PatentDe  


Dokumentenidentifikation EP1207657 13.12.2007
EP-Veröffentlichungsnummer 0001207657
Titel Verfahren und Vorrichtung zur Detektion phasenmodulierter CCK-Symbole mit einer Korrelatorbank
Anmelder Lucent Technologies Inc., Murray Hill, N.J., US
Erfinder Awater, Geert Arnout, 3511 PX Utrecht, NL;
Kopmeiners, Robert John, 7555 GH Hengelo, NL;
Van Nee, Didier Johannes Richard, 3454 XR De Meern, NL
Vertreter Klunker, Schmitt-Nilson, Hirsch, 80797 München
DE-Aktenzeichen 60036949
Vertragsstaaten DE, GB
Sprache des Dokument EN
EP-Anmeldetag 20.11.2000
EP-Aktenzeichen 003102902
EP-Offenlegungsdatum 22.05.2002
EP date of grant 31.10.2007
Veröffentlichungstag im Patentblatt 13.12.2007
IPC-Hauptklasse H04L 23/02(2006.01)A, F, I, 20051017, B, H, EP
IPC-Nebenklasse H04L 27/227(2006.01)A, L, I, 20051017, B, H, EP   

Beschreibung[en]

The invention relates to a method for the detection of a symbol from a received signal wherein the symbol is a selected symbol out of a predetermined set of symbols, wherein each symbol of the predetermined set is a Complementary Code Keying, CCK symbol comprising a sequence of chips wherein each of the chips is PSK-modulated according to a selected modulation code wherein each of the selected modulation codes comprises a first sub-modulation code which is a selection from a plurality of first sets of predetermined phase modulating elements and a second sub-modulation code which is a selection from one second set of predetermined phase modulating elements wherein at least one of said predetermined phase modulating elements of said second set is a complex value such as defined in the high speed IEEE 802.11b standard, wherein a modulation code is selected from said modulation codes which correlates according to a correlation method with the received signal.

The invention also relates to an apparatus for the detection of a symbol from a received signal wherein the symbol is a selected symbol out of a predetermined set of symbols, wherein each symbol of the predetermined set is a CCK symbol comprising a sequence of chips wherein each of the chips is PSK-modulated according to a selected modulation code wherein each of the selected modulation codes comprises a first sub-modulation code which is a selection from a plurality of first sets of predetermined phase modulating elements and a second sub-modulation code which is a selection from one second set of predetermined phase modulating elements wherein at least one of said predetermined phase modulating elements of said second set is a complex value such as defined in the high speed IEEE 802.11b standard, the apparatus comprising correlating means for correlating the received signal with said modulation codes according to a correlation method and means for selecting a modulation code from said modulation codes on the basis of the correlation.

Methods and apparatus of this type are known in practice. Usually methods and apparatus of this type use a bank of correlators which is employed in the receiver. On the basis of the correlation results with the received signal, which is performed in the bank of correlators, the symbol of the received signal can be detected. For this detection the output of each correlator is the input argument of a mathematical function. The mathematical function is maximum for the correlator corresponding to the maximum function. According to said method and apparatus, which uses a pre-determined set of symbols, the symbol detection can be performed in such a way that it minimizes sensitivity to noise in the received signal. Examples of possible pre-determined sets of symbols are given in the high speed standard in the IEEE 802.11b standard. This IEEE 802.11b standard is especially meant for the 2.4 [GHz] band, also called Industrial Scientific Medical Band (ISMB-band), in the United States. It is noticed that corresponding bands are available in most other regions in the world. Users have free access to the ISMB-band if they comply with the standards of the standard proposal. A first important issue of the standard proposal is that the each used symbol has a relatively flat frequency power spectrum, which minimises risks of jamming fellow-users. A second important issue of the IEEE 802.11b standard is that not all possible symbols in the pre-determined set of symbols are used. This results in a redundant and robust detection mechanism.

A first disadvantage of the known methods and apparatus for the detection of a symbol of a received signal is the large number of correlators which are used in the correlator-bank. A second disadvantage of the type of known methods and apparatus is the large processing power which is required for performing the mathematical function, which function is used for the selection of a correlator in the correlator-bank, and operates on the complex output of each of the correlators. This mathematical function normally calculates the length of complex input argument, which leads to at least two multiplications per correlator. In order to reduce the processing power several approximations of said mathematical function have been proposed. However, these approximations only yields sub-optimal detection performance.

It is an object of the invention to realise a reduction of the number of correlators in the correlation- bank. It is also an object of the invention to reduce the required processing power for the evaluation of said mathematical function. Furthermore it is an object of the invention to obtain an optimal detection performance. More in particular it is an object of the invention to offer a detection method which, despite the reduction in the number of correlators and the reduction in the required processing power of the mathematical function, yields the performance of a maximum likelihood detection method. Finally, the invention seeks a method having the advantages stated above which can be used for receive-signals which comply with IEEE 802.11. For this, the method according to the invention is characterised in that the method comprises at least the following steps:

  • a. correlating the received signal with each of the possible first sub-modulation codes for obtaining first correlation results and selecting a correlation result;
  • b. phase-modulating the selected first correlation result with one of said possible second sub-modulation codes for each possible second sub-modulation code for obtaining second correlation results;
  • c. selecting the maximum second correlation result from the second correlation results;
  • d. selecting the symbol of the received signal on the basis of a combination the first and second correlating results.
In the method according to the invention two main parts of the correlation method can be distinguished. In the first part the first correlation results are determined and in the second part the second correlation results are determined. The second correlation results are obtained by rotating one selected first correlation result to several positions in the complex plane. Since the second part only comprises processing of one selected first correlation result this yields a reduction in required processing power compared with a situation wherein each first correlation result has to be rotated in the complex plane.

