Channel state information reference signal (CSI-RS) resource mapping scheme management for massive MIMO systems

Abstract

A network node utilizes a standard-defined CSI-RS resource mapping scheme defined for 32 logical ports to manage CSI reporting from a terminal where an antenna system of the network node includes more than 32 logical antenna ports. The network node selects a preferred CSI-RS mapping scheme from a plurality of CSI-RS mapping schemes that facilitate CSI reporting for antenna systems having more than 32 logical ports. Based on conditions, the network node can send a first CSI-RS configuration message to the terminal for a density-adjusted CSI-RS resource mapping scheme where one or more transmission modes of the standard-defined CSI-RS resource mapping scheme are limited to densities less than 1.0. Based on conditions, the network node can send a second CSI-RS configuration message to the terminal for a resource-adjusted CSI-RS mapping scheme where additional resources are used for one or more transmission modes of the standard-defined CSI-RS resource mapping scheme.

Description

CHANNEL STATE INFORMATION REFERENCE SIGNAL (CSI-RS) RESOURCE MAPPING SCHEME MANAGEMENT FOR MASSIVE MIMO SYSTEMSCLAIM OF PRIORITY

[0001] The present application claims priority to Provisional Application No. 63 / 624,389, entitled “CSI-RS Transmission for Extremely Large Massive MIMO Systems”, docket number KWIC 00002 PRO, filed January 24, 2024, and to Provisional Application No. 63 / 554,337, entitled “Method to Switch CSI-RS Transmission for Extremely Large Massive MIMO Systems”, docket number KWIC 00005 PRO, filed February 16, 2024, both assigned to the assignee hereof and hereby expressly incorporated by reference in their entirety.FIELD

[0002] This invention generally relates to wireless communications and more particularly to Channel State Information Reference Signal (CSI-RS) resource mapping schemes for Massive MIMO systemsBACKGROUND

[0003] Many conventional wireless communication systems employ network nodes such as, base stations or gNBs, to transmit and receive wireless signal to and from terminals, such as user equipment (UE) devices. A network node may include an antenna array with multiple antenna elements. The antenna array is often part of an antenna system having a plurality of logical antenna ports that are mapped to the multiple antenna elements of the antenna array. Communication through the antenna array is often managed by precoding signals and adjusting parameters to manipulate the antenna pattern of the antenna array. In order to select the appropriate precoder and antenna parameters to maximize efficient communication with a terminal, a terminal measures reference signals transmitted by a network node and transmits a report to the network node. A technique employed in conventional systems includes sendingChannel State Information Reference Signals (CSI-RSs) that are received and measured by the terminal where the network node sends a CSI-RS configuration message to the terminal. The CSI-RS configuration message includes Radio Resource Control (RRC) parameters that are applied to a standard-defined CSI-RS resource mapping scheme to determine the resources elements where the reference signals to be measured will be transmitted. For conventional systems, the standard-defined CSI- RS resource mapping scheme is defined by the 3GPP communication specification where the CSI-RS resource mapping scheme defines 18 different reference signal transmission schemes and where the standard-defined CSI-RS resource mapping scheme can be represented by a table having 18 rows and that supports transmission modes for transmitting reference signals for up to 32 logical antenna ports.SUMMARY

[0004] A network node utilizes a standard-defined CSI-RS resource mapping scheme defined for up to 32 logical ports to manage CSI reporting from a terminal where an antenna system of the network node includes more than 32 logical antenna ports. The network node selects a preferred CSI-RS resource mapping scheme from a plurality of CSI-RS resource mapping schemes that facilitate CSI reporting for antenna systems having more than 32 logical ports. Based on conditions, the network node can send a first CSI-RS configuration message to the terminal for a density-adjusted CSI resource mapping scheme where one or more transmission modes of the standard- defined CSI-RS resource mapping scheme are limited to one or more values of the reference signal transmission density to less than 1.0. Based on conditions, the network node can send a second CSI-RS configuration message to the terminal for a resource- adjusted CSI resource mapping scheme where additional resources are used for one or more transmission modes of the standard-defined CSI-RS resource mapping scheme.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 is a block diagram of a system for an example of CSI-RS reporting by a terminal where the number (NLP) of logical antenna ports in an antenna system at anetwork node is greater than a number of logical antenna ports (MSLP) defined by a standard-defined CSI-RS resource mapping scheme used by the terminal that provides a CSI report to the network node.

[0006] FIG. 2 is a block diagram of an example of a base station suitable for use as a network node.

[0007] FIG. 3 is a block diagram of an example of a LIE device suitable for use as a terminal device.

[0008] FIG. 4 is a block diagram of an example of an antenna system suitable for use as the antenna system.

[0009] FIG. 5 is an illustration of an example of a standard-defined CSI-RS resource mapping scheme table.

[0010] FIG. 6A is a block diagram of an example of resource block transmissions of a density-adjusted CSI resource mapping scheme supporting 64 logical antenna ports.

[0011] FIG. 6B is a block diagram of an example of resource block transmissions of a density-adjusted CSI resource mapping scheme supporting 48 logical antenna ports.

[0012] FIG. 7 is an illustration of an example of a modified standard-defined CSI-RS resource mapping scheme table.

[0013] FIG. 8 is an illustration of an example of a modified standard-defined CSI-RS resource mapping scheme table.

[0014] FIG. 9 is a block diagram of an example of resource block transmissions of a density-adjusted CSI resource mapping scheme supporting 128 logical antenna ports.

[0015] FIG. 10A is a block diagram of an example of an odd resource block for a density-adjusted CSI-RS resource mapping scheme supporting 64 logical antenna ports where the transmission mode includes a cdm-Type of fd-CDM2

[0016] FIG. 10B is a block diagram of an example of an even resource block for the density-adjusted CSI-RS resource mapping scheme.

[0017] FIG. 11 is a block diagram of an example of a resource block of a resource- adjusted CSI-RS resource mapping scheme supporting 48 logical antenna ports.

[0018] FIG. 12 is a block diagram of the system for an example where the network node 108 switches between a resource-adjusted CSI-RS resource mapping scheme and a density-adjusted CSI-RS resource mapping scheme.

[0019] FIG. 13 is a flow chart of an example of a method of managing a CSI-RS resource mapping scheme for CSI reporting from a terminal for antenna ports in addition to the antenna ports defined by the CSI-RS resource mapping scheme stored at the terminal.

[0020] FIG. 14 is a flow chart of an example of CSI reporting performed at a terminal for antenna ports in addition to the antenna ports defined by the CSI-RS resource mapping scheme stored at the terminal.DETAILED DESCRIPTION

[0021] In order to manage multiple-element antenna arrays, conventional systems use a standard-defined Chanel State Information Reference Signal (CSI-RS) resource mapping scheme defined for up to 32 logical ports by at least one revision of the 3GPP communication specification to configure terminals to measure and provide CSI reports. As discussed above, the 3GPP communication specification defines a CSI-RS resource mapping scheme for up to 32 logical antenna ports that can be represented by a table having 18 rows. Such a CSI-RS resource mapping scheme is defined and discussed with reference to “Table 7.4.2.5.3-1: CSI-RS locations within a slot” in Release 18. The relationships and calculations of the standard-defined CSI-RS resource mapping scheme is known to each terminal. In order for the terminal to identify the resource elements used for a particular RS transmission, however, the terminal requires additional information. The additional information is provided by a network node in a Radio Resource Control (RRC) message that includes specific parameters to be applied by the terminal to the CSI-RS mapping scheme to determine the resource elements where the reference signals will be transmitted by the network node. These parameters are typically referred to as “RRC parameters”. Therefore, after a network node, such as a gNB, determines the reference signal transmission scheme to transmit to a terminal, the network node transmits, to the terminal, an RRC message including the RRCparameters for the CSI-RS resource mapping. The terminal, such as user equipment device (UE device), evaluates the parameters to identify which of the 18 possible RS transmission modes of the standard-defined CSI-RS resource mapping scheme is being used. The terminal then applies the RRC parameters to the identified transmission mode to determine the RS resource elements where the reference signals will be transmitted by the network node. The terminal receives and measures the reference signals transmitted via the resource elements and generates a CSI report for transmission to the network node.

[0022] Multiple-input multiple-output (MIMO) systems can significantly increase the throughput of wireless systems. As a result, MIMO is an integral part of 4th and 5th generation wireless systems. Some 5G systems employ MIMO systems with a large number of antennas which are often referred to as massive MIMO systems. Typically, a massive MIMO system is set up with Nt transmit and Nr receive antennas, also called Nt Transmit and Nr Receive (TR) antennas. A conventional 32 TR system consists of 32 baseband ports and 32 radio branches. In some situations, the number, Nt, of Transmit antennas may be different from the number, Nr, of receive antennas.

[0023] Some conventional massive MIMO systems, referred to as active antenna systems (AAS), can support 192 antenna elements (AE) deployed in a frequency range of 3-4 GHz, regardless of the number of TRs. An antenna panel with 192 antenna elements, for example, may include 8 columns and 2 rows with cross-polarization (i.e. (8x2x2x6=192 AE). Often, a 32 TR massive MIMO system includes a radio branch connected to 6 elements, referred to as subarrays. Beamforming may be performed at both the baseband and the antenna panel.

[0024] Massive MIMO systems are likely to be deployed at higher frequencies where a larger number of smaller antenna elements in an array may be deployed due to the shorter wavelength of the signals. Frequencies in the range of 7-20 GHz are being considered for allocation to terrestrial communication systems, for example.

[0025] In order to support the larger antenna arrays of extremely massive MIMO systems, the subarray size may be increased while maintaining the conventional number of radio branches to 32. For example, the subarray may be increased to 12 or24 such that a 32 TR system could use a 1X12 subarray to support a 384 AE antenna array or use a 1X24 subarray to support a 768 AE antenna array. With an increased subarray size, however, antenna beams are narrow and produce many sidelobes that can cause interference to other terminals.

[0026] Another potential option for supporting a larger antenna array includes increasing the baseband / radio ports to a higher value while maintaining a reasonably sized subarray. For example, a 1x6 subarray could be used in a 64 TR system to support a 384 AE antenna array or a 1x3 subarray could be used in a 128 TR system to support a 384 AE antenna array. Similarly, a 1x6 subarray could be used in a 128 TR system to support a 768 AE antenna array. Since the 3GPP specification supports terminal up to only 32 CSI-RS antenna ports, however, the terminal can only provide feedback for precoding / beamforming up to 32 antenna ports. As a result, the achievable gains due to the larger antenna arrays are limited by the fixed mapping of antenna ports to antenna elements. Despite the terminal reporting specific beamforming to the terminal, substantial gains of extremely massive MIMO cannot be achieved.

