ITTO20111140A1 - METHOD AND APPARATUS OF TRANSMISSION AND / OR RECEPTION OF DIGITAL SIGNALS, COMPATIBLE WITH THE DVB-S2 PROTOCOL, ABLE TO OPERATE ON TRANSPONDERS VIA SATELLITE WIDE BAND. - Google Patents

Description

"METHOD AND APPARATUS FOR TRANSMISSION AND / OR RECEPTION OF DIGITAL SIGNALS, COMPATIBLE WITH THE DVB-S2 PROTOCOL, ABLE TO OPERATE ON VERY WIDE BAND SATELLITE TRANSPONDITORS"

DESCRIPTION

FIELD OF APPLICATION OF THE INVENTION

The present invention is located in the telecommunications sector, and in particular it refers to a method and an apparatus for transmitting and / or receiving digital signals via satellite compatible with those described in the DVB-S2 standard (ETSI EN 302 307 specification), as well as a device for the transmission and a device for the reception of said signals.

More specifically, the invention applies to very high symbol rate (or symbol rate) transmissions on broadband satellite channels, where the computational power of the receivers is limited.

STATE OF THE TECHNIQUE

The transmission via satellite transponder (or transponder) of digital signals with DVB-S2 protocol is widely used for the broadcasting of interactive radio, television and multimedia programs over large territories, both for broadcast services without a return channel, and for unicast services (such as for example Internet services) using a return channel on which various protocols are implemented (RCS, RCT, â € ¦).

The DVB-S2 standard allows to operate with various modulation formats (QPSK, 8PSK, â € ¦) and channel coding for error protection (also known as FEC, Forward Error Correction). In particular, the DVB-S2 standard prescribes the use of LDPC (low-density parity-check) codes with different possible coding rates (for example 1/2, 2/3, 3/4, etc.), both statically over time (mode known as CCM, Constant Coding and Modulation), both dynamically over time but independent of the reception conditions (mode known as VCM, Variable Coding and Modulation), and dynamically over time depending on the reception conditions (mode known as ACM, Adaptive Coding and Modulation).

The DVB-S2 standard is schematically represented in Figure 1, known to those skilled in the art.

DVB-S2 allows to transmit up to N input data streams (where N <256), each of which can be in MPEG Transport Stream format or in generic packet or continuous format. Each input stream (hereinafter input stream) can carry various audio, video or multimedia services and is identified by an ISI (Input Stream Identifier) parameter, which in the DVB-S2 standard consists of 8 bits, placed in the Base Band Header (BB-Header).

The Merger-Slicer block takes a bit packet from an input and composes a frame (frame) of baseband data called the Base-Band Frame (BBFrame) which is protected by the FEC encoding which includes both LDPC and BCH codes. The BB Frame is then modulated with one of the possible digital modulations (for example QPSK, 8PSK, â € ¦) to thus constitute a data frame called Physical-Layer Frame (hereinafter PL-Frame), which includes a header ( hereinafter PL-Header) which is made up of 90 binary symbols modulated according to the Ï € / 2BPSK modulation, known to the expert in the sector.

In the DVB-S2 standard, each PL-frame carries information coming from a single input stream and adopts a format of FEC and homogeneous modulation for the whole frame, while the transmitted signal is a continuous sequence of PL-Frames.

It is known that the DVB-S2 standard requires a high processing capacity in the receiver, as the receiver must decode the FEC codes for all PL-Frames transmitted, even if the specific service selected and used by the user it constitutes only a small portion of the received stream (for example if it is transmitted on a single ISI). Typically, the receivers currently on the market are able to receive DVB-S2 transmissions with a symbol speed of the order of 30-40 million symbols per second (hereinafter: Msimboli / s).

As known to the expert in the field, with the launch of satellites that have very wide band transponders (for example from 50 MHz to 500 MHz), the need arises to extend the speed of DVB-S2 signals up to 200- 500 Msymbols / s, because it is more efficient to transmit a single modulated carrier at very high symbol rate than to transmit many carriers at lower, frequency division multiplexed (FDM) symbol rates. However this increase in transmission speed, although allowed by the DVB-S2 standard, creates problems in the realization of the receivers, mainly due to the complexity of decoding LDPC codes at very high speed.

To overcome this technical problem, the possibility of using the time-slicing technique is known, already used for example in the DVB-H standard for the transmission of digital signals on terrestrial networks. The advantage of time slicing consists in being able to activate the receiver only to receive and decode the PL-Frames that contain the service selected by the user (concept similar to the well-known time division multiplexing, TDM).

