DMRS Design with CDM Group Expansion

Abstract

The present disclosure relates to demodulation reference signal (DMRS) design with code division multiplexing (CDM) group expansion. A network device may be configured to generate a DMRS and transmit the DMRS to a wireless device. The DMRS may be encoded using one of a plurality of extended orthogonal cover codes (OCCs) belonging to an extended CDM group. The extended CDM group may be generated by expanding a legacy CDM group that includes a plurality of legacy OCCs. The number of frequency domain elements in each of the plurality of extended OCCs may be expanded to twice the number of frequency domain elements in each of the plurality of legacy OCCs.

Description

Technical Field

[0001] This application generally relates to a wireless communication system, including the design of a demodulation reference signal (DMRS) for transmission between a wireless device and a network device.

Background Art

[0002] Wireless mobile communication technology uses various standards and protocols to transmit data between a base station and a wireless communication device. Wireless communication system standards and protocols can include, for example, the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) (e.g., 4G), 3GPP New Radio (NR) (e.g., 5G), and the IEEE 802.11 standard for Wireless Local Area Network (WLAN) (commonly known to the industry as Wi-Fi (registered trademark)).

[0003] As envisioned by 3GPP, different wireless communication system standards and protocols can use various Radio Access Networks (RANs) to communicate between a base station of the RAN (commonly called a RAN node, network node, or simply a node) and a wireless communication device known as a User Equipment (UE). 3GPP RAN can include, for example, Global System for Mobile Communications (GSM), Enhanced Data Rate for GSM Evolution (EDGE) RAN (GERAN), Universal Terrestrial Radio Access Network (UTRAN), Evolved Universal Terrestrial Radio Access Network (E-UTRAN), and / or Next Generation Radio Access Network (NG-RAN).

[0004] Each RAN can perform communication between a base station and a UE using one or more radio access technologies (RATs). For example, GERAN implements GSM and / or EDGE RAT, UTRAN implements universal mobile telecommunication system (UMTS) RAT, or other 3GPP RATs, E-UTRAN implements LTE RAT (sometimes simply called LTE), and NG-RAN implements NR RAT (also sometimes called 5G RAT, 5G NR RAT, or simply NR in this specification). In certain deployments, E-UTRAN can also implement NR RAT. In certain deployments, NG-RAN can also implement LTE RAT.

[0005] The base station used by a RAN can correspond to that RAN. An example of an E-UTRAN base station is an evolved universal terrestrial radio access network (E-UTRAN) Node B (commonly also called an evolved Node B, enhanced Node B, eNode B, or eNB). An example of an NG-RAN base station is a next-generation Node B (sometimes called a Node B or gNB).

[0006] The RAN provides communication services with external entities via a connection to the core network (CN). For example, E-UTRAN can utilize the evolved packet core (EPC), and NG-RAN can utilize the 5G core network (5GC). SUMMARY OF THE INVENTION

[0007] The demodulation reference signal (DMRS) can be used for channel estimation and demodulation. In particular, DMRS symbols with a specific pattern can be carried by resource blocks and transmitted from a transmitter to a receiver. The receiver can use the received DMRS symbols with a specific pattern that is pre-known to the receiver to estimate the channel.

[0008] Multiple DMRS symbols may be transmitted via a plurality of orthogonal DMRS ports respectively corresponding to a plurality of antenna ports. To ensure the orthogonality of the plurality of DMRS ports, time division multiplexing (TDM), frequency division multiplexing (FDM), or code division multiplexing (CDM) can be applied to the DMRS symbols. For CDM, a plurality of CDM groups are designed. Each CDM group includes a plurality of orthogonal cover codes (OCCs), and the OCCs can be superimposed on the DMRS symbols so that DMRS symbols occupying the same time and frequency resources are orthogonalized by CDM.

[0009] Recently, a method of supporting more orthogonal DMRS ports has been discussed to meet current or future communication requirements. One possible way to support more orthogonal DMRS ports may be to expand the CDM groups so that each CDM group can provide more orthogonal OCCs.

[0010] Embodiments in the present disclosure relate to devices and methods for DMRS design involving CDM group expansion.

[0011] A network device according to some embodiments of the present disclosure may be configured to generate DMRS and transmit the DMRS to a wireless device. The DMRS may be encoded with one of a plurality of extended OCCs belonging to an extended CDM group. The extended CDM group may be generated by expanding a legacy CDM group including a plurality of legacy OCCs. The number of frequency domain elements in each of the plurality of extended OCCs may be expanded to twice the number of frequency domain elements in each of the plurality of legacy OCCs.

[0012] Wireless devices according to some embodiments of the present disclosure may be configured to receive DMRS from a network device and perform channel estimation based on the DMRS. The DMRS may be encoded with one of a plurality of extended OCCs belonging to an extended CDM group. The extended CDM group may be generated by extending a legacy CDM group that includes a plurality of legacy OCCs. The number of frequency domain elements in each of the plurality of extended OCCs may be extended to twice the number of frequency domain elements in each of the plurality of legacy OCCs.

[0013] Network devices according to some embodiments of the present disclosure may be configured to receive DMRS from a wireless device and perform channel estimation based on the DMRS. The DMRS may be encoded with one of a plurality of extended OCCs belonging to an extended CDM group. The extended CDM group may be generated by extending a legacy CDM group that includes a plurality of legacy OCCs. The number of frequency domain elements in each of the plurality of extended OCCs may be extended to twice the number of frequency domain elements in each of the plurality of legacy OCCs.

[0014] Wireless devices according to some embodiments of the present disclosure may be configured to receive a control signal from a network device and, in response to the control signal, generate DMRS to be transmitted to the network device. The DMRS may be encoded with one of a plurality of extended OCCs belonging to an extended CDM group. The extended CDM group may be generated by extending a legacy CDM group that includes a plurality of legacy OCCs. The number of frequency domain elements in each of the plurality of extended OCCs may be extended to twice the number of frequency domain elements in each of the plurality of legacy OCCs.

[0015] A method for a network device according to some embodiments of the present disclosure may include generating DMRS and transmitting the DMRS to a wireless device. The DMRS may be encoded with one of a plurality of extended OCCs belonging to an extended CDM group. The extended CDM group may be generated by extending a legacy CDM group including a plurality of legacy OCCs. The number of frequency domain elements in each of the plurality of extended OCCs may be extended to twice the number of frequency domain elements in each of the plurality of legacy OCCs.

[0016] A method for a wireless device according to some embodiments of the present disclosure may include receiving DMRS from a network device and performing channel estimation based on the DMRS. The DMRS may be encoded with one of a plurality of extended OCCs belonging to an extended CDM group. The extended CDM group may be generated by extending a legacy CDM group including a plurality of legacy OCCs. The number of frequency domain elements in each of the plurality of extended OCCs may be extended to twice the number of frequency domain elements in each of the plurality of legacy OCCs.

[0017] A method for a network device according to some embodiments of the present disclosure may include receiving DMRS from a wireless device and performing channel estimation based on the DMRS. The DMRS may be encoded with one of a plurality of extended OCCs belonging to an extended CDM group. The extended CDM group may be generated by extending a legacy CDM group including a plurality of legacy OCCs. The number of frequency domain elements in each of the plurality of extended OCCs may be extended to twice the number of frequency domain elements in each of the plurality of legacy OCCs.

[0018] Methods for a wireless device according to some embodiments of the present disclosure may include receiving a control signal from a network device and generating DMRS to be transmitted to the network device in response to the control signal. The DMRS may be coded with one of a plurality of extended OCCs belonging to an extended CDM group. The extended CDM group may be generated by extending a legacy CDM group including a plurality of legacy OCCs. The number of frequency domain elements in each of the plurality of extended OCCs may be extended to twice the number of frequency domain elements in each of the plurality of legacy OCCs.

