Orientation determination in telecommunication systems

1 . An apparatus operating as a Transmission-Reception Point (TRP) or gNodeB (gNB), the apparatus comprising:

at least one processor; and

at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to:

establish a positioning session with a user apparatus to support an Extended Reality (XR) session, wherein the positioning session is initiated in response to a request from a Location Management Function (LMF) that is communicatively coupled to an XR server;

configure, as a part of the positioning session, the user apparatus to transmit a corresponding Sounding Reference Signal (SRS) from each of at least two antennas of the user apparatus on a periodic basis;

receive, from the user apparatus, a configuration of the user apparatus, wherein the configuration indicates positions of the at least two antennas with respect to a center point of rotation of the user apparatus, and wherein the configuration is received as an update via medium access control (MAC) layer signaling using one or more MAC control elements (CEs);

receive, from the user apparatus, sensor data, wherein the sensor data comprises data from at least one of an Inertial Measurement Unit (IMU) or a camera of the user apparatus;

receive, from the at least two antennas of the user apparatus through a radio interface or a direct link interface, at least two Sounding Reference Signals (SRSs),

wherein the at least two SRSs are separable at the apparatus using a multiplexing scheme,

wherein the multiplexing scheme includes time-division, frequency-division, Orthogonal Frequency Division Multiplexing (OFDM), or code-division, and

wherein the direct link interface is a PC5 interface;

determine, from each of the at least two SRSs, a corresponding micro-Doppler frequency shift,

wherein the corresponding micro-Doppler frequency shift is caused by a rotational micro-motion of the user apparatus, and

wherein the determination is based on a model where each corresponding micro-Doppler frequency shift is proportional to:

a carrier frequency (f c ) of the corresponding SRS, and

an angular velocity (ω) of the user apparatus;

determine an orientation, an angular velocity, a location, a translational velocity of the user apparatus using the determined at least two micro-Doppler frequency shifts, the received sensor data, and the received configuration of the user apparatus; and

send the determined orientation and the determined location to the XR server.

2 . The apparatus of claim 1 , wherein the apparatus receives the at least two SRSs simultaneously, concurrently or quasi concurrently.

3 . A user apparatus, wherein the user apparatus is an Extended Reality (XR) device comprising a headset, the user apparatus comprising:

at least one processor;

at least two antennas;

at least one of an Inertial Measurement Unit (IMU) or a camera; and

at least one memory storing instructions that, when executed by the at least one processor, cause the user apparatus at least to:

establish a positioning session with a Location Management Function (LMF) in response to a location request initiated by an XR Server, wherein the positioning session has a Quality of Service (QoS) profile for an XR service;

transmit, during an initiation phase of the positioning session, an initial configuration of the user apparatus to the LMF, wherein the configuration defines a body frame of the user apparatus and positions of the at least two antennas with respect to a center point of rotation of the user apparatus;

transmit, from the at least two antennas to a Transmission-Reception Point (TRP) or gNB, a plurality of Sounding Reference Signals (SRSs),

wherein the plurality of SRSs from each of the at least two antennas are structured to be separable using one of a time-division, frequency-division, or code-division multiplexing scheme, and

wherein each SRS of the plurality of SRSs is uniquely associated with a respective antenna of the at least two antennas;

transmit sensor data from the at least one of the Inertial Measurement Unit (IMU) or the camera directly to the LMF;

transmit, to the LMF, an updated configuration in response to a change in the positions of one or more of the at least two antennas using Medium Access Control (MAC) layer signaling comprising one or more MAC control elements (CEs),

transmit, to an XR server, user XR data for rendering;

receive, from the XR server, rendered user XR data, wherein the rendered user XR data is based on an orientation and an angular velocity of the user apparatus determined by the LMF from the transmitted SRSs and the transmitted sensor data; and

present, via the headset, the rendered user XR data as immersive content synchronized with movement of the user apparatus.

