PARTICLEREDDY (STRAYDOG) wrote:
> the conclusion is taken from the below paper
> 
> http://www.i3s.unice.fr/~deneire/pap/tubbax01vtc.pdf
> 
> and here is little bit modified and SUBMITTED in another confernce,
> 
> www.i3s.unice.fr/~deneire/pap/tubbax01wpmc.pdf
> 
> regards
> Particlereddy
> 
Most recent reference in this paper is April 2001.

 From the paper...

"Therefore, all recent standards for WLANs [2, 3] support OFDM 
modulation. However, OFDM requires an expensive and power inefficient 
frontend [4], because of the high Peak-to-Average Power Ratio
(PAPR) of the OFDM signal."

"Expensive" relative to what? Things have changed. X-OFDM is less 
expensive while 8-VSB is more today. The operative word in this 2001 
paper is "ALL".

ALL WLANs support OFDM modulation. That is still true today almost six 
years later in a tech world moving at warp speed.

It would be interesting to hear what the authors of this paper thought 
today.

Maybe one of the authors, Mark Engels has a new idea from time to time. 
His book,

Wireless OFDM Systems How to make them work?,

came out a year after the paper in 2002.

http://www.amazon.com/exec/obidos/ASIN/1402071167/spreadspectrum08

Doesn't sound like he is selling single carrier systems.

Here he is again talking about curbing that power hungry OFDM in 2006 
which may be even more relevant.

http://portal.acm.org/citation.cfm?id=1146909.1147050

Bob Miller

PARTICLEREDDY (STRAYDOG) wrote:
> i think this discussion has also been worked in out in terms of
> research
> 
> this one paper's utlimate conclusion
> 
> We compared OFDM and Single Carrier-Cyclic Prefix for WLAN modems. To
> that end we have set up a simulation environment to study the
> effect of front-end non-idealities on digital modem performance.
> We have shown that OFDM and SC-CP display the same sensitivity
> to some parameters, such as phase noise and I/Q imbalance.
> However, SC-CP systems significantly increase the power
> efficiency of the modem and lower the dynamic range of the
> transmitted signals, while preserving the data rate and bit error
> rate. Therefore, SC-CP is a very good candidate for portable
> high data rate terminals
> 
One paper? Which one.

Maybe Eric Jacobsen should weigh in here about how excited both Motorola 
and Intel are with the potential for TDS-OFDM for WiMax. A lot of energy 
for OFDM everywhere, none for single carrier that I am aware of.

NO one is going to use a single carrier system in any such venture and 
succeed IMO.

Bob Miller

Vladimir Vassilevsky wrote:
> 
> 
> Rune Allnor wrote:
> 
>> Randy Yates skrev:
>>
>>> Is it possible to design
>>> single-carrier systems (including the receiver) which are just as
>>> immune to multipath as multi-carrier systems?
>>
>>
>> The answer is no.
> 
> The answer is yes. Considering the same bandwidth.
> 
> VLV

>
The argument that Randy refers to raging in other forums has another 
parameter.

8-VSB is being considered in those discussions ONLY as it pertains to 
current receivers in the US. Legacy receivers and their limitations are 
the box we are in.

Theoretical possibilities for 8-VSB are irrelevant. The latest VSB 
variant is one of the dual Chinese standard modulations, ADTB-T, and 
even though it is more advanced than the US 8-VSB and represents the 
best that the best RF minds in Jiaotong University could come up with 
under intense competition with Tsinghua University over many years, IT 
HAS FAILED. It is being totally rejected.

No reason not to continue forever trying to perfect a single carrier 
modulation in the lab but time to stop wasting our time in the US on our 
outmoded garbage of a standard, our 1994 8-VSB and BTW MPEG2. Best to 
get rid of both of them.

Each is reason enough to start over.

The discussion is about an outmoded 8-VSB that is hemmed in by the 
requirement that any "fix" or improvement to the US standard be 
COMPATIBLE with all current and past 8-VSB receivers sold.

A much different argument than is being carried on in this forum which 
is OK as long as the premise of this thread is not that somehow we can 
fix the US 8-VSB standard without making all current receivers obsolete.

The best example of trying to do that is A-VSB being pursued by Samsung 
and Rohde and Schwarz. And they would be the first to tell you that 
their solution is not going to challenge the best modulations available 
but is a kludge. The best we can do under unfortunate circumstances.

