DVB-H Planning with ICS Telecom

White Paper July 2006

DVB-H radio-planning aspects in ICS telecom Coverage Emmanuel Grenier

Spectrum : COFDM SFN / MFN

Convergence – back channel

Software solutions in radiocommunications 3

Abstract

This white paper addresses the problem of efficient planning DVB-H networks with ICS telecom. This document is intended for radio-planner, technical director, project manager, consultant to be aware of the important goals to pursue when planning a DVB-H network.

It focuses not only on macro-scale DVB-H planning and its analysis on the geo-marketing point of view, but also provides methodologies for deep-indoor network densification, at the address level.

The suggested methodologies are divided into three topics:

 Defining the coverage model :

o by defining the right threshold for a given service class;

o by densifying the DVB-H network in dense urban areas.

 Enhancing the business model according to technical inputs :

o analyzing the impact of the chosen coverage model on the population;

o ensuring interactive/billing service by complementing the DVB-H network with a cellular infrastructure.

 Analyzing the impact of the integration of a DVB-H service in the existing spectrum, as well as checking the COFDM interference areas for SFN networks.

Table of Content 1 Acronyms ______1 2 Coverage aspects ______2 2.1 Cartographic data ______2 2.1.1 Cartographic environment for Macro-scale design ______2 2.1.2 Cartographic environment for Micro-scale design ______3 2.2 Technical parameters of the sites ______3 2.2.1 Main parameters ______3 2.2.2 Radiation patterns ______4 2.2.3 Advanced parameters ______5 2.3 Propagation models and planning thresholds ______6 2.3.1 The propagation models ______6 2.3.2 The planning thresholds ______8 2.3.2.1 KTBF of the equipment ______8 2.3.2.2 The service class ______9 2.3.2.3 Antenna gain ______9 2.3.2.4 Equivalent FS without taking into consideration the propagation ______9 2.3.2.5 Additional margins ______10 2.3.2.5.1 Height loss (if the ITU-R 1546 model is used) ______10 2.3.2.5.2 Location percentage requirement ______10 2.3.2.6 Planning threshold : some values ______13 2.3.2.6.1 Band IV using Medium Resolution cartography ______13 2.3.2.6.2 Band IV using High Resolution cartography ______14 2.3.2.6.3 Band V using Medium Resolution cartography ______15 2.3.2.6.4 Band V using High Resolution cartography ______16 2.4 Coverage analysis ______17 2.4.1 Macro-scale mode ______17 2.4.2 Gap fillers ______18 2.4.3 Micro-scale mode ______19 2.4.4 The back channel ______21 2.5 Population analysis ______23 3 Spectrum aspects ______24 3.1 MFN networks ______24 3.2 SFN networks ______25 3.2.1 Theory ______25 3.2.2 Methodologies of synchronization ______30 3.2.2.1 Single Signal environment ______30 3.2.2.2 Multi-signal environment : Strongest signal ______32 3.2.2.3 Multi-signal environment: First signal above a threshold level ______33 3.3 Interaction between analogue and digital services ______34 4 Conclusion ______35 1 1

1/35 DVB-H RADIO-PLANNING ASPECTS WITH ICS TELECOM

Note : all provided values are FOR IN FORMATION ONLY, and can be replaced with values specific to equipment vendors or provided in ETSI reference documents.

1 Acronyms

AGL Above Ground Level QAM Quadrate Amplitude Modulation Protection for a given frequency offset C/I between the Wanted and the Unwanted C/N Carrier-to-Noise ratio Coded Orthogonal Frequency Division COFDM Multiplex Differential Quadrate (Quaternary) Phase- DQPSK Shift Keying DVB Digital Video Broadcasting DVB-H DVB - Handheld EIRP Effective Isotropic Radiated Power FFT Fast Fourier Transform GMSK Gaussian Minimum Shift Keying HR High Resolution HRP Horizontal radiation pattern IFFT Inverse Fast Fourier Transform ISI Inter-Symbol Interference LOS Line Of Sight MFN Multiple Frequency Network Multi-Protocol Encapsulation - Forward Error MPE-FEC Correction MR Medium Resolution NFS Nuisance Field Strength Near Line of Sight. Received signal with large nLOS Fresnel zone blocking but in line of sight Non Line of Sight (Diffraction in Outdoor, NLOS Diffusion in Indoor) QPSK Quadrate (Quaternary) Phase-Shift Keying SFN Single Frequency Network UHF Ultra High Frequency UW Unwanted (potential interferer) VRP Vertical radiation pattern W Wanted (Potential victim of interference)

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2/35 2 Coverage aspects

2.1 Cartographic data ICS telecom manages cartographic layers necessary for : • The computation of the coverage. • The display of the coverage. • The analysis of the coverage.

