FR2765445A1 - PROTOCOL AND ADAPTIVE BROADBAND AUDIO BROADCAST ADAPTIVE NETWORK FOR MOBILE RADIO FREQUENCY RECEIVERS - Google Patents

Abstract

An audio-video broadband adaptive broadcast protocol and network for mobile receivers is disclosed. The audio-video signal is subjected to source encoding (1001), wideband channel encoding (1002), to broadcast (1003) over a first general coverage area at a first central frequency F1, with transposition and re-transmission (1004) over a local coverage area at a second central frequency F2 for reception by mobile receivers. The broadcasting (1003) and retransmission (1004) operations are performed from fixed or mobile stations. Application to the implementation of adaptive single-frequency networks with configurable coverage areas.

Description

Adaptive Audio-Video Broadband Broadcast Protocol and Adaptive Network

  for mobile radio receivers.

  A protocol and an adaptive broadband audio-video broadcast network for

  mobile radio frequency receivers.

  The transmission of audio-video information to mobile radio-frequency receivers is currently poorly resolved or can not, at least, be envisaged

  the framework of terrestrial, fixed wireless networks.

  Among the transmission techniques used, the analog channel coding techniques are indeed resistant to the Doppler effect, causing a shift or frequency shift due to the relative transceiver speed, only when the coding process is

  spectrally limited to a narrow band.

  More recently, various digital techniques of

  channel coding have been developed. These techniques allow

  a broadband transmission compatible with the aforementioned Doppler effect. Among the aforementioned techniques, COFDM channel coding is used in particular in the context of digital audio transmission or DAB, for Digital Audio Broadcasting. In the two cases mentioned above, broadcasting

  intervenes by radio, terrestrial or satellite.

  Broadcasting by satellite radio allows reception over very large geographic areas, continent-wide, and finally over any geographical area included in the general coverage area of the satellite transponder, regardless of whether this geographical zone is

  fixed or evolves over time. A geographical area

  of time can, for example, be materially

  within the general coverage area by a combination of vehicles moving in that area of coverage

General.

  However, the currently available telecommunication satellites do not make it possible to ensure correct direct reception by a mobile radio-frequency receiver. Indeed, firstly, it is necessary that the mobile radio receiver has an external satellite dish whose pointing is enslaved on the transmitting satellite. Such servo systems are

expensive, fragile and bulky.

  On the other hand, because of the frequencies of

  the carrier wave used by telecommunications satellites

  downlink, broadcast channel, in the general coverage area, frequency above GHz, any interposed mask on the path, in direct view, satellite

  - Antenna of the radio frequency receiver, condemns the reception

  correctness of the latter. This is particularly the case of buildings in urban areas, works of art on major roads or railways, and forests or

trees in rural areas.

  For a mobile reception DAB reception test report highlighting the existence of these problems, it is useful to refer to the article entitled "Mobile and portable reception of satellite-delivered DAB" published by Peter SHELSWELL, Sound Digital, Third International Symposium on Digital Audio Broadcasting, 4-5 June 1996,

Montreux, Switzerland.

  The terrestrial hertzian channel therefore appears at present only possible in order to allow reception by unmarked mobile radio-frequency receivers, in which no slave receiving antenna installation

is not necessary.

  However, current terrestrial wireless networks are fixed and the coverage area of this type of network can not be reconfigured in real time. The only possibility of serving a geographically evolving geographical area in time would be through such

  networks, to cover a general area of coverage

  to encompass any evolution of this evolving geographical area. Such a solution can not in practice be considered, because, on the one hand, of the very high cost of infrastructure, prohibitive, and, on the other hand, of the permanent occupation of a reception frequency on this zone of blanket

  in the field of terrestrial terrestrial frequencies

  very. The present invention aims to overcome the aforementioned drawbacks by the implementation of a protocol

  and an adaptive broadband audio broadcast network.

  video allowing direct reception by receivers

  unmarked mobile radio frequencies.

  Another object of the present invention is the implementation of a protocol and an adaptive broadband audio-video broadcasting network, this network being

configurable in real time.

  The protocol and the adaptive broadband audio-video broadcasting network for mobile radio frequency receivers, which are the subject of the present invention, are remarkable in that each consists in respectively making it possible to subject the audio-video signal to a source coding in order to generate a signal. encoded source and subjecting the encoded source signal to channel coding to generate a broadband coded signal, which broadband coded signal consists of a series of time-spaced fixed duration symbols of a time guard interval and distributed in the frequency domain over disjoint frequency intervals, the carrier waves of each of the

  symbols being separated by a frequent guard interval

  tial. The broadband encoded signal is transmitted at a first center frequency, broadcast frequency, to a broadband encoded signal broadcast over a general coverage area. The broadcast broadband coded signal is transposed to a second central frequency and retransmitted from at least one retransmission relay, located in the general coverage area, the second center frequency being equal to the reception frequency, on at least one a zone of

  local coverage, instantaneous seat of radiofrequency

  mobile devices, which makes it possible to adapt the coverage area

  ture at the position of the radio frequency receivers

  mobile phones for optimal reception.

  The protocol and adaptive broadband broadcast network, objects of the present invention, will be better

  understood from reading the description and from the observation

  following drawings in which: - Figure 1 shows, in block diagram form, a general flowchart of the broadcast protocol to

  broadband audio-video signal for radio receivers

  mobile frequencies, object of the present invention; FIGS. 2a and 2b show a detail of implementation of two successive source coding steps

  and broadband channel coding respectively, constituting

  protocol, object of the present invention, as shown in Figure 1;

