Signaling feedback at bit 1 to configure or change devices of a communication system

Abstract

This application discloses a one-bit signaling feedback apparatus for configuring or changing a communication system. In the communication system, a transmitter is configured to change transmission characteristics used for communicating with a receiver, wherein the receiver is configured to determine the reception quality of the communication link between the transmitter and the receiver, and to send feedback information indicating whether the reception quality has changed or the direction of the reception quality change or whether the transmission characteristics should be maintained to the transmitter, wherein the transmitter is configured to further change the transmission characteristics used for communicating with the receiver based on the feedback information received from the receiver.

Description

[0001] This application is a divisional application of the Fraunhofer Association for the Promotion of Applied Scientific Research, filed on June 13, 2017, with application number 201780050292.1, entitled "Apparatus for 1-bit Signaling Feedback to Configure or Change a Communication System". Technical Field

[0002] The embodiments relate to transmitters and receivers. Other embodiments relate to methods for transmitting and methods for receiving. Some embodiments relate to 1-bit signaling feedback to configure or change settings of a communication system. Some embodiments relate to 1-bit signaling feedback to improve the performance of full-dimensional MIMO. Background Technology

[0003] In any communication system consisting of a transmitter and a receiver communicating over a noisy channel, resources are required, where the system configuration is obtained from feedback from the receiver to the transmitter. Figure 1 A schematic block diagram of such a communication system 100 is shown, comprising a transmitter 12 and a receiver 14 communicating over a channel 11 that overlaps with noise 13. Whenever the set of possible configurations increases, the feedback 30 for selecting a particular configuration also increases. Therefore, the limited feedback channel 30 also limits the number of possible configurations that can be selected from it.

[0004] Communication systems can be wired communication systems such as the Internet, or wireless communication systems such as WLAN (WLAN = Wireless Local Area Network), GSM (GSM = Global System for Mobile Communications), UMTS (UMTS = Universal Mobile Telecommunications System) and LTE (LTE = Long Term Evolution).

[0005] The settings of a communication system that can be changed or configured using feedback channel 30 may include the modulation and / or code rate selected therefrom, the set and combination of transmitters, the number of beamformers / precoders in a wireless system with multiple antenna transmitters, and in a wireless system with a resource pool, such as in the frequency domain, spatial domain, or code domain.

[0006] In the recently completed LTE Release 12, up to eight antennas and multiplexed streams are considered. For example, in the research project in Release 13 entitled "Study on Elevation Beamforming / Full-Dimension (FD) MIMO for LTE" [3GPP, "Study on Elevation Beamforming / Full-Dimension (FD) MIMO for LTE", 3rd Generation Partnership Project, Volume 13.0.0, July 2015], the trend continues towards more antennas and thus more streams to increase total spectral efficiency, considering up to 64 antennas and 16 streams. The existing mechanisms for amplifying LTE, due to the insertion of the Reference Signal (RS) and Channel State Information Reference Signal (CSI-RS) in the Physical Downlink Shared Channel (PDSCH), lead to increased downlink overhead and signaling. Figure 2 The main signal flow of precoded downlink MIMO in a frequency division duplex (FDD) system is shown in the figure.

[0007] Figure 2 The signal flow in a precoded downlink MIMO FDD system is shown from [Li, J., Su, X., Zeng, J., Zhao, Y., Yu, S., Xiao, L., and Xu, X. (June 2013). Codebook design for uniform rectangular arrays of massive antennas. Vehicular Technology Conference (VTC Spring), 2013 IEEE, pp. 77 (1-5), IEEE]. Specifically, Figure 2 A schematic block diagram of a MIMO system 10 including a multi-antenna transmitter 12 and a multi-antenna receiver 14 is shown. The multi-antenna transmitter 12 includes a pre-encoder (precoding unit) 16 and a plurality of antennas 18 (e.g., N) connected to the pre-encoder 16. t There are N antennas, of which N t N is a natural number greater than or equal to 2. t ≥2). The multi-antenna receiver 14 includes a demodulator (or demodulation unit) 20 and a plurality of antennas 22 (e.g., N) connected to the demodulator 20. r There are N antennas, of which N r N is a natural number greater than or equal to 2. r≥2). Furthermore, the multi-antenna receiver 14 includes a CSI extractor 24 (CSI = Channel State Information), a codebook 26, and a codeword selector 28. The CSI extractor 24 is configured to extract channel state information. The codebook 26 includes multiple codewords. Each codeword can be associated with a codebook index. The codeword selector is configured to select one of the codewords in the codebook based on the channel state information provided by the CSI extractor 24. The multi-antenna receiver 14 is configured to transmit the codebook index of the selected codeword to the multi-antenna transmitter 12 using uplink feedback 30. The multi-antenna transmitter 12 also includes a codebook 32, which includes multiple codewords, wherein the codebook 32 is configured to select one of the codewords based on the codebook index received from the multi-antenna receiver 14 on uplink feedback 30 and provide the selected codeword to the precoder 16.

[0008] The insertion of SR and CSI-RS in PDSCH limits the codebook size at the receiver and thus the codeword selection. As is known from the literature, the finite codebook of the beamformer / precoder (which can be used interchangeably in this document) also limits performance through beamforming gain. The codebook is a quantization of the channel and results in a mismatch (loss of beamforming gain) compared to precoding at the transmitter using perfect channel state information (CSI) [D. Love, R. Heath, V. Lau, D. Gesbert, B. Rao and M. Andrews, “An overview of limited feedback in wireless communication systems”, Selected Areas in Communications, IEEE Journal on, Vol. 26, pp. 1341-1365, October 2008].

[0009] Similar to the simulation assumptions in [3GPP, “Study on Elevation Beamforming / Full-Dimension (FD) MIMO for LTE”, 3rd Generation Partnership Project, Volume V13.0.0, July 2015], Figure 3 The possible gains from the increased codebook size are given. Specifically, Figure 3The SINR (Signal-to-Interference-plus-Noise Ratio) due to the increased codebook size is illustrated graphically, similar to the assumptions of the research project in LTE Release 13 [3GPP, “Study on Elevation Beamforming / Full-Dimension (FD) MIMO for LTE”, 3rd Generation Partnership Project, Volume V13.0.0, July 2015]. Figure 3 In this study, an approximately 10 dB gain in SINR can be observed for beamformers ranging from 16 to 200. Therefore, it is expected that a larger codebook without additional signaling overhead can increase spectral efficiency through the increased beamforming gain.

[0010] In the research project "Study on Elevation Beamforming / Full-Dimension (FD) MIMO for LTE" [3GPP, "Study on Elevation Beamforming / Full-Dimension (FD) MIMO for LTE", 3rd Generation Partnership Project, Volume V13.0.0, July 2015], the problem was addressed by directly increasing the amount of Reference Signal (RS) and Channel State Information Reference Signal (CSI-RS) in the Physical Downlink Shared Channel (PDSCH). There is a trade-off between reduced PDSCH efficiency and the spatial multiplexing gain from a larger number of streams. Even by limiting the number of streams, for example to 16, there is still a gain expected from the increased codebook size or higher quantization of the CSI.

