WO2015131920A1

WO2015131920A1 - Scheduling in wireless backhaul networks

Info

Publication number: WO2015131920A1
Application number: PCT/EP2014/054064
Authority: WO
Inventors: Martin HESSLER; Stefan Parkvall; Ke Wang Helmersson
Original assignee: Telefonaktiebolaget L M Ericsson (Publ)
Priority date: 2014-03-03
Filing date: 2014-03-03
Publication date: 2015-09-11

Abstract

There is provided scheduling in a wireless backhaul network providing backhaul to an end-user access network. The wireless backhaul network comprises a hub node and a client node providing backhaul to at least one radio base station in the end-user access network. Scheduling information of the at least one radio base station is acquired. Based on the scheduling information a scheduling of a first wireless link of two consecutive wireless links, one of which being a wireless link between the hub node and the client node, is determined, wherein the scheduling is based on scheduling information of a second wireless link of the two consecutive wireless links. The scheduling is provided to at least one of the hub node and the client node.

Description

SCHEDULING IN WIRELESS BACKHAUL NETWORKS

TECHNICAL FIELD

Embodiments presented herein relate to scheduling in wireless backhaul networks, and particularly to a method, a network node, a computer program, and a computer program product for scheduling in a wireless backhaul network providing backhaul to an end-user access network.

BACKGROUND

In communications networks, it may be challenging to obtain good performance and capacity for a given communications protocol, its parameters and the physical environment in which the communications network is deployed.

For example, increase in traffic within communications networks such as mobile broadband systems and an equally continuous increase in terms of the data rates requested by end-users accessing services provided by the communications networks may impact how cellular communications networks are deployed. One way of addressing this increase is to deploy lower-power network nodes, such as micro network nodes or pico network nodes, within the coverage area of a macro cell served by a macro network node. Examples where such additional network nodes may be deployed are scenarios where end-users are highly clustered. Examples where end-users may be highly clustered include, but are not limited to, around a square, in a shopping mall, or along a road in a rural area. Such a deployment of additional network nodes is referred to as a heterogeneous or multi-layered network deployment, where the underlying layer of low-power micro or pico network nodes does not need to provide full-area coverage. Rather, low- power network nodes may be deployed to increase capacity and achievable data rates where needed. Outside of the micro- or pico-layer coverage, end- users would access the communications network by means of the overlaid macro cell. Backhauling based on the Long Term Evolution (LTE) telecommunications standards may be carried either over normal IMT-bands, e.g. the 2.6 GHz frequency band, or by running LTE baseband communications on higher radio frequencies, such as in the 28 GHz frequency band. LTE based backhauling implies that the pico network nodes are connected to a client node which is used to create a wireless link to a hub node.

In any of the above two cases, the wireless links are typically managed by LTE core control mechanisms. For example, the LTE Mobility Management Entity (MME) may be utilized for session control of the LTE links, and the Home Subscription Service (HSS) may be utilized for storing security and Quality of Service (QoS) characteristics of the wireless links individual wireless end- user terminals embedded in the pico network node.

Moreover, in practice more than one client node may connect to a common hub node. This implies support for Radio Resource Management (RRM) functions, such as scheduling and prioritization of the traffic to and from the different clients, at the hub node.

To each client node there might be several pico network nodes, each of which may offer one or several different radio access technologies, such as based on the Universal Mobile Telecommunications System (UMTS), LTE, or IEEE 802. lix to the wireless end-user terminals of the end-users. Therefore there is a need to differentiate between the corresponding backhaul traffic to different nodes in the communications network. For example, any LTE compliant traffic may need to end up in nodes such as the serving gateway (SGW) or the MME and any WiFi compliant traffic may end up in an edge router or an Evolved Packet Data Gateway (ePDG).

Moreover, for a given radio access technology (RAT), QoS differentiation is provided to the end-users (i.e., to the wireless end-user terminals of the end- users) so that e.g. guaranteed bitrate (GBR) services, such as voice calls, will not be disturbed by best effort (BE) services, such as web browsing. In order to enable this, QoS differentiation is needed also on the backhaul links. If the wireless backhaul is based on LTE, there are tools that provide both the routing functions and QoS differentiation, such as based on the LTE bearer concept. Typically then, for each type of RAT, one GBR and one BE bearer are established on the backhaul links. Different frameworks may be used to prioritize between different traffic, for example to determine if io Mbit/s Voice over Internet protocol (VoIP) data to/from one wireless end-user terminal is more or less prioritized than 100 Mbit/s web-surfing data to/from another wireless end-user terminal.

