WO2019081020A1

WO2019081020A1 - Client device, network access node and methods thereof

Info

Publication number: WO2019081020A1
Application number: PCT/EP2017/077414
Authority: WO
Inventors: Bengt Lindoff; Wenquan HU; Neng Wang; Chaitanya TUMULA
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2017-10-26
Filing date: 2017-10-26
Publication date: 2019-05-02
Also published as: CN111279624B; CN111279624A

Abstract

The invention relates to a client device (100) for a wireless communication system (500) configured to obtain a first uplink timing advance associated with a first uplink beam (502) to be used for transmission of a first symbol (S1) to a network access node (300) at a first symbol time instance; and obtain a second uplink timing advance associated with a second uplink beam (504) to be used for transmission of a second symbol (S2) to the network access node (300) at a consecutive second symbol time instance. The client device (100) is further configured to determine whether a transmission of the first symbol (S1) will at least partially overlap in time with a transmission of the second symbol (S2) based on the first uplink timing advance and the second uplink timing advance. The client device (100) is further configured to transmit at least one of the first symbol (S1) in the first uplink beam (502) and the second symbol (S2) in the second uplink beam (504) based on an uplink transmission rule if it is determined that the transmission of the first symbol (S1 ) will at least partially overlap in time with the transmission of the second symbol (S2). Furthermore, the invention also relates to a network access node (300), corresponding methods, and a computer program product.

Description

CLIENT DEVICE, NETWORK ACCESS NODE AND METHODS THEREOF Technical Field

The invention relates to a client device and a network access node. Furthermore, the invention also relates to corresponding methods and a computer program.

Background

The 5G cellular system, also called new radio (NR), is currently being standardized. NR is targeting radio spectrum from below 1 GHz up to and above 60 GHz. To allow for such diverse radio environments not only different system bandwidths will be supported, but also different numerologies, such as different sub-carrier-spacings (SCS). Furthermore, for carriers over 10 GHz multiple antennas and beamforming will be needed to combat the higher path loss at such high radio frequencies. When beamforming is used, a next generation nodeB (gNB) transmits data in several directions in different transmit beams. The user equipment (UE) therefore has to tunes its own receive antennas in different receive beam directions to communicate with the gNB. In order for the UE to be able to detect and track the transmit beams of the gNB, the UE need to perform beam monitoring. Hence, the gNB transmits known pilot signals in adjacent beams, which the UE receives and uses to detect possible transmit beams to switch to in case of changes in the radio environment. The principles behind beam monitoring can be compared to the cell search in legacy long term evolution (LTE), wideband code division multiple access (WCDMA) and high speed packet access (HSPA) systems. In such systems, the UE on a regular basis need to scan neighbouring cells for possible handover candidates.

Each possible connection between the UE and the gNB is called a beam pair link (BPL), where a BPL consists of the best match between a transmit beam and a receive beam. The gNB will configure a set of BPLs for the UE to monitor. The configured set of monitored BPLs may be based on which BPL the UE has detected. This set can for example comprise all the BPLs associated with control channels and data channels between the gNB and the UE. The gNB will also configure a set of serving BPLs which will be used to transmit associated control information to the UE. The set of serving BPLs is a subset or equal to the set of monitored BPLs. The UE monitors the quality of the set of monitored BPLs and reports the quality in beam measurement report to the gNB. When a monitored BPL beam becomes stronger than the current serving BPL a beam switch could be initiated. The exact procedure for the beam switching is not yet defined in the NR standard. One approach could be that the UE triggers a beam measurement report comprising the event that a target BPL is stronger than the current serving BPL. Another scenario would be that the gNB determines, e.g. using uplink management procedures, that a target BPL has become a suitable serving BPL. The gNB could then order a beam switch to the target BPL. To be in synchronization with the gNB in the uplink the UE performs uplink transmission in advance to downlink reception, according to timing advance commands received from the gNB. Upon a beam switch the timing of the uplink BPL may change significantly, e.g. when the new serving uplink BPL has a much shorter radio path than the old serving uplink BPL. This may cause uplink timing problems and result in uplink interference. Similar uplink timing problems may occur in multi-beam transmission where the timing advances associated with the beams differs significantly.

Summary

An objective of embodiments of the invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions.

The above and further objectives are solved by the subject matter of the independent claims. Further advantageous embodiments of the present invention can be found in the dependent claims.

According to a first aspect of the invention, the above mentioned and other objectives are achieved with a client device for a wireless communication system, the client device being configured to

obtain a first uplink timing advance associated with a first uplink beam to be used for transmission of a first symbol to a network access node of the wireless communication system at a first symbol time instance;

obtain a second uplink timing advance associated with a second uplink beam to be used for transmission of a second symbol to the network access node at a consecutive second symbol time instance;

determine whether a transmission of the first symbol will at least partially overlap in time with a transmission of the second symbol based on the first uplink timing advance and the second uplink timing advance;

transmit at least one of the first symbol in the first uplink beam and the second symbol in the second uplink beam based on an uplink transmission rule if it is determined that the transmission of the first symbol will at least partially overlap in time with the transmission of the second symbol. Generally, an uplink timing advance corresponds to how long before a downlink reception the client device needs to start an uplink transmission, such that the uplink transmission reaches the network access node at a correct time instance. Hence, the uplink timing advance is an indication of the time period it takes for a radio signal to propagate from the client device to the network access node.

A symbol can in this disclosure be understood to be a number of modulated information bits (e.g. associated to data symbols, control symbol or pilot symbols), where the number of bits per symbol is determined by different factors, such as e.g. modulation format or type, bandwidth and carrier spacing. Each symbol can be transmitted at a corresponding symbol time instance. That the second symbol time instance is consecutive can in this disclosure be understood to mean that the second symbol time instance is the next time instance after the first symbol time instance. An uplink transmission rule can comprise one or more rules which indicates or stipulates how the client device should handle uplink transmissions that will partially overlap in time.

