User's Manual

Exalt Installation and Management Guide
ExtendAir
®
(TDD) Series Direct Mount
50 000000-001
2011-08-26
internal sync function may be necessary for these networks. See Time Division Duplex (TDD)
Factors and Link Orientation and Synchronization for more information.
• 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
).
• Radio Collocation parameters can be enabled when an Exalt GPS receiver is connected to Radio A
or when using internal sync between two collocated radios or when using the ExaltSync
Collocation kit to synchronize multiple radio links at one location. 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 synchronization timing signal is lost.
– The Normal parameter is a time period that allows the timing signal to be recovered. The
default time to wait is set between 5 and 10 min. The system then resynchronizes to the
timing signal without impact to traffic. If Normal is selected and timing is not recovered
within the set time period, the system stops transmitting (loss of link) until 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 the timing source when the timing source is detected.
This allows the link to continue to operate, however, if a timing 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 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.
– When using Internal timing, select the radio to be the Sync Source (master) for the other
collocated radios, Sync Auto for a radio to receive sync and run indefinitely if sync is lost (this
provides the same results as infinite flywheel parameter), or Sync Recipient, which disables a
radio if sync is lost, but eliminates the opportunity of self-interference.
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.