Micro network nodes or pico network nodes are often deployed to meet high traffic demands as requested by wireless end-user terminals. However, the traffic load of the micro or pico network nodes may vary over time. Since the traffic load pattern thus might change, the need for a certain backhaul capacity may change over time. In general terms, the traffic from a micro or pico network node to a backhaul providing network node is in LTE mapped to a limited number of Evolved Packet Core (EPC) bearers, potentially only one or two.

Currently each micro or pico network node (including WiFi access nodes, etc.) operates in a non-coordinated fashion with respect to the wireless links between these nodes and the backhaul providing network nodes. This implies among other things that the micro or pico network node in the wireless backhaul network could be forced to buffer excessive amounts of data both in downlink (DL) and uplink (UL). One illustrative example is a too high bitrate fixed rate video streaming in the downlink (e.g. 10 Mbit/s) when the backhaul downlink has higher bitrate (e.g. 20 Mbit/s) than the downlink bitrate (e.g. 4 Mbit/s) of the end-user wireless terminal. In this illustrative example, using the disclosed numbers, the network may be forced to buffer 6 Mbit/s.

Further, the Transmission Control Protocol (TCP) or application layer rate- control mechanism may limit the amount of data that is sent from the server hosting the video streaming content without a reply from the wireless end- user terminal. In general terms, the micro or pico network node could have very critical data to transmit that would potentially be blocked if the wireless backhaul used for this data is over-loaded. This may be the case because the traffic to/from the micro or pico network node is unknown from the perspective of the hub node and/or client node in the wireless backhaul network. It has been proposed to use deep packet inspection (DPI) in the core network to check the content of the data packets that the backhaul network serves towards the end-users. In LTE this is not always possible to implement at the micro or pico network node as the data may be encrypted. Hence the hub node and/or client node typically knows the amount of data and QoS of the bearer but do not have any information relating to the end-user traffic on the bearer. Hence, even if only one QoS class for the wireless end-user terminals is mapped to the wireless backhaul bearer it does not know how this maps to end-users. For example, loo MB to 10 wireless end-user terminals typically has higher priority than 100 MB to 1 wireless end-user terminal of the same QoS class.

Hence, there is a need for an improved scheduling in wireless backhaul networks.

SUMMARY

An object of embodiments herein is to provide improved scheduling in wireless backhaul networks.

According to a first aspect there is presented a method for scheduling in a wireless backhaul network providing backhaul to an end-user access network. The wireless backhaul network comprises a hub node and a client node providing backhaul to at least one radio base station in the end-user access network. The method is performed by a network node. The method

comprises acquiring scheduling information of the at least one radio base station. The method comprises determining, based on the scheduling information, a scheduling of a first wireless link of two consecutive wireless links, one of which being a wireless link between the hub node and the client node, and wherein the scheduling is based on scheduling information of a second wireless link of the two consecutive wireless links. The method comprises providing the scheduling to at least one of the hub node and the client node.

Advantageously this provides efficient scheduling in wireless backhaul networks. Advantageously, the disclosed scheduling enables efficient utilization of limited radio link capacity both on the backhaul links and on the end-user access links through a decision on the usage of backhaul and end-users access wireless links.

Advantageously, the disclosed scheduling enables severe congestion problems due to over assignment of resources that can arise if only the backhaul QoS is considered to be avoided.

Advantageously, the disclosed scheduling enables efficient QoS

differentiation between end-users through better granularity in the

prioritization of data on the backhaul links. Advantageously, the disclosed scheduling enables lower memory

requirements in the physical network node hosting the client node due to that over dimensioned buffers can be removed.

According to a second aspect there is presented a network node for

scheduling in a wireless backhaul network arranged to provide backhaul to an end-user access network. The wireless backhaul network comprises a hub node and a client node arranged to provide backhaul to at least one radio base station in the end-user access network. The network node comprises a processing unit and a non-transitory computer readable storage medium. The non-transitory computer readable storage medium comprises instructions executable by the processing unit. The network node is operative to acquire scheduling information of said at least one radio base station. The network node is operative to determine, based on the scheduling information, a scheduling of a first wireless link of two consecutive wireless links, one of which being a wireless link between the hub node and the client node, and wherein the scheduling is based on scheduling information of a second wireless link of the two consecutive wireless links. The network node is operative to provide the scheduling to at least one of the hub node and the client node. According to a third aspect there is presented a computer program for scheduling in a wireless backhaul network, the computer program

comprising computer program code which, when run on a network node, causes the network node to perform a method according to the first aspect.

According to a fourth aspect there is presented a computer program product comprising a computer program according to the third aspect and a computer readable means on which the computer program is stored.

