WO2013183030A2 - Method and apparatuses for improving the efficiency of the opportunistic access to the electromagnetic spectrum - Google Patents

Abstract

A substantial portion of the electromagnetic spectrum is reserved for broadcast transmissions over large areas. It is possible that in some areas and during certain time intervals, no receiver is turned on in the reception of some signals transmitted in broadcast mode. It is possible that the intensity of the broadcast signals transmitted over large areas is small in a number of environments: in particular, many television signals have low power levels in indoor environments. The present invention describes methods and secondary transmitting apparatuses which enable secondary users to use radio resources occupied by primary broadcast transmissions. This is possible in areas where such primary transmissions are not particularly intense, and in circumstances where it is possible to ascertain that said secondary users do not disturb any receiver tuned on the broadcasted signal.

Description

TITLE:

METHOD AND APPARATUSES FOR IMPROVING THE EFFICIENCY OF THE OPPORTUNISTIC ACCESS TO THE ELECTROMAGNETIC SPECTRUM

DESCRIPTION:

The main scope of the present invention relates to the opportunistic use of the TV radio spectrum for short and medium range applications.

In general, the concept of opportunistic use of resources of the

electromagnetic spectrum stipulates that these resources are primarily allocated for certain purposes and users, which are called primary users. However, when the primary users do not use these resources, other users can have the opportunity to use said resources of the electromagnetic spectrum. Said other users, who can access those resources of the

electromagnetic spectrum only if they have the opportunity, since the primary users are not using them, are called secondary users.

The opportunistic access to radio spectrum assumes that a secondary user uses certain frequencies only "when" and "where" the primary user is not using them.

In fact, the primary user is the owner of the right to use these frequencies whenever it needs them, and only when they are not used by the primary user it is possible to make them available for other purposes for the benefit of other users which, for this reason, are called secondary users. The fundamental problem in this type of access to radio spectrum consists in establishing whether the primary user is not using certain frequencies.

There is a great interest in this method of access, both because the

transmission capacity that may be available is remarkable (especially in some areas), and because it is a method that is not yet exploited and therefore it is still rich in its potentiality.

In general, there are many theoretical studies concerning the opportunistic exploitation of the frequencies for radio communications in all radio bands; but, today, the focus is primarily concentrated on the potential opportunistic use of the bandwidth allocated to terrestrial television broadcasters, where, worldwide, significant unused transmission capacity is estimated. The term "White Spaces" generally indicates such radio frequency bands allocated to television broadcasting services but not used on the entire territory and therefore available to make opportunistic access.

The various organizations that deal with these issues generally refer to the following definition of "White Space": "portion of the radio spectrum that becomes available for radio applications in a given time and in a given geographical area that do not disturb the primary services and other services with the highest priority . The opportunistic access is therefore performed on these "White Spaces", defined as just reported.

The activities aimed to the efficient exploitation of the "White Spaces" (hereafter WS) is not just about technology, but they are also defining the regulatory and standardization frameworks needed for a fast and practical exploitation of the opportunistic access methods. The CEPT (European Conference of Postal and Telecommunications Administrations), for example, set up a "working group", the WG SE43 with the aim of:

• Developing the correct approach to WS combining geolocation database and spectrum sensing

• Studying the impact that will have white space devices (WSD) on services in frequency adjacent to those of 470-790 MHz band

• Defining requirements for cognitive radio systems operating in the white spaces of the 470-790 MHz band

• Ensure the protection of services of primary users in certain frequencies

• Quantifying the potential increase in available spectrum with WS

The end of the work is scheduled for the month of September 2012.

The opportunistic access to the television band is a possibility that, if

exploited, can support new services over a considerable amount of newly available bandwidth. That's why in many countries there is great interest in this opportunity.

Even the industry is very active in this area, and there are various DSA

(Dynamic Spectrum Access) devices that are able to activate radio

communications in a dynamic way, using opportunistic access to television spectrum.

The theme is also very treated in terms of patents and patent applications. Therefore, there is a lot of prior art on the subject. Such a large amount of prior art has all in common the fact that a certain band of radio frequencies is considered "used" by the primary user (to which it is reserved by priority) in a determined "space" and in a determined "time" when said primary user is not transmitting in this band in that determined "space" and "time". The methods used to identify the bands that can be used opportunistically essentially belong to two families:

• "carrier sensing" based methods,

• methods based on "geo-localizzation" plus "data base".

