EP3278466A1

EP3278466A1 - Scheduling in a full-dimension mimo system

Info

Publication number: EP3278466A1
Application number: EP15714497.3A
Authority: EP
Inventors: Mihai Enescu; Karol Schober
Original assignee: Nokia Solutions and Networks Oy
Current assignee: Nokia Solutions and Networks Oy
Priority date: 2015-04-02
Filing date: 2015-04-02
Publication date: 2018-02-07
Also published as: WO2016155840A1

Abstract

In response to two user devices wanting to use resources in the same beam, a way to schedule both user devices includes determining which one of the user devices is a primary user device, scheduling the primary user device to the beam, and off-loading the other to its next best beam.

Description

DESCRIPTION TITLE

SCHEDULING IN A FULL-DIMENSION MIMO SYSTEM

TECHNICAL FIELD

The invention relates to wireless communications.

BACKGROUND

The following description of background art may include insights, discoveries, understandings or disclosures, or associations together with dis-closures not known to the relevant art prior to the present invention but provided by the invention. Some such contributions of the invention may be specifically pointed out below, whereas other such contributions of the invention will be apparent from their context.

In recent years, the phenomenal growth of mobile Internet services and proliferation of smart phones and tablets has increased use of mobile broadband services, and hence use of available spectrum. One solution to increase spectral effi- ciency is to make use of a full-dimension multiple-input multiple-output(FD-MIMO) system. In an FD-MIMO system, a base station with two-dimensional active array supports multi-user joint elevation and azimuth beamforming, also called as three dimensional beam-forming, which results in much higher cell capacity compared to conventional systems. However, in practice, the number of beams remains limited and a beam width is limited by the size of the array. Therefore it may happen that multiple user apparatuses may want to obtain service over the same beam.

BRIEF DESCRIPTION

According to an aspect, there is provided the subject matter of the independent claims. Embodiments are defined in the dependent claims. BRIEF DESCRIPTION OF DRAWINGS

In the following, the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which

Figure 1 shows simplified architecture of a system and block diagrams of some apparatuses according to an exemplary embodiment;

Figure 2 shows an exemplary FD-MIMO beamforming; Figures 3 to 5 are flow charts illustrating exemplary functionalities; and

Figures 6 and 7 are schematic block diagrams of exemplary apparatuses.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

The following embodiments are exemplary. Although the specification may refer to "an", "one", or "some" embodiment(s) in several locations, this does not nec- essarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments.

The present invention is applicable to any network/system configured to support full-dimension multiple-input multiple-output, FD-MIMO, or any correspond- ing/similar way to utilize available over the air spectrum, and entities/nodes/apparatuses in such a network/system. Examples of such networks/systems include Long Term Evolution Advanced (LTE-A) access system, Worldwide Interoperability for Microwave Access (WiMAX), LTE Advanced, 4G (fourth generation) and beyond, such as and 5G (fifth generation), cloud networks using In- ternet Protocol, mesh networks, and ad-hoc networks, such as LTE direct and mobile ad-hoc network (MANET), or any combination thereof. The specifications of different systems and networks, especially in wireless communication, develop rapidly. Such development may require extra changes to an embodiment. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the embodiment. For example, future networks will most probably utilize network functions virtualization (NFV) which is a network architecture concept that proposes virtualizing network node functions into "building blocks" or entities that may be operationally dynamically instantiated, connected or linked together to provide network services. A virtualized network function (VNF) may comprise one or more virtual machines that run computer program codes using standard or general type servers instead of customized hardware. In other words, the concept proposes to consolidate many network equipment (apparatus, node) types onto standard servers whose hardware can run computer program codes implementing network functions, without a need for installation of new equipment. Cloud computing and/or data storage may also be utilized. In radio communications this may mean node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head. It is also possible that node operations will be distributed amongst a plurality of servers, nodes or hosts. Another networking paradigm is software-defined networking (SDN) in which lower-level functionality is abstracted by decoupling data forwarding (data plane) from overlying control decisions, such as routing and resource allocations. This is achieved by means of one or more software-based SDN controllers that allow the underlying network to be programmable via the SDN controllers independent of underlying network hardware. Hence, it should be understood that the distribution of labor between core network operations and base station operations and user appa- ratuses may differ from that of the LTE-A, or even be non-existent, and the below described access node (evolved node B) functionality may be migrated to any corresponding abstraction or apparatus.

An extremely general architecture of an exemplary system 100 is illustrated in Figure 1. Figure 1 is a simplified system architecture only showing some elements and functional entities, all being logical units whose implementation may differ from what is shown. It is apparent to a person skilled in the art that the system comprises other functions and structures that are not illustrated, for example connections to the core network/system.

In the embodiment illustrated in Figure 1 , the system 100 comprises a wireless access network (not illustrated in Figure 1 ) providing access to the system for user apparatuses 1 10 (UE, user equipment, only one shown in Figure 1 ) by means of access point nodes 120 (only one shown in Figure 1 ).

The user apparatus 1 10 refers to a portable computing device (equipment), and it may also be referred to as a user terminal, user device, or mobile termi- nal. Such computing devices (apparatuses) include wireless mobile communication devices operating with or without a subscriber identification module (SIM) in hardware or in software, including, but not limited to, the following types of devices: mobile phone, smart-phone, personal digital assistant (PDA), handset, laptop and/or touch screen computer, e-reading device, tablet, game console, notebook, multimedia de- vice, sensor, and a radio-head. The user apparatus 1 10 is configured to support FD- MIMO load balancing. For that purpose the user apparatus 1 10 comprises an enhanced interference cancellation unit e-IC-u 1 1 1 whose functionality will be described in more detail below. It should be appreciated that the user apparatus 1 10 is depicted to include 2 antennas only for the sake of clarity. The number of reception and/or transmission antennas may naturally vary according to a current implementation.

