RU2451414C2 - Method of generating reference signal in wireless communication system - Google Patents

Abstract

FIELD: information technology.

SUBSTANCE: method of generating a reference signal involves obtaining a base sequence and obtaining a reference signal sequence with length N from a base sequence. Good PAPR/CM characteristics of the reference signal may be stored to improve data demodulation characteristics or uplink scheduling.

EFFECT: generation of a sequence with desirable characteristics.

14 cl, 8 dwg

Description

Technical field

[1] This invention relates to wireless communications and, in particular, to a method for generating a reference signal in a wireless communication system.

State of the art

[2] Basically, a sequence is used for various channels and signals in a wireless communication system. A sequence in a wireless communication system must satisfy the following characteristics:

[3] (1) good correlation characteristics to ensure high quality detection;

[4] (2) low CM (Cube Metric - cubic metric), increasing the efficiency of the power amplifier;

[5] (3) the possibility of forming a large number of sequences to transmit large amounts of information or to provide cell planning;

[6] (4) the possibility of forming in a limited form to reduce the amount of memory for the sequence.

[7] The downlink synchronization channel is used to perform time and frequency synchronization between the base station and the user equipment and to perform a cell search. The downstream synchronization signal, that is, the sequence, is transmitted on the downlink synchronization channel, and synchronization is carried out through a correlation operation with the received downstream synchronization signal. The physical cell ID can be identified by a downlink synchronization channel. Since a unique cell ID must be identified as the number of available sequences increases, this is beneficial in terms of cell planning.

[8] The uplink synchronization channel is used to perform time and frequency synchronization and to perform access for network registration, scheduling request, or the like. The sequence is transmitted on the uplink synchronization channel, and each corresponding sequence is recognized as the only one possible. After detecting the sequence, the base station can recognize through which possible user equipment the uplink synchronization channel was transmitted. In addition, time tracking, residual frequency offset, and the like can be estimated through the detected sequence. As the number of possible options increases, the likelihood of collisions between units of user equipment can be reduced. Therefore, a large number of sequences are preferable in terms of cell planning. The upstream synchronization channel is called a random access channel (RACH) or a band selection channel depending on the system.

[9] A sequence may be used to transmit control information on a control channel. This means that control information such as ACK (Acknowledgment) / NACK (Negative-Acknowledgment), CQI (Channel Quality Indicator, channel quality indicator), etc., can be displayed on a sequence. The large number of available sequences favors the transfer of various control information.

[10] A scrambling code is used to randomize or lower the peak-to-average power ration (PAPR). From the point of view of cell planning, a large number of sequences favor the use for scrambling codes.

[11] When multiple users are multiplexed on a separate channel using code division multiplexing (CDM), the sequence can be used to guarantee orthogonality among users. Multiplexing capacity is related to the number of available sequences.

[12] The reference signal is used by the receiver to estimate channel fading and / or is used to demodulate data. In addition, the reference signal is used to achieve synchronization when the user equipment goes into active mode from time / frequency tracking or into standby mode. Thus, the reference signal is used in various ways. The reference signal uses a sequence, and a large number of sequences are advantageous in terms of cell planning. The reference signal is also called a pilot signal.

[13] There are two types of uplink reference signals: a demodulation reference signal and a sounding reference signal. A demodulation reference signal is used to estimate a channel for demodulating data, and a sounding reference signal is used to schedule users. In particular, the uplink reference signal is transmitted by user equipment with limited battery capacity, therefore, the characteristics of the PARP or CM sequences used for the uplink reference signal are critical. In addition, to reduce the cost of user equipment, it is necessary to reduce the amount of memory required for the formation of sequences.

Disclosure of invention

Technical problem

[14] A search was conducted for a method of generating a sequence suitable for an uplink reference signal.

[15] A search was conducted for a method for transmitting an uplink reference signal.

Technical solution

[16] A search was conducted for a method of generating a sequence suitable for an uplink reference signal, as set forth in paragraph 1 of the claims.

[17] More specifically, the invention relates to a method for generating a reference signal in a wireless communication system, the method comprising obtaining a basic sequence x _u (n) and obtaining a sequence r (n) of a reference signal of length N from a basic sequence x _u (n), wherein the sequence x _u (n) is expressed as

[eighteen]

[19] and, if N = 12, then at least one of the values provided in the table below is used as the value of the phase parameter p (n):

[twenty]

p (0), ..., p (11) -1 3 -1 1 1 -3 -3 -1 -3 -3 3 -1 -1 3 1 3 1 -1 -1 3 -3 -1 -3 -1 -1 -3 1 1 1 1 3 1 -1 1 -3 -1 -1 3 -3 3 -1 3 3 -3 3 3 -1 -1

[21] Further, if N = 24, then at least one of the values provided in the table below can be used as the value of the phase parameter p (n):

[22]

p (0), ..., p (23) -1 -3 3 -1 -1 -1 -1 -1 1 1 -3 3 1 3 3 1 -1 1 - 3 1 - 3 1 1 -3 -1 -1 -3 3 -3 -3 -3 -1 -1 -3 -1 -3 3 1 3 -3 -1 3 -1 1 -1 3 - 3 1 -1 -1 1 -3 1 3 -3 1 -1 -3 -1 3 1 3 1 -1 -3 -3 -1 -1 -3 -3 -3 -1 -3 1 1 3 -3 1 1 -3 -1 -1 1 3 1 3 1 -1 3 1 1 -3 -1 -3 -1 -1 -3 -1 -1 1 -3 -1 -1 1 -1 -3 1 1 -3 1 -3 -3 3 1 1 -1 -1 3 -1

[23] The sequence r (n) of the reference signal can be obtained as

[24]

[25] by cyclic shift α of the base sequence x _u (n).

[26] In addition, a method is being sought for transmitting an uplink reference signal as set forth in claim 4.

[27] More specifically, the invention relates to a method for transmitting a reference signal in a wireless communication system, the method comprises obtaining a sequence r (n) of a reference signal of length N from a base sequence x _u (n), displaying a sequence of a reference signal at N subcarrier frequencies and transmitting the displayed sequence of the reference signal to the upward channel, and the basic sequence x _u (n) is expressed as

,[28]

,

[29] and if N = 12, then at least one of the values provided in the table below is used as the value of the phase parameter p (n):

[thirty]

p (0), ..., p (11) -1 3 -1 1 1 -3 -3 -1 -3 -3 3 -1 -1 3 1 3 1 -1 -1 3 -3 -1 -3 -1 -1 -3 1 1 1 1 3 1 -1 1 -3 -1 -1 3 -3 3 -1 3 3 -3 3 3 -1 -1

[31] In yet another aspect, a method for transmitting a reference signal in a wireless communication system includes obtaining a sequence r (n) of a reference signal having a length N from a base sequence x _u (n), displaying a sequence of a reference signal at N subcarrier frequencies and transmitting the displayed reference signal sequence to the uplink.

Positive effects

[32] The sequences generated using the closed-form formation formula are compared with comparative sequences, of which those that have good correlation and SM characteristics are used as an upstream reference signal. Although these sequences with good correlation and CM characteristics are used along with the comparative sequences as an uplink reference signal, the desired sequence characteristics can be maintained to thereby improve data demodulation characteristics and perform accurate uplink scheduling.

Brief Description of the Drawings

[33] Figure 1 is a block diagram of a transmitter in accordance with an embodiment of the present invention.

[34] FIG. 2 is a block diagram of a signal conditioner in accordance with an SC-FDMA scheme.

[35] Figure 3 shows the structure of a radio frame.

[36] FIG. 4 is an exemplary view showing a resource grid for an uplink slot.

[37] FIG. 5 shows the structure of an uplink subframe.

[38] FIG. 6 is a conceptual view showing a cyclic expansion.

[39] FIG. 7 shows a truncation method.

[40] FIG. 8 is a flowchart illustrating a process of a method for transmitting a reference signal in accordance with an embodiment of the present invention.

The principle of operation of the invention

[41] Hereinafter, the downlink refers to communication from the base station (BS) with the user equipment (UE), and the uplink refers to communication from the UE to the BS. In the downstream direction, the transmitter may be part of the BS and the receiver may be part of the UE. In the upstream direction, the transmitter may be part of the UE and the receiver may be part of the BS. User equipment (UE) may be fixed or mobile and may be referred to by other terminology such as mobile station (MS), user terminal (user terminal, UT), subscriber station (subscriber station, SS), wireless device (wireless device), etc. .d. A BS station is usually a fixed station that communicates with the UE and may be referred to by other terminology, such as Node B, base transceiver system (BTS), access point (access point), etc. There may be one or more cells within the BS coverage area.

[42] I. System

[43] FIG. 1 is a block diagram depicting a transmitter in accordance with an embodiment of the present invention.

[44] Referring to FIG. 1, a transmitter 100 includes a reference signal generator 110, a data processor 120, a physical resource display device 130, and a signal generator 140.

