Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 1 OPNET UNIVERSITY 2000 Transceiver Pipeline and Radio Modeling

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 2 OPNET UNIVERSITY 2000 Goals Introduce the OPNET Transceiver Pipeline –Capabilities –Defaults Modify pipeline –Show openness and extensibility –Model custom wireless effects

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 3 OPNET UNIVERSITY 2000 Overview Wireless modeling overview Transceiver pipeline Pipeline architecture and default stages –Lab: Closure - Custom Pipeline Statistic –Break –Lab: Channel Match - Doppler Shifts –Break –Lab: Power, Inoise, ECC - Signal Lock vs. Power Lock Conclusion

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 4 OPNET UNIVERSITY 2000 Wireless Modeling Overview Wireless communications –Broadcast medium –Communication more likely to be problematic –Less of a controlled environment than wireline Wireless channels need to be characterized appropriately –Model real-world channel behavior -Frequencies, power, line-of-sight, interference, etc. –Channel characteristics affect higher layer protocol behavior Simulation tool must support wireless modeling –Node mobility -Car, ship, aircraft, satellite, etc. –Link-budget-analysis computation

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 5 OPNET UNIVERSITY 2000 Transceiver Pipeline Models packet transmission across communications channel Implements physical layer characteristics Divided into multiple stages Determines if packet can be received TxRx S1S2S3S13... Each stage models an aspect of the channel’s behavior Packet

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 6 OPNET UNIVERSITY 2000 Pipeline Stages Sequence of ‘C’ or ‘C++’ procedures –Computes line-of-sight, signal strength, bit errors, etc. –Can indicate packet is not receivable Each procedure has a defined interface (prototype) –Argument is typically a packet –Information typically obtained and stored as Transmission Data Attributes (TDA)

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 7 OPNET UNIVERSITY 2000 Transmission Data Attributes (TDA) Scope –Special packet storage areas -Part of every packet –Carry numerical values -Integer, Object ID, floating point, or pointer –Initialized by kernel at start of transmission –Readable during a packet’s life –Writable only in pipeline Purpose –Carry pipeline information -Kernel to pipeline stage -Pipeline stage to kernel -Between pipeline stages User-Defined Pre-DefinedTDA TxRx

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 8 OPNET UNIVERSITY 2000 Pipeline Models Scope –Each stage uses a pipeline model –Stages are referenced via a pipeline model object attributes -Point-to-Point - link attributes -Bus -Bus attributes -Radio - transceiver attributes –Stages must be compiled prior to reference Modeling method –Create stage in context of the pipeline model –Compile stage into object form –Change pipeline model object attribute to reference stage NOTE: Stage and procedure (pipeline model context) can be used interchangeably

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 9 OPNET UNIVERSITY 2000 Pipeline Model Attributes Point-to-point –4 stages –Specified as link attributes Bus –6 stages –Specified as bus attributes Radio –14 stages –Specified as transceiver attributes

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 10 OPNET UNIVERSITY 2000 Default Pipeline Stage Location Default stages – / /models/std/links Default stage prefixes –dpt_* - default point-to-point –dbu_* - default bus –dra_* - default radio NOTE: OPNET can access pipeline stages from any path in mod_dirs

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 11 OPNET UNIVERSITY 2000 Pipeline Stage Conventions File naming –.ps.c - C procedure –.ps.cpp - C++ procedure –.ps.o - object form Procedure naming –Same as file name w/o extension Compilation –op_mko -type ps -m –Generates.ps.o NOTE: Choices for pipeline stages in OPNET are taken from the set of.ps.o files located in mod_dirs.

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 12 OPNET UNIVERSITY 2000 Point-to-Point Pipeline Models Execution for one transmission receiver transmitter Transmission Delay 0 Propagation Delay 1 Error Allocation Error Correction 23

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 13 OPNET UNIVERSITY 2000 Bus Pipeline Models Execution sequence for one transmission multiple receivers transmitter Transmission Delay Closure Propagation Delay Propagation Delay Propagation Delay Closure Collision Error Allocation Error Allocation Error Allocation Error Allocation Error Correction Error Correction Error Correction Propagation Delay Error Correction stage 0 executed once per transmission stages 2 and up are executed separately for each receiver collision stage may be executed zero or more times

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 14 OPNET UNIVERSITY 2000 Radio Pipeline Models Execution sequence for one transmission transmitter (Continued on the next slide) Receiver Group Receiver Group Receiver Group Receiver Group Transmission Delay Link Closure Link Closure Link Closure Link Closure Channel Match Channel Match Channel Match Tx Antenna Gain Tx Antenna Gain Tx Antenna Gain Tx Antenna Gain Propagation Delay Propagation Delay Propagation Delay Propagation Delay Channel Match executed once at the start of simulation for each pair of transmitter and receiver channels stage 1 executed once per transmission stages 2-6 executed separately for each receiver