Two main types of cartographic datasets can be highlighted:

2.1.1 Cartographic environment for Macro-scale design A typical medium resolution cartographic dataset for DVB-H radio-planning in ICS telecom would include • a Digital Terrain Model; The DTM provides XYZ information on the area of interest. It is used by ICS telecom in order to check the path between the transmitter and the handset. The mobile unit can be in Line Of Sight (LOS), non Line of Sight (NLOS) or near Line of Sight (nLOS) • a Ground occupancy file ("clutter"); The clutter layer is used in order to refine the calculated path according the environment on top of the topography. • imagery, such as a topographic map; • population data at the post-code level.

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2.1.2 Cartographic environment for Micro-scale design A typical high resolution cartographic dataset for DVB-H radio-planning in ICS telecom would include : • a Digital Terrain Model; • a building height file, providing for each building its corresponding height above ground level; • a Ground occupancy file ("clutter"); The clutter layer is used in order not only to locate the vegetation areas, but also to define the diffusion loss per building type for accurate outdoor->Indoor planning. • imagery, such as a true-orthophoto; • geo-marketing data at the address level.

2.2 Technical parameters of the sites

2.2.1 Main parameters The main technical parameters of each sites can be configured :

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2.2.2 Radiation patterns ICS telecom manages radiation patterns in the horizontal and the vertical plane. They can be manually configured, imported from an equipment database or calculated using the positions and the technical parameters of each panel they are made with (HRP, VRP, V Phase, H Phase…) using Antios©.

Even though the vertical pattern of broadcasting sites located remotely does not have a major impact on the overall coverage, it has quite a big impact when the site is located in urban environment, specially in terms of interference with regards to alternative service in the same spectrum (Analog TV for instance).

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2.2.3 Advanced parameters The area covered by a DVB-H transmitter is strongly depending on the type of COFDM signal selected, which depends itself on: • the Modulation used; • the coding rate.

Field strength 64QAM 7/8

16QAM C/N 3/4 QPSK 1/2 C/N C/N Noise Floor

Distance

Typical required C/N Modulation Code rate dB QPSK ½ 8.5 QPSK 2/3 11.05 16QAM ½ 14.5 16QAM 2/3 17.5 Typical required C/N (GI = ¼)

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6/35 2.3 Propagation models and planning thresholds

2.3.1 The propagation models ICS telecom offers a flexible interface for the selection of the propagation model to be used. The choice of the propagation model is made among : • deterministic models (Fresnel method + ITU-R 526 diffraction and multipath effects for instance); • empirical models (COST 231 for instance) :

• coordination/regulation models (ITU-R 1546 for instance) :

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Each model has its own "range" of possible selection. Several inputs need to be considered before selecting a propagation model: • what is the purpose of the prediction? Is it for accurate planning, or for a compatibility analysis during a coordination process? • what is the quality of the cartographic database used as an input? • what is the average distance between the transmitters and the target area? • do we have a measurement campaign over the area of interest that would model tuning? • … Deterministic Empirical Coordination Coordination Purpose Accurate planning Accurate planning Licensing Large scale planning From 2m including From 2m including Low resolution Cartography available building height to 100m building height to 100m 100m and above including a clutter file including a clutter file Possible limitation for Possible limitation for Average distance long distances (when the No limitation but the short distances between the main transmitter is quality of the cartography (transponders in urban transmitters and the outside the city, which is itself areas for deep indoor target area usually the case in coverage) broadcasting) Useful Availability of a the planning margin Useless measurement according to the standard Compulsory these models shall not be campaign for model deviation of the model tuned improvement can be reduced

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2.3.2 The planning thresholds The planning threshold is the minimum signal level required in order to overcome noise. The required equivalent field strength is expressed in dBµV/m and is based upon: • the KTBF of the equipment; • the C/N ratio required; • additional margins.

