Stephen A. Wilkus

Prototype experience for MIMO BLAST over third-generation wireless system

In this paper, a multiple-input-multiple-output (MIMO) extension for a third-generation (3G) wireless system is described. The integration of MIMO concepts within the existing UMTS standard and the associated space-time RAKE receiver are explained. An analysis is followed by a description of an actual experimental MIMO transmitter and receiver architecture, both realized on digital signal processors (DSPs) and FPGAs within a precommercial OneBTS base station. It uses four transmit and four receive antennas to achieve downlink data rates up to 1 Mb/s per user with a spreading factor of 32 and the UMTS chip rate of 3.84 MHz. Furthermore, different MIMO detectors are evaluated, comparing their performance and complexity. System performance is evaluated through simulations and indoor over-the-air measurements. Capacity and bit-error rate measurement results are presented.

Assisted GPS for Wireless Phone Location — Technology and Standards

Many approaches have been advanced for locating the geographic position of wireless phones, both for emergency response purposes and for emerging location-based services. Depending mainly upon the services envisioned and the particulars of the air interface, one or another approach appears appealing. Increasingly, the assisted-GPS approach is gaining recognition as the approach that can best meet all requirements. Among the important requirements are those mandated in the USA by the Federal Communications Commission (FCC) for Enhanced 911. Assisted GPS provides the best accuracy for use in location services. It is rooted in the suitability of wireless networks to provide data over the air to enable fast acquisition and lower power consumption, as well as provide indoor operation-capabilities that conventional GPS cannot provide. The assisted-GPS approach promises to enable a new industry of location-based services and important new safety measures.

Field Measurements of a Hybrid DVB-SH Single Frequency Network With an Inclined Satellite Orbit

Field measurements of a DVB-SH network with both satellite and terrestrial transmitters are presented. The system is a Single Frequency Network transmitting video streams to vehicular terminals with up to 4 branches of receiver antenna diversity. The signal is transmitted in the S-band at 2.1859 GHz with both time and frequency synchronization of the terrestrial repeaters with the satellites signal. The time and frequency variations are cancelled out at the satellite gateway, but because these can not be canceled at all locations, and because the satellites position in space is variable (in an inclined orbit) the terrestrial repeaters are made to cancel the residual time and frequency variation. The field measurements include data taken in late 2008 through 2009 with multiple repeaters located in several cities including Las Vegas, NV, Raleigh and Durham, NC, as well as various morphologies, and with elevation angles to the satellite ranging from 25° to 52° . This paper presents coverage data for these various morphologies, modulation and code rates, as well as various MPE-iFEC interleaver settings used to ameliorate the effects of long shadowed intervals such as when the vehicle goes under highways or bridges where there signal is obscured for several seconds. We observed excellent performance in hybrid mode with better than 99% of the measured seconds error free. In satellite-only mode, the MPE-iFEC interleaver raised the performance from 81% to 91% averaged over all environments, including dense urban.

Geolocation and wireless multimedia

Federal Communications Commission (FCC) mandates locating wireless phones that are in an emergency 911 call and many technologies were proposed and developed to meet that requirement. We review these techniques here because geolocation will have an even greater future role as a basis for value-added services and applications that integrate positioning and wireless multimedia. We explore in more detail one of the geolocation technologies, Assisted GPS, which has exceptional accuracy and cost-effectiveness. We also show how the SAMPS (System Assisted Mobile Positioning through Satellite) geolocation standard for TDMA wireless networks, based on assisted GPS, enables positioning-based services and enhances the performance of GPS receivers built into wireless handsets.