CN102202027B

CN102202027B - A kind of production method of pilot frequency sequence and device

Info

Publication number: CN102202027B
Application number: CN201010133375.7A
Authority: CN
Inventors: 孙云锋; 张文峰; 姜静; 张峻峰
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2010-03-26
Filing date: 2010-03-26
Publication date: 2015-08-12
Anticipated expiration: 2030-03-26
Also published as: CN102202027A; WO2011116651A1

Abstract

The invention discloses a kind of production method of pilot frequency sequence, comprise: carry out in demodulation reference mark (DMRS) port that code divides with frequency division and/or time division mixed multiplexing at each, different code division multiplexing groups selects OCC according to different criterions from orthogonal mask (OCC) set, and/or different code division multiplexing groups produces the scramble sequence of DMRS according to different criterions; Selected OCC is multiplied with scramble sequence and produces the final pilot frequency sequence of each DMRS port.The invention also discloses a kind of generation device of pilot frequency sequence.By method and apparatus of the present invention, corresponding layer can be reduced between different code division multiplexing port set, reduce the inter-carrier interference that causes due to Doppler frequency shift and timing error problem to the impact of channel estimating, improve the precision of channel estimating.

Description

Method and device for generating pilot frequency sequence

Technical Field

The present invention relates to inter-carrier interference processing technologies in the field of wireless communications, and in particular, to a method and an apparatus for generating a pilot sequence.

Background

The high-order multi-antenna technology is one of the key technologies of an Advanced Long Term Evolution (LTE-a) system, and is used to improve the transmission rate of the system. In order to realize channel quality measurement and data demodulation after introducing a high-order multi-antenna technology, an LTE-a system defines two types of pilot symbols respectively: data Demodulation pilot (DMRS) and Channel quality measurement pilot (CSI-RS). The DMRS is a reference symbol for demodulation of a Physical Downlink Shared Channel (PDSCH), which is referred to as a demodulation reference symbol for short; the CSI-RS is a reference symbol used for measuring Channel State Information (CSI), which is referred to as a measurement reference symbol for short, and is used for reporting Information such as Channel Quality Indicator (CQI), Precoding Matrix Indicator (PMI), Rank Indicator (RI), and the like. The structure of the two types of reference symbols can be used for supporting new technical features of LTE-a, such as Coordinated Multi-Point (CoMP), spatial multiplexing, and the like.

In the LTE system, a Common Reference Symbol (CRS) is used for pilot measurement, that is, all users use a Common pilot to perform channel estimation, and the Common Reference symbol needs the transmitting end to additionally inform the receiving end of what preprocessing method is used for the transmitted data, so that the pilot overhead is high. In addition, in the multi-user Multiple-input Multiple-Output (MU-MIMO) technique, since a plurality of UEs use the same CRS and cannot orthogonalize pilots, interference cannot be estimated.

In an LTE-A system, in order to reduce the overhead of pilot frequency, a measurement reference symbol and a demodulation reference symbol + + are separately designed, the demodulation reference symbol and data adopt the same preprocessing mode, and the demodulation reference symbol is mapped with the reference symbol according to the available rank (rank) information of a channel corresponding to a scheduling user, so that the overhead can be adaptively adjusted according to the rank information, and the overhead can be greatly reduced under the condition of lower rank.

The design pattern of the demodulation reference symbol determined in LTE-a is shown in fig. 1, 2, and 3, where fig. 1 is a schematic diagram of a DMRS pattern corresponding to a normal subframe, fig. 2 is a schematic diagram of a DMRS pattern corresponding to an OFDM symbol in which a downlink pilot time slot is 11 or 12, and fig. 3 is a schematic diagram of a DMRS pattern corresponding to an OFDM symbol in which a downlink pilot time slot is 9 or 10. Hatched portion in the figureCRS is represented, the horizontal direction of the DMRS pattern represents the time domain and the vertical direction represents the frequency domain. When the rank number used for downlink transmission is less than or equal to 2, only the shaded portion is usedThe Resource Elements (REs) shown are used for the transmission of DMRS and are scrambled over two Orthogonal Frequency Division Multiplexing (OFDM) symbols adjacent in the time domain using an Orthogonal Code (OCC) of length 2. When the rank number is greater than or equal to 3 and less than or equal to 4, two sets of REs are used, respectively as shaded portionsAndshown, where the number of DMRS layers for maximum orthogonal Code Division Multiplexing (CDM) on each group of REs is 2, each group of REs employs a length of 2 on two OFDM symbols adjacent in the time domainThe OCC performs orthogonal scrambling. When the rank number is greater than 4, two sets of REs are used, respectively as shaded portionsAndas shown, each group of REs is orthogonally scrambled in the time domain direction with an OCC of length 4, and the number of DMRS layers of the maximum orthogonal CDM on each group of REs is 4.

Based on the DMRS patterns shown in fig. 1, 2, and 3, in a hybrid Multiplexing DMRS scheme, such as a hybrid Multiplexing DMRS scheme based on CDM and Frequency Division Multiplexing (FDM) and/or Time Division Multiplexing (TDM), if there are problems of doppler shift and timing error, inter-carrier interference may occur. The analysis was as follows:

in a DMRS multiplexing mode based on CDM and FDM/TDM hybrid multiplexing, part of demodulation reference symbols of the DMRS ports adopt a CDM mode and part of the DMRS ports adopt an FDM/TDM mode among different DMRS ports. As shown by the DMRS patterns shown in fig. 1, 2, and 3. Shaded partThe RE shown corresponds to a set of code division multiplexed DMRS ports, shadedThe shown REs correspond to another group of REs that are code division multiplexed.

