Method and apparatus for signal path calibration

Abstract

A method comprising: operating, by a user equipment (UE) transmitting an uplink signal, a switch component to establish a first antenna circuit, the first antenna circuit being a transmission path of the UE between a baseband unit of the UE and a first antenna; determining a first signal characteristics for a first part of the first antenna circuit; determining a second signal characteristics for a second part of the first antenna circuit; determining transmission characteristics for the transmission path of the user terminal based on the first signal characteristics and the second signal characteristics; operating the switch component to establish a second antenna circuit comprising the first antenna circuit and a receiving path of the UE between the first antenna and the baseband unit; determining a third signal characteristics for the second antenna circuit; determining receiving characteristics for the receiving path of the user terminal based on the determined transmission characteristics and the determined third signal characteristics; and determining an absolute difference of characteristics between the transmission path and the receiving path between the first antenna and the baseband unit.

Description

METHOD AND APPARATUS FOR SIGNAL PATH CALIBRATIONTECHNICAL FIELD

[0001] The present invention relates to calibrating transmission and reception signal paths of a terminal apparatus.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 achieve the same performance, but with half of the resource used in the conventional UL Carrier Aggregation (UL-CA), where a UE can transmit two UL carriers at the same time but on different frequencies. In UL-MiMo, the amplifiers of the UE are transmitting at the same frequency, which enables pre-coding to be used for the configured UL-layers to optimize the performance of the transmission and the reception. The achieved performance of UL pre-coding depends on the accuracy of the channel characterizations, which can be obtained either as codebook-based UL MiMo or non-codebook -based UL MiMo.

[0003] The codebook-based UL MiMo does not require a fully characterized / calibrated UE, but it involves additional signaling with the gNB. The non-codebook-based MiMo is based on reference signals only and has no feedback loop, thus having less overhead and latency. However, non-codebook-based precoding requires full channel reciprocity between the gNB and the UE, for the UE to be able to derive the correct pre-coding values. This requires that the difference between the absolute power and phase transition of the received signal in the RX part of the UE and the power and phase transition of the transmitted signal in the Tx part of the UE must be known and compensated for.

[0004] However, the RX and TX signal paths between an antenna and the baseband (BB) circuit are very different and will change dynamically as the RF front-end is reconfigured or whenever the user is handling the UE. Thus, the absolute power and phase differences between the RX and TX signal paths need to be determined continuously.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 a method, 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 a switch component configured to establish a first antenna circuit, the first antenna circuit being a transmission path of the apparatus between a baseband unit of the apparatus and a first antenna; means for transmitting an uplink signal; means for determining a first signal characteristics for a first part of the first antenna circuit; means for determining a second signal characteristics for a second part of the first antenna circuit; means for determining transmission characteristics for the transmission path of the user terminal based on the first signal characteristics and the second signal characteristics, wherein the switch component is further configured to establish a second antenna circuit comprising the first antenna circuit and a receiving path of the apparatus between the first antenna and the baseband unit; the apparatus further comprising means for determining a third signal characteristics for the second antenna circuit; means for determining receiving characteristics for the receiving path of the user terminal based on the determined transmission characteristics and the determined third signal characteristics; and means for determining an absolute difference of characteristics between the transmission path and the receiving path between the first antenna and the baseband unit.

[0008] According to an embodiment, the swich component of the apparatus may comprise a transmission path switch, a receiving path switch and an antenna switch, the apparatus comprising means for operating the switch component to connect the antenna switch to the first antenna and the transmission path switch to a transmitting state and thereceiving path switch to a transmitting state for determining the first signal characteristics; connect the antenna switch to a calibration state, the transmission path switch to a transmitting state and the receiving path to transmission state for determining the second signal characteristics; and connect the antenna switch to the calibration state, the transmission path switch to transmitting state and the receiving path switch to the calibration state or a receiving state for determining the third signal characteristics.

[0009] According to an embodiment, the apparatus may comprise a coupler component in the transmission path of the apparatus between the baseband unit of the apparatus and the first antenna, wherein the coupler component is configured to connect the uplink signal to a feedback receiver path for determining the first signal characteristics for the first part of the first antenna circuit; and connect a signal reflected from said switch component to the feedback receiver path for determining the second signal characteristics for the second part of the first antenna circuit.

[0010] According to an embodiment, the apparatus may comprise one or more antennas, each provided with the switch component, and a multiplexer configured to switch between a plurality transmission path and the receiving path between any of said one or more antennas and the baseband unit to determine antenna-specific second and third signal characteristics.

[0011] According to an embodiment, the apparatus may comprise an antenna tuner configured to be detuned for the duration of measuring any one of the characteristics.

[0012] According to an embodiment, the means for determined signal characteristics of the apparatus is configured to determine the absolute power and phase difference of the signal.

[0013] According to an embodiment, the apparatus may comprise a calibration attenuator wherein the receiving path switch to the attenuation calibration state.

[0014] According to an embodiment, the means for determining the first signal characteristics for a first part of the first antenna circuit of the apparatus is configured to determine first signal characteristics from a Sounding Reference Signal, SRS, Physical Uplink Control Channel, PUCCH, and / or Physical Uplink Shared Channel, PUSCH transmission.

[0015] According to an embodiment, the means for determining of the first signal characteristics for a first part of the first antenna circuit of the apparatus is configured to determine first signal characteristics from a calibration signal.