[0019] The techniques described herein may be implemented in and / or used with several different types of devices including, but not limited to, any of a cellular phone, a tablet computer, a wearable computing device, a portable media player, and various other computing devices.

[0020] This summary of the invention is intended to provide some brief overviews of the subject matter described in this document. Thus, the above features are merely examples and should not be construed as narrowing the scope or spirit of the subject matter described herein. Other features, aspects, and advantages of the subject matter described herein will become apparent from the following detailed description, the drawings, and the claims.

[0021] To readily identify the discussion of any particular element or act, the leading digit(s) of the reference number refers to the figure number in which that element was first introduced. BRIEF DESCRIPTION OF THE DRAWINGS

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[0033] Various embodiments are described with respect to a UE. However, the reference to the UE is provided for illustrative purposes only. The exemplary embodiments may be used with any electronic component, and any electronic component can establish a connection to a network and is composed of hardware, software, and / or firmware for exchanging information and data with the network. Therefore, the UE described herein is used to represent any suitable electronic component.

[0034] FIG. 1 shows an exemplary architecture of a wireless communication system 100 according to an embodiment disclosed herein. The following description is provided for an exemplary wireless communication system 100 that operates in conjunction with an LTE system standard and / or a 5G or NR system standard as provided by 3GPP technical specifications.

[0035] As shown by FIG. 1, the wireless communication system 100 includes UE102 and UE104 (although any number of UEs can be used). In this example, UE102 and UE104 are shown as smartphones (e.g., handheld touchscreen mobile computing devices that can connect to one or more cellular networks), but can also include any mobile or non-mobile computing device configured for wireless communication.

[0036] UE102 and UE104 can be configured to communicatively couple with RAN106. In an embodiment, RAN106 can be, for example, NG-RAN, E-UTRAN, etc. UE102 and UE104 utilize a connection (or channel) to RAN106 (shown as connection 108 and connection 110, respectively), each of which includes a physical communication interface. RAN106 can include one or more base stations, such as base station 112 and base station 114, that enable connection 108 and connection 110.

[0037] In this example, connection 108 and connection 110 are air interfaces for enabling such communication coupling and can, for example, conform to the RAT(s) used by RAN106, such as LTE and / or NR.

[0038] In some embodiments, UE102 and UE104 can also directly exchange communication data via sidelink interface 116. UE104 is configured to access an access point (shown as AP118) via connection 120, as shown. As an example, connection 120 can include a local wireless connection, such as a connection that conforms to any IEEE 802.11 protocol, and AP118 can include a Wi-Fi (registered trademark) router. In this example, AP118 can be connected to other networks (e.g., the Internet) without going through CN124.

[0039] In an embodiment, UE102 and UE104 can be configured to communicate with each other or with base station 112 and / or base station 114 using orthogonal frequency division multiplexing (OFDM) communication signals via multi-carrier communication channels according to various communication technologies. These various communication technologies can be, for example, orthogonal frequency division multiple access (OFDMA) communication technology (e.g., for downlink communication), or single carrier frequency division multiple access (SC-FDMA) communication technology (e.g., for uplink and ProSe or sidelink communication), but are not limited thereto, and the scope of the embodiments is not limited in this regard. The OFDM signal can include a plurality of orthogonal subcarriers.

[0040] In some embodiments, all or part of base station 112 or base station 114 can be implemented as one or more software entities executed on a server computer as part of a virtual network. Additionally, or in other embodiments, base station 112 or base station 114 can be configured to communicate with each other via interface 122. In an embodiment where wireless communication system 100 is an LTE system (e.g., when CN124 is an EPC), interface 122 can be an X2 interface. The X2 interface may be defined between two or more base stations (e.g., two or more eNBs, etc.) connected to the EPC, and / or between two eNBs connected to the EPC. In an embodiment where wireless communication system 100 is an NR system (e.g., when CN124 is a 5GC), interface 122 can be an Xn interface. The Xn interface is defined between two or more base stations (e.g., two or more gNBs, etc.) connected to the 5GC, between base station 112 (e.g., gNB) connected to the 5GC and an eNB, and / or between two eNBs connected to the 5GC (e.g., CN124).

[0041] RAN106 is shown to be communicatively coupled to CN124. CN124 may comprise one or more network elements 126 configured to provide various data and telecommunications services to customers / subscribers (e.g., users of UE102 and UE104) connected to CN124 via RAN106. The components of CN124 may be implemented on one physical device or separate physical devices, including components for reading and executing instructions from a machine-readable medium or computer-readable medium (e.g., a non-transitory machine-readable storage medium).

[0042] In an embodiment, CN124 may be an EPC, and RAN106 may be connected to CN124 via an S1 interface 128. In an embodiment, the S1 interface 128 may be split into two parts: an S1 user plane (S1-U) interface for carrying traffic data between base station 112 or base station 114 and a serving gateway (S-GW), and an S1-MME interface which is a signaling interface between base station 112 or base station 114 and a mobility management entity (MME).

[0043] In an embodiment, CN124 may be a 5GC, and RAN106 may be connected to CN124 via an NG interface 128. In an embodiment, the NG interface 128 can be split into two parts: an NG user plane (NG-U) interface for carrying traffic data between base station 112 or base station 114 and a user plane function (UPF), and an S1 control plane (NG-C) interface which is a signaling interface between base station 112 or base station 114 and an access and mobility management function (AMF).

[0044] In general, the application server 130 can be an element that provides an application using an Internet Protocol (IP) bearer resource (e.g., packet switched data service) with CN124. The application server 130 can also be configured to support one or more communication services (e.g., VoIP session, group communication session, etc.) for the UEs 102 and 104 via CN124. The application server 130 may communicate with CN124 via the IP communication interface 132.

[0045] FIG. 2 shows a system 200 for performing signaling 234 between a wireless device 202 and a network device 218 according to an embodiment disclosed herein. The system 200 can be a part of a wireless communication system as described herein. The wireless device 202 can be, for example, a UE of a wireless communication system. The network device 218 can be, for example, a base station (e.g., eNB or gNB) of a wireless communication system.

[0046] The wireless device 202 can include one or more processors 204. The processor(s) 204 can execute instructions so that various operations of the wireless device 202 are performed as described herein. The processor(s) 204 can include, for example, a central processing unit (CPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a controller, a field programmable gate array (FPGA) device, another hardware device, a firmware device, or one or more baseband processors implemented using any combination thereof configured to perform the operations described herein.

[0047] Wireless device 202 may include a memory 206. Memory 206 may be a non-transitory computer-readable storage medium that stores instructions 208 (which may include instructions being executed by a processor(s) 204). Instructions 208 may also be referred to as program code or a computer program. Memory 206 may also store data used by processor(s) 204 and results calculated by processor 204.

[0048] Wireless device 202 may include one or more transceivers 210 that use antennas 212 of wireless device 202 to facilitate signaling (e.g., signaling 234) to and / or from wireless device 202 with other devices (e.g., network device 218) according to a corresponding RAT.

[0049] Wireless device 202 may include one or more antennas 212 (e.g., one, two, four, or more). In embodiments having multiple antennas 212, wireless device 202 may utilize the spatial diversity of such multiple antennas 212 to transmit and / or receive multiple different data streams on the same time and frequency resources. This behavior may be referred to as, for example, multi-input multi-output (MIMO) behavior (referring to the multiple antennas used in each of the transmitting and receiving devices enabling this mode). MIMO transmission by wireless device 202 can be achieved according to precoding (or digital beamforming) applied in wireless device 202 that multiplexes data streams across antennas 212 according to known or assumed channel characteristics such that each data stream is received at a desired location in the spatial domain (e.g., the location of the receiver associated with that data stream) with an appropriate signal strength relative to other streams. Some embodiments may use single-user MIMO (SU-MIMO) methods (where all data streams are directed to a single receiver) and / or multi-user MIMO (MU-MIMO) methods (where individual data streams can be directed to individual (different) receivers at different locations in the spatial domain).