In the prior art, when DMRS pilot sequences are generated, two groups of DMRSs first generate scrambling sequences r (m) in the same manner, that is:

wherein N is_RB ^max，DLAnd the number of Resource Blocks (RBs) corresponding to the downlink system bandwidth is shown. The pseudo-random sequence c (i) is generated according to the mode defined in section 7.2 of the existing standard 36.211, specifically:

c(n)＝(x₁(n+N_C)+x₂(n+N_C))mod2

x₁(n+31)＝(x₁(n+3)+x₁(n))mod2 (2)

x₂(n+31)＝(x₂(n+3)+x₂(n+2)+x₂(n+1)+x₂(n))mod2

wherein x is₁(0)＝1，x₁(n)＝0，n＝1，2，...，30，x₂(i) Can be calculated by the following two equations:

in the above formula, n_SCIDRepresenting scrambling code sequence ID, taking the value of 0 or 1, and taking the default condition of 0; mod denotes the modulo operation, N_ID ^cellID, n, indicating the cell in which the UE is located_sIndicating the current subframe number, c_initFor initializing x₂The intermediate variable of (1).

In normal cyclic prefix, according to the resource position of the scheduled user, truncating the corresponding length of r from the scrambling sequence r (m), and multiplying it by the OCC to generate a pilot sequence, as shown in the following formula:

wherein s is^pGeneration formula of OCC corresponding to DMRS port p, n_PRBAn index representing a physical resource block in a frequency domain; l 'and m' are used to indicate the position of the truncated sequence, determined by the configuration relationship of the frame structure.

According to the pattern of the DMRS, the length of the OCC is different when the number of layers is different, and the length of the OCC is 2 when the number of layers is 3-4; when the number of layers is 5-8, the OCC length is 4. Therefore, in the prior art, in the process of generating the pilot sequence, the scrambling codes of each group of DMRS ports for code division multiplexing correspond to one same sequence r (3.l'. N)_RB ^max，DL+3·n_PRB+ m'), and generating pilot sequences corresponding to the sets of code division multiplexed DMRS ports through different OCCs corresponding to the sets of DMRS ports.

When scrambling a sequence with OCC, s is determined according to the direction of code division multiplexing (code division multiplexing on resources corresponding to the time domain direction or code division multiplexing on resources corresponding to the frequency domain direction) of each group of ports of DMRS^pA value on each resource. Taking the example that the length of OCC in LTE-A is equal to 4, and assuming that ports corresponding to DMRS are respectively p ∈ { 7-14 }, in a subframe of a normal cyclic prefix, pilot sequence formats of all DMRS ports on the l-th OFDM symbol and the k-th subcarrier position after OCC processing are as follows:

in the above formula, l ═ mod2+5

m′＝0，1，2

Wherein N is_sc ^RBIndicates the number of subcarriers contained in one RB in the frequency domain direction, n_PRBDenotes the index of the corresponding physical resource block in the frequency domain, n_sIndicating the slot number. When special subframes are considered,/, can be configured to

The following values are taken:

m′＝0，1，2

when a sequence is processed by OCC, the positional relationship between DMRS sequences and code division multiplexing resources must be considered, and therefore, OCC calculation for a sequence must be associated with such sequences. For example: OCC [ 1111 ]]Corresponding to DMRS port 7, then s⁷1 is ═ 1; and OCC [ 1-111 ]]Corresponding to DMRS port 8, and multiplexing port 8 with other ports of its group in the time domain direction, then s⁸Can be expressed as

Are used here only for the purpose of illustrating s^pIn practical application, s can be represented by a corresponding formula according to the corresponding relationship between the OCC and the antenna port and the pattern mapping relationship based on the hybrid multiplexing mode^pThe formula at the corresponding resource location.

As shown in fig. 1, 2 and 3, when there are two groups of DMRS ports that are code division multiplexed, the two groups of ports correspond to the shaded portions in fig. 1, 2 and 3 respectivelyAndunder the condition of the resources, if doppler frequency offset or timing error exists in the system, interference may occur between carriers, as shown in fig. 4(a) and 4(b), where fig. 4(a) is a schematic diagram of carriers without doppler frequency offset or timing error; fig. 4(b) is a diagram illustrating intercarrier interference in the presence of doppler frequency offset.

For example: DMRS ports { P) of a first code division multiplexing group in resource locations mapped by the code division multiplexed DMRS ports shown in fig. 1, 2, and 3_1，0，P_1，1，P_1，2，P_1，3The corresponding OCCs are sequentially OCCs₀、OCC₁、OCC₂、OCC₃And a second code division multiplexed set of DMRS ports { P }_2，0，P_2，1，P_2，2，P_2，3OCCs are selected in the same order. Let us assume that the leakage factor between adjacent carriers is β due to the presence of doppler shift or timing error, taking the total number of layers equal to 5 as an example, while for convenience, defining { P }_1，0，P_1，1，P_1，2，P_1，3Are respectively corresponding to ports 781113 and P_2，0，P_2，1，P_2，2，P_2，3Corresponding to ports 9101214, respectively.

