CHANNEL ESTIMATION THROUGH DYNAMIC PORT ALLOCATION IN UPLINK TRANSMISSION FOR MULTI-USER, MULTIPLE-INPUT, MULTIPLE-OUTPUT (MU- MIMO) SYSTEMS

Abstract

A method and system for enabling transmission of uplink signal in a Multi-User Multiple Input Multiple-Output (MU-MIMO) system through dynamic DM-RS port allocation is provided. The method comprises of creating a scheduling information and a scheduling decision for MU-MIMO Scheduling of a plurality of User equipment's (UE's), transmitting the scheduling information as Downlink Control Indicator (DCI) payload bits over a Physical Downlink Control Channel (PDCCH) to the one or more paired UEs, demultiplexing the paired UEs based on the scheduling information, performing a Physical Uplink Shared Channel (PUSCH) Modulation based on the scheduling information extracted from the PDCCH from the one or more paired UEs, performing Cyclic Redundancy Check encoding and bit processing of the obtained DCI payload bits, performing antenna resource remapping and beam combining on the PUSCH channel, selecting DM-RS references for channel estimation and obtaining improved channel estimates at the receiver.

Claims

1. A method of enabling transmission of uplink signal in a Multi-User Multiple Input Multiple-Output (MU-MIMO) system through dynamic DM-RS port allocation in a 5G New Radio network, the method comprising: creating (502), by a priority Quality of Service (QoS) scheduler, a scheduling information and a scheduling decision for MU-MIMO Scheduling of a plurality of User equipment's (UE's); transmitting (504) the scheduling information as Downlink Control Indicator (DCI) payload bits over a Physical Downlink Control Channel (PDCCH) to the one or more paired UEs; Demultiplexing (506), by a demultiplexer (UE.sub.DE−MUX), one of more paired UEs of the plurality of UE's based on the scheduling information; performing (508) a Physical Uplink Shared Channel (PUSCH) Modulation based on the scheduling information extracted from the PDCCH from the one or more paired UEs; performing (510) Cyclic Redundancy Check (CRC) encoding and bit processing of the DCI payload bits obtained from each of the one or more UE's; performing (512), at a receiver, at least one of data modulation mapping, layer mapping, precoding and resource mapping of a processed DCI payload bit data; performing (514) antenna resource remapping and beam combining on the PUSCH channel; and selecting (516), by a resource de-mapper at the receiver, DM-RS references from a received DM-RS sequence or and the PUSCH payload for channel estimation; and obtaining (518), by a channel estimator unit, at the receiver improved channel estimates by dynamically reducing a despreading factor in Variable Spreading Factor Orthogonal Cover Code (VSFOCC) based on a Partial port occupancy (P-Poi) at a Base-station, wherein the channel estimates obtained are interpolated (520) using a liner or DFT interpolator to estimate the channel over N.sub.PRB subcarriers.

2. The method of claim 1, further comprising: inputting the determined channel estimates to an equalizer module; and performing one or more of demodulation, scrambling, Low-Density Parity-Check (LDPC) processing and CRC detachment of the inputted channel estimates.

3. The method of claim 1, wherein the scheduling decisions comprises at least one of user pairing details, user layers, Modulation and Coding Scheme (MCS) assignment and resource assignment across time frequency grids.

4. The method of claim 1, wherein bit processing comprises at least one of Code Block segmentation, LDPC Encoding, Rate-Matching, Code-block concatenation and Scrambling at ULSCH (Uplink transport block).

5. The method of claim 4, further comprising: performing a Hybrid automatic repeat request (HARQ) Process for each transport block by storing different Redundancy version (RV) of the data for each code-block corresponding to the ULSCH for retransmission; and scheduling HARQ retransmissions based on CRC failure and data corresponding to HARQ process data maintained in a HARQ buffer.

6. The method of claim 1, wherein the Scheduling Aware UE Port Mapper performs port assignment for reference signal (DM-RS) ports based on a Scheduling Information structure, where the Scheduling Information structure to assign the DM-RS ports comprises data layers, allocated MCS and the number of antenna ports.

7. The method of claim 1, wherein channel estimation is performed through at least one of least square, OCC de-spreading, frequency domain interpolation and denoising and time axis interpolation of DMRS reference signals.

