MXPA05012354A - A unified receiver for layered and hierarchical modulation systems - Google Patents

Abstract

A satellite receiver includes a down converter for providing a received signal and a demodulator having at least two demodulation modes for demodulating the received signal, wherein one demodulation mode is hierarchical demodulation and another demodulation mode is layered demodulation.

Description

UNIFIED RECEIVER FOR MODULATION SYSTEMS IN LAYERS AND HIERARCHICAL FIELD OF THE INVENTION The present invention relates in general, with communication systems and more in particular, to a satellite-based communication system.

BACKGROUND OF THE INVENTION As described in U.S. Patent No. ,966,412, issued on October 12 for Ramaswamy, hierarchical modulation in a satellite system can be used as a way to continue supporting existing legacy receivers and, at the same time, provide a growth path to offer new services. In other words, the satellite system based on a regressive compatible hierarchical modulation offers additional features or services that can be added into the system without requiring existing users to acquire new satellite receivers. In a communication system based on hierarchical modulation, at least two signals, for example, an upper stratum signal (UL) and a signal! of lower stratum (LL), are added together in order to generate a satellite signal modulated in synchronized form for transmission. In the context of a satellite-based communication system that provides backward compatibility, the LL signal provides additional services, while the UL signal provides legacy services, that is, the UL signal is, in effect, the same signal that was transmitted before - In this way, the satellite transmission signal can continue to evolve without impact for users with legacy receivers. As such, the user who already has a legacy receiver can continue to use the legacy receiver until the user decides to upgrade with a receiver or box that can retrieve the LL signal to provide additional services. In a similar way, a communication system based on the modulation of strata can also be used to provide a measure that is backward compatible. In the system based on stratum modulation at least two signals are modulated (again, for example, a UL signal (legacy services) and an LL signal (additional services) on the same carrier (possibly asynchronously to each other) The transmission of the UL signal and the LL signal occurs separately through two transponders and the front end of a stratum modulation receiver combines them before recovering the data transported therein.

BRIEF DESCRIPTION OF THE INVENTION It has been observed that a receiver designed to receive and demodulate signals based on hierarchical modulation can not receive and demodulate signals based on the modulation of strata and vice versa. In this way, separate receivers must be designed and designated for each respective modulation system. Therefore, and in accordance with the principles of the invention, a receiver includes a down converter to provide a received signal and a demodulator having at least two demodulation modes for demodulating the received signal, wherein a demodulation mode is a hierarchical demodulation mode and the other demodulation mode is a layer demodulation mode. In one embodiment of the invention, a satellite communication system comprises a transmitter, a satellite transponder and a receiver. The transmitter transmits an ascending multiple-level modulated signal (hierarchical modulation or stratum modulation) to the satellite transponder, which broadcasts the multi-level modulated signal in descending fashion to one or more receivers. At least one receiver has the ability to operate in any of a number of demodulation modes to process the received signal. In particular, the receiver selects a demodulation process to be carried out as a function of the demodulation mode, wherein at least two of the number of demodulation modes are a hierarchical demodulation mode and a demodulation mode by strata, and the The receiver then demodulates the received signal in accordance with the selected demodulation mode.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a satellite communication system that incorporates the principles of the invention. Figure 2 shows an illustrative block diagram of a transmission path through the satellite 15 of Figure 1. Figure 3 shows a modality for implementing the hierarchical modulation in the transmitter 5 of Figure 1. Figure 4 shows constellations of illustrative symbol for use in an upper layer and the lower layer. Figure 5 shows an illustrative resulting symbol constellation for a multi-level signal. Figure 6 shows another illustrative embodiment for implementing the hierarchical modulation in the transmitter 5 of Figure 1. Figure 7 is an illustrative stratum modulation mode for use in the transmitter 5 of Figure 1. Figure 8 shows a block diagram illustrative of a satellite transmission path in the context of a system based on stratum modulation. Figure 9 shows an illustrative block diagram of a receiver in accordance with the principles of the invention. Figure 10 shows an illustrative block diagram of a unified demodulator / decoder 320 of Figure 9 in accordance with the principles of the invention. Figures 11 to 15 show several block diagrams of different portions of a demodulator / decoder 320 unified in accordance with the principles of the invention. Figure 16 shows an illustrative signal space. Figure 17 shows a query probability registration table in accordance with the principles of the invention. Figure 18 shows an illustrative symbol constellation.

Figures 19 and 20 illustrate the probability of registration calculations. Figure 21 another variation of the mux 395 H-L of Figure 10. Figures 22 and 23 show other illustrative embodiments of a unified demodulator / decoder in accordance with the principles of the invention; and Figure 24 shows an illustrative flow chart in accordance with the principles of the invention. Figure 25 shows another embodiment in accordance with the principles of the invention.

