WO2015078483A1

WO2015078483A1 - Method and apparatus for combining half- and full duplex transmission in a relay

Info

Publication number: WO2015078483A1
Application number: PCT/EP2013/074684
Authority: WO
Inventors: Esa Tapani Tiirola; Kari Pekka Pajukoski; Ilkka HARJULA; Olav Tirkkonen; Risto Wichman
Original assignee: Nokia Solutions And Networks Oy
Priority date: 2013-11-26
Filing date: 2013-11-26
Publication date: 2015-06-04
Also published as: CN105765880A; EP3075080A1

Abstract

Antenna usage in communications A method is disclosed for controlling a relay station in communications, the method comprising defining a first antenna group of the relay station (602) and a second antenna group of the relay station according to a radiation pattern. When uplink data traffic is transmitted from the relay station, the first antenna group of the relay station is controlled to operate in a Tx phase, and the second antenna group of the relay station is controlled to operate in a Rx phase or is not in use. When downlink data traffic is received in the relay station, the first antenna group of the relay station is controlled to operate in the Rx phase, and the second antenna group of the relay station is controlled to operate in the Tx phase or is not in use.

Description

METHOD AND APPARATUS FOR COMBINING HALF- AND FULL DUPLEX TRANSMISSION IN A RELAY

FIELD OF THE INVENTION

The exemplary and non-limiting embodiments of this invention relate generally to wireless communications networks, and more particularly to an antenna configuration.

BACKGROUND ART

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.

A directional antenna, also referred to as a beam antenna, is an antenna that radiates or receives radio waves more effectively in some directions than in others. An increased performance on transmit and receive and a reduced interference from unwanted sources is achievable by means of the directional antenna. The directional antenna may be realized as an antenna array consisting of a group of radiators.

For efficient heterogeneous network planning, a concept of relay nodes (RN) has been introduced in 3GPP LTE-advanced. In LTE-advanced, the relay nodes (also referred to as relay stations, RS) are low power eNode-Bs that provide enhanced coverage and capacity at cell edges. Relaying enables providing extended LTE coverage in targeted areas at low cost. It is anticipated that 5G systems provide inbuilt support for relaying and

selfbackhauling.

SUMMARY

The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later. Various aspects of the invention comprise methods, an apparatus, and a computer program product as defined in the independent claims. Further embodiments of the invention are disclosed in the dependent claims.

An aspect of the invention relates to a method for controlling a relay station in

communications, the method comprising defining a first antenna group of the relay station and a second antenna group of the relay station according to a radiation pattern, wherein when uplink data traffic is transmitted from the relay station, the first antenna group of the relay station is controlled to operate in a transmit (Tx) phase, and the second antenna group of the relay station is controlled to operate in a receive (Rx) phase or is not in use, and when downlink data traffic is received in the relay station, the first antenna group of the relay station is controlled to operate in the receive (Rx) phase, and the second antenna group of the relay station is controlled to operate in the transmit (Tx) phase or is not in use.

A further aspect of the invention relates to an apparatus comprising at least one processor; and at least one memory including a computer program code, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to perform any of the method steps.

A still further aspect of the invention relates to a computer program product comprising program instructions which, when run on a computing apparatus, causes the computing apparatus to perform the method.

Although the various aspects, embodiments and features of the invention are recited independently, it should be appreciated that all combinations of the various aspects, embodiments and features of the invention are possible and within the scope of the present invention as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

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

Figure 1 illustrates a scenario for half-duplex and full duplex operation with high unbalance between upstream and downstream data; Figure 2 illustrates exemplary antenna usage in mode 1 ;

Figure 3 illustrates exemplary antenna usage in mode 2;

Figure 4 illustrates an exemplary frame structure with mode 1 for control part; Figure 5 illustrates an exemplary frame structure with FDMA & mode 2 for control part;

Figure 6 shows a simplified block diagram illustrating exemplary system architecture;

Figure 7 shows a simplified block diagram illustrating exemplary apparatuses;