The access point node 120, or any corresponding network entity (network apparatus, network node) is an apparatus providing over-the-air access, including resource allocation, to a network (wireless or wired) the access point is connected to, and the access point node may be configured to support one or more wireless access. Examples of such apparatuses include an evolved node B and a base station. The access node 120 is configured to provide FD-MIMO load balancing. For that purpose the access node comprises an FD-MIMO load balancing unit (l-b-u) 121 whose functionality will be described in more detail below. It should be appreciated that the access node 120 is depicted to include 2 antennas only for the sake of clarity. Further, in the illustrated example, the access node is configured to maintain beam index associ- ations 122. A beam index association means herein that a beam index is associated with one or more bundles, a bundle comprising a set of parameters, such as demodulation reference signal (DMRS), channel state information - reference signals (CSI- RS), scrambling identifier (nSCID), virtual cell identifier (VCID), quasi-colocation information (QCL), modulation, precoder information (PMI), rank indication (Rl), user apparatus receiver assumption, etc. Examples of the user apparatus receiver assumption, also called UE receiver assumption, include liner with turbo decoding feedback, linear without turbo decoding feedback, non-linear with turbo decoding feedback and non-linear without turbo decoding feedback. In other words, the UE receiver assumptions describe assumed signal processing style of a receiver. By means of the beam index association, a bundle is identifiable through a beam index, and the beam index and members of the bundle are identifiable through one member of the bundle, for example through DMRS, or CSI-RS. In addition, although not illustrated in Figure 1 , the access node is configured with two-dimensional active array and configured to support multi-user joint elevation and azimuth beamforming, or with corresponding means providing the capability to create beams.

Below different functionality is described using an evolved node B as an example of an access node, and LTE-advanced as an example of wireless network in which a Multi User-Multiple Input Multiple Output (MU-MIMO) transmission is realized with precoding and user apparatus pairing, without restricting the examples to such a solution.

Figure 2 illustrates FD-MIMO beamforming 200. It should be appreciated that only a part of FD-MIMO beams 201 provided by an evolved node B 210 are illustrated in Figure 2. In Figure 2, by means of elevation domain beamforming, for example, narrow vertical sectors, also called sub-sectors, are created (within a traditional cell-sector that is not illustrated in Figure 2). Users, i.e. user apparatuses using the wireless service, located in neighboring sub-sectors may experience orthogonal or semi-orthogonal transmissions without interference or with little interference, and they may be multiplexed spatially. Hence users in these vertical sectors may use the same time/frequency resources as well as reference symbols. In other words, the same DMRS positions, for example, may be used by the sub-sector users. Further, each vertical sub-sector may be further separated by means of beamforming, i.e. by means of precoding matrix indicator (PMI) precoding in azimuth, the result being a group of beams 201 , each beam having an index, illustrated by #N, #M, #P and #Q as beam index examples. Within each beam, legacy MU-MIMO transmissions may be performed on reference symbol ports visible within the beam, for example, by pairing users with orthogonal PMIs, or by means of zero-forcing (ZF) enforcing orthogonality between layers.

Figure 3 illustrates an exemplary functionality of the evolved node B, or more precisely an exemplary functionality of the FD-MIMO load balancing unit.

Referring to Figure 3, as a preliminary step, and therefore depicted by dashed line, the evolved node B creates in step 300 bundles of DMRS, CSI-RS, nSCID, VCID, QCL, PMI, Rl, UE receiver assumption, etc., and assigns in step 300 each beam created (as explained above with Figure 2) its own bundles, i.e. a subset of DMRS, CSI-RS, nSCID, VCID, etc. After the preliminary step has been performed, i.e. the beams exist and have bundles, the information, including the bundles, may be broadcast, or otherwise signaled, for example, to user apparatuses and hence beams are detectable/foundable, and thereby usable, by user apparatuses. It should be appreciated that the preliminary step may also be performed by another unit, for example by a beam forming unit.

As a kind of use request, the evolved node B receives in step 301 feed- back information from a user apparatus, called herein UE1 , the feedback information indicating best beam choices to be utilized for downlink transmission to UE1 . The feedback information may be a radio resource management (RRM) report, such as a measurement report, containing at least channel state information (CSI) on at least one beam. Further, the feedback information indicates n best beams, wherein n is an integer, the value of which may be 1 , 2, 3, etc. Examples of the feedback information are described in more detail below with Figure 4.

Using the received feedback information, the best beam to UE1 is determined in step 302. Then it is checked in step 303, whether or not the best beam to UE1 is occupied. In other words, it is checked, whether or not the beam has been already scheduled to another user apparatus.

In the illustrated exemplary embodiment, if the beam has already been scheduled to another user apparatus, i.e. is occupied, the evolved node B checks in step 304, whether or not UE1 and the user apparatus already scheduled to the beam are suitable for MU-MIMO multiplexing. The user apparatuses are suitable for MU- MIMO multiplexing if orthogonal DMRSs are used for the paired user apparatuses. Also the eNB may be configured to utilize ZF in order to induce orthogonality between MU-MIMO user apparatuses, or in case common reference symbols (CRS) are used, MU-MIMO user apparatuses could utilize advanced receiver interference cancellation (IC) capability. Further, there may be one or more other restrictions for MU-MIMO multiplexing. Examples of such other restrictions include that at least one of the user apparatus have a higher rank than rank 1 , and that both have rank 1 PMIs that are not suitable for legacy MU-MIMO operation, i.e. reported non-orthogonal PMIs.

