在VANET 中，節點具有高移動性，也因此網路拓樸的變化極為頻繁，使得 節點之間的連線不穩定，傳統網路使用Source Routing 的方式，在來源端決定封 包的傳送路徑，但是在動態網物拓樸中，在封包傳輸過程中路徑斷裂造成封包遺 失的問題， VDTN 的路由利用 store-carry-forward 的技術，使用 Contact Routing 的方式，克服傳輸路徑斷裂的問題。
本論文提出HPVR 解決下列幾點問題:
(1) 為了解決在 IVC 環境下無法使用 RSU 得知節點的地理位置，因此我們 使用History table 記錄所有遇過節點的地理資訊，History table 只有在節點連線 時才能更新History table 的內容，借此方式可以不用透過 RSU 也能得知目的端 的地理資訊。
(2) 使用 History table 會有地理資訊不一致的問題，使用錯誤的地理資訊可 能會使封包轉送的過程中遠離目的端，所以我們使用象限篩選機制減少此問題發 生。當來源端產生封包時，HPVR 從 History table 取出目的端的歷史位置資訊，
我們提出的預測目的端位置公式，使用記錄在History table 的目的端移動向量和 時間，計算目前目的端的位置(PD)。我們觀察來源端的移動方向與 PD 的之間的
With Vector 和 Without Vector 兩種類型，HPVR、SD_MPAR、HVR 為 With Vector，
Epidemic、VR 為 Without Vector，由實驗可觀察出在不同節點數量的情況下，
With Vector 路由在 Delivery ratio 比 Without Vector 路由高，Overhead 與 Latency 也比Without Vector 低，由此可知考量目的端移動方向是可靠的。
HPVR 與 Epidemic 的 Delivery ratio 比較可以看出我們能夠解決封包封包氾 濫的問題，與相同使用History table 的 HVR 的 Latency 比較，我們解決了 History table 地理資訊不一致的問題，確保封包轉送方向是往目的端方向靠近，我們與 相同考量節點移動方向的SD_MPAR 比較，因為 SD_MPAR 使用 RSU 可以隨時 更新目的端的地理資訊，封包可以往目的端位置的方向轉送，所以封包可以在較 少的Latency 內到達目的端，然而 HPVR 的 Latency 比 SD_MPAR 高，因為我們 使用象限篩選機制確保往目的端靠近的中繼節點，確保封包的轉送路徑的方向。
以實驗結果證實使用象限篩選和預測目的端位置是可靠的。
目前 HPVR 主要提升到達率和減少傳輸開銷，若在節點數量高的環境下，
Latency 可能表現不理想，這是因為我們提出的象限篩選機制篩選的條件比較嚴 謹，造成排除可能增加封包複製數量但能夠快速到達目的端的候選點，HPVR 雖 然能夠減少 Overhead 與提高 Delivery ratio， Latency 可能會輸給使用 RSU 的 SD_MPAR，未來可能朝向動態調整篩選條件的方向研究。
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附錄
1. package routing;
2.
3. import java.util.ArrayList;
4. import java.util.Collections;
5. import java.util.Comparator;
6. import java.util.HashMap;
7. import java.util.List;
8. import java.util.Map;
9.
10. import core.Connection;
11. import core.DTNHost;
12. import core.Message;
13. import core.Settings;
14. import core.SimClock;
15. import core.Tuple;
16.
17. public class HPVR extends ActiveRouter{
18. private Map<DTNHost, List> ConnectTable;
19. private Map<Connection, Integer> DistanceQueue;
20. private Map<Message, Map> TempMap;
21. List<Map.Entry<Connection, Integer>> tempList;
22.
36. String MSG_COUNT_PROPERTY = "property";
42. // TODO Auto-generated constructor stub 43. }
51. this.ConnectTable = new HashMap<DTNHost, List>();
52. } 53.
