LTE Training

LTE Overview and Optimization

LTE Overview and OptimizationKashif Hussain4/26/14

MobileNet Services Inc.Superior Engineering Solutions

1/15/2015#AgendaLTE OverviewBackgroundArchitectureAir InterfaceCall Flows and HandoversLTE OptimizationNetwork and RF Optimization ProcessesLT RF Optimization ObjectsTroubleshootingHandover success rateThroughput

1/15/2015#Mobile Communication Standard Timeline

1/15/2015#3GPP Evolution

1/15/2015#Requirements and Target for LTE Technology

1/15/2015#UMTS vs. LTE

1/15/2015#EPS (Evolved Packet System)

1/15/2015#LTE Bandwidths - Frequency domain

Channel Bandwidth [MHz]1.435101520Duplexing SchemeFDDFDDFDD/ TDDFDD/ TDDFDD/ TDDFDD/ TDDTransmission Bandwidth configuration# RBs615 255075100# SCs721803006009001200MHz1.082.74.59.013.518.0GuardbandMHz0.320.30.51.01.52.0%23%10%10%10%10%10%

The smallest bandwidth for deployment is 6 Resource Blocks1,08 MHz + guard band = 1.4 MHzThe largest bandwidth for deployment is 100 Resource Blocks18 MHz + guard band = 20 MHz

1/15/2015# 2011-01-11 8This is a simplified diagram of LTE band

OFDMA signal is carried by a number of parallel subcarriers, 15 kHz each. Twelve of these consecutive subcarriers (i.e. 180 kHz) are grouped into what is called a Resource Block.

Flexible Spectrum Migration Strategy w/CDMAEfficient use of the entire spectrumCDMA carrier can remain for roaming businessLTE provides flexible spectrum migration path for CDMA operators

LTE 1st Carrier - 5MHz10MHz License

LTE 2ndCarrier1.4MHz

1st CDMACarrier2009

Optional2nd CDMACarrier

Optional3rd CDMACarrier

LTE 1st 5MHz Carrier2010

LTE 2nd Carrier Expand to 3MHz

LTE2011

LTE2012

1/15/2015# 2011-01-11 9This slide illustrates an example where an operator who has 10 MHz license with 3 CDMA carriers in operation- Can start with a 5MHz LTE deployment and thereby successively replacing the CDMA carriers with 1.4 and 3MHz LTE. Moving the traffic to LTE.

3GPP Frequency Bands* Most used bands world wide

1/15/2015# 2011-09-29 Best before April 1, 2012 10Verizon 700 c upper Band Class 13

UE Capability


1/15/2015#

Architecture Section ScopeDescribe the Evolved Packet System Architecture.List the Control and user plane protocols Explain the General Protocol model and Protocol interactionsDescribe the various traffic cases in EPSObjectives

ScopeEvolved Packet System ArchitectureControl and user plane protocolsGeneral Protocol model and Protocol interactions

1/15/2015#13The scope of this module includes:Evolved Packet System ArchitectureControl and user plane protocolsGeneral Protocol model and Protocol interactions

After the completion of this module you will be able to:Describe the Evolved Packet System ArchitectureList the control and user plane protocols Explain the General Protocol model and the interactions between protocolsDescribe the various traffics cases in EPS

3GPP LTE and SAE & Work Items

LTE

EUTRAN Specifications(36 series)

TSG RANSpecification GroupWork ItemResult

SAE

EPC Specifications(From Rel 8 onwards)

TSG SASpecification GroupWork ItemResultLTE: Long Term EvolutionEUTRAN: Evolved UMTS Terrestrial Radio Access NetworkSAE: System Architecture EvolutionEPC: Evolved Packet Core

1/15/2015#LTE and SAE are work items or project names under 3GPP.LTE describes the new radio network, E-UTRAN.SAE is all about the new core network, the EPC. EPC is PS domain only.The whole network, E-UTRAN + EPC is known as the EPS, Evolved Packet System.

Evolved Packet System Architecture

eNB

eNB

eNB

S1 X2X2X2

SAE (System ArchitectureEvolution) LTE (Long Term Evolution)EPC (Evolved Packet Core)

E-UTRAN

EPS (Evolved Packet System)

UE

Uu

MME

MME

HSS P/S-GW P/S-GWS6a

1/15/2015#15E-UTRAN, EPC and the UE together form the Evolved Packet System. An overview of the EPC architecture and its nodes are presented in this figure.The nodes within EPC are MME (Mobility Management Entity), S-GW (Serving Gateway), P-GW (Packet Data Network Gateway) and the HSS (Home Subscriber Server).In E-UTRAN, which is the radio access network, only one node exists, the eNodeB. The interface between the eNodeBs is called X2 and the interface between the EPC and the E-UTRAN is S1.

1 liner functions of each nodeUE = User Equipment. The terminal.eNodeB evolved NodeB. Provide Wireless access to the UE. All connection: CallP, handover, resource management.MME Mobility Management Entity. Local subscription-related data for each UE (like VLR). Tracks UE location in idle mode for paging purposes. Signalling interface between eNB/S-GW/HSS.S-GW Serving Gateway. In charge of user data traffic coming from the UEs. Interfaces and switches the User Plane side of the eNodeBs (like PCF).PDN GW Packet Data Network Gateway. Assigns IP address and is anchor point to interconnect external IP networks (like PDSN).HSS Home Subscriber Server. User data repository for UEs accessing over the LTE-RAN (like HLR).PCRF Policy and Charging Rules Function. Contains policy control decision and flow-based charging control functionalities.

1/15/2015# 16Read the definitions

LTE/EPC Architecture

LTE

LTE

PDN GWServ GWPCRF

ExternalIP networksHSS

IMSMME

S1-MMES1-US10S11S5/S8SGiS6aGxRxX2

eNBeNodeB Cell resource management Broadcast information MME selection Transfer of transparent NAS signallingRouting of user data towards the S-GWIntra-LTE handover, inter-MME pool handover initiation, inter-RAT handover initiationQoS realization SecurityHSS Maintain and provide subscriptiondataUser Identification handlingAccess AuthorisationProvide Keys for Authentication and EncryptionUser Registration managementMaintain knowledge of used PDN GWMME Authentication NAS signalling GW selection Roaming (S6a to home HSS) Bearer management Idle mode tracking Paging Inter-MME and IRAT mobilityNAS Ciphering and Integrity protection S GW part In visited network in case of roaming Intra-LTE mobility anchor Packet routing & forwarding Lawful intercept LTE idle mode DL buffering Charging per UE, PDN and QCI Bearer bindings for PMIP S5/S8 PCRFProvides Service Data Flow gatingSet QoS for each Service Data FlowDefine Charging for each Service Data FlowEnables Bearer QoS ControlCorrelation between Application and Bearer chargingNotification of bearer events to application functionBearer bindings towards Serv-GW for PMIP based S5PDN GW part External IP point of interconnect IP address allocation Packet routing & forwarding Lawful intercept Policy enforcement In home or visited network

LTE

LTE

LTE

LTE

LTE

1/15/2015# 1717The Evolved Packet System (EPS) consists of a number of core network nodes and LTE radio base stations, all interconnected using IP infrastructure.

LTE is a packet-only radio access technology, also referred to as E-UTRAN, which consists of eNodeBs. The eNodeBs are in charge of: Cell resource managementBroadcast informationMME selectionTransfer of transparent NAS signalingRouting of user data towards the S-GWIntra-LTE handoverInter-MME pool handover initiationInter-RAT handover initiationQoS realization and Security

The Mobile Management Entity (MME) is in charge of: AuthenticationNAS signalingGW selectionRoaming (S6a to home HSS)Bearer managementIdle mode trackingPagingInter-MME and IRAT mobilityNAS Ciphering and Integrity protection

The HSS database holds subscription information for UE subscribing to the EPS network, it also stores the location of the UE and authentication parameters. HSS is in charge of: Maintaining and providing subscription dataUser Identification handlingAccess AuthorizationProviding Keys for Authentication and EncryptionUser Registration managementMaintaining knowledge of used PDN GW

The Serving Gateway routes the user plane communication from the UE to the PDN Gateway. The UE is attached to the same Serving Gateway during the complete session. The Serving Gateway is responsible for: In-visited network in case of roamingIntra-LTE mobility anchoringPacket routing & forwardingLawful interceptLTE idle mode DL bufferingCharging per UEPDN and QCIBearer bindings for PMIP S5/S8

The PDN Gateway sits between the internal EPS network and external data networks. The UE can be connected to several PDN Gateways simultaneously to access multiple PDNs. The PDN Gateway is responsible for: External IP point of interconnectIP address allocationPacket routing & forwardingLawful interceptPolicy enforcementIn home or visited network

The PCRF handles policy control decisions and flow-based charging control functionalities. The PCRF is responsible for: Service Data Flow gatingSetting QoS for each Service Data FlowDefining Charging for each Service Data FlowEnabling Bearer QoS ControlCorrelation between Application and Bearer chargingNotification of bearer events to application functionBearer bindings towards Serv-GW for PMIP based S5

The SASN is an optional node in the network and provides the following functions: Packet Inspection and Service ClassificationCredit ControlQuality of Service (QoS) ControlContent FilteringAccess ControlPolicy ControlContent EnrichmentTraffic RedirectionUsage Records and Security

EPS Protocol Categories

L3 SignallingL2 Transport Non Access Stratum (NAS) Communication between UE and MME Radio Resource Control (RRC) Communication between UE and eNodeB Packet Data Convergence Protocol (PDCP) - Ciphering and integrity protection for RRC messages - IP header compression/decompression for user plane Radio Link Control (RLC) - Transfer of RRC messages and user data using: * Acknowledged Mode (AM) * Transparent Mode (TM) or * Unacknowledged Mode (UM) - Error Correction (ARQ) Medium Access Control (MAC) - Error Correction (HARQ) - Transfer of RRC messages and user data using: - Priority handling (scheduling) - Transport Format selection GPRS Tunneling Protocol Control (GTP-C) - Communication between MME and SGW - Communication between SGW and PGW - Communication between MME and MME S1 Application Protocol (S1AP) Communication between eNodeB and MME X2 Application Protocol (X2AP) Communication between eNodeB and eNodeB GPRS Tunneling Protocol User (GTP-U) Transfers data between GPRS tunneling endpoints

1/15/2015#L3 signaling protocols are used to communicate between nodes using various messages with a defined structure.NAS, messages are signaling messages between UE and MME which are always transparent in the eNodeB.RRC is the control plane connection between UE and eNodeB.S1AP is the application protocol in the S1 CP.X2 is the application protocol in the X2 CP.GTP-C is the control plane protocol in the S11, S5 CP, and S10 interfaces.