A client device according to the first aspect provides a number of advantages over conventional solutions. An advantage of the client device according to the first aspect is that uplink transmissions that will partially overlap in time can be identified and avoided. Thereby, decreasing the risk of uplink interference. Furthermore, using uplink timing advance to identify uplink transmissions that will partially overlap in time, results in a solution with low complexity.

In an implementation form of a client device according to the first aspect, the client device is further configured to

drop one of the first symbol or the second symbol based on the uplink transmission rule.

That a symbol is dropped can in this disclosure be understood to mean that the transmission of the symbol is cancelled or discarded.

An advantage with this implementation form is that partially overlapping uplink transmissions can be avoided and that the client device can control which of the first symbol and the second symbol to transmit. In an implementation form of a client device according to the first aspect, the client device is further configured to

obtain a first priority associated with the transmission of the first symbol; obtain a second priority associated with the transmission of the second symbol;

drop one of the first symbol or the second symbol based on the uplink transmission rule in dependence on the first priority and the second priority. An advantage with this implementation form is that that the client device can control which of the first symbol and the second symbol to transmit based on their respective priority.

In an implementation form of a client device according to the first aspect, the dropped symbol belongs to a set of symbols associated with an uplink control channel or an uplink shared channel and the client device is further configured to at least one of

increase a transmission power when transmitting the remaining symbols of the set of symbols associated with the uplink control channel or the uplink shared channel; and

drop the remaining symbols of the set of symbols associated with the uplink control channel or the uplink shared channel.

An advantage with this implementation form is that by increasing the power for the remaining symbols, the decoding at the network access node can be improved.

In an implementation form of a client device according to the first aspect, the client device is further configured to at least one of

drop the second symbol if the first symbol comprises a hybrid automatic repeat request acknowledgement or a hybrid automatic repeat request negative acknowledgement; and drop the first symbol if the first symbol is a sounding reference symbol and a previous first symbol transmitted in the first uplink beam is a sounding reference symbol.

An advantage with this implementation form is that the type of information comprised in the symbols can be used to determine whether the first symbol or the second symbol should be dropped. In an implementation form of a client device according to the first aspect, the client device is further configured to

transmit the first symbol in the first uplink beam using a first sub-carrier spacing;

transmit the second symbol in the second uplink beam using a second sub-carrier spacing, wherein the first sub-carrier spacing and the second sub-carrier spacing are different sub-carrier spacings given by the uplink transmission rule. An advantage with this implementation form is that by using different sub-carrier spacings a gap can be created between the transmission of the first symbol and the transmission of the second symbol. The gap allows the first symbol and the second symbol to be transmitted without an overlap in time.

generate a first control message if it is determined that the transmission of the first symbol will at least partially overlap in time with the transmission of the second symbol, wherein the first control message indicates that the transmission of the first symbol will at least partially overlap in time with the transmission of the second symbol;

transmit the first control message to the network access node.

An advantage with this implementation form is that the client device can inform the network access node about uplink transmissions that will partially overlap in time. Thereby, the network access node can initiate actions such as uplink reconfigurations to avoid partially overlapping uplink transmissions.

receive a second control message from the network access node, wherein the second control message indicates the uplink transmission rule.

An advantage with this implementation form is that the network access node can control how the client device handles uplink transmissions that will partially overlap in time. Thereby, reducing the impact on system performance due to partially overlapping uplink transmissions.

In an implementation form of a client device according to the first aspect, the uplink transmission rule is given by a pre-defined rule.

An advantage with this implementation form is that the uplink transmission rule can be standardized and thereby easy to implement. Further, consistent client device behaviour is achieved thereby improving the general system performance of the wireless communication system.

In an implementation form of a client device according to the first aspect, the client device is further configured to receive a third control message from the network access node, wherein the third control message indicates a first uplink network timing advance and a second uplink network timing advance;

obtain the first uplink timing advance based on the first uplink network timing advance; obtain the second uplink timing advance based on the second uplink network timing advance.

An advantage with this implementation form is that the first uplink timing advance and the second uplink timing advance can be obtained from information provided by the network access node, i.e. using a low complexity method.

obtain a first downlink timing for a first downlink beam associated with the first uplink beam;

obtain a second downlink timing for a second downlink beam associated with the second uplink beam;

obtain the first uplink timing advance based on the first downlink timing;

obtain the second uplink timing advance based on the second downlink timing.

An advantage with this implementation form is that the first uplink timing advance and the second uplink timing advance can be obtained even when no network timing advance information is available. According to a second aspect of the invention, the above mentioned and other objectives are achieved with a network access node for a wireless communication system, the network access node being configured to

generate a second control message comprising an uplink transmission rule for a client device, wherein the uplink transmission rule indicates a rule for uplink transmission of at least one of a first symbol in a first uplink beam at a first symbol time instance and a second symbol in a second uplink beam at a consecutive second symbol time instance from the client device to the network access node if it is determined that the transmission of the first symbol will at least partially overlap in time with the transmission of the second symbol;

transmit the second control message to the client device.

A network access node according to the second aspect provides a number of advantages over conventional solutions. An advantage of the network access node is that it can control how the client device handles uplink transmissions that will partially overlap in time. Thereby, reducing the impact on system performance due to partially overlapping uplink transmissions.

In an implementation form of a network access node according to the second aspect, the network access node is further configured to

receive, prior to the generation of the second control message, a first control message from the client device, wherein the first control message indicates that the transmission of the first symbol will at least partially overlap in time with the transmission of the second symbol; transmit the second control message in response to the reception of the first control message.

An advantage with this implementation form is that the network access node can provide the uplink transmission rule to the client device when uplink transmissions that will partially overlap has been identified. Thereby, the network access node can control how the client device handles the partially overlapping uplink transmissions.

determine a first uplink network timing advance;

determine a second uplink network timing advance;

generate a third control message indicating the first uplink network timing advance and the second uplink network timing advance;

transmit the third control message to the client device. An advantage with this implementation form is that the client device is informed about network timing advances.

transmit the second control message to the client device in any of a downlink control information, DCI, media access control control-element, MAC CE, or radio resource control, RRC, message.

