Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) Communication in Heterogeneous Wireless Network - Performance Evaluation

Transcription

1 Vehicle-to-Vehicle (VV) and Vehicle-to-Infrastructure (VI) Communication in Heterogeneous Wireless Network - Performance Evaluation Kakan Chandra Dey, Ph.D. Postdoctoral Fellow, Glenn Department of Civil Engineering G Lowry Hall, Clemson University, SC kdey@clemson.edu Tel: +-() -, Fax: +-() - Anjan Rayamajhi PhD Student, School of Computing, McAdams Hall, Clemson, SC arayama@g.clemson.edu Tel: +-()--, Fax: +-()-- Parth Bhavsar, Ph.D. Postdoctoral Fellow, Glenn Department of Civil Engineering Lowry Hall, Clemson University, SC parthb@clemson.edu Tel: +-() -, Fax: +-() - Sean Stamm Undergraduate Student, University of North Carolina at Asheville stamm@unca.edu, Tel: +-() - Mashrur Chowdhury,* Ph.D., P.E., F.ASCE Eugene Douglas Mays Professor of Transportation Glenn Department of Civil Engineering Lowry Hall, Clemson University, SC mac@clemson.edu Tel: +-() -, Fax: +-() - Jim Martin, Ph.D. Associate Professor School of Computing, Clemson University McAdams Hall, Clemson, SC jim.martin@cs.clemson.edu Tel: +-()--, Fax: +-()-- *Corresponding author Number of Figures = Word count= ( words +* figures and tables) Submission date: August,

2 Dey, Rayamajhi, Bhavsar, Stamm, Chowdhury and Martin ABSTRACT Connected Vehicle Technology (CVT) requires wireless data communication between devices within vehicles and between vehicles (VV) and vehicle to infrastructure (VI). To support these growing wireless communication demands in CVT, integration of multiple communication technologies is crucial. Evaluation of different wireless network performances for VV and VI communication is a prerequisite to robust wireless communication network design and development for CVT applications. Though dedicated short range communication (DSRC) has been considered as the primary communication technology in VV and VI communication for safety critical applications, utilization of other wireless technologies such as cellular, Wi-Fi, and WiMAX technologies can supplement longer range communications and throughput requirements that could not be supported by DSRC communications alone or during DSRC communication failure. For a broad range of CVT applications, a viable communication option should include VV and VI capable of utilizing a heterogeneous wireless network without losing connectivity while moving from one communication technology range to another. Optimum utilization of existing built networks, such as Wi-Fi and cellular networks will reduce the need for massive investment of new VV and VI communication networks. In this study, we have evaluated the performance of Wi-Fi and cellular technologies in Clemson University s heterogeneous wireless network (HetNet) for VV and VI communications. Our field evaluations show that HetNet provides a viable option for various CVT applications beyond DSRC.