L2 transport protocols are used to carry signaling and user data across the EPC interfaces.PDCP, RLC and MAC are the 3 sublayer protocols in the CP and UP between the UE and the eNodeB.GTP-U transfers the user plane data in the S1 UP and the S5 UP.

General Protocol ModelFor each layer the payload is called SDU (Service Data Unit)For each layer SDU+Protocol Header is called PDU (Packet Data Unit) Layer n PDU = Layer n+1 SDUE.g. A PDCP PDU = RLC SDU and RLC PDU = RLC Header+RLC SDU

PayloadHeaderLayer n SDU

Layer n PDULayer nLayer n+1

Layer n+1 SDU

Payload

Layer n+1 PDUHeader

1/15/2015#19This picture shows the general concept of SDUs (Service Data Units) and PDUs (Packet Data Units).For each layer, the payload is called SDU (Service Data Unit). whereas, for each layer, the payload plus the protocol header is called PDU (Packet Data Unit). For layer n, the PDU, when it is forwarded to the layer n+1, is considered payload for layer n+1 and thus it is called layer n+1 SDU. Then layer n+1 adds the protocol header for layer n+1 and the new layer n+1 PDU is created. For example, an RRC PDU is carried in a PDCP SDU. The PDCP SDU plus the PDCP header becomes the PDCP PDU. This PDCP PDU is carried in the RLC SDU, and so on...

EPS Bearer Service (S1-UP)EPS Bearer service & Signaling Connection

UE

RBSMMES/P-GW

Data Radio Bearer

Signalling Radio Bearer

NAS Signalling Connection

1/15/2015#EPS Bearer is the user plane connection between the UE and PGW.The NAS Signaling Connection is the control plane connection between the UE and the MME.It consist of the RRC connection or SRB between the UE and the eNodeB and the S1 control plane between the eNodeB and the MME.A UE having an RRC connection with the eNodeB is said to be in RRC connected state.There is no soft or softer handover for the UE in LTE.

EPS Bearer is the user plane connection between the UE and PGW.Within the EPS bearer is an ERAB between the UE and the SGW and the DRB between the UE and eNodeB.EPS bearer can be default or dedicated.Default EPS bearer has no QoS defined and is always NonGBR. There is always one default EPS bearer for a UE attached to a PDN.This gives the UE the paradigm of an always on or always ready IP connectivity.Dedicated EPS bearer can be GBR or NonGBR.A UE can have a maximum of 8 EPS bearers, 1 default and up to 7 dedicated.

UE Protocol Stack

Header Compression

TM

AM

UM

Physical LayerL2PDCPRLCMACRRCNAS

Integrity/Ciphering

System InfoAquisitionCell SelectionPaging ReceptionMobility ManagementSession ManagementConnected Mode MobilityNAS Security

IPApplicationAS SecurityRRC ConnectionRB ManagementvMeasurement Reporting

Control/Report SAPs

RA ControlHARQControl

RA ControlHARQControl

1/15/2015#21In this figure we see the UE protocol stack and the main functionality that each layer is responsible for. The Non Access Stratum, NAS, protocols are responsible for Mobility management for idle UEs, NAS Security and Session Management. The NAS messages are transported by the RRC layer either concatenated with other RRC messages, or encapsulated in dedicated RRC messages.

The Radio Resource Control, RRC layer and protocol are responsible for :Broadcast of System Information,Paging,Establishment, maintenance and release of an RRC connection between the UE and E-UTRAN,Establishment, maintenance and release of point to point Radio Bearers.Also RRC is responsible for Mobility functions including: UE measurement reporting and control of the reporting for inter-cell, I-RAT mobility, UE cell selection/reselection and UE Context transfer between eNodeBs. On the network side, the RRC layer is terminated by the eNodeB.

Packet Data Convergence Protocol, PDCP provides its services to the NAS and RRC layers at the UE or the relay at the evolved Node B. It supports the following functions:header compression and decompression of IP data flows, transfer of data,maintenance of PDCP sequence numbers for radio bearers mapped on Radio Link Control, RLC, acknowledged mode,in-sequence delivery of upper layer PDUs at Handover,duplicate elimination of lower layer SDUs at Handover for radio bearers mapped on RLC acknowledged modeciphering and deciphering of user plane data and control plane data integrity protection of control plane data.PDCP uses the services provided by the RLC layer.

Radio Link Control, RLC, protocol is responsible for data transfer in unacknowledged, acknowledged or transparent mode. For example, unacknowledged mode could be used for Voice over IP while acknowledged mode is used to carry TCP-based traffic. The transparent mode shall be only used to send RRC messages when no RLC unacknowledged or acknowledged mode entity is set up yet.

Medium Access Control, MAC, layer is responsible for Uplink/Downlink Scheduling, Link Adaptation, Preamble based Random Access, Mapping between Logical channels to Transport channels, Error Correction by means of The Hybrid ARQ (HARQ) protocol.The Physical Layer is responsible for the actual transmission over the radio interface. It is also responsible for channel coding, Modulation and the mapping between Transport Channels to Physical Channels.

Segmentation, ARQ

Ciphering

Header Compr.

Hybrid ARQHybrid ARQ

MAC multiplexing

Antenna and resrouce mappingCoding + RM Data modulation Antenna and resource mapping Coding

Modulation

Antenna and resource assignmentModulationscheme

MAC schedulerRetransmission controlPriority handling, payload selectionPayload selection

RLC#iPHYPDCP#iUser #i

User #j

MAC

Concatenation, ARQ

Deciphering

Header Compr.

Hybrid ARQHybrid ARQ

MAC demultiplexing

Antenna and resrouce mappingCoding + RM Data modulation Antenna and resource demapping Decoding

Demodulation

RLCPHYPDCP

MACeNodeBUE

Redundancy version

IP packet

IP packet

EPS bearers

E-UTRAN Radio Bearers

Logical Channels

Transport ChannelsPhysical Channels

Protocol Interaction

1/15/2015#22The protocol interaction and main functionality is illustrated in this picture. At the left side, there is the eNodeB and to the right there is the UE.Starting from top in the eNodeB, we see that PDCP performs header compression, ciphering. It also adds sequence numbers to the PDCP PDUs which are used for security algorithms and to guarantee in-sequence delivery at handovers. PDCP also provides ciphering and integrity functions. The RLC protocol may perform segmentation of large packets or concatenation of small packets. Also, ARQ (Automatic Repeat Request) is performed by this protocol. ARQ performs retransmissions of erroneously received blocks. A block is erroneous when the CRC (Cyclic Redundancy Check) at the receiver indicates an error.The MAC protocol handles scheduling of radio resources. The scheduler informs RLC of the amount of data to be sent, so that the RLC protocol can make decisions whether to perform segmentation or concatenation. MAC multiplexing is done in order to multiplex several logical channels onto transport channels.HARQ (Hybrid ARQ) is used in order to enable very rapid retransmissions over the radio interface. The scheduler controls both initial transmissions and retransmissions. The retransmissions are combined with the initial transmission. This is referred to as soft combining.Part of MAC protocol functionality is also transport format selection and link adaptation, which dynamically adapts the transport block size and modulation scheme to the current radio channel conditions. The physical layer adds the CRC to the transport block and performs Forward Error Correction, coding, modulation and the mapping of the transport block onto the physical resource blocks and mapping onto 1, 2 or 4 antennas.At the receiver side everything is done approximately in the reverse order.

UE MME Control Plane

L1

IP

SCTPS1-MMEMME

S1-AP

NAS

SCTP

L2

L1

IPeNodeBS1- APMAC

RLC

PDCPRRC

Relay

MAC

L1RLC

PDCPUE

RRC

NAS

L2

Uu

L1

1/15/2015#23The control plane signaling between the UE and the network is handled by the RRC and the NAS, Non Access Stratum, protocols.The NAS protocol is responsible for the signaling between the UE and the core network node MME. The RRC protocol is responsible for the signaling between the UE and the eNodeB, but also carries the NAS signaling over the radio interface, Uu.The control plane signaling is carried by PDCP, RLC, MAC and the physical layer over the radio interface and by the S1 Application Protocol, Stream Control Transmission Protocol (SCTP), Internet Protocol (IP) and, typically, Ethernet (layer1/layer2) over the S1 interface.

UE Packet Data NW Gateway User Plane

Serving GWPDN GWS5/S8

UDP/IPUDP/IP

L2 L2L1

L1

UDP/IP

L2

L1

GTP-U

IP

SGiS1-UUueNodeB

RLC

L2 PDCP

MAC

L1L1

PDCP

RLC

MAC

L1

IP

ApplicationUE

UDP/IP

GTP-U

Relay

GTP-U

RelayGTP-U

1/15/2015#24Over the air interface, the user plane between the UE and the packet gateway is carried by the PDCP, RLC, MAC protocols. Over S1, the user plane is carried by GTP-U (Gateway Tunneling Protocol- User plane), UDP (User Datagram Protocol), IP (Internet Protocol) and typically Ethernet (Layer1/Layer2). The end-to-end application is carried transparently in EPS over IP.In order to transmit information between the UE and the EPS, each layer sends packets to the lower layer or forwards data received from the lower layer to the upper layer. The next figure explains how each layer sends a packet to the next layer.

