User's Manual

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BreezeACCESS Version 4.3 Operations and Administration
Manual Revision: 3.0
 Minimum Contention Window – The BreezeACCESS system uses a
special mechanism based on detecting the presence of a carrier
signal (Carrier Sense Multiple Access-CSMA) and analyzing the
information contained in the transmissions of the AU to estimate
the activity of other SUs served by the same AU. The target is to
minimize collisions in the wireless media resulting from trials of
more than one unit to transmit at the same time. The contention
window is the time that a unit will wait from the time it has decided
that there are no transmissions by other units until it will attempt
to transmit. The contention window is a random number whose
maximum value is determined by the value of the Minimum
Contention Window parameter and the number of previous trials
to transmit the frame. The higher the number of SUs served by the
same AU, the higher the Minimum Contention Window for each SU
should be.
The Valid values are from 7 to 255.
The default value is 31.
 Carrier Sense Level – This is the threshold level that is used prior
to initiating a transmission by the unit to determine the existence of
transmission from another unit. As long as the level of a received
signal is above this threshold, the unit will assume that another
unit is transmitting and will refrain from trying to transmit in order
to prevent collisions.
Available values: -100 to -40 (dBm)
The Default Value is -85dBm.
Maximum Multicast Rate (AU only)– Determines the maximum rate
of multicast and broadcast transmissions. Multicast and broadcast
transmissions are not acknowledged; therefore there is a chance
that such transmissions will not be properly received without the
possibility of using the acknowledgement mechanism for
retransmission. Therefore, it is recommended to use a lower rate for
transmission of broadcast, multicast and control frames, to increase
the probability that they will be received without errors.
The available selections are 1, 2, and 3 Mbps.
The default is the minimum possible rate, 1Mbps.
 Multi-Rate – Link quality dynamically changes, due to various
environmental conditions. Dynamically switching between the
possible transmission rates increases the probability of using the
maximum rate for the current radio link quality at any given
moment. Decreasing the rate one step improves the receiver
sensitivity by 6-8dB. When enabled, the transmission rate decisions
are made separately for each unit. This algorithm is completely
separated from the retransmission mechanism defined by Number
of Retransmission and Number of Dwells to Retransmit
parameters. The algorithm provides Access Units with
simultaneous, adaptive support for multiple Subscriber Units at
different rates. The decision on the rate of each transmission (first