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THE WHITE SPACE: STATE OF ART
ICTP – White Space Technologies - Trieste 3 -14 March 2014
Summary
1- Wireless services: need for additional spectrum ..................................................................................................................2
2 - Defining the “White Space” ............................................................................................................................................................2
3 - The license for primary services .................................................................................................................................................3
4 - License-exempt for secondary services ...................................................................................................................................3
5 – Evaluating TVWS demand .............................................................................................................................................................4
6 - Sensing devices to find idle spectrum .......................................................................................................................................4
6.1 Cognitive Radio .............................................................................................................................................................................4
6.2 Geo-location database................................................................................................................................................................5
7 - Standards for sensing devices ......................................................................................................................................................5
7.1 Wireless Regional Area Networks (WRAN). ....................................................................................................................6
7.2 Machine-to Machine communication (M2M) ..................................................................................................................6
8. Exploring value of spectrum ...........................................................................................................................................................6
9 - Optimizing spectrum management ............................................................................................................................................8
10 - The long-term ICT strategies.....................................................................................................................................................8
11. ICT statistics and forecast..............................................................................................................................................................9
12 – Planning future availability of TVWS .....................................................................................................................................9
13 – Trend of TVWS applications ................................................................................................................................................... 10
14. Conclusions ....................................................................................................................................................................................... 11
Abstract
Since 2005, Administrations and Providers, in the telecom sector, are carrying out studies and
tests with the objective of accessing unused broadcast band (TV White Space) to route wireless
services suffering network shortage. The potential demand to access the TV White Spaces varies
as a function of: population density, of TV coverage, of TV operation and of the level of development of national ICT infrastructure.
The availability of TV spectrum, in terms of time and location, is tested by sensing devices (Cognitive Radio, Geo-location Database) whose standards are defined by national regulation and
whose costs add up to the basic cost of transmission mean. Access to TV band is permitted under
licence (primary services) or under licence-exempt (secondary services).
The economic value of spectrum is the reference basis when fixing the prices for the use of TV
band. Starting from basic costs, economic strategies, subject to national social and economic constraints, should be developed to meet market expectation, to provide affordability, to face competition, to possibly decide economic return.
In the long term, the potential future implementation of TV White Space depends by some technical (transition to digital TV, ICT expansion), regulatory (spectrum allocation), and economical
(reduce digital gap) factors. The availability of TVWS is subject to some risks as a function of TV
expansion broadcast. An unexpected evolution in TV sector (increase operation, expand coverage) might suddenly reduce band usable by TVWS. To forecast future availability of TV White
appears, at present, a little difficult.
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1- Wireless services: need for additional spectrum
When market for telecommunication services is expanding and an increasing number of users are
applying for connection, the dedicated national network is expected to gradually saturate: especially in developing regions the transmission means assigned to services is, actually, a finite resource. In absence of significant implementation of national network, an intensive demand of
access can drive the whole system to unbalance.
Because of that, Administrations and Providers started looking for alternative network solutions:
in particular the attention was turned to recover part of TV spectrum to route part of wireless service demand. The TV spectrum, considered available, includes either the frequency band imposed between TV channels (guard band) and the spectrum which turns free (unused spectrum)
when TV broadcast moves from analogue to digital technology. The concept of reallocation of
unused TV band was, so far, quite successful: the chance of satisfying additional wireless demand
and the opportunity of optimizing utilization of TV spectrum, stimulated the interest to use the
UHF resource and raised the expectation of its availability in the long-term.
Studies and experiments started in the year 2005 to analyze the constraints and the problems concerning the coexistence of TV signals and wireless services over the same band. The first practical
study (2007) was related to the potential interference among services. Special cognitive devices
(white space devices) were designed to detect the presence of unused TV band, following a CEPT
Study (2008). The first experiments did not give positive results, but a Coalition of eight companies (1) succeeded (2009) to deliver internet access to US consumers via TV available frequencies.
Experiments in USA and Europe have finalized the use of Geo-location Sensing System to ensure the protection of DTT (Digital Terrestrial Television) services. The test became operational
in 2013: ten installations located on University campus in Cape Town delivered broadband internet services to ten primary and secondary schools within a 10 km radius.
2 - Defining the “White Space”
According to ITU Report “Digital Dividend: insights for spectrum decisions”, the portions of spectrum
left unused by TV broadcasting is defined as “TV White Space” (TVWS) and is referred to as the
unoccupied portions of spectrum in the television frequency bands (mainly VHF and UHF).
