Credit to Peter for posting this as an answer to a customer question originally, but I think it's a very useful explanation.
To explain the columns in the Link Test results I will use the following results obtained from a Cambium test sector.
The columns in the first table, are :
VC : virtual circuit queue
Rate : delivered data rate averaged during the test
Efficiency : fragment success rate during the link test
Transmit fragments : number of fragments transmitted during the test
Receive fragments : number of fragments received during the test
Downlink rate : downlink rate adapt modulation mode at the end of the test
The first row details the totals for the test showing an aggregate of 211.25 Mbps Subsequent rows detail results for individual VCs
The second table details the grouping statistics achieved during the link test. The columns are :
Group size : each of the possible spatially multiplexed group sizes from 1 to 7
% distribution : the proportion of transmissions using this group size
average slot count : average number of slots per TDD used for transmissions with this group size
For these results all transmissions achieved a grouping of 3. VCs 18 and 21 are always grouped with one of the remaining four VC. None of the remaining 4 VCs could be grouped because the spatial seperation were too small. Consequently transmissions occur to VCs 18 and 21 every TDD cycle. and transmissions to the remaining VCs every 4 TDD cycles due to the round robin scheduler.
The reported TX fragment count for VC 18 is also consistent with the estimate based on
6 fragments/slot due to 64QAM modulation
x 55 slots/TDD (reported in the second table)
x 400 TDD/s (configured TDD rate)
x 10 s test time