Method for multiplexing DMRS ports with time-domain bundling

Abstract

Described is a UE apparatus (202) is configured to: obtain demodulation reference signals, DMRS, information from a base station, BS, apparatus (201), the DMRS information comprising a DMRS configuration, the DMRS configuration comprising an indication of the number of supported orthogonal DMRS ports, the indication for triggering bundling of time divisions each corresponding to different DMRS ports. In this way, more orthogonal DMRS ports are supported to enable more simultaneous data transmissions without significant reduction in channel estimation performance.

Description

[0001] METHOD FOR MULTIPLEXING DMRS PORTS WITH TIME-DOMAIN BUNDLING

[0002] TECHNICAL FIELD

[0003] This disclosure relates to apparatuses and methods for multiplexing DMRS ports with time-domain bundling.

[0004] BACKGROUND

[0005] Based on previously estimated channel state information, transmitters perform optimized data transmissions by precoding and / or scheduling, among other actions. Due to said optimization actions adapted to channel conditions, the effective channel experienced at the receiver differs from the original channel. Said effective channel is estimated from demodulation reference signals (DMRS) embedded in the data transport channel to perform coherent demodulation of the data.

[0006] The achieved throughput of the transmissions relies on the accuracy of estimation of the effective channel and number of resource elements (REs) available for data. To avoid pilot contamination and support accurate channel estimation of the effective channels for different layers and / or users, DMRS are orthogonal either in the time-, frequency- or code-domain. For example, when performing multi-user multiple-input multiple-output (MU-MIMO) grouping, the different layers and / or users will rarely have perfect orthogonality, therefore there will be some level of pilot contamination within a cell if resource elements (REs) allocated for DMRS are not orthogonal in time-, frequency- or code-domain. Pilot contamination on DMRS severely affects the achieved throughput. Therefore, the number of users that can be simultaneously supported depends on the number of orthogonal DMRS ports.

[0007] Current fifth generation wireless communication system (5G) supports up to 24 orthogonal DMRS ports. A communication network in the future is expected to support significantly more DMRS ports compared to 5G-Advanced (5G-A) (e.g., double the amount corresponds to 48 DMRS ports). Given the significant increased amount of bandwidth that could be allocated to users, simply increasing the sparsity of DMRS in the frequency domain will decrease the channel estimation performance in frequency-selective channel. Moreover, the orthogonality of current orthogonal cover codes (OCC) is potentially lost for frequency-selective channel.

[0008] Additional challenges relate to the already increased signalling overhead to indicate DMRS ports. As of Release 18, the signalling overhead is already 8 bits for 24 layers. There is a need to minimally increase signalling overhead when indicating the extended DMRS ports.

[0009] A number of state-of-the-art solutions to address the overhead of reference signals in massive MIMO systems exist:

[0010] Solution 1: DMRS Configuration Type I: 3GPP defines a regular DMRS resource structure, so-called “comb” structure to multiplex DMRS from different DMRS ports belonging to same user or different users in the frequency or code domain across allocated sub-band to user. Based on the mobility pattern of users and channel environment, 3GPP specified pre-defined additional time-domain locations of DMRS. DMRS has an equivalent “comb-2” structure, where DMRS are multiplexed with a different frequency offset of DMRS or an orthogonal cover code (OCC) is used to code division multiplex (CDM) co-located DMRS of different users / layers, where users using co-located DMRS belong to the same CDM group. The OCC is applied to a pseudo-random Gold sequence across the frequency domain with limited length. The enhanced version of Configuration Type I includes a 2D OCC applied across the frequency and time-domain. When DMRS is allocated on two consecutive OFDM symbols, it can support up to 16 orthogonal DMRS ports. Solution 2: DMRS Configuration Type II: 3GPP defines a second regular DMRS resource structure, where DMRS are located in two adjacent subcarriers (SCs) in the frequency domain and are sparser compared to DMRS Configuration Type I. Due to implicit averaging of the channel lead to improve channel estimation with a implementation-specific channel estimation algorithms. Similar to Configuration Type I DMRS from different DMRS ports are multiplexed in the frequency or code domain, and when DMRS is allocated on two consecutive OFDM symbols it can support up to 24 DMRS ports in its enhanced version.

[0011] These solutions may have the following disadvantages:

[0012] Solution 1: DMRS Configuration Type I: The extension of Configuration Type I DMRS resource structure to support more orthogonal DMRS supports while maintaining channel estimation performance is challenging. Double sparsity of DMRS in frequency domain such as “comb-4”, would only support 32 orthogonal DMRS ports and the channel estimation performance would reduce significantly due to the potential loss of orthogonality between different OCCs in frequency-selective channel. Selectivity in the frequency domain becomes more influential due to wider bandwidths that are expected in a communication network in the future.