Even though ICS telecom features the corresponding calculator, some typical values are provided here-below.

Threshold calculator for DVB systems in ICS telecom

2.3.2.1 KTBF of the equipment These values can be provided by the equipment manufacturer, or these values can be used if any:

Bandwidth KTBF (MHz) (dBm) 8 (7.61) -100.2 7 (6.66) -100.7 6 (5.71) -101.4

5 (4.76) -102.2

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2.3.2.2 The service class The EBU specifies 4 classes of receivers : Class Name Description A Outdoor portable Outdoor reception at 1.5m AGL or above at very low or no speed B Indoor portable Indoor reception at 1.5m AGL or floor level at very low or no speed C Outdoor mobile Mobile outdoor reception at 1.5m AGL or above D Indoor mobile Mobile indoor reception at 1.5m AGL or floor level

2.3.2.3 Antenna gain Band Class Gain A, B and D -12dBd IV C -2dBd A, B and D -7dBd IV C -1dBd

2.3.2.4 Equivalent FS without taking into consideration the propagation

Once the gains of the receiving antennas have been taken into account, the equivalent field strength in dBµV/m according to the C/N are as follow : C/N (dB) 2 8 14 20 26 Band Class Required field strength without regards to the propagation effects (dBµV/m) A, B and D 44 50 56 62 68 IV C 34 40 46 52 58 A, B and D 43 49 55 61 67 V C 37 43 49 55 61

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2.3.2.5 Additional margins

2.3.2.5.1 Height loss (if the ITU-R 1546 model is used) If the ITU-R 1546 model is used, the receiver is considered by default at 10m AGL. This height cannot be considered as realistic for planning a portable reception. Correction factors are provided in order to adjust the 1546 calculation to a receiver located at 1.5m AGL. This height loss correction shall only be used in case the 1546 model is selected, and the Rx antenna height fixed at 10m.

Environment Band Rural Suburban Urban IV 11 dB 16 dB 22 dB V 13 dB 18 dB 24 dB Height loss correction to apply to a 1546 prediction in order to obtain the signal received at 1.5m AGL

2.3.2.5.2 Location percentage requirement The values provided in §Error! Reference source not found. are regardless of any propagation effects. However it is necessary to consider these effects when considering DVB-H reception in a practical environment. In defining coverage it is indicated that due to the very rapid transition from near perfect to no reception at all, it is necessary that the minimum required signal level is achieved at a high percentage of locations.

Class Acceptable reception Good reception A 70% Outdoor 95% Outdoor Portable B 70% Indoor 95% Indoor C 90% Outdoor 99% Outdoor Mobile D 90% Indoor 99% Indoor

Indicative percentage of locations to take into account for a given quality of reception

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The location correction factor C depends on 2 parameters: • the standard deviation  of the selected model :

For outdoor DVB-H services , this value can be obtained per clutter code by performing a correlation between a DVB-H measurement campaign and an ICS telecom prediction. For indoor DVB-H services, this value can also be obtained by correlation once the building diffusion coefficient has been setup in ICS telecom (see the ATDI White Paper "mixed models").

• a distribution factor , considering the received signal obeys a log-normal distribution

C = µ .  Percentage of locations 70 90 95 99 Distribution factor 0.52 1.28 1.64 2.33

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4 Location correction factor (dB) factor correction Location

50 53 56 59 62 65 68 71 74 77 80 83 86 89 92 95 98 Percentage of locations

3dB standard deviation 5.5 dB standard deviation 6 dB standard deviation

Location correction factor according to the standard deviation of the model

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2.3.2.6 Planning threshold : some values