An advantage with this implementation form is that existing signalling elements can be used to convey the second control message. Hence, simplifying the implementation of embodiments of the invention. According to a third aspect of the invention, the above mentioned and other objectives are achieved with a method for a client device, the method comprises

obtaining a first uplink timing advance associated with a first uplink beam to be used for transmission of a first symbol to a network access node of the wireless communication system at a first symbol time instance;

obtaining a second uplink timing advance associated with a second uplink beam to be used for transmission of a second symbol to the network access node at a consecutive second symbol time instance;

determining whether a transmission of the first symbol will at least partially overlap in time with a transmission of the second symbol based on the first uplink timing advance and the second uplink timing advance;

transmitting at least one of the first symbol in the first uplink beam and the second symbol in the second uplink beam based on an uplink transmission rule if it is determined that the transmission of the first symbol will at least partially overlap in time with the transmission of the second symbol.

The method according to the third aspect can be extended into implementation forms corresponding to the implementation forms of the client device according to the first aspect. Hence, an implementation form of the method comprises the feature(s) of the corresponding implementation form of the client device.

The advantages of the methods according to the third aspect are the same as those for the corresponding implementation forms of the client device according to the first aspect. According to a fourth aspect of the invention, the above mentioned and other objectives are achieved with a method for a network access node, the method comprises

generating a second control message comprising an uplink transmission rule for a client device, wherein the uplink transmission rule indicates a rule for uplink transmission of at least one of a first symbol in a first uplink beam at a first symbol time instance and a second symbol in a second uplink beam at a consecutive second symbol time instance from the client device to the network access node if it is determined that the transmission of the first symbol will at least partially overlap in time with the transmission of the second symbol;

transmitting the second control message to the client device. The method according to the fourth aspect can be extended into implementation forms corresponding to the implementation forms of the network access node according to the second aspect. Hence, an implementation form of the method comprises the feature(s) of the corresponding implementation form of the network access node.

The advantages of the methods according to the fourth aspect are the same as those for the corresponding implementation forms of the network access node according to the second aspect.

The invention also relates to a computer program, characterized in code means, which when run by processing means causes said processing means to execute any method according to the present invention. Further, the invention also relates to a computer program product comprising a computer readable medium and said mentioned computer program, wherein said computer program is included in the computer readable medium, and comprises of one or more from the group: ROM (Read-Only Memory), PROM (Programmable ROM), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically EPROM) and hard disk drive.

Further applications and advantages of the present invention will be apparent from the following detailed description.

Brief Description of the Drawings

The appended drawings are intended to clarify and explain different embodiments of the present invention, in which:

- Fig. 1 shows a client device according to an embodiment of the invention;

- Fig. 2 shows a method according to an embodiment of the invention;

- Fig. 3 shows a network access node according to an embodiment of the invention; - Fig. 4 shows a method according to an embodiment of the invention;

- Fig. 5 shows a wireless communication system according to an embodiment of the invention;

- Fig. 6 shows downlink receptions and uplink transmissions at a client device;

- Fig. 7 shows a flow chart according to an embodiment of the invention;

- Fig. 8 shows uplink transmissions according to different uplink transmission rules according to an embodiment of the invention;

- Fig. 9 shows signalling between a client device and a network access node according to an embodiment of the invention. Detailed Description

Fig. 1 shows a client device 100 according to an embodiment of the invention. In the embodiment shown in Fig. 1 , the client device 100 comprises a processor 102, a transceiver 104, and a memory 106. The processor 102 is coupled to the transceiver 104 and the memory 106 by communication means 108 known in the art. The client device 100 further comprises an antenna 1 10 coupled to the transceiver 104, which means that the client device 100 is configured for wireless communications in a wireless communication system. That the client device 100 is configured to perform certain actions should in this disclosure be understood to mean that the client device 100 comprises suitable means, such as e.g. the processor 102 and the transceiver 104, configured to perform said actions.

The client device 100 is configured to obtain a first uplink timing advance associated with a first uplink beam 502 (shown in Fig. 5) to be used for transmission of a first symbol S1 to a network access node 300 (shown in Fig. 3) of a wireless communication system 500 (shown in Fig. 5) at a first symbol time instance. The client device 100 is further configured to obtain a second uplink timing advance associated with a second uplink beam 504 (shown in Fig. 5) to be used for transmission of a second symbol S2 (Fig. 8) to the network access node 300 at a consecutive second symbol time instance. Furthermore, the client device 100 is configured to determine whether a transmission of the first symbol S1 will at least partially overlap in time with a transmission of the second symbol S2 based on the first uplink timing advance and the second uplink timing advance. Since timing advance is a measure on how much an uplink transmission should be advanced compared to the downlink reception timing, different timing advances for different adjacent symbols (e.g. the first symbol S1 and the second symbol S2) will mean that the adjacent symbols in some cases will partly overlap. The client device 100 is further configured to transmit at least one of the first symbol S1 in the first uplink beam 502 and the second symbol S2 in the second uplink beam 504 based on an uplink transmission rule if it is determined that the transmission of the first symbol S1 will at least partially overlap in time with the transmission of the second symbol S2. The different timing advances for the different uplink beams 502, 504 are a result of different signal propagation paths for the different uplink beams 502, 504 as for example illustrated in Fig. 5.

Fig. 2 shows a flow chart of a corresponding method 200 which may be executed in a client device 100, such as the one shown in Fig. 1 . The method 200 comprises obtaining 202 a first uplink timing advance associated with a first uplink beam 502 to be used for transmission of a first symbol S1 to a network access node 300 of the wireless communication system 500 at a first symbol time instance. The method 200 further comprises obtaining 204 a second uplink timing advance associated with a second uplink beam 504 to be used for transmission of a second symbol S2 to the network access node 300 at a consecutive second symbol time instance. The method 200 further comprises determining 206 whether a transmission of the first symbol S1 will at least partially overlap in time with a transmission of the second symbol S2 based on the first uplink timing advance and the second uplink timing advance. Furthermore, the method 200 comprises transmitting 208 at least one of the first symbol S1 in the first uplink beam 502 and the second symbol S2 in the second uplink beam 504 based on an uplink transmission rule if it is determined that the transmission of the first symbol S1 will at least partially overlap in time with the transmission of the second symbol S2.

