Specifications

Chapter 4 - Operation and Administration Menus and Parameters
BreezeACCESS 4900 178 System Manual
interval. The advertised K value is used by each SU to calculate the amount of
data that can be transmitted. This algorithm ensures fair resource distribution
among SUs, based on their configured CIR/MIR values.
The MIR Threshold Percent parameter determines the level of wireless link
utilization above which the MIR/CIR mechanism is activated. A Threshold of 0%
allows CIR only. A threshold of 100% means MIR only. For other values, if the
actual wireless link utilization is below the threshold, K is set to 1. As the link
utilization increases above the threshold, K is decreased as described above.
The simple solution for managing the information rate in such cases can result in
an unfair allocation of resources, as subscribers with a higher CIR actually receive
an IR lower than the CIR designated for subscribers in a lower CIR bracket.
A special algorithm for graceful degradation is incorporated into the AU, ensuring
that the degradation of performance for each individual Subscriber Unit is
proportional to its CIR.
The MIR/CIR algorithm uses buffers to control the flow of data. To balance the
performance over time, a special Burst Duration algorithm is employed to enable
higher transmission rates after a period of inactivity. If no data intended for a
certain SU (in the AU) or for the AU (in an SU) is received from the Ethernet port
during the last N seconds, the unit is allowed to transmit to this destination N
times its allowed IR value without any delay. For example, if the Burst Duration is
set to 0.5 second (or more), then after a period of inactivity of 0.5 seconds up to
128 Kbits x 0.5 = 64 Kbits may be transmitted to a unit whose IR is 128 Kbps,
without any delay (provided overall conditions in the wireless link allow this
burst).
4.2.6.6.2.1 MIR: Downlink (SU only)
Sets the Maximum Information Rate of the downlink from the AU to the SU. The
MIR value cannot be lower than the corresponding CIR value.
Available values range is from 128 to 53888 Kbps.
Available values range and default value are shown in Table 4-20.
4.2.6.6.2.2 MIR: Uplink (SU only)
Sets the Maximum Information Rate of the up-link from the SU to the AU. The
MIR value cannot be lower than the corresponding CIR value.
The actual value will be the entered value rounded to the nearest multiple of 128
(N*128).
4.2.6.6.2.3 CIR: Downlink (SU only)
Sets the Committed Information Rate of the downlink from the AU to the SU. The
CIR value cannot be higher than the corresponding MIR value.