Patent Publication Number: US-2023146269-A1

Title: Beam management procedures for network nodes and terminal devices

Description:
TECHNICAL FIELD 
     Embodiments presented herein relate to methods, a network node, a terminal device, computer programs, and a computer program product for performing a beam management procedure. 
     BACKGROUND 
     In communications networks, there may be a challenge to obtain good performance and capacity for a given communications protocol, its parameters and the physical environment in which the communications network is deployed. 
     For example, for future generations of mobile communications networks, frequency bands at many different carrier frequencies could be needed. For example, low such frequency bands could be needed to achieve sufficient network coverage for wireless devices and higher frequency bands (e.g. at millimeter wavelengths (mmW), i.e. near and above 30 GHz) could be needed to reach required network capacity. In general terms, at high frequencies the propagation properties of the radio channel are more challenging and beamforming both at the network node of the network and at the wireless devices might be required to reach a sufficient link budget. 
     Narrow beam transmission and reception schemes might be needed at such high frequencies to compensate the expected high propagation loss. For a given communication link, a respective beam can be applied at both the network-end (as represented by a network node or its transmission and reception point, TRP) and at the terminal-end (as represented by a terminal device), which typically is referred to as a beam pair link (BPL). A BPL (i.e. both the beam used by the network node and the beam used by the terminal device) is expected to be discovered and monitored by the network using measurements on downlink reference signals, such as channel state information reference signals (CSI-RS) or synchronization signal block (SSB) signals, used for beam management. 
     A beam management procedure can be used for discovery and maintenance of beam pair links. In some aspects, the beam management procedure is defined in terms of a P-1 sub-procedure, a P-2 sub-procedure, and a P-3 sub-procedure. 
     The CSI-RS for beam management can be transmitted periodically, semi-persistently or aperiodically (event triggered) and they can be either shared between multiple terminal devices or be device-specific. The SSB are transmitted periodically and are shared for all terminal devices. In order for the terminal device to find a suitable network node beam, the network node, during the P-1 sub-procedure, transmits the reference signal in different transmission (TX) beams on which the terminal device performs measurements, such as reference signal received power (RSRP), and reports back the N best TX beams (where N can be configured by the network). Furthermore, the transmission of the reference signal on a given TX beam can be repeated to allow the terminal device to evaluate a suitable reception (RX) beam. Reference signals that are shared between all terminal devices served by the TRP might be used to determine a first coarse direction for the terminal devices. It could be suitable for such a periodic TX beam sweep at the TRP to use SSB as the reference signal. One reason for this is that SSB are anyway transmitted periodically (for initial access/synchronization purposes) and SSBs are also expected to be beamformed at higher frequencies to overcome the higher propagation losses noted above. 
     A finer beam sweep in more narrow beams than used during the P-1 sub-procedure might then be performed at the network node during a P-2 sub-procedure to determine a more detailed direction for each terminal device. Here, the CSI-RS might be used as reference signal. As for the P-1 sub-procedure, the terminal device performs measurements, such as reference signal received power (RSRP), and reports back the N best TX beams (where N can be configured by the network). 
     Furthermore, the CSI-RS transmission in the transmission beam selected during the P-2 sub-procedure can be repeated in a P-3 sub-procedure to allow the terminal device to evaluate suitable RX beams at the terminal device. 
     However, in some aspects, which beam in the respective beam management sub-processes is reported and/or selected by a terminal device as the best beam (e.g., in terms of RSRP) to some extent depends on the antenna architecture at the terminal device. Such aspects are not considered during current beam management procedures. 
     Hence, there is still a need for improved beam management procedures. 
     SUMMARY 
     An object of embodiments herein is to provide beam management procedures that take into account the antenna architecture at the terminal device. 
     According to a first aspect there is presented a method for performing a beam management procedure. The method is performed by a network node. The method comprises obtaining configuration information from a terminal device for which the network node provides network access. The configuration information specifies that the terminal device is in need for evaluating different polarization states in different time units during the beam management procedure. The method comprises performing the beam management procedure with the terminal device. The beam management procedure involves the network node to, per slot, transmit reference signals according to a reference signal transmission scheme. The reference signal transmission scheme depends on the obtained configuration information. 
     According to a second aspect there is presented a network node for performing a beam management procedure. The network node comprises processing circuitry. The processing circuitry is configured to cause the network node to obtain configuration information from a terminal device for which the network node provides network access. The configuration information specifies that the terminal device is in need for evaluating different polarization states in different time units during the beam management procedure. The processing circuitry is configured to cause the network node to perform the beam management procedure with the terminal device. The beam management procedure involves the network node to, per slot, transmit reference signals according to a reference signal transmission scheme. The reference signal transmission scheme depends on the obtained configuration information. 
     According to a third aspect there is presented a network node for performing a beam management procedure. The network node comprises an obtain module configured to obtain configuration information from a terminal device for which the network node provides network access. The configuration information specifies that the terminal device is in need for evaluating different polarization states in different time units during the beam management procedure. The network node comprises a beam management module configured to perform the beam management procedure with the terminal device. The beam management procedure involves the network node to, per slot, transmit reference signals according to a reference signal transmission scheme. The reference signal transmission scheme depends on the obtained configuration information. 
     According to a fourth aspect there is presented a computer program for performing a beam management procedure. The computer program comprises computer program code which, when run on processing circuitry of a network node, causes the network node to perform a method according to the first aspect. 
     According to a fifth aspect there is presented a method for performing a beam management procedure. The method is performed by a terminal device. The method comprises providing configuration information to a network node that provides network access to the terminal device. The configuration information specifies that the terminal device is in need for evaluating different polarization states in different time units during the beam management procedure. The method comprises performing the beam management procedure with the network node. The beam management procedure involves the terminal device to, per slot, receive reference signals from the network node according to a reference signal reception scheme. The reference signal reception scheme depends on the provided configuration information. 