Figure 8 shows a messaging diagram illustrating exemplary signalling; Figure 9 shows a schematic diagram of a flow chart according to an exemplary embodiment of the invention;

Figure 10 shows a schematic diagram of a flow chart according to another exemplary embodiment of the invention.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

An exemplary embodiment relates to local area (LA) optimization of LTE-advanced which can materialize as 4G evolution or 5G. An exemplary embodiment considers full-duplex and half-duplex multi-hop forwarding in a 5G local area network. In the network, there is a high density of self-backhauling relay nodes (relay stations, RS) that simultaneously act as access points towards the users in addition to few nodes with a wired backhaul. The access is framed and synchronized along the multi-hop flow, and the nodes utilize frequency resources of an unpaired frequency band.

An exemplary embodiment enables controlling relay operation (especially antennas & transmit/receive (Tx/Rx) chains) in order to optimize relay functionality in various situations and use cases. Both half-duplex and full duplex operation have their own pros and cons (see also exemplary Figure 1 ). Full-duplex is a type of communication in which data can flow back and forth between two devices at the same time. Full duplex refers to simultaneous bidirectional communication. Full duplex operation mode may suffer from the self- interference. Half-duplex is a type of communication in which data can flow back and forth between two devices, but not simultaneously. Each device in a half-duplex system can send and receive data, but only one device is able to transmit at a time.

In full duplex operation mode, the antenna arrays are typically arranged in a manner that Tx and Rx directions are different. Thus, while the relay station is forwarding a data stream, the relay station receives signals from one direction and transmits to another, making it difficult to listen to e.g. control signals arriving from the Tx direction. This may be critical, for example, while forwarding data in upstream, since the control information from an access point (AP) is arriving downstream. Half-duplex mode reduces the throughput by up-to 50% compared to full duplex mode in a case with high unbalance between up-stream traffic and down-stream traffic (up-stream traffic originates from UE side; down-stream traffic originates from the network side).

Half duplex and full duplex are known operation modes for relays. However, there exists an unbalanced load between uplink (UL) and downlink (DL). In one scenario to solve the problem of unbalanced traffic load for UL and DL, a full duplex base station (BS) communicates with a full duplex user equipment (UE), but the traffic load is not symmetrical for both link directions. Thus, an access scheme may be used where part of the traffic is carried out in half duplex and part of the traffic is carried out in full duplex. However, that access scheme focuses solely on the BS - UE link.

An exemplary embodiment discloses how to control relay operation from (relay) device point of view.

An exemplary embodiment relates to a relay station, wherein the functionality of antennas (including Tx/Rx circuits) is adjusted w.r.t. each other. In an exemplary embodiment, the relay station has at least two (Tx/Rx) antennas, and the relay station utilizes the same frequency band for transmission and reception (w/o duplex filters). In an exemplary embodiment, the relay station has at least two (Tx/Rx) antennas, and the relay station utilizes different frequency bands for transmission and reception, respectively. In an exemplary embodiment, the relay station has at least two (Tx/Rx) antennas, and the relay station utilizes a different frequency band or a same frequency band for transmission and reception of the control information, and utilizes a same frequency band or a different frequency band for transmission and reception of data.

An exemplary embodiment relates to a scheme including two modes for configuring antennas (including Tx/Rx circuits). In an exemplary embodiment, in mode 1 , each of the antennas is configured to operate either in a Tx phase or in a Rx phase. In an exemplary embodiment, in mode 2, at least one antenna operates in the Tx phase and at least one other antenna operates in the Rx phase.

In an exemplary embodiment, when the relay station is transmitting and/or receiving data, only one of modes 1 and 2 is used at a time. Regardless of the selected mode, the usage of the antennas depends also on antenna patterns w.r.t. a link direction of the traffic stream such that upstream and downstream traffic utilize the available antennas (including Tx/Rx circuits) in different ways. The antenna usage changes dynamically based on the link direction of the data stream (this is a part of dynamic scheduling). Figure 2 illustrates exemplary antenna usage in mode 1 . Figure 3 illustrates exemplary antenna usage in mode 2. Both Figure 2 and Figure 3 assume that the access point AP and the user equipment UE are placed similarly as in Figure 1 .

