Digitally controllable scatterer (DCS) assisted transmit diversity

Abstract

Disclosed is a controller device (4) for Digitally Controllable Scatterer, DCS, assisted transmit diversity. The controller device (4) comprises a processor (41), configured to: determine (803) an encoding function (C) for encoding one or more information symbols (X, X i ) to encoded symbols (χ i , χ j,i ); and determine (804) a frequency mapping (F) for mapping the encoded symbols (χ i , χ j,i ) to frequency resources (f i ) being based on an allocated frequency (f dcs ) of a DCS (24). The controller device (4) further comprises a control communication interface (42), configured to: transmit (805) the encoding function (C) to a transmitter device (1); transmit (807) the frequency mapping (F) to the transmitter device (1) and the receiver device (3); and transmit (808) the allocated frequency (f dcs ) of the DCS (24) to a DCS device (2). This provides new space frequency coding via joint design of the DCS configuration phasors, the transmitter encoding function and the receiver processing, enabling the receiver device (3) to perform diversity combining of the received signal in order to estimate the information symbol without any CSI knowledge requirements at the DCS device (2) and transmitter device (1) and without transmitting data knowledge at the DCS.

Description

[0001]DIGITALLY CONTROLLABLE SCATTERER (DCS) ASSISTED TRANSMIT DIVERSITY TECHNICAL FIELD The present disclosure relates generally to the field of radio communications, more specifically Digitally Controllable Scatterer(DCS) assisted transmit diversity. Particularly, the present disclosure relates to various devices for DCS-assisted transmitdiversity and methods of operating the same. BACKGROUND ART DCS-assisted transmit diversity may be achieved between a transmitting node, a receiving node and a DCS, i.e., a two- dimensional surface of engineered material comprising an array of reflecting elements each having a controllable phase shift. A DCS may also be referred to as a Reconfigurable Intelligent Surface (RIS), an Intelligent Reflecting Surface (IRS), a Large Intelligent Surface (LIS), or a smart repeater. A radio signal originating from the transmitting node may reach the receiving node via a direct link and also via a non-direct link involving an interaction with the DCS. The added spatial dimension by the DCS gives the potential in proposing new types of diversity space based DCS codes. Diversity space based DCS codes proposed in literature are limited in their suitability for practical deployment, as they do not satisfy open loop conditions (i.e., not requiring the transmitting note to have CSI knowledge, and not requiring the DCS to haveCSI or data knowledge) or turn out to be unsuitable for fast time varying scenarios.SUMMARY It is an object to overcome these and other drawbacks of the prior art. The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.According to a first aspect, a controller device is provided for DCS assisted transmit diversity. The controller device comprisesa processor, configured to: determine an encoding function for encoding one or more information symbols to encoded symbols;and determine a frequency mapping for mapping the encoded symbols to frequency resources being based on an allocated frequency of a DCS. The controller device further comprises a control communication interface, configured to: transmit the encoding function to a transmitter device; transmit the frequency mapping to the transmitter device and the receiver device; and transmit the allocated frequency of the DCS to a DCS device. Transmit diversity as used herein may refer to a radio communication involving more than one propagation path between a transmitter and a receiver.Encoding as used herein may refer to a process of turning one or more information symbols into encoded symbols in accordancewith an encoding function. An allocated frequency of a DCS as used herein may refer to a controllable characteristic (i.e., common phasor) of the DCSresulting from a controllable phase shift of each of its reflecting elements.The controller device provides new open loop space based DCS codes by jointly designing transmitter encoding scheme, DCSconfiguration phasors and receiver processing. This results in transmitted and scattered signals that allow the receiver toperform diversity combining of the received signal in order to estimate the information symbol without any CSI knowledgerequirements at the DCS and transmitter and without transmitting data knowledge at the DCS.The new open loop space based DCS codes, in particular Space Frequency based DCS Codes (SFDC), satisfy open loopconditions and require only one-time resource / slot by exploiting the frequency dimension, thus being more suitable for timevarying scenarios than Space Time based DCS Codes (STDC) which require more than one-time resources.In a possible implementation form, the allocated frequency of the DCS may comprise half of a bandwidth allocated to the transmitter device. According to a second aspect, a transmitter device is provided for DCS assisted transmit diversity. The transmitter devicecomprises a control communication interface, configured to: receive an encoding function from a controller device; and receivea frequency mapping from the controller device. The transmitter device further comprises a processor, configured to: encodeone or more information symbols to encoded symbols in accordance with the encoding function; and modulate the encodedsymbols in accordance with the frequency mapping. The transmitter device further comprises a data communication interface,configured to transmit the modulated signal. Modulating as used herein may refer to a process of up-conversion of encoded symbols to frequency resources in accordance with a frequency mapping.In a possible implementation form, the encoded symbols may comprise real and imaginary components of the informationsymbols. In a possible implementation form, the data communication interface may further be configured to transmit a pilot signal to the receiver