[0027] For the examples herein, however, large antenna array systems having more than 32 logical antenna ports achieve greater gains while utilizing the basic format of the conventional 32 port standard-defined CSI-RS resource mapping scheme at the terminal.

[0028] In one example, a density-adjusted CSI-RS resource mapping scheme includes a set of CSI-RS transmission modes identical to the set of 18 CSI-RS transmission modes of the conventional standard-defined CSI-RS mapping scheme except that at least some of the transmission modes are limited to a density reference signal transmission rate that that is lower than 1 . Since the resource elements are not used in every resource block for the single transmission mode, different reference signal transmissions may be applied in different resource blocks. As a result, the network node can transmit reference signals for feedback pertaining to logical antenna ports in addition to the 32 logical antenna ports. The total number of transmission modes available for configuration is increased by the number of transmission modes only using the lower density transmission rates. For example, where a transmission mode in the standard-defined CSI-RS resource mapping scheme allows for density transmissionrates of 1 and 0.5, the network node may utilize the 0.5 density transmission rate such that first reference signals associated with a first set of logical antenna ports are transmitted in odd resource blocks and second reference signals associated with a second set of logical antenna ports are transmitted in even resource blocks.

[0029] In another example of a density-adjusted CSI-RS resource mapping scheme, the density-adjusted CSI-RS resource mapping scheme includes a set of CSI-RS transmission modes identical to the set of 18 CSI-RS transmission modes of the conventional standard-defined CSI-RS resource mapping scheme except that at least some of the transmission modes include an additional density reference signal transmission rate that is lower than the conventional density reference signal transmission rate(s) for the transmission mode. As a result, the total number of transmission modes available for configuration is increased by a number of transmission modes determined by the number of transmission modes with additional density transmission rates, the number of additional density transmission rates, and the values of the additional density transmission rates. Such a technique, however, requires the CSI-RS resource mapping scheme configured at the terminal to include the additional transmission density rates. Accordingly, for such an implementation, a standard body such as the 3GPP may need to redefine the standard-defined CSI-RS resource mapping scheme to include additional densities or may need to supplement the standard to allow for the network to configure or otherwise indicate to the terminal that a density lower than the density associated with a transmission mode of the current standard-defined CSI-RS resource mapping scheme is being used.

[0030] In another example, a resource-adjusted CSI-RS mapping scheme includes a set of CSI-RS transmission modes including the set of 18 CSI-RS transmission modes of the conventional CSI-RS mapping scheme and additional transmission modes. Each additional transmission mode is based on one of the 18 CSI-RS transmission modes of the conventional CSI-RS mapping scheme with different resource elements. In other words, an additional transmission mode is identical to one of the conventional transmission modes except that the resource elements used for the transmission are different from the resource elements used for transmission of the conventional transmission mode.

[0031] In some examples, the CSI-RS configuration at the terminal is switched by the network node between a CSI-RS configuration based on a transmission mode from the density-adjusted CSI-RS configuration mapping and another CSI-RS configuration based on another transmission mode defined by the resource-adjusted CSI-RS configuration mapping. Therefore, the network node may select a transmission mode from one of multiple CSI-RS configuration mapping schemes based on conditions.

[0032] A network node is any apparatus, equipment, device, or combination of devices, on the network side of the communication system that is connected to the communication network or is part of communication network. Some examples of a network node include a base station, a node B, an E-UTRA Node B, Evolved Node B, eNodeB, eNB, a New Generation eNB (ng-eNB), a gNodeB (also known as a gNB) in new radio (NR) technology, a macro station, pico station, and a femto station. The network node may form, or be a part of, the radio access network (RAN) that provides a connection between the core network and terminal communication devices. A RAN may be organized into three functional blocks including a Radio Unit (RU), a Distributed Unit (DU) and a Centralized Unit (CU). The RU transmits, receives, amplifies, and digitizes radio frequency signals and typically located near, or integrated into, the antenna. The DU and CU perform computations and / or processing to send and receive digitalized radio signals to and from the core network. The DU is typically located at or near the RU and the CU may be closer to the core network. The infrastructure or connection between the RU and the DU is often referred to as fronthaul and the infrastructure or connection between the DU and the CU is often referred to as a midhaul. The communication node, therefore, may perform the functions of one or more of the RU, DU and / or CU depending on the particular implementation.

[0033] A terminal communication device (terminal), such as a remote terminal and a relay terminal, is a communication device on the terminal side of the communication system and is sometimes referred to as user equipment (UE), a UE device, a terminal device, wireless mobile device, wireless communication device and other terms. Some examples of a terminal communication device include a mobile phone, a smart phone, a personal digital assistant (PDA), tablet, and laptop computer. In some situations, the terminal communication device is a machine type communication (MTC) communicationdevice or Internet-of-Things (IOT) device. In addition, the terminal communication device may be, or may be a part of, a wearable device or a vehicle where the vehicle may be terrestrial vehicle, watercraft, or aircraft (including unmanned aerial vehicles). The terminal communication device, therefore, is any fixed, mobile, or portable equipment that performs the functions of the terminal device described herein.

[0034] FIG. 1 is a block diagram of a system 100 for an example of CSI-RS reporting by a terminal 102 where the number (NLP) of logical antenna ports 104 in an antenna system 106 at a network node 108 is greater than a number of logical antenna ports (MSLP) defined by a standard-defined CSI-RS resource mapping scheme 110 maintained and used by the terminal 102 that provides a CSI report 112 to the network node 108. For the example, the number of antenna elements (NAE) of the antenna array 114 at the network node 108 is greater than 32 and the number (NLP) of logical antenna ports 104 is greater than 32. The antenna system 106 at the network node 108 includes the antenna array 114 having multiple antenna elements where the antenna array 114 is accessible to other communication components at the network node 108 through the logical antenna ports 104. The plurality of logical antenna ports 104 are mapped to the multiple antenna elements of the antenna array 114. Communication through the antenna array 114 is managed by precoding signals and adjusting parameters to manipulate the antenna pattern of the antenna array 114. In order to select the appropriate precoder and antenna parameters to maximize efficient communication with the terminal 102, the terminal 102 measures one or more reference signals 116 transmitted by the network node 108 and transmits the CSI report 112 to the network node 108 which can be used by the network node 108 to adjust antenna parameters, signals and precoders. The network node 108 configures the terminal 102 to receive and measure the reference signals 116 and to report the results of the measurements in the CSI report 112. The reference signals 116 are transmitted over selected resource elements 118 within a time-frequency resource set 120 arranged in resource blocks (RBs). For the examples herein, the network node 108 transmits one or more CSI configuration messages 122 that include Radio Resource Control (RRC) parameters that the terminal 102 applies to the standard-defined CSI-RS resource mapping scheme 110 maintained at the terminal 102. The terminal 102 is preconfigured or otherwiseconfigured with information defining the standard-defined CSI-RS resource mapping scheme 110 before receiving a CSI-RS configuration message with RRC parameters. The terminal 102 applies the RRC parameters to the standard-defined CSI-RS resource mapping scheme 110 to at least determine the resource elements 118 that will be used by the network node 108 to transmit the reference signals 116 and that are to be measured by the terminal 102. The standard-defined CSI-RS resource mapping scheme 110 maintained at the terminal 102 is defined by at least one revision of the 3GPP communication specification where the standard-defined CSI-RS resource mapping scheme defines 18 different reference signal transmission modes and supports 32 logical antenna ports. As discussed above, the network node 108 is limited to receiving CSI reports from a terminal for 32 logical antenna ports in conventional systems. Accordingly, antenna systems with more than 32 logical antenna ports that utilize conventional techniques are unable to fully take advantage of the additional performance offered by antenna arrays including more than 32 antenna elements. For the examples herein, however, the network node 108 receives CSI reports 112 providing feedback from more than 32 logical antenna ports even though the terminal 102 is configured with the standard-defined CSI-RS resource mapping scheme 110 for 32 logical ports. Generally, where the CSI-RS resource mapping scheme 110 at the terminal 102 supports a number (MSLP) of mapping scheme logical ports and the antenna system 106 at the network node 108 includes a number (NLP) of logical antenna ports 104, the network node 108 configures the terminal 102 to provide feedback for more than MSLP logical ports. Therefore, the network node 108 is able to more effectively manage communication through an antenna array having NAE antenna elements where NAE > MSLP and NLP > MSLP.

[0035] The examples described herein include at least two types of density-adjusted CSI-RS resource mapping schemes, a resource-adjusted CSI-RS resource mapping scheme, and a dynamic CSI-RS resource mapping scheme where the network node switches between a density-adjusted CSI-RS resource mapping scheme and a resource-adjusted CSI-RS resource mapping scheme based on conditions. In one density-adjusted CSI-RS resource mapping scheme example, the density-adjusted CSI- RS resource mapping scheme includes a set of CSI-RS transmission modes identical tothe set of 18 CSI-RS transmission modes of the standard-defined CSI-RS resource mapping scheme except that at least some of the transmission modes only use a density reference signal transmission rate that that is lower than 1 .0. Since the resource elements are not used in every time slot for a single transmission mode, different reference signal transmissions may be applied in different resource blocks using that transmission mode. As a result, the network node 108 can transmit reference signals for feedback pertaining to logical antenna ports in addition to the 32 logical antenna ports supported by the standard-defined CSI-RS resource mapping scheme 110. The total number of transmission modes available for configuration is increased by the number of transmission modes only using the lower density transmission rates. For a more specific example, where a transmission mode in the standard-defined CSI-RS resource mapping scheme allows for density transmission rates of 1.0 and 0.5, the network node 108 may utilize the 0.5 density transmission rate such that first reference signals associated with a first set of logical ports are transmitted in odd time resource blocks and second reference signals associated with a second set of logical ports are transmitted in even resource blocks. The network node 108 sends one or more CSI-RS configuration messages 122 to the terminal 102 where the RRC parameters identify a transmission density rate less than 1.0 for a transmission mode in the standard-defined CSI-RS resource mapping scheme 110. Based on the received RRC parameters and the standard-defined CSI-RS resource mapping scheme 110, the terminal 102 determines the transmission mode and identifies the resource elements in the designated resource block (designed time slot period) where the reference signals will be transmitted. The terminal 102 receives and measures the reference signals 116 as dictated by the RRC parameters and the standard-defined CSI-RS resource mapping scheme 110 and reports the measurements in the CSI report 112.

