Alvarion SW VERSION 5.1 User Manual

Chapter 4 - Operation and Administration 

 

BreezeACCESS VL System Manual

 

The default is Enable. 

4.2.6.5.7.2  Burst Mode Time Interval 

The Burst Mode Time Interval defines the burst size, which is the time in which 
data frames are sent immediately without contending for the wireless medium. 

The range is 1 to the value of the Maximum Burst Duration defined for the Sub-
Band. 

The default is 5 milliseconds or the value of Maximum Burst Duration defined for 
the Sub-Band (the lower of the two values).   

4.2.6.5.8  Adaptive Modulation  

The Adaptive Modulation algorithm enables adapting the modulation level of 
transmitted data to the prevailing conditions of the applicable radio link. The 
algorithm provides Access Units with simultaneous, adaptive support for multiple 
Subscriber Units at different modulation levels, as transmission’s modulation 
level decisions are made separately for each associated SU.  

Link quality fluctuates due to various environmental conditions. Dynamically 
switching between the possible modulation levels increases the probability of 
using the maximum modulation level suitable for the current radio link quality at 
any given moment. 

When enabled, the Adaptive Modulation algorithm, constantly evaluates the 
acievable throughput for a particular modulation by counting the number of 
packets that are successfully transmitted and the packets that are not received 
and that need to be retransmitted. Based on these statistics, and on each 
modulation’s specific data rate, it will calculate the real throughput that the unit 
can support in the current conditions for a particular modulation. 

When choosing between modulations, up to a limit, a small number of 
retransmissions on a higher modulation is compensated by the overall better 
performance ensured by that modulation. When a critical retransmissions 
percentage is reached however, it is necessary to decrease the modulation to 
achieve better throughputs as shown in Table 4-13.