User Manual

Advanced WaveLAN Parameters
Medium Reservation
4-8 WaveLAN IEEE 802.11 PC Card User’s Guide
Medium Reservation 4
It is normal behavior for WaveLAN stations to defer transmissions
automatically when they sense that another WaveLAN device is
using the wireless medium.
This behavior also referred to as the Carrier Sense Multiple
Access/Collision Avoidance protocol (CSMA/CA) will avoid that
wireless messages would collide in situations where two or more
stations would start transmissions at the same time.
The Medium Reservation mechanism enables you to improve
wireless performance in network environments where the CSMA/
CA protocol would fail due to the “hidden station” problem as
pictured in Figure 4-4 on page 4-9.
Medium Reservation may provide a solution for networks where:
■ The density of WaveLAN stations and WavePOINT-II access
points is very low.
■ You witness poor network performance due to excessive frame
collisions at the WavePOINT-II access points.
About the Hidden Station Problem 4
A hidden station is a situation in which two stations are within
range of the same WavePOINT-II, but are not within range of each
other.
Figure 4-4 on page 4-9 illustrates an example of the “Hidden
Station” problem. Both Station A and Station B are within range of
the WavePOINT-II access point however, Station B cannot “hear”
Station A, therefore Station A is a “hidden station” for Station B.