[0036] In another example of a density-adjusted CSI-RS resource mapping scheme, the density-adjusted CSI-RS resource mapping scheme includes a set of CSI-RS transmission modes identical to the set of 18 CSI-RS transmission modes of the conventional standard-defined CSI-RS resource mapping scheme except that at least some of the transmission modes include one or more additional density reference signal transmission rates that are lower than the conventional density reference signaltransmission rate(s) for the transmission mode. As a result, the total number of transmission modes available for configuration is increased by a number of transmission modes determined by the number of transmission modes with additional density transmission rates, the number of additional density transmission rates, and the values of the additional density transmission rates. Such a technique, however, may require that the standard-defined CSI-RS resource mapping scheme 110 configured at the terminal 102 includes the additional transmission density rates. In some situations, the CSI-RS configuration message, or other signaling from the network node 108, may indicate that one or more transmission modes are to be used with an additional density reference signal transmission rate. In some deployments, therefore the CSI-RS configuration message comprises a standard-defined density parameter indicating a standard-defined density of the transmission mode of the standard-defined CSI-RS resource mapping scheme and a density override parameter indicating that the CSI-RS transmission will be transmitted at a lower density than the standard-defined density. In other deployments, the CSI-RS configuration message comprises a standard-defined density parameter indicating a standard-defined density of the transmission mode of the standard-defined CSI-RS resource mapping scheme and the network node transmits a density override parameter indicating that the CSI-RS transmission will be transmitted at a lower density than the standard-defined density where the density override parameter is transmitted in a message different from the CSI-RS configuration message.In still other deployments, the standard-defined CSI-RS resource mapping scheme includes densities less than 1 for at least one standard-defined transmission mode supporting 2 logical ports, at least one standard-defined transmission mode supporting 4 logical ports, at least one standard-defined transmission mode supporting 8 logical ports, and at least one standard-defined transmission mode supporting 12 logical ports. For example, an RRC parameter in the CSI-RS configuration message may indicate that the transmission modes in the standard-defined CSI-RS resource mapping scheme 110 that include a 0.5 density also include a 0.25 density. Such signaling and changes to the standard-defined CSI-RS resource mapping scheme may be need to be defined by a standard body.

[0037] In another example, a resource-adjusted CSI-RS mapping scheme uses additional resources for one or more transmission modes of the standard-defined CSI- RS resource mapping scheme. Such a scheme may be interpreted as scheme that defines a set of CSI-RS transmission modes including the set of 18 CSI-RS transmission modes of the standard-defined CSI-RS resource mapping scheme and additional transmission modes since one or more the conventional transmissions modes are “reused”. Each additional transmission mode is based on one of the 18 CSI-RS transmission modes of the conventional CSI-RS mapping scheme with different resource elements. In other words, an additional transmission mode is identical to one of the conventional transmission modes except that the resource elements 118 used for the transmission are different from the resource elements 118 used for transmission of the conventional transmission mode.

[0038] In other examples, the network node 108 may dynamically switch from using a density-adjusted CSI-RS resource mapping scheme and a resource-adjusted CSI-RS resource mapping scheme based on conditions. For example, the network node 110 may send a CSI-RS configuration message 122 that results in a transmission mode where the reference signals are transmitted in even time slot periods when the mobility of the terminal 102 is low. If the mobility of the terminal 102 increases, the network node may send another CSI-RS configuration message 122 to utilize a resource-adjusted CSI-RS resource mapping scheme where additional resource elements are used to transmit reference signals in every time slot period. Therefore, the network node 108 may select a transmission mode from one of multiple CSI-RS resource mapping schemes based on conditions. The mobility may be determined by tracking the position of the terminal to determine the speed in some situations. In many situations, however, the network or network node does not have such a capability. The network node may track the communication performance as an indicator of mobility. For example, the Bit Error Rate (BER) or Channel Estimation may be monitored. In other examples, the network node may estimate mobility based on the HARQs or the UE CSI feedback to monitor channel conditions. Other factors may cause or contribute to lower performance in addition to mobility. Adjustments to the CSI-RS resource mapping scheme, therefore, may be made by the network node in response to changes in measurements,parameters and / or information provided by the terminal where changes in such measurements, parameters and information may or may not be indicative of changes in mobility but nonetheless may warrant a change in the CSI-RS mapping scheme and transmission.

[0039] Generally, therefore, the network node 108 utilizes a standard-defined CSI- RS resource mapping scheme 110 defined for 32 logical ports to configure a terminal 102 for CSI reporting where an antenna system 106 of the network node 108 includes more than 32 logical antenna ports 104. Although the terminal 102 is using the standard-defined CSI-RS mapping scheme 110 maintained at the terminal 102 and limited to 32 logical ports, the terminal 102 is capable of providing CSI feedback for more than 32 logical ports. The network node 108 efficiently manages reference signal transmissions by selecting between at least a density-adjusted CSI-RS resource mapping scheme and a resource-adjusted CSI-RS resource mapping scheme that both use the standard-defined CSI-RS resource mapping scheme 110 maintained at the terminal 102.

[0040] FIG. 2 is a block diagram of an example of a base station 200 suitable for use as a network node 108. The base station 200 includes electronics 204, a transmitter 206, a receiver 208, and the antenna system 106, as well as other electronics, hardware, and code. The base station 200 is any fixed, mobile, or portable equipment that performs the functions described herein. The various functions and operations of the blocks described with reference to the base station 200 and network node 102 may be implemented in any number of devices, circuits, or elements. Two or more of the functional blocks may be integrated in a single device, and the functions described as performed in any single device may be implemented over several devices. The base station 200 may be a fixed device or apparatus that is installed at a particular location at the time of system deployment. Examples of such equipment include fixed base stations or fixed transceiver stations. Although the base station may be referred to by different terms, the base station is typically referred to as a gNodeB or gNB when operating in accordance with one or more revisions of the 3GPP communication specification. In some situations, the base station 200 may be mobile equipment that is temporarily installed at a particular location. Some examples of such equipment includemobile transceiver stations that may include power generating equipment such as electric generators, solar panels, and / or batteries. Larger and heavier versions of such equipment may be transported by trailer. In still other situations, the base station 200 may be a portable device that is not fixed to any particular location.

[0041] The electronics 204 include any combination of hardware, software, and / or firmware for communicating with and controlling other base station components to execute the functions described herein as well as facilitating the overall functionality of the base station 200. The electronics 204, therefore, cooperatively operate with other base station 200 components to initiate tasks and perform the operations and functions of the base station 200. An example of suitable electronics 204 includes code running on a microprocessor or processor arrangement connected to memory 214. The transmitter 206 includes electronics configured to transmit wireless signals. In some situations, the transmitter 206 may include multiple transmitters. The receiver 208 includes electronics configured to receive wireless signals. In some situations, the receiver 208 may include multiple receivers. The receiver 208 may receive signals through multiple antennas or through a selected antenna of the antenna system 106. The antenna system 106 may include separate transmit and receive antennas in some situations.

[0042] The transmitter 206 and receiver 208 in the example of FIG. 2 perform radio frequency (RF) processing including modulation and demodulation. The receiver 208, therefore, may include components such as low noise amplifiers (LNAs) and filters. The transmitter 206 may include filters and amplifiers. Other components may include isolators, matching circuits, and other RF components. These components in combination or cooperation with other components perform the base station functions. The required components may depend on the particular functionality required by the base station 200.

[0043] The transmitter 206 includes a modulator (not shown), and the receiver 208 includes a demodulator (not shown). The modulator modulates the signals to be transmitted as part of the downlink signals and can apply any one of a plurality of modulation orders. The demodulator demodulates any uplink signals received at the base station 200 in accordance with one of a plurality of modulation orders. Theelectronics 204 in conjunction with the transmitter 206 apply a precoder matrix to signals transmitted through the multiple antennas 210.

[0044] The base station 200 includes a communication interface 212 for communicating with other base stations and other network components, and other entities, such as servers and databases. The communication interface 212 may be connected to a backhaul or network enabling communication with other base stations. In some situations, the link between base stations may include at least some wireless portions. The communication interface 212, therefore, may include wireless communication functionality and may utilize some of the components of the transmitter 206 and / or receiver 208.

[0045] The electronics 204, in conjunction with the receiver 208, measure and evaluate signals transmitted by UE devices. The electronics 204 and the receiver 208, therefore, can receive, measure, and evaluate uplink signals including reference signals transmitted by UE devices. Signal measurements and evaluations can be stored in a memory 214 and are used to determine the location of UE devices in some circumstances.

[0046] The electronics 204, in conjunction with the transmitter 206 and antenna system 106, process outgoing signals to precode signals transmitted to terminals (UE devices). Accordingly, the electronics 204 and transmitter 206 apply the appropriate MU -Ml MO precoder to signals transmitted to a specific UE device. As discussed herein, the base station 200 may transmit reference signals and receive feedback from the terminals in order to determine the appropriate precoders, antenna system settings, and other transmission parameters.

[0047] FIG. 3 is a block diagram of an example of a UE device 300 suitable for use as a terminal device 102. In some examples, the UE device 300 is any wireless communication device such as a mobile phone, a transceiver modem, a personal digital assistant (PDA), a tablet, or a smartphone. In other examples, the UE device 300 is a machine type communication (MTC) communication device or Internet-of-Things (IOT) device. The UE device 300, therefore is any fixed, mobile, or portable equipment that performs the functions described herein. The various functions and operations of theblocks described with reference to UE device 300 may be implemented in any number of devices, circuits, or elements. Two or more of the functional blocks may be integrated in a single device, and the functions described as performed in any single device may be implemented over several devices.

[0048] The UE device 300 includes at least electronics 302, a transmitter 304 and a receiver 306. The electronics 302 include any combination of hardware, software, and / or firmware for communicating with and controlling other UE device components to execute the functions described herein as well as facilitating the overall functionality of a communication device. The electronics 302, therefore, cooperatively operate with other UE device components to initiate tasks and perform the operations and functions of the UE device 300. An example of suitable electronics 302 includes code running on a microprocessor or processor arrangement connected to memory 310. The transmitter 304 includes electronics configured to transmit wireless signals. In some situations, the transmitter 304 may include multiple transmitters. The receiver 306 includes electronics configured to receive wireless signals. In some situations, the receiver 306 may include multiple receivers. The receiver 306 and transmitter 304 receive and transmit signals, respectively, through antenna 308. The antenna 308 may include separate transmit and receive antennas. In some circumstances, the antenna 308 may include multiple transmit and receive antennas.