3 Dey, Rayamajhi, Bhavsar, Stamm, Chowdhury and Martin INTRODUCTION A robust and seamless communication network is essential for connected transportation systems. Availability of reliable vehicle-to-vehicle (VV) and vehicle-to-infrastructure (VI) communication is the most critical component of connected transportation systems. Connected transportation systems will bring numerous advantages in terms of improved traffic safety, efficient traffic operations, and improved mobility performance. Connected vehicle technology (CVT) is enabled by VV and VI communications. One of the primary challenges of VV and VI is that communication is required when vehicles are moving at high speeds. Though there are several communication options available, such as Wi-Fi, WiMAX, Cellular, and DSRC- not all can support low latency, accuracy, and the reliability of data transmission required for safety applications (). While the USDOT is committed to the use of Dedicated Short Range Communication (DSRC) for safety-related VV to VI applications, policy makers have realized that relying only on DSRC may prove detrimental to the connected transportation system; as a result, they are promoting research efforts for all wireless technologies that can enhance VV and VI communications (). The wireless communication research community has been looking for specific Wi-Fi, WiMAX and cellular communication technologies to combine with DSRC to provide multi-channel communication (). However availability of discrete Wi-Fi, WiMAX, and cellular network coverage often creates a heterogeneous network (HetNet). Moving from one network to another network requires mobile devices to perform successful handoffs between wireless networks for continuous connectivity. In this research, the authors explored the potential of a heterogeneous wireless network to provide connectivity for VV and VI communications. To conduct field experiments, the authors utilized a Clemson University Science Wireless Network (SciWiNet) infrastructure, which supports WiMAX, G and LTE as well as the campus-wide Wi-Fi network. This SciWiNet project is sponsored by the National Science Foundation (NSF) to support a mobile virtual network operator (MVNO) for academic research communities (). In this study SciWiNet and the campus-wide Wi-Fi network were utilized to form a HetNet for VV and VI communication evaluation. The objectives of this research were to: assess the current state of wireless coverage on the Clemson University s campus for supporting the VV and VI communications; evaluate the performance of HetNet for VI communications; and evaluate the performance of HetNet for VV communications. PREVIOUS STUDIES ON HETEROGENEOUS WIRELESS NETWORK Heterogeneous wireless communications have differences in characteristics such as security requirement, data rates and coverage radius (). However, in everyday scenario, mobile devices access heterogeneous networks for continuous connectivity. Routing data traffic during movement of mobile hosts has been considered a major issue of importance since the wide adoption of mobile devices such as smart phone and laptop computers (). One of the big challenges in heterogeneous wireless networks is the handoff duration, which requires the user to switch from one network to another network. However, handoff time between networks requires significant time which hampers the user experience and reliability of the heterogeneous network (). A modified version of the MIPv handoff protocol, PMIPv, could be more appropriate for localized application while MIPv could be utilized for global mobility to minimize the handoff time (). PFMIPv, a handoff scheme, communicates with next wireless access point by measuring mobile node s signal strength (). Ning et al. () proposed a Markov-decision

4 Dey, Rayamajhi, Bhavsar, Stamm, Chowdhury and Martin process-based handoff algorithm, which considers received signal strength as a primary measure of effectiveness (MOE) to minimize average handoff frequency (). In another study of simultaneous binding enabling PMIPv (SPMIPv), researchers were able to reduce handoff time within one round trip time (RTT), which is less than ms (). To minimize the packet loss during hand-off scenarios, Baojiang proposed a packet routing strategy which can provide advance information to en-route networks to reduce authentication time and thereby transmit overlapped packets from en-route network (). A similar study found that authentication and security information provided to a local key holder to process quick authentication processing could reduce handoff time significantly in a heterogeneous network, which included WiMAX and Wi-Fi. (). Magagula et al. introduced a network-wide handoff coordinator to reduce handoff time (). Kim et al. developed a layer- IP based handoff strategy in WiMAX mesh networks to minimize handoff latency and packet loss (). Wisitpongphan and Bai () developed a multi-criteria Ad hoc Real-time Streaming (CARS) algorithm to improve the quality of service in a multi-hop vehicular network enabled by DSRC technology (). CARS algorithms continuously monitored the signal strength between available networks and switched between networks to maximize video streaming quality (). Several studies reported the centralized resources allocation for a heterogeneous network rather than distributed systems (- ). Researchers also compared different algorithms used in different handoff schemes. Stevens- Navarro and Wong () compared four handoff algorithms (MEW, SAW, TOPSIS, and GRA) considering different performance criteria and reported that MEW, SAW, and TOPSIS were very similar when compared against all performance criteria, but GRA performed better (). To evaluate the performance of heterogeneous networks for IPv, Izard et al. () developed an open source test-bed which resolved triangular routing issues for the Global Environment for Network Innovations (GENI) project sponsored by NSF (). Though there has been a substantial amount of research conducted to develop more efficient ways for fast handoff to the best of our knowledge-there are no studies which have investigated heterogeneous network performance in connected vehicle scenarios. Our objective covers that facet of understanding handoff behavior in connected vehicles with vehicle to vehicle and vehicle to infrastructure connectivity tests. METHOD This study was performed in three phases. In the first phase we developed a wireless coverage map of the main campus of Clemson University, and based on this coverage map, we identified locations for VI and VV handoff tests. Phase and Phase included VI and VV handoff tests. An application layer handoff testing tool using UDP and TCP sockets was created for this study. The objective was to understand seamless communication between vehicles in a HetNet system subjected to hard handoff. The tool was designed to detect hard handoff controlled by a Linux Network Manager. The detection of hard handoff was followed by creating a new socket and reattempting the connection. The tool recorded information regarding the handoff such as the interface being used before and after the handoff, packet loss during handoff, and the time needed for the handoff to complete. The detailed description of each phase is provided in the subsequent sections. Phase : Develop wireless coverage map for Clemson University s main campus for VV and VI communication evaluation To identify locations for wireless connectivity for VI and VV communication, it is necessary to develop a wireless coverage map. To develop the coverage map of Wi-Fi and SciWiNet