8. The method of claim 1, wherein the PUSCH resources to be mapped to time-frequency grid is derived from the Scheduling Information.

9. The method of claim 1, wherein the priority QoS scheduler creates the scheduling information based on the PHY measurements and buffer status of the uplink PDI from the higher layers.

10. The method of claim 1, wherein the PUSCH data generated from the one or more UEs are combined through a Precoder, mapped to antennae through Antenna Mapping and subjected to orthogonal frequency-division multiplexing (OFDM) Modulation and Radio Processing at the UE.

11. A Multi-User Multiple Input Multiple-Output (MU-MIMO) system (400) for enabling transmission of uplink signal through dynamic DM-RS port allocation in a 5G New Radio (NR) network, the system comprising: a transmitter (402) comprising of: a priority Quality of Service (QoS) scheduler (404) to: generate a scheduling information and a scheduling decision for MU-MIMO Scheduling of a plurality of User equipment's (UE's); transmit the scheduling information as Downlink Control Indicator (DCI) payload bits over a Physical Downlink Control Channel (PDCCH) to one or more paired UEs; a demultiplexer (UE.sub.DE−MUX) (406) to demultiplex one of more paired UEs of the plurality of UE's based on the scheduling information; a Physical Uplink Shared Channel (PUSCH) Modulation unit (408) to perform a PUSCH modulation based on the scheduling information extracted from the PDCCH from the one or more paired UEs; a Cyclic Redundancy Check (CRC) Unit (410) to perform Cyclic Redundancy Check (CRC) encoding and bit processing of the DCI payload bits obtained from each of the one or more paired UEs; and a receiver comprising of: a Scheduling Aware UE Port Mapper Unit (416) to: perform at least one of data modulation mapping, layer mapping, precoding and resource mapping of a processed DCI payload bit data; perform antenna resource remapping and beam combining on the PUSCH channel; and select DM-RS references from a received DM-RS sequence or and the PUSCH payload for channel estimation; and a channel estimator unit (418) to obtain improved channel estimates by dynamically reducing a despreading factor in Variable Spreading Factor Orthogonal Cover Code (VSFOCC) based on a Partial port occupancy (P-Poi) at a Base-station, an interpolator (420) to interpolate the channel estimates obtained to estimate the channel over N.sub.PRB subcarriers.

12. The system (400) of claim 11, wherein the channel estimator unit (418) is further configured to: input the determined channel estimates to an equalizer module; and perform one or more of demodulation, scrambling, Low-Density Parity-Check (LDPC) processing and CRC detachment of the inputted channel estimates.

13. The system (400) of claim 11, wherein the scheduling decisions comprises at least one of user pairing details, user layers, Modulation and Coding Scheme (MCS) assignment and resource assignment across time frequency grids.

14. The system (400) of claim 11, wherein bit processing comprises at least one of Code Block segmentation, LDPC Encoding, Rate-Matching, Code-block concatenation and Scrambling at ULSCH (Uplink transport block).

15. The system (400) of claim 14, wherein the Scheduling Aware UE Port Mapper Unit is further configured to: perform a Hybrid automatic repeat request (HARQ) Process for each transport block by storing different Redundancy version (RV) of the data for each code-block corresponding to the ULSCH for retransmission; and schedule HARQ retransmissions based on CRC failure and data corresponding to HARQ process data maintained in a HARQ buffer.

16. The system (400) of claim 11, wherein the Scheduling Aware UE Port Mapper Unit performs port assignment for reference signal (DM-RS) ports based on a Scheduling Information structure, where the Scheduling Information structure to assign the DM-RS ports comprises data layers, allocated MCS and the number of antenna ports.

17. The system (400) of claim 11, wherein the channel estimator unit performs channel estimation through at least one of least square, OCC de-spreading, frequency domain interpolation and denoising and time axis interpolation of DMRS reference signals.

18. The system of claim 11, wherein the PUSCH resources to be mapped to time-frequency grid is derived from the Scheduling Information.

19. The system of claim 11, wherein the priority QoS scheduler creates the scheduling information based on the PHY measurements and buffer status of the uplink PDU from the higher layers.

