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Yu Y.,National University of Singapore | Tang S.,ATR Adaptive Communications Research Laboratories | Zimmermann R.,National University of Singapore
GIS: Proceedings of the ACM International Symposium on Advances in Geographic Information Systems | Year: 2013

Geo-fencing is a promising technique for emerging location-based services. Its two basic spatial predicates, INSIDE and WITHIN pairings between points and polygons, can be addressed by state-of-the-art methods such as the crossing number algorithm. In the era of big-data, however, geo-fencing has to process millions of points and hundreds of polygons or even more in real-time. In this paper, we propose an efficient algorithm to improve the scalability of geo-fencing, which consists of two main stages. At the first stage, an R-tree is used to quickly detect whether a point is inside the minimum bounding rectangle of a polygon. In the second stage, instead of an exhaustive search, we design an edge-based locality sensitive hashing scheme adapted to the crossing number algorithm. As for the case of WITHIN detection, a probing scheme is suggested to locate adjacent buckets so as to check all edges near to a target point. By further exploiting batch processing and multi-threading programming, our algorithm can achieve a fast speed while retaining 100% accuracy over all training datasets provided by the GIS Cup 2013 organizers. © 2013 Authors. Source


Tang S.,ATR Adaptive Communications Research Laboratories | Kubo N.,Tokyo University of Marine Science and Technology | Ohashi M.,ATR Adaptive Communications Research Laboratories
2012 12th International Conference on ITS Telecommunications, ITST 2012 | Year: 2012

In an intelligent transportation system, preventing collision accidents from happening requires to maintain a safe distance between vehicles, which is usually computed from position information. In urban areas, however, non-correlated errors due to multipath propagation in absolute positions degrade the accuracy of relative position. On the other hand, simply removing reflected signals might lead to a shortage of satellites in fixing positions. In this paper, we suggest a cooperative relative positioning (CoRelPos) scheme. Vehicles learn measured information of nearby vehicles by inter-vehicle communications. Correlated information, including that of reflected signals, is used to compute relative position. Statistical analysis of experimental logs verifies that information measured by nearby vehicles is highly correlated under most cases. But exceptions do exist, which require correlation detection. Simulation evaluation and initial experimental results confirm that the proposed scheme can effectively improve the accuracy of relative position compared with the state-of-the-art schemes. © 2012 IEEE. Source


Saito F.,Kansai University | Yomo H.,Kansai University | Abe K.-I.,NEC Communication Systems LTD. | Hasegawa A.,ATR Adaptive Communications Research Laboratories
IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC | Year: 2013

In order to reduce energy wastefully consumed by access points (APs) in wireless LAN (WLAN), Radio-On-Demand (ROD) WLAN has been proposed, which offers wireless access only when and where it is needed in an on-demand manner. Each AP in ROD is equipped with a wake-up receiver, which transits a state of AP from sleep to active by receiving a wake-up signal from a station (STA). However, if there are several APs having the same wake-up ID around a STA, a wake-up request from STA causes more than one AP to wake up though STA only needs a single AP. In this paper, in order to reduce the number of APs redundantly woken up in such a situation, we propose a probability-based wake-up mechanism. With the proposed mechanism, each AP does not always wake up after receiving the wake-up request. Instead, each AP decides whether it should wake up or not based on the wake-up probability. This probability is adjusted in such a way that only APs suited for serving the corresponding STA have the higher probability to wake up while the other APs maintain a lower probability. By computer simulations, we show that our proposed mechanism can significantly reduce the number of redundant wake-up while keeping the adverse impact on their usability and quality of service (QoS) small. © 2013 IEEE. Source


Yomo H.,Kansai University | Kondo Y.,ATR Adaptive Communications Research Laboratories | Namba K.,Kansai University | Tang S.,ATR Adaptive Communications Research Laboratories | And 2 more authors.
IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC | Year: 2012

This paper investigates wake-up ID and protocol design for radio-on-demand (ROD) wireless LAN (WLAN) where wake-up radio is applied to access point (AP) in order to save energy consumed by WLAN. Each AP in ROD WLAN is transited to a sleep state when there is no associated user. A wake-up receiver installed into each AP is used to detect a wake-up signal transmitted by a station (STA) upon communications demands. Each STA specifies an AP to wake up by embedding ID of the target AP into the wake-up signal. In this paper, we propose a wake-up ID assignment and ID matching which can reduce the probability of false wake-up caused by bit errors over wireless channels. The proposed scheme generates wake-up ID of each AP based on ESSID in such a way that certain number of hamming distances is maintained among different wake-up IDs. The AP wakes up when the hamming distance between the received ID, possibly containing bit errors, and its assigned ID is less than a predetermined value. The numerical results obtained by theoretical analysis and computer simulation show that the proposed scheme can effectively reduce the false wake-up probabilities with short ID length and very simple operations at wake-up receivers. We also propose a wake-up protocol for ROD WLAN to reduce energy wastefully consumed by APs which are redundantly woken up with the proposed ID assignment/matching. Our simulation results show that ROD WLAN with the proposed protocol achieves much better energy-efficiency than ROD WLAN without the proposed protocol and WLAN without applying ROD technologies. © 2012 IEEE. Source


Yomo H.,Kansai University | Kondo Y.,ATR Adaptive Communications Research Laboratories | Miyamoto N.,Kansai University | Tang S.,ATR Adaptive Communications Research Laboratories | And 2 more authors.
GLOBECOM - IEEE Global Telecommunications Conference | Year: 2012

In this paper, we design a simple, low-cost, and low-power wake-up receiver which can be used for an IEEE 802.11-compliant device to remotely wake up the other devices by utilizing its own wireless LAN (WLAN) signals. A typical usage scenario of such a wake-up receiver is energy management of WiFi device: a device equipped with the wake-up receiver turns WiFi interface off when there is no communication demand, which is powered-on only when the wake-up receiver detects a wake-up signal transmitted by the other WiFi device. The employed wake-up mechanism utilizes the length of 802.11 data frame generated by a WiFi transmitter to differentiate the information conveyed to the wake-up receiver. The wake-up receiver is designed to reliably detect the length of transmitted data frame only with simple envelope detection and limited signal processing. We develop a prototype of the wake-up receiver and investigate the detection performance of the envelope of 802.11 signals. Based on the obtained experimental results, we select appropriate parameters employed by the wake-up receiver to improve the detection performance. Our numerical results show that the proposed wake-up receiver achieves much larger detection range than the off-the-shelf, commercial receiver having the similar functionality. © 2012 IEEE. Source

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