A further embodiment of the method according to the invention is characterised in that in step a. for each first correlation result the value of a function of the correlation result is determined and subsequently the first correlation result which provides the maximum value of the function is selected wherein the function is determined by the type of modulation of the second sub-modulation code. Preferably the function is a function of the real and/or imaginary parts of the first correlation result. The evaluation of this function requires less processing power than conventional functions wherein the length of a complex correlation result is calculated, while still leading the optimal Maximum Likelihood Detection symbol.

In an advantageous embodiment of the method of the invention the number of first modulation results obtained in step a. equals to C1*C2*...*Ci-1*Ci*Ci+1*...*Cn wherein Ci is the number of elements of the ith first set of the first sets, and preferably the number of second modulation results obtained in step c. equals the number of predetermined phase modulating elements of the second set.

A further embodiment of the method of the invention is characterised in that in step b in a first substep the selected first correlation result is phase-modulated with each of said possible second sub-modulation codes and in a second substep real values are determined from results obtained in the first substep for obtaining the second correlation results.

In an embodiment according to the invention in step c. a predetermined phase modulating element of the second set is selected which provides the selected second correlation result, and in step d. the predetermined phase modulating elements of the first sets are selected which provide the selected first correlation result. A further embodiment of the method is characterised in that the selected predetermined phase modulating elements of the second set and the predetermined phase modulating elements of the first sets are combined to obtain the symbol of the received signal.

In an advanced embodiment of the method of the invention in step a. a first correlator bank comprising a number of correlators is used, wherein this number of correlators equals the number of first correlation results, and in step b. a second correlator bank is used which comprises a number of correlators, wherein this number of correlators equals the number of second correlation results.

The apparatus according to the invention is characterised in that the apparatus comprises the following means:

  • a first correlator bank for correlating the received signal with each of the possible first sub-modulation codes for obtaining first correlation results;
  • first selection means for selecting a first correlation result from the first correlation results;
  • a second correlator bank for phase-modulating the first correlation result with one of said possible second sub-modulation codes for each possible second sub-modulation code for obtaining second correlation results;
  • second selection means for selecting the maximum second correlation result from the second correlation results;
  • a control-unit comprising means for controlling the first selecting means on the basis of the first correlation results;
third selecting means for selecting the symbol of the received signal on the basis of the first and second correlation results.

In a favourable embodiment of the apparatus of the invention the third selection means select a predetermined phase modulating element of the second set which provides the selected second correlation result and also select predetermined phase modulating elements of the first sets which provide the selected first correlation results. Preferably the third selection means of the apparatus of the invention combine the selected predetermined phase modulating element of the second set and the selected predetermined phase modulating elements of the first sets to obtain the symbol in the received signal.

In the accompanying drawings, in which certain modes of carrying out the present invention are shown for illustrative purposes:

  • Figure 1 is diagram schematically showing an embodiment of an apparatus according to the invention for the detection of a symbol from a received signal;
  • Figure 2 is a schematic example of a symbol from a received signal;
  • Figure 3 is a co-ordinate system in the complex plane illustrating a second sub-modulation code for the chips in the symbol of figure 2.

An embodiment of an apparatus 2 for the detection of a symbol from a received signal according to the invention is schematically shown in figure 1. The apparatus 2 comprises a first correlator bank 4 for obtaining first correlation results 6.m (m=1,2,...,M) on the basis of an input signal 8 and first selection means 10 for selecting one of the first correlation results. Furthermore the apparatus 2 comprises a second correlator bank 12 which receives the selected first correlation result 14 and generates second correlation results 16.k (k=1,2,...,K). The apparatus 2 also comprises second selection means 18 for selecting one of the second correlation results, a control unit 20 for controlling the first selection means 10 and third selection means 22 for selecting the detection symbol. The third selection means 22 select the detection symbol on the basis of the selected first correlation result 6.m corresponding to the correlator 24.m in the first correlator bank 4 and the selected second correlation result 16.k corresponding to the correlator 26.k in the second correlator bank 12. The third selection means receives an input signal 28 comprising information about the selected correlator 24.m and an input signal 30 comprising information about the selected correlator 26.k, the output signal 32 comprises information about the detection symbol from the received signal 8. The first selection means 10 comprises a kind of a switch which can connect the output of one correlator of any correlator 24.m (m=1,2,...,M) to the second correlator bank 12. The switch 34 is controlled with the control signal 36 on the basis of the first correlation results 6.m (m=1,2,...,M).

The symbol from the received signal 8 is a selected symbol out of a predetermined set of symbols wherein each symbol of the predetermined set is a Complementary Coded Keying symbol (short: CCK-symbol). A CCK-symbol comprises a sequence of chips wherein each of the chips is Phase Shift Keying modulated (short: PSK-modulated). The PSK-modulation is based on a selected modulation code wherein each of the selected modulation codes comprises a first sub-modulation code which is a selection form a plurality of first sets of predetermined phase modulating elements and a second sub-modulation code which is a selection from one second set of predetermined phase modulating elements. At least one of said predetermined phase-modulating elements of the second sets is a complex value.

Figure 2 presents an example of a symbol 38, out of a predetermined set of symbols, comprising eight chips 40 wherein each chip is phase modulated. This phase modulation is defined with the complex numbers si up to s8. With these complex numbers the symbol 38 can be written in vector notation as s=[s1,s2,...,s8]T. An example of a set of high speed CCK-symbols 38 is given in the high speed IEEE 802.11b standard according to: s = e j ϕ 1 + ϕ 2 + ϕ 3 + ϕ 4 , e j ϕ 1 + ϕ 3 + ϕ 4 , e j ϕ 1 + ϕ 2 + ϕ 4 , - e j ϕ 1 + ϕ 4 , e j ϕ 1 + ϕ 2 + ϕ 3 , e j ϕ 1 + ϕ 3 , - e j ϕ 1 + ϕ 2 , e j ϕ 1 T , wherein j is a complex number and wherein the predetermined phase modulating elements e jϕ1 ,e jϕ2 ,e jϕ3 ,e jϕ4 can take on a set of predetermined-values. The predetermined phase modulating elements are divided in three first sets and one second set. The three first sets contain the predetermined phase modulating elements e jϕ2 ,e jϕ3 ,e jϕ4 and the second set contains the predetermined phase modulating element e jϕ1 .

