WO2011116651A1

WO2011116651A1 - Method and apparatus for generating pilot sequence

Info

Publication number: WO2011116651A1
Application number: PCT/CN2011/071492
Authority: WO
Inventors: 孙云锋; 张文峰; 姜静; 张峻峰
Original assignee: 中兴通讯股份有限公司
Priority date: 2010-03-26
Filing date: 2011-03-03
Publication date: 2011-09-29
Also published as: CN102202027A; CN102202027B

Abstract

The present invention discloses a method for generating a pilot sequence. The method includes that: in each demodulation reference symbol (DMRS) port where hybrid multiplexing is performed, different code division multiplexing (CDM) groups select orthogonal cover codes (OCCs) from an orthogonal cover code set and/or generate scrambling sequences of the DMRS according to different rules，wherein the hybrid multiplexing can be hybrid multiplexing of code division, frequency division and time division, hybrid multiplexing of code division and frequency division, or hybrid multiplexing of code division and time division; the final pilot sequence for each DMRS port is generated by multiplying the selected OCC by the scrambling sequence. The present invention also discloses an apparatus for generating the pilot sequence. With the method and apparatus of the present invention, corresponding layers among different CDM port groups can be reduced, the influence of inter-carrier interference on channel estimation can be reduced, wherein the inter-carrier interference is caused by Doppler shift and timing error, and the precision of the channel estimation can also be improved.

Description

Method and device for generating pilot sequence

The present invention relates to inter-carrier interference processing techniques in the field of wireless communications, and in particular, to a method and apparatus for generating pilot sequences. Background technique

High-order multi-antenna technology is one of the key technologies of the LTE-A (Long Term Evolution Advanced) system to increase the system transmission rate. In order to implement channel quality measurement and data demodulation after introducing high-order multi-antenna technology, LTE-A systems respectively define two types of pilot symbols: DMRS (Demodulation Reference Signal) and channel quality measurement pilot ( CSI-RS, Channel State Information-Reference Signal). The DMRS is a reference symbol used for demodulation of a Physical Downlink Shared Channel (PDSCH), and is referred to as a demodulation reference symbol; CSI-RS is a reference for channel state information (CSI) measurement. The symbol, the cylinder is called a measurement reference symbol, and is used for reporting a channel quality indicator (CQI, Channel Quality Indicator), a precoding matrix indicator (PMI, Precoding Matrix Indicator), and a hierarchical indicator (RI, Rank Indicator). The structure of these two types of reference symbols can be used to support new technical features of LTE-A such as CoMP (Coordinated Multi-Point), spatial multiplexing, and the like.

In the LTE system, the common reference symbol (CRS, Common Reference Signal) is used for pilot measurement, that is, all users use common pilots for channel estimation. This common reference signal requires the transmitter to additionally notify the receiver to use the transmitted data. The pre-processing method has a large pilot overhead. In addition, in the multi-user multiple-input multiple-output (MU-MIMO) technology, since multiple UEs use the same CRS, pilot orthogonality cannot be achieved, and thus interference cannot be estimated. In the LTE-A system, in order to reduce the overhead of the pilot, the measurement reference symbol and the demodulation reference symbol are separately designed, and the demodulation reference symbol and the data adopt the same preprocessing manner, and the demodulation reference symbol is according to the scheduling user corresponding channel. The available rank information maps the reference symbols, so that the overhead can be adaptively adjusted according to the rank information, so that in the case of a lower rank, the overhead can be greatly reduced.

The design of the demodulation reference symbol determined in LTE-A is as shown in FIG. 1, 2, and 3, FIG. 1 is a schematic diagram of a DMRS pattern corresponding to a normal subframe, and FIG. 2 is a corresponding downlink pilot slot of 11 or 12. A schematic diagram of a DMRS pattern of an OFDM symbol, and FIG. 3 is a schematic diagram of a DMRS pattern of an OFDM symbol corresponding to a downlink pilot slot of 9 or 10. The shaded countries in the figure represent CRS, and the horizontal representation of the DMRS pattern represents the time domain and the longitudinal direction represents the frequency domain. When the number of ranks used for downlink transmission is less than or equal to 2, only the resource unit (RE, Resources Element) shown by the shaded part 用于 is used for DMRS transmission, and an orthogonal mask of length 2 (OCC, Orthogonal) is used. Cover Code) Performs power interference on two adjacent Orthogonal Frequency Division Multiplexing (OFDM) symbols in the time domain. When the rank number is greater than or equal to 3 and less than or equal to 4, two sets of REs are used, as shown by the shaded parts Ξ and 分别, respectively, where the maximum orthogonal code division multiplexing (CDM) of each group of REs is used. The number of DMRS layers is 2, and each group of REs is orthogonally scrambled with an OCC of length 2 on two adjacent OFDM symbols in the time domain. When the rank number is greater than 4, two sets of REs are used, as shown by the shaded parts Ξ and E3, respectively, and each group of REs is orthogonally scrambled with an OCC of length 4 in the time domain direction, and each group has the largest RE. The number of DMRS layers that can be orthogonal CDM is 4. The shaded parts in Fig. 2 and Fig. 3 represent the OFDM symbols occupied by the Uplink Pilot Transmission Slot (UpPTI) in the special subframe.

