KR20080097116A - Method for setting cyclic shift sequence against frequency offset - Google Patents

Abstract

A cycle shift sequence setup method is provided to minimize the influence of a frequency offset in a high mobility cell. A cycle shift sequence setup method comprises the following steps of: computing the distance between the channel response locations of the alias of the sequence, generated due to the channel response location and frequency offset of the sequence, by using the index of a sequence; and setting up a cycle shift application section by computing the number of cycle shifts per group comprising the sequence according to the sections of the computed distance. The step for setting up the cycle shift applying section comprises the following steps of: calculating the number of cycle shifts per group and the length of the group according to the interval of the computed distance; and setting up the cycle shift applying section by using the length of the group and the number of cycle shifts per group.

Description

Method for setting cyclic shift sequence against frequency offset

The present invention relates to a sequence in a wireless communication system. In particular, a method for allocating a sequence to each cell in consideration of characteristics of a CAZAC sequence for solving a frequency offset problem, and setting a cyclic shift to be applied thereto. It's about how.

The Constant Amplitude Zero Auto-Correlation (CAZAC) sequence is one of the sequences that is actively discussed in 3GPP LTE. The places where the CAZAC sequence can be used are channels for extracting various IDs or information using the sequence. These channels include synchronization channels (eg, primary-SCH, secondary-SCH, BCH) for downlink synchronization, synchronization channels (eg, RACH) for uplink synchronization, pilot channels (eg, , Data pilot, channel quality pilot). In addition, the above-described CAZAC sequence may be used for scrambling.

Regarding the use of the CAZAC sequence, two types of sequences, namely, a method of changing a root index and a method of circularly moving one root sequence are mainly discussed. The distinction between different root indices, although there is some cross-correlation, is not a constraint on the design of sequence use. However, in the case of cyclic movement, since they have a feature of zero correlation with each other, they are used when a high rejection ratio is required between each other. In particular, it is used to distinguish different signals / UEs when transmitting data / control signals by sharing the same time-frequency resources in the same cell.

As an example of a CAZAC sequence, Zadoff-Chu (ZC, hereinafter referred to as 'ZC') sequence is defined as follows.

for odd Nzc

for odd Nzc

for even Nzc

for even Nzc

Where n represents a sampling index, Nzc represents a length of a ZC sequence, and u represents an index of a ZC sequence.

Restricted cyclic shift for high mobility cells is also a subject of LTE research.

However, when an offset may occur in the frequency axis, such as when transmitting a CAZAC sequence in the OFDM scheme, performance deterioration may occur rapidly.

In particular, when cyclic shift is applied to the CAZAC sequence, the degree of frequency offset or timing offset is severe, which makes it difficult to distinguish the sequence.

Accordingly, an aspect of the present invention is to provide a method of setting a cyclic shift sequence in preparation for a frequency offset that can prevent a performance degradation of a sequence, particularly a CAZAC sequence, in a situation where a frequency offset occurs.

In order to achieve the above technical problem, an embodiment of the present invention calculates the distance between the channel response position of the sequence and the channel response position of Elias of the sequence generated due to the frequency offset, and according to the interval of the calculated distance The present invention provides a method for setting a circular movement applying interval by calculating the number of circular movements per group constituting the sequence.

Preferably, in an embodiment of the present invention, the number of groups, the number of cyclic movements per group, and the length of the group may be calculated according to the calculated distance interval in the process of setting a circular movement applying interval. The cycle movement application section may be set using the number of groups, the number of cycle movements per group, and the length of the group.

Preferably, in one embodiment of the present invention, in the process of setting a circular movement interval, when the index of the circular movement is a decimal number, the index is the number of circular movements multiplied by the length of the circular movement, and then rounds off the shift position. It may include a process of calculating.

Preferably, in an embodiment of the present invention, in the process of setting the cycle movement applying section, the cycle movement applying section may be set according to two or more sections divided based on a position corresponding to 1/3 of the length of the sequence. have.

In order to achieve the above technical problem, another embodiment of the present invention calculates the distance between the channel response position of the sequence and the channel response position of the Elias of the sequence caused by the frequency offset, and according to the interval of the calculated distance The method provides a method for setting a cycle movement application section having a shift position that is a multiple of the cycle movement length by calculating the number of cycle movements per group and the number of additional cycle movements not belonging to the group.

Preferably, another embodiment of the present invention, in the process of setting the cycle movement applying interval, checks whether there is a first additional circular movement that does not belong to the group, and if the first additional circular movement does not exist, the second This may include checking for the presence of additional circular movements.

Preferably, another embodiment of the present invention in the process of setting the cycle movement applying interval, the number of the group, the number of the cyclic movement per group, the length of the group and the additional cyclic movement according to the calculated interval of the distance The number of times may be calculated, and a cycle movement interval may be set using the number of groups, the number of cycle movements per group, the length of the group, and the number of additional cycle movements.

Preferably, in another embodiment of the present invention, in the process of setting the cycle movement applying section, the cycle movement applying section may be set according to two or more sections divided based on a position corresponding to 1/3 of the length of the sequence. have.

In order to achieve the above technical problem, another embodiment of the present invention is a method for setting a cyclic shift sequence in a mobile communication system including a plurality of cells, by acquiring cell information to determine whether the cell is a highly mobile cell and If the identified cell is a highly mobile cell, calculate the distance between the channel response position of the sequence and the channel response position of Elias of the sequence caused by the frequency offset, and configure the sequence according to the interval of the calculated distance It provides a method for setting the interval for applying a circular movement by calculating the number of circular movements per group.

