Xetawave Xeta9-E, Руководство пользователя

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The “ Master Repeat ” sets the maximum number of times the master will repeat a
transmit packet in the absence of an acknowledgement from the remote unit. This is
applicable only for a Point-to-Multi-Point network. Thus if set to 3, then the master will
repeat a packet up to three times unless the remote unit acknowledges receipt at which
time the master will move to the next packet.
that there will be a near equal number of “0” bits and “1” bits. If the data is not
scrambled, then there may be significantly more “0” or “1” bits which could affect
performance.
The “ Protocol ” options are “ Serial ” and “ Ethernet ” and this is set based upon the type
of data being carried on the network. Due to the larger size of Ethernet frames,
additional RF overhead is needed to maintain the frame size. The Serial data is passed
as it is received with no assumed framing.
Finally, if any data is changed, the “Modify Radio Settings” button must be selected
which will copy the data into the radio and reset the radio to the new conditions.
Following this, the data on the screen must be refreshed from the radio.
3.4.3 Hop Tables
Hop tables are generated automatically based upon the modulation mode chosen and
the frequency range(s) in use. For low speed (150kHz bandwidth) modes (57kbps,
114kbps, 229kbps), the radio is capable of using 159 RF channels which is above the
legal requirements. For mid-speed (225kHz bandwidth) modes (153kbps and 305kbps)
105 channels are available. For the high-speed DTC modes 20 channels are available for
speeds of 886kbps or faster and 25 channels are available for the 663kbps DTS mode.
3.4.4 Modulation and Packet Size Tradeoffs
The choices of modulation and packet size are closely coupled due to their interaction
with the required signal strength. Quoted sensitivity numbers are based on an error
rate of 10
-4
, or one bit error out of 10,000 bits. If the radio transmits each bit
individually, then this would be the raw error rate that the user would experience.
However, since bits are combined into a packet and the whole packet is either good or
bad, the error rate changes in how it impacts the experienced data rate. For example, if
the packet size 1024 Bytes (approximately 10,000 bits), then on average there will be
one bit error in every packets. ON AVERAGE, this means that no successful packets
would be transmitted. (In reality some packets may have multiple errors and other
packets may have no errors.) However, this demonstrates that a single bit error may
result in the loss of multiple bits. The radio is designed to recover from errors by
multiple methods such as repeating the data until the receiving radio acknowledges
successful receipt. This effectively reduces the data rate since the same data is now
sent multiple times. Thus the optimal packet size setting is a function of the number