[45] The reference signal generator 110 generates a sequence for the reference signal. There are two types of reference signals: a demodulation reference signal and a sounding reference signal. A demodulation reference signal is used to estimate a channel for demodulating data, and a sounding reference signal is used to schedule an uplink. The same reference signal sequence can be used for the demodulation reference signal and the sounding reference signal.

[46] A data processor 120 processes user data to generate complex value symbols. The physical resource mapper 130 displays complex-value symbols for the reference signal sequence and for user data on physical resources. Symbols with complex values can be mapped onto mutually exclusive physical resources. Physical resources may be called resource elements or subcarrier frequencies.

[47] The signal generator 140 generates a time-domain signal for transmission through the transmitting antenna 190. The signal generator 140 can generate a time-domain signal in accordance with a single carrier-frequency division multiple access (SC-FDMA) ) and, in this case, the time-domain signal at the output of the signal generator 140 is called an SC-FDMA symbol or an orthogonal frequency division multiple access (OFDMA) symbol.

[48] In the following description, it is assumed that the signal conditioner 140 uses an SC-FDMA scheme, but this is only an example and there is no limitation on the multiple access scheme to which the present invention is applied. For example, the present invention can be applied to various other multiple access schemes, such as OFDMA, code division multiple access (CDMA), time division multiple access (TDMA), or multiple access frequency division multiple access (FDMA).

[49] Figure 2 is a block diagram of a signal conditioner in accordance with an SC-FDMA scheme.

[50] With reference to FIG. 2, the signal driver 200 includes a discrete Fourier transform (DFT) unit 220 for performing a discrete Fourier transform (DFT), a frequency subcarrier mapper 230, and an inverse fast block 240 inverse fast Fourier transform (DFT) Fourier transform, IFFT) to perform the inverse fast Fourier transform (IFFT). DFT unit 220 performs DFT on the input data and forms symbols in the frequency domain at the output. The subcarrier mapper 230 maps the symbols in the frequency domain to each subcarrier, and the IFFT unit 230 performs IFFT on the input symbols in order to output a signal in the time domain.

[51] A reference signal may be generated in the time domain and fed to the input of a DFT unit 220. Alternatively, a reference signal may be generated in the frequency domain and directly mapped to frequency subcarriers.

[52] Figure 3 shows the structure of a radio frame.

[53] With reference to FIG. 3, a radio frame includes ten subframes. Each subframe includes two slots. The interval for transmitting an individual subframe is called the transmission time interval (TTI). For example, a TTI may be 1 millisecond (ms) and a slot interval may be 0.5 ms. A slot may include multiple SC-FDMA symbols in the time domain and multiple resource blocks in the frequency domain.

[54] The structure of the radio frame is just an example, and the number of subframes included in the radio frame, the number of slots included in the subframe, and the number of SC-FDMA symbols included in the slot may vary.

[55] FIG. 4 shows a resource grid for an uplink slot.

[56] Referring to FIG. 4, an upstream slot includes a plurality of SC-FDMA symbols in a time domain and a plurality of resource blocks in a frequency domain. Here, it is shown that the upstream slot includes seven SC-FDMA symbols, and the resource block includes twelve frequency subcarriers, but these are merely examples, and the present invention is not limited to this.

[57] Each element of the resource grid is called a resource element. A separate resource block includes 12 × 7 resource elements. The number (N ^UL ) of resource blocks included in the uplink slot depends on the transmission capacity of the uplink.

[58] FIG. 5 shows the structure of an uplink subframe.

[59] With reference to FIG. 5, the upstream subframe can be divided into two parts: a control area and a data area. The middle part of the subframe is allocated for the data area, and both side parts of the data area are allocated for the control area. A control area is an area for transmitting control signals that are typically allocated to a control channel. A data area is an area for transmitting data that is usually allocated to a data channel. The channel allocated to the control area is called the physical uplink control channel (PUCCH), and the channel allocated to the data area is called the physical uplink shared channel (PUSCH). The UE cannot transmit PUCCH and PUSCH at the same time.

[60] The control signal includes an ACK / NACK (Negative-Acknowledgement) signal, which is the feedback of a hybrid automatic repeat request (HARQ) for downstream data, a quality indicator channel (channel quality indicator, CQI) indicating the state of the downstream channel, scheduling request signal, which is used to request uplink radio resources, etc.

[61] The PUCCH channel uses a separate resource block, which occupies mutually different frequencies in each of the two subframe slots. The two resource blocks allocated for the PUCCH jump in frequency at the slot boundary. Here, it is illustrated that two PUCCH channels, one having m = 0 and the other having m = 1, are allocated for a subframe, but a plurality of PUCCH channels can be allocated for a subframe.

[62] II. Zadoff-Chu Sequence (ZC)

[63] The Zadoff-Chu (ZC) sequence is commonly used in wireless communications due to good CM characteristics and correlation characteristics. The ZC sequence is one of the sequences based on sequences with constant amplitude and zero auto correlation (CAZAC). The ZC sequence has ideal characteristics with a constant amplitude both in the frequency domain and in the time domain through DFT (or IDFT) and periodic autocorrelation in the form of a pulse. Thus, applying a ZC sequence to DFT-based OFDMA or SC-FDMA shows very good PAPR (or CM) characteristics.

[64] The formula for forming a ZC sequence with a length of N _zc has the following form:

[65] Mathematical expression 1

[Formula 1]

[66] where 0≤m≤N _ZC -1, and 'u' denotes the root index, which is a real number no greater than N _ZC. The root index u is a relatively prime number with N _ZC . This means that when N _{ZC is} determined, the number of indices becomes the number of available root ZC sequences. Accordingly, when Nzc is a prime number, the largest number of root ZC sequences can be provided. For example, if N _ZC is 12, which is a composite number, the number of available root ZC sequences is 4 (u = 1, 5, 7, 11). If N _ZC is 13, which is a prime number, the number of available root ZC sequences is 12 (u = 1, 2, ..., 10).

[67] In general, a ZC sequence having a prime number length has better CM or correlation characteristics than ZC sequences having a composite number length. Based on this, there are two ways to increase the number of ZC sequences when the length of the ZC sequence required for formation is not a prime number. One of the methods is based on cyclic expansion, and the other method is based on truncation.

[68] FIG. 6 is a conceptual view showing a cyclic expansion method. The cyclic extension method relates to a method in which (1) when the length of the required ZC sequences is 'N', (2) ZC sequences are formed by selecting a prime number less than the required length N as N _ZC , and (3) the generated ZC sequences are cyclically expand to the remainder (NN _ZC ) to form ZC sequences of length N. For example, if N is 12, then N _ZC is selected 11 to obtain all 10 cyclically extended ZC sequences.

[69] By using the ZC sequence x _u (m) of formula 1, cyclically extended sequences r _CE (n) can be expressed as shown below.

[70] Mathematical expression 2

[Formula 2]

[71] where 0≤n≤N-1, "a mod b" denotes a modulo operation, which means the remainder provided by dividing 'a' by 'b1', and N _ZC denotes the largest prime number among natural numbers not greater than N.

[72] FIG. 7 is a conceptual view showing a truncation method. The truncation method relates to a method in which (1) when the length of the required ZC sequences is N, (2) N _ZC is selected as a prime greater than the required length N to form ZC sequences, and (3) the remainder of (Nzc-N ) is truncated to form ZC sequences with length N. For example, if N is 12, Nzc is selected equal to 13 to provide all twelve truncated ZC sequences.

[73] By using the ZC sequence x _u (m) of formula 1, truncated and generated sequences r _TR (n) can be expressed as shown below.

[74] Mathematical expression 3

[Formula 3]

[75] where 0≤n≤N-1, and Nzc denotes the smallest prime number among the natural numbers is not less than N.

[76] When sequences are formed by using the ZC sequences described above, the number of available sequences is maximized when Nzc is a prime. For example, if the length N of the desired sequence is 11, when ZC sequences Nzc = 11 are formed, then the number of available sequences is at most 10. If the amount of required information or the number of sequences used must be more than ten sequences, then the ZC sequence cannot be used.

[77] If the length of the desired sequence is N = 12, then N _ZC = 11 is selected and cyclic expansion is performed or Nzc = 13 is selected and truncation is performed so as to form ten ZC sequences in the case of cyclic expansion and twelve ZC sequences in the case of truncation. In this case, however, if more sequences are required (for example, 30 sequences), ZC sequences having such good characteristics as satisfying said sequences cannot be formed.

[78] In particular, if sequences having good CM characteristics are required, then the number of available sequences can be seriously reduced. For example, preferably, the sequences used for the reference signal are lower than the CM value in quadrature phase shift keying (QPSK) when power increase is considered. When using the SC-FDMA scheme, the CM value for QPSK transmission is 1.2 dB. If sequences satisfying the QPSK CM requirements are selected from among the available ZC sequences, then the number of available sequences to use for the reference signal will be reduced. In more detail, the table below shows the SM values of the sequences formed after cyclic expansion by choosing Nzc = 1 in the case where the length of the desired sequence is N = 12.

