4.0 E
XTENDED
R
ADIO
P
ACKET
M
ODEM
F
EATURES
4.1 T
HROUGH
P
UT
The RPM1 supports three rates, max (3.6kbps), slots (1.2kbps) and slotsw (600bps), of over-air
throughput.
M
AX
: When set to maximum and streaming data at the RPM1, the data is sent as quick as
possible. For host baud rates of 4800bps 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 3.6kbps with ACK and 5.4kbps without ACK.
Figure 8: RPM1 pair streaming data without gap for another RPM1 pair
In Figure 8, RS232 serial data bytes accumulated in the receive buffer is transmitted as two 10kbps
bursts by transmitting RPM1 with gaps just enough to receive ACK from receiving RPM1.
F
IGURE
9: RPM1 pair streaming9600bps serial data with ACK at maximum throughput
For continuous data transmission at baud rates above 2400bps (with ACK) or 4800bps (without ACK),
hardware flow control should be used to prevent the host from causing receive buffer overrun errors.
RPM1 will signal CTS pin to stop/allow the host depending on its Receiver Buffer level.
Radiometrix Ltd.
VHF Narrow Band FM Radio Packet Modem
page 10
RADIOMETRIX [ RADIOMETRIX LTD ]
