Data Throughput - LTE - RLC Factors

 

 

 

Details would come later

 

 

 

Example 1 >  PHY throughput and RLC Throughput in a drive test

 

Following plot is from the data captured by a drive test tool Azenqos Drive Test tool (AZQ Android) . I got the log captured by the tool and exported the data as csv file and then plot it on Microsoft Excel. This is a log captured from downloading a big file.  

Just from this single capture, it is hard to understand how each of the RLC parameters influencing the final throughput. But I want to show you overall correlation between RLC throughput and Physical layer throughput.

 

Overall trend that you can easily notice and is easily understandable is

  • There is high correlation between RLC throughput and PHY throughput

One thing I found strange (interesting) in this example is

  • RLC throughput is generally higher than PHY throughput. This would be understandable if this is uplink throughput measured on UE, but it looks a little strange to me that this happens in downlink measured on UE. Probably, RLC buffering may affect the throughput measurement, but not sure.

One thing that may interest you (I am not saying this is abnormal.. just to let you see the plot in more detail)

  • Comparing section (A) and (B), (A) throughput (peak throughput) is a little bit higher at PHY but become a little bit lower at RLC
  • Comparing section (C) and (D), (C) throughput (peak throughput) is a little bit higher at PHY but become a little bit lower at RLC
  • Section (E) shows much bigger difference between PHY throughput and RLC throughput.
  • I think all of these differences are within normal variation, but if you see very large differences it would be something worth further investigation.

 

 

Following is the RLC configuration that is configured in this test.

    drb-ToAddModList: 1 item

         Item 0

             DRB-ToAddMod

                 eps-BearerIdentity: 5

                 drb-Identity: 1

                 pdcp-Config

                     discardTimer: infinity (7)

                     rlc-AM

                         .... ...1 statusReportRequired: True

                     headerCompression: notUsed (0)

                         notUsed: NULL

                 rlc-Config: am (0)

                     am

                         ul-AM-RLC

                             t-PollRetransmit: ms40 (7)

                             pollPDU: p32 (3)

                             pollByte: kB25 (0)

                             maxRetxThreshold: t32 (7)

                         dl-AM-RLC

                             t-Reordering: ms50 (10)

                             t-StatusProhibit: ms50 (10)

                 logicalChannelIdentity: 3

                 logicalChannelConfig

                     ul-SpecificParameters

                         priority: 11

                         prioritisedBitRate: kBps8 (1)

                         bucketSizeDuration: ms300 (3)

                         logicalChannelGroup: 3