On Jun 10, 6:00�pm, Manny <mlou...@hotmail.com> wrote:
> On Jun 10, 8:56�pm, dbd <d...@ieee.org> wrote:
>
>
>
> > On Jun 10, 10:48 am, robert bristow-johnson
>
> > <r...@audioimagination.com> wrote:
> > > On Jun 10, 11:45 am, Richard Owlett <rowl...@atlascomm.net> wrote:
> > > > rickman wrote:
> > > ...
>
> > .> > > I think your post would have been even more annoying to V if
> > you had
> > .> > > just left out the reference to his insult altogether. �Most
> > trolls are
>
> > > > > infuriated if, while he is standing right next to you, you continue
> > > > > your conversation as if he wasn't even in the room.
> > > > It may be even more effective to politely acknowlege V's existence and
> > > > then carry on a polite conversation. IT might catch on - though I doubt
> > > > he'll notice.
>
> > ,> i don't even know what it is? �student with a "pi" stuck in it?
> > ,>
> > ,> curiopius,
>
> > > r b-j
>
> > Gee guys, are you sure that V-dude is trying to be insulting?
>
> > I always thought "STUPIDENT" was simply an involuntary utterance. Sort
> > of a self-deprecating keyboard based version of Tourette's syndrome
> > that produces a response whenever his subconscious detects a posting
> > that he lacks the knowledge, competence, communication skills, common
> > decency and cool to reply adequately to, even though this doesn't
> > always deter him from responding. It seemed less likely at first, but
> > by now the evidence seems overwhelming.
>
> > Dale B. Dalrymple
>
> It also could be a vicious cycle of insolence he's caught up with.
> Freud would trace this back to an early childhood abuse. It's like
> mother_1 who's having a hard time disciplining children_1. Mother_1
> not feeling in the mood, Boss is not having _s e x_ lately. Growing
> ever grumpy, boss starts reprimanding father excessively at work.
> Becoming polarized, father can't help but passing on his negative
> energy to mother_2 who, in turn, passes it on to children_2.
> Children_2 go about bullying other children on the block and as a
> result children_1 end up getting some of their own medicine. On and on
> the cycle goes. What remains is for us to know where in the chain he
> truly lies.
For whatever reason, my problem is that I hate seeing the word
"STUPIDENT" in a subject line. It's almost a phobia... what does that
say about me?
Even worse is the word "STUDIOT", but that seems to have fallen out of
use.
Rick
Reply by Scott Gravenhorst●June 13, 20092009-06-13
On Wed, 10 Jun 2009 10:48:51 -0700 (PDT), robert bristow-johnson
<rbj@audioimagination.com> wrote:
>On Jun 10, 11:45�am, Richard Owlett <rowl...@atlascomm.net> wrote:
>> rickman wrote:
>...
>> > I think your post would have been even more annoying to V if you had
>> > just left out the reference to his insult altogether. �Most trolls are
>> > infuriated if, while he is standing right next to you, you continue
>> > your conversation as if he wasn't even in the room.
>>
>> It may be even more effective to politely acknowlege V's existence and
>> then carry on a polite conversation. IT might catch on - though I doubt
>> he'll notice.
>
>i don't even know what it is? student with a "pi" stuck in it?
>
>curiopius,
>
>r b-j
I want to take nothing away from Vlad's DSP skill and intellect.
However, his skill in personal relationships, such as courtesy to
others is sadly lacking.
I've seen Vladimir's posts with "STUPIDENT" in the subject line.
These posts are just to make Vlad feel larger than he actually is.
I dare say that there was/is a time when Vladdy didn't know something
and he may have actually asked a question of someone who knew more
than he (is that ACTUALLY possible?). Any one of those times, some
person of low regard for others could have called him a "stupident" as
he does so frequently and callously to others here.
Most people come to these forums to learn something. Not everyone who
asks questions here has a PhD - or any degree for that matter. There
is no charter that states question askers must have any specific
degree or qualification that I'm aware of, so I would expect a wide
range of skill levels to visit here, and I would also expect that
their questions will reflect that.
Vlad: Calling people you don't value names will not make them run away
and not return. Personally, my advice to you, Vlad is the same as
your mother ought to have taught you:
-- If you have nothing nice or helpful to say - STFU.
Reply by cpshah99●June 12, 20092009-06-12
>
I am not replicating anything. They just gave experimental results, which
does nt say much. I am doing simulation. Because we have done some
experiment as well and the multipath was one symbol!!!!! And nobody can
afford to go to sea everytime apart from these MIT/WHOI guys. I know even u
r from MIT. Recently I found soft copy of your thesis as well. And then I
thot, no wonder this guy knows a lot abt timing synchronization...
To tell u the fact 4ksys/sec is nothing. We have successfully demonstrated
and developed modems for 10ksys/sec for underwater comms for ranges up to
10kms!!! and still we use LMS, not even NLMS or RLS.
It is just that I like simulations a lot so was doing all these.
Reply by julius●June 12, 20092009-06-12
On Jun 12, 4:19�am, "cpshah99" <cpsha...@rediffmail.com> wrote:
> ]
>
>
>
> >And you chose the modulation and data rate because .... ?
>
> The reason for QPSK is that for underwater applications you cant go for
> higher order modulations, you will face more trouble.
>
> And the data rate selection is because hardly you are going to have good
> channel bandwidth.
>
> Also the carrier frequency is 12kHz. But that is not an issue because I
> did simulation at baseband.