Based on the DMRS patterns shown in Figures 1, 2, and 3, in the hybrid multiplexed DMRS mode, such as based on CDM and Frequency Division Multiplexing (FDM), and/or Time Division Multiplexing (TDM). Hybrid multiplexing DMRS mode, if In the case of Doppler shift and timing error, inter-carrier interference is generated. The analysis is as follows: In the DMRS multiplexing mode based on CDM and FDM/TDM hybrid multiplexing, the demodulation reference symbols of some DMRS ports are in CDM mode between different DMRS ports, and FDM is used between some DMRS ports. /TDM way. The DMRS pattern shown in Figures 1, 2, and 3 is shown. The RE shown by the shaded portion 对应 corresponds to a group of code division multiplexed DMRS ports, and the RE shown by the shaded portion E3 corresponds to another group of REs that are code division multiplexed.

In the prior art, when generating a DMRS pilot sequence, the two sets of DMRS first generate the scrambling sequence r( ) in the same manner, namely: r(m) c(2m + 1)), = 0, l, .. "12N ^ ^pL — 1 ( 1 )

The N ' ^DL indicates the number of resource blocks (RBs) corresponding to the downlink system bandwidth. The pseudo-random sequence c (0 is generated in the manner defined in section 7.2 of the existing standard 36.211, specifically:

c{n) = (x _l (n + N _c ) + x ₂ (n + N _c )) mod2

x {n + 3\) = ( [ (n + 3) + x _l («)) mod2 (2) χ ₂ (η + 3ϊ) = (x ₂ (n + 3) + x ₂ (n + 2) + x ₂ (η + ϊ) + x ₂ («)) mod 2

Where ^(0) = 1,^(«) = 0,« = 1,2,...,30, (0 can be calculated by the following two formulas:

c _fflit -(k 2j + l)-(2 ¹ +l)-2 ¹⁶ _+3⁄4ro (3 )

^ _it =∑; ₂ ( -2 ⁱ (4) where _cm represents the scrambling sequence ID, which is 0 or 1, and the default is 0; mod represents the modulo operation, and N ¹¹ represents the cell in which the UE is located. ID, indicating the current subframe number, c _{M is} used to initialize the intermediate variable of x ₂ .

In the normal cyclic prefix, according to the resource location of the scheduled user, the corresponding length of r is intercepted from the scrambling sequence, and multiplied by OCC to generate a pilot sequence, as shown in the following equation:

5 ^p -r(3-/'-NTM +3- _PRB +m') (5 ) Wherein, the formula for generating the OCC corresponding to the DMRS port p, " _PRB indicates the index of the physical resource block in the frequency domain; /' and m' are used to indicate the position of the intercepted sequence, which is determined by the configuration relationship of the frame structure.

According to the pattern of DMRS, the length of OCC is different when the number of layers is different. When the number of layers is 3~4, the length of OCC is 2; when the number of layers is 5~8, the length of OCC is 4. Therefore, in the process of generating a pilot sequence in the prior art, the scrambling codes of each group of DMRS ports that perform code division multiplexing correspond to the same sequence, (3.

+ 3. " _PRB + m'), and generate a pilot sequence corresponding to each group of code division multiplexed DMRS ports by different OCCs corresponding to each group of DMRS ports.

When the sequence is scrambled by the OCC, the direction of code division multiplexing is performed according to each group of ports of the DMRS (the code division multiplexing is performed on the corresponding resources in the time domain direction, or the code division is performed on the resources corresponding to the frequency domain direction). Use) to determine the value of ^ on each resource. For example, in the LTE-A, the OCC length is equal to 4, and the ports corresponding to the DMRS are respectively pe {7 ~ 14}. In the subframe of the normal cyclic prefix, after the OCC processing, the DMRS port is in the /th. The OFDM symbol, the pilot sequence format at the A-subcarrier position is:

, = s ^p - r(3 - PN ^PL + 3-« _PRB +m') (6) k_ (5- m'+NTM · ^ + 1 ρ = Ί, 8,11, orl3

5. '+N _s ^M . p = 9,10,12,orl4

, , , , l 2 /'mod2 + 5

In the above formula,

m'= 0,1,2

Where N is the number of subcarriers included in one RB in the frequency domain direction, " _PRB " indicates the index of the corresponding physical resource block in the frequency domain, and /^ indicates the slot number. When considering special sub-frames, / can /'mod2 + 2

/ = /'mod2 + 2 + 3.L/'/2"

/'mod2 + 5

0,1,2,3 if n _s mod2 = 0, special subframe type 1 is configured as follows: I, 0,1 if n mod2^0, normal subframe

2,3 if n _s mod2=l , normal subframe

m'= 0,1,2

When the sequence is processed by OCC, the positional relationship between the DMRS sequence and the code division multiplexing resource must be considered. Therefore, the OCC must correspond to the sequence operation. For example: OCC[l 111] corresponds to DMRS port 7, then =1; while OCC [1 -1 1 1] corresponds to DMRS port 8, and port 8 is multiplexed with other ports of the group in the time domain direction, it can represent for

5 ⁸ = (-i) ^{ffl, +r+H} TM. This is only for the purpose of illustrating the correspondence between _s ^p and occ. In practical applications, according to the correspondence between the OCC and the antenna port, and the mapping relationship based on the mixed multiplexing mode, the corresponding formula is used to represent the corresponding resource location. The formula is expressed.