5 Dey, Rayamajhi, Bhavsar, Stamm, Chowdhury and Martin around main campus, we utilized Android phone apps, CyberTiger and SciWiNet, which were developed in the Networking Laboratory at Clemson University (-). We developed the coverage map by driving, walking and biking around the campus with an Android smartphone running one of the apps. The previously studied coverage map of SciWiNet s G/G coverage, available at was also used for this study. The primary objective was to develop different network coverage maps and to identify a particular route that could be used for handoff testing using the tool our team had developed for VV and VI communications. Phase : Vehicle-to-infrastructure (VI) handoff tests To evaluate the efficacy of VI data communication in a HetNet (Objective ), a client-to-server packet transfer model was developed, in which the client sends data to a server with GPS coordinates, time stamps, and signal strengths at different network interfaces including currently used interface by Layer for packet routing. Field tests were conducted in a HetNet with Wi-Fi and SciWiNet connectivity. As shown in Figure, the campus Wi-Fi was available near the Clemson University Brooks Center for the Performing Arts, but the vehicle lost the Wi-Fi signal as it moved out of the Wi-Fi range. Initially all packets were routed using the Wi-Fi interface, and when first going out of range, the Linux Network Manager took charge switching with a handoff at Layer to the next available network, which in this case was SciWiNet. A vertical handoff was defined for the case when the underlying network changed during the handoff. This was a hard-handoff where a connection was broken before attempting to reconnect. Our testing tool was designed to detect such a handoff at Layer and make appropriate changes so that devices (both in-vehicle and infrastructure) remain connected after the handoff. UDP and TCP data communication protocol-based tests were performed multiple times. Data was collected for (i) the number of packet lost between client and server during handoff, and (ii) the time between successive packets during handoff. Number of packets lost over time for multiple tests and throughputs were calculated.

6 Dey, Rayamajhi, Bhavsar, Stamm, Chowdhury and Martin FIGURE VI field test experiment setup. Phase : Vehicle-to-vehicle (VV) handoff tests Vehicle-to-vehicle (VV) handoffs were tested using ad-hoc Wi-Fi networks and SciWiNet. Coping with the changing IP address of a server node as it moved along coverage areas of different network technologies was the technical challenge added in this case. To solve this problem, an ad-hoc Wi-Fi connection was used for the initial setup where public IP address of the server node under a different network interface was shared with a connecting client node. Established connection between client and server underwent handoff when the two vehicles moved away from each other. To investigate impact of vehicle speed on handoff, tests were conducted at mph and mph speeds. After the handoff occurred from ad-hoc Wi-Fi network to SciWiNet, communication between vehicles continued in SciWiNet. Linux laptops with commodity hardware - Aircard U were used to connect to SciWinet. Our testing tool was again able to detect the handoff as it happened in VV tests. When vehicles were out of Wi-Fi

7 Dey, Rayamajhi, Bhavsar, Stamm, Chowdhury and Martin range, the tool maintained the socket and tried to recover from handoff. VV field test sites are shown in Figure and the flow chart for VV communication tests is illustrated in Figure. FIGURE VV communication experiment set up.

