KR101328952B1 - Method For Generating Signals - Google Patents

Abstract

Disclosed is a signal generation method having flexibility for transmitting various types of transmission signals.

That is, information symbols are input to at least one of the frequency domain and the time domain, and the input information symbols are sequentially modulated in the frequency domain and the time domain, and such frequency domain and time domain modulation multiplexes each domain input symbol. Disclosed is a method of setting up to be performed after a flush.

In addition, the information symbol is spread in symbol units in the first region, which is one of a frequency domain and a time domain, and the first spreading symbol is modulated in the first region to generate a first region modulation symbol. A method of generating a transmission signal by modulating a first region modulation symbol in a second region, which is another one of a time domain and a frequency domain, is disclosed.

Symbolic Unit Spreading, Multiplexing, and Flexibility

Description

Method for Generating Signals

1 is a schematic diagram showing a configuration of a transmitting end of a typical SC-FDM communication system.

2 is a flowchart illustrating a method of generating a transmission signal according to an embodiment of the present invention.

3 illustrates a channel structure that may be used when transmitting only a control signal without data.

4 illustrates a channel structure that may be used when data and control signals are transmitted together.

5 is a diagram for describing a method of generating a TTI unit symbol modulated in a time and frequency direction according to a sequence modulation scheme according to an embodiment of the present invention;

FIG. 6 is a diagram for describing a method of generating a transmission unit symbol modulated in a time and frequency direction according to another embodiment of the present invention. FIG.

FIG. 7 illustrates a method of spreading an information symbol in a frequency unit in a symbol unit according to an exemplary embodiment of the present invention, and then performing modulation in each region through multiplexing of time and frequency domain modulation / masking sequences to perform transmission signal transmission. Figure showing how to create.

FIG. 8 illustrates spreading an information symbol in a time domain according to a preferred embodiment of the present invention, and then performing modulation in each domain through multiplexing of time and frequency domain modulation / masking sequences to perform transmission signal transmission. Figure showing how to create.

FIG. 9 illustrates an example for applying control signals of various formats when the size of the control signal channel is fixed according to an exemplary embodiment of the present invention. FIG.

10 shows an example of a method of defining a spreading format based on a control signal format in each UE.

FIG. 11 is a diagram for explaining one preferred method that can be used when defining different resources according to a control signal format. FIG.

The following description is directed to a signal generation method having flexibility for transmitting various types of transmission signals.

In a Universal Mobile Telecommunications System (UMTS) communication system including 3GPP 3rd Generation Partnership Project Long Term Evolution (LTE), a transmitting end is a time unit for transmitting one or more transmission blocks, that is, higher layer transmission information simultaneously. Transmission Time Interval (“TTI”) is defined. In case of small packet data transmission such as VoIP, a slot included in the 1 TTI is defined as a unit for transmitting corresponding information at the same time. Such a TTI may include a plurality of OFDM symbols in the time direction. In the current 3GPP LTE, it is assumed that 14 OFDM symbols are included in 1 TTI and 2 slots are included in 1 TTI.

Meanwhile, in 3GPP LTE, specific information is transmitted in units of one OFDM symbol. For example, the SC-FDM scheme used as an uplink transmission scheme including a control signal in the 3GPP LTE scheme is as follows.

When the terminal transmits a control signal to the base station, one of the most important points is coverage. That is, the bandwidth of the signal transmitted by the terminal is not large, it is important to concentrate the power to transmit in one place, and it is also preferable that the change width (PAPR or CM) of the transmission signal is also small. To this end, in 3GPP LTE, it is discussed to use SC-FDM (Single Carrier Frequency Division Multiplexing) as an uplink signal transmission.

1 is a schematic diagram illustrating a configuration of a transmitting end of a general SC-FDM communication system.

SC-FDM is a transmission scheme for improving PAPR characteristics by making a small amount of signal change, and has a wider coverage effect when the same power amplifier is used. As can be seen through the configuration of the transmitter of the SC-FDM scheme as shown in Figure 1, the biggest feature of the SC-FDM is that the transmission signal is first spread by the DFT module 101 to the DFT. This spread signal is mapped to a transmission signal (Tx Signal) in the OFDM symbol unit by the IDFT module, preferably the IFFT module 102 as shown in FIG. The generated transmission signal is concentrated and transmitted in the transmission frequency band, and the generated signal has the same effect as that transmitted through a single carrier.

Meanwhile, the transmission signal currently proposed in 3GPP LTE using the SC-FDM scheme as described above is based on the structure that information is transmitted in one OFDM symbol unit. However, a control signal currently proposed in 3GPP LTE does not clearly present a method for supporting multiple formats, obtaining various spreading gains, or increasing the number of UEs.

