WO2009063098A1 - Método y dispositivo de transmisión y de recepción digital de señales de información - Google Patents
Método y dispositivo de transmisión y de recepción digital de señales de información Download PDFInfo
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- WO2009063098A1 WO2009063098A1 PCT/ES2007/000640 ES2007000640W WO2009063098A1 WO 2009063098 A1 WO2009063098 A1 WO 2009063098A1 ES 2007000640 W ES2007000640 W ES 2007000640W WO 2009063098 A1 WO2009063098 A1 WO 2009063098A1
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- sequence
- bipolar
- sequences
- signal
- pair
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- 230000005540 biological transmission Effects 0.000 title claims abstract description 30
- 238000000034 method Methods 0.000 title claims description 41
- 238000012549 training Methods 0.000 claims description 22
- 238000006073 displacement reaction Methods 0.000 claims description 20
- 125000004122 cyclic group Chemical group 0.000 claims description 16
- 238000004891 communication Methods 0.000 claims description 12
- 238000012937 correction Methods 0.000 claims description 3
- 239000000284 extract Substances 0.000 claims description 3
- 238000000926 separation method Methods 0.000 claims description 3
- 230000009466 transformation Effects 0.000 claims description 2
- 238000003780 insertion Methods 0.000 claims 1
- 230000037431 insertion Effects 0.000 claims 1
- 230000008054 signal transmission Effects 0.000 claims 1
- 230000000295 complement effect Effects 0.000 abstract description 19
- 230000000875 corresponding effect Effects 0.000 abstract 2
- 230000002596 correlated effect Effects 0.000 abstract 1
- 230000008901 benefit Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 2
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- 238000001228 spectrum Methods 0.000 description 2
- 101150012579 ADSL gene Proteins 0.000 description 1
- 102100020775 Adenylosuccinate lyase Human genes 0.000 description 1
- 108700040193 Adenylosuccinate lyases Proteins 0.000 description 1
- 238000005311 autocorrelation function Methods 0.000 description 1
- 238000005314 correlation function Methods 0.000 description 1
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- BABWHSBPEIVBBZ-UHFFFAOYSA-N diazete Chemical compound C1=CN=N1 BABWHSBPEIVBBZ-UHFFFAOYSA-N 0.000 description 1
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/0001—Arrangements for dividing the transmission path
- H04L5/0014—Three-dimensional division
- H04L5/0016—Time-frequency-code
- H04L5/0021—Time-frequency-code in which codes are applied as a frequency-domain sequences, e.g. MC-CDMA
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J13/00—Code division multiplex systems
- H04J13/0007—Code type
- H04J13/0011—Complementary
- H04J13/0014—Golay
Definitions
- the invention described has its scope in the transmission and reception systems of multiple information channels based on the OFDM modulation technique (Multiplexing by Division of
- OFDM modulation and its variants are used today for applications such as ADSL data transmission technology, digital terrestrial television (DTT), wireless transmission systems (such as WiMAX), digital radio, among others that can be cited as an example.
- ADSL data transmission technology digital terrestrial television (DTT)
- DTT digital terrestrial television
- WiMAX wireless transmission systems
- digital radio among others that can be cited as an example.
- OFDM modulation consists of taking a Transform
- IFFT Fast Fourier Inverse
- Two sequences A and B are complementary (or what is the same: they constitute a Golay pair) if the sum of the autocorrelations of these two sequences is equal to zero except for a null offset, that is, they satisfy the following equation: where AC () [n] expresses the autocorrelation function and L is the length of the sequences. This property of the sequences that form a Golay pair allows to encode up to L data streams. It is also important to review the fact that given a pair of Golay (A, B) you can always find another pair of complementary sequences that is orthogonal to the first, defining the orthogonality between pairs (A, B) and (C, D) of The following way:
- C (A, C) [n] + C (B, D) [n] 0 V n, n and N.
- C (,) [n] is the correlation function.
