MXPA05011877A - Adaptive soft demodulation for reception of distorted signals - Google Patents

Abstract

A satellite communications system comprises a transmitting ground station, including a transmitter and a receiver, a satellite transponder and a receiving ground station. The transmitter transmits an uplink signal to the satellite transponder, which broadcasts the received uplink signal as a downlink signal to the receiving ground station. The transmitting ground station monitors the downlink signal through the receiver and calculates log-likelihood ratios (LLRs) as a function of the monitored downlink signal. These LLRs are illustratively stored in a look-up table, which are then transmitted to the receiving ground station for use in recovering data from a received data signal.

Description

For two-letter codes and other abbreviations, he referred to the "Guid-ance Notes on Codes and Abbreviations" appearing to the ihe begin-ning ofeach regular issue of the PCT Gazette.

APPARATUS AND METHOD FOR USING IN ITERATIVE DECODIFICATION FIELD OF THE INVENTION The present invention relates in general to communications systems, and more particularly, to a satellite-based communication system.

BACKGROUND OF THE INVENTION In a general sense, in a communication system, a ground station transmits an "up" signal to a satellite transponder, which re-transmits the "down" signal to a receiving station. One form of the satellite communications system employing a hierarchical modulation is described in U.S. Patent No. 5,966,412 issued October 12, 1999 to Ramaswamy. The hierarchical compatible backward modulation (BCHM) can be used in a satellite system as a way to continue support for 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 hierarchical modulation allows additional features or services that can be added to 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, a signal of upper stratum (UL) and a lower stratum signal (LL) are added together in order to generate a satellite signal modulated in synchronized form for transmission. In the context of a satellite-based communications 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 hereditary receiver until the user decides to update with a receiver or box that can retrieve the LL signal to provide additional services. In communication systems, error detection / correction codes (and interleavers) are used to improve transmission accounting. Such error detection / correction codes include techniques, which are not limited to convolutional or grid codes, a concatenated forward error correction scheme (FEC), where a convolutional code of ratio 1_, 2/3, 4 is used. / 5 or 6/7 as the internal code, and a Reed Solomon code is used as the outer code; LDPC codes (low density parity revision code), etc.). For example, in the context of the satellite system based on the hierarchical modulation described above, the Ul signal is typically coded with the use of a convolutional code or a block code short, while the LL signal is typically encoded with the use of a turbo code or an LDPC code. In the context of a turbo code or an LDPC code, the receiver typically uses an iterative decoding technique such as that represented by the programmable input-programmable input (SISO) technique. SISO is typically based on "programmable metrics" such as log likelihood ratios (LLR). In general terms, an LLR is related to the probability that the value of a particular bit received (binary digit) is a logical "one" or a logical "zero". In particular, the transmitter transmits symbols from a predefined space, each transmitted symbol has associated with it a copy (b,) of determined bits to symbol, where M are the destination symbols and b, = 0,1, .. B- 1, are the bits to be copied, where B is the number of bits in each symbol. For example, in a 16-QAM signal space (quadrature amplitude modulation), there are 16 symbols, each symbol copied from a particular four-bit value (B = 4). In the receiver, the received signal is processed in a stream of signal points, each signal point resides in the aforementioned signal space (but does not necessarily correspond to a particular symbol transmitted due to noise). The receiver calculates the LLR, that is, the probability that a particular bit value was received given a received signal point. In general, the probability relation function for the 0 bit of the value of bit B is calculated as follows: Where z, is the value of the received signal point. In general, when the LLR value is positive, the bit is more likely to be 1, while when the LLR value is negative, it is very likely that the bit is zero. The receiver decodes the received signal iteratively with the use of calculated LLRs.