[0011] US2015 / 0016560A1 discloses a system and method for feedback in a precoded MIMO communication system. Specifically, in a closed-loop wireless communication system, a codebook-based feedback mechanism is provided to enable non-uniform precoding for multi-stream transmission, wherein appropriate transmit power allocation and AMC are used for optimization in each stream. The codebook-based feedback mechanism uses a precoding codebook with a power allocation matrix constrained to always apply full power to a predetermined beam for a given beamforming. With this constraint, a 1-bit power allocation feedback index can be used to switch between beamforming and spatial multiplexing. Summary of the Invention

[0012] Therefore, the object of the present invention is to provide a concept that allows for an increase in the number of different possible configurations of the communication system to be selected without increasing the signaling overhead of configuration selection.

[0013] This objective is addressed by the independent claims.

[0014] The embodiment provides a transmitter for communicating with a receiver, wherein the transmitter is configured to change transmission characteristics for communicating with the receiver, wherein the transmitter is configured to further change the transmission characteristics for communicating with the receiver based on feedback information received from the receiver, the feedback information indicating whether the reception quality has changed or the direction of the reception quality change or whether the transmission characteristics should be maintained.

[0015] Other embodiments provide a receiver configured to establish a communication link with a transmitter, wherein the receiver is configured to determine the reception quality of the communication link, and wherein the receiver is configured to send feedback information to the transmitter indicating whether the reception quality has changed or the direction of the change in reception quality or whether the transmission characteristics should be maintained.

[0016] According to the concept of the present invention, feedback information (e.g., 1-bit feedback information) transmitted from the receiver to the transmitter is used to indicate to the transmitter whether the reception quality has changed or the direction of the change, or whether the transmission characteristics should be maintained. Based on the feedback information, the transmitter can adjust its transmission characteristics for communicating with the receiver.

[0017] Other embodiments provide a method for sending, the method including:

[0018] - Establish a communication link with the receiver;

[0019] - Change the transmission characteristics used to communicate with the receiver; and

[0020] - Depending on the feedback information received from the receiver, the transmission characteristics used to communicate with the receiver are further modified. The feedback information indicates whether the reception quality has changed or the direction of the change in reception quality, or whether the transmission characteristics should be maintained.

[0021] Other embodiments provide a method for receiving, the method including:

[0022] - Establish a communication link with the transmitter;

[0023] - Determine the reception quality of the communication link; and

[0024] - Feedback information indicating whether the reception quality has changed, the direction of the change in reception quality, or whether the transmission characteristics should be maintained will be sent to the transmitter.

[0025] Advantageous embodiments are listed in the dependent claims.

[0026] In an embodiment, the feedback information may include exactly one bit.

[0027] When the received quality value detected by the receiver is greater than a reference value, the feedback information may include a first value; and when the received quality value detected by the receiver is equal to or less than the reference value, the feedback information may include a second value different from the first value. The reference value may be a previous value of the received quality or the minimum or maximum value among multiple previous values ​​of the received quality.

[0028] When the received quality value detected by the receiver is less than a reference value, the feedback information may include a first value; and when the received quality value detected by the receiver is equal to or greater than the reference value, the feedback information may include a second value different from the first value. The reference value may be a previous value of the received quality or the minimum or maximum value among multiple previous values ​​of the received quality.

[0029] In an embodiment, the reception quality can be at least one of the following: signal-to-interference-plus-noise ratio, signal-to-noise ratio, channel quality indication, received signal power, and effective data throughput.

[0030] In an embodiment, the transmission characteristics may be at least one of transmission power, code rate, set of arranged resources, beamforming pattern, precoder settings, and set of access nodes for coordinated transmission in a single-frequency network.

[0031] In an embodiment, in a first operating mode, the transmitter may be configured to select one of a plurality of different transmission features for communicating with the receiver, depending on selection information received from the receiver.

[0032] In an embodiment, in a first operating mode, the transmitter can be configured to randomly select one of a plurality of different transmission features for communicating with the receiver.

[0033] In an embodiment, in a first operating mode, the transmitter can be configured to select a default transmission feature.

[0034] In an embodiment, in a second operating mode, the transmitter can be configured to change the transmission characteristics used for communicating with the receiver, wherein the transmitter can be configured to further change the transmission characteristics used for communicating with the receiver depending on feedback information received from the receiver.

[0035] The transmitter can be configured to switch to a first operating mode for establishing a communication link between the transmitter and the receiver. Furthermore, the transmitter can be configured to switch to a second mode that continuously includes at least two changes in transmission characteristics over a period of time.

[0036] The transmitter can be configured to signal changes in operating mode to the receiver. Alternatively, the transmitter can be configured to change its operating mode based on signaling information received from the receiver.

[0037] The transmitter can be configured to transmit control information (e.g., reference signals, pilots) in a second operating mode without using the downlink channel from the transmitter to the receiver. The control information indicates to the receiver the transmission characteristics to be used.

[0038] In an embodiment, the transmitter may be configured to iteratively further change the transmission characteristics used for communicating with the receiver, depending on feedback information received from the receiver.

[0039] In an embodiment, the transmitter may include multiple antennas, wherein the transmission feature may be a beam pattern, and the transmitter may be configured to change or further change the beam pattern by changing the direction of the main lobe of the beam pattern.

[0040] The transmitter can be configured to change the orientation of the main lobe in the same direction when feedback indicates high reception quality. Furthermore, the transmitter can be configured to change the orientation of the main lobe in different directions when feedback indicates low reception quality.

[0041] The transmitter can be configured to change or further alter the beam pattern by continuously changing the main lobe of the beam pattern in the same direction until feedback indicates that the characteristics of the beam pattern should be maintained.

[0042] In an embodiment, in a first operating mode, the receiver may be configured to select one of a plurality of different transmission features depending on a determined reception quality, and send selection information indicating the transmission feature to be used by the transmitter among the plurality of different transmission features to the transmitter.

[0043] In an embodiment, in a second operating mode, the receiver can be configured to send feedback information to the transmitter.

[0044] The receiver can be configured to switch to a first operating mode for establishing a communication link between the transmitter and the receiver. Furthermore, the receiver can be configured to switch to a second mode that continuously includes at least two changes in transmission characteristics over a period of time.

[0045] The receiver can be configured to switch to a first operating mode or a second operating mode depending on signaling information received from the transmitter. Alternatively, the receiver can be configured to switch to the first operating mode or the second operating mode and signal the current operating mode to the transmitter.

