wp(02)102.doc

8th Meeting - ECC Project Team 1 (ECC/PT1)

Berlin 11 – 13th September 2002

ECC PT1 (02)148

Date issued: 4 September 2002

Source: Deutsche Telekom, Nokia, Siemens 1

Subject: Spectrum Requirement Estimation Methodology

Background

Efficient usage and availability of radio spectrum is a key prerequisite for wireless mobile services. This requires efficient methodologies to estimate the spectrum needs of mobile communication systems in order to make available the spectrum resources for network operation in a timely manner according to the market requirement. Current methodologies to estimate spectrum requirements are limited and should be augmented to allow improved estimations, taking into consideration the cooperative usage of different wireless systems and a broad, ever increasing range of services.

In the Annex attached the applicability of spectrum requirements estimation methods used for current specified wireless systems are reviewed and fields for amendments are identified in order to consider new spectrum requirements with predictions for future mobile communication beyond 2010. Current methodologies are spreadsheet based, limited to a selected example service/market scenario and restricted in the examined deployment scenarios. As the current methods do not take into account convergence scenarios and cooperation networks, a new spectrum requirement methodology estimation framework is proposed and outlined to accomplish the envisaged scenario of ubiquitous mobile services and ambient wireless networks foreseen in the next decades.

Flexible, statistical methods and Monte-Carlo simulation models are suggested for the estimation of frequency requirements. Such models allow the consideration of spatial and temporal distributions of the market requirements and network deployment scenarios in virtually unlimited flexibility. In the proposed methodology framework relevant parameters are defined as statistical distribution functions. The results are not fixed spectrum numbers but a range of results, reflecting the broad range of assumptions used in the modelling which reflect also future scenarios of spectrum sharing and inter-working of different radio access systems.

Within the process of identifying spectrum for mobile communications ITU (in particular ITU-R WP8F ‘IMT-2000 and systems beyond IMT-2000’) is playing a role as a leader and catalyst to ensure that the correct environment is developed for future spectrum needs, emerging technologies and new services. To support these activities on a global basis on the one hand and to contribute the views of European industries in terms of manufacturers and network operators on the other hand, it is of great importance that a common understanding is achieved and Europe speaks with one voice.

1 This work has been performed in the framework of the IST project IST-2000-28584 MIND, which is partly funded by the European Union. The authors would like to acknowledge the contributions of their colleagues, although the views expressed are those of the authors and do not necessarily represent the project

/TT/FILE_CONVERT/556878F5D8B42A3B7B8B500E/DOCUMENT.DOC 16.09.02 16.09.02

UK WP8FWP(02)102

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For this purpose, contributing the harmonised European views to the Global process of specification will help to play a key role in evolving 3G and the process towards development of systems beyond 3G as well. This will be the key to a continuing success of the European industry in advancing and expanding the global wireless marketplace.

It should be noted, that ITU-R plans to contact Administrations and Sector Members requesting to conduct research activities on the future development of IMT-2000 and systems beyond IMT-2000, targeting February 2003 for the first round of contribution. Areas of investigations which have been identified are in particular ,

market estimations,

traffic characteristics,

access network related issues, radio interfaces and

spectrum related issues.

The concept on spectrum estimation methodologies for future mobile communication currently developed within the ‘IST MIND Project’2 perfectly fits in these study requirements of ITU-R. This is particularly the case concerning the investigations needed for the development of the methodology to assess spectrum needs for radio systems in terms of enhancement of IMT-2000 and systems beyond IMT-2000.

In order to apply spectrum estimations on the basis of methodologies like the one addressed in Annex 1, new market studies need to be conducted to investigate mobile communication market subsequent to the year 2010.

Proposal

The document attached in the annex on a ‘Spectrum Estimation Methodology for Mobile Communication Systems’ provides new ideas on how to calculate the spectrum needs for Radio Access Technologies in terms of the future enhancement of IMT-2000 and systems beyond IMT-2000 using Monte Carlo methods. Special attention is given to

Complementary access systems,

Seamless inter-working of access systems from customers point of view,

Economical conditions of network deployment and operation,

in order to allow frequency requirement considerations for mobile communication subsequent to the year 2010.

This contribution is intended to trigger the start of the discussion within CEPT on this issue with the objective of developing a common European view on this subject to be contributed to the ITU-R work within WP8F. It is proposed, that Annex 1 shall be used basis for the development of ECC PT1 ‘Spectrum Estimation Methodology for Mobile Communication Systems’.

Annexes: 1

2 The comprehensive documentation is given in Deliverable 3.3 of project IST-2000-28584 MIND

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ANNEX 1

SPECTRUM ESTIMATION METHODOLOGY FOR MOBILE COMMUNICATION SYSTEMS

1 Introduction

New technology concepts for wireless communications in terms of evolution of 3G and systems beyond 3G are envisioned within the wireless community. Coincidentally there is an increasing possibility and movements towards a convergence of different services coming from completely different backgrounds. Such areas of convergence are, for example, mobile communications, Internet, broadcasting, wireless LANs. Each of these represents a variety of applications, services and delivery mechanisms. From customers point of view, this differing information flows are desired to be available regardless of the means and manner of delivery. With the advent of network roll out of 3G mobile communications and DVB-T broadcasting as well as new wireless LAN technologies in the 5GHz band seamless communication opportunities will evolve. Nucleus of this process in terms of evolution of wireless communications and convergence of Radio Access Technologies towards seamless applications will be 3G following the global success of GSM.

Increasing traffic volumes to be carried in future mobile communication systems will likely lead to higher spectrum resources being required, even if spectrum efficiency of the mobile communication systems progresses simultaneously to some extent.. For the time being frequencies for 3G mobile communications, supporting the market expectations until 2010 for peak transmission capacities up to 2 Mbps and full mobility have been identified. On the other hand, frequency resources for wireless LAN technology are envisaged to be identified at WRC'03 in the 5 GHz band. With the ongoing enhancement of 3G services in term of increasing data rates as well as the consideration of new elements beyond 3G it is anticipated that traffic volume will further increase significantly. Hence, additional spectrum resources will be required in the medium and longer term. Bands suitable for mobile communications are limited in frequency due to propagation conditions. The process of spectrum identification typically requires a period in the order of 8 -10 years from the allocation or identification of a frequency band until the spectrum is available for network operation. Reasons for this long transition process are e.g. re-farming of existing applications and standardisation activities of equipment in timely manner. Hence, if frequency bands shall be available around and subsequent to 2015 the frequency allocation/identification should be made around 2006.

In analysing the spectrum implications of the future development of 3G and systems beyond 3G, key issue to be addressed is the future market of mobile communications in terms of services, applications and traffic projections. In the past, estimation of spectrum requirements of mobile applications has been considered as a static framework focussing on a single system and market scenario applying simple spreadsheet calculations. With the advent of a convergence of mobile and fixed telecommunication and multi network environments as well, supporting attributes like seamless inter-working between different complementary access systems, application of such a simple approach is no longer suitable. For the estimation of frequency requirements, new statistical based simulation models have to be developed and applied which are based on the Monte Carlo method. Such models allow for consideration of spatial and temporal distributions of the market requirements and network deployment scenarios as well.

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The Monte-Carlo simulation method is based upon the principle of taking samples or snapshots of random situations. Such a methodology is capable to address virtually all scenarios under consideration. This flexibility is achieved by defining the relevant parameters as statistical distribution functions. It is therefore possible to model even very complex situations by relatively simple elementary functions. Such architecture itself has to be designed versatile enough to allow flexible treatment of all relevant issues from market and technology perspective. Special attention has to be drawn to the fact, that inter-working between different access-systems will be performed in terms of vertical handover or session continuation amongst the candidate access systems. Availability of different access systems as well as customers access strategies have to be taken into consideration. Hence, results provided by such methodology will not give simple numbers of required bandwidth. Ranges of required spectrum resources for different RAT under consideration will be the result, depending on the assumptions be defined within the simulation process. This allows studying different sets of assumptions in order to identify the impact on the spectrum requirements themselves. On the other hand consideration of economical conditions of network operation as a function of available frequency resources is possible as well. Hence, new spectrum management methods like enhanced spectrum sharing or spectrum pooling may be supported by such results.

As a consequence, the methodology to estimate the spectrum requirements themselves has to imply as much flexibility as possible, so that decisions are not made prematurely which may endanger the flexibility needed for the future. This general objective is the basis of the methodology for spectrum estimations proposed in this document. However, results in terms of frequency requirements for further enhancement and systems beyond 3G can realistically be achieved only if market expectations are available for application. Hence, once such spectrum requirement methodology is ready to be applied, market research has to provide the relevant information for the spectrum estimation itself.

