Patent Description:
NR may support various wireless communication services, such as Enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g. <NUM> beyond), millimeter wave (mmW) targeting high carrier frequency (e.g. <NUM>), massive MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra-reliable low latency communications (URLLC).

Wireless communication systems may also include or support networks used for vehicle based communications, also referred to as vehicle-to-everything (V2X), vehicle-to-vehicle (V2V) networks, and/or cellular V2X (C-V2X) networks. Vehicle based communication networks may provide always on telematics where UEs, e.g., vehicle UEs (v-UEs), communicate directly to the network (V2N), to pedestrian UEs (V2P), to infrastructure devices (V2I), and to other v-UEs (e.g., via the network). The vehicle based communication networks may support a safe, always-connected driving experience by providing intelligent connectivity where traffic signal/timing, real-time traffic and routing, safety alerts to pedestrians/bicyclist, collision avoidance information, etc., are exchanged.

Such network supporting vehicle based communications, however, may also be associated with various requirements, e.g., communication requirements, security and privacy requirements, etc. Other example requirements may include, but are not limited to, reduced latency requirements, higher reliability requirements, and the like. For example, vehicle-based communications may include communicating sensor data that may support self-driving cars. Sensor data may be used between vehicles to improve the safety of self-driving cars.

<CIT> discloses methods and systems for enabling the rectification of deteriorated channel conditions on a communication link are described. In particular, the methods and systems can employ mechanisms that prioritize beams in accordance with signal quality measures, direction of departures of transmission beams and/or direction of arrivals of reception beams to address variable channel conditions.

The choice of a transmit (Tx)-Receive (Rx) beam pair out of many available beam pairs between a base station and a mmW-capable UE is directly related to the performance of transmission between the base station and the UE. A currently prevalent approach to selecting a serving Tx-Rx beam pair is to measure each beam pair from multiple available beam pairs in a round-robin manner and to determine a new serving beam pair based on the measurement results. In this round-robin manner, every beam pair has equal opportunity to be measured in a synchronization cycle. In fact, due to factors such as line of sight (LoS) and proximity between the beam pairs, chances for the beam pairs to be selected as the serving beam pair are different. The round robin approach does not distinguish among the beam pairs and thus may result in long latency in selecting the serving beam pair.

Thus, there is a need for a method, apparatus, and computer-readable medium at a user equipment (UE) in a mmW communications environment to assign a priority to each beam pair, taking into consideration dynamic information and static information of the beam pair, to quickly converge on one a good serving beam pair.

A network that includes both small cell and macro cells may be known as a heterogeneous network. The base stations <NUM> / UEs <NUM> may use spectrum up to F MHz (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) bandwidth per carrier allocated in a carrier aggregation of up to a total of Yx MHz (x component carriers) used for transmission in each direction. Allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or less carriers may be allocated for DL than for UL).

The base station may also be referred to as a gNB, Node B, evolved Node B (eNB), an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), or some other suitable terminology. The base station <NUM> provides an access point to the EPC <NUM> for a UE <NUM>. Examples of UEs <NUM> include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, a tablet, a smart device, a wearable device, a vehicle, an electric meter, a gas pump, a toaster, or any other similar functioning device. Some of the UEs <NUM> may be referred to as IoT devices (e.g., parking meter, gas pump, toaster, vehicles, etc.).

Referring again to <FIG>, in certain aspects, the UE <NUM> may be configured to include a serving beam pair selection component (<NUM>) that enables the UEs <NUM> to determine a serving beam pair among multiple beam pairs efficiently. This in turn enables the UE to set up a link between the UE and the base station with minimal latency, especially in a dynamical environment, where the UE is in a fast motion and the current serving beam pair may need frequent updating.

For example, cooperation may be present within a TRP and/or across TRPs via the ANC <NUM>.

In one example aspect, the Radio Resource Control (RRC) layer, Packet Data Convergence Protocol (PDCP) layer, Radio Link Control (RLC) layer, Medium Access Control (MAC) layer, and a Physical (PHY) layers may be adaptably placed at the DU or CU (e.g., TRP or ANC, respectively).