[0046] The receiver can be configured to receive control information in a second operating mode without using the downlink channel from the transmitter to the receiver, the control information indicating to the receiver the transmission feature to be used.

[0047] Other embodiments provide a multi-antenna transmitter configured to establish a communication link with a receiver, wherein the multi-antenna transmitter is configured to change a beamforming pattern used for communicating with the receiver, wherein the multi-antenna transmitter is configured to further change the beamforming pattern used for communicating with the receiver depending on feedback information received from the receiver, the feedback information indicating whether the received SINR has changed or the direction of the change in the received SINR or whether the characteristics of the beamforming pattern should be maintained.

[0048] In this embodiment, the feedback information includes exactly one bit.

[0049] In an embodiment, in a first operating mode, the multi-antenna transmitter can be configured to select one of a plurality of different beamforming patterns for communicating with the receiver, depending on selection information received from the receiver, wherein the selection information indicates one of the plurality of different beamforming patterns to be used by the multi-antenna transmitter.

[0050] In an embodiment, in a second operating mode, the multi-antenna transmitter can be configured to change the beamforming pattern used for communicating with the receiver, wherein the multi-antenna transmitter can be configured to further change the beamforming pattern used for communicating with the receiver depending on feedback information received from the receiver.

[0051] The multi-antenna transmitter can be configured to switch to a first operating mode for establishing a communication link between the multi-antenna transmitter and the receiver, and wherein the multi-antenna transmitter can be configured to switch to a second operating mode for a duration including at least two changes in the beam pattern.

[0052] A multi-antenna transmitter can be configured to signal changes in mode to the receiver.

[0053] The multi-antenna transmitter can be an LTE transmitter. Therefore, the multi-antenna transmitter can be configured to transmit control information in a second operating mode without using the PDSCH, the control information indicating the beam pattern to be used to the receiver.

[0054] In an embodiment, the multi-antenna transmitter can be configured to iteratively further change the beamforming pattern used for communicating with the receiver, depending on feedback information received from the receiver.

[0055] In an embodiment, the multi-antenna transmitter can be configured to change or further change the beam pattern by altering the direction of the main lobe of the beam pattern.

[0056] A multi-antenna transmitter can be configured to change the direction of the main lobe in the same direction when the feedback information indicates a high SINR. Furthermore, the multi-antenna transmitter can be configured to change the direction of the main lobe in different directions when the feedback information indicates a low SINR.

[0057] In an embodiment, a multi-antenna transmitter can be configured to change or further change the beam pattern by altering the direction of the main lobe of the beam pattern in the azimuth and elevation directions, respectively, after each other.

[0058] In an embodiment, a multi-antenna transmitter can be configured to change or further alter the beam pattern by continuously changing the main lobe of the beam pattern in the same direction until feedback information indicates that the characteristics of the beam pattern should be maintained.

[0059] Other embodiments provide a receiver configured to establish a communication link with a multi-antenna transmitter, wherein the receiver is configured to determine the SINR of the communication link, and wherein the receiver is configured to send feedback information indicating whether the received SINR has changed or the direction of the change in the received SINR or whether the beam pattern should be maintained to the multi-antenna transmitter.

[0060] In this embodiment, the feedback information includes exactly one bit.

[0061] In an embodiment, in a first operating mode, the receiver may be configured to select one of a plurality of different beamforming patterns depending on a determined SINR, and send selection information indicating the beamforming pattern to be used by the multi-antenna transmitter among the plurality of different beamforming patterns to the multi-antenna transmitter.

[0062] In an embodiment, in a second operating mode, the receiver can be configured to send feedback information to a multi-antenna transmitter.

[0063] The receiver can be configured to switch to a first operating mode for establishing a communication link between the multi-antenna transmitter and the receiver. Furthermore, the receiver can be configured to switch to a second operating mode that continuously includes at least two time periods of beam pattern variation.

[0064] The receiver can be configured to switch to a first operating mode or a second operating mode depending on the signaling information received from the multi-antenna transmitter.

[0065] The receiver can be an LTE receiver. Therefore, the receiver can be configured to transmit control information in a second operating mode without using the PDSCH, the control information indicating the selected beam pattern from among several different beam patterns selected by the multi-antenna transmitter.

[0066] Other embodiments provide a method for multi-antenna transmission, the method including:

[0067] - Establish a communication link with the receiver;

[0068] - Change the beamforming pattern used for communication with the receiver; and

[0069] - Depending on the feedback information received from the receiver, the beamforming pattern used for communication with the receiver is further modified. The feedback information indicates whether the received SINR has changed or the direction of the change in the received SINR, or whether the characteristics of the beamforming pattern should be maintained.

[0070] Other embodiments provide a method for receiving, the method including:

[0071] - Establish a communication link with the multi-antenna transmitter;

[0072] - Determine the SINR of the communication link; and

[0073] - Feedback information indicating whether the received SINR has changed or the direction of the change in received SINR, or whether the characteristics of the beam pattern should be maintained, will be sent to the multi-antenna transmitter. Attached Figure Description

[0074] Embodiments of the present invention are described herein with reference to the accompanying drawings.

[0075] Figure 1 A schematic block diagram of a prior art communication system is shown;

[0076] Figure 2 A schematic block diagram of a prior art MIMO system is shown;

[0077] Figure 3 A graph showing SINR (in dB) versus codebook size (in number of codewords) for a single user and a single base station;

[0078] Figure 4 A schematic block diagram of a transmitter according to an embodiment is shown;

[0079] Figure 5 A schematic block diagram of a receiver according to an embodiment is shown;

[0080] Figures 6a-6c A schematic block diagram of a communication system including a transmitter and a receiver at different points in time;

[0081] Figures 7a-7e A schematic block diagram of a communication system including a transmitter and a receiver at different points in time;

[0082] Figure 8 A schematic block diagram of a communication system including a multi-antenna transmitter and receiver according to an embodiment is shown;

[0083] Figure 9 A flowchart illustrating a method for operating a communication system including a multi-antenna transmitter and a (MIMO) receiver according to an embodiment;

[0084] Figure 10A flowchart illustrating a method for transmission according to an embodiment is shown; and

[0085] Figure 11 A flowchart illustrating a method for receiving according to an embodiment is shown. Detailed Implementation

[0086] In the following description, equal or identical elements or elements having equal or identical functions are indicated by equal or identical reference numerals.

[0087] In the following description, numerous details are set forth to provide a more comprehensive explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention can be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention. Furthermore, unless otherwise specifically stated, features of the different embodiments described herein can be combined with each other.

[0088] Figure 4 A schematic block diagram of a transmitter 100 for communicating with a receiver according to an embodiment of the present invention is shown. The transmitter 100 is configured to change transmission characteristics for communicating with the receiver, wherein the transmitter 100 is configured to further change the transmission characteristics for communicating with the receiver depending on feedback information 120 received from the receiver, the feedback information 120 indicating whether the reception quality has changed or the direction of the reception quality change or whether the transmission characteristics should be maintained.

