WO2023191673A1

WO2023191673A1 - Method and network node for handling a phased array antenna module of a network node of a wireless communication network

Info

Publication number: WO2023191673A1
Application number: PCT/SE2022/050318
Authority: WO
Inventors: Bo Göransson; Jing Rao
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2022-03-30
Filing date: 2022-03-30
Publication date: 2023-10-05

Abstract

Disclosed is a method performed by a network node (130) of a wireless communication network (100) for handling of a Phased Array Antenna Module, PAAM, of the network node (130). The method comprises splitting the PAAM into a first part and a second part, whereby the first part and the second part each supports the PAAM bandwidth, but a frequency range can be set individually for the first part and the second part. The method further comprises communicating signals with any of UEs (140, 141) using the first part of the PAAM over a first set of carriers spanning a first frequency range and a second set of carriers spanning a second frequency range, the first and second frequency range together summing up to the PAAM bandwidth or a smaller bandwidth, and communicating signals with any of the UEs (140, 141 ) using the second part of the PAAM over the second set of carriers and a third set of carriers spanning a third frequency range, the second and third frequency range together summing up to the PAAM bandwidth or a smaller bandwidth.

Description

METHOD AND NETWORK NODE FOR HANDLING A PHASED ARRAY ANTENNA MODULE OF A NETWORK NODE OF A WIRELESS COMMUNICATION NETWORK

Technical Field

[0001] The present disclosure relates generally to methods and network nodes for handling a phased array antenna module (PAAM) of a network node of a wireless communication network. The present disclosure further relates to computer programs and carriers corresponding to the above methods and nodes.

Background

[0002] In order to cater for the increasing demand of throughput in wireless communication networks, and especially over the air interface between a wireless communication device, also known as User Equipment (UE), and a base station, also known as network node, Multiple Input Multiple Output (MIMO) techniques have been developed. MIMO techniques have first been adopted to practice in Long Term Evolution (LTE), aka 4G. In New Radio (NR), aka 5G, it becomes one key technology component, which will be deployed in a much larger scale than in LTE. In MIMO, the network node has a large number of antenna branches for transmitting and receiving wireless signals, each antenna branch having at least one antenna element or, shortly, antenna. It may also be possible that the UE has a plurality of antenna branches.

[0003] In MIMO techniques, the antenna branches are used for beamforming wireless signals to be transmitted and received. Beamforming means focusing the sent signals in different directions, for a network node especially in a direction of a UE with which the network node communicates. Hereby, transmission capacity of the network node is saved.

[0004] There are time-domain and frequency-domain beamforming, as well as digital and analog beamforming. In time-domain analog beamforming, the same signal is distributed in time-domain into at least a part of all antenna branches of a network node. By only adjusting the phase of the signal at the individual antenna branches, a narrow, sharp beam with a rather high gain can be created by the wirelessly transmitted resulting signal, resulting from the simultaneous transmission of signals from the individual antenna branches. When all antenna branches are used simultaneously for transmission to one UE, or for one user layer, over one and the same frequency resource, it is called single-user MIMO (SU-MIMO). When one beam in one direction is used to serve a first UE and another beam in another direction is used to serve a second UE simultaneously over the same frequency resource, it is called multi-user MIMO (MU-MIMO). In analog beamforming, MU-MIMO may be accomplished by splitting the antenna panel so that a first set of antenna branches are used for beamforming and transmission to the first UE and a second set of antenna branches are used for beamforming and transmission simultaneously to the second UE over the same frequency resource.

[0005] Current radio frequency (RF) front-end and beamforming functionality are usually built on a phased array antenna module (PAAM) concept. This means that beamforming and RF Integrated Circuits (RFICs) are mounted on an antenna array panel with dual polarized antenna elements, and each RFIC is connected to a set of antenna elements, different antenna elements for different RFICs. Mainly, analog BF is used, but the principle will be the same when digital beamforming is introduced. An example of a PAAM implementation is shown in fig. 1 . On one side of a PAAM 30, four RFICs 41 , 43, 45, 47 are mounted. In this example, each RFIC serves 16 dual polarized antenna elements 42, 44, 46, 48, respectively. The antenna elements are shown in fig. 1 to be on one side of the RFIC but in reality, they are in this example situated on the opposite site of the PAAM 30 from the RFICs 41 , 43, 45, 47. However, they may be situated anywhere as long as the antenna elements are connected to their respective RFIC.

[0006] The PAAM supports a certain bandwidth, for example 400MHz, which will limit the use if the operator of the wireless communication network has access to a larger spectrum, that is, if the network node is allowed to transmit over a frequency range that spans a larger bandwidth than the bandwidth the PAAM supports. To solve this, the PAAM can be divided into two or more parts, a so called PAAM split. Then half of the RFICs 41 , 43 of the PAAM serves half of the antenna elements 42, 44 of the PAAM and the other half of the RFICs 45, 47 serves the other half of the antenna elements 46, 48. Then each part can be allocated to support a bandwidth of 400MHz. Fig 2 shows in the left illustration a non-split PAAM 50 that serves a frequency range of 0-400 MHz (before transforming to RF) and forms one dual-polarized antenna beam 51a, 51 b. The middle illustration of fig. 2 shows a PAAM 52 that have been split into two parts, a first part 54 and a second part 56. By this, a total bandwidth of 800MHz can be supported; 0-400 MHz by the first part 54 that forms one dual-polarized antenna beam 55a, 55b and 400-800 MHz by the second part 56 that forms another dualpolarized antenna beam 57a, 57b. By splitting the PAAM, each part will not only be served by half of the available power amplifiers it will also use only half of the total amount of antenna elements on the array. By this, the Effective Isotropic Radiated Power (EIRP) for each PAAM part will have 3+3 = 6dB lower EIRP compared to if the full PAAM is used for a carrier. It is possible to achieve the same bandwidth expansion without EIRP loss by adding an additional PAAM to support the 800MHz, but this comes of course with an increased cost in size, power consumption and bill of material.

