WO2012135995A1

WO2012135995A1 - Method of transmitting reference signal, transmission point device and user equipment

Info

Publication number: WO2012135995A1
Application number: PCT/CN2011/072427
Authority: WO
Inventors: Zhi Zhang; Ming Xu; Masayuki Hoshino; Daichi Imamura
Original assignee: Panasonic Corporation
Priority date: 2011-04-02
Filing date: 2011-04-02
Publication date: 2012-10-11

Abstract

A wireless communication method, transmission point device, user equipment, signal multiplexing method and device are provided. The wireless communication method of transmitting to user equipment a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources, the method comprising: a multiplexing step of multiplying the plurality of layers of signals selectively by one of a first and a second orthogonal cover codes (OCCs) each of which contains two parts; an orthogonalizing step of multiplying a first part and a second part of one of the first and the second OCCs respectively by two sequence values, and multiplying a first part and a second part of the other OCC respectively by mappings of the two sequence values; and a transmitting step of transmitting the plurality of layers of resource blocks obtained from the orthogonalizing step to the user equipment. With the present disclosure, peak power and zero power on Rx side can be randomized thus reducing power fluctuation, meanwhile the orthogonality between the multiplexed RS signals can be preserved.

Description

METHOD OF TRANSMITTING REFERENCE SIGNAL, TRANSMISSION POINT

DEVICE AND USER EQUIPMENT

TECHNICAL FIELD

The present disclosure relates to the field of signals multiplexing method and reference signal design in communication system.

BACKGROUND

CDM (Code Division Multiplexing) is widely used in wireless communication systems. The typical CDM technique utilizes orthogonal sequences to spread and multiplex signal in order to cancel the interference among signals.

Fig.1 is a schematic diagram showing an example of the properties of CDM multiplexing based on length-4 orthogonal Walsh code. As shown in Fig.1 , the codes used in CDM are orthogonal to each other, or the cross correlation among codes are all zero. In CDM, different symbols S1 , S2, S3, S4 are multiplied with different codes, which generates the symbol spreading. The addition of the symbol spreading generates the multiplexed signals A, B, C, D. The multiplexed signals A, B, C, D are transmitted on the wireless channels. In CDM, the symbols can be spread either in time domain or in frequency domain or in combinations of them. In the CDM de-multiplexing, correlating the spreading signals with the orthogonal codes can recover the symbols S1 , S2, S3, S4 before spreading. In wireless communications, the most widely used orthogonal codes are Walsh code with length 2, 4, 8, 16... (powers of 2).

Generally, it is considered the following three scenarios. Scenario 1 In a MIMO-OFDM (Multiple Input-Multiple Output-Orthogonal Frequency Division Modulation) system, such as LTE-A (Long-Term Evolution-Advanced) system, multiple layers (containing data) are multiplexed into a RB (resource block) with the same time and frequency resource but with different pre-coding. So these layers are spatially multiplexed. To correctly de-multiplex these layers, LTE-A system provides DMRSs (orthogonal demodulation reference signals) for these layers, which are pre-coded the same ways as the corresponding layers. The multiplexing method for these orthogonal DMRSs is CDM. Fig.2(a)-2(c) show examples of DMRSs being multiplexed by CDM in LTE-A Rel-9. In Fig.2(a), there are shown resource blocks RB1 and RB2 of layers 1 and 2. The abscissa axis (T) of the RB (resource block) represents time (OFDM symbols), and its vertical axis (F) represents width of frequency band (sub-carriers). For each of RBs, the abscissa axis is divided into 14 sections, each of which forms an OFDM symbol in the vertical axis direction. The vertical axis is divided into 12 sections, each of which forms a sub-carrier in the abscissa axis direction. Each small block within the resource block represents a resource element, and all 12X14 resource elements of one RB form a sub- frame, which includes slot 1 and slot 2 along the abscissa axis direction. The REs (resource elements) 201 are used to transmit the DMRS for the specific channels of a transmission point, in which the DMRS is used to demodulate the transmitted signals containing data in a UE (user equipment). Here, the predetermined number of DMRSs is included in each of the RBs, and allocated in different predetermined locations of the RBs. l l

In Fig.2(a), length-2 Walsh codes (or length-2 orthogonal cover code, length-2 l -l

OCC) are used to multiplex DMRS of 2 layers. It is noted that for DMRS assigned with OCC [1 ,-1 ], the OCC mapping reverses its directions every adjacent sub-carrier in order to balance the peak power between adjacent DMRS symbols. If such alternating OCC ([1 ,-1 ]) mapping is not adopted, the overlap of "1" in two OCCs will generate a peak power in one DMRS OFDM symbol while the overlap of "1" and "-Γ in two OCCs will generate a bottom value in the adjacent DMRS OFDM value. There is a random sequence [a1 , a2, a3, a4, ... ] multiplied to both OCCs to randomize the potential interference to the adjacent transmission point, the random sequence [a1 , a2, a3, a4, ... ] is initialized by a random seed with SICD=0, in which the random seed is (L«, /2j+l) - (2N₇ + \) - 2¹⁶ + SCID . This random sequence is selected from the QPSK alphabet and the value of this random sequence is decided by the index of the sub- carrier and initialized by a random seed. This random seed changes with the sub-frame index, cell ID and a UE specific binary parameter SCID. In single user case, the default value of SCID is 0.

Fig.2(b) shows an example of DMRS being multiplexed with two OCCs and two sequences for MU case. In MU (Multi-user) case, there are two sequences initialized by a binary parameter SCID which is signaled to UE explicitly. For MU case, two OCCs plus two sequences can be used to multiplex up to 4 layers of DMRS, as shown in Fig.2(b). In Fig.2(b), UE1 can be assigned with two OCCs [1 , 1 ], [1 ,-1 ] and the sequence [a1 , a2, a3, a4, ... ] initialized by a random seed

- 2¹⁶ + SCID with SCID=0; UE2 can be assigned with the two OCCs and the sequence [b1 , b2, b3, b4, ... ] initialized by a random seed

- 2¹⁶ + SClD with SCID=1 . is alternatively multiplied to the OCC on the first and the second slots with sequence of SCID=1 . With this alternating the length-4 OCC can either be performed on time domain or on frequency domain, in other words, 2-D (two-dimension) orthogonality can be achieved.

Fig.2(c) further shows the detailed procedure how the frequency domain detection is performed for the case of Fig.2(b). In Fig.2(c), A, B, C and D represents the actual value on such RE on the Rx side. v1 ~v4 represent the BF (beam-forming) vectors corresponding to layer 1 ~ layer 4, and "h" is the channel vector. From the formulas in Fig.2(c), it is found that if [b1 ,b2] ±[a1 ,a2], i.e. (b1 ^*)a1 +(b2^*)a2=0 or (a1 ^*)b1 +(a2^*)b2=0, then frequency domain detection is not available. Here, the symbol " ^* " indicates conjugate. Since the sequences are from QPSK alphabet (four values), it is not a marginal probability to have [b1 , b2] _L[a1 ,a2]. So to have correct frequency domain detection, this problem had to be solved.

Fig.3 is a diagram showing a generation of the problem in scenarios 1. The concept level of the problem as described above is shown in the Fig.3.. In Fig.3, there are two Walsh OCCs, OCC i and OCC j, of length-2ⁿ. OCC i and OCC j are constructed from Walsh-Hardama transform using a length^^"1 OCC t as illustrated in Fig.3. Sequence values of a and b are scrambled to OCC i such that the first part of OCC i is multiplied by a and the second part of OCC i is multiplied by b. Sequence values c and d are scrambled to OCC j such that the first part of OCC j is multiplied by c and the second part of OCC j is multiplied by d. If (a^*)c+(b^*)d=0 or [a,b] _L[ c,d], information carried by OCC i and OCC j can not be correctly detected. It is noted that a, b, c and d can be from the same or different sequences, for example, [a, b] could be in sequence 1 and [c, d] could be in sequence 2, wherein sequence 1 and sequence 2 are initialized by two different seeds. The reason behind is that the orthogonality between OCC i and OCC j is from the Walsh-Hardama transform that multiplying on the second part of OCC j; however, if (a^*)c+(b^*)d=0, [a,b] and [c,d] also provide the orthogonality for OCC i and OCC j. The "overlap" of these two orthogonalities just counteracts each other and destructs the orthoginality.

Generally, QPSK based random sequence is most widely used in communication systems and assumed in this disclosure, i.e, sequence values are randomly selected from the QPSK alphabet sqrt(2){1 +j, -1 -j}/2. But it is noted here that the ideas can be applied to any random sequences.

Scenario 2

The general model in Fig.3 is not restricted in the DMRS usage, it also can apples to other RS design cases, such as CSI-RS (Channel Status Information Reference Signal). Fig.4(a)-4(d) show examples of Release-10 CSI-RSs being multiplexed. In Fig.4(a), 8 ports of the CSI-RS signals are CDM and FDM multiplexed. Specifically, the CSI-RSs of ports 0, 1 are CDM multiplexed; the CSI-RSs of ports 2, 3 are CDM multiplexed; the CSI-RSs of ports 4, 5 are CDM multiplexed; and the CSI-RSs of ports 6, 7 are CDM multiplexed. The four pairs of ports of CSI-RSs are further FDM multiplexed. For CDM, length-2 Walsh OCC, i.e, [1 , 1 ] and [1 ,-1 ], is used. These 8 CSI-RS ports 0, 1 , ..., 7 occupy 2 OFDM symbols T1 , T2, and two sequences [A1 , A2, ...] and [B1 , B2, ...] initialized by the indexes of OFDM symbols T1 , T2 respectively are scrambled to these 8 CSI-RS ports. Specifically, the sequence [A1 , A2, ...] is applied to the OFDM symbol T1 , and the sequence [B1 , B2, ...] is applied to the OFDM symbol T2. Because of length-2 Walsh OCC, when "1 " in OCCs encounter, peak power appears on the Rx side; when "1 " and "- encounters, bottom power appears on the Rx side.

When UE needs to measure neighbor transmission points' CSI-RS in such as CoMP case, the CSI-RSs from all transmission points may be allocated in the same OFDM symbols as shown in Fig.4(b). It can be seen from Fig.4(b) that CSI-RS of transmission points 1 , 2, 3 are multiplexed in the same OFDM symbols T1 , T2, so that the peak and zero power effects are accumulated and generates severe power fluctuation on the Rx side. The power fluctuation will case low power utilization to the UE.

Fig.4(c) shows one possible solution for the case of Fig.4(b). In Fig.4(c), sequences for CSI-RS port with OCC [1 ,1 ] and CSI-RS port with OCC [1 ,-1 ] can be initialized by different random seeds. This results the four sequences in Fig 4(c) [A1 ,A2..], [B1 ,B2], [C1 ,C2..] and [D1 ,D2..], which are initialized by four random seeds (including indexes of CSI-RS port and OFDM symbol). The four sequences applying to two CSI-RS ports will randomize the peak and zero power as shown in Fig.4(d). However, as indicated in Fig.4(d), it is found from the formulas that if [A1 , C1 ] _L[B1 , D1 ], the orthogonality between the CDMed CSI-RS ports is destroyed. Thus, these four sequences will destroy the orthogonality. This is the same problem raised in Fig. 3.

Scenario 3

Fig.5(a)-5(d) show the case where UE (belongs to transmission point 1 ) measures CSI- RSs from transmission points 1 and 2 simultaneously. This application case is also about CSI-RS, but considering a different scenario. As shown in Fig.5(a), if the timing offset between transmission points 1 and 2 are larger than the CP (Cyclic prefix) length, then the UE cannot receive complete symbol from transmission point 2, and the signal from the transmission point 2 is considered as interference. Thus, there will be inter- carrier interference (ICI) for CSI-RS in transmission point 2. Fig.5(b) further shows interferences in this case. Referring back to Fig 4(a), ports 0, 1 and ports 4, 5 are assigned into adjacent radio resource such as sub-carriers. Accordingly, with ICI, ports 0, 1 and ports 4, 5 interfere with each other. Fig.5(c) further shows the worst case for interferences of Fig.5(b). In Fig.5(c), a and b represent two difference sequences which are respectively applied to symbols T1 , T2. ho, h-i , h₄, h₅ respectively represent channel vectors for ports 0, 1 , 4, 5. In case of severe ICI between two sub-carriers F1 and F2, the detection for ports 0, 1 , 4, 5 on Rx (receiving) side is shown on the lower portion of the Fig.5(c). It can be seen from the lower portion that the ICI of a port is from one port with the same OCC on the adjacent sub-carrier. Specifically, in the worst case, port 0 and port 4 will interfere with each other because they use the same OCC [1 , 1 ]; port 1 and port 5 will also interfere with each other because they also use the same OCC [1 ,-1 ], which is illustrated in Fig.5(c). Fig.5(d) shows one possible solution for the case of Fig.5(c). The solution is to apply different sequences to port 4 and 5, as shown in Fig.5(d). In Fig.5(d), a, b are two sequences for port 0 and port 1 ; c, d are the other two sequences for port 4 and port 5. With the different sequences, even if there are ICI between port 0, 1 and 4, 5, such ICI can be randomized on the frequencies as shown in calculations in the lower portion of Fig.5(d). Comparing Fig.5(c) and Fig.5(d), we find that, in Fig.5(c), the ICI to port 0 is only from port 4 because they have the same OCC; but in Fig.5(d), the ICI to port 0 is from both port 4 and port 5 even if such ICI can be randomized on frequency domain. The reason is that in Fig.5(d), port 0, 1 and port 4, 5 use different sequences, so the orthogonality provided by OCC is destroyed. This also comes back to the general model in Fig.3. SUMMARY OF THE DISCLOSURE

In one aspect of the present disclosure, there is provided a wireless communication method of transmitting to user equipment a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources, the method comprising steps of: multiplying the plurality of layers of signals selectively by one of a first and a second orthogonal cover codes (OCCs) each of which contains two parts; multiplying a first part and a second part of one of the first and the second OCCs respectively by two sequence values, and multiplying a first part and a second part of the other OCC respectively by mappings of the two sequence values; and transmitting the plurality of layers of resource blocks obtained from the orthogonalizing step to the user equipment.