Summary of Core LTE Network


1/15/2015#OFDMALTE uses OFDMA(Orthogonal Frequency Division Multiplexing Access) OFDMA divides the wideband frequency channel into orthogonal Narrowband sub channels, avoiding the need for guard-bands, making it highly spectrum efficientThe spacing between the subcarriers in OFDMA is such that they can be perfectly separated at the receiver.

1/15/2015#OFDMA Continued.

1/15/2015#SC-FDMASC-FDMA is a new hybrid transmission scheme combining the low PAR single carrier methods of current systems with the frequency allocation flexibility and long symbol time of OFDMASC-FDMA is sometimes referred to as Discrete Fourier Transform Spread OFDM = DFT-SOFDM

1/15/2015#Comparing OFDM and SC-FDMAQPSK example using N=4 subcarriers

1/15/2015#Why SC-FDMA

1/15/2015#High PAPR

1/15/2015#LTE Air interface SummaryOFDM radio access technique is used in downlinkSC-FDMA in uplinkOrthogonal properties in uplink as well as in downlinkOwn cell interference is lowAdaptive modulation: QPSK, 16QAM or 64QAMMIMO technology in downlinkSupports both FDD and TDD (only FDD is covered here)Transmission modes

1

2354G1G2G1G4G5G3G4G5G2

SignalInterference

SIMO 1x2

eNodeB

TxDiv 2x2

eNodeB

MIMO 2x2

eNodeB

Stream 1Stream 1Stream 1Stream 2Rx DiversityRx DiversityMIMO

UEUEUE

20 MHz, 2x2 MIMONetwork design that maximizes both coverage and SINR is required

1/15/2015# 2011-01-11 33

LTE Throughput Calculation1 slot = 0.5ms = 1 symbol1 sub frame = 2 slots= 1 ms = 1 TT11 RB (12 sub carriers) has 1 subframe =14 slots , therefore =12x14= 168 symbols1 radio frame = 10 sub frames 1 radio frame = 1680 symbols@10 MHz = 100 RB (resource block)Therefore @ 10 MHz , 1 Radio frame =168000 symbols= 16800000 = 16.8Msps@64QAM each symbols carries 6 bits/symbol ; 16.8M x 6 = 100.8Mbps With 2x2 = 201.6 Mbps

1/15/2015#FDD Radio Frame

1/15/2015#TDD Radio Frame

1/15/2015#3 Types of OTA MessagesSIB = System Information BlockBroadcast overhead informationMonitored in both idle and traffic modes (like EvDO)Strictly speaking, SIBs are also part of RRCRRC = Radio Resource ControlBetween UE and eNBAnything to do with the radio link itself (connection setup and teardown, measurements and handover)Spec 36.331NAS = Non Access StratumBetween UE and MMEAnything to do with establishing the context (Attach i.e. registration, IP address) or mobility at the network granularity (Tracking Area) Encapsulated in RRC (either piggy-back on RRC or use Information Transfer if no RRC message is due)Spec 24.301

1/15/2015#TerminologyCQI = Channel Quality IndicatorRange 1 (worst) to 15 (best), conveys SINR to the eNB, just like DRC in EvDONot to be confused with QCI which relates to QoS prioritisation (DSCP) within the networkMCS = Modulation Coding SchemeRange 0 to 31Index from 0 to 28 for first time transmissionsAlthough index 28 not available if the maximum broadcast channel size is usedEach MCS consists of a modulation type (QPSK, 16QAM or 64QAM) and coding protection level, the combination of which decides the number of user payload bits for that schemeRoughly 13:1 (MCS 1) error correction to 1.1:1 (MCS 28)HARQ re-TX index 29, 30, 31 for 1st repeat, 2nd repeat, 3rd repeat.RB = Resource BlockIn the OFDM matrix, 1 RB is 0.5mS long x 180kHz wideScheduling BlockIn the OFDM matrix, 1 scheduling block is 1mS long x 180kHz wideMinimum amount that UE will be allocated

1/15/2015#Terminology ContTTI = Transmission Time Interval = 1mSRepresents one scheduling intervalThe minimum time a given user will be scheduled forHARQ = Hybrid Automatic Repeat reQuestPhysical layer retransmissionsThe target BLER is intended to be achieved after a given number of HARQ transmissions, unlike target PER in EvDO which is fixed at 1% and then HARQ has the potential to improve on thatBLER = Block Error RateDefault target is 10%RLC = Radio Link Control (equivalent of RLP in EvDO)Acknowledged Mode (AM) RLC cleans up the 10% BLER before passing the data to higher layersCan also be run in passthrough modes (TM=Transparent Mode and UM=Unacknowledged Mode) e.g. for streaming video where we dont want to wait for re-transmissions. TM reserved for any signalling that happens before actual RLC config has been negotiated.

1/15/2015#Terminology ContRSSI = Received Signal Strength IndicatorTotal received power of all Reference Signals as measured by the UE over all cells visible in the signal bandwidthRSRP = Reference Signal Received PowerThe average power of just the Reference Signals of the serving cellThis is the basis for intra LTE handover in our systemUsually 10 to 20dB below RSSI, depending on how many cells are influencing RSSIRSRQ = Reference Signal Received QualityRSRQ is defined as the ratio:NRSRP/(E -UTRA carrier RSSI)where N is the number of Resource Blocks of the E-UTRA carrier RSSI measurement bandwidth

1/15/2015#ISI (Inter Symbol Interference)

1/15/2015#Inter Symbol InterferenceDelay Spread is 1-2s in urban/Sub-urban environmentDelay spread is 20s in hilly environmentIf Symbol duration < Delay spread ISILTE symbol 71.4 s, with a CP of 4.7 s.For hilly we can use a CP of 16.7 s

1/15/2015#Resource Definition

1/15/2015#Resource Block

1/15/2015#

12 sub-carriers180 kHz

time

frequency

One subframe = 1 ms TTI = 14 OFDM symbols

1 sub-carrier15 KHz

One Scheduling Block

Two Resource Blocks

1 radio frame = 10 subframes

One Resource ElementLTE Radio Access Downlink

1/15/2015# 45We start with the DL frequency-time grid and pick out one of the scheduled users.

A basic definition: The smallest element or basic unit in the LTE world is an OFDM symbol or also called a resource element. Each little square in the grid here is an OFDM symbol. It is in these symbols the actual bits are coded.

The OFDM symbols are grouped together 14 at a time into a subframe which is 1ms long. Reason for this is that the scheduling of resources in LTE can be taken every 1ms. This means every OFDM symbol is about 71s long, 1ms div by 14.

Also 12 of the 15kHz sub-carriers are grouped together in the frequency domain. So now we have 180kHz times 1ms and this is called a Scheduling Block, SB. You will very often also hear something called a Resource Block, RB. That is defined as 180kHz times 0.5ms but let us here stay with Scheduling Blocks.

What I just described is for DL but this is also valid for the uplink, only difference is that the SBs must be contiguous.We have now only been looking at LTE in paired spectrum mode, that is FDD but TDD is also supported. In TDD mode the same frequency is used for DL and UL which means the switch of transmission direction has to be done and this is of course also standardized how that shall be done but please consult the literature references at the end of this tutorial.

The assignment of resources is done by the UL and DL schedulers, both placed in the eNodeB. So let us look at scheduling.

Scheduling Block

f

180 kHz

0.5ms0.5ms

Two RBs

1 ms

One Scheduling Block

1/15/2015#46IPTV Template2008-12-0946The smallest time/frequency entity that the scheduler may assign consists of twelve sub-carriers (180 kHz) in the frequency domain and a sub-frame (1ms) in time. This corresponds to two physical resource blocks that are consecutive in time and is referred to as a Scheduling Block (SB).

User 1User 2User 3User 1User 2User 3Scheduling in DL & UL

1/15/2015#47IPTV Template2008-12-0947In the downlink, the scheduler may assign a set of resource blocks to a user according to the agreed PDCCH scheme, while in the uplink, resource blocks assigned to a specific user must be contiguous in the frequency to preserve the SC-FDMA structure.

Prioritization in DL & UL

Modulation, coding

Buffer

Multiplexing

Scheduler

Buffer

Scheduler

Multiplexing

Buffer

Modulation, coding

Priority handling

Buffer

eNodeBeNodeBUEUE

StatusDownlinkUplink

1/15/2015#48IPTV Template2008-12-0948In the downlink, where the eNB has immediate access to the transmit buffers of the radio bearers, the scheduler performs the prioritization both between users and different radio bearers of a user.

In the UL on the other hand the scheduler only prioritizes between different users based on buffer status reports from the UE. The prioritization between different logical channels within one UE will be done in the UE with assistance from the network.

DL Scheduling Mechanism

CQI reporteNodeBDL schedulerUE

Reference signals

Resource allocationData

1/15/2015#49IPTV Template2008-12-0949This is the overall scheduling concept for the downlink. To support fast channel dependent link adaptation and channel dependent time and frequency domain scheduling the UE may be configured to report the Channel Quality Indicator (CQI) reports. Typically, the UE bases the CQI reports on measurements on DL reference signals. Based on the CQI reports and QoS requirements of the different logical channels the scheduler assigns time and frequency resources, i.e. scheduling blocks. The resource assignment is signaled on the Physical Downlink Control Channel (PDCCH). The UE monitors the control channels to determine if it is scheduled on the shared channel (PDSCH) and if so, what physical layer resources to find the data scheduled.

UL Scheduling Mechanism

Resource assignmenteNodeBUL schedulerUE

Scheduling Request

Buffer status reportData

Channel sounding, RSData

1/15/2015#50IPTV Template2008-12-0950This is the basic UL scheduling concept. The UE informs the scheduler when data arrives in the transmit buffer with a Scheduling Request (SR). The scheduler selects the time/frequency resources the UE shall use. With support from the link adaptation function also the transport block size, modulation, coding and antenna scheme is selected, i.e. the link adaptation is performed in the eNB.