     According to a sixth aspect there is presented a terminal device for performing a beam management procedure. The terminal device comprises processing circuitry. The processing circuitry is configured to cause the terminal device to provide configuration information to a network node that provides network access to the terminal device. The configuration information specifies that the terminal device is in need for evaluating different polarization states in different time units during the beam management procedure. The processing circuitry is configured to cause the terminal device to perform the beam management procedure with the network node. The beam management procedure involves the terminal device to, per slot, receive reference signals from the network node according to a reference signal reception scheme. The reference signal reception scheme depends on the provided configuration information. 
     According to a seventh aspect there is presented a terminal device for performing a beam management procedure. The terminal device comprises a provide module configured to provide configuration information to a network node that provides network access to the terminal device. The configuration information specifies that the terminal device is in need for evaluating different polarization states in different time units during the beam management procedure. The terminal device comprises a beam management module configured to perform the beam management procedure with the network node. The beam management procedure involves the terminal device to, per slot, receive reference signals from the network node according to a reference signal reception scheme. The reference signal reception scheme depends on the provided configuration information. 
     According to an eighth aspect there is presented a computer program for performing a beam management procedure, the computer program comprising computer program code which, when run on processing circuitry of a terminal device, causes the terminal device to perform a method according to the fifth aspect. 
     According to a ninth aspect there is presented a computer program product comprising a computer program according to at least one of the fourth aspect and the eighth aspect and a computer readable storage medium on which the computer program is stored. The computer readable storage medium could be a non-transitory computer readable storage medium. 
     Advantageously, these aspects enable the beam management procedures to take into account the antenna architecture at the terminal device. 
     Advantageously, these aspects improve the beam management procedure. 
     Advantageously, these aspects improve the beam management procedure by enabling improvement in the beam selection at the terminal device. 
     Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings. 
     Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to “a/an/the element, apparatus, component, means, module, step, etc.” are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, module, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The inventive concept is now described, by way of example, with reference to the accompanying drawings, in which: 
         FIG.  1    is a schematic diagram illustrating a communication network according to embodiments; 
         FIG.  2    schematically illustrates the antenna architecture of a terminal device according to an embodiment; 
         FIG.  3    schematically illustrates a beam management procedure according to embodiments; 
         FIGS.  4  and  5    are flowcharts of methods according to embodiments; 
         FIGS.  6  and  7    are schematic illustrations of transmission of reference signals in OFDM symbols of a slot according to embodiments; 
         FIG.  8    is a schematic diagram showing functional units of a network node according to an embodiment; 
         FIG.  9    is a schematic diagram showing functional modules of a network node according to an embodiment; 
         FIG.  10    is a schematic diagram showing functional units of a terminal device according to an embodiment; 
         FIG.  11    is a schematic diagram showing functional modules of a terminal device according to an embodiment; 
         FIG.  12    shows one example of a computer program product comprising computer readable means according to an embodiment; 
         FIG.  13    is a schematic diagram illustrating a telecommunication network connected via an intermediate network to a host computer in accordance with some embodiments; and 
         FIG.  14    is a schematic diagram illustrating host computer communicating via a radio base station with a terminal device over a partially wireless connection in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the inventive concept are shown. This inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description. Any step or feature illustrated by dashed lines should be regarded as optional. 
       FIG.  1    is a schematic diagram illustrating a communication network  100  where embodiments presented herein can be applied. The communication network  100  could be a third generation (3G) telecommunications network, a fourth generation (4G) telecommunications network, a fifth generation (5G) telecommunications network, or any evolvement thereof, and support any 3GPP telecommunications standard, where applicable. 
     The communication network  100  comprises a network node  200  configured to provide network access to terminal devices, as represented by terminal device  300 , in a radio access network  110 . The radio access network  110  is operatively connected to a core network  120 . The core network  120  is in turn operatively connected to a service network  130 , such as the Internet. The terminal device  300  is thereby enabled to, via the network node  200 , access services of, and exchange data with, the service network  130 . 
     The network node  200  comprises, is collocated with, is integrated with, or is in operational communications with, a transmission and reception point (TRP)  150 . The network node  200  (via its TRP  140 ) and the terminal device  300  is configured to communicate with each other in beams, one of which is illustrated at reference numeral  150 . In this respect, beams that could be used both as TX beams and RX beams will hereinafter simply be referred to as beams. 
     Examples of network node  200  are radio access network nodes, radio base stations, base transceiver stations, Node Bs, evolved Node Bs, g NBs, access points, access nodes, and backhaul nodes. Examples of terminal devices  300  are wireless devices, mobile stations, mobile phones, handsets, wireless local loop phones, user equipment (UE), smartphones, laptop computers, tablet computers, network equipped sensors, network equipped vehicles, and so-called Internet of Things devices. 
     There could be different types of antenna arrangements that the terminal device  300  is provided with in order for the terminal device  300  to efficiently communicate with the TRP  140 . In this respect, an antenna panel might be defined as a rectangular antenna array of dual-polarized antenna elements with typically one transmit/receive unit (TXRU) per polarization. An analog distribution network with phase shifters can be used to steer a directional beam as generated at each such antenna panel. Alternatively, the terminal device  300  is configured for digital wideband (time domain beamformed) beamforming that mimics the operation and function of the analog distribution network. Multiple antenna panels might be stacked next to each other and digital beamforming can be performed across the antenna panels. For the terminal device  300 , depending on its physical orientation, signals might arrive and emanate from all different directions. Hence, it might be beneficial to have an antenna implementation at the terminal device  300  which is enabled to generate omni-directional-like coverage for the terminal device  300  in addition to high gain narrow directional beams. One way to increase the omni-directional coverage at the terminal device  300  is to provide the terminal device  300  with multiple antenna panels, where at least two of the antenna panels have different pointing directions. 