It is to be noted that any feature of the first, second, third and fourth aspects may be applied to any other aspect, wherever appropriate. Likewise, any advantage of the first aspect may equally apply to the second, third, and/or fourth aspect, respectively, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings.

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

The inventive concept is now described, by way of example, with reference to the accompanying drawings, in which: Figs la and lb are schematic diagrams illustrating a communications network according to embodiments;

Fig 2a is a schematic diagram showing functional units of a network node according to an embodiment; Fig 2b is a schematic diagram showing functional modules of a network node according to an embodiment;

Fig 3 shows one example of a computer program product comprising computer readable means according to an embodiment;

Figs 4 and 5 are flowcharts of methods according to embodiments; and Figs 6 and 7 schematically illustrate data and control signalling between nodes according to embodiments.

DETAILED DESCRIPTION

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

Fig la is a schematic diagram illustrating a communications network 10a where embodiments presented herein can be applied. The communications network 10a comprises macro radio base stations (MBS) 12a, 12b providing wireless backhaul to pico radio base stations (PBS) 13a, 13b, 13c, 13d. The macro radio base stations i2a-b are operatively connected to a core network 14 which in turn is operatively connected to a service providing Internet Protocol based network 15. A wireless end-user terminal (WT) 11a, 11b served by a pico radio base station i3a-d is thereby able to access services and data provided by the IP network 15. The wireless end-user terminals 11a, lib have a wireless connection to the pico radio base stations i3a-d. The pico radio base stations i3a-d and their respective links towards served wireless end- user terminals 11a, 11b define an end-user access network 10c (see, Fig lb). The pico radio base stations i3a-d may provide one or a combination of several radio access technologies over its radio access links, e.g. 3GPP LTE, 3GPP HSPA (high speed packet access), 3GPP GSM (global system for mobile communications) or IEEE 802. nx (WiFi). Additionally, the pico radio base stations i3a-d may have one or more wired interfaces towards the wireless end-user terminals 11a, 11b. Each pico radio base station i3a-d needs to backhaul the end-user access network traffic and uses a wireless link towards a macro radio base station i2a-b for this purpose.

The pico radio base stations i3a-d may be backhauled by means of "client nodes" (CN) and "hub nodes" (HN). In general terms, the client node and the hub node are logical entities. The client node establishes a backhaul connection to the core network via the hub node. In case of a wireless backhaul, the term "client node" thus denotes the unit (or subunit within a micro or pico radio base station) that connects the micro or pico radio base station i3a-d to the hub node. The hub node denotes the other end (with respect to the client node) of the wireless backhaul link where the wireless backhaul continues over a wired or wireless connection to the core network.

Fig lb is a schematic diagram illustrating a communications network where embodiments presented herein can be applied. The communications network of Fig lb comprises a macro radio base station (MBS) 12a and a pico radio base station (PBS) 13a. Fig lb further schematically illustrates a wireless backhaul network 10b and an end-user access network 10c. In the end-user access network 10c a wireless end-user terminal (WT) 11a is served by the pico radio base station 13a over a wireless link 19. In the wireless backhaul network 10b the macro radio base station 12a provides wireless backhaul over a wireless link 18 to the pico radio base station 13a. As illustrated in Fig lb, a hub node 16a may be co-located with a macro radio base station 12a and a client node 17a may be co-located with a pico radio base station 13a. Hence, the hub node 16a may be implemented in a macro radio base station, and the client node 17a may be implemented in a micro radio base station or a pico radio base station 13a. However, the pico radio base station i3a-d and client node 17a do not have to be co-located. The same applies for the hub node 16a and the macro radio base station i2a-b.

The herein disclosed embodiments are based on considering information about both the end-user access network 10c and the wireless backhaul network 10b when performing scheduling in the hub nodes 16a, the client nodes 17a, and/or the radio base stations i3a-d. The embodiments disclosed herein thus relate to scheduling in a wireless backhaul network 10b. In order to obtain such scheduling there is provided a network node, a method performed by the network node, and a computer program comprising code, for example in the form of a computer program product, that when run on the network node, causes the network node to perform the method.

Fig 2a schematically illustrates, in terms of a number of functional units, the components of a network node 20 according to an embodiment. A processing unit 21 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), application specific integrated circuit (ASIC), field programmable gate arrays (FPGA) etc., capable of executing software instructions stored in a computer program product 31 (as in Fig 3), e.g. in the form of a storage medium 23. Thus the processing unit 21 is thereby arranged to execute methods as herein disclosed. The storage medium 23 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory. The network node 20 may further comprise a communications interface 22 for communications with any of at least one hub node 16a and at least one client node 17a. As such the communications interface 22 may comprise one or more transmitters and receivers, comprising analogue and digital components and a suitable number of antennas for radio communications and/or interfaces for wired communications. The processing unit 21 controls the general operation of the network node 20 e.g. by sending data and control signals to the

communications interface 22 and the storage medium 23, by receiving data and reports from the communications interface 22, and by retrieving data and instructions from the storage medium 23. Other components, as well as the related functionality, of the network node 20 are omitted in order not to obscure the concepts presented herein.

