WO2022066077A1

WO2022066077A1 - Scheduling uplink data in a multi-connectivity network

Info

Publication number: WO2022066077A1
Application number: PCT/SE2020/050904
Authority: WO
Inventors: Ulf HÄNDEL; Vengatanathan KRISHNAMOORTHI
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2020-09-25
Filing date: 2020-09-25
Publication date: 2022-03-31

Abstract

The present disclosure relates to a method of a radio base station (103) of monitoring (S101) a difference in latency between a first communication link established between the radio base station (103) and the wireless communication device (101) and a second communication link comprising a communication link established between another radio base station (102) of another RAT and the wireless communication device (101) and further comprising a communication link established between the radio base station (103) and said another radio base station (102) and if the determined latency exceeds a latency threshold value, scheduling (S102) the uplink data received from the wireless communication device (101 ) via the first communication link for transmission to the recipient (107) with a delay based on the monitored difference in latency, the delay being selected such that a difference in propagation time between data over the first and the second communication link is reduced.

Description

SCHEDULING UPLINK DATA IN A MULTI-CONNECTIVITY NETWORK

TECHNICAL FIELD

[0001] The present disclosure relates to a method of a radio base station of scheduling uplink data in a communications network allowing connectivity of a wireless communication device to multiple radio access technologies, and a radio base station performing the method.

BACKGROUND

[0002] In a wireless communications system utilizing a dual connectivity approach such as for instance Evolved Universal Mobile Telecommunications System Terrestrial Radio Access Network (E-UTRAN) New Radio (NR) Dual Connectivity, commonly referred to as EN-DC, a wireless communication terminal has the possibility to transmit uplink data using a Master Cell Group (MCG) bearer, a Secondary Cell Group (SCG) bearer, or split bearer.

[0003] In other words, the terminal may send uplink data using Long Term Evolution (LTE) Radio Access Technology (RAT), NR or both. However, each of these RATs have different characteristics, primarily in terms of latency and bandwidth.

[0004] When a wireless communication terminal uses both these RATs in EN-DC without carefully considering the different characteristics, the communication performance may be degraded.

SUMMARY

[0005] One objective is to solve, or at least mitigate, this problem and to provide a method for scheduling of uplink data to a recipient in a communications network allowing improved connectivity of a wireless communication device to multiple RATs.

[0006] In a first aspect, a method of a radio base station of scheduling uplink data to a recipient in a communications network allowing connectivity of a wireless communication device to multiple RATs is provided. The method comprises monitoring a difference in latency between a first communication link established between the radio base station and the wireless communication device and a second communication link comprising a communication link established between another radio base station of another RAT and the wireless communication device and further comprising a communication link established between the radio base station and said another radio base station and if the determined latency exceeds a latency threshold value, scheduling the uplink data received from the wireless communication device via the first communication link for transmission to the recipient with a delay based on the monitored difference in latency, the delay being selected such that a difference in propagation time between data transmitted in the uplink from the wireless communication device over the first communication link to the recipient via said radio base station and data transmitted in the uplink from the wireless communication device over the second communication link to the recipient via the radio base station and said another radio base station is reduced.

[0007] In a second aspect, a radio base station configured to schedule uplink data to a recipient in a communications network allowing connectivity of a wireless communication device to multiple RATs is provided. The radio base station comprises a processing unit and a memory, said memory containing instructions executable by said processing unit, whereby the radio base station is operative to monitor a difference in latency between a first communication link established between the radio base station and the wireless communication device and a second communication link comprising a communication link established between another radio base station of another RAT and the wireless communication device and further comprising a communication link established between the radio base station and said another radio base station and if the determined latency exceeds a latency threshold value, to schedule the uplink data received from the wireless communication device via the first communication link for transmission to the recipient with a delay based on the monitored difference in latency, the delay being selected such that a difference in propagation time between data transmitted in the uplink from the wireless communication device over the first communication link to the recipient via said radio base station and data transmitted in the uplink from the wireless communication device over the second communication link to the recipient via the radio base station and said another radio base station is reduced.

[0008] If a difference in latency between a first communication link from a wireless communication device to a first radio base station (RBS) and a second link from the wireless communication device to a second RBS and further on to the first RBS via which the data of the wireless communication device is scheduled and transmitted in the uplink to a recipient, data from the wireless communication device will not be delivered in-order to the recipient. That is, data travelling along the second link experiencing a higher latency than the first link will arrive at the recipient later than the data travelling along the first link.

