Ad Hoc Network. Asso. Prof. Anan Phonphoem, Ph.D.

Transkript

1 Wireless LANs June September 2009 Ad Hoc Network.. Asso. Prof. Anan Phonphoem, Ph.D. Computer Engineering Department Kasetsart University, Bangkok, Thailand 1

2 Outline Definition and Challenges Media Access Control Routing Protocols Research topics 2

3 Ad Hoc Network Meaning form / deform temporary mobile 2 or more devices Within radio range they communicate Outside communication range need relay node 3

4 Ad Hoc Network Node Diversity of mobile devices Notebook, PDA, phone, badge, etc. Heterogeneous / Homogeneous Fixed transmission range Limited battery Unrestricted movement No collision detection 4

5 Ad Hoc Network Topology Self-organizing Adaptive (dynamic) topology join and leave the network at any time no predefined structure no global topology info 5

6 Ad Hoc Network Key Points Shared transmission medium Each node responses for forwarding data packets for others Network partitions can occur Collision avoidance (no collision detection) 6

7 Mobile Ad Hoc Network (MANET) Set of mobile nodes communicate with each other roam around at will No supporting base stations No guarantee of direct connection single-hop Use intermediate nodes to relay packets multi-hop 7

8 MANET Applications Immediate network deployment Battlefields Major disaster areas Sensor networks Areas without base stations Areas where fixed network structures are unavailable 8

9 Challenges Spectrum Allocation (ISM Band) Media Access No centralized : TDMA cannot be used Mobility Access without collision Routing Link break often Topology change 9

10 Challenges Multicasting Tree formation might not work? Energy Efficiency battery Packet forwarding TCP Performance Connection oriented assumes node to be static Packet loss and long RTT Service Location Security and Privacy 10

12 Media Access Problem Hidden terminal problem contention-based protocol CSMA, IEEE RTS/CTS (incompleteness) Exposed node problem overhearing from neighbor separate control channels directional antennas 12

13 MAC Protocols Receiver-Initiated receiver informs sender (ready to receive) only one control message (no RTS/CTS) Multiple access with collision avoidance By Invitation (MACA-BI) Sender-Initiated sender informs receiver (has data for receiver) MACA MACA with ack (MACAW) 13

14 Receiver-Initiated MAC RTR RTR #1 #2 #3 #4 Data Data 14

15 Sender-Initiated MAC RTS RTS Data Data #1 #2 #3 #4 CTS CTS 15

16 MAC examples Multiple access with collision avoidance (MACA) Multiple access with collision avoidance by Invitation (MACA-BI) Power-Aware Multi-Access Protocol with Signaling (PAMAS) Dual Busy Tone Multiple Access (DBTMA) Media Access with Reduced Handshake (MARCH) 16

17 MACA Amateur packet radio network (Phil Karn) Single frequency network Aim to solve hidden node / exposed node problems 3-way handshake RTS-CTS-Data no carrier sense Power control features adjust power according to receiver 17

18 MACA-BI (by invitation) Fabrizio Talucci 2-way handshake RTR-Data (no RTS, CTS RTR) cannot tx if not receive RTR Receiver guesses (predict) the arrival rate (by queue length) Performance Good for constant bit rate (CBR) Same as MACA for bursty data 18

19 Power-Aware Multi-Access Protocol with Signaling (PAMAS) Based on MACA Add separate signaling channel for RTS-CTS Selectively power off not active (no Tx Rx) Operations Sender RTS Receiver CTS Receiver busy tone on signaling channel Others power off Others transmit node has no data to send/receive probing to detect when should power up 19

20 Dual Busy Tone Multiple Access (DBTMA) BTMA (by Fouad Tobagi) aim to solve hidden terminal problem relay on last-hop architecture centralize nodes for others DBTMA (by Zygmunt Haas) two out-of-band busy tones different frequencies 20

21 Media Access with Reduced Handshake (MARCH) Multi-hop ad hoc network Reduce control overhead Utilize overheard CTS for invitation to relay node reduce RTS packets 21

22 MARCH #1 #2 RTS #3 1 #4 CTS 1 CTS 1 Data Data CTS 2 CTS 2 Data Data CTS 3 CTS 3 Data 22

24 Issues in Ad Hoc Networks Communication in mobility environment connection initialization path selection path reliability Energy consumption vs. latency Throughput Scalability Incompatibility standards 24

25 IEFT MANET Working Group Goals standardize an interdomain unicast (IP) routing protocol define modes of efficient operation support both static and dynamic topologies A dozen candidate routing protocols have been proposed 25

26 Routing??????????????????????????????? Ants Searching for Food? from Prof. Yu-Chee Tseng s slides 26

27 Routing (Ants scenario) 27

28 Three Main Issues in Ants Life Route Discovery: searching for the places with food Packet Forwarding: delivering foods back home Route Maintenance: when foods move to new place 28

29 Routing Protocols Proactive (Global/Table Driven) route determination at startup maintain using periodic update Reactive (On-demand) route determination as needed route discovery process Hybrid combination of proactive and reactive 29

