Patent Application
20250070935
The present disclosure relates generally to telecommunications, and, in particular embodiments, to a system and method for providing additional DM-RS ports for 5G MU-MIMO transmission.
Downlink and uplink transmissions in 5G new radio (NR) are based on demodulation reference signals (DM-RSs). In single user/multi user multi input multi output (SU/MU-MIMO) transmissions, each DM-RS port may carry DM-RS(s) used for channel estimation for demodulation of the corresponding data layer transmitted on the same port. It is desirable to have a large number of orthogonal DM-RS ports and multiplexing scheme(s) with relatively small DM-RS overhead, while ensuring good demodulation performance to support a large number of data layers for massive SU/MU-MIMO transmissions.
According to one aspect of the present disclosure, a method is provided that includes: receiving, by a user equipment (UE) from a gNB, a configuration configuring a first orthogonal cover code (OCC) length that is 4 and a second OCC length that is 2 for demodulation reference signal (DM-RS) communication between the gNB and the UE; receiving, by the UE, a signaling indicating the UE to communicate DM-RS(s) according to the first OCC length or the second OCC length; and communicating, by the UE with the gNB, a DM-RS according to the first OCC length or the second OCC length that is indicated by the signaling.
Optionally, in any of the preceding aspects, the signaling is a RRC signaling.
Optionally, in any of the preceding aspects, the signaling is carried in a medium access control (MAC) control element (CE).
Optionally, in any of the preceding aspects, the signaling is carried in a downlink control information (DCI) message.
Optionally, in any of the preceding aspects, the method further includes: sending, by the UE to the gNB, a message acknowledging receipt of the configuration.
Optionally, in any of the preceding aspects, communicating the DM-RS comprises: receiving or sending, by the UE, the DM-RS over DM-RS port(s) associated with OCC(s) of the first OCC length when the first OCC length is indicated by the signaling, or over DM-RS port(s) associated with OCC(s) of the second OCC length when the second OCC length is indicated by the signaling.
Optionally, in any of the preceding aspects, the method further includes: receiving, by the UE, a physical downlink shared channel (PDSCH) over the DM-RS port(s) associated with the OCC(s) of the first OCC length or over the DM-RS port(s) associated with OCC(s) of the second OCC length; or transmitting, by the UE, a physical uplink shared channel (PUSCH) over the DM-RS port(s) associated with the OCC(s) of the first OCC length or over the DM-RS port(s) associated with OCC(s) of the second OCC length.
Optionally, in any of the preceding aspects, an OCC of the first OCC length comprises: [+1+1+1+1], [+1−1+1−1], [+1+j−1−j], or [+1−j−1+j].
Optionally, in any of the preceding aspects, the method further includes: receiving, by the UE, a DCI message comprising an indication; and receiving, by the UE, a DM-RS port offset bit, the indication and the DM-RS port offset bit in combination indicating information of DM-RS port(s) to be used by the UE.
Optionally, in any of the preceding aspects, the method further includes: when the first OCC length is indicated by the signaling and the DM-RS port offset bit has a first value, determining, by the UE, that the DM-RS port(s) to be used have first port number(s) corresponding to the indication according to a first correspondence associated with the second OCC length; or when the first OCC length is indicated by the signaling and the DM-RS port offset bit has a second value, determining, by the UE, that the DM-RS port(s) to be used have second port number(s) obtained by adding a non-zero integer and the first port number(s), respectively.
Optionally, in any of the preceding aspects, the non-zero integer is 8 or 12.
Optionally, in any of the preceding aspects, the method further includes: when the first OCC length is indicated by the signaling and the DM-RS port offset bit has a first value, determining, by the UE, that the DM-RS port(s) to be used have port number(s) according to a first correspondence between the port number(s) and the indication, the first correspondence associated with the second OCC length; or when the first OCC length is indicated by the signaling and the DM-RS port offset bit has a second value, determining, by the UE, that the DM-RS port(s) to be used have port number(s) according to a second correspondence between the port number(s) and the indication, the second correspondence associated with the first OCC length.
Optionally, in any of the preceding aspects, the DM-RS port offset bit is comprised in the DCI message.
Optionally, in any of the preceding aspects, the DCI message is a legacy DCI message.
Optionally, in any of the preceding aspects, a number of DM-RS ports associated with the first OCC length of 4 is: 8 when one symbol is configured for type-1 DM-RS transmissions, 16 when 2 symbols are configured for type-1 DM-RS transmissions, 12 when one symbol is configured for type-2 DM-RS transmissions, or 24 when two symbols are configured for type-2 DM-RS transmissions.
Optionally, in any of the preceding aspects, the communications of DM-RSs comprise type-1 DM-RS transmissions or type-2 DM-RS transmissions.
According to another aspect of the present disclosure, a method is provided that includes: transmitting, by a communication device, a first demodulation reference signal (DM-RS) over first DM-RS port(s) associated with a orthogonal cover code (OCC) of length 4; or receiving, by the communication device, a second DM-RS over second DM-RS port(s) associated with an OCC of length 4.
Optionally, in any of the preceding aspects, the communication device is a user equipment (UE) or a gNB.
Optionally, in any of the preceding aspects, the OCC comprises: [+1+1+1+1], [+1−1+1−1], [+1+j−1−j], or [+1−j−1+j].
Optionally, in any of the preceding aspects, the method further includes: receiving, by the communication device being a user equipment (UE), a DCI message comprising an indication; and receiving, by the UE, a DM-RS port offset bit, the indication and the DM-RS port offset bit in combination indicating information of the DM-RS port(s).
Optionally, in any of the preceding aspects, the method further includes: when the DM-RS port offset bit has a first value, determining, by the UE, that the DM-RS port(s) have first port number(s) corresponding to the indication according to a first correspondence associated with an OCC having a length of 2; or when the DM-RS port offset bit has a second value, determining, by the UE, that the DM-RS port(s) have second port number(s) obtained by adding a non-zero integer and the first port number(s), respectively.
Optionally, in any of the preceding aspects, the non-zero integer is 8 or 12.
Optionally, in any of the preceding aspects, the method further includes: when the DM-RS port offset bit has a first value, determining, by the UE, the DM-RS port(s) according to a first correspondence between the port number(s) and the indication, the first correspondence associated with an OCC having a length of 2; or when the DM-RS port offset bit has a second value, determining, by the UE, the DM-RS port(s) according to a second correspondence between the port number(s) and the indication, the second correspondence associated with the OCC having the length of 4.
Optionally, in any of the preceding aspects, the method further includes: sending, by the communication device being a gNB, a DCI message comprising an indication; and sending, by the gNB, a DM-RS port offset bit, the indication and the DM-RS port offset bit in combination indicating the DM-RS port(s).
Optionally, in any of the preceding aspects, the DM-RS port offset bit is comprised in the DCI message.
Optionally, in any of the preceding aspects, the DCI message is a legacy DCI message.
Optionally, in any of the preceding aspects, a number of DM-RS ports associated with the OCC having the length of 4 is: 8 when one symbol is configured for Type-1 DM-RS transmissions, 16 when two symbols are configured for Type-1 DM-RS transmissions, 12 when one symbol is configured for Type-2 DM-RS transmissions, or 24 when two symbols are configured for Type-2 DM-RS transmissions.
Optionally, in any of the preceding aspects, the first DM-RS or the second DM-RS comprises a Type-1 DM-RS or a Type-2 DM-RS.
According to another aspect of the present disclosure, a method is provided that includes: sending, by a gNB to a user equipment (UE), a configuration configuring a first orthogonal cover code (OCC) length that is 4 and a second OCC length that is 2 for demodulation reference signal (DM-RS) communication between the gNB and the UE; sending, by the gNB, a signaling indicating the UE to communicate DM-RS(s) according to the first OCC length or the second OCC length; and communicating, by the gNB with the UE, a DM-RS according to the first OCC length or the second OCC length that is indicated by the signaling.
