The main goals of user interface evaluation are assessment of both system functionality and user experience, as well as the identification of specific system problems. Various evaluation approaches are in widespread use, which can be classified along the dimensions of analytical vs. empirical, and/or expert analysis vs. end user participation.
Published in Chapter:
Ultra-Wideband Solutions for Last Mile Access Network
Sabira Khatun (University Putra Malaysia, Malaysia), Rashid A. Saeed (MIMOS BERHAD, Malaysia), Nor Kamariah Nordin (University Putra Malaysia, Malaysia), and Borhanuddin Mohd Ali (MIMOS BERHAD, Malaysia)
Copyright: © 2009
|Pages: 10
DOI: 10.4018/978-1-60566-014-1.ch195
Abstract
Ultra-wideband (UWB) is an alternative wireless communications technology that offers high bandwidth wireless communications without the constraints of spectrum allocation. Fundamentally different from conventional radio frequency communications, UWB relies on a series of narrow, precisely timed pulses to transmit digital data. Transmitters and receivers that use UWB can be much simpler to build than their conventional counterparts, resulting in lower cost and higher power efficiency. Moreover, the inherent properties of UWB emissions allow them to potentially coexist with conventional wireless systems on a noninterfering basis. In April 2002, the Federal Communications Commission (FCC) released UWB emission masks and introduced the concept of coexistence with traditional and protected radio services in the frequency spectrum, which allows the operation of UWB systems mainly in the 3.1 to 10.6 GHz band, limiting the power level emission to -41dBm/MHz. Within the power limit allowed under the current FCC regulations, Ultra-wideband can not only carry huge amounts of data over a shortto- medium distance at very low power (this range can be extended by using ad-hoc or mesh networks), but it also has the ability to carry signals through doors and other obstacles that tend to reflect signals at more limited bandwidths and a higher power (Reed, 2005). At higher power levels, UWB signals can travel to significantly greater ranges. In March 2005, the FCC granted the waiver request, filed by the multiband Orthogonal Frequency Division Multiplexing (OFDM) alliance (MBOA), in which it approved the change in measurement for the all UWB technologies (neutral approach) (Barret, 2005). The FCC’s waiver grants effectively removes the previous transmit power penalties for both frequency-hopping (OFDM) and gated UWB technologies (TH and DS). Hence, they are allowed to transmit at higher power levels and then become idle for some time, as long as they meet the limits for average power density. This new rules allow those technologies to achieve up to four times better performance and double the range.