[0050] In some embodiments having multiple antennas, wireless device 202 may implement analog beamforming techniques, whereby the phase of the signals transmitted by antennas 212 is relatively adjusted so that the (joint) transmission by antennas 212 can be directed (which may be referred to as beam steering).

[0051] Wireless device 202 may include one or more interfaces 214. The interface(s) 214 may be used to provide an input to or an output from the wireless device 202. For example, the wireless device 202, which is a UE, may include interface(s) 214 such as a microphone, a speaker, a touch screen, buttons, etc. to enable an input to and / or an output from the UE by a user of the UE. Other interfaces of such a UE may be composed of a transmitter, a receiver, and other circuits (e.g., other than the transceiver(s) 210 / antenna(s) 212 already described) that enable communication between the UE and other devices, and may operate according to known protocols (e.g., Wi-Fi®, Bluetooth®, etc.).

[0052] Network device 218 can include one or more processors 220. The processor(s) 220 may execute instructions so that various operations of the network device 218 are performed as described herein. The processor(s) 204 may include, for example, one or more baseband processors implemented using a CPU, a DSP, an ASIC, a controller, an FPGA device, another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein.

[0053] Network device 218 can include a memory 222. The memory 222 may be a non-transitory computer-readable storage medium that stores instructions 224 (which may include instructions executed by the processor(s) 220). The instructions 224 may also be referred to as program code or a computer program. The memory 222 may also store data used by the processor(s) 220 and results calculated by the processor 220.

[0054] The network device 218 may include one or more transceivers 226 that may include RF transmitter and / or receiver circuitry that uses the antenna(s) 228 of the network device 218 to facilitate signaling (e.g., signaling 234) to and / or from the network device 218 with other devices (e.g., wireless device 202) according to the corresponding RAT.

[0055] The network device 218 may include one or more antenna(s) 228 (e.g., one, two, four, or more). In embodiments having multiple antenna(s) 228, the network device 218 may perform MIMO, digital beamforming, analog beamforming, beam steering, etc., as described.

[0056] The network device 218 may include one or more interface(s) 230. The interface(s) 230 may be used to provide an input to or an output from the network device 218. For example, the network device 218, which is a base station, enables the base station to communicate with other devices within the core network and / or enables the base station to communicate with an external network, computer, database, etc., for the purposes of operation, management, and maintenance of the transmitter, receiver, and other equipment operably connected to the base station or the base station itself. The interface(s) 230 may include other circuitry (e.g., other than the transceiver(s) 226 / antenna(s) 228 already described).

[0057] Referring now to FIGS. 3 - 6, the legacy DMRS configuration and legacy CDM group will first be described. Note that the term "legacy" as used herein means any existing scheme prior to the present disclosure and includes, without limitation, any scheme related to LTE system standards and / or 5G or NR system standards as provided by 3GPP technical specifications.

[0058] There are two legacy DMRS configuration types (hereinafter also simply referred to as DMRS types) 1 and 2 having different DMRS patterns. FIGS. 3 and 4 show related legacy CDM groups including legacy DMRS configuration type 1 and legacy OCC, and FIGS. 5 and 6 show related legacy CDM groups including legacy DMRS configuration type 2 and legacy OCC.

[0059] DMRS type 1 is shown in FIG. 3. For simplicity, FIG. 3 shows only two DMRS symbols k and k + 1 in the time domain (horizontal direction in FIG. 3) of one physical resource block (PRB), and omits other orthogonal frequency division multiplexing (OFDM) symbols in this PRB.

[0060] In the case of DMRS type 1, as shown in FIG. 3, for each of DMRS symbols k and k + 1, in the frequency domain (vertical direction in FIG. 3) of the physical resource block (PRB), the DMRS resource elements (REs) are distributed at an interval of one resource element. There are two possible DMRS patterns shown in FIG. 3 by "A" and "B" respectively.

[0061] In the case of DMRS pattern A in DMRS type 1, the REs at even positions in the frequency domain of the PRB are occupied as DMRS REs, and thus the DMRS symbol for DMRS pattern A is DMRS symbol A k =[RE 0 ,RE 2 ,RE 4 ,RE 6 ,RE 8 ,RE 10 T , and DMRS symbol A k+1 =[RE 0 ,RE 2 ,RE 4 ,RE 6 ,RE 8 ,RE 10 T can be shown as.

[0062] ​​In the case of DMRS pattern B in DMRS type 1, the REs in the odd positions in the frequency domain of the PRB are occupied as DMRS REs. Therefore, the DMRS symbol for DMRS pattern B is DMRS symbol B k =[RE 1 ,RE 3 ,RE 5 ,RE 7 ,RE 9 ,RE 11 T , DMRS symbol B k+1 =[RE 1 ,RE 3 ,RE 5 ,RE 7 ,RE 9 ,RE 11 T can be shown as such.

[0063] For different DMRS patterns A and B, different CDM groups can be assigned. For example, DMRS symbol A k and A k+1 can be assigned to CDM group 0, and DMRS symbol B k and B k+1 can be assigned to CDM group 1.

[0064] The detailed configuration of the CDM groups for DMRS type 1 is shown in Figure 4.

[0065] In Figure 4, two CDM groups 0 and 1 are provided for DMRS type 1. Each CDM group has the same size to include the same number of OCCs. In the case of CDM group 0, four OCCs are included and are respectively assigned to DMRS ports 0, 1, 4, 5. In the case of CDM group 1, four OCCs are included and are respectively assigned to DMRS ports 2, 3, 6, 7.

[0066] ​​For each OCC, two time-domain elements (denoted as "TD-OCC elements") and two frequency-domain elements ("FD-OCC elements") are included. The values of the FD-OCC elements and TD-OCC elements are designed such that the four OCCs included in each CDM group are orthogonal to each other. For multiple DMRS symbols occupying the same time and frequency resources, they can be encoded using the OCCs within one CDM group such that the multiple DMRS symbols can be orthogonalized by CDM. Further, for different CDM groups from each other, as can be seen from FIG. 4, the number of OCCs is the same, and the values of each OCC are also the same, but the RE positions of the FD-OCC elements are different, corresponding to each DMRS pattern. For example, for CDM group 0 corresponding to DMRS pattern A, the FD-OCC elements within each OCC are located in even-numbered REs, while for CDM group 1 corresponding to DMRS pattern B, the FD-OCC elements within each OCC are located in odd-numbered REs.

[0067] FIG. 4 shows the values of the FD-OCC elements and TD-OCC elements within CDM groups 0 and 1 as '+' and '-' indicating '+1' and '-1' respectively. For each CDM group shown in FIG. 4, the four OCCs are orthogonal to each other. It should be noted that the OCC design is not limited to the values shown in FIG. 4, and other values for the FD-OCC elements and TD-OCC elements can be designed.

[0068] For the encoding of DMRS using CDM groups, the DMRS type (e.g., belonging to type 1 or type 2), the DMRS pattern (e.g., belonging to pattern A or pattern B), and the corresponding DMRS port can be determined first. Next, the OCC for encoding the DMRS can be determined. For example, for 2-symbol DMRS A k and A k+1 in the case of

Number

[0069] In addition, the OCC repeats in the frequency domain (3 times for DMRS type 1) using the next entry in the DMRS sequence so that each DMRS RE within a PRB can be encoded using the corresponding OCC element.

[0070] For example, for 2-symbol DMRS A represented as follows k及びk+1 in the case of

Number

Number

Number

Number

[0071] In the above description, 2-symbol DMRS was exemplified. For 2-symbol DMRS for DMRS type 1, 2 CDM groups can be provided, and each CDM group can include 4 orthogonal OCCs. Therefore, up to 8 DMRS ports can be supported. For 1-symbol DMRS for DMRS type 1, similarly, 2 CDM groups can be provided, and each CDM group can include 2 orthogonal OCCs. Therefore, up to 4 DMRS ports can be supported.

