Link Capacity Research Articles

Gain Clamped Bi-Doped Fiber Amplifier With 150 nm Bandwidth for O- and E-Bands

Global data traffic is continuously growing year by year. In this regard, telecom companies faced the problem of increasing data transmission rate, which is becoming more and more challenging. One of options that could help to increase optical links capacity is an expansion of the spectral range of DWDM systems used in telecom by inclusion of the O-band and/or the E-band. An ability to engage these spectral ranges directly related to the presence of suitable effective optical amplifiers. In this work, we studied different modifications of Bi-doped fiber amplifier operating in the O- and E-bands in order to obtain the widest gain spectrum in a single device. In particular, one- and two-wavelength pumping and gain-clamped schemes, as well as usage of a Bi:P<inline-formula><tex-math notation="LaTeX">$_\text {2}$</tex-math></inline-formula>O<inline-formula><tex-math notation="LaTeX">$_\text {5}$</tex-math></inline-formula>-SiO<inline-formula><tex-math notation="LaTeX">$_\text {2}$</tex-math></inline-formula> and Bi:GeO<inline-formula><tex-math notation="LaTeX">$_\text {2}$</tex-math></inline-formula>-SiO<inline-formula><tex-math notation="LaTeX">$_\text {2}$</tex-math></inline-formula> fibers combination, were considered. As a result, an amplifier with 150 nm &#x2013;6 dB bandwidth, <inline-formula><tex-math notation="LaTeX">$&gt;$</tex-math></inline-formula>25 dB peak gain operating in the range from <inline-formula><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula>1300 to <inline-formula><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula>1450 nm was developed. To achieve the highest spectral width, we compare a gain-clamped at 1280 nm cavity pumped at 1180 nm with dual pump scheme at 1180 nm and 1270 nm along with a combination of active media composed of Bi:P<inline-formula><tex-math notation="LaTeX">$_\text {2}$</tex-math></inline-formula>O<inline-formula><tex-math notation="LaTeX">$_\text {5}$</tex-math></inline-formula>-SiO<inline-formula><tex-math notation="LaTeX">$_\text {2}$</tex-math></inline-formula> and Bi:GeO<inline-formula><tex-math notation="LaTeX">$_\text {2}$</tex-math></inline-formula>-SiO<inline-formula><tex-math notation="LaTeX">$_\text {2}$</tex-math></inline-formula> fibers.

Improving Efficiency in Congested Traffic Networks: Pareto-Improving Reservations through Agent-Based Timetabling

In an urban transportation network, congestion occurs in the form of a queue behind a bottleneck. Many studies have considered a reservation-based optimization approach for queuing systems. To control the traffic density behind a bottleneck so that it does not exceed the link capacity, and to reduce the emissions and improve the sustainability of cities, we propose a new mobility service system to offer a Pareto-improving schedule for both the portion of agents making reservations and others with fixed departure time schedules. This reservation system takes the agents’ (i.e., users or vehicles here) actual arrival and departure times from a conventional system without reservations as the preferred time windows at both the origins and destinations. Such a centralized mobility service system could maintain or improve the end-to-end traveling performance for all users. The proposed reservation and end-to-end timetabling problem is formulated as a multicommodity flow optimization problem in a discretized space–time network. We use a modified dynamic programming method for the reservation strategy on the space–time network and further adopt the alternative direction method of multiplier (ADMM) based on prime and dual theory to solve the large-scale instances. A comprehensive discussion is also provided regarding the technical challenges and potential solutions when operating such a system in a real-world setting.

