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LTE RF Design Guidelines

AT&T LTE RFP – Nov. 2008

LTE Planning Guidelines

TABLE OF CONTENTS INTRODUCTION ................................................................................................. 3 DETAILS.............................................................................................................. 4 1.

LINK BUDGET & AIR-INTERFACE DIMENSIONING .......................... 4

2.

PLANNING INPUTS & ASSUMPTONS ................................................ 6

2.1 2.2 2.3 2.4

Air-Interface Dimensioning Assumptions ............................................................................. 7 Clutter Map Inputs................................................................................................................ 7 Propagation Model Inputs .................................................................................................... 7 Service & Coverage Requirements...................................................................................... 7

3.

LTE PLANNING TOOLS & SETUP ...................................................... 8

4.

PROPAGATION MODEL & TUNING.................................................. 10

5.

LTE NOMINAL PLANNING................................................................. 12

5.1 5.2 5.3

Creation of LTE Coverage Maps ....................................................................................... 12 LTE SINR & DL Throughput Results ................................................................................. 13 Optimization of Nominal Plan............................................................................................. 15

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LTE Planning Guidelines

INTRODUCTION This document has been prepared by the Network Planning Team, Nokia Siemens Networks North America with the purpose of giving a GENERAL overview on LTE Planning. The LTE standards are still in the process of being finalized; hence this guide highlights the major steps that might be involved in planning an LTE network. As more and more details become available, this guideline shall be updated to explain in-depth these steps as well as LTE specific issues, parameters and inputs.

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DETAILS 1. LINK BUDGET & AIR-INTERFACE DIMENSIONING Air interface dimensioning is a first step that a radio network planner has to take into account during radio planning process. It gives a general overview of site count, site density, cell ranges and areas estimated for considered site layouts, clutter types and simulation cases. Air interface dimensioning process is based on successive steps in link budget calculation for a set of input parameters from which we can form several groups:

• General parameters – the group defines possible center frequencies (operating bands), channel bandwidths, clutter types, simulation cases, etc.

• Equipment parameters – the group provides equipment specifications, antenna configurations, gains and losses etc.

• Radio propagation parameters – the group consists of parameters which describe wave propagation in a specific radio environment, e.g. channel models, mobility, etc.

• Capacity dimensioning – the group is necessary in E-UTRAN for correct definition of

power and resource sharing among users. • Interferences – the group of parameters related to interference calculation e.g. cell loads, G-factor, etc. • Radio propagation prediction – the group of parameters related to propagation models e.g intercept points, propagation model slopes, eNodeB antenna and UE heights. • Radio Network Configuration – the group specifies cell layout and sectorization. The results coming from air interface dimensioning are the following: • Maximum Allowable Path Loss • Cell ranges based on propagation models’ formulae • Site-to-Site distance and site areas for different site layouts which finally allows for estimation of number of sites and site density required to cover the given area.

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The figure below presents a snapshot of the process

General Parameters

Equipment Parameters

Radio Propagation Parameters

Maximum Path Loss

Radio Propagation Prediction

Cell Range

Radio Network Conf.

Cell Area, Site to Site Distance

User Service Characteristics

The Dimensioning Process is explained in detail in the Dimensioning Guidelines provided along with the Planning Guidelines.

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LTE Planning Guidelines

2. PLANNING INPUTS & ASSUMPTONS Network planning includes multiple tasks and it can be expressed with a basic process chart. This document focuses on detailed planning, typically during the beginning of the rollout. However, some of the generic principles outlined here can also be used during the operational phase, and as the network grows. The following figure gives an idea of network planning tasks.

Detailed planning involves the following steps: • Site Selection and Planning • Practical site selection based on target site locations and available sites • Site implementation plan • Actual site locations and implementation plans • Configuration Planning • Configuration planning is related to possible configurations as well as feature implementation • Future configuration takes into account the possibility to expand • Coverage and Capacity Planning • Coverage and Capacity Planning is very much tied to Site selection and Configuration planning • Coverage requirements need to be met • Capacity requirements estimated as well as future expansions need to be noted • Parameter Planning • Initial parameter configuration • Neighbor plan

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• Detailed parameter planning • Optimized/verified parameter plan At this stage we are mostly concentrating on creating a LTE based NOMINAL PLAN. The most Important Inputs and assumptions involved in this process are:

2.1

Air-Interface Dimensioning Assumptions

These usually involve eNode B inputs like Tx Parameters, UE Inputs, MIMO configurations, Antenna Details, Feeder loss values, Frequency Settings, Throughput Requirements and Area Level Coverage Probability Inputs. These values are usually taken from the Dimensioning Process, so that the Path Loss process during the Nominal Planning is same as that obtained during the dimensioning process.

2.2

Clutter Map Inputs

For a good Nominal Plan, the quality of clutter Maps used is very important. Usually Clutter Maps used involve: a. Clutter Data (Minimum 12 Class data is recommended) b. DEM or Height Data c. Transportation and Mapping Vectors It is recommended to use at least 30m resolution clutter maps.