In another aspect of the present disclosure, there is provided a transmission point device for transmitting to user equipment a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources, comprising: a multiplexing unit configured to multiply the plurality of layers of signals selectively by one of a first and a second orthogonal cover codes (OCCs) each of which contains two parts; an orthogonalizing unit configured to multiply a first part and a second part of one of the first and the second OCCs respectively by two sequence values, and multiply a first part and a second part of the other OCC respectively by mappings of the two sequence values; and a transceiver unit configured to transmit the plurality of layers of resource blocks obtained from the orthogonalizing step to the user equipment.

In a further aspect of the present disclosure, there is provided a user equipment for receiving from a transmission point a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources, comprising: a transceiver unit configured to receive the plurality of layers of resource blocks; and a demodulation unit configured to detect the plurality of layers of resource blocks in time domain and/or frequency domain to obtain the plurality of layers of signals, wherein the plurality of layers of signals are multiplied selectively by one of a first and a second orthogonal cover codes (OCCs) each of which contains two parts, and wherein a first part and a second part of one of the first and the second OCCs are multiplied respectively by two sequence values, and a first part and a second part of the other OCC are multiplied respectively by mappings of the two sequence values.

In a further aspect of the present disclosure, there is provided a signal multiplexing method of multiplexing a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources wherein the plurality of layers of signals including at least two groups each including two layers, comprising steps of: multiplying the first layer of each of two groups of signals by a first orthogonal cover code (OCC) and multiplying the second layer of each of two groups of signals by a second OCC, wherein each of OCCs contains two parts; and multiplying the first part and the second part of the first OCC multiplied with the first layer of the first group of signals respectively by two sequence values [a, b], multiplying the first part and the second part of the second OCC multiplied with the second layer of the second group of signals respectively by the two sequence values [a, b], multiplying the first part and the second part of the second OCC multiplied with the second layer of the first group of signals respectively by mappings of the two sequence values which are based on a mapping function f1 (x), and multiplying the first part and the second part of the first OCC multiplied with the first layer of the second group of signals respectively by mappings of the two sequence values which are based on a mapping function f2(x).

In a further aspect of the present disclosure, there is provided a signal multiplexing device for multiplexing a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources wherein the plurality of layers of signals including at least two groups each including two layers, comprising: a multiplexing unit configured to multiply the first layer of each of two groups of signals by a first orthogonal cover code (OCC) and multiply the second layer of each of two groups of signals by a second OCC, wherein each of OCCs contains two parts; and an orthogonalizing unit configured to multiply the first part and the second part of the first OCC multiplied with the first layer of the first group of signals respectively by two sequence values [a, b], multiply the first part and the second part of the second OCC multiplied with the second layer of the second group of signals respectively by the two sequence values [a, b], multiply the first part and the second part of the second OCC multiplied with the second layer of the first group of signals respectively by mappings of the two sequence values which are based on a mapping function fl (x), and multiply the first part and the second part of the first OCC multiplied with the first layer of the second group of signals respectively by mappings of the two sequence values which are based on a mapping function f2(x).

In a further aspect of the present disclosure, there is provided a signal multiplexing method of multiplexing a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources wherein the plurality of layers of signals including at least two groups each including two layers, comprising steps of: multiplying the first layer of each of two groups of signals by a first orthogonal cover code (OCC) and multiplying the second layer of each of two groups of signals by a second OCC, wherein each of OCCs contains two parts; and multiplying the first part and the second part of the first OCC multiplied with the first layer of the first group of signals respectively by two sequence values [a, b], multiplying the first part and the second part of the second OCC multiplied with the second layer of the second group of signals respectively by the two sequence values [a, b], multiplying the first part and the second part of the second OCC multiplied with the second layer of the first group of signals respectively by mappings of the two sequence values which are based on mapping functions f1 (x), f2(x), and multiplying the first part and the second part of the first OCC multiplied with the first layer of the second group of signals respectively by mappings of the two sequence values which are based on mapping functions f1 (x), f2(x). In a further aspect of the present disclosure, there is provided a signal multiplexing device for multiplexing a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources wherein the plurality of layers of signals including at least two groups each including two layers, comprising: a multiplexing unit configured to multiply the first layer of each two groups of signals by a first orthogonal cover code (OCC), and multiply the second layer of each of two groups of signals by a second OCC, wherein each of OCCs contains two parts; and an orthogonalizing unit configured to multiply the first part and the second part of the first OCC multiplied with the first layer of the first group of signals respectively by two sequence values [a, b], multiply the first part and the second part of the second OCC multiplied with the second layer of the second group of signals respectively by the two sequence values [a, b], multiply the first part and the second part of the second OCC multiplied with the second layer of the first group of signals respectively by mappings of the two sequence values which are based on mapping functions f1 (x) and f2(x), and multiply the first part and the second part of the first OCC multiplied with the first layer of the second group of signals respectively by mappings of the two sequence values which are based on mapping functions f1 (x) and f2(x).

In a further aspect of the present disclosure, there is provided a signal multiplexing method for multiplexing a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources, wherein the plurality of layers of signals including N groups each including two layers, wherein N is an integer larger than 1 , comprising steps of: multiplying the first layer of each of N groups of signals by a first orthogonal cover code (OCC) and multiplying the second layer of each of N groups of signals by a second OCC, wherein each of OCCs contains two parts; and multiplying the first part and the second part of the first OCC multiplied with the first layer of each of N groups of signals respectively by two sequence values [a, b], multiplying the first part and the second part of the second OCC multiplied with the second layer of each of N groups of signals respectively by different mappings of the two sequence values. In a further aspect of the present disclosure, there is provided a signal multiplexing device for multiplexing a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources, wherein the plurality of layers of signals including N groups each including two layers, wherein N is an integer larger than 1 , comprising: a multiplexing unit configured to multiply the first layer of each of N groups of signals by a first orthogonal cover code (OCC) and multiply the second layer of each of N groups of signals by a second OCC, wherein each of OCCs contains two parts; and an orthogonalizing unit configured to multiply the first part and the second part of the first OCC multiplied with the first layer of each of N groups of signals respectively by two sequence values [a, b], multiply the first part and the second part of the second OCC multiplied with the second layer of each of N groups of signals respectively by different mappings of the two sequence values. In a further aspect of the present disclosure, there is provided a signal multiplexing method of multiplexing signals assigned on predetermined radio resource of resource blocks, wherein different signals located on different radio resources being sent from different transmission points respectively, and corresponding to a plurality of

multiplexing patterns being divided into N subsets, N being an integer number more than 1 , comprising steps of: informing a user equipment of index of a subset to be used by the user equipment; multiplexing the signals of the different transmission points with the multiplexing patterns belong to the informed subset.

In a further aspect of the present disclosure, there is provided a signal multiplexing device of multiplexing signals assigned on predetermined radio resource of resource blocks, wherein different signals located on different radio resources being sent from different transmission points respectively, and corresponding to a plurality of

multiplexing patterns being divided into N subsets, N being an integer number more than 1 , comprising: a transceiver unit configured to inform a user equipment of index of a subset to be used by the user equipment; a multiplexing unit configured to multiplex the signals of the different transmission points with the multiplexing patterns belong to the informed subset.

In the present disclosure, by applying sequence mappings to OCCs assigned to RS signals being CDM multiplexed or FDM multiplexed or both, peak power and zero power on Rx side can be randomized thus reducing power fluctuations, meanwhile orthogonality between multiplexed RS signals can be preserved.

The foregoing is a summary and thus contains, by necessity, simplifications,

generalization, and omissions of details; consequently, those skilled in the art will appreciate that the summary is illustrative only and is not intended to be in any way limiting. Other aspects, features, and advantages of the devices and/or processes and/or other subject matters described herein will become apparent in the teachings set forth herein. The summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several embodiments in accordance with the disclosure and are, therefore, not to be

considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings, in which:

Fig.1 is a schematic diagram showing an example of the properties of CDM multiplexing based on length-4 orthogonal Walsh code;

Fig.2(a)-2(c) show examples of DMRSs being multiplexed by CDM in LTE-A Rel-9;

Fig.3 is a diagram showing a generation of the problem in scenario 1 ; Fig.4(a)-4(d) show examples of Release-10 CSI-RSs being multiplexed;

Fig.5(a)-5(d) show the case where UE (belongs to transmission point 1 ) measures CSI-RSs from transmission points 1 and 2 simultaneously;

Fig.6 is a block diagram showing a transmission point device according to the first embodiment of the present disclosure;

Fig.7 shows a general design for RS signals according to the first embodiment of the present disclosure;

Fig.8 is a block diagram showing user equipment according to the first

embodiment of the present disclosure;

Fig.9(a) and 9(b) show an example for designing RS signals according to the second embodiment of the present disclosure;

Fig.10 shows an example of DMRSs being multiplexed by CDM in LTE-A

Release-9 according to the second embodiment of the present disclosure;

Fig.1 1 (a) and 1 1 (b) show an example of Release-10 CSI-RSs being CDM multiplexed according to the second embodiment of the present disclosure;

Fig.12 shows another example of Release-10 CSI-RSs from different

transmission points being FDM multiplexed according to the second embodiment of the present disclosure;

Fig.13(a) and 13(b) show a case of CSI-RS being CDM and FDM multiplexed according to the third embodiment of the present disclosure;

Fig.14 shows a general design for RS signals according to the fourth embodiment of the present disclosure;

Fig.15 shows an example of CSI-RS signals being CDM multiplexed according to the fifth embodiment of the present disclosure;

Fig.16 shows an example of CSI-RS signals being CDM multiplexed according to the sixth embodiment of the present disclosure;

Fig.17(a) and 17(b) show a case of CSI-RS being CDM and FDM multiplexed according to the seventh embodiment of the present disclosure;

Fig.18 shows an example of multiplexed CSI-RSs of different transmission points with same cell ID according to the eighth embodiment of the present disclosure; Fig.19(a) and 19(b) show a case of multiplexed CSI-RSs of different transmission points with same cell ID according to the ninth embodiment of the present disclosure

Fig.20 shows an example of multiplexed CSI-RSs of different transmission points with same cell ID according to the tenth embodiment of the present disclosure;

Fig.21 shows an example of multiplexed CSI-RSs of different transmission points with same cell ID according to the eleventh embodiment of the present disclosure;

Fig.22 shows an example of multiplexed CSI-RSs of different transmission points with different cell IDs according to the Twelfth embodiment of the present disclosure;

Fig.23(a) and 23(b) show a case of multiplexed CSI-RSs of different transmission points according to the thirteenth embodiment of the present disclosure;

Fig.24 is a diagram showing a flow chart of a wireless communication method according to the twelfth embodiment of the present disclosure.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the Figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

(The First Embodiment)

Fig.6 is a block diagram showing a transmission point device according to the first embodiment of the present disclosure.

The transmission point device 600 according to the first embodiment of the present disclosure is used for communicating with at least one UE (user equipment) in a communication system. The transmission point device 600 transmits, to the at least one UE, a plurality of layers of RS signals, in which the plurality of layers of RS signals are assigned on predetermined locations (radio resource, which means the time and/or frequency resource such as sub-carrier, sub-frame, etc.) of a plurality of layers of resource blocks with the same time and frequency resources. As shown in Fig.6, the transmission point device 600 includes: a multiplexing unit 601 which multiplies the plurality of layers of RS signals selectively by one of the first and second orthogonal cover codes (OCCs) each of which is divided into two parts; an orthogonalizing unit 602 which multiplies the first part and the second part of one of the first and the second OCCs respectively by two sequence values, and multiplies the first part and the second part of the other OCC respectively by mappings of the two sequence values; and a transceiver unit 603 which transmits the plurality of layers of resource blocks obtained from the orthogonalizing unit 602 to the at least one UE. It should be noted that RS signals here can be any kinds of RS signals such as DMRS, CSI-RS and the like.