[0016] According to a second aspect there is provided a method comprising operating, by a user equipment (UE) transmitting an uplink signal, a switch component to establish a first antenna circuit, the first antenna circuit being a transmission path of the UE between a baseband unit of the UE and a first antenna; determining a first signal characteristics for a first part of the first antenna circuit; determining a second signal characteristics for a second part of the first antenna circuit; determining transmission characteristics for the transmission path of the user terminal based on the first signal characteristics and the second signal characteristics; operating the switch component to establish a second antenna circuit comprising the first antenna circuit and a receiving path of the UE between the first antenna and the baseband unit; determining a third signal characteristics for the second antenna circuit; determining receiving characteristics for the receiving path of the user terminal based on the determined transmission characteristics and the determined third signal characteristics; and determining an absolute difference of characteristics between the transmission path and the receiving path between the first antenna and the baseband unit.

[0017] An apparatus according to a third aspect comprises a switch component, a first antenna circuit, the first antenna circuit being a transmission path of the apparatus between a baseband unit of the apparatus and a first antenna transmit an uplink signal, a second antenna circuit comprising the first antenna circuit and a receiving path of the apparatus between the first antenna and the baseband unit, and 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; operate the switch component to establish the first antenna circuit; determine a first signal characteristics for a first part of the first antenna circuit; determine a second signal characteristics for a second part of the first antenna circuit; determine transmission characteristics for the transmission path of the user terminal based on the first signal characteristics and the second signal characteristics; operate the switch component to establish a second antenna circuit comprising the first antenna circuit and a receiving path of the apparatus between the first antenna and the baseband unit;determine a third signal characteristics for the second antenna circuit; determine receiving characteristics for the receiving path of the user terminal based on the determined transmission characteristics and the determined third signal characteristics; and determine an absolute difference of characteristics between the transmission path and the receiving path between the first antenna and the baseband unit.

[0018] 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

[0019] 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:

[0020] Fig. 1 shows a schematic block diagram of an apparatus for incorporating a system information acquisition according to the embodiments;

[0021] Fig. 2 shows schematically a layout of an apparatus according to an example embodiment;

[0022] Fig. 3 shows a part of an exemplifying radio access network;

[0023] Fig. 4 shows an overview of major downlink MIMO 5G schemes;

[0024] Fig. 5a shows an example of codebook based uplink MIMO procedure;

[0025] Fig. 5b shows an example of non-codebook based uplink MIMO procedure;

[0026] Fig. 6 shows a flow chart for the signal path calibration method according to an embodiment;

[0027] Fig. 7 shows a block diagram for the apparatus according to an embodiment;

[0028] Fig. 8 shows a block chart of the switching component according to an embodiment;

[0029] Fig. 9a shows a block diagram or the apparatus according to an embodiment wherein the components of the part of the first antenna circuit are highlighted;

[0030] Fig. 9b shows a block diagram or the apparatus according to an embodiment wherein the components of the first antenna circuit are highlighted;

[0031] Fig. 9c shows a block diagram or the apparatus according to an embodiment wherein the components of the part of the second antenna circuit are highlighted;

[0032] Fig. 10 shows a block chart of the switching component according to an embodiment;

[0033] Fig. 11 shows a block chart of the switching component according to an embodiment;DETAILED DESCRIPTON OF SOME EXAMPLE EMBODIMENTS

[0034] 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.

[0035] In this regard, reference is first made to Figures 1 and 2, where Figure 1 shows a schematic block diagram of an exemplary apparatus or electronic device 50, which may incorporate the arrangement according to the embodiments. Figure 2 shows a layout of an apparatus according to an example embodiment. The elements of Figs. 1 and 2 will be explained next.

[0036] The electronic device 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.

[0037] 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 otherembodiments 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.

[0038] 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.

[0039] The apparatus 50 may comprise radio interface circuitry 52 connected to the controller and suitable for generating wireless communication signals for example for communication 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).

[0040] 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.

[0041] 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.

[0042] The example of Figure 3 shows a part of an exemplifying radio access network.

[0043] 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)NodeB is 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.

[0044] 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 thesystem, 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).

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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 as macro-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.

[0050] 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.

[0051] 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.

[0052] 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 by previous 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.

[0053] 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 aswireless 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).

[0054] 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.

[0055] 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).

[0056] 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).

[0057] 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.

[0058] 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 cells and 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.

[0059] 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, inaddition 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.

[0060] 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).

[0061] The transitions between the states is 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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 antenna array 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.

[0067] 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 practicallive 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 gNodeB with a fully pre-characterized lookup table of precoding values.

[0068] 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.

[0069] Independently from the above-described downlink schemes, the current UL-MIMO procedure can be either codebook-based or non-codebook based. In the codebookbased approach, the network sends a Transmitted Precoding Matrix Indicator (TPMI) to the UE to control the UL precoding at UE. This procedure is shown in Figure 5a as comprising the steps:1) SRS resources are transmitted from UE to network (as defined in 3GPP TS 38.214).The SRS can be sent sequentially or simultaneously, depending on the UE capabilities. However, simultaneously transmitted SRSs will reduce the coverage due to the requirements for maximum combined Tx power at the UE.2) Network estimates the channel based on previous step and determines best SRS, SRS resource indicator (SRI) and rank.3) Network transmits the SRI, rank and TPMI to the UE.4) PUSCH transmission uses the latest indicated precoding at the UE based on previous step.