       FIG.  2    schematically illustrates an example antenna architecture of the terminal device  300 . According to the illustrated antenna architecture, the terminal device  300  is equipped with at least one antenna array  340   a,    340   b.  Each antenna array  340   a,    340   b  has dual-polarized antenna elements. In the illustrated example, each antenna array  340   a,    340   b  has eight dual-polarized antenna elements but as the skilled person understands, each antenna array  340   a,    340   b  might have less than eight dual-polarized antenna elements or more than eight dual-polarized antenna elements. The antenna arrays  340   a,    340   b  are connectable to a baseband chain  350  in the terminal device  300  (via a switch  360 ). In some examples the terminal device  300  is equipped with more than one antenna array  340   a,    340   b.  Then the two or more antenna arrays  340   a,    340   b  could selectively be connected to one and the same baseband chain  350 , one at a time. This enables the terminal device  300  to comprise just one single baseband chain  350  despite comprising two or more antenna arrays  340   a,    340   b.  In other examples, the terminal device  300  comprises two or more baseband chains  350 , where each baseband chain  350  is connectable to one or more antenna arrays  340   a,    340   b.  This enables each antenna array  340   a,    340   b  to have its own baseband chain  350 . The antenna architecture might be part of a communications interface  320  of the terminal device  300 . Thus, in some embodiments, the terminal device  300  is equipped with an antenna array  340   a,    340   b  having dual-polarized antenna elements, where the antenna array  340   a,    340   b  is connected to a baseband chain  350  in the terminal device  300 . 
     As disclosed above there is still a need for improved beam management procedures. Reference is therefore made to  FIG.  3    that schematically illustrates a beam management procedure consisting of three sub-procedures, referred to as P-1, P-2, and P-3 sub-procedures. These three sub-procedures will now be disclosed in more detail. 
     One main purpose of the P-1 sub-procedure is for the network node  200  to find a coarse direction towards the terminal device  300  by transmitting reference signals in wide, but narrower than sector, beams that are swept over the whole angular sector. The TRP  140  is expected to, for the P-1 sub-procedure, utilize beams, according to a spatial beam pattern  160   a,  with rather large beam widths. During the P-1 sub-procedure, the reference signals are typically transmitted periodically and are shared between all terminal devices  300  served by the network node  200  in the radio access network  110 . The terminal device  300  uses a wide, or even omni-directional beam for receiving the reference signals during the P-1 sub-procedure, according to a spatial beam pattern  170   a.  The reference signals might be periodically transmitted CSI-RS (or, formally, CSI-RS resources) or SSB. The terminal device  300  might then to the network node  200  report the N≥1 best beams and their corresponding quality values, such as reference signal received power (RSRP) values. The beam reporting from the terminal device  300  to the network node  200  might be performed rather seldom (in order to save overhead) and can be either periodic, semi-persistent or aperiodic. 
     One main purpose of the P-2 sub-procedure is to refine the beam selection at the TRP  140  by the network node  200  transmitting reference signals whilst performing a new beam sweep with more narrow directional beams, according to a spatial beam pattern  160   b,  than those beams used during the P-1 sub-procedure, where the new beam sweep is performed around the coarse direction, or beam, reported during the P-1 sub-procedure. During the P-2 sub-procedure, the terminal device  300  typically uses the same beam as during the P-1 sub-procedure, according to a spatial beam pattern  170   b.  The terminal device  300  might then to the network node  200  report the N≥1 best beams and their corresponding quality values, such as reference signal received power (RSRP) values. One P-2 sub-procedure might be performed per each terminal device  300  or per each group of terminal devices  300 . The reference signals might be aperiodically or semi-persistently transmitted CSI-RS (or, formally, CSI-RS resources). The P-2 sub-procedure might be performed more frequently than the P-1 sub-procedure in order to track movements of the terminal device  300  and/or changes in the radio propagation environment. 
     One main purpose of the P-3 sub-procedure is for terminal devices  300  utilizing analog beamforming, or digital wideband (time domain beamformed) beamforming, to find best beam. During the P-3 sub-procedure, the reference signals are transmitted, according to a spatial beam pattern  160   c,  in the best reported beam of the P-2 sub-procedure whilst the terminal device  300  performs a beam sweep, according to a spatial beam pattern  170   c.  The P-3 sub-procedure might be performed at least as frequently as the P-2 sub-procedure in order to enable the terminal device  300  to compensate for blocking, and/or rotation. 
     Due to the physical radio environment, which is reported as the best beam might be different for different polarizations. For example, for some non-line of sight (NLOS) radio propagation environments, what is reported as the strongest beam in one polarization might correspond to the weakest beam in the orthogonal polarization. One way to mitigate this is to switch the polarization of the beams at the TRP  140  between transmission of consecutive SSB. However, such switching might create problems for automatic gain control (AGC) as performed by the terminal device  300 . On reason for this is due to that the received power of the two reference signals transmitted for the two orthogonal polarizations might differ too much, for example more than 10 dB. 
     One alternative way for the terminal device  300  to find its best beam, instead of using a P-3 sub-procedure is for the terminal device  300  to evaluate different beams during the periodic SSB transmission after initial network access. Since each SSB consists of four orthogonal frequency-division multiplexing (OFDM) symbols, a maximum of four beams can be evaluated during each SSB burst transmission. One benefit with this is that no extra overhead of CSI-RS transmission is needed. One drawback, however, with determining the beam to use at the terminal device  300  based on SSB transmission is that an SSB only has one TRP port, and hence only is transmitted over one polarization (per each unique direction), which implies that the terminal device  300  might only be able to evaluate suitable beams for one polarization. But as disclosed above, in case the RSRP differs significantly for different polarizations there is a risk that a non-optimal beam is selected at the terminal device  300 . 
