Wi-Fi 1 1 2 1 3G 3G Wi-Fi Wi-Fi Wi-Fi Wi-Fi Offloading Method for Outdoor Mobile Users using Smartphones in Vehicles as Moving Access Points Abstract: With the increasing popularity of smart-phone, 3G networks are currently overloaded with mobile data traffic. Due to this explosion of data traffic, communication quality deteriorates and communication failure occurs. To solve this problem, there have been proposed Wi-Fi offloading methods to offload mobile data traffic to WiFi network. However, there is a problem that outdoor mobile users like a waking pedestrian cannot offload mobile data, while they are out of Wi-Fi access area. In this paper, we propose a new WiFi offloading method which uses the vehicle passing near the user as a relay node. In addition, we focus on the fact that contact duration between vehicles and pedestrians is likely to be longer near the intersection. In order to increase the probability of successful data reception at a mobile user from the Internet, we propose a method which selects a vehicle with a higher probability of encountering the mobile user. 1. 3G 3G 1 Nara Institute of Science and Technology 2 Tokyo University of Science, Yamaguchi 3G 3G 3G 2 3.9G 4G Wi-Fi Wi-Fi Wi-Fi AP 100 Wi-Fi AP Wi-Fi 3G Wi-Fi 3G c 2012 Information Processing Society of Japan 1
Wi-Fi AP 3G Wi-Fi Wi-Fi 3G Wi-Fi AP Wi-Fi [1] Wi-Fi AP Wi-Fi Wi-Fi AP Wi-Fi Wi-Fi AP 2 3 4 5 2. Wi-Fi Wi-Fi AP Wi-Fi AP 3G Wi-Fi AP Wi-Fi [1], [2], [3], [4], [5], [6], [7] Wi-Fi AP 3G Balasubramanian [1] Wiffler Wiffler Wi-Fi AP AP Wi-Fi AP 3G Deshpande[5] Wi-Fi AP Wi-Fi AP Wi-Fi AP [8], [9] Kyunghan [8] 65% 100 1 Pralhad [9] Wi-Fi AP c 2012 Information Processing Society of Japan 2
1 Wi-Fi Wi-Fi AP [10] 3. Wi-Fi Wi-Fi 3G 3.1 3.1.1 1 U S s S Wi-Fi AP Wi-Fi AP AP A a A Wi-Fi AP WI-Fi AP AP Wi-Fi AP SSID Wi-Fi AP 3.1.2 Web 3.1.3 I E G=(I,E) i I P i (road b, road a ) road b road a road b D Σ roada DP i (road b, road a ) = 1 i, j i j t (i,j) E T 3.1.4 Wi-Fi 3G E I G GPS Wi-Fi c 2012 Information Processing Society of Japan 3
(a) (b) 2 3.1.5 3G 3.2 3.2.1 2 ( 2(a) ) ( 1 ) Wi-Fi AP AP ( 2 ) Wi-Fi AP Wi-Fi AP ( 3 ) 3G ( 4 ) ( 2(b) ) ( 1 ) 3G GPS Wi-Fi SSID ( 2 ) ( 3 ) Wi-Fi AP Wi-Fi AP ( 4 ) Wi-Fi AP AP Wi-Fi AP SSID ( 5 ) Wi-Fi AP SSID SSID AP ( 6 ) 3G c 2012 Information Processing Society of Japan 4
3 3.2.2 3 u i s m s m Wi-Fi AP u i s m u i s m Wi-Fi AP s m Wi-Fi AP u i s m u i s m 4. Wi-Fi 4.1 4 4.2 4 ( 1 ) 3G ( 2 ) d user d user t enc 5 ( 3 ) Wi-Fi AP Wi-Fi AP AP ( 4 ) AP a a d car t enc a t enc d car a c 2012 Information Processing Society of Japan 5
