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CDMA Rake receiver vs. 802.11 receivers

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Jim cage

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Hi All,

1- Is Rake receiver unique for CDMA only? if it solves the problem of multipath why it is not used in other types of communication systems for example 802.11a/g or gsm?

2- If the incoming signal has two paths with opposite phase (which cancell each other) how would rake receiver solve the problem of the multipath? the signal is Zero at the input due to multipath. Does anyone knows the answer?

Thanks,
 

802.11 uses both OFDM and CDMA. You have CDMA with OFDM technologies used.
Rake only for CDMA amd OFDM takes into account MP.

Hope this helps
 
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Jim cage said:
2- If the incoming signal has two paths with opposite phase (which cancell each other) how would rake receiver solve the problem of the multipath? the signal is Zero at the input due to multipath. Does anyone knows the answer?
Click to expand...

RAKE receiver is not the ultimate solution, it has its limitations too. so a completely faded signal nannot be recovered.


Naveed
 

A Rake Receiver is a useful way to mitigate the effects of multi-path fading caused by selective channels. you have to use it with CDMA due to the orthogonality of the signals over a period reciprocal of its bandwidth. if you do not use a rake receiver with cdma you may face internal noise generated due to lack of orthogonality and that would decrease your performance.
in case of OFDM, rake receiver is not used. because it uses multi-carriers each delivering low bit rate. rake receiver is useful when using a single carrier signal delivering high bit rate like the case of cdma or w-cdma.
;)
 

may i get rake reciever code ,i need it as soon as possible brother,

i am working on it ,plz help me as soon as possible
 
m_pourfathi said:
A Rake Receiver is a useful way to mitigate the effects of multi-path fading caused by selective channels. you have to use it with CDMA due to the orthogonality of the signals over a period reciprocal of its bandwidth. if you do not use a rake receiver with cdma you may face internal noise generated due to lack of orthogonality and that would decrease your performance.
in case of OFDM, rake receiver is not used. because it uses multi-carriers each delivering low bit rate. rake receiver is useful when using a single carrier signal delivering high bit rate like the case of cdma or w-cdma.
;)
Click to expand...

If I use the Rake in GSM where will be the noise be generated ?
In your CDMA there are two types of MRCs possible.
1. Chip level
Where MRC is done at chip level and then despreading is done.
2. Symbol level.
MRC is done at symbol level after the chips are despreaded.

If I remove the despreading in the 1st case then it is appliciable to GSM.
But then in this case processing gain is limited to diversity receptions.
In the CDMA extra processing gain is possible due to despreading done after the MRC.
 

Hi everybody !!!
Now, i'm begin study about Rake Reciever. i need some document about it
Thank you so much for your help
My email adress : pmquyet44@gmail.com
 

Hello every one,
im doing my b.tech project on CDMA Rake receiver.
can anyone help me out by sending the matlab code for it.
also that im searching for simulation and software radio for mobile communication by harada and prasad.
please send me the pdf link for the same.
my email id: manojsurya99@gmail.com
thank you.
 

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