[0049] The transmitter 304 and receiver 306 in the example of FIG. 3 perform radio frequency (RF) processing including modulation and demodulation. The receiver 306, therefore, may include components such as low noise amplifiers (LNAs) and filters. The transmitter 304 may include filters and amplifiers. Other components may include isolators, matching circuits, and other RF components. These components in combination or cooperation with other components perform the communication device functions. The required components may depend on the particular functionality required by the communication device.

[0050] The transmitter 304 includes a modulator (not shown), and the receiver 306 includes a demodulator (not shown). The modulator can apply any one of a plurality of modulation orders to modulate the signals to be transmitted as part of the uplink signals.The demodulator demodulates the downlink signals in accordance with one of a plurality of modulation orders.

[0051] The UE device 300 is capable of transmitting and receiving sidelink signals to and from other UE devices as well as communicating with base stations. The electronics 302, in conjunction with the receiver 306, measure an evaluate signals transmitted by other devices, such as base stations and UE devices. The electronics 302 and the receiver 306, therefore, can receive, measure, and evaluate downlink reference signals transmitted by a base station. Signal measurements and evaluations can be stored in the memory 310. The electronics 302 and receiver 306 can also receive, measure and evaluate discovery signals transmitted by nearby UE devices to generate a neighbor list that includes neighbor UE devices within the maximum distance. The neighbor list is stored in the memory 310 and may be transmitted to a base station.

[0052] FIG. 4 is a block diagram of an example of an antenna system 400 suitable for use as the antenna system 106. Port-element mapping function 402 maps the plurality of logical antenna ports to the plurality of physical antenna elements 404 of the antenna array 114. Each antenna port has a dedicated resource grid of resource blocks (RBs) including resource elements (REs). The resource grids are used to allocate resources for transmission and reception. The data symbols of data to be transmitted are precoded where the precoding prepares the data for transmission over multiple antenna elements. The precoded data symbols are then mapped to the resource elements in the resource grid. The port-element mapping maps a logical antenna port to a single physical antenna element or to multiple physical antenna elements.

[0053] FIG. 5 is an illustration of an example of a standard-defined CSI-RS resource mapping scheme table 500 that represents the standard-defined CSI-RS source mapping scheme 110. The table 500 is a representation of the “Table 7.4.2.5.3-1 : CSI- RS locations within a slot” of Release 18 of the 3GPP communication specification which is a suitable example of a table that may represent the standard-defined CSI-RS resource mapping scheme 110 configured at the terminal 102. In some situations, other schemes may be used for the standard-defined CSI-RS resource mapping scheme 110.For example, the standard-defined CSI-RS resource mapping scheme 110 may be a new mapping scheme issued in a future release of the 3GPP communication specification that revises the current standard-defined CSI-RS resource mapping scheme.

[0054] The table 500 includes 18 rows 502 of transmission modes defined by information in six columns for parameters, values, and relationships including a number of ports (X) 504, a transmission density rate (p) 506, a cdm-Type 508,510, a CDM group index ( / ) 512, k' 514, and I' 516. A terminal 102 receives RRC parameters in the CSI-RS configuration message 122 that at least include the frequency domain allocation, number of ports, cdm-Type, the location of the first OFDM symbol in the time domain and the transmission density corresponding to a row of the table. The terminal 102 matches the parameters to the table (i.e., scheme) to identify the row (transmission mode) and then applies the parameters and calculations associated with the identified row (transmission mode) to determine the resource elements that will be used to transmit the reference signals to be measured by the terminal 102. For example, the terminal evaluates the RRC parameters identifying the number of ports (X) and the cdm-Type to determine the transmission mode (i.e., row). As discussed above, the standard-defined CSI-RS resource mapping scheme 110 is limited to transmission modes for 32 ports. In the examples below, however, the network node 108 utilizes the standard-defined CSI-RS resource mapping scheme 110 to implement CSI-RS resource mapping schemes that support more than 32 ports.

[0055] For density-adjusted examples, the network node transmits a CSI-RS configuration message identifying a RS density transmission rate (density) less than 1.0 for a transmission mode and manages the RS transmission modes such that the resource elements are re-used over multiple resource blocks for different RS transmissions at different times which facilitate CSI reporting that supports different logical ports. For resource-adjusted examples, the network node 108 transmits a CSI- RS configuration message identifying additional resources for a transmission mode in the standard-defined CSI resource mapping scheme and manages the RS transmission modes such that the resource elements allow for RS transmissions that support CSI reporting for more than 32 ports.

[0056] FIG. 6A is a block diagram of an example of resource block transmissions of a density-adjusted CSI resource mapping scheme supporting 64 logical antenna ports. For the example of FIG. 6A, the network node identifies one or more transmission modes in the standard defined CSI resource mapping scheme 110 that will be limited to a RS transmission density of 0.5. Resource elements 602 within an odd resource block 604 are designated for a first set of RS transmissions supporting a first set of 32 logical antenna ports and resource elements 606 within an even resource block 608 are designated for a second set of RS transmissions supporting a second set of 32 logical antenna ports. The selected transmission mode(s) may include a single transmission mode supporting 32 logical antenna ports or a combination of transmission modes that support 32 logical antenna ports in the aggregate. For example, the network node may select the transmission mode of row 16 of the standard-defined CSI resource mapping scheme. With such a section, for example, the network node may utilize the resource elements of the odd resource block for RS transmissions associated with logical antenna ports 1 -32 and may utilize the same resource elements in the even resource block for RS transmissions associated with logical antenna ports 33-64 where the RS transmissions are in accordance with the transmission mode of row 16. In another example, the network node may select the transmission modes of rows 11 and row 12 such that the 16 ports of each transmission mode combine to support logical ports 32- 64 with RS transmissions in the even resource block.

[0057] FIG. 6B is a block diagram of an example of resource block transmissions of a density-adjusted CSI resource mapping scheme supporting 48 logical antenna ports. For the example of FIG. 6A, the network node identifies one or more transmission modes in the standard defined CSI resource mapping scheme that will be limited to a RS transmission density of 0.5. Resource elements 610 within an odd resource block 612 are designated for a first set of RS transmissions supporting a first set of 32 logical antenna ports and resource elements 614 within an even resource block 616 are designated for a second set of RS transmissions supporting an additional set of 16 logical antenna ports. The selected transmission mode(s) may include a single transmission mode supporting 16 logical antenna ports or a combination of transmission modes that support 16 logical antenna ports in the aggregate. For example, the networknode may select the transmission mode of row 11 of the standard-defined CSI resource mapping scheme. With such a section, for example, the network node may utilize the resource elements of the odd resource block for RS transmissions associated with logical antenna ports 1 -32 and may utilize a subset of the same resource elements in the even resource block for RS transmissions associated with logical antenna ports 33- 48 where the RS transmissions are in accordance with the transmission mode of row 11.

[0058] In some examples, the density-adjusted CSI-RS resource mapping scheme includes using one or more additional densities for one or more transmission modes in the standard-defined CSI-RS resource mapping scheme. In one example, the standard- defined CSI-RS resource mapping scheme 110 is modified to include the additional densities. Such an implementation may require a revision of the 3GPP specification. In other words, a future release of the 3GPP specification may include a revised version of Table 7.4.2.5.3-1. An example of such a table is discussed below with reference to FIG. 7.

[0059] In a second example, the network node 108 sends an indication to the terminal that an additional density should be used for a transmission mode listed in the standard-defined CSI-RS reference mapping scheme 110. In one implementation of the second example, the network node 108 includes an indicator in the CSI configuration message. For example, an additional field in the CSI configuration message may indicate a density of 0.5 for a transmission mode in the standard-defined CSI-RS resource mapping scheme that includes only a density of 1 .0. More specifically, the CSI configuration message may include RRC parameters indicating row 8 is being used but may also include an indicator that 0.5 should be used for the density. As a result, the terminal 102 applies the transmission mode for row 8 in accordance with conventional techniques except that the terminal determines that the reference signals will be transmitted in every other resource block (e.g., even resource blocks). In one specific example of such a technique, the network node 108 utilizes a CSI-RS resource mapping scheme where the transmission modes of rows 7 and 8 are used to provide support for additional logical ports to enable a scheme that supports 48 logical ports. The resources of the transmission modes of row 7 and row 8 are reused fortransmissions in the even resource blocks to support 16 additional ports (e.g., ports 33- 48). Such an arrangement could also be used to support 64 logical ports where rows 7 and 8 are used in combination with row 11 , at a density of 0.5, to support 32 additional ports.

[0060] FIG. 7 is an illustration of an example of a modified standard-defined CSI-RS resource mapping scheme table 700. The table 700 is a representation of a modified version of the “Table 7.4.2.5.3-1 : CSI-RS locations within a slot” of Release 18 except that rows 4-10 include the additional density of 0.5. Accordingly, the transmission modes associated with these rows can be utilized in a density-adjusted CSI-RS resource mapping scheme to support additional antenna ports. As discussed above, for example, transmission modes at the reduced density (e.g. 0.5) for rows 7, 8, and 11 can be combined to support 32 additional ports in a mapping scheme for 64 ports.

[0061] FIG. 8 is an illustration of an example of a modified standard-defined CSI-RS resource mapping scheme table 800. The table 800 is a representation of a modified version of the “Table 7.4.2.5.3-1 : CSI-RS locations within a slot” of Release 18 except that rows 16, 17, and 18 include the additional density of 0.25. Accordingly, the transmission modes associated with these rows can be utilized in a density-adjusted CSI-RS resource mapping scheme to support additional antenna ports. In an example of a mapping scheme that supports 128 ports, the resources for 32 ports can be reused over three additional resource blocks such that a first RB includes resources for CSI-RS transmission to support ports 1 -32, a second RB includes resources for CSI-RS transmission to support ports 33-64, a third RB includes resources for CSI-RS transmission to support ports 65-96 and a fourth RB includes resources for CSI-RS transmission to support ports 97-128.

