Senior Design Project OPNET Modeler & Short-Range Wireless Routing

1. Senior Design ProjectOPNET Modeler & Short-Range Wireless Routing Erin Butler & Emmy Lai Advisor: Professor H. C. Chang

2. Grant • Funded by a grant from CRA-W, a subset of the National Science Foundation,

3. Objective of Project • Research Existing Wireless Routing Algorithms • Design and Implement these Algorithms • Explore OPNET Modeler • A network technology development environment • Simulate a Variety of Networks, Observing Performance Metrics

4. OPNET Modeler • Three Main Domains • Network • Node • Process

5. Network Domain • Subnetworks • Encapsulates other network objects • Communication Nodes • Model network objects with definable internal structure • Communication Links • Mechanism to transport information between nodes • Fixed, Mobile, Satellite Variations

6. Node Domain • Node Model defines the internal structure of the communication nodes • Node Modules • Processor: primary building block, sends/receives packets, overall processing • Queue: extended functionality of processor, array of internal resources, subqueues • Transmitter: interface between internal packet streams & external communication links • Receiver: interface between external communication links & internal packet streams • Connections: • Packet Stream: support flow of data between modules • Statistic Wires: support transmission of numerical state information • Logical Associations: bind two modules, allowing them to perform function together

7. Process Domain • The Process Model defines the behavior of the processor and queue modules • Interrupt Driven Execution: • Caused by the invocation of an event • Alternating Blocked and Active states • Dynamic Processes: • Processes invoked by other processes • Share Memory Architecture • Parent-Child establish pair establish block of memory for two-way communication

8. Process Domain (cont.) • Dynamic Library operations • State Transition Diagrams: • State: a mode the process can enter, state information • Enter & Exit Executives • Unforced state: wait for interrupt • Forced state: continual execution of state • Transition: possible movements of a process from state to state • Source & destination state, condition & executive expression • Input & Output Streams

9. Data Analysis • Analysis Tool • Graphs • Statistics • Output Scalar Files: data collected in vector files during a simulation run, combine results from multiple simulations

10. Project Editor Node Editor Process Model Editor Link Model Path Editor Packet Format Editor Antenna Pattern Editor Interface Control Information Editor Probability Density Function Editor Probe Editor Simulation Tool Analysis Tool Filter Editor OPNET Editors

11. Project Editor • Main staging area for creating a network simulation • Create a network model using models from the standard library • Collect statistics about the network • Run the simulation • View Results

12. Node Editor • Define the behavior, which is defined by modules, of each network object • A network object is made up of multiple modules defining its behavior • Each module models some internal aspect of the node behavior (ex: data creation/storage)

13. Process Model Editor • Create process models which control the underlying functionality of the node models created in node editor • Represented by finite state machines • Created with icons that represent states and lines that represent transitions between states • Operations performed in each state or for a transition are described in embedded c or c++ code blocks

14. Link Model • Create new types of link objects • Each new type of link can have different attribute interfaces and representation

15. Path Editor • Create new path objects which define a traffic route • Any protocol model that uses logical connections or virtual circuits (MPLS, ATM, Frame Relay…etc) can use paths to route traffic

16. Packet Format Editor • Defines the internal structure of a packet as a set of fields • A packet format contains one or more fields, represented in the editor as colored rectangular boxes • Size of the box is proportional to the number of bits specified as the field’s size

17. Antenna Pattern Editor • Models the direction dependent gain properties of antennas • Gain patterns are used to determine gain values, given knowledge of the relative positions of nodes

18. Interface Control Information Editor • Defines the internal structure of ICIs (Interface Control Information) which are used to formalize interrupt-based inter-process communication

19. Probability Density Function Editor • Describes the spread of probability over a range of possible outcomes • Models the likelihoods associated with packet interarrival times • Models the probability of transmission errors

20. Probe Editor • Specifies the statistic to be collected during simulation • Sets additional characteristics of each probe • Different probes collect different statistics including global statistics, link statistics, node statistics, attribute statistics, and several types of animation statistics.

21. Simulation Tool • Specifies additional simulation constraints • Simulation sequences are represented by simulation icons which contain a set of attributes that control that simulation’s run-time characteristics

22. Analysis Tool • Creates scalar graphs and parametric studies • Defines templates to which statistical data is applied • Creates analysis configurations

23. Filter Editor • Creates additional filters on top of the ones that are already provided by OPNET • Built by combining existing models with each other

24. OPNET Overview Layout

25. Carrier Sense Multiple Access Protocol (CSMA) • Protocols in which stations listens for a carrier or transmission and act accordingly • Three versions of CSMA • 1 persistent • non persistent • p persistent

26. 1 – persistent CSMA • When a station has data to send, it first listens to the channel to see if anyone else is transmitting at that moment • If the channel is busy, the station waits until it becomes idle • When the station detects an idle channel, it transmits a frame • If a collision occurs, the station waits a random amount of time and starts all over again • Transmits with a probability of 1 whenever it finds the channel idle

