Patent Publication Number: US-2023155803-A1

Title: Demodulation reference signal (dmrs) modifications for multiple signaling, multiple transmission reception point (trp) operation

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/013,514, entitled, “DEMODULATION REFERENCE SIGNAL (DMRS) MODIFICATIONS FOR MULTIPLE SIGNALING, MULTIPLE TRANSMISSION RECEPTION POINT (TRP) OPERATION,” filed on Sep. 4, 2020, and also claims the benefit of U.S. Provisional Patent Application No. 62/902,836, entitled, “DEMODULATION REFERENCE SIGNAL (DMRS) MODIFICATIONS FOR MULTIPLE SIGNALING, MULTIPLE TRANSMISSION RECEPTION POINT (TRP) OPERATION,” filed on Sep. 19, 2019, which is expressly incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to demodulation reference signal (DMRS) and cell specific reference signal (CRS) collision avoidance procedures. 
     DESCRIPTION OF THE RELATED TECHNOLOGY 
     Wireless communication networks are widely deployed to provide various communication services such as voice, video, packet data, messaging, broadcast, and the like. These wireless networks may be multiple-access networks capable of supporting multiple users by sharing the available network resources. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. One example of such a network is the Universal Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). Examples of multiple-access network formats include Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA) networks. 
     A wireless communication network may include a number of base stations or node Bs that can support communication for a number of user equipments (UEs). A UE may communicate with a base station via downlink (DL) and uplink (UL). The DL (or forward link) refers to the communication link from the base station to the UE, and the UL (or reverse link) refers to the communication link from the UE to the base station. A base station may transmit data and control information on the downlink to a UE or may receive data and control information on the uplink from the UE. On the downlink, a transmission from the base station may encounter interference due to transmissions from neighbor base stations or from other wireless radio frequency (RF) transmitters. On the uplink, a transmission from the UE may encounter interference from uplink transmissions of other UEs communicating with the neighbor base stations or from other wireless RF transmitters. This interference may degrade performance on both the downlink and uplink. 
     As the demand for mobile broadband access continues to increase, the possibilities of interference and congested networks grows with more UEs accessing the long-range wireless communication networks and more short-range wireless systems being deployed in communities. Research and development continue to advance the UMTS technologies not only to meet the growing demand for mobile broadband access, but also to advance and enhance the user experience with mobile communications. 
     SUMMARY 
     The systems, methods and devices of this disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein. 
     One innovative aspect of the subject matter described in this disclosure can be implemented in a method of wireless communication. The method includes receiving, by a user equipment (UE), a first message scheduling a first transmission, and receiving, by the UE, a second message scheduling a second transmission. The first transmission is associated with a first demodulation reference signal (DMRS), and the second transmission is associated with a second DMRS. The method further includes determining, by the UE, whether one or more cell specific reference signal (CRS) patterns overlaps with the first DMRS or the second DMRS, and modifying, by the UE, at least one DMRS symbol of the first DMRS or at least one DMRS symbol of the second DMRS responsive to determining that at least one CRS pattern of the one or more CRS patterns overlaps with at least one DMRS symbol of the first DMRS or the second DMRS. 
     In some implementations, modifying the at least one DMRS symbol of the first DMRS or the at least one DMRS symbol of the second DMRS can include modifying the at least one DMRS symbol of the first DMRS and the at least one DMRS symbol of the second DMRS. 
     In some implementations, the method can include receiving, by the UE, the first transmission, the first transmission having modified DMRS symbols. In some such implementations, the method can include receiving, by the UE, the second transmission, the second transmission having modified DMRS symbols. 
     In some implementations, the first message corresponds to a first transmission reception point (TRP), and the second message corresponds to a second TRP. 
     In some implementations, the UE is operating in a multiple downlink control information (DCI), multiple transmission reception point (TRP) mode. 
     In some implementations, the first TRP is associated with a first CRS pattern, and the second TRP is associated with a second CRS pattern. 
     In some implementations, the first message corresponds to downlink control information (DCI). 
     In some implementations, the first message is a periodic grant and corresponds to downlink control information (DCI) or a Radio Resource Control (RRC) message that is configured to schedule multiple transmissions including the first transmission. 
     In some implementations, the first message is received on a Physical Downlink Control Channel (PDCCH). 
     In some implementations, the first transmission is received on a Physical Downlink Shared Channel (PDSCH). 
     In some implementations, modifying the at least one DMRS symbol of the first DMRS or the second DMRS can include adjusting a location of the at least one DMRS symbol of the first DMRS. 
     In some implementations, modifying the at least one DMRS symbol of the first DMRS or the second DMRS can include: incrementing a location value of each DMRS symbol of the first DMRS of the first transmission by one; and incrementing a location value of each DMRS symbol of the second DMRS of the second transmission by one. 
     In some implementations, the method can include determining whether the first transmission at least partially overlaps with the second transmission. 
     In some implementations, determining whether the one or more CRS patterns overlap with the first DMRS or the second DMRS is performed responsive to determining that first resources of the first transmission at least partially overlap with second resources of the second transmission. 
     In some implementations, first resources of the first transmission are orthogonal to second resources of the second transmission in a time domain, a frequency domain, or both. 
     In some implementations, first resources of the first transmission do not overlap with second resources of the second transmission in a time domain, a frequency domain, or both. 
     In some implementations, the UE performs DMRS shifting for multiple downlink control information (DCI), multiple transmission reception point (TRP) modes independent of CRS and TRP associations. 
     In some implementations, the UE performs DMRS shifting across multiple transmission reception points (TRPs), and the UE performs rate matching per TRP. 
     In some implementations, the first message corresponds to a first transmission reception point (TRP) or a first control resource set (CORESET) group, and the second message corresponds to a second TRP or a second CORESET group, and the first and second CORESET groups are indicated by higher level signaling. 
     In some implementations, the method can include, prior to receiving the first message, transmitting, by the UE, a capabilities message indicating that the UE is configured for DMRS shifting for multiple downlink control information (DCI), multiple transmission reception point (TRP) modes. 
     In some implementations, the method can include, prior to receiving the first message, receiving, by the UE, a message indicating that the UE is to perform DMRS shifting for multiple downlink control information (DCI), multiple transmission reception point (TRP) modes. 
     Another innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus configured for wireless communication. The apparatus includes at least one processor and a memory coupled to the at least one processor. The at least one processor is configured to receive, by a user equipment (UE), a first message scheduling a first transmission, the first transmission associated with a first demodulation reference signal (DMRS). The at least one processor is also configured to receive, by the UE, a second message scheduling a second transmission, the second transmission associated with a second DMRS. The at least one processor is configured to determine, by the UE, whether one or more cell specific reference signal (CRS) patterns overlaps with the first DMRS or the second DMRS. The at least one processor is further configured to modify, by the UE, at least one DMRS symbol of the first DMRS or at least one DMRS symbol of the second DMRS responsive to determining that at least one CRS pattern of the one or more CRS patterns overlaps with at least one DMRS symbol of the first DMRS or the second DMRS. 
     In some implementations, the apparatus is configured to perform a method as in any of the implementations described above. 
     Another innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus configured for wireless communication. The apparatus includes means for receiving, by a user equipment (UE), a first message scheduling a first transmission, the first transmission associated with a first demodulation reference signal (DMRS). The apparatus also includes means for receiving, by the UE, a second message scheduling a second transmission, the second transmission associated with a second DMRS. The apparatus includes means for determining, by the UE, whether one or more cell specific reference signal (CRS) patterns overlaps with the first DMRS or the second DMRS. The apparatus further includes means for modifying, by the UE, at least one DMRS symbol of the first DMRS or at least one DMRS symbol of the second DMRS responsive to determining that at least one CRS pattern of the one or more CRS patterns overlaps with at least one DMRS symbol of the first DMRS or the second DMRS. 
     In some implementations, the apparatus is configured to perform a method as in any of the implementations described above. 
     Another innovative aspect of the subject matter described in this disclosure can be implemented in a non-transitory computer-readable medium storing instructions that, when executed by a processor, cause the processor to perform operations including receiving, by a user equipment (UE), a first message scheduling a first transmission, the first transmission associated with a first demodulation reference signal (DMRS). The operations also include receiving, by the UE, a second message scheduling a second transmission, the second transmission associated with a second DMRS. The operations include determining, by the UE, whether one or more cell specific reference signal (CRS) patterns overlaps with the first DMRS or the second DMRS. The operations further include modifying, by the UE, at least one DMRS symbol of the first DMRS or at least one DMRS symbol of the second DMRS responsive to determining that at least one CRS pattern of the one or more CRS patterns overlaps with at least one DMRS symbol of the first DMRS or the second DMRS. 
     In some implementations, the processor is configured to perform a method as in any of the implementations described above. 
     Another innovative aspect of the subject matter described in this disclosure can be implemented in a method of wireless communication. The method includes transmitting, by a network entity, a first message scheduling a first transmission, the first transmission associated with a first demodulation reference signal (DMRS). The method also include transmitting, by the network entity, a second message scheduling a second transmission, the second transmission associated with a second DMRS. The method includes determining, by the network entity, whether one or more cell specific reference signal (CRS) patterns overlaps with the first DMRS or the second DMRS. The method further includes modifying, by the network entity, at least one DMRS symbol of the first DMRS or at least one DMRS symbol of the second DMRS responsive to determining that at least one CRS pattern of the one or more CRS patterns overlaps with at least one DMRS symbol of the first DMRS or the second DMRS. 
     In some implementations, modifying the at least one DMRS symbol of the first DMRS or the at least one DMRS symbol of the second DMRS can include modifying the at least one DMRS symbol of the first DMRS and the at least one DMRS symbol of the second DMRS. 
     In some implementations, the method can include transmitting, by the network entity, the first transmission with a modified DMRS symbol. In some such implementations, the method can include transmitting, by the network entity, the second transmission with a modified DMRS symbol. 
     In some implementations, the first message corresponds to a first transmission reception point (TRP), and the second message corresponds to a second TRP. 
     In some implementations, the network entity is operating in a multiple downlink control information (DCI), multiple transmission reception point (TRP) mode. 
     In some implementations, the first TRP is associated with a first CRS pattern, and the second TRP is associated with a second CRS pattern. 
     In some implementations, the first message corresponds to downlink control information (DCI). 
     In some implementations, the first message is a periodic grant and corresponds to downlink control information (DCI) or a Radio Resource Control (RRC) message that is configured to schedule multiple transmissions including the first transmission. 
     In some implementations, the first message is received on a Physical Downlink Control Channel (PDCCH). 
     In some implementations, the first transmission is (received on?) a Physical Downlink Shared Channel (PDSCH). 
     In some implementations, modifying the at least one DMRS symbol of the first DMRS or the second DMRS can include adjusting a location of the at least one DMRS symbol of the first DMRS. 
     In some implementations, modifying the at least one DMRS symbol of the first DMRS or the second DMRS can include: incrementing a location value of each DMRS symbol of the first DMRS of the first transmission by one; and incrementing a location value of each DMRS symbol of the second DMRS of the second transmission by one. 
     In some implementations, first resources of the first transmission partially overlap with second resources of the second transmission in a time domain, a frequency domain, or both. 
     In some implementations, first resources of the first transmission fully overlap with second resources of the second transmission in a time domain, a frequency domain, or both. 
     In some implementations, first resources of the first transmission are orthogonal to second resources of the second transmission in a time domain, a frequency domain, or both. 
     In some implementations, first resources of the first transmission do not overlap with second resources of the second transmission in a time domain, a frequency domain, or both. 
     In some implementations, the network entity performs DMRS shifting for multiple downlink control information (DCI), multiple transmission reception point (TRP) modes independent of CRS and TRP associations. 
     In some implementations, the network entity performs DMRS shifting across multiple transmission reception points (TRPs), and the network entity performs rate matching per TRP. 
     In some implementations, the first message corresponds to a first transmission reception point (TRP) or a first control resource set (CORESET) group, and the second message corresponds to a second TRP or a second CORESET group, and the first and second CORESET groups are indicated by higher level signaling. 
     In some implementations, the method can include, prior to transmitting the first message, receiving, by the network entities, a capabilities message indicating that the UE is configured for DMRS shifting for multiple downlink control information (DCI), multiple transmission reception point (TRP) modes. 
