EP4639789A1

EP4639789A1 - Methods and network node for transmission of wireless signals towards a wireless device through time domain beamforming, and corresponding wireless device

Info

Publication number: EP4639789A1
Application number: EP22838830.2A
Authority: EP
Inventors: Sairamesh Nammi; Minkeun Chung; Yi-Ju Chen
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2022-12-20
Filing date: 2022-12-20
Publication date: 2025-10-29
Also published as: WO2024132119A1; WO2024132377A1

Abstract

Disclosed are methods, network nodes (130) and wireless devices (140) for improving throughput when transmitting signals downlink from a network node (130) of a wireless communication network (100) towards the wireless device (140) when the wireless signals are directed by the network node (130) using time domain beamforming. Throughput is improved by transmitting traffic data in probing slots used for testing transmission quality of sets of time domain beamforming weights, in addition to transmitting reference signals in the same probing slots.

Description

METHODS AND NETWORK NODE FOR TRANSMISSION OF WIRELESS

SIGNALS TOWARDS A WIRELESS DEVICE THROUGH TIME DOMAIN BEAMFORMING, AND CORRESPONDING WIRELESS DEVICE

Technical Field

[0001] The present disclosure relates generally to methods and network nodes for transmission of wireless signals towards a wireless device through time domain beamforming. The present disclosure further relates to methods and corresponding wireless devices for communication with a such a network node. The present disclosure further relates to computer programs and carriers corresponding to the above methods, devices and nodes.

Background

[0002] To meet the huge demand for higher bandwidth, higher data rates and higher network capacity, due to e.g., data centric applications, existing 4^th Generation (4G) wireless communication network technology, aka Long-Term Evolution (LTE) is being extended or enhanced into a 5^th Generation (5G) technology, also called New Radio (NR) access. The following are requirements for 5G wireless communication networks:

- Data rates of several tens of megabits per second should be supported for tens of thousands of users;

- 1 gigabit per second is to be offered simultaneously to tens of workers on the same office floor;

- Several hundreds of thousands of simultaneous connections are to be supported for massive sensor deployments;

- Spectral efficiency should be significantly enhanced compared to 4G;

- Coverage should be improved;

- Signaling efficiency should be enhanced; and

- Latency should be reduced significantly compared to 4G.

[0003] Multiple Input Multiple Output (MIMO) is a method for multiplying the data carrying capacity of a radio link using multiple transmission and receiving antennas at the RAN node and possibly also at the wireless device to exploit multipath propagation. For these reasons, MIMO is an integral part of the 3^rd generation (3G) as well as the 4G wireless communication networks. 5G networks will also employ MIMO. Here it may be called massive MIMO systems as there may be hundreds of antennas at the transmitter side and/or the receiver side of the RAN node. Typically, with a (Nt, N_r), where Nt denotes the number of transmitter antennas and N_r denotes the number of receiver antennas, the peak data rate multiplies with a factor of Nt over single antenna systems in a rich scattering environment.

[0004] Fig. 1 shows a schematic block diagram of a distributed base station system, in which functionality of a base station, e.g., a gNodeB, is split in three blocks or units. The three blocks or units are: a baseband unit 50, which performs physical and medium access control functions within a baseband frequency range; a radio unit 60, which converts the baseband signals from baseband frequency to radio frequency signals for transmission; and an antenna unit 70 through which the radio frequency signals are transmitted.

[0005] Conventionally, in massive MIMO systems, optimal performance is obtained with full digital beamforming, that is, each antenna element has separate RF circuitry supporting an independent signal to each antenna branch. Fig. 2 shows an example of the distributed base station of fig. 1 in more detail in which the full digital beamforming is performed entirely in the frequency domain. In the baseband unit 50, incoming input bits are passed through a forward error correction (FEC)/rate matching unit 51 where additional parity bits are added for error protection. The resultant bits are then passed through a scrambling unit 52 that adds cell-specific scrambling operations for interference avoidance from neighboring cells. The resultant bits are then passed through a modulator 53 that converts the bit stream to complex symbols. The resultant symbols are passed through a layer mapping unit 54 that maps the resultant modulated symbols to different user layers. The resultant symbols per layer are fed through a Frequency Domain Beamforming (FDBF) unit 55, which may also be called baseband precoder 55, where the resultant symbols are multiplied with FDBF weights, aka precoding coefficients. Thereafter the resultant symbols are fed through a resource element (RE) mapping unit 56 that maps the symbols to REs assigned to the user. The mapped resultant bits are then sent to the radio unit 60 over an interface between the baseband unit 50 and the radio unit 60, as one signal per antenna element.

[0006] In the radio unit 60, the resultant bit streams are passed through an inverse fast Fourier transform (IFFT) block 61 for converting from frequency domain to time domain. Note that an IFFT block 61 is applied for each antenna element. That is, if we for example have 64 Transmit and Receive (TR) baseband branches or trains, we need to have 64 IFFT blocks. At the IFFT block 61 , or closer to the antennas, also a cyclic prefix (CP) may be added. The resultant time domain signals per each TR antenna element are passed through a Digital to Analog converter (DAC) 62 for converting to analog domain. The resultant analog signal is multiplied by the analog signal generated from a local oscillator (LO) 63 and passed through a power amplifier (PA) 64 for amplification. The resultant signal is passed through to the antenna unit 70, the antenna unit comprising a number of antenna elements.

[0007] However, when using such a massive Ml MO with full frequency domain beamforming at the baseband unit 50 providing independent signal paths between the baseband unit 50 and the radio unit 60, the cost, size, weight and power consumption will be driven up. For example, with full frequency domain beamforming over higher bandwidths, e.g., over 100 MHz, and hundreds of antenna elements, huge signaling interface bandwidth for transmitting a baseband signal to RF circuitry will be required, as one signal per antenna is needed to be sent over the interface between the baseband unit 50 and the radio unit 60.

[0008] Hence, to reduce cost and design complexity, an alternative architecture at least partly using time domain beamforming is preferred. Such an architecture is described in fig. 3. In time domain beamforming, a time domain beamforming (TDBF) unit 66 is installed in the radio unit 60. Such a TDBF unit 66 is then situated after the IFFT block 61 but, in case it is digital beamforming, before the DAC 62 at the radio unit 60. Consequently, at the TDBF unit 66, beamforming weights that are individual per antenna element are applied in the radio unit, after the IFFT operation. Hereby, one common signal for all antenna elements is sent from the baseband unit 50 to the radio unit 60. Thereby, interface bandwidth between the baseband unit 50 and the radio unit 60 is lowered quite a lot compared to full frequency domain beamforming where one signal is sent per antenna element over the interface between baseband and radio unit. An alternative is to perform hybrid beamforming in which frequency domain beamforming is performed in the baseband unit 50, using the FDBF unit 55 and time domain beamforming is performed in the radio unit 60 using the TDBF unit 66.

[0009] With the introduction of time domain beamforming, methods need to be incorporated to steer the time domain beams, i.e., to select time domain beamforming weights (TDBFW) so that the transmission beam from the plurality of antennas is directed in a certain transmission direction described by a transmission direction angle, in the direction of the wireless device that is to receive the transmission.

