Power-conditional uplink data transmission

Abstract

There is provided techniques for uplink data transmission. A method is performed by a UE. The method comprises receiving an uplink transmission grant from a network node. The uplink transmission grant corresponds to at least one uplink resource and is associated with a criterion related to received power of at least one downlink reference signal. The method comprises receiving the at least one downlink reference signal associated with the uplink transmission grant and measuring received power of the received at least one downlink reference signal. The method comprises transmitting uplink data in the at least one uplink resource to the network node with or without adapted uplink transmission of the at least one uplink resource. Whether to adapt the uplink transmission of the at least one uplink resource or not is based on whether the criterion for the measured received power is met or not.

Description

[0001] POWER-CONDITIONAL UPLINK DATA TRANSMISSION

[0002] TECHNICAL FIELD

[0003] Embodiments presented herein relate to a method, a user equipment, a computer program, and a computer program product for uplink data transmission. Embodiments presented herein further relate to a method, a network node, a computer program, and a computer program product for granting the uplink data transmission.

[0004] BACKGROUND

[0005] In general terms, there are two basic classes of medium access control procedures for uplink data transmission; scheduled based uplink transmissions and contention-based uplink transmissions. Som advantages and disadvantages with both types of procedures will be summarized next.

[0006] Scheduled based uplink transmission can deliver superior capacity in high-load scenarios. When a scheduler on the network side owns and controls all radio resources and provides user equipments (UEs) with transmission grants, inter-cell interference can be avoided in a straightforward manner. The cost for achieving this is that more radio resources are required both on the downlink (to provide scheduling grants to the UEs) and on the uplink (to provide scheduling requests and buffer status reports from the UEs to the network scheduler). In addition, there is a user plane latency penalty since UEs are not allowed to immediately transmit data. Instead, the UEs must wait to be scheduled by the network before data transmission can occur. Thus, scheduled uplink data transmission increases capacity at high load but increases latency. Scheduled uplink data transmission also adds overhead signaling. All such signaling consumes power in the UE and at the network side.

[0007] Contention based transmission is well suited in low interference scenarios. Low interference can occur either from low traffic or from the use of interference suppressing beamforming at the UE side and / or at the network side. The user-plane latency is also typically lower with a contention based medium access control procedures compared to with a scheduling based medium access control procedures. One drawback of contention based transmission is that the performance can quickly degrade once the interference is no longer low. Thus, contention based transmission reduces latency but suffers from reduced capacity at high traffic load.

[0008] Inter-cell interference reduces uplink capacity and user data rates. Neither medium access control procedures based on scheduled uplink transmission nor based on contention-based uplink transmission addresses inter-cell interference.

[0009] Hence, there is still a need for improved medium access control procedures. SUMMARY

[0010] An object of embodiments herein is to provide a medium access control procedure that does not suffer from the above issues, or at least where the above issues have been mitigated or reduced.

[0011] A particular object is to retain the advantages of both scheduled based uplink transmissions and contention-based uplink transmissions whilst avoiding their drawbacks.

[0012] A particular object is thus to provide a medium access control procedure that can deliver low latency at low load and high capacity at high load whilst maintaining protection from inter-cell interference when needed.

[0013] According to a first aspect there is presented a method for uplink data transmission. The method is performed by a UE. The method comprises receiving an uplink transmission grant from a network node. The uplink transmission grant corresponds to at least one uplink resource and is associated with a criterion related to received power of at least one downlink reference signal. The method comprises receiving the at least one downlink reference signal associated with the uplink transmission grant and measuring received power of the received at least one downlink reference signal. The method comprises transmitting uplink data in the at least one uplink resource to the network node with or without adapted uplink transmission of the at least one uplink resource. Whether to adapt the uplink transmission of the at least one uplink resource or not is based on whether the criterion for the measured received power is met or not.

[0014] According to a second aspect there is presented a UE for uplink data transmission. The UE comprises processing circuitry. The processing circuitry is configured to cause the UE to receive an uplink transmission grant from a network node. The uplink transmission grant corresponds to at least one uplink resource and is associated with a criterion related to received power of at least one downlink reference signal. The processing circuitry is configured to cause the UE to receive the at least one downlink reference signal associated with the uplink transmission grant and measuring received power of the received at least one downlink reference signal. The processing circuitry is configured to cause the UE to transmit uplink data in the at least one uplink resource to the network node with or without adapted uplink transmission of the at least one uplink resource. Whether to adapt the uplink transmission of the at least one uplink resource or not is based on whether the criterion for the measured received power is met or not.

[0015] According to a third aspect there is presented a computer program for uplink data transmission. The computer program comprises computer code which, when run on processing circuitry of a UE, causes the UE to perform actions. One action comprises the UE to receive an uplink transmission grant from a network node. The uplink transmission grant corresponds to at least one uplink resource and is associated with a criterion related to received power of at least one downlink reference signal. One action comprises the UE to receive the at least one downlink reference signal associated with the uplink transmission grant and measuring received power of the received at least one downlink reference signal. One action comprises the UE to transmit uplink data in the at least one uplink resource to the network node with or without adapted uplink transmission of the at least one uplink resource. Whether to adapt the uplink transmission of the at least one uplink resource or not is based on whether the criterion for the measured received power is met or not.

[0016] According to a fourth aspect there is presented a method for granting uplink data transmission. The method is performed by a network node. The method comprises transmitting an uplink transmission grant corresponding to at least one uplink resource for a UE. The uplink transmission grant is associated with a criterion related to received power of at least one downlink reference signal. The method comprises transmitting the at least one downlink reference signal associated with the uplink transmission grant. The method comprises receiving uplink data in the at least one uplink resource from the UE according to the uplink transmission grant.

