Systems and methods for NR V2X CSI feedback without dedicated reference signals

Abstract

A user equipment (UE) configured for multi-antenna communication, the UE estimating at least one of a rank indicator and a channel quality indicator for device-to-device (D2D) communication based on communication data associated with a plurality of packets transmitted using the D2D communication and without using a dedicated reference signal for the D2D communication. The UE may be configured to be used as at least one of a transmitter (Tx) and a receiver (Rx) for vehicle-to-everything (V2X) communication over a sidelink channel.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims the benefit of Provisional Patent Application No. 62 / 739,047, filed on September 28, 2018, which is hereby incorporated by reference in its entirety. Technical Field

[0003] The present application relates generally to wireless communication systems, and more particularly to device-to-device (D2D) communication. Background Art

[0004] Wireless mobile communication technology uses various standards and protocols to transmit data between base stations and wireless mobile devices. Wireless communication system standards and protocols may include the third generation partnership project (3GPP) long term evolution (LTE); the Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard, which is often referred to as the Worldwide Interoperability for Microwave Access (WiMAX) by industry organizations; and the IEEE 802.11 standard for wireless local area networks (WLANs), which is often referred to as Wi-Fi by industry organizations. In the 3GPP radio access network (RAN) in the LTE system, the base station may include a RAN node such as an evolved universal terrestrial radio access network (E-UTRAN) node B (also often referred to as an evolved node B, enhanced node B, eNodeB or eNB) and / or a radio network controller (RNC) in the E-UTRAN, which communicates with a wireless communication device called a user equipment (UE). In the fifth generation (5G) wireless RAN, the RAN node may include a 5G node, a new radio (NR) node or a gNodeB (gNB).

[0005] The RAN uses radio access technologies (RATs) to communicate between RAN nodes and UEs. The RAN may include Global System for Mobile Communications (GSM), Enhanced Data Rates for GSM Evolution (EDGE) RAN (GERAN), Universal Terrestrial Radio Access Network (UTRAN), and / or E-UTRAN, which provide access to communication services through a core network. Each of the RANs operates according to a specific 3GPP RAT. For example, GERAN implements GSM and / or EDGE RAT, UTRAN implements Universal Mobile Telecommunications System (UMTS) RAT or other 3GPP RAT, and E-UTRAN implements LTE RAT.

[0006] The core network may be connected to the UE via a RAN node. The core network may include a serving gateway (SGW), a packet data network (PDN) gateway (PGW), an access network detection and selection function (ANDSF) server, an enhanced packet data gateway (ePDG) and / or a mobility management entity (MME). BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 and Figure 2 A graph showing BLER versus SNR for various feedback scenarios is shown.

[0008] Figure 3 is a flow chart of a method for a UE configured for multi-antenna D2D communication according to one embodiment.

[0009] Figure 4 is a flow chart of a method for using HARQ information according to one embodiment.

[0010] Figure 5 is a flow chart of a method for estimating a channel quality indicator based on a DMRS according to one embodiment.

[0011] Figure 6 is a flow chart of a method for determining a rank indicator based on long-term channel statistics according to one embodiment.

[0012] Figure 7 is a flow chart of a method for determining a rank indicator based on a precoder cycle according to one embodiment.

[0013] Figure 8 A system according to one embodiment is shown.

[0014] Fig. 9 An apparatus according to one embodiment is shown.

[0015] Fig.10 An exemplary interface according to one embodiment is shown.

[0016] Fig.11 A system according to one embodiment is shown.

[0017] Fig.12 Components according to one embodiment are shown. DETAILED DESCRIPTION

[0018] In order to effectively and efficiently use multi-antenna technologies (e.g., Multiple Input Multiple Output (MIMO)) for advanced Vehicle-to-Everything (V2X) communications, the transmitter (Tx) UE obtains information about the propagation channel, i.e., Channel State Information (CSI), Channel Quality Indicator (CQI), and / or Rank Indicator (RI) for the design and / or selection of the correct precoding matrix. This is particularly useful for unicast and multicast transmission modes, where the overall performance can be improved if MIMO with precoding is adopted. Typically, cellular systems adopt CSI feedback based on specific or dedicated reference signals (RS) in downlink and uplink. For example, for the NR downlink air interface, the CSI-RS is transmitted by the gNB and the UE reports one or several of the following indicators: RI, Precoding Matrix Indicator (PMI) or CQI, CSI Resource Index (CRI), and / or Layer Indicator (LI) for Phase Tracking Reference Signal (PTRS), depending on the network configuration. This feedback is periodic or aperiodic. However, if a closed-loop MIMO approach is adopted in the eV2X sidelink, there are problems with the approach. For example, even for low to medium vehicle speeds, the CSI expires quickly, making the feedback almost useless. In addition, RS causes additional overhead, which reduces the overall spectrum efficiency.

[0019] Generally speaking, the PMI expires very quickly because it mainly depends on the instantaneous realization of the channel. Figure 1 and Figure 2 The graphs shown are shown in the evaluation of the graphs which show the block error rate (BLER) versus the signal-to-noise ratio (SNR) in decibels (dB) for various feedback scenarios.

[0020] Figure 1 A graph 100 of line of sight (LOS) operation is shown, with the graph on the left corresponding to a vehicle speed of zero (0) kilometers per hour (km / h) and the graph on the right corresponding to a relative vehicle speed of 30 km / h.

[0021] Similarly, Figure 2 A graph 200 for non-line-of-sight (NLOS) operation is shown, where the graph on the left corresponds to a vehicle speed of 0 km / h and the graph on the right corresponds to a relative vehicle speed of 30 km / h.

[0022] According to 3GPP TS 38.214, the minimum delay between the time slots required to transmit feedback, calculation of CSI, transmission of RS for PMI estimation and application of feedback information at the transmitter is three time slots. In addition, since PMI is changing, PMI needs to be transmitted periodically. Figure 1 and Figure 2In the legend of FIG. , the abbreviation DzPy (e.g., D3P5, D3P10, and D3P20) represents a delay of z time slots and a periodicity of y time slots. Figure 1 and Figure 2 In the example shown, narrowband (NB) and wideband (WB) feedback and precoder loop (CPMI) are evaluated. The example shows that even for a very moderate relative speed of 30 km / h, the performance of the open loop PMI loop exceeds the performance of the closed loop PMI feedback.

[0023] Therefore, according to certain embodiments herein, various methods are disclosed for correctly obtaining transmitter side channel state information (Tx-CSI) to improve D2D communications, such as sidelink enhanced V2X (eV2X) performance when employing MIMO technology (i.e., multiple Tx and Rx antennas).

[0024] The existing LTE-V2X sidelink physical layer specification assumes that only broadcast communication mode is used. In this case, any channel adaptation may not be applicable because it may not be practical to obtain knowledge of all channels. For example, it is impractical to use channel-dependent MIMO precoding because it is generally not possible to find an optimal solution for many different links between a Tx UE and multiple Rx UEs.

[0025] In the downlink and uplink of NR, CSI-RS and Sounding Reference Signal (SRS) are used for channel sounding respectively to potentially report an indicator to the other side, which can be, for example, a specific precoding matrix. This is the so-called closed-loop MIMO approach.

[0026] Another alternative solution is to apply channel reciprocity. In this case, CSI is also obtained in the reverse link based on the RS used for channel sounding, that is, CSI is obtained when receiving, and a reciprocal channel is assumed for transmission because the same channel and bandwidth are used for Tx and Rx in this case.

