Ultrawideband Radio Design: The Promise of High-Speed, Short-Range Wireless Connectivity SUMIT ROY, JEFF R. FOERSTER, V. SRINIVASA SOMAYAZULU, AND DAVE G. LEEPER Invited Paper This paper provides a tutorial overview of ultrawideband (UWB) radio technology for high-speed wireless connectivity. Subsequent to establishing a historical and technological context, it describes the new impetus for UWB systems development and standardiza- tion resulting from the FCC’s recent decision to permit unlicensed operation in the [3.1,10.6] GHz band subject to modified Part 15 rules and indicates the potential new applications that may result. Thereafter, the paper provides a system architect’s perspectives on the various issues and challenges involved in the design of link layer subsystems. Specifically, we outline current developments in UWB system design concepts that are oriented to high-speed applications and describe some of the design tradeoffs involved. Keywords—Personal area networks, wireless, ultrawide band. I. INTRODUCTION AND BACKGROUND Ultrawideband (UWB) technology is at present defined by the Federal Communications Commission (FCC) as any wireless transmission scheme that occupies a fractional bandwidth where is the transmission bandwidth and is the band center frequency, or more than 500 MHz of absolute bandwidth. In traditional UWB systems, such large bandwidths were achieved by using very narrow time-duration baseband pulses of appropriate shape and duration—these include the family of Gaussian shaped pulses and their derivatives [2]. To confine the transmitted spectrum to a desired passband, postfiltering of the baseband pulse spectrum including the impact of the transmit antenna characteristics has traditionally been assumed. There are several benefits to using such large bandwidths—in an additive Gaussian noise-limited environment, expanding Manuscript received August 6, 2003; revised November 10, 2003. This work was completed while S. Roy was on academic leave at Intel Wireless Technology Lab, Hillsboro, OR 97124-5961 USA. S. Roy is with the University of Washington, Seattle, WA 98101 USA. (e-mail: roy@ee.washington.edu). J. R. Foerster, V. S. Somayazulu, and D. G. Leeper are with the Wireless Technology Division, Intel Labs, Hillsboro, OR 97124-5961 USA. Digital Object Identifier 10.1109/JPROC.2003.821910 Fig. 1. UWB spectral mask and FCC Part 15 limits. bandwidth (when feasible) is the preferred cost-effective pathway to achieving higher data rates without the need to increase transmit power (or equivalently, resorting to sophis- ticated error control coding and higher order modulation schemes). In a multipath dominated environment, larger transmission bandwidths result in the ability for increasingly fine resolution of multipath arrivals, which leads to reduced fading per resolved path, since the impulsive nature of the transmitted waveforms prevents significant overlap and, hence, reduces possibility of destructive combining. The FCC recently approved [1] the deployment of UWB 1 on an unlicensed basis in the 3.1–10.6 GHz band subject to a modified version of Part 15.209 rules. The essence of this ruling is to limit the power spectral density (PSD) mea- sured in a 1–MHz bandwidth at the output of an isotropic transmit antenna to that shown in Fig. 1. The above spec- tral mask allows UWB-enabled devices to overlay existing 1 At the time of writing, UWB is being considered in both Europe and Japan for unlicensed bands but is yet to be approved. 0018-9219/04$20.00 © 2004 IEEE PROCEEDINGS OF THE IEEE, VOL. 92, NO. 2, FEBRUARY 2004 295