Method and apparatus for addressing self-interference components

Abstract

A method comprising initiating, by a UE, an UL MiMo configuration for a plurality of MiMo layers, wherein said UE comprises at least a first antenna in a first transmission branch and a second antenna in a second transmission branch; determining a first Signal-to-Interference Ratio (SIR) value at an output of an amplifier of the second transmission branch as an output power level of a second signal at the amplifier of the second transmission branch deducted by a power level of a first signal radiated from the first antenna and coupled to the output of the amplifier of the second transmission branch; comparing the first SIR value to a first predetermined threshold value of SINR; adjusting, in response to the first SIR value being lower than said first predetermined threshold value of SINR, an attenuator in the second transmission branch to a higher attenuation value; and increasing an amplification of the amplifier of the second transmission branch to compensate for the higher attenuation value

Description

METHOD AND APPARATUS FOR ADDRESSING SELFINTERFERENCE COMPONENTSTECHNICAL FIELD

[0001] The present invention relates to addressing self-interference components.BACKGROUND

[0002] In user equipment (UE) implementation, multi carrier UL transmission at the same frequency (i.e. uplink Multiple Input Multiple Output; UL-MiMo) may involve individual UL power control for each configured UL MiMo layer to compensate for power imbalance between the different antenna ports (AP) at the UE. These power imbalances are partly coming from the multi-layer channel between the network node (gNB) and the UE, but also from the antenna characteristics of the antennas implemented on a real UE, which are far from isotropic with perfect orthogonal behavior, as typically used for simulation within 3 GPP. The antenna characteristics of each UE antenna differ at least in terms of total radiation efficiency, directivity and angular direction of the maximum gain. Such differences in antenna characteristics will result in increased Signal-to-Interference+Noise Ratio (SINR) imbalance at the gNB for the different UL MiMo layers. Moreover, the use scenarios (a user holding the UE) typically increase antenna gain differences between the antennas of the UE.

[0003] Per MiMO layer power control, which could be implemented as single codeword (common modulation and coding scheme; MCS) or multi codeword (layer-specific MCSs) approach, enables the UE to adjust transmission (Tx) power levels of each UL MiMo layer individually, thereby improving the SINR imbalance at the gNB.

[0004] However, allowing the UE to increase the power level of a first UL MiMo layer transmitted at a first Tx branch might cause UL-to-UL self-interference at a second UL MiMo layer transmitted at a second Tx branch at a lower power level.SUMMARY

[0005] Now, an improved method and technical equipment implementing the method has been invented, by which the above problems are alleviated. Various aspects include amethod, an apparatus and a non-transitory computer readable medium comprising a computer program, or a signal stored therein, which are characterized by what is stated in the independent claims. Various details of the embodiments are disclosed in the dependent claims and in the corresponding images and description.

[0006] The scope of protection sought for various embodiments of the invention is set out by the independent claims. The embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention.

[0007] According to a first aspect, there is provided an apparatus comprising at least a first antenna in a first transmission branch and a second antenna in a second transmission branch: means for initiating an uplink Multiple Input Multiple Output (UL MiMo) configuration for a plurality of MiMo layers; means for determining a first Signal-to-Interference Ratio (SIR) value at an output of an amplifier of the second transmission branch as an output power level of a second signal at the amplifier of the second transmission branch deducted by a power level of a first signal radiated from the first antenna and coupled to the output of the amplifier of the second transmission branch; means for comparing the first SIR value to a first predetermined threshold value of Signal-to-Interference+Noise Ratio (SINR); means for adjusting, in response to the first SIR value being lower than said first predetermined threshold value of SINR, an attenuator in the second transmission branch to a higher attenuation value; and means for increasing an amplification of the amplifier of the second transmission branch to compensate for the higher attenuation value.

[0008] According to an embodiment, the apparatus comprises means for determining whether said amplifier has sufficient power headroom to compensate for the higher attenuation value; and if affirmative, activating said means for adjusting the attenuator and means for increasing the amplification.

[0009] According to an embodiment, the apparatus comprises means for measuring a current level of antenna coupling between the first and second antennas; means for determining a pathloss towards a network node for the first and second antennas; means for determining a power imbalance level between the first and the second signal; and meansfor determining a second threshold value for power level difference between the first and the second signal.

[0010] According to an embodiment, among at least the first transmission branch and the second transmission branch, the second transmission branch has a lowest pathloss value.

[0011] According to an embodiment, the first predetermined threshold value of SINK is at least partly based on a modulation and coding scheme (MCS) currently allocated to the apparatus.

[0012] According to an embodiment, the apparatus comprises a digital predistortion (DPD) unit, and the first predetermined threshold value of SINK is at least partly based on current parameter values of the DPD unit.

[0013] According to an embodiment, the apparatus comprises means for determining a second Signal-to-Interference Ratio (SIR) value from a radiated signal of the second antenna as a radiated power level of the second signal at the second antenna deducted by the power level of the first signal coupled to and reflected from the second antenna.

[0014] According to an embodiment, the apparatus comprises means for comparing the second SIR value to the first predetermined threshold value of SINR; and means for adjusting, in response to the second SIR value being lower than said first predetermined threshold value of SINR, the level of reflected power at the second antenna by matching an impedance of the second antenna closer to 50 Q.

[0015] According to an embodiment, the apparatus comprises means for determining whether impedance matching of the second antenna can be improved; and if affirmative, activating said means for adjusting the level of antenna coupling.

[0016] According to an embodiment, the apparatus comprises an adjustable attenuator in each transmission branch.

[0017] An apparatus according to a second aspect comprises at least a first antenna in a first transmission branch and a second antenna in a second transmission branch, at least one processor and at least one memory, said at least one memory stored with computer program code thereon, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform: initiate an uplink Multiple Input Multiple Output (UL MiMo) configuration for a plurality of MiMo layers;determine a first Signal-to-Interference Ratio (SIR) value at an output of an amplifier of the second transmission branch as an output power level of a second signal at the amplifier of the second transmission branch deducted by a power level of a first signal radiated from the first antenna and coupled to the output of the amplifier of the second transmission branch; compare the first SIR value to a first predetermined threshold value of Signal-to-Interference+Noise Ratio (SINR); adjust, in response to the first SIR value being lower than said first predetermined threshold value of SINR, an attenuator in the second transmission branch to a higher attenuation value; and increase an amplification of the amplifier of the second transmission branch to compensate for the higher attenuation value.

[0018] The method according to a third aspect comprises initiating, by a user equipment (UE), an uplink Multiple Input Multiple Output (UL MiMo) configuration for a plurality of MiMo layers, wherein said UE comprises at least a first antenna in a first transmission branch and a second antenna in a second transmission branch; determining a first Signal-to-Interference Ratio (SIR) value at an output of an amplifier of the second transmission branch as an output power level of a second signal at the amplifier of the second transmission branch deducted by a power level of a first signal radiated from the first antenna and coupled to the output of the amplifier of the second transmission branch; comparing the first SIR value to a first predetermined threshold value of Signal-to-Interference+Noise Ratio (SINR); adjusting, in response to the first SIR value being lower than said first predetermined threshold value of SINR, an attenuator in the second transmission branch to a higher attenuation value; and increasing an amplification of the amplifier of the second transmission branch to compensate for the higher attenuation value.

[0019] Computer readable storage media according to further aspects comprise code for use by an apparatus, which when executed by a processor, causes the apparatus to perform the above methods.BRIEF DESCRIPTION OF THE DRAWINGS

[0020] For a more complete understanding of the example embodiments, reference is now made to the following descriptions taken in connection with the accompanying drawings in which:

[0021] Fig. 1 shows a schematic block diagram of an apparatus for incorporating a system information acquisition according to the embodiments;

[0022] Fig. 2 shows schematically a layout of an apparatus according to an example embodiment;

[0023] Fig. 3 shows a part of an exemplifying radio access network;

[0024] Fig. 4 illustrates a high-level categorization of the different types of Downlink MI MO schemes in 5G NR;

[0025] Figs. 5a and 5b show exemplifying simulations of antenna gain differences between four antennas implemented on a UE for a Free Space (FS) scenario at 2600 MHz and a use case including the right hand (RH) grip of a user, respectively;

[0026] Fig. 6 shows a flow chart for addressing self-interference according to an embodiment;

[0027] Fig. 7 shows an example of detecting two different self-interference contributions in a Tx branch of an UE;

[0028] Fig. 8 shows an example of a UE implementation with two Tx branches and the resulting UL-to-UL self-interference contributions upon UL MiMo configuration for at least two MiMo layers according to an embodiment;

[0029] Fig. 9 shows a flow chart for addressing a first self-interference component according to an embodiment; and

[0030] Figs. 10a and 10b show flow chart for addressing two self-interference components according to an embodiment.DETAILED DESCRIPTON OF SOME EXAMPLE EMBODIMENTS

[0031] The following describes in further detail suitable apparatus and possible mechanisms carrying out the invention and the embodiments. While the following focuses on 5G networks, the embodiments as described further below are by no means limited to be implemented in said networks only, but they are applicable in any network supporting system information acquisition, especially 6G and any future generation networks.

[0032] In this regard, reference is first made to Figures 1 and 2, where Figure 1 shows a schematic block diagram of an exemplary apparatus, such as an electronic device 50, which may incorporate the arrangement according to the embodiments. Figure 2 shows alayout of an apparatus according to an example embodiment. The elements of Figs. 1 and 2 will be explained next.

[0033] The apparatus 50 may for example be a mobile terminal or user equipment of a wireless communication system. The apparatus 50 may comprise a housing 30 for incorporating and protecting the device. The apparatus 50 further may comprise a display 32 and a keypad 34. Instead of the keypad, the user interface may be implemented as a virtual keyboard or data entry system as part of a touch-sensitive display.

[0034] The apparatus may comprise a microphone 36 or any suitable audio input which may be a digital or analogue signal input. The apparatus 50 may further comprise an audio output device, such as anyone of: an earpiece 38, speaker, or an analogue audio or digital audio output connection. The apparatus 50 may also comprise a battery 40 (or the device may be powered by any suitable mobile energy device such as solar cell, fuel cell or clockwork generator). The apparatus may further comprise a camera 42 capable of recording or capturing images and / or video. The apparatus 50 may further comprise an infrared port 41 for short range line of sight communication to other devices. In other embodiments the apparatus 50 may further comprise any suitable short-range communication solution such as for example a Bluetooth wireless connection or a USB / firewire wired connection.

[0035] The apparatus 50 may comprise a controller 56 or processor for controlling the apparatus 50. The controller 56 may be connected to memory 58 which may store both user data and instructions for implementation on the controller 56. The memory may be random access memory (RAM) and / or read only memory (ROM). The memory may store computer-readable, computer-executable software including instructions that, when executed, cause the controller / processor to perform various functions described herein. In some cases, the software may not be directly executable by the processor but may cause a computer (e.g., when compiled and executed) to perform functions described herein. The controller 56 may further be connected to codec circuitry 54 suitable for carrying out coding and decoding of audio and / or video data or assisting in coding and decoding carried out by the controller.

[0036] The apparatus 50 may comprise radio interface circuitry 52 connected to the controller and suitable for generating wireless communication signals for example forcommunication with a cellular communications network, a wireless communications system or a wireless local area network. The apparatus 50 may further comprise an antenna 44 connected to the radio interface circuitry 52 for transmitting radio frequency signals generated at the radio interface circuitry 52 to other apparatus(es) and for receiving radio frequency signals from other apparatus(es).

[0037] In the following, different exemplifying embodiments will be described using, as an example of an access architecture to which the embodiments may be applied, a radio access architecture based on Long Term Evolution Advanced (LTE Advanced, LTE-A) or new radio (NR, 5G), without restricting the embodiments to such an architecture, however. A person skilled in the art appreciates that the embodiments may also be applied to other kinds of communications networks having suitable means by adjusting parameters and procedures appropriately. Some examples of other options for suitable systems are the universal mobile telecommunications system (UMTS) radio access network (UTRAN or E-UTRAN), long term evolution (LTE, the same as E-UTRA), wireless local area network (WLAN or WiFi), worldwide interoperability for microwave access (WiMAX), Bluetooth®, personal communications services (PCS), ZigBee®, wideband code division multiple access (WCDMA), systems using ultra-wideband (UWB) technology, sensor networks, mobile ad-hoc networks (MANETs) and Internet protocol multimedia subsystems (IMS) or any combination thereof.

[0038] Figure 3 depicts examples of simplified system architectures only showing some elements and functional entities, all being logical units, whose implementation may differ from what is shown. The connections shown in Figure 3 are logical connections; the actual physical connections may be different. It is apparent to a person skilled in the art that the system typically comprises also other functions and structures than those shown in Figure 3. The embodiments are not, however, restricted to the system given as an example but a person skilled in the art may apply the solution to other communication systems provided with necessary properties.

[0039] The example of Figure 3 shows a part of an exemplifying radio access network.

[0040] Figure 3 shows user devices 300 and 302 configured to be in a wireless connection on one or more communication channels in a cell with an access node (such as (e / g)NodeB) 304 providing the cell. The physical link from a user device to a (e / g)NodeBis called uplink or reverse link and the physical link from the (e / g)NodeB to the user device is called downlink or forward link. It should be appreciated that (e / g)NodeBs or their functionalities may be implemented by using any node, host, server or access point etc. entity suitable for such a usage.

[0041] A communication system typically comprises more than one (e / g)NodeB in which case the (e / g)NodeBs may also be configured to communicate with one another over links, wired or wireless, designed for the purpose. These links may be used for signaling purposes. The (e / g)NodeB is a computing device configured to control the radio resources of communication system it is coupled to. The NodeB may also be referred to as a base station, an access point or any other type of interfacing device including a relay station capable of operating in a wireless environment. The (e / g)NodeB includes or is coupled to transceivers. From the transceivers of the (e / g)NodeB, a connection is provided to an antenna unit that establishes bi-directional radio links to user devices. The antenna unit may comprise a plurality of antennas or antenna elements. The (e / g)NodeB is further connected to core network 310 (CN or next generation core NGC). Depending on the system, the counterpart on the CN side can be a serving gateway (S-GW, routing and forwarding user data packets), packet data network gateway (P-GW), for providing connectivity of user devices (UEs) to external packet data networks, or mobile management entity (MME), etc. The CN may comprise network entities or nodes that may be referred to management entities. Examples of the network entities comprise at least an Access and Mobility Management Function (AMF).

[0042] The user device (also called a user equipment (UE), a user terminal, a terminal device, a wireless device, a mobile station (MS) etc.) illustrates one type of an apparatus to which resources on the air interface are allocated and assigned, and thus any feature described herein with a user device may be implemented with a corresponding network apparatus, such as a relay node, an eNB, and an gNB. An example of such a relay node is a layer 3 relay (self-backhauling relay) towards the base station.