  FIGS. 3a, 3b and 3c show diagrams

  my temporal, respectively frequency, illustrative of parameters and constraints relating to these broadband channel coding parameters, to ensure adequate transmission - diffusion to different mobile radio frequency receivers; FIGS. 4a and 4b represent spatiotemporal diagrams illustrating the constraints to be applied to two retransmission transmissions originating from the same global coverage area at the second central frequency towards the same mobile radio frequency receiver, respectively at two

  sources of diffusion illuminated by the same source of origin

  and transmitting and broadcasting at the first center frequency to the same re-transmission station after transposition; FIGS. 5a, 5b and 5c show, in illustrative form, a transmission and broadcasting module of the broadband coded signal in a broadband coded signal broadcast at a first central frequency over a general coverage area; FIGS. 6a and 6b show, in illustrative form, a retransmission station module of the broadcast broadband coded signal, after transposition, at a second central frequency;

  FIG. 6c represents a variant of embodiment

  5a and 6a in the more specific case o

  an additional modulation step, such as a modula-

  frequency, is introduced to ensure a transmission of

satellite transmission;

  FIG. 7 represents a particular application

  non-limiting manner in which the module for transmitting and broadcasting the broadband encoded signal at the first central frequency is constituted by a terrestrial hertzian station located on a high point, in direct vision of a source of satellite origin, and o the module retransmission is constituted by a module as shown in Figure 6a, embarked on an aircraft shown in Figure 6b, such a configuration being more particularly suitable for the coverage of a sports event accompanied by a caravan of vehicles each having a radio frequency receiver the frequency of reception is granted on the

second center frequency.

  A description of the wide diffusion protocol

  an audio-video signal to radio receivers

  mobile frequencies, in accordance with the purpose of this

  invention will now be given in connection with FIG.

re 1.

  The broadband broadcast protocol of an audio-video signal to mobile radio-frequency receivers, these receivers being tuned to a reception frequency,

  means a series of technical steps, which correspond to

  in fact to a process to ensure the dissemination

  from an audio-video signal to banal mobile receivers

  which corresponds to the definition given above.

in the description.

  The protocol, object of the present invention, is

  primarily intended for broadcasting audiofrequency

  these, video-frequency signals, data signals as well as audio-video signals for example, such as television signals, as will be described later in

the description.

  Consequently, as shown in FIG. 1, it is indicated that the protocol, object of the present invention, is implemented starting from a step 1000,

  starting stage according to which an audio signal is available.

  video for example in baseband, noted for this reason savY the audio-video signal sav is then submitted, in a step 1001, to a source coding to generate a signal

coded source, which is noted ssc.

  As will be described later in the

  description, it is indicated that the source signal coded ssc

  advantageously consists of a single binary train

  so many specific characteristics allowing the trans-

  mission and broadcast this signal over the air or

satellite, for example.

  The aforementioned step 1001 is itself followed by a step 1002 in which the ssc encoded source signal is subjected to channel coding in order to generate a coded signal.

  broadband, noted sclb in Figure 1.

  More specifically, it is indicated that the broadband coded signal sclb consists of a series of time-resolved symbols spaced in the time domain of a time guard interval and distributed in the frequency domain over disjoint frequency intervals. carrying waves of each of the symbols being separated by a

  specific frequency guard interval.

  The above-mentioned step 1002 is itself followed by a step 1003 of transmitting and broadcasting the broadband coded signal sclb from at least one broadcasting source at a first central frequency, denoted Fl for example, and designating the broadcast frequency, in a coded broadband signal broadcast over a general coverage area. In FIG. 1, the broadcast broadband coded signal sclbdl is noted, the index 1 recalling the character of

  broadcasting this signal to the first center frequency F1.

  By general coverage area, it is indicated that it corresponds for example to a regional geographical area with a diameter of two to three hundred kilometers, or even continental depending on the applications of the broadcast protocol according to the subject of the present invention. With regard to the transmission and broadcasting operation of the broadband coded broadband signal sclbd, it is indicated that this operation is carried out by a frequency change from the broadband coded signal sclbd, which is obtained in a band of basis, as will be described so

  more precise later in the description.

  Finally, the transmission and dissemination step 1003

  mentioned above is itself followed by a step 1004 of transposi-

  re-transmission at a second central frequency, denoted F2, from at least one retransmission relay located in the general coverage area of the same broadband broadcast coded signal sclbd, transposed to this second central frequency F2, this signal broadband coded broadband transposed being for this reason noted sclbd2, with reference to the second central frequency F2 supra. Of course, the second center frequency F2 is equal to the reception frequency of the mobile receivers on which they are tuned. The reissue operation is thus

  carried out in a local coverage area,

  partly or wholly within the general area of coverage, this local coverage area being, of course, the

  instantaneous mobile radio frequency receivers.

  It is thus understood that, because of the re-transmission at the second central frequency F2, reception frequency, on the local coverage area and in the conditions of transmission and reception by the mobile radio-frequency receivers corresponding substantially to those of a radio network. the reception of the broadcast signal, denoted 1005 in FIG. 1, can thus be made optimal.

  It is understood in particular, according to a particular aspect

  1 of the present invention, that the retransmission relay (s) can be activated as a function of the position of the mobile or of the collection of mobiles provided with the radio frequency receivers tuned to the reception frequency and located in the zone of reception. local coverage, so as to adapt this area of

  local coverage according to the movement of the collection

  mobile devices, the retransmission relay (s) may also, as will be described later in the

  description, be mobile themselves in order to adapt by

  moving the local coverage area to the geographical area

  in which is found the collection of aforementioned mobiles.

  A more detailed description of the steps previously

  described, allowing the implementation of the protocol, object of the present invention, will now be given in

connection with Figures 2a and 2b.

  Figure 2a describes in more detail the

  steps 1000 and 1001 shown in FIG.

  With regard to obtaining the audio signal,

  video baseband SA, it is indicated that it may comprise, as shown in Figure 2a above, an analog audio signal component, an analog video signal component, or an analog data signal component for example , or even a combination

  of these signals delivered by corresponding sources.

  When the aforementioned signals are in analog form, they are subjected to digitization, audio digitization, video digitization and data digitization, as shown in FIG. 2a. Thus, an audio-digital signal, a video-digital signal and a digital data signal provided by the corresponding sources are provided. In the same way, it is possible, according to a particularly advantageous aspect of the protocol, object of

  the present invention, to have an audio-video signal

  digital, delivered by a corresponding source, this audio-digital video signal being able to be delivered by a telecommunication satellite for example or any other source

adapted.