     The embodiments disclosed herein therefore relate to mechanisms for performing a beam management procedure. In order to obtain such mechanisms there is provided a network node  200 , a method performed by the network node  200 , a computer program product comprising code, for example in the form of a computer program, that when run on processing circuitry of the network node  200 , causes the network node  200  to perform the method. In order to obtain such mechanisms there is further provided a terminal device  300 , a method performed by the terminal device  300 , and a computer program product comprising code, for example in the form of a computer program, that when run on processing circuitry of the terminal device  300 , causes the terminal device  300  to perform the method. 
     Reference is now made to  FIG.  4    illustrating a method for performing a beam management procedure as performed by the network node  200  according to an embodiment. 
     The network node  200  is to perform a beam management procedure that is dependent on information of the terminal device  200 . Hence, the network node  200  is configured to perform step S 102 : 
     S 102 : The network node  200  obtains configuration information from a terminal device  300  for which the network node  200  provides network access. The configuration information specifies that the terminal device  300  is in need for evaluating different polarization states in different time units during the beam management procedure. 
     The obtained information is then used when the beam management procedure is performed. In particular, the network node  200  is configured to perform step S 104 : 
     S 104 : The network node  200  performs the beam management procedure with the terminal device  300 . The beam management procedure involves the network node  200  to, per slot, transmit reference signals according to a reference signal transmission scheme. The reference signal transmission scheme depends on the obtained configuration information. 
     Embodiments relating to further details of performing a beam management procedure as performed by the network node  200  will now be disclosed. 
     Each reference signal might correspond to a respective CSI-RS resource or SSB. 
     There could be different types of reference signal transmission schemes. In some aspects, the reference signal transmission scheme defines where in the slot the reference signals are to be transmitted. In particular, in some embodiments where each of the different time units corresponds to a respective OFDM symbol, the reference signal transmission scheme defines at which OFDM symbols per slot that the reference signals are to be transmitted. 
     Embodiments according to which the amount of reference signals to be transmitted can be adapted according to the configuration information will now be disclosed. In some aspects, these embodiments can be readily combined with the above described P-2 sub-procedure. Further aspects relating thereto are also disclosed below with reference to  FIG.  6   . 
     In some aspects, the total number of reference signals to be transmitted per slot is equal to twice the number of beams in which the reference signals are to be transmitted at the TRP  140 . That is, according to an embodiment, according to the beam management procedure, the reference signals are to be transmitted in beams, and, according to the reference signal transmission scheme, each reference signal is to be transmitted twice in each beam per slot. 
     The above embodiments enable the terminal device  300  to, during a beam sweep of a P-2 sub-procedure, measure the RSRP for each beam for both polarizations at the terminal device  300 . This can be achieved by, at the TRP  140 , transmitting CSI-RS resources twice in each beam. 
     Embodiments according to which positions in the slot where the reference signals are placed can be adapted according to the configuration information will now be disclosed. In some aspects, these embodiments can be readily combined with the above described P-3 sub-procedure. Further aspects relating thereto are also disclosed below with reference to  FIG.  7   . 
     In some aspects, the terminal device  300  is configured to uses N&gt;1 beams per polarization. Therefore, in some embodiments, the configuration information further specifies that the terminal device  300  is configured to generate N&gt;1 beams per polarization of the antenna elements. However, this does not imply that the terminal device  300  actually is to generate all N beams during the beam management procedure, only that the terminal device  300  is configured to generate these beams. 
     In some aspects, the number of reference signals that are to be transmitted per slot as part of the beam management procedure depends on the value of N. In particular, in some embodiments, how many reference signals that are to be transmitted per slot depends on the value of N. In this respect, according to a first example, the total number of reference signals to be transmitted per slot as part of the beam management procedure is less than 2·N. That is, in some embodiments, according to the reference signal transmission scheme, fewer reference signals than 2·N are to be transmitted per slot. According to a second example, the total number of reference signals to be transmitted per slot as part of the beam management procedure is equal to N+2. That is, in some embodiments, according to the reference signal transmission scheme, exactly N+2 reference signals are to be transmitted per slot. 
     In some aspects, two of the reference signals are in the slot separated in time from the remaining reference signals. That is, in some embodiments, according to the reference signal transmission scheme, two of the reference signals are in the slot separated by at least one OFDM symbol from the remaining N reference signals, and these two of the reference signals are to be transmitted before the remaining N reference signals. 
     There could be different ways to in the slot separate these two of the reference signals in time from the remaining reference signals. In some aspects, two reference signals are placed first in the slot and the remaining reference signals are placed last in the same slot. That is, in some embodiments, according to the reference signal transmission scheme, two of the reference signals are placed to be transmitted as early as possible in the slot, and the remaining N reference signals are placed to be transmitted as late as possible in the same slot. 
     In some aspects, all reference signals are transmitted using the same beam. That is, in some embodiments, all the reference signals per slot are to be transmitted using one and the same beam (as generated at the TRP  140 ). 
     The above embodiments enable the terminal device  300  to, during a beam sweep of a P-3 sub-procedure, first evaluate the preferred polarization, and then evaluate a preferred narrow beam for the preferred polarization. This can be achieved by, at the network node  200 , adapt the positions in the slot where the CSI-RS resources are transmitted. 
     Reference is now made to  FIG.  5    illustrating a method for performing a beam management procedure as performed by the terminal device  300  according to an embodiment. 