For example, if the high-speed DVB-S2 carrier carries a data stream of 500 Mbit / s distributed over 10 input streams, the receiver will only decode the PL-Frames of the single input stream that contains the service selected by the user, the which will be at lower speed, for example a 5 Mbit / s video program, thus decoding an LDPC code at 50 Mbit / s instead of 500 Mbit / s.

To avoid that the receiver has to operate with an irregular packet flow, the transmitter cyclically organizes the PL-Frames according to an increasing ISI order (input stream = 1,2,3,4, .., M). The regular sequence of PL-Frames transmitted according to the time-slicing technique is referred to as â € œsuper-frameâ €.

Each PLFrame block constitutes a time slice, that is, a portion of data that corresponds to a specific ISI. Each service (for example audio-video program, or interactive IP session) is carried by a single time-slice, but a time-slice can still contain multiple services. A superframe is therefore constituted by a PL-Frame of time-slice 1, then of time-slice 2, and so on up to time-slice M. A solution of the known art, represented in Figure 2, to allow the receiver to synchronize easily with the superframe and detect the PLFrame containing the chosen service, is to use the ISI parameter to mark each time-slice with its sequential index in the periodic structure of the superframe and the total number of time-slices that make up the superframe (referred to above as M).

For example, the ISI parameter, which in the DVB-S2 standard consists of 8 bits, can be structured in two 4-bit subparameters, i.e. (i, M), where i is the sequential index and M the total number of input streams into which the total stream is broken down.

For each â € œServiceâ €, the time-slice that transports it is typically reported in appropriate signaling tables inserted in the data transport flow, such as for example the NIT (Network Information Table) tables specified in the DVB-SI standard (EN 300468) and MPEG-2 (ISO / IEC 13818-1). The NIT table can be repeated in all time slices or only in the first time slice of the superframe.

This solution has several disadvantages.

A first disadvantage is that, in order to synchronize the receiver with the superframe frame, it is not sufficient to decode the simple header of the PLFrame (PL-Header), which in the DVB-S2 standard consists of 90 binary symbols, but the entire PL-frame must be decoded (including the LDPC + BCH code word). In fact, the ISI parameters are protected by these LDPC + BCH codes.

A second disadvantage is that the number of input streams allowed in the system (ISI parameter, which in the DVB-S2 standard offers 256 values) must be reduced to 16 values, as the sub-parameters i and M consist of only 4 bits.

A third disadvantage is that the DVB-S2 system with time slicing, having to use the ISI parameter to constitute the superframe, can no longer freely use this parameter for other functions, as instead provided by the DVB-S2 standard itself (see for example the functions described in Annex H5, Figure H.8: IP Unicasting and ACM: Multiple input streams - uniform protection for input stream of the EN302307 specification).

In order to overcome the second disadvantage described above, a solution known in the art is to optimize the encoding of the ISI parameter in order to extend it to a greater number of values. However, this solution does not allow to obtain a sufficiently large number of ISI possible as in the case of DVB-S2 without time slicing. Furthermore, it does not solve the first and third disadvantages described above.

To overcome the three disadvantages described above, a solution of the known art is not to use the ISI parameter to signal the superframe structure, but to `` mark '' the first PL-Frame of the superframe (called anchor slice). In this solution, the rule of constructing the superframe as a periodic sequence of PL-Frames, each constituting a slice, is maintained and the slices are numbered in order starting from the anchor slice. The receiver will have to identify the PL-Frame â € œmarkedâ € as anchor slice, count how many slices separate two anchor slices to obtain the length M of the superframe, decode the YES signal that indicates which slice carries the service selected by the user, and then â € œtuneâ € inside the superframe on the selected slice, discarding all the others. In this solution there is no longer a one-to-one relationship between the superframe structure and the ISI parameter. The prior art based on the anchor slice however does not specify how to use the flexibility of the ISI parameter within the superframe while maintaining compatibility with the DVB-S2 standard to achieve multiple input stream transmissions in each slice.