[0017] According to a fifth aspect there is presented a network node for granting uplink data transmission. The network node comprises processing circuitry. The processing circuitry is configured to cause the network node to transmit an uplink transmission grant corresponding to at least one uplink resource for a UE. The uplink transmission grant is associated with a criterion related to received power of at least one downlink reference signal. The processing circuitry is configured to cause the network node to transmit the at least one downlink reference signal associated with the uplink transmission grant. The processing circuitry is configured to cause the network node to receive uplink data in the at least one uplink resource from the UE according to the uplink transmission grant.

[0018] According to a sixth aspect there is presented a computer program for granting uplink data transmission. The computer program comprises computer code which, when run on processing circuitry of a network node, causes the network node to perform actions. One action comprises the network node to transmit an uplink transmission grant corresponding to at least one uplink resource for a UE. The uplink transmission grant is associated with a criterion related to received power of at least one downlink reference signal. One action comprises the network node to transmit the at least one downlink reference signal associated with the uplink transmission grant. One action comprises the network node to receive uplink data in the at least one uplink resource from the UE according to the uplink transmission grant.

[0019] According to a seventh aspect there is presented a computer program product comprising a computer program according to at least one of the third aspect and the sixth aspect and a computer readable storage medium on which the computer program is stored. The computer readable storage medium could be a non-transitory computer readable storage medium.

[0020] Advantageously, these aspects provide a medium access control procedure that does not suffer from the above issues, or at least where the above issues have been mitigated or reduced. Advantageously, these aspects enable the advantages of both scheduled based uplink transmissions and contention-based uplink transmissions to be retained whilst avoiding their drawbacks.

[0021] Advantageously, these aspects provide a medium access control procedure that can deliver low latency at low load and high capacity at high load whilst maintaining protection from inter-cell interference when needed.

[0022] Advantageously, these aspects provide efficient enable controllable intra-cell interference and reduced inter-cell interference. This in turn leads to better link adaptation accuracy and higher capacity for uplink transmissions in the wireless network.

[0023] Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings.

[0024] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, module, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, module, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

[0025] BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The inventive concept is now described, by way of example, with reference to the accompanying drawings, in which:

[0027] Fig. 1 is a schematic diagram illustrating a communication network according to embodiments;

[0028] Figs. 2 and 3 are flowcharts of methods according to embodiments;

[0029] Fig. 4 is a schematic diagram illustrating a sequence of events according to embodiments;

[0030] Fig. 5 is a schematic illustration of a TDD resource grid according to embodiments;

[0031] Fig. 6 is a schematic illustration of a first TDD resource grid and a scenario where the first TDD resource grid is used according to embodiments;

[0032] Fig. 7 is a schematic illustration of a second TDD resource grid and a scenario where the second TDD resource grid is used according to embodiments;

[0033] Fig. 8 is a schematic diagram showing structural units of a UE according to an embodiment; Fig. 9 is a schematic diagram showing structural units of a network node according to an embodiment; and

[0034] Fig. 10 shows one example of a computer program product comprising computer readable means according to an embodiment.

[0035] DETAILED DESCRIPTION

[0036] The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the inventive concept are shown. This inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description. Any step or feature illustrated by dashed lines should be regarded as optional.

[0037] Fig. 1 is a schematic diagram illustrating a communication network 100 where embodiments presented herein can be applied. The communication network 100 comprises a network node 120. The network node 120 could be any of a (radio) access network node, radio base station, base transceiver station, node B (NB), evolved node B (eNB), gNB, access point, access node, transmission and reception point (TRP), integrated access and backhaul (IAB) node, etc. The network node 120 is configured to provide network access, and thus serve, UEs 110a over wireless links 130a, 130b. Each UE 110a, 110b could be any of a portable wireless device, mobile station, mobile phone, handset, wireless local loop phone, smartphone, laptop computer, tablet computer, wireless modem, wireless sensor device, network-equipped vehicle, etc.

[0038] As disclosed above, there is still a need for improved medium access control procedures.

[0039] At least some of the herein disclosed embodiments are based on providing uplink medium access control procedures where scheduled and contention-based uplink transmission are coordinated through transmission of downlink reference signals and conditional uplink grants. In more detail, the uplink transmission grant may explicitly or implicitly indicate if the provided grant is conditional or not. In this respect, the grant is considered conditional (and may hence be referred to as a conditional uplink grant) in case the grant is associated with a criterion related to received power of at least one downlink reference signal. Likewise, the grant is considered unconditional (and may hence be referred to as an unconditional uplink grant, or simply just an uplink grant) in case the grant is without any association with such a criterion.

[0040] Reference is now made to Fig. 2 illustrating a method for uplink data transmission as performed by the UE 110a according to an embodiment. In essence, when the UE 110a is scheduled with a conditional uplink grant, the UE 110a modifies its uplink data transmission dependent on the received power of one or more downlink reference signals.

[0041] SI 04: The UE 110a receives an uplink transmission grant from a network node 120. The uplink transmission grant corresponds to at least one uplink resource and is associated with a criterion related to received power of at least one downlink reference signal.

[0042] SI 06: The UE 110a receives the at least one downlink reference signal associated with the uplink transmission grant and measures received power of the received at least one downlink reference signal.

[0043] SI 08: The UE 110a transmits uplink data in the at least one uplink resource to the network node 120 with or without adapted uplink transmission of the at least one uplink resource. Whether to adapt the uplink transmission of the at least one uplink resource or not is based on whether the criterion for the measured received power is met or not.