It should be noted that the term "antennas" used herein may also refer to antenna beams, wherein usage of directional antennas cover also a case in which directivity (i.e. a directional radiation pattern) is achieved via a beam forming technique including the usage of antenna arrays. This means that it is not required to have physically different antennas for the Tx and Rx link directions. Different beams of the same antenna may be used for communication in the Tx and Rx link directions associated with the antenna. Thus, in an exemplary embodiment, even if the antennas were identical (i.e. the radiation pattern of an individual Tx/Rx antenna is the same), there may be a difference on the antenna orientation/beam direction, wherein the radiation pattern is different for different antenna groups.

In an exemplary embodiment, the relationship between the direction of the data stream and the usage of directional antennas may be as follows. The antennas (or beams) are grouped into two groups (A, B) in a predetermined way according to a radiation pattern. A radiation pattern, also named as an antenna pattern or far-field pattern, of an antenna refers to a directional (angular) dependence of the strength of the radio waves from the antenna.

Upstream traffic triggers that one of the groups, A (or B), operates in the Tx phase - whereas the other group of antennas, B (or A), operates in the Rx phase (mode 2) or is not in use (mode 1 ). Downstream traffic triggers that one of the groups, A (or B), operates in the Rx phase - whereas the other group of antennas, B (or A), operates in the Tx phase (mode 2) or is not in use (mode 1 ).

In an exemplary embodiment, eNB/AP makes a decision on a selected relay mode. The decision may be made in a semi-static or dynamic manner. The selection may be done for the entire subframe/radio frame/any predefined time duration (for the time being).

Alternatively, the relay mode is selected separately for a control part and a data part of the subframe.

The relay mode may also be selected in a channel-specific manner. For example, in case the relay node is receiving some critical channel (e.g. PRACH) the relay node may temporarily use the half-duplex mode even if the relay node has been configured to use the full-duplex mode.

In an exemplary embodiment, it is also possible to separate the upstream and

downstream traffic in frequency using different subcarriers for their transmission while using the full duplex mode. This relates to FDM separation between upstream and downstream (see the control part in Figure 5). This allows very flexible resource allocation between the downstream and upstream traffic, and enables having additional attenuation caused by FDMA separation between the stream directions. In an exemplary embodiment, the frame may be divided into data and control parts, and these parts may be allocated with different operation modes. For example, it may be possible to a) use mode 2 for both data and control traffic, b) use mode 2 for the data traffic and mode 1 for the control traffic, and/or c) use mode 2 for the data traffic and mode 2 with FDMA for the control traffic. Figure 4 illustrates an exemplary frame structure with mode 1 for the control part. Figure 5 illustrates an exemplary frame structure with FDMA & mode 2 for the control part. It should be noted that for simplicity, possible guard periods (or switching gaps) needed in some scenarios between different modes (mode 1 and mode 2) and/or between Tx and Rx phases (mode 1 ) are not shown in the figure.

In an exemplary embodiment, the relay operation mode may be selected based on a ratio of the up-stream traffic (denoted as A) and the down-stream traffic (denoted as B). Mode 1 is selected in case |A-B|<threshold. Mode 2 is selected in case |A-B|>threshold. Threshold setting may be based on various aspects such as the traffic load, traffic type (e.g. priority, QoS, latency requirements), interference conditions, etc.

In an exemplary embodiment, regarding the selection of the forwarding time, based on the selected relay mode, the reception initiates (forwarding) transmission without any need for separate triggering/resource allocation. In mode 1 , Tx timing is derived based on reception timing (x) + pre-defined (maximum) processing time (Tp), and duration of the current Rx phase (y). In mode 1 , the actual transmission time is obtained by quantizing/ceiling (x+y+Tp) with the predefined frame timing. In mode 2, the Tx timing is derived based on reception timing (x) + Pre-defined (maximum) processing time (Tp), and duration of the Rx phase (y). In mode 2, the actual transmission time is obtained by quantizing/ceiling (x+ Tp) with the predefined frame timing.