20. The system of claim 11, wherein the PUSCH data generated from the one or more UEs are combined through a Precoder, mapped to antennae through Antenna Mapping and subjected to orthogonal frequency-division multiplexing (OFDM) Modulation and Radio Processing at the UE.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which:

[0023] FIG. 1 is a block diagram illustrating uplink transmission in MU-MIMO systems according to a prior art illustration;

[0024] FIGS. 2A-2B are block diagrams illustrating uplink transmission in MU-MIMO systems according to a prior art illustration;

[0025] FIGS. 3A-3B are structural block diagrams illustrating uplink transmission in MU-MIMO systems to which embodiments of the present disclosure can be applied;

[0026] FIG. 4 is a block diagram illustrating a Multi-User Multiple Input Multiple-Output (MU-MIMO) system for enabling transmission of uplink signal through dynamic DM-RS port allocation in a 5G New Radio (NR) network system, according to the embodiments herein; and

[0027] FIG. 5 is a flow chart illustrating a method for enabling transmission of uplink signal in a Multi-User Multiple Input Multiple-Output (MU-MIMO) system through dynamic DM-RS port allocation in a 5G New Radio network according to the embodiments herein.

DETAILED DESCRIPTION OF THE DRAWINGS

[0028] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

[0029] The embodiments herein enable enhancement in the overall throughput or fairness with improved Channel Estimation on selected MU-MIMO ports in uplink transmission. Scheduling aware port allocation involves the allocation of ports to users based on the scheduling information like MCS and the number of users sharing the same time-frequency resource. Scheduling aware DM-RS port allocation ensures the allocation of users in a specific order as propose, wherein the allocation of the DM-RS ports allows the receiver to de-spread the received pilots such that some ports get the benefit with an increased number of distinct channel estimates. The base station applies the optimized Channel estimation for the UE by bypassing the frequency despreading process. The increase of the number of distinct channel estimates is possible because the FD-CDM de-spreading is no longer required for certain ports. Such a de-spreading with a lower spreading factor is allowed because the OCCs used in DM-RS can be seen as codes in the branches of an Orthogonal Variable Spreading Factor (OVSF) code tree. The increased number of distinct channel estimates improve the mean-squared error of the frequency interpolator for channels with high selectivity. This can translate to a block error rate (BLER) improvement for the associated ports. The improved channel estimate can also enable upgradation to a higher-order modulation scheme or a higher code rate, which could improve the fairness if the associated port had a lower order modulation or code rate than the others. Alternately, the improvement in BLER results in throughput improvement.

[0030] The embodiments disclosed herein may be applied to any pilot-on-pilot based OFDM communication system that employs reference signals, where the orthogonality of ports is decided by the Nested Codes. The term nested code is used herein to signify the codes for which sub-sequences of codes are orthogonal to the original code when orthogonality is examined over the length of the sub-sequence.

[0031] As mentioned, there remains a need for a system and a method to enable improved Channel estimation quality for some ports in both Uplink for partially loaded DM-RS ports without compromising the estimation performance on the other ports. Referring now to the drawings, and more particularly to FIGS. 3A through 5, where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments.

[0032] FIGS. 3A-3B are block diagrams illustrating uplink transmission signal chain in MU-MIMO systems to which embodiments of the present disclosure can be applied. In the uplink flow based on the PHY Measurements, buffer status of the uplink PDU from higher layers, and the Priority QoS Scheduler 302 creates the scheduling information and the scheduling decisions like the user pairing, user layers, MCS assignment, resource assignment across time frequency grids etc. According to the embodiments of the present disclosure, the MU-MIMO Scheduling of the users is considered. Based on the scheduling decisions the paired UEs are demultiplexed in Uplink, UE De-MUX 304. The Scheduling Information structure is packed as DCI payload bits and sent across the Channel 306 to the scheduled UE's 308. DCI extracted from the PDCCH Channel 310 from the UE side uses the scheduling information and performs the PUSCH Channel Modulation with appropriate MCS, DMRS Configurations.

