Atoll_3.3.0_LTE

(1)

(2)

1. LTE Concepts

2. LTE Planning Overview

3. Modelling a LTE Network

4. LTE Predictions

5. Neighbours Allocation

6. Automatic Resource Allocation

7. MIMO Features

Training Programme

(3)

Overview

OFDM Definition

Advanced OFDM: OFDMA

Benefits of OFDM/OFDMA

Multiple Access Techniques and Duplexing Methods

LTE Radio Interface

(4)

What is 4G?

Evolution of 3GPP standards

Release 99: UMTS FDD (3G)

Release 4: UMTS TDD + FDD repeaters (3G) Release 5: HSDPA (3.5G)

Release 6: HSUPA (enhanced uplink) + MBMS (3.5G)

Release 7: HSPA+ (2x2 MIMO, higher order modulations, etc.) (3.75G) Release 8: LTE FDD and TDD (3.9G) + HSPA+ multi-carrier

Release 10: LTE advanced (4G)

Technologies 3GPP Release 5/6 3GPP Release 99/4 3GPP Release 7/8 LTE 3GPP Release 8 LTE Adv. 3GPP Release 10

WCDMA

384 kbps downlink 128 kbps uplink

HSDPA/HSUPA

14 Mbps peak downlink 5.7 Mbps peak uplink

HSPA+

42,2 Mbps peak downlink 11 Mbps peak uplink

LTE

100 Mbps peak downlink 50 Mbps peak uplink

LTE Adv.

100 Mbps to 1Gbps peak downlink WCDMA WCDMA + Enhanced architecture + Higher order modulations

WCDMA + MIMO + Dual-carrier OFDMA SC-FDMA MIMO

+ Carrier aggregation (DL/UL) + HetNets

+ enhanced MIMO (8*8)

(5)

What is OFDM ?

OFDM = Orthogonal Frequency Division Multiplexing

Frequency domain organization

Advanced form of Frequency Division Multiplexing (FDM)

Principle:

• Wideband channel split into multiple orthogonal narrowband radio carriers (subcarriers)

• Subcarriers are spaced in a manner that the centre of each subcarrier corresponds to a zero crossing point of the neighbouring subcarriers

• Good spectral efficiency compared to FDM systems

(6)

OFDM Frequency and Time Domains

Time domain organization

Adjustable guard period referred to as cyclic prefix

• Used to fight against multipath effects (delay spread)

Two configurations depending on the environment

• Normal cyclic prefix: 4.7 us • Extended cyclic prefix: 16.7 us

Typical values of delay spread:

• Open environment: 0.2 us

• Suburban: 0.5 us

• Urban: 3 us

• Hilly area: 3-10 us

(7)

Division Multiplexing

OFDM allocates users in time domain only

The entire channel bandwidth is allocated to one user

Division Multiple Access

OFDMA allocates users in time and frequency

domains

Several users served at once

R e s ource B lock s

(8)

Benefits of OFDM/OFDMA

OFDM(A) summary:

No ICI and ISI:

No intra-cell interference in theory

Possibility to support less robust modulations like 16QAM, 64QAM… for higher throughput !

Narrowband orthogonal subcarriers

• Negligible inter-carrier interference (ICI)

• No frequency selective fading

Long symbol durations + cyclic prefix

(9)

OFDMA in DL

Each subcarrier carries one specific data symbol (QPSK, 16QAM...)

SC-FDMA in UL (OFDMA variant)

Single-Carrier Frequency Division Multiple Access

Each subcarrier carries information of

all data symbols

Technique well suited to LTE UL requirements

• Lower PAPR*

• Power consumption limited

LTE can be deployed in FDD and TDD

(10)

LTE Radio Interface

LTE channel structure

A channel is composed of more than 1 frequency block (FB)

• Fixed width = 180 kHz (LTE system level constant)

• 1 frequency block over 1 slot = 1 resource block (RB)

• Each FB is composed of many subcarriers

• Two subcarrier widths possible: 15 kHz, 7.5 kHz (specified for MBMS/SFN services)

• 1 FB = 12 SCa of 15 kHz OR 24 SCa of 7.5 kHz

• 1 subcarrier over 1 SD (symbol duration) = 1 resource element (RE)

(11)

LTE PHY layer supports a wide range of bandwidths

Spectrum flexibility

Channel

bandwidth

Subcarrier

spacing

Number

of FBs

Number of

subcarriers

Sampling

frequency

FFT size

1.4 MHz

15 kHz

(7.5 kHz for

MBMS)

6

72 1.92 MHz

(1/2 x 3.84)

128 3 MHz

15

180 3.84 MHz

(1 x 3.84)

256 5 MHz

25

300 7.68 MHz

(2 x 3.84)

512 10 MHz

50

600 15.36 MHz

(4 x 3.84)

1024

15 MHz

75

900 23.04 MHz

(6 x 3.84)

1536

20 MHz

100 1200

30.72 MHz

(8 x 3.84)

2048

(12)

LTE Frame Structure

Time domain structure (for both UL and DL)

Specific frame structures for TDD and FDD

1 frame = 10 ms = 2 half-frames (TDD) = 10 sub-frames or TTI (each 1 ms) = 20 slots (each 0.5 ms)

1 slot (0.5 ms) = 6 or 7 symbol durations (depending on the cyclic prefix duration)

1 FB over 1 sub-frame (1ms) = smallest unit that can be allocated by the scheduler (scheduling block) Control channels transmitted on sub-frames 0 and 5 (always DL)

LTE Frame

10 ms

SF 0

SF 1

………..

SF 9

1 ms

Slot 0 Slot 1 Slot 2 Slot 3

………..

