Difference between revisions of "LTE UL and DL Power Measurements"

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("enb uepool chans")
(Setting fixed UL power on PUSCH)
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To enable fixed UL power, set the PuschFixedPower configuration parameter to true:
 
To enable fixed UL power, set the PuschFixedPower configuration parameter to true:
 
<pre>
 
<pre>
 +
[basic]
 
; Fixed UL power
 
; Fixed UL power
 
; If true, the output power is p0_NominalPUSCH
 
; If true, the output power is p0_NominalPUSCH
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This parameter is not supported in the LMI, and needs to be set in the enb-custom.conf file in the /etc/yate/sdr directory.
 
This parameter is not supported in the LMI, and needs to be set in the enb-custom.conf file in the /etc/yate/sdr directory.
(If you do not already have such a file, just create one.)
+
(If you do not already have such a file, just create one. ''Be sure to indicate the "[basic]" section at the start of the file.'')
  
 
In fixed UL power mode, the output power of the UE is controlled by p0_NominalPUSCH, which ''is'' available in the LMI, in the "Access Channels : PUSCH" page.
 
In fixed UL power mode, the output power of the UE is controlled by p0_NominalPUSCH, which ''is'' available in the LMI, in the "Access Channels : PUSCH" page.

Revision as of 18:02, 26 June 2018

This page describes UL and DL power measurements that can be made with the YateENB.

UL Power

Setting fixed UL power on PUSCH

In normal operation, the ENB uses dynamic power control to adjust the output power of the UE so that the RSSI at the ENB receiver meets a target level.

To make path loss and power measurements easier, the ENB supports fixed UL power as a special test mode.

To enable fixed UL power, set the PuschFixedPower configuration parameter to true:

[basic]
; Fixed UL power
; If true, the output power is p0_NominalPUSCH
; BE CAREFUL in direct-wired connections. The UE might have enough power to damage the ENB receiver.
PuschFixedPower=true

This parameter is not supported in the LMI, and needs to be set in the enb-custom.conf file in the /etc/yate/sdr directory. (If you do not already have such a file, just create one. Be sure to indicate the "[basic]" section at the start of the file.)

In fixed UL power mode, the output power of the UE is controlled by p0_NominalPUSCH, which is available in the LMI, in the "Access Channels : PUSCH" page. So if you set PuschFixedPower, be sure to check this value also.

The absolute output power of the UE will be p0_NominalPUSCH in dBm per resource block. To maintain fixed power, the ENB will fix all PUSCH allocations at 6 resource blocks. This severely limits UL data throughput, but gives a consistent power level on PUSCH.

With the fixed allocation of 6 resource blocks, the PUSCH total power is

total PUSCH power = p0_NominalPUSCH + 7.8 dBm

Note: This control does not affect PUCCH or PRACH, and so a raw power measurement of the UE transmitter may still show a different power level.

Getting PUSCH RSSI

The ENB calculates PUSCH RSSI in dBm. These estimates are accurate to about +/-3 dbm. These measurements are for PUSCH only and do not include PUCCH or PRACH.

"enb uepool chans"

The "enb uepool chans" command shows short-term average RSSI for each active UE under the heading "RSSI dBm".

Example with RSSI -32 dBm:

RNTI    PHR     RSSIdB  RSSIdBm UL-SNR  UL-FER  UL-HFER UL-eff  64QAM   ULbytes DL-eff  256QAM  DLbytes DL-NACK UC-RSSI UC-SNR  UC-miss Age     Idle    RSRP    RSRQ    UL-BSR  DL-BSR
61      30      -12     -32     20      2%      2%      15      false   2962    21      false   5314    0%      -26     43      0%      5       0       -100    -3      0       0

"enb measurements pat= TB.UlRssiAvg"

The YateeNB KPI-related measurements track long-term average RSSI for all connected UEs. The measurement name is "TB.UlRssiAvg".

enb measurements pat= TB.UlRssiAvg
TB.UlRssiAvg=-56
LastClearTime=1529775690
CurrentTime=1529776604

The "enb measurements clear" command clears and restarts the averaging period.

UL Power Headroom

The UE reports to the ENB a "power headroom" or "PHR", which is the number of dB between the UE's current transmission power and its maximum available transmission power. For example, if a received PHR value is 10, that means that the PUSCH transport block that carried the PHR report was transmitted at 10 dB below the maximum power of the UE.

The ENB saves and expresses PHR values in dB-per-resource-block. For example, if the ENB shows a PHR of 10 for a given UE, that means that a single-resource-block transmission would be 10 dB below the UE's maximum power, but a 10-resource-block transmission would be exactly at that maximum power. (This information is used by the scheduler to avoid requesting more power than the UE can deliver.)

In fixed power mode, all PUSCH allocations are 6 resource blocks, so the actual transmit power of the UE is

UE transmit power = maximum power - PHR - 7.8 dBm

"enb uepool chans"

The "enb uepool chans" command shows short-term average PHR for each active UE under the heading "PHR".

Example with PHR of 30 dB:

RNTI    PHR     RSSIdB  RSSIdBm UL-SNR  UL-FER  UL-HFER UL-eff  64QAM   ULbytes DL-eff  256QAM  DLbytes DL-NACK UC-RSSI UC-SNR  UC-miss Age     Idle    RSRP    RSRQ    UL-BSR  DL-BSR
61      30      -12     -32     20      2%      2%      15      false   2962    21      false   5314    0%      -26     43      0%      5       0       -100    -3      0       0

"enb measurements pat= TB.UlRssiAvg"

The YateeNB KPI-related measurements track long-term average PHR for all connected UEs. The measurement name is "TB.UlPhrAvg".

enb measurements pat= TB.UlPhrAvg
TB.UlPhrAvg=15
LastClearTime=1529780687
CurrentTime=1529782244

The "enb measurements clear" command clears and restarts the averaging period.

DL Power

The UE reports to the ENB a received power level called "RSRP". RSRP is the power level in dBm-per-resource element for the CSRS part of the LTE signal.

Total LTE DL power varies with activity. The total output power of and idle ENB, averaged over a frame, is about 10 dB higher than RSRP, depending on the bandwidth, CFI setting, and SIB sizes and scheduling. For an active ENB, the output is 20 - 30 dB higher than RSRP, depending on the configured bandwidth.

Getting RSRP

"enb uepool chans"

The "enb uepool chans" command shows short-term average RSRP for each active UE under the heading "RSRP".

"enb measurements pat= TB.UlRssiAvg"

The YateeNB KPI-related measurements track long-term average PHR for all connected UEs. The measurement name is "RRC.MeasReportRSRP".

enb measurements pat= RRC.MeasReportRSRP
RRC.MeasReportRSRP=-85
LastClearTime=1529780687
CurrentTime=1529782819

The "enb measurements clear" command clears and restarts the averaging period.