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In this article, we propose a medium access control (MAC) scheme, called STation pREsence-Aware MAC (STREAM), that offers equal contention opportunities to the stations in a network. STREAM is designed to preserve its performance in crowded and high-traffic networks. The scheme improves channel access, utilization, and service fairness of stations. STREAM detects collided transmissions or idle events in the network to estimate the number of active stations. STREAM sets the contention period as a function of the number of stations in the network. As a result, the number of contention opportunities is enlarged and the access to the transmission channel in the network is improved. In this way, STREAM overcomes the performance degradation of IEEE 802.11 under heavy traffic and crowded networks. We analyze the throughput of STREAM, fairness of service, and the probability that a station experiences collisions as a function of the number of stations in the network. We also present performance evaluations and comparisons with IEEE 802.11 and other high-performing schemes. We extend the application of STREAM on traffic with different priorities and quality of service. Our evaluations show that STREAM outperforms IEEE 802.11 and the compared schemes. We show that STREAM is an ideal candidate as a fallback mechanism for IEEE 802.11 under overwhelming conditions.
Paa Kwesi Esubonteng; Roberto Rojas-Cessa. STREAM: Medium Access Control With Station Presence Awareness in Crowded Networks. IEEE Systems Journal 2021, PP, 1 -10.
AMA StylePaa Kwesi Esubonteng, Roberto Rojas-Cessa. STREAM: Medium Access Control With Station Presence Awareness in Crowded Networks. IEEE Systems Journal. 2021; PP (99):1-10.
Chicago/Turabian StylePaa Kwesi Esubonteng; Roberto Rojas-Cessa. 2021. "STREAM: Medium Access Control With Station Presence Awareness in Crowded Networks." IEEE Systems Journal PP, no. 99: 1-10.
The United States Centers for Disease Control and Prevention considers saliva contact the lead transmission mean of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes the coronavirus disease 2019 (COVID-19). Saliva droplets or aerosols expelled by sneezing, coughing, breathing, and talking may carry this virus. People in close distance may be exposed directly to these droplets or indirectly when touching the droplets that fall on surrounding surfaces and ending up contracting COVID-19 after touching the mucosa tissue of their faces. It is of great interest to quickly and effectively detect the presence of SARS-CoV-2 in an environment, but the existing methods only work in laboratory settings, to the best of our knowledge. However, it may be possible to detect the presence of saliva in the environment and proceed with prevention measures. However, detecting saliva itself has not been documented in the literature. On the other hand, many sensors that detect different organic components in saliva to monitor a person’s health and diagnose different diseases, ranging from diabetes to dental health, have been proposed and they may be used to detect the presence of saliva. This paper surveys sensors that detect organic and inorganic components of human saliva. Humidity sensors are also considered in the detection of saliva because a large portion of saliva is water. Moreover, sensors that detect infectious viruses are also included as they may also be embedded into saliva sensors for a confirmation of the presence of the virus. A classification of sensors by their working principles and the substances they detect is presented, including the sensors’ specifications, sample size, and sensitivity. Indications of which sensors are portable and suitable for field application are presented. This paper also discusses future research and challenges that must be resolved to realize practical saliva sensors. Such sensors may help minimize the spread of not only COVID-19 but also other infectious diseases.
Priya Dave; Roberto Rojas-Cessa; Ziqian Dong; Vatcharapan Umpaichitra. Survey of Saliva Components and Virus Sensors for Prevention of COVID-19 and Infectious Diseases. Biosensors 2020, 11, 14 .
AMA StylePriya Dave, Roberto Rojas-Cessa, Ziqian Dong, Vatcharapan Umpaichitra. Survey of Saliva Components and Virus Sensors for Prevention of COVID-19 and Infectious Diseases. Biosensors. 2020; 11 (1):14.
Chicago/Turabian StylePriya Dave; Roberto Rojas-Cessa; Ziqian Dong; Vatcharapan Umpaichitra. 2020. "Survey of Saliva Components and Virus Sensors for Prevention of COVID-19 and Infectious Diseases." Biosensors 11, no. 1: 14.
In this paper, we show a strong correlation between turnstile entries data of the New York City (NYC) subway provided by NYC Metropolitan Transport Authority and COVID-19 deaths and cases reported by the NYC Department of Health from March to May 2020. This correlation is obtained through linear regression and confirmed through the prediction of the number of deaths by a Long Short-Term Memory neural network. The correlation is significantly accentuated through the consideration of incubation and symptomatic phases of this disease as experienced by people who died from it. We extend the analysis to each individual NYC borough. We also estimate the dates when the number of COVID-19 deaths and cases would approach zero by using the Auto-Regressive Integrated Moving Average model on the reported deaths and cases. We also backward forecast the dates when the first cases and deaths may have occurred.