[0062] FIG. 9 is a block diagram of an example of resource block transmissions of a density-adjusted CSI resource mapping scheme supporting 128 logical antenna ports. For the example of FIG. 9, the network node identifies one or more transmission modes in the revised standard-defined CSI resource mapping scheme 800 that will be limited to a RS transmission density of 0.25. Resource elements 902 within a first resource block 904 are designated for a first set of RS transmissions supporting a first set of 32 logical antenna ports (ports 1-32). Resource elements 906 within a second resource block 908are designated for a second set of RS transmissions supporting a second set of 32 logical antenna ports (ports 33-64). Resource elements 910 within a third resource block 912 are designated for a third set of RS transmissions supporting a third set of 32 logical antenna ports (ports 65-96). Resource elements 914 within a fourth resource block 916 are designated for a fourth set of RS transmissions supporting a fourth set of 32 logical antenna ports (ports 97-128). The RS transmission for the first set of ports is repeated over the resource elements 902 in the fifth resource block 918. The RS transmission for the second set of ports is repeated over the resource elements 908 in the sixth resource block 920. Accordingly, the transmissions in a manner such that reference signals for a set of ports is repeated every fourth resource block.

[0063] FIG. 10A is a block diagram of an example of an odd resource block 1000 for a density-adjusted CSI-RS resource mapping scheme supporting 64 logical antenna ports where the transmission mode includes a cdm-Type of fd-CDM2, and FIG. 10B is a block diagram of an example of an even resource block 1002 for the density-adjusted CSI-RS resource mapping scheme. For the examples of FIG. 10A and FIG. 10B, the network node selects the transmission mode of row 16 of the standard-defined CSI-RS resource mapping scheme and selects an RS transmission density of 0.5. Resource elements 1004 within the odd resource block 1000 are designated for a first set of RS transmissions supporting a first set of 32 logical antenna ports. Resource elements 1006 within the even resource block 1002 are designated for a second set of RS transmissions supporting a second set of 32 logical antenna ports (ports 33-64). Each square associated with a resource in the illustration of the resource blocks includes multiple port numbers to indicate that a time-frequency resource supports simultaneous reference signal transmission with Code Division Multiplexing (CDM). Since the cdm- Type is fd-CDM2 for the example, each square includes two numbers with plus (+) or minus (-) sign. The pluses and minuses associated with each port number represent the orthogonality between the ports when reference signals are transmitted simultaneously from multiple ports. These orthogonal cover codes are defined in at least one revision of the 3GPP specification for the four CDM types found in the transmission modes of the standard-defined CSI-RS resource mapping scheme. TS 38.211 defines the orthogonalcovers. For example, CDM2 and CD4 are defined in the Table 7.4.1 .5.3-3 and Table 7.4.1 .5.3-4 below.

[0064] Table 7.4.1.5.3-3: The sequencesWf^ andfor cdm-Type equal to 'fd-CDM2' are shown as:

[0065] Table 7.4.1.5.3-4: The sequencesfor cdm-Type equal to'cdm4-FD2-TD2'.

[0066] FIG. 11 is a block diagram of an example of a resource block 1100 of a resource-adjusted CSI-RS resource mapping scheme supporting 48 logical antenna ports. The network node identifies one or more transmission modes in the standard- defined CSI-RS resource mapping scheme that will be utilized for a first set of antenna ports and also used for a second set of antenna ports using different resource elements of the resource block. For the example of FIG. 11 , a first set of antenna ports (ports CI- 31 ) are supported by reference signal transmissions over a first set of resource elements 1102 and a second set of antenna ports (ports 32-47) are supported by reference signal transmissions over a second set of resource elements 1104. FIG 11 shows the first set of resource elements 1102 with single cross-hatching and the second set of resource elements 1104 with double cross-hatching. The numbers indicate the port numbers and the pluses and minuses associated with each port number represent the orthogonality between the ports when reference signals are transmitted simultaneously from multiple ports. The example of FIG. 11 is based on a cdm-Type of fd-CDM2. Accordingly, each square includes two numbers with plus (+) or minus (-) sign. Additional resources elements can be used to support additional antenna ports. For example, the second set of resource elements 1104 can be extended to includeOFDM symbols 11 and 12 for reference signal transmissions supporting 64 antenna ports.

[0067] FIG. 12 is a block diagram of the system 100 for an example where the network node 108 switches between a resource-adjusted CSI-RS resource mapping scheme and a density-adjusted CSI-RS resource mapping scheme. For the example, the number (NLP) of logical antenna ports 104 in the antenna system 106 is greater than a number of logical antenna ports (MSLP) defined by the standard-defined CSI-RS resource mapping scheme 110 used by the terminal 102. Also, for the example, the number of antenna elements (NAE) of the antenna array 114 at the network node 108 is greater than 32 and the number (NLP) of logical antenna ports 104 is greater than 32. As discussed above, the network node 108 configures the terminal 102 to receive and measure the reference signals 116 and to report the results of the measurements in CSI reports 112. The network node 108 evaluates conditions and selects a selected CSI-RS resource mapping scheme from at least two CSI-RS resource mapping schemes including a resource-adjusted CSI-RS resource mapping scheme and a density- adjusted CSI-RS resource mapping scheme. As discussed above, the resource- adjusted CSI-RS resource mapping scheme and a density-adjusted CSI-RS resource mapping scheme allow the network node 108 to receive CSI reports 112 providing feedback from more than 32 logical antenna ports even though the terminal 102 is configured with the standard-defined CSI-RS resource mapping scheme 110 for 32 logical ports. In response to a change in conditions, the network node 108 may switch from the resource-adjusted CSI-RS resource mapping scheme to the density-adjusted CSI-RS resource mapping scheme and vice versa.

[0068] For the example of FIG. 12, the network node 108 selects the resource- adjusted CSI-RS resource mapping scheme and sends a CSI-RS configuration message 1202 including RRC parameters for the resource-adjusted CSI-RS resource mapping scheme. The terminal 102 evaluates the RRC parameters and identifies the transmission mode of the standard-defined CSI-RS resource mapping scheme 110. The terminal 102 applies the RRC parameters to the transmission mode to calculate, or otherwise determine, the resource elements being used for the reference signal transmission by the network node 108.

[0069] The network node 108 transmits the reference signals 1204 for the resource- adjusted CSI-RS resource mapping scheme and the terminal 102, based on the CSI-RS configuration message 1202, receives and measures the received signals transmitted over the resources 1206 identified by the CSI-RS configuration message. As discussed above, the resource-adjusted CSI resource mapping scheme used by the network node 108 results in the use of resource elements 1206 in addition to the resource elements used by the standard-defined CSI-RS resource mapping scheme 110. The RRC parameters provided by the network node in CSI-RS configuration message identify the additional resource elements 1206 within the resource block 1208 that support the additional antenna ports. As a result, the transmission mode of the standard-defined CSI-RS resource mapping scheme 110 may be used for the first set of antenna ports using a first set of resources and reused for a second set of antenna ports with a second set of resources. The terminal generates a CSI report 1210 including the measurements of the reference signals 1204 and sends the CSI report 1210 to the network node 108.

[0070] The network node 108 monitors communication conditions and, in response to determining that conditions have changed such that a different CSI-RS resource mapping scheme should be used, selects another CSI-RS resource mapping scheme. An example of a condition that is monitored includes the mobility of the terminal, such as the speed of movement of the terminal. Other examples include the level of communication traffic, the availability of communication resources, and the level of service required by the terminal device as well as the level of service required by other terminal devices in the area.

[0071] Therefore, dynamic management of CSI-RS resource scheme selection leverage strengths of a density-adjusted CSI-RS resource mapping scheme and a resource-adjusted CSI-RS resource mapping scheme. The dynamic-selection CSI-RS resource scheme facilitates configuration adjustments to meet varying network conditions and terminal capabilities, optimizing capacity and coverage without sacrificing overall service quality.

[0072] The network node may employ one or more performance-related criteria to select the CSI-RS resource mapping scheme for a specific terminal. After evaluatingthese criteria, the network node selects the most suitable CSI-RS transmission method for the terminal and configures, or reconfigures, the terminal with the selected mapping scheme to report the Channel State Information to the network node. Some examples of such performance specific criteria for selecting the appropriate CSI-RS transmission mode include terminal capabilities, terminal location within the serving cell, geometry of the terminal, cell traffic load, QoS requirements, and any combination thereof.

[0073] For the examples, the terminal informs the network node of the capability of the terminal to support either one or both of the density-adjusted CSI-RS resource mapping scheme and the resource-adjusted CSI resource mapping scheme. In situations where the terminal indicates support for only one scheme, the network node configures the terminal with that specific scheme. Where the terminal indicates that it can support more than one CSI-RS transmission scheme, the network node dynamically configures the terminal based on conditions.

[0074] The network node may select a scheme based on a location of the terminal within the cell. When the terminal is closer to the network node (gNodeB), for example, the network node may select the resource-adjusted CSI-RS resource mapping scheme. Such a selection may be beneficial since terminals near the gNB typically report higher modulation, and channel estimation quality becomes crucial at high SNR levels. Conversely, when the terminal is located at the cell edge, the gNB may configure the terminal with the density adjusted CSI-RS resource mapping scheme.

[0075] Examples of techniques that can be used by the network node to determine the location of the terminal include one or more positioning techniques and / or signal measurements relevant to radio operations. Positioning methods and their respective measurements include GNSS (e.g., GPS) measurements, enhanced cell ID (E-CID) measurements such as UE or BS Rx-Tx time difference measurements, timing advance (TA), angle of arrival (AoA), and OTDOA RSTD. Examples of signal measurements pertinent to radio operations include reported CQIs and mobility-related measurements such as RSRP and RSRQ measurement reports. Additionally, the size of the Neighbor Cell List (NCL) required by the UE may also indicate whether the terminal is near the cell center. For example, if the serving cell's RSRP is below a certain threshold (e.g., - 100 dBm), the gNB may infer that the terminal is near the cell border.

[0076] In some situations, the network node evaluates the terminal’s geometry in selecting the appropriate CSI-RS resource mapping scheme. At low geometries (e.g., lower SINR), a terminal is inclined to opt for a lower modulation scheme which may lead to the network node selecting the density-adjusted CSI-RS resource mapping scheme. Conversely, at high geometries (e.g., higher SINR), where a higher data rate is achievable, the terminal is better suited for a higher modulation scheme. The network node may select the resource-adjusted CSI-RS resource mapping scheme. On example of the determining the geometry of the terminal includes calculating the average SINR through uplink channel estimates or by averaging the CQI reported by the terminal.

