simulations and tools for telecommunication - oulu · simulations and tools for telecommunication...

Simulations and Tools for TelecommunicationTietoliikenteen simuloinnit ja työkalut 521365S

2008

Harri SaarnisaariPhone: 5532832

Email: [email protected]

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Course Description

• Lectures

– Tue 12:15 – 14:00 TS128, starting 12.2.2008

• Course includes

– Lectures

– Compulsory simulation exercise (with Simulink)

– Final exam

• Lectures include

– theoretical part

– Simulation tools introduction part

• Details, schedule and notes at http://www.telecomlab.oulu.fi/kurssit/521365A_tietoliikennetekniikan_simuloinnit_ja_tyokalut/

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Planned schedule

• Lectures

• Note: TBU denotes "to be updated", do not take these slides, they are from the previous year

• lecture 12.2: Introduction,• lecture 19.2: Introduction to Matlab, ROOM TS135 • lecture 26.2: Communication simulations,• lecture 11.3: Link simulations & Random number generation and fading channels• lecture 18.3: Communication simulation example with MATLAB & used m-file & Summary

• Lecture 1.4: ?• lecture 8.4: Introduction to Simulink and simulation exercise, Esa Kunnari, TS135 • lecture 15.4: Introduction to ADS, Juha-Pekka Mäkelä• lecture 22.4: Introduction to OPNET, Jarmo Prokkola• Lecture 29.4: Introduction to SUPERNEC, Timo Kumpuniemi

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Course Description …

• Lectures answer to questions

– Why we simulate?

– When we simulate?

– How we simulate?

• Lectures consider simulations of

– Communication systems

– Protocols

– Algorithms

– Transceiver RF/IF-parts

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• Theoretical part includes

– Modeling of communication systems using simulations

– Simulation methods

– Confidence limits of simulations

– Noise and random number generation

– Modeling of fading channel

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• Introduction to simulation tools part includes

– MATLAB (Harri Saarnisaari)

• Algorithm simulation

– SIMULINK (Esa Kunnari)

• Algorithm and system simulation (build on Matlab)

– ADS (Juha-Pekka Mäkelä)

• RF/DSP-simulation tool

– OPNET (Jarmo Prokkola)

• Network simulation tool

– SUPERNEC (Timo Kumpuniemi)

• RF tool

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• Compulsory exercise includes

– Simulation exercise with Simulink

– Managed by Esa Kunnari

– Has to be passed acceptably before credit units are earned

• Final exam

– Some easy theoretical questions

– 6.5

• Credit points

– 3.5

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• NOTE: Exercise may be part of your candidate work (another course is tietoliikennetekniikan laboratoriotyöt, telecommunication laboratory exercises)– Although the work itself may be done in groups of 2, the report is written personally!• At least abstract and conclusions have to be different, written individually (theory part may be co-operated)

– Follow DI thesis writing rules • own pages & instructions will be made for this thesis, when???

– Thus: do the report carefully, it may be part of an official thesis!• It will be rejected if not carefully done and against instructions

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• Candidate work structure– Two parts; reports from two course works– Common abstract!– Work 1 report– Work 2 report

• Report structure (like a journal/conference paper)– Abstract– Introduction– Theory/background– Measurements & analysis– Conclusions

• You may also write your candidate degree maturity work (kypsyysnäyte) from this topic (or from lab. exercises).– After exercise has been returned

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• Course book– Michel C. Jeruchim, Philip Balaban & K. Sam Shanmugan: “Simulation of

Communication Systems: Modeling, Methodology and Techniques”, KluwerAcademic/Plenum Publishers, 907 s., 2000.

– The course uses the following parts of the book• Chapter 1: 1−12 (12 s)• Chapter 2: 13−54 (42 s)• Chapter 3: 55−63, 74−91 (27 s) • Chapter 4: 181−192 , 195−198 (16 s)• Chapter 6: 289−294, 308−316, 320, 328−334, 350−356 (30 s)• Chapter 7: 371−379, 383−389, 392−393 (18 s)• Chapter 8: 407−410, 534−540 (11 s)• Chapter 9: 545−563, 572−576, 614−621 (32 s)• Chapter 10: 625, 636−642, 655−657, 664−667 (15 s)• Chapter 11: 669, 678−688, 693−694, 696, 710−716, 737−742, 757−758 (30 s)• Chapter 12: 763−793 (31 s)

• These are good-to-know background material, and may involve material asked in the exam

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• Material available

– Notes at the course home page

• as soon as they are ready

– Mentioned pages of the book in the Tutor-room and Telecommunications Laboratory library

• Contact

– You may contact me by phone or email and ask for meeting

– Best times are before or after the lectures

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Simulation

• Definition (a possible)– The discipline whose objective is to imitate one or more aspects of reality in a way that is as close to that reality as possible

• Synonym (sometimes used) to simulation– Artificial reality (man made reality)

• Motivation behind simulation – It is a way to “try things out” before building the real thing

– What (approximately) occurs in reality if I have devices/algorithms like these? Do results satisfy my requirements, or should I change something?