8 Dey, Rayamajhi, Bhavsar, Stamm, Chowdhury and Martin FIGURE VV communication field test data transfer flowchart. FIELD EVALUATION RESULTS AND DISCUSSION Phase test results Using the Android phone apps, a figurative coverage map based on signal presence, ping tests, latency tests, and TCP and UDP bandwidth tests were used to understand the status of SciWiNet and Wi-Fi around campus area. One of the tests was designed to help the researchers to understand the leaked Wi-Fi from campus buildings surrounding the reflection pool as well as G and LTE coverage around the same route (Figure ). This gave us intuition about testing handoffs while switching from Wi-Fi to SciWiNet near buildings where Wi-Fi network was available. Similarly, a campus coverage map was studied from the online SciWiNet map website (Figure ) which helped us identify the route we had to take for VV tests.

9 Dey, Rayamajhi, Bhavsar, Stamm, Chowdhury and Martin Signal Strength Legends: FIGURE Wi-Fi (left), LTE (middle) and G (right) Coverage map around Reflection Pool on Campus. Signal Strength Legends: FIGURE. Coverage map of SciWiNet in Clemson University. Phase test results VI communication tests were conducted in both UDP and TCP mode. Number of packets lost during handoff between client and server from Wi-Fi network to SciWiNet was calculated. Packet loss rate was higher during the handoff. Figure shows the field test setup and the route, which tvehicles took to evaluate the HetNet handoff scenario from Wi-Fi network to SciWiNet. Packet loss during handoff from Wi-Fi to SciWiNet is presented for TCP mode in Figures and, and for UDP mode in Figure and. When vehicles were within Wi-Fi range, inter-packet arrival time was about five seconds for both TCP and UDP mode. The high inter packet arrival time was due to the testing tool losing GPS fix every time, which was an issue the team hopes to overcome in future. Handoff occurred when vehicle drove out of Wi-Fi network into SciWiNet. In both TCP and UDP handoff scenarios, the packet loss time and time between arrivals of successive packets were similar (Figure to ).

10 Dey, Rayamajhi, Bhavsar, Stamm, Chowdhury and Martin Packet loss seen at the server with TCP connection test test test Number of packets lost FIGURE Packets lost with TCP mode at server end. Time between packets (seconds) Time between packets seen at the server with TCP connection test test test FIGURE Time between packets with TCP mode at the server end.

11 Dey, Rayamajhi, Bhavsar, Stamm, Chowdhury and Martin Packet loss observed at the server with UDP test test test test Number of packet lost FIGURE Packets lost with UDP mode at server end. Time between packets observed at the server with UDP Time between packets (seconds) test test test test FIGURE Time between packets with UDP mode at the server end. Phase test results Test : UDP mode at low speed test Data transfer at maximum allowable speed of Mbps with bytes of datagram size was started using ad-hoc Wi-Fi network between two vehicles traveling in the opposite direction.

12 Dey, Rayamajhi, Bhavsar, Stamm, Chowdhury and Martin First communication was established when vehicles were close through ad-hoc Wi-Fi which was followed by handoff to SciWiNet as the vehicles moved away from each other (Figures and ). Handoff happened at low packet loss but a large number of packets lost and delays were observed with SciWiNet. The packet arrival rate was less in Wi-Fi; furthermore, in SciWiNet, after a certain distance, packet loss began. Similarly arrival time between successive packets was found to be higher due to packet loss (Figures and ). Initially a longer time was observed between successive packets, and that was due to the exchange of IP address between server and client. The packet loss in SciWiNet could be accounted to increased routing time in the SciWiNet infrastructure. UDP Packet loss at speed Mph Number of packet lost Handoff occureed - Time index FIGURE VV communication in HetNet, UDP mode, vehicle speed mph.. Time Between Successive Packets at Speed mph Time between packets Time index FIGURE VV communication in HetNet, time between packets with TCP mode, vehicle speed mph. Test : UDP mode test at mph A similar test at mph was conducted for UDP mode with vehicles carrying laptops with NetGear SciWiNet dongle (AirCard U), which drove in opposite directions. For each test run, Wi-Fi Ad-hoc network was created and connection was established between vehicles while they