The transmission point device 600 according to the present disclosure may further include a CPU (Central Processing Unit) 610 for executing related programs to process various data and control operations of respective units in the transmission point device 600, a ROM (Read Only Memory) 613 for storing various programs required for performing various process and control by the CPU 610, a RAM (Random Access Memory) 615 for storing intermediate data temporarily produced in the procedure of process and control by the CPU 610, and/or a storage unit 617 for storing various programs, data and so on. The above multiplexing unit 601 , orthogonalizing unit 602, transceiver unit 603, CPU 610, ROM 613, RAM 615 and/or storage unit 617 etc. may be interconnected via data and/or command bus 620 and transfer signals between one another.

Respective units as described above do not limit the scope of the present disclosure. According to one embodiment of the disclosure, the function of any of the above multiplexing unit 601 , orthogonalizing unit 602, and transceiver unit 603 may also be implemented by functional software in combination with the above CPU 610, ROM 613, RAM 615 and/or storage unit 617 etc.

The detailed description will be given to the operations of respective units of the transmission point device 600 with reference to the drawings below.

Fig.7 shows a general design for RS signals according to the first embodiment of the present disclosure. In Fig.7, there are two Walsh OCCs, OCC i and OCC j, of length-2ⁿ. OCC i and OCC j are constructed from Walsh-Hardama transform using a length-2^n"1 OCC t. Sequence values of a and b are scrambled to OCC i such that the first part of OCC i is multiplied by a and the second part of OCC i is multiplied by b. F(b) and F(a) are scrambled to OCC j such that the first part of OCC j is multiplied by F(b) and the second part of OCC j is multiplied by F(a). Here, F(b) and F(a) are mappings of sequence values a and b respectively, where F(x) is a function of x. The general design for RS signals shown in Fig.7 is the general solution for the problem raised in Fig.3. Compared with Fig.3, instead of using the other set of sequence values (c, d) scrambled on OCC j, the present embodiment uses mappings of (a, b), i.e. F(b) and F(a) on OCC j as shown in Fig.7. It should be noted that it is possible to multiply the first part of OCC j by F(a) and the second part of OCC j by F(b). However, it is preferred that the first part of OCC j is multiplied by F(b) and the second part of OCC j is multiplied by F(a) as shown in Fig.7. By properly choosing function F(), the case of [a,b] _L[ c,d] in Fig.3 can be avoid and thus the orthogonality between multiplexed RS signals can be preserved meanwhile randomizing the peak and zero power as described in the background section. In the following, it will be given detailed examples on how to choose the function F().

Fig.8 is a block diagram showing a user equipment (UE) according to the first embodiment of the present disclosure.

The UE 800 according to the first embodiment of the present disclosure is used for communicating with a transmission point device in a communication system. The UE 800 receives from the transmission point device a plurality of layers of RS signals, in which the plurality of layers of RS signals are assigned on predetermined locations (radio resource, which means the time and/or frequency resource such as sub-carrier, sub-frame, etc.) of a plurality of layers of resource blocks with the same time and frequency resources. As shown in Fig.8, the UE 800 includes: a transceiver unit 801 which receives the plurality of layers of resource blocks; and a demodulation unit 802 which detects the plurality of layers of resource blocks in time domain and/or frequency domain to obtain the plurality of layers of RS signals, wherein the plurality of layers of RS signals are multiplied selectively by one of the first and second orthogonal cover codes (OCCs), and the first part and the second part of one of the first and the second OCCs are multiplied respectively by two sequence values while the first part and the second part of the other OCC are multiplied respectively by mappings of the two sequence values.

As described previously with reference to Fig.7, sequence values of a and b are scrambled to OCC i such that the first part of OCC i is multiplied by a and the second part of OCC i is multiplied by b. F(b) and F(a) are scrambled to OCC j such that the first part of OCC j is multiplied by F(b) and the second part of OCC j is multiplied by F(a). Here, F(b) and F(a) are mappings of sequence values a and b respectively, where F(x) is a function of x. By properly choosing function F(), the orthogonality between multiplexed RS signals can be preserved meanwhile randomizing the peak and zero power as described in the background section.

The UE 800 according to the present disclosure may further include a CPU (Central Processing Unit) 810 for executing related programs to process various data and control operations of respective units in the UE 800, a ROM (Read Only Memory) 813 for storing various programs required for performing various process and control by the CPU 810, a RAM (Random Access Memory) 815 for storing intermediate data temporarily produced in the procedure of process and control by the CPU 810, and/or a storage unit 817 for storing various programs, data and so on. The above transceiver unit 801 , demodulation unit 802, CPU 810, ROM 813, RAM 815 and/or storage unit 817 etc. may be interconnected via data and/or command bus 820 and transfer signals between one another.

Respective units as described above do not limit the scope of the present disclosure. According to one embodiment of the disclosure, the function of any of the above transceiver unit 801 and demodulation unit 802 may also be implemented by functional software in combination with the above CPU 810, ROM 813, RAM 815 and/or storage unit 817 etc.

According to the present embodiment, by applying sequence mappings to OCCs assigned to RS signals being CDM multiplexed or FDM multiplexed or both, peak power and zero power on Rx side can be randomized thus reducing power fluctuations, meanwhile orthogonality between multiplexed RS signals can be preserved.

(The Second Embodiment)

Fig.9(a) and 9(b) show an example for designing RS signals according to the second embodiment of the present disclosure.

In Fig.9(a), there is shown a detailed example on how to decide the mapping function F(), i.e, F(b) and F(a) in the first embodiment. In the present embodiment, the F(x) is defined as F(x)=x^* or the conjugate of x, where real part of x is unchanged and the imaginary part of x is reversed. Fig.9(b) further shows the effects of the RS signal designing in Fig.9(a). In Fig.9(b), Si is the information conveyed by OCC i and Sj is the information conveyed by OCC j. A is the Rx (receiving) values on the first part of OCC and B is the Rx value on the second part of OCC at the Rx side (such as UE 800). From the calculation on the right side of Fig.9(b), i.e. ,

bA+aB

£^■ = ^■

lab

bA-aB .

S,. = , and

³ 2

it is found that although OCC i and OCC j are scrambled by different sequence values, the orthogonality between them is preserved. Fig.10 shows an example of DMRSs being multiplexed by CDM in LTE-A Release-9 according to the second embodiment of the present disclosure. In Fig.10, the case of applying the RS signal designing of Fig.9(a) to Scenario 1 as described above is shown. Compared with Fig.2(b), only partial RB1 is shown in Fig.10 for convenience of illustration. In Fig.10, two layers of DMRSs corresponding to UE1 which are assigned with sequence values [a1 , a2] with SCID=0 in Fig.2(b) are shown on the left side, and two layers of DMRSs corresponding to UE2 which are assigned with sequence values [b1 , b2] with SCID=1 in Fig.2(b) are shown on the right side. However, OCC with SCID=1 is scrambled with a couple of conjugate values [a2^*, a1 ^*] in Fig.10 instead of sequence values [b1 , b2] in Fig.2(b). Specifically, for OCC scrambled to DMRSs of UE2 (on the right side of Fig.10), OCC on one sub-carrier is multiplied by the conjugate of the reference value which is multiplied with OCC scrambled to DMRSs of UE1 on the other sub-carrier. With the use of mapping as described above, the orthogonality between DMRSs can be preserved.

Figs.11 (a) and 11 (b) show an example of Release-10 CSI-RSs being CDM multiplexed according to the second embodiment of the present disclosure. In Figs.11 (a) and 11 (b), the case of applying the RS signal designing of Fig.9(a) to Scenario 2 as described in the background section is shown. Compared with Fig.4(a), only some REs of RBs shown in Fig.4(a) is shown in Fig.11 (a) for convenience of illustration. Specifically, the first row of REs in Fig.11 (a) are from the upper RB of Fig.4(a), where the left two REs show the layer of CSI-RS port 0 and the right two REs represent the layer of CSI-RS port 1. Similarly, the second row of REs in Fig.11 (a) are from the lower RB of Fig.4(a), where the left two REs show the layer of CSI-RS port 0 and the right two REs represent the layer of CSI-RS port 1. Further, compared with the solution for Scenario 2 as shown in Fig.4(c), it can be seen from Fig.11 (a) that, in the present embodiment, for port 0 with OCC [1 ,1 ], sequences [a1 ,a2...] and [b1 ,b2...] are scrambled on symbols T1 and T2 respectively, which is similar with Fig.4(c). However, for port 1 with OCC [1 ,-1 ], in Fig.11 (a), sequences [b1^*, b2^*...] and [a1^*,a2^*...], that is, mappings of sequences [b1 ,b2...] and [a1 ,a2...], are scrambled on symbols T1 and T2 respectively, instead of scrambling other sets of sequences [C1 , C2...] and [D1 , D2...] on symbols T1 and T2 respectively as shown in Fig.4(c).

The effects of applying the RS signal designing of Fig.9(a) to Scenario 2 is further shown in Fig.11 (b). Receiving power on the Rx side (such as UE 800) is calculated through the formulas shown in Fig.11 (b). Without this mapping, symbol T1 always has peak power because "1" overlaps, and symbol T2 always has zero power because "1" and "-Γ encounters. With this mapping, if a1^* b1 =j or -j, then symbols T1 and T2 have equal power. Considering that [a1 ,a2..] and [b1 ,b2..] are randomized on the frequency domain, the peak and zero power is also randomized on the frequency domain. With the use of mapping as described above, the orthogonality between CSI-RSs can be preserved while randomizing peak and zero power on the RX side.

Fig.12 shows another example of Release-10 CSI-RSs from different transmission points being FDM multiplexed according to the second embodiment of the present disclosure. In Fig.12, the case of applying the RS signal designing of Fig.9(a) to Scenario 3 as described in the background section is shown. In Scenario 3, UE (belongs to transmission point 1 ) measures CSI-RSs from transmission points 1 and 2 simultaneously. As shown in Fig.5(a) and there is ICI between ports 0, 1 and ports 4, 5 because they use adjacent radio resource such as sub-carriers. To resolve the worst case as shown in Fig.5(c), Fig.5(d) shows one possible solution that is to apply different sequences [c, d] to port 4 and 5. With the different sequences, such ICI can be randomized on the frequencies. However, the orthogonality provided by OCC is destroyed. In the present embodiment, as shown in Fig.12, on port 0 and 1 , sequence values [a, b] are used respectively for symbols T1 and T2, which is the same as Fig.5(d), while on port 4 and 5, mappings [b^*, a^*] of sequence values [b, a] are used instead of scrambling other sets of sequence values [c, d]. Here, similarly with Fig.5(d), ports 0, 1 and ports 4, 5 are assigned on adjacent radio resource such as sub-carriers. Port 0 and 4 are multiplexed with OCC [1 , 1 ]; Port 1 and 5 are multiplexed with OCC [1 , -1 ]. In Fig.12, also, ho, h-i , h , h₅ respectively represent channel responses for ports 0, 1 , 4, 5. In case of severe ICI between two sub-carriers F1 and F2, the detection for ports 0, 1 , 4, 5 on Rx side (such as UE 800) is shown on the lower portion of the Fig.12. In Fig.12, the ICI on port 0 is only from port 4 because they use the same OCC; while in Fig.5(d), ICI on port 0 is from both port 4 and 5. Thus, by comparing Fig.12 with Fig.5(d), it is found that with these mappings, in which , ICI from adjacent radio resource such as sub-carriers can be randomized on the frequency domain and ICI from adjacent radio resource such as sub-carriers is only from the port with the same OCC. Thus, the orthogonality provided by OCC can be preserved.

It should be noted that the ideas described in this disclosure can be applied to all Scenarios. On the following embodiments, for the sake of simplicity, we only focus on Scenario 2 & 3 (CSI-RS). But it is noted here that it can also be applied to DMRS case (Scenario 1 ).

(The Third Embodiment)

Scenario 2 as described in the background section considers how to arrange the sequences for CDM multiplexed CSI-RS ports while Scenario 3 as described in the background section focuses on how to arrange the sequences for FDM multiplexed CSI-RS ports. Taking Scenarios 2 and 3 into consideration simultaneously, the present embodiment gives the solution.

Fig.13(a) and 13(b) show a case of CSI-RS being CDM and FDM multiplexed according to the third embodiment of the present disclosure. Also, for the sake of simplicity, Fig.13(a) and 13(b) show only some REs transmitting CSI-RS signals in one RB on the Tx (transmitter) side (such as transmission point device 600). In Fig.13(a), CSI-RS ports 0 and 1 are CDM multiplexed on the same sub-carrier F1 by assigning OCC [1 , 1 ] and [1 , -1 ] respectively. They occupy two symbols T1 and T2 on the time domain. Similarly, CSI-RS ports (also be referred simply to as "ports" hereinafter) 4 and 5 are CDM multiplexed on the same sub-carrier F2 by assigning OCC [1 , 1 ] and [1 , -1 ] respectively. They occupy the same two symbols T1 and T2 on the time domain. Accordingly, ports 0 and 4 are multiplexed with the same OCC [1 , 1 ] but on adjacent sub-carriers F1 and F2 respectively; ports 1 and 5 are multiplexed with the same OCC [1 , -1 ] but on adjacent sub-carriers F1 and F2 respectively.

