LTE: Measurement GAP Calculator

E-UTRAN provides the UE with measurement GAP configuration if UE requires measurement gaps to identify and measure inter-frequency and/or inter-RAT cells
The MeasGapConfig consists of gap pattern type (gp0 or gp1) which identifies the periodicity and gapOffset

Each gap starts at an SFN and subframe meeting the following condition:
SFN mod T = FLOOR (gapOffset/10);
subframe =  gapOffset mod 10;
with T  = MGRP/10 and MGRP is 40 for gp0 and 80 for gp1
For FDD, the UE shall not transmit in the subframe occurring immediately after the measurement gap.
For TDD, the UE shall not transmit in the uplink subframe occurring immediately after the measurement gap if the subframe occurring immediately before the measurement gap is a downlink subframe
One can calculate measurement gap occasions by providing gap pattern type and gapOffset in the below tool. 

 measGAP calculations

Select GAP Pattern               Select GAP Offset               UL-DL Config
                                                  

                        Is TDD?

Measurement GAP Occasions will be displayed here
Posted by KP
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34 comments:

  1. BollylifeSeptember 6, 2015 at 5:40 PM

    can you say that in which situation gp0 and gp1 will used?

    ReplyDelete
    Replies
    1. KPSeptember 7, 2015 at 8:36 AM

      I think that there could be three factors affecting on which gap pattern to be used:
      1. If the UE is comfortable with the current cell conditions and there is no hurry at the moment to do measurements at a faster rate (gp0)
      2. Amount of measurements needed i.e., for example if there are multiple inter frequency cells to be measured etc...then gp0 might be needed to finish the measurement of all the frequencies in quick time...
      3. UE's data activity...if for example the UE is transmitting at a higher data rate and if the cell is good, then using gp0 might reduce the data rate.
      Finally, different eNB vendors might have different algorithms on what triggers the use of gp0/gp1 etc...I hope it clarifies

      Delete
    2. AnonymousJuly 13, 2017 at 11:34 AM

      so gapoffset it not fixed by parameter ? which is GAP_PATTERN_TYPE_1 or GAP_PATTERN_TYPE_2

      Delete
    3. KPSeptember 6, 2017 at 10:14 PM

      Yes GapOffset can take different values depending upon the Gap Pattern. If gp0 is used (40ms periodicity) then the gapOffset could be between 0 to 39, or if gp1 is used (80ms periodicity) then gapOffset could be any value between 0 to 79

      Delete
    4. AnonymousSeptember 6, 2017 at 10:43 PM

      whats the best configuration?

      Delete
    5. KPSeptember 7, 2017 at 8:55 AM

      1. If the UE is comfortable with the current cell conditions and there is no hurry at the moment to do measurements at a faster rate (gp0)
      2. Amount of measurements needed i.e., for example if there are multiple inter frequency cells to be measured etc...then gp0 might be needed to finish the measurement of all the frequencies in quick time...
      3. UE's data activity...if for example the UE is transmitting at a higher data rate and if the cell is good, then using gp0 might reduce the data rate.
      Finally, different eNB vendors might have different algorithms on what triggers the use of gp0/gp1 etc...I hope it clarifies

      Delete
    6. AnonymousSeptember 7, 2017 at 9:05 AM

      how do you explain the increase of thp after changing gp0 to gp1 in huawei fdd lte?

      Delete
    7. KPSeptember 7, 2017 at 9:39 AM

      As explained above, by changing to gp1 the measurement gap periodicity is changed from 40ms to 80ms which saves 7 subframes (6+1) once in 40ms...which means these 7 subframes are available for data transmission/reception -> hence increase in throughput

      Delete
    8. AnonymousSeptember 7, 2017 at 12:06 PM

      Thanks a lot.
      So by using GAP0 (40ms) the InterFreq process will be delayed.
      Any other negative impact of GAP0 versus GAP1 ?
      Thanks.

      Delete
    9. KPSeptember 7, 2017 at 12:22 PM

      No.
      GAP0: 40ms periodicity - more opportunities for measurements -> quicker measurements -> More impact on throughput
      GAP1: 80ms Periodicity - less opportunities for measurements -> slower measurements -> less impact on throughput

      Delete
    10. AnonymousSeptember 7, 2017 at 12:42 PM

      thanks. I saw Now.

      Does anyone has an idea how to change it in Nokia FL16A, from GAP_PATTERN_TYPE_0 --> GAP_PATTERN_TYPE_1 ? Which is the parameter ?
      thanks a lot.

      Delete
  2. Telecom Protocol IssuesDecember 4, 2015 at 11:00 AM

    why we have 40ms for gp0 why not less than 40ms ..i need to understnd can any one explain that ...

    ReplyDelete
    Replies
    1. AnonymousMarch 4, 2016 at 2:08 PM

      For each frequency measured, the UE needs 6 gaps ( 6*6 = 36ms ) and hence a minimum of 40ms

      Delete
    2. UnknownJuly 13, 2017 at 11:23 AM

      What's the impact to increase the waiting time between Gap from 40-->80ms (means changing from GAP_PATTERN_TYPE_1 --> GAP_PATTERN_TYPE_2 in LTE FDD HUAWEI) ? any drawback effects ?