[0072] Next, with reference to FIGS. 5 and 6, a related legacy CDM group including DMRS configuration type 2 and legacy OCC will be described.

[0073] DMRS type 2 is shown in FIG. 5. For simplicity, FIG. 5 shows only two DMRS symbols k and k + 1 within one physical resource block (PRB), and omits other OFDM symbols within this PRB.

[0074] In the case of DMRS type 2, as shown in FIG. 5, the distribution of DMRS REs in the frequency domain of the PRB is different from that of DMRS type 1 where DMRS REs are continuously distributed in the frequency domain.

[0075] There are three possible DMRS patterns respectively indicated by "A", "B", and "C" in FIG. 5. The DMRS symbols for DMRS pattern A in DMRS type 2 are A k =[RE 0 ,RE 1 ,RE 6 ,RE 7 , and A k+1 =[RE 0 ,RE 1 ,RE 6 ,RE 7 and can be shown as such. The DMRS symbols for DMRS pattern B in DMRS type 2 are B k =[RE 2 ,RE 3 ,RE 8 ,RE 9 and B k+1 =[RE 2 ,RE 3 ,RE 8 ,RE 9 and can be shown as such. The DMRS symbols for DMRS pattern C in DMRS type 2 are C k =[RE 4 ,RE 5 ,RE 10 ,RE 11 and C k+1 =[RE 4 ,RE 5 ,RE 10, RE 11 can be shown as.

[0076] For different DMRS patterns A, B, and C, different CDM groups can be assigned. For example, DMRS symbol A for DMRS pattern A k and A k+1 can be assigned to CDM group 0, and DMRS symbol B for DMRS pattern B k and B k+1 can be assigned to CDM group 1, and DMRS symbol C for DMRS pattern C k and C k+1 can be assigned to CDM group 2.

[0077] The detailed configuration of the CDM group for DMRS type 2 is shown in FIG. 6.

[0078] In FIG. 6, three CDM groups 0, 1, and 2 are provided for DMRS type 2. Each CDM group has the same size to include the same number of OCCs. In the case of CDM group 0, four OCCs are included and are respectively assigned to DMRS ports 0, 1, 6, 7. In the case of CDM group 1, four OCCs are included and are respectively assigned to DMRS ports 2, 3, 8, 9. In the case of CDM group 2, four OCCs are included and are respectively assigned to DMRS ports 4, 5, 10, 11.

[0079] For each OCC, two TD-OCC elements and two FD-OCC elements are included. The values of the FD-OCC elements and TD-OCC elements are designed such that the four OCCs included in each CDM group are orthogonal to each other. For multiple DMRS symbols occupying the same time and frequency resources, they can be encoded using the OCCs within one CDM group such that the multiple DMRS symbols can be orthogonalized by CDM. Further, for different CDM groups, as can be seen from FIG. 6, the number of OCCs is the same, and the values of each OCC are also the same, but the RE positions of the FD-OCC elements are different, which correspond to each DMRS type. For example, for CDM group 0 corresponding to DMRS pattern A, the FD-OCC elements within each OCC are located at RE 0 and RE 1 . For CDM group 1 corresponding to DMRS pattern B, the FD-OCC elements within each OCC are located at RE 2 and RE 3 . For CDM group 1 corresponding to DMRS pattern C, the FD-OCC elements within each OCC are located at RE 4 and RE 5 .

[0080] FIG. 6 shows the values of the FD-OCC elements and TD-OCC elements within CDM groups 0, 1, and 2 as ‘+’ and ‘-’ indicating ‘+1’ and ‘-1’ respectively. For each CDM group shown in FIG. 6, the four OCCs are orthogonal to each other. It should be noted that the OCC design is not limited to the values shown in FIG. 6, and other values for the FD-OCC elements and TD-OCC elements can be designed.

[0081] For the encoding of DMRS using CDM groups, the DMRS type (e.g., belonging to type 1 or type 2), the DMRS pattern (e.g., belonging to pattern A or pattern B), and the corresponding DMRS port can be determined first. Next, the OCCs for encoding the DMRS can be determined. For example, for 2-symbol DMRS A k and A k+1 having DMRS type 2, DMRS pattern A, and DMRS port 1,

Number

[0082] In addition, OCC repeats (twice in the case of DMRS type 2) in the frequency domain using the next entry in the DMRS sequence so that each DMRS RE within a PRB can be encoded using the determined OCC.

[0083] For example, for 2-symbol DMRS A represented as follows k及びk+1 in the case of

Number

Number

Number

Number

[0084] In the above description, 2-symbol DMRS was exemplified. For 2-symbol DMRS for DMRS type 2, three CDM groups can be provided, and each CDM group can include four orthogonal OCCs. Thus, up to 12 DMRS ports can be supported. Similarly, for 1-symbol DMRS for DMRS type 1, three CDM groups can be provided, and each CDM group can include two orthogonal OCCs. Thus, up to 6 DMRS ports can be supported.

[0085] Recently, methods for supporting more orthogonal DMRS ports have been discussed to meet current or future communication requirements. One possible way to support more orthogonal DMRS ports could be to expand the CDM group so that each CDM group can provide more orthogonal OCCs. The DMRS design involving CDM group expansion according to the present disclosure will be described in detail with reference to FIGS. 7-10.

[0086] In some embodiments, a legacy CDM group can be expanded to generate an expanded CDM group. The expanded CDM group can have a larger size (including more OCCs) than the legacy CDM group. To achieve more OCCs within one CDM group while maintaining the orthogonality of the OCCs within one CDM group, the number of frequency domain elements within the legacy OCCs included in the legacy CDM group can be increased. In some embodiments, the number of frequency domain elements in each of the plurality of expanded OCCs can be expanded to twice the number of frequency domain elements in each of the plurality of legacy OCCs.

[0087] Thereby, an expanded CDM group including a larger size than the legacy CDM group can support more orthogonal DMRS ports. On the other hand, since the frequency or time occupancy of the DMRS within the PRB does not increase, CDM group expansion can be achieved without increasing the DMRS overhead.

[0088] In some embodiments, a pair of expanded OCCs can be generated based on one legacy OCC. One of the expanded OCCs in the pair can be generated by repeating the frequency domain elements in the legacy OCC twice, and the other expanded OCC in the pair can be generated by concatenating the frequency domain elements in the legacy OCC and the phase-inverted frequency domain elements in the legacy OCC.

[0089] For example, the legacy OCC corresponding to DMRS port 0 0 has two FD-OCC elements [FD-OCC 1 , FD-OCC 2 = [+, +] T for DMRS symbol k. A pair of extended OCCs from the legacy OCC can be generated as the extended OCC 1 and the extended OCC 2 . The extended OCC 1 is extended to include four FD-OCC elements [FD-OCC 0 , FD-OCC 1 , FD-OCC 2 = [+, +, +, +] 11 , FD-OCC 12 , FD-OCC 13 , FD-OCC 14 generated by repeating the FD-OCC elements [FD-OCC T in the legacy OCC twice. Further, the extended OCC 2 is extended to include four FD-OCC elements [FD-OCC 21 , FD-OCC 22 , FD-OCC 23 , FD-OCC 24 = [+, +, -, -] T , which is generated by concatenating the frequency domain element ([+, +] 0 ) in the legacy OCC T and the phase-inverted frequency domain element (-, -) 0 = [-,-] T = [-,-] T in the legacy OCC

[0090] A Kronecker product operation between the FD-OCC elements [FD-OCC 1 , FD-OCC 2 of one legacy OCC and the operator (+, -) T can be applied to generate the double frequency domain elements in the pair of extended OCCs. The element '+' in the operator indicates the repetition of the FD-OCC element, and the element '-' in the operator indicates the concatenation of the original FD-OCC element and the phase-inverted FD-OCC element.