According to FIG. 1, 2, and 3, when there are two sets of code division multiplexed DMRS ports, and if the two sets of ports correspond to the resources shown in the shaded parts 图 and 图 in FIG. 1, 2, and 3, respectively, if If there is Doppler frequency offset or timing error in the system, interference will occur between the carriers, as shown in Figure 4 (a), 4 (b), Figure 4 (a) is no Doppler frequency offset or timing error Schematic diagram of carrier; Figure 4 (b) is a schematic diagram of inter-carrier interference when there is Doppler frequency offset.

For example: the resource location mapped by the code division multiplexed DMRS port shown in Figures 1, 2, and 3, and the DMRS port of the first code division multiplexing group. The corresponding OCC of ^, ^, ^) is OCC. , OCC, OCC ₂ , OCC, , and the DMRS port of the second code division multiplexing group. , corpse ₁ , corpse ₂ , ^ ₃ } Select occ in the same order.殳 Due to the presence of Doppler shift or timing error, the leakage factor between adjacent carriers is, for example, the total number of layers is equal to 5, and for convenience, the definition, , , ₂ , y correspond to the port {781113} , { ₂ ,. , corpse ₂₁ , corpse ₂₂ , corpse ₂₃ } correspond to the port {910 1214}. The first set of resources (such as the shaded part Ξ) multiplexed ports are 7, 8; the second set of resources (such as the shaded part Ε 3) multiplexed ports are 9, 10, 12. At the same time, the channel coefficients corresponding to ports 7, 8, 9, 10, and 12 are: Η _Ί , Η ₉ , Η _ιο and Η , ₂ , and the corresponding sequence set on the two sets of REs is intercepted as? . Take port 7 as an example. If the same OCC is used between the two groups of REs, s ¹ OCC ₀ s ^s ^ OCC,

s ⁹ OCC ₀ s ^w ^ OCC, s ¹¹ OCC ₂

Where oc and oc are orthogonal, i≠j. When there is interference between carriers (here only in the case of two carriers), the signal received by port 7 is:

H r _c +H _{8 c} +fi-(H ₉ s ⁹ r _c +H s ^w r _c +

The sequence of the pilot is removed; after that, it is H + + β . ( i _9S ⁹ + H _l0 s ^w + Η _ί2 ² , then despreading with the corresponding OCC OCC, due to OCC _; and OCC _; orthogonal, estimated The resulting channel coefficient will be H ₇ + ^H ₉ , where the part is the interference.

Based on the above analysis, how to reduce the influence of inter-carrier interference on channel estimation, the prior art cannot provide an effective solution. Summary of the invention

In view of this, the main object of the present invention is to provide a method and apparatus for generating a pilot sequence to reduce the influence of inter-carrier interference on channel estimation in a hybrid multiplexed DMRS mode.

In order to achieve the above object, the technical solution of the present invention is achieved as follows:

The present invention provides a method for generating a pilot sequence, the method comprising:

Selecting an OCC from an orthogonal mask (OCC) set for different code division multiplexing groups in different demodulation reference symbol (DMRS) ports for performing code division and frequency division and/or time division hybrid multiplexing. And/or generating a scrambling sequence of the DMRS according to different criteria for different code division multiplexing groups;

Multiplying the selected OCC with the scrambling sequence to generate the final pilot sequence for each DMRS port Column.

The selecting the OCC from the OCC set according to different criteria for the different code division multiplexing groups is specifically:

The different code division multiplexing groups are aggregated from the OCC in reverse order. ,...^^^ Select OCC, where A is the number of OCCs in the OCC set, which is an integer greater than 1.

In the different code division multiplexing groups, only part of the OCCs are selected from the OCC set in reverse order, including: In two different code division multiplexing groups, the first M DMRS ports are in the same order from the OCC. The first M OCCs are selected in the set, and the last N DMRS ports select the next N OCCs from the OCC set in reverse order, where is the maximum number of multiplexable DMRS ports in each code division multiplexing group.

Setting different selection starting position offsets δ _ί for the different code division multiplexing groups, each code division multiplexing group selects OCC according to the step order from the beginning of its own correspondence, where / represents code division multiplexing number group. and 4 "are integers, and 0 l≤A _ttp" <

For the first DMRS port of the first code division multiplexing group, the corresponding IOC of the OCC is selected as follows: (· + «. _{step J} + a) mod k ,

Where mod is the modulo operation, when 4^ is odd, the value is 0; when 4^. is even

The different code division multiplexing groups generate a scrambling sequence of the DMRS according to different criteria, which are:

The different code division multiplexing groups use different initialization methods to generate the scrambling sequence of the DMRS Column, when there are two sets of code division multiplexing groups, the first group generates DMRS according to the initialization method of c _{i it} = ([n /2j + l)-(2N^ ^u + 1)·2 ¹⁶ + n _scro The scrambling sequence, where default is ";^ = ^ = 0 or 1; the second group generates a scrambling sequence of DMRS according to the initialization mode of _{3⁄4 cro} = ( +l) mod2.

