Direct Sequence; Coding; Channel Selection - ADTRAN TRACER User Manual

61280.003L1-1B
D S
IRECT EQUENCE
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.
C
ODING
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 spectrum systems
to operate in the presence of one another with minimal interference
if they are operating with different sequences. The Tracer allows
the selection of one of ten different 120-bit long sequences.
C S
HANNEL ELECTION
The FCC has allocated 83.5 MHz of spectrum in the band in which
the Tracer operates. A Tracer system fully uses the available
bandwidth -- transmitting in one half and receiving in the other.
The figure below illustrates the bandwidth division.
4/12/99
2441 MHz
2400 MHz
T
RACER
2483.5 MHz
Figure 1-2. Bandwidth Division
P 3
AGE
D
ESCRIPTION