<FIG> is a diagram <NUM> illustrating a base station <NUM> in communication with a UE <NUM>. Referring to <FIG>, the base station <NUM> may transmit a beamformed signal to the UE <NUM> in one or more of the directions 402a, 402b, 402c, 402d, 402e, 402f, <NUM>, <NUM>. The UE <NUM> may receive the beamformed signal from the base station <NUM> in one or more receive directions 404a, 404b, 404c, 404d. The UE <NUM> may also transmit a beamformed signal to the base station <NUM> in one or more of the directions 404a-404d. The base station <NUM> may receive the beamformed signal from the UE <NUM> in one or more of the receive directions 402a-<NUM>.

<FIG> is a diagram 500a illustrating a base station <NUM> in communication with a UE <NUM>, in accordance with one or more aspects of the present disclosure. The diagram 500a shows a set of transmit beam 502a-502d at a <NUM> base station and a set of receive beam 506a-506d at the UE. One of the transmit beams 502a-502d may pair up with one of the receive beam 506a-506d to form a serving Tx-Rx beam pair to carry a signal through a millimeter wave channel <NUM> between the base station <NUM> and the UE <NUM>.

In one example aspect, before any communication between <NUM> mmW base station <NUM> and the UE <NUM>, the base station <NUM> may first broadcast all <NUM> (Tx) beams <NUM>-<NUM> or 502a-502d in a beam reference signal (BRS) cycle to all the device in the transmission range. The UE <NUM> in turn pairs up the received Tx beams with its Rx beams to find the most suitable beam pair for transmissions between the UE <NUM> and the base station <NUM>. Larger the number of Tx beams and number of Rx beams are, longer it may take to find the most suitable beam pair, or a new serving beam pair. In the diagram <NUM>, there are <NUM> Tx beams and <NUM> Rx beams. That is, the size of Tx beams and Rx beams are M=<NUM>, and N=<NUM> respectively.

A BRS cycle is a synchronization cycle which may include a predetermined number of synchronization periods. Different terms may be used for a synchronization period. For example, a synchronization period may be referred to as a synchronization frame (SF). During a synchronization frame, a number of candidate Tx-Rx beam pairs may be selected and measured to determine a new serving Tx-Rx beam pair. For example, in one SF, each of Tx beams may be paired with one of the Rx beams to form a candidate Tx-Rx beam pair sequence for beam pair measurement, if the selection method is to allow Tx beams to vary. To select a reasonably stable serving beam pair, predetermined number of synchronization cycles may be needed.

The quality of a candidate Tx-Rx beam pair, in one aspect, may be measured in terms of beam gain. Several factors may affect the measured beam gain of a candidate beam pair, including line of sight (LoS). In general, a beam pair with LoS has a better beam gain than a beam pair without LoS, provided everything else being equal.

In one example aspect, during one synchronization cycle, all Tx beams are expected to emit in a fixed pattern, because a base station may not change its location frequently. Referring to <FIG> again, the Tx-Rx beam pair (<NUM>,<NUM>) and the Tx-Rx beam pair (<NUM>,<NUM>) are expected to have better beam gains because Rx beam <NUM> has a LoS with the Tx beams <NUM> and <NUM>, if only LoS is considered for beam gain measurements.

<FIG> illustrates an example sequence 500b of Tx-Rx beams pairs, in accordance with one or more aspects of the present disclosure. Based on the Tx-Rx beam pairs of <FIG> illustrates a sequence of beam pairs for measurement based on a round-robin approach. The example sequence 500b illustrates a synchronization cycle or BRS cycle that includes <NUM> synchronization frames 512a-512d. According to the round robin approach, one of the Rx beams is selected sequentially to pair with each of Tx beams within a SF to form M candidate beam pairs for beam gain measurement, M being the size of Tx beam set. As shown in <FIG>, during the SF 512a, the Rx beam <NUM> is paired with each of the <NUM> Tx beams <NUM> through <NUM>, for measurement, and then next Rx beam, Rx beam <NUM>, is paired with each of the <NUM> Tx beams <NUM> through <NUM> for measurement. All N Rx beams are measured in a round-robin fashion.