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Simulation ...

• Questions to be asked

– What elements of reality I have to verify in this simulation?• Meaningfulness (often all aspects need not be taken into account): affects time, complexity, …

– What elements I can ignore? How the ignored elements may affect the results?• Reliability, consequences of ignoring

– How should I model the blocks of the system?• Perfect model (all aspects)

• High level model: tranfer function, only effects modeled

• Assume to have not effects at all– E.g., ideal band pass filter

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Simulation ...

– What simulation method to use?• How they are used right?

– What results I want or have to obtain? • What parameters I have to change in the simulations?

– How to make a flexible simulator by same efforts?• Felible simulator can be used to simulate also effects of other aspect, not given to me right now – e.g., ignored elements, different set of device parameters or different device models

• Needs general parameterized model building

– Result analysis, comparison to the existing (early) results or to theoretical results• Are the results expected?• Why there is difference?• What has to be changed to obtain desired results?

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Simulation …

• Simulations concern how the waveforms or signals flow through the system

– How subsystems (blocks) and their different parameters affect the system’s performance?

• Use and importance of simulations has been grown recently since the digital computers have developed and became more powerful

– More complex and more real things can be simulated

– Difference between simulations and reality has been decreased

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Simulation …

• The goal in any system development is to do it in a timely, cost-effective and effort-free manner

• Communication systems have become more complex

– More complicated overall systems and operating environments

– More complicated signal processing

– More complicated microwave & other devices

• As a consequence, computer-aided analysis and design is the only way to achieve the goal

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Simulation …

• In the system development one has to design a system to meet some requirements and often has some limitations

• The designer usually can select possible candidate solutions based on his/her prior knowledge and/or analytical results– These analytical results are usually obtained using simplified assumptions of reality (often oversimplified)

– The used formulas are often evaluated using digital computers, although simple paper-based rules also exist in some cases

– These formula-based techniques provide considerable insight to the problem but cannot solve all questions

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Simulation …

• The designer then creates a simulation model that are closer the reality than simplified analytical results

– Based on simulation results he/she chooses a smaller set of candidate solutions

• Piece of hardware (a prototype) is then (possibly) build to verify critical parts and/or new technology

– Measured demonstrator/prototype parameters may be used in simulations to increase the simulation accuracy

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Simulation …

• Differences between simulation and measured results?

– Due to errors/simplifications in the simulations?

– Due to errors or incapability to produce in prototyping?

• The goal is to build the required hardware, but this may fail – Build hardware is different than the simulated one

– It is not working as it should

• One has to find out the source for the difference before continuing the process and then solve the problem or find another solution

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Simulation …

• Once all the aspects are considered and designed satisfactory (requirements and limitations are satisfied), the product may be build

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Simulation …

• In general, the designer has three tools

– Formula based

– Simulation

– Prototyping

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Simulation …

• All can be used separately but usually a hybrid of these is used, and it is most often the most powerful way– Formula based method is not sufficient since it often simplifies real life effects

– Prototyping is the most close the reality, but it is often time-consuming, expensive and has a limited flexibility

– Simulations are flexible (parameters can be changed rather freely), they are rather close to reality (if the used model is) but a disadvantage is that more complex simulation models require more powerful computers and/or more computation time

– Increased simulation capabilities (quality in terms of reality) have caused a trend that prototyping is reduced as much as possible; some even dream to build products directly after simulation

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Simulation …

• Analysis is still a valid and powerful method

– Results are usually valid for several parameter values

– More complex analysis can nowadays be made since analysis methods develop and more powerful computer tools become available

• Simulation results cannot usually be generalized to different parameters, but the simulations show what happens with those particular parameters

• Simulations are also used to verify analysis results, i.e., to check are the made simplifications too misleading or not

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Simulation …

• The simulation model usually includes changeable parameters

• The designer simulates the effects of the parameters to the performance of the systems and selects between the parameters and/or makes trade-offs since different parameters may affect differently to the different parts of the system

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Simulation …

• The system is usually build of several subsystems

• These subsystems are modeled and the signal (or its relevant features) is passed through the models

• Simulations are also used to verify a subsystem (block) or a set of subsystems, not the whole system

• However, the subsystem designer should be aware of effects of this subsystem to other subsystems/overall system to avoid “bad” parameter selections (from point of view of the other subsystems/overall system)

– Good overall picture on designer’s research/work field is important to him/her

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Simulation …

• The accuracy (how close to the reality it is) of the simulation depends on the accuracy of the models– Erroneous models yield misleading results, conclusions and selections and may be costly

– Simulation models should correspond the reality tried to imitate!