Sina Fathi-Kazerooni; Roberto Rojas-Cessa; Ziqian Dong; Vatcharapan Umpaichitra. Correlation of subway turnstile entries and COVID-19 incidence and deaths in New York City. Infectious Disease Modelling 2020, 6, 183 -194.
AMA StyleSina Fathi-Kazerooni, Roberto Rojas-Cessa, Ziqian Dong, Vatcharapan Umpaichitra. Correlation of subway turnstile entries and COVID-19 incidence and deaths in New York City. Infectious Disease Modelling. 2020; 6 ():183-194.
Chicago/Turabian StyleSina Fathi-Kazerooni; Roberto Rojas-Cessa; Ziqian Dong; Vatcharapan Umpaichitra. 2020. "Correlation of subway turnstile entries and COVID-19 incidence and deaths in New York City." Infectious Disease Modelling 6, no. : 183-194.
Supply chains are challenged with providing transparency and trust among participants and stakeholders and ensuring an efficient operation. However, some of these challenges are difficult to resolve because the records of a supply chain can be altered by its participants. The emergence of blockchain technology has been identified as a promising solution to resolve these challenges. Blockchain is an immutable distributed ledger. Here, we introduce blockchain and survey different blockchain frameworks that have been recently proposed to address some of the supply chain challenges. We describe the operation of these blockchain frameworks and their components. We identify the objectives and motivation in each of the surveyed use cases and highlight the advantages and disadvantages of each adopted framework by different industries. We analyze how the reported blockchain frameworks address supply chain challenges. We present a comparative summary of existing literature on blockchain for supply chain. We also summarize the properties of a blockchain framework for its successful adoption in future supply chains and discuss several challenges and opportunities that remain for future research.
Denisolt Shakhbulatov; Jorge Medina; Ziqian Dong; Roberto Rojas-Cessa. How Blockchain Enhances Supply Chain Management: A Survey. IEEE Open Journal of the Computer Society 2020, 1, 230 -249.
AMA StyleDenisolt Shakhbulatov, Jorge Medina, Ziqian Dong, Roberto Rojas-Cessa. How Blockchain Enhances Supply Chain Management: A Survey. IEEE Open Journal of the Computer Society. 2020; 1 (99):230-249.
Chicago/Turabian StyleDenisolt Shakhbulatov; Jorge Medina; Ziqian Dong; Roberto Rojas-Cessa. 2020. "How Blockchain Enhances Supply Chain Management: A Survey." IEEE Open Journal of the Computer Society 1, no. 99: 230-249.
In this paper, we introduce a novel traffic masking method, called Generative Adversarial Network (GAN) tunnel, to protect the identity of applications that generate network traffic from classification by adversarial Internet traffic classifiers (ITCs). Such ITCs have been used in the past for website fingerprinting and detection of network protocols. Their use is becoming more ubiquitous than before for inferring user information. ITCs based on machine learning can identify user applications by analyzing the statistical features of encrypted packets. Our proposed GAN tunnel generates traffic that mimics a decoy application and encapsulates actual user traffic in the GAN-generated traffic to prevent classification from adversarial ITCs. We show that the statistical distributions of the generated traffic features closely resemble those of the actual network traffic. Therefore, the actual user applications and information associated with the user remain anonymous. We test the GAN tunnel traffic against high-performing ITCs, such as Random Forest and eXtreme Gradient Boosting (XGBoost), and we show that the GAN tunnel protects the identity of the source applications effectively.
Sina Fathi-Kazerooni; Roberto Rojas-Cessa. GAN Tunnel: Network Traffic Steganography by Using GANs to Counter Internet Traffic Classifiers. IEEE Access 2020, 8, 125345 -125359.
AMA StyleSina Fathi-Kazerooni, Roberto Rojas-Cessa. GAN Tunnel: Network Traffic Steganography by Using GANs to Counter Internet Traffic Classifiers. IEEE Access. 2020; 8 ():125345-125359.
Chicago/Turabian StyleSina Fathi-Kazerooni; Roberto Rojas-Cessa. 2020. "GAN Tunnel: Network Traffic Steganography by Using GANs to Counter Internet Traffic Classifiers." IEEE Access 8, no. : 125345-125359.