First set of resources (e.g. shaded portions)Shown position) the multiplexed ports are 7, 8; second set of resources (e.g. shaded portion)The positions shown) are 9, 10, 12. Meanwhile, the channel coefficients corresponding to the ports 7, 8, 9, 10, and 12 are respectively: h₇、H₈、H₉、H₁₀And H₁₂The corresponding sequences on the two sets of REs are truncated to r_c. Taking port 7 as an example, if the same OCC is used between two sets of REs,

<math> <mrow> <msup> <mi>s</mi> <mn>7</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>0</mn> </msub> </mrow> </math>

<math> <mrow> <msup> <mi>s</mi> <mn>8</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>1</mn> </msub> </mrow> </math>

<math> <mrow> <msup> <mi>s</mi> <mn>9</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>0</mn> </msub> </mrow> </math>

<math> <mrow> <msup> <mi>s</mi> <mn>10</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>1</mn> </msub> </mrow> </math>

<math> <mrow> <msup> <mi>s</mi> <mn>11</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>2</mn> </msub> </mrow> </math>

wherein OCC_iAnd OCC_jOrthogonal, i ≠ j. When there is interference between carriers (here, only the case of two carriers is taken as an example), the signal received by the port 7 is:

H₇s⁷r_c+H₈s⁸r_c+β·(H₉s⁹r_c+H₁₀s¹⁰r_c+H₁₂s¹²r_c)

removing pilot sequences r_cThen is H₇s⁷+H₈s⁸+β·(H₉s⁹+H₁₀s¹⁰+H₁₂s¹²) Then using s⁷Corresponding OCC₀When performing despreading, due to OCC_iAnd OCC_jOrthogonal, the estimated channel coefficient will beH₇+β·H₉Wherein beta. H₉Part of this is interference.

Based on the above analysis, the prior art has not provided an effective solution for reducing the influence of the inter-carrier interference on the channel estimation.

Disclosure of Invention

In view of the above, the main objective of the present invention is to provide a method and an apparatus for generating a pilot sequence to reduce the influence of inter-carrier interference on channel estimation in the hybrid multiplexing DMRS manner.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

the invention provides a method for generating a pilot frequency sequence, which comprises the following steps:

selecting an orthogonal code division code (OCC) from an OCC set according to different criteria for different code division multiplexing groups and/or generating scrambling sequences of the DMRS according to different criteria for different code division multiplexing groups in each demodulation reference symbol (DMRS) port which performs code division and frequency division and/or time division hybrid multiplexing;

and multiplying the selected OCC by the scrambling sequence to generate a final pilot sequence of each DMRS port.

Selecting the OCC from the OCC set according to different criteria for different code division multiplexing groups specifically includes:

the different code division multiplexing groups are assembled from OCCs [ OCCs ] in reverse order₀，...，OCC_k-1]Wherein k represents the number of OCCs in the OCC set, and k is an integer greater than 1.

in the different code division multiplexing groups, only part of OCCs are selected from the OCC set according to the reverse order, which specifically includes: in two different code division multiplexing groups, the first M DMRS ports select the first M OCCs from the OCC set according to the same sequence, and the last N DMRS ports select the last N OCCs from the OCC set according to the opposite sequence, wherein M + N is the maximum reusable DMRS port number in each code division multiplexing group.

setting different selected initial position offsets for the different code division multiplexing groups respectively_iEach code division multiplexing group corresponding to itself_iAt the beginning, according to the step length lambda_{step_i}Sequentially selecting OCCs, where i denotes the sequence number of the code division multiplex group,_iand λ_{step_i}Is an integer of 0 to less_i＜k，1≤λ_{step_i}＜k。

For the nth DMRS port of the ith code division multiplexing group, the index of the OCC corresponding to the nth DMRS port is selected according to the following mode: (_i+n·λ_{step_i}+α)mod k，

Wherein mod is a modulo operation when λ_{step_i}When the number is odd, the value of alpha is 0; when lambda is_{step_i}In the case of an even number, the number of the first,

the generating of the scrambling sequences of the DMRS for different code division multiplexing groups according to different criteria specifically includes:

the different code division multiplexing groups adopt different initialization modes to generate scrambling sequences of DMRS, and when two groups of code division multiplexing groups exist, the first group generates scrambling sequences according to the code division multiplexing groupsThe initialization mode of (3) generates a scrambling sequence of the DMRS by default Or 1; a second group according toThe initialization method of (3) generates a scrambling sequence of the DMRS.

The multiplying the selected OCC by the scrambling sequence to generate the final pilot sequence of each DMRS port specifically includes:

and when the selected OCC is multiplied by the scrambling sequence, reverse mapping is carried out on the OCCs corresponding to all the DMRS ports on the adjacent DMRS carriers.

corresponding to different code division multiplexing groups i, different or same initial positions are adopted during OCC mapping_{occ_i}Offset, wherein 0 is less than or equal to_{occ_i}< L-1, L represents the length of OCC.

The above-mentioned_{occ_i}The value of (is mod (SubcarierIndex +)_iAnd, L), wherein subbcariierindex denotes a subcarrier index, and L denotes a length of each OCC.

The present invention also provides a pilot sequence generating apparatus, which includes:

the selection module is used for selecting OCCs from the OCC set for different code division multiplexing groups according to different criteria and/or generating scrambling sequences of DMRS for different code division multiplexing groups according to different criteria in each DMRS port for code division and frequency division and/or time division hybrid multiplexing;

and the pilot sequence generating module is used for multiplying the selected OCC by the scrambling sequence to generate a final pilot sequence of each DMRS port.

The selection module is further configured to select [ OCC ] from the OCC set for different code division multiplex groups in reverse order₀，...，OCC_k-1]Of OCC, whichAnd k represents the number of OCCs in the OCC set, and k is an integer greater than 1.

The selection module is further configured to select, in different code division multiplexing groups, only a portion of OCCs from the set of OCCs in a reverse order.

