KR101221907B1 - Method For Multiplexing UE Signals Having Different Bandwidth, And Method For Transmitting Uplink Signal - Google Patents

Abstract

The present invention relates to a multiplexing method of user equipment signals having various bandwidths and an uplink signal transmission method therefor. According to the present invention, a bandwidth corresponding to a common factor of bandwidths of a plurality of user devices having different bandwidths is set as a default bandwidth, a basic sequence having a default bandwidth length is selected, and multiplexing is performed. When the bandwidth is wider than that, the signals of the plurality of user equipments are multiplexed by using a repeating sequence in which the basic sequence is repeated. Through this, orthogonality can be maintained between sequences used for multiplexing, and signals of user equipment having different bandwidths can be easily distinguished by the base station.

CAZAC, repeating sequence

Description

Method for multiplexing user equipment signals having various bandwidths and method for transmitting uplink signals {Method For Multiplexing UE Signals Having Different Bandwidth, And Method For Transmitting Uplink Signal}

1 is a diagram illustrating a method of multiplexing a signal of a user equipment (UE) having a different bandwidth by FDM scheme.

FIG. 2 is a diagram for explaining the transmission of a separate pilot for measuring channel quality of a band where each user does not transmit his or her data in the FDM scheme. FIG.

3 is a view for explaining the possibility that inter-cell interference occurs in the FDM scheme.

4 and 5 are diagrams for explaining a multiplexing scheme between UEs having different bandwidths according to an embodiment of the present invention.

6 is a flowchart illustrating a method for transmitting an uplink signal by a UE according to an embodiment of the present invention.

1.3GPP, R1-060046, NTT DoCoMo, et al., "Orthogonal Pilot Channel Structure in E-UTRA Uplink"

The present invention relates to a communication system, and more particularly, to a multiplexing method of a user equipment signal having various bandwidths and an uplink signal transmission method therefor.

The 3GPP LTE system considers using two reference signals or pilot blocks for uplink. When UEs present in one system, ie, in the same cell or sector, have the same bandwidth, in the 3GPP LTE system, the CDM scheme, the FDM scheme, and the hybrid scheme of the CDM and FDM as a scheme for distinguishing the above-described pilots (Hybrid CDM and FDM) scheme, etc. are being considered.

In the CDM scheme, each UE multiplies a signal to be transmitted by a predetermined sequence and transmits it through uplink, and the base station receiving the UE distinguishes a signal of each UE by using a sequence multiplied by the transmission signal. That's the way. In such a CDM scheme, it is common to use the following CAZAC sequence. GCL CAZAC and Zadoff-Chu CAZAC are two types of CAZAC sequences. They are conjugated to each other and GCL CAZAC can be obtained by taking the conjugate complex number of Zadoff-Chu. Zadoff-Chu CAZAC is given by

Here k denotes a sequence index, N denotes a length of a CAZAC sequence to be generated, and M denotes a sequence ID.

When the Zadoff-Chu CAZAC sequence given by Equation 1 and Equation 2 and the GCL CAZAC sequence in a conjugate complex relationship thereof are represented by c (k; N, M), all three features are as follows.

Equation 3 shows that a CAZAC sequence always has a size of 1, and Equation 4 shows that an auto-correlation function of a CAZAC sequence is represented as a delta function. Here autocorrelation is based on circular correlation. Also, Equation 5 shows that the cross-correlation is always constant.

On the other hand, since there are several UEs in one base station or sector in uplink, it is necessary to distinguish each UE accordingly. Conventionally, when a CDM scheme is applied to a UE having the same transmission bandwidth in a system applying a CAZAC sequence, a circular shift method is mainly used for a CAZAC sequence to distinguish pilots of UEs. That is, when there are N UEs, the pilots of the respective UEs are multiplexed by applying a cyclic shift to the sequence using a shift value of the length L / N divided by the length L of the sequence L by the number N of UEs. Done. More specifically, a method of applying a cyclic shift to a sequence has been invented by the inventor and filed by the present applicant, which is incorporated herein by reference, and "Code sequences in a communication system and methods and apparatus for transmitting and generating them". (Patent Application 2006-64091).