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2 Evolution from IMT-2000 to beyond IMT-2000 systems

The future development of mobile communication in terms of IMT-2000 and systems beyond IMT-2000 is envisaged by ITU-R WP 8F to be a three step incremental process:

Future development of IMT-2000: The vision for the future development of IMT-2000 is that there will be a steady and continuous evolution. For example, the current capabilities of some of the terrestrial radio interfaces are already being extended towards 10 Mbps and it is anticipated that these will be extended even further over the next decade. The vision for the future development of IMT-2000 is to raise the down-stream transmission speed (from the base station to a terminal) to about 30 Mbps by around the year 2005

Future development of IMT-2000 in relation with future development of other radio systems.: In conjunction with the future development of IMT-2000 there may be an inter-relationship with other radio systems, for example wireless LANs, digital video broadcast, etc.

Systems beyond IMT-2000: For systems beyond IMT-2000, there may be a requirement for a new complementary wireless access technology for the terrestrial component, sometime after the year 2010. This will complement the future development of IMT-2000 and future development of other radio systems. Present digital cellular systems have evolved by adding more and more system capabilities and enhancements to make them resemble the capabilities of IMT-2000 systems. It is anticipated that with IMT-2000 there will also be a continuum of enhancements that may render those systems practically indistinguishable from systems beyond IMT-2000; indeed, the user should see a continuous increase in capability. The vision for a potential new radio interface is to support up to 50-100 Mbps in the mobile environment and up to 1 Gbps in the stationary environment in the down-stream transmission by around the year 2010

In the future, wireless service provision will be characterised by global mobile access (terminal and personal mobility), high Quality of Service (full coverage, intelligible, no drop and no/lower call blocking and latency), and easy and simple access to multimedia services for voice, data, message, video, world-wide web, GPS, etc. via one user terminal.

End-to-end secured services will be fully co-ordinated, via access control, authentication use of biometric sensors and/or smart card and mutual authentication, data integrity and encryption with no intermediate gateway(s) for decryption/re-encryption. User added encryption feature for higher level of security will be part of the system.

The vision from the user perspective can be implemented by integration of these different evolving and emerging access technologies in a common flexible and expandable platform to provide a multiplicity of possibilities for current and future services and applications to users in a single terminal. Systems beyond 3G will mainly be characterised by a horizontal communication model, where different access technologies as cellular, cordless, WLAN type systems, short range connectivity and wired systems will be combined on a common platform to complement each other in an optimum way for different service requirements and radio environments. Figure 2-1 shows the capabilities of IMT-2000 and systems beyond IMT-2000. These access systems will be connected to a common, flexible and seamless core network. The mobility management will be part of a new Medium Access System as interface between the core network and the particular access technology to connect a user via a single number for different access systems to the network. This will correspond to a generalised access network. Global roaming for all access technologies is required. The inter-working between these different access systems in terms of horizontal and vertical

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handover and seamless services with service negotiation including mobility, security and Quality of Service will be a key requirement, which will be handled in the newly developed Medium Access System and the core network.

This vision "Optimally Connected Anywhere, Anytime" results in a seamless network (including a variety of inter-working access systems), as seen in Figure 2-2 which are connected to a common IP based core network. The Medium Access System connects each access system to a common core network. Due to the different application areas, cell ranges and radio environments the different access systems can be organised in a layered structure (according to Figure 2-3) similar to hierarchical cell structures in cellular mobile radio systems. However, in addition to different cell layers also different access technologies are complementing each other on a common platform. Multi-mode terminals and new appliances are key components, which will be adaptive based on Software Defined Radio technology using high signal processing power.

FIGURE 2-1Illustration of capabilities of IMT-2000 and systems beyond

denotes interconnection between systems via networks or the like, which allows

flexible use in any environments without making users aware of constituent systems.

Dark gray color indicates existing capabilities, medium gray color indicates enhancements to IMT-2000,and the lighter gray color indicates new capabilities of Systems Beyond IMT-2000.

The degree of mobility as used in this figure is described as follows: Low mobility covers pedestrian speed, and highmobility covers high speed on highways or fast trains (60 km/h to ~250 km/h, or more).

Illustration of Capabilities of IMT-2000 and Systems Beyond

IMT-2000

Mobility

Low

High

1 10 100 1000

New CapabilitiesOf Systems Beyond

IMT-2000

Peak Useful Data Rate (Mb/s)

NewMobileAccess

New Nomadic / LocalArea Wireless Access

EnhancedIMT-2000

Enhancement

Systems Beyond IMT-2000 willencompass the capabilities ofprevious systems

Dashed line indicatesthat the exact datarates associated withSystems Beyond are

not yet determined.

KEY:

Digital Broadcast SystemsNomadic / Local Area Access Systems

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FIGURE 2-2:Seamless future network of systems beyond IMT-2000 including a variety of inter-working

access systems

FIGURE 2-3Illustration of complementary access systems

distribution layer

cellular layer

hot spot layer WLAN typee.g. ETSI BRAN

DAB and/or DVB

2G: e.g.GSM

IMT-2000UMTS

personal network layer

XX X X X X X X XX X X Xfixed (wired) layer

• full coverage• global access• full mobility• not necessaryindividual links

• full coverageand hot spots

• global roaming• full mobility• individual links

• local coverage• hot spots• global roaming• local mobility• individual links

• short rangecommunication(e.g. Bluetooth, DECT)

• global roaming• individual links

• no mobility• global roaming• individual links

horizontal handover within a system vertical handover between systems

possible return channels

S erv ices and

applications

IP based core network

IM T-2000UMTS

W LA N

type

cellu larGSM

short range

connectiv ity

W ireline

xDSL

other

entities

DA B

DV B

re turn chann el:

e. g. G SM

download channel

New radio

interface

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3 IMT-2000 spectrum

3.1 IMT-2000 spectrum allocation process

The process of identifying the spectrum requirements for public mobile service applications in the year 2010 has been applied with the result that a total amount of spectrum of e.g. 550 MHz for Europe has been identified for IMT-2000 since WRC'00. The frequency bands being globally allocated as well as the situation in Europe are illustrated in Figure 3-1. A two steps approach has been applied with the result of identifying the IMT-2000 core bands at WARC'92 and the extension bands at WRC'00. However, any estimation of a spectrum requirement for many years into the future is not an exact calculation. In particular, the methodology applied for IMT-2000 is not intended to include the second or third order effects, but rather the calculations capture the significant first order influences which are the primary factors for terrestrial spectrum needed. For the consideration of spectrum requirements for systems beyond IMT-2000 an improvement of this methodology is of vital interest.

FIGURE 3-1Spectrum identified for IMT-2000

3.2 Frequency bands identified for IMT-2000

3.2.1 IMT-2000 core band spectrum (WARC 1992)

The first phase of identifying spectrum for IMT-2000 aimed to achieve the following primary general objectives:

Make efficient and economical use of the radio spectrum consistent with providing service at an acceptable cost;

Provide services with a quality of service comparable to the fixed networks (e.g. ISDN);

Provide these services over a wide range of user densities and geographic coverage areas;

Ensure the continuing flexible extension of service provision, subject to the constraints of radio transmission, spectrum efficiency and system economics;

Resulting in the overall objective in providing services supported by user bit rates up to approximately 2 Mbps.

Considerations on spectrum took into account the estimated traffic, the available and foreseeable techniques, the propagation characteristics and time scale for meeting the users’ needs. To comply

1850 1900 1950 2000 2050 2100 2150 2200 2250

UMTS GSM 1800 DECT

MSS

IMT 2000 IMT 2000

MSS UMTS

MSS MSS ITU Allocations

Europe

IMT-2000 spectrum

1700 1750 1800 950 1000 800 850 900

IMT-2000

IMT 2000

2500 2550 2600 2650 2700

IMT 2000

GSM 900

W ARC 1992 identified bands

MHz

MSS: Satellite component of IM T-2000 WRC 2000 identified bands

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with IMT-2000 service requirements, namely the concept of regional and/or worldwide roaming, worldwide common frequency bands had to be considered as the first choice to enable universal access particularly for personal stations.

Traffic estimations have been focused on expectation that:

Circuit-switched services being dominated mainly for vehicle-mounted stations.

Mobile Terminals (outdoor and indoor) contribute significant lower traffic.

Non-voice traffic is less than 10% of the voice traffic.

The Estimation of spectrum needs identified a minimum spectrum bandwidth required for voice and non-voice services of approximately 230 MHz. The total requirement is 167 MHz for vehicular mounted stations and 60 MHz for mobile terminals(see Table 3-1).

TABLE 3-1:

Spectrum requirements in different environments combining the uplink and downlink components

Vehicular Terminal outdoor Terminal indoor

Voice services 111 MHz 27 MHz 24 MHz

Non voice services 56 MHz 3 MHz 6 MHz

This spectrum has been identified for IMT-2000 at WARC'92 on a global basis.