device.According to a third aspect, a receiver device is provided for DCS assisted transmit diversity. The receiver device comprises acontrol communication interface, configured to receive a frequency mapping from a controller device. The receiver devicefurther comprises a data communication interface, configured to receive a modulated signal comprising a component modulatedby a transmitter device and another component modulated by the transmitter device and a DCS device. The receiver devicefurther comprises a processor, configured to: demodulate signals from the received signal in accordance with the frequencymapping; diversity combine signals from the demodulated signals in accordance with a combining matrix that depends onfrequency responses of a direct link channel and a non-direct link channel via the DCS device, respectively, between thetransmitter device and the receiver device; and decode real and imaginary components of transmitted information symbols from the combined signals. Demodulating as used herein may refer to a process of down-conversion of encoded symbols from frequency resources in accordance with a frequency mapping.Diversity combining as used herein may refer to a process of combining spatially diverse signals in accordance with acombining matrix, such as an equivalent Alamouti channel matrix. Decoding as used herein may refer to a process of turning encoded symbols into one or more information symbols in accordance with a reciprocal encoding function or an equivalent decoding approach.In a possible implementation form, the data communication interface may further be configured to receive a received pilotsignal from the transmitter device via the direct link channel and / or via the non-direct link channel; and the processor mayfurther be configured to estimate frequency responses of the direct link channel and / or the non-direct link channel, respectively,in accordance with the received pilot signal and the pilot signal.In a possible implementation form, for demodulating the signals from the received signal in accordance with the frequencymapping, the processor may further be configured to: demodulate the signals from the received signal by means of Fourieranalysis; and form a complex conjugate of the demodulated signal of a second frequency resource of the frequency mapping.In a possible implementation form, for diversity combining the demodulated signals in accordance with the combining matrix,the processor may further be configured to multiply the demodulated signals with a conjugate transpose of the combiningmatrix. In a possible implementation form, for decoding the real and imaginary components of the transmitted information symbols from the combined signals, the processor may further be configured to: calculate a real component of a first combined signalof the combined signals; and calculate an imaginary component of a second combined signal of the combined signals.In a possible implementation form, for decoding the real and imaginary components of the transmitted information symbols from the combined signals, the processor may further be configured to: calculate a real component of a third combined signalof the combined signals; and calculate an imaginary component of a fourth combined signal of the combined signals.In a possible implementation form, the control communication interface may further be configured to receive a reciprocal encoding function from the controller device. In a possible implementation form, the frequency mapping may comprise one or more of: an indication of a system frequency spacing, an indication of a bandwidth allocated to the transmitter device, an indication of a first frequency resource, and an indication of a second frequency resource, A system frequency spacing as used herein may refer to a consistent frequency spacing between adjacent carriers of a transmission system.According to a fourth aspect, a Digitally Controllable Scatterer, DCS, device is provided for DCS assisted transmit diversity.The DCS device comprises a DCS. The DCS device further comprises a control communication interface, configured to receivean allocated frequency of the DCS from the controller device. The DCS device further comprises a processor, configured toconfigure a phasor vector of the DCS in accordance with one or more of: an elements specific phasor of the DCS, and a common phasor of the DCS in accordance with the allocated frequency of the DCS.A phasor vector as used herein may refer to a mathematical description of an aggregate of the controllable phase shifts of thereflecting elements of the DCS. A common phasor as used herein may refer to a common component (i.e., factor) of the controllable phase shifts of the reflecting elements of the DCS.An elements specific phasor as used herein may refer to the elements-specific components (i.e., factors) of the controllablephase shifts of the reflecting elements of the DCS.According to a fifth aspect, a method is provided of operating a controller device for Digitally Controllable Scatterer, DCS,assisted transmit diversity. The method comprises: determining an encoding function for encoding one or more informationsymbols to encoded symbols; determining a frequency mapping for mapping the encoded symbols to frequency resources beingbased on an allocated frequency of a DCS; transmitting the encoding function to a transmitter device; transmitting the frequency mapping to the transmitter device and a receiver device; and transmitting the allocated frequency of the DCS to a DCS device. In a possible implementation form, the method may be performed by the controller device of the first aspect or any of its implementations. According to a sixth aspect, a method is provided of operating a transmitter device for Digitally Controllable Scatterer, DCS, assisted transmit diversity. The method comprises: receiving an encoding function from a controller device; receiving afrequency mapping from the controller device; encoding one or more information symbols to encoded symbols in accordancewith the encoding function; modulating the encoded