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

When the selected OCC is multiplied by the scrambling sequence, the OCC corresponding to each DMRS port is inversely mapped on the adjacent DMRS carrier.

Corresponding to different code division multiplexing groups, different or identical starting positions S are used in OCC mapping. _∞ ”offset, where _{0≤S 0∞J} <L-1 , L represents the length of the OCC.

Said <J. The value of _{CC t} is mo & (SubcarierIndex + £ _t , L) , where Subcarierlndex represents a subcarrier index indicating the length of each OCC.

The invention also provides a device for generating a pilot sequence, the device comprising:

a selection module, configured to select an OCC from a set of OCCs for different code division multiplexing groups in different DMRS ports for performing code division and frequency division and/or time division hybrid multiplexing, and/or different The code division multiplexing group generates a scrambling sequence of the DMRS according to different criteria;

A pilot sequence generating module is configured to multiply the selected OCC by a scrambling sequence to generate a final pilot sequence for each DMRS port.

The selection module is further configured to collect from the occ [occ] in different orders for different code division multiplexing groups. ,...,6>cc _fe — j selects occ, where k represents the number of occ in the occ set, which is an integer greater than 1.

The selection module is further configured to, in different code division multiplexing groups, select only a portion of the OCCs from the set of OCCs in reverse order. The selecting module is further configured to separately set different selection start position offsets for the different code division multiplexing groups, and each code division multiplexing group selects OCC according to the step length in order from the corresponding one _; Wherein, the sequence number indicating the code division multiplexing group, and A _ste;) are integers, and 0 ≤ < l ≤ A _{step i <} k.

The selecting module is further configured to: for the first DMRS port of the first code division multiplexing group, select an index of the corresponding OCC according to the following manner: (· + «. λ _{3ίψ ;} ten a) mod k ,

Where mod is a modulo operation, when it is an odd number, the value is 0; when ...: is an even number,

The selecting module is further configured to generate a scrambling sequence of the DMRS by using different initialization modes for different code division multiplexing groups. When there are two sets of code division multiplexing groups, the first group according to c _Mt = ([n / The initialization mode of 2j + l)-(2N^ ^u + 1)·2 ¹⁶ + n _scro generates a scrambling sequence of DMRS, where the default is " _scro = , = 0 or 1; the second group follows " _scro = (p + l The initialization mode of mod2 generates a scrambling sequence of DMRS.

The pilot sequence generating module is further configured to perform reverse mapping on the adjacent DMRS carrier for the OCC corresponding to each DMRS port when the selected OCC is multiplied by the scrambling sequence.

The pilot sequence generating module is further configured to correspond to different code division multiplexing groups, and use different or the same starting position in the OCC mapping. _; Offset, where 0≤ _∞ <£ -1, L represents the length of the OCC.

The value of ^„co is mod(SwbcarierIndex 十 . , where Subcarierlndex represents the subcarrier index, and Z represents the length of each OCC.

A method and apparatus for generating a pilot sequence provided by the present invention, in different DMRS ports for performing code division multiplexing, for different code division and frequency division and/or time division hybrid multiplexing groups according to different criteria from OCC Selecting an OCC in the set, and/or generating a scrambling sequence of the DMRS according to different criteria for different code division multiplexing groups; multiplying the selected OCC by the scrambling sequence to generate each DMRS The final pilot sequence of the port. According to the present invention, when the OCC used by the two groups is orthogonal, and there is Doppler frequency offset or timing error, the influence of inter-subcarrier interference on the position of the demodulated pilot reference symbol can be reduced by OCC despreading. Thereby, the accuracy of the channel estimation is improved; and by the processing method of the present invention, in the case of limited OCC, the OCC orthogonality between the two groups can be ensured as much as possible, thereby reducing the influence on the channel estimation in the case of limited OCC. DRAWINGS

1 is a schematic diagram 1 of a design drawing of a DMRS in the prior art;

2 is a schematic diagram 2 of a design drawing of a DMRS in the prior art;

3 is a schematic diagram 3 of a design drawing of a DMRS in the prior art;

4( a ) is a schematic diagram of a carrier in the prior art without Doppler frequency offset or timing error; FIG. 4 ( b ) is a schematic diagram of inter-carrier interference when Doppler frequency offset exists in the prior art; FIG. A flowchart of a method for generating a pilot sequence of the present invention;

6 is a schematic diagram of an OCC allocation manner according to Embodiment 1 of the present invention;

7 is a schematic diagram of an OCC allocation manner according to Embodiment 2 of the present invention;

8 is a schematic diagram of an OCC allocation manner according to Embodiment 3 of the present invention;

FIG. 9 is a schematic diagram of an OCC allocation manner according to Embodiment 4 of the present invention. detailed description

The technical solutions of the present invention are further elaborated below in conjunction with the accompanying drawings and specific embodiments. A method for generating a pilot sequence provided by the present invention, as shown in FIG. 5, mainly includes the following steps:

Step 501: In each DMRS port that performs code division multiplexing, select an OCC from the OCC set for different code division and frequency division and/or time division hybrid multiplexing groups according to different criteria, and/or be a different code division. The multiplexing group generates a scrambling sequence of the DMRS according to different criteria.

