Patent Description:
A user equipment (UE) can communicate with a base station (for example, an evolved Node B (eNB), a next generation node B (gNB), or other base station) over a communication link in a wireless communication system, e.g., New Radio (NR) system, a millimeter wave (mmWave) communication system, or other communication systems. In a communication system, a reference signal normally refers to the so-called "pilot signal" used for channel related functions, e.g., estimation, demodulation, by the receiver. Sometimes, a reference signal is a predefined signal transmitted over a set of predefined resource elements in a resource grid. Downlink reference signals are used by a UE for downlink channel measurement and/or coherent demodulation of downlink transmissions. There are various reference signals defined in downlink, e.g., cell-specific reference signal (CRS), UE-specific demodulation reference signal (DMRS), channel status information reference signal (CSI-RS), and more. However, existing reference signal designs may not be able to meet the diverse needs of various wireless communication systems, e.g., mmWave communication systems. Further background information can be found in the following documents:
<CIT>, which describes joint determination of demodulation and channel state information reference signals. <CIT>, which describes a demodulation reference signal indication method and system. <NPL>), XP051299820, which pertains to a discussion on considerations in designing NR uplink DMRS focusing on the common downlink/uplink DMRS design and PUSCH and DMRS multiplexing. <CIT>, which describes selecting a demodulation reference signal pattern based on channel characteristics.

Some aspects of this disclosure relate to apparatuses and methods for adaptive configurations of resource elements to carry reference signals for a user equipment (UE) in a multiple input multiple output (MIMO) wireless communication systems, e.g., a New Radio (NR) MIMO system, or a millimeter wave (mmWave) communication system. A configuration of resource elements to carry reference signals for a UE can be adaptively determined by a base station based on a coherence bandwidth of a channel between the UE and the base station, a coherence time of the channel, a preference associated with channel status information reference signal (CSI-RS) by the UE, or a preference associated with demodulation reference signal (DMRS) by the UE. The configuration indicates a set of resource elements, and one or more orthogonal cover codes (OCCs) applied to at least a subset of the set of resource elements to carry the CSI-RS or DMRS for one or more antenna ports of the UE.

Some aspects of this disclosure relate to a UE. The UE includes a transceiver configured to communicate with a base station through a channel between the UE and the base station, and a processor communicatively coupled to the transceiver. In some examples, the channel has one or more frequencies above <NUM>, e.g., between <NUM> and <NUM>. The processor sends, using the transceiver and to the base station, a coherence bandwidth of the channel, a coherence time of the channel, a preference associated with CSI-RS, or a preference associated with DMRS for the UE. The processor further receives, using the transceiver and from the base station, a configuration of resource elements to carry reference signals for the UE. In detail, the processor can receive a radio resource control (RRC) signal, a medium access control (MAC) control element (CE), or a downlink control information (DCI) to indicate the configuration of resource elements to carry reference signals for the UE. The configuration is determined by the base station based on or in response to the coherence bandwidth of the channel, the coherence time of the channel, the preference associated with CSI-RS, or the preference associated with DMRS. The configuration indicates a set of resource elements, and one or more OCCs applied to at least a subset of the set of resource elements to carry the CSI-RS or DMRS for one or more antenna ports of the UE. The one or more OCCs applied to at least the subset of the set of resource elements for the one or more antenna ports can be semi-statically configured by the RRC signal, or dynamically configured by the MAC-CE or the DCI. In some examples, the processor can assign the subset of the set of resource elements or an OCC applied to the subset of the set of resource elements to an antenna port of the one or more antenna ports of the UE. The UE can have multiple antenna ports, e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or more antenna ports. Afterwards, the processor performs DMRS or CSI-RS reference signal processing based on the configuration of resource elements to carry reference signals for the UE.

In some examples, the configuration of resource elements to carry reference signals for the UE indicates a set of resource elements including at least two adjacent resource elements at two consecutive sub-carriers in a frequency domain and a symbol in a time domain. Additionally and alternatively, the set of resource elements can include at least two adjacent resource elements at two consecutive sub-carriers in the frequency domain and two adjacent symbols in the time domain. In addition, the configuration of resource elements to carry reference signals for the UE can indicate the one or more OCCs including frequency domain (FD) OCCs applied to the two adjacent resource elements at two consecutive sub-carriers in the frequency domain. Similarly, the configuration of resource elements to carry reference signals for the UE can indicate the one or more OCCs including time domain (TD) OCCs applied to the two adjacent resource elements of two adjacent symbols in the time domain. In some examples, the configuration of resource elements to carry reference signals for the UE indicates that only FD-OCCs, or TD-OCCs are applied, based on a relationship between a sub-carrier spacing (SCS) interval between the two consecutive sub-carriers at the frequency domain and the coherence bandwidth of the channel. Further in some examples, the subset of the set of resource elements having the one or more OCCs applied to is empty, and the configuration indicates no OCC is applied to the set of resource elements allocated to the one or more antenna ports of the UE.

Some aspects of this disclosure relate to a base station. The base station includes a transceiver configured to communicate over a wireless network with a UE, and a processor communicatively coupled to the transceiver. The processor receives, using the transceiver and from the UE, a coherence bandwidth of the channel, a coherence time of the channel, a preference associated with CSI-RS, or a preference associated with DMRS for the UE. The processor further determines, based on the coherence bandwidth of the channel, the coherence time of the channel, the preference associated with CSI-RS, or the preference associated with DMRS, a configuration of resource elements to carry reference signals for the UE. The configuration indicates a set of resource elements, and one or more OCCs applied to at least a subset of the set of resource elements to carry the CSI-RS or DMRS for one or more antenna ports of the UE. In some example, the processor can assign the subset of the set of resource elements or an OCC applied to the subset of the set of resource elements to an antenna port of the one or more antenna ports of the UE. In addition, the processor transmits, using the transceiver and to the UE, the configuration of resource elements to carry reference signals for the UE. In detail, the processor transmits a RRC signal, a MAC-CE, or a DCI to indicate the configuration of resource elements to carry reference signals for the UE. The one or more OCCs applied to at least the subset of the set of resource elements for the one or more antenna ports are semi-statically configured by the RRC signal, or dynamically configured by the MAC-CE or the DCI.

