COBHAM Sailor 250 FleetBroadband, Training Manual, Page: 27 / 270

17
SAILOR FleetBroadBand
Training Manual
1
Hence connections that exceed their target rate target in one
scheduling interval are not punished in subsequent scheduling
intervals. Any remaining capacity after all the target rates are
serviced is shared between the connections weighted by the
connection’s traffic class, a component of the connection’s 3G QoS
parameters. There are three degrees of congestion for variable bit
rate IP traffic – no congestion, acute congestion and moderate
sharing. If a FleetBroadband Terminal is the sole user of a bearer,
i.e. no congestion then the peak bit rate it achieves on a variable
bit rate packet connection will be limited by the available capacity
in the bearer and the FleetBroadband Terminals link quality. At
the other extreme under acute congestion conditions where all
FleetBroadband Terminals are sending or receiving, the RNC will
only try to service at the target rate for each connection. Note that
under acute congestion all connections with the same QoS receive
the same target rate irrespective of the FleetBroadband Terminals
link quality – weaker FleetBroadband Terminals get the same data
rates in these circumstances. In between these two extremes there
is moderate sharing state where capacity in excess of the target
rates is shared between the connections. Where connections have
the same QoS the excess slots or busts are allocated equally.
FleetBroadband Terminals with better link quality use the slots/
blocks more efficiently so the excess translates into higher bit
rates for the more powerful FleetBroadband Terminal classes.
1.7 Bearers
The Forward and Return Bearers have different layouts.
Forward Bearer Return Bearer
Frequency L-band: 1525,000
MHz - 1559,000 MHz
Frequency L-band: 1626,500
MHz - 1660,500 MHz
TDM (Time Division Multiplex) TDMA (Time Division
Multiplex Access.
Total of 170 sub-bands (max.
5% of max. power per spot)
Total of 170 sub-bands
200 KHz bandwidth (10.5 - 21
- 42 - 84 - 189 KHz)
200 KHz bandwidth(10.5 - 21
- 42 - 84 - 189 KHz)
Modulation: 16QAM or QPSK Modulation: 16QAM or QPSK
Symbol rate: 8.4 - 16.8 - 33.6
- 67.2 - 151.2 kSym/sec
Symbol rate: 16.8 - 33.6 -
67.2 - 151.2 kSym/sec
Variable code rate Variable code rate
Data rate: 4.5 - 512 kbps Data rate: 8.4 - 492.8 kbps
5 msec or 20 msec burst
slots
C/No: 55 - 65 (4.5X8B)
Figure 1-25: Entries of the Forward and Return Bearers