Patent Application
20250062820
The present disclosure relates to beam alignment.
Conventionally, a beam alignment procedure between a gNB and a UE may have three phases P1 to P3 (see Table 1):
When a connection is established via the beam alignment procedure (P1-P2-P3 process), the P3 process allows a UE to perform a beam sweep as depicted in
During P3 process, the UE measures RSRP with each of its Rx beams as shown in
UEs with analogue beamforming can operate only one beam at a time. Hence the conventional P3 beam alignment procedure outlined hereinabove spans multiple time intervals (OFDM symbols) over which UE does measurements with one beam at a time. During this time, base station transmits the reference signal (aperiodic CSI-RS with repetition) on the beam selected in P2. It occupies resources, typically over an entire bandwidth part (BWP).
The UE signals the number X of OFDM symbols required for a complete P3 beam sweep as a static UE capability, maxNumberRxBeam, which can range typically from 2 to 8 but is in general not limited. Thus, the UE indicates a single value for the preferred number of NZP CSI-RS resource repetitions per CSI-RS resource set. I.e., X is equal to the number of beams. This procedure is typically repeated every time there is a handover, SSB beam switch, UE panel switch, or radio channel angular change due to blockers appearing during UE mobility, etc.
It is an object of the present invention to improve the prior art.
According to a first aspect of the invention, there is provided an apparatus comprising:
According to a second aspect of the invention, there is provided an apparatus comprising:
According to a third aspect of the invention, there is provided a method comprising:
According to a fourth aspect of the invention, there is provided a method comprising:
Each of the methods of the third and fourth aspects may be a method of beam alignment.
According to a fifth aspect of the invention, there is provided a computer program product comprising a set of instructions which, when executed on an apparatus, is configured to cause the apparatus to carry out the method according to any of the third and fourth aspects. The computer program product may be embodied as a computer-readable medium or directly loadable into a computer.
According to some embodiments of the invention, at least one of the following advantages may be achieved:
In detail, some example embodiments of the invention reduce the number of OFDM symbols required to complete the P3 UE Rx beam sweeping procedure. Depending on the implementation and radio conditions, the number may be as low as 2 symbols. This gives more resources to the network scheduler for actual data transfer and thereby increases the cell throughput. Some example embodiments reduce the UE power consumption during the P3 procedure.
It is to be understood that any of the above modifications can be applied singly or in combination to the respective aspects to which they refer, unless they are explicitly stated as excluding alternatives.
Further details, features, objects, and advantages are apparent from the following detailed description of the preferred embodiments of the present invention which is to be taken in conjunction with the appended drawings, wherein:
Herein below, certain embodiments of the present invention are described in detail with reference to the accompanying drawings, wherein the features of the embodiments can be freely combined with each other unless otherwise described. However, it is to be expressly understood that the description of certain embodiments is given by way of example only, and that it is by no way intended to be understood as limiting the invention to the disclosed details.
Moreover, it is to be understood that the apparatus is configured to perform the corresponding method, although in some cases only the apparatus or only the method are described.
When several UEs in a cell need to align their respective Rx beams, the resource elements overhead grows linearly and becomes a very undesirable effect because these resources could otherwise be used, e.g. for data traffic, and thus could increase the system's spectral efficiency.
For example, if a UEs in a cell is moving at 36 km/h, it will require roughly 100 updates/second based on 10 updates/m. Thus, the P3 sweeps require 100*8 OFDM symbols per second if maxNumberRxBeam is 8. This is a large overhead for a beam alignment of one UE given that there are only 8000 slots (11200 OFDM symbols) per second with 120 KHz SCS used in FR2.
Thus, it is highly beneficial from both throughput and UE power consumption perspective if the P3 procedure can be carried out over as few time intervals as possible.
Some example embodiments of the invention reduce the number of time intervals (OFDM symbols) needed for a UE to complete the P3 beam sweep. For this purpose, UE having X beams uses the first N symbols with the aperiodic NZP CSI-RS to do the beam sweep. The UE measures the received power in each beam over a respective time period (“time slice”) of a same duration, denoted “slice duration”. According to some example embodiments N<X, so the duration available for each Rx beam (the “slice duration”) is smaller than the duration of a OFDM symbol.