[0007] It is noted that a PAAM split can also be used to support MU-MIMO or higher order SU-MIMO, which means many user layer signals are communicated with one UE. In the right illustration of fig. 2, the same frequency range (0-400 MHz) has been added to the two split PAAM parts 64, 66. Hereby, one UE can be served by a dual polarized beam 65a, 65b by the first part 64 of the PAAM while another UE is served on the same frequency range by a dual polarized beam 67a, 67b by the second part 66. In the illustrations of fig. 2 it is further assumed that both polarizations are mapped to one UE, but it is assumed that one beamforming per polarization is available so that the two polarizations can be directed in two different directions if needed.

[0008] A problem with the prior art splits shown in fig. 2 occurs when, for example, only 600MHz of frequency spectrum is available by the network node for deployment. In such a case, when there is maximum 400 MHZ PAAM bandwidth, it will not be possible to use all the available spectrum of 600 MHz without a PAAM split. But it will also be wasteful to split the PAAM according to the middle illustration of fig. 2 since 200MHz in one part will not be usable since only 600MHz spectrum is available for the network node. Similarly, if the PAAM is split for MU-MIMO support as in the right illustration of fig. 2, it will not be possible to use more than 400MHz of the available spectrum. As shown, there is a need for an improved PAAM handling that efficiently makes use of an available spectrum that is larger than the PAAM bandwidth but smaller than twice the PAAM bandwidth.

Summary

[0009] It is an object of the invention to address at least some of the problems and issues outlined above. It is an object of embodiments of the invention to achieve an efficient PAAM handling. It is an object of embodiments of the invention to achieve a PAAM handling that efficiently uses a spectrum available to the network node in relation to the PAAM bandwidth. It is an object of embodiments of the invention to achieve a PAAM handling that efficiently makes use of an available spectrum that is larger than the PAAM bandwidth but smaller than twice the PAAM bandwidth. It is possible to achieve one or more of these objects and possibly others by using methods and network nodes as defined in the attached independent claims.

[00010] According to one aspect, a method for PAAM handling is provided that is performed by a network node of a wireless communication network. The network node comprises the PAAM, whereby the network node is capable of forming beams for directed communication of wireless signals with a number of UEs, the PAAM supporting a PAAM bandwidth. The method comprises splitting the PAAM into a first part and a second part, whereby the first part and the second part each supports the PAAM bandwidth, but a frequency range can be set individually for the first part and the second part. The method further comprises communicating signals with any of the number of UEs using the first part of the PAAM over a first set of carriers spanning a first frequency range and a second set of carriers spanning a second frequency range, the second set of carriers being on different frequencies than the first set of carriers, the first and second frequency range together summing up to the PAAM bandwidth or a smaller bandwidth, and communicating signals with any of the number of UEs using the second part of the PAAM over the second set of carriers and a third set of carriers spanning a third frequency range, and the third set of carriers being on different frequencies than the first and second set of carriers, the second and third frequency range together summing up to the PAAM bandwidth or a smaller bandwidth.

[00011] According to another aspect, a network node is provided configured to operate in a wireless communication network. The network node is configured for PAAM handling. The network node comprises the PAAM, whereby the network node is capable of forming beams for directed communication of wireless signals with a number of UEs. The PAAM supports a PAAM bandwidth. The network node comprises a processing circuitry and a memory. Said memory contains instructions executable by said processing circuitry, whereby the network node is operative for splitting the PAAM into a first part and a second part, whereby the first part and the second part each supports the PAAM bandwidth, but a frequency range can be set individually for the first part and the second part. The network node is further operative for communicating signals with any of the number of UEs using the first part of the PAAM over a first set of carriers spanning a first frequency range and a second set of carriers spanning a second frequency range, the second set of carriers being on different frequencies than the first set of carriers, the first and second frequency range together summing up to the PAAM bandwidth or a smaller bandwidth, and communicating signals with any of the number of UEs using the second part of the PAAM over the second set of carriers and a third set of carriers spanning a third frequency range, and the third set of carriers being on different frequencies than the first and second set of carriers, the second and third frequency range together summing up to the PAAM bandwidth or a smaller bandwidth.

[00012] According to other aspects, computer programs and carriers are also provided, the details of which will be described in the claims and the detailed description. [00013] Further possible features and benefits of this solution will become apparent from the detailed description below.

Brief Description of Drawings

[00014] The solution will now be described in more detail by means of exemplary embodiments and with reference to the accompanying drawings, in which:

[00015] Fig. 1 is a schematic block diagram of a PAAM in which the present invention may be used.

[00016] Fig. 2 is a block diagram illustrating a non-split PAAM and two prior art PAAM splits.