[0043] The user device typically refers to a portable computing device that includes wireless mobile communication devices operating with or without a subscriber identification module (SIM), including, but not limited to, the following types of devices: a mobile station (mobile phone), smartphone, personal digital assistant (PDA), handset,device using a wireless modem (alarm or measurement device, etc.), laptop and / or touch screen computer, tablet, game console, notebook, and multimedia device. It should be appreciated that a user device may also be a nearly exclusive uplink only device, of which an example is a camera or video camera loading images or video clips to a network. A user device may also be a device having capability to operate in Internet of Things (loT) network which is a scenario in which objects are provided with the ability to transfer data over a network without requiring human-to-human or human-to-computer interaction. Accordingly, the user device may be an loT-device. The user device may also utilize cloud. In some applications, a user device may comprise a small portable device with radio parts (such as a watch, earphones or eyeglasses) and the computation is carried out in the cloud. The user device (or in some embodiments a layer 3 relay node) is configured to perform one or more of user equipment functionalities. The user device may also be called a subscriber unit, mobile station, remote terminal, access terminal, user terminal or user equipment (UE) just to mention but a few names or apparatuses.

[0044] Various techniques described herein may also be applied to a cyber-physical system (CPS) (a system of collaborating computational elements controlling physical entities). CPS may enable the implementation and exploitation of massive amounts of interconnected ICT devices (sensors, actuators, processors microcontrollers, etc.) embedded in physical objects at different locations. Mobile cyber physical systems, in which the physical system in question has inherent mobility, are a subcategory of cyberphysical systems. Examples of mobile physical systems include mobile robotics and electronics transported by humans or animals.

[0045] Additionally, although the apparatuses have been depicted as single entities, different units, processors and / or memory units (not all shown in Fig. 1) may be implemented.

[0046] 5G enables using multiple input - multiple output (MIMO) antennas, many more base stations or nodes than the LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and employing a variety of radio technologies depending on service needs, use cases and / or spectrum available. The access nodes of the radio network form transmission / reception (TX / Rx) points (TRPs), and the UEs are expected to access networks of at least partly overlapping multi-TRPs, such asmacro-cells, small cells, pico-cells, femto-cells, remote radio heads, relay nodes, etc. The access nodes may be provided with Massive MIMO antennas, i.e. very large antenna array consisting of e.g. hundreds of antenna elements, implemented in a single antenna panel or in a plurality of antenna panels, capable of using a plurality of simultaneous radio beams for communication with the UE. The UEs may be provided with MIMO antennas having an antenna array consisting of e.g. dozens of antenna elements, implemented in a single antenna panel or in a plurality of antenna panels. Thus, the UE may access one TRP using one beam, one TRP using a plurality of beams, a plurality of TRPs using one (common) beam or a plurality of TRPs using a plurality of beams.

[0047] The 4G / LTE networks support some multi-TRP schemes, but in 5G NR the multi-TRP features are enhanced e.g. via transmission of multiple control signals via multi-TRPs, which enables to improve link diversity gain. Moreover, high carrier frequencies (e.g., mmWaves) together with the Massive MIMO antennas require new beam management procedures for multi-TRP technology.

[0048] 5G mobile communications supports a wide range of use cases and related applications including video streaming, augmented reality, different ways of data sharing and various forms of machine type applications (such as (massive) machine-type communications (mMTC), including vehicular safety, different sensors and real-time control. 5G is expected to have multiple radio interfaces, namely below 6GHz, cmWave and mmWave, and also capable of being integrated with existing legacy radio access technologies, such as the LTE. Integration with the LTE may be implemented, at least in the early phase, as a system, where macro coverage is provided by the LTE and 5G radio interface access comes from small cells by aggregation to the LTE. In other words, 5G is planned to support both inter-RAT operability (such as LTE-5G) and inter-RI operability (inter-radio interface operability, such as below 6GHz - cmWave, below 6GHz - cmWave - mmWave). One of the concepts considered to be used in 5G networks is network slicing in which multiple independent and dedicated virtual sub-networks (network instances) may be created within the same infrastructure to run services that have different requirements on latency, reliability, throughput and mobility.

[0049] Frequency bands for 5G NR are separated into two frequency ranges: Frequency Range 1 (FR1) including sub-6 GHz frequency bands, i.e. bands traditionally used byprevious standards, but also new bands extended to cover potential new spectrum offerings from 410 MHz to 7125 MHz, and Frequency Range 2 (FR2) including frequency bands from 24.25 GHz to 52.6 GHz. Thus, FR2 includes the bands in the mmWave range, which due to their shorter range and higher available bandwidth require somewhat different approach in radio resource management compared to bands in the FR1.

[0050] The current architecture in LTE networks is fully distributed in the radio and fully centralized in the core network. The low latency applications and services in 5G require to bring the content close to the radio which leads to local break out and multiaccess edge computing (MEC). 5G enables analytics and knowledge generation to occur at the source of the data. This approach requires leveraging resources that may not be continuously connected to a network such as laptops, smartphones, tablets and sensors. MEC provides a distributed computing environment for application and service hosting. It also has the ability to store and process content in close proximity to cellular subscribers for faster response time. Edge computing covers a wide range of technologies such as wireless sensor networks, mobile data acquisition, mobile signature analysis, cooperative distributed peer-to-peer ad hoc networking and processing also classifiable as local cloud / fog computing and grid / mesh computing, dew computing, mobile edge computing, cloudlet, distributed data storage and retrieval, autonomic self-healing networks, remote cloud services, augmented and virtual reality, data caching, Internet of Things (massive connectivity and / or latency critical), critical communications (autonomous vehicles, traffic safety, real-time analytics, time-critical control, healthcare applications).

[0051] The communication system is also able to communicate with other networks, such as a public switched telephone network or the Internet 312, or utilize services provided by them. The communication network may also be able to support the usage of cloud services, for example at least part of core network operations may be carried out as a cloud service (this is depicted in Fig. 3 by “cloud” 314). The communication system may also comprise a central control entity, or a like, providing facilities for networks of different operators to cooperate for example in spectrum sharing.

[0052] Edge cloud may be brought into radio access network (RAN) by utilizing network function virtualization (NFV) and software defined networking (SDN). Using edge cloud may mean access node operations to be carried out, at least partly, in a server,host or node operationally coupled to a remote radio head or base station comprising radio parts. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. Application of cloudRAN architecture enables RAN real time functions being carried out at the RAN side (in a distributed unit, DU) and non-real time functions being carried out in a centralized manner (in a centralized unit, CU 308).

[0053] It should also be understood that the distribution of labor between core network operations and base station operations may differ from that of the LTE or even be nonexistent. Some other technology advancements probably to be used are Big Data and all-IP, which may change the way networks are being constructed and managed. 5G (or new radio, NR) networks are being designed to support multiple hierarchies, where MEC servers can be placed between the core and the base station or nodeB (gNB). It should be appreciated that MEC can be applied in 4G networks as well. The gNB is a next generation Node B (or, new Node B) supporting the 5G network (i.e., the NR).

[0054] 5G may also utilize non-terrestrial nodes 306, e.g. access nodes, to enhance or complement the coverage of 5G service, for example by providing backhauling, wireless access to wireless devices, service continuity for machine-to-machine (M2M) communication, service continuity for Internet of Things (loT) devices, service continuity for passengers on board of vehicles, ensuring service availability for critical communications and / or ensuring service availability for future railway / maritime / aeronautical communications. The non-terrestrial nodes may have fixed positions with respect to the Earth surface or the non-terrestrial nodes may be mobile nonterrestrial nodes that may move with respect to the Earth surface. The non-terrestrial nodes may comprise satellites and / or HAPSs. Satellite communication may utilize geostationary earth orbit (GEO) satellite systems, but also low earth orbit (LEO) satellite systems, in particular mega-constellations (systems in which hundreds of (nano)satellites are deployed). Each satellite in the mega-constellation may cover several satellite-enabled network entities that create on-ground cells. The on-ground cells may be created through an on-ground relay node 304 or by a gNB located on-ground or in a satellite.

