8. Propagation Summary
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| University of Dar es Salaam | Department of Electronics and Telecommunications Engineering | _______________________________________________________________________________ Introduction to Wireless Communications ------------------------------------------------------------------------------------------------------------------------ | TE 412 Introduction to Wireless Communications | Christine Mwase | 10/03/2014 | Slide 1/8 | Propagation Summary | University of Dar es Salaam | Department of Electronics and Telecommunications Engineering | _______________________________________________________________________________ Mobile Radio Propagation - Outline • Introduction • Radiowave Propagation Challenges – Free Space Attenuation ------------------------------------------------------------------------------------------------------------------------ | TE 412 Introduction to Wireless Communications | Christine Mwase | 10/03/2014 | Slide 2/8 | – Free Space Attenuation – Multipath and Shadowing – Time Delay Spread • Radiowave Propagation Mitigation Strategies • Conclusion | University of Dar es Salaam | Department of Electronics and Telecommunications Engineering | _______________________________________________________________________________ Radiowave Propagation - Summary Irreducible Error Caused by two main mechanisms: ------------------------------------------------------------------------------------------------------------------------ | TE 412 Introduction to Wireless Communications | Christine Mwase | 10/03/2014 | Slide 3/8 | • Firstly, for the narrowband scenario: DOPPLER • Secondly, for the wideband scenario: DELAY SPREAD | University of Dar es Salaam | Department of Electronics and Telecommunications Engineering | _______________________________________________________________________________ Radiowave Propagation - Summary Doppler – Amplitude and phase variations of fading channel produce error rate that is directly proportional to users ------------------------------------------------------------------------------------------------------------------------ | TE 412 Introduction to Wireless Communications | Christine Mwase | 10/03/2014 | Slide 4/8 | produce error rate that is directly proportional to users speed and frequency of transmission. – As data rate increases, problems due to Doppler reduce although these are then replaced by difficulties of delay spread.
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Propagation Summary
Transcript of 8. Propagation Summary
| University of Dar es Salaam | Department of Electronics and Telecommunications Engineering |
_______________________________________________________________________________
Introduction to Wireless
Communications
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| TE 412 Introduction to Wireless Communications | Christine Mwase | 10/03/2014 | Slide 1/8 |
Communications
Propagation Summary
| University of Dar es Salaam | Department of Electronics and Telecommunications Engineering |
_______________________________________________________________________________
Mobile Radio Propagation - Outline
• Introduction
• Radiowave Propagation Challenges– Free Space Attenuation
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| TE 412 Introduction to Wireless Communications | Christine Mwase | 10/03/2014 | Slide 2/8 |
– Free Space Attenuation
– Multipath and Shadowing
– Time Delay Spread
• Radiowave Propagation Mitigation Strategies
• Conclusion
| University of Dar es Salaam | Department of Electronics and Telecommunications Engineering |
_______________________________________________________________________________
Radiowave Propagation - Summary
Irreducible Error
Caused by two main mechanisms:
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| TE 412 Introduction to Wireless Communications | Christine Mwase | 10/03/2014 | Slide 3/8 |
• Firstly, for the narrowband scenario:
DOPPLER
• Secondly, for the wideband scenario:
DELAY SPREAD
| University of Dar es Salaam | Department of Electronics and Telecommunications Engineering |
_______________________________________________________________________________
Radiowave Propagation - Summary
Doppler
– Amplitude and phase variations of fading channel produce error rate that is directly proportional to users
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| TE 412 Introduction to Wireless Communications | Christine Mwase | 10/03/2014 | Slide 4/8 |
produce error rate that is directly proportional to users speed and frequency of transmission.
– As data rate increases, problems due to Doppler reduce although these are then replaced by difficulties of delay spread.
| University of Dar es Salaam | Department of Electronics and Telecommunications Engineering |
_______________________________________________________________________________
Radiowave Propagation - Summary
Narrowband vs. Wideband
• Data rate at which a channel can be considered wideband varies depending on environment. E.g
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| TE 412 Introduction to Wireless Communications | Christine Mwase | 10/03/2014 | Slide 5/8 |
– GSM is regarded as wideband, data rate = 270 kb/s
– DECT is considered narrowband, data rate = 1.1 Mb/s
– Major difference is the typical rms delay spread:
• DECT delay spread = 100ns. GSM delay spread = 4µs
• If the rms delay spread is normalized to the data rate then DECT = 0.11 (100ns×1.1Mb/s). GSM = 1.08 (4µs×270kb/s).
| University of Dar es Salaam | Department of Electronics and Telecommunications Engineering |
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Radiowave Propagation - Summary
Delay Spread
• Generally, normalized delay spread < 0.1 � narrowband:
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| TE 412 Introduction to Wireless Communications | Christine Mwase | 10/03/2014 | Slide 6/8 |
– majority of irreducible errors will arise as a result of the time
variations in the channel.
• Once normalized delay spread > 0.1 � channel starts to
exhibit wideband characteristics
– equalization may be required to maintain a low overall error rate
| University of Dar es Salaam | Department of Electronics and Telecommunications Engineering |
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| TE 412 Introduction to Wireless Communications | Christine Mwase | 10/03/2014 | Slide 7/8 |
| University of Dar es Salaam | Department of Electronics and Telecommunications Engineering |
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Relation
between study
on propagation
and wireless
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| TE 412 Introduction to Wireless Communications | Christine Mwase | 10/03/2014 | Slide 8/8 |
and wireless
communication
system design