According to the existing approach, it normally requires at least a complete BRS or synchronization cycle for all Rx beams to be paired with Tx beams for beam gain measurement to find a new serving Tx-Rx beam pair. As a UE may have more than one Rx beam, it may take a number of BRS cycles before finding a suitable serving beam pair. This may result in a non-trivial latency and undesirable delay in establishing a connection between the base station and the UE. Based on the round-robin approach to determining a new serving Tx-Rx beam pair, the length of latency is proportional to the number of Rx beams.

Thus, the existing round-robin approach likely wastes synchronization SF resources, in part because some of the beam pair may have little or zero chance to be selected as the serving beam pair, due to their directions, lack of LoS or other factors. For example, referring to both <FIG>, Tx beam <NUM> and <NUM> should see more gains than <NUM> and <NUM>, if LoS is assumed. Accordingly, assigning the <NUM> Tx beams the same equal opportunity for measurement in one BRS cycle may not be necessary and may be wasteful.

<FIG> illustrate an example of a wireless communications system <NUM> that supports dynamic beam pair selection in accordance with one or more aspects of the present disclosure. The wireless communications system <NUM> includes a base station <NUM> and a UE <NUM>. At <NUM>, the base station <NUM> broadcast Tx beams available at the base station <NUM>.

At <NUM>, the UE <NUM> applies a dynamic beam pair selection process, such as the one illustrated in <FIG>, to select candidate Tx-Rx beam pairs for measurement based on the priority of each beam pair. The phrase beam pair selection is also termed beam pair scheduling. Based on the dynamic beam pair selecting process, those beam pairs with higher priorities have more chances to be selected for measurement. Thus, those beam pairs have better opportunities to become the new serving beam pair. This may result in an improved latency and delay in finding a suitable serving beam pair and establishing a connection between the base station and the UE. The details of the beam pair scheduling or selection method are shown in <FIG>, <FIG>, and <FIG> and described in the corresponding sections.

At <NUM>, the UE <NUM> reports the determined new serving beam pair to the base station <NUM>. Then at <NUM>, the UE <NUM> and base station <NUM> receive and transmit data using the new serving beam pair.

<FIG> is a flowchart for a method <NUM> of wireless communication in accordance with one or more aspects of the present disclosure. The method <NUM> may be performed by one of the UEs <NUM> of <FIG>, the UE3 <NUM> of <FIG>, the UE <NUM> of <FIG>, or apparatus <NUM>/<NUM>' of <FIG> and <FIG>. An optional step is indicated in a dashed boarder.

At <NUM>, the method <NUM> includes selecting one candidate Tx-Rx beam pair by the UE, based in part on a priority value, or priority for short, associated with the candidate Tx-Rx beam pair. In contrast to an existing round-robin approach, which assigns equal likelihood to all beam pairs, the likelihood of the beam pair being selected for measurement may not be the same as that of other beam pairs. The priority value represents the likelihood of the beam pair being selected for measurement and thus the chance of the candidate beam pair eventually becoming the new serving Tx-Rx beam pair. As will be explained shortly, the priority value is based on a combination of static information and dynamic information associated with the candidate Tx-Rx beam pair.

The UE selects a candidate beam pair also based on a beam pattern of the Tx-Rx beam pairs. In one example aspect, the Tx beams have a fixed pattern. That is, the base station such as a gNB may broadcast a fixed sequence of Tx beams that the gNB expects a UE to follow, in measurements or other situations. There may be various reasons for a fixed Tx beam pattern, such as a gNB design choice by a gNB vendor or a choice by a service provider that operates the gNB. As a result, the UE may freely select a Rx beam but follows a fixed emission pattern of the Tx beams. For example, <FIG> shows a sequence of beam pairs with a fixed Tx beam pattern that has a sequence the Tx beams ranging from Tx beam1 to Tx beam <NUM>, sequentially. In most scenarios, it is assumed that the antenna arrays at a base station are stationary in relation to the UE.