[79] Table 1

[Table 1] Index u CM [dB] sequences 0 one 0.17 one 2 1.32 2 3 1,50 3 four 0.85 four 5 0.43 5 6 0.43 6 7 0.85 7 8 1,50 8 9 1.32 9 10 0.17

[80] As indicated in the table above, if the threshold value is 1.2 dB, the requirements are QPSK CM, then the number of available sequences is reduced from ten to six (u = 0, 4, 5, 6, 7, 10).

[81] Therefore, a method of forming sequences is required that can have good SM and correlation characteristics and can reduce the memory capacity required to form or store available sequences.

[82] III. Sequence Formula

[83] The closed-loop formation formula for generating sequences having good SM and correlation characteristics is a polynomial expression with the same size and k-th order phase component.

[84] The formation formula in closed form with respect to the sequence r (n) has the following form:

[85] Mathematical expression 4

[Formula 4]

,

,

,

,

[86] where m = 0, 1, ..., N-1, N denotes the length of the sequence r (n), and u ₀ , u ₁ , ..., u _k denote arbitrary real numbers. The sequence x _u (m) is the base sequence for forming the sequence r (n). The value 'u' represents the index of the sequence and is in one to one relationship with the combination of u ₀ , u ₁ , ..., u _k .

[87] Here, u _k is a component for the phase shift of the entire sequence and does not affect the formation of the sequence. Thus, Formula 4 can be represented as follows:

[88] Mathematical expression 5

[Formula 5]

,

,

,

,

[89] In an excellent example, the closed-loop formation formula with respect to the r (n) sequence, obtained by approximating or quantizing the phase value in the sequence of formula 4, can be expressed as follows:

[90] Mathematical expression 6

[Formula 6]

,

,

,

,

[91] where m = 0, 1, ..., N-1, N denotes the length of the sequence r (n), and u ₀ , u _1, ..., u _k denote arbitrary real numbers. The quan (.) Function denotes a quantization function, which means approximating or quantizing to a specific value.

[92] The actual value and imaginary value of the sequence results in Formula 6 can be approximated / quantized as shown below.

[93] Mathematical expression 7

[Formula 7]

,

,

,

,

[94] where m = 0, 1, ..., N-1, and p _n denotes the normalization coefficient for controlling the amplitude of the generated sequence.

могут квантоваться в число Nq. Квантованые значения могут аппроксимироваться до координат QPSK {0,7071+j0,7071, 0,7071-j0,7071, -0,7071+j0,7071, -0,7071-j0.7071} или аппроксимироваться до {exp(-j*2*π*0/8), exp(-j*2*π*l/8), exp(-j*2*π*2/8), exp(-j*2*π*3/8), exp(-j*2*π*4/8), exp(-j*2*π*5/8), exp(-j*2*π*6/8), exp(-j*2*π*7/8)} в форме 8-PSK.[95] In Formula 6, values on the complex unit circle, which

can be quantized into the number Nq. Quantized values can be approximated to the QPSK coordinates {0,7071 + j0,7071, 0,7071-j0,7071, -0,7071 + j0,7071, -0,7071-j0.7071} or approximated to {exp (-j * 2 * π * 0/8), exp (-j * 2 * π * l / 8), exp (-j * 2 * π * 2/8), exp (-j * 2 * π * 3/8 ), exp (-j * 2 * π * 4/8), exp (-j * 2 * π * 5/8), exp (-j * 2 * π * 6/8), exp (-j * 2 * π * 7/8)} in the form of 8-PSK.

[96] In this case, in accordance with the approximation methods, said values can be approximated to the nearest values, to the same or the nearest small values, or to the same or the nearest large values.

[97] In Formula 7, the real value and imaginary values generated from the values of the exponential function are approximated to the nearest unique combination. That is, for example, they are approximated to M-PSK or M-QAM. In addition, the real value and imaginary value can be approximated to {+1, -1, 0} through the sign function, which gives the sign of the value.

[98] In Formulas 6 and 7, in order to approximate to the nearest QPSK, the value of u _k can be set to π * 1/4. In addition, a rounding function, meaning rounding as a specific form of the quantization function, can be used. The quantization function can be used over the phase part of the quantization function or over the entire exponential function.

[99] Variables can be set in accordance with a specific criterion to form sequences from formulas of formation. A criterion may consider SM or correlation characteristics. For example, the CM value and cross-correlation threshold can be set to form sequences.

[100] Detailed formation formulas for generating sequences from the general formation formulas described above will now be described.

[101]

[102] First embodiment: a simple form of polynomial expression (k = 3)

[103] The following formation formula can be selected:

[104] Mathematical expression 8

[Formula 8]

,

,

,

,

[105] where m = 0, 1, ..., N-1, N denotes the length of the sequence r (n), and u ₀ , u _1, u ₂ denote arbitrary real numbers.

[106]

[107] Second embodiment: modified ZC sequence

[108] The following formation formula can be selected:

[109] Mathematical expression 9

[Formula 9]

,

,

,

,

[110] where m = 0,1, ..., N-1, N denotes the length of the sequence r (n), and u ₀ , u ₁ , ..., u _k-1 denote arbitrary real numbers.

[111] This formation formula has the following advantages. First, ZC sequences having good characteristics that can be created with a length of N can be included in the set of available sequences. For example, if k = 2, u ₁ = 0 and u ₀ is an integer, it is equivalent to the ZC sequence when N in Formula 1 is an even number. If k = 2, u ₁ and u ₀ are integers, and u ₁ = u ₀ , it is equivalent to the ZC sequence when N in Formula 1 is an odd number. Secondly, sequences having good characteristics are as close as the Euclidean distance of the original optimized ZC sequence.

[112]

[113] Third Embodiment: Cyclically Enhanced Adjusted ZC Sequence

[114] The following formation formula can be selected:

[115] Mathematical expression 10

[Formula 10]

,

,

,

,

[116] where m = 0, 1, ..., N-1, N denotes the length of the sequence r (n), and u ₀ , u ₁ , ..., u _k-1 denote arbitrary real numbers. The number N _ZC is the largest prime number among the natural numbers less than N. This formation formula is advantageous in that the existing ZC sequence can be included in the set of available sequences. For example, if k = 2, u ₁ and u ₀ are integers, and u ₁ = u ₀ , it is equivalent to the value obtained by cyclic extension of the ZC sequence.

[117]

[118] Fourth embodiment: a truncated modified ZC sequence

[119] The following formation formula can be selected:

[120] Mathematical expression 11

[Formula 11]

,

,

,

,

[121] where m = 0, 1, ..., N-1, N denotes the length of the sequence r (n), and u ₀ , u ₁ , ..., u _k-1 denote arbitrary real numbers. The number N _ZC is the largest prime number among natural numbers greater than N. This formation formula is advantageous in that the existing ZC sequence can be included in the set of available sequences. For example, if k-2, and u ₁ and u ₀ are integers, then it is equivalent to the value obtained by truncating the ZC sequence.

[122]

[123] Fifth embodiment: a modified ZC sequence having a limitation.

[124] The following formation formula can be selected:

[125] Mathematical expression 12

[Formula 12]

,

,

,

,

[126] where m = 0, 1, ..., N-1, N denotes the length of the sequence r (n), u ₀ , u ₁ , ..., u _k-1 denote arbitrary numbers, and 'a' denotes an arbitrary real number, 'a' serves to limit the fractionality of the variables u ₀ , u ₁ , ..., u _k-1 . Because the fractionality of the variables u ₀ , u ₁ , ..., u _k-1 can be converted to a whole unit through such a restriction, the amount of memory required to store sequence information can be reduced.

[127]

[128] Sixth embodiment: a modified ZC sequence having two limitations

[129] The following formation formula can be selected:

[130] Mathematical expression 13

[Formula 13]

,

,

,

,

[131] where m = 0, 1, ..., N-1, N denotes the length of the sequence r (n), u ₀ , u ₁ , ..., u _k-1 denote arbitrary numbers, 'a' denotes an arbitrary real number, and b ₀ , b ₁ , ..., b _k-1 denote arbitrary real numbers, 'a' serves to limit the fractionality of the variables u ₀ , u ₁ , ..., u _k-1 . Perhaps a different restriction of variables through b ₀ , b ₁ , ..., b _k-1 . The amount of memory required to store sequence information can be reduced by changing the fractionality of the variables u ₀ , u ₁ , ..., u _k-1 by an integer unit through two restrictions, and a sequence with better characteristics can be provided by controlling the fragmentation of the variables.

[132]

[133] Seventh embodiment: a modified ZC sequence (k = 3) having two limitations

[134] The following formation formula can be selected:

[135] Mathematical expression 14

[Formula 14]

,

,

,

,

[136] where m = 0, 1, ..., N-1, N denotes the length of the sequence r (n), u ₀ , u ₁ , u ₂ denote arbitrary numbers, 'a' denotes an arbitrary real number, and b ₀ , b ₁ , b ₂ denote arbitrary numbers, 'a' serves to limit the fractionality of the variables u ₀ , u _1, u ₂ . Perhaps a different restriction of variables through b ₀ , b ₁ , b ₂ .