[0044] Embodiments relating to further details of uplink data transmission as performed by the UE 110a will now be disclosed with continued reference to Fig. 2.

[0045] In some aspects, the UE 110a receives necessary configuration information for receiving the downlink reference signal. Therefore, in some embodiments the UE 110a is configured to perform (optional) step SI 02.

[0046] SI 02: The UE 110a receives configuration of the at least one downlink reference signal from the network node 120. The at least one downlink reference signal is then received in accordance with the configuration.

[0047] The configuration may comprise information about pilot sequence indexes and physical pilot sequence resources used by the downlink reference signal. The configuration may comprise information about multiple pilot sequences, and the UE 110a may perform measurements for each pilot sequence. Hence, in some embodiments, the network node 120 is a first network node, and at least one of the at least one downlink reference signal is received from a second network node. The UE may then be informed what pilot sequence corresponds to which network node. Hence, in one example, the UE 110a may measure on each received downlink signal individually, and then the criterion needs to be fulfilled for only one of the received downlink signals for the UE 110a to transmits the uplink data in the at least one uplink resource to the network node 120 with adaptation. The pilot sequence indexes may reflect the propagation properties towards (a set ol) network nodes, and the UE 110a may use the measurements to estimate the sum of the channels of all other potential reference signal transmissions to determine whether the uplink data is to be transmitted with or without adaptation in the at least one uplink resource to the network node 120. Hence, in another example, the UE 110a may add, or linearly combine, multiple measurements of the downlink reference signal, e.g., as received along multiple paths, and the criterion is then related to the sum of measurements. In some aspects, the resource configured for the UE 110a to measure on is larger or different from the resource where the downlink reference signal is configured for the UE 110a. Hence, in some embodiments, the at least one downlink reference signal is received over a bandwidth, and the received power is measured on less than an entire bandwidth of the at least one downlink reference signal. As an example, the UE may be configured with a downlink reference signal using a comb or a subset of all resource elements in the measurement resource. In some examples the measurement resource is not mapped to the corresponding frequency resources used for the uplink data transmission. Instead, a mapping is configured or provided from the specification on how to map measurements onto the reference resource to different uplink data frequency allocations. The granularity of the measurement resource could also be significantly different from the uplink data allocation. For example, one or a few different measurements could be provided mapping to different parts or to the full (maximum possible) uplink data transmission bandwidth.

[0048] There may be different ways to formulate the criterion for the measured received power. In some embodiments, the criterion is met when the received power exceeds a power threshold. Then, the uplink data can be transmitted with adapted uplink transmission of the at least one uplink resource when the criterion is met. Likewise, the uplink data can be transmitted without adapted uplink transmission of the at least one uplink resource when the criterion is not met.

[0049] Different ways in which the UE 110a may transmit the uplink data in the at least one uplink resource to the network node 120 with adaptation will be disclosed next.

[0050] In some aspects, the modification pertains to link adaptation, uplink power control decisions, and / or beamforming decisions (e.g., null forming). Hence, in some embodiments, the adapted uplink transmission of the at least one uplink resource pertains to at least one of: applying interference suppressing beamforming to the at least one uplink resource, reducing transmission power of the at least one uplink resource, reducing transmission bandwidth of the at least one uplink resource.

[0051] Further, the criterion can be so formulated that it may prevent the UE 110 from performing the transmission of the uplink data. For example, according to the criterion, the UE 110a may only be allowed to transmit on the at least one uplink resource if the UE 110a can avoid causing interference towards the network node from which the downlink reference signal was received. That is, in some embodiments, a direction in which interference suppressing beamforming is performed is based on an estimated direction in which the at least one downlink reference signal was received and using uplinkdownlink channel reciprocity. In this respect, the UE 110a may estimate the long-term properties of the channel over which the reference signal has been received, and perform beamforming with nulls placed in the dominant eigen-components of the so-obtained spatial covariance matrix. That is, in some embodiments, the interference suppressing beamforming is based on a spatial covariance matrix obtained from wideband, time-averaged, or frequency-averaged properties of a channel over which the reference signal was received, with nulls placed in dominant eigen-components of the spatial covariance matrix. For example, if the UE 110a is equipped with multiple antennas (or antenna ports) and reciprocity- calibrated such that received downlink reference signal can be used to estimate the uplink channel, instead of estimating the instantaneous channel when performing interference suppression beamforming, the UE 110a can estimates the long-term properties of the channel. For example, the UE 110a may estimate the second-order statistics (such as the spatial correlation matrix) of the channel. Then, when performing the interference suppression beamforming, the UE 110a may place a spatial null into one or more of the dominant eigenvectors of the so-estimated spatial correlation matrix.

[0052] A single-antenna UE 110a may therefore have no other alternative than to avoid transmitting on the at least one uplink resource. A multi-antenna UE 110a, on the other hand, may be capable of transmitting in the uplink in a way that causes zero interference the towards the network node from which the downlink reference signal was received (by exploiting uplink-downlink channel reciprocity). Alternatively, the UE 110a may reduce the uplink transmission power such that any uplink interference it causes in a neighboring cell can be assumed to be below some acceptable threshold. This requires the UE 110a to estimate at least the average path gain of the channel to the neighboring channel (which does not require reciprocity calibration).

[0053] For example, the UE 110a may only be allowed to perform the transmission on the at least one uplink resource (i) if the UE can is capable of interference suppressing beamforming towards the direction of the received downlink reference signal, using for example reciprocity -based beamforming at the UE, (ii) if the power of the received downlink reference signal is below a pre -determined threshold, (iii) if the priority of the uplink data is above a pre -determined threshold, (iv) with a transmission power that is a decreasing function of the power of the received downlink reference signal, for example inversely proportional, and / or (v) if the UE 110 can avoid transmitting on physical resource blocks where the power of the received downlink reference signal was above a threshold.