[00010] Published International patent application W02022010394 shows a method for identifying such a transmission direction angle. Here it is explained how the network node can compute a set of TDBFWs that resembles the transmission direction angle based on separately received Channel State Information Reference Signal (CSI-RS) resource sets. Firstly, the network node informs the wireless device to derive information on channel quality i.e., CSI reports (including CSI-RS resource sets) on received first and a second reference signals separately. For this purpose, we may for example use a certain Radio Resource Control (RRC) signaling in the NR specification 3GPP TS 38.214, called timeRestrictionForChannelMeasurements (TR=1) in CSI-ReportConfig. TR=1 indicates to the wireless device that the wireless device shall derive the channel measurements for computing CSI reported in uplink slot n based on only the most recent CSI-RS. Hereby it is avoided that the device averages the channel measurements from different CSI-RS occasions. A message sequence chart of an example of a proposed algorithm is shown in Fig. 4. The network node 130 sends 1.1. an RRC signaling with Time Restriction (TR) =1 , where TR =1 signals to the device that the UE shall derive the channel measurements for computing CSI reported in uplink slot n based on only the most recent CSI-RS. The network node then sends 1 .2 first set of reference signal using first elevation beamforming weights BFiCSI-RS directed in a first elevation angle. The device 140 then computes 1.3 channel quality information, i.e., CSI, for the first reference signal. The channel quality information may comprise one or more of CSI-RS Resource Indicator (CRI), Rank Indicator (Rl), channel quality indicator (CQI), Precoding Matrix Indicator (PMI) and Layer Indicator (LI). The device sends 1 .4 the channel quality information in, e.g., a feedback channel to the network node. Thereafter, the network node sends 1 .5 the second set of reference signals using second elevation beamforming weights BF2CSI-RS directed in a second elevation angle different from the first elevation angle. The device 140 then computes 1.6 channel quality information for the second reference signal such as CRI, Rank, CQI, PMI and LI. The device sends 1.7 the channel quality information, i.e., CSI, in e.g., a feedback channel to the network node. The network node then determines 1 .8 the elevation beam forming (DBF) weights to use for transmission of data to the device 140 using the separately received channel quality information on the first and second set of reference signals. Thereafter, the network node may send 1 .9 RRC with T=0 to disable the time restriction.

[00011] As mentioned, such a so-called CSI-RS sweeping method is used to probe the wireless device for identifying the set of TDBFWs that has the highest signal quality for TDBF transmission to the wireless device. The set of TDBFWs that was determined to have the highest signal quality aka transmission quality is then used for transmission of data in one or more consecutive data slots.

However, over time the wireless device may move and thereby the transmission angle towards the wireless device may change and thus also the optimal set of TDBFWs. Thereby, the set of TDBFWs to use for future transmissions needs to be re-evaluated over time. This means that a sweeping method is used repeatedly during a communication session with a wireless device. So, repeatedly during a communication session, a plurality of slots is used for probing to determine the set of TDBFWs with highest signal quality of the probed TDBFs and a plurality of slots are used as traffic slots for sending traffic data using the determined TDBFWs with highest signal quality. Then a plurality of slots is used again for probing to determine a new set of optimal TDBFWs etc.

[00012] In total, as shown in fig. 5, the data throughput with different wireless device locations for time domain beamforming using such CSI-RS sweeping is not very high. Fig. 5 shows link throughput with time domain beamforming using CSI- RS sweeping for a wireless device location at 3 degrees as elevation. The baseline (BASELINE) shown has 64 Transmitter-Receiver (TR) chains and 192 antenna elements (AE), and the beamforming is fully digital and completely performed in frequency domain. As seen from fig. 5, the data throughput using time domain beamforming and repeatedly performed CSI-RS sweeping (CSIRS SWEEP in fig. 5) is lower than the BASELINE, at least up to 25 dB Signal to Noise Ratio (SNR). CSI-RS periodicity is the same for BASELINE and for CSIRS SWEEP. For comparison purposes, a Genie-aided performance (GENIE-AIDED) is shown, which would be the throughput if the network node knows the location of the wireless device all the time, i.e. , it does not need to make any CSI-RS sweeping. The data throughput for repeatedly performed CSI-RS sweeping is much lower than the Genie-aided performance.

[00013] Consequently, there is a need for a method for improving throughput for communication of traffic data to a wireless device when employing time domain beamforming.

Summary

[00014] 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 improve throughput of traffic data from a network node to a wireless device when using time domain beamforming. It is possible to achieve these objects and others by using methods, network nodes and wireless devices as defined in the attached independent claims.

[00015] According to aspects of the invention, the throughput of traffic data is increased by not only sending reference signals in the probing slots but also sending traffic data in the probing slots. However, it is not possible to change the TDBFWs within a slot. But the inventors have found out that by sending traffic data in the probing slots using the TDBFWs used for the reference signals, the total throughput of traffic data will actually be increased.

[00016] According to one aspect, a method is provided that is performed by a network node of a wireless communication network for transmission of wireless signals towards a wireless device through time domain beamforming. The network node has a plurality of antennas. A second set of time domain beamforming weights, TDBFW, has been determined to have a highest transmission quality for transmission to the wireless device in one or more consecutive data slots out of a plurality of different sets of TDBFWs. Each of the plurality of sets of TDBFWs correspond to a transmission direction angle and the transmission direction angles of the plurality of sets are mutually different. The method comprises transmitting, to the wireless device, in a first probing slot, a reference signal beamformed with a first set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the first set of TDBFWs. The method further comprises receiving, from the wireless device, first channel state information determined by the wireless device based on the reference signal beamformed with the first set of TDBFWs. Further, the method comprises transmitting, to the wireless device, in the one or more consecutive data slots, traffic data beamformed with the second set of TDBFWs and transmitting, to the wireless device, in a second probing slot, a reference signal beamformed with the second set of TDBFWs and other traffic data also beamformed with the second set of TDBFWs. The method further comprises receiving, from the wireless device, second channel state information determined by the wireless device based on the reference signal beamformed with the second set of TDBFWs. Further, the method comprises determining, based on the received first and second channel state information, a set of TDBFWs out of the first and second set of TDBFWs that has the highest transmission quality and therefore to be used for transmission of traffic data to the wireless device in a later data slot that is later in time than the first probing slot, the second probing slot and the one or more consecutive data slots. [00017] According to another aspect, a method is provided performed by a wireless device connected to a network node of a wireless communication network, the network node having a plurality of antennas. Further, a second set of TDBFWs has been determined to have a highest transmission quality for transmission from the network node to the wireless device in one or more consecutive data slots out of a plurality of different sets of TDBFWs. Each of the plurality of sets of TDBFWs corresponds to a transmission direction angle, the transmission direction angles of the plurality of sets being mutually different. The method comprises receiving, from the network node, in a first probing slot, a reference signal beamformed with a first set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the first set of TDBFWs, and transmitting, to the network node, first channel state information determined by the wireless device based on the reference signal beamformed with the first set of TDBFWs. The method further comprises receiving 306, from the network node, in the one or more consecutive data slots, traffic data beamformed with the second set of TDBFWs of the plurality of different sets of TDBFWs. The method further comprises receiving, from the network node, in a second probing slot, a second reference signal beamformed with the second set of TDBFWs and traffic data also beamformed with the second set of TDBFWs, and transmitting, to the network node, second channel state information determined by the wireless device based on the reference signal beamformed with the second set of TDBFWs. Hereby, the network node is able to determine, based on the transmitted first and second channel state information, a set of TDBFWs out of the first and second set of TDBFWs that has the highest transmission quality and therefore to be used for transmission of traffic data to the wireless device in a later data slot that is later in time than the first probing slot, the second probing slot and the one or more consecutive data slots.

[00018] According to another aspect, a network node is provided that is configured to operate in a wireless communication network and configured for directing wireless signals towards a wireless device through beamforming. The network node has a plurality of antennas. The network node is operative for determining a second set of TDBFWs to have a highest transmission quality for transmission to the wireless device in one or more consecutive data slots out of a plurality of different sets of TDBFWs. Each of the plurality of sets of TDBFWs corresponds to a transmission direction angle and the transmission direction angles of the plurality of sets are mutually different. 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 transmitting, to the wireless device, in a first probing slot, a reference signal beamformed with a first set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the first set of TDBFWs, and receiving, from the wireless device, first channel state information determined by the wireless device based on the reference signal beamformed with the first set of TDBFWs. The network node is further operative for transmitting, to the wireless device, in the one or more consecutive data slots, traffic data beamformed with the second set of TDBFWs. The network node is further operative for transmitting, to the wireless device, in a second probing slot, a reference signal beamformed with the second set of TDBFWs and other traffic data also beamformed with the second set of TDBFWs, and receiving, from the wireless device, second channel state information determined by the wireless device based on the reference signal beamformed with the second set of TDBFWs. The network node is further operative for determining, based on the received first and second channel state information, a set of TDBFWs out of the first and second set of TDBFWs that has the highest transmission quality and therefore to be used for transmission of traffic data to the wireless device in a later data slot that is later in time than the first probing slot, the second probing slot and the one or more consecutive data slots.