Optionally, in any of the preceding aspects, sending the configuration comprises: sending, by the gNB, the configuration in a radio resource control (RRC) signaling.
Optionally, in any of the preceding aspects, the signaling is a RRC signaling.
Optionally, in any of the preceding aspects, the signaling is carried in a medium access control (MAC) control element (CE).
Optionally, in any of the preceding aspects, the signaling is carried in a downlink control information (DCI) message.
Optionally, in any of the preceding aspects, the method further includes: receiving, by the gNB from the UE, a message acknowledging receipt of the configuration.
Optionally, in any of the preceding aspects, communicating the DM-RS comprises: receiving or sending, by the gNB, the DM-RS over DM-RS port(s) associated with OCC(s) of the first OCC length when the first OCC length is indicated by the signaling, or over DM-RS port(s) associated with OCC(s) of the second OCC length when the second OCC length is indicated by the signaling.
Optionally, in any of the preceding aspects, the method further includes: sending, by the gNB, a physical downlink shared channel (PDSCH) over the DM-RS port(s) associated with the OCC(s) of the first OCC length or over the DM-RS port(s) associated with OCC(s) of the second OCC length; or receiving, by the gNB, a physical uplink shared channel (PUSCH) over the DM-RS port(s) associated with the OCC(s) of the first OCC length or over the DM-RS port(s) associated with OCC(s) of the second OCC length.
Optionally, in any of the preceding aspects, an OCC of the first OCC length comprises: [+1+1+1+1], [+1−1+1−1], [+1+j−1−j], or [+1−j−1+j].
Optionally, in any of the preceding aspects, the method further includes: sending, by the gNB, a DCI message comprising an indication; and sending, by the gNB, a DM-RS port offset bit, the indication and the DM-RS port offset bit in combination indicating DM-RS port(s) to be used.
Optionally, in any of the preceding aspects, when the first OCC length is indicated by the signaling and the DM-RS port offset bit has a first value, the DM-RS port(s) to be used have first port number(s) corresponding to the indication according to a first correspondence associated with the second OCC length; or when the first OCC length is indicated by the signaling and the DM-RS port offset bit has a second value, the DM-RS port(s) to be used have second port number(s) obtained by adding a non-zero integer and the first port number(s), respectively.
Optionally, in any of the preceding aspects, the non-zero integer is 8 or 12.
Optionally, in any of the preceding aspects, when the first OCC length is indicated by the signaling and the DM-RS port offset bit has a first value, the DM-RS port(s) to be used have port number(s) according to a first correspondence between the port number(s) and the indication, the first correspondence associated with the second OCC length; or when the first OCC length is indicated by the signaling and the DM-RS port offset bit has a second value, the DM-RS port(s) to be used have the port number(s) according to a second correspondence between the port number(s) and the indication, the second correspondence associated with the first OCC length.
Optionally, in any of the preceding aspects, the DM-RS port offset bit is comprised in the DCI message.
Optionally, in any of the preceding aspects, the DCI message is a legacy DCI message.
Optionally, in any of the preceding aspects, a number of DM-RS ports associated with the first OCC length of 4 is: 8 when one symbol is configured for type-1 DM-RS transmissions, 16 when 2 symbols are configured for type-1 DM-RS transmissions, 12 when one symbol is configured for type-2 DM-RS transmissions, or 24 when two symbols are configured for type-2 DM-RS transmissions.
Optionally, in any of the preceding aspects, the communications of DM-RSs comprise Type-1 DM-RS transmissions or Type-2 DM-RS transmissions.
According to another aspect of the present disclosure, an apparatus is provided that includes a non-transitory memory storage comprising instructions, and one or more processors in communication with the memory storage, wherein the instructions, when executed by the one or more processors, cause the device to perform a method in any of the preceding aspects.
According to another aspect of the present disclosure, a non-transitory computer-readable media is provided, which stores computer instructions, that when executed by one or more processors, cause the one or more processors to perform a method in any of the preceding aspects.
According to another aspect of the present disclosure, a system is provided that includes a gNB and a user equipment (UE) in communication with the gNB; wherein the UE is configured to perform: receiving, from a gNB, a configuration configuring a first orthogonal cover code (OCC) length that is 4 and a second OCC length that is 2 for demodulation reference signal (DM-RS) communication between the gNB and the UE; receiving a signaling indicating the UE to communicate DM-RS(s) according to the first OCC length or the second OCC length; and communicating, with the gNB, a DM-RS according to the first OCC length or the second OCC length that is indicated by the signaling; and wherein the gNB is configured to perform: sending the configuration to the UE; sending the signaling to the UE; and communicating the DM-RS with the UE.
According to another aspect of the present disclosure, an apparatus is provided that includes: a receive module configured to receive, from a gNB, a configuration configuring a first orthogonal cover code (OCC) length that is 4 and a second OCC length that is 2 for demodulation reference signal (DM-RS) communication between the gNB and the UE, and receive a signaling indicating the UE to communicate DM-RS(s) according to the first OCC length or the second OCC length; and a communication module configured to communicate, with the gNB, a DM-RS according to the first OCC length or the second OCC length that is indicated by the signaling.
According to another aspect of the present disclosure, an apparatus is provided that includes: a transmit module configured to transmit a first demodulation reference signal (DM-RS) over first DM-RS port(s) associated with an orthogonal cover code (OCC) of length 4; or a receive module configured to receive a second DM-RS over second DM-RS port(s) associated with an OCC of length 4.
According to another aspect of the present disclosure, an apparatus is provided that includes: a transmit module configured to: transmit, to a user equipment (UE), a configuration configuring a first orthogonal cover code (OCC) length that is 4 and a second OCC length that is 2 for demodulation reference signal (DM-RS) communication between the gNB and the UE; and transmit a signaling indicating the UE to communicate DM-RS(s) according to the first OCC length or the second OCC length; and a communication module configured to communicate, with the UE, a DM-RS according to the first OCC length or the second OCC length that is indicated by the signaling.
The above aspects in the present disclosure enable communication of DM-RSs according to an OCC length 4. This increases the number of orthogonal DM-RS ports that can be used for DM-RS communication with relatively small DM-RS overhead, allows for good demodulation performance, and enables supporting a large number of data layers for massive SU/MU-MIMO transmissions. The above aspects in the present disclosure also enable fast switching between communication of DM-RSs according to an OCC length 4 and communication of DM-RSs according to an OCC length 2. This allows for dynamic switching between robust and high throughput SU/MU-MIMO transmissions according to a UE's channel environment and communication need.
For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.
The making and using of embodiments of this disclosure are discussed in detail below. It should be appreciated, however, that the concepts disclosed herein can be embodied in a wide variety of specific contexts, and that the specific embodiments discussed herein are merely illustrative and do not serve to limit the scope of the claims. Further, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of this disclosure as defined by the appended claims.
Downlink and uplink transmissions, e.g., in 5G new radio (NR), are based on DM-RSs (demodulation reference signals). For example, in single user/multi user multi input multi output (SU/MU-MIMO) transmissions, each DM-RS port may carry a DM-RS, which will be used for channel estimation in order for demodulation of the corresponding data layer transmitted on the same port. The DM-RS design needs to consider different scenarios, and various and sometimes conflicting requirements. It is desirable to have a large number of orthogonal DM-RS ports and multiplexing scheme(s) with relatively small DM-RS overhead (e.g., frequency and/or time resources used for DM-RS transmission), while ensuring good demodulation performance to support the large number of data layers for massive SU/MU-MIMO transmissions.
For DM-RS time and frequency pattern in the grid of sub-carriers (in the frequency domain) and orthogonal frequency division multiplexing (OFDM) symbols (in the time domain), two types (i.e., Type-1 and Type-2) of DM-RS configurations are introduced in NR. Type-1 DM-RS configuration supports up to 4 orthogonal DM-RS ports when 1 OFDM symbol is configured for DM-RS transmission, and up to 8 orthogonal DM-RS ports when 2 OFDM symbols are configured for DM-RS transmission. Type-2 DM-RS configuration supports up to 6 orthogonal DM-RS ports when 1 OFDM symbol is configured for DM-RS transmission, and up to 12 orthogonal DM-RS ports when 2 OFDM symbols are configured for DM-RS transmission. The orthogonal DM-RS ports configured for DM-RS transmission are multiplexed in the time domain and the frequency domain using orthogonal cover codes (OCCs). Both types of DM-RS configurations are configurable for downlink and uplink transmissions. The Type-1/Type-2 of DM-RS configuration may be referred to as Type-1/Type-2 DM-RS configuration, or Type-1/Type-2 configuration, or DM-RS configuration Type 1/Type 2 (type 1/type 2) in the present disclosure. The Type-1 configuration for legacy UEs is referred to as legacy Type-1 DM-RS configuration or legacy Type-1 configuration. The Type-2 configuration for legacy UEs is referred to as legacy Type-2 DM-RS configuration or legacy Type-2 configuration. DM-RS configured according to the Type-1/Type-2 DM-RS configuration may be referred to as Type-1/Type-2 DM-RS.
In embodiments of the present disclosure, a representation “n,s” shown on a RE (e.g., a box in
When two (2) OFDM symbols are configured for the legacy Type-1 configuration, a time domain OCC of length 2 may further be used to generate orthogonal DM-RS ports, which gives a total of 8 orthogonal ports, as shown in
For DM-RS Type-2 configuration, a frequency domain OCC of length 2 over adjacent 2 REs and frequency division multiplexing (FDM) are used to support 6 orthogonal DM-RS ports when 1 OFDM symbol is configured for DM-RS transmission.
When 2 OFDM symbols are configured for DM-RS transmission, a time domain OCC of length 2 may further be used to generate orthogonal DM-RS ports according to the DM-RS Type-2 configuration, which gives a total of 12 orthogonal ports.
Two configurable 16-bit DM-RS scrambling IDs are supported for scrambling DM-RSs. Configuration of the DM-RS scrambling IDs may be made using RRC signaling. A DM-RS scrambling ID may also be dynamically selected and indicated by downlink control information (DCI). Before the utilization of the RRC configured 16-bit DM-RS scrambling IDs, a cell ID is used for DM-RS scrambling.
When mapping to symbol locations of a physical downlink shared channel/Physical uplink shared channel (PDSCH/PUSCH) transmission within a slot, front-loaded DM-RS symbol(s) (for front-loaded DM-RS) only or front-loaded DM-RS plus additional DM-RS symbol(s) (for front-loaded DM-RS and additional DM-RS) can be configured. The additional DM-RS, when present, may have the same configuration as that of the front-loaded DM-RS for the PDSCH/PUSCH transmission, i.e., they may have the same number of symbols, antenna ports, sequence, and so on.
For PDSCH/PUSCH mapping Type-A, the front-loaded DM-RS starts from the third or fourth symbol of each slot (or each hop if frequency hopping is supported). For PDSCH/PUSCH mapping Type-B, the front-loaded DM-RS starts from the first symbol of the transmission duration. The number of additional DM-RS symbol(s) can be 1, 2, or 3 per network configuration.
Many antennas are envisioned in NR networks, while a relatively small number of antennas is at the handsets. Multi-user (MU) multiple input multiple output (MIMO) technology is used to take advantage of the spatial dimension of the multi-antenna system for high spectrum efficiency. To achieve good tradeoff between MU-MIMO performance and MU-MIMO overhead associated with the large number of layers for UEs, explicit indication of DM-RS antennas ports utilized for multiple UEs is supported. To support an even larger number of layers of single user (SU)/MU-MIMO transmissions, it is desirable to increase the number of orthogonal DM-RS ports without increasing the associated overhead. The associated overhead may include the time resources and/or frequency resources used for DM-RS transmission. For UEs under favorable conditions, e.g., short path propagation delay and high SINR, network enabling UEs to operate with additional orthogonal DM-RS ports may greatly improve system MU-MIMO spectrum efficiency.
To achieve high spectrum efficiency, MU-MIMO transmission and reception need to adapt dynamically to channel conditions, UE distribution, data traffic, and various other conditions. This implies that the number of MIMO layers and the occupied DM-RS ports for paired UEs (e.g., two intended UEs in DL MU-MIMO transmission) may vary with time (from transmission to transmission) and frequency (from resource block group (RBG) to RBG). More transmission layers may provide higher throughput at the cost of DM-RS overhead. In NR, in addition to the DM-RS ports used for data transmission (e.g., PDSCH or PUSCH) of an intended UE, DCI may be used to indicate the number of DM-RS code division multiplexing (CDM) group(s) that have no data mapped to their corresponding REs (resource elements). These DM-RS CDM groups may include, e.g., CDM group(s) of DM-RS ports of an intended UE, and may also include CDM group(s) of DM-RS ports for other UEs. The DCI can be used to indicate a MU-MIMO transmission and used to dynamically adjust the overhead associated with the MU-MIMO transmission. In the following, the terms of “DM-RS CDM group” and “CDM group” are used interchangeably, the terms of “DM-RS port”, “orthogonal CDM DM-RS ports”, “orthogonal DM-RS ports”, “orthogonal port” and “port” are used interchangeably, and the terms of “antenna port” and “port” are used interchangeably, unless otherwise provided.
To increase the number of DM-RS ports based on existing 5G NR DM-RS definitions/configurations, one possible approach is to double the maximum number of DM-RS ports supported in 5G NR Release 17 (Rel. 17) and previous releases (e.g., for legacy UEs), for both 1 and 2 OFDM symbol(s) configurations and both the Type-1 and Type-2 configurations. That is, for Type-1 DM-RS, there will be maximally 8 orthogonal ports for 1 OFDM symbol configuration (i.e., when one symbol is configured for DM-RS transmission) and 16 orthogonal ports for 2 OFDM symbols configuration (i.e., when two symbol are configured for DM-RS transmission) that can be supported; and for Type-2 DM-RS, there will be maximally 12 orthogonal ports for 1 OFDM symbol configuration and 24 orthogonal ports for 2 OFDM symbols configuration that can be supported. This approach has benefits that the Rel. 17 DM-RS configurations could be maximally preserved and reused, and the efforts for providing additional port(s) configuration and signaling indications could be minimized.
Embodiments of the present disclosure provide mechanisms to provide additional orthogonal DM-RS ports in addition to the orthogonal DM-RS ports supported according to the existing 5G NR DM-RS definitions/configurations (e.g., the Type-1/Type-2 configurations in 5G SU/MU-MIMO transmission described above). In some embodiments, the maximum number of the orthogonal DM-RS ports currently supported in the Type-1/Type-2 configurations may be doubled. Two embodiment schemes (i.e., scheme 1 and scheme 2) may be considered to achieve this, which will be described in the following using the Type-1 DM-RS configuration as an example. Those of ordinary skill in the art would recognize that the schemes may be similarly applied to the Type-2 configuration, and any other applicable DM-RS configuration(s). Further, scheme 1 and scheme 2 may be combined and applied to a DM-RS configuration to provide more DM-RS ports.
