Jooyoung Kim

Analysis of positioning accuracy corresponding to the number of BLE beacons in indoor positioning system

In these days, a technology that utilize of Bluetooth Low Energy (BLE) beacon, has been attracted attention to provide variety of convenience services. Especially, not limited to the service that can assist to people directly such as public safety, healthcare, proximity-based service, mobile payment, etc., a technology that can provide convenience indirectly such as asset tracking has also been proposed. Most of all, the indoor location awareness using BLE beacon is the essential technique that can realize these services, it is expected to be more focused if the more BLE beacon is spread in the future. In this paper, we first analyse practical path loss model of BLE signals with compared to that of Wi-Fi signals in order to take advantage of the BLE beacon for indoor positioning. To estimate the practical path loss model, we employed four BLE beacons (each two beacon is the same manufacturer) and two of Wi-Fi AP. Each signal was measured during one minute at each reference distance from lm to 13m (with 2m interval) in a Line-of-Sight (LOS) environment. The calculated path loss model was used to generate a BLE signal virtually, we applied the model to configure the BLE radiomap and generate positioning measurement data in our simulation. Since BLE signal has relatively lower tx power compared to Wi-Fi APs, it requires much more beacons to achieve comparable positioning accuracy. We focused on the relationship between the number of installed beacon and its positioning accuracy in this paper.

Fingerprint DB generating system exploiting PDR based dynamic collection for indoor localization of smart-phone users

The fingerprinting has been considered as a promising method for indoor localization due to the robustness from the multi-path than other methods exploiting wireless signals. However, the fingerprinting method has serious limitation which it requires too much time and cost to construct a DB (Data Base) before positioning. In conventional static collection based fingerprint DB generation system, it usually takes up to several minutes to obtain a radio pattern for a single reference point comprising very small part of whole service areas. To overcome the drawback, the fingerprint DB generation system based on the dynamic collection, which breaks the tradition of the radio pattern collection, is proposed. In contrast to the conventional collection method, a collector carrying a smart-phone moves pre-designated routes in service areas, and the position and the radio patterns are autonomously gathered by the collecting application in the smart-phone at every seconds. With the dynamically collected data, then, the fingerprint DB is finally generated by averaging method. From the experimental results, it is validated that the proposed collection method remarkably improves the efficiency of the collection. Also, the positioning using the generated DB shows reasonable accuracy, 2.62m, in an indoor office environment.

K-NN based positioning performance estimation for fingerprinting localization

The positioning system have been paid lots of attention to deal with numerous demands of providing location based services to users. To develop a positioning system, a target accuracy should be defined for reliable services. Though a same system is applied, however, the positioning performance is not always identical since signal environments and structure of indoor areas are different. If a system cannot achieve the target accuracy, the system and environments should be re-examined to find out a solution to meet the accuracy. As a result, additional costs are required to establish a positioning system soundly operable in broad areas. To reduce the cost, in this paper, a system for positioning performance estimation is addressed, especially for fingerprinting positioning system. The proposed system measures signal distances between location fingerprints constituting a radio-map to evaluate the similarity between the signal patterns. Ambiguous patterns bring larger positioning errors when signal fluctuations are introduced; therefore, by calculating the similarity the performance it gives an evidence to estimate degree of positioning errors. The experimental results in subway stations in Seoul, Korea, verify the feasibility of the proposed system.

Performance evaluation of fingerprint based location system using dynamic collection

The fingerprinting location system has been considered as a possible solution for indoor localization. However, it has a problem for building radiomaps for broad areas due to the laborious site-surveying process. A dynamic collection based radiomap generation system is proposed in the literature for solving the problem. With the same dynamically collected measurements, however, the positioning performance may vary significantly. In this paper, therefore, the performances of the fingerprinting location system which exploits dynamic collection are evaluated in various environments. The experimental results verify that the positioning performances are affected by some parameters, so they should be thoroughly decided.

GPR based Wi-Fi radio map construction from real/virtual indoor dynamic surveying data

The scalable and cost-effective Wi-Fi radio-map construction is very important to revitalize indoor location-based service. Considering indoor dynamic surveying data for this purpose, the noble radio map construction method is necessary. With the limitation of indoor dynamic surveying, that is, only access to public area and sensitive signal strength reception, the GPR (Gaussian Process Regression) based radio-map construction method exploiting both realistic and virtual indoor dynamic surveying data is proposed and evaluated. The virtual indoor dynamic surveying data consists of a set of locations and its RSSI where the realistic surveying data is rare, by using access points signal propagation model. The results show that this method can obtain not only high accuracy but also high availability in the whole indoor service area even though the realistic indoor surveying data is rare and its distribution is lack of uniformity.

Standards analysis on Korean positioning system for public safety

In public safety, the position information of the rescue requester is an important element to provide public safety services to the rescue requester in time. Usually mobile network operators acquire the position information of the rescue requester through their positioning system and provide it to the national public safety agency using their own interfaces. Since each mobile operator implements and operates their own proprietary platform, an interoperability of the system among mobile operators is not assured and it sometimes causes system errors. Thus the stable and interoperable positioning system is required for the public safety. In US and EU, the standard on the positioning system for public safety is being discussed and tested due to reasons described above. In Korea, the discussion to create standards on the positioning system for public safety was initiated in 2015 as well, and recently a standard work on system interfaces is finalized. In this paper, requirements, architecture and interfaces of the positioning system for public safety standardized in Korea are analysed. And also the solution to develop the positioning system to ensure a system interoperability among mobile operators is proposed.