The three first sets of predetermined phase modulating elements are respectively defined according to: e j ϕ 2 , with < . > e j ϕ 3 , with . e j ϕ 4 , with . wherein ϕ234 are the phase parameters of the respective predetermined phase modulating elements. The phase parameters define the possible values of the respective phase modulating elements. The phase parameters can only take on one value out of a limited set of values. For the high speed IEEE 802.11b standard this set is defined according to < ϕ 1 0 , &pgr; 2 , - &pgr; , - &pgr; 2 > , ϕ 2 0 , &pgr; 2 , - &pgr; , - &pgr; 2 , ϕ 3 0 , &pgr; 2 , - &pgr; , - &pgr; 2 The so-called 5.5 Mbit/s fallback rate corresponds to a different set which set is defined with (IIB): < ϕ 2 &pgr; 2 , - &pgr; 2 > , ϕ 3 0 , ϕ 4 0 &pgr; . The predetermined phase modulating element in the second set is defined by: e j ϕ 1 , wherein ϕ1 is a phase parameter. The phase parameter ϕ1 can take on one value out of the following set of values: ϕ 1 0 , &pgr; 2 , - &pgr; , - &pgr; 2

The modulation codes of the set of CCK-symbols follow from the value combinations of the phase modulating elements from the first sets (II) and the second set (III). From equation (I) it follows that the phase modulating element e jϕ1 is a common element for all chips of the symbol (I).

The modulation code of the symbol (I) is divided in a first sub-modulation code and a second modulation code. The first sub-modulation code s1 is defined in terms of the predetermined phase modulating elements of the first sets according to: s 1 = e j ϕ 2 + ϕ 3 + ϕ 4 , e j ϕ 3 + ϕ 4 , e j ϕ 2 + ϕ 4 , - e j ϕ 4 , e j ϕ 2 + ϕ 3 , e j ϕ 3 , - e j ϕ 2 , 1 T , wherein s1 is an eight-dimensional vector representing one specific value combination out of a set of possible value combinations, which combinations are defined with (IIA, IIB). The number of possible value combinations for the first sub-modulation code equals C1*C2*...*Ci-1*Ci*Ci+1*...*Cn wherein Ci is the number of elements of the ith first set of the n first sets. In this example n=3, C1=2, C2=1, C3=2 which yields 4 possible value combinations for the first sub-modulation code. In this example the number of first correlators M equals the number of possible value combinations in the first sub-modulation code.

The second sub-modulation code s2 is given by: s 2 = e j ϕ 1 , wherein s2 is one specific value out of the set of possible values for the second sub-modulation code, wherein set is defined with (IIIA, IIIB). These possible values are depicted in figure 3. In this figure the values 42.1 up to 42.4 are depicted in the complex co-ordinate system 44 comprising a real axis Re 46 and an imaginary axis Im 48. The second sub-modulation code is a common modulation for all chips of the symbol (I).

It is stressed that the set CCK-symbols (I) as described hereinbefore is just one example. Various sets of symbols can be chosen with different numbers of chips per symbol and different modulation codes. However in the second modulation code always at least one value will be a complex number.

Each of the correlators 24.m (m=1,2,...,M) performs a correlation of the received signal 8 with one of the possible first sub-modulation codes c1 (IV). The number of correlators equals the number of first sub-modulation codes (=C1*C2*...* Ci-1*Ci*Ci+1*...*Cn). The correlation is performed as a matched filter, which means that the output signal of the correlator 24.m is given with the complex inner product: Cor m = s 1 m r , wherein Cor m is a complex scalar value, S̅1 m is the complex conjugated of the M-dimensional vector s1 m , where s1 m is the mth first sub-modulation code of the first sub-modulation codes corresponding to the correlator 24.m, r is the M-dimensional receive signal 8 and {}·{} is the complex inner product between its arguments. Thus each of the first correlators 24.m yields a first corelation result 6.m (m=1,2,...,M). These M first correlation results are passed to the control-unit 20. Next the control-unit determines for each first correlation result 6.m the value of a function of the correlation result wherein the function is predetermined by the type of modulation of the second sub-modulation code. The type of modulation is defined with (IIIB) and (V). The function is a function of the real and/or imaginary parts of the first correlation result for selecting the value of phase-modulating elements of the first sub-modulation code which are incorporated in the symbol of the received signal. The function firstly leads the Maximum Likelihood detection symbol and secondly leads to a minimum of necessary processing time. For the chosen type of second sub-modulation (defined with (IIIB) and (V)) this optimal function Crit1 may be given with: Crit 1 = Max Re Cor m Im Cor m ) , wherein the function Max() selects the maximum value of its input arguments, the function |()| yields the absolute value of its input argument, the function Re() gives the real part of its complex input argument and the function Im() gives the imaginary part of its complex argument. The control-unit 20 subsequently controls the switch 34 in the first selection means 10 on the basis of the maximum value of the function (VII) in such a way that the corresponding first correlation result 6.m is selected by the first selection means 10 and passed to the second correlator-bank 12. Furthermore, the control unit selects the pre-determined phase modulating elements e ϕ ^ 2 , e ϕ ^ 3 , e ϕ ^ 4 (which correspond to the selected phase parameters ϕ̂2,ϕ̂3,ϕ̂4 belonging to the first sub-modulation code which corresponds to the selected correlator) out of the set (II). A signal 28, comprising this first sub modulation code of correlator 6.m, is subsequently passed by the control unit 20 to the third selecting means 22.