[0009] Advantageously, by having the first RBS - being subjected to a lower link latency than the second RBS -monitor the difference in latency and subsequently compensate for the difference in latency by delaying the data received directly from the wireless communication device when scheduling the transmission of that data in the uplink to the recipient, the data will be delivered in-order to the recipient (or at least with less delay variation).

[0010] This will further advantageously improve dual-connectivity performance for the end-users and reduce degradations in long-term throughput achieved when using dual connectivity.

[0011] In an embodiment, the scheduling of the uplink data received from the wireless communication device for transmission to the recipient with a delay is performed if the determined latency does not exceed a maximum allowable latency threshold value.

[0012] In an embodiment, the scheduling of the uplink data received from the wireless communication device for transmission to the recipient with a delay is performed if the determined latency exceeds a minimum allowable latency threshold value.

[0013] In an embodiment, the delay is selected to be equal to the monitored difference in latency between the first communication link and second communication link.

[0014] In an embodiment, the delay is selected such that the scheduled uplink data is transmitted in the order the data originally was transmitted by the wireless communication device to the radio base station and said another radio base station.

[0015] In an embodiment, the scheduling of the uplink data received from the wireless communication device for transmission to the recipient with a delay is performed for payload data. [0016] In an embodiment, the scheduling of the uplink data received from the wireless communication device for transmission to the recipient with a delay is performed for acknowledgements.

[0017] In an embodiment, the monitoring of the difference in latency between the first communication link and the second communication link comprises communicating with said another base station to acquire a measure of latency for the second communication link.

[0018] In an embodiment, the monitoring of the difference in latency between the first communication link and the second communication link comprises communicating with a core network node to acquire a measure of the difference in latency.

[0019] In an embodiment, the monitoring of the difference in latency between the first communication link and the second communication link comprises measuring the difference in time for receiving a first data packet in a stream of data packets via the first communication link and a consecutive second data packet in the stream of data packets via the second communication link.

[0020] In an embodiment, the difference in latency between the first communication link and the second communication link is the average difference in latency.

[0021] In a third aspect, a computer program is provided comprising computerexecutable instructions for causing a radio base station to perform steps of the method of the first aspect when the computer-executable instructions are executed on a processing unit included in the radio base station.

[0022] In a fourth aspect, a computer program product is provided comprising a computer readable medium, the computer readable medium having the computer program according to the third aspect embodied thereon.

[0023] 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, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, 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.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Aspects and embodiments are now described, by way of example, with reference to the accompanying drawings, in which:

[0025] Figure 1 illustrates a wireless communications network allowing EN-DC, in which embodiments may be implemented;

[0026] Figure 2 shows a flowchart illustrating a method of a secondary radio base station of scheduling uplink data to a recipient according to an embodiment;

[0027] Figure 3 shows a flowchart illustrating a method of a secondary radio base station of scheduling uplink data to a recipient according to a further embodiment;

[0028] Figure 4 shows a flowchart illustrating a method of a secondary radio base station of scheduling uplink data to a recipient according to still a further embodiment; and

[0029] Figure 5 illustrates a secondary radio base station configured to schedule uplink data to a recipient according to an embodiment.

DETAILED DESCRIPTION

[0030] The aspects of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown.

[0031] These aspects may, however, be embodied in many different forms and should not be construed as limiting; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and to fully convey the scope of all aspects of invention to those skilled in the art. Like numbers refer to like elements throughout the description.

[0032] Figure 1 illustrates a wireless communications network 100 allowing EN- DC where a wireless communication terminal 101 commonly referred to as User Equipment (UE) communicates via both LTE and NR with a party such as a server 107, in which embodiments maybe implemented. [0033] The LTE communication of the UE 101 occurs via a master radio base station 102, a so-called Evolved Node B (eNB), in this case referred to as a Master eNB (MeNB), while NR communication occurs via a secondary radio base station 103 referred to as Secondary gNB (SgNB).

[0034] Control plane signalling between the MeNB 102 and the SgNB 103 is performed over an X2-C interface, while data is communicated over a user plane interface X2-U.

