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http://www.linkedin.com/groups/How-UE-knows-about-MIMO-1180727.S.203081816

How UE knows about the MIMO configurations?

Right,, UE know whether the servicing eNB MIMO configuraitons through SIB2 after UE is able to camp on the eNB. SIB2 indicates

radio resource configuration common IE, then from this IE, UE can get Antenna information common that indicates detail antenna # for the serving cell.

EswarEswar GuptaSoftware Engineer at Aricent Technologies

can you tell me the exact parameter in SIB2o Like o Reply privately o Flag as inappropriate o 11 months ago

HarshHarsh RastogiSenior Wireless Protocol Application Engineer at AnritsuTo my understanding, The number of Transmit antenna in the cell is deternined by the UE itself, and this info is not broadcasted in the System Information ie SIB2. eNB tranmist the RS using Transmit diversity if more than one antenna port is used, and the UE then does the channel estimates for all the probable antenna ports and determines if eNB had used more than one Antenna, The "AntennaInfoCommon" IE carries Antenna Port Info used in the serving cell, but this IE is carried only in the "MobilityControlInfo" as part of "RRC Connection Reconfiguration", which will be used during handover. And RRC Connection Setup/Reconfiguration msg carries "AntennaInfoDedicated", which commands the UE to use which exact Transmission Mode (1 to 8) is being used during this radio connection.

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Chung-Wei W. likes this

PeterPeter LauroComputer Software Consultant and ContractorThis information is a part of RRC connection setup and reconfiguration messages: (for example rrcConnectionReconfiguration):

+ rrcConnectionReconfiguration-r8 -> radioResourceConfigDedicated -> physicalConfigDedicated -> antennaInfo: +-explicitValue ::= SEQUENCE [0]

| | +-transmissionMode ::= ENUMERATED [tm1]

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| | +-codebookSubsetRestriction ::= CHOICE OPTIONAL:Omit

| | +-ue-TransmitAntennaSelection ::= CHOICE [release]

| | +-release ::= NULL

For Transmission modes: two,three, four, five, six the already mentioned antennaInfo is used For Transmission mode eight - structure PhysicalConfigDedicated->Extension_Addition_Group->antennaInfo_v920


Muhammad Saad F. likes this

Xiaoxia (Michael)Xiaoxia (Michael) TanRF System Engineer IV at Ericsson

The UE obtain MIMO information from following two different scenarios:

During LTE system information acquisition, the UE, may be in IDLE or CONNECTED, needs to go through SI acquisition procedure to get enough SI which is broadcasted by eUTRAN. This includes: •Power on •Cell reselection •Inter-RAT HO To know whether the LTE servicing network has MIMO support capability for above three cases, the UE has to get system information: (UE must be able to decode those SI from PDCCH with SI-RNTI) •MIB •SIB1 •SIB2 Once receiving SIB2, the UE shall perform the configuration setting based on received radioResourceConfigComman IE, which the antennaInfoCommon is included. Therefore, UE obtains MIMO information from SIB2.

When the UE goes through RRC connection after system qcquisition, in eUTRAN -> UE with RRC connection setup, RRC connection re-establishment, and RRC connection reconfiguration, the UE should have a physicalConfigDedicated IE from redioRerouceConfigDedicated IE in RRCCoonectionSetup , RRCConnectionReestablishment, RRCConnectionReconfiguration messages. Therefore, the specific MIMO method recommended from the serving eNB based on the UE CQI/RI/PMI reported will be indicated in antennaInfodedicated IE in physicalConfigDedicated IE. Therefore, UE obtains MIMO information from above three RRC messages.


Michael B. likes this

HarshHarsh RastogiSenior Wireless Protocol Application Engineer at AnritsuIf we look at 3gpp 36.331 v10.4.0 (Release-10) , Page-182, it statest that :

RadioResourceConfigCommon The IE RadioResourceConfigCommonSIB and IE RadioResourceConfigCommon are used to specify common radio resource configurations in the system information and in the mobility control information, respectively.

RadioResourceConfigCommonSIB ::= SEQUENCE { rach-ConfigCommon RACH-ConfigCommon, bcch-Config BCCH-Config, pcch-Config PCCH-Config, prach-Config PRACH-ConfigSIB, pdsch-ConfigCommon PDSCH-ConfigCommon, pusch-ConfigCommon PUSCH-ConfigCommon,



pucch-ConfigCommon PUCCH-ConfigCommon, soundingRS-UL-ConfigCommon SoundingRS-UL-ConfigCommon, uplinkPowerControlCommon UplinkPowerControlCommon, ul-CyclicPrefixLength UL-CyclicPrefixLength, ..., [[ uplinkPowerControlCommon-v1020 UplinkPowerControlCommon-v1020 OPTIONAL -- Need OR ]] }