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 15 OPNET UNIVERSITY 2000 Radio Pipeline Models (cont.) Execution sequence for one transmission (cont.) multiple receivers Received Power Background Noise Interference Noise Signal-to-Noise Ratio Bit Error Rate Error Allocation Error Allocation Received Power Received Power Rx Antenna Gain Background Noise Background Noise Received Power Interference Noise Interference Noise Signal-to-Noise Ratio Signal-to-Noise Ratio Interference Noise Bit Error Rate Bit Error Rate Signal-to-Noise Ratio Error Allocation Error Allocation Error Allocation Error Allocation Error Allocation Background Noise Bit Error Rate Stages 9-11 may be executed zero or more times Stages may be executed one or more times Rx Antenna Gain Rx Antenna Gain Rx Antenna Gain Error Correction 13

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 16 OPNET UNIVERSITY 2000 Radio Pipeline Model Attributes Radio TransmitterRadio Receiver 8 Stages (6-13) Associated with Radio Receiver 6 Stages (0-5) Associated with Radio Transmitter Receiver Group Transmission Delay Link Closure Channel Match Tx Antenna Gain Propagation Delay Rx Antenna Gain Received Power Background Noise Interference Noise Signal-to-Noise Ratio Bit Error Rate Error Allocation Error Correction

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 17 OPNET UNIVERSITY 2000 Stage 0: Receiver Group Invocation –Once at start of simulation Purpose –Filter out ineligible receiver channels -Simulation runtime improvements –Possible uses -Disjunct frequency bands -Excessive physical separation -Antenna Nulls Requirements –Return value of OPC_TRUE or OPC_FALSE Results –Defines destination channel set for each transmitting channel Tx Rx 0 Rx 1 Rx 2 Rx 3 Rx 0 Rx 1 Rx 3 Example:

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 18 OPNET UNIVERSITY 2000 Stage 0: Receiver Group (default) Name –dra_rxgroup Computation –None Result –All receivers are potential destinations -Returns OPC_TRUE Tx Rx Default: Tx Rx Custom:

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 19 OPNET UNIVERSITY 2000 Stage 1: Transmission Delay Invocation –First dynamic stage –Start of packet transmission –Single invocation for all destination channels Purpose –Computes time required to transmit packet Requirements –Sets TX_DELAY TDA Results –Kernel schedules end-of-transmission event -Signals start of transmission of next packet in transmitter queue

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 20 OPNET UNIVERSITY 2000 Stage 1: Transmission Delay (default) Name –dra_txdel Computation –Based on channel data rate and packet length -Data rate (bits/sec) from TX_DRATE TDA -Packet length (bits) from op_pk_total_size_get () Result –Places computed delay value in TX_DELAY TDA Tx Time Tx StartTx End Tx Delay Default:

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 21 OPNET UNIVERSITY 2000 Stage 2: Closure Invocation –Once for each destination channel –Called immediately after stage 1 - no intervening events Purpose –Determines if signal can reach destination –Allows dynamic enabling/disabling of links Requirements –Sets PROP_CLOSURE TDA Results –Occlusion (obstruction) -Packet destroyed by kernel -No further stages are called for packet

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 22 OPNET UNIVERSITY 2000 Stage 2: Closure (default) Name –dra_closure Computation –Based on ray-tracing line of sight model –Assumes Earth is spherical –Three occlusion checks -Case 1:   90 o -Case 2:   90 o,  < 90 o -Case 3:   90 o,   90 o, d  Earth Radius Result –If any case fails, occlusion exists -PROP_CLOSURE set to OPC_FALSE Tx Rx T  > 90 D R Case 1: Case 2: Case 3: Tx Rx T  < 90 D R  > 90 d Tx Rx T  < 90 D R  < 90

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 23 OPNET UNIVERSITY 2000 Lab: Link Closure - Overview Problem –Higher layer protocols implemented and tested to operate over wireline –Models were updated to include wireless transceivers –Results show no traffic received Goals –Determine link closure status -Modify closure stage to record statistic –Eliminate any occlusions -Use closure stage that guarantees link closure is met Purpose –Show how stages can be modified –Guarantee link closure

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 24 OPNET UNIVERSITY 2000 Lab: Link Closure - Project/Scenario Start OPNET Modeler (Radio) –Double desktop icon Open project –Closure View scenario –Zero_Antenna_Height_Failure -Transmitter -Receiver NOTE: When OPNET is not being used, minimize application

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 25 OPNET UNIVERSITY 2000 Lab: Link Closure - Choose Results / Simulation Observe chosen results –Pulldown menu: Simulation  Choose Individual Statistics -Node Statistics:Radio Receiver: Traffic Received (bits/sec) -Node Statistics:Radio Transmitter: Traffic Sent (bits/sec) -Node Statistic:Radio Transmitter: Link Closure Failure (failures/sec) Execute simulation –Pulldown menu: Simulation  Run Simulation