30 Proactive Destination-sequenced distance vector (DSDV) Wireless routing protocol (WRP) Global state routing (GSR) Fisheye state routing (FSR) Source-tree adaptive routing (STAR) Distance routing algorithm for mobility (DREAM) Cluster-head gateway switch routing (CGSR) 30

31 Reactive Associativity-base routing (ABR) Dynamic source routing (DSR) Ad hoc on-demand distance vector (AODV) Temporally ordered routing algorithm (TORA) Routing on-demand acyclic multi-path (ROAM) Light-weight mobile routing (LMR) Signal stability adaptive (SSA) Cluster-based routing protocol (CBRP) 31

32 Hybrid Zone routing protocol (ZRP) Zone-based hierarchical link state (ZHLS) Distributed spanning trees (DST) Distributed dynamic routing (DDR) Scalable location update routing pro. (SLURP) 32

33 Flooding Simplest of all routing protocols Send all info to everybody If data not for you, send to all neighbors Robust destination is guaranteed to receive data Resource Intensive unnecessary traffic load increases, network performance drops quickly 33

34 Routing Examples Destination Sequenced Distance Vector (DSDV) Cluster Gateway Switch Routing (CGSR) Ad hoc On-demand Distance Vector (AODV) Dynamic Source Routing (DSR) Zone Routing Protocol (ZRP) Location-Aided Routing (LAR) Distance Routing effect Algorithm for mobility (DREAM) Power-Aware Routing (PAR) 34

35 Destination Sequenced Distance Vector (DSDV) Table-driven Based on the distributed Bellman-Ford routing algorithm Each node maintains a routing table Routing hops to each destination Sequence number 35

36 DSDV Problem a lot of control traffic in the network Solution: two types of route update packets full dump (All available routing info) incremental (Only changed info) 36

37 Cluster Gateway Switch Routing (CGSR) Table-driven for inter-cluster routing Uses DSDV for intra-cluster routing C2 C1 M2 C3 37

38 Ad hoc On-demand Distance Vector (AODV) On-demand driven Nodes that are not on the selected path do not maintain routing information Route discovery source broadcasts a route request packet (RREQ) destination (or intermediate node with fresh enough route to destination) replies a route reply packet (RREP) 38

39 AODV N2 N5 N8 Destination Source N1 N4 N7 N3 N6 N2 N5 N8 Destination RREQ Source N1 N4 N7 N3 N6 RREP 39

40 AODV Problem a node along the route moves Solution upstream neighbor notices the move propagates a link failure notification message to each of its active upstream neighbors source receives the message and re-initiate route discovery 40

41 Dynamic Source Routing (DSR) On-demand driven Based on the concept of source routing Required to maintain route caches Two major phases Route discovery (flooding) Route maintenance A route error packet 41

42 DSR N1 N2 N1-N2 N5 N1-N2-N5 N8 N1-N3-N4 N1-N3-N4-N7 N1 N1 N3 N4 N1-N3 N1-N3-N4 N1-N3-N4 N6 N7 N1-N3-N4-N6 N1-N2-N5- N8 N5 N1-N2-N5- N8 N2 N1-N2-N5- N8 N8 Route Discovery N1 N4 N7 N3 Route Reply N6 42

43 Modified DSR Route information determined by the current network conditions number of hops congestion node energy Other considerations fairness number of route requests 43

44 Zone Routing Protocol (ZRP) Hybrid protocol On-demand Proactive ZRP has three sub-protocols Intrazone Routing Protocol (IARP) Interzone Routing Protocol (IERP) Bordercast Resolution Protocol (BRP) 44

45 Zone Routing Protocol (ZRP) Zone of Node Y Border Node Zone Radius = r Hops Border Node Node X Zone of Node Z Node Z Zone of Node X Bordercasting 45

46 Location-Aided Routing (LAR) Location information via GPS Shortcoming (maybe not anymore 2005) GPS availability is not yet worldwide Position information come with deviation 46

47 LAR Request Zone Expected Zone (Xd+R, Yd+R) Destination (Xd,Yd) R source(xs,ys) 47

48 Distance Routing effect Algorithm for mobility (DREAM) Position-based Each node maintains a position database regularly floods packets to update the position Temporal resolution Spatial resolution 48

49 Power-Aware Routing (PAR) N1 + N2 + SRC + + DES T N3 + N4 + 49

50 Outline Definition and Challenges Media Access Control Routing Protocols Research Topics 50

51 Current routing protocols Many do not consider energy conservation lead to partitions shorten network life fairness to intermediate nodes not incorporated fail to work well in both sparse and dense networks 51

52 Interesting Research Topics Energy Awareness Routing Multipath Routing more paths used to send information, more reliable the transmission Clustering (Hierarchical Routing) dynamic management of subnetworks 52

53 More Research Topics Topology Control adjustment of transmission power to simplify routing Internetworking managing wired and wireless networks Heterogeneous Networks Different devices on the network have different capabilities Content Aware Networks Location of services within the network (Printers) 53

54 References Ad Hoc Mobile Wireless Networks Protocols and System, C-K Toh, Prentice Hall, 2002, ISBN: Introduction to Ad Hoc Networking, Prof. Yu-Chee Tseng 54