In order to achieve the above technical problem, another embodiment of the present invention is a method for setting a sequence in a mobile communication system including a plurality of cells, by acquiring cell information to determine whether the cell is a highly mobile cell, If the identified cell is a highly mobile cell, calculate the distance between the channel response position of the sequence and the channel response position of the aliases of the sequence generated due to the frequency offset, and per group constituting the sequence according to the interval of the calculated distance. A method for setting a cycle movement application section having a shift position that is a multiple of the cycle movement length by calculating the number of cycle movements and the number of additional cycle movements not belonging to the group.

Preferably, another embodiment of the present invention may include the step of allocating an unassigned sequence to the high mobility cell if the identified cell is not a high mobility cell in the process of setting a cyclic mobility application interval. have.

Preferably, another embodiment of the present invention may include a process of acquiring the cell information and determining a cell having a frequency offset of a predetermined level or more as a high mobility cell in the process of confirming whether the cell is a high mobility cell.

According to one embodiment of the present invention, regardless of the domain in which the sequence is generated, even if the received signal is shifted due to the channel delay spread and the propagation delay, the positions do not overlap each other in consideration of the channel response of the received sequence and the position of the aliases of the received sequence. By setting the cyclic shift section in a simple way, the detection error and false alarm rate due to the frequency offset can be greatly reduced, and when a sequence for applying cyclic shift is assigned to a cell having a frequency offset above a predetermined level, There is an effect to minimize the influence of the frequency offset.

1 to 5 will be described on the basis of the case that the cyclic movement unit is T ₀ .

By designing according to components in the RACH, a cyclically shifted preamble can be generated and transmitted. However, in an environment in which frequency offset exists in OFDM, a receiver may easily mistake a different sequence.

In order to prevent this, it is easy to think of a method of providing an additional circular movement margin as shown in FIG. 1.

In FIG. 1, Delay Spread represents delay spread of a channel, and Round Trip Delay represents time for propagation of a physical distance between a UE and a base station. In the case of an additional circular shift margin, the size of the margin is adjusted for each sequence to reduce the influence of the frequency offset in using the sequence.

As shown in FIG. 1, when a frequency offset is to be implemented using an additional margin, a unit of a cyclic shift is determined as a function of a CAZAC sequence. That is, for the CAZAC index m, the unit of cyclic shift is expressed by Equation 2 below.

는 시퀀스 인덱스에 상관없이 적용되는 공통 순환이동 단위이고,

은 시퀀스 인덱스가 m인 경우에 적용되는 추가적인 마진이다. 이 마진은 시퀀스와 시프트의 사용 방법에 따라 다른 방법들에 의해서 정해질 수 있다. 따라서 수학식 2에서의 순환이동 단위는 적어도 2M이 되야 한다. From here

Is a common unit of rotation movement applied regardless of the sequence index,

Is an additional margin applied when the sequence index is m. This margin can be determined by other methods, depending on how the sequence and the shift are used. Therefore, the cyclic shift unit in Equation 2 should be at least 2M.

2A and 2B show the above situation. In FIG. 2A and FIG. 2B, the hatched portion on the right side shows a cyclic shift opportunity.

를 포함하게 되면,

임을 알 수 있다. CAZAC 인덱스가

보다 작을 때는 도 2a와 도 2b에서 보듯 기본 단위인

즉, 수학식 2에 의해서 순환이동을 정의해야 함을 알 수 있다.If the position of the signal that is not affected by the frequency offset is at t, the pulses affected by the frequency offset can be generated one by one to the left and right.

If you include

It can be seen that. CAZAC index

When smaller than the basic unit as shown in Figures 2a and 2b

That is, it can be seen that cyclic shift should be defined by Equation 2.

이 커지게 되고 결국 사용할 수 있는 순환이동 는 1개로 줄어드는 상황이 발생할 수 있다. 따라서 이와 같이, 사용 가능한 순환이동이 줄어드는 것을 방지하기 위해서, CAZAC 인덱스가 큰 경우에 대해서는 상세히 살펴볼 필요가 있다. In this way, a robust cyclic shift can be defined for frequency offset / timing offset by simply applying additional margin to all indexes. But as the sequence index grows,

This situation may increase and eventually reduce the number of circular movements that can be used. Therefore, in order to prevent the usable circular movement from decreasing, it is necessary to look at the case where the CAZAC index is large.

~

인 경우와

~

인 경우를 표시하고 있다. 도 3a의 경우는 기본 순환이동 단위를 고려하고도 중간에 공간이 남아서 추가적인 순환이동 셋(빗금부분)을 더 넣을 수 있는 것을 볼 수 있다. 도 3b의 경우는 공간이 더 넓어서 2개까지 들어가는 것을 볼 수 있다. 3A and 3B show the CAZAC index M

To

If and

To

Is displayed. In the case of FIG. 3A, it can be seen that even after considering the basic circular movement unit, a space remains in the middle so that an additional circular movement set (hatched portion) can be added. In the case of Figure 3b it can be seen that the space is wider to go up to two.

인 경우에 총 P개의 순환이동 셋이 만들어짐을 알 수 있다. 이러한 3M의 단위를 순환이동 그룹이라고 한다.Generalizing this, slots are defined in a hatched shape within a range where blocks are made of pulses as shown in FIG.

We can see that a total of P circular movement sets are made. This unit of 3M is called a cyclic shift group.

As shown in FIG. 4, units of a cyclic shift group may be defined for the entire sequence, and each cyclic shift group may be defined as shown in FIG. 3C. When the number of circular movement groups is G and the number of circular movements in each group is P, it can be seen that the total usable number of circular movements is P * G. In an embodiment of the present invention, as shown in FIG. 4, it is assumed that the sequence is divided into groups and the limited circular movements available within each group are found.