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 26 OPNET UNIVERSITY 2000 Lab: Closure - View Results View Results –Pulldown menu: Results  View Results –Select statistics -Object Statistics:Closure:Transmitter:Radio Transmitter: Traffic Sent (bits/sec) -Object Statistics:Closure:Receiver:Radio Receiver: Traffic Received (bits/sec) Show results –Click Show Conclusion –Traffic is being generated by transmitter –Traffic is not being received by receiver

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 27 OPNET UNIVERSITY 2000 Lab: Closure - Stage Modification Overview Goal –Modify the link closure stage –Collect a custom statistic Approach –Modify the pipeline stage -Add code to collect new statistic –Update Models -Project: Create new scenario -Node: Update node model –Execute simulation –View results

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 28 OPNET UNIVERSITY 2000 Lab: Closure - Open Pipeline Stage Open pipeline stage –Open Windows NT Explorer -Double click desktop icon –Go to directory containing file -c:\users\student\op_models –Double click to open file -opnetwork_closure_stats.ps.c –Pipeline stage should open in Microsoft Development Studio

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 29 OPNET UNIVERSITY 2000 Lab: Closure - Modify Pipeline Stage Modify stage –Observe code block at end of file -Line 99 through 142 –Cut lines -Line 103: #if 0 -Line 142: #endif –Save file NOTE: When Microsoft Development Studio is not being used, minimize application

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 30 OPNET UNIVERSITY 2000 Lab: Closure - Compile Pipeline Stage Compile the pipeline stage –Open a Command Prompt window -Double click desktop icon –Execute the compile command -op_mko -type ps -m opnetwork_closure_stats NOTE: When Command Prompt is not being used, minimize application

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 31 OPNET UNIVERSITY 2000 Lab: Closure - Duplicate Scenario Return to OPNET Modeler (Radio) –Maximize application Refresh model directories –Pulldown menu: File  Refresh Model Directories –Required for OPNET to know about new files Duplicate scenario –Pulldown menu: Scenarios  Duplicate Scenario –Scenario name: Zero_Antenna_Height_Failure_Stats

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 32 OPNET UNIVERSITY 2000 Lab: Closure - Update Node Model Open Transmitter node model –Double click Transmitter object -Node model: closure_rt Change transmitter module attribute –Right click transmitter module –Change attribute -closure model : opnetwork_closure_stats –Save node model -Pulldown menu: File  Save As -Filename: closure_stats_rt Close node editor

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 33 OPNET UNIVERSITY 2000 Lab: Closure - Update Network Model Change Transmitter node attribute –Right click Transmitter node -Select Edit Attributes –Change model attribute value -Select Edit... -Select closure_stats_rt –Close attribute edit box -Select Close Execute simulation –Pulldown menu: Simulation  Run Simulation

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 34 OPNET UNIVERSITY 2000 Lab: Closure - View Results View Results –Pulldown menu: Results  View Results –Select Statistics -Object Statistics:Closure:Transmitter:Radio Transmitter: Link Closure Failure (failures/sec) Show results –Click Show Conclusion –Closure is failing, causing undesired packet loss

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 35 OPNET UNIVERSITY 2000 Lab: Closure - Stage Modification Overview Goal –Modify the link closure model to eliminate closure failure Approach –Update Models -Project: Create new scenario -Node: Update node model –Execute simulation –View results

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 36 OPNET UNIVERSITY 2000 Lab: Closure - Duplicate Scenario Duplicate scenario –Pulldown menu: Scenarios  Duplicate Scenario -Scenario name: Zero_Antenna_Height_Success

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 37 OPNET UNIVERSITY 2000 Lab: Closure - Update Node Model Open Transmitter node model –Double click Transmitter object -Node model: closure_stats_rt Change module attribute –Right click transmitter module –Change attribute -closure model : dra_closure_all –Save node model -Pulldown menu: File  Save As -Filename: closure_all_rt Close node model

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 38 OPNET UNIVERSITY 2000 Lab: Closure - Closure All Stage Open pipeline stage –Return to Windows NT Explorer –Go to directory containing file -c:\users\student\op_models –Double click to open file -dra_closure_all.ps.c Closure All –Performs no computation –Link closure met for all destination channels –Sets CLOSURE TDA to OPC_TRUE

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 39 OPNET UNIVERSITY 2000 Lab: Closure - Update Network Model Return to OPNET Modeler (Radio) –Maximize application Change Transmitter object –Right click Transmitter node -Edit Attributes –Change model attribute value -Select Edit... -Select closure_all_rt Execute simulation –Pulldown menu: Simulation  Run Simulation

