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Wireless Networks: Topic 05 - Fading, Multipath, and Power Delay Profile, Slides of Wireless Networking

A part of the cs698t course notes on 'wireless networks: principles & practice' taught by bhaskaran raman at iit kanpur during january-april 2007. Topic 05 covers the concepts of fading, multipath, received signal strength, channel impulse response, power delay profile, and their implications on wireless communication systems.

Typology: Slides

2011/2012

Uploaded on 02/16/2012

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Jan-Apr 2007 CS698T: “Wireless Networks: Principles & Practice”, Bhaskaran Raman, Dept. of CSE, IIT Kanpur Topic 05
CS698T
Wireless Networks:
Principles and Practice
Topic 05
Fading, Multipath
Bhaskaran Raman,
Department of CSE, IIT Kanpur
http://www.cse.iitk.ac.in/users/braman/courses/wless-spring2007/
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Download Wireless Networks: Topic 05 - Fading, Multipath, and Power Delay Profile and more Slides Wireless Networking in PDF only on Docsity!

CS698T

Wireless Networks:

Principles and Practice

Topic 05

Fading, Multipath

Bhaskaran Raman,

Department of CSE, IIT Kanpur

http://www.cse.iitk.ac.in/users/braman/courses/wless-spring2007/

Received Signal Strength

It is a function of three components

– Path loss

– Long-term fading (slow)

– Short-term fading (fast)

Path loss  d

−

 is in the range 34

log(dist)

Path-loss (dB)

Short-term vs. Long-term

Fading

Source: Mobile Communications, Jochen Schiller

Channel Impulse Response

Channel

Impulse

(Power vs time)

Response

(Power vs time)

P ∞

 t  0

Measured Indoor

Power Delay Profile

Source: Wireless Communications, Theodore Rappaport

An Example Calculation

Power Time -30dBm -20dBm -10dBm 0dBm 10dBm 1us 2us 3us 4us 5us

=^

0.01×0.50.1×1.5 1 ×2.5 1 ×3.5

=2.92^ s   2 = 0.01×0. 2 0.1×1. 2  1 ×2. 2  1 ×3. 2  0.010.1 1  1    2 =8.88 s 2  

2 =0.59 s

Some Remarks

RMS delay spread is a good measure of

multi-path

– Urban environments: 2-10 us

– Indoors: 10-500 ns

Symbol time: time to transmit a bit (0/1)

Symbol time ~ RMS delay spread ==> Inter-

Symbol Interference (ISI)

– Equalization required

– Generally, ISI results when

symbol time < 10 x RMS-delay-spread