DE10203784B4 - Generation of pilot signatures for channel estimation in a cellular radio communication system - Google Patents

Abstract

method for generating pilot signatures for channel estimation in a cellular radio communication system with at least one transmitting subscriber station and at least a receiving base station associated with a radio cell (Z1 ... Z8), the above an uplink radio channel are interconnected with the channel estimate of the uplink radio channel on an analysis of one of the at least one subscriber station transmitted pilot signature, characterized in that each Subscriber station of the at least one radio cell as a pilot signature a different column vector (SV1 ... SV8) of a Hadamard matrix and that from each in the Hadamard matrix consecutive Column vectors (SV1, SV2, SV3, SV4, SV5, SV6, SV7, SV8) of the Hadamard matrix corresponding to a plurality of respectively adjacent radio cells (Z1, Z2, Z3, Z4; Z5, Z6, Z7, Z8) have a plurality of non-overlapping ones Submatrices are formed, with the number of sub-matrices corresponds to the number of radio cells of the plurality of radio cells, that each radio cell (Z1, Z2, Z3, Z4, Z5, Z6, Z7, Z8) of the plurality of Radio cells assigned to another sub-matrix of the Hadamard matrix becomes...

Description

The The invention relates to a method for generating pilot signatures to the canal estimation in a cellular radio communications system having at least one transmitting subscriber station and at least one of a radio cell assigned receiving base stations, according to the preamble of Claim 1.

In Radio communication systems become information (for example Language, image information, video information, SMS [Short Message Service] or other data) by means of electromagnetic waves over one Radio interface between transmitting and receiving station (subscriber station or base station). The radiation of the electromagnetic waves takes place with Carrier frequencies, in the for the respective system provided frequency band lie.

For future radio communication systems with CDMA or OFDM transmission methods, such as UMTS (Universal Mobile Telecommunication System), Hiperlan, IEEE802.11a or DVB (Digital Video Broadcast) are frequencies in the frequency band of approx. 2-6 GHz provided. These systems are developed with the goals of worldwide Radio coverage and / or a wide range of services for data transfer and, above all, flexible management of the capacity of the radio interface, in radio communication systems, the interface with the lowest Resources is.

Of the Access from stations to the common radio resources of the transmission medium, such as time, frequency, power or space, is at these Radio communication systems using multiple access methods (Multiple Access, MA).

at Code Division Multiple Access (CDMA) is determined by a spreading code, which consists of many individual so-called chips to be transferred Performance / Information station-specific coded, whereby the to be transmitted Performance by code at random over one huge Frequency range is spread. The from different stations use spreading codes within a cell / base station respectively mutually orthogonal or at least substantially orthogonal, whereby a receiver recognizes its intended signal power and suppresses other signals. By CDMA, the radio resource performance by spreading codes subscriber station specific separated.

at orthogonal frequency division multiple access (OFDM) are the Broadband data transmitted, where the frequency band is in equidistant, orthogonal subcarriers is divided so that the simultaneous phase shift of the subcarriers one two-dimensional data flow in the Time-frequency range spans. The up during a time unit transmitted to the orthogonal subcarriers summarized data symbols are called OFDM symbols.

at A multicarrier code division multiple access (MC-CDMA; Multi Carrier CDMA) is a combination of the CDMA and the OFDM method, wherein the spreading is applied in frequency space. On each orthogonal subcarrier OFDM method, the chips of the codes are different Subscriber stations are timed in parallel with the code length, i. the number of chips, the number of subcarriers corresponds. By MC-CDMA The radio resources become frequency and power subscriber station specific separated.

at the radio transmission between a transmitting station and a receiving station of a radio communication system It now comes as a result of the frequency selectivity of the transmission channels in terms on the transmission characteristics to interference phenomena, called intersysmbol interference and Multiple access interference is known. These interferences the transmission signals distort the stronger, the greater the transmission bandwidth of the transmission channel is. This is therefore particularly relevant for broadband CDMA or OFDM radio communication systems.

traditionally, the transmission signals at the transmitting station are disregarded the effective radio channels generated. The then in the receiver occurring interference phenomena are, at least approximately, by appropriate adapted and generally very expensive Method for detecting the transmitted Data at the receiving stations eliminated.