Methods based on "carrier sensing" are based on measurements taken by the secondary systems that, before starting to transmit, check that the frequency band they intend to use is not already occupied with other transmissions. In any case, the "carrier sensing" function is in general implemented in DSA devices, as well as for the detection of WS, also to handle the eventual disturbances and to avoid to produce disturbances to other eventual secondary users.

The methods based on "carrier sensing" have essentially the problem of reliability, since sensed spectrum necessarily refers to a point in the space, i.e. to the point where the sensor is located, while the noise generated by a transmission generally involves a larger space, that's why, when used, these methods apply very precautionary margins which considerably reduce the advantages of using the opportunistic access.

Given the difficulty of use of methods based on "carrier sensing", these are usually confined to specific applications and, in general, when applied, they use extremely sensitive (and expensive) receivers so as to manage the very prudential assessments, in order to note the presence of even the weakest signals.

Methods based on "data base" requires that the primary user declares in advance where and when it intends to transmit (or not to transmit) in the band assigned to him, and that it makes such information available in a database. In this way, secondary users can refer to this data base and use the radio band when and where this does not serve the primary user.

Methods based on "data base" are certainly more reliable, conceptually simpler, and more easily applicable in wider contexts.

The main problem associated with such methods based on "data base" is that the information is not generally very detailed and it is based on propagation models which are necessarily approximate. They lend themselves well just to some cases, such as the case in which a television broadcaster who has a license in a large territory, decides not to transmit in a particular part of that territory in which he hasn't a significant "share". Such broadcaster can therefore declare his choice and allow others to use "his" frequencies in that territory. This method works for large areas in which a broadcaster give up his rights, and therefore small areas where, accidentally, a signal is not present with the necessary power to be received and decoded cannot be considered. The application of methods based on the "data base" expects, however, that there is an infrastructure designed to manage such information and

communications between secondary users and the "data base".

Both methods however, even if hypothetical^ applied with success and absolute precision, underestimate the bandwidth that can be opportunistically used. In fact, a frequency can be truly considered used only when, on that frequency, in addition to the presence of someone who transmits, there is also someone who receives.

If someone transmits but none is receiving, in theory, this frequency can not be said to be used in a radio communication. The main scope of the present invention is to propose a method and related apparatuses which permit the use of frequencies in an opportunistic manner to a greater extent than it is implemented with the methods and apparatuses according to the known art.

This object is achieved through the use of secondary transmitter apparatus or system capable of transmitting radio signals through the opportunistic occupation of resources of the electromagnetic spectrum, and characterized in that said secondary transmitter apparatus or system has means to execute a procedure to verify that no primary receiver systems active in an area surrounding said second transmitter device is receiving on a channel that uses said resources of the electromagnetic spectrum opportunistically occupied by said secondary transmitter apparatus or system.

It is noted that, in this description, the terms apparatus or device or system are used interchangeably. This is due to the fact that both the transmitters and the receivers are always systems composed of at least an element of signal processing and an element of radio transceiver, and that, in the case of systems embedded in contexts of opportunistic use of radio resources, there are also additional elements for information processing. In many cases all of these parts can be integrated as functions of a single apparatus or device, in other cases they can be distinguished. A typical example of system that, in general, is not integrated in a single apparatus is given by the primary television receivers: in fact the television receiving antenna is usually located away from the TV set or the decoder needed to complete the reception of television channels.

This invention determines other advantages which will be made more evident by the following description, the appended claims, which form an integrated part of the description itself, and some examples of practical embodiment described below (without limitation to said examples) and in the

accompanying drawings in which :

figure 1 shows a case of opportunistic use of radio band according to the prior art;

figure 2 shows a case of opportunistic use of the radio band according to the invention in a simple case;

figure 3 shows a case of opportunistic use of the radio band according to the invention in a more general case;

figure 4 shows a case of opportunistic use of the radio band according to the invention in a case characterized by a possible variation.

In figure 1 the essential elements involved in an application of opportunistic access to the radio band are shown. The number 100 designates a

transmitting station of a primary user of the frequencies. The number 130 indicates a primary receiver that receives from the primary station 100, and must not be disturbed by interferences on the transmission frequency on that it is receiving. The number 200 indicates a secondary station which can transmit on frequencies of a primary user when he does not use it.

