversaturated demand scenarios. The simulation experiments show that the algorithm can delay queue spillbacks by distributing queues over upstream links that would otherwise be underused. The findings from the experiments also show that the signal settings optimized by the queue growth equalization (QGE) algorithm outperform those optimized using the conventional signal optimization software, TRANSYT-7F, for all the performance measures examined in this paper, i.e., compared with TRANSYT-7F, the QGE results in higher outflows, higher vehicle miles traveled, shorter delays, less sensitivity to various demand scenarios, and delayed queue spillbacks. In addition, the algorithm is computationally light to provide a promising groundwork for large-scale signal optimization.

Delta channel networks: 1. A graph‐theoretic approach for studying connectivity and steady state transport on deltaic surfaces

AbstractRiver deltas are intricate landscapes with complex channel networks that self‐organize to deliver water, sediment, and nutrients from the apex to the delta top and eventually to the coastal zone. The natural balance of material and energy fluxes, which maintains a stable hydrologic, geomorphologic, and ecological state of a river delta, is often disrupted by external perturbations causing topological and dynamical changes in the delta structure and function. A formal quantitative framework for studying delta channel network connectivity and transport dynamics and their response to change is lacking. Here we present such a framework based on spectral graph theory and demonstrate its value in computing delta's steady state fluxes and identifying upstream (contributing) and downstream (nourishment) areas and fluxes from any point in the network. We use this framework to construct vulnerability maps that quantify the relative change of sediment and water delivery to the shoreline outlets in response to possible perturbations in hundreds of upstream links. The framework is applied to the Wax Lake delta in the Louisiana coast of the U.S. and the Niger delta in West Africa. In a companion paper, we present a comprehensive suite of metrics that quantify topologic and dynamic complexity of delta channel networks and, via application to seven deltas in diverse environments, demonstrate their potential to reveal delta morphodynamics and relate to notions of vulnerability and robustness.

Practical 12.5-Gb/s, 12.5-GHz spaced ultra-dense WDM PON.

We report a practical 12.5-Gb/s, 12.5-GHz-spaced ultra-dense wavelength-division-multiplexed passive optical network (UD-WDM PON). For the cost-effectiveness, we implement the downstream links by using electro-absorption modulated lasers (EMLs) in the 4-level pulse amplitude modulation (4PAM) format and PIN receivers, and the upstream links by using reflective semiconductor optical amplifiers (RSOAs) modulated in the quadrature phase-shift-keying (QPSK) format and low-cost self-homodyne receivers. To further enhance its cost-effectiveness, we also utilize an optical frequency comb generator, instead of a large number of wavelength-selected lasers, to provide the seed light for these colorless RSOAs. We optimize the operating conditions of the EMLs and RSOAs to maximize the power margins in the presence of the crosstalk arising from closely spaced neighboring channels and the inter-symbol interference (ISI) caused by the narrow passband of the cascaded arrayed-waveguide gratings (AWGs) as well as the limited modulation bandwidths of RSOAs. The experimental results show that we can secure the power margins of >2.5 dB for both upstream and downstream links of the proposed UD-WDM PON.

Electrical code divided multiplexing orthogonal frequency division multiplexing-based 60-GHz radio-over-fiber system with extended wireless transmission and optical beating interference noise mitigation in upstream link

This paper proposes an electrical code divided multiplexing orthogonal frequency division multiplexing (ECDM-OFDM) modulation-based radio-over-fiber (ROF) system at the 60-GHz band. Compared with conventional OFDM ROF system, it can increase the distance of wireless links as well as suppressing the optical beating interference noise in the upstream link. The 4.68 Gb/s ECDM-OFDM signal at 60 GHz with a 25-km fiber and 8-m air transmission is experimentally demonstrated. The wireless distance of the ECDM-OFDM signal has been extended 3 m with the same transmitted power. For the upstream signal, no significant receiver power penalties are observed after transmission.