Slot 18 Slot 19

0.5 ms

OFDM Symbol 0

CP CP _{Symbol 1}OFDM CP _{Symbol 2}OFDM CP _{Symbol 3}OFDM CP _{Symbol 4}OFDM CP _{Symbol 5}OFDM CP _{Symbol 6}OFDM

(13)

eNode-B

HARQ feedback, CQI reporting,

UL scheduling request, CQI reporting for MIMO related feedback Traffic Pilot (channel estimation), slot/frame synchronization and cell identification Traffic, MBMS, system information, paging HARQ feedback, transport format, UL scheduling grants, DL resource allocation Slide 13

(14)

OFDMA LTE Frame (DL)

Structure of a resource block

Frame structure of type I (FDD), 1 antenna port, ΔF = 15 kHz

• Standard frequency block:

• Any frequency block within the centre 6 frequency blocks:

Legend:

Downlink reference signals

PBCH (Physical Broadcast Channel) PSS (Primary Synchronisation Signal) SSS (Secondary Synchronisation Signal)

PDCCH / PHICH / PCFICH (Physical - Downlink Control / HARQ Indicator / Control Format Indicator - Channels) PDSCH (Physical Downlink Shared Data Channel)

RBs allocated to mobiles are not necessarily adjacent  interference coordination

(15)

OFDM symbol 0

CP CP _{symbol 1}OFDM CP _{symbol 2}OFDM CP _{symbol 3}OFDM CP _{symbol 4}OFDM CP _{symbol 5}OFDM CP _{symbol 6}OFDM

Legend:

Downlink reference signals PBCH PSS SSS PDCCH / PHICH / PCFICH PDSCH 1 subframe = 2 slots (1 ms) 1 frame (10 ms) = 10 subframes (1 ms) = 20 slots (0.5 ms) SF 0 SF 1 SF 2 SF 3 SF 4 SF 5 SF 6 SF 7 SF 8 SF 9 0 1 2 3 4 5 6 0 1 2 3 4 5 6 C en tr e 6 RB s 180 kHz C h an n el b an d w id th Slide 15

(16)

SC-FDMA LTE Frame (UL)

Legend:

UL DRS (Uplink Demodulation Reference Signal)

UL SRS (Uplink Sounding Reference Signal)

PUCCH (Physical Uplink Control Channel) (incl. HARQ feedback and CQI reporting)

Demodulation Reference Signal for PUCCH PUSCH (Physical Uplink Shared Channel)

1 subframe = 2 slots (1 ms) SF 0 SF 1 SF 2 SF 3 SF 4 SF 5 SF 6 SF 7 SF 8 SF 9 0 1 2 3 4 5 6 0 1 2 3 4 5 6 1 frame (10 ms) = 10 subframes (1 ms) = 20 slots (0.5 ms) 180 kHz C h an n el b an d w id th Slide 16 OFDM symbol 0

CP CP _{symbol 1}OFDM CP _{symbol 2}OFDM CP _{symbol 3}OFDM CP _{symbol 4}OFDM CP _{symbol 5}OFDM CP _{symbol 6}OFDM 7 OFDM symbols at normal CP per slot (0.5 ms)

(17)

1. LTE Concepts

2. LTE Planning Overview

3. Modelling a LTE Network

4. LTE Predictions

5. Neighbours Allocation

6. Automatic Resource Allocation

7. MIMO Features

(18)

2. LTE Planning Overview

LTE Features Supported in Atoll

LTE Planning Workflow in Atoll

(19)

Atoll fully supports LTE/LTE-A networks

Various E-UTRA frequency bands

Scalable channel bandwidths (from 1,4 MHz to 20 MHz)

Support of TDD and FDD frame structures

Normal and extended cyclic prefixes

Downlink and uplink control channels and overheads

• Downlink and uplink reference signals, PSS, SSS, PBCH, PDCCH, PUCCH, etc.

Physical Cell IDs implementation

Network capacity analysis using Monte-Carlo simulations

RSRP, RSSI and RSRQ support in predictions and simulations

(20)

LTE Features Supported in Atoll

Atoll fully supports LTE/LTE-A networks

Inter-cell interference coordination (ICIC) support

• Hard FFR (Fractional Frequency Reuse),

• Time-switched FFR,

• Soft FFR,

• Partial soft FFR

• eICIC (enhanced ICIC)

Support of fractional power control (UL)

Modelling of multi-layer heterogeneous networks (HetNets)

• Small Cells, Relay nodes

• Layers and eICIC features

Services can be mapped to QoS Class Identifiers (QCI)

Beamforming modelling (smart antennas)

Possibility of fixed subscriber database for fixed applications

(21)

Atoll fully supports LTE/LTE-A networks

Carrier Aggregation up to 5 carriers of 20 MHz

Dynamic Multiple Input Multiple Output (MIMO) systems

• Transmit and receive diversity

• Single-user MIMO or spatial multiplexing

• Dynamic MIMO switching

• Modelling of Multi-User MIMO (MU-MIMO)

• AAS (Active Antenna Systems) with beamforming

Tools for automatic resource allocation

• Automatic allocation of neighbours

• Automatic allocation of Physical Cell IDs (PCI)

• Automatic allocation of frequencies

• PRACH RSI (root sequence indexes)

Network verification using drive test data

Specific module (AFP)

(22)

LTE Planning Workflow in Atoll

Open an existing project or create a new one

Prediction study reports Traffic maps

Network configuration - Add network elements

- Change parameters

User-defined values Automatic or manual neighbour allocation

Basic predictions (Best server, signal level)

Monte-Carlo simulations

Signal quality and throughput predictions Cell load conditions Subscriber lists And/or Frequency plan analysis

Automatic or manual frequency planning

Automatic or manual Physical Cell ID and PRACH Root Sequence Index planning ACP

(23)

1. LTE Concepts

2. LTE Planning Overview

3. Modelling a LTE Network

4. LTE Predictions

5. Neighbours Allocation

6. Automatic Resource Allocation

7. MIMO Features

(24)

3. Modelling a LTE Network

Global Settings

Frequency bands and channels definition Global LTE frame definition

Radio Parameters

Sites

Transmitters Cells

Multi-layer Networks (HetNets)

HetNets Configuration eICIC

Relay links

(25)

Frequency bands and channels definition

Atoll can model multi-band networks within the same document

2 duplexing methods available: FDD and TDD

Bandwidths from 1,4 MHz to 20 MHz supported

(26)

Global LTE frame definition

System-level constants (hard-coded)

Width of a resource block (180 kHz) Frame duration (10 ms)

Other control channel overheads defined by 3GPP

• Reference signals, PSS, SSS, PBCH, etc.