The selected transport format is signaled together with information on the user ID to the UE. This means that the UE is mandated to use a certain transport format and that the eNB is already aware of the transmission parameters when detecting the UL data transmission. As a consequence there is no need for an UL control channel to inform the eNB. This reduces the amount of control signaling required in the uplink, which is important from a coverage perspective.

The assigned resources and transmission parameters is revealed to the UE. Additional Scheduling Information (SI) such as Buffer Status Report (BSR) may be transmitted together with data. The eNB may configure the UE to transmit a wide-band sounding reference signal that can be used for estimating the UL channel quality. Additional channel quality estimates can be obtained from other UL transmissions such as, data transmission or control signaling (CQI reports and HARQ ACK/NACK signals).

UL Scheduling AllocationWithout Time Spread AllocationUser 1User 2User 3With Time Spread AllocationUser 1User 2User 3

1/15/2015#51IPTV Template2008-12-0951To increase capacity and coverage, Time Spread Allocation Scheduling is used in uplink. This enables multiple user equipment to be scheduled in one subframe by distributing one user equipment transmission over several subframes, but at a lower bandwidth. This leads to an improved link budget and improved capacity and coverage.

Semi-persistent Scheduling

Semi-persistent transmission resources for first attempts

Potential HARQ retransmissions (dynamic scheduling)

High signaling overheadLimit load for regular arrival rate sources

1/15/2015#52IPTV Template2008-12-0952Fully dynamic scheduling allows for flexibility but it also leads to high signaling overhead as a grant needs to be signaled in each scheduling instance, for example for each VoIP packet in case of VoIP. To limit the signaling load for sources with regular arrival rate a concept referred to as semi-persistent scheduling has been agreed in 3GPP. The idea is to assign resources on a long-term basis. The eNB assigns semi-persistently time and frequency resources for the initial transmission attempts. All HARQ retransmissions are scheduled dynamically.

Reference Signals and Channel Estimation

1/15/2015#Reference Signals and Channel Estimation

1/15/2015#Synchronization and Cell Search

1/15/2015#Primary and secondary synchronization signals (PSS & SSS) in LTE

Cell synchronization is the very first step when UE wants to camp on any cell. From this, UE acquires physical cell id (PCI), time slot and frame synchronization, which will enable UE to readsystem informationblocks from a particular network.

UE will tune it radio turn by turning to different frequency channels depending upon which bands it issupporting. Assuming that it is currently tuned to a specific band / channel, UE first finds the primarysynchronization signal (PSS) which is located in the last OFDM symbol of first time slot of the first subframe (subframe 0) of radio frame as shown in figure (green squares). This enables UE to be synchronized on subframe level. The PSS is repeated in subframe 5 which means UE is synchronized on 5ms basis since each subframe is 1ms. From PSS, UE is also able to obtain physical layer identity (0 to 2).

In the next step UE finds the secondary synchronization signal (SSS). SSS symbols are also located in the same subframe of PSS but in the symbol before PSS as shown in the figure(yellow squares). From SSS, UE is able to obtain physical layer cell identity group number (0 to 167).

Using physical layer identity and cell identity group number, UE knows the PCI for this cell now. In LTE 504 physical layer cell identities (PCI) are allowed and are divided into unique 168 cell layer identity groups where each group consist of three physical layer identity. As mentioned earlier, UE detects physical layer identity from PSS and physical layer cell identity group from SSS. Assuming physical layer identity = 1 and cell identity group=2 then the PCI for given cell is

PCI = 3*(Physical layer cell identity group)+ physical layer identity = 3*2+1 = 7

Once UE knows the PCI for a given cell, it also knows the location of cell Reference signals as shown in figure (red and black squares). Reference signals are used in channel estimation, cell selection / reselection and handover procedures.

55

UL-SCH

Channel Mapping*

PCHDL-SCH

PCCHLogical Channels type of information (traffic/control)Transport Channelshow and with what characteristics (common/shared/mc/bc)DownlinkUplink

PDSCHPhysical Channelsbits, symbols, modulation, radio frames etc

MTCH

MCCH

BCCH

DTCH

DCCH

DTCH

DCCH

CCCH

PRACH

RACH

CCCH

MCH

BCH

PUSCH

PBCH

PCFICH

PUCCH-CQI -ACK/NACK-Sched req.-Sched TF DL-Sched grant UL-Pwr Ctrl cmd-HARQ infoMIB SIB

PMCH

PHICH

PDCCHACK/NACKPDCCH info

Physical Signalsonly L1 info

RS

SRS

P-SCH

S-SCH

RS-meas for DL sched -meas for mobility-coherent demod-half frame sync-cell id -frame sync-cell id group -coherent demod-measurements for UL schedulingKey channels in redChannel Mapping

1/15/2015#Layer 1 DL Phy Control Channel

1/15/2015#Layer 1 Uplink Phy Control Channel

1/15/2015#

PDCCH**Physical Downlink Control ChannelCarries Downlink scheduling assignmentsPDSCH resource indicationTransport formatHybrid-ARQ informationTransport block sizeMIMO-related control information PUCCH power control commandsCarries Uplink scheduling grantsPUSCH resource indicationTransport formatHybrid-ARQ related informationPUSCH power control commands

1/15/2015#PUCCH**Physical Uplink Control ChannelCarries uplink control informationNever transmitted simultaneously with PUSCH dataPUCCH conveys control information includingChannel quality indication (CQI)ACK/NACKHARQUplink scheduling requestsPUCCH transmission is frequency hopped at the slot boundary

1/15/2015#Modulation Schemes

1/15/2015#CQI-to-SINR Mapping Table

CQI-to-SINR Mapping

1/15/2015#System InformationSIB Channel ListSIB1Access related parameters (e.g. Whether UE is permitted to camp on the cell)Scheduling details for other SIBsCell Identity unique identity (28 bits)SIB2Common and shared channel information (access barring information, random access, physical layer parameters)SIB3Cell reselection informationSIB4Intra frequency LTE neighbors - non standard configurationsSIB5Inter frequency LTE neighborsSIB6IRAT cell reselection to UTRANSIB7IRAT cell reselection to GSMSIB8IRAT cell reselection to CDMA2000 SIB9Home eNode B informationSIB10ETWS Primary Notification SIB11ETWS Secondary Notification

1/15/2015#Earthquake and Tsunami Warning System (ETWS63

LTEInitial Cell Access StepsInitial access procedure for LTE has three steps Cell SearchDetecting cell reference symbols

System Information DetectionReceiving information about the cell and its neighbors

Random Access Accessing the cell to Tx and Rx data

Poweron

Initial cellsearch

DetectSystemInformation

RandomAccess

Tx and RxUser data

1/15/2015#MIB, SIB1, SIB2 and 3 examplesNote how SIBs 2 and 3 are bundled in one System Information message

1/15/2015#

ECM-IDLEEMM-DEREGISTERED

MMETracking Area (TA)

UE positionnot known in network

Signaling connection establishmentSignaling connection releaseAttach accept, TAU acceptDetach, Attach reject, TAU rejectEMM-REGISTEREDECM-CONNECTED

HandoverPLMN selectionUE position known on Cell level in eNodeBUE pos known on TA level in MMEeNB

RRC_IDLERRC_IDLERRC_CONNECTED

ECM: EPC Connection ManagementEMM: EPC Mobility ManagementRRC: Radio Resource ManagementProtocol states and Mobility*

TAUmessageProtocol states and mobility

1/15/2015#AttachEquivalent to the combined steps of getting a session and PPP (IP address) in EvDOOn the data dongles, this is triggered by Connecting using the dialler software that comes with the cardE.G LG Connection Manager

1/15/2015#Sample Attach in LLDM (LGs tool)

Some NAS piggy-backed with RRC (RRC_ConnectionRequest in this case)NAS sent in InformationTransfer

1/15/2015# 68SIBs shown once each by toolRRC vs NAS

1/15/2015#Idle Mobility and PagingOnce attached, UE may now move from cell to cell in idle mode according to the Cell Reselection thresholds conveyed in SIB3If the UE encounters a new TAC (Tracking Area Code), it will send a TAU (Tracking Area Update) to notify the MME of its new location.Cf. paging zone in 1xThere is also a timer based update (based on timer T3412 which is in turn based on parameter S1_MobileReachableTimer)If MME has not heard from UE for S1_ImplicitDetachTimer, it will implicitly detach it with notifyingAn example paging scheme could be:Last visited eNB: 1 attemptsLast visited TA: 1 attemptsTAI List: 2 attemptsWhere TAI List can be setup as currentAndLastTai i.e. the last visited and the one beforeUEs only wake up on a DRX Cycle (parameter defaultPagingCycle, like SCI) and monitor specific PO (Paging Offset) according to a formula that includes their IMSI to seed the calculation.A Paging Indicator Channel is used (like Quick Paging in 1xRTT)DRX in Connected Mode arrives in L11B (allows battery saving)

1/15/2015#Page Message ExampleDay 1142100:23:52.045 [00]0xB0C0 LTE RRC OTA Packet -- PCCHPkt Version = 1RRC Release Number.Major.minor = 8.7.0Radio Bearer ID = 0, Physical Cell ID = 383Freq = 5230SysFrameNum = 732, SubFrameNum = 9PDU Number = PCCH Message, Msg Length = 9Interpreted PDU:value PCCH-Message ::= { message c1 : paging : { pagingRecordList { { ue-Identity s-TMSI : { mmec '10101001'B, m-TMSI '11110000 00011011 01001011 11100100'B }, cn-Domain ps } } }}

1/15/2015#Connection Setup: RACH ProcessRandom Access Preambles sent to:Establish UL timingFirst step of requesting access to the networkNo message content at this stepInitial power based on:Ref Signal power (in SIB)Allows pathloss calcTarget UL power at eNBPower ramping, similar to 1x/DO, is used when a RA burst fails (i.e. no RA Response to RA Preamble)SIB2 has datafill for power step, number of steps etc.Will hear the RACH steps referred to as Message 1, Message 2 etc.Message 3 carries the RRC Connection RequestCBRA

Random Access Preamble

1

Random Access Response

RA Preamble Assignment

2

0UEeNB

Scheduled TransmissionRRC Connect Request

Contention Resolution

3

4

HARQ

HARQ

MME

L2/L3 Message

L2/L3 MessageResponse

RRC Connect ResponseCFRA

Connection Request not in initial probe (unlike DO/1x)

1/15/2015# 72Connection Request not in probe (unlike EvDO)

LTE Random AccessApplication of CBRA and CFRARA ScenarioCBRACFRAInitial access from RRC_IDLEInitial access after radio link failureHandover requiring random access procedureDL data arrival Requiring UL resyncUL data arrival Requiring UL resync

Random Access procedures takes two distinct formsCBRA ( Applicable to all 5 eventsCFRA (applicable to only handover and DL data arrival)Normal DL/UL transmission can only take place after RA procedures.