[0070] In the codebook-based approach, the UE relies on a pre-determined codebook specified in 3GPP TS 38.211. This codebook was derived under the assumption of Uniform Linear array (ULA) of omni-directional cross pol elements at the UE side leading to a Discrete Fourier Transform (DFT) based “grid of beams” (GOB). However, UE antenna arrays are not uniform and linear as the antenna’s patterns have directive variationof gain and phase, as well as inter-antenna distances that are rarely half a wavelength. This will result in a non-optimal codebook.

[0071] Therefore, a non-codebook-based procedure has been specified as well (3 GPP TS 38.214), letting the UE to determine its precoding by using downlink CSI-RS and leveraging DL-UL reciprocity at the UE TRX. This procedure is depicted in Figure 5b as comprising the steps:1) CSI-RS s are sent from the network to the UE, where the UE estimates the channel and calculates a precoder for UL at the UE.2) Pre-coded SRSs are sent in UL from the UE to the network based on previous steps.3) Network performs a selection of the best SRS and indicates this to the UE using the SRI.4) PUSCH transmission uses the latest calculated precoding at the UE based on the indicated SRI.

[0072] Dual carrier UL transmission has typically been implemented as UL Carrier Aggregation (UL-CA), where a UE can transmit two UL carriers at the same time but on different frequencies. Therein, two individual transmissions each uses a single power amplifier (PA) for the different frequency ranges that can be controlled independently.

[0073] However, dual carrier UL transmission at the same frequency (UL-MiMo) could achieve the same performance, but with half of the resource used in the conventional UL-CA, where a UE can transmit two UL carriers at the same time but on different frequencies. In UL-MiMo, the PAs of the UE are transmitting at the same frequency, which enables pre-coding to be used for the configured UL-layers to optimize the performance of the transmission and the reception. The achieved performance of UL precoding depends on the accuracy of the channel characterizations, which can be obtained either as the codebook-based UL MiMo or the non-codebook -based UL MiMo, as described above.

[0074] The codebook-based UL MiMo does not require a fully characterized / calibrated UE HW, but it requires that the UE sends (additional) SRS signals per UE antenna port for UL channel characterization whereafter the UE will receive a TPMI as feedback from the gNB. The non-codebook-based MiMo is based on demodulation reference signal (DMRS) and / or CSI-RS only and has no feedback loop, thus having less overhead and latency. Inaddition, it can obtain a more accurate pre-coding (by not using a pre-determined low-resolution codebook). However, non-codebook-based precoding requires full channel reciprocity between the gNB and the UE, for the UE to be able to derive the correct precoding values. This requires that the difference between the absolute power and phase transition of the received signal in the RX part of the HW and the power and phase transition of the transmitted signal in the Tx part of the HW must be known and compensated for.

[0075] However, the RX and TX signal paths between an antenna and the baseband (BB) circuit are very different and will change dynamically as the RF front-end is reconfigured or whenever the user is handling the UE. Thus, the absolute power and phase differences between the RX and TX signal paths need to be determined continuously.

[0076] In the following, an enhanced method for calibrating the signal paths within the UE 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 operating (600), by a user equipment (UE) transmitting an uplink signal, a switch component to establish a first antenna circuit, the first antenna circuit being a transmission path of the UE between a baseband unit of the UE and a first antenna; determining (602) a first signal characteristics for a first part of the first antenna circuit; determining (604) a second signal characteristics for a second part of the first antenna circuit; determining (606) transmission characteristics for the transmission path of the user terminal based on the first signal characteristics and the second signal characteristics; operating (608) the switch component to establish a second antenna circuit comprising the first antenna circuit and a receiving path of the UE between the first antenna and the baseband unit; determining (610) a third signal characteristics for the second antenna circuit; determining (612) receiving characteristics for the receiving path of the user terminal based on the determined transmission characteristics and the determined third signal characteristics; and determining (614) an absolute difference of characteristics between the transmission path and the receiving path between the first antenna and the baseband unit.

[0078] Thus, the UE establishes a first antenna circuit by operating a switch component. The first antenna circuit is established between the baseband transmitter of the UE and theswitch component for determining characteristics of the antenna circuit impact on a transmitted signal in the uplink direction. The determination of a first signal characteristics for the first part of the first antenna circuit provides the characteristics of the transmission path, which is common for all antenna configurations. It can be measured, for example, between the baseband transmitter and a feedback receiver of the UE. A second signal characteristics is thereafter determined for the second part of the first antenna circuit being the remaining part of the first circuit between the baseband transmitter and the switching component. The second signal characteristics may be considered an antenna-circuit specific part of the transmission path. The characteristics of the second part of the first antenna circuit is determined based on a received signal at the feedback receiver of the UE, which signal has been reflected from the switch component. The characteristics of the transmission path is determined based on the determined the first signal characteristics and the second signal characteristics.

[0079] By operating the switch component appropriately, the transmission path of the UE may be connected to the receiving path of the UE establishing a second antenna circuit. Thus, a third antenna characteristics is determined for a path from the baseband transmitter of the UE utilising the transmission path and the receiving path of the UE to the baseband receiver. The characteristics of the of the receiving path of the UE may be determined based on the characteristics of the transmission path and determined third antenna circuit characteristics.

[0080] According to an embodiment, the determined signal characteristics comprises measurements for absolute power and phase difference.

[0081] Determined measurements for absolute power and phase difference provide information that can be considered when compensating the characteristics of the transmission path and the receiving path of the UE at the transceiver and baseband of the UE. Based on the determination, corrections on the phase and power may be accordingly applied for the transmitted signal to compensate the attenuation and phase shift the components along the transmitting path and the receiving path have caused to the signals.