[0027] The disadvantages of previous solutions include: the feedback of CSI can expire quickly due to high mobility; CSI-RS and SRS, or any specific RS used for channel sounding, means increased overhead, i.e., reduced overall spectrum efficiency; and the reciprocity approach limits the implementation options for configuration and antenna allocation for automotive companies. For example, in some specific implementations, vehicles can use different sets of antennas for Tx and Rx. In addition, correct calibration may be required, which means additional overhead, complexity, and increased delay.

[0028] Thus, certain embodiments disclosed herein obtain Tx-CSI suitable for NR D2D communications such as sidelink V2X communications. Such embodiments provide reduced CSI RS overhead, flexible implementation of antenna configurations, and adaptation to long-term parameters of the system rather than instantaneous implementation for V2X services. To achieve this performance, certain embodiments determine CQI and RI from other existing RSs that are reused for demodulation and / or synchronization. In addition or in other embodiments, precoding cycles are used for RI estimation and reporting.

[0029] Certain embodiments disclosed herein provide: significant improvements in V2V demodulation performance of future cellular-V2X systems supporting advanced use cases; significant improvements in spectral efficiency and reliability of future cellular-V2X communications to improve advanced safety and non-safety related use cases; improvements in modems of vehicle telematics control units (TCUs) used in the automotive industry; and / or providing optimized communication standards to facilitate rapid adoption of the system.

[0030] As mentioned above, Figure 1 and Figure 2 The evaluation shown in concludes that PMI feedback may not provide gain even with knowledge of the ideal channel at the receiver, even in relatively slow fading scenarios with a relative mobile speed of 30 km / h between Tx and Rx. Since it is generally beneficial to adjust the transmission rank and modulation coding format to optimize resource utilization and provide sufficient reliability, these parameters may need to be known at the transmitter. The inventors of this article realized through PMI simulation that the instantaneous realization of the channel is changing rapidly, but as shown in ICT-619555RESCUE, "D4.3 Report on channelanalysis and modelling", Aug.2015 and the simulation assumptions in 3GPP TR 37.885, the large-scale parameters remain constant in a large area. At least, the area where the large-scale parameters are similar is in the range of about 7 meters (m) to about 10m. In addition, it should be considered that one of the applications for unicast and multicast will be platooning, where vehicles travel in the same direction at similar distances. Therefore, the large-scale parameters remain coherent even longer. Therefore, for NR V2X, there is a benefit of adapting large-scale parameters.

[0031] In the next step, the transmitter can acquire channel information based on large-scale parameters. This is different from the uplink and downlink cases, where feedback is based only on the instantaneous realization of the channel. Since some embodiments are adapted to longer-term parameters of the system, it is considered that dedicated reference signals can be considered as a large overhead because these reference signals need to be transmitted periodically. Since averaging can be performed over multiple realizations, this is a larger overhead compared to operations in the uplink and downlink. Therefore, some embodiments herein provide for estimating these parameters of the system using other signals transmitted during the continuous exchange of information.

[0032] According to current assumptions of the NR V2X study project, in certain embodiments, it is assumed herein that the handshake is also used to exchange preliminary information about the channel quality. Thereafter, during continuous exchange of data, CQI and RI are estimated by each device and feedback is sent to other participating transmitters. In various embodiments described below, CQI is adapted according to outer loop link adaptation, CQI is based on long term channel statistics, RI is based on long term channel statistics, and / or RI is based on precoder cycles without PMI feedback.

[0033] Adaptive CQI based on outer loop link adaptation

[0034] In one embodiment, outer loop link adaptation is employed based on hybrid automatic repeat request (HARQ). CQI can then be derived based on acknowledgement (ACK) responses and negative acknowledgement (NACK) responses. In this case, if a modulation coding scheme is selected and the amount of NACKs increases over a time period, the bits per symbol can be reduced. In a similar manner, if no NACK responses occur or the NACK responses decrease over a time period, the spectral efficiency may be too small and the bits per symbol may increase. This adjustment may occur in the transmitter itself, as it will require feedback of this information to initiate a retransmission, or the adjustment may be part of the feedback from the receiver to the transmitter. In addition, in some embodiments, the adaptation may be a gradual process, in which the modulation coding scheme is readjusted only once every X received ACK / NACK responses. For example, the modulation coding scheme may be adjusted once every ten received ACK / NACK responses.

[0035] In addition or in other embodiments, the outer loop may consider overall load and interference measurements in the environment.Considering that a vehicle UE may always be expected to perform sensing and reception from other UEs, the vehicle UE is expected to be well aware of the radio environment conditions.

[0036] CQI based on long-term channel statistics

[0037] In one embodiment, the CQI may be based on long-term channel statistics. The receiver typically estimates the channel based on a demodulation reference signal (DMRS) to demodulate the transmission. This information can be used to calculate the CQI based on the estimated long-term statistics of the channel. The CQI based on the long-term statistics of the channel can then be reported to the transmitter. The DMRS can also be used, for example, to measure the interference level of each subchannel (e.g., each physical resource block (PRB)). Both channel and interference measurements can be averaged or weighted, for example, over a specific time period and / or transmission bandwidth, and used for CQI estimation.

[0038] RI based on long-term channel statistics

[0039] In one embodiment, the RI may also be estimated based on long-term channel statistics. For example, the DMRS may also be the basis for the RI estimate. In some such embodiments, if the channel coefficients received at different receive antennas at the same subcarrier and orthogonal frequency division multiplexing (OFDM) symbol are highly correlated, the channel has a rank defect and cannot support multiple spatial layers. However, if the channel coefficients are only weakly correlated, multiple spatial layers may be supported. In some embodiments, the estimate of the correlation may be an average of multiple receptions and may then be fed back to the transmitter.

[0040] In addition or in other embodiments, if the precoder is composed of a single matrix or simulates the TX antenna selection, the precoder loop can also implement MIMO channel measurement. Therefore, knowledge of the MIMO channel can be derived from the DMRS signal and used for RI detection and feedback.

[0041] RI based on precoder loop without PMI feedback

[0042] In one embodiment, the RI may be based on a precoder cycle without PMI feedback. As described above, PMI feedback may not provide benefit to the system. Therefore, in order to increase diversity, a precoder cycle should be used. The device may, for example, exchange information about the codebook used and which part of the codebook is used during the initial handshake or used inside the accompanying control information during each transmission. With the information about the precoding matrix used, the receiver can, for example, estimate the channel without precoding from a DRMS-based channel estimate that is used for demodulation. Based on the precoding matrix information, the rank of the channel can, for example, be estimated and fed back to the transmitter.

[0043] Exemplary Methods

[0044] Figure 33 is a flow chart of a method 300 for a UE configured for multi-antenna D2D communication according to one embodiment. The UE may be configured as a transmitter (Tx) and / or a receiver (Rx) for V2X communication, for example, via a sidelink channel. In block 302, based on communication data associated with a plurality of packets transmitted via the sidelink channel and without using a dedicated reference signal for the sidelink channel, the method 300 estimates at least one of a rank indicator and a channel quality indicator of the sidelink channel. In block 304, the method 300 encodes a feedback message to one or more transmitters participating in communication using the sidelink channel, the feedback message indicating at least one of the rank indicator and the channel quality indicator.

[0045] In some embodiments, the communication data includes HARQ information including ACK responses and NACK responses associated with a plurality of packets transmitted over a sidelink channel. For example, Figure 4 4 is a flow chart of a method 400 for using HARQ information according to one embodiment. In block 402, for a selected modulation and coding scheme, the method 400 monitors ACK responses and NACK responses. In block 404, if the NACK responses increase during a time period, the method 400 adjusts the modulation and coding scheme to reduce the number of bits per symbol. In block 406, if the NACK responses decrease or are below a threshold amount during the time period, the method 400 adjusts the modulation and coding scheme to increase the number of bits per symbol. In block 408, the method 400 encodes a feedback message to include an indication of the adjustment to the modulation and coding scheme.