To â € œbrandâ € the anchor slice, the known literature proposes to use the MODCOD parameter contained in the PLHeader on 5 bits, and which communicates the type of modulation and the coding rate used in the PLFrame. In fact, not all the values that this parameter can assume are currently used in the DVB-S2 standard; for example the value 31D is not used and is declared as â € œreserved for future useâ €. This last solution, if on the one hand it allows to overcome the three disadvantages described above, on the other it introduces a new important disadvantage, namely the loss of backward compatibility with the DVB-S2 standard. In fact, a DVB-S2 standard compliant receiver that receives a PL-Frame with MODCOD = 31D (for example), will identify the content of this PLFrame as â € œUnknownâ € and, in the absence of information on the coding rate and the modulation used in the anchor PLFrame, it will not be able to access the data contained therein. The only solution to maintain backward compatibility with previous receivers would therefore be to not use the Anchor Slice (marked with a reserved MODCOD parameter) to carry useful data, but this would clearly lead to a considerable waste of capacity.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to provide a method and an apparatus for transmitting and / or receiving digital signals via satellite compatible with those described in the DVB-S2 standard, in combination with the use of time slicing, and which allows to overcome the disadvantages of the known art described above. Furthermore, the invention relates to a device for transmitting and a device for receiving said signals.

In particular, the purpose of the present invention is to realize a transmission and reception method that allows the use of time slicing in such a way that the receiver can access and synchronize with the superframe structure without having to decode the LDPC code, without introduce changes or limitations to the flexibility of use of the ISI parameter, and without wasting capacity using anchor frames without data.

More in detail, the method of the present invention provides for marking the anchor slice in the transmitter without changing the value of any of the parameters contained in the PL-Header, but in such a way that it is detected by a receiver that implements the present invention (hereinafter TS-RX).

This purpose is achieved by introducing an angular rotation in transmission in some symbols of the PL-Header, as described in Figure 3.

This angular rotation is conveniently added to the 26 â € œfixedâ € symbols contained in the SOF (Start Of Frame) field, modulating these symbols with a pseudo-random sequence, called anchor marker. Preferably, the aforementioned phase modulation is not introduced on the other symbols of the PL-Header (MODCOD and TYPE fields) in order not to degrade their performance in the presence of transmission noise and distortions, however this implementation allows easier identification of the anchor marker.

The phase rotation introduced must be large enough to be recognized by a receiver implementing the present invention, but low enough not to prevent the recognition of the SOF parameter by previous receivers conforming to the DVB-S2 standard.

The aforementioned object is achieved through a method and apparatus for transmitting and / or receiving digital signals, compatible with the DVB-S2 protocol, capable of operating on very broadband satellite transponders, having the characteristics set out in the attached claims which form an integral part of this description.

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be described in detail in some of its preferred embodiments, given by way of non-restrictive example, with reference to the attached drawings, in which:

- Figure 1 is a block diagram of the transmission part according to the DVB-S2 standard;

- Figure 2 represents the super-frame of known type in the case of signal with time slicing, based on the ISI parameter,

- Figure 3 represents an embodiment of the present invention, with the insertion of the phase modulation in the SOF field of the PL-Header to identify the anchor slice that demarcates the superframe, - Figure 4 represents an embodiment of the present invention, where the super-frame is built with two levels of mergers,

- Figure 5 represents an embodiment of a known receiver according to the DVB-S2 standard,

Figure 6 represents an embodiment of the receiver according to the present invention

The same reference numbers and letters in the figures identify the same elements or components.

DETAILED DESCRIPTION OF EXAMPLES OF IMPLEMENTATION

Figure 2 represents the superframe in the case of time sliced signal.

According to an embodiment of the present invention, as shown in Figure 3, the first slice of the superframe sequence represents the Anchor Slice, and is marked by introducing an angular rotation equal to akï † on a field of the PL-Header, for example on the 26 symbols of the SOF field of the PL-Header.

In the expression akï †, k is the index of the symbol inside the SOF field (k = 1, â € ¦26); akà is a pseudo-random sequence that takes values (+1; -1), called â € œanchor markerâ €;

ï † is an appropriate angle to be optimized according to the minimum signal-to-noise ratio at which the system must operate, but in any case less than or equal to Ï € / 2 radians. If the value of ï † is high, as for example in the case where ï † = Ï € / 4, the phase distortion introduced on the SOF symbol will be large and the recognition of the SOF by DVB-S2 receivers that do not implement the present invention can undergo degradations. On the other hand, the recognition of the SOF by the receivers implementing the present invention (TS-RX) is facilitated. On the contrary, if ï † is small, as for example in the case where ï † = ï ° / 8, the phase distortion introduced on the SOF symbol will be small and therefore the recognition of the SOF by the previous DVB-S2 receivers is easy, while the recognition of the superframe by the TS-RX receivers that implement the present invention becomes more complicated. In the preferred embodiment, ï † = ï ° / 4, in order to have acceptable synchronization performances for the minimum signal / noise ratio in the DVB-S2 standard, and equal to SNR = -2.35 dB.