In the embodiment scheme 1, for the Type-1 DM-RS configuration, the number of combs in the frequency domain may be kept to 2 and the number of cyclic shifts in the time domain may be doubled. Doubling the number of cyclic shifts in the time domain may be achieved through applying more OCC patterns in the frequency domain. In an embodiment, two (2) new OCC patterns may be introduced. By using the 2 new OCC patterns, together with the 2 legacy patterns, OCC patterns/sequences having a size/length of 4 may be formed, and four (4) orthogonal DM-RS ports may be formed for each comb. An example of the 4 OCC patterns may be [+1+1+1+1], [+1−1+1−1], [+1+j−1−j], [+1−j−1+j]. Other OCC sequences of length 4 may also be applicable for generating orthogonal DM-RS ports, for example, the 4 OCC patterns may be [+1+1+1+1], [+1−1+1−1], [+1+1−1−1], [+1−1−1+1].
As an example, for the 1 OFDM symbol configuration (i.e., when one symbol is configured for DM-RS transmission), with the 4 patterns on each of the 2 combs, the embodiment scheme 1 provides 8 total orthogonal DM-RS ports, as shown in
As another example, for the 2 OFDM symbols configuration (i.e., when two symbols are configured for DM-RS transmission), in addition to applying the two new OCC patterns in the frequency domain, the same time domain legacy OCCs of length 2, i.e., {[+1+1], [+1−1]}, may further be used to double the orthogonal DM-RS ports, giving a total of 16 orthogonal DM-RS ports, as shown in
In the embodiment scheme 1, the number of CDM groups may remain to be the same as that in the Rel. 17 Type-1 DM-RS configuration.
Therefore, by using scheme 1, the Type-1 configuration can support 8 ports with a signal OFDM symbol configured and 16 ports with double OFDM symbols configured. For description convenience, the ports provided by the Type-1 configuration in 5G NR Rel. 17 and previous releases may be referred to as a first set of Type-1 (DM-RS) ports, and the ports provided by the Type-1 configuration with scheme 1 applied may be referred to as a second set of Type-1 ports. The second set of Type-1 ports includes the first set of Type-1 ports and additional DM-RS ports added through scheme 1. Scheme 1 doubles the first set of Type-1 ports. The second set of Type-1 ports each may be assigned with an index p, where p=0, 1, . . . 15. For description convenience, port numbers 0-7 are used to refer to the legacy DM-RS ports, and port numbers 8-15 are used to refer to the additional DM-RS ports added by using scheme 1.
In some embodiments, to map a DM-RS sequence to the resource elements (REs) for each DM-RS port indexed with p=0, 1, . . . , 15, based on the modified equations from Section 7.4.1.1.2 in TS 38.211, a UE may assume the mapping according to:
where βPDSCHDMRS is a scaling factor, αk,l(p,u) is a resulting value of the DM-RS sequence to be mapped to resource element (k, l)p,u, k and l are a subcarrier index and a symbol index, respectively, indicating the resource element, wt(l′) and the time domain related parameters,
Table 1 below shows example parameters used for the mapping. Table 1 is obtained by modifying the Table 7.4.1.1.2-1 in TS 38.211. As an example, the parameter “p” in Table 1 is associated with the DM-RS port indexes (0, 1, . . . , 15) and p=1000 +DM-RS port index. In each entry of Table 1, the parameter wf(k′), k′=0, 1, 2, 3 indicates the frequency domain (FD)-OCC of length 4 associated with the corresponding parameter p in the entry and its associated DM-RS port (e.g., DM-RS port index=p−1000). The FD-OCC herein refers to an OCC applied in the frequency domain, e.g., applied to REs in the same OFDM symbol. For example, the entry for p=1008 indicates that the FD-OCC pattern [+1−j−1+j] is applied to DM-RS port 8, and the entry for p=1009 indicates that the FD-OCC pattern [+1+j−1−j] is applied to DM-RS port 9. In Table 1, the association of the DM-RS port indicated by the parameter “p” and the FD-OCC indicated by the parameter wf(k′) is shown merely as an example. Other alternatives/variations to associate the DM-RS port and the FD-OCC are also possible. For example, the FD-OCC patterns for p=1008 and p=1009 shown in Table 1 may be switched such that FD-OCC pattern [+1+j−1−j] is applied to DM-RS port 8 and FD-OCC pattern [+1−j−1+j] is applied to DM-RS port 9. Similarly, the FD-OCC patterns for p=1010 and p=1011 may be switched. Similar switching may be applied to p=1012 and p=1013, as well as p=1014 and p=1015.
In Rel. 17, to achieve good tradeoff between the MU-MIMO performance and overhead associated with the potentially large number of layers for UEs, explicit indication of DM-RS antennas ports utilized for multiple UEs is supported. A DCI message, e.g., Format 1-1,is used to indicate, to a UE, the scheduled number of DM-RS ports, an index of each DM-RS port, and CDM groups of co-scheduling UE(s) for MU-MIMO transmission. Detailed DM-RS port(s) indexing, mapping and co-scheduling CDM group(s) may be obtained by reading an entry corresponding to an antenna port(s) bits value in the DCI message, from lookup tables in 5G NR TS 38.212 specification, i.e., Table 7.3.1.2.2-1 and Table 7.3.1.2.2-1A for Type-1 1 OFDM symbol configuration, Table 7.3.1.2.2-2 and Table 7.3.1.2.2-2A for Type-12 OFDM symbols configuration, Table 7.3.1.2.2-3 and Table 7.3.1.2.2-3A for Type-2 1 OFDM symbol configuration, and Table 7.3.1.2.2-4 and Table 7.3.1.2.2-4A for Type-2 2 OFDM symbol configuration.
Reducing either the DM-RS density in the frequency domain or cyclic shift duration in the time domain may cause MU-MIMO performance degradation for UEs in certain channel conditions, e.g., a channel having a long path propagation delay. Reducing DM-RS resource overhead for each port may be prone to poorer DM-RS channel estimation because of lower effective operating signal to interference and noise ratio (SINR). Thus, it is desirable for UEs to have the choice to operate under legacy DM-RS port(s) configuration, indexing, mapping, and indicating.
With the number of maximum orthogonal DM-RS ports doubled, the ports combination, signaling indications and message mapping grow substantially. If providing the additional orthogonal DM-RS ports is solely for MU-MIMO transmission, and Rel. 17 designs on ports combination, signaling indication and message mapping are satisfactory, it is desirable to leverage the legacy design as much as possible, and make necessary modifications as little as possible to minimize standard efforts for enjoying the performance enhancement brought by the additional orthogonal DM-RS ports.
Therefore, it would be appreciated that the design of port indexing, grouping, and signaling for scheme 1 considers backward compatibility with legacy UEs as much as possible, and avoids redesigning of port indexing, grouping, and signaling completely. If adding additional DR-MS ports in Rel. 18 is targeting MU-MIMO scenarios, it would be desirable that legacy DM-RS port indexing, grouping, and signaling may be reused as much as possible.
For the SU-MIMO scenarios, the legacy design may be reused. A UE may be scheduled with a few DM-RS ports by using the antenna port indexes in DCI format 1_1 as described in Clause 7.3.1.2 of [5, TS 38.212], which is hereby incorporated by reference in its entirety.
TS 38.212 specifies that, for DM-RS configuration type 1,
In some embodiments, for the SU/MU-MIMO scenarios and the DM-RS configuration type 1 with scheme 1 applied, a UE may be configured with two modes of operation for DM-RS port(s) indication: Mode 1 and Mode 2. When the network indicates DM-RS ports to be used in communication with the UE, the UE may interpret the indication based on its mode. When operating in mode 1, the DM-RS ports usable by the UE may only include the first set of Type-1 ports supported by the type-1 configuration; when operating in mode 2, the DM-RS ports usable by the UE may include the second set of Type-1 ports generated according to scheme 1.
