Operation
RFI-9256 Radio Modem User Manual
Page 27 of 109
For more information on configuring the RSSI trigger level, see section B.1.2 on page 72
FRAME TIME
The frame time is the amount of time that the RFI-9256 will spend on each channel in the hopping pattern.
This is also referred to as the channel dwell time. The frame time can be adjusted to suit each application.
The frame time duration and throughput is shown in Table 7.
Frame
Time (ms)
Bytes
per
Packet
Throughput One Way (kbps)
Throughput Total (kbps)
Over the air
Serial
Over the air
Serial
5
5
8
10
16
16
8
26
26
32.5
52
65
10
41
32
40
64
80
15
77
41
51.25
82
102.5
20
113
45
56.25
90
112.5
25
149
48
60
96
120
30
185
49
61.25
98
122.5
35
221
51
63.75
102
127.5
Table 7: Frame time configuration
Selection of frame time will trade off maximum throughput against latency. A low frame time will decrease
both latency and throughput, while a high frame time will increase both latency and throughput. This is
discussed in the section Latency Reduction on page 30.
DIRECTIONAL BIAS
A single frame on the RFI-9256 contains two packets, one from the master and one from the slave. In the
default configuration the size of both packets is the same, so the system is unbiased. In many systems data
will flow in one direction substantially more than in the other direction. When this is the case the RFI-9256
can be configured to bias its frames so that the master packet and slave packet are of different lengths.
In order to configure a link for directional bias, one radio must be set to the outgoing radio, and one to the
incoming radio. The link from the outgoing radio to the incoming radio has more bandwidth, while the link
from the incoming radio to the outgoing radio has its bandwidth reduced.
Table 8 shows the throughput obtained for each frame time configuration when directional bias is used.
Main -> Radio -> Radio Characteristics
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