This Summary is provided merely for purposes of illustrating some aspects to provide an understanding of the subject matter described herein. Accordingly, the above-described features are merely examples and should not be construed to narrow the scope of the subject matter in this disclosure. Other features, aspects, and advantages of this disclosure will become apparent from the following Detailed Description, Figures, and Claims.

The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present disclosure and, together with the description, further serve to explain the principles of the disclosure and enable a person of skill in the relevant art(s) to make and use the disclosure.

The present disclosure is described with reference to the accompanying drawings. In the drawings, generally, like reference numbers indicate identical or functionally similar elements.

The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. This repetition does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

It is noted that references in the specification to "one embodiment," "an embodiment," "an example embodiment," "exemplary," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phases do not necessarily refer to the same embodiment. Further, when a particular feature, structure or characteristic is described in connection with an embodiment, it would be within the knowledge of one skilled in the art to effect such feature, structure or characteristic in connection with other embodiments whether or not explicitly described. In addition, words related to logical relationship, "and," "or" may mean the logic relationship. For example, "A or B" can include "A and B" or "A or B.

Wireless communication network and systems play an important role in the current society. There are many wireless communication systems, e.g., wireless systems based on 3rd Generation Partnership Project (3GPP) release <NUM> (Rel-<NUM>), release <NUM> (Rel-<NUM>), New Radio (NR) wireless systems. The next-generation wireless communication networks, e.g., NR wireless systems, provide fast data rates and greater capacity, and seamless and real-time interaction between humans and billions of intelligent devices. Millimeter wave (mmWave) communication system can operate on frequencies close to NR systems, e.g., having one or more frequencies above <NUM>, and can bring commercial opportunities for high data rate communications, e.g., licensed or unlicensed spectrum between <NUM> and <NUM>.

The opportunities in mmWave communication systems also bring challenges. Operations at mmWave communication systems may demand designs different from the NR systems. For example, a mmWave communication system can have a different numerology including subcarrier spacing (SCS), and channel bandwidth. Increased SCS can be used for a mmWave communication system to ensure robustness of the system to phase noise. However, increased SCS can result in resource elements having an interval larger than the coherence bandwidth of the channel, causing failures to some communication techniques. In a communication system, a reference signal normally refers to the so-called "pilot signal" used for channel functions, e.g., estimation or demodulation, by the receiver. Orthogonal cover codes (OCCs) have been applied to resource elements to carry various reference signals, e.g., UE-specific DMRS, CSI-RS. In a mmWave communication system, due to the increased SCS, OCCs applied to resource elements can fail sometimes. New designs for OCCs applied to resource elements to carry reference signals are desired.

Some aspects of this disclosure provide improved solutions to the problems caused by increased SCS in a communication system, e.g., a mmWave communication system. Instead of using fixed OCCs applied to resource elements to carry various reference signals, a base station can determine a configuration for adaptively applying OCCs to a set of resource elements to carry reference signals. The configuration can be determined based on parameters provided by a UE. For example, a UE can provide to a base station a coherence bandwidth of the channel, a coherence time of the channel, a preference associated with CSI-RS, or a preference associated with DMRS for the UE. The base station can determine a configuration to have one or more OCCs applied to a set of resource elements semi-statically or dynamically. The configuration indicates a set of resource elements, and one or more OCCs applied to a subset of the set of resource elements to carry the CSI-RS or DMRS for one or more antenna ports of the UE. In detail, the configuration can indicate that frequency domain (FD) OCCs can be applied to at least two adjacent resource elements at two consecutive sub-carriers in the frequency domain, time domain (TD) OCCs applied to at least two adjacent resource elements of two adjacent symbols in the time domain, both FD-OCCs and TD-OCCs are applied, or none of FD-OCC and TD-OCC is applied. When both FD-OCCs and TD-OCCs are applied to the set of resource elements, the set of resource elements can carry reference signals for more antenna ports. When one or both of FD-OCC and TD-OCC are disabled from being applied to the set of resource elements, the set of resource elements can carry reference signals for fewer antenna ports. By trading off the number of antenna ports to receive reference signals, techniques provided herein can increase the reliability of the FD-OCC and TD-OCC when applied to the set of resource elements.

Although some examples of configurations for carrying reference signals, e.g., CSI-RS or DMRS, for the UE, are presented in a mmWave communication system are provided above, the aspects of this disclosure are not limited to these examples. The examples can be applicable to other wireless communication systems.

<FIG> illustrates an example MIMO wireless system <NUM> implementing designs for configurations of resource elements to carry reference signals for a UE <NUM>, according to some aspects of the disclosure. The wireless system <NUM> is provided for the purpose of illustration only and does not limit the disclosed aspects. The system <NUM> can include, but is not limited to, a network node (herein referred to as base station) <NUM> and an electronic device (hereinafter referred to as UE) <NUM>.

According to some aspects, the base station <NUM> can include a node configured to operate based on a wide variety of wireless communication techniques such as, but not limited to, techniques for a mmWave communication system with one or more frequencies above <NUM>, or techniques based on 3GPP standards. For example, base station <NUM> can include a node configured to operate using Rel-<NUM>, Rel-<NUM>, or other present / future 3GPP standards. The base station <NUM> can be a fixed station, and may also be called a base transceiver system (BTS), an access point (AP), a transmission/reception point (TRP), an evolved NodeB (eNB), a next generation node B (gNB), or some other equivalent terminology.

According to some aspects, the UE <NUM> can include an electronic device configured to operate based on a wide variety of wireless communication techniques, e.g., techniques for a mmWave communication system with one or more frequencies above <NUM>. These techniques can also include, but are not limited to, techniques based on 3rd Generation Partnership Project (3GPP) standards. For example, the UE <NUM> can include an electronic device configured to operate using Rel-<NUM>, Rel-<NUM> or other present / future 3GPP standards. The UE <NUM> can include, but is not limited to, a wireless communication device, a smart phone, a laptop, a desktop, a tablet, a personal assistant, a monitor, a television, a wearable device, an Internet of Things (IoTs), a vehicle's communication device, a mobile station, a subscriber station, a remote terminal, a wireless terminal, a user device, or the like.

