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無線網路路由及模擬實驗簡介 演講人:王朱福 (屏東教育大學資訊科學系) Outline… Wireless networks architectures Routing protocols for wireless networks Mobile ad-hoc Networks (MANETs) Wireless Sensor Networks (WSNs) Vehicle ad-hoc networks (VANETs) Network Simulator for performance evaluation Concluding remarks 2 Wireless network architectures Infrastructure-based wireless networks Fixed base stations / access points are used. Infrastructure-less wireless networks (Ad-hoc networks) No fixed infrastructure support are available. Hybrid wireless networking architecture 3 Two types of wireless networks – with infrastructure Single-hop communication 4 Two types of wireless networks – without infrastructure (also known as ad-hoc network) No centralized server Multi-hop communications 5 Outline… Wireless networks architectures Routing protocols for wireless networks Mobile ad-hoc Networks (MANETs) Wireless Sensor Networks (WSNs) Vehicle ad-hoc networks (VANETs) Network Simulator for performance evaluation Concluding remarks 6 Routing protocols for wireless networks – MANETs Some challenges to MANETs routing. MANETs are more unstable than wired-networks because of the lack of a centralized entity. Mobility will cause network topology to change, which results in a great change in connection between two hosts. The connectivity between network nodes is not guaranteed, so intermittent connectivity is common. 7 The main routing problems for MANETs 8 10 9 7 4 6 Node mobility Routing path broken frequently 2 3 5 1 Traditional routing protocols will be no longer fit. 8 Ad-hoc routing protocols 9 Routing protocols for MANETs Flooding-type routing protocol (flooding) Table-driven routing protocol (proactive) On-demand routing protocol (reactive) Hybrid routing protocol 10 Flooding 9 10 8 2 20 3 11 7 1 Broadcast storm problem 4 19 12 16 6 13 15 18 17 11 14 Routing protocols for MANETs (cont.) Table-driven routing protocol (proactive): They maintain the global topology information in the form of tables at every node. These tables are updated frequently in order to maintain consistent and accurate network state information. For example, DSDV, WRP, and STAR. enhanced version of the distributed Bellman-Ford algorithm 12 DSDV (Destination Sequenced Distance-Vector Routing Protocol) Example: Routing table for Node 1 15 14 13 11 12 10 9 8 6 4 7 5 3 1 2 13 Dest 2 3 4 5 6 7 8 9 10 11 12 13 14 15 NextNode 2 2 5 5 6 2 5 2 6 6 5 5 6 5 Dist 1 2 2 1 1 3 3 4 2 2 3 4 3 4 seqNo 22 26 32 134 144 162 170 186 142 176 190 198 214 256 DSDV (cont.) Routing table for Node 1 15 Dest NextNode 2 2 3 2 4 5 5 5 6 6 7 2 8 5 9 2 10 6 11 5 12 5 13 5 14 6 15 5 14 13 11 12 10 8 9 6 4 7 5 3 1 2 14 Dist 1 2 2 1 1 3 3 4 2 4 3 4 3 4 seqNo 22 26 32 134 144 162 170 186 142 180 190 198 214 256 Routing protocols for MANETs (cont.) On-demand routing protocol (reactive): They execute the path-finding process and exchange routing information only when a path is required by a node to communicate with a destination. For example, AODV and DSR. 15 The AODV routing procedure (cont.) The Route discovery process: It begins with the creation of a RouteRequest (RREQ) packet. Broadcasting is done via flooding. Broadcast ID gets incremented each time a source node uses RREQ. Broadcast ID and source IP address form a unique identifier for the RREQ. Type Reserved Hop Count Broadcast ID RREQ packet format Destination IP Address Destination Sequence Number Source IP Address Source Sequence Number Time Stamp 16 The AODV routing procedure (cont.) 2. Sender S broadcasts a RREQ to all its neighbors, each node receiving RREQ forwards RREQ to its neighbors. *Sequence numbers help to avoid the possibility of forwarding the same packet more than once. 3. An intermediate node (not the destination) may also send a RouteReply (RREP) packet provided that it knows a more recent path than the one previously known to sender S. Type Reserved Hop Count Destination IP Address RREP packet format Destination Sequence Number Source IP Address Life Time 17 The AODV routing procedure (cont.) 4. As an intermediate node receives the RREP packet, it sets up a forward path entry to the destination in its routing table. 