BRIEF DESCRIPTION OF THE INVENTION It has been observed that the aforementioned LLR calculations in the receiver can be affected by non-linear distortions in the communication system. For example, the amplitude-to-amplitude (A-AM) characteristics of a satellite transponder may cause a non-linear distortion that effectively distorts certain of the transmitted symbols. In addition, these nonlinear distortions may change over time. For example, the characteristics of the AM-AM distortion in the satellite transponder may change with the age of the transponder. As such, the LLRs determined by the receiver may be inaccurate. Therefore, and in accordance with the principles of the invention, an endpoint of a communication system receives a signal, determines the programmable metrics as a function of the received signal and stores the programmable query metrics in a look-up table for used in recovering data from the received data signal. In one embodiment of the invention, a satellite communication system comprises the following elements: a transmitting terrestrial station, including a transmitter and a receiver, a satellite transponder and a receiving ground station. The transmitter transmits an upward signal to the satellite transponder, which transmits the upward signal received as a downward signal to the receiving ground station. The transmitting terrestrial station monitors the downward signal through the receiver and calculates the LLRs as a function of the monitored downward signal. These LLRs are stored in illustrative form, in a look-up table, which are then transmitted to a receiving land station to be used in processing the received data signal for the reception of data therefrom. In another embodiment of the invention, the end point of a communication system is a receiver, which constructs a look-up table of the values of programmable query metrics. In particular, the receiver receives a training signal from the end point and calculates the values of programmable query metrics as a function of the received training signal. The receiver then stores the values of programmable query metrics calculated in the look-up table to be used in the processing of the received data signal for the reception of data therefrom.

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 an illustrative embodiment in accordance with the principles of the invention for use in the transmitting land station 1 of the Figure 1. Figures 4 and 5 show illustrative flow charts in accordance with the principles of the present invention. Figures 6 to 10 show various illustrations of a signal space. Figures 11 and 12 illustrate a LLR LUT in accordance with the principles of the invention. Figure 13 shows an illustrative embodiment in accordance with the principles of the invention for use in a receiver 30 of Figure 1. Figure 14 shows an illustrative flow chart in accordance with the principles of the invention for use in the receiver 30 of Figure 1. Figure 15 shows another illustrative embodiment in accordance with the principles of the invention for use in the receiver 30 of Figure 1. Figure 16 shows another illustrative embodiment in accordance with the principles of the invention for use in the receiver 30 of the Figure 1; and Figure 17 shows another flow chart in accordance with the principles of the invention for use in the receiver 30 of Figure 1.