In an exemplary embodiment, regarding signalling, dedicated higher layer signalling is used to configure the mode to be applied. In case the relay mode is selected dynamically, it is also possible to use scheduling grants and/or implicit signalling (i.e. an absence of the scheduling grant) to indicate the applied relay mode (including the direction of the stream). The antenna usage changes dynamically based on the direction of the data stream (this may be a part of dynamic scheduling).

An exemplary embodiment enables optimizing the relay operation (especially antennas & Tx Rx chains) in different situations (e.g. with antenna types applied). An exemplary embodiment enables an improved resource allocation (& relay operation in general) between the downstream and upstream traffic. An exemplary embodiment enables maintaining the quality of critical control information also in the case where the full duplex relay is in use. Thus, an exemplary embodiment relates to an antenna configuration of the full duplex relays. A hybrid combination of HDR (half-duplex relay) and FDR (full-duplex relay) is provided in order to achieve the full duplex operation mode while allowing dynamic operation in the half duplex modes to accommodate varying channel/antenna/traffic conditions. The nodes for full-duplex and half-duplex multi-hop forwarding operating on the unpaired frequency band include two parts, i.e. antenna configurations, where mode 1 = HDR, and mode 2 = FDR. The frame is divided into the control and data parts, and a selection is performed between the HDR and FDR mode based on some selection criteria.

In an exemplary embodiment, the relay station utilizes an unpaired band (the same frequency band for transmission and reception) (w/o duplex filters) by grouping antennas (or beams) into two groups (A, B) in a predetermined way according to the radiation pattern, wherein the usage of the directional antennas is controlled based on the direction of the data stream. The upstream traffic causes that one of the groups (A) operates in the Tx phase, whereas the other group of antennas (B) operates in the Rx phase (full duplex mode) or is switched off (half duplex mode). The downstream traffic causes that one of the groups (A) operates in the Rx phase, whereas the other group of antennas (B) operates in the Tx phase (full duplex mode) or is switched off (half duplex mode). An exemplary embodiment may be applied, for example, to different usage of the directional antennas, e.g. for control and data, criteria for the usage of the directional antennas, etc. An exemplary embodiment provides hybrid operation modes (full duplex and half duplex) control for the relay mode, and the full duplex/half duplex mode is controlled by configuring the relay node antenna to Rx or Tx mode. An exemplary embodiment is applicable to future communication protocols, e.g. 5G cellular and also potentially to other next generation backhaul (i.e. mesh related) networks and 802.1 1 xx. Although the term frequency band(s) is (are) utilized above illustrating various relay operations, an exemplary embodiment is not so limited. In this regard, frequency and/or frequencies within the same frequency band or within different frequency bands may be applicable to the relay operations without departing from the spirit and scope of the various embodiments of the invention. Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Although the specification may refer to "an", "one", or "some" embodiment(s) in several locations, this does not necessarily 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. Like reference numerals refer to like elements throughout.

The present invention is applicable to any user terminal, network node, server, corresponding component, and/or to any communication system or any combination of different communication systems that support antenna usage with relays. The communication system may be a fixed communication system or a wireless

communication system or a communication system utilizing both fixed networks and wireless networks. The protocols used, the specifications of communication systems, servers and user terminals, 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.

In the following, different embodiments will be described using, as an example of a system architecture whereto the embodiments may be applied, an architecture based on LTE (or LTE-A) (long term evolution (advanced long term evolution)) network elements, without restricting the embodiment to such an architecture, however. The embodiments described in these examples are not limited to the LTE radio systems but can also be implemented in other radio systems, such as UMTS (universal mobile telecommunications system), GSM, EDGE, WCDMA, Bluetooth network, WLAN or other fixed, mobile or wireless network. In an embodiment, the presented solution may be applied between elements belonging to different but compatible systems such as LTE and UMTS. A general architecture of a communication system 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. The connections shown in Figure 1 are logical connections; the actual physical connections may be different. It is apparent to a person skilled in the art that the systems also comprise other functions and structures. It should be appreciated that the functions, structures, elements and the protocols used in or for antenna configurations with HDR/FDR relays, are irrelevant to the actual invention. Therefore, they need not to be discussed in more detail here.