54. public void changedConnection(Connection con) { 55. if(con.isUp()){
56. DTNHost ContactNode = con.getOtherNode(getHost());
57. othertowardAngle = this.getAngle(ContactNode);
58. othertowardQuadrant = this.countQuadrant(ContactNode);
59. List<Double> CoordList = new ArrayList<Double>();
60. CoordList.add(ContactNode.getLocation().getX());//0 61. CoordList.add(ContactNode.getLocation().getY());//1 62. CoordList.add(SimClock.getTime());//2
63. CoordList.add(othertowardAngle);//3 64. CoordList.add(othertowardQuadrant);//4
65. CoordList.add(this.getnodeSpeed(ContactNode));//getSpeed 5 66. ConnectTable.put(ContactNode, CoordList);
67. checkTable(ContactNode, this.getHost());
68. }
69. }
70. private Tuple<Message, Connection> tryOtherMessages() {
71. List<Tuple<Message, Connection>> messages = new ArrayList<Tuple<Message, Connection>>();
72. DistanceQueue = new HashMap<Connection, Integer>();
73. TempMap = new HashMap<Message, Map>();
74. for(Connection con : this.getConnections())
75. {
76. DTNHost ContactNode = con.getOtherNode(getHost());
77. towardAngle = this.getAngle(this.getHost());
78. towardQuadrant = this.countQuadrant(this.getHost());
79. othertowardAngle = this.getAngle(ContactNode);
80. othertowardQuadrant = this.countQuadrant(ContactNode);
81. for(Message m : getMessageCollection())
82. {
83. if(this.ConnectTable.containsKey(m.getTo())){
84. boolean Q =
this.compareQuadrant(this.ConnectTable.get(m.getTo()), this.getHost(), ContactNode, m.getTo());
85. int CopyNumber =
getCopyNumber(this.ConnectTable.get(m.getTo())); int propertyValue = (Integer) m.getProperty(MSG_COUNT_PROPERTY) ;
86. if(propertyValue == -1){
87. m.updateProperty(MSG_COUNT_PROPERTY, CopyNumber);
88. }
89.
90. if(Q){
91. int distance =
(int)getDistance(con.getOtherNode(getHost()), ConnectTable.get(m.getTo()));
92. int ArrvialTime = this.getArrivalTime(distance,
getHost());
93. DistanceQueue.put(con, ArrvialTime);
94. TempMap.put(m, DistanceQueue);
95. }
96. }
97. }
98. }
99.
100. if(!TempMap.isEmpty()){
101. for(Object key:TempMap.keySet()){
102. tempList = new ArrayList<Map.Entry<Connection,
103. Collections.sort(tempList, new Comparator<Map.Entry<Connection, Integer>>(){
104. public int compare(Map.Entry<Connection, Integer> entry1, Map.Entry<Connection, Integer> entry2){
105. return (entry1.getValue() - entry2.getValue());
106. }
107. });
108. boolean State = true;
109. for(Object
conkey:tempList.get(0).getKey().getOtherNode(getHost()).getMessageCollection()){
110. if(key.toString().equals(conkey.toString())){
111. State = false;
112. }
113. }
114. if(State == true){
115. messages.add(new Tuple<Message, Connection>((Message)key, tempList.get(0).getKey()));
123. return tryMessagesForConnected(messages);
124. } 125.
126. @Override
127. protected int checkReceiving(Message m) { 128. int recvCheck = super.checkReceiving(m);
129. if (recvCheck == RCV_OK) {
130. /* don't accept a message that has already traversed this node */
131. if (m.getHops().contains(getHost())) {
132. recvCheck = DENIED_OLD;
133. }
134. }
135.
136. if (isTransferring()) {
137. return TRY_LATER_BUSY; // only one connection at a time
138. }
145. if ( hasMessage(m.getId()) || isDeliveredMessage(m) ){
146. return DENIED_OLD; // already seen this message -> reject it
147. }
157. if (isTransferring() || !canStartTransfer()) {
158. return;
159. }
160.
161. if (exchangeDeliverableMessages() != null) {
162. return;
163. }
164. tryOtherMessages();
165. } 166.
167. @Override
168. public HPVR replicate() {
169. // TODO Auto-generated method stub 170. return new HPVR(this);
171. }
174. public boolean createNewMessage(Message msg) { 175. makeRoomForNewMessage(msg.getSize());
176. msg.addProperty(MSG_COUNT_PROPERTY, -1);
177. msg.addProperty(MSG_CREATTIME, SimClock.getTime());
178. addToMessages(msg, true);
179. return true;
180. } 181.