If UE1 and the user apparatus already scheduled to the beam are not suitable for MU-MIMO multiplexing (step 304), the evolved node B determines in step 305 which one of the user apparatuses is a primary user apparatus (UE) for the beam. The criteria used for determining which one is the primary user apparatus may be any criteria. For example, one or more fairness metrics, such as a Propotional Fair metric indication of how much throughout a UE got at a particular time, may be used. The advantage provided by fairness metrics is that they help the system to ensure that user apparatuses have a fair access to system resources in such away that individual throughputs of the user apparatuses are maximized. Another example of a criteria to use is simly consider the user apparatus already occupying the beam as the primary user apparatus. In other words, it is determined which one of the user apparatus should be scheduled to the beam.

If the primary user apparatus is not UE1 (step 306), it is checked in step 307, whether or not in the best n beams there are beams whose occupation situation has not yet been checked. Typically the best n beams comprise two or more beams, and if the best beam is occupied, there is at least one beam left to be processed. In such situations this checking is not performed after step 306.

If in the best n beams there are beams whose occupation situation has not yet been checked (step 307), the next best beam is determined in step 308, using the received feedback information. Then it is checked in step 309, whether or not the next best beam of UE1 is occupied. If the next best beam has already been scheduled to another user apparatus, i.e. is occupied, the evolved node B checks in step 310, whether or not UE1 and the user apparatus already scheduled to the next best beam are suitable for MU-MIMO multiplexing. If not, the primary user apparatus for the next best beam is determined in step 31 1. If the primary user apparatus is not UE1 (step 312), the process returns to step 307 to check, whether in the best n beams there are beams whose occupation situation has not yet been checked. The steps 309 to 31 1 correspond to step 303 to 305, and therefore are not described in more detail here.

If the next best beam is not occupied (step 309), UE1 is scheduled in step 313 to the next best beam. Further, since UE1 is scheduled to a sub-optimal beam, the evolved node B indicates in step 313 network assistance for interference cancellation (NAICS) to UE1. The indication of the network assistance may be sending, for example signaling, one or more physical downlink shared channel (PDSCH) transmission characteristics of the user apparatus occupying the best beam of UE1 on which UE1 was not scheduled, or in the case that UE1 was not scheduled to one or more next best beams, transmission characteristics of each user apparatus occupying a next best beam on which UE1 was not scheduled. The signaling may be dynamic, i.e. corresponding to radio resource management signaling, or semi-static, i.e. corresponding to physical downlink control channel signaling. Examples of interfering PDSCH characteristics include beam index of the interfering PDSCH, and/or modulation order, modulation and coding scheme (MCS) indication, power offsets, transmission mode and rank. The beam index of the interfering PDSCH may correspond to DMRS characteristics, nSCID, CSI-RS and VCID configuration, QCL, PMI, Rl, UE receiver type, etc.

If the user apparatuses already scheduled to the next best beam are suitable for MU-MIMO multiplexing (step 310), the process proceeds to step 313 described above.

If the primary user apparatus for the next best beam is UE1 (step 312) UE1 is scheduled in step 314 to the next best beam. Further, and since UE1 is scheduled to a sub-optimal beam, the evolved node B indicates in step 313 network assistance for interference cancellation (NAICS) to UE1 , as described above. Further, since the user apparatus occupying the beam UE1 is now scheduled to needs to be rescheduled, the above described offloading process from step 307 forward is performed to the user apparatus that was determined to be the secondary user appa- ratus.

If the best beam is not occupied (step 303), or if UE1 and the user apparatus already scheduled to the best beam are suitable for MU-MIMO multiplexing, UE1 is scheduled in step 315 to the best beam.

If UE1 is the primary user apparatus for the best beam (step 306), UE1 is scheduled in step 316 to the best beam and the user apparatus occupying the best beam needs to be rescheduled, the above described offloading process from step 307 forward is performed to the user apparatus that was determined to be the secondary user apparatus in step 306.

If occupation situation of all best n beams has been checked (step 307), UE1 is not scheduled (step 317). In another embodiment, the primary UE is determined after the best beam

(or the next best beam) has been determined. In another alternative, after receiving the feedback, order of the beams is determined, i.e. steps 302 and 308 are kind of integrated. Another example includes that primary UEs for n beams are determined also before starting to check, whether or not the corresponding beam is occupied.

In a further embodiment, it is assumed that the user apparatus already scheduled to the beam remains there, and steps 305, 306, 312 and 313 are skipped over.

In a still further embodiment, if the beam has already been scheduled to another user apparatus, the suitability for MU-MIMO multiplexing is not performed, and it is assumed that the user apparatus already scheduled to the beam remains there, i.e. steps 304, 305, 306, 31 1 , 312 and 313 are skipped over. In the embodiment, the evolved node B assigns the un-scheduled UE1 to an un-occupied (free) beam.

As can be seen from the above, the result may be a chain offloading effect where user apparatuses are scheduled on their non-best beams instead of not being scheduled at all. This will increase overall system throughput.

Figure 4 illustrates functionality of the user apparatus.

Referring to Figure 4, the user apparatus performs in step 401 measurements on beams heard/detected by the user apparatus.

The user apparatus may measure RRM measurements, such as reference signal received power (RSRP) and reference signal received quality (RSRQ), and/or CSI measurements, such as precoding matrix indicator (PMI), channel quality indicator (CQI) and rank indication (Rl).