  Thus, all the digital signals provided in FIG. 2a are submitted, at step 1001, to the source coding process mentioned above, which

  advantageously, for each audio signal

  video, digital audio, digital video and digital data, to perform actual source coding followed by a compression process to reduce

volume of transmitted data.

  Following the compression process applied to

  audio-video-digital, audio-digital, video-

  digital and digital data above, there are corresponding compressed digital signals, which can then advantageously be subjected to an audio / video / data temporal multiplexing process, this multiplexing process for delivering a single bit stream constituting the source signal coded ssc previously mentionned

in the description.

  The operations performed in step 1001, as represented in FIG. 2a, are operations of conventional type and, for this reason, will not be described of

in more detail.

  With respect to step 1002 of broadband channel coding, it is indicated that the channel coding process retained for the implementation of the protocol, object of the present invention, is a coding functionally similar to the COFDM coding used until 'to date for

DAB transmission applications.

  In general, the COFDM coding is a coding derived from the OFDM coding, the COFDM coding making it possible to

  to guarantee excellent immunity to destructive interference

  between the symbols and a good protection against frequency distortions of the transmission channel. The COFDM coding is an OFDM type coding in which, by coding, an addition of redundancy between

  signals and interleaving in time and frequency

quence of transmitted symbols.

  It is indicated that the performances of the COFDM coding are then linked to an average criterion of signal-to-noise ratio, this signal-to-noise ratio then being reinforced thanks to the presence of echoes at the reception with constructive interference, that is to say echoes that can be exploited

  to enhance the quality of the information transmitted.

  The essential steps of the channel coding process implemented at step 1002 of FIG.

represented in FIG. 2b.

  These various steps comprise, successively applied to the ssc coded source signal, an optional energy dispersing step 1002a, a convolutional coding step 1002b, a time interleaving step 1002c, a digital symbol forming step 1002d, the formation of digital symbols being made from a synchronization signal, denoted SYNCHRO, a step 1002e consisting of operations on the symbols obtained

  in step 1002d and for the purpose of introducing a space-

  time between these symbols and a decomposition on orthogonal carrier waves, a PSK or QAM carrier modulation step 1002f, a frequency interleaving step 1002g, and finally a carrier multiplexing step 1002h. At the end of step 1002h, the coded broadband signal sclb is obtained in baseband

  as mentioned earlier in the description in

connection with Figure 1.

  With regard to the previously mentioned synchronization signal, it is indicated that it contains two symbols, the first being empty of any signal and the second including all the carriers whose phases originally were fixed, in order to allow the mobile receivers to synchronize in time, frequency

and phase.

  With regard to the operation 1002f of carrier modulation, it is indicated that each carrier is in fact associated with a modulation of the symbol corresponding to a

  number of bits, which describe a state of ampli-

study and / or phase.

  The following modulations can be used: - 4-PSK, four-phase phase shift keying associated with two successive bits;

  - 16-QAM, quadrature, amplitude, modulation, or 64-

QAM for example.

  For a more detailed description of the step of

  broadband channel code 1002 previously mentioned, reference may be made to the article entitled

  "Principles of modulation and channel coding in broadcasting

  digital fusion towards mobiles ", published by M.ALARD and

  R. LASSALLE, EBU - Technical Review No. 224, August 1987.

  A more detailed description of the structure

  temporal or frequency signals obtained during the implementation of the channel coding step 1002, mentioned above, will now be given in connection with

Figures 3a, 3b and 3c.

  FIG. 3a shows the temporal succession of the generated symbols, in order to carry out the aforementioned channel modulation. This temporal succession of symbols is that obtained following the implementation of the

steps 1002d and 1002e.

  Thus, for symbols of duration Ts, the succession of symbols is separated by a time guard interval 6 by a determined value. So the time period

  of appearance of the symbols is referenced T = Ts + 6.

  In practice, and in the case of a DAB broadcast, it is indicated that 6 is of the order of 20% of the duration of the period T. This value makes it possible to ensure, on the one hand, a value sufficient for time guard interval and, on the other hand, a sufficient flow of symbols during the transmission. The time guard interval 8 thus makes it possible, for any delay echo t 5 6, to take into account the value of this echo at a mobile receiver, for example, to ensure, on the one hand, the discrimination of the echoes posterior to each symbol, and, on the other hand, the reinforcement of the useful signal from any echo received during the interval

temporal custody.

  Of course, the value of the guard interval 6 is also much less than the duration of a symbol Ts. It is recalled that in the context of the DAB radio transmission, in normalized modes I, II and III, the time guard interval is equal to 1/4 of the duration

Ts of each symbol.

  Figure 3b shows, in the frequency domain

  tiel, the spectrum of the signal obtained following the orthogonal carrier decomposition in step 1002e. Thus, in the aforementioned frequency domain, a plurality of carrier waves, denoted f ... f, ... fn, are obtained, each carrier being spaced apart from an adjacent carrier of a carrier.

  frequency interval Af in terms of central frequency.

  By way of nonlimiting example, in the standardized modes I, II and III mentioned above, the respective number of carriers is 1536, 384, 192, the carrier space Af = 1, 4, 8 kHz for a width of total band

  in baseband equal to 1.536 MHz.

  Finally, FIG. 3c shows, after multiplexing the carriers at step 1002h of FIG. 2b and frequency change for frequency transposition at the first center frequency F1, the frequency spectrum in the frequency space of the broadband code signal. broadcast sclbd1. It will be recalled simply that as regards the broadband coded signal broadcast after transposition at the second central frequency F2, this signal has a spectral distribution in the frequency space similar to that shown in FIG. 3c, the term F1 being simply replaced by the term F2. For this reason, this spectral distribution of the broadcast broadband coded signal sclbd2 is simply represented in the drawing by

substitution of F2 for Fl.

