WO2018112760A1 - Pilot structure, pilot sending method, and user channel estimation method - Google Patents

Abstract

The present invention relates to a pilot structure, a pilot sending method, and a user channel estimation method, the pilot structure comprising L uplink pilot time slots and one frame for uplink data, each uplink pilot time slot being provided with K candidate orthogonal pilot sequences, the L uplink pilot time slots respectively being uplink pilot time slot 1 to uplink pilot time slot L ordered sequentially, the uplink data being arranged after uplink pilot time slot L, wherein L>1 and K≥1. Comparing the pilot structure of the present invention with existing pilot structures, existing pilot structures only have one uplink pilot time slot, whereas the present invention has L(L>1) uplink pilot time slots, greatly reducing the likelihood of pilot conflict during user random access in a cell.

Description

Pilot structure, pilot transmission method and user channel estimation method Technical field

The present invention relates to the field of multi-user large-scale antenna array communication systems, and in particular, to a pilot structure, a pilot transmission method, and a user channel estimation method.

Background technique

In a multi-user large-scale antenna array communication system, multiple users simultaneously transmit a pilot sequence and uplink data, and each user's uplink transmission time is synchronized with each other. In each uplink pilot time slot, multiple users may send pilot sequences, but If the pilot sequences transmitted by each user are sine waves of different frequencies or symbols of different time or codes orthogonal to each other, the pilot sequences of each user can be orthogonal, and the base station can correctly estimate each user. The channel is used to solve the uplink data of each user; but if multiple users select the same pilot sequence, it is called pilot collision, and the base station receiver cannot obtain the channel estimation and uplink data of the conflicting user, which is solved in the prior art. The method of pilot collision is: the solution in LTE is to increase the number of interactions between the terminal and the base station, and finally the base station selects a user from the user who has a pilot collision to continue to access. However, for the MTC scenario, the device is mostly random access; the number of terminals is large, the collision probability is high; the bandwidth is narrow, and the interaction with the base station takes time.

Summary of the invention

The technical problem to be solved by the present invention is to provide a pilot structure, a pilot transmission method, and a user channel estimation method, which greatly reduce the random access occurrence of users in a cell without increasing the pilot time-frequency resource overhead. The probability of frequency conflicts.

The technical solution of the present invention to solve the above technical problem is as follows: A pilot structure includes L uplink pilot time slots and one frame uplink data, and each of the uplink pilot time slots is provided with K candidate orthogonal guides. Frequency sequence, L of the uplink pilot time slots are sequentially arranged uplink pilot time slots 1 to uplink Pilot time slot L, the uplink data is arranged after the uplink pilot time slot L, where L>1, K≥1.

The invention has the beneficial effects that the pilot structure of the present invention has only one uplink pilot time slot compared with the existing pilot structure, and the present invention has L (L>1). The uplink pilot time slots can greatly reduce the probability of pilot collisions caused by random access of users in the cell.

Based on the above technical solutions, the present invention can also be improved as follows.

Further, the K candidate orthogonal pilot sequences include sine waves of different frequencies, symbols of different time, and one of mutually orthogonal codes.

The advantage of using the above further solution is that the pilot sequence is a sine wave of different frequencies or a symbol of different time or mutually orthogonal codes, which can ensure that the pilot sequences are orthogonal, further reducing the probability of occurrence of pilot collision.

Based on the above pilot structure, the present invention also provides a pilot transmission method.

A pilot transmission method for transmitting based on a pilot structure described above includes the following steps:

Step 1: randomly selecting one uplink pilot time slot in every J uplink pilot time slots;

Step 2: randomly select one candidate orthogonal pilot sequence in the K candidate candidate orthogonal pilot sequences of the uplink pilot time slot as a pilot for uplink transmission;

Where 1≤J≤L, and L=D*J, D is a positive integer.

The invention has the beneficial effects that the method for transmitting the pilot of the present invention avoids increasing the number of interactions between the terminal and the base station, and greatly reduces the pilot collision of the random access of the user in the cell without increasing the frequency resource overhead of the pilot time slot. The probability of increasing interaction efficiency.

Based on the above pilot transmission method, the present invention also provides a user channel estimation method.