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 bitstreams 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. In Figure 1 a communication system 50 is shown illustrative in accordance with the principles of the invention. The communication system 50 includes a terrestrial transmitting station 1, a satellite 15, a receiving terrestrial station 2 and a television 35 (TV). Although described in more detail below, the following is a summary of the communication system 50. The transmitting terrestrial station 1 comprises a transmitter 5, a transmitting antenna 10 and a receiving antenna 40. It should be noted that the transmitting terrestrial station 1, the receiving terrestrial station 2, the transmitter 5, the receiver 30 and the satellite 15 can be considered as the end points of the communication system in the respective paths, for example, the satellite 15 is the endpoint of the path between the satellite 15 and the transmitter 5, similarly, the receiver 30 of the receiving ground station 2 is an endpoint of the path between the transmitter 5 and the receiving ground station 2 (and through the satellite 15). The transmitter 5 receives a data signal 4 (representative of one or more data streams) and provides the modulated signal 6. Illustratively, the data streams represent the control signaling, content (eg, video), etc., of a satellite TV system and may be independent of each other or related to another or combination thereof. The transmitting antenna 10 provides the signal 6 modulated as a signal 11 rising to the satellite 15. With brief reference to Figure 2, an illustrative block diagram of the path of transmission through satellite 15 for a signal. The satellite 15 includes an input filter 155, a traveling wave tube amplifier (TWTA) 165 and an output filter 175. The upstream signal 11 is first filtered by the input filter 155, after it is 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 descending signal). As such, the satellite 15 provides for the retransmission of the upward signal received through the downlink signal 16 to a broadcast area. This transmission area typically encompasses a predefined geographical region, for example, a portion of the United States as represented by the receiving ground station 2. With reference to Figure 1, the receiving terrestrial station 2 comprises a receiving antenna 20 and a receiver 30. The receiving antenna 20 receives the downward signal 16 and provides the signal 29 received to a receiver 30., which demodulates and decodes the received signal 29 to provide, for example, the content to the TV 35, through the signal 31, to be seen therein. As mentioned before, the transmission characteristics of satellite 15 can also distort the signal (eg, the aforementioned AM-AM distortion of for example, TWTA 165 of Figure 2), and also, these transmission characteristics can change with time. Therefore, and in accordance with the principles of the invention, the transmitter 5 monitors the signal 16 descending through the receiving antenna 40 and the received signal 41 to adjust, adaptively or dynamically, the values of programmable query metrics, which are used in the receiver to process the received data signal to recover data therefrom. Referring now to Figure 3, there is shown an illustrative embodiment of the transmitter 5 in accordance with the principles of the invention. The transmitter 5 (also called as a modulator, since the transmitter 5 includes the modulation and demodulation functions) comprises an encoder / copier 305, a multiplexer 315, a modulator 320, an upconverter 325, a probability relation lookup table register (LLR LUT) 335, a downstream converter 355, a demodulator 360, a training signal generator 330, a delay element 370 and a processor 350. The latter is a control processor with stored program, for example, one or more microprocessors or one or more digital signal processors (DSP) and includes a memory (not shown). A data signal 4 is applied to the encoder / copier 305, which implements the known error detection / correction codes. Illustratively, at least a portion of the encoder / copier 305 implements a coding scheme such that a corresponding receiver carries out the SISO decoding. For example, the encoder / copier 305 implements a turbo code, LDPC, etc. In addition, a convolutional interleaver (not shown) can be used. It is assumed that encoder / copier 305 provides a sequence of symbols 306, each symbol selected from a predefined signal space or a symbol constellation (not shown). Illustratively, the sequence of symbols 306 occurs at a symbol rate of 1 / T. By ignoring the momentary signals 331 and 352, this sequence of symbols is applied to the multiplexer 315. The symbol sequence (signal 316) of the multiplexer output is applied to the modulator 320. The modulator 320 provides the signal 321 modulated to a converter 325 upstream , which also provides the modulated signal 6 at the appropriate transmission frequency. In accordance with the principles of the invention, the transmitter 5 in adaptive or dynamic form determines the LLRs to be used by the receiver to recover data from the received data signal. Reference should be made to Figure 4, which shows an illustrative method for use by the apparatus of Figures 1 and 3. In step 405, the transmitter 5 monitors a received signal, illustrated here as the signal 41 received from the Figure 3. In step 410, the transmitter 5 stores the LLR calculated in the LLR LUT 335 of Figure 3. In step 415, the transmitter 5 sends through, for example, the encoder / copier 305, the content of LLR LUT to the receiver (e.g., receiver 30 of Figure 1) to be used therein. It should be noted that the contents of LLR LUT 335 can be sent through a different encoder / copier or through an out-of-band channel. An illustrative type of received signal that can be used for according to the principles of the invention is a training signal. As is known in the art, a training signal is a predefined signal, for example, a predefined symbol sequence that is known a prior! for the elements of the communications system. With respect to this, the embodiment of Figure 3 has a number of operational modes, two of which are a training mode and a data mode. In the data mode, the transmitter 5 encodes and transmits data as described above. However, in the training mode, the transmitter 5 transmits a training signal to dynamically determine the LLRs stored in LLR LUT 335. The processor 350 stores the LLRs in the LLR LUT 335 through the signal 352. The mode Training of the transmitter 5 can be executed periodically, for example, at certain times of the day, weekly, or annual, or without periodic form, for example, when certain events occur, for example, initiation of the transmission, or even continuously (described below). At this time, reference should be made to Figure 5, which shows an illustrative method to be used in the transmitter 5 in the training mode. In step 505, the transmitter 5 transmits an upward training signal to the satellite 15. With reference again to Figure 3, the processor 350, through the signal 351, causes the transmission of a training signal 331 through the multiplexer 315. The training signal 331 is provided by the generator 339 of training signal and is any predefined symbol sequence. Preferably, the training signal is a predefined sequence that encompasses all symbols of the symbol constellation. For example, when the symbol constellation of Figure 6 is used, the training sequence includes all 16 symbols, each of which has a component in phase (I) and a quadrature component (Q), as represented by the symbol 83, which has a component 81 I and a component 82 Q in the signal space 79. As such, and with reference to Figure 3, the signal 331 represents a sequence of training symbols, which is applied to the multiplexer 315 for the upward transmission of the satellite 15 through an upward converter 325. In step 510 of Figure 5, the transmitter 5 receives the received signal 41, which is representative of the downward signal 16 from the satellite 15 of Figure 1. The received signal 41 (ie, the downlink signal) now includes the training signal so altered by the non-linear characteristics of the communication channel. The downstream converter 355 downconverts and filters the received signal 41 to provide a near-band-base signal 356 (in the digital domain) to the demodulator 360. As such, it is assumed that the downstream converter 355 includes an analog to digital converter (not shown). The demodulator 360 demodulates the near-baseband signal 356 to provide a sequence of received symbols 361, i.e., the received training signal.