[0035] The MeNB 102 performs control signalling via a core network Mobility Management Entity (MME) 104 over an Si-MME interface, while both the MeNB 102 and the SgNB 103 communicates user data via an Si-U interface with a Serving Gateway (S-GW) 105 and further on to e.g. an external network 106 such as the Internet to which the server 107 is connected.

[0036] As is understood, in an EN-DC network, control plane signalling with the core network is performed via the master radio base station, while the secondary base station only performs data plane signalling with the core network.

[0037] With respect to Figure 1, the roles of the eNB and the gNB may be reversed, i.e. the eNB is the secondary base station while the gNB is the master base station performing control plane signalling with an NR core network (in which case the base stations would be referred to as SeNB and MgNB, respectively), wherein the network is referred to as an NR-E-UTRAN (NE) DC network.

[0038] When transferring data to the server 107 via the S-GW 106 from the UE 101, only one Si-U connection is used. That is, the data to/from the server 107 is either exchanged between the LTE S-GW 105 and the MeNB 102 or between the LTE S-GW 105 and the SgNB 103 (but not both simultaneously).

[0039] For instance, the server 107 may receive user data from the SgNB 103 which either is transmitted by the UE 101 directly to the SgNB 103 over a first communication link formed by an NR communication link or which is transmitted by the UE 101 to the SgNB 103 via MeNB 102 over a second communication link formed by an LTE communication link between the UE 101 and the MeNB 102 and by an X2- U communication link between the MeNB 102 and the SgNB 103. This is, as previously mentioned, referred to as split bearer. [0040] For Packet Data Convergence Protocol (PDCP) data packets being sent in uplink (UL) direction, the difference in latency between the first link (i.e. the NR link) and the second link (i.e. the link comprising the LTE link and the X2-U link) may potentially be great from the moment a scheduling request is sent by the UE 101.

[0041] When downlink (DL) data is being sent to the UE 101 using Transmission Control Protocol (TCP) as the transport protocol, the UE 101 sends UL acknowledgements (ACKs) to the sender of the data, in this case exemplified by the server 107. TCP relies on feedback from the UE 101 to determine sending rate, which is a dynamic process.

[0042] Congestion control is a mechanism to ensure that the sender (i.e. the server 107) does not send too much data to the receiver (i.e. the UE 101), thereby avoiding overloading the network and ultimately inducing losses to other clients by sending too much data. For each connection, TCP maintains a congestion window, limiting the total number of unacknowledged packets that may be in transit end-to- end.

[0043] In general, the congestion control algorithm keeps track of the timing, information that are received in these ACKs, amount of data sent in the previous transmission, the next packet that needs to be acknowledged, etc. Using these variables, the sender computes the number of bytes/packets that can be sent to a receiver in every iteration (thereby forming the congestion window).

[0044] Once the number of unacknowledged packets reaches the congestion window limit, TCP stops transmitting data until an ACK for the first unacknowledged packet is received. Note that an acknowledgement for a packet transmitted much later in the packet stream still could arrive at the sender, while absence of ACK to an earlier packet could be interpreted as packet loss and therefore ACKs for all packets prior to a current packet should arrive within the expected time window to consider all packets up to the current packet to be delivered successfully. Similarly, TCP guarantees in-order delivery at the receiving side, i.e., if a packet has not been received, subsequent packets will not be passed to higher layers, although received, until the missing packets are received.

[0045] When the UE 101 sends ACKs over both the LTE communication link and the NR communication link, there can be a significant difference in arrival time at the server 107 of the transmitted ACKs being transported via at the MeNB 102 and the SgNB 103, respectively.

[0046] For example, in a scenario where the server 107 has been receiving ACKs in average every x ms via the NR communication link, TCP functionality of the server 107 keeps track of a running average of the time until which the next acknowledgement should arrive - e.g. at x + 8 ms - where 8 is an overhead added to allow for network jitter, etc.

[0047] Whenever an ACK from the UE 101 for the next packet takes a longer time than x + 8 (or at least a sufficiently longer time than x + 8), the TCP functionality of the server 107 interprets this larger delay as a packet loss, and thus retransmits this packet. In addition to retransmitting the unacknowledged packet, TCP also scales the congestion window size by a multiplicative decrease factor d, i.e., the maximum number of packets that can be sent now will amount to the previous congestion window size divided by d, which will result in a significant decrease in instantaneous throughput over both the NR and LTE link.