In some examples, the UE <NUM> can include a transceiver <NUM> configured to wirelessly communicate with the base station <NUM> through a channel <NUM> between the UE <NUM> and the base station <NUM>. The UE <NUM> further includes a processor <NUM> communicatively coupled to the transceiver <NUM>. Similarly, the base station <NUM> can include a transceiver <NUM> configured to wirelessly communicate with the UE <NUM> through the channel <NUM>, and a processor <NUM> communicatively coupled to the transceiver <NUM>. More detailed operations of the transceiver <NUM>, the processor <NUM>, the transceiver <NUM>, and the processor <NUM> are shown in more details in <FIG> and <FIG>. In some examples, the channel <NUM> can have one or more frequencies above <NUM>, e.g., between <NUM> and <NUM>. The UE <NUM> can include multiple antenna ports, e.g., an antenna port <NUM>, an antenna port <NUM>, an antenna port <NUM>, an antenna port <NUM>. The number of antenna ports is shown for example only, and is not limiting. For example, the UE <NUM> can include <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or more antenna ports.

The base station <NUM> can send various downlink reference signals to the UE <NUM> for downlink channel measurement and/or coherent demodulation of downlink transmission. There are various reference signals defined in downlink, e.g., cell-specific reference signal (CRS), UE-specific DMRS, CSI-RS, and more. A DMRS or CSI-RS reference signal can be processed by the UE <NUM> according to a configuration <NUM> stored in the UE <NUM>. In the current disclosure, a DMRS or CSI-RS signal is used as an example to describe techniques presented herein. Accordingly, these techniques can be applicable to other reference signals with little or no change. Similar techniques can be applied to uplink reference signals as well.

In some examples, the configuration <NUM> can be determined by the base station <NUM>, and further received from the base station <NUM> by the UE <NUM>. The configuration <NUM> can be adaptively determined by the base station <NUM> based on information or parameters provided by the UE <NUM>. In some detail, the UE <NUM> can send to the base station <NUM> an uplink information <NUM>, where the uplink information <NUM> can include a coherence bandwidth of the channel, a coherence time of the channel, a preference associated with CSI-RS, or a preference associated with DMRS for the UE <NUM>. The base station <NUM> can receive the uplink information <NUM>, and further determine a configuration based on the coherence bandwidth of the channel, the coherence time of the channel, the preference associated with CSI-RS, e.g., carried in sounding reference signal (SRS), or the preference associated with DMRS. Afterwards, the base station <NUM> can send to the UE <NUM> the determined configuration. The UE <NUM> can receive the configuration from the base station <NUM>, which can be saved by the UE <NUM> to become the configuration <NUM>.

In some examples, the configuration <NUM> can indicate a set of resource elements <NUM>, and one or more OCCs <NUM> applied to at least a subset of the set of resource elements to carry reference signals, e.g., CSI-RS or DMRS, for one or more antenna ports, e.g., the antenna port <NUM>, the antenna port <NUM>, of the UE <NUM>.

In some examples, the set of resource elements <NUM> includes at least two adjacent resource elements (REs) at two consecutive sub-carriers in a frequency domain and a symbol in a time domain. In other words, the set of resource elements <NUM> includes at least multiple adjacent REs formed of one symbol. More details of such resource elements are shown in <FIG>. In some other examples, the set of resource elements <NUM> includes at least two adjacent REs at two consecutive sub-carriers in the frequency domain and two adjacent symbols in the time domain. In other words, the set of resource elements <NUM> includes at least multiple adjacent REs formed of two symbols. More details of such resource elements are shown in <FIG>.

In some examples, the one or more OCCs <NUM> include frequency domain (FD) OCCs applied to the two adjacent resource elements at two consecutive sub-carriers in the frequency domain, or time domain (TD) OCCs applied to the at least two adjacent resource elements of two adjacent symbols in the time domain. In some examples, the configuration <NUM> indicates that only FD-OCCs, or only TD-OCCs are applied, based on a relationship between a sub-carrier spacing (SCS) interval between the two consecutive sub-carriers at the frequency domain and the coherence bandwidth of the channel. In some examples, there may be no OCCs applied to the set of REs <NUM>, and the one or more OCCs <NUM> will not be available. More details of the applications of OCCs are shown in <FIG> and <FIG>. Furthermore in some examples, the number of resource elements can be adjusted to keep within the coherence bandwidth, even if the resources elements can have an interval between them.

In some examples, the processor <NUM> and the processor <NUM> can be configured to perform methods supporting designs for configurations of carrying reference signals for a UE, e.g., the configuration <NUM>. More details of the operations of the processor <NUM> and the processor <NUM> are shown in <FIG> and <FIG> below.

<FIG> illustrates an example method <NUM> for the UE <NUM> supporting mechanisms for implementing designs for configurations of resource elements to carry reference signals for a UE. Method <NUM> can be performed by the UE <NUM>, which can be implemented by the system <NUM> of <FIG> and/or computer system <NUM> of <FIG>. But method <NUM> is not limited to the specific aspects depicted in those figures and other systems may be used to perform the method as will be understood by those skilled in the art. It is to be appreciated that not all operations may be needed, and the operations may not be performed in the same order as shown in <FIG>.

At <NUM>, using a transceiver, a UE sends, to a base station, a coherence bandwidth of the channel, a coherence time of the channel, a preference associated with CSI-RS, or a preference associated with DMRS for the UE. For example, using the transceiver <NUM>, the UE <NUM> sends, to the base station <NUM>, the uplink information <NUM> that includes a coherence bandwidth of the channel, the coherence time of the channel, a preference associated with CSI-RS, or a preference associated with DMRS for the UE <NUM>, as described for <FIG>.

