Alvarion BreezeACCESS VL System Manual page 200

Chapter 4 - Operation and Administration
4.2.6.5.8.2 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).
4.2.6.5.9 Adaptive Modulation Algorithm (Multi Rate)
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.
The decisions made by the Adaptive Modulation Algorithm for the modulation
level to be used are based on multiple parameters, including information on
received signal quality (SNR) that is received periodically from the destination
unit, the time that has passed since last transmission to the relevant unit, and
the recent history of successful and unsuccessful
transmissions/retransmissions. In the AU the decision algorithm is performed
separately for each SU.
The transmission/retransmission mechanism operates as follows:
Each new frame (first transmission attempt) will be transmitted at a
1
modulation level selected by the Adaptive Modulation algorithm.
If first transmission trial has failed, the frame will be retransmitted at the
2
same modulation level up to the maximum number of retransmission
attempts defined by the Number of HW Retries parameter.
The Adaptive Modulation Parameters menu includes the following parameters:
4.2.6.5.9.1 Adaptive Modulation Option
The Adaptive Modulation Option enables or disables the Adaptive Modulation
decision algorithm. When enabled, the algorithm supports decrease/increase of
transmission's modulation levels between the lowest possible level to the value
configured for the Maximum Modulation Level parameter. If the Maximum
Modulation Level is set at the lowest possible level, the Adaptive Modulation
algorithm has no effect.
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BreezeACCESS VL System Manual