In this case, the design for CSI-RS as shown in Fig.7 may also apply to CSI-RS signals CDM and FDM multiplexed. In the present embodiment, sequence values [a, b] are scrambled to ports 0 and 5, then mappings [f1 (b), f 1 (a)] are scrambled to ports 1 and mappings [f2(b), f2(a)] are scrambled to port 4, where f1 () and f2() could be the same or different mapping functions. For summarization, the design principle in the present embodiment is as follows:

(1 ) on the CDMed ports, such as port 0 and 1 , mappings are used, but orthogonality should be preserved;

(2) on FDMed ports with same OCC, such as port 0 and port 4, mappings are used; (3) on FDMed ports with different OCC, such as port 0 and port 5, same sequence values can be used; if use mappings, orthogonality between OCC should be preserved.

With the above CSI-RS design principle, effects of randomizing can be obtained not only between CDM multiplexed ports but also between ports on adjacent radio resource such as sub-carriers (i.e. FDM multiplexed ports). And, the orthogonality provided by OCC can be preserved.

Fig.13(b) further gives a detailed example for Fig.13(a), where mapping functions f1 (x) and f2(x) are both x^* (conjugate of x). Using a similar analysis with that in the second embodiment, we can see the effects of Fig.13(b) include: peak power is randomized because ports 0 and 1 use mappings and ports 4 and 5 also use mapping; ICI between ports 0 and 4 and between ports 1 and 5 are randomized because of mappings; orthogonality between ports 0 and 5 and between ports 1 and 4 are preserved because they use the same sequences. Therefore, in the present embodiment, such a signal multiplexing method of

multiplexing a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources, wherein the plurality of layers of signals including at least two groups (a group of port 0 and port 1 , and a group of port 4 and port 5) each including two layers, may be performed, as shown in Fig.13(a). The method comprises the following steps:

multiplying the first layer (port 0 and port 4) of each of two groups of signals by a first orthogonal cover code (OCC) such as [1 , 1 ] and multiplying the second layer (port 1 and port 5) of each of two groups of signals by a second OCC such as [1 , -1 ], wherein each of OCCs is divided into two parts; and multiplying the first part [1 ] and the second part [1 ] of the first OCC [1 , 1 ] multiplied with the first layer (port 0) of the first group of signals respectively by two sequence values [a, b], multiplying the first part [1 ] and the second part [-1 ] of the second OCC [1 , -1 ] multiplied with the second layer (port 5) of the second group of signals respectively by the two sequence values [a, b], multiplying the first part [1 ] and the second part [-1 ] of the second OCC [1 , -1 ] multiplied with the second layer (port 1 ) of the first group of signals respectively by mappings of the two sequence values which are based on a mapping function f1 (x), and multiplying the first part [1 ] and the second part [1 ] of the first OCC [1 , 1 ] multiplied with the first layer (port 4) of the second group of signals respectively by mappings of the two sequence values which are based on a mapping function f2(x).

In addition, similar with the above description, although it is not shown here, the present disclosure can provide a device for multiplexing a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources, wherein the plurality of layers of signals including at least two groups each including two layers. The device may comprises: a

multiplexing unit for multiplying the first layer of each of two groups of signals by a first orthogonal cover code (OCC) and multiplying the second layer of each of two groups of signals by a second OCC, wherein each of OCCs is divided into two parts; and a orthogonalizing unit for multiplying the first part and the second part of the first OCC multiplied with the first layer of the first group of signals respectively by two sequence values [a, b], multiplying the first part and the second part of the second OCC multiplied with the second layer of the second group of signals respectively by the two sequence values [a, b], multiplying the first part and the second part of the second OCC multiplied with the second layer of the first group of signals respectively by mappings of the two sequence values which are based on a mapping function f1 (x), and multiplying the first part and the second part of the first OCC multiplied with the first layer of the second group of signals respectively by mappings of the two sequence values which are based on a mapping function f2(x).

(The Fourth Embodiment)

Fig.14 shows a general design for RS signals according to the fourth embodiment of the present disclosure. In Fig.14, there are two Walsh OCCs, OCC i and OCC j, of length-2ⁿ. OCC i and OCC j are constructed from Walsh-Hardama transform using a length-2^n"1 OCC t. Similarly with Fig.7, sequence values of a and b are scrambled to OCC i such that the first part of OCC i is multiplied by a and the second part of OCC i is multiplied by b in Fig.14. As shown in Fig.7, the basic idea of the first embodiment is to use [F(b), F(a)] as mappings of [a, b] to be scrambled on OCC j, that is, the first part of OCC j is multiplied by F(b) and the second part of OCC j is multiplied by F(a). In the first embodiment, mappings of the sequences [a, b] scrambled on OCC j are based on the same function F(x). However, as shown in Fig.14, in the present embodiment, the mappings of the sequences [a, b] scrambled on OCC j can be based on different mapping functions, i.e. [F1 (b), F2(a)], where F1 (x) and F2(x) could be the same or different functions. Specifically, the first part of OCC j is multiplied by F1 (b) and the second part of OCC j is multiplied by F2(a) as shown in Fig.14. When F1 (x)=F2(x), the case in the present embodiment is equal to that in the first embodiment. Thus, RS design of the present embodiment (Fig.14) may be considered as an extension of that of the first embodiment (Fig.7).

However, in the present embodiment, it should be noted that the choosing of F1 (x) and F2(x) cannot destroy the orthogonality between OCC i and OCC j. In the following embodiments, we will give detailed examples on how to choose different functions F1 (x) and F2(x) to achieve various effects.

(The Fifth Embodiment)

Fig.15 shows an example of CSI-RS signals being CDM multiplexed according to the fifth embodiment of the present disclosure. In Fig.15, sequence values [A1 , B1 ] is scrambled to OCC [1 , 1 ] and mappings [B1^*, A1 ] are scrambled to OCC [1 , -1 ]. Specifically, the sequence value A1 is multiplied with the first part "1" of OCC [1 , 1 ], the sequence value B1 is multiplied with the second part "1" of OCC [1 , 1 ], the mapping B1^* of the sequence value B1 is multiplied with the first part "1 " of OCC [1 , -1 ], and the mapping A1 of the sequence value A1 is multiplied with the second part "-Γ of OCC [1 , -1 ].

In Fig.15, R1 and R2 are respectively Rx signals on two symbols at Rx side (such as UE 800), and H1 and H2 indicate respectively channel vectors corresponding to different CSI-RS ports which are assigned with different OCCs [1 , 1 ] and [1 , -1 ] respectively. According to the calculation in Fig.15, if sequences are all selected from QPSK alphabet, the orthogonality between the two OCCs is always preserved. In the Fig.15, Re() indicates the real part of what is in the bracket, and lm() indicates the imaginary part of what is in the bracket.

If using general model in Fig.14 or the fourth embodiment to express, F1 (x)=x^* and F2(x)=x. An equivalent solution is F1 (x)=x and F2(x)=x^*, that is, mappings [B1^*, A1 ] are scrambled to OCC [1 , -1 ].

(The Six Embodiment)

Fig.16 shows an example of CSI-RS signals being CDM multiplexed according to the sixth embodiment of the present disclosure. In Fig.16, sequence values [A1 , B1 ] is scrambled to OCC [1 , 1 ] and mappings [expG91 )B1 , expG92)A1 ] are scrambled to OCC [1 , -1 ]. Specifically, the sequence value A1 is multiplied with the first part "1" of OCC [1 , 1 ], the sequence value B1 is multiplied with the second part "1" of OCC [1 , 1 ], the mapping expQGI )B1 of the sequence value B1 is multiplied with the first part "1 " of OCC [1 , -1 ], and the mapping expG92)A1 of the sequence value A1 is multiplied with the second part of OCC [1 , -1 ].

In Fig.16, R1 and R2 are respectively Rx signals on two symbols at Rx side (such as UE 800), and H1 and H2 indicate respectively channel vectors corresponding to different CSI-RS ports which are assigned with different OCCs [1 , 1 ] and [1 , -1 ] respectively. According to the calculation in Fig.16, if sequences are all selected from QPSK alphabet and Θ1 -Θ2≠ηττ72, where n is an integer, the orthogonality between two OCCs is preserved. If using general model in Fig.14 or the fourth embodiment, F1 (x)=expG91 )*x and F2(x)=expG92)*x. According to the present embodiment, by applying sequence mappings to OCCs assigned to RS signals being CDM multiplexed or FDM multiplexed or both, peak power and zero power on Rx side can be randomized thus reducing power fluctuations, meanwhile orthogonality between multiplexed RS signals can be preserved.

(The Seventh Embodiment)

Fig.17(a) and 17(b) show a case of CSI-RS being CDM and FDM multiplexed according to the seventh embodiment of the present disclosure. The present embodiment is to apply the concept of the fourth embodiment (Fig.14) to the case of the third embodiment (Fig.13(a)), as shown in Fig.17(a). That is, for CDM and FDM multiplexed CSI-RS case, the mappings of sequences are based on different mapping functions between adjacent symbols. Specifically, in Fig.17(a), CSI-RS ports 0 and 1 are CDM multiplexed on the same sub-carrier F1 by assigning OCC [1 , 1 ] and [1 , -1 ] respectively. They occupy two symbols T1 and T2 on the time domain. Similarly, CSI-RS ports 4 and 5 are CDM multiplexed on the same sub-carrier F2 by assigning OCC [1 , 1 ] and [1 , -1 ] respectively. They occupy the same two symbols T1 and T2 on the time domain. Accordingly, ports 0 and 4 are multiplexed with the same OCC [1 , 1 ] but on adjacent sub-carriers F1 and F2 respectively; ports 1 and 5 are multiplexed with the same OCC [1 , -1 ] but on adjacent sub-carriers F1 and F2 respectively. In the present embodiment, the sequence values [a, b] are scrambled to ports 0 and 5, and different mappings [F1 (b), F2(a)] are scrambled to ports 1 and 4, where F1 (x) and F2(x) could be the same or different functions. The CSI-RS design principle in the present embodiment is the same as those in the third embodiment. Specifically, on the CDMed (CDM multiplexed) ports, mappings are used but orthogonality should be preserved; on the FDMed (FDM multiplexed) ports with the same OCC, mappings are used; on FDMed ports with different OCCs, the same sequence values can be used and if use mappings, orthogonality between OCCs should be preserved. Fig.17(b) further shows a detailed example of Fig.17(a), where F1 (x)=x^* and F2(x)=x, that is, mappings [b^*, a] are scrambled to ports 1 and 4. But it is equivalent to set F1 (x)=x and F2(x)=x^*, that is, mappings [b, a^*] are scrambled to ports 1 and 4. According to the present embodiment, by applying sequence mappings to OCCs assigned to RS signals being CDM multiplexed or FDM multiplexed or both, peak power and zero power on Rx side can be randomized thus reducing power fluctuations, meanwhile orthogonality between multiplexed RS signals can be preserved. (The Eighth Embodiment)

In Fig.4(b), it is seen that CSI-RSs of different transmission points can be allocated in the same OFDM symbols. The sequences scrambled to the CSI-RS signals, i.e, [Ai] and [Bi] in Fig.4(b) is initialized by the cell ID. When different transmission points have different cell IDs, the sequences scrambled to CSI-RS signals of different transmission points are different from each other. But it is possible that different transmission points have the same cell ID. In this case, the sequences [Ai] and [Bi] for CSI-RSs of different transmission points are all the same. That is, if the different transmission points have the same cell ID, the sequence such as [a, b] (i.e, [Ai] and [Bi] in Fig.4(b)) is the same for all the different transmission points. Then, if there is power unbalance for one transmission point, such unbalance will be accumulated for all transmission points.

The solution as described in foregoing embodiments is also applied to this case. That is, different mapping patterns are used for different CSI-RS patterns. These different CSI- RS patterns could be CSI-RSs from different transmission points or could be CSI-RSs of the same transmission point but in different radio resource such as sub-carriers. Fig.18 shows an example of multiplexed CSI-RSs of different transmission points with the same cell ID according to the eighth embodiment of the present disclosure. In Fig.18, there are shown three modes 1 , 2, 3 corresponding to three transmission points 1 , 2, 3 respectively. It is assumed that sequences for OCC [1 , 1 ] of the three modes are all [A1 , B1 ], which means three transmission points have the same cell ID. The concept of the fourth embodiment (Fig.14) is applied to three modes respectively, that is, the sequence mappings for OCC [1,-1] of these three transmission points are [F11 (B1), F12(A1)], [F21(B1), F22(A1)] and [F31(B1), F32(A1)] respectively.