[0013] Solution 2: DMRS Configuration Type II: The extension of Configuration Type II DMRS resource structure to support more orthogonal DMRS supports in the frequency or code domain is also challenging due to the delay spread (DS) as in Solution 1. The challenge is more pronounced for Configuration Type II than Configuration Type I due to the higher sparsity of DMRS in the frequency domain. To support the target of 48 or 64 orthogonal DMRS ports, such as CDM-16 will reduce performance in scenarios with significant selectivity in the frequency domain. The inclusion of a third consecutive OFDM symbol with DMRS will significantly increase the overhead of reference signals in the data transport channel.

[0014] It is desirable to develop an apparatus and method that overcomes the above problems.

[0015] SUMMARY

[0016] According to a first aspect, there is provided a user equipment, UE, apparatus, the UE apparatus comprising one or more processors and a memory storing in non-transient form data defining program code executable by the one or more processors, wherein the program code is executable by the one or more processors so that the UE apparatus is configured to: obtain demodulation reference signals (DMRS) information from a base station, BS, apparatus, the DMRS information comprising a DMRS configuration, the DMRS configuration comprising an indication of the number of supported orthogonal DMRS ports, the indication for triggering bundling of time divisions each corresponding to different DMRS ports. In this way, UE assumes bundled time divisions have similar channel characteristics, therefore, if UE measures DMRS at time division N, UE does not measure DMRS at time division N+l . Freed resources are then used by DMRS of other UEs where each UE applies the same behaviour. In this way, more orthogonal DMRS ports are simultaneously supported without significant reduction in channel estimation performance.

[0017] In some implementations, the UE apparatus may be configured to undertake session establishment with the BS apparatus, the session establishment comprising obtaining the DMRS information from the BS apparatus. In some implementations, the UE apparatus may be configured to undertake transmission session with the BS apparatus, the transmission session comprising obtaining the DMRS information from the BS apparatus. In this way, the DMRS information may be provided during session establishment and then updated dynamically. In some implementations, the indication may be an M-bit that indicates bundling time division N up to time division N+K-l , where K corresponds to the number of bundled time divisions for multiplexing DMRS ports. In this way, orthogonal DMRS ports may be configured with a M-bit signalling with low signalling overhead where each codepoint corresponds to a different number of supported orthogonal DMRS ports.

[0018] In some implementations, the indication may indicate bundling of K time divisions for multiplexing DMRS ports, wherein DMRS ports in time division N are not overlapped with DMRS ports up to time division N+K-l . In this way, DMRS ports are not overlapped in the bundled time divisions and pilot contamination between users or layers is avoided.

[0019] In some implementations, the UE apparatus may be configured to configure bundled time divisions to multiplex DMRS ports by mapping the indication to integer U that indicates the number of supported orthogonal DMRS ports using the formula. In this way, a predetermined procedure in the formula may be used to map indication to number of supported orthogonal DMRS ports.

[0020] In some implementations, the DMRS configuration may comprise an integer U that indicates the number of supported orthogonal DMRS ports. In this way, the DMRS configuration itself may provide the number of supported orthogonal DMRS ports.

[0021] In some implementations, the UE apparatus may be configured to use a formula to map the number of supported orthogonal DMRS ports to the number of bundled time divisions K. In this way, a predetermined procedure in the formula may be used in the mapping of number of supported orthogonal DMRS ports U to number of bundled time divisions K.

[0022] In some implementations, the UE apparatus may be configured, upon receiving DMRS port index A, to configure DMRS port index with further formula which extends DMRS port indices to support the additional DMRS ports. In this way, DMRS port indices may be extended based on the predetermined procedure in the further formula.

[0023] In some implementations, the UE apparatus may be configured to receive DMRS in accordance with the configured DMRS ports with the indication. In this way, the DMRS may be received under the control of the indication.

[0024] In some implementations, the UE apparatus may be configured to execute specific behaviour in dependence on the indication, the specific behaviour comprising one or more of: wait until DMRS(s) at time division N+2 are received before channel estimation and demodulation, replicate estimated channel matrix from time division N to time division N+l, joint channel estimation across time divisions, use channel matrix estimated from time division N to estimate channel matrix from time division N+l to decode data. In this way, indication may control the types of specific behaviour executed.

[0025] In some implementations, after the bundled time divisions to multiplex DMRS ports are configured, the UE apparatus may be configured to perform channel estimation and / or data demodulation in accordance with the configured bundled time divisions to multiplex DMRS ports. In this way, the configured bundled time divisions to multiplex DMRS ports may be used to control the channel estimation and / or data demodulation behaviour associated to the DMRS(s) of the same DMRS port at time division N and at time division N+K.

[0026] In some implementations, the apparatus may be configured to receive simultaneous downlink data transmissions with DMRS according to the configured DMRS ports supporting up to U simultaneous data transmissions. In this way, the configured DMRS ports with the indication may be used to support up to U simultaneous downlink data transmissions while avoiding significant reduction in channel estimation performance. According to a second aspect, there is provided a base station, BS, apparatus, the BS apparatus comprising one or more processors and a memory storing in non-transient form data defining program code executable by the one or more processors, wherein the program code is executable by the one or more processors so that the BS apparatus is configured to: send demodulation reference signals (DMRS) information to a user equipment, UE, apparatus, the DMRS information comprising a DMRS configuration, the DMRS configuration comprising an indication of the number of supported orthogonal DMRS ports, the indication for triggering bundling of time divisions each corresponding to different DMRS ports. In this way, UE assumes bundled time divisions have similar channel characteristics, therefore, if UE measures DMRS at time division N, UE does not measure DMRS at time division N+l . Freed resources are then used by DMRS of other UEs where each UE applies the same behaviour. In this way, more orthogonal DMRS ports are simultaneously supported without significant reduction in channel estimation performance.

[0027] According to a third aspect, there is provided a method, carried out by a user equipment, UE, apparatus, comprising: obtaining demodulation reference signals (DMRS) information from a base station, BS, apparatus, the DMRS information comprising a DMRS configuration, the DMRS configuration comprising an indication of the number of supported orthogonal DMRS ports, the indication for triggering bundling of time divisions each corresponding to different DMRS ports. In this way, UE assumes bundled time divisions have similar channel characteristics, therefore, if UE measures DMRS at time division N, UE does not measure DMRS at time division N+l . Freed resources are then used by DMRS of other UEs where each UE applies the same behaviour. In this way, more orthogonal DMRS ports are simultaneously supported without significant reduction in channel estimation performance.

[0028] According to a fourth aspect, there is provided a method, carried out by a base station, BS, apparatus, comprising: sending demodulation reference signals (DMRS) information to a user equipment, UE, apparatus, the DMRS information comprising a DMRS configuration, the DMRS configuration comprising an indication of the number of supported orthogonal DMRS ports, the indication for triggering bundling of time divisions each corresponding to different DMRS ports. In this way, UE assumes bundled time divisions have similar channel characteristics, therefore, if UE measures DMRS at time division N, UE does not measure DMRS at time division N+l . Freed resources are then used by DMRS of other UEs where each UE applies the same behaviour. In this way, more orthogonal DMRS ports are simultaneously supported without significant reduction in channel estimation performance.

[0029] BRIEF DESCRIPTION OF THE FIGURES

[0030] The present disclosure will now be described by way of example with reference to the accompanying drawings. In the drawings:

[0031] Figure 1 is a schematic illustration of a time-frequency resource grid to support more orthogonal DMRS ports by bundling consecutive time divisions where DMRS ports in time division N are not overlapped with time division N+l .

[0032] Figure 2 is a schematic illustration of an example procedure of the present system.

[0033] Figure 3a is a table describing the mapping of codepoint (bits) to the configuration related to time-domain bundling of DMRS ports. Figure 3b is a diagram describing M-bit highLayerTransmission indication.

[0034] Figure 4 is a table describing alternative mapping of codepoint (bits) to configuration related to time-domain bundling of DMRS ports.

[0035] Figure 5 is a table mapping from highLayerTransmission indication to mimberOI'SiipportedDM RS Ports U. Figure 6 is a new table extended from Table 7.3.1.2.2 from TS 38.214.

[0036] Figure 7a shows example information elements for the RRC configuration. Figure 7b shows example information elements for the DCI format.

[0037] Figure 8 shows an example of a computer implemented method of the procedure of the present system.

[0038] Figure 9 shows an example of a computer apparatus configured to perform the methods described herein.

[0039] DETAILED DESCRIPTION

[0040] The apparatuses and methods described herein concern apparatuses and methods for multiplexing DMRS ports with timedomain bundling.

[0041] Embodiments of the present disclosure may tackle one or more of the problems previously mentioned by: obtaining demodulation reference signals (DMRS) information from a base station, BS, apparatus, the DMRS information comprising a DMRS configuration, the DMRS configuration comprising an indication of the number of supported orthogonal DMRS ports, the indication for triggering bundling of time divisions each corresponding to different DMRS ports. In this way, UE assumes bundled time divisions have similar channel characteristics, therefore, if UE measures DMRS at time division N, UE does not measure DMRS at time division N+l . Freed resources are then used by DMRS of other UEs where each UE applies the same behaviour. In this way, more orthogonal DMRS ports are simultaneously supported without significant reduction in channel estimation performance

[0042] The following acronyms are used herein:

[0043] Fifth-generation mobile network 5G

[0044] Long Term Evolution LTE

[0045] New Radio NR

[0046] Radio Access Network RAN

[0047] Base Station BS

[0048] User Equipment UE

[0049] Time Division Duplex TDD

[0050] Multiple-Input-Multiple-Output MIMO

[0051] Multi-user Multiple-Input-Multiple-Output MU-MIMO

[0052] Demodulation Reference Signals DMRS

[0053] Resource element RE

[0054] Sub-carrier SC

[0055] Delay Spread DS

[0056] Doppler Spread DOS

[0057] Resource block RB

[0058] Physical uplink control channel PUCCH

[0059] Uplink control information UCI physical downlink control channel PDCCH Downlink control information DCI

[0060] Orthogonal Cover Code OCC Code Division Multiplex CDM

[0061] The following key terms are used herein:

[0062] Pilot signals: Known signals both to transmitter and receiver used in modem communication systems to perform channel estimation, Multiple-Input Multiple-Output (MEMO) precoding, Adaptive Modulation and Coding (AMC), scheduling, beammanagement, and other procedures related to adapting the transmission to the current channel conditions. These signals are typically “scrambled” with data signals in time and frequency domains so the channel conditions experienced by pilots and data are as identical as possible.

[0063] Demodulation Reference Signals (DMRS): These are pilot signals used by receivers to estimate the effective channel within the data transport channel to perform coherent demodulation of data. DMRS are embedded with the resources used for data transmission and are used for both uplink (UL) and downlink (DL) transmissions between a particular UE and gNB. The achieved throughput relies on the accuracy of estimation of the effective channel as well as the number of resource elements (REs) available for data transmission. The optimization actions performed by the transmitter on the data to adapt to current channel conditions include precoding, scheduling, etc.

[0064] Pilot Contamination: Phenomenon which occurs when reference signals from transmitter A reach receiver and are interfered by signals of other transmitters. As a consequence, channel estimation performance degrades significantly as the composite received signal differs significantly from the known reference signal due to interference.

[0065] DMRS port: Set of resource elements (RE) allocated for DMRS which are orthogonal in the time-, frequency- or code-domain with respect to other users. Therefore, DMRS can support accurate channel estimation of the effective channel for coherent data demodulation. The word “port” refers to an analogy to wired communication, where a port of a network device won’t interfere other connected ports.

[0066] The present system may solve the technical problem of the need to support 48 / 64 or more orthogonal DMRS ports.

[0067] Requirements:

[0068] • Avoid significant reduction in channel estimation performance (e.g., CDM with sparse pilots along freq, domain will decrease performance in frequency-selective channel).

[0069] • Limited signalling overhead to indicate DMRS port (already 8 bits for 24 layers in R18).

[0070] • Interoperable with current DMRS pattern configurations.

[0071] The present system provides the time-domain bundling of DMRS ports where time divisions correspond to different DMRS ports. As an example, in Figure 1, the multiplexing of DMRS ports with bundling of consecutive time divisions is shown. Figure 1 shows a time-frequency resource grid example to support more consecutive time-divisions bundled to support more DMRS ports. In this context, bundling means to assume channel remains with similar characteristics across consecutive time divisions (e.g., slots or OFDM symbols). Therefore, receivers assume a specific behaviour for the channel estimation / data demodulation process across bundled time-divisions, while system supports simultaneous transmission of significantly more layers / users (e.g., with 2 bundled time-divisions 101, 102, 48 layers are supported; and with 3 bundled time-divisions 103, 104, 105, 64 layers are supported, etc). The intuition of the present system is that receivers based on the time-domain bundling of DMRS ports, will assume channel characteristics within the bundled time divisions remain similar. Therefore, since there are already DMRS measurements from time division N, the device does not perform DMRS measurements on time division N+l . The freed resources are then used by DMRS ports associated to other layers or users. The additional DMRS ports apply the same principles. In this way, the number of DMRS ports that can be supported is duplicated (e.g., doubled in the case of two bundled time divisions). For example, to achieve channel estimation performance, then devices perform a specific behaviour including but not limited to: waiting until DMRS measurement occasion at time division N+2 (for 48 DMRS ports) is received before demodulation, replicate estimated channel matrix, cross-time-division interpolation, use channel matrix estimated from previous time division N to estimate channel matrix from time division N+l .

[0072] Figure 2 shows an example procedure 200 of the present system. The system may comprise a base station (BS) apparatus 201, and one or more user equipment (UE) apparatus 202a, 202b. The BS 201 and the one or more UE 202 may communicate with one another.

[0073] In summary, the BS 201 may send demodulation reference signals (DMRS) information to the UE 202. The DMRS information may comprise a DMRS configuration. The DMRS configuration may comprise an indication of the number of supported orthogonal DMRS ports. The indication may be used for triggering bundling of time divisions each corresponding to different DMRS ports. In response to receiving the indication, the UE may configure the bundling of time divisions each corresponding to different DMRS ports.

[0074] The DMRS information may be sent from the BS 201 to the UE 202 during session establishment 203, and / or dynamically 212. The DMRS information may be sent during step 0 203, and / or during step 8 212.

[0075] In more detail, the BS 201 indicates UE(s) 202a, 202b with high-layer transmission indication. The BS 201 indicates a high- layer transmission indication to UE(s) 202a, 202b (e.g., due to high number of users) to multiplex DMRS ports by bundling time division N with time division N+(K-1 ), where K corresponds to the number of bundled-time divisions for multiplexing DMRS ports.

[0076] BS 201 (transmits) highLayerTransmission indication: is an M-bit indication that indicates bundling of K time divisions to multiplex DMRS ports, where DMRS ports in time division N are not overlapped up to time division N+(K-1 ). The indication can be performed during session establishment 203 or dynamically 204.

[0077] Optionally, BS 201 (transmits) numberOfSupportedDMRSPorts: integer that indicates the number of supported orthogonal DMRS ports U. The indication can be performed during session establishment 203. A formula (e.g., table) may be used to map highLayerTransmission indication to time-domain bundling configuration of DMRS ports.

[0078] After the session establishment 203, the system may carry out the following steps:

[0079] At step 1, a CSI-RS signal 204 may be sent from the BS 201 to the UE 202.

[0080] At step 2a, the UE 202 may estimate channel and estimate intercell interference 205a.

[0081] At step 2b, the UE 202 may computer CSI information 205b, such as OI, RI, RSRP, SINR etc.

[0082] At step 3, the UE 202 may send a CSI report 206 to the BS 201.

[0083] At step 4, the UE 202 may send SRS 207 to the BS 201.

[0084] At step 5, the BS 201 may obtain an estimated channel from the SRS 208.

[0085] At step 6, the BS 201 may send a precoded PDSCH 209 to the UE 202.

[0086] This may be a continuous process.

[0087] Following this, the UE 202 may send a CSI report 210 to the BS 201.

[0088] At step 7, the BS 201 may receive data in RLCBuffer for UE 211.

[0089] Following this, dynamically, at step 8 the BS 201 may send the UE 202 a grant signal 212. The grant signal may include the DMRS information, such as a dmrs-highLayerTransmission.

[0090] In a particular embodiment, the indication of time-domain bundling of DMRS ports may be illustrated by Figures 3a and 3b. The indication may be a M-bit highLayerTransmission indication. The M-bit indicates bundling time division N up to time division N+K- 1. In this case, K corresponds to the number of bundled time divisions for multiplexing DMRS ports. K> 1. Put another way, two or more time divisions may be bundled. In a specific embodiment, the indication indicates bundling of K time divisions for multiplexing DMRS ports, wherein DMRS ports in time division N are not overlapped with DMRS ports up to time division N+K-l . A formula may be used to map the number of supported orthogonal DMRS ports to the number of bundled time divisions K.

[0091] The table 300 in Figure 3a describes the mapping of codepoint (bits) to configuration related to time-domain bundling of DMRS ports. The M-bit indication may be as shown in the table 300 in Figure 3a, in particular:

[0092] Codepoint ‘00’: refers to when there is no time domain bundling.

[0093] Codepoint ‘01’: refers to time domain repetition (TS 28.14 Clause 6.1.7) of DMRS ports to perform joint channel estimation or transport block processing across time-divisions.

[0094] Codepoint ‘10’: refers to a 48-layer transmission where time division N+l is mapped to DMRS ports 24-47.

[0095] Codepoint ‘11’: refers to a 64-layer transmission where time division N+ 1 is mapped to DMRS ports 24-47, time division N+2 is mapped to DMRS ports 48-63. Figure 3b illustrates the buddling 301 of the DMRS ports according to the indication in the table 300 in Figure 3a.

[0096] In a particular sub-embodiment, the indication of the time-domain bundling of DMRS ports may be illustrated by Figure 4. The bundled time divisions may be configured to multiplex DMRS ports by mapping the indication to integer U that indicates the number of supported orthogonal DMRS ports using a formula. The DMRS configuration may comprise integer U that indicates the number of supported orthogonal DMRS ports

[0097] Table 400 in Figure 4 describes an alternative mapping of codepoint (bits) to configuration related to time-domain bundling of DMRS ports. The indication may be:

[0098] Codepoint ‘O’: refers to when there is no time domain bundling of DMRS ports. The configuration of PUSCH bundling / time domain repetition can be configured independently as Clause 6.1.7 and TS 28.14.

[0099] Codepoint ‘1’: refers to time domain bundling of DMRS ports for high-layer transmissions based on a pre-configured numberOlSupportedDMRSPorts U during session establishment (e.g., RRC configuration). For example, based on numberOlSupportedDMRSPorts U, K is determined based on the quotient between U and the number of DMRS ports supported with the current DMRS configuration (e.g., DMRS Configuration Type II currently supports up to 24 DMRS ports). In addition, alternatively, the DMRS port indices table can be extended (described in table 600): Alternative Configuration of time-domain bundling of DMRS ports).

[0100] The indication described in present sub-embodiment can be performed dynamically or during session establishment.

[0101] In a particular embodiment, the indication of the time-domain bundling of DMRS ports may be illustrated by Figure 5.

[0102] The UE 202, upon the reception of the M-bit highLayerTransmission indication 203, 212, maps the configuration associated to the highLayerTransmission indication to numberOlSupportedDMRSPorts U. Said mapping can be described in Table 500. Table 500 shows mapping from highLayerTransmission indication to numberOlSupportedDMRSPorts U.

[0103] The UE 202, when highLayerTransmission = 10, uses the numberOlSupportedDMRSPorts U from table 500 to understand the DMRS port indication as A=A+U. Other alternatives to configure numberOlSupportedDMRSPorts U are detailed in information elements 700, 701 : DMRS Dynamic and Session Establishment Configuration.

[0104] The UE 202, upon the reception and decoding of DCI 212, may read the antenna port index and may map it to DMRS ports A using for example Table 7.3.1.2.2 from TS 38.214. For sake of explanation, as an example, consider UE 202 is indicated with antenna port index 9 with two codewords, according to Table 7.3.1.2.2 from TS 38.214 and highLayerTransmission = 10. Therefore, UE 202 will map antenna port index 9 to DMRS ports 0-3, 12-15 and (0-3) + (U=24), (12-15)+(U=24). UE 202 will utilize DMRS ports 0-3, 12-15, 24-47 and 36-39.

[0105] Thereafter, UE 202 may perform implementation-specific channel estimation / data demodulation according to the bundling of time-divisions to multiplex DMRS ports. For example, UE 202 may estimate the channel with least-squares and interpolation in time-division N and extends (e.g., replicates) channel estimate to time-division N+l for DMRS ports 0-3, 12-15. UE 202 may estimate the channel with least-squares and interpolation in time-division N+l for DMRS ports 24-47 and 36-39.UE extends (e.g., replicates) channel estimate for time-division N+2, and so forth. UE 202 implementation-specific behaviour for channel estimation / data demodulation / decoding may comprise one or more of: wait until DMRS(s) at time division N+2 are received before channel estimation and demodulation, replicate estimated charnel matrix from time division N to time division N+l, joint channel estimation across time divisions, and use channel matrix estimated from time division N to estimate channel matrix from time division N+l to decode data.

[0106] In a particular sub-embodiment, the indication of the time-domain bundling of DMRS ports may be illustrated by Figure 6.

[0107] The UE 202, upon the reception and decoding of DCI 212, may read antenna port index and maps it to DMRS ports using a new extended formula. Put simply, the UE 202 may, upon receiving DMRS port index A, configure DMRS port index with a further formula which extends DMRS port indices to support the additional DMRS ports. For example, a new table 600 in Figure 6, extended from Table 7.3.1.2.2 from TS 38.214, may be used. Extended Antenna Port Indices Table (Table X.X.X.X- X) Antenna Port(s) (1000+DMRS port), dmrs-Type=2, dmrs-TypeEnh is configured, maxLength=l .

[0108] In a particular embodiment, the detailed description of the extension / modifications of message fields in the RRC protocol for Session Establishment Configuration (TS 38.331) and dynamic configuration in DCI (TS 38.214) of highLayerTransmission and numberOlSupportedDMRSPorts may be used as shown in the information elements 700 or information elements 701 in Figures 7a and 7b.

[0109] For session establishment 203 in step 0, the highLayerTransmission and numberOlSupportedDMRSPorts can be included as message fields in PDSCH-Config or PUSCH-Config, as in 700.

[0110] For dynamic configuration 212 in step 8, the highLayerTransmission can be included as message fields in DCI format 1_1 for dynamic indication of high-layer-transmission, as in 701.

[0111] At step 9, the UE(s) 202 configures bundled DMRS ports in time-domain and executes specific behaviour) 213a, 213b. The UE 202, upon indication from BS 201, configures bundled DMRS port(s) in time-domain and executes specific behaviour based 213 on the high-layer transmission indication 203, 212.

[0112] The UE 202, upon received indication from BS 201, may map the highLayerTransmission indication to numberOlSupportedDMRSPorts U and may reuse the DMRS port indices associated to existing DMRS resource patterns. UE 202 may receive indicated DMRS port A and configures new DMRS port index based on numberOlSupportedDMRSPorts U. Optionally, an additional table extends the DMRS port indices.

[0113] UE 202, upon received indication from BS 201, may execute a specific channel estimation and / or data demodulation process across the bundled time-divisions. UE 202 may demodulate data symbols by performing specific behaviour including but not limited to: waiting until DMRS occasion at time division N+2 (for 48 DMRS ports) is received before demodulation, replicating estimated channel matrix, cross-time-division interpolation, use channel matrix estimated from time division N to estimate channel matrix from time division N+l to decode data.

[0114] A first formula (e.g., table) to map highLayerTransmission indication to the number of simultaneously supported orthogonal DMRS ports numberOlSupportedDMRSPorts U may be used.

[0115] Optionally, if the formular above is not used, a second formula (e.g., table) to extend the DMRS port indices to support the additional DMRS ports may be used. A third formula to map indicated DMRS port A to new DMRS port index based on DMRS port A and numberOlSupportedDMRSPorts U may be used.

[0116] UE 201 may transmit the DMRS sequence in the configured DMRS ports.

[0117] Once configured, the UE 202 may be configured to receive DMRS in accordance with the configured DMRS ports with the indication.

[0118] The UE 202 may receive simultaneous downlink data transmissions with DMRS according to the configured DMRS ports supporting up to U simultaneous data transmissions.

[0119] The present system may be applied to the 5G Radio Access Network architecture defined by 3GPP and are documented in TS 38.214, TS 38.211 and TS 38.331.

[0120] The present system may have the following innovative points, and corresponding advantageous effects:

[0121] UE 202 may receive a signalling indicating number of required DMRS ports (i.e., highLayerTransmission) that triggers a configuration bundling of several time divisions where each time division corresponds to different DMRS ports. This may mean that is no need for a new DMRS pattern that reduces DMRS density in the frequency domain and thus reduce performance.

[0122] Signalling may be a N-bit that indicates DMRS ports in different time divisions, where DMRS port in time division 1 are not overlapped with time division N. This may provide low signalling overhead to support 48 / 64 or more layers transmission.

[0123] Device may receive indicated DMRS port A it will use configured number X and will use DMRS port A + X. X is derived from indication or pre-configured. This means it is not necessary to extend antenna ports table and we can reuse current DMRS pattern configurations.

[0124] Device may demodulate data by performing specific behaviour including but not limited to: waiting until DMRS occasion at time division N+2 (for 48 DMRS ports) is received before demodulation, replicating estimated channel matrix, cross-time- division interpolation. In this way, receivers may achieve channel estimation performance with the presence of double or triple DMRS ports (i.e., layers) than in current system (i.e., 5G NR).

[0125] Figure 8 summarises an example of a first method 800. At step 801, the method 700 comprises obtaining demodulation reference signals (DMRS) information from a base station, BS, apparatus, the DMRS information comprising a DMRS configuration, the DMRS configuration comprising an indication of the number of supported orthogonal DMRS ports, the indication for triggering bundling of time divisions each corresponding to different DMRS ports.

[0126] An example of computer apparatus 201, 202 configured to implement the method 700 is schematically illustrated in Figure 9. The apparatus 201, 202 in Figure 9 may apply to either the BS 201 or the UE 202. The computer apparatus 201, 202 may carry out the procedure 200 illustrated in Figure 2. The computer apparatus 201, 202 may be implemented on an electronic device, such as a computer, a computer for a vehicle, laptop, tablet, or smart phone. The computer apparatus 201 , 202 may be connected to the internet.

[0127] The computer apparatus 201, 202 comprises a processor 901 configured to process the datasets in the manner described herein. For example, the processor 901 may be implemented as a computer program running on a programmable device such as a Central Processing Unit (CPU). The computer apparatus 201, 202 comprises a memory 902 which is arranged to communicate with the processor 901. Memory 902 may be a non-volatile memory . The processor 901 may also comprise a cache (not shown in Figure 9), which may be used to temporarily store data from memory 902. The computer apparatus 201, 202 may comprise more than one processor 901 and more than one memory 902. The memory 902 may store data that is executable by the processor 901. The processor 901 may be configured to operate in accordance with a computer program stored in non-transitory form on a machine-readable storage medium. The computer program may store instructions for causing the processor to perform its methods in the manner described herein. The method steps described herein may be carried out by a computer- readable storage medium. The method steps described herein may be carried out by a computer program product.