[0055] A person skilled in the art appreciates that the depicted system is only an example of a part of a radio access system and in practice, the system may comprise a plurality of (e / g)NodeBs, the user device may have an access to a plurality of radio cellsand the system may comprise also other apparatuses, such as physical layer relay nodes or other network elements, etc. At least one of the (e / g)NodeBs or may be a Home(e / g)nodeB. Additionally, in a geographical area of a radio communication system a plurality of different kinds of radio cells as well as a plurality of radio cells may be provided. Radio cells may be macro cells (or umbrella cells) which are large cells, usually having a diameter of up to tens of kilometers, or smaller cells such as micro-, femto- or picocells. The (e / g)NodeBs of Fig. 1 may provide any kind of these cells. A cellular radio system may be implemented as a multilayer network including several kinds of cells. Typically, in multilayer networks, one access node provides one kind of a cell or cells, and thus a plurality of (e / g)NodeBs are required to provide such a network structure.

[0056] For fulfilling the need for improving the deployment and performance of communication systems, the concept of “plug-and-play” (e / g)NodeBs has been introduced. Typically, a network which is able to use “plug-and-play” (e / g)Node Bs, includes, in addition to Home (e / g)NodeBs (H(e / g)nodeBs), a home node B gateway, or HNB-GW (not shown in Fig. 1). A HNB Gateway (HNB-GW), which is typically installed within an operator’s network may aggregate traffic from a large number of HNBs back to a core network.

[0057] The Radio Resource Control (RRC) protocol is used in various wireless communication systems for defining the air interface between the UE and a base station, such as eNB / gNB. This protocol is specified by 3GPP in in TS 36.331 for LTE and in TS 38.331 for 5G. In terms of the RRC, the UE may operate in LTE and in 5G in an idle mode or in a connected mode, wherein the radio resources available for the UE are dependent on the mode where the UE at present resides. In 5G, the UE may also operate in inactive mode. In the RRC idle mode, the UE has no connection for communication, but the UE is able to listen to page messages. In the RRC connected mode, the UE may operate in different states, such as CELL DCH (Dedicated Channel), CELL FACH (Forward Access Channel), CELL PCH (Cell Paging Channel) and URA PCH (URA Paging Channel). The UE may communicate with the eNB / gNB via various logical channels like Broadcast Control Channel (BCCH), Paging Control Channel (PCCH), Common Control Channel (CCCH), Dedicated Control Channel (DCCH), Dedicated Traffic Channel (DTCH).

[0058] The transitions between the states are controlled by a state machine of the RRC. When the UE is powered up, it is in a disconnected mode / idle mode. The UE may transit to RRC connected mode with an initial attach or with a connection establishment. If there is no activity from the UE for a short time, eNB / gNB may suspend its session by moving to RRC Inactive and can resume its session by moving to RRC connected mode. The UE can move to the RRC idle mode from the RRC connected mode or from the RRC inactive mode.

[0059] The actual user and control data from network to the UEs is transmitted via downlink physical channels, which in 5G include Physical downlink control channel (PDCCH) which carries the necessary downlink control information (DCI), Physical Downlink Shared Channel (PDSCH), which carries the user data and system information for user, and Physical broadcast channel (PBCH), which carries the necessary system information to enable a UE to access the 5G network.

[0060] The user and control data from UE to the network is transmitted via uplink physical channels, which in 5G include Physical Uplink Control Channel (PUCCH), which is used for uplink control information including HARQ feedback acknowledgments, scheduling request, and downlink channel-state information for link adaptation, Physical Uplink Shared Channel (PUSCH), which is used for uplink data transmission, and Physical Random Access Channel (PRACH), which is used by the UE to request connection setup referred to as random access.

[0061] For the 5G technology and for further generations, such as 6G, one of the most important design goals has been improved metrics of reliability and latency, in addition to network resilience and flexibility.

[0062] Especially when considering the operating of the UE in the Frequency Range 2 (FR2; 24.25 GHz to 52.6 GHz) including the mmWave range, the UE implementation is expected to have multiple antenna panels (Multi-Panel UE, MPUE) to perform beam steering over a large solid angle aiming to maximize the reliability.

[0063] In FR2, both gNB and UE are expected to operate using “narrow” beams meaning that gNB operates using radiation patterns narrower than sector-wide beams and UE operates using radiation patterns narrower than omni-directional beams. Beamformed data transmission is realized by transmitting the signal from all the elements in the antennaarray in the desired direction by applying an amplitude and phase precoding / beamforming weights, i.e., beam-weights. Beamformed transmission from large antenna array in massive MIMO of a network element, such as a base station (gNb), provides improved signal strength to the desired user equipment (UE) but may create significant interference to other UEs, if the beams create unwanted interference in the direction of the other UEs.

[0064] Figure 4 illustrates a high-level categorization of the different types of Downlink MIMO schemes in 5G NR, where the downlink MIMO schemes are categorized into Single-User MIMO schemes (SU-MIMO) or Multi-User MIMO schemes (MU-MIMO). The SU-MIMO schemes are typically either Sounding Reference Signal (SRS) based, or Channel State Information-Reference Signal (CSI-RS) based with Precoding Matrix Indicator (PMI) feedback from UE (the CSI-RS can be either precoded / beamformed or non-pr ecoded). It can also be based on grid-of-beams sweep with reference signal received power (RSRP) feedback. SRS-based schemes have typically been discarded in practical live networks (since most UEs are typically implemented with more parallel receiver chains than transmitter chains), leaving mainly deployment to use the CSI-RS based schemes. However, SRS-based schemes are expected to become more popular with large arrays deployed in the upper FR1 TDD bands and in the new bands expected for 6G (7GHz and 15GHz). The CSI-RS-based SU-MIMO schemes can use a Type I codebook, which is based on very specific antenna assumptions at gNB with a fully pre-characterized lookup table of precoding values.

[0065] On the other hand, typical DL MU-MIMO schemes are also based on either SRS or precoded / non-precoded CSI-RS. However, for MU-MIMO transmission, the Type II codebook can provide better performance than the Type I codebook due to a more accurate matching of the precoding to the radio channel, however, Type II has not yet been deployed in live networks so far.

[0066] Regarding the current UL-MIMO procedure, multi carrier UL transmission at the same frequency (UL-MiMo) may involve individual UL power control for each configured UL MiMo layer to compensate for power imbalance between the different Antenna Ports (AP) at the UE. These power imbalances are partly coming from the multilayer channel between the gNB and the UE, but also from the antenna characteristics of the antennas implemented on a real UE, which are far from isotropic with perfect orthogonalbehavior, as typically used for simulation within 3 GPP. In addition, the antenna characteristics of each UE antenna differ at least in terms of total radiation efficiency, directivity and angular direction of the maximum gain. Such differences in antenna characteristics will result in increased Signal-to-Interference+Noise Ratio (SINR) imbalance at the gNB for the different UL MiMo layers. Moreover, the use scenarios (a user holding the UE) typically increase antenna gain differences between the antennas of the UE.

[0067] Figures 5a and 5b illustrate exemplifying simulations of antenna gain differences between four antennas implemented on a UE for a Free Space (FS) scenario at 2600 MHz and a use case including the right hand (RH) grip of a user, respectively. Among the three curves in both figures, the curve on the left shows the antenna gain difference when selecting the best two antennas out of four for each angular direction. The curves in the middle depict selecting the best three antennas out of four, and the curves on the right are with all four antennas in usage.

[0068] In these examples, the antenna gain differences are between 1.5 dB to 5.5 dB for 50thpercentile for FS (Fig. 5a) and between 2 dB and 17 dB when including the hand of the user (Fig. 5b). It is noted that left curves (i.e. selection of the best two out of four antennas) in Figures 5a and 5b are best-case scenarios, provided that the UE is always capable of selecting the best two antennas. This will require special antenna switching capabilities and RF architecture, which do not exist in all UEs. Such UEs will have even larger variation of antenna gain values across ports and can be expected to have performances comparable to selecting 3 antennas out of four (curves in the middle).