[0077] For the examples herein, network node evaluates the cell traffic load in selecting the CSI-RS resource mapping scheme. High traffic volumes may lead to congestion which affects the ability of the terminal to effectively communicate with the network node. To mitigate such a condition, the network node adjusts the CSI-RS transmission based on real-time traffic load analysis. During peak traffic periods, for example, the network or network node may select a CSI-RS resource mapping scheme that prioritizes efficiency and bandwidth conservation such as CSI-RS transmission scheme with reduced density. As a result, the network node may select the density- adjusted CSI-RS resource mapping scheme during such situations. Such a dynamic adjustment ensures that the network remains resilient under varying load conditions, maintaining optimal service quality for all users. The network node may determine the traffic load using any of several methods and techniques. Some examples of suitable techniques include measurement of Physical Resource Block (PRB) usage, evaluating an active user count, evaluating uplink and downlink traffic volume, evaluating Quality of Service (QoS) metrics, evaluating interference measurements, and applying machine learning algorithms.

[0078] Where measurement of PRB usage is applied, the network node monitors the utilization of PRBs, which are the smallest units of radio resources in LTE and 5G NR networks. By analyzing the percentage of PRBs in use over time, the network node can estimate the current traffic load. Where an active user count is evaluated, the network node counts the number of active users or sessions at any given time and estimates the traffic load based on the suer count. Such a technique may consider users in both thedata transfer state and those in the signaling state. Where uplink and downlink traffic volume is evaluated, the network node monitors the total uplink and downlink data volume over time which provides information regarding the traffic load in the network. Such a technique may include the analysis of the volume of data packets or bytes transmitted and received by the network node. In evaluating QoS metrics, the network node may analyze QoS metrics such as packet delay, packet loss rate, and data throughput to estimate or determine the traffic load. High delays or loss rates may suggest congestion and high traffic load. The network node may evaluate interference measurements where higher levels of interference in the radio environment indirectly indicate a high traffic load because more active users typically generate more interference. Machine learning algorithms may be utilized to predict traffic load based on historical data and real-time network metrics. These algorithms can analyze complex patterns in data usage, user mobility, and network performance indicators to forecast traffic load with high accuracy.

[0079] Quality of Service (QoS) requirements are important for tailoring the CSI-RS transmission to the needs of different services and applications. Each application, such as real-time voice, video streaming, or loT communications, has unique requirements in terms of latency, data rate, and reliability. By analyzing the QoS requirements of the active services of the terminal, the network node can select a CSI-RS transmission scheme that aligns with these needs. For example, applications requiring low latency and high reliability might benefit from a transmission technique with higher CSI-RS density, ensuring more accurate channel information for optimal performance. Accordingly, the network may select the resource-adjusted CSI-RS resource mapping scheme in these situations. Such an approach allows the network to efficiently allocate resources and ensure that QoS expectations are met or exceeded. The network node may determine the Quality of Service (QoS) requirements of terminals through a combination of predefined QoS profiles for various services, explicit signaling from the terminals, and network policies. Examples of suitable techniques include evaluating parameters and situations such as predefined QoS profiles, terminal signaling, Application Function (AF) communication, dynamic QoS negotiation, and network policies and user subscriptions. Once the service is active, the network node and thenetwork continue to monitor service quality and may adjust QoS parameters in real-time to adapt to changing network conditions, ensuring that the agreed QoS requirements are met.

[0080] Where the predefined QoS profiles are evaluated, the network node examines standard QoS profiles defined by the networks for different types of services, such as voice, video streaming, online gaming, and loT applications. Each profile specifies parameters such as priority level, packet delay budget, packet error rate, and guaranteed bit rate. As service is associated with a corresponding QoS profile when the service is initiated.

[0081] During the setup of a new service or communication session, the terminal may signal the QoS requirements to the network. This is often done through the Radio Resource Control (RRC) protocol, where the terminal includes details about the service type and the QoS expectations in the connection or service request.

[0082] For certain services, especially those requiring application-level awareness, an Application Function within the network can communicate the service's QoS requirements to the Policy Control Function (PCF) or similar entities responsible for policy enforcement. Such a technique is common in networks utilizing network function virtualization (NFV) and service-based architectures such as those in 5G. Accordingly, the network node may monitor the AF communication to determine QoS.

[0083] In some scenarios, QoS requirements can be dynamically negotiated between the terminal and the network based on current network conditions, UE capabilities, and service needs. This dynamic adjustment allows for more efficient resource utilization and ensures service quality even under varying network conditions.

[0084] Where network policies and user subscriptions are evaluated to determine the QoS, the network or network node considers the user's subscription details and network policies. For example, a premium subscription may guarantee higher data rates and priority for certain services. Network policies might also dictate QoS levels based on current network load, with the aim of optimizing overall performance and fairness among users.

[0085] The determination or estimation of QoS requirements may be performed using one or more of the techniques discussed above in addition to other techniques. Inaddition, the network node may use any combination of the parameters and criteria discussed above to select the CSI-RS resource mapping scheme.

[0086] For the example, the network node 108 selects the density-adjusted CSI-RS resource mapping scheme. Such as selection may be based on the network node determining that the mobility of the terminal 102 is sufficiently low or that the terminal is no longer in motion. The selection may further be based on a determination that communication resources should be directed to the transmission of other reference signals. In the interest of efficiency, therefore, the network node 108 may select different CSI-RS resource mapping schemes for different terminals. The selection of the selected CSI-RS resource mapping scheme may be based on a plurality of conditions and / or one or more algorithms designed to maximize efficient communication. The selection may also be dynamic such that different algorithms or thresholds may be applied based on the communication conditions and / or other factors. In some situations, Artificial Intelligence (Al) or machine learning techniques may be applied to select the CSI-RS resource mapping schemes.

[0087] After selecting the density-adjusted CSI-RS resource mapping scheme, the network node 108 generates and transmits, to the terminal, a CSI-RS configuration message with RRC parameters for the density-adjusted CSI-RS resource mapping scheme 1212.

[0088] The terminal 102 evaluates the RRC parameters and identifies the transmission mode of the standard-defined CSI-RS resource mapping scheme 110. The terminal 102 applies the RRC parameters to the transmission mode to calculate, or otherwise determine, the resource elements being used for the reference signal transmission by the network node 108.

[0089] The network node 108 transmits the reference signals 1214 for the density- adjusted CSI-RS resource mapping scheme and the terminal 102, based on the CSI-RS configuration message 1212, receives and measures the received signals transmitted over the resources 1216 identified by the CSI-RS configuration message 1212. As discussed above, the density-adjusted CSI resource mapping scheme used by the network node 108 results in the use of resource elements 1216 at a reference signal transmission density rate less than 1. Accordingly, the reference signals are nottransmitted in every resource block. The RRC parameters provided by the network node in CSI-RS configuration message identify the resource elements 1216 within the resource block 1218 and the density. As a result, the transmission mode of the standard-defined CSI-RS resource mapping scheme 110 may be used for the first set of antenna ports using a first set of resources in first resource block and reused for a second set of antenna ports in another resource block. As discussed above, the resource blocks including the reference signals 1214 may be sent every other time slot period for density of 0.5. In some situations, only the densities included in the standard- defined CSI-RS resource mapping scheme are used. In other situations, the standard- defined CSI-RS resource mapping scheme 110 maintained at the terminal 102 may be modified to include additional densities for one or more transmission modes (e.g., rows of the table). Therefore, the reference signals 1214 may be transmitted in a resource block every third time slot period for density of 0.33 or every fourth time slot period for density of 0.25. As an alternative to modifying the standard-defined CSI-RS resource mapping scheme 110 maintained at the terminal 102, the terminal 102 may be notified via signaling from the network node 108 to use an additional density for one or more transmission modes. The CSI-RS confirmation message 1212 may be modified, for example, to include an additional field with a value or flag indicating an additional density should be used for the identified transmission mode. Other techniques may also be used to implement additional densities to the densities in the standard-defined CSI- RS resource mapping scheme.

[0090] After receiving and measuring the reference signals, the terminal generates a CSI report 1220 including the measurements of the reference signals 1214 and sends the CSI report 1220 to the network node 108. The network node 108 continues to monitor communication conditions to determine whether the selected RSI-RS resource mapping scheme should be changed.

[0091] The network node 108, therefore, manages the selection of the CSI-RS resource mapping scheme based on conditions to efficiently transmit CSI reference signals for CSI reports that support more antenna ports than defined in the standard- defined CSI-RS resource mapping scheme maintained at the terminal 102. As discussed above, the standard-defined CSI-RS resource mapping scheme 110maintained at the terminal 102 is defined by at least one revision of the 3GPP communication specification where the standard-defined CSI-RS resource mapping scheme defines 18 different reference signal transmission modes and supports 32 logical antenna ports. The network node 108 is limited to receiving CSI reports from a terminal for 32 logical antenna ports in conventional systems. The network node, however, receives CSI reports 112 (1210, 1220) providing feedback from more than 32 logical antenna ports even though the terminal 102 is configured with the standard- defined CSI-RS resource mapping scheme 110 for 32 logical ports. Generally, where the CSI-RS resource mapping scheme 110 at the terminal 102 supports a number (MSLP) of mapping scheme logical ports and the antenna system 106 at the network node 108 includes a number (NLP) of logical antenna ports 104, the network node 108 configures the terminal 102 to provide feedback for more than MSLP logical ports. Therefore, the network node 108 is able to more effectively manage communication through an antenna array having NAE antenna elements where N E > MSLP and NLP > MSLP.

[0092] In some situations, a selected CSI-RS resource mapping scheme may be a hybrid-adjusted CSI-RS resource mapping scheme where at least some of the transmission modes include a density adjustment and a resource adjustment. For example, a transmission mode may include a combination of two standard-defined transmission modes that are limited to a density less than 1 .

[0093] In some situations, the network node 108 may switch between two density- adjusted CSI-RS resource mapping schemes, between two resource-adjusted CSI-RS resource mapping schemes, between two hybrid-adjusted CSI-RS resource mapping schemes, or between a hybrid-adjusted CSI-RS resource mapping scheme and a density-adjusted CSI-RS resource mapping scheme or resource-adjusted CSI-RS resource mapping scheme. The network node may make such switching determinations on the conditions discussed above as well as other factors or combination of factors and conditions. In one example of a situation where the network node switches between two resource-adjusted CSI-RS resource mapping schemes, the network node may determine that one combination of transmission modes to achieve the desired number of antenna ports utilizes resource elements that are more susceptible to interferencethan the resource elements of another combination. In one specific example, the network node configures a transmission mode for 48 logical antenna ports and selects a combination of two transmission modes supporting 24 antenna ports, each. Due to detected interference on the some of the resource elements of this combination, the network node may determine that a transmission mode including a combination of a transmission mode supporting 32 ports and transmission port supporting 16 ports is preferred because the resource elements used in the second combination are less susceptible to interference.