In this way, all usable circular movements are defined up to an index having one circular movement group. When the length of a sequence is N, this range is an index between 1 and N / 3 and 2N / 3 and N-1. Here, the k-th index has the same cyclic shift group and cyclic shift set as the N-k th index according to the symmetry characteristic.

5 illustrates a position where a pulse is generated due to interference when a CAZAC index belongs to an N / 3 to N / 2 interval.

In FIG. 5, one square represents a unit of circular movement. As shown in FIG. 5, when the CAZAC index exceeds N / 3, all of the consecutive circular shift positions (however, circular shift positions defined as To) may not be used and may be used according to a predetermined rule.

Constrained cyclic shifts applied to the present invention have been proposed to prevent high Doppler frequency effects. The cyclic shift offset C _off depends on the root index u used. Since the preamble may be generated in the time domain or in the frequency domain, the relationship between C _off and u depends on the domain generating the preamble.

If the ZC sequence is generated in the frequency domain and the cyclic shift is generated in the time domain, C _off may be derived as follows.

It is assumed that the signal energy spreads by a value from the adjacent sub-carriers due to the Doppler frequence. And it is assumed that what comes over from the adjacent carrier only comes from one adjacent subcarrier location (first order case). In this case, the received signal in a specific subcarrier is composed of three terms as shown in Equation 3 below in the presence of a frequency offset.

s (n) = p (-f _off ) c (n) + p (-w ₀ -f _off ) c (n-1) + p (w ₀ -f _off ) c (n + 1)

Here, the pulse shape function, that is, p (f), can be simply defined as a raised cosine or sinc function. For convenience, the constants c ₀ , c _-1 , and c ₁ s (n) = c ₀ c (n) + c _-1 c (n-1) + c ₁ c (n + 1). When a sequence is detected from this, multiplying the conjugate of the sequence gives the following equation (4).

s (n) c ^* (n) = c ^* (n) (c ₀ c (n) + c _-1 c (n-1) + c ₁ c (n + 1)) = c ₀ + c _-1 c (n-1) c ^* (n) + c ₁ c (n + 1) c ^* (n)

는 c(n)=x(n)가 CAZAC일 때, 다음의 수학식 4와 같이 주어진다.From here

Is given by Equation 4 when c (n) = x (n) is CAZAC.

Therefore, when Equation 5 is applied to Equation 4, it can be seen that s (n) is composed of three signals. The first item is a simple DC component, the second is a complex exponential wave with frequency M / N, and the third is a complex exponential wave with frequency -M / N.

Therefore, C _off is defined as follows according to the index u of the ZC sequence.

C _{off, u} = u

On the other hand, if the ZC sequence is generated in the time domain and the cyclic shift is generated in the time domain, C _off is derived as follows.

If the RACH preamble received without a frequency offset is r (n), the RACH signal received with a frequency offset is as follows.

이고,

는 주파수 옵셋을 Hz 단위로 나타낸 것이며, f_s는 RACH 프리엠블의 샘플링 비율(sampling rate)을 나타낸다. here

ego,

Denotes a frequency offset in Hz, and f _s denotes a sampling rate of the RACH preamble.

의 자기상관(auto-correlation)은 수학식 8과 같이, r(n) = x_u(n)의 설정으로 구해진다. 여기서 u는 ZC 시퀀스의 인덱스를 나타낸다.

The auto-correlation of is obtained by setting r (n) = x _u (n), as shown in Equation (8). Where u represents the index of the ZC sequence.

의 자기상관은 수학식 9와 같이,

의 설정으로 구해진다.If C _{off, u} is the margin value by frequency offset,

The autocorrelation of is given by Equation 9,

It is obtained by setting of.

를 타이밍 오류(timing error)에 응답하는 재샘플링 비율(re-sampling ratio)이라 하면,

가 된다.Where () zc represents a modular operation for Nzc. C _{off, u} '= u * C _{off, u} is called the root index relative to the sample shifts,

Is the re-sampling ratio in response to a timing error,

Becomes

가 된다. 채널 응답 위치를 메인 로브(main lobe), +/-의 도플러 주파수의 영향을 받은 채널의 엘리어스 응답 위치를 사이드 로브(side lobe)라고 한다. 즉, 메인로브는 0 offset에 의한 위치로서, 도플러 주파수의 영향이 없을 때의 제대로 된 채널 응답 위치를 나타낸다. 사이드 로브 중 +사이드 로브는 +옵셋에 의한 위치로서, +도플러 주파수의 영향을 받은 엘리어스의 응답 위치이고, -사이드 로브는 -옵셋에 의한 위치로서, -도플러 주파수의 영향을 받은 엘리어스의 응답 위치이다. 수학식 9로부터 자기상관의 피크(peak)의 메인 로브는 C_off,u=0 혹은 C_off,u'=0 에서 나타남을 알 수 있다. 수학식 9로부터 사이드 로브의 쌍은 다음의 수학식 10과 같은 조건하에서 나타남을 알 수 있다.By Equation 8 and Equation 9

Becomes The channel response position is called the main lobe, and the alias response position of the channel affected by the Doppler frequency of +/- is called the side lobe. That is, the main lobe is a position by 0 offset, and represents a proper channel response position when there is no influence of the Doppler frequency. Of the side lobes, the + side lobe is the position of ++ offset, which is the response of Ellis under the influence of the + Doppler frequency. . It can be seen from Equation 9 that the main lobe of the peak of autocorrelation appears at C _{off, u} = 0 or C _{off, u} '= 0. It can be seen from Equation 9 that the pair of side lobes appear under the same condition as Equation 10 below.

(u * C _{off, u} ) _Nzc = -1

Therefore, u * C _{off, u} -m * Nzc = -1. That is, C _{off, u} = (m * Nzc-1) / u. Where m is the smallest integer that makes C _{off, u} an integer. For example, if the length of the ZC sequence is 839 and the root index is 300, m is 59 and C _{off, u} is 165.