  In FIG. 3c, AF is represented by a sliding

  frequency, either of the signal at the center frequency F1, that is, of the broadband coded signal sclbdl, or of the broadband coded signal at the second frequency

central F2 sclbd2.

  Thus, a relative speed between a transmitter and a receiver introduces a slip or frequency shift of the

signal by Doppler effect.

  The decomposition of the signal into carrier waves separated by disjoint frequency intervals, as shown in FIG. 3b or 3c, spaced apart by a higher frequency interval Δf of the Doppler shift, thus makes it possible, thanks to the channel coding performed, to provide the reception of the coded broadband signal broadcast by a mobile

  in relative displacement with respect to the transmitter.

  This is particularly the case with regard to the retransmission relay (s) in relation to the source (s).

  as well as for each radio frequency

  these mobile vis-à-vis each reissue relay.

  Under these conditions, and for a relative speed of value v1 of the source of diffusion at the first central frequency of value F1 with respect to the retransmission relay concerned, and for a relative speed of value v2 of the retransmission relay at the second frequency with the relevant mobile radio frequency receiver F2, the global frequency offset AF of the signal received by the mobile receiver then verifies the relation (1):

AF = [F1.v1 + F2.v2] / c <Af / K.

  In this relation, according to a particularly advantageous aspect of the protocol, object of the present invention, c designates the speed of propagation of an electromagnetic wave in the atmosphere and K denotes a coefficient, greater than 2, which makes it possible, of course, to provide a latching zone sufficiently wide for reception, substantially corresponding to at most half of the inter-carrier spacing Af, as shown in FIG. 3c for the first center frequency F1 and the

second center frequency F2.

  Under these conditions, not only the offset or frequency shift due to the Doppler effect on each carrier poses no problem at the reception, but also

  this shift or shift is small enough to

  No confusion between successive carriers.

  The inter-carrier spacing may for example be equal to l / Ts to obtain maximum spectral efficiency. By way of a purely illustrative example, it is indicated that, for a relative speed v 2 of 300 km / h between the retransmission relay and a mobile, for a reception frequency of 2 GHz, the contribution of the relative speed v 2 to the Doppler effect reaches the value of 556 Hz. This value is much lower than the Af spacing in mode III by

example, which is equal to 8 KHz.

  Thus, in view of the above relation (1), the COFDM-type broadband channel coding parameters being chosen, the mobility of the one or more broadcast sources, the re-transmission stations and, if appropriate, the mobile radio-frequency receivers can then be be chosen to satisfy the reception latching constraints, in order to maintain the quality of the reception during any displacement or adaptation of the local coverage area. The gripping condition is expressed as a constraint on the global value of slip or frequency shift according to the aforementioned relation (1), shift or global slip which must of course remain

  much lower than the inter-carrier spacing Af.

  Recall that in relation (1) above, the summation between the contributions of each relative speed v1 and v2 is an algebraic summation taking into account the

  approximation and / or the relative remoteness of the transmitter / receiver

  tor. Of course, besides the frequency constraint

  previously mentioned, there is a relative constraint

  adaptation of the local coverage area, this

  constraint being induced by the modification of the configuration

  geometric adaptation of the adaptive network when this adaptive network is constituted by a plurality of diffusion sources, that is, when, in fact, more than one scattering source at the first center frequency F1 is used, and, d On the other hand, when more than one

  retransmission are also used in the coverage area.

local level.

  This so-called geometric constraint is in fact induced by a condition relating to the delay time of the echoes that are likely to be received by any mobile radio frequency receiver M, the notion of echo obviously covering any signal similar to the same central frequency received by the mobile M along two distinct paths, as well as

  that it will be explained in connection with Figure 4a.

  FIG. 4a shows the case where a transmission-diffusion source at the first center frequency F1 and two retransmission relays located in the zone are considered.

  general coverage of the transmission source -

  aforementioned broadcast and whose local coverage area overlaps, a mobile radio frequency receiver M being located in the zone of intersection of local coverage areas

two relay reissue.

  It is understood in this case that the adaptive network thus formed is in fact an adaptive monofrequency network, the re-transmission at the second central frequency

  being carried out by the two aforementioned retransmission relays.

  In such a case, the step of retransmitting from at least one reissue relay. the broadcast broadband coded signal sclbd2 at the second center frequency of value F2 is made from a plurality of retransmission relays constituting the aforementioned single-frequency network at the reception frequency. Under these conditions, two retransmission relays as represented in FIG. 4a are at most distant from a maximum distance D satisfying the relation (2):

2 D + O

c

  In this relationship, t denotes the maximum delay of

  introduced by the retransmission operation in each of the two retransmission relays, 2, and 1; denoting the delay of each retransmission operation, and 6 denotes the maximum allowable time offset between the reception signals received by each mobile radio frequency receiver, the receiver M in FIG. 4a, offset at most equal to the time guard interval separating two symbols in the time domain, as mentioned previously in

the description.

  In fact, with reference to FIG. 4a, it is indicated that: on the one hand, the difference in path between the diffusion source and the mobile RF receiver M remains less than or equal to 2 D when the reception paths go through the retransmission relay station 1 and retransmission relay station 2; on the other hand, the delays corresponding to the processing operations performed at each of the re-transmission relays 1 and 2 can not differ by more than

  the value t previously mentioned.

  Thus, the activation or inhibition of any of the retransmission relays, provided that the criterion

  maximum distance D satisfies the relationship (2) above.

  may not in any case disturb reception for any mobile located in the local coverage area as well

  because, under these conditions, the ignition or extinguishing

  the aforementioned retransmission relay adds or removes a

  non-disruptive echo for this reception.

  Thus, the adaptive configuration of a network comprising, for example, as shown in FIG. 4a, several COFDM coded retransmission relay stations, can be carried out without difficulty, provided that the constraint relating to the compatibility of the echoes, offset of the echoes

  below the time guard interval 6, be satisfactory

  you. Under these conditions, the presence of several retransmission relay stations at the second central frequency F2 is thus not destructive of the reception conditions as soon as the different signals arriving at the same point, the mobile M in FIG. 4a, are temporally staggered

  more than the time guard interval 6.