A cost-effective ultra-dense WDM PON system with speed of 12.5 Gbit/s and channel spacing of 12.5 GHz

A cost-effective ultra-dense wavelength-division-multiplexed passive optical network (UD-WDM PON) with speed of 12.5 Gbit/s and channel spacing of 12.5 GHz is proposed and demonstrated. The distributed feedback (DFB) lasers modulated in 4-level pulse amplitude modulation (4-PAM) format are used for downstream links, and the reflective semiconductor optical amplifiers (RSOAs) together with an optical frequency comb modulated in quadrature phase shift keying (QPSK) format are used for upstream links. We can achieve the error-free transmission of the upstream signals with speed of 12.5 Gbit/s even after 20 km single-mode fiber (SMF). The power penalty obtained by using the frequency comb generator instead of a tunable laser is around 0.5 dB. By using 11 DFB lasers and a set of intensity and phase modulators, it is possible to provide the seed light for 297 optical network units (ONUs) within the C-band.

A Stable Routing Framework for Tree-Based Routing Structures in WSNs

Achieving industry standards for transmission of data is an ultimate goal for wireless sensor network (WSN) designers. Such standards are difficult to attain due to the challenging communications environment in which WSNs operate where best transmission routes may change rapidly. In such dynamic environments, it is not only advantageous, but commonly necessary to change the used route for better performance. However, with so many changing routes, it is possible to introduce instability, which can hinder the provision of services. Route instability can be particularly detrimental in a tree-based routing structure. In these scenarios, it is beneficial to maintain more stable routes in the tree to preserve high standards. The focus of this paper is the development of a route stability framework, whereby currently used metrics are adapted to promote routes that achieve greater stability in highly dynamic network conditions. The central concept introduces neighborhood heuristics (NHs), a method of combining a sensor’s routing metric with those of its neighbors to highlight both the quality of the current route and the quality of the routing options available to the sensor should its current route become unavailable. The additional information afforded by the new combined metric allows sensors to choose good quality routes that can better maintain quality despite the degradation of an upstream link. The NHs framework is implemented with the routing protocol for low power and lossy networks routing protocol. Experiments are conducted both in simulation and on an open public testbed, which compare routing stability using the expected transmissions (ETX) metric and ETX under the NHs stability framework (ETX-NH), showing a marked increase in route stability for ETX-NH over using ETX.

Symmetric 40-Gb/s TWDM-PON with 51-dB loss budget by using a single SOA as preamplifier, booster and format converter in ONU.

In this paper, we propose to use a semiconductor optical amplifier (SOA) in the optical network unit (ONU) to improve the loss budget in time and wavelength division multiplexed-passive optical network (TWDM-PON) systems. The SOA boosts the upstream signal to increase the output power of the electro-absorption modulated laser (EML) and simultaneously pre-amplifies the downstream signal for sensitivity improvement. The penalty caused by cross gain modulation (XGM) effect is negligible due to the low extinction ratio (ER) of upstream signal and the large wavelength difference between upstream and downstream links. In order to achieve a higher output power, the SOA is driven into its saturation region, where the self-phase modulation (SPM) effect converts the intensity into phase information and realizes on-off-keying (OOK) to phase-shifted-keying (PSK) format conversion. In this way, the pattern effect is eliminated, which releases the requirement of gain-clamping on SOA. To further improve the loss budget of upstream link, an Erbium doped fiber amplifier (EDFA) is used in the optical line terminal (OLT) to pre-amplify the received signal. For the downstream direction, directly modulated laser (DML) is used as the laser source. Taking advantage of its carrier-less characteristic, directly modulated signal shows high tolerance to fiber nonlinearity, which could support a downstream launch power as high as + 16 dBm per channel. In addition, the signal is pre-amplified by the SOA in ONU before being detected, so the sensitivity limitation for downstream link is also removed. As a result, a truly passive symmetric 40-Gb/s TWDM-PON was demonstrated, achieving a link loss budget of 51 dB.

Beyond 90-km Reach of a 16 × 2.5 Gb/s C/L-band Dense Wavelength-Division Multiplexing Metropolitan Network Based on Self-Seeded Reflective Semiconductor Optical Amplifiers

This article reports the operation of a cost-effective, colorless, dense wavelength-division multiplexing metropolitan network based on self-seeded reflective semiconductor optical amplifiers. All reflective semiconductor optical amplifiers used in the experiments are packaged in commercial small form-factor pluggable modules. The proposal architecture is simple and symmetric thanks to utilization of two cyclic array waveguide gratings. Downstream link functions in the C-band wavelength range and the upstream link functions in the L-band wavelength range. By using erbium-doped fiber amplifiers to extend the reach, an error-free transmission over 90 km for 16 channels at 2.5 Gb/s was experimentally demonstrated for both directions, and an optical budget over 35 dB was obtained.