     In some implementations, the method can include, prior to transmitting the first message, transmitting, by the network entity, a message indicating that a user equipment (UE) is to perform DMRS shifting for multiple downlink control information (DCI), multiple transmission reception point (TRP) modes. 
     Another innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus configured for wireless communication. The apparatus includes at least one processor and a memory coupled to the at least one processor. The at least one processor is configured to transmit, by a network entity, a first message scheduling a first transmission, the first transmission associated with a first demodulation reference signal (DMRS). The at least one processor is also configured to transmit, by the network entity, a second message scheduling a second transmission, the second transmission associated with a second DMRS. The at least one processor is configured to determine, by the network entity, whether one or more cell specific reference signal (CRS) patterns overlaps with the first DMRS or the second DMRS. The at least one processor is further configured to modify, by the network entity, at least one DMRS symbol of the first DMRS or at least one DMRS symbol of the second DMRS responsive to determining that at least one CRS pattern of the one or more CRS patterns overlaps with at least one DMRS symbol of the first DMRS or the second DMRS. 
     In some implementations the apparatus is configured to perform a method as in any of the implementations described above. 
     Another innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus configured for wireless communication. The apparatus includes means for transmitting, by a network entity, a first message scheduling a first transmission, the first transmission associated with a first demodulation reference signal (DMRS). The apparatus also includes means for transmitting, by the network entity, a second message scheduling a second transmission, the second transmission associated with a second DMRS. The apparatus includes means for determining, by the network entity, whether one or more cell specific reference signal (CRS) patterns overlaps with the first DMRS or the second DMRS. The apparatus further includes means for modifying, by the network entity, at least one DMRS symbol of the first DMRS or at least one DMRS symbol of the second DMRS responsive to determining that at least one CRS pattern of the one or more CRS patterns overlaps with at least one DMRS symbol of the first DMRS or the second DMRS. 
     In some implementations, the apparatus is configured to perform a method as in any of the implementations described above. 
     Another innovative aspect of the subject matter described in this disclosure can be implemented in a non-transitory computer-readable medium storing instructions that, when executed by a processor, cause the processor to perform operations including transmitting, by a network entity, a first message scheduling a first transmission, the first transmission associated with a first demodulation reference signal (DMRS). The operations also include transmitting, by the network entity, a second message scheduling a second transmission, the second transmission associated with a second DMRS. The operations include determining, by the network entity, whether one or more cell specific reference signal (CRS) patterns overlaps with the first DMRS or the second DMRS. The operations further include modifying, by the network entity, at least one DMRS symbol of the first DMRS or at least one DMRS symbol of the second DMRS responsive to determining that at least one CRS pattern of the one or more CRS patterns overlaps with at least one DMRS symbol of the first DMRS or the second DMRS . 
     In some implementations, the processor is configured to perform a method as in any of the implementations described above. 
     Another innovative aspect of the subject matter described in this disclosure can be implemented in a method of wireless communication. The method includes transmitting, by a network entity, a first message scheduling a first transmission, the first transmission associated with a first demodulation reference signal (DMRS). The method also includes determining, by the network entity, whether one or more cell specific reference signal (CRS) patterns overlaps with the first DMRS. The method includes modifying, by the network entity, at least one DMRS symbol of the first DMRS responsive to determining that at least one CRS pattern of the one or more CRS patterns overlaps with at least one DMRS symbol of the first DMRS. The method further includes transmitting, by the network entity, the first transmission with a modified DMRS symbol. 
     In some implementations, the method can include determining, by the network entity, whether the one or more CRS patterns overlaps with a second DMRS associated with a second transmission by another network entity, where modifying the at least one DMRS symbol of the first DMRS is further responsive to determining whether the at least one CRS pattern of the one or more CRS patterns overlaps with at least one DMRS symbol of the second DMRS. 
     In some implementations, the method can include modifying, by the network entity, at least one DMRS symbol of the second DMRS responsive to determining that at least one CRS pattern of the one or more CRS patterns overlaps with the at least one DMRS symbol of the first DMRS or the at least one DMRS symbol of the second DMRS. 
     Another innovative aspect of the subject matter described in this disclosure can be implemented in a method of wireless communication. The method includes receiving, by a user equipment (UE), a configuration message including at least one list of cell specific reference signal (CRS) patterns for a component carrier, where a list of the at least one list is associated with a control resource set (CORESET) group. The method also includes receiving, by the UE, a first message scheduling a first transmission, and receiving, by the UE, a second message scheduling a second transmission. The first transmission is associated with a first demodulation reference signal (DMRS) and is for the component carrier, and the second transmission is associated with a second DMRS and is for the component carrier. The method further includes modifying, by the UE, at least one DMRS symbol of the first DMRS or at least one DMRS symbol of the second DMRS based on the list being configured for the component carrier. 
     In some implementations, the first transmission is associated with the CORESET group, and the second transmission is associated with a second CORESET group. 
     In some implementations, determining that the at least one list is configured for DMRS shifting indicates that one or more CRS patterns overlap with the first DMRS or the second DMRS. 
     In some implementations, the method can include determining, by the UE, whether one or more CRS patterns of the at least one list overlaps with the first DMRS or the second DMRS, and where modifying the at least one DMRS symbol of the first DMRS or the at least one DMRS symbol of the second DMRS is further responsive to determining that at least one CRS pattern of the one or more CRS patterns overlaps with at least one DMRS symbol of the first DMRS or the second DMRS. 
     In some implementations, the at least one list of CRS patterns being configured for the component carrier enables DMRS shifting, rate matching, or both. 
     In some implementations, modifying the at least one DMRS symbol of the first DMRS or the at least one DMRS symbol of the second DMRS can include modifying the at least one DMRS symbol of the first DMRS and the at least one DMRS symbol of the second DMRS. 
     In some implementations, the method can include receiving, by the UE, the first transmission, the first transmission having modified DMRS symbols. 
     In some implementations, the method can include receiving, by the UE, the first transmission, the first transmission having modified DMRS symbols. 
     Another innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus for wireless communication. The apparatus includes at least one processor and a memory coupled to the at least one processor. The at least one processor is configured to receive a configuration message including at least one list of cell specific reference signal (CRS) patterns for a component carrier, where a list of the at least one list is associated with a control resource set (CORESET) group. The processor is also configured to receive a first message scheduling a first transmission, and to receive a second message scheduling a second transmission. The first transmission is associated with a first demodulation reference signal (DMRS) and is for the component carrier, and the second transmission is associated with a second DMRS and is for the component carrier. The processor is further configured to modify at least one DMRS symbol of the first DMRS or at least one DMRS symbol of the second DMRS based on the list being configured for the component carrier. 
     In some implementations, the apparatus is operating in a multiple downlink control information (DCI), multiple transmission reception point (TRP) mode. 
     In some implementations, a second CORESET group is associated with a second list of CRS patterns of the at least one list of CRS patterns. 
     In some implementations, the first message is received on a Physical Downlink Control Channel (PDCCH), and the first transmission is received on a Physical Downlink Shared Channel (PDSCH). 
     In some implementations, modifying the at least one DMRS symbol of the first DMRS or the second DMRS can include adjusting a location of the at least one DMRS symbol of the first DMRS. 
     In some implementations, modifying the at least one DMRS symbol of the first DMRS or the second DMRS can include: incrementing a location value of each DMRS symbol of the first DMRS of the first transmission by one; and incrementing a location value of each DMRS symbol of the second DMRS of the second transmission by one. 
     In some implementations, the apparatus performs DMRS shifting for multiple downlink control information (DCI), multiple transmission reception point (TRP) modes independent of CRS and TRP associations. 
     In some implementations, the apparatus performs DMRS shifting across multiple transmission reception points (TRPs), and the apparatus performs rate matching per TRP. 
     Another innovative aspect of the subject matter described in this disclosure can be implemented in a method of wireless communication. The method includes transmitting, by a network entity, a configuration message including at least one list of cell specific reference signal (CRS) patterns for a component carrier, where a list of the at least one list is associated with a control resource set (CORESET) group. The method also include transmitting, by the network entity, a first message scheduling a first transmission associated with a first demodulation reference signal (DMRS) and for the component carrier. The method includes transmitting, by the network entity, a second message scheduling a second transmission associated with a second DMRS and for the component carrier. The method further includes modifying, by the network entity, at least one DMRS symbol of the first DMRS or at least one DMRS symbol of the second DMRS responsive to determining that the list is configured for the component carrier. 
     In some implementations, the first transmission is associated with the CORESET group, and the second transmission is associated with a second CORESET group. 
     In some implementations, modifying the at least one DMRS symbol of the first DMRS or the at least one DMRS symbol of the second DMRS can include modifying the at least one DMRS symbol of the first DMRS and the at least one DMRS symbol of the second DMRS. 
     In some implementations, the method can include: transmitting, by the network entity, the first transmission with a modified DMRS symbol; transmitting, by the network entity, the second transmission with a modified DMRS symbol; or both. 
     In some implementations, a second CORESET group is associated with a second list of CRS patterns of the at least one list of CRS patterns. 
     In some implementations, the first message corresponds to downlink control information (DCI). 
     In some implementations, the first message is a periodic grant and corresponds to downlink control information (DCI) or a Radio Resource Control (RRC) message that is configured to schedule multiple transmissions including the first transmission. 
     Another innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus for wireless communication. The apparatus includes at least one processor and a memory coupled to the at least one processor. The at least one processor is configured to transmit a configuration message including at least one list of cell specific reference signal (CRS) patterns for a component carrier, where a list of the at least one list is associated with a control resource set (CORESET) group. The at least one processor is also configured to transmit a first message scheduling a first transmission associated with a first demodulation reference signal (DMRS) and for the component carrier. The at least one processor is configured to transmit a second message scheduling a second transmission associated with a second DMRS and for the component carrier. The at least one processor is further configured to modify at least one DMRS symbol of the first DMRS or at least one DMRS symbol of the second DMRS responsive to determining that the list is configured for the component carrier. 
     In some implementations, modifying the at least one DMRS symbol of the first DMRS or the second DMRS can include adjusting a location of the at least one DMRS symbol of the first DMRS. 
     In some implementations, modifying the at least one DMRS symbol of the first DMRS or the second DMRS can include: incrementing a location value of each DMRS symbol of the first DMRS of the first transmission by one; and incrementing a location value of each DMRS symbol of the second DMRS of the second transmission by one. 
     In some implementations, first resources of the first transmission at least partially overlap with second resources of the second transmission in a time domain, a frequency domain, or both. 
     In some implementations, first resources of the first transmission are orthogonal to second resources of the second transmission in a time domain, a frequency domain, or both. 
     In some implementations, first resources of the first transmission do not overlap with second resources of the second transmission in a time domain, a frequency domain, or both. 
     In some implementations, the first message corresponds to the CORESET group, the second message corresponds to a second CORESET group, and the CORESET groups are indicated by higher level signaling. 
     Details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, the drawings and the claims. Note that the relative dimensions of the following figures may not be drawn to scale. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a block diagram illustrating details of an example wireless communication system. 
         FIG.  2    is a block diagram conceptually illustrating an example design of a base station and a user equipment (UE). 
         FIG.  3    is a diagram illustrating an example of a wireless communication system that operates in multi-transmission/reception point (TRP) schemes. 
         FIG.  4    is a block diagram illustrating an example of a process flow for different multi-TRP schemes. 
         FIGS.  5 A- 5 D  are diagrams illustrating different example multi-TRP schemes. 
         FIG.  6    is a block diagram illustrating an example of a wireless communications system that enables DMRS modifications. 
         FIGS.  7 A- 7 C  are block diagrams illustrating an example of DMRS modifications for a single PDSCH. 
         FIGS.  8 A- 8 C  are block diagrams illustrating an example of DMRS modifications for multiple PDSCHs. 
         FIG.  9    is a block diagram illustrating example blocks executed by a UE. 
         FIG.  10    is a block diagram illustrating example blocks executed by a network entity. 
         FIG.  11    is a block diagram conceptually illustrating an example design of a UE. 
         FIG.  12    is a block diagram conceptually illustrating an example design of a network entity. 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     The following description is directed to certain implementations for the purposes of describing the innovative aspects of this disclosure. However, a person having ordinary skill in the art will readily recognize that the teachings herein can be applied in a multitude of different ways. 