[0046] In some embodiments, the communication data includes demodulation information associated with demodulation of a plurality of packets received at the UE over a sidelink channel over a period of time. For example, the demodulation information may include a DMRS. Figure 5 5 is a flow chart of a method 500 for estimating a channel quality indicator based on a DMRS according to one embodiment. In block 502, the method 500 determines an estimated channel based on the DMRS to demodulate a plurality of packets transmitted over a sidelink channel. In block 504, the method 500 calculates a channel quality indicator based on long-term statistics of the estimated channel. In certain such embodiments, the method 500 determines (in block 506) an interference measurement for each physical resource block (PRB) based on the DMRS, and determines (in block 508) a channel quality indicator by averaging or weighting both the estimated channel and the interference measurement over the time period.

[0047] In some implementations, the rank indicator may also be estimated based on the DMRS or other long-term channel statistics. Figure 66 is a flow chart of a method 600 for determining a rank indicator based on long-term channel statistics according to one embodiment. In block 602, if channel coefficients received at different receive antennas of the UE corresponding to the same subcarrier and OFDM symbol are highly correlated, the method 600 configures the UE to use a single spatial layer for the sidelink channel. In block 604, if the channel coefficients are weakly correlated, the method 600 configures the UE to use multiple spatial layers for the sidelink channel.

[0048] Figure 7 7 is a flow chart of a method 700 for determining a rank indicator based on a precoder cycle. In block 702, the method 700 exchanges codebook information with one or more transmitters or receivers communicating with a UE via a sidelink channel. The codebook information indicates a cycle of a precoder for a plurality of packets. In block 704, the method 700 estimates a MIMO channel based on the cycle of the precoder. In block 706, the method 700 determines a rank indicator based on the MIMO channel.

[0049] Exemplary Systems and Apparatus

[0050] Figure 8 The architecture of a system 800 of a network according to some embodiments is shown. The system 800 is shown to include a UE 802; a 5G access node or RAN node (shown as (R) AN node 808); a user plane function (shown as UPF 804); a data network (DN 806), which can be, for example, an operator service, Internet access, or a 3rd party service; and a 5G core network (5GC) (shown as CN 810).

[0051] CN 810 may include an authentication server function (AUSF 814); a core access and mobility management function (AMF 812); a session management function (SMF 818); a network exposure function (NEF 816); a policy control function (PCF 822); a network function (NF) repository function (NRF 820); a unified data management (UDM 824); and an application function (AF 826). CN 810 may also include other elements not shown, such as a structured data storage network function (SDSF), an unstructured data storage network function (UDSF), etc.

[0052] The UPF 804 may act as an anchor point for intra-RAT and inter-RAT mobility, an external PDU session point interconnected with the DN 806, and a branch point to support multi-homed PDU sessions. The UPF 804 may also perform packet routing and forwarding, packet inspection, user plane portion of policy rule enforcement, lawful interception of packets (UP collection); traffic usage reporting, QoS processing for the user plane (e.g., packet filtering, gating, UL / DL rate enforcement), uplink traffic validation (e.g., SDF to QoS flow mapping), transport level packet marking in uplink and downlink, and downlink packet buffering and downlink data notification triggering. The UPF 804 may include an uplink classifier to support routing of traffic flows to the data network. The DN 806 may represent various network operator services, Internet access, or third-party services.

[0053] AUSF 814 may store data and handle authentication-related functions for authentication of UE 802. AUSF 814 may facilitate a common authentication framework for various access types.

[0054] AMF 812 may be responsible for registration management (e.g., responsible for registering UE 802, etc.), connection management, reachability management, mobility management, and lawful interception of AMF-related events, as well as access authentication and authorization. AMF 812 may provide transport for SM messages of SMF 818 and act as a transparent proxy for routing SM messages. AMF 812 may also provide services for UE 802 and SMS function (SMSF) ( Figure 8 The AMF 812 may provide for transmission of short message service (SMS) messages between the AUSF 814 and the UE 802 (not shown). The AMF 812 may act as a security anchor function (SEAF), which may include interaction with the AUSF 814 and the UE 802, receiving intermediate keys established as a result of the UE 802 authentication process. In the case of using USIM-based authentication, the AMF 812 may retrieve security materials from the AUSF 814. The AMF 812 may also include a secure content management (SCM) function that receives keys from the SEA for deriving access network-specific keys. In addition, the AMF 812 may be the termination point for the RAN CP interface (N2 reference point), the termination point for NAS (NI) signaling, and perform NAS encryption and integrity protection.

[0055] AMF 812 may also support NAS signaling with UE 802 via the N3 interworking function (IWF) interface. N3IWF may be used to provide access to untrusted entities. N3IWF may be an endpoint of the N2 and N3 interfaces for the control plane and user plane, respectively, and may therefore handle N2 signaling for PDU sessions and QoS from SMF and AMF, encapsulate / decapsulate packets for IPSec and N3 tunnels, mark N3 user plane packets in the uplink, and enforce QoS corresponding to the N3 packet marking taking into account the QoS requirements associated with such markings received via N2. N3IWF may also relay uplink and downlink control plane NAS (NI) signaling between UE 802 and AMF 812, and relay uplink and downlink user plane packets between UE 802 and UPF 804. N3IWF also provides a mechanism for establishing an IPsec tunnel with UE 802.

[0056] SMF 818 may be responsible for session management (e.g., session establishment, modification, and release, including tunnel maintenance between UPF and AN nodes); UE IP address allocation & management (including optional authorization); selection and control of UP functions; configuring traffic steering at UPF to route traffic to the correct destination; terminating the interface towards the policy control function; control part of policy enforcement and QoS; lawful interception (for SM events and interface with LI system); terminating the SM part of NAS messages; downlink data notification; initiator of AN-specific SM information sent to AN via AMF over N2; determining the SSC mode of the session. SMF 818 may include the following roaming functions: handling local execution to apply QoS SLA (VPLMN); charging data collection and charging interface (VPLMN); lawful interception (for SM events and interface with LI system, in VPLMN); supporting interaction with external DNs to transmit signaling for PDU session authorization / authentication over external DNs.

[0057] NEF 816 may provide components for securely exposing services and capabilities provided by 3GPP network functions for third parties, internal exposure / re-exposure, application functions (e.g., AF 826), edge computing or fog computing systems, etc. In such embodiments, NEF 816 may authenticate, authorize and / or restrict AF. NEF 816 may also convert information exchanged with AF 826 and information exchanged with internal network functions. For example, NEF 816 may convert between AF service identifiers and internal 5GC information. NEF 816 may also receive information from other network functions (NFs) based on their exposure capabilities. The information may be stored at NEF 816 as structured data or at a data storage NF using a standardized interface. The stored information may then be re-exposed to other NFs and AFs by NEF 816 and / or used for other purposes such as analysis.

[0058] NRF 820 can support service discovery function, receive NF discovery request from NF instance, and provide information of discovered NF instance to NF instance. NRF 820 also maintains information of available NF instances and services supported by these instances.

[0059] PCF 822 may provide policy rules for control plane functions to perform these functions and may also support a unified policy framework for managing network behavior. PCF 822 may also implement a front end (FE) to access subscription information related to policy decisions in the UDR of UDM 824.