      Delete
    3. KPSeptember 6, 2017 at 10:14 PM

      I think that there could be three factors affecting on which gap pattern to be used:
      1. If the UE is comfortable with the current cell conditions and there is no hurry at the moment to do measurements at a faster rate (gp0)
      2. Amount of measurements needed i.e., for example if there are multiple inter frequency cells to be measured etc...then gp0 might be needed to finish the measurement of all the frequencies in quick time...
      3. UE's data activity...if for example the UE is transmitting at a higher data rate and if the cell is good, then using gp0 might reduce the data rate.
      Finally, different eNB vendors might have different algorithms on what triggers the use of gp0/gp1 etc...I hope it clarifies

      Delete
  3. UnknownJanuary 25, 2016 at 7:21 PM

    Is there any gap pattern Diff in FDD ad TDD frame structure ?

    ReplyDelete
    Replies
    1. KPJanuary 26, 2016 at 9:03 AM

      No Difference in the pattern except unavailability of contiguous DL subframes for measurement gap in the case of TDD.

      Delete
  4. MithrilJune 8, 2016 at 2:51 PM

    Could you please tell me what is the "UL-DL Config" parameter you are using in calculating the measGaps.

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    Replies
    1. KPJune 9, 2016 at 5:03 PM

      UL-DL Config is the parameter specific to TDD. Please refer to Table 4.2-2 from 36.211

      Delete
    2. MithrilJune 13, 2016 at 3:46 PM

      Thank you for the reply.

      One more question: For example , let the gapOffset be 5 and gapPattern as gp1. As per the calculator,

      Measurement GAP Starts at: SFN = 0, Subframe = 5
      Measurement GAP for Rx Ends at: SFN = 1, Subframe = 0
      Measurement GAP for Tx Ends at: SFN = 1, Subframe = 1

      Measurement GAP for Rx Ends at: SFN = 1, Subframe = 0, does this mean inclusive of SFN = 1, Subframe = 0 or excluding it?

      Also, if you don't mind could you please point me to 3GPP specification which says "Measurement gap for Rx ends 5ms after the gap start" and "Measurement gap for Tx ends 6ms after the gap start".

      Thanks in advance.

      Delete
    3. KPJune 20, 2016 at 9:14 AM

      Answer to the first question: The measurement gap is inclusive of the mentioned SFN-subframes. In this case SFN=1 and subframe=0 is included since gap length is 6ms.

      From 36. 133, refer to section 8.1.2.1. For FDD, the UE shall not transmit in the subframe occurring immediately after the measurement gap

      Delete
    4. MithrilJune 20, 2016 at 9:06 PM

      Thank you very much for the response.


      "For FDD, the UE shall not transmit in the subframe occurring immediately after the measurement gap"
      - This means to say that UE should not be scheduled in uplink for the frame occurring immediately after the measurement gap? i.e. UE will not transmit (or is not supposed to transmit) for 6 + 1 = 7 milliseconds?

      Delete
    5. KPJuly 11, 2016 at 11:39 AM

      Yes, your understanding is correct

      Delete
    6. BalsOctober 23, 2018 at 3:44 AM

      Let us assume, measurement gap starts at subframe = 1. If the measConfig IE includes MGTA (Measurement Gap Timing Advance), scheduling shouldn't be done at subframe = 0 as the UE should start the measurement earlier (MGTA). Here the impacted subframes are already 7 (1+6). If UE should not be scheduled the immediate subframe then it becomes 8.

      Delete
  5. UnknownAugust 25, 2016 at 6:16 AM

    Your comment, No Difference in the pattern except unavailability of contiguous DL subframes for measurement gap in the case of TDD

    What does it mean?

    ReplyDelete
    Replies
    1. KPAugust 31, 2016 at 10:13 AM

      I mean to say that there is no difference in the gap pattern in case of TDD as compared to FDD. But the DL subframes during measurement gap might not be contiguous in case of TDD

      Delete
  6. UnknownApril 25, 2017 at 5:43 PM

    So if there is a periodic CQI/RI configured such that it falls just after meas gap then UE will skip it...or will UE drop measurement gap itself? Is there any other such periodic configuration which can impact this?

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    Replies
    1. KPMay 15, 2017 at 9:22 AM

      The UE Skips any Tx or Rx during the measGap. MeasGap is always the top priority.

      Delete
    2. AnonymousNovember 11, 2018 at 11:31 AM

      Hi Kumar

      ragarding cqi and measGap. In the case that Hersh was presented, what should we do on the CQI subframe. Since we didn't have the oppurtunity to make measurements we can't send CQI. Should we do RX on that subframe or do nothing since the enodeB assume that this is UL subframe (CQI)

      Delete
  7. AnonymousJune 29, 2017 at 8:47 AM

    Is there any chance of inclusion of 'measGapConfig ' in Intra Freq measurements ?

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  8. skJuly 19, 2020 at 8:35 PM

    if 50 mbps data is running on UE how much data can loss during HO while config gap0 or gap1?

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    Replies
    1. RajeshMarch 11, 2021 at 9:07 AM

      Please answer for this question @ kumar Swamy sir

      Delete
  9. AnonymousAugust 14, 2024 at 9:40 AM

    gap0 : (2+6+2)/40 = 25%, gap1: (2+6+2)/80 = 12,5% theorical amount of thp degradation. 6 sub frame for measurement gap, scheduler does not schedule grants 2 sub frame before the measurement gap and 2 subframe after the measurement gap

    ReplyDelete

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