User Manual

Exalt Installation and Management Guide
ExtendAir (TDD) Series Digital Microwave Radios
203591-002 51
2009-12-18
• Set the TX/RX Throughput Ratio (%) parameter to program radio symmetry. The default setting is
50/50 for symmetrical, full-duplex throughput. Other throughput ratio options are 20/80, 80/20,
and 65/35, 35/65. See Link Symmetry
.
– For asymmetric throughput, only TDD frame size settings of 2ms and 5ms and RF Bandwidth
settings of 16MHz and higher are supported.
– The 64MHz/Mode2 configuration does not support asymmetry due to capacity limitations of
the 100BaseT interface. Set the Radio Collocation parameter to control parameters related to
the GPS Synchronization feature (see Radio Synchronization
).
This parameter can be enabled when an Exalt GPS receiver is connected to Radio A. There are two
additional features:
– Set the Flywheel Period parameter to ‘Normal’ (default) or ‘Infinite.’ This is the period of time
that the radio will run on the internal timing signal if the GPS timing signal is lost.
• The Normal parameter is a time period that allows the GPS timing signal to be recovered.
The default time to wait is set between 5 and 10 min. The system then resynchronizes to
the GPS signal without impact to traffic. If Normal is selected and GPS timing is not
recovered within the set time period, the system stops transmitting (loss of link) until GPS
timing is recovered. This prevents self-interference to local systems, but loses the link.
• The Infinite parameter allows the radio to run on the internal clock source with no limit
and attempts to resynchronize with GPS when the GPS timing source is detected. This
allows the link to continue to operate, however, if a GPS signal is not detected within
approximately 10 minutes, the radio may start to cause interference to other collocated
systems, and other collocated systems may start to cause interference with it. If after this
interval GPS timing is restored, a temporary outage due to the resynchronization
requirement may occur.
– Set the Tx Timing Offset (uSec) parameter to allow the administrator to delay transmitter
timing from the GPS timing pulse by a fixed time, in microseconds. This is useful if multiple
GPS-synchronized Exalt radio systems are present, separated by distance, such as when using
a repeater. This delay is required to offset the difference in speed-of-light between the two
locations. It is recommended to add a 5uSec delay for every mile of difference in path length.
For example, if there is one link with no delay, delay the link within the field-of-view of the
first link on the same or overlapping frequency channel accordingly so that it is synchronized,
including the speed-of-light delay between the two sites.
• Buzzer Timeout (minutes) parameter creates an audio signal for antenna alignment. Turn on the
buzzer continuously during antenna alignment or preset a period of time that the buzzer will
sound. If the buzzer stops before alignment activities are complete, change the selection and press
the Update button or select the ON option until alignment activities are complete.
• Aggregate User Throughput parameter provides information about user capacity of the wireless
link, in the current configuration. The ‘new value’ column reflects throughput if changes are made
to Bandwidth, Mode, Link Distance, and/or TDD Frame Size. Click the “Aggregate User
Throughput” link for details on aggregate capacity.
Note: Changing the TDD Frame Size parameter will temporarily interrupt traffic. TDD
Frame Size parameters must match at each end. Adjust the far-end radio first, and then the
near-end radio. If the TDD Frame Size parameter is set to a value that cannot be supported for
the link distance, the link may be lost and unrecoverable through GUI control. If the link is
lost due to this situation, travel to the radio location(s) may be required to reset the value.