Doppler codebook-based precoding and CSI reporting for wireless communications systems
A communication device providing CSI feedback in a wireless communication system includes a transceiver to receive downlink reference signals and downlink signals including a reference signal configuration. A processor estimates an explicit CSI in the frequency domain. The processor selects a Doppler-delay-beam precoder matrix for a composite Doppler-delay-beam three-stage precoder, which is based on one or more codebooks including one or more transmit-side spatial beam components, one or more delay components, and one or more Doppler-frequency components, The processor calculates a CQI and/or a PMI and/or a rank indicator, RI, using the explicit CSI and the composite Doppler-delay-beam three-stage precoder, and reports the CSI feedback including the CQI, and/or the PMI and/or the RI. The one or more delay and/or Doppler-frequency components are defined by one or more sub-matrices of a DFT matrix or an oversampled DFT matrix.
1. A communication device for providing a channel state information, CSI, feedback in a wireless communication system,
wherein the communication device receives a reference signal resource configuration including a parameter, the parameter indicating a time-domain-repetition of downlink reference signals,
wherein the communication device determines the CSI feedback based on the repeated downlink reference signals and reports the determined CSI feedback,
wherein the communication device determines the CSI feedback by
selecting, based on a performance metric, a Doppler-delay-beam precoder matrix, W, for a composite Doppler-delay-beam three-stage precoder,
the CSI feedback including a precoder matrix indicator, PMI, and a rank indicator, RI,
wherein the Doppler-delay-beam three-stage precoder is based on
a first codebook, Ω 1 , for one or more spatial beam components of the composite Doppler-delay-beam three-stage precoder,
a second codebook, Ω 2 , for one or more delay components of the composite Doppler-delay-beam three-stage precoder, and
a third codebook, Ω 3 , for one or more Doppler-frequency components of the composite Doppler-delay-beam three-stage precoder,
wherein the communication device is configured by the transmitter or another network entity with a first parameter indicating a subset of columns of a DFT or oversampled DFT matrix forming the second codebook, Ω 2 , and/or with a second parameter indicating a subset of columns of a DFT or oversampled DFT matrix forming the third codebook, Ω 3 , and
wherein the communication device selects from the second codebook, Ω 2 , and/or from the third codebook, Ω 3 , the one or more delay components according to the first parameter and/or the one or more Doppler-frequency components according to the second parameter.
2. The communication device of claim 1 , wherein the Doppler-delay-beam three-stage precoder is further based on
a set of combination coefficients for complex scaling/combining one or more of the vectors selected from the first, second and third codebook, and
wherein the entries of the second codebook, Ω 2 , are given by a S×S DFT-matrix or a S×SO 2 oversampled DFT matrix, where S denotes the number of subbands, O 2 ∈{1, 2, 3 . . . } denotes the oversampling factor and/or
wherein the entries of the third codebook matrix, Ω 3 , are given by a T×T DFT-matrix or a T×TO 3 oversampled DFT matrix, where T refers to a number of time instances during the observation time, and O 3 ∈{1, 2, 3 . . . } denotes the oversampling factor.
3. The communication device of claim 1 , wherein the precoder matrix, W (l) for the p-th polarization and the l-th layer is composed of:
U (l) beamforming vectors b u (l) selected from the first codebook,
D u (l) delay vectors d p,u,d (l) selected from the second codebook for the u-th beam,
F d,u (l) Doppler-frequency vectors f p,u,d,v (l) selected from the third codebook for u-th beam and d-th delay, and
a set of combination coefficients γ p,u,d,v (l) for complex scaling/combining the vectors selected from the first, second and third codebook.