As described above, using the CAZAC sequence to which the cyclic shift is applied takes advantage of the property that zero cross correlation is maintained between the CAZAC sequences to which the cyclic shift is applied to different degrees. Orthogonality ".

Currently, 3GPP LTE is discussing UEs using various bandwidths. In view of the above-described CDM scheme, there is a problem in that orthogonality is not maintained between sequences having different bandwidths, that is, sequences having different bandwidths, due to the characteristics of the CAZAC sequence when multiplexing between UEs having different transmission bandwidths. In addition, the above-mentioned pilot block among the uplink signals should be divided so that orthogonality is maintained between UEs, and when the orthogonality is broken, degradation due to channel estimation occurs, thereby causing a performance limitation. Therefore, a new method for applying the CDM scheme between UEs having different bandwidths is needed.

In this regard, when UEs in the system have different transmission bandwidths, DoCoMo proposed the following distributed FDMA scheme for pilot classification of different transmission bandwidths.

FIG. 1 is a diagram illustrating a method of multiplexing signals of a user equipment (UE) having different bandwidths in an FDM scheme.

1 shows a case where UEs having transmission bandwidths of, for example, 1.25 MHz, 5 MHz, and 10 MHz exist on one system, ie in one cell, or sector. In this case, among UEs having different bandwidths such as 1.25 MHz, 5 MHz, and 10 MHz within 10 MHz of the entire band available to the UE, each UE can be distinguished by using different frequency bands on the frequency axis in a distributed FDMA manner. That's how it works. In addition, different original sequences (e.g., CAZAC # 1, CAZAC # 2, etc.), orthogonal sequences having different degrees of cyclic shift in the same original sequence within the transmission band of each UE having the same bandwidth (e.g., , CAZAC # 1, shift # 1 to CAZAC # 1, shift #N, etc.) to apply the multiplexing method by the CDM method.

However, in the case of the FDM method may have the following problems.

FIG. 2 is a diagram for explaining the transmission of a separate pilot for measuring channel quality of a band in which each user does not transmit his data in the FDM scheme.

In the case of FDM, each UE (each UE having a different bandwidth) transmits data by receiving one of the frequency bands allocated to the UEs using the bandwidth as the frequency band used by the UE. In addition, a separate pilot (for example, a CQ pilot) for transmitting channel quality is transmitted for the remaining frequency bands (out-band). This is because it is possible to transmit a signal through the band when it is judged that the channel quality of the other frequency band is better than the frequency band currently used, but transmitting the CQ pilot to all the frequency bands other than the frequency band to be used is a kind of over. It may not be desirable as a head. On the other hand, in the case of the CDM scheme, not only the pilot signals of the UEs are distinguished by the code sequence but also the pilot is allocated to the CDM scheme for all the bands available to the remaining UEs in addition to the frequency band for transmitting data allocated thereto. Therefore, since there is no need for a CQ pilot to separately check the quality of the unused channel, such an overhead can be reduced.

3 is a view for explaining the possibility of inter-cell interference in the FDM scheme.

In case of FDM multiplexing, if there are UEs (eg, UE a in cell A and UE b in cell B) that use the same frequency band in adjacent cells as in cell A and cell B in FIG. Interference may occur between uplink signals. Of course, even in the case of the CDM scheme, signal interference with neighboring cells cannot be completely excluded, but in the case of CDM using the entire bandwidth available in the cell, the influence of the interference signal from the neighboring cell may cause signal interference in a specific bandwidth, such as FDM. It is not as critical as the problem, and there is an advantage that the indirect problem between adjacent cells can be easily solved through a method of differently allocating sequences for distinguishing UEs in each cell.

In addition, due to a problem that an error may occur due to a deterioration of a channel condition of a specific frequency band in FDM, a technique for multiplexing signals of UEs having different bandwidths while still maintaining the CDM scheme is required. have.

In order to solve the above problems, an object of the present invention is to provide a method for multiplexing so that a base station can easily distinguish uplink signals of UEs having different transmission bandwidths while maintaining a CDM scheme.

Another object of the present invention is to provide a method for transmitting an uplink signal in a UE in order to perform such multiplexing.