[0060] The UDM 824 may process subscription-related information to support the handling of communication sessions by network entities, and may store subscription data for the UE 802. The UDM 824 may include two parts: an application FE and a user data repository (UDR). The UDM may include a UDM FE that is responsible for handling credentials, location management, subscription management, and the like. In different transactions, several different front ends may serve the same user. The UDM-FE accesses subscription information stored in the UDR and performs authentication credential processing; user identity processing; access authorization; registration / mobility management; and subscription management. The UDR may interact with the PCF 822. The UDM 824 may also support SMS management, where the SMS-FE implements similar application logic discussed previously.

[0061] AF 826 can provide the influence of applications on traffic routing, access network capability exposure (NCE), and interact with the policy framework for policy control. NCE can be a mechanism that allows 5GC and AF 826 to provide information to each other via NEF 816, which can be used for edge computing implementation. In such implementations, network operators and third-party services can be hosted near the UE 802 access point of the attachment to achieve effective service delivery through reduced end-to-end delay and load on the transmission network. For edge computing implementations, 5GC can select UPF 804 near UE 802 and perform traffic steering from UPF 804 to DN 806 via the N6 interface. This can be based on UE subscription data, UE location and information provided by AF 826. In this way, AF 826 can affect UPF (re) selection and traffic routing. Based on operator deployment, when AF 826 is considered a trusted entity, the network operator can allow AF 826 to interact directly with the relevant NF.

[0062] As discussed previously, CN 810 may include SMSF, which may be responsible for SMS subscription checking and verification, and relaying SM messages from / to other entities, such as SMS-GMSC / IWMSC / SMS routers, to / from UE 802. SMS may also interact with AMF 812 and UDM 824 for notification procedures that UE 802 is available for SMS transmission (e.g., setting a UE unreachable flag and notifying UDM 824 when UE 802 is available for SMS).

[0063] System 800 may include the following service-based interfaces: Namf: a service-based interface presented by AMF; Nsmf: a service-based interface presented by SMF; Nnef: a service-based interface presented by NEF; Npcf: a service-based interface presented by PCF; Nudm: a service-based interface presented by UDM; Naf: a service-based interface presented by AF; Nnrf: a service-based interface presented by NRF; and Nausf: a service-based interface presented by AUSF.

[0064] System 800 may include the following reference points: N1: a reference point between UE and AMF; N2: a reference point between (R)AN and AMF; N3: a reference point between (R)AN and UPF; N4: a reference point between SMF and UPF; and N6: a reference point between UPF and data network. There may be more reference points and / or service-based interfaces between NF services in these NFs, however, these interfaces and reference points are omitted for clarity. For example, the NS reference point may be between PCF and AF; the N7 reference point may be between PCF and SMF; the N11 reference point may be between AMF and SMF, etc.; In some embodiments, CN 810 may include an Nx interface, which is an inter-CN interface between MME and AMF 812, so as to enable intercommunication between CN 810 and other core networks.

[0065] Despite Figure 8 Not shown, the system 800 may include multiple RAN nodes (such as (R)AN node 808), wherein the Xn interface is defined between two or more (R)AN nodes 808 (e.g., gNB, etc.) connected to the 5GC 410, defined between the (R)AN node 808 (e.g., gNB) connected to the CN 810 and the eNB, and / or defined between two eNBs connected to the CN 810.

[0066] In some specific implementations, the Xn interface may include an Xn user plane (Xn-U) interface and an Xn control plane (Xn-C) interface. The Xn-U may provide non-guaranteed delivery of user plane PDUs and support / provide data forwarding and flow control functions. The Xn-C may provide management and error handling functions for managing the functions of the Xn-C interface; mobility support for UE802 in connected mode (e.g., CM connection) includes functions for managing UE mobility in connected mode between one or more (R)AN nodes 808. The mobility support may include context transfer from an old (source) serving (R)AN node 808 to a new (target) serving (R)AN node 808; and control of a user plane tunnel between the old (source) serving (R)AN node 808 and the new (target) serving (R)AN node 808.

[0067] The protocol stack of Xn-U may include a transport network layer built on an Internet Protocol (IP) transport layer, and a GTP-U layer for carrying user plane PDUs on top of a UDP and / or IP layer. The Xn-C protocol stack may include an application layer signaling protocol (referred to as the Xn Application Protocol (Xn-AP)) and a transport network layer built on an SCTP layer. The SCTP layer may be located on top of the IP layer. The SCTP layer provides guaranteed delivery of application layer messages. In the transport IP layer, point-to-point transmission is used to deliver signaling PDUs. In other specific implementations, the Xn-U protocol stack and / or the Xn-C protocol stack may be the same or similar to the user plane and / or control plane protocol stacks shown and described herein.

[0068] Fig. 9 Example components of a device 900 according to some embodiments are shown. In some embodiments, the device 900 may include at least an application circuit 902, a baseband circuit 904, a radio frequency (RF) circuit (shown as RF circuit 920), a front-end module (FEM) circuit (shown as FEM circuit 930), one or more antennas 932, and a power management circuit (PMC) (shown as PMC 934) coupled together as shown. The components of the exemplary device 900 may be included in a UE or a RAN node. In some embodiments, the device 900 may include fewer elements (for example, the RAN node may not utilize the application circuit 902, but include a processor / controller to process IP data received from the EPC). In some embodiments, the device 900 may include additional elements, such as a memory / storage device, a display, a camera, a sensor, or an input / output (I / O) interface. In other embodiments, the following components may be included in more than one device (for example, the circuit may be separately included in more than one device for a cloud-RAN (C-RAN) specific implementation).

[0069] The application circuit 902 may include one or more application processors. For example, the application circuit 902 may include circuits such as, but not limited to, one or more single-core or multi-core processors. The one or more processors may include any combination of general-purpose processors and special-purpose processors (e.g., graphics processors, application processors, etc.). These processors may be coupled to or may include a memory / storage device and may be configured to execute instructions stored in the memory / storage device to enable various applications or operating systems to run on the device 900. In some embodiments, the processor of the application circuit 902 may process IP data packets received from the EPC.

[0070] The baseband circuit 904 may include circuits such as, but not limited to, one or more single-core or multi-core processors. The baseband circuit 904 may include one or more baseband processors or control logic components to process baseband signals received from the receive signal path of the RF circuit 920 and generate baseband signals for the transmit signal path of the RF circuit 920. The baseband circuit 904 may interact with the application circuit 902 to generate and process baseband signals and control the operation of the RF circuit 920. For example, in some embodiments, the baseband circuit 904 may include a third generation (3G) baseband processor (3G baseband processor 906), a fourth generation (4G) baseband processor (4G baseband processor 908), a fifth generation (5G) baseband processor (5G baseband processor 910) or other baseband processors 912 of other existing generations, under development or to be developed in the future (e.g., second generation (2G), sixth generation (6G), etc.). The baseband circuit 904 (e.g., one or more of the baseband processors) may handle various radio control functions that implement communication with one or more radio networks via the RF circuit 920. In other embodiments, some or all of the functions of the exemplary baseband processor may be included in a module stored in the memory 918 and executed via the central processing unit (CPU 914). The radio control functions may include, but are not limited to, signal modulation / demodulation, encoding / decoding, radio frequency shifting, etc. In some embodiments, the modulation / demodulation circuit of the baseband circuit 904 may include a fast Fourier transform (FFT), precoding, or constellation mapping / demapping function. In some embodiments, the encoding / decoding circuit of the baseband circuit 904 may include convolution, tail-biting convolution, turbo, Viterbi, or low-density parity check (LDPC) encoder / decoder functions. The implementation of the modulation / demodulation and encoder / decoder functions is not limited to these examples, and may include other suitable functions in other embodiments.

