Applications; Spread Spectrum; Direct Sequence; Coding - ADTRAN TRACER 2xT1 User Manual

61280003L2-1B
Section 1 TRACER Description

APPLICATIONS

Any application that would typically use metallic T1 as a transport can use the TRACER instead. Figure
1-1 illustrates a typical application.
Mast Unit
TRACER
Baseband Processor
VT-100
RS-232
Terminal
T1
T1
Switch
2xT1, Mast-mounted RFC
Mast and Rack mount RFCs may be mixed to accommodate individual system requirements.
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.

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.

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.

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
2
Antenna
RF Cable
IF Cable
MSC
Figure 1-1. Typical Application
Preliminary
Antenna
RF Cable
TRACER
Baseband Processor
T1
T1
Cell Radio
Cellular/PCS Site
2xT1, Rack-mounted RFC
TRACER 2xT1 User's Manual
Rack-mount RFC