Where different code division multiplexing groups can be collected from the OCC in reverse order Select occ in [occ^.^occ^], where k is the number of occ in the occ set, which is an integer greater than ι. In the following example, the two code division multiplexing groups select OCC from the OCC set in reverse order. The order of the first code division multiplexing group to select the OCC from the OCC set is: According to the first code. The OCC is sequentially selected from the OCC set in the order of the DMRS ports in the group, and corresponds to each port, that is, B occ ₀ , s ^p " ^ occ , , s ^P ^ occ ₂ , 5 ^Λ · ³ ^ oca , and the second code point The order in which the occ group selects occ from the occ set is: According to the order of the DMRS ports in the second code division multiplexing group, the OCC is selected in reverse order from the OCC set to correspond to each port, that is, s ^p " OCC ₃ , s ^P OCC ₂ , s ^P2 - ² OCC _x , s OCC ₀ . Wherein, the first DMRS port in the code division multiplexing group is represented.

For the convenience of analysis, in the following embodiments, ₂ , ₃ } correspond to ports {7 8 1 1 13 }, {Ρ ₂ , respectively. , Ρ _{2 1} , Ρ ₂ , ₂ , } respectively correspond to the port {9 10 12 14} as an example. It is worth noting that, in practical applications, it can also be defined in other forms, for example: When the maximum is 8 DMRS ports, Define the DMRS port number {0~7}, {χ^Ά} to another ¹ J corresponding to the port {0 1 4 6} , {/>. , /> ₁ , > ₂ , corpse ₃ } correspond to port {2 3 5 7}.

Based on the above port correspondence mode, when the number of layers is 5, if the OCC selected in the first code division multiplexing group is: OCC:. ^ OCC, , then the OCC selected in the second code division multiplexing group is: OCC ₃ , S ^[0 ^ OCC ₂ > ^ ¹² ^ OCC, , at this time due to the OCC used by DMRS port 7 (ie occ. ) The occ of each port in the second code division multiplexing group is different, so it is used. When performing despreading, the interference that is leaked from the RE corresponding to the second code division multiplexing group will be completely eliminated. When the maximum support layer is 8 and the mapping of each DMRS port is in the hybrid multiplexing mode of CDM+FDM, the specific OCC allocation mode is as shown in FIG. 6, that is, the occ selected in the first code division multiplexing group is : occ. ^ occ _x . s ¹¹ ^ oc . s OCC,; The OCC selected in the second code division multiplexing group is: s ⁹ H OCC ₃ , s ¹⁰ H occ ₂ , ^ ¹² OCC, OCC. It should be noted that the DMRS port in the present invention is not limited to Choose from {7~14}.

In addition, the present invention may also set different selection start position offsets for different code division multiplexing groups, and each code division multiplexing group starts from its own correspondence and selects according to the step size.

OCC, where denotes the sequence number of the code division multiplexing group, and _; is an integer, and 0 ≤ < t, l ≤ A < k. For the first DMRS port of the ίth code division multiplexing group, the corresponding OCC index is selected as follows: (δ, +η' λ , + a) mod/t, where mod is a modulo operation,

In

when . When it is odd, the value of "is 0; when .;; when it is even, the following example enters k

The line description sets a different starting position offset between the two code division multiplexing groups. And , and select occ according to step 4". With ^ =0, =1, but —. =/1 - 1 is an example, namely:

s ¹ OCC, s ^s OCC _x

s ⁹ OCC, s ¹⁰ 0CC ₂ s ^u OCC ₃ When 0CC is selected according to the given offset and step size above, when the maximum supported 8 layers and the mapping of each port DMRS adopts the hybrid multiplexing mode of CDM+FDM The specific 0CC selection is shown in Figure 7, that is, the OCC selected in the first code division multiplexing group is: _s ⁷ occ. , s ^s ^ OCC, , s ^ll ^0CC ₂ . s ^u ^ OCC,; The OCC selected in the second code division multiplexing group is: OCQ, s ¹⁰ ^ OCC ₂ , s ¹² OCC, s ^1A ^ OCC ₀ . j), when despreading with the corresponding 00 00^ pair + + .(^ +^ .+ ² ), since the OCC used by ports 8, 9, 10, and 12 are orthogonal to the OCC of the port ,, Therefore, the channel coefficient can be accurately recovered.

