EP0938796A1 - Method for decoding complementary codes - Google Patents
Method for decoding complementary codesInfo
- Publication number
- EP0938796A1 EP0938796A1 EP97946738A EP97946738A EP0938796A1 EP 0938796 A1 EP0938796 A1 EP 0938796A1 EP 97946738 A EP97946738 A EP 97946738A EP 97946738 A EP97946738 A EP 97946738A EP 0938796 A1 EP0938796 A1 EP 0938796A1
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- EP
- European Patent Office
- Prior art keywords
- phases
- phase
- signal
- decoding
- decoding signals
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2602—Signal structure
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2614—Peak power aspects
- H04L27/2615—Reduction thereof using coding
- H04L27/2617—Reduction thereof using coding using block codes
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2614—Peak power aspects
- H04L27/2621—Reduction thereof using phase offsets between subcarriers
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2649—Demodulators
Definitions
- the invention relates to a method for decoding signals of a multi-carrier transmission method, which are encoded with complementary codes, according to the preamble of the main claim.
- OFDM Orthogonal Fequency Division Multiplexing
- Transmission linear transmitters with low efficiency are used to avoid non-linear distortion of the signals.
- the method according to the invention for decoding with the characterizing features of the main claim contains a regulation according to which the phases of the coded signal are evaluated and used for the calculation of the phases of the original signal.
- the calculation and decoding of phases that is to say "polar coordinates" gives a simple solution which requires few arithmetic operations.
- the decoding method works with high performance, the implementation effort being correspondingly low.
- a particularly simple decoding uses a weighted summation of the phase component to determine the original phases.
- the method can be optimized by weighting the phase components in proportion to the signal-to-noise ratio. In some cases it is better to choose the weighting of the phase components proportional to the ratio of the total power of the signal to the power of the phase component.
- a particularly simple sum Mation is obtained if you do not carry out weighting but set all weighting factors to one.
- An improvement in the decoding can be achieved by selecting the phase component which has the greatest weight for each partial decoding.
- a simplification with regard to the number of arithmetic operations is obtained by determining the negligible code symbols by comparing their amounts with a predetermined threshold value.
- FIG. 1 shows the schematic structure of a multi-carrier transmitter and receiver.
- a transmission signal of a multi-carrier method is considered, which is transmitted using OFDM technology.
- the method used for the transmission of digital radio signals uses differential 4-phase shift keying (DQPSK differential quadrature phase shift keying). Since it is not the phase itself, but the difference that is transmitted between two successive phases, there is a phase difference coding with eight possible carrier phases. In order to reduce the crest factor, the ratio of peak power to medium power, the independent
- y (i) (P ⁇ (i) exp ( ⁇ _ (i)), p 2 (i) exp ( ⁇ 2 (i)), ..., p N (i) exp ( ⁇ N (i))), the case being a real one (disturbed) transmission is characterized by an additional amplitude factor p v (i) e R and by ⁇ v (i) ⁇ ⁇ v (i).
- the task of decoding is to recover the information-carrying phases ⁇ p v (i).
- the received complex code symbols x v (i) e C are not used, but rather the associated phases
- the decoding is based on the solution of the system of equations (1) according to known methods e.g. the exchange procedure according to Stiefel. It is sufficient to use K of the N equations, since the remaining K equations are linearly dependent on the others as follows, i.e. in the case of an ideal transmission, they do not provide any additional information:
- the resulting decoding rule is:
- REPLACEMENT BUTT (RULE 26) the performance of the individual components related to the total performance of all sub-components is used
- Equal-gain combining is the weighted summation of the sub-components, the weighting factor being 1 for all sub-components.
- ⁇ 2 (o . [( ⁇ , (0- ⁇ 2 (' ' )) + ( ⁇ 3 (- 4 () + ( ⁇ 5 ⁇ - ⁇ 6 (0) + ( ⁇ 7 (- ⁇ 8 ( ) ]
- y ⁇ * (i) l 2 / ⁇ ⁇ / or p v 2 (i)
- y v (i) I 2 can be considered.
- y * denotes the complex conjugate value of y.
- the subcomponents are selected whose amount is greater than a certain threshold. This sub-component is used until its amount falls below the threshold. In this case, a new sub-component is determined that fulfills the selection condition.
- a simplification with regard to the number of arithmetic operations is obtained by selecting the negligible code symbols not by searching, but by comparing their amounts with a specific, predetermined threshold. The identified subset is retained during decoding until the condition is no longer met.
- decoding instructions can be implemented, for example, by means of a suitable digital signal processor (DSP).
- DSP digital signal processor
- Figure 1 shows a simplified block diagram of an OFDM transmitter and receiver.
- the information symbol a arrives in the parallel / serial converter 1 and from there into the M-stage phase shift keying PSK modulator 2. This produces a signal from the input symbol a, which is modulated in phase positions ⁇ .
- the complementary multi-phase code is applied to the signal.
- the implementation takes place e.g. through matrix multiplication as in the case of non-systematic block codes.
