Fm simulcast broadcast signal broadcast transmission system and receiver device for same

Translation of description of equivalent WO 2007101642 A2

p0001description

p0002FM-simulcast broadcast signal, broadcasting system and receiver means for

p0003The invention relates to an FM-simulcast broadcast signal according to the preamble loan features of claim 1 and radio communication system and a receiver device, which operates with such signals.

p0004For the transmission of data broadcasting programs are modulated and transmitted over a radio interface to remote receiver. So far it has not been able to successfully introduce a digital successor to the several decades old VHF radio system which is based on a frequency modulation in the market. A major problem is that developed standards such as "Digital Audio Broadcasting" (EUREKA 147) does not allow the same frequency grid as in the previous system. While the new standards work with a bandwidth of 1.5 MHz per signal FM pattern used about 300 kHz on the contrary. A "gentle" migration by switching from channel by channel for individual channels is not possible, but it must always five adjacent analogue services will be switched off in order to introduce a digital multiplex for digital signal transmission can. However, new, expensive receivers are required for the reception of digital programs, which hardly have spread at launch, so that a program provider by introducing, for example, the digital broadcasting on the FM band would allow his audience to fall to virtually zero. Therefore, a primary objective is to provide a via a radio^¬ interface transmittable signal to define, which both analog means of classical FM demodulation and can be digitally decoded at a fixed bandwidth.

p0005At present, in producing an FM demodulated signal, a sinusoidal signal is used as the carrier whose amplitude is maintained at a constant value, for example the value 1. The modulation takes place of this carrier signal by a modulation of the phase. In frequency modulation, the phase is modulated with an integrated signal, whereby a sinusoidal signal with a changing zero distance signal is generated. Such transmitted via a radio interface a- naloges signal is received from a conventional radio as a receiving apparatus and its phase differentiation in time in the receiver to reconstruct the original analog signal from user data and be able to output.

p0006In current implementations of parallel digital signals to analog signals according to the principle of the frequency

p0007Multiplex procedure. A classical FM-modulated analog signal are provided digital support to the side. The E nergy the digital carrier is automatically adjusted so that the noise in the analog signal re- main in the acceptable range.

p0008From the USA, a method called IBOC (InBand On Channel) is known, adding that the analog spectrum digitally modulated signals and greatly lowered at the sides back. The disturbances are mitigated or predicted, wherein a transition between digital and analog decoded signals can occur with poor reception. Ultimately, however, there is a strict spectral separation of analog and digital signals with an allowed overlapping area.

p0009A disadvantage of the IBOC method that up in Europe due the narrow channel spacing is not easy to use. Moreover, the scope would be reduced between adjacent channels.

p0010In addition is disadvantageous that the data rate of the digitally modulated signal is relatively low. This is partly due to the relatively low energy of these signals, since these must not affect too much the quality of the analog signal. Low energy implies the need for better protection against transmission errors, ie a higher redundancy, thereby reducing the effective amount of transmittable data. On the other is the carriers relatively little bandwidth available, which also leads to a reduction in the data rate.

p0011EP 1276257 Bl describes a DRM / AM simulcast signal (DRM:

p0012Digital Radio Mondeal), in which an amplitude modulated signal is hidden in a digital signal, the signal must come at a presentation in the complex space on the real axis. is disadvantageous in that it is not applicable or not suitable for FM-modulated signals.

p0013The object of the invention is to provide an FM simulcast broadcast signal for providing a total signal for transmitting as a broadcast signal, especially for providing or processing of FM signals to propose, with such a modulated signal a better utilization of a fixed, predetermined frequency range for the transmission of is intended to enable analog and digital signal components. This object is achieved by an FM-simulcast broadcast signal according to the features of claim. 1

p0014Advantageous embodiments are the subject of dependent claims.

p0015Preferably Accordingly, an FM simulcast broadcast signal, are combined for transmission in which at least one digital and one analog signal in a transmission channel with limited bandwidth as a total signal (S) having a first phase velocity (vs). Here, an auxiliary signal (hs) is provided which in the complex domain from the to be transmitted modulated digital signal (ds) and to transfer lowing FM modulated analog signal (as), having a second phase velocity (vas), is formed. This auxiliary signal (hs) is added a non-or at least largely unused by the digital signal frequency range in at least. Furthermore, there is for transmitting provided for ne total signal (s) from the auxiliary signal (HS) and the FM modulated digital signal (DS), wherein the first phase velocity (vs) of the total signal (S) at least approximately the second phase velocity (Vas) of the analog signal (as) equivalent.

p0016The total signal is preferably formed as the sum signal from the at least one digitally modulated carrier with the digital signal and from the auxiliary signal on the other carriers for the auxiliary signal. The auxiliary signal is advantageously formed as an approximated difference signal. The difference signal is preferably formed as the difference, in particular subtraction, of at least one digital signal and at least one analog signal to be transmitted by means of the total signal. The auxiliary signal is preferably formed from an analog signal which is FM-inoduliert in the complex base band, from a second digital signal as a digitally modulated signal and a difference formation of the complex baseband FM-modulated signal and the second digital modulated signal to form a difference signal. The digitally modulated signal preferably has a limited bandwidth, which was radio services assigned to a station for a given round. The auxiliary signal is formed in particular as an approximation of the difference signal.

p0017The difference signal may form the auxiliary signal with respect to the energy of the difference signal optimized in particular be minimized. The difference signal may be modified to form the auxiliary signal on the restriction on spectral components within a predetermined range.

p0018The total signal is preferably a digital block, especially a digital block with a bandwidth between about 50 - limited to 400 kHz, so that a filtering and thus better decoding is possible. The digital block may advantageously be right or left of a center frequency with an auxiliary signal of the same bandwidth on the other side positioned. The block or a digital carrier may also be positioned on a center frequency and compensating signals may be positioned on both sides of the center frequency.

p0019Advantageously, a method in which the total signal is generated for transmission over a multi-carrier carrier with a plurality of subcarriers, wherein the digital signal components are varied in the subcarriers. In this case, the degree of freedom is exploited, which thereby follows that such variation does not affect the analog signal components from an analog receiver detectable. Preference is given according to a method for processing a received total signal which has been created in such a way, at least a digital signal from the total signal in a receiving device to filter out and / or in which of the total signal at least an analog signal tion by demodulation in the manner of a analog FM -modulierten signal is recovered. Preferably, both of which can be performed by one and the same receiving device, so that the receiving device in regions can be used universally with only analog or only digital transmission ler.

p0020are preferably independently corresponding to a transmission apparatus for providing such an overall signal with a signal generator and a receiving device for receiving such a broadcast signal. The receiving apparatus is preferably configured and / or controlled to generate both at least one digital signal and at least one analog signal from the overall signal.

p0021The receiving device preferably comprises a signal generator for providing the analog signal is designed and / or controlled conventional components for generating an analog signal from a FM-modulated radio signal. One such signal generator is preferably configured to filter out at least a digital signal from the received total signal.

p0022According to the preferred procedure, for providing a signal, a spectral separation is avoided that the digitally modulated carrier are part of this signal. In this case, finds a classic generating an FM signal application. In order to continue to allow a reception on old receivers, such as FM radio, the primary for the FM demodulation characteristics of an FM signal can be approximated with an artificial signal in the non-digital frequencies used. Such primary property is especially that the differentiated phase to be modulated audio signal arising needs. Secondary properties which find for demodulation in the classic receiver no or mandatory use, such as a constant amplitude, are in favor of the integration of the digital carrier abandoned ger. Characterized a degree of freedom is provided in particular by the insertion of a not constant but variable amplitude, which is utilized for the transmission of digital signals.

p0023A particular advantage is that in the signal generation and assignment to individual carriers of the available band, the number of digital carrier and its localization in the spectrum essentially lead does not matter. For example, alternate for an auxiliary signal to FM signal modulation is always a real disk to a digital signal and a carrier. Particularly advantageous is the provision of a digital blocks from eg. 50 - 100 kHz bandwidth, which allows a filtering and therefore better decoding of the digital signals or signal components. Such a block may, for. Example, the right or left can be positioned with an auxiliary signal of the same bandwidth on the other side of the center frequency of a band-limited provided. Also advantageous is a position on the center frequency itself with compensation signals to both sides.

