. Any use is subject to the Terms of Use as given at the website. Analog Wireless Telephony (AMPS) Analog Wireless Telephony (AMPS) If the handoff does succeed, the base station starts making measurements and run- ning its power control algorithm. In this sequential paragraph form, the handoff process seems cut and dried. The steps of the handoff process fit neatly into the mental picture of a car driving smoothly out of one hexagon into a neighboring hexagon. The AMPS designers knew full well that the handoff procedure had to be robust enough to handle some oddball cases. Even so, there are cases of strange handoff behavior. The measurements and thresh- old can do strange things. In the early Chicago days, we had a street corner in Elmhurst, Illinois, where we would sit at the red light and watch the channel indica- tor on our test unit cycle through three cells as A handed off to B, B handed off to C, and C handed off back to A. There is an important disparity in the AMPS system design. In hindsight, it is easy to say somebody should have thought of this, but it certainly was not obvious at the time. The initial call setup is done by the mobile telephone, and the handoffs are done by the base station. This means there is a transfer of radio control from mobile tele- phone to base station just as the call is getting underway. There is a higher frequency of handoffs in the first 15 seconds of AMPS calls than after that.4 4 6.7 Conclusion The AMPS system pioneered cellular technology in support of mobile telephony and de- fined many of the engineering issues and solutions still in use today. As we shall see the next two chapters, many issues remained the same even as cellular engineering made the huge leap from analog to digital. Maybe back in 1978 somebody did think of it and decided it was okay. When we noticed the ef- fect in our 1985 simulation work, we were concerned about the effect on system capacity of so many extra handoffs. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineering