Station Access Research Articles

The Influence of Novel Power System Characteristics on 330kV Power Grid Short-circuit Current

Under the development goal of “Carbon Peak, Carbon Neutralization”, the concept of novel power system is proposed. Its representative features include AC/DC interconnection of power grid and large-scale access of new energy power stations. Under these characteristics, higher requirements are put forward for the short-circuit current breaking capacity of the circuit breaker. The DC component of short-circuit current and the injection of new energy into the system short-circuit current cannot be ignored. Based on the 330kV local power grid in Northwest China, this paper studies the power grid operation mode, DC component of short-circuit current and the influence of photovoltaic power station on short-circuit current. The influence law of DC component of short-circuit current on the actual breaking capacity of circuit breaker and access of photovoltaic power station on the short-circuit current are summarized. It can provide a theoretical basis for the selection of circuit breaker in novel power system.

Premium quality or guaranteed fluidity? Client-transparent DASH-aware bandwidth allocation at the radio access network

In this paper we propose a novel client-transparent Dynamic Adaptive Streaming over HTTP (DASH)-aware bandwidth allocation strategy. The approach, while being application layer transparent, guarantees fluidity to all users but it provides priority-based services to premium users, identified by their Willingness-To-Pay (WTP) profiles. Since different service qualities can be accommodated using WTP, the approach can be extended to XR services, immersive videos, live uplink streaming. To achieve this goal, the allocation problem is firstly formulated as a classical Game Theory problem whose closed form solution is clearly understood in the literature. In a nutshell, the WTP-based, Game Theoretically Optimal Bandwidth Allocation (WTP-GTOBA), firstly satisfies the minimum bandwidth needs of each user and then fairly distributes the residual bandwidth. WTP-GTOBA can be approximately implemented by a greedy, application layer transparent algorithm to be implemented at a DASH-aware network element managing different neighbouring radio access stations. Thereby, the proposed method is suitable for integration of WTP and resource management among multiple service providers and heterogeneous client groups. Numerical simulations carried out under a realistic scenario show that the proposed approach outperforms state-of-the-art application-layer transparent competitors, providing premium quality and/or guaranteed fluidity to different users based on their WTP.

An electric vehicle charging station access equilibrium model with M/D/C queueing

Despite the dependency of electric vehicle (EV) fleets on charging station availability, charging infrastructure remains limited in many cities. Three contributions are made. First, we propose an EV-to-charging station user equilibrium (UE) assignment model with a M/D/C queue approximation as a nondifferentiable nonlinear program. Second, to address the non-differentiability of the queue delay function, we propose an original solution algorithm based on the derivative-free Method of Successive Averages. Computational tests with a toy network show that the model converges to a UE. A working code in Python is provided free on Github with detailed test cases. Third, the model is applied to the large-scale case study of New York City Department of Citywide Administrative Services (NYC DCAS) fleet and EV charging station configuration as of July 8, 2020, which includes unique, real data for 563 Level 2 chargers and 4 Direct Current Fast Chargers (DCFCs) and 1484 EVs distributed over 512 Traffic Analysis Zones. The arrival rates of the assignment model are calibrated in the base scenario to fit an observed average utilization ratio of 7.6% in NYC. The model is then applied to compare charging station investment policies of DCFCs to Level 2 charging stations based on two alternative criteria. Results suggest a policy based on selecting locations with high utilization ratio instead of with high queue delay.