[137]

[138] Eighth embodiment: modified ZC sequence having one limitation and cyclic extension

[139] The following formation formula can be selected:

[140] Mathematical expression 15

[Formula 15]

,

,

,

,

[141] where m = 0, 1, ..., N _zc -1, N denotes the length of the sequence r (n), u ₀ , u ₁ , ..., u _k-1 denote arbitrary numbers, 'a' denotes an arbitrary real number, and N _ZC denotes the largest prime number among natural numbers less than 'N'. The number 'a' serves to limit the fractionality of the variables u ₀ , u ₁ , ..., u _k-1 . Due to the fragmentation of the variables u ₀ , u ₁ , ..., u _k-1 can be changed by one unit through such a restriction, the amount of memory required to store sequence information can be reduced.

[142]

[143] Ninth embodiment: a modified ZC sequence having two restrictions and cyclic extension

[144] The following formation formula can be selected:

[145] Mathematical expression 16

[Formula 16]

,

,

,

,

[146] where m = 0, 1, N _ZC -1, N denotes the length of the sequence r (n), u ₀ , u ₁ , ..., u _k-1 denote arbitrary numbers, 'a' denotes an arbitrary real number, b ₀ , b ₁ , ..., b _k-1 denote arbitrary numbers, and N _ZC denotes the largest prime number among the natural numbers less than 'N'. The number 'a' serves to limit the fractionality of the variables u ₀ , u ₁ , ..., u _k-1 . Perhaps a different restriction of variables through b ₀ , b ₁ , ..., b _k-1 . The amount of memory required to store sequence information can be reduced by changing the fractionality of the variables u ₀ , u ₁ , ..., u _k-1 by one unit through two restrictions, and a sequence with better characteristics can be provided by controlling the fragmentation of the variables.

[147]

[148] 10th embodiment: a modified ZC sequence having limitations (k = 3) and cyclic extension

[149] The following formation formula can be selected:

[150] Mathematical expression 17

[Formula 17]

,

,

,

,

[151] where m = 0, 1, N-1, N denotes the length of the sequence r (n), u ₀ , u _1, u ₂ denote arbitrary numbers, 'a' denotes an arbitrary real number, b ₀ , b ₁ , b ₂ denote arbitrary numbers, and N _ZC denotes the largest prime number among natural numbers less than N. The number 'a' serves to limit the fractionality of the variables u ₀ , u ₁ , u ₂ . Perhaps a different restriction of variables through b ₀ , b ₁ , b ₂ .

[152]

[153] 11th embodiment: a modified ZC sequence having one restriction and truncation

[154] The following formation formula can be selected:

[155] Mathematical expression 18

[Formula 18]

,

,

,

,

[156] where m = 0, 1, ..., N _ZC -1, N is the length of the sequence r (n), u ₀ , u ₁ , ..., u _k-1 are arbitrary numbers, 'a' is arbitrary real number, and N _ZC is the largest prime number among natural numbers greater than N. The number 'a' serves to limit the fractionality of the variables u ₀ , u ₁ , ..., u _k-1 . Due to the fragmentation of the variables u ₀ , u ₁ , ..., u _k-1 can be changed by one unit through such a restriction, the amount of memory required to store sequence information can be reduced.

[157]

[158] 12th embodiment: a modified ZC sequence having two restrictions and truncation

[159] The following formation formula can be selected.

[160] Mathematical expression 19

[Formula 19]

,

,

,

,

[161] where m = 0, 1, ..., N _ZC -1, N is the length of the sequence r (n), u ₀ , u ₁ , ..., u _k-1 are arbitrary numbers, the number 'a' is arbitrary real number, b ₀ , b ₁ , ..., b _k-1 are arbitrary numbers, and N _ZC is the smallest prime number among natural numbers greater than N. The number 'a' serves to limit the fractionality of the variables u ₀ , u ₁ , ..., u _k-1 Perhaps a different restriction of variables through b ₀ , b ₁ , ..., b _k-1 . The amount of memory required to store sequence information can be reduced by changing the fractionality of the variables u ₀ , u ₁ , ..., u _k-1 by one unit through two restrictions, and a sequence with better characteristics can be obtained by controlling the fragmentation of the variables.

[162]

[163] 13th embodiment: a modified ZC sequence having two constraints (k = 3) and truncation

[164] The following formation formula can be selected:

[165] Mathematical expression 20

[Formula 20]

,

,

,

,

[166] where m = 0, 1, ..., N _ZC -1, N is the length of the sequence r (n), u ₀ , u ₁ , u ₂ are arbitrary numbers, the number 'a' is an arbitrary real number, b ₀ , b ₁ , b _{2 are} arbitrary numbers, and N _ZC is the smallest prime number among natural numbers greater than N. The number 'a' serves to limit the fractionality of the variables u ₀ , u ₁ , u ₂ . Perhaps a different restriction of variables through b ₀ , b ₁ , b ₂ .

[167]

[168] 14th embodiment: Cyclic expansion taking into account a cyclic shift in the time domain

[169] In an OFDMA system or an SC-FDMA system, the number of available sequences can be increased by using cyclic shifts for each root sequence. In addition to the cyclic shift, the starting point for the formation of the sequence can be combined with a specific frequency index so as to be determined. This is a limitation of the forced control of the starting points that are overlapped by different sequences in the frequency domain, having the advantage that the correlation characteristics of the modified ZC sequence can be supported, having one or more limitations.

[170] For example, the following sequence formation formula may be selected:

[171] Mathematical expression 21

[Formula 21]

,

,

,

,

[172] where m = 0, 1, ..., N _ZC -1, N is the length of the sequence r (n), u ₀ , u ₁ , ..., u _k-1 are arbitrary numbers, 'a' is arbitrary real number, and N _ZC is the largest prime number among natural numbers less than N. The expression e ^jαn is the expression, in the frequency domain, of performing a cyclic shift by 'α' in the time domain, θ is the offset value of the shift and indicates the execution of the cyclic expansion after a shift by θ. If Formula 21 is expressed in the frequency domain, then θ indicates the offset value of the frequency index.

[173] As another example, the following sequence formation formula can be selected:

[174] Mathematical expression 22

[Formula 22]

,

,

,

,

[175] where m = 0, 1, ..., N _ZC -1, N is the length of the sequence r (n), u ₀ , u ₁ , ..., u _k-1 are arbitrary numbers, the number 'a' is arbitrary real number, b ₀ , b _{1, ...,} b _k-1 are arbitrary numbers, and N _ZC is the largest prime number among natural numbers less than N. Expression e ^jαn is an expression, in the frequency domain, of performing cyclic the shift by 'α' in the time domain, θ is the shift offset value and indicates the completion of cyclic expansion after the shift by θ.

[176] As another example, the following sequence formation formula can be selected:

[177] Mathematical expression 23

[Formula 23]

,

,

,

,

[178] where m = 0, 1, ..., N _ZC -1, N is the length of the sequence r (n), u ₀ , u ₁ , u ₂ are arbitrary numbers, the number 'a' is an arbitrary real number, b ₀ , b ₁ , b ₂ are arbitrary numbers, and N _ZC is the largest prime number among natural numbers less than N. The expression e ^jαn is the expression, in the frequency domain, of performing a cyclic shift by 'α' in the time domain , θ is the offset value of the shift.

[179]

[180] 15th embodiment: truncation in view of the cyclic shift in the time domain

[181] For example, the following sequence formation formula may be selected:

[182] Mathematical expression 24

[Formula 24]

,

,

,

,

[183] where m = 0, 1, ..., N _ZC -1, N is the length of the sequence r (n), u ₀ , u ₁ , ..., u _k-1 are arbitrary numbers, the number 'a' is an arbitrary real number, and N _ZC is the largest prime number among natural numbers less than N. The expression e ^jαn is an expression, in the frequency domain, of performing a cyclic shift by 'α' in the time domain.

[184] As another example, the following sequence formation formula may be selected.

[185] Mathematical expression 25

[Formula 25]

,

,

,

,

[186] As another example, the following sequence formation formula may be selected.

[187] Mathematical expression 26

[Formula 26]

,

,

,

,

[188] In Formula 26, if k = 3, then a = 0.125, b ₀ = 2 and b ₁ = b ₂ = 1, then the following formula can be provided.

[189] Mathematical expression 27

[Formula 27]

,

,

,

,

[190] IV. Sequencing

[191] In order to show an example of sequence formation, the following sequence formation formula is considered:

[192] Mathematical expression 28

[Formula 28]

,

,

,

,

[193] where m = 0, 1, ..., Nzc-1, N is the length of the sequence r (n), u ₀ , u ₁ , u ₂ are arbitrary numbers, θ is the offset value of the shift, and Nzc is the largest prime number among natural numbers is less than N. This formula is obtained by determining α = 0, k = 3, α = 0.125, b ₀ = 2, b ₁ = b ₂ = 1. The reason for choosing a = 0.125 is to reduce the number of calculations. Namely, because 0.125 is equal to 1/8, this can be implemented in three times the bit shift operation.

[194] The variables u ₀ , u ₁ , u _{2 are} determined by using the SM and the cross-correlation threshold value.