4. The communication device of claim 1 , wherein the Doppler-delay-beam precoder matrix, W, of the l-th transmission layer and p-th polarization is represented by
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where
U (l) is the number of beams per polarization for the l-th layer,
D u (l) is the number of delays for the l-th layer and u-th beam,
F d,u (l) is the number of Doppler-frequency components for the l-th layer, u-th beam and d-th delay,
f p,u,d,v (l) is the v-th Doppler-frequency vector of size T×1 associated with the l-th layer, d-th delay, u-th spatial beam, and the p-th (p=1, 2) polarization of the precoder;
d p,u,d (l) is the d-th delay vector of size S× 1 associated with the l-th layer, u-th spatial beam and the p-th polarization of the precoder;
b u (l) is the u-th spatial beam associated with the l-th layer;
γ p,u,d,v (l) is the Doppler-delay complex combination coefficient associated with the l-th layer, u-th spatial beam, d-th delay, v-th Doppler-frequency and the p-th polarization of the precoder, and
p (l) is a scalar normalization factor to ensure a certain average total transmission power.
5. The communication device of claim 4 , wherein, for quantizing the complex Doppler-delay coefficients γ p,u,d,v (l) with a codebook approach, each coefficient is represented by,
γ p,u,d,v (l) ={circumflex over (γ)} p,u,d,v (l) ϕ p,u,d,v′ (l)
where
{circumflex over (γ)} p,u,d,v (l) is a polarization-, beam-, delay- and Doppler-frequency-dependent amplitude coefficient which is quantized with N bits; and
ϕ p,u,d,v (l) represents a phase which is represented by a BPSK, or QPSK, or 8PSK, or any other higher-order PSK constellation, or
wherein each coefficient is represented by its real and imaginary part as
γ p,u,d,v (l) =Re{{circumflex over (γ)} p,u,d,v (l) }+j ·Imag{{circumflex over (γ)} p,u,d,v (l) },
where Re{{circumflex over (γ)} p,u,d,v (l) } and Imag{{circumflex over (γ)} p,u,d,v (l) } are quantized each with N bits.
6. The communication device of claim 1 , wherein the communication device is configured with a CSI-RS reporting configuration via a higher layer for reporting the RI and/or the PMI for a beam-formed CSI-RS, the vectors in the first codebook matrix represented by N 1 N 2 -length column vectors, where the m-th vector (m=1, . . . , N 1 N 2 ) comprises a single 1 at the m-th position and zeros elsewhere.
7. A transmitter in a wireless communication system the transmitter comprising:
an antenna array comprising a plurality of antennas for a wireless communication with one or more communication devices of the wireless communication system for providing a channel state information, CSI, feedback to the transmitter; and
a precoder connected to the antenna array, the precoder to apply a set of beamforming weights to one or more antennas of the antenna array to form, by the antenna array, one or more transmit beams or one or more receive beams,
a transceiver configured to
transmit, to the communication device, downlink reference signals, CSI-RS, according to a CSI-RS configuration comprising a number of CSI-RS antenna ports and a parameter indicating a time-domain-repetition of the downlink reference signals and downlink signals comprising the CSI-RS configuration; and
receive uplink signals comprising one or more CSI reports from the communication device; and
a processor configured to:
extract at least a precoder matrix identifier, PMI and a rank indicator, RI, from the one or more CSI reports; and
construct a Doppler-delay-beam precoder matrix applied on the antenna ports using a first component and a second component of the PMI, and determine the beamforming weights responsive to the constructed precoder matrix.