DETAILED DESCRIPTION OF THE INVENTION Other than the inventive concept, the elements shown in the Figures are well known and will not be described in detail. Also, familiarity with satellite-based systems is presumed and will not be described in detail. For example, different from the inventive concept, satellite transponders, descending signals, symbol constellations, the front end of radio frequency (rf) or a receiver section, such as a low noise block down converter, the methods formatting and coding (such as the Standard for Moving Pictures Experts Group (MPEG) -2 Systems (ISO / IEC 13818-1)) to generate transport bit streams and decoding methods such as registration probability ratios, programmable input decoders, programmable output (SISO), Viterbi decoders are well known and are not described here. In addition, the inventive concept can be implemented with the use of conventional programming techniques, which as such, will not be described here. Finally, similar reference numbers in the Figures represent similar elements. An illustrative communication system 50 in accordance with the principles of the invention is shown in Figure 1. The communication system 50 includes a transmitter 5, a satellite channel 25, a receiver 30 and a television 35 (TV). Although described in more detail below, the following is a summary of the communications system 50. Transmitter 5 receives a number of data streams as represented by signals 4-1 through 4-K and in accordance with the principles of the invention, provides a multi-level modulated signal 6 to satellite transmission channel 25. . Illustratively, these data streams represent the control signaling, the content (eg, video), etc., of a satellite TV system and may be independent of each other or may be related to each other, or a combination thereof. the same. The multi-level modulated signal 6 represents a signal with a hierarchical modulation base or a signal with a stratum modulation base having K strata, where K >; _ 2. It should be noted that the words "strata" or "level" are used interchangeably. The satellite channel 25 includes a transmitting antenna 10, a satellite 15 and a receiving antenna 20. The transmitting antenna 10 (representative of a terrestrial transmitting station) provides the multi-level modulated signal 6 as a signal 11 ascending to the satellite 15. With brief reference to Figure 2, an illustrative block diagram of the transmission path to through satellite 15 for a signal. The satellite 15 includes an input filter 155, a traveling wave tube amplifier 165 (TWTA) and an output filter 175. The rising signal 11 is first filtered by the output filter 175, then amplified for retransmission by the TWTA 165. The output signal from the TWTA 165 is then filtered by the output filter 175 to provide the downward signal 16 (which it is typically at a different frequency than the rising signal). As such, the satellite 15 provides for the retransmission of the upward signal received through the downlink signal 16 to a broadcast area. The diffusion area typically encompasses a defined geographic region, for example, a portion of the United States. Referring again to Figure 1, the downward signal 16 is received by the receiving antenna 20, which provides the signal 29 received to a receiver 30, which demodulates and decodes the signal 29 received in accordance with the principles of the invention for provide, for example, the content to the TV 35, through the signal 31 for viewing. It should be noted that although not described here, the transmitter 5 can also pre-distort the signal before transmission to compensate for non-linearities in the channel. As mentioned before, in the context of this description, the multi-level modulated signal 6 represents a signal based on hierarchical modulation or a signal based on stratum modulation. In the case of the first, an illustrative block diagram for the transmitter 5 according to the principles of the invention is shown in Figure 3, while for the second, an illustrative block diagram for the transmitter 5 in accordance with the principles of the invention. In the remainder of this description, it is presumed that there are two data streams, ie, K = 2. It should be noted that the invention is not limited to K = 2, and in fact, a particular data stream as the signal 4 -1 can represent an aggregate of other data streams (not shown). Referring first to Figure 3, an exemplary hierarchical modulation transmitter for use in transmitter 5 is shown. Hierarchical modulation is simply described as a synchronized modulation system, wherein the lower stratum signal is incorporated in synchronized form within a higher stratum signal to create a higher order modulation alphabet.

In Figure 3, the hierarchical modulation transmitter comprises a UL encoder 105, a UL modulator 115, an LL encoder 110, a LL modulator 120, multipliers (or amplifiers) 125 and 130, a combiner (or adder) 135 and a converter 140 ascending. The upper stratum path (UL) is represented by the UL encoder 105, the modulator 115 and the amplifier 125; while the lower stratum path (LL) is represented by the encoder 110 LL, the modulator 120 LL, and the amplifier 130. As used herein, the term "UL signal" refers to any signal in the UL path and will be apparent within the context. For example, in the context of Figure 3, this is one or more of the signals 4-1, 106, 116 and 126. Similarly, the term "LL signal" refers to any signal in the LL path. Again, in the context of Figure 3, this is one or more of the signals 4-2, 111, 121 and 131. In addition, each of the coders implements known error detection / correction codes (e.g. convolutivos or of grid, a scheme of correction of error front (FEC) concantenado, where a convolutional code of proportion? A, 2/3, 4/5 or 6/7 like the internal code is used, and a code is used Reed Solomon as the external code, LDPC codes (low density parity revision code), etc.). For example, typically the UL 105 encoder uses a convolutional code or a short block code, while the encoder 110 LL uses a turbo code or LDPC code. For the purposes of this description, it is assumed that the encoder 110 LL uses an LDPC code. In addition, a convolutional interleaver (not shown) can be used.

As can be seen from Figure 3, the signal 4-2 is applied to the encoder 110 LL, which provides a signal 111 encoded to the modulator 120. In the same way, the signal 4-1 is applied to an encoder 105 UL , which provides a signal 106 encoded to the 115 UL modulator. The encoded signal 106 represents N bits per symbol interval T; while the encoded signal 111 represents M each T symbol intervals, where N may or may not be equal to M. The modulators 115 and 120 modulate the respective signals applied thereto, in order to provide the modulated signals 116 and 121. , respectively. It should be noted that since there are two modulators, 115 and 120, the modulation may be different in the UL path and in the LL path. Again, for the purposes of this description, it is assumed that the number of UL coded data bits is two, ie, N = 2, and that the UL modulator 115 generates a modulated signal 116 that is in one of the four quadrants of a signal space. That is, the UL 115 modulator copies two bits of data encoded into one of four symbols. Similarly, the number of encoded data bits LL is also assumed to be two, ie, M = 2, and the modulator LL1 also generates a modulated signal 21 which is in one of the four quadrants of the signal space . An illustrative symbol constellation 89 for use in both UL and LL is shown in Figure 4. It should be noted that the signal space 89 is illustrative only and that symbol constellations of other sizes and shapes can be used.