[00019] According to another aspect, a wireless device is provided that is operable in a wireless communication network and configured for communicating wireless signals with a network node comprising a plurality of antennas. A second set of TDBFWs out of a plurality of different sets of TDBFWs has been determined to have a highest transmission quality for transmission from the network node to the wireless device in one or more consecutive data slots. Each of the plurality of sets of TDBFWs corresponds to a transmission direction angle. The transmission direction angles of the plurality of sets are mutually different. The wireless device comprises a processing circuitry and a memory. Said memory contains instructions executable by said processing circuitry, whereby the wireless device is operative for receiving, from the network node, in a first probing slot, a reference signal beamformed with a first set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the first set of TDBFWs, and transmitting, to the network node, first channel state information determined by the wireless device based on the reference signal beamformed with the first set of TDBFWs. Further, the wireless device is operative for receiving, from the network node, in the one or more consecutive data slots, traffic data beamformed with the second set of TDBFWs of the plurality of different sets of TDBFWs. Further, the wireless device is operative for receiving, from the network node, in a second probing slot, a second reference signal beamformed with the second set of TDBFWs and traffic data also beamformed with the second set of TDBFWs, and transmitting, to the network node, second channel state information determined by the wireless device based on the reference signal beamformed with the second set of TDBFWs.

[00020] 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.

[00021] Further possible features and benefits of this solution will become apparent from the detailed description below.

Brief Description of Drawings

[00022] The solution will now be described in more detail by means of exemplary embodiments and with reference to the accompanying drawings, in which:

[00023] Fig. 1 is a schematic block diagram of a distributed base station in which the present invention may be used.

[00024] Fig. 2 is a schematic block diagram in more detail of a distributed base station applying frequency domain digital beamforming according to prior art. [00025] Fig. 3 is a schematic block diagram of a distributed base station applying time domain digital beamforming according to prior art.

[00026] Fig. 4 is a signaling diagram of a CSI-RS sweeping method for determining TDBFWs according to prior art.

[00027] Fig. 5 is an x/y-diagram comparing throughput for frequency domain beamforming and time domain beamforming using the CSIRS sweeping method.

[00028] Fig. 6 is a schematic diagram of a wireless communication network in which the present invention may be used.

[00029] Fig. 7 is a schematic block diagram of consecutive downlink slots for communication between a network node and a wireless device as for example in fig. 6.

[00030] Fig. 8 is a flow chart illustrating a method performed by a network node, according to possible embodiments.

[00031] Fig. 9 is a flow chart illustrating a method performed by a wireless device, according to possible embodiments.

[00032] Fig. 10 is a signaling diagram of communication between a network node and a wireless device according to possible embodiments.

[00033] Fig. 11 is a flow chart of a method performed by a network node, according to possible embodiments.

[00034] Fig. 12 is a block diagram illustrating a network node in more detail, according to further possible embodiments.

[00035] Fig. 13 is a block diagram illustrating a wireless device in more detail, according to further possible embodiments.

Detailed Description

[00036] Fig. 6 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. The network node 130 provides radio access in a cell 150 covering a geographical area.

[00037] 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.

[00038] 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).

[00039] 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.

[00040] Fig. 7 shows a plurality of consecutive time slots 171-181 for downlink transmission of data and reference signals from a network node to a wireless device according to a possible embodiment employing time domain beamforming. Each time slot, aka slot, comprises a plurality of symbols Fig. 8 describes a method according to an aspect in which data and reference signals may be sent as described in the time slots of Fig. 7. In the following, the method described in Fig. 8 refers to the wireless communication network described in fig. 6 and the slots described in Fig. 7.

[00041] Fig. 8 shows a method performed by a network node 130 of a wireless communication network 100 for transmission of wireless signals towards a wireless device 140 through time domain beamforming. The network node 130 has a plurality of antennas. A second set of time domain beamforming weights, TDBFW, has been determined to have a highest transmission quality for transmission to the wireless device 140 in one or more consecutive data slots 171- 181 , out of a plurality of different sets of TDBFWs, each of the plurality of sets of TDBFWs corresponding to a transmission direction angle, the transmission direction angles of the plurality of sets being mutually different. The method comprises transmitting 202, to the wireless device 140, in a first probing slot 171 , a reference signal beamformed with a first set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the first set of TDBFWs. The method further comprises receiving 204, from the wireless device 140, first channel state information determined by the wireless device 140 based on the reference signal beamformed with the first set of TDBFWs. Further, the method comprises transmitting 206, to the wireless device 140, in the one or more consecutive data slots 172, 173, traffic data beamformed with the second set of TDBFWs and transmitting 208, to the wireless device 140, in a second probing slot 174, a reference signal beamformed with the second set of TDBFWs and other traffic data also beamformed with the second set of TDBFWs. The method further comprises receiving 210, from the wireless device 140, second channel state information determined by the wireless device 140 based on the reference signal beamformed with the second set of TDBFWs. Further, the method comprises determining 220, based on the received 204, 210 first and second channel state information, a set of TDBFWs out of the first and second set of TDBFWs that has the highest transmission quality and therefore to be used for transmission of traffic data to the wireless device in a later data slot 181 that is later in time than the first probing slot 171 , the second probing slot 174 and the one or more consecutive data slots 172, 173.

[00042] By such a method, extra space in the probing slots 171 , 174, i.e., the slots where the reference signals are sent, can be used for sending traffic data as well. In prior art, traffic data is only sent in the data slots 172-173 using the set of TDBFW that was determined to have the highest transmission quality from previous transmissions. Here the inventors have come to the conclusion that it is possible to send traffic data also in a probing slot, as long as the same set of TDBFWs is used as is used for the reference signal in the same probing slot. By using this extra space in the probing slots, i.e. non-used symbols of the probing slot, for sending traffic data, the total throughput of traffic data will be increased. Further the method still makes it possible to determine 220 the set of TDBFWs that has the highest transmission quality and therefore to be used for a later transmission of traffic data, based on the different sets of TDBFWs tested in the probing slots 171 , 174.

[00043] The reference signals mentioned, i.e., the reference signal beamformed with the first set of TDBFWs and the reference signal beamformed with the second set of TDBFWs, and any other reference signals used could be for example CSI- RS or Tracking reference signal (TRS). The mentioned transmission quality could also be called channel quality. It defines the set of TDBFWs that when used for transmitting signals to the wireless device provides the highest channel or transmission quality out of a plurality of sets of TDBFWs. The transmission quality could be determined by the CQI, which may be determined by the wireless device from the received reference signals and sent by the wireless device to the network node. Alternatively, the transmission quality could be determined as a quality factor defined as RI*CQI. The transmission quality could be a transmission quality value reported from the wireless device and related to a measuring of quality performed by the wireless device on reference signals transmitted by the network node. The first and second channel state information received from the wireless device each comprises information indicative of the transmission quality at reception at the wireless device of the respective reference signal transmitted by the network node. The transmission direction angle could be an elevation angle or an azimuth angle, or a combination of both.

[00044] Fig. 7 defines a possible time-relation of the probing slots and the data slots mentioned in the method of fig. 8. As seen, the first probing slot 171 is first here in a time-relation, followed by one or more data slots 172-173 (in the example of fig. 7 it is two data slots), followed by a second probing slot 174 followed by one or more data slots 175-176 followed by a possible third probing slot 177 followed by one or more possible data slots 178-179. According to an embodiment, traffic data is sent not only in the data slots 172-173, 175-176, 178-179 using the second set of TDBFWs that were determined to have the highest signal quality but also in the probing slots 171 , 174, 177 using the same set of TDBFWs as used for the reference signals.