In particular, even when the same user transmits different amounts of control signals, a control channel structure that can flexibly support this is required, but no clear method has been proposed.

In accordance with the above-described aspect, an embodiment of the present invention is to provide a method for generating a transmission signal capable of supporting multiple formats or obtaining various spreading gains.

In addition, even if the number of UEs is increased, interference between signals of the UE can be minimized, and a transmission signal generation method capable of supporting a user transmitting various amounts of signals is provided.

A signal generation method according to an embodiment of the present invention for achieving the above object comprises the steps of: inputting an information symbol in at least one of a frequency domain and a time domain; And sequentially modulating the input information symbol in the frequency domain and the time domain, wherein the frequency domain and time domain modulation is performed after multiplexing each domain input symbol.

In this case, in the information symbol input step, the information symbols may be input by spreading the information symbols in symbol units.

On the other hand, the signal generation method according to another embodiment of the present invention for achieving the above object comprises the steps of spreading the information symbol in the symbol unit in the first region which is one of a frequency domain and a time domain; Generating a first region modulation symbol by modulating the information symbol spread in the symbol unit in the first region; And generating a transmission signal by modulating the first region modulation symbol in a second region, which is another one of the time domain and the frequency domain.

At this time, in the symbol unit spreading step, the symbol unit spread gain of the information symbol may be set in proportion to the service quality level required for the information symbol.

The generating of the first region modulation symbol may include: multiplexing information symbols spread on a per symbol basis; And modulating the multiplexed information symbol in the first region, wherein the transmitting signal generation step comprises: multiplexing the second region modulation sequence in the second region; And performing the second region modulation on the first region modulation symbol by using the multiplexed second region modulation sequence.

In addition, when the size of the channel for transmitting the transmission signal is fixed, the information symbol is to have a predetermined size by any one or more of channel coding, spreading, and rate matching the control signal or data having different sizes The information symbols may be generated by being spread by performing control channel specific spreading to remove interference between signals from different user equipments. In addition, when the channel size for transmitting the transmission signal is variable, it is preferable to divide the channel into one or more channels having a small number of subcarriers.

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.

As described above, the present invention provides a method of generating a transmission signal capable of supporting multiple formats or obtaining various spreading gains. To this end, first, as an embodiment of the present invention, a method of generating a symbol of a transmission unit based on a unit of simultaneously transmitting predetermined information such as a TTI or a slot, rather than a symbol unit, is proposed. Such an embodiment has the advantage that additional information can be transmitted to the transmission information through modulation in the time and / or frequency direction, and further described in terms of generating a transmission signal through time and frequency domain modulation. The present invention can be applied to a transmission signal generation method supporting various control signal formats according to an exemplary embodiment of the present invention.

2 is a flowchart illustrating a method of generating a transmission signal according to an embodiment of the present invention.

That is, the method of generating a transmission signal as shown in FIG. 2 is for explaining a comprehensive method of generating a transmission signal through time and frequency domain modulation.

First, in step S201, a predetermined sequence representing a transmission signal is modulated in either the time direction or the frequency direction (hereinafter referred to as "first direction"). If the first direction modulation is modulation in the time domain, the first direction modulation may be performed by multiplying with a time direction modulation sequence having an OFDM symbol length included in a transmission unit of a corresponding system, such as 1 TTI or 1 slot. When the modulation is modulation in the frequency domain, the modulation may be performed by multiplying a frequency direction modulation sequence having a length equal to the number of subcarriers used to transmit conventional unit information. However, in a preferred embodiment of the present invention, a process of spreading each information symbol in symbol units may be set to transmit various amounts of transmission signals in the first direction modulation process. Preferably, the first direction modulation may be performed after multiplexing the input sequence in order to give flexibility to the length of the input signal during the first direction modulation.

Meanwhile, the time direction modulation and the frequency direction modulation mean a process of spreading or scrambling a predetermined transmission sequence in the time direction or the frequency direction.

In addition, the first directional modulation sequence used may be an exponential function sequence for applying a cyclic shift to another region and the same region when the transmission sequence is a CAZAC sequence. Sequences can be used.

Accordingly, the first direction sequence is generated in step S202. That is, the first direction sequence refers to a sequence in which the transmission sequence is modulated in one of a time direction and a frequency direction.

Thereafter, in step S203, the first direction sequence generated by step S202 is modulated in a direction other than the first direction in the time direction or the frequency direction (hereinafter referred to as "second direction"). In one embodiment of the present invention, the second direction modulation is the same as the first direction modulation described above, or the OFDM symbol length or one included in the time domain in one TTI or slot, the first direction sequence generated by step S202. It may be performed by multiplying with a second direction modulation sequence having a length equal to the number of subcarriers used to transmit unit information of. In a preferred embodiment of the present invention, the first direction sequence is generated by multiplexing the modulated sequence in the first direction modulation step, and a second direction sequence is generated for the first direction sequence generated as described above. The second direction modulation may be performed through a multiplexed symbol, thereby providing flexibility in modulation in each region.