The second correlator-bank 12 receives the selected first modulation signal 14 and subsequently performs a phase-modulation on this signal based on the second sub-modulation code (V). Each of the second correlators 26.k (k=1,...,K) performs a phase-modulation corresponding to one of the values of the second sub-modulation code c2 from (III) and (V). The result of these phase-modulations are the second correlation results 16.k (k=1,...,K). In this example K=4. The second correlation results are passed to the second selection means 18. The third selection means 22 selects the pre-determined phase-modulating element e ϕ ^ 1 which corresponds to the second sub-modulation code of the correlator 16.k for which the following function Crit2 is maximum: Crit 2 = Re Cor m c 2 , wherein Corm is the selected first correlation result and c2 is the second sub-modulation code from (V). The calculation of the function Crit2 yields the second correlation results. It follows from (VIII) that the number of second correlation results equals the number of possible values of the phase parameter ϕ1 of the second set (IIIB). The pre-determined phase-modulating element e ϕ ^ 1 of the second sub modulation code for which Crit2 is maximum is the output signal 30.

The third selection means 22 receives a signal 30 comprising the selected predetermined phase modulating element e ϕ ^ 1 of the second set which yields the selected second sub-modulation result and a signal 28 comprising the selected predetermined phase modulating elements e ϕ ^ 2 , e ϕ ^ 3 , e ϕ ^ 4 of the first sets which yields the selected first sub-modulation result. On the basis of the signals 28 and 30 and the equation (I) the third selection means 22 can determine the detection symbol: e j ϕ ^ 1 + ϕ ^ 2 + ϕ ^ 3 + ϕ ^ 4 , e j ϕ ^ 1 + ϕ ^ 3 + ϕ ^ 4 , e j ϕ ^ 1 + ϕ ^ 2 + ϕ ^ 4 , - e j ϕ ^ 1 + ϕ ^ 4 , e j ϕ ^ 1 + ϕ ^ 2 + ϕ ^ 3 , e j ϕ ^ 1 + ϕ ^ 3 , - e j ϕ ^ 1 + ϕ ^ 2 , e j ϕ ^ 1 T from the received signal 8.

The apparatus 2 according to the invention is not limited to the second sub modulation given with (V) for the set of values of the phase parameter ϕ1 (IIIB). A variety of types of second sub modulation codes with a corresponding function Crit 1 can be used without departing from the scope of the invention. A few number of non-limiting examples are given below.

Example 1. The second sub modulation code s2 is defined as: s 2 = e j ( ϕ 1 ) , for which the phase parameter ϕ1 can take on the values in the following set: ϕ 1 &pgr; 4 3 &pgr; 4 5 &pgr; 4 7 &pgr; 4 , such that the number K=4 of second correlators in the second correlator bank 12. The corresponding function Crit1 is given with: Crit 1 = Re Cor m + = Im Cor m , wherein Corm is the selected first correlation result.

Example 2. The second sub modulation code s2 is defined as: s 2 = e j ϕ 1 for which the phase parameter ϕ1 can take on the values in the following set: ϕ 1 &pgr; 4 k &pgr; 4 k + 1 &pgr; 4 K &pgr; 4 , such that the number K=8 of second correlators in the second correlator bank 12. The corresponding function Crit1 is given with: Crit 1 = Max Re Cor m , Im Cor m , 1 2 2 Re Cor m + Im Cor m , wherein Corm is the selected first correlation result.

Example 3. The second sub modulation code s2 is defined as: s 2 = e j ϕ 1 , for which the phase parameter ϕ1 can take on the values in the following set: ϕ 1 &pgr; 8 k &pgr; 8 k + 1 &pgr; 8 16 &pgr; 8 such that the the number K=16 of second correlators in the second correlator bank 12 and corresponding function Crit1 is given with: Crit 1 = Max Re Cor m , Im Cor m , 1 2 2 - 2 Max Re Cor m Im Cor m + 1 2 2 - 2 Min Re Cor m , Im Cor m , 1 2 2 Re Cor m + Im Cor m , wherein Corm is the selected first correlation result.

In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiments. However, it should be noted that the invention can be practised otherwise than as specifically illustrated and described without departing from its scope. For example,

it is possible to combine in the first and/or the second sub-modulation code a phase modulation with an amplitude modulation.


Anspruch[de]
Verfahren zum Detektieren eines Symbols (38) aus einem empfangenen Signal (8), wobei das Symbol ein ausgewähltes Symbol aus einer vorbestimmten Symbolmenge ist, jedes Symbol der vorbestimmten Menge ein Complementary-Code-Keying-(CCK-)Symbol ist, umfassend eine Sequenz von Chips (40), von denen jedes Chip gemäß einem ausgewählten Modulationscode phasenumtast-, PSK-moduliert ist, wobei jeder der ausgewählten Modulationscodes einen ersten Submodulationscode, bei dem es sich um eine Auswahl aus einer Mehrzahl erster Mengen vorbestimmter Phasenmodulationselemente handelt, und einen zweiten Submodulationscode, bei dem es sich um eine Auswahl aus einer zweiten Menge vorbestimmter Phasenmodulationselemente handelt, aufweist, wobei mindestens eines der vorbestimmten Phasenmodulationselemente der zweiten Menge ein komplexer Wert ist, wie er in der High-Speed-IEEE-802.11-Norm definiert ist, wobei ein Modulationscode ausgewählt ist aus den Modulationscodes, der gemäß einem Korrelationsverfahren mit dem empfangenen Signal korreliert,

dadurch gekennzeichnet, dass

das Verfahren mindestens die folgenden Schritte aufweist: - a) Korrelieren des empfangenen Signals mit jedem der möglichen ersten Submodulationscodes, um erste Korrelationsergebnisse (6.1...6.M) zu erhalten und Auswählen eines Korrelationsergebnisses; - b) Phasenmodulieren des ausgewählten ersten Korrelationsergebnisses (14) mit einem der möglichen zweiten Submodulationscodes für jeden möglichen zweiten Submodulationscode, um zweite Korrelationsergebnisse (16.1...16.K) zu erhalten; - c) Auswählen des maximalen zweiten Korrelationsergebnisses aus den zweiten Korrelationsergebnissen; - d) Auswählen des Symbols des empfangenen Signals auf der Grundlage einer Kombination aus ersten und zweiten Korrelationsergebnissen.
Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass

im Schritt a) für jedes erste Korrelationsergebnis der Wert einer Funktion des Korrelationsergebnisses bestimmt und anschließend das erste Korrelationsergebnis, welches den Maximumwert der Funktion liefert, ausgewählt wird, wobei die Funktion bestimmt wird durch den Modulationstyp des zweiten Submodulationscodes.
Verfahren nach Anspruch 2, dadurch gekennzeichnet dass

die Funktion eine Funktion des Real- und/oder Imaginärteils des ersten Korrelationsergebnisses ist.
Verfahren nach einen vorhergehenden Anspruch, dadurch gekennzeichnet, dass die Anzahl erster Modulationsergebnisse, die im Schritt a) erhalten werden, C1*C2*...*Ci-1*Ci*Ci+1*...*Cn ist, wobei Ci die Anzahl von Elementen in der i-ten ersten Menge der ersten Mengen ist. Verfahren nach einem vorhergehenden Anspruch, dadurch gekennzeichnet, dass innerhalb des Schritts b) innerhalb eines ersten Teilschritts das ausgewählte erste Korrelationsergebnis phasenmoduliert wird mit jedem der möglichen zweiten Submodulationscodes, und in einem zweiten Teilschritt Realwerte aus den Ergebnissen bestimmt werden, die in dem ersten Teilschritt gewonnen wurden, um die zweiten Korrelationsergebnisse zu erhalten. Verfahren nach einem vorhergehenden Anspruch, dadurch gekennzeichnet, dass die Anzahl zweiter Modulationsergebnisse, die im Schritt c) erhalten werden, der Anzahl vorbestimmter Phasenmodulationselemente in der zweiten Menge gleicht. Verfahren nach einem vorhergehenden Anspruch, dadurch gekennzeichnet, dass im Schritt c) ein vorbestimmtes Phasenmodulationselement der zweiten Menge ausgewählt wird, welches das ausgewählte zweite Korrelationsergebnis liefert. Verfahren nach einem vorhergehenden Anspruch, dadurch gekennzeichnet, dass im Schritt d) die vorbestimmten Phasenmodulationselemente der ersten Menge ausgewählt werden, die das ausgewählte erste Korrelationsergebnis liefern. Verfahren nach Anspruch 7 und 8, dadurch gekennzeichnet, dass im Schritt d) das ausgewählte vorbestimmte Phasenmodulationselement der zweiten Menge und die vorbestimmten Phasenmodulationselemente der ersten Mengen kombiniert werden, um das Symbol im empfangenen Signal zu erhalten. Verfahren nach einem vorhergehenden Anspruch, dadurch gekennzeichnet, dass im Schritt a) eine erste Korrelatorbank mit einer Anzahl von Korrelatoren verwendet wird, wobei diese Anzahl von Korrelatoren der Anzahl erster Korrelationsergebnisse gleicht. Verfahren nach einem vorhergehenden Anspruch, dadurch gekennzeichnet, dass im Schritt b) eine zweite Korrelatorbank mit einer Anzahl von Korrelatoren verwendet wird, wobei diese Anzahl von Korrelatoren der Anzahl zweiter Korrelationsergebnisse gleicht. Vorrichtung (2) zum Detektieren eines Symbols (38) aus einem empfangenen Signal (8), wobei das Symbol ein ausgewähltes Symbol aus einer vorbestimmten Menge von Symbolen ist, von denen jedes Symbol der vorbestimmten Menge ein Complementary-Code-Keying-, CCK-Symbol ist, umfassend eine Sequenz von Chips (40), wobei jedes der Chips phasenumtast-, PSK-moduliert ist, gemäß einem ausgewählten Modulationscode, wobei jeder der ausgewählten Modulationscodes einen ersten Submodulationscode, bei dem es sich um eine Auswahl aus einer Mehrzahl erster Mengen vorbestimmter Phasenmodulationselemente handelt, und einen zweiten Submodulationscode, bei dem es sich um eine Auswahl aus einer zweiten Menge vorbestimmter Phasenmodulationselemente handelt, aufweist, wobei mindestens eines der vorbestimmten Phasenmodulationselemente der zweiten Menge ein komplexer Wert ist, wie er in der High-Speed-IEEE-802.11-Norm definiert ist, und die Vorrichtung (2) eine Korrelationseinrichtung zum Korrelieren des empfangenen Signals mit den Modulationscodes nach einem Korrelationsverfahren und eine Einrichtung zum Auswählen eines Modulationscodes aus den Modulationscodes auf der Grundlage der Korrelation aufweist,