Furthermore, considering the compatibility with the low rank case, in the case of low rank (rank 1 to 4), in the different code division multiplexing groups, only part of the OCCs may be selected from the OCC set in reverse order. In two different code division multiplexing groups, the first M DMRS ports select the first M OCCs from the OCC set in the same order, and the last N DMRS ports select the next N OCCs from the OCC set in reverse order, Where M + N is the largest reusable DMRS in each code division multiplexing group The number of ports, M and N, are all integers greater than or equal to 0, less than or equal to the maximum number of multiplexable DMRS ports in each DMRS port group, preferably M = N. For example, when the OCC is allocated in two code division multiplexing groups, the parts in the OCC set can be reversely allocated. For the convenience of analysis, the DMRS port corresponding to the first code division multiplexing group is still {7811 13}. The second code division multiplexing group corresponds to the DMRS port as {9101214}. For each port of the first code division multiplexing group, the OCC can be selected in order. , OCC, , OCC OCC ₃ , and for each port of the second code division multiplexing group, only the part in the OCC set is reversely selected, and the order of each DMRS port of the second code division multiplexing group is separately allocated. For occ. , occ occ ₃ , occ ₂ . The specific occ allocation method is shown in Figure 8.

For different code division multiplexing groups, the parts of the scrambling sequence of the DMRS are generated according to different criteria. Different code division multiplexing groups may use different initialization methods to generate a scrambling sequence of the DMRS, when there are two sets of code division multiplexing groups. When the first group generates a scrambling sequence of DMRS according to the initialization mode of c _mit = (ln _s 12"+l). (2NS ¹¹ + 1).2 ¹⁶ + n _scm ,

0 or 1; The second group generates a scrambling sequence of the DMRS according to the initialization mode of (iP+l) mod2, and the process of generating the scrambling sequence according to the c _imt is the same as the background art. Then, when different sequences are used, since the sequences are semi-orthogonal, when there is interference between carriers (here, only two carriers are taken as an example), the signals received by port 7 are:

H ₇ r _cl +H r _{cl +} -{H ₉ s ⁹ r _{c2 +} H _w s ^w r _{c2 +} H _n s ⁿ r _c2 ) After removing the sequence of the pilot ^, it is H ₇ s ⁷ + + β . H ₉ s ⁹ r _c + H _lo s ^l0 r _c2 + H _n s ¹² r _c2 ) ' conj{r _cl ) , where conj-fx) denotes a conjugate of the elements in the sequence, and then uses the corresponding OCCOCC . When performing despreading, let the length of the OCC be _H , ₊ PW ^H after despreading. ⁺ H\ . It can be seen that the interference is k

--(Η ₉ +Η _ιο +Η _η ) ^ Since , _Η , _ο , ₁₂ are pseudo-random numbers, so compared to k in the prior art

The interference H ₉ is small. Step 502: Multiply the selected OCC with the scrambling sequence to generate a final pilot sequence for each DMRS port.

In the OCC selection manner given in each embodiment in step 501, in order to avoid different powers on different OFDM symbols, on the adjacent DMRS carrier, the OCC corresponding to each DMRS port of the same code division multiplexing group may be reversed or Cyclic offset mapping. Here, a method of performing cyclic offset mapping on the adjacent carrier according to the OCC corresponding to each DMRS port will be described as an example. The same is true for other OCC options.

The OCCs used between the layers of the same code division multiplexing group are respectively OCC. : [1 1 1 1], OC : [1 -1 1 -1], OCC ₂ : [1 -1 -1 1], OCC,: [1 1 -1 -1]. On the adjacent DMRS subcarriers, the scrambling sequences used are sum, oAwA+wA+w, and assumed

1 1 1 1

1 1 -1 -1

The precoding weight on the PRB is _w : , after the OCC processing, the same wave pair

1 -1 1 -1

1 -1 -1 1

The pilot signals on the different OFDM symbols are represented as one-to-one

One by one

When the reverse or offset mapping of the OCC is not performed, the transmit signals of the different OFDM symbols corresponding to the same DMRS carrier on each antenna port are:

DMRS DMRS DMRS DMRS OFDM OFDM OFDM OFDM

Symbol 1 symbol 2 symbol 3 symbol 4

Port 0 "4 ₀ 0 0 0

Port 1 0 0 , ₂ 0

Port 2 0 0 0

Port 3 0 45. 0 0

. It can be seen that for any one port, the power appearing on a certain DMRS OFDM symbol increases, while the power drop on other DMRS OFDM symbols does not even have a signal transmission problem. Similarly, for adjacent carriers, if there is no reverse mapping of OCC, DMRS DMRS DMRS DMRS

OFDM OFDM OFDM OFDM

Symbol 1 symbol 2 symbol 3 symbol 4

Port 0 0 0 0

Port 1 0 0 0

Port 2 0 0 0 4s _i+

0 0 0

The other carriers are exactly the same as the above format, port ³ , because for a certain port, such as DMRS port 0, the power is always the highest on a certain DMRS OFDM symbol (port 0 corresponds to DMRS OFDM symbol 1), and on other symbols There are no signals, resulting in different powers for different DMRS OFDM symbols. Since the code division multiplexing group 2 adopts the same OCC allocation method, it is the same as the case of the code division multiplexing group 1.