27. Non-persistent CSMA • Attempts to be less greedy than 1-persistent • Before sending, a station senses the channel • If no one else is sending, the station begins doing so itself • If the channel is already in use, it waits a random period of time and then repeats the algorithm • Leads to a better channel utilization and longer delays than 1-persistent

28. p-persistent CSMA • Applies to slotted channels • When a station becomes ready to send, it senses the channel • If it is idle, it transmits with a probability p • A probability of q=1-p is deferred until the next slot • If that slot is also idle, it either transmits or defers again, with the probabilities p and q • Process repeats until either the frame has been transmitted or another station has begun transmitting • If another station has begun transmitting, it acts as if there had been a collision (ie, it waits a random time and starts again) • If the station initially senses the channel busy, it waits until the next slot and applies the above algorithm

29. OPNET & CSMA • Basic Components • CSMA project network • Transmitter Node Model – sends packets • Receiver Node Model – performs network monitoring

30. CSMA Process Model • Verifies the channel is free before transmitting • If channel is not free, enters the wt_free state until a “channel goes free” interrupt is received

31. CSMA • At the node level, the statistic wire is triggered when the busy statistic changes to 0.0. • The trigger is activated by enabling the wire’s falling edge trigger attribute

32. CSMA Scenario • CSMA network model • 20 transmitter nodes • Uses transmitter nodes designed previously in node editor • Network is ready for simulation

33. CSMA Simulation • Change attributes to run simulation • Duration time • Seed • Value per statistics • In this case, for the CSMA, seed is changed to 11

34. CSMA Simulation Results • Graph of channel throughput S vs. channel traffic G • Achieves maximum throughput at about 0.5

35. Comparing Protocols (CSMA vs. Aloha)

36. Introduction to Dynamic Wireless Networks • These networks consist of mobile hosts that communicate to one another over wireless links without any static network interaction • Due to the limited range of wireless transceivers, mobile hosts’ communication links only implemented in their geographic reason • Need for a complex network to handle and maintain the forwarding of data packets

37. Previous Work & Routing Standards • Set of Conventional Standards • Simplicity • Loop-free • Low Convergence time • Low computation & transmission overhead • Problems in terms of Dynamic Networks • Frequent broadcast cause high overhead due to changing topology • Heavy computational burden • Limited bandwidth in wireless networks

38. Temporally Ordered Routing Algorithm (TORA) • A network routing protocol which has been designed for use in Mobile Wireless Networks • Envisioned as a collection of routers which are free to move about arbitrarily • Routers are equipped with wireless receivers/transmitters • Status of communication links between routers is a function of their positions, transmission power levels, antenna patterns, cochannel interference levels….etc • Designed to minimize reaction to topological changes

39. Properties that makes TORA well suited for use in the mobile wireless networking environment • Executes distributedly • Provides loop-free routes • Provides multiple routes (to alleviate congestion) • Establishes routes quickly (so as to be used before the topology changes) • Minimize algorithmic reactions/communication overhead (to conserve available BW and increase adaptability)

40. Methods to minimize overhead & maximize routing efficiency • Establish routes only when necessary by constructing a direct acyclic graph rooted at the destination using a query/reply process • React to link failure only when necessary (ex: when a node loses its last downstream link) • Scope of failure reactions minimized (ie: the number of nodes that must participate) • No reaction to link activation

41. TORA’s Link Reversal Algorithm • When a node has no downstream links, it reverses the direction of one or more links • Links are directed based on a metric, maintained by nodes in the network, that can conceptually be viewed as a height • Goals: • Discover routes on demand • Provide multiple routes to a destination • Establish routes quickly • Minimize overhead • Make shortest path routing of second importance

42. TORA Basic Functions • Creating Routes – Query/Reply on demand • Query packet (QRY) is flooded through network • Update packet (UPD) propagates back if routes exist • Maintaining Routes – Base on “link-reversal” algorithm • UPD packets reorient the route structure • Erasing Routes – • Clear packet (CLR) is flooded through network to erase invalid routes

43. TORA FSM

44. Create Route State Diagram

45. Maintain Route State Diagram

46. Erase Route State Diagram

47. TORA Application • A separate copy of TORA is run at each node • Node adjust height at a discovery of an invalid route • Node without neighbor of finite height with respect to destination, attempts to find new route • Sends CLR packet upon network partition • Exchange of UPD packets

48. TORA Application cont… • Complete path can be found using distance table • Each router maintains its own information with respect to its neighbor

49. Node Height • Each height table for a node contains the following information • Hi = (i, oid, ri, i, i) • I = time tag • oid = originator ID • ri = bit used to divide each reference level into 2 sublevels • I = integer used to order nodes • I = unique identifier of node • Height of each node (except for the destination) is initially set to NULL: Hi = ( -, -, -, -, i)

50. Route Creation (-,-,-,-,A) (-,-,-,-,B) QRY (-,-,-,-,C) (-,-,-,-,E) (-,-,-,-,D) (-,-,-,-,G) (-,-,-,-,F) DEST (-,-,-,-,H)