2.3.2.6.1 Band IV using Medium Resolution cartography

C/N Class 2 8 14 20 26 A - Portable outdoor 44 50 56 62 68 Typical std dev. 5 dB in Outdoor Planning Acceptable - 70% 46.6 52.6 58.6 64.6 70.6 threshold Good - 95% 52.2 58.2 64.2 70.2 76.2 B - Portable indoor 44 50 56 62 68 Typical std dev. 8 dB in indoor Planning Acceptable - 70% 48.2 54.2 60.2 66.2 72.2 threshold Good - 95% 57.1 63.1 69.1 75.1 81.1 C - Mobile outdoor 34 40 46 52 58 Typical std dev. 5 dB in Outdoor Vehicle entry loss 7 dB Planning Acceptable - 90% 47.4 53.4 59.4 65.4 71.4 threshold Good - 99% 52.7 58.7 64.7 70.7 76.7 D - Mobile indoor 44 50 56 62 68 Typical std dev. 8 dB in indoor Planning Acceptable - 90% 54.2 60.2 66.2 72.2 78.2 threshold Good - 99% 62.6 68.6 74.6 80.6 86.6

Typical DVB-H planning thresholds in band IV using medium resolution cartography in ICS telecom

Note 1: The height loss is not highlighted on purpose here. Please refer to § 2.3.2.5.1 in case the ITU-R 1546 model has been used (5.5 dB standard deviation), and the coverage calculated at 10m AGL.

Note 2 : The standard deviations provided here above use: • a deterministic propagation model; • a medium resolution clutter file with appropriate clutter heights and losses; • the "Rx over ground" mode for the location of the Rx according to the clutter file.

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2.3.2.6.2 Band IV using High Resolution cartography

C/N Class 2 8 14 20 26 A - Portable outdoor 44 50 56 62 68 Typical std dev. 3 dB in Outdoor Planning Acceptable - 70% 45.6 51.6 57.6 63.6 69.6 threshold Good - 95% 48.9 54.9 60.9 66.9 72.9 B - Portable indoor 44 50 56 62 68 Typical std dev. 3 dB in indoor Planning Acceptable - 70% 45.6 51.6 57.6 63.6 69.6 threshold Good - 95% 48.9 54.9 60.9 66.9 72.9 C - Mobile outdoor 34 40 46 52 58 Typical std dev. 3 dB in Outdoor Vehicle entry loss 7 dB Planning Acceptable - 90% 44.8 50.8 56.8 52.8 68.8 threshold Good - 99% 48 54 60 66 72 D - Mobile indoor 44 50 56 62 68 Typical std dev. 3 dB in indoor Planning Acceptable - 90% 47.8 53.8 59.8 65.8 71.8 threshold Good - 99% 51 57 63 69 75

Typical DVB-H planning thresholds in band IV using high resolution cartography in ICS telecom (including building heights)

Note 1: The height loss is not highlighted on purpose here, as the 1546 model is considered as not applicable when high resolution cartography is used.

Note 2 : The standard deviations provided here above use: • a deterministic propagation model; • a building height file; • appropriate diffusion coefficients for the building types.

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2.3.2.6.3 Band V using Medium Resolution cartography

C/N Class 2 8 14 20 26 A - Portable outdoor 43 49 55 61 67 Typical std dev. 5 dB in Outdoor Planning Acceptable - 70% 45.6 51.6 57.6 63.6 69.6 threshold Good - 95% 51.2 57.2 63.2 69.2 75.2 B - Portable indoor 43 49 55 61 67 Typical std dev. 8 dB in indoor Planning Acceptable - 70% 47.2 53.2 59.2 65.2 71.2 threshold Good - 95% 56.1 62.1 68.1 74.1 80.1 C - Mobile outdoor 37 43 49 55 61 Typical std dev. 5 dB in Outdoor Vehicle entry loss 7 dB Planning Acceptable - 90% 50.4 56.4 52.4 68.4 74.4 threshold Good - 99% 55.7 61.7 67.7 73.7 79.7 D - Mobile indoor 43 49 55 61 67 Typical std dev. 8 dB in indoor Planning Acceptable - 90% 53.2 59.2 65.2 71.2 77.2 threshold Good - 99% 61.6 67.6 73.6 79.6 85.6

Typical DVB-H planning thresholds in band V using medium resolution cartography in ICS telecom

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2.3.2.6.4 Band V using High Resolution cartography

