Comtech EF Data SLM-5650A Vipersat Parameter Editor - Manual (Page 29)

Chapter 2 - Using Parameter Editor 2-13
Vipersat
Note: The STDMA group number and the network ID are independent. There
can be multiple STDMA groups within a single network.
Stats Collection
This field appears for Hub modem only.
The Burst Controller monitors statistics in the received ACK from each Remote.
The statistics report the fill status of the STDMA buffers. The Burst Controller
builds a table of the group and calculates the relative buffer fill for each Remote.
It then calculates the length of the Data Slot for each Remote based on the Mini-
mum Slot Size plus a percentage of the Available Bandwidth. Idle Remotes
would receive a Data Slot equal to the Minimum Slot size.
In the Dynamic Slot mode, the dynamic range of STDMA is a function of the
difference between the Nominal Data Slot size and the Minimum Data Slot size
parameters. These parameters are operator selectable. The speed with which
STDMA reacts to changes in dynamic load is a function of the Stats Collection
parameter and the Cycles per Map parameter, both of which are also operator
selectable.
The value entered in the Stats Collection field defines the period of time, in
seconds, over which the SLM-5650A will collect statistics. A longer time will
average out peak conditions, a shorter time will shorten the VMS reaction time
to changing network conditions.
Guard Band
This field appears for Hub modem only.
This field, which appears for all Hub configurations, specifies the length of the
Slot Guardband in milliseconds for the Remotes in the group. The Slot Guard-
band is the amount of time between the point when one Remote completes
transmitting data and the point when the next Remote in the cycle begins trans-
mitting. This prevents the Remote from overrunning the next terminal in the
cycle.
The setting for this parameter should be obtained using the Vipersat STDMA
Calculator—a free tool available from Vipersat Customer Support.
Preamble
This field appears for Hub modem only.
This field, which appears in all Hub configurations, specifies the current Slot
Preamble size in milliseconds and bytes for the Remotes in the group. The Slot
Preamble is the period between when the Remote begins to transmit (sends an
ACK) to the Hub and when the first data packet is sent. This allows time for
NOTE