A multiplexing method according to an embodiment of the present invention for achieving the above object comprises the steps of setting a bandwidth corresponding to a common factor of bandwidths used by each of a plurality of user equipment as a basic bandwidth; Selecting basic sequences corresponding to the basic bandwidths for signal multiplexing of the plurality of user equipments; And multiplexing the basic sequence using a repeated sequence in the case of a signal of the user equipment using a bandwidth equal to or greater than the basic bandwidth among the plurality of user equipments.

In this case, the number of times of repeating the basic sequence in the multiplexing step may correspond to the number of bandwidths of a user device using a bandwidth equal to or greater than the basic bandwidth divided by the basic bandwidth, and selecting a basic sequence corresponding to the basic bandwidth. The base sequences selected from may be sequences selected from the group consisting of different original sequences, sequences in which orthogonality is maintained by applying different cyclic shifts to the same original sequence, and a combination thereof.

On the other hand, the uplink signal transmission method according to another embodiment of the present invention comprises the steps of selecting a predetermined sequence as a signal to be transmitted; And transmitting the selected predetermined sequence through uplink, wherein the predetermined sequence repeats the basic sequence when the bandwidth used by the user equipment is wider than the bandwidth of the basic sequence. It is characterized by a sequence of one form.

In this case, the basic sequence may be a sequence having a bandwidth corresponding to a common factor of bandwidths of a plurality of user equipments serviced by the same base station as the user equipment, and the basic sequence may be different from original source sequences. It may be a sequence selected from the group consisting of sequences that maintain orthogonality with each other by applying different cyclic shifts to the original sequence, and a combination thereof.

Finally, a signal classification method according to another embodiment of the present invention includes the steps of receiving an uplink signal; And identifying which user equipment the received signal is transmitted from by using the predetermined sequence used for the received signal, wherein the predetermined sequence includes a plurality of user equipments serviced by the base station. It is characterized in that the base sequence having a basic bandwidth corresponding to the common factor of the bandwidth.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following detailed description, together with the accompanying drawings, is intended to illustrate exemplary embodiments of the invention and is not intended to represent the only embodiments in which the invention may be practiced. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, those skilled in the art will appreciate that the present invention may be practiced without these specific details. In some instances, well-known structures and devices are omitted or shown in block diagram form around the core functions of each structure and device in order to avoid obscuring the concepts of the present invention. In addition, the same components will be described with the same reference numerals throughout the present specification.

The present invention relates to a reference signal multiplexing method and a method for transmitting an uplink signal for distinguishing a reference signal or a pilot between these UEs even when UEs present in the system have different transmission bandwidths as described above. .

To this end, if UEs present in the same cell or sector have different transmission bandwidths, it is set as the default transmission bandwidth based on the common factor of the different transmission bandwidths, and accordingly the CAZAC sequence length is assigned to the default sequence length, It is proposed to use a method of transmitting a repetitive sequence for a UE having a transmission bandwidth of more than the transmission bandwidth. Specifically, the above-described method will be described in detail with reference to FIGS. 4 and 5.

4 and 5 are diagrams for explaining a multiplexing scheme between UEs having different bandwidths according to an embodiment of the present invention.

First, referring to FIG. 4, FIG. 4 illustrates one example of UEs having a transmission band of 1.25 MHz, UEs having 5 MHz, and UEs having 10 MHz. That is, for UEs having three different transmission bandwidths of 1.25 MHz, 5 MHz, and 10 MHz, a common factor of three different bandwidths, most preferably, a maximum common factor of 1.25 MHz is regarded as a basic transmission bandwidth and is based on the length. A CAZAC sequence of may be generated as a base sequence. In one embodiment of the present invention, the basic transmission band may be set to any bandwidth as long as it is a bandwidth corresponding to a common factor of bandwidths of different UEs, but when a sequence is applied to a narrow bandwidth, orthogonality is maintained and cyclic shift is applied. Since the number of orthogonal sequences can be reduced, it is preferable to set the bandwidth corresponding to the greatest common divisor as described above.