Then a measurement report is created in step 402. The measurement re- port for UE1 may be as follows:

• UE1 :

o (RSRP, PMI, CQI, ...)_UE1_beam#N

o (RSRP, PMI, CQI, ...)_UE1_beam#M,

o

However, the measurement report may contain different information for different beams, for example as follows:

UE1 :

o (RSRP, CQI, ...)_UE1_beam#N,

o (RSRP)_UE1_beam#M, In other words, the measurement report may contain all bundle components, some of the bundle components, or a mere beam index which then indicates bundle components that are assumed to be reported as feedback information.

Further, the information in the measurement report may be in a form of a wideband report, or in a form of a frequency selective report, or some of it may be in the form of the wideband report and some in the form of the frequency selective report. For example, a report for the best beam may contain frequency selective reports while reports for the other beams contain wideband measurements relative to the best beam reports.

Depending on an embodiment, the measurement reports may be ordered, i.e. be in an order of superiority so that the best beam is first. The order may be based on RSRP and/or CQI. Alternatively, the evolved node B may determine the order.

Once the report has been created, it is sent in step 403 from the user apparatus to the evolved node B as a feedback information. Further, in the illustrated example, the user apparatus stores in step 404 the measurement report temporarily, i.e. at least until a next report is created and sent. By storing the measurement report, the user apparatus links (associates) the different parameters to the beam index, and to each other.

Figure 5 illustrates an exemplary functionality of the user apparatus, or more precisely an exemplary functionality of the enhanced interference cancellation unit.

Referring to Figure 5, the user apparatus receives in step 501 in scheduling information from the evolved node B an indication on DMRS utilized for downlink PDSCH decoding. The scheduling information may comprise CSI-RS, which may be linked to the beam index, and hence to DMRS, thanks to the measurement report stored in step 404 of Figure 4. The user apparatus compares the indicated DMRS to DMRS associated with the best beam determined based on the measurements described above with Figure 4 to find out whether DMRSs correspond to each other (step 502).

If the indicated DMRS does not correspond to DMRS associated with the best beam (step 502), the user apparatus detects in step 503 that it has been offloaded to a sub-optimal beam, and starts to perform in step 503 inter-beam interference cancellation (IC). In other words, the interference cancellation capability of advanced receivers is utilized. An advanced receiver may be a non-linear receiver that is able to cancel PDSCH of the user apparatus in the better beam as long as the transmission strength of the interferer, i.e. the user apparatus in the better beam, is powerful enough to enable the user apparatus (victim) to estimate the characteristics of the interfering user apparatus.

Further, the user apparatus receives in step 504 the network assistance, i.e. NAICS, described above with Figure 3, and uses in step 505 NAICS in the inter- beam interference cancellation.

If the received DMRS corresponds to DMRS of the best beam (step 502), there is no offloading and hence no inter-beam interference cancellation performed (step 506) because of the offloading. Nevertheless, the user apparatus may still perform inter-beam interference cancellation, for example because of non-orthogonal multiple access, and/or receive network assistance for performing intra-beam interfer- ence cancellation, for example in context of super-position coding, or legacy MU- MIMO.

Using the beamforming illustrated in Figure 2, and the above described procedures, the current principle "only one user apparatus is being served by one beam at a particular time and frequency resource" will be fulfilled and yet service can be provided to user apparatuses having the same beam as the best beam, as will be described by means of following examples. It should be appreciated that two or three user apparatuses, and beams provided by one evolved node B are used in the examples only for the sake of clarity; the illustrated principles remain the same for multimple user apparatuses and in situations in which the best beam and the beam whereto a user apparatus is offloaded are provided by different evolved node Bs.

In an exemplary situation UE1 has indicated that its best beam is #N, and second best beam is #M. UE1 is scheduled to #N. UE2 reports its best beam is #N, and second best beam is #P. Assuming that MU-MIMO is not suitable in beam #N, UE2 is scheduled to beam #P, receives NAICS of UE1 and performs IC of UE1 . Fur- thermore, since eNB receives feedback for UE1 , UE2 and beams #N and #P, eNB will be able to predict efficiency and post-IC CQI of UE2.

In another exemplary situation UE1 has indicated that its best beam is #N, and second best beam is #M and UE3 has indicated that its best beam is #P, and second best beam is #Q. UE1 is scheduled to #N and UE3 is scheduled to #P. UE2 reports its best beam is #N, and second best beam is #P. Assuming that MU-MIMO is not suitable for UE1 in beam #N but suitable for UE3 in beam #P, UE2 is scheduled to beam #P in MU-MIMO mode with UE3. In this situation UE2 receives NAICS of UE1 and performs IC of UE1 of beam#N. Furthermore, since eNB receives feedback for UE1 , UE2 and beams #N and #P, eNB will be able to predict efficiency and post-IC CQI of UE2. In a further exemplary situation UE1 has indicated that its best beam is

#N, and second best beam is #M and UE3 has indicated that its best beam is #P, and second best beam is #Q. UE1 is scheduled to #N and UE3 is scheduled to #P. UE2 reports its best beam is #N, and second best beam is #P. Assuming that MU-MIMO is not suitable for UE1 in beam #N and for UE3 in beam #P and that UE2 is a primary user apparatus to #P, UE2 is scheduled to beam #P and UE3 is removed from #P and rescheduled to #Q. In this situation UE2 receives NAICS of UE1 and performs IC of UE1 of beam #N, UE3 receives NAICS of UE2 and performs IC of UE2 of beam #P. Furthermore, since eNB receives feedback for UE1 , UE2, UE3 and beams #N, #P and #Q, eNB will be able to predict efficiency and post-IC CQI of UE2 and UE3.