symbols in accordance with the frequency mapping; and transmitting themodulated signal.In a possible implementation form, the method may be performed by the transmitter device of the second aspect or any of itsimplementations. According to a seventh aspect, a method is provided of operating a receiver device for Digitally Controllable Scatterer, DCS,assisted transmit diversity. The method comprises: receiving a frequency mapping from a controller device; receiving amodulated signal comprising a component modulated by a transmitter device and another component modulated by thetransmitter device and a DCS device; demodulating signals from the received signal in accordance with the frequency mapping;diversity combining the demodulated signals in accordance with a combining matrix that depends on frequency responses of adirect link channel and a non-direct link channel via the DCS device, respectively, between the transmitter device and the receiver device; and decoding real and imaginary components of transmitted information symbols from the combined signals.In a possible implementation form, the method may be performed by the receiver device of the third aspect or any of itsimplementations. According to an eighth aspect, a computer program is provided, comprising a program code for performing the method of any one of the fifth, sixth or seventh aspect or any of their implementations when executed on a computer. BRIEF DESCRIPTION OF DRAWINGS The above-described aspects and implementations will now be explained with reference to the accompanying drawings, in which the same or similar reference numerals designate the same or similar elements. The drawings are to be regarded as being schematic representations, and elements illustrated in the drawings are not necessarily shown to scale. Rather, the various elements are represented such that their function and general purpose become apparent to those skilled in the art.FIG. 1 schematically illustrates devices in accordance with the present disclosure; andFIG. 2 schematically illustrates methods of operating the devices of FIG. 1 in accordance with the present disclosure.FIG.3 schematically illustrates various possible implementations of a DCS. DETAILED DESCRIPTIONS OF DRAWINGS In the following description, reference is made to the accompanying drawings, which form part of the disclosure, and which show, by way of illustration, specific aspects of embodiments of the invention or specific aspects in which embodiments of the present invention may be used. It is understood that embodiments of the invention may be used in other aspects and comprise structural or logical changes not depicted in the figures. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.For instance, it is understood that a disclosure in connection with a described method may also hold true for a correspondingapparatus or system configured to perform the method and vice versa. For example, if one or a plurality of specific method steps are described, a corresponding device may include one or a plurality of units, e.g. functional units, to perform the described one or plurality of method steps (e.g. one unit performing the one or plurality of steps, or a plurality of units each performing one or more of the plurality of steps), even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, for example, if a specific apparatus is described based on one or a plurality of units, e.g. functional units, a corresponding method may include one step to perform the functionality of the one or plurality of units (e.g. one step performing the functionality of the one or plurality of units, or a plurality of steps each performing the functionality of one or more of the plurality of units), even if such one or plurality of steps are not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary embodiments and / or aspects described herein may be combined with each other, unless specifically noted otherwise. FIG.1 schematically illustrates devices 1, 2, 3, 4 in accordance with the present disclosure, and FIG.2 schematically illustrates an interaction between the devices 1, 2, 3, 4 of FIG. 1, via., the methods 5, 6, 7, 8 of operating said devices 1, 2, 3, 4, in accordance with the present disclosure. The present disclosure considers a communication system that comprises a transmitter device having at least one antenna, a DCS device, and a receiver device having at least one antenna.The DCS device provides an added spatial dimension giving a potential in proposing new types of diversity space codes, spacebased DCS codes, where the added spatial diversity is to be exploited with an additional channel dimension (e.g., time, frequency). Such diversity space based DCS codes should be designed as open loop schemes in order to be practical, and thus should satisfy the following open loop conditions:1) Relies on the Channel State Information (CSI) at the receiving node only: The DCS should not require any CSI knowledgeat the transmitting node or at the DCS node.2) Does not require any data knowledge at the DCS side: The DCS should not require any full / partial knowledge of thetransmitted data by the transmitted nodes for the design of the space based DCS codes. The present disclosure considers how to design open loop diversity schemes that satisfy the aforementioned open loop conditions and exploit the spatial diversity added by the DCS, via a joint design of the DCS phasors, the transmitter encoding function and the receiver processing. The proposed Space Frequency DCS Codes (SFDC) use DCS added spatial diversity and frequency resources where it requires at least:^ a single time resource, thus, it is suitable to time varying scenarios,^ single transmitting and receiving antennas,^ single DCS, and^ two frequency resources (e.g., subcarriers).The proposed SFDC is an open loop scheme that enables diversity combining at the receiver device wherein the DCS configuration design does not require any knowledge of the CSI and of the information symbols to be transmitted. Also, the transmitting encoding function does not require any CSI