8.1.1 REFERENCESIGNALPOWER
The Reference Signal Power is a key RF parameter that impacts coverage.
Parameter referenceSignalPower configures the DL RS absolute power applied per Resource Element (REG) and per transmit antenna. This level is used as a power level reference (the power levels for all the other DL signals and channels are set relative to it).
ATTENTION! When modifying this parameter, all other signal power setting will be adjusted in accordance to a re-calculated power offset relative to the referenceSignalPower.
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LTE/IRC/APP/032749 V06.03 / EN Approved Standard 28/Oct/2013 Page 32/290 This parameter is expressed in dBm. It is converted into linear scale (miliwatts) according to the following formula:
Expected behaviour when changing this parameter:
The higher the setting, the larger the cell coverage on the downlink, but leaves smaller power headroom available for other downlink signals and channels.
The lower the value, the smaller the cell coverage on the downlink axis, but larger power headroom is available for other downlink signals and channels.
Note: The following Table 8-1 translates the expected behaviour in terms of cellDLTotalPower when changing the reference Signal Power; some difference may occur if other sets of parameters are used also.
TLA6.0 supports 8 antennas and 2 antennas with OLC eNB (One Logical Cell, also named Supper Cell), 2 Antennas OLC eNB supports transmission mode 1/2/3/4 and 8 Antennas eNB supports transmission mode 1/2/3/7/8.
For RSRP, RSSI, RSRQ relationship, please refer to 3GPP TS36.214.
Antennas transmissionMode cellDLTotalPower (dBm) n100-20MHz 13 (per of 2 carriers) or
16 (single carrier) Table 8-1: In the trial mode, the default setting for parameter referenceSignalPower Note that, since TLA6.0 MIM15.1.3 template v12, the CRS power boosting by increasing
referenceSignalPower and decreasing paOffset are recommended (for detail info please refer to section 8.2.5).
The recent change in terms of recommendation for the CRS booting is due to live testing at JQHQ OTA field test results, SINR increasing were seen after tuning power setting from the non-CRS power boosting values.
The testing procedure should comprise the following steps:
Step 1: Set the referenceSignalPower and other DL signal/channels power setting as default sets of values without RS boosting.
Step 2: Connect the UE in Near-Cell radio conditions with DL full buffer FTP transfer and perform driver test towards Celledge till UE drop. For a more consistent data we recommend a drive back as well logged in another trace.
Step 3: Using the same cell and same route, choose referenceSignalPower and other DL signal/channels as the sets of values with RS boosting and repeat Step2.
Step 4: Post process the logged data and provide results in terms of RSRP, SINR and coverage statistic.
P [mW] = 100.1×referenceSignalPower
Recommended & Default Value = Check Table 8-1
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LTE/IRC/APP/032749 V06.03 / EN Approved Standard 28/Oct/2013 Page 33/290 Figure 8.1-1: CRS boosting Vs. non-boosting test route (Field Results JQHQ OTA–SubUrban)
Figure 8.1-2: SINR with CRS boosting Vs. without CRS boosting (Field Results JQHQ OTA–
SubUrban)
Based on the test results, we can conclude that, SINR with RS boosting is about 2~5dB higher than that without RS boosting. This will make benefit for downlink channel quality estimation and improve DL coverage, although based on JQHQ OTA field test, basically no gain on throughput could be seen after CRS power boosting, further field tests will be done in CMCC commercial deployment.
8.1.2 PHICHRESOURCE
PHICH channels are grouped in PHICH groups. Each PHICH group consists of 8 PHICH channels (hence conveys 8 ACK/NACKs) that use the same resources, PHICH channels of a same group being separated by orthogonal sequences.
The number of PHICH groups in TDD subframe i is:
0 2 4 6 10 8 12 14 16 18 20 22 24 26 28 30 32 34
-123 -120 -117 -114 -111 -108 -105 -102 -99 -96 -93 -90 -87 -84 -81 -78 -75 -72 -69 -66
SINR
RSRP
JQHQ OTA RSRP Vs. SINR
Avg. SINR without CRS boosting
Avg. SINR with CRS boosting
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LTE/IRC/APP/032749 V06.03 / EN Approved Standard 28/Oct/2013 Page 34/290 Where:
Ng ∈{1/6 ,1/2 , 1, 2} and is configured by parameter phichResource
NDLRB is the total number of RBs in the downlink and is configured by parameter FrequencyAndBandwidthTDD :: Bandwidth
In TDD, the number of PHICH groups may vary between downlink subframes and is given by
group
A PHICH group consists of 3 REGs over either 1 or 3 OFDM symbols, depending on the value of parameter phich-Duration (“normal” or “extended”). This parameter can only be set to “extended”
if the CFI is equal to 3.
Expected behaviour when changing this parameter:
Setting the value low will result in lower number of PHICH groups in a subframe, so the higher the number of ACK/NACKs that need to be sent out the longer the buffer, eventually leading to failing to transmit the messages.
Setting value high will impact in having a higher number of PHICH groups in a subframe, so the fewer ACK/NACKs needed to be transmitted, OFDM symbols are not used and the allocated resources for this process go to waste.
Note that, currently, ALU LTE eNB only support Ng=1, i.e. parameter phichResource=1.
8.1.3 N310 AND T310
n310 defines the maximum number of consecutive "out-of-sync" indications received from lower layers for the UE to detect physical layer problems. It is broadcasted in SIB2.
t310 specifies the start value for the UE timer T310. This timer is started in the UE in RRC connected mode upon detecting radio link problems. At timer expiry the UE will go to RRC idle mode if security is not activated, else initiate the RRC connection re-establishment procedure. It is broadcasted in SIB2.
i
Recommended Value & Only Supported Value= "1"
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LTE/IRC/APP/032749 V06.03 / EN Approved Standard 28/Oct/2013 Page 35/290 After UE low layer report n310 times of "DL out-of sync", UE high layer will start t310 timer and wait for UE low layer report "DL in-sync", if UE doesn't receive "DL in-sync" before t310 expired, then UE will assume it is "out of sync" in downlink.
Expected behaviour when changing these two parameters:
Setting the value low will result in higher risk of OOS and easier to go to RRC idle (drop) or RRC re-establishment.
Setting the value high will help to reduce the risk of OOS, thus the traffic transmission could be more stable, but may also cause UE hard to drop or re-establish RRC even when the RF condition is really poor.