182. @Override
183. protected void transferDone(Connection con) { 184. Integer nrofCopies;
185. String msgId = con.getMessage().getId();
186. //get this router's copy of the message 187. Message msg = getMessage(msgId);
188.
189. if (msg == null) { // message has been dropped from the buffer after..
190. return; // ..start of transfer -> no need to reduce amount of copies
191. }
192.
193. // reduce the amount of copies left
194. nrofCopies = (Integer)msg.getProperty(MSG_COUNT_PROPERTY);
195. if(nrofCopies == 0){
196. this.deleteMessage(con.getMessage().getId(), false);
197. }
198. else
199. nrofCopies--;
200. msg.updateProperty(MSG_COUNT_PROPERTY, nrofCopies);
201. } 202.
203. private int getArrivalTime(double dis, DTNHost host){
204. int arrivaltime = 0;
205. double AnlgeCos = this.getnodeSpeed(host) * Math.cos(this.getAngle(host));
206. arrivaltime = (int)(dis/AnlgeCos);
207. return arrivaltime;
208. } 209.
210. //check and update ConnectTable
211. private void checkTable(DTNHost otherhost, DTNHost host){
212. HPVR otherNode = (HPVR)otherhost.getRouter();
213. Map<DTNHost, List> otherTable = otherNode.ConnectTable;
214. HPVR hostNode = (HPVR)host.getRouter();
215. Map<DTNHost, List> thisTable = hostNode.ConnectTable;
216.
217. for(Map.Entry<DTNHost, List> i : otherTable.entrySet()){
218. if(!thisTable.containsKey(i.getKey())){
219. thisTable.put(i.getKey(), i.getValue());
220. }
221. }
222. for(Map.Entry<DTNHost, List> j : thisTable.entrySet()){
223. if(!otherTable.containsKey(j.getKey())){
224. otherTable.put(j.getKey(), j.getValue());
225. }
226. }
227.
228. //contain with thisTable from otherTable
229. for(Map.Entry<DTNHost, List> i : otherTable.entrySet()){//other i
230. for(Map.Entry<DTNHost, List> j : thisTable.entrySet()){ //this j
231. if(i.getKey() == j.getKey()){
232. double otherTime = (double)i.getValue().get(2);//get time 233. double hostTime = (double)j.getValue().get(2);
234.
235. if(hostTime < otherTime){
236. j = i;//update the new value
237. thisTable.put(i.getKey(), i.getValue());
238. }
239. else if(otherTime < hostTime){
240. i = j;
241. otherTable.put(j.getKey(), j.getValue());
242. }
243. }
244. }
245. }
248.
249. public double getnodeSpeed(DTNHost host){
250. double speed = 0;
251. if(host.getPath() != null && host.getPath().hasNext()){
252. speed = host.getPath().getSpeed();
253. }
254. return speed;
255. } 256.
257. public double getDistance(DTNHost host, List ConnectList){
258. double x = (double)ConnectList.get(0) - host.getLocation().getX();
259. double y = (double)ConnectList.get(1) - host.getLocation().getY();
260. double dis = Math.sqrt(x*x + y*y);
261. return dis;
262. } 263.
264.
265. public double getAngle(DTNHost host){
266. double Angle = 0;
267. if(host.getPath() != null && host.getPath().hasNext()){
268. double nextX = host.getPath().getNextWaypoint().getX();
269. host.getPath().BeforenextWpIndex();
270. double nextY = host.getPath().getNextWaypoint().getY();
271. host.getPath().BeforenextWpIndex();
272. double X = host.getLocation().getX();
273. double Y = host.getLocation().getY();
274. Angle = Math.atan2(nextY - Y, nextX - X);
281. public double countQuadrant(DTNHost host){
282. double Q = 0;
283. if(host.getPath() != null && host.getPath().hasNext()){
284. double nextX = host.getPath().getNextWaypoint().getX();
285. host.getPath().BeforenextWpIndex();
286. double nextY = host.getPath().getNextWaypoint().getY();
287. host.getPath().BeforenextWpIndex();
288. Q = Quadrant(nextX - host.getLocation().getX(), nextY - host.getLocation().getY());
289. }
290. return Q;
291. } 292.