knowledge.FIG. 1 (far left) and FIG. 2 (top far left) respectively show a transmitter device 1 for DCS-assisted transmit diversity.According to FIG. 2, a method 5 of operating the transmitter device 1 comprises: receiving 505 an encoding function ^ from acontroller device 4; receiving 507 a frequency mapping ℱ from the controller device 4; encoding 510 one or more informationsymbols ^, ^^ to encoded symbols ^^ , ^^,^ in accordance with the encoding function ^ ; modulating 511 the encodedsymbols^^ , ^^,^ in accordance with the frequency mapping ℱ; and transmitting 512 the modulated signal ^(^). In particular,the method 5 may be performed by the transmitter device 1. Where for the single transmitting antenna embodiment, the notation^ refers to the information symbol, and ^^ refers to its encoded version to be transmitted over the ^^^subcarrier, while for the embodiment with two transmitting antennas, the notation ^^refers to the information symbol allocated to the ^^^antenna, and ^^,^refers to its encoded version to be transmitted over the ^^^subcarrier and the ^^^antenna.FIG. 1 (half-left) and FIG. 2 (top half-left) respectively show a DCS device 2 for DCS-assisted transmit diversity.FIG. 1 (half-right) and FIG. 2 (top half-right) respectively show a receiver device 3 for DCS-assisted transmit diversity.According to FIG. 2, a method 7 of operating the receiver device 3 comprises: receiving 707 a frequency mapping ℱ from acontroller device 4; receiving 712 a modulated signal ^(^) comprising a component ^^(^) modulated by a transmitter device1 and another component ^^(^) modulated by the transmitter device 1 and scattered by a DCS device 2; demodulating 713signals ^^ from the received signal ^(^) in accordance with the frequency mapping ℱ ; diversity combining 714 thedemodulated signals ^^ in accordance with a combining matrix ^ that depends on frequency responses^^ , ^^; ^^,^ , ^^,^ , ^^,^ , ^^,^ of a direct link channel and a non-direct link channel via the DCS device 2, respectively, betweenthe transmitter device 1 and the receiver device 3; and decoding 715 real and imaginary components of transmitted informationsymbols ^, ^^ from the combined signals ^. In particular, the method 7 may be performed by the receiver device 3.FIG. 1 (far right) and FIG. 2 (top far right) respectively show a controller device 4 for DCS-assisted transmit diversity.A method 8 of operating the controller device 4 comprises: determining 803 an encoding function ^ for encoding one or moreinformation symbols ^, ^^ to encoded symbols^^ , ^^,^ ; determining 804 a frequency mapping ℱ for mapping the encodedsymbols ^^ , ^^,^ to frequency resources ^^ being based on an allocated frequency ^^^^ of a DCS 24; transmitting 805 theencoding function ^ to a transmitter device 1; transmitting 807 the frequency mapping ℱ to the transmitter device 1 and areceiver device 3; and transmitting 808 the allocated frequency ^^^^ of the DCS 24 to a DCS device 2. In a possibleimplementation form, the method 8 may be performed by the controller device 4 of the first aspect or any of its implementations.According to FIG. 1, the transmitter device 1 comprises a processor 11, a control communication interface 12 and a datacommunication interface 13.According to FIG. 2, the data communication interface 13 of the transmitter device 1 may be configured to transmit 501 a pilotsignal ^^(^) to the receiver device 3.According to FIG. 1, the receiver device 3 comprises a processor 31, a control communication interface 32 and a datacommunication interface 33.According to FIG. 2, the data communication interface 33 of the receiver device 3 may be configured to receive 701 a receivedpilot signal ^^(^) from the transmitter device 1 via a direct link channel and / or via a non-direct link channel via the DCS device2.The processor 31 of the receiver device 3 may be configured to estimate 702 frequency responses ^^ , ^^; ^^,^, ^^,^, ^^,^, ^^,^of the direct link channel and / or the non-direct link channel, respectively, in accordance with the received pilot signal ^^(^)and the pilot signal ^^(^).According to FIG. 1, the controller device 4 comprises a processor 41 and a control communication interface 42.The controller device 4 conducts the joint design of an encoding function ^, a frequency mapping ℱ and a DCS configurationphasor. This joint design leads to the creation of the SFDC at the receiver.According to FIG. 2, the processor 41 of the controller device 4 is configured to determine 803 an encoding function ^ forencoding one or more information symbols ^, ^^ to encoded symbols ^^, ^^,^ .In particular, the encoded symbols comprise real and imaginary components of the information symbols ^, ^^ orany rotated version of these symbols.Note that in the following two particular implementations will be explained in more detail:^ Single Tx implementation: single transmitting antenna, single receiving antenna, single DCS, and two frequency resources,and^ Double Tx implementation: two transmitting antennas, single receiving antenna, single DCS, and two frequency resources.We have two information symbols ^^ and ^^ to be encoded into ^^,^, ^^,^ and^^,^, ^^,^, respectively, where the encodedsymbols of each information symbol are transmitted over a different transmitting antenna: ^^,^ , ^^,^ are transmitted overTx1 and ^^,^ , ^^,^ are transmitted over Tx2. Single Tx implementation:The encoding function ^ for the single transmitting antenna may be designed as follows:^(^): ^ → ^^ (given ∝^=∝^= 1, ∝^= ±1, ∝^= ∓1)denotes taking the real part of the information symbol ^ and ℑ{^} denotes taking the imaginary part of ^ while^ = √−1 is the unit imaginary number.Double Tx implementation:The encoding function ^ for the ^^^ transmitting antenna, where ^ ∈ {1,2}, may be designed as follows:^(^^): ^^ → ^^,^ (given ∝^=∝^= 1, ∝^= ±1, ∝^= ∓1)Where ℜ{^^} denotes taking the real part of the information symbol ^^ and ℑ{^^} denotes taking the imaginary part of ^^while ^ = √−1 is the unit imaginary number.The processor 41 of the controller device 4 is further configured to determine 804 a frequency mapping ℱ for mapping theencoded symbols ^^ , ^^,^ to frequency resources ^^ being based on an allocated frequency ^^^^ of a DCS 24:Single Tx implementation: Double Tx implementation: That is to say, encoded symbol ^^ , ^^,^ is to be sent over a first frequency resource ^^ = ^^Δ^ where Δ^ is a subcarrier spacing,and encoded symbol ^^ , ^^,^ is to be sent over a second frequency resource ^^ = ^^Δ^.The frequency mapping ℱ may be designed such that the frequency resources ^^have similar channel responses: ℎ(^^) ≈ ℎ(^^)(given ^^ − ^^ ≤ ^^^)Where ^^^denotes a coherence bandwidth of the channel. The frequency mapping ℱ may further be designed such that the frequency resources ^^are spaced in accordance with theallocated frequency ^^^^ of the DCS 24:^^ − ^^ = ^^^^In particular, the allocated frequency ^^^^ of the DCS 24 may comprise half of a bandwidth ^^ allocated to the transmitterdevice 1:^^ ^^^^= 2In particular, the frequency mapping ℱ may comprise one or more of: an indication ^^ of the system frequency spacing ^^,an indication ^^ , ^ of the bandwidth ^^ allocated to the transmitter device 1, an indication ^^ , ^^ of a first frequencyresource ^^, and an indication ^^, ^^ of a second frequency resource ^^:^^ = ^^^^^ = ^^^^Where ^ denotes a total number of subcarriers within the considered system, and ^^ stands for a system frequency spacing.According to FIG. 2, the control communication interface 42 of the controller device 4 is configured to transmit 805 theencoding function ^ to the transmitter device 1. Likewise, the control communication interface 12 of the transmitter device 1is configured to receive 505 the encoding function ^ from the controller device 4.The control communication interface 42 of the controller device 4 may further be configured to transmit 806 a reciprocalencoding function ^^^ to the receiver device 3; and the control communication interface 32 of the receiver device 3 may furtherbe configured to receive 706 the reciprocal encoding function ^^^ from the controller device 4.The control communication interface 42 of the controller device 4 is further configured to transmit 807 the frequency mappingℱ to the transmitter device 1 and the receiver device 3. Then, the control communication interface 12 of the transmitter device1 and the control communication interface 32 of the receiver device 3 are respectively configured to receive 507, 707 thefrequency mapping ℱ from the controller device 4.The control communication interface 42 of the controller device 4 is further configured to transmit 808 the allocated frequency^^^^ of the DCS 24 to the DCS device 2.According to FIG. 1, the DCS device 2 comprises a processor 21, a control communication interface 22 and a DCS 24.According to FIG. 2, the control communication interface 22 of the DCS device 2 is configured to receive 607 the allocatedfrequency ^^^^ of the DCS 24 from the controller device 4.The processor 21 of the DCS device 2 is arranged to configure 608 a phasor vector ^(^) ∈ ℂ1×^ of the DCS 24 in accordancewith one or more of: an elements specific phasor ^^^ of the DCS 24, and a common phasor of the DCS 24 in accordancewith the allocated frequency ^^^^ of the DCS 24. The common phasor is designed using the allocated frequency ^^^^: ^^^(^) = ^^^(^) = ^^^^^^^^^ = ^^^^^^, ^^ (given ^^^^= ^=^^)The elements specific phasor ^^^ ∈ ℂ^×^ could be designed independently from the common phasor to achieve differentobjectives, such as maximizing the received signal power at the receiver device 3 or optimizing certain quality metrics.According to FIG. 2, the processor 11 of the transmitter device 1 is further configured to encode 510 one or more informationsymbols ^, ^^ to encoded symbols ^^ , ^^,^ in accordance with the encoding function ^ (see above).The processor 11 of the transmitter device 1 is further configured to modulate 511 the encoded symbols ^^ , ^^,^ in accordancewith the frequency mapping ℱ.The data communication interface 13 of the transmitter device 1 is further configured to transmit 512 the modulated signal^(^). Correspondingly, the data communication interface 33 of the receiver device 3 is configured to receive 712 the modulatedsignal ^(^) comprising a component ^^(^) modulated by the transmitter device 1 and another component ^^(^) modulatedby the transmitter device 1 and the DCS device 2.Single Tx implementation:The transmitter uses the designed frequency mapping ℱ to send its the encoded symbols ^^ , ^^ over the mapped frequencyresources ^^ , ^^ where ^^ is transmitted over and ^^ is transmitted over ^^. Thus, the time domain transmitted signal ^(^) isbased on the encoded symbols as follows:^^^^^^ ^^^^^^ ^(^) = ^^^1+ ^^^2+ ^(^)Where ^(n) represents the transmitted signal of the symbols carried over subcarriers ^ ∉ {^^, ^^}.The received signal ^(^) that contains the transmitted encoded symbols via the direct and non-direct links could be written asfollows: Where ^^(^) denotes the noiseless received signal via the direct link, ^^(^) denotes the noiseless received signal via the non-direct link and ^(^) is the time domain additive noise.Double Tx implementation:The ^^^ transmitting antenna uses the designed frequency mapping ℱ to send its the encoded symbols ^^,^ , ^^,^ over the mappedfrequency resources ^^ , ^^ where ^^,^ is transmitted over and ^^,^ is transmitted over ^^: Where ^^ (n) represents the transmitted signal of the symbols carried over subcarriers ^ ∉ {^^ , ^^} via the ^^^antenna.The received signal ^(^) that contains the transmitted encoded symbols via the direct and non-direct links could be writtenas follows: Where ^^(^) denotes the noiseless received signal via the direct link, ^^(^) denotes the noiseless received signal via the non-direct link and ^(^) is the time domain additive noise.The processor 31 of the receiver device 3 is configured to demodulate 713 signals ^^ from the received signal ^(^) inaccordance with the frequency mapping ℱ: ^^ = ^^^ + ^^^ + ^^Where ^^and ^^represent additive noise at ^^and ^^, respectively.For demodulating 713 the signals ^^ from the received signal ^(^) in accordance with the frequency mapping ℱ, the processor31 may further be configured to demodulate the signals ^^ from the received signal ^(^) by means of Fourier analysis: Single Tx implementation:^^^ and ^^^ correspond to the demodulated version of ^^(^) that extract ^^ and ^^ as follows: Where ^^denotes the Fourier transformation of the direct link channel and is equivalent on frequencies ^^and ^^since ^^−^^ ≤ ^^^.Note that in the direct link:^ ^^ is received at ^^, and^ ^^is received at ^^.