2.3

Propagation Model Inputs

The quality of a Nominal plan is linked directly to the details of the Propagation Model used. It is strongly recommended to use a TUNED Propagation Model. For LTE Planning @ 700 MHz, only assumed values are available at this time. Hence it is important that propagation modeling be performed @ 700 MHz to create a tuned Model.

2.4

Service & Coverage Requirements

The Nominal Planning involves Coverage and Service Probability Plots based on a specific service as well as coverage requirements. Typical Service Requirements for LTE can range from 512 Kbps to 1 Mbps DL Cell Edge Throughput requirements and 128 to 512 Kbps UL Cell Edge Throughput requirements. Typical Area Coverage Probability requirements are 90 to 95%.

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LTE Planning Guidelines

3. LTE PLANNING TOOLS & SETUP Nokia Siemens Networks has an RF planning tool, ACORN, which can carry out all of the steps described in Section 2 above, and also features automated optimization capability. The LTE module is currently in prototype, but development will continue along with the development of LTE equipment. Additionally, Nokia Siemens Networks’ NetAct Multiradio planner is scheduled to support LTE by 2Q09, and will be tightly integrated with the other elements in the NetAct suite of tools. Finally, there are 3rd party tools such as ATOLL from Forsk that either currently support LTE or have LTE support as a roadmap item for 2009. Desired capabilities in a LTE Radio Planning Tool include: • • • • • • • • • •

Support for all LTE frequency band and carrier bandwidths Support for adaptive modulation and coding and the ability to calculate the best bearer based on user defined requirements Support for all radio resource management and scheduling algorithms (e.g. proportional fair, max aggregate, etc) Mobility management, to include neighbor list management, and different user- defined radio condition requirements based on mobile speed Full support for various MIMO configurations Modeling of various services, to include the guaranteed and maximum throughput Modeling of different classes of mobiles, including support for MIMO and directional antennas Support for different subscriber classes Support for traffic modeling from a variety of sources (live traffic, 3G network traffic, marketing estimates, etc.) Monte Carlo simulation that properly accounts for the radio resource management of all the control channels, guaranteed services rates, etc.

Usually the following steps are involved in LTE Nominal Planning: • Import of planning data to NSN tool (Geodata/site database/ antennas etc.) • Project setup in NSN tooling • Pathloss prediction calculation • Import/Generation of traffic data • Calculation of G-Factor (= wide band SINR) distribution • Own-to-Other interference per pixel • Mapping to throughput values • Per pixel and cumulated per cell????? • For different configurations????? • Iteration for different system settings

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This can be explained by the following process diagram as well.

Clutter and DTM maps

Project Setup in Tool

(antenna 67º HBW)

Pathloss Calculation

Propagation Model Assignment

Relative Traffic Raster Spread

Traffic Import

Site Database

Automatic Tilt Optimization outer loop inner loop

SINR per Pixel Calculation Assign Antenna

Traffic

(45º/85º HBW)

(Live/Uniform)

Mapping to DL Throughput

Postprocessing (Reporting)

Schema of Investigation

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LTE Planning Guidelines

4. PROPAGATION MODEL & TUNING Accurate propagation modeling is fundamental to LTE Radio network planning. The key inputs to propagation modeling are the propagation model itself, the digital terrain map (DTM) and the site configuration data. Radio network planning is often completed using a set of propagation models rather than a single propagation model. Different models may be tuned for specific antenna heights or specific cell ranges. Digital terrain maps often become out-of-date and subsequently become a source of error. The site configuration data relies upon the accuracy of the antenna gain pattern as well as the antenna height, azimuth and tilt data. Operators may have existing propagation models for their 2G and 3G radio networks. They may wish to use the same models for LTE radio network planning. In case of LTE Planning @ 700 MHz, it is recommended to perform Propagation Modeling. When a project requires the definition of a new propagation model the following tasks should be completed: • DTM specification, purchase and validation • Selection of propagation model type based upon requirements • Planning and completion of drive survey • RF measurement post-processing and propagation model calibration • Propagation model validation and continuous auditing An example of 700 MHz Model that can be used as a basis for Propagation Modeling is given below:

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5. LTE NOMINAL PLANNING LTE Nominal Planning involves the following steps:

5.1

Creation of LTE Coverage Maps

The Coverage Maps are based on path-loss predictions and are independent of the technology. They are based on eNodeB transmit power, Link Budget parameters and assumptions. Below is an example of a 700 MHz Coverage Map.

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LTE Planning Guidelines

5.2

LTE SINR & DL Throughput Results

Based on Coverage results, LTE Simulations are used to produce SINR (dB) and Throughput Results. Examples of these are given below.

SINR Results (dB)

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DL Throughput (Mbps) Instantaneous

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5.3

Optimization of Nominal Plan

Based on the Coverage and Throughput results, Tilts and Azimuths can be optimized to improve the SINR and to tune the Nominal Plan.

Initial Scenario

After Tilt Tuning Tilt

Signal to Noise (PDF)

Coverage Level (PDF) Initial

Optimized

Optimized Nominal Plan after Tuning

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