5. The source node can begin data transmission upon receiving the first RREP. 18 Outline… Wireless networks architectures Routing protocols for wireless networks Mobile ad-hoc Networks (MANETs) Wireless Sensor Networks (WSNs) Vehicle ad-hoc networks (VANETs) Network Simulator for performance evaluation Concluding remarks 19 WSNs & VANETs Two special types of ad-hoc network • WSNs (Wireless Sensor Networks) • VANETs (Vehicular Ad-hoc Networks) 20 Introduction to WSNs -- Applications Military applications Home applications Environmental applications Applications Health applications 21 Other commercial applications Introduction to WSNs – Sensor node Introduction to WSNs – Sensor node (cont.) Aqua node Introduction to WSNs – Sensor node (cont.) Aqua node The applications of WSNs Precision Agriculture, Water quality management 25 The differences between WSNs and ad-hoc networks The number of sensor nodes in a sensor network can be several orders of magnitude higher. Sensor nodes are densely deployed. Sensor nodes are prone to failures. Sensor nodes are limited in power, computational capacities, and memory. Routing protocols for WSNs Flat-based All nodes are typically assigned equal roles or functionality. Hierarchical-based Nodes will play different roles in the network. Location-based Sensor node’s positions are exploited to route data in the network. Flat-based routing example SPIN (Sensor Protocols for Information via Negotiation) ADV DATA REQ A ADV REQ DATA 1. Data is described by meta-message (ADV). 2. Send ADV to neighbors. 3. If neighbor do not have the data, sends REQ; otherwise, do nothing. 4. As the REQ received by sender, then it sends the data to the neighbor. Hierarchical-based routing Hierarchical routing is two-layer routing. Higher-energy nodes can be used to process and send the information, while low-energy nodes can be used to perform the sensing in the proximity of the target. The creation of clusters and assigning special tasks to cluster heads can greatly contribute to overall system scalability, lifetime, and energy efficiency. Hierarchical-based routing example TEEN (Threshold-Sensitive Energy Efficient Sensor Network SProtocol) Sink Cluster Node 1st cluster head 2nd cluster head D Hierarchical-based routing example TEEN (Threshold-Sensitive Energy Efficient Sensor Network Protocol) Cluster-based routing. Node transmits sensed data only if both of the following conditions hold: 1. The sensed value is greater than a Hard Threshold. 2. The sensed value differs from last transmitted value by more than a Soft Threshold. Routing compare Hierarchical-based routing Flat-based routing Reservation-based scheduling Contention-based scheduling Collisions avoided Collision overhead present Reduced duty cycle due to periodic sleeping Variable duty cycle by controlling sleep time of nodes Data aggregation by cluster head Node on multi-hop path aggregates incoming data from neighbors Simple but non-optimal routing Routing can be made optimal but with an added complexity Requires global and local synchronization Links formed on the fly without synchronization Overhead of cluster formation throughout the network Routes formed only in regions that have data for transmission