dadurch gekennzeichnet, dass die Vorrichtung aufweist: - eine erste Korrelatorbank (4) zum Korrelieren des empfangenen Signals (8) mit jedem der möglichen ersten Submodulationscodes, um erste Korrelationsergebnisse zu erhalten; - eine erste Auswahleinrichtung (10) zum Auswählen eines ersten Korrelationsergebnisses aus den ersten Korrelationsergebnissen (6.1...6.M); - eine zweite Korrelatorbank (12) zum Phasenmodulieren des ausgewählten ersten Korrelationsergebnisses mit einem der möglichen zweiten Submodulationscodes für jeden möglichen zweiten Submodulationscode, um zweite Korrelationsergebnisse (16.1...16.K) zu erhalten; - eine zweite Auswahleinrichtung (18) zum Auswählen des maximalen zweiten Korrelationsergebnisses aus den zweiten Korrelationsergebnissen; - eine Steuereinheit (20), umfassend eine Einrichtung zum Steuern der ersten Auswahleinrichtung auf der Grundlage der ersten Korrelationsergebnisse; - eine dritte Auswahleinrichtung (22) zum Auswählen des Symbols des empfangenen Signals auf der Grundlage des ersten und des zweiten Korrelationsergebnisses.
Vorrichtung nach Anspruch 12, dadurch gekennzeichnet, dass die Steuereinheit (20) für jedes erste Korrelationsergebnis den Wert einer Funktion des Korrelationsergebnisses bestimmt, wobei die Funktion durch den Typ der Modulation des zweiten Submodulationscodes bestimmt wird, und anschließend die erste Auswahleinrichtung (10) auf der Grundlage des Maximumwerts der Funktion derart steuert, dass das entsprechende erste Korrelationsergebnis durch die erste Auswahleinrichtung (10) ausgewählt und an die zweite Korrelatorbank (12) weitergeleitet wird. Vorrichtung nach Anspruch 13, dadurch gekennzeichnet, dass die Funktion eine Funktion der Real- und/oder Imaginärteile des ersten Korrelationsergebnisses ist. Vorrichtung nach einem der Ansprüche 12 bis 14, dadurch gekennzeichnet, dass die Anzahl erster Korrelationsergebnisse die von der ersten Korrelatorbank (4) gewonnen werden, C1*C2*...*Ci-1*Ci*Ci+1*...*Cn ist, wobei Ci die Anzahl von Elementen der i-ten ersten Menge der ersten Mengen ist. Vorrichtung nach einem der vorhergehenden Ansprüche 12 bis 15, dadurch gekennzeichnet, dass die zweite Korrelatorbank (12) eine Einrichtung zur Phasenmodulation des ausgewählten ersten Korrelationsergebnisses mit jedem der möglichen zweiten Submodulationscodes ist, um Phasenmodulationsergebnisse zu erhalten, außerdem eine Einrichtung aufweist zum Bestimmen der Realteile der gewonnen phasenmodulierten Ergebnisse, um die zweiten Korrelationsergebnisse zu erhalten. Vorrichtung nach einem der vorhergehenden Ansprüche 12 bis 16, dadurch gekennzeichnet, dass die Anzahl zweiter Korrelationsergebnisse der Anzahl vorbestimmter Phasenmodulationselemente in der zweiten Menge gleicht. Vorrichtung nach einem der Ansprüche 12 bis 17, dadurch gekennzeichnet, dass die dritte Auswahleinrichtung (22) ein vorbestimmtes Phasenmodulationselement der zweiten Menge auswählt, welches das ausgewählte zweite Korrelationsergebnis liefert. Vorrichtung nach einem der vorhergehenden Ansprüche 12 bis 18, dadurch gekennzeichnet, dass die dritte Auswahleinrichtung (22) vorbestimmte Phasenmodulationsergebnisse der ersten Mengen auswählt, was das ausgewählte erste Korrelationsergebnis liefert. Vorrichtung nach Anspruch 18 oder 19, dadurch gekennzeichnet, dass die dritte Auswahleinrichtung (22) das ausgewählte vorbestimmte Phasenmodulationselement der zweiten Menge und die ausgewählten vorbestimmten Phasenmodulationselemente der ersten Mengen kombiniert, um das Symbol des empfangenen Signals (32) zu erhalten.
Anspruch[en]
A method for the detection of a symbol (38) from a received signal (8) wherein the symbol is a selected symbol out of a predetermined set of symbols, wherein each symbol of the predetermined set is a Complementary Code Keying, CCK, symbol comprising a sequence of chips (40) wherein each of the chips is Phase Shift Keying, PSK, modulated according to a selected modulation code wherein each of the selected modulation codes comprises a first sub-modulation code which is a selection from a plurality of first sets of predetermined phase modulating elements and a second sub-modulation code which is a selection from one second set of predetermined phase modulating elements wherein at least one of said predetermined phase modulating elements of said second set is a complex value such as defined in the high speed IEEE 802.11 standard, wherein a modulation code is selected from said modulation codes which correlates according to a correlation method with the received signal,

characterised in that,

the method comprises at least the following steps: • a. correlating the received signal with each of the possible first sub-modulation codes for obtaining first correlation results (6.1...6.M) and selecting a correlation result; • b. phase-modulating the selected first correlation result (14) with one of said possible second sub-modulation codes for each possible second sub-modulation code for obtaining second correlation results (16.1 ... 16.K); • c. selecting the maximum second correlation result from the second correlation results; • d. selecting the symbol of the received signal on the basis of a combination the first and second correlating results.
A method according to claim 1, characterised in that, in step a. for each first correlation result the value of a function of the correlation result is determined and subsequently the first correlation result which provides the maximum value of the function is selected wherein the function is determined by the type of modulation of the second sub-modulation code. A method according to claim 2, characterised in that the function is a function of the real and/or imaginary parts of the first correlation result. A method according to any preceding claim, characterised in that, the number of first modulation results obtained in step a. equals to C1*C2*...*Ci-1*Ci*Ci+1*...*Cn wherein Ci is the number of elements of the ith first set of the first sets. A method according to any preceding claim, characterised in that, in step b in a first substep the selected first correlation result is phase-modulated with each of said possible second sub-modulation codes and in a second substep real values are determined from results obtained in the first substep for obtaining the second correlation results. A method according to any preceding claim, characterised in that, the number of second modulation results obtained in step c. equals the number of predetermined phase modulating elements of the second set. A method according to any preceding claim, characterised in that, in step c. a predetermined phase modulating element of the second set is selected which provides the selected second correlation result. A method according to any preceding claim, characterised in that, in step d. the predetermined phase modulating elements of the first sets are selected which provides the selected first correlation result. A method according to claims 7 and 8, characterised in that in step d. the selected predetermined phase modulating element of the second set and the predetermined phase modulating elements of the first sets are combined to obtain the symbol in the received signal. A method according to any preceding claim, characterised in that, in step a. a first correlator bank comprising a number of correlators is used, wherein this number of correlators equals the number of first correlation results. A method according to any preceding claim, characterised in that, in step b. a second correlator bank comprising a number of correlators is used, wherein this number of correlators equals the number of second correlation results. An apparatus (2) for the detection of a symbol (38) from a received signal (8) wherein the symbol is a selected symbol out of a predetermined set of symbols, wherein each symbol of the predetermined set is a Complementary Code Keying, CCK, symbol comprising a sequence of chips (40) wherein each of the chips is Phase Shift Keying, PSK, modulated according to a selected modulation code wherein each of the selected modulation codes comprises a first sub-modulation code which is a selection from a plurality of first sets of predetermined phase modulating elements and a second sub-modulation code which is a selection from one second set of predetermined phase modulating elements wherein at least one of said predetermined phase modulating elements of said second set is a complex value such as defined in the high speed IEEE 802.11 standard, the apparatus (2) comprising correlating means for correlating the received signal with said modulation codes according to a correlation method and means for selecting a modulation code from said modulation codes on the basis of the correlation,