5 t relay 5 a ( 5 ) t relay a t relay a ( 6 ) a t enc ( 7 ) 3G (i) d user d car (ii) AP (iii) 4.2.1 d user d car [11] d user d car 3G GPS d user d user d user [12] d car 4.2.2 AP AP AP AP AP AP AP AP AP AP AP AP a a a i 1 i k i 1 i k i 1, i 2,..., i k i 1 i k fc k 2 fc(1, k) = P ((i j, i j+1 ), (i j+1, i j+2 )). (1) j=1 P ((i i, i j ), (i j, i k )) i i i j i j i k a /sec a i k ta ta = t 1,2 fc(1, k). (2) t 1,2 a i 1 i 2 Wi-Fi AP AP (2) AP AP AP 1 2 AP AP 1 c 2012 Information Processing Society of Japan 6
AP AP (2) AP 4.2.3 AP 1 t relay AP 1 AP i 1 fc(1, k) N 1 i k q 1 NIC Athrm 5.2km/h WL54AG (km/h) madwifi ( Mbps ) 1 24 54 iperf (Byte) 256 512 1024 LAN 802.11g IP (go), (come) UDP ( km/h ) 20 40 5.1.1 5 7 8 q = 1 (1 fc(1, k)) N. (3) q α q α N AP N 5. 5.1 6 1 5 6 7 24Mbps 20km/h 35.01 40km/h 14.55 2 1/2 6 24Mbps (come) 40km/h 20km/h 1024Byte 7824KByte 1776KByte 1Mbps 46.78 24Mbps 16.40 54Mbps ( 0 ) 8 20km/h c 2012 Information Processing Society of Japan 7
24Mbps 20km/h 3000 8000KByte 54Mbps 20km/h Wi-Fi AP : Wi-Fi AP Wi-Fi AP 2 6. 8 20km/h 3G Wi-Fi 5.2 5.2.1 2 2 Scenargie Sumo Open Street Map Wi-Fi AP Wi-Fi 5.2.2 Web 3G Wi-Fi AP : [1] A. Balasubramanian, R. Mahajan, and A. Venkataramani: Augmenting Mobile 3G Using WiFi, In Proc. of MobiSys 10, pp. 209 222, 2010. [2] P. Deshpande, A. Kashyap, C. Sung, and Samir R.Das: Predictive Methods for I,proved Vehicular WiFi Access, In Proc. of MobiSys 09, pp. 263 276, 2009. [3] A. Balasubramanian, R. Mahajan, A. Vekataramani, B. Neil Levine, and J. Zahorjan: Interactive WiFi Connectivity For Moving Vehicles, In Proc. of SIGCOMM, pp. 427 438, 2008. [4] J. Jeong, S. Guo, Y. GU, T. He, and D. H.C Du: TSF:Trajectory-based Statistical Forwarding for Infrastructure-to-Vehicle Data Delivery in Vehicular Networks, In Proc. of ICDCS, pp. 557 566, 2010. [5] J. Eriksson, H. Balakrishnan, and S. Madden: Cabernet: Vehicular Content Delivery Using WiFi, In Proc. of MobiCom, pp. 199 210, 2008. [6] Z. Zheng, Z. Lu, P. Sinha, and S. Kumar: Maximinzing the Contact Opportunity for Vehicular Internet Access, In Proc. of INFOCOM, pp. 1109 1117, 2010. [7] A. Balasubramanian, Y. Zhou, B. Croft, B. Neil Levine, and A. Venkataramani: Web Search From a Bus, In Proc. of CHANTS, pp. 59 66, 2007. [8] K. Lee, I. Rhee, J. Lee, S. Chong, and Y. Yi: Mobile Data Offloading: How Much Can WiFi Deliver?, In Proc. of Co-Next, pp. 425 426, 2010. [9] P. Deshpande, X. Hou, and S. R.Das: Performance Comparison of 3G and Metro-Scale WiFi for Vehiclular Network Access, In Proc. of IMC,pp. 301 307, 2010. [10],,, : Wi-Fi In Proc. of DICOMO2012, pp. 53 62, 2012. [11] Goldman, J., Shilton, K., Burke, J., Estrin, D., Hansen, M., Ramanathan, N., Reddy, S., Samanta, V. and Srivastiva, M.: Participatory Sensing: A citizenpowered approach to illuminating the patterns that shape our world, Foresight &Governance Project, White Paper (2009). [12] R. K. Balan, N. X. Khoa, and L. Jiang: Real-Time Trip Information Service for a Large Taxi Fleet, In Proc. of MobiSys, pp. 99 112, 2011. c 2012 Information Processing Society of Japan 8