Bob Miller

k_gideon@hotmail.com wrote:
> A method of dealing with frequency-selective fading multipath in a
> single carrier system is:
> direct-sequence spread-spectrum (DS-SpSp). A very popular application
> in cellular communications is in DS-CDMA, used in the original CDMA
> (IS-95), and now in WCDMA (UMTS).
> 
> The idea is to use a higher symbol-rate, as you say:
> "single-carrier data rate is going to be many times higher than the
> rate across any one carrier of a comparable OFDM signal"
> 
> but not all the bandwidth is used to increase the symbol-rate. Rather,
> a large multiple of the bandwidth is used by "fattening" the signal
> spectrum with a known spreading sequence. The known spreading sequence
> multiplies the high-rate symbol-rate.
> 
> In DS-CDMA (DS-SpSp), the fading multipath is combated by resolving the
> multipath components separately for each of the stronger multipaths. In
> OFDM this is not necessary if the cyclic-prefix is longer than the
> delay-spread (the most-delayed strong multipath).
> 
> When everything is considered, a DS-CDMA (DS-SpSp) receiver has
> relatively similar overall complexity compared to an OFDM receiver.
> Each of the 2 methods has strengths and weaknesses, and the system
> complexity is not low in either of them, if high performance ("almost
> optimum") is required.
> 
> You will find DS-CDMA (DS-SpSp) described in almost every modern
> communication book because of its popularity in the cellular world.
> 
And Qualcomm is reported to be betting on OFDM in the future. There 
MediaFlo is OFDM and I hear that they will replace CDMA with OFDM in the 
future. Just bought Flarion which is OFDM technology and Qualcomm owns 
50 plus OFDM patents.

Bob Miller

Vladimir Vassilevsky wrote:
> 
> 
> Randy Yates wrote:
> 
>> OK, now that I've got my OFDM question off my chest, here's a related
>> question.
>>
>> If one used a normal single-carrier signal in place of OFDM, you'd
>> have a relatively huge bandwidth to deal with, which means your
>> single-carrier data rate is going to be many times higher than the
>> rate across any one carrier of a comparable OFDM signal.
>>
>> Well, given all that freakin' bandwidth, it seems that there must be
>> SOME way to fight frequency-selective multipath that works comparably
>> to the OFDM approach. It also seems pretty obvious that this is going
>> to be some "extra" stuff in the receiver, for example, a whitening
>> filter, or equalization, or some-such.
> 
> 
> Strictly speaking, it does not matter how are you going to utilize the 
> bandwidth. All kinds of modulations are equivalent. It is just the 
> matter of convenience which one to prefer.
> 
>>
>> So I guess I have two questions: 1) Is it possible to design
>> single-carrier systems (including the receiver) which are just as
>> immune to multipath as multi-carrier systems?
> 
> Certainly. Although it will require a huge amount of computation.
> 
> 
>  and 2) Would it be safe
>> to say that the receiver design for single-carrier systems is more
>> complex compared with a comparable OFDM receiver?
> 
> Yes.
> The OFDM advantage is in the low symbol rate and the simple equalization 
> in the frequecy domain. This allows for relatively simple receivers.
> 
$35 simple receivers in the UK. DMB-TH initial MSRP for receivers start 
at $30. What competition will do in the first years who knows.

IMO China will be the dominant manufacturing country for TV sets. Just 
to save on inventory cost they will make world TV sets that work with 
all major modulations. The one fly in that soup is the cost of 8-VSB 
royalties and the amount and cost of silicon required.

However if a world TV becomes the norm the rational for different 
countries to have different modulations becomes moot. Same with codecs. 
The world TV will come with a processor that allows for use of all 
relevant codecs and is upgradeable OTA.

The only issue is initial cost of design and where does the cost to 
benefit line cross between inventory and chip come. I think it is 
already here.