characterised in that,

the apparatus (2) comprises: • a first correlator bank (4) for correlating the received signal (8) with each of the possible first sub-modulation codes for obtaining first correlation results; • first selection means (10) for selecting a first correlation result from the first correlation results (6.1 ... 6. M); • a second correlator bank (12) for phase-modulating the selected first correlation result with one of said possible second sub-modulation codes for each possible second sub-modulation code for obtaining second correlation results (16.1... 16.K) • second selection means (18) for selecting the maximum second correlation result from the second correlation results; • a control-unit (20) comprising means for controlling the first selecting means on the basis of the first correlation results; • third selecting means (22) for selecting the symbol of the received signal on the basis of the first and second correlation results.
An apparatus according to claim 12, characterised in that, the control-unit (20) determines for each first correlation result the value of a function of the correlation result, wherein the function is determined by the type of modulation of the second sub-modulation code, and subsequently controls the first selection means (10) on the basis of the maximum value of the function in such a way that the corresponding first correlation result is selected by the first selection means (10) and passed to the second correlator-bank (12). An apparatus according to claim 13, characterised in that the function is a function of the real and/or imaginary parts of the first correlation result. An apparatus according to any one of the claims 12-14, characterised in that, the number of first correlation results obtained by the first correlator-bank (4) equals C1*C2*...*Ci-1*Ci*Ci+1*...*Cn wherein Ci is the number of elements of the ith first set of the first sets. An apparatus according to any one of the preceding claims 12-15, characterised in that, the second correlator-bank (12) comprises means for phase-modulating the selected first correlation result with each of said possible second sub-modulation codes for obtaining phase modulation results and also comprises means for determining real values of the obtained phase-modulated results for obtaining the second correlation results. An apparatus according to any one of the preceding claims 12-16, characterised in that, the number of second correlation results equals the number of predetermined phase modulating elements of the second set. An apparatus according to any one of the preceding claims 12-17, characterised in that, the third selection means (22) selects a predetermined phase modulating element of the second set which provides the selected second correlation result. An apparatus according to any one of the preceding claims 12-18, characterised in that, the third selection means (22) selects predetermined phase modulating elements of the first sets which provides the selected first correlation result. An apparatus according to claim 18 or 19, characterised in that the third selection means (22) combines the selected predetermined phase modulating element of the second set and the selected predetermined phase modulating elements of the first sets to obtain the symbol of the received signal (32).
Anspruch[fr]
Procédé destiné à la détection d'un symbole (38) à partir d'un signal (8) reçu où le symbole est un symbole sélectionné parmi un ensemble prédéterminé de symboles, où chaque symbole de l'ensemble prédéterminé est un symbole de Modulation à Code Complémentaire CCK comportant une séquence de tranches (40) où chacune des tranches est Modulée par Déplacement de Phase PSK conformément à un code de modulation sélectionné où chacun des codes de modulation sélectionné comporte un premier code de sous-modulation qui est une sélection à partir d'une pluralité de premiers ensembles d'éléments de modulation de phase prédéterminés et un deuxième code de sous-modulation qui est une sélection à partir d'un deuxième ensemble d'éléments de modulation de phase prédéterminés où au moins l'un desdits éléments de modulation de phase prédéterminés dudit deuxième ensemble est une valeur complexe telle que définie dans la norme IEEE 802.11 à haute vitesse, où un code de modulation est sélectionné à partir desdits codes de modulation, qui est en corrélation conformément à un procédé de corrélation avec le signal reçu,