     Wireless communications systems operated by different network entities may share spectrum. In some instances, two network entities may be configured to send transmissions to multiple user equipments (UE). Thus, in order to enable network entities to use more of the shared spectrum, and in order to mitigate interfering communications between the different network entities, certain resources may be shifted to avoid collisions and interference with an effort to enable successful reception and decoding. 
     For example, when a network entity and UE are operating in a single transmission reception point (TRP) mode, there are some cases where a demodulation reference signal (DMRS) is shifted to avoid collisions with a cell-specific reference signal (CRS) pattern or with reserved resources of a control resource set (CORESET). In other words, a location of the DMRS symbols may be shifted due to collisions with other resources. 
     However, when operating in multiple TRP modes, conventional networks and devices are unable to perform DMRS shifting. For example, when the two transmissions are at least partially overlapping, if the DMRS location for one of the transmissions is shifted due to collision of a corresponding CRS pattern, the alignment of the transmissions may be altered. If DMRS symbols of overlapping transmissions are not aligned, interference may occur to the DMRS symbols, or the UE may not be able to receive and decode one or more of the transmissions due to poor channel estimation performance. On the other hand, if alignment of the DMRS symbols of overlapping transmissions is ensured, and the DMRS ports of the overlapping transmissions are separate and belong to different code division multiplexing (CDM) groups, the actual DMRS resource elements (REs) become orthogonal in the frequency domain, which enhances the channel estimation performance. Thus, the implementations described herein enable procedures for performing DMRS shifting in multiple TRP modes. Such shifting may enable the alignment of the DMRS locations for both transmissions to enable reception and decoding of the transmissions by the UE. For example, the DMRS symbols of both transmissions may be shifted responsive to determining an overlap for one of the transmissions. Thus, both of the transmissions may be DMRS shifted and remain aligned with each other. 
     Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. For example, by enabling DMRS shifting for multiple TRP modes, a network may send overlapping transmissions to increase bandwidth and reduce latency. Additionally, the network may be able to operate in multi-TRP modes for carrier aggregation or dual connectivity, such as by using multiple signaling, multiple TRP modes. 
     This disclosure relates generally to providing or participating in authorized shared access between two or more wireless communications systems, also referred to as wireless communications networks. In various implementations, the techniques and apparatus may be used for wireless communication networks such as code division multiple access (CDMA) networks, time division multiple access (TDMA) networks, frequency division multiple access (FDMA) networks, orthogonal FDMA (OFDMA) networks, single-carrier FDMA (SC-FDMA) networks, LTE networks, GSM networks, 5 th  Generation (5G) or new radio (NR) networks (sometimes referred to as “5G NR” networks/systems/devices), as well as other communications networks. As described herein, the terms “networks” and “systems” may be used interchangeably. 
     A CDMA network may implement a radio technology such as universal terrestrial radio access (UTRA), cdma2000, and the like. UTRA includes wideband-CDMA (W-CDMA) and low chip rate (LCR). CDMA2000 covers IS-2000, IS-95, and IS-856 standards. 
     A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM). 3GPP defines standards for the GSM EDGE (enhanced data rates for GSM evolution) radio access network (RAN), also denoted as GERAN. GERAN is the radio component of GSM/EDGE, together with the network that joins the base stations (for example, the Ater and Abis interfaces) and the base station controllers (A interfaces, etc.). The radio access network represents a component of a GSM network, through which phone calls and packet data are routed from and to the public switched telephone network (PSTN) and Internet to and from subscriber handsets, also known as user terminals or user equipments (UEs). A mobile phone operator&#39;s network may include one or more GERANs, which may be coupled with UTRANs in the case of a UMTS/GSM network. Additionally, an operator network may include one or more LTE networks, or one or more other networks. The various different network types may use different radio access technologies (RATs) and radio access networks (RANs). 
     An OFDMA network may implement a radio technology such as evolved UTRA (E-UTRA), IEEE 802.11, IEEE 802.16, IEEE 802.20, flash-OFDM and the like. UTRA, E-UTRA, and GSM are part of universal mobile telecommunication system (UMTS). In particular, long term evolution (LTE) is a release of UMTS that uses E-UTRA. UTRA, E-UTRA, GSM, UMTS and LTE are described in documents provided from an organization named “3rd Generation Partnership Project” (3GPP), and cdma2000 is described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). These various radio technologies and standards are known or are being developed. For example, the  3 rd Generation Partnership Project (3GPP) is a collaboration between groups of telecommunications associations that aims to define a globally applicable third generation (3G) mobile phone specification. 3GPP long term evolution (LTE) is a 3GPP project aimed at improving the universal mobile telecommunications system (UMTS) mobile phone standard. The 3GPP may define specifications for the next generation of mobile networks, mobile systems, and mobile devices. The present disclosure may describe certain aspects with reference to LTE, 4G, 5G, or NR technologies; however, the description is not intended to be limited to a specific technology or application, and one or more aspects described with reference to one technology may be understood to be applicable to another technology. Indeed, one or more aspects the present disclosure are related to shared access to wireless spectrum between networks using different radio access technologies or radio air interfaces. 
     5G networks contemplate diverse deployments, diverse spectrum, and diverse services and devices that may be implemented using an OFDM-based unified, air interface. To achieve these goals, further enhancements to LTE and LTE-A are considered in addition to development of the new radio technology for 5G NR networks. The 5G NR will be capable of scaling to provide coverage (1) to a massive Internet of things (IoTs) with an ultra-high density (such as ˜1M nodes/km 2 ), ultra-low complexity (such as ˜10s of bits/sec), ultra-low energy (such as ˜10+ years of battery life), and deep coverage with the capability to reach challenging locations; (2) including mission-critical control with strong security to safeguard sensitive personal, financial, or classified information, ultra-high reliability (such as ˜99.9999% reliability), ultra-low latency (such as ˜1 millisecond (ms)), and users with wide ranges of mobility or lack thereof; and (3) with enhanced mobile broadband including extreme high capacity (such as ˜10 Tbps/km 2 ), extreme data rates (such as multi-Gbps rate, 100+ Mbps user experienced rates), and deep awareness with advanced discovery and optimizations. 
     5G NR devices, networks, and systems may be implemented to use optimized OFDM-based waveform features. These features may include scalable numerology and transmission time intervals (TTIs); a common, flexible framework to efficiently multiplex services and features with a dynamic, low-latency time division duplex (TDD)/frequency division duplex (FDD) design; and advanced wireless technologies, such as massive multiple input, multiple output (MIMO), robust millimeter wave (mmWave) transmissions, advanced channel coding, and device-centric mobility. Scalability of the numerology in 5G NR, with scaling of subcarrier spacing, may efficiently address operating diverse services across diverse spectrum and diverse deployments. For example, in various outdoor and macro coverage deployments of less than 3GHz FDD/TDD implementations, subcarrier spacing may occur with 15 kHz, for example over 1, 5, 10, 20 MHz, and the like bandwidth. For other various outdoor and small cell coverage deployments of TDD greater than 3 GHz, subcarrier spacing may occur with 30 kHz over 80/100 MHz bandwidth. For other various indoor wideband implementations, using a TDD over the unlicensed portion of the 5 GHz band, the subcarrier spacing may occur with 60 kHz over a 160 MHz bandwidth. Finally, for various deployments transmitting with mmWave components at a TDD of 28 GHz, subcarrier spacing may occur with 120 kHz over a 500 MHz bandwidth. 
     The scalable numerology of 5G NR facilitates scalable TTI for diverse latency and quality of service (QoS) requirements. For example, shorter TTI may be used for low latency and high reliability, while longer TTI may be used for higher spectral efficiency. The efficient multiplexing of long and short TTIs to allow transmissions to start on symbol boundaries. 5G NR also contemplates a self-contained integrated subframe design with uplink/downlink scheduling information, data, and acknowledgement in the same subframe. The self-contained integrated subframe supports communications in unlicensed or contention-based shared spectrum, adaptive uplink/downlink that may be flexibly configured on a per-cell basis to dynamically switch between uplink and downlink to meet the current traffic needs. 
     For clarity, certain aspects of the apparatus and techniques may be described below with reference to example 5G NR implementations or in a 5G-centric way, and 5G terminology may be used as illustrative examples in portions of the description below; however, the description is not intended to be limited to 5G applications. 
     Moreover, it should be understood that, in operation, wireless communication networks adapted according to the concepts herein may operate with any combination of licensed or unlicensed spectrum depending on loading and availability. Accordingly, it will be apparent to one of ordinary skill in the art that the systems, apparatus and methods described herein may be applied to other communications systems and applications than the particular examples provided. 
       FIG.  1    is a block diagram illustrating details of an example wireless communication system. The wireless communication system may include wireless network  100 . The wireless network  100  may, for example, include a 5G wireless network. As appreciated by those skilled in the art, components appearing in  FIG.  1    are likely to have related counterparts in other network arrangements including, for example, cellular-style network arrangements and non-cellular-style-network arrangements, such as device to device or peer to peer or ad hoc network arrangements, etc. 
     The wireless network  100  illustrated in  FIG.  1    includes a number of base stations  105  and other network entities. A base station may be a station that communicates with the UEs and may be referred to as an evolved node B (eNB), a next generation eNB (gNB), an access point, and the like. Each base station  105  may provide communication coverage for a particular geographic area. In 3GPP, the term “cell” can refer to this particular geographic coverage area of a base station or a base station subsystem serving the coverage area, depending on the context in which the term is used. In implementations of the wireless network  100  herein, base stations  105  may be associated with a same operator or different operators, such as the wireless network  100  may include a plurality of operator wireless networks. Additionally, in implementations of the wireless network  100  herein, the base stations  105  may provide wireless communications using one or more of the same frequencies, such as one or more frequency bands in licensed spectrum, unlicensed spectrum, or a combination thereof, as a neighboring cell. In some examples, an individual base station  105  or UE  115  may be operated by more than one network operating entity. In some other examples, each base station  105  and UE  115  may be operated by a single network operating entity. 
     A base station may provide communication coverage for a macro cell or a small cell, such as a pico cell or a femto cell, or other types of cell. A macro cell generally covers a relatively large geographic area, such as several kilometers in radius, and may allow unrestricted access by UEs with service subscriptions with the network provider. A small cell, such as a pico cell, would generally cover a relatively smaller geographic area and may allow unrestricted access by UEs with service subscriptions with the network provider. A small cell, such as a femto cell, would also generally cover a relatively small geographic area, such as a home, and, in addition to unrestricted access, may provide restricted access by UEs having an association with the femto cell, such as UEs in a closed subscriber group (CSG), UEs for users in the home, and the like. A base station for a macro cell may be referred to as a macro base station. A base station for a small cell may be referred to as a small cell base station, a pico base station, a femto base station or a home base station. In the example shown in  FIG.  1   , base stations  105   d  and  105   e  are regular macro base stations, while base stations  105   a  - 105   c  are macro base stations enabled with one of 3 dimension (3D), full dimension (FD), or massive MIMO. Base stations  105   a  - 105   c  take advantage of their higher dimension MIMO capabilities to exploit 3D beamforming in both elevation and azimuth beamforming to increase coverage and capacity. Base station  105   f  is a small cell base station which may be a home node or portable access point. A base station may support one or multiple cells, such as two cells, three cells, four cells, and the like. 
     The wireless network  100  may support synchronous or asynchronous operation. For synchronous operation, the base stations may have similar frame timing, and transmissions from different base stations may be approximately aligned in time. For asynchronous operation, the base stations may have different frame timing, and transmissions from different base stations may not be aligned in time. In some scenarios, networks may be enabled or configured to handle dynamic switching between synchronous or asynchronous operations. 
