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E Series Ethernet Radio – User Manual
Automatic Diagnostic Reports
This option allows the configuration of automatic diagnostics.
This option automatically appends diagnostics messages when
user data is transmitted. This option can be toggled on and off by
clicking the “Enable” button.
Minimum Report Interval : Specifies the amount of time before a
diagnostics message is appended to the next user data message.
Diagnostic Stream: Specifies the SID code used for the automatic
diagnostics message.
Controller Destination Address: Specifies the address of the
Diagnostics Controller Software that is receiving the automatic
messages and displaying them. This value must match that
specified in the TVIEW diagnostics software configuration.
Collision Avoidance
In a point to multipoint system the master unit (usually a base
station) can transmit at any time and the remotes will all receive
the broadcast signal. However, if more than one remote unit
transmits at a time, then a collision will occur during the multiple
transmissions, resulting in a loss of data from one or more units.
Two collision avoidance mechanisms have been included in the
modem. The standard (Digital) method utilises a signalling channel
which is embedded in overhead data transmitted over the radio
channel. The second method utilises detection of a carrier signal to
postpone transmission of data. Both methods require configuration
of several options for successful operation.
The desired option for collision avoidance is selected by checking
the control button to the left of the description on the main window.
None
When selected this turns off all collision avoidance mechanisms.
This should only be used in point to point applications.
Digital
This is the standard method of collision avoidance and utilises a
channel busy indication bit in the signalling channel transmitted to
all remotes for control. When selected a dialogue box appears and
several options must be configured:
•
Mode – “Master” or “Remote”. When the master unit
receives a valid transmission from a remote unit it sets the
channel busy indication bit. This busy bit is interpreted by
the other remotes to not transmit. Once the transmission
from the first remote ends the master unit resets the busy
Part I – TVIEW+ Management Suite - Programmer
bit to indicate the channel is now clear to transmit on. The
master unit, which is normally a base station, takes about
5ms to detect a transmission from a remote unit and set the
channel busy indication bit on the radio channel. During this
period collision of remote transmissions can still occur and
is unavoidable.
Note: The master must be permanently keyed.
•
Backoff Method – “Retry after Tx Attempt” or “Delay before
Tx Attempt”. The method chosen is system dependent and
can only be configured if the mode is “remote”. The former
is best used when data responses from remotes are largely
asynchronous. The latter is best used when this is not the
case.
•
Backoff Timing – “Maximum Slots”, “Time per Slot”. This
can only be configured if the mode is “remote”. When a
remote is ready to transmit data but it finds the busy bit from
the master set it holds back its transmission for a random
“backoff” time after which it tries to transmit data again. This
ensures that modems waiting to be allowed to transmit do
not re-attempt to do so at the same time. The “Maximum
Slots” (1 to 16) and the “Time per Slot” (1 to 255ms) are
used to calculate the backoff time by multiplying the slot
time by a random number between 1 and the maximum slot
number. For example if the time per slot is 30ms and the
maximum slots is 4, the random backoff times can be 30,
60, 90 or 120ms.
As the channel busy indication bit is critical for reliable operation
default interpretation of this bit is defined in the remote units. If
the master modem stops transmission (or has not yet started) the
remote will interpret that the channel is busy and will not transmit
until the master comes on line.
Carrier Detect
This method of collision avoidance utilises a carrier transmitted
to all remotes to indicate that the radio channel is busy. When
selected a dialogue box appears and several options must be
configured:
•
Mode – “Master” or “Remote”. When the master unit
receives a valid transmission from a remote unit it transmits
a carrier signal to indicate busy. Of course the master
will also initiate a transmission if it has data to send. The
transmitted carrier is interpreted by the other remotes to not
transmit. Once the transmission from the first remote ends
the master unit stops transmission to indicate the channel is
now clear to transmit on. The master unit, which is normally
a base station, takes about 5ms to detect a transmission
from a remote unit and transmit a carrier signal. During this
period collision of remote transmissions can still occur and
is unavoidable.
Note: The master can only be a full duplex unit and cannot
be permanently transmitting. For half duplex and simplex
systems all units should be set as “Remote” (no Master).