As can be seen from Figure 3, the training signal 331 also applies to a delay element 370, which compensates for processing, transmission and descending delays as a transmitted training symbol, is compared by the processor 2350 in the corresponding received training symbol through signals 371 and 361, respectively. As such, in step 515 of Figure 5, the processor 350 calculates the LLRs as a function of the received signal z and the respective target symbol and stores the calculated LLRs in the LLR LUT 335. After completing the training, the processor 350 causes the LLR data contents of the LLR LUT 335 to be transmitted to a receiver, for example, the receiver 30 of Figure 1, in step 520. With respect to the determination when the training is completed, after a certain time and / or after N sequences transmitted from the training signal, where N > 0, etc. Also, it should be noted in Figure 3 that the transmitter 5 can also provide the symbol sequence 361 received to another processing equipment (not shown) for the reception of other data or for another use of the training signal. It should be noted that when combined data or data symbols 306 and training symbols 316 are applied to delay element 370, then when comparing signals 371 and LLR values 361 can be calculated without the need for a predefined training sequence; that is, normal data symbols will eventually encompass all the symbols of the constellation. It should be noted that the transmitted symbols can be sliced, such that the received symbols 361 are compared with their sliced values for the LLR calculation, rather than with the delayed transmitted symbols 371, which eliminates the need for the delay element 371. It should be noted that when a training sequence is used, the sequence 371 of the transmitted symbols can be reconstructed by correlating the received symbols 361 with the known training sequence, which eliminates the need for the delay element 370. It should be noted that a pre-distorter may be available after the multiplexer 315 to pre-compensate for the non-linear satellite distortions, and that the same received symbol pairs and the received symbols reconstructed or sliced or delayed transmitted., can be used to train the pre-distorter as well as for training the LLR board. With respect to determining the LLR, each signal point received from the sequence of the received signal points 361 includes a component (I) in phase and a quadrature component (Q) in the signal space. This is also illustrated in Figure 7 for a received z signal point, where: Z = IREC + JQREC (2) Different from the inventive concept, as is known in the art, for a given bit-to-symbol copy M (bi) ), where M are the symbols destiny and b; ¡= 0,1,, B-1 are the bits to be copied, where B is the number of bits in each symbol (for example, B is equal to two bits for QPSK, three bits for 8-PSK, etc.), the function of register probability relation for the ° bit is defined in equation (1) above and is repeated below: LLR (i, z) = log l (prob (A- = l l __)) / (prob (b¡ = 0 l z))]; (3) where bi is the ° bit and z is the signal point received in the signal space. The notation "prob (bi = 1 / z)" represents the probability that the 0 bit is a "1" given that the signal point z was received. Similarly, the notation "prob (bi = 0 / z)" represents the probability that the 0 bit is a "0" given that the signal point z was received. For a two-dimensional signal space, the probabilities within equation (3) are assumed to be based on the aggregate Gaussian white noise that has the 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 illustration of the calculation of an LLR relationship is shown in Figure 9 for the illustrative symbol constellation shown in Figure 8. For simplicity, a constellation of QPSK (quadrature phase shift lock) of 4 is shown in Figure 8. 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 16-QAM hierarchical, etc. From Figure 8 it can be seen that there are four symbols in the signal space 89, each symbol associated with a particular two-bit copy (b1, bO). Referring now to Figure 9, a received signal point z is shown relative to the symbols of the signal space 89. From Figure 9 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 (-d12 / (2s2)) + exp (-d32 / (2s2)) + exp (-d22 / (2s2) + exp (-d42 / (2s2))) (6C) A similar representation of a LLR is shown in Figure 10 for a signal space 79 (described above). For simplicity, in Figure 10 only some distances di, for a particular z-signal point received, are shown. In determining the LLR, the processor 350 effectively divides the signal space into a number of regions. This is illustrated in Figure 11. As can be seen from Figure 11, a signal space, for example, signal space 89, is divided or quantized into a number of regions, each region is identified by a component I and a component Q as represented by the region 399. For each region, the processor 350 determines an associated LLR and stores this LLR in the LLR LUT 335. An illustrative structure for the LLR LUT 335 is shown in the Figure 12. In particular, each row of the LLR LUT 335 is associated with a value of the particular component I (a row value l), while each column of the LLR LUT 335 is associated with a value of the particular component Q (a value of column Q). The LLR LUT 335 has rows L and columns J. As illustrated, the LLR determined for region 339 is copied into the LLR LUT 335 as shown in Figure 11. It should be noted that in this example, the processor 350 also copies or translates the coordinate system of the signal space into the respective rows and columns directions of the LLR LUT 335. Referring now to Figure 13, an illustrative portion of the receiver 30 is shown in accordance with principles of the invention. The receiver 30 includes a down converter 905, a demodulator 910, a LLR LUT 915, a computer 955 LLR, a multiplexer 960 (mux), a decoder 925 and a processor 950. The latter is a control processor with stored program, example, one or more microprocessors or one or more digital signal processors (DSP) and includes memory (not shown). The operation of the receiver 30 is first described within the context of receiving data, eg, video content, to be viewed on the TV set 35. With respect to this, the processor 950 adjusts the mux 960, through the signal 952, so that the output signal from the LLR LUT 915, the signal 916 is applied to the decoder 925 through the signal 961. With respect to at the signal 29 received, the down converter 905 converts into and descends and filters the received signal 29 to provide a near baseband signal 906 (in the digital domain) to the demodulator 910. As such, the downstream converter 905 is assumed to include an analog to digital converter (not shown). The demodulator 910 demodulates the baseband signal 906 almost to provide a sequence of received signal points 911. As mentioned above in