     As disclosed above, the network node  200  is to perform a beam management procedure that is dependent on information of the terminal device  200 . Hence, the terminal device  300  is configured to perform step S 202 : 
     S 202 : The terminal device  300  provides configuration information to the network node  200  that provides network access to the terminal device  300 . The configuration information specifies that the terminal device  300  is in need for evaluating different polarization states in different time units during the beam management procedure. 
     The provided information is then used when the beam management procedure is performed. In particular, the terminal device  300  is configured to perform step S 204 : 
     S 204 : The terminal device performs the beam management procedure with the network node  200 . The beam management procedure involves the terminal device  300  to, per slot, receive reference signals from the network node  200  according to a reference signal reception scheme. The reference signal reception scheme depends on the provided configuration information. 
     Although the reference signal reception scheme might be regarded as dictated based on information received from the network node  200 , the reference signal reception scheme itself is not necessarily signaled to the terminal device  300  from the network node  200 . Rather, the reference signal reception scheme is defined by the way the terminal device  300  operates. 
     Embodiments relating to further details of performing a beam management procedure as performed by the terminal device  300  will now be disclosed. 
     There could be different types of reference signal reception schemes. In some aspects, the reference signal reception scheme defines where in the slot the reference signals are to be received. In particular, in some embodiments where each of the different time units corresponds to a respective OFDM symbol, the reference signal reception scheme defines at which OFDM symbols per slot that the reference signals are to be received. 
     Embodiments according to which the amount of reference signals to be transmitted, and thus be received by the terminal device  300 , can be adapted according to the configuration information will now be disclosed. In some aspects, these embodiments can be readily combined with the above described P-2 sub-procedure. Further aspects relating thereto are also disclosed below with reference to  FIG.  6   . 
     As disclosed above, in some aspects, the total number of reference signals to be transmitted per slot is equal to twice the number of beams in which the reference signals are to be transmitted at the TRP  140 . Therefore, half of the reference signals might be received in each polarization. That is, in some embodiments, when performing the beam management procedure, half of the reference signals are received using a first polarization whereas the remaining half of the reference signals are received using a second polarization. Further, as disclosed above, according to the beam management procedure, the reference signals might be transmitted in beams. Then, according to the reference signal reception scheme, each reference signal per beam and per slot might be received once using the first polarization and once using the second polarization. Further in this respect, the terminal device  300  might be notified about which reference signals are transmitted in the same beam and which reference signals are transmitted in different beams. 
     The above embodiments enable the terminal device  300  to, during a beam sweep of a P-2 sub-procedure, measure the RSRP for each beam for both polarizations at the terminal device  300 . 
     Embodiments according to which positions in the slot where the reference signals are placed can be adapted according to the configuration information will now be disclosed. In some aspects, these embodiments can be readily combined with the above described P-3 sub-procedure. Further aspects relating thereto are also disclosed below with reference to  FIG.  7   . 
     As disclosed above, in some embodiments, the configuration information further specifies that the terminal device  300  is configured to generate N&gt;1 beams per polarization of the antenna elements. 
     As disclosed above, in some embodiments, how many reference signals that are to be received per slot depends on N. 
     As disclosed above, according to a first example, the total number of reference signals to be transmitted per slot as part of the beam management procedure is less than 2·N. Therefore, in some embodiments, according to the reference signal reception scheme, fewer reference signals than 2·N are to be received per slot. As further disclosed above, according to a second example, the total number of reference signals to be transmitted per slot as part of the beam management procedure is equal to N+2. Therefore, in some embodiments, according to the reference signal reception scheme, exactly N+2 reference signals are to be received per slot. 
     As disclosed above, two of the reference signals might in the slot be separated in time from the remaining reference signals. Therefore, in some embodiments, according to the reference signal reception scheme, two of the reference signals are in the slot separated by at least one OFDM symbol from the remaining N reference signals, and these two of the reference signals are to be received before the remaining N reference signals. 
     As disclosed above, two reference signals might be placed first in the slot and the remaining reference signals might be placed last in the same slot. Therefore, in some embodiments, according to the reference signal reception scheme, two of the reference signals are placed to be received as early as possible in the slot, and wherein said remaining N reference signals are placed to be received as late as possible in the slot. 
     In some aspects, the terminal device  300  first evaluates the preferred polarization and then uses best polarization when receiving the remaining reference signals. When evaluating the preferred polarization, the terminal device  300  might use a comparatively wider beam, or beams, than the beam, or beams, used for receiving the remaining reference signals. This is also illustrated in  FIG.  7    as referred to below. In particular, in some embodiments, when performing the beam management procedure, RSRP of a first of the two of the reference signals as received using a first polarization is compared to RSRP of a second of the two of the reference signals as received using a second polarization, and wherein the remaining N reference signals are received using that polarization (of the first polarization and the second polarization) yielding highest RSRP. 
     The above embodiments enable the terminal device  300  to, during a beam sweep of a P-3 sub-procedure, first evaluate the preferred polarization, and then evaluate a preferred narrow beam for the preferred polarization. 
     One example of how some of the herein disclosed embodiments can be readily combined with the above described P-2 sub-procedure will now be disclosed. 