[0128] The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present disclosure may consist of any such individual feature or combination of features. In view of the foregoing description, it will be evident to a person skilled in the art that various modifications may be made within the scope of the disclosure.

Claims

CLAIMS1. A user equipment, UE, apparatus (202), the UE apparatus (202) comprising one or more processors (901) and a memory (902) storing in non-transient form data defining program code executable by the one or more processors (901), wherein the program code is executable by the one or more processors (901) so that the UE apparatus (202) is configured to: obtain demodulation reference signals, DMRS, information from a base station, BS, apparatus (201), the DMRS information comprising a DMRS configuration, the DMRS configuration comprising an indication of the number of supported orthogonal DMRS ports, the indication for triggering bundling of time divisions each corresponding to different DMRS ports.

2. A UE apparatus (202) according to claim 1, wherein the UE apparatus (202) is configured to undertake session establishment (203) with the BS apparatus (201), the session establishment (203) comprising obtaining the DMRS information from the BS apparatus (201); and / or wherein the UE apparatus (202) is configured to undertake transmission session (212) with the BS apparatus (201), the transmission session (212) comprising obtaining the DMRS information from the BS apparatus (201).

3. A UE apparatus (202) according to any preceding claim, wherein the indication is an M-bit that indicates bundling time division N up to time division N+K-l, where K corresponds to the number of bundled time divisions for multiplexing DMRS ports.

4. A UE apparatus (202) according to claim 3, wherein the indication indicates bundling of K time divisions for multiplexing DMRS ports, wherein DMRS ports in time division N are not overlapped with DMRS ports up to time division N+K-l.

5. A UE apparatus (202) according to any preceding claim, wherein the UE apparatus (202) is configured to configure bundled time divisions to multiplex DMRS ports by mapping the indication to an integer U that indicates the number of supported orthogonal DMRS ports using a formula.

6. A UE apparatus (202) according to claim 5, wherein the DMRS configuration comprises integer U that indicates the number of supported orthogonal DMRS ports.

7. A UE apparatus (202) according to claim 6, wherein the UE apparatus (202) is configured to use the formula to map the number of supported orthogonal DMRS ports to the number of bundled time divisions K.

8. A UE apparatus (202) according to claim 7, wherein the UE apparatus (202) is configured, upon receiving DMRS port index A, to configure DMRS port index with further formula which extends DMRS port indices to support the additional DMRS ports.

9. A UE apparatus (202) according to claim 8, wherein the UE apparatus (202) is configured to receive DMRS in accordance with the configured DMRS ports with the indication.

10. A UE apparatus (202) according to any preceding claim, wherein the UE apparatus (202) is configured to execute specific behaviour in dependence on the indication, the specific behaviour comprising one or more of: wait until DMRS(s) at time division N+2 are received before channel estimation and demodulation, replicate estimated channel matrix from time division N to time division N+l , joint channel estimation across time divisions, use channel matrix estimated from time division N to estimate channel matrix from time division N+l to decode data.

11. A UE apparatus (202) according to any of claims 8 to 10, wherein, after the bundled time divisions to multiplex DMRS ports are configured, the UE apparatus (202) is configured to perform channel estimation (205a) and / or data demodulation (205b) in accordance with the configured bundled time divisions to multiplex DMRS ports.

12. A UE apparatus (202) according to claim 11, wherein the apparatus (202) is configured to receive simultaneous downlink data transmissions (209) with DMRS according to the configured DMRS ports supporting up to U simultaneous data transmissions.

13. A base station, BS, apparatus (201), the BS apparatus (201) comprising one or more processors (901) and a memory (902) storing in non-transient form data defining program code executable by the one or more processors (901), wherein the program code is executable by the one or more processors (901) so that the BS apparatus (201) is configured to: send demodulation reference signals (DMRS) information to a user equipment, UE, apparatus (202), the DMRS information comprising a DMRS configuration, the DMRS configuration comprising an indication of the number of supported orthogonal DMRS ports, the indication for triggering bundling of time divisions each corresponding to different DMRS ports.

14. A method (800), carried out by a user equipment, UE, apparatus (202), comprising: obtaining (801) demodulation reference signals (DMRS) information from a base station, BS, apparatus, the DMRS information comprising a DMRS configuration, the DMRS configuration comprising an indication of the number of supported orthogonal DMRS ports, the indication for triggering bundling of time divisions each corresponding to different DMRS ports.

15. A method (800), carried out by abase station, BS, apparatus (201), comprising: sending (801) demodulation reference signals (DMRS) information to a user equipment, UE, apparatus, the DMRS information comprising a DMRS configuration, the DMRS configuration comprising an indication of the number of supported orthogonal DMRS ports, the indication for triggering bundling of time divisions each corresponding to different DMRS ports.

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