The exemplary radio system of Figure 6 comprises a network node 601 of a network operator. The network node 601 may include e.g. an LTE/LTE-A base station (eNB), radio network controller (RNC), or any other network element, or a combination of network elements. The network node 601 may be connected to one or more core network (CN) elements (not shown in Figure 6) such as a mobile switching centre (MSC), MSC server (MSS), mobility management entity (MME), gateway GPRS support node (GGSN), serving GPRS support node (SGSN), home location register (HLR), home subscriber server (HSS), visitor location register (VLR). In Figure 6, the radio network node 601 that may also be called eNB (enhanced node-B, evolved node-B) or network apparatus of the radio system, hosts the functions for radio resource management in a public land mobile network. Figure 6 shows one or more relay stations RS 602 located in the service area of the radio network node 601 . The relay station refers to a low power LTE-A base station which may also be referred to as a relay node (RN). In the example situation of Figure 6, the relay station 602 is capable of connecting to the radio network node 601 via a connection 603. The relay station 602 may also be capable of connecting to a user equipment, such as a mobile station (not shown in Figure 6).

Figure 7 is a block diagram of an apparatus according to an embodiment of the invention. Figure 7 shows a relay station 602 located in the area of a radio network node 601 . The relay station 602 is configured to be in connection with the radio network node 601 . The relay station 602 comprises a controller 701 operationally connected to a memory 702 and a transceiver 703. The controller 701 controls the operation of the relay station 602. The memory 702 is configured to store software and data. The transceiver 703 is configured to set up and maintain a wireless connection 603 to the radio network node 601 . The transceiver 703 is operationally connected to a set of antenna ports 704 connected to an antenna arrangement 705. The antenna arrangement 705 may comprise a set of antennas. The number of antennas may be one to four, for example. The number of antennas is not limited to any particular number. The relay station 602 may also comprise various other components; they are not displayed in the figure due to simplicity. The radio network node 601 , such as an LTE-A base station (eNode-B, eNB) comprises a controller 706 operationally connected to a memory 707, and a transceiver 708. The controller 706 controls the operation of the radio network node 601 . The memory 707 is configured to store software and data. The transceiver 708 is configured to set up and maintain a wireless connection to the relay station 602 within the service area of the radio network node 601 . The transceiver 708 is operationally connected to an antenna arrangement 709. The antenna arrangement 709 may comprise a set of antennas. The number of antennas may be two to four, for example. The number of antennas is not limited to any particular number. The radio network node 601 may be operationally connected (directly or indirectly) to another network element (not shown in Figure 7) of the communication system, such as a radio network controller (RNC), a mobility management entity (MME), an MSC server (MSS), a mobile switching centre (MSC), a radio resource management (RRM) node, a gateway GPRS support node, an operations, administrations and maintenance (OAM) node, a home location register (HLR), a visitor location register (VLR), a serving GPRS support node, a gateway, and/or a server, via an interface. The embodiments are not, however, restricted to the network given above as an example, but a person skilled in the art may apply the solution to other communication networks provided with the necessary properties. For example, the connections between different network elements may be realized with internet protocol (IP) connections.

Although the apparatus 601 , 602 has been depicted as one entity, different modules and memory may be implemented in one or more physical or logical entities. The apparatus may also be a user terminal which is a piece of equipment or a device that associates, or is arranged to associate, the user terminal and its user with a subscription and allows a user to interact with a communications system. The user terminal presents information to the user and allows the user to input information. In other words, the user terminal may be any terminal capable of receiving information from and/or transmitting information to the network, connectable to the network wirelessly or via a fixed connection. Examples of the user terminals include a personal computer, a game console, a laptop (a notebook), a personal digital assistant, a mobile station (mobile phone), a smart phone, and a line telephone. The apparatus 601 , 602 may generally include a processor, controller, control unit 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. The processor may corn-prise a computer processor, application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), and/or other hardware components that have been programmed in such a way to carry out one or more functions of an embodiment.