     The UEs  115  are dispersed throughout the wireless network  100 , and each UE may be stationary or mobile. It should be appreciated that, although a mobile apparatus is commonly referred to as user equipment (UE) in standards and specifications promulgated by the  3 rd Generation Partnership Project (3GPP), such apparatus may additionally or otherwise be referred to by those skilled in the art as a mobile station (MS), a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal (AT), a mobile terminal, a wireless terminal, a remote terminal, a handset, a terminal, a user agent, a mobile client, a client, or some other suitable terminology. Within the present document, a “mobile” apparatus or UE need not necessarily have a capability to move, and may be stationary. Some non-limiting examples of a mobile apparatus, such as may include implementations of one or more of the UEs  115 , include a mobile, a cellular (cell) phone, a smart phone, a session initiation protocol (SIP) phone, a wireless local loop (WLL) station, a laptop, a personal computer (PC), a notebook, a netbook, a smart book, a tablet, and a personal digital assistant (PDA). A mobile apparatus may additionally be an “Internet of things” (IoT) or “Internet of everything” (IoE) device such as an automotive or other transportation vehicle, a satellite radio, a global positioning system (GPS) device, a logistics controller, a drone, a multi-copter, a quad-copter, a smart energy or security device, a solar panel or solar array, municipal lighting, water, or other infrastructure; industrial automation and enterprise devices; consumer and wearable devices, such as eyewear, a wearable camera, a smart watch, a health or fitness tracker, a mammal implantable device, gesture tracking device, medical device, a digital audio player (such as MP 3  player), a camera, a game console, etc.; and digital home or smart home devices such as a home audio, video, and multimedia device, an appliance, a sensor, a vending machine, intelligent lighting, a home security system, a smart meter, etc. In one aspect, a UE may be a device that includes a Universal Integrated Circuit Card (UICC). In another aspect, a UE may be a device that does not include a UICC. In some aspects, UEs that do not include UICCs may be referred to as IoE devices. The UEs  115   a  - 115   d  of the implementation illustrated in  FIG.  1    are examples of mobile smart phone-type devices accessing the wireless network  100  A UE may be a machine specifically configured for connected communication, including machine type communication (MTC), enhanced MTC (eMTC), narrowband IoT (NB-IoT) and the like. The UEs  115   e  - 115   k  illustrated in  FIG.  1    are examples of various machines configured for communication that access 5G network  100 . 
     A mobile apparatus, such as UEs  115 , may be able to communicate with any type of the base stations, whether macro base stations, pico base stations, femto base stations, relays, and the like. In  FIG.  1   , a communication link (represented as a lightning bolt) indicates wireless transmissions between a UE and a serving base station, which is a base station designated to serve the UE on the downlink or uplink, or desired transmission between base stations, and backhaul transmissions between base stations. Backhaul communication between base stations of the wireless network  100  may occur using wired or wireless communication links. 
     In operation at the 5G network  100 , the base stations  105   a  - 105   c  serve the UEs  115   a  and  115   b  using 3D beamforming and coordinated spatial techniques, such as coordinated multipoint (CoMP) or multi-connectivity. Macro base station  105   d  performs backhaul communications with the base stations  105   a  - 105   c  , as well as small cell, the base station  105   f  . Macro base station  105   d  also transmits multicast services which are subscribed to and received by the UEs  115   c  and  115   d  . Such multicast services may include mobile television or stream video, or may include other services for providing community information, such as weather emergencies or alerts, such as Amber alerts or gray alerts. 
     The wireless network  100  of implementations supports mission critical communications with ultra-reliable and redundant links for mission critical devices, such the UE  115   e  , which is a drone. Redundant communication links with the UE  115   e  include from the macro base stations  105   d  and  105   e  , as well as small cell base station  105   f  . Other machine type devices, such as UE  115   f  (thermometer), the UE  115   g  (smart meter), and the UE  115   h  (wearable device) may communicate through the wireless network  100  either directly with base stations, such as the small cell base station  105   f  , and the macro base station  105   e  , or in multi-hop configurations by communicating with another user device which relays its information to the network, such as the UE  115   f  communicating temperature measurement information to the smart meter, the UE  115   g  , which is reported to the network through the small cell base station  105   f  . The 5G network  100  may provide additional network efficiency through dynamic, low-latency TDD/FDD communications, such as in a vehicle-to-vehicle (V2V) mesh network between the UEs  115   i  - 115   k  communicating with the macro base station  105   e.    
       FIG.  2    is a block diagram conceptually illustrating an example design of a base station  105  and a UE  115 . The base station  105  and the UE  115  may be one of the base stations and one of the UEs in  FIG.  1   . For a restricted association scenario (as mentioned above), the base station  105  may be the small cell base station  105   f  in  FIG.  1   , and the UE  115  may be the UE  115   c  or  115   d  operating in a service area of the base station  105   f  , which in order to access the small cell base station  105   f  , would be included in a list of accessible UEs for the small cell base station  105   f  . Additionally, the base station  105  may be a base station of some other type. As shown in  FIG.  2   , the base station  105  may be equipped with antennas  234   a  through  234   t  , and the UE  115  may be equipped with antennas  252   a  through  252   r  for facilitating wireless communications. 
     At the base station  105 , a transmit processor  220  may receive data from a data source  212  and control information from a controller/processor  240 . The control information may be for the physical broadcast channel (PBCH), physical control format indicator channel (PCFICH), physical hybrid-ARQ (automatic repeat request) indicator channel (PHICH), physical downlink control channel (PDCCH), enhanced physical downlink control channel (EPDCCH), MTC physical downlink control channel (MPDCCH), etc. The data may be for the PDSCH, etc. The transmit processor  220  may process, such as encode and symbol map, the data and control information to obtain data symbols and control symbols, respectively. Additionally, the transmit processor  220  may generate reference symbols, such as for the primary synchronization signal (PSS) and secondary synchronization signal (SSS), and cell-specific reference signal. Transmit (TX) multiple-input multiple-output (MIMO) processor  230  may perform spatial processing on the data symbols, the control symbols, or the reference symbols, if applicable, and may provide output symbol streams to modulators (MODs)  232   a  through  232   t  . For example, spatial processing performed on the data symbols, the control symbols, or the reference symbols may include precoding. Each modulator  232  may process a respective output symbol stream, such as for OFDM, etc., to obtain an output sample stream. Each modulator  232  may additionally or alternatively process the output sample stream to obtain a downlink signal. For example, to process the output sample stream, each modulator  232  may convert to analog, amplify, filter, and upconvert the output sample stream to obtain the downlink signal. Downlink signals from modulators  232   a  through  232   t  may be transmitted via the antennas  234   a  through  234   t  , respectively. 
     At the UE  115 , the antennas  252   a  through  252   r  may receive the downlink signals from the base station  105  and may provide received signals to the demodulators (DEMODs)  254   a  through  254   r  , respectively. Each demodulator  254  may condition a respective received signal to obtain input samples. For example, to condition the respective received signal, each demodulator  254  may filter, amplify, downconvert, and digitize the respective received signal to obtain the input samples. Each demodulator  254  may further process the input samples, such as for OFDM, etc., to obtain received symbols. MIMO detector  256  may obtain received symbols from demodulators  254   a  through  254   r  , perform MIMO detection on the received symbols if applicable, and provide detected symbols. Receive processor  258  may process the detected symbols, provide decoded data for the UE  115  to a data sink  260 , and provide decoded control information to a controller/processor  280 . For example, to process the detected symbols, receive processor  258  may demodulate, deinterleave, and decode the detected symbols. 
     On the uplink, at the UE  115 , a transmit processor  264  may receive and process data (such as for the physical uplink shared channel (PUSCH)) from a data source  262  and control information (such as for the physical uplink control channel (PUCCH)) from the controller/processor  280 . Additionally, transmit processor  264  may generate reference symbols for a reference signal. The symbols from the transmit processor  264  may be precoded by TX MIMO processor  266  if applicable, further processed by the modulators  254   a  through  254   r  (such as for SC-FDM, etc.), and transmitted to the base station  105 . At base station  105 , the uplink signals from UE  115  may be received by antennas  234 , processed by demodulators  232 , detected by MIMO detector  236  if applicable, and further processed by receive processor  238  to obtain decoded data and control information sent by UE  115 . Receive processor  238  may provide the decoded data to data sink  239  and the decoded control information to controller/processor  240 . 
     Controllers/processors  240  and  280  may direct the operation at base station  105  and UE  115 , respectively. Controller/processor  240  or other processors and modules at base station  105  or controller/processor  280  or other processors and modules at UE  115  may perform or direct the execution of various processes for the techniques described herein, such as to perform or direct the execution illustrated in  FIGS.  9  and  10   , or other processes for the techniques described herein. Memories  242  and  282  may store data and program codes for base station  105  and UE  115 , respectively. Scheduler  244  may schedule UEs for data transmission on the downlink or uplink. 
     In some cases, the UE  115  and the base station  105  may operate in a shared radio frequency spectrum band, which may include licensed or unlicensed, such as contention-based, frequency spectrum. In an unlicensed frequency portion of the shared radio frequency spectrum band, the UEs  115  or the base stations  105  may traditionally perform a medium-sensing procedure to contend for access to the frequency spectrum. For example, the UE  115  or base station  105  may perform a listen-before-talk or listen-before-transmitting (LBT) procedure such as a clear channel assessment (CCA) prior to communicating in order to determine whether the shared channel is available. A CCA may include an energy detection procedure to determine whether there are any other active transmissions. For example, a device may infer that a change in a received signal strength indicator (RSSI) of a power meter indicates that a channel is occupied. Specifically, signal power that is concentrated in a certain bandwidth and exceeds a predetermined noise floor may indicate another wireless transmitter. In some implementations, a CCA may include detection of specific sequences that indicate use of the channel. For example, another device may transmit a specific preamble prior to transmitting a data sequence. In some cases, an LBT procedure may include a wireless node adjusting its own backoff window based on the amount of energy detected on a channel or the acknowledge/negative-acknowledge (ACK/NACK) feedback for its own transmitted packets as a proxy for collisions. 
     Use of a medium-sensing procedure to contend for access to an unlicensed shared spectrum may result in communication inefficiencies. This may be particularly evident when multiple network operating entities, such as network operators, are attempting to access a shared resource. In the 5G network  100 , the base stations  105  and the UEs  115  may be operated by the same or different network operating entities. In some examples, an individual base station  105  or UE  115  may be operated by more than one network operating entity. In other examples, each base station  105  and UE  115  may be operated by a single network operating entity. Requiring each base station  105  and UE  115  of different network operating entities to contend for shared resources may result in increased signaling overhead and communication latency. 
       FIG.  3    illustrates an example of a wireless communications system  300  that supports different multi-TRP schemes. In some examples, wireless communications system  300  may implement aspects of wireless communication system  100 . For example, wireless communications system  300  may include multiple UEs  115  and base stations  105 . The base stations  105  may communicate with the UEs  115  using TRPs  305 . Each base station  105  may have one or more TRPs  305 . For example, base station  105 - a  may include TRP  305 - a  and TRP  305 - b  , while base station  105 - b  may include TRP  305 - c  . UE  115 - a  may communicate with the network using a single TRP  305 , using multiple TRPs  305  corresponding to a single base station  105  (such as TRPs  305 - a  and  305 - b  at base station  105 - a  ), or using multiple TRPs  305  corresponding to multiple different base stations  105  (such as TRP  305 - a  at base station  105 - a  and TRP  305 - c  at base station  105 - b  , where base stations  105 - a  and  105 - b  may be connected via a backhaul connection). 
     In a communication scheme that includes multiple TRPs  305 , a single DCI message may configure the communications for the multiple TRPs  305 . In an example, base station  105 - a  may communicate using a first TRP  305 - a  and a second TRP  305 - b  . Base station  105 - a  may transmit DCI using TRP  305 - a  on a PDCCH  310 - a  to UE  115 - a  . The DCI may include communication configuration information for the TCI state(s). The TCI state(s) may determine whether the communications correspond to single TRP communication or multiple TRP communication. The TCI state(s) also may indicate the type of communication scheme (such as TDM, FDM, SDM, etc.) configured for the communication. If the TCI configuration is one TCI state, the one TCI state may correspond to single TRP communication. If the TCI configuration is multiple TCI states, the multiple TCI states may correspond to communication with multiple TRPs. In some cases, the wireless communications system  300  may support up to M candidate TCI states for the purpose of quasi-co-location (QCL) indication. Of these M candidates (such as 128 candidate TCI states), a subset of TCI states may be determined based on a medium access control (MAC) control element (CE). The MAC-CE may correspond to a certain number (such as 2 N , such as  8  TCI states) of candidate TCI states for PDSCH QCL indication. One of these 2 N  TCI states can be dynamically indicated in a message (such as DCI) using N bits. 
