coverage in metropolitan areas and along traffic corridors. WWANs are owned
by a service provider or carrier. Data rates are low and charges are based on
usage. Specialized applications are characteristically designed around short,
burst messaging.
Advanced FAQ
1. What is Ad Hoc mode ?
A wireless network consists of a number of stations without access points.
Without using an access point or any connection to a wired network.
2. What is Infrastructure mode ?
Infrastructure mode implies connectivity to a wired communications
infrastructure. If such connectivity is required the Access Points must be used
to connected to the wired LAN backbone. Wireless clients have their
configurations set for "infrastructure mode" in order to utilize access points
relaying.
3. 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.
4. 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.
5. 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