3.2.2 IMT-2000 extension band spectrum (WRC 2000)

Identification of IMT-2000 core bands followed a very simple approach estimating the requirements based on simple market assumptions prior to WARC 1992. For the aim of estimating the frequency requirements within the time frame of 2010 several research activities have been carried out in order to provide enhanced methodologies for identifying the additional spectrum requirements. These activities were not limited to the issue of additional spectrum for IMT-2000. Objective was to estimate the market and spectrum requirements for all public mobile radio services around the year 2010 including 2G services as well. Concerning the spectrum requirement itself, the additional spectrum requirements had to be identified with respect to the IMT-2000 core bands. Supportive activities describing the expectations on IMT-2000 in terms of:

Service definition (circuit switched, packet switched)

Market studies

Development of spectrum calculation methodologies

have been started in the early 1990s and went on until WRC 2000 where the IMT-2000 extension bands have been identified. ITU-R Recommendations on services and spectrum calculation methodologies have been developed (M.687-2, M.816-1, M. 1390). Based on market studies carried out for different regions in terms of terrestrial and satellite components of IMT-2000 the estimation of the spectrum requirements has been approved mid 1999 in terms of ITU-R Report 2023. This report provides distinct spectrum requirements for the services under consideration:

Speech service

Simple messaging

Switched data

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Asymmetrical multimedia services

Symmetrical multimedia services.

Applying a market study for the European situation from 1998 this lead to the spectrum requirements in terms of services and environments as illustrated in Table 3-2.

TABLE 3-2:

Spectrum requirements in different environments combining the uplink and downlink components

Environments High density-in building

Urban pedestrian

Urban vehicular

Speech 11.2 MHz 145.8 MHz 2.8 MHz

Simple Message 0.2 MHz 1.2 MHz 0.05 MHz

Switched Data 5.8 MHz 64.9 MHz 1.0 MHz

Medium Multimedia 3.5 MHz 44.7 MHz 0.9 MHz

High Multimedia 20.8 MHz 124.9 MHz 4.2 MHz

High Interactive Multimedia

10.5 MHz 61.1 MHz 1.5 MHz

By summation of the single requirements of all services the total requirements have been estimated. Considering that the identified total terrestrial mobile spectrum consists of the spectrum already identified for terrestrial IMT-2000 and also the spectrum used for first and second generation mobile systems, the resultant additional IMT-2000 terrestrial component spectrum required for Europe is given in Table 3-3. An additional requirement of 160 MHz has been communicated in WRC 2000. WRC 2000 decided to identify 190 MHz for terrestrial component of IMT-2000 in the 2500 – 2690 MHz band, including an option to use the 2500-2520 and 2670-2690 MHz for satellite component due to market demand. This band is expected to be available in most European countries around and subsequent the year 2008 supporting expectations of the market of mobile communication for the year 2010 for services with up to 2 Mbps peak data rates.

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TABLE 3-3:

Mobile terrestrial spectrum requirement for the year 2010

Total terrestrial mobile spectrum requirement for

the year 2010

Terrestrial mobile spectrum identified for IMT 2000

Forecasted additional IMT-2000 terrestrial mobile spectrum requirements for

the year 2010

555 MHz 395 MHz 160 MHz

3.2 Spectrum estimation methodology

3.2.1 Limitations of ITU-R Rec. M.1390 methodology

ITU-R Recommendation ITU-R M.1390 applied for the spectrum requirement expectations of mobile communication in the year 2010 provides a methodology based on blended 2G and 3G technology networks projected to exist between now and around 2005 to 2010. For this methodology the model of service delivery is a voice-based traffic architecture including data services with some higher data rate services up to 2Mbps peak data rates that are characterised by a simple peak-traffic model. An estimate of the spectrum required to carry the projected traffic for 2010 was developed in Report ITU-R M.2023. The traffic assumptions used in Report ITU-R M.2023 are from the 1996-1998 time period.

This results in limitations which may not allow to apply this methodology for the consideration of spectrum requirements for the further enhancement of 3G and systems beyond 3G:

Focus on cellular networks only

Busy hour concept rather than time dependent access consideration

No clear distinction between packet and circuit switched applications

Limitation to frequency bands below 3 GHz

system capabilities assumed to be the same for all environments and mobility requirements

simple assumptions on improvement of spectrum efficiency

independent treatment of the various environments

coincident busy hours for all applications and environments with a simple weighting to correct for non-simultaneous busy hour traffic

However, the most important drawback is the focus on network technology rather services and markets which does not allow to consider inter-working and handover processes between different applications. Hence, the applicability of the existing ITU-R spectrum estimation methodology for future enhancements of 3G and systems beyond 3G has to be questioned.

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3.2.2 Scope of future spectrum estimation methodologies

3G mobile communication systems will offer mobile wide-band multimedia services with high data rate up to 2 Mbps offering a quality of service comparable to fixed networks. This requires huge transmission capacity especially in local areas of:

High population;

Concentrated industrial activity or

Campus settings.

Evolution of 3G and systems beyond will go along with the convergence of services and applications in terms of increasing transmission capacity per user and combination of different applications like cellular networks and WLAN. On the other hand mobility of users has to be considered in a broader sense e.g. nomadic users have to be taken into account rather than focussing on typical cellular users only. However, the spectrum calculation methodology provided by ITU-R Rec. M.1390 has a clear focus on cellular mobile networks. The consideration of the operational conditions expected for 3G applications is the starting point of the existing methodology in terms of considered cell sizes. Hence the spectrum calculation is directly related to possible cell implementations of 3G cellular networks. From the viewpoint of convergence this limitation does not allow to consider the issue of combination of different technologies.

As a consequence the existing methodology needs to be modified. In order to meet the requirement for flexibility in terms of combination of services and applications, the focus of the spectrum calculation methodology has to be set to the consideration of general service and capacity requirements for mobile communications applications rather than providing cellular cell size related estimations only.

The first step for a generally applicable spectrum calculation methodology is the consideration of service and application requirements of mobile communication systems in different environments grounded on market expectations. The key issue in that respect is the market forecast for 3G and systems beyond 3G for identifying the services and markets of future mobile service applications. Furthermore a wide range of frequency bands need to be considered including the bands already identified for 3G mobile services.

3.2.3 Market and technology aspects

The basics for all considerations concerning 3G networks are the market expectations for mobile communications services within the framework of 10 to 15 years time from now. The key issue in this respect is the forecast of the required communication capacities for uplink and downlink operations of the mobile users within 3G and systems beyond 3G.

Estimations of the market expectations for mobile communications services need to be based upon a market forecast tool, being usable for many regions of the world with varying demographical and economical data. Spectrum requirement calculations have to be focused on the peak capacity requirements e.g. in densely populated regions or central business districts. In order to allow the consideration of the combination of different applications an estimate of full coverage networks of regions outside the hot spots of a network are necessary as well. Furthermore, the impact of market shares, economical frameworks of network deployment and operation has to be considered as well in order to identify spectrum for different access technologies.

With the envision of an increasing possibility and movements towards convergence of different services coming from completely different backgrounds for example, mobile communications, Internet, broadcasting, wireless LANs, convergence of a variety of applications, services and delivery mechanisms will be a key issue for the future. Differing information flows are desired by

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the users to be available regardless of the means and manner of delivery. This will lead to complementary access systems combined via vertical hand-over procedures in terms of seamless inter-working.

3.2.4 The way to an enhanced spectrum estimation methodology

The technical process of estimating spectrum requirements for mobile communications has to be grounded on four essential issues:

Definition of services

Market expectations

Technical and operational framework

Spectrum calculation methodology

The general interrelations of this process are illustrated in Figure 3-2.

FIGURE 3-2:Interrelationship of spectrum identification work items

Combined with a vision on the timeframe under consideration the spectrum to be accommodated has to be calculated. This requires a step-by-step approach considering several partly overlapping work items in terms of timelines as illustrated in Figure 3-3.

Methodology Technologies

Market studies

Suitable frequency bands

Spectrum requirements

Services

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FIGURE 3-3Timelines and phases of spectrum requirement estimations

The requirements concerning the traffic volume to be transported in terms of peak offered bit quantity is the basis for estimating the spectrum requirements for mobile communication systems. The service capability of mobile communication systems in terms of

Capacity per service area or cell

Impact of user mobility on network capabilities

Vertical handover capabilities

Frequency bandwidth of application

Suitable frequency bands

Frequency cluster and sectoring

Economical framework of network operation

Possible density of access points

Market shares of network operators

will determine the spectrum requirement. Special attention has to be drawn to the aspect of economical conditions. In principle it may be possible to provide the required capacities with a minimum amount of spectrum using the most efficient technology. However, such a concept would lead to such dense networks which are highly uneconomic in their deployment and operation. A balance has to be found between economical framework for network operation on the one hand and efficient use of the spectrum on the other hand. Objective of such an approach is to provide 3G

Vision on Mobile Communication

Services

Technologies

Market Assessment

Spectrum Calculation Methodolgy

Frequency Requirements

Suitable Frequency Bands


Services

Technologies

Market Assessment





Services

Technologies

Market Assessment




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mobile services in densely as well as sparsely populated areas for high mobility as well as low mobility/nomadic access under economically feasible conditions. Hence, it has to be distinguished between frequency requirements for

rural

urban and

hot spots

in combination with the mobility requirements of mobile service users, in particular in urban areas and hot spots a concept of vertical handover needs to be considered and appropriately be incorporated into a spectrum requirement estimation process. On the other hand requirements of the network operators in terms of

efficient planning

fast network rollout

cost effectiveness

have to be considered as well.