[195] First, the formation of a sequence with a length of N = 12 will now be described.

[196] When the SM level was set to 1.2 dB and the cross-correlation threshold was set to 0.6, the values of the variables u ₀ , u ₁ , u ₂ and the SM values of the corresponding sequences obtained from the formation formula are shown in the table below .

[197] Table 2

[Table 2] Sequence index u ₀ u ₁ u ₂ CM [dB] 0 0 9 8 0.17 one 0 32 32 0.85 2 0 40 40 0.43 3 0 48 48 0.43 four 0 56 56 0.85 5 0 80 80 0.17 6 0 19 10 1,08 7 0 26 0 1.12 8 0 61 0 0.87 9 0 68 3 1.18 10 one 78 22 1,11 eleven 2 25 60 0.99 12 3 62 2 1.15 13 3 73 four 1.15 fourteen 3 80 37 1.10

fifteen four 82 8 1.18 16 eleven 38 86 1.18 17 12 65 75 1.12 eighteen fourteen 73 52 1.20 19 16 83 61 1.05 twenty eighteen 34 eleven 1,11 21 eighteen fifty 41 1.16 22 22 17 44 0.88 23 25 61 36 1.14 24 25 88 eleven 1.17 25 27 39 5 1.12 26 32 23 85 1.12 27 34 17 52 1.10 28 38 36 31 1,04 29th 40 6 8 1.18

[198] In the above table, sequences with indices 0 through 5 refer to a set of sequences satisfying the CM level among the ZC sequences formed by applying conventional cyclic extension.

[199] Table 3 shows the values of the real numbers of the sequence generated from Table 2, and Table 4 shows the values of the imaginary numbers of the sequence generated from Table 2.

[200] Table 3

[202] If N = 12 and when the sequences generated by the proposed formation formula and ZC sequences formed by applying traditional cyclic expansion, then six sequences that satisfy the QPSK CM criterion of 1.2 dB are included.

[203] Table 5 shows a comparison between the ZC sequence generated by the application of traditional cyclic expansion, and the proposed sequence.

[204] Table 5

[Table 5] Traditional ZC sequence Suggested sequence Number of sequences 10 thirty Number of sequences <CM 1.2 dB 6 thirty The maximum value of CM [dB] 1,50 1.20 The maximum value of cross-correlation 0.44 0.60 Cross-correlation average 0.25 0.25 The median cross-correlation value 0.28 0.24

[205] It should be noted that when sequences are formed by the proposed method, the number of available sequences can be increased, while the cross-correlation characteristics are almost the same. When frequency jumps are considered in a real environment, the characteristics of the block error rate (BLER) become better as the average correlation value decreases. Since the average correlation of both sequences is the same, the characteristics of BLER are the same.

[206] Formation of a sequence with a length of N = 24 will now be described.

[207] The table below shows the variables u ₀ , u ₁ , u ₂ obtained from the formation formula and the corresponding SM values when the SM level is set to 1.2 dB and the cross-correlation threshold value is set to 0.39.

[208] Table 6

[Table 6] Sequence index u ₀ u ₁ u ₂ CM [dB] 0 0 8 8 -0.09 one 0 32 32 0.83 2 0 48 48 0.68 3 0 64 64 0.38 four 0 72 72 0.49

5 0 88 88 0.18 6 0 96 96 0.18 7 0 112 112 0.49 8 0 120 120 0.38 9 0 136 136 0.68 10 0 152 152 0.83 eleven 0 176 176 -0.09 12 0 6 17 1,11 13 0 6 182 0.87 fourteen 0 25 16 1.14 fifteen 0 29th 82 0.95 16 0 35 132 0.92 17 0 44 27 0.83 eighteen 0 48 four 1.01 19 0 54 eighteen 1.13 twenty 0 54 122 1.14 21 0 58 0 1,07 22 0 64 fourteen 0.61 23 0 68 21 0.98 24 0 88 eleven 0.58 25 0 96 116 0.63 26 0 112 0 0.49 27 0 126 133 1.05 28 0 130 fifteen 1,07 29th 0 178 39 1,11

[209] In the above table, sequences with indices 0 through AND refer to a set of sequences that satisfy the SM criterion among ZC sequences formed by applying traditional cyclic extension.

[210] Table 7 shows the real numbers of the sequences generated from Table 6, and Table 8 shows the imaginary values of the generated sequences.

[211] Table 7

[214]

[215] The following table 9 shows a comparison between the sequences formed by the proposed formation formula and ZC sequences formed by applying traditional cyclic expansion when N = 24.

[216] Table 9

[Table 9] Traditional ZC sequence Suggested sequence Number of sequences 22 thirty Number of sequences <CM 1.2 dB 12 thirty The maximum value of CM [dB] 2.01 1.14 The maximum value of cross-correlation 0.36 0.39

Cross-correlation average 0.19 0.18 The median cross-correlation value 0.20 0.18 Standard cross-correlation value 0,07 0.09

[217] It should be noted that when sequences are formed in accordance with the proposed method, the number of available sequences increases and the best mutual correlation characteristics are obtained. When frequency jumps are considered under real conditions, the BLER characteristics become better as the average correlation value decreases. Thus, the BLER characteristics of the proposed sequence are better.

[218] V. Restriction on the order of the phase formula

[219] The relationship between the order of 'k' of the phase formula with respect to the phase component of the sequence, the number of sequences available and the correlation characteristics are as follows.

[220] As the order of 'k' increases, the number of available sequences increases, but the correlation characteristics deteriorate. As the order of 'k' decreases, the number of available sequences decreases, but the correlation characteristics improve. If k = 2, then ZC sequences can be formed in such a way, if k> 2, then a constraint is required for the formation of sequences.

[221] A method for restricting the order of the phase formula in accordance with the length of the desired sequence in accordance with the required number of available sequences, taking into account the number of available sequences and correlation characteristics, when a polynomial expression of the third order and higher is applied to the phase components of the sequences will now be considered. When the required number of minimum available sequences is Nseq, if the number of sequences (Nposs) that can be formed using the second-order phase formula with the required length N of the sequence is greater than or the same as Nseq (i.e., Nposs> = Nseq ), then the second-order phase formula is used. If Nposs <Nseq, then a third or higher order phase formula is used.

[222] This can be expressed in steps as follows.

[223] Step 1: The required number Nseq of minimum available sequences is determined.

[224] Step 2: The number Nposs of available sequences that can be formed by a second-order phase formula (k = 2) is determined from the length N of the desired sequences.

[225] Step 3: If the Nposs are larger or the same as Nseq, sequences are formed using a second-order phase formula, and if Nposs are smaller than Nseq, sequences are formed using a third-order phase formula.

[226] The first embodiment

[227] The following sequence formation formula having third-order phase formulas with k = 3 is considered.

[228] Mathematical expression 29

[Formula 29]

,

,

,

,

[229] where m = 0, 1, ..., N _zc -1, N is the length of the sequence r (n), u ₀ , u ₁ , ..., u _k-1 are arbitrary numbers, the number 'a' is is an arbitrary real number, and N _ZC is the largest prime number among natural numbers less than N. e ^jαn is an expression, in the frequency domain, of performing a cyclic shift by 'α' in the time domain, θ is the value of the shift offset and indicates the execution cyclic expansion after a shift by θ.

[230] It is assumed that the length N of the desired sequence is possible in the following case:

[231] N = [12 24 36 48 60 72 96 108 120 144 180 192 216 240 288 300]

[232] In step 1, the number Nseq of the minimum available sequences is set to 30. In step 2, if for the second phase formula a = 1, u ₀ = 0, u ₁ = u ₂ = u, b ₀ = 0 and b ₁ = b ₂ = 1 in Formula 29, then the available number of Nposs of available ZC sequences for each N is as follows:

[233] Nposs = [10 22 30 46 58 70 88 106 112 138 178 190 210 238 282 292]

[234] In step 3, the length of the sequences that can use the second-order phase formula is N = [36 48 60 72 96 108 120 144 180 192 216 240 288 300], and the length of the sequences that can use the third-order phase formula, equal to N = [12 24].

[235] Second Embodiment

[236] The following sequence formation formula is considered having a third-order phase formula with k = 3.

[237] Mathematical expression 30

[Formula 30]

,

,

,

,

[238] It is assumed that the length N of the desired sequence is possible in the following case:

[239] N = [12 24 36 48 60 72 96 108 120 144 180 192 216 240 288 300]

[240] In step 1, the number Nseq of the minimum available sequences is 30. In step 2, if for the second-order phase formula a = 1, u ₀ = 0 and u ₁ = u ₂ = u in Formula 30, then the available number Nposs of available ZC sequences for each N are as follows:

[241] Nposs = [10 22 30 46 58 70 88 106 112 138 178 190 210 238 282 292]

[242] In step 3, the length of the sequences that can use the second-order phase formula is N = [36 48 60 72 96 108 120 144 180 192 216 240 288 300], and the length of the sequences that can use the third-order phase formula, equal to N = [12 24].