[0069] It is noted that such power difference values are significant. One option for addressing this problem would be using per MiMO layer power control. Per MiMO layer power control, which could be implemented as single codeword (common MCS) or multi codeword (layer-specific MCSs) approach, enables the UE to adjust Tx power levels of each UL MiMo layer individually, thereby improving the SINR imbalance at the gNB.

[0070] However, allowing the UE to increase the power level of a first UL MiMo layer transmitted at a first Tx branch might cause UL-to-UL self-interference at a second UL MiMo layer transmitted at a second Tx branch at a lower power level.

[0071] The level of such self-interference will depend on the antenna characteristics of the configured antennas at the UE, and it can be illustrated by the following example. Let us assume that the configured Po level at the gNB is -80 dBm, which means that all UEs connected to said gNB will adjust their UL power to reach that received power level at the gNB (for open-loop power control). A multi antenna port UE connected to a gNB will adjust the power level of its best link (typically based on DL reference signal measurements), which will most likely be the antenna with the highest gain value (directivity) towards the gNB to fulfill the Po requirement of the gNB. The antenna with the second highest antenna gain value towards the gNB will most likely be used for the second best link. As illustrated in Figures 5a and 5b, the second highest antenna gain value may in best case be almost comparable to the best link, but on the other hand, it may in worst cases be up to 15 dB worse than the best link, when the same power amplifier (PA) power level is used for both links.

[0072] The difference of the first and second UE antenna gain towards the gNB for a given angular direction is addressed by the UE with a PA power boost for the second MiMo layer to ensure SINK balance at the gNB. The strength of this power boost will depend on the radiation patterns of the configured antennas for the two-layer UL MiMo transmission. The channel between the UE and the P-gNB can also contribute to SINK imbalance at the P-gNB.

[0073] While addressing the antenna gain difference as described above seems a straightforward approach, it is noted that it is only valid for a UE with ideal isolation (i.e. no coupling) between the antennas and ideally impedance-matched antennas. However, as mentioned above, real antenna implementations on UEs always have imperfections. UE antennas have a common ground plane (the chassis of the phone), which will induce current coupling between the different antennas on a UE, in addition to the coupling Over-The-Air (OTA).

[0074] The effect on UL-to-UL induced self-interference on SINK at the gNB with coupling between the antennas on the UE and the non-ideal impedance matching of the antennas can be expressed as simplified as:AntennaCoupling< —Required SNR for Selected MCS — Delta Tx Power between Antennas

[0075] Thus, an increase in Delta Tx Power (i.e. the antenna gain difference) will decrease the SINK of the MiMo layer transmitted with lower power for a given coupling between the antennas. The SINR requirement for maximum modulation and coding scheme (MCS) is about 30 dB, which means that having a very low antenna coupling will enable the capability to handle higher delta power values between the two MiMo layers. Handheld devices like smartphones can have antenna couplings ranging from -10 dB to -40 dB depending on the frequency, the physical location of the two antennas and the current influence of the user. As such, the optimal delta Tx power setting for optimal MCS of the two MiMo layers will change dynamically and sometimes be limited by higher antenna coupling.

[0076] In the following, an enhanced method for addressing self-interference will be described in more detail, in accordance with various embodiments.

[0077] The method, which is disclosed in flow chart of Figure 6 as reflecting the operation of a terminal apparatus, such as a user equipment (UE), comprises initiating (600), by a user equipment (UE), an uplink Multiple Input Multiple Output (UL MiMo) configuration for a plurality of MiMo layers, wherein said UE comprises at least a first antenna in a first transmission branch and a second antenna in a second transmission branch; determining (602) a first Signal-to-Interference Ratio (SIR) value at an output of an amplifier of the second transmission branch as an output power level of a second signal at the amplifier of the second transmission branch deducted by a power level of a first signal radiated from the first antenna and coupled to the output of the amplifier of the second transmission branch; comparing (604) the first SIR value to a first predetermined threshold value of Signal-to-Interference+Noise Ratio (SINR); adjusting (606), in response to the first SIR value being lower than said first predetermined threshold value of SINR, an attenuator in the second transmission branch to a higher attenuation value; and increasing (608) an amplification of the amplifier of the second transmission branch to compensate for the higher attenuation value.

[0078] Thus, the UE is configured to determine the UL-to-UL self-interference values between the transmission branches and limit the level of UL-to-UL self-interference upon individual power control of multiple UL MiMo layers. A first contribution of UL-to-UL self-interference relating to a first signal radiated from a first antenna and received at asecond antenna is identified. The resulting Signal-to-Interference Ratio (SIR) contribution may be referred to as SIR1, which is determined at the output of the second power amplifier (PA) of the second transmission (TX) branch and is equal to the output power level of the second signal at the second PA minus the power level of the first signal coupled to the output of the second PA.

[0079] Determining the first contribution of UL-to-UL self-interference can be illustrated by the example of Figure 7. A first signal radiated from a first antenna (Ant#l) and received at a second antenna (Ant#2) will be directed into a second Tx branch connected to the second antenna. This contribution of UL-to-UL self-interference is referred to as Coupled Contribution of Layer# 1 in Figure 7. The power level of the coupled first signal will be present at the output of the PA in the second Tx branch and can affect the linearity of a second wanted and amplified signal, decreasing the SINR level at the gNB. This contribution is especially critical for PA implementation relying on Digital PreDistortion (DPD), which is a typical implementation in UEs.

[0080] Since SIR1 is measured only for a part of the second TX branch, the effect of SIR1 at the second PA is further affected by the implementation loss of the components of the TX branch (typically including e.g. a multiplexing and filter circuitry), which is dependent of the RF Front-End configuration. An adjustable attenuator is used as a part of the signal path of the second TX branch, which enables the UE to increase or decrease SIR1 contribution in the second TX branch.

[0081] According to an embodiment, the method comprises determining, prior to said adjusting, whether said amplifier has sufficient power headroom to compensate for the higher attenuation value; and if affirmative performing said adjusting the attenuator and increasing the amplification.

[0082] Adjusting the attenuation, especially increasing it, may involve ensuring that the PA in the second RF branch has sufficient power headroom to compensate for the added loss to compensate for the radiated level of the second MiMo layer to remain unchanged.

[0083] According to an embodiment, the first predetermined threshold value of SINR is at least partly based on a modulation and coding scheme (MCS) currently allocated to the UE.

[0084] In order to reach high coding efficiency, the gNB typically aims to allocate as high MCS as possible for the UE to enable more useful bits to be transmitted with in a symbol. Thus, the first SIR (SIR1) value is compared to a SINR value, which is required for the currently allocated MCS, and if this threshold cannot be reached by SIR1, the above procedure for adjusting the attenuator and increasing the amplification may be performed.

[0085] According to an embodiment, the UE comprises a digital predistortion (DPD) unit, and the first predetermined threshold value of SINR is at least partly based on current parameter values of the DPD unit.

[0086] Thus, in addition to, or alternatively, to the requirements set by the current MCS, the first predetermined threshold value of SINR may be based on the requirements of the current DPD settings.

[0087] According to an embodiment, the method comprises measuring a current level of antenna coupling between the first and second antennas; determining a pathloss towards a network node for the first and second antennas; determining a power imbalance level between the first and the second signal; and determining a second threshold value for power level difference between the first and the second signal.

[0088] After initiating the UL MiMo configuration for the plurality of MiMo layers, the UE may measure the current level of antenna coupling between the antennas configured for UL MiMo transmission. Then the PathLoss (PL) to the gNB for each of the selected antennas (RF branch) is determined. On the basis of these, the power imbalance level between the first and the second signal is determined, which may be a full power imbalance value or a part of it, depending e.g. on the measured antenna coupling value. Then an appropriate Delta Power Value, i.e. the threshold value for power level difference between the first and the second signal at the first and second antennas, respectively, is determined.