Mobile service networks in the scope of 3G and systems beyond 3G will be organised in hierarchical structures. Different applications different service area sizes and different mobility requirements are necessary to accommodate the needs according to the capacity requirements in different geographical regions. In that respect the network capabilities are of special interest and need to be considered for all possible radio access technologies in terms of:

Mobility to be supported

Transmission capacities for up- and down-link

Envisaged operational environments of network deployment

In practice the mobility requirements will dominate the consideration of amount of spectrum to accommodate capacity requirements. In principle the higher the mobility of the users under consideration the lower the frequency efficiency of the system due to higher necessary redundancy to cope with the propagation conditions in terms of multipath and doppler effects. On the other hand high mobility users need large cell sizes or service areas to limit the number of handover procedures to the extent possible. Thus, for all scenario (combination of mobility, environment and transmission direction) frequency requirements have to be considered separately and frequency ranges best suited need to be identified. The combination of all scenarios leads to the overall frequency requirements for mobile communications in terms of 3G and systems beyond 3G. A wide range of frequency bands for different user requirements will be the result of such estimations.

Since such networks and services are characterised by high dynamics, there is a requirement for traffic and system capability parameters to be represented by statistical functions. Thereby their interaction can be simulated by a modelling technique applying a Monte Carlo simulation approach.

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4 Enhanced Methodology for spectrum requirement estimations in mobile communication

4.1 General principle

The radio spectrum is a scarce and limited resource and can only be used optimally, if frequency allocation complies with market demand for radio services to the greatest extent possible. Mobile technology is set to change the face of telecommunications. Following the global success of GSM, effort of the last decade has been concentrating on third generation systems (3G) as the means to support higher bit rate flexible data services for customers on the move. With the ongoing enhancement of 3G services as well as the advent of elements beyond 3G it is anticipated that traffic volume will further increase significantly. Higher traffic volumes to be carried will lead to an increase of spectrum resources being required. Frequency bands suitable for mobile communications are limited in frequency due to propagation conditions. Within these suitable frequency bands mobile services are competing on frequencies with other radio services like broadcasting, fixed service or radar applications. Compared with these incumbent frequency users who are using these bands since decades, the mobile service is a newcomer, prospering since the beginning of the 1990s. Allocation of frequency bands suitable for mobile applications have been made in the mid of the 20th century when mobile communications has not been considered as a mass market with a high demand of frequency resources. Hence, the amount of frequency resources readily available to mobile applications is very limited and does not cope with today’s requirements expected. Thus, any additional spectrum has to be acquired from bands where other services may already be deployed. This requires a transition process of re-farming of existing services or, if feasible, shared use of frequency bands with other services.

Systems beyond 3G will likely include attributes of seamless inter-working between different complementary access systems in a deployment area. Such inter-working between different access systems will be performed in terms of vertical handover or session continuation including service negotiation to adapt the application to the service capabilities of the candidate access systems. The different layers to be considered correspond to the:

Distribution layer: Digital broadcast type systems to distribute the same information to many users simultaneously through unidirectional links. Other duplex access systems can be used as a return channel.

Cellular layer: The cellular networks with different cell size and or different access systems.

Hot spot layer networks for very high data rate applications, very high traffic density and individual links, e.g., in very dense urban areas, campus areas, conference centres, and airports. Microcells of mobile networks and nomadic/local wireless access of systems beyond IMT-2000 are part of this layer.

Personal network layer: Short range direct communication between devices in terms of ad hoc networks.

Fixed layer: Fixed access system

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FIGURE 4-1Layers of future mobile communication

Details of this layer concept are illustrated in Figure 4-1. Such conception requires a flexible and scalable environment for the allocation of system capacity in a deployment area, where one or several systems may be deployed according to the needs. Convergence between fixed and mobile applications is considered whereby users access the same services and applications but these are adapted to their current terminal and location. It is important to note that different technologies, such as WLAN, short range connectivity systems and cellular mobile systems may be present in many devices operating across the various networks at any particular time. With the ongoing growth of user penetration of mobile communications, the anticipated growth of data applications and bandwidth a further demand for new additional spectrum is expected. On the other hand new methods of spectrum management need to be considered allowing e.g. enhanced spectrum sharing/pooling in order to use the available frequency resources efficiently to the greatest extent possible.

Distribution Layer

Cellular Layer

Fixed (Wired) Layer

Possible return channels

X X X X X X X XX X X X X X X

Hot Spot" Layer

Personal Network Layer

• full coverage• global access• full mobility• not necessarilyindividual links


•

•••

full coverageand "hot spots"


• local coverage• "hot spots"• global roaming• local mobility• individual links

• local coverage• "hot spots"•• local mobility• individual links

• short range


• short rangecommunication




horizontal: handover within a system


vertical: handover between systems

Distribution Layer

Cellular Layer

Fixed (Wired) Layer

Possible return channels


Hot Spot" Layer

Personal Network Layer





•

•••



•

•••







• short range




• short range








horizontal: handover within a system


vertical: handover between systems

- 18 -

FIGURE 4-2Expectations on Global growth of mobile and fixed communication markets

For the future development of 3G and systems beyond 3G, it is important to understand the market trends that will affect the development of such systems. In particular, increasing user expectations and the growing demand for mobile services, as well as the evolving nature of the services and applications that may become available will have significant impact on the future development of mobile communication markets. It is envisaged that, by 2020, potentially the whole population of the world could have access to advanced mobile communications devices, subject to, amongst other considerations, favourable cost structures being achieved. The number of portable handsets already exceeds and will continue to grow more rapidly than the number of fixed line devices connected to the Internet. Mobile terminals will be the major devices to access and exchange information. Already the number of mobile telephones exceeds the number of fixed line telephones (see Figure 4-2). To support this market development sufficient frequency resources for all Radio Access Technologies is vital to provide services to the customers at affordable costs. It has to be noted that the variety of multimedia services expected for the future will address different market segments in terms of business and private users. Hence demand of traffic volume as a function of daytime will not be the same for all services.

Objective of this critical consideration in realizing the vision for the future development of 3G and systems beyond 3G is the availability of adequate spectrum to support future services. In analysing the spectrum implications of the future development of 3G and systems beyond 3G, many issues must be addressed, including, but not limited to:

Market of mobile communications (services, applications and traffic projections);

Evolution of IMT-2000 systems;

Mobile Internetsubscribers

Mobilesubscribers

0

200

400

600

800

1000

1200

1400

1600

1800

1995 2000 2005 2010

Subscriptions worldwide (millions)

Mobile subscribers

Fixed subscribers

Mobile Internet

Fixed Internet

Mobile Internetsubscribers

Mobilesubscribers

0

200

400

600

800

1000

1200

1400

1600

1800

1995 2000 2005 2010

Subscriptions worldwide (millions)

Mobile subscribers

Fixed subscribers

Mobile Internet

Fixed Internet

- 19 -

Radio transmission characteristics and spectrum efficiency; (TDD/FDD, duplex direction, transmit/receive separation, modulation and access schemes, etc.);

Harmonized use of spectrum and technical solutions to facilitate global roaming;

Investigation of new methods for reuse and sharing of spectrum (techniques of dynamic spectrum sharing and pooling);

Economies of scale of network deployment and terminal costs.

This determines the potential need for and identification of additional spectrum. On the other hand, evolving technology advances may allow a more efficient use of spectrum.

Estimation of spectrum requirements of mobile applications like IMT-2000 has been considered in the past as a static framework focussing on a single system and market scenario applying simple spread sheet calculations. With the advent of a convergence of mobile and fixed telecommunication and multi network environments as well, application of such a simple approach is no longer suitable for the estimation of frequency requirements. New statistical based simulation models have to be developed and applied which are based on the Monte Carlo method. Such model allow the consideration of spatial and temporal distributions of the market requirements and network deployment scenarios as well.

The Monte Carlo simulation method is based upon the principle of taking samples or snapshots of random variables from their defined probability density functions also called distributions. Such methodology is capable to address virtually all scenarios under consideration.. This flexibility is achieved by the way the relevant parameters are defined. Each random parameter is input as a statistical distribution function. It is therefore possible to model even very complex situations by relatively simple elementary functions. A number of diverse issues in the framework of spectrum requirement estimation can be treated by Monte Carlo methods, such as:

Services and user penetration

Customers access to the several Radio Access Technologies

Network deployment and user distribution

Propagation conditions.

