KEYWORDS: Global Positioning System, Receivers, Modulation, Telecommunications, Mobile devices, Wireless communications, Digital video discs, Imaging systems, Antennas, Multimedia
The prime radio spectrum is a non-depleting but finite natural resource that is highly congested in a small set of bands -- such as the unlicensed and “PCS” bands -- but unbelievably underutilized over most of the other allocated frequencies. Enter Ultra-Wideband. Ultra-wideband may be the most over-hyped technology to surface within the past few years, but with 7.5 GHz of available and unlicensed spectrum and a little imagination, it poses a tremendous opportunity to drive a whole new generation of wireless devices. This paper, which is primarily informational in nature, highlights some of the fundamental issues surrounding the use of Ultra-wideband for wireless communications and also discusses its forecasted role in the evolution of future wireless systems.
The future proliferation of UWB-enabled devices raises legitimate concerns for the impact of its use on the performance of incumbent radio systems. In this paper, we present analytical models that quantify the blocking probability and the increase in forward traffic channel power allocation in the presence of noise-like UWB interference. The cdma2000 forward link has a fixed maximum transmit power but can control the fraction of total forward link power allocated to each traffic channel. If a terminal experiences a loss in sensitivity due to the presence of UWB energy, the base station can raise its power allocation to compensate for these conditions, up to a limit. If, however, the conditions at the handset require more power than that which is allowed by the system, then the traffic channel is blocked. In this study, we consider system performance as a function of the UWB power spectral density and its separation from the victim cdma2000 1X terminal. Although further study is pending, our analysis generally shows that protection of the cdma2000 forward link for indoor reception requires the UWB indoor emission limit to at least be below 20 dB below the currently specified emission limit when there is a single radiating UWB source.
KEYWORDS: Data modeling, Radio propagation, Global system for mobile communications, Standards development, Antennas, Environmental sensing, Signal attenuation, Receivers, Buildings, Cell phones
Mobile location is one of the fastest growing areas for the development of new technologies, services and applications. This paper describes the channel models that were developed as a basis of discussion to assist the Technical Subcommittee T1P1.5 in its consideration of various mobile location technologies for emergency applications (1997 - 1998) for presentation to the U.S. Federal Communication Commission (FCC). It also presents the PCS 1900 extension to this model, which is based on the COST-231 extended Hata model and review of the original Okumura graphical interpretation of signal propagation characteristics in different environments. Based on a wide array of published (and non-publicly disclosed) empirical data, the signal propagation models described in this paper were all obtained by consensus of a group of inter-company participants in order to facilitate the direct comparison between simulations of different handset-based and network-based location methods prior to their standardization for emergency E-911 applications by the FCC. Since that time, this model has become a de-facto standard for assessing the positioning accuracy of different location technologies using GSM mobile terminals. In this paper, the radio environment is described to the level of detail that is necessary to replicate it in a software environment.
KEYWORDS: Clocks, Error analysis, Signal to noise ratio, Time metrology, Computer simulations, Global system for mobile communications, Standards development, Algorithm development, Control systems, Wireless communications
The Enhanced Observed Time Difference (E-OTD) method is one of the emergency positioning technologies that has been standardized for use with GSM systems in the United States. In this paper, we apply the E-OTD approach to a (30 kHz) IS-136 TDMA system in order to study the effect of a linearly increasing BTS clock drift on RMS OTD estimation accuracy. We investigate performance of the OTD estimation algorithm as a function of the SNR, C - I and the magnitude of the BTS clock drift error. Our simulation results indicate that the RMS OTD estimation error can initially be reduced by increasing the observation interval, but that beyond a certain number of measurements (depending on the SNR and C - I), the BTS clock drift becomes the dominant error source and causes the RMS OTD error to rise.
KEYWORDS: Global Positioning System, Standards development, Satellites, Navigation systems, Signal detection, Global system for mobile communications, Liquid crystals, Receivers, Internet, Wireless communications
Developing mobile station (MS) location technologies that meet the U.S. Federal Communications Commission's (FCC) wireless E-911 requirement for emergency location has become an increasingly important topic. The FCC has currently ruled that the carriers begin selling and activating ALI (Automatic Location Identification)-capable handsets no later than October 1, 2001 and has also granted a limited waiver of the accuracy standards to certain carriers. Since location information can potentially be used for other location-dependent applications, there is also an explosive interest in the development of new location-based commercial services. In this paper, we present a summary of the location technologies that could potentially be used as solutions to comply with the E-911 ruling. We also discuss the emergence of location commercial services and explore how mobile location information can be used to (1) improve performance in different layers of the systems, and (2) increase wireless system functionality for location commercial services.
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