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TRACER 2xT1 User’s Manual
61280003L2-1B
Section 1 TRACER Description
2
Preliminary
APPLICATIONS
Any application that would typically use metallic T1 as a transport can use the TRACER instead. Figure
1-1 illustrates a typical application.
1-1 illustrates a typical application.
The TRACER can be used in any application requiring that data be shared at a high rate of speed. In
addition to telephony applications, TRACER can be used in data communications such as inter-
networking, video conferencing, and telemetry.
addition to telephony applications, TRACER can be used in data communications such as inter-
networking, video conferencing, and telemetry.
SPREAD SPECTRUM
Spread spectrum is a form of communication in which the bandwidth of a message signal is intentionally
increased or “spread.” The FCC rules allow two methods of spreading – frequency hopping and direct
sequence. TRACER employs direct sequence spread spectrum.
increased or “spread.” The FCC rules allow two methods of spreading – frequency hopping and direct
sequence. TRACER employs direct sequence spread spectrum.
Direct Sequence
A direct sequence transmitter spreads the signal by mixing the data with the output of a pseudorandom
number generator which changes state at a rate higher than the data rate. This rate is called the
“chipping” rate. The TRACER chipping rate is twelve times the data rate.
number generator which changes state at a rate higher than the data rate. This rate is called the
“chipping” rate. The TRACER chipping rate is twelve times the data rate.
Coding
Many different pseudorandom sequences exist. The sequences are called pseudorandom because,
although they appear noise-like, they are determinant and repeat after a specific number of chips. The
longer a code is, the better correlation characteristics it possesses. These traits allow multiple spread
although they appear noise-like, they are determinant and repeat after a specific number of chips. The
longer a code is, the better correlation characteristics it possesses. These traits allow multiple spread
Figure 1-1. Typical Application
Terminal
VT-100
Switch
Cell Radio
RS-232
Cellular/PCS Site
Antenna
Antenna
IF Cable
RF Cable
Mast Unit
Mast and Rack mount RFCs may be mixed to accommodate individual system requirements.
TRACER
Baseband Processor
Baseband Processor
2xT1, Rack-mounted RFC
TRACER
Baseband Processor
Baseband Processor
T1
T1
T1
T1
MSC
T1
B
DATA
AIS
B
DATA
AIS
T1
POW
TRANSCEI
TRACER
2xT1, Mast-mounted RFC
TRACER
T1
BP
DATA
AIS
B
DATA
AIS
T1
POW
TRANSCEI
TRACER
Rack-mount RFC
RF Cable