p0024Particularly advantageous such a signal generation and assignment to individual carriers is the fact that a continuous transition is possible from analogue to digital operation. In the case of an FM station can thus over time individual carriers are switched from one assignment for analog signal transmissions to digital signal transmissions, the auxiliary signals are replaced by digitally modulated carrier signals.

p0025When switching such but is respected appropriate to the fact that the number of available auxiliary signals for carrier is sufficiently large to provide a signal Decoding and signal demodulation in an analog radio receiver still be able to ensure sufficient quality. In this regard, it is preferred that the number of carriers for digital signals less than half of the total available limited frequency range make up so that sufficient support for the transmission of auxiliary signals. Particularly in the case of an assignment of more than half of the frequency range for auxiliary signals is sufficient energy for transmission of an analog broadcast signal to parallel digital broadcast signals. In other frequency bandwidths, as is usual at present in Europe, can in this respect according to a greater or lesser number of carriers for transmitting the auxiliary signal be required accordingly.

p0026Because especially in the mobile space increasingly variable or adaptive bandwidth of the prefilter find FM receiver application, it is advantageous in calculating the auxiliary signals to configure the components of the spectral edge areas for the safety of initial FM signal characteristics low.

p0027An exemplary embodiment is explained in reference to the drawings. Show it:

p0028Fig. 1 shows schematically an arrangement of a transmission apparatus for providing a radio interface to be transmitted overall signal, and receiver-side apparatuses for receiving and processing of such a total signal, said total signal is composed of digital signals and from supplied to the analog signal transmitting auxiliary signals,

p0029Fig. 2 schematically shows a vector representation in the complex-plane to illustrate the generation of such auxiliary signal, Fig. 3 by way of example a section of the frequency spectrum of the invention FM-simulcast broadcast signal, and

p0030Fig. 4 shows an arrangement corresponding to Fig. 1 with a combined reception device for receiving both digital and analog signal portions of the total signal.

p0031FIG. 1 shows an exemplary arrangement of a Rundfunksys- system, s are transmitted between the transmitter-side and receiver-side devices in the FM-modulated signals in the form of a total signal, as is known transmission of FM broadcasting, for example, when Ü. The description is therefore very limited and essentially only in view of the preferred procedure for generating such a total signal s or its demodulation.

p0032On the transmitter side, a total signal s is generated and provided in a transmitting device in a signal generator SSG radiated via a transmitting antenna S. In the illustrated embodiment, however, not a pure a- naloges broadcast signal or a pure digital transmission signal is provided. In terms of a simulcast system for digitizing based on frequency modulation broadcast systems a digital total signal s is provided instead, which includes analog or pseudo-analog signal components which can be received and processed by a conventional analog receiver.

p0033In the illustrated embodiment, it is assumed that a first, especially analog signal sl is ready, which is to be the receiving end processed and reproduced as an analog signal, and that a second, in particular digital signal s2 is ready, which receiver side is to be received and processed as a digital signal. The signal generator SSG processed in accordance with the first and second signals sl, s2 such that these are transmitted by means of the total signal s.

p0034The total signal s is set to a limited bandwidth fb, which is assigned to the corresponding transmitting device within the transmission spectrum theoretically available for a particular region and for a particular broadcast service. Within the limited bandwidth fb is a plurality of carriers d, h are available, for example, carriers in the form of individual frequency sub-bands. In principle, a feasibility is however possible to other vehicle types, as they are known, for example, from systems with time division multiplexing, frequency separation and the like. In particular, an orthogonal frequency separation multiplex (OFDM: Orthogonal Frequency Division Multiplex), for example, for transmission of the total signal s are used.

p0035Within the limited bandwidth fb, the plurality of available carrier d, h to the signal components to be transmitted individual signals and of the total signal is split s. In the illustrated division are alternately a carrier d a digital signal ds and an auxiliary signal-carrier h an auxiliary signal hs assigned. In principle, however, other allocation methods are possible. Particularly preferred is an allocation of carriers to the auxiliary signals hs h in a manner that the receiver side of a conventional analog receiver for receiving frequency-modulated signals, a sufficient reception quality of an analog signal AS is ensured. In current available limited bandwidth fb doing an assignment of carriers d, h is made such that preferably more than Half of the carrier, that is in particular more than half of the available frequency range, the auxiliary signals hs is assigned. For a very large number of carriers d, h within a large available limited bandwidth fb but such a number could be in principle recognized also lower. Conversely, a larger number of carriers d, h preferably for the auxiliary signal hs compared to carriers of the digital signal ds when only a very small limited bandwidth available.