In a yet further exemplary situation UE1 has indicated that its best beam is

#N, and second best beam is #M and UE3 has indicated that its best beam is #P, and second best beam is #Q. UE1 is scheduled to #N and UE3 is scheduled to #P. UE2 reports its best beam is #N, second best beam is #P and third best beam is #Q. Assuming that MU-MIMO is not suitable for UE1 in beam #N and for UE3 in beam #P and that UE3 is a primary user apparatus to #P, and that beam #Q is not occupied, UE2 is scheduled to beam #Q. In this situation UE2 receives NAICS of UE1 and NAICS of UE3, and performs IC of UE1 of beam #N, and IC of UE3 of beam #P. Furthermore, since eNB receives feedback for UE1 , UE2, UE3 and beams #N, #P and #Q, eNB will be able to predict efficiency and post-IC CQI of UE2.

The steps, messages (i.e. information exchange) and related functions described above in Figures 3 to 5 are in no absolute chronological order, and some of the steps may be performed simultaneously or in an order differing from the given one. Other functions can also be executed between the steps or within the steps, and other information may be sent. Some of the steps or part of the steps can also be left out or replaced by a corresponding step or part of the step.

The techniques described herein may be implemented by various means so that an apparatus/network node/user device implementing one or more functions/operations of a corresponding apparatus/access node/user device described above with an embodiment/example, for example by means of Figure 2, Figure 3, Figure 4 and/or Figure 5, comprises not only prior art means, but also means for implementing the one or more functions/operations of a corresponding functionality described with an embodiment, for example by means of Figure 2, Figure 3, Figure 4 and/or Figure 5, and it may comprise separate means for each separate function/operation, or means may be configured to perform two or more func- tions/operations. For example, one or more of the means and/or the enhanced inter- ference cancellation unit and/or the FD-MIMO load-balancing unit and/or algorithms for one or more functions/operations described above may be software and/or software-hardware and/or hardware and/or firmware components (recorded indelibly on a medium such as read-only-memory or embodied in hard-wired computer circuitry) or combinations thereof. Software codes may be stored in any suitable, proces- sor/computer-readable data storage medium(s) or memory unit(s) or article(s) of manufacture and executed by one or more processors/computers, hardware (one or more apparatuses), firmware (one or more apparatuses), software (one or more modules), or combinations thereof. For a firmware or software, implementation can be through modules (e.g., procedures, functions, and so on) that perform the functions described herein. More detailed descriptions are provided by means of Figures 6 and 7.

Figure 6 is a simplified block diagram illustrating some units for an apparatus 600 configured to be a wireless access apparatus (access node), comprising at least the FD-MIMO load-balancing unit, or configured otherwise to perform functionali- ty described above, for example by means of Figure 3, or some of the functionalities if functionalities are distributed in the future. In the illustrated example, the apparatus comprises an interface (IF) entity 601 for receiving and transmitting information, an entity 602 capable to perform calculations and configured to implement at least the FD-MIMO load-balancing unit described herein, or at least part of functionali- ties/operations described above, for example by means of Figure 2 and/or Figure 3, as a corresponding unit or a sub-unit if distributed scenario is implemented, with corresponding algorithms 603, and memory 604 usable for storing a computer program code required for the FD-MIMO load-balancing unit, or a corresponding unit or sub- unit, or for one or more functionalities/operations described above, for example by means of Figure 2 and/or Figure 3, i.e. the algorithms for implementing the functionality/operations described above by means of Figure 2 and/or Figure 3. The memory 604 is also usable for storing other possible information, like the bundles and the beam index associations, etc. The interface entity 601 may be a radio interface entity, for example a remote radio head, providing the apparatus with capability for radio communications. The entity 602 may be a processor, unit, module, etc. suitable for carrying out embodiments or operations described above, for example by means of Figure 2 and/or Figure 3.

In other words, an apparatus configured to provide the wireless access apparatus (access node), or an apparatus configured to provide one or more corre- sponding functionalities as described above, for example by means of Figure 2 and/or Figure 3, is a computing device that may be any apparatus or device or equipment or node configured to perform one or more of corresponding apparatus functionalities described with an embodiment/example above, for example by means of Figure 2 and/or Figure 3, and it may be configured to perform functionalities from different embodiments/examples. The FD-MIMO load-balancing unit, as well as corresponding units and sub-units and other units, and/or entities described above with an apparatus may be separate units, even located in another physical apparatus, the distributed physical apparatuses forming one logical apparatus providing the functionality, or integrated to another unit in the same apparatus.

The apparatus configured to provide the wireless access apparatus (ac- cess node), or an apparatus configured to provide one or more corresponding functionalities described above, for example by means of Figure 2 and/or Figure 3, may generally include a processor, controller, control unit, micro-controller, or the like, connected to a memory and to various interfaces of the apparatus. Generally the processor is a central processing unit, but the processor may be an additional operation processor. Each or some or one of the units/sub-units and/or algorithms for functions/operations described herein, for example by means of Figure 2 and/or Figure 3, may be configured as a computer or a processor, or a microprocessor, such as a single-chip computer element, or as a chipset, including at least a memory for providing storage area used for arithmetic operation and an operation processor for executing the arithmetic operation. Each or some or one of the units/sub-units and/or algorithms for functions/operations described above, for example by means of Figure 2 and/or Figure 3, may comprise one or more computer processors, application-specific integrated circuits (ASIC), digital signal processors (DSP), digital signal processing devices (DSPD), programmable logic devices (PLD), field-programmable gate arrays (FPGA), and/or other hardware components that have been programmed and/or will be programmed by downloading computer program code (one or more algorithms) in such a way to carry out one or more functions of one or more embodiments/examples. An embodiment provides a computer program embodied on any client-readable distribution/data storage medium or memory unit(s) or article(s) of manufacture, comprising program instructions executable by one or more processors/computers, which instructions, when loaded into an apparatus, constitute the FD-MIMO load-balancing unit or an entity providing corresponding functionality. Programs, also called program products, including software routines, program snippets constituting "program libraries", applets and macros, can be stored in any medium and may be downloaded into an apparatus. In other words, each or some or one of the units/sub-units and/or the algo- rithms for one or more functions/operations described above, for example by means of Figure 2 and/or Figure 3, may be an element that comprises one or more arithmetic logic units, a number of special registers and control circuits.