In figure 2 further elements, involved in the application of the present invention, are highlighted. Since the invention is usually applicable in indoor environments, the number 301 indicates a house inside which the secondary station 200 is placed. Furthermore, since the invention is applicable with advantage in the spectrum of the frequencies used for terrestrial television broadcast transmissions, the considered primary receiver is a system consisting of an antenna for television reception 1 10 and a television 120 that tunes to a channel transmitted by the primary station 100. In figure 2 a local communications network 310 that allows the exchange of information between the TV 120 and the secondary station 200 is also highlighted.

In figure 3 a more general scenario is represented in which there is more than one house, and so, in addition to the house 301 , there is also an house 302. A network WTL (Watch Television Lan) 220, and a WTL server 210 are also shown. The network WTL 220 precisely supports the communication among the devices connected to the various networks 310 of the single homes and optionally with a WTL server 210. The WTL server 210 is a server which can store a database that can contain information about the status of reception and transmission of the various primary and secondary transmitters and receivers. In particular it is important that such WTL server 210 contains updated information on the state of tune of the primary receivers: it is essential that what the primary receivers are getting is known, instant by instant, since such reception must be preserved free from any interference potentially caused by secondary transmitters 200.

It is important to note that, in the scenario represented the figure 3, it is also essential that the secondary transmitter systems 200 are provided with means to communicate with a remote server and means for executing programs for consultation of a computer data base, and that the primary receiver systems are provided with means to communicate with a remote server and to update some of the data stored in said server.

In figure 4 the case in which the house 301 is not connected to the network WTL 220 and the television 120 is not a "connected TV" is considered. In this case, the television 120 may communicate the channel which it is tuned to by means of a radio transmission system which allows to carry out a

transmission 230 which can be received from the secondary transmitters 200 which are present in the area reached by the transmission 230. In this case it is important to note that the secondary transmitters 200 should be able to receive the transmission 230 carried by the primary receiver systems.

In general: the secondary transmitters systems according to the invention must be able to acquire configuration parameters in order to exclude the use of certain resources of the electromagnetic spectrum. In particular: the resources that are used for the transmission of signals on which there is some primary receiver tuned to, in the surrounding area, shall be excluded. Such a configuration can be acquired from secondary transmitters in different ways: may be the possibility of manual configuration, such as automatic. In the case of automatic configurations, it can be computed on the basis of information collected from suitable data base or information received from other means.

The basis of the invention is, first of all, a more careful reading of the aforementioned definition of "White Space" as: "portion of the radio spectrum that becomes available for radio applications in a given time and in a given geographical area that do not disturb the primary services and other services with the highest priority .

Basically, what needs to be assured is that the services with the highest priority are not disturbed and, in practice, a radio transmission is disturbed if the received signal is disturbed, and consequently if no one is receiving in a particular area, of course, no one may be disturbed.

It is also noteworthy that the television signal has certain values in outdoor environment and in free space (i.e., in the roofs where are normally placed the receiving antennas of the televisions) and significantly attenuated values in indoor environments. In fact, it is common experience that portable TVs with built-in antenna receive badly, and not all channels, when they are used in indoor environments.

If the television spectrum were used in indoor environment and for short- range applications (e.g. few rooms), the transmission could take place, by a secondary transmitter at relatively low power, it would suffice to remain 20-30 dB above the attenuated television signal (which, as mentioned, is usually not very intense) present in the indoor environment in which the secondary communication is established.

The problem caused by this way to proceed is given by the fact that such transmission is superimposed on the television signal, at worst obscuring it. This overlap is limited in space, then there will be an area in which the secondary transmission, the intensity of which is given by the needs of the specific transmission and is determined case by case, makes excessively disturbed the television signal in such surrounding area .

As a consequence, all the receiving antennas placed in that space are disturbed by the secondary transmission.

However, these antennas, while still receiving all the TV channels are typically used to receive only one channel at a time (or a few channels at a time).

To avoid misunderstandings, it should be clarified that the term "channel" (referring to a TV transmission) is the radio resource necessary for the transmission of a television service: it is clear that, in general, multiple services are multiplexed on a carrier using a time division multiplexing, then each TV channel uses a radio resource defined in frequency and in time, and such resource, so understood, may be considered available for possible opportunistic use. Figure 2 helps to exemplify, in a simple case, the basic idea.