[0048] After reducing the size of the congestion window using the factor d, TCP enters a phase referred to as additive increase, where the congestion window size increases by a constant factor. This effectively means that when TCP detects a loss, the TCP functionality aggressively decreases the size of the congestion window and then slowly increases the window size again to as data packets are acknowledged thereby successively providing for a greater throughput. As is understood, maintaining a large congestion window size is important for providing a high data throughput.

[0049] In line with the above example, assuming that the latency between the UE

101 and the server 107 over the link including the LTE communication link and the X2-U communication link (since the X2-U also may suffer from latency) is y ms and y > x + 8. i.e. the latency of the LTE link and X2-U link is higher than what is acceptable compared to the latency of the NR link, as will be described in more detail in the following.

[0050] The TCP functionality of the server 107 will, based on the absence of prior ACKs, not transmit further data packets to the UE 101 since the congestion window size will not increase for out-of-order ACKs and in a case where the missing ACKs arrive too late, the data packets will be retransmitted and the congestion window size will be decreased. In cases where data packets arriving at the server 107 contain payload data, the server 107 and any higher layers will have to wait until all out-of- order data packets are received before the TCP functionality passes the data packets upstream.

[0051] As a result, the TCP functionality of the server 107 will interpret the delayed arrival of the group of packets as a loss and decrease the congestion window size. As discussed hereinabove, decreasing the congestion window size will greatly reduce data throughput.

[0052] In other words, if the latency of the second link formed by the LTE link and the X2-U link is too high in relation to the latency of the first link formed by the NR link, the server 107 must queue up data packets received via the NR link, thereby waiting for packets transmitted by the UE 101 via the slower second link, since inorder delivery of data packets from the SgNB 103 to the server 107 must be ensured.

[0053] If there is a large number of out-of-order packets queuing for delivery or if no ACK is received for a sufficiently large number of unacknowledged data packets or if any other event triggers the server 107 to assume congestion, congestion is concluded to occur and the congestion window is hence decreased.

[0054] Figure 2 shows a flowchart illustrating a method of the SgNB 103 of scheduling UL data to the server 107 according to an embodiment in order to overcome, or at least mitigate, this problem.

[0055] As described hereinabove, if the latency D_m of the LTE link and the X2-U link becomes too great with respect to the latency D_s of the NR link, the number of unacknowledged packets at the server 107 arriving via the SgNB 103 will eventually exceed a maximum allowable number.

[0056] Again, assuming that the average uplink latency D_s of the NR link from the UE 101 to the server 107 is x ms and that a latency x + 8 ms still is acceptable to provide for some margin.

[0057] As previously discussed, if the difference in latency D_m - D_s between the communication link from the UE 101 to the SgNB 103 via the MeNB 102, i.e. the LTE link and the X2-U link, and the NR link established directly between the UE 101 and the SgNB 103 becomes substantial, such as for instance greater than a latency threshold TL = A (i.e. y > x + 8 + A), then the server 107 must start queuing up data packets arriving via the SgNB 103 and the NR link. In other words, the difference in latency between the second link formed by the LTE link and X2-U link and the first link comprising the NR link may become is higher than what is acceptable.

[0058] Hence, in a first step S101, the SgNB 103 - being the radio base station of the fastest of the two communication links - monitors the difference D_m - D_s in latency between the two links.

[0059] This may be performed in an embodiment by the SgNB 103 communicating with the MeNB 102 over the X2 interface and continuously requesting the MeNB 102 to report the latency D_m of the link constituted by the LTE link and the X2-U link. The SgNB 103 has access to the latency D_s of the NR link (possibly by communicating with the UE 101 to derive the latency D_s).

[0060] Now, assuming that the reported latency of the LTE link and the X2-U link amounts to y = x + 8; if so, the difference in latency is considered sufficiently small (in this case the difference would be zero) and the SgNB 103 will continue transporting uplink data packets without taking further action.

[0061] To the contrary, if the reported latency D_m of the LTE link and the X2-U link is just over x + 8 + A, meaning that the difference in latency D_m - D_s > A, the SgNB 103 will in step S102 introduce a delay - for instance equal to A - for data received from the UE 101 via the NR link which is being scheduled for uplink transmission from the SgNB 103 to the server 107 to compensate for the great difference in latency between the LTE link - X2-U link and the NR link.