[0082] According to an embodiment, the switch component comprises a transmission path switch, a receiving path switch and an antenna switch, the method comprising operating the switch component toconnect the antenna switch to the first antenna and the transmission path switch to a transmitting state and the receiving path switch to a transmitting state for determining the first signal characteristics;connect the antenna switch to a calibration state, the transmission path switch to a transmitting state and the receiving path to transmission state for determining the second signal characteristics;connect the antenna switch to the calibration state, the transmission path switch to transmitting state and the receiving path switch to the calibration state or a receiving state for determining the third signal characteristics.

[0083] The switch component may be arranged in various positions, these positions being based on the state of a plurality of switches such as a transmission switch and an antenna switch. The antenna switch being connected to a first antenna and the transmission switch arranged in the transmitting state establishes the first signal circuit, the transmission path of the UE. Thus, the first characteristics of a part of the first signal circuit, i.e. transmission path, may be determined from transmitted SRS, PUCCH and / or PUSCH signals. Alternatively, the first characteristics for the part of the first signal circuit may also be determined when the transmission path switch is in receiving state and / or the antenna switch is in calibration state, thereby enabling a better isolation towards the antenna compared when the determination is performed using signals that are not allocated for uplink transmission.

[0084] When the switch component is arranged to a position wherein the transmission switch and the antenna switch are arranged to the calibration state, the second signal characteristics may be determined for the transmission path of the UE. In this state, the transmission path is, by the antenna being in the calibration state, isolated from the air interface and thus not transmitting the signal provided from the transceiver and baseband of the UE. Instead, the signal transmitted for the calibration reflects from the switch component, using at least partly the same path, to the feedback receiver of the UE.

[0085] The third signal characteristics may be determined when the switch component is arranged to a position wherein the receiving path switch is arranged to a calibration state, the antenna switch is arranged to a calibration state and the transmission switch is arranged to a calibration state. Alternatively, the receiving path switch may be arranged to areceiving state. Thus, the transmission path of the UE is coupled to the receiving path and based on the first signal characteristics and the second characteristics the receiving path characteristics of the UE may be determined. Thus, the calibration signal used for determining the third signal characteristics has been transmitted by the baseband transmitter of the UE, propagating through the transmission circuit of the UE and the receiving path of the UE and received at the baseband receiver of the UE.

[0086] According to an embodiment, the UE comprises a coupler component, such as an RF coupler, in the transmission path of the UE between the baseband unit of the UE and the first antenna, the method further comprising: operating the coupler component to connect the uplink signal to a feedback receiver path for determining the first signal characteristics for the first part of the first antenna circuit; and operating the coupler component to connect a signal reflected from said switch component to the feedback receiver path for determining the second signal characteristics for the second part of the first antenna circuit.

[0087] Operating the coupler component enables to direct the correct signal to the feedback receiver of the UE. In a first state the coupler component connects the uplink signal to the feedback receiver enabling the determination of the first part of the first antenna circuit. In a second state the coupler component connects the reflected signal in the determination of the second signal characteristics of the second signal circuit. Thus, the correct calibration signal may be received at the feedback receiver in respect to the determined signal characteristics.

[0088] According to an embodiment, the UE comprises one or more antennas, each provided with the switch component, and a multiplexer, the method further comprising operating the multiplexer to switch between a plurality transmission path and the receiving path between any of said one or more antennas and the baseband unit to determine antenna-specific second and third signal characteristics.

[0089] The multiplexer may switch between the any of said one or more antennas to connect the antenna for measuring the second signal characteristics and third signal characteristics for the connected antenna. Thus, the calibration signals used for determining the second and third signal characteristics are propagating to the antenna specific part ofthe transmission and receiving circuits of the UE. It should be noted that the multiplexer may be common for at least a part of the plurality of antennas.

[0090] According to an embodiment, the UE comprises an antenna tuner, the method further comprising detuning the antenna tuner for the duration of measuring any one of the characteristics.

[0091] An antenna tuner associated with the antenna of the UE may be detuned or terminated to an impedance load of e.g. 50 Q for reducing radiated power of the calibration signal towards the antenna of the UE. Thus, the isolation of unscheduled uplink transmissions or uplink transmissions utilizing a scheduled measurement gap is improved.

[0092] The method and some of the embodiments can be implemented by an apparatus, such as a user equipment (UE), wherein the implementation may be illustrated by referring to the block chart of Figure 7, which discloses an apparatus 700. The apparatus 700 comprises a transceiver and baseband 702 unit. The transceiver and baseband unit may have connectors for a transmitter, Tx, feedback receiver, FBR, and for a receiver, Rx. The apparatus 700 further comprises a power amplifier 704 for amplifying the signal received from transceiver and baseband unit, and a coupler component 706, and a switch 708. For instance, the coupler component may comprise a coupler 706 and a switch 708. The apparatus 700 further comprises a multiplexer and filter component 722 associated with the transmission path of the UE and the receiving path of the UE. The switching component 710 of the apparatus 700 further comprises a transmission switch 712, an antenna switch 714 and a receiving path switch 716. The antenna swich is associated with an antenna of the UE 718. The apparatus 700 may further comprise a calibration attenuator 720 for the receiving path of the UE to avoid saturation of the receiver, when high power calibration signals are used. The apparatus 700 may further comprise a low-noise amplifier 724 for providing a suitable signal level for the receiver of the transceiver and baseband 702 unit of the UE.