From operational and administrative point of view, a first main hierarchical separation can be
stated between TV Broadcasting and the wireless services routed over TVWS: the first one is a
“primary service” and has access priority to TV band, the other one is a “secondary service” and
access TV band only when TV broadcast band is, temporarily or definitely, off-line.
Consequently, when using White Space, secondary services are subjected to the constraint of
avoiding interference with TV broadcasting which has priority as primary service: in particular,
the European Conference of Postal and Telecommunications (CEPT), carried out extensive studies to check, in the band 470-790 MHz, the co-existence between services allocated on TVWS
and the TV broadcast, when they are operating in the same frequency band.
1
(Microsoft, Google, Dell, HP, Intel, Philips, Samsung)
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3 - The license for primary services
Television broadcasting is considered a public service. As such, it should have the right of exclusive use when accessing dedicated TV band. The relevant license should include the necessary
regulation in order to ensure priority to TV broadcast as primary service.
The incumbent radio services authorized for operation on a given frequency band, include:
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Terrestrial Broadcasting Service
Program Making and Special Events (PMSE)
Radio Astronomy Service (RAS) in the 608-614 MHz band
Aeronautical Radio Navigation Service (ARNS) in the 645-790 MHz band
Mobile Service (MS) below 470 MH and above 790 MHz
Different mechanisms for licensing spectrum at national level have been used as part of national
spectrum management frameworks (channels utilization), which define the rights and the obligations of spectrum users and provide a framework for user responsibility. Whether licenses involve
property rights, they can assure more flexibility for commercial mobile services requiring high
QoS (Quality of Service). Licensing options allow different levels of flexibility:
1. Fixed-term licences under periodic review;
2. Revolving licences with automatic renewal;
3. Perpetual licences with provision for recovery.
In practice, the characteristics of the spectrum to be licensed play a significant role in determining
its licence duration and security of ownership. Users should have the certainty that the duration
in time stated by licence is respected: government re-appropriation, restructuring or reorganization of spectrum should not affect the length in time assigned. And this in the interest of
provider (market trade) and to the benefit of users (trust to Provider).
Some details are given in Annex 1.
4 - License-exempt for secondary services
No license is necessary to secondary services for the use of additional spectrum, but strict rules
are necessary to regulate the allocation of wireless services into the new available band. The full
availability of analogue TV band is obtained once the transition from the analogue TV service to
the digital TV service is completed and the “switch-off” of the analogue service is carried out. Only then, the vacated TV bands can be deployed for use to the secondary services, whose nature
(bidirectional) is not compatible with the TV broadcasting service (unidirectional). If both services were to operate in the same frequency band, harmful interference would occur, rendering
both services useless.
Access to spectrum is either open to all users or to a group of users who access that spectrum in
common. The simplification of administrative requirement for spectrum use, stated by licenceexempt, together with the technological implementation of TV network and with service innovation, lowers barriers to market entry and stimulate TV network expansion.
Licence-exempt spectrum use is, at present, permitted in two forms. The first one involves low
power transmissions, where interference is limited by strict power constraints and by regulatory
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equipment approval. This allows low-power users to co-exist in bands simultaneously used for
higher power emissions. The second one involves spectrum use in bands allocated for licenceexempt use like industrial, scientific and medical (2,4GHz; 5 GHz) bands. Most regulators require users of these bands to be subject to certain restrictions, such as output power limits or
communication protocols aimed at minimizing interference.
5 – Evaluating TVWS demand
The growth of advanced consumer mobile applications has considerably increased the usage of
bandwidth either in dedicated mobile network and license-exempt available TV spectrum. Spectrum demand varies by different regions. It depends, mainly, on population density, on national
income, and on the level of expansion of broadband fixed networks (ICT).
In urban markets, where developed infrastructures exist, the demand for new mobile products is
high and it might be difficult to fully satisfy the consumers’ application, using TVWS, unless an
efficient form of spectrum utilization exists. In case of bandwidth shortage, the technical choices
to overcome the problem would be to explore forms of dynamic spectrum access as to achieve
maximum spectrum efficiency.
In developing markets, the main existing problem is the national “digital divide”. When the level
of fixed broadband infrastructure is not sufficiently widespread to adequately satisfy most of the
connectivity demand, the use of TVWS might help meet national demand for wireless broadband
communication especially in peripheral areas. Even in these cases, in many urban centres, with
high concentration of population, the growing demand and the intensive applications create,
again, bandwidth bottlenecks which reduce the TVWS availability.
