Operations Manual

OPERATIONS 4-26
O&M of the MCC-545B PACKET DATA RADIO
12/2000
4.8.1.1.2 Half Duplex Network
Some situations require a dense connectivity between Masters and Remotes where any Remote
can communicate to any Master, and any Master can communicate with any other Master. This
topology requires a single Tx and Rx frequency and therefore can not operate in a full duplex
mode. The Masters are set up to operate in half duplex and some contention can result between
Masters that is solved by one of the following methods. To select this mode, enter the command:
HALF DUPLEX, MS where MS is the number of milliseconds between idle probes.
IDLE IDLE
ACQ
SOM
TEXT TEXT
ACQ
TEXT TEXT
METEOR
Half Duplex Master
Half Duplex Remote
4.8.1.1.3 Master Probe/Transpond Role
Adjacent half duplex Master Stations will have difficulty establishing an RF link quick enough to
make efficient use of meteor trails if they both transmit idle probes continuously. This state
occurs because the use of a single frequency causes contention when both transmit at the same
time. The Masters must take turns transmitting. One way to do this is to set one Master to a
probe role, while the other is set to transpond role. The prober continually transmits the idle
probe while the transponder is in a receive-only mode. When the transponder receives the probe
from the other Master, it transmits a response and the two Masters exchange data. Note that
while this setup allows good performance between Masters, one of them is not transmitting idle
probes and cannot initiate communication with a Remote Station.
Example: ROLE, PROBE or
ROLE, TRANSPOND
4.8.1.1.4 Master Active/Passive Role
This network operation mode allows full or half duplex communication between two Masters
and also allows both Masters to communicate with Remotes. This condition is accomplished by
assigning time slots for each of the Masters to transmit idle probes. The Master in the active role
transmits idle probes during even minutes. The Master in the passive role transmits idle probes
during odd minutes. They effectively swap between the probe and transpond roles each minute.