uwb Vs. Spread Spectrum communication

Both UWB & Spread Spectrum are using in wider bandwidth communication.
What is the difference between two ?

If we increase the Bandwidth, then power level will be too small. Then there is a probability to interpret the received signals as noise or affecting the transmitted signals by channel noise. How we can get rid of this problem ?

I think of UWB as one form of spread spectrum transmission. There are many forms.

You may find this book interesting :

The Art and Science of Ultra-Wideband Antennas, Hans Shanz

One idea behind UWB is that it looks like low power noise to a conventional narrow band receiver and thus introduces only minimal disturbances. (I know this may start a debate.)

More bandwidth, more spread spectrum gain, the SNR should be better at the same power level. That mean smaller transmitter power needed for telecomm system, so more users can be supported, because the others users is interference for one user.
The spread spectrum telecomm uses CDMA, every user has a specific code. These codes should be oxthogonal each other. One code multiplies the code is 1, one code multiplies the other codes is zero. So at receiver, only the specific code can be demodulated. They also use veterbi algorithm to de-coded.
You should find some CDMA telecomm textbook for answers.
Normally spread spectrum telecomm only use CDMA.
But UWB uses not only CDMA but also OFDM.

But there exist two types of UWB,
1. DS (Direct Sequence) impulse radio
2. MB OFDM

And 3. C-Wave fielded by (defunct/almost defunct) PulseLink.

There are probably other contenders as well. Is anyone trying to do a frequency hopper in UWB?

In the early days there was "time hopping" which is a form of UWB. The problem with this is that there is no correlation gain. You get the full bandwidth of interference. In frequency hopping you are sometimes lucky to land on a frequency with no interference there. In direct spread you get the correlation gain.

Hi Flatulent,

I really like the underlying idea in the various UWB implementations, namely create a modulation that is spread and noise like to other services in the same bandwidth. I particularly like the idea that if UWB looks like very low level noise it will not disrupt existing services and the FCC can reissue licenses on top of other existing carriers. Same old story of five pounds more "Stuff" in a two pound bag.

The way I see it, for the moment OFDM has the best shot at tailoring their spectrum to fill the FCC mask and use all the power allowed. The next problem is how to avoid in-band interference. Really, the winner will be the one who has the best SNR and the highest energy per bit. OFDM seems to be the current best bet, but we will see. Or maybe UWB is dead unless the FCC turns up the power limitation a bit.

We all would like a robust, high speed wireless option to replace all the cables we now have everywhere. Oh yes, it needs to cost less than the cables. 100% reliability is given.

Yes, you are right, there are two standard. You can check the standards for details. If my memory is correct, the standards is 802.15.3a by IEEE TG3 workgroup, which is dismissed on Jan., 2006.
MB-OFDM is supported by WiMedia，including Intel, TI, Panasonic, Staccato、Wisair、Alereon, etc. DS-UWB includes Freescale, etc. Both standrads have UWB IC and products.
UWB means the bandwidth is more than 500M. FCC has another definition, the bandwidth is more than 25% or higher than 1.5G. The center freq is between 3G and 10G. the air interface datarate is about 10~480Mb/s.
IEEE 802.15.4a is another UWB for positioning.