how is it different?

Conventional RF systems can all be thought of as narrowband when compared with UWB, even though in practice their bandwidth varies. The common feature of narrowband systems is that they transmit a long train of RF waves. UWB is different because it transmits short pulses of RF. Transmitting short pulses gives WB the following advantages over conventional RF:

• Very precise range measurement for tracking systems. It's simply easier to measure accurately when using a fine measurement scale - how can you measure the width of a human hair with a yardstick? UWB can measure ranges to within a few inches as opposed to several feet for a narrowband system.
• Excellent performance in very difficult RF environments. A difficult RF environment is one which is very reflective, like inside a building, factory, ship etc. When signals bounce around, they can overlap and cancel each other, or at the very least confuse a tracking system trying to time the arrival of signals. Very short pulses rarely overlap, making the task of maintaining excellent performance in highly reflective RF environments a key UWB feature.
• The ability to track very large numbers of tags. Short pulses simply don't take very long to transmit, meaning that many of them can be on the air at the same time without colliding. This translate into an ability to keep track of thousands of tags per second when using UWB.
• Very sensitive motion detection. A technology that can measure range accurately can measure changes in range (motion) very accurately too. A UWB radar can detect a person's breathing, even through a wall.
• Radar target classification for very low false alarm rates. A radar that can measure motion very sensitively can distinguish the characteristics of a human vs. an animal vs. a vehicle, for example. This means that a UWB radar can be used very effectively for applications like perimeter security since it can maintain a very low false alarm rate by triggering only on intruders and not every rabbit that hops by.

from ultrasound?

UWB and ultrasound are in fact very similar, and many of the signal processing techniques used in ultrasonic systems can be applied to UWB systems. The key difference is that ultrasound is strictly a line of sight technology, or if not then extremely short range (it is best know for medical imaging where it typically works only over a few inches).

UWB is different because, instead of using high frequency sound waves which do not penetrate obstacles, it uses RF pulses which can travel through several walls. This makes UWB viable for wide area applications where obstacles are certain to be encountered, whereas ultrasound becomes in operable in these circumstances.

from infrared?

Once again, UWB and infrared (IR) are very similar in that they both use short pulses in order to achieve excellent range measurement accuracy. Like ultrasound though, IR is strictly a line of sight technology whereas UWB can operate through multiple walls.

from millimeter wave radar?

Millimeter wave (mmW) radars are radar that operate at high frequency, giving them a wavelength of the order of millimeters. These, then, are excellent devices for measuring range and motion, and are often used in these applications. Like ultrasound and IR however, RF systems at these high frequencies are line of sight only. Additionally, mmW radars can be very costly. UWB is different because it can operate through walls and vegetation, and at cost effective prices.

from LIDAR?

LIDARs are radars but using lasers at optical frequencies to achieve the ultimate in range accuracy and imaging potential. Like mmW, these can be expensive and are limited to line of sight applications only. Worse, LIDARs do not operate well through obscurants such as rain, dust and smoke. UWB is different because it not only operates through walls and vegetation, but also through typical obscurants such as rain, dust and smoke.