[243] A sequence formation formula for which the order of the phase formula is limited can be expressed in two ways. In the first expression method, it is assumed that a sequence of length N is displayed in the frequency domain. This means that each element of the sequence is mapped to the N number of subcarrier frequencies. First, it is assumed that the sequence r (n) is represented as follows.

[244] Mathematical expression 31

[Formula 31]

,

,

[245] According to the first type of sequence formation formula, when the length of the N sequence is greater than or the same as 36, the basic sequence x _u (m) is represented as follows:

[246] Mathematical expression 32

[Formula 32]

[247] where m = 0, 1, ..., N _ZC -1.

[248] If the length N of the sequence is less than 36, then the basic sequence x _u (m) is represented as follows.

[249] Mathematical expression 33

[Formula 33]

[250] In accordance with the formula for forming a sequence of the second type, the basic sequence x _u (m) is represented as follows.

[251] Mathematical expression 34

[Formula 34]

[252] where when the length of the N sequence is greater than or the same as 36, a = 1 and u ₁ = u ₂ = u, and if the length of the N sequence is less than 36 if a = 0.125 and N = 12, u ₁ and u _{2 are} determined by table 10 below.

[253] Table 10

[Table 10] Sequence index u ₁ u ₂ CM [dB] one 0 8 0.17 2 0 32 0.85 3 0 40 u ₃ 0.43 four 0 48 8 0.43 5 0 56 32 0.85 6 0 80 80 0.17 7 0 19 10 1,08 8 0 26 0 1.12 9 0 61 0 0.87 10 0 68 3 1.18 eleven one 78 22 1,11 12 2 25 60 0.99 13 3 62 2 1.15 fourteen 3 73 four 1.15 fifteen 3 80 37 1.10 16 four 82 8 1.18 17 eleven 38 86 1.18 eighteen 12 65 75 1.12 19 fourteen 73 52 1.20 twenty 16 83 61 1.05 21 eighteen 34 eleven 1,11 22 eighteen fifty 41 1.16 23 22 17 44 0.88 24 25 61 36 1.14 25 25 88 eleven 1.17 26 27 39 5 1.12 27 32 23 85 1.12 28 34 17 52 1.10 29th 38 36 31 1,04 thirty 40 6 8 1.18

[254] If N = 24, u ₁ and u _{2 are} determined by table 11 below.

[255] Table 11

[Table 11] Sequence index u ₁ u ₂ u ₃ one 0 8 8 2 0 32 32 3 0 48 48 four 0 64 64 5 0 72 72 6 0 88 88 7 0 96 96 8 0 112 112 9 0 120 120 10 0 136 136 eleven 0 152 152 12 0 176 176 13 0 6 17 fourteen 0 6 182 fifteen 0 25 16 16 0 29th 82 17 0 35 132 eighteen 0 44 27 19 0 48 four twenty 0 54 eighteen 21 0 54 122 22 0 58 0 23 0 64 fourteen 24 0 68 21 25 0 88 eleven 26 0 96 116 27 0 112 0 28 0 126 133 29th 0 130 fifteen thirty 0 178 39

[256] VI. Sequencing for a reference signal

[257] The following sequence formation formula is considered:

[258] Mathematical expression 35

[Formula 35]

,

,

,

,

[259] where m = 0, 1, ..., N _ZC -1, a = 0.0625, u ₃ = 1/4, N is the length of the sequence r (n), u ₀ , u ₁ and u ₂ are arbitrary numbers, θ is the value of the shift offset, and Nzc is the largest prime number among natural numbers less than N. The quantization function quan (.) approximates to the nearest {0, 1/2, 1, 3/2, 2, ... }. Namely, the quantization function quan (x) approximates to an integer or integer +0.5, closest to 'x'. This can be expressed as quan (x) = round (2x) / 2, and round (x) is an integer directly less than x + 0.5.

[260] Memory can be saved through quantization. The range of values of u ₀ , u ₁ and u ₂ can be expanded to increase the degree of freedom, so as to form a larger number of sequences with good characteristics. In this regard, however, an increase in the range of values of u ₀ , u ₁ and u ₂ leads to an increase in the number of bits for representing the values of u ₀ , u ₁ and u ₂ . Thus, with the restriction of QPSK modulation so that only two bits are required per value, regardless of the range of values of u ₀ , u ₁ and u ₂ . In addition, because the basic formation formula is based on the CAZAC sequence, sequences with good correlation characteristics can be formed. For example, if the range 0 <u ₀ <1024, 0 <u ₁ <1024 and 0 <u ₂ <1024 is provided to form sequences of length 12, a memory capacity of 30 bits (= 10 bits +10 bits +10 bits) is used in the sequence so 900 bits of memory capacity are required for 30 sequences. However, when quantization is performed, the memory capacity of 720 bits (= 2 bits × 12 × 30) is sufficient for the sequence, regardless of the range of values of u ₀ , u ₁ and u ₂ .

[261] The above formation formula may be equivalent to the value obtained by approximating the elements of a sequence before combining the QPSK phase. This is because each value can be approximated by Nq by the number of quantized values between 0 and 2π, which can be expressed in phases through the quantization function. Namely, the values in the complex unit disk e ^−jθ can be quantized to Nq of the number of values and thus approximate each value.

[262] In this case, in accordance with the approximation methods, the values can be approximated to the nearest values, to the same or the nearest smallest values, or to the same or nearest largest values.

[263] Elements of sequences can be approximated to the values {π / 4, 3π / 4, -π / 4, -3π / 4} corresponding to the QPSK phases. This means that the quantized values are approximated to the QPSK coordinates {0.7071 + j0.7071, 0.7071-j0.7071, -0.7071 + j0.7071, -0.7071-j0.7071}.

[264] Hereinafter, the extended sequence formation will be considered, but the truncated sequence as in the following formula can also be used in accordance with the length N of the desired sequence and the length N _ZC ZC of the sequence.

[265] Mathematical expression 36

[Formula 36]

,

,

,

,

[266] Alternatively, if the length N of the desired sequence and the length Nzc of the ZC sequence are the same, then the sequences as in the following formula can also be used.

[267] Mathematical expression 37

[Formula 37]

,

,

,

,

[268] Significant examples to form a sequence for generating a reference signal will now be considered.

[269] In the uplink subframe, the PUCCH or PUSCH is scheduled by the resource block device, and the resource block includes twelve frequency subcarriers. Thus, a sequence with a length of N = 12 is required for a separate resource block, a sequence with a length of N = 24 is required for two resource blocks. A sequence with a length of N = 12 can be formed by a cyclically expandable sequence with Nzc = 11, and a sequence with a length of N = 24 can be formed by a cyclically expandable sequence with Nzc = 23.

[270] (1) The sequence of the reference signal for N = 12

[271] The table below shows u ₀ , u ₁ and u ₂ when N = 12. It shows 30 combinations of sequences that do not have such a high cross-correlation with extended ZC sequences corresponding to three resource blocks, as was searched from sequences that do not exceed 1.22 dB SM, by preferable considering CP (Cyclic Prefix - cyclic prefix) as SM .

[272] Table 12

[Table 12] Index (u) u ₀ u ₁ u ₂ 0 29995 30337 2400 one 32762 2119 36039 2 35746 37587 26527 3 18603 33973 25011 four 18710 2129 19429 5 5033 28145 14997 6 6940 23410 7920 7 19235 26638 38189 8 2037 29th 16723 9 8965 29795 25415 10 35666 2400 4229 eleven 7660 31762 17023 12 23501 14111 6290 13 32271 14654 3822 fourteen 16265 29599 640 fifteen 26931 38734 3401 16 11963 29706 22674 17 9560 24757 22880 eighteen 22707 14318 7654 19 16440 14635 3587 twenty 22209 13004 10470 21 23277 2967 19770 22 25054 36961 9673 23 39007 36984 21639 24 5353 38653 26803 25 36686 19758 36923 26 3768 37064 30757 27 15927 15525 13082 28 33614 17418 37090 29th 33995 7240 12053

[273] The sequence r (n) of the reference signal with a length of 12, formed from the above table, can be expressed by the following formula:

[274] Mathematical expression 38

[Formula 38]

,

,

,

,

[275] where 'α' is the value of the cyclic shift, and the values of the parameters p (n) of the phase of the base sequences x _u (n) are given in the following table:

[276] Table 13

[277] (2) The reference signal sequence for N = 24

[278] The table below shows u ₀ , u ₁ and u ₂ when N = 12. It shows 30 combinations of sequences that do not have such a high cross-correlation with extended ZC sequences corresponding to three resource blocks, as was searched from sequences that do not exceed 1.22 dB SM, by preferable considering CP (Cyclic Prefix - cyclic prefix) as SM .