Assessment of the Perception of Security Based on CPTED in Bundaran HI TOD

CPTED studies has been popular since 1960-1970s, however studies in Indonesian city context showed limited references. This paper identified the need of CPTED study followed a massive MRT network development in Jakarta City, as the need for re-design and city beautification to fit with the vibrant TOD urban lifestyle may create moments as well to promote CPTED implementation. The perception survey was developed to understand the perceived crime risk level among the MRT users of Bundaran HI Station. The survey conducted in two scopes of context, i.e. the TOD precinct, an area of 800 radius from the station, and inside the station itself. Finding from the TOD context showed that the maintenance and information have been the most significant but often mostly ignored. These two component may lead to under-rated other CPTED components, weaken the territorial reinforcement and natural surveillance. Out of 56 parameters, 26 parameters or almost halve have rated below 3, alarmed for a more comprehensive design and intervention at the TOD neighbourhood level that emphasizes on the implementation of CPTED principles. Finding from the Bundarin HI station context showed that under the Likert scale 1 (the lowest risk) to 5 (the highest risk), most of the CPTED rated from 4 – 5. There were a variation in the perceived security among different respondents based on gender, time pattern, location pattern, and mode chosen for station access. However, these rating differences were not significant according to the ANOVA and the t-test statistics. The chi-square test found no association between the perceived securities with the type of mode uses for station access. These preliminary findings suggested that the Bundaran HI TOD station is secured from crime risk according to perception of MRT users; therefore little variation in the rating of perceived security gave little information to draw any association with other important variables such as the mode choice for station access. However, taken the measures on wider context at the TOD precinct, the rating of CPTED consistently lower in all components, suggested the urban design and land use zoning-and transportation intervention that consider CPTED principles to be emphasizing at wider area to support the security of the station.

Improving Network Entry Procedure in Broadband Wi-Fi Networks

Efficient handling for subscribers' initial access to wireless networks is highly needed, particularly when the number of subscribers is expected to be significant, as, for example, in the case of new technologies like the Internet of Things (IoT). This paper provides a set of entry algorithms (based on 802.11 entry protocols) for a Time Division Duplex (TDD) mode to allow Subscriber Stations (STAs) to enter broadband base stations Access Points (AP) without significant delay. In this paper, a new method based on a pre-defined hashed backoff STA entry will be discussed. The proposed method is shown to achieve better contention window utilization by STAs, especially the time advance process and the collision-free hashed backoff method compared to the well-known exponential backoff method. It is worth noting that the proposed algorithm maintains compliance with industry standards such as IEEE 802.11.xx and it is currently used in real devices.

Step-free railway station access in the UK: the value of inclusive design

BackgroundDespite substantial investment in step-free access at UK railway stations, persons with reduced mobility (PRMs) continue to travel less than their able-bodied counterparts and little is known about the value of step-free access. This research examines the benefits of step-free access and its relationship with rail usage among PRMs, and the wider benefits of railway station accessibility.MethodsThese issues are explored through a mixed methods approach. Semi-structured interviews with ten key organisations were undertaken, as was an analysis of Senior/Disabled Persons Railcard data from 17 railway stations in Buckinghamshire, each with varying levels of step-free accessibility.ResultsThe results show that the benefits of step-free access extend beyond benefits at the individual level typically associated with those limited to PRMs, and demonstrate the potential to positively affect the society at large economically, environmentally, and socially. The findings also show a positive correlation between the level of step-free accessibility at a railway station and the percentage of PRMs using it.ConclusionsThis research argues that government and interested stakeholders should commit to expanding the number and coverage of step-free stations throughout the UK. They should ensure that the appraisal process for investment in step-free accessibility appropriately captures both user and non-user benefits.

Diversity and density of urban functions in station areas

The diversity and density of urban functions have been known to affect urban vibrancy positively, but the relation between the two has not been empirically examined; if high density is associated with low diversity in an area, its vibrancy may not increase. To obtain a better understanding of the metabolism of cities and directions for urban planning interventions, this paper offers empirical evidence on the association between the diversity and density of urban functions in the Tokyo Metropolitan Area, using a robust density index that was determined via a Monte Carlo simulation. By conducting association analyses, it was found that highly dense station areas tended to display low diversity at multiple scales. Further investigation indicated that this negative correlation was owing to different spatial characteristics of functions and complementary functioning among highly accessible station areas. This paper argues for considering both diversity and density in urban planning to make station areas vibrant and resilient.