However, the output signals from the modulator 115 UL and the modulator 120 LL are adjusted in amplitude by a predefined UL gain and a predefined gain LL through the amplifiers 125 and 130, respectively. It should be noted that the gains of the lower and upper stratum signals determine the final placement of the points in the signal space. For example, the UL gain can be adjusted in the unit, that is, 1, while the LL gain can be adjusted in .5. The signal UL and the signal LL are then combined in the combiner, or adder 135 which provides the combined signal 136. In this way, the modulator of Figure 3, for example, the amplifiers 125 and 130, together with the combiner 135, effectively re-arranges and divides the signal space, so that the UL signal specifies one of the four quadrants of the signal space, while the LL signal specifies one of a number of sub-quadrants of a particular quadrant of the signal space as illustrated in Figure 5 by the signal space 79. In effect, the resulting signal space 79, also referred to herein as a combined signal space 79, comprises 16 symbols, each symbol is located at a particular signal point in the signal space and is associated with four particular bits. For example, the symbol 83 is associated with the four-bit sequence "01 01". The lower two-bit portion 81 is associated with the UL and specifies a quadrant of the signal space 79, while the upper two-bit portion 82 is associated with the LL and specifies a quadrant sub-quadrant specified by the 81nd portion of two. bits. It should be noted that since the UL signal identifies a quadrant, the LL signal effectively resembles noise in the UL signal. With respect to this, the combined signal space 79 represents the concept and the distances between symbols that are not scalable. Referring again to Figure 3, the combined signal 136 is applied to an upward converter 140, which provides the multi-level modulated signal 6 at an appropriate transmission frequency. With brief reference to Figure 6, there is shown another illustrative embodiment for implementing the hierarchical modulation in the transmitter 5. Figure 6 is similar to Figure 3, except that the hierarchical modulator 180 carries out a copy of the upper layer bits and the lower stratum within the combined signal space. For example, the upper layer may be a QPSK signal space (quadrature phase shift key), while the lower layer is a BPSK signal space (key with binary phase shift): in this case, the space of The resulting combined signal will, for example, be a non-uniform 8-PSK signal. Referring now to Figure 7, there is shown an illustrative block diagram of a stratum modulator according to the present invention, for use with the transmitter 5 of Figure 1. Here, although the elements of the transmitter 5 are similar to the previously described for Figure 3, the transmitter 5 comprises two separate paths of the transmitter. The upper stratum path includes the UL 105 encoder, the UL 115 modulator, and an upstream converter 240. The lower stratum path includes an encoder 110 LL, a modulator 120 LL and an upconverter 245. The signal 4-1 is encoded by the UL encoder 105 to provide an encoded signal 106 that represents N bits each symbol interval, TU, and the signal 4-2 is encoded by the encoder 110 LL to provide the encoded signal 111 that represents M bits each T _ symbol intervals, where M may or may not be equal to N. The encoded UL signal 106 is then modulated by the UL modulator 115 to provide the UL modulated signal 116, which is converted upwardly into a appropriate frequency band by the upstream converter 240 to provide the 6-1 UL signal. Similarly, the LL-encoded signal 111 is modulated by the modulator 120 to provide the LL-modulated signal 121, which is then up-converted by the up-converter 245 to provide the signal 6-2 LL. From Figure 7, it should be noted that the transmitter 5 transmits two signals, ie the multi-level modulated signal 6 comprising the signal 6-1 LL and the signal 6-2 LL. Typically, the 6-2 LL signal is transmitted at a lower power level than the 6-1 UL signal. In fact, a stratum modulation system typically requires more careful power control between the upper stratum path and the lower stratum path, so that recovery in the receiver occurs significantly. As such and with reference now to Figure 8 for a system based on the modulation of strata, the rising signal 11 represents two rising signals, - the rising signal 11-1 UL and the rising signal 11-2 LL, while the downward signal 16 represents two downward signals, the falling signal 16-2 LL and the signal 16-1 downward UL. In this example, the satellite 15 of Figure 1 can be a single satellite with two different transponders (one for the UL signal and another for the LL signal) or two different satellites. Either one or two satellites, as shown in Figure 8 there are, in effect, two satellite transmission paths. The UL satellite path includes a UL input 255 filter, a UL TWTA 265. and a UL output filter 275, which provides UL downward signal 16-1.; while the satellite path LL includes an input filter 260 LL; the LL TWTA 270 and the output filter 280, LL, which provides the downward signal 16-2 LL. Each of these elements of Figure 8 function in a manner similar to the respective elements shown in Figure 2 and described above. As mentioned before, after reception of the descending signal 16 by the receiving antenna 20, the receiver 30 demodulates and decodes the received signal 29 to provide, for example, the content to the TV 35 for viewing therein. An illustrative portion of the receiver 30 according to the principles of the present invention is shown in Figure 9. The receiver 30 includes a front end filter 305, an analog to digital converter 310, and a unified demodulator / decoder 320. The front end filter 305 downconverts and filters the received signal 29 to provide a near baseband signal to the A / D 310, which samples the down converted signal to convert the signal to the digital domain and provides a sequence of samples 311 (also referred to as the multi-level signal 311) to the unified demodulator / decoder 320. The latter, in accordance with the principles of the present invention, has a number of demodulation modes, wherein at least two modes of The demodulation represents a hierarchical demodulation mode and a layer demodulation mode. The selection of a particular demodulation mode is provided by the signal 389 of demodulation mode, which is set illustrative a priori. The demodulation mode signal 389 can be set in any of a number of ways, for example, a jump setting, configuration information (not shown) of the receiver 30 that can be seen, for example, in the TV set 35 and it can be adjusted, for example, through a remote control (not shown), or from the data transmitted in a band or out-of-band signaling channel. When in the hierarchical demodulation mode, the unified demodulator / decoder 320 performs the hierarchical demodulation of the multi-level signal 311 and provides a number of signals 321-1 to 321-K output, representative of transported data. by the multi-level signal 311 in the strata K. The data from one or more output signals is provided to the TV apparatus 35 via the signal 31.

