ABILITY TO WORK WITH LOW SIGNAL-TO-NOISE RATIOS
The Hartley-Shannon formula for maximum capacity (Equation 1–5) also indicates that the channel capacity is only logarithmically dependent on signal-to-noise ratio (SNR). Therefore, UWB communications systems are capable of working in harsh communication channels with low SNRs and still offer a large channel capacity as a result of their large
bandwidth.

LOW PROBABILITY OF INTERCEPT AND DETECTION
Because of their low average transmission power, as discussed in previous sections, UWB communications systems have an inherent immunity to detection and intercept. With such low transmission power, the eavesdropper has to be very close to the transmitter (about 1 meter) to be able to detect the transmitted information. In addition, UWB pulses are time modulated with codes unique to each transmitter/receiver pair. The time modulation of extremely narrow pulses adds more security to UWB transmission, because detecting picosecond pulses without knowing when they will arrive is next to impossible. Therefore, UWB systems hold significant promise of achieving highly secure, low probability of intercept and detection (LPI/D) communications that is a critical need for military operations.

RESISTANCE TO JAMMING
Unlike the well-defined narrowband frequency spectrum, the UWB spectrum covers a vast range of frequencies from near DC to several gigahertz and offers high processing gain for UWB signals. Processing gain (PG) is a measure of a radio system’s resistance to jamming and is defined as the ratio of the RF bandwidth to the information bandwidth of a signal:

The frequency diversity caused by high processing gain makes UWB signals relatively resistant to intentional and unintentional jamming, because no jammer can jam every frequency in the UWB spectrum at once. Therefore, if some of the frequencies are jammed, there is still a large range of frequencies that remains untouched. However, this resistance
to jamming is only in comparison to narrowband and wideband systems. Hence, the performance of a UWB communications system can still be degraded, depending on its modulation scheme, by strong narrowband interference from traditional radio transmitters coexisting in the UWB receiver’s frequency band [2, 4, 5].

SUPERIOR PENETRATION PROPERTIES
Unlike narrowband technology, UWB systems can penetrate effectively through different materials. The low frequencies included in the broad range of the UWB frequency spectrum have long wavelengths, which allows UWB signals to penetrate a variety of materials, including walls. This property makes UWB technology viable for through-the-wall communications and ground-penetrating radars. However, the material penetration capability of UWB signals is useful only when they are allowed to occupy the low-frequency portion of the radio spectrum.