- a complex signal sequence x of length N arises in cathesic coordinates.
- a fast inverse Fourier transformer IFFT 4 processes the transmission signal 5.
- the transmission signal 5 is received in the receiving unit and converted via the fast Fourier transformer 6 FFT.
- the Cartesian coordinates y are converted into polar coordinates, i.e. the recovery of the phases.
- the signal is processed in block decoder 8 in accordance with the decoding specification.
- the information symbol a (i) is recovered from the decoded phases by quantization, and the signal is then converted again in parallel / serial 10. The reconstructed signal is thus present.
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
Abstract
Disclosed is a method for decoding signals from a multi-carrier system, modulated using a complementary multiphase code. The phases of the received signal are assessed and, based on these phases, those of the non encoded signal are calculated so as to retrieve the original signal.
Description
Verfahren zur Decodierung von komplementären CodesMethod for decoding complementary codes
Stand der TechnikState of the art
Die Erfindung geht aus von einem Verfahren zur Decodierung von Signalen eines Multiträger-Übertrag ngsverfahrens, die mit komplementären Codes codiert werden, nach der Gattung des Hauptanspruchs.The invention relates to a method for decoding signals of a multi-carrier transmission method, which are encoded with complementary codes, according to the preamble of the main claim.
Sendesignale bei Multiträger-Übertragungsverfahren, wie sie z.B. aus dem für den digitalen Rundfunk verwendeten Orthogonal Fequency Division Multiplexing (OFDM) bekannt sind, wei- sen eine nicht konstante Einhüllende auf. Infolge der z.B. gaußförmigen Verteilung der Einhüllenden des Sendesignals müssen Sende- und Empfangsstufen für hohe Pegel ausgelegt werden. Die Schwankungen der Einhüllenden werden durch den sogenannten Crestfaktor, dem Verhältnis aus Spitzenleistung und mittlerer Leistung, beschrieben. Es kommen bei der OFDM-Transmission signals in multi-carrier transmission methods, such as those e.g. are known from the Orthogonal Fequency Division Multiplexing (OFDM) used for digital broadcasting have a non-constant envelope. As a result of e.g. Gaussian distribution of the envelope of the transmission signal, transmission and reception stages must be designed for high levels. The fluctuations in the envelope are described by the so-called crest factor, the ratio of peak power to medium power. The OFDM-
Übertragung lineare Sendeverstärker mit niedrigem Wirkungsgrad zum Einsatz, um nichtlineare Verzerrungen der Signale zu vermeiden.Transmission linear transmitters with low efficiency are used to avoid non-linear distortion of the signals.
Aus der Veröffentlichung "Minimisation of the Peak-to-Mean Envelope Power Ration of Multicarrier Transmission Schemeε by Block Coding", T.A. Wilkinson, A.E. Jones, Proc . IEEE Ve- hicular Technology Conference S. 825-829, 1995, ist bekannt,
daß der Crestfaktor des Signals mit komplementären Codes deutlich reduziert werden kann.From the publication "Minimization of the Peak-to-Mean Envelope Power Ration of Multicarrier Transmission Schemeε by Block Coding", TA Wilkinson, AE Jones, Proc. IEEE Vehicular Technology Conference pp. 825-829, 1995, is known that the crest factor of the signal can be significantly reduced with complementary codes.
Vorteile der ErfindungAdvantages of the invention
Das erfindungsgemäße Verfahren zur Decodierung mit den kennzeichnenden Merkmalen des Hauptanspruchs enthält eine Vorschrift, nach der die Phasen des codierten Signals ausgewertet und für die Berechnung der Phasen des ursprünglichen Si- gnals herangezogen werden. Durch die Berechnung und Decodierung von Phasen, also von „Polarkoordinaten" erhält man einen einfachen Lösungsweg, der wenige Rechenoperationen erfordert. Das Decodierverfahren arbeitet mit hoher Leistungsfähigkeit, wobei der Implementierungsaufwand entsprechend gering ist.The method according to the invention for decoding with the characterizing features of the main claim contains a regulation according to which the phases of the coded signal are evaluated and used for the calculation of the phases of the original signal. The calculation and decoding of phases, that is to say "polar coordinates", gives a simple solution which requires few arithmetic operations. The decoding method works with high performance, the implementation effort being correspondingly low.
Weiterhin ist es vorteilhaft, daß zur Decodierung eine geringere Verstärkung erforderlich ist. Dies ist deshalb der Fall, weil aufgrund des reduzierten Crestfaktors die Sende- verstärker höher ausgesteuert werden können, was den Wir- kungsgrad erhöht. Die Sendeleistung ist daher bei gleichem Aufbau des Senders höher, so daß der Aufwand beim Empfänger zu reduzieren ist.It is also advantageous that a lower gain is required for decoding. This is the case because, due to the reduced crest factor, the transmit amplifiers can be modulated to a higher level, which increases the efficiency. The transmission power is therefore higher with the same structure of the transmitter, so that the effort for the receiver can be reduced.