C/N Class 2 8 14 20 26 A - Portable outdoor 43 49 55 61 67 Typical std dev. 3 dB in Outdoor Planning Acceptable - 70% 44.6 50.6 56.6 62.6 68.6 threshold Good - 95% 47.9 53.9 59.9 65.9 71.9 B - Portable indoor 43 49 55 61 67 Typical std dev. 3 dB in indoor Planning Acceptable - 90% 44.6 50.6 56.6 62.6 68.6 threshold Good - 99% 47.9 53.9 59.9 65.9 51.9 C - Mobile outdoor 37 43 49 55 61 Typical std dev. 3 dB in Outdoor Vehicle entry loss 7 dB Planning Acceptable - 70% 47.8 53.8 59.8 65.8 71.8 threshold Good - 95% 51 57 63 69 75 D - Mobile indoor 43 49 55 61 67 Typical std dev. 3 dB in indoor Planning Acceptable - 90% 46.8 52.8 58.8 64.8 70.8 threshold Good - 99% 50 56 62 68 74

Typical DVB-H planning thresholds in band IV using high resolution cartography in ICS telecom (including building heights)

Note 1: The height loss is not highlighted on purpose here, as the 1546 model is considered as not applicable when high resolution cartography is used.

Note 2 : The standard deviations provided here above use: • a deterministic propagation model; • a building height file; • appropriate diffusion coefficients for the building types.

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2.4 Coverage analysis

2.4.1 Macro-scale mode ICS telecom features exhaustive functionalities in order to display and analyze the coverage result.

Composite coverage of a DVB-H SFN network for an in-car mobile receiver

Best Server coverage of a DVB-H SFN network for an indoor mobile receiver

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2.4.2 Gap fillers Based upon that kind of results shown in §2.4.1, ICS telecom can automatically design a gap filler network in order to improve the coverage of the targeted area.

Auto-plan of gap fillers of an initial coverage: in blue the areas to be covered by the gap fillers, in red the potential locations the gap fillers can be selected among

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2.4.3 Micro-scale mode If appropriate data is used, the radio-planner can analyze the impact of the addition of transponders for deep indoor-coverage. In order to do so, there is no need to have high resolution building data over the entire area to cover, but only where the business plan considers that deep-indoor coverage should be achieved. All the rest can be managed using macro-scale cartography.

² Upper left : initial coverage in macro-scale mode Right : macro-scale coverage over the high resolution data Lower left : macro-scale coverage filtered to the buildings Lower right : indoor coverage when a transponder is added

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Note that the calculation of the coverage with high resolution data is using ICS telecom's indoor diffusion engine instead of applying a simple indoor loss offset, as well as ray tracing for the outdoor propagation.

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2.4.4 The back channel

Convergence : use of DVB-H for broadcasting the signal, and use of a cellular infrastructure for interactive/billing services (source: BA)

In order to provide interactivity and/or individual billing services, the DVB-H network can be joined to an alternative cellular infrastructure that provide the "back-channel". In terms of radio-planning, it means that both network should cover the same area. ICS telecom can be used in order to "mix" both infrastructures, in order to highlight their respective coverage holes. For the cellular mobile network, two methodologies can be used: • plan the cellular network using ICS telecom; • import the cellular coverage from an alternative cellular planning tool using standard GIS formats :

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In blue : area covered by the cellular infrastructure In green : area covered by the DVB-H network In Red : area not covered In red : area not covered

In yellow : area covered by both networks : the back channel is ensured In orange : area covered in DVB-H but not with the cellular infrastructure In red : area not covered in DVB-H

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2.5 Population analysis ICS telecom can also be used in order perform a geo-marketing analysis of the population covered according to a given class of receiver.