1/15/2015#Connection Setup: RRC{ message c1 : rrcConnectionRequest : { criticalExtensions rrcConnectionRequest-r8 : { ue-Identity s-TMSI : { mmec '00000010'B, m-TMSI '11110000 00000000 00111010 01110001'B }, establishmentCause mo-Data, spare '0'B } }}{ message c1 : rrcConnectionSetupComplete : { rrc-TransactionIdentifier 0, criticalExtensions c1 : rrcConnectionSetupComplete-r8 : { selectedPLMN-Identity 1, registeredMME { mmegi '10000000 00000010'B, mmec '00000010'B }, dedicatedInfoNAS '17CC8ECC68060748000BF6030246800202 ...'H } }}{ message c1 : rrcConnectionSetup : { rrc-TransactionIdentifier 0, criticalExtensions c1 : rrcConnectionSetup-r8 : { radioResourceConfigDedicated { srb-ToAddModList { { srb-Identity 1, rlc-Config explicitValue : am : { ul-AM-RLC { t-PollRetransmit ms45, pollPDU pInfinity, pollByte kBinfinity, maxRetxThreshold t32 }, dl-AM-RLC { t-Reordering ms35, t-StatusProhibit ms0 } }, logicalChannelConfig explicitValue : { ul-SpecificParameters { priority 1, prioritisedBitRate infinity, bucketSizeDuration ms50, logicalChannelGroup 0 } } } }, mac-MainConfig explicitValue : { ul-SCH-Config { maxHARQ-Tx n4, periodicBSR-Timer sf5, retxBSR-Timer sf320, ttiBundling FALSE }, timeAlignmentTimerDedicated sf5120, phr-Config setup : { periodicPHR-Timer sf200, prohibitPHR-Timer sf200, dl-PathlossChange dB3 } }, physicalConfigDedicated { pdsch-ConfigDedicated { p-a dB-3 }, pusch-ConfigDedicated { betaOffset-ACK-Index 10, betaOffset-RI-Index 9, betaOffset-CQI-Index 10 }, cqi-ReportConfig { cqi-ReportModeAperiodic rm30, nomPDSCH-RS-EPRE-Offset 0, cqi-ReportPeriodic setup : { cqi-PUCCH-ResourceIndex 0, cqi-pmi-ConfigIndex 37, cqi-FormatIndicatorPeriodic widebandCQI : NULL, ri-ConfigIndex 322, simultaneousAckNackAndCQI FALSE } }, antennaInfo explicitValue : { transmissionMode tm3, codebookSubsetRestriction n2TxAntenna-tm3 : '11'B, ue-TransmitAntennaSelection release : NULL }, schedulingRequestConfig setup : { sr-PUCCH-ResourceIndex 0, sr-ConfigIndex 6, dsr-TransMax n64 } } } } }}

Encapsulated NAS msgNo way to know who this subscriber is from this msg alone (since TMSI)Connection Setup mainly defines a signalling radio bearer and some CCH config

1/15/2015#Connection Setup ContFull connection setup:Reconfiguration step defines measurements and actual traffic bearer

1/15/2015#Neighbour Identity and Neighbour ListsNeighbours are identified over the air by a PCI = Physical Cell IdentifierRange 0 to 503No equivalent of pilot increment required i.e. all 504 are available for use, although there are some recommendations for PCI planning to speed up the search processThey are not based on timing offsets so no equivalent of PN aliasingThe Reference Signals carry this informationInternally to the eNB there is a neighbour list where they are mapped to a full cell identifier (to resolve PCI re-use)UEs can search all possible PCIs very quickly so:Neighbour lists are not required to be broadcast over the air!i.e. SIB 4 is optional (and was not used in Bell trial)In fact we want UEs to search and report on all PCIs to support Automatic Neighbour Relations (ANR) feature (see later slides on ANR)Beware the usage of the term Cell. In 3GPP a Cell is a Sector so one Site normally has 3 Cells per frequencySo Physical Cell Identifier does define right down to the sector level (1 site has 3 PCIs)

1/15/2015#MOSHELL Nbr List DUmpHAMe011405541================= 832 ENodeBFunction=1,EUtranCellFDD=HAMe011405541,EUtranFreqRelation=1,EUtranCellRelation=HAMe011410721 833 ENodeBFunction=1,EUtranCellFDD=HAMe011405541,EUtranFreqRelation=1,EUtranCellRelation=HAMe011413302 834 ENodeBFunction=1,EUtranCellFDD=HAMe011405541,EUtranFreqRelation=1,EUtranCellRelation=HAMe011407832 835 ENodeBFunction=1,EUtranCellFDD=HAMe011405541,EUtranFreqRelation=1,EUtranCellRelation=HAMe011409712 836 ENodeBFunction=1,EUtranCellFDD=HAMe011405541,EUtranFreqRelation=1,EUtranCellRelation=HAMe011409761 837 ENodeBFunction=1,EUtranCellFDD=HAMe011405541,EUtranFreqRelation=1,EUtranCellRelation=HAMe011406622 838 ENodeBFunction=1,EUtranCellFDD=HAMe011405541,EUtranFreqRelation=1,EUtranCellRelation=HAMe011410722 839 ENodeBFunction=1,EUtranCellFDD=HAMe011405541,EUtranFreqRelation=1,EUtranCellRelation=HAMe011405542 840 ENodeBFunction=1,EUtranCellFDD=HAMe011405541,EUtranFreqRelation=1,EUtranCellRelation=HAMe011409762 841 ENodeBFunction=1,EUtranCellFDD=HAMe011405541,EUtranFreqRelation=1,EUtranCellRelation=HAMe011409713 842 ENodeBFunction=1,EUtranCellFDD=HAMe011405541,EUtranFreqRelation=1,EUtranCellRelation=HAMe011409711 843 ENodeBFunction=1,EUtranCellFDD=HAMe011405541,EUtranFreqRelation=1,EUtranCellRelation=HAMe011405543 844 ENodeBFunction=1,EUtranCellFDD=HAMe011405541,EUtranFreqRelation=1,EUtranCellRelation=HAMe011407831HAMe011405542==============880 ENodeBFunction=1,EUtranCellFDD=HAMe011405542,EUtranFreqRelation=1,EUtranCellRelation=HAMe011405543 881 ENodeBFunction=1,EUtranCellFDD=HAMe011405542,EUtranFreqRelation=1,EUtranCellRelation=HAMe011409762 882 ENodeBFunction=1,EUtranCellFDD=HAMe011405542,EUtranFreqRelation=1,EUtranCellRelation=HAMe011405541 883 ENodeBFunction=1,EUtranCellFDD=HAMe011405542,EUtranFreqRelation=1,EUtranCellRelation=HAMe011409712 884 ENodeBFunction=1,EUtranCellFDD=HAMe011405542,EUtranFreqRelation=1,EUtranCellRelation=HAMe011413302 885 ENodeBFunction=1,EUtranCellFDD=HAMe011405542,EUtranFreqRelation=1,EUtranCellRelation=HAMe011409761 886 ENodeBFunction=1,EUtranCellFDD=HAMe011405542,EUtranFreqRelation=1,EUtranCellRelation=HAMe011410722 887 ENodeBFunction=1,EUtranCellFDD=HAMe011405542,EUtranFreqRelation=1,EUtranCellRelation=HAMe011409711 888 ENodeBFunction=1,EUtranCellFDD=HAMe011405542,EUtranFreqRelation=1,EUtranCellRelation=HAMe011413303 889 ENodeBFunction=1,EUtranCellFDD=HAMe011405542,EUtranFreqRelation=1,EUtranCellRelation=HAMe011410721

1/15/2015#Intra-LTE Mobility Solution3 Types of Intra-LTE HandoverEvolved Packet Core

S1S1S1X2Intra RBS handoverRBS

MMES-GW

X2 handoverS1 handover

1/15/2015#Intra-LTE HandoverX2 Handover Preparation

UE measures RSRP & RSRQ

1/15/2015#X2 Handover Execution & Completion

~20 ms serviceinterruptionData ForwardingLower Outage Time

Source eNode BMaintains UE context info for short time

1/15/2015#Intra-Freq (Intra-LTE) HandoffsNo soft handoffUEs searching all PCIsMeasurements are reported to eNB based on EventsOur intra-freq handover uses event a3:Start reporting when neigh > serving by X dB for timeToTriggerStop reporting when neigh < serving by Y dB for timeToTrigger (normally doesnt happen since handover already occurred)X and Y determined by the combination of Offset and Hysteresis parametersPay attention to Meas-Id (ANR vs HO)RSRP = Reference Signal Received PowerThe average power of just the Reference Signals of the serving cellThis is the basis for intra LTE handover in our systemUsually 10 to 20dB below RSSI, depending on how many cells are influencing RSSIRSRQ = Reference Signal Received QualitySome debate on how this should be measured and not clear how UEs are doing it!Not used for handovereNBs negotiate the handover between themselvesCan be over X2 or via S1 interfacesOnly as a last step is the MME truly involved when it is informed that the data path needs to switch to the target eNBUE goes through a full RACH process to acquire target cellSpecial Contention Free process is reserved for this

1/15/2015#LTE Handover PARAMETERS**ParametersA3offset The offset value for EventA3. triggerQuantityA3 The quantity that triggers the EventA3 (RRSP or RSRQ)hysteresisA3 The hysteresis value for EventA3.timeToTriggerA3 The time the EventA3 criterion has to be fulfilled before the first measurement report is sent.reportQuantityA3 The quantities to include in the measurement report.reportIntervalA3 The interval for event triggered periodic measurement reports.reportAmountA3 Indicates the number of reports to send when EventA3 is triggered.