In a digital microgrid (DMG), different from an analogous microgrid, energy is transmitted in well-defined amounts and in a store-and-forward fashion. Nodes of a DMG network, or energy packet switches (EPSs), use supercapacitors as temporary energy storage units to control the amount of energy supplied to a load. An EPS aggregates energy coming from different inputs or sources and forwards it to other EPSs or to a load. Rather than referring to electrical power, we measure the delivery of it as energy. An EPS is built with many supercapacitors to be able to provide significant amounts of energy to one or multiple loads. An EPS dedicates a configurable number of supercapacitors to an energy flow. In this paper, we find the conditions to achieve the smallest energy loss in the supply of energy from energy sources to loads in a DMG and propose a routing algorithm to find a path with small capacitance in a DMG network built with store-and-forward energy nodes. In addition, because an EPS has a finite amount of capacitance, the number of flows that the DMG can sustain may be limited. Exacerbating this problem, the passive transfer of energy between energy units may suffer losses as a result of the capacitance used and energy transmitted between supercapacitors. Therefore, the path between a source and a load has to be carefully selected. To solve this problem, our proposed routing algorithm finds the smallest capacitance paths to enable the scalability of the DMG. We analyze a path of supercapacitor-based networks and underscore the conditions to achieve minimal energy losses, to minimize the path capacitance, and to balance these two conflicting objectives. We analyze these approaches and show numerical examples on a small power network. Results show that total energy loss in this DMG is path independent as this loss depends on only the voltage of the capacitors at Node 1; the node connected to the source. In addition, results show that by adopting the proposed algorithm, the scalability of the DMG can be increased by finding the smallest capacitance paths to transfer energy between the sources and the loads. We show how store-and-forward transfer works on an actual DMG testbed with two EPSs and two loads.
Zhengqi Jiang; Roberto Rojas-Cessa. Finding Efficient and Lower Capacitance Paths for the Transfer of Energy in a Digital Microgrid. Electronics 2020, 9, 822 .
AMA StyleZhengqi Jiang, Roberto Rojas-Cessa. Finding Efficient and Lower Capacitance Paths for the Transfer of Energy in a Digital Microgrid. Electronics. 2020; 9 (5):822.
Chicago/Turabian StyleZhengqi Jiang; Roberto Rojas-Cessa. 2020. "Finding Efficient and Lower Capacitance Paths for the Transfer of Energy in a Digital Microgrid." Electronics 9, no. 5: 822.
Determining the qualitative states of the Internet requires an accurate knowledge of queueing delay over an end-to-end path. However, the measurement of queueing delay in a large network is still considered a complex and open problem. Existing schemes that measure queueing delay compensate for this complexity using a high infrastructural support and administrative access to the path under test even though their feasibility and accuracy on the Internet are low. In this paper, we propose an active scheme, called COMPRESS: COMpound Probe compRESSion, to measure queueing delay on all routers over an end-to-end path. The proposed scheme performs per-hop measurement using UDP-based probing packets. It is both simple and self-sufficient in comparison to the existing schemes. We have implemented the proposed scheme in a simulation environment to present a controlled performance evaluation under different levels (e.g., light, moderate, and heavy) and types (e.g., symmetric and asymmetric) of queueing delays over single- and multiple-hop paths. Our simulation results show that the scheme is sensitive to the induced queueing delays and consistently provides a high measurement accuracy. Overall, the scheme has an average measurement error of around 20% or below over the simulated paths.
Khondaker M. Salehin; Ki Won Kwon; Roberto Rojas-Cessa. A Simulation Study of the Measurement of Queueing Delay Over End-to-End Paths. IEEE Open Journal of the Computer Society 2020, 1, 1 -11.
AMA StyleKhondaker M. Salehin, Ki Won Kwon, Roberto Rojas-Cessa. A Simulation Study of the Measurement of Queueing Delay Over End-to-End Paths. IEEE Open Journal of the Computer Society. 2020; 1 (99):1-11.
Chicago/Turabian StyleKhondaker M. Salehin; Ki Won Kwon; Roberto Rojas-Cessa. 2020. "A Simulation Study of the Measurement of Queueing Delay Over End-to-End Paths." IEEE Open Journal of the Computer Society 1, no. 99: 1-11.
In this paper, we propose the greedy smallest-cost-rate path first (GRASP) algorithm to route power from sources to loads in a digital microgrid (DMG). Routing of power from distributed energy resources (DERs) to loads of a DMG comprises matching loads to DERs and the selection of the smallest-cost-rate path from a load to its supplying DERs. In such a microgrid, one DER may supply power to one or many loads, and one or many DERs may supply the power requested by a load. Because the optimal method is NP-hard, GRASP addresses this high complexity by using heuristics to match sources and loads and to select the smallest-cost-rate paths in the DMG. We compare the cost achieved by GRASP and an optimal method based on integer linear programming on different IEEE test feeders and other test networks. The comparison shows the trade-offs between lowering complexity and achieving optimal-cost paths. The results show that the cost incurred by GRASP approaches that of the optimal solution by small margins. In the adopted networks, GRASP trades its lower complexity for up to 18% higher costs than those achieved by the optimal solution.
