LTE Interfaces and Protocols

The main interfaces in LTE are Uu, S1-MME, X2, S1-U, S11 and S5.

LTE Uu: -

This is the air interface between UE and eNB. LTE layer 1 is dealt with later. RRC is the protocol that is used for communication between UE and eNB. Above RRC there is a NAS layer in UE. This NAS layer terminates at MME and eNB shall silently pass the NAS messages to MME.

LTE S1-MME: -

eNB and MME communicate using this IP interface. S1-AP is application layer interface. The transport protocols used here is SCTP. (Stream control transmission protocol)

LTE X2: -

This interface is used by a eNB to communicate to other eNB. This again is a IP interface with SCTP as transport. X2-AP is the application protocol used by eNB’s to communicate.

LTE S11: -

An IP interface between MME and SGW! GTPv2 is the protocols used at the application layer. GTPv2 runs on UDP transport. This interface must and should run GTPv2.

LTE S5: -

This is the interface between SGW and PGW. This again is an IP interface and has two variants. S5 can be a GTP interface or PMIP interface. PMIP variant is used to support non-trusted 3GPP network access.

LTE S1-U: -

User plane interface between eNB and SGW! GTP-U v1 is the application protocol that encapsulates the UE payload. GTP-U runs on UDP.

All the above IP interfaces can be of IPv4 or IPv6. Few interfaces can be of IPv4 and few can be of IPv6. From the specification side there are no restrictions.

LTE Idle Mode – Cell Reselection

After cell selection UE performs measurement and carry out cell reselection of new candidate cell. This is based on certain criterion. Reselection process involves 2 steps

1.    Measurements Condition:  Specifies when to start measuring neighboring cells. Once condition is met UE measures the RSRP level of the E-UTRA cells on the current frequency and any inter-frequency and inter-RAT frequency carriers.

2.     Reselection Condition: Specifies reselection criteria for candidate cell. There are two different mechanisms for cell reselection:

 Legacy Based

Priority Based

Cell reselection can be either Legacy or Priority based.

Legacy Based

 This is classical Ranking based system and is applied to intra-frequency reselection.

• It is also applied to inter frequencies which are equally prioritized.

• UE applies cell ranking R criterion on serving cell and neighboring cell.

Priority Based

Priority values in the range [0..7] are used, where 0 indicates lowest priority and 7 indicates highest priority.

Priorities can be set for:

Inter Frequencies: Lower, Equal or Higher Priority

Inter-Rat Frequencies: Higher or Lower Priority

Equal priorities between different RATs are not supported

Idle Mode – Cell Reselection: Priority Based

CellReselectionPriority    :           Absolute reselection priority for E-UTRA or IRAT frequency

sNonIntraSearch :           Threshold for inter and IRAT frequency

threshXLow                    :           Threshold for Srx value of serving cell below which UE performs cell

 reselection towards a lower priority cell.

threshXLow                    :           Threshold for Srx value of target cell for cell reselection towards a

                                                lower priority Inter or IRAT frequency.

tReselectionEutra           :           Cell reselection timer value for EUTRAN

tReselectionUtra :           Cell reselection timer value for UTRAN 

LTE Idle Mode – Cell Reselection

After cell selection UE performs measurement and carry out cell reselection of new candidate cell. This is based on certain criterion. Reselection process involves 2 steps

1.    Measurements Condition:  Specifies when to start measuring neighboring cells. Once condition is met UE measures the RSRP level of the E-UTRA cells on the current frequency and any inter-frequency and inter-RAT frequency carriers.

2.     Reselection Condition: Specifies reselection criteria for candidate cell. There are two different mechanisms for cell reselection:

 Legacy Based

Priority Based

Cell reselection can be either Legacy or Priority based.

Legacy Based

 This is classical Ranking based system and is applied to intra-frequency reselection.

• It is also applied to inter frequencies which are equally prioritized.

• UE applies cell ranking R criterion on serving cell and neighboring cell.

Priority Based

Priority values in the range [0..7] are used, where 0 indicates lowest priority and 7 indicates highest priority.