Changes in equity of bikeshare access and use following implementation of income-eligible membership program & system expansion in Greater Boston

IntroductionWhile bikeshare programs represent a promising platform for promoting physical activity and health, critics are concerned about their equity. In 2018, Greater Boston launched a low-income bikeshare membership program and expanded the number of available stations. This study examines: 1) changes in equity of station access and 2) changes in equity of bikeshare use as a result of the equity initiative. MethodsWe used publicly available trip history data to identify stations and trips during the pre-intervention (July 2013–December 2017) and intervention (January 2018–July 2019) periods. Using five transit and environmental justice indicators, we categorized census block groups by bikeshare need, then examined the number of block groups with full access to a station before and during the intervention. Logistic regression was used to evaluate the change in probability of a trip starting or ending in a high need block group during the intervention period. ResultsFollowing the implementation of Boston's equity initiative, bikeshare access and use increased across the city, although gains were smallest for communities most in need of access to alternative transportation options. ConclusionsBoston's bikeshare system is an important public health and physical activity promotion opportunity. However, further improvements are needed to promote equity in access and use.

GCACS-IoD: A certificate based generic access control scheme for Internet of drones

Internet of drones (IoD) has gained significant importance in recent times due to its applications in several critical domains ranging from commercial to defense and rescue operations. With several drones flying in different zones to carry out specified tasks, the IoD can be beneficial to gather the real time data for interpretation by the users. However, the data access is carried out through an open channel and battery operated drones. Therefore, the drones’ security and privacy are crucial for accomplishing mission-critical, safety-critical, or surveillance operations. In 2020, Bera et al. presented a certificate based access control scheme for securing the IoD access and argued the scheme’s security through formal and informal methods. However, the analysis presented in this paper shows that the scheme of Bera et al. does not provide anonymity and is insecure against multiple threats, including drone impersonation, the man in the middle, and replay attacks. We then designed a generic certificate based access control scheme to provide inter-drone and drone to ground station access control/authentication in the IoD domain (GCACS-IoD). The GCACS-IoD is provably secure against the known attacks and provides anonymity. GCACS-IoD extends security while preserving computation and communication efficiencies.

Improved Method of Local Feeder Automation Considering Small Hydro-power Connection

With the access of small hydro-power stations (SHS), the distribution system presents a multiple power supply pattern, which has a negative impact on the original local feeder automation (LFA) which is suitable for single side power supply system. In view of this effect, the phase to phase short-circuit fault (PPF) and single-phase grounding fault (SPGF) are treated differently, and an improved LFA method (IMLFA) considering SHS’s access based on low-frequency load shedding (LFLS) and high-frequency generator tripping (HFGT) is proposed. In case of SPGF, the section switch (SSW) and the outgoing circuit breaker of the substation shall be opened in sequence, and the isolated network (IN) generated in the process can be operated stably by cooperating with LFLS or HFGT while the fault is preliminary isolated. The SSW and the breaker are added with the function of no-voltage detection and synchronization detection. In case of instantaneous fault, the power supply in the fault area can be restored after a series of operations, and the IN can be connected to the grid. If it is a permanent fault, the section switches (SSWs) around the fault area will be locked to close in order to isolate the fault effectively, and the IN, not separated by the fault area from the grid, can be connected to the grid. Analysis and simulation show that the method is correct and feasible.

Integrated satellite-ground post-disaster emergency communication networking technology

The reconstruction of the communication network is a precondition for the smooth implementation of rescue and disaster recovery after geological disasters. Although traditional post-disaster emergency communication equipment, such as emergency communication vehicles, satellite access stations and satellite communication terminals, to a certain extent, can solve communication problems, the firmware of them makes such equipment faced with difficulty in adapting to the complex disaster environment, limited network coverage and poor mobility of such devices. To settle those problems, we have proposed an integrated satellite-ground emergency constructed-network after disaster technology. The nodes of the network specifically including Mesh AP (access point) nodes and satellite portable stations, adopt a portable design which can be easily carried by the Network deployer and deployed to the corresponding location. The actual deployment test results of the multi-site network show that our technical solution can build a stable emergency communication network within 30 ​min and support multi-user access, on which users can carry out audio and video communication, file transmission and other services.

STREAM: Medium Access Control With Station Presence Awareness in Crowded Networks

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.