     The DCI on the PDCCH  310 - a  may schedule PDSCH  315 - a  transmissions from TRP  305 - a  for single TRP communication configurations. Alternatively, the DCI on the PDCCH  310 - a  may schedule multiple PDSCH  315  transmissions from multiple TRPs  305 . For example, the DCI may schedule PDSCH  315 - a  transmissions from TRP  305 - a  and PDSCH  315 - b  transmissions from TRP  305 - b  or PDSCH  315 - a  transmissions from TRP  305 - a  and PDSCH  315 - c  transmission from TRP  305 - c  for multiple TRP communication configurations. A UE  115  may be configured with a list of different candidate TCI states for the purpose of QCL indication. Each TCI code point in a DCI may correspond to one or more TCI states (such as corresponding to one or more reference signal (RS) sets for indicating the QCL relationships). 
     In cases where the network communicates with a UE  115  with TRPs  305 , whether in a single TRP configuration or a multiple TRP configuration, there may be multiple different schemes with which to communicate with the TRP(s)  305 . The TRP communication scheme may be determined by the TCI states. The TCI state(s) for communication on the PDSCH  315  may be indicated in the DCI by one or more bits, where the one or more bits indicate a TCI code point. The TCI code point in the DCI can correspond to one or more TCI states (such as either one or two TCI states). If the TCI code point in the DCI indicates one TCI state, the UE  115  is configured for single TRP operation. If the TCI code point in the DCI indicates two TCI states (and, correspondingly, two QCL relationships), the UE  115  is configured for multiple TRP operation. For example, if two TCI states are indicated within a TCI code point, each TCI state may correspond to one DMRS code division multiplexing (CDM) group. 
     In a first example multi-TRP scheme, TRPs  305  may communicate by utilizing SDM. In this case, different spatial layers may be transmitted from different TRPs  305  on the same RBs and symbols. Each TCI state also may correspond to different DMRS port groups. The DMRS ports in a DMRS CDM port group may be quasi-collocated (QCLed). This may allow a UE  115  to estimate each channel separately. In SDM, each antenna port used on the downlink may belong to a different CDM group. Base station  105 - a  may indicate the antenna port groups using an antenna port(s) field in DCI. 
     The SDM scheme may include different TCI states within a single slot, where the TCI states overlap in time, frequency, or both. Different groups of spatial layers (which may correspond to different TCI states) may use the same modulation order. Cases where multiple groups use the same modulation order may be signaled through the modulation and coding scheme (MCS). In some cases, base station  105 - a  may indicate the MCS in the DCI. In cases where the different groups of spatial layers use different modulation orders, each of the different modulation orders may be signaled to UE  115 - a  . Different DMRS port groups may correspond to different TRPs, QCL relationships, TCI states, or a combination thereof. 
     In other examples of multi-TRP schemes, TRPs  305  may communicate with UE  115 - a  by utilizing FDM or TDM communication schemes. In an FDM scheme, one set of RBs or a set of PRGs may correspond to a first TRP  305 - a  and a first TCI state, and a second set of RBs or PRGs may correspond to a second TRP  305 - b  and a second TCI state. The RBs allocated for each TRP may be distinct from each other, so that each TRP communicates on a designated set of RBs that are distinct form the other set of RBs (but may overlap in the same OFDM symbol). The frequency domain resource assignment field in the DCI may indicate both the first set and the second set or RBs or PRGs. In some cases, base station  105 - a  may use additional signaling in the DCI to indicate which RBs belong to the first set and which belong to the second set. In some cases, the system may support a limited number of possibilities for allocating the frequency resources to the different TRPs (such as to reduce the overhead). 
     In a TDM scheme, a similar table of possibilities may be used to signal the resource allocation for different TRPs. In this case, each TRP is allocated to different sets of OFDM symbols rather than to different sets of RBs. Such a TDM scheme may support TDMed transmissions within a single slot (such as transmission time interval (TTI)). In some cases, a TDM scheme may implement slot aggregation, where transmissions using different TCI states may be spread across different slots (such as TTIs). In slot aggregation, the transmissions over the different TRPs may use separate rate matching, but may have the same or different modulation orders. 
     The network may communicate with UE  115 - a  using multiple TRPs and any of the communication schemes described herein. Further, some communication schemes may include a combination of TDM and FDM, or cases where TDM may or may not be in a slot aggregation configuration. The schemes also may include some cases where rate matching is joint and some cases where rate matching is separate for different TRPs, and the schemes also may include cases where the different TRPs have the same or different modulation orders. Each scheme also may utilize different parameters that are included in signaling, such as which DMRS ports are used (such as for an SDM scheme) or how RBs are split up (such as for an FDM scheme). 
     To efficiently configure UE  115 - a  with the TCI state information—and the corresponding TRP scheme—base station  105 - a  may generate bits for a DCI message and may transmit the DCI on PDCCH  310 - a  . The DCI message may be transmitted to UE  115 - a  using TRP  305 - a  . UE  115 - a  may determine which scheme is configured for communication with TRPs  305  based on one or more fields of the received DCI. The DCI may be the same size across all communication schemes, and the formatting (such as a number of bits) of DCI fields may remain the same across the communication schemes. 
       FIG.  4    is a block diagram illustrating an example of a process flow for different multi-TRP schemes.  FIG.  4    illustrates an example of a process flow  400  that supports different multi-TRP schemes. In some examples, process flow  400  may implement aspects of a wireless communications system  100  or  300 . For example, a base station  105  and UE  115 , such as base station  105 - c  and UE  115 - b  , may perform one or more of the processes described with reference to process flow  400 . Base station  105 - c  may communicate with UE  115 - b  by transmitting and receiving signals through TRPs  405 - a  and  405 - b  . In other cases, TRPs  405 - a  and  405 - b  may correspond to different base stations  105 . Alternative examples of the following may be implemented, where some steps are performed in a different order than described or are not performed at all. In some cases, steps may include additional features not mentioned below, or further steps may be added. 
     At  410 , base station  105 - c  may generate DCI. The generation may include generating a first set of bits (such as a TCI field) that may indicate a set of TCI states for communication with UE  115 - b  . The generation also may include generating a second set of bits (such as an antenna port(s) field) that may indicate a set of antenna ports and, in some cases, a multi-TRP communication scheme for multiple TRP communication operation. In some cases, the second set of bits may additionally indicate a modulation order for at least one TCI state (such as a second TCI state for TRP  405 - b  ), an RV for a TB for at least one TCI state (such as the second TCI state for TRP  405 - b  ), or a combination thereof. 
     At  415 , base station  105 - c  may transmit the generated DCI to UE  115 - b  . UE  115 - b  may receive the DCI from base station  105 - c  . The DCI may be transmitted on a PDCCH from TRP  405 - a  . The DCI may schedule upcoming PDSCH transmissions and may include other control information. The DCI may include an indication of the first set of bits and the second set of bits. For example, the DCI may include coded bits based on the first set of bits and the second set of bits. 
     At  420 , UE  115 - b  may read the TCI field (such as the first set of bits) received in the DCI message. UE  115 - b  may identify, using the first set of bits, one or more TCI states for communication with base station  105 - c  using one or more TRPs  405 . 
     At  425 , UE  115 - b  may determine the TCI state configuration based on reading the TCI field of the DCI. For example, a value (such as tci-PresentInDCI) in the TCI field may not be configured for the CORESET scheduling the PDSCH, or the value may correspond to one TCI state. In these cases, the communication scheme may be configured for one TRP. In other cases, the TCI field value may correspond to more than one TCI state. In these other cases, the communication may be configured for communication with multiple TRPs. 
     UE  115 - b  may read the antenna port(s) field of the DCI and may interpret the value of the field based on the determined TCI state configuration. For example, if UE  115 - b  determines that the TCI field indicates a single TCI state, UE  115 - b  may identify, using the second set of bits, a set of antenna ports for the PDSCH transmission. At  430 , UE  115 - b  may access a table (such as pre-configured in memory or configured by the network) to determine one or more antenna ports corresponding to the antenna port(s) field value. 
     Alternatively, if UE  115 - b  determines that the TCI field indicates multiple TCI states, UE  115 - b  may identify, using the second set of bits, a set of antenna ports and a multi-TRP communication scheme based on identifying the set of TCI states. The second set of bits may include the same number of bits whether the field indicates just the set of antenna ports for single TRP operation or the set of antenna ports and the multi-TRP scheme for multi-TRP operation. At  430 , UE  115 - b  may access a lookup table to determine the set of antenna ports and multi-TRP scheme based on the antenna port(s) field value. In some cases, UE  115 - b  may select the lookup table from a set of lookup tables, where the set may include one lookup table to use for single TRP operation and one lookup table to use for multiple TRP operation. 
     The lookup table may include information mapping both the set of antenna ports and the multiple TRP scheme to the second set of bits. In some cases, the lookup table mapping both the set of antenna ports and the multiple TRP communication scheme to the second set of bits may be preconfigured in memory, and in some cases it may be dynamically configured by base station  105 - c  . UE  115 - b  may identify the second set of antenna ports and multiple TRP schemes based on the selected lookup table. In the lookup table for multi-TRP operation, along with indications of the DMRS ports, the table may include indications of the multiple TRP scheme (such as SDM, FDM, TDM, or some combination thereof). The antenna port(s) field lookup table may indicate that a value in the antenna port(s) field of the DCI corresponds to a set of DMRS ports, where the set of DMRS ports further corresponds to a communication scheme, such as SDM or FDM. The antenna port(s) field value also may indicate if rate matching is joint or separate. If the antenna port(s) field value indicates the use of an FDM communication scheme, the table may additionally indicate an RB configuration for the FDMed TCI states, as shown in the “Possibility” column of the table below. If the lookup tables are configurable by the network, the network may define the sets of possible DMRS ports and the type of schemes using radio resource control (RRC) signaling. 
     In some cases, UE  115 - b  may identify, using the second set of bits, a modulation order for at least one TCI state of the set of possible TCI states. Different modulation orders also may be used across different TCI states. A first modulation order may be indicated in a modulation order field. The first modulation order may correspond to a first TCI state in a multi-TRP operation. A second modulation order may be indicated in one of the tables above based on the received value for the antenna port(s) field. For example, a column in the antenna port(s) field lookup table may indicates if the modulation order corresponding to the second TCI state is the same as the modulation order indicated in the MCS (i.e., the modulation order for the first TCI state). If the modulation order is not the same as the modulation order indicated in the MCS, the value of the modulation order for the second TCI state may be indicated in the antenna port(s) field. The value of the modulation order may be an absolute value or may be a relative value with respect to the first modulation order. 
     If the TCI state configuration is determined to indicate communication with a single TRP, UE  115 - b  may receive a transmission from one TRP  405 - a  at  435 . UE  115 - b  may communicate with the single TRP  405 - a  based on the determined communication scheme. 
     If the TCI state configuration is determined to indicate communication with multiple TRPs  405 , UE  115 - b  may receive a transmission from one TRP  405 - a  at  435  and also may receive a transmission from another TRP  405 - b  at  440  (where, in some cases,  435  and  440  may correspond to a same time or OFDM symbol). UE  115 - b  may communicate with the network via the multiple configured TRPs  405  based on the determined communication scheme. 
     Systems and methods described herein are directed to DMRS modifications for multiple messaging and multiple TRP modes. The DMRS modifications may enable enhanced or improved operation in multi-TRP modes. In some implementations, the systems and methods described herein enable DMRS shifting in multiple DCI based multi-TRP modes. Accordingly, such systems and methods can be utilized for multiple TRP modes. 
       FIGS.  5 A- 5 D  are diagrams illustrating different example multi-TRP schemes. Referring to  FIGS.  5 A- 5 D , examples of diagrams for different multiple TRP modes are illustrated. In  FIG.  5 A , a diagram illustrating carrier aggregation is illustrated.  FIG.  5 A  depicts one base station  105   a  which communicates with UE  115   a  . Base station  105   a  may transmit data and control information; base station  105  may transmit (and receive) information using different equipment or settings (such as different frequencies). In  FIG.  5 B , a diagram illustrating dual connectivity is illustrated.  FIG.  5 B  depicts two base stations,  105   a  and  105   b  which communicate with UE  115   a  . UE  115   a  communicates data with both base stations and control information with one base station, main base station  105   a.    