(In this regard, the receiver 30 may also process the data prior to its application in the TV apparatus 35 and / or directly provide the data to the TV apparatus 35). In the following example, the number of levels is two, that is K = 2, but the inventive concept is not limited. For example, in the hierarchical demodulation mode, the unified demodulator / decoder 320 provides signal 321-1 UL and signal 321-2 LL. The first ideally represents what was transmitted in the upper layer, that is, the signal 4-1 of Figure 3; while the second ideally represents what was transmitted in the lower layer, that is, signal 4-2 of Figure 3. Similarly, when set in the demodulation mode by strata, the unified demodulator / decoder 320 leads to performed the demodulation by strata of the multi-level signal 311 to provide signal 321-1 UL and signal 321-2 LL, which ideally represent signals 4-1 and 4-2 of Figure 7. Referring now to Figure 10 shows an illustrative architecture for the unified demodulator / decoder 320. The unified demodulator / decoder 320 comprises a 330 UL demodulator, a delay / equalizer element 345, a 335 UL decoder, a 350 UL re-modulator / recoder, a combiner 375, the LL demodulator 390, the HL multiplexer (mux HL) 395 ( also called as selector 395 HL), and a decoder 340 LL. The multi-level signal 311 is applied to a 330 UL demodulator, which demodulates this signal and provides thereon a UL carrier signal 332, a re-sampled multi-level signal 316, and the demodulated UL signal, represented by the current 333 of demodulated UL signal point. Referring now to Figure 11, an illustrative block diagram of demodulator 330 UL is shown. The 330 UL demodulator includes a digital re-sampler 415, an equalized filter 420, an anti-spiker 425, a time recovery element 435 and a carrier recovery element 440. The multi-level signal 311 is applied to the digital re-sampler 415, which re-samples the multi-level signal 311 with the use of the UL time signal 436, which is provided by the recovery element 435. time, to provide the re-sampled multi-level signal 316. The re-sampled multi-level signal 316 is applied to the matched filter 420 and is also provided to the delay / equalizer element 345 (described above). The matched filter 420 is a bandpass filter for filtering the multi-level signal 316 re-sampled at approximately the frequency of the UL carrier to provide a filtered signal to the anti-spiker 425 and the aforementioned time recovery element 435. , which generates from it a signal 436 of UL time. The anti-rotator 425 does not rotate, that is, it removes the carrier from the filtered signal to provide a demodulated UL signal point current 333. The carrier recovery element 440 utilizes the demodulated UL signal point stream 333 to recover therefrom the UL carrier signal 332, which is applied to the anti-rotator 425 and the 350 UL re-modulator / recoder (further described ahead).

