User Guide

Technical Documentation
NHD–4
System Overview
PAMS
Page 3–5
Original 11/97
Cellular History
Mobile Radios have been in use for approximately 70 years and the cellular concept
was conceived in the 1940s. Public cellular mobile radio was not introduced in the
US until 1983.
In the beginning of the twentieth century, mobile radios were limited to shipboard
use due to the high power requirements and bulky tube radio technology.
Automotive systems in the 1920s operated on 6 volt batteries with a limited storage
capacity.
One of the first useful means of automotive mobile radio occurred in 1928 by the
Detroit police department. Transmission was broadcast from a central location and
could only be received by the mobile police radios.
Introduction of the first two way mobile application was delayed until 1933. This
simplex AM (Amplitude Modulation) push to talk system was introduced by the
police department in Bayonne, New Jersey. The first FM (Frequency Modulation)
mobile transmission (two frequency simplex) was used by the Connecticut State
Police at Hartford in 1940.
The first step towards mobile radio connection with the land line telephone network
was established in St. Louis in 1946. It was called an “urban” system and only
supported three channels.
In 1976, New York City had only 12 radio channels that supported 545 subscribers
with a waiting list of 3700.
In the 1970s, available cellular spectrum was constrained to frequencies above 800
MHz due to equipment design limitations and poor radio propagation characteristics
at frequencies above 1–GHz, this resulted in the allocation of the 825–890 MHz
region.
In 1974, 40 MHz of spectrum was allocated for cellular service and in 1986, an
additional 10 MHz of spectrum was added to facilitate expansion. The present
frequency assignments for the US Cellular system mobile phone is
824.040–848.970 MHz transmit and 869.040–893.970 MHz receive These bands
have been frequency divided (FDMA) into 30 kHz channels. This results in a
maximum capacity of 832 channels. These channels were then divided into two
groups with 416 channels assigned to each system.