This document discusses spread spectrum techniques for bandwidth utilization. Spread spectrum combines signals from different sources to fit into a larger bandwidth in order to prevent eavesdropping and jamming. There are two main types of spread spectrum: frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS). FHSS works by rapidly switching a carrier among many frequency channels, while DSSS spreads the signal across a very wide band by using a code sequence to modulate the signal.

1. 6.1
Chapter 6
Bandwidth Utilization:
Multiplexing and
Spreading
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2. 6.2
6-1 SPREAD SPECTRUM
In spread spectrum (SS), we combine signals from
different sources to fit into a larger bandwidth, but our
goals are to prevent eavesdropping and jamming. To
achieve these goals, spread spectrum techniques add
redundancy.
 Frequency Hopping Spread Spectrum (FHSS)
 Direct Sequence Spread Spectrum (DSSS)
Topics discussed in this section:

3. 6.3
Spread Spectrum
 A signal that occupies a bandwidth of B, is
spread out to occupy a bandwidth of Bss
 All signals are spread to occupy the same
bandwidth Bss
 Signals are spread with different codes so
that they can be separated at the receivers.
 Signals can be spread in the frequency
domain or in the time domain.

4. 6.4
Figure 6.27 Spread spectrum

5. 6.5
Figure 6.28 Frequency hopping spread spectrum (FHSS)

6. 6.6
Figure 6.29 Frequency selection in FHSS

7. 6.7
Figure 6.30 FHSS cycles

8. 6.8
Figure 6.31 Bandwidth sharing

9. 6.9
Figure 6.32 DSSS

10. 6.10
Figure 6.33 DSSS example