[00045] The second set of TDBFWs that when the method of fig. 8 starts has been determined to have a highest transmission quality for transmission to the wireless device 140 in the one or more data slots 172-173, 175-176 and 178-179, were determined to have the highest transmission quality out of a plurality of TDBFWs before the first probing slot 171 occurs. The method for determining that the second set of TDBFWs had the highest transmission quality may have been the one described in fig. 4. It may also have been the method described in fig. 8, i.e., the same method as in fig. 8, but used also before the method of fig. 8 is accomplished. In other words, it is possible and even probable that the method of fig. 8 is repeated in an ongoing downlink data transmission or session between the network node 130 and the wireless device 140. As for the second set of TDBFWs, the first set of TDBFWs may have been evaluated beforehand, i.e., before the transmission of the first probing slot 171 . If so, the first set of TDBFWs were determined to have a lower transmission quality as the second set of TDBFWs. An alternative is that no evaluation was made beforehand for the first set of TDBFWs.

[00046] According to an embodiment, the transmitting 202 in the first probing slot 171 of the reference signals and the traffic data uses a first modulation and coding scheme (MCS); that is more robust than a second MCS used in the transmitting 206 of the traffic data in the one or more consecutive data slots 172, 173. [00047] That the first MCS is more robust than the second MCS signifies that the second MCS has a lower number of useful bits carried in one symbol than a less robust MCS. In other words, a less robust MCS fits more useful bits into a symbol than a more robust MCS but therefore the transmission using the less robust MCS is more sensitive to dips in channel quality than the transmission using the more robust MCS. A more robust MCS is preferably used for the probing slots to be sure that the reference signals are received correctly. It has also been proven to be difficult to use a different MCS for traffic data than for reference signals which are sent in the same slot. Then, here the requirements of the reference signals will be decisive. Still, in total, more traffic data can be transmitted to the wireless device compared to prior art of not sending any traffic data to the wireless device in the probing slots. The more robust MCS used for the probing slots may be a default probing MCS that is used for transmission in all probing slots or that is used for transmission in probing slots for which there is no recent information of transmission quality for the set of TDBFWs to be used for the transmission in the current probing slot. Alternatively, the MCS used for transmission in the probing slots could have been determined from earlier received channel state information for transmissions using the current set of TDBFWs.

[00048] According to an embodiment, when a channel state information for the first set of TDBFWs is not known when the reference signal and the traffic data is to be transmitted 202 in the first probing slot 171 , the first MCS is set to a default MCS, the default MCS being one of the most robust MCSs of a plurality of selectable MCS. In case the network node does not have any channel state information indicating transmission quality for the first set of TDBFWs when the reference signal and the traffic data is to be transmitted in the first probing slot, the most robust MCS at hand, or at least one of the 2-3 most robust MCSs at hand is used. This enhances the possibility that the reference signal and the traffic data sent in the first probing slot is received correctly even when the network node does not have any information on transmission quality for transmissions using the first set of TDBFWs. [00049] According to another embodiment, the first MCS is determined based on a channel state information determined by the wireless device 140 from an earlier reference signal transmitted by the network node 130 in a probing slot that is earlier than the first probing slot 171 , the earlier reference signal being beamformed with the first set of TDBFWs. As such channel state information then comprises channel quality information, the MCS can be set in accordance with the channel quality information determined by the wireless device from reception of the earlier reference signal and thereby get a relevant value for achieving safe receipt of the reference signal and the traffic data transmitted in the first probing slot, but still get a good throughput.

[00050] According to yet another embodiment and with reference to Fig. 7 and Fig. 8, the method further comprises transmitting 212 to the wireless device 140, in one or more additional consecutive data slots 175-176 following the second probing slot 174, traffic data beamformed with the second set of TDBFWs.

[00051] According to yet another embodiment, the method further comprises transmitting 214, to the wireless device 140, in a third probing slot 177, a reference signal beamformed with a third set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the third set of TDBFWs, and receiving 216, from the wireless device 140, third channel state information determined by the wireless device 140 based on the reference signal beamformed with the third set of TDBFWs. Further, the determining 220 of the set of TDBFWs that has the highest transmission quality is performed based on the received 204, 210, 216 first, second and third channel state information so that the determining 220 is performed out of the first, the second and the third set of TDBFWs. Hereby, three different sets of TDBFWs are tested, each representing a transmission angle or transmission direction. The first set of TDBFWs may represent a first angle, the second set a second angle and the third set a third angle, and the first and third angle may be on separate sides of the second angle, i.e., the third angle is larger than the second angle and the first angle is smaller than the second angle. For example, if the second angle is 6 degrees, the first angle may be 3 degrees and the third angle may be 9 degrees. Then with this method it is tested whether the wireless device has moved in either direction from the 6-degree angle in direction of any of the closely laying angles.

[00052] According to a variant of the embodiment described in the paragraph immediately above, the method further comprises transmitting 218 to the wireless device 140, in one or more second additional consecutive data slots 178-179 following the third probing slot 177, traffic data beamformed with the second set of TDBFWs.

[00053] According to yet another embodiment, the second set of TDBFWs was determined to have the highest transmission quality for the transmission 206 to the wireless device 140 in the one or more consecutive data slots by the following steps: Transmitting, to the wireless device 140, in a first previous probing slot, a reference signal beamformed with the first set of TDBFWs; Receiving, from the wireless device 140, first previous channel state information determined by the wireless device 140 based on the reference signal transmitted in the first previous probing slot and beamformed with the first set of TDBFWs; Transmitting, to the wireless device 140, in a second previous probing slot, a reference signal beamformed with the second set of TDBFWs; Receiving, from the wireless device 140, second previous channel state information determined by the wireless device 140 based on the reference signal transmitted in the second previous probing slot and beamformed with the second set of TDBFWs; and determining, based on the received first and second previous channel state information, that the second set of TDBFWs out of the first and second set of TDBFWs had the highest transmission quality, wherein the first and second previous probing slots are transmitted before the first probing slot 171. This embodiment describes a possible way of how it was determined that the second set of TDBFs was the set of the plurality of possible sets with the highest transmission quality and therefore the set to use for the transmitting 206 of traffic data in the one or more consecutive data slots 172, 173 and for the optional transmitting 212 in the one or more additional consecutive data slots 175, 176 mentioned in the embodiments above.

[00054] Fig. 9 describes a method performed by a wireless device 140 connected to a network node 130 of a wireless communication network 100, the network node 130 having a plurality of antennas. Further, a second set of TDBFWs has been determined to have a highest transmission quality for transmission from the network node 130 to the wireless device 140 in one or more consecutive data slots 172, 173, out of a plurality of different sets of TDBFWs. Each of the plurality of sets of TDBFWs corresponds to a transmission direction angle, the transmission direction angles of the plurality of sets being mutually different. The method comprises receiving 302, from the network node 130, in a first probing slot 171 , a reference signal beamformed with a first set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the first set of TDBFWs, and transmitting 304, to the network node 130, first channel state information determined by the wireless device 140 based on the reference signal beamformed with the first set of TDBFWs. The method further comprises receiving 306, from the network node 130, in the one or more consecutive data slots 172, 173, traffic data beamformed with the second set of TDBFWs of the plurality of different sets of TDBFWs. The method further comprises receiving 308, from the network node 130, in a second probing slot 174, a second reference signal beamformed with the second set of TDBFWs and traffic data also beamformed with the second set of TDBFWs, and transmitting 310, to the network node 130, second channel state information determined by the wireless device 140 based on the reference signal beamformed with the second set of TDBFWs. Hereby, the network node 130 is able to determine, based on the transmitted 304, 310 first and second channel state information, a set of TDBFWs out of the first and second set of TDBFWs that has the highest transmission quality and therefore to be used for transmission of traffic data to the wireless device in a later data slot 181 that is later in time than the first probing slot 171 , the second probing slot 174 and the one or more consecutive data slots 172, 173.