Fig. 3 shows a network access node 300 according to an embodiment of the invention. In the embodiment shown in Fig. 3, the network access node 300 comprises a processor 302, a transceiver 304, and a memory 306. The processor 302 is coupled to the transceiver 304 and the memory 306 by communication means 308 known in the art. The network access node 300 may be configured for both wireless and wired communications in wireless and wired communication systems, respectively. The wireless communication capability is provided with an antenna 310 coupled to the transceiver 304, while the wired communication capability is provided with a wired communication interface 312 coupled to the transceiver 304.

That the network access node 300 is configured to perform certain actions should in this disclosure be understood to mean that the network access node 300 comprises suitable means, such as e.g. the processor 302 and the transceiver 304, configured to perform said actions.

The network access node 300 is configured to generate a second control message 620 (shown in Fig. 9) comprising an uplink transmission rule for a client device 100. The uplink transmission rule indicates a rule for uplink transmission of at least one of a first symbol S1 in a first uplink beam 502 at a first symbol time instance and a second symbol S2 in a second uplink beam 504 at a consecutive second symbol time instance from the client device 100 to the network access node 300 if it is determined that the transmission of the first symbol S1 will at least partially overlap in time with the transmission of the second symbol S2. The network access node 300 is further configured to transmit the second control message 620 to the client device 100.

Fig. 4 shows a flow chart of a corresponding method 400 which may be executed in a network access node 300, such as the one shown in Fig. 3. The method 400 comprises generating 402 a second control message 620 comprising an uplink transmission rule for a client device 100. The uplink transmission rule indicates a rule for uplink transmission of at least one of a first symbol S1 in a first uplink beam 502 at a first symbol time instance and a second symbol S2 in a second uplink beam 504 at a consecutive second symbol time instance from the client device 100 to the network access node 300 if it is determined that the transmission of the first symbol S1 will at least partially overlap in time with the transmission of the second symbol S2. The method 400 further comprises transmitting 404 the second control message 620 to the client device 100. Fig. 5 shows a wireless communication system 500 according to an embodiment. The wireless communication system 500 comprises a client device 100 and a network access node 300 configured to operate in the wireless communication system 500. For simplicity, the wireless communication system 500 shown in Fig. 5 only comprises one client device 100 and one network access node 300. However, the wireless communication system 500 may comprise any number of client devices 100 and any number of network access nodes 300 without deviating from the scope of the invention.

In the wireless communication system 500, beamforming is used such that data is transmitted in several directions in different beams between the client device 100 and the network access node 300. In Fig. 5, a first downlink beam 512 associated with a first uplink beam 502, as well as a second downlink beam 514 associated with a second uplink beam 504, is shown. However, any number of uplink beams and/or downlink beams may exist between the client device 100 and the network access node 300 without deviation from the scope of the invention. The first uplink beam 502 is a serving uplink beam for uplink transmissions from the client device 100 to the network access node 300. Hence, the first uplink beam 502 is used for uplink transmissions of symbols comprising data from the client device 100 to the network access node 300. The second uplink beam 504 may be an additional serving uplink beam used for uplink transmissions of symbols comprising data from the client device 100 to the network access node 300. Alternatively, the second uplink beam 504 may be a candidate uplink beam which may be suitable to become a serving uplink beam as the client device 100 moves in the direction indicated by the arrow A in Fig. 5. In this case, the second uplink beam 504 may be used for uplink transmissions of references signals from the client device 100 to the network access node 300. The reference signals are used to monitor the quality of the second uplink beam 504. As can be seen in Fig. 5, the radio signal distance between client device 100 and network access node 300 for the second uplink beam 504 is much shorter than the corresponding radio signal distance for the first uplink beam 502. Hence, the uplink timing advance associated with the second uplink beam 504 will differ from (will be smaller than) the uplink timing advance associated with the first uplink beam 502. This may lead to a partial overlap in time of transmissions of symbols on the first uplink beam 502 and the second uplink beam 504 as will now be described with reference to Fig. 6. Fig. 6 shows transmissions of symbols in the first downlink beam 512, the second downlink beam 514, the first uplink beam 502 and the second uplink beam 504 at symbol time instances 1 -7. In Fig. 6 the first downlink beam 512 and the first uplink beam 502 are serving beams. Hence, the client device 100 receives and transmit symbols comprising data, herein called data symbols, in the first downlink beam 512 and the first uplink beam 502. In the embodiment shown in Fig. 6, the client device 100 receives data symbols DSs in the first downlink beam 512 at symbol time instances 1 and 3. In addition, the client device 100 transmits data symbols DSs in the first uplink beam 502 at symbol time instances 5 and 7. Furthermore in Fig. 6, the second downlink beam 514 and the second uplink beam 504 are candidate uplink beams. Hence, the client device 100 receives and transmit symbols comprising reference signals, herein called reference symbols, in the second downlink beam 514 and the second uplink beam 504. Examples of reference symbols are channel state information (CSI) refence signals (RSs) in the downlink beam, and sounding reference signals (SRSs) in the uplink beam. In Fig. 6, the client device 100 receives a reference symbol RS from the network access node 300 in the second downlink beam 514 at symbol time instance 2 and transmits a reference symbol RS in the second uplink beam 504 at symbol time instance 6. It is assumed that the timing advance has been measured by the network access node 300 and that the client device 100 has been configured with a respective timing advance value for proper timing of uplink transmissions in the first uplink beam 502 and the second uplink beam 504. As shown in Fig. 5, the radio signal distance for the second uplink beam 504 is much shorter than the radio signal distance for the first uplink beam 502. Hence, the end of the transmission of the reference symbol RS in the second uplink beam 504 at symbol time instance 6 will partially overlap in time with the beginning of the transmission of the data symbol DS in the first uplink beam 502 at symbol time instance 7, as shown in Fig. 6. Embodiments of the invention provide ways to avoid this partial overlap of uplink transmissions which will now be described in more detail with reference to Fig. 7 and 8.