[00017] Fig. 3 schematic diagram of a wireless communication network in which the present invention may be used.

[00018] Fig. 4 is a flow chart illustrating a method performed by a network node, according to possible embodiments.

[00019] Fig. 5 is a frequency diagram illustrating an example of allocation of frequencies to PAAM subpanels according to possible embodiments.

[00020] Fig. 6 is a schematic diagram of a vertical split of a PAAM illustrating phase offset between the vertically split parts, according to possible embodiments.

[00021] Fig. 7 is a frequency diagram illustrating an example of allocation of frequencies to PAAM subpanels when digital beamforming is used, according to possible embodiments.

[00022] Fig. 8 comprises two diagrams of beam patterns in azimuth and elevation defined space.

[00023] Fig. 9 is a schematic block diagram of a network node in more detail, according to possible embodiments. Detailed Description

[00024] In the following is focused on the embodiment when two beams (one per polarization) can be generated by a PAAM or a PAAM part after split. This is most often the case when analog beamforming is used. In a digital beamforming implementation, the number of simultaneous beams is restricted by the number of (complex) matrix multipliers available in the RFIC. If more than two simultaneous beams can be generated, the same basic principles will still be valid, e.g., if 4 beams can be generated, a split is needed if more than 4 beams are needed in a specific situation. Furthermore, with analog beamforming the same beam is used for the total PAAM bandwidth, e.g. 400MHz, while if a digital implementation is considered it might be possible to allocate beams per carrier with a carrier bandwidth of e.g. 100MHz.

[00025] Fig. 3 shows a wireless communication network 100 comprising a radio access network (RAN) node aka network node 130 that is in, or is adapted for, wireless communication with a wireless communication device aka wireless device 140, aka UE. The network node 130 provides radio access in a cell 150 covering a geographical area.

[00026] The wireless communication network 100 may be any kind of wireless communication network that can provide radio access to wireless devices. Example of such wireless communication networks are networks based on Global System for Mobile communication (GSM), Enhanced Data Rates for GSM Evolution (EDGE), Universal Mobile Telecommunications System (UMTS), Code Division Multiple Access 2000 (CDMA 2000), Long Term Evolution (LTE), LTE Advanced, Wireless Local Area Networks (WLAN), Worldwide Interoperability for Microwave Access (WiMAX), WiMAX Advanced, as well as fifth generation (5G) wireless communication networks based on technology such as New Radio (NR), and any possible future sixth generation (6G) wireless communication network.

[00027] The network node 130 may be any kind of network node that can provide wireless access to a wireless device 140 alone or in combination with another network node. Examples of network nodes 130 are a base station (BS), a radio BS, a base transceiver station, a BS controller, a network controller, a Node B (NB), an evolved Node B (eNB), a gNodeB (gNB), a Multi-cell/multicast Coordination Entity, a relay node, an access point (AP), a radio AP, a remote radio unit (RRU), a remote radio head (RRH) and a multi-standard BS (MSR BS).

[00028] The wireless device 140 may be any type of device capable of wirelessly communicating with a network node 130 using radio signals. For example, the wireless device 140 may be a User Equipment (UE), a machine type UE or a UE capable of machine to machine (M2M) communication, a sensor, a tablet, a mobile terminal, a smart phone, a laptop embedded equipped (LEE), a laptop mounted equipment (LME), a USB dongle, a Customer Premises Equipment (CPE), an Internet of Things (loT) device, etc.

[00029] The PAAM supports a bandwidth, i.e. the PAAM can transmit signals spanning over a total PAAM bandwidth, when operating in full mode, that is when all antennas are used for forming beams for one transmission. In other words, the RFICs of the PAAM has a maximum work span of the PAAM bandwidth. However, the frequency range over which the PAAM bandwidth spans can vary. For example, if the PAAM bandwidth is 400 MHZ, the frequency range can be e.g. 2GHz-2.4GHZ or 28GHz-28.4GHz.

[00030] However, it may happen that the operator of the network has more than the PAAM bandwidth available for deployment. Taking the above PAAM bandwidth of 400 MHZ as an example, the operator may have let us say 600 MHz spectrum available. In prior art shown in the middle illustration of fig. 2, the PAAM 52 is split into two parts 54, 46 where one part 54 transmits in a first frequency range of 0-400 MHz and the second part in another frequency range of 400-800 MHz, following the first span. But the operator only had 600 MHz available so the network node cannot use such a PAAM split. So, what is needed is an improved PAAM handling or configuration method that efficiently makes use of an available frequency spectrum that is larger than the PAAM bandwidth but smaller than twice the PAAM bandwidth [00031] Fig. 4, in connection with fig. 3, shows a method for PAAM handling performed by a network node 130 of a wireless communication network 100. The network node 130 comprises the PAAM 30 (see e.g., fig. 1 ), whereby the network node is capable of forming beams for directed communication of wireless signals with a number of UEs 140, 141 , the PAAM 30 supporting a PAAM bandwidth. The method comprises splitting 202 the PAAM into a first part and a second part, whereby the first part and the second part each supports the PAAM bandwidth, but a frequency range can be set individually for the first part and the second part. The method further comprises communicating 208 signals with any of the number of UEs 140, 141 using the first part of the PAAM over a first set of carriers spanning a first frequency range and a second set of carriers spanning a second frequency range, the second set of carriers being on different frequencies than the first set of carriers, the first and second frequency range together summing up to the PAAM bandwidth or a smaller bandwidth, and communicating 210 signals with any of the number of UEs 140, 141 using the second part of the PAAM over the second set of carriers and a third set of carriers spanning a third frequency range, and the third set of carriers being on different frequencies than the first and second set of carriers, the second and third frequency range together summing up to the PAAM bandwidth or a smaller bandwidth.