According to an embodiment of the present invention, one CAZAC sequence index is selected for selecting an original sequence for multiplexing a signal of a corresponding UE among multiple sequence indexes having the base frequency band length determined as described above. Thereafter, a cyclic shift version that applies a predetermined amount of cyclic shift to the CAZAC sequence of the selected index, that is, another type of CAZAC sequence shift # 1, CAZAC sequence shift # 2, ... is selected. Of course, the sequences to which such a circular shift is applied should be orthogonal to each other.

As described above, the UE that selects a basic sequence having a default transmission bandwidth length takes a sequence form of repeating it to fit its own transmission bandwidth and configures it as a sequence for CDM. For example, in case of a UE having a 5 MHz bandwidth, a sequence of four times the CAZAC sequence shift # 2 selected as a base sequence having a basic transmission bandwidth length of 1.25 MHz is configured as a sequence for CDM, and 10 MHz In case of a UE having a bandwidth, a sequence of 8 times the CAZAC sequence shift # 3 selected as a basic sequence is configured as a sequence for CDM.

In such a configuration, when receiving an uplink signal from the base station, all the signals of the UEs can be viewed as a format in which a cyclically shifted CAZAC sequence having a length of 1.25 MHz is received. Multiplexing of these reference signals or pilots is possible without compromising orthogonality. That is, the uplink signal classification method of the base station for receiving signals from a plurality of UEs according to an embodiment of the present invention and distinguishing which signals are received from which UEs through a sequence used for each signal is as described above. A UE that has transmitted a signal may be distinguished based on which base sequence among base sequences having a bandwidth corresponding to common factors of a plurality of UEs is used.

Next, referring to FIG. 5, in FIG. 5, when the entire transmission band is 20 MHz, one example of UEs having a transmission band of 10 MHz and UEs having 15 MHz is shown. That is, for UEs having two different transmission bandwidths of 10 MHz and 15 MHz, a common factor, preferably a maximum common factor of 5 MHz, is set as a basic transmission bandwidth at two different bandwidths, and a CAZAC having a length based thereon Create a sequence.

In addition, one CAZAC sequence index among a plurality of sequence indexes having a base bandwidth length determined as described above is selected. Thereafter, a cyclic shift version that performs a cyclic shift on the CAZAC sequence of the selected index, that is, another type of CAZAC sequence shift # 1, CAZAC sequence shift # 2, ..., is selected, and the corresponding UEs are adapted to their transmission bandwidths. It can be repeated to form a code sequence for use in the CDM. Accordingly, since the CAZAC sequence having a length of 5 MHz is received when the base station receives the base station, the base station can multiplex the reference signals or pilots of UEs having different transmission bandwidths.

In the above-described example, the description has been made mainly on the case where a plurality of user devices perform multiplexing using CAZAC sequences having different bandwidth lengths, but the plurality of user devices multiplex using CAZAC sequences having different time lengths. Even when performing, the CAZAC having a length corresponding to the common divisor of these time lengths is set as the base sequence, and the UEs maintain the orthogonality by repeatedly using the UE according to the time length of the sequence that each UE uses for the CDM. An example of classifying an uplink signal may also be possible.

In addition, the repetition method of the CAZAC sequence may be implemented by direct repetition insertion in the time domain / frequency domain. Alternatively, the CAZAC sequence may be generated as a repetitive sequence by predetermined processing in a region different from the repeated time domain / frequency domain. It may be apparent to those skilled in the art.

Hereinafter, a method of transmitting an uplink signal from a UE for signal multiplexing of UEs having different frequency bands by using the CDM scheme as described above will be described.

6 is a flowchart illustrating a method of transmitting an uplink signal by a UE according to an embodiment of the present invention.

In the uplink signal transmission method according to an embodiment of the present invention as shown in FIG. 6, the UE selects a basic sequence to be used for its uplink signal multiplexing in step S601. The base sequence is a sequence selected from the group consisting of different original sequences, such as CAZAC sequences having different IDs, orthogonal sequences that maintain orthogonality with each other by applying different cyclic shifts to the same original sequence, and a combination thereof. A sequence having a basic bandwidth as described above with reference to FIGS. 4 and 5.

When the above-described multiplexing scheme as described in FIG. 4 and FIG. 5 is defined in a specific communication system, the communication system may preset the above-described base frequency band and basic sequences in consideration of bandwidths of UEs, and accordingly, The UE may select a sequence to be used for its multiplexing among predetermined base sequences in the communication system when the uplink signal is transmitted.

