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 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– 4 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– 5 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– 6 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– 7 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– 8 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– 9 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– 10 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– 11 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– 12 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– 13 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– 14 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– 15 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– 16 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– 17 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– 18 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– 19 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– 20 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– 21 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– 22 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– 23 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– 24 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– 25 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– 26 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– 27 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– 28 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– 29 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– 30 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– 31 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– 32 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– 33 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– 34 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– 35 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– 36 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– 37 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– 38 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– 39 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– 40 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– 41 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– 42 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