Standard distribution functions like Gaussian and Rayleigh distribution are applicable as well as individually defined distribution functions, depending on the issue considered.

A general architecture of the envisaged spectrum calculation methodology is given in Figure 4-3. Such an architecture itself has to be designed versatile enough to allow flexible treatment of all the issues under consideration.

- 20 -

FIGURE 4-3:Architecture of an enhanced spectrum calculation methodology

Key issues of such methodology are:

Market of mobile communications in terms of services and customer requirements;

Available Radio Access Technologies in terms of systems and coverage aspects;

Estimation of required frequency resources for all Radio Access Technologies under consideration taking into account the economical framework of network deployment and operation;

Regulatory framework of spectrum allocation and identification.

Combination of all these aspects leads to the spectrum requirements for future mobile communications. In particular the impact of:

Complementary access systems;

Economical conditions of network deployment and operation;

Market scenarios in terms of full market versus competitive environment on the frequency resources be required shall be considered.

TechnicalCharacteristics

DistributionFunctions

Spectrumrequirements

Market of MobileCommunication

Map customers requestonto Radio Access Technology

Estimation of frequency ressourcesper Radio Access Technology

EconomicalFramework







EconomicalFramework













EconomicalFrameworkEconomicalFramework

- 21 -

4.2 Spectrum requirement estimation methodology

4.2.1 Functionality

The proposed methodology for estimating spectrum requirements of mobile communication is subdivided into four functions. These functions are defined such that a clear input output relation exists. Figure 4-4 depicts all functions embedded within the overall methodology flow. A brief description of the functions is given below a more detailed treatment can be found in sections 4.2.2 to 4.2.5.

Current methodologies for the calculation of e.g. IMT-2000 terrestrial spectrum requirements apply a top down approach in which parameters are set at the beginning of the methodological flow and kept constant until the final step of the calculation process. Within the proposed enhanced methodology however, an iterative approach has been incorporated, which allows to iteratively modify the calculation parameters dependent on the outcome of certain calculation steps in order to achieve the optimum result in terms of economical aspects. Iterations might be necessary in order to find the e g. optimum trade-off between terminal complexity – and therefore costs – and spectrum efficiency, or because of an unfeasibly network structure in terms of cellular structures or access point density.

Such iteration loops are generally handled within the functions themselves (inner iterations). However iterations across blocks need to be performed as well in terms of process repetition with different assumptions if the simulation e. g. fails to find a feasible result. For instance, if it is impossible to achieve an economically satisfying result, it might be necessary to modify the market input parameters and to restart the simulation process.

Another rather new aspect of the methodology proposed is the incorporation of different Radio Access Technologies (RAT) e.g. 2G and 3G generation mobile communications systems or terrestrial broadcast systems as well as WLAN type of systems into the calculation. From a spectrum requirements point of view, all available and suitable Radio Access Technologies will be treated as integral parts of mobile communication in terms of a future development of 3G and systems Beyond 3G.

- 22 -

FIGURE 4-4Flow chart of the spectrum calculation methodology

SystemSpecifications

MarketExpectations

Key technicalCharacteristics

Identification of Radio Access Technologies

(RATs)

2Market of MobileCommunication

1

Mapping Services ontoRadio Access Technologies

3

Estimation of the amountof frequency resources

required by different RATs

4

Servicedemand per

Environment

Densities ofPotential users

User requests perEnvironment

and RAT

Required spectrum for Mobile communication

SystemSpecifications

MarketExpectations

Key technicalCharacteristics

Identification of Radio Access Technologies

(RATs)

2Market of MobileCommunication

1

Mapping Services ontoRadio Access Technologies

3

Estimation of the amountof frequency resources

required by different RATs

4

Servicedemand per

Environment

Densities ofPotential users

User requests perEnvironment

and RAT

Required spectrum for Mobile communication

- 23 -

The "Market of mobile communications"-function (1) uses as input existing market forecast studies. From these studies the kind of required services, the user penetration per service as well as the user traffic characteristics shall follow. Additionally population data per environment (urban, suburban, rural, etc.) shall be an input parameter to this function. The outputs of this function is the demand for the identified services which need to be served with a specific quality within the specified environments (urban, suburban, rural, etc.). (If not all services are covered in existing market forecast studies additional forecasts need to be initiated).

The "Identification of RATs"-function (2) analyses the technical specifications of potential Radio Access Technologies in terms of their key technical characteristics. Here the Radio Access Technologies are analysed in terms of their target deployment environment and service/application for which they were designed. Additionally potential Beyond 3G air interface concepts which are not yet developed and their respective properties can be taken into account here. The output is a description of key technical characteristics, e.g. max. transmit power, min. receiver sensitivity, max. delay spread, max. data rate, service type, max number of users per km², etc. of the system under consideration.

The "Mapping user service requests onto RATs"-function (3) uses as inputs the output of the "Market of mobile communications"-function and the description of key technical characteristics (technical capabilities) of Radio Access Technologies potentially suitable to be part of a Beyond 3G system from the "Identification of RATs"-function. The output of this function delivers the probability distributions of the number of concurrent usage requests per environment, service and RAT as a function of daytime using Monte Carlo based random processes.

The "Estimation of the amount of frequency resources required by different RATs"-function (4) assesses the required amount of spectrum by Monte Carlo type of system simulations. Inputs to this function are the probability distributions of usage demands (output from "Mapping user service requests onto RATs"-function), the description of the key technical characteristics of the Radio Access Technologies under consideration, the deployment environment with its accompanying radio propagation conditions and economical considerations (e.g. access point density, terminal complexity) as a measure for economically feasible network operation. The output of this function is the required amount of spectrum per environment (bandwidth) for mobile communication systems giving a certain but feasible split of the total estimated traffic between existing and emerging Radio Access Technologies. In order to obtain the final aggregate spectrum for all environments it has to be taken into account which of the envisaged environments co-exist. This function is certainly the one of highest complexity since all the statistical properties of the network topology and traffic to be served need to be carefully modelled.

4.2.2 Market of mobile communications

Market studies on mobile communications intend to look into the future in order to derive a realistic picture on the mobile communications demands in terms of services provided to the customers, traffic volumes and capacities, deployment expectations of networks, user penetrations,

- 24 -

communication costs, etc.. Such information is one key issue for the estimation of frequency requirements for future mobile communications applications. The large variety of information available from market studies requires a process of extraction of the relevant ones. For this purpose it is necessary to define a comprehensive set of parameters to be extracted from market studies, which are most relevant for spectrum requirements estimation.

4.2.2.1 Description of different types of services

Communications market studies available in general describe services by means of their characteristics properties. A common way ,as used in e.g. in the identification process for IMT-2000 spectrum, is to classify services in different categories as shown in the example given in Table 4-1. The classification is made according to the type of channel, which describes the services asymmetry, the throughput and the interactivity for example.

TABLE 4-1:

Example of Service Categories

Channel Type Type of Services

Asymmetric

VHMM (Very High Multi Media)

HMM (High Multi Media)

MMM (Medium Multi Media)

Symmetric

VHIMM (Very High Interactive Multi Media)

SM (Simple Message)

SD (Switched Data)

S (Speech)

In detail these example service types may represent communication means providing capacities in the order of:

The VHMM service gathers all multimedia services, which require high bit rate: 20Mbps in downlink and 2Mbps in uplink.

The HMM service has a user bit rate of 2Mbps in downlink and 128 kbps in uplink.

The MMM service has a user bit rate of 384 kbps in downlink and 64 kbps in uplink.

The VHIMM service has the same characteristics as the VHMM, but it has the characteristic of symmetry and a bit rate of 2Mbps in uplink and downlink.

The SM service has a user bit rate of 64kbps in both downlink and uplink.

The SD service has a user bit rate of 14kbps in both downlink and uplink.

The S service has a user bit rate of 14kbps in both downlink and uplink.

This example list is not exhaustive, additional services with significant higher data rates may be added in the future.

- 25 -

4.2.2.2 Parameters required for estimation process

From the information given in existing market studies for future mobile services, difficulties may appear in order to get precise values for the various relevant parameters. In the most cases – for the sake of simplicity – there is only static and deterministic assumptions on parameter values, even though a parameter may be characterised by a dynamic and/or a stochastic nature in the real world. For a realistic system and traffic modelling, however, a consideration of this fact for future spectrum estimation methodologies is seen to be of crucial importance.