  To the contribution of the echoes likely to reach each mobile radio-frequency receiver M with respect to two or more re-transmission relays, as represented in FIG. 4a, the contribution of echoes must be added.

  generated for example by two sources of transmission -

  diffusion, source 1 and source 2, compared to a source

  of origin, such as a telecommunications satellite,

  transmission station - remission, as well as

represented in FIG. 4b.

  In such a case, and because of the same assumptions as in the case of FIG. 4a, the transmission and broadcasting operation is however carried out by means of a plurality of transmissions and diffusicns of the broadband coded signal broadcast at the first central frequency of value F1, diffusion frequency, over a plurality of

  areas of general coverage, from the source of origin

  ensuring the illumination of the two sources of

* sion - diffusion 1 and 2 above, the two sources of diffusion must then be distant from a maximum distance D 'verifying the relation (3):

2 D '+ I' <6.

  c In relation (3) above, by analogy with relation (2):

  I 'denotes the delay of the treatment introduced by the operation

  broadcast of each broadband coded signal from the original source; 6 denotes the maximum allowable time offset between the reception signals received by the retransmission station represented in FIG. 4b, this offset being at most equal to the time guard interval separating

  two symbols in the time domain.

  Of course, in the general case and for substantially identical technologies implemented at the level of the diffusion sources 1 and 2 at the first central frequency F1, the relative processing delay introduced by the diffusion operation, for substantially identical values. of treatment delay t'1 and t'2 from each of the diffusion sources, can be considered as

substantially zero.

  Under these conditions, the relation (3) above becomes, relation (4):

2D '/ c s 6.

  In the most general case o several sources of

  are used and o several repeater relays

  are also used, it goes without saying that for each

  mobile radio frequency receiver M, the reception condition

  correct, taking into account the adaptation of the single frequency network thus constituted, corresponds to the superposition of the conditions previously described, according to the relations (2) and (3) or respectively (4), that is to say in the summation of the all the delays caused by the double paths constituting possible echoes. Under these conditions, the condition becomes the relation (5) below:

2 (D + D ') / c + to + the 5 6.

  Thus, the protocol, object of the present invention, allows the implementation of an adaptive broadband broadcast network of an audio-video signal for mobile receivers. The adaptive nature of this network appears: - because of the possibility of configuring the coverage area of the service at one and the same frequency

  to form a single frequency network as to its location.

  overall satellite coverage or displacement of

  the emitter of the diffusion layer or transmission layer

  Harbor; due to the possibility of real-time reconfiguration of the coverage area in location and in shape by displacement, operation or inhibition of transmitters or retransmission sources, that is to say relays

reissue.

  The possibilities of reconfiguration appear particularly high because of the types of transmitters that

  can be used to build the repeater relays

  These re-transmission relays can also be moved within the global coverage area.

  according to specific configurations, provided that the con-

  above mentioned stresses are respected.

  A more detailed description of the adaptive network

  broadband broadcast of an audio-video signal for mobile receivers, in accordance with the subject of the present invention, will now be given in connection with the

Figures 5a to 5c, in the first place.

  As shown in FIG. 5a, this comprises a source encoding module of the audio-video signal making it possible to generate an encoded source signal and a channel coding module that makes it possible, from the coded source signal,

  generating a coded wide band baseband signal.

  In FIG. 5a, the two aforementioned elements are represented

  dotted by a single block because the broadband coded signal obtained from step 1002 of Figure 1, sclb signal, can be generated by means of conventional elements, according to the operations shown in figures 2a and 2b, in all points of the network and in particular

  be transmitted by means of a telecommunications satellite

  communication to a broadcast source, as shown in FIG. 5a, the transmission and broadcasting source

  bearing the reference 1 in Figure 5a. In a classical way

  that this transmission and diffusion source 1 comprises a baseband frequency transposition module at the first center frequency F1, this module bearing the reference 10 in FIG. 5a. It will of course be understood that the sclb signal is available at the transmission and broadcasting source 1 by any conventional means of transport, which, as such, will not be described in detail. The transmission and broadcasting source 1 at the first center frequency F1 also includes, of course, a frequency synthesizer at the aforementioned frequency F1, bearing the reference 11, and in a conventional manner,

  a pre-amplifier with the reference 12 and an amplifier

  transmission transmitter with the reference 13 making it possible to ensure, by means of a transmitting antenna 14, the transmission and broadcasting of the broadband coded signal broadcast over the overall coverage area, this signal

  corresponding to the signal sclbd in Figure 1.

  In general, it is indicated that the first central frequency F1 can have a value of 1.35 GHz. Under these conditions, the transmitting antenna 14 may consist of

  a satellite dish for example.

  FIG. 5b shows the different types of emission sources that can be used for implementing the adaptive wideband broadcasting network of an audio-video signal conforming to the object of the present invention.

present invention.

  As represented in the above-mentioned figure, this source may be constituted by a satellite transmitter, receiving, at a reception frequency F0 or F1, equal to the first central frequency, the information of the broadband coded signal, this information being of course transposed into a baseband signal for subsequent processing by the transposition module 11, the preamplifier and

  the amplifier 13 and diffusion by the antenna 14.

  Another type of source may consist of a substantially fixed or slow speed air transmitter

  variable. In this case, the broadcast source 1 is

  on an airship, for example, a tethered balloon or the like. In the same way, the transmission and broadcasting source 1 can also be embarked on an aircraft. Whereas, in the first two cases, the transmission and broadcasting source can be considered as substantially fixed in the case where the satellite transmitter is embarked on a geostationary satellite and in the case where it is embarked on a dirigible balloon for example, in the case where embarkation is performed on an aircraft, the transmission and broadcasting source 1 is considered

as a mobile air source.

  As further shown in FIG. 5b, the transmission and broadcasting source can also be associated with a fixed terrestrial transmission station or transmitter. In this case, of course, the sclb baseband broadband coded signal may be available at

  level of the earth station transmitting facilities.