Global Settings (2/2)

TDD option only: Special subframe

selection Number of SD for PDCCH

(from 0 to 4) carrying DL and UL resource allocation

information Normal (default) or extended cyclic prefix

 at 15 kHz, 7 SD/slot (normal), or 6 SD/slot (extended)

Average number of resource blocks for

PUCCH

(27)

Downlink Cell-specific Reference Signals

Reference Signal Power Boost

• With more than one antenna port

• Each antenna uses different resource elements to transmit reference signals

• Resource elements of one antenna port that correspond to reference signal transmission on another antenna port are not used (DTX)

Different LTE equipment and vendors may support different methods for reusing the energy corresponding to the “unused” resource elements

0  l 0 R 0 R 0 R 0 R 6  l l0 0 R 0 R 0 R 0 R 6  l O n e an te n n a p o rt T w o a n te n n a p o rt s 0  l 0 R 0 R 0 R 0 R 6  l l0 0 R 0 R 0 R 0 R 6  l l0 1 R 1 R 1 R 1 R 6  l l0 1 R 1 R 1 R 1 R 6  l 0  l 0 R 0 R 0 R 0 R 6  l l0 0 R 0 R 0 R 0 R 6  l l0 1 R 1 R 1 R 1 R 6  l l0 1 R 1 R 1 R 1 R 6  l F o u r an te n n a p o rt s 0  l l6l0 2 R 6  l l0 l6l0 l6 2 R 2 R 2 R 3 R 3 R 3 R 3 R

even-numbered slots odd-numbered slots Antenna port 0

(28)

Advanced Settings (2/2)

Downlink Transmit power calculation

0-Max Power defined manually in the cell table. The energy of the “unused” resource elements is distributed on the downlink channels.

1-RS EPRE defined manually. The Max Power will automatically be calculated

2-Max Power defined manually in the cell table. The energy of the “unused” resource elements is allotted to reference signal resource elements only (RS Power Boost = 3dB for 2 antennas and 6dB for 4 antennas) 3-Max Power defined manually in the cell table. The energy of the “unused” resource elements is lost 4-Max power and RS EPRE defined manually in the cell table.

(29)

Sites

Characterized by their X (longitude) and Y (latitude) coordinates

Transmitters

Activity

Antenna configuration (model, height, azimuth, mechanical/electrical tilts...) UL and DL losses / UL noise figure

Propagation (model, radius and resolution)

Cells

Frequency band & channel Layer

Cell Type Physical Cell ID

Power definition of DL channels Min. RSRP

DL and UL traffic loads Diversity support (MIMO) Neighbours

Presented in the “General Features” course

Slide 29

Specific parameters for LTE technology

(30)

Transmitter Parameters

Transmitter parameters

Propagation settings Antenna configuration and losses

parameters Antenna configuration DL and UL total losses, UL noise figure

(31)

Main parameters

Cell activity

• Only active cells are considered in predictions

Frequency band and channel number

Physical Cell ID

• PSS/SSS ID automatically computed

Powers and energy offsets

• Computed from RS EPRE*

Min. RSRP

• Used as a cell coverage limit

Load conditions

• DL traffic load (%)

• UL noise rise due to surrounding mobiles (dB)

(32)

Cell Parameters

Main parameters

Automatic resource allocation parameters

• Allocation status

• Channels

• Physical Cell ID

• PRACH RSI

(33)

Main parameters

Layer

• Similar to HCS layers in 2G networks and layers in 3G

• Used to model HetNets*

Frame configuration (optional)

• See next slide

MIMO configuration

• Diversity support DL/UL:

• Transmit diversity

• SU-MIMO

• AAS: Advanced Antenna Systems

• MU-MIMO

Neighbours-related parameters

(34)

Cell Parameters

Specific frame configurations

Each cell can be assigned a specific frame configuration (optional)

PDCCH/PUCCH overheads and cyclic prefix can be set for each frame

• Override values defined in global parameters

PRACH preamble format

• Defines a max. distance limiting the best server coverage (see 3GPP specs.)

Specific parameters used in case of interference coordination support (ICIC)

• Group 0/1/2 frequency blocks, ICIC mode, cell-edge power boost (DL)

TDD parameter: Special Subframe Configuration

(35)

What is HetNets?

HetNets, or Heterogeneous Networks, are comprised of traditional large macrocells and smaller cells like:

• Microcells (< 5W)

• Picocells (< 1W)

• Femtocells (~ 200mW)

HetNets provide two basic benefits to operators:

• Increase capacity in hotspots as traffic is not uniformly distributed

• Improve coverage in places where macro coverage is not adequate

(36)

Multi-layer Networks (HetNets)

Heterogeneous network deployment

Atoll LTE fully supports multi-layer networks

• Different layers with different priorities

• Taken into account to determine the best serving cell ( they are not used in simulation)

• The definition of layers can be based on the operating frequencies

• Each cell has to be mapped to a layer

• You can also assign supported layers to different services and terminals

Layers management

You can define network layers with corresponding:

• Priorities

• Supported mobile speeds

(37)

Layers management

Principle of the cell selection margins

• Due to the wide difference of power levels between macro and pico/femtocells, most of the UEs will get associated to the macrocells resulting in a load imbalance throughout the network

• To counterbalance this effect, and thus enhance the system performance, an offset is to be added to the actual RSRP value from the pico/femtocells (range expansion) during the cell selection process

• Cell range expansion concept modelled by cell selection margins in Atoll

Area where the picocell is received with a higher power than the macrocell

(38)

The Handover Margin is used for selecting the best server and for avoiding the ping-pong effect* between cells.