A user channel estimation method for performing user channel estimation on a pilot transmitted in a pilot transmission method, including the following steps,

S1, the receiving end of the base station receives sampling data Y _l sent by all users in each uplink pilot time slot, where l=1, 2, 3, ..., L;

S2, the base station receiving end correlates the local K candidate orthogonal pilot sequences with the sample data Y _l received in each uplink pilot time slot, respectively, to obtain each pilot correlation result matrix B _l , where ,l=1,2,3,...,L;

S3, based each pilot correlation matrix of the linear relationship between the results of the pilot sequence A _l B _l with each user transmitting frequency be calculated by channel estimation for all users.

The invention has the beneficial effects that the channel estimation method of the present invention can accurately obtain the channel estimation of all users, and can clearly reflect the performance improvement when using the pilot transmission method of the present invention for pilot transmission.

Based on the above technical solutions, the present invention can also be improved as follows.

Further, a total of N users transmit sampling data in the uplink pilot time slot 1, the base station receiving end has M base station antennas, and the base station receiving end samples Q data on each base station antenna, and Q is also the pilot sequence length. , l=1, 2, 3, ..., L, then the S1 is specifically,

The sampling data Y _l sent by the N users received by the receiving end of the base station in each uplink pilot time slot is Y _l = HP + W, Y _l ∈ □ ^{M × Q} ;

Where: P is a matrix of N pilot sequences randomly selected by N users from K candidate orthogonal pilot sequences, H is a channel response matrix of N users, and W is noise.

Further, in the S2,

The expression of each pilot correlation result matrix B _l is B _l =Y _l S ^H ;

Wherein, S ^H represents a conjugate transpose of the matrix S, and S=[s ₁ , s ₂ , . . . , s _K ] ^T , which are K kinds of candidate orthogonal pilot sequences.

Further, in the S3,

The linear relationship between each pilot correlation result matrix B _l and the pilot sequence A _l transmitted by each user is A _l H=B _l , A _l ∈ □ ^{K × N} .

Further, the S3 is specifically,

S31. Obtain a guide relationship between all pilot correlation result matrices B and all users according to a linear relationship A _l H=B _l between each pilot correlation result matrix B _l and each pilot sequence A _l transmitted by the user. The linear relationship between the frequency sequences A is AH = B, where A = [A ₁ ^T A ₂ ^T ... A _L ^T ] ^T , B = [B ₁ ^T B ₂ ^T ... B _L ^T ] ^T ;

S32: Obtain a channel response matrix H of all users according to a linear relationship AH=B between all pilot correlation result matrices B and pilot sequences A transmitted by all users, as channel estimation of all users:

H = A ^-1 B, H = [h ₁ , h ₂ , ..., h _N ].

DRAWINGS

1 is a schematic structural view of a pilot structure of the present invention;

2 is a flowchart of a method for transmitting a pilot according to the present invention;

3 is a flowchart of a method for estimating a user channel according to the present invention;

4 is a graph of user channel estimation probability in a user channel estimation method according to the present invention.

detailed description

The principles and features of the present invention are described in the following with reference to the accompanying drawings.

As shown in FIG. 1 , a pilot structure includes L uplink pilot slots and one frame of uplink data, and each of the uplink pilot slots is provided with K candidate orthogonal pilot sequences, L The uplink pilot time slots are respectively sequentially arranged uplink pilot time slots 1 to uplink pilot time slots L, and the uplink data is arranged after the uplink pilot time slots L, where L>1 and K≥1. The K candidate candidate orthogonal pilot sequences include sine waves of different frequencies, symbols of different time, and one of mutually orthogonal codes.

A pilot structure of the present invention has only one uplink pilot time slot compared to the existing pilot structure, and the present invention has L (L>1) uplink pilot time slots. The probability of pilot collisions occurring in random access of users in the cell can be greatly reduced.

Based on the above pilot structure, the present invention also provides a pilot transmission method.

As shown in FIG. 2, a method for transmitting a pilot, which is sent based on a pilot structure described above, includes the following steps:

Step 1: randomly selecting one uplink pilot time slot in every J uplink pilot time slots;

Step 2: randomly select one candidate orthogonal pilot sequence in the K candidate candidate orthogonal pilot sequences of the uplink pilot time slot as a pilot for uplink transmission;

Where 1≤J≤L, and L=D*J, D is a positive integer.

That is to say: there are L times of uplink pilot time slots, the user randomly selects once every J pilot time slots, selects one pilot time slot, and there are K kinds of candidate orthogonal guides in each pilot time slot. The frequency sequence is selected by the user, and the user randomly selects one of the K candidate pilot sequences randomly as the pilot for uplink transmission in each pilot time slot.