The new SOF of the anchor slice, modulated in phase, will be referred to hereafter as SOF (PM). The pseudo-random sequence ak which modulates the SOF field in phase can preferably be extracted from the sequence of maximum length 2 <5>, truncated to 26 elements and choosing a portion with 13 positive and 13 negative values, such as the sequence:

ak = [+ 1, + 1, -1, + 1, + 1, -1, -1, -1, + 1, + 1, + 1, + 1, + 1, -1, -1, + 1 , + 1, -1, + 1, -1, -1, + 1, -1, -1, -1, -1] Note that the proposed phase modulation does not affect, if not marginally, the synchronization performance of current DVB-S2 receivers. In fact, the frame synchronization of the receivers, according to known techniques, proceeds in two phases: a latching phase (in the specific case, search for the SOF sequence) and a tracking phase. The search phase of the SOF sequence (through correlation algorithms between the received symbols and the transmitted sequence, known a priori to the receiver) starts randomly, and once the SOF sequence has been identified it is searched again for confirmation a few times, at the known distance of a PL-Frame. It is evident the little influence on the locking times of the presence of the distortion on a SOF sequence, in the presence of many undistorted (M-1) SOF sequences in the superframe. In the tracking phase, the receivers abandon the synchronism acquired in the previous phase only in the presence of many unrecognizable SOF symbols. It is therefore evident that even in this phase the distortion of a SOF symbol in the superframe does not significantly worsen performance.

As previously mentioned, the anchor slice-based prior art did not specify how to use the flexibility of the ISI parameter within the superframe to achieve multiple input stream broadcasts in each slice, while maintaining compatibility with the DVB standard. S2.

According to an embodiment of the present invention, if a multiple input stream configuration is intended in each time-slice, the input streams to be transmitted in a single slice are gathered in a `` group '' of input streams (identified by a subset of ISI values). To obtain this result, Figure 4 represents a realization of the present invention, in which the DVB-S2 merger (see Figure 1) is ideally divided into two merger levels, where the first level defines the â € œgroups of input streamsâ € and the second level operates periodically to create the superframe slices. In the i-th time slice the ISI parameter has a value taken as a whole assigned to the i-th group. Other input stream groups will use other subsets of the ISI parameter, so as not to have repetitions and remain compatible with the DVB-S2 protocol in relation to the total stream (in fact in the DVB-S2 protocol each input stream must be identified by a different ISI parameter) .

For example in Figure 4 the 16 incoming data streams are divided into 4 groups, where the streams with ISI 1 to 4 are combined into group 1 by merger 1, the streams with ISI 5 to 8 are combined into group 2 by merger 2, streams with ISI 9 to 12 are combined into group 3 from merger 3, streams with ISI 13 to 16 are combined into group 4 from merger 4.

The 4 groups of streams thus obtained are combined by the level 2 merger and transmitted alternately over time using the time slicing technique, whereby a BB-frame of group 1 is transmitted in slice 1, a BB-Frame of group 2 in slice 2, one of group 3 in slice 3 and one of group 4 in slice 4, and then start over from group 1. Level 1 Mergers can operate cyclically (ISI = 1,2,3,4â € ¦) but also according to other criteria, while the level 2 one always operates cyclically on the groups, to guarantee the regularity of the superframe. Note that the DVB-S2 standard leaves ample freedom in how the merger organizes the input streams.

The global signal obtained is still compatible with the S2 protocol, as is each slice.

In the case of the codifications of the known type reported above VCM and ACM, to generate time-slices containing an equal number of symbols useful in transmission (excluding the PL-Header and any pilot symbols), the level 1 merger reads from each input group streams 2 successive BB-frames from the same ISI when modulation is QPSK, 3 BB-frames when modulation is 8-PSK, 4 BB-frames when modulation is 16APSK and 5 BB-frames when modulation is 32 -APSK. Since the DVB-S2 standard foresees two possible types of frames, the normal ones (64800 bits) and the short ones (16200 bits, that is 1⁄4 of the normal one), this is valid when the frames are either all normal or all short.

When both normal and short frames are present on the DVB-S2 carrier, the short ones are inserted in quadruple number, in order to keep constant the number of useful symbols per time-slice. To be compatible with the DVB-S2 protocol, the sequences of multiple BB-Frames (example 3 BB-Frames for 8PSK modulation) are associated with multiple PL-Headers (and not a single PL-Header): therefore the sequence of SOF is not equally spaced in terms of symbols transmitted.