Zhengqi Jiang; Vinit Sahasrabudhe; Ahmed Mohamed; Haim Grebel; Roberto Rojas-Cessa. Greedy Algorithm for Minimizing the Cost of Routing Power on a Digital Microgrid. Energies 2019, 12, 3076 .
AMA StyleZhengqi Jiang, Vinit Sahasrabudhe, Ahmed Mohamed, Haim Grebel, Roberto Rojas-Cessa. Greedy Algorithm for Minimizing the Cost of Routing Power on a Digital Microgrid. Energies. 2019; 12 (16):3076.
Chicago/Turabian StyleZhengqi Jiang; Vinit Sahasrabudhe; Ahmed Mohamed; Haim Grebel; Roberto Rojas-Cessa. 2019. "Greedy Algorithm for Minimizing the Cost of Routing Power on a Digital Microgrid." Energies 12, no. 16: 3076.
We propose a three-stage load balancing packet switch and its configuration scheme. The inputand central-stage switches are bufferless crossbars, and the output-stage switches are buffered crossbars. We call this switch ThRee-stage Clos-network swItch with queues at the middle stage and DEtermiNisTic scheduling (TRIDENT), and the switch is cell based. The proposed configuration scheme uses predetermined and periodic interconnection patterns in the input and central modules to load-balance and route traffic, therefore; it has low configuration complexity. The operation of the switch includes a mechanism applied at input and output modules to forward cells in sequence. TRIDENT achieves 100% throughput under uniform and nonuniform admissible traffic with independent and identical distributions (i.i.d.). The switch achieves this high performance without resorting to central-stage expansion nor memory speedup. Our discussion includes throughput and in-order forwarding analysis and performance simulation under uniform and nonuniform i.i.d. traffic.
Oladele Theophilus Sule; Roberto Rojas-Cessa. TRIDENT: A Load-Balancing Clos-Network Packet Switch With Queues Between Input and Central Stages and In-Order Forwarding. IEEE Transactions on Communications 2019, 67, 6885 -6896.
AMA StyleOladele Theophilus Sule, Roberto Rojas-Cessa. TRIDENT: A Load-Balancing Clos-Network Packet Switch With Queues Between Input and Central Stages and In-Order Forwarding. IEEE Transactions on Communications. 2019; 67 (10):6885-6896.
Chicago/Turabian StyleOladele Theophilus Sule; Roberto Rojas-Cessa. 2019. "TRIDENT: A Load-Balancing Clos-Network Packet Switch With Queues Between Input and Central Stages and In-Order Forwarding." IEEE Transactions on Communications 67, no. 10: 6885-6896.
In this letter, we propose a novel indirect diffused light free-space optical communications (ID-FSOC) system based on laser light. This ID-FSOC system aims to provide highspeed (i.e., ≥ 1 Gbps) Internet access to vehicles. This approach extends the FSOC reach to locations that are out-of-sight from the transmitter. The proposed communications system employs diffuse reflectors (DRs) to uniformly emit diffused incident laser light to all directions, except towards the DR, which enable the receivers to receive the diffused light despite having no direct LOS to the transmitter but only having direct LOS to the DR. In our approach, the LOS is required between the transmitter and the DR and between the receiver and the DR. We model the received power of the diffused light and estimate the power and bit error rate as perceived by a moving vehicle. Furthermore, we introduce possible operation modes to realize full duplex communications with ID-FSOC. Our results show the relationship between the transmission power and the DRreceiver distance and show that high data rates are achievable on practical DR-receiver distances.
Yagiz Kaymak; Sina Fathi-Kazerooni; Roberto Rojas-Cessa. Indirect Diffused Light Free-Space Optical Communications for Vehicular Networks. IEEE Communications Letters 2019, 23, 814 -817.
AMA StyleYagiz Kaymak, Sina Fathi-Kazerooni, Roberto Rojas-Cessa. Indirect Diffused Light Free-Space Optical Communications for Vehicular Networks. IEEE Communications Letters. 2019; 23 (5):814-817.
Chicago/Turabian StyleYagiz Kaymak; Sina Fathi-Kazerooni; Roberto Rojas-Cessa. 2019. "Indirect Diffused Light Free-Space Optical Communications for Vehicular Networks." IEEE Communications Letters 23, no. 5: 814-817.