[00032] "Splitting" means dividing the PAAM into two different parts, wherein the first part is used for forming a first beam and the second part is used for forming a second beam that is separate from the first beam. So, the splitting means that the first part and second part work separately after the split for forming beams. The PAAM comprises a plurality of RFICs, where each RFIC is connected to a set of antenna elements. The splitting 202 is performed so that the first part of the PAAM comprises a first number of RFICs and the sets of antenna elements connected to those RFICs, and the second part comprises a second number of RFICs and the sets of antenna elements connected to those RFICs. According to an embodiment, the network node 130 may be distributed, i.e., it may be made up of two or more cooperating units. For example, certain control functionality could be located in a box that is separate from the PAAM. [00033] According to an embodiment, each carrier normally has the same bandwidth. According to another embodiment, the carriers are arranged on different and normally non-overlapping frequency ranges. The first set of carriers comprises one or more such carriers that may be arranged one after the other in frequency. The second set of carriers comprises one or more such carriers that may be arranged one after the other in frequency, but on different frequencies than the first set of carriers.

[00034] According to an embodiment, the frequencies covered by the first and the second frequency range together sums up to the PAAM bandwidth, i.e. the whole PAAM bandwidth is used over the first part of the PAAM. However, it might happen that the frequencies covered by the first and second frequency range together is smaller or slightly smaller than the PAAM bandwidth. For example, according to the 3GPP specification, there are a number of pre-defined carrier bandwidths. For FR2 (mmWave) they are 50, 100, 200 and 400MHz. Then there may be cases when not all carriers are allocated. E.g., 4x100MHz may be allocated on the first PAAM part, and only 3x100MHz on the second PAAM part. That is, not using the full PAAM bandwidth on both parts. According to another example, there is in total 550MHz spectrum available for the network node, and the PAAM bandwidth is 400 MHz. Then it may happen that 50 + 3*100 MHz is allocated on the first PAAM part and 4*100 MHZ on the second PAAM part.

[00035] By splitting the PAAM into two (or more) parts, a larger bandwidth can be used by the network node than the bandwidth supported by the PAAM without a split. Further, by communicating signals over frequencies in such an overlapping manner, i.e., so that the first part of the PAAM communicates signals partly over the same carrier frequencies as the second part of the PAAM, a spectrum available for the network node that is higher than the PAAM bandwidth but still lower than twice the PAAM bandwidth can be efficiently used. It also applies to any spectrum available to the network node that is not a multiple of the PAAM bandwidth. Such an overlapping of signal communication between the split parts of the PAAM results in a more efficient usage of the resources of the network node. [00036] According to an embodiment, the second set of carriers are adjacent in frequency to the first set of carriers and higher in frequency than the first set of carriers. Further, the third set of carriers are adjacent in frequency to the second set of carriers and higher in frequency than the second set of carriers. In other words, the second set of carriers that are used by both PAAM parts is the middle frequency part. That the first and second set of carriers and the second and third, respectively, are arranged adjacent in frequency also includes it being possible to have a small gap of some muted Physical Resource Blocks (PRBs) in between the set of carriers, In other words, that the set of carriers are arranged adjacent means that there are not any other carrier frequencies in between the set of frequencies over which any data is transmitted. As frequency spectrum is often given to the network node in one frequency range, such an arrangement is advantageous.

[00037] According to an embodiment, the signals communicated 208 using the first part of the PAAM over the second set of carriers are communicated with a first UE 140 of the number of UEs 140, 141 , and the signals communicated 210 using the second part of the PAAM over the second set of carriers are communicated with a second UE 141 of the number of UEs 140, 141. In other words, the signals communicated over the same second set of carriers from the first and the second PAAM part are communicated in MU-MIMO. Hereby, more UEs can be provided with communication with the network node than without the method, i.e. , a capacity increase of the network is achieved. Such MU-MIMO usage of the split PAAM is especially advantageous in good coverage situations, i.e., in cases where the signals communicated with the UEs in MU-MIMO have good signal quality.

[00038] According to another embodiment, the signals communicated 208 using the first part of the PAAM over the second set of carriers are communicated with a first UE 140 of the number of UEs 140, 141 . Also, the signals communicated 210 using the second part of the PAAM over the second set of carriers are also communicated with the first UE 140. In other words, the signals communicated over the same second set of carriers from the first and second part of the PAAM are communicated in SU-MIMO. Hereby, the first and second part of the PAAM can be used for directing signals to the same UE so there can be as high signal quality as when using the full PAAM, however only over the shared second carriers. In total, there will be an increase in signal quality to the UE compared to the prior art splits shown in fig. 2. The signals communicated using the first part of PAAM over the second set of carriers can be the same signals or data streams as the signals communicated using the second PAAM part over the second set of carriers, or they can be different signals or data streams.