[0054] In yet further examples, the decision whether the UE 110a is to transmit the uplink data in the at least one uplink resource to the network node 120 with or without adapted uplink transmission of the at least one uplink resource may also depend on time to achieve proportional fairness. For example, if the UE 110a has used a comparably high transmission rate, then the UE 110a may adapt the transmission such that a comparably low transmission rate is used, or vice versa.

[0055] Reference is now made to Fig. 3 illustrating a method for granting uplink data transmission as performed by the network node 120 according to an embodiment.

[0056] S204: The network node 120 transmits an uplink transmission grant corresponding to at least one uplink resource for the UE 110a. The uplink transmission grant is associated with a criterion related to received power of at least one downlink reference signal. S208: The network node 120 transmits the at least one downlink reference signal associated with the uplink transmission grant. The at least one downlink reference signal may be a channel state information reference signal or a downlink channel sounding reference signal.

[0057] S210: The network node 120 receives uplink data in the at least one uplink resource from the UE 110a according to the uplink transmission grant.

[0058] Embodiments relating to further details of granting uplink data transmission as performed by the network node 120 will now be disclosed with continued reference to Fig. 3.

[0059] As disclosed above, the UE 110a receives necessary configuration information for receiving the downlink reference signal. Therefore, in some embodiments the network node 120 is configured to perform (optional) step S202.

[0060] S202: The network node 120 transmits configuration of the at least one downlink reference signal.

[0061] Hence, in some examples, the UE 110a is specifically configured. In this respect, different UEs served by the same network node 120 may be configured with different downlink reference signals, where the UEs may then suppress or adapt also to intra-cell interference in a multi-user (MU) multiple-input multipleoutput (MIMO) scenario.

[0062] Alternatively, the uplink transmission grant may comprise information of configuration of the at least one downlink reference signal.

[0063] Details of the configuration have been disclosed above and apply here as well.

[0064] Aspects of the uplink transmission grant will be disclosed next.

[0065] The uplink transmission grant may indicate the physical resources for the upcoming uplink data transmission. Further, the uplink transmission grant may comprise configuration of the downlink reference signal as transmitted in step S208. This configuration could e.g., be a one-bit indicator indicating if an associated downlink reference signal with a preconfigured index is to be transmitted or not. The physical resources used for the associated downlink reference signal may be derived from (e.g., be the same as) the physical resources provided in the uplink transmission grant.

[0066] Aspects of the at least one downlink reference signal will be disclosed next.

[0067] The downlink reference signal may be transmitted using downlink beamforming approximately corresponding to the intended uplink beamformer for reception of the scheduled uplink data transmission from the UE 110a. When receiving the uplink data transmission, the uplink beamformer may utilize uplink demodulation reference signals that are not available at this time. Hence the term approximate is used to indicate that the downlink beamformer used in this step is based on the best available knowledge of the channel to the scheduled UE 110a at the time of transmitting the downlink reference signal. In fixed-beam systems, the beamwidth used for transmitting the downlink reference signal may indicate the amount of a-priori channel state information the network node 120 has at this time (e.g., derived from uplink reference signals or previous uplink data transmissions).

[0068] In some examples the downlink reference signal is not transmitted in case the channel state information is not good enough. For example, when a first transmission after a time of no UE activity occurs, no downlink reference signal signal is transmitted. But when a second sub-sequent transmission occurs shortly after the first transmission the channel state information is deemed good enough and a downlink reference signal is then transmitted.

[0069] The frequency allocation of the downlink reference signal approximately matches the scheduled future uplink transmission grant.

[0070] In some examples, the downlink reference signal has one or more of the following properties. The downlink reference signal uses only dynamic scheduling (i.e., it is not periodic) and it is co-scheduled with uplink data transmission grants. The downlink reference signal uses a cell-specific sequence (known in neighboring cells and by UEs in neighboring cells). Hence, in some embodiments, the at least one downlink reference signal comprises a cell-specific sequence of a cell served by the network node. The downlink reference signal is transmitted in the downlink on scheduled resources for uplink data transmission. The downlink beamformer corresponds to an expected uplink beamformer.

[0071] In some embodiments the UE 110a is a first UE 110a, the at least one uplink resource is a first at least one uplink resource, the uplink transmission grant is a first uplink transmission grant that is transmitted in a first time interval, and the network node 120 is configured to perform (optional) step S206.

[0072] S206: The network node 120 transmits, in a second time interval, a second uplink transmission grant corresponding to a second at least one uplink resource for a second UE 110b.

[0073] Here, the network node 120 may have assigned a higher prioritization to uplink transmission from the second UE 110b than to uplink transmission from the first UE 110a. Therefore, the second uplink grant may be a prioritized (i.e., e non-conditional grant). Hence, in some embodiments, the second uplink transmission grant is without restrictions with respect to the criterion related to received power of at least one downlink reference signal.

[0074] The second grant may overlap at least partly with the first grant. That is, in some embodiments, the second at least one uplink resource at least partly overlaps in time and / or frequency with the first at least one uplink resource.

[0075] At least one downlink reference signal may then be transmitted on frequency resource corresponding to the second uplink grant. Hence, in some embodiments, the at least one downlink reference signal is also associated with the second uplink transmission grant. Further, the at least one downlink reference signal may be transmitted using a transmit beamformer corresponding to channel state information for the second time interval and the second UE 110b.

[0076] The second UE 110b may then perform an uplink data transmission in accordance with the second uplink transmission grant. Hence, in some embodiments the network node 120 is configured to perform (optional) step S212.

[0077] S212: The network node 120 receives uplink data in the second at least one uplink resource from the second UE 110b according to the second uplink transmission grant.

[0078] In some embodiments the uplink data of the first UE 110a and the uplink data of the second UE 110b are received in a fourth time interval, and the network node 120 is configured to perform (optional) step S214.

[0079] S214: The network node 120 estimates interference caused by the first UE 110a to the second UE 110b in the fourth time interval.

[0080] Then, in case interference above some pre-determined threshold is observed, the network node 120 could act on this. Therefore, in some embodiments the network node 120 is configured to perform (optional) step S216.

[0081] S216: The network node 120 performs an interference mitigation action responsive to the interference exceeding an interference threshold.

[0082] For example, the interference mitigation action may involve interference suppressing receiver beamforming, interference cancellation, interference rejection combining (IRC), adaptation of transmission power of at least one downlink reference signal, etc.

[0083] Reference is next made to Fig. 4 which in (a), (b), and (c) illustrate different parts of a sequence of events in a scenario where a first UE 410a is served by a first network node 420a and a second UE 410b is served by a second network node 420b. It is assumed that the UEs 410a, 410b have been configured as in above-disclosed steps S102 and S202.

[0084] In part (a), each of the network nodes 420a, 420b transmits a conditional uplink grant 430a, 430b towards its respective served UE 410a, 410b. In other words, each of the network nodes 420a, 420b transmits an uplink grant as in step S204.

[0085] In part (b), each of the network nodes 420a, 420b transmits a downlink reference signal in a beam 440a, 440b towards its respective served UE 410a, 410b. In other words, each of the network nodes 420a, 420b transmits a downlink reference signal as in step S208. Here, it is assumed that UE 410a only receives the downlink reference signal transmitted from network node 420a, whereas UE 410b receives the downlink reference signals as transmitted from both network nodes 420a, 420b. The UEs 410a, 410b receive and process any received downlink reference signal as in step SI 06. It is here assumed that for UE 410b the received power of the reference signal received from network node 420a exceeds a power threshold.

[0086] In part (c) UE 410a performs a beamformed transmission 450 according to which UE 410a transmits uplink data in the at least one uplink resource to the network node 120 without adapted uplink transmission of the at least one uplink resource. UE 410b, on the other hand, refrains from any transmission of uplink data. This is because only UE 410a was allowed to transmit using the conditional uplink grant since it did not detect the downlink reference signal from network node 420b with a power above a threshold. Here, it is thus for simplicity assumed that the only possible adaption that UE 410b can made to its uplink data transmission is to not make any transmission at all. As disclosed above, this could be the case where UE 410b is a single-antenna UE. If, on the other hand, UE 410b was a multi-antenna UE, it could be capable of transmitting in the uplink in a way that causes zero interference towards network node 420a.

[0087] Reference is next made to Fig. 5 which illustrates an example of a time-division duplex (TDD) resource grid 500. For simplicity, but without loss of generality, the resource grid 500 is composed of downlink (D) slots 510 and uplink (U) slots 520, and hence does not include any “special slots”. Signals and channels as used will now be described, along the timeline.

[0088] The uplink sounding reference signal (SRS) transmissions 530 from a first and a second UE are denoted UL SRS1 and UL SRS2, respectively. These signals are “Legacy SRS” used for e.g. average path-gain, radio link monitoring, link-adaptation bootstrap, heartbeat, access point selection, etc. These signals are depicted in the example for completeness, but they are not exclusively used only to support the herein disclosed embodiments. Typically, the UL SRS signals can have a relatively long periodicity compared to the uplink scheduling rate, or they may be transmitted on-demand. The reference signal sequences used for the uplink SRS transmissions are typically configured using radio resource control (RRC) signaling where each UE is configured with a specific sequence.

[0089] The physical downlink control channels (PDCCHs) 540a, 540b for the first UE and the second UE are denoted PDCCH1 and PDCCH2, respectively. The PDCCH contains downlink control information (DCI) to the UE. In this example, the PDCCH provides the grant for uplink physical resources of a future uplink transmission as well as a scheduling of corresponding downlink reference signal transmissions.

[0090] A respective downlink channel state information reference signal (DL CSI-RS) 550a, 550b is transmitted on the physical resources used for upcoming scheduled uplink transmissions. In this example the DL CSI- RS transmissions are not denoted with indices (e.g. 1 and 2 related to a first and second UE) as in the examples listed above. One reason is that in some examples, the DL CSI-RS uses a cell-specific sequence. I.e. the sequence is known in neighboring cells, and by UEs scheduled for uplink transmissions in neighboring cells. It is not strictly needed that these sequences are known in neighboring cells. In some examples, only the physical resources to estimate covariance on are known in neighboring cells.

[0091] The physical uplink shared channel 570a, 570b, for the first UE and the second UE is denoted PUSCHI and PUSCH2, respectively and its time and frequency resources are indicated (as illustrated by arrows 560a, 560b) in PDCCH1 and PDCCH2, respectively.