[0062] Hence, by introducing the delay, uplink data packets arriving at the SgNB 103 from the UE 101 via the NR link and being scheduled for the server 107 will be delayed with A before being transmitted to the server 107 in step S102.

[0063] As a result, difference in propagation time between data transmitted in the uplink from the UE 101 over the NR link to the server 107 via the SgNB 103 and data transmitted in the uplink from the UE 101 over the LTE link to the server 107 via the MeNB 102 - which is passed over the X2-U interface from the MeNB 102 to the SgNB 103 for further transmission to the server 107 - will be close to zero.

[0064] Advantageously, since the propagation time between the UE 101 and the server 107 becomes the same regardless of via which of the MeNB 102 and the SgNB 103 uplink data is transported, in-order delivery of the uplink data packets being transported to the server 107 from the UE 101 via the MeNB 102 and the SgNB 103 is enabled.

[0065] In other words, in an example embodiment, a data packet Pi in a stream of packets sent at time t_n from the UE 101 via the LTE link and the MeNB 102 will arrive at the SgNB 103 at t_n + x + 8 + A, while a subsequent second data packet P2 in the stream sent at a next available time t_n+i from the UE 101 directly to the SgNB 103 over the NR link will arrive at the SgNB 103 at t_n+i + x + 8. Hence, given that the difference in latency A exceeds (t_n+i - t_n), the second packet P2 will arrive at the SgNB 103 before the first packet Pi.

[0066] Thus, when scheduling transmission of the second packet P2 to the server 107, a delay A will be applied to the second packet P2 having the effect that upon receiving the first data packet Pi from the MeNB 102 over the X2-U link, the PDCP entity of the SgNB 103 will schedule transmission of the first data packet Pi and the second data packet P2 in the originally intended order, albeit with a delay amounting to x + 8 + A.

[0067] While an increase in round-trip time (RTT) suggests a lower throughput, a larger congestion window size can advantageously compensate for a larger RTT; by maintaining the RTT at more or less a fixed value and avoiding packet losses, the congestion window can remain larger for a considerably larger time, thereby achieving a larger throughput.

[0068] As should be understood, while the described embodiment assumes that the LTE link has the higher latency and the NR link has the lower latency, the opposite may well prevail, in which case the delay instead would be applied to uplink data transmitted by the MeNB 102 for any user data received over the X2-U interface from the SgNB 103. It may even be envisaged that at a given occasion, latency of the NR link is compensated for by applying a delay accordingly at the MeNB 102 while at another given occasion latency of the LTE link is compensated for by applying a delay accordingly at the SgNB 103, or vice versa. Thus, it is envisaged that both the master radio base station and the secondary base station occasionally may have to compensate for latencies occurring in the link served by the other base station. [0069] Further, even though embodiments are described herein with reference to an EN-DC network, the embodiments maybe implemented in any dual-connectivity network, such as NE-DC, Next-Generation (NG) EN-DC, etc., or even LTE-WiFi DC.

[0070] It may also be envisaged that embodiments are implemented in future DCs such as 5^th Generation (5G) and 6^th Generation (6G) RATs, e.g. 5G-6G DC, LTE-6G DC, or even LTE-5G-6G Triple Connectivity.

[0071] With reference to the flowchart of Figure 3, in another embodiment, if after the SgNB 103 monitoring the difference D_m - D_s in latency between the second link including the LTE link and the X2-U link and the first link including the NR link in step S101 determines that the difference D_m - D_s in latency is too great and exceeds a maximum latency threshold TLMAX being set to a higher value than TL, no delay will be introduced by the SgNB 103 scheduling the uplink data received from the UE 101 over the NR link, since the RTT in such case would become too great for data transported over the NR link, even in a situation where D_m - D_s > TL. In other words, if Dm - D_s exceeds TL while at the same time not exceeding TLMAX, the SgNB 103 will in step S102 introduce a delay A for data received over the NR link from the UE 101 being scheduled for transmission from the SgNB 103 towards the server 107.