[00039] According to another embodiment, shown in fig. 4, the method further comprises determining 204 a phase offset between the first part of the PAAM and the second part of the PAAM. Further, the signals communicated 208, 210 over the second set of carriers using the first and the second part of the PAAM are communicated based on the determined phase offset so that they become coherently combined. “They" here refer to the signals communicated over the second set of carriers from the first and the second part of the PAAM module. The determined phase offset is applied to one of the first or second part of the PAAM module when communicating the signals to achieve the coherent combining. The determining of the phase offset may be determined in real-time, such as after or immediately before the split, or it may be determined at startup of the network node or at any regular maintenance. By coherently combining the signals communicated over the second set of carriers using the first and the second part of the PAAM, an EIRP equivalent to the EIRP received when using a full PAAM can be achieved over the second set of carriers.

[00040] According to a first embodiment, the phase offset 204 is determined by the following: Determining a first channel estimate based on measurements performed on UL signals received at antennas of the first part of the PAAM, the UL signals being transmitted as first signals by the first UE 140 over the second set of carriers; Determining a second channel estimate based on measurements performed on UL signals received at antennas of the second part of the PAAM, the UL signals being transmitted as the first signals by the first UE 140 over the second set of carriers, and Determining the phase offset based on the first and second channel estimate. [00041] According to a second embodiment, the phase offset 204 is determined by the following: Transmitting, from the first part of the PAAM, reference signals towards the first UE 140; Transmitting, from the second part of the PAAM, the reference signals towards the first UE 140; Receiving, from the first UE 140, a Precoding Matrix Indicator (PMI) that the first UE determined to give the highest received signal quality out of a number of possible PMIs, when at the first UE receiving and combining the reference signals transmitted from the first and second part of the PAAM, and determining the phase offset based on the received PMI. Signal quality could be determined in many different known ways such as Reference Signal received Power (RSRP) as defined in 3GPP, signal strength (SS), signal to noise ratio (SNR) or signal to interference and noise ratio (SINR).

[00042] In the following, an embodiment will be described with reference to fig. 5, in which analog beamforming may be used. In fig. 5, the PAAM has been split into a first part, here called first subpanel and a second part here called second subpanel. In this embodiment, it is here assumed that each carrier is 100 MHz wide, the PAAM bandwidth is 400 MHz, and the set of carriers comprises two carriers each, however other carrier bandwidths, PAAM bandwidths and number of carriers in a set of carriers may apply. So, the first subpanel communicates signals with any of UEs over a first set of carriers 306 spanning frequencies X to X + 200 MHz and it also communicates signals with any of UEs over a second set of carriers 308 spanning frequencies X + 200 MHz to X + 400 MHz. Further, the second subpanel communicates signals with any of UEs over the second set of carriers 308 spanning frequencies X + 200 to X + 400 MHz and it also communicates signals with any of UEs over a third set of carriers 310 spanning frequencies X + 400 to X + 600 MHz. The first and third set of carriers 306, 310 are here communicated using SU-MIMO, i.e. , to one UE each. The second set of carriers 308 are communicated from both subpanels and can be scheduled in either SU-MIMO mode by e.g., coherent combining of the two subpanels, or in MU-MIMO mode with one user per subpanel. Beam 1 H and Beam 2V symbolizes the two polarization beams of subpanel 1 whereas Beam 3H and Beam 4V are the two polarization beams of subpanel 2. “H” stands for horizontal and “V stands for vertical. However, other polarizations may apply as well, such as Left-Right circular polarization or +45Z-45 slanted polarization.

[00043] By allocating carriers between the first and second subpanels in such a way, it will be possible to support larger bandwidth than supported by a full PAAM, i.e. a PAAM without splitting into subpanels. Certain carriers, here the first two 306, and the last two 310, will have an EIRP 6dB lower than the full PAAM, however the two carriers 308 transmitted from both subpanels can be combined to generate an EIRP similar to the full PAAM and hence there is no penalty on coverage for these carriers. Alternatively, for users in a favorable coverage situation, the two carriers 308 transmitted from both subpanels can be used for MU-MIMO and hence provide a capacity increase compared to the full PAAM case.

[00044] If carrier allocation is done according to the discussed embodiments, there exists at least two different ways to utilize both subpanels for the “middle” 200MHz. Fig. 6 illustrates a vertical subpanel split of a PAAM into a first subpanel 402 and a second subpanel 404, the two subpanels being vertically stacked. The first and second subpanels 402, 404 may have an unknown phase offset (|) between them and hence direct combining of the two beam is not preferred since the phase offset will lead to non-coherent combining. To regain the EIRP available for the full PAAM, such an unknown phase offset can be estimated and thereafter compensated for so that coherent combining can be achieved.

[00045] According to a first embodiment, the unknown phase offset (|) is estimated based on uplink (UL) measurements. A first channel estimate is determined based on measurements performed on UL signals, preferably UL reference signals received at antennas of the first subpanel 402, the UL signals being transmitted by the first UE 140 over the second set of carriers. Further, a second channel estimate is determined based on measurements performed on the same UL signals received at antennas of the second subpanel 404. The phase offset is then determined based on the first and second channel estimates. The phase offset is then applied to one of the subpanels when communicating to achieve coherent combining for the PAAM.

[00046] According to another embodiment, a 3GPP codebook transmission can be configured. In this mode, reference signals, such as Channel State Information Reference Signals (CSI-RS) are transmitted from each of the first and second subpanel 402, 404 towards the UE, and the UE reports back which PMI that would be preferred for a transmission interval. The reported PMI is then used to phase rotate the two beams transmitted from each subpanel. This would lead to coherent combining of the beams in the UE antenna.

[00047] Fig. 7 shows an embodiment of the invention in which digital beamforming is used. One of the differences between analog and digital beamforming is that an analog beamforming system forms same beam over the whole PAAM bandwidth, as shown in Fig. 5, while a digital beamforming system can form different beams over the PAAM bandwidth. As shown in the example of fig. 7, a first beam 1 H and its polarization beam 1V are sent from the first subpanel in a first of the first set of carriers 306 whereas a second beam 2H and its polarization beam 2V are sent in a second of the first set of carriers 306. Similarly, a third beam 3H and its polarization beam 3V are sent from the first subpanel in a first of the second set of carriers 308 whereas a fourth beam 4H and its polarization beam 4V are sent in a second of the second set of carriers 308. Still further, a fifth beam 5H and its polarization beam 5V are sent from the second subpanel in a first of the second set of carriers 308 whereas a sixth beam 6H and its polarization beam 6V are sent in a second of the second set of carriers 308. Similarly, a seventh beam 7H and its polarization beam 7V are sent from the second subpanel in a first of the third set of carriers 310 whereas an eighth beam 8H and its polarization beam 8V are sent in a second of the third set of carriers 310. Observe that such a split of beams are just an example to show how a split with digital beamforming can be made, but other splits for digital beamforming might be used as well. Also, other polarizations may apply as well, such as Left- Right circular polarization or +45Z-45 slanted polarization [00048] Note that when using the full PAAM, the generated beams will be “narrow” in both azimuth and elevation domain. The beam width is typically inverse proportional to a length of the array. If the beamwidth of a single element is 100°, the beam width generated by an array of 12 such elements with half wavelength separation is approximately 100/12=8°. With a horizontal split in two equal sized subpanels, the vertical beamwidth of a beam generated from the upper (or lower) part will have a beamwidth twice of that for a beam from the full PAAM. The upper diagram of fig. 8 illustrates a beam pattern from a full PAAM whereas the lower diagram of fig. 8 illustrates a beam pattern from an upper or lower part of such a horizontal split PAAM. Further, when coherently combining beams from upper and lower part of the PAAM in the case of SU-MIMO transmissions, the resulting beam will then resemble beams from using the full PAAM, i.e., the upper diagram of fig. 8.

[00049] Fig. 9, in conjunction with fig. 1 , discloses a network node 130 configured to operate in a wireless communication network 100. The network node is configured for PAAM handling. The network node 130 comprises the PAAM 606, whereby the network node is capable of forming beams for directed communication of wireless signals with a number of UEs 140, 141. The PAAM 606 supports a PAAM bandwidth. The network node 130 comprises a processing circuitry 603 and a memory 604. Said memory contains instructions executable by said processing circuitry, whereby the network node 130 is operative for splitting the PAAM 606 into a first part and a second part, whereby the first part and the second part each supports the PAAM bandwidth, but a frequency range can be set individually for the first part and the second part. The network node is further operative for communicating signals with any of the number of UEs 140, 141 using the first part of the PAAM over a first set of carriers spanning a first frequency range and a second set of carriers spanning a second frequency range, the second set of carriers being on different frequencies than the first set of carriers, the first and second frequency range together summing up to the PAAM bandwidth or a smaller bandwidth, and communicating signals with any of the number of UEs 140, 141 using the second part of the PAAM over the second set of carriers and a third set of carriers spanning a third frequency range, and the third set of carriers being on different frequencies than the first and second set of carriers, the second and third frequency range together summing up to the PAAM bandwidth or a smaller bandwidth.

[00050] According to an embodiment, the second set of carriers are adjacent in frequency to the first set of carriers and higher in frequency than the first set of carriers. Further, the third set of carriers are adjacent in frequency to the second set of carriers and higher in frequency than the second set of carriers.

[00051 ] According to another embodiment, the network node 130 is operative for communicating the signals using the first part of the PAAM 606 over the second set of carriers with a first UE 140 of the number of UEs 140, 141 , and operative for communicating the signals using the second part of the PAAM over the second set of carriers with a second UE 141 of the number of UEs 140, 141 .

[00052] According to another embodiment, the network node 130 is operative for communicating the signals using the first part of the PAAM 606 over the second set of carriers with a first UE 140 of the number of UEs 140, 141 , and operative for communicating the signals using the second part of the PAAM over the second set of carriers also with the first UE 140.

[00053] According to another embodiment, the network node 130 is further operative for determining a phase offset between the first part of the PAAM 606 and the second part of the PAAM, and operative for communicating the signals over the second set of carriers using the first and the second part of the PAAM based on the determined phase offset so that they become coherently combined.

[00054] According to yet another embodiment, the network node 130 is further operative for determining the phase offset by determining a first channel estimate based on measurements performed on UL signals received at antennas of the first part of the PAAM 606, the UL signals being transmitted as first signals by the first UE 140 over the second set of carriers, determining a second channel estimate based on measurements performed on UL signals received at antennas of the second part of the PAAM, the UL signals being transmitted as the first signals by the first UE 140 over the second set of carriers, and determining the phase offset based on the first and second channel estimate.