Referring again to Figure 10, the decoder 335 UL acts in a complementary fashion to the corresponding UL encoder 105 of the transmitter 5 and decodes the demodulated UL signal point stream 333 to provide the 321-1 UL signal. As mentioned before, signal 321-1 UL represents the data transported in the upper layer, for example, as represented by signal 4-1 of Figures 3 and 7. It should be noted that the 321-1 UL decoder recovers the data transported in the UL, when treating the LL signal as noise in the UL signal. In other words, the UL decoder 335 operates as if the 321-1 UL signal represented selected symbols from the signal space 89 of Figure 4. As an alternative to de-rotate the reconstructed signal from its subtraction., the combined signal can be un-rotated for subtraction. Signal 321-1 UL also applies to a remodulator / recoder 350 which responds to the UL carrier signal 332, which locally reconstructs the UL modulated signal. In particular, the remodulator / recoder 350 recodes and then remodulates signal 321-1 UL to provide the modulated signal 351 at a negative input terminal of combiner 375. With brief reference to Figure 12, a block diagram of a reproducer / recoder 350 illustrative. The remodulator / recoder 350 includes a rotary phase-delay element 445, an encoder 470, a re-rotator 465 and a pulse-forming element 460. The encoder 470 recodes and recopies the UL 321-1 signal symbols to provide a coded signal 471 to the anti-spiker 465, which re-spins the signal 471 encoded by a delayed version of the locally generated UL carrier frequency. , as determined by the upper layer carrier recovery element 440. The output signal of the re-rotator 465 is applied to the pulse formation element 460, which also shapes the reconstructed signal to provide the UL modulated signal 351. Referring again to Figure 10, the combiner 375 subtracts the UL modulated signal 351 from a delayed and equalized version (signal 346) of the re-sampled multi-level signal 316 to provide a signal representative of only the LL modulated signal. received, that is, the signal modulated LL 376, which is also used to update the sockets (not shown) of the equalizer of element 345 equalizer / delay. The two input signals for the combiner 375 are at the same sampling rate, which is typically an integer multiple of the symbol rate of the upper layer. An illustrative block diagram of the delay / equalizer element 345 is shown in Figure 13. The delay / equalizer element 345 includes a signal delay element 450 and an equalizer 455. The signal delay element 450 compensates for the delay in the delay. the signal processing path through the 330 UL demodulator, the 335 decoder and the 350 re-modulator / recoder; while the equalizer 455 attempts to remove the linear distortions, such as the slopes in the signal path in the tuner, since the combiner 375, in effect, cancels as much of the UL signal as possible from the multi-level signal 316 resampled for provide a clean modulated LL signal 376. In other words, the equalization is carried out to match optimally with the UL component of the multi-level signal 316 resampled for the reconstructed UL modulated signal 351, thus optimally removing the UL signal before demodulating and decoding the LL signal . Referring again to Figure 10, the LL modulated signal 376 is then applied to the demodulator 390 LL which retrieves therefrom a demodulated LL signal, as represented by the demodulated LL signal point stream 391. An illustrative block diagram of demodulator 390 LL is shown in Figure 14. The LL demodulator 390 includes a digital resampler 515, a matching filter 520, a time recovery element 535, an anti-twist 525, a carrier recovery element 540. The modulated LL signal 376 is applied to the digital resampler 515, which resamples the LL modulated signal 376 with the use of a time signal 536 to bring the LL signal to the initial processing speed LL, which typically is an integer multiple of the symbol speed of the lower layer. The digital resampler 515 operates together with the time recovery element 535. The resampled LL modulated signal 516 is applied to the matched filter 520, which is a bandpass filter for filtering and shaping the modulated signal LL 5 resampled at approximately the carrier frequency LL to provide a filtered signal to both the anti-spinner 525 and to the aforementioned time recovery element 535, which generates therefrom a LL time signal 536. The anti-rotator 525 does not rotate the filtered signal, ie it removes the carrier from the filtered signal, to provide a demodulated LL signal point current 391, which is also applied to the carrier recovery element 540. The latter uses the demodulated LL signal point stream 391 to provide a recovered LL carrier signal to the anti-rotator 525. Referring again to FIG. 10, the mux 395 HL receives the demodulated UL signal point current 333 and the current 391 of demodulated LL signal point. In accordance with the principles of the invention, the mux 395 HL selects the signal point current 333 UL or the signal point current 391 LL for processing and its subsequent application to the decoder 340 LL, as a function of the signal 389 in demodulation mode. When the demodulation mode signal 389 indicates the demodulation by strata, then the mux 395 H-L selects the signal point current 391 LL for processing. However, when the demodulation selection signal 389 indicates a hierarchical demodulation, then the mux H-L 395 selects the signal point stream 333 for processing. Attention should be given to Figure 15, which shows an illustrative block diagram of the mux 395 H-L. The latter comprises a multiplexer (mux) 565 and a query table (LUT) 570 of query probability relation (LLR). The input signals to the mux 395 are received signal point values (either from the UL or LL), and the output signals from the mux 395 HL are programmable values that represent the probability that certain bits were received . In particular, the mux 565 selects either the UL signal point current 333 or the signal point current 391 LL as a function of the demodulation mode signal 389, as described above, and provides the signal selected as the signal. signal 566 received. As such, the received signal 566 is a stream of the received signal points, each received signal point having a component (572) in phase (IREC) of a quadrature component (571) in a signal space. This is illustrated in Figure 16 for a ZREC point of received signal, where: Z = lrec + jQrec (1) The lREC and QREC components of each received signal point are applied to the LUT 570 LLR. The latter stores a LUT 599 of precomputed LLR values as illustrated in Figure 17. In particular, each row of LUT 599 is associated with a value of the particular component l (a row value I), while each column of the LUT 599 is associated with a particular Q component value (a value of column Q). The LUT 599 has rows L and columns J. The LUT 570 LLR quantizes the values of the lREc and QREC components of a signal point received from the received signal 566 to form an input address, which is used as an index within the LUT 599 to select from it a respective precomputing LLR. Each symbol interval T L, the selected LLR is provided through the signal 396 to the decoder 340 LL. For example, when the value of the lREC component of the signal 566 is quantized with the first row and the value of the QREC component of the signal 566 is quantized in the first column, then the LLR 598 will be selected and provided through the signal 396 of Figure 15, to decoder 340 LL of Figure 10. Different from the inventive concept, and as is known in the art, for a copy M (b) from bit to symbol, where M are the destination and bi-symbol = 0, 1, ... B-1, are the bits to be copied where B is the number of bits in each symbol (for example, B can be two bits for QPSK, three bits for 8-PSK, etc. ), the probability relation function of the bit of a bit value B is: LLR (iz) = register ((prob (bj = / z)) / (prob (b, = 0 / z))); (2) where bi is the ° bits and z is the signal point received in the signal space. The notation "prob" (bj = 1 / z) represents the probability that the ° bits is a "1" given that the signal point z was received. Similarly, the notation "Priv. (Bi = 0 / z)" represents the probability that the 1st bit is a "0" given that the signal point z was received. For a two-dimensional signal space, the probabilities within equation (2) are assumed to be based on white Gaussian noise (AWGN) that has a probability density function (PDF) of: Therefore, the LLR for A given bit and a received signal point are defined as: From equation (4) it can be seen that the LLR of a received signal z point is a function of z, the target symbols M and the noise level s rms. An LLR is also an example of a "soft metric". An illustration of the calculation of an LLR relationship is shown in Figures 18 and 19. Figure 18 shows an illustrative LL symbol constellation. For simplicity of a QPSK constellation (Quadrature Phase Shift Lock) of 4 symbols, however, it should be noted that other sizes and shapes of symbol constellations can be used, for example, 3 bits for 8-PSK, 4 bits for 16-QAM, a hierarchical 16-QAM, etc. From Figure 18 it can be seen that there are four symbols in the signal space 89, each symbol associated with a particular two-bit copy (b 1, bO). Referring now to Figure 19, a signal z-point received relative to the symbols of the signal space 89 is shown. From Figure 19 it can be seen that the received signal point z is located at different distances d, from each of the symbols of the signal space 89. For example, the received signal point z is located at a distance d4 from the symbol associated with the copy of two bits "01". As such, the LLR (bO) is: In (probability bO is one) / (probability bO is zero); or (5A) In (probability (symbol 01 or 11)) / (probability (symbol 00 or 10))); or (5B) In ((exp (-d42 / (2s2)) + exp (-d32 / (2))) + exp (-d22 / (2s2))) + exp (-d? 2 / (2s2))). (5C) While the LLR (b1) is: In (probability b1 is one) / (probability b1 is zero); or (6A) In (probability (symbol 10 or 11)) / (probability (symbol 00 or 01))); or (6B) In ((exp (-d-, 2 / (2s2)) + exp (-d32 / (2s2)) + exp (-d22 / (2s2) + exp (-d42 / (2s2))) (6C) With reference again to Figure 15, it can be seen that LLR LUT 570 (i.e., LUT 599) is initiated to any one of a group of 573 hierarchical LLR values or 574 LLR values of strata depending on the respective mode of each 30 receiver. For example, the LLR values in strata are calculated a priori with respect to the symbol constellation LL, as illustrated in Figures 4, 18 and 19, while the hierarchical LLR values are calculated a priori with respect to the combined symbol constellation. as illustrated in Figure 5 and shown again in Figure 20. In other words, the hierarchical LLRs for the LL are determined - not with respect to the signal space LL (eg, the signal space 89 of Figure 4 ) - but with respect to the combined signal space (for example, space 79 of Figure 5) For each received signal z point, a distance between each symbol of the Signal space 79 and the received signal point z are determined and used when calculating an LLR. For simplicity, only some distances dl are shown in Figure 20. Hierarchical values LLR 573 and LLR values 574 of strata can be formed in a variety of ways. For example, the receiver 30 can carry out the calculations with the use of for example, a training signal, provided by the transmitter 5 either during the start, or the re-initialization of communications between the two endpoints (transmitter). 5 and receiver 30). As is known in the art, a training signal is a predefined signal, for example, a predefined symbol sequence that is known a priori by the receiver. You can also define a predefined "initial agreement" sequence, where the endpoints exchange signals before communicating data between them. Alternatively, the calculations can be carried out remotely, for example, at the location of the transmitter 5 and sent to the receiver 30 through a band or out-of-band signaling channel (it can even be through a dialing facility (wired and / or wireless) (not shown) Alternatively, the calculations can be carried out in analytical form and hierarchical LLR values 573 or stratus values 574 can be pre-programmed into the memory of the receiver at the time of manufacture With reference again to Figure 10, in accordance with the principles of the present invention, the decoder 340 LL receives the sequence of the LLR (programmable input data), through the signal 396, and provides therewith the signal 321.2. The decoder 340 LL operates in a manner complementary to that of the encoder 110 LL. It should be noted that the decoder 340 LL can be a programmable input-programmable input decoder, and provides programmable output values, which are also processed (not shown) to form the signal 321-2 LL.

