Various example embodiments relate to a method and apparatus for triggering a user equipment beam reconfiguration procedure.
In a wireless telecommunications network, such as a 5G network, uplink and downlink beams are formed between user equipment and a network node to support communication between the user equipment and the network node. Although techniques exist for configuring those uplink and downlink beams, poor communication performance between the user equipment and the network node can occur. Accordingly, it is desired to provide an improved technique for supporting communication between the user equipment and the network node.
The scope of protection sought for various embodiments of the invention is set out by the independent claims. The embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention.
According to various, but not necessarily all, embodiments of the invention there is provided a method, comprising: receiving, at a user equipment, channel parameters relating an uplink channel and a downlink channel; determining, at the user equipment, from the channel parameters whether there is a mismatch in uplink channel and downlink channel performance and, if so; triggering, at the user equipment, a user equipment beam reconfiguration procedure.
The triggering may comprise triggering, at the user equipment, at least one of an uplink beam and a downlink beam reconfiguration and an uplink beam and a downlink beam realignment procedure.
The at least one channel parameter may comprise an indication of an uplink channel reconfiguration.
The at least one channel parameter may comprise an indication of a downlink channel performance.
The determining may comprise determining that there is the mismatch when the channel parameters indicate a request to reconfigure the uplink channel to increase performance of the uplink channel in an absence of an indication of a corresponding decrease in performance of the downlink channel.
The determining may comprise determining that there is the mismatch when the channel parameters indicate the request to reconfigure the uplink channel to increase performance of the uplink channel by a first amount in the absence of the indication of the corresponding decrease in performance of the downlink channel by at least the first amount.
The determining may comprise determining that there is the mismatch when the channel parameters indicate the request to reconfigure the uplink channel to increase performance of the uplink channel by the first amount in the absence of the indication of the corresponding decrease in performance of the downlink channel by a threshold amount greater than the first amount.
The method may comprise varying the threshold amount based on uplink channel reconfigurations made by the user equipment.
The method may comprise receiving an indication of the threshold amount from a network node.
The determining may comprise determining that there is the mismatch when the channel parameters indicate the request to reconfigure the uplink channel to increase performance of the uplink channel by the first amount in the absence of the indication of the corresponding decrease in performance of the downlink channel by greater than the first amount over a period of time.
The period of time may be indicated by at least one of a counter, a timer and a number of transmission frames.
The method may comprise receiving an indication of the period of time from a network node.
The request to reconfigure the uplink channel may comprise at least one of a request to increase an uplink transmission power and a request change to an uplink modulation scheme.
The indication of the downlink channel performance may comprise an indication of at least one of a downlink signal strength, a downlink signal power, a downlink signal quality, a downlink channel quality and a downlink rank indicator.
The method may comprise preventing the triggering during at least one of an uplink and a downlink reconfiguration procedure.
The method may comprise preventing the triggering during a user equipment initial access procedure.
The method may comprise preventing the triggering during an open loop power control procedure.
The method may comprise preventing the triggering prior to completing a user equipment beam alignment procedure.
The method may comprise preventing the triggering prior to completing a P3 beam alignment procedure.
The uplink beam and downlink beam realignment procedure may comprise at least one of a beam correspondence evaluation procedure and an array reconfiguration.
The method may comprise preventing, at a network node, triggering of the beam correspondence evaluation procedure when the mismatch in uplink channel and downlink channel performance is expected.
The method may be a user equipment method and/or performed at a user equipment.
According to various, but not necessarily all, embodiments of the invention there is provided a computer program comprising instructions for causing an apparatus to perform at least the following: receiving, at said apparatus comprising a user equipment, channel parameters relating an uplink channel and a downlink channel; determining, at the user equipment, from the channel parameters whether there is a mismatch in uplink channel and downlink channel performance and, if so; triggering, at the user equipment, a user equipment beam reconfiguration procedure.
The computer program may comprise instructions for causing an apparatus to perform the method set out above.
According to various, but not necessarily all, embodiments of the invention there is provided an apparatus, comprising: means for receiving, at said apparatus comprising a user equipment, channel parameters relating an uplink channel and a downlink channel; means for determining, at the user equipment, from the channel parameters whether there is a mismatch in uplink channel and downlink channel performance and; means for triggering, at the user equipment, a user equipment beam reconfiguration procedure responsive to the means for determining the mismatch.
The means for triggering may trigger, at the user equipment, at least one of an uplink beam and a downlink beam reconfiguration and an uplink beam and a downlink beam realignment procedure.
The at least one channel parameter may comprise an indication of an uplink channel reconfiguration.
The at least one channel parameter may comprise an indication of a downlink channel performance.
The means for determining may determine that there is the mismatch when the channel parameters indicate a request to reconfigure the uplink channel to increase performance of the uplink channel in an absence of an indication of a corresponding decrease in performance of the downlink channel.
The means for determining may determine that there is the mismatch when the channel parameters indicate the request to reconfigure the uplink channel to increase performance of the uplink channel by a first amount in the absence of the indication of the corresponding decrease in performance of the downlink channel by at least the first amount.
The means for determining may determine that there is the mismatch when the channel parameters indicate the request to reconfigure the uplink channel to increase performance of the uplink channel by the first amount in the absence of the indication of the corresponding decrease in performance of the downlink channel by a threshold amount greater than the first amount.
The apparatus may comprise means for varying the threshold amount based on uplink channel reconfigurations made by the user equipment.
The apparatus may comprise means for receiving an indication of the threshold amount from a network node.
The means for determining may determine that there is the mismatch when the channel parameters indicate the request to reconfigure the uplink channel to increase performance of the uplink channel by the first amount in the absence of the indication of the corresponding decrease in performance of the downlink channel by greater than the first amount over a period of time.
The period of time may be indicated by at least one of a counter, a timer and a number of transmission frames.
The apparatus may comprise means for receiving an indication of the period of time from a network node.
The request to reconfigure the uplink channel may comprise at least one of a request to increase an uplink transmission power and a request change to an uplink modulation scheme.
The indication of the downlink channel performance may comprise an indication of at least one of a downlink signal strength, a downlink signal power, a downlink signal quality, a downlink channel quality and a downlink rank indicator.
The apparatus may comprise means for preventing the triggering during at least one of an uplink and a downlink reconfiguration procedure.
The apparatus may comprise means for preventing the triggering during a user equipment initial access procedure.
The apparatus may comprise means for preventing the triggering during an open loop power control procedure.
The apparatus may comprise means for preventing the triggering prior to completing a user equipment beam alignment procedure.
The apparatus may comprise means for preventing the triggering prior to completing a P3 beam alignment procedure.
The uplink beam and downlink beam realignment procedure may comprise at least one of a beam correspondence evaluation procedure and an array reconfiguration.
The apparatus may comprise means for preventing, at a network node, triggering of the beam correspondence evaluation procedure when the mismatch in uplink channel and downlink channel performance is expected.
Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims as appropriate, and in combinations other than those explicitly set out in the claims.
Where an apparatus feature is described as being operable to provide a function, it will be appreciated that this includes an apparatus feature which provides that function or which is adapted or configured to provide that function.
Some example embodiments will now be described with reference to the accompanying drawings in which:
Before discussing the example embodiments in any more detail, first an overview will be provided. Some embodiments provide a user equipment technique for the autonomous detection of uplink and downlink beam misalignment. Once stable power control has been achieved, the user equipment interprets uplink and downlink evaluation parameters, decides if a reconfiguration or realignment is needed and, if so, requests that reconfiguration or realignment. This enables the user equipment to autonomously trigger the reconfiguration or realignment which ensures that such reconfiguration or realignment is only requested when required, which saves on network overheads and ultimately improves throughput. In particular, the user equipment uses information such as channel parameters about its current operating state or condition and from these is able to make an assessment of whether reciprocal channel conditions should occur, where changes in the link quality are reflected in both uplink and downlink. Many different channel parameters like Reference Signal Received Power (RSRP), Modulation Coding Scheme (MCS) and Signal to Noise and Interference Ratio (SINR) and the like are aimed at adapting the link to the current channel conditions. These channel parameters are utilized by the user equipment to identify when the channel conditions are no longer reciprocal, which may indicate that a beam misalignment has occurred and indicate that a reconfiguration or realignment is needed to be triggered.
Uplink Beam Misalignment
As can be seen in
As can be seen in
Hence, uplink/downlink beam correspondence is preserved if: Identical antenna element weights used for uplink and downlink results in identical beam gain and direction for uplink and downlink; Antenna element weights can be offset by pre-characterized values to obtain identical beam gain and direction for uplink and downlink; Two “codebooks” of beam weight vectors have been established, one for uplink and a second for downlink. Each beam weight vector in the uplink codebook is paired 1-1 with a beam weight vector in the downlink codebook such that the paired uplink and downlink beam weight vectors have identical beam and gain directions. If these are not fulfilled, then beam correspondence is broken and the uplink will be misaligned as depicted in
The impedance mismatches within the user equipment 20 can be seen in more detail in
User Equipment Operation
At block S10, the user equipment 20 determines whether it is in RRC_connected mode, where RRC is Radio Resource Control. If it is, then processing proceeds to block S20.
At block S20, the user equipment 20 compares downlink channel performance measurements and compares these against uplink channel reconfiguration requests, as will be described in more detail below, processing then proceeds to block S30.
At block S30, a determination is made as to whether there is an offset which indicates that the channels are no longer reciprocal and so the misalignment may occur.
Reciprocal and Non-Reciprocal
However, as can be seen in
The user equipment 20 correlates a downlink measurement to an uplink request. In the above, the downlink measurement is for example an RSRP measure and the uplink request is a TPC Command to increase power. It will be appreciated that embodiments are not restricted to these specific measures, as the downlink measurement could also be, for example, an SINR measure and the uplink request could be, for example, a change in Modulation Coding Scheme (MCS). Other metrics are not precluded.
The user equipment 20 decision mechanism to trigger beam correspondence evaluation is:
The user equipment 20 decision mechanism can be summarised as follows:
If TPC Command Field>1 & RSRP stable=>trigger beam correspondence evaluation
If TPC Command Field>1 & RSRP decreased=>do not trigger beam correspondence evaluation
Thresholds and counters may be part of the triggering decision, as explained in more detail below.
TPC Command Field>1 means increase power at the user equipment 20.
Note that in the above example for the user equipment 20 decision mechanism, the gNB reaction to uplink deterioration is through a TPC Command to request to increase the uplink power. However, this user equipment 20 method to trigger beam correspondence evaluation is also valid if the gNB 10 action was to decrease the modulation index (MCS) for example while RSRP remains stable. That is to say, this method can be generalized to correlating unexpected uplink requests (e.g. metrics on power, modulation, etc.) with reference to downlink measurements (e.g. metrics on power, interference, etc.) and user equipment 20 a-priori knowledge (e.g. load mismatch detection), thus implying non-reciprocal channel conditions.
If no misalignment is indicated then processing returns to block S10.
Triggering
If a misalignment is indicated then processing proceeds to block S40 where a gNB 10 assisted beam correspondence check is triggered. Hence, the user equipment 20 may trigger the beam correspondence check at S40 and request that the misalignment is corrected autonomously, using information already available to the user equipment 20. In some situations, the gNB 10 may have requested the TPC for a specific reason (for example, a gNB panel split). In such situations it can choose to ignore the user equipment beam correspondence evaluation request and processing may return to block S10.
Processing then proceeds to block S50 where a beam correspondence evaluation occurs using uplink misalignment detection and/or through downlink alignment verification at block S60. The beam correspondence evaluation may be performed through Sounding Reference Signal (SRS) sweeps. The beam correspondence evaluation may be initiated by the UE reporting L1 SINR which is the user equipment 20 action that initiates the beam correspondence evaluation and/or beam realignment. Processing then proceed to block S70.