For efficient suppression of the interference phenomena of the effective transmission channels in the receiver, in particular in an OFDM multiple access method, which transmits over a radio interface An efficient estimation of the channel properties is of great importance. One way of channel estimation is to transmit on the transmit side complex amplitudes known in the receiver. These known complex amplitudes are generally referred to as pilot symbols, which in turn are data-containing with special pilot signatures. From the analysis of these pilot symbols with specific pilot signatures of individual subscriber stations in the receiver, it is possible to compensate for the interference phenomena of the effective radio channel at least partially.

at a multi-party radio communication system, i. in a system with possibly several subscriber stations within one Radio cell, it is possible that several subscriber stations simultaneously use their pilot symbols, each with different pilot signatures, transmit and thus the complex Superimpose sum amplitudes of the signals of the individual participants in the receiver. The channel estimation must in this case based on the knowledge of the pilot symbols of all sending Subscriber stations and the measured complex signal amplitudes the received signal for all subscriber stations are carried out together. Compared to the case of a single subscriber station results in multiple subscribers Radio communication systems, however, due to the simultaneous activity of several Subscriber stations a degradation of the signal-to-noise ratio (SNR), i. For lead a single participant each other participants to increase the interference phenomena and thus to a reduction / degradation of the signal-to-interference ratio. In the channel estimation In a subscriber station, SNR degradation is the deciding factor Size for the quality of the channel estimation.

With Help the pilot signatures, it is possible, the interference phenomena positively influence between the subscriber stations. there plays the generation of pilot signatures for channel estimation in one cellular radio communication system with at least one transmitting Subscriber station and at least one associated with a radio cell receiving base stations communicating with each other via an uplink radio channel an important role. The channel estimate of the Upward radio channel is based on an analysis of one of the at least one subscriber station sent pilot signature.

Of the The invention is therefore based on the object, an improved method for generating pilot signatures. In particular, should the for the individual subscriber stations generated pilot signatures as possible to a negligible Degradation of the signal-to-noise ratio to lead. additionally The pilot signatures generated in this way are to be used in several radio cells can be so that even between the subscriber stations different Radio cells, the degradation of the signal-to-noise ratio negligible is.

These Task is with respect to the method by a method with the features of claim 1 solved.

refinements and further developments of the invention are subject of the dependent claims.

According to the invention, everyone will Subscriber station of the at least one radio cell as a pilot signature a different column vector assigned to a Hadamard matrix.

Using the column vectors of the Hadamard matrix as pilot signatures results in the degradation of the signal-to-noise ratio dropping substantially to 0 dB and thus being minimal. A disturbing interference by interference phenomena by pilot signatures of other subscriber stations is excluded in this choice of pilot signatures. The Hadamard matrix W ^(N) of dimension N × N, where N is a power of two, has the following form

Starting with the Hadamard matrix W ⁽¹⁾ of dimension 1X1 W (1) = (1) the Hadamard matrices of higher dimension are formed recursively; the elements W (2 · N) / i, j of the Hadamard matrix W ^{(2 · N)} of dimension 2N × 2N is obtained from the elements W (N) / i, j of the Hadamard matrix W ^(N) of dimension N × N, corresponding to i and j natural numbers

Next the minimum degradation of the signal-to-noise ratio by this choice of Pilot signatures is not a big effort for the design the pilot signatures needed. The generation of the column vectors of the Hadamard matrices is a easy to perform Method that requires little computational effort. Furthermore points the channel estimator an easy and reusable in all subscriber stations Structure on. The channel estimation is for all subscriber stations identical, with the individual subscriber stations differ only by the different pilot signatures. Usually The column vectors of Hadamard matrices are also called Walsh Codes.

• – werden aus jeweils in der Hadamard-Matrix aufeinanderfolgenden Spaltenvektoren der Hadamard-Matrix entsprechend einer Mehrzahl an jeweils benachbarten Funkzellen eine Mehrzahl von nicht überlappenden Untermatrizen gebildet, wobei die Anzahl der Untermatrizen der Anzahl an Funkzellen der Mehrzahl an Funkzellen entspricht,
• – wird jeder Funkzelle der Mehrzahl der Funkzellen eine andere Untermatrix der Hadamard-Matrix zugeordnet und
• – wird jeder Teilnehmerstation jeder Funkzelle der Mehrzahl der Funkzellen als Pilotsignatur ein unterschiedlicher Spaltenvektor der dieser Funkzelle der Mehrzahl der Funkzellen zugeordneten Untermatrix der Hadamard-Matrix zugeordnet.