Durch die in den Unteransprüchen aufgeführten Maßnahmen sind vorteilhafte Weiterbildungen und Verbesserungen des im Hauptanspruch angegebenen Verfahrens möglich.Advantageous further developments and improvements of the method specified in the main claim are possible through the measures listed in the subclaims.
Eine besonders einfache Decodierung verwendet eine gewichte- te Summation der Phasenkomponente zur Bestimmung der ur- sprünglichen Phasen. Das Verfahren kann durch die Gewichtung der Phasenkomponenten proportional zum Signal- Rauschverhältnis optimiert werden. In machen Fällen ist es besser, die Gewichtung der Phasenkomponenten proportional zum Verhältnis der Gesamtleistung des Signals zur Leistung der Phasenkomponente zu wählen. Eine besonders einfache Sum-
mation erhält man, wenn man keine Gewichtung durchführt sondern alle Gewichtungsfaktoren zu eins setzt.A particularly simple decoding uses a weighted summation of the phase component to determine the original phases. The method can be optimized by weighting the phase components in proportion to the signal-to-noise ratio. In some cases it is better to choose the weighting of the phase components proportional to the ratio of the total power of the signal to the power of the phase component. A particularly simple sum Mation is obtained if you do not carry out weighting but set all weighting factors to one.
Eine Verbesserung der Decodierung kann dadurch erreicht wer- den, daß für jede Teildecodierung die Phasenkomponente ausgewählt wird, welche das größte Gewicht aufweist. Eine Vereinfachung bezüglich der Anzahl der Rechenoperationen erhält man, indem die vernächlässigbaren Codesymbole durch Vergleich deren Beträge mit einem vorgegebenen Schwellwert be- stimmt werden.An improvement in the decoding can be achieved by selecting the phase component which has the greatest weight for each partial decoding. A simplification with regard to the number of arithmetic operations is obtained by determining the negligible code symbols by comparing their amounts with a predetermined threshold value.
Zeichnungdrawing
Ein Ausführunσsbeiεpiel der Erfindung ist in der Zeichnung dargestellt und in der nachfolgenden Beschreibung näher erläutert. Es zeigt Figur 1 den schematischen Aufbau eines Multiträgersenders und Empfängers.An exemplary embodiment of the invention is shown in the drawing and explained in more detail in the description below. FIG. 1 shows the schematic structure of a multi-carrier transmitter and receiver.
Beschreibung des AusführungsbeispielsDescription of the embodiment
Betrachtet wird im folgenden Beispiel ein Sendesignal eines Multitragerverfahrens, das nach OFDM-Technik übertragen wird. Das für die Übertragung von digitalen Rundfunksignalen verwendete Verfahren verwendet eine differentielle 4-Phasen- Umtastung (DQPSK Differential Quadratur Phase Shift Keying) . Da nicht die Phase selbst, sondern die Differenz zwei aufeinanderfolgenden Phasen übertragen wird ergibt sich eine Phasendifferenzcodierung mit acht möglichen Trägerphasen. Um den Crestfaktor, das Verhältnis aus Spitzenleistung und mittlerer Leistung zu reduzieren, werden die unabhängigenIn the following example, a transmission signal of a multi-carrier method is considered, which is transmitted using OFDM technology. The method used for the transmission of digital radio signals uses differential 4-phase shift keying (DQPSK differential quadrature phase shift keying). Since it is not the phase itself, but the difference that is transmitted between two successive phases, there is a phase difference coding with eight possible carrier phases. In order to reduce the crest factor, the ratio of peak power to medium power, the independent