[279] Table 14

[Table 14] Index (u) u ₀ u ₁ u ₂ 0 35297 9057 9020 one 24379 861 26828 2 15896 4800 31943 3 6986 9180 7583 four 22605 15812 10886 5 852 3220 18552 6 16048 10573 27569 7 15076 9412 26787 8 15074 3760 38376 9 38981 11775 37785 10 29686 14549 13300 eleven 21429 7431 34668 12 28189 33097 5721 13 6551 34694 36165 fourteen 25833 17562 20508 fifteen 38286 20581 17410 16 17305 10299 10752 17 27571 8218 1477 eighteen 16602 31085 15253 19 14199 11732 25429 twenty 1665 9415 24015 21 33837 26684 9587 22 20569 33119 21324 23 27246 33775 21065 24 18611 30085 28779 25 29485 39582 28791 26 21508 25272 21422 27 5956 25772 2113 28 17823 13894 23873 29th 5862 3810 35855

[280] The sequence r (n) of the reference signal with a length of 24, formed from the above table, can be expressed by the following formula:

[281] Mathematical expression 39

[Formula 39]

,

,

,

,

[282] where 'α' is the cyclic shift value, and the parameter values p (n) of the phase sequence x _u (n) are given in the following table:

[283] Table 15

[284] VII. Sequence selection for the reference signal

[285] In the above description, sequences are formed from the formation formula in closed form with respect to N = 12 and N = 24. However, in a real wireless communication system, sequences generated from a separate formation formula may not be applicable, but mixed with other sequences. Thus, the correlation characteristics or SM characteristics between the sequences thus formed and other sequences require consideration.

[286] Here, a method in which 30 sequences generated from Formula 38 and Table 13 when N = 12 are compared with 26 comparative sequences and four sequences with good correlation characteristics are selected as reference signal sequences will now be described. In addition, a method in which 30 sequences generated from Formula 39 and Table 15 when N = 24 are compared with 25 comparative sequences and five sequences with good correlation characteristics are selected as reference signal sequences will now be described.

[287] (I) In the case of N = 12

[288] If N = 12, the sequence formation formula is a cyclic shift of the base sequence x _u (n) similar to Formula 38, and the parameter values p (n) of the phase sequence x _u (n) are given as shown in Table 13. Here, the method in which 30 sequences are formed when N = 12 are compared with 26 comparative sequences and four sequences with good correlation characteristics are selected will now be described. The number of cases where four base sequences are selected among 30 base sequences is 27405 ( ₃₀ C ₄ = 30 * 29 * 28 * 27/4/3/2/1 = 27405). Thus, in order to reduce the number of cases, first, the SM of the base sequence is considered.

[289] The table below shows the basic sequences arranged in order of size CM. In the table, the largest value among the SM values of all possible cyclic shifts of the base sequences is defined as the representative of the SM.

[290] Table 16

[Table 16] Sequence index CM 23 0.6486 26 0.6634 29th 0.8258 21 0.8961 fifteen 0.9052 12 0.9328 fourteen 0.977 28 0.9773 19 0.987 25 0,9991 one 1,0015 5 1,0019 22 1,0273 eleven 1,035 twenty 1,0376 eighteen 1,0406 10 1,0455 3 1.05 0 1,0608 17 1,066 8 1,073 24 1,0927 9 1,1054 2 1,1054 four 1,1248 27 1,1478 6 1,1478 16 1,1502 7 1.1616 13 1,1696

[291] When N = 12, namely because the length of the base sequences corresponding to a particular resource block is short, many sequences have similar mutual correlation characteristics, therefore sequences with CM greater than a certain value are excluded. Here, the sequences [23 26 29 21 15 12 14 28 19 25 1 5 22 11 20 18 10 3 0 17 8] having CM lower than 1.09 are considered.

[292] It is assumed that the parameters p ^c (n) of the phase of the comparative sequences that can be used together with the base sequences are shown in the table below. In this case, the comparative sequences differ in their phase parameters, but the same in form as the basic sequences.

[293] Table 17

[294] Of the 30 base sequences, the best 25 combinations among the combinations with maximum cross-correlation with the comparative sequences are shown in the table below.

[295] Table 18

[Table 18] No. Sequence Index Combinations Average correlation Maximum correlation one 0 3 8 17 0.2568 0.644 2 3 8 17 25 0.2567 0.6546 3 0 8 17 25 0.2567 0.6546 four 0 3 17 25 0.2576 0.6546 5 0 3 8 25 0.2561 0.6546 6 8 17 25 28 0.2568 0.6546 7 3 17 25 28 0.2576 0.6546 8 0 17 25 28 0.2577 0.6546 9 3 8 25 28 0.2561 0.6546 10 0 8 25 28 0.2562 0.6546 eleven 0 3 25 28 0.2571 0.6546 12 3 8 17 28 0.2568 0.6546 13 0 8 17 28 0.2569 0.6546 fourteen 0 3 17 28 0.2577 0.6546 fifteen 0 3 8 28 0.2562 0.6546 16 17 25 28 29 0.2576 0.6755 17 8 25 28 29 0.2561 0.6755 eighteen 3 25 28 29 0.257 0.6755 19 0 25 28 29 0.257 0.6755 twenty 8 17 28 29 0.2568 0.6755 21 3 17 28 29 0.2576 0.6755 22 0 17 28 29 0.2577 0.6755 23 3 8 28 29 0.2560 0.6755 24 0 8 28 29 0.2562 0.6755 25 0 3 28 29 0.2571 0.6755

[296] From the above table, if four sequences that have good average mutual characteristics and maximum mutual characteristics, when compared with comparative sequences and satisfy the required SM characteristics, are selected among 30 sequences having the same basic sequence formation formula as Formula 36, and having the parameter values p (n) of the phase, as provided in Table 13, four sequences having indexes of [3 8 28 29] sequences will be bases E sequences.

[297] Finally, the sequence r (n) of the reference signal with a length N = 12 is as follows:

[298] Mathematical expression 40

[Formula 40]

,

,

[299] where 'α' is the cyclic shift value and the parameter values p (n) of the phase sequence x _u (n) are shown in the table below.

[300] Table 19

[Table 19] p (0), ..., p (11) -1 3 -1 1 1 -3 -3 -1 -3 -3 3 -1 -1 3 1 3 1 -1 -1 3 -3 -1 -3 -1 -1 -3 1 1 1 1 3 1 -1 1 -3 -1 -1 3 -3 3 -1 3 3 -3 3 3 -1 -1

[301]

[302] (2) In the case of N = 24

[303] When N = 24, the sequence formation formula is a cyclic shift of the base sequence x _u (n) similar to Formula 37, and the parameter values p (n) of the phase sequence x _u (n) are given in Table 15. Here, the method in of which 30 sequences formed when N = 24 are compared with 25 comparative sequences and five sequences with good correlation characteristics are selected will now be described. The number of cases of selecting five base sequences among 30 base sequences is 142506 ( ₃₀ C ₄ = 30 * 29 * 28 * 27 * 26/5/4/3/2/1 = 142506).

[304] It is assumed that the parameters p ^c (n) of the phase of the comparative sequences that can be used together with the base sequences are shown in the table below. In this case, the comparative sequences differ only in their phase parameters, but are the same in form as the basic sequences.

[305] Table 20

[306] 20 combinations with the best mutual correlation characteristics among all possible combinations are shown in the table below.

[307] Table 21

[Table 21] No. Sequence Index Combinations Average correlation Maximum correlation one 9 11 16 21 27 0.1811 0.4791 2 11 12 16 21 25 0.181 0.4844 3 9 12 16 21 25 0.181 0.4844 four 9 11 12 21 25 0.1812 0.4844 5 9 11 12 16 25 0.1812 0.4844 6 9 11 12 16 25 0.1811 0.4844 7 12 16 21 24 25 0.1806 0.4917 8 11 16 21 24 25 0.1808 0.4917 9 9 16 21 24 25 0,1807 0.4917

10 11 12 21 24 25 0.1808 0.4917 eleven 9 12 21 24 25 0,1807 0.4917 12 9 11 21 24 25 0.189 0.4917 13 11 12 16 24 25 0.1809 0.4917 fourteen 9 12 16 24 25 0.1808 0.4917 fifteen 9 11 16 24 25 0.181 0.4917 16 9 11 12 24 25 0.181 0.4917 17 11 12 16 21 24 0,1807 0.4917 eighteen 9 12 16 21 24 0.1806 0.4917 19 9 11 16 21 24 0.1808 0.4917 twenty 9 11 12 21 24 0.1808 0.4917

[308] Among all combinations, the combinations {7, 8, 9, 10, 11, 12, 13, 14, 17, 18, 19, 20} have an average correlation value greater than 0.181.

[309] The table below shows the basic sequences arranged in order of size CM. In the table, the largest value among the SM values of all possible cyclic shifts of the base sequence is defined as the representative of the SM.

[310] Table 22

[Table 22] Sequence index CM 6 0.6423 12 0.7252 23 0.7632 twenty 0.8265 8 0.883 9 0.8837 19 0.9374 10 0.966 25 0.9787 eleven 0.9851 13 0,9966 29th 1,0025 fourteen 1,0112 28 1,0113 27 1,0143 17 1,0176 7 1,0191 22 1,0316 24 1,0387 5 1,0407 eighteen 1,059 fifteen 1,0722 3 1,0754 0 1,0761 21 1,094 one 1,0952 16 1,1131 26 1,1193 four 1,1223 2 1,1251

[311] Sequence indices included in selectable combinations are 9, 11, 12, 16, 21, 24, 25, of which the index of 16 sequences is excluded because it has low CM characteristics of the base sequence. Thus, selectable combinations are reduced to the next four sequence indices.