[00055] According to yet another embodiment, the network node 130 is further operative for determining the phase offset by transmitting, from the first part of the PAAM 606, reference signals towards the first UE 140, transmitting, from the second part of the PAAM, the reference signals towards the first UE 140, receiving, from the first UE 140, a Precoding Matrix Indicator, PMI, that the UE determined to give the highest received signal quality out of a number of possible PMIs, when at the UE receiving and combining the reference signals transmitted from the first and second part of the PAAM, and determining the phase offset based on the received PMI.

[00056] According to other embodiments, the network node 130 may further comprise a communication unit 602, which may be considered to comprise conventional means for wireless communication with the UEs 140, 141 , such as a transceiver for wireless transmission and reception of signals in the communication network. The communication unit 602 may also comprise conventional means for communication with other network nodes of the wireless communication network 100. The instructions executable by said processing circuitry 603 may be arranged as a computer program 605 stored e.g. in said memory 604. The processing circuitry 603 and the memory 604 may be arranged in a sub-arrangement 601. The sub-arrangement 601 may be a micro-processor and adequate software and storage therefore, a Programmable Logic Device, PLD, or other electronic component(s)/processing circuit(s) configured to perform the methods mentioned above. The processing circuitry 603 may comprise one or more programmable processor, application-specific integrated circuits, field programmable gate arrays or combinations of these adapted to execute instructions.

[00057] The computer program 605 may be arranged such that when its instructions are run in the processing circuitry, they cause the network node 130 to perform the steps described in any of the described embodiments of the network node 130 and its method. The computer program 605 may be carried by a computer program product connectable to the processing circuitry 603. The computer program product may be the memory 604, or at least arranged in the memory. The memory 604 may be realized as for example a RAM (Randomaccess memory), ROM (Read-Only Memory) or an EEPROM (Electrical Erasable Programmable ROM). In some embodiments, a carrier may contain the computer program 605. The carrier may be one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or computer readable storage medium. The computer-readable storage medium may be e.g. a CD, DVD or flash memory, from which the program could be downloaded into the memory 604. Alternatively, the computer program may be stored on a server or any other entity to which the network node 130 has access via the communication unit 602. The computer program 605 may then be downloaded from the server into the memory 604.

[00058] Although the description above contains a plurality of specificities, these should not be construed as limiting the scope of the concept described herein but as merely providing illustrations of some exemplifying embodiments of the described concept. It will be appreciated that the scope of the presently described concept fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the presently described concept is accordingly not to be limited. Reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more." All structural and functional equivalents to the elements of the abovedescribed embodiments that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed hereby. Moreover, it is not necessary for an apparatus or method to address each and every problem sought to be solved by the presently described concept, for it to be encompassed hereby. In the exemplary figures, a broken line generally signifies that the feature within the broken line is optional.

Claims

1 . A method performed by a network node (130) of a wireless communication network (100) for Phased Array Antenna Module, PAAM, handling, the network node (130) comprising the PAAM (30), whereby the network node is capable of forming beams for directed communication of wireless signals with a number of user equipment, UE (140, 141 ), the PAAM (30) supporting a PAAM bandwidth, the method comprising: splitting (202) the PAAM into a first part and a second part, whereby the first part and the second part each supports the PAAM bandwidth, but a frequency range can be set individually for the first part and the second part; communicating (208) signals with any of the number of UEs (140, 141 ) using the first part of the PAAM over a first set of carriers spanning a first frequency range and a second set of carriers spanning a second frequency range, the second set of carriers being on different frequencies than the first set of carriers, the first and second frequency range together summing up to the PAAM bandwidth or a smaller bandwidth, and communicating (210) signals with any of the number of UEs (140, 141 ) using the second part of the PAAM over the second set of carriers and a third set of carriers spanning a third frequency range, and the third set of carriers being on different frequencies than the first and second set of carriers, the second and third frequency range together summing up to the PAAM bandwidth or a smaller bandwidth.

2. Method according to claim 1 , wherein the second set of carriers are adjacent in frequency to the first set of carriers and higher in frequency than the first set of carriers, and wherein the third set of carriers are adjacent in frequency to the second set of carriers and higher in frequency than the second set of carriers.

3. Method according to claim 1 or 2, wherein the signals communicated (208) using the first part of the PAAM over the second set of carriers are communicated with a first UE (140) of the number of UEs (140, 141 ), and the signals communicated (210) using the second part of the PAAM over the second set of carriers are communicated with a second UE (141 ) of the number of UEs (140, 141 ).

4. Method according to claim 1 or 2, wherein the signals communicated (208) using the first part of the PAAM over the second set of carriers are communicated with a first UE (140) of the number of UEs (140, 141 ), and the signals communicated (210) using the second part of the PAAM over the second set of carriers are also communicated with the first UE (140).

5. Method according to claim 4, further comprising: determining (204) a phase offset between the first part of the PAAM and the second part of the PAAM, wherein the signals communicated (208, 210) over the second set of carriers using the first and the second part of the PAAM are communicated based on the determined phase offset so that they become coherently combined.