Some parameters might be represented by stochastic processes instead of deterministic values. Consequently, parameters might be first of all classified into those, which are deterministic and those, which are stochastic in nature. In case of a deterministic parameter, a further classification into static (i.e. constant value over time) or dynamic (i.e. changing value over time) is necessary. In case a parameter value is best represented by a stochastic process a further classification into those processes, which are stationary (i.e. constant statistical properties, e.g. mean value, variance, etc. over time) and those, which are non-stationary statistical processes (i.e. changing statistical properties over time) is necessary.

There are several of market reports, which allow picking out relevant parameters and determining how to treat parameters in a static or in a dynamic way. An example list of relevant parameters, including their tentative classification, for the estimations process of spectrum requirements are given in Table 4-2. It is distinguished deterministic and stochastic parameters. Furthermore, dependent on the classification into deterministic or stochastic, it is indicated whether the respective parameter is static/dynamic or stationary/non-stationary respectively.

TABLE 4-2:

Key market parameters

Parameter DescriptionRecommended classification

Density of potential users

It represents the number of persons per unit area of a selected area (e.g. urban, sub-urban, rural). For an efficient spectrum allocation between different systems, e.g. UMTS, WLAN, DVB-T etc. it is of crucial interest how the density of potential usesr change over time.

Deterministic and dynamic

Call/session arrival rate

It represents the number of calls/sessions per unit time.

This parameter is best characterised by a stochastic process. Since the number of users per environment per unit area changes over time, it is additionally a non-stationary process.

Stochastic and non-stationary

Call/session duration

It is the duration of a successfully initiated call or session. It is best represented by a

Stochastic and stationary

- 26 -


stochastic process. Despite the service usage time might heavily depend on the daytime (depending on the operators' charging policies) the process representing this parameter can be considered as stationary for a simulation run since the daytime is fixed prior to the execution of the evaluation process

Service bandwidth

Or

Throughput

It is the minimum acceptable net user bit rate for a given service. It is a deterministic and static parameter, since it is a minimum requirement

Deterministic and static

Service bandwidth symmetry

Or

Uplink factor

It is the ratio between uplink and downlink service bandwidth and therefore is used to consider asymmetric uplink/downlink traffic. It is a deterministic and static parameter, since it is a requirement.


Quality of Service (QoS)

It determines the minimal required quality according for example to the type of service and the type of user (e.g. maximum connection set-up time, delay and error tolerance)

The QoS is a deterministic parameter from a single user's perspective, since it is a requirement per user. Further more it can be seen as dynamic with respect of the daytime (depending on the operators' charging policies), however for one simulation run it can be assumed as static, since the daytime is fixed prior to the execution of the evaluation process. QoS is furthermore user and service specific. Depending on the realisation of the spectrum estimation methodology, QoS might therefore be represented as a stochastic stationary process with respect to the whole of users.

Deterministic and static (single user)Stochastic and stationary (the whole of users)

Terminal mobility

It is a characterisation of the mobility of the users according to her/his velocity within a given environment (urban, sub-urban, rural). In general, velocity is a function of time and can be seen as dynamic. However, the anticipated spectrum requirements evaluation process consider very short time intervals

Deterministic and static (single user)

Stochastic and stationary (the whole of users)

- 27 -


(snapshots) for which velocity can be assumed to be constant i.e. static. Since different users have different velocities and thus different degrees of mobility this parameter can be best represented by a stationary stochastic process with respect to the whole of users.

Traffic locality

It describes the percentage of traffic, which can be handled by the network without involvement of fixed infrastructures (i.e. Base Stations and Access Points) with respect to the total amount of traffic within that area. This parameter is especially important in connection with ad-hoc and multi-hop networking services, since their suitability in terms of spectrum efficiency and specific applications respectively heavily depends on the geographical distribution of communication partners. It might best be described by a stationary stochastic process. Even through traffic locality might change over daytime, it can be seen as static since daytime is fixed prior the execution of the evaluation process


Communication type

It determines the number of users involved in communication event (person-to-person, person-to-many-person, person-to-machine, etc.).

The value of this parameter can best be represented as stationary stochastic process, since the number of users might be different for different communication events.


Establish mode

It determines if the communication is initiated by the user or by the system.

It depends on the service. As the spectrum estimation is done after the choice of the service, this parameter can be considered as static.


The key market parameters described in Table 4-2 need to be provided by market studies, which have to be started and executed prior to an actual spectrum requirements estimation. However, in order to make sure, that usable results are delivered from these market studies. It is important to have a clear understanding of the spectrum estimation methodology beforehand. Only this can ensure the right output from market studies. The parameters described in Table 4-2 are seen to be the most important, however, there might be others, which have to be added to the list in the future.

- 28 -

4.2.3 Identification of radio access technologies

At some point within the spectrum requirements estimation process it is necessary to identify a suitable Radio Access Technologies for a specific type of service. To allow for a mapping of services onto Radio Access Technologies yielding the best possible result in terms of efficient spectrum usage and economically feasibility, it is essential to fist of all identify the distinguishing features of a possible candidate Radio Access Technologies.

As an example is not only important that a Radio Access Technology can offer a channel with a certain throughput, delay, mobility and error correction capabilities but also what is the required BS density for seamless coverage.

4.2.3.1 Specifications of radio access technologies

Anticipating that future mobile communication will likely include attributes of seamless inter-working between different complementary access systems in a deployment area, different layers have to be considered corresponding to significant numbers of Radio Access Technologies:

Distribution layer: DVB, DAB, etc.

Cellular layer: GSM, GPRS, UMTS, Enhanced IMT-2000, Systems Beyond IMT-2000, etc.

Hot spot layer: UMTS, Enhanced IMT-2000, Systems Beyond IMT-2000, WLAN, etc.

Personal network layer: DECT, Bluetooth, WLAN, etc.

If specifications are not available for the time being, assumptions have to be applied to the extent possible.

4.2.3.2 Distinguishing features of Radio Access Technologies

For the selection process of suitable Radio Access Technologies to be considered in the spectrum estimation the key technical features have to be analysed. The following list summarises a number of distinguishing features, which might be used for the decision whether a Radio Access Technology is suitable or not for a specific service type and application. The list is certainly not complete and it is in general difficult to predict which of the various features might be the most important for the future applications and deployment scenarios, however, it might give a first impression. Therefore the exact parameter list can only be completed after all key requirements of future mobile communication services are known.

Radio Frequency band

Maximum cell size/range

Maximum/Minimum transmitter power

Minimum sensitivity

Error robustness

Maximum user density per given spectrum

Target deployment environment

Supported degree of mobility and terminal velocity

Support of vertical handover

Supported channels and their characteristics (bit rate including return channel, delays, mobility and Quality of Service support functionality

Duplex scheme (TDD/FDD)

- 29 -

Network topology (cellular, ad-hoc/multi-hop, etc.)

Support of multicast/broadcast

Current commercial footprint

Suitability for spectrum sharing/pooling.

4.2.4 Mapping user service requests onto Radio Access Technologies

In a convergent environment of seamless inter-working of mobile communications systems the customers or the operators will have the opportunity to select between different technologies providing similar services in the same local environments. For instance voice communication and all Radio Access Technologies under consideration will provide messaging, whereas high capacity multimedia applications may be restricted to 3G and the systems beyond 3G or WLAN. On the other hand the relationship between Quality of Service (QoS) and communications costs will become a very important selection criteria from the operators and customers points of view. Hence, mapping of services onto RAT will no more be a process applying simple conversion tables. In particular in densely populated regions or hot spots where several networks will be available a complex decision process will be necessary taking into consideration:

Service offering,

Quality of service and mobility requirements,

Communication costs,

Vertical and horizontal handover strategies,

Giving special attention to customer's strategies for the selection of the appropriate Radio Access Technology.

4.2.4.1 Functionality

Based on the output of the "Market of mobile communications"-function and the description of key technical characteristics and capabilities of Radio Access Technologies, the distribution of usage demands per service, environment and Radio Access Technology as a function of daytime will be estimated considering different mobility functions of the Radio Access Technologies as well (refer to Figure 4-5).

Market studies are typically not that detailed as required to perform mapping of user service requests onto Radio Access Technologies directly. In particular customers behaviour in terms of selection of the preferred Radio Access Technology out of the available set is unlikely to be provided by such studies. Hence, in order to cover this subject Monte Carlo simulations based on assumptions concerning customers strategies as distribution functions can help to find results. On the other hand it is likely that different assumptions on such distributions functions have significant impact on the results themselves. Variation of these assumptions can help to find realistically expected spectrum requirements for the different scenarios. Moreover, areas to be further studied in terms of market expectations may be identified as well.

