FHSS versus DSSS

There are reasons why some WLANs use FHSS rather than DSSS and
vice versa. When you need to transmit, it is important to spread out the
energy of the signal to reduce interference to other users in the radio
spectrum you are using. As a result, FHSS was used by many vendors in the 2.45-GHz ISM band who were using power levels greater than 1 mW
since it provided a reasonable level of “inherent” security.
Any systems using either FHSS or DSSS are permitted to transmit
power up to 1000 mW, so they have sufficient power for WLAN connectivity.
The algorithm that specifies the hop sequence for HomeRF is
published and available through the SWAP specification; and the hop
sequences are used more for regulatory compliance than for increasing
security.


FHSS systems use “frequency agility” to satisfy regulatory requirements.
The HomeRF beacon sends the hop-set identification information
unencrypted in each CP beacon. If the hop-set identification information
were not transmitted in clear text, it could still be easily deciphered just
by eavesdropping on the traffic on each hopping channel. HomeRF has
an FHSS system of frequency agility that does not have any security
advantages over a DSSS system, regardless of the hype any analyst
might tell you.