[0072] With reference to the flowchart of Figure 4, in another embodiment, if after the SgNB 103 monitoring the difference D_m - D_s in latency between the NR link and the link including the LTE link and the X2-U link in step S101 determines that the difference D_m - D_s in latency is small and is equal to or less than a minimum latency threshold TLMIN being set to a lower value than TL, no delay will be introduced by the SgNB 103 scheduling the uplink data received from the UE 101 over the NR link, since difference in latency is too small to motivate introduction of any delay. Again, this holds even in a situation where D_m - D_s > TL. In other words, if D_m - D_s exceeds TL while at the same time exceeding TLMIN, the SgNB 103 will in step S102 introduce a delay A for data being scheduled for transmission from the SgNB 103 towards the server 107. In Figure 4, both TLMIN and TLM X are considered, but it may be envisaged that only TLMIN is considered without considering TLMAX.

[0073] In an embodiment, when monitoring the difference in latency, average latency values - Dmn and D_S|-t - are used for the respective link rather than using instantaneous values. [0074] In practice, the latencies experienced on the respective radio base station will vary with a certain mean (p) and a standard deviation (8). The latency difference may thus be computed as Dmn - Ds^.

[0075] A large jitter in latencies indicates potential congestion and it should be expected that the TCP congestion control loop will react to these large variations automatically. By using the average values, the variations in delay jitter in the MeNB branch should be allowed to naturally affect TCP and compensation for extreme variations in latency is not necessarily preferred.

[0076] In an embodiment, the delay is applied to packets containing payload data received from the UE 101 over the NR link and scheduled for uplink transmission, while in another embodiment the delay is applied to packets containing only acknowledgements received from the UE 101 over the NR link and scheduled for uplink transmission. Either way, the TCP ACKs sent in the uplink and received by the server 107 will appear to have been transported via two links having a same, or at least similar, latency regardless of whether or not the ACKs are indirectly transported via the MeNB 102 and the X2-U link 102 or directly via the SgNB 103.

[0077] By ensuring that the ACKs sent over the respective links appear to have similar delay characteristics, several advantages can be achieved, for instance that the variation in the RTTs for ACKs transport over the respective link is reduced or even minimized. As a result, TCP retransmissions and congestion window reduction events can be avoided. Fewer congestion window reductions events directly correlate to a higher/ steadier throughput, and fewer TCP retransmissions implies that a smaller share of the capacity of the network is used to carry retransmission data.

[0078] Another related improvement achieved by pacing the TCP ACKs is that the maximum delay between two consecutive TCP ACKs can be reduced thus reducing the maximum RTT and thus increasing the lowest TCP transmission rate.

[0079] In a numerical example, it is assumed that the latency D_m of the link including the LTE link and the X2-U link between the UE 101 and the SgNB 103 via the MeNB 102 is distributed within a range 1-101 ms while the latency D_s of the NR link between the UE 101 and the SgNB 103 is distributed within a range 1-11 ms.

[0080] Assuming that the latency in practice effectively is centred around the respective average value, Dnm = 51 ms and D_SLl = 6 ms; the difference in (average) latency will thus amount to 51 - 6 = 45 ms for data received at the server 107 (if no compensation is performed at the SgNB 103).

[0081] If in this example a delay of A = 35 ms is introduced by the SgNB 103 for the uplink data received directly from the UE 101 and scheduled for transmission to the server 107, the distribution in experienced latency of the NR link via the SgNB 103 - from the perspective of the server 107 - will be from (1+35) to (11+35), i-e. in the range 36-46 ms, and the average latency experienced by the server 107 for the NR link will be centred at 41 ms.

[0082] This means that the server 107 will only observe a minimum average disparity of 10 ms between data sent directly from the UE 101 over the SgNB 103 as compared to data sent from the UE 101 over the MeNB 102 and further via the SgNB 103. Note that these are average values (i.e. at 50 percentile), and the disparity will be much smaller at higher percentiles.

[0083] In an embodiment, the SgNB 103 monitors the difference D_m - D_s in latency by acquiring the information from a core network node such as the S-GW 105, which may estimate the difference in latency between the first communication link formed by the NR link and the second communication link formed by the LTE link and the X2-U link by measuring the difference in time for receiving two or more consecutive data packets in a stream of packets. If there is no difference in latency, the S-GW 105 should receive two consecutive packets at a given interval tp. Any additional delay of consecutive packets would imply a difference in latency between the first and the second link.