equation (2), each received z signal point has an associated component I (IREC) and associated component (QREC). These components (signals 912 and 913 of Figure 13) are used as indices or addresses within the LLR LUT 915. In particular, in each signaling interval T, each received signal point is applied to the LLR LUT 915, whose structure is identical to the LLR LUT 335 as illustrated in Figure 12 and whose values have been set by the processor 950, as described below. Each received signal point is quantized in a corresponding I and Q component associated with a particular region of the signal space, where the received signal point falls (remember Figure 11, above) and is copied into the corresponding column and row of the LLR LUT 915 (see Figure 12, above) to select from them a respective precalculated LLR, that is, LLR (IREC; QREC). Each symbol interval T, the selected LLR is provided through the signal 916 to the decoder 925. For example, when z falls within the region 399 of the signal space illustrated in Figure 11, then the value of the iREC component of ia 911 signal is quantified (and copied) in the first row and the value of the QREc component of the signal 911 is quantified (and copied) in the first column of LLR LUT 915 (as illustrated in Figure 12) and the LLR stored therein is selected and is provided through the signal 916 to the decoder 925 of Figure 13. The decoder 925 operates at the LLR values applied thereto and acts in a manner complementary to the corresponding 305 of the transmitter 5 to decode the sequence of the received signal points 911 to provide the decoded 926 signal . The data of the signal 926 is provided to the TV set 35 via the signal 31. (In this regard, the receiver 30 can also process the data before it is applied to the TV set 35 and / or directly provide the data. to the TV set 35). As mentioned above, and in accordance with the principles of the invention, the processor 950 adjusts the LLR LUT 915 values. An illustrative method for using the receiver 30 to adjust LLR LUT 915 values is shown in Figure 14. To adjust the values of LLR LUT 915, the processor 950 adjusts the mux 960 in such a way that the LLR values processed by the decoder 925 are received from the computer 955 LLR. The latter works as in the prior art and calculates the LLR values for the respective received signal points. In step 605, the processor 950 receives the LLR values from the transmitter 5 through the received signal 29. This can be achieved as part of an initialization sequence, a training process or the restart. The LLR values are provided from the decoder 925 to the processor 950, which set LLR LUT 915 through signal 951 in step 610. In step 615, processor 950 configures receiver 30 to start receiving data and adjusts mux 960 in such a way that the LLR values used by decoder 925 are provided to LLR LUT 915. In Figure 15 another mode of the receiver according to the principles of the invention is shown. This embodiment is similar to that described above with respect to Figure 13, except that it is assumed that an out-band or in-band signaling channel is directly available to the processor 950, through the signal 914, for the initialization of the LLR. LUT 915. Although it is described within the context of a transmitter 5 by first determining the LLR values to be sent to the receiver 30, this process can also be performed within the receiver 30. In this regard, another embodiment for use in the receiver 30 is shown in Figure 16. The receiver 30 includes a down converter 905, a demodulator 910, a training element 930 of signal, a processor 950, a LLR LUT 915, and a decoder 925. With respect to receiving data, this mode operates as described above (except with respect to mux 960, which is not present). In particular, LLR values from LLR LUT 915 are applied to decoder 925 for data reception. With respect to adjusting values for the LLR LUT 915, the processor 950 performs the LLR calculations previously performed by the transmitter 5. Now we must turn our attention to Figure 17, the which shows an illustrative flow chart in accordance with the principles of the invention. Here, a process for use in the receiver 30 of FIG. 1 is shown. In step 805, the receiver 30 starts (or resets) communications with the transmitter 5 and receives a predefined training signal comprising predefined symbols as described. before. In step 810, the receiver 30 calculates the LLRs (as described above) from the received training signal with respect to the predefined training signal (provided by the training signal element 930, via the signal 931). In step 815, the receiver 30 stores the calculated LLRs in the LLR LUT 915. Finally, in step 820, the receiver 30 switches to a data communication mode and begins to receive the data transmitted from the transmitter 5 of the Figure 1. As described above, and in accordance with the principles of the invention, in a communications system the LLR values are transmitted to a receiver based on the analysis of the expected distortions of the communications channel and the expected values of the received symbols. The centers of gravity of the expected values of the received symbols are used illustratively in the LLR calculation. Alternatively, the LLR values are calculated in each receiver, by observing the centers of gravity of the symbol training sequence and calculating the LLRs. In view of the above, it should be noted that although it is described within the context of a communications system by satellite, the inventive concept is not limited. For example, although not shown for simplicity of description, the transmitter 5 may transmit a multi-level signaling scheme such as hierarchical modulation or layer modulation, wherein the corresponding receiver uses programmable query metrics for data reception from one or more layers. In addition, it should also be noted that the groupings of components for the particular elements described and shown herein are merely illustrative. For example, the transmitting terrestrial station 1 may comprise only one transmitting antenna 10 such that the transmitter 5 is located further upstream in a distribution system, etc. In the same way, the receiver 30 can be located, for example, at the front end, which retransmits the content to other nodes and / or receivers of a network. 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 that although not explicitly described, incorporate the principles of the invention and are within the scope of the invention. of his spirit and reach. 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 can be implemented in a stored program controlled processor, for example, a processor. digital signal (DSP), or a microprocessor executing associated software, for example, corresponding to one or more of the steps shown in Figures 4 and 5. 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 (30)