The selection module is further configured to set different selected start position offsets for the different code division multiplexing groups respectively_iEach code division multiplexing group corresponding to itself_iAt the beginning, according to the step length lambda_{step_i}Sequentially selecting OCCs, where i denotes the sequence number of the code division multiplex group,_iand λ_{step_i}Is an integer of 0 to less_i＜k，1≤λ_{step_i}＜k。

The selection module is further configured to, for an nth DMRS port of an ith code division multiplexing group, select an index of an OCC corresponding to the nth DMRS port in the following manner: (_i+n·λ_{step_i}+α)mod k，

Wherein mod is a modulo operation when λ_{step_i}When the number is odd, the value of alpha is 0; when lambda is_{setp_i}In the case of an even number, the number of the first,

the selection module is further used for generating the scrambling sequences of the DMRS by adopting different initialization modes for different code division multiplexing groups, and when two groups of code division multiplexing groups exist, the first group generates the scrambling sequences of the DMRS according to the code division multiplexing groupsThe initialization mode of (3) generates a scrambling sequence of the DMRS by default Or 1; a second group according toThe initialization method of (3) generates a scrambling sequence of the DMRS.

And the pilot sequence generation module is further used for carrying out reverse mapping on OCCs corresponding to all DMRS ports on adjacent DMRS carriers when the selected OCCs are multiplied by the scrambling sequences.

The pilot sequence generation module is further used for adopting different or same initial positions corresponding to different code division multiplexing groups i during OCC mapping_{occ_i}Offset, where 0 ≦ λ_{occ_i}< L-1, L represents the length of OCC.

The above-mentioned_{occ_i}The value of (is mod (SubcarierIndex +)_iL), where subbcariierindex denotes a subcarrier index, and L denotes a length of each OCC.

In each DMRS port for code division multiplexing, selecting OCC from an OCC set according to different criteria for different code division and frequency division and/or time division hybrid multiplexing groups, and/or generating a scrambling sequence of the DMRS for different code division multiplexing groups according to different criteria; and multiplying the selected OCC by the scrambling sequence to generate a final pilot sequence of each DMRS port. By the invention, under the condition that two groups of used OCCs are orthogonal and Doppler frequency offset or timing error exists, the influence of inter-subcarrier interference on the position of a demodulation pilot frequency reference symbol can be reduced through OCC de-spreading, thereby improving the precision of channel estimation; by the processing mode of the invention, OCC orthogonality between two groups can be ensured as much as possible under the condition of limited OCC, so that the influence on channel estimation is reduced under the condition of limited OCC.

Drawings

Fig. 1 is a first schematic diagram of a design pattern of a DMRS in the prior art;

fig. 2 is a schematic diagram of a design pattern of a DMRS in the prior art;

fig. 3 is a schematic diagram of a design pattern of a DMRS in the prior art;

FIG. 4(a) is a diagram of a carrier without Doppler frequency offset or timing error in the prior art;

FIG. 4(b) is a diagram illustrating the inter-carrier interference in the presence of Doppler frequency offset in the prior art;

FIG. 5 is a flow chart of a method for generating a pilot sequence according to the present invention;

fig. 6 is a schematic diagram illustrating an OCC allocation manner according to a first embodiment of the present invention;

FIG. 7 is a schematic diagram illustrating an OCC allocation method according to a second embodiment of the present invention;

FIG. 8 is a schematic diagram illustrating an OCC allocation method according to a third embodiment of the present invention;

fig. 9 is a schematic diagram of an OCC allocation method according to a fourth embodiment of the present invention.

Detailed Description

The technical solution of the present invention is further elaborated below with reference to the drawings and the specific embodiments.

The method for generating a pilot sequence provided by the present invention, as shown in fig. 5, mainly comprises the following steps:

step 501, in each DMRS port performing code division multiplexing, selecting OCCs from an OCC set according to different criteria for different code division and frequency division and/or time division hybrid multiplexing groups, and/or generating DMRS scrambling sequences for different code division multiplexing groups according to different criteria.

Wherein different code division multiplexing groups can be assembled from OCC [ OCC ] in reverse order₀，...，OCC_k-1]Selecting OCC, wherein k represents the number of OCC in the OCC set, and k is an integer larger than 1. The following examples illustrate: OCCs are selected from OCC sets in reverse order between two code division multiplexing groups, the first code division multiplexing group being selected from OCC setsThe OCC sequence selected in the list is: according to the sequence of DMRS ports in the first code division multiplexing group, sequentially selecting OCCs from the OCC set to correspond to the ports, namely

<math> <mrow> <msup> <mi>s</mi> <msub> <mi>p</mi> <mn>1,0</mn> </msub> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>0</mn> </msub> <mo>,</mo> </mrow> </math>

<math> <mrow> <msup> <mi>s</mi> <msub> <mi>p</mi> <mn>1,1</mn> </msub> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>1</mn> </msub> <mo>,</mo> </mrow> </math>

<math> <mrow> <msup> <mi>s</mi> <msub> <mi>p</mi> <mn>1,2</mn> </msub> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>2</mn> </msub> <mo>,</mo> </mrow> </math>

<math> <mrow> <msup> <mi>s</mi> <msub> <mi>p</mi> <mn>1,3</mn> </msub> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>3</mn> </msub> <mo>;</mo> </mrow> </math>

The second code division multiplexing group selects OCCs from the OCC set in the following order: according to the sequence of DMRS ports in the second code division multiplexing group, selecting OCC from the OCC set in reverse order to correspond to each port, namely

<math> <mrow> <msup> <mi>s</mi> <msub> <mi>p</mi> <mn>2,0</mn> </msub> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>3</mn> </msub> <mo>,</mo> </mrow> </math>

<math> <mrow> <msup> <mi>s</mi> <msub> <mi>p</mi> <mn>2,1</mn> </msub> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>2</mn> </msub> <mo>,</mo> </mrow> </math>

<math> <mrow> <msup> <mi>s</mi> <msub> <mi>p</mi> <mn>2,2</mn> </msub> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>1</mn> </msub> <mo>,</mo> </mrow> </math>

<math> <mrow> <msup> <mi>s</mi> <msub> <mi>p</mi> <mn>2,3</mn> </msub> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>0</mn> </msub> <mo>.</mo> </mrow> </math>

Wherein p is_i，jIndicating the jth DMRS port in the code division multiplex group i.

