Specifications

Chapter 4 - Operation Menus and Parameters
BreezeNET B 152 System Manual
 Ethernet Frame Size
 Concatenation Parameters
4.2.6.5.1 RTS Threshold
The RTS Threshold parameter defines the minimum frame size that requires an
RTS/CTS (Request To Send/Clear To Send) handshake. Frames whose size is
smaller than the RTS Threshold value are transmitted directly to the wireless link
without being preceded with RTS frames. Setting this parameter to a value larger
than the maximum frame size eliminates the RTS/CTS handshake for frames
transmitted by this unit.
The available values range from 20 to 4092 bytes.
The default value for BU/RB-B14 and BU/RB-B28 units is 2200 bytes (this is the
largest packet size that can be supported by these units when concatenation is
enabled).
The default value for BU/RB-B10 and BU/RB-B100 units is 4092 bytes.
4.2.6.5.2 Minimum Contention Window
The Minimum Contention Window parameter determines the time that a unit
waits from the time it has concluded that there are no detectable transmissions by
other units until it attempts to transmit. The BreezeNET B system uses a special
mechanism based on detecting the presence of a carrier signal to estimate the
activity of another unit. The target is to minimize collisions in the wireless
medium resulting from attempts of more than one unit to transmit at the same
time.
The time interval between two consecutive transmissions of frames is called
Inter-Frame Spacing (IFS). This is the time during which the unit determines
whether the medium is idle using the carrier sense mechanism. The IFS depends
on the type of the next frame to be transmitted, as follows:
 SIFS (Short Inter-Frame Spacing) is used for certain frames that should be
transmitted immediately, such as ACK and CTS frames. The value of SIFS is
16 microseconds.
 DIFS (Distributed coordination function Inter-Frame Spacing) is typically used
for other frame types when the medium is free. If the unit decides that the
medium is not free, it will defer transmission by DIFS plus a number of time
slots as determined by the Contention Window back-off algorithm (see below)
after reaching a decision that the medium has become free.