1. A method for being used at an end point of a communication system, the method is characterized in that it comprises: receiving a signal; determine values of programmable query metrics from the received signal; and storing the values of programmable query metrics in a look-up table to be used in subsequent data reception from the received signal.

The method according to claim 1, characterized in that the values of programmable query metrics are registration probability relationships (LLR).

3. The method according to claim 1, characterized in that the end point is an element of a satellite communication system.

4. The method according to claim 1, characterized in that the received signal comprises a training signal and a signal carrying data.

5. The method according to claim 1, characterized in that the end point is a transmitter for transmitting the data signal.

6. The method according to claim 1, characterized in that the end point is a receiver that receives the data signal.

The method according to claim 6 characterized in that the determination step determines the values of programmable query metrics as a function of a comparison between the received signal and the sliced version thereof.

The method according to claim 1, characterized in that it further comprises the step of sending a query table of the programmable query metric values to another endpoint to be used therein.

The method according to claim 8, characterized in that the other endpoint is a receiving land station of a satellite system.

The method according to claim 1, characterized in that the look-up table of the programmable query metric values is arranged in such a way that the in-phase and quadrature components associated with the data signal are indexes within the table Query values of programmable query metrics.

The method according to claim 1, characterized in that the received signal is a training signal comprising a sequence of predefined symbols.

The method according to claim 11, characterized in that the determination step includes the step of comparing the training signal with a transmitted version of the training signal to calculate the values of programmable query metrics as a function of it.

The method according to claim 1, characterized in that the received signal comprises a sequence of data symbols.

14. A method for use in a receiver, the method is characterized in that it comprises: receiving values of programmable query metrics from another endpoint; store the values of programmable query metrics in a lookup table; converting the received data signal in descending order to provide a sequence of received signal points; directing the look-up table as a function of an in-phase component and the quadrature component of each of the sequence of received signal points to provide a sequence of the programmable query metric values; and using the sequence of the programmable query metric values for the reception of data from the received data signal.

The method according to claim 14, characterized in that the values of programmable query metrics are registration probability values.

16. A method for use in a receiver, the method is characterized in that it comprises: receive a signal from another end point; determine values of programmable query metrics as a function of the received signal; store the values of programmable query metrics in a lookup table; converting in a descending manner a received signal to provide a sequence of received signal points; directing the look-up table as a function of an in-phase component and the quadrature component of each of the sequence of received signal points to provide a sequence of the programmable query metric values; and using the sequence of the programmable query metric values for the reception of data from the received data signal.

17. The method according to claim 16, characterized in that the values of programmable query metrics are registration probability values.

18. The method according to claim 16, characterized in that the received signal is a training signal.

The method according to claim 18, characterized in that the determination step includes the step of comparing the training signal with a stored version of the training signal to calculate the values of programmable query metrics as a function thereof. .

20. The method according to claim 16, characterized in that the determination step determines the values of programmable query metrics as a function of the comparison between the received signal and the sliced version thereof.

21. A transmitter characterized in that it comprises: a look-up table for storing the programmable metric values for use by a receiver for the reception of data from a data-carrying signal; and a modulator for transmitting the values of programmable query metrics stored to the receiver for use therein.

The transmitter according to claim 21, characterized in that it also comprises a demodulator for receiving a training signal and a processor for determining the values of programmable query metrics as a function of the received training signal.

23. The transmitter according to claim 21, characterized in that the values of programmable query metrics are registration probability relations.

24. A receiver characterized in that it comprises: a demodulator for providing a sequence of signal points from a received signal; a memory for storing the values of programmable query metrics in a look-up table, the values of programmable query metrics provided from the transmitter and wherein the lookup table is addressed as a function of an in-phase component and a quadrature component of each of the signal point sequence to provide a sequence of query metric values programmable; and a decoder for using the sequence of programmable query metric values for receiving data from the received data signal.

25. The receiver according to claim 24, characterized in that the values of programmable query metrics are registration probability values.

26. A receiver characterized in that it comprises: a demodulator for providing a sequence of signal points from a received signal; a processor for determining the values of programmable query metrics as a function of the sequence of signal points; a memory for forming a query table of programmable query metric values, wherein the look-up table is directed as a function of an in-phase component and a quadrature component of each of the signal point sequence to provide a sequence of values of programmable query metrics; and a decoder to use the sequence of programmable query metric values for data reception from the received data signal.

27. The receiver according to claim 26, characterized in that the values of programmable query metrics are registration probability relations.

28. The receiver according to claim 26, characterized in that it further comprises a slicer to provide a sequence of destination symbols from the sequence of signal points, and wherein the processor determines the values of programmable query metrics as a function of the comparison between the sequence of signal points and the sequence of destination symbols.

29. The receiver according to claim 28, characterized in that the values of programmable query metrics are registration probability relations.

30. The receiver according to claim 26, characterized in that the received signal comprises a training signal and a data carrying signal.