An Optimization method for the Internet of vehicles oriented to moving relay

Moving relay (MR) is a relay node deployed on public transportation such as cars and trains, which can effectively combat the vehicle penetration loss (VPL) problem in vehicle communication. outage probability (OP) is an expression of link capacity. When the link capacity cannot meet the required user rate, an outage will occur. For the downlink multi-user network, we compared the performance of direct transmission and MR-assisted transmission with the probability of interruption as a performance indicator. Subsequently, we design a joint optimization scheme for transmission mode selection and user scheduling, select the transmission mode suitable for the user, schedule the user with the largest information rate, and derive the closed-form expression of the scheduling scheme. And compared with random selection scheduling. The experiment compares random scheduling with the scheduling scheme we proposed. Experimental results show that compared with random selection and scheduling scheme, the proposed scheduling scheme can reduce OP, thereby improving system performance.

Intra-Data Centre Flexible PAM Transmission System Using an Integrated InP-Si3N4 Dual Laser Module

Flexible Pulse Amplitude Modulation (FlexPAM) consists of the use of non-standard PAM formats, such as PAM-5 or PAM-6, to increase the granularity of the link capacity for a given baud rate. In this paper, we demonstrate FlexPAM systems as a scalable solution for future data center interconnects, introduce a symbol-to-bit mapping that minimizes the effect of intensity noise in the performance of non-power of two number of levels formats, and present experimental and simulation results of an unamplified FlexPAM transmission system over 1 km of single-mode fiber. 20 GBaud transmission was successfully demonstrated experimentally for modulation formats ranging from OOK up to PAM-16 using an integrated InP-Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> laser. In addition, a simulation to closely replicate the experiment was used to determine the system requirements to achieve transmission rates of up to 200 Gbps on a single wavelength, at a baud rate of 53.5 Gbaud with component bandwidth limitations of 30 GHz.

Performance evaluation of wireless local area network with congested fading channels

The IEEE 802.11ay wireless communication standard consents gadgets to link in the spectrum of millimeter wave (mm-Wave) 60 Giga Hertz band through 100 Gbps bandwidth. The development of promising high bandwidth in communication networks is a must as QoS, throughput and error rates of bandwidth-intensive applications like merged reality (MR), artificial intelligence (AI) related apps or wireless communication boggling exceed the extent of the chronic 802.11 standard established in 2012. Thus, the IEEE 802.11ay task group committee has newly amended recent physical (PHY) and medium access control (MAC) blueprints to guarantee a technical achievement especially in link delay on multipath fading channels (MPFC). However, due to the congestion of super bandwidth intensive apps such as IoT and big data, we propose to diversify a propagation delay to practical extension. This article then focuses on a real-world situation and how the IEEE 802.11ay design is affected by the performance of mm-Wave propagation. In specific, we randomize the unstable MPFC link capacity by taking the divergence of congested network parameters into account. The efficiency of congested MPFC-based wireless network is simulated and confirmed by advancements described in the standard.

Interaction of flange and web slenderness, overstrength factor and proposed stiffener arrangements for long links

This paper is aimed to investigate the interaction of flange and web slenderness ratio, overstrength factor and also to improve the behavior of long links. Pursuant to these goals, 150 numerical models of different long links were developed and exposed to cyclic loading protocol mandated by AISC 341. Link length ratio, flange and web slenderness and stiffener configurations are selected as parameters. The results revealed that the flange slenderness ratio can be relaxed to 0.38(E/Fy)0.5 for long links if the web slenderness ratio is <1.5 (E/Fy)0.5. The shear capacity of long links decreases as the link length ratio increases. The results of shear capacity showed the overstrength factor required by AISC 341 overestimates the shear capacity; therefore, two different equations to predict the overstrength factor for long links are proposed. The stiffener configuration recommended by AISC 341 limits the potential of long links. To mitigate this drawback, different stiffener configurations are proposed to empower the behavior of long links. Using additional one stiffener at each link ends can enhance shear strength, energy dissipation and plastic rotation capacities by 25%, 447% and 322%, respectively. When two additional stiffeners are introduced, these ratios modify to 29%, 479% and 332%. Moreover, rupture index values are utilized to verify proposed stiffener configurations further.