[00055] According to an embodiment, the method further comprises determining 303 the first channel state information based on the received reference signal beamformed with the first set of TDBFWs and determining 309 the second channel state information based on the received reference signal beamformed with the second set of TDBFWs. [00056] According to another embodiment, the reference signals and the traffic data received 302, 308 in the first probing slot 171 is coded with a first MCS that is more robust than a second MCS by which the traffic data received 306 in the one or more consecutive data slots 172, 173 is coded.

[00057] According to yet another embodiment, the method further comprises receiving 312, from the network node 130, in one or more additional consecutive data slots 175-176 following the second probing slot 174, traffic data beamformed with the second set of TDBFWs.

[00058] According to yet another embodiment, the method further comprises receiving 314, from the network node 130, in a third probing slot 177, a reference signal beamformed with a third set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the third set of TDBFWs, and transmitting 316, to the network node 130, third channel state information determined by the wireless device 140 based on the reference signal beamformed with the third set of TDBFWs. The method may also comprise determining 315 the third channel state information based on the received reference signal beamformed with the third set of TDBFWs.

[00059] In the following, embodiments of the present invention are described with reference to the signaling diagram of fig. 10. In this embodiment, as an example, it is assumed that the network node 130, hereinafter called base station (BS), configures the wireless device 140, hereinafter called UE, with a CSI-RS process for Channel State Information (CSI) estimation that uses one downlink (DL) slot for transmitting a CSI-RS and one uplink (UL) slot for the UE reporting back to the BS the CSI that the UE determines from the received CSI-RS. The transmission of CSI-RS in this example has a periodicity of 5 slots, although other periodicity may be used as well, e.g., 2 or 3. The slots in which CSI-RS is transmitted are called probing slots as they are used for testing or probing different sets of TDBFWs, each set of TDBFWs resembling a certain transmission direction or angle. In the example of fig. 10, probing slots are slot (1 +5x), where x = 0, 1 , 2, .... In a first probing slot (slot 1), the BS 130 transmits 3.1 a CSI-RS beamformed with a first set of TDBFWs (TDBFW1) towards the UE 140. The UE 140 determines CSI from the received reference signal (RS) and transmits 3.2 the CSI corresponding to the CSI-RS transmitted using TDBFW1 to the BS 130. In the next probing slot (slot 6), the BS 130 transmits 3.4 a CSI-RS beamformed with a second set of TDBFWs (TDBFW2) for probing the UE 140. The UE 140 determines CSI from the received reference signal (RS) and transmits 3.5 the CSI corresponding to the CSI-RS transmitted using TDBFW2 to the BS 130. In the example of fig. 3, there is also a third probing slot (slot 11) in which the BS 130 transmits 3.7 a CSI-RS beamformed with a third set of TDBFWs (TDBFW3) for probing the UE 140. The UE 140 determines CSI from the received reference signal (RS) and transmits 3.8 the CSI corresponding to the CSI-RS transmitted using TDBFW3 to the BS 130. The BS 130 then compares the CSI received during these three probing instances to determine 3.10 which of the reference signals sent in probing slots 1 , 6 and 11 that had the highest transmission quality and therefore which of the TDBFW1 , TDBFW2 and TDBFW3 that was the best to use for transmission of data traffic to the UE 140. The CSI may comprise PMI, Rl and CQI. The transmission quality may be determined as a quality metric (QM) where QM = RI * CQI.

[00060] As seen in fig. 10, there are data slots 2-5, 7-10, 12-15 in between the probing slots 1 , 6, 11 and after probing slot 11 in which data slots traffic data is sent. In case this is the first traffic data sent from this BS 130 towards this UE 140 in one session, the BS 130 does not know which set of TDBFWs was the best to use for transmitting traffic data towards the UE 140 from any earlier transmission. Then the BS 140 may use a default set of TDBFWs, alternatively, no traffic data may be sent until a set of TDBFWs has been determined to have a highest transmission quality. However, as soon as any of the set TDBFWs has been determined from earlier transmissions to have the highest transmission quality towards the UE, that set of TDBFWs are used for the transmission of traffic data in the data slots and the probing slots are used for transmission of reference signals using different sets of TDBFWs to determine which of the sets of TDBFWs that now has the highest transmission quality to be used for future data transmissions, and so on. In the example of fig. 10, the TDBFW2 set was determined to have the highest transmission quality from earlier transmissions and is, consequently, used for beamforming the traffic data transmitted 3.3 in slots 2-5, transmitted 3.6 in slots 7-10 and transmitted 3.9 in slots 12-15.

[00061] However, and according to embodiments of the present invention, in the probing slots 1 , 6 and 11 when the BS 130 probes the UE 140 with different sets of TDBFWs, there are empty symbols in which the BS schedules the UE for data traffic transmission, in e.g. a Physical Download Shared Channel (PDSCH), using the same set of TDBFWs as was used for the transmission of the CSI-RS. This is seen fig. 10 as the “Data (TDBFWx)” after each of steps 3.1 , 3.4 and 3.7, where x = 1-3. Hereby, otherwise vacant space in the probing slots is used for sending traffic data whereby the total DL throughput is increased. It is not possible to change the set of TDBFWs per symbol within a slot, as such change would create adjacent channel interference and spurious emissions in the network, which will negatively impact other BSs in the network. This may be a reason that it has not been thought of earlier to transmit traffic data in those probing slots when using TDBF. In other words, even though the BS 140 determines an optimal set of TDBFWs, i.e. an optimal transmission angle, and the corresponding CSI for determining the scheduling parameters for PDSCH transmission, the BS chooses the set of TDBFWs and the CSI based on the probing angle rather than the optimal angle for transmission of traffic data in the probing slots.

[00062] As mentioned, the probing slots are used for testing different sets of TDBFWs to determine an optimal set of TDBFWs for future transmissions. As such, not only a recent optimal set of TDBFWs is tested but also one or more other set of TDBFWs. As the one or more sets of TDBFWs that are tested but where not optimal either had a lower transmission quality or had not been tested before at all, it may be beneficial to use a more robust MCS for transmission of the traffic data sent in the same slot as the CSI-RS and thereby beamformed using the same set of TDBFWs as the MCS used for transmitting traffic data in a data slot. In the example of fig. 10, the CSI-RS and data beamformed with the TDBFW1 set and sent in slot 1 would then be modulated with a more robust MCS than the traffic data beamformed with the TDBFW2 set that had the highest transmission quality. In the example of fig. 10, the transmissions 3.1 , 3.7 that are beamformed using the TDBFW1 and TDBFW3 sets do not have as good transmission quality as the transmissions 3.3, 3.4, 3.6 and will therefore get a more robust MCS than the transmissions 3.3, 3.4, 3.6.

[00063] In case transmission quality for the first set of TDBFWs is not known when the reference signal and the traffic data is to be transmitted 3.1 in the first probing slot 171 , the first MCS may be set to a default MCS, which can be the most robust MCS available to the BS, or at least one of two or three of the most robust MCSs of a plurality of MCSs that the BS can choose from.

[00064] Alternatively, it may be possible to determine the first MCS based on a channel state information determined by the UE 140 from an earlier reference signal transmitted by the network node in a probing slot that is earlier than the first probing slot, the earlier reference signal being beamformed with the first set of TDBFWs.