Bob Miller

Bob Miller

> 
> 
> Vladimir Vassilevsky
> 
> DSP and Mixed Signal Design Consultant
> 
> http://www.abvolt.com
> 
> 
> 
> 
> 

Steve Underwood wrote:
> Eric Jacobsen wrote:
>> On Tue, 26 Sep 2006 03:31:14 GMT, Randy Yates <yates@ieee.org> wrote:
>>
>>
>>> Randy Yates <yates@ieee.org> writes:
>>>
>>>> [...]
>>>
>>> OK, let me tip my hand.
>>> There are some folks/circles that are ragingly debating
>>> whether the COFDM used in DVB/T is better than the US's
>>> 8VSB. I'm wondering if there is any real difference IF
>>> the end-to-end systems are designed "properly."
>>
>>
>> Oh, gag a maggot.
>> I can't believe anybody still thinks that 8VSB is a good idea for
>> anything, anywhere, under any circumstances.
>>
>> [... a long and accurate rant about the dumbness of 8-VSB clipped ....]
> 
> Well, I find the rant accurate, but the statement before misses a key 
> issue. 8-VSB seems like its about to become the dominant approach across 
> the world, because the Chinese just chosen a variant of it. They did 
> this because they believe they have sidestepped the patents for which 
> Americans are paying heavy royalties. The believed they couldn't do this 
> with DVB/T. In a world of heavy royalties, any crappy technology which 
> can sidestep them is often a much preferred solution.
> 
> Steve

>
They chose two standards in China. One that is VSB based and one that is 
TDS-OFDM based. There is, however, no instruction that requires any 
receiver to receive both.

So the VSB standard will not be supported by anyone.

There are already 150 companies from around the world feverishly working 
on implementing DMB-TH receivers, modulators and everything else 
involved all for the DMB-TH TDS-OFDM standard.

NO one will have anything to do with the VSB one. It is dead.

Bob Miller

the conclusion is taken from the below paper

http://www.i3s.unice.fr/~deneire/pap/tubbax01vtc.pdf

and here is little bit modified and SUBMITTED in another confernce,

www.i3s.unice.fr/~deneire/pap/tubbax01wpmc.pdf

regards
Particlereddy

"PARTICLEREDDY (STRAYDOG)" <particlereddy@gmail.com> writes:

> i think this discussion has also been worked in out in terms of
> research
>
> this one paper's utlimate conclusion
>
> We compared OFDM and Single Carrier-Cyclic Prefix for WLAN modems. To
> that end we have set up a simulation environment to study the
> effect of front-end non-idealities on digital modem performance.
> We have shown that OFDM and SC-CP display the same sensitivity
> to some parameters, such as phase noise and I/Q imbalance.
> However, SC-CP systems significantly increase the power
> efficiency of the modem and lower the dynamic range of the
> transmitted signals, while preserving the data rate and bit error
> rate. Therefore, SC-CP is a very good candidate for portable
> high data rate terminals

Hi PARTICLEREDDY,

Interesting! Can you please cite the reference?
-- 
%  Randy Yates                  % "So now it's getting late,
%% Fuquay-Varina, NC            %    and those who hesitate
%%% 919-577-9882                %    got no one..."
%%%% <yates@ieee.org>           % 'Waterfall', *Face The Music*, ELO
http://home.earthlink.net/~yatescr

i think this discussion has also been worked in out in terms of
research

this one paper's utlimate conclusion

We compared OFDM and Single Carrier-Cyclic Prefix for WLAN modems. To
that end we have set up a simulation environment to study the
effect of front-end non-idealities on digital modem performance.
We have shown that OFDM and SC-CP display the same sensitivity
to some parameters, such as phase noise and I/Q imbalance.
However, SC-CP systems significantly increase the power
efficiency of the modem and lower the dynamic range of the
transmitted signals, while preserving the data rate and bit error
rate. Therefore, SC-CP is a very good candidate for portable
high data rate terminals

On Fri, 13 Oct 2006 00:53:10 GMT, Randy Yates <yates@ieee.org> wrote:

>Randy Yates <yates@ieee.org> writes:
>
>Eric (et al.), I also wanted to throw this in: I read somewhere
>in one of the ATSC documents that the system requires on the order
>of 15 dB SNR to get acceptable picture performance. Does that
>sound like a reasonable SNR requirement for John Q. Public? 

Yes, it's 14.9dB in some of the early docs that I have.   I bet that's
in AWGN, too, which isn't the real channel model.

For the broadcaster, getting the coverage that they want is then
dictated by the power output of the transmitter.   I don't know what
the detection threshold is for the typical NTSC analog receiver, but I
wouldn't be surprised if it's in the same general range.

Eric Jacobsen
Minister of Algorithms, Intel Corp.
My opinions may not be Intel's opinions.
http://www.ericjacobsen.org