Fig 2b schematically illustrates, in terms of a number of functional modules, the components of a network node 20 according to an embodiment. The network node 20 of Fig 2b comprises a number of functional modules; an acquire module 21a, a determine module 21b, and a provide module 21c. The network node 20 of Fig 2b may further comprises a number of optional functional units, such as a weigh module 2id. The functionality of each functional module 2ia-d will be further disclosed below in the context of which the functional units may be used. In general terms, each functional module 2ia-d may be implemented in hardware or in software. The processing unit 21 may thus be arranged to from the storage medium 23 fetch instructions as provided by a functional module 2ia-d and to execute these instructions, thereby performing any steps as will be disclosed hereinafter. The network node 20 may be provided as a standalone device or as a part of a further device. For example, the network node 20 may be provided as part of a radio base station, such as an evolved Node B. The network node 20 may be co-located with a radio resource management (RRM) functionality. The network node 20 may be provided as an integral part of the radio base station. That is, the components of the network node 20 may be integrated with other components of the radio base station some components of the radio base station and the network node 20 may be shared. For example, if the radio base station as such comprises a processing unit, this processing unit may be arranged to perform the actions of the processing unit 21 of the network node 20. Alternatively the network node 20 may be provided as a separate unit in the radio base station. Figs 4 and 5 are flow chart illustrating embodiments of methods for scheduling in a wireless backhaul network 10b. The methods are performed by the network node 20. The methods are advantageously provided as computer programs 32. Fig 3 shows one example of a computer program product 31 comprising computer readable means 33. On this computer readable means 33, a computer program 32 can be stored, which computer program 32 can cause the processing unit 21 and thereto operatively coupled entities and devices, such as the communications interface 22 and the storage medium 23 to execute methods according to embodiments described herein. The computer program 32 and/or computer program product 31 may thus provide means for performing any steps as herein disclosed.

In the example of Fig 3, the computer program product 31 is illustrated as an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-Ray disc. The computer program product 31 could also be embodied as a memory, such as a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM) and more particularly as a non-volatile storage medium of a device in an external memory such as a USB (Universal Serial Bus) memory. Thus, while the computer program 32 is here schematically shown as a track on the depicted optical disk, the computer program 32 can be stored in any way which is suitable for the computer program product 31.

Reference is now made to Fig 4 illustrating a method for scheduling in a wireless backhaul network 10b according to an embodiment. The wireless backhaul network 10b provides backhaul to an end-user access network 10c. The wireless backhaul 10b network comprises a hub node 16a and a client node 17a providing backhaul to at least one radio base station 13a, 13b, 13c, 13d in the end-user access network 10c. The method may be performed by a network node 20. The scheduling in the wireless backhaul network 10b is based on scheduling information of at least one radio base station i3a-d. Hence, the processing unit 21 of the network node 20 is arranged to, in a step S102, acquire scheduling information of the at least one radio base station i3a-d.

The thus acquired scheduling information of the at least one radio base station i3a-d is then used to determine scheduling in the wireless backhaul network 10b. Particularly, the processing unit 21 of the network node 20 is arranged to, in a step S104, determine a scheduling of a first wireless link of two consecutive wireless links 18, 19 based on the scheduling information. One of the two consecutive wireless links 18, 19 is a wireless link between the hub node 16a and the client node 17a. The scheduling is based on scheduling information of a second wireless link of the two consecutive wireless links.

The thus determined scheduling is then communicated to at least one node of the the wireless backhaul network 10b. The processing unit 21 of the network node 20 is thus arranged to, in a step S106, provide the scheduling to at least one of the hub node 16a and the client node 17a. This enables the wireless backhaul network 10b to be able to differentiate between different end-user requirements and capabilities; this can be implemented, by forwarding information from a scheduler in the radio base station i3a-d to at least one of the hub node 16a and the client node 17a in the wireless backhaul network 10b and/or the network node 20. Using the provided information the wireless backhaul network 10b may assign resources taking into account the situation in the radio base stations i3a-d using, for example, prioritization of wireless end-user terminals na-b, their channel conditions and buffer status.

There may still be two separate schedulers for the two consecutive wireless links 18, 19. But the scheduling decision per one wireless link is based on scheduling information from the other wireless link.