[0089] In an embodiment, transmitter 100 may include at least one antenna 102, for example for transmitting signal 122 to a receiver and / or for receiving signal 124 from a receiver. Therefore, transmitter 100 may be a transceiver.

[0090] In an embodiment, the feedback information 120 may include exactly one bit.

[0091] For example, when the received quality value detected by the receiver is greater than a reference value, the feedback information 120 may include a first value (e.g., logic 1), and when the received quality value detected by the receiver is equal to or less than the reference value, the feedback information 120 may include a second value different from the first value (e.g., logic 0). Naturally, when the received quality value detected by the receiver is less than the reference value, the feedback information may also include a first value (e.g., logic 1), and when the received quality value detected by the receiver is equal to or greater than the reference value, the feedback information may also include a second value (e.g., logic 0). The reference value may be a previous value of the received quality or the minimum or maximum of a plurality of previous values ​​of the received quality.

[0092] Receive quality can be at least one of the following: signal-to-interference plus-noise ratio (SINR), signal-to-noise ratio (SNR), channel quality indication (CQI), received signal power and effective data throughput (considering coding overhead and block error), and interference power level.

[0093] Transmission characteristics can be one of the following: transmission power, code rate, set of resources arranged, beamforming pattern, precoder settings, or set of access nodes (e.g., a set of serving or jamming transmitters) used for coordinated transmission in a single-frequency network.

[0094] In an embodiment, the transmitter 100 may be configured to iteratively further change the transmission characteristics used for communicating with the receiver, depending on the feedback information 120 received from the receiver.

[0095] In an embodiment, the transmitter 100 can be configured to switch between a first operating mode and a second operating mode.

[0096] In a first operating mode, transmitter 100 can be configured to select one of a plurality of different transmission features for communicating with the receiver, depending on selection information 130 received from the receiver. Alternatively, in the first operating mode, transmitter 100 can be configured to randomly select one of a plurality of different transmission features for communicating with the receiver. Alternatively, in the first operating mode, transmitter 100 can be configured to select a default transmission feature.

[0097] In the second operating mode, the transmitter 100 can be configured to change the transmission characteristics used for communicating with the receiver, wherein the transmitter 100 can be configured to further change the transmission characteristics used for communicating with the receiver depending on feedback information received from the receiver.

[0098] Transmitter 100 can be configured to switch to a first operating mode for establishing a communication link between transmitter 100 and receiver, and switch to a second operating mode after establishing the communication link between transmitter 100 and receiver, for example, for a given period of time, the period of time including at least two changes in transmission characteristics.

[0099] Furthermore, transmitter 100 can be configured to signal a change in operating mode to receiver. Alternatively, transmitter 100 can be configured to change operating mode based on signaling information received from receiver.

[0100] Furthermore, transmitter 100 can be configured to transmit control information in a second operating mode without using the downlink channel from transmitter to receiver, the control information indicating the transmission characteristics to be used to the receiver. For example, no signaling from transmitter to receiver is used, therefore it is transparent to the receiver and does not add additional signaling overhead.

[0101] Figure 5 An exemplary block diagram of a receiver 150 for communicating with a transmitter 100 according to an embodiment of the present invention is shown. The receiver 150 is configured to establish a communication link with the transmitter 100, wherein the receiver 150 is configured to determine the reception quality of the communication link, and wherein the receiver 150 is configured to send feedback information 120 indicating whether the reception quality has changed or the direction of the reception instruction change or whether the transmission characteristics should be maintained to the transmitter 100.

[0102] In an embodiment, receiver 150 may include at least one antenna 152, for example for transmitting signal 124 to transmitter 100 and / or receiving signal 122 from transmitter. Receiver 150 may be a transceiver.

[0103] In an embodiment, the feedback information 120 may include exactly one bit.

[0104] For example, when the received quality value detected by the receiver is greater than a reference value, the feedback information 120 may include a first value (e.g., logic 1), and when the received quality value detected by the receiver is equal to or less than the reference value, the feedback information 120 may include a second value different from the first value (e.g., logic 0). Naturally, when the received quality value detected by the receiver is less than the reference value, the feedback information may also include a first value (e.g., logic 1), and when the received quality value detected by the receiver is equal to or greater than the reference value, the feedback information may also include a second value (e.g., logic 0). The reference value may be a previous value of the received quality or the minimum or maximum of a plurality of previous values ​​of the received quality.

[0105] In an embodiment, receiver 150 can be configured to switch between a first operating mode and a second operating mode.

[0106] In the first operating mode, receiver 150 can be configured to select one of a plurality of different transmission features depending on the determined reception quality, and send selection information 130, indicating the transmission feature to be used by the transmitter, to the transmitter.

[0107] In the second operating mode, receiver 150 can be configured to send feedback information 120 to transmitter 100.

[0108] Receiver 150 can be configured to switch to a first operating mode for establishing a communication link or communication channel between transmitter 100 and receiver 150, and switch to a second operating mode after establishing the communication link or communication channel between transmitter 100 and receiver 150, for example, for a given period of time, the period of time including at least two changes in transmission characteristics.

[0109] Furthermore, receiver 150 can be configured to switch to a first operating mode or a second operating mode depending on signaling information received from transmitter 100. Alternatively, receiver 150 can be configured to switch to the first operating mode or the second operating mode and signal the current operating mode to transmitter.

[0110] Furthermore, receiver 150 can be configured to receive control information in a second operating mode without using the downlink channel from transmitter to receiver, the control information indicating to the receiver the transmission feature to be used.

[0111] In an embodiment, feedback information (e.g., 1-bit feedback) is sent from the receiver to the transmitter to indicate whether a particular performance indicator measured by the receiver has increased or decreased. This means, for example, when interested in the maximum value of the performance indicator, a 1 (or 0) is sent if the value is large, and a 0 (or 1) is sent if the value is the same or smaller. The same operation can be performed when interested in the minimum value of the performance indicator, when the value is small. The reference value used for comparison can be a previous value (see the example in Figure 6) or a maximum / minimum value within the time period when the transmitter begins to change the settings. Whenever a new maximum / minimum value is received, the maximum / minimum value used for comparison is updated, see the example in Figure 7. Using this scheme, the transmitter can change the system settings to any desired configuration that is not limited by the feedback channel. The initial settings from which it begins are most likely obtained through existing technology-level mechanisms, but can also be random settings. For example, this could be:

[0112] First, the modulation and / or code rate are selected. The transmitter can change the code rate, for example, to a lower code rate to increase effective data throughput. Effective data throughput means throughput without redundancy added by the code and only successfully received and decoded messages. This means that, on the one hand, increasing the code rate adds redundancy and reduces effective throughput, and on the other hand, decreasing the code rate increases the rate of unsuccessfully received and decoded messages. In a feedback system, the receiver signals the transmitter with the available code rates from a finite set. Using the scheme proposed here, the transmitter can change the code rate to other values ​​not included in the finite set (but technically possible in the system) and receive feedback from the receiver on whether the effective data throughput has increased.