^^^ and ^^^ correspond to the demodulated version of ^^(^) that extract ^^ and ^^ as follows: Where ^^denotes the Fourier transformation of the non-direct link channel and is equivalent on frequencies ^^and ^^since^^ − ^^ ≤ ^^^.Note that a frequency swapping occurs in the non-direct link:^ ^^ is received at ^^, and^ ^ is received This desired frequency swapping phenomena in the non-direct link is the result of the joint design of the frequency mapping,the DCS allocated frequency, and the receiver processing.Accordingly, the demodulated signals ^^ may be identified as: ^^ = ^^ ^ℑ^{^} + ^^ ℜ^^{^} + ^^^2^1Double Tx implementation:^^^ and ^^^ correspond to the demodulated version of ^^(^) that extract ^^ and ^^ as follows: ^^^ = ^^,^^2,1 + ^^,^^2,2Where ^^,^denotes the Fourier transformation of the direct link channel between ^^^transmitting antenna and the receiver.This channel is equivalent on frequencies ^^ and ^^ since ^^ − ≤ ^^^.^^^ and ^^^ correspond to the demodulated version of ^^(^) that extract ^^ and ^^ as follows:^^^ = ^^,^^2,1 + ^^,^^2,2 Where ^^,^denotes the Fourier transformation of the non-direct link channel between the ^^^transmitting antenna and thereceiver. This channel is equivalent on frequencies ^^ and ^^ since ^^ − ≤ ^^^.Consequently, the demodulated signals ^^ may be identified as: For demodulating 713 the signals ^^ from the received signal ^(^) in accordance with the frequency mapping ℱ, the processor31 may further be configured to form a complex conjugate of the demodulated signal ^(^) of a second frequency resource ^^of the frequency mapping ℱ: Single Tx implementation: Double Tx implementation: Where ^ is a combining matrix that depends on frequency responses ^^ , ^^; ^^,^ , ^^,^ , ^^,^ , ^^,^ of the direct link channeland the non-direct link channel via the DCS device 2. The combining matrix ^ is also known as equivalent Alamouti channelmatrix.The processor 31 of the receiver device 3 is further configured to diversity combine 714 signals ^^ from the demodulatedsignals ^^ in accordance with the combining matrix ^ that depends on frequency responses ^^ , ^^; ^^,^ , ^^,^ , ^^,^ , ^^,^ of thedirect link channel and the non-direct link channel via the DCS device 2, respectively, between the transmitter device 1 and thereceiver device 3.For diversity combining 714 the demodulated signals ^^ in accordance with the combining matrix ^, the processor 31 mayfurther be configured to (left-)multiply the demodulated signals ^^ with a conjugate transpose of the combining matrix ^:^ = ^^ + ^^ = ^^^ = ^^(^^ + ^)Single Tx implementation: 1 |^|^ + |^ |^^ = ^^ ^0 0|^ |^ + | |^^ ^1 ^2^ + ^^^^^^ ^ 2^ ^^ ^Double Tx implementation: The processor 31 of the receiver device 3 is further configured to decode 715 real and imaginary components of transmittedinformation symbols ^, ^^ from the combined signals ^.For decoding 715 the real and imaginary components of the transmitted information symbols ^, ^^ from the combined signals^, the processor 31 may further be configured to: calculate a real component of a first combined signal ^^ of the combinedsignals ^; and calculate an imaginary component of a second combined signal ^^ of the combined signals ^.The receiver device 3 may decode the transmitted information symbol ^ real and imaginary parts as follows:Single Tx implementation: From the above, note the maximum diversity combining without additional interference where both ^ = and ^^^ℑ{^} have an equivalent channel gain of (|^^|^ + |^^|^).For decoding 715 the real and imaginary components of the transmitted information symbols ^, ^^ from the combined signals^, the processor 31 may further be configured to: calculate a real component of a third combined signal ^^ of the combinedsignals ^; and calculate an imaginary component of a fourth combined signal ^^ of the combined signals ^.Double Tx implementation: Where ^^̅ represents the overall noise component that contains the additive noise ^^^and the additional interference due to the non-diagonal elements of the matrix ^^^. Note from the above the maximum diversity combining where both ^^,^and ^^,^have an equivalent channel gain of ^^^ FIG.3 schematically illustrates various possible implementations of a DCS 24. As depicted, the DCS 24 can be implemented as a single block or as multiple blocks, as plane surfaces or any type of surface, an aggregation of surfaces or a sub-surface of one or more DCSs. In a nutshell, the present disclosure proposes open loop space-frequency based DCS codes via joint design of DCS configurationphasors, transmitter encoding function, and receiver / UE processing. The transmitter encoder function encodes the informationsymbol to be transmitted over multiple frequency resources wherein the DCSs are configured such that their scattered signal results at the receiver in frequency domain symbols that are cyclically shifted over the frequency domain after some signal processing at the receiver. This enables spatial diversity combining at the receiver that decodes the transmitted information symbol. The present disclosure has been described in conjunction with various embodiments as examples as well as implementations. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed matter, from the studies of the drawings, this disclosure and the independent claims. In the claims as well as in the description the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. Asingle element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certainmeasures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation. A computer program may be stored / distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