[0094] FIG. 13 is a flow chart of an example of a method of managing a CSI-RS resource mapping scheme for CSI reporting from a terminal for antenna ports in addition to the antenna ports defined by the CSI-RS resource mapping scheme stored at the terminal. The method may be performed in a system such the system 100 discussed herein. For the example, the method is performed by a network node, such as the network node 108. The method may be performed using any of several techniques involving any combination of software, hardware, and firmware. For example, software code running on electronics including a processor, computer or other processor arrangement within the network node may facilitate the generation, formatting, reception, and transmission of signals and messages as well as facilitating measurements, evaluations and determinations. One or more of the steps may be omitted, combined, performed in parallel, or performed in a different order than that described herein or shown in FIG. 13. In still further examples, additional steps may be added that are not explicitly described in connection with the example discussed with reference to FIG. 13.

[0095] At step 1302, network node obtains information regarding the communication conditions. The information may be based on measurements by the network node or terminal, reports provided by the terminal or other terminals and network nodes, or other tracked parameters. Some examples of the information related to communication conditions include terminal mobility, the level of communication traffic, available capacity at the network, mobility of other terminals, and quality of service (QoS) required for communication by the terminal and other terminals.

[0096] At step 1304, the network node 108 selects a CSI-RS resource mapping scheme from a plurality of CSI-RS resource mapping schemes to identify a selected CSI-RS resource mapping scheme. Based at least partially in the communication conditions, the network node 108 determines a preferred CSI-RS resource mapping scheme to use in obtaining CSI feedback for managing transmission from the antenna system including more than 32 logical antenna ports. For the example of FIG. 13, the network node selects the selected CSI-RS resource mapping scheme from a density- adjusted CSI-RS resource mapping scheme and a resource-adjusted CSI-RS resource mapping scheme. The method continues at step 1306 if the resource-adjusted CSI-RS resource mapping scheme is selected and proceeds to step 1308 if the density-adjusted CSI-RS resource mapping scheme is selected.

[0097] At step 1306, the network node 108 selects a transmission mode from the 18 defined transmission modes in the standard-defined CSI-RS resource mapping scheme and selects the RRC parameters that characterize the reference signal transmission that the network node will use. The RRC parameters indicate to the terminal (in conjunction with the standard-defined CSI-RS resource mapping scheme) resources that will be used for the reference signal transmission as well as other characteristics of the transmission. For the example, the network selects one or more transmission modes from the standard-defined CSI-RS resource mapping scheme that will include resources for transmitting reference signals for supporting the set of 32 logical ports and resources for transmitting reference signals for supporting additional logical ports in addition to the 32 logical ports. Accordingly, a transmission mode from the standard- defined CSI-RS resource mapping scheme is used for at least two sets of reference signals to support more than 32 logical antenna ports. Therefore, the resource-adjusted CSI-RS resource mapping scheme allocating additional resources for one or more transmission modes of the standard-defined CSI-RS resource mapping scheme for reference signal transmissions to support CSI feedback from the terminal for more than 32 logical antenna ports.

[0098] At step 1310, the network node 108 transmits, to the terminal 102, a CSI-RS configuration message with the RRC parameters identifying at least the transmissionmode and resource mapping to the additional resources. After receiving the CSI-RS configuration message, the terminal determines the resources that will be used to transmit the reference signals.

[0099] At step 1312, the network node 108 transmits the CSI reference signals in accordance with the RRC parameters provided to the terminal 102. The CSI reference signals are transmitted using the additional resources that allow for the support of a number of logical antenna ports that is greater than the number for the standard-defined CSI-RS resource mapping scheme.

[0100] At step 1314, the network node receives a CSI report from the terminal 102 that is based on the measurements of the reference signals.

[0101] At step 1308, the network node 108 selects the transmission mode and RRC parameters for the reference signal transmissions using the density-adjusted CSI-RS resource mapping scheme. The network node 108 selects a transmission mode of the standard-defined CSI-RS resource mapping scheme and selects a reference signal transmission density to less the 1.0 such that resource elements may be reused in other resource blocks for other reference signal transmission for other logical antenna ports. Accordingly, in selecting the density-adjusted CSI-RS resource mapping scheme and limiting one or more transmission modes of the standard-defined CSI-RS resource mapping scheme to reference signal transmission densities to values less than 1 .0, the network node enables reference signal transmissions supporting CSI feedback from a terminal for more than 32 logical antenna ports.

[0102] At step 1316, the network node 108 transmits a CSI-RS configuration message to the terminal. The CSI-RS configuration message includes RRC parameters that allow the terminal 102 to identify the transmission mode from the 18 transmission modes of the standard-defined CSI-RS resource mapping scheme and to identify the resources that will be used for the reference signal transmission. The RRC parameters indicate a density less than 1 .

[0103] At step 1318, the network node 108 transmits the CSI reference signals in accordance with the RRC parameters provided to the terminal 102. The CSI reference signals are transmitted using the identified density less than 1.0 that facilitates CSIfeedback for a number of logical antenna ports that is greater than the number for the standard-defined CSI-RS resource mapping scheme. After reception of the CSI report from the terminal 102 at step 1314, method returns to step 1302 to monitor conditions.

[0104] FIG. 14 is a flow chart of an example of CSI reporting performed at a terminal for antenna ports in addition to the antenna ports defined by the CSI-RS resource mapping scheme stored at the terminal. The method may be performed in a system such the system 100 discussed herein. For the example, the method may be performed by a terminal, such as the terminal 102. The method may be performed using any of several techniques involving any combination of software, hardware, and firmware. For example, software code running on electronics including a processor, computer or other processor arrangement within the network node may facilitate the generation, formatting, reception, and transmission of signals and messages as well as facilitating measurements, evaluations and determinations. One or more of the steps may be omitted, combined, performed in parallel, or performed in a different order than that described herein or shown in FIG. 14. In still further examples, additional steps may be added that are not explicitly described in connection with the example discussed with reference to FIG. 14.

[0105] At step 1402, the terminal receives a first set of one or more CSI-RS configuration messages. The CSI-RS configuration messages include RRC parameters.

[0106] At step 1404, the terminal evaluates each configuration message and, based on a standard-defined CSI-RS resource mapping scheme maintained at the terminal, identifies first resource elements for receiving density-adjusted reference signals transmitted in accordance with a density-adjusted CSI-RS resource mapping scheme. The density-adjusted CSI-RS resource mapping scheme is used by the network node 108 and is based on the standard-defined CSI-RS resource mapping scheme where one or more of the transmission modes of the standard-defined CSI-RS resource mapping scheme are limited to a reference signal transmission density having a value less than 1 .0. Accordingly, the reference signals for a particular configuration are not transmitted in every resource block of series of resource blocks allowing the same resources to be used in different resource blocks for different configurations.

[0107] At step 1406, the terminal receives and measures density-adjusted reference signals transmitted over the identified resources. The terminal generates a first set of one or more CSI reports based on the measurements.

[0108] At step 1408, the terminal 102 transmits the first set of one or more CSI reports to provide feedback to the network node for more than 32 logical antenna ports. The CSI reports are typically transmitted at different times where each CSI-RS report is based on a current CSI-RS configuration. Since the resource elements are reused for reference signals in different resource blocks for different logical antenna ports, the reference signals support feedback for more than 32 logical antenna ports even though the standard-defined CSI-RS resource mapping scheme maintained at the terminal defines 18 transmission modes to support 32 logical ports.

[0109] At step 1410, the terminal 102 receives a second set of one or more CSI-RS configuration messages. The CSI-RS configuration messages include RRC parameters.

[0110] At step 1412, the terminal evaluates each configuration message and, based on a standard-defined CSI-RS resource mapping scheme maintained at the terminal, identifies first resource elements for receiving resource-adjusted reference signals transmitted in accordance with a resource-adjusted CSI-RS resource mapping scheme. The resource-adjusted CSI-RS resource mapping scheme is used by the network node 108 and is based on the standard-defined CSI-RS resource mapping scheme where one or more of the transmission modes of the standard-defined CSI-RS resource are used with additional resources. Accordingly, the reference signals for two or more CSI- RS configurations can be transmitted using the same transmission mode with different resources where the transmission mode is one of the 18 transmission modes of the standard-defined CSI-RS resource mapping scheme 110.

[0111] At step 1414, the terminal receives and measures resource-adjusted reference signals transmitted over the identified resources. The terminal generates a second set of one or more CSI reports based on the measurements.

[0112] At step 1416, the terminal 102 transmits the second set of one or more CSI reports to provide feedback to the network node for more than 32 logical antenna ports. The CSI reports are typically transmitted at different times where each CSI-RS report isbased on a current CSI-RS configuration. Since the same transmission mode is reused for reference signals in using different resource for different logical antenna ports, the reference signals support feedback for more than 32 logical antenna ports even though the standard-defined CSI-RS resource mapping scheme maintained at the terminal defines 18 transmission modes to support 32 logical ports.

[0113] To clearly illustrate this interchangeability of hardware, firmware 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, firmware or software, or a combination of these techniques, depends upon the particular application and design constraints imposed on the overall system. The described functionality may be implemented in various ways for each particular application, but such implementation decisions do not cause a departure from the scope of the present disclosure. In accordance with various embodiments, a processor, device, component, circuit, structure, machine, module, etc. can be configured to perform one or more of the functions described herein. The term "configured to" or "configured for" as used herein with respect to a specified operation or function refers to processors, devices, components, circuits, electronics, and equipment that are physically constructed, programmed, instructed and / or arranged to perform the specified operation or function. Furthermore, the various illustrative logical blocks, modules, devices, components and circuits described herein can be implemented within or performed by an integrated circuit (IC) that can include a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), other electronics or combinations thereof. (ASIC), a field programmable gate array (FPGA) or other programmable logic device, or any combination thereof. The logical blocks, electronics, and circuits can further include antennas and / or transceivers to communicate with various components within the network or within the device. A general-purpose processor can be a microprocessor, but in the alternative, the processor can be any conventional processor, controller, or state machine. A processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suitable configuration to perform the functions described herein.

[0114] When implemented in software, the functions can be stored as one or more instructions or code on a computer-readable medium. Thus, the steps of a method or algorithm disclosed herein can be implemented as software stored 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 or code from one place to another. A storage media can be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer.

[0115] Therefore, the methods and apparatus of this invention may take the form, at least partially, of program logic or program code (i.e., instructions) embodied in tangible media, such as a machine-readable storage medium. When the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the invention. The methods and apparatus of the present invention may also be embodied in the form of program code that is transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via any other form of transmission. When the program code is received and loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the invention. When implemented on a general-purpose processor, the program code combines with the processor to provide a unique apparatus that operates analogously to specific logic circuits.