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 40 OPNET UNIVERSITY 2000 Lab: Closure - View Results View Results –Pulldown menu: Results  View Results –Select statistics -Object Statistics:Closure:Transmitter:Radio Transmitter: Traffic Sent (bits/sec) -Object Statistics:Closure:Receiver:Radio Receiver: Traffic Received (bits/sec) Show results –Click Show Conclusion –Traffic is being generated by transmitter –Traffic is being received by receiver –Closure was failing due to occlusions

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 41 OPNET UNIVERSITY 2000 Lab: Closure - Summary Zero antenna height (altitude) –common problem of packet loss Pipeline stage modification –Record custom statistic -Helps assess problem –Use of dra_closure_all -Eliminates closure computations -Causes no link failures due to occlusions NOTE: Another common problem of packet loss in the pipeline is due to the ECC threshold. The same approach as above can be applied to isolate the problem and counter with a pipeline modification.

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 42 OPNET UNIVERSITY 2000 Stage 3: Channel Match Invocation –Once for each destination channel satisfying stage 2 –Called immediately after stage 2 - no intervening events Purpose –Classifies the transmission -Valid, noise, or ignore -Based on frequency, bandwidth, data rate, spreading code, etc. Requirements –Sets MATCH_STATUS TDA Results –Kernel destroys ignored packets –If ignore, no further stages are called for packet

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 43 OPNET UNIVERSITY 2000 Stage 3: Channel Match (default) Name –dra_chanmatch Computation –Accounts for frequency overlap, data rate, modulation, and spreading code –Three cases -Case 1: No frequency overlap - ignored -Case 2: Partial characteristic match - noise -Case 3: Full characteristic match - valid Result –Sets MATCH_STATUS TDA based on case Case 1: Case 2: Case 3: Mod Tx  Mod Rx DR Tx  DR Rx F Tx  F Rx DR Tx  DR Rx Mod Tx  Mod Rx F Tx  F Rx

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 44 OPNET UNIVERSITY 2000 Stage 4: Transmitter Antenna Gain Invocation –Once for each destination channel satisfying stage 2 and stage 3 –Called immediately after stage 3 - no intervening events Purpose –Computes transmitter antenna gain in the direction of the receiver Requirements –Sets TX_GAIN TDA Results –Typically used by stage 7 for receiver power computation

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 45 OPNET UNIVERSITY 2000 Stage 4: Transmitter Antenna Gain (default) Name –dra_tagain Computation –Distance vector between tx and rx –Aligns all entities w.r.t. same coordinate system -Antenna patterns / pointing directions, node locations -Majority of the computation –Determines lookup angles –Performs table lookup to obtain gain (dB) Result –Value placed in TX_GAIN for use by stage 7 Gain (dB) Tx Rx Default:

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 46 OPNET UNIVERSITY 2000 Stage 5: Propagation Delay Invocation –Once for each destination channel –Called immediately after stage 4 - no intervening events Purpose –Calculates signal propagation time from transmitter to receiver –Usually dependent on distance and propagation velocity Requirements –Sets START_PROPDEL and END_PROPDEL TDAs Results –Kernel schedules -Start of reception event -End of reception event

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 47 OPNET UNIVERSITY 2000 Stage 5: Propagation Delay (default) Name –dra_propdel Computation –Based on distance and propagation velocity –Computed for start and end of transmission -Takes into account mobility –Obtains distances (in meters) -START_DIST and END_DIST TDAs Result –Places computed values in START_PROPDEL and END_PROPDEL TDAs –Kernel schedules start and end reception events Default: Rx Time Rx StartRx End Prop Delay Rx

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 48 OPNET UNIVERSITY 2000 Lab: Doppler Shifts - Overview Problem –Doppler shifts - caused by transceiver mobility –Receiver must handle frequency effects –Default stages assume no frequency shift Goals –Determine appropriate stage location –Implement Doppler shifting and record frequency shift statistic Purpose –Show pipeline stage modifications to account for Doppler shifts –Show use of external files

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 49 OPNET UNIVERSITY 2000 Lab: Doppler - Project/Scenario Return to OPNET Modeler (Radio) –Maximize application Open project –Doppler View scenario –No_Doppler_Shift -Transmitter - aircraft -Receiver

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 50 OPNET UNIVERSITY 2000 Lab: Doppler - Choose Results / Simulation Observe chosen results –Pulldown menu: Simulation  Choose Individual Statistics -Node Statistics:Radio Receiver: Traffic Received (bits/sec) -Node Statistics:Radio Transmitter: Traffic Sent (bits/sec) -Node Statistic:Radio Transmitter: Transmission Frequency - Unshifted (Hz) -Node Statistic:Radio Transmitter: Transmission Frequency - Shifted (Hz) Execute simulation –Pulldown menu: Simulation  Run Simulation