[0071] In some embodiments, the baseband circuit 904 may include a digital signal processor (DSP), such as one or more audio DSPs 916. The one or more audio DSPs 916 may include elements for compression / decompression and echo cancellation, and may include other suitable processing elements in other embodiments. In some embodiments, the components of the baseband circuit may be appropriately combined in a single chip, a single chipset, or disposed on the same circuit board. In some embodiments, some or all of the components of the baseband circuit 904 and the application circuit 902 may be implemented together, such as on a system on a chip (SOC).

[0072] In some embodiments, the baseband circuit 904 may provide communications compatible with one or more radio technologies. For example, in some embodiments, the baseband circuit 904 may support communications with an Evolved Universal Terrestrial Radio Access Network (EUTRAN) or other wireless metropolitan area network (WMAN), wireless local area network (WLAN), wireless personal area network (WPAN). Embodiments in which the baseband circuit 904 is configured to support radio communications of more than one wireless protocol may be referred to as multi-mode baseband circuits.

[0073] The RF circuit 920 can implement communication with a wireless network through a non-solid medium using modulated electromagnetic radiation. In various embodiments, the RF circuit 920 may include switches, filters, amplifiers, etc. to facilitate communication with a wireless network. The RF circuit 920 may include a receive signal path, which may include circuits for down-converting RF signals received from the FEM circuit 930 and providing baseband signals to the baseband circuit 904. The RF circuit 920 may also include a transmit signal path, which may include circuits for up-converting baseband signals provided by the baseband circuit 904 and providing RF output signals for transmission to the FEM circuit 930.

[0074] In some embodiments, the receive signal path of the RF circuit 920 may include a mixer circuit 922, an amplifier circuit 924, and a filter circuit 926. In some embodiments, the transmit signal path of the RF circuit 920 may include a filter circuit 926 and a mixer circuit 922. The RF circuit 920 may also include a synthesizer circuit 928 for synthesizing frequencies used by the mixer circuit 922 of the receive signal path and the transmit signal path. In some embodiments, the mixer circuit 922 of the receive signal path may be configured to down-convert the RF signal received from the FEM circuit 930 based on the synthesized frequency provided by the synthesizer circuit 928. The amplifier circuit 924 may be configured to amplify the down-converted signal, and the filter circuit 926 may be a low pass filter (LPF) or a band pass filter (BPF) configured to remove unwanted signals from the down-converted signal to generate an output baseband signal. The output baseband signal may be provided to the baseband circuit 904 for further processing. In some embodiments, although this is not required, the output baseband signal may be a zero frequency baseband signal. In some embodiments, mixer circuit 922 of the receive signal path may include a passive mixer, although the scope of the embodiments is not limited in this respect.

[0075] In some embodiments, mixer circuit 922 of the transmit signal path may be configured to up-convert an input baseband signal based on a synthesized frequency provided by synthesizer circuit 928 to generate an RF output signal for FEM circuit 930. The baseband signal may be provided by baseband circuit 904 and may be filtered by filter circuit 926.

[0076] In some embodiments, the mixer circuit 922 of the receive signal path and the mixer circuit 922 of the transmit signal path may include two or more mixers and may be arranged for quadrature down-conversion and up-conversion, respectively. In some embodiments, the mixer circuit 922 of the receive signal path and the mixer circuit 922 of the transmit signal path may include two or more mixers and may be arranged for image suppression (e.g., Hartley image suppression). In some embodiments, the mixer circuit 922 of the receive signal path and the mixer circuit 922 of the transmit signal path may be arranged for direct down-conversion and direct up-conversion, respectively. In some embodiments, the mixer circuit 922 of the receive signal path and the mixer circuit 922 of the transmit signal path may be configured for superheterodyne operation.

[0077] In some embodiments, the output baseband signal and the input baseband signal may be analog baseband signals, although the scope of the embodiments is not limited in this respect. In some alternative embodiments, the output baseband signal and the input baseband signal may be digital baseband signals. In these alternative embodiments, the RF circuit 920 may include an analog-to-digital converter (ADC) and a digital-to-analog converter (DAC) circuit, and the baseband circuit 904 may include a digital baseband interface to communicate with the RF circuit 920.

[0078] In some dual-mode embodiments, separate radio IC circuits may be provided to process signals for each spectrum, although the scope of the embodiments is not limited in this respect.

[0079] In some embodiments, synthesizer circuit 928 may be a fractional-N synthesizer or a fractional N / N+1 synthesizer, but the scope of the embodiments is not limited in this regard, as other types of frequency synthesizers may also be suitable. For example, synthesizer circuit 928 may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer including a phase-locked loop with a frequency divider.

[0080] Synthesizer circuit 928 may be configured to synthesize an output frequency based on a frequency input and a divider control input for use by mixer circuit 922 of RF circuit 920. In some embodiments, synthesizer circuit 928 may be a fractional-N / N+1 synthesizer.

[0081] In some embodiments, the frequency input may be provided by a voltage controlled oscillator (VCO), although this is not required. The divider control input may be provided by baseband circuitry 904 or application circuitry 902 (such as an application processor) according to the desired output frequency. In some embodiments, the divider control input (e.g., N) may be determined from a lookup table based on the channel indicated by application circuitry 902.

[0082] The synthesizer circuit 928 of the RF circuit 920 may include a frequency divider, a delay locked loop (DLL), a multiplexer, and a phase accumulator. In some embodiments, the frequency divider may be a dual-mode frequency divider (DMD), and the phase accumulator may be a digital phase accumulator (DPA). In some embodiments, the DMD may be configured to divide the input signal by N or N+1 (e.g., based on carry) to provide a fractional division ratio. In some example embodiments, the DLL may include a cascaded, tunable, delay element, a phase detector, a charge pump, and a D-type flip-flop set. In these embodiments, the delay element may be configured to divide the VCO cycle into Nd equal phase groups, where Nd is the number of delay elements in the delay line. In this way, the DLL provides negative feedback to help ensure that the total delay through the delay line is one VCO cycle.

[0083] In some embodiments, the synthesizer circuit 928 can be configured to generate a carrier frequency as an output frequency, while in other embodiments, the output frequency can be a multiple of the carrier frequency (e.g., twice the carrier frequency, four times the carrier frequency) and can be used with a quadrature generator and divider circuit to generate multiple signals with multiple different phases relative to each other at the carrier frequency. In some embodiments, the output frequency can be the LO frequency (fLO). In some embodiments, the RF circuit 920 can include an IQ / polarity converter.

[0084] The FEM circuitry 930 may include a receive signal path that may include circuitry configured to operate on RF signals received from one or more antennas 932, amplify the received signals, and provide an amplified version of the received signals to the RF circuitry 920 for further processing. The FEM circuitry 930 may also include a transmit signal path that may include circuitry configured to amplify transmit signals provided by the RF circuitry 920 for transmission by one or more of the one or more antennas 932. In various embodiments, amplification by the transmit or receive signal path may be accomplished only in the RF circuitry 920, only in the FEM circuitry 930, or in both the RF circuitry 920 and the FEM circuitry 930.

[0085] In some embodiments, the FEM circuit 930 may include a TX / RX switch to switch between transmission mode and reception mode operation. The FEM circuit 930 may include a receive signal path and a transmit signal path. The receive signal path of the FEM circuit 930 may include an LNA to amplify the received RF signal and provide the amplified received RF signal as an output (e.g., to the RF circuit 920). The transmit signal path of the FEM circuit 930 may include a power amplifier (PA) to amplify the input RF signal (e.g., provided by the RF circuit 920), and one or more filters to generate an RF signal for subsequent transmission (e.g., through one or more of the one or more antennas 932).