[0116] Additionally, memory or other storage, as well as communication components, may be employed in embodiments of the present disclosure. It will be appreciated that, for clarity purposes, the above description has described embodiments of the present disclosure with reference to different functional units and processors. However, it will be apparent that any suitable distribution of functionality between different functional units, processing logic elements or domains may be usedwithout detracting from the present disclosure. For example, functionality illustrated to be performed by separate processing logic elements, or controllers, may be performed by the same processing logic element, or controller. Therefore, references to specific functional units are only references to a suitable means for providing the described functionality, rather than indicative of a strict logical or physical structure or organization.

[0117] Clearly, other embodiments and modifications of this invention will occur readily to those of ordinary skill in the art in view of these teachings. The above description is illustrative and not restrictive. This invention is to be limited only by the following claims, which include all such embodiments and modifications when viewed in conjunction with the above specification and accompanying drawings. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.

Claims

CLAIMS1 . A method comprising: selecting a density-adjusted Channel State Information Reference Signal (CSI- RS) resource mapping scheme limiting one or more transmission modes of a standard- defined CSI-RS resource mapping scheme to reference signal transmission densities to values less than 1 .0, the density-adjusted CSI-RS resource mapping scheme for reference signal transmissions supporting CSI feedback from a terminal for more than 32 logical antenna ports; transmitting, to the terminal, a first CSI-RS configuration message comprising first Radio Resource Control (RRC) parameters identifying a first transmission mode of the standard-defined CSI-RS resource mapping scheme and identifying first resources for transmission of first reference signals in accordance with the density-adjusted CSI- RS resource mapping scheme; transmitting, the first reference signals at a reference signal transmission density less than 1 .0; selecting a resource-adjusted CSI-RS resource mapping scheme allocating additional resources for one or more transmission modes of the standard-defined CSI- RS resource mapping scheme for reference signal transmissions to support CSI feedback from the terminal for more than 32 logical antenna ports; transmitting, to the terminal, a second CSI-RS configuration message comprising second RRC parameters identifying a second transmission mode of the standard- defined CSI-RS resource mapping scheme and identifying second resources for transmission of second reference signals in accordance with the resource-adjusted CSI- RS resource mapping scheme; and transmitting the second reference signals to the terminal.

2. The method of claim 1 , further comprising: selecting the resource-adjusted CSI-RS resource mapping scheme based, at least partially, on communication conditions; and selecting the density-adjusted CSI-RS resource mapping scheme based, at least partially, on the communication conditions.

3. The method of claim 2, wherein the communication conditions comprise a mobility of the terminal.

4. The method of claim 2, wherein the communication conditions comprise level of communication traffic or an available capacity at the network node.

5. The method of claim 1 , wherein the standard-defined CSI-RS resource mapping scheme is defined by one or more revisions of the Third Generation Partnership Project (3GPP) communication specification.

6. The method of claim 1 , wherein: the standard-defined CSI-RS resource mapping scheme comprises 18 transmission modes to support 32 logical antenna ports; the density-adjusted CSI-RS resource mapping scheme for reference signal transmissions supports CSI feedback from the terminal for at least one of 48 logical antenna ports, 64 logical antenna ports, 96 logical antenna ports, or 128 logical antenna ports; and the resource-adjusted CSI-RS resource mapping scheme for reference signal transmissions supports CSI feedback from the terminal for at least one of 48 logical antenna ports, 64 logical antenna ports, 96 logical antenna ports, or 128 logical antenna ports.

7. The method of claim 1 , wherein: the density-adjusted CSI-RS resource mapping scheme utilizes at least one of three transmission modes associated with 32 ports in the standard-defined CSI-RS resource mapping scheme at a reference signal transmission density of 0.5, the density-adjusted CSI-RS resource mapping scheme for reference signal transmissions comprises transmitting a first set of reference signals supporting CSI feedback from the terminal for a first set of 32 logical antenna ports, andthe density-adjusted CSI-RS resource mapping scheme for reference signal transmissions comprises transmitting a second set of reference signal supporting CSI feedback from the terminal for a second set of 32 logical antenna ports different from the first set of 32 logical antenna ports.

8. The method of claim 1 , wherein: the resource-adjusted CSI-RS resource mapping scheme utilizes at least one of three transmission modes associated with 32 ports in the standard-defined CSI-RS resource mapping scheme, the resource-adjusted CSI-RS resource mapping scheme for reference signal transmissions comprises transmitting, over a first set of resources within a resource block, a first set of reference signals supporting CSI feedback from the terminal for a first set of 32 logical antenna ports, and the resource-adjusted CSI-RS resource mapping scheme for reference signal transmissions comprises transmitting, over a second set of resources within the resource block, a second set of reference signal supporting CSI feedback from the terminal for a second set of 32 logical antenna ports different from the first set of 32 logical antenna ports.

9. The method of claim 1 , wherein: the first transmission mode and the second transmission mode are the same transmission mode in the standard-defined CSI-RS resource mapping scheme.

10. A network node comprising: electronics configured to select a density-adjusted Channel State Information Reference Signal (CSI-RS) resource mapping scheme limiting one or more transmission modes of a standard-defined CSI-RS resource mapping scheme to reference signal transmission densities to values less than 1.0, the density-adjusted CSI-RS resource mapping scheme for reference signal transmissions supporting CSI feedback from a terminal for more than 32 logical antenna ports; anda transmitter configured to transmit, to the terminal, a first CSI-RS configuration message comprising first Radio Resource Control (RRC) parameters identifying a first transmission mode of the standard-defined CSI-RS resource mapping scheme and identifying first resources for transmission of first reference signals in accordance with the density-adjusted CSI-RS resource mapping scheme and to transmit, the first reference signals at a reference signal transmission density less than 1 .0, the electronics configured to select a resource-adjusted CSI-RS resource mapping scheme allocating additional resources for one or more transmission modes of the standard-defined CSI-RS resource mapping scheme for reference signal transmissions to support CSI feedback from the terminal for more than 32 logical antenna ports, the transmitter configured to transmit, to the terminal, a second CSI-RS configuration message comprising second RRC parameters identifying a second transmission mode of the standard-defined CSI-RS resource mapping scheme and identifying second resources for transmission of second reference signals in accordance with the resource-adjusted CSI-RS resource mapping scheme and to transmit the second reference signals to the terminal.11 . The network node of claim 10, wherein the electronics are further configured to: select the resource-adjusted CSI-RS resource mapping scheme based, at least partially, on communication conditions; and select the density-adjusted CSI-RS resource mapping scheme based, at least partially, on the communication conditions.

12. The network node of claim 11 , wherein the communication conditions comprise a mobility of the terminal.

13. The network node of claim 11 , wherein the communication conditions comprise a level of communication traffic or an available capacity at the network node.

14. The network node of claim 10, wherein the standard-defined CSI-RS resource mapping scheme is defined by one or more revisions of the Third Generation Partnership Project (3GPP) communication specification.

15. The network node of claim 10, wherein: the standard-defined CSI-RS resource mapping scheme comprises 18 transmission modes to support 32 logical antenna ports; the density-adjusted CSI-RS resource mapping scheme for reference signal transmissions supports CSI feedback from the terminal for at least one of 48 logical antenna ports, 64 logical antenna ports, 96 logical antenna ports, or 128 logical antenna ports; and the resource-adjusted CSI-RS resource mapping scheme for reference signal transmissions supports CSI feedback from the terminal for at least one of 48 logical antenna ports, 64 logical antenna ports, 96 logical antenna ports, or 128 logical antenna ports.

16. The network node of claim 10, wherein: the density-adjusted CSI-RS resource mapping scheme utilizes at least one of three transmission modes associated with 32 ports in the standard-defined CSI-RS resource mapping scheme at a reference signal transmission density of 0.5, the density-adjusted CSI-RS resource mapping scheme for reference signal transmissions comprises transmitting a first set of reference signals supporting CSI feedback from the terminal for a first set of 32 logical antenna ports, and the density-adjusted CSI-RS resource mapping scheme for reference signal transmissions comprises transmitting a second set of reference signal supporting CSI feedback from the terminal for a second set of 32 logical antenna ports different from the first set of 32 logical antenna ports.

17. The network node of claim 10 wherein: the resource-adjusted CSI-RS resource mapping scheme utilizes at least one of three transmission modes associated with 32 ports in the standard-defined CSI-RS resource mapping scheme, the resource-adjusted CSI-RS resource mapping scheme for reference signal transmissions comprises transmitting, over a first set of resources within a resource block, a first set of reference signals supporting CSI feedback from the terminal for a first set of 32 logical antenna ports, and the resource-adjusted CSI-RS resource mapping scheme for reference signal transmissions comprises transmitting, over a second set of resources within the resource block, a second set of reference signal supporting CSI feedback from the terminal for a second set of 32 logical antenna ports different from the first set of 32 logical antenna ports.

18. The network node of claim 10, wherein the first transmission mode and the second transmission mode are the same transmission mode in the standard-defined CSI-RS resource mapping scheme.

19. A method comprising: receiving a first set of one or more CSI-RS configuration messages; identifying, at least partially based on the first set of one or more CSI-RS configuration messages and a standard-defined CSI-RS resource mapping scheme, first resource elements for receiving density-adjusted reference signals transmitted in accordance with density-adjusted CSI-RS resource mapping scheme comprising one or more transmission modes of the standard-defined CSI resource mapping scheme that are limited to a density less than 1 .0; measuring the density-adjusted reference signals to generate a first set of one or more CSI reports; transmitting the first set of one or more CSI reports to provide feedback to the network node for more than 32 logical antenna ports; receiving a second set of one or more CSI-RS configuration messages;identifying, at least partially based on the second set of one or more CSI-RS configuration messages and the standard-defined CSI-RS resource mapping scheme, second resource elements for receiving resource-adjusted reference signals transmitted in accordance with a resource-adjusted CSI-RS resource mapping scheme comprising one or more transmission modes of the standard-defined CSI resource mapping scheme, the one or more transmission modes allocating a first set of resources for transmitting reference signals for 32 logical ports and allocating a second set of resources for transmitting reference signals for additional logical ports in addition to the 32 logical ports; measuring the resource-adjusted reference signals to generate a second set of one or more CSI reports; and transmitting the second set of one or more CSI reports to provide feedback to the network node for more than 32 logical antenna ports.

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