6. Method according to claim 5, wherein the phase offset (204) is determined by: determining a first channel estimate based on measurements performed on UL signals received at antennas of the first part of the PAAM, the UL signals being transmitted as first signals by the first UE (140) over the second set of carriers; determining a second channel estimate based on measurements performed on UL signals received at antennas of the second part of the PAAM, the UL signals being transmitted as the first signals by the first UE (140) over the second set of carriers, and determining the phase offset based on the first and second channel estimate.

7. Method according to claim 5, wherein the phase offset (204) is determined by: transmitting, from the first part of the PAAM, reference signals towards the first UE (140), transmitting, from the second part of the PAAM, the reference signals towards the first UE (140); receiving, from the first UE (140), a Precoding Matrix Indicator, PMI, that the UE determined to give the highest received signal quality out of a number of possible PMIs, when at the UE receiving and combining the reference signals transmitted from the first and second part of the PAAM, and determining the phase offset based on the received PMI.

8. A network node (130) configured to operate in a wireless communication network (100), and configured for Phased Array Antenna Module, PAAM, handling, the network node (130) comprising the PAAM (606), whereby the network node is capable of forming beams for directed communication of wireless signals with a number of user equipment, UE (140, 141 ), the PAAM (606) supporting a PAAM bandwidth, the network node (130) comprising a processing circuitry (603) and a memory (604), said memory containing instructions executable by said processing circuitry, whereby the network node (130) is operative for: splitting the PAAM into a first part and a second part, whereby the first part and the second part each supports the PAAM bandwidth, but a frequency range can be set individually for the first part and the second part; communicating signals with any of the number of UEs (140, 141 ) using the first part of the PAAM over a first set of carriers spanning a first frequency range and a second set of carriers spanning a second frequency range, the second set of carriers being on different frequencies than the first set of carriers, the first and second frequency range together summing up to the PAAM bandwidth or a smaller bandwidth, and communicating signals with any of the number of UEs (140, 141 ) using the second part of the PAAM over the second set of carriers and a third set of carriers spanning a third frequency range, and the third set of carriers being on different frequencies than the first and second set of carriers, the second and third frequency range together summing up to the PAAM bandwidth or a smaller bandwidth.

9. Network node (130) according to claim 8, wherein the second set of carriers are adjacent in frequency to the first set of carriers and higher in frequency than the first set of carriers, and wherein the third set of carriers are adjacent in frequency to the second set of carriers and higher in frequency than the second set of carriers.

10. Network node (130) according to claim 8 or 9, operative for communicating the signals using the first part of the PAAM (606) over the second set of carriers with a first UE (140) of the number of UEs (140, 141 ), and operative for communicating the signals using the second part of the PAAM over the second set of carriers with a second UE (141 ) of the number of UEs (140, 141 ).

11 . Network node (130) according to claim 8 or 9, operative for communicating the signals using the first part of the PAAM (606) over the second set of carriers with a first UE (140) of the number of UEs (140, 141 ), and operative for communicating the signals using the second part of the PAAM over the second set of carriers also with the first UE (140).

12. Network node (130) according to claim 11 , further being operative for: determining a phase offset between the first part of the PAAM (606) and the second part of the PAAM, and operative for communicating the signals over the second set of carriers using the first and the second part of the PAAM based on the determined phase offset so that they become coherently combined.

13. Network node (130) according to claim 12, operative for determining the phase offset by: determining a first channel estimate based on measurements performed on UL signals received at antennas of the first part of the PAAM (606), the UL signals being transmitted as first signals by the first UE (140) over the second set of carriers; determining a second channel estimate based on measurements performed on UL signals received at antennas of the second part of the PAAM, the UL signals being transmitted as the first signals by the first UE (140) over the second set of carriers, and determining the phase offset based on the first and second channel estimate.

14. Network node (130) according to claim 12, operative for determining the phase offset by: transmitting, from the first part of the PAAM (606), reference signals towards the first UE (140), transmitting, from the second part of the PAAM, the reference signals towards the first UE (140); receiving, from the first UE (140), a Precoding Matrix Indicator, PMI, that the UE determined to give the highest received signal quality out of a number of possible PMIs, when at the UE receiving and combining the reference signals transmitted from the first and second part of the PAAM, and determining the phase offset based on the received PMI.

15. A computer program (605) comprising instructions, which, when executed by at least one processing circuitry (603) of a network node (130) of a wireless communication network, the network node (130) comprising a Phased Array Antenna Module, PAAM (606), whereby the network node is capable of forming beams for directed communication of wireless signals with a number of user equipment, UE (140, 141 ), causes the network node (130) to perform the following steps: splitting the PAAM into a first part and a second part, whereby the first part and the second part each supports the PAAM bandwidth, but a frequency range can be set individually for the first part and the second part; communicating signals with any of the number of UEs (140, 141 ) using the first part of the PAAM over a first set of carriers spanning a first frequency range and a second set of carriers spanning a second frequency range, the second set of carriers being on different frequencies than the first set of carriers, the first and second frequency range together summing up to the PAAM bandwidth or a smaller bandwidth, and communicating signals with any of the number of UEs (140, 141 ) using the second part of the PAAM over the second set of carriers and a third set of carriers spanning a third frequency range, and the third set of carriers being on different frequencies than the first and second set of carriers, the second and third frequency range together summing up to the PAAM bandwidth or a smaller bandwidth

16. A carrier containing the computer program (605) according to claim 15, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, an electric signal or a computer readable storage medium.