13 Dey, Rayamajhi, Bhavsar, Stamm, Chowdhury and Martin were moving in opposite directions and when in Wi-Fi range of the ad-hoc network. Multiple test runs were performed covering scenarios where the vehicles were moving in opposite directions, and they were at stopped at the same red light. As the vehicles were driven away they maintained connection by switching to SciWiNet through handoff. Figures and show packet loss seen in UDP and also a peak packet loss due to handoff. It can be seen that the switching time of vertical handoff was less than seconds. Number of packet lost UDP Packet loss at speed mph Handoff Time index FIGURE VV communication in HetNet, UDP mode, vehicle speed mph. Time between packets Time between successive packets at mph. Handoff Time index FIGURE VV communication in HetNet, time between packets with UDP mode, vehicle speed mph. Test : TCP mode test at mph TCP mode was applied for maintaining transport layer for VV communication at speed of mph (Figures and ). Two test runs were conducted and each produced similar results. The maximum allowable for TCP was dropped down to Kbps. The first seconds in Run was due to the client waiting for server to send the IP address during initialization. As expected, TCP had no packet loss apart from the handoff.

14 Dey, Rayamajhi, Bhavsar, Stamm, Chowdhury and Martin Number of packet lost... TCP packet loss during handover at mph Run Run Handoff Handoff Time index FIGURE VV communication in HetNet, TCP mode, vehicle speed mph. Time between packets at mph Run Run Time between packets Time index FIGURE VV communication in HetNet, time between packets with TCP mode, vehicle speed mph. CONCLUSIONS To utilize the full potential of connected vehicles, seamless communications for VV and VI applications is required. Latency, security and reliability requirements of different connected vehicle applications involve multiple wireless communication options at the same time. Though dedicated short range communication (DSRC) has been considered as the primary communication technology in VV and VI communication for safety critical applications, utilization of other wireless technologies such as cellular, Wi-Fi, and WiMAX technologies can supplement longer range communications and throughput requirements that could not be supported by DSRC communications alone or during DSRC communication failure. For a broad range of CVT applications, a viable communication option should include VV and VI capable of utilizing a heterogeneous wireless network without losing connectivity while moving from one communication technology range to another.