Further, the apparatus configured to provide the wireless access apparatus (access node), or an apparatus configured to provide one or more correspond- ing functionalities described above, for example by means of Figure 2 and/or Figure 3, may generally include volatile and/or non-volatile memory, for example EEPROM, ROM, PROM, RAM, DRAM, SRAM, double floating-gate field effect transistor, firmware, programmable logic, etc. and typically store content, data, or the like. The memory or memories may be of any type (different from each other), have any possi- ble storage structure and, if required, being managed by any database management system. In other words, the memory may be any computer-usable non-transitory medium within the processor, or corresponding entity suitable for performing required operations/calculations, or external to the processor or the corresponding entity, in which case it can be communicatively coupled to the processor or the corresponding entity via various means. The memory may also store computer program code such as software applications (for example, for one or more of the units/sub- units/algorithms) or operating systems, information, data, content, or the like for the processor or the corresponding entity to perform steps associated with operation of the apparatus in accordance with examples/embodiments. The memory, or part of it, may be, for example, random access memory, a hard drive, or other fixed data memory or storage device implemented within the processor/apparatus or external to the processor/apparatus in which case it can be communicatively coupled to the processor/network node via various means as is known in the art. An example of an external memory includes a removable memory detachably connected to the apparatus, a distributed database and a cloud server.

The apparatus configured to provide the wireless access apparatus (access node), or an apparatus configured to provide one or more corresponding functionalities described above, for example by means of Figure 2 and/or Figure 3, may generally comprise different interface units, such as one or more receiving units and one or more sending units. The receiving unit and the transmitting unit each provides an interface entity in an apparatus, the interface entity including a transmitter and/or a receiver or any other means for receiving and/or transmitting information, and performing necessary functions so that the information, etc. can be received and/or sent. The receiving and sending units/entities may be remote to the actual apparatus and/or comprise a set of antennas, the number of which is not limited to any particular num- ber.

Figure 7 is a simplified block diagram illustrating some units for an apparatus 700 configured to be a user device, comprising at least an enhanced interference cancellation unit, or configured otherwise to perform functionality described above, for example by means of Figure 4 and/or Figure 5. In the illustrated example, the apparatus comprises an interface (IF) entity 701 for receiving and transmitting information, one or more user interface (U-IF) entities 701 ' for user interaction, an entity 702 capable to perform calculations and configured to implement at least the enhanced interference cancellation unit described herein, or at least part of functionalities/operations described above, for example by means of Figure 4 and/or Figure 5, with corresponding algorithms 703, and memory 704 usable for storing a computer program code required for the enhanced interference cancellation unit, or a corresponding unit for one or more functionalities/operations described above, for example by means of Figure 4 and/or Figure 5, i.e. the algorithms for implementing the functionality/operations described above by means of Figure 4 and/or Figure 5. The memory 504 is also usable for storing other possible information, like the measurement reports, and/or information associating DMRS with CSI-RS, etc. The entity 702 may be a processor, unit, module, etc. suitable for carrying out embodiments or operations described above, for example by means of Figure 4 and/or Figure 5.

In other words, an apparatus configured to provide the user device, or an apparatus configured to provide one or more corresponding functionalities as described above, for example by means of Figure 4 and/or Figure 5, is a computing device that may be any apparatus or device or equipment or node configured to perform one or more of corresponding user device functionalities described with an embodiment/example above, for example by means of Figure 4 and/or Figure 5, and it may be configured to perform functionalities from different embodiments/examples. The enhanced interference cancellation unit, as well as corresponding unit or one or more sub-units and other units, and/or entities described above may be separate units/entities, even located in another physical apparatus, the distributed physical apparatuses forming one logical apparatus providing the functionality, or integrated to another unit/entity in the same apparatus.

The apparatus configured to provide the user device, or an apparatus configured to provide one or more corresponding functionalities described above, for example by means of Figure 4 and/or Figure 5, may generally include a processor, controller, control unit, micro-controller, or the like connected to a memory and to various interfaces of the apparatus. Generally the processor is a central processing unit, but the processor may be an additional operation processor. Each or some or one of the units/sub-units and/or algorithms for functions/operations described herein, for example by means of Figure 4 and/or Figure 5, may be configured as a computer or a processor, or a microprocessor, such as a single-chip computer element, or as a chipset, including at least a memory for providing storage area used for arithmetic operation and an operation processor for executing the arithmetic operation. Each or some or one of the units/sub-units and/or algorithms for functions/operations described above, for example by means of Figure 4 and/or Figure 5, may comprise one or more computer processors, application-specific integrated circuits (ASIC), digital signal processors (DSP), digital signal processing devices (DSPD), programmable logic devices (PLD), field-programmable gate arrays (FPGA), and/or other hardware components that have been programmed and/or will be programmed by downloading computer program code (one or more algorithms) in such a way to carry out one or more functions of one or more embodiments/examples. An embodiment provides a computer program embodied on any client-readable distribution/data storage medium or memory unit(s) or article(s) of manufacture, comprising program instructions executable by one or more processors/computers, which instructions, when loaded into an apparatus, constitute the enhanced interference cancellation unit or an entity providing corresponding functionality. Programs, also called program products, including software routines, program snippets constituting "program libraries", applets and mac- ros, can be stored in any medium and may be downloaded into an apparatus. In other words, each or some or one of the units/sub-units and/or the algorithms for one or more functions/operations described above, for example by means of Figure 4 and/or Figure 5, may be an element that comprises one or more arithmetic logic units, a number of special registers and control circuits.