Multi-layer Networks (HetNets)

Can be defined in the transmitter properties dialogue

Cell Layer parameter [Cells tab]

The CIO is used in order to rank the potential servers for best serving cell selection in connected mode

Cell Selection Threshold (CST) is used to adjust the Min RSRP threshold of cells belonging to different priority layers

(39)

Compatibility between services, terminals and network layers

Managed in the services and terminals properties

(40)

Best Server Identification

Best Server determination

(1) Filter the potentials serving cells based on

• Cell, service and terminal compatibility with the selected layer

• Layer’s maximum speed ≤ Mobility Type’s speed (Layers table and Mobility Type table)

• UECell distance ≤ PRACH maximum cell range

• RSRP > min RSRP (Cell table)

(2) Identify the initial serving cell

• On each pixel, Atoll selects the serving cells corresponding to the highest priority layer

• Atoll verifies if these servers respect a RSRP level > min RSRP + Cell Selection threshold

• If they do, the server with the maximum RSRP level will be considered as initial serving cell

(3) Atoll calculates the best server criterion (BSc) for the initial serving cell and the other potential serving cells

• Initial serving cell: BSc = RSRP + Handover Margin + CIO • Other serving cells: BSc = RSRP + CIO

(4) The server with the highest best server criterion (BSc) will be considered as best server (for all potential serving cells from all layers)

(41)

Use case : 1 Macro site 800 MHz + 2 Micro sites 1800 MHz + 6 Small Cells 2600 MHz

Cell Table

(42)

Cell Type RSRP Level

(dBm) Distance (m) Layer

Layer Max Speed

Small 3 -114 88 Small Cell 2600 50

Macro 2 -106 1860 Macro 800 120

Micro 2_3 -108 744 Micro 1800 50

Micro 2_2 -110 744 Micro 1800 50

Small 4 -118,5 118 Small Cell 2600 50

Micro 2_1 -122 744 Micro 1800 50

Best Server Identification

Step 1 : Atoll filters potential serving cells

Use case inputs:

• In Cells Table, minimum RSRP = -120 dBm

• For Pedestrian Mobility Type, average speed 3 km/h

• High Speed Internet Service: All layers allowed

• MIMO Terminal: All layers allowed

• Default configuration for frame configuration => PRACH format 0 (max distance 14521 m)

Potential serving cells respecting conditions

(43)

Cell Type RSRP Level (dBm)

Cell Selection Threshold

Minimum

level targeted Layer

Layer Priority (Lowest 0)

Small 3 -114 2 -118 Small Cell 2600 2

Macro 2 -106 0 -120 Macro 800 0

Micro 2_3 -108 0 -120 Micro 1800 1

Micro 2_2 -110 0 -120 Micro 1800 1

Small 4 -118,5 2 -118 Small Cell 2600 2

Step 2 : Identify the initial serving cell

Atoll selects the serving cells corresponding to the highest priority layer from the potential serving cells and verifies if these servers respect a RSRP level > min RSRP + Cell Selection threshold

If the servers respect this minimum condition, Atoll selects the server with the highest RSRP level and consider it as the initial serving cell

The Small Cell 3 is the initial serving cell in this use case

(44)

Cell Type RSRP Level (dBm) Handover Margin (dB) Cell Individual offset (dB) BSc (dB) Small 3 -114 4 4 -106 Macro 2 -106 0 0 -106 Micro 2_3 -108 2 1 -107 Micro 2_2 -110 2 1 -109 Small 4 -118,5 4 4 -114,5

Step 3 : Atoll calculates the best server criterion (BS

_C

) for the initial serving cell and the other

potential serving cells

Best serving cell candidate: BS_C = RSRP + Handover Margin + CIO

Other serving cells: BS_C = RSRP + CIO

Best Server Identification

Handover Margin applied for the cell candidate only

CIO applied for all serving cells.

(45)

Step 4: Atoll considers the cell with the highest BS

_c

as the best server: Small Cell 3

The serving cell with the highest RSRP level is not necessarily the best server. The selection is based on the BSc calculation.

MACRO 900

MICRO 2100

Small cell range expansion: The Small cell maintains connection with the UE outside its best server area.

The expansion is impacted by the CIO and the Handover Margin.

(46)

Range expansion analysis: LTE specific predictions are impacted by the new best server algorithm

Impact on a Effective Signal Analysis displaying the RSRP level per best server area

The handover margin and the CIO impact the RSRP level shown per pixel. The best server area is changed so the RSRP level is automatically changed

Best Server Identification

(47)

Best server selection new algorithm

Potential serving cells based on

•Service/Terminal compatibility

•Minimum RSRP level •Mobility type vs layer

max speed •PRACH max cell

range Rank the different servers based on •Layer’s priority •Maximum level considering CST* Atoll analyses the Cell Individual Offset and Handover Margin Best Server identified

(48)

Carrier Aggregation (LTE-A)

Definition

Carrier Aggregation (CA) increases the channel bandwidth by combining multiple RF carriers

• Each individual RF carrier is known as a Component Carrier (CC)

• All CCs belong to the same eNodeB

5 CCs may be aggregated to reach a maximum of 100 MHz

• However, initial LTE-A deployments will likely be limited to 2 CCs

Carrier Aggregation is applicable to both DL and UL, and both FDD and TDD

3 general types of Carrier Aggregation scenario have been defined by 3GPP

• Intra-band contiguous

• Intra-band non-contiguous

• Inter-band

(49)

Carrier Aggregation categorises cells as:

Primary Cell

• The cell upon which the UE performs initial connection establishment

• Each connection has a single primary cell

• The primary cell can be changed during the handover procedure

• Used to generate inputs during security procedures

• Used to define NAS mobility information (e.g. Tracking Area Identity)

Secondary Cell

• A cell which has been configured to provide additional radio resources after connection establishment

• Each connection can have multiple secondary cells

Serving Cell

• Both primary and secondary cells are categorised as serving cells

• There is one HARQ entity per serving cell at the UE

• The different serving cells may have different coverage

(50)

Carrier Aggregation (LTE-A)

Primary and Secondary cells are modelled in

Atoll via the parameter “Cell Type”

Defines whether the cell supports LTE (3GPP Rel-8/9) and/or LTE‐A (3GPP Rel-10 and later)

• A cell can be configured to be a LTE cell, a LTE‐A P-Cell (Primary Cell), and a LTE‐A S-Cell (Secondary Cell)

• If the cell type is left empty, Atoll considers it as LTE‐only

Both LTE and LTE‐A users can connect to LTE‐only cells without the possibility to perform Carrier Aggregation