At <NUM>, using the transceiver, the UE receives, from the base station, a configuration of resource elements to carry reference signals for the UE, where the configuration is determined by the base station based on the coherence bandwidth of the channel, the coherence time of the channel, the preference associated with CSI-RS, or the preference associated with DMRS. For example, the UE <NUM> receives, from the base station <NUM>, the configuration <NUM> for CSI-RS or DMRS for the UE, as described for <FIG>. The configuration <NUM> can be used for other reference signals as well.

In detail, the processor <NUM> of the UE <NUM> receives a RRC signal, a MAC-CE, or a DCI to indicate the configuration <NUM> for CSI-RS or DMRS for the UE <NUM>. The configuration <NUM> includes the set of resource elements <NUM>, and one or more OCCs <NUM> applied to at least a subset of the set of resource elements to carry the CSI-RS or DMRS for one or more antenna ports of the UE <NUM>. In some examples, the one or more OCCs <NUM> applied to at least the subset of the set of resource elements for the one or more antenna ports can be semi-statically configured by the RRC signal, or dynamically configured by the MAC-CE or the DCI.

At <NUM>, the UE assigns the subset of the set of resource elements or an OCC applied to the subset of the set of resource elements to an antenna port of the UE. For example, the UE <NUM> assigns the subset of the set of resource elements or an OCC applied to the subset of the set of resource elements to an antenna port of the UE, as described for <FIG>. Operations at <NUM> can be optional. In some examples, the assignments of the resource elements or the OCCs to an antenna port can be based on a standard, or assigned by the base station instead of the UE. More detailed examples of such assignments are shown in <FIG> and <FIG>.

At <NUM>, the UE performs DMRS or CSI-RS reference signal processing based on the configuration of resource elements to carry reference signals for the UE. For example, the UE <NUM> performs DMRS or CSI-RS reference signal processing based on the configuration <NUM> for CSI-RS or DMRS for the UE, as described for <FIG>.

<FIG> illustrates an example method <NUM> for the base station <NUM> supporting mechanisms for implementing designs for configurations of resource elements to carry reference signals for a UE. Method <NUM> may also be performed by system <NUM> of <FIG> and/or computer system <NUM> of <FIG>. But method <NUM> is not limited to the specific aspects depicted in those figures and other systems may be used to perform the method as will be understood by those skilled in the art. It is to be appreciated that not all operations may be needed, and the operations may not be performed in the same order as shown in <FIG>.

At <NUM>, a base station receives, using a transceiver and from the UE, a coherence bandwidth of the channel, a coherence time of the channel, a preference associated with CSI-RS, or a preference associated with DMRS for the UE. For example, the base station <NUM> receives, using the transceiver <NUM> and from the UE <NUM>, the uplink information <NUM> that includes a coherence bandwidth of the channel, the coherence time of the channel, a preference associated with CSI-RS, or a preference associated with DMRS for the UE, as described for <FIG>.

At <NUM>, the base station determines, based on the coherence bandwidth of the channel, the coherence time of the channel, the preference associated with CSI-RS, or the preference associated with DMRS, a configuration of resource elements to carry reference signals for the UE. For example, the base station <NUM> determines, based on the coherence bandwidth of the channel, the coherence time of the channel, the preference associated with CSI-RS, or the preference associated with DMRS contained in the uplink information <NUM>, a configuration of resource elements to carry reference signals for the UE <NUM>. The configuration includes a set of resource elements, and one or more OCCs applied to at least a subset of the set of resource elements to carry the CSI-RS or DMRS for one or more antenna ports of the UE <NUM>.

At <NUM>, the base station assigns the subset of the set of resource elements or an OCC applied to the subset of the set of resource elements to an antenna port of the UE. For example, the base station <NUM> assigns the subset of the set of resource elements or an OCC applied to the subset of the set of resource elements to an antenna port of the UE, as described for <FIG>. Operations at <NUM> can be optional. In some examples, the assignments of the resource elements or the OCCs to an antenna port can be based on a standard, or assigned by the UE instead of the base station <NUM>. More detailed examples of such assignments are shown in <FIG> and <FIG>.

At <NUM>, the base station transmits, using the transceiver and to the UE, the configuration of resource elements to carry reference signals for the UE. For example, the base station <NUM> transmits, using the transceiver <NUM> and to the UE <NUM>, the configuration of resource elements to carry reference signals for the UE <NUM>, which is saved by the UE <NUM> as the configuration <NUM>, as described for <FIG>. In detail, the processor <NUM> of the base station <NUM> can transmit a RRC signal, a MAC-CE, or a DCI to indicate the configuration <NUM> for CSI-RS or DMRS for the UE <NUM>. The configuration <NUM> includes the set of resource elements <NUM>, and one or more OCCs <NUM> applied to at least a subset of the set of resource elements to carry the CSI-RS or DMRS for one or more antenna ports of the UE <NUM>. In some examples, the one or more OCCs <NUM> applied to at least the subset of the set of resource elements for the one or more antenna ports are semi-statically configured by the RRC signal, or dynamically configured by the MAC-CE or the DCI.

<FIG> illustrate example configurations of resource elements to carry reference signals for a UE, according to some aspects of the disclosure. The configurations can be an example of the configure <NUM> shown in <FIG>. The configurations in <FIG> indicate a set of resource elements <NUM>, and one or more OCCs applied to at least a subset of the set of resource elements <NUM> to carry the CSI-RS or DMRS for one or more antenna ports of the UE.

In some examples, as shown in <FIG>, the set of resource elements <NUM> is a resource block (RB) of <NUM> resource elements (REs), where each resource element (RE) includes one orthogonal frequency division multiplexing (OFDM) symbol on one subcarrier. The set of resource elements <NUM> is shown in an exemplary OFDM time-frequency grid <NUM> in the time domain and the frequency domain. In the frequency domain, the physical resources are divided into adjacent subcarriers with a subcarrier spacing (SCS). In some example, the SCS can be <NUM>. In a mmWave system, the SCS can be larger than <NUM>. The number of subcarriers varies according to the allocated system bandwidth. The OFDM time-frequency grid <NUM> includes <NUM> subcarriers over <NUM> symbols. The <NUM> symbols can form a subframe of one millisecond. In some examples, a subframe can have <NUM> symbols if an extended cyclic prefix is used.