[00065] Fig. 11 shows an embodiment for selecting CSI based on in which type of slot traffic data is to be transmitted. When the UE is ready for data transmission 402, it is determined 404 whether transmission is to be performed in a probing slot, i.e., whether the traffic data is to be transmitted in the same slot as a reference signal (e.g., CSI-RS) is to be transmitted. In case the transmission is to be performed in a probing slot, CSI corresponding to the CSI-RS probing angle is determined to be used 406 for scheduling the transmission of both the CSI-RS and the traffic data in the probing slot. In case the transmission is to be performed in a data slot, CSI corresponding the optimal angle according to the CSI is determined to be used 408 for scheduling the transmission of the traffic data. Thereafter, the network node determines 410 from the CSI determined 406, 408 to be used, the MCS, Precoder coefficients, number of layers and set of TDBFWs for the transmission in the respective probing slot or data slot.

[00066] Fig. 12, in conjunction with Fig. 6, shows a network node 130 configured to operate in a wireless communication network 100, and configured for directing wireless signals towards a wireless device 140 through beamforming. The network node 130 has a plurality of antennas. The network node is operative for determining a second set of TDBFWs to have a highest transmission quality for transmission to the wireless device 140 in one or more consecutive data slots, out of a plurality of different sets of TDBFWs. Each of the plurality of sets of TDBFWs corresponds to a transmission direction angle and the transmission direction angles of the plurality of sets are mutually different. 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 transmitting, to the wireless device 140, in a first probing slot 171 , a reference signal beamformed with a first set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the first set of TDBFWs, and receiving, from the wireless device 140, first channel state information determined by the wireless device 140 based on the reference signal beamformed with the first set of TDBFWs. The network node 130 is further operative for transmitting, to the wireless device 140, in the one or more consecutive data slots 172, 173, traffic data beamformed with the second set of TDBFWs. The network node 130 is further operative for transmitting, to the wireless device 140, in a second probing slot 174, a reference signal beamformed with the second set of TDBFWs and other traffic data also beamformed with the second set of TDBFWs, and receiving, from the wireless device 140, second channel state information determined by the wireless device 140 based on the reference signal beamformed with the second set of TDBFWs. The network node 130 is further operative for determining, based on the received first and second channel state information, a set of TDBFWs out of the first and second set of TDBFWs that has the highest transmission quality and therefore to be used for transmission of traffic data to the wireless device in a later data slot 181 that is later in time than the first probing slot 171 , the second probing slot 174 and the one or more consecutive data slots 172, 173.

[00067] According to an embodiment, the network node 130 is operative for using a first MCS in the transmitting in the first probing slot 171 of the reference signal and the traffic data, wherein the first MCS is more robust than a second MCS used in the transmitting of the traffic data in the one or more consecutive data slots 172, 173.

[00068] According to another embodiment, when a channel state information for the first set of TDBFWs is not known when the reference signal and the traffic data is to be transmitted in the first probing slot 171 , the network node is operative for setting the first MCS to a default MCS, the default MCS being one of the most robust MCSs of a plurality of selectable MCSs.

[00069] According to another embodiment, the network node 130 is operative for determining the first MCS based on a channel state information determined by the wireless device 140 from an earlier reference signal transmitted by the network node 130 in a probing slot that is earlier than the first probing slot 171 , the earlier reference signal being beamformed with the first set of TDBFWs.

[00070] According to another embodiment, the network node 130 is further operative for transmitting to the wireless device 140, in one or more additional consecutive data slots 175-176 following the second probing slot 174, traffic data beamformed with the second set of TDBFWs.

[00071] According to another embodiment, the network node 130 is further operative for transmitting, to the wireless device 140, in a third probing slot 177, a reference signal beamformed with a third set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the third set of TDBFWs. Further, the network node 130 is operative for receiving, from the wireless device 140, third channel state information determined by the wireless device 140 based on the reference signal beamformed with the third set of TDBFWs. Also, the network node is operative for the determining of the set of TDBFWs that has the highest transmission quality based on the received first, second and third channel state information so that the determining is performed out of the first, the second and the third set of TDBFWs.

[00072] According to yet another embodiment, the network node 130 is operative to have determined the second set of TDBFWs to have the highest transmission quality for transmission to the wireless device 140 in the one or more consecutive data slots by:

- transmitting, to the wireless device 140, in a first previous probing slot, a reference signal beamformed with the first set of TDBFWs; receiving, from the wireless device 140, first previous channel state information determined by the wireless device 140 based on the reference signal transmitted in the first previous probing slot and beamformed with the first set of TDBFWs; transmitting, to the wireless device 140, in a second previous probing slot, a reference signal beamformed with the second set of TDBFWs; receiving, from the wireless device 140, second previous channel state information determined by the wireless device 140 based on the reference signal transmitted in the second previous probing slot and beamformed with the second set of TDBFWs, and determining, based on the received first and second previous channel state information, that the second set of TDBFWs out of the first and second set of TDBFWs had the highest transmission quality, wherein the first and second previous probing slots are transmitted before the first probing slot 171 .

[00073] 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 wireless device 140, 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.

[00074] 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 Random-access memory (RAM), Read-Only Memory (ROM) or an Electrical Erasable Programmable ROM (EEPROM). 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.

[00075] Fig. 13, in conjunction with Fig. 6, shows a wireless device 140 operable in a wireless communication network 100 and configured for communicating wireless signals with a network node 130 comprising a plurality of antennas. A second set of TDBFWs out of a plurality of different sets of TDBFWs has been determined to have a highest transmission quality for transmission from the network node 130 to the wireless device 140 in one or more consecutive data slots. Each of the plurality of sets of TDBFWs corresponds to a transmission direction angle. The transmission direction angles of the plurality of sets are mutually different. The wireless device 140 comprises a processing circuitry 703 and a memory 704. Said memory contains instructions executable by said processing circuitry, whereby the wireless device 140 is operative for receiving, from the network node 130, in a first probing slot 171 , a reference signal beamformed with a first set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the first set of TDBFWs, and transmitting, to the network node 130, first channel state information determined by the wireless device 140 based on the reference signal beamformed with the first set of TDBFWs. Further, the wireless device 140 is operative for receiving, from the network node 130, in the one or more consecutive data slots 172, 173, traffic data beamformed with the second set of TDBFWs of the plurality of different sets of TDBFWs. Further, the wireless device 140 is operative for receiving, from the network node 130, in a second probing slot 174, a second reference signal beamformed with the second set of TDBFWs and traffic data also beamformed with the second set of TDBFWs, and transmitting, to the network node 130, second channel state information determined by the wireless device 140 based on the reference signal beamformed with the second set of TDBFWs.

[00076] According to an embodiment, the reference signals and the traffic data received in the first probing slot 171 is coded with a first MCS that is more robust than a second MCS by which the traffic data received in the one or more consecutive data slots 172, 173 is coded.

[00077] According to another embodiment, the wireless device 140 is further operative for receiving, from the network node 130, in one or more additional consecutive data slots 175-176 following the second probing slot 174, traffic data beamformed with the second set of TDBFWs.

[00078] According to another embodiment, the wireless device 140 is further operative for receiving, from the network node 130, in a third probing slot, a reference signal beamformed with a third set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the third set of TDBFWs, and transmitting, to the network node 130, third channel state information determined by the wireless device 140 based on the reference signal beamformed with the third set of TDBFWs.

[00079] According to other embodiments, the wireless device 140 may further comprise a communication unit 702, which may be considered to comprise conventional means for wireless communication with the network node 130, such as a transceiver for wireless transmission and reception of signals in the communication network. The instructions executable by said processing circuitry 703 may be arranged as a computer program 705 stored e.g., in said memory 704. The processing circuitry 703 and the memory 704 may be arranged in a subarrangement 701 . The sub-arrangement 701 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 703 may comprise one or more programmable processor, application-specific integrated circuits, field programmable gate arrays or combinations of these adapted to execute instructions. The wireless device 140 may also comprise a battery 706 for providing electrical power.