Cells that only support LTE‐A, and not LTE, can only serve LTE‐A users

• The process of only allowing LTE‐A users to connect to a cell and excluding all LTE users is called Cell Barring

(51)

UE Categories in Atoll

Specific UE Categories

LTE-A to LTE Downgrade Category: Used to define the UE category to consider when a LTE-A mobile is connected to a LTE Rel-8/9 cell

(52)

Carrier Aggregation (LTE-A)

LTE-A terminals in Atoll

Carrier Aggregation support is defined at the terminal level

• You have to define the maximum number of Secondary Cells supported in DL and UL

• The number of UL Secondary Cells must be less than or equal to the number of DL Secondary Cells

• Setting the maximum number of Secondary Cells to 0 means that the terminal does not support Carrier Aggregation

(53)

Services in Atoll

Define whether a service can manage carrier aggregation or not

(54)

Carrier Aggregation (LTE-A)

Improvements in predictions for Carrier Aggregation

You can carry out coverage predictions for different serving cells

• Main (P-Cell or LTE Rel-8/9 cells)

• Nth S-Cell

You can also perform aggregated throughput predictions including all serving cells, or even some of them

(55)

Example: Coverage by throughput

Intra-band contiguous Carrier Aggregation

• Co-located cells with similar coverage

• Channel width = 20 + 20 MHz

• MIMO 2 X 2 (TX DIV+SU-MIMO)

(56)

Carrier Aggregation (LTE-A)

Improvements in the Point Analysis Tool for Carrier Aggregation

Aggregated throughput

(57)

1. LTE Concepts

2. LTE Planning Overview

3. Modelling a LTE Network

4. LTE Predictions

5. Neighbours Allocation

6. Automatic Resource Allocation

7. MIMO Features

(58)

4. LTE Predictions

Introduction

Parameters used in Predictions

Prediction Settings

Fast Link Adaptation Modelling

Coverage Prediction Examples

Point Analysis Studies

(59)

• RSRP level: Receive Signal Receive Power calculated for one RE

• RS level: Reference Signal level calculated on the whole bandwidth

Coverage predictions

• RSRQ: Reference Signal receive Quality

• PDSCH C/I+N: Signal-to-interference-plus-noise ratio based on the PDSCH

channel

• RS C/I+N: Signal-to-interference-plus-noise ratio based on the Reference Signal

channel

Quality predictions

• Based on the RLC or Application layers

• Peak, Effective or Average throughput

• Carried out for one or several users

(60)

Introduction

Principle of LTE studies based on traffic

Study calculated for:

• Given load conditions:

• UL noise rise (dB)

• DL traffic load (%)

• A non-interfering user with:

• A service • VoIP, • Web browsing, • FTP download... • A mobility • Fixed, • Pedestrian, • 50 Km/h... • A terminal type • Smartphone, • Rooftop terminal...

LTE

prediction

UL

noise

rise

DL

traffic

load

Service

Mobility

Terminal

(61)

Load conditions, defined in the cells properties

Traffic load (DL) (%) UL noise rise (dB)

Values taken into consideration in

predictions for each cell

(62)

Service Properties

Service: parameters used in predictions

Highest/lowest bearers in UL and DL Body loss

Application throughput parameters

(63)

Mobility: parameters used in predictions

Mapping between mobility and thresholds in bearer and quality indicator determination (as radio conditions depend on user speed)

Reception equipment properties

(64)

Terminal Properties

Terminal: parameters used in predictions

Min/max terminal power Gain and losses

Noise figure

Antenna settings (incl. MIMO support) Carrier aggregation settings

Number of antenna ports in UL and DL in case of MIMO support Min/max terminal power + noise figure + losses

Support of MIMO Carrier aggregation parameters

(65)

Atoll determines, on each pixel, the highest bearer that each user can obtain

After the layer determination, connection to the best server in terms of RS level or RSRP Bearer chosen according to the radio conditions (PDSCH and PUSCH CINR levels)

Process: prediction done via look-up tables

RS level (C) or

RSRP evaluation

Best server area

determination

(limited by min.

RSRP)

Radio conditions

estimation

(PDSCH and

PUSCH CINR

calculation)

Bearer selection

Throughput &

quality indicator

predictions (BER

and BLER)

(66)

Interference Estimation

Atoll calculates PDSCH and PUSCH CINR according to:

The victim traffic (PUSCH or PDSCH) power [C]

The sum of interfering signals [I], affected by:

• The interfering signals’ EIRP (power + gains - losses) weighted by traffic loads (in DL)

• The path loss from the interferers to the victim

• The shadowing effect and the indoor losses (optional)

• The interference reduction factor applied to interfering base stations transmitting on adjacent channels (adjacent channel suppression factor)

• The interference reduction due to static ICIC (optional)

(67)

Coverage by transmitter

(based on RSRP levels)

Cell dominance (overlapping zones)

(based on RSRP levels)

(68)

Prediction Examples (Dedicated Studies)

Coverage by RSRP level

(with power boost)

(69)

Application Channel

Throughput (UL)

Coverage by PUSCH CINR

(70)

Point Analysis Tool: Reception

Radio reception diagnosis at a given point

Choice of UL/DL load conditions:

if (cells table) is selected analysis based on DL load and UL noise rise from cells table

Definition of the user (layer or channel, terminal, service,

mobility) Cell bar graphs (best server on top)

Analysis details on reference signals, PDSCH and PUSCH Reference signals, PDSCH and PUSCH availability (or not) Selection of the value to be

displayed (RS, SS, PDSCH, RSRP)

(71)

Radio interference diagnosis at a given point

Choice of UL/DL load conditions:

if (cells table) is selected  analysis based on DL load and UL noise rise from cells table

Definition of the user (layer or channel, terminal, service,

mobility)

Selection of the value to be displayed (RS, SS, PDSCH, RSRP) Serving cell (C) Total level of interference (I + N)

List of interfering cells

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1. LTE Concepts

2. LTE Planning Overview

3. Modelling a LTE Network

4. LTE Predictions

5. Neighbours Allocation

6. Automatic Resource Allocation

7. MIMO Features

Training Programme

(73)