Specifically, for mode 1 (transmission point 1), the sequence value A1 is multiplied with the first part "1" of OCC [1, 1], the sequence value B1 is multiplied with the second part "1" of OCC [1, 1], the sequence mapping F11(B1) of the sequence value B1 is multiplied with the first part "1" of OCC [1, -1], and the sequence mapping F12(A1) of the sequence value A1 is multiplied with the second part "-1 " of OCC [1 , -1 ]. For mode 2 (transmission point 2), the sequence value A1 is multiplied with the first part "1" of OCC [1, 1], the sequence value B1 is multiplied with the second part "1" of OCC [1, 1], the sequence mapping F21(B1) of the sequence value B1 is multiplied with the first part "1" of OCC [1, -1], and the sequence mapping F22(A1) of the sequence value A1 is multiplied with the second part "-Γ of OCC [1, -1]. For mode 3 (transmission point 3), the sequence value A1 is multiplied with the first part "1" of OCC [1, 1], the sequence value B1 is multiplied with the second part "1" of OCC [1, 1], the sequence mapping F31(B1) of the sequence value B1 is multiplied with the first part "1" of OCC [1, -1], and the sequence mapping F32(A1) of the sequence value A1 is multiplied with the second part of OCC [1, -1]. The design principle in the present embodiment should follow:

(1) for one transmission point, the orthogonality between OCC [1,1] and [1,-1] should be preserved;

(2) for different transmission points, different mappings on OCC [1,-1] should have the ability to randomize the peak power among CSI-RS of different patterns.

Although there are three transmission points shown in the present disclosure, the number of transmission points is not limited to three and can be expanded to any other numbers, such as four as shown in Fig.19(b) in the ninth embodiment, for which the present disclosure is also applicable. Therefore, in the present embodiment, such a signal multiplexing method of

multiplexing a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources, wherein the plurality of layers of signals including N groups which are sent from different transmission points respectively, and each group including two layers wherein N is an integer larger than 1 , may be performed. The method may comprises the following steps: multiplying the first layer of each of N groups of signals by a first orthogonal cover code (OCC) [1 , 1 ] and multiplying the second layer of each of N groups of signals by a second OCC [1 , -1 ], wherein each of OCCs is divided into two parts; and multiplying the first part "1 " and the second part "1 " of the first OCC [1 , 1 ] multiplied with the first layer of each of N groups of signals respectively by two sequence values [a, b], multiplying the first part "1 " and the second part "- of the second OCC [1 , -1 ] multiplied with the second layer of each of N groups of signals respectively by different mappings of the two sequence values.

In addition, although it is not shown herein, the present disclosure can provide a device for multiplexing a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources wherein the plurality of layers of signals including N groups each including two layers wherein N is an integer larger than 1 . The device may comprises: a multiplexing unit for multiplying the first layer of each of N groups of signals by a first orthogonal cover code (OCC) such as [1 , 1 ] and multiplying the second layer of each of N groups of signals by a second OCC such as [1 , -1 ], wherein each of OCCs is divided into two parts; and a orthogonalizing unit for multiplying the first part and the second part of the first OCC multiplied with the first layer of each of N groups of signals respectively by two sequence values [a, b], multiplying the first part and the second part of the second OCC multiplied with the second layer of each of N groups of signals respectively by different mappings of the two sequence values. According to the present disclosure, for i-th group of signals, the first part of the second OCC is multiplied with a mapping function Fi1 (b), and the second part of the second OCC is multiplied with a mapping function Fi2(a), where 1≤i≤N. On the following, it will further give three examples on how to choose different mappings regarding different CSI-RS patterns (corresponding to different transmission points).

(The Ninth Embodiment)

Figs.19(a) and 19(b) show a case of multiplexed CSI-RSs of different transmission points with the same cell ID according to the ninth embodiment of the present disclosure. This embodiment is to use the combination of the fifth embodiment (Fig.15) and the sixth embodiment (Fig.16) to the eighth embodiment (Fig.18). Fig.19(a) shows the details of CSI-RS design for a single CSI-RS pattern case. In Fig.19(a), the sequence values [A1 , B1 ] are scrambled to OCC [1 , 1 ] and mappings [exp(j9)B1^*, exp(j9)A1 ] are scrambled to OCC [1 , -1 ]. Specifically, the sequence value A1 is multiplied with the first part "1" of OCC [1 , 1 ], the sequence value B1 is multiplied with the second part "1" of OCC [1 , 1 ], the mapping exp(j9)B1^* of the sequence value B1 is multiplied with the first part "1" of OCC [1 , -1 ], and the mapping expG9)A1 of the sequence value A1 is multiplied with the second part "-1 " of OCC [1 , -1 ].

In Fig.19(a), R1 and R2 are respectively Rx signals on two symbols at Rx side (such as UE 800), and H1 and H2 indicate respectively channel vectors corresponding to different CSI-RS ports which are assigned with different OCCs [1 , 1 ] and [1 , -1 ] respectively. According to the calculation in Fig.19(a), if sequences are all selected from QPSK alphabet, the orthogonality is always preserved. With the similar analysis as before, it can be seen that the best angle Θ should be ττ/4+ηττ/2, where n is an integer.

Here, if using general model in Fig.14 or the fourth embodiment, F1 (x)=exp(j9)x^* and F2(x)=expG9)x. It is equivalent to set F1 (x)=expG9)x and F2(x)=expG9)x^*, that is, the mapping expG9)B1 of the sequence value B1 is multiplied with the first part "1" of OCC [1 , -1 ], and the mapping expG9)A1^* of the sequence value A1 is multiplied with the second part of OCC [1 , -1 ]. There are multiple combinations between values of Θ and the conjugate operation " ^* ". Fig.19(b) shows how to apply these multiple combinations to multiple CSI-RS patterns. Fig.19(b) gives four different combinations for four CSI-RS patterns. In Fig.19(b), there are shown four modes 1 , 2, 3, 4 corresponding to four transmission points 1 , 2, 3, 4 respectively. It is assumed that sequences for OCC [1 , 1 ] of the four modes are all [A1 , B1 ], which means the four transmission points have the same cell ID. Different mappings by different combinations of Θ and the conjugate operation " ^* " are scrambled to OCC [1 , -1 ] of the four modes respectively.

Specifically, for mode 1 (transmission point 1 ), the sequence value A1 is multiplied with the first part "1 " of OCC [1 , 1 ], the sequence value B1 is multiplied with the second part "1" of OCC [1 , 1 ], the sequence mapping exp(jTr/4)B1^* of the sequence value B1 is multiplied with the first part "1 " of OCC [1 , -1 ], and the sequence mapping expGTr/4)A1 of the sequence value A1 is multiplied with the second part "-Γ of OCC [1 , -1 ]. For mode 2 (transmission point 2), the sequence value A1 is multiplied with the first part "1 " of OCC [1 , 1 ], the sequence value B1 is multiplied with the second part "1 " of OCC [1 , 1 ], the sequence mapping expG5Tr/4)B1^* of the sequence value B1 is multiplied with the first part "1" of OCC [1 , -1 ], and the sequence mapping exp(j5Ti74)A1 of the sequence value A1 is multiplied with the second part of OCC [1 , -1 ]. For mode 3 (transmission point 3), the sequence value A1 is multiplied with the first part "1 " of OCC [1 , 1 ], the sequence value B1 is multiplied with the second part "1" of OCC [1 , 1 ], the sequence mapping expG3Tr/4)B1 of the sequence value B1 is multiplied with the first part "1" of OCC [1 , -1 ], and the sequence mapping expG3Tr/4)A1 ^* of the sequence value A1 is multiplied with the second part "-Γ of OCC [1 , -1 ]. For mode 4 (transmission point 4), the sequence value A1 is multiplied with the first part "1 " of OCC [1 , 1 ], the sequence value B1 is multiplied with the second part "1 " of OCC [1 , 1 ], the sequence mapping expG7Ti74)B1 of the sequence value B1 is multiplied with the first part "1" of OCC [1 , -1 ], and the sequence mapping exp(j7Ti74)A1 ^* of the sequence value A1 is multiplied with the second part "-1 " of OCC [1 , -1 ].

If using the form of F(x), the sequence mappings for OCC [1 ,-1 ] of these four transmission points in Fig.19(b) can be expressed as [F11 (B1 ), F12(A1 )], [F21 (B1 ), F22(A1 )], [F31 (B1 ), F32(A1 )] and [F41 (B1 ), F42(A1 )] respectively, where F11 (x)=exp(j91 )x^*, F12(x)=expG91 )x, F21 (x)=expG92)x^*, F22(x)=exp(j92)x, F31 (x)=exp(j91 )x, F32(x)=expG91 )x^*, F41 (x)=exp(j92)x, F42(x)=exp(j92)x^*, and here Θ1 =ττ74, Θ2=5ττ74. Of course, by changing Θ, such as θ=3ττ/4, 7ττ/4, there will be more options.

It is noted that the idea itself is not restricted to select Θ1 and Θ2 inside the set {ττ/4, 3ττ/4, 5TT/4, 7TT/4}. But multiple of ττ/4 is best for balancing the power. According to the present embodiment, by applying sequence mappings to OCCs assigned to RS signals being CDM multiplexed or FDM multiplexed or both, peak power and zero power on Rx side can be randomized thus reducing power fluctuations, meanwhile orthogonality between multiplexed RS signals can be preserved. (The Tenth Embodiment)

Fig.20 shows an example of multiplexed CSI-RSs of different transmission points with the same cell ID according to the tenth embodiment of the present disclosure. The present embodiment is to apply the combination of the second embodiment (Fig.9(a)) and the fifth embodiment (Fig.15) to the case of multiple CSI-RS patterns or multiple transmission points. In Fig.20, there are shown three modes 1 , 2, 3 corresponding to three transmission points 1 , 2, 3 respectively. It is assumed that sequences for OCC [1,1] of the three modes are all [A1, B1], which means three transmission points have the same cell ID. Different mappings of sequence values [A1, B1] are scrambled to OCC [1,-1] of the three modes respectively. Specifically, for mode 1 (transmission point 1), the sequence value A1 is multiplied with the first part "1" of OCC [1, 1], the sequence value B1 is multiplied with the second part "1" of OCC [1, 1], the sequence mapping B1^* of the sequence value B1 is multiplied with the first part "1" of OCC [1, -1], and the sequence mapping A1^* of the sequence value A1 is multiplied with the second part of OCC [1, -1]. For mode 2 (transmission point 2), the sequence value A1 is multiplied with the first part "1" of OCC [1, 1], the sequence value B1 is multiplied with the second part "1" of OCC [1, 1], the sequence mapping B1^* of the sequence value B1 is multiplied with the first part "1" of OCC [1, -1], and the sequence mapping A1 of the sequence value A1 is multiplied with the second part "-Γ of OCC [1, -1]. For mode 3 (transmission point 3), the sequence value A1 is multiplied with the first part "1" of OCC [1, 1], the sequence value B1 is multiplied with the second part "1" of OCC [1, 1], the sequence mapping B1 of the sequence value B1 is multiplied with the first part "1" of OCC [1, -1], and the sequence mapping A1^* of the sequence value A1 is multiplied with the second part "-1 " of OCC [1 , -1 ]. If using the form of F(x), the sequence mappings for OCC [1,-1] of these three transmission points in Fig.20 can be expressed as [F11(B1), F12(A1)], [F21(B1), F22(A1)] and [F31(B1), F32(A1)] respectively, where F11(x)=F12(x)=x^*, F21(x)=x^*, F22(x)=x, F31(x)=x, F32(x)=x^*. By the similar analysis as before, total Rx power P1 and P2 on two adjacent symbols, on which CSI-RS signals from the three transmission points are multiplexed, received on the Rx side (such as UE 800) is calculated respectively by taking four general cases as four examples, that is, example 1 (A1=1+j, B1=1+j, A1^*B1^*=-j), example 2 ( A 1 = 1 -j , B1=1+j, A1^*B1^*=1), example 3 (A1=1-j, B1=1-j, A1^*B1^*=j) and example 4 (A1=-1+j, B1=1+j, A1^*B1^*=-1). By the calculation, the result is obtained that P1=8 and P2=8 for example 1, P1=10 and P2=2 for example 2, P1=8 and P2=4 for example 3, and P1=2 and P2=10 for example 4. From the result of calculation, it can be seen that the worst case that one of two adjacent symbols has zero power after accumulation of multiple CSI-RSs has been avoided. According to the present embodiment, by applying sequence mappings to OCCs assigned to RS signals being CDM multiplexed or FDM multiplexed or both, peak power and zero power on Rx side can be randomized thus reducing power fluctuations, meanwhile orthogonality between multiplexed RS signals can be preserved. (The Eleventh Embodiment)

Fig.21 shows an example of multiplexed CSI-RSs of different transmission points with the same cell ID according to the eleventh embodiment of the present disclosure. The present embodiment is to further apply partial rotation of ττ/4 to the tenth embodiment (Fig.20) for the case of multiple CSI-RS patterns or multiple transmission points. In Fig.21 , there are shown three modes 1 , 2, 3 corresponding to three transmission points 1 , 2, 3 respectively. It is assumed that sequences for OCC [1 , 1 ] of the three modes are all [A1 , B1 ], which means three transmission points have the same cell ID. Different mappings of sequence values [A1 , B1 ] are scrambled to OCC [1 , -1 ] of the three modes respectively.