From Figure 10, in a stratum demodulation mode, the receiver 30 sequentially demodulates the received signal to the first retrieve the UL signal through the demodulator 330 UL and the decoder 335. The recovered UL signal is then recoded and the signal is demodulated for the subtraction from the received signal to discover the signal LL for demodulation by the LL demodulator 390. The resulting demodulated LL signal stream 391 is then processed to generate the programmable input data, for example, LLRs with respect to the symbol constellation LL. In contrast, in a hierarchical demodulation mode, the UL signal point current 333 from which the LL signal is directly determined is recovered. This is referred to here as a simultaneous decoding mode. In particular, the UL signal point stream 333 is processed to generate programmable input data eg, LLR to retrieve the LL data therefrom. Other variations of the mux 395 H-L are possible. For example, Figure 21 shows an illustration where two separate lookup tables (555 and 560) are located in front of mux 565, which selects the appropriate signal) either signal 556 or 561) in accordance with signal 389 in demodulation mode. In Figure 22 another embodiment in accordance with the principles of the invention is illustrated. Illustratively, in this embodiment a unified demodulator / decoder 320 'sequentially decodes the received signal when it is in the operating hierarchical mode. For the sequential decoding of a signal based on hierarchical modulation, the receiver first decodes the UL signal and then decodes the LL signal. From Figure 22, it can be seen that the unified demodulator / decoder 320 'is similar to the unified demodulator / decoder 320 of Figure 10, except for the addition of the combiner or adder 380, the delay element 355 and the mux 395 'HL. The delay element 355 compensates for the processing delay of the UL decoder 335, the encoder 470, etc. Illustratively, the adder 380 receives as input signals, the demodulated UL signal point current 333 'and the symbol signal 471, which are available from the UL 350 remodulator / recoder, as shown in FIG. 12.

