SPM2-433 Datasheet, PDF (10/15 Pages) List of Unclassifed Manufacturers – UHF SpacePort Modem

4.0 EXTENDED SPACEPORT FEATURES
4.1 THROUGHPUT
The SPM supports two rates, MAX and SLOTS, of over-air throughput. A third rate is also provided
which can be used during normal operation, but is specifically supplied for compliance with FCC
regulations.
MAX: When set to MAXimum and streaming data at the SPM, the data is sent as quick as
possible. For host baud rates of 19200 and above, data is transmitted continuously with
minimal delay between sequential packets. When this occurs, there is effectively no airtime for
another pair, operating in close proximity, to transmit without causing collisions. The maximum
over-air throughput that can be achieved is 14400bps.
MAXIMUM ON-AIR THROUGHPUT
With baud rates >9600bps
A
A
A
A
Figure 5: A SPACEPORT MODEM pair streaming at maximum throughput
Time
SLOTS: Setting the throughput to SLOTS provides a method of opening ‘time slots’ for other SPM
pairs operating in close proximity. The effective streaming on-air throughput between a pair of
SPM is effectively reduced to approximately 2400bps.
SLOT ON-AIR THROUGHPUT
With baud rates >4800bps
A
B
A
B
Figure 6: Two SpacePort Modem pairs operating Slot throughput
Time
FCC: This setting is effectively the same as SLOTS, however it further slows the over-air
throughput to approximately 1200bps. This mode is provided to enforce the modem to comply
with FCC regulations of 10% maximum airtime usage. The THRUPUT should be set to FCC for
all SPM modules used in all equipment subject to FCC regulations.
Radiometrix Ltd, SpacePort Modem
page 10