Detailed information about neighbours allocation is available in

Atoll_3.3.0_Neighbours.pdf

(74)

1. LTE Concepts

2. LTE Planning Overview

3. Modelling a LTE Network

4. LTE Predictions

5. Neighbours Allocation

6. Automatic Resource Allocation

7. MIMO Features

Training Programme

(75)

Automatic Physical Cell ID planning

AFP overview

Automatic resource allocation process Interference matrix calculation

Physical Cell ID overview PCI allocation process

Running the automatic resource allocation PCI allocation examples

Automatic frequency planning

Running the automatic resource allocation Frequency allocation examples

Automatic PRACH Root Sequences

PRACH channel

PRACH RSI Planning Theory Automatic PRACH RSI Planning

(76)

AFP Overview (1/2)

Prerequisite: AFP license

Goal: Optimize resource allocation (channels, PCI or PRACH RSIs) following the user-defined

constraints

• To minimize interference (channels)

• To avoid collisions (PCI)

• To avoid PRACH root sequence index collisions (PRACH RSIs)

Tool based on an iterative cost-based algorithm

The algorithm starts with the current frequency plan (used as initial state)

Different frequency plans are then evaluated and a cost is calculated for each of them The best frequency allocation plan is the one with the lowest global cost

(77)

The cost is calculated thanks to:

Interference matrices

• Probabilities of interference in co- and adjacent channel cases

• A probability is calculated for each case and for each interfered-interfering cell pair

Distance relation

• Avoid frequency reuse between cells for which the inter-site distance is lower than a “min. reuse distance”

• Taking into account distance and cells’ azimuth

Neighbours

• Taking into account neighbours importance (can be calculated by Atoll)

(78)

Automatic Resource Allocation Process

Define radio parameters at cells level

• Frequency band allocation

• Allocation status: not allocated or locked • Minimum reuse distance (optional)

Import / calculate a neighbour plan

Import / calculate an interference matrix

Run the automatic resource allocation tool

(79)

Interference matrix definition

For each cell pair, interference probability for co and adjacent channel cases

Probabilities of interference are stated as the ratio between:

• The interfered area within the best server area of the victim

• Best server area of the victim

Co-channel interference occurs when:

TX_A Victim Transmitter Serving Area TX_B Interfering Transmitter

Area where TX_B is interfering TX_A

 Interference probability = 50%

 In other words, 50% of TX_A’s serving area is interfered by TX_B







ReferenceSignal



N C Min N M I C Q    Slide 79

(80)

Interference Matrix Calculation (2/2)

(81)

Physical Cell ID definition

Cell search and identification is based on Physical Cell IDs

• Optimised allocation needed to avoid unnecessary problems in cell recognition and selection

504 Physical Cell IDs defined by 3GPP

Physical Cell ID grouped into:

• 168 unique Cell ID groups (SSS IDs in Atoll, from 0 to 167)

• Each group containing 3 unique identities (PSS IDs in Atoll, from 0 to 2)

Each cell’s reference signal transmits a pseudo random sequence corresponding to the Physical Cell ID of the cell

When Physical Cell ID + pseudo-random sequence is known, cell is recognized by mobile based on the received reference signal

Channel estimation performed on reference signals

(82)

Physical Cell ID Allocation Process

PCI allocation to cells

Main requirement

• Avoid PCI collision and confusion

• Not allocate the same PCI to nearby cells

• To avoid problems in cell search and selection

Secondary requirements

• Different PSS ID at nearby cells

• Avoid RS-RS collisions

• Preferably the same SSS ID at co-site cells (especially in the case of 3-sector sites)

• May facilitate neighbour cell identification

• May help in measurements and handover procedures

PCI A PCI A PCI collision PCI A PCI B PCI B PCI confusion Slide 82

(83)

(84)

Running the Automatic Resource Allocation (2/6)

Automatic resource allocation process

Allocation constraints

Possibility to allocate channels or Physical Cell IDs

Run the calculation

(85)

Automatic resource allocation process

Possibility to allocate channels or Physical Cell IDs

Run the calculation

Slide 85

(86)

Running the Automatic Resource Allocation (4/6)

During the optimisation, you can monitor the reduction of the total cost

(87)

You can compare the distribution histograms of the initial and current allocation plans

(88)

Running the Automatic Resource Allocation (6/6)

Once Atoll has finished allocating Physical Cell IDs, the proposed allocation plan is available on

the Results tab

The proposed PCI plan can be assigned automatically to the cells of the network if you click Commit

(89)

Automatic Physical Cell ID allocation in Atoll (example)

Same PCI all over - RS coverage C/(I+N) with DL traffic load = 0%

(90)

Physical Cell ID Allocation Results (2/2)

Automatic Physical Cell ID allocation in Atoll (example)

Automatic PCI allocation with AFP - RS coverage C/(I+N) with DL traffic load = 0%

(91)

Philosophy of the channels automatic allocation is really similar to PCI allocation

Automatic channels allocation prerequisites

Define radio parameters at cells level

• Frequency band

• Channel allocation status

• Minimum reuse distance

Neighbour plan

Interference matrix (as explained previously)

(92)

Automatic Frequency Planning (2/2)

Philosophy of the channels automatic allocation is really similar to PCI allocation

(93)

Basic frequency allocation (Single Frequency Network)

Same channel all over (15 MHz) - RS coverage C/(I+N):

(94)

Frequency Allocation Examples (2/2)

Optimised frequency allocation with AFP

3 channels (5 MHz) - RS coverage C/(I+N):

(95)

You can visualise channels and PSS ID reuse on the map

Possibility to find cells which are assigned a given:

• Frequency band + channel

• Physical Cell ID

• PSS ID

• SSS ID

Way to use this tool

Create and calculate a coverage by transmitter with a colour display by transmitter

Open the “Find on map” tool available in the “tools” menu

• or use [Ctrl+F],

• or directly in the toolbar

(96)

Channel Search

Channel reuse on the map

Colours given to transmitters: • Red: co-channel transmitters

• Yellow: multi-adjacent channel (-1 and +1) transmitters • Green: adjacent channel (-1) transmitters

• Blue: adjacent channel (+1) transmitters • Grey thin line: other transmitters

(97)

Physical Cell ID, PSS ID or SSS ID reuse on the map

Colours given to transmitters:

• Red or grey thin line: if the transmitters carries or not the specified resource value (Physical Cell ID, PSS ID or SSS ID)

(98)

You can check if your constraints are satisfied by the current allocation by performing an audit

Respect of a minimum reuse distance

Respect of neighbourhood constraints (two neighbour cells must have a different PCI) Respect of PSS/SSS ID allocation strategy

PCI Allocation Audit (1/2)

(99)

Audit results

The exclamation mark icon ( ) means that the collision may or may not be a problem depending on your network design rules and selected strategies.