[0092] Reference is next made to Fig. 6(a) which illustrates a first simplified version of the TDD resource grid in Fig. 5. Accordingly, the TDD resource grid 600 is composed of downlink (DL) and uplink (UL) slots. In this example, two PDCCHs points to one and the same PUSCH. The TDD resource grid 600 is used in the scenario illustrated in Fig. 6(b). As illustrated in Fig 6(b), UEs 610a:610g are served by network nodes 620a:620c. It is assumed that UEs 610a, 610c are served by network node 620a, that UEs 610d, 610e, 610g are served by network node 620b, and that UEs 610b, 610f are served by network node 620c. This is an example of a MU MIMO scenario. At least some of the UEs 610a:610g in this example are given conditional uplink transmission grants. UEs 610a, 610c are scheduled by network node 620a in accordance with the TDD resource grid 600 and UEs 610b, 610d, 610e as scheduled by the other network nodes 620b, 620c also receive the downlink reference signals as transmitted by network node 620a in beams 630a, 630b. In this example each downlink reference signal is associated with each scheduled uplink data transmission grant. In this example the downlink reference signal has rank 2 since both UEs 610a, 610c are scheduled on the same time-and-frequency resource. Due to spatial separation, UEs 610a, 610c can only hear the downlink reference signal indicating its own uplink data grant, and hence both UEs 610a, 610c make a respective uplink data transmission, as indicated by the received grants, in a respective beam 640a, 640b. It is assumed that at least one of UEs 610b, 610d, 610e has also received a conditional uplink grant from their serving base network node, but since UEs 610b, 610d, 610e receive the downlink reference signal as transmitted from network node 620, i.e., from a non-serving network node, with a power above a threshold, they abstain from transmitting. As disclosed above, depending on whether the UEs are one-antenna UEs or multi-antenna UEs, UEs 610b, 610d, 610e may transmit in the uplink in a way that causes zero interference the towards the network node from which the downlink reference signal was received. The downlink reference signal in this example represents one scheduled uplink transmission layer that network node 620a wants to be protected from uplink inter-cell interference. The downlink reference signal is transmitted with an expected uplink beamformer in mind. In the represent example the beamwidth of beam 630a is wider the beam 630b. This may e.g., reflect that the channel state information available at the network node 620a at the time of transmitting the downlink reference signals is different. For example, the channel state information related to UE 610a may be fresher than the channel state information related to UE 610c.

[0093] Reference is next made to Fig. 7, which illustrates a second simplified version of the TDD resource grid in Fig. 5. Accordingly, the TDD resource grid 700 is composed of downlink (DL) and uplink (UL) slots. The TDD resource grid 700 is used in the scenario illustrated in Fig. 7(b). A first UE 710a is receiving a prioritized (i.e. non-conditional) uplink transmission grant while a second UE 710b has received a conditional grant for contention-based transmission. The conditional grant in this example may e.g. be persistent such that the UEs are allowed to transmit in any time slot if the received downlink reference signal power on these resources is below a threshold. At (i) the network node 720 transmits, in its cell 730, a downlink reference signal to indicate to UE 710b that the resources of the uplink transmission grant are occupied for scheduled traffic. UE 710b (with no prioritized grant) does detect the downlink reference signal with strong power on some, but not all, physical resource blocks. UE 710b hence concludes that it is allowed to transmit uplink data on some of the uplink resources that do not overlap with explicitly scheduled uplink data transmissions. At (ii) uplink data transmissions occur in respective beams 740a, 740b from UE 710a and UE 710b, respectively. In this example, contention-based and scheduled transmissions can thus coexist for one and the same network node 720, without collisions and with a minimum of coordination. A UE (represented by UE 710b in the present example) with a contention-based persistent grant can be allowed to transmit on the UL in case strong DL SRS received power is not detected.

[0094] From a system perspective, two overlapping uplink grants can thus be provided in one and the same cell; a contention-based grant and a prioritized (contention-based, scheduled) grant. Traditionally, this would result in colliding uplink transmission and significant uplink interference. But thanks to the herein disclosed embodiments, at the time of reception the transmissions do not overlap. Any UE with a contention-based grant is only allowed to transmit on resources where the downlink reference signal is detected with a power below a threshold (regardless if the downlink reference signal is received from its serving network node or from a network node in another cell). Conditional, contention-based transmissions can only occur on non-scheduled uplink resources in each beam. However, only scheduled transmissions are protected from potential inter-cell interference, while no such protection is provided for contention-based transmission.

[0095] Fig. 8 schematically illustrates, in terms of a number of structural units, the components of a UE 800 according to an embodiment. Processing circuitry 810 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product 1010a (as in Fig. 10), e.g. in the form of a storage medium 830. The processing circuitry 810 may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA).

[0096] Particularly, the processing circuitry 810 is configured to cause the UE 800 to perform a set of operations, or steps, as disclosed above. For example, the storage medium 830 may store the set of operations, and the processing circuitry 810 may be configured to retrieve the set of operations from the storage medium 830 to cause the UE 800 to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus the processing circuitry 810 is thereby arranged to execute methods as herein disclosed. The storage medium 830 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

[0097] The UE 800 may further comprise a communications (comm.) interface 820 for communications with other entities, functions, nodes, and devices in order to perform the methods as disclosed herein. As such the communications interface 820 may comprise one or more transmitters and receivers, comprising analogue and digital components.

[0098] The processing circuitry 810 controls the general operation of the UE 800 e.g. by sending data and control signals to the communications interface 820 and the storage medium 830, by receiving data and reports from the communications interface 820, and by retrieving data and instructions from the storage medium 830. Other components, as well as the related functionality, of the UE 800 are omitted in order not to obscure the concepts presented herein.

[0099] Fig. 9 schematically illustrates, in terms of a number of structural units, the components of a network node 900 according to an embodiment. Processing circuitry 910 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product 1010b (as in Fig. 10), e.g. in the form of a storage medium 930. The processing circuitry 910 may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA).

