Mark A. Birchler

A 64 kbps digital land mobile radio system employing M-16QAM

The authors describe a 64 kbps digital mobile radio system which has been tailored for trunked radio system applications. Using a combination of digital speech coding, time division multiple access (TDMA), and spectrally efficient linear modulation technologies, up to 6 voice links are supported per 25 kHz RF channel. A key feature of the system is a new modulation method, M-16QAM, which makes possible high speed signaling in land mobile radio channels without the use of an equalizer. After a brief description of the overall system, including the TDMA frame/slot structure and speech coder, focus is shifted to the modulation technique. The motivation behind M-16QAM, as well as its design and simulated performance, are discussed in more detail. Results of field trials of an experimental modem are also discussed.<<ETX>>

Subscriber based TDOA location techniques for the Motorola iDEN system

This paper discusses development of the technology required to enable location services on Motorolas iDEN cellular phone system. Our approach consists of handset based time difference of arrival (TDOA) measurement. The performance of this system has been determined both by computer simulation and field trials. The overall TDOA system and specific algorithms utilized are described. Performance estimates for numerous special cases are discussed. These cases include highway, in-building, and coverage fringe. Particular attention is paid to the effects of propagation environments (e.g., urban, rural, etc.) on accuracy performance. In addition, bench test and field test performance data is reported and compared to computer simulation predictions.