Brief History of Wireless Systems and Multipath Propagation Environment, Slides of Software Engineering

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Digital Signal

Processing

Abdul Basit

Brief

History of

Wireless

Systems

Brief

History of

Wireless

Systems

Brief History of Wireless Systems

• 2

nd

Generation  (90’s)

• GSM  (Global system for mobile communication (10Kbps)
• CDMA  Code division multiple access (10Kbps)
• GPRS  General packet radio services (250Kbps)
• EDGE  Enhanced data for GSM Evolution (200Kbps)
• 3

rd

Generation (2000~2010)

• WCDMA/UMTS  Wideband CDMA/Universal mobile telecommunication system (384Kbps)
• CDMA-2000  384 (Kbps)
• 3.5 Generation

HSDPA/HSUPA  High speed downlink/uplink packet access (5~30Mbps)

EVDO  Evolution data optimization (3~30Mbps)

Multipath Propagation Environment

Single Input Single Output

Multiple Input Single Output

• .

Multiple Input Multiple Output

• .

Multipath Propagation Environment

• Superposition of signals
• Interference

Constructive Interference

Destructive Interference

Multipath Propagation Environment

Superposition of signals

Multipath Propagation Environment

Scenario

 

0      t  

 

2      t  

 

3      t  







 

L-

L L L L

   t 

  

 

1      t  

Multipath Propagation Environment

Scenario

• is the multipath channel response
• That is sum of all the responses (Paths)

Multipath response  Sum of individual responses

ht 

         

0 0 1 1 2 2 L 1 L 1

h t   t    t    t    t 

           

   

L

i i

i

h t   t 

 



For 0

th

Path

𝜎

𝛧

• For th real scenario.

If a signal is transmitted over wireless channel through 0

th

path

It will experience time/delay

• A pass band signal is attenuated by and delayed by

𝜎

0

(

𝑡 − 𝑍

0

)

 

 

0

0 path =

c

j f t th

e

t e

  

 

 

 

 

 

1

1

1 path =

L-1 path =

c

c L

j f t st

e

j f t th

e L

t e

t e

  

  



 





 

Wireless Fading Channel Model

   

 

=

c i

L

j f t

p e i i

i

y t t e

  

 



Received pass band signal  Sum of var ious multipath components

   

 

 

 

 

 

=

Complex Baseband Part =

c i c i

c i

c i

L

j f j f t

p e i i

i

L

j f

e i i

i

j f t

y t t e e

t e

CarrierComponent e

  

  

 

 







   

= =

c i

L

j f

p i b i

i

Complex base band Rx signal y t S t e

 