[0084] In another embodiment, the SgNB 103 monitors the difference D_m - D_s in latency by itself estimating the difference in latency between the first communication link formed by the NR link and the second communication link formed by the LTE link and the X2-U link by measuring the difference in time for receiving two or more consecutive data packets in a stream of packets. If there is no difference in latency, the SgNB 103 should receive a packet in a stream of packets via the MeNB 102 and a subsequent packet directly from the UE 101 at a given interval tp. Any additional delay of consecutive packets would imply a difference in latency between the first and the second link. [0085] Figure 5 illustrates a radio base station, in this case the SgNB 103 but may alternatively be embodied by the MeNB 102, configured to schedule uplink data to a recipient such as the server 107 in a communications network 100 allowing connectivity of a UE 101 to multiple RATs; in this description exemplified by LTE and NR.

[0086] The steps of the method performed by the SgNB 103 are in practice performed by a processing unit 121 embodied in the form of one or more microprocessors arranged to execute a computer program 122 downloaded to a suitable storage volatile medium 123 associated with the microprocessor, such as a Random Access Memory (RAM), or a non-volatile storage medium such as a Flash memory or a hard disk drive.

[0087] The processing unit 121 is arranged to cause the SgNB 103 to carry out the method according to embodiments when the appropriate computer program 122 comprising computer-executable instructions is downloaded to the storage medium 123 and executed by the processing unit 121. The storage medium 123 may also be a computer program product comprising the computer program 122. Alternatively, the computer program 122 maybe transferred to the storage medium 123 by means of a suitable computer program product, such as a Digital Versatile Disc (DVD) or a memory stick. As a further alternative, the computer program 122 maybe downloaded to the storage medium 123 over a network. The processing unit 121 may alternatively be embodied in the form of a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a complex programmable logic device (CPLD), etc

[0088] The aspects of the present disclosure have mainly been described above with reference to a few embodiments and examples thereof. 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 invention, as defined by the appended patent claims.

[0089] Thus, while various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims

1. A method of a radio base station (103) of scheduling uplink data to a recipient (107) in a communications network (100) allowing connectivity of a wireless communication device (101) to multiple radio access technologies, RATs, comprising: monitoring (S101) a difference in latency between a first communication link established between the radio base station (103) and the wireless communication device (101) and a second communication link comprising a communication link established between another radio base station (102) of another RAT and the wireless communication device (101) and further comprising a communication link established between the radio base station (103) and said another radio base station (102); and if the determined latency exceeds a latency threshold value: scheduling (S102) the uplink data received from the wireless communication device (101) via the first communication link for transmission to the recipient (107) with a delay based on the monitored difference in latency, the delay being selected such that a difference in propagation time between data transmitted in the uplink from the wireless communication device (101) over the first communication link to the recipient (107) via said radio base station (103) and data transmitted in the uplink from the wireless communication device (101) over the second communication link to the recipient via the radio base station (103) and said another radio base station (102) is reduced.

2. The method of claim 1, the scheduling (S102) of the uplink data received from the wireless communication device (101) for transmission to the recipient (107) with a delay being performed if the determined latency does not exceed a maximum allowable latency threshold value.

3. The method of claims 1 or 2, the scheduling (S102) of the uplink data received from the wireless communication device (101) for transmission to the recipient (107) with a delay being performed if the determined latency exceeds a minimum allowable latency threshold value.

4. The method of any one of the preceding claims, the delay being selected to be equal to the monitored difference in latency between the first communication link and second communication link.

5. The method of any one of the preceding claims, the delay being selected such that the scheduled uplink data is transmitted in the order the data originally was transmitted by the wireless communication device (101) to the radio base station (103) and said another radio base station (102).

6. The method of any one of the preceding claims, the scheduling of the uplink data received from the wireless communication device (101) for transmission to the recipient (107) with a delay being performed for payload data.

7. The method of any one of the preceding claims, the scheduling of the uplink data received from the wireless communication device (101) for transmission to the recipient (107) with a delay being performed for acknowledgements.

8. The method of any one of the preceding claims, the monitoring (S101) of the difference in latency between the first communication link and the second communication link comprising communicating with said another base station (102) to acquire a measure of latency for the second communication link.