Phasen φv (i) , v=l, ...K, die in unserem Beispiel K=4 betragen, auf N=8 Phasen θμ (i) , μ=l, 2 , ...N, zum Zeitpunkt i mittels der Vorschrift abgebildet:
θ,( ) = φ1( +φ2( +φ3( +φ4(0 θ2(/) = φ,( )+φ3( )+φ4( θ3( = φ,(0+φ2 φ4 ') θ4( = ψjC +φ^ +πPhases φ v (i), v = 1, ... K, which in our example are K = 4, on N = 8 phases θμ (i), μ = 1, 2, ... N, at time i using depicted in the regulation: θ, () = φ 1 ( + φ 2 ( + φ 3 ( + φ 4 (0 θ 2 (/) = φ, () + φ 3 () + φ 4 (θ 3 (= φ, (0 + φ 2 φ 4 ' ) θ 4 (= ψ j C + φ ^ + π
(1) θ5( = φ1( )+φ2( +φ3( ) θ6( = φ,( +φ3( θ7( ) = φ,( )+φ2( )-π θ8( = φ,((1) θ 5 (= φ 1 () + φ 2 (+ φ 3 () θ 6 (= φ, ( + φ 3 (θ 7 () = φ, () + φ 2 () -π θ 8 ( = φ, (
Es wird eine M-stufige PSK Modulation zugrundegelegt, wodurch die informationstragenden Phasen durch φv(i) =av(i) 2π/M, ave"ι 0, 1...M-l^, v=l,...K, gegeben sind, und av(i) die durch log2 (M) binären Informationssymbolen determinierten, zugehörigen Signalpunkte darstellen. Damit wird ein Informationswort der Länge K auf ein Codewort der Länge N abgebildet. Das gesendete Codewort ist dementsprechend durch x(i) = (exp (θ1 (i) ) , exp (θ (i) ) , . • • , exp(θN(i))) gegeben. Das empfangene Codewort wird im folgenden mit y(i) = (Pι (i)exp(φι_ (i) ) , p2 (i)exp(φ2(i) ) , ... , pN (i) exp (φN(i) ) ) bezeichnet, wobei der Fall einer realen (gestörten) Übertragung durch einen zusätzlichen Amplitudenfaktor pv(i)e R und durch φv(i)≠θv(i) charakterisiert wird.An M-stage PSK modulation is used, whereby the information-carrying phases are characterized by φ v (i) = a v (i) 2π / M, a v e "ι 0, 1 ... Ml ^, v = l, .. .K, and a v (i) represent the associated signal points determined by log 2 (M) binary information symbols. Thus, an information word of length K is mapped onto a code word of length N. The transmitted code word is accordingly represented by x ( i) = (exp (θ 1 (i)), exp (θ (i)),. • •, exp (θ N (i))). The code word received is given below with y (i) = (Pι (i) exp (φι_ (i)), p 2 (i) exp (φ 2 (i)), ..., p N (i) exp (φ N (i))), the case being a real one (disturbed) transmission is characterized by an additional amplitude factor p v (i) e R and by φ v (i) ≠ θ v (i).
Im Fall einer idealen Übertragung (verzerrungsfreie Übertragung) wird das gesendete Codewort fehlerfrei empfangen, d.h. y(i)=x(i). Aufgabe der Decodierung ist die Zurückgewinnung der informationstragenden Phasen <pv(i). Hierzu werden nicht die empfangenen, komplexen Codesymbole xv(i) e C verwendet, sondern vielmehr die zugehörigen PhasenIn the case of an ideal transmission (distortion-free transmission), the transmitted code word is received without errors, ie y (i) = x (i). The task of decoding is to recover the information-carrying phases <p v (i). For this purpose, the received complex code symbols x v (i) e C are not used, but rather the associated phases
(Θ-L (i) , θ2 (i) , • • .θN(i) ) , wobei der konstante Term π in (1) allein zur Reduktion des Crestfaktors dient, und dementspre-(Θ-L (i), θ 2 (i), • • .θ N (i)), whereby the constant term π in (1) serves only to reduce the crest factor, and accordingly
ERSATZBLÄΪT(REGEL 26)
chend vor der Decodierung durch entsprechende Subtraktion wegfällt .SPARE BLADE (RULE 26) before decoding by appropriate subtraction.