[0093] Figure 8 discloses an exemplary implementation of the switching component 710. The switching component comprises three switches, a transmission switch 712, an antenna switch 714 and a receiving path switch 716. The transmission switch 712 comprises two states, a receiving state 802 and a transmitting / calibration state 804. The antenna switch comprises two states, a transmitting / receiving state 806 and a calibrationstate 808. The receiving path switch 716 comprises three states, a receiving state 810, a calibration attenuation state 812 and a transmitting / calibration state 814.

[0094] Figure 9 A, Figure 9B, and Figure 9C disclose the components comprising in the first part of the first antenna circuit, the second part of the first antenna circuit and the second antenna circuit, and the respective configuration of the coupler component 706, the switch 708 and the switching component 710.

[0095] It is noted that the implementations as depicted herein are only examples of the antenna circuits and configurations of the related components. For example, the first antenna circuit may be divided into more than said two parts (i.e. the first and the second part) and provided with further relevant components. The second antenna circuit may also be divided into two or more parts with further relevant components, if needed. However, such implementations typically increase the complexity of the UE implementation.

[0096] Three steps of the calibration process are described in detail by the three antenna circuits below. The steps are performed independently from each other, each requiring the switches of the switch component to be in correct states. Additionally, this applies for the switch of the coupler component.

[0097] Figure 9 A describes the first part of the first antenna circuit comprising the power amplifier 704 and the coupler component 706 of the transmission path. The calibration signal is provided via the transmitting connector of the transceiver and baseband unit 702 and propagated through the power amplifier, the coupler component and its switch. The calibration signal is then received the feedback receiver of the UE. Thus, the first part of the first antenna circuit is Tx the power amplifier 704 — the coupler component 706 the switch 708 FBR. In this situation the switch 708 is in the forward state to couple the port of the coupler associated with the forward mode to the feedback receiver. The transmission switch 712 is coupled to the transmission and calibration state 804. Alternatively, if an unscheduled calibration signal is used instead of a scheduled uplink transmission, the transmission switch 712 is in the receiving state 802 to ensure sufficient isolation at the antenna.

[0098] The characteristics of the first part of the first antenna circuitry may be determined by using a scheduled uplink signal as the calibration signal transmitted by the transceiver and baseband 702 unit. The uplink signal is routed to the power amplifier,coupler, multiplexer and filter component, switch component and the antenna.Additionally, part of the signal amplified by the power amplifier 704 for the transmission, is routed by the coupler 706 to the feedback receiver utilizing the switch 708 to establish the coupler to be in a forward mode.

[0099] The characteristics may then be determined based on the received signal at the feedback receiver as follow:Cal(TxPA) = Meas(Tx + FBR) — Con(FBR),where, Meas(Tx + FBR~) is the signal measured at the feedback receiver and Con FBR') is the known characteristics of the path from the coupler to the feedback receiver input at the transceiver and baseband unit of the UE.

[0100] Figure 9B describes the first antenna circuit comprising the power amplifier 704 of the transmission path, the coupler component 706, the multiplexer 722 and the switching component 710. The calibration signal is provided via the transmitting connector of the transceiver and baseband unit and propagated through the power amplifier 704, the coupler component 706, the multiplexer 722, and the switching component 710. Within the switching component 710, the transmission switch 712 is configured in the transmission / calibration mode and the antenna switch 714 is configured in the calibration mode. The calibration signal is then reflected back due to the antenna switch 714 of the switching component 710 being in a calibration state. The coupler component 706 and the switch 708 are now configured for the reverse mode, and thus the reflected calibration signal is received the feedback receiver of the UE. Thus, the path for determining the characteristic of the transmission path the first antenna circuit is Tx — the power amplifier 704 the coupler component 706 the multiplexer 722— >■ the transmission switch 712 — the antenna switch 714 — the transmission switch 712 — the multiplexer 722 — the coupler component 706 —>■ the switch 708 — >FBR. The antenna switch 714 may be open or alternatively a short connection to avoid frequency dependent open-ended capacitance.

[0101] Characteristics of the transmission path may be determined using a calibration signal transmitted at the transceiver an baseband unit 702, routed to through the power amplifier, coupler component, multiplexer and filter component to the switch component, wherein the signal is reflected at the uncoupled antenna switch back to the multiplexer andfilter component and the coupler, wherein it is routed by the coupler to the feedback receiver utilizing the switch 708 to establish the coupler to be in reverse mode.

[0102] Thus, the characteristics of the transmission path may be derived as follow:Cal(Tx ) > Meas(TxpA+2 * TxAnt+FBR')-Con(FBR')-Cal(TxpA)wherein the measured Meas(TxPA+ 2 * TxAnt+ FBR) comprises the known Con FBR'), being the characteristics of the path from the coupler to the feedback receiver input at the transceiver and baseband unit of the UE and the known Cal(TxPA), being the characteristics of the result of the determined in the preceding step for the path from the transceiver and baseband unit to the power amplifier.

[0103] Figure 9C describes the second antenna circuit wherein the first antenna circuit is coupled to the receiving path of the UE at the switching component. The calibration signal is received at the receiver of the UE through the receiving circuit comprising the downlink path of the multiplexer and a low-noise amplifier. Thus, the second antenna circuit is Tx the power amplifier 704 — >the coupler component 706 the multiplexer 722 — the transmission switch 712 —> the receiving path switch 716 —> the multiplexer 722 — the low-noise amplifier 724 — >Rx.