Based on the above pilot transmission method, the present invention also provides a user channel estimation method.

As shown in FIG. 3, a user channel estimation method performs user channel estimation by using a pilot transmitted in a pilot transmission method, which includes the following steps.

S1, the receiving end of the base station receives sampling data Y _l sent by all users in each uplink pilot time slot, where l=1, 2, 3, ..., L;

S2, the base station receiving end correlates the local K candidate orthogonal pilot sequences with the sample data Y _l received in each uplink pilot time slot, respectively, to obtain each pilot correlation result matrix B _l , where ,l=1,2,3,...,L;

S3, based each pilot correlation matrix of the linear relationship between the results of the pilot sequence A _l B _l with each user transmitting frequency be calculated by channel estimation for all users.

specific:

A total of N users transmit sampling data in the uplink pilot time slot 1, the base station receiving end has M base station antennas, and the base station receiving end samples Q data on each base station antenna, and Q is also the pilot sequence length, l =1, 2, 3, ..., L, the S1 is specifically that the sampling data Y _l sent by the N users received by the receiving end of the base station in each uplink pilot time slot is Y _l = HP + W, Y _l ∈ □ ^{M × Q} ; where: P is a matrix of N pilot sequences randomly selected by N users from K candidate orthogonal pilot sequences, since the pilot sequences are randomly selected, so P The specific value is unknown; H is the channel response matrix of N users; W is noise, because the pilot sequence is randomly selected, so the noise W here is also random, not a known value; □ ^M×Q is a matrix The row and column dimensions of Y _l .

In the S2, the expression of each pilot correlation result matrix B _l is B _l =Y _l S ^H ; where S ^H represents the conjugate transpose of the matrix S, S=[s ₁ , s ₂ ,... , s _K ] ^T , are K candidate orthogonal pilot sequences.

In the S3, each of the linear relationship between the pilot sequence A _l B _l pilot matrix correlation result with each transmission frequency of a user _{A l H = B l, A} l ∈ □ K × N. Where A _l is a matrix with one and only one remaining ₁ in each column, l=1, 2, . . . , L. A _l H=B _l is obtained based on the physical relationship between the system model and the data.

The S3 is specifically S31, and according to the linear relationship A _l H=B _l between each pilot correlation result matrix B _l and the pilot sequence A _l sent by each user, all pilot correlation result matrices B are obtained. The linear relationship AH=B between the pilot sequences A transmitted by all users, where A=[A ₁ ^T A ₂ ^T ... A _L ^T ] ^T , B=[B ₁ ^T B ₂ ^T ... B _L ^T ] ^T ; S32, according to the linear relationship AH=B between all the pilot correlation result matrix B and the pilot sequence A transmitted by all users, the channel response matrix H of all users is obtained as the channel estimation of all users: H=A ^{- 1} B, H = [h ₁ , h ₂ , ..., h _N ], that is to say, when A is full, all user channel estimates can be obtained.

The following is a description of the beneficial effects of user channel estimation based on the pilot transmission method of the present invention in combination with a conventional pilot transmission method for user channel estimation.

User channel estimation based on the traditional pilot transmission method: only one uplink pilot time slot, that is, L=1 at this time, each user will randomly select K*L candidates in the uplink pilot time slot. One of the pilot sequences is selected to be transmitted as a pilot. At this time, according to a user channel estimation method of the present invention, a matrix A ∈ □ ^{K * L × N is obtained} , and the matrix A satisfies each column and only one of them 1 is 0.

User channel estimation based on the pilot transmission method of the present invention: there are a total of L uplink pilot slots, where L>1, and each of the uplink pilot slots has K candidate orthogonal pilot sequences, each The uplink user randomly selects one of the K candidate pilot sequences randomly as the pilot transmission in each uplink pilot time slot, and the matrix A∈□ ^K*L obtained according to a user channel estimation method according to the present invention ^{. ×N} , A = [A ₁ ^T A ₂ ^T ... A _L ^T ] ^T , where A _l is a matrix with one column and only one remaining 0, l = 1, 2, ..., L.

Therefore, the matrix A full rank probability in the user channel estimation method based on the pilot transmission method of the present invention is much larger than the matrix A full rank probability in the user channel estimation method based on the conventional pilot transmission method.