According to the second direction modulation, in step S204, time and frequency direction modulation symbols of a transmission unit are generated, through which the additional information can be transmitted in the modulation step to each region as well as the information of the transmission sequence itself. Signal transmission in various formats can be performed by generating a transmission signal by performing symbol unit modulation in the direction modulation, and / or multiplexing the modulated signal in each region to perform modulation in another region.

For example, when the CAZAC sequence is used as a transmission sequence, two sequences having different cyclic shifts applied to the corresponding transmission sequence can be allocated to each UE, and each can be used to indicate ACK / NACK information. The movement may be directly applied in the process of transmitting the transmission sequence. However, when the transmission unit symbol as in the present embodiment is used, the movement may be applied in the process of performing time domain or frequency domain modulation on the transmission sequence. In addition, for the above-described information such as ACK / NACK that requires a low BER requirement, by spreading to have a high spreading gain in a symbol unit spreading step during the first direction modulation, a transmission signal is generated, thereby providing various service levels. Can support

Meanwhile, the "transmission unit" used in the embodiment of the present invention described above with reference to FIG. 2 is a concept including all of time units for transmitting transmission information such as TTI and slot at the same time. The following description focuses on the case where the above-mentioned transmission unit is TTI for convenience of description, but it is not necessary to limit the transmission unit to the TTI as described in the following embodiments.

Meanwhile, the scheme described above with reference to FIG. 2 may be applied to a control channel for transmitting a control signal in uplink using SC-FDM, and thus, the transmission signal may have a greater number of transmission signal uniformity (PAPR / CM) and cell coverage. Control information can be transmitted at the same time. In this regard, the channel structure used when transmitting a control signal in the SC-FDM scheme will be described.

There is a part to be considered when transmitting a control signal in the above-described SC-FDM scheme. First, when transmitting a control signal, different channel structures may be used as follows depending on whether or not there is data.

3 is a diagram illustrating a channel structure that may be used when only a control signal is transmitted without data.

When transmitting a control signal, when there is no data to be sent together, as shown in FIG. 3, a structure in which the control signal is divided into frequency division multiplexing (hereinafter, referred to as "FDM") and allocated to a portion of the system band may be used. Specifically, the control channel region allocated for control signal transmission without data transmission may be single at both ends of the system band as shown in FIG. 3.

The terminal transmitting only the control signal according to the control channel formed as described above may demodulate and transmit the control signal in the SC-FDM format to the allocated area. The method of transmitting a control signal in this allocated area may be FDM or code division multiplexing (hereinafter, referred to as "CDM") between the control signals of the terminal in the allocated area.

4 illustrates a channel structure that may be used when data and control signals are transmitted together.

Even when data and control signals are transmitted together, some bands of the system band may be divided for FDM scheme and allocated for control channel transmission as shown in FIG. 3. In this case, the transmission scheme cannot be viewed as an SC-FDM scheme. This corresponds to a multi-carrier transmission scheme. Accordingly, even when data and control signals are simultaneously transmitted, data and control signals are transmitted together through DFT spreading in order to maintain the SC-FDM scheme and reduce the PAPR of the transmission signals. In this case, the method of combining the data and the control signal may be time division multiplexing (“TDM”), CDM, or modulation-based transmission, and FIG. 4 illustrates that the control signal and the data are transmitted in the TDM scheme.

In the structure shown in FIG. 4, a method of increasing coverage in the absence of a control signal may be similarly implemented. When it is necessary to send a control signal robustly, a method of repeatedly inserting a specific control signal in each OFDM symbol is required. to be. This can increase the power of the control signal approximately 10 * log ₁₀ (12) = 10.8 dB.

The following description of the control channel structure described above will focus on the case where a time and frequency direction modulated transmission signal is applied to a control channel transmitting only a control signal without data according to each embodiment of the present invention. That is, in the basic control channel structure as shown in FIG. 3, more control information can be transmitted without affecting the uniformity of PAPR / CM, etc. of the control signal, and control information of various formats is required according to the required service level. We propose a control signal transmission structure that can be flexibly modulated. However, the method of generating the transmission signal and transmitting the signal according to each embodiment of the present invention may not necessarily be used only for the above-described control signal transmission, and may be applied to any system.

On the other hand, when the above-described embodiment of the present invention is transmitted using a channel for transmitting only a control signal without data, a CAZAC sequence, specifically a Zadoff-Chu (ZC) CAZAC sequence, is used as a sequence used for transmitting a control signal. Do.

Hereinafter, the above-described CAZAC sequence will be described.

