Something about UWB Modulation, some question

I have read some papers for UWB modulation, because i am not a student for communication engineering , i don't understand clearly about the modulation scheme about UWB

There are two different groups for supporting their own modulation scheme, one is based on CDMA supported by Motorolla, the other is OFDM supported by Intel et al, i wonder whether Impulse radio systems is given up . or The carrierless style is given up, now the standarization for 802.15.3a is based on carrier modulation,

Therefore, is there something useless for us developing RF system based on impulse radio?

From math you could receive if crosscorrelate(fold) your input with the assumed send signal.

For a carrier based signal you use the natural physical properties of a tank circuit (oscillator) and correlate with the resulting sine waveforms.

For a sequence based signal you could the matching number. This is done with 1-4bits accumulators in digital logic.

So there are two known implementation methods for correlation signals types. If other signals types are used more generic A/D+DSP correlation/receive methods should be used. In most cases a combination of carrier based and generic based method is used e.g. 802.11a.

Engineering is a known selection from what could be done from the math standpoint and what are the implementation result in the physical world taking in mind the human demand.

If there are some effective implemenation methods for UWB arbitary pulse based signals engineering will have further options.