In this mode of operation, a DCI message may be transmitted and interpreted in the same way as described in Section 7.3.1.2.2 of TS 38.212 and Section 5.1.6.2 of TS 38.214 which is hereby incorporated by reference in its entirety. The definitions of the DM-RS ports follow the legacy definitions. The DCI message may indicate one or more of the first set of Type-1 ports. The usage for this mode may be for better handling of longer propagation path delay or backward compatible with legacy UEs.
In this mode of operation, scheme 1 is applied, and the number of DM-RS ports is doubled and the time duration corresponding to its cyclic shift time location of each DM-RS port is halved. The DM-RS ports in this mode include the second set of Type-1 ports as described above. This mode may be used for multiplexing more UE transmissions simultaneously.
In some embodiments, to indicate the orthogonal DM-RS ports using DCI for mode 2 operation, a new bit may be defined in addition to a legacy DCI message, or a bit in the legacy DCI message may be defined with a new definition. This bit may be referred to as a DM-RS port offset bit, and in one embodiment, may be designed as follows:
For example, the maximum length of OFDM symbols (e.g., the maximum number of OFDM symbols for front-loaded DM-RS) is 2, and Table 7.3.1.2.2-2 in 38.212 (shown below as Table 2) is used for table lookup for DM-RS ports. Assuming that one codeword is enabled and the antenna port(s) bits have a value 26 (i.e., value=26 in Table 2), DM-RS ports 0,1,4 are indicated according to Table 2. If the DM-RS port offset bit is 0, a UE may expect the DM-RS transmission on the DM-RS ports 0,1,4. If the DM-RS port offset bit is 1, the UE may expect the DM-RS transmission on ports 8,9,12 by adding 8 to 0,1,4.
In some embodiments, a new lookup table may be created providing DM-RS ports for the mode 2 operation when the DM-RS port offset bit is 1. Using the same example as above where value=26, if the DM-RS port offset bit is 1, the UE may read the DMRS port(s) index(es) directly from the new lookup table, e.g., Table 3 below, which is obtained by modifying Table 7.3.1.2.2-2 in 38.212. Table 7.3.1.2.2-1, 7.3.1.2.2-1A and 7.3.1.2.2-2A may be modified similarly.
In one embodiment, one of the two modes of operation may be configured to a UE specifically and activated, e.g., through high layer signaling such as radio resource control (RRC) signaling. In another embodiment, the two modes of operation may be configured to a UE through high layer (e.g., RRC) signaling, and one of the two modes may be activated by, e.g., RRC signaling, a medium access control-control element (MAC-CE), or DCI. For network flexible scheduling, it is desirable for the network to have the capability to co-schedule MU-MIMO UEs with mixed operating modes.
In some embodiments, the network may signal a UE to switch between these two modes dynamically by defining a new bit in addition to the legacy DCI message, or defining a bit in the legacy DCI message with new definition. The bit may be referred to as a DM-RS operation mode bit, and may be defined as follows:
As an example, assuming the maximum length of OFDM symbols is 1, Table 7.3.1.2.2-1 in TS 38.212 (shown below as Table 4) may be used for table lookup.
In this example, 4 UEs (UE1-UE4) are scheduled for MU-MIMO transmission, and the network may signal a mode to each UE, indicating the UE to operate in the signaled mode. Each UE determines the DM-RS ports based on the signaled mode, an indicated value (antenna port bits value) corresponding to DM-RS port(s) (e.g., “Value” in Table 4), an indicated DM-RS port offset bit value, and the lookup table, as follows:
In some embodiments, to provide additional DM-RS ports for the Type-1 configuration, the number of combs in the frequency domain may be increased, e.g., from 2 to 4, and the number of cyclic shifts in the time domain may be kept to 2. Doubling the number of combs in the frequency domain reduces the DM-RS RE density by half (subcarriers occupied by each DM-RS port in a resource block is reduced by half). Each comb carries 2 orthogonal DM-RS ports by cyclic shift CDM (e.g., using frequency domain OCC patterns), and the 4 combs together give 8 ports for the single OFDM symbol configuration. For the double OFDM symbols configuration, the same time domain legacy OCC of length 2, i.e., {[+1+1], [+1−1]}, may be used to double the orthogonal DM-RS ports, which gives a total of 16 orthogonal DM-RS ports.
In some embodiments, to map the DM-RS sequence to the resource elements for the DM-RS ports with indexes p=0, 1, 2, . . . , 15 in scheme 2, based on the modified equations from Section 7.4.1.1.2 in TS 38.211, a UE may assume the mapping according to:
where wt(l′) and the time domain related parameters,
Similarly to those described with respect to scheme 1, the design of port indexing, grouping, and signaling for scheme 2 also needs to strive for backward compatible with legacy UEs as much as possible, and to avoid redesigning of port indexing, grouping, and signaling completely. When the purpose of adding additional DR-MS ports in Rel. 18 is solely targeting MU-MIMO instead of SU-MIMO scenarios, legacy DM-RS port indexing, grouping, and signaling may be reused as much as possible.
For the SU-MIMO scenario, the design for legacy may be reused. A UE may be scheduled with a few DM-RS ports by the antenna port index(es) in DCI format 1_1 as described in Clause 7.3.1.2 of [5, TS 38.212].
TS 38.212 specifies that, for DM-RS configuration type 1,
For description convenience, the ports provided by the Type-1 configuration with scheme 2 applied may be referred to as a third set of Type-1 ports. The third set of Type-1 ports includes the first set of Type-1 ports and additional DM-RS ports added through scheme 2. In some embodiments, for the SU/MU-MIMO scenario and the DM-RS configuration type 1 with scheme 2 applied, the UE may be configured with three modes of operation for the DM-RS port(s) indication:
In this mode of operation, a DCI message is transmitted and interpreted in the same way as described in Section 7.3.1.2.2 of TS 38.212 and Section 5.1.6.2 of TS 38.214. The definitions of the DM-RS ports follow the legacy definitions. The DCI message may indicate one or more of the first set of Type-1 ports. The usage for this mode may be for better handling of longer propagation path delay or backward compatible with legacy UEs.
In this mode of operation, scheme 2 is applied, and the number of DM-RS CDM ports doubles and the frequency density of each DM-RS CDM port is halved. The number of DM-RS CDM groups without data is also doubled based on the scheduled number of DM-RS CDM groups without data. The DM-RS ports in this mode include the third set of Type-1 ports as described above. The usage for this mode may be for multiplexing more UE transmission simultaneously.
In this mode of operation, the number of DM-RS CDM ports is doubled and the frequency density of each DM-RS CDM port is halved. The number of DM-RS CDM groups without data is not doubled. The DM-RS ports in this mode include the third set of Type-1 ports as described above. This mode may be used for high spectrum efficiency and reducing UE DM-RS overlapping in frequency domain.
To indicate the DM-RS ports for mode 2 and 3, a new bit, i.e., a DM-RS port offset bit, may be defined in addition to the legacy DCI message, or a bit in the legacy DCI message may be defined with new definition. In an embodiment, the bit may be defined as follows:
For DM-RS type 1 with doubled ports with scheme 2 applied, the maximum number of DM-RS CDM groups without data is increased from 2 to 4. The indication of the number of DM-RS CDM group(s) without data also changes accordingly. Mode 2 and mode 3 are configured to handle this situation differently.
For mode 2, the network schedules multiple UEs for simultaneous transmission. In an embodiment, a UE may determine the number of CDM groups and the DM-RS ports as described in the following. The UE may derive DM-RS port(s) transmission information according to the antenna port(s) bits and the DM-RS port offset bit indicated in received DCI signaling. The UE may search a lookup table and read the entry in the lookup table corresponding to the received antenna port(s) bits. The UE may derive the number of CDM groups without data by always doubling the corresponding number in the entry. The additional DM-RS CDM group index(es) without data may be obtained by adding 2 to the DM-RS CDM group index(es) in the entry.