The combiner 380 subtracts the coded signal 471 from the demodulated UL signal current 333 ', delayed to provide a signal point current 381 of signal LL to an input of the mux 395' H-L. As before, the mux 395 'H-L selects the applied signals, here, a signal point current 381 LL or the demodulated signal LL current 391 as a function of the selected demodulation mode. A block diagram of the mux 395 'H-L is shown in Figure 23. In this example, mux 395 'H-L includes mux 565 and calculator 580 LLR. The mux 565 selects between the LL signal point current 381 or the demodulated LL signal point stream 391 as a function of the demodulation mode signal 389 to provide the received signal point stream 566. The latter applies to a programmable data generator, such as those represented by the 580 LLR computer, which provides the 396 LLR data to the decoder 340 LL, as described above. Attention is now directed to Figure 24, which shows an illustrative flow chart in accordance with the principles of the present invention of a process for use in a receiver 30 of Figure 1. In step 605, the receiver 30 selects one of the demodulation modes. Illustratively, there are at least two modes of demodulation, hierarchical demodulation and layer demodulation. As noted above, this selection can be carried out for example, with a jump setting, a configuration screen (not shown) of the receiver 30 or from the data transmitted in an out-of-band or in-band signaling channel. In step 610, the receiver 30 receives the multi-level signal. In step 615, the receiver 30 determines the demodulation process to be performed as a function of the selected demodulation mode. When the demodulation mode is hierarchical, then the receiver 30 carries out the hierarchical demodulation of the multi-level signal received in step 620. On the other hand, when the demodulation mode is in layers, then the receiver 30 performs the layer demodulation of the multi-level signal received in step 625. It should be noted that the selection of the demodulation mode (step 605) can be carried out after receiving the multi-level signal (step 610). In Figure 25, another illustrative embodiment of the inventive concept is shown. However, only the portions relevant to the inventive concept are shown. For example, for the purpose of simplification, analogue to digital converters, filters, decoders, etc. are not shown. In this illustrative embodiment an integrated circuit (IC) 705 for use in a receiver (not shown) includes a unified demodulator / decoder 320 and at least one register, 710, which is coupled with a busbar 751. The latter offers the communication to and from other components of the receiver as represented by the processor 750. The register 710 represents one or more records of the IC or of portions thereof, the IC 705 may be read only, write only or read / write. In accordance with the principles of the invention, the unified demodulator / decoder 320 decodes a received multi-level modulated signal and at least one bit, for example, bit 709 of register 710 is a programmable bit that can be adjusted eg , by the processor 750, to control the operation of the unified demodulator / decoder 320. In the context of Figure 16, the IC 705 receives the signal 701 to process it through an input pin, or guide of the IC 705. A derivative of this signal, 311 is applied to the unified demodulator / decoder 320. The latter provides signals 31-1 to the 321-K output as described above. The unified demodulator / decoder 320 is coupled to the register 710 through the internal bus 711 which represents other signal paths and / or components of the IC 705 to interface with the unified demodulator / decoder 320 of the register 710 as is known in the technique. As described above, and in accordance with the inventive concept, a receiver handles both hierarchical modulation and stratum modulation in a unified structure. Although demodulation modes are described herein, the inventive concept is not limited and, as such, the receiver in accordance with the principles of the invention may have more than two demodulation modes. It should be noted that although the inventive concept is described in the context of an LL decoder 340 to receive the programmable metrics, the decoder 340 LL can receive signal points, and as such, can process the received signal point data to derive from the same the LLR as described above. In this context, the mux element HL described above is simply a multiplexer for selecting the signal point current received as the mux 565 of Figure 23. Also, it should be noted that although it is described within the context of a receiver coupled with a deployment, represented by TV 35, the inventive concept is not limited. For example, the receiver 30 can be located upstream in a distribution system, for example, at the head end which then retransmits the content to other nodes and / or receivers in a network. In addition, although hierarchical modulation and stratum modulation are described within the context of providing communication systems that are regressively compatible, it is not a requirement of the present invention. Also, it should be noted that the groupings of components for particular elements described and shown herein are merely illustrative. For example, whether one or both of the decoder 335 UL and the decoder 340 LL can be external to the element 320, which is essentially a demodulator that provides at least one demodulated upper stratum signal and a demodulated lower stratum signal. As such, the foregoing only illustrates the principles of the invention and will be recognized by those skilled in the art, and thus will have the ability to contemplate various alternative arrangements which, although not explicitly described, incorporate the principles of the invention and are within the scope of the invention. of his spirit and

Claims (21)

scope. For example, although illustrated in the context of separate functional elements, these functional elements may be incorporated into one or more integrated circuits (IC). Similarly, although they are shown as separate elements, any or all of the elements may be implemented in a stored program controlled processor, for example, a digital signal processor (DSP), or a microprocessor that executes associated software, for example. example, corresponding to one or more of the steps shown in Figure 24 In addition, although they are shown as separate elements, the elements may be distributed in different units in any combination thereof. For example, the receiver 30 may be part of a TV 35. Therefore, it is intended that various changes may be made to the illustrative embodiments and other arrangements may be contemplated without departing from the spirit and scope of the present invention, as defined in the appended claims. CLAIMS