Farther

• A plurality of non-overlapping sub-matrices are formed from each of the Hadamard matrix consecutive column vectors corresponding to a plurality of adjacent radio cells, the number of sub-matrices corresponding to the number of radio cells of the plurality of radio cells,
• - Each radio cell of the plurality of radio cells is assigned to a different sub-matrix of the Hadamard matrix and
• Each subscriber station of each radio cell of the plurality of radio cells is assigned as a pilot signature a different column vector of the sub-matrix of the Hadamard matrix assigned to this radio cell of the plurality of radio cells.

By the division of the Hadamard matrix into sub-matrices makes it possible to have several Radio cells, each with a certain number of subscriber stations include allocating a sub-matrix. Subscriber stations in the individual radio cells will turn the column vectors of assigned to the radio cell associated sub-matrix as pilot signatures. The number of subscriber stations in the radio cells is through the number of column vectors is limited in the associated submatirx. By the inventive method is it possible to generate different pilot signatures not only for a radio cell, but also for several neighboring radio cells, characterized by the interference phenomena can affect negatively. By this division according to the invention the column vectors it is possible that on the one hand, the degradation of the signal-to-noise ratio within the radio cell 0 dB, on the other hand, the degradation of the signal-to-noise ratio between the radio cells, which are assigned to the respective Untermatirzen is also 0 dB. The Number of radio cells, for the sub-matrices, and the associated column vectors, in one Hadamard matrix is freely selectable and is only by the Size of Hadamard Limited matrix. If the number of sub-matrices in the Hadamard matrix is reduced, so can the number of possible Subscriber stations per subcell increase. The use of Hadamard matrix does not have to be exclusive to the entire radio communication system can be provided, but special can be limited to a part of the radio cells. If the assignment of the column vectors does not follow the method according to the invention carried out, but by chance Each subscriber station is a column vector of a Hadamard matrix assigned, so leads this means that the degradation of the signal-to-noise ratio is usually in the Magnitude of at least 3 dB.

In a further development of the invention, each sub-matrix of the Hadamard matrix has an identical number of column vectors, wherein the number of column vectors of each sub-matrix is a 2 ^N -th part of the number of column vectors of the Hadamard matrix, with N of a natural number. By this division, the number of radio cells, to which a sub-matrix can be assigned, is equal to 2N, whereby each radio cell can supply the identical number of subscriber stations with pilot signatures.

Advantageously, in the radio communication system, the Hadamard matrix is reused after a certain spatial distance from the one plurality of respectively adjacent radio cells in at least one other plurality of other respectively adjacent radio cells. The radio cells assigned to the sub-matrices of a Hadamard matrix can be grouped together. Spatially separated, which means that the interference phenomena are negligible due to the Piltosignaturen between the groups, the groups can reuse the Hadamard matrix and be used for the entire radio communication system. The number of subscriber stations which can be supplied in one radio cell is determined by the dimension of the Hadamard matrix and thus by the number of radio cells combined in a group. The interference phenomena by pilot signatures of other groups have the character of white noise due to the properties of the column vectors of the Hadamard matrices, so that no additional complications are to be expected from these interference phenomena.

With particular advantage of the invention finds an application, if the Radio communication system according to the OFDM standard is specified. OFDM radio communication systems are very broadband Radio systems, with numerous subcarriers, where the channel estimation essential contributes to the correct detection of the received signal. at the radio transmission These systems come between a transmitting station and a receiving station due to the frequency selectivity the transmission channels to interference phenomena, as intersymbol interference and multiple access interference are known. These interferences distort the transmission signals all the more stronger, the larger the transmission bandwidth the transmission channel is. The inventive method can especially here significantly to reduce the interference phenomena contribute through pilot signatures.

When Usually in OFDM radio communication systems applies that the number of Subscriber stations in the radio cells of a group multiplied with the channel length (Length the impulse response) is at most equal to the number of subcarriers N and thus the dimension N × N corresponds to the Hadamard matrix. In general, the number of subcarriers a lot bigger than the channel length.

In Further development of the invention comprises the OFDM radio communication system a number N of subcarriers, with N of a number of power 2, and the Hadamard matrix is accordingly at least of the dimension N × N. For the Case of the OFDM radio communication system may be the Hadamard matrix adapted to the radio communication system such that the Dimension of the Hadamard matrix is equal to the number of subcarriers.

in the With regard to the cellular radio communication system, the above said task by a radio communication system with the features solved according to claim 6.

