no of fingers in WCDMA RAKE RECEIVER?

wcdma rake receiver

HI!

Please anybody explain me how many number of fingers(minimum), i should use for WCDMA RAKE RECEIVER SImulation with proper explanation?

I suppose in IS95 3 fingers are used, i have heard that for WCDMA we have to use 9 fingers. is it so?

wcdma rake receiver fingers

Hello Amitdegada,

I think that the answer to your question is: the number of fingers depends from the channel.
Let me try to explain: the discrete time impulsive response of the channel could be modeled by a finite sum

h = ∑ Ai * δ(t-n*Ti)

i=1 ... M, Ai complex tap and Ti i-path delay

where each complex tap value Ai describes one propagation path from TX to RX.
Hence I think that you can choose a RAKE with a maximum number of fingers equals to the number of taps M used to model the channel: in fact considering that the main feature of a RAKE RCV is the capability to exploit the multipath tuning each finger on a single path it is worthless using a higher number. On the contrary if the channel has N "main" paths over M taps (e.g. the paths characterized by abs(Ai) >> than the other ) could be sufficient limit the RAKE fingers number to N thus reducing the complexity at the expense of slightly lower performances.

Regards
Mowgli

wcdma finger

Thanks for the information.....

Would you please highlight about channel TAp, i dont have concept clear. Suggest any book or material for that......

what is a finger in wcdma

'tap' refers to each 'element' we give in a sequence representing an FIR filter that represents a radio channel. (I hope you know that we can represent FIR impulse/frequency response to match of a channel). Since in Flat fading we only have attenuation (constant attenuation, actually), single tap FIR suffices, maybe the tap is -1 denoting some loss to the signal that passes through it

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