The functionality of the network node 20 may be co-located with the functionality of the client node 17a. The scheduling may then in step S106 be provided to the hub node 16a and the at least one radio base station i3a-d. Alternatively the functionality of the network node 20 may be co-located with the functionality of the hub node 16a. The scheduling may then in step S106 be provided to the client node 17a.

The other of the two consecutive wireless links may be a wireless link between one of the at least one radio base station 13a and an wireless end- user terminal 11a, 11b served by the one of the at least one radio base station 13a. The two consecutive wireless links may either both be uplinks or both be downlinks.

Embodiments relating to further details of scheduling in a wireless backhaul network will now be disclosed.

There may be different ways to schedule the first wireless link. Different embodiments relating thereto will now be described in turn.

For example, the first wireless link may be scheduled based on a limitation of the second wireless link. For example, the scheduling information may comprise an estimated channel capacity of the second wireless link. The limitation may be based on the estimated channel capacity. For example, the limitation may be related available radio resource of the second wireless link, and/or a Quality of Service (QoS) fulfilment of end-user data to be

transmitted on the second wireless link. There may be different types of information provided in the scheduling as provided to at least one of the hub node 16a and the client node 17a in step S106. Different examples relating thereto will now be described in turn. For example, the scheduling may comprise a policy request for the at least one radio base station i3a-d. For example, the scheduling may relate to use of radio resources in the end-user access network 10. For example, the scheduling may relate to resources of a physical uplink shared channel, PUSCH, of said at least one radio base station. For example, the scheduling may involve assigning and multiplexing end-user data to a physical downlink shared channel (PDSCH). The scheduling may comprise, or involve, at least two of the above disclosed examples. Reference is now made to Fig 5 illustrating methods for scheduling in a wireless backhaul network according to further embodiments. According to an embodiment the scheduling information is received from at least two network elements. The network element may be radio base stations i3a-d, wireless end-user terminals na-b, or any combination thereof. According to this embodiment the processing unit 21 of the network node 20 is arranged to, in an optional step Si04a, weigh scheduling information from the at least two network elements during the step S104 of determining.

The scheduling may be based on different aspects of priority information and/or prioritization. Different aspects relating thereto will now be described in turn.

In general terms, for legacy LTE mechanism for providing wireless backhaul, QoS is managed using the EPC bearer concept. The herein disclosed embodiments may be used to, based on configuration as performed according to the legacy LTE mechanism, dynamically optimize the scheduling by taking into account the momentary traffic whilst using legacy QoS settings. In general terms, a LTE based wireless backhaul network may be configured to translate the QoS settings to a priority pi(t) for end-user i. Particularly, according to the herein disclosed embodiments the at least two network elements are radio base stations i3a-d and the scheduling information comprises priority information of wireless end-user terminals na-b served by the at least two radio base stations i3a-d. The weighting in step Si04a may be based on the priority information. The priority information may, for example, relate to importance of end-user data transmitted to or from the wireless end-user terminals na-b. In more detail, the translation for best effort QoS may be accomplished using a proportional fair scheduler where the priority pi(t) of end-user i is scaled with the inverse of the historic average rate Ri(t) at time t, using a fairness value β. That is:

Pi(t) ~ ι/¾(ΐ)^β. The values of pi(t) and Ri(t) may be determined by the radio base stations i3a-d. According to another example the translation for a low latency QoS, i.e. for a delay sensitive service, is accomplished using a delay scheduler where the priority pi(t,T) of end-user i increase with the age, calculated as t-T, of the packet, where t is the current time and T is the time of the oldest buffered data. That is:

_Pi(t,T) > _Pi(t,T+i).

As the skilled person understands, also other scheduling priorities or combinations of the above mentioned priorities may be used and fall within the scope of the herein disclosed embodiments.

Priority information may be signaled through a connection from the radio base stations i3a-d to the network node 20 as well as the hub node 16a and/or client node 17a. As noted above, the radio base station i3a-d and the client node 17a may be co-located, and implemented in the same physical box. The connection between the radio base station i3a-d and the client node 17a may then be implemented within a computer program or through a local Ethernet connection enabling low latency signaling. This may be

advantageous since the prioritization of end-user data is first known by the radio base stations i3a-d as it may depend on per transmission time interval (TTI) information.

The priority pi of the end-users from the different radio base stations i3a-d connected to the client node 17a may have been mapped to comparable prioritization weights, for example, according to a function f(*,t). This function may be limited to only concern the mapping of the end-user traffic to different bearers with different QoS. Manual configuration may be needed, for example, if the wireless backhaul network 10b is shared between radio base stations i3a-d from different network operators.