Lower latency as multiple hops network formed by cluster heads always available Latency in waking up intermediate nodes and setting up the multipath Research view of WSNs’ routing Forest fire detection sin k From: www.nps.gov/slbe/planyourvisit/psbeechmaple.htm 33 Research view of WSNs’ routing (cont.) Forest fire detection (cont.) Sink Sensor Sensor Sensor Event Sensor Sensor User Sensor Sensor Sensor From: www.nps.gov/slbe/planyourvisit/psbeechmaple.htm 34 Sensor The most important design issue is . . . Energy saving! Energy saving! The objective: To maximize the network lifetime (網路壽命最大化) How to estimate the network lifetime of a WSN? 35 How to estimate the network lifetime of a WSN? Example: Routing (energy-aware routing) Sink Sensor Sensor Sensor Energy consumption for Event Sensor Sensor Data transmitting: Etx=6 User Sensor Sensor Data receiving: Erx=3 Sensor 45 -9 50 -9 70 -6 40 ∞ 35 60 55 36 Sensor -9 90 65 Objective: To maximize network lifetime Example: Routing (energy-aware routing) Sink Sensor Sensor Sensor Energy consumption for Event Sensor Sensor Data transmitting: Etx=6 User Sensor Sensor Data receiving: Erx=3 Sensor 36 41 Sensor 64 -6 31 ∞ 35 -9 60 -9 37 55 -9 90 -9 65 -9 How to estimate the network lifetime of a WSN – an expected approach Define: E_consumptionv(u) Etx (k , d (u, successor (u )) E _ consumptionv (u ) Erx (k ) Etx (k , d (u, successor (u ))) 0 if u v if u v and u Pvs if u Pvs Define:The expected energy consumption for node u during one transmission round (ELE(u)) ELE(u ) P(v) E _ consumpionv (u ) vV p(v): the probability of an event occurring in node v 38 How to estimate the network lifetime of a WSN – an expected approach (cont.) Let Etx=6 E_consumptionE(B)=6+3=9 Erx=3 E_consumptionF(B)=6+3=9 E and let p(v)=1/n F E_consumptionA(B)=0 A B B E_consumptionB(B)=6 D C E_consumptionD(B)=6+3=9 E_consumptionc(B)=0 ELE(B) P( A) E _ consumpionA ( B) P(B) E _ consumpionB (B)) ... P(F ) E _ consumpionF ( B) =1/6(0+6+0+9+9+9)=5.5 S 39 How to estimate the network lifetime of a WSN – an expected approach (cont.) The expected network lifetime (ENL(G)) ENL(G) min vV r (v) / ELE(v) 10 30 E F18 ELE(E)=3 ELE(F)=2 50 A 12.5 40 B ELE(A)=4 7.27 ELE(B)=5.5 ELE(C)=10 S 40 D ELE(D)=4 70 C 20 7 5 9 Sensors deployment issues 1 Pre-deployment Sensor Sensor Sensor Sensor 2 Post-deployment Sensor Sensor Sensor Sensor Sensor 3 Topology adjustment 41 The major concerns of sensor deployment No coverage holes No communication holes Maximize network lifetime Uniformly distributed v.s. Non-uniformly distributed sin k sin k 42 Introduction to some deployment problems Post-deployment problem Topology adjustment The Optimization of Sensor Relocation in Wireless Mobile Sensor Networks Pre-deployment problem Joint Optimization of Energy Allocation and Routing Problems in Wireless Sensor Networks 43 Topology adjustment The Optimization of Sensor Relocation in Wireless Mobile Sensor Networks Mobile node sin k 44 Problem formulation Network model B F cluster cluster D A cluster cluster E cluster C cluster Sink sensor sensor sensor sensor sensor sensor sensor sensor sensor sensor cluster cluster 45 sensor Problem formulation (cont.) B F sensor sensor sensor sensor sensor sensor sensor sensor sensor cluster sensor D A cluster sensor sensor sensor sensor sensor sensor sensor sensor sensor sensor sensor cluster sensor cluster sensor E sensor sensor sensor C sensor sensor sensor cluster sensor sensor sensor sensor sensor KEY Sensor moving cluster Routing Sink 46 Problem formulation (cont.) To determine a relocation scheme to optimize the resulting network lifetime. B F sensor sensor sensor sensor sensor sensor sensor sensor cluster sensor cluster A D sensor sensor sensor