The transmitting primary station 100 (in this case a television tower) transmits many channels, all received by the antenna 110 of the home 301 , but the TV receiver 120 of the home 301 is tuned to a single channel (or few channels, in a more general case). If the secondary station 200 transmits on a physical channels on which the receivers 120 inside the house 301 are not tuned to, they can continue to receive the channels they are tuned to, without being affected by noise.

The idea is to perform the secondary transmission only in the physical channels that no one in the area that is disturbed, is receiving (i.e. channels that no one is watching or recording): in fact any damage is determined in interfering channel in an area where no one is tuned into that channel.

The example shown in Figure 2 is very simple but, in any case, immediately emerges the first problem for applying such a method: it is necessary "to inform" the secondary transmitter 200, about the channels that can be interfered.

The easiest and most direct way is to connect to a local network 310 both television receivers 120 and the secondary transmitters 200. In this way each secondary transmitter 200 may be aware of the channel or channels that TVs 120 are tuned to and which channels may be disturbed.

A first important observation lies in the fact that the TV frequencies are made to be received by televisions, and television sets are systems of a certain complexity, then they can be easily arranged to work in a mode that supports methods for the opportunistic use of television frequencies, for example they can provide the information relating to their tune. In fact, it is relatively simple the modification to be made to televisions so that they make available in an appropriate form the information of the channel which they are tuned to.

In general, it can be said that it is possible to assume that the primary receivers may be equipped with means to export information about the physical radio resources that in a given time must not be caught, and such information may be easily made available on a database or, in general , on any device suitable for the storage of information in electronic format.

A particular embodiment of the present invention assumes that the primary receiver systems, and in particular the televisions 120, are equipped with means of communication to transmit to a remote server the data that allow to trace the radio resources on which there must be no disturbance, so they can receive correctly on said radio resources.

The example illustrated so far does not show, however, a further problem that is instead clarified in Figure 3 which presents a more general case, in which a secondary transmitter 200 may disturb the television reception of the

neighborhood, and not only of the primary receivers working in the same house in which the secondary transmitter 200 is transmitting.

The first question that arises analyzing the general case concerns the precautions to be taken to reduce the number of antennas for television reception within the disturbed area.

And 'no doubt important to minimize the number of antennas that can be disrupted by each secondary transmitter 200. In this regard, it is to be observed that the television antennas 1 10 on roofs receive TV signals coming from the top or from the horizon and their reception lobes are certainly not on the downside, while the secondary transmitters 200 are, as a rule, in a lower position than the television antennas 1 10 as they are generally placed inside the premises.

Further shielding the television antennas 110 at their base (or in the opposite directions to those of the origin of the television signal), it is possible to mitigate the interference signals generated by the secondary transmitter devices 200, limiting the potential problems to those caused by the secondary transmitter devices 200 placed in the space comprised within a certain angle with respect to the direction of reception of television antennas.

As already said, in general, inside a given indoor environment (typically a private home), the nearest television receiving antenna 110 is the one serving the television receivers 120 of these environments: these receivers may then communicate the channels on which they are tuned to the secondary transmitter 200, and then the closest television antenna 110, even if it is inside the disturbed space, can be free from serious disorders as the channels on which the receivers 120 connected to this antenna 110 are tuned to can be left free from secondary transmissions. The most serious problem is posed for the antennas 110 placed inside the space disturbed by the

transmission performed by secondary transmitters 200, but that cannot communicate through a residential local area network 310 with the secondary transmitter 200, and therefore it is not an immediate job, to communicate to such secondary transmitter 200 the channels on which receivers 120, connected to these nearby antennas 1 10, are tuned to.

The problem is quite manageable in the widespread context of "Connected TV" where TV receivers 120 are connected to networks accessible from the outside. For example, these television receivers 120 may be managed by a "Residential Server" which may publish, or make available in any known way, channels to leave undisturbed.

According to many analysts, from the commercial point of view, this scenario of widespread presence of "Connected TV" will take place relatively quickly. Figure 3 illustrates such a scenario, in which you can define and implement a sort of joint management of information about the channels on which the various televisions 120 are tuned. In figure 3 it is assumed the

implementation of a WTL (Watch Television LAN) 220 and a server WTL 210. The ability to connect to the server WTL 210 through a network 220 (which can also be a virtual network) allows: the television receiver 120 to

communicate the channels on which they should not be disturbed, and the secondary transmitters 200 to check whether the channel they are using is received by some television 120 nearby.