The memory 702, 707 may include volatile and/or non-volatile memory and typically stores content, data, or the like. For example, the memory 702, 707 may store computer program code such as software applications (for example for the detector unit and/or for the adjuster unit) or operating systems, information, data, content, or the like for a processor to perform steps associated with operation of the apparatus in accordance with embodiments. The memory may be, for example, random access memory (RAM), a hard drive, or other fixed data memory or storage device. Further, the memory, or part of it, may be removable memory detachably connected to the apparatus.

The techniques described herein may be implemented by various means so that an apparatus implementing one or more functions of a corresponding mobile entity described with an embodiment comprises not only prior art means, but also means for implementing the one or more functions of a corresponding apparatus described with an embodiment and it may comprise separate means for each separate function, or means may be configured to perform two or more functions. For example, these techniques may be implemented in 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. The software codes may be stored in any suitable, processor/computer-readable data storage medium(s) or memory unit(s) or article(s) of manufacture and executed by one or more processors/computers. The data storage medium or the memory unit may be implemented within the processor/computer or external to the processor/computer, in which case it can be communicatively coupled to the processor/computer via various means as is known in the art.

The signalling chart of Figure 8 illustrates the required signalling. In the example of Figure 8, an apparatus 601 such as a network node (e.g. a LTE-A base station eNB or access point AP) may select/configure/define an operation mode for an apparatus 602 (e.g. a relay station RS) in item 801 . In a message 802, the network node 601 transmits information on/allocates the selected/configured/defined operation mode to the relay station 602. In item 803, the message 802 is received in the relay station 602. Based on the received message, the relay station adjusts 803 its operation mode. In item 804, the relay station may transmit (or receive) data traffic by using the adjusted operation mode. Alternatively (instead or in addition to the relay station operation mode being "statically" defined in the base station 601 ) the relay station operation mode may be selected 803 dynamically (or semi-statically) in the relay station 602 e.g. based on the direction of the data stream.

Figure 9 is a flow chart illustrating an exemplary embodiment. The apparatus 601 (which may comprise e.g. a LTE-A base station eNB or access point AP), may

select/configure/define an operation mode for an apparatus 602 (e.g. a relay station RS) in item 901 . In item 902, the apparatus 601 may transmit information on/allocate the selected/configured/defined operation mode to the relay station 602, in order the relay station 602 to be able to adjust its operation mode. Figure 10 is a flow chart illustrating an exemplary embodiment. The apparatus 602 (which may comprise e.g. a relay station RS), may receive, in item 101 , a message from apparatus 601 (which may comprise e.g. a LTE-A base station eNB or access point AP) in which message the base station 601 transmits information on/allocates a

selected/configured/defined operation mode to the relay station 602. Based on the received message, the relay station may adjust 102 its operation mode. In item 103, the relay station may transmit (or receive) data traffic by using the adjusted operation mode. Alternatively (instead or in addition to the relay station operation mode being "statically" received from the base station 601 ) the relay station operation mode may be selected 102 dynamically (or semi-statically) in the relay station 602 e.g. based on the direction of the data stream.

The steps/points, signalling messages and related functions de-scribed above in Figures 1 to 10 are in no absolute chronological order, and some of the steps/points may be performed simultaneously or in an order differing from the given one. Other functions can also be executed between the steps/points or within the steps/points and other signalling messages sent be-tween the illustrated messages. Some of the steps/points or part of the steps/points can also be left out or replaced by a corresponding step/point or part of the step/point. The apparatus operations illustrate a procedure that may be implemented in one or more physical or logical entities. The signalling messages are only exemplary and may even comprise several separate messages for transmitting the same information. In addition, the messages may also contain other information.

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.

