Motorola PTP 400 Series - Manual (Page 78)

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Link Mode Optimization: By default, Link Mode Optimization of a point-to-point link is set to
‘IP Traffic’. In this configuration the wireless minimizes packet transmission errors by
automatically adapting the active modulation mode based on instantaneous vector error
measurements and the presence of codeword errors. This mode of operation is
recommended for connection oriented IP traffic protocols where packet loss is perceived by
the protocols as an indication of network congestion. It is recommended that when using this
mode of operation the ARQ state is set to ‘enabled’. The ‘TDM Traffic’ mode is recommended
for E1 / T1 applications and connectionless oriented protocols. In this mode the wireless link
is optimized for minimum transmission latency and preservation of data throughput by
allowing the link to maintain a higher modulation mode in the presence of a limited number of
codeword errors. It is recommended that when operating the link in TDM mode that the ARQ
state is set to disabled and that the Spectrum Management controls are used to fix the
wireless link to a single frequency. This can be achieved by using the installation wizard to
configure single frequency operation. In either case, a system reboot will be required.
Link Symmetry: By default Link Symmetry of a point-to-point link is ‘Symmetrical Data Rate
(1:1)’ in this configuration the ratio of time the wireless link spends transmitting and receiving
is equal. When Link Symmetry is configured to Asymmetric Data Rate (2:1) the wireless link
Master will spend twice as long transmitting as receiving. It should be noted that the data rate
available to the end users might not follow these ratios exactly. The exact data rates will be
dependant on the prevailing modulation modes.
Throughput Optimization: Throughput Optimization has two distinct modes:
• Data Throughput configures the wireless link for maximum data throughput.
• Low Latency configures the wireless link to minimize packet latency during transmission
over the wireless link. When Low Latency mode is selected, the Link Symmetry is
automatically reconfigured to a symmetric link. Link asymmetry is not supported in Low
Latency mode.
Note: The “Throughput Optimization" option is not available on 4.9GHz variants.
ARQ State: Automatic Repeat reQuest (ARQ) is a mechanism where packets lost due to
transmission errors over the wireless link are retransmitted rapidly. The retransmission helps
to prevent TCP congestion mechanisms from inadvertently interpreting intermittent packet
loss as network congestion. ARQ must be enabled on both ends of the point-to-point link for it
to function.