  Finally, as also shown in FIG. 5b, the transmission and broadcasting source can be

  mounted on a mobile terrestrial station, that is,

  say embedded on a motor vehicle.

  FIG. 5c shows schematically the general coverage area thus obtained thanks to the use of one or more sources of

transmission and dissemination.

  In addition, the adaptive broadband broadcast network of an audio-video signal to mobile receivers,

  object of the present invention, comprises, as well as

  6b, at least one mobile retransmission relay, referenced 2 in Figure 6a. The retransmission relay 2 provides reception in the general opening area at the first center frequency F1 of the broadband coded signal.

  sclbd, the transposition of this signal and the reissue

  encoded broadband signal at a second frequency.

  the central frequency F2 distinct from the first center frequency F1 and, of course, equalizes with the reception frequency. This re-transmission is ensured on the local coverage area, instantaneous seat of the mobile receivers equipped with receiving stations at the second frequency

central F2.

  Advantageously, as represented in FIG. 6b, each retransmitting relay 2 may comprise a

  receiving antenna 2. pointed towards the source of

  sion and dissemination previously described in the description

  tion. The receiving antenna 2o may for example be constituted by a parabclic antenna. The reception antenna 2o is interconnected with a filtering module, denoted 2;, which is tuned to the first central frequency F1. The filtering module 2 delivers a filtered signal to a frequency translation module 22 of the first frequency.

  F1 to the baseband signal through the

  of a frequency synthesizer 23 delivering a

  signal at the frequency F1 above. The transposi-

  22 delivers a reconstructed baseband broadband coded signal to a baseband frequency translation module to the second center frequency F2, labeled 24. A second frequency synthesizer 25 is provided which provides a signal at the second center frequency F2, allows: by frequency change to deliver to a pre-amplifier 26 and then to an amplifier 27 the broadband coded signal to the second

  center frequency F2, previously designated in the description

  by sclbd2. An antenna 2, retransmission makes it possible to

  re-transmitting this signal over the coverage area

  local as previously mentioned in the description.

  In order to provide the previously mentioned local coverage area, it is indicated that the reissue antenna 29 may

  advantageously constitute a YAGI antenna for example.

  With regard to the type of mobile relay used, it will be understood, with reference to FIG. 6b, that the mobile retransmission relay can be on board, either on an airship or air balloon or captive, and therefore at a slowly variable speed or as may be the case may be fixed, on an aircraft, or consist of a terrestrial wireless transmission station, where appropriate on a

motorized vehicle.

  It will be understood in these conditions, in connection with FIG. 6b, that the adaptation of the local coverage area can be carried out either by moving the retransmission relay relative to a fixed wireless network for example, or, if appropriate, by inhibiting or putting into operation one or more retransmission relays, as shown in dashed lines in FIG. 6b. Thus, the local coverage area can be reconfigured in real time according to the movement requirements of the collection of

  vehicles with mobile radio frequency receivers.

  Of course, for a determined frequency value

  In the first center frequency, the adaptation of the local coverage area can be performed by moving the retransmission relay at a relative linear speed, mobile retransmission relay / transmission and broadcasting source, less than a first value of limit speed V1, depending on the value of the first frequency

Fl.

  In the same way, for a frequency value

  determined F2 of the second central frequency, the adaptation

  the local coverage area can be realized by moving the mobile retransmission relay at a relative linear velocity M mobile receiver / mobile retransmission relay lower than a second limit velocity value V2, depending on the value of the second central frequency

F2.

  It will of course be understood that, given the COFDM coding parameters used for the implementation of the protocol, object of the present invention, the previous limit values V1 and V2 are determined from the

  relation (1) previously mentioned in the description.

  Furthermore, as will be understood from the observation of FIG. 6b, the adaptive broadband diffusion network

  an audio-video signal to radio-frequency receivers.

  Mobile quences, object of the present invention, may comprise a plurality of retransmission relays at the second single central frequency F2, distinct from the first central frequency F1, on a plurality of reconfigurable local coverage areas so in real time for

  actually constitute a single frequency subnetwork.

  It is understood in particular that for this purpose, as shown in Figure 6b above, the single frequency sub-network may comprise a zero-speed mobile reissue relay constituted by the fixed terrestrial transmitter, constituting a basic single frequency subnetwork , as well as a system for synchronizing the retransmission of each retransmission relay. It will be understood in particular that the synchronization system may for example be implemented at each retransmission relay and take advantage of the synchronization signal transmitted and broadcast with the broadband coded signal broadcast at the first center frequency F1, the signal sclbd1. This synchronization system will not be described in detail because it corresponds to a conventional synchronization process in single frequency radio networks. In addition, the single frequency subnetwork represented in

  FIG. 6b may comprise an activation control system

  tion / inhibition of retransmission of at least some relay

  mobile or fixed retransmission. The activation / inhibition command

  bition can be constituted by a separate control terrestrial hertzian link implanted for example on the motorized vehicle support of the mobile terrestrial transmitter.

  In these circumstances, it is stated that, of course, the

  tion or operation of a reissue relay such as that shown in dotted lines in Figure 6b, can then be performed from the motorized vehicle, support of the mobile terrestrial transmitter, given the constraints of maximum distances previously introduced in the

  description, in accordance with relation 2. Thus, thanks to the

  implementing the retransmission relay activation / inhibition control system, it is possible to adapt in real time the local coverage area resulting from the retransmission activation of all or part of the plurality of relays mobile or fixed reissue according to the law of displacement of a

or multiple mobile receivers.