In this paper, we propose an adaptive beam that adapts its divergence angle according to the receiver aperture diameter and the communication distance to improve the received power and ease the alignment between the communicating optical transceivers in a free-space optical communications (FSOC) system for high-speed trains (HSTs). We compare the received power, signal-to-noise ratio, bit error rate, and the maximum communication distance of the proposed adaptive beam with a beam that uses a fixed divergence angle of 1 mrad. The proposed adaptive beam yields a higher received power with an increase of 33 dB in average over the fixed-divergence beam under varying visibility conditions and distance. Moreover, the proposed adaptive divergence angle extends the communication distance of a FSOC system for HSTs to about three times under different visibility conditions as compared to a fixed divergence beam. We also propose a new ground transceiver placement that places the ground transceivers of a FSOC system for HSTs on gantries placed above the train passage instead of placing them next to track. The proposed transceiver placement provides a received-power increase of 3.8 dB in average over the conventional placement of ground-station transceivers next to the track.
Yagiz Kaymak; Sina Fathi-Kazerooni; Roberto Rojas-Cessa; Jianghua Feng; Nirwan Ansari; Mengchu Zhou; Tairan Zhang. Beam with Adaptive Divergence Angle in Free-Space Optical Communications for High-Speed Trains. 2018, 1 .
AMA StyleYagiz Kaymak, Sina Fathi-Kazerooni, Roberto Rojas-Cessa, Jianghua Feng, Nirwan Ansari, Mengchu Zhou, Tairan Zhang. Beam with Adaptive Divergence Angle in Free-Space Optical Communications for High-Speed Trains. . 2018; ():1.
Chicago/Turabian StyleYagiz Kaymak; Sina Fathi-Kazerooni; Roberto Rojas-Cessa; Jianghua Feng; Nirwan Ansari; Mengchu Zhou; Tairan Zhang. 2018. "Beam with Adaptive Divergence Angle in Free-Space Optical Communications for High-Speed Trains." , no. : 1.
We propose a configuration scheme for a Load-Balancing Clos-network (LBC) packet switch that has split central modules and buffers in between the split modules. Our split-central-buffered LBC switch is cell-based. The switch has four stages, namely input, central-input, central-output, and output stages. The proposed configuration scheme uses a pre-determined and periodic interconnection pattern in the input and split central modules to load-balance and route traffic. The LBC switch has low configuration complexity. The operation of the switch includes a mechanism applied at input and split-central modules to forward cells in sequence. The switch achieves 100% throughput under uniform and nonuniform admissible traffic with independent and identical distributions (i.i.d.). These high switching performance and low complexity are achieved while performing in-sequence forwarding and without resorting to memory speedup or central-stage expansion. Our discussion includes throughput analysis, where we describe the operations that the configuration mechanism performs on the traffic traversing the switch, and proof of in-sequence forwarding. A simulation study is presented as a practical demonstration of the switch performance on uniform and nonuniform i.i.d. traffic.
Oladele Theophilus Sule; Roberto Rojas-Cessa; Ziqian Dong; Chuan-Bi Lin. A Split-Central-Buffered Load-Balancing Clos-Network Switch With In-Order Forwarding. IEEE/ACM Transactions on Networking 2018, 27, 467 -476.
AMA StyleOladele Theophilus Sule, Roberto Rojas-Cessa, Ziqian Dong, Chuan-Bi Lin. A Split-Central-Buffered Load-Balancing Clos-Network Switch With In-Order Forwarding. IEEE/ACM Transactions on Networking. 2018; 27 (2):467-476.
Chicago/Turabian StyleOladele Theophilus Sule; Roberto Rojas-Cessa; Ziqian Dong; Chuan-Bi Lin. 2018. "A Split-Central-Buffered Load-Balancing Clos-Network Switch With In-Order Forwarding." IEEE/ACM Transactions on Networking 27, no. 2: 467-476.
The growing deployment and advanced development of high-speed train systems calls for provisioning of broadband Internet services, which cannot be readily provided by the existing radio frequency technology. Thus, an alternative technology, namely, free space optics (FSO), has been proposed to overcome the bandwidth bottleneck problem. However, as each FSO base station (BS) only covers a short length along the track, a large number of BSs are required to realize the seamless coverage, thus incurring high capital expenditures to the railway operator as well as frequent handover processes, which may degrade the system performance. In order to solve this problem, we propose a dual transceivers scheme in a ground-to-train communications system. Since two transceivers of a BS can point to different directions, laser beams of the BS can be transmitted forwardly and backwardly such that the total coverage length of each BS is remarkably extended. Furthermore, the two coverage areas of a BS's transceivers are not contiguous along the track, thus forming a blackout area between them. In this case, two transceivers of a train, which are deployed at the front and back of a train respectively, can cooperate to maintain continuous ground-totrain FSO communications. Therefore, the number of the BSs is reduced and the impact of frequent handovers is alleviated. The performance of the proposed scheme is demonstrated via extensive simulations.