For analytical convenience, { P ] is given in the following examples_1，0，P_1，1，P_1，2，P_1，3Are respectively corresponding to ports 781113 and P_2，0，P_2，1，P_2，2，P_2，3It should be noted that, in practical applications, other forms can be defined, for example, that { 9101214 } corresponds to each port, for example: defining DMRS port serial numbers { 0-7 }, and { P } when the maximum number of the DMRS ports is 8_1，0，P_1，1，P_1，2，P_1，3Respectively corresponding to ports 0146 and P_2，0，P_2，1，P_2，2，P_2，3Are respectively corresponding to ports 2357.

Based on the port mapping method, if the number of layers is 5, the OCC selected in the first code division multiplexing group is:

<math> <mrow> <msup> <mi>s</mi> <mn>7</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>0</mn> </msub> <mo>,</mo> </mrow> </math>

<math> <mrow> <msup> <mi>s</mi> <mn>8</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>1</mn> </msub> <mo>,</mo> </mrow> </math>

the OCC selected in the second code division multiplex group is then:

<math> <mrow> <msup> <mi>s</mi> <mn>9</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>3</mn> </msub> <mo>,</mo> </mrow> </math>

<math> <mrow> <msup> <mi>s</mi> <mn>10</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>2</mn> </msub> <mo>,</mo> </mrow> </math>

<math> <mrow> <msup> <mi>s</mi> <mn>11</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>1</mn> </msub> <mo>,</mo> </mrow> </math>

this time due to the OCC used by DMRS port 7 (i.e., OCC)₀) Different from OCC of each port in the second code division multiplexing group, therefore, OCC is used when using₀When the despreading is performed, the interference leaked from the RE corresponding to the second code division multiplexing group will be completely eliminated. When 8 layers are supported maximally and the mapping of each DMRS port adopts a CDM + FDM hybrid multiplexing method, a specific OCC allocation method is shown in fig. 6, that is, the OCC selected in the first code division multiplexing group is:

<math> <mrow> <msup> <mi>s</mi> <mn>11</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>2</mn> </msub> <mo>,</mo> </mrow> </math>

<math> <mrow> <msup> <mi>s</mi> <mn>13</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>3</mn> </msub> <mo>;</mo> </mrow> </math>

the OCC selected in the second code division multiplex group is:

<math> <mrow> <msup> <mi>s</mi> <mn>12</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>1</mn> </msub> <mo>,</mo> </mrow> </math>

<math> <mrow> <msup> <mi>s</mi> <mn>14</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>0</mn> </msub> <mo>.</mo> </mrow> </math>

the DMRS ports in the invention are not limited to be selected from p ∈ {7 to 14 }.

In addition, the invention can also set different selected initial position offsets for different code division multiplexing groups respectively_iEach code division multiplexing group corresponding to itself_iAt the beginning, according to the step length lambda_{step_i}Sequentially selecting OCCs, where i denotes the sequence number of the code division multiplex group,_iand λ_{step_i}Is an integer of 0 to less_i＜k，1≤λ_{step_i}< k. For the nth DMRS port of the ith code division multiplexing group, the index of the corresponding OCC is selected according to the following mode: (_i+n·λ_{step_i}+ α) mod k, where mod is a modulo operation, when λ_{step_i}When the number is odd, the value of alpha is 0; when lambda is_{step_i}In the case of an even number, the number of the first,the following examples illustrate: setting different initial position offset between two code division multiplexing groups₀And₁and according to step length lambda_{step_i}And selecting the OCC. To be provided with₀＝0，₁＝1，λ_{step_0}＝λ_{step_1}As an example, 1:

<math> <mrow> <msup> <mi>s</mi> <mn>9</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>1</mn> </msub> </mrow> </math>

<math> <mrow> <msup> <mi>s</mi> <mn>10</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>2</mn> </msub> </mrow> </math>

<math> <mrow> <msup> <mi>s</mi> <mn>11</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>3</mn> </msub> </mrow> </math>

when the OCC is selected according to the given offset and step size, and when the maximum supports 8 layers and the DMRS mapping of each port adopts the CDM + FDM hybrid multiplexing mode, the specific OCC selection is as shown in fig. 7, that is, the OCC selected in the first code division multiplexing group is:

<math> <mrow> <msup> <mi>s</mi> <mn>12</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>3</mn> </msub> <mo>;</mo> </mrow> </math>

the OCC selected in the second code division multiplex group is:

<math> <mrow> <msup> <mi>s</mi> <mn>9</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>1</mn> </msub> <mo>,</mo> </mrow> </math>

<math> <mrow> <msup> <mi>s</mi> <mn>12</mn> </msup> <mo>&LeftRightArrow;</mo> <msub> <mi>OCC</mi> <mn>3</mn> </msub> <mo>,</mo> </mrow> </math>

at this time, when using s⁷Corresponding OCC₀To H₇s⁷+H₈s⁸+β·(H₉s⁹+H₁₀s¹⁰+H₁₂s¹²) When in despreading, the OCC adopted by the ports 8, 9, 10 and 12 is orthogonal to the OCC of the port 7, so the channel coefficient H can be accurately recovered₇。