The present invention can reduce the influence of the inter-carrier inter-channel 4 without channel estimation by performing reverse mapping or S _occJ offset mapping on the OCC and combining different OCC allocations in different code division multiplexing groups. The starting position offset ^^ here is the offset of the OCC for each length of the OCC in the OCC set. _∞ — , The specific offset method can be referred to the following embodiment.

Generally, each code division multiplexing group has a different precoding weight corresponding to the DMRS port, so the role of the reverse mapping or cyclic offset mapping can be explained by a code division multiplexing group. In an actual application, the reverse mapping or cyclic offset mapping of the second code division multiplexing group can be obtained according to the same format in the reverse mapping or cyclic offset mapping manner of the first code division multiplexing group. It should be noted that, in the several OCC selection modes described above, the mapping method is applicable. In the following embodiments, the manner of cyclic offset is taken as an example for explanation.

When used. . ―,. When the cyclic offset is used, it corresponds to different code division multiplexing groups! · When OCC mapping, different or the same starting position is used. . _; Offset, where _{0≤ S DCCJ <L - 1,} L represents the length of the OCC. The starting position _∞ here is the offset of the OCC for each OCC in the OCC set, _∞ ”. One value is <5" occ _f = mod(SubcarierIndex + £ _i , L), where Subcarierlndex represents the subcarrier index and L represents the length of each OCC. The same value or different value can be taken with ^ ε;, indicates a different code The relative offset between the sub-multiplex groups. For the convenience of description, only ς = ^ is taken as an example here. For a code division multiplexing group, the scrambling sequences used are still summed in the adjacent DMRS subcarriers. A _{+ U} , , ₂ , , _{3 are} examples. When the first code division multiplexing group corresponds

DMRS DMRS DMRS DMRS OFDM OFDM OFDM OFDM

End t

End!:

End t

The mapping method on the DMRS carrier is

At the time of the ί + l

DMRS DMRS DMRS DMRS

OFDM OFDM OFDM OFDM

Symbol 1 symbol 2 symbol 3 symbol 4 port 0

Port 1 ^ϊ

Port 2 one

Port 3

Corresponding to the code division multiplexing group,

The mapping mode on the DMRS carrier is abc. Then in the above ζ· + 1

On the DMRS carrier, the mapping of the OCC to the respective DMRS ports on the four OFDM symbols is (abc ί ) and (bcda) respectively. Similarly, on f + 3 + 4, the OCC corresponds to each DMRS port on the four OFDM symbols. The mappings are (cda 6) and (ί/ abc). Assuming the precoding weight ^, the power on the adjacent 4 carriers is

DMRS DMRS DMRS DMRS DMRS DMRS DMRS DMRS OFDM OFDM OFDM OFDM OFDM OFDM OFDM

Port 0 - ; ₀ 0 0 0 "Port 0 0 0 43⁄4

Port 1 0 0 4 0 Port 1 0 0 0

Port 2 0 4 0 0 port 2 ten 0 0

Port 3 0 0 0 4 — Port 3 0 ₊₁ , 0 DMRS DMRS DMRS DMRS DMRS DMRS DMRS DMRS

OFDM OFDM OFDM OFDM OFDM OFDM OFDM

Symbol 1 symbol 2 symbol 3 symbol 4 symbol] symbol 2 symbol 3

Port 0 0 0 0 End 0 0 0

Port 1 0 0 0 0 0 0 4

Port 2 0 0 0 0 0 0

Port 0 0 0 0 0 0

It can be seen that each DMRS port has a maximum value cyclically on each symbol, thereby avoiding the problem of excessive transmission power of an OFDM symbol on a certain symbol.

When OCC (ΚΧ, OCC ₂ , OCC _{3 is} allocated for the first code division multiplexing group and OCC OCC OCC ₃ and OCC ₂ are allocated to the second code division multiplexing group, the corresponding allocation mode is as shown in FIG. .

The present invention further provides a pilot sequence generating apparatus, including: a selecting module and a pilot sequence generating module. a selection module, configured to select an OCC from a set of OCCs for different code division multiplexing groups in different DMRS ports for performing code division and frequency division and/or time division hybrid multiplexing, and/or different The code division multiplexing group generates a scrambling sequence of the DMRS according to different criteria. Specifically: the selection module may select the OCC from the OCC set [OCC ^OCG_J in different orders for different code division multiplexing groups; in the case of low rank, different code division multiplexing groups, or only The partial OCCs are selected from the OCC set in the reverse order; different pick start position offsets are also set for different code division multiplexing groups, and each code division multiplexing group starts from its own corresponding, according to the step size _; The OCC is selected; the different DMARS scrambling sequences can also be generated by different initialization methods for different code division multiplexing groups.

And a pilot sequence generating module, configured to multiply the selected OCC and the scrambling sequence to generate a final pilot sequence of each DMRS port. Specifically, when the selected OCC is multiplied by the scrambling sequence, the adjacent DMRS carriers may be inversely mapped for the OCC corresponding to each DMRS port; or, when the different code division multiplexing groups are mapped in the OCC, Different or identical starting positions S are used. _CCJ offset, where 0 ≤ < L - L represents the length of the OCC.