- 30 -

FIGURE 4-3:General principle of mapping services onto RAT

5.2.4.2 Radio Access Technology Mapping Simulation flow

For each environment under consideration the statistics of usage demands per Radio Access Technology, environment and service category as a function of daytime is estimated. Starting with the mobile communications market in the environment considered, different steps are necessary to identify the traffic volume:

Definition of customer's communications requirements

Identification of the suitable Radio Access Technologies

Selection of the best suited Radio Access Technology

At the end of this process the traffic volume for the different Radio Access Technologies is available. Objective of this process is to provide a comprehensive picture of the traffic volumes to be supported by the several Radio Access Technologies in all environments under consideration as a function of daytime. A detailed flowchart of the simulation process to map the services onto Radio Access Technologies is illustrated in Figure 4-6.

MobileMarket

Radio AccessTechnologies

CustomersDemands

RATIdentification

RATSelection

TrafficVolumeStatisticsof RATs

Mapping user service requests onto RATs

MobileMarketMobileMarket

Radio AccessTechnologiesRadio AccessTechnologies

CustomersDemands

CustomersDemands

RATIdentification

RATSelection

RATSelection



Mapping user service requests onto RATs

- 31 -

FIGURE 4-6:Simulation Process Flowchart of Mapping user service requests onto RATs

Active communication eventsof the snapshot

RAT1 RAT2 RATn. . .

Market

RATs

Customerprofiles

Select environmentand daytime

Initialisation

Draw a usagedemand

RATidentification

RATselection

UserActive ?

All demandsconsidered ?

No

Yes

No

Traffic Volume statistic per RAT

Yes

SpectrumEstimation


RAT1 RAT2 RATn. . .


RAT1 RAT2 RATn. . .

MarketMarket

RATsRATs

Customerprofiles

Customerprofiles



InitialisationInitialisation

Draw a usagedemand

Draw a usagedemand

RATidentification

RATidentification

RATselection

RATselection

UserActive ?

All demandsconsidered ?

No

Yes

No

Traffic Volume statistic per RATTraffic Volume statistic per RAT

Yes

SpectrumEstimationSpectrumEstimation

- 32 -

Select environment and daytime: The environment and relevant daytime to be considered is selected. It should be noted that not all daytime options are necessarily being considered. It may be sufficient to restrict the evaluation to such time periods of the day where highest traffic demand is expected, taking into account that different services may have their business hour at different times.

Initialisation: The pool of potential communications events is created. The amount of users within this pool is based on the user density figures of “Market of mobile communications” and the area under consideration. The necessary information for the phase of “Estimation of the amount of frequency resources required by different RATs” will be provided. A snapshot of customers and their communication demand will be generated. For each potential customer the individual basic parameters will randomly be defined:

Service,

Mobility of transceivers,

Traffic volume,

Activity factor,

according to the parameters provided by the market evaluation function. Due to the significant number of dynamic factors and their statistics to be considered, the initialisation function can provide a variety of snapshots of potential customers and their communication demand for the same environment and daytime. Multiple application of this function will lead to distribution functions accordingly.

Draw a usage demand: A communications event is drawn from the pool of potential events. Based on the statistical evaluation of the activity factor it is determined whether the event is active during the current snapshot. If the communication event is active this event will be considered in the mapping process. If the event is not active the next event will be drawn from the pool. This process applies for all customers and their communication demand within the snapshot defined by the initialisation process.

RAT identification: This block identifies the Radio Access Technologies which are likely be deployed in the considered environment and which are in principle able to provide the services requested. Especially in densely populated regions multiple Radio Access Technologies may be accessible to provide a demanded service. All Radio Access Technologies which are in principle able to fulfil the usage demand will be identified.

RAT selection: Within this process a priority list of the suitable Radio Access Technologies will be developed taking into consideration the customer's requirements in terms of customer profiles defining requirements on:

minimum quality of service,

communications costs,

accessible Radio Access Technologies and individual handover strategies.

- 33 -

Taking additionally into account statistical assumptions on congestion scenarios (e.g. typical network blocking scenarios) for the different Radio Access Technologies, the best-suited one will be selected. This must not necessarily be the one with the highest priority.

If all customers and their communications demands within the snapshot defined by the initialisation process have been considered, traffic intensity in form of usage demand distributions is generated as output. Each snapshot result consists of a traffic volume in terms of a list of active communication events of each Radio Access Technology during the snapshot in the environment under consideration. Hence, in principle the output of the mapping services onto RAT function can directly be used in the ‘Estimation of the amount of frequency resources’ process, the next phase of consideration.

Table 4-5 provides an example of such result, scaled to 1 km² network deployment area.

TABLE 4-5:

Example of service snapshot

Environment: urban

Daytime: 14:00 – 15:00 hours

Service Mobility User per km² RAT Capacity in kbps

Uplink Downlink

Multimedia Urban vehicular

2 WCDMA 144 2048

Streaming Indoor 5 WLAN 12 8192

Voice Urban pedestrian

7 GSM 16 16

Statistics in form of cumulative distribution of usage demands for services in terms of a traffic volume per Radio Access Technology as a function of daytime can be generated by evaluating a sufficiently high number of snapshots in the environment and time frame considered.

Concerning the interface to the following ‘Spectrum Estimation Process’ two possibilities are feasible:

Delivery of distribution functions in terms of usage demands for services per Radio Access Technology into the spectrum estimation process as described in the flowchart,

Integration of the ‘Mapping user service requests onto RATs’ process into the spectrum estimation by applying every snapshot directly for individual spectrum requirement calculation.

4.2.5 Estimation of the Amount of Frequency Resources

Estimation of the amount of frequency resources is final step in the process of identifying the spectrum requirements of the different Radio Access Technologies. Based on the information provided by previous steps of the estimation methodology Monte Carlo type of simulations to obtain the estimates of the required spectrum have to be applied. Two different types of simulations are necessary to conduct this process step:

- 34 -

System Simulations and

supportive Link Simulations.

Link Simulations are applied to provide the minimum tolerable carrier-to-interface (C/I) and/or signal-to-noise ratio (C/N) thresholds required for each combination of service, RAT, environment and frequency band. The system simulations themselves are then used to derive the total amount of spectrum required by the RAT under consideration in combining all services.

Static snapshot based system simulations shall be performed with the separate Radio Access Technology specific simulators covering the statistically relevant issues of the overall estimation process:

by nature stochastic key elements of wireless communication environment like propagation conditions, link distances of wanted and interfering links as well.

System immanent capabilities and functionalities like adaptive modulation schemes to improve spectral efficiency.

Variety of envisaged network topologies including non-cellular multi-hop or ad-hoc deployment.

Economical framework of network rollout of the wireless infrastructure like density of base-stations or access points and their relationship to the amount of available spectrum.

Such analysis allows to consider how features such as multiple services in the same RAT, spectrum pooling and spectrum sharing has an effect on the required spectrum resources.

The principles of the process of estimating the spectrum requirements of a Radio Access Technology under consideration is illustrated in Figure 4-7.

- 35 -

FIGURE 4-7:Simulation Process Flowchart of Estimation of RAT spectrum requirements

Required Radio channelsof the snapshot

Select environment

Creation of access network

Snapshot ofactive customers

Assignment ofRadio channels

Systemspecification

Stabledistributionfunction ?

No

Channel requirement per environment

Yes

RAT Spectrum Estimation

TrafficVolume

Select RAT

Allenvironmentsconsidered ?

No

Yes

LinkSimulation

Network QualityRequirement



Select environment

Creation of access network



Assignment ofRadio channelsAssignment ofRadio channels

SystemspecificationSystemspecification

Stabledistributionfunction ?

No



Yes



TrafficVolume

TrafficVolume

Select RAT

Allenvironmentsconsidered ?

No

Yes

LinkSimulationLinkSimulation



- 36 -

4.2.5.1 System Simulations

The system simulations have to be performed separately for each RAT. This simulation approach is an iterative process which allows adjustment of several key parameters during the process, e. g.:

Consideration of trade-off terminal complexity/costs and spectrum efficiency.

adjustment of the offered bit statistics if the results indicate that a Radio Access Technology cannot support the required traffic capacity economically feasible network deployment.

At the end of this process the spectrum required by each Radio Access Technology under consideration will be estimated for the different expected deployment areas and expected market share in terms of peak spectrum demand and statistical distribution of spectrum demand as well. Due to the foreseen feedback possibilities to the ‘Market of Mobile Communication’ and ‘Mapping services onto Radio Access Technologies’ parts of the methodology, different assumptions may be compared and issues like migration of spectrum between Radio Access Technologies may be considered as well.

Basis for the system simulation process are information on

Key technical characteristics of the Radio Access Technologies under consideration

Transport capacities required by the different services in the different environments under consideration

which will be used in the different steps of the system simulation process.

Simulations have to be applied independently for each Radio Access Technology and potential deployment environment as well. Combining the spectrum estimations, the environments considered will lead to total spectrum required by the Radio Access Technology. In particular the following steps are necessary to achieve the results:

“Creation of Access Network”: A network of the Radio Access Technology in the environment under consideration will be created in terms of physical structures, e.g. cell size or access point density, frequency cluster etc. The number of theoretically available frequency channels will not be limited. The simulation may start with the assumption that there is one channel cluster available. Depending on the Radio Access Technology under consideration, different network topologies like ‘Single Hop Cellular Network’ or ‘Multi Hop Cellular Network’ including peer-to-peer communication need to be generated (refer to 4.2.5.3) .