In some examples, the set of resource elements <NUM> is divided into multiple subsets of resource elements to carry the CSI-RS or DMRS for one or more antenna ports of the UE. For example, as shown in <FIG>, the resource elements <NUM> is divided into two disjoint subsets, a subset <NUM> of REs, and a subset <NUM> of REs. The subset <NUM> of REs includes multiple pairs of REs, e.g., a pair of REs <NUM>, a pair of REs <NUM>, and a pair of REs <NUM>. The pair of REs <NUM>, the pair of REs <NUM>, or the pair of REs <NUM> includes two adjacent resource elements at two consecutive sub-carriers in the frequency domain and a symbol in the time domain. For example, the pair of REs <NUM> includes two adjacent resource elements at two consecutive sub-carriers <NUM> and <NUM>, and the symbol <NUM> in the time domain, since the pair of REs <NUM> is part of the set of resource elements <NUM>. The subset <NUM> of REs has similar structures as the subset <NUM> of REs.

Without the use of OCCs, the subset <NUM> of REs can be assigned to an antenna port, e.g., port <NUM>, while the subset <NUM> of REs can be assigned to another antenna port, e.g., port <NUM>. However, the subset <NUM> of REs can only be assigned to one antenna port without the use of OCCs. Therefore, the set of resource elements <NUM> is split into two subsets of REs to carry the CSI-RS or DMRS for two antenna ports of the UE.

In some examples, an OCC can be used to maintain orthogonality between antenna ports allocated to the same REs. As shown in <FIG>, two OCCs, {<NUM><NUM>} and {<NUM> -<NUM>} can be applied to the subset <NUM> of REs in the frequency domain so that the same subset <NUM> of REs can carry reference signals for two antenna ports of the UE. The OCC {<NUM><NUM>} is represented by "+" "+" marked on two resource elements at two consecutive sub-carriers in the frequency domain, while the OCC {<NUM> -<NUM>} is represented by "+" "-" marked on two resource elements at two consecutive sub-carriers in the frequency domain. Accordingly, the subset <NUM> of REs with the OCC {<NUM><NUM>} applied to the REs can be assigned to an antenna port, e.g., antenna port <NUM>, and the subset <NUM> of REs with the OCC {<NUM> -<NUM>} applied to the REs can be assigned to an antenna port, e.g., antenna port <NUM>. The subset <NUM> of REs with two OCCs applied in the frequency domain form a code division multiplexing (CDM) group <NUM>.

Similarly, two OCCs, {<NUM><NUM>} and {<NUM> -<NUM>} can be applied to the subset <NUM> of REs in the frequency domain so that the same subset <NUM> of REs can carry reference signals for two antenna ports of the UE. Accordingly, the subset <NUM> of REs with the OCC {<NUM><NUM>} applied to the REs can be assigned to an antenna port, e.g., antenna port <NUM>, and the subset <NUM> of REs with the OCC {<NUM> -<NUM>} applied to the REs can be assigned to an antenna port, e.g., antenna port <NUM>. The assignments of a subset of REs together with an OCC to an antenna port can be performed dynamically by a UE or a base station, or by a standard known ahead of time.

In some examples, as shown in <FIG>, the set of resource elements <NUM> is divided into three subsets of resource elements, a subset <NUM> of REs, a subset <NUM> of REs, and a subset <NUM> of REs, to carry the CSI-RS or DMRS for one or more antenna ports of the UE. The subset <NUM> of REs, the subset <NUM> of REs, the subset <NUM> of REs, includes multiple pairs of resource elements, where a pair of REs includes two adjacent resource elements at two consecutive sub-carriers in the frequency domain and a symbol in the time domain.

Without the use of OCCs, the subset <NUM> of REs can be assigned to a first antenna port, e.g., port <NUM>, the subset <NUM> of REs can be assigned to a second antenna port, e.g., port <NUM>, while the subset <NUM> of REs can be assigned to a third antenna port, e.g., port <NUM>. However, each subset of REs can only be assigned to one antenna port without the use of OCCs.

In some examples, an OCC can be used to maintain orthogonality between antenna ports allocated to the same DMRS REs. Two OCCs, {<NUM><NUM>} and {<NUM> -<NUM>} can be applied to the subset <NUM> of REs in the frequency domain so that the same subset <NUM> of REs can carry reference signals for two antenna ports of the UE. Accordingly, the subset <NUM> of REs with the OCC {<NUM><NUM>} applied to the REs can be assigned to an antenna port, e.g., antenna port <NUM>, and the subset <NUM> of REs with the OCC {<NUM> -<NUM>} applied to the REs can be assigned to an antenna port, e.g., antenna port <NUM>. The subset <NUM> of REs with two OCCs applied in the frequency domain form a code division multiplexing (CDM) group <NUM>.

Similarly, two OCCs, {<NUM><NUM>} and {<NUM> -<NUM>} can be applied to the subset <NUM> of REs in the frequency domain so that the same subset <NUM> of REs can carry reference signals for two antenna ports of the UE. Accordingly, the subset <NUM> of REs with the OCC {<NUM><NUM>} applied to the REs can be assigned to an antenna port, e.g., antenna port <NUM>, and the subset <NUM> of REs with the OCC {<NUM> -<NUM>} applied to the REs can be assigned to an antenna port, e.g., antenna port <NUM>. The subset <NUM> of REs with two OCCs applied in the frequency domain form a code division multiplexing (CDM) group <NUM>.

<FIG> illustrate example configurations of resource elements to carry reference signals for a UE, according to some aspects of the disclosure. The configurations can be an example of the configure <NUM> shown in <FIG>. The configurations in <FIG> indicate a set of resource elements <NUM>, and one or more OCCs applied to at least a subset of the set of resource elements to carry the CSI-RS or DMRS for one or more antenna ports of the UE.