In one example aspect, selecting the Tx-Rx beam pair may include selecting the Tx-Rx beam pair for a number of time for re-measurements during a predetermined number of synchronization cycles. The number of times for re-measurements is proportional to the priority value of the selected beam pair relative to priority values of other Tx-Rx beam pairs. In other words, a candidate beam pair with a higher priority value may be selected for measurement and re-measurements more frequently than a candidate beam pair with a lower priority value.

At <NUM>, the method <NUM> includes updating the priority value of the selected beam pair. In one example aspect, the priority value may be based on two types of information: static information and dynamic information. In one aspect, the static information of Tx-Rx beam pair may include spatial relationship between the Tx-Rx beam pair, such as proximity information, a line of sight (LoS) and non LoS (NLoS), among others.

The dynamic information of the priority value may include the information that may change from one instance to the next, and from one measurement to the next. In one example aspect, the dynamic information may include one or more of the latest beam measurements of the selected Tx-Rx beam pair.

In one example aspect, the static information and the dynamic information each may have an associated weight for updating the priority value. The associated weight may be adjustable, based on the circumstances. For example, if the UE is expected to be in a very dynamic environment, the weight for the dynamic information may be greater relative to that of the static information.

In one example aspect, updating the priority for the selected beam pair may include one or more of: updating the weight associated with the static information, updating the weight associated with the dynamic information, and combining the dynamic information and the static information of the Tx-Rx beam pair, based in part on one or both of the two weights. In one example aspect, updating the priority value is performed in such a way that a higher priority value results in a higher chance of the Tx-Rx beam pair being selected for the measurement and re-measurements.

In one example aspect, the static and dynamic information may be combined, first based on the dynamic information and then on the static information. For example, for each beam pair, a priority is calculated based on the dynamic information such as one or more latest beam measurements of the beam pair. The beam pair with the highest priority value may be selected or scheduled for measurement or re-measurement. When multiple beam pairs have a same priority value, the static information such as spatial neighboring relationship with the current serving beam pair is then factored into consideration to distinguish between the beam pairs. Other similar or alternative approaches to combining the dynamic information and static information for determination of a priority value for a beam pair may also be employed, depending on specific circumstances.

At <NUM>, the method <NUM> includes ascertaining the selected beam pair by the UE. In one example, ascertaining the selected beam pair may include repeating the step of selecting the beam pair at <NUM> and updating the priority value for the selected beam pair at <NUM> for a number of times during a predetermined number of synchronization cycles. One effect of ascertaining the selected beam pair is to ensure that the measurement obtained from the selected beam pair achieves certain degree of reliability. This is particularly relevant when the UE is in a very dynamic environment. For example, if the UE is in a fast rotation motion, the Rx beams may change their physical locations relative to the fixed Tx beam pattern at a high frequency. Thus, one measurement that is valid at one moment may not be valid at next moment.

At <NUM>, in an alternative aspect, ascertaining the selected beam pair may include ascertaining selected n beam pairs which have highest priority values in the current round of measurement. This is in place of selecting beam pair at <NUM> and updating the priority value at <NUM> for a large number of times. The number n may be predetermined and adjustable. This may result in a faster convergence on a new serving beam pair.

At <NUM>, the method <NUM> includes determining a new serving Tx-Rx beam pair for transmissions between the UE and the base station. In one example aspect, the UE determines the new serving Tx-Rx beam pair by selecting the Tx-Rx beam pair with a highest priority value, after ascertaining selected candidate beam pairs for a predetermined number of synchronization cycles.

At <NUM>, the method <NUM> includes switching to the newly determined Tx-Rx beam pair from the current Tx-Rx beam pair. Then the UE may carry on transmissions with the base station on the new serving Tx-Rx beam pair. In one example aspect, the newly determined Tx-Rx beam pair may be the same as the current serving Tx-Rx beam pair. In this case, the step at <NUM> may be avoided.

The method <NUM> may be triggered for various occasions. One such occasion is when the UE enters transmission range of the base station and just receives the Tx beams broadcast from the base station. Another occasion is when the UE's location has changed in a non-trivial way such that the current serving beam is no longer effective and the performance of the current serving Tx-Rx beam pair has degraded beyond a predetermined threshold.