A radio base station i3a-d j may have prioritization weights pij(t), estimated channel capacities Cij(t) and/or estimated amount of data d_¾(t) that may be calculated per TTI at time t and end-user i. The weighting may thus be valid for one ΤΠ the at least one radio base stationi3a-d. For the details regarding the estimated channel capacities Cij(t) and the estimated amount of data dij(t) will be disclosed below. The prioritizations weights may be such that for a particular TTI at time t they order the importance of the data from different end-users, possibly using different QoS. Hence, for data received at the same time these values may determine the scheduling priority also on the wireless links 18 of the wireless backhaul network 10b. If the data is buffered there may be a need to up prioritize the older data. That is: f(_Pij(t),t+2) > f(_Pij(t),t+l). The older data may be prioritized by accessing information about how the delay scheduler calculates the weights. As the skilled person understands, the specific choice and properties of f(*,t) depends on the use-case and is out of scope of the present disclosure.

Further details regarding the estimated channel capacities Cij(t) and the estimated amount of data dij(t) will now be disclosed.

For scheduling of LTE based downlinks in the wireless backhaul network 10b, Cij(t) may be implemented by forwarded channel state information (CSI) received from an wireless end-user terminal 11a i served by radio base station I3a-d j. For scheduling of LTE based uplinks and/or downlinks in the wireless backhaul network 10b, Cij(t) link adaptation channel state estimates from radio base station i3a-d j is forwarded to the network node 20 as well as the hub node 16a and/or client node 17a. For scheduling of uplinks and/or downlinks in the wireless backhaul network iob,Cij(t) historic average channel capacity from radio base station i3a-d j is forwarded to the network node 20 as well as the hub node 16a and/or client node 17a. Hence, according to an embodiment the at least two network elements are radio base stations i3a-d and the scheduling information comprises estimated channel capacities of wireless links 19 between the at least two radio base stations i3a-d and wireless end-user terminals 11a, lib served thereby. The weighting is then based on the estimated channel capacities. The estimated amount of data dij(t) in the uplink and/or downlink may comprise buffer state estimates from radio base station i3a-d j. Hence, according to an embodiment the scheduling information comprises estimated amounts of end-user data to be transmitted or received by the at least two network elements (radio bases stations i3a-d, wireless end-user terminals na-b, or any combination thereof). The weighting is then based on the estimated amounts of end-user data. The weighting may be based on a QoS requirement of the end-user data. As will be further disclosed below, there may be some differences relating to how these estimates may be used depending on if the estimate relates to uplink or downlink, respectively.

Further, the scheduling information comprises a buffer status report of the at least one radio base station i3a-d. In more detail, the estimated amount of data dij(t) in the uplink and/or downlink may comprise both, or functions of, the buffer estimates and service class information about the wireless end- user terminal 11a, lib i. The service class information may comprise, for example, the maximum supported throughput of the wireless end-user terminal 11a, 11b, for examples as determined from a subscription service of the wireless end-user terminal 11a, 11b.

As the skilled person understands, if the network node 20 is not co-located with the hub node 16a, the hub node 16a may similarly forward information to the network node 20.

The hub node 16a may perform an optimization of the available capacity on the wireless backhaul links 18. The capacity is here defined as an estimated number of data bits that can be supported per unit of time. These bits may then be distributed between the radio base stations i3a-d so that the best known outcome is ensured for the end-users of the end-user access network 10c. Hence the amount of bits assigned to a radio base station i3a-d may be limited, for example, by the capacity of the wireless backhaul network 10b, the capacity of the radio base stations i3a-d, the amount of estimated data in/towards the radio base stations i3a-d of suitable priority. l8

There may be different ways to handle scheduling and control signaling with respect to the uplink and the downlink. As noted above there may be some differences in the scheduling and control signaling between uplink and downlink. For example, in the downlink the radio base stations I3a-d may not always serve as much traffic as the wireless backhaul network 10b can provide. Alternatively, the wireless backhaul network 10b cannot serve as much traffic in the uplink as the aggregated traffic from the connected client nodes 17a and/or radio base stations i3a-d. Hence, using the herein disclosed information exchange (for examples as accomplished in step S102), the hub node 16a may identify the limiting wireless link and control either its downlink scheduling or the uplink scheduling of the radio base stations 13a- d. Further, the prioritization between the different radio base stations i3a-d may take into account the actual prioritization and amount of traffic served by the radio base stations i3a-d. Further considerations relating thereto will now be described in turn by means of two illustrative scenarios relating thereto.