Qiang Fan; Nirwan Ansari; Jianghua Feng; Roberto Rojas-Cessa; Mengchu Zhou; Tairan Zhang. Reducing the Number of FSO Base Stations With Dual Transceivers for Next-Generation Ground-to-Train Communications. IEEE Transactions on Vehicular Technology 2018, 67, 11143 -11153.
AMA StyleQiang Fan, Nirwan Ansari, Jianghua Feng, Roberto Rojas-Cessa, Mengchu Zhou, Tairan Zhang. Reducing the Number of FSO Base Stations With Dual Transceivers for Next-Generation Ground-to-Train Communications. IEEE Transactions on Vehicular Technology. 2018; 67 (11):11143-11153.
Chicago/Turabian StyleQiang Fan; Nirwan Ansari; Jianghua Feng; Roberto Rojas-Cessa; Mengchu Zhou; Tairan Zhang. 2018. "Reducing the Number of FSO Base Stations With Dual Transceivers for Next-Generation Ground-to-Train Communications." IEEE Transactions on Vehicular Technology 67, no. 11: 11143-11153.
This paper presents a comprehensive survey on acquisition, tracking, and pointing (ATP) mechanisms used in free-space optical (FSO) communications systems. ATP mechanisms are a critical component for a wide variety of use cases of mobile FSO communications. ATP mechanisms are used to align FSO transmitter and receiver to attain line-of-sight, which is required for effective operation of FSO communications. Motion is not only associated to mobile stations but also to temporary displacements experienced by stationary FSO terminals, such as in building-to-building FSO communications. The surveyed ATP mechanisms are categorized according to their working principles, use cases, and implementation technology. The advantages and disadvantages of surveyed ATP mechanisms are listed and discussed. We also discuss current challenges and future research directions.
Yagiz Kaymak; Roberto Rojas-Cessa; Jianghua Feng; Nirwan Ansari; Meng Chu Zhou; Tairan Zhang. A Survey on Acquisition, Tracking, and Pointing Mechanisms for Mobile Free-Space Optical Communications. IEEE Communications Surveys & Tutorials 2018, 20, 1104 -1123.
AMA StyleYagiz Kaymak, Roberto Rojas-Cessa, Jianghua Feng, Nirwan Ansari, Meng Chu Zhou, Tairan Zhang. A Survey on Acquisition, Tracking, and Pointing Mechanisms for Mobile Free-Space Optical Communications. IEEE Communications Surveys & Tutorials. 2018; 20 (2):1104-1123.
Chicago/Turabian StyleYagiz Kaymak; Roberto Rojas-Cessa; Jianghua Feng; Nirwan Ansari; Meng Chu Zhou; Tairan Zhang. 2018. "A Survey on Acquisition, Tracking, and Pointing Mechanisms for Mobile Free-Space Optical Communications." IEEE Communications Surveys & Tutorials 20, no. 2: 1104-1123.
In this paper, we propose two different free-space-optics (FSO) coverage models for next-generation high-speed-train communications. To the best of our knowledge, these are the first coverage models proposed for FSO seamless handover. The models provide different coverage areas for performing seamless signal handover and uninterrupted ground-to-train communication. The first model uses two different wavelengths in adjacent covered areas and the second one uses a single wavelength. We find the optimal distance from the train track to a ground base station and the distance between base stations to provide seamless connectivity and handover while minimizing the number of base stations along the track. We base our estimations on a realistic model of an FSO system and provide numerical evaluations demonstrating the performance of the proposed coverage models. We show the different amounts of received power on ground-to-train communications as a function of the location of ground base stations. We also consider the effect of fog on the FSO link as the most attenuating condition for FSO communications. Our results show that communication rates of 1 Gpbs and higher may be achieved with the proposed station positioning and coverage models.
Sina Fathi-Kazerooni; Yagiz Kaymak; Roberto Rojas-Cessa; Jianghua Feng; Nirwan Ansari; Mengchu Zhou; Tairan Zhang. Optimal Positioning of Ground Base Stations in Free-Space Optical Communications for High-Speed Trains. IEEE Transactions on Intelligent Transportation Systems 2017, 19, 1940 -1949.