[0113] Secondly, there is a set of transmitters or a subset thereof. In this example, the receiver has a set of transmitters from which to select for transmission. The receiver can indicate a specific transmitter to be used or a specific set of transmitters. However, whenever the number of transmitters is large, the required feedback is also large. By measuring specific values ​​again (such as receiver signal strength or signal-to-noise ratio (SNR) or signal-to-noise plus interference ratio (SINR) at the receiver), the set of transmitters can be changed and the receiver indication value can be increased or decreased by 1 or 0.

[0114] Third, the number of beamformers / precoders in a wireless system with multiple antenna transmitters. In a wireless system where the transmitter has multiple antennas (e.g., WiFi, LTE), the number of beamformers / precoders to be used is defined from a codebook that the receiver can select from, see Figure 6. With a larger codebook, the amount of feedback for the transmission indication also increases. Using the proposed 1-bit feedback scheme, the transmitter can change the beamformer / precoder to improve specific performance indications at the receiver. This performance indication can be, but is not limited to, received signal power, SNR, SINR, block error rate, bit error rate, and interference plus noise power.

[0115] Fourth, wireless systems with resource pools in, for example, the frequency domain, spatial domain, or code domain. In wireless systems with large resource pools in the frequency, spatial, or code domains, users must report which resources are the best resources for the transmitter to use. This requires a large amount of feedback from the receiver. This problem is even more severe in shared access systems when multiple receivers use the same uplink channel (control, feedback, or data channel) to report their resources. Using the proposed 1-bit scheme, the transmitter can allocate specific resources to the receiver and then, based on the user's 1-bit feedback, begin to change the resources assigned to the receiver. Again, the measured values ​​can be, but are not limited to, received signal power, SNR, SINR, block error rate, bit error rate, and interference plus noise power.

[0116] Figures 6a-6c A schematic block diagram of a communication system 180, including a transmitter 100 and a receiver 150, is shown at different points in time. The transmitter 100 and receiver 150 communicate on a communication channel 182 that overlaps with noise 184. In other words, Figures 6a-6c An example using previous values ​​for comparison illustrates a communication system based on 1-bit feedback. Here, the performance of smaller measurements is indicated by 0, while values ​​equal to or greater than the minimum are indicated by 1.

[0117] exist Figure 6aIn the first time point (time point 1), the transmitter 100 is configured to communicate with the receiver 150 using a first transmission feature (configuration n1), wherein the receiver 150 is configured to determine (e.g., measure) the reception quality to obtain a first performance indication (PI1).

[0118] exist Figure 6b In the second time point (time point 2), transmitter 100 is configured to change the transmission characteristic from a first transmission characteristic (configuration n1) to a second transmission characteristic (configuration n2) different from the first transmission characteristic. Receiver 150 is configured to determine the reception quality, obtain a second performance indicator (PI2), compare the second performance indicator (PI2) with a reference value, and provide 1-bit feedback information based on the comparison between the second performance indicator (PI2) and the reference value. As exemplarily shown in FIG6, the reference value is the previous performance indicator, i.e., the first performance indicator (PI1). In the example shown in FIG6... Figure 6b In the example, the second performance indicator (PI2) is less than the first performance indicator (PI1) so that the 1-bit feedback information includes logic 0.

[0119] exist Figure 6c In the process, at a third time point (time point 3), transmitter 100 is configured to change the transmission characteristic from a second transmission characteristic (configuration n2) to a third transmission characteristic (configuration n3) different from the second transmission characteristic, wherein receiver 150 is configured to determine the reception quality to obtain a third performance indicator (PI3), compare the third performance indicator (PI3) with a reference value, and provide 1-bit feedback information based on the comparison between the third performance indicator (PI3) and the reference value. Figure 6c As illustrated, the reference value is the previous performance indicator, namely the second performance indicator (PI2). Figure 6c In the example shown, the third performance indicator (PI3) is greater than or equal to the second performance indicator (PI2) so that the 1-bit feedback information includes logic 1.

[0120] Figures 7a-7e A schematic block diagram of a communication system 180, including a transmitter 100 and a receiver 150, is shown at different points in time. The transmitter 100 and receiver 150 communicate on a communication channel 182 that overlaps with noise 184. In other words, Figures 7a-7e An example using the minimum value for comparison illustrates a communication system based on 1-bit feedback.

[0121] exist Figure 7a At a first time point (time point 1), transmitter 100 is configured to communicate with receiver 150 using a first transmission feature (configuration n1), wherein receiver 150 is configured to determine (e.g., measure) the reception quality to obtain a first performance indication (PI1).

[0122] exist Figure 7b At a second time point (time point 2), transmitter 100 is configured to change its transmission characteristics from a first transmission characteristic (configuration n1) to a second transmission characteristic (configuration n2) different from the first transmission characteristic, wherein receiver 150 is configured to determine the reception quality to obtain a second performance indicator (PI2), compare the second performance indicator (PI2) with a reference indicator, and provide 1-bit feedback information based on the comparison between the second performance indicator (PI2) and the reference indicator. Figure 7b As exemplarily shown, the reference indicator is the minimum indicator among the previous performance indicators. Since the first performance indicator (PI1) is the minimum indicator among the previous performance indicators or the only available performance indicator, the receiver 150 is configured to compare the second performance indicator (PI2) and the first performance indicator (PI1). In the example shown... Figure 7b In the example, the second performance indicator (PI2) is less than the first performance indicator (PI1) so that the 1-bit feedback information includes a logic 0. The second performance indicator is the new reference indicator.

[0123] exist Figure 7c In the process, at the third time point (time point 3), the transmitter 100 is configured to change the transmission characteristic from the second transmission characteristic (configuration n2) to a third transmission characteristic (configuration n3) different from the second transmission characteristic, wherein the receiver 150 is configured to determine the reception quality to obtain a third performance indicator (PI3), compare the third performance indicator (PI3) with a reference value, and provide 1-bit feedback information based on the comparison between the third performance indicator (PI3) and the reference value. Figure 7c As exemplarily shown, the reference indicator is the lowest indicator among the previous performance indicators. Since the second performance indicator (PI2) is the lowest indicator among the previous performance indicators, the receiver 150 is configured to compare the second performance indicator (PI2) and the third performance indicator (PI3). In the example shown... Figure 7c In the example, the third performance indicator (PI3) is greater than or equal to the second performance indicator (PI2) so that the 1-bit feedback information includes a logic 1. The second performance indicator remains a reference indicator.

