TABLE OF CONTENTS Many of the problems commonly associated with the mobile-radio environment have already been discussed in the preceding chapters. To briefly summarize, the natural phenomena that result in excess path loss over that normally occurring as free-space path loss were discussed in Chaps. 3 and 4. Multipath fading and the effects of random FM were discussed in Chaps. 6 and 7. Improving signal reception by increasing transmitted power and/or transmission bandwidth was discussed in Chap. 8. The option of using diversity techniques instead of increasing the transmitted power to improve performance was discussed in Chap. 9. And finally, the techniques for improving performance through the use of diversity combining were described in Chap. 10. In this chapter, the problems encountered in sending and receiving both voice, which uses analog transmission, and control signals, which use digital data transmission, through the mobile-radio environment are discussed. By designing a waveform for the control signal, we can filter the voice and the control signal at the baseband.
Problems relating to signal transmission in the mobile-radio environment are usually associated with the variables of distance and vehicular velocity, the waveforms of the transmitted pulses, and the time-delay spread attributable to the mobile-transmission medium. These problem areas are briefly described in the following paragraphs.
In Sec. 8.3 of Chap. 8, the error rate was found to be a function of the carrier-to-noise ratio (cnr). The cnr is affected by the distance between the transmitting location and the receiving...