Resilient Transportation Network Design under Uncertain Link Capacity Using a Trilevel Optimization Model

This study addresses uncertainty in a transportation network by proposing a trilevel optimization model, which improves resiliency against uncertain disruptions. The goal is to minimize the total travel time by designing a resilient transportation network under uncertain disruptions and deterministic origin-destination demands. The trilevel optimization model has three levels. The lower level determines the network flow, and the middle level assesses the network’s resiliency by identifying the worst-case scenario disruptions that could lead to maximal travel time. The upper-level takes the system perspective to expand the existing transportation network to enhance resiliency. We also propose a formulation for the network flow problem to significantly reduce the number of variables and constraints. Two algorithms have been developed to solve the trilevel model. The results of solving the highway network in Iowa show that the trilevel optimization model improves the total travel time by an average of 41%.

Reliable auxiliary communication of UAV via relay cache optimization

With the continuous reduction of drone costs and the miniaturization of equipment, many new applications have emerged in the civil and commercial fields. The remote sensing technology of Unmanned Aerial Vehicle (UAV) is used to manage and partition farmland accurately. Compared with the traditional field grid sampling method, UAV remote sensing technology can break through operating conditions, continuously collect data at low altitudes, monitor the area more flexibly, and significantly reduce labor and safety costs. Since UAVs can only provide data transmission services to users through wireless backhaul links established with ground base stations, the need to access the network is easy to lead to the disclosure of user privacy. The capacity of wireless backhaul links is limited, limiting the transmission rate of drones and reducing the user’s quality of service. Therefore, we apply edge caching technology to the assisted relay communication network to study the impact of caching technology on the performance of mobile relay systems. In particular, we propose the horizontal position design method in the buffer auxiliary relay single-user system, and the 3D position design method in the buffer auxiliary relay multi-user system. Position system, which can be reached by the maximum system average and the optimal speed, is designed. Besides, with the help of objective function conversion and classic derivation analysis method, the semi-closed expression of the optimal position of the UAV is obtained, and the intersection of the mobile relay end velocity and the user end velocity is used as the initial value. Meanwhile, the solution formula is substituted after continuous iteration so that the best advantage of local velocity can be obtained. In addition, mobile relay system is deployed to establish a two-hop wireless link to achieve reliable communication between Base Station (BS) and users security trust. The simulation experiment proves that compared with other methods, the method proposed in this paper has considerable performance improvement in power convergence, speed, trajectory path loss, and energy cost, which can provide higher-quality communication services for users in the system and better support for the broad application of drones.

Identifying critical links using network capacity-based indicator in multi-modal transportation networks

This article aims to develop a new link criticality indictor based on the network capacity concept of a multimodal transportation network. Model formulation and solution algorithm are developed for this multimodal transportation network capacity problem. To improve the efficiency, a sensitivity-based approximation approach is also developed to avoid the need to repeatedly solve the bi-level network capacity problem for each disrupted link as in the typical network scanning approach. Numerical experiments are conducted and compared to the traditional efficiency-based criticality indicator. The findings reveal the proposed network capacity-based indicator indeed is more useful than the efficiency-based indicator when the link capacity limit is violated in the degraded network.

Weigh-in-Motion: Lightweight Real-Time Identification of Gbps Wireless Traffic.

Distinguishing between wireless and wired traffic in a network middlebox is an essential ingredient for numerous applications including security monitoring and quality-of-service (QoS) provisioning. The majority of existing approaches have exploited the greater delay statistics, such as round-trip-time and inter-packet arrival time, observed in wireless traffic to infer whether the traffic is originated from Ethernet (i.e., wired) or Wi-Fi (i.e., wireless) based on the assumption that the capacity of the wireless link is much slower than that of the wired link. However, this underlying assumption is no longer valid due to increases in wireless data rates over Gbps enabled by recent Wi-Fi technologies such as 802.11ac/ax. In this paper, we revisit the problem of identifying Wi-Fi traffic in network middleboxes as the wireless link capacity approaches the capacity of the wired. We present Weigh-in-Motion, a lightweight online detection scheme, that analyzes the traffic patterns observed at the middleboxes and infers whether the traffic is originated from high-speed Wi-Fi devices. To this end, we introduce the concept of ACKBunch that captures the unique characteristics of high-speed Wi-Fi, which is further utilized to distinguish whether the observed traffic is originated from a wired or wireless device. The effectiveness of the proposed scheme is evaluated via extensive real experiments, demonstrating its capability of accurately identifying wireless traffic from/to Gigabit 802.11 devices.