[0104] Characteristics for the receiving path may be determined using a calibration signal transmitted at the transceiver and baseband unit 702, routed through the power amplifier, coupler component, multiplexer and filter component to the transmission and receiving path switches. Where the calibration is performed using an unscheduled uplink signal or a scheduled measured gap is allocated for the calibration, the antenna switch 714 is in calibration state. The transmission switch 712 is in the transmission state 804 and the receiving path switch 716 is in the receiving state 810. Alternatively, the receiving path switch 716 may be in the calibration attenuation state 812 to attenuate a high power calibration signal. From the receiving path switch the calibration signal propagates through the multiplexer and filter component and low-noise amplifier to the receiving port, Rx, of the transceiver and baseband unit of the UE.

[0105] Thus, the characteristics for the receiving path may be determined as follow:Cal(TxAnt) = Meas(TxPA+ TxAnt+ RxTot) - Cal(TxPA) - Cal(TxAnt) wherein, the Cal(TxPA) and Cal(TxAnt) are the determined characteristics of the parts of the transmission path, being the path between the transceiver and baseband unit to thecoupler component and the path from the coupler component to the switch component, determined in the preceding steps.

[0106] It is noted that the RF front-end (i.e. the transceiver and baseband unit) for a UE is very complex and can support more than 10.000 different configuration to support different system bands, carrier bandwidths, CA combinations, dual connectivity, etc. As such the RF front-end can be implemented and designed in many ways. However, the RX to TX calibration with switching component is independent of RF front-end implementation and designed to capture these changes. As such, any change in the RF front-end will be captured by the calibration procedure, whereafter the correct amplitude and phase settings can be applied to the Tx signals, for coherent Tx transmission with optimal precoding based on DL reference signals only.

[0107] Figure 10 discloses an exemplary implementation of an apparatus 1000 which may be used to implement the method and some of the embodiments. The apparatus 1000 comprises a front-end module 1002 and an antenna tuner 1004, the antenna tuner being placed between the switch module 710 of the front-end module and the antenna 718. The calibration attenuator 720 may be placed outside of the front-end module for avoiding a saturation in high power calibration mode, e.g. to the low-noise amplifier 724. The antenna tuner may be detuned during some of the calibration phases to reduce the level of radiated power.

[0108] Figure 11 discloses an exemplary implementation of an apparatus 1100 which may be used to implement the method and some of the embodiments. The apparatus 1100 comprises a front-end module 1102 and an antenna tuner and switch component module 1104. The antenna tuner and switch component module comprises a switch component 710 and an antenna tuner 1106. Thus, the antenna tuner and switch component module may be separated from the front-end module to enable a more accurate calibration, when the switch component 710 is located close to the antenna. Thus, the characteristics of the transmission path and the receiving path may be determined as close the antenna as possible improving the accuracy of the determination. The antenna tuner and switch component may be connected to the front-end module with a connection for the transmission path of the UE and a connection for the receiving path of the UE.

[0109] The methods and the related embodiments may provide various advantages. The methods and the related embodiments enable the calculation of the absolute power and phase differences between the receiving path and the transmission path of a UE by establishing only a few additional components. The antenna is used as the common Rx and Tx reference point for the determining the Rx and Tx branch characteristics, whereupon the process is independent of which Rx and Tx branch is connected at the antenna. In a similar manner, an arrangement with a plurality of antennas may be introduced without adding any complexity to the RF circuity compared to a case of only one antenna.Furthermore, the presence of the RF coupler component associated with the output of the power amplifier, which is typically used for digital pre-distortion and general power control, may be utilised for the calibration.

[0110] An apparatus, such as a UE, according to an aspect comprises a switch component configured to establish a first antenna circuit, the first antenna circuit being a transmission path of the apparatus between a baseband unit of the apparatus and a first antenna; means for transmitting an uplink signal; means for determining a first signal characteristics for a first part of the first antenna circuit; means for determining a second signal characteristics for a second part of the first antenna circuit; means for determining transmission characteristics for the transmission path of the user terminal based on the first signal characteristics and the second signal characteristics, wherein the switch component is further configured to establish a second antenna circuit comprising the first antenna circuit and a receiving path of the apparatus between the first antenna and the baseband unit; the apparatus further comprising means for determining a third signal characteristics for the second antenna circuit; means for determining receiving characteristics for the receiving path of the user terminal based on the determined transmission characteristics and the determined third signal characteristics; and means for determining an absolute difference of characteristics between the transmission path and the receiving path between the first antenna and the baseband unit.

[0111] According to an embodiment, the swich component of the apparatus may comprise a transmission path switch, a receiving path switch and an antenna switch, the apparatus comprising means for operating the switch component to connect the antenna switch to the first antenna and the transmission path switch to a transmitting state and thereceiving path switch to a transmitting state for determining the first signal characteristics; connect the antenna switch to a calibration state, the transmission path switch to a transmitting state and the receiving path to transmission state for determining the second signal characteristics; and connect the antenna switch to the calibration state, the transmission path switch to transmitting state and the receiving path switch to the calibration state or a receiving state for determining the third signal characteristics.

[0112] According to an embodiment, the apparatus may comprise a coupler component in the transmission path of the apparatus between the baseband unit of the apparatus and the first antenna, wherein the coupler component is configured to connect the uplink signal to a feedback receiver path for determining the first signal characteristics for the first part of the first antenna circuit; and connect a signal reflected from said switch component to the feedback receiver path for determining the second signal characteristics for the second part of the first antenna circuit.