One difference is that for the UL, a scheduler may be implemented in the client node 17a (or in the network node 20) to differentiate the traffic from different radio base stations i3a-d. This situation is schematically illustrated in Fig 6. Fig 6 schematically illustrates uplink data and control signalling between nodes according to embodiments. According to the illustrative example of Fig 6 the clients (denoted "Client 1" and "Client 2") buffer data for served radio bases stations (as symbolized by "RBS 1 scheduler", "RBS 2 scheduler", "RBS 3 scheduler", and "RBS 4 scheduler"). These buffers may be of any type. According to the example illustrated in Fig 6 the buffers are Fifo (first in first out) type buffers (denoted "Fifo 1", "Fifo 2", "Fifo 3", "Fifo 4"). That is, according to the example illustrated in Fig 6 the prioritization order as performed by the RBS 1, 2, 3, 4 schedulers is reused as the packets of end- user data arrive at the Fifo 1, 2, 3, 4 buffers in the order that the RBS 1, 2, 3, 4 schedulers originally prioritized them. Client 1 and Client 2 here prioritize between its buffers using its UL scheduler that would be controlled using implemented control signaling according to the herein disclosed methods for scheduling. The Hub UL scheduler may know an estimate of the buffer status of, for example, Client 1 and control the resources to Client 1 and to Client 2. Further, Client 1 controls the mix of data (3 white and 3 black) from RBS 1 scheduler and RBS 2 scheduler, and Client 2 controls (the mix) of data (10 black) from RBS 3 scheduler and RBS 4 scheduler. The Hub UL scheduler may be based upon a legacy LTE scheduler enhanced by that scheduling prioritizes and restrictions are exchanged with Client 1 and Client 2 and the RBS 1, 2, 3, 4 schedulers according to the herein disclosed embodiments for scheduling. Further, the Hub UL scheduler may implement functionality to control Client 1 and Client 2 and the RBS 1, 2, 3, 4 schedulers through signalled scheduling, for example as in step S106. Examples of such scheduling have been provided above. The scheduling may, for example, imply, that an RBS 1, 2, 3, 4 scheduler will know when it only will have a wireless limited backhaul link and hence cannot schedule more PUSCH than this limitation. This could imply both better interference situation on the end-user access network 10c and that the buffers can be managed and do not need to be over-dimensioned for short traffic peaks on the wireless links in the end-user access network 10c. In the uplink the best scheduling decision may be ensured by signaling an uplink restriction on the number of bits to schedule for end-user uplink traffic. The restriction can be both on a TTI resolution and as an average over a number of TTIs.

Fig 7 schematically illustrates downlink data and control signalling between nodes according to embodiments. In the downlink situation, as schematically illustrated in the example of Fig 7, Client 1 and Client 2 do only need to implement routing functionality, and hence not any scheduling functionality. The needed scheduling functionality may thus all recede in the Hub DL scheduler which may implement scheduling as herein disclosed. Based on an information exchange between the RBS 1, 2, 3, 4 schedulers and the Hub DL scheduler, the Hub DL scheduler is able to schedule data taking into account properties such as end-user prioritization weights. Further, the herein disclosed scheduling enables that the Hub DL scheduler knows not to schedule a lot of resources (for examples as provided in buffers (denoted "Buffer l", "Buffer 2", "Buffer 3", and "Buffer 4")) to an end-user with a high priority (high pij(t)) and a low end-user channel capacity (low Cij(t)). Without this knowledge a high amount of data could end up in the buffers of the RBS 1, 2, 3, 4 schedulers and potentially also block the scheduling of wireless end- user terminals 11a, 11b that could transmit data over the end-user access network 10c but has not received its data because of the capacity of the wireless backhaul network 10b is used by a high priority end-user terminal 11a, 11b with poor end-user channel capacity Cij(t). In the downlink the best scheduling decision may be ensured by assigning and multiplexing data in the downlink PDSCH channel according to the best found decision (as determined in step S104).

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

Claims

1. A method for scheduling in a wireless backhaul network (lob) providing backhaul to an end-user access network (IOC), wherein said wireless backhaul network comprises a hub node (16a) and a client node (17a) providing backhaul to at least one radio base station (13a, 13b, 13c, 13d) in said end- user access network, the method being performed by a network node (20), the method comprising the steps of:

acquiring (S102) scheduling information of said at least one radio base station;

determining (S104), based on said scheduling information, a scheduling of a first wireless link of two consecutive wireless links (18, 19), one of which being a wireless link between said hub node and said client node, and wherein said scheduling is based on scheduling information of a second wireless link of said two consecutive wireless links; and

providing (S106) said scheduling to at least one of said hub node and said client node.

2. The method according to claim 1, wherein said first wireless link is scheduled based on a limitation of said second wireless link.