In some examples, as shown in <FIG>, the set of resource elements <NUM> is a resource block (RB) of <NUM> REs over two symbols, symbol <NUM> and symbol <NUM>. The set of resource elements <NUM> is shown in an exemplary OFDM time-frequency grid <NUM> in the time domain and the frequency domain. The OFDM time-frequency grid <NUM> includes <NUM> subcarriers over <NUM> symbols. The <NUM> symbols can form a subframe of one millisecond. In some examples, a subframe can have <NUM> symbols if an extended cyclic prefix is used.

In some examples, the set of resource elements <NUM> is divided into multiple subsets of resource elements to carry the CSI-RS or DMRS for one or more antenna ports of the UE. For example, as shown in <FIG>, the resource elements <NUM> is divided into two disjoint subsets, a subset <NUM> of REs, and a subset <NUM> of REs. The subset <NUM> of REs or the subset <NUM> of REs includes multiple pairs of REs. A pair of REs includes two adjacent resource elements at two consecutive sub-carriers in the frequency domain and two adjacent symbols in the time domain.

In some examples, an OCC can be used to maintain orthogonality between antenna ports allocated to the same DMRS REs. Two OCCs, {<NUM><NUM>} and {<NUM> -<NUM>} can be applied to the subset <NUM> of REs in the frequency domain. In addition, two OCCs, {<NUM><NUM>} and {-<NUM> -<NUM>} can be applied to the subset <NUM> of REs in the time domain. Overall, the subset <NUM> of REs with the corresponding FD-OCCs and TD-OCCs can be assigned to four antenna ports, e.g., antenna port <NUM>, antenna port <NUM>, antenna port <NUM>, and antenna port <NUM>.

Similarly, two OCCs, {<NUM><NUM>} and {<NUM> -<NUM>} can be applied to the subset <NUM> of REs in the frequency domain. In addition, two OCCs, {<NUM><NUM>} and {-<NUM> -<NUM>} can be applied to the subset <NUM> of REs in the time domain. Overall, the subset <NUM> of REs with the corresponding FD-OCCs and TD-OCCs can be assigned to four antenna ports, e.g., antenna port <NUM>, antenna port <NUM>, antenna port <NUM>, and antenna port <NUM>.

In some examples, as shown in <FIG>, the set of resource elements <NUM> is divided into four disjoint subsets, a subset <NUM> of REs, a subset <NUM> of REs, a subset <NUM> of REs, a subset <NUM> of REs, each of which includes multiple pairs REs. A pair of REs includes two adjacent resource elements at two consecutive sub-carriers in the frequency domain and one symbol in the time domain.

Without the use of OCCs, the subset <NUM> of REs can be assigned to an antenna port, e.g., port <NUM>. Similarly, each of the subset <NUM> of REs, the subset <NUM> of REs, and the subset <NUM> of REs can be assigned to an antenna port, e.g., port <NUM>, port <NUM>, port <NUM>. Therefore, the set of resource elements <NUM> is split into four subsets of REs to carry the CSI-RS or DMRS for four antenna ports of the UE.

In some examples, an OCC can be used to maintain orthogonality between antenna ports allocated to the same DMRS REs. Two OCCs, {<NUM><NUM>} and {<NUM> -<NUM>} can be applied to the subset <NUM> of REs in the frequency domain. Hence, the subset <NUM> of REs with the corresponding FD-OCCs can be assigned to two antenna ports, e.g., antenna port <NUM>, antenna port <NUM>. Similarly, the subset <NUM> of REs with the corresponding FD-OCCs can be assigned to two antenna ports, e.g., antenna port <NUM>, antenna port <NUM>; the subset <NUM> of REs with the two corresponding FD-OCCs can be assigned to two antenna ports, e.g., antenna port <NUM>, antenna port <NUM>; and the subset <NUM> of REs with the two corresponding FD-OCCs can be assigned to two antenna ports, e.g., antenna port <NUM>, antenna port <NUM>. As shown above, only FD-OCCs are applied to a subset of REs, without applying any TD-OCCs. A base station can make such a determination to apply only FD-OCCs based on a relationship between a SCS interval at the frequency domain and the coherence bandwidth of the channel. When the coherence bandwidth of the channel is small compared to the SCS interval, TD-OCCs may not be applied to the subset of REs. Similarly, the base station can make a determination to apply only TD-OCCs without FD-OCCs to some other subsets of REs, not shown.

In some examples, as shown in <FIG>, the set of resource elements <NUM> is divided into six disjoint subsets, a subset <NUM> of REs, a subset <NUM> of REs, a subset <NUM> of REs, a subset <NUM> of REs, a subset <NUM> of REs, and a subset <NUM> of REs, each of which includes multiple pairs REs. A pair of REs includes two adjacent resource elements at two consecutive sub-carriers in the frequency domain and one symbol in the time domain.

Without the use of OCCs, the subset <NUM> of REs can be assigned to an antenna port, e.g., port <NUM>. Similarly, each of the subset <NUM> of REs, the subset <NUM> of REs, the subset <NUM> of REs, the subset <NUM> of REs, and the subset <NUM> of REs, can be assigned to an antenna port, e.g., port <NUM>, port <NUM>, port <NUM>, port <NUM>, port <NUM>. Therefore, the set of resource elements <NUM> is split into <NUM> subsets of REs to carry the CSI-RS or DMRS for <NUM> antenna ports of the UE.

In some examples, an OCC can be used to maintain orthogonality between antenna ports allocated to the same DMRS REs. Two OCCs, {<NUM><NUM>} and {<NUM> -<NUM>} can be applied to the subset <NUM> of REs in the frequency domain. Hence, the subset <NUM> of REs with the corresponding FD-OCCs can be assigned to two antenna ports, e.g., antenna port <NUM>, antenna port <NUM>. Similarly, the subset <NUM> of REs with the corresponding FD-OCCs can be assigned to two antenna ports, e.g., antenna port <NUM>, antenna port <NUM>; the subset <NUM> of REs with the corresponding FD-OCCs can be assigned to two antenna ports, e.g., antenna port <NUM>, antenna port <NUM>; the subset <NUM> of REs with the corresponding FD-OCCs can be assigned to two antenna ports, e.g., antenna port <NUM>, antenna port <NUM>; the subset <NUM> of REs with the corresponding FD-OCCs can be assigned to two antenna ports, e.g., antenna port <NUM>, antenna port <NUM>; the subset <NUM> of REs with the corresponding FD-OCCs can be assigned to two antenna ports, e.g., antenna port <NUM>, antenna port <NUM>.