“Snapshot of active customers”: On the basis of the results of the “Mapping services onto RAT” in terms of statistics of cumulative distribution of usage demands for services, a snapshots of active customers in the access network is generated. The active customers of a snapshot are randomly deployed in the network area and be accommodated with the service requested.

“Assignment of radio channels”: On the basis of supportive link simulation C/I or C/(I+N) conditions of the individual link are investigated including consideration of intra system interference. Objective of this effort is the decision whether the customers request under consideration can be accommodated by the already assigned frequency channels. If this is not possible, due to congestion in the assigned channels, an additional frequency channel-cluster has to be assigned to the Radio Access Technology.

“Required Radio channels of snapshot”: Considering all customer requests of the snapshot the number of physical radio channel-clusters are known to accommodate the communication requests of all the customers within the individual snapshot under consideration. Since the required spectrum may vary significantly between snapshots, a cumulative distribution of spectrum requirements of the Radio Access Technology and environment under consideration is the result.

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“Channel requirement per environment”: When applying a sufficiently high number of snapshots, a statistical distribution of the required number of physical frequency channel-clusters to satisfy the communication requests to be expected over 24 hours daytime will be achieved, including its peak value. The channel requirement of the Radio Access Technology in the environment considered can be defined taking additional issues into consideration, e.g. acceptable blockage levels for the access to the network, Quality of Service degradation possibilities. In that respect the overall network quality in terms of coverage, horizontal handover procedures etc. has to be considered as well. Such general technical framework of network operation will have significant impact on the number radio channels be needed per RAT.

“RAT Spectrum estimation”: Considering all expected/possible deployment areas of the RAT under consideration the spectrum requirements for the several environments are estimated which may differ significantly between environments.

4.2.5.2 Link Simulations

Objective of supportive link simulations is to obtain the C/(I+N) thresholds that are needed in the process of “Assignment of Radio Channels’ within Radio Access Technology spectrum estimation consideration.. The result of such Link Simulations are Bit Error Rates as a function Signal-to-Interference-Plus-Noise Ratio for the various technology and service combinations.

Depending on the kind of modulation and multiple access scheme in use, it may be necessary to model besides the wanted link interfering links as well, in order to be able to take Multiple Access Interference into account (e.g. in CDMA based systems).

In principle Link Simulations comprise the following issues:

Channel Coding: Within the channel coding block the information sequence will be coded such that its robustness against transmission errors on the channel is improved and adapted to the channel characteristics. Interleaving is known to be a powerful method for combating fading on the wireless transmission channel and has to be considered as well.

Transmitter: Modelling of the transmitter is heavily dependent on the Radio Access Technology under consideration. In general functions like Bit-to-Symbol Mapping, modulation and transmit filtering have to be included.

Radio Channel: Propagation effects have to be considered, such as multi path propagation and Rayleigh fading, Doppler effect, which affect the received signals significantly in terms of path delay and relative power.

Receiver: Modelling of the receiver has to take into consideration functions like Demodulation, Receive Filtering, De-Interleaving and Channel Decoding. The original un-coded information sequence will be reconstructed from the erroneous received sequence.

BER Evaluation: The received and transmitted binary sequence is compared and transmission errors are counted. The final result in terms of the probability of error as a function of the Signal to Interference Plus Noise Ratio is generated to obtain appropriately the C/(I+N) thresholds for the service technology under consideration.

4.2.5.3 Network Simulations

Creation of Access Networks is a key function within the system simulation process. Taking into account the technical characteristics of the Radio Access Technology under consideration typical networks will be created in terms of physical structures, e.g. cell size or access point density, frequency cluster etc. Depending on the technology considered, different network topologies like

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Single Hop Cellular Network,

Multi Hop Network (including peer-to-peer communication)

need to be generated. Frequency assignment to the network elements is done within the environment model in terms of frequency clustering (including single frequency networks) and frequency re-use conditions. Additionally, if static coverage prediction data is available from e.g. mobile radio network planning tools, they may be incorporated to ensure a feasible network plan. Special attention has to be put on the economical aspects such as the base station density and its impact on the amount of spectrum to be assigned to the system in order to avoid unrealistic (uneconomical) parameter settings and network structures.

To ensure feasible network planning conditions appropriate path loss models have to considered as well.

4.2.5.3.1 Single Hop Cellular Network

The Single Hop Cellular Network topology uses the classical cellular concept in which the available spectrum is re-used throughout the deployment area of a wireless communications system. Partitioning of the network deployment area into cells is necessary due to the in general limited resource spectrum but also due to practical range limitations of real systems caused by frequency dependent path loss, limitations in transmit power especially at the mobile terminal and limitations in terms of maximum signal transmission time between BS and terminal. A number of cells is grouped into a cluster which uses all the available spectrum i.e. all available frequencies are allocated to the cells of a cluster. However, single frequency networks are possible as well. This cluster repeats itself throughout the deployment area of the network. Homogeneous hexagonal network layouts, which are extensively used when evaluation theoretical system performance analytically or by means of simulations, should be applied because of its simple geometric properties. An example of such geometry in homogeneous hexagonal network topology is illustrated in Figure 4-8; cells labelled by the same letter use the same group of frequencies.

FIGURE 4-8Geometry in homogeneous hexagonal network topology

cluster

base

cell

D

A A

A A

B

B B

B

C

C

C

C

d

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4.2.5.3.2 Multi Hop Network

In Multi-hop Cellular Network (MCN) Topologies coverage of the service area is not solely achieved by the BS itself, but also by mobile terminal which serve as relays in case that a direct terminal to BS connection is not possible. On the other hand, a reduction of the coverage area of a BS is achieved by reducing the transmission power of the BS. This may relax the co- and adjacent channel problems significantly. However, in Multi-hop Cellular Networks the problem of mutual interference between co- and adjacent channels is shifted from the network side to the terminal. Figure 4-9 depicts the general principle of a pure Multi-hop Cellular Network topology. For instance, assume two terminals in close mutual proximity at the cell edges of two different but neighbouring cells. If both terminals would transmit within the same channel (e.g. within the same time slot of the same RF channel) either directly towards their respective BS or towards the next reachable terminal when out of BS coverage, the mutual interference will severely degrade transmission quality for both terminals. However, when due to some intelligent channel assignment strategy such a situation at the cell boarders can be avoided, i.e. with respect to the above example both of the terminals would transmit in different channels, mutual interference would be avoided. Therefore, the level of co- and adjacent channel interference in Multi-hop Cellular Networks and hence the spectrum efficiency heavily depends on the traffic situation (load and geographical distribution) within the network as well as on the performance of the channel assignment algorithms deployed.

Combinations of Single Hop Cellular Networks and Multi Hop Cellular Networks are possible as well in terms of bypassing obstructions on the propagation path instead of simply increasing transmit power to compensate such additional path attenuation caused by the obstacle; this will in turn improve the overall intra system interference situation. Hence, certain advantage can be expected when considering Multi Hop Cellular Networks as an extension to traditional cellular technology under severe shadowing conditions.

On the other hand, consideration of multi-hop networking within the spectrum estimation methodology requires quite exhaustive definitions of specific network deployment scenarios which are agreed on to be representative for the use of such multi-hop technology in the future. By means of these agreed scenarios it will be possible to predict the gain of multi-hop networking in terms of increased spectrum efficiency. Possible multi-hop deployment scenarios to be considered could be:

pure Multi-hop Cellular Network topology as defined in which terminals serve as relay and router respectively

multi-hop as extension to classical cellular concept to extend coverage in difficult propagation conditions in e.g. areas of heavy shadowing due to buildings.

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FIGURE 4-9Principle of pure Multi-hop Cellular Network topology

5 Conclusion

This document provides considerations on an enhanced spectrum calculation methodology framework to support spectrum requirement estimation work for future mobile communication. It is certainly not a complete description on how to calculate a spectrum requirement figures but rather a collection of ideas how to overcome the drawbacks of the methodologies applied in the past. Hence, this document should be seen as a starting point for the considerations on spectrum requirements for mobile communication in terms of the future development of 3G and systems beyond 3G. There is still a lot of work to do, especially in the simulator implementation details and related parameters. However, the most beneficial way for the process of spectrum requirements identification is to develop a generally agreed methodology and perhaps a software tool set which can be provided to all the relevant parties involved in the process. This would ensure that every party performs its calculations on the same methodological basis, with the same set of tools, once market expectations of future mobile communication is available for timeframe subsequent to the year 2010.

cellarea BS

MCN cellarea

BS coveragearea

MS