– The error should be in an acceptable level

– Avoid using misleading models!

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Simulation …

• Models may be obtained from existing knowledge of the subsystems

– E.g., RF-devices used to build real systems

• One may also found a model using simplified analysis of the subsystem

– E.g. assume that subsystem is linear although in reality it may be non-linear

• If subsystem model is totally unknown, it may be measured

– E.g., measurement of a radio channel characteristics for the current problem

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Simulation …

• However, use of more accurate models may be costly in terms of computer resources and programming time

• Less accurate models have (very often) to be used in real life simulations

• Modeling errors can be made in

– System modeling

– Device modeling

– Random process modeling

– Processing

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Simulation …

– System modeling errors• Systems may include several elements and some of them (maybe those believed to have an insignificant effect to the investigated behavior) are ignored from the simulation model

– Device modeling errors• Errors between the model and actual device

– Random process modeling errors• Real life signals are random ones (or include such components)

• Errors to model actual random processes and errors to generate (in computer) the modeled processes

– Processing errors• Due to limitations of computing medium and methodology

• E.g., actual analog waveforms modeled by discrete signals in computers (high over sampling rates, which may be used to model analog signals more precisely yield to increased simulation times)

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Simulation …

• The models have to be validated (correctness check)

– A single block

– A bunch of blocks

– The overall system

• A possibility is to test them in a simplified environment where analytical results exist, and if the simulated results coincide with the analytical ones, the correctness has been “proved”, or, at least, some evidences about the correctness have been achieved

• Also the random process generators have to be validated

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Simulation …

• In summary, simulations are used

– Since accurate analysis are very difficult or too time consuming

– To verify are simplified analyses accurate or misleading

– When one has to decide between different options (parameters, algorithms, building blocks, …) which may have nonlinearities (= hard to analyze)

• Simulations are often much faster way to obtain the results

– To fasten and saving costs in production• Simulations are a tool in the design process!

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Simulation …

• In summary, in simulations

– One has to program the model of the system and its components (subsystems)• Existing simulation tools involve many prepared models simplifying the programming

• However, one has to validate the correctness of the simulation program (if it s not already done by others)

– The modeling accuracy affects the simulation accuracy and also the efforts needed to make the simulation system • Often simplified models are used

• One has to be careful with simulation error sources and validate correctness of his/her simulations

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Simulation …

• In summary, prepared simulation programs

– Usually contain only necessary parts of the system

• Parts which are believed to have insignificant effects are ignored for simplicity (and to save efforts and time)

– Use a high-level model if possible (if their accuracy is sufficient)

• High-level model is e.g. a filter transfer function

• Low-level models include details of (sub)systems– E.g., build a filter model using models of actual elements used to build those filters

– Low-level modeling is time and effort consuming, and may not be necessary for the particular problem

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Simulation …

• Once more

– Simulations are used to imitate reality (not vice verse as sometimes erroneously stated by students)

– They may be used to check system’s performance and expected behavior

– However, the product (a mess of hardware and software) may not perform like simulations (and analysis) predict. Why?

• Too simplified analysis & simulation models

• Errors in modeling

• Errors in simulation and analysis

• Errors and/or incapability in producing

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Examples

• Examples of industry fields where simulations are used

– Aerospace and defense

– Communications

– Automotive

– Biotechnology

– Medicine

– Electronics

– Financial modeling

– Semiconductors

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Examples

• Aerospace and Defense

– Every major aerospace and defense organization in the world uses simulation products and services to develop air, naval, land, and space systems.

– Engineers and scientists rely on simulation tools for Model-Based Design and technical computing in programs such as the Airbus A380, F-35 Joint Strike Fighter, Mars Exploration Rover, as well as unmanned aerial vehicles and advanced wireless systems.

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Example: algorithm design

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A “serious” example

• E.g., you want to simulate your way from a bar to your home so that you can estimate how long it takes – You have to think what things affect the model

• Amount of alcohol, your capability to walk directly after certain amount of alcohol, ….• How you take your steps

– front, back and sides (what is the random process describing this)

• Are there enticements» Open bars on your route, a grill, irresistible persons (different/same sex depending on your tendency)

– You have to think how much time you want to spend to build the model• Will you make a perfect model (takes possibly a long time and a lot of efforts) • or do you ignore some effects that are too cumbersome to program

– and end up to a more easily made simulation model which possibly does not give as good results as the more accurate model

– After the simulator is ready, you will • run the simulations • compare simulation results to reality (if you could remember the reality)

– If simulations and reality coincide (within certain limits which you have to set) you are satisfied to your simulator, otherwise you have to improve your models (used inside the simulator)

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