1/15/2015#Sample Measurement configExtracted from: rrcConnectionReconfiguration reportConfigToAddModList { { reportConfigId 1, reportConfig reportConfigEUTRA : { triggerType event : { eventId eventA3 : { a3-Offset 0, reportOnLeave FALSE }, hysteresis 8, timeToTrigger ms40 }, triggerQuantity rsrp, reportQuantity both, maxReportCells 4, reportInterval ms480, reportAmount infinity } },

a3Offset: set to 0 for Bell trialA3 hysteresis: 8 = 4dBA3 timeToTrigger 40mSOther reporting criteria

1/15/2015#Sample Measurement Report================================================================================2010/11/11 11:08:00.840 0xB469 RRC message 3(ASN.1) (Not Verified Yet.......... LOG_CH_TYPE = 1 (0x01) LENGTH = 8 (0x0008) SIG_MSG = 08 19 A4 88 00 49 A8 88 ================================================================================ Channel Type = UL_DCCH, Message Length = 8 Interpreted PDU:value UL-DCCH-Message ::= { message c1 : measurementReport : { criticalExtensions c1 : measurementReport-r8 : { measResults { measId 1, measResultServCell { rsrpResult 36, rsrqResult 34 }, measResultNeighCells measResultListEUTRA : { { physCellId 18, measResult { rsrpResult 40, rsrqResult 34 } } } } } }}Current Cell (PCI not given)Neighbour Cell PCI18Neighbour Cell is 4dB stronger (rrsp 40 vs 36)

1/15/2015#Sample Measurement Reports for ANR{ message c1 : measurementReport : { criticalExtensions c1 : measurementReport-r8 : { measResults { measId 20, measResultServCell { rsrpResult 32, rsrqResult 34 }, measResultNeighCells measResultListEUTRA : { { physCellId 24, measResult { rsrpResult 37, rsrqResult 34 } } } } } }}{ message c1 : measurementReport : { criticalExtensions c1 : measurementReport-r8 : { measResults { measId 1, measResultServCell { rsrpResult 34, rsrqResult 34 }, measResultNeighCells measResultListEUTRA : { { physCellId 24, measResult { rsrpResult 40, rsrqResult 34 } } } } } }}MeasId 20 is purely for ANR and does not trigger handoverMeasId 1 does trigger handover

1/15/2015#Handover Diagram

1/15/2015#Event A3: Entry and leave criteria

1/15/2015#Sample Handover MessagesNote how rrcConnectionReconfiguration used here (as well as connection setup)

1/15/2015#

1/15/2015#Dormancy TimerReturn to idle is controlled by the dormancy timer:tInactivityTimerRemember there are no physical resources (like CEs, Mac Index) reserved so less penalty than in EvDO for hanging on to a connectionDefault value 61 secs (!) but Vz using 10 secsHaving said that, beware there are limits on the number of connected users (R&D constraint)Improving over the future releasesE/// view (200 per DUL in L11 but projected at 3000 in L13)

1/15/2015#Call Drop Rules: eNB sideOn the eNB, there are 2 cases that will lead to Call Drop declaration:1. RLC failureThis occurs when maximum retransmission has occurred at RLC level (ARQ). Parameters in eNB:MO: SignalingRadioBearer/DataRadioBearerAttributes: dlMaxRetxThreshold/ulMaxRetxThreshold

2. L1 Sync lost (Time Alignment)When UL Timing loses sync Parameters in eNB:MO: MacConfiguration Attribute: tTimeAlignmentTimer

1/15/2015#Call Drop Rules: UE sideAs defined in 3GPP specsNot known if UEs have any proprietary rules36.133 defines Qout and Qin which are signal quality levels at which the UE judges the PDCCH is lost/re-acquired respectively36.213 then describes how these thresholds are used to provide notification of in/out of sync to higher layersFinally 36.331 describes how timer T310 and counters N310 and N311 are applied. In summary:If N310 consecutive out of sync received, start timer T310If N311 consecutive in sync received, stop T310If T310 expires, declare call dropDefault settings are:t310 ms2000n310 n20n311 n1See attached 3GPP specification sections for more details:

1/15/2015#SIB3 and 8 Examples sib8 : { searchWindowSize 10, parametersHRPD { preRegistrationInfoHRPD { preRegistrationAllowed FALSE }, cellReselectionParametersHRPD { bandClassList { { bandClass bc1, cellReselectionPriority 2, threshX-High 16, threshX-Low 14 } }, neighCellList { { bandClass bc1, neighCellsPerFreqList { { arfcn 775, physCellIdList { 284 } } } } }, t-ReselectionCDMA2000 5 } } } sib3 : { cellReselectionInfoCommon { q-Hyst dB4 }, cellReselectionServingFreqInfo { s-NonIntraSearch 0, threshServingLow 31, cellReselectionPriority 7 }, intraFreqCellReselectionInfo { q-RxLevMin -60, s-IntraSearch 31, allowedMeasBandwidth mbw6, presenceAntennaPort1 FALSE, neighCellConfig '01'B, t-ReselectionEUTRA 2 } }


1/15/2015#Network Optimization FlowchartPage 95New site on airSingle siteverificationAre clustersready?RF optimizationService test and parameter optimizationAre KPI requirements met?NoYesYesNoEnd

1/15/2015#95

Network Optimization ProcessSingle site verificationValidate that no alarms are presentValidate antenna azimuth, tilt and height are per RF designReview and validate sweep and PIM test reportsAll parameters are correctly configured (Vendor Golden parameters)NeighborList (PCI), Power parameters, Handover parameters.Execute functional call test on each siteRF optimizationRF (or cluster) optimization starts after all sites in a planned area are installed and verified. RF optimization aims to make sure that RF environment is at its bestInterference minimizedDominant server Neighbor relations are correctCoverage holes are identified and eliminatedObjective is to meet desired KPIs ( accessibility, Retainability, Handover Success Rate and throughput)Page 96

1/15/2015#96

RF Optimization FlowchartPage 97

1/15/2015#97

Preparations for RF OptimizationPage 98ChecklistNetwork plan, network structure diagram, site distribution, site information, and engineering parametersDrive test results (such as service drop points and handover failure points) in the current areaReference signal received power (RSRP) coverage plotSignal to interference plus noise ratio (SINR) distribution plotMeasured handover success rates and related KPIs.Areas to be optimized can be determined by comparing the distribution of RSRPs, SINRs, and handover success rates with the optimization baseline.

1/15/2015#Network Optimization MethodsPage 99RF optimization involves adjustment of azimuths, tilts, antenna height, eNodeB transmit power, feature algorithms, and performance parameters. Optimization methods in different standards are similar, but each standard has its own measurement definition.

Network OptimizationAzimuth AdjustmentTilt Adjustment Feature ConfigurationReselection and Handover Parameter AdjustmentPower AdjustmentAntenna Height


1/15/2015#LTE RF Optimization Objects and Target Baseline Page 101What are differences between LTE and 3G optimization?

TextRSRP

SINRHandover success rateHow are these counters defined?

LTE optimization objects

1/15/2015#RSRPRSRPs near a cell, in the middle of a cell, and at the edge of a cell are determined based on the distribution of signals on the entire network.Generally, the RSRP near a cell is -85 dBm, the RSRP in the middle of a cell is -95 dBm, and the RSRP at the edge of a cell is -105 dBm. Currently, the minimum RSRP for UEs to camp on a cell is -120 dBm.Empirical RSRP at the edge of a cell:The RSRP is greater than -110 dBm in 99% areas at the TD-LTE site in Norway.The RSRP is greater than -110 dBm in 98.09% areas in the Huayang field in Chengdu.Page 102

Reference signal received power (RSRP), is determined for a considered cell as the linear average over the power contributions (in [W]) of the resource elements that carry cell-specific reference signals within the considered measurement frequency bandwidth.

3GPP definition

1/15/2015#SINRThe SINR is not specifically defined in 3GPP specifications. UEs typically use SINR to calculate the CQI (Channel Quality Indicator) and it report to the network.

SINR = S/(I + N) S: indicates the power of measured usable signals. Reference signals (RS) and physical downlink shared channels (PDSCHs) are mainly involved. I: indicates the power of measured signals or channel interference signals from other cells in the current system and from inter-RAT cells. N: indicates background noise, which is related to measurement bandwidths and receiver noise coefficients.

Empirical SINR at the edge of a cell: The SINR is greater than -3 dB in 99% areas in Norway. The SINR is greater than -3 dB in 99.25% areas in the Huayang field in Chengdu.Page 103

1/15/2015#RSRQ is a measure of signal quality. It is measured by the UE and reported back to the network to aid in the handover procedure. For those used to working in UMTS WCDMA is it equivalent to CPICH Ec/N0. Unlike UTMS WCDMA though it is not used for the process of cell selection and reselection (at least in the Rel08 version of the specs).

The 3GPP spec description is"RSRQ (Reference Signal Received Quality) is defined as the ratio:NRSRP/(E -UTRA carrier RSSI)where N is the number of Resource Blocks of the E-UTRA carrier RSSI measurement bandwidth.

Finally SINR is a measure of signal quality as well. Unlike RSRQ, it is not defined in the 3GPP specs but defined by the UE vendor. It is not reported to the network. SINR is used a lot by operators, and the LTE industry in general, as it better quantifies the relationship between RF conditions and throughput. UEs typically use SINR to calculate the CQI (Channel Quality Indicator) they report to the network.

