# US 2019/0173652 A1 · Transmission concept using multi-user superposition coding

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- Number: US 2019/0173652 A1
- Document ID: US20190173652A1
- Status: Published application
- Kind: A1
- Application number: 16/271,741
- Filed: 2019-02-08
- Published: 2019-06-06
- Earliest claimed: 2016-08-11
- Assignees: Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung e.V.
- Applicants: Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung e.V.
- Inventors: Thomas FEHRENBACH; Baris GOEKTEPE; Cornelius HELLGE; Johannes DOMMEL; Lars THIELE
- Web page: https://patentgrep.com/patent/US20190173652A1

## CPC

- H04L 5/0073: {Allocation arrangements that take into account other cell interferences}
- H04L 5/0037: {Inter-user or inter-terminal allocation}
- H04L 25/0204: {of multiple channels}
- H04L 27/0014: {Carrier regulation (of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657)}
- H04L 27/2621: {Reduction thereof using phase offsets between subcarriers}
- H04L 27/2662: {Symbol synchronisation}
- H04L 27/3488: {Multiresolution systems}
- H04L 27/367: {using predistortion}
- H04L 5/0051: {of dedicated pilots, i.e. pilots destined for a single user or terminal}
- H04L 27/3411: {reducing the peak to average power ratio or the mean power of the constellation; Arrangements for increasing the shape gain of a signal set}
- H04L 27/3455: {in order to facilitate carrier recovery at the receiver end, e.g. by transmitting a pilot or by using additional signal points to allow the detection of rotations}
- H04L 2027/002: {using feedback from a remote receiver}
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

The transmission of data signals transmitted by a plurality of transmitters may be rendered more efficient by combining multi-user superposition coding with appropriate phase shift estimation at the receiver so that phase shift compensation at the transmitter's side may lead to a superposition of the data signals which may be demapped correctly so as to obtain information data per data signal. Owing to the combination, the concept is applicable to typical uplink situations or downlink situations of separate contributing BSs: contrary to the simple downlink situation where the data signals stem from one BS and are superimposed in one domain, namely the base station's domain, the data signals to be superimposed stem from separate transmitters, such as user entities or mobile terminals in the typical uplink situation, or different base stations in the downlink situation.

## Claims

### Claim 1

A receiver for receiving data signals from a plurality of transmitters using multi-user superposition coding, the receiver configured to
estimate a phase shift between channels via which the receiver receives the data signals to acquire a phase shift information between the channels;
send a phase shift compensation signal to at least one of the plurality of transmitters, the phase shift compensation signal depending on the phase shift information; and
demap the data signals by performing demapping on a superposition of the data signals to acquire information data per data signal.

### Claim 2 (depends on 1)

The receiver according to claim 1, wherein the receiver is configured to send the phase shift compensation signal such that the phase shift compensation signal instructs the at least one of the plurality of transmitters to reduce the phase shift between the channels.

### Claim 3 (depends on 2)

The receiver according to claim 2, wherein the receiver is further configured to
estimate a power ratio between the channels via which the receiver receives the data signals to acquire an power ratio information;
send a power ratio compensation signal to at least one of the plurality of transmitters, the power ratio compensation signal depending on the power ratio information,
the power ratio compensation signal depending on the power ratio information and the phase shift compensation signal depending on the phase shift information such that
the phase shift compensation signal reduces a phase shift between the channels; and
the power ratio compensation signal reduces a deviation of the power ratio between the channels from a target ratio.

### Claim 4 (depends on 3)

The receiver according to claim 3, wherein the number of data signals and transmitters is two, respectively, and the target ratio is outside interval [0.9, 1.1] and inside interval [0.1, 10].

### Claim 5 (depends on 3)

The receiver according to claim 3, wherein the data signals are N>1 data signals, the target ratio is a1:a2: . . . :aN from a first to Nth data signal, with a1,a2<a3,a4< . . . <aN, each data signal being separately BPSK modulated with the (2n+1)th data signal's BPSK constellation being rotated relative to the (2(n+1))th data signal's data signal's BPSK constellation, with −1<n<N/2, wherein the receiver is configured to use, for demapping the superposition, a composed constellation resulting from recursively copying the BPSK constellations of the Nth to first data signals one upon the other sequentially.

### Claim 6 (depends on 1)

The receiver according to claim 1, wherein the data signals are modulated separately according to respective modulation schemes and the receiver is configured to use, for demapping the superposition, a composed constellation resulting from copying a first constellation of a modulation scheme of a first data signal at constellation points of a second constellation of a modulation scheme of a second data signal.