This is shown in
After the RSSI is measured for each of the beams of the UE, the beam with maximum RSSI is determined (“best beam”). The best beam may then be used by the UE for the communication with the gNB in OFDM symbols following the determination of the best beam. In some example embodiments, after the determining the best beam and prior to PDSCH decoding, UE determines the channel quality of the best beam and measures at least one of SINR and CQI for the best beam and reports them to the gNB. Thus the overall time for completing the P3 Rx beam alignment can be reduced to just 1 or 2 OFDM symbols. This number is denoted A, i.e. N=1, A=2 in the present example if SINR and CQI for the best beam are measured and reported, and N=A=1 if SINR and CQI for the best beam are not measured and reported. A is an integer equal to or larger than N. For example, a conventional UE requests the network to transmit 8 repetitions of OFDM symbols of an aperiodic NZP-CSI-RS (if the UE has 8 beams to sweep), whereas the UE according to some example embodiments of the invention requests only A=2 repetitions of OFDM symbols of the aperiodic NZP-CSI-RS even if it has 8 beams to sweep.
Thus, some example embodiments of the invention provide in particular:
The symbol rate (CSI-RS symbols) is relatively low compared with the sampling rate and fast switching time of RF front end components. This make solutions according to some example embodiments practical as illustrated by the numbers and facts summarized below:
There is a reasonable margin because one OFDM symbol is 8.9 μs, as indicated above. The numbers used above are by no means exotic and, if dedicated HW is developed for procedures according to some example embodiments, even shorter sampling time and/or switching time may be expected. The sample time of 2 ns comes from known practical implementations. The number of samples used will obviously affect the amount of averaging. Thus, the number of samples required to have reasonable probability of false detection varies with RSSI. And there exists a Threshold below which this scheme should preferably not be used. This Threshold depends on implementation and may be stored in the respective apparatus, but is expected to be about 3 to 6 dB above the noise floor
Details of the process are as depicted in the state diagram in
If the current RSSI is greater than Threshold then UE signals to gNB that it needs A symbols, where A≤X. The value of A may be dependent indirectly on the number of Rx beams X and/or directly or indirectly on the current RSSI. As another option, it may be statically configured to be a fixed value, e.g. A=2. It then moves to state 0 where it waits for the first symbol of the NZP-CSI-RS.
When the first symbol of the aperiodic NZP-CSI-RS is scheduled and the current RSSI is greater than the threshold, the process moves to state 1 in which the first phase of the scheme is carried out. In state 1, the raw power measurements (RSSI) are done during the first N symbols over X different beams. The beam switching can be done in any feasible way, such as in round robin fashion or in a hierarchical way. After N symbols the scheme moves to state 2 in which the RLM measurements (i.e. RSRP, CSI) are done. State 2 is optional and may be omitted in some example embodiments of the invention. In this case, A=N. For example, state 2 may be omitted if the best beam is the same as the previous best beam and the current RSSI of the best beam is substantially as large as the previous RSSI of the best beam. If State 2 is omitted, the process moves from State 1 directly to State 4.
Thus, depending on implementation, UE may signal to gNB either the number N=A of OFDM symbols required to determine the best beam, or the number A required to determine the best beam and to determine the channel quality on the best beam. A and N depend directly and unambiguously from each other (e.g. A=N if the channel quality of the beast beam is not determined, or A=N+1 if one additional OFDM symbol is required to determine the channel quality). A does not depend directly on X. If UE transmits N, gNB has to derive the number A of required repetitions of OFDM symbols of the reference signal from the known direct and unambiguous relationship between N and A.
Some example embodiments of the invention are explained with CSI-RS used as the reference signal for P3 of the beam alignment procedure. However, the invention is not limited to CSI-RS. The reference signal may be arbitrary if it fulfills the following conditions:
The detailed actions in states 1 and 2 of
For hierarchical beam sweeping, the steps for state 1 are as follows:
For each polarization, the output of each FR2 RFFE panel 1 is routed to a mixer 2 which produces IF output and is further routed to a tunable bandpass filter 3. If the IF is less than 7 GHz then the bandpass filter 3 may be implemented for example using 5 GHZ Wifi filter or Band 41 filter etc. The bandpass filter 3 may be tuned to eliminate interference outside of the CSI-RS bandwidth.
