SAF FreeMile, User Manual

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The SAF FreeMile Series Full Outdoor Unit Technical Description and Configuration Guide • Rev. 1.3
© SAF Tehnika JSC 2012
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1. Modem configuration – allows choosing appropriate mode comprising channel
bandwidth (10 or 30 MHz), capacity at maximum modulation and E1 or T1 channels.
By default 30MHz / 100Mbps mode is selected;
2. By pressing “Apply” changes made to the corresponding section apply only for the
local side SAF FreeMile. If “Rollback on” is selected, configuration will be reverted in
case erroneous configuration changes are applied.
3. Pressing “Apply for local and remote” applies changes made to the corresponding
section both for local and remote side SAF FreeMile FODUs.
Adaptive Coding and Modulation (ACM) technology allows operators to achieve high ‐ capacity
data transmission over microwave links and improve the link utilization. This reduces both
operational and capital expenditures for maintaining high ‐ capacity links. ACM can maintain the
highest link spectral efficiency possible at any given time in any link condition.
In traditional voice ‐ dominated wireless backhaul transmission networks, service availability levels
of 99.995% are the norm.
However, newer services such as Internet browsing, video streaming and video conferencing can
operate at more relaxed availability levels. With use of QoS prioritizing ACM can allocate the required
availability based on the priority. As a result, high ‐ priority services such as voice enjoy 99.995%
availability, while low ‐ priority services like video streaming are allocated lower priorities.
Use of QoS prioritizing defines which services should be transmitted under any link condition and
which services should be adapted whenever the link condition is degraded and the link payload is
decreased.
For example, when bad weather has decreased the channel capacity of a link, ACM maintains
high ‐ priority services – such as E1 channels – with full bandwidth capacity while adapting the
bandwidth capacity of low ‐ and mid ‐ priority services such as Internet browsing (see Figure 4.4 ).
Figure 4.3. ACM bandwidth capacity adaptation
Traffic can be mapped into different priorities, which define the level of service for each
application. Figure 4.3 illustrates how different services – such as rich voice and video – are mapped
into different classes of availability (CoA) such as 99.995% or 99.985%.
The implementation of multiple priorities increases the available capacity up to 10 times that of
standard links. When conditions are clear, the wireless link operates at maximum capacity and
provides all services with the full data rate. When link conditions are poor – during harsh rain, for
example – predefined high ‐ availability services such as voice are not affected. However, the capacity
of low ‐ priority services is adapted dynamically to the changing link conditions. This is done by
provisioning bandwidth according to the link conditions and traffic priority.
(!) Note that ACM (Adaptive Coding and Modulation) feature is enabled by default.