Die Decodierung basiert auf die Lösung des Gleichungssystems (1) nach bekannten Verfahren z.B. dem Austauschverfahren nach Stiefel. Hierbei genügt es, K der N Gleichungen heranzuziehen, da die restlichen K Gleichungen wie folgt von den anderen linear abhängig sind, d.h. sie liefern im Fall einer idealen Übertragung keine zusätzliche Information:The decoding is based on the solution of the system of equations (1) according to known methods e.g. the exchange procedure according to Stiefel. It is sufficient to use K of the N equations, since the remaining K equations are linearly dependent on the others as follows, i.e. in the case of an ideal transmission, they do not provide any additional information:
θ4() = -θ,( +θ2(0+θ3( e6 = -Θ,( +Θ2( -Θ5(θ 4 () = -θ, (+ θ 2 (0 + θ 3 (e 6 = -Θ, (+ Θ 2 (-Θ 5 (
(2) θ7( = -θ,(0+θ3(0+θ5(0 θ8(ι) = -2θ,(0+θ2(/)+θ3(/)-θ5(ι)(2) θ 7 (= -θ, (0 + θ 3 (0 + θ 5 (0 θ 8 (ι) = -2θ, (0 + θ 2 (/) + θ 3 (/) - θ 5 (ι )
Die resultierende Decodiervorschrift lautet :The resulting decoding rule is:
φ,( = -2θ,( +θ2()+θ3( +θ5( φ2( = θ,(/)-θ2(/)φ, (= -2θ, (+ θ 2 () + θ 3 (+ θ 5 (φ 2 (= θ, (/) - θ 2 (/)
(3a)
φ4(0 = θ,( )-θ5(/)(3a) φ 4 (0 = θ, () -θ 5 (/)
oderor
φ2(0 = Θ, ( ) -Θ2(Oφ 2 (0 = Θ, () -Θ 2 (O
9,(0 = θ,(0-φ2(0-φ3(0-φ4(0 •9, (0 = θ, (0-φ 2 (0-φ 3 (0-φ 4 (0 •
ERSATZBUTT (REGEL 26)
Für die Phasendifferenzen in (3) ergeben sich aus (2) und (1) infolge der linearen Abhängigkeit weiterhin die Identitäten:REPLACEMENT BUTT (RULE 26) For the phase differences in (3), the identities result from (2) and (1) due to the linear dependency:
θ,(0-θ2 (0 = θ3 ()-θ4(0 = θ5(0-θ6(0 = θ7(0-θ8(0 θ,(0-θ3(0 = θ2 (0-θ4 (0 = θ5(0-θ7(0 = θ6(0-θ8(0) θ,(0-θ5 (0 = θ2 (0-θ6 (0 = θ3(0-θ7(0 = θ4(0-θ8(0 (4) θ,(0-φ2 (0-φ3 (0-φ(4) = θ2 (/)-φ3(0-φ(0 = θ3(0-φ,(0-φ4(0 = θ4(ι φ4(0θ, ( 0-θ 2 ( 0 = θ 3 () -θ 4 (0 = θ 5 (0-θ 6 (0 = θ 7 (0-θ 8 (0 θ, ( 0-θ 3 (0 = θ 2 ( 0-θ 4 ( 0 = θ 5 (0-θ 7 (0 = θ 6 (0-θ 8 (0) θ, ( 0-θ 5 ( 0 = θ 2 ( 0-θ 6 ( 0 = θ 3 (0-θ 7 (0 = θ 4 (0-θ 8 (0 (4) θ, ( 0-φ 2 ( 0-φ 3 ( 0-φ ( 4 ) = θ 2 (/) -φ 3 ( 0-φ (0 = θ 3 (0-φ, (0-φ 4 (0 = θ 4 (ι φ 4 (0
= θ5 (0-φ2 (0-φ3 (0 = θ6 (0-φ3(0 = θ7(0-φ2(0 = θ8(0.= θ 5 ( 0-φ 2 ( 0-φ 3 ( 0 = θ 6 ( 0-φ 3 (0 = θ 7 (0-φ 2 (0 = θ 8 (0.
Im Fall einer realen (gestörten) Übertragung weichen die empfangenen Phasen von den gesendeten Phasen ab, d.h. φv(i)≠θv(i). Dieses impliziert, daß die Identitäten (2) bzw. (4) nicht mehr gegeben sind, d.h. die im Idealfall linear abhängigen Phasen beinhalten zusätzliche InformationIn the case of a real (disturbed) transmission, the received phases differ from the transmitted phases, ie φ v (i) ≠ θ v (i). This implies that identities (2) and (4) no longer exist, ie the ideally linearly dependent phases contain additional information
(Diversityeffekt) , welche zur Optimierung der Decodierung des komplementären Codes herangezogen werden können. Betrachtet man die Decodiervorschrift (3) im Zusammenhang mit (4) , so ergibt sich durch entsprechende Kombination einzel- ner Teilkomponenten (Phasendifferenzen) eine Vielzahl möglicher Vorschriften zur Decodierung der empfangenen Phasen.(Diversity effect), which can be used to optimize the decoding of the complementary code. If one considers the decoding rule (3) in connection with (4), a corresponding combination of individual sub-components (phase differences) results in a large number of possible regulations for decoding the received phases.
In Analogie zu bekannten Antennen-Diversityverfahren können die folgenden Strategien zur Decodierung angewandt werden:In analogy to known antenna diversity methods, the following strategies for decoding can be used:
- Maximum-ratio combining ist die gewichtete Summation der Teilkomponenten, wobei die Gewichtung proportional zum Signal-Rausch-Verhältnis (S/N-Verhältnis) der einzelnen Teilkomponenten erfolgt. Anstatt des S/N-Verhältnis kann auch- Maximum-ratio combining is the weighted summation of the sub-components, the weighting being proportional to the signal-to-noise ratio (S / N ratio) of the individual sub-components. Instead of the S / N ratio, too