In the rural areas there is a lack of connectivity: the population is sparsely distributed, the consumption and the need for connection is low, the geographic coverage may not be sufficient. The
implementation of fixed line infrastructure in these areas is capital-intensive: so that the relevant
low economic return would discourage Providers. A wireless alternative is a more viable choice;
the alternatives can include wireless networks in lower frequency bands (below 1 GHz).
6 - Sensing devices to find idle spectrum
Sensing devices have the objective to help achieving maximum spectrum efficiency by exploring
forms of dynamic spectrum access (mainly: cognitive radio, geo-location database), as well as by
checking alternative tests for spectrum sharing.
When, the deployment of TVWS services involves large number of sensing devices distributed in
different regions (with different purposes), more attention must be paid to determine the levels of
interference and avoid its negative impact on TVWS bandwidth availability. To this extent, the
CEPT (ECC Report 159) emphasizes the need for more studies to understand the impact of
TVWS sensing devices in the bands adjacent to 470-790 MHz which will require careful attention
especially in cross-border situations.
6.1 Cognitive Radio
Cognitive Radio (ITU-R Report SM.2152) is a radio system employing technology that allows
the system to obtain knowledge of its operational and geographical environment. In particular, a
cognitive radio is a software radio whose control capacity lets provide an intelligent process to
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access unused band. The empty spectrum is detected autonomously, the destinations of calls is
stored and, as last step, their routing is arranged by available carriers.
When implementing real sensing process, CR users cannot distinguish between primary signals
and other user signals, so that the hole detection may become more difficult; moreover, sensing
and transmission cannot be performed at the same time: in consequence, during the sensing time,
all the CR users have to stop transmitting. Efficient spectrum sensing is essential in CR so it is
important to find the optimal sensing technique with the optimal sensing period and observation
time that maximizes the efficiency maintaining a given interference level.
When there are many CR users that may access the same frequency bands at the same time and
location, a CR user needs to coordinate its access with other users. The spectrum availability
changes over time and over space and, in consequence, a dynamic inter-cell spectrum sharing is
needed in a CR network. The spectrum sharing technique should maximize the cell capacity,
minimize interference to neighbour users and protect primary users.
6.2 Geo-location database
Geo-location databases are an alternative to sensing techniques in Cognitive Radio. They offer a
practical solution to monitor capabilities and primary transmissions. A secondary user has access
to a database system to get information about the primary users in a given area. The secondary
user interact with the database to know which frequencies are free in a certain time and in a certain location and determine the transmission power they are allowed to use.
To offer the White Space distribution over the frequency bands, the geo-location database needs
some parameters and information such as primary user’s frequency of operation, transmitted
power, size and type of transmit antenna, etc. these parameters are provided to the database system by primary users. Although the database systems solve the problems of location uncertainties, fading effect and detection errors of sensing techniques, they have the trade off of synchronizing and updating the database appropriately.
A more precise reuse of spectrum is possible thanks to database systems and the US FCC has presented it as the main tool to detect white spaces. In Europe on the other hand, a use of both a database system and sensing techniques has been proposed.
It facilitates the spectrum sharing collaboration among regulators, broadcasters and TV White
Space industry. Although the geo-location database had been introduced by the TV White Space
industry, the collaboration assumes that also broadcasters and wireless microphones participate
in contributing information to the database and benefit by doing so.
7 - Standards for sensing devices
The research of alternative forms of spectrum utilization could drive, in recent years, to new devices and to the definition of their structure. They are intended to face the increasing demand for
wireless connectivity as part of the evolution of ICTs in the “Digital Information Era”. Providing
access to efficient ICT infrastructure has become a main objective worldwide, especially considering the important role that ICT play in the word society.
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7.1 Wireless Regional Area Networks (WRAN).
The WRAN includes standards for low-power devices able to deliver broadband connectivity
mainly in rural areas: their operation does not produce interference on TV primary bands. Such
development has taken place under the IEEE 802.22 standards which suggest the specific rules
for devices operating in TVWS. One of the objectives of this technical standard concerns interference protection of the incumbent television broadcasting service.
Protection of interference to TV broadcasting service is, as well, provided to other authorized radio transmitters which operate in the band, such as wireless microphones, used when attending
events or local and public meetings. An important aim of this standard is based upon the development of cognitive radio technology for implementing non-interfering spectrum use in a sharedspectrum environment.