For example, if the configuration of DM-RS is type 1 and the maximum length of OFDM symbols is 2, then Table 7.3.1.2.2-2 in TS 38.212 (Table 2 above) may be used for table lookup. In this example, one codeword is enabled and the antenna port(s) bits have a value 26. From the entry corresponding to value 26 in the lookup table (Table 2), the indicated DM-RS ports are 0,1,4, and the indicated number of DM-RS CDM groups without data is 2, i.e. two DM-RS CDM groups with indexes {0,1}. Then the UE doubles the number of 2 to get a new number of DM-RS CDM groups without data, which is 4. The UE may then add 2 to {0,1} to obtain two new indexes of DM-RS CDM groups without data, i.e., {2,3}, and combine it with group indexes {0,1} to get the final DM-RS CDM groups without data indexes, i.e., {0,1,2,3}. If the DM-RS port offset bit is 0, the UE shall expect the DM-RS transmission on ports 0,1,4. If the DM-RS port offset bit is 1, the UE shall add 8 to {0,1,4},and expect the DM-RS transmission on ports 8,9,12.
In some embodiments, if the DM-RS port offset bit is 0, the UE may read the DM-RS port(s) index(es) and the number of DM-RS CDM group(s) without data directly from a new lookup table, which is obtained by modifying Table 7.3.1.2.2-2. If the DM-RS port offset bit is 1, the UE may read the DM-RS port(s) index(es) and the number of DM-RS CDM group(s) without data directly from another new lookup table x which is obtained by modifying Table 7.3.1.2.2-2. Table 7.3.1.2.2-1, 7.3.1.2.2-1A and 7.3.1.2.2-2A may be modified similarly.
For mode 3, the network schedules multiple UE for simultaneous transmission. In some embodiments, a UE may derive DM-RS port(s) transmission information according to the antenna port(s) bits and the DM-RS port offset bit indicated in received DCI signaling. The UE may search a lookup table and read the entry in the lookup table corresponding to the received antenna port(s) bits. If the DM-RS port offset bit is 0, the DM-RS CDM group index(es) without data is the same as that of the entry. If the DM-RS port offset bit is 1, the DM-RS CDM group index(es) without data may be derived by adding 2 to DM-RS CDM group index(es) in the entry.
For example, if the configuration of DM-RS is type 1 and the maximum length of OFDM symbols is 2, then table 7.3.1.2.2-2 in TS 38.212 (Table 2 above) may be used for table lookup. In this example, one codeword is enabled and the antenna port(s) bits have a value 26. From the entry corresponding to value 26 in the lookup table (Table 2), the indicated DM-RS ports are 0, 1, 4, and the number of DM-RS CDM groups without data is 2, i.e., two DM-RS CDM groups with indexes {0,1}. If the DM-RS port offset bit is 0, the UE may derive the indexes of the DM-RS CDM groups without data directly from the indicated value {0,1} (based on the number of CDM group(s) without data and the indicated DMRS port(s)) and expect DM-RS transmission on ports 0, 1, 4. If the DM-RS port offset bit is 1, the UE adds 2 to {0,1} to get indexes of the final DM-RS CDM groups without data, i.e., {2,3}, and shall expect the DM-RS transmission on ports 8, 9, 12 by adding 8 to ports 0, 1, 4.
In some embodiments, if the DM-RS port offset bit is 0, the UE may read the DM-RS port(s) index(es) and the number of DM-RS CDM group(s) without data directly from a new lookup, which may be obtained by modifying Table 7.3.1.2.2-2. If the DM-RS port offset bit is 1, the UE may read the DM-RS port(s) index(es) and the number of DM-RS CDM group(s) without data directly from another new lookup table x which may be obtained by modifying Table 7.3.1.2.2-2. Table 7.3.1.2.2-1, 7.3.1.2.2-1A and 7.3.1.2.2-2A may be modified similarly.
In one embodiment, one of the three modes of operations may be configured to each UE specifically and activated through high layer signaling, e.g., RRC signaling. In another embodiment, one of mode combinations, e.g., the mode combination of modes 1 and 2, or the mode combination modes 1 and 3, may be configured to each UE through high layer signaling, e.g., RRC signaling, and one mode of the two modes in the configured mode combination may be activated by, e.g., RRC signaling, a MAC-CE or DCI.
In some embodiments, the network may dynamically signal a UE to switch between one of the two modes within the configured mode combination, i.e., modes 1 and 2, or modes 1 and 3, by defining a new bit in addition to the legacy DCI message, or defining a bit in the legacy DCI message with new definition. The bit may be referred to as a DM-RS operation mode bit.
When the bit is configured for the mode combination of modes 1 and 2, the bit may be defined as follows, as an example:
When the bit is configured for the mode combination of modes 1 and 3, the bit may be defined as follows, as an example:
As an example, assuming that the maximum length of OFDM symbols is 1, Table 7.3.1.2.2-1 in 38.212 (Table 4 above) may be used for table lookup. For a case where 4 UEs are scheduled for MU-MIMO transmission, the network may signal a mode to each UE. Each UE may determine the DM-RS ports based on the signaling from the network as follows:
For the operations of modes of scheme 1 and scheme 2,
In response to receiving the configuration and activation in step 1502, the UE may send a configuration acknowledge to the gNB (step 1504). The gNB may then schedule a PDSCH for the UE through a DCI message on a PDCCH (step 1506), and transmit the PDSCH accordingly (step 1508). DM-RS corresponding to the PDSCH is also transmitted to the UE. The DCI includes the DM-RS port information. The UE obtains information about the DM-RS ports based on the DCI and the activated mode as discussed above, receives a DM-RS on the obtained DM-RS ports and receives the PDSCH based on the DM-RS. The UE may send PDSCH acknowledgement/negative acknowledgement (ACK/NACK) to the gNB to indicate whether the PDSCH is successfully received (step 1510). Steps 1508 and 1510 may be implemented conventionally.
Scheme 1 or scheme 2 fulfill the objective of doubling the number of orthogonal DM-RS ports without increasing DM-RS resource overhead. For scheme 1, the time duration of cyclic shifts in the time domain to accommodate UE channel impulse response is halved. In the case of MU-MIMO having several UEs with long path propagation delays, mutual interference from the channel impulse response between the cyclic shifts may cause extra DM-RS channel estimation errors, and may degrade system MU-MIMO performance. For scheme 2, the effective time window duration without overlap for each comb is halved, and for UEs with long path propagation delays, extra DM-RS channel estimation errors may degrade system performance as a result of impulse response partial overlap and interference.
For the legacy Type-2 DM-RS configuration, a frequency domain OCC of length 2 over adjacent 2 REs and frequency division multiplexing (FDM) are used to support 6 orthogonal DM-RS ports when 1 OFDM symbol is configured (as shown in
In some embodiments, to provide additional DM-RS ports for the Type-2 configuration, the 6 pairs of adjacent 2 REs in a resource block may all be used to support different orthogonal ports. With the use of a frequency domain OCC of length2 over each pair of adjacent RES, 12 orthogonal DM-RS ports may be supported for the single OFDM symbol configuration. For the double OFDM symbols configuration, the same legacy time domain OCC of length2, {[+1+1], [+1−1]}, may further be used to double the orthogonal DM-RS ports, giving a total of 24 orthogonal DM-RS ports in the frequency domain.
In some embodiments, to map the DM-RS sequence to the resource elements for the additional DM-RS ports, based on the modified equations from Section 7.4.1.1.2 in TS 38.211, a UE may assume the mapping according to:
where wt(l′) and the time domain related parameters,
Similarly, the design of port indexing, grouping, and signaling needs to consider backward compatibility with legacy DM-RS ports definition as much as possible. The design may also need to avoid redesigning of port indexing, grouping, and signaling completely. When the purpose of adding additional DR-MS ports in Rel. 18 is solely targeting MU-MIMO instead of SU-MIMO scenarios, legacy DM-RS port indexing, grouping, and signaling may be reused as much as possible.