At block S70, the misalignment data between the uplink and the downlink beams is converted to a misalignment angle and at block S80, a revised uplink antenna configuration is determined for the misalignment angle and processing proceeds to block S90 where the antenna array is reconfigured to improve gain under the misalignment conditions.
For example, after the user equipment 20 has decided to trigger beam correspondence evaluation, an example of user equipment 20 action may be as follows:
1. Request beam correspondence evaluation—for example, report L1-SINR (using existing signalling) to request SRS UL sweep, and/or trigger uplink misalignment detection.
2. Reconfigure array—for example, optimize the user equipment 20 uplink pattern to mitigate degradation and avoid radio link failure until beam realignment can be performed.
Furthermore, if the user equipment 20 already knows it has no means for beam realignment, an alternative user equipment 20 action is to:
1. Request downlink verification to have/update the reference—for example, send Channel State Information-Reference Signal (CSI-RS) repetition request (using existing signalling) to trigger DL verification.
2. Reconfigure array—for example, optimize the user equipment 20 uplink pattern to mitigate degradation and avoid radio link failure until beam realignment can be performed.
Note that the order of the actions is interchangeable.
Processing then proceeds to block S100.
Optionally, at block S100 should the antenna array reconfiguration not sufficiently improve the alignment between the uplink and the downlink beams then a full realignment procedure is initiated and processing returns to block S10.
Thresholds and Counters
Offset=requested transmission power−expected transmission power.
Applying this threshold to the user equipment 20 decision mechanism would look like the following:
If Offset>n dB & RSRP stable=>trigger beam correspondence evaluation
Moreover, the evaluation metric is not necessarily on absolute power levels but can also be on a number m of consecutive TPC Commands requiring to, for example, increase power. Applying this counter to user equipment 20 decision mechanism would look like the following:
If #(TPC Command Field>1)>m & RSRP stable=>trigger beam correspondence evaluation
Finally, to avoid consecutive requests from the user equipment 20, a timer limiting the number of requests to x requests per frames can be considered. The user equipment 20 decision mechanism taking power offset, counter and timer is explained in more detail below. All the aforementioned parameters can be user equipment 20 specific or configured by the network. They may reset after a single or a given number of beam correspondence evaluation requests.
Hence, at block S10, the user equipment 20 determines whether it is in connected mode.
Processing then proceeds to block S110.
At block S110, it is determined whether the TPC command field is greater than one. If not, then the counters are reset and processing returns to block S10.
If there is a TPC command, then processing proceeds to block S120 where the TPC counter and the cumulative power offset is incremented.
Processing then proceeds to block S130 where it is determined whether the TPC counter is greater than the threshold amount n or whether the cumulative requested power offset is greater than a threshold m. If not, then the counters are reset and processing returns to block Si.
If either of these conditions is true, then processing proceeds to block S140 where it is determined whether the power headroom quantity of the power headroom report (PHR) has a value less than or equal to zero. If not, then the counters are reset and processing returns to block S10.
If this condition is met, then processing proceeds to block S150 where it is determined whether the mismatch is due to an unexplained uplink downlink power imbalance. In particular, a determination is made as to whether RSRP has remained within thresholds. If not, then the counters are reset and processing returns to block S10.
If this condition is met, then processing proceeds to block S160 where it is determined whether the MCS has changed. If the MCS has not changed, then the counters are reset and processing returns to block S10.
If this condition is met, then processing proceeds to block S170 where it is determined whether the downlink SINR has changed. If not, then the counters are reset and processing returns to block S10.
If this condition is met, then processing proceeds to block S180 where it is determined whether a beam correspondence evaluation has been requested recently. In particular, it is determined whether more than a threshold number of slots have passed since the last beam correspondence evaluation. If not, then the counters are reset and processing returns to block S10.
If this condition is met, then the counters are reset and processing proceeds to block S40 where a beam correspondence evaluation is requested.