The output of bandpass filters 3 for horizontal and vertical polarization is routed to a conventional FR2 transceiver 4 and further through ADC/DAC 5 to baseband unit 6. The output of the bandpass filter 3 is additionally routed to a parallel receive circuitry 7 for further down conversion, if necessary, e.g. a low IF receiver, single or dual conversion receiver followed by a diode detector, a ASK receive circuitry. This is then fed via a low pass filter 8 to a power integrator 9 with a reset switch 10. The integrator 9 may be implemented using a capacitor which does an analogue raw power measurement (RSSI). The output voltage of the capacitor is then sampled by a ADC with sample and hold circuitry 11 at the end of each time slice. After each measurement, the integrator 9 is reset before starting measurement on the next beam.
The sampled output for each polarization is stored in digital logic 12 which also provides the max_beam_index with highest power from the number of beams measured so far. It sums up the measured voltage for each polarization per beam. The storage in this logic box is reset before the entire P3 procedure begins.
The next digital logic box 13 in the chain is responsible for controlling the beam sweeping procedure in the two states described above. In state 1, it chooses the next beam for power measurement, while in state 2 it chooses the best beam for doing RSRP and/or CSI measurements in the baseband.
This solution may also save power of the UE because all of the FR2 transceiver chain 4, 5 after the bandpass filter 3 and the baseband unit 6 are not required to be turned on when the UE is in state 1.
This example embodiment is very similar to Example embodiment 1. A difference is that instead of routing the output of the bandpass filter 3 directly to the integrator circuitry 9 for each polarization, the outputs of the bandpass filters 3 for H polarization and V polarization are added in a power splitter 31 (combiner) and the output of the power splitter 31 is routed to the power integrator 9 afterwards (if needed via receive circuitry 7 and low pass filter 8). This reduces the number of integrators 9, reset switches 10, and ADCs 11. Only one of them is needed instead of one of them per polarization.
Example embodiment 3 is also similar to Example embodiment 1 in most aspects. The difference is in the integrator 9 (with corresponding reset switch 10) and the logic 121 to select the max_beam_index. It has 1 integrator 9 per beam with its corresponding reset switch 10. All the integrators 9 are reset before the beam sweeping procedure begins. So the time for resetting the integrators 9 during beam sweeping itself, as done in example embodiment 1, is eliminated from the beam sweeping procedure. The integrators 9 are fed via a multi level switch which is controlled by the logic which chooses the codeword for next beam. The output of the integrators 9 is then compared using a multi input comparator 121. It replaces the digital logic 12 for finding the max_beam_index according to example embodiments 1 and 2.
Thus, the procedure for state 1 of
This example embodiment is different from example embodiments 1 to 3 because it implements the entire process in digital logic. The digital logic may be implemented in the baseband unit 6.
In this example embodiment, the FR2 transceiver 4 as well as the baseband unit 6 are turned on for doing the P3 beam sweeping scheme described hereinabove. The RSSI measurement for each beam is done on the complex values (IQ samples) sampled by the ADC 5. This is done in the digital logic on the baseband.
The baseband unit 6 also controls, in the state 1, the process of determining the next beam.
This example embodiment does not require any new hardware (such as the integrator 9 with reset switch 10) to be added specifically for the P3 procedure because all the additional digital logic may be implemented in the baseband unit 6. However, the entire chain from RFFE 1 via Transceiver 4 to baseband unit 6 is turned on in State 1 such that energy consumption may be higher than for example embodiments 1 to 3.
The apparatus comprises means for determining 110 and means for identifying 120. The means for determining 110 and means for identifying 120 may be a determining means and identifying means, respectively. The means for determining 110 and means for identifying 120 may be a determiner and identifier, respectively. The means for determining 110 and means for identifying 120 may be a determining processor and identifying processor, respectively.
The means for determining 110 determines, subsequently for each of X beams, a characteristic of a power of a reference signal received on the respective beam over a respective period of time (S110). X is an integer equal to or larger than 2. Each of the periods of time has a same duration denoted a slice duration. The slice duration is shorter than a duration of one symbol of the reference signal.
The means for identifying 120 identifies a best beam among the X beams such that the determined characteristic of the power of the best beam is extreme among the characteristics of the powers received on the X beams over the respective period of time (S120). I.e., the means for identifying 120 identifies the best beams as the beam on which the determined characteristic of the power of S110 is extreme among the X beams. “Extreme” may mean “minimum” or maximum.
For example, the characteristic of the power of the reference signal may comprise at least one of
In these example cases, the characteristic of the power of the best beam is typically maximum among the characteristics of the power received on the X beams over the respective period of time.