As the CAZAC sequence, two kinds of the aforementioned Zadoff-Chu CAZAC and GCL CAZAC are used. They are conjugated to each other and GCL CAZAC can be obtained by taking the conjugated complex number of Zadoff-Chu. Zadoff-Chu CAZAC is given as follows.

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

On the other hand, the above-described ZC sequence is the most available sequence when the sequence length N is a prime number, and if the length of the sequence is not a prime number, the ZC sequence is valid only for a decimal M value relative to N (M is from 1). Up to N-1). Therefore, it is better to make the sequence to be small so as to be the length.

In case of transmitting a control signal without data in 3GPP LTE, a control channel is configured as shown in FIG. 3, and a basic allocation unit is called a resource block (RB), and the number of subcarriers is 12. No matter how the default allocation unit is set, if the value is not prime, it is recommended to generate a fractional length sequence for this length. Currently, the methods mentioned above generate a sequence with a fractional length longer than N, There are two ways to cut and write only N, create a sequence with a fractional length shorter than N, fill the rest with zeros, or copy and fill a portion of the sequence. In addition, even if N is not a prime number, there is a method of generating a CAZAC sequence as it is. In this case, the number of generated sequences is very small. Signal uniformity in the time / frequency domain (PAPR, cubic metric, etc.) is a good feature.

In the following detailed description of the present invention, it is assumed that all three schemes described above can be used, and the method is selected according to the appropriate RB size and the number of symbols used in the TTI.

In addition, two methods of transmitting information through a CAZAC sequence may be considered as a method of using a CAZAC index and a method of representing information by applying a circular shift to a sequence corresponding to each CAZAC index. In addition, the cyclic shift method includes a direct cyclic shift of the applied CAZAC sequence and a domain transformation (for example, multiplying an exponential function in the frequency domain to apply a time domain cyclic shift or an exponent in the time domain). Cyclic shift using a multiplication function to apply a frequency domain cyclic shift).

Based on this, the following describes two methods (direct modulation and sequence modulation) as specific examples of the above-described embodiment of the present invention as shown in FIG. .

The direct modulation method is a method of performing OFDM modulation after performing DFT spreading on a transmission signal. That is, after performing the spreading process by the DFT spreading module 101 of FIG. 1, after performing the frequency direction modulation and the additional time direction modulation according to the above-described embodiment of the present invention, the transmission unit symbol is performed by the IFFT module 102. This is how you create it.

In contrast, the sequence modulation method is a method in which a specific sequence (eg, CAZAC, Walsh, Hadamad, Golay, PN, etc.) is loaded on a subcarrier. That is, the sequence itself is used as information. Circular movement may be additionally applied to this specific sequence.

Hereinafter, each method will be described with reference to the accompanying drawings.

5 is a diagram for describing a method of generating a TTI unit symbol modulated in a time and frequency direction according to a sequence modulation method according to an embodiment of the present invention.

As shown in FIG. 5, for example, the above-described specific transmission sequence such as CAZAC, Walsh, Hadamad, Golay, PN, etc. may be carried on each subcarrier. In this case, a sequence carried on each subcarrier according to the present embodiment includes a time domain in which the specific transmission sequences s0 to s13 such as CAZAC, Walsh, Hadamad, Golay, and PN have a length of 1 TTI as shown in FIG. It may be a form multiplied by the modulation sequence (x0 to x13).

That is, specific sequences modulated into the time domain (s (0) x (0) to s (13) x (13)) may be mapped and transmitted to each subcarrier.

On the other hand, the above-described time domain modulation sequences (s (0) x (0) to s (13) x (13)) mapped and transmitted to each subcarrier are multiplied by the frequency domain modulation sequence c (k). You can enter In this case, the frequency domain modulation sequence c (k) may have the following exponential function form so that the transmission sequence s (n) may be cyclically moved in the time domain (n is a time domain symbol index).

Here, k may be a frequency domain subcarrier index, w ₀ may be a unit phase to which cyclic shift is applied, and S may be an index value indicating a degree of cyclic shift to be applied.

Therefore, in the time and frequency domain modulated TTI unit sequence finally generated according to the embodiment as described above, the transmission information is (1) cyclic shift of c (k), (2) transmission sequence of s (n), ( 3) can be divided into cyclic shift information of x (n).

 When generating and transmitting a transmission unit symbol according to the above-described scheme, PAPR / CM and the like are not distorted at all and more transmission information can be transmitted. Meanwhile, the use of s (n) here may vary depending on the amount of data to be transmitted. That is, s (n) may have the same value for all n (in this case, the transmission information is passed to the remaining two options), or different values may be used.

FIG. 6 is a diagram for describing a method of generating a transmission unit symbol modulated in a time and frequency direction according to a direct modulation method according to another embodiment of the present invention.