[0124] exist Figure 7d In the process, at the fourth time point (time point 4), transmitter 100 is configured to change the transmission characteristic from the third transmission characteristic (configuration n3) to a fourth transmission characteristic (configuration n4) different from the third transmission characteristic, wherein receiver 150 is configured to determine the reception quality to obtain a fourth performance indicator (PI4), compare the fourth performance indicator (PI4) with a reference value, and provide 1-bit feedback information based on the comparison between the fourth performance indicator (PI4) and the reference value. Figure 7dAs exemplarily shown, the reference indicator is the lowest indicator among the previous performance indicators. Since the second performance indicator (PI2) is the lowest indicator among the previous performance indicators, the receiver 150 is configured to compare the second performance indicator (PI2) and the fourth performance indicator (PI4). In the example shown... Figure 7d In the example, the fourth performance indicator (PI4) is less than the second performance indicator (PI2) so that the 1-bit feedback information includes a logic 0. The fourth performance indicator is the new reference indicator.

[0125] exist Figure 7e In the process, at the fifth time point (time point 5), the transmitter 100 is configured to change the transmission characteristic from the fourth transmission characteristic (configuration n4) to a fifth transmission characteristic (configuration n5) different from the fourth transmission characteristic, wherein the receiver 150 is configured to determine the reception quality to obtain a fifth performance indicator (PI5), compare the fifth performance indicator (PI5) with a reference value, and provide 1-bit feedback information based on the comparison between the fifth performance indicator (PI5) and the reference value. Figure 7e As exemplarily shown, the reference indicator is the lowest indicator among the previous performance indicators. Since the fourth performance indicator (PI4) is the lowest indicator among the previous performance indicators, the receiver 150 is configured to compare the fifth performance indicator (PI5) and the fourth performance indicator (PI4). In the example shown... Figure 7e In the example, the fifth performance indicator (PI5) is greater than or equal to the fourth performance indicator (PI4) so ​​that the 1-bit feedback information includes a logic 1. The fourth performance indicator remains a reference indicator.

[0126] Figure 8 A schematic block diagram of a communication system 180 including a multi-antenna transmitter 100 and a receiver 150 according to an embodiment is shown.

[0127] Transmitter 100 can be configured to establish a communication link with receiver 150, wherein multi-antenna transmitter 100 is configured to change the beamforming pattern used for communicating with receiver 150, wherein multi-antenna transmitter 100 can be configured to further change the beamforming pattern used for communicating with receiver 150 depending on feedback information 120 received from receiver 150, the feedback information 120 indicating whether the received SINR has changed or the direction of the received SINR change or whether the characteristics of the beamforming pattern should be maintained.

[0128] Receiver 150 can be configured to establish a communication link with multi-antenna transmitter 100, wherein receiver 150 can be configured to determine the SINR of the communication link, wherein receiver 150 can be configured to send feedback information 120 indicating whether the received SINR has changed or the direction of the received SINR change or whether the beam pattern should be maintained to multi-antenna transmitter 100.

[0129] For example, a multi-antenna transmitter 100 may include multiple antennas 102 for transmitting signal 122 to and receiving signal 124 from receiver 150. Receiver 150 may include one antenna 150 or more than one antenna 152 for receiving signal 122 from transmitter 100 and transmitting signal 124 to transmitter 100 (i.e., receiver 150 may be a multi-antenna receiver).

[0130] Feedback information 120 can include exactly 1 bit, that is, logic 1 or logic 0.

[0131] For example, when the received SINR value is greater than a reference value, the feedback information 120 may include a first value (e.g., logic 1), and when the received SINR value is equal to or less than the reference value, the feedback information 120 may include a second value different from the first value (e.g., logic 0). Naturally, when the received SINR value is less than the reference value, the feedback information may also include a first value (e.g., logic 1), and when the received SINR value is equal to or greater than the reference value, the feedback information may also include a second value (e.g., logic 0). The reference value may be a previous value of SINR or the minimum or maximum of a plurality of previous values ​​of SINR.

[0132] In an embodiment, the multi-antenna transmitter 100 may be configured, in a first operating mode, to select one of a plurality of different beamforming patterns, depending on selection information received from the receiver 150 (e.g., from a codebook), the selection information (e.g., a codebook index) indicating one of the plurality of different beamforming patterns to be used by the multi-antenna transmitter.

[0133] Furthermore, the multi-antenna transmitter 100 can be configured to change the beamforming pattern used for communicating with the receiver 150 in a second operating mode, wherein the multi-antenna transmitter 100 can be configured to further change the beamforming pattern used for communicating with the receiver depending on feedback information received from the receiver.

[0134] In an embodiment, receiver 150 may be configured to select one of a plurality of different beamforming patterns in a first operating mode depending on a determined SINR (e.g., from a codebook), and to send beamforming pattern selection information (e.g., codebook index) indicating one of the plurality of different beamforming patterns used by multi-antenna transmitter 100 to multi-antenna transmitter 100.

[0135] In addition, receiver 150 can be configured to send feedback information 120 to multi-antenna transmitter 100 in a second operating mode.

[0136] In one embodiment, the multi-antenna transmitter 100 may be configured to switch to a first operating mode for establishing a communication link between the multi-antenna transmitter 100 and the receiver 150, and wherein the multi-antenna transmitter 100 may be configured to switch to a second operating mode for a duration including at least two changes in the beam pattern.

[0137] Similarly, receiver 150 can be configured to switch to a first operating mode for establishing a communication link between multi-antenna transmitter 100 and receiver 150, wherein receiver 150 is configured to switch to a second operating mode for a duration including at least two changes in beam pattern.

[0138] The multi-antenna transmitter 100 can be configured to send signaling information to the receiver 150, the signaling information signaling a change in operating mode to the receiver.

[0139] Receiver 150 can be configured to switch to a first operating mode or a second operating mode depending on the signaling information received from multi-antenna transmitter 100.

[0140] In this embodiment, by using a 1-bit feedback from receiver 150 to transmitter 100, a large codebook without additional signaling in the PDSCH can be used. The 1-bit feedback indicates on the transmitter side whether the beamformer / precoder selected by the receiver has been changed without informing the receiver whether the change has increased the received SINR.