The WRAN devices would be available either in fixed and mobile modes; in order to prevent interference to the TV service, a database assignment process has been proposed for operation.
This database assignment approach adopted in the US (FCC), consists of a geo-location capability of devices operating in TVWS.
7.2 Machine-to Machine communication (M2M)
Also referred as M2M communication, it consists of very low-power radio transmitters used for
low-data rate industrial and commercial applications such as monitoring, tracking, metering and
control (smart machines). They are intended for operation under a license-exempt framework,
always under a non interference basis. Recently, in the United Kingdom (Special Interest Group
= SIG), open specification for M2M devices, for operation in TVWS, has been agreed as a preliminary stage. This group released, in April 2013, a specification for low-data rates M2M devices
to operate in the terrestrial television bands, transmitting data over idle TV frequency channels in
geographical areas where TVWS is available. As the use of M2M devices grows, and more applications are requested, it is expected that numbers of M2M devices deployed will grow exponentially especially considering the higher coverage ranges offered by the terrestrial television frequency bands.
8. Exploring value of spectrum
Increased traffic on wireless networks increases the demand for the spectrum on which these
wireless broadband services run. As a consequence, advanced wireless networks are taking more
significant place in many national economies, increasing the need to assess the value of spectrum
accessed. Considering the economic scenario (competition, market affordability), within which
technology for Broadband Wireless Access (BWA) is expanding, there arises the need for regulators to find, at least, a viable estimate of spectrum valuation.
The perceived value of a spectrum licence comes, mainly, from the comparison between the economic evaluation of market demand (potential revenue) and network investment. To balance
demand and spectrum supply, regulators should rely on pure economic models, letting market
forces play a larger role in spectrum management.
Therefore most valuation models involve a calculation of cost associated with network infrastructure, including equipment and construction costs, as well as cost of capital and labour (management and maintenance). Some of these costs can be known or, at least well estimated, through
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benchmarking and survey of existing equipment market. Such cost calculations are made on a
forward-looking, incremental basis, as to account for ongoing costs.
Opportunity cost. The opportunity cost is defined (New Oxford American Dictionary) as “the
loss of potential gain from other alternative when one alternative is chosen”. That is: it is assumed to be the best choice among several exclusive alternatives. Essentially, the opportunity
cost is the amount that a potential buyer would have to confront before giving up or change alternative.
For example, for a user of a point-to-point fixed service band, a possible real alternative to the use
of original band would be either to move to more efficient system or to relocate to higher frequencies.
Marginal cost. Marginal cost is the change in the total cost that arises when the quantity produced has a unit increment. In other words, it is the cost of producing one more unit of service.
Whether “cost” and “quantity” are given as continuous functions, the marginal cost is:
Marginal cost (MC) = dC(cost)/dQ(quantity)
It is the tangent to the total cost curve at the point “Q”: the marginal costs is not related with
fixed cost (initial investment). Under monopoly, there could be an infinite number of prices associated with a given quantity. Under a perfectly competitive markets, Firms decide the quantity to
be produced based on marginal costs and sale price. If the sale price is higher than the marginal
cost, then they supply the unit and sell it. If the marginal cost is higher than the price, it would
not be profitable to produce it and another strategy should be decided.
Net Present Value. In economic terms the decision of supplying spectrum is not only based on
costs, but also on a projection of future revenues. The decision is based on the comparison between the efficiency of the technology and the potential revenue from demand. Again, measurements of potential revenues might be forecasted with some reliability, through benchmarking
identical services in other markets.
Final results can be captured in the concept of “Net Present Value”(NPV), which balances the net
cost against the net cash inflow over time. From the point of view of a potential operator choosing whether or not to invest in a particular BWA (Broadband Wireless Access) market, this can
translate into a calculation of the total net value of a project. This allows an assessment of whether positive outputs (revenues) will exceed input costs over time.
Internal Rate of Return. The Internal Rate of Return on an investment, or project, is the “annualized effective compounded return rate” that makes Net Present Value of all cash flows from a
particular investment equal to zero. It can also be defined as the discount rate at which the present value of all future cash flow is equal to the initial investment or, in other words, the rate at
which an investment breaks even.
IRR calculations are commonly used to evaluate the desirability of investments or projects. The
higher a project’s IRR, the more desirable it is to undertake the project. Assuming all projects require the same amount of up-front investment, the project with the higest IRR would be considered the best and undertaken first.