The various configurations of resource elements to carry reference signals for a UE, with or without FD-OCCs or TD-OCCs, as shown in <FIG> and <FIG>, are for examples only, and are not limiting. For example, the set of resource elements <NUM> or the set of resource elements <NUM> can be split into multiple subsets of REs in different ways. In addition, different OCCs, e.g., other length-<NUM> OCCs, or length-<NUM> OCCs can be assigned to a subset of REs, resulting to assignments to a number of antenna ports different from what are shown in <FIG> and <FIG>.

<FIG> illustrates a block diagram of an example system <NUM> of an electronic device implementing designs for configurations of resource elements to carry reference signals for a UE, according to some aspects of the disclosure. System <NUM> may be any of the electronic devices (e.g., the base station <NUM>, the UE <NUM>) of system <NUM>. The system <NUM> includes a processor <NUM>, one or more transceivers <NUM>, communication infrastructure <NUM>, memory <NUM>, operating system <NUM>, application <NUM>, and one or more antenna <NUM>. Illustrated systems are provided as exemplary parts of system <NUM>, and system <NUM> can include other circuit(s) and subsystem(s). Also, although the systems of system <NUM> are illustrated as separate components, the aspects of this disclosure can include any combination of these, less, or more components.

Memory <NUM> may include random access memory (RAM) and/or cache, and may include control logic (e.g., computer software) and/or data. Memory <NUM> may include other storage devices or memory such as, but not limited to, a hard disk drive and/or a removable storage device/unit. According to some examples, operating system <NUM> can be stored in memory <NUM>. Operating system <NUM> can manage transfer of data from memory <NUM> and/or one or more applications <NUM> to processor <NUM> and/or one or more transceivers <NUM>. In some examples, operating system <NUM> maintains one or more network protocol stacks (e.g., Internet protocol stack, cellular protocol stack, and the like) that can include a number of logical layers. At corresponding layers of the protocol stack, operating system <NUM> includes control mechanism and data structures to perform the functions associated with that layer.

According to some examples, application <NUM> can be stored in memory <NUM>. Application <NUM> can include applications (e.g., user applications) used by wireless system <NUM> and/or a user of wireless system <NUM>. The applications in application <NUM> can include applications such as, but not limited to, Siri™, FaceTime™, radio streaming, video streaming, remote control, and/or other user applications.

System <NUM> can also include communication infrastructure <NUM>. Communication infrastructure <NUM> provides communication between, for example, processor <NUM>, one or more transceivers <NUM>, and memory <NUM>. In some implementations, communication infrastructure <NUM> may be a bus. Processor <NUM> together with instructions stored in memory <NUM> performs operations enabling system <NUM> to implement mechanisms for configurations of resource elements to carry reference signals for a UE, as described herein for the system <NUM> as shown in <FIG>.

One or more transceivers <NUM> transmit and receive communications signals that support mechanisms for configurations of resource elements to carry reference signals for a UE as shown in <FIG>. Additionally, one or more transceivers <NUM> transmit and receive communications signals that support mechanisms for transmitting the configurations of resource elements to carry reference signals for a UE as shown in <FIG>. According to some aspects, one or more transceivers <NUM> may be coupled to antenna <NUM>. Antenna <NUM> may include one or more antennas that may be the same or different types. One or more transceivers <NUM> allow system <NUM> to communicate with other devices that may be wired and/or wireless. In some examples, one or more transceivers <NUM> can include processors, controllers, radios, sockets, plugs, buffers, and like circuits/devices used for connecting to and communication on networks. According to some examples, one or more transceivers <NUM> include one or more circuits to connect to and communicate on wired and/or wireless networks.

According to some aspects of this disclosure, one or more transceivers <NUM> can include a cellular subsystem, a WLAN subsystem, and/or a Bluetooth™ subsystem, each including its own radio transceiver and protocol(s) as will be understood by those skilled arts based on the discussion provided herein. In some implementations, one or more transceivers <NUM> can include more or fewer systems for communicating with other devices.

In some examples, one or more transceivers <NUM> can include one or more circuits (including a WLAN transceiver) to enable connection(s) and communication over WLAN networks such as, but not limited to, networks based on standards described in IEEE <NUM>.

Additionally, or alternatively, one or more transceivers <NUM> can include one or more circuits (including a Bluetooth™ transceiver) to enable connection(s) and communication based on, for example, Bluetooth™ protocol, the Bluetooth™ Low Energy protocol, or the Bluetooth™ Low Energy Long Range protocol. For example, one or more transceivers transceiver <NUM> can include a Bluetooth™ transceiver.

Additionally, one or more transceivers <NUM> can include one or more circuits (including a cellular transceiver) for connecting to and communicating on cellular networks. The cellular networks can include, but are not limited to, <NUM>/<NUM>/<NUM> networks such as Universal Mobile Telecommunications System (UMTS), Long-Term Evolution (LTE), mmWave systems, and the like. For example, one or more transceivers <NUM> can be configured to operate according to one or more of Rel-<NUM>, Rel-<NUM>, Rel-<NUM>, or other present / future 3GPP standards.