9. The method of any one of the preceding claims, the monitoring (S101) of the difference in latency between the first communication link and the second communication link comprising communicating with a core network node to acquire a measure of said difference in latency.

10. The method of any one of the preceding claims, the monitoring (S101) of the difference in latency between the first communication link and the second communication link comprising measuring the difference in time for receiving a first data packet in a stream of data packets via the first communication link and a consecutive second data packet in the stream of data packets via the second communication link.

11. The method of any one of the preceding claims, the difference in latency between the first communication link and the second communication link being the average difference in latency.

12. The method of any one of the preceding claims, said base station (103) being a base station enabling connection to a New Radio, NR, RAT, while said another base station enabling connection to a Long Term Evolution, LTE, RAT, or vice versa.

13. A computer program (122) comprising computer-executable instructions for causing a radio base station (103) to perform steps recited in any one of claims 1-12 18 when the computer-executable instructions are executed on a processing unit (121) included in the radio base station (103).

14. A computer program product comprising a computer readable medium (123), the computer readable medium having the computer program (122) according to claim 13 embodied thereon.

15. A radio base station (103) configured to schedule uplink data to a recipient (107) in a communications network (100) allowing connectivity of a wireless communication device (101) to multiple radio access technologies, RATs, the radio base station (103) comprising a processing unit (121) and a memory (123), said memory containing instructions (122) executable by said processing unit (121), whereby the radio base station (103) is operative to: monitor a difference in latency between a first communication link established between the radio base station (103) and the wireless communication device (101) and a second communication link comprising a communication link established between another radio base station (102) of another RAT and the wireless communication device (101) and further comprising a communication link established between the radio base station (103) and said another radio base station (102); and if the determined latency exceeds a latency threshold value: schedule the uplink data received from the wireless communication device (101) via the first communication link for transmission to the recipient (107) with a delay based on the monitored difference in latency, the delay being selected such that a difference in propagation time between data transmitted in the uplink from the wireless communication device (101) over the first communication link to the recipient (107) via said radio base station (103) and data transmitted in the uplink from the wireless communication device (101) over the second communication link to the recipient via the radio base station (103) and said another radio base station (102) is reduced.

16. The radio base station (103) of claim 15, further being operative to schedule the uplink data received from the wireless communication device (101) for transmission to the recipient (107) with a delay if the determined latency does not exceed a maximum allowable latency threshold value. 19

17. The radio base station (103) of claims 15 or 16, further being operative to schedule the uplink data received from the wireless communication device (101) for transmission to the recipient (107) with a delay if the determined latency exceeds a minimum allowable latency threshold value.

18. The radio base station (103) of any one of claims 15-17, further being operative select the delay to be equal to the monitored difference in latency between the first communication link and second communication link.

19. The radio base station (103) of any one of claims 15-18, further being operative to select the delay such that the scheduled uplink data is transmitted in the order the data originally was transmitted by the wireless communication device (101) to the radio base station (103) and said another radio base station (102).

20. The radio base station (103) of any one of claims 15-19, further being operative to perform the scheduling of the uplink data received from the wireless communication device (101) for transmission to the recipient (107) with a delay for payload data.

21. The radio base station (103) of any one of claims 15-20, further being operative to perform the scheduling of the uplink data received from the wireless communication device (101) for transmission to the recipient (107) with a delay for acknowledgements.

22. The radio base station (103) of any one of claims 15-21, further being operative to, when monitoring the difference in latency between the first communication link and the second communication link, communicate with said another base station (102) to acquire a measure of latency for the second communication link.

23. The radio base station (103) of any one of claims 15-22, further being operative to, when monitoring the difference in latency between the first communication link and the second communication link, communicating with a core network node to acquire a measure of said difference in latency.

24. The radio base station (103) of any one of claims 15-23, further being operative to, when monitoring the difference in latency between the first communication link and the second communication link, measuring the difference in time for receiving a first data packet in a stream of data packets via the first communication link and a 20 consecutive second data packet in the stream of data packets via the second communication link.

25 The radio base station (103) of any one of claims 15-24, the difference in latency between the first communication link and the second communication link being the average difference in latency.

26. The radio base station (103) of any one of claims 15-25, said base station (103) being a base station enabling connection to a New Radio, NR, RAT, while said another base station enabling connection to a Long Term Evolution, LTE, RAT, or vice versa.