- the sequences of the Golay pair can be bipolar;
- the present invention takes advantage of the complementary sequences as well as the OFDM modulation using orthogonal frequencies for multiplexing in digital communication, in order to manage to reduce the number of errors that occur in said communication when using OFDM modulation with classic encodings, such as for example a coding with Hadamard sequences.
- One aspect of the invention relates to a method of digital transmission of information signals, which uses complementary sequences of
- the proposed coding includes the following steps: i) Convolution of each of the F data flows with the two bipolar sequences (A, B) of the Golay pair. ii) Cyclic displacement of each of the sequences resulting from the convolution performed in step i) with the first bipolar sequence (A) of the Golay pair, a certain number of times as corresponds to each data flow. The number of displacements is different for each of the sequences obtained in step i) and is always a number less than the length (L) of the sequences of the Golay pair.
- step i) are two pairs of F sequences: an F number of sequences (one for each data stream) obtained from the convolution with the first bipolar sequence (A) of the Golay pair and an equal number (F) of sequences corresponding to the convolution with the second bipolar sequence (B) of the Golay pair; where F ⁇ L (L is equal to the length of the sequences of the Golay pair (A, B)).
- steps iv) and v) are two intermediate sequences, a first intermediate sequence corresponding to the operation with the first bipolar sequence (A) of the Golay pair and a second intermediate sequence obtained from operating in the same way with the second bipolar sequence ( B) of the Golay pair.
- the proposed method can include the simultaneous transmission of more data flows using an additional pair: the orthogonal Golay pair at (A, B). For this, the convolution steps, displacements and sums described are performed, but applying the orthogonal Golay pair.
- phase modulation is also performed of the intermediate sequence resulting from the coding with the bipolar sequence (C) of the orthogonal pair, as well as quadrature modulating the result of the coding with the bipolar sequence (D), to obtain another complex signal.
- the two complex signals that result from using the two Golay pairs finally also add up. That is to say: a third intermediate sequence is obtained by adding together the sequences corresponding to the result of carrying out the convolution and displacement steps using the first bipolar sequence (C) of the orthogonal Golay pair.
- a fourth intermediate sequence is obtained by adding together the sequences corresponding to the result of carrying out the convolution and displacement steps using the second bipolar sequence (D) of the orthogonal Golay pair; if necessary, to reach a length equal to a power of two, the precise zeros are added to each of these (third and fourth) intermediate sequences; the third intermediate sequence is modulated in phase and the fourth intermediate sequence quadrature, obtaining a second complex signal; - the (first) complex signal corresponding to the pair of
- IFFT Fast Inverse Fourier Transform
- this transmission method can introduce a training signal that in reception is used to estimate the influence of the channel and be able to equalize the received signal.
- Another aspect of the invention relates to a method of receiving digital information signals, adapted to receive an input signal transmitted by the transmission method described above.
- the transmitter sends all data streams together but each receiver extracts a single data stream.
- the receiver first separates said training signal from the input signal. If a cyclic prefix added to the symbols that make up the input information signal has also been sent, said prefix is removed at reception.
- the proposed digital reception method demodulates the received signal, applying a Direct Direct Fourier Transform onto said signal. From the resulting complex signal the components corresponding to the zeros added in the transmitter are eliminated, thus obtaining a complex signal composed of two sequences: one in phase and one in quadrature of size L.
- the reception method proceeds to extract from it a data flow, which contains the communicated information, for which it uses a pair of bipolar sequences with a length (L): a first pair of complementary bipolar sequences (A, B), that is, forming a Golay pair; or, a second pair of bipolar sequences (C, D), forming an orthogonal Golay pair to the first pair.
- L length
- A, B complementary bipolar sequences
- C, D second pair of bipolar sequences
- the use of (A, B) or (C, D) depends on what is the flow of data to be extracted, that is, which Golay pair the transmitter has used to encode that particular flow.
- a first is distinguished bipolar sequence (A or C) and a second bipolar sequence (B or D).
