IEEE 802.11p也稱做WAVE(車用環境無線存取技術)，是即將被使用在未來交通系統上的標準協定，目的在提供車用通訊上安全性及商業性的應用。IEEE 802.11p修改自IEEE 802.11a，兩者皆基於正交分頻多工處理技術。IEEE 802.11a和IEEE 802.11p最主要的差異在於802.11p使用10 MHz的頻道頻寬(為802.11a的一半頻寬)，這是為了使訊號更強勁地對抗衰減和增加對多重路徑傳播效應的能力以適用於車用環境。在這研究中，我們透過實際實驗來探討IEEE 802.11a和IEEE 802.11p在V-to-I通訊上的效能差異。我們實測了802.11p和802.11a接觸時間以及在直視線和非視線的環境下封包遺失的比較。此外，我們研究不同調變在不同的車載設備跟路測設備之間距下的吞吐量來評估使用傳輸速率調適在非安全性之V-to-I應用的可行性。所有的結果數據皆使用工研院研發的WAVE設備實測取得。

IEEE 802.11p, also known as WAVE (Wireless Access in Vehicular Environments), which is an upcoming standard protocol intended for future traffic system in order to support safety and commercial non-safety applications for vehicular communication. IEEE 802.11p is modified from IEEE 802.11a, both are based on OFDM (Orthogonal frequency-division multiplexing). The main difference between IEEE 802.11a and IEEE 802.11p is that 802.11p is proposed to use 10 MHz frequency bandwidth (half of bandwidth of 802.11a) in order to make the signal more robust against fading and increase the tolerance for multipath propagation effects of signal in vehicular environment. In this work, we try to investigate the performance difference between IEEE 802.11a and IEEE 802.11p for Vehicle-to-Infrastructure communication through real-world experiments. We measure contact duration and losses of 802.11p and 802.11a in both LOS and NLOS environment. In addition, we investigate their throughput with different modulations over various distances between OBU and RSU to evaluate the feasibility of using rate adaptation for non-safety V-to-I applications. All results are measured from field study by using IWCU (ITRI WAVE/DSRC Communications Unit).

[1] Arijit Khan, Shatrugna Sadhu, and Muralikrishna Yeleswarapu: A comparative analysis of DSRC and 802.11 over Vehicular Ad hoc Networks. In: Dept. of Computer Science, University of California (2008).
[2] Annette Böhm and Magnus Jonsson: Position-Based Data Traffic Prioritization in Safety-Critical, Real-Time Vehicle-to-Infrastructure Communication. In: proc. IEEE Vehicular Networking and Applications Workshop (VehiMobil 2009) in conjunction with the IEEE International conference on Communication (ICC), Dresden, Germany (2009).
[3] D. Jiang, V. Taliwal, A. Meier, W. Holfelder, and R. Herrtwich.: Design of 5.9 GHz DSRC-based vehicular safety communication.In: IEEE Wireless Communications, pp. 36--43 (2006).
[4] Eichler, S.: Performance Evaluation of the IEEE 802.11p WAVE Communication Standard. In: IEEE 66th Vehicular Technology Conference. VTC-2007, pp.2199--2203 (2007).
[5] F. Bai, T. ElBatt, G. Holland, H. Krishnan, and V. Sadekar.: Towards characterizing and classifying communication-based automotive applications from a wireless networking perspective. In: First IEEE Workshop on Automotive Networking and Applications (AutoNet 2006), in conjunction with Globecom (2006).
[6] Hannes Hartenstein, Kenneth Laberteaux. VANET Vehicular Applications and Inter-Networking Technologies. John Wiley & Sons Inc. US. p184. 2010.
[7] I. N. L. Tan, W. Tang, K. Laberteaux, and A. Bahai: Measurement and analysis of wireless channel impairments in DSRC vehicular communications. In: Elect. Eng. Comput. Sci. Dept., Univ. California, Berkeley, Berkeley, CA, Tech. Rep. UCB/EECS-2008-33 (2008).
[8] J. Heiskala and J. Terry. OFDM Wireless LANs: A theoretical and practical guide.
SAMS, 2001.
[9] John Bicket. Bit-rate selection in wireless networks. Master's thesis, Massachusetts Institute of Technology, February 2005.