[0113] According to an embodiment, the apparatus may comprise one or more antennas, each provided with the switch component, and a multiplexer configured to switch between a plurality transmission path and the receiving path between any of said one or more antennas and the baseband unit to determine antenna-specific second and third signal characteristics.

[0114] According to an embodiment, the apparatus may comprise an antenna tuner configured to be detuned for the duration of measuring any one of the characteristics.

[0115] According to an embodiment, the means for determined signal characteristics of the apparatus is configured to determine the absolute power and phase difference of the signal.

[0116] According to an embodiment, the apparatus may comprise a calibration attenuator wherein the receiving path switch to the attenuation calibration state.

[0117] According to an embodiment, the means for determining the first signal characteristics for a first part of the first antenna circuit of the apparatus is configured to determine first signal characteristics from a Sounding Reference Signal, SRS, Physical Uplink Control Channel, PUCCH, and / or Physical Uplink Shared Channel, PUSCH transmission.

[0118] According to an embodiment, the means for determining of the first signal characteristics for a first part of the first antenna circuit of the apparatus is configured to determine first signal characteristics from a calibration signal.

[0119] According to a second aspect there is provided a method comprising operating, by a user equipment (UE) transmitting an uplink signal, a switch component to establish a first antenna circuit, the first antenna circuit being a transmission path of the UE between a baseband unit of the UE and a first antenna; determining a first signal characteristics for a first part of the first antenna circuit; determining a second signal characteristics for a second part of the first antenna circuit; determining transmission characteristics for the transmission path of the user terminal based on the first signal characteristics and the second signal characteristics; operating the switch component to establish a second antenna circuit comprising the first antenna circuit and a receiving path of the UE between the first antenna and the baseband unit; determining a third signal characteristics for the second antenna circuit; determining receiving characteristics for the receiving path of the user terminal based on the determined transmission characteristics and the determined third signal characteristics; and determining an absolute difference of characteristics between the transmission path and the receiving path between the first antenna and the baseband unit.

[0120] An apparatus according to a further aspect comprises a switch component, a first antenna circuit, the first antenna circuit being a transmission path of the apparatus between a baseband unit of the apparatus and a first antenna transmit an uplink signal, a second antenna circuit comprising the first antenna circuit and a receiving path of the apparatus between the first antenna and the baseband unit, and 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; operate the switch component to establish the first antenna circuit; determine a first signal characteristics for a first part of the first antenna circuit; determine a second signal characteristics for a second part of the first antenna circuit; determine transmission characteristics for the transmission path of the user terminal based on the first signal characteristics and the second signal characteristics; operate the switch component to establish a second antenna circuit comprising the first antenna circuit and a receiving path of the apparatus between the first antenna and the baseband unit;determine a third signal characteristics for the second antenna circuit; determine receiving characteristics for the receiving path of the user terminal based on the determined transmission characteristics and the determined third signal characteristics; and determine an absolute difference of characteristics between the transmission path and the receiving path between the first antenna and the baseband unit.

[0121] According to an embodiment, the swich component of the apparatus may comprise a transmission path switch, a receiving path switch and an antenna switch, the apparatus comprising code configured to cause the apparatus to operate the switch component to connect the antenna switch to the first antenna and the transmission path switch to a transmitting state and the receiving path switch to a transmitting state for determining the first signal characteristics; connect the antenna switch to a calibration state, the transmission path switch to a transmitting state and the receiving path to transmission state for determining the second signal characteristics; and connect the antenna switch to the calibration state, the transmission path switch to transmitting state and the receiving path switch to the calibration state or a receiving state for determining the third signal characteristics.

[0122] According to an embodiment, the apparatus may comprise a coupler component in the transmission path of the apparatus between the baseband unit of the apparatus and the first antenna, wherein the coupler component is configured to connect the uplink signal to a feedback receiver path for determining the first signal characteristics for the first part of the first antenna circuit; and connect a signal reflected from said switch component to the feedback receiver path for determining the second signal characteristics for the second part of the first antenna circuit.

[0123] According to an embodiment, the apparatus may comprise one or more antennas, each provided with the switch component, and a multiplexer configured to switch between a plurality transmission path and the receiving path between any of said one or more antennas and the baseband unit to determine antenna-specific second and third signal characteristics.

[0124] According to an embodiment, the apparatus may comprise an antenna tuner configured to be detuned for the duration of measuring any one of the characteristics.

[0125] According to an embodiment, the code configured to cause the apparatus to determine signal characteristics of the apparatus comprises code configured to cause the apparatus to determine the absolute power and phase difference of the signal.

[0126] According to an embodiment, the apparatus may comprise a calibration attenuator wherein the receiving path switch to the attenuation calibration state.

[0127] According to an embodiment, the code configured to cause the apparatus to determine the first signal characteristics for a first part of the first antenna circuit of the apparatus comprises code configured to cause the apparatus to determine first signal characteristics from a Sounding Reference Signal, SRS, Physical Uplink Control Channel, PUCCH, and / or Physical Uplink Shared Channel, PUSCH transmission.

[0128] According to an embodiment, the code configured to cause the apparatus to determine the first signal characteristics for a first part of the first antenna circuit of the apparatus comprises code configured to cause the apparatus to determine first signal characteristics from a calibration signal.

[0129] Such apparatuses may comprise e.g. the functional units disclosed in any of the Figures 1 - 3 and 7 - 11 for implementing the embodiments.

[0130] 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.

[0131] 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.

[0132] 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 wellas 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.