When using a ZC sequence defined in the time domain, C _off is defined as in Equation 12 below.

C _{off, u} = (N _zc m-1) / u

Where m is the smallest positive integer that makes C _off an integer, and Nzc is the length of ZC. All indexes u are already relative primes for Nzc. Therefore, there is a positive integer u _inv = 1 / u that satisfies u * u _inv = 1 mod Nzc. Therefore, C _{off, u} can be simply expressed as Equation 12 below.

The negative sign (-) only changes the sign of the + offset and the offset. Therefore, it can be expressed as Equation 13 without the negative sign.

C _{off, u} = 1 / u mod N _zc

In summary, if you use the CAZAC sequence defined in the frequency domain, the index u of the CAZAC sequence is C _off . If you use the CAZAC sequence defined in the time domain, the index u of the CAZAC sequence is 1 / u mod Nzc. The value is C _off .

When using the ZC sequence defined in the frequency or time domain, using the conjugate property of C _off and the ZC sequence, the distance d _u between the main lobe and the side lobes is defined as .

Embodiments according to the present invention propose various methods for establishing a restricted circular shift. Embodiments according to the present invention propose a method for setting a restricted cyclic shift without two fixed cyclic shift positions and a method for setting a restricted cyclic shift with a fixed cyclic shift position. The first method involves a restricted cyclic shift without taking into account a predefined shift position, and the second method involves a restricted cyclic shift taking into account a predefined shift position. with pre-defined shift position).

In relation to the first method, there is a method of directly using a shift value of the V _a -th limiting circular shift, for example, a method of obtaining a shift value C _Va and setting a circular shift interval. That is, the cyclically shifted sequence is x _{u, V} (n) = x _u ((n + C _Va ) mod N _zc ). In addition, with respect to the first method, there is a method of using a prime number V _a for the V _a th limited circular shift, for example, a method of setting a cyclic shift interval by obtaining _a shift index prime number V _a . That is, if the length of the circular shift is Ncs, the circularly shifted sequence is x _{u, Va} (n) = x _u ((n + round (v _a N _cs )) mod N _zc ). Here, round means a rounding function.

Obtaining the two in relation to the first method, _a second V restriction method using a constant V for _a circular movement, for example, shift index integer V _a a method of setting the rotation movement division. That is, the cyclically shifted sequence is x _{u, Va} (n) = x _u ((n + v _a N _cs ) mod N _zc ).

On the other hand, in the case of circular shift in multiples of Ncs, for the u th root ZC sequence, random access preambles having a zero correlation region (ZCZ) are x _{u, v} (n) = x is defined as _u ((n + vN _cs ) mod N _zc ). This definition is suitable for low / middle cells where high frequency offset does not matter. However, the above definition is not relevant when constrained circular shift is used in high mobility cells. In particular, the value of available v is limited and the number of available ZCZ preambles is reduced by one third than in the usual case.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description, which will be given below with reference to the accompanying drawings, is intended to explain exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced.

In the following figures, the position where Elias occurs by + Doppler frequency is indicated by the position of "+ offset", and the position where Elias occurs by-Doppler frequency is shown by the position of "-offset".

6A and 6B illustrate the case where Nzc = 839, Ncs = 100, and d _u = 155, and show how the number of ZCZ preamble sequences is reduced due to an alias response.

In FIG. 6A, the circular movement can be started at any position. In FIG. 6B, the circular movement is possible only at the position of multiples of Ncs. In Figures 6a and 6b the Ncs values are the same, only the starting position of each circular shift is different.

In conclusion, the case of FIG. 6A may constitute more circular movements than the case of FIG. 6B. That is, in the case of FIG. 6A, additional restriction circular movement can be obtained by removing the restriction on the start position of the circular movement.

FIG. 7 shows the rate of increase of available limited circular shift as Nzc = 839, removing the constraint on the starting position of circular shift.

The elimination of the constraints on the initiation of circular movements above does not increase any hardware complexity.

Therefore, constrained circular shift is preferred, which does not take into account predefined shift positions. However, the present invention can also be applied to the case of constrained circular shift having a predefined shift position according to the embodiment, and therefore both cases will be described below.

First, the case of the constrained cyclic shift (Case 1) not considering the predefined shift position will be described as follows.

Regardless of the preamble generation domain, Equation 14 represents an alias distance. Since the number of limited circular shifts available per root ZC sequence depends on the root index and Ncs, different equations for different alias distance ranges are needed.

In particular, there are two Elias distance intervals in which the Elias response is indistinguishable. Unless the circular movement division and the two intervals overlap each other Elias, interval limits rotation movement is available is given by _{Ncs≤d u ≤ (Nzc-Ncs)} / 2.

Here, d _u = u when the preamble is generated in the frequency domain and d _u = 1 / u mod Nzc when it is generated in the time domain. The number of constrained circular shifts is given by

Where P denotes the number of restricted circular shifts per group, and G denotes the number of groups appearing in one preamble sequence. R denotes the number of additional constrained circular shifts in the remaining circular shift region after allocating a non-integral group group.

Ncs ≤ d _u ≤ (Nzc-Ncs) / 2 where limited cyclic shift is available is based on Nzc / 3, where Ncs≤d _u <(Nzc / 3) and (Nzc / 3) ≤d _u ≤ (Nzc- Ncs) / 2 can be divided.

The reason for dividing the Elias distance section based on Nzc / 3 is as follows.