[0086] In some embodiments, the PMC 934 can manage the power provided to the baseband circuit 904. Specifically, the PMC 934 can control power selection, voltage scaling, battery charging, or DC-DC conversion. When the device 900 is capable of being powered by a battery, for example, when the device 900 is included in a UE, the PMC 934 can generally be included. The PMC 934 can improve power conversion efficiency while providing a desired specific implementation size and heat dissipation characteristics.

[0087] Fig. 9 PMC 934 is shown coupled only to baseband circuitry 904. However, in other embodiments, PMC 934 may additionally or alternatively be coupled to other components (such as, but not limited to, application circuitry 902, RF circuitry 920, or FEM circuitry 930) and perform similar power management operations for these components.

[0088] In some embodiments, the PMC 934 may control or otherwise be part of various power saving mechanisms of the device 900. For example, if the device 900 is in the RRC_Connected state, where the device is still connected to the RAN node because it expects to receive traffic immediately, then after a period of inactivity, the device may enter a state known as discontinuous reception mode (DRX). During this state, the device 900 may be powered off for short time intervals, thereby saving power.

[0089] If there is no data traffic activity for an extended period of time, the device 900 may transition to the RRC_Idle state, in which the device is disconnected from the network and does not perform operations such as channel quality feedback, handover, etc. The device 900 enters a very low power state and performs paging, in which the device periodically wakes up again to listen to the network and then powers down again. The device 900 cannot receive data in this state, and in order to receive data, the device must transition back to the RRC_Connected state.

[0090] An additional power saving mode can keep a device from using the network for longer than the paging interval (which can range from a few seconds to several hours). During this time, the device is completely unable to connect to the network and can be completely powered down. Any data sent during this time will be significantly delayed, and it is assumed that the delay is acceptable.

[0091] The processor of the application circuit 902 and the processor of the baseband circuit 904 can be used to execute elements of one or more instances of the protocol stack. For example, the processor of the baseband circuit 904 can be used alone or in combination to perform layer 3, layer 2, or layer 1 functions, while the processor of the application circuit 902 can utilize data received from these layers (e.g., packet data) and further perform layer 4 functions (e.g., transport communication protocol (TCP) and user datagram protocol (UDP) layers). As mentioned herein, layer 3 may include a radio resource control (RRC) layer, which will be described in further detail below. As mentioned herein, layer 2 may include a medium access control (MAC) layer, a radio link control (RLC) layer, and a packet data convergence protocol (PDCP) layer, which will be described in further detail below. As mentioned herein, layer 1 may include a physical (PHY) layer of a UE / RAN node, which will be described in further detail below.

[0092] Fig.10 An exemplary interface 1000 of a baseband circuit according to some embodiments is shown. As described above, Fig. 9 The baseband circuit 904 may include a 3G baseband processor 906, a 4G baseband processor 908, a 5G baseband processor 910, other baseband processors 912, a CPU 914, and a memory 918 used by the processor. As shown, each of these processors may include a corresponding memory interface 1002 to send data to / receive data from the memory 918.

[0093] The baseband circuit 904 may also include one or more interfaces to communicatively couple to other circuits / devices, such as a memory interface 1004 (e.g., an interface for sending / receiving data to / from a memory external to the baseband circuit 904), an application circuit interface 1006 (e.g., an interface for sending / receiving data to / from a memory external to the baseband circuit 904), and an application circuit interface 1007 (e.g., an interface for sending / receiving data to / from a memory external to the baseband circuit 904). Fig. 9 The application circuit 902 sends / receives data), the RF circuit interface 1008 (for example, for sending / receiving data to / from Fig. 9 an interface for sending / receiving data to / from a RF circuit 920), a wireless hardware connection interface 1010 (e.g., for sending / receiving data to / from a near field communication (NFC) component, Parts (e.g. Low power consumption), components and other communication components to send / receive data) and a power management interface 1012 (for example, an interface for sending / receiving power or control signals to / from the PMC 934).

[0094] Fig.11 1 is a block diagram illustrating components of a NFV-enabled system 1100 according to some example embodiments. The system 1100 is shown to include a virtualization infrastructure manager (shown as VIM 1102), a network function virtualization infrastructure (shown as NFVI 1104), a VNF manager (shown as VNFM 1106), virtualized network functions (shown as VNF 1108), an element manager (shown as EM 1110), a NFV orchestrator (shown as NFVO 1112), and a network manager (shown as NM 1114).

[0095] The VIM 1102 manages resources of the NFVI 1104. The NFVI 1104 may include physical or virtual resources and applications (including a hypervisor) for executing the system 1100. The VIM 1102 may utilize the NFVI 1104 to manage the lifecycle of virtual resources (e.g., creation, maintenance, and teardown of virtual machines (VMs) associated with one or more physical resources), track VM instances, track performance, failures, and security of VM instances and associated physical resources, and expose VM instances and associated physical resources to other management systems.

[0096] The VNFM 1106 may manage the VNF 1108. The VNF 1108 may be used to perform EPC components / functions. The VNFM 1106 may manage the lifecycle of the VNF 1108 and track the performance, failures, and security of the VNF 1108 in virtual terms. The EM 1110 may track the performance, failures, and security of the VNF 1108 in functional terms. The tracking data from the VNFM 1106 and the EM 1110 may include, for example, performance measurement (PM) data used by the VIM 1102 or the NFVI 1104. The VNFM 1106 and the EM 1110 may both scale up / down the number of VNFs of the system 1100.

[0097] NFVO 1112 may coordinate, authorize, release, and engage resources of NFVI 1104 in order to provide requested services (e.g., execute EPC functions, components, or slices). NM 1114 may provide an end-user functional grouping responsible for network management, which may include network elements with VNFs, non-virtualized network functions, or both (management of VNFs may occur via EM 1110).

[0098] Fig.121 is a block diagram illustrating a component 1200 capable of reading instructions from a machine-readable or computer-readable medium (e.g., a non-transitory machine-readable storage medium) and capable of performing any one or more of the methods discussed herein, according to some example embodiments. Specifically, Fig.12 A schematic diagram of hardware resources 1202 is shown, including one or more processors 1212 (or processor cores), one or more memory / storage devices 1218, and one or more communication resources 1220, each of which can be communicatively coupled via a bus 1222. For embodiments in which node virtualization (e.g., NFV) is utilized, a hypervisor 1204 can be executed to provide an execution environment for one or more network slices / sub-slices to utilize the hardware resources 1202.

[0099] Processor 1212 (e.g., a central processing unit (CPU), a reduced instruction set computing (RISC) processor, a complex instruction set computing (CISC) processor, a graphics processing unit (GPU), a digital signal processor (DSP) (such as a baseband processor), an application specific integrated circuit (ASIC), a radio frequency integrated circuit (RFIC), another processor, or any suitable combination thereof) may include, for example, processor 1214 and processor 1216.

[0100] The memory / storage device 1218 may include main memory, disk storage, or any suitable combination thereof. The memory / storage device 1218 may include, but is not limited to, any type of volatile or non-volatile memory, such as dynamic random access memory (DRAM), static random access memory (SRAM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, solid-state memory, etc.

[0101] The communication resources 1220 may include interconnect or network interface components or other suitable devices to communicate with one or more peripheral devices 1206 or one or more databases 1208 via the network 1210. For example, the communication resources 1220 may include wired communication components (e.g., for coupling via a universal serial bus (USB)), cellular communication components, NFC components, Parts (e.g. Low power consumption), components and other communication components.

