User's Manual

Table Of Contents
146 Operation
Chapter 4 - Operation and Administration
Uplink (Rx) Frequency: Computed from the configured Downlink (Tx)
Frequency according to the Duplex Separation of the applicable Frequency
Band. In TDD systems the Uplink (Tx) Frequency is the same as the Downlink
(Tx) Frequency.
Frequency Band: The Configured ODU Frequency Band. If there is a
mismatch between the Configured ODU Frequency Band and its actual band,
both values will be displayed.
Operational Status
4.8.5.3.4 Multirate Parameters
BreezeMAX employs a multirate algorithm to dynamically adapt the modulation
scheme and Forward Error Correction (FEC) coding to actual link conditions. The
algorithm is managed by the AU taking into account also information received
from the served SUs. Optimal values are calculated separately for the uplink and
downlink for each SU. MAP messages transmitted to the SUs include information
on the uplink rate that should be used by each SU for its next transmission.
The Basic Rate is the minimum rate to be used by the Multirate algorithm. This is
also the rate to be used for downlink broadcasts and multicasts. Broadcasts and
multicasts messages are not acknowledged, so that the ARQ mechanism cannot
be used and there is no way to guarantee that all intended recipients will receive
them properly. In addition, multicasts and broadcasts are sent to multiple
recipients with different link qualities. Therefore, it is preferable to use a relatively
low rate for these transmissions, thus reducing the probability of errors and
increasing the likelihood that all intended recipients will receive them properly.
In the uplink, this is the rate to be used by SUs for non-scheduled transmissions,
such as during the contention period.
The Basic Rate is also the initial rate to be used by the algorithm for each new SU
that joins the cell when the Multirate algorithm is enabled.
When the Multirate algorithm is disabled, communication with connected SUs will
continue using the last uplink and downlink rates selected by the Multirate
algorithm. The Set Rates option in the SU (see Section 4.9.7.3.4.2), which
becomes available only when the Multirate algorithm is disabled in the AU,
enables setting the Uplink Current Rate and the Downlink Current Rate to any of
the values listed in Table 4-5.
The multirate algorithm chooses dynamically between 8 rates. These are also the
rates that can be configured for the Basic Rate parameters.