The user channel estimation based on the conventional pilot transmission method and the pilot transmission method based on the present invention can obtain the probability of all user channel estimations (A full rank probability), as shown in FIG. 4: FIG. The coordinates represent the parameter L (the L*K is constant at 48), the ordinate represents the probability that the base station receiver can obtain all user channel estimates, the curve labeled 1 represents the number of users N=3, and the curve labeled 2 represents the user. The number N=5, the curve labeled 3 represents the number of users N=7, the curve labeled 4 represents the number of users N=9, L=1 is the traditional pilot transmission method, and L>1 is the pilot of the invention Sending methods, you can clearly see the performance improvement.

The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalents, improvements, etc., which are within the spirit and scope of the present invention, should be included in the protection of the present invention. Within the scope.

Claims (8)

1. A pilot structure, comprising: L uplink pilot time slots and one frame of uplink data, wherein each of the uplink pilot time slots is provided with K candidate orthogonal pilot sequences, L of the foregoing The uplink pilot time slots are respectively sequentially arranged uplink pilot time slots 1 to uplink pilot time slots L, and the uplink data is arranged after the uplink pilot time slots L, where L>1 and K≥1.
2. A pilot structure according to claim 1, wherein the K candidate orthogonal pilot sequences comprise sine waves of different frequencies, symbols of different time, and one of mutually orthogonal codes.
3. A method for transmitting a pilot, characterized in that: transmitting according to a pilot structure according to claim 1 or 2, comprising the following steps:

   Step 1: randomly selecting one uplink pilot time slot in every J uplink pilot time slots;

   Step 2: randomly select one candidate orthogonal pilot sequence in the K candidate candidate orthogonal pilot sequences of the uplink pilot time slot as a pilot for uplink transmission;

   Where 1≤J≤L, and L=D*J, D is a positive integer.
4. A user channel estimation method, characterized in that: performing user channel estimation on a pilot transmitted in a pilot transmission method according to claim 3, comprising the following steps,

   S1, the receiving end of the base station receives sampling data Y _l sent by all users in each uplink pilot time slot, where l=1, 2, 3, ..., L;

   S2, the base station receiving end correlates the local K candidate orthogonal pilot sequences with the sample data Y _l received in each uplink pilot time slot, respectively, to obtain each pilot correlation result matrix B _l , where ,l=1,2,3,...,L;

   S3, based each pilot correlation matrix of the linear relationship between the results of the pilot sequence A _l B _l with each user transmitting frequency be calculated by channel estimation for all users.
5. A user channel estimation method according to claim 4, wherein a total of N users transmit sampling data in the uplink pilot time slot 1, and the base station receiving end has M base station antennas, and The receiving end of the base station samples Q data on each base station antenna, and Q is also the length of the pilot sequence, l=1, 2, 3, ..., L, then the S1 is specifically,

   The sampling data Y _l sent by the N users received by the receiving end of the base station in each uplink pilot time slot is Y _l = HP + W, Y _l ∈ □ ^{M × Q} ;

   Where: P is a matrix of N pilot sequences randomly selected by N users from K candidate orthogonal pilot sequences, H is a channel response matrix of N users, and W is noise.
6. A user channel estimation method according to claim 5, wherein in said S2,

   The expression of each pilot correlation result matrix B _l is B _l =Y _l S ^H ;

   Wherein, S ^H represents a conjugate transpose of the matrix S, and S=[s ₁ , s ₂ , . . . , s _K ] ^T , which are K kinds of candidate orthogonal pilot sequences.
7. A user channel estimation method according to claim 6, wherein in said S3,

   The linear relationship between each pilot correlation result matrix B _l and the pilot sequence A _l transmitted by each user is A _l H=B _l , A _l ∈ □ ^{K × N} .
8. The user channel estimation method according to claim 7, wherein the S3 is specifically

   S31. Obtain a guide relationship between all pilot correlation result matrices B and all users according to a linear relationship A _l H=B _l between each pilot correlation result matrix B _l and each pilot sequence A _l transmitted by the user. The linear relationship between the frequency sequences A is AH = B, where A = [A ₁ ^T A ₂ ^T ... A _L ^T ] ^T , B = [B ₁ ^T B ₂ ^T ... B _L ^T ] ^T ;

   S32. Obtain a channel response matrix H of all users as a channel estimation of all users according to a linear relationship AH=B between all pilot correlation result matrices B and pilot sequences A transmitted by all users:

   H = A ^-1 B, H = [h ₁ , h ₂ , ..., h _N ].

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