The level 2 merger regularly reads a slice from group 1, a slice from group 2, and so on up to group M, and then starts over.

Each slice therefore consists of n PL-FRAME (as mentioned, in the CCM case n = 1, in the ACM / VCM case n = 2 for QPSK, 3 for 8PSK and so on), organized in a periodic superframe.

In the case of single input stream per slice and of VC // ACM, the previous description is still valid, where however the level 1 mergers are connected with a single input stream, and therefore have the sole purpose of reading from input n BB -Frame (N = 2 for QPSK, 3 for 8PSK and so on).

For each service, the time-slice that transports it is suitably reported in the DVB-SI (NIT) transport information, which is repeated in all the time slices.

The further operations carried out in transmission are substantially of a known type, and conform to the provisions of the DVB-S2 standard, and to what is described above in relation to Figure 1.

A transmission apparatus according to the present invention comprises means for carrying out the method described above.

A TS-RX receiving apparatus in accordance with the present invention is able to perform substantially reverse functions to those of transmission, with the following clarifications.

Figure 5 describes the main functions of a known DVB-S2 receiver, which include carrier and symbol synchronism recovery, PL-Frame synchronism recovery and PL-Header decoding, quadrature signal demodulation, LDPC and BCH decoding, BB-Header decoding and reconstruction of the output baseband signal. To perform the synchronization of PL-Frame, first of all it carries out the acquisition phase, searching for a random SOF field in the received sequence, through correlation algorithms with the known sequence, as well known to the expert in the art (see for example the € ™ article â € œA Multiple Correlation Peak Value Detecting Method for Frame Synchronization of DVB-S2, Rui Xue Chunfang Wang * Xiaoru Li * North China Institute of Aerospace Engineering National Meteorological Information Center133 Aimin Road No. 46, Zhongguancun Nandajie, Haidian District Langfang , Hebei 065000 China Beijing100081 China). It then performs the decoding of the PL-Header, to derive the length of the PL-Frame as a function of the MODCOD and Type parameters. After verifying the presence of the SOF field in the required position for an adequate number of times, it enters the tracking phase, where an appropriate number of SOF signal non-detections are required before abandoning the previous synchronization and initializing a new acquisition phase.

The TS-RX receiver implementing the present invention, described in Figure 6, performs the PL-Frame synchronization like a conventional DVB-S2 receiver with prior art. Then, through the functional block â € œDemod. SOF and Anchor marker search of Figure 6, multiplies the SOF symbols it receives with the SOF sequence of the DVB-S2 standard, thus extracting, where present, the phase modulated `` anchor marker '' sequence superimposed on the 26 symbols according to the present invention, which is present only in the PL-Frame anchor, and is affected by transmission noise.

Using known correlation algorithms with the marker sequence, TS-RX identifies the superframe structure (only the anchor slice has the marker sequence in the SOF).

The TS-RX receiver, through the functional block â € œfilter sliceâ €, lets the anchor slice pass (or another slice if the signaling information of the SI table is repeated on all the slots), and decodes the LDPC codes + BCH getting the information from the BB-Header. The subsequent functional block “PSI / SI decoding” extracts the information on the service of interest and on the relative slice to be selected in the superframe structure. After decoding the BB-Header, the receiver knows the CCM / ACM parameter. In the case of the CCM, then each PL-Frame is a slice. Otherwise, in the case of the VCM / ACM, then the multiple PL-frames are reconnected into a single slice (2 for QPSK, 3 for 8PSK, ...) as explained above.

The functional block â € œSync Superframe Recovery, Superframe Length Recovery Mâ € of the TS-RX receiver (see Figure 6)) counts the slices that separate two successive Anchor slices, thus obtaining the superframe structure. At this point the functional block â € œfilter sliceâ € has all the information to filter in the superframe structure only the slice selected by the user, discarding all the other slices (continuing to decode all the PL-Headers to maintain the synchronization of PL- Frame and superframe).

The examples described above relating to the present invention are purely indicative, and there may be other examples which constitute application of the principles of the present invention, without thereby departing from the scope of protection as it results from the attached claims.

For example, the sequence used to introduce the phase rotation in the PL-Header may be different from that indicated in the example of realization, as well as the phase modulation angle.

Furthermore, said phase rotation could be introduced in other fields of the header other than the SOF.