The WTL 220, in this case, could be a protected and closed network, accessible only from certain devices that would be enabled to pass only a few type of M2M type (Machine to Machine) communications in which the security of the data would be easily manageable using known methods.

In the absence of the residential local network 310 or television receivers 120 designed to communicate on that residential local network 310, there are other methods that made secondary transmitters 200 aware about the channels on which are tuned the television receivers 120 working nearby and which could potentially be disturbed, therefore these channels should not be caught by the secondary transmitters 200 active in the area.

It is clear that, in order to make such a communication, it is still necessary to make a change to the TV set 120: but such amendments may generally be kept as simple as possible. These alternative methods of communication can be designed to

communicate the tuned channel:

• to the "WTL server" 210,

• or directly to the secondary transmitters 200 nearby.

In the case of communication to the "WTL server" 210, a certainly interesting opportunity is to transmit the information using "powerline" techniques.

Downstream of a first segment of "powerline" transmission by receivers TV 120, are then possible several communication scenarios.

For example, in the case of the widespread presence of "smart meters" for the distribution of electricity, the information about the tuned channel can be communicated with a "powerline" technique to the "smart meters" that manages the loads of the premises in which the receivers television 120 are present. At that point the "smart meter" is, by definition, electronically

connected to a few service center so that it could easily take responsibility to update the "WTL server" 210; such idea, admits several variants and details that can certainly be explored and which have in common the fact of utilizing a first communication segment with "powerline" techniques, i.e. using the electrical network to transmit a small amount of data.

In the case of communicating information directly to the interested secondary transmitters 200, it is possible to use the television receiving antennas to transmit too, and the transmission power may be regulated at a suitable level, with the result that the signal is received only by secondary transmitters 200 which are so close as to be the very ones that could potentially disturb said antennas. Figure 4 illustrates this case. In this case the residence 301 is not provided with a local network 310 then describes the case that the television receiver 120 that is located inside the house 301 communicates the channel on which it is tuned through a radio communication carried out with the antenna 110 (as in the case in the figure) or with another antenna that could be installed near the television receiving antenna 110. Such radio communication is represented by the dotted arrow, and with the number 230. This

communication 230 will be receivable by the secondary transmitters 200 active nearby. In figure 4 is represented a secondary transmitter 200 which is located inside the house 302: in this way, said secondary transmitter 200 which is located inside the house 302 is in the condition to transmit in an opportunistic manner using channels that do not disturb the reception of the television receiver 120 that is located inside of the house 301.

This method provides a solution that can be adopted by those who do not own a "Connected TV", and represents an alternative way to have a

guarantee of non-interference on TVs tuned on channels that could be used by secondary transmitters 200 active nearby.

The method just described has the disadvantages of requiring the set up of a transmission system to support the communication 230, but it also has some advantages: it allows the protected viewing of television programs also in a scenario of non-connected TVs, and directly affects only the secondary transmitters 200 that are located in the vicinity of the television receiver 120 that should not be disturbed.

This solution, although potentially achievable with relative simplicity, has few critical aspects that may hinder the diffusion. A confidential information is transmitted in the air (a certain confidentiality must be guaranteed): a channel characterized by suitable mechanisms that make it "difficult to decipher" should therefore be used. It is clear that this information should still be decipherable by the secondary transmitter devices and therefore potentially readable by the owners of the devices themselves, but it is a M2M communication, this operation could be limited to equipment approved for the purpose, in which the information is not exportable; but this would require the introduction of a specific regulatory plant and the

associated control procedures.

This problem could be overcome in part by providing that the channels used by the secondary transmitter devices 200 are only some channels defined "reportable" and for which the confidentiality of vision would not be

guaranteed. In this way the TVs tuned to channel "not reportable" would have the confidentiality of vision guaranteed without the need of declaring the vision. However, this option too provides the introduction of a norm.

In any case, communication 230 should be standardized, and the TV wishing to have recourse to such communication should be made compatible with this operation (it could be a single object replacing the decoder or a new

functionality integrated in the new TVs), as well as the antenna plant should be amended or supplemented.