Post-code map in ICS telecom

Addionnal covered population when switching from 16QAM2/3 to QPSK1/2

350000 300000 250000 200000 150000

Population 100000 50000 0 Class A Class B Class C Class D Acceptable coverage (70% outdoor, 90% indoor)

Example of population analysis

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24/35 3 Spectrum aspects

3.1 MFN networks The Multi-Frequency Network technique can be used if : • the DVB-H network is in MFN mode; • the DVB-H network is made of several SFNs, in that case, two sites belonging to the same SFN area not interfering one another (they share the same network ID in ICS telecom) :

The Nuisance Field Strength delivered by Tx2 at the receiver's location M relatively to Tx1 is given by the formula :

NFS2->1 (dBµV/m) = C2 (dBµV/m)+ C/Irequired (dB)– RxPat1 (dB)- XPD (dB) Where:

C2 : field strength received from 2 in M

C/Irequired : protection ratio corresponding : unwanted DVB-H xxMHz BW/ wanted DVB-H xxMHz BW

RxPat1 is the antenna discrimination of the receiver, is the azimuth of 2 when pointing to 1. The DVB-H receiver is usually considered as omnidirectional. XPD is the cross-polar discrimination when the wanted and the unwanted do not share the share polarization :

In Pink : interference area between two sites in MFN one with each other "1" will be considered as interfered in M if: • Single interferer mode (from 2 or 3) :

o C1 > Threshold for a given handheld class;

o C1 < Max(NFS). • Summed interferer mode (from 2 and 3) :

o C1 > Threshold for a given handheld class;

o C1 < "Sum"(NFS).

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3.2 SFN networks The theory of this paragraph is mainly based upon a document written by M. Brugger (IRT) and M. Hemingway (BBC), concerning the impact on coverage of inter-symbol interference and FFT window positioning. DVB-H commonly uses the single-frequency network (SFN) technique. In such networks, the treatment of inter-symbol interference and the synchronization strategy of the receivers is a crucial aspect in planning the networks and achieving the desired coverage : • Firstly, the performance of the receiver is strongly dependent on the way in which it locates the FFT window relative to the several received signals that can be present in a multipath environment or in an SFN. The position of the FFT window affects the receivers' behavior with regards to inter-symbol interference (ISI). • Secondly, the modeling of receiver behavior in network coverage simulations has to be in line with the synchronization strategies and the treatment of inter-symbol interference in the receivers, in order to give reliable coverage predictions. However, the synchronization strategies of individual manufacturers are right protected and not publicly available. Therefore, predictions have to be carried out on the basis of assumptions.

3.2.1 Theory In OFDM, the information is carried via a large number of individual carriers in a frequency multiplex. Each carrier transports only a relatively small amount of information, and high data capacities are achieved by using a large number of carriers within a frequency multiplex. Each carrier has a fixed phase and amplitude for a certain time duration, during which a small portion of the information is carried. This unit of data is called a symbol; the time it lasts is called the symbol duration. After that time period, the modulation is changed and the next symbol carries the next portion of information. Modulation and demodulation are accomplished by the use of Inverse Fast Fourier Transformation (IFFT) and Fast Fourier Transformation (FFT) respectively.

In general, signals arriving at a receiver by different paths show different time delays which result in inter- symbol interference (ISI), and degradation in reception. An OFDM system with a multipath capability allows for the constructive combination of these signals. This is achieved by inserting a guard interval. The FFT window, i.e. the time period for the OFDM demodulation, is then positioned in such a way that a minimum of inter-symbol interference occurs. This mechanism - as far as it is of interest for coverage predictions and network planning - is described in more detail in the following paragraphs.

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Symbol n-1 Symbol n Symbol n+1

FFT window Time

Three consecutive symbols in time, denoted by n.1, n and n+1, and the setting of the FFT window such that symbol n is evaluated by the receiver (no guard interval is used in this example, and the FFT window has the same duration as the symbol)

In an environment where several useful signals (either from multipath echoes or from other transmitters in an SFN) are available to the receiver, things become more complex. Usually, the signals arrive at different times at the receiver which, in the absence of a guard interval, makes correct synchronization to all the signals impossible.

Symbol n-1 Symbol n Symbol n+1 1 Symbol n-1 Symbol n Symbol n+1 2 ISI

FFT window Time

Synchronization to symbol n of signal 1 leads to an overlap of the FFT window with the preceding symbol n.1 of the delayed signal 2. Since this symbol n.1 carries different information from symbol n, the overlap acts as inter-symbol interference to the evaluation of symbol n. Original symbol

In order to overcome the inter-symbol interference problem, part of the Tu symbol is copied from the beginning of the symbol to the end, increasing its duration by a certain amount of time called the guard interval . Extended symbol

Ts = Tu + The new increased symbol duration is denoted by Ts and the original symbol duration is often called the useful symbol duration Tu. The duration of the FFT window during which the symbol is evaluated is kept at the original value Tu. The orthogonally relationship is kept with the original symbol duration Tu, not the extended Ts.