[0089] According to an embodiment, among the at least first transmission branch and the second transmission branch, the second transmission branch has a lowest pathloss value.

[0090] Thus, the pathloss towards the gNB may used as an indicator about the MiMo layer transmitted at lower power and requiring UL-to-UL self-interference components to be addressed.

[0091] According to an embodiment, the method comprises determining a second Signal-to-Interference Ratio (SIR) value from a radiated signal of the second antenna as a radiated power level of the second signal at the second antenna deducted by the power level of the first signal coupled to and reflected from the second antenna.

[0092] Referring back to the example of Figure 7, the second contribution of UL-to-UL self-interference can be determined as a first signal radiated from a first antenna and reflected at a second antenna. This second contribution of UL-to-UL self-interference is referred to as Antenna Reflected Contribution of Layer#! in Figure 7. The power level of the reflected first signal will be present at the radiated second signal from the second antenna. The contribution of the first signal at the radiated second signal will be seen as noise of those portions of the H-matrix (H22 & H21). It affects the SINR at the gNB, since that noise contribution cannot be removed at the receiver side.

[0093] According to an embodiment, the method comprises comparing the second SIR value to the first predetermined threshold value of SINR; and adjusting, in response to the second SIR value being lower than said first predetermined threshold value of SINR, the impedance match of the second antenna closer to 50 Q.

[0094] Thus, the second UL-to-UL interference contribution (SIR2) can be at least reduced by matching the second antenna to 50 Q, whereby, in theory, all the coupled energy from the first antenna received at the second antenna is directed into the second Tx branch. However, while total elimination of SIR2 (i.e. no reflected portion of the coupled energy) may be impossible due to implementation constraints, as explained further below, this will at least reduce the reflected level of the first signal at the second antenna.

[0095] According to an embodiment, the method comprises determining whether impedance matching of the second antenna can be improved; and if affirmative, performing said adjusting the level of antenna coupling.

[0096] Thus, prior to adjusting the level of antenna coupling between the first and second antennas by matching an impedance of the second antenna closer to 50 Q, it is first examined whether the impedance matching of the second antenna can be further improved.

[0097] The method and some of the embodiments are further illustrated by referring to the block chart of Figure 8, which discloses a UE implementation with two Tx branches and the resulting UL-to-UL self-interference contributions upon UL MiMo configurationfor at least two MiMo layers. Both Tx branches comprise a power amplifier (PA) connected to a RF coupler. The signal in both Tx branches goes through a multiplexing (MUX) and filtering unit to the respective antenna (Ant#l, Ant#2). If the power levels of the SIR contributions are expressed in decibels (dB), the SIR contributions in the second Tx branch may be determined as follows:SIR@PA#2 PAtiZpwrPwr ^^^^-RecPwr $IR@Ant#2 Ant#Z RadPwrPA#2 Ant#Z RefPwrPA#lwherein the SIR at the output of the second PA (PA#2), i.e. SIR1, is equal to the output power level of the second signal at the second PA (PA#2pwrPwr) minus the power level of the first signal coupled to the output of the second PA PA#lRecpwr), and the SIR of the radiated signal from the second antenna (Ant#2), i.e. SIR2, is equal to the radiated power level of the second signal at the second antenna (Ant#2RadpwrpA#2) minus the power level of the first signal coupled to and reflected from the second antenna (Ant#2RejpwrpA#i).

[0098] Since the SIR level of the first contribution (SIR1) is at the output of the RF coupler of the second Tx branch and not derived directly at the second antenna, the SIR1 level is affected by the implementation loss of the MUX & filter circuitry in between the second antenna and the RF coupler in the second Tx branch. This is a static loss for a given RF Front End (RFFE) configuration and cannot directly be adjusted as a function of the antenna coupling.

[0099] Now, an adjustable attenuator may be added directly in the signal path of the second TX branch, which will enable the UE to increase or decrease the first SIR1 contribution at the RF coupler in the second TX branch. It is noted that using the adjustable attenuator in the second TX branch relates to the present example, where the (any) second TX branch is considered to have higher antenna gain towards the gNB than the (any) first TX branch, requiring higher PA power level at the first TX branch for SINR power balance at the gNB. Thus, in practical implementations, the adjustable attenuator may be included in all TX branches to address the variations among antenna gains of different Tx branches.

[0100] Increasing the attenuation is preferably carried out only when the PA in the second RF branch has sufficient power headroom the compensate for the added loss, ensuring that the radiated level of the second MiMo layer remains unchanged. Adding aloss by the attenuator and simultaneously increasing the PA output power with the same amount will increase the SIR1 by a factor of two of that value at the output of the PA, reducing the influence of the DPD feedback loop.

[0101] The first UL-to-UL interference contribution, i.e. SIR1 (or SIRPA#2) can be derived as follows:AP#2 Pwr = PA#2 FwdPwr — (Loss RFFE + LossAtt) PA#1 RecPwr = AP#lPwr+ AntCpi- (LOSSRFFE+ LossAtt)SIRPA#2 = kAPPwr~ AntCpl+ 2 * (LOSSRFFE+ LossAtt^where AAPpwr= AP#lpwrAP#2pwr.

[0102] In the above equations, AP#lpwrand AP#2pwrare the output power level of the first and second signal at the first and second antenna port, respectively, as shown in Figure 8. These parameters are known by the UE, as well as PA#lpwrPwr and PA#2pWrPwr, which refer to the output power level of the first and second signal at the first and second PA, respectively. Also the loss of the Mux & Filters (LOSSRFFE) is known for all RFFE configurations.

[0103] The UE can measure the current level of antenna coupling (AntcPi) between the first and second antennas, as well as the power level of the first signal coupled to the output of the second PA (PA#lRecpwr), which can be measured directly at the reverse path of the coupler in the second Tx branch, while the PA in the first Tx branch is activated alone.

[0104] The second SIR contribution SIR2 (or SIRAnt#2) can be derived as follows:Ant$2Rac[PwrPA:~2 AP#2PwrAntH:2Re^PwrPAp^ = AP#lPwr+ AntCpi+ AntH:2M af-cR$IRAnt#2 AAPpwrAntCpi— Ant#2 Match

[0105] Herein, the UE may measure Ant#2Matoh at the reverse path of the coupler in the second Tx branch, while the PA in the second Tx branch is activated alone.

[0106] As mentioned above, the second UL-to-UL interference contribution (SIR@Ant#2) can be reduced by matching the second antenna to 50 Q, whereby all the coupled energy from the first antenna received at the second antenna is theoreticallydirected into the second Tx branch. However, this may be practically impossible due to the bandwidth of the transmitted signal, tuning granularity of the antenna impedance tuners and the Q-factor of the second antenna, whereby this contribution must be derived and taken in account.

[0107] The flow chart of Figure 9 illustrates the method and various embodiments related thereto, where the calibration procedure of the self-interference contribution takes into account only the first UL-to-UL interference contribution, i.e. SIR1 (or SIRPA#2).

[0108] Thus, in the beginning of the calibration procedure, the UE is in RRC connected mode towards the gNB (900). The UE is then requested to initiate (902) an UL MiMo configuration for at least two MiMo layers. The UE measures (904) the current level of antenna coupling between the at least two antennas configured for UL MiMo transmission. Then the PathLoss (PL) to the gNB is derived (906) for each of the selected antennas (RF branches). The UE derives (908) the power imbalance level and determines an appropriate Delta Power Value as the difference of the output power level of the first and second signal at the first and second antenna. The UE then calculates (910) the initial value of SIRPA#2 e.g. using the above equations. The value of SIRPA#2 is compared (912) to the required SINR level of the configured MCS and / or the current DPD requirements. It is checked (914) whether the value of SIRPA#2 is better than the SINR value required for the current allocated MCS or the current DPD requirements. If yes, the UE keeps (916) the current settings of the attenuator in the Tx branch with the lowest measured PL value. If no, it is determined (918) if the current power headroom of the PA is sufficient to compensate for the intended loss value of the attenuator. If yes, the attenuation of the attenuator is increased (920) with a value allowed by the current power headroom of the PA and the amplification of the PA is increased with the same value for the TX branch with the lowest measured PL value. If there is no sufficient power headroom of the PA currently, then the UE is configured to keep (916) the current settings of the attenuator in the Tx branch with the lowest measured PL value.