### Claim 7 (depends on 1)

The receiver according to claim 1, wherein the receiver is configured to receive the data signals via spectrally collocated subcarriers of OFDM signals from the plurality of transmitters, wherein resource blocks of first OFDM signals from a first transmitter are subdivided into K sub-bands corresponding to physical resource blocks of second OFDM signals sent from a second transmitter.

### Claim 8 (depends on 7)

The receiver according to claim 7, wherein the receiver is configured to receive the first and second data signals using multi-user superposition, wherein the receiver is configured to send the phase shift compensation signal to the first transmitter so that the phase shift compensation signal comprises a phase shift value per spectral subband into which physical resource blocks of the first OFDM signals are subdivided.

### Claim 9 (depends on 1)

The receiver according to claim 1, wherein the receiver is configured to send to the first transmitter a blanking scheduling signal instructing the first transmitter as to when to blank OFDM transmission in order not to interfere with at least a subset of second channel estimation reference signals sent by the second transmitter for channel estimation purposes, wherein the receiver is configured to perform channel estimation on the basis of second channel estimation reference signals sent by the second transmitter.

### Claim 10 (depends on 9)

The receiver according to claim 9, wherein the receiver is configured to use the subset of second channel estimation reference signals as phase shift estimation reference signal.

### Claim 11 (depends on 9)

The receiver according to claim 9, wherein the receiver is configured to send the blanking scheduling signal via a downlink control information message and/or via a radio resource control message.

### Claim 12 (depends on 1)

The receiver according to claim 1, wherein the receiver is configured to perform the phase shift estimation by receiving a phase shift estimation reference signal from the at least one of the plurality of transmitters at an end of active phases of a Physical Random Access Channel so that random access PRACH signals do not interfer with the phase shift estimation reference signal.

### Claim 13 (depends on 1)

The receiver according to claim 1, wherein the receiver is configured to send to the at least one of the plurality of transmitters a reference-signal scheduling signal instructing the at least one of plurality of transmitters when to send, and/or on which spectral band to send, a phase shift estimation reference signal to the receiver, wherein the receiver is configured to perform the phase shift estimation on the basis of the phase shift estimation reference signal.

### Claim 14 (depends on 13)

The receiver according to claim 13, wherein the receiver is configured to indicate within the reference-signal scheduling signal the phase shift estimation reference signal out of a number of possible phase shift estimation reference signals.

### Claim 15 (depends on 13)

The receiver according to claim 13, wherein the receiver is configured to send the reference signal scheduling signal via a downlink control information message and/or via a radio resource control message.

### Claim 16 (depends on 1)

The receiver according to claim 1, wherein the receiver is configured to send the phase shift compensation signal via a downlink control information message and/or via a radio resource control message.

### Claim 17 (depends on 1)

The receiver according to claim 1, wherein the receiver is configured to send the phase shift compensation signal within messages of a first type and messages of a second type, wherein the messages of the first type are sent less frequently compared to the messages of the second type, and the phase shift compensation signal within the messages of the first type allows for signaling phase offsets not representable by the phase shift compensation signal within the messages of the second type.

### Claim 18 (depends on 1)

The receiver according to claim 1, wherein the receiver is configured to send the phase shift compensation signal within messages comprising an indicator field and a phase shift field, wherein a value within the indicator field changes a mapping between a value within the phase shift field and a phase shift value to be used for phase shift compensation.

### Claim 19 (depends on 1)

The receiver according to claim 1, wherein the receiver is configured to send the phase shift compensation signal in a manner indicating a phase shift to be taken into account next absolutely or relatively to a current phase shift.

### Claim 20 (depends on 1)

The receiver according to claim 1, wherein the receiver is configured to predict the phase shift on the basis of weighting past phase shifts using a prediction algorithm determined by weights and send an update of the weights as phase shift compensation signal.

### Claim 21 (depends on 1)

The receiver according to claim 1, wherein the receiver is configured to train a model to follow the phase shift and send information on the model trained as phase shift compensation signal.

### Claim 22 (depends on 1)

The receiver according to claim 1, wherein the receiver is a base station and the data signals are transmitted by the plurality of transmitters in uplink direction to the receiver, or the receiver is a mobile terminal and the data signals are transmitted by the plurality of transmitters in downlink direction to the receiver, with the transmitters being separate base stations.

### Claim 23 (depends on 1)

The receiver according to claim 1, wherein the receiver is a base station of, and the plurality of transmitters are mobile terminals of, an OFDM/SC-FDM or an OFDMA/SC-FDMA wireless communication system, wherein the data signals are received on frequency-overlapping subcarriers of temporally overlapping OFDM symbols provided by the plurality of transmitters in uplink direction.

