Download/Upload Efficiency

Can someone give me a clear definition of Download/Upload Efficiency?

Basic definition is intact vs. corrupt frames. 99% efficiency = 1% retransmissions.

At least that's how I was told!

Thanks for the reply. At what % does it start affecting the data speed?

Anything less than 100% means less air time is being used for transmission of data. You can see this reflected in the link capacity bit rate results

Can you recommend some documentation? 

I did a quick search through a number of PMP450 documents/guides/etc, and couldn't really find any in depth information on download/upload efficiency.

I've not seen any DETAILED official documentation, rather spoken with our CSE in the past. The best reading material I can suggest is the PMP Solutions User Guide, and the actual Link Capacity Test itself. The bitrate numbers tell you everything you need to know as far as speed impact.

Clay, thanks for your question. Unfortunately, I do not know of any official detailed documentation.

Efficiency is the number of 64 byte fragments that were “Expected” to be transmitted divided by the number of “Actual” transmissions.

Efficiency is not the best way to evaluate the results from a Link Capacity Test. Throughput is the most important to look at. This shows what throughput the RF link can push. All the other information is secondary and informational.

In addition, efficiency can be misleading because it depends on your transmit modulation. If the efficiency gets to low, the radio will modulate down. After modulation down the efficiency will go up. Eventually, if the efficiency at that modulation stays high, the radio will attempt to modulate up. The radio is constantly measuring efficiency to determine the best modulation to give the highest throughput.