Mimosa Backhaul Help Content
Mimosa Backhaul Performance
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Link Latency
Product Applicability: B5/B5c, B5-Lite
Link latency is the delay between the time a packet enters the local radio and exits the remote radio in one
direction. In many cases, constraining latency across one link (or more) is a requirement for providing services such
as VoIP that are more sensitive to packet arrival times.
Average link latency is configured with the TDMA Window Size. Available options include 2, 4, and 8 ms. Operators
should take into account the total number of hops when setting TDMA Window Size to ensure that total latency
meets requirements.
In practice, the average latency (in the presence of noise and resulting retries) in one direction is 1.25 * the TDMA
Window Size:
1-Way Latency (ms) = 1.25 * TDMA Window Size (2/4/8 ms)
For example, 2 hops (back-to-back links) with a 4 ms TDMA Window would result in 10 ms average latency (2 hops *
4 ms * 1.25 = 10 ms) in one direction.
Latency tests are usually performed from a command line or embedded interface with the ping command, which
returns the round trip time (RTT) across the link and back. The implication is that ping results will be double of the 1-
Way Latency.
Round Trip Time (ms) = 2.5 * TDMA Window Size (2/4/8 ms)
Note that RF interference, and resulting packet errors (indicated as PER on the Dashboard), can lead to retries and
more round-trips to complete a ping.
Asymmetric TDMA Traffic splits (75/25 or 25/75) have a negligible affect on RTT since the total time always adds up
to one full cycle.
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