uhf tacsat /dama multi-service tactics, techniques ... - UHF-Satcom.com

f. While there are selections that can accommodate up to 22 time-slots and
selections that can accommodate 16-kbps data/voice users, the most common Navy
selections are the 257 and 259 formats (shown in Figure I-13). These formats allow five
narrowband voice users at a 2.4-kbps data rate on the channel along with several lower
data rate users. The benefit to the user is that five voice nets can be placed on one
channel instead of five separate channels. These formats require ideal conditions in
which burst rates can be at their highest speed.
g. Adjustments to the frame format are made for different data rates and different
requirements of the users. The UCC, RSSC, or JMINI control station operator always
determines the frame format. Users only supply the requests for access to the channels
and information (such as data rates, type of communications, length of transmissions,
and disadvantaged terminals within the network) supporting the use of the time-slots.
This allows the control operators to adjust the channels to support the greatest number
of users with the highest quality communications slots available.
I-22
Figure I-13. Typical Navy 25-kHz DAMA Assignments
h. While these may be the most common frame formats used, they are not the only
formats available. Frame formats can, and should, be based on the communications
requirements submitted, then updated based on the quality of communications
provided. When a unit has disadvantaged users (such as manpack, 20w radio with a
low-look angle to the satellite) within the network, the frame format should be adjusted
to provide a more robust time-slot. This may include reducing the number of time-slots
available to allow for lower burst rates. The lower burst rates (19.2 and 9.6) allow for
communications to be established when the burst rate of 32 does not support the
majority of users.