Popularity-Guided Cost Optimization for Live Streaming in Mobile Edge Computing

Live streaming service usually delivers the content in mobile edge computing (MEC) to reduce the network latency and save the backhaul capacity. Considering the limited resources, it is necessary that MEC servers collaborate with each other and form an overlay to realize more efficient delivery. The critical challenge is how to optimize the topology among the servers and allocate the link capacity so that the cost will be lower with delay constraints. Previous approaches rarely consider server collaborations for live streaming service, and the scheduling delay is usually ignored in MEC, leading to suboptimal performances. In this paper, we propose a popularity-guided overlay model which takes the scheduling delay into consideration and utilizes MEC collaboration to achieve efficient live streaming service. The links and servers are shared among all channel streams and each stream is pushed from cloud servers to MEC servers via the trees. Considering the optimization problem is NP-hard, we propose an effective optimization framework called cost optimization for live streaming (COLS) to predict the channel popularity by a LSTM model with multiscale input data. Finally, we compute topology graph by greedy scheme and allocate the capacity with convex programming. Experimental results show that the proposed approach achieves higher prediction accuracy, reducing the capacity cost by more than 40% with an acceptable delay compared with state-of-the-art schemes.

Backhaul-Aware Drone Base Station Placement and Resource Management for Fso Based Drone Assisted Mobile Networks

In drone assisted mobile networks, drones mounted small cell base stations (DBSs) are responsively and flexibly deployed over any Places of Interest (PoI), such as sporadic hotspots and disaster-struck areas, where the existing mobile network infrastructure is unable to provide wireless coverage. Here, a DBS is a relay node to relay traffic between a nearby macro base station (MBS) and the users. In addition, Free-space optics (FSO) is applied as the backhauling solution to significantly increase the capacity of the backhaul link between an MBS and a DBS in a drone assisted mobile network. Most of the existing DBS placement solutions assume the FSO based backhaul link provides sufficient link capacity, which may not be true, especially when a DBS is placed far away from an MBS (e.g., > 10 km in disaster-struck areas) or in a bad weather condition. In this paper, we formulate a problem to jointly optimize bandwidth allocation and DBS placement by considering the FSO based backhaul link capacity constraint. A Backhaul awaRe bandwidth allOcAtion and DBS placement (BROAD) algorithm is designed to efficiently solve the problem, and the performance of the algorithm is demonstrated via extensive simulations.

Self-Explanation and Empty-Base Explanation

AbstractThis paper explores a novel notion of self-explanation that combines ideas from two sources: (1) the tripartite account of explanation, according to which a proposition can help explain another either in the capacity of a reason why the latter obtains or in the capacity of an explanatory link, and (2) the notion of an empty-base explanation, which generalizes the ideas of explanation by zero-grounding and explanation by status. After having introduced these ideas and the novel notion of self-explanation, I argue that the latter has the potential to resist extant arguments against the possibility of self-explanation. In the remainder of the paper, I discuss candidates for such self-explanatory propositions and suggest possible applications for Humeanism about laws of nature, the debate on the grounds of ground, the rationalist tradition, and philosophical theology.