The apparatus comprises first means for monitoring 210, second means for monitoring 220, and means for transmitting 230. The first means for monitoring 210, second means for monitoring 220, and means for transmitting 230 may be a first monitoring means, second monitoring means, and transmitting means, respectively. The first means for monitoring 210, second means for monitoring 220, and means for transmitting 230 may be an first monitor, second monitor, and transmitter, respectively. The first means for monitoring 210, second means for monitoring 220, and means for transmitting 230 may be a first monitoring processor, second monitoring processor, and transmitting processor, respectively.
The first means for monitoring 210 monitors whether an indication is received that a terminal has X beams (S210). The second means for monitoring 220 monitors whether a request to transmit N symbols of a reference signal for beam alignment of the terminal is received (S220). N is an integer equal to or larger than 1. X is an integer equal to or larger than 2. N is smaller than X (N<X).
S210 and S220 may be performed in an arbitrary sequence. They may be performed fully or partly in parallel.
If the request to transmit N symbols is received (S220=yes), the means for transmitting 230 transmits A symbols of the reference signal without transmitting more than the A symbols of the reference signal (S230). I.e., the means for transmitting 230 transmits exactly A symbols of the reference signal. The means for transmitting 230 transmits each of the A symbols of the reference signal with a same spatial characteristic. Typically, the A symbols are transmitted consecutively. A is an integer equal to or larger than N. A depends directly and unambiguously on N and does not depend directly on X.
Typically, the UE informs the gNB on the required number of repeated OFDM symbols (i.e. on N or A, depending on implementation), and gNB repeats only A transmissions, but not more than A transmissions. In some example embodiments, UE does not inform gNB on N or A, or gNB ignores this information. In these example embodiments, gNB transmits X (number of beams) OFDM symbols of the reference signal, as conventionally. In such embodiments, UE may ignore X-A transmissions, e.g. the transmissions after the first A transmissions. Thus, the UE still may save energy compared to a UE employing a conventional method evaluating the X transmissions.
Some example embodiments are explained with respect to a 5G network. However, the invention is not limited to 5G. It may be used in other radio networks, too, e.g. in previous of forthcoming generations of 3GPP networks such as 4G, 6G, or 7G, etc, if a UE uses plural beams. It may be used in non-3GPP mobile communication networks if the respective base station (e.g. access point etc.) transmits a reference signal for beam alignment by the terminal.
One piece of information may be transmitted in one or plural messages from one entity to another entity. Each of these messages may comprise further (different) pieces of information.
Names of network elements, network functions, protocols, and methods are based on current standards. In other versions or other technologies, the names of these network elements and/or network functions and/or protocols and/or methods may be different, as long as they provide a corresponding functionality.
If not otherwise stated or otherwise made clear from the context, the statement that two entities are different means that they perform different functions. It does not necessarily mean that they are based on different hardware. That is, each of the entities described in the present description may be based on a different hardware, or some or all of the entities may be based on the same hardware. It does not necessarily mean that they are based on different software. That is, each of the entities described in the present description may be based on different software, or some or all of the entities may be based on the same software. Each of the entities described in the present description may be deployed in the cloud.
According to the above description, it should thus be apparent that example embodiments of the present invention provide, for example, a terminal (such as a UE or a MTC device) or a component thereof, an apparatus embodying the same, a method for controlling and/or operating the same, and computer program(s) controlling and/or operating the same as well as mediums carrying such computer program(s) and forming computer program product(s). According to the above description, it should thus be apparent that example embodiments of the present invention provide, for example, a base station (such as a gNB or eNB) or a component thereof, an apparatus embodying the same, a method for controlling and/or operating the same, and computer program(s) controlling and/or operating the same as well as mediums carrying such computer program(s) and forming computer program product(s).
Implementations of any of the above described blocks, apparatuses, systems, techniques or methods include, as non-limiting examples, implementations as hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof. Each of the entities described in the present description may be embodied in the cloud.
It is to be understood that what is described above is what is presently considered the preferred example embodiments of the present invention. However, it should be noted that the description of the preferred example embodiments is given by way of example only and that various modifications may be made without departing from the scope of the invention as defined by the appended claims.
The phrase “at least one of A and B” comprises the options only A, only B, and both A and B. The terms “first X” and “second X” include the options that “first X” is the same as “second X” and that “first X” is different from “second X”, unless otherwise specified.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/087534 | 12/23/2021 | WO |