Thereafter, the UE checks whether the frequency bandwidth used by the UE is wider than the aforementioned basic frequency bandwidth in step S602. If its use frequency bandwidth is wider than the base frequency band, the process proceeds to step S603 in which the UE repeats the base sequence selected in step S601 to have a bandwidth length used by itself, and repeats the repeated sequence in this manner in step S604. Configure as a signal. The configuration of the CDM signal may be a repetitive sequence, for example, a CAZAC sequence of a reversal type when the signal to be transmitted is a pilot signal.In contrast, when the signal to be transmitted is specific data, a CAZAC of repetitive form is applied to the corresponding data. ) May be multiplied by a sequence. Thereafter, the CDM signal thus generated is transmitted via step S606.

On the other hand, if the bandwidth used by the UE is not greater than the default bandwidth, the flow proceeds to step S605, where the UE generates a CDM signal using the basic sequence as it is and transmits the generated CDM signal in uplink through step S606. do. Of course, the generated CDM signal may be a base sequence itself when the transmission signal is a pilot, and may be a form in which the base sequence is multiplied by the data when the transmission signal is specific data.

In the case of the CDM signal generated as described above, even if the sequence used in the transmission signal is detected through a sequence corresponding to the fundamental frequency bandwidth length even when the sequence used is different from the sequence used by another UE, the orthogonality is maintained. It can be easily distinguished from which UE the transmission signal is a signal transmitted.

The detailed description of the preferred embodiments of the invention disclosed as described above is provided to enable any person skilled in the art to make and practice the invention. Although the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art will variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. I can understand that you can. Accordingly, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

According to one embodiment of the present invention as described above, a bandwidth corresponding to a common factor of different transmission bandwidths of a plurality of UEs is set as a basic bandwidth, and a basic sequence applied to the basic bandwidth is selected to be equal to the bandwidth of the corresponding UE. By using it repeatedly, orthogonality can be maintained even when the lengths are different among sequences used for multiplexing, and the base station can easily distinguish from which UE a received uplink signal is transmitted while maintaining the CDM scheme as the multiplexing scheme. Can be.

In addition, the UE transmits a signal by the uplink transmission method as described above, thereby implementing CDM multiplexing according to the present invention.

Claims (7)

Setting a bandwidth corresponding to a common factor of bandwidths used by each of the plurality of user devices as a default bandwidth; Selecting basic sequences corresponding to the basic bandwidths for signal multiplexing of the plurality of user equipments; And And multiplexing the basic sequence using a repeated sequence in the case of signals of the user equipment using a bandwidth equal to or greater than the basic bandwidth among the plurality of user equipments. The method of claim 1, The number of times to repeat the basic sequence in the multiplexing step, And a bandwidth of a user device using a bandwidth greater than or equal to the basic bandwidth divided by the basic bandwidth. The method of claim 1, The base sequences selected in the base sequence selection step corresponding to the base bandwidth, And a sequence selected from the group consisting of different original sequences, sequences in which orthogonality is maintained by applying different circular shifts to the same original sequence, and a combination thereof. Selecting a predetermined sequence as a signal to be transmitted; And In the uplink signal transmission method of the user equipment comprising the step of transmitting the selected predetermined sequence over the uplink, The predetermined sequence is an uplink signal transmission method, characterized in that the repeating of the base sequence when the bandwidth used by the user equipment is larger than the bandwidth of the base sequence. 5. The method of claim 4, The basic sequence is And a sequence having a bandwidth corresponding to a common factor of bandwidths of a plurality of user equipments serviced by the same base station as the user equipment. 6. The method of claim 5, The basic sequence is And a sequence selected from the group consisting of different original sequences, sequences in which orthogonality is maintained by applying different cyclic shifts to the same original sequence, and a combination thereof. Receiving an uplink signal; And In the signal classification method of the base station comprising the step of identifying from which user equipment the received signal is transmitted through a predetermined sequence used for the received signal, And the predetermined sequence is a basic sequence having a basic bandwidth corresponding to a common factor of bandwidths of a plurality of user equipments serviced by the base station.

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