p0036On the receiver side, two exemplary receiving devices are shown, a first receiver EA for receiving or for providing an analog signal as and a second digital receiver ED for receiving the digital signal ds. Accordingly, the two receivers EA, ED are each equipped with a receiving antenna E and a connected signal generator SG, SG °. The signal generator SG of the analog receiver EA receives the total over the radio interface received signal s in a conventional manner such as an FM-modulated conventional radio signal, demodulates it and provides an analog signal as ready, which amplified by an amplifier V and via a speaker L can be output as an acoustic signal s2 in the usual manner. In the analog receiver EA thus is a conventional radio receiver for receiving for example the FM transmitted FM modulated radio broadcasts.

p0037The digital reception device ED also has a designed for receiving digital devices ED in a conventional manner the signal generator SG °, wherein the total signal over the radio interface received analyzed s with respect to digital signals ds on the available carriers and d on suitable carriers d transmitted digital signals ds from the total signal s filters out and as an amplifier V applies for amplification and output via a speaker L as an acoustic signal sl. In digital receiving device ED thus it is preferably a conventional digital receiver ED with this conventional components and functions.

p0038To supply such a simulcast system for digitization, transmission and to allow demodulating based on frequency modulation broadcasting systems, the total signal s is generated in a manner in which the digital signals DS, DS ° on these allocated digital media d in for digital signals ds conventional manner generated iS PROVIDED and transmitted. A special feature is the provision of auxiliary signals hs, hs ° which on this assigned auxiliary signal carriers than the other carriers h are transmitted Ü. The auxiliary signals hs are thereby generated such that the analog receiver EA or its signal generator SG, which the total signal s is applied, a supposedly analog frequency-modulated signal is supplied.

p0039In order to enable the function of both receiving devices, that is, the digital receiving device ED and the analog receiver EA is utilized with this is that in conventional frequency modulated transmissions for the analog receiver ultimately only part of the information theoretically available is relevant. This part constitutes a primary property, the primary characteristic, for. Example, is that the differentiated phase must result in the case of a broadcasting system to be modulated audio signal. Accordingly, the overall signal is s so con- structed that the phase information, in particular the information of the differentiated phase portion, is so constructed that for the analog receiver EA is present an apparently common analogue reception signal. Secondary properties of the analog frequency-modulated system such as a constant-left, that is unused amplitude information, however, constitute a degree of freedom, which is utilized for the transmission of digital signals ds. Accordingly, the overall signal comprises an amplitude information s and amplitude modulation, in which the information for the digital reception apparatus ED are included.

p0040Hereinafter, a method, as partially sketched in Fig. 2, described with which such a total signal s may be generated. In principle, however, other approaches for generating such a total signal can be used, wherein for the transmission of the analog signal portion only, the primary properties are used in order to use the secondary properties for incorporation of digital signals.

p0041In a first step, the transmitted analog signal SL, which is present in particular as an analog audio signal, FM modulated in the signal generator SSG of the transmitting apparatus in the complex baseband. The result is a complex, that is complex-valued signal which is represented by a pointer length of 1, as sketched in Fig. 2 by the analog signal to the point represented as pointers. If the carrier unmodulated, a sinusoidal signal with a high frequency on the real axis would be represented re lying, so that the amplitude and length of the underlying pointer would unmodulated. By frequency modulation moves Point as the analog signal, however, within the maximum allowable frequency deviation continuously with a frequency modulation about the real axis re around.

p0042Thereafter, but optionally also beforehand or in parallel, a second digital signal S2 is provided as a digitally modulated signal limited bandwidth. Such a digital signal in the complex plane which re in FIG. 2 by the real and the imaginary axis, is biased in the listed, outlined by a dot for the digital signal DS. A leading to this point ds of the digital signal arrowhead preferably in digital broadcasting systems customary manner on a significantly lower amplitude or pointer length.