4 . A system, comprising:

a first apparatus comprising a Transmission-Reception Point (TRP) or gNodeB (gNB) the first apparatus comprising:

at least first processor; and

at least first memory storing instructions that, when executed by the at least one processor, cause the first apparatus at least to:

establish a positioning session with a user apparatus to support an Extended Reality (XR) session;

configure, as a part of the positioning session, the user apparatus to transmit a corresponding Sounding Reference Signal (SRS) from each of at least two antennas of the user apparatus on a periodic basis;

receive, from the at least two antennas of a user apparatus through a radio interface or a direct link interface, at least two Sounding Reference Signals (SRSs),

wherein the at least two SRSs are separable at the first apparatus using a multiplexing scheme,

wherein the multiplexing scheme includes time-division, frequency-division, Orthogonal Frequency Division Multiplexing (OFDM), or code-division, and

wherein the direct link interface is a PC5 interface;

determine, from each of the at least two SRSs, a corresponding micro-Doppler frequency shift resulting in at least two micro-Doppler frequency shifts,

wherein the corresponding micro-Doppler frequency shift is caused by a micro-motion of the user apparatus, wherein the micro-motion comprises a rotation motion, and

wherein the determination is based on a model where each of the corresponding micro-Doppler frequency shift is proportional to:

a carrier frequency (f c ) of the corresponding SRS, and

an angular velocity (ω) of the user apparatus; and

report, via NR Positioning Protocol A (NRPPa), the determined at least two micro-Doppler frequency shifts to a Location Management Function (LMF); and

a second apparatus comprising the LMF, the second apparatus communicatively coupled to the first apparatus, the second apparatus comprises:

at least second processor; and

at least second memory storing instructions that, when executed by the at least one processor, cause the second apparatus to:

receive a location request for the user apparatus from an Extended Reality (XR) Server;

establish the positioning session with the user apparatus,

wherein the positioning session comprises:

an exchange of XR device capabilities,

positioning assistance data, and

an initial location of the user apparatus;

receive, from the first apparatus, the reported at least two micro-Doppler frequency shifts;

receive sensor data from the user apparatus, wherein the sensor data is received from at least one of an Inertial Measurement Unit (IMU) or a camera of the user apparatus;

determine an orientation, an angular velocity, and a location of the user apparatus by performing a joint Extended Kalman Filter (EKF) tracking configured to track a state of the user apparatus, the state comprising the orientation, the angular velocity, the location, and a translational velocity of the user apparatus using the determined at least two micro-Doppler frequency shifts, the received sensor data, and a configuration of the user apparatus,

wherein the configuration indicates at least one of:

a body frame of the user apparatus, or

positions of the antennas of the user apparatus with respect to a center point of rotation of the user apparatus, wherein the positions are defined by a distance (r j ) from the center point of rotation and an initial angle (α j ) relative to the body frame of the user apparatus,

the configuration further indicating a distance (R BS ) and an angle (φ BS ) between the TRP or gNB and the center point of rotation of the user apparatus,

wherein the configuration is initially exchanged during the positioning session,

wherein the second apparatus is further configured to receive subsequent updates to the configuration via medium access control (MAC) layer signaling, and

wherein the orientation is a relative orientation or absolute orientation;

repeatedly cause the first apparatus to perform the receiving of the at least two SRSs and the determining of the at least two micro-Doppler frequency shifts and repeatedly perform the receiving of the sensor data and the determining of the orientation, angular velocity, and location at intervals of 10 milliseconds or less; and

send the determined orientation, the angular velocity and the location as a six degrees of freedom (6DoF) state to the XR Server for rendering user XR data after receiving the user XR data from the user apparatus,

wherein the rendering is synchronized with the determined orientation, the angular velocity, and the location,

wherein the rendering comprises pre-processing of the user XR data based on a predicted future 6DoF state derived from the determined angular velocity and the translational velocity, and

wherein the XR Server is further configured to deliver the rendered user XR data back to the user apparatus.

5 . The system of claim 4 , wherein the pre-processing of the user XR data based on the predicted future 6DoF state enables at least part of the user XR data to be processed beforehand.

6 . The system of claim 4 , wherein the configuration is updated by the user apparatus in response to a change in the user apparatus that affects the configuration, wherein the change comprises a change in the positions of the at least two antennas.

7 . The system of claim 6 , wherein the first apparatus is one of a set of L network apparatuses, where L≥2, and wherein the joint EKF tracking performed by the second apparatus is based on micro-Doppler frequency shift measurements received from each of the L network apparatuses to perform the joint EKF tracking for the user apparatus.

8 . The system of claim 4 , wherein, the direct link interface is the PC5 interface, and wherein the first apparatus is another user apparatus, and the orientation is determined with respect to the another user apparatus based on sidelink reference signals transmitted over the PC5 interface.