(100)

Automatic PRACH RSI

PRACH channel

PRACH RSI Planning Theory

Automatic PRACH RSI Planning

(101)

The Physical Random Access CHannel (PRACH) is used to transmit the random access preamble

used to initiate the random access procedure. This channel allows UEs to achieve uplink time

synchronisation

PRACH resources are multiplexed with PUSCH and PUCCH

CYCLIC

PREFIX SEQUENCE

GUARD TIME 839 subcarriers for preamble format 0 to 3 => 6 RB

139 subcarriers for preamble format 4

Duration depends on the preamble format

1.25 kHz wide Subcarriers for formats 0 to 3 7.5 KHz wide Subcarriers for format 4

(102)

PRACH Channel

Different sections of the network can be planned with different preamble formats if the cell

range varies from one area to another

The format 0 is the default format as it generates a small overhead and allows reaching a maximum cell range of 15 km which the most common situation

Preamble Format Duplex Mode Cyclic Prefix Duration Sequence Duration Guard Time Total Length Typical Max. Cell Range 0 FDD/TDD 103,13 us 800 us 96,88 us 1 ms 14,5 km 1 FDD/TDD 648,38 us 800 us 515,63 us 2 ms 77,3 km 2 FDD/TDD 203,13 us 800 us 196,88 us 2 ms 29,5 km 3 FDD/TDD 684,38 us 800 us 715,63 us 3 ms 100,2 km 4 TDD 14,58 us 133 us 9,38 us 0,16 ms 1,4 km

(103)

Purpose: Determine different preamble sequences to allow multiple UE using the same

frequency and time domain resources to simultaneously connect to an eNB. Each sequence is

generated by cyclic shifting one or several root sequence index (RSI).

Preamble sequences are CAZAC* codes generated using the Zadoff-Chu method Each cell has 64 preamble sequences (16 were available for UMTS/HSPA)

838 RSI are available for FDD (format 0 to 3) and 138 for TDD (format 4).

Depending on the PRACH format (or cell size), a different quantity of RSI is required per cell.

* CAZAC: Constant Amplitude Zero Autocorrelation

15 km

RSI 10-19 _{4 km}

RSI 0-2

Suburban-Rural Cell 10 RSI required per cell

Urban Cell 3 RSI required per cell

(104)

PRACH RSI Planning Theory

The root sequence index values allocated to each cell should ensure that neighbouring cells have

different sets of root sequences

A maximum RSI re-use can be implemented when a minimum number of RSI is used

For the urban case, 3 RSI are necessary per cell. 838 different RSI are available, so 838/3  279 cells can be allocated before reuse

For the rural case, 10 RSI are used per cell  838/10  83 cells can be allocated before reuse

10 RSI required per cell

Urban Cell 3 RSI required per cell

(105)

Atoll will allow the user to directly enter the number of required root sequence per cell.

This approach provides the most flexibility in case of different equipment and propagation environments imply additional delays and margins which impact the calculation of the quantity of required root

sequence per cell.

The mapping tables show values calculated for ideal conditions, i.e., no delay spread and perfect equipment. There are shown for information only .

3GPP parameters used for the PRACH RSI allocation are described in the following table

Parameter Range Description

PRACH Configuration Index 0 to 63 Determines the preamble format, version and density Zero Correlation Zone 0 to 15

Determines the size of the cyclic shift and the number of preamble sequence that can be generated from each root sequence

High Speed Flag True/False Reduce Doppler effect at very high speed (> 200 km/h) Root Sequence Index 0 to 837 Preamble sequence generated form root sequence

index

PRACH Frequency Offset 0 to 94 Determines the PRACH preambles position in the frequency domain

(106)

Automatic PRACH RSI Planning (2/8)

(107)

Automatic resource allocation process

Allocation constraints

Resource selection

Run the calculation

Slide 107

Initial cost calculation before planning

(108)

Automatic PRACH RSI Planning (4/8)

Automatic resource allocation process

Specify PRACH RSI resources to be used for the allocation

Slide 108

(109)

Once Atoll has finished allocating PRACH RSIs, the proposed allocation plan is available on the

Results tab

The proposed PRACH RSI plan can be assigned automatically to the cells of the network if you click Commit

(110)

Automatic PRACH RSI Planning (6/8)

A quantity of 10 PRACH RSIs has been automatically allocated per cell because of the cell table

configuration

(111)

The LTE prediction, Cell Identifier collision zones, allows verifying if any collisions occur between

cells with one or several identical PRACH RSIs

(112)

You can check if your constraints are satisfied by the current allocation by performing an audit

Respect of a minimum reuse distance

Respect of neighbourhood constraints (two neighbour cells must have different PRACH RSIs) Interference matrix consideration

Automatic PRACH RSI Planning (8/8)

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1. LTE Concepts

2. LTE Planning Overview

3. Modelling a LTE Network

4. LTE Predictions

5. Neighbours Allocation

6. Automatic Resource Allocation

7. MIMO Features

(114)

8. MIMO Features

Introduction

MIMO Techniques Overview

MIMO Settings in Atoll

Dynamic MIMO Switching

Diversity and Throughput Gains

Calculation Details

Use Case: 4x2 MIMO (TX DIV+SU-MIMO)

(115)

Shannon’s formula

Theoretical limit to transmit without error: 𝐶ℎ𝑎𝑛𝑛𝑒𝑙 𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦 = 𝑊. 𝑙𝑜𝑔2(1 + SNR) , (bits/s)

How to increase the channel capacity ?