Priorities can be set for:

Inter Frequencies: Lower, Equal or Higher Priority

Inter-Rat Frequencies: Higher or Lower Priority

Equal priorities between different RATs are not supported

Idle Mode – Cell Reselection: Priority Based

CellReselectionPriority    :           Absolute reselection priority for E-UTRA or IRAT frequency

sNonIntraSearch :           Threshold for inter and IRAT frequency

threshXLow                    :           Threshold for Srx value of serving cell below which UE performs cell

 reselection towards a lower priority cell.

threshXLow                    :           Threshold for Srx value of target cell for cell reselection towards a

                                                lower priority Inter or IRAT frequency.

tReselectionEutra           :           Cell reselection timer value for EUTRAN

tReselectionUtra :           Cell reselection timer value for UTRAN 

LTE Idle Mode Cell Selection

Once a cell meets all requirements, Criterion S is considered for cell selection.

Srxlev = [Qrxlevmeas – (Qrxlevmin + Qrxlevminoffset) – Pcompensation] > 0

Where  

Pcompensation = [max (PEMAX – PUMAX , 0)]

Example: (Ignoring Offset and Pcompensation)

Srxlev = (Qrxlevmeas –Qrxlevmin) => -105 – (-120) = 15 db > 0

Parameter

Parameter	Description
QrxLevmeas	Measured RSRP value by UE (dBm)
Qrxlevmin	Required minimum RSRP level in the cell (dBm)
Qrxlevminoffset	Offset to Qrxlevmin
PUMAX	Maximum UE power according to its class
PEMAX	Maximum UE power to be used in a cell. Ericsson equivalent is pMaxServingCell

LTE parameters for IRAT cell reselection in WCDMA

arfcnValueUtranDl   : Indicates the ARFCN applicable for a downlink UTRA carrier frequency, 

cellReselectionPriority  : The absolute priority of the carrier frequency used by the cell reselection procedure. Default Value :7

ellReselectionPriority : The absolute priority of the concerned carrier frequency, as used by the cell reselection procedure. Default Value :6

pMaxUtra : The maximum allowed transmission power on the (uplink) carrier frequency. Default Value :33

sNonIntraSearch :Threshold for inter-frequency and inter-RAT measurements on frequencies of equal or lower priority. Default Value :0

threshServingLow Threshold for the signal strength of the serving cell, below which the UE performs cell reselection towards a lower priority inter-frequency or inter-RAT frequency. Default Value :0

threshXHigh : Specifies the threshold used by the UE when reselecting towards the higher priority frequency X than current serving frequency. Each frequency of UTRAN might have a specific threshold Default Value :4

threshXLow : Specifies the threshold used in reselection towards frequency X priority from a higher priority frequency. Each frequency of UTRAN might have a specific threshold. Default Value :0 

tReselectionUtra : Cell reselection timer value TreselectionRAT for UTRAN (1). Default Value :2

qQualMin : Minimum required quality level in the cell expressed in dB. Default Value :-119

qRxLevMin : Minimum required RX level in the cell expressed in dBm.

Bands for LTE

The latest revision of the LTE standard defines bands of operation, including both paired and unpaired spectrum. 1-32 bands are for paired (FDD) operation, while bands 33-40 are for unpaired (TDD) operation

Paired (FDD) and Unpaired (TDD) Operating Bands for LTE with Uplink & Downlink Frequency 

America Movil Signs Deal to Take Control of Telekom Austria

Maxico's America Movil is launching a takeover bid for the Telekom Austria Group with secure an agreement with the Austrian government's own holding company IAG.

America Movil and ÖIAG have initially signed a shareholders’ agreement to effectively pool their stakes in the telecoms company into a single syndicate.

America Movil already owns 26.4% of the company, while the government owns 28.4% of the telco.

Now that the agreement, which had been expected, has been signed, the two companies jointly control more than 30% of the shares and are required by Austrian stock market rules to launch a takeover bid for the company.

Subject to the closing of the takeover bid, the two shareholders will also pump an additional EUR1 billion into the company to help fund network upgrades.

America Movil will take over management of the company, although it is expected that the Austrian government would, through ÖIAG remain the larger of the two shareholders. ÖIAG also has the right to nominate the CEO and Chairman of the company.

Telekom Austria currently operates in Austria, Belarus, Bulgaria, Croatia, Serbia, Macedonia, Liechtenstein and Slovenia.

Post Date 24-April-2014