293. //host and other Quadrant
294. public double relativeLocation(DTNHost host, DTNHost otherhost){
295. double relativeX = otherhost.getLocation().getX() - host.getLocation().getX();
296. double relativeY = otherhost.getLocation().getY() - host.getLocation().getY();
297. //judgment Quadrant
298. return (Quadrant(relativeX,relativeY));
299. } 300.
301.
302. //Destination and Connect Angle
303. public double ConnectToDesvector(DTNHost host, List des){
304. double Angle = 0;
305. //double CNnew = 0;
306. double otherX = host.getLocation().getX();
307. double otherY = host.getLocation().getY();
308. //vector of host
309. double vectorX = (double)des.get(0) - otherX;
310. double vectorY = (double)des.get(1) - otherY;
311. Angle = Math.atan2(vectorY, vectorX);
317. private double ConnectToPreDesvector(DTNHost host,double x, double y){
318. double Angle = 0;
321. double vectorX = x - hostX;
322. double vectorY = y - hostY;
323. Angle = Math.atan2(vectorY, vectorX);
324. Angle = Angle*180/Math.PI;
325. return Angle;
326. } 327.
328. //Quadrant
329. public static double Quadrant(double X,double Y){
330. double Q = 0;
357. //System.out.println("X = "+X+"; Y = "+Y+"---->"+Q+" Quadrant");
358. return Q;
359. } 360.
361. public boolean compareQuadrant(List desInfo, DTNHost host, DTNHost ContactNode, DTNHost des){
362.
363.
364. DesTowardQuadrant = (double)desInfo.get(4);//Destination toward Quadrant 365. DesTime = SimClock.getTime() - (double)desInfo.get(2);//the time
Destination has traveled
366. DesSpeed = (double)desInfo.get(5);
367. DesTowardAngle = (double)desInfo.get(3);
368. DesX = (double)desInfo.get(0);
369. DesY = (double)desInfo.get(1);
370.
377. if(towardAngle != 0 && othertowardAngle != 0){
378. PreDesX = DesSpeed * DesTime * Math.cos(DesTowardAngle) + DesX;
379. PreDesY = DesSpeed * DesTime * Math.sin(DesTowardAngle) + DesY;
380. PreDesQuadrant = Quadrant(PreDesX - host.getLocation().getX(), PreDesY - host.getLocation().getY());//Predict Destination
381. ConToDesAngle = ConnectToPreDesvector(ContactNode, PreDesX, PreDesY);
382.
383. Angle = Math.abs(othertowardAngle - ConToDesAngle);
384. if(Angle > 180){
385. Angle = 360 - Angle;
386. }
387.
388. if(Angle < 50){
389. double HostToConQuadrant = relativeLocation(host,ContactNode);
390. double Q3 = Math.abs(PreDesQuadrant - towardQuadrant);//Host and
391. double Q4 = Math.abs(PreDesQuadrant - HostToConQuadrant);//Host and Predict Destination
392. if(Q3 == 0){//Host and Predict Destination same Quadrant 393. if(Q4 == 0){//Connect and Predict Destination same Quadrant
394. //MesCopy = 20; 402. if(Q4 == 0){//Connect and Predict Destination same Quadrant
403. return true;
404. }
405. else if(HostToConQuadrant == towardQuadrant){//Connect and HostToward same Quadrant
406. return true;
412. else if(Q3 == 2){//Host and Destination relative Quadrant 413. if(towardQuadrant == HostToConQuadrant){//Connect and
HostToward same Quadrant
414. return false;
426. return true;
427. else
428. return false;
429. }
430. public int getCopyNumber(List desInfo){
431. int copy = 0;
432. DesTowardQuadrant = (double)desInfo.get(4);//Destination toward Quadrant 433. double DesSpeed = (double)desInfo.get(5);
434. double DesTowardAngle = (double)desInfo.get(3);
435. double DesX = (double)desInfo.get(0);
436. double DesY = (double)desInfo.get(1);
437. double PreDesX = DesSpeed * DesTime * Math.cos(DesTowardAngle) + DesX;
438. double PreDesY = DesSpeed * DesTime * Math.sin(DesTowardAngle) + DesY;
439. double PreDesQuadrant = Quadrant(PreDesX - this.getHost().getLocation().getX(),
440. PreDesY -
this.getHost().getLocation().getY());
441.
442. double Q = Math.abs(PreDesQuadrant - towardQuadrant);
443. if(Q == 0){