In the case of the direct modulation scheme, unlike the sequence modulation scheme described with reference to FIG. 5, the transmission sequence is directly loaded on a subcarrier. In the case of generating a signal as described above, the generated signal must be spread by the DFT module 101 of FIG. 1, and a sequence used as a mask at a subcarrier level is used in a spectral shaping format. do.

In this case, when the same value is applied for each OFDM symbol in the transmission sequence s (k) carried on the subcarrier, additional information (for example, from the frequency direction modulation sequence c (k) used as subcarrier directional masking) is used. , Circular movement). In addition, unlike the case described above, if different symbols are applied to subcarriers of all OFDM symbols, the frequency direction modulation sequence c (k) may be a simple scrambling sequence.

Meanwhile, according to the present embodiment, the frequency-domain modulated sequence is additionally modulated in the time domain by the time-domain modulation sequences x (0) to x (13) in the TTI unit as shown in FIG. Can be.

Therefore, in the time and frequency direction modulated TTI unit symbols generated as shown in FIG. 6, the transmission information is (1) each subcarrier symbol s (k) as a transmission sequence, and (2) subcarrier level modulation. In addition to the sequence c (k), it may be carried by (3) a TTI unit time domain modulation sequence x (n).

In the case of generating the control signal using the method as illustrated in FIGS. 5 and 6, when the terminal transmits the control signal, only a specific number of bits need to be transmitted, for example, ACK / NACK. If it is necessary to transmit, simply detect the sequence non-coherently by using a combination of sequences to find out, or by using any number of symbols as a pilot from the generated transmission signal as described above (in this case, the OFDM symbol to be actually used as a pilot) The number of s should be optimized). A method of finding the data through phase correction of data symbols can be applied.

However, for a control channel configured in the manner as shown in FIGS. 5 and 6, flexibility may be reduced when the number of bits of information to be transmitted is changed. That is, if one resource block is configured as a channel for control signals, and the maximum number of bits that can be transmitted within a specific error rate is 10 bits, another channel structure must be designed to send more bits than this. However, if the same channel structure is not used between adjacent cells, they interfere with each other, so simply setting different channel structures does not solve the problem. Therefore, it is important to design a structure that can deliver a variable amount of information while having a structure for reducing interference between adjacent cells.

Therefore, in a preferred embodiment of the present invention to be described below, in transmitting the control signal, while maintaining the PAPR / CM characteristics of the control signal, each user has a problem in operation in multiple cells while supporting various control signal formats. The present invention proposes a method of generating a transmission signal having a structure that does not occur.

FIG. 7 illustrates a method of spreading an information symbol in a frequency unit in a symbol unit according to an exemplary embodiment of the present invention, and then performing modulation in each region through multiplexing of time and frequency domain modulation / masking sequences to perform transmission signal transmission. It is a figure which shows the method of generating.

That is, according to the method illustrated in FIG. 7, unlike the methods illustrated in FIGS. 5 and 6, the length of the spreading or modulation / masking sequence may be used within the corresponding channel as well as the case where the length of the spreading or modulation / masking sequence is set to the total length available in the corresponding channel. Even when the length is smaller than the total length, a signal that can be transmitted through the corresponding channel can be generated.

Specifically, in the case of using the method shown in FIGS. 5 and 6, a sequence using all the maximum lengths available in a given region in a corresponding channel is used. In this case, all of the transmitted control signals have the same robustness. (E.g., BER or FER). However, in the case of the control signal, ACK / NACK has a very small BER requirement as described above, but information such as CQI / PMI allows a relatively high BER. Considering this case, the method described above with reference to FIGS. 5 and 6 may not satisfy all of the requirements for different control channel signals.

On the other hand, as shown in FIG. 7, when the constraint on the length of the spread / modulation sequence on the frequency axis or the time axis is relaxed, the control signal having various requirements according to the quality of service (QoS) level required for each control signal. Can be generated. For example, the method shown in FIG. 7 will be described in detail. The information symbol is applied with a spread length of a predetermined length in symbol units (for example, as shown in FIG. 7, a spread gain = 2), and this is a frequency domain. After multiplexing at, modulation (eg, SC-FDM) is performed. Then, time-domain modulation is applied to each symbol unit (e.g., OFDM symbol) of the modulated symbol in the frequency domain by applying a time-domain sequence, for example, a time-domain sequence having a length of 4 as shown in FIG. As shown in FIG. 7, since the time-domain modulation sequence is applied in a multiplexed form in the time domain, the length of the sequence may not be limited. In this case, a signal of each UE may be distinguished through a combination of a sequence applied to the information symbol and a sequence applied to the generated modulation symbol.