[0091] For example, in the case of DMRS symbol k, for the two FD-OCC elements [FD-OCC 1 , FD-OCC 2 =[+,-] T in the legacy OCC corresponding to DMRS port 1 that includes 1 the four FD-OCC elements in the extended OCC 1 can be generated as [+,-,+,-] T and the four FD-OCC elements in the extended OCC 2 can be generated as [+,-,-,+] T .

[0092] Note that the CDM group extension according to the present disclosure is not limited to the above example, and different extended OCCs may be generated. For example, by applying the Kronecker product operation between the FD-OCC elements [FD-OCC 1 , FD-OCC 2 of one legacy OCC and different operators (-, +) T , the double-frequency domain elements in the pair of extended OCCs may be generated. Further, as long as the extended OCCs within one extended CDM group are orthogonal to each other, other extended OCCs may be generated.

[0093] The above extension can be applied to each legacy OCC within the legacy CDM group. According to the extension, one legacy OCC can be split into two new OCCs, and while maintaining the orthogonality of the extended OCCs within one extended CDM group, the total number of extended OCCs within one extended CDM group is doubled. Therefore, the number of supported DMRS ports can be doubled. Also, since only the FD-OCC elements are extended and the number of TD-OCC elements is not changed, the DMRS overhead does not increase.

[0094] FIG. 7 and FIG. 8 show the extended CDM groups for DMRS type 1 and DMRS type 2, respectively.

[0095] As shown in FIG. 7, the number of supportable DMRS ports for 2-symbol DMRS in DMRS type 1 is 16, which is twice the maximum supportable DMRS ports (8 ports) based on the legacy CDM group as shown in FIG. 4. Further, as shown in FIG. 8, the number of supportable DMRS ports for 2-symbol DMRS in DMRS type 2 is 24, which is doubled from the maximum supportable DMRS ports (12 ports) based on the legacy CDM group as shown in FIG. 6. In the case of 1-symbol DMRS, similarly, the supportable DMRS ports for DMRS type 1 can be doubled from 4 to 8, and the supportable DMRS ports for DMRS type 2 can be doubled from 6 to 12.

[0096] In some embodiments, one of the extended OCCs in a pair may be assigned to the same DMRS port n corresponding to the legacy OCC, and the other extended OCC in the pair may be assigned to DMRS port (n + M), where M is the maximum number of legacy supportable DMRS ports.

[0097] For example, in the case of DMRS type 1, M = 8 for 2-symbol DMRS. Thus, for a pair of extended OCCs split from the legacy OCC corresponding to legacy DMRS port 0, the pair of extended OCCs may be assigned to DMRS port 0 and DMRS port 8, respectively. For a pair of extended OCCs split from the legacy OCC corresponding to legacy DMRS port 1, the pair of extended OCCs may be assigned to DMRS port 1 and DMRS port 9, respectively. Similar assignments can be performed for other extended OCCs. The assignment is shown in FIG. 7.

[0098] With the above assignment, the new DMRS ports 0 to 7 still correspond to the legacy DMRS ports 0 to 7. Thus, better backward compatibility can be achieved, and coordinated scheduling of both legacy DMRS and new DMRS may be possible.

[0099] In the case of DMRS type 2, a similar allocation can be applied. For example, in the case of DMRS type 2, M = 12 for 2-symbol DMRS. Therefore, for a pair of extended OCCs split from the legacy OCC corresponding to legacy DMRS port 0, the pair of extended OCCs can be allocated to DMRS port 0 and DMRS port 12, respectively. For a pair of extended OCCs split from the legacy OCC corresponding to legacy DMRS port 1, the pair of extended OCCs can be allocated to DMRS port 1 and DMRS port 13, respectively. Similar allocations can also be performed for other extended OCCs. The allocation is shown in FIG. 8.

[0100] With the above allocation, the new DMRS ports 0 to 11 still correspond to the legacy DMRS ports 0 to 11. Therefore, better backward compatibility can be achieved, and coordinated scheduling of both legacy DMRS and new DMRS may be possible.

[0101] In the above description with reference to FIGS. 7 and 8, the expansion of the CDM group is performed without changing the DMRS configuration type in order to achieve better backward compatibility. In some embodiments, the DMRS configuration type may be redesigned along with the expansion of the CDM group. Hereinafter, two options for DMRS configuration design can be described with reference to FIGS. 9 and 10.

[0102] FIG. 9 shows a DMRS pattern design for DMRS configuration type 1 according to some embodiments disclosed herein.

[0103] Option 1 shown in FIG. 9 corresponds to the case where the DMRS configuration type is not changed compared to the legacy DMRS configuration type. As shown in Option 1 of FIG. 9, DMRS patterns A and B are the same as the legacy DMRS type 1 shown in FIG. 3.

[0104] As another option, the DMRS design can be changed for DMRS type 1. For example, in some embodiments, as shown in option 2 of FIG. 9, the frequency occupancy for the REs of the DMRS can be doubled by repeating the frequency occupancy of the legacy DMRS pattern in consecutive frequency domain resource elements.

[0105] For example, for DMRS symbol A k in the case of, the frequency occupancy REs of the DMRS in FIG. 3 k,0 are repeated as the DMRS REs in FIG. 9 k,0 and REs k,1 and other DMRS REs are similarly repeated to generate a new DMRS symbol A' for DMRS pattern A represented as follows. k及びk-1 To generate.

Number

Number

[0106] FIG. 10 shows the DMRS pattern design for DMRS configuration type 2 according to some embodiments disclosed herein.

[0107] Option 1 shown in FIG. 10 corresponds to the case where the DMRS configuration type is not changed compared to the legacy DMRS configuration type. As shown in option 1 of FIG. 10, the DMRS patterns A, B, and C are the same as the legacy DMRS type 2 shown in FIG. 5.

[0108] As another option, the DMRS design can be changed for DMRS type 2. For example, in some embodiments, as shown in option 2 of FIG. 10, the frequency occupancy for the REs of the DMRS can be doubled by repeating the frequency occupancy of the legacy DMRS pattern in consecutive frequency domain resource elements.

[0109] For example, for DMRS symbol A k in the case of, the frequency occupancy REs of DMRS in FIG. 5 k,0 and REs k,1 are repeated as DMRS REs in FIG. 10 k,0 , RE k,1 , RE k,2 , RE k,3 and so on. Other DMRS REs are similarly repeated to generate a new DMRS symbol A’ for DMRS pattern A as shown below k及びk+1 . [Number] B’ for DMRS pattern B k及びk+1 is represented as follows. [Number] C’ for DMRS pattern C k及びk+1 is represented as follows. [Number]

[0110] According to the DMRS patterns of Option 2 shown in FIGS. 9 and 10, the distances between different DMRS REs within a DMRS symbol can be maintained closer than in Option 1, so the changes in channel state for different DMRS REs within a DMRS symbol can be less than those for Option 1. Therefore, Option 2 can be more robust against frequency-selective fading channels.

[0111] Note that the extended CDM groups described with reference to FIGS. 7 and 8 may be applied to either Option 1 or Option 2 of DMRS Types 1 and 2, respectively.

[0112] The DMRS design with CDM group extension according to the present disclosure can be used in transmissions between a network device and a wireless device.

[0113] Figure 11 shows a signaling diagram of an exemplary method for downlink DMRS transmission between a network device and a wireless device. The network device may correspond to either base station 112, 114 described in FIG. 1 or network device 218 described in FIG. 2. The wireless device may correspond to either UE 102, 104 described in FIG. 1 or wireless device 202 described in FIG. 2.

[0114] At 1110, the network device generates DMRS. The DMRS may correspond to DMRS designed using CDM group extension according to any of the embodiments described in the present disclosure.

[0115] At 1120, the network device transmits the DMRS to the wireless device.

[0116] At 1130, the wireless device receives the DMRS.