That is, when d _u is smaller than Nzc / 3, when there is one group as shown in FIG. 3C, both sides thereof are the response positions of Elias. In the lower figure of Fig. 4, when there is one limiting circular movement, both sides thereof are the Elias position. In the lower part of FIG. 4, only the middle part of the three parts is actually used for transmission, and both of the two parts are not used for transmission to the Elias part (parts separated by +/- M) and used only for detection. These three parts combine to form the size of one group. From the total length Nzc, it is possible to obtain the number of additional cyclic shifts in the remaining portion except for the total size of these groups. In FIG. 4, there are G groups, and there are P elements in each group.

On the contrary, when d _u is larger than Nzc / 3, the position where the aliases occur is changed as shown in FIG. 5. Elias no longer occurs on both sides of circular movements.

In each section, using the first left-hand rectangle, Elias occurs at locations (1 + M) and (1-M mod Nzc), separated by + M and -M. The size of one group is limited to the length of N-2M in the middle portion, and the number of groups is determined by how many groups can be added while keeping the Elias not overlapping in the left length M section. Here, the first additional cyclic shift R ₁ occurs depending on whether the group is placed in the left-length M section and can be used more in the remainder. In particular, when using a predefined shift position, it is necessary to determine whether there is a second additional circular shift R ₂ possible in the section having the right length M, not just considering the section having the left length M.

Therefore, since Ncs≤d _u ≤ (Nzc-Ncs) / 2 has a different aliasing position based on Nzc / 3, Ncs≤d _u <(Nzc / 3) and (Nzc / 3) ≤d _u ≤ Examine the intervals of (Nzc-Ncs) / 2.

If the start position of the first group is 0, the interval of the V _a th limit circular shift is defined as [C _{Va, start} , C _{Va, end} ] in Equations 16 and 17.

C _{Va, end} = C _{Va, start} + Ncs-1

And Elias occurs at positions 18 and 19.

Where () _Nzc represents a modular operation on Nzc.

개의 그룹이 있고, 그룹당

개의 제한 순환이동이 있으며, 각 그룹의 길이는

이다. 그리고, 이용 가능한 추가 순환이동은 R 이 양수이면,

이 된다. First, the alias distance interval Ncs ≤ d _u <(Nzc / 3) (alias distance interval 1)

Groups, per group

Limiting circular movements, the length of each group

to be. And the available additional circular shift is that if R is positive,

Becomes

8 illustrates a cyclic shift in the case of Nzc = 839, Ncs = 40, and d _u = 150. There is one group having three cyclic shifts per group, and there are two additional cyclic shifts in the remaining section. In this example, the total limit circular movement is five.

In an embodiment of the present invention, a cycle movement application period is set by applying the number of groups, the number of limited circular movements per group, and the length of the group to the equations (16) and (17).

이고, 각 그룹의 길이는

이 되며,

개의 그룹이 있다. 추가 순환이동은 가운데 부분과 오른쪽 부분의 남은 영역에서 가능한 수 중에서 작은 수로 선택 된다. 즉, 추가 순환이동의 수는 R이 양수일 때,

이다. V_a번째 제한 순환이동의 시작 위치는 위의 파라미터들을 수학식 16 및 수학식 17에 적용하여 연산한다. Next, the number of cycles available per group in the Elias distance interval (Nzc / 3) ≤ d _u ≤ (Nzc-Ncs) / 2 (alias distance interval 2)

And the length of each group

Will be

There are groups of dogs. Additional circular movements are chosen from the smallest possible numbers in the remaining areas of the middle and right parts. That is, the number of additional circular shifts is when R is positive,

to be. The starting position of the V _a th limit circular shift is calculated by applying the above parameters to Equations 16 and 17.

9 illustrates an example in which Nzc = 839, Ncs = 40, and d _u = 399. There are four groups having one circular shift per group and one additional circular shift. In this example, the total limit rotation is five.

In an embodiment of the present invention, a cycle movement application period is set by applying the number of groups, the number of limited circular movements per group, and the length of the group to the equations (16) and (17).

The equal sign (=) of the two Elias distance sections identified above may not have a significant meaning. For example, when using an 839-length ZC sequence, (Nzc / 3) = 279.67, the interval is Ncs≤d _u <(Nzc / 3) and (Nzc / 3) ≤d _u ≤ (Nzc-Ncs) / 2. Dividing by and dividing interval by Ncs≤d _u ≤ (Nzc / 3) and (Nzc / 3) <d _u ≤ (Nzc-Ncs) / 2 have the same result.

Next, the case of the constrained circular shift (Case 2) taking into account the predefined shift position will be described.

With a predefined shift position, the method of generating a constrained circular shift is changed. In each Elias distance interval, there are G groups with P circular shifts and there is the first additional circular shift that does not belong to the R ₁ group. In addition, when using a predefined shift position, there is a special additional cyclic shift unlike the case where there is no predefined shift position in the alias distance interval 2 region. In the Elias distance interval 2 region, the main region generally appears in the front samples of the sequence and alias regions appear in the samples later in the sequence, whereas the main region appears in the rear samples of the sequence and Elias areas appear in the front samples of. This second additional circular shift is represented by R ₂ . This second additional circular shift does not occur in Elias distance interval 1. The total number of limited circular shifts is expressed by Equation 20 below.

Assuming that the start position of the first group is 0, the V _a th limit circular shift is defined in the [C _{Va, start} , C _{Va, end} ] region as shown in Equations 21 and 22.

C _{Va, end} = C _{Va, start} + Ncs-1

And the related aliases occur at positions 23 and 24.

Where () _Nzc represents a modular operation on Nzc.

개의 제한 순환이동을 가지는

개의 그룹이 있고, 그룹의 길이는

이다. 첫 번째 추가 순환이동의 수는 R₁이 양수일 때,

개이다. 엘리어스 거리 구간 1에서 두 번째 추가 순환이동의 수는 항상 0이다.First, in the Elias distance interval Ncs≤d _u <(Nzc / 3) (alias distance interval 1), respectively

With restricted circular movements

Groups, the length of the group

to be. The first number of additional circular shifts is when R ₁ is positive,

Dog. The second additional circular shift in Elias distance interval 1 is always zero.