       FIGS.  5 C and  5 D  depict DCI based operations for multiple TRP modes.  FIG.  5 C  depicts a single DCI operation mode, and  FIG.  5 D  depicts a multiple DCI operation mode. In  FIGS.  5 C and  5 D , a system includes a first TRP  505   a  , a second TRP  505   b  , and a UE  115 . The second TRP  505   b  may be included with the first TRP  505   a  (such as two TRPs of first base station  105   a  of  FIG.  5 A ) or may be separate from the first TRP  505   a  (such as a TRP from each of first and second base stations  105   a  and  105   b  of  FIG.  5 B ). In  FIG.  5 C , the first TRP  505   a  transmits downlink control information or DCIs, as illustrated by first PDCCH  512 . In  FIG.  5 C , the first PDCCH  512  schedules two PDSCHs, first PDSCH  522  and second PDSCH  524 . 
     Conversely, in  FIG.  5 D , both the first TRP  505   a  and the second TRP  505   b  transmit a DCI, as illustrated by PDCCHs  512  and  514 . Each PDCCH  512  and  514  schedules a corresponding PDSCH, PDSCHs  522 ,  524 . The PDSCH resources can be overlapping, partially overlapping, or non-overlapping. For the PDCCHs  512  and  515 , different CORESETs or CORESET groups may be used for the two TRPs  505   a  and  505   b  (i.e., a first CORESET group for first transmissions for the first TRP  505   a  and a second CORESET group for second transmissions for the second TRP  505   b  ). Each CORESET or CORESET group may have a different TCI state. 
     The CORESET groups may or may not be indicated to the UE. For example, when signaled to the UE, the CORESET groups may be indicated by higher layer signaling. The CORESET group information may be used for DMRS modifications, CRS rate matching, or both. As another example, when not signaled, the UE may be unaware of the CORESET groups and may not utilize the CORESET group data for DMRS modifications, CRS rate matching, or both. 
       FIG.  6    is a block diagram illustrating an example of a wireless communications system that enables DMRS modifications.  FIG.  6    illustrates an example of a wireless communications system  600  that supports DMRS modifications. In some examples, wireless communications system  600  may implement aspects of wireless communication system  100 . For example, wireless communications system  600  may include network entity  605  (such as base station  105 ), UE  115 , and optionally second network entity  607  (such as second base station  105  or a second TRP of base station  105 ). DMRS modification operations may enable multi-DCI based multi-TRP operations and operation with other types of networks, such as LTE. Operating on multiple networks and bandwidth may enable increased throughput and reliability and reduced latency. 
     Network entity  605  and UE  115  may be configured to communicate via frequency bands, such as FR1 having a frequency of  410  to 7125 MHz or FR2 having a frequency of 24250 to 52600 MHz for mm-Wave. It is noted that sub-carrier spacing (SCS) may be equal to 15, 30, 60, or 120 kHz for some data channels. Network entity  605  and UE  115  may be configured to communicate via one or more component carriers (CCs), such as representative first CC  681 , second CC  682 , third CC  683 , and fourth CC  684 . Although four CCs are shown, this is for illustration only, as more or fewer than four CCs may be used. One or more CCs may be used to communicate a Physical Downlink Control Channel (PDCCH), a Physical Downlink Shared Channel (PDSCH), a Physical Uplink Control Channel (PUCCH), or a Physical Uplink Shared Channel (PUSCH). In some implementations, such transmissions may be scheduled by dynamic grants. In some other implementations, such transmissions may be scheduled by one or more periodic grants and may correspond to semi-persistent scheduling (SPS) grants or configured grants of the one or more periodic grants. 
     Each periodic grant may have a corresponding configuration, such as configuration parameters/settings. The periodic grant configuration may include SPS configurations and settings. Additionally, or alternatively, one or more periodic grants (such as SPS grants thereof) may have or be assigned to a CC ID, such as intended CC ID. 
     Each CC may have a corresponding configuration, such as configuration parameters/settings. The configuration may include bandwidth, bandwidth part, hybrid automatic repeat request (HARQ) process, TCI state, RS, control channel resources, data channel resources, or a combination thereof. Additionally, or alternatively, one or more CCs may have or be assigned to a Cell ID, a Bandwidth Part (BWP) ID, or both. The Cell ID may include a unique cell ID for the CC, a virtual Cell ID, or a particular Cell ID of a particular CC of the plurality of CCs. Additionally, or alternatively, one or more CCs may have or be assigned to a HARQ ID. Each CC also may have corresponding management functionalities, such as, beam management, BWP switching functionality, or both. In some implementations, two or more CCs are quasi co-located, such that the CCs have the same beam or same symbol. 
     In some implementations, control information may be communicated via network entity  605  and UE  115 . For example, the control information may be communicated suing MAC-CE transmissions, RRC transmissions, DCI, transmissions, another transmission, or a combination thereof. 
     UE  115  includes processor  602 , memory  604 , transmitter  610 , receiver  612 , encoder,  613 , decoder  614 , DMRS modifier  615 , CRS rate matcher  616 , and antennas  252   a - r  . Processor  602  may be configured to execute instructions stored at memory  604  to perform the operations described herein. In some implementations, processor  602  includes or corresponds to controller/processor  280 , and memory  604  includes or corresponds to memory  282 . Memory  604  also may be configured to store DMRS data  606 , CRS data  608 , CORESET groups data  642 , modification parameter data  644 , or a combination thereof, as further described herein. 
     The DMRS data  606  corresponds to DMRS data of or associated with the network entity  605 , the second network entity  607 , or both. To illustrate, DMRS data  606  may include DMRS symbols for transmissions, such as PDSCH transmissions, and locations of the DMRS symbols in the transmissions. The CRS data  608  includes or corresponds to CRS data of or associated with the network entity  605 , the second network entity  607 , or both. To illustrate, CRS data  608  may include timing and location data for CRS data, often referred to as a CRS pattern. The CRS data  608  may include or indicate one or more CRS patterns, and may include or correspond to a CRS pattern parameter, such as lte-CRS-ToMatchAround. Some CRS pattern parameters, may include or be associated with multiple CRS patterns, (thus such CRS pattern parameters are known and referred to in the art as a list of CRS patterns). Such CRS pattern parameters (including lists) are known in the art as being associated with a particular component carrier as they are configured per component carrier. 
     The CORESET groups data  642  includes or corresponds to data which associates or links a network entity, such as a base station, cell, or TRP thereof, and optionally transmissions thereof, to a particular DMRS, a particular CRS pattern, or both. The CORESET groups data  642  may be indicated by higher layer signaling, such as RRC signaling (such as a configuration message). Alternatively, only the network entities include such association data, and the UE is unaware of such associations. In such implementations, the UE may perform DMRS modifications (such as shifting), CRS rate matching, or both independent of network entity associations. 
     The modification parameter data  644  includes or corresponds to data which is used by UE  115  to modify DMRS data  606 , such as configured to modify DMRS data  606  to generate modified DMRS data, such as  696 ,  698 . The DMRS data  606  may further include modified DMRS data ( 696 ,  698 ) of or associated with the network entity  605 , the second network entity  607 , or both. To illustrate, DMRS data  606  may include modified locations of the DMRS symbols in the transmissions. 
     Transmitter  610  is configured to transmit data to one or more other devices, and receiver  612  is configured to receive data from one or more other devices. For example, transmitter  610  may transmit data, and receiver  612  may receive data, via a network, such as a wired network, a wireless network, or a combination thereof. For example, UE  115  may be configured to transmit or receive data via a direct device-to-device connection, a local area network (LAN), a wide area network (WAN), a modem-to-modem connection, the Internet, intranet, extranet, cable transmission system, cellular communication network, any combination of the above, or any other communications network now known or later developed within which permits two or more electronic devices to communicate. In some implementations, transmitter  610  and receiver  612  may be replaced with a transceiver. 
     Additionally, or alternatively, transmitter  610 , receiver,  612 , or both may include or correspond to one or more components of UE  115  described with reference to  FIG.  2   . 
     Encoder  613  and decoder  614  may be configured to encode and decode, such as encode or decode transmissions with modified DMRS locations, respectively. DMRS modifier  615  may be configured to perform DMRS modification. For example, DMRS modifier  615  is configured to modify a location of one or more DMRS symbols for a encoding or decoding transmission. To illustrate, responsive to determining collision or overlap with a CRS resource, a partial or full overlap with a second transmission, or both, the DMRS modifier  615  adjusts a location of the overlapping DMRS symbol. In some implementations, the DMRS modifier  615  adjusts, such as increments or decrements, the location of each DMRS symbol of each transmission, that is the DMRS symbols of the first and second transmissions. 
     CRS rate matcher  616  may be configured to perform CRS rate matching of a transmission (such as the first PDSCH transmitted from the first TRP associated with the first value of higher index or the first PDSCH transmitted from the first TRP associated with the first value of higher index) around a particular LTE CRS or LTE CRS pattern. Such rate matching procedures enable coexistence of NR and LTE as the data transmission of NR (such as the first PDSCH or the second PDSCH) is rate matched around one or more LTE CRS pattern(s). 
     Network entity  605  includes processor  630 , memory  632 , transmitter  634 , receiver  636 , encoder  637 , decoder  638 , DMRS modifier  639 , CRS rate matcher  640 , and antennas  234   a - t . Processor  630  may be configured to execute instructions stores at memory  632  to perform the operations described herein. In some implementations, processor  630  includes or corresponds to controller/processor  240 , and memory  632  includes or corresponds to memory  242 . Memory  632  may be configured to store DMRS data  606 , CRS data  608 , CORESET group data  642 , modifying parameters  644 , or a combination thereof, similar to the UE  115  and as further described herein. 
     Transmitter  634  is configured to transmit data to one or more other devices, and receiver  636  is configured to receive data from one or more other devices. For example, transmitter  634  may transmit data, and receiver  636  may receive data, via a network, such as a wired network, a wireless network, or a combination thereof. For example, network entity  605  may be configured to transmit or receive data via a direct device-to-device connection, a local area network (LAN), a wide area network (WAN), a modem-to-modem connection, the Internet, intranet, extranet, cable transmission system, cellular communication network, any combination of the above, or any other communications network now known or later developed within which permits two or more electronic devices to communicate. In some implementations, transmitter  634  and receiver  636  may be replaced with a transceiver. Additionally, or alternatively, transmitter  634 , receiver,  636 , or both may include or correspond to one or more components of network entity  605  described with reference to  FIG.  2   . Encoder  637 , and decoder  638  may include the same functionality as described with reference to encoder  613  and decoder  614 , respectively. DMRS modifier  639  and CRS rate matcher  640  may include the same functionality as described with reference to DMRS modifier  615  and CRS rate matcher  616 , respectively. 
     During operation of wireless communications system  600 , network entity  605  may determine that UE  115  has DMRS shifting capability for multiple TRP operating modes, such as multi-DCI, multi-TRP operating modes. For example, UE  115  may transmit a message  648 , such as a capabilities message, that includes DMRS shifting indicator  672 . Indicator  672  may indicate enhanced DMRS shifting capability or a particular type of DMRS shifting, such as by incrementing location values. In some implementations, network entity  605  sends control information to indicate to UE  115  that DMRS shifting capability for multiple TRP operating modes is to be used. For example, in some implementations, message  648  (or another message, such as response or trigger message) is transmitted by the network entity  605 . 
     In the example of  FIG.  6   , network entity  605  transmits an optional a configuration transmission  649 . The configuration transmission  649  may include or indicate a DMRS modification configuration, such as modifying parameters data  644 . The configuration transmission  649  (such as  644  thereof) may indicate how to adjust a location of DMRS symbols or what type of DMRS shifting mode to operate in, such as per TRP, across all TRPs, independent of CRS rate matching, etc. 
     After transmission of the message  648  (such as a DMRS shifting configuration message, such as a RRC message or a DCI), transmissions may be scheduled by the network entity  605 , the network entity  607 , the UE  115 , or both. Such scheduled transmissions may include shared channel transmissions, such as PDSCH or PUSCH. Such transmissions may be scheduled by dynamic grant or by periodic grant. The periodic grants are configured to schedule one or more SPS grants (such as PDSCHs). 
