路由議題在車用無線隨意網路（VANETs）中比在行動隨意無線網路（MANETs）上來的更具挑戰性。車用無線隨意網路獨特的性質，如高度變動的網路拓樸、固定的道路路線，都讓傳統使用在行動隨意無線網路的路由方式顯得不適合。
許多論文都嘗試特別針對單點廣播的情況，研究車用無線隨意網路上的路由議題。而在多重廣播的情況下，最主要的問題是，如何在因為車輛快速移動所造成的高度變動的網路拓樸下，維持多重廣播樹
在這篇論文中，我們提出了車用無線隨意網路中群播機制之研究Static Intersection Node-based Adaptive Multicast (SINAM) 的協定，可以在車用無線隨意網路內支援多重廣播路由。SINAM結合了反應式方法來達到尋找路線與節點參與，以及利用地理資訊來轉傳封包至多重目標節點。在本協定裡，會員的管理交由固定式路口節點static intersection node (SIN)來處理。SIN會放在每個交叉路口，負責多重廣播樹的建置以及維持。
當來源端有封包要送時，它會開始利用氾濫JOIN_REQUEST封包到整個網路進行尋找路線，並等待JOIN_REPLY。想要加入群組的車輛就回覆JOIN_REPLY封包至它所收到JOIN_REQUEST的SIN。在多重廣播樹建置好之後，來源端會沿著地理資訊所得的路線以及SIN的幫助傳送資料封包。我們把維持變動的多重廣播樹的機制完全交由SIN處理。由於路口的數量少於車輛的數量，所以我們相信此機制能有效的降低維持廣播樹的負擔，並改善傳輸延遲。
我們的成果顯示，在多種情況下，SINAM能保障封包傳輸率，且同時改善傳輸延遲與負擔。

Routing issues in VANETs are become more challenging than in MANETs. Unique characteristics of VANETs such as high dynamic topology and static road geometry make many conventional routings in MANET unsuitable.
Many papers try to address this routing issue in VANETs especially for unicast case. In multicast case, the main problem is how to maintain the multicast tree under high dynamic topology caused by rapid movement of vehicles.
In this paper we present Static Intersection Node-based Adaptive Multicast (SINAM) Protocol which is support multicast routing in VANETs. SINAM combines reactive based for route discovery and joining process and geographic based to forward the data packet to multi destinations. Membership management in this protocol is maintained by static intersection nodes (SINs) which are placed on every intersection. Those SINs involve in multicast tree construction and maintenance.
When the source has a packet to send, it begins route discovery process by flooding JOIN_REQUEST to the whole network and waiting for JOIN_REPLY. Vehicles want to join the multicast group will send JOIN_REPLY to one of its previous SIN from which it receives JOIN_REQUEST. After multicast tree has already constructed, the source forwards the data packet using geographic based routing along the assistance of static intersection nodes. We implement adaptive tree maintenance mechanism handled by SINs only. Since the number of intersections is smaller than the number of vehicles, we believe this mechanism can reduce the maintenance overhead and improve the delivery delay.
Our performance evaluation results show that SINAM can guarantee packet delivery ratio while improve the average delay and the routing overhead under various scenarios.

[1] A. Bachir and A Benslimane, “A Multicast Protocol in Ad hoc Networks Inter-
Vehicle Geocast”, in Proceedings of the 57th IEEE Semiannual Vehicular
Technology Conference, vol. 4, pp. 2456 – 2460, 2003
[2] B. Burns, O. Brock, and B. Levine, “MV Routing and Capacity Building in
Disruption Tolerant Networks,” in InfoCom, 2005.
[3] J. Burgess, B. Gallagher, D. Jensen, and B. N. Levine, “Maxprop: Routing for
vehicle-based disruption-tolerant networking,” in InfoCom, 2006.
[4] D. Choffnes and F. Bustamante, “An Integrated Mobility and Traffic Model for
Vehicular Wireless Networks,” in Proceedings of VANET, 2005.
[5] I. Chatzigiannakis, S. Nikoletseas, and P. Spirakis, “An Efficient Communication
Strategy for Ad-Hoc Mobile Networks,” in DISC, 2001.
[6] Z. Chen, H. Kung, and D. Vlah, “Ad Hoc Relay Wireless Networks over Moving
Vehicles on Highways,” in MobiHoc, 2001.
[7] J. A. Davis, A. H. Fagg, and B. N. Levine, “Wearable computers as packet transport
mechanisms in highly-partitioned ad-hoc networks,” in ISWC ’01: Proceedings of
the 5th IEEE International Symposium on Wearable Computers, 2001.
[8] Y. Ding, C. Wang and L. Xiao, “A Static-Node Assisted Adaptive Routing Protocol
in Vehicular Networks”, Proceedings of Vehicular Ad Hoc Networks'2007.
pp.59~68.
[9] A. Ho, Y. Ho, and K. Hua, “A connectionless approach to mobile ad hoc networks
in street environments”, In Proc. of the 2005 IEEE Intelligent Vehicles Symposium,
2005, pp. 575–582.