The present invention can be advantageously carried out by means of a computer program which comprises coding means for carrying out one or more steps of the method, when this program is executed on a computer. Therefore, it is intended that the protection scope extends to said computer program and further to computer readable means comprising a recorded message, said computer readable means comprising program coding means for carrying out one or more steps of the method, when said program is run on a computer.

From the above description the person skilled in the art is able to realize the object of the invention without introducing further construction details. For this purpose, the person skilled in the art will use the knowledge already acquired, for example relating to the construction of known type of equipment for the transmission and / or reception of digital signals via satellite in accordance with what is described in the DVB-S2 or DVB-T2 standard.

Claims (10)

CLAIMS 1. Method of transmission of digital signals, compatible with the DVB-S2 protocol, suitable for operating on transponders via very broadband satellite, said method providing for processing digital input signals (input stream) with a merger-slicer function to compose baseband data frames (BBFrame), then encode and digitally modulate said baseband data frames (BBFrame) to obtain Physical-Layer Frame (PL-Frame) data frames with headers (PL-Header), organized cyclically in super-frames by time-slicing, characterized by the fact that it includes the step of marking the first PL-Frame of each super-frame as â € œanchor-sliceâ € by means of an angular rotation, equal to akï †, of a field of the PL-Header. Method according to claim 1, wherein in said angular rotation akï †, k is the index of the symbol inside said field of the PL-Header; akà is a pseudo-random â € œanchor markerâ € sequence; ï † is a phase rotation value less than or equal to ï ° / 2 radians, preferably ï ° / 4. 3. Method according to claim 2, wherein said PL-Header field subject to angular rotation (akï †) is the SOF field, and said pseudo-random anchor marker sequence akà is extracted from the sequence of maximum length truncated a 26 elements and choosing a portion with 13 positive and 13 negative values, for example (+ 1, + 1, -1, + 1, + 1, -1, -1, -1, + 1, + 1, + 1 , + 1, + 1, -1, -1, + 1, + 1, -1, + 1, -1, -1, + 1, -1, -1, -1, -1) 4. Method according to any one of the preceding claims, in which the transmission of the multiple input stream type is carried out on each slice, in which said merger-slicer function is divided into two levels, a first level defining groups of input streams which will be transmitted each group in a single slice, and a second level operating periodically to create said superframe. Method according to claim 4, wherein said digital input signals (input stream) identify services, each service being carried by a single timeslice, a group of input streams, identified by a subset of values of an ISI parameter, being mapped on a single time-slice, in each time-slice the ISI parameter having a specific value taken in the set assigned to the i-th group. Method according to any one of claims 1, 2, 3, in which, in the case of VCM and ACM type encodings, said merger-slicer function reads from each input stream two successive BB-frames from the same ISI parameter when modulation It is QPSK, three BB-frames when modulation is 8-PSK, four BB-frames when modulation is 16APSK, five BB-frames when modulation is 32-APSK, to create slices formed from multiple PL-Frames of similar duration. 7. Method according to claim 5, in which, in the case of VCM and ACM type encodings, said first level of merger-slicer reads from each group of input streams two successive BB-frames from the same ISI parameter when the modulation is QPSK , three BB-frames when modulation is 8-PSK, four BB-frames when modulation is 16APSK, five BB-frames when modulation is 32-APSK, to create slices formed from multiple PL-Frames of similar duration . 8. Digital signal transmission apparatus, compatible with the DVB-S2 protocol, suitable for operating on very broadband satellite transponders, comprising means for implementing the method of any one of the preceding claims. 9. Method for receiving digital signals, compatible with the DVB-S2 protocol, suitable for operating on transponders via very broadband satellite, said method providing for receiving and processing digital signals organized in transmission according to the method of any one of claims from 1 to 7, said receiving method comprising the steps of: - synchronization to the PL-Frame structure with known techniques, such as search of the SOF sequence, decoding of the PL-Header and extraction of the MODCOD and TYPE fields; - execution of a synchronization of the input super-frames, which consists in the removal of the modulation of the PL-Header, and in the search of said field subject to angular rotation through correlation algorithms with the known sequence â € œanchor markerâ €; - identify the super-frame structure by counting the slices that separate two successive Anchor slices; - decode the data of the anchor slice or other slice and extract from the PSI / SI signal the value of the slice of the service selected by the user - filter the slice selected by the user in the super-frame structure, discarding all other slices. 10. Apparatus for receiving digital signals, compatible with the DVB-S2 protocol, suitable for operating on transponders via very broadband satellite, comprising means for implementing the method of claim 8.