In-Hye Shin

Analysis of the Passenger Pick-Up Pattern for Taxi Location Recommendation

This paper analyzes a pick-up pattern of taxi service in Jeju area based on the real-life location history data collected from the Taxi Telematics system, aiming at obtaining useful background data necessary to design a location recommendation service for empty taxis. Out of the great amount of location records, pick-up data are extracted by tracing the state change in the predefined taxi state diagram. To decide a reasonable granularity of location recommendation, refined clustering is performed by means of the well-known k-means method supported by the E-Miner statistics software package. In addition, within each cluster, the temporal analysis creates time-dependent pick-up pattern change along the time axis. As a result, the cluster and its spatio-temporal pick-up frequency make it possible to suggest that the empty taxi go to the nearby cluster location, resulting in the reduction of empty taxi ratio.

On employing hierarchical structure in PCS networks

Since the location update process requires heavy signaling traffics, reducing the location update cost has been a critical reserach issue. This paper proposes to employ hierarchical structure in PCS networks to reduce the location update cost. The paper also develops analytical models to evaluate the performance of the proposed approach. The evaluation shows that the proposed approach reduces the location update costs by reducing the update rate of the home location register. The reduction of the location update cost becomes larger when the degree of hierarchy is larger, the size of location area is smaller, and the average residual time of mobile users is smaller.

Design of a Cache Management Scheme for Gateways on the Vehicular Telematics Network

This paper proposes and measures the performance of a cache management scheme for vehicular telematics network so as to provide an advanced route recommendation service, concentrating on gateways which relay information between a specific server and vehicles. As an enhanced version of pure FAR (Furthest Away Replacement), the proposed scheme 1) replaces Euclidean distance by network distance in estimating the distance to a data item, 2) binds each cache item to a link in the target road network, 3) introduces a directional weight to consider the directional tendency of current traffic flow, and finally 4) schedules the cache requests according to their angular locations to efficiently deal with the multiple pending requests. Simulation results, conducted using the real-life trajectory data obtained from a tracking system currently in operation, show that the proposed scheme can improve the cache hit ratio by up to 9.2 %, compared with FAR as well as that the proposed angle-based scheduling scheme can further improve the cache hit ratio by up to 2.3 %.

Association analysis of location tracking data for various telematics services

This paper proposes an approach that extracts the association information from the location data obtained from the real fields but ignored so far. We provide and apply the approach to the real-life location tracking data collected from the Taxi Telematics system developed in Jeju, Korea. The analysis aims at obtaining taxies’ meaningful moving patterns for the efficient operations of them. The proposed approach provides the flow chart which would not only take a glance around the overall analysis process but also help save temporal and economic costs required to employ the same or similar data mining analysis to similar services such as public transportations, distribution industries, and so on. Especially, we perform an association analysis on both of refined data and interesting factors extracted from the elementary analysis. The paper proposes the refined association rule mining process as follow: 1) obtaining the integrated dataset through the data cleaning process, 2) extracting the interesting factors from the integrated dataset using frequency and clustering method, 3) performing the association analysis, 4) extracting the meaningful and value-added information such as moving pattern, or 5) returning the feedback to adjust inappropriate factors. The result of the analysis shows that the association analysis makes it possible to detect the hidden moving patterns of vehicles that will greatly improve the quality of Telematics services considering the business requirements.

Design of a Reliable Traffic Control System on City Area Based on a Wireless Network

This paper designs and analyzes the performance of a reliable communication scheme for the traffic control system, which has a grid topology, based on WirelessHart, a newly developed wireless process control protocol. Besides the main communication schedule, additional schedule is defined with a different channel hopping sequence to make a node take an alternative route in the same slot when the channel on the primary path is not clear. Using the split-merge function augmented to the original WirelessHart node operation, the transmission success ratio can be significantly improved on the rectangular path without extending the control loop. The performance evaluation result measured by simulation using a discrete event scheduler demonstrates that the proposed scheme improves the transmission success ratio for 4 × 4 grid by up to 29 % and each split-merge operation can recover almost all channel errors, especially for long hop transmission.

Design of intersection switches for the vehicular network

This paper proposes an efficient message switch scheme on the vehicular telematics network, especially for the intersection area where routing decision may be complex due to severe trafic concentration. Each switch node opens an external interface to exchange messages with vehicles proceeding to the intersection from the pre-assigned branch as well as switches the received messages via the internal interfaces, accessing two shared channels according to slot-based MAC. Within each synchronized slot, channel probing and switching can efficiently deal with channel errors. The simulation result shows that the proposed scheme improves the delivery ratio by up to 13 % for the channel error rate range as well as up to 8.1 % for the given network load distribution.

An Efficient Bandwidth Reclaim Scheme for the Integrated Transmission of Real-Time and Non-Real-Time Messages on the WLAN

This paper proposes and analyzes bandwidth reclaim scheme for IEEE 802.11 WLAN, which may suffer from severe bandwidth waste resulting from not only the variation of transmission rate and message length but also the overallocation to the real-time traffic in compensating for the delay due to the intervention of non-real-time messages. Built on top of the weighted round robin scheduling policy, we address that the polling order rearrangement according to the degree of overallocation can enhance reclaimability of unused network time and that the rearranegable slot has its message pending at the rearranging time. The simulation results show that the proposed scheme is able to reclaim up to 52.3 % of bandwidth waste when the number of streams is 2 and that it also provides stable throughput for utilization of 0.5 through 0.8.

A research on operating systems of Electric Vehicles

Electric Vehicles (EVs) have attracted a lot of attention due to their eco-friendly properties. Many researches have been done in order to increase the performance of the EV and also in order to provide convenient services to EV users. This paper introduces the research outputs of the project aiming to enhance the users convenience. The main research outputs involve the monitoring system of EVs, the charging infrastructure associated with renewable energy, and the EV-specific navigation. The monitoring system mainly provides the information on the location of and the battery remains of the EVs. The system also provides EV users with information on the location of charging stations, the number of and the type of chargers in the stations, and the current status of chargers. The EV-specific navigation provides not only the route to the destination but also the required battery remains to reach the destination.

A control loop reduction scheme for wireless process control on traffic light networks

This paper designs a loop reduction scheme and measures its performance for the wireless process control application running on the grid-style traffic light network, aiming at improving the response time of the control system. Based on the WirelessHART standard, which assigns a slot to each (sender, receiver) pair according to the routing schedule, the allocation scheme puts all the pairs having no interference to a single slot, reducing the loop length. For further reduction, the classic Dijkstra’s shortest path algorithm is modified such that the number of end-to-end paths starting from the horizontal links and the vertical link, respectively, is almost same. The transmission of the controller, which initiates all message delivery and is the main bottleneck point, will not be blocked. The simulation result demonstrates that the proposed scheme can significantly reduce the control loop length, and the modified path finding algorithm further achieves about 9.8 % improvement, just sacrificing the 3.2 % of transmission success ratio.

Design of an Advertisement Scenario for Electric Vehicles Using Digital Multimedia Broadcasting

This paper designs an integrative advertisement system based on digital multimedia broadcasting for the electric vehicles, which need a lot of driving information for battery efficiency and charge planning. The advertiser interface interacts with the advertisement processing system to pay the fee and have the contents endorsed. The advertisement contents are registered, monitored, encoded, and finally delivered to vehicles according to the contract via the broadcasting center. Here, this paper defines a new frame format on the data service stream and is in the process of developing and verifying the encoder and decoder modules. Our system is expected to provide the fundamentals for the development of diverse electric vehicle services.