For the SU-MIMO scenario, the design for the legacy DM-RS ports may be reused. A UE may be scheduled with a few DM-RS ports by the antenna port index(es) in DCI format 1_1 as described in Clause 7.3.1.2 of [5, TS 38.212].
TS 38.212 specifies that, for DM-RS configuration type 2,
For the SU/MU-MIMO scenario and the DM-RS configuration type 2, a UE may be configured with three modes of operation for DM-RS port(s) indication, as described in the following.
In this mode of operation, a DCI message is transmitted and interpreted in the same way as described in Section 7.3.1.2.2 of TS 38.212 and Section 5.1.6.2 of TS 38.214. The definitions of DM-RS ports follow the legacy DM-RS ports definitions. The usage for this mode may be for targeting better handling of longer propagation path delay or backward compatible with legacy UEs.
In this mode of operation, the number of DM-RS CDM ports doubles and the frequency density of each DM-RS CDM port is halved. The number of DM-RS CDM groups without data is also doubled based on the scheduled number of DM-RS CDM groups without data. This mode may be used for multiplexing more UE transmission simultaneously.
In this mode of operation, the number of DM-RS CDM ports doubles and the frequency density of each DM-RS CDM port is halved. The number of DM-RS CDM groups without data is not doubled and is the same as the scheduled number of DM-RS CDM groups without data. This mode may be used for providing high spectrum efficiency and reducing UE DM-RS overlapping in the frequency domain from different transmitters.
To indicate the additional DM-RS ports for mode 2 and 3, in some embodiments, a new bit may be defined in addition to the legacy DCI message, or a bit in the legacy DCI message may be defined with new definition. This bit is referred to as a DM-RS port offset bit. In one embodiment, the bit may be designed as follows:
For DM-RS type 2 with doubled ports, the maximum number of DM-RS CDM groups without data is increased from 3 to 6. The indication of the number of DM-RS CDM group(s) without data also changes accordingly. Mode 2 and mode 3 are configured to handle this situation differently.
For mode 2, the network schedules multiple UEs for simultaneous transmission. In an embodiment, a UE may determine the number of CDM group(s) without data and the DM-RS ports as described in the following, which is referred to as mode 2 approach. The UE may derive DM-RS port(s) transmission information according to the antenna port(s) bits and the DM-RS port offset bit indicated in received DCI signaling. The UE may search a lookup table and read the entry corresponding to the received antenna port(s) bits. The UE may derive the number of CDM group(s) without data by doubling the corresponding number of CDM group(s) without data in the entry. The additional DM-RS CDM group index(es) without data may be obtained by adding 3 to the index(es) in the entry.
For example, if the configuration of DM-RS is type 2 and the maximum length of OFDM symbols is 2, then Table 7.3.1.2.2-4 in 38.212 (Table 7 below) may be used for table lookup. In this example, one codeword is enabled and the antenna port(s) bits have a value 45. From the entry corresponding to value 45 in the lookup table (Table 7), the indicated DM-RS ports are 0,1,6,7, and the number of DM-RS CDM groups without data is 3, i.e., 3DM-RS CDM groups with indexes {0,1,2}. Then the UE doubles the number of 3 to get a new number of DM-RS CDM groups without data, which is 6. The UE may add 3 to {0,1,2} to obtain 3 new indexes of DM-RS CDM group without data, i.e., {3,4,5}, and combine it with {0,1,2} to get the indexes of the final DM-RS CDM groups without data, i.e., {0,1,2,3,4,5}. If the DM-RS port offset bit is 0, the UE shall expect the DM-RS transmission on ports 0,1,6,7.If DM-RS port offset bit is 1, the UE shall add 12 to {0,1,6,7}, and expect the DM-RS transmission on ports 12,13,18,19.
For another example, if the configuration of DM-RS is type 2 and the maximum length of OFDM symbols is 2, then Table 7.3.1.2.2-4 in 38.212 (Table 7) may be used for table lookup. In this example, one codeword is enabled and the antenna port(s) bits have a value 7. From the entry corresponding to value 7 in the lookup table, the indicated DM-RS ports are 0,1 and the number of DM-RS CDM groups without data is 2, i.e., two DM-RS CDM groups with indexes {0,1}. Then the UE shall double the number of 2 to get a new number of DM-RS CDM groups without data, which is 4. The UE may add 3 to {0,1} (resulted in {3,4}) and combines with {0,1} to get the indexes of the final DM-RS CDM groups without data, {0,1,3,4}. If the DM-RS port offset bit is 0, the UE shall expect the DM-RS transmission on ports 0,1. If the DM-RS port offset bit is 1, the UE shall add 12 to {0,1} and expect the DM-RS transmission on ports 12, 13.
In some embodiments, if the DM-RS port offset bit is 0, the UE may read the DM-RS port(s) index(es) and the number of DM-RS CDM group(s) without data directly from a new lookup table, e.g., Table 8 below, which is obtained by modifying Table 7.3.1.2.2-4. If the DM-RS port offset bit is 1, the UE may read the DM-RS port(s) index(es) and the number of DM-RS CDM group(s) without data directly from another new lookup, e.g., Table 9 below which is obtained by modifying Table 7.3.1.2.2-4. Table 7.3.1.2.2-3, 7.3.1.2.2-3A and 7.3.1.2.2-4A may be modified in the similar way.
For mode 3, the network schedules multiple UEs for simultaneous transmission. In some embodiments, a UE may determine the number of CDM group(s) without data and the DM-RS ports as described in the following, which is referred to as mode 3 approach. The UE may derive DM-RS port(s) transmission information according to antenna port(s) bits and the DM-RS port offset bit indicated/included in received DCI signaling. The UE may search the lookup table and read the entry corresponding to the received antenna port(s) bits. If the DM-RS port offset bit is 0, the DM-RS CDM group index(es) without data is the same as that of the entry. If the DM-RS port offset bit is 1, the DM-RS CDM group index(es) without data may be derived by adding 3 to index(es) in the entry.
For example, if the configuration of DM-RS is type 2 and the maximum length of OFDM symbols is 1, then table 7.3.1.2.2-3 in 38.212 (Table 10 below) may be used for table lookup. In this example, one codeword is enabled and the antenna port(s) bits have a value 8. From the entry corresponding to value 8 in the lookup table, the indicated DM-RS ports are 2,3 and the number of DM-RS CDM groups without data is 2, i.e., two DM-RS CDM groups indexed with {0,1}. If the DM-RS port offset bit is 0, the UE may derive the indexes of the DM-RS CDM groups without data directly from the indicated value {0,1} and shall expect the DM-RS transmission on ports 2,3. If the DM-RS port offset bit is 1, UE adds 3 to {0,1} to get indexes of the final DM-RS CDM groups without data, i.e., {3,4}, and shall expect the DM-RS transmission on ports 14,15 (i.e., port 2,3 +12=port 14,15).
In some embodiments, if the DM-RS port offset bit is 1, the UE may read the DM-RS port(s) index(es) and the number of DM-RS CDM group(s) without data directly from a new lookup table x, e.g., Table 11 below, which is obtained by modifying Table 7.3.1.2.2-3. Table 7.3.1.2.2-34, 7.3.1.2.2-4 and 7.3.1.2.2-4A may be modified in the similar way.
In one embodiment, one of the three modes of operations may be configured to each UE specifically, and activated through high layer RRC signaling. In another embodiment, one of mode combinations, e.g., a combination of modes 1 and 2, or modes 1 and 3, may be configured to each UE through high layer RRC signaling, and one mode of the configured mode combination may be activated by RRC signaling, a MAC-CE or DCI.