[0109] The flow chart of Figures 10a and 10b illustrates the method and various embodiments related thereto, where the calibration procedure of the self-interference contribution takes into account both the first UL-to-UL interference contribution, i.e. SIR1 (or SIRPA#2) and second UL-to-UL interference contribution, i.e. SIR2 (or SIRAnt#2).Figures 10a and 10b illustrate the same method as split into two parallel flow charts having common steps indicated by the reference numbers.

[0110] The first steps of the calibration procedure are similar to those of the calibration procedure of Figure 9. Thus, the steps 1000 - 1008 correspond to the steps 900 - 908 of Figure 9. Now the UE measures (1010) the current antenna impedance match of the antenna with the lowest PL to the gNB. The antenna impedance can initially be tuned for broadband operation or be affected by environmental factors like the user or other objects. The UE then calculates (1012) the initial values of SIRPA#2 and SIRAnt#2 e.g. using the above equations. The value of SIRpA#2and SIRAnt#2are compared (1014) to the required SINR level of the configured MCS and / or the current DPD requirements. It is checked (1016, 1018, 1020) whether both or only either of the values of SIRPA#2 and SIRAnt#2 are better than the SINR value required for the current allocated MCS or the current DPD requirements. If the value of SIRPA#2 is better than the SINR value, the UE keeps (1022) the current settings of the attenuator in the Tx branch with the lowest measured PL value. If the value of SIRAnt#2 is better than the SINR value, the UE keeps (1024) the current settings of impedance match of the antenna in the Tx branch with the lowest measured PL value.

[0111] In terms of SIR1 (i.e. SIRPA#2), the final steps in Figure 10a are similar to those of the calibration procedure of Figure 9. Thus, if the value of SIRPA#2 is lower than the SINR value, the UE determines (1026) if the current power headroom of the PA is sufficient to compensate for the intended loss value of the attenuator. If yes, the attenuation of the attenuator is increased (1028) with a value allowed by the current power headroom of the PA and the amplification of the PA is increased with the same value for the TX branch with the lowest measured PL value. If there is no sufficient power headroom of the PA currently, then the UE is configured to keep (1022) the current settings of the attenuator in the Tx branch with the lowest measured PL value.

[0112] In terms of SIR2 (i.e. SIRAnt#2), as shown in Figure 10b, if the value of SIRAnt#2 is lower than the SINR value, the UE determines (1030) if the impedance match of the antenna in the Tx branch with the lowest measured PL value can be further improved. If yes, the UE is configured to improve (1032) the impedance match of the antenna in the Tx branch with the lowest measured PL value to the desired level. If the impedance matchcannot be improved, the UE is configured to keep (1024) the current settings of impedance match of the antenna in the Tx branch with the lowest measured PL value.

[0113] The apparatus, the method and the related embodiments, as described herein, may provide various advantages. The apparatus, the method and the related embodiments enable to equalize the SIR of both self-interference contributions (SIR1 or SIRPA#2 and SIR2 or SIRAnt#2) by matching the impedance of the second antenna and the value of the attenuator to an appropriate level, thus matching the configurated MCS. UL MiMo performance is maintained in case of high antenna coupling when asymmetric power control between UL streams is applied. The method can also be used in a case of equal PA power for both Tx branches, when the antenna coupling is high and the MCS requires high SINR. Moreover, optimum SIR mitigation of both self-interference contributions can be achieved as a function of antenna coupling.

[0114] An apparatus, such as a UE, according to an aspect comprises at least a first antenna in a first transmission branch and a second antenna in a second transmission branch: means for initiating an uplink Multiple Input Multiple Output (UL MiMo) configuration for a plurality of MiMo layers; means for determining a first Signal-to-Interference Ratio (SIR) value at an output of an amplifier of the second transmission branch as an output power level of a second signal at the amplifier of the second transmission branch deducted by a power level of a first signal radiated from the first antenna and coupled to the output of the amplifier of the second transmission branch; means for comparing the first SIR value to a first predetermined threshold value of Signal-to-Interference+Noise Ratio (SINR); means for adjusting, in response to the first SIR value being lower than said first predetermined threshold value of SINR, an attenuator in the second transmission branch to a higher attenuation value; and means for increasing an amplification of the amplifier of the second transmission branch to compensate for the higher attenuation value.

[0115] According to an embodiment, the apparatus comprises means for determining whether said amplifier has sufficient power headroom to compensate for the higher attenuation value; and if affirmative, activating said means for adjusting the attenuator and means for increasing the amplification.

[0116] According to an embodiment, the apparatus comprises means for measuring a current level of antenna coupling between the first and second antennas; means for determining a pathloss towards a network node for the first and second antennas; means for determining a power imbalance level between the first and the second signal; and means for determining a second threshold value for power level difference between the first and the second signal.

[0117] According to an embodiment, among at least the first transmission branch and the second transmission branch, the second transmission branch has a lowest pathloss value.

[0118] According to an embodiment, the first predetermined threshold value of SINK is at least partly based on a modulation and coding scheme (MCS) currently allocated to the apparatus.

[0119] According to an embodiment, the apparatus comprises a digital predistortion (DPD) unit, and the first predetermined threshold value of SINK is at least partly based on current parameter values of the DPD unit.

[0120] According to an embodiment, the apparatus comprises means for determining a second Signal-to-Interference Ratio (SIR) value from a radiated signal of the second antenna as a radiated power level of the second signal at the second antenna deducted by the power level of the first signal coupled to and reflected from the second antenna.

[0121] According to an embodiment, the apparatus comprises means for comparing the second SIR value to the first predetermined threshold value of SINR; and means for adjusting, in response to the second SIR value being lower than said first predetermined threshold value of SINR, the level of reflected power at the second antenna by matching an impedance of the second antenna closer to 50 Q.

[0122] According to an embodiment, the apparatus comprises means for determining whether impedance matching of the second antenna can be improved; and if affirmative, activating said means for adjusting the level of antenna coupling.

[0123] According to an embodiment, the apparatus comprises an adjustable attenuator in each transmission branch.

[0124] An apparatus according to a further aspect comprises at least a first antenna in a first transmission branch and a second antenna in a second transmission branch, at leastone processor and at least one memory, said at least one memory stored with computer program code thereon, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform: initiate an uplink Multiple Input Multiple Output (UL MiMo) configuration for a plurality of MiMo layers; determine a first Signal-to-Interference Ratio (SIR) value at an output of an amplifier of the second transmission branch as an output power level of a second signal at the amplifier of the second transmission branch deducted by a power level of a first signal radiated from the first antenna and coupled to the output of the amplifier of the second transmission branch; compare the first SIR value to a first predetermined threshold value of Signal-to-Interference+Noise Ratio (SINR); adjust, in response to the first SIR value being lower than said first predetermined threshold value of SINR, an attenuator in the second transmission branch to a higher attenuation value; and increase an amplification of the amplifier of the second transmission branch to compensate for the higher attenuation value.

[0125] According to an embodiment, the apparatus comprises code configured to cause the apparatus to determine whether said amplifier has sufficient power headroom to compensate for the higher attenuation value; and if affirmative, perform said adjusting the attenuator and increasing the amplification.