[312] Table 23

[Table 23] Sequence Index Combinations Average correlation Maximum correlation 11 12 21 24 25 0.1808 0.4917 9 12 21 24 25 0,1807 0.4917 9 11 12 21 24 0.1806 0.4917 9 11 21 24 25 0.1809 0.4917

[313] If five sequences that have good mutual correlation characteristics and SM characteristics with comparative sequences and have minimal correlation values will be selected from the above combinations, the sequences [9 11 12 21 24] will be the base sequences.

[314] Finally, the sequence r (n) of the reference signal with a length N = 24 is as follows:

[315] Mathematical expression 41

[Formula 41]

,

,

[316] where 'α' is the cyclic shift value, and the parameter values p (n) of the phase sequence x _u (n) are given in the table below.

[317] Table 24

[Table 24] p (0), ..., p (23) -1 -3 3 -1 -1 -1 -1 -1 1 1 -3 3 1 3 3 1 -1 1 -3 1 -3 1 1 -3 -1 -1 -3 3 -3 -3 -3 -1 -1 -3 -1 -3 3 1 3 -3 -1 3 -1 1 -1 -1 3 -3 1 -1 -1 -1 1 -3 1 3 -3 1 -1 -3 -1 3 1 3 1 -1 -3 -3 -1 -1 -3 -3 -3 -1 -1 -3 1 1 3 -3 1 1 -3 -1 -1 1 3 1 3 1 -1 3 1 1 -3 -1 -3 -1 -1 -3 -1 -1 1 -3 -1 -1 1 -1 -3 1 1 -3 1 -3 -3 3 1 1 -1 -1 3 -1 -1

[318] All 30 base sequences can be provided by using phase parameter values of 25 comparative sequences shown in Table 20.

[319] FIG. 8 is a flowchart illustrating a process of a method for transmitting a reference signal in accordance with an embodiment of the present invention.

[320] Referring to FIG. 8, in step S210, the following basic sequence x _u (n) is obtained.

[321] Mathematical expression 42

[Formula 42]

[322] The phase parameter p (n) is determined in accordance with the length of the base sequence, namely, the number of allocated resource blocks. In the case of one resource block (N = 12), at least one of the 30 phase p (n) parameters given in Table 17 and Table 19 can be used. In the case of two resource blocks (N = 24), at least one of the 30 phase p (n) parameters given in Table 20 and Table 24 can be used.

[323] In step S220, a reference signal sequence r (n) determined by the following formula is obtained by cyclic shift 'α' of the base sequence x _u (n).

[324] Mathematical expression 43

[Formula 43]

,

,

[325] In step S230, the reference signal sequence r (n) is mapped to a physical resource. In this case, the physical resource may be an element of resources or a subcarrier of frequency.

[326] In step S240, the reference signal sequence mapped to the physical resource is converted to an SC-FDMA signal, which is then transmitted in the upstream direction.

[327] Sequences having good correlation characteristics and SM characteristics compared with comparative sequences are selected from the sequences generated by the closed-form formation formula and used as an uplink reference signal. Although the sequences are used as the uplink reference signal along with the comparative sequences, the desired sequence characteristics can be maintained, therefore, the demodulation characteristics of the data can be improved and accurate uplink scheduling can be performed if possible.

[328] Each function, as described above, can be performed by a processor such as a software-based microprocessor with a code to perform such a function, program code, etc., a controller, a microcontroller, a specialized integrated circuit (ASIC, Application Specific Integrated Circuit ) etc. The planning, development, and implementation of such codes may be apparent to those skilled in the art based on the description of the present invention.

[329] Although embodiments of the present invention have been disclosed for purposes of illustration, those skilled in the art will understand that various modifications, additions, and possible changes are possible without departing from the scope of this invention. Accordingly, embodiments of the present invention are not limited to the embodiments described above, but are defined by the claims, which follows along with their full scope of equivalents.

Claims (14)

1. A method of transmitting a reference signal in a wireless communication system, comprising:
displaying (S230) the sequence r (n) of the reference signal corresponding to the base sequence x _u (n) and having a length N onto N subcarrier frequencies;
and transmitting (S240) the mapped uplink reference signal sequence r (n),
the basic sequence x _u (n) is expressed as

,
and, if N = 12, at least one of the sets of values shown in the table below is used as the set of values of the phase parameter p (n):
p (0), ..., p (11) -1 3 -1 1 1 -3 -3 -1 -3 -3 3 -1 -1 3 1 3 1 -1 -1 3 -3 -1 -3 -1 -1 -3 1 1 1 1 3 1 -1 1 -3 -1 -1 3 -3 3 -1 3 3 -3 3 3 -1 -1 2. The method according to claim 1, in which, if N = 24, at least one of the sets of values shown in the table below is used as a set of values of the parameter p (n) of the phase:
p (0), ..., p (23) -1 -3 3 -1 -1 -1 -1 -1 1 1-3 3 1 3 3 1 -1 1 -3 1 -3 1 1 -3 -1 -1 -3 3 -3 -3 -3 -1 -1 -3 -1 -3 3 1 3 -3 -1 3 -1 1 -1 -1 3 -3 1 -1 -1 1 -3 1 3 -3 1 -1 -3 -1 3 1 3 1 -1 -3 -3 -1 -1 -3 -3 -3 -1 -3 1 1 3 -3 1 1 -3 -1 -1 1 3 1 3 1 -1 3 1 1 -3 -1 -3 -1 -1 -3 -1 -1 1 -3 -1 -1 1 -1 -3 1 1 -3 1 -3 -3 3 1 1 -1 -1 3 -1 3. The method according to claim 1, in which the sequence r (n) of the reference signal corresponds to the basic sequence x _u (n) as follows:

through the cyclic shift α of the base sequence x _u (n). 4. The method according to claim 1, in which the uplink channel is a physical uplink control channel (physical uplink control channel, PUCCH). 5. The method according to claim 1, in which the uplink channel is a physical uplink shared channel (physical uplink shared channel, PUSCH). 6. The method according to claim 1, in which the sequence r (n) of the reference signal is a demodulation reference signal used to demodulate upstream data. 7. The method according to claim 1, in which the sequence r (n) of the reference signal is a sounding reference signal used for user planning. 8. A mobile communication terminal (100), configured to transmit a reference signal in a wireless communication system, comprising:
antenna (190);
a communication module, operatively connected to the antenna; and
a processor (130) operatively connected to the communication module, the specified processor, configurable for
display (S230) the sequence r (n) of the reference signal corresponding to the base sequence x _u (n) and having a length N on N subcarrier frequencies;
and transmitting (S240) the mapped uplink reference signal sequence r (n), wherein the base sequence x _u (n) is expressed

and, if N = 12, at least one of the sets of values shown in the table below is used as a set of values of the phase parameter p (n):
p (0), ..., p (11) -1 3 -1 1 1 -3 -3 -1 -3 -3 3 -1 -1 3 1 3 1 -1 -1 3 -3 -1 - 3 -1 -1 -3 1 1 1 1 3 1 -1 1 -3 -1 -1 3 -3 3 -1 3 3 -3 3 3 -1 -1 9. The mobile communication terminal of claim 8, in which, if N = 24, at least one of the sets of values shown in the table below is used as a set of values of the phase parameter p (n):
p (0), ..., p (23) -1 -3 3 -1 -1 -1 -1 -1 1 1 -3 3 1 3 3 1 -1 1 -3 1 -3 1 1 -3 -1 -1 -3 3 -3 -3 -3 -1 -1 -3 -1 -3 3 1 3 -3 -1 3 -1 1 -1 -1 3 -3 1 -1 -1 1 -3 1 3 -3 1 -1 -3 -1 3 1 3 1 -1 -3 -3 -1 -1 -3 -3 -3 -1 -3 1 1 3 -3 1 1 -3 -1 -1 1 3 1 3 1 -1 3 1 1 -3 -1 -3 -1 -1 -3 -1 -1 1 -3 -1 -1 1 -1 -3 1 1 -3 1 -3 -3 3 1 1 -1 -1 3 -1 10. The mobile communication terminal of claim 8, in which the sequence r (n) of the reference signal corresponds to the basic sequence x _u (n) as follows:

by cyclic shift α of the base sequence x _u (n). 11. The mobile communication terminal of claim 8, in which the uplink channel is a physical uplink control channel (physical uplink control channel, PUCCH). 12. The mobile communication terminal of claim 8, in which the uplink is a physical uplink shared channel (PUSCH). 13. The mobile communication terminal of claim 8, in which the sequence r (n) of the reference signal is a demodulation reference signal used to demodulate upstream data. 14. The mobile communication terminal of claim 8, wherein the reference signal sequence r (n) is a sounding reference signal used for user scheduling.

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