>
>
>
> >And the distribution of energy in the channel is �... ?
>
> The distribution of the energy is not like what xsong said. It is
> distributed by taking into acount reflections loss at surface and bottom.
>
> The direct path has 40% of total energy and rest is distributed
> accordingly.
>
> It is pretty bad channel. This modelling of channel is for short range
> where you will see that the channel is very nasty.
>
>
>
> >Still not enough information for me to even start recommending what
> >to consider.
>
> >Julius
>
> Chintan
Based on your other posts you are trying to replicate what Stojanovic
et al did at MIT/WHOI in the late nineties. Similar channel
description and basically same approach with DFE and RLS. But your
choice of data rate is higher than theirs. Why is this so?
Julius
Reply by cpshah99●June 12, 20092009-06-12
]
>
>And you chose the modulation and data rate because .... ?
The reason for QPSK is that for underwater applications you cant go for
higher order modulations, you will face more trouble.
And the data rate selection is because hardly you are going to have good
channel bandwidth.
Also the carrier frequency is 12kHz. But that is not an issue because I
did simulation at baseband.
>
>And the distribution of energy in the channel is ... ?
The distribution of the energy is not like what xsong said. It is
distributed by taking into acount reflections loss at surface and bottom.
The direct path has 40% of total energy and rest is distributed
accordingly.
It is pretty bad channel. This modelling of channel is for short range
where you will see that the channel is very nasty.
>
>Still not enough information for me to even start recommending what
>to consider.
>
>Julius
Chintan
Reply by julius●June 11, 20092009-06-11
On Jun 11, 12:36�pm, "cpshah99" <cpsha...@rediffmail.com> wrote:
> Hi Guys
>
> I thot when I say the delay spread is 200 symbols, it will make sense.
>
> But anyways. My delay spread in time is 50ms. and data rate is 4ksys/sec
> so the delay spread in terms of symbol is 200.
>
[snip]
And you chose the modulation and data rate because .... ?
And the distribution of energy in the channel is ... ?
Still not enough information for me to even start recommending what
to consider.
Julius
Reply by xsong●June 11, 20092009-06-11
On Jun 11, 12:36�pm, "cpshah99" <cpsha...@rediffmail.com> wrote:
> Hi Guys
>
> I thot when I say the delay spread is 200 symbols, it will make sense.
>
> But anyways. My delay spread in time is 50ms. and data rate is 4ksys/sec
> so the delay spread in terms of symbol is 200.
>
> I think I clearly mentioned that modulation is QPSK.
>
> Now, as VLV said, it is irrelevant because when I say 5 taps mean 5
> distinguishable paths, that deos nt mean they r spaced with a symbol
> delay
There you go.
>
> The channel that I have modelled is realistic in the sense that it is
> modelled from a given geometry of ocean. And I am supremely confident tht
> the modelling is correct.
>
> So, I think the experiment that i did, where my DFE is shorter than
> channel impulse response, is not bad (if not good).
>
It depends on how your channel delay profile is like. If 99% of the
power is in the first tap, you
do not even need an equalizer.
> Thanks
>
> Chintan
Reply by cpshah99●June 11, 20092009-06-11
Hi Guys
I thot when I say the delay spread is 200 symbols, it will make sense.
But anyways. My delay spread in time is 50ms. and data rate is 4ksys/sec
so the delay spread in terms of symbol is 200.
I think I clearly mentioned that modulation is QPSK.
Now, as VLV said, it is irrelevant because when I say 5 taps mean 5
distinguishable paths, that deos nt mean they r spaced with a symbol
delay.
The channel that I have modelled is realistic in the sense that it is
modelled from a given geometry of ocean. And I am supremely confident tht
the modelling is correct.
So, I think the experiment that i did, where my DFE is shorter than
channel impulse response, is not bad (if not good).
Thanks
Chintan
Reply by xsong●June 11, 20092009-06-11
On Jun 11, 11:31�am, Vladimir Vassilevsky <antispam_bo...@hotmail.com>
wrote:
> xsong wrote:
> > If the channel has 5 taps, how can the delay spread be 200 symbols?
>
> Irrelevant.
> Think of rake receiver.
>
> VLV
For any receiver including rake, the number of taps of a channel is
delta_t*W, where delta_t is
the delay spread in time and W is the sampling bandwidth. 1/W is
symbol duration T. So if the channel has 5 taps,
then the maximum delay spread is 5 symbols.
Reply by julius●June 11, 20092009-06-11
On Jun 11, 10:42�am, xsong <songxiao...@gmail.com> wrote:
> On Jun 11, 9:04�am, "cpshah99" <cpsha...@rediffmail.com> wrote:
>
> > Hi Julius
>
> > So the observations are as follows:
>
> > System Parameters:
>
> > Delay spread of channel is 200 symbols, QPSK modultion, 511 long training
> > sequence, rate 1/2 turbo code, adaptive DFE with LMS algorithm. The FF taps
> > =50 and FB taps =50. The channel has 5 taps and taps are time varying.
>
> If the channel has 5 taps, how can the delay spread be 200 symbols?
>
>
He already chose for us the modulation and symbol rate. So much for a
complete system description.
Cintan, give the information in real world values please. Not
normalized to your baseband.
>
> > So I fixed the SNR at 14 dB and after one time equalization and 3 turbo
> > iterations I am getting BER of 10^-5. Which I think is quite good.
>
> > Next I will be more specific when I ask any que.
>
> > Thanks as always
>
> > Chintan