[0126] According to an embodiment, the apparatus comprises code configured to cause the apparatus to measure a current level of antenna coupling between the first and second antennas; determine a pathloss towards a network node for the first and second antennas; determine a power imbalance level between the first and the second signal; and determine a second threshold value for power level difference between the first and the second signal.

[0127] According to an embodiment, among at least the first transmission branch and the second transmission branch, the second transmission branch has a lowest pathloss value.

[0128] According to an embodiment, the first predetermined threshold value of SINR is at least partly based on a modulation and coding scheme (MCS) currently allocated to the apparatus.

[0129] According to an embodiment, the apparatus comprises a digital predistortion (DPD) unit, and the first predetermined threshold value of SINR is at least partly based on current parameter values of the DPD unit.

[0130] According to an embodiment, the apparatus comprises code configured to cause the apparatus to determine a second Signal-to-Interference Ratio (SIR) value from a radiated signal of the second antenna as a radiated power level of the second signal at the second antenna deducted by the power level of the first signal coupled to and reflected from the second antenna.

[0131] According to an embodiment, the apparatus comprises code configured to cause the apparatus to compare the second SIR value to the first predetermined threshold value of SINR; and adjust, in response to the second SIR value being lower than said first predetermined threshold value of SINR, the level of reflected power at the second antenna by matching an impedance of the second antenna closer to 50 Q.

[0132] According to an embodiment, the apparatus comprises code configured to cause the apparatus to determine whether impedance matching of the second antenna can be improved; and if affirmative, perform said adjusting the level of antenna coupling.

[0133] According to an embodiment, the apparatus comprises an adjustable attenuator in each transmission branch.

[0134] A further aspect relates to a computer program product, stored on a non-transitory memory medium, comprising computer program code, which when executed by at least one processor, causes an apparatus comprising at least a first antenna in a first transmission branch and a second antenna in a second transmission branch at least to perform: initiate an uplink Multiple Input Multiple Output (UL MiMo) configuration for a plurality of MiMo layers; determine a first Signal-to-Interference Ratio (SIR) value at an output of an amplifier of the second transmission branch as an output power level of a second signal at the amplifier of the second transmission branch deducted by a power level of a first signal radiated from the first antenna and coupled to the output of the amplifier of the second transmission branch; compare the first SIR value to a first predetermined threshold value of Signal-to-Interference+Noise Ratio (SINR); adjust, in response to the first SIR value being lower than said first predetermined threshold value of SINR, an attenuator in the second transmission branch to a higher attenuation value; and increase an amplification of the amplifier of the second transmission branch to compensate for the higher attenuation value.

[0135] Such apparatuses may comprise e.g. the functional units disclosed in any of the Figures 1- 3, 7 and 8 for implementing the embodiments.

[0136] In general, the various embodiments of the invention may be implemented in hardware or special purpose circuits or any combination thereof. While various aspects of the invention may be illustrated and described as block diagrams or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0137] Embodiments of the inventions may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

[0138] Programs, such as those provided by Synopsys, Inc. of Mountain View, California and Cadence Design, of San Jose, California automatically route conductors and locate components on a semiconductor chip using well established rules of design as well as libraries of pre stored design modules. Once the design for a semiconductor circuit has been completed, the resultant design, in a standardized electronic format (e.g., Opus, GDSII, or the like) may be transmitted to a semiconductor fabrication facility or "fab" for fabrication.

[0139] The foregoing description has provided by way of exemplary and non-limiting examples a full and informative description of the exemplary embodiment of this invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended examples. However, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention.

Claims

CLAIMS1. An apparatus comprising at least a first antenna in a first transmission branch and a second antenna in a second transmission branch:means for initiating an uplink Multiple Input Multiple Output (UL MiMo) configuration for a plurality of MiMo layers;means for determining a first Signal-to-Interference Ratio (SIR) value at an output of an amplifier of the second transmission branch as an output power level of a second signal at the amplifier of the second transmission branch deducted by a power level of a first signal radiated from the first antenna and coupled to the output of the amplifier of the second transmission branch;means for comparing the first SIR value to a first predetermined threshold value of Signal-to-Interference+Noise Ratio (SINR);means for adjusting, in response to the first SIR value being lower than said first predetermined threshold value of SINR, an attenuator in the second transmission branch to a higher attenuation value; andmeans for increasing an amplification of the amplifier of the second transmission branch to compensate for the higher attenuation value.

2. The apparatus according to the claim 1, further comprisingmeans for determining whether said amplifier has sufficient power headroom to compensate for the higher attenuation value; and if affirmativeactivating said means for adjusting the attenuator and means for increasing the amplification.

3. The apparatus according to the claim 1 or 2, further comprisingmeans for measuring a current level of antenna coupling between the first and second antennas;means for determining a pathloss towards a network node for the first and second antennas;means for determining a power imbalance level between the first and the second signal; andmeans for determining a second threshold value for power level difference between the first and the second signal.

4. The apparatus according to the claim 3, wherein among at least the first transmission branch and the second transmission branch, the second transmission branch has a lowest pathloss value.

5. The apparatus according to any preceding claim, wherein the first predetermined threshold value of SINK is at least partly based on a modulation and coding scheme (MCS) currently allocated to the apparatus.

6. The apparatus according to any preceding claim, wherein the apparatus comprises a digital predistortion (DPD) unit, and the first predetermined threshold value of SINK is at least partly based on current parameter values of the DPD unit.

7. The apparatus according to any preceding claim, further comprisingmeans for determining a second Signal -to-Interference Ratio (SIR) value from a radiated signal of the second antenna as a radiated power level of the second signal at the second antenna deducted by the power level of the first signal coupled to and reflected from the second antenna.

8. The apparatus according to claim 7, further comprisingmeans for comparing the second SIR value to the first predetermined threshold value of SINR; andmeans for adjusting, in response to the second SIR value being lower than said first predetermined threshold value of SINR, the level of reflected power at the second antenna by matching an impedance of the second antenna closer to 50 Q.

9. The apparatus according to the claim 8, further comprisingmeans for determining whether impedance matching of the second antenna can be improved; and if affirmativeactivating said means for adjusting the level of antenna coupling.

10. The apparatus according to any preceding claim, further comprising an adjustable attenuator in each transmission branch.

11. A method comprising:initiating, by a user equipment (UE), an uplink Multiple Input Multiple Output (UL MiMo) configuration for a plurality of MiMo layers, wherein said UE comprises at least a first antenna in a first transmission branch and a second antenna in a second transmission branch;determining a first Signal-to-Interference Ratio (SIR) value at an output of an amplifier of the second transmission branch as an output power level of a second signal at the amplifier of the second transmission branch deducted by a power level of a first signal radiated from the first antenna and coupled to the output of the amplifier of the second transmission branch;comparing the first SIR value to a first predetermined threshold value of Signal-to-Interference+Noise Ratio (SINR);adjusting, in response to the first SIR value being lower than said first predetermined threshold value of SINR, an attenuator in the second transmission branch to a higher attenuation value; andincreasing an amplification of the amplifier of the second transmission branch to compensate for the higher attenuation value.

12. The method according to the claim 11, further comprisingdetermining whether said amplifier has sufficient power headroom to compensate for the higher attenuation value; and if affirmativeperforming said adjusting the attenuator and increasing the amplification.

13. The method according to the claim 11 or 12, further comprisingmeasuring a current level of antenna coupling between the first and second antennas; determining a pathloss towards a network node for the first and second antennas; determining a power imbalance level between the first and the second signal; and determining a second threshold value for power level difference between the first and the second signal.

14. The method according to the claim 13, wherein among at least the first transmission branch and the second transmission branch, the second transmission branch has a lowest pathloss value.

15. The method according to any of claims 11 - 14, wherein the first predetermined threshold value of SINK is at least partly based on a modulation and coding scheme (MCS) currently allocated to the UE.

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