     Since the network node  200  obtains configuration information from the terminal device  300  where the configuration information specifies that the terminal device  300  is in need for evaluating different polarization states in different time units during the beam management procedure, the network node  200  might schedule a P-2 sub-procedure according to which a beam sweep is performed such that the terminal device  300  can evaluate reference signals transmitted in each beam for both the first polarization and the second polarizations at the terminal device  300 . This can be achieved for example, by the network node  200  scheduling transmission of the reference signals in the beams by repeating a CSI-RS resource transmission in each beam two times. This enables the reference signals transmitted in each beam to, by the terminal device  300 , be received using first the first polarization and then the second polarization, or vice versa. This is schematically illustrated in  FIG.  6   . In further detail,  FIG.  6    illustrates transmission of reference signals in OFDM symbols of a slot  600  as well as the beams  630  used by the TRP  140  to transmit the reference signals and the beams  640  used by the terminal device  300  to receive the reference signals. The slot boo is made up of  14  OFDM symbols  610 ,  620 . The six last OFDM symbols, one of which is identified at reference numeral  620 , contain CSI-RS resources (for beam management), whereas the remaining OFDM symbols, one of which is identified at reference numeral  610 , do not contain any CSI-RS resources (for beam management). According to the examples of  FIG.  6   , the terminal device  300  is enabled to evaluate three different beams in which reference signals are sent. The reference signals are transmitted twice per each beam such that each of the three beams can be evaluated in each of the first polarization and the second polarization at the terminal device  300 . This will improve the beam selection at the TRP  140  due to reduced risk of polarization mismatching. 
     One example of how some of the herein disclosed embodiments can be readily combined with the above described P-3 sub-procedure will now be disclosed. 
     Since the network node  200  obtains configuration information from the terminal device  300  where the configuration information specifies that the terminal device  300  is in need for evaluating different polarization states in different time units during the beam management procedure, the network node  200  might schedule a P-3 sub-procedure according to which the terminal device  303  is enabled to first evaluate the preferred polarization state, and then perform a beam sweep for the preferred polarization state. This is schematically illustrated in  FIG.  7   . In further detail,  FIG.  7    illustrates transmission of reference signals in OFDM symbols of a slot  700  as well as the beams  730 ,  740  used by the terminal device  300  to receive the reference signals. 
     The slot  700  is made up of 14 OFDM symbols  710 ,  720 . The two first OFDM symbols and the four last OFDM symbols, one of which is identified at reference numeral  720 , contain CSI-RS resources (for beam management), whereas the remaining OFDM symbols, one of which is identified at reference numeral  710 , do not contain any CSI-RS resources (for beam management). For reception of the first two CSI-RS resources, the terminal device  300  generates two wide beams  730  of mutually orthogonal polarizations (defined by the first polarization and the second polarization). Based on RSRP measurements of the first two CSI-RS resources the terminal device  300  determines which polarization that is preferred. In the illustrative example of  FIG.  7    it is assumed that the first polarization yielded highest RSRP and thus represents the preferred polarization. The terminal device  300  when receiving the last four OFDM symbols containing CSI-RS resources sweeps through four narrow beams  740  in the preferred polarization. 
       FIG.  8    schematically illustrates, in terms of a number of functional units, the components of a network node  200  according to an embodiment. Processing circuitry  210  is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product  1210   a  (as in  FIG.  12   ), e.g. in the form of a storage medium  230 . The processing circuitry  210  may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA). 
     Particularly, the processing circuitry  210  is configured to cause the network node  200  to perform a set of operations, or steps, as disclosed above. For example, the storage medium  230  may store the set of operations, and the processing circuitry  210  may be configured to retrieve the set of operations from the storage medium  230  to cause the network node  200  to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus the processing circuitry  210  is thereby arranged to execute methods as herein disclosed. 
     The storage medium  230  may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory. 
     The network node  200  may further comprise a communications interface  220  for communications with other entities, functions, nodes, and devices of the communication network  100  as well as entities, functions, nodes, and devices operatively connected to, or served, by, the communication network  100 . As such the communications interface  220  may comprise one or more transmitters and receivers, comprising analogue and digital components. 
     The processing circuitry  210  controls the general operation of the network node  200  e.g. by sending data and control signals to the communications interface  220  and the storage medium  230 , by receiving data and reports from the communications interface  220 , and by retrieving data and instructions from the storage medium  230 . Other components, as well as the related functionality, of the network node  200  are omitted in order not to obscure the concepts presented herein. 
       FIG.  9    schematically illustrates, in terms of a number of functional modules, the components of a network node  200  according to an embodiment. The network node  200  of  FIG.  9    comprises a number of functional modules; an obtain module  210   a  configured to perform step S 102 , and a beam management module  210   b  configured to perform step S 104 . The network node  200  of  FIG.  9    may further comprise a number of optional functional modules, such represented by functional module  210   c.  In general terms, each functional module  210   a - 210   c  may be implemented in hardware or in software. Preferably, one or more or all functional modules  210   a - 210   c  may be implemented by the processing circuitry  210 , possibly in cooperation with the communications interface  220  and/or the storage medium  230 . The processing circuitry  210  may thus be arranged to from the storage medium  230  fetch instructions as provided by a functional module  210   a - 210   c  and to execute these instructions, thereby performing any steps of the network node  200  as disclosed herein. 
     The network node  200  may be provided as a standalone device or as a part of at least one further device. For example, the network node  200  may be provided in a node of the radio access network  110  or in a node of the core network  120 . Alternatively, functionality of the network node  200  may be distributed between at least two devices, or nodes. These at least two nodes, or devices, may either be part of the same network part (such as the radio access network  110  or the core network  120 ) or may be spread between at least two such network parts. In general terms, instructions that are required to be performed in real time may be performed in a device, or node, operatively closer to the cell than instructions that are not required to be performed in real time. In this respect, at least part of the network node  200  may reside in the radio access network, such as in the radio access network node, for cases when embodiments as disclosed herein are performed in real time. 
