issues need to be resolved in UWB

Although UWB signals can be transmitted below the noise floor, it may be desirable to transmit with more power. If a UWB system is operated under current FCC Part 15 regulations, narrow band signals operating in the same band will be adversely affected. The narrow band users will see the UWB signal as an increase in the noise floor by about 10 dB. The FCC is currently proposing new regulations to resolve this issue. On suggested solution would be to only allow UWB operation above a certain frequency.
Currently UWB Transmitter and Receiver must be time synchronized. GPS makes this task feasible for production systems, however a system where synchronization is not required is desirable.
High sampling rate receivers are required.
Efficient Pulse Shaping is required.
Current Transmitter designs consume large amounts of power in the generation and processing of the pulses. Although the period of high power consumption is very short, and probably will not affect battery life compared to a narrow band system, it does lead to problems in designing a transmitter on a chip.