Fig. 7 shows a flow chart illustrating embodiments of the invention. A client device 100 is in connection with a network access node 300 via a first uplink beam 502 and a second uplink beam 504. In step 602, the client device 100 obtains a first uplink timing advance associated with a first uplink beam 502 to be used for transmission of a first symbol S1 to a network access node 300 at a first symbol time instance. The transmission of the first symbol S1 may e.g. be a data transmission based on an uplink grant from the network access node 300, a reference signal transmission configured by the network access node 300, or a response transmission to indicate decoding success or failure, but is not limited to these scenarios. In step 604, the client device 100 obtains a second uplink timing advance associated with a second uplink beam 504 to be used for transmission of a second symbol S2 to the network access node 300 at a consecutive second symbol time instance. In the same way as for the transmission of the first symbol S1 , the transmission of the second symbol S2 may e.g. be a data transmission based on an uplink grant from the network access node 300, a reference signal transmission configured by the network access node 300, or a response transmission to indicate decoding success or failure, but is not limited to these scenarios.

The client device 100 may obtain the first uplink timing advance and the second uplink timing advance in different ways. According to embodiments of the invention the client device 100 may e.g. obtain the first uplink timing advance and the second uplink timing advance based on network timing advance information or based on downlink timing. In embodiments where network timing advance information is used, the network timing advance information may be received by the client device 100 from the network access node 300 in a third control message 630 (shown in fig. 9). The third control message 630 indicates a first uplink network timing advance and a second uplink network timing advance. The client device 100 obtains the first uplink timing advance based on the first uplink network timing advance, and the second uplink timing advance based on the second uplink network timing advance. In embodiments where downlink timing is used, the client device 100 may obtain a first downlink timing for the first downlink beam 512 associated with the first uplink beam 502, and obtain a second downlink timing for the second downlink beam 514 associated with the second uplink beam 504. The client device 100 obtains the first uplink timing advance based on the first downlink timing and obtains the second uplink timing advance based on the second downlink timing. This approach may be suitable when uplink-downlink beam correspondence or reciprocity holds, e.g. when the same beam pair link is used for both uplink and downlink communications. The obtaining of the first uplink timing advance and the second uplink timing advance is not limited to these two described methods, any known way of obtaining timing advances may be used without deviating from the scope of the invention.

Based on the obtained uplink timing advance and the obtained second uplink timing advance the client device 100 determines whether the transmission of the first symbol S1 will at least partially overlap in time with the transmission of the second symbol S2. This determination which is based on whether the first timing advance for the first symbol S1 and the second timing advance for the second symbol S2 substantially differs, is performed in step 606. For example, the difference between the first timing advance and the second timing advance could be compared to a threshold value, such that if the difference is larger than the threshold value it is determined that the transmission of the first symbol S1 will at least partially overlap in time with the transmission of the second symbol S2. The threshold value can be static or dynamically adjusted. Dynamic adjustment of the threshold value could e.g. be controlled by the network. In such an implementation the threshold value could be transmitted in a control message to the client device 100 (not shown in the Figs.). The threshold value can be determined or adjusted based on considerations related to error rate, latency, priority, etc.

If the outcome of the determining in step 606 is No, i.e. there is no overlap in time between the transmission of the first symbol S1 and the transmission of the second symbol S2, the client device 100 transmits the first symbol S1 in the first uplink beam 502 and the second symbol S2 in the second uplink beam 504 in step 608. In this case, no adjustments are made to the uplink transmission of the first symbol S1 and the transmission of the second symbol S2, i.e. the first symbol S1 and the second symbol S2 are transmitted as intended which implies that no adjustment of the uplink transmission of the first symbol S1 and the second symbol S2 is needed.

On the other hand, if the outcome of the determining in step 606 is Yes, the client device 100 transmits at least one of the first symbol S1 in the first uplink beam 502 and the second symbol S2 in the second uplink beam 504 based on an uplink transmission rule, in step 610. The uplink transmission rule is designed to avoid partial overlap in time of the transmission of the first symbol S1 and the transmission of the second symbol S2 by adjusting the transmission of the first symbol S1 and/or the transmission of the second symbol S2. Hence, the uplink transmission rule may indicate a rule upon which the transmission of at least one of the first symbol S1 and the second symbol S2 is based. Furthermore, the uplink transmission rule may e.g. be pre-configured in the client device 100 or received from the network access node 300 (as shown in Fig. 9). In addition, the uplink transmission rule may be given by a pre-defined rule, e.g. a pre-defined rule set by the wireless communication standard, such as the NR standard.

