Motorola Timeport P8190, Service Manual

Page: 14 / 149

© 2000 Motorola, Inc.
TDMA Timeport™ P8190 Cellular Overview
2
The cellular radio frequency spectrum has
been divided by the FCC into two equal seg-
ments or bands to allow two independent cel-
lular carriers to coexist and compete in the
same geographic coverage area. Each band
occupies one half of the available channels
in the cellular spectrum. Initially there were
666 channels available across the entire cel-
lular spectrum, but that number was ex-
panded to 832 channels in 1987, and with
NAMPS to 2,412 channels in 1991. Digital
cellular promises to make a further expan-
sion. To guarantee nationwide compatibil-
ity, the signaling channel frequencies have
been pre-assigned to each segment (band).
The two bands and their assigned channels
are defined in Figure 1.
Originally the B Band was assigned to the
telephone company (referred to by a euphe-
mism, the Wireline carrier). The A Band, by
default, was referred to as the Non-Wireline
carrier, guaranteed competition to the tele-
phone company. Today the terms Wireline
and Non-Wireline have little meaning since
telephone company carriers now operate A
Band systems, and vice-versa.
Control (Data) Channels
A cellular telephone in the cellular system is
under the indirect control of the switch, or
central controller. The central controller uses
dedicated control channels to provide the sig-
US Cellular Frequency Band
832 channels
001
1023
991 666
667
716
717
799
333
312
313
334
354
355
A' A' B'
Voice
Channels
Voice
Channels
Control
Channels
B B
A A
Band A Band B
A'
666
667
716
717
799
TDMA Secondary
Control Channels
737 - 757 688 - 708
Figure 2. US Cellular Frequency Band
Introduction