In summary, the present invention can reduce the corresponding layer between different CDM port groups, and reduce The accuracy of channel estimation is improved due to the influence of inter-carrier interference on channel estimation caused by Doppler shift and timing error.

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

Claims

Claim

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

The selected OCC is multiplied by the scrambling sequence to produce the final pilot sequence for each DMRS port.

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

The different code division multiplexing groups are aggregated from the OCC in reverse order. ,...,. ^^^ Select OCC, where A is the number of OCCs in the OCC set, and /t is an integer greater than 1.

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

Setting different selection start position offsets for the different code division multiplexing groups, each code division multiplexing group starts from its own correspondence, and selects OCC according to the step size ^, wherein ί indicates a code division multiplexing group. The serial number, and 4^· are integers, and 0 l _{≤ tep i <} k .

The method for generating a pilot sequence according to claim 4, wherein the index of the corresponding OCRS port of the i-th code division multiplexing group is selected as follows: δ _; +η- _step + a) mod k ,

Where mod is the modulo operation, and when it is an odd number, the value of "is 0; when ^ is even

The method for generating a pilot sequence according to claim 1, wherein the different code division multiplexing groups generate a scrambling sequence of the DMRS according to different criteria, specifically:

The different code division multiplexing groups use different initialization methods to generate a # sequence of DMRS. When there are two sets of code division multiplexing groups, the first group follows c _iBit = (k 2j + l)-(2N^ ^u + 1)·2 ¹⁶ + n _scro initialization method generates a scrambling sequence of DMRS, where 默 « _scro = , ζ 3 = 0 or 1; the second group generates DMRS according to the initialization mode of _cm = (p + l) mod2 Scrambling sequence.

The method for generating a pilot sequence according to any one of claims 1 to 6, wherein the multiplying the selected OCC and the scrambling sequence to generate a final pilot sequence of each DMRS port is specifically:

Corresponding to different code division multiplexing groups, when OCC mapping, different or the same starting position is used - and offset 'where 0 ≤ ^ < - 1, indicating the length of the OCC.

The method for generating a pilot sequence according to any one of the preceding claims, wherein the value of the 3⁄4cc i is mod (SubcarierIndex + e L), where Subcarierlndex represents a subcarrier cable Quote, indicating the length of each OCC.

10. A device for generating a pilot sequence, the device comprising:

The apparatus for generating pilot sequences according to claim 10, wherein the selection module is further configured to collect from the OCCs in different orders for different code division multiplexing groups [0. ,...,6> ^—J selects OCC, where / 1 represents the number of OCCs in the OCC set, and t is an integer greater than 1.

The apparatus for generating a pilot sequence according to claim 11, wherein the selecting module is further configured to: select, in a different code division multiplexing group, only part of the OCCs from the OCC set in reverse order .

The apparatus for generating a pilot sequence according to claim 10, wherein the selecting module is further configured to separately set different selection start position offsets for the different code division multiplexing groups, each code The sub-multiplexing group starts from its own correspondence and selects according to the step size

OCC , where _ζ · represents the sequence number of the code division multiplexing group, and l _{step i} is an integer, JL 0 ≤ d _i < k , ι ≤ 0.

The apparatus for generating a pilot sequence according to claim 13, wherein the selecting module is further configured to: select, for the DMRS port of the i-th code division multiplexing group, according to the following manner Index of OCC: ( + " · X _{step t} + a) mod k ,

Where mod is the modulo operation, when ^ is an odd number, the value is 0; when Λ _{ρ ί} is an even number, = .

k

The apparatus for generating a pilot sequence according to claim 10, wherein the selecting module is further configured to: use different initialization manners for different code division multiplexing groups to generate a ADD sequence of the DMRS, when When two sets of code division multiplexing groups, the first group generates a scrambling sequence of DMRS according to the initialization mode of c _iBit = ([n /2j + l) - (2N∞ ^u + 1) · 2 ¹⁶ + n _scro , where the default ^ = , = 0 or 1 ; The second group generates the DMRS sequence according to the initialization method of _scro = (p+l) mod2.

The pilot sequence generating apparatus according to any one of claims 10 to 15, wherein the pilot sequence generating module is further configured to: when multiplying the selected OCC by the scrambling sequence, adjacent On the DMRS carrier, reverse mapping is performed for the OCC corresponding to each DMRS port.

The pilot sequence generating apparatus according to any one of claims 10 to 15, wherein the pilot sequence generating module is further configured to correspond to different code division multiplexing groups ί, when OCC mapping, Use different or the same starting position U as the shift, where 0 ≤ «^ _; < _l, L represents the length of the OCC.

The apparatus for generating a pilot sequence according to any one of claims 17 to 17, wherein the value of ^occ; is a value of <i(SubcarierIndex + £„L), where 'Subcarierlndex indicates a subcarrier index, Indicates the length of each OCC.