p0043In a subsequent step, a com- plexwertiges error or difference signal fs is formed by subtracting the FM modulated analog signal as the digital signal ds in the time domain. This error signal corresponding to an Ideal for BiI- fertil for auxiliary signals hs in the range of spectra is not used by the digital signal ds. The error signal fs thus represents a basis for generating the content or the auxiliary signals hs.

p0044In principle, it is so that the auxiliary signal hs - a simple graphic presentation of Figure 2 assumes - has its starting point at ds and initially may end somewhere on the line of the signal as, because it depends only on the angle w. These various signals hs are marked by dashed lines in Fig. 2. In a second condition of the found signal is, however, required that the phase velocity of the vas analog signal as the phase velocity vs of the total signal S corresponds at least approximately. In the simplest and most ideal case, it is then so that the phase angle w of the analog signal as well, or at least approximately the phase angle of the total signal s.

p0045In Fig. 3 an example of the frequency spectrum of the FM simulcast broadcast signal is illustrated. In an exemplary assumed center frequency of 100 MHz, the frequency spectrum of the digital signal DS is having a bandwidth of eg., About 50 KHz to about 100 KHz. Left and right of described can be found outside an upper and lower frequency spectrum for two auxiliary signals HSL and HSR arising summed in the complex plane, the auxiliary signal hs. Overall, the gE has samtsignal s approximately a bandwidth of 300 KHz to about 400 KHz.

p0046Since the error signal fs spectral throughout useful spectrum has, that is in the digital range, it is modified so that it has only spectral components in the permitted range. A further criterion the e nergy of the error signal fs is preferably optimized, in particular minimized. To perform the modification and optimization can be used on their known numerical methods for optimization purposes, in particular methods based on known gradient. By modifying the error lersignals fs there is a resultant of the analog signal. The modification caused by the amplitude fluctuation does not have any effect on the transmitted data of the analog signal due to the FM modulation. Characterized a degree of freedom is provided, which is exploitable for the digital data. Especially in the case of a so-called multicarrier

p0047Support, ie a support with many sub- or sub-carriers are, variier- the digital signal components in the sub-carriers bar without affecting the analog reconstruction in an analog receiver.

p0048In this way, the total signal is produced as a cast Simultaneous signal that no more than a pure FM signal is present, but in which only the differentiated phase which actually corresponds to the modulating analog signal sl.

p0049Fig. 3 shows an embodiment in which, instead of two separate receivers EA, ED, a single receiving apparatus is used as a combined receiver EAD. Accordingly subsequently received only on different aspects and guides the remainder on training to Fig referenced.. 1

p0050Over a reception antenna E a modified signal generator SG is again * the total signal over the radio interface received s applied. The signal generator SG is however modified such that it can perform both a signal processing in the sense of an analog receiver and a signal processing for the purposes of a digital receiver and according to an analog signal as and of separate digital signal ds provides at one or two outputs. The analog signal as the digital signal ds and can be further processed in a conventional manner, for example, output via interfaces to other devices or amplifier V for acoustic reproduction through loudspeakers L are amplified. According to a modification, however, can also NEN two separate signal generators in such a combined receiver EAD be provided, which for a digital or an analog Signalbereit- Position are formed and each get the total received signal s applied.

p0051According to the preferred embodiment, a sum Thus, signal as the total signal S is formed and transmitted, wherein the sum signal or a hand from a digitally modulated carrier D to the or the digital signals DS and the other part from the auxiliary signal HS as a preferably approximation of the differential . error signal fs is formed. The GE samtsignal s including the components of the auxiliary signal or the auxiliary signals hs lies within the specified by the limited bandwidth fb band limiting of, for example 300 kHz. The digital components in the form of digital signals ds d on the space reserved for these carriers are arranged so that they are individually filtered out, for example, using time division multiplexing or frequency separation.

p0052The procedure for signal generation has been described with an exemplary broadcast system in the VHF range.

p0053In principle, however, an implementation of the process is possible also to other frequency ranges and transmission system types. In particular, a transfer to image-transmitting systems or image- and tonübertragende systems as in the case of transmission of television signals is possible.