According to some aspects of this disclosure, processor <NUM>, alone or in combination with computer instructions stored within memory <NUM>, and/or one or more transceiver <NUM>, implements the methods and mechanisms discussed in this disclosure. For example, processor <NUM>, alone or in combination with computer instructions stored within memory <NUM>, and/or one or more transceiver <NUM>, implements mechanisms for configurations of resource elements to carry reference signals for a UE as shown in <FIG>. According to some aspects of this disclosure, processor <NUM>, alone or in combination with computer instructions stored within memory <NUM>, and/or one or more transceiver <NUM>, can send, to the base station, a coherence bandwidth of the channel, a coherence time of the channel, a preference associated with CSI-RS, or a preference associated with DMRS for the UE. In addition, processor <NUM> can receive, using the transceiver and from the base station, a configuration of resource elements to carry reference signals for the UE; and further perform DMRS or CSI-RS reference signal processing based on the configuration of resource elements to carry reference signals for the UE.

Various aspects can be implemented, for example, using one or more computer systems, such as computer system <NUM> shown in <FIG>. Computer system <NUM> can be any well-known computer capable of performing the functions described herein such as devices <NUM>, <NUM> of <FIG>, or <NUM> of <FIG>. Processor <NUM> is connected to a communication infrastructure <NUM> (e.g., a bus). Computer system <NUM> also includes a main or primary memory <NUM>, such as random access memory (RAM). Main memory <NUM> may include one or more levels of cache. Main memory <NUM> has stored therein control logic (e.g., computer software) and/or data.

According to some aspects, secondary memory <NUM> may include other means, instrumentalities or other approaches for allowing computer programs and/or other instructions and/or data to be accessed by computer system <NUM>. Such means, instrumentalities or other approaches may include, for example, a removable storage unit <NUM> and an interface <NUM>. Examples of the removable storage unit <NUM> and the interface <NUM> may include a program cartridge and cartridge interface (such as that found in video game devices), a removable memory chip (such as an EPROM or PROM) and associated socket, a memory stick and USB port, a memory card and associated memory card slot, and/or any other removable storage unit and associated interface.

In some examples, main memory <NUM>, the removable storage unit <NUM>, the removable storage unit <NUM> can store instructions that, when executed by processor <NUM>, cause processor <NUM> to perform operations for a UE, e.g., the UE <NUM>, or a base station, e.g., the base station <NUM>. In some examples, the operations include sending, to the base station, a coherence bandwidth of the channel, a coherence time of the channel, a preference associated with CSI-RS, or a preference associated with DMRS for the UE; receiving, from the base station, a configuration of resource elements to carry reference signals for the UE; and performing DMRS or CSI-RS reference signal processing based on the configuration of resource elements to carry reference signals for the UE. In addition, the operations include receiving, from the UE, a coherence bandwidth of the channel, a coherence time of the channel, a preference associated with CSI-RS, or a preference associated with DMRS for the UE; determining, based on the coherence bandwidth of the channel, the preference associated with CSI-RS, or the preference associated with DMRS, a configuration of resource elements to carry reference signals for the UE; and transmitting, to the UE, the configuration of resource elements to carry reference signals for the UE.

The operations in the preceding aspects can be implemented in a wide variety of configurations and architectures. Therefore, some or all of the operations in the preceding aspects may be performed in hardware, in software or both. In some aspects, a tangible, non-transitory apparatus or article of manufacture includes a tangible, non-transitory computer useable or readable medium having control logic (software) stored thereon is also referred to herein as a computer program product or program storage device. This includes, but is not limited to, computer system <NUM>, main memory <NUM>, secondary memory <NUM> and removable storage units <NUM> and <NUM>, as well as tangible articles of manufacture embodying any combination of the foregoing. Such control logic, when executed by one or more data processing devices (such as computer system <NUM>), causes such data processing devices to operate as described herein.

Based on the teachings contained in this disclosure, it will be apparent to persons skilled in the relevant art(s) how to make and use aspects of the disclosure using data processing devices, computer systems and/or computer architectures other than that shown in <FIG>. In particular, aspects may operate with software, hardware, and/or operating system implementations other than those described herein.

While the disclosure has been described herein with reference to exemplary aspects for exemplary fields and applications, it should be understood that the disclosure is not limited thereto. Other aspects and modifications thereto are possible, and are within the scope of the disclosure. For example, and without limiting the generality of this paragraph, aspects are not limited to the software, hardware, firmware, and/or entities illustrated in the figures and/or described herein. Further, aspects (whether or not explicitly described herein) have significant utility to fields and applications beyond the examples described herein.

Aspects have been described herein with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. In addition, alternative aspects may perform functional blocks, steps, operations, methods, etc. using orderings different from those described herein.

References herein to "one embodiment," "an embodiment," "an example embodiment," or similar phrases, indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it would be within the knowledge of persons skilled in the relevant art(s) to incorporate such feature, structure, or characteristic into other aspects whether or not explicitly mentioned or described herein.

The scope of the disclosure should not be limited by any of the above-described exemplary aspects, but should be defined only in accordance with the following claims.

Claim 1:
A user equipment, UE (<NUM>), comprising:
a transceiver configured to wirelessly communicate with a base station (<NUM>) through a channel between the UE (<NUM>) and the base station (<NUM>); and
a processor (<NUM>) communicatively coupled to the transceiver (<NUM>) and configured to:
send, using the transceiver (<NUM>) and to the base station (<NUM>), a coherence bandwidth of the channel, a coherence time of the channel, a preference associated with channel status information reference signal, CSI-RS, or a preference associated with demodulation reference signal, DMRS, for the UE (<NUM>);
receive, using the transceiver (<NUM>) and from the base station (<NUM>), a configuration of resource elements to carry reference signals for the UE (<NUM>), wherein the configuration is based on the coherence bandwidth of the channel, the coherence time of the channel, the preference associated with CSI-RS, or the preference associated with DMRS sent from the UE to the base station, and the configuration indicates a set of resource elements, and one or more orthogonal cover codes, OCCs, comprising a frequency domain, FD, OCC or a time domain, TD, OCC applied to at least a subset of the set of resource elements to carry a CSI-RS or DMRS for one or more antenna ports of the UE (<NUM>), wherein the configuration is determined by trading off a number of antenna ports of the UE to increase reliability of the FD-OCC or the TD-OCC; and
perform DMRS or CSI-RS reference signal processing based on the configuration of resource elements to carry reference signals for the UE (<NUM>).