15 Dey, Rayamajhi, Bhavsar, Stamm, Chowdhury and Martin As homogenous communication networks will not be available everywhere, it will require VV and VI communication to switch from one type of network to another in a HetNet environment (e.g., Wi-Fi to WiMAX/cellular). Fundamentally, these different networks have not been designed for seamless transfer from one network to another for moving nodes. To develop robust synchronized HetNet, networks needs to be reconfigurable. In this study we have explored the potential of VV and VI in HetNet with Wi-Fi and cellular network to access the reconfigurability performance. We observed that when switching/handoff between networks, it takes several seconds to establish connection and resume data transfer. That means, HetNet will perform better for non-safety applications such as traffic management, and will provide additional connectivity for safety critical connected vehicle applications. Current research focused on VV communication at MPH because of the limitations of the existing test bed at Clemson. Future research will include evaluating VV communication tests for a heterogeneous network with vehicle speeds higher than mph. This study focused on only two vehicles which will be expanded to multiple vehicles in the follow-up research. REFERENCES. RITA, Overview of Dedicated Short Range Communications (DSRC) Technology,. Link: Accessed on July,.. Dar, K., M. Bakhouya, J. Gaber, M. Wack, and P. Lorenz, Wireless communication technologies for ITS applications [Topics in Automotive Networking]. Communications Magazine, IEEE, (), -,.. Martin, J., K.C. Wang, I. Seskar, SciWiNet: a Science Wireless Network for the Research Community,. Link: Accessed on July,.. Magagula, L., and H.A. Chan, Optimized handover delay in Proxy Mobile IPv using IEEE. MIH Services, Southern Africa telecommunication networks and applications conference,.. Giovanardi, A., and G. Mazzini, Transparent mobile IP: an approach and implementation. In Global Telecommunications Conference, GLOBECOM', IEEE (Vol., pp. - ). IEEE,.. Kong, K. S., W. Lee, Y. H. Han, M. K. Shin, and H. You, Mobility management for all- IP mobile networks: mobile IPv vs. proxy mobile IPv, Wireless Communications, IEEE, (), -,.. Kim, M. S., S. Lee, D. Cypher, and N. Golmie, Fast handover latency analysis in proxy mobile IPv. In Global Telecommunications Conference (GLOBECOM ), IEEE (pp. -). IEEE,.. Ning, Z., Q. Song, Y. Liu, F. Wang, and X. Wu, Markov-based vertical handoff decision algorithms in heterogeneous wireless networks. Computers & Electrical Engineering, (), -,.. Bargh, M., B. Hulsebosch, H. Eertink, G. Heijenk, J. Idserda, J. Laganier, A.R. Prasad, and A. Zugenmaier, Reducing handover latency in future IP-based wireless networks: Proxy Mobile IPv with simultaneous binding, In World of Wireless, Mobile and Multimedia Networks, WoWMoM. International Symposium on a, pp. -. IEEE,.

16 Dey, Rayamajhi, Bhavsar, Stamm, Chowdhury and Martin. Baojiang, W., An Efficient Fast Handoff Scheme with Network Mobility in Heterogeneous Networks, th International ICST Conference on Communications and Networking in China (CHINACOM),.. Huang, K-L., K-H. Chi, J-T. Wang, and C-C. Tseng, A Fast Authentication Scheme for WiMAX WLAN Vertical Handover, Wireless Personal Communications, Volume, Issue, pp -,.. Magagula, L. A., H. A. Chan, and O. E. Falowo, Achieving seamless mobility through handover coordination in a network-based localized mobility managed heterogeneous environment. In Personal Indoor and Mobile Radio Communications (PIMRC), IEEE st International Symposium on (pp. -). IEEE,.. Kim, M., J. M. Kim, H. S. Kim, and I. K. Ra, A proxy mobile IP based layer- handover scheme for mobile WiMAX based wireless mesh networks. In Ubiquitous and Future Networks (ICUFN), Second International Conference on (pp. -). IEEE,.. Wisitpongphan, N., and F. Bai, Microscopic Experimental Evaluation of Multi-hop Video Streaming Protocol in Vehicular Networks, IEEE Vehicular Networking Conference,.. Amin, R., J. Martin, and H. Russell, Assessing Performance Gains Via the Use of Global Resource Controller for Realistic Heterogeneous Wireless Networks, Proceedings of the IEEE WCNC Conference,.. Li, L., M. Pal, and Y. Yang, Proportional Fairness in Multi-Rate Wireless LANs, Proceedings of INFOCOM, pp. -,.. Baid, A., M. Schapira, and I. Seskar, Network Co-operation for Client-AP Association Optimization, Proceedings of International Workshop on Resource Allocation and Cooperation in Wireless Networks,.. Enrique, S-N., and V.W.S. Wong, Comparison between vertical handoff decision algorithms for heterogeneous wireless networks, Vehicular technology conference, VTC -Spring. IEEE rd, vol., pp. -. IEEE,.. Izard, R., A. Hodges, J. Liu, J. Martin, K.C. Wang, K. Xu, An Openflow Testbed for the Evaluation of Vertical Handover Decision Algorithms in Heterogeneous Wireless Networks, to appear in the Proceedings of TRIDENT,.. CyberTiger,, Accessed on August,. SciWiNet, Tools and Services provided by SciWiNet, Accessed on August,