[0141] The implementation enables quantization of virtually unlimited codebooks or channels. The codebook structure of the full-dimensional codebook C_FD is theoretically assumed to be a rectangular antenna array at the transmitter, as follows:

[0142]

[0143] Where C_v is the codebook for elevation beamforming and C_h is the codebook for azimuth beamforming. Details can be found in [3GPP, “Study on Elevation Beamforming / Full-Dimension (FD) MIMO for LTE”, 3rd Generation Partnership Project, Vol. 13.0.0, July 2015] and [YHNam, MSRahman, Y.Li, G.Xu, E.Onggosanusi, J.Zhang and JYSeol, “Full dimension MIMO for LTE-Advanced and 5G”, Information Theory and Applications Workshop (ITA), 2015, pp. 143-148, February 2015]. To construct C_v and C_h, discrete Fourier transform (DFT) matrices can be used. This means a structured codebook where specific columns (streams) of the codebook correspond to specific directions. This side information can be utilized in the following steps:

[0144] 1. Each receiver selects the most suitable beamformer (column) from C_FD;

[0145] 2. Each receiver feedback corresponds to a precoding matrix indication (PMI) for the entry selected in step 1;

[0146] 3. The transmitter begins transmission to the receiver using the beamformer selected in step 2;

[0147] 4. The transmitter informs the receiver that it is now initiating a rapid 1-bit feedback mode;

[0148] 5. The transmitter begins to modify the beamformer so that the main lobe of the beam is different from the beamformer used in step 3 or in the previous iteration of step 5.

[0149] 6. If the received SINR of the beamformer used in step 5 is higher (feedback 1) or lower (feedback 0) than the received SINR of the beamformer used in step 3 or a previous iteration of step 5, the receiver sends 1 bit of feedback.

[0150] Based on the feedback in step 6, depending on the specific algorithm of each operator, the process of further beamformer modification can continue to step 5 or terminate.

[0151] Figure 9 A flowchart illustrating a method 200 for operating a communication system including a multi-antenna transmitter 100 and a (multi-antenna) receiver 150 according to an embodiment is shown. In other words, Figure 9 This illustrates one implementation of the process in which beamformers are changed in the azimuth and elevation directions respectively after each other.

[0152] In the first operating mode (first phase) 202, receiver 150 may be configured to select one of a plurality of different beamforming patterns based on a determined SINR (e.g., from a codebook), and transmit beamforming pattern selection information (e.g., a codebook index) indicating one of the plurality of different beamforming patterns used by multi-antenna transmitter 100 to multi-antenna transmitter 100. Multi-antenna transmitter 100 may be configured to select one of a plurality of different beamforming patterns for communicating with receiver based on the selection information (e.g., a codebook index) received from receiver 150 (e.g., from a codebook).

[0153] For example, such as Figure 9 As shown, in the first operating mode 202, the transmitter 100 (e.g., a base station) can transmit Channel State Information (CSI) and Demodulation Reference Signal (DRMS) to the receiver 150 (e.g., a User Equipment (UE)). The receiver 150 can be configured to measure 204 SINR and store it for comparison purposes. Furthermore, the receiver 150 can be configured to transmit PMI to the transmitter 100.

[0154] In the second operating mode (phase 2) 206, the multi-antenna transmitter can be configured to change the beamforming pattern used for communication with receiver 150. The receiver can be configured to determine the SINR of the communication link and send feedback indicating a higher (e.g., logic 1) or lower (e.g., logic 0) SINR to the multi-antenna transmitter 100. The multi-antenna transmitter 100 can be configured to further change the beamforming pattern used for communication with receiver 150 based on the feedback received from receiver 150. Subsequently, the multi-antenna transmitter 100 can be configured to iteratively further change the beamforming pattern used for communication with receiver 150 based on the feedback received from receiver.

[0155] The multi-antenna transmitter 100 can be configured to change or further change the beam pattern by altering the direction of the main lobe of the beam pattern. Thus, the multi-antenna transmitter can be configured to change or further change the beam pattern by changing the direction of the main lobe of the beam pattern individually or jointly in the azimuth and elevation directions after each other.

[0156] like Figure 9As indicated, the multi-antenna transmitter 100 can be configured to change or further alter the beam pattern by continuously changing the main lobe of the beam pattern in the same direction until feedback information indicates that the beam pattern should be maintained. For example, the feedback information may include another bit indicating that the transmission strategy is maintained or that the transmission strategy should be updated using prediction or other side information (e.g., a total of two bits of feedback). Alternatively, information may be included regarding how long the transmission strategy should be maintained and fixed.

[0157] Specifically, in the second operating mode (second stage) 206, transmitter 100 can be configured to move its main lobe in the elevation direction. Receiver can be configured to measure 206 SINR and send 1 bit of feedback information to multi-antenna transmitter 100 depending on the measured SINR. For example, if the current SINR (or new SINR) is less than 208 previous SINR (or old SINR), the feedback information may include logic 0, while if the current SINR (or new SINR) is greater than 210 previous SINR (or old SINR), the feedback information may include logic 1. Thus, the multi-antenna transmitter can be configured to continuously move 212 beams until its reception logic 1, i.e., until the current SINR (or new SINR) is greater than the previous SINR (or old SINR). This process can be repeated until 1 bit is received when the multi-antenna transmitter begins to move 214 beams in the azimuth direction. Similarly, receiver can be configured to measure 206 SINR and send 1 bit of feedback information to multi-antenna transmitter 100 depending on the measured SINR. When the multi-antenna transmitter 100 receives 1 bit, it stops moving the beamformer 216.

[0158] Figure 10 A flowchart of a method 300 for transmission is shown. Method 300 includes a step 302 of establishing a communication link with a receiver. Furthermore, method 300 includes a step 304 of changing transmission characteristics used for communicating with the receiver. Additionally, method 300 includes a step 306 of further changing the transmission characteristics used for communicating with the receiver based on feedback information received from the receiver, the feedback information indicating whether the reception quality has changed or the direction of the change in reception quality, or whether the transmission characteristics should be maintained.

[0159] Figure 11 A flowchart of method 320 for receiving is shown. Method 320 includes step 322 of establishing a communication link with the transmitter. Furthermore, method 300 includes step 324 of determining the reception quality of the communication link. Additionally, method 320 includes step 326 of sending feedback information to the transmitter indicating whether the reception quality has changed, the direction of the change, or whether transmission characteristics should be maintained.

[0160] In an embodiment, additional fast 1-bit feedback based on the rate of change of the beamformer at the transmitter is provided and included in the protocol, indicating whether the changed beamformer has a higher received SNR / SINR than the previous beamformer compared to the last or maximum value within a specific window in the past.

[0161] The embodiment provides at least one of the following advantages. First, the received SNR is increased by virtually utilizing a codebook with an infinite size, because any step size for changing the beamformer direction can be selected and is limited only by the hardware at the transmitter. Second, no additional signaling overhead is required in the PDSCH. Third, very short feedback intervals are enabled per TTI (TTI = Transmission Time Interval) due to the low additional 1-bit feedback.

[0162] Although some aspects have been described in the context of the apparatus, it is clear that these aspects also represent a description of the corresponding method, wherein blocks or devices correspond to method steps or features of method steps. Similarly, aspects described in the context of method steps also represent a description of corresponding blocks or items or features of the corresponding apparatus. Some or all of the method steps may be executed by (or using) hardware devices, such as microprocessors, programmable computers, or electronic circuits. In some embodiments, one or more of the most important method steps may be executed by such devices.