[10] J. Harri, F. Filali, C. Bonnet,”On Meaningful Parameters for Routing in VANETs
Urban Environments under Realistic Mobility Patterns”, AutoNet 2006, 1st IEEE
Workshop on Automotive Networking and Applications, December 1, 2006 – San
Francisco, CA, USA
[11] J Haerri, M Fiore, F Filali, C Bonnet, ”VanetMobiSim: generating realistic
mobility patterns for VANETs, in VANET 2006, 3rd ACM International
Workshop on Vehicular Ad Hoc Networks, September 29, 2006, Los Angeles, USA.
[12] P. Juang, H. Oki, Y. Wang, M. Martonosi, L. Peh, and D. Rubenstein, “Energy
efficient computing for wildlife tracking: Design tradeoffs and early experiences
with zebranet,” in ASPLOS, Oct. 2002.
[13] G. Korkmaz, E. Ekici, F. Özgüner, and U. Ösgüner, “Urban multi-hop broadcast
protocol for inter-vehicle communication systems”, In Proc. of the first ACM
workshop on Vehicular ad hoc networks, 2004, pp. 76–85.
[14] M. Kihl, M. Sichitiu, T. Ekeroth and M. Rozenberg, “Reliable Geographical
Multicast Routing in Vehicular Ad-hoc Networks”, Lecture Notes in Computer
Science 4517 LNCS, pp. 315-325. 2007
[15] T. Kosch, C. Schwingenschlögl, and L. Ai, “Information dissemination in multihop
inter-vehicle networks”, In Proc. of the IEEE 5th International Conference on
Intelligent Transportation Systems, 2002, pp. 685–690.
[16] Y. KO and N. Vaidya, “Flooding-based geocasting protocols for mobile ad hoc
networks,” Mobile Networks and Applications, no. 7, pp. 471–480, 2000
[17] C. Lochert, H. Hartenstein, J. Tian, H. Füssler, D. Hermann, and M. Mauve, “A
routing strategy for vehicular ad hoc networks in city environments”, in Proc. of the
IEEE Intelligent Vehicles Symposium, 2003, pp. 156–161.
[18] Q. Li and D. Rus, “Sending messages to mobile users in disconnected ad-hoc
wireless networks,” in Mobile Computing and Networking, 2000.
[19] T. Little and A. Agarwal, “An information propagation scheme for VANETs”, In
Proc. of the 8th International IEEE Conference on Intelligent Transportation
Systems, 2005, pp. 155–160.
[20] C. Maihöfer, C. Cseh, W. Franz, and R. Eberhardt, “Performance evaluation of
stored geocast”, In Proc. of IEEE 58th Vehicular Technology Conference, 2003, pp.
2901–2905.
[27] R. Mangharam, D. Weller, R. Rajkumar, D. Stancil, and J. Parikh, “GrooveSim: A
Topography-Accurate Simulator for Geographic Routing in Vehicular Networks,”
in Proceedings of VANET, 2005.
[28] V. Naumov, R. Baumann, T. Gross, “An Evaluation of Inter-Vehicle Ad Hoc
Network Based on Relistic Vehicular Traces“, ACM MobiHoc’06: Proceedings of
the 7th ACM International Symposium on Mobile Ad Hoc Networking and
Computing. Pp. 108 – 119, 2006
[29] D. Niculescu and B. Nath, “Trajectory Based Forwarding and Its Applications,” in
MobiCom, 2003.
[30] A. K. Saha and D. B. Johnson, “Modeling Mobility for Vehicular Ad Hoc
Networks,” in Proceedings of VANET, pp. 91 – 92, 2004.
[31] R. Santos, A. Edwards, R. Edwards, and N. Seed, “Performance evaluation of
routing protocols in vehicular ad-hoc networks”, International Journal of Ad Hoc
and Ubiquitous Computing, vol. 1, pp. 80–91, 2005.
[32] J. Tian, L. Han, K. Rothermel, and C. Cseh, “Spatially Aware Packet Routing for
Mobile Ad Hoc Inter-vehicle Radio Networks,” in Proc. of the IEEE 6th Intl. Conf.
on Intelligent Transportation Systems (ITSC), 2003.
[33] A. Vahdat and D. Becker, “Epidemic routing for partially connected ad hoc
networks,” Tech. Rep., 2000.
[34] H. Wu, R. Fujimoto, R. Guensler, and M. Hunter, “MDDV: Mobility-Centric Data
Dissemination Algorithm for Vehicular Networks,” in Proceedings of VANET,
2004.
[35] W. Zhao, M. Ammar, and E. Zegura, “A message ferrying approach for data
delivery in sparse mobile ad hoc networks,” in MobiHoc, 2004.
[36] J. Zhao and G. Cao, “VADD: Vehicle-Assisted Data Delivery in Vehicular Ad Hoc
Networks,” in InfoCom, 2006.