     Thus, a first portion of the instructions performed by the network node  200  may be executed in a first device, and a second portion of the instructions performed by the network node  200  may be executed in a second device; the herein disclosed embodiments are not limited to any particular number of devices on which the instructions performed by the network node  200  may be executed. Hence, the methods according to the herein disclosed embodiments are suitable to be performed by a network node  200  residing in a cloud computational environment. Therefore, although a single processing circuitry  210  is illustrated in  FIG.  8    the processing circuitry  210  may be distributed among a plurality of devices, or nodes. The same applies to the functional modules  210   a - 210   c  of  FIG.  9    and the computer program  1220   a  of  FIG.  12   . 
       FIG.  10    schematically illustrates, in terms of a number of functional units, the components of a terminal device  300  according to an embodiment. Processing circuitry  310  is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product  1210   b  (as in  FIG.  12   ), e.g. in the form of a storage medium  330 . The processing circuitry  310  may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA). 
     Particularly, the processing circuitry  310  is configured to cause the terminal device  300  to perform a set of operations, or steps, as disclosed above. For example, the storage medium  330  may store the set of operations, and the processing circuitry  310  may be configured to retrieve the set of operations from the storage medium  330  to cause the terminal device  300  to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus the processing circuitry  310  is thereby arranged to execute methods as herein disclosed. 
     The storage medium  330  may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory. 
     The terminal device  300  may further comprise a communications interface  320  for communications at least with the network node  200  via the TRP  140 . As such the communications interface  320  may comprise one or more transmitters and receivers, comprising analogue and digital components. In this respect, the communications interface  320  might comprise, or be operatively connected to, an antenna architecture as described above with reference to  FIG.  2   . 
     The processing circuitry  310  controls the general operation of the terminal device  300  e.g. by sending data and control signals to the communications interface  320  and the storage medium  330 , by receiving data and reports from the communications interface  320 , and by retrieving data and instructions from the storage medium  330 . Other components, as well as the related functionality, of the terminal device  300  are omitted in order not to obscure the concepts presented herein. 
       FIG.  11    schematically illustrates, in terms of a number of functional modules, the components of a terminal device  300  according to an embodiment. The terminal device  300  of  FIG.  11    comprises a number of functional modules; a provide module  310   a  configured to perform step S 202 , and a beam management module  310   b  configured to perform step S 204 . The terminal device  300  of  FIG.  11    may further comprise a number of optional functional modules, as represented by functional module  310   c.  In general terms, each functional module  310   a - 310   c  may be implemented in hardware or in software. Preferably, one or more or all functional modules  310   a - 310   c  may be implemented by the processing circuitry  310 , possibly in cooperation with the communications interface  320  and/or the storage medium  330 . The processing circuitry  310  may thus be arranged to from the storage medium  330  fetch instructions as provided by a functional module  310   a - 310   c  and to execute these instructions, thereby performing any steps of the terminal device  300  as disclosed herein. 
       FIG.  12    shows one example of a computer program product  1210   a,    1210   b  comprising computer readable means  1230 . On this computer readable means  1230 , a computer program  1220   a  can be stored, which computer program  1220   a  can cause the processing circuitry  210  and thereto operatively coupled entities and devices, such as the communications interface  220  and the storage medium  230 , to execute methods according to embodiments described herein. The computer program  1220   a  and/or computer program product  1210   a  may thus provide means for performing any steps of the network node  200  as herein disclosed. On this computer readable means  1230 , a computer program  1220   b  can be stored, which computer program  1220   b  can cause the processing circuitry  310  and thereto operatively coupled entities and devices, such as the communications interface  320  and the storage medium  330 , to execute methods according to embodiments described herein. The computer program  1220   b  and/or computer program product  1210   b  may thus provide means for performing any steps of the terminal device  300  as herein disclosed. 
     In the example of  FIG.  12   , the computer program product  1210   a,    1210   b  is illustrated as an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-Ray disc. The computer program product  1210   a,    1210   b  could also be embodied as a memory, such as a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM) and more particularly as a non-volatile storage medium of a device in an external memory such as a USB (Universal Serial Bus) memory or a Flash memory, such as a compact Flash memory. Thus, while the computer program  1220   a,    1220   b  is here schematically shown as a track on the depicted optical disk, the computer program  1220   a,    1220   b  can be stored in any way which is suitable for the computer program product  1210   a,    1210   b.    
       FIG.  13    is a schematic diagram illustrating a telecommunication network connected via an intermediate network  420  to a host computer  430  in accordance with some embodiments. In accordance with an embodiment, a communication system includes telecommunication network  410 , such as a 3GPP-type cellular network, which comprises access network  411 , such as radio access network no in  FIG.  1   , and core network  414 , such as core network  120  in  FIG.  1   . Access network  411  comprises a plurality of radio access network nodes  412   a,    412   b,    412   c,  such as NBs, eNBs, gNBs (each corresponding to the network node  200  of  FIG.  1   ) or other types of wireless access points, each defining a corresponding coverage area, or cell,  413   a,    413   b,    413   c.  Each radio access network nodes  412   a,    412   b,    412   c  is connectable to core network  414  over a wired or wireless connection  415 . A first UE  491  located in coverage area  413   c  is configured to wirelessly connect to, or be paged by, the corresponding network node  412   c.  A second UE  492  in coverage area  413   a  is wirelessly connectable to the corresponding network node  412   a.  While a plurality of UE  491 ,  492  are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole terminal device is connecting to the corresponding network node  412 . The UEs  491 ,  492  correspond to the terminal device  300  of  FIG.  1   . 
     Telecommunication network  410  is itself connected to host computer  430 , which may be embodied in the hardware and/or software of a standalone server, a cloud-implemented server, a distributed server or as processing resources in a server farm. Host computer  430  may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. Connections  421  and  422  between telecommunication network  410  and host computer  430  may extend directly from core network  414  to host computer  430  or may go via an optional intermediate network  420 . Intermediate network  420  may be one of, or a combination of more than one of, a public, private or hosted network; intermediate network  420 , if any, may be a backbone network or the Internet; in particular, intermediate network  420  may comprise two or more sub-networks (not shown). 