[0117] At 1140, the wireless device performs downlink channel estimation based on the DMRS.

[0118] Figure 12 shows a signaling diagram of an exemplary method for uplink DMRS transmission between a network device and a wireless device. The network device may correspond to either base station 112, 114 described in FIG. 1 or network device 218 described in FIG. 2. The wireless device may correspond to either UE 102, 104 described in FIG. 1 or wireless device 202 described in FIG. 2.

[0119] At 1210, the network device transmits a control signal to the wireless device. The control signal may be dynamically transmitted to the wireless device (e.g., through downlink control information (DCI)).

[0120] At 1220, the wireless device generates DMRS based on the control signal transmitted at 1210. The DMRS may correspond to a DMRS designed using CDM group expansion according to any of the embodiments described in this disclosure.

[0121] At 1230, the wireless device transmits the DMRS to the network device.

[0122] At 1240, the network device performs uplink channel estimation based on the DMRS.

[0123] The DMRS described in FIG. 11 or FIG. 12 can be based on a DMRS design with CDM group expansion according to one or more of the embodiments of the present disclosure described above. Further, the DMRS design with CDM group expansion according to the present disclosure can be applied as a common design for both uplink DMRS and downlink DMRS. This works particularly for CP - OFDM (Circular Prefix - OFDM) where the same DMRS pattern is used for both downlink and uplink.

[0124] FIG. 13 shows a case where an extended CDM crosses a precoding resource block group (PRG) boundary according to some embodiments disclosed herein.

[0125] For DMRS type 1, the size of the CDM group extended in the frequency domain (equal to the size of the extended OCC included in the extended CDM group) is 4 FD - OCC elements, but the total number of DMRS REs in the frequency domain is 6, so the CDM group may cross two different PRBs. Further, the PRG can include two or more PRBs with the same precoding being performed on the two or more included PRBs. Thus, the extended CDM group may cross the PRG boundary. Note that the expression "the CDM group crosses the PRG boundary" means that the DMRS REs to be encoded by one OCC within the CDM group cross the PRG boundary.

[0126] As shown in FIG. 13, the even PRBs and the odd PRBs are consecutive and belong to PRG N and PRG N+1, respectively.

[0127] For DMRS pattern A in option 1 of DMRS type 1, one extended OCC (e.g., repeating

Number

Number

Number

[0128] Similarly, in the case of option 2 in DMRS type 1, there are three sets of DMRS REs 1330, 1340, and 1350 to be encoded by the same extended OCC, and the set of DMRS REs 1340 crosses the PRG boundary. Therefore, the extended OCC for encoding DMRS is regarded as crossing the PRG boundary, which means that the extended CDM group crosses the PRG boundary.

[0129] One PRG can include two or more PRBs, and the same precoding is applied to two or more PRBs. For another PRG, different precodings can be configured. In this situation, the same extended OCC is used to encode the DMRS set, but the DMRS RE sets across the PRG boundary may be precoded differently, and as a result, the accuracy of channel estimation based on this DMRS RE set may be affected. Therefore, in some embodiments, the network device can configure the same precoding for two consecutive PRGs (such as PRG N and PRG N+1 shown in FIG. 13) where the extended CDM group crosses the boundary between two consecutive PRGs.

[0130] With this configuration, the same precoding is applied to the DMRS RE sets across the PRG boundary, so the accuracy of channel estimation based on this DMRS RE set can be ensured.

[0131] In some embodiments, when the wireless device receives the DMRS transmitted from the network device, the wireless device may not use the DMRS for channel estimation when the extended CDM group crosses the boundary between two consecutive PRGs. For example, the DMRS RE sets 1310 or 1340 may not be used by the wireless device for channel estimation because the corresponding CDM group crosses the PRG boundary. Therefore, even if the DMRS RE set across the PRG boundary is encoded by one extended OCC but precoded differently, this DMRS RE set may not be used by the wireless device for channel estimation, and the accuracy of channel estimation may not be affected by that DMRS RE set.

[0132] Next, the alignment of the CDM group will be described.

[0133] In the case of frequency-selective precoding, the PRG is configured with reference to a fixed reference point (e.g., point A corresponding to common resource block 0).

[0134] In some embodiments, the network device can configure the starting point of the extended CDM group with reference to a reference point (such as point A) for configuring the PRG. The "starting point of the extended CDM group" according to the present disclosure means the starting point (e.g., PRB) for encoding the DMRS RE with one extended OCC within the extended CDM group. With this configuration, the encoding for DMRS using the extended CDM group can be aligned with the PRG so as to avoid the CDM group crossing the PRG boundary (and the extended OCC for encoding the DMRS crossing the PRG boundary).

[0135] For resource allocation type 0 configured with a bitmap, the resource block group (RBG) is configured with reference to point A. The RBG is configured to include an even number of PRBs. In the case of an even number of PRBs, since the extended OCC always repeats three times in two consecutive PRBs, the CDM group does not cross the PRG boundary. Therefore, by configuring the starting point of the extended CDM group to refer to the same point A, it is possible to avoid the case where the CDM group crosses the PRG boundary.

[0136] For resource allocation type 1 composed of the starting PRB of the scheduled physical downlink shared channel (PDSCH) and the number of PRBs for the PDSCH, in some embodiments, in addition to configuring the starting point of the extended CDM group for encoding the DMRS to refer to the same point A, the network device can configure the starting PRB of the PDSCH to have an even number of PRB distances to the reference point. Thereby, since the starting PRB of the PDSCH is configured to have an even number of PRB distances to point A, it is possible to avoid the case where the CDM group crosses the PRG boundary.

[0137] In some embodiments, when the number of frequency domain resource elements occupied by the DMRS in one PRB adjacent to the PRG boundary is less than the size of the extended OCC in the frequency domain, the network device can transmit a DMRS with the frequency occupancy of the plurality of frequency domain resource elements excluded, which means that the transmission of the plurality of frequency domain resource elements of the DMRS is cancelled. For example, if there are only two DMRS REs in the frequency domain of one PRB adjacent to the PRG boundary and the extended OCC used to encode the two DMRS REs has the size of four FD-OCC elements, there are not enough DMRS REs for encoding. In this case, the corresponding two DMRS REs are not transmitted.

[0138] The above embodiments disclose DMRS pattern design with CDM group extension. Hereinafter, the DMRS indication design with CDM group extension will be described.

[0139] The legacy DMRS indication is used to indicate the legacy DMRS ports to be used by the DMRS. The legacy DMRS indication can be dynamically configured by the network device (e.g., through DCI). The wireless device can determine the corresponding legacy DMRS port based on the legacy DMRS indication by referring to the legacy antenna port indication table.

[0140] In some embodiments, the legacy antenna port indication table can be reused for the DMRS indication according to the present disclosure.

[0141] For each legacy DMRS port indicated by DCI, it corresponds to two new ports. For example, as described above, legacy DMRS port n can be split into a pair of new DMRS port n and new DMRS port (n + M), where M is the maximum number of legacy supportable DMRS ports. For DMRS type 1, M = 4 for 1-symbol DMRS and M = 8 for 2-symbol DMRS. For DMRS type 2, M = 6 for 1-symbol DMRS and M = 12 for 2-symbol DMRS.

[0142] In some embodiments, the network device can indicate the correspondence between DMRS and DMRS ports to the wireless device. The correspondence indicates one of (1) the DMRS corresponding to DMRS port n, (2) the DMRS corresponding to DMRS port (n + M), (3) the DMRS corresponding to both DMRS port n and DMRS port (n + M), and (4) the DMRS not corresponding to either DMRS port n or DMRS port (n + M).

[0143] In this way, for example, by further using a 2-bit correspondence indication, the legacy antenna port indication table can be reused, and the DMRS indication according to the present disclosure can have backward compatibility.