List of abbreviations 5G 5th generation AP access point DL downlink eNB enhanced node-B

FDMA frequency division multiple access LA local area

PRACH physical random access channel

Rx receiver

Tx transmitter

UL uplink

Claims

1. A method for controlling a relay station in communications, the method comprising defining a first antenna group of the relay station (602) and a second antenna group of the relay station according to a radiation pattern, wherein when uplink data traffic is transmitted from the relay station, the first antenna group of the relay station is controlled to operate in a transmit Tx phase, and the second antenna group of the relay station is controlled to operate in a receive Rx phase or is not in use, and when downlink data traffic is received in the relay station, the first antenna group of the relay station is controlled to operate in the receive Rx phase, and the second antenna group of the relay station is controlled to operate in the transmit Tx phase or is not in use.

2. A method according to claim 1, characterized in that the relay station comprises at least two transmit/receive Tx/Rx antennas.

3. A method according to claim 1 or 2, characterized in that a same frequency band is utilized in the relay station for transmission and reception.

4. A method according to claim 1 or 2, characterized in that a different frequency band is utilized in the relay station for transmission and reception.

5. A method according to claim 1 or 2, characterized in that a different frequency band is utilized in the relay station for transmission and reception of the control information and a same frequency band is utilized in the relay station for transmission and reception of data.

6. A method as claimed in any one of the preceding claims, characterized in that the method comprises configuring antennas into two modes, wherein in mode 1 , each of the antennas is configured to operate either in the transmit Tx phase or in the receive Rx phase, and in mode 2, at least one antenna operates in the transmit Tx phase and at least one other antenna operates in the receive Rx phase.

7. A method as claimed in claim 6, characterized in that when the relay station is transmitting and/or receiving data, only one of the modes is used at a time.

8. A method as claimed in any one of the preceding claims, characterized in that usage of the antennas depends on the radiation patterns in relation to a direction of traffic stream such that uplink and downlink traffic utilize available antennas in a different way.

9. A method as claimed in any one of the preceding claims, characterized in that the method applies dynamic scheduling such that antenna usage changes dynamically based on a direction of data stream.

10. A method as claimed in any one of the preceding claims, characterized in that a decision on a selected relay station mode is made in a base station.

11. A method as claimed in any one of the preceding claims, characterized in that a decision on a selected relay station mode is made in a semi-static or dynamic manner.

12. A method as claimed in any one of the preceding claims, characterized in that a relay station mode is selected for an entire subframe, radio frame or other predefined time duration.

13. A method as claimed in any one of the preceding claims 1-11, characterized in that a relay station mode is selected separately for a control part and a data part of a subframe.

14. A method as claimed in any one of the preceding claims, characterized in that a relay station mode is selected in a channel specific manner, wherein the relay station temporarily uses half-duplex mode even if it has been configured to use full-duplex mode, or vice versa.

15. A method as claimed in any one of the preceding claims, characterized in that a frame may be divided into a data part and a control part, wherein it is possible to allocate the data part and the control part with different relay station modes.

16. A method as claimed in any one of the preceding claims, characterized in that a relay station mode is selected based on a ratio of uplink traffic and downlink traffic, wherein mode 1 is selected if |uplink traffic - downlink traff ic| < a predefined threshold value, and mode 2 is selected if |uplink traffic - downlink traff ic| > the predefined threshold value.

17. A method according to claim 16, characterized in that the predefined threshold value is set based on traffic load, traffic type, and/or interference conditions.

18. A method as claimed in any one of the preceding claims, characterized in that a relay station forwarding time is selected based on a selected relay station mode, wherein reception initiates forwarding transmission without separate triggering or resource allocation.

19. A method as claimed in any one of the preceding claims, characterized in that dedicated higher layer signalling is used to configure a relay station mode.

20. A method as claimed in any one of the preceding claims, characterized in that if a relay station mode is selected dynamically, it is possible to use a scheduling grant and/or absence of the scheduling grant to indicate the applied relay station mode.

21. An apparatus comprising at least one processor; and at least one memory including a computer program code, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus (601 , 602) to perform any of the method steps of claims 1 to 20.

22. A computer program product comprising program instructions which, when run on a computing apparatus, causes the computing apparatus to perform a method according to any one of the claims 1 to 20.