E. Symbol n-1 E. Symbol n E. Symbol n+1 1 E. Symbol n-1 E. Symbol n E. Symbol n+1 2

FFT window Tu Time

The guard interval now allows for the FFT window to be positioned so that there is no overlap with a preceding or subsequent symbol, thus avoiding ISI.

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The fact that the duration of the FFT window is now smaller than the symbol duration allows for a variety of different possible FFT window positions for the evaluation of a symbol.

E. Symbol n-1 E. Symbol n E. Symbol n+1

Diffrent positions for the FFT window

Time

In a multipath or SFN environment, where Interfering component many potentially useful signals are available to the receiver, the choice of the Useful component FFT window position becomes more complex: all signals with time delays that cannot be absorbed by the guard interval, in the way described above, introduce a Tp degradation of reception. -Tu Tu + In the case of DVB-H, because of the pilot carriers that are needed for coherent demodulation, the total loss of constructive signal components occurs beyond a relative delay Tp. The formula Tp = 7Tu/24 is often quoted and this gives a sensible practical limit in the case of real filter designs. The failure of the equalization algorithm after Tp produces a more rapid performance degradation versus the echo delay.

Synchronization Tu Tp t

Case 1 Case 3 Case 5

Case 2 Case 4

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The corresponding formulas are the following:

CWiCi I(1Wi)Ci i i

Case 1 Wi0 if t   - Tp Full destructive field strength

Case 2 Partial constructive field strength Wi Tut ²  Tu  if  - Tp < t  0 Partial destructive field strength

Case 3 Wi1 if 0 < t < Full constructive Field strenth

Case 4  (Tu)t  Partial constructive field strength Wi ²  Tu  if  < t  Tp Partial destructive field strength

Case 5 if Tp < t Full destructive field strength

Where : C : total power of the effective useful signal

Ci : power contribution from the I-th signal at the reciver input I : Total effective interfering power Wi : weighting coefficient for the I-th signal, with the following cases: Tu : length of the useful symbol Tp : interval during which signals usefully contribute  : length of the guard interval t : arrival time

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2K mode 4K mode 8K mode Tu (µs) 224 448 896  / Tu 1/4 1/8 1/16 1/32 1/4 1/8 1/16 1/32 1/4 1/8 1/16 1/32 Guard Interval 56 28 14 7 112 56 28 14 224 112 56 28 Total symbol 280 252 238 231 560 504 476 482 1120 1008 952 924 duration

The recommended G.I for SFN are: • for 2K: 1/4, • for 4K: 1/4, 1/8, • for 8K: 1/4, 1/8.

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3.2.2 Methodologies of synchronization Different strategies for second-stage synchronization (i.e. positioning of the FFT window) are commonly used in receiver modeling. The strategy employed by a receiver determines: • which peak, in the time-domain impulse response of the received signal, the receiver uses for synchronization; • where the receiver sets the FFT window relative to this peak.

3.2.2.1 Single Signal environment

In a single-signal environment, the synchronization configuration is simple and clear. The principle was already explained in §Error! Reference source not found.. FFT window synchronization is of particular importance for mobile and portable reception, when the receiver will need to be able to synchronize in a rapidly changing environment and in the presence of pre and post-echoes.

E. Symbol n-1 E. Symbol n E. Symbol n+1 1 E. Symbol n-1 E. Symbol n E. Symbol n+1 2

FFT window Tu Time

This is managed by ICS telecom using its ray-tracing engine :

Where : the Maximum ToA is the total symbol duration (case of a DVB-H 2K ¼ signal) the margin is the co-channel protection ratio (case of a DVB-H QPSK Rayleigh channel) the synchronization threshold is explained in §3.2.2.3

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This methodology is useful in dense urban environment, using High Resolution cartography. The network in the dense urban areas is usually densified with transponders in order to achieve deep-indoor coverage (see §2.4.3): the reflections on the building sides might generate a self-interference case between the reflected symbols of the same signal coming from a given transponders.

