User's Manual

Exalt Installation and Management Guide
ExtendAir (TDD) Series Digital Microwave Radios
16 203591-010
2012-09-04
When Sync is Lost
If the primary sync source (for example, the GPS source) signal is lost due to equipment failure, a
disconnected sync cable, loss of satellite link, or other condition, the radio is said to be flywheeling.
When flywheeling, the radio’s clock is free-running off internal clocking and is no longer
synchronized to any source. If the original sync source is restored to the flywheeling radio’s
configuration, it attempts to synchronize to this signal without causing transmission interruption.
When the flywheeling radio runs independently for long periods of time, the synchronization signal
may be too far outside the capture range of the synchronization loop, and portions of transmission
frames can be lost during this re-synchronization process. This condition is temporary and all
interconnected radios will re-synchronize to the sync source, as necessary.
If the flywheeling period is exceeded, the radio will stop transmitting. There is a setting for infinite
flywheeling; however, long periods of flywheeling can cause interference with collocated radios.
Virtual Local Area Network (VLAN)
VLAN segments information in a single connection and creates multiple separate connections to
secure information of one type or for one set of users from other information types or for other sets of
users. Exalt’s VLAN communications implementation adheres to the IEEE standard 802.1q.
In most cases, an Exalt radio acting as a Layer 2 bridge between two locations is only required to pass
traffic with VLAN tagging. Without additional configuration, all Exalt radios support frame sizes in
excess of 1900 bytes, which currently supports all defined VLAN packet sizes.
Some situations require Exalt radios to act upon VLAN traffic and perform any or all of the following
functions:
• Connect specific traffic, using VLAN tagging, to different purposes, such as management traffic to
the radio’s NMS system.
• Allow only traffic with specifically assigned VLANs to pass across the link, blocking all other
VLANs or any non-VLAN traffic.
• Allow management access only through a VLAN connection, leaving the main traffic transparent.
• Allow management access without a VLAN connection, but flowing only specific VLAN traffic
across the link.
Link Symmetry
The default configuration of ExtendAir (TDD) Series radios provides 50/50 symmetrical throughput.
The Tx/Rx Throughput Ratio setting enables programming different symmetry for applications where
significantly higher throughput in one direction is anticipated such as for video broadcast, video
aggregation, or remote server/storage WANs.
Exalt does not recommend placing two links with asymmetry back-to-back in a serial configuration
due to the TDD cycle of the radios. This configuration requires that one radio transmits in an
overlapping time period while another radio is receiving. Physical antenna isolation and/or frequency
channel spacing may accommodate this configuration. Asymmetry is, however, ideal for single-hop,
multi-link hub/spoke architectures, or simply single independent links.
Note: If an application only requires the transparent passing of VLAN traffic, disable the VLAN
function.