A further method for preserving certain channels from potential disturbances in a given area trivially consists in the possibility to directly configure the secondary transmitters 200 so that they do not use one or more channels at certain times. Even this option, which can be seen as a characteristic of the secondary transmitters 200, as better explained later, can be of some utility in certain scenarios.

The main advantage of the described invention is that it makes

opportunistically available a considerable amount of bandwidth at very valuable frequencies for radio communications.

In fact, if we consider a frequency occupied because a TV station is

transmitting, in practice the entire spectrum may be busy (in many places, and in Italy in particular), while if we consider the bandwidth occupied only when a TV receiver is tuned to a radio channel on that bandwidth, in practice, in each point of the space, only few channels (the ones that TV receivers present in the "surroundings" are tuned to) against many channels used for broadcast diffusion: in practice, a significant percentage of the television spectrum would be reusable for short-range networks.

The intensive re-use of TV band is essentially the main advantage of the invention. In the following are mentioned some considerations that highlight facilitators aspects for the diffusion of the present invention and that, resulting overall positive, may be considered as additional advantages brought by the invention.

The establishment of a WTL 220 which serve the purpose is definitely a simple action and it is compatible with a scenario of the near future

characterized by:

- the presence (in many countries) of infrastructure to access the database for the use of "White Spaces";

- a significant diffusion of "Connected TV"; - widespread dissemination of "smart meters" in association with electrical distribution

A further advantage of the method is that it can be introduced gradually. In fact it can be expected that, initially, only a limited number of channels is usable in an opportunistic manner by secondary transmitters 200 according to the teachings of the present invention. These channels would therefore have a guarantee not to be disturbed only for users who are equipped to

communicate that they are watching them.

In this way, a significant number of secure channels may be preserved, visible with the old mode, i.e. without requiring anything new to the viewer because these will still have the guarantee of a non-disturbed vision. It is clear, however, that for those who live in isolated environments, and at a certain distance from other houses, the risks of being disturbed (or of disturbing the others) are drastically reduced to be almost nil.

In any case, a person who wish to continue to use an old TV, not prepared to communicate its tune, would still be able to "defend himself" with alternative methods, e.g. by shielding the antenna from the side of neighbor jammers, or communicating in any other way to keep some channels protected (e.g. by paying an extra fee, a user can preserve free from noise up to a maximum of N channels) in his area. In that case, the secondary transmitter devices 200 that may interfere with a particular user, referring to "WTL server" 210 would find the information about the channels not to be used opportunistically in that given area.

An additional mechanism that might be expected, is to manually enter in the secondary transmitter device 200 one or more channels not to be used. This feature may be useful, for example, for a user who had an old portable TV kept into his garage and used to see some channels while dedicating his hobbies (it is obviously an example), well in this way such user could

preserve those channels at least by noise coming from his own secondary devices 200.

Ultimately, however, the concept is that the application of the present invention can take place without the old TVs, which will continue to exist for a long time, become totally unusable in a short time, but they may continue to be used, perhaps with a guarantee of vision for a smaller number of channels only, or using some measures by the user himself.

The studies and proposals that are currently in the field for the exploitation of the "White Spaces" are calibrated on initiatives that can now, and quickly, be implemented. It is also important to mention them in the context of the present invention, since they can provide a guidance about the secondary transmitters equipment that could soon be widely diffused in many countries of the world. It seems that these apparatuses, in addition to be very similar to present WI-FI RFP, will be characterized from integrating two peculiar performances:

1. the ability to access a centralized data base to check the availability of a frequency.

2. the ability to carry out a "spectrum sensing" with a good precision.

The "Spectrum Sensing" (also called "Carrier Sensing") performance is already present in existing equipment operating in unlicensed band (the WI-FI RFP) with the aim of managing the mutual interference that may occur when a plurality of private WI-FI coverages are present in the same area. Said performance, in the future, will also be used by secondary transmitters devices to avoid interference with the primary user.

In general, therefore, it is observed that many of the technical problems that must be resolved for the practical realization of devices operating according to the teachings of the present invention are the similar to those that are already present in the field of prior art, in the attempt to achieve devices able to opportunistically exploit the radio band, according to the commonly adopted definition for the concept of "White Space".

