how to remove noise in 4QAM transmission?

[bee]

hi
kindly tell me a way to remove the noise from the 4QAM signal at thr reciever. following is the genral expression i am using..

y(t)=x(t) * h(t) + n(t)....
where * is convolution...

h(t) is flat fading channel

x(t) is 4QAM signal
y(t) is output
and n(t) is noise to be removed.

waiting....

 

[melc]

adding -n(t) ? :twisted:

You have a mathematical question. What kind of answer do you expect ?

 

[fam_marufi]

sim

 

[bee]

i can subtract n(t) at the RX but how would i know the value of n(t) at the RX ???

 

[cwjcwjcwj]

In communication system, no one actually can predict n(t)......

If you really want to remove it, try using the error correcting codes ......

 

[spweda]

Since noise is random, you could not subtract noise from the recevide signal. However, you coudl use some digital filter, average to reduce the effects of the noise.

 

[pangpangfish]

You can never remove noise. If you can, there is no need for the subject of communications.f

A naiive way is to jack up your signal power so that the noise becomes negligible.

You can however design a best receiver or detection scheme to minimize the noise effect (in MAP or ML sense). Or, as someone pointed out, you can use coding or add redundancy into your digital bits to combat the noise. The coding approach comes at a price of additional bandwidth.

 

[gaffar]

In flat fading channels, increasing SNR will supress the effect of awgn(n(t)) but overall performance depends another parameter, receiver design. There are many strategies for flat fading channels. Channel estimation may be useful.

 

[pangpangfish]

In flat fading channels, increasing SNR will supress the effect of awgn(n(t)) but overall performance depends another parameter, receiver design. There are many strategies for flat fading channels. Channel estimation may be useful.

It is not true. Channel estimation will not improve the performance on a flat fading channel.

 

[dch316]

Hi all,
the optimum receiver would have a matched filter at the begining. this filter (root raised cosine e.g.) maximizes de SNR in AWGN environment, thus minimizes noise n(t).
regards
Dani

 

[gaffar]

In flat fading channels, increasing SNR will supress the effect of awgn(n(t)) but overall performance depends another parameter, receiver design. There are many strategies for flat fading channels. Channel estimation may be useful.

It is not true. Channel estimation will not improve the performance on a flat fading channel.

Pilot-based channel estimation will improve the overall performance on flat fading channels.