[0100] Particularly, the processing circuitry 910 is configured to cause the network node 900 to perform a set of operations, or steps, as disclosed above. For example, the storage medium 930 may store the set of operations, and the processing circuitry 910 may be configured to retrieve the set of operations from the storage medium 930 to cause the network node 900 to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus the processing circuitry 910 is thereby arranged to execute methods as herein disclosed.

[0101] The storage medium 930 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

[0102] The network node 900 may further comprise a communications interface 920 for communications with other entities, functions, nodes, and devices in order to perform the methods as disclosed herein. As such the communications interface 920 may comprise one or more transmitters and receivers, comprising analogue and digital components.

[0103] The processing circuitry 910 controls the general operation of the network node 900 e.g. by sending data and control signals to the communications interface 920 and the storage medium 930, by receiving data and reports from the communications interface 920, and by retrieving data and instructions from the storage medium 930. Other components, as well as the related functionality, of the network node 900 are omitted in order not to obscure the concepts presented herein.

[0104] The network node 900 may be provided as a standalone device or as a part of at least one further device. For example, the network node 900 may be provided in a node of a (radio) access network or in a node of the core network. Alternatively, functionality of the network node 900 may be distributed between at least two devices, or nodes. These at least two nodes, or devices, may either be part of the same network part (such as the (radio) access network or the core network) or may be spread between at least two such network parts. In general terms, instructions that are required to be performed in real time may be performed in a device, or node, operatively closer to the cell than instructions that are not required to be performed in real time. Thus, a first portion of the instructions performed by the network node 900 may be executed in a first device, and a second portion of the instructions performed by the network node 900 may be executed in a second device; the herein disclosed embodiments are not limited to any particular number of devices on which the instructions performed by the network node 900 may be executed. Hence, the methods according to the herein disclosed embodiments are suitable to be performed by a network node 900 residing in a cloud computational environment. Therefore, although a single processing circuitry 910 is illustrated in Fig. 9 the processing circuitry 910 may be distributed among a plurality of devices, or nodes. The same applies to the computer program 1020b of Fig. 10.

[0105] Fig. 10 shows one example of a computer program product 1010a, 1010b comprising computer readable means 1030. On this computer readable means 1030, a computer program 1020a can be stored, which computer program 1020a can cause the processing circuitry 810 and thereto operatively coupled entities and devices, such as the communications interface 820 and the storage medium 830, to execute methods according to embodiments described herein. The computer program 1020a and / or computer program product 1010a may thus provide means for performing any steps of the UE 110a, 800 as herein disclosed. On this computer readable means 1030, a computer program 1020b can be stored, which computer program 1020b can cause the processing circuitry 910 and thereto operatively coupled entities and devices, such as the communications interface 920 and the storage medium 930, to execute methods according to embodiments described herein. The computer program 1020b and / or computer program product 1010b may thus provide means for performing any steps of the network node 120, 900 as herein disclosed.

[0106] In the example of Fig. 10, the computer program product 1010a, 1010b is illustrated as an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-Ray disc. The computer program product 1010a, 1010b could also be embodied as a memory, such as a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM) and more particularly as a non-volatile storage medium of a device in an external memory such as a USB (Universal Serial Bus) memory or a Flash memory, such as a compact Flash memory. Thus, while the computer program 1020a, 1020b is here schematically shown as a track on the depicted optical disk, the computer program 1020a, 1020b can be stored in any way which is suitable for the computer program product 1010a, 1010b.

[0107] The inventive concept has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended patent claims.

Claims

CLAIMS1. A method for uplink data transmission, the method being performed by a user equipment, UE (110a), the method comprising: receiving (S104) an uplink transmission grant from a network node (120), wherein the uplink transmission grant corresponds to at least one uplink resource and is associated with a criterion related to received power of at least one downlink reference signal; receiving (SI 06) the at least one downlink reference signal associated with the uplink transmission grant and measuring received power of the received at least one downlink reference signal; and transmitting (S108) uplink data in the at least one uplink resource to the network node (120) with or without adapted uplink transmission of the at least one uplink resource, wherein whether to adapt the uplink transmission of the at least one uplink resource or not is based on whether the criterion for the measured received power is met or not.

2. The method according to claim 1, wherein the criterion is met when the received power exceeds a power threshold.

3. The method according to claim 2, wherein the uplink data is transmitted without adapted uplink transmission of the at least one uplink resource when the criterion is not met.

4. The method according to claim 2, wherein the uplink data is transmitted with adapted uplink transmission of the at least one uplink resource when the criterion is met.

5. The method according to any preceding claim, wherein the adapted uplink transmission of the at least one uplink resource pertains to at least one of: applying interference suppressing beamforming to the at least one uplink resource, reducing transmission power of the at least one uplink resource, reducing transmission bandwidth of the at least one uplink resource.

6. The method according to claim 5, wherein a direction in which interference suppressing beamforming is performed is based on an estimated direction in which the at least one downlink reference signal was received and using uplink-downlink channel reciprocity.

7. The method according to claim 5 or 6, wherein the interference suppressing beamforming is based on a spatial covariance matrix obtained from wideband, time-averaged, or frequency-averaged properties of a channel over which the reference signal was received, with nulls placed in dominant eigen- components of the spatial covariance matrix.

8. The method according to any preceding claim, wherein the method further comprises:receiving (SI 02) configuration of the at least one downlink reference signal from the network node (120), and wherein the at least one downlink reference signal is received in accordance with the configuration.

9. The method according to any preceding claim, wherein the at least one downlink reference signal is received over a bandwidth, and wherein the received power is measured on less than an entire bandwidth of the at least one downlink reference signal.

10. The method according to any preceding claim, wherein the network node (120) is a first network node, and wherein at least one of the at least one downlink reference signal is received from a second network node.