Further, the apparatus configured to provide the user device, or an apparatus configured to provide one or more corresponding functionalities described above, for example by means of Figure 4 and/or Figure 5, may generally include volatile and/or non-volatile memory, for example EEPROM, ROM, PROM, RAM, DRAM, SRAM, double floating-gate field effect transistor, firmware, programmable logic, etc. and typically store content, data, or the like. The memory or memories may be of any type (different from each other), have any possible storage structure and, if required, being managed by any database management system. In other words, the memory may be any computer-usable non-transitory medium within the processor, or corresponding entity suitable for performing required operations/calculations, or external to the processor or the corresponding entity, in which case it can be communicatively coupled to the processor or the corresponding entity via various means. The memory may also store computer program code such as software applications (for example, for one or more of the units/sub-units/algorithms) or operating systems, information, data, content, or the like for the processor or the corresponding entity to perform steps associated with operation of the apparatus in accordance with exam- pies/embodiments. The memory, or part of it, may be, for example, random access memory, a hard drive, or other fixed data memory or storage device implemented within the processor/apparatus or external to the processor/apparatus in which case it can be communicatively coupled to the processor/network node via various means as is known in the art. An example of an external memory includes a removable memory detachably connected to the apparatus, a distributed database and a cloud server.

The apparatus configured to provide the user device, or an apparatus configured to provide one or more corresponding functionalities described above, for example by means of Figure 4 and/or Figure 5, may generally comprise different interface entities/units, such as one or more user interfaces and one or more receiving units and one or more sending units. The receiving unit and the transmitting unit each provides an interface entity in an apparatus, the interface entity including a transmitter and/or a receiver or any other means for receiving and/or transmitting information, and performing necessary functions so that the information, etc. can be received and/or sent. The receiver, or in case of multiple receivers, at least one of them, is a receiver with interference cancellation capability. The user interfaces and the receiving and sending units may be remote to the actual apparatus. Further, the receiving and sending units may comprise a set of antennas, the number of which is not limited to any particular number.

Although in the above the embodiments and examples are described us- ing FD-MIMO, it is obvious for one skilled in the art how to implement the described embodiments and examples to other multiple input multiple output systems using the same principles as FD-MIMO.

It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

1. A method comprising:

receiving feedback information from a first user device;

determining from the feedback a best beam to the first user device;

detecting that a second user device is already scheduled to the best beam;

using a predetermined criteria to decide which one of the first user device and the second user device is a primary user device to the best beam; and

offloading, in response to the second user device being the primary user device, the first user device to a beam indicated as a next best beam in the feedback information.

2. A method as claimed in claim 1 , further comprising performing, in response to the first user device being the primary user device, the following:

offloading the second user device to a beam indicated as a next best beam in feedback information from the second user device; and

scheduling the first user device to the best beam.

3. A method as claimed in claim 1 or 2, further comprising:

causing sending network assistance for interference cancellation of the primary user device to the user device offloaded to the next best beam.

4. A method as claimed in any preceding claim, further comprising:

detecting that Multi User-Multiple Input Multiple Output mode is suitable for the first user device and the second user device in the best beam;

scheduling the first user device to the best beam in the Multi User-Multiple

Input Multiple Output mode with the second user device instead of offloading one of the first user device and the second user device.

5. A method as claimed in any preceding claim, further comprising:

detecting that a further user device is already scheduled to the next best beam; and

repeating deciding the primary user device and offloading until a non- occupied beam is found or Multi User-Multiple Input Multiple Output mode is suitable.

6. A method as claimed in any preceding claim, further comprising:

creating a set of bundles, a bundle comprising at least demodulation reference signal and channel state information- reference signal; and

assigning beams with bundles, a bundle for a beam being identifiable via a beam index of the beam.

7. A method as claimed in claim 6, wherein the bundle further comprises UE receiver assumption and/or scrambling identifier and/or virtual cell identifier and/or quasi-colocation information and/or modulation, and/or precoder information and/or rank indication.

8. A method comprising:

receiving in an apparatus scheduling information from an access node; detecting that the apparatus is offloaded from a best beam for the apparatus; and

performing interference cancellation of interference caused by an apparatus scheduled in the best beam.

9. A method as claimed in claim 8, further comprising:

receiving, from the access node, network assistance for the interference cancellation; and

performing the interference cancellation using the network assistance.

10. A method as claimed in claim 8 or 9, further comprising:

comparing a demodulation reference signal indicated in the scheduling in- formation with a demodulation reference signal of the best beam; and

detecting the offloading in response to the demodulation reference signals being different.

1 1. A method as claimed in claim 10, further comprising:

associating in the apparatus at least for n best beams a demodulation reference signal and a channel state information - reference signal with a beam index, wherein n is an integer;

receiving in the scheduling information a channel state information - reference signal; and

determining the indicated demodulation reference signal by means of the received channel state information - reference signal and the association.