     In the example of  FIG.  6   , the network entity  605  transmits a first message  650  and optionally transmits a second message  660 . For example, the network entity  605  is a base station that include multiple TRPs, and different TRPs transmit the messages  650 ,  660 . In some other implementations, the second network entity  607  transmits the second message  660 . For example, in such implementations, each of the network entities  605 ,  607  may include or correspond to a TRP of different panels or of different base stations. 
     First and second message  650 ,  660  may include or correspond to DCIs or RRC messages and may be sent via corresponding PDCCHs. The first message  650  and the second message  660  each schedule one or more corresponding downlink transmissions. In the example of  FIG.  6   , the first message  650  schedules first transmission  652  and the second message  660  schedules second transmission  662 . 
     Each of the first message  650  and the second message  660  has or is associated with a corresponding DMRS for the corresponding downlink transmission or transmissions. In  FIG.  6   , these corresponding DMRSs include a first DMRS  692  of or associated with the first transmission  652  and a second DMRS  694  of or associated with the second transmission  662 . In some implementations, the first DMRS  692  and the second DMRS  694  are similar. For example, they have the same number of DMRS symbols and the DMRS symbols are located in the symbol position or slot, referred to as symbol location. 
     Additionally, each of the first message  650  and the second message  660  has or is associated with a corresponding CRS. The CRS may be associated with the particular network entity that transmits the message, or may be associated with a particular value of the higher layer index configured per CORESET (i.e., associated with a CORESET group representing a TRP). To illustrate, each TRP may have an associated CRS pattern. Alternatively, a single CRS pattern may be used for multiple TRPs, such as multiple TRPs of a single base station or serving cell. When multiple CRS patterns are used, the UE  115 , the network entity  605 , the network entity  607 , or a combination thereof, may generate a combined CRS pattern, such as a union of CRS patterns which includes each of the resources of the multiple CRS patterns. 
     After transmission of the first message  650 , the second message  660 , or both, the UE  115 , the network entity  605 , the network entity  607 , or a combination thereof, may determine whether the one or more associated CRS patterns overlap the associated DMRS of the first message  650  or the second message  660 . Although not illustrated in  FIG.  6   , the CRS patterns may be sent in messages  650 ,  660  or other messages, such as by RRC message or configuration. 
     To illustrate, the UE  115  may determine whether any resources of the one or more associated CRS patterns overlap any resources, such as DMRS symbols, of the first and second DMRS  692 ,  694  for the first and second transmissions  652 ,  662  indicated by messages  650 ,  660 . Responsive to determining no overlap, the UE  115  may refrain from performing DMRS shifting. For example, the UE  115  may refrain from determining whether one or more CRS resource and DMRS symbols overlap. As another example, the UE  115  may refrain from modifying or not modify, such as shift, DMRS symbols even though the UE  115  determines that one or more CRS resource and DMRS symbols overlap. 
     Responsive to determining an overlap, the UE  115  may performing DMRS shifting. In some implementations, the above determination is only performed when the first transmission  662  and the second transmission  662  at least partially overlap in time, frequency, or both. In such implementations, the above determination is not performed when the first transmission  662  and the second transmission  662  do not overlap, such as when the resources thereof (such as resource blocks (RBs)) are orthogonal and the CRS pattern does not have an association with the first transmission, or optionally any transmission. Examples of overlapping include partial overlap of the first transmission  652  with the second transmission  662  in time, frequency, or both, or full overlap of the first transmission  652  with the second transmission  662  in time, frequency, or both. As an illustrative example, if the transmissions  652 ,  662  are frequency division multiplexed, they may be partially or fully overlapping in the time domain, such as by occupying at least one common ODFM symbol in orthogonal resource blocks. 
     The UE  115  and the network entity  605  or network entities  605  and  607  modify DMRS  692 ,  694  to generate modified DMRS  696 ,  698 . The transmissions  652 ,  662  include the modified DMRS, that is DMRS  696  and  698 , respectively. 
     Network entity  605  or network entities  605  and  607  may encode the transmissions  652 ,  662  to be transmitted, such as via the same serving cell (such as a same CC) or multiple serving cell (such as multiple CCs). For example, network entity  605  may transmit first transmission  652  via first CC  681  and may transmit second transmission  662  via second CC  682 . 
     UE  115  receives the transmissions  652 ,  662  including the modified DMRS  696  and  698 . For example, UE  115  decodes or processes the transmissions  652 ,  662  based on the modified DMRS  696  and  698 . Based on the decoding of messages  650 ,  660 , transmissions  652 ,  662 , or both, UE  115  may send one or more acknowledgment messages (such as PUCCHs) to network entities  605 ,  607 . It is noted that the acknowledgment message may include or correspond to a positive or negative acknowledgment, such as an ACK/NACK. UE  115  may send an ACK or a NACK based on a determination of whether the first transmission  652 , the second transmission  662 , or both, were successfully decoded. To illustrate, an ACK is communicated if decoding is successful and a NACK is communicated if decoding is unsuccessful. 
     Referring to  FIGS.  7 A- 7 C and  8 A- 8 C , diagrams illustrating DMRS modifications are depicted.  FIGS.  7 A- 7 C  are block diagrams illustrating an example of DMRS modifications for a single PDSCH.  FIGS.  7 A- 7 C  corresponds to DMRS modifications for a single PDSCH, and  FIGS.  8 A- 8 C  correspond to DMRS modifications for multiple PDSCHs. In  FIGS.  7 A- 7 C and  8 A- 8 C , symbols of PDSCHs are illustrated with pattern filling. 
     Referring to  FIG.  7 A  a block diagram illustrating an example DMRS pattern/scheme is illustrated.  FIG.  7 A  depicts an example of a DMRS pattern for a PDSCH, such as a portion thereof. The PDSCH, such as the portion of the PDSCH, includes 10 symbols in the example of  FIG.  7 A . The 10 symbols may be used for DMRS and data, such as DMRS symbols and data symbols. As illustrated in  FIG.  7 A , the DMRS of the PDSCH includes four DMRS symbols and six data symbols. The four DMRS symbols are located at symbols 1, 5, and 8 of the PDSCH, when the numbering starts from 1. 
     Referring to  FIG.  7 B , a block diagram illustrating an example CRS pattern/scheme is illustrated.  FIG.  7 B  depicts an example of a CRS pattern. Similar to  FIG.  7 B , the PDSCH includes 10 symbols in the example of  FIG.  7 B . All or a portion of the symbols of the PDSCH may be used for CRS, such as for CRS rate matching, and may correspond to CRS blocks. As illustrated in  FIG.  7 B , the CRS includes or occupies four symbols. The four symbols are located at symbols 1, 4, 5, and 8 of the PDSCH, when the numbering starts from 1. 
     Referring to  FIG.  7 C , a block diagram illustrating an example DMRS modification is illustrated.  FIG.  7 C  illustrates DMRS shifting by modifying of a location of one or more DMRS symbols of a transmission, such as PDSCH. 
     In  FIG.  7 C , a single PDSCH is illustrated. The PDSCH has the DMRS pattern or scheme as illustrated in  FIG.  7 A . Additionally, the PDSCH has or is associated with the CRS pattern or scheme illustrated in  FIG.  7 B . As illustrated in  FIG.  7 C , multiple DMRS symbols, locations thereof, may overlap with the CRS blocks of the CRS pattern illustrated in  FIG.  7 B . Specifically, each of the DMRS symbols (1, 4, and 8) overlap with the CRS resources/symbols of the CRS pattern. Accordingly, each DMRS symbol of each PDSCH is modified based on the overlap of one or more DMRS symbols and CRS blocks/locations. 
     For example, a location of each DMRS symbol of the PDSCH is modified based on modification parameters. In the example illustrated in  FIG.  7 C , each DMRS symbol location is incremented by a first value, that is one. 
       FIGS.  8 A- 8 C  are block diagrams illustrating an example of DMRS modifications for multiple PDSCHs. Referring to  FIG.  8 A  a block diagram illustrating an example DMRS pattern/scheme is illustrated.  FIG.  8 A  depicts an example of a DMRS pattern for a PDSCH. The PDSCH includes 14 symbols in the example of  FIG.  8 A . A first four symbols are unused by the DMRS and for data (that is not assigned to PDSCH), and may correspond to gaps or control data. The remaining 10 symbols may be used for DMRS and data. As illustrated in  FIG.  8 A , the DMRS of the PDSCH includes 4 DMRS symbols. The four DMRS symbols are located at symbols 5, 9, and 12 of the PDSCH, when the numbering starts from 1. 
     Referring to  FIG.  8 B , a block diagram illustrating an example CRS pattern/scheme is illustrated.  FIG.  8 B  depicts an example of a CRS pattern (such as one CRS pattern of possibly many CRS patterns configured for a component carrier). Similar to  FIG.  8 A , the PDSCH includes 14 symbols in the example of  FIG.  8 B . All or a portion of the symbols of the PDSCH may be used for CRS, such as for CRS rate matching, and may correspond to CRS blocks. As illustrated in  FIG.  8 B , the CRS includes or occupies  6  symbols. The six symbols are located at symbols 1, 2, 5, 8, 9, and 12 of the PDSCH, when the numbering starts from 1. 
     Referring to  FIG.  8 C , a block diagram illustrating an example DMRS modification is illustrated.  FIG.  8 C  illustrates DMRS shifting by incrementing of a location of each DMRS symbol of overlapping transmissions, such as PDSCHs. 
     In  FIG.  8 C , two partially overlapping PDSCHs are illustrated. The PDSCHs (which correspond to two TRPs, two higher layer indices, or two CORESET groups) have the DMRS pattern or scheme as illustrated in  FIG.  8 A . Additionally, the PDSCHs have or are associated with the CRS pattern or scheme illustrated in  FIG.  8 B . Alternatively, the CRS pattern may be associated with only one of the PDSCHs. As illustrated in  FIG.  8 C , multiple DMRS symbols, locations thereof, overlap with the CRS blocks of the CRS pattern illustrated in  FIG.  8 B . Specifically, each of the DMRS symbols (5, 9, and 12) of each PDSCH overlap with the CRS resources/symbols of the CRS pattern. Accordingly, each DMRS symbol of each PDSCH is modified based on the overlap of one or more DMRS symbols and CRS blocks/locations. This may be done irrespective of the association of the CRS pattern with the two PDSCH (i.e., is done for both PDSCHs). 
     For example, a location of each DMRS symbol of each PDSCH is modified based on modification parameters. In the example illustrated in  FIG.  8 C , each DMRS symbol location is incremented by a first value, that is one. Although incrementing is shown, in some other implementations, the DMRS symbol locations may be decremented, divided, multiplied, adjusted using a table or formula, or a combination thereof. Additionally, although a value of one is applied to the incrementing of DMRS symbol locations, in some other implementations, other values may be used, such as two, three, four, etc. 
     Although each DMRS symbol overlaps with a CRS resource and each DMRS symbol is moved, in some other implementations, each DMRS symbol is moved based on only a single DMRS symbol and CRS resource overlap in one PDSCH. Additionally, or alternatively, although the PDSCHs partially overlap in both time and frequency, the PDSCHs may fully overlap in time, frequency, or both, or may partially overlap in time or frequency in some other implementations. 
     When there are one or more CRS patterns (such as lte-CRS-ToMatchAround or its extension for multiple CRS patterns) to rate match around for deciding whether any DMRS symbols of the two PDSCHs (corresponding to the two TRPs, two higher layer indices, or two CORESET groups) are shifted, the one or more CRS patterns may be considered for both PDSCHs irrespective of the association of the PDSCHs to the CRS patterns (i.e., the association with the TRPs, higher layer indices, or CORESET groups). 
     For example, when only one CRS pattern or set of CRS patterns (such as lte-CRS-ToMatchAround) is configured and is associated with the first TRP (such as a first higher layer index value, i.e., a first CORESET group), and the two PDSCHs are partially/fully overlapping, DMRS of both PDSCHs shift even though the CRS pattern(s) is/are associated only with one PDSCH (such as the second PDSCH). 