According to the invention the radio communication system means for assigning column vectors a Hadamard matrix to the subscriber station as a pilot signature.

The Radio communication system is particularly suitable for carrying out the method described above.

For the invention are in a radio communication system in particular the components Base stations, receiving devices, subscriber stations and transmitting devices significant.

there Each base station and each receiving device comprise at least Means for receiving and analyzing one of the at least one Subscriber station sent pilot signature.

• – Mittel zur Zuordnung von Spaltenvektoren einer Hadamard-Matrix als Pilotsignatur und
• – Mittel zum Senden der Pilotsignatur.

Furthermore, each subscriber station and each transmitter comprise at least

• Means for assigning column vectors of a Hadamard matrix as a pilot signature and
• - means for sending the pilot signature.

The Base stations, receiving devices, subscriber stations and transmitting devices are particularly suitable for carrying out the above-described Process.

details and details of the invention are described below with reference to a drawing and an illustrated embodiments explained in more detail.

in this connection shows:

1 : a cellular radio communication system with the assignment of pilot signatures according to the invention.

1 shows by way of example a cellular radio communication system with eight radio cells Z1 to Z8, which is in each case divided into two groups G1 and G2 with the radio cells Z1 to Z4 and the radio cells Z5 to Z8, as illustrated by the hatching of the radio cells shown as hexagons ,

Based on an OFDM radio communication system with eight subcarriers, the Hadamard Matrix W ⁽⁸⁾ dimension 8 × 8 is used as a starting point for the assignment of the pilot signatures. According to the above-mentioned rule in OFDM radio communication systems, according to which the number of subscriber stations in the radio cells of a group multiplied by the channel length (length of the impulse response) is at most equal to the number of Sub carrier eight and thus the dimension 8 × 8 of the Hadamard shown below Matrix W ⁽⁸⁾ corresponds.

One way of assigning the column vectors of this Hadamard matrix to the individual radio cells is to use the Hadamard Martix W ⁽⁸⁾ of dimension 8 × 8 in four sub-matrices W (8) / 1, W (8) / 2, W (8) / 3 and divide W (8) / 4 of 8 × 2 dimension. Ie. from each of the Hadamard matrix W ⁽⁸⁾ successive column vectors of the Hadamard matrix W ⁽⁸⁾ corresponding to a plurality of respective adjacent radio cells, a plurality of non-overlapping sub-matrices W (8) / 1, W (8) / 2, W (8) / 3 and W (8) / 4, wherein the number of sub-matrices corresponds to the number of radio cells of the plurality of radio cells in the group G1.

there the sub-matrices W (8) / 1 of the radio cell Z1, W (8) / 2 of the radio cell Z2, W (8) / 3 of the radio cell Z3 and W (8) / 4 assigned to the radio cell Z4.

Based on these sub-matrices W (8) / 1, W (8) / 2, W (8) / 3 and W (8) / 4, two subscriber stations of the radio cells Z1 to Z4 may each have as pilot signature a different column vector, namely SV1 or SV2 in Z1, SV3 or SV4 in Z2, SV5 or SV6 in Z3 and SV7 or SV8 in Z4, the sub-matrices W (8) / 1, W (8) / 2, W (8) / 3 and W (8) / 4 are assigned to the Hadamard matrix, with

In the exemplary OFDM radio communication system, since the interference of the pilot signatures in the adjacent group G2 can be neglected 1 the Hadamard matrix is reused after a certain spatial distance from the one plurality of respectively adjacent radio cells, namely in the group G1, in at least one other plurality of other respectively adjacent radio cells, namely the group G2. Based on these sub-matrices W (8) / 1, W (8) / 2, W (8) / 3 and W (8) / 4, in each case two subscriber stations of the radio cells Z5 to Z8 can again use a different column vector, specifically SV1, as the pilot signature or SV2 in Z5, SV3 or SV4 in Z6, SV5 or SV6 in Z7 and SV7 or SV8 in Z8, the sub-matrices W (8) / 1, W (8) / 2, W (8) / 3 and W (8) / 4 are assigned to the Hadamard matrix.