The components of the SINR calculation can be defined as:

S: indicates the power of measured usable signals. Reference signals (RS) and physical downlink shared channels (PDSCHs) are mainly involved

I: indicates the power of measured signals or channel interference signals from other cells in the current system

N: indicates background noise, which is related to measurement bandwidths and receiver noise coefficients

So that is it! I have also included a real life measurement from a Sierra Wireless card that includes the above mentioned metrics so you can see what is the typical output from a UE. Using that and the table above you should be able to deduce the RF condition category it is in at the time of measurement.103

Handover Success RateAccording to the signaling process in 3GPP TS 36.331, eNodeB statistics(1) Handover success rate = Number of handovers/Number of handover attempts x 100%(2) Number of handover attempts: indicates the number of eNodeB-transmitted RRCConnectionReconfiguration messages for handovers.(3) Number of handovers: indicates the number of eNodeB-received RRCConnectionReconfigurationComplete messages for handovers.

Handover success rate The handover success rate is greater than 97% at the TD-LTE site in Norway. The handover success rate is 100% in the Huayang field in Chengdu.Page 104

1/15/2015#DL Power AdjustmentCell specific reference signals (RS) are embedded into the overall signal bandwidth.RS are the highest powered component within the DL signal.The power level of the reference signal is signaled within system information to the device, it is cell-specific, and is in the range of -60 to +50 dBm per 15 kHz.It is a requirement that the LTE base station transmits all reference signals with constant power over the entire bandwidth. The power of all other signal components (synchronization signals, PBCH, PCFICH, PDCCH, PDSCH and PHICH) is set relative to this value.There are OFDM symbols that do contain RE carrying RS and there are that dont, the power implications differ in those cases.The relative PDSCH power for those symbols is given by two different parameters pAand pB.

Subcarriers share the transmit power of an eNodeB, and therefore the transmit power of each subcarrier depends on the configured system bandwidth (such as 5 MHz and 10 MHz). A larger bandwidth will result in lower power of each subcarrier. LTE uses PA and PB parameters to adjust power.A: indicates the ratio of the data subcarrier power of OFDM symbols excluding pilot symbols to the pilot subcarrier power.B: indicates the ratio of the data subcarrier power of OFDM symbols including pilot symbols to the pilot subcarrier power.

Definitions in 3GPP specifications

1/15/2015#DL Power AdjustmentFor the majority of cases pAcorresponds to the parameter PA, that is signaled via higher layers. Only for some special cases, like transmit diversity with four antennas or Multi-user MIMO, pAis computed differently. PAis device specific, comes as part of the RRCConnectionSetup message, and can take one out of eight different valuesPBis related to the cell-specific RS power and can not be changed dynamically. It can take one out of four integer values. Depending on the number of used transmit antennas (1, 2 or 4) each value corresponds to a certain ratio and thus power offset.LTE networks that are currently deployed worldwide are supporting 2x2 MIMO. Lets assume PB= 3. In that case the RE carrying data in that OFDM symbol where RS are present, are transmitted with an additional offset of 3 dB compared to symbols without RS [Ref.3]. For only one transmit antenna (SISO) PB= 3 translates to -3.98 dB.

1/15/2015#Why is DL Power Adjustment necessary?The overall goal is to have a constant power for all OFDM symbols to avoid power variations at the receiver (UE). With less PDSCH power given by PBthe boost of reference signals is compensated, compared to OFDM symbols that do not contain reference signals. The PDSCH power depends always on the allocation, i.e. the number of allocated Resource Blocks (RB). Allocation can change from subframe to subframe, thus PAcan also change on a 1 millisecond basis. While incorporating PAand PBit is ensured that the overall OFDM symbol power remains constant, even when the PDSCH allocation is changed.

1/15/2015#Classification of Coverage Problems (RSRP is mainly involved) Page 108Lack of a dominant cell

Imbalance between uplink and downlinkCross coverageWeak coverage and coverage holes

Continuous coverage must be ensured.The actual coverage must be consistent with the planned one to prevent service drops caused by isolated islands during handovers.Uplink and downlink losses must be balanced to resolve uplink and downlink coverage problems. Each cell on a network must have a dominant coverage area to prevent frequent reselections or handovers caused by signal changes.

1/15/2015#Factors Affecting CoveragePage 109

1Downlink:Equivalent isotropic radiated power (EIRP)Total transmit powerCombining lossPath loss (PL)Frequency bandDistance between a receive point and an eNodeBScenarios (urban and suburban areas) and terrains (plains, mountains, and hills) of electric wave propagationAntenna gainAntenna heightAntenna parameters (antenna pattern)Antenna tiltAntenna azimuth

2Uplink:eNodeB receiver sensitivityAntenna diversity gainUE transmit powerPropagation loss of uplink radio signalsImpact of tower-mounted amplifiers (TMAs) on uplink

1/15/2015#Weak Coverage and Coverage Holes Page 110

The signal quality in cells is poorer than the optimization baseline in an area. As a result, UEs cannot be registered with the network or accessed services cannot meet QoS requirements.

If there is no network coverage or coverage levels are excessively low in an area, the area is called a weak coverage area. The receive level of a UE is less than its minimum access level (RXLEV_ACCESS_MIN) because downlink receive levels in a weak coverage area are unstable. In this situation, the UE is disconnected from the network. After entering a weak coverage area, UEs in connected mode cannot be handed over to a high-level cell, and even service drops occur because of low levels and signal quality.

Weak coverageCoverage holes

1/15/2015#Resolving Weak Coverage Problems Page 111Analyze geographical environments and check the receive levels of adjacent eNodeBs.Analyze the EIRP of each sector based on parameter configurations and ensure EIRPs can reach maximum values if possible.Increase pilot power.Adjust antenna azimuths and tilts, increase antenna height, and use high-gain antennas.Deploy new eNodeBs if coverage hole problems cannot be resolved by adjusting antennas.Increase coverage by adjacent eNodeBs to achieve large coverage overlapping between two eNodeBs and ensure a moderate handover area.Note: Increasing coverage may lead to co-channel and adjacent-channel interference.Use RRUs, indoor distribution systems, leaky feeders, and directional antennas to resolve the problem with blind spots in elevator shafts, tunnels, underground garages or basements, and high buildings. Analyze the impact of scenarios and terrains on coverage.

1/15/2015#Case: Searching for a Weak Coverage Area by Using a Scanner or Performing Drive Tests on UEsPage 112

Weak coverage area

Perform drive tests in zero-load environments to obtain the distribution of signals on test routes. Then, find a weak coverage area based on the distribution, as shown in the figure. Adjust RF parameters of the eNodeB covering the area.

1/15/2015#Lack of a Dominant Cell Page 113

In an area without a dominant cell, the receive level of the serving cell is similar to the receive levels of its neighboring cells and the receive levels of downlink signals between different cells are close to cell reselection thresholds. Receive levels in an area without a dominant cell are also unsatisfactory. The SINR of the serving cell becomes unstable because of frequency reuse, and even receive quality becomes unsatisfactory. In this situation, a dominant cell is frequently reselected and changed in idle mode. As a result, frequent handovers or service drops occur on UEs in connected mode because of poor signal quality. An area without a dominant cell can also be regarded as a weak coverage area.

Lack of a dominant cell

1/15/2015#Resolving Problems with Lack of a Dominant Cell Page 114Adjust engineering parameters of a cell that can optimally cover the area as required.Determine cells covering an area without a dominant cell during network planning, and adjust antenna tilts and azimuths to increase coverage by a cell with strong signals and decrease coverage of other cells with weak signals.

1/15/2015#Case: Searching for an Area Without a Dominant Cell

SymptomUEs frequently perform cell reselections or handovers between identical cells.AnalysisAnalysis can be based on signaling procedures and PCI distribution.According to PCI distribution shown in the figure, PCIs alternate in two or more colors if there is no dominant cell.SolutionAccording to the coverage plan, cell 337 is a dominant cell covering the area and cell 49 also has strong signals. To ensure handovers between cells 337 and 49 at crossroads, increase tilts in cell 49.

Lack of a dominant cell

1/15/2015#Cross Coverage / OvershootPage 116

Cross coverage means that the coverage scope of an eNodeB exceeds the planned one and generates discontinuous dominant areas in the coverage scope of other eNodeBs. For example, if the height of a site is much higher than the average height of surrounding buildings, its transmit signals propagate far along hills or roads and form dominant coverage in the coverage scope of other eNodeBs. This is an island phenomenon. If a call is connected to an island that is far away from an eNodeB but is still served by the eNodeB, and cells around the island are not configured as neighboring cells of the current cell when cell handover parameters are configured, call drops may occur immediately once UEs leave the island. If neighboring cells are configured but the island is excessively small, call drops may also occur because UEs are not promptly handed over. In addition, cross coverage occurs on two sides of a bay because a short distance between the two sides. Therefore, eNodeBs on two sides of a bay must be specifically designed.

Cross coverage

1/15/2015#Resolving Cross Coverage ProblemsPage 117Adjust antenna tilts or replace antennas with large-tilt antennas while ensuring proper antenna azimuths. Tilt adjustment is the most effective approach to control coverage. Tilts are classified into electrical tilts and mechanical tilts. Electrical tilts are preferentially adjusted if possible. Adjust antenna azimuths properly so that the direction of the main lobe slightly obliques from the direction of a street. This reduces excessively far coverage by electric waves because of reflection from buildings on two sides of the street. Decrease the antenna height for a high site. Decrease transmit power of carriers when cell performance is not affected.