  FIG. 6c shows a particular case

  not limitative, in the case where the transmission of

  The transmission of the broadband coded broadband signal sclbd1 is performed taking into account a specific modulation, such as a frequency modulation for satellite transport. In FIG. 6c, it is thus understood that the coded broadband baseband signal is transmitted to the transmission-broadcasting source, constituted for example by a satellite, after modulation, such as the aforementioned FM modulation, by via a remodulation device for satellite transport, bearing the reference 11. In this case, the signal, given

  this remodulation is transmitted to the source of

  rediffusion, for example at the same frequency F1 as the first center frequency, or at any frequency F0

  distinct from this first central frequency, the transmission

  transmission of the broadcast broadband encoded signal sclbd, at the first center frequency Fl being of course

  performed considering this additional modulation.

  In such a case, as shown in FIG. 6c, any retransmission relay, bearing the reference 2 in the above-mentioned figure, comprises, in addition to the elements 20 to 27

  previously described in the description in connection with the

  FIG. 5b, an FM demodulation element, corresponding to the operation opposite to that performed by the element 15 previously mentioned, this demodulation element carrying

reference 29.

  A specific application of the Adaptive Broadband Protocol and Adaptive Network from an audio-video signal to mobile radio-frequency receivers will now be

  given in connection with Figure 7.

  In this application, it is indicated that the collection of mobile radio frequency receivers is constituted as part of a sports event such as a major cycling race, such as the Tour de France, by the vehicles of the following sports directors and race directors cyclists and wish to have, in their vehicle, images of the race broadcast live by a television operator as well as corresponding data such as lap times, gaps, for example. These images are available on terrestrial analogue programs broadcast in France using the SECAM process and TELECOM 2 satellite broadcasting, for example. These images and the corresponding information relate to the last three hours of each step, for example, either

  about the last eighty kilometers.

  The collection of vehicles equipped with radiofrequency receivers is distributed over an area whose size

  linear is around 30 km.

  The direct reception of the emission of images of

  satellite television is tricky at the level of

  the aforementioned, as mentioned previously in the

description.

  With regard to broadcast television programs

  by analogue terrestrial networks or by satellite

  you, the reception is very poor quality as he has

  previously indicated in the description of

  tion. The overall coverage of all stages by a fixed terrestrial wireless network appears very costly

  the duration and relative importance of the event.

  Moreover, the layout and topography of each step vary from year to year. As shown in FIG. 7, the broadcasting of real-time television images of the race by a telecommunication satellite, such as the TELECOM satellite

2 for example, is used.

  In accordance with the protocol and the adaptive network, objects of the present invention, my transmission and broadcasting system is constituted by a terrestrial hertzian source receiving in direct vision at a high point the emission of the TELECOM 2 satellite broadcast by the television operator. . Following the reception of: ellite broadcast television images, these images e; the associated sounds, and any associated data, are digitized and then subjected to MPEG source coding at 1.5 Mbps / s and then to COFD-M channel coding at the transmission source. broadcast 1 above. This source of

  broadcast transmission makes it possible to

  encoded broad-beam encoded signal sclbd1 at the first center frequency F1 in the form of COFDM blocks at 1.5 MHz bandwidth in a so-called uplink channel, actually constituting a transport layer on the

figure 7.

  It is understandable that, for each step, the

  high point is chosen near the middle of the four-

  The last twenty kilometers of the stage ..... at the level of this high point is installed for example a mobile land station, mounted on a motorized vehicle, as represented in

Figure 6b.

  The broadcast transmission source 1 performs the following functions: reception of the television images of the step in real time transmitted by the television operator on the

satellite TELECOM 2, for example.

  To ensure this function, the transmission transmission source comprises a parabolic antenna of the order of 1.20 m in diameter and the means necessary to ensure the transposition of the received signal transmitted by satellite v-oie into a baseband signal. The composite audio and video components are extracted from the baseband signal and transmitted to the encoder performing the source coding step. - digital audio-video coding derived from the DVB-T standard according to ETS 300 744 standard comprising: ISO / MPEG2 audio / video encoding and multiplexing, 20. DVB energy dispersion, Reed-Solomon DVB coding for a final bit rate of 1.728 Mbit / s

DVB convolutive interleaving. the digital train corresponding to the coded source signal ssc is then

  subject to DAB channel coding type channel coding in accordance with ETS 300 401 with operations of: energy dispersion DAB convolutional coding DAB of yield 3/4 convolutional interleaving DAB multiplex DAB frequency interleaving DAB mode III COFDM coding with 6 = 30 ps for a

bandwidth of 1.536 MHz.

  the CODFM block obtained is then transmitted and broadcast at the first center frequency F1, for example band III for a sufficient range: after amplification of power as a function of the frequency F1 and the range of the retransmission relay to be reached at a distance of About 60 km,

  5. the transmitting antenna corresponding to the transmitting antenna

  sion 14 in FIG. 5a can then be constituted by

  a quarter-wave dipole antenna, antenna with

  in order to obtain the general coverage area

  the. A single retransmitting station or relay 2 is then used, this retransmission relay being embarked on a TB20 type plane then flying over the collection of the destination vehicles by describing loops at a reduced speed of less than 300 km / h and at an altitude of

  between 1000 and 3000 meters in relation to the moving area

  vehicles. The retransmission relay corresponds to that shown in FIG. 6a. The reception antenna at frequency F1, referenced 2o in FIG. 6a, can be fixed under the apparatus. This antenna is a conventional antenna for DAB reception in band 3. The value of the frequency F2 of the second central frequency is chosen in L-band for example. The broadband coded signal broadcast at this second center frequency fclbd2 is then broadcast after amplification with a power of 50 W by the transmitting or retransmitting antenna, bearing the reference 2s in FIG. 6a, this antenna being able for example to be incorporated

  by a quarter-wave dipole antenna fixed under the plane.

  With regard to the vehicles equipped with a mobile radio-frequency receiver, it is indicated that these receivers receive the COFDM blocks emitted by the aircraft or more precisely by the retransmitting station 2 at the second central frequency F2, each vehicle and the associated receivers. these vehicles are then equipped with a conventional L-band DAB reception antenna. The mobile receiver then performs reception and decoding operations integrated hereafter: radiofrequency reception according to the DAB ETS 300 401 standard of sensitivity greater than -98 dBm if F2 is in L-band; - DAB channel decoding; - DVB decoding, including convolutional interleaving, Reed-Solomon coding and energy dispersion; - decoding and demultiplexing MPEG type 2 to output the audio and video components; the audio and video components are then reproduced using amplified loudspeakers and a

  TV monitor type monitor.