- a first step consists in carrying out the demodulation in phase and quadrature through which the components in phase (I) and quadrature (Q) of the received signal are obtained, for then correlate each of said components with the sequence of the corresponding Golay pair.
- the reception method correlates the component in phase (I) with the corresponding bipolar sequence: the first sequence of the Golay pair, A or C, cyclically displaced a number of times equal to the displacement of the flow to be extracted.
- the correlation of the quadrature component (Q) is made with the second bipolar sequence of the pair, B or D, cyclically displaced the same number of times.
- the proposed reception method estimates the impulse response of the communication channel from the training signal. It is understood here by impulse response or impulse response Ia that the channel presents in front of a very short signal, or impulse, that is transmitted.
- the proposed reception method uses this channel estimate to equalize the received and demodulated signal (after having passed through the Fast Fourier Transform
- the reception method proceeds to the decoding to obtain a data flow containing the communicated information.
- the same bipolar sequences (A, B) or (C, D) are used, depending on the flow of data to be obtained, used in the transmitter and forming a Golay pair.
- the two bipolar sequences (A, B) of the Golay pair, or, if applicable, the other two bipolar sequences (C, D) of the orthogonal Golay pair, used to decode The received signal is subjected to a cyclic shift. The number of times each sequence moves is equal to that applied in transmission for the coding of the corresponding data flow. The sequences thus displaced are used for the correlation of the components in phase (I) and quadrature (Q) of the received signal, already explained.
- aspects of the invention are a transmitter and a digital receiver designed to be incorporated into a communications system based on modulation by orthogonal frequencies, which respectively implement the method of transmission and reception of information signals using multiplexing by complementary sequences as have described
- Figure 2. Shows a block diagram of a detail of the OFDM modulator, according to a preferred embodiment of the invention, included in the transmitter illustrated in the previous figure.
- Figure 3. Shows a schematic representation of the coding process performed on the transmitter, according to the object of
- Figure 4.- Shows a block diagram of a detail of the digital receiver that constitutes another aspect of the invention, according to a preferred embodiment.
- a "downlink" system for synchronous communication between a base station and a user terminal is described.
- the data streams that are to be multiplexed, S f [n] are encoded in a digital transmitter, partially represented in Figure 1, using complementary sequences that have a length (L) greater than or equal to the number (F) of streams of data to be transmitted for each complementary sequence used, ie, L ⁇ F.
- Each bit of information is encoded with the two members of the torque and the resulting sequences are cyclically displaced a number of times equal to one shift, d A ⁇ [f
- the results that come from the first bipolar sequence (A) are added together, as well as those that come from the second bipolar sequence (B), resulting in two sequences of length L. At this point the sequences are completed with zeros until reaching a length that is a power of two.
- the sequence resulting from the coding with the first bipolar sequence (A) is modulated in phase and the one resulting from coding with the second bipolar sequence (B) is modulated in quadrature.
- the result of the sum generated with this first bipolar sequence (A) is modulated in phase to obtain the component in phase (I).
- the encoder (1) produces the displacement of the sequences resulting from the convolution with the second bipolar sequence (B) and these are added obtaining the quadrature component (Q) of the signal to be transmitted.
- the encoder (1) can use two other bipolar sequences (C, D) that form the orthogonal Golay pair to the first and perform the same procedure as with the pair ( A, B), then adding the complex results obtained from the two Golay pairs.
- the symbols to be transmitted including in the intermediate sequences if the addition of zeros (3A) is necessary to reach a power length of two, are obtained by means of an IFFT or inverse fast Fourier transform (3B) and a prefix is added to them cyclic (3C); steps (3A, 3B, 3C) that are implemented by a modulator (3) in OFDM baseband, as illustrated in Figure 2.
- ⁇ and ⁇ are the numbers of zeros that are included respectively before and after the convoluted signal, so that ⁇ + L + ⁇ is a power of 2,
- the choice of the symbol period makes the frequencies describing the symbol orthogonal to each other, reducing interference between subchannels.