The method <NUM> is for illustration purpose and shows one possible process for selecting candidate beam pairs for measurement and for determining a new serving beam pair. In practice, one or more steps shown in illustrative flowchart for the method <NUM> may be combined with other steps, performed in any suitable order, performed in parallel (e.g., simultaneously or substantially simultaneously), or removed. For example, updating the priority value of the selected Tx-Rx beam pair at <NUM> may be performed in parallel to or before ascertaining the selected Tx-Rx beam pair at <NUM>.

<FIG> illustrates an example beam pair sequence <NUM> for measurement, in accordance with one or more aspects of the present disclosure. The beam pair sequence <NUM> includes four synchronization periods <NUM>-<NUM> and within each synchronization period, four beam pairs are selected and measured. In contrast to the equal-opportunity, round-robin fixed sequence of beam pairs for measurement, as shown in <FIG>, <FIG> shows a sequence of beam pairs with a fixed Tx beam pattern. In <FIG>, the UE can freely choose Rx beams, but not Tx beams. For example, during the synchronization periods <NUM>-<NUM>, the UE follows a fixed Tx beam pattern, selecting Tx beam <NUM> through Tx beam <NUM> sequentially during each of the synchronization periods.

In another example aspect, a higher priority value of a selected beam pair may result in more opportunities for the beam pair to be selected for measurement and re-measurements. As discussed earlier, the priority value of a beam pair may be based on dynamic information and static information. In one example scenario, the Tx-Rx beam pairs (<NUM>,<NUM>) and (<NUM>,<NUM>) may have higher priority values, in part because the weight for the static part of the priority value may be greater. For example, Rx beam <NUM> has at least partial LoS with Tx beams <NUM> and <NUM>, as shown in <FIG>. Thus, Tx-Rx beam pairs (<NUM>,<NUM>) and (<NUM>,<NUM>) may have higher priority values. Additionally, the weight for dynamic part of the priority values of Tx-Rx beam pairs (<NUM>, <NUM>) and (<NUM>, <NUM>) may also be greater, because their previous measurements of beam gain may be higher than other beam pairs.

As a result, the beam pairs including Rx beam <NUM> are measured more frequently than Rx beams <NUM> and <NUM>. For example, as shown in <FIG>, Rx beam <NUM> is paired with Tx beams <NUM> and <NUM> and measured more frequently while the Rx beam <NUM>, which is located opposite of Rx beam <NUM> and has a NLoS, has far fewer opportunities to be selected for measurements.

<FIG> shows the performance chart <NUM> of different methods for selecting beam pairs for measurement. The chart <NUM> is for a scenario where the Tx beams have a fixed Tx beam pattern and the UE is free to select Rx beam for measurements. One such scenario may be that the UE itself is in a fast rotation. While the UE is in a fast rotation, the serving Tx-Rx beam pair may need to be re-selected frequently to maintain a desirable performance in term of beam gains.

The Y axis of <FIG> shows the cumulative density function (CDF) F(x) values, representing the opportunity values for beam pairs being selected based on the designated method. The X axis show the beam gains for the designated beam pair selection method. The base line <NUM> represents the result of the fixed, round-robin beam pair selection method. The genie line <NUM> represents theoretical optimal results. The line <NUM> represent performance results based on the dynamic beam pair selection method, as described in the present disclosure, and illustrated in <FIG>. The performance chart <NUM> show that the performance based on the dynamic beam pair selection method is very close to that of theoretical optimal line <NUM>, and much better than that of the round-robin beam pair selection method.

<FIG> is a conceptual data flow diagram <NUM> illustrating the data flow between different means/components in an exemplary apparatus <NUM>. The apparatus may be a mmW capable UE in communication with a base station. The apparatus includes a reception component <NUM> that is configured to receive data and control information from the base station. For example, the reception component <NUM> of the mmW capable UE may receive a set of Tx beams from the base station in a broadcast message.