[10] J. Miller, Jeffrey, Ellis Horowitz.: FreeSim – A Free Real-Time Freeway Traffic Simulator. In: IEEE 10th Intelligent Transportation Systems Conference (2007).
[11] Kevin Slattery, Harry Skinner.: Platform Interference in Wireless Systems: Models, Measurement, and Mitigation. In: Newnes. p17. (2008).
[12] Kun-chan Lan, Chung-Ming Huang and Chang-Zhou Tsai, “On the locality of vehicle movement for vehicle-infrastructure communication,” 8th International Conference on ITS Telecommunications, pp. 116-120, Oct. 2008.
[13] L. Cheng, B. Henty, R. Cooper, D. Standi, and T. F. Bai, “A Measurement Study of Time-Scaled 802.11a Waveforms Over The Mobile-to-Mobile Vehicular Channel at 5.9 GHz,” Communications Magazine, IEEE, vol. 46, no. 5, pp. 84–91, May 2008.
[14] Lee, K.C., Navarro, J.M., Chong, T.Y., Uichin Lee, Gerla, M.: Trace-based Evaluation of Rate Adaptation Schemes in Vehicular Environments. In: Vehicular Technology Conference (VTC 2010-Spring), pp. 16--19 (2010).
[15] M. Lacage, M. H. Manshaei, and T. Turletti.: IEEE 802.11 Rate Adaptation: A Practical Approach. In: ACM MSWiM (2004).
[16] Martin Müller: WLAN 802.11p measurements for vehicle to vehicle (V2V) DSRC Application Note. In: Rohde & Schwarz (2009).
[17] Msadaa, I.C.; Cataldi, P.; Filali, F.: A Comparative Study between 802.11p and Mobile WiMAX-based V2I Communication Networks. In: 2010 Fourth International Conference on Next Generation Mobile Applications, Services and Technologies (NGMAST), pp. 186--191 (2010).
[18] P. Shankar, T. Nadeem, J. Rosca, and L. Iftode.: CARS: Context Aware Rate Selection for Vehicular Networks. In: ICNP (2008).
[19] P. Keeratiwintakorn, E. Thepnorarat, and A. Russameesawang: Ubiquitous Communication for V2V and V2I for Thailand Intelligent Transportation System. In: NTC International Conference, Thailand (2009).
[20] P. Fuxjäger et al.: IEEE 802.11p Transmission Using GNURadio. In Proceedings of the IEEE 6th Karlsruhe Workshop on Software Radios (WSR), pp. 83--86 (2010).
[21] Theodore S. Rappaport. Wireless Communications: Principles and Practice. Prentice Hall PTR, Upper Saddle River, NJ, USA, 2002.
[22] Z. Wang and M. Hassan: How much of DSRC is available for non-safety use. In: ACM VANET 2008, pp.23--29 (2008).
[23] Draft P802.11p/D3.0: the IEEE 802.11 Working Group of the IEEE 802 Committee (2007).
[24] Family of standards for Wireless Access in Vehicular Environments (WAVE). In: IEEE 1609.
[25] IEEE 1609.3 Trial-Use Standard for Wireless Accesses in Vehicular Environments (WAVE) - Networking Services,In: IEEE Vehicular Technology Society (2006).
[26] ITRI WAVE/DSRC Communication Unit (IWCU) User’s Guide, Version 1.03
[27] Intelligent Transport Systems, http://www.etsi.org/website/Technologies/Intelligent TransportSystems.aspx
[28] Standard specification for telecommunications and information exchange between roadside and vehicle systems -5.9 GHz Band Dedicated Short Range Communications (DSRC) Medium Access Control (MAC) and Physical Layer (PHY) Specifications. In: ASTM, (E2213-03) (2003).
[29] L. Stibor, Y. Zang and H-J. Reumermann, “Evaluation of communication distance of broadcast messages in a vehicular ad-hoc network using IEEE 802.11p,” in Proc. IEEE Wireless Communications and Networking Conf., Hong Kong, China, Mar. 2007, pp. 254-257.
[30] Y. Xiao and J. Rosdahl, Throughput and delay limits of IEEE 802.11, IEEE Communications Letters, vol. 6, no. 8, pp. 355–357, Aug. 2002.
[31] http://www.cohdawireless.com/