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3.2.2.2 Multi-signal environment : Strongest signal

3 A natural approach for the FFT window 2 positioning is to synchronize to the strongest 4

1 Signal strength signal. In order to demonstrate the principle, a configuration with four signals is chosen as an example. The drawing on the right shows the Time ISI channel response function for the configuration, where the peaks represent a characteristic time instant of the signals, such as the start of symbol E. Symbol n. Signal 3 is the strongest signal. Accordingly, the FFT window is synchronized to signal 3. FFT window Since relevant contributions of further signals may be found preceding signal 3 or following signal 3, it seems reasonable to locate the centre of the FFT window at the centre of symbol n of signal 3. In the example, signals 3 and 4 contribute fully to the evaluation of symbol n, whereas the FFT window exhibits an overlap with symbol n+1 of the signals 1 and 2, which results in a certain amount of ISI.

C/N map in COFDM with synchronization on the first server (Class B acceptable coverage)

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3.2.2.3 Multi-signal environment: First signal above a threshold level

2 Signal strength

1 4 Synchronization threshold

Margin Noise floor Time

E. Symbol

ISI

FFT window This strategy takes the first signal of the time impulse response as a reference for the FFT window. Normally, a minimum synchronization threshold level is necessary for a signal in order to be accepted as a trigger. The first signal above the synchronization threshold is signal 2. It serves here as the trigger for the FFT window. With this synchronization strategy, signals 1 and 2 contribute fully constructively, whereas signal 3 and 4 add a certain amount of ISI. The choice of the synchronization threshold value is a specific issue of this synchronization strategy (It may be taken, or not, as the power corresponding to the minimum field strength, meaning planning threshold). In ICS telecom, the synchronization threshold is defined using a margin above the KTBF, and the synchronization and the planning thresholds are independent from each other.

C/N map in COFDM with synchronization on the strongest server (Class B acceptable coverage)

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3.3 Interaction between analogue and digital services As being a planning tool able to simulate both analogue and digital broadcasting technologies, ICS telecom can be used in order to analyze the impact from a DVB-H network to an existing analogue broadcast network, or the other way around.

In order to do so, each network shall be configured using : • their signal types (TV BG for the analogue, DVB 8 MHz for the digital for instance) • a unique network ID (Analogue / DVB-H).

The sites of both networks can be collocated. The analysis is then performed in MFN mode, with the internal interference cases of each network forbidden to be calculated, only the external interference cases can be highlighted.

According to the signal types of the wanted and the unwanted, ICS telecom can automatically select what the corresponding protection ratio to use (according to the ITU-R 1368 for instance).

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4 Conclusion

ICS telecom features dedicated functionalities for an exhaustive DVB-H radio-planning : • Coverage aspects o Macro-scale coverage for different services classes of DVB-H handhelds (Outdoor/Indoor, In car or not, in mobility or not… o Micro-scale gap-filling for deep-indoor coverage in order to cope with the indoor diffusion effect o Geo-marketing analysis of the covered population • Convergence aspects : Import or calculation of the back-channel coverage based for instance on the cellular infrastructure • Spectrum aspects o Analysis of the introduction of the DVB-H service with regards to the spectrum already occupied by an existing service o Analysis of MFN-type of DVB-H networks o Analysis of SFN-type of DVB-H networks by modeling the Inter-Symbol interference during the COFDM synchronization

References ETSI TR 102 377 Digital Video Broadcasting (DVB): DVB-H Implementation Guidelines ETSI TR 101 190 Digital Video Broadcasting (DVB):Implementation guidelines for DVB terrestrial services, Transmission aspects ETSI EN 300 744 Digital Video Broadcasting (DVB): Framing structure, channel coding and modulation for digital terrestrial television EBU Project Group B/CP-T (Brugger and Hemingway) OFDM receivers: impact on coverage of inter- symbol interference and FFT window positioning ITU-R P.1546 Method for Point-to-Area predictions for terrestrial services in the frequency range 30 MHz to 3000 MHz

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