RadioResourceConfigCommon ::= SEQUENCE { rach-ConfigCommon RACH-ConfigCommon prach-Config PRACH-Config, pdsch-ConfigCommon PDSCH-ConfigCommon pusch-ConfigCommon PUSCH-ConfigCommon, phich-Config PHICH-Config pucch-ConfigCommon PUCCH-ConfigCommon soundingRS-UL-ConfigCommon SoundingRS-UL-ConfigCommon uplinkPowerControlCommon UplinkPowerControlCommon antennaInfoCommon AntennaInfoCommon p-Max P-Max tdd-Config TDD-Config ul-CyclicPrefixLength UL-CyclicPrefixLength, ..., [[ uplinkPowerControlCommon-v1020 UplinkPowerControlCommon-v1020 ]] }

And from Page-148 SystemInformationBlockType2 information element:

SystemInformationBlockType2 ::= SEQUENCE { ac-BarringInfo SEQUENCE { ac-BarringForEmergency BOOLEAN, ac-BarringForMO-Signalling AC-BarringConfig ac-BarringForMO-Data AC-BarringConfig } radioResourceConfigCommon RadioResourceConfigCommonSIB, ue-TimersAndConstants UE-TimersAndConstants, ........ ... }

So my understanding is that RadioResourceConfigCommonSIB doesn't contain Antenna Info.

Can you kindly elaborate then from where this AntennaInfo is getting transmitted in the SIB2. Is there any gap in my understanding.

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EikoEiko SeidelCTO and 3GPP RAN Standardisation Expert

How can you read the SIBs in any case if you do not know the number of antennas and the eNB can use transmit diversity !

As Harsh was saying, different Reference Symbols are send in case of different number of eNB antennas. So the UE has to try 1, 2 or 4 antenna ports. In standardisation it was discussed to put it on MIB to get to know the number of antenna, but it was decided to spare that two bits to reduce the size of MIB and increase reliability at the expense of UE complexity.



Chung-Wei W. likes this

Xiaoxia (Michael)Xiaoxia (Michael) TanRF System Engineer IV at Ericsson

My understand was that 3GPP proposed antenna # to be in MIB, but I don't know whether this propose was finally accepted as you mentioned about. The method is that MIB has CRC, which scrambled with one of 3 sequences of PBCH CRC mask that maps to # of antennas on the serving cell. LTE UEs need to blindly detect the # of antenna ports used to send PBCH. #of transmit antenna ports at eNB PBCH RCR Mask (ant0,ant1,...ant15) 1 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 2 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1 4 0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1

I think it is only way for the UE to know the antenna # on the serving eNB before it can receive all other SIBs.

if 3GPP accept it, all mobile vendors may have to follow up the way and figure out how to detect the antenna ports from MIB.


Shailesh C. likes this

VenkatVenkat RNProject Lead at L&T Infotech

Yes. I do think same as Eiko.

How UE understand TX-Antennas Ports even though this is not part of MIB content: MIB has CRC which gets scrambled with one of 3 sequences which represents (One, Two OR Four Anttenas). UE when it received it tries to decode with all three based on CRC check UE understands what is TXAntennas.

PBCH can use single antenna or transmit diversity transmission modes. UE blindly detects number of antenna ports used for PBCH using CRC scrambling sequence. From this UE determines number of cell specific reference signals configured in the cell. If cell is configured with 2 antenna ports, SFBC transmit diversity scheme is used for BCH, PCH and L1/L2 Control signalling. If 4 antenna ports are detected, SFBC/FSTD transmit diversity is used for BCH, PCH and L1/L2 control signalling.

Copy/Pasting the above from my tech blog :).o Like o Reply privately o Flag as inappropriate o 11 months ago

ShaileshShailesh chidrawarProficient Wireless Testing Professional

Simple answer: With the CRC mask of PBCH data

- Transmitter (eNB) will calculate CRC for 24 bits of MIB information and masked with 16teen 0's if there is one antenna, 16teen 1's if there is two antennas and alternate 1010101010101010 if there are 4 antennas.

- Receiver (UE) will remove this CRC bits (16 bit) and calculate CRC for remaining data i.e. 24 bits of MIB data.

- Calculated CRC is again masked with 16teen 0's at UE side and CRC out come is cross checked with received CRC




bits. If both are matching then UE comes to know about number of antennas = 1 used.

- If above is not matching, then Calculated CRC is again masked with 16teen 1's for this received 24 bits of MIB information at UE side. CRC Mask Outcome is matches with received CRC bits then UE comes to know about number of antennas = 2 used

- If above is not matching, then Calculated CRC is again masked with 1010101010101010 for this received 24 bits of MIB information, at UE side. CRC Mask Outcome is matches with received CRC bits then UE comes to know about number of antennas = 4 used.

- If nothing is matched then UE come to know that the received MIB data contain Errors, so can not be decoded and should look for new MIB data in sub sequent frames.


Somnath R. likes this


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