ERSATZBUTT(REGEL 26)
die auf die Gesamtleistung aller Teilkomponenten bezogene Leistung der einzelnen Komponenten verwendet werden.REPLACEMENT BUTT (RULE 26) the performance of the individual components related to the total performance of all sub-components is used
Φ3(0 = α13(')(Φ1(0-φ3( )+o24(0(Φ2(0-φ4(0)+ 57(0(Φ5(0-φ7(0) +α68(0(Φ6( -φ8(0) Φ4(0 = α15( (Φ1(0-φ5(0) +α26(0(Φ2ω-φ6(0) +α37(0(Φ3(0-φ7(0)+α48(0(Φ4 -)-φ8ω)Φ 3 (0 = α 13 (') (Φ 1 (0-φ 3 () + o 24 (0 (Φ 2 (0-φ 4 (0) + 57 (0 (Φ 5 (0-φ 7 (0 ) + α 68 (0 (Φ 6 (-φ 8 (0) Φ 4 (0 = α 15 ((Φ 1 (0-φ 5 (0) + α 26 (0 (Φ 2 ω-φ 6 (0) + α 37 (0 (Φ 3 (0-φ 7 (0) + α 48 (0 (Φ 4 -) - φ 8 ω)
Φ,(0 = ,(0(Φ1 (0-φ2 (0-φ3 (0-φ4 '))+α2 (0(Φ2 (0-φ3 ( -φ4 (0)+α3 ( (Φ3( -φ2 ( -φ4 ()) + +α4(0(φ4(0-φ4 ')) +α5(Φ5(0-φ2(0-φ3(0) + 6(0(Φ6(0-φ3( ) + 7(0(Φ7 (0"Φ2 (0) + +α8 (0Φ8(0 • (5) mitΦ, ( 0 =, ( 0 ( Φ 1 ( 0-φ 2 ( 0-φ 3 ( 0-φ 4 ')) + α 2 ( 0 ( Φ 2 ( 0-φ 3 ( -φ 4 ( 0 ) + α 3 (( Φ3 ( -φ 2 ( -φ 4 ()) + + α 4 (0 (φ 4 (0-φ 4 ' )) + α 5 (Φ 5 (0-φ 2 (0-φ 3 ( 0) + 6 (0 (Φ 6 (0-φ 3 () + 7 (0 (Φ 7 ( 0 "Φ 2 ( 0 ) + + α 8 ( 0Φ 8 (0 • (5) with
2 α (i) = PvO) Λ'V ' ' (6b)2 α (i) = PvO) Λ 'V''(6b)
- Equal-gain combining ist die gewichtete Summation der Teilkomponenten, wobei der Gewichtungsfaktor 1 für alle Teilkomponenten beträgt.- Equal-gain combining is the weighted summation of the sub-components, the weighting factor being 1 for all sub-components.
Φ2(o = .[(Φ,(0-Φ2(''))+(Φ3( - 4( )+(Φ5ω-Φ6(0)+(Φ7( -Φ8 ( )]Φ 2 (o =. [(Φ, (0-Φ 2 ('' )) + (Φ 3 (- 4 () + (Φ 5 ω-Φ 6 (0) + (Φ 7 (-Φ 8 ( ) ]
Φ3(o +CΦβ j-Φgω)]
Φ 3 (o + CΦβ j-Φgω ) ]
Φ4(O = .[(Φ1 ( -Φ5 ( )+(Φ2( -Φ6 ( )+(Φ3 ( -Φ7 '))+(Φ4( -Φ8 ( )] (7) Φ 4 (O = . [(Φ 1 ( -Φ 5 () + (Φ 2 (-Φ 6 () + (Φ 3 ( -Φ7 ' )) + ( Φ4 ( -Φ 8 ()] (7)
φ, (0 = i[(φ , (0 -Φ2( -Φ3( -Φ4( ) + (Φ 2 (0 -Φ3 (0 -Φ4( ) + (Φ 3« -Φ2( -<M ) + oφ, (0 = i [(φ, (0 -Φ 2 (-Φ 3 (-Φ 4 () + (Φ 2 ( 0 -Φ 3 ( 0 -Φ 4 ( ) + ( Φ 3 «-Φ 2 ( - <M ) + o
+(Φ4(0-Φ4(0) +(Φ5(0-φ2ω-φ3( ) +(Φ6(0-Φ3 ( ) +(Φ7 (0-Φ2W) +Φ8 (')] -
- Selective combining: Es wird die Teilkomponente mit den größten S/N-Verhältnis ausgewählt, wobei in der Praxis der Betrag anstatt des S/N-Verhältnis herangezogen wird. Die Auswahl der empfangenen, redundanten Codesymbole yv(i) kann nicht beliebig erfolgen, sondern es muß gewährleistet werden, daß mindestens eine Teilkomponente pro individuelle Vorschrift zur Zurückgewinnung der Informationsphasen φv(i) vorhanden sein muß. Hierzu ist folgende Strategie denkbar: + (Φ 4 (0-Φ 4 (0 ) + ( Φ 5 (0-φ 2 ω-φ 3 () + (Φ 6 (0-Φ 3 ( ) + ( Φ 7 ( 0-Φ 2 W ) + Φ 8 ( ' ) ] - - Selective combining: The subcomponent with the largest S / N ratio is selected, whereby in practice the amount is used instead of the S / N ratio. The selection of the received, redundant code symbols y v (i) cannot be made arbitrarily, but it must be ensured that at least one sub-component per individual regulation must be available for the recovery of the information phases φ v (i). The following strategy is conceivable for this:
Für jede Teildecodiervorschrift wird die Teilkomponente ausgewählt, welche den größten Gewicht αv„(i) bzw. αv(i) aufweist, wobei vereinfachend das Produkt pv 2 (i) p„2 (i) =- lyv(i)yμ* (i)l 2/ ≠μ/ bzw. pv 2 (i) =| yv (i) I 2 betrachtet werden kann. Hierbei bezeichnet y* den komplex konjugierten Wert von y.For each partial decoding rule, the subcomponent is selected which has the greatest weight α v "(i) or α v (i), the product p v 2 (i) p" 2 (i) = - ly v (i) being simplified. yμ * (i) l 2 / ≠ μ / or p v 2 (i) = | y v (i) I 2 can be considered. Here y * denotes the complex conjugate value of y.