3. The method according to claim 2, wherein said scheduling information comprises an estimated channel capacity of said second wireless link, and wherein said limitation is based on said estimated channel capacity.

4. The method according to any one of the preceding claims, wherein said scheduling information is received from at least two network elements, and wherein said determining comprises:

weighting (Si04a) scheduling information from said at least two network elements.

5. The method according to claim 4, wherein said at least two network elements are radio base stations, wherein said scheduling information comprises priority information of wireless end-user terminals served by said at least two radio base stations, and wherein said weighting is based on said priority information.

6. The method according to claim 5, wherein said priority information relates to importance of end-user data transmitted to or from said wireless end-user terminals.

7. The method according to claim 4, wherein said at least two network elements are radio base stations, wherein said scheduling information comprises estimated channel capacities of wireless links between said at least two radio base stations and wireless end-user terminals served thereby, and wherein said weighting is based on said estimated channel capacities.

8. The method according to claim 4, wherein said scheduling information comprises estimated amounts of end-user data to be transmitted or received by said at least two network elements, and wherein said weighting is based on said estimated amounts of end-user data.

9. The method according to claim 8, wherein said weighting is based on a Quality of Service, QoS, requirement of said end-user data.

10. The method according to claim 4, wherein said weighting is valid for one transmission time interval, TTI, of said at least one radio base station.

11. The method according to any one of the preceding claims, wherein said scheduling information comprises a buffer status report of said at least one radio base station.

12. The method according to any one of the preceding claims, wherein said scheduling comprises a policy request for said at least one radio base station.

13. The method according to any one of the preceding claims, wherein said scheduling relates to use of radio resources in said end-user access network.

14. The method according to claim 2, wherein said limitation is related to at least one of available radio resource of said second wireless link, and a Quality of Service, QoS, fulfilment of end-user data to be transmitted on said second wireless link.

15. The method according to claim 1, wherein said two consecutive wireless links are uplinks.

16. The method according to claim 1, wherein said two consecutive wireless links are downlinks.

17. The method according to claim 1, wherein said scheduling relates to resources of a physical uplink shared channel, PUSCH, of said at least one radio base station.

18. The method according to claim 1, wherein said scheduling involves assigning and multiplexing end-user data to a physical downlink shared channel, PDSCH.

19. The method according to claim 1, wherein said method is performed by the client node, and wherein said scheduling is provided to said hub node and said at least one radio base station.

20. The method according to claim 1, wherein said method is performed by the hub node, and wherein said scheduling is provided to said client node.

21. The method according to claim 1, wherein the other of said two consecutive wireless links is a wireless link between one of said at least one radio base station and an wireless end-user terminal served by said one of said at least one radio base station.

22. The method according to claim 1, wherein the hub node is implemented in a macro radio base station.

23. The method according to claim 1, wherein the client node is

implemented in a micro radio base station or a pico radio base station.

24. A network node (20) for scheduling in a wireless backhaul network (10b) arranged to provide backhaul to an end-user access network (10c), wherein said wireless backhaul network comprises a hub node (16a) and a client node (17a) arranged to provide backhaul to at least one radio base station (13a, 13b, 13c, 13d) in said end-user access network, the network node comprising a processing unit (21) and a non-transitory computer readable storage medium (23), said non-transitory computer readable storage medium comprising instructions executable by said processing unit whereby said network node is operative to:

acquire scheduling information of said at least one radio base station; determine , based on said scheduling information, a scheduling of a first wireless link of two consecutive wireless links (18, 19), one of which being a wireless link between said hub node and said client node, and wherein said scheduling is based on scheduling information of a second wireless link of said two consecutive wireless links; and

provide said scheduling to at least one of said hub node and said client node.

25. The network node according to claim 24, wherein the network node is part of an evolved Node B.

26. A computer program (32) for scheduling in a wireless backhaul network (10b) providing backhaul to an end-user access network (10c), wherein said wireless backhaul network comprises a hub node (16a) and a client node (17a) providing backhaul to at least one radio base station (13a, 13b, 13c, 13d) in said end-user access network, the computer program comprising computer code which, when run on a network node (20), causes the network node to: acquire (S102) scheduling information of said at least one radio base station;

determine (S104), based on said scheduling information, a scheduling of a first wireless link of two consecutive wireless links (18, 19), one of which being a wireless link between said hub node and said client node, and wherein said scheduling is based on scheduling information of a second wireless link of said two consecutive wireless links; and

provide (S106) said scheduling to at least one of said hub node and said client node.

27. A computer program product (31) comprising a computer program (32) according to claim 26 and a computer readable means (33) on which the computer program is stored.