[0144] In some embodiments, one correspondence can be indicated for multiple DMRSs. For example, the correspondence may be configured semi-statically for multiple DMRSs (e.g., through radio resource control (RRC) signaling), so that the same correspondence between DMRS and DMRS port is applied to these DMRSs. Thereby, the overhead for correspondence indication can be reduced. The correspondence can also be configured via a media access control (MAC) control element (CE) or DCI.

[0145] In some embodiments, the correspondence may be shown separately for each DMRS. For example, the correspondence may be dynamically configured by a network device (e.g., through DCI). Thereby, a flexible correspondence between DMRS and DMRS ports can be realized.

[0146] The above DMRS indication according to the present disclosure is described by way of an example of downlink DMRS. It should be noted that the DMRS indication design according to the present disclosure can be similarly applied to uplink DMRS. More specifically, with the DMRS indication according to the present disclosure, the legacy antenna port indication tables in 3GPP specifications (e.g., 38.212) for both downlink and uplink can be reused based on the DMRS indication design according to the present disclosure. The legacy antenna port indication tables include Tables 7.3.1.1.2-8 / 9 / 10 / 11 / 12 / 13 / 14 / 15 / 16 / 17 / 18 / 19 / 20 / 21 / 22 / 23 for UL DCI format 0_1 / 0_2 and Tables 7.3.1.2.2-1 / 2 / 3 / 4 / 1A / 2A / 3A / 4A for DL DCI format 1_1 / 1_2 shown below.

[0147] The legacy DMRS indication corresponds to the column "Value" of the following tables, and the corresponding DMRS port(s) can be determined based on the column "DMRS port(s)" of these tables. Taking Table 7.3.1.2.2-3 as an example, when the DMRS indication value is "10", it can be determined that DMRS ports 0-3 should be used for DMRS transmission.

[0148] By adding the correspondence indication between the DMRS and the DMRS ports, when the correspondence indicates the DMRS corresponding to the DMRS port n, the DMRS ports 0 to 3 can be determined for the DMRS indication value of "10". When the correspondence indicates the DMRS corresponding to the DMRS port (n + M), the DMRS port M - (3 + M) can be determined. When the correspondence indicates the DMRS corresponding to both the DMRS port n and the DMRS port (n + M), the DMRS ports 0 to 3 and M - (3 + M) can be determined. Further, when the correspondence indicates the DMRS that does not correspond to either the DMRS port n or the DMRS port (n + M), the DMRS port is not determined.

Table 1

Table 2

Table 3

Table 4

Table 5

Table 6

Table 7

Table 8

Table 9

Table 10

Table 11

Table 12

Table 13

Table 14

Table 15

Table 16

Table 17

Table 18

Table 19

Table 20

Table 21

Table 22

Table 23-1

Table 23-2

Table 24-1

Table 24-2

[0149] Embodiments contemplated in this specification include an apparatus comprising means for performing one or more elements of the signaling shown in FIGS. 11 and 12. This apparatus can be, for example, an apparatus of a base station (such as the network device 218 which is a base station as described in this specification) or an apparatus of a UE (such as the wireless device 202 which is a UE as described in this specification).

[0150] Embodiments contemplated herein may include one or more non-transitory computer-readable media including instructions that, when executed by one or more processors of an electronic device, cause the electronic device to perform one or more elements of the signaling shown in FIGS. 11 and 12. Such non-transitory computer-readable media may be, for example, the memory of a base station (such as the memory 222 of the network device 218 which is a base station as described herein) or the memory of a UE (such as the memory 206 of the wireless device 202 which is a UE as described herein).

[0151] Embodiments contemplated herein include an apparatus comprising logic, module, or circuitry for performing one or more elements of the signaling shown in FIGS. 11 and 12. Such apparatus may be, for example, an apparatus of a base station (such as the network device 218 which is a base station as described herein) or an apparatus of a UE (such as the wireless device 202 which is a UE as described herein).

[0152] Embodiments contemplated herein include an apparatus comprising one or more processors and one or more computer-readable media including instructions that, when executed by the one or more processors, cause the one or more processors to perform one or more elements of the signaling shown in FIGS. 11 and 12. Such apparatus may be, for example, an apparatus of a base station (such as the network device 218 which is a base station as described herein) or an apparatus of a UE (such as the wireless device 202 which is a UE as described herein).

[0153] Embodiments contemplated herein include signals described in, or associated with, one or more elements of the signaling shown in FIGS. 11 and 12.

[0154] Embodiments contemplated herein include a computer program or computer program product that includes instructions, and execution of the program by a processing element causes the processing element to execute one or more elements of the signaling shown in FIGS. 11 and 12. The processor may be a processor of a base station (such as the processor(s) 220 of the network device 218 which is a base station as described herein). These instructions may be located, for example, within the processor and / or on the memory of the base station (such as the memory 222 of the network device 218 which is a base station as described herein). The processor may be a processor of a UE (such as the processor(s) 204 of the wireless device 202 which is a UE as described herein). These instructions may be located, for example, within the processor and / or on the memory of the UE (such as the memory 206 of the wireless device 202 which is a UE as described herein).

[0155] For one or more embodiments, at least one of the components described in one or more of the foregoing figures may be configured to perform one or more operations, techniques, processes, and / or methods as described herein. For example, the baseband processor described above in connection with one or more of the figures herein may be configured to operate in accordance with one or more of the examples described herein. As another example, circuitry associated with a UE, base station, network element, etc., as described above in connection with one or more of the foregoing figures may be configured to operate in accordance with one or more of the examples described herein.

[0156] Any of the above embodiments, unless otherwise specified, can be combined with any other embodiment (or combination of embodiments). The foregoing description of one or more implementations provides illustration and description, but is not intended to be exhaustive or to limit the scope of the embodiments to the precise forms disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the various embodiments.

[0157] Embodiments and implementations of the systems and methods described herein can include various operations that can be embodied in machine-executable instructions executed by a computer system. The computer system may include one or more general-purpose or special-purpose computers (or other electronic devices). The computer system may include hardware components that include specific logic for performing the operations, or may include a combination of hardware, software, and / or firmware.

[0158] It should be recognized that the systems described herein include descriptions of specific embodiments. These embodiments can be combined in a single system, partially combined with other systems, divided among multiple systems, or divided or combined in other ways. Additionally, it is contemplated that parameters, attributes, aspects, etc. of one embodiment can be used in another embodiment. The parameters, attributes, aspects are described in one or more embodiments only for clarity, and it is recognized that the parameters, attributes, aspects, etc. can be combined with or substituted for the parameters, attributes, etc. of another embodiment unless specifically disclaimed herein.

[0159] The use of personal information should be fully understood to comply with privacy policies and practices that are generally recognized as meeting or exceeding industry or government requirements for maintaining user privacy. In particular, personal information data should be managed and handled to minimize the risk of unintended or unauthorized access or use, and the nature of the authorized use should be clearly shown to the user.

[0160] Although the foregoing has been described in some detail for clarity, it will be apparent that certain changes and modifications can be made without departing from the principles thereof. It should be noted that there are many alternative ways of implementing both the processes and apparatus described herein. Accordingly, this embodiment should be regarded as illustrative and not restrictive, and the description is not to be limited to the details given herein but may be modified within the scope of the appended claims and their equivalents.

Claims

1. A network device, comprising: a memory in which instructions are stored; at least one processor, the at least one processor executing the instructions stored in the memory to generate a demodulation reference signal (DMRS), and transmit the DMRS to a wireless device, wherein the DMRS is encoded with one of a plurality of extended orthogonal cover codes (OCCs) belonging to an extended code division multiplexing (CDM) group, the extended CDM group being generated by extending a legacy CDM group including a plurality of legacy OCCs, and the number of frequency domain elements in each of the plurality of extended OCCs is extended to twice the number of frequency domain elements in each of the plurality of legacy OCCs. A network device.