The apparatus <NUM> also includes a dynamic beam pair selection and measurement component <NUM> that receives beam pairs from the reception component <NUM>, selects a candidate beam pair and measure the selected beam pair. The apparatus <NUM> also includes a serving Tx-Rx beam pair determination component <NUM> that receives measurement results from the beam pair selection and measurement component <NUM>, updates the priority value of each selected beam pair, based in part on the measurement results, and determines a new serving Tx-Rx beam pair based in part on the updated priority values. The apparatus <NUM> further includes the transmission component <NUM> that transmits the determined serving Tx-Rx beam pair to the base station <NUM>.

<FIG> is a diagram <NUM> illustrating an example of a hardware implementation for an apparatus <NUM>' employing a processing system <NUM>. The processing system <NUM> may be implemented with a bus architecture, represented generally by the bus <NUM>. The bus <NUM> may include any number of interconnecting buses and bridges depending on the specific application of the processing system <NUM> and the overall design constraints. The bus <NUM> links together various circuits including one or more processors and/or hardware components, represented by the processor <NUM>, the components <NUM>, <NUM>, <NUM>, and <NUM>, and the computer-readable medium / memory <NUM>. The bus <NUM> may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further.

The processing system <NUM> may be coupled to a transceiver <NUM>. The transceiver <NUM> is coupled to one or more antennas <NUM>. The transceiver <NUM> provides a means for communicating with various other apparatus over a transmission medium. The transceiver <NUM> receives a signal from the one or more antennas <NUM>, extracts information from the received signal, and provides the extracted information to the processing system <NUM>, specifically the transmission component <NUM>. In addition, the transceiver <NUM> receives information from the processing system <NUM>, specifically the reception component <NUM>, and based on the received information, generates a signal to be applied to the one or more antennas <NUM>.

The processing system <NUM> includes a processor <NUM> coupled to a computer-readable medium / memory <NUM>. The processor <NUM> is responsible for general processing, including the execution of software stored on the computer-readable medium / memory <NUM>. The software, when executed by the processor <NUM>, causes the processing system <NUM> to perform the various functions described supra for any particular apparatus. The computer-readable medium / memory <NUM> may also be used for storing data that is manipulated by the processor <NUM> when executing software. The processing system <NUM> further includes at least one of the components <NUM>, <NUM>, <NUM>, and <NUM>. The components may be software components running in the processor <NUM>, resident/stored in the computer readable medium / memory <NUM>, one or more hardware components coupled to the processor <NUM>, or some combination thereof. The processing system <NUM> may be a component of the UE <NUM> and may include the memory <NUM> and/or at least one of the TX processor <NUM>, the RX processor <NUM>, and the controller/processor <NUM>.

Claim 1:
A method of wireless communication performed by a user equipment, UE (<NUM>) capable of millimeter wave, mmW communication, comprising:
selecting (<NUM>) by the UE (<NUM>) a Transmit, Tx-Receive, Rx, beam pair from a plurality of Tx-Rx beam pairs available at the UE for measurement, based in part on a priority of the Tx-Rx beam pair, wherein the plurality of Tx-Rx beam pair comprises a set of Tx beams and a set of Rx beams, said priority representing a likelihood of a pair being selected for measurement;
updating (<NUM>) the priority of the selected Tx-Rx beam pair based in part on a combination of static information and dynamic information of the selected Tx-Rx beam pair, wherein the static information of Tx-Rx beam pair comprises a spatial relationship of the Tx-Rx beam pair, or a presence or an absence of line of sight between the Tx-Rx beam pair, or a combination thereof; and wherein the dynamic information includes one or more latest beam measurements of the selected Tx-Rx beam pair;
ascertaining (<NUM>) the selected Tx-Rx beam pair by re-measuring the selected Tx-Rx beam pair and updating the priority value for the selected Tx-Rx beam pair within a predetermined number of synchronization cycles;
determining (<NUM>) a new serving Tx-Rx beam pair based on priorities of the plurality of Tx-Rx beam pairs by selecting as the new serving Tx-Rx beam pair, the Tx-Rx beam pair of the plurality of pairs with a highest priority value after ascertaining selected candidate beam pairs for the predetermined number of synchronization cycles; and
switching (<NUM>) to the new serving Tx-Rx beam pair from a current beam pair.