Also, if the sequences used do not have scalability problems (i.e. the cross-correlation between small and long sequences is small), then the length of each sequence is the same frequency / It may have a different value above the time resource region. On the other hand, if you are going to use sequences with scalability issues, it is better to use the same structure (for example, the same length combination) on the same resource.

The sequences usable here include walsh, CAZAC, pseudo-noise (PN) sequences, and the like. In general, it is preferable to use a PN sequence to avoid scalability problems. Otherwise, it is possible to consider the cross-correlation characteristics of the sequences used for different lengths, and then limit the use to combinations that do not cause correlation problems when mixed together (e.g., when using CAZAC sequences). ).

Meanwhile, as a modified example of the embodiment illustrated in FIG. 6, the lengths of the spreading sequences applied to each information symbol may have different lengths within the same area. That is, although the symbol unit spreading of the information symbols in the frequency domain is shown in FIG. 7, all spreading sequences having a length of 2 are used, but the length of the spreading sequence applied to each symbol does not always need to be the same, and according to each information symbol. Different lengths can be applied. As such, by varying the spreading gain applied to each symbol unit, each information symbol can be set to have a different BER requirement. As such, when the spreading sequence applied to each information symbol is composed of different combinations of lengths, the same combinations are always used for each user (when the cross-correlation value between sequences of different lengths is large), or different combinations are used for each user. Use cases (where cross-correlation values between sequences of different lengths are small) can be allowed in each case.

FIG. 8 illustrates spreading an information symbol in a time domain according to a preferred embodiment of the present invention, and then performing modulation in each domain through multiplexing of time and frequency domain modulation / masking sequences to perform transmission signal transmission. It is a figure which shows the method of generating.

That is, the embodiment illustrated in FIG. 8 relates to a method of applying information symbols on the time axis, unlike the embodiment described above with reference to FIG. 7. At this time, the sequence of the frequency axis is used for the effect of giving a spreading gain (that is, multi-user interference (MUI) removal), and FIG. 8 illustrates that spreading is performed in units of symbols before applying an information symbol to the time axis. .

If the actual transmission unit is fixed to a specific time length (for example, TTI), when the information symbol is applied with a spreading effect on the time axis, the amount of information that can be sent is reduced by that amount. On the other hand, in the embodiment described above with reference to FIG. 7, even if the transmission unit has a fixed TTI, the length on the frequency axis can be adjusted so that the amount of information that can be sent varies. In other words, in order to allow more UEs to send more information in the same space, they simply increase resources on the frequency axis.

On the other hand, in the embodiment shown in FIG. 8, although the information amount is limited as described above, in order to accommodate more UEs, the length may be increased along the frequency axis, but the number of supported UEs is determined by the type of sequence used. (For example, if only the same root sequence is used in the case of CAZAC, the maximum number of UEs that can be supported is determined by the delay spread length of the channel).

In the above description with reference to FIGS. 7 and 8, the description has been focused on the application of the information symbol to any one of the frequency domain and the time domain. However, the region to which the information symbol is applied need not be limited to any one region. That is, in the transmission signal generation method according to the present embodiment, information symbols can be transmitted in both the frequency domain and the time domain. In this case, although the spreading gain and the number of supportable UEs are reduced, the amount of information that can be transmitted can be increased. In addition, the control channel may be configured by extending resources on a frequency / time axis to compensate for the problem of decreasing spreading gain and the number of UEs that can be supported.

Meanwhile, a more general method for supporting various control channel formats will be described below.

There are two main approaches to supporting various control signal formats. One is to define the same control signal channel structure and to adjust the data carried on that channel. In other words, when the actual amount of information varies, the code rate is adjusted accordingly and transmitted. Another method is to define and use a control channel structure according to the control channel format. This method may be further divided into a method in which a plurality of UEs share a location of resources to be used by a control channel and a method of defining and using different resources for transmitting control signals.

First, when a fixed size of the control signal channel is used, the total number of generated symbols is limited for the generation of modulation symbols that enter the 'information symbol' position in FIGS. 7 and 8. That is, since the number of symbols generated to apply to the information symbol positions in FIGS. 7 and 8 is limited, only specific control signal formats or different lengths of control signal formats are used. The number of modulation symbols of the control signal generated to apply to the information symbol position in U must be fixed.

One way to implement this is to adjust the coding rate of channel coding, or to adjust the spreading gain, as shown in FIG.

FIG. 9 is a diagram for one example of applying a control signal of various formats when the size of the control signal channel is fixed according to an exemplary embodiment of the present invention.

That is, different coding rates / spreading coefficients / rate matching may be applied to control signals having various lengths to a fixed control signal channel size. Accordingly, control signal symbols suitable for the corresponding control signal channel size may be applied. Can be generated. In this way, it is possible to apply control signals of various formats and to support different BER / FER performances required for each control signal.

