UWB (OFDM vs frequency hopping)

Hi!

Can someone explains to me what is the difference between using OFDM
and frequency hopping technique for UWB?

Thanks.
L

"lindah74@gmail.com" <lindah74@gmail.com> writes:

> Hi!
>
> Can someone explains to me what is the difference between using OFDM
> and frequency hopping technique for UWB?

I wasn't aware UWB was frequency hopping. I thought it was simply
a wideband modulation technique. Further, it doesn't (or may not)
even use a carrier at all - the baseband signal is so wideband it
is directly input to the transmitter.
-- 
%  Randy Yates                  % "Remember the good old 1980's, when 
%% Fuquay-Varina, NC            %  things were so uncomplicated?"
%%% 919-577-9882                % 'Ticket To The Moon' 
%%%% <yates@ieee.org>           % *Time*, Electric Light Orchestra
http://home.earthlink.net/~yatescr

As Randy said, all I have heard concerning UWB is that it's an ultra 
wide baseband signal.
I don't believe it requires any frequency hopping, as demodulation of 
the signal should reduce the processed power of any narrowband 
interferer as well as that of non-correlated wideband interferers.


> "lindah74@gmail.com" <lindah74@gmail.com> writes:
> 
>> Hi!
>>
>> Can someone explains to me what is the difference between using OFDM
>> and frequency hopping technique for UWB?
> 
> I wasn't aware UWB was frequency hopping. I thought it was simply
> a wideband modulation technique. Further, it doesn't (or may not)
> even use a carrier at all - the baseband signal is so wideband it
> is directly input to the transmitter.

Randy Yates wrote:

   ...
>  the baseband signal is so wideband it is directly input to the transmitter.

Does it extend down to DC? What sort of antenna is used?

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������

On 17 Mar 2006 18:40:15 -0800, "lindah74@gmail.com"
<lindah74@gmail.com> wrote:

>Hi!
>
>Can someone explains to me what is the difference between using OFDM
>and frequency hopping technique for UWB?
>
>Thanks.
>L

Pretty much what it says:   One technique hops in frequency and one
using multiple carriers.

Since UWB devices occupy so much spectrum they must take measures to
both avoid interferers as well as avoid generating interference.  The
WiMedia system using a multi-carrier technique (essentially OFDM) and
turns certain subcarriers off to avoid interference.

I think the "other" technique hops instead, and modifies its hopping
pattern for the same reason.

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

lindah74@gmail.com skrev:

> Hi!
>
> Can someone explains to me what is the difference between using OFDM
> and frequency hopping technique for UWB?
>
> Thanks.
> L

OFDM is a "normal" way of doing transmissions also used in many other
standards.
wlan etc..

the other standard is a totally different way of doing it, it's pulses
kinda like
the earliest spark transmitters I guess. Afaik the pulse shape and
maybe filters
limit the frequency range to comply with regulations. I believe the
position 
and sign of the pulses is what transfers data.
 
-Lasse