8. A wireless communication network, comprising:
at least one communication device, wherein
the communication device receives a reference signal resource configuration including a parameter, the parameter indicating a time-domain-repetition of downlink reference signals,
the communication device determines the CSI feedback based on the repeated downlink reference signals and reports the determined CSI feedback,
wherein the communication device determines the CSI feedback by selecting, based on a performance metric, a Doppler-delay-beam precoder matrix, W, for a composite Doppler-delay-beam three-stage precoder, the CSI feedback including a precoder matrix indicator, PMI, and a rank indicator, RI,
wherein the Doppler-delay-beam three-stage precoder is based on
a first codebook, Ω 1 , for one or more spatial beam components of the composite Doppler-delay-beam three-stage precoder,
a second codebook, Ω 2 , for one or more delay components of the composite Doppler-delay-beam three-stage precoder, and
a third codebook, Ω 3 , for one or more Doppler-frequency components of the composite Doppler-delay-beam three-stage precoder,
wherein the communication device is configured by the transmitter or another network entity with a first parameter indicating a subset of columns of a DFT or oversampled DFT matrix forming the second codebook, Ω 2 , and/or with a second parameter indicating a subset of columns of a DFT or oversampled DFT matrix forming the third codebook, Ω 3 , and
wherein the communication device selects from the second codebook, Ω 2 , and/or from the third codebook, Ω 3 , the one or more delay components according to the first parameter and/or the one or more Doppler-frequency components according to the second parameter, and
at least one base station or transmitter, comprising:
an antenna array comprising a plurality of antennas for a wireless communication with one or more communication devices of claim 1 for providing a channel state information, CSI, feedback to the transmitter; and
a precoder connected to the antenna array, the precoder to apply a set of beamforming weights to one or more antennas of the antenna array to form, by the antenna array, one or more transmit beams or one or more receive beams,
a transceiver configured to
transmit, to the communication device, downlink reference signals, CSI-RS, according to a CSI-RS configuration comprising a number of CSI-RS antenna ports and a parameter, e.g., referred to as CSI-RS BurstDuration, indicating a time-domain-repetition of the downlink reference signals, e.g., in terms of a number of consecutive slots the downlink reference signals are repeated in, and downlink signals comprising the CSI-RS configuration; and
receive uplink signals comprising a plurality of CSI reports from the communication device; and
a processor configured to:
extract at least the two component precoder matrix identifier and the rank indicator from the plurality of CSI reports; and
construct a Doppler-delay-beam precoder matrix applied on the antenna ports using a first component and a second component of the PMI, and determine the beamforming weights responsive to the constructed precoder matrix.
9. A method for providing a channel state information, CSI, feedback in a wireless communication system, the method comprising:
receiving a reference signal resource configuration including a parameter, the parameter indicating a time-domain-repetition of downlink reference signals,
determining the CSI feedback based on the repeated downlink reference signals, and
reporting the determined CSI feedback,
wherein the CSI feedback is determined by selecting, based on a performance metric, a Doppler-delay-beam precoder matrix, W, for a composite Doppler-delay-beam three-stage precoder, the CSI feedback including a precoder matrix indicator, PMI and a rank indicator, RI,
wherein the Doppler-delay-beam three-stage precoder is based on
a first codebook, Ω 1 , for one or more spatial beam components of the composite Doppler-delay-beam three-stage precoder,
a second codebook, Ω 2 , for one or more delay components of the composite Doppler-delay-beam three-stage precoder, and
a third codebook, Ω 3 , for one or more Doppler-frequency components of the composite Doppler-delay-beam three-stage precoder,
wherein the communication device is configured by the transmitter or another network entity with a first parameter indicating a subset of columns of a DFT or oversampled DFT matrix forming the second codebook, Ω 2 , and/or with a second parameter indicating a subset of columns of a DFT or oversampled DFT matrix forming the third codebook, Ω 3 , and
wherein one or more delay components and/or one or more Doppler-frequency components of the composite Doppler-delay-beam three-stage precoder are selected from the second codebook, Ω 2 , according to the first parameter and/or from the third codebook, Ω 3 , according to the second parameter.
10. A non-transitory digital storage medium having a computer program stored thereon to perform the method of claim 9 , when said computer program is run by a computer.
11. A method for transmitting in a wireless communication system comprising a communication device and a transmitter, the method comprising:
transmitting, to a communication device, downlink reference signals according to a CSI-RS configuration comprising a number of CSI-RS antenna ports and a parameter indicating a time-domain-repetition of the downlink reference signals and downlink signals comprising the CSI-RS configuration;
receiving, at the transmitter, uplink signals comprising a plurality of CSI reports from the communication device;
extracting, at the transmitter, at least the two component precoder matrix identifier and the rank indicator from the plurality of CSI reports;
constructing, at the transmitter, a Doppler-delay-beam precoder matrix applied on the antenna ports using a first component and a second component of the PMI, and
determining, responsive to the constructed precoder matrix, beamforming weights for a precoder connected to an the antenna array of the transmitter,
wherein the one or more delay components and/or the one or more Doppler-frequency components of the composite Doppler-delay-beam three-stage precoder are defined by one or more sub-matrices of a DFT matrix or by one or more sub-matrices of an oversampled DFT matrix.