Further details related to the uplink transmission rule will now be described with reference to Fig. 8. Fig. 8 shows uplink transmissions according to different uplink transmission rules according to embodiments of the invention. In scenario I and scenario II in Fig. 8, the uplink transmission rule indicates that one of the first symbol S1 or the second symbol S2 should be dropped, i.e. the transmission of either the first symbol S1 (scenario II) or the second symbol S2 (scenario I) should be cancelled or discarded. In this case, the client device 100 drops one of the first symbol S1 or the second symbol S2 based on the uplink transmission rule and hence only transmits the first symbol S1 or the second symbol S2. The client device 100 may determine which of the symbols to drop based on priorities associated with the transmissions of the symbols. To make a determination based on priority, the client device 100 may obtain a first priority associated with the transmission of the first symbol S1 and a second priority associated with the transmission of the second symbol S2. The priority, e.g. in terms of an explicit priority value, may for instance be based on what type of information that is contained in the first symbol S1 and the second symbol S2, respectively. For instance, the symbols may be reference symbols or pilot symbols, symbols containing data, or symbols containing control information. Depending on the content of the first symbol S1 and the second symbol S2, respectively, different priority rules is thus applied. The client device 100 further drops one of the first symbol S1 or the second symbol S2 based on the uplink transmission rule in dependence on the first priority and the second priority. For example, if the uplink transmission rule indicates that one of the first symbol S1 or the second symbol S2 should be dropped and the obtained first priority is higher than the obtained second priority, the client device 100 transmits the first symbol S1 and drops the second symbol S2. This case is shown in Fig. 8 as scenario I. On the other hand, if the second priority is higher than the first priority, the client device 100 would instead transmit the second symbol S2 and drop the first symbol S1 , as shown in scenario II in Fig. 8. Moreover, the client device 100 may determine which of the symbols to drop based on the type of information comprised in the symbols. For example, if a symbol comprises a hybrid automatic repeat request (HARQ) acknowledgement (ACK) or a HARQ negative acknowledgement (NACK) it is important that said information reaches the network access node 300. This is due to the fact that if HARQ ACK and NACK are not received by the network access node 300, a data packet need to be retransmitted in HARQ schemes, introducing unnecessary latency if the received data packet actually was correctly decoded. Hence, according to embodiments of the invention the client device 100 may drop the second symbol S2 if the first symbol S1 comprises a HARQ ACK or a HARQ NACK. On the other hand, if a symbol is part of a periodic transmission the loss of one symbol will generally not have a major impact on performance. For example, when a client device 100 transmits periodic SRSs, the loss of one SRSs does not have a major impact on the ability of the network access node 300 to measure and estimate the quality of the radio link to the client device 100. Hence, according to embodiments of the invention the client device 100 may drop the first symbol S1 if the first symbol S1 is a SRS, i.e. a symbol comprising a SRS, and a previous first symbol transmitted in the first uplink beam 502 is a sounding reference symbol. A previous first symbol may e.g. be a first symbol transmitted within a pre-defined time period before the first symbol S1 is to be transmitted, where the time period may be tracked e.g. with a timer. In embodiments of the invention where a symbol is dropped, the client device 100 may adjust the transmission of symbols associated with the dropped symbol to decrease the impact of dropping the symbol. One possible adjustment is to adjust the transmit power of the transmission of symbols associated with the dropped symbol. This adjustment may e.g. be used when the dropped symbol belongs to a set of symbols associated with an uplink control channel or an uplink shared channel. The client device 100 would then increase a transmission power when transmitting the remaining symbols of the set of symbols associated with the uplink control channel or the uplink shared channel. The set of symbols may e.g. be symbols transmitted in the same transmission time interval (TTI), code block (CB), code block group (CBG), or transport block (TB). If one of the symbols in such a set of symbols is dropped the client device 100 may transmit the remaining symbols of the set of symbols with higher transmission power. The transmission power may be increased (over a nominal pre-defined transmission power value obtained from the uplink power control loop) in proportion to the fraction of the dropped symbol in the TTI, CB, CBG, or TB.

Alternatively, when the dropped symbol belongs to a set of symbols associated with an uplink control channel or an uplink shared data channel, the client device 100 may drop the remaining symbols of the set of symbols associated with the uplink control channel or the uplink shared channel. For example, if an SRS is transmitted in one uplink beam, and a symbol associated with an uplink shared data channel in another uplink beam, the entire TTI, CB, CBG or TB included in the uplink shared data channel may be dropped, and the system will in such case rely on retransmission of the entire TTI, CB, CBG or TB. Such a solution may be preferred in scenarios when a simple pre-defined uplink transmission rule is more important than an actual maximum uplink transmission data rate.

Scenario III in Fig. 8 shows an embodiment where the uplink transmission rule indicates that the first symbol S1 and the second symbol S2 should be transmitted using different sub-carrier spacings. Such an approach is suitable in case when orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform spread (DFTS) OFDM is used in the uplink. In such embodiments, the client device 100 may transmit the first symbol S1 in the first uplink beam 502 using a first sub-carrier spacing and may transmit the second symbol S2 in the second uplink beam 504 using a second sub-carrier spacing. The first sub-carrier spacing and the second sub-carrier spacing are different sub-carrier spacings given by the uplink transmission rule. In scenario III in Fig. 8, the second symbol S2 is transmitted with a larger sub-carrier-spacing than the first symbol S1 . When a larger sub-carrier-spacing is used, the symbol time is reduced, as by construction of OFDM symbol generation. Thereby, natural gaps are created between the symbols and partial overlap in time of transmissions of symbols can be avoided. This approach may e.g. be suitable if the transmission of the second symbol S2 is a SRS. Assume a sub-carrier spacing of 30 kHz is used for transmission of regular uplink symbols including the first symbol S1 in Fig. 8. If the client device 100 uses a sub-carrier- spacing of 60 kHz for the transmission of the second symbol S2, the symbol time of the second symbol S2 is reduced to half the symbol time of the regular uplink symbols, as shown in scenario III in Fig. 8. Hence, the transmission of the first symbol S1 and the transmission of the second symbol S2 will not overlap in time. Fig. 9 shows signalling between the client device 100 and the network access node 300 according to embodiments of the invention. Control messages may be transmitted to exchange information about timing advances, partial overlaps in time and uplink transmission rules. Step I and step II in Fig. 9 show the generation and transmission of an optional third control message 630, respectively. The third control message 630 allows the network access node 300 to inform the client device 100 about uplink timing advance information available to the network access node 300, herein called uplink network timing advances.

