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QPSK and BPSK

Started by yingmu ●January 21, 2009
Hi all,

I've some queries regarding the above subj.

1) QPSK is actually 2 BPSK. Is there any difference in their power?  What
I understand, Power (P) = [sqrt(real(signal).^2 + imag(signal).^2)].^2
                    = amplitude.^2

2) If QPSK requires 2P (BPSK needs P), and I transmit both using the same
amplitude, will I get 2P for QPSK and 1P for BPSK when I plot it in terms
of power?

3) With regards to 2), will the BER get affected if amplitude are the same
for both QPSK and BPSK?

Thank you.

Yingmu
Reply by John ●January 21, 20092009-01-21
On Jan 21, 10:17&#4294967295;am, "yingmu" <yingm...@yahoo.com.sg> wrote:

> Hi all,
>
> I've some queries regarding the above subj.
>
> 1) QPSK is actually 2 BPSK. Is there any difference in their power? &#4294967295;What
> I understand, Power (P) = [sqrt(real(signal).^2 + imag(signal).^2)].^2
> &#4294967295; &#4294967295; &#4294967295; &#4294967295; &#4294967295; &#4294967295; &#4294967295; &#4294967295; &#4294967295; &#4294967295; = amplitude.^2
>
> 2) If QPSK requires 2P (BPSK needs P), and I transmit both using the same
> amplitude, will I get 2P for QPSK and 1P for BPSK when I plot it in terms
> of power?
>
> 3) With regards to 2), will the BER get affected if amplitude are the same
> for both QPSK and BPSK?
>
> Thank you.
>
> Yingmu


I can provide you answers to within 3 dB.
Reply by Dilip Warrier ●January 21, 20092009-01-21
On Jan 21, 10:17&#4294967295;am, "yingmu" <yingm...@yahoo.com.sg> wrote:

> Hi all,
>
> I've some queries regarding the above subj.
>
> 1) QPSK is actually 2 BPSK. Is there any difference in their power? &#4294967295;What
> I understand, Power (P) = [sqrt(real(signal).^2 + imag(signal).^2)].^2
> &#4294967295; &#4294967295; &#4294967295; &#4294967295; &#4294967295; &#4294967295; &#4294967295; &#4294967295; &#4294967295; &#4294967295; = amplitude.^2
>
> 2) If QPSK requires 2P (BPSK needs P), and I transmit both using the same
> amplitude, will I get 2P for QPSK and 1P for BPSK when I plot it in terms
> of power?
>


If you use the same amplitude in both dimensions for QPSK as compared
to a single dimension in BPSK, then yes, you will have 2P for QPSK
and
P for BPSK.


> 3) With regards to 2), will the BER get affected if amplitude are the same
> for both QPSK and BPSK?
>


BER will be the same if the amplitude is the same.


> Thank you.
>
> Yingmu