Claims (12)

  1. Broadband broadcast protocol of an audio-video signal to mobile radio-frequency receivers at a reception frequency, characterized in that said protocol consists in: - subjecting said audio-video signal to a source coding to generate an encoded source signal; - subjecting said coded source signal to a channel coding for generating a broadband coded signal consisting of a sequence of temporally spaced time duration symbols Ts of a time guard interval and distributed in the frequency domain over intervals of disjoint frequencies, the carrier waves of each of the symbols being separated by a frequency guard interval Af; transmitting and broadcasting said broadband coded signal at a first center frequency F1, broadcast frequency to a broadcast broadband coded signal over a general coverage area; retransmitting from at least one retransmission relay located in said general coverage area and providing reception at the first center frequency F1 of said broadband coded signal broadcast to a second   center frequency F2 equal to said reception frequency   on at least one local coverage area, instantaneous seat of said mobile radio frequency receivers, which makes it possible to adapt said local coverage area to the position of said mobile radio-frequency receivers for a optimal reception.   2. Protocol according to claim 1, characterized in that, for a relative speed v. from the broadcast source at the first center frequency F1 and said re-transmission relay and for a relative speed v2 of the retransmission relay at the second center frequency F2 and of each mobile radio receiver, the global frequency offset AF of the signal received by said mobile receiver, check the relation: AF = [Fl.v. + F2.v:] / C S Af / K o K> 2 and c denotes the speed of propagation of the light in the atmosphere.   3. Protocol according to one of claims 1 or 2,   characterized in that the step of retransmitting from at least one retransmission relay said broadband coded signal broadcast at said second center frequency F2 is performed from a plurality of retransmission relays, constituting a single-frequency network , two retransmission relays being at most distant from a maximum distance D verifying the relation: 2 D + 6   c relationship in which: x is the maximum treatment delay introduced by   the reissue operation in each repeater relay   if we; 6 is the maximum allowable time offset between the reception signals received by each mobile radio frequency receiver, i.e. temporal guard.   4. Protocol according to one of claims 1 to 3,   characterized in that the step of transmitting and distributing   sion is achieved by means of a plurality of substantially simultaneous transmissions and broadcasts of said broadband coded signal broadcast at the first center frequency F1, broadcast frequency, over a plurality of general coverage areas, two transmission and broadcast sources being distant from a maximum distance D 'satisfying the relation: 2 D' + t '<6 c relation in which: t' denotes the maximum treatment delay introduced by   the reissue operation in each repeater relay   if we; 6 denotes the maximum allowable time offset between the receive signals received by each mobile radio frequency receiver, i.e., the time guard interval. An adaptive broadband broadcasting network of an audio-video signal to mobile radio receivers tuned to a reception frequency, characterized in that it comprises:   source encoding means of said audio signal   video for generating a coded source signal; channel coding means making it possible, from said coded source signal, to generate a broadband coded signal; means for transmitting and broadcasting at a first central frequency F1 of this broadband coded signal into a broadband coded signal broadcast over a general coverage area; at least one mobile relay retransmission means receiving, in the general coverage area at the first center frequency F1, said broadband coded broadband signal and retransmitting said broadband coded broadband signal at a second center frequency F2, distinct from the first center frequency F1 and equal to the reception frequency, over a local coverage area, instantaneous seat of said mobile receivers equipped with reception means at the second center frequency F2, which makes it possible to adapt said local coverage area to the   position of said mobiles for optimal reception.   Adaptive network according to claim 5,   characterized in that for a determined frequency value   born F1 of the first central frequency, the adaptation of   said local coverage area is achieved by moving   said mobile relay retransmission means at a relative linear velocity, means for retransmission of the mobile relay / transmission and diffusion means, less than a first limit velocity value Vi depending on the value   of said first center frequency Fl.   Adaptive network according to claim 6,   characterized in that for a determined frequency value   born F2 of the second central frequency, the adaptation of   said local coverage area is achieved by moving   said mobile retransmission means at a relative linear speed, mobile receivers / mobile relay retransmission means, less than a second limit velocity value V2, a function of the value of said second frequency central F2.   Adaptive network according to one of the claims   7, characterized in that it comprises a plurality   mobile relay retransmission means ensuring the reception of   in the general coverage area at the first center frequency F1, of said broadband coded signal, and the retransmission of this broadband coded signal at a second central frequency F2 unique, distinct from said first center frequency F1, on a plurality of local coverage areas, said plurality of mobile relay reissue means and local coverage areas constituting a single frequency subnetwork.   9. adaptive network according to claim 8, characterized in that said single-frequency subnetwork comprises: - zero speed mobile relay retransmission means constituting a basic single frequency subnetwork; means for synchronizing the retransmission of each mobile relay retransmission means; control means for activation / inhibition of retransmission of each mobile relay retransmission means, two mobile relay retransmission means whose broadband coded broadcast signal has the same second central frequency   F2 being controlled in conditional retransmission activation   to a criterion of separation distance of relay relay retransmission means at most equal to the echo distance   maximum, depending on the broadband coding mode.   10. adaptive network according to claim 9, characterized in that it further comprises means for managing the control means for activation / inhibition of retransmission of each retransmission means, which allows   to adapt structurally in real time the area covered by   resulting localization of the re-transmission activation of all or part of the plurality of mobile relay retransmission means, depending on the law of displacement of one or several mobile receivers.   11. Adaptive network according to one of the claims   at 10, characterized in that said transmission and diffusion means at a first central frequency F1 of   encoded broadband signal belong to the transpon-   satellite, land or air station, fixed or mobile.   12. Adaptive network according to one of the claims   at 11, characterized in that said means for retransmission   mobile relays are embedded on an aircraft.