Specifically, for mode 1 (transmission point 1 ), the sequence value A1 is multiplied with the first part "1 " of OCC [1 , 1 ], the sequence value B1 is multiplied with the second part "1" of OCC [1 , 1 ], the sequence mapping B1^* of the sequence value B1 is multiplied with the first part "1 " of OCC [1 , -1 ], and the sequence mapping A1^* of the sequence value A1 is multiplied with the second part of OCC [1 , -1 ]. For mode 2 (transmission point 2), the sequence value A1 is multiplied with the first part "1 " of OCC [1 , 1 ], the sequence value B1 is multiplied with the second part "1" of OCC [1 , 1 ], the sequence mapping expGTr/4)B1 ^* of the sequence value B1 is multiplied with the first part "1" of OCC [1 , -1 ], and the sequence mapping A1 of the sequence value A1 is multiplied with the second part "-Γ of OCC [1 , -1 ]. For mode 3 (transmission point 3), the sequence value A1 is multiplied with the first part "1 " of OCC [1 , 1 ], the sequence value B1 is multiplied with the second part "1 " of OCC [1 , 1 ], the sequence mapping B1 of the sequence value B1 is multiplied with the first part "1 " of OCC [1 , -1 ], and the sequence mapping expGTr/4)A1^* of the sequence value A1 is multiplied with the second part "-Γ of OCC [1 , -1 ].

If using the form of F(x), the sequence mappings for OCC [1 ,-1 ] of these three transmission points in Fig.21 can be expressed as [F11 (B1 ), F12(A1 )], [F21 (B1 ), F22(A1 )] and [F31 (B1 ), F32(A1 )] respectively, where F11 (x)=F12(x)=x^*. F21

By the similar analysis as before, total Rx power P1 and P2 on two adjacent symbols, on which CSI-RS signals from the three transmission points are multiplexed, received on the Rx side (such as UE 800) is calculated respectively by taking four general cases as four examples, that is, example 1 (A1 =1+j, B1 =1+j, A1^*B1^*=-j), example 2 ( A 1 = 1 -j , B1 =1+j, A1^*B1^*=1 ), example 3 (A1 =1 -j, B1 =1 -j, A1^*B1^*=j) and example 4 (A1 =-1 +j, B1 =1+j, A1 ^*B1 ^*=-1 ). By the calculation, the result is obtained that P1=8+2sin(Tr/4) and P2=8-2sin(TT/4) for example 1 , P1=8+2COS(TT/4) and P2=4-2COS(TT/4) for example 2, P1 =8-2sin(TT/4) and P2=4+2sin(Ti74) for example 3, and P1=4-2COS(TT/4) and P2=8+2COS(TT/4) for example 4. From the result of calculation, it can be seen that, compared with the tenth embodiment in which there is still severe power fluctuation on the two adjacent symbols when A1^*B1^* is 1 or -1 (example 2 or 4), peak power fluctuation is further reduced by partially rotating ττ/4 in the present embodiment. Thus, the present embodiment is the improvement to the tenth embodiment. It is noted that the idea itself is not restricted to select rotating angle as ττ/4. But ττ/4 is best for balancing the power.

According to the present embodiment, by applying sequence mappings to OCCs assigned to RS signals being CDM multiplexed or FDM multiplexed or both, peak power and zero power on Rx side can be randomized thus reducing power fluctuations, meanwhile orthogonality between multiplexed RS signals can be preserved. (The Twelfth Embodiment)

Fig.22 shows an example of multiplexed CSI-RSs of different transmission points with different cell IDs according to the Twelfth embodiment of the present disclosure.

Fig.18~Fig 21 all assume that different transmission points with the same celljd. In fact, the ideas in Fig.18~Fig 21 can be extended to transmission points with different celljd case. Fig.22 gives such extension to Fig. 18. The difference between Fig 18 and Fig. 22 is that Fig. 22 utilizes different sequences for different transmission points because these transmission points use different celljd. That is, if the different transmission points have different cell IDs, the sequence such as [a, b] is different for the different transmission points. The mappings (including the functions used in mapping) in Fig. 18 and Fig.22 are the same. In Fig.22, there are shown three modes 1 , 2, 3 corresponding to three transmission points 1 , 2, 3 respectively. It is assumed that sequences for OCC [1 , 1] of the three modes are [A11 , B11 ], [A21 , B21 ], [A31 , B31], which means three transmission points have different cell IDs. The idea of the eighth embodiment (Fig.18) is applied to three modes of the present embodiment respectively, that is, the sequence mappings for OCC [1 ,-1 ] of these three transmission points are [F11 (B11 ), F12(A11 )], [F21 (B21 ), F22(A21 )] and [F31 (B31 ), F32(A31 )] respectively.

Specifically, for mode 1 (transmission point 1 ), the sequence value A11 is multiplied with the first part "1" of OCC [1 , 1 ], the sequence value B11 is multiplied with the second part "1" of OCC [1 , 1 ], the sequence mapping F11 (B11 ) of the sequence value B11 is multiplied with the first part "1 " of OCC [1 , -1 ], and the sequence mapping F12(A11 ) of the sequence value A11 is multiplied with the second part "-Γ of OCC [1 , -1 ]. For mode 2 (transmission point 2), the sequence value A21 is multiplied with the first part "1 " of OCC [1 , 1 ], the sequence value B21 is multiplied with the second part "1 " of OCC [1 , 1 ], the sequence mapping F21 (B21 ) of the sequence value B21 is multiplied with the first part "1 " of OCC [1 , -1 ], and the sequence mapping F22(A21 ) of the sequence value A21 is multiplied with the second part "-Γ of OCC [1 , -1 ]. For mode 3 (transmission point 3), the sequence value A31 is multiplied with the first part "1" of OCC [1 , 1 ], the sequence value B31 is multiplied with the second part "1" of OCC [1 , 1 ], the sequence mapping F31 (B31 ) of the sequence value B31 is multiplied with the first part "1" of OCC [1 , -1 ], and the sequence mapping F32(A31 ) of the sequence value A31 is multiplied with the second part of OCC [1 , -1 ].

With Fig.22, Fig.19~Fig.21 can also be extended to different celljd case without changing the mapping and corresponding functions.

Although there are three transmission points shown in the present disclosure, the number of transmission points is not limited to three and can be expanded to any other numbers, for which the present disclosure is also applicable. According to the present embodiment, by applying sequence mappings to OCCs assigned to RS signals being CDM multiplexed or FDM multiplexed or both, peak power and zero power on Rx side can be randomized thus reducing power fluctuations, meanwhile orthogonality between multiplexed RS signals can be preserved. (The Thirteenth Embodiment)

Previous embodiments discuss how to design different mapping patterns for reference signal. This embodiment will discuss how to configure these mapping patterns to the user equipments. Fig.23(a) and 23(b) show a case of multiplexed CSI-RSs of different transmission points according to the thirteenth embodiment of the present disclosure. In Fig. 23(a), there are two transmission points' CSI-RS which needs the user equipments to measure the CSI-RS power by assuming there are total eight modes of CSI-RS mapping patterns. In Fig.23(b), from less power fluctuation perspective, the rotation angles for the two transmission points' CSI-RS should have 180 degrees (ττ) phase offset, and partial conjugate should be alternatively assigned to these two points' CSI-RS. In this sense, the potential CSI-RS mapping assignments could be either of the following: {model & 2}^ point 1 & 2; {mode3 & 4}^ point 1 & 2; {mode5 & 6}^ point 1 & 2; {mode7 & 8}^ point 1 & 2.

From this assignment strategy, we can find the total 8 CSI-RS mapping patterns can be divided into 4 subsets or groups, then inform the user equipment on which subset or group is used is fine. If directly informing the user equipment about which mode in Fig.23(b) is used, then 3 bits for each point's CSI-RS is required, for example:

000-»mode1 , 001 ^mode2, 010^mode3, 01 1 ^mode4, 100^mode5, 101 ^mode6, 1 10^mode7, 1 1 1 ^mode8. If just informing the user equipment about which subset is used, then 2 bits for each point's CSI-RS is required, for example: OO^subset 1={mode 1 &2}; 01 -^subset 2={mode 3 & 4}; 10^subset 3={mode 5 & 6}; 1 1 -^subset 4={mode 7 & 8}.

In this case, 1 bit overhead is reduced for each point's CSI-RS configuration. In the subset, the exact mode can be determined by the exact position of CSI-RS, such as using the starting sub-carrier index of each resource block. For example, when points 1 and 2 in Fig.23(a) are both configured to subset 1 , the point 1 uses mode 1 and the point 2 uses mode 2, which is decided by their sub-carrier index. Specifically, a signal multiplexing method of multiplexing signals such as CSI-RS assigned on predetermined radio resource of resource blocks is provided according to the present embodiment. In the embodiment, different signals such as CSI-RSs which are located on different radio resources are sent from different transmission points respectively, such as transmission point 1 and transmission point 2 as shown in Fig.23(a). The signals such as CSI-RS correspond to a plurality of multiplexing patterns such as modes 1-8, and the modes 1-8 can be divided into N subsets, here N can be any integer number more than 1. such as 4, as shown in Fgi.23(b). The signal multiplexing method according to the present embodiment may comprise steps of informing a user equipment of index of a subset to be used by the user equipment, and multiplexing the signals of the different transmission points with the multiplexing patterns belong to the informed subset.

In the present embodiment, the signals may be transmitted on two layers, so the method according to the present embodiment may further comprise steps of multiplying the first layer of signals by a first orthogonal cover code (OCC) [1 , 1 ], and multiplying the second layer of signals by a second OCC [1 , -1 ], wherein each of OCCs contains two parts; and multiplying the first part [1 ] and the second part [1 ] of the first OCC respectively by sequence values [a, b] of the multiplexing pattern belong to the informed subset, multiplying the first part [1 ] and the second part [-1 ] of the second OCC respectively by different mappings of the sequence values [a, b] of the

multiplexing pattern belong to the informed subset.

Specifically, the signal multiplexing method according to the present embodiment may further comprise steps of: multiplying the first part [1 ] of the first OCC by a first sequence value a; multiplying the second part [1 ] of the first OCC by a second sequence value b; multiplying the first part [1 ] of the second OCC by a mapping of the second sequence value b, which is based on a mapping function F1 (x); and multiplying the second part [-1 ] of the second OCC by a mapping of the first sequence value a, which is based on a mapping function F2(x). More specifically, for the signal multiplexing method according to the present embodiment, in a first multiplexing pattern belong to the informed subset,

F1 (b)=expG91 )b*, F2(a)=exp(j91 )a, and in a second multiplexing pattern belong to the informed subset, F1 (b)=expG92)b, F2(a)=exp(j92)a*, where Θ1 -Θ2=ττ, and " ^*" indicate the conjugate. As shown in Fig.23(b), a=A1 , and b=B1. For example, in the mode 1 of the first subset, F1 (B1 )=exp(jTT/4)B1*, F2(A1 )=exp(jTi74)A1 , and in the mode 2 of the first subset, F1 (B1 )=exp(j5TT/4)B1 , F2(A1 )=exp(j5TT/4)A1*, where Θ1 -Θ2=ττ. In the mode 5 of the third subset, F1 (B1

, and in the mode 6 of the third subset, F1 (B1

, F2(A1 )=expG7/4)A1*, where Θ1 -Θ2=π.

More specifically, for the signal multiplexing method according to the present embodiment, in a first multiplexing pattern belong to the informed subset,

F1 (b)=expG91 )b, F2(a)=exp(j91 )a*, and in a second multiplexing pattern belong to the informed subset, F1 (b)=expG92)b*, F2(a)=exp(j92)a, where Θ1 -Θ2=ττ, and " ^* " indicate the conjugate. As shown in Fig.23(b), a=A1 , and b=B1. For example, In the mode 3 of the second subset, F1 (B1 )=expG"n74)B1 , F2(A1 )=expG"n74)A1*, and in the mode 4 of the second subset, F1 (B1 )=expG5Tr/4)B1*, F2(A1

, where Θ1 -Θ2=ττ. In the mode 7 of the fourth subset, F1 (B1 )=expG3Tr/4)B1 , F2(A1 , and in the mode 8 of the fourth subset, F1 (B1 )=expG7Tr/4)B1*, F2(A

, where Θ1 - Θ2=π. The above description considers dividing 8 modes into 4 subsets. In fact, it is also possible that dividing 8 modes into 2 subsets, such as subset 1={mode 1 , 2, 5, 6} and subset 2= {mode 3, 4, 7, 8}. The exact mode in each subset is decided by the frequency location of CSI-RS. It is noted that in each subset, four possible phase values, i.e { ττ/4, 3ττ/4, 5ττ/4, 7ττ/4 } are all used. On practice, the way of subset partition is also possible to configure. For example, on broadcasting channel (BCH), to inform all UEs on subset partition: dividing 8 modes into 2 subsets or dividing 8 modes into 4 subsets.

According to the present embodiment, the Θ1 and Θ2 may be ηττ/4, where n is an integer number. And, the first and second OCCs are orthogonal Walsh Codes, wherein the first OCC is [1 , 1 ], the second OCC is [1 , -1 ], and they are assigned to the same radio resource of the resource block.

