User guide

6-20
BreezeNET DS.11b User’s Guide
Manual Version 1.0
Designing High Capacity
Networks
In networking environments where you have either data intensive users, or a
large number of users in a small area, you may wish to improve the throughput
efficiency and/or load balancing of your Base Stations.
This solution described in this section allows you to balance “maximum range
for minimum hardware investments” versus “maximum throughput
performance for higher hardware investments”.
About the CSMA/CA Protocol
In normal network configurations, all equipped devices apply a standard
mechanism to avoid collision of wireless messages. When a station intends
transmitting a message, it will first sense whether no other station is already
transmitting (“using the wireless medium”).
! If no other transmissions are sensed, the station will start its transmission.
! If it does sense another transmission carrier, the station will apply a random
defer timer. After the timer has expired it will start sensing the medium
again to see if it can start transmitting.
This protocol, also referred to as the “Carrier Sense Multiple Access/Collision
Avoidance” (CSMA/CA) protocol works fine in most networking environments.
The user of a wireless computing device will hardly notice the deferral behavior
of the wireless radio.
In network environments with many wireless users in the vicinity of one
another and/or wireless stations that are engaged in heavy data traffic, you may
perceive that wireless stations show a degrading performance, perceived as
long network response times when communicating via the network.
Where poor performance is typically caused by poor radio link quality
(identified by a poor a signal to noise ratio (SNR)), the scenario described above
may also be perceived in areas where:
! Site monitor measurements show an excellent wireless coverage by at least
two Base Stations or more on every location.
! Link test measurements at such locations may show:
" An excellent SNR for communications between wireless stations
and the Base Station.
" A large number of messages transmitted at lower rates.