Next, a case in which the structure of the control signal channel can be configured to be reconfigurable according to the purpose will be described.

As shown in FIG. 7 and FIG. 8, if the control signal channel structure is configured to be reconfigurable according to a purpose, the number of transmittable information symbols may be adjusted. For example, in the case of transmitting each information symbol without spreading, as many information symbols as subcarriers can be transmitted, spreading factors for the information symbols are 2, 3, 4, and so on. Increasing this, the number of information symbols that can be transmitted is reduced by its spreading factor.

To generate an information symbol corresponding to the control channel length, a technique as shown in FIG. 9 may be used as it is. For example, in the case of ACK / NACK, since the number of information symbols is one or two small, spreading can be performed long, and high BER / FER requirements can be satisfied therefrom. On the other hand, when many information symbols such as CQI / PMI require a short spread length and maintain a large number of information symbols, many bits of information can be transmitted according to a weakened BER / FER requirement. The method of generating a control channel by adjusting the spreading gain has an advantage of presenting variable performance through one structure, but it is necessary to consider the effect of interference from different cells and mixing of different UEs.

To this end, when a control signal is transmitted by sharing the same resource, a method of removing interference generated between signals from different UEs and signals from different cells will be described.

In this embodiment, the spreading gain for each symbol can be set regardless of the kind used as the spreading / mixing sequence for the information symbol. That is, in FIG. 7 and FIG. 8, the spreading gain of each symbol is set to 2, but if the number of information symbols transmitted therein is adjusted, the spreading gain applied to each symbol may be adjusted. Therefore, each control signal format can be defined through a combination of sequences having different spreading gains and transmitted.

However, this method has the possibility that different UEs transmit signals on the same resource or that signals from different cells may interfere with each other. Thus, in order to be able to adjust the spreading gain for each symbol as described above, coordination of sequence use may be necessary. That is, sequences to be used by different UEs in a specific cell may be allocated so as not to interfere with each other, and adjacent cells may be adjusted or randomized so that interference is small between sequences.

One way to do this is to perform sequence hopping. However, the use of sequences of different lengths for spreading by symbol has a burden on interference, so it is appropriate to combine the spreading sequence as one. Instead it may be appropriate to readjust the information symbols themselves. That is, the most basic spreading sequence combination is configured, and the UEs are classified by a combination of a sequence index or a shift index for the combination, and an information symbol is generated for adjusting the spreading gain in each UE. It is appropriate to do it as a change in the way you do it.

10 is a diagram illustrating an example of a method of defining a spreading format based on a control signal format in each UE.

First, in order to distinguish interference between UEs or interference between adjacent cells, coordination should be possible. To do this, it is necessary to limit the use of the sequence and to adjust the sequence to be used by each UE. If this part is variable, it is forced to use a method such as random sequence hopping in the actual implementation. Therefore, for this part, it is proposed to change only the method of generating the information symbol without changing the information related to the control signal format for the part which constitutes the UE specific sequence combination. do.

Specifically, the left side of FIG. 10 shows a relationship of mapping information symbols to spreading sequences in FIGS. 7 and 8, respectively, and the right side of the diagram shows a control channel specific spreading layer in the middle in addition to this spreading technique. It shows how to apply one more. When the additional layer is set to adjust the spread gain and the number of information symbols, signals of each UE can be distinguished from each other without touching a UE-specific sequence combination, so that cell planning, coordination, and hopping can be freely implemented. The control channel format can be freely defined. In particular, even when resources are extended in the direction of the resource axis (that is, the time / frequency axis) in which the information symbol is loaded, the scalability of the information symbol can be easily provided. The sequence to be used in the control channel specific layer may be any sequence, but it is preferable to use a sequence having excellent orthogonal properties in order to suppress noise or to suppress residual interference from another UE / other cell.

Next, a case of transmitting a control signal by defining different resources in the control channel will be described.

In this case, if the number of information symbols is the same for each control signal format, it is commonly transmitted on the same resource. Otherwise, a region is separately defined and transmitted. In other words, when the number of generated information symbols is different, different resource regions are defined and transmitted. Therefore, interferences generated between different formats do not need to be considered. Or keep it low). However, regardless of the number of UEs used in the format, a control channel for the format must be defined separately, which makes it difficult to use resources efficiently.

In the definition of resources for different formats, different resource blocks may be defined in an allocation unit on the frequency axis (12 subcarriers are defined as 1 resource block in the case of 3GPP LTE and subcarriers are allocated as basic units). However, this approach does not define efficient resources. On the other hand, when spreading gain or mixing is applied using a sequence as in FIG. 7 or 8, a method of distributing resources according to sequence generation ease and characteristics is preferred. That is, when the CAZAC sequence is used as the base unit, the base unit of the spreading / mixing sequence is appropriate to be a prime number.In order to apply this, the base unit of the spreading / mixing sequence is first divided into the frequency axis and allocated as a control signal resource when supporting a different control signal format. It is appropriate to use the subcarriers by dividing the subcarriers into a small number.