[0102] The instructions 1224 may include software, programs, applications, applet, applications, or other executable code for causing at least any one of the processors 1212 to perform any one or more of the methodologies discussed herein. The instructions 1224 may reside completely or partially in at least one of the processors 1212 (e.g., within a cache memory of the processor), the memory / storage device 1218, or any suitable combination thereof. In addition, any portion of the instructions 1224 may be transmitted to the hardware resources 1202 from any combination of the peripheral device 1206 or the database 1208. Therefore, the memory of the processor 1212, the memory / storage device 1218, the peripheral device 1206, and the database 1208 are examples of computer-readable and machine-readable media.

[0103] For one or more embodiments, at least one of the components shown in one or more of the foregoing figures may be configured to perform one or more operations, techniques, processes and / or methods described in the following examples section. For example, the baseband circuit described above in conjunction with one or more of the foregoing figures may be configured to operate according to one or more of the following embodiments. For another example, the circuits associated with the UE, base station, network element, etc. described above in conjunction with one or more of the foregoing figures may be configured to operate according to one or more of the embodiments shown in the examples section below.

[0104] Examples

[0105] The following examples relate to additional embodiments.

[0106] Embodiment 1 is an apparatus for a user equipment (UE) configured for multi-antenna communication. The apparatus includes a memory interface and a processor. The memory interface is used to: send to or receive from a memory device communication data associated with a plurality of packets transmitted using device-to-device (D2D) communication. The processor is used to: estimate at least one of a rank indicator and a channel quality indicator for the D2D communication based on the communication data and without using a dedicated reference signal for the D2D communication; and encode a feedback message to one or more transmitters participating in the D2D communication, the feedback message indicating at least one of the rank indicator and the channel quality indicator.

[0107] Embodiment 2 is the apparatus of embodiment 1, wherein the UE is configured to function as at least one of a transmitter (Tx) and a receiver (Rx) for vehicle-to-everything (V2X) communication.

[0108] Embodiment 3 is the apparatus of embodiment 1, wherein the communication data includes hybrid automatic repeat request (HARQ) information, the HARQ information including acknowledgement (ACK) responses and negative acknowledgement (NACK) responses associated with the plurality of packets.

[0109] Embodiment 4 is an apparatus according to embodiment 3, wherein the processor is further configured to: monitor the ACK response and the NACK response for a selected modulation and coding scheme; if the NACK response increases within a time period, adjust the modulation and coding scheme to reduce the number of bits per symbol; if the NACK response decreases or is below a threshold amount within the time period, adjust the modulation and coding scheme to increase the number of bits per symbol; and encode the feedback message to include an indication of the adjustment to the modulation and coding scheme.

[0110] Embodiment 5 is the apparatus of embodiment 1, wherein adjusting the modulation and coding scheme comprises adjusting the modulation and coding scheme only once every X received ACK / NACK responses.

[0111] Embodiment 6 is the apparatus of embodiment 1, wherein the communication data includes demodulation information associated with demodulation of the plurality of packets received at the UE using the D2D communication within a time period.

[0112] Embodiment 7 is the apparatus of embodiment 6, wherein the demodulation information comprises a demodulation reference signal (DMRS).

[0113] Embodiment 8 is the apparatus of embodiment 7, wherein the processor is further configured to: determine an estimated channel based on the DMRS to demodulate the plurality of packets; and calculate the channel quality indicator based on long-term statistics of the estimated channel.

[0114] Embodiment 9 is an apparatus according to embodiment 8, wherein the processor is further configured to: determine an interference measurement for each subchannel based on the DMRS; and determine the channel quality indicator by averaging or weighting both the estimated channel and the interference measurement within at least one of the time period and the bandwidth used for transmission.

[0115] Embodiment 10 is the apparatus of embodiment 8, wherein the processor is further configured to estimate the rank indicator based on the long-term statistics of the estimated channel.

[0116] Embodiment 11 is an apparatus according to embodiment 10, wherein the processor is further configured to: if the channel coefficients received at different receiving antennas of the UE corresponding to the same subcarrier and orthogonal frequency division multiplexing (OFDM) symbol are highly correlated, configure the UE to use a single spatial layer for the D2D communication; and if the channel coefficients are weakly correlated, configure the UE to use multiple spatial layers for the D2D communication.

[0117] Embodiment 12 is an apparatus according to embodiment 1, wherein the processor is further configured to: use the D2D communication to exchange codebook information with one or more transmitters or receivers communicating with the UE, the codebook information indicating a cycle of a precoder used for the multiple groups; estimate a multiple-input multiple-output (MIMO) channel based on the cycle of the precoder; and determine the rank indicator based on the MIMO channel.

[0118] Embodiment 13 is a non-transitory computer-readable storage medium. The computer-readable storage medium includes instructions that, when executed by a baseband processor of a vehicle-to-everything (V2X) device, cause the baseband processor to: estimate at least one of a rank indicator and a channel quality indicator for device-to-device (D2D) communication based on communication data associated with a plurality of packets transmitted using the D2D communication and without using a dedicated reference signal for the D2D communication; and encode a feedback message to one or more transmitters participating in the communication using the D2D communication, the feedback message indicating at least one of the rank indicator and the channel quality indicator.

[0119] Embodiment 14 is a computer-readable storage medium according to embodiment 13, wherein the communication data includes hybrid automatic repeat request (HARQ) information, the HARQ information including acknowledgement (ACK) responses and negative acknowledgement (NACK) responses associated with multiple packets transmitted.

[0120] Embodiment 15 is a computer-readable storage medium according to embodiment 14, wherein the instructions further configure the baseband processor to: monitor the ACK response and the NACK response for a selected modulation and coding scheme; if the NACK response increases within a time period, adjust the modulation and coding scheme to reduce the number of bits per symbol; if the NACK response decreases or is below a threshold amount within the time period, adjust the modulation and coding scheme to increase the number of bits per symbol; and encode the feedback message to include an indication of the adjustment to the modulation and coding scheme.

[0121] Embodiment 16 is the apparatus of embodiment 15, wherein adjusting the modulation and coding scheme comprises adjusting the modulation and coding scheme only once every X received ACK / NACK responses.

[0122] Embodiment 17 is a computer-readable storage medium according to embodiment 13, wherein the communication data includes demodulation information associated with demodulation of the plurality of packets received at the V2X device within a time period.

[0123] Embodiment 18 is the computer-readable storage medium of embodiment 17, wherein the demodulation information comprises a demodulation reference signal (DMRS).

[0124] Embodiment 19 is a computer-readable storage medium according to embodiment 18, wherein the instructions further configure the baseband processor to: determine an estimated channel based on the DMRS to demodulate the multiple packets; and calculate the channel quality indicator based on long-term statistics of the estimated channel.

[0125] Embodiment 20 is a computer-readable storage medium according to embodiment 19, wherein the instructions further configure the baseband processor to: determine an interference measurement for each subchannel based on the DMRS; and determine the channel quality indicator by averaging or weighting both the estimated channel and the interference measurement within at least one of the time period and the bandwidth used for transmission.

[0126] Embodiment 21 is a computer-readable storage medium according to embodiment 19, wherein the instructions further configure the baseband processor to estimate the rank indicator based on the long-term statistics of the estimated channel.

[0127] Embodiment 21 is a computer-readable storage medium according to embodiment 20, wherein the instructions further configure the baseband processor to: if the channel coefficients received at different receiving antennas of the V2X device corresponding to the same subcarrier and orthogonal frequency division multiplexing (OFDM) symbol are highly correlated, configure the UE to use a single spatial layer for the D2D communication; and if the channel coefficients are weakly correlated, configure the V2X device to use multiple spatial layers for the D2D communication.