According to the present embodiment, the above steps can be executed by any one or more of the multiplexing unit 601 , the orthogonalizing unit 602, and the transceiver unit 603 of the transmission point device 600, or by any one or more of the transceiver unit 801 and the demodulation unit 802 of the user equipment 800.

Therefore, in the present embodiment, the multiple reference signal mapping patterns can be divided into some subsets, and on mapping patterns configurations, only inform the user equipment on which subset is used. The exact pattern in each subset may be connected to other parameters of the reference signals (these parameters are necessary information for the reference signal and are also known to the user equipment), such as frequency domain position (sub-carrier index) of CSI-RS or SCID of DMRS. The way of subset partition is also configurable to UE. Firstly, the user equipments are informed of how to partition the subset, then the user equipments are informed of which subset will be used.

The advantage of dividing all mapping patterns into subsets according to the present embodiment is that the signaling (inform the user equipment of mapping pattern) overhead is reduced.

(The Fourteenth Embodiment)

As shown in Fig.24, the wireless communication method according to the seventh embodiment of the present disclosure is used for transmitting to user equipment (UE) a plurality of layers of RS signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources. In the step S2401 , the plurality of layers of RS signals are multiplied selectively by one of the first and second orthogonal cover codes (OCCs) each of which is divided into two parts. In the step S2402, the first part and the second part of one of the first and the second OCCs are multiplied respectively by two sequence values, and the first part and the second part of the other OCC are multiplied respectively by mappings of the two sequence values. In the step S2403, the plurality of layers of resource blocks obtained from the step 2402 is transmitted to the at least one UE.

According to the present embodiment, the above step S2401 can be executed by the multiplexing unit 601 , the above step S2402 can be executed by the orthogonalizing unit 602, and the above step S2403 can be executed by the transceiver unit 603.

According to the present disclosure, in step S2402, the first part of the first OOC is multiplied by a first sequence value, the second part of the first OCC is multiplied by a second sequence value, the first part of the second OCC is multiplied by a mapping of the second sequence value which is based on a mapping function F1 (x), and the second part of the second OCC is multiplied by a mapping of the first sequence value which is based on a mapping function F2(x).

According to the present disclosure, F1 (x)=F2(x)=F(x).

According to the present disclosure, F(x)=x^* where " ^* " indicate the conjugate of x.

According to the present disclosure, F1 (x)=x^* and F2(x)=x, or F1 (x)=x and F2(x)=x^*. According to the present disclosure, F1 (x)=expG91 )x and F2(x)=expG92)x, where Θ1 - Θ2≠ηττ72, where n is a integer number.

According to the present disclosure, the first and second OCCs are orthogonal Walsh Codes, wherein the first OCC is [1 , 1 ], the second OCC is [1 , -1 ], and they may be assigned to the same radio resource.

According to the present disclosure, the first and second OCCs are orthogonal Walsh Codes, wherein the first OCC and the second OCC are selectively one of [1 , 1 ] and [1 , - 1 ], and they may be assigned to different radio resources. According to the present disclosure, the first and second sequence values are selected from the QPSK alphabet, and are initialized by random seeds, wherein the first and second sequence values are initialized by different seeds. According to the present disclosure, the signals are reference signals such as DMRS or CSI-RS.

The above embodiments of the present disclosure are only exemplary description, and their specific structures and operations do not limit the scope of the disclosure. Those skilled in the art can combine different parts and operations in the above respective embodiments to produce new implementations which equally accord with the concept of the present disclosure.

The embodiments of the present disclosure may be implemented by hardware, software and firmware or in a combination thereof, and the way of implementation thereof does not limit the scope of the present disclosure.

The connection relationships between respective functional elements (units) in the embodiments of the present disclosure do not limit the scope of the present disclosure, in which one or multiple functional element(s) or unit(s) may contain or be connected to any other functional elements.

Although several embodiments of the present disclosure has been shown and described in combination with attached drawings as above, those skilled in the art should understand that variations and modifications which still fall into the scope of claims and their equivalents of the present disclosure can be made to the embodiments without departing from the principle and spirit of the disclosure.

Claims

CLAIMS WHAT IS CLAIMED IS:

1 . A communication method of transmitting to user equipment a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources, comprising the steps of:

multiplying the plurality of layers of signals selectively by one of a first and a second orthogonal cover codes (OCCs) each of which contains two parts;

multiplying a first part and a second part of one of the first and the second OCCs respectively by two sequence values, and multiplying a first part and a second part of the other OCC respectively by mappings of the two sequence values; and

transmitting the plurality of layers of resource blocks obtained from the orthogonalizing step to the user equipment.

2. The communication method according to claim 1 , further comprising steps of multiplying the first part of the first OCC by a first sequence value, multiplying the second part of the first OCC by a second sequence value, multiplying the first part of the second OCC by a mapping of the second sequence value which is based on a mapping function F1 (x), and multiplying the second part of the second OCC by a mapping of the first sequence value which is based on a mapping function F2(x).

3. The communication method according to claim 2, wherein F1 (x)=F2(x)=F(x).

4. The communication method according to claim 3, wherein F(x)=x^*, where " ^* " indicate the conjugate of x.

5. The communication method according to claim 2, wherein F1 (x)=x^* and F2(x)=x, or F1 (x)=x and F2(x)=x^*, where " ^* " indicate the conjugate of x.

6. The communication method according to claim 2, wherein F1 (x)=expG91 )x,

F2(x)=expG92)x, where Θ1 -Θ2≠ηττ72, where n is a integer number.

7. The communication method according to claim 2, wherein the first and second OCCs are orthogonal Walsh Codes, wherein the first OCC is [1 , 1 ], the second OCC is [1 , -1 ], and they are assigned to the same radio resource.

8. The communication method according to claim 2, wherein the first and second sequence values and the mappings of the first and second sequence values are assigned to different radio resources.

9. The communication method according to claim 2, wherein the first and second sequence values are selected from the QPSK alphabet, and are initialized by random seeds, wherein the first and second sequences are initialized by different seeds.

10. The communication method according to claim 1 , wherein the signals are reference signals.

1 1. The communication method according to claim 1 , wherein the reference signals are DMRS or CSI-RS.

12. A transmission point device for transmitting to user equipment a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources, comprising:

a multiplexing unit configured to multiply the plurality of layers of signals selectively by one of a first and a second orthogonal cover codes (OCCs) each of which contains two parts;

an orthogonalizing unit configured to multiply a first part and a second part of one of the first and the second OCCs respectively by two sequence values, and multiply a first part and a second part of the other OCC respectively by mappings of the two sequence values; and

a transceiver unit configured to transmit the plurality of layers of resource blocks obtained from the orthogonalizing unit to the user equipment.

13. The transmission point device according to claim 12, the orthogonalizing unit further multiplies the first part of the first OOC by a first sequence value, multiplies the second part of the first OCC by a second sequence value, multiplies the first part of the second OCC by a mapping of the second sequence value which is based on a mapping function F1 (x), and multiplies the second part of the second OCC by a mapping of the first sequence value which is based on a mapping function F2(x).

14. The transmission point device according to claim 13, wherein F1 (x)=F2(x)=F(x).

15. The transmission point device according to claim 14, wherein F(x)=x^* , where " ^* " indicate the conjugate of x.

16. The transmission point device according to claim 13, wherein F1 (x)=x^* , F2(x)=x, or F1 (x)=x, F2(x)=x^*.

17. The transmission point device according to claim 13, wherein F1 (x)=expG91 )x and F2(x)=expG92)x, where Θ1 -Θ2≠ηττ72, where n is a integer number.

18. The transmission point device according to claim 13, wherein the first and second OCCs are orthogonal Walsh Codes, wherein the first OCC is [1 , 1 ], the second OCC is [1 , -1 ], and they are assigned to the same radio resource.

19. The transmission point device according to claim 13, wherein the first and second sequence values and the mappings of the first and second sequence values are assigned to different radio resources.

20. The transmission point device according to claim 13, wherein the first and second sequence values are selected from the QPSK alphabet, and are initialized by random seeds, wherein the first and second sequences are initialized by different seeds.

21. The transmission point device according to claim 12, wherein the signals are reference signals.

22. A user equipment for receiving from a transmission point a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources, comprising:

a transceiver unit configured to receive the plurality of layers of resource blocks; and

a demodulation unit configured to detect the plurality of layers of resource blocks in time domain and/or frequency domain to obtain the plurality of layers of signals, wherein, the plurality of layers of signals are multiplied selectively by one of a first and a second orthogonal cover codes (OCCs) each of which contains two parts, and a first part and a second part of one of the first and the second OCCs are multiplied respectively by two sequence values, and a first part and a second part of the other OCC are multiplied respectively by mappings of the two sequence values.

23. The user equipment according to claim 22, wherein the first part of the first OOC is multiplied by a first sequence value, the second part of the first OCC is multiplied by a second sequence value, the first part of the second OCC is multiplied by a mapping of the second sequence value which is based on a mapping function F1 (x), and the second part of the second OCC is multiplied by a mapping of the first sequence value which is based on a mapping function F2(x).

24. The user equipment according to claim 23, wherein F1 (x)=F2(x)=F(x).

25. The user equipment according to claim 24, wherein F(x)=x^* , where " ^* " indicate the conjugate of x.

26. The user equipment according to claim 23, wherein F1 (x)=x^* and F2(x)=x, or F1 (x)=x and F2(x)=x^*.

27. The user equipment according to claim 23, wherein F1 (x)=expG91 )x and

F2(x)=expG92)x, where Θ1 -Θ2≠ηττ72, where n is a integer number.

28. The user equipment according to claim 23, wherein the first and second OCCs are orthogonal Walsh Codes, wherein the first OCC is [1 , 1 ], the second OCC is [1 , -1 ], and they are assigned to the same radio resource.

29. The user equipment according to claim 23, wherein the first and second sequence values and the mappings of the first and second sequence values are assigned to different radio resources.

30. The user equipment according to claim 23, wherein the first and second sequence values are selected from the QPSK alphabet, and are initialized by random seeds, wherein the first and second sequences are initialized by different seeds.

31. The user equipment according to claim 22, wherein the signals are reference signals.

32. A signal multiplexing method of multiplexing a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources wherein the plurality of layers of signals including at least two groups each including two layers, comprising steps of:

multiplying the first layer of each of two groups of signals by a first orthogonal cover code (OCC) and multiplying the second layer of each of two groups of signals by a second OCC, wherein each of OCCs contains two parts; and

multiplying the first part and the second part of the first OCC multiplied with the first layer of the first group of signals respectively by two sequence values [a, b], multiplying the first part and the second part of the second OCC multiplied with the second layer of the second group of signals respectively by the two sequence values [a, b], multiplying the first part and the second part of the second OCC multiplied with the second layer of the first group of signals respectively by mappings of the two sequence values which are based on a mapping function f1 (x), and multiplying the first part and the second part of the first OCC multiplied with the first layer of the second group of signals respectively by mappings of the two sequence values which are based on a mapping function f2(x).

33. The signal multiplexing method according to claim 32, further comprising steps of multiplying the first part and the second part of the second OCC multiplied with the second layer of the first group of signals respectively by f 1 (b) and f1 (a), and multiplying the first part and the second part of the first OCC multiplied with the first layer of the second group of signals respectively by f2(b) and f2(a).

34. The signal multiplexing method according to claim 33, wherein f1 (x)=f2(x)=x^* , where " ^*" indicate the conjugate of x.

35. The signal multiplexing method according to claim 32, wherein the signals are reference signals, the first and second OCCs are orthogonal Walsh Codes, wherein the first OCC is [1 , 1 ], and the second OCC is [1 , -1 ], the two sequence values [a, b] are selected from the QPSK alphabet.

36. A signal multiplexing device for multiplexing a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources wherein the plurality of layers of signals including at least two groups each including two layers, comprising:

a multiplexing unit configured to multiply the first layer of each two groups of signals by a first orthogonal cover code (OCC), and multiply the second layer of each of two groups of signals by a second OCC, wherein each of OCCs contains two parts; and an orthogonalizing unit configured to multiply the first part and the second part of the first OCC multiplied with the first layer of the first group of signals respectively by two sequence values [a, b], multiplying the first part and the second part of the second

OCC multiplied with the second layer of the second group of signals respectively by the two sequence values [a, b], multiplying the first part and the second part of the second

OCC multiplied with the second layer of the first group of signals respectively by mappings of the two sequence values which are based on a mapping function f1 (x), and multiplying the first part and the second part of the first OCC multiplied with the first layer of the second group of signals respectively by mappings of the two sequence values which are based on a mapping function f2(x).

37. The signal multiplexing device according to claim 36, wherein the orthogonalizing unit multiplies the first part and the second part of the second OCC multiplied with the second layer of the first group of signals respectively by f 1 (b) and f1 (a), and multiplying the first part and the second part of the first OCC multiplied with the first layer of the second group of signals respectively by f2(b) and f2(a).

38. The signal multiplexing device according to claim 37, wherein f1 (x)=f2(x)=x^* , where " ^*" indicate the conjugate of x.

39. The signal multiplexing device according to claim 36, wherein the signals are reference signals, the first and second OCCs are orthogonal Walsh Codes, wherein the first OCC is [1 , 1 ], and the second OCC is [1 , -1 ], the two sequence values [a, b] are selected from the QPSK alphabet.