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 51 OPNET UNIVERSITY 2000 Lab: Doppler - View Results View Results –Pulldown menu: Results  View Results –Select statistics -Object Statistics:Doppler:Transmitter:Radio Transmitter: Transmission Frequency - Unshifted (Hz) Show results –Click Show Conclusion –Default behavior observed –No shift in frequency –No Doppler shift computations

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 52 OPNET UNIVERSITY 2000 Lab: Doppler - Stage Modification Overview Goal –Modify the pipeline to compute Doppler shifts –Record the shifted frequency Approach –Find the appropriate pipeline location –Modify the pipeline stage -Add code to compute Doppler shift –Update Models -Project: Create new scenario -Node: Update node model –Execute simulation –View results

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 53 OPNET UNIVERSITY 2000 Lab: Doppler - Stage Location Stage Location dependencies –Requires computed results from previous stages –Prior to computations in future stages –Similar computations already exist Stage Location Possibilities –Channel match model obtains frequency information -Results could be used for MATCH_STATUS TDA –Computations require start and end distance computations -START_DIST and END_DIST TDAs -Initialized by kernel at start of transmission Stage Location –Channel match model

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 54 OPNET UNIVERSITY 2000 Lab: Doppler - Open Pipeline Stage Open pipeline stage –Return to Windows NT Explorer –Go to directory containing file -c:\users\student\op_models –Double click to open file -opnetwork_chanmatch_no_doppler.ps.c

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 55 OPNET UNIVERSITY 2000 Lab: Doppler - Modify Pipeline Stage Modify stage –Change procedure name and FIN -Lines 17 and 26 -opnetwork_chanmatch_doppler –Cut lines -Line 45: #if 0 -Line 47: #endif –Save file -opnetwork_chanmatch_doppler

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 56 OPNET UNIVERSITY 2000 Lab: Doppler - Doppler Shift Computation Required values –Start and end distances -START_DIST and END_DIST TDAs –Propagation velocity -Transmitter module extended attribute –Transmission delay -TX_DELAY TDA Computation Result –Values placed in user-definable TDAs -MAX_INDEX + 1 -MAX_INDEX + 2

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 57 OPNET UNIVERSITY 2000 Lab: Doppler - Compile Stage / External File Compile the pipeline stage –Return to a Command Prompt –Execute the compile command -op_mko -type ps -m opnetwork_chanmatch_doppler -op_mko -type ex -m doppler_shift

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 58 OPNET UNIVERSITY 2000 Lab: Doppler - Duplicate Scenario Return to OPNET Modeler (Radio) –Maximize application Refresh model directories –Pulldown menu: File  Refresh Model Directories –Required for OPNET to know about new files Duplicate scenario –Pulldown menu: Scenarios  Duplicate Scenario –Scenario name: Doppler_Shift Include external file –Pulldown menu: File  Declare External Files -Change doppler_shift status to included

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 59 OPNET UNIVERSITY 2000 Lab: Doppler - Update Node Model Open Transmitter node model –Double click Transmitter object -Node model: no_doppler_rt Change transmitter module attribute –Right click transmitter module –Change attribute -chanmatch model : opnetwork_chanmatch_doppler –Save node model -Pulldown menu: File  Save As -Filename: doppler_rt Close node model

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 60 OPNET UNIVERSITY 2000 Lab: Doppler - Update Network Model Return to the Project/Scenario –Doppler-Doppler_Shift Change Transmitter node attribute –Right click Transmitter node -Select Edit Attributes –Change model attribute value -Select Edit... -Select doppler_rt –Close attribute edit box -Select Close Execute simulation –Pulldown menu: Simulation  Run Simulation

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 61 OPNET UNIVERSITY 2000 Lab: Doppler - View Results View Results –Pulldown menu: Results  View Results –Select Statistics -Object Statistics:Doppler:Transmitter:Radio Transmitter: Transmission Frequency - Unshifted (Hz) -Object Statistics:Doppler:Transmitter:Radio Transmitter: Transmission Frequency - Shifted (Hz) Show results –Click Show Conclusion –Frequency shifts +/- 40 Hz

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 62 OPNET UNIVERSITY 2000 Lab: Doppler - Summary Doppler shifts –Common problem in mobile systems –Potential packet loss due to receivers inability to lock onto shifting frequency Pipeline stage modification –Computed Doppler shifts –Did not use computed shift, but recorded shift statistic -Observed that a shift does exist –Use of external file -Shows how procedures can be called from within a stage -Useful for interfacing to other applications

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 63 OPNET UNIVERSITY 2000 Stage 6: Receiver Antenna Gain Invocation –Once for each destination channel –First stage after start of reception event Purpose –Computes receiver antenna gain in the direction of the transmitter Requirements –Sets RX_GAIN TDA Results –Typically used by stage 7 for receiver power computation