[0128] Embodiment 23 is a computer-readable storage medium according to embodiment 13, wherein the instructions further configure the baseband processor to: exchange codebook information with one or more transmitters or receivers communicating with the V2X device, the codebook information indicating a cycle of a precoder used for the multiple groups; estimate a multiple-input multiple-output (MIMO) channel based on the cycle of the precoder; and determine the rank indicator based on the MIMO channel.

[0129] Unless explicitly stated otherwise, any of the above embodiments may be combined with any other embodiment (or combination of embodiments). The foregoing description of one or more specific implementations provides illustration and description, but is not intended to be exhaustive or to limit the scope of the embodiments to the precise form disclosed. Modifications and variations are possible in view of the above teachings or may be obtained from the practice of the various embodiments.

[0130] Embodiments and implementations of the systems and methods described herein may include various operations that may be embodied in machine executable instructions to be executed by a computer system. A computer system may include one or more general or special purpose computers (or other electronic devices). A computer system may include hardware components that include specific logic components for performing operations, or may include a combination of hardware, software, and / or firmware.

[0131] It should be appreciated that the systems described herein include descriptions of specific embodiments. These embodiments may be combined into a single system, partially incorporated into other systems, separated into multiple systems, or otherwise divided or combined. In addition, it is contemplated that parameters / attributes / aspects, etc. of one embodiment may be used in another embodiment. For clarity, these parameters / attributes / aspects, etc. are described only in one or more embodiments, and it should be appreciated that unless otherwise stated herein, these parameters / attributes / aspects, etc. may be combined with or substituted for parameters / attributes, etc. of another embodiment.

[0132] Although the foregoing has been described in considerable detail for the sake of clarity, it will be apparent that certain changes and modifications may be made without departing from the principles of the invention. It should be noted that there are many alternative ways to implement both the processes and the apparatus described herein. Therefore, the embodiments of the present invention are to be regarded as illustrative rather than restrictive, and the description is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.

Claims

1. An apparatus for a user equipment UE configured for multi-antenna communication, the apparatus comprising: a memory interface for sending to or receiving from a memory device communication data associated with a plurality of packets transmitted using device-to-device (D2D) communication, wherein the communication data comprises demodulation information associated with demodulation of the plurality of packets received at the UE using the D2D communication within a time period, and wherein the demodulation information comprises a demodulation reference signal (DMRS); and A processor, the processor being configured to: estimating at least one of a rank indicator or a channel quality indicator for the D2D communication based on the communication data and without using a dedicated reference signal for the D2D communication; and encoding a feedback message to one or more transmitters participating in the D2D communication, the feedback message indicating at least one of the rank indicator or the channel quality indicator; determining an estimated channel based on the DMRS to demodulate the plurality of packets; determining an interference measurement for each subchannel based on the DMRS; and The channel quality indicator is determined by averaging or weighting both the estimated channel and the interference measurement over at least one of the time period and a bandwidth used for transmission.

2. The apparatus according to claim 1, wherein the UE is configured as at least one of a transmitter Tx and a receiver Rx for vehicle-to-everything (V2X) communication.

3. The apparatus of claim 1, wherein the communication data comprises hybrid automatic repeat request (HARQ) information, the HARQ information comprising acknowledgement (ACK) responses and negative acknowledgement (NACK) responses associated with the plurality of packets.

4. The apparatus of claim 3, wherein the processor is further configured to: monitoring the ACK response and the NACK response for a selected modulation and coding scheme; If the NACK responses increase over a period of time, adjusting the modulation coding scheme to reduce the number of bits per symbol; If the NACK responses decrease or fall below a threshold number within the time period, adjusting the modulation coding scheme to increase the number of bits per symbol; and The feedback message is encoded to include an indication to adjust the modulation coding scheme.

5. The apparatus of claim 4, wherein adjusting the modulation and coding scheme comprises: The modulation coding scheme is adjusted only once every X received ACK / NACK responses.

6. The apparatus of claim 1, wherein the processor is further configured to: The channel quality indicator is calculated based on long term statistics of the estimated channel.

7. The apparatus of claim 6, wherein the processor is further configured to estimate the rank indicator based on the long-term statistics of the estimated channel.

8. The apparatus of claim 7, wherein the processor is further configured to: If channel coefficients received at different receive antennas of the UE corresponding to the same subcarrier and orthogonal frequency division multiplexing (OFDM) symbol are highly correlated, configuring the UE to use a single spatial layer for the D2D communication; and If the channel coefficients are weakly correlated, configuring the UE to use multiple spatial layers for the D2D communication.

9. The apparatus of claim 1, wherein the processor is further configured to: exchanging codebook information with one or more transmitters or receivers communicating with the UE using the D2D communication, the codebook information indicating a cycle of a precoder for the plurality of packets; estimating a multiple-input multiple-output MIMO channel based on a cycle of the precoder; as well as The rank indicator is determined based on the MIMO channel.

10. A non-transitory computer-readable storage medium comprising instructions that, when executed by a baseband processor of a vehicle-to-everything (V2X) device, cause the baseband processor to: estimating at least one of a rank indicator or a channel quality indicator for device-to-device (D2D) communication based on communication data associated with a plurality of packets transmitted using the D2D communication and without using a dedicated reference signal for the D2D communication, wherein: The communication data includes demodulation information associated with demodulation of the plurality of packets received at the V2X device within a certain time period, and wherein the demodulation information includes a demodulation reference signal (DMRS); and encoding a feedback message to one or more transmitters participating in the D2D communication, the feedback message indicating at least one of the rank indicator or the channel quality indicator; determining an estimated channel based on the DMRS to demodulate the plurality of packets; determining an interference measurement for each subchannel based on the DMRS; and The channel quality indicator is determined by averaging or weighting both the estimated channel and the interference measurement over at least one of the time period and a bandwidth used for transmission.

11. The computer-readable storage medium of claim 10, wherein the communication data comprises hybrid automatic repeat request (HARQ) information, the HARQ information comprising acknowledgement (ACK) responses and negative acknowledgement (NACK) responses associated with a plurality of transmitted packets.

12. The computer-readable storage medium of claim 11, wherein the instructions further configure the baseband processor to: monitoring the ACK response and the NACK response for a selected modulation and coding scheme; If the NACK responses increase over a period of time, adjusting the modulation coding scheme to reduce the number of bits per symbol; If the NACK responses decrease or fall below a threshold amount within the time period, adjusting the modulation coding scheme to increase the number of bits per symbol; and The feedback message is encoded to include an indication to adjust the modulation coding scheme.

13. The computer-readable storage medium of claim 12, wherein adjusting the modulation coding scheme comprises: The modulation coding scheme is adjusted only once every X received ACK / NACK responses.

14. The computer-readable storage medium of claim 10, wherein the instructions further configure the baseband processor to: The channel quality indicator is calculated based on long term statistics of the estimated channel.

15. The computer-readable storage medium of claim 14, wherein the instructions further configure the baseband processor to estimate the rank indicator based on the long-term statistics of the estimated channel.

16. The computer-readable storage medium of claim 10, wherein the instructions further configure the baseband processor to: If channel coefficients received at different receive antennas of the V2X device corresponding to the same subcarrier and orthogonal frequency division multiplexing (OFDM) symbol are highly correlated, configuring the V2X device to use a single spatial layer for the D2D communication; and If the channel coefficients are weakly correlated, configuring the V2X device to use multiple spatial layers for the D2D communication.

17. The computer-readable storage medium of claim 10, wherein the instructions further configure the baseband processor to: exchanging codebook information with one or more transmitters or receivers in communication with the V2X device, the codebook information indicating a cycle of a precoder used for the plurality of packets; estimating a multiple-input multiple-output MIMO channel based on a cycle of the precoder; and The rank indicator is determined based on the MIMO channel.

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