Given the cash flow pairs (n, Cn) (where “n” measures time in years), and the total number of
periods “N”, the Internal Rate of Return “r” is given by the following (NPV =Net Present Value):
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NPV = Σ(0-N)Cn/(1+r)n = 0
A detailed description is given in Annex 2.
Benchmarking. In combination with direct valuation estimates, it may be possible to compare
the results of different assignment transactions across different economies. Anyway, in 2008, report for the Australian Communication and Media Authority noted that the use of market
benchmarks to make opportunity cost estimates remain difficult.
Optimum band. The service area covered by a base station is proportionate to the square of the
frequency. For example, the minimum provision of service over a low population density region
will require twice the number of base stations at 1 GHz than at 700 MHz, eight times more at 2
GHz and 14 times more at 2,6 GHz: the cost of deploying a mobile network in such a region will
rise in proportion. This explains why the frequencies around 700 MHz are known as “golden frequencies”, and why these frequencies are increasingly in demand for BWA services.
9 - Optimizing spectrum management
The progress made in digital technologies supported the evolution of terrestrial television, which,
in turn, drove to more efficient use of spectrum by allowing, through digital compression techniques, the transmission of multiple high-quality TV programmes in one single spectrum channel
(before it was possible to transmit only one program per channel). Such advancement resulted in
the opportunity to reallocate the available TV spectrum for larger value uses, like the mobile service, in response to the rapidly growing of demand for mobile bandwidth.
The above situation shows the importance of a sound spectrum management, which has been
achieved, over time, through the collaborative efforts of countries. Some common spectrum decisions were adopted at regional level with the aim of revising and updating the International Radio Regulations and related International Table of Frequency Allocations. Such Revisions and
updating were made under collaborative technical studies (ITU-R Study Groups) carried out
jointly between regulators, private sector and other stakeholders.
The World Radio Conferences was, and still is, the appropriate place to adjust rules and procedures as well as to identify and allocate spectrum in a collaborative way. These regulatory developments are significant indicators of the ongoing international revision of UHF spectrum utilization and planning in the mid and long terms.
10 - The long-term ICT strategies
Attention should be paid to the potential impacts that spectrum planning might have over the expansion of local markets. It depends, in fact, from market reaction to achieve long-term benefits
(implementation of ICT sector, GDP distribution, job market creation and support to innovation). Then, from regulatory perspective, it is significant to harmonize the potential supply of
TVWS spectrum with the outcomes of national ICT strategy.
As well, the gap between rural and urban areas should be assigned high priority. Connectivity,
directed to rural economies, can integrate rural business into national and global markets.
Through this, it is possible to empower rural enterprises, providing them with the tools to explore
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possible market strategies. Within this scenario, some countries have given significant priority to
the connectivity needs of rural and unserved areas by introducing sufficient flexibility into their
licensing process and by applying various coverage obligations to spectrum licensees.
Collaborative efforts among all stakeholders are the best way forward to ensure that the finite
spectrum resource is optimally used, while encouraging social and economic growth through
technological innovation. In order to achieve such outcomes, consensus and participation in the
decision-making processes will continue to support a sustainable development of ICTs from
which society can continue to benefit.
The main reference is, anyway, the long term ICT infrastructure which should have enough capacity to handle market demand. A long-term national ICT strategy, should include the planning
of wireless broadband connectivity and should be designed within a scenario based upon long
term assessment of technical, legal, economic, social variables.
11. ICT statistics and forecast
According to ITU estimate there were 6,8 billion mobile-cellular subscriptions by the end of 2013:
but, even if the figure is close to 100% of population covered by mobile signal, not everyone has a
mobile telephone. This takes to an estimate of 4,4 billion people who are not yet on line.
Fixed-broadband showed only 10% annual growth rate within the last three years (2010-2013).
The services that had a significant growth worldwide were the mobile cellular and the mobile Internet. Mobile-cellular penetration was approaching 96% by end 2013: mobile broadband continued to grow strongly, at a rate of increase of 40% in the last three years (2010 – 2013). Mobile
Internet did also accelerate over the past three years, mainly in the developing world, and reached
a penetration rate of over 40% by 2013. It is growing rapidly not only in developed but also in
developing countries, where subscriptions doubled over the past two years.
The significant growth of mobile broadband and the deployment of mobile infrastructure raise
the expectations that mobile-broadband services will expand as mobile cellular telephony in the
near future. Ericsson forecasts that by 2018 there will be 6,5 billion of mobile broadband subscriptions, almost as many as there are mobile-cellular telephone subscriptions in 2013.