- the guard time is introduced to reduce the effect of interference between symbols and help the subchannels remain orthogonal.
- the digital transmitter proposed here additionally has a generator (2) of a training sequence, which is concatenated to the complex signal obtained after coding.
- the IFFT is applied to this signal, since both the information signal to be transmitted and the training sequence generated pass through the OFDM modulator (3).
- the training sequence generated and inserted allows the equalization of the signal that reaches the receiver.
- the signal to be transmitted is finally achieved by a parallel to series transformation (4).
- the received signal is transformed from series to parallel (5) and then separation means (6) Ia separate from said training signal before passing the input signal to a demodulator ( 7) OFDM baseband.
- the receiver estimates the impulse response of the channel (8) that averages over time for an equalizer (9) to correctly compensate for the distortion produced by the channel.
- the equalized signal passes to a decoder (10) that extracts a flow of data by executing the reverse process to that performed by the transmitter with the pair of complementary sequences (A, B) or (C, D).
- a decoder 10 that extracts a flow of data by executing the reverse process to that performed by the transmitter with the pair of complementary sequences (A, B) or (C, D).
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- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Computer Networks & Wireless Communication (AREA)
- Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
Abstract
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Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
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ES201090030A ES2380703B1 (es) | 2007-11-12 | 2007-11-12 | Metodo y dispositivo de transmision y de recepcion digital de señales de informacion |
PCT/ES2007/000640 WO2009063098A1 (es) | 2007-11-12 | 2007-11-12 | Método y dispositivo de transmisión y de recepción digital de señales de información |
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PCT/ES2007/000640 WO2009063098A1 (es) | 2007-11-12 | 2007-11-12 | Método y dispositivo de transmisión y de recepción digital de señales de información |
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Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
ES2164613A1 (es) | 2000-08-16 | 2002-02-16 | Fuente Vicente Diaz | Metodo, transmisor y receptor para comunicacion digital de espectro ensanchado mediante modulacion de secuencias complementarias golay. |
US20040202103A1 (en) * | 2003-04-08 | 2004-10-14 | Samsung Electronics Co., Ltd. | Apparatus and method for generating a preamble sequence in an OFDM communication system |
US20050152326A1 (en) * | 2004-01-08 | 2005-07-14 | Rajiv Vijayan | Frequency error estimation and frame synchronization in an OFDM system |
-
2007
- 2007-11-12 ES ES201090030A patent/ES2380703B1/es not_active Expired - Fee Related
- 2007-11-12 WO PCT/ES2007/000640 patent/WO2009063098A1/es active Application Filing
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
ES2164613A1 (es) | 2000-08-16 | 2002-02-16 | Fuente Vicente Diaz | Metodo, transmisor y receptor para comunicacion digital de espectro ensanchado mediante modulacion de secuencias complementarias golay. |
US20040202103A1 (en) * | 2003-04-08 | 2004-10-14 | Samsung Electronics Co., Ltd. | Apparatus and method for generating a preamble sequence in an OFDM communication system |
US20050152326A1 (en) * | 2004-01-08 | 2005-07-14 | Rajiv Vijayan | Frequency error estimation and frame synchronization in an OFDM system |
Non-Patent Citations (2)
Title |
---|
S. HARA; R. PRASAD: "Overview of multicarrier CDMA", IEEE COMMUNICATION MAGAZINE, vol. 35, no. 12, December 1997 (1997-12-01), pages 126 - 133, XP000858431, DOI: doi:10.1109/35.642841 |
V. DIAZ ET AL.: "An emerging technology: orthogonal time division multiplexing (OTDM)", IEEE, vol. 2, 2003, pages 133 - 136, XP010671011, DOI: doi:10.1109/ETFA.2003.1248683 |
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ES2380703A1 (es) | 2012-05-17 |
ES2380703B1 (es) | 2013-01-29 |
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