`Hi All,`

I have 2 major doubts:

1)In the process of generating OFDM symbols,I try to use Sinc filters

at the Tx & Rx end for pulse shaping.Now,I understand that convolution

of Sinc with a Sinc is a Sinc,however,when I upsample by 4,every 4rth

sample of the convoluted Sinc doesn't fall at exact 0 on the

X-Axis.So,as a result,the demodulated(QAM in my case) doesn't converge

at the same point & results in scatterd pattern(Even without

noise).However,if I use a single Sinc,there is no such problem.

I would like to know if it is a problem with the conv function in

Matlab or conceptually,this is hwo the conv of 2 sincs work? If yes,

what can I do to rectify this?

Also,if I use sqrt raised cosine filters on both ends,I want to work on

a smaller roll-off(say 0.009),however,the result isn't good.So,I'm

using 0.5 as of now,but I would appreaciate it if anyone can throw some

light on this one.

2)I'm trying to study ACE(Active Constellation Extension) in OFDM

systems to reduce PAPR. I've tried to go through a few

papers,however,there seems to be too much math involved & I'm just

looking for that one paper which can help me start off with this

subject...as in basic understanding of how extending the constellation

can help in reducing PAPR etc.

I appreciate any help.

Thanks!

Bavithi.

I have 2 major doubts:

1)In the process of generating OFDM symbols,I try to use Sinc filters

at the Tx & Rx end for pulse shaping.Now,I understand that convolution

of Sinc with a Sinc is a Sinc,however,when I upsample by 4,every 4rth

sample of the convoluted Sinc doesn't fall at exact 0 on the

X-Axis.So,as a result,the demodulated(QAM in my case) doesn't converge

at the same point & results in scatterd pattern(Even without

noise).However,if I use a single Sinc,there is no such problem.

I would like to know if it is a problem with the conv function in

Matlab or conceptually,this is hwo the conv of 2 sincs work? If yes,

what can I do to rectify this?

Also,if I use sqrt raised cosine filters on both ends,I want to work on

a smaller roll-off(say 0.009),however,the result isn't good.So,I'm

using 0.5 as of now,but I would appreaciate it if anyone can throw some

light on this one.

2)I'm trying to study ACE(Active Constellation Extension) in OFDM

systems to reduce PAPR. I've tried to go through a few

papers,however,there seems to be too much math involved & I'm just

looking for that one paper which can help me start off with this

subject...as in basic understanding of how extending the constellation

can help in reducing PAPR etc.

I appreciate any help.

Thanks!

Bavithi.