AMPS Cellular课件.ppt

精品文档 精品文档 Registration When you first turn your phone on, it does a self diagnostic check. It then scans each of the 21 forward control channels (base station to cellular), camping on the strongest one. The phone rescans every 7 seconds to make sure that this channel is still the strongest. The mobile then decodes the data stream being sent by the base station. Note: The data paths are actually digital. So, AMPS is actually a hybrid system, though the voice is analog. The data stream has information on what network the phone is on. Using this, the phone can decided if it is roaming. 精品文档 AMPS Cellular ENGR 475 – Telecommunications October 24, 2006 Harding University Jonathan White Based on: /mt_cellbasics/ 精品文档 Outline Introduction Cellular History Cellular Terminology AMPS Definition – 1st Gen 1 phone system How all Cellular communications operate How AMPS operates Why AMPS is being replaced but is still with us today. 精品文档 Introduction 1906: 1st radio transmission of Human voice. What’s the medium? Used an RC circuit to modulate a carrier frequency that radiated up and down an antenna. Receiver had a matched RC circuit with an antenna 精品文档 Intro 1910: Lars Ericsson in Sweden invents the first car phone. However, Morse Code continues to be the primary method of sending information without a wire. 精品文档 Intro. 1934: Federal Communications Commission is founded by Roosevelt’s New Deal. Charged to allocate the radio spectrum with the public interest in mind. The FCC was corrupt until the mid 60’s, it propped up AM radio for years to keep out newer FM stations. The FCC gave priority in terms of broadcast channels to emergency and government units. 精品文档 Intro. WW2: Many innovations, including RADAR. Also the first mobile FM Transmitter/Receiver. Weighed over 30 lbs. More like a Walkie Talkie. Developed by Motorola. 精品文档 Intro. 1946: In St. Louis, ATT and Southwestern Bell introduced the first mobile telephone service. There were 6 channels in the 150 MHz band