CHECKLIST ON FAUNA DIVERSITY GUNUNG HALIMUN SALAK NATIONAL PARK: Cikaniki-Citalahab

The Cikaniki resort is one of the most accessible research stations located in the Gunung Halimun Salak National Park (GHSNP). It is in adjacent with Citalahab village. The Research Center for Biology, Indonesian Institute of Sciences and other institutions have conducted intensive research on the fauna diversity of GHSNP from this station. Here we formulate a checklist on fauna diversity surrounding the Cikaniki Research Station and Citalahab, GHNSP from various sources, i.e. field work, museum collections (Museum Zoologicum Bogoriense), scientific publications, and technical report. The study was conducted from October 2019 until October 2020. The latest field work was conducted from 8-10 October 2019 under the framework of the Jungle Survival and Biological Collection Management 2019 program. In total, 821 fauna species were recorded in Cikaniki-Citalahab areas which comprises of 48 species of Mollusca, five species of Malacostraca, 523 species of Insects, 22 species of Actinopterygii, 63 species of Amphibia and Reptiles, 115 species of Aves and 45 species of Mammals. The diversity contributes 62.1% of the total 1,323 known fauna species in GHSNP. Five number of species were assigned as endangered and three species critical endangered by IUCN. In addition, 123 species were endemic to Java and 34 species protected by Regulation of the Ministry of Environment and Forestry Republic of Indonesia Number P.106/MENLHK/SETJEN/KUM.1/12/2018. The areas of Cikaniki and Citalahab are rich in biodiversity. Although both areas are in close intact with human activity, research and ecotourism, the need of continuously spreading awareness and enforce species and area conservation is inevitable.

A Study on System Improvement to Activate the Supply of Public Rental Housing by Private Sector in the Station Area of Daejeon Metropolitan

Looking at the comprehensive housing plan recently announced by the Ministry of Land, Infrastructure and Transport, various residential welfare policies and supports are planned for homeless low-income households. At a time when controversy over the rise in prices and supply of housing and real estate emerged across the country, Daejeon Dream Town was introduced to promote housing stability and local economy for young people and newlyweds. Daejeon Dream Town is expected to reduce the budget in Daejeon while relaxing the system to induce private development in the accessible station area and the nodules of public transportation, and providing apartment houses in a location suitable for the needs of youth and newlyweds with part of the increased development profit. In order for Daejeon Dream Town to become more revitalized, it was considered necessary to expand the range of the station area, improve public contribution plans, and improve the ratio of non-residential uses according to the use area, and parking lots. However, it is believed that it is necessary to preserve the regional characteristics and identity of Daejeon, as long as it does not disturb the urban spatial structure and development density system of Daejeon.

Позиционирование транспортных средств в сверхплотных сетях радиодоступа V2X/5G с использованием расширенного фильтра Калмана

This work is devoted to the study of mathematical models of vehicle positioning in ultra-dense V2X / 5G radio access networks using the extended Kalman filter. Based on the study of the probability of line-of-sight availability in the conditions of ultra-dense distribution of reference radio access stations and vehicles, as well as existing mathematical prototype positioning models, a new simulation model for constructing the trajectory of a vehicle has been developed to assess compliance with the requirements for the accuracy of coordinate assessment on the example of the scenario of priority passage of intersections. The simulation model implements the procedures for collecting primary angle and rangefinder measurements by reference stations received from the vehicle for subsequent secondary processing using the extended Kalman filter, as a result of which the vehicle trajectory is built in real time. In contrast to the existing prototype models, the simulation model developed in this work makes it possible to assess compliance with the specified requirements and other specifications depending on the current conditions of line-of-sight availability, as well as the accuracy of collecting primary angle measurements determined by the antenna array installed on the support device. The results of simulation are consistent with the known estimates of prototype models and confirm the possibility of achieving an accuracy of up to 1 m for a traffic control scenario with an error in determining the angle of arrival of a signal of 2 °.

Теоретический анализ возникновения помех в системах спутниковой связи при использовании многостанционного доступа с кодовым разделением каналов

Abstract. To ensure the most effective use of the limited radio resource of the repeater, various methods of multistation access of earth stations to the repeater are developed and applied, based on one or another method of channel separation. The article presents a theoretical analysis of the occurrence of mutual and combination interference in satellite communication systems when using multi -station access with code separation of channels. Recommendations for further experimental studies are proposed.

OPTIMUM PATH DETERMINATION TO FACILITATE FIRE STATION RESCUE MISSIONS USING ANT COLONY OPTIMIZATION ALGORITHMS (CASE STUDY: CITY OF KARAJ)

Abstract. The successful conduct of a rescue mission in urban areas is directly related to the timely deployment of equipment and personnel to the incident location which justifies the quest for optimum path selection for emergency purposes. In this study, it is attempted to use Ant Colony Optimization (ACO) to find the optimum paths between fire stations and incident locations. It is also attempted to build up an evaluation tool using ACO to detect critical road segments that the overall accessibility to fire station services throughout the urban area is constituted upon their excellent functionality. Therefore, an ACO solution is designed to find optimum paths between the fire station and some randomly distributed incident locations. Regarding different variants of ACO, the algorithm enjoys the Simple Ant Colony Optimization deployment strategy combined with Ant Algorithm Transition rules. Iteration best pheromone updating is also used as the pheromone reinforcement strategy. The cost function used to optimize the path considers the shortest Euclidean distance on the network. The results explicitly state that the proposed method is successful to create the optimum path in 95.45 percent of all times, compared to Dijkstra deterministic approaches. Moreover, the pheromone map as an indicator of the criticality of road elements is generated and discussed. Visual inspection shows that the pheromone map is verified as the road criticality map concerning fire station access to the region and therefore pre-emptive measures can be defined by analyzing the generated pheromone map.

Route choice effects of changes from a zonal to a distance-based fare structure in a regional public transport network

By using a hypothetical transport network that reflects common origin and destination relations in a regional transport network, we illustrate the effects of changing fares from a zonal to a distance-based structure. We take the zonal fare as a base case and model the effect of different fare/km, including non-additive fares, where the marginal price per km is decreasing with a typical regional network. We restrict our analysis to a fixed total demand and consider the effects of fares on route choice including station access choice and walking to nearby destinations. The results indicate some general trends that can be expected, such as the fare range in order to achieve similar fare revenue incomes. At this fare parity point the total travel time tends to be reduced in the distance-based case but the flows become less dispersed. Furthermore, in case of a non-additive distance-based fare, we show that total utility could be improved at the fare parity point compared to additive fares.

Performance contributors of bus rapid transit systems: An ordered choice approach

The potential contributors to bus rapid transit (BRT) performance are investigated within an ordered choice modelling framework, in which the dependent variable is the BRT standard (Gold, Silver, Bronze or Basic), developed by the Institute for Transportation and Development Policy (ITDP). The identified significant predictors are peak-hour speed, peak frequency, the average distance between stations, the length of dedicated busway, passing lanes at BRT station, covered station access, enhanced station environment, pre-board and automated fare collection and fare verification, and network integration. Based on a business-as-usual prediction and what–if analysis, this paper offers information for decision makers to plan a high-standard BRT system in line with the ITDP BRT standard.

A Spatial Group-Based Multi-User Full-Duplex OFDMA MAC Protocol for the Next-Generation WLAN.

The Wireless Local Area Network (WLAN) has become a dominant piece of technology to carry wireless traffic for Internet of Things (IoT). The next-generation high-density WLAN scenario is very suitable for the development trend of the industrial wireless sensor network. However, in the high-density deployed WLAN scenarios, the access efficiency is low due to severe collisions, and the interference is diffused due to the scattered locations of the parallel access stations (STAs), which results in low area throughput, i.e., low spatial reuse gain. A spatial group-based multi-user full-duplex orthogonal frequency division multiple access (OFDMA) (GFDO) multiple access control (MAC) protocol is proposed. Firstly, the STAs in the network are divided into several spatial groups according to the neighbor channel sensing ability. Secondly, a two-level buffer state report (BSR) information collection mechanism based on P-probability is designed. Initially, intra-group STAs report their BSR information to the group header using low transmission power. After that, group headers report both their BSR information collected from their members and inter-group interference information to the access point (AP). Finally, AP schedules two spatial groups without mutual interference to carry on multi-user full duplex transmission on the subchannels in cascading mode. The closed-form formulas are theoretically derived, including the number of uplink STAs successfully collected by AP, the network throughput and area throughput under saturated traffic. The simulation results show that the theoretical analysis coincide with the simulation results. The system throughput of the GFDO protocol is 16.8% higher than that of EnFD-OMAX protocol.