[0163] Depending on specific implementation requirements, embodiments of the present invention can be implemented in hardware or software. This implementation can be performed using a digital storage medium on which electrically readable control signals are stored, such as a floppy disk, DVD, Blu-ray, CD, ROM, PROM, EPROM, EEPROM, or flash memory, the electrically readable control signals cooperating (or capable of cooperating) with a programmable computer system to perform the corresponding methods. Therefore, the digital storage medium can be computer-readable.

[0164] Some embodiments of the invention include a data carrier having electrically readable control signals that are capable of cooperating with a programmable computer system to perform one of the methods described herein.

[0165] Typically, embodiments of the present invention can be implemented as a computer program product having program code operable to perform one of the methods when the computer program product is run on a computer. For example, the program code can be stored on a machine-readable medium.

[0166] Other embodiments include a computer program stored on a machine-readable medium for performing one of the methods described herein.

[0167] In other words, embodiments of the method of the present invention are therefore computer programs having program code that, when run on a computer, performs one of the methods described herein.

[0168] Therefore, another embodiment of the method of the present invention is a data carrier (or digital storage medium, or computer-readable medium) including a computer program recorded thereon, the computer program being used to perform one of the methods described herein. The data carrier, digital storage medium, or recording medium is typically tangible and / or non-transitory.

[0169] Therefore, another embodiment of the method of the present invention represents a data stream or signal sequence for performing one of the methods described herein. For example, the data stream or signal sequence may be configured to be transmitted via a data communication connection (e.g., via the Internet).

[0170] Another embodiment includes a processing component, such as a computer or programmable logic device, configured or adapted to perform one of the methods described herein.

[0171] Another embodiment includes a computer having a computer program mounted thereon for performing one of the methods described herein.

[0172] Another embodiment of the invention includes an apparatus or system configured to transmit (e.g., electronically or optically) a computer program for performing one of the methods described herein to a receiver. For example, the receiver may be a computer, mobile device, memory device, etc. For example, the apparatus or system may include a file server for transmitting the computer program to the receiver.

[0173] In some embodiments, a programmable logic device (e.g., a field-programmable gate array) may be used to perform some or all of the functions of the methods described herein. In some embodiments, the field-programmable gate array may cooperate with a microprocessor to perform one of the methods described herein. Generally, the methods are preferably performed by any hardware device.

[0174] The apparatus described herein may be implemented using hardware devices, or using a computer, or using a combination of hardware devices and a computer.

[0175] The apparatus described herein, or any component thereof, may be implemented at least in part in hardware and / or software.

[0176] The methods described herein can be performed using hardware devices, computers, or a combination of hardware devices and computers.

[0177] The methods described herein, or any component of the apparatus described herein, may be performed at least in part by hardware and / or software.

[0178] The embodiments described above are merely illustrative of the principles of the invention. It should be understood that modifications and variations of the arrangements and details described herein will be apparent to those skilled in the art. Therefore, the intent is limited only by the scope of the appended claims and not by the specific details presented in the manner described and explained in the embodiments herein.

Claims

1. A transmitter (100) for communicating with a receiver (150), wherein the transmitter (100) is configured to iteratively change a transmission characteristic for communicating with the receiver (150) depending on feedback information (120) received from the receiver (150), the feedback information (120) indicating whether a received signal power is increased or decreased or whether the transmission characteristic should be kept, wherein the transmission characteristic is a transmission power.

2. The transmitter (100) of claim 1, wherein The feedback information (120) comprises exactly 1 bit.

3. The transmitter (100) of claim 2, wherein The feedback information (120) comprises a first value when a value of a received signal power detected by the receiver (150) is greater than a reference value, and a second value different from the first value when the value of the received signal power detected by the receiver (150) is equal to or less than the reference value; Or wherein the feedback information (120) comprises a first value when a value of a received signal power detected by the receiver (150) is less than a reference value, and a second value different from the first value when the value of the received signal power detected by the receiver (150) is equal to or greater than the reference value; wherein the reference value is a previous value of the received signal power, or a minimum or maximum of a plurality of previous values of the received signal power.

4. The transmitter (100) of claim 1, wherein The transmitter (100) comprises a plurality of antennas, and wherein the transmission characteristic is a beam pattern, wherein the transmitter (100) is configured to change or further change the beam pattern by changing a direction of a main lobe of the beam pattern.

5. The transmitter (100) of claim 4, wherein The transmitter (100) is configured to change the direction of the main lobe in the same direction when the feedback information indicates a higher received signal power, or wherein the transmitter (100) is configured to change the direction of the main lobe in a different direction when the feedback information indicates a lower received signal power.

6. The transmitter (100) of claim 4, wherein The transmitter (100) is configured to change or further change the beam pattern by constantly changing the main lobe of the beam pattern in the same direction until the feedback information indicates that the characteristic of the beam pattern should be kept.

7. A receiver (150) for communicating with a transmitter (100) via a communication link, wherein the receiver (150) is configured to iteratively determine a received signal power of the communication link and to send feedback information to the transmitter (100) indicating whether a received signal power is increased or decreased or whether a transmission characteristic should be kept, wherein the transmission characteristic is a transmission power.

8. The receiver (150) according to claim 7, wherein the feedback information comprises exactly 1 bit.

9. The receiver (150) according to claim 8, wherein the feedback information comprises a first value when a value of a received signal power detected by the receiver (150) is greater than a reference value, and a second value different from the first value when the value of the received signal power detected by the receiver (150) is equal to or less than the reference value; or wherein the feedback information comprises a first value when a value of a received signal power detected by the receiver (150) is less than a reference value, and a second value different from the first value when the value of the received signal power detected by the receiver (150) is equal to or greater than the reference value; wherein the reference value is a previous value of the received signal power, or a minimum or maximum of a plurality of previous values of the received signal power.

10. The receiver (150) of claim 7, wherein, the received signal power is at least one of a signal to interference plus noise ratio, a signal to noise ratio, a channel quality indication, and an effective data throughput.

11. A communication system comprising: a transmitter (100) according to claim 1 ; and a receiver (150) according to claim 7.

12. A method for operating a transmitter, the method comprising: iteratively changing a transmission characteristic used for communication with a receiver (150) in dependence on feedback information (120) received from the receiver (150), the feedback information (120) indicating whether a received signal power is increased or decreased or whether the transmission characteristic should be kept, wherein the transmission characteristic is a transmission power.

13. A method for operating a receiver (150), the method comprising: iteratively determining a received signal power of a communication link with a transmitter (100), and transmitting feedback information (120) to the transmitter (100) indicating whether the received signal power is increased or decreased or whether a transmission characteristic should be kept, wherein the transmission characteristic is a transmission power.

14. A computer program product comprising a computer program which, when executed by a processor, implements the method of claim 12 or 13.

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