[00080] The computer program 705 may be arranged such that when its instructions are run in the processing circuitry, they cause the wireless device 140 to perform the steps described in any of the described embodiments of the wireless device 140 and its method. The computer program 705 may be carried by a computer program product connectable to the processing circuitry 703. The computer program product may be the memory 704, or at least arranged in the memory. The memory 704 may be realized as for example a Random-access memory (RAM), Read-Only Memory (ROM) or an Electrical Erasable Programmable ROM (EEPROM). In some embodiments, a carrier may contain the computer program 705. 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 704. Alternatively, the computer program may be stored on a server or any other entity to which the wireless device 140 has access via the communication unit 702. The computer program 705 may then be downloaded from the server into the memory 704. [00081] 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 transmission of wireless signals towards a wireless device (140) through time domain beamforming, the network node (130) having a plurality of antennas, wherein a second set of time domain beamforming weights, TDBFW, has been determined to have a highest transmission quality for transmission to the wireless device (140) in one or more consecutive data slots, out of a plurality of different sets of TDBFWs, each of the plurality of sets of TDBFWs corresponding to a transmission direction angle, the transmission direction angles of the plurality of sets being mutually different, the method comprising: transmitting (202), to the wireless device (140), in a first probing slot (171), a reference signal beamformed with a first set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the first set of TDBFWs, receiving (204), from the wireless device (140), first channel state information determined by the wireless device (140) based on the reference signal beamformed with the first set of TDBFWs; transmitting (206), to the wireless device (140), in the one or more consecutive data slots (172, 173), traffic data beamformed with the second set of TDBFWs, transmitting (208), to the wireless device (140), in a second probing slot (174), a reference signal beamformed with the second set of TDBFWs and other traffic data also beamformed with the second set of TDBFWs, receiving (210), from the wireless device (140), second channel state information determined by the wireless device (140) based on the reference signal beamformed with the second set of TDBFWs, and determining (220), based on the received (204, 210) first and second channel state information, a set of TDBFWs out of the first and second set of TDBFWs that has the highest transmission quality and therefore to be used for transmission of traffic data to the wireless device in a later data slot (181) that is later in time than the first probing slot (171), the second probing slot (174) and the one or more consecutive data slots (172, 173).

2. Method according to claim 1 , wherein the transmitting (202) in the first probing slot (171) of the reference signal and the traffic data uses a first modulation and coding scheme, MCS, that is more robust than a second MCS used in the transmitting (206) of the traffic data in the one or more consecutive data slots (172, 173).

3. Method according to claim 2, wherein when a channel state information for the first set of TDBFWs is not known when the reference signal and the traffic data is to be transmitted (202) in the first probing slot (171), the first MCS is set to a default MCS, the default MCS being one of the most robust MCSs of a plurality of selectable MCSs.

4. Method according to claim 2, wherein the first MCS is determined based on a channel state information determined by the wireless device (140) from an earlier reference signal transmitted by the network node (130) in a probing slot that is earlier than the first probing slot (171), the earlier reference signal being beamformed with the first set of TDBFWs.

5. Method according to any of the preceding claims, further comprising: transmitting (212) to the wireless device (140), in one or more additional consecutive data slots (175-176) following the second probing slot (174), traffic data beamformed with the second set of TDBFWs.

6. Method according to any of the preceding claims, further comprising: transmitting (214), to the wireless device (140), in a third probing slot

(177), a reference signal beamformed with a third set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the third set of TDBFWs, and receiving (216), from the wireless device (140), third channel state information determined by the wireless device (140) based on the reference signal beamformed with the third set of TDBFWs, wherein the determining (220) of the set of TDBFWs that has the highest transmission quality is performed based on the received (204, 210, 216) first, second and third channel state information so that the determining (220) is performed out of the first, the second and the third set of TDBFWs.

7. Method according to any of the preceding claims, wherein the second set of TDBFWs was determined to have the highest transmission quality for transmission to the wireless device (140) in the one or more consecutive data slots by: transmitting, to the wireless device (140), in a first previous probing slot, a reference signal beamformed with the first set of TDBFWs, receiving, from the wireless device (140), first previous channel state information determined by the wireless device (140) based on the reference signal transmitted in the first previous probing slot and beamformed with the first set of TDBFWs; transmitting, to the wireless device (140), in a second previous probing slot, a reference signal beamformed with the second set of TDBFWs; receiving, from the wireless device (140), second previous channel state information determined by the wireless device (140) based on the reference signal transmitted in the second previous probing slot and beamformed with the second set of TDBFWs; and determining, based on the received first and second previous channel state information, that the second set of TDBFWs out of the first and second set of TDBFWs had the highest transmission quality, wherein the first and second previous probing slots are transmitted before the first probing slot (171).

8. A method performed by a wireless device (140) connected to a network node (130) of a wireless communication network (100), the network node (130) having a plurality of antennas, wherein a second set of time domain beamforming weights, TDBFW, has been determined to have a highest transmission quality for transmission from the network node (130) to the wireless device (140) in one or more consecutive data slots, out of a plurality of different sets of TDBFWs, each of the plurality of sets of TDBFWs corresponding to a transmission direction angle, the transmission direction angles of the plurality of sets being mutually different, the method comprising: receiving (302), from the network node (130), in a first probing slot (171), a reference signal beamformed with a first set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the first set of TDBFWs; transmitting (304), to the network node (130), first channel state information determined by the wireless device (140) based on the reference signal beamformed with the first set of TDBFWs; receiving (306), from the network node (130), in the one or more consecutive data slots (172, 173), traffic data beamformed with the second set of TDBFWs of the plurality of different sets of TDBFWs; receiving (308), from the network node (130), in a second probing slot (174), a second reference signal beamformed with the second set of TDBFWs and traffic data also beamformed with the second set of TDBFWs, and transmitting (310), to the network node (130), second channel state information determined by the wireless device (140) based on the reference signal beamformed with the second set of TDBFWs.

9. Method according to claim 8, wherein the reference signals and the traffic data received (302, 308) in the first probing slot (171) is coded with a first modulation and coding scheme, MCS, that is more robust than a second MCS by which the traffic data received (306) in the one or more consecutive data slots (172, 173) is coded.

10. Method according to claim 8 or 9, further comprising: receiving (312), from the network node (130), in one or more additional consecutive data slots (175-176) following the second probing slot (174), traffic data beamformed with the second set of TDBFWs.

11 . Method according to any of claims 8-10, further comprising: receiving (314), from the network node (130), in a third probing slot, a reference signal beamformed with a third set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the third set of TDBFWs, and transmitting (316), to the network node (130), third channel state information determined by the wireless device (140) based on the reference signal beamformed with the third set of TDBFWs.

12. A network node (130) configured to operate in a wireless communication network (100), and configured for directing wireless signals towards a wireless device (140) through beamforming, the network node (130) having a plurality of antennas, the network node being operative for determining a second set of time domain beamforming weights, TDBFW, to have a highest transmission quality for transmission to the wireless device (140) in one or more consecutive data slots, out of a plurality of different sets of TDBFWs, each of the plurality of sets of TDBFWs corresponding to a transmission direction angle, the transmission direction angles of the plurality of sets being mutually different, 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: transmitting, to the wireless device (140), in a first probing slot (171), a reference signal beamformed with a first set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the first set of TDBFWs, receiving, from the wireless device (140), first channel state information determined by the wireless device (140) based on the reference signal beamformed with the first set of TDBFWs; transmitting, to the wireless device (140), in the one or more consecutive data slots (172, 173), traffic data beamformed with the second set of TDBFWs, transmitting, to the wireless device (140), in a second probing slot (174), a reference signal beamformed with the second set of TDBFWs and other traffic data also beamformed with the second set of TDBFWs, receiving, from the wireless device (140), second channel state information determined by the wireless device (140) based on the reference signal beamformed with the second set of TDBFWs, and determining, based on the received first and second channel state information, a set of TDBFWs out of the first and second set of TDBFWs that has the highest transmission quality and therefore to be used for transmission of traffic data to the wireless device in a later data slot (181) that is later in time than the first probing slot (171), the second probing slot (174) and the one or more consecutive data slots (172, 173).