### Claim 24

A transmitter for transmitting a data signal with superposition with a further data signal of a further transmitter at a receiver seeking to receive at least the further data signal using multi-user superposition coding, the transmitter configured to
send a phase shift estimation reference signal to the receiver;
receive a phase shift compensation signal responsive to the phase shift estimation reference signal; and
map data using a constellation in a manner phase shift compensated according to the phase shift compensation signal to acquire the data signal.

### Claim 25 (depends on 24)

The transmitter according to claim 24, wherein the transmitter is further configured to
receive a power ratio compensation signal from the receiver or a recipient of the data signal,
set a power, at which the data signal is transmitted, depending on the power ratio compensation signal.

### Claim 26 (depends on 24)

The transmitter according to claim 24, wherein the transmitter is configured to transmit the data signal via a subcarrier of an OFDM signal with the further data signal being transmitted via a spectrally collocated subcarrier of a second OFDM signal, wherein the first OFDM signal is shorter and has a lower spectral sub-carrier density than compared to a second OFDM signal.

### Claim 27 (depends on 26)

The transmitter according to claim 26, wherein the transmitter is configured to map data using a respective constellation in a manner phase shift compensated according to the phase shift compensation signal on a band of spectrally adjacent subcarriers of the first OFDM signal so as to lead to a superposition with corresponding collocated subcarriers of the second OFDM signal, wherein the transmitter is configured to read from the phase shift compensation signal a phase shift value per spectral subband into which physical resource blocks of the carrier to which the first OFDM signal belongs, is further subdivided by physical resource blocks of the carrier to which the second OFDM signal belongs.

### Claim 28 (depends on 24)

The transmitter according to claim 24, configured to, responsive to a blanking scheduling signal from the receiver or the recipient of the data signal, as to when to blank OFDM transmission in order not to interfere with at least a subset of second channel estimation reference signals sent by the further transmitter for channel estimation purposes.

### Claim 29 (depends on 28)

The transmitter according to claim 28, configured to receive the blanking scheduling signal via a downlink control information message and/or via a radio resource control message.

### Claim 30 (depends on 24)

The transmitter according to claim 24, configured to send the phase shift estimation signal at an end of active phases of a Physical Random Access Channel.

### Claim 31 (depends on 24)

The transmitter according to claim 24, wherein the transmitter is further configured to
receive a reference-signal scheduling signal from the receiver or the recipient of the data signal; and
send a phase shift estimation reference signal to the receiver at a time scheduled depending on, and/or at a spectral band depending on, the reference-signal scheduling signal.

### Claim 32 (depends on 31)

The transmitter according to claim 31, wherein the transmitter is configured to construct the phase shift estimation reference signal depending on the reference-signal scheduling signal.

### Claim 33 (depends on 31)

The transmitter according to claim 31, wherein the transmitter is configured to receive the reference-signal scheduling signal via a downlink control information message and/or via a radio resource control message.

### Claim 34 (depends on 24)

The transmitter according to claim 24, wherein the transmitter is configured to receive the phase shift compensation signal via a downlink control information message and/or via a radio resource control message.

### Claim 35 (depends on 24)

The transmitter according to claim 24, wherein the transmitter is configured to receive the phase shift compensation signal within messages of a first type and messages of a second type, wherein the messages of the first type are received less frequently compared to the messages of the second type, and the transmitter is configured to interpret the phase shift compensation signal within the messages of the first type as signaling phase offsets not representable by the phase shift compensation signal within the messages of the second type.

### Claim 36 (depends on 24)

The transmitter according to claim 24, wherein the transmitter is configured to receive the phase shift compensation signal within messages comprising an indicator field and a phase shift field, and to change, depending on a value within the indicator field, a mapping between a value within the phase shift field and a phase shift value used for the phase shift compensated mapping of the data.

### Claim 37 (depends on 24)

The transmitter according to claim 24, wherein the transmitter is configured to rotate the constellation depending on the phase shift compensation signal relative to a predetermined fixed rotational state or relative to a current rotational state.

### Claim 38 (depends on 24)

The transmitter according to claim 24, wherein the transmitter is configured to predict a phase shift used in the mapping on the basis of weighting past phase shifts using a prediction algorithm determined by weights and update of the weights according to the phase shift compensation signal.

### Claim 39 (depends on 24)

The transmitter according to claim 24, wherein the transmitter is configured to receive information on a model via the phase shift compensation signal and use the model to follow a phase shift used in the mapping.