Claims

CLAIMS1. A controller device (4) for Digitally Controllable Scatterer, DCS, assisted transmit diversity, the controller device (4)comprising: aprocessor (41), configured to:- determine (803) an encoding function for encoding one or more information symbols to encoded symbols; and- determine (804) a frequency mapping for mapping the encoded symbols to frequency resources being based onan allocated frequency of a DCS (24); anda control communication interface (42), configured to:- transmit (805) the encoding function to a transmitter device (1);- transmit (807) the frequency mapping to the transmitter device (1) and the receiver device (3); and- transmit (808) the allocated frequency of the DCS (24) to a DCS device (2).

2. The controller device (4) of claim 1,wherein the allocated frequency of the DCS (24) comprises half of a bandwidth allocated to the transmitter device (1).

3. A transmitter device (1) for Digitally Controllable Scatterer, DCS, assisted transmit diversity, the transmitter device (1)comprising: acontrol communication interface (12), configured to:- receive (505) an encoding function from a controller device (4); and- receive (507) a frequency mapping from the controller device (4);a processor (11), configured to:- encode (510) one or more information symbols to encoded symbols in accordance with the encoding function;and -modulate (511) the encoded symbols in accordance with the frequency mapping; anda data communication interface (13), configured to- transmit (512) the modulated signal.

4. The transmitter device (1) of claim 3 or the controller device (4) of claim 1 or claim 2,wherein the encoded symbols comprise real and imaginary components of the information symbols.

5. The transmitter device (1) of claim 3 or claim 4,wherein the data communication interface (13) is further configured to:- transmit (501) a pilot signal to the receiver device (3).

6. A receiver device (3) for Digitally Controllable Scatterer, DCS, assisted transmit diversity, the receiver device (3) comprisinga control communication interface (32), configured to:- receive (707) a frequency mapping from a controller device (4);a data communication interface (33), configured to:- receive (712) a modulated signal comprising a component modulated by a transmitter device (1) and anothercomponent modulated by the transmitter device (1) and a DCS device (2); anda processor (31), configured to:- demodulate (713) signals from the received signal in accordance with the frequency mapping;- diversity combine (714) the demodulated signals in accordance with a combining matrix that depends onfrequency responses of a direct link channel and a non-direct link channel via the DCS device (2), respectively,between the transmitter device (1) and the receiver device (3); and- decode (715) real and imaginary components of transmitted information symbols from the combined signals.