Secure Mobile Edge Computing Networks in the Presence of Multiple Eavesdroppers

In this paper, we investigate a secure mobile edge computing (MEC) network in the presence of multiple eavesdroppers, where multiple users can offload parts of their tasks to the computational access point (CAP). The multiple eavesdroppers may overhear the confidential task offloading, which leads to information leakage. In order to address this issue, we present the minimization problem of the secrecy outage probability (SOP), by jointly taking into account the constraints from the latency and energy consumption. With the aim to improve the system secrecy performance, we then introduce three user selection criteria to choose the best user among multiple ones. Specifically, <i>criterion I</i> maximizes the locally computational capacity, while <i>criterion II</i> and <i>III</i> maximize the secrecy capacity and data rate of main links, respectively. For these criteria, we further analyze the system secrecy performance by deriving analytical and asymptotic expressions for the SOP, from which we can conclude important insights for the system design. Finally, simulation and analytical results are provided to verify the proposed analysis. The results show that the three criteria can efficiently safeguard the MEC networks, compared to the traditional local computing and fully offloading, especially with a large value of user number.

Optical multiplexing techniques and their marriage for on-chip and optical fiber communication: a review

Herein, an attention-grabbing and up-to-date review related to major multiplexing techniques is presented which includes wavelength division multiplexing (WDM), polarization division multiplexing (PDM), space division multiplexing (SDM), mode division multiplexing (MDM) and orbital angular momentum multiplexing (OAMM). Multiplexing is a mechanism by which multiple signals are combined into a shared channel used to showcase the maximum capacity of the optical links. However, it is critical to develop hybrid multiplexing methods to allow enhanced channel numbers. In this review, we have also included hybrid multiplexing techniques such as WDM-PDM, WDM-MDM and PDM-MDM. It is probable to attain <italic>N</italic>×<italic>M</italic> channels by utilizing <italic>N</italic> wavelengths and <italic>M</italic> guided-modes by simply utilizing hybrid WDM-MDM (de)multiplexers. To the best of our knowledge, this review paper is one of its kind which has highlighted the most prominent and recent signs of progress in multiplexing techniques in one place.

Blockage-Aware Flow Control in E-UTRA-NR Dual Connectivity for QoS Enhancement

Millimeter-wave (mmWave) communication included in new radio (NR) provides high throughput to meet the stringent requirements of modern applications. However, its performance is highly dependent on whether obstacles are blocking line-of-sight (LOS) paths. Blockages on the LOS paths jeopardize reliable connections. E-UTRA-NR dual connectivity (EN-DC) is one option for managing unstable connectivity using robust long-term evolution (LTE) as well as mmWave NR. EN-DC aggregates and utilizes multiple links to provide a better quality of service (QoS) to users. However, the performance of EN-DC is strongly affected by flow control due to the possibility of out-of-order packet delivery at the packet data convergence protocol (PDCP) layer. In this paper, we propose a blockage-aware flow control scheme (BAFC) that appropriately responds to the dynamics of mmWave links in the presence of mobile blockages and improves users&#x2019; QoS. To this end, we also develop PDCP scheduling schemes that satisfy various users&#x2019; QoS requirements. Through extensive simulations, we verify that BAFC exploits over 99% of the sum capacity of links on average under rapidly changing channels due to mobile blockages. Moreover, BAFC combined with PDCP scheduling achieves higher throughput or reduces latency by up to 43.9% with minimal throughput degradation.

DTN Architecture With Resource-Aware Rate Adaptation for Multiple Bundle Transmission in InterPlanetary Networks

The world of telecommunications, from some years, is revitalizing an high interest to Deep Space Communication (DSC) and Delay Tolerant Network (DTN) architecture as enabling technologies to offer internet services for aerospace vehicles or orbital stations. The communications between the planets in the solar system is well known to present a series of problems that need to be faced. The fundamental challenge with InterPlanetary Communication (IPC) is the intermittent Line of Sight (LoS) caused by planets movement and the significant propagation time. A possible way to face with it is the use of a DTN approach where routers use a store-and-forward transmission in a hop-by-hop message exchange mechanism. Thanks to this approach, it is possible to face many issues related to the transport layer. The main contribution of this work concerns the proposal of a bundle management layer able to assign at the receiver the appropriate bundle rate on the basis of concurrent bundle transmissions, the output link capacity and buffer resources. The proposed strategy can be integrated with a routing algorithm for InterPlanetary Networks (IPNs) and DTN networks. In our case we consider the Earliest Arrival Optimal Delivery Ratio (EAODR) routing that applies a modified temporal graph to select the IPN nodes. Performance evaluation have been led out to show the benefits of our proposal on the single links and also on the routing scheme in terms of bundle delivery ratio and average bundle delivery time.