AMA StyleSina Fathi-Kazerooni, Yagiz Kaymak, Roberto Rojas-Cessa, Jianghua Feng, Nirwan Ansari, Mengchu Zhou, Tairan Zhang. Optimal Positioning of Ground Base Stations in Free-Space Optical Communications for High-Speed Trains. IEEE Transactions on Intelligent Transportation Systems. 2017; 19 (6):1940-1949.
Chicago/Turabian StyleSina Fathi-Kazerooni; Yagiz Kaymak; Roberto Rojas-Cessa; Jianghua Feng; Nirwan Ansari; Mengchu Zhou; Tairan Zhang. 2017. "Optimal Positioning of Ground Base Stations in Free-Space Optical Communications for High-Speed Trains." IEEE Transactions on Intelligent Transportation Systems 19, no. 6: 1940-1949.
The growing deployment and advanced development of high-speed train (HST) systems, coupled with the reliance on and demand for constant Internet connectivity anytime anywhere, have necessitated the imminent provisioning of broadband Internet services in HSTs. Ground-to-train free space optical (FSO) communications suffer from frequent handovers due to high mobility of HSTs, thus shortening the connection time between the train and ground, and greatly impacting passengers' user experience. To provision high-speed Internet services in HSTs, we propose the rotating transceiver scheme to mitigate the impact of handover processes with steerable FSO transceivers in a ground-to-train communications system. Owing to the rotating feature of the scheme, the on-roof transceiver of a train can maintain a reliable link with a base station (BS) for a longer time, and remarkably reduce the number of handover processes, thus provisioning higher data rates of the system. Meanwhile, since the separation distances between BSs are extended, the total number of BSs required to be deployed along the track is also reduced, thus reducing the deployment cost for service providers. Moreover, a new handover method is designed to mitigate the impact of each handover delay, especially on live streaming applications. Finally, the performance improvement of the proposed scheme over the existing fixed transceiver one is demonstrated via simulation results.
Qiang Fan; Mina Taheri; Nirwan Ansari; Jianghua Feng; Roberto Rojas-Cessa; Mengchu Zhou; Tairan Zhang. Reducing the Impact of Handovers in Ground-to-Train Free Space Optical Communications. IEEE Transactions on Vehicular Technology 2017, 67, 1292 -1301.
AMA StyleQiang Fan, Mina Taheri, Nirwan Ansari, Jianghua Feng, Roberto Rojas-Cessa, Mengchu Zhou, Tairan Zhang. Reducing the Impact of Handovers in Ground-to-Train Free Space Optical Communications. IEEE Transactions on Vehicular Technology. 2017; 67 (2):1292-1301.
Chicago/Turabian StyleQiang Fan; Mina Taheri; Nirwan Ansari; Jianghua Feng; Roberto Rojas-Cessa; Mengchu Zhou; Tairan Zhang. 2017. "Reducing the Impact of Handovers in Ground-to-Train Free Space Optical Communications." IEEE Transactions on Vehicular Technology 67, no. 2: 1292-1301.
We overview different alternative energy resources and comment on their benefits and challenges. We highlight some features of alternative and sustainable energy resources and discuss some challenges for their integration into the power grid. In view of global trend toward blending alternatives and conventional energy resources in electrical power grids, a more robust energy distribution approach is necessary. Here, we present an alternative to the power grid with great potential for integrating alternative energy sources and defining microgrids—the Controlled-Delivery Grid (CDG). We comment how this new digital approach enhances the distribution of energy may help to resolve those challenges. We also examine the role of energy storage elements (batteries, super-capacitors), and sustainable energy resources in this new approach to the power grid. We provide some numerical analysis on the performance of energy distribution of the CDG and some experimental results that highlight some of its features. © 2017 American Institute of Chemical Engineers Environ Prog, 2017
Roberto Rojas‐Cessa; Haim Grebel; Zhengqi Jiang; Camila Fukuda; Henrique Pita; Tazima S. Chowdhury; Ziqian Dong; Yu Wan. Integration of alternative energy sources into digital micro‐grids. Environmental Progress & Sustainable Energy 2017, 37, 155 -164.
AMA StyleRoberto Rojas‐Cessa, Haim Grebel, Zhengqi Jiang, Camila Fukuda, Henrique Pita, Tazima S. Chowdhury, Ziqian Dong, Yu Wan. Integration of alternative energy sources into digital micro‐grids. Environmental Progress & Sustainable Energy. 2017; 37 (1):155-164.
