User's Manual

Appendix
BreezeNET PRO.11 Series 8-11 User’s Guide
Figure 9.5: The Common Coverage Area of a Multi-cell Structure
Dynamic Rate Switching
The data rate of each station is automatically adjusted according to the
received signal quality. Performance (throughput) is maximized by
increasing the data rate and decreasing re-transmissions. This is very
important for mobile applications where the signal quality fluctuates
rapidly, but less important for fixed outdoor installations where signal
quality is stable.
Media Access
When many users are located in the same area, performance becomes an
issue. To address this issue, wireless LANs use the Carrier Sense Multiple
Access (CSMA) algorithm with a Collision Avoidance (CA) mechanism in
which each unit senses the medium before it starts to transmit.
If the medium is free for several microseconds, the unit can transmit for a
limited time. If the medium is busy, the unit will back off for a random time
before it senses again. Since transmitting units compete for air time, the
protocol should ensure equal fairness between the stations.