Comtech EF Data SDM-300A - Manual (Page 235)

SDM-300A Satellite Modem Revision 6
Buffering SDM300A.IOM
8–7
Table 8-1. Minimum Doppler/Plesiochronous Buffer Capacity Requirements
Satellite Orbit Inclination
Buffer Capacity (ms)
For Various Circuit Configuration
(Degrees) Master/Master Master/Slave
0.1 (Nomnal) 1.5 2.4
0.5 2.5 4.4
1.0 3.9 7.4
1.5 5.5 10.4
2.0 6.9 13.2
2.5 8.5 16.4
3.0 9.9 19.2
4.0 12.9 25.2
Notes:
1. The above minimum buffer capacities include a factor of two to allow the buffer to start in the
center and then drift in either direction. In the Master/Slave case, where the TX timing at one end
of the link is derived from the demodulator and used to TX back to either the station which
originated the timing signal or to a different station, another factor of two has been applied to the
Doppler contribution to account for the passage of the timing signal twice through the satellite.
2. Adding the buffer requirements due to satellite delay variations (Doppler) and that due to the
interfacing of different national clocks (plesiochronous) derived the above capacities.
3. Actual buffer capacity is likely to be larger due to the need to slip primary order streams on a
multiframe basis.