At the last World Radio Conference (WRC-12) countries in ITU-R Region 1 (Europe, Africa and
Middle East) agreed to allocate the band 694-790 MHz for mobile, and to start its operation in
2015 (WRC-12, Resolution 232). After the decision taken at WRC-12, other studies have been
carried out in Europe, on the long term approach for reallocation of UHF spectrum, in order to
respond to the increasing bandwidth demand of mobile services.
12 – Planning future availability of TVWS
When White Space is recovered from Digital Terrestrial Television, a greater number of applications can be accommodated in the available band by squeezing secondary services in the unused
spectrum. Nevertheless, a rational planning is necessary to avoid that the use of free broadcasting
channels might reduce the long term availability of TVWS.
In the long run, Policy-Makers and Regulators should evaluate possible risks which might affect
their expected economic return. If, for instance, DTT transition were not being completed, there
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might appear uncertainty about the future availability of TV channels for TVWS services.
Whether the primary TV services increase over time, their priority use of dedicated band will
limit the availability of TVWS band: it might, then, become necessary to revise the regulatory
scheme by redefining primary and secondary services.
At present stage, the regulation adopted for the use of TVWS should include some constraints
which fix some limits for TVWS implementation and assure sufficient safeguards to the system
(TV broadcast and wireless services). In case TV and TVWS would become incompatible, TVWS
devices should cease operation or should reallocate to another band. While this policy approach
would provide some level of flexibility for future change, it presents, again, some risks. Here is a
risk that consumers relying on TVWS broadband services would experience temporary or permanent service disruptions.
The development of wireless technologies needs a stable regulatory environment, and this for the
satisfaction of users (market demand) and for the benefit of providers (economic return). Modifications in the regulatory environment for wireless (UHF spectrum) might have significant impacts on services: the changes should be planned for the future otherwise, under spectrum bottleneck, regulatory and policy decisions could be unable to provide economically viable return.
Despite the rapid success got by some services, provided over licence-exempt spectrum, significant concerns remain regarding the long-term viability of an open access regime. Over time, it
would be possible that the increasing and intense use of such bands would gradually increase the
potential for congestion and interference causing a degradation in service quality.
13 – Trend of TVWS applications
The communication industry, manufacturer and operators, appear to have reached a stable period where they are looking to minimize investment and maximize economic returns. Nevertheless, the introduction of new technology, that can increase network flexibility and communications capacity, might attract industry attention as they will eventually allow operators to maximize the use of their existing spectrum.
At the WRC-12 it was agreed to take the following action: “to consider additional spectrum allocations to mobile service on a primary basis and to identify additional frequency bands for international Mobile Telecommunications to facilitate the development of terrestrial mobile broadband application, in accordance with Resolution 233 (WRC-12)”.
When exploring solutions for longer-term period, some key regulatory aspects at the technical,
economic and legal levels should be considered. The analysis of these aspects can help regulators
and policy makers in identifying options to provide an adequate regulatory environment where
TVWS broadband applications can develop sustainably over time.
From technical point of view, the main question concerning the future of UHF band is closely
related with the finalization of the transition to digital TV. The future TVWS availability might
be provided whether and when it will be possible solve bandwidth constraints as to affect the
broadband service provision through TVWS unless a potential future expansion of digital TV
network might restrict the delivery of TVWS broadband services.
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From economic point of view, the national digital gap is becoming of interest. Total cost for the
connectivity chain linked to TVWS rural broadband is high and, because of the quality of market,
the long term economic gains from implementing TVWS in comparison to other choices does not
appear attractive. Neither monopolies nor Service Providers are in a position as to estimate risks
(low demand) or the increased costs with reference to present situation.
In terms of market competition, there might be future legal disputes between Service Providers in
cases of limited TVWS availability. Regulatory rules should charge the responsibility of potential
spectrum allocation of UHF TV spectrum. It would be necessary to asses legal requirements fo
the provision of TVWS database service.
14. Conclusions
A consistent number of policy and regulatory alternatives should be considered when looking to
the long term evolution of TVWS. Several variables are to be considered when, moving from present situation, the new technology available for the use of unused TV band is transferred into
long term expectation. Many risks, connected with TV broadcast expansion and difficult to foresee, might reduce the reliability of a forecast. Same constraints apply to the possible estimate of
long term benefits. So, from technical and economic points of view, some uncertainty exists
about the implementation of TVWS. More reliable statistics might help estimate the process even
if some confidence limits should be evaluated as to ensure possible margin of error.
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