CAPTON—Centralized All-Path Transmission for Over-Subscribed Datacenter Networks

This work addresses an often-overlooked challenge in designing datacenter traffic control schemes. Specifically, most existing schemes were designed for network topologies with non-blocking network core. While this enabled the development of elegant solutions, core networks in practice are more likely to be <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">over-subscribed</i> by the access layer network due to cost considerations. Consequently, existing traffic control schemes may perform sub-optimally in real-world over-subscribed datacenter networks. This work proposes a new centralized flow-based scheduling scheme called CAPTON which schedules flow according to remaining flow size and link capacities to avoid congestion in over-subscribed networks. CAPTON employs all-path transmission to exploit all available paths and redundant links between source and destination hosts to maximize resource utilization and eliminate the need for routing. Unlike switch-based approaches, CAPTON does not require additional support from network switches and thus can be readily deployed in current datacenters equipped with commodity switches.

Channel Assignment Based on CSMA-Aware Interference Model With Overlapped Channels in Multiradio Multichannel Wireless Mesh Networks

Multi-radio Multi-channel Wireless Mesh Networks (MRMC WMNs) implemented on IEEE 802.11 standards are widely used owing to their adaptability in practical network scenarios. The channel assignment problem in MRMC WMNs has been extensively studied. However, in most of the existing works, only orthogonal wireless channels are considered owing to the complexity of the channel assignment problem, which results in a low level of spatial utilization. This paper introduces partially overlapping channels into the CSMA-aware interference and shared link capacity models to fully exploit the spectrum resource and improve network capacity, utilizing both orthogonal channels and partially overlapping channels in IEEE 802.11 2.4 GHz bands. We formulate this problem as a mixed-integer linear program (MILP). We propose a traffic-demand-aware collision-free partially overlapping channel assignment (TAC-POCA), which uses all the available channels and achieves collision-free end-to-end flow transmissions to attain load balance. Simulation results show that TAC-POCA leads to better utilization of the spectrum resource and throughput improvement in both grid and random topology networks than in the case of using only orthogonal channels.

User Rate Optimization for Fronthaul-Constrained Cell-Free Massive MIMO-OFDM Systems: A Quadratic Transform-Based Approach

As a promising candidate for the future generations of mobile communication networks, the cell-free (CF) massive multiple-input multiple-output (mMIMO) networks have been shown to provide high spectral efficiency (SE) and more uniform signal coverage than cellular mMIMO networks, enabling smart cities more diverse application services. The fronthaul link in such networks, defined as the transmission link between the central processing unit and the access point, requires a high capacity, but is often constrained. Hence, the optimization of the user rate under the limited capacity of fronthaul is the key problem to be solved in a CF networks. In this paper, we consider the downlink transmission of CF mMIMO orthogonal frequency division multiplexing (OFDM) systems with constrained transmit power and fronthaul capacity. Based on the min-max and sum-max principles, quadratic transform-min max (QT-MM) and quadratic transform-sum max (QT-SM) optimization algorithms are proposed, respectively. Simulation results show that compared with the weighted minimum mean square error (WMMSE) algorithm, both of the proposed algorithms can effectively prevent very low user rates when the fronthaul capacity is limited. When the fronthaul link capacity constraint is high, the QT-SM algorithm has better rate performance than the distributed WMMSE-d algorithm and the centralized WMMSE-c algorithm.