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 64 OPNET UNIVERSITY 2000 Stage 6: Receiver Antenna Gain (default) Name –dra_ragain Computation –Distance vector between tx and rx –Aligns all entities w.r.t. same coordinate system -Antenna patterns / pointing directions, node locations -Majority of the computation –Determines lookup angles –Performs table lookup to obtain gain (dB) Result –Value placed in TX_GAIN for use by stage 7 Gain (dB) Tx Rx Default:

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 65 OPNET UNIVERSITY 2000 Signal Lock Scope –Attribute of each destination channel –Provides ability for receiver to lock onto arriving packet –Lock is maintained for duration of transmission Procedure –First valid packet arrival at destination channel -Signal lock obtained –Subsequent valid packet arrivals -Match status changed to noise –First valid packet completes arrival -Signal lock released RxTx 1 2 Valid RxTx 1 2 Valid Noise 

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 66 OPNET UNIVERSITY 2000 Stage 7: Receiver Power Invocation –Once for each destination channel –Called immediately after stage 6 - no intervening events Purpose –Computes signal power level at receiver –Typically based on transmitter power and frequency, distance, and antenna gains –Computed only for valid and noise packets Requirements –Sets RCVD_POWER TDA Results –Kernel uses value to record receiver power channel statistic –Places packets in separate lists based on match status

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 67 OPNET UNIVERSITY 2000 Stage 7: Receiver Power (default) Name –dra_power Computation –Determines if signal lock is active –Computes received power -valid and noise packets -Computes path loss - free space -Determines in-band transmission power -Obtains tx and rx antenna gains Result –Value placed in RCVD_POWER for use by stage 9

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 68 OPNET UNIVERSITY 2000 Stage 8: Background Noise Invocation –Called immediately after stage 7 - no intervening events Purpose –Represents effects of all background noise sources –Typically includes -thermal or galactic noise -neighboring electronics emissions -other unmodeled radio transmissions (commercial/amateur radio, TV) Requirements –Sets BKGNOIS TDA Results –Typically used by stage 10 in signal-to-noise computation

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 69 OPNET UNIVERSITY 2000 Stage 8: Background Noise (default) Name –dra_bknoise Computation –Constant ambient noise –Constant background noise –Constant thermal noise Result –Value placed in BKGNOISE for use by stage 10 in signal-to-noise computation

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 70 OPNET UNIVERSITY 2000 Packet Segments Portion of packet with constant signal-to-noise –Segmentation performed by kernel –SNR computation performed by pipeline model –Upon packet completion, kernel subtracts SNR of completing packet SNR Variations

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 71 OPNET UNIVERSITY 2000 Stage 9: Interference Noise Invocation –Only if packet collision occurs Purpose –Accounts for concurrent transmissions –Compute the effect of noise on valid packets Requirements –Sets NOISE_ACCUM TDA –Sets NUM_COLLS TDA Results –Accumulates noise of interfering packets –Noise from packet completing reception is subtracted by kernel –Typically used in stage 10 for signal-to-noise ratio computations

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 72 OPNET UNIVERSITY 2000 Stage 9: Interference Noise (default) Name –dra_inoise Computation –Increments collision count –Adds received power of colliding packet -Obtains power from RCVD_POWER TDA Result –Places accumulated noise in NOISE TDA –Value used in stage 10 in signal-to-noise computation RxTx 1 2 Valid RxTx 1 2 Noise Valid RxTx 1 2 Valid Noise Case 1: Case 2: Case 3:

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 73 OPNET UNIVERSITY 2000 Stage 10: Signal-to-Noise Ratio Invocation (only for valid packets) –Operates on valid packets - those in valid list –Does not require collision for invocation Purpose –Computes the current average SNR –Typically based on received power and noise Requirements –Sets SNR TDA Results –Used by kernel to update receiver channel statistics –Used by later stages RxTx Valid RxTx 1 2 Noise Valid RxTx 1 2 Valid Noise Case 1: Case 2: Case 3:

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 74 OPNET UNIVERSITY 2000 Stage 10: Signal-to-Noise Ratio (default) Name –dra_snr Computation –Obtains received power from RCVD_POWER TDA -Computed in stage 7 –Obtains background noise from BKGNOISE _TDA -Computed in stage 8 –Obtains interference noise from NOISE_ACCUM TDA -Computed in stage 9 –Computes signal-to-noise ratio (in dB) Result –Places in SNR TDA –Value used in stage 11 in bit-error-rate computation

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 75 OPNET UNIVERSITY 2000 Stage 11: Bit Error Rate Invocation –Operates on valid packets - those in valid list –Does not require collision for invocation Purpose –Derives the probability of bit errors –Computed for each packet segment - constant SNR –Value typically obtained from modulation curve Requirements –Sets BER TDA Results –Used by the kernel to record BER statistic –Typically used in stage 12 for allocating errors RxTx Valid RxTx 1 2 Noise Valid RxTx 1 2 Valid Noise Case 1: Case 2: Case 3:

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 76 OPNET UNIVERSITY 2000 Stage 11: Bit Error Rate (default) Name –dra_ber Computation –Obtains signal-to-noise ratio from SNR TDA -Computed in stage 10 –Obtains processing gain from PROC_GAIN TDA -Attribute of receiver channel –Computes effective SNR –Determines expected bit-error-rate -Modulation table lookup Result –Records BER TDA for use in stage 12 in error allocation computation

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 77 OPNET UNIVERSITY 2000 Stage 12: Error Allocation Invocation –Called immediately after stage 11 - no intervening events Purpose –Estimates bit errors for packet segment Requirements –Sets bit-error accumulation in NUM_ERRORS TDA –Sets empirical bit error rate in ACTUAL_BER TDA Results –Kernel maintains a bit accumulator - NUM_ERRORS TDA –Kernel updates BER statistic - ACTUAL_BER TDA –Typically used in stage 13 for error correction

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 78 OPNET UNIVERSITY 2000 Stage 12: Error Allocation (default) Name –dra_error Computation –Does not perform bit-by-bit error computations -Cannot retain bit-error location –Obtains probability of error - BER TDA –Computes probability of k errors –Generates uniform random number: r = (0 1] –Integrates probability mass over possible outcomes Result –Records NUM_ERRORS TDA

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 79 OPNET UNIVERSITY 2000 Stage 13: Error Correction Invocation –Once for each valid packet –Called immediately after stage 12 - no intervening events Purpose –Determines acceptability of arriving packet Requirements –Sets PK_ACCEPT TDA Results –Rejected -destroyed by Kernel –Accepted -forwarded on output stream

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 80 OPNET UNIVERSITY 2000 Stage 13: Error Correction (default) Name –dra_ecc Computation –Obtains threshold from ECC_TRESH TDA -Percentage of packet in error that still yields acceptability –Obtains packet length from op_pk_total_size_get () –Obtains number of errors from NUM_ERRORS TDA –Computes the percent error Result –Packet accepted or rejected depending on threshold and error –Releases signal lock

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 81 OPNET UNIVERSITY 2000 Lab: Capture Mode - Overview Problem –Default pipeline stages use signal lock –Systems can lock on to lowest power signal -Higher power signal does not have lock, but dominates channel -Drowns out lower powered signal -Causes both communications to fail Goals –Modify stages to incorporate signal lock and power lock –Compare results between the two capture modes Purpose –Show additional stage modification –Incorporate power lock capability

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 82 OPNET UNIVERSITY 2000 Lab: Capture Mode - Project/Scenario Return to OPNET Modeler (Radio) –Maximize application Open project –Capture_Mode View scenario –Signal_Lock -High powered transmitter -Low powered transmitter -Receiver

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 83 OPNET UNIVERSITY 2000 Lab: Capture Mode - Choose Results / Simulation Observe chosen results –Pulldown menu: Simulation  Choose Individual Statistics -Node Statistics:Radio Transmitter: Traffic Sent (bits/sec) -Node Statistics:Radio Receiver: Traffic Received (bits/sec) -Node Statistic:Radio Receiver: Traffic Received High Powered Tx (bits/sec) -Node Statistic:Radio Receiver: Traffic Received Low Powered Tx (bits/sec) Execute simulation –Pulldown menu: Simulation  Run Simulation

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 84 OPNET UNIVERSITY 2000 Lab: Capture Mode - View Results View Results –Pulldown menu: Results  View Results –Select statistics -Object Statistics:Capture Mode:High Powered Transmitter:Radio Transmitter: Traffic Sent (bits/sec) -Object Statistics:Capture Mode:Low Powered Transmitter:Radio Transmitter: Traffic Sent (bits/sec) -Object Statistics:Capture Mode:Receiver:Radio Receiver: Traffic Received (bits/sec) -Object Statistics:Capture Mode:Receiver:Radio Receiver: Traffic Received High Powered Tx(bits/sec) -Object Statistics:Capture Mode:Receiver:Radio Receiver: Traffic Received Low Powered Tx(bits/sec)

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 85 OPNET UNIVERSITY 2000 Lab: Capture Mode - View Results (cont.) Show results –View mode -Statistics Overlaid –Filter -As Is -Average –Click Show Conclusion –Low powered transmission dominating -Longer packet lengths - longer signal lock retention –High powered transmission loss -Short packet lengths - shorter signal lock retention

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 86 OPNET UNIVERSITY 2000 Lab: Capture Mode - Stage Modification Overview Goal –Modify three pipeline stages to model power lock –Modifications will eliminate signal lock Approach –Modify the pipeline stages -power model -inoise model -ecc model –Update Models -Project: Create new scenario -Node: Update node model –Execute simulation –View results

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 87 OPNET UNIVERSITY 2000 Lab: Capture Mode - Open Pipeline Stage Open pipeline stage –Return to Windows NT Explorer –Go to directory containing file -c:\users\student\op_models –Double click to open file -opnetwork_capture_mode_power.ps.c