1. A receiver characterized in that it comprises: a down converter to provide a received signal; and a demodulator having at least two demodulation modes for demodulating the received signal, wherein one demodulation mode is a hierarchical demodulation and the other demodulation mode is a layer demodulation. The receiver according to claim 1, characterized in that the demodulator responds to the demodulation mode signal which specifies one of the number of demodulation modes that the demodulator will perform. The receiver according to claim 1, characterized in that the demodulator comprises: an upper layer demodulator for processing the received signal to provide a demodulated upper layer signal; an upper layer decoder for decoding the demodulated upper layer signal to provide a decoded upper layer signal; an upper layer remodulator / recoder that responds to the decoded upper stratum signal to provide a reconstructed modulated upper stratum signal; a combiner for combining the received signal with the reconstructed modulated upper stratum signal, such that a higher stratum signal component of the received signal is essentially reduced therefrom to provide a received lower stratum signal; a lower stratum demodulator for processing the received lower stratum signal to provide a demodulated lower stratum signal; a selector for providing a lower stratum signal derived from the demodulated lower stratum signal or from the demodulated upper stratum signal; and a lower layer decoder for decoding the lower stratum signal to provide a decoded lower stratum signal. The receiver according to claim 3, characterized in that the selector responds to the demodulation mode signal to select the demodulated lower stratum signal or the demodulated upper stratum signal to be used when deriving the lower stratum signal. The receiver according to claim 4, characterized in that the selector responds to the demodulation mode signal to select one of a number of registration probability relation (LLR) query tables to be used in deriving the stratum signal. lower. The receiver according to claim 3, characterized in that it includes an equalizer arranged between the received signal and the combiner to equalize the received signal. The receiver according to claim 1, characterized in that the demodulator comprises: an upper layer demodulator for processing the received signal to provide a demodulated upper layer signal; an upper layer decoder for decoding the demodulated upper layer signal to provide a decoded upper layer signal; an upper layer remodulator / recoder that responds to the decoded upper stratum signal to provide a reconstructed, modulated upper stratum signal and a reconstructed coded upper stratum signal; a combiner for combining the received signal with the reconstructed modulated upper stratum signal, such that a higher stratum signal component of the received signal is essentially reduced therefrom to provide a received lower stratum signal; a combiner for combining the demodulated upper stratum signal and the reconstructed coded upper stratum signal, such that a higher stratum symbol component of the demodulated upper stratum signal is essentially reduced to provide a first demodulated lower stratum signal; a lower stratum demodulator for processing the received lower stratum signal to provide a second demodulated lower stratum signal; a selector for providing a lower stratum signal derived from the first demodulated lower stratum signal or from the second demodulated upper stratum signal; and a lower layer decoder for decoding the lower stratum signal to provide a decoded lower stratum signal. The receiver according to claim 7, characterized in that the selector responds to the demodulation mode signal to select the demodulated lower stratum signal or the demodulated upper stratum signal for use in deriving the lower stratum signal. The receiver according to claim 8, characterized in that the selector also includes a programmable input generator for converting the selected signal into programmable input data, which is then provided as the lower layer signal. The receiver according to claim 9, characterized in that the programmable input generator is a register probability ratio generator. The receiver according to claim 7, characterized in that it includes an equalizer arranged between the received signal and the combiner to equalize the received signal. The receiver according to claim 1, characterized in that the demodulator provides at least one demodulated upper stratum signal and the demodulated lower stratum signal, the receiver also comprises: an upper stratus decoder for decoding the upper stratum signal demodulated to provide a decoded upper layer signal; and a lower layer decoder for decoding the demodulated lower layer signal to provide a decoded lower layer signal. 13. An apparatus characterized in that it comprises: a television apparatus for displaying video content; and a multi-mode receiver coupled to the television apparatus for receiving a signal carrying the video content, wherein the receiver includes a hierarchical demodulation mode and a layer demodulation mode. The apparatus according to claim 13, characterized in that the received signal is a satellite signal. 15. A method for use in a receiver, characterized in that the method comprises: receiving a signal; selecting one of a number of demodulation modes, wherein at least two of the number of demodulation modes are the hierarchical demodulation mode and the layer demodulation mode; and demodulating the received signal in accordance with the selected demodulation mode. The method according to claim 15, characterized in that the demodulation step includes the steps of: demodulating the received signal to provide a demodulated upper layer signal and a demodulated lower layer signal; decoding the demodulated upper layer signal to provide a decoded upper layer signal; selecting, as a function of the selected demodulation mode, either the demodulated lower layer signal or the demodulated upper layer signal to provide a lower stratum signal, wherein the demodulated lower layer signal is selected when the demodulation mode is the demodulation mode by strata and the demodulated upper stratum signal is selected when the demodulation mode is the hierarchical demodulation mode; and decoding the lower stratum signal to provide a decoded lower stratum signal. The method according to claim 15, characterized in that the selection step includes the steps of: selecting a registration probability relation (LUT) query table (LLR) as a function of the demodulation mode signal; and generating register probability relationships from the LUT LLR as a function of the selected signal to provide a lower stratum signal. The method according to claim 15, characterized in that the demodulation step includes the steps of: demodulating the received signal to provide a demodulated upper layer signal and a demodulated lower layer signal; decoding the demodulated upper layer signal to provide a decoded upper layer signal; recoding the decoded upper stratum signal to provide a recoded high stratum signal; subtracting the recoded upper stratum signal from the demodulated upper stratum signal to provide a coded lower stratum signal; selecting, as a function of the selected demodulation mode, either the demodulated lower stratum signal or the lower stratified signal coded to provide a lower stratum signal, wherein the demodulated lower stratum signal is selected when the demodulation mode is the demodulation mode by strata and the encoded lower stratum signal is selected when the demodulation mode is the hierarchical demodulation mode; and decoding the lower stratum signal to provide a decoded lower stratum signal. The method according to claim 18, characterized in that the selection step includes the step of generating registration probability ratios of the selected signal to provide the lower stratum signal. 20. An apparatus characterized in that it comprises: a demodulator for processing a received signal based on multi-level modulation comprising at least a first signal layer and a second signal layer; and at least one register for use in controlling a demodulation mode of the demodulator wherein at least one demodulation mode is a hierarchical demodulation mode and the other demodulation mode is a layer demodulation mode. The apparatus characterized in that it comprises: a guide for receiving a received signal based on the multi-level modulation comprising at least a first signal layer and a second layer signal; and a demodulator for processing the received signal with modulation basis; wherein the demodulator has a number of demodulation modes and wherein at least one demodulation mode is a hierarchical demodulation mode and the other demodulation mode is a layer demodulation mode.