12. A method as claimed in claim 8, 9, 10 or 1 1 , further comprising:

performing by the apparatus measurements on beams;

creating a measurement report comprising channel state information on one or more beams, channel state information for a beam comprising either a result associated with a beam index or one or more bundle components associated with a corresponding value, a bundle for the beam comprising as bundle components demodulation reference signal and channel state information- reference signal and zero or more from the following group comprising UE receiver assumption, scrambling identifier, virtual cell identifier, quasi-colocation information, modulation, precoder information and rank indication;

causing transmitting the measurement report as feedback information to the access node.

13. A method as claimed in claim 12, further comprising:

listing beams in the measurement report in a descending order, starting from the best beam, the report containing at least a reference signal received power and a channel quality indicator of the best beam and for each other beam at least a reference signal received power of the beam.

14. A method as claimed in any preceding claim, wherein the best beam and the next best beam are for downlink transmissions in a full-dimension Multiple Input Multiple Output system.

15. An apparatus comprising:

at least one processor and at least one memory including a computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus at least to:

determine, from received feedback information from a first user device, a best beam to the first user device;

upon detecting that a second user device is already scheduled to the best beam to use a predetermined criteria to decide which one of the first user device and the second user device is a primary user device to the best beam; and

to offload, in response to the second user device being the primary user device, the first user device to a beam indicated as a next best beam in the feedback information.

16. An apparatus as claimed in claim 15, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to:

offload, in response to the first user device being the primary user device, the second user device to a beam indicated as a next best beam in feedback information from the second user device; and

schedule the first user device to the best beam.

17. An apparatus as claimed in claim 15 or 16, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to send network assistance for interference cancellation of the primary user device to the user device offloaded to the next best beam.

18. An apparatus as claimed in claim 15, 16 or 17, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to schedule, detecting that Multi User- Multiple Input Multiple Output mode is suitable for the first user device and the second user device in the best beam, the first user device to the best beam in the Multi User- Multiple Input Multiple Output mode with the second user device instead of offloading one of the first user device and the second user device.

19. An apparatus as claimed in claim 15, 16, 17 or 18, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to repeate deciding the primary user device and offloading until a non-occupied beam is found or Multi User-Multiple Input Multiple Output mode is suitable.

20. An apparatus as claimed in any of claims 15 to 19, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to:

create a set of bundles, a bundle comprising at least demodulation reference signal and channel state information- reference signal; and

assign beams with bundles, a bundle for a beam being identifiable via a beam index of the beam.

21. An apparatus as claimed in claim 20, wherein the bundle further comprises UE receiver assumption and/or scrambling identifier and/or virtual cell identifier and/or quasi-colocation information and/or modulation, and/or precoder information and/or rank indication.

22. An apparatus as claimed in any of claims 15 to 21 , wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to provide beams in a f u II- dimension Multiple Input Multiple Output system, and wherein the best beam and the next best beam are for downlink transmissions in a full-dimension Multiple Input Multiple Output system.

23. An apparatus comprising:

at least one processor and at least one memory including a computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus at least to perform, upon detecting from scheduling information received from an access node that the apparatus is offloaded from a best beam for the apparatus, interference cancellation of inter- ference caused by an apparatus scheduled in the best beam.

24. An apparatus as claimed in claim 23, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to perform, upon receiving from the ac- cess node network assistance for the interference cancellation, the interference cancellation using the network assistance.

25. An apparatus as claimed in claim 23 or 24, wherein the at least one memory and the computer program code are configured to, with the at least one pro- cessor, further cause the apparatus at least to::

compare a demodulation reference signal indicated in the scheduling information with a demodulation reference signal of the best beam; and

detect the offloading in response to the demodulation reference signals being different.

26. An apparatus as claimed in claim 25, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to:

associate in the apparatus at least for n best beams a demodulation reference signal and a channel state information - reference signal with a beam index, wherein n is an integer; and

determine, upon receiving in the scheduling information a channel state information - reference signal, the indicated demodulation reference signal by means of the received channel state information - reference signal and the association.

27. An apparatus as claimed in claim 23, 24, 25 or 26, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to:

perform measurements on beams;

create a measurement report comprising channel state information on one or more beams, channel state information for a beam comprising either a result asso- ciated with a beam index or one or more bundle components associated with a corresponding value, a bundle for the beam comprising as bundle components demodulation reference signal and channel state information- reference signal and zero or more from the following group comprising UE receiver assumption, scrambling identifier, virtual cell identifier, quasi-colocation information, modulation, precoder infor- mation and rank indication; and

cause transmitting the measurement report as feedback information to the access node.

creating a measurement report

28. An apparatus as claimed in claim 27, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to list beams in the measurement report in a descending order, starting from the best beam, the report containing at least a reference signal received power and a channel quality indicator of the best beam and for each other beam at least a reference signal received power of the beam.

29. An apparatus as claimed in claim any of claims 23 to 28, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to support full-dimension Multiple Input Multiple Output system.

30. An apparatus as claimed in claim any of claims 23 to 29, wherein the apparatus comprises at least one receiver with interference cancellation capability.

31. An apparatus comprising means for carrying out the method according to any one of claims 1 to 14.

32. A non-transitory computer readable media having stored there-on in- structions that, when executed by an apparatus, cause the apparatus to:

33. A non-transitory computer readable media having stored there-on instructions that, when executed by an apparatus, cause the apparatus to perform, upon detecting from scheduling information received from an access node that the apparatus is offloaded from a best beam for the apparatus, interference cancellation of interference caused by an apparatus scheduled in the best beam.

34. A computer program product comprising program instructions configuring an apparatus to perform any of the steps of a method as claimed in any preceding claims 1 to 14 when the computer program is run.