Coordination among potential users of the same opportunistically used frequency band, can be managed by methods similar to the known ones or evolutions of these, due to the availability of a hardware dedicated to the "Spectrum Sensing".

In general, most of the problems to implement and manage the devices which are necessary to the practical implementation of the present invention are the same that are encountered for the realization and management of the apparatuses for opportunistic exploitation of radio spectrum according to the prior art, and therefore the feasibility and applicability of the invention presents no substantially higher difficulties than those that would be

encountered in the application of the prior art.

In fact, it can be assumed that the application of the prior art provides that each secondary transmitter device, is not only equipped with hardware suitable for the "Spectrum Sensing", but also that it is an apparatus arranged to consult a remote "data base". Then each secondary transmitter device (both according to the prior art and to the invention) has the advantage of having context information, as it must necessarily "talk" with a server authorizing it to use certain frequencies. This server, not only can contain and provide information on televisions, it can also keep track of other active secondary transmitters, and provide this information for purposes of coordination of the various active secondary transmitters (many algorithms can be proposed in this latter matter).

A possible application of the inventive idea is that secondary transmitters devices are expected to behave, in the first instance, like the devices according to the prior art and refer to a remote "data base" for access to information about the transmission by primary users on each frequency.

Based on this first information, the devices can detect the presence of a "White Space" in its area (according to the current meaning), and then can transmit according to the known methods that are already agreeing in many countries. However, in some countries these "White Spaces" would be too rare or practically non-existent in many large areas, nevertheless the information on the user's primary transmission is also very useful for the application of the present invention. In fact, the secondary transmitter device which, as mentioned, will also have electric field sensors, can compare the predicted power of the primary signal (under open field propagation

hypothesis) with the power of the signal which is really present. By doing so the secondary transmitter device can estimate the extra-attenuation due to the fact of being in an indoor environment. It is clear that this information is very useful even in the context of the present invention, to decide on which channel to transmit and at what power.

The secondary transmitter device will search the channel that allows it to transmit at the lowest possible power (so determining the smaller circle within which shall check that there are no televisions tuned). This information will also be useful to make sure that the secondary transmitter device has different behaviors when installed in attics or terraces or in very internal indoor environments, and this will ensure that even the owners of these devices are encouraged to observe certain guidelines in placing their devices. Who will place his device near to a window, outdoors or in other positions particularly disturbing, would not have great performance as those who place it in the innermost room of his apartment.

It should be noted in this regard that, unlike target services designed to the so-called "super Wi-Fi" (the service based over opportunistic band that will soon be allowed in the United States), the services thought in conceiving the present invention are designed for short-range indoor coverage.

It is clear that in a communication method according to the invention, not only the RFPs transmit and receive, but also the terminals. These latter are mobile and can occasionally be in less screened positions, and consequently they can disturb (and be disturbed) more than the RFPs. It is clear, however, that, for the establishment of a radio connection on a certain channel, a proper protocol should be implemented: this protocol will also rely on measurements or estimates of BER and SNR (as commonly happens in the case of the establishment of radio link connections between mobile devices); through said measures and a comparison with the expected performances from the radio channel, both the secondary transmitter of the base station and that of the terminal can obtain sufficient information to determine whether a channel is usable for the connection or not, and they can also adjust the right power. Finally, the terminals too can use information derived by "Spectrum Sensing", and even this information can be useful to determine how the terminal is shielded with respect to the free space. As we see, the establishment of a connection on opportunistic frequency bands is, on the one hand, rightly more articulated, on the other it can still rely on many pieces of information that allows to search for the frequencies on which the transmissions can be performed at the lowest possible power. It is clear that the establishment of these connections will also make use of slightly more articulated control protocols than the current ones since they must manage some additional evaluations for the choice of radio resource to be committed.

In reality, the issue is evolving very quickly.

It was just September 2010, when the FCC decided that a good portion of television frequencies, when not in use, will be available to provide wireless access and, to refer to these services, it has been coined a new name which certainly sounds evocative: "Super Wi-Fi". Very soon, a similar measure will be taken also by OFCOM. The regulation framework for the opportunistic use of such frequencies is expected imminently and, initially, methods based on data-base and geo-location will probability be adopted. In other words a system (a server) accessible to DSA devices will be launched, in which the information on the usable frequencies in a given point will be made available. It is clear that this system is already set to evolve into the WTL concept just described: it is enough that it is accessible to televisions too, in addition to DSA devices,.