FIG. 10 illustrates an example in which Nzc = 839, Ncs = 40, and d _u = 150, where there is one group having three circular shifts per group and there are two additional circular shifts. In this example, the total limit rotation is five.

In another embodiment of the present invention, the number of groups calculated in this way, the number of limited circular shifts per group, and the length of the group are applied to Equations 21 and 22 to set the cyclic shift application interval.

이고, 각 그룹의 길이는

이 되며,

개의 그룹이 있다. 첫 번째 추가 순환이동은 앞서의 구간에서와 같은 방식으로 구해지며, 그 수는 R₁이 양수일 때,

이다. R₁=0이면, 두 번째 추가 순환이동이 있는지 확인해야 한다. 두 번째 추가 순환이동은 도 11의 마지막 순환이동과 같이, 기존 순환이동와 반대의 형태를 가지게 된다. 두 번째 추가 순환이동의 엘리어스 구간이 사용 가능한 구간인지 체크 즉,

인지 확인하고, 순환이동 구간이 사용 가능한지 체크 즉

인지 확인하여, 사용 가능하면 R₂=1이 된다. 이때 엘리어스 구간의 사용 여부 체크는 생략 가능하다. 여기서

이다.Next, the number of cycles available per group in the Elias distance interval (Nzc / 3) ≤ d _u ≤ (Nzc-Ncs) / 2 (alias distance interval 2)

And the length of each group

Will be

There are groups of dogs. The first additional circular shift is obtained in the same way as in the previous section, and the number is when R ₁ is positive,

to be. If R ₁ = 0, then there must be a second additional circular shift. The second additional circular movement has a form opposite to the existing circular movement, as in the last circular movement of FIG. 11. Check whether the Ellipse interval of the second additional circular movement is an available interval,

Check whether the circular motion section is available,

Check that it is, if available, R ₂ = 1. In this case, it is possible to omit the use of the alias section. here

to be.

11 illustrates a case where Nzc = 839, Ncs = 40, and d _u = 399. There are three groups having one circular shift per group and there are 0 first additional circular shifts. In addition, there is one second additional circular movement in which the relative positions of the main region and the alias region are opposite to the general case. This second additional circular shift does not occur as shown in FIG. 9 when the fixed circular shift position is not used. In this example, the total limit rotation is four.

In another embodiment of the present invention, the number of groups calculated in this way, the number of limited circular shifts per group, and the length of the group are applied to Equations 21 and 22 to set the cyclic shift application interval.

As in another embodiment of the present invention, in a specific system in which the circular movement is fixed, the circular movement may be determined through the following process.

First, the entire sequence interval is divided by the cyclic shift value.

Next, the interval (± u or ± (m * Nzc-1) / u) where the interference occurs due to the offset for the first interval (n = 1) is found. At this time, the section in which interference occurs is a plurality of sections. For example, when only the first interference is considered, a section in which interference occurs may be configured up to four sections.

Next, if the first interval and the plurality of interference intervals due to the offset do not overlap with each other, the first interval is set as the interval for which the cyclic shift is available, and the remaining multiple intervals due to the offset are set as the prohibited interval.

The process proceeds to the next section (n = n + 1), and repeats the process of finding the section where the interference occurs due to the offset in the nth section.

In the process of finding the section where the interference due to the offset occurs in the nth section, if the observation section, the plurality of sections due to the offset, the previously set available section, and the previously set prohibited section do not overlap each other, Set it as an available section and set a plurality of sections due to the offset for the current section. By repeating this process to the last section, it is possible to determine cyclic movement in a system in which cyclic movement is fixed.

As another embodiment of the present invention, in the mobile communication system including a plurality of cells, it is possible to apply the cyclic shift application interval set as above only to the cell identified as the high mobility cell.

In this case, whether the cell is a high mobility cell may be determined based on whether the frequency offset for the cell is greater than or equal to a predetermined level by acquiring the cell information. In this case, the predetermined level is a frequency offset value that can be easily set and changed by a person of ordinary skill in the art (hereinafter referred to as a person skilled in the art). Whether the cell is a high mobility cell can be determined by the base station or the terminal. However, it is difficult for the terminal to estimate the frequency offset values of other terminals in the cell. Therefore, after the base station determines this in consideration of the plurality of terminals in the cell, it is preferable to broadcast whether it is a high mobility cell through a broadcast channel.

Meanwhile, another embodiment of the present invention may include a process of allocating an unassigned sequence to the high mobility cell if the identified cell is not a high mobility cell.

In the present invention, even when the method described in Case 1 and Case 2 is used as it is, the equation may be represented by another equation. The following example shows some mathematical expressions.

Meanwhile, in all the following equations, d _u is equal to Equation 25 when generating a ZC sequence in the frequency domain.

In addition, when generating a ZC sequence in the time domain, d _u is represented by Equation 26.

Where m is the smallest positive integer that makes d _u an integer, and Nzc is the length of ZC. Equation 26 may be expressed as Equation 27.

The v th circular shift for the u th root index is defined as x _{u, V} (n) = x _u ((n + C _V ) mod N _zc ). Here, in the case of general circular movement, C _v = v * N _cs , and in the case of limited circular movement, C _v is determined by the following equation.

First, the case of the constrained cyclic shift (Case 1) which does not consider the predefined shift position will be described with the equation different from the above.

The u th root ZC sequence with the region of zero correlation, the v th random access preamble, is defined according to x _{u, V} (n) = x _u ((n + C _V ) mod N _zc ).

Here, C _V is the same as Equation 28.