40. A signal multiplexing method of multiplexing a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources wherein the plurality of layers of signals including at least two groups each including two layers, comprising steps of:

multiplying the first part and the second part of the first OCC multiplied with the first layer of the first group of signals respectively by two sequence values [a, b], multiplying the first part and the second part of the second OCC multiplied with the second layer of the second group of signals respectively by the two sequence values [a, b], multiplying the first part and the second part of the second OCC multiplied with the second layer of the first group of signals respectively by mappings of the two sequence values which are based on mapping functions f1 (x), f2(x), and multiplying the first part and the second part of the first OCC multiplied with the first layer of the second group of signals respectively by mappings of the two sequence values which are based on mapping functions f1 (x), f2(x).

41 . The signal multiplexing method according to claim 40, further comprising steps of multiplying the first part and the second part of the second OCC multiplied with the second layer of the first group of signals respectively by f 1 (b) and f2(a), and multiplying the first part and the second part of the first OCC multiplied with the first layer of the second group of signals respectively by f1 (b) and f2(a).

42. A signal multiplexing device for multiplexing a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources wherein the plurality of layers of signals including at least two groups each including two layers, comprising:

a multiplexing unit configured to multiply the first layer of each two groups of signals by a first orthogonal cover code (OCC), and multiply the second layer of each of two groups of signals by a second OCC, wherein each of OCCs contains two parts; and an orthogonalizing unit configured to multiply the first part and the second part of the first OCC multiplied with the first layer of the first group of signals respectively by two sequence values [a, b], multiply the first part and the second part of the second OCC multiplied with the second layer of the second group of signals respectively by the two sequence values [a, b], multiply the first part and the second part of the second OCC multiplied with the second layer of the first group of signals respectively by mappings of the two sequence values which are based on mapping functions f1 (x) and f2(x), and multiply the first part and the second part of the first OCC multiplied with the first layer of the second group of signals respectively by mappings of the two sequence values which are based on mapping functions f1 (x) and f2(x).

43. The signal multiplexing device according to claim 42, wherein the orthogonalizing unit multiplies the first part and the second part of the second OCC multiplied with the second layer of the first group of signals respectively by f 1 (b) and f2(a), and multiplying the first part and the second part of the first OCC multiplied with the first layer of the second group of signals respectively by f1 (b) and f2(a).

44. A signal multiplexing method of multiplexing a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources, wherein the plurality of layers of signals including N groups, which are sent from different transmission points respectively, and each group including two layers, wherein N is an integer larger than 1 , comprising steps of: multiplying the first layer of each of N groups of signals by a first orthogonal cover code (OCC) and multiplying the second layer of each of N groups of signals by a second OCC, wherein each of OCCs contains two parts; and

multiplying the first part and the second part of the first OCC multiplied with the first layer of each of N groups of signals respectively by sequence values [a, b], multiplying the first part and the second part of the second OCC multiplied with the second layer of each of N groups of signals respectively by different mappings of the sequence values.

45. The signal multiplexing method according to claim 44, wherein if the different transmission points have the same cell ID, the sequence [a, b] is the same for all the different transmission points.

46. The signal multiplexing method according to claim 44, wherein if the different transmission points have different cell IDs, the sequence [a, b] is different for the different transmission points.

47. The signal multiplexing method according to claim 45 or 46, wherein for i-th group of signals, the first part of the second OCC is multiplied with a mapping function Fi1 (b), and the second part of the second OCC is multiplied with a mapping function Fi2(a), where 1≤i≤N.

48. The signal multiplexing method according to claim 47, wherein N=4, F11 (x)=exp(j91 )x^*, F12(x)=exp(j91 )x, F21 (x)=exp(j92)x^*, F22(x)=expG92)x,

F31 (x)=exp(j91 )x, F32(x)=expG91 )x^*, F41 (x)=exp(j92)x, F42(x)=exp(j92)x^*.

49. The signal multiplexing method according to claim 48, wherein either Θ1 or Θ2 is one of TT/4, 3ττ/4, 5ττ/4 or 7ττ/4, and Θ1≠Θ2.

50. The signal multiplexing method according to claim 47, wherein N=3, and

F1 1 (x)=F12(x)=x^*, F21 (x)=x^*, F22(x)=x, F31 (x)=x, F32(x)=x^*.

51. The signal multiplexing method according to claim 47, wherein N=3, and

F11 (x)=F12(x)=x^*, F21 (x)=exp(jTT/4)x^*, F22(x)=x, F31 (x)=x, F32(x)=exp(jTT/4)x^*.

52. The signal multiplexing method according to claim 47, wherein the signals are reference signals, the first and second OCCs are orthogonal Walsh Codes, wherein the first OCC is [1 , 1 ], and the second OCC is [1 , -1 ], the two sequence values [a, b] are selected from the QPSK alphabet.

53. A signal multiplexing device for multiplexing a plurality of layers of signals assigned on predetermined radio resource of a plurality of layers of resource blocks with the same time and frequency resources wherein the plurality of layers of signals including N groups, which are sent from different transmission points respectively, and each group including two layers wherein N is an integer larger than 1 , comprising:

a multiplexing unit configured to multiply the first layer of each of N groups of signals by a first orthogonal cover code (OCC) and multiply the second layer of each of N groups of signals by a second OCC, wherein each of OCCs contains two parts; and an orthogonalizing unit configured to multiply the first part and the second part of the first OCC multiplied with the first layer of each of N groups of signals respectively by sequence values [a, b], multiplying the first part and the second part of the second OCC multiplied with the second layer of each of N groups of signals respectively by different mappings of the sequence values.

54. The signal multiplexing device according to claim 53, wherein if the different transmission points have the same cell ID, the sequence [a, b] is the same for all the different transmission points.

55. The signal multiplexing device according to claim 53, wherein if the different transmission points have different cell IDs, the sequence [a, b] is different for the different transmission points.

56. The signal multiplexing device according to claim 54 or 55, wherein for i-th group of signals, the first part of the second OCC is multiplied with a mapping function Fi1 (b), and the second part of the second OCC is multiplied with a mapping function Fi2(a), where 1≤i≤N.

57. The signal multiplexing device according to claim 56, wherein N=4,

F1 1 (x)=exp(j91 )x^*, F12(x)=exp(j91 )x, F21 (x)=exp(j92)x^*, F22(x)=expG92)x,

F31 (x)=exp(j91 )x, F32(x)=expG91 )x^*, F41 (x)=exp(j92)x, F42(x)=exp(j92)x^*.

58. The signal multiplexing method according to claim 57, wherein either Θ1 or Θ2 is one of TT/4, 3ττ/4, 5ττ/4 or 7ττ/4, and Θ1≠Θ2.

59. The signal multiplexing device according to claim 56, wherein N=3, and

F1 1 (x)=F12(x)=x^*, F21 (x)=x^*, F22(x)=x, F31 (x)=x, F32(x)=x^*.

60. The signal multiplexing device according to claim 56, wherein N=3, and

61. The signal multiplexing device according to claim 56, wherein the signals are reference signals, the first and second OCCs are orthogonal Walsh Codes, wherein the first OCC is [1 , 1 ], and the second OCC is [1 , -1 ], the two sequence values [a, b] are selected from the QPSK alphabet.

62. A signal multiplexing method of multiplexing signals assigned on predetermined radio resource of resource blocks, wherein different signals located on different radio resources being sent from different transmission points respectively, and corresponding to a plurality of multiplexing patterns being divided into N subsets, N being an integer number more than 1 , comprising steps of:

informing a user equipment of index of a subset to be used by the user equipment; multiplexing the signals of the different transmission points with the multiplexing patterns belong to the informed subset.

63. The signal multiplexing method according to claim 62, further comprising a step of:

Informing the user equipment how to partition the plurality of multiplexing patterns into subsets.

64. The signal multiplexing method according to claim 62, wherein the exact pattern in each subset is connected to other parameters of the reference signals, which are necessary information for the reference signal and are also known to the user equipment.

65. The signal multiplexing method according to claim 64, wherein the parameters are frequency domain position of CSI-RS or SCID of DMRS.

66. The signal multiplexing method according to claim 62, wherein the signals are transmitted on two layers, the method further comprising steps of:

multiplying the first layer of signals by a first orthogonal cover code (OCC) and multiplying the second layer of signals by a second OCC, wherein each of OCCs contains two parts; and multiplying the first part and the second part of the first OCC respectively by sequence values [a, b] of the multiplexing pattern belong to the informed subset, multiplying the first part and the second part of the second OCC respectively by different mappings of the sequence values [a, b] of the multiplexing pattern belong to the informed subset.

67. The signal multiplexing method according to claim 66, further comprising steps of: multiplying the first part of the first OCC by a first sequence value a;

multiplying the second part of the first OCC by a second sequence value b;

multiplying the first part of the second OCC by a mapping of the second sequence value b, which is based on a mapping function F1 (x); and

multiplying the second part of the second OCC by a mapping of the first sequence value a, which is based on a mapping function F2(x).

68. The signal multiplexing method according to claim 67, wherein in a first multiplexing pattern belong to the informed subset, F1 (b)=expG91 )b*, F2(a)=exp(j91 )a, and in a second multiplexing pattern belong to the informed subset, F1 (b)=expG92)b,

F2(a)=expG92)a*, where Θ1 -Θ2=ττ, and " ^* " indicate the conjugate.

69. The signal multiplexing method according to claim 67, wherein in a first multiplexing pattern belong to the informed subset, F1 (b)=expG91 )b, F2(a)=expG91 )a*, and in a second multiplexing pattern belong to the informed subset, F1 (b)=expG92)b*,

F2(a)=expG92)a, where Θ1 -Θ2=ττ, and " ^* " indicate the conjugate.

70. The signal multiplexing method according to claim 68 or 69, wherein Θ1 and Θ2=ηττ74, where n is an odd integer number.

71. The signal multiplexing method according to claim 66, wherein the first and second OCCs are orthogonal Walsh Codes, wherein the first OCC is [1 , 1 ], the second OCC is [1 , -1 ], and they are assigned to the same radio resource.

72. A signal multiplexing device of multiplexing signals assigned on predetermined radio resource of resource blocks, wherein different signals located on different radio resources being sent from different transmission points respectively, and corresponding to a plurality of multiplexing patterns being divided into N subsets, N being an integer number more than 1 , comprising:

a transceiver unit configured to inform a user equipment of index of a subset to be used by the user equipment;

a multiplexing unit configured to multiplex the signals of the different transmission points with the multiplexing patterns belong to the informed subset.

73. The signal multiplexing device according to claim 72, further the transceiver unit further configured to Inform the user equipment how to partition the plurality of multiplexing patterns into the subsets.

74. The signal multiplexing device according to claim 72, wherein the exact pattern in each subset is connected to other parameters of the reference signals, which are necessary information for the reference signal and are also known to the user equipment.

75. The signal multiplexing device according to claim 74, wherein the parameters are frequency domain position of CSI-RS or SCID of DMRS.

76. The signal multiplexing device according to claim 72, wherein the signals are transmitted on two layers, wherein the multiplexing unit multiplies the first layer of signals by a first orthogonal cover code (OCC) and multiplies the second layer of signals by a second OCC, wherein each of OCCs contains two parts, and the multiplexing unit multiplies the first part and the second part of the first OCC

respectively by sequence values [a, b] of the multiplexing pattern belong to the informed subset, multiplies the first part and the second part of the second OCC respectively by different mappings of the sequence values [a, b] of the multiplexing pattern belong to the informed subset.

77. The signal multiplexing device according to claim 76, wherein the multiplexing unit multiplies the first part of the first OCC by a first sequence value a, multiplies the second part of the first OCC by a second sequence value b, multiplies the first part of the second OCC by a mapping of the second sequence value b, which is based on a mapping function F1 (x), and multiplies the second part of the second OCC by a mapping of the first sequence value a, which is based on a mapping function F2(x).

78. The signal multiplexing device according to claim 77, wherein in a first multiplexing pattern belong to the informed subset, F1 (b)=expG91 )b*, F2(a)=exp(j91 )a, and in a second multiplexing pattern belong to the informed subset, F1 (b)=expG92)b,

F2(a)=expG92)a*, where Θ1 -Θ2=ττ, and " ^* " indicate the conjugate.

79. The signal multiplexing device according to claim 77, wherein in a first multiplexing pattern belong to the informed subset, F1 (b)=expG91 )b, F2(a)=expG91 )a*, and in a second multiplexing pattern belong to the informed subset, F1 (b)=expG92)b*,

F2(a)=expG92)a, where Θ1 -Θ2=ττ, and " ^* " indicate the conjugate.

80. The signal multiplexing device according to claim 78 or 79, wherein Θ1 and Θ2=ηττ74, where n is an odd integer number.

81. The signal multiplexing device according to claim 72, wherein the first and second OCCs are orthogonal Walsh Codes, wherein the first OCC is [1 , 1 ], the second OCC is [1 , -1 ], and they are assigned to the same radio resource.