caractérisé en ce que,

le procédé comporte au moins les étapes suivantes : • a. de corrélation du signal reçu avec chacun des premiers codes de sous-modulation possibles pour obtenir des premiers résultats (6.1 ... 6.M) de corrélation et sélectionner un résultat de corrélation ; • b. de modulation en phase du premier résultat (14) de corrélation sélectionné avec l'un desdits deuxièmes codes de sous-modulation possibles pour chaque deuxième code de sous-modulation possible afin d'obtenir des deuxièmes résultats (16.1 ... 16.K) de corrélation ; • c. de sélection du deuxième résultat de corrélation maximum à partir des deuxièmes résultats de corrélation ; • d. de sélection du symbole du signal reçu sur la base d'une combinaison des premiers et deuxièmes résultats de corrélation.
Procédé selon la revendication 1, caractérisé en ce que, dans l'étape a., pour chaque premier résultat de corrélation la valeur d'une fonction du résultat de corrélation est déterminée et par la suite le premier résultat de corrélation qui fournit la valeur maximum de la fonction est sélectionné, où la fonction est déterminée par le type de modulation du deuxième code de sous-modulation. Procédé selon la revendication 2, caractérisé en ce que la fonction est une fonction des parties réelle et/ou imaginaire du premier résultat de corrélation. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que le nombre de premiers résultats de modulation obtenus dans l'étape a. est égal à C1*C2*...*Ci-1*Ci*Ci+1* ...*Cn où Ci est le nombre d'éléments du ie premier ensemble des premiers ensembles. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que, dans l'étape b., dans une première sous-étape, le premier résultat de corrélation sélectionné est modulé en phase avec chacun desdits deuxièmes codes de sous-modulation possibles et dans une deuxième sous-étape, des valeurs réelles sont déterminées à partir de résultats obtenus dans la première sous-étape afin d'obtenir les deuxièmes résultats de corrélation. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que le nombre de deuxièmes résultats de modulation obtenu dans l'étape c. est égal au nombre d'éléments de modulation de phase prédéterminés du deuxième ensemble. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que, dans l'étape c., un élément de modulation de phase prédéterminé du deuxième ensemble est sélectionné ce qui fournit le deuxième résultat de corrélation sélectionné. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que, dans l'étape d., les éléments de modulation de phase prédéterminés des premiers ensembles sont sélectionnés ce qui fournit le premier résultat de corrélation sélectionné. Procédé selon les revendications 7 et 8, caractérisé en ce que, dans l'étape d., l'élément de modulation de phase prédéterminé du deuxième ensemble ainsi que les éléments de modulation de phase prédéterminés des premiers ensembles sont combinés pour obtenir le symbole dans le signal reçu. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que, dans l'étape a., on utilise une première banque de corrélateurs comportant un certain nombre de corrélateurs, où ce nombre de corrélateurs est égal au nombre de premiers résultats de corrélation. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que, dans l'étape b., on utilise une deuxième banque de corrélateurs comportant un certain nombre de corrélateurs, où ce nombre de corrélateurs est égal au nombre de deuxièmes résultats de corrélation. Dispositif (2) destiné à la détection d'un symbole (38) à partir d'un signal (8) reçu où le symbole est un symbole sélectionné parmi un ensemble de symboles prédéterminé, où chaque symbole prédéterminé de l'ensemble est un symbole de Modulation à Code Complémentaire CCK comportant une séquence de tranches (40) où chacune des tranches est Modulée par Déplacement de Phase PSK, conformément à un code de modulation sélectionné où chacun des codes de modulation sélectionné comporte un premier code de sous-modulation qui est une sélection à partir d'une pluralité de premiers ensembles d'éléments de modulation de phase prédéterminés et un deuxième code de sous-modulation qui est une sélection à partir d'un deuxième ensemble d'éléments de modulation de phase prédéterminés où au moins l'un desdits éléments de modulation de phase prédéterminés dudit deuxième ensemble est une valeur complexe telle que définie dans la norme IEEE 802.11 à haute vitesse, le dispositif (2) comportant un moyen de corrélation destiné à corréler le signal reçu avec lesdits codes de modulation conformément à un procédé de corrélation ainsi qu'un moyen destiné à sélectionner un code de modulation à partir desdits codes de modulation sur la base de la corrélation,

caractérisé en ce que,

le dispositif (2) comporte : • une première banque (4) de corrélateurs pour corréler le signal (8) reçu avec chacun des premiers codes de sous-modulation possible pour obtenir des premiers résultats de corrélation ; • un premier moyen (10) de sélection pour sélectionner un premier résultat de corrélation à partir des premiers résultats (6.1 ... 6.M) de corrélation ; • une deuxième banque (12) de corrélateurs pour moduler en phase le premier résultat de corrélation sélectionné avec l'un desdits deuxièmes codes de sous-modulation possibles pour chaque deuxième code de sous-modulation possible pour obtenir des deuxièmes résultats (16.1 ... 16.K) de corrélation ; • un deuxième moyen (18) de sélection pour sélectionner le deuxième résultat de corrélation maximum à partir des deuxièmes résultats de corrélation ; • un module (20) de commande comportant un moyen pour commander le premier moyen de sélection sur la base des premiers résultats de corrélation ; • un troisième moyen (22) de sélection pour sélectionner le symbole du signal reçu sur la base des premiers et deuxièmes résultats de corrélation.
Dispositif selon la revendication 12, caractérisé en ce que le module (20) de commande détermine pour chaque premier résultat de corrélation la valeur d'une fonction du résultat de corrélation, où la fonction est déterminée par le type de modulation du deuxième code de sous-modulation, et commande par la suite le premier moyen (10) de sélection sur la base de la valeur maximum de la fonction de telle façon que le premier résultat de corrélation correspondant est sélectionné par le premier moyen (10) de sélection et passé à la deuxième banque (12) de corrélateurs. Dispositif selon la revendication 13, caractérisé en ce que la fonction est une fonction des parties réelle et/ou imaginaire du premier résultat de corrélation. Dispositif selon l'une quelconque des revendications 12 à 14, caractérisé en ce que le nombre de premiers résultats de corrélation obtenu par la première banque (4) de corrélateurs est égal à C1*C2*...*Ci-1*Ci*Ci+1* ...*Cn où Ci est le nombre d'éléments du ie premier ensemble de premiers ensembles. Dispositif selon l'une quelconque des revendications précédentes 12 à 15, caractérisé en ce que la deuxième banque (12) de corrélateurs comporte un moyen pour moduler en phase le premier résultat de corrélation sélectionné avec chacun desdits deuxièmes codes de sous-modulation possibles afin d'obtenir des résultats de modulation de phase et comporte également un moyen pour déterminer des valeurs réelles des résultats modulés en phase obtenus pour obtenir les deuxièmes résultats de corrélation. Dispositif selon l'une quelconque des revendications précédentes 12 à 16, caractérisé en ce que le nombre de deuxièmes résultats de corrélation est égal au nombre d'éléments de modulation de phase prédéterminés du deuxième ensemble. Dispositif selon l'une quelconque des revendications précédentes 12 à 17, caractérisé en ce que le troisième moyen (22) de sélection sélectionne un élément de modulation de phase prédéterminé du deuxième ensemble ce qui fournit le deuxième résultat de corrélation sélectionné. Dispositif selon l'une quelconque des revendications précédentes 12 à 18, caractérisé en ce que le troisième moyen (22) de sélection sélectionne des éléments de modulation de phase prédéterminés des premiers ensembles ce qui fournit le premier résultat de corrélation sélectionné. Dispositif selon les revendications 18 ou 19, caractérisé en ce que le troisième moyen (22) de sélection combine l'élément de modulation de phase prédéterminé sélectionné du deuxième ensemble et les éléments de modulation de phase prédéterminés sélectionnés des premiers ensembles pour obtenir le symbole du signal (32) reçu.






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