1/15/2015#Case: Cross Coverage Caused by Improper Tilt Settings SymptomAs shown in the upper right figure, cross coverage occurs in a cell whose PCI is 288. Therefore, the cell interferes with other cells, which increases the probability of service drops.AnalysisThe most possible cause for cross coverage is excessively antenna height or improper tilt settings. According to a check on the current engineering parameter settings, the tilt is set to an excessively small value. Therefore, it is recommended that the tilt be increased.SolutionAdjust the tilt of cell 288 from 3 to 6. As shown in the lower right figure, cross coverage of cell 288 is significantly reduced after the tilt is adjusted. Page 118

1/15/2015#

118

Case: Inverse Connections Involved in the Antenna SystemSymptom The RSRPs of cells 0 is > than Cell 1 in front cell 1Analysis After installation and commissioning are complete, the RSRP in the direction of the main lobe in cell 1 is low. Result from drive shows cell 1 antenna is pointing in the wrong direction. Cell 0 is filling up the hole.SolutionAdjust antennas properly.

1/15/2015#Imbalance Between Uplink and DownlinkPage 120

When UE transmit power is less than eNodeB transmit power, UEs in idle mode may receive eNodeB signals and successfully register in cells. However, the eNodeB cannot receive uplink signals because of limited power when UEs perform random access or upload data. In this situation, the uplink coverage distance is less than the downlink coverage distance. Imbalance between uplink and downlink involves limited uplink or downlink coverage. In limited uplink coverage, UE transmit power reaches its maximum but still cannot meet the requirement for uplink BLERs. In limited downlink coverage, the downlink DCH transmit code power reaches its maximum but still cannot meet the requirement for the downlink BLER. Imbalance between uplink and downlink leads to service drops. The most common cause is limited uplink coverage.

Imbalance between uplink and downlink

Uplink coverage areaDownlink coverage areacoverage area

1/15/2015#Resolving Problems with Imbalance Between Uplink and DownlinkPage 121If no performance data is available for RF optimization, trace a single user in the OMC equipment room to obtain uplink measurement reports on the Uu interface, and then analyze the measurement reports and drive test files. If performance data is available, check each carrier in each cell for imbalance between uplink and downlink based on uplink and downlink balance measurements.If uplink interference leads to imbalance between uplink and downlink, monitor eNodeB alarms to check for interference. Check whether equipment works properly and whether alarms are generated if imbalance between uplink and downlink is caused by other factors, for example, uplink and downlink gains of repeaters and trunk amplifiers are set incorrectly, the antenna system for receive diversity is faulty when reception and transmission are separated, or power amplifiers are faulty. If equipment works properly or alarms are generated, take measures such as replacement, isolation, and adjustment.


1/15/2015#Signal Quality (SINR is mainly involved)Page 123

Frequency plan Site selectionAntenna height

Process of analyzing SINR problems

Antenna azimuths Antenna tilts

Cell layout

X

1/15/2015#Resolving Signal Quality IssuesChange and optimize frequencies based on drive test and performance measurement data.Optimizing frequenciesAdjust antenna azimuths and tilts to change the distribution of signals in an interfered area by increasing the level of a dominant sector and decreasing levels of other sectors.Adjusting the antenna systemIncrease power of a cell and decrease power of other cells to form a dominant cell.Decrease RS power to reduce coverage if the antenna pattern is distorted because of a large antenna tilt. Power adjustment and antenna system adjustment can be used together.Adding dominant coverageAdjusting power

1/15/2015#

124

Case: Adjusting Antenna Azimuths and Tilts to Reduce InterferencePage 125Symptom Cross coverage occurs at sites 1, 2, 3, 7, 8, 9, 10, 11, and 12, and co-channel interference occurs in many areas. Analysis According to the analysis of engineering parameters and drive test data, cell density is large in coverage areas. Coverage by each cell can be reduced by adjusting antenna azimuths and tilts.Solution Change the tilt in cell 28 from 2 degrees to 4 degrees so that the direction points to a demonstration route. Change the tilt in cell 33 from 3 degrees to 6 degrees so that the direction points to the Wanke Pavilion. Change the tilt in cells 50 and 51 from 3 degrees to 6 degrees so that the direction points to the Communication Pavilion. Decrease the transmit power in cell 33 by 3 dB to reduce its interference to overhead footpaths near China Pavilion.

SINR before optimization in Puxi SINR after optimization in Puxi

Poor signal quality before optimization

1/15/2015#Case: Changing PCIs of Intra-frequency Cells to Reduce InterferenceSymptom Near Japan Pavilion, UEs access a cell whose PCI is 3 and SINRs are low. UEs are about 200 m away from the eNodeB. This problem may be caused by co-channel interference.Analysis This problem is not caused by co-channel interference because no neighboring cell has the same frequency as the current cell. Cell 6 interferes with cell 3. SINRs increase after cell 6 is disabled. In theory, staggered PCIs can reduce interference.Solution Change PCI 6 to PCI 8. Test results show that SINRs increase by about 10 dB.

SINR when cell 6 is enabled SINR when cell 6 is disabled SINR when PCI 6 is changed to PCI 8

1/15/2015#Case: Handover Failure Caused by Severe InterferenceSymptom During a test, handovers from PCI 281 to PCI 279 fail.Analysis Cell 281 is a source cell and is interfered by cells 279 and 178. Delivered handover commands always fail and cannot be received correctly by UEs. Cell 279 is a target cell for handover, and its coverage is not adjusted preferentially because the signal strength in the handover area can ensure signal quality after handovers. Therefore, cell 178 must be adjusted to reduce its interference to cell 281.Solution Adjust antenna tilts to decrease coverage by cell 178.Page 127


1/15/2015#Analysis of Handover Success Rate Problems

Page 129

Neighboring cell optimization must be performed to ensure that UEs in idle or connected mode can promptly perform reselection to or be handed over to optimal serving cells. This helps achieve continuous coverage. In addition, problems with delay, ping-pong, and non-logical handovers can be resolved by optimizing coverage, interference, and handover parameters.

1/15/2015#Handover Problem AnalysisChecking handover validity Obtain source and target cells using drive test software and then check whether handovers are performed between two cells that are geographically far using Mapinfo.Checking interferenceCheck interference in both source and target cells because handover failures may be caused by uplink or downlink interference.

Checking coverage Check source and target cells for cross coverage, imbalance between uplink and downlink, and carrier-level receive quality and level.

Check contents Check handovers based on RSRPs measured in UE drive tests. 1. Verify that RSRPs in the expected source and target cells are maximum. 2. Verify that the absolute RSRPs in the source and target cells are reasonable at a handover point. In other words, handovers are not allowed if signal quality is excessively poor. Specific RSRPs are determined based on the entire RSRPs on a network.Page 130

1/15/2015#Case: Service Drops Caused by Missing Neighboring Cell ConfigurationSymptom As shown in the upper right figure, a UE sends multiple measurement reports but is not handed over, which may be caused by missing neighboring cell configuration.Analysis According to measurement reports, the UE sends an A3 report of cell 64. However, the RRCConnectionReconfiguration message in the lower right figure shows that the current cell is cell 278 (the first cell) and cell 64 is not included in the message. This indicates that cells 278 and 64 are not configured as neighboring cells. Neighboring cell configuration on live networks can be checked for further confirmation.Solution Configure cells 278 and 64 as neighboring cells. Page 131

1/15/2015#DL Throughput troubleshooting

1/15/2015#Low throughput causes in DL LTEStep 1: Identify Cell with Low DL throughputStep 2: Identify DL interferenceLow CQI cellsLow CQI may be due to interferenceCheck for Interfering sourceStep 3 :Validate BLER valuesRun BLER report in the identified cells, BLER10 is acceptable, Otherwise poor RF environmentImprove RF environment.

1/15/2015#Throughput Troubleshooting

1/15/2015#SummaryRF optimization involves adjustment of neighboring cell lists and engineering parameters. Most coverage and interference problems can be resolved by taking the following measures (sorted in descending order by priority):Adjusting antenna tiltsAdjusting antenna azimuthsAdjusting antenna heightAdjusting antenna positionAdjusting antenna typesAdding TMAsAdjusting site positionAdding sites or RRUsPage 135

This document describes what are involved in the RF optimization phase of network optimization. RF optimization focuses on improvement of signal distribution and provides a good radio signal environment for subsequent service parameter optimization. RF optimization mainly use drive tests, which can be supplemented by other tests. RF optimization focuses on coverage and handover problems, which can be supplemented by other problems. RF optimization aims to resolve handover, service drop, access, and interference problems caused by these problems. Engineering parameters and neighboring cell lists are adjusted in the RF optimization phase, while cell parameters are adjusted in the parameter optimization phase.

1/15/2015#Backup

1/15/2015#

LTE identifiers overview**

1/15/2015#Synchronization and Cell Search

1/15/2015#Channel Mapping

1/15/2015# 139Reference signals sprinkled to facilitate wideband CQIBroadcast and sync in centre

Multi-antenna transmissionPotential benefitsDirectivityAntenna/Beamforming gain

Example

Transmit signal in the best direction

Channel knowledge (average/instant)DiversityReduce fading

Example

Transmit signal in all directions

DelaySpatial multiplexingData rate multiplication

Example

Transmit several signals in different directions

S-P

1/15/2015# 2011-03-14 140

LTE transmission modespositioning of some of the modesDirectivityAntenna/Beamforming gain

DiversityReduce fading

Spatial multiplexingData rate multiplication

TM2 Transmit diversityTM3 Open loop spatial multiplexingTM4 Closed loop spatial multiplexingTM7 single layer with proprietary pre-codingTM8 dual layer with proprietary pre-coding

1/15/2015# 2011-03-14 141

LTE Antenna Configurations (dl)3GPP TS 36.213Transmissions modes3GPP TS 36.213Transmission schemesMax rankEricsson configurations ExamplesTypical TX antenna configuration Mode 1Single-antenna port- Single-antenna port 01Single transmit antenna1x2 single transmit antenna (see Note 1)IMode 2Transmit diversity- Transmit diversity12-antenna transmit diversity2x2 transmit diversity (see Note 1)X4-antenna transmit diversity4x2 transmit diversity (see Note 1)X XMode 3Open-loop spatial multiplexing- Transmit diversi

Date post:	17-Nov-2015
Category:	Documents
Upload:	habibtel7020
View:	169 times
Download:	49 times

LTE Training

Documents