11. A method for granting uplink data transmission, the method being performed by a network node (120), the method comprising: transmitting (S204) an uplink transmission grant corresponding to at least one uplink resource for a user equipment, UE (110a), wherein the uplink transmission grant is associated with a criterion related to received power of at least one downlink reference signal; transmitting (S208) the at least one downlink reference signal associated with the uplink transmission grant; and receiving (S210) uplink data in the at least one uplink resource from the UE (110a) according to the uplink transmission grant.

12. The method according to claim 11, wherein the uplink transmission grant comprises information of configuration of the at least one downlink reference signal.

13. The method according to claim 11 or 12, wherein the at least one downlink reference signal comprises a cell-specific sequence of a cell served by the network node (120).

14. The method according to any of claims 11 to 13, wherein the UE (110a) is a first UE (110a), wherein the at least one uplink resource is a first at least one uplink resource, wherein the uplink transmission grant is a first uplink transmission grant that is transmitted in a first time interval, and wherein the method further comprises: transmitting (S206), in a second time interval, a second uplink transmission grant corresponding to a second at least one uplink resource for a second UE (110b).

15. The method according to claim 14, wherein the second uplink transmission grant is without restrictions with respect to the criterion related to received power of at least one downlink reference signal.

16. The method according to claim 14 or 15, wherein the second at least one uplink resource at least partly overlaps in time and / or frequency with the first at least one uplink resource.

17. The method according to any of claims 14 to 16, wherein the at least one downlink reference signal is also associated with the second uplink transmission grant.

18. The method according to any of claims 14 to 17, wherein the method further comprises: receiving (S212) uplink data in the second at least one uplink resource from the second UE (110b) according to the second uplink transmission grant.

19. The method according to any of claims 14 to 18, wherein the at least one downlink reference signal is transmitted using a transmit beamformer corresponding to channel state information for the second time interval and the second UE (110b).

20. The method according to any of claims 14 to 19, wherein the network node (120) assigns a higher prioritization to uplink transmission from the second UE (110b) than to uplink transmission from the first UE (HOa).

21. The method according to any of claims 14 to 20, wherein the uplink data of the first UE (110a) and the uplink data of the second UE (110b) are received in a fourth time interval, and wherein the method further comprises: estimating (S214) interference caused by the first UE (110a) to the second UE (110b) in the fourth time interval.

22. The method according to claim 21, wherein the method further comprises: performing (S216) an interference mitigation action responsive to the interference exceeding an interference threshold.

23. The method according to any of claims 11 to 22, wherein the method further comprises: transmitting (S202) configuration of the at least one downlink reference signal.

24. The method according to any preceding claim, wherein the at least one downlink reference signal is a channel state information reference signal or a downlink channel sounding reference signal.

25. A user equipment, UE (110a) for uplink data transmission, the UE (110a) comprising processing circuitry (810), the processing circuitry being configured to cause the UE (110a) to:receive an uplink transmission grant from a network node (120), wherein the uplink transmission grant corresponds to at least one uplink resource and is associated with a criterion related to received power of at least one downlink reference signal; receive the at least one downlink reference signal associated with the uplink transmission grant and measuring received power of the received at least one downlink reference signal; and transmit uplink data in the at least one uplink resource to the network node (120) with or without adapted uplink transmission of the at least one uplink resource, wherein whether to adapt the uplink transmission of the at least one uplink resource or not is based on whether the criterion for the measured received power is met or not.

26. The UE (110a) according to claim 25, further being configured to perform the method according to any of claims 2 to 10.

27. A network node (120) for granting uplink data transmission, the network node (120) comprising processing circuitry (910), the processing circuitry being configured to cause the network node (120) to: transmit an uplink transmission grant corresponding to at least one uplink resource for a user equipment, UE (110a), wherein the uplink transmission grant is associated with a criterion related to received power of at least one downlink reference signal; transmit the at least one downlink reference signal associated with the uplink transmission grant; and receive uplink data in the at least one uplink resource from the UE (110a) according to the uplink transmission grant.

28. The network node (120) according to claim or 27, further being configured to perform the method according to any of claims 12 to 24.

29. A computer program (1020a) for uplink data transmission, the computer program comprising computer code which, when run on processing circuitry (810) of a user equipment, UE (110a), causes the UE (110a) to: receive (S104) an uplink transmission grant from a network node (120), wherein the uplink transmission grant corresponds to at least one uplink resource and is associated with a criterion related to received power of at least one downlink reference signal; receive (SI 06) the at least one downlink reference signal associated with the uplink transmission grant and measuring received power of the received at least one downlink reference signal; andtransmit (S108) uplink data in the at least one uplink resource to the network node (120) with or without adapted uplink transmission of the at least one uplink resource, wherein whether to adapt the uplink transmission of the at least one uplink resource or not is based on whether the criterion for the measured received power is met or not.

30. A computer program (1020b) for granting uplink data transmission, the computer program comprising computer code which, when run on processing circuitry (910) of a network node (120), causes the network node (120) to: transmit (S204) an uplink transmission grant corresponding to at least one uplink resource for a user equipment, UE (110a), wherein the uplink transmission grant is associated with a criterion related to received power of at least one downlink reference signal; transmit (S208) the at least one downlink reference signal associated with the uplink transmission grant; and receive (S210) uplink data in the at least one uplink resource from the UE (110a) according to the uplink transmission grant.

31. A computer program product (1010a, 1010b) comprising a computer program ( 1020a, 1020b) according to at least one of claims 29 and 30, and a computer readable storage medium (1030) on which the computer program is stored.

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