     In some implementations, for shifting the DMRS pattern (i.e., if the DMRS is in the same symbol as the CRS), both PDSCHs follow the same behavior irrespective of association of the CRS pattern. Additionally, or alternatively, for rate matching, only the first PDSCH may be rate matched around the resources of the CRS pattern and the second PDSCH may not be rate matched around the resources of the CRS pattern (which is configured for the CORESET and component carrier). That is, even though PDSCH rate matching may take into account the association of a CRS pattern (or a list of CRS patterns) with a TRP (or with a CORESET group), DMRS shifting is performed irrespective of the association of PDSCHs with a TRP (or with a CORESET group) or the association of a CRS pattern (or a list of CRS patterns) with a TRP (or with a CORESET group). 
     A CRS pattern or list of CRS patterns can be configured for a multi-TRP UE in general, configured in a serving cell, and configured for a higher layer index value (i.e., CORESET group). Accordingly, the one or more CRS patterns are intended as design options for a component carrier and a TRP (CORESET group) within the component carrier, and thus the one or more CRS patterns are configured for a component carrier and a TRP. 
     Though the PDSCHs have the same DMRS pattern in the example provided herein, in some other implementations the PDSCHs may have different DMRS patterns from each other. In such implementations, the DMRS pattern of one or both may be adjusted based on a collision of either of the DMRS patterns. 
       FIG.  9    is a block diagram illustrating example blocks executed by a UE. The example blocks will also be described with respect to the UE  115  as illustrated in  FIG.  11   .  FIG.  11    is a block diagram conceptually illustrating an example design of a UE.  FIG.  11    illustrates a UE  115  configured according to one aspect of the present disclosure. The UE  115  includes the structure, hardware, and components as illustrated for the UE  115  of  FIG.  2  or  6   . For example, the UE  115  includes the controller/processor  280 , which operates to execute logic or computer instructions stored in the memory  282 , as well as controlling the components of the UE  115  that provide the features and functionality of the UE  115 . The UE  115 , under control of the controller/processor  280 , transmits and receives signals via the wireless radios  1101   a - r  and the antennas  252   a - r  . The wireless radios  1101   a - r  includes various components and hardware, as illustrated in  FIG.  2    for the UE  115 , including the modulator/demodulators  254   a - r  , the MIMO detector  256 , the receive processor  258 , the transmit processor  264 , and the TX MIMO processor  266 . 
     As shown, the memory  282  may include DMRS Modification Logic  1102 , CRS Rate Matching Logic  1103 , CORESET Group Logic  1104 , DMRS data  1105 , modified DMRS data  1106 , DMRS Modification data  1107 , CRS data  1108 , and CORESET Group data  1109 . The DMRS data  1105 , the modified DMRS data  1106 , the DMRS modification data  1107 , CRS data  1108 , and the CORESET Group data  1109  may include or correspond to DMRS data  606 , CRS data  608 , CORESET data  642 , and modifying parameters  644 . The DMRS Modification Logic  1102  may include or correspond to the DMRS modifier  615 . The CRS Rate Matching Logic  1103  may include or correspond to the CRS rate matcher  616 . The CORESET Group Logic  1104  may include or correspond to the DMRS modifier  615 , the CRS rate matcher  616 , or both. In some aspects, the logic  1102 - 1104 , may include or correspond to processor(s)  280 . The UE  115  may receive signals from or transmit signals to a base station or base stations, such as the base station  105  or the network entity or entities  605 ,  607 . When communicating with a single base station or serving cell, the UE  115  may receive signals from or transmit signals to multiple TRPs of the single base station or serving cell. 
     Referring to  FIG.  9   , at block  900 , the UE receives a configuration message including at least one list of CRS patterns for a component carrier. A list of the at least one list is associated with a control resource set (CORESET) group. 
     At block  901 , the UE receives a first message scheduling a first transmission associated with a first demodulation reference signal (DMRS) and for the component carrier. 
     At block  902 , the UE receives a second message scheduling a second transmission associated with a second DMRS and for the component carrier. In some implementations, the first and second messages are DCIs or RRC messages. Additionally, or alternatively, the first and second transmissions are PDSCH transmissions. The first and second DMRS may be aligned, such as have the same symbol locations in some implementations. 
     At block  903 , the UE optionally determines whether one or more CRS patterns overlap with the first DMRS or the second DMRS. The determination may be based on whether the one or more CRS patterns are configured for the UE (for example, as described in Technical Specification (TS) 38.211 v16.1.0, section 7.4.1.1.2). In some implementations, a single CRS pattern associated with multiple TRPs is used. In some other implementations, each TRP has an associated CRS pattern, and each CRS pattern is checked for overlap with each DMRS. 
     At block  904 , the UE modifies at least one DMRS symbol of the first DMRS or at least one DMRS symbol of the second DMRS based on the list being configured for the component carrier. 
     In some implementations, the method may further include determining whether the first transmission at least partially overlaps with the second transmission (such as same component carrier and different CORESET groups). For example, first resources of the first transmission are checked for overlap with second resources of the second transmission, in a time domain, frequency domain, or both. In some such implementations, one or more of the previous described blocks are performed responsive to or based on such as determination. To illustrate, DMRS modification or determinations for overlap may not be performed based on the UE determining that the first transmission does not overlap with the second transmissions, such as in the case of orthogonal resource blocks. 
     In some implementations, the method may further include receiving the first and second transmission with modified DMRS symbols. To illustrate, the UE  115  may receive the first and second transmission which have locations of DMRS symbols shifted as compared to the DMRS patterns indicated by or associated with the correspond first and second messages. 
       FIG.  10    is a block diagram illustrating example blocks executed by a network entity. The network entity may include or correspond to as base station or TRP thereof, configured according to an aspect of the present disclosure. The example blocks will also be described with respect to gNB  105  (or eNB) as illustrated in  FIG.  12   .  FIG.  12    is a block diagram conceptually illustrating an example design of a network entity.  FIG.  12    illustrates a gNB  105  configured according to one aspect of the present disclosure. The gNB  105  includes the structure, hardware, and components as illustrated for gNB  105  of  FIG.  2   . For example, gNB  105  includes controller/processor  240 , which operates to execute logic or computer instructions stored in memory  242 , as well as controlling the components of gNB  105  that provide the features and functionality of gNB  105 . The gNB  105 , under control of controller/processor  240 , transmits and receives signals via wireless radios  120   a - t  and antennas  234   a - r  . Wireless radios  1201   a - t  includes various components and hardware, as illustrated in  FIG.  2    for gNB  105 , including modulator/demodulators  232   a  -t, MIMO detector  236 , receive processor  238 , transmit processor  220 , and TX MIMO processor  230 . The data  1202 - 1209  in memory  242  may include or correspond to the corresponding data  1102 - 1109  in memory  282 , respectively. 
     Referring to  FIG.  10   , at block  1000 , the network entity transmits a configuration message including at least one list of CRS patterns for a component carrier. A list of the at least one list is associated with a control resource set (CORESET) group. 
     At block  1001 , a network entity transmits a first message scheduling a first transmission associated with a first demodulation reference signal (DMRS) and for the component carrier. 
     At block  1002 , the network entity transmits a second message scheduling a second transmission associated with a second DMRS and for the component carrier. In some implementations, the first and second message are DCIs or RRC messages. Additionally, or alternatively, the first and second transmissions are PDSCH transmissions. The first and second DMRS may be the same, such as have the same symbol locations in some implementations. 
     At block  1003 , the network entity optionally determines whether one or more CRS patterns overlap with the first DMRS or the second DMRS. The determination may be based on whether the one or more CRS patterns are configured for the UE (for example, as described in 5G NR Technical Specification (TS) 38.211 v   16 . 1 . 0   , section    7 . 4 . 1 . 1 . 2   ). In some implementations, a single CRS pattern associated with multiple TRPs is used. In some other implementations, each TRP has an associated CRS pattern, and each CRS pattern is checked for overlap with each DMRS. 
     At block  1004 , the network entity modifies at least one DMRS symbol of the first DMRS or at least one DMRS symbol of the second DMRS responsive to determining that the list is configured for the component carrier. 
     In some implementations, the method may further include determining whether the first transmission at least partially overlaps with the second transmission (such as same component carrier and different CORESET groups). For example, first resources of the first transmission are checked for overlap with second resources of the second transmission, in a time domain, frequency domain, or both. In some such implementations, one or more of the previous described blocks are performed responsive to or based on such as determination. To illustrate, DMRS modification or determinations for overlap may not be performed based on the network entity determining that the first transmission does not overlap with the second transmissions, such as in the case of orthogonal resource blocks. 
     In some implementations, the method may further include transmitting the first transmission, the second transmission, or both. When transmitted, the first and second transmissions may have modified DMRS symbols. To illustrate, the network entity may transmit the first and second transmission which have locations of DMRS symbols shifted as compared to the DMRS patterns indicated by or associated with the correspond first and second messages. 
     It is noted that one or more blocks (or operations) described with reference to  FIGS.  9  and  10    may be combined with one or more blocks (or operations) of another of figure. For example, one or more blocks of  FIGS.  9  and  10    may be combined with one or more blocks (or operations) of another of  FIG.  2 ,  3 ,  4 ,  6   , or  10 . Additionally, or alternatively, one or more operations described above with reference to  FIGS.  1 - 6    may be combined with one or more operations described with reference to  FIGS.  9  and  10   . 
     Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. 
     Components, the functional blocks, and the modules described herein (such as components of  FIG.  6   , functional blocks of  FIGS.  9  and  10   , and modules in  FIG.  2   ) may include processors, electronics devices, hardware devices, electronics components, logical circuits, memories, software codes, firmware codes, etc., or any combination thereof. In addition, features discussed herein relating to components, the functional blocks, and the modules described herein (such as components of  FIG.  6   , functional blocks of  FIGS.  9  and  10   , and modules in  FIG.  2   ) may be implemented via specialized processor circuitry, via executable instructions, or combinations thereof. 
     Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the disclosure herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure. Skilled artisans will also readily recognize that the order or combination of components, methods, or interactions that are described herein are merely examples and that the components, methods, or interactions of the various aspects of the present disclosure may be combined or performed in ways other than those illustrated and described herein. 
     The various illustrative logics, logical blocks, modules, circuits and algorithm processes described in connection with the implementations disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. The interchangeability of hardware and software has been described generally, in terms of functionality, and illustrated in the various illustrative components, blocks, modules, circuits and processes described above. Whether such functionality is implemented in hardware or software depends upon the particular application and design constraints imposed on the overall system. 
     The hardware and data processing apparatus used to implement the various illustrative logics, logical blocks, modules and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose single- or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, or any conventional processor, controller, microcontroller, or state machine. In some implementations, a processor may be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some implementations, particular processes and methods may be performed by circuitry that is specific to a given function. 
     In one or more aspects, the functions described may be implemented in hardware, digital electronic circuitry, computer software, firmware, including the structures disclosed in this specification and their structural equivalents thereof, or in any combination thereof. Implementations of the subject matter described in this specification also can be implemented as one or more computer programs, i.e., one or more modules of computer program instructions, encoded on a computer storage media for execution by, or to control the operation of, data processing apparatus. 
     If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. The processes of a method or algorithm disclosed herein may be implemented in a processor-executable software module which may reside on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that can be enabled to transfer a computer program from one place to another. A storage media may be any available media that may be accessed by a computer. By way of example, and not limitation, such computer-readable media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to store desired program code in the form of instructions or data structures and that may be accessed by a computer. Also, any connection can be properly termed a computer-readable medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. Additionally, the operations of a method or algorithm may reside as one or any combination or set of codes and instructions on a machine readable medium and computer-readable medium, which may be incorporated into a computer program product. 
     Various modifications to the implementations described in this disclosure may be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of this disclosure. 
     Thus, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein. 
     Additionally, a person having ordinary skill in the art will readily appreciate, the terms “upper” and “lower” are sometimes used for ease of describing the figures, and indicate relative positions corresponding to the orientation of the figure on a properly oriented page, and may not reflect the proper orientation of any device as implemented. 
     Certain features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. 
     Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Further, the drawings may schematically depict one more example processes in the form of a flow diagram. However, other operations that are not depicted can be incorporated in the example processes that are schematically illustrated. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the illustrated operations. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results.