Assessing the welfare effects of congestion charges in a real world setting

The standard textbook analysis shows that drivers as a group lose from congestion charges. However, it omits taste heterogeneity, shorter travel times far out in the larger network arising from less blocking back of upstream links and the possibility for drivers to reschedule. Taking account of these factors, using a dynamic scheduling model with heterogeneous users we find that all three add significantly to the benefit of the Stockholm congestion charges and that drivers as a group benefit from these charges even without recycling of revenues. This paper also provides an update on the consumer benefits of the Stockholm charges.

Quasi-dynamic traffic assignment with residual point queues incorporating a first order node model

Static traffic assignment models are still widely applied for strategic transport planning purposes in spite of the fact that such models produce implausible traffic flows that exceed link capacities and predict incorrect congestion locations. There have been numerous attempts to constrain link flows to capacity. Capacity constrained models with residual queues are often referred to as quasi-dynamic traffic assignment models. After reviewing the literature, we come to the conclusion that an important piece of the puzzle has been missing so far, namely the inclusion of a first order node model. In this paper we propose a novel path-based static traffic assignment model for finding a stochastic user equilibrium in general transportation networks. This model includes a first order (steady-state) node model that yields more realistic turn capacities, which are then used to determine consistent capacity constrained traffic flows, residual point (vertical) queues (upstream bottleneck links), and path travel times consistent with queuing theory. The route choice part of the model is specified as a variational inequality problem, while the network loading part is formulated as a fixed point problem. Both problems are solved using existing techniques to find a solution. We illustrate the model using hypothetical examples, and also demonstrate feasibility on large-scale networks.

Energy-Efficient Opportunistic Routing Protocol in Wireless Sensor Networks

The paper presents energy-efficiency opportunistic multicast routing protocol (EOMR) for the multicast energy consumption minimization problem in wireless sensor networks. The protocol divides the network into single grids, so each node determines their own coordinates according to the grid, which they locate in a certain period of time. The nodes only need to know the topology of their own grid, instead of the topology of the entire network. Nodes in the same grid determine the priority in light of the upstream and downstream links metrics, and use the opportunistic routing to send messages to the next hop. The destinations calculate the optimal path in accordance with the hops and links cost, and transmission acknowledgement to source along the optimal path selected. If all nodes in the current grid transmission messages failure, the neighbor grids are in charge of retransmission. The results of simulation show that, compared with traditional multicast routing, EOMR is effective in reducing the consumption of links cost, so that it improves the link reliability and reduces the delay.

Coherent UDWDM PON with joint subcarrier reception at OLT.

In this contribution, we report on the experimental investigation of an ultra-dense wavelength-division multiplexing (UDWDM) upstream link with up to 700 × 2.488 Gb/s polarization-division multiplexing differential quadrature phase-shift keying parallel upstream user channels transmitted over 80 km of standard single-mode fiber. We discuss challenges of the digital signal processing in the optical line terminal arising from the joint reception of several upstream user channels. We present solutions for resource and cost-efficient realization of the required channel separation, matched filtering, down-conversion and decimation as well as realization of the clock recovery and polarization demultiplexing for each individual channel.

Recent development on time and wavelength-division multiplexed passive optical network (TWDM-PON) for next-generation passive optical network stage 2 (NG-PON2)

The second stage of next-generation passive optical network (NG-PON2) based on time and wavelength division multiplexed passive optical network (TWDM-PON) was proposed by a telecommunication group research to enhance the performance of broadband access networks. TWDM-PON was selected as the best candidate for NG-PON2 solution because of its ability to support the NG-PON2 requirements, such as enhanced bandwidth capacity, 40Gb/s, and coexistence with previously existing generations without any change to optical distribution network (ODN). This paper reviewed the recent progress carried out on a TWDM-PON system configuration, with emphasis on tunable transmitter and receiver optical network unit (ONU) in terms of the amount of tuning range reported in exploiting the wavelength plan provided with cost efficiency. The speed of data rate transmitted on the downstream and upstream links between optical line terminal (OLT) and ONU with the way of stacking approach in NG-PON2 is reviewed. In addition, the power system budget is reviewed to determine the number of users allocated with the system with each transmission allowed.

