ND SatCom SKYWAN IDU 7000, Manual

Page: 35 / 154

2010-10-26 Network Design and Engineering Guide 31
General Carrier Design
Essential SkyWAN
®
Satellite Link Layer Features
Figure 2-12 Two Uplink Populations with Cross-Strapped Transponder
2.3.5 SkyWAN
®
Reference Burst Modes
Sky WAN
®
networks support three different reference burst modes:
- Standard Multiple Reference Burst mode (MRB),
- Multiple Reference Burst with Dual Uplink Beam (MRB-DUB),
- No Direct Feedback on Reference Burst with Dual Uplink Beam (NFB-DUB).
The characteristics of these modes are outlined lelow.
MRB Mode
For a network with <N> downlink populations, the first <N> carriers carry a reference burst. Ad-
ditional carriers without reference burst may be added for reception on the second demodula-
tor. Maximum number of downlink populations is 8. Only one uplink population is possible,
therefore all slave stations send ranging and request burst on carrier 1 only. Symbolrate, mod-
ulation and coding may be set differently on each carrier. A graphical representation of the
frame structure has been given in the section ’MF-TDMA Functionality’, refer to figure 2-9.
MRB-DUB Mode
For a network with <N> downlink populations carrier 1 and 3,..,N+1 carry a reference burst.
There is no reference burst on carrier 2! The number of downlink populations can range from
2 to 7. There are two uplink populations, slave stations belonging to uplink population 1 use
carrier 1 for ranging and request bursts, the other stations use carrier 2. The following restric-
tions apply:
- Master stations must be equipped with two demodulator boards: Home Channel Two on
master station(s) must be set to carrier 2.
- Symbolrate, modulation and coding on carrier 1 and 2 must be identical.
- Slave stations in uplink population 2 by default operate in star topology. The master sta-
tions serve as hub stations for these slaves. If meshing between stations in uplink pop-
ulation 2 is required every slave herein needs a second demodulator board.