sensor sensor sensor sensor sensor sensor sensor sensor sensor cluster cluster E C sensor sensor sensor sensor sensor sensor sensor sensor sensor sensor cluster cluster 47 Introduction to some deployment problems Post-deployment problem Topology adjustment The Optimization of Sensor Relocation in Wireless Mobile Sensor Networks Pre-deployment problem Joint Optimization of Energy Allocation and Routing Problems in Wireless Sensor Networks 48 Pre-deployment problem Joint Optimization of Energy Allocation and Routing Problems in Wireless Sensor Networks Energy-aware routing problem 45 -9 50 -9 70 -6 40 -9 ∞ 35 60 55 49 90 65 Pre-deployment problem Joint Optimization of Energy Allocation and Routing Problems in Wireless Sensor Networks Energy allocation problem r(B)=150 p(B)=1/6 r(D)=90 p(D)=1/6 r(A)=100 p(A)=1/6 50 r(C)=200 p(C)=1/6 r(F)=300 p(F)=1/6 r(E)=250 p(E)=1/6 Pre-deployment problem Joint Optimization of Energy Allocation and Routing Problems in Wireless Sensor Networks Joint energy allocation and routing problem r(B)=150 p(B)=1/6 r(D)=90 p(D)=1/6 r(A)=100 p(A)=1/6 51 r(C)=200 p(C)=1/6 r(F)=300 p(F)=1/6 r(E)=250 p(E)=1/6 Pre-deployment problem Joint Optimization of Energy Allocation and Routing Problems in Wireless Sensor Networks 52 Introduction to VANETs Applications in a VANET fall into two categories comfort applications safety applications Introduction to VANETs (cont.) Vehicle mobility creates a highly dynamic topology. VANETs are potentially large-scale networks. Vehicles can provide more resources than other types of mobile networks such as: large batteries antennas processing power Routing for VANETs Disconnected due to sparse Two Paths: (1) Ia => Ic => Id => Ib (2) Ia => Ib Delayacdb < Delayab The Intermittent connected routing problem In case of the nodes density of a VANET is sparse, it will cause the intermittent connected routing problem, and consequently the traditional routing protocols will be no longer fit. 56 Intermittent connected routing problem 57 Epidemic routing protocol Epidemic is a simple routing protocol to resolve the intermittent connected routing problem. The nodes adopt store-carry-forward communication scheme. A node can carry the messages in its cache if no any direct routing path to the destination is available. If a node moves into the node’s transmission range, they will exchange the carried messages between them. 58 3 5 2 4 1 (Epidemic routing) S 59 Outline… Wireless networks architectures Routing protocols for wireless networks Mobile ad-hoc Networks (MANETs) Wireless Sensor Networks (WSNs) Vehicle ad-hoc networks (VANETs) Network Simulator for performance evaluation Concluding remarks 60 Introduction to network simulator -- NS-2 Network Simulator (Version 2) is an event driven simulation tool for studying communication networks. NS2 is a free simulation tool. NS2 can be used to evaluate the performance of a routing protocol. NS2 installation 62 NS-2 architecture Network simulation 兩部機器n0及n1透過2Mbps的有線網路來進 行資料傳遞(參數設定如下圖所示)。 Scenario --- tcl file description 創造節點n0,n1 開啟*.tr記錄檔並寫入。*為檔名可更改。 開啟*.nam記錄檔並寫入。*為檔名可更改。 Scenario --- tcl file description (cont.) 設定節點的Agent 設定封包產生器 開始發送的時間 、封包大小及發 送區間、 Scenario --- tcl file description (cont.) 執行完ns指令,自動 執行 nam animation Simulation results Simulation results (cont.) Wireless network routing simulation (Flooding) 移動範圍: 1,000m*1,000m大小 模擬時間100秒 利用Flooding路由協定 情境設定: 固定節點n0(100,100)為來源節點並發送封包,在第5秒時,n1節點(目的端節點)開始以每 秒5公尺的速率往(500,100)地方前進,而第60秒時,n1節點開始以每秒10公尺速率往 (200,100)方向移動回去,最後停留在(200,100)位置。 Wireless network routing simulation (AODV) 移動範圍:1,000m*1,000m 模擬時間200秒 各節點座標及移動情境如下圖所示。 利用AODV路由協定 TCL codes for Flooding (partial) MFlood TCL codes for AODV (partial) Simulation results