Chicago/Turabian StyleRoberto Rojas‐Cessa; Haim Grebel; Zhengqi Jiang; Camila Fukuda; Henrique Pita; Tazima S. Chowdhury; Ziqian Dong; Yu Wan. 2017. "Integration of alternative energy sources into digital micro‐grids." Environmental Progress & Sustainable Energy 37, no. 1: 155-164.
We compare narrow and wide laser beams in a free-space optical (FSO) communications system for high-speed train communications and analyze the tradeoffs among the received power, coverage area, and the complexity of the acquisition-tracking-pointing (ATP) mechanism. We propose to employ a divergence angle of a wide beam in the range [0.07$^{\circ }$, 2.002 $^{\circ }$] to relax the steering speed of the fast steering mirror, which is a major component of the ATP mechanism in an FSO transceiver. In addition, we overcome the negative effects of train vibrations by using a proposed divergence-angle range for a wide beam. The proposed range of divergence angles provides a large link range and effective coverage length, and contact time as compared to a narrow beam.
Yagiz Kaymak; Roberto Rojas-Cessa; Jianghua Feng; Nirwan Ansari; Mengchu Zhou. On Divergence-Angle Efficiency of a Laser Beam in Free-Space Optical Communications for High-Speed Trains. IEEE Transactions on Vehicular Technology 2017, 66, 7677 -7687.
AMA StyleYagiz Kaymak, Roberto Rojas-Cessa, Jianghua Feng, Nirwan Ansari, Mengchu Zhou. On Divergence-Angle Efficiency of a Laser Beam in Free-Space Optical Communications for High-Speed Trains. IEEE Transactions on Vehicular Technology. 2017; 66 (9):7677-7687.
Chicago/Turabian StyleYagiz Kaymak; Roberto Rojas-Cessa; Jianghua Feng; Nirwan Ansari; Mengchu Zhou. 2017. "On Divergence-Angle Efficiency of a Laser Beam in Free-Space Optical Communications for High-Speed Trains." IEEE Transactions on Vehicular Technology 66, no. 9: 7677-7687.
The growing deployment and advanced development of high-speed train (HST) systems, coupled with the reliance on and demand for constant Internet connectivity any time any where, have necessitated the imminent provisioning of broadband Internet services in HSTs. Train-to-ground communications mostly suffers from frequent handoffs due to the high mobility of the trains. To provision high-speed Internet services in HSTs, we propose a novel solution named Free-space OptiCs Utilization in high-Speed trains (FOCUS). Our solution takes advantage of the high optical bandwidth of free space optics (FSO) to provide high data rates. FOCUS aims to improve the trainto- ground communications system by deploying on-roof FSO transceivers. To minimize the number of handoff processes, the control unit inside the train forwards each request to go through the proper transceiver. The proposed mechanism decreases the packet loss ratio and increases network performance in high-speed train communications.
Mina Taheri; Nirwan Ansari; Jianghua Feng; Roberto Rojas-Cessa; Mengchu Zhou. Provisioning Internet Access Using FSO in High-Speed Rail Networks. IEEE Network 2017, 31, 12 -17.
AMA StyleMina Taheri, Nirwan Ansari, Jianghua Feng, Roberto Rojas-Cessa, Mengchu Zhou. Provisioning Internet Access Using FSO in High-Speed Rail Networks. IEEE Network. 2017; 31 (4):12-17.
Chicago/Turabian StyleMina Taheri; Nirwan Ansari; Jianghua Feng; Roberto Rojas-Cessa; Mengchu Zhou. 2017. "Provisioning Internet Access Using FSO in High-Speed Rail Networks." IEEE Network 31, no. 4: 12-17.
Ziqian Dong; Zheng Wang; Wen Xie; Obinna Emelumadu; Chuan-Bi Lin; Roberto Rojas-Cessa. An Experimental Study of SmallWorld Network Models for Wireless Networks. Journal of Cyber Security and Mobility 2016, 4, 259 -278.
AMA StyleZiqian Dong, Zheng Wang, Wen Xie, Obinna Emelumadu, Chuan-Bi Lin, Roberto Rojas-Cessa. An Experimental Study of SmallWorld Network Models for Wireless Networks. Journal of Cyber Security and Mobility. 2016; 4 (4):259-278.
Chicago/Turabian StyleZiqian Dong; Zheng Wang; Wen Xie; Obinna Emelumadu; Chuan-Bi Lin; Roberto Rojas-Cessa. 2016. "An Experimental Study of SmallWorld Network Models for Wireless Networks." Journal of Cyber Security and Mobility 4, no. 4: 259-278.