A novel full duplex 16 Gbps SCM/ASK radio over fiber WDM-PON sharing wavelength for up- and down-link using bidirectional reflective filter

In this paper, a new bidirectional wavelength division multiplexing radio-over-fiber (WDM-RoF) using Subcarrier Multiplexing/Amplitude Shift Keying (SCM/ASK) is proposed which shares the same wavelengths for both up-link and down-link. A bidirectional reflective filter (BRF) is utilized in the upstream link to provide a reliable bidirectional optical channel. WDM is used to further increase the capacity of system. Simulation of the proposed scheme demonstrates 1Gbps down- and up-link data stream for 16 channels over the length of 25km with acceptable Q-factor (>6dB).

ROS-PIASγ cross talk channelizes ATM signaling from resistance to apoptosis during chemosensitization of resistant tumors

With the existing knowledge of ATM's role in therapeutic resistance, the present study aimed at identifying the molecular mechanisms that influence ATM to oscillate between chemoresistance and chemosensitivity. We observed that the redox status of tumors functions as a major determinant of ATM-dependent ‘resistance-to-apoptosis' molecular switch. At a low reactive oxygen species (ROS) condition during genotoxic insult, the ATM/sumoylated-IKKγ interaction induced NFκB activation that resisted JNK-mediated apoptosis, whereas increasing cellular ROS restored ATM/JNK apoptotic signaling. A search for the upstream missing link revealed that high ROS induces oxidation and ubiquitin-mediated degradation of PIASγ, thereby disrupting PIASγ-IKKγ cross talk, a pre-requisite for IKKγ sumoylation and subsequent NFκB activation. Interruption in the PIASγ-mediated resistance pathway channels ATM signaling toward ATM/JNK pro-death circuitry. These in vitro results also translated to sensitive and resistant tumor allograft mouse models in which low ROS-induced resistance was over-ruled in PIASγ knockout tumors, while its overexpression inhibited high ROS-dependent apoptotic cues. Cumulatively, our findings identified an unappreciated yet critical combinatorial function of cellular ROS and PIASγ in regulating ATM-mediated chemosensitization of resistant tumors. Thus, therapeutic strategies employing ROS upregulation to inhibit PIASγ during genotoxic therapy may, in future, help to eliminate the problems of NFκB-mediated tumor drug resistance.

188: Dengue infection generates an early NADPH-oxidase dependent ROS production required for antiviral and inflammatory responses

The rapid host response to virus infection is crucial for establishment of the antiviral state and for the release of pro-inflammatory mediators that coordinate the adaptive immune response. Induction of antiviral and inflammatory genes is achieved largely through recognition of viral nucleic acid motifs by pattern recognition receptors. Dengue virus (DENV) is a significant human pathogen that causes a wide spectrum of clinical symptoms, ranging from mild dengue fever to severe hemorrhagic fever and shock syndrome. The cytosolic receptors RIG-I/MDA5 as well as the membrane-bound TLR3/TLR7 localized in the endosomes are important sensors of DENV infection. The role of reactive oxygen species (ROS) in the activation of biological processes such as autophagy, necrosis, and inflammasome activation adds another layer of complexity to the regulation of immune sensing. Transcriptome analysis of DENV-infected human monocyte-derived dendritic cells (Mo-DC) revealed the activation of distinct patterns of gene transcription, with involvement of pathways including the antiviral response, the TNF superfamily and late activation of death receptor signaling. Interestingly, a dominant early gene network associated with the Nrf2-dependent antioxidant response was also identified; DENV infection induced an early production of ROS that was dependent on NADPH-oxidase, and was essential for the activation of inflammatory and antiviral programs, through NF-κB and IRF-3 transcription factors, respectively. Using a high throughput qPCR assay, we demonstrated that interfering with NADPH-oxidase inhibited DENV-induced antiviral and inflammatory responses. We also demonstrated that the antioxidant pathway controlled by the transcription factor Nrf2 is a pivotal upstream link to the regulation of DENV-induced antiviral and inflammatory responses under oxidative conditions. In conclusion, these findings demonstrate that ROS production is crucial for effective activation of pathways leading to innate immune responses against DENV infection in human Mo-DC.

