How Many Access Points Are Required In A Given Area; What Is Direct-Sequence Spread Spectrum Technology - (Dsss); What Is Frequency-Hopping Spread Spectrum Technology - (Fhss); Do I Need The Same Kind Of Antenna On Both Sides Of A Link - ZyXEL Communications P-2812HNU-51c Support Notes

P-2812HNU-51C Support Notes

How many Access Points are required in a given area?

This depends on the surrounding terrain, the diameter of the client population, and
the number of clients. If an area is large with dispersed pockets of populations then
extension points can be used for extend coverage.
What is Direct-Sequence Spread Spectrum Technology – (DSSS)?
DSSS spreads its signal continuously over a wide frequency band. DSSS maps the
information bearing bit-pattern at the sending station into a higher data rate bit
sequence using a "chipping" code. The chipping code (also known as processing gain)
introduces redundancy which allows data recovery if certain bit errors occur during
transmission. The FCC rules the minimum processing gain should be 10, typical
systems use processing gains of 20. IEEE 802.11b specifies the use of DSSS.
What is Frequency-hopping Spread Spectrum Technology – (FHSS)?
FHSS uses a narrowband carrier which hops through a predefined sequence of
several frequencies at a specific rate. This avoids problems with fixed channel
narrowband noise and simple jamming. Both transmitter and receiver must have
their hopping sequences synchronized to create the effect of a single "logical
channel". To an unsynchronized receivers an FHSS transmission appears to be
short-duration impulse noise. 802.11 may use FHSS or DSSS.

Do I need the same kind of antenna on both sides of a link?

No. Provided the antenna is optimally designed for 2.4GHz or 5GHz operation. WLAN
NICs often include an internal antenna which may provide sufficient reception.

Why the 2.4 Ghz Frequency range?

This frequency range has been set aside by the FCC, and is generally labeled the ISM
band. A few years ago Apple and several other large corporations requested that the
FCC allow the development of wireless networks within this frequency range. What
we have today is a protocol and system that allows for unlicensed use of radios
within a prescribed power level. The ISM band is populated by Industrial, Scientific
and Medical devices that are all low power devices, but can interfere with each
other.
All contents copyright (c) 2009 ZyXEL Communications Corporation.