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 88 OPNET UNIVERSITY 2000 Lab: Capture Mode - Modify Pipeline Stage Modify stage –Observe code block in middle of file -Line 59 through 91 –Cut entire else statement -Line 59: start cutting -Line 91: end cutting –Save file

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 89 OPNET UNIVERSITY 2000 Lab: Capture Mode - Modify Pipeline Stage (cont.) Open pipeline stage –Return to Windows NT Explorer –Go to directory containing file -c:\users\student\op_models –Double click to open file -opnetwork_capture_mode_inoise.ps.c Modify stage –Modifications already complete –Observe code block at end of file -Line 69

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 90 OPNET UNIVERSITY 2000 Lab: Capture Mode - Modify Pipeline Stage (cont.) Open pipeline stage –Return to Windows NT Explorer –Go to directory containing file -c:\users\student\op_models –Double click to open file -opnetwork_capture_mode_ecc.ps.c Modify stage –Modifications already complete –Observe code block at end of file -Line 60

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 91 OPNET UNIVERSITY 2000 Lab: Capture Mode - Compile Stages Compile the pipeline stage –Return to a Command Prompt –Execute the compile command -op_mko -type ps -m opnetwork_capture_mode_power -op_mko -type ps -m opnetwork_capture_mode_inoise -op_mko -type ps -m opnetwork_capture_mode_ecc

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 92 OPNET UNIVERSITY 2000 Lab: Capture Mode - Duplicate Scenario Return to OPNET Modeler (Radio) –Maximize application Refresh model directories –Pulldown menu: File  Refresh Model Directories –Required for OPNET to know about new files Duplicate scenario –Pulldown menu: Scenarios  Duplicate Scenario –Scenario name: Power_Lock

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 93 OPNET UNIVERSITY 2000 Lab: Capture Mode - Update Node Model Open Receiver node model –Double click High Powered Receiver object -Node model: no_doppler_rt Change receiver module attribute –Right click receiver module –Change attribute -power model : opnetwork_capture_mode_power -inoise model : opnetwork_capture_mode_inoise -ecc model : opnetwork_capture_mode_ecc –Save node model -Pulldown menu: File  Save As -Filename: capture_mode_power_lock_rr Close node Model

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 94 OPNET UNIVERSITY 2000 Lab: Capture Mode - Update Network Model Return to the Project/Scenario –Capture_Mode-Power_Lock Change Receiver node attribute –Right click Receiver node -Select Edit Attributes –Change model attribute value -Select Edit... -Select capture_mode_power_lock_rr –Close attribute edit box -Select Close Execute simulation –Pulldown menu: Simulation  Run Simulation

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 95 OPNET UNIVERSITY 2000 Lab: Capture Mode - View Results View Results –Pulldown menu: Results  View Results –Select statistics -Object Statistics:Capture Mode:High Powered Transmitter:Radio Transmitter: Traffic Sent (bits/sec) -Object Statistics:Capture Mode:Low Powered Transmitter:Radio Transmitter: Traffic Sent (bits/sec) -Object Statistics:Capture Mode:Receiver:Radio Receiver: Traffic Received (bits/sec) -Object Statistics:Capture Mode:Receiver:Radio Receiver: Traffic Received High Powered Tx(bits/sec) -Object Statistics:Capture Mode:Receiver:Radio Receiver: Traffic Received Low Powered Tx(bits/sec)

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 96 OPNET UNIVERSITY 2000 Lab: Capture Mode - View Results (cont.) Show results –View mode -Statistics Overlaid –Filter -As Is -Average –Click Show Conclusion –High powered transmission dominating -Obtaining power lock –Low powered transmission loss

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 97 OPNET UNIVERSITY 2000 Lab: Capture Mode - Summary Signal lock –Representative of most systems –Locks on to first arriving signal –All other signals are noise, regardless of power level Power lock –Locks on to highest power signal –All other signals are noise –Example: IS-95 -Mobile unit moving between cells -Soft handoff process -Constantly demodulates 3 incoming signals in parallel -Monitors 4th incoming signal -Any of 3 active signals become weak, mobile can switch to high-powered signal

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 98 OPNET UNIVERSITY 2000 Conclusion Transceiver pipeline –Scope –Capabilities –Default Pipeline Modifications –Closure model –Channel match model –Power, Inoise, and ECC models Pipeline stages –Flexible –Open –Extensible

Copyright © 2000 MIL 3, Inc. Modeling Custom Wireless Effects– 99 OPNET UNIVERSITY 2000 Further Information Documentation –Modeling Concepts -Communication Mechanisms –General Models -Pipeline Stages / Bus Link -Pipeline Stages / Point-to-Point Link -Pipeline Stages / Radio Link