- Scanning diversity: Es wird die Teilkomponenten gewählt, deren Betrag größer als eine bestimmte Schwelle ist. Diese Teilkomponente wird solange verwendet, bis deren Betrag die Schwelle unterschreitet. In diesem Fall wird eine neue Teilkomponente bestimmt, welche die Auswahlbedingung erfüllt. Eine Vereinfachung bezüglich der Anzahl der Rechenoperationen erhält man, indem die vernachlässigbaren Codesymbole nicht durch Suche ausgewählt werden, sondern durch Vergleich deren Beträge mit einer bestimmten, vorgegebenen Schwelle. Die identifizierte Teilmenge wird solange bei der Decodierung beibehalten, bis die Bedingung nicht mehr erfüllt ist.- Scanning diversity: The subcomponents are selected whose amount is greater than a certain threshold. This sub-component is used until its amount falls below the threshold. In this case, a new sub-component is determined that fulfills the selection condition. A simplification with regard to the number of arithmetic operations is obtained by selecting the negligible code symbols not by searching, but by comparing their amounts with a specific, predetermined threshold. The identified subset is retained during decoding until the condition is no longer met.
Da (6) und (7) ein Mittelungεprozeß bezüglich der Phasenkom- ponenten darstellt, müssen zusätzliche Maßnahmmen getroffen werden, um das korrekte Ergebnis infolge der Phasenmehrdeutigkeit zu erhalten.
Die Implementierung der obigen Decodiervorschriften kann z.B. mittels eines geeigneten digitalen Signalprozessors (DSP) erfolgen.Since (6) and (7) represent an averaging process with regard to the phase components, additional measures must be taken in order to obtain the correct result due to the phase ambiguity. The above decoding instructions can be implemented, for example, by means of a suitable digital signal processor (DSP).
Figur 1 zeigt ein vereinfachtes Blockschaltbild eines OFDM- Senders und -Empfängers. Das Informationssymbol a gelangt in den Parallel/Seriell-Wandler 1 und von dort in den M- stufigen Phase Shift Keying PSK-Modulator 2. Dadurch wird aus dem Eingangssymbol a ein Signal gewonnen, das in Phasen- lagen φ moduliert ist. Im Blockencoder 3 wird der komplementäre Multi Phasencode auf das Signal aufgebracht. Der Elock- encoder bildet K unabhängige Phasen auf N Phasen ab, wobei die Coderate R=K+N beträgt. Die Realisierung erfolgt z.B. durch Matrixmultiplikation wie im Fall nicht systematischer Blockcodes. Es entsteht eine komplexe Signalfolge x der Länge N in kathesischen Koordinaten. Ein schneller inverser Fouriertransformator IFFT 4 bereitet das Sendesignal 5 auf. In der Empfangseinheit wird das Sendesignal 5 empfangen und über den schnellen Fouriertransformator 6 FFT gewandelt. In der Einheit 7 erfolgt die Umwandlung der kartesischen Koordinaten y in Polarkoordinaten, d.h. die Rückgewinnung der Phasen. Im Blockdecoder 8 wird das Signal entsprechend der Decodiervorschrift bearbeitet. Im Entεcheider 9 durch Quantisierung aus den decodierten Phasen das Informationssymbol a (i) zurückgewonnen und das Signal anschließend wieder parallel/seriell 10 gewandelt .Damit liegt das rekonstruierte Signal ä vor.
Figure 1 shows a simplified block diagram of an OFDM transmitter and receiver. The information symbol a arrives in the parallel / serial converter 1 and from there into the M-stage phase shift keying PSK modulator 2. This produces a signal from the input symbol a, which is modulated in phase positions φ. In the block encoder 3, the complementary multi-phase code is applied to the signal. The Elock encoder maps K independent phases to N phases, the code rate being R = K + N. The implementation takes place e.g. through matrix multiplication as in the case of non-systematic block codes. A complex signal sequence x of length N arises in cathesic coordinates. A fast inverse Fourier transformer IFFT 4 processes the transmission signal 5. The transmission signal 5 is received in the receiving unit and converted via the fast Fourier transformer 6 FFT. In unit 7 the Cartesian coordinates y are converted into polar coordinates, i.e. the recovery of the phases. The signal is processed in block decoder 8 in accordance with the decoding specification. In the decider 9, the information symbol a (i) is recovered from the decoded phases by quantization, and the signal is then converted again in parallel / serial 10. The reconstructed signal is thus present.