However, it is also possible to group the column vectors of this Hadamard matrix differently and accordingly to make the division of the radio cells differently. For example, the Hadamard Martix W ⁽⁸⁾ of dimension 8 × 8 can also be subdivided into sub-matrices of dimension 8 × 1, 8 × 4 or 8 × 8. Accordingly, either eight radio cells can each be assigned one subscriber station, two radio cells each have four subscriber stations, or one radio cell can be assigned to eight subscriber stations.

In Real OFDM mobile radio systems typically become sub-carrier numbers of 512 or even 1024 used. This means starting out from a 512x512 or 1024 × 1024 Hadamard Matrix awarded a total of 512 or 1024 pilot signatures can be. Taking a subdivision into 4 sub-matrices, i. 4 radio cells, On, then this means that per radio cell 128 or 256 subscriber stations can be supplied with pilot signatures.

Claims (10)

A method of generating pilot signatures for channel estimation in a cellular radio communication system having at least one transmitting subscriber station and at least one receiving base station associated with a radio cell (Z1 ... Z8) interconnected via an uplink channel, the channel estimate of the uplink channel being based on an analysis a pilot signature sent by the at least one subscriber station, characterized in that each subscriber station of the at least one radio cell as pilot signature a different column vector (SV1 ... SV8) is assigned to a Hadamard matrix, and that of each in the Hadamard matrix consecutive column vectors (SV1, SV2, SV3, SV4, SV5, SV6, SV7, SV8) of the Hadamard matrix corresponding to a plurality of respective adjacent radio cells (Z1, Z2, Z3, Z4, Z5, Z6, Z7, Z8) a plurality of non-overlapping ones Submatrices are formed, wherein the number of sub-matrices d the number of radio cells of the plurality of radio cells corresponds to each radio cell (Z1, Z2, Z3, Z4; Z5, Z6, Z7, Z8) of the plurality of radio cells a different sub-matrix of the Hadamard matrix is assigned and that each subscriber station of each radio cell of the plurality of radio cells as a pilot signature a different column vector (SV1, SV2, SV3, SV4, SV5, SV6; SV7, SV8) is assigned to the subcatrix of the Hadamard matrix assigned to the radio cell of the plurality of radio cells. A method according to claim 1, characterized in that each sub-matrix of the Hadamard matrix has an identical number of column vectors, the number of column vectors of each sub-matrix being a 2 ^N -th part of the number of column vectors of the Hadamard matrix, with N being a natural number , Method according to one of claims 1 to 2, characterized that in the radio communication system the Hadamard matrix after a certain spatial Distance from the one plurality of each adjacent radio cells (Z1, Z2, Z3, Z4) in at least one other plurality of others each adjacent radio cells (Z5, Z6, Z7, Z8) reused becomes. Method according to one of claims 1 to 3, characterized the radio communication system is specified according to the OFDM standard is. Method according to claim 4, characterized in that the OFDM radio communication system comprises a number N of subcarriers, with N of a number of power 2, and the Hadamard matrix accordingly at least of the dimension N × N is. Arrangement in the form of a cellular radio communication system with at least one transmitting subscriber station and at least a receiving base stations associated with a radio cell for performing a Method according to one of the preceding claims, comprising: - Medium for assigning column vectors of a Hadamard matrix to the subscriber station as a pilot signature, - Medium for forming a plurality of non-overlapping sub-matrices from each in the Hadamard matrix consecutive column vectors the Hadamard matrix corresponding to a plurality of adjacent ones Radio cells, where the number of sub-matrices of the number of radio cells corresponds to the plurality of radio cells, Means for allocating to Plurality of radio cells another sub-matrix of the Hadamard matrix, - funds for assigning to each subscriber station each cell of the plurality the radio cells of a different column vector of this Radio cell of the plurality of radio cells associated sub-matrix of the Hadamard matrix as a pilot signature. Base station in a radio communication system according to Claim 6 comprising: - Medium for receiving and analyzing one of the at least one subscriber station sent pilot signature. Receiving device in a base station according to claim 7 comprising: - Medium for receiving and analyzing one of the at least one subscriber station sent pilot signature. Subscriber station in a radio communication system according to claim 6 comprising: - Means of allocation of Column vectors of a Hadamard matrix as a pilot signature - Medium to send the pilot signature. Transmitting device in a subscriber station Claim 9 comprising: - Medium for assigning columns of a Hadamard matrix as a pilot signature - Medium to send the pilot signature.