On the other hand, the invention, which is invented by the present inventors and filed on April 3, 2007 by the present applicant, uses a small number of sequence block based transmission and reception methods (Korean Patent Application No. 2007-0032725). Disclosed is a method of dividing subcarriers in a resource block (RB) into a predetermined number of channels including a prime number of subcarriers and transmitting a signal through the divided number of channels. According to the present invention, it is possible to secure the number of available sequences, which is advantageous in a multi-cell design (hereinafter, the present invention is referred to as the "32725 invention"). The method according to the 32725 application of the present invention will be briefly described with reference to FIG. 11.

FIG. 11 is a diagram for describing one preferred method that can be used when defining different resources according to a control signal format.

Hereinafter, FIG. 11 will be described assuming that one physical resource block (“PRB”) or two PRBs are allocated for a control channel in the description of the 32725 application. However, three or more PRBs will be described. The same can be applied to the case where is allocated for the control channel. Specifically, assuming that 1 PRB or 2 PRBs are allocated for the control channel, and 1 PRB includes 12 subcarriers, according to the 32725 application of the present invention, these PRBs are assigned to a small number of subcarriers in various combinations as shown in Table 1 below. The control channel may be formed by dividing into two control channels including a, and may be divided and disposed at both ends of the system bandwidth as illustrated in FIG. 11. The number of subcarriers included in each control channel is represented by N _A and N _B.

Meanwhile, FIG. 11 illustrates a form in which two divided control channels are distributed at both ends of the system band as shown in Table 1, but it is not necessary to distribute the two control channels at both ends of the system band.

In addition, the 32725 application discloses a method for configuring a more diverse number of subcarrier combinations according to the number of PRBs allocated to a control channel when the sequence used is a CAZAC sequence.

On the other hand, if the sequence used is a Walsh / Hadamard sequence other than the CAZAC sequence as the base unit, the number of subcarriers should be determined by the length of 2 (for example, 2, 4, 8, 16, 32, etc.). It is appropriate to use them separately. This application applies in the same way to the sequence of time axes as well as the sequence of frequency axes of FIGS. 7 and 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The foregoing description of the preferred embodiments of the present invention has been presented for those skilled in the art to make and use 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 the method according to an embodiment of the present invention as described above, more information can be transmitted by generating and transmitting a symbol by performing time and frequency direction modulation in a predetermined transmission unit such as a TTI or a slot instead of a symbol unit. .

In addition, by masking and transmitting the transmission sequence in the time domain, it is possible to apply a symbol unit cyclic shift to the time domain in the case of a CAZAC sequence, thereby transmitting more information.

In addition, when generating a transmission signal according to an embodiment of the present invention it is possible to generate a transmission signal that can be applied to a signal of various formats, can effectively reduce the interference between cells between users, each transmission signal It is possible to generate a transmission signal to satisfy different service quality levels required for.

Claims (8)

Inputting an information symbol into at least one of a frequency domain and a time domain; And Sequentially modulating the input information symbol in the frequency domain and the time domain, The frequency domain and time domain modulation is performed after multiplexing each domain input symbol. The method of claim 1, The information symbol input step, And spreading the information symbols in symbol units to input spread information symbols. Spreading the information symbols in symbol units in a first region, which is one of a frequency domain and a time domain; Generating a first region modulation symbol by modulating the information symbol spread in the symbol unit in the first region; And Generating a transmission signal by modulating the first region modulation symbol in a second region, which is another one of the time domain and the frequency domain. The method of claim 3, wherein In the symbol unit spreading step, the symbol unit spread gain of the information symbol is set in proportion to the quality of service required for the information symbol. The method of claim 3, wherein Generating the first region modulation symbol, Multiplexing the information symbols spread in units of symbols; And Modulating the multiplexed information symbol in the first region, The transmitting signal generation step, Multiplexing the second region modulation sequence in the second region; And Performing the second region modulation on the first region modulation symbol using the multiplexed second region modulation sequence. The method of claim 3, wherein When the size of the channel for transmitting the transmission signal is fixed, Wherein the information symbol is generated to have a control signal or data having a different size to have a predetermined size by any one or more of channel coding, spreading, and rate matching. The method of claim 3, wherein And the information symbol is spread and generated by performing a control channel specific spreading to remove interference between signals from different user equipments. The method of claim 3, wherein If the size of the channel for transmitting the transmission signal is variable, And dividing the channel into one or more channels having a small number of subcarrier sizes.

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