Uplink Power Control
Uplink power control is done in one of two ways, depending on if the user equipment 20 is in idle or in connected mode: open or closed loop. The user equipment 20 uses open loop for the Physical Random Access Channel (PRACH) under initial access (i.e. PRACH msg1 power ramping). Thereafter, the user equipment 20 is in closed loop (e.g. TPC Command in the Re-Authorization Request (RAR)). The gNB 10 corrects the power offset from the open loop transmission estimate on the user equipment 20. The gNB 10 might issue TPC commands that do not relate to a RSRP change, only to settle the initial uplink/downlink power relationship. Note that a beam correspondence evaluation should not be triggered based on these early TPC Commands relating to initial access. It is only after P3 is completed and the uplink/downlink power relation settles to become reciprocal, and the user equipment 20 can use this uplink/downlink reciprocal balance for the beam correspondence evaluation trigger (including thresholds and counters). Hence, only after the TPC<->RSRP relation settles (i.e. after P3 beam alignment is complete and power relation has settled) can the user equipment 20 interpret non-reciprocal channel conditions and trigger beam correspondence evaluation when detecting a broken power relation between uplink/downlink.
Summing up, preconditions for using the trigger are:
1. Closed loop power control, and
2. UL/DL relation settled.
TPC Commands within RAR during initial access and in RRC_Connected mode are detailed table 1. The field TPC command relates to how much power should be reduced or increased for user equipment 20 transmission.
UE Action Overview
At block S200, the user equipment connects to the network. Processing proceeds to block S210.
At block S210, the initial access completes, the user equipment 20 is in the RRC_connected state (see block S10 above) and the uplink/downlink power relationship is stable. Processing proceeds to block S220.
At block S220, the user equipment 20 moves to closed loop power control and the user equipment 20 knows the expected transmission and reception power levels which are expected to be reciprocal as illustrated in
At block S230, the user equipment 20 receives an uplink control request. Processing proceeds to block S235.
At block S235, the user equipment 20 determines whether a non-reciprocal power relationship is occurring as illustrated in
Note that in the example above, the first user equipment 20 action is to request Channel State Information Reference Signal (CSI-RS) repetition, the steps following that can be as specified or could be other messages depending future implementation (e.g. with Synchronization Signal/Physical broadcast channel (PBCH) block (SSB) repetition and Sounding Reference Signal (SRS) signals).
Furthermore, the order of the user equipment 20 actions could be reversed (e.g. first reconfigure array and then initiate beam correspondence evaluation) as the misalignment might be so severe that the priority is to avoid radio link failure. The user equipment 20 or the gNB 10 might also choose to skip the downlink verification (if, for example, it is judged that a previous measurement is still valid), then user equipment 20 would directly trigger beam correspondence evaluation. Similarly, the user equipment 20 could choose to skip downlink verification and beam correspondence evaluation altogether (for example, if it knows it cannot realign anyway) and directly trigger the array reconfiguration.
Some advantages of triggering beam correspondence evaluation based on uplink/downlink power relationship breaking apart (non-reciprocal correspondence) are as follows:
A person of skill in the art would readily recognize that steps of various above-described methods can be performed by programmed computers. Herein, some embodiments are also intended to cover program storage devices, e.g., digital data storage media, which are machine or computer readable and encode machine-executable or computer-executable programs of instructions, wherein said instructions perform some or all of the steps of said above-described methods. The program storage devices may be, e.g., digital memories, magnetic storage media such as a magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media. The embodiments are also intended to cover computers programmed to perform said steps of the above-described methods. A person of skill in the art would also recognize that the illustration of a specific order of blocks does not necessarily imply that there is a required or preferred order for the blocks and that the order may be varied. A person of skill in the art would furthermore recognize that it may be possible to omit a block or blocks.
Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed.
Features described in the preceding description may be used in combinations other than the combinations explicitly described.
Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.
Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.
Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.
Number | Date | Country | Kind |
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20205747 | Jul 2020 | FI | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2021/069085 | 7/8/2021 | WO |