13. Network node (130) according to claim 12, operative for using a first modulation and coding scheme, MCS, in the transmitting in the first probing slot (171) of the reference signal and the traffic data, wherein the first MCS is more robust than a second MCS used in the transmitting of the traffic data in the one or more consecutive data slots (172, 173).

14. Network node (130) according to claim 13, wherein when a channel state information for the first set of TDBFWs is not known when the reference signal and the traffic data is to be transmitted in the first probing slot (171), the network node is operative for setting the first MCS to a default MCS, the default MCS being one of the most robust MCSs of a plurality of selectable MCSs.

15. Network node (130) according to claim 13, operative for determining the first MCS based on a channel state information determined by the wireless device (140) from an earlier reference signal transmitted by the network node (130) in a probing slot that is earlier than the first probing slot (171), the earlier reference signal being beamformed with the first set of TDBFWs.

16. Network node (130) according to any of claims 12-15, further being operative for transmitting to the wireless device (140), in one or more additional consecutive data slots (175-176) following the second probing slot (174), traffic data beamformed with the second set of TDBFWs.

17. Network node (130) according to any of claims 12-16, further being operative for: transmitting, to the wireless device (140), in a third probing slot (177), a reference signal beamformed with a third set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the third set of TDBFWs, and receiving, from the wireless device (140), third channel state information determined by the wireless device (140) based on the reference signal beamformed with the third set of TDBFWs, wherein the network node is operative for the determining of the set of TDBFWs that has the highest transmission quality based on the received first, second and third channel state information so that the determining is performed out of the first, the second and the third set of TDBFWs.

18. Network node (130) according to any of claims 12-17, operative to have determined the second set of TDBFWs to have the highest transmission quality for transmission to the wireless device (140) in the one or more consecutive data slots by: transmitting, to the wireless device (140), in a first previous probing slot, a reference signal beamformed with the first set of TDBFWs, receiving, from the wireless device (140), first previous channel state information determined by the wireless device (140) based on the reference signal transmitted in the first previous probing slot and beamformed with the first set of TDBFWs; transmitting, to the wireless device (140), in a second previous probing slot, a reference signal beamformed with the second set of TDBFWs; receiving, from the wireless device (140), second previous channel state information determined by the wireless device (140) based on the reference signal transmitted in the second previous probing slot and beamformed with the second set of TDBFWs; and determining, based on the received first and second previous channel state information, that the second set of TDBFWs out of the first and second set of TDBFWs had the highest transmission quality, wherein the first and second previous probing slots are transmitted before the first probing slot (171).

19. A wireless device (140) operable in a wireless communication network (100) and configured for communicating wireless signals with a network node (130) comprising a plurality of antennas, wherein a second set of time domain beamforming weights, TDBFW, has been determined to have a highest transmission quality for transmission from the network node (130) to the wireless device (140) in one or more consecutive data slots, out of a plurality of different sets of TDBFWs, each of the plurality of sets of TDBFWs corresponding to a transmission direction angle, the transmission direction angles of the plurality of sets being mutually different, the wireless device (140) comprising a processing circuitry (703) and a memory (704), said memory containing instructions executable by said processing circuitry, whereby the wireless device (140) is operative for: receiving, from the network node (130), in a first probing slot (171), a reference signal beamformed with a first set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the first set of TDBFWs; transmitting, to the network node (130), first channel state information determined by the wireless device (140) based on the reference signal beamformed with the first set of TDBFWs; receiving, from the network node (130), in the one or more consecutive data slots (172, 173), traffic data beamformed with the second set of TDBFWs of the plurality of different sets of TDBFWs; receiving, from the network node (130), in a second probing slot (174), a second reference signal beamformed with the second set of TDBFWs and traffic data also beamformed with the second set of TDBFWs, and transmitting, to the network node (130), second channel state information determined by the wireless device (140) based on the reference signal beamformed with the second set of TDBFWs.

20. Wireless device (140) according to claim 19, wherein the reference signals and the traffic data received in the first probing slot (171) is coded with a first modulation and coding scheme, MCS, that is more robust than a second MCS by which the traffic data received in the one or more consecutive data slots (172, 173) is coded.

21. Wireless device (140) according to claim 19 or 20, further being operative for receiving, from the network node (130), in one or more additional consecutive data slots (175-176) following the second probing slot (174), traffic data beamformed with the second set of TDBFWs.

22. Wireless device (140) according to any of claims 19-21 , further being operative for: receiving, from the network node (130), in a third probing slot, a reference signal beamformed with a third set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the third set of TDBFWs, and transmitting, to the network node (130), third channel state information determined by the wireless device (140) based on the reference signal beamformed with the third set of TDBFWs.

23. A computer program (605) comprising instructions, which, when executed by at least one processing circuitry of a network node (130) configured for directing wireless signals towards a wireless device (140) through beamforming, the network node (130) having a plurality of antennas, the network node being operative for determining a second set of time domain beamforming weights, TDBFW, to have a highest transmission quality for transmission to the wireless device (140) in one or more consecutive data slots, out of a plurality of different sets of TDBFWs, each of the plurality of sets of TDBFWs corresponding to a transmission direction angle, the transmission direction angles of the plurality of sets being mutually different, causes the network node (130) to perform the following steps: transmitting, to the wireless device (140), in a first probing slot (171), a reference signal beamformed with a first set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the first set of TDBFWs, receiving, from the wireless device (140), first channel state information determined by the wireless device (140) based on the reference signal beamformed with the first set of TDBFWs; transmitting, to the wireless device (140), in the one or more consecutive data slots (172, 173), traffic data beamformed with the second set of TDBFWs, transmitting, to the wireless device (140), in a second probing slot (174), a reference signal beamformed with the second set of TDBFWs and other traffic data also beamformed with the second set of TDBFWs, receiving, from the wireless device (140), second channel state information determined by the wireless device (140) based on the reference signal beamformed with the second set of TDBFWs, and determining, based on the received first and second channel state information, a set of TDBFWs out of the first and second set of TDBFWs that has the highest transmission quality and therefore to be used for transmission of traffic data to the wireless device in a later data slot (181) that is later in time than the first probing slot (171), the second probing slot (174) and the one or more consecutive data slots (172, 173).

24. A carrier containing the computer program (605) according to claim 23, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, an electric signal or a computer readable storage medium.

25. A computer program (705) comprising instructions, which, when executed by at least one processing circuitry of wireless device (140) configured for communicating wireless signals with a network node (130) comprising a plurality of antennas, wherein a second set of time domain beamforming weights, TDBFW, has been determined to have a highest transmission quality for transmission from the network node (130) to the wireless device (140) in one or more consecutive data slots, out of a plurality of different sets of TDBFWs, each of the plurality of sets of TDBFWs corresponding to a transmission direction angle, the transmission direction angles of the plurality of sets being mutually different, causes the wireless device (140) to perform the following steps: receiving, from the network node (130), in a first probing slot (171), a reference signal beamformed with a first set of TDBFWs of the plurality of different sets of TDBFWs, and traffic data also beamformed with the first set of TDBFWs; transmitting, to the network node (130), first channel state information determined by the wireless device (140) based on the reference signal beamformed with the first set of TDBFWs; receiving, from the network node (130), in the one or more consecutive data slots (172, 173), traffic data beamformed with the second set of TDBFWs of the plurality of different sets of TDBFWs; receiving, from the network node (130), in a second probing slot (174), a second reference signal beamformed with the second set of TDBFWs and traffic data also beamformed with the second set of TDBFWs, and transmitting, to the network node (130), second channel state information determined by the wireless device (140) based on the reference signal beamformed with the second set of TDBFWs.

26. A carrier containing the computer program (705) according to claim 25, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, an electric signal or a computer readable storage medium.