In consideration of compatibility with the low rank case, in the low rank (rank is 1 to 4), only some OCCs may be selected from the OCC set in reverse order among different code division multiplexing groups. In two different code division multiplexing groups, the first M DMRS ports select the first M OCCs from the OCC set according to the same sequence, and the last N DMRS ports select the last N OCCs from the OCC set according to the opposite sequence, wherein M + N is the maximum reusable DMRS port number in each code division multiplexing group, and the preferable M is equal to N. For example: when the OCC is allocated in two code division multiplexing groups, the part in the OCC set can be allocated reversely, for the convenience of analysis, the corresponding DMRS port of the first code division multiplexing group is { 781113 }, the corresponding DMRS port of the second code division multiplexing group is { 9101214 }, for example, the OCC can be selected for each port of the first code division multiplexing group in sequence₀、OCC₁、OCC₂、OCC₃And for each port of the second code division multiplexing group, only part of the ports in the OCC set is selected reversely, and the sequence of each DMRS port of the second code division multiplexing group is respectively allocated to be OCC₀、OCC₁、OCC₃、OCC₂. A specific OCC allocation is shown in fig. 8.

For the part of different code division multiplexing groups generating the scrambling sequences of the DMRS according to different criteria, different code division multiplexing groups can adopt different initialization modes to generate the scrambling sequences of the DMRS, and when two groups of code division multiplexing groups exist, the first group generates the scrambling sequences of the DMRS according to different criteriaThe initialization mode of (3) generates a scrambling sequence of the DMRS by default Or 1; a second group according toGenerates a scrambling sequence of the DMRS according to the initialization pattern of c_initThe procedure for generating the scrambling sequence is the same as in the background art. Then when different sequences are used, because the sequences are semi-orthogonal, when there is interference between carriers (here, the case of only two carriers is taken as an example), the signal received by the port 7 is:

H₇s⁷r_c1+H₈s⁸r_c1+β·(H₉s⁹r_c2+H₁₀s¹⁰r_c2+H₁₂s¹²r_c2)

removing pilot sequences r_c1Then is H₇s⁷+H₈s⁸+β·(H₉s⁹r_c2+H₁₀s¹⁰r_c2+H₁₂s¹²r_c2)·conj(r_c1) Wherein conj (x) represents conjugating elements in the sequence x, and s is used⁷Corresponding OCC₀When despreading is performed, the length of OCC is set as k, and after despreading, the length is set as

It can be seen that the interference isDue to H₉、H₁₀、H₁₂Is pseudo-random number, and therefore, is compared with the interference beta H in the prior art₉Is small.

And 502, multiplying the selected OCC by the scrambling sequence to generate a final pilot sequence of each DMRS port.

In the OCC selection manner given in each embodiment in step 501, to avoid different powers on different OFDM symbols, on adjacent DMRS carriers, the OCCs corresponding to each DMRS port in the same code division multiplexing group may perform reverse or cyclic offset mapping. Here, a description will be given taking, as an example, a scheme of performing cyclic offset mapping on adjacent carriers according to OCCs corresponding to respective DMRS ports. The same applies to other OCC selection modes.

Assume OCCs employed between layers of the same code division multiplexing group are OCCs respectively₀：[1 1 1 1]、OCC₁：[1 -1 1 -1]、OCC₂：[1 -1 -1 1]、OCC₃：[1 1 -1 -1]. On adjacent DMRS subcarriers, the scrambling sequences used are respectively s_i，0，s_i，1，s_i，2，s_i，3And s_i+1，0，s_i+1，1，s_i+1，2，s_i+1，3And assume that the precoding weight on this PRB is

w = [\begin{matrix} 1 & 1 & 1 & 1 \\ 1 & 1 & - 1 & - 1 \\ 1 & - 1 & 1 & - 1 \\ 1 & - 1 & - 1 & 1 \end{matrix}],

After OCC processing, the pilot signals on different OFDM symbols corresponding to the same carrier are expressed as

[\begin{matrix} s_{i, 0} & s_{i, 1} & s_{i, 2} & s_{i, 3} \\ s_{i, 0} & {- s}_{i, 1} & s_{i, 2} & - s_{i, 3} \\ s_{i, 0} & - s_{i, 1} & - s_{i, 2} & s_{i, 3} \\ s_{i, 0} & s_{i, 1} & {- s}_{i, 2} & - s_{i, 3} \end{matrix}] .

When the OCC is not mapped in the reverse direction or in the offset direction, the transmission signals of different OFDM symbols corresponding to the same DMRS carrier at each antenna port are:it can be seen that for any one port, the power increase that occurs on a certain DMRS OFDM symbol, while the power decrease on other DMRS OFDM symbols is even without signaling problems. Similarly, for adjacent carriers, if there is no reverse mapping of OCC, the formats on other carriers are exactly the same as the above formatsSince for a certain port, e.g. DMRS port 0, the power is always the largest on a certain DMRS OFDM symbol (port 0 corresponds to DMRS OFDM symbol 1), while there is no signal on other symbols, resulting in different power of different DMRS OFDM symbols. Since the code division multiplexing group 2 uses the same OCC assignment method, the same situation as the case of the code division multiplexing group 1 is used.

The invention carries out reverse mapping on OCC or_{occ_i}And offset mapping is adopted, and different OCC allocations are adopted in different code division multiplexing groups, so that the influence of the inter-carrier interference on channel estimation can be reduced. Starting position offset here_{occ_i}Refer to for each of the OCC setsOCCs of length L, offset of the OCC_{occ_i}The specific offset manner can be described with reference to the following embodiments.