[0133] 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:a switch component configured to establish a first antenna circuit, the first antenna circuit being a transmission path of the apparatus between a baseband unit of the apparatus and a first antenna;means for transmitting an uplink signal;means for determining a first signal characteristics for a first part of the first antenna circuit;means for determining a second signal characteristics for a second part of the first antenna circuit;means for determining transmission characteristics for the transmission path of the user terminal based on the first signal characteristics and the second signal characteristics;wherein the switch component is further configured to establish a second antenna circuit comprising the first antenna circuit and a receiving path of the apparatus between the first antenna and the baseband unit;means for determining a third signal characteristics for the second antenna circuit;means for determining receiving characteristics for the receiving path of the user terminal based on the determined transmission characteristics and the determined third signal characteristics; andmeans for determining an absolute difference of characteristics between the transmission path and the receiving path between the first antenna and the baseband unit.

2. The apparatus according to claim 1, wherein the switch component comprises a transmission path switch, a receiving path switch and an antenna switch, the apparatus comprising means for operating the switch component to:connect the antenna switch to the first antenna and the transmission path switch to a transmitting state and the receiving path switch to a transmitting state for determining the first signal characteristics;connect the antenna switch to a calibration state, the transmission path switch to a transmitting state and the receiving path to transmission state for determining the second signal characteristics;connect the antenna switch to the calibration state, the transmission path switch to transmitting state and the receiving path switch to the calibration state or a receiving state for determining the third signal characteristics.

3. The apparatus according to any of claims 1 or 2, wherein the apparatus comprises a coupler component in the transmission path of the apparatus between the baseband unit of the apparatus and the first antenna, wherein the coupler component is configured to:connect the uplink signal to a feedback receiver path for determining the first signal characteristics for the first part of the first antenna circuit; andconnect a signal reflected from said switch component to the feedback receiver path for determining the second signal characteristics for the second part of the first antenna circuit.

4. The apparatus according to the any of the preceding claims, wherein the apparatus comprises one or more antennas, each provided with the switch component, and a multiplexer configured to:switch between a plurality transmission path and the receiving path between any of said one or more antennas and the baseband unit to determine antenna-specific second and third signal characteristics.

5. The apparatus according to the any of the preceding claims, wherein the apparatus comprises an antenna tuner configured to be detuned for the duration of measuring any one of the characteristics.

6. The apparatus according to any of the preceding claims, wherein the means for determined signal characteristics is configured to determine the absolute power and phase difference of the signal.

7. The apparatus according to any of the preceding claims, comprising a calibration attenuator wherein the receiving path switch to the attenuation calibration state.

8. The apparatus according to any of the preceding claims, wherein the means for determining the first signal characteristics for a first part of the first antenna circuit is configured to determine first signal characteristics from a Sounding Reference Signal, SRS, Physical Uplink Control Channel, PUCCH, and / or Physical Uplink Shared Channel, PUSCH transmission.

9. The apparatus according to any of the claims 1 — 6, wherein the means for determining the first signal characteristics for a first part of the first antenna circuit is configured to determine first signal characteristics from a calibration signal.

10. A method comprising:operating, by a user equipment (UE) transmitting an uplink signal, a switch component to establish a first antenna circuit, the first antenna circuit being a transmission path of the UE between a baseband unit of the UE and a first antenna; determining a first signal characteristics for a first part of the first antenna circuit; determining a second signal characteristics for a second part of the first antenna circuit;determining transmission characteristics for the transmission path of the user terminal based on the first signal characteristics and the second signal characteristics; operating the switch component to establish a second antenna circuit comprising the first antenna circuit and a receiving path of the UE between the first antenna and the baseband unit;determining a third signal characteristics for the second antenna circuit; determining receiving characteristics for the receiving path of the user terminal based on the determined transmission characteristics and the determined third signal characteristics; anddetermining an absolute difference of characteristics between the transmission path and the receiving path between the first antenna and the baseband unit.

11. The method according to the claim 10, wherein the switch component comprises a transmission path switch, a receiving path switch and an antenna switch, the method comprising operating the switch component toconnect the antenna switch to the first antenna and the transmission path switch to a transmitting state and the receiving path switch to a transmitting state for determining the first signal characteristics;connect the antenna switch to a calibration state, the transmission path switch to a transmitting state and the receiving path to transmission state for determining the second signal characteristics;connect the antenna switch to the calibration state, the transmission path switch to transmitting state and the receiving path switch to the calibration state or a receiving state for determining the third signal characteristics.

12. The method according to the claim 11, wherein the UE comprises a coupler component in the transmission path of the UE between the baseband unit of the UE and the first antenna, the method further comprising:operating the coupler component to connect the uplink signal to a feedback receiver path for determining the first signal characteristics for the first part of the first antenna circuit; andoperating the coupler component to connect a signal reflected from said switch component to the feedback receiver path for determining the second signal characteristics for the second part of the first antenna circuit.

13. The method according to the any of claims 10 - 12, wherein the UE comprises one or more antennas, each provided with the switch component, and a multiplexer, the method further comprising:operating the multiplexer to switch between a plurality transmission path and the receiving path between any of said one or more antennas and the baseband unit to determine antenna-specific second and third signal characteristics.

14. The method according to the any of claims 10 - 13, wherein the UE comprises an antenna tuner, the method further comprising:detuning the antenna tuner for the duration of measuring any one of the characteristics.

15. The method according to any of claims 10 - 14, wherein the determined signal characteristics comprises measurements for absolute power and phase difference.

Images