With reference to Fig. 9, in step I, the network access node 300 generates a third control message 630 indicating a first uplink network timing advance and a second uplink network timing advance. The first uplink network timing advance and the second uplink network timing advance may be determined by the network access node 300 based on well known techniques. In step II, the network access node 300 transmits the third control message 630 to the client device 100. Step I and step II are optional steps as indicated by dashed lines in Fig. 9. If performed, step II gives the client device 100 information about the first uplink network timing advance and the second uplink network timing advance, from which the client device 100 can obtain the first uplink timing advance and the second uplink timing advance. However, the client device 100 may instead use other methods to obtain the first uplink timing advance and the second uplink timing advance, as previously described. Step III and step IV in Fig. 9 may be performed to inform the network access node 300 that uplink transmissions in the client device 100 will partially overlap in time. In step III, the client device 100 generates a first control message 610. Step III may be performed if it is determined that the transmission of the first symbol S1 will at least partially overlap in time with the transmission of the second symbol S2. The first control message 610 indicates that the transmission of the first symbol S1 will at least partially overlap in time with the transmission of the second symbol S2. In step IV, the client device 100 transmits the first control message 610 to the network access node 300. The described procedure of indicating to a network access node that uplink transmissions will partially overlap in time may e.g. be beneficial in a scenario where a client device 100 is in connection with two network access nodes. Each network access node typically controls the respective timing advance loop independent of each other. A control device in one of the network access node may coordinate the transmission between the two network access nodes via backhaul signalling. However, the backhaul signalling between the network access nodes may be on a slower time scale than the radio communication with the client device 100. Hence, the client device 100 may be the first to identify that a partial overlap of uplink transmissions will occur. By letting the client device 100 indicate to one of the network access node that uplink transmissions will partially overlap in time, the network access node may mitigate the problem earlier and in a controlled way.

Step V and step VI in Fig. 9 may be performed to allow the network access node 300 to configure the client device 100 with an uplink transmission rule. In step V, the network access node 300 generates a second control message 620 comprising an uplink transmission rule for a client device 100. The uplink transmission rule indicates a rule for uplink transmission of at least one of a first symbol S1 in a first uplink beam 502 at a first symbol time instance and a second symbol S2 in a second uplink beam 504 at a consecutive second symbol time instance from the client device 100 to the network access node 300 if it is determined that the transmission of the first symbol S1 will at least partially overlap in time with the transmission of the second symbol S2. In step VI, the network access node 300 transmits the second control message 620 to the client device 100. The network access node 300 may e.g. transmit the second control message 620 to the client device 100 in any of downlink control information (DCI), media access control control-element (MAC CE), or a radio resource control (RRC) message. By transmitting the second control message 620 in DCI, the network access node 300 has full control over the behaviour of the client device 100. The network access node 300 may e.g. transmit a blank or empty DCI to avoid scheduling in one of the uplink beams and thereby avoid that uplink transmissions will partially overlap in time. In embodiments of the invention, the client device 100 may be configuration with the uplink transmission rule already at the set-up of a multi-beam uplink transmission. Hence, prior to identifying that uplink transmissions will partial overlap in time. In this case, the network access node 300 typically would configure the client device 100 with an uplink transmission rule using RRC messages.

The client device 100 receives the second control message 620 from the network access node 300, where the second control message 620 indicates the uplink transmission rule. The uplink transmission rule is used by the client device 100 to avoid a partial overlap of the transmission of the first symbol S1 and the transmission of the second symbol S2 as previously described with reference to Fig. 8. In Fig. 9, step V and step VI are performed in response to the reception of the first control message 610. Hence, the network access node 300 in Fig. 9 receives, prior to the generation of the second control message 620 in step V, the first control message 610 from the client device 100. Furthermore, the network access node 300 transmits the second control message 620 in response to the reception of the first control message 610. However, in embodiments of the invention step V and step VI may instead be independently performed by the network access node 300, without first receiving a first control message 610 indicating that uplink transmissions will partial overlap in time. In such embodiments, the network access node 300 may e.g. determine that the transmission of the first symbol S1 will at least partially overlap in time with the transmission of the second symbol S2 based on previously received uplink signal timing received from the first uplink beam 502 and the second uplink beam 504, and hence computed timing advance values transmitted to the client device 100. The client device 100 herein, may be denoted as a user device, a User Equipment (UE), a mobile station, an internet of things (loT) device, a sensor device, a wireless terminal and/or a mobile terminal, is enabled to communicate wirelessly in a wireless communication system, sometimes also referred to as a cellular radio system. The UEs may further be referred to as mobile telephones, cellular telephones, computer tablets or laptops with wireless capability. The UEs in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another receiver or a server. The UE can be a Station (STA), which is any device that contains an IEEE 802.1 1 - conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM). The UE may also be configured for communication in 3GPP related LTE and LTE-Advanced, in WiMAX and its evolution, and in fifth generation wireless technologies, such as New Radio.

The network access node 300 herein may also be denoted as a radio network access node, an access network access node, an access point, or a base station, e.g. a Radio Base Station (RBS), which in some networks may be referred to as transmitter, "gNB", "eNB", "eNodeB", "NodeB" or "B node", depending on the technology and terminology used. The radio network access nodes may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. The radio network access node can be a Station (STA), which is any device that contains an IEEE 802.1 1 - conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM). The radio network access node may also be a base station corresponding to the fifth generation (5G) wireless systems.

Furthermore, any method according to embodiments of the invention may be implemented in a computer program, having code means, which when run by processing means causes the processing means to execute the steps of the method. The computer program is included in a computer readable medium of a computer program product. The computer readable medium may comprise essentially any memory, such as a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), or a hard disk drive.

Moreover, it is realized by the skilled person that embodiments of the client device 100 and the network access node 300 comprises the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing the present solution. Examples of other such means, units, elements and functions are: processors, memory, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selecting units, switches, interleavers, de-interleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiver units, transmitter units, DSPs, MSDs, TCM encoder, TCM decoder, power supply units, power feeders, communication interfaces, communication protocols, etc. which are suitably arranged together for performing the present solution.

Especially, the processor(s) of the client device 100 and the network access node 300 may comprise, e.g., one or more instances of a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The expression "processor" may thus represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above. The processing circuitry may further perform data processing functions for inputting, outputting, and processing of data comprising data buffering and device control functions, such as call processing control, user interface control, or the like.

Finally, it should be understood that the invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.