Since the precoding weights applied to the DMRS ports corresponding to each code division multiplexing group are different in general, the effect of reverse mapping or cyclic offset mapping can be described by one code division multiplexing group. In practical applications, the reverse mapping or cyclic offset mapping manner of the second code division multiplexing group can be obtained according to the same format according to the reverse mapping or cyclic offset mapping manner of the first code division multiplexing group. It should be noted that, under the foregoing several OCC selection manners, the mapping manner is applicable. In the following examples, a cyclic shift method is exemplified.

When adopting_{occ_i}Corresponding to different code division multiplexing groups i during cyclic shift, and adopting different or same initial positions during OCC mapping_{occ_i}Offset, wherein 0 is less than or equal to_{occ_i}< L-1, L represents the length of OCC. Starting position here_{occ_i}Refers to the offset of each OCC with length L in the OCC set_{occ_i}. A kind of_{occ_i}Is valued in a manner of_{occ_i}＝mod(SubcarierIndex+_iL), where subcariierindex denotes a subcarrier index and L denotes a length of each OCC._iCan be combined with_jTaking the same value or a different value,_i、_jindicating the relative offset between different code division multiplex groups. For convenience of description, the following description is only provided_i＝_jThe description is given for the sake of example.

For a certain code division multiplexing group, on adjacent DMRS subcarriers, the scrambling sequences used are still respectively s_i，0，s_i，1，s_i，2，s_i，3And s_i+1，0，s_i+1，1，s_i+1，2，s_i+1，3For example. When the mapping mode on the DMRS carrier corresponding to the ith code division multiplexing group isWhen the temperature of the water is higher than the set temperature,then the mapping mode on the DMRS carrier corresponding to the i +1 th code division multiplexing group is

Is provided with

(\begin{matrix} {OCC}_{0} \\ {OCC}_{1} \\ {OCC}_{2} \\ {OCC}_{3} \end{matrix}) = (\begin{matrix} 1 & 1 & 1 & 1 \\ 1 & - 1 & 1 & - 1 \\ 1 & 1 & - 1 & - 1 \\ 1 & - 1 & - 1 & 1 \end{matrix}) = (\begin{matrix} a & b & c & d \end{matrix}) .

Then, on the above i and i +1 DMRS carriers, the mappings of the OCC to the DMRS ports on 4 OFDM symbols are (a b c d) and (b c d a), and similarly, on i +3 and i +4, the mappings of the OCC to the DMRS ports on 4 OFDM symbols are (c d a b) and (d a b c), respectively.

Assuming precoding weights

w = [\begin{matrix} 1 & 1 & 1 & 1 \\ 1 & 1 & - 1 & - 1 \\ 1 & - 1 & 1 & - 1 \\ 1 & - 1 & - 1 & 1 \end{matrix}],

The power on the adjacent 4 carriers is respectively It can be seen that each DMRS port cyclically has a maximum value on each symbol, thereby avoiding the problem of excessive transmission power of a certain OFDM symbol on a certain symbol.

When OCC is allocated to the first code division multiplexing group₀、OCC₁、OCC₂、OCC₃And allocating OCC to the second code division multiplexing group₀、OCC₁、OCC₃、OCC₂The corresponding allocation scheme is shown in fig. 9.

Corresponding to the method for generating the pilot sequence, the invention also provides a device for generating the pilot sequence, which comprises the following steps: a selection module and a pilot sequence generation module. And the selection module is used for selecting OCCs from the OCC set for different code division multiplexing groups according to different criteria and/or generating the scrambling sequences of the DMRS for different code division multiplexing groups according to different criteria in each DMRS port for performing code division and frequency division and/or time division hybrid multiplexing. Specifically, the method comprises the following steps: the selection module may assemble [ OCC ] from OCC sets in reverse order for different code division multiplex groups₀，...，OCC_k-1]Selecting OCC; in the case of low rank, in different code division multiplexing groups, only part of OCCs may be selected from the OCC set in the reverse order; different selected initial position offsets are set for different code division multiplexing groups respectively_iEach code division multiplexing group corresponding to itself_iAt the beginning, according to the step length lambda_{step_i}Sequentially selecting OCCs; and different initialization modes can be adopted for different code division multiplexing groups to generate the scrambling sequences of the DMRS.

And the pilot sequence generating module is used for multiplying the selected OCC by the scrambling sequence to generate a final pilot sequence of each DMRS port. Specifically, the method comprises the following steps: when the selected OCC is multiplied by the scrambling sequence, reverse mapping can be performed on the OCCs corresponding to the DMRS ports on the adjacent DMRS carriers; or, corresponding to different code division multiplexing groups i, different or same initial positions are adopted during OCC mapping_{occ_i}Offset, wherein 0 is less than or equal to_{occ_i}< L-1, L represents the length of OCC.

In summary, the invention can reduce the corresponding layers between different CDM port groups, reduce the influence of inter-carrier interference on channel estimation caused by doppler shift and timing error problems, and improve the accuracy of channel estimation.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention.

Claims

1. A method for generating a pilot sequence, the method comprising:

selecting an orthogonal code mask (OCC) from an OCC set according to different criteria for different code division multiplexing groups in each demodulation reference symbol (DMRS) port which performs code division and frequency and/or time division hybrid multiplexing, and generating scrambling sequences of the DMRS according to different criteria for different code division multiplexing groups;

2. The method for generating a pilot sequence according to claim 1, wherein the OCC is selected from the OCC set for different code division multiplexing groups according to different criteria, specifically:

the different code division multiplexing groups are assembled from OCCs [ OCCs ] in reverse order₀,...,OCC_k-1]Wherein k represents the number of OCCs in the OCC set, and k is an integer greater than 1.