     The communication system of  FIG.  13    as a whole enables connectivity between the connected UEs  491 ,  492  and host computer  430 . The connectivity may be described as an over-the-top (OTT) connection  450 . Host computer  430  and the connected UEs  491 ,  492  are configured to communicate data and/or signaling via OTT connection  450 , using access network  411 , core network  414 , any intermediate network  420  and possible further infrastructure (not shown) as intermediaries. OTT connection  450  may be transparent in the sense that the participating communication devices through which OTT connection  450  passes are unaware of routing of uplink and downlink communications. For example, network node  412  may not or need not be informed about the past routing of an incoming downlink communication with data originating from host computer  430  to be forwarded (e.g., handed over) to a connected UE  491 . Similarly, network node  412  need not be aware of the future routing of an outgoing uplink communication originating from the UE  491  towards the host computer  430 . 
       FIG.  14    is a schematic diagram illustrating host computer communicating via a radio access network node with a UE over a partially wireless connection in accordance with some embodiments. Example implementations, in accordance with an embodiment, of the UE, radio access network node and host computer discussed in the preceding paragraphs will now be described with reference to  FIG.  14   . In communication system  500 , host computer  510  comprises hardware  515  including communication interface  516  configured to set up and maintain a wired or wireless connection with an interface of a different communication device of communication system  500 . Host computer  510  further comprises processing circuitry  518 , which may have storage and/or processing capabilities. In particular, processing circuitry  518  may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. Host computer  510  further comprises software  511 , which is stored in or accessible by host computer  510  and executable by processing circuitry  518 . Software  511  includes host application  512 . Host application  512  may be operable to provide a service to a remote user, such as UE  530  connecting via OTT connection  550  terminating at UE  530  and host computer  510 . The UE  530  corresponds to the terminal device  300  of  FIG.  1   . In providing the service to the remote user, host application  512  may provide user data which is transmitted using OTT connection  550 . 
     Communication system  500  further includes radio access network node  520  provided in a telecommunication system and comprising hardware  525  enabling it to communicate with host computer  510  and with UE  530 . The radio access network node  520  corresponds to the network node  200  of  FIG.  1   . Hardware  525  may include communication interface  526  for setting up and maintaining a wired or wireless connection with an interface of a different communication device of communication system  500 , as well as radio interface  527  for setting up and maintaining at least wireless connection  570  with UE  530  located in a coverage area (not shown in  FIG.  14   ) served by radio access network node  520 . Communication interface  5 ≢may be configured to facilitate connection  560  to host computer  510 . Connection  560  may be direct or it may pass through a core network (not shown in  FIG.  14   ) of the telecommunication system and/or through one or more intermediate networks outside the telecommunication system. In the embodiment shown, hardware  525  of radio access network node  520  further includes processing circuitry  528 , which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. Radio access network node  520  further has software  521  stored internally or accessible via an external connection. 
     Communication system  500  further includes UE  530  already referred to. Its hardware  535  may include radio interface  537  configured to set up and maintain wireless connection  570  with a radio access network node serving a coverage area in which UE  530  is currently located. Hardware  535  of UE  530  further includes processing circuitry  538 , which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. UE  530  further comprises software  531 , which is stored in or accessible by UE  530  and executable by processing circuitry  538 . Software  531  includes client application  532 . Client application  532  may be operable to provide a service to a human or non-human user via UE  530 , with the support of host computer  510 . In host computer  510 , an executing host application  512  may communicate with the executing client application  532  via OTT connection  550  terminating at UE  530  and host computer  510 . In providing the service to the user, client application  532  may receive request data from host application  512  and provide user data in response to the request data. OTT connection  550  may transfer both the request data and the user data. Client application  532  may interact with the user to generate the user data that it provides. 
     It is noted that host computer  510 , radio access network node  520  and UE  530  illustrated in  FIG.  14    may be similar or identical to host computer  430 , one of network nodes  412   a,    412   b,    412   c  and one of UEs  491 ,  492  of  FIG.  13   , respectively. This is to say, the inner workings of these entities may be as shown in  FIG.  14    and independently, the surrounding network topology may be that of  FIG.  13   . 
     In  FIG.  14   , OTT connection  550  has been drawn abstractly to illustrate the communication between host computer  510  and UE  530  via network node  520 , without explicit reference to any intermediary devices and the precise routing of messages via these devices. Network infrastructure may determine the routing, which it may be configured to hide from UE  530  or from the service provider operating host computer  510 , or both. While OTT connection  550  is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network). 
     Wireless connection  570  between UE  530  and radio access network node  520  is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to UE  530  using OTT connection  550 , in which wireless connection  570  forms the last segment. More precisely, the teachings of these embodiments may reduce interference, due to improved classification ability of airborne UEs which can generate significant interference. 
     A measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring OTT connection  550  between host computer  510  and UE  530 , in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring OTT connection  550  may be implemented in software  511  and hardware  515  of host computer  510  or in software  531  and hardware  535  of UE  530 , or both. In embodiments, sensors (not shown) may be deployed in or in association with communication devices through which OTT connection  550  passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software  511 ,  531  may compute or estimate the monitored quantities. The reconfiguring of OTT connection  550  may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not affect network node  520 , and it may be unknown or imperceptible to radio access network node  520 . Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling facilitating host computer&#39;s  510  measurements of throughput, propagation times, latency and the like. The measurements may be implemented in that software  511  and  531  causes messages to be transmitted, in particular empty or ‘dummy’ messages, using OTT connection  550  while it monitors propagation times, errors etc. 
     The inventive concept has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended patent claims.