Claims

1 . A client device (100) for a wireless communication system (500), the client device (100) being configured to

obtain a first uplink timing advance associated with a first uplink beam (502) to be used for transmission of a first symbol (S1 ) to a network access node (300) of the wireless communication system (500) at a first symbol time instance;

obtain a second uplink timing advance associated with a second uplink beam (504) to be used for transmission of a second symbol (S2) to the network access node (300) at a consecutive second symbol time instance;

determine whether a transmission of the first symbol (S1 ) will at least partially overlap in time with a transmission of the second symbol (S2) based on the first uplink timing advance and the second uplink timing advance;

transmit at least one of the first symbol (S1 ) in the first uplink beam (502) and the second symbol (S2) in the second uplink beam (504) based on an uplink transmission rule if it is determined that the transmission of the first symbol (S1 ) will at least partially overlap in time with the transmission of the second symbol (S2).

2. The client device (100) according to claim 1 , configured to

drop one of the first symbol (S1 ) or the second symbol (S2) based on the uplink transmission rule.

3. The client device (100) according to claim 2, configured to

obtain a first priority associated with the transmission of the first symbol (S1 );

obtain a second priority associated with the transmission of the second symbol (S2); drop one of the first symbol (S1 ) or the second symbol (S2) based on the uplink transmission rule in dependence on the first priority and the second priority.

4. The client device (100) according to claim 2 or 3, wherein the dropped symbol belongs to a set of symbols associated with an uplink control channel or an uplink shared channel; and wherein the client device (100) is configured to at least one of

5. The client device (100) according to any of claims 2 to 4, configured to at least one of drop the second symbol (S2) if the first symbol (S1 ) comprises a hybrid automatic repeat request acknowledgement or a hybrid automatic repeat request negative acknowledgement; and

drop the first symbol (S1 ) if the first symbol (S1 ) is a sounding reference symbol and a previous first symbol transmitted in the first uplink beam (502) is a sounding reference symbol.

6. The client device (100) according to any of the preceding claims, configured to

transmit the first symbol (S1 ) in the first uplink beam (502) using a first sub-carrier spacing;

transmit the second symbol (S2) in the second uplink beam (504) using a second sub- carrier spacing, wherein the first sub-carrier spacing and the second sub-carrier spacing are different sub-carrier spacings given by the uplink transmission rule.

7. The client device (100) according to any of the preceding claims, configured to

generate a first control message (610) if it is determined that the transmission of the first symbol (S1 ) will at least partially overlap in time with the transmission of the second symbol (S2), wherein the first control message (610) indicates that the transmission of the first symbol (S1 ) will at least partially overlap in time with the transmission of the second symbol (S2); transmit the first control message (610) to the network access node (300).

8. The client device (100) according to any of the preceding claims, configured to

receive a second control message (620) from the network access node (300), wherein the second control message (620) indicates the uplink transmission rule.

9. The client device (100) according to any of the preceding claims, wherein the uplink transmission rule is given by a pre-defined rule.

10. The client device (100) according to any of the preceding claims, configured to

receive a third control message (630) from the network access node (300), wherein the third control message (630) indicates a first uplink network timing advance and a second uplink network timing advance;

1 1 . The client device (100) according to any of the preceding claims, configured to

obtain a first downlink timing for a first downlink beam (512) associated with the first uplink beam (502); obtain a second downlink timing for a second downlink beam (514) associated with the second uplink beam (514);

obtain the first uplink timing advance based on the first downlink timing;

obtain the second uplink timing advance based on the second downlink timing.

12. A network access node (300) for a wireless communication system (500), the network access node (300) being configured to

generate a second control message (620) comprising an uplink transmission rule for a client device (100), wherein the uplink transmission rule indicates a rule for uplink transmission of at least one of a first symbol (S1 ) in a first uplink beam (502) at a first symbol time instance and a second symbol (S2) in a second uplink beam (504) at a consecutive second symbol time instance from the client device (100) to the network access node (300) if it is determined that the transmission of the first symbol (S1 ) will at least partially overlap in time with the transmission of the second symbol (S2);

transmit the second control message (620) to the client device (100).

13. The network access node (300) according to claim 12, configured to

receive, prior to the generation of the second control message (620), a first control message (610) from the client device (100), wherein the first control message (610) indicates that the transmission of the first symbol (S1 ) will at least partially overlap in time with the transmission of the second symbol (S2);

transmit the second control message (620) in response to the reception of the first control message (610).

14. The network access node (300) according to claim 12 or 13, configured to

determine a first uplink network timing advance;

determine a second uplink network timing advance;

generate a third control message (630) indicating the first uplink network timing advance and the second uplink network timing advance;

transmit the third control message (630) to the client device (100).

15. A method (200) for a client device (100) in a wireless communication system (500), the method (200) comprising:

obtaining (202) a first uplink timing advance associated with a first uplink beam (502) to be used for transmission of a first symbol (S1 ) to a network access node (300) of the wireless communication system (500) at a first symbol time instance; obtaining (204) a second uplink timing advance associated with a second uplink beam (504) to be used for transmission of a second symbol (S2) to the network access node (300) at a consecutive second symbol time instance;

determining (206) whether a transmission of the first symbol (S1 ) will at least partially overlap in time with a transmission of the second symbol (S2) based on the first uplink timing advance and the second uplink timing advance;

transmitting (208) at least one of the first symbol (S1 ) in the first uplink beam (502) and the second symbol (S2) in the second uplink beam (504) based on an uplink transmission rule if it is determined that the transmission of the first symbol (S1 ) will at least partially overlap in time with the transmission of the second symbol (S2).

16. A method (400) for a network access node (300) in a wireless communication system (500), the method (400) comprising:

generating (402) a second control message (620) comprising an uplink transmission rule for a client device (100), wherein the uplink transmission rule indicates a rule for uplink transmission of at least one of a first symbol (S1 ) in a first uplink beam (502) at a first symbol time instance and a second symbol (S2) in a second uplink beam (504) at a consecutive second symbol time instance from the client device (100) to the network access node (300) if it is determined that the transmission of the first symbol (S1 ) will at least partially overlap in time with the transmission of the second symbol (S2);

transmitting (404) the second control message (620) to the client device (100).

17. A computer program product comprising a computer program with program code for performing a method according to claim 15 or 16.