The parameters of the high mobility cell are defined as follows.

개 존재하고, 길이

인

개의 그룹이 존재하며, 추가 제한 순환이동은

개 존재한다. In the Elias distance interval of Ncs≤d _u <(Nzc / 3), the cyclic shift per group

Dogs exist, length

sign

Groups exist, and additional limit rotation

Dog exists.

개 존재하고, 길이

인

개의 그룹이 존재하며, 추가 제한 순환이동은

개 존재한다.In the Elias distance interval of (Nzc / 3) ≤d _u ≤ (Nzc-Ncs) / 2, the cyclic shift per group

Dogs exist, length

sign

Groups exist, and additional limit rotation

Dog exists.

In addition, the equations may be expressed as follows.

이고,

,

인 경우에 Ncs≤d_u<(Nzc/3) 의 엘리어스 거리 구간에서, P=E,

,

,

로 표현되고, (Nzc/3)≤d_u≤(Nzc-Ncs)/2의 엘리어스 거리 구간에서, P=F,

,

,

로 표현될 수 있다.That is, C _v =

ego,

,

In the Elias distance interval of Ncs≤d _u <(Nzc / 3), P = E,

,

,

In the Elias distance interval of (Nzc / 3) ≤d _u ≤ (Nzc-Ncs) / 2, P = F,

,

,

It can be expressed as.

Next, the case of the constrained cyclic shift (Case 2) in consideration of the predefined shift position will be described as follows.

The u th root ZC sequence with the region of zero correlation, the v th random access preamble, is defined according to x _{u, V} (n) = x _u ((n + C _v ) mod N _zc ). Here, C _v is the same as Equation 29.

이다.here,

to be.

At this time, the parameters of the high mobility cell is defined as follows.

,

,

로 표현되고, 첫 번째 추가 제한 순환이동 개로, 두 번째 추가 제한 순환 이동 R₂=0 개로 표현될 수 있다.In other words, in the Elias interval of Ncs≤d _u <(Nzc / 3),

,

,

Expressed as, and the first additional constrained rotation Can be expressed as the second additional limiting circular shift R ₂ = 0.

,

,

로 표현되고, 첫 번째 추가 제한 순환이동

개로, 두 번째 추가 제한 순환이동 R₂는 R₁=0 이고 X - Ncs < 2 d_u인 경우에만 R₂=1개로 표현될 수 있다. 여기서,

이다.In addition, in the Elias interval of (Nzc / 3) ≤d _u ≤ (Nzc-Ncs) / 2,

,

,

Expressed as, and the first additional constrained rotation

In addition, the second additional limiting circular shift R ₂ can be expressed as R ₂ = 1 only if R ₁ = 0 and X − Ncs <2 d _u . here,

to be.

Constrained circular shift x _{u, V} (n) = x _u ((n + C _v ) mod N _zc ) gives an example of how to directly use the shift value of the v th limited circular shift. Alternatively, the restricted circular movement may be applied using Va for the Va th limited circular movement. That is, similar cyclic shifts can be generated using x _{u, Va} (n) = x _u ((n + round (v _a N _cs )) mod N _zc ). In the case of generating a circular movement in this manner, the basic concept is the same as the above description. However, the equation is changed as follows.

First, the case of the constrained cyclic shift (Case 1) which does not consider the predefined shift position will be described with the equation different from the above.

At this time, the index v for the cyclic movement is expressed as in Equation 30.

,

,

이고, 추가적인 제한 순환이동

으로 표현된다.In the Elias interval of Ncs≤d _u <(Nzc / 3),

,

,

Additional constrained rotation

It is expressed as

_,

이고,

_,

으로 표현된다.In the Elias interval of (Nzc / 3) ≤d _u ≤ (Nzc-Ncs) / 2,

_,

ego,

_,

It is expressed as

,

인 경우에, Ncs≤d_u<(Nzc/3)의 엘리어스 구간에서, P=E,

,

,

로 달리 표현되고, (Nzc/3)≤d_u≤(Nzc-Ncs)/2의 엘리어스 구간에서, P=F,

_,

_,

로 표현될 수 있다.Also, the expression above

,

In the case of Ellis interval of Ncs≤d _u <(Nzc / 3), P = E,

,

,

In the Ellis interval of (Nzc / 3) ≤d _u ≤ (Nzc-Ncs) / 2, P = F,

_,

_,

It can be expressed as.

Next, the case of the constrained cyclic shift (Case 2) in consideration of the predefined shift position will be described as follows.

At this time, the index v for the cyclic movement is expressed by Equation 31.

,

,

이고, 첫 번째 추가 제한 순환이동

이고, 두 번째 추가 제한 순환이동 R₂=0로 표현될 수 있다.In the Elias interval of Ncs≤d _u <(Nzc / 3),

,

,

, The first additional constrained rotation

And a second additional limiting circular shift R ₂ = 0.

,

,

,

이고, R₁=0이고

인 경우에 R₂=1 로 표현될 수 있다. 여기서,

이다.In the Elias interval of (Nzc / 3) ≤d _u ≤ (Nzc-Ncs) / 2,

,

,

,

R ₁ = 0

It may be expressed by R ₂ = 1 when. here,

to be.

,

인 경우에,Also, the expression above

,

in case of,

,

으로 달리 표현되고, (Nzc/3)≤d_u≤(Nzc-Ncs)/2의 엘리어스 구간에서, P=F, S=2F+F',

,

이고, R₁=0이고

인 경우에 R₂=1로 표현될 수 있다. 여기서,

이다.In the Elias interval of Ncs≤d _u <(Nzc / 3), P = E, S = 3E + E ',

,

In other words, P = F, S = 2F + F ', in the Ellis interval of (Nzc / 3) ≤ d _u ≤ (Nzc-Ncs) / 2

,

R ₁ = 0

It can be expressed by R ₂ = 1 when. here,

to be.