### Claim 40 (depends on 24)

The transmitter according to claim 24, wherein the receiver is a base station and the data signal is transmitted in uplink direction to the receiver, or the receiver is a mobile terminal and the data signal is transmitted in downlink direction to the receiver, with the transmitter and the further transmitter being separate base stations.

### Claim 41 (depends on 24)

The transmitter according to claim 24, wherein the receiver is a base station of, and the transmitter is a mobile terminal of, an OFDM/SC-FDM or an OFDMA/SC-FDMA wireless communication system, wherein the data signal is transmitted on subcarriers of a OFDM symbol.

### Claim 42

A receiver for receiving a wanted data signal from a served transmitter, the receiver configured to
estimate a phase shift between channels via which the receiver receives the wanted data signal and a interfering data signal sent from a transmitter served by a further receiver in a manner superpositioned with the wanted data signal to acquire a phase shift information between the channels;
send a phase shift compensation signal to the further base station so as to be forwarded to the further transmitter, the phase shift compensation signal depending on the phase shift information; and
demap the wanted data signal by performing demapping on a superposition of the wanted and interfering data signals using multi-user superposition decoding to acquire an information data for the wanted data signal.

### Claim 43

A method for receiving data signals from a plurality of transmitters using multi-user superposition coding, the method comprising
estimate a phase shift between channels via which the receiver receives the data signals to acquire a phase shift information between the channels;
send a phase shift compensation signal to at least one of the plurality of transmitters, the phase shift compensation signal depending on the phase shift information; and
demap the data signals by performing demapping on a superposition of the data signals to acquire information data per data signal.

### Claim 44

A method for transmitting a data signal with superposition with a further data signal of a further transmitter at a receiver seeking to receive at least the further data signal using multi-user superposition coding, the method comprising
sending a phase shift estimation reference signal to the receiver;
receiving a phase shift compensation signal responsive to the phase shift estimation reference signal; and
mapping data using a constellation in a manner phase shift compensated according to the phase shift compensation signal to acquire the data signal.

### Claim 45

A method for receiving a wanted data signal from a served transmitter, the method comprising
estimate a phase shift between channels via which the receiver receives the wanted data signal and a interfering data signal sent from a transmitter served by a further receiver in a manner superpositioned with the wanted data signal to acquire a phase shift information between the channels;
send a phase shift compensation signal to the further base station so as to be forwarded to the further transmitter, the phase shift compensation signal depending on the phase shift information; and
demap the wanted data signal by performing demapping on a superposition of the wanted and interfering data signals using multi-user superposition decoding to acquire an information data for the wanted data signal.

### Claim 46

A user entity for receiving a wanted data signal from a base station, the user entity configured to
estimate a phase shift between channels via which the user entity receives the wanted data signal and an interfering data signal sent from a further user entity served by a further base station in a manner superpositioned with the wanted data signal to acquire a phase shift information between the channels;
send a phase shift compensation signal to the base station so as to be forwarded to the further base station, the phase shift compensation signal depending on the phase shift information; and
demap the wanted data signal by performing demapping on a superposition of the wanted and interfering data signals using multi-user superposition decoding to acquire an information data for the wanted data signal.

### Claim 47

A method for receiving a wanted data signal from a base station, the method comprising
estimating a phase shift between channels via which the user entity receives the wanted data signal and an interfering data signal sent from a further user entity served by a further base station in a manner superpositioned with the wanted data signal to acquire a phase shift information between the channels;
sending a phase shift compensation signal to the base station so as to be forwarded to the further base station, the phase shift compensation signal depending on the phase shift information; and
demapping the wanted data signal by performing demapping on a superposition of the wanted and interfering data signals using multi-user superposition decoding to acquire an information data for the wanted data signal.

### Claim 48

A non-transitory digital storage medium having a computer program stored thereon to perform the method for receiving data signals from a plurality of transmitters using multi-user superposition coding, the method comprising
estimate a phase shift between channels via which the receiver receives the data signals to acquire a phase shift information between the channels;
send a phase shift compensation signal to at least one of the plurality of transmitters, the phase shift compensation signal depending on the phase shift information; and
demap the data signals by performing demapping on a superposition of the data signals to acquire information data per data signal,
when said computer program is run by a computer.

### Claim 49

A non-transitory digital storage medium having a computer program stored thereon to perform the method for transmitting a data signal with superposition with a further data signal of a further transmitter at a receiver seeking to receive at least the further data signal using multi-user superposition coding, the method comprising
sending a phase shift estimation reference signal to the receiver;
receiving a phase shift compensation signal responsive to the phase shift estimation reference signal; and
mapping data using a constellation in a manner phase shift compensated according to the phase shift compensation signal to acquire the data signal,
when said computer program is run by a computer.