In some embodiments, the network may signal a UE to switch between the two modes dynamically within the configured mode combination, i.e., modes 1 and 2, or modes 1 and 3, by defining a new bit in addition to the legacy DCI message, or defining a bit in the legacy DCI message with new definition. This bit may be referred to as a DM-RS operation mode bit, as described above with respect to the Type-1 configuration.
When the bit is configured for the mode combination of modes 1 and 2, the bit may be defined as follows:
When the bit is configured for the mode combination of modes 1 and 3, the bit may be defined as follows:
As an example, assuming that the configuration of DM-RS is type 2 and the maximum length of OFDM symbols is 1, Table 7.3.1.2.2-3 in TS 38.212 (e.g., Table 10 above) may be used for table lookup. In this example, 4 UEs are scheduled for MU-MIMO transmission, and the network may signal a mode to each UE. Each UE determines the DM-RS ports based on the signaling from the network as follows:
The embodiment methods described in
Embodiments of the present disclosure may be implemented as computer-implemented methods. The embodiments may be performed by a processing system.
In some embodiments, the processing system 2500 is included in a network device that is accessing, or part otherwise of, a telecommunications network. In one example, the processing system 2500 is in a network-side device in a wireless or wireline telecommunications network, such as a base station, a relay station, a scheduler, a controller, a gateway, a router, an applications server, or any other device in the telecommunications network. In other embodiments, the processing system 2500 is in a user-side device accessing a wireless or wireline telecommunications network, such as a mobile station, a user equipment (UE), a personal computer (PC), a tablet, a wearable communications device (e.g., a smartwatch, etc.), or any other device adapted to access a telecommunications network. In some embodiments, one or more of the interfaces 2510, 2512, 2514 connects the processing system 2500 to a transceiver adapted to transmit and receive signaling over the telecommunications network.
The transceiver 2600 may transmit and receive signaling over any type of communications medium. In some embodiments, the transceiver 2600 transmits and receives signaling over a wireless medium. For example, the transceiver 2600 may be a wireless transceiver adapted to communicate in accordance with a wireless telecommunications protocol, such as a cellular protocol (e.g., long-term evolution (LTE), etc.), a wireless local area network (WLAN) protocol (e.g., Wi-Fi, etc.), or any other type of wireless protocol (e.g., Bluetooth, near field communication (NFC), etc.). In such embodiments, the network-side interface 2602 comprises one or more antenna/radiating elements. For example, the network-side interface 2602 may include a single antenna, multiple separate antennas, or a multi-antenna array configured for multi-layer communication, e.g., single input multiple output (SIMO), multiple input single output (MISO), multiple input multiple output (MIMO), etc. In other embodiments, the transceiver 2600 transmits and receives signaling over a wireline medium, e.g., twisted-pair cable, coaxial cable, optical fiber, etc. Specific processing systems and/or transceivers may utilize all of the components shown, or only a subset of the components, and levels of integration may vary from device to device.
The following provides example proposals as described in the above embodiments:
According to one aspect of the present disclosure, a method is provided that includes: receiving, by a user equipment (UE), a downlink control information (DCI) message comprising an antenna port(s) bits field and a demodulation reference signal (DM-RS) port offset bit; obtaining, by the UE, a first DM-RS port number(s) from an antenna port table based on the antenna port(s) bits field; when the DM-RS port offset bit is a first value, determining, by the UE, a second DM-RS port number(s) by adding the first DM-RS port number(s) and a pre-configured number, and communicating, by the UE, DM-RSs using antenna port(s) corresponding to the second DM-RS port number(s).
Optionally, in any of the preceding aspects, the method may further include: when the DM-RS port offset bit is a second value, communicating, by the UE, DM-RSs using antenna port(s) corresponding to the first DM-RS port number(s).
Optionally, in any of the preceding aspects, the method may further include: determining, by the UE, a number of DM-RS code division multiplexing (CDM) group(s) without data base on the antenna port(s) bits field from the antenna port table.
Optionally, in any of the preceding aspects, the pre-configured number is 8.
Optionally, in any of the preceding aspects, the method may further include: obtaining, by the UE, a first number of DM-RS code division multiplexing (CDM) groups without data from the antenna port table based on the antenna port(s) bits field; determining, by the UE, a second number of DM-RS CDM groups without data, which is two times of the first number of DM-RS CDM groups without data; and communicating, by the UE, based on the second number of DM-RS CDM groups without data.
Optionally, in any of the preceding aspects, the method may further include: determining, by the UE, a first set of CDM group indexes corresponding, respectively, to the first number of DM-RS CDM groups without data; determining, by the UE, a second set of CDM group indexes by adding an offset and the first set of CDM group indexes; and combining, by the UE, the first set of CDM group indexes and the second set of CDM group indexes to obtain a third set of CDM group indexes, the third set of CDM group indexes corresponding, respectively, to the second number of DM-RS CDM groups without data.
Optionally, in any of the preceding aspects, the method may further include: obtaining, by the UE, a first number of DM-RS code division multiplexing (CDM) groups without data from the antenna port table based on the antenna port(s) bits field; when the DM-RS port offset bit is the first value, obtaining, by the UE from the antenna table based on the antenna port(s) bits field, a first set of CDM group indexes; and determining, by the UE, a second set of CDM group indexes by adding an offset and the first set of CDM group indexes, the second set of CDM group indexes corresponding, respectively, to the first number of DM-RS CDM groups without data.
Optionally, in any of the preceding aspects, the offset is 2.
An apparatus is also provided for implementing the methods in any of the preceding aspects.
An advantage of embodiments of the present disclosure includes increased number of orthogonal DM-RS ports with relatively small DM-RS overhead. The embodiments allow for good demodulation performance, and enable to support a large number of data layers for massive SU/MU-MIMO transmissions.
It should be appreciated that one or more steps of the embodiment methods provided herein may be performed by corresponding units or modules. For example, a signal may be transmitted by a transmitting unit or a transmitting module. A signal may be received by a receiving unit or a receiving module. A signal may be processed by a processing unit or a processing module. Other steps may be performed by a configuring unit/module, an activating unit/module, a table searching or lookup unit/module, a determining unit/module, a signaling unit/module, and/or an indicating unit/module. The respective units/modules may be hardware, software, or a combination thereof. For instance, one or more of the units/modules may be an integrated circuit, such as field programmable gate arrays (FPGAs) or application-specific integrated circuits (ASICs).
While this disclosure has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the disclosure, will be apparent to persons skilled in the art upon reference to the description. It is therefore intended that the appended claims encompass any such modifications or embodiments.
The following provides acronyms that may be used in the present disclosure.
This patent application is a continuation of International Patent Application No. PCT/US2023/017608 filed on Apr. 5, 2023, and entitled “SYSTEM AND METHOD FOR PROVIDING ADDITIONAL DM-RS PORTS FOR 5G MU-MIMO TRANSMISSION,” which claims priority to U.S. Provisional Application No. 63/335,590, filed on Apr. 27, 2022 and entitled “SYSTEM AND METHOD FOR ADDING ADDITIONAL DM-RS PORTS FOR 5G MU-MIMO TRANSMISSION,” and U.S. Provisional Application No. 63/335,606, filed on Apr. 27, 2022 and entitled “SYSTEM AND METHOD FOR ADDING ADDITIONAL DM-RS PORTS FOR 5G MU-MIMO TRANSMISSION,” which are hereby incorporated by reference herein as if reproduced in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| 63335590 | Apr 2022 | US | |
| 63335606 | Apr 2022 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2023/017608 | Apr 2023 | WO |
| Child | 18916113 | US |