Multi-objective evolutionary optimization for greywater reuse in municipal sewer systems

Sustainable design and implementation of greywater reuse (GWR) has to achieve an optimum compromise between costs and potable water demand reduction. Studies show that GWR is an efficient tool for reducing potable water demand. This study presents a multi-objective optimization model for estimating the optimal distribution of different types of GWR homes in an existing municipal sewer system. Six types of GWR homes were examined. The model constrains the momentary wastewater (WW) velocity in the sewer pipes (which is responsible for solids movement). The objective functions in the optimization model are the total WW flow at the outlet of the neighborhoods sewer system and the cost of the on-site GWR treatment system. The optimization routing was achieved by an evolutionary multi-objective optimization coupled with hydrodynamic simulations of a representative sewer system of a neighborhood located at the coast of Israel. The two non-dominated best solutions selected were the ones having either the smallest WW flow discharged at the outlet of the neighborhood sewer system or the lowest daily cost. In both solutions most of the GWR types chosen were the types resulting with the smallest water usage. This lead to only a small difference between the two best solutions, regarding the diurnal patterns of the WW flows at the outlet of the neighborhood sewer system. However, in the upstream link a substantial difference was depicted between the diurnal patterns. This difference occurred since to the upstream links only few homes, implementing the same type of GWR, discharge their WW, and in each solution a different type of GWR was implemented in these upstream homes. To the best of our knowledge this is the first multi-objective optimization model aimed at quantitatively trading off the cost of local/onsite GW spatially distributed reuse treatments, and the total amount of WW flow discharged into the municipal sewer system under unsteady flow conditions.

Influence of modulation formats performance of the combined modulation in WDM-PON system

Different modulation modes of DPSK and OOK are separately employed in the upstream and downstream link, after the comparison with different modulation formats in the downstream including the codes of non return-to-zero (NRZ), return-to-zero (RZ) and inverse return-to-zero (IRZ), the symmetric rate of 10Gbps with 20km transmission is realized without the dispersion compensation. It can be shown that in the combined modulation mode with the downstream of IRZ code, higher extinction ratio in the downstream and better performance of dispersion tolerance in the upstream could be achieved, enhancing the overall property of the transmission system.

Wavelength reuse in a bidirectional UWB over fiber system

Wavelength reuse in a bidirectional UWB over fiber system using a polarization modulator (PolM) and an electro-absorption modulator (EAM) is proposed and experimentally demonstrated. Since the PolM functions as a special phase modulator that supports phase modulation along the two principal axes with opposite modulation indices and the EAM is a polarization-independent component, the signals due to the phase-modulation to intensity-modulation (PM-IM) conversion along the two orthogonal directions in the upstream link will be complementary and cancelled out, thus the impact of the downstream signal to the upstream transmission due to the PM-IM conversion is fully eliminated. Error-free bidirectional transmission of a 1.25-Gbps UWB signal over 17 km single-mode fiber (SMF) is demonstrated. A power penalty due to the wavelength reuse for upstream transmission is measured to be as low as 0.2 dB.

Direct interaction between E47 and p21 controls LT-HSC proliferation and functional longevity (P4471)

Abstract Long-term hematopoietic stem cells (LT-HSCs) are important multipotent cells that replenish all immune cells lost due to natural turnover, infection or injury. LT-HSC proliferation is controlled by cell cycle regulators and upstream transcription factors but direct links between the two have not been established. Here, we demonstrate a mechanistic link between the transcription factor E47 and the major cell cycle regulator p21 in controlling LT-HSC proliferation, self-renewal, and functional competence. Gain-of-function and loss-of-function studies show that E47 directly regulates p21 transcription in HSCs. Using E47/p21 compound heterozygotes, a powerful approach for analyzing HSC activity in vivo, we show a 2-fold increase in BrdU+ LT-HSCs compared to WT or single HET controls in both steady state conditions and under transplantation stress. E47HETp21HET HSCs are also more sensitive to mitotoxic challenge with 5-FU resulting in a 45% decrease in HSC numbers compared to treated controls. In serial adoptive transfer assays, a rigorous challenge to HSC self-renewal, E47HETp21HET HSCs were decreased by 40% and 60% in secondary and tertiary recipients, respectively. In addition to hyperproliferation and poor self-renewal, E47HETp21HET adoptive transfer recipients had selective myeloid bias indicating HSC skewing. Together, these data suggest a developmental stage-specific, cell-intrinsic collaboration between E47 and p21 in the regulation of LT- HSC competence in vivo.