7. The receiver device (3) of claim 6,wherein the data communication interface (33) is further configured to:- receive (701) a received pilot signal from the transmitter device (1) via the direct link channel and / or via thenon-direct link channel; and wherein the processor (31) is further configured to:- estimate (702) frequency responses of the direct link channel and / or the non-direct link channel, respectively,in accordance with the received pilot signal and the pilot signal.

8. The receiver device (3) of claim 6 or claim 7,wherein for demodulating (713) the signals from the received signal in accordance with the frequency mapping, theprocessor (31) is further configured to:- demodulate the signals from the received signal by means of Fourier analysis; and- form a complex conjugate of the demodulated signal of a second frequency resource of the frequency mapping.

9. The receiver device (3) of any one of the claims 6 – 8,wherein for diversity combining (714) the demodulated signals in accordance with the combining matrix, the processor(31) is further configured to:- multiply the demodulated signals with a conjugate transpose of the combining matrix.

10. The receiver device (3) of any one of the claims 6 – 9,wherein for decoding (715) the real and imaginary components of the transmitted information symbols from thecombined signals, the processor (31) is further configured to:- calculate a real component of a first combined signal of the combined signals; and- calculate an imaginary component of a second combined signal of the combined signals.

11. The receiver device (3) of claim 10,wherein for decoding (715) the real and imaginary components of the transmitted information symbols from thecombined signals, the processor (31) is further configured to:- calculate a real component of a third combined signal of the combined signals; and- calculate an imaginary component of a fourth combined signal of the combined signals.

12. The receiver device (3) of any one of the claims 6 – 11,the control communication interface (32) further configured to:- receive (706) a reciprocal encoding function from the controller device (4).

13. The controller device (4) of claim 1 or claim 2 or the transmitter device (1) of any one of the claims 3 – 5 or the receiverdevice (3) of any one of the claims 6 – 12,wherein the frequency mapping comprises one or more of: -an indication of a system frequency spacing,- an indication of a bandwidth allocated to the transmitter device (1),- an indication of a first frequency resource, and- an indication of a second frequency resource,14. A Digitally Controllable Scatterer, DCS, device (2) for DCS assisted transmit diversity, the DCS device (2) comprisinga DCS (24);a control communication interface (22), configured to:- receive (607) an allocated frequency of the DCS (24) from the controller device (4); anda processor (21), configured to:- configure (608) a phasor vector of the DCS (24) in accordance with one or more of:- an elements-specific phasor of the DCS (24), and- a common phasor of the DCS (24) in accordance with the allocated frequency of the DCS (24).

15. A method (8) of operating a controller device (4) for Digitally Controllable Scatterer, DCS, assisted transmit diversity, themethod (8) comprising:- determining (803) an encoding function for encoding one or more information symbols to encoded symbols;- determining (804) a frequency mapping for mapping the encoded symbols to frequency resources being basedon an allocated frequency of a DCS (24);- transmitting (805) the encoding function to a transmitter device (1);- transmitting (807) the frequency mapping to the transmitter device (1) and a receiver device (3); and- transmitting (808) the allocated frequency of the DCS (24) to a DCS device (2).

16. The method of claim 15, being performed by the controller device (4) of any one of the claims 1 – 2.

17. A method (5) of operating a transmitter device (1) for Digitally Controllable Scatterer, DCS, assisted transmit diversity, themethod (5) comprising:- receiving (505) an encoding function from a controller device (4);- receiving (507) a frequency mapping from the controller device (4);- encoding (510) one or more information symbols to encoded symbols in accordance with the encoding function;- modulating (511) the encoded symbols in accordance with the frequency mapping; and- transmitting (512) the modulated signal.

18. The method (5) of claim 17,being performed by the transmitter device (1) of any one of the claims 3 – 5.

19. A method (7) of operating a receiver device (3) for Digitally Controllable Scatterer, DCS, assisted transmit diversity, themethod (7) comprising:- receiving (707) a frequency mapping from a controller device (4);- receiving (712) a modulated signal comprising a component modulated by a transmitter device (1) and anothercomponent modulated by the transmitter device (1) and a DCS device (2);- demodulating (713) signals from the received signal in accordance with the frequency mapping;- diversity combining (714) the demodulated signals in accordance with a combining matrix that depends onfrequency responses of a direct link channel and a non-direct link channel via the DCS device (2), respectively,between the transmitter device (1) and the receiver device (3); and- decoding (715) real and imaginary components of transmitted information symbols from the combined signals.

20. The method (7) of claim 19,being performed by the receiver device (3) of any one of the claims 6 – 14.

21. A computer program, comprising: aprogram code for performing the method (5, 7, 8) of any one of the claims 15 – 20 when executed on a computer.

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