It is clear that in some countries, or rather, in some places of some countries, the newly available bandwidth will be significant because few primary stations are transmitting, but in other places there will not be enough bandwidth available due to the presence of issuers in all frequencies . Here the criterion of opportunistic use introduced in this invention could drastically increase the rate of reusability of the frequencies.

Finally, it is worth framing this inventive idea in the wider context of the "Cognitive Radio": in the most general sense, the "Cognitive Radio"

techniques have the objective of allowing two devices to communicate via radio searching and employing in an opportunistic manner a radio band and, in general, by adopting, case by case, the transmission parameters that most fit with the application. All while offering maximum flexibility. The argument is not developed here, it is only mentioned in order to report a very advanced topic that is currently attracting great interest from many universities and research centers and presents some significant connections with the

proposed invention and its developments .

It is clear that such an objective is absolutely ambitious if thought in its general sense, consequently the studies currently in the field are

concentrated on proposals that limit the objective itself.

Among these proposals, some can be attributed to a trend that deserves special mention: these are proposals that make use of the definition of a so- called CPC (Cognitive Pilot Channel). According to some of these proposals based on CPC, it is assumed the implementation of a network dedicated to the distribution of information functional to the establishment of "Cognitive Radio" type communications.

It is clear that the possible existence of a specific network for the distribution of the CPC may be usefully exploited also for packaging some embodiments of the present invention.

Not only, however, the "Cognitive Radio" context may be conducive to the development and evolution of the present invention, but also the basic idea of the invention can be incorporated in the topic of "Cognitive Radio". Indeed, so far the studies on the proposed algorithms and processes (also known as: Cognitive Brain Engine) are based on information relating to the transmitters, while it might also be useful to elaborate the information relating to receivers active in the area too.

Claims

1. Secondary transmitter apparatus or system (200) capable of transmitting radio signals through the opportunistic occupation of resources of the electromagnetic spectrum, and characterized in that said secondary transmitter apparatus or system (200) has means to execute a

procedure to verify that no primary receiver systems active in an area surrounding said second transmitter device (200) is receiving on a channel that uses said resources of the electromagnetic spectrum opportunistically occupied by said secondary transmitter apparatus or system (200).

2. Secondary transmitter apparatus or system (200) according to claim 1 , characterized in that at least one of said means for performing said verification procedure, performed before the opportunistic occupation of resources of the electromagnetic spectrum, is an electronic processor programmed to execute a program of consultation of a database

3. Secondary transmitter apparatus or system (200) according to claim 1 , characterized in that at least one of said means for performing said verification procedure, performed before the opportunistic occupation of resources of the electromagnetic spectrum, is an electronic communication system able to establish a suitable electronic connection with an electronic device (210)

4. Secondary transmitter apparatus or system (200) according to claim 1 , ready to receive dynamically and automatically or manually, a

configuration setting that precludes the use of the resources of the electromagnetic spectrum that should not be occupied for

opportunistically made transmissions.

5. Primary receiver apparatus or system characterized in that it is prepared to export the information about the resources of the electromagnetic spectrum that should not be used by secondary transmitters which are active in the area surrounding said primary receiver apparatus or system

6. Primary receiver apparatus or system according to the preceding claim characterized in that it has means to access a database or an electronic information storage system via an electronic communication system and it is able to update information stored in said database or electronic information storage system on the current state of its own tune.

7. Primary receiver system according to the preceding claim that includes a television (120).

8. Primary receiver system according to claim 5 comprising a radio

transmission subsystem capable of transmitting, in an area sufficiently large to reach all secondary transmitters which could potentially generate noise for said primary receiver system, the information about the resources of the electromagnetic spectrum that should not be used by said secondary transmitters

9. Method for the opportunistic use of electromagnetic spectrum including at least the following steps:

a. identification of resources of the electromagnetic spectrum to be accessed opportunistically;

b. verification that there are no primary receivers tuned to radio transmissions made on said radio spectrum resources and within the area where the possible opportunistic use of said radio spectrum resources by a secondary radio transmitter may cause interference to the reception of said primary receivers; c. if the above referred check is true, establishment of a radio

communication that uses said resources of the electromagnetic spectrum identified in the above item a..