Increase the bandwidth (W )

Improve the Signal to Noise Ratio (SNR )

Limitation of SISO* systems to reach very high data rates

Why MIMO ?

The usage of multiple antennas improves dramatically the channel capacity without additional bandwidth or transmit power

Expected benefits with MIMO

• Higher throughput

• Better coverage

(116)

Introduction (2/2)

General concept of MIMO

Multiple Input Multiple Output (MIMO) configurations benefit from multiple antenna elements at the transmitter and multiple antenna elements at the receiver

Terminology

Similar terminology is used for Single Input Multiple Output (SIMO), Multiple Input Single Output (MISO), and Single Input Single Output (SISO)

Propagation channel 4x2 MIMO Propagation channel 1x4 SIMO Propagation channel 4x1 MISO Propagation channel SISO

(117)

Four different MIMO techniques can be listed

Transmit diversity

• Aims to improve the signal quality by sending several times the same data stream • Usually used in areas with bad CINR conditions

Single-User MIMO (or SU-MIMO, also referred to as Spatial Multiplexing)

• Aims to improve the signal throughput by transmitting simultaneously (i.e. using the same set of time/frequency resources) multiple data streams to a single user

• Usually used in areas with good CINR conditions

Beamforming

• Aims to improve both signal quality and throughput by focusing the signal energy towards the receiver

Multi-User MIMO (or MU-MIMO)

• Aims to improve the system capacity by sending simultaneously different data streams to different users

(118)

Transmitters Settings

You have to set the appropriate number of antenna ports at the Transmitters level

In this example, 4 ports are defined for the transmission (used for DL calculations), and 2 ports for the reception (used for UL calculations) Propagation channel 4x? MIMO (DL)

?

Propagation channel ?x2 MIMO (UL)

?

Depends on the number of reception antenna ports defined in the terminal properties (see slide 49)

Depends on the number of transmission antenna ports defined in the terminal properties (see slide 49)

(119)

MIMO techniques support

You can define the MIMO techniques supported by your equipment in UL/DL in the Cells properties

AAS = Active Array System (beamforming)

• For more information see the training course “LTE Features – Advanced”

MU-MIMO

• For more information see the training course “LTE Features – Advanced”

(120)

Terminal Settings

You have to configure a terminal that supports MIMO

support

Number of antenna ports in UL and DL in case of MIMO support (1Tx/2Rx is the most common configuration at the moment)

LTE equipment defining SU-MIMO and diversity gains

(121)

Definition

Atoll can dynamically switch between different MIMO techniques depending on the radio condition Different option can be implemented:

• TX DIV  SU-MIMO, TX DIV  MU-MIMO, TX DIV  MU-MIMO  SU-MIMO

• In this example, Atoll can automatically switch from SU-MIMO to Tx/Rx diversity as the radio conditions deteriorate

Advantages

Improves the throughput for users situated near the transmitter Increases the signal quality for cell edge users

-> Use of SU-MIMO -> Better throughput

Bad radio conditions -> Use of Tx/Rx diversity -> Better CINR

Transition area between SU-MIMO and Tx/Rx diversity -> Determined by the SU-MIMO threshold (see next slide)

(122)

The SU-MIMO threshold is the parameter used to switch from SU-MIMO to Tx/Rx diversity

It can be defined in the reception equipment properties

• Default Cell Equipment (for UL calculations)

• Default UE Equipment (for DL calculations)

It is expressed in dB and refers to the Reference Signal or the PDSCH/PUSCH quality

Dynamic MIMO mode (2/3)

(123)

You can choose the criterion the SU-MIMO threshold will be based upon in the LTE global

settings

Reference Signal C/N or C/(I+N) PDSCH or PUSCH C/(I+N)

(124)

Diversity and/or throughput gains can be applied when using certain MIMO techniques

They depend on the MIMO configuration used (2x1 MIMO, 2x2 MIMO, 4x4 MIMO…) Besides PDSCH and PUSCH, PBCH and PDCCH can also benefit from diversity gains All values set here should be in line with your vendor specific equipment

Diversity and Throughput Gains (1/2)

(125)

Additional diversity and throughput gains are defined in the clutter classes properties

Diversity and throughput gains can be tuned according to the environment

(126)

Calculation Details (1/2)

CINR improvement with the transmit diversity technique

Let’s consider for instance the CINRPDSCH

(127)

Throughput improvement with the SU-MIMO technique

Let’s consider for instance the DL peak RLC channel throughput

(128)

Use Case: 4x2 MIMO DL (TX DIV+SU-MIMO) (1/5)

Atoll configuration

4 transmission antenna ports

• Transmitters properties

2 reception antenna ports

• Terminal properties

Diversity support (DL)

• TX DIV + SU-MIMO

(129)

Peak RLC Channel Throughput Analysis (DL)

Conditions:

• Traffic load (DL) = 75%

• Channel width = 10 MHz

• Normal CP, PDCCH overhead = 2

• SU-MIMO threshold = 12 dB (RS CINR)

• Service = High Speed Internet

• Mobility = Pedestrian

Without MIMO

4x2 MIMO (TX DIV+SU-MIMO)

SU-MIMO

threshold Tx/Rx _diversity

(130)

Use Case: 4x2 MIMO DL (TX DIV+SU-MIMO) (3/5)

Peak RLC Channel Throughput Analysis (DL) – near the transmitter

Results based on pixels where the SU-MIMO technique is used (RS CINR > 12 dB)

0 10 20 30 40 50 60 70 80 90 100 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 Peak RLC Throughput (Mbps) Without MIMO AMS 4x2

(131)

Quality analysis - PDSCH C/(I+N)

Conditions:

• Traffic load (DL) = 75%

• Channel width = 10 MHz

• Normal CP, PDCCH overhead = 2

• SU-MIMO threshold = 12 dB (RS CINR)

• Service = High Speed Internet

• Mobility = Pedestrian

Without MIMO 4x2 MIMO (TX DIV+SU-MIMO) SU-MIMO threshold No service Tx/Rx diversity SU-MIMO