3. The method for generating a pilot sequence according to claim 1, wherein the OCC is selected from the OCC set for different code division multiplexing groups according to different criteria, specifically:

4. The method for generating a pilot sequence according to claim 1, wherein the OCC is selected from the OCC set for different code division multiplexing groups according to different criteria, specifically:

setting different selected initial position offsets for the different code division multiplexing groups respectively_iEach code division multiplexing group corresponding to itself_iAt the beginning, according to the step length lambda_{step_i}Sequentially selecting OCCs, where i denotes the sequence number of the code division multiplex group,_iand λ_{step_i}Is an integer of 0 to less_i<k，1≤λ_{step_i}<k and k represent the number of OCCs in the OCC set, and k is an integer greater than 1.

5. The method of generating the pilot sequence as claimed in claim 4, wherein the n-th DMRS terminal for the i-th code division multiplexing groupThe index of the OCC corresponding to the port is selected according to the following mode: (_i+n·λ_{step_i}+α)mod k，

Wherein mod is a modulo operation when λ_{step_i}When the number is odd, the value of alpha is 0; when lambda is_{step_i}In the case of an even number, the number of the first,k represents the number of OCCs in the OCC set, and k is an integer greater than 1.

6. The method for generating the pilot sequence according to claim 1, wherein the scrambling sequences for DMRSs are generated for different code division multiplexing groups according to different criteria, specifically:

the different code division multiplexing groups adopt different initialization modes to generate scrambling sequences of DMRS, and when two groups of code division multiplexing groups exist, the first group generates scrambling sequences according to the code division multiplexing groupsThe initialization mode of (3) generates a scrambling sequence of the DMRS by defaultOr 1; a second group according toGenerating a scrambling sequence of the DMRS in the initialization mode; wherein,ID, n, indicating the cell in which the UE is located_sIndicating the current subframe number.

7. The method for generating the pilot sequence according to any one of claims 1 to 6, wherein the step of multiplying the selected OCC by the scrambling sequence generates a final pilot sequence for each DMRS port, specifically:

8. The method for generating the pilot sequence according to any one of claims 1 to 6, wherein the step of multiplying the selected OCC by the scrambling sequence generates a final pilot sequence for each DMRS port, specifically:

corresponding to different code division multiplexing groups i, different or same initial positions are adopted during OCC mapping_{occ_i}Offset, wherein 0 is less than or equal to_{occ_i}<L-1, L represents the length of OCC.

9. The method of claim 8, wherein the pilot sequence is generated by a method of generating a pilot sequence of the pilot signal_{occ_i}The value of (is mod (SubcarierIndex +)_iL), where subbcariierindex denotes a subcarrier index, L denotes a length of each OCC,_iindicating the relative offset between different code division multiplex groups.

10. An apparatus for generating a pilot sequence, the apparatus comprising:

the selection module is used for selecting OCCs from the OCC set for different code division multiplexing groups according to different criteria and generating scrambling sequences of DMRS for different code division multiplexing groups according to different criteria in each DMRS port for performing code division and frequency division and/or time division hybrid multiplexing;

11. The apparatus of claim 10, wherein the selection module is further configured to select the different code division multiplexing groups in reverse order from the OCC set [ OCC ]₀,...,OCC_k-1]Wherein k represents the number of OCCs in the OCC set, and k is an integer greater than 1.

12. The apparatus of claim 11, wherein the selection module is further configured to select only a portion of the OCCs in different code division multiplexing groups from the OCC set in reverse order.

13. The apparatus of claim 10, wherein the selection module is further configured to set different starting position offsets for the different code division multiplexing groups respectively_iEach code division multiplexing group corresponding to itself_iAt the beginning, according to the step length lambda_{step_i}Sequentially selecting OCCs, where i denotes the sequence number of the code division multiplex group,_iand λ_{step_i}Is an integer of 0 to less_i<k，1≤λ_{step_i}<k and k represent the number of OCCs in the OCC set, and k is an integer greater than 1.

14. The apparatus of claim 13, wherein the selecting module is further configured to, for the nth DMRS port of the ith code division multiplexing group, select the index of the OCC corresponding to the nth DMRS port as follows: (_i+n·λ_{step_i}+α)mod k，

15. The apparatus of claim 10, wherein the selection module is further configured to generate the DMRS scrambling sequences using different initialization schemes for different code division multiplexing groups, and when there are two code division multiplexing groups, the first group is according to the code division multiplexing groupThe initialization mode of (3) generates a scrambling sequence of the DMRS by defaultOr 1; a second group according toGenerating a scrambling sequence of the DMRS in the initialization mode; wherein,ID, n, indicating the cell in which the UE is located_sIndicating the current subframe number.

16. The apparatus for generating the pilot sequence according to any one of claims 10 to 15, wherein the pilot sequence generating module is further configured to perform reverse mapping on the OCCs corresponding to the respective DMRS ports on adjacent DMRS carriers when the selected OCCs are multiplied by the scrambling sequence.

17. The apparatus of any of claims 10 to 15, wherein the pilot sequence generation module is further configured to use different or the same starting positions for OCC mapping corresponding to different code division multiplexing groups i_{occ_i}Offset, wherein 0 is less than or equal to_{occ_i}<L-1, L represents the length of OCC.

18. The apparatus for generating the pilot sequence as claimed in claim 17, wherein the pilot sequence is generated by a frequency synthesizer_{occ_i}The value of (is mod (SubcarierIndex +)_iL), where subbcariierindex denotes a subcarrier index, L denotes a length of each OCC,_iindicating the relative offset between different code division multiplex groups.