As described above, according to one embodiment of the present invention, when implementing a cyclic shifted sequence using a CAZAC sequence, a cyclic shift set that can eliminate shift ambiguity due to frequency offset or timing offset ( cyclic shift set) can be defined. In addition, according to one embodiment of the present invention, when accessing a channel that is not synchronized, the frequency offset or timing offset is not matched, so that such a channel can be made robust and influenced by a pulse shaping filter. Depending on the range, the cyclic shift set may be defined considering not only the first order but also the interference of the second order or higher order.

The detailed description of the preferred embodiments of the present invention has been provided to enable any person skilled in the art to make and implement the present 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. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to cover the widest scope consistent with the principles and novel features disclosed herein.

The present invention relates to a method for allocating a sequence to each cell in consideration of characteristics of a CAZAC sequence for solving a frequency offset problem and a method for setting a cyclic shift to be applied thereto. Can be.

FIG. 1 illustrates a method of setting a circular shift applying unit by adding an additional margin to a conventional circular shift applying unit.

2A and 2B illustrate an example of applying the additional margin of FIG. 1 when the sequence index is small.

3A and 3B illustrate an example of applying the additional margin of FIG. 1 when the sequence index is large.

3C shows an example of one group consisting of P circular movement sets.

4 illustrates a circular movement applying group and a method of setting a circular movement applying section in each group.

5 illustrates an example of a cyclic shift unit when the length of the sum of the channel response of the reception sequence and each alias of the reception sequence is greater than the total length of the sequence.

FIG. 6A shows the position of the circular movement and the position of the offset in the case of the limited circular movement without considering the predefined shift position.

FIG. 6B shows the position of the circular shift and the position of the offset in the case of the limited circular shift with a predefined shift position.

FIG. 7 is a graph showing an increase in the number of usable cyclic shifts in the case of a restrictive cyclic shift having a predefined shift position in FIG. 6B in the case of a restrictive cyclic shift without considering the predefined shift position of FIG. 6A.

8 and 9 illustrate examples of the position of the cyclic movement and the position of the offset obtained by applying the cyclic shift sequence setting method to the frequency offset according to an embodiment of the present invention.

10 and 11 illustrate examples of the positions of the cyclic movements and the positions of the offsets obtained by applying the cyclic shift sequence setting method to the frequency offset according to another embodiment of the present invention.

Claims (12)

Calculating a distance between a channel response position of the sequence and a channel response position of an alias of the sequence caused by a frequency offset using an index of the sequence; And And calculating a cycle movement application period by calculating the number of cycle movements per group constituting the sequence according to the calculated distance interval. The method of claim 1, The setting of the circular movement applying section, Calculating the number of groups, the number of cyclic movements per group, and the length of the group according to the calculated distance section; And And setting a cycle movement application period by using the number of groups, the number of cycle movements per group, and the length of the group. The method of claim 1, The setting of the circular movement applying section, And calculating the shift position by multiplying the index of the cyclic shift, which is the prime number, by cyclic multiplication with the length of the motion, when the index of the cyclic shift is a prime number. The method of claim 1, The setting of the circular movement applying section, And setting a circular movement applying section according to at least two sections which are divided based on positions corresponding to 1/3 of the length of the sequence. Calculating a distance between a channel response position of the sequence and a channel response position of an alias of the sequence caused by a frequency offset using an index of the sequence; And Setting a cyclic shift application section having a shift position that is a multiple of the cyclic shift length by calculating the number of cyclic shifts per group constituting the sequence and the number of additional cyclic shifts not belonging to the group according to the calculated interval section Including, a circular sequence sequence setting method. The method of claim 5, wherein The step of calculating the shift position, Checking whether there is a first additional circular movement that does not belong to the group; And And if the first additional circular movement does not exist, checking whether a second additional circular movement exists. The method of claim 5, wherein The step of calculating the shift position, Calculating the number of groups, the number of circular movements per group, the length of the group, and the number of additional circular movements according to the calculated distance intervals; And And setting a circular movement applying interval by using the number of the group, the number of circular movements per group, the length of the group, and the number of additional circular movements. The method of claim 5, wherein The step of calculating the shift position, And setting a circular movement applying section according to at least two sections which are divided based on positions corresponding to 1/3 of the length of the sequence. In a method for setting a cyclic shift sequence in a mobile communication system including a plurality of cells, Acquiring cell information to determine whether the corresponding cell is a high mobility cell; And If the identified cell is a high mobility cell, the distance between the channel response position of the sequence and the channel response position of the alias of the sequence occurring due to the frequency offset is calculated using the index of the sequence, and the interval of the calculated distance And setting the cycle movement interval by calculating the number of cycle movements per group constituting the sequence. In the method for setting a sequence in a mobile communication system comprising a plurality of cells, Acquiring cell information to determine whether the corresponding cell is a high mobility cell; And If the identified cell is a high mobility cell, the distance between the channel response position of the sequence and the channel response position of the alias of the sequence occurring due to the frequency offset is calculated using the index of the sequence, and the interval of the calculated distance Calculating a number of circular movements per group constituting the sequence and the number of additional circular movements not belonging to the group, and setting a circular movement application section having a shift position that is a multiple of the circular movement length. How to set up a sequence. The method according to any one of claims 9 to 10, The setting of the circular movement applying section, If the identified cell is not a high mobility cell, assigning a sequence not assigned to the high mobility cell. The method according to any one of claims 9 to 10, Determining whether or not the high mobility cell And acquiring the cell information and determining a cell having a frequency offset equal to or higher than a predetermined level as a high mobility cell.

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