Claims
1. Verfahren zur Decodierung von Signalen eines Multiträgerüber- tragungsverfahrens (OFDM) , wobei die zu sendenden Informationen ( aL) mit einem komplementären Multiphasen-Code codiert und abgesendet werden, dadurch gekennzeichnet, daß1. A method for decoding signals of a multi-carrier transmission method (OFDM), the information to be transmitted (a L ) being encoded and sent with a complementary multi-phase code, characterized in that
- die Phasen (φi) des empfangenen, codierten Signals (5) ausgewertet werden- The phases (φi) of the received, encoded signal (5) are evaluated
- und aus diesen Phasen (φ die Phasen (φ ) der erhaltenen, un- codierten Informationen (aL) berechnet werden.- and from these phases (φ the phases (φ) of the received, non-coded information (a L ) are calculated.
2. Verfahren zur Decodierung von Signalen nach Anspruch 1, dadurch gekennzeichnet, daß die Phasen (φi) durch eine gewichtete Summation der Phasenkomponenten (φi) in der linaren Beziehung ermittelt werden.2. A method for decoding signals according to claim 1, characterized in that the phases (φi) are determined by a weighted summation of the phase components (φi) in the linear relationship.
3. Verfahren zur Decodierung von Signalen nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Gewichtung der Phasenkompo- nenten (φi) proportional zum Signal/Rausch-Verhältnis der Pha- senkomponenten erfolgt.3. A method for decoding signals according to claim 1 or 2, characterized in that the weighting of the phase components (φi) is proportional to the signal / noise ratio of the phase components.
4. Verf hren zur Decodierung von Signalen nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Gewichtung der Phasenkompo- nenten (φ proportional zum Verhältnis der Gesamtleitung des Signals zur Leistung der Phasenkomponente erfolgt.4. Procedure for decoding signals according to claim 1 or 2, characterized in that the weighting of the phase compo- nenten (φ proportional to the ratio of the overall conduction of the signal to the power of the phase component.
5. Verfahren zur Decodierung von Signalen nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß der Gewichtungsfaktor für alle5. A method for decoding signals according to claim 1 or 2, characterized in that the weighting factor for all
Phaεenkomponenten (φL) eins beträgt.Phase components (φ L ) is one.
6. Verfahren zur Decodierung von Signalen nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Phasendifferenz mit dem grδß- ten Signal/Rausch-Verhältnis zur Berechnung der Phasen (φx) herangezogen wird.6. A method for decoding signals according to claim 1 or 2, characterized in that the phase difference with the largest signal / noise ratio is used to calculate the phases (φ x ).
7. Verfahren zur Decodierung von Signalen nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Phasendifferenz, deren Betrag einen bestimmten Schwellwert überschreitet, zur Berechnung der Phasen (φ herangezogen wird. 7. A method for decoding signals according to claim 1 or 2, characterized in that the phase difference, the amount of which exceeds a certain threshold value, is used to calculate the phases (φ.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19646299A DE19646299A1 (en) | 1996-11-11 | 1996-11-11 | Method for decoding complementary codes |
| DE19646299 | 1996-11-11 | ||
| PCT/DE1997/002437 WO1998021860A1 (en) | 1996-11-11 | 1997-10-22 | Method for decoding complementary codes |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| EP0938796A1 true EP0938796A1 (en) | 1999-09-01 |
Family
ID=7811157
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP97946738A Withdrawn EP0938796A1 (en) | 1996-11-11 | 1997-10-22 | Method for decoding complementary codes |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0938796A1 (en) |
| JP (1) | JP2001504289A (en) |
| DE (1) | DE19646299A1 (en) |
| WO (1) | WO1998021860A1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6452958B1 (en) | 1996-07-30 | 2002-09-17 | Agere Systems Guardian Corp | Digital modulation system using extended code set |
| US6404732B1 (en) | 1996-07-30 | 2002-06-11 | Agere Systems Guardian Corp. | Digital modulation system using modified orthogonal codes to reduce autocorrelation |
| US5862182A (en) | 1996-07-30 | 1999-01-19 | Lucent Technologies Inc. | OFDM digital communications system using complementary codes |
| DE102005059566B4 (en) * | 2005-12-13 | 2022-04-21 | Brueninghaus Hydromatik Gmbh | Device and method for condition-based maintenance of hydrostatic displacement units |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5862182A (en) * | 1996-07-30 | 1999-01-19 | Lucent Technologies Inc. | OFDM digital communications system using complementary codes |
-
1996
- 1996-11-11 DE DE19646299A patent/DE19646299A1/en not_active Withdrawn
-
1997
- 1997-10-22 WO PCT/DE1997/002437 patent/WO1998021860A1/en not_active Application Discontinuation
- 1997-10-22 JP JP52202098A patent/JP2001504289A/en active Pending
- 1997-10-22 EP EP97946738A patent/EP0938796A1/en not_active Withdrawn
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| See references of WO9821860A1 * |
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| Publication number | Publication date |
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| DE19646299A1 (en) | 1998-05-14 |
| WO1998021860A1 (en) | 1998-05-22 |
| JP2001504289A (en) | 2001-03-27 |
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