Experimental performance results of an indoor wireless extension of IS-136 based on π/8 D8PSK, coded modulation, and antenna diversity

This paper reports the performance results of an experimental study of a digital communication system designed as an extension of the IS-136 North American digital cellular system. The proposed system has been designed to achieve twice the effective bit rate (up to 16 kb/s end user data rates) for transmission of high quality coded speech in slow fading indoor wireless environments. This study has covered numerous aspects of the system design including the evaluation of the real time voice communications quality. To create as complete a prototype as practical and to provide means for testing over real and simulated RF channels, the implementation included building a 900 MHz ISM band transceiver. We describe the physical layer design, real time experimental platform implementation and measured performance results of the physical layer on the forward link. Modifications to the IS-136 system include replacing the π/4-QPSK modulation with π/8-D8PSK modulation, changing the channel coding and modulation approach, as well as adding preselection diversity in the handset receiver. Most of the IS-136 slot and frame structure is preserved. The effects of channel and receiver impairments are documented and compared against theoretical and simulation results. Results are reported in the form of frame error rates relevant for speech communications. We show that a frame error rate of about 1 percent is achievable at a 20 dB signal to noise ratio in a 1 Hz Rayleigh fading environment when preselection diversity is active with a 16 kb/s end user data rate