An Adaptive Cross-Layer Multi-Path Routing Protocol for Urban VANET 指導教授：許子衡　教授 學　　生：董藝興　學生 作者：Yufeng Chen; Zhengtao Xiang; Wei Jian; Weirong Jiang;  出處：Automation and Logistics (ICAL), 2010 IEEE International Conference on 

INTRODUCTION To construct networks between vehicles for future applications, such as active safety and traffic management, suitable routing protocols are needed. When designing routing protocols, we should select routing metrics firstly, which influence routing performance heavily. 輛之間構建網絡為未來的應用，如主動安全和交通管理，適當的路由協議是必要的。 在設計路由協議，我們首先應該選擇路由度量，這嚴重影響路由性能。

INTRODUCTION In VANET, high mobility and complex environment may cause connections to break off with high probability, which means high requirements of route rediscovery. Multi-path routing protocol works better in such circumstances because candidate routes can be used to avoid frequent route rediscovery. 在VANET，高流動性和複雜的環境可能會導致連接中斷的概率很高，這意味著高要求的路線重新發現。 多路徑路由協議在這種情況下工作得更好，因為候選人路線可以用來避免頻繁的路由重新發現。

INTRODUCTION Thus, we adopted multi-path routing protocol to decrease the route discovery frequency and mitigate broadcast storm problem. Based on the above considerations, an adaptive cross- layer multi-path routing protocol is proposed based on the improvement of Ad hoc On-demand Multipath Distance Vector (AOMDV) protocol. 因此，我們採用多路徑路由協議來減少路由發現頻率和減輕廣播風暴問題。 基於上述考慮，一種自適應跨層多路徑路由協議基礎上，提出改進的Ad hoc按需距離矢量多徑（AOMDV）協議。

Adaptive Routing Metric When selecting metric of link-quality information, we adopted the Maximum Retransmission Counts (MRC) along one path The MRC gives the estimation of the worst link along one path. 當選擇公噸的鏈路質量信息，我們採取了最大重新傳輸計數（MRC分）沿一條路徑 [3]。 在“MRC”提供估計的最壞鏈接沿著一條路徑。

Adaptive Routing Metric α is the weight of hop-count, β is the weight of MRC, (1-α-β) is the weight of speed, K is the number of paths to destination node D, MAX_HOP(K), MAX_MAXRETRAN(K) and MAX_MAXSPEED(K) are the maximum hop-count, the maximum MaxREtran, and the maximum MaxSpeed of the K paths. 滿足以下條件的路徑將被選中轉發數據包，（公式），其中α是權重跳數，β是權重MRC，（1 -α-β）是速度權重，K是數到目的節點 D的路徑，MAX_HOP（金），MAX_MAXRETRAN（K）和MAX_MAXSPEED（金）是最大跳數，最大MaxREtran，最高車速和最大的K路徑。 α為權重設置為固定值0.4，以確保在跳數路徑可以是有限的。 如果MAX_MAXRETRAN（金）小於 2，這意味著該鏈接的質量是好的，β設置為 0.1。在這種情況下，速度指標，更重要的是比MRC的路由決策。

Designing Routing Protocol The MaxREtran of bi-directional paths should be obtained respectively and stored in routing tables. However, the measurement of MaxREtran of S→D should be stored in the routing table of source node S. 該 MaxREtran雙向路徑應分別獲得並儲存在路由表。 然而，測量 MaxREtran的S→D應儲存在路由表源結點 s

Designing Routing Protocol Routing table The routing table entry structure and route list structure of R-S-AOMDV are shown in Fig.1 and Fig.2. 路由表的路由表項的結構和路由表結構的RS - AOMDV都顯示在圖 1和圖 2。 在這裡，ForwardMaxRetran字段表示的MRC沿路徑從當前節點到目的節點 D 該 ReverseMaxRetran字段表示的MRC沿路徑從目的節點 D到當前節點，這是用來計算的MRC的D→S如果節點是中間節點和節點有一個可用的轉發路徑，節點 D 在最高車速方面，不僅表明了最大速度沿路徑，但也被用來計算相應的最大速度，如果節點是一個中間節點和節點有一個可用的轉發路徑，節點 D

Designing Routing Protocol Routing protocol When source node S needs a route to destination node D, and there are not available paths, the source node will initiate a route discovery process. --First, node S broadcasts RREQ routing packet, as source nodes do in AOMDV. 路由協議，當源節點 S需要一個路由到目的節點 D和有沒有可用的路徑，源節點將啟動一個路由發現過程。 第一，節點 S廣播 RREQ消息路由數據包，作為源節點做AOMDV。

Designing Routing Protocol --Second, when other nodes receive duplicate RREQ packets, they will establish or update the reverse paths to source node S according to different first hops of RREQ. --Third, if RREP packets are received by other nodes, the forward paths to node D will be established in routing table according to different RREP First Hops and RREQ First Hops in RREP packets. - 其次，當其他節點收到重複 RREQ分組，他們將建立或更新反向路徑到源節點 S根據不同的第一跳數的RREQ。 - 第三，如果其他節點收到RREP數據包，根據不同的RREP第一跳，第一hops RREP的RREQ封包，將建立路由表路徑向前節點 D。

Designing Routing Protocol --Fourth, when other node receives a RRETRAN packet with marked ACK from a neighbor, it will search their routing table to find a reverse path whose Last Hop is identical with the First Hop of the RRETRAN packet. - 第四，當其他節點收到顯著的ACK包，RRETRAN從一個鄰國，它會搜索自己的路由表中找到一個反向路徑的最後一跳是等同採用第一跳的RRETRAN包。

Designing Routing Protocol --Fifth, when other nodes receive RRETRAN packets with non-marked ACK from their neighbors, they will identify the forward paths according to the neighbors. --Sixth, when forwarding data packets, the weights of hop-count, MRC and speed are adjusted according to the current MAX_MAXRETRAN(K). - 第五，當其他節點的數據包接收RRETRAN與非標記的ACK從他們的鄰居，根據鄰居他們會確定前進道路。 - 第六，在轉發數據包，權重跳數，湄公河委員會和速度是按照目前的MAX_MAXRETRAN（金）。

PERFORMANCE EVALUATION Simulation time is 300 seconds. We simulated two urban scenarios, one for sparse scenario with 20 nodes and the other for dense with 50 nodes. The maximal speed is 15 m/s. Acceleration is set to 0.5 m/s 2 . The 802.11 MAC layer is used with Shadowing propagation model and the communication range is 250m. 仿真時間為 300秒。 我們模擬兩個城市的情況，一個稀疏的情況與 20個節點，而另外密集，50個節點。 最大速度為 15米/秒 加速設置為 0.5米/秒2。 802.11 MAC層使用具有跟踪傳播模型，通信範圍為 250米。

PERFORMANCE EVALUATION

PERFORMANCE EVALUATION

PERFORMANCE EVALUATION