2. The frequency occupancy for the resource element of the DMRS is doubled by repeating the frequency occupancy of the legacy DMRS pattern in consecutive frequency domain resource elements. The network device according to claim 1.

3. The pair of extended OCCs is generated based on one legacy OCC, one of the extended OCCs in the pair being generated by repeating the frequency domain elements in the legacy OCC twice, and the other extended OCC in the pair being generated by concatenating the frequency domain elements in the legacy OCC and the phase-inverted frequency domain elements in the legacy OCC. The network device according to claim 1.

4. The at least one processor further executes the instructions stored in the memory to further configure the same precoding for the two consecutive precoding resource block groups (PRGs) across the boundary between the two consecutive PRGs where the extended CDM group crosses. The network device according to claim 1.

5. The at least one processor further executes the instructions stored in the memory to configure the start point of the extended CDM group with reference to a reference point for constituting a PRG. The network device according to claim 1.

6. The at least one processor executes the instructions stored in the memory to The starting physical resource block (PRB) of the scheduled physical downlink shared channel (PDSCH) is further configured to be one having the even PRB distance to the reference point. The network device according to claim 5.

7. The at least one processor executes the instructions stored in the memory to when the number of frequency domain resource elements occupied by the DMRS in one PRB adjacent to the boundary of the PRG is less than the size of the extended OCC in the frequency domain, further configured to cancel the transmission of the plurality of frequency domain resource elements of the DMRS. The network device according to claim 5.

8. One of the extended OCCs in the pair is assigned to the same DMRS port n corresponding to the legacy OCC, and the other extended OCC in the pair is assigned to the DMRS port (n + M), where M is the maximum number of legacy supportable DMRS ports. The network device according to claim 3.

9. The at least one processor executes the instructions stored in the memory to further configure the wireless device to indicate the correspondence between the DMRS and the DMRS port, The correspondence is (1) the DMRS corresponding to the DMRS port n, (2) the DMRS corresponding to the DMRS port (n + M), (3) the DMRS corresponding to both the DMRS port n and the DMRS port (n + M), (4) the DMRS not corresponding to either the DMRS port n or the DMRS port (n + M), and indicates one of them. The network device according to claim 8.

10. One correspondence relationship is shown for a plurality of DMRSs. The network device according to claim 9.

11. A wireless device, comprising a memory in which instructions are stored, and at least one processor, and the at least one processor executes the instructions stored in the memory to receive a demodulation reference signal (DMRS) from a network device, configured to perform channel estimation based on the DMRS. The first DMRS is encoded by one of a plurality of first orthogonal cover codes (OCCs) belonging to a first code division multiplexing (CDM) group, and the first CDM group is generated by expanding a second CDM group including a plurality of second OCCs. The number of frequency domain elements in each of the plurality of first OCCs is expanded to twice the number of frequency domain elements in each of the plurality of second OCCs. A wireless device.

12. The frequency occupancy for the resource element of the DMRS is doubled by repeating the frequency occupancy of the legacy DMRS pattern in consecutive frequency domain resource elements. The wireless device according to claim 11.

13. The pair of the expanded OCCs is generated based on one legacy OCC. One of the expanded OCCs in the pair is generated by repeating the frequency domain elements in the legacy OCC twice, and the other expanded OCC in the pair is generated by concatenating the frequency domain elements in the legacy OCC and the phase-inverted frequency domain elements in the legacy OCC. The wireless device according to claim 11.

14. The at least one processor executes the instructions stored in the memory to When the expanded CDM group crosses the boundary between two consecutive PRGs, it is further configured not to use the DMRS for channel estimation. The wireless device according to claim 11.

15. One of the expanded OCCs in the pair is assigned to the same DMRS port n corresponding to the legacy OCC, and the other expanded OCC in the pair is assigned to DMRS port (n + M), where M is the maximum number of legacy supportable DMRS ports. The wireless device according to claim 13.

16. The at least one processor executes the instructions stored in the memory to The wireless device is further configured to receive an indication of the correspondence between the DMRS and the DMRS port, The correspondence is (1) The DMRS corresponding to DMRS port n, (2) The DMRS corresponding to DMRS port (n + M), (3) The DMRS corresponding to both DMRS port n and DMRS port (n + M), (4) The DMRS corresponding to neither DMRS port n nor DMRS port (n + M), and indicates one of them. The wireless device according to claim 15.

17. One correspondence relationship is shown for a plurality of DMRSs, The wireless device according to claim 16.

18. A network device, A memory in which instructions are stored, At least one processor, and the at least one processor executes the instructions stored in the memory to Receive a demodulation reference signal (DMRS) from a wireless device, Be configured to perform channel estimation based on the DMRS, The DMRS is encoded by one of a plurality of extended orthogonal cover codes (OCCs) belonging to an extended code division multiplexing (CDM) group, and the extended CDM group is generated by extending a legacy CDM group including a plurality of legacy OCCs, and the number of frequency domain elements in each of the plurality of extended OCCs is extended to twice the number of frequency domain elements in each of the plurality of legacy OCCs. A network device.

19. A wireless device, A memory in which instructions are stored, At least one processor, and the at least one processor executes the instructions stored in the memory to Receive a control signal from a network device, Be configured to generate a demodulation reference signal (DMRS) to be transmitted to the network device in response to the control signal, The DMRS is encoded by one of a plurality of extended orthogonal cover codes (OCCs) belonging to an extended code division multiplexing (CDM) group, and the extended CDM group is generated by extending a legacy CDM group including a plurality of legacy OCCs, and the number of frequency domain elements in each of the plurality of extended OCCs is extended to twice the number of frequency domain elements in each of the plurality of legacy OCCs. A wireless device.

20. A method for a network device, Generating a demodulation reference signal (DMRS), and Transmitting the DMRS to a wireless device, The method is such that the DMRS is encoded by one of a plurality of extended orthogonal cover codes (OCCs) belonging to an extended code division multiplexing (CDM) group, the extended CDM group is generated by extending a legacy CDM group including a plurality of legacy OCCs, and the number of frequency domain elements in each of the plurality of extended OCCs is extended to twice the number of frequency domain elements in each of the plurality of legacy OCCs.

21. A method for a wireless device, comprising: receiving a demodulation reference signal (DMRS) from a network device; performing channel estimation based on the DMRS. The first DMRS is encoded by one of a plurality of first orthogonal cover codes (OCCs) belonging to a first code division multiplexing (CDM) group, the first CDM group is generated by extending a second CDM group including a plurality of second OCCs, and the number of frequency domain elements in each of the plurality of first OCCs is extended to twice the number of frequency domain elements in each of the plurality of second OCCs.

22. A method for a network device, comprising: receiving a demodulation reference signal (DMRS) from a wireless device; performing channel estimation based on the DMRS. The DMRS is encoded by one of a plurality of extended orthogonal cover codes (OCCs) belonging to an extended code division multiplexing (CDM) group, the extended CDM group is generated by extending a legacy CDM group including a plurality of legacy OCCs, and the number of frequency domain elements in each of the plurality of extended OCCs is extended to twice the number of frequency domain elements in each of the plurality of legacy OCCs.

23. A method for a wireless device, comprising: receiving a control signal from a network device; generating a demodulation reference signal (DMRS) to be transmitted to the network device in response to the control signal. The DMRS is encoded by one of a plurality of extended orthogonal cover codes (OCCs) belonging to an extended code division multiplexing (CDM) group, the extended CDM group being generated by extending a legacy CDM group including a plurality of legacy OCCs, and the number of frequency domain elements in each of the plurality of extended OCCs is extended to twice the number of frequency domain elements in each of the plurality of legacy OCCs. Claim 24 A non-transitory computer-readable memory medium storing program instructions that, when executed by a computer system, cause the computer system to execute the method according to any one of claims 20 to 23. Claim 25 A computer program product comprising program instructions that, when executed by a computer, cause the computer to execute the method according to any one of claims 20 to 23.

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