[0033] These transport blocks from each UE are subjected to CRC encoding followed by bit processing steps which involve the Code Block segmentation, LDPC Encoding, Rate-Matching, Code-block concatenation and Scrambling at ULSCH 312. HARQ Process for each transport block is managed by storing different Redundancy version (RV) of the data for each code-blocks corresponding to the transport block for retransmissions. The transmission of the data corresponding to the specific RV index is managed by the HARQ 314 Process. The Code-rate (MCS) for the LDPC and rate-matching is intimated in the Scheduling Information Structure. The Data modulation mapping is applied on the post bit processed data followed by Layer Mapping, Precoding and Resource Mapping 316. MCS is also used to select the required Modulation. The PUSCH resources to be mapped to time-frequency grid are derived from the Scheduling Information. The PUSCH data generated from all the UEs 308 are combined through the Precoder 318 and Mapped to antennae through the Antenna Mapping 320 and then subjected to Orthogonal Frequency Division Multiplexing (OFDM) 324 and Radio Processing 322 at the UE 308.

[0034] Antenna resource remapping is performed on the PUSCH Channel 326 followed by beam combining using a beam combiner 332. The weights for the beam combiner is computed using weight computation 332 from the SRS Channel estimator 338 through SRS channel estimation. Further, the resource de-mapper 334 separates out the references like DM-RS or PT-RS and the PUSCH payload. The DMRS reference 344 is used in the PUSCH DMRS Channel estimator 342 which typically has steps like determining a Least square at 346, VSFOCC despreading 348, Frequency Interpolation in a frequency domain interpolator 350 and Denoising and finally time axis interpolation at 352. The embodiments of the present disclosure increase number of finer channel estimates 354 and optimal estimates by dynamically reducing the despreading factor in the OCC stage (Variable Spreading Factor OCC) based on the Partial port occupancy known at the Base-station. These Channel Estimates 354 are further fed to Equalizer module 336 followed by Demodulation, Scrambling, LDPC Processing and CRC detachment. HARQ retransmissions are scheduled based on the CRC failures and soft data corresponding to HARQ process is maintained in the HARQ Buffer 314.

[0035] According to the embodiments herein, the port assignment for reference signal (DM-RS) is done using a Scheduling Aware UE Port Mapper 324 where the UE's, Corresponding Layers, Allocated MCS and the number of Antenna ports form the Scheduling Information structure are used for appropriately assigning the DM-RS ports. Group Casting must be done to send the P-Poi to all UEs scheduled, such that the UE getting MSE advantage will use the lower spreading factor while doing the channel estimation.

[0036] FIG. 4 is a block diagram of a Multi-user, multiple-input, multiple-output (MU-MIMO) system enabling DM-RS port allocation in uplink signal transmission, according to the embodiments of the present disclosure. The MU-MIMO system 400 includes a transmitter 402 and a receiver 414. The transmitter 402 comprises a QoS Scheduler 404. a demultiplexer 406, PUSCH Modulation Unit 408, Cyclic Redundancy Check (CRC) unit 410 and a signalling unit 412.

[0037] The priority Quality of Service (QoS) scheduler 404 generates a scheduling information and a scheduling decision for MU-MIMO Scheduling of a plurality of User equipment's (UE's) and transmits the scheduling information as Downlink Control Indicator (DCI) payload bits over a Physical Downlink Control Channel (PDCCH) to one or more paired UEs. The demultiplexer (UE.sub.DE−MUX) 406 demultiplexes one of more paired UEs of the plurality of UE's based on the scheduling information. The Physical Uplink Shared Channel (PUSCH) Modulation unit 408 performs a PUSCH modulation based on the scheduling information extracted from the PDCCH from the one or more paired UEs. The Cyclic Redundancy Check (CRC) Unit 410 further preforms a Cyclic Redundancy Check (CRC) encoding and bit processing of the DCI payload bits obtained from each of the one or more paired UEs.

[0038] According to the embodiments herein, the receiver 414 comprises a Schedule Aware UE Port Mapper unit 416, a channel estimator unit 418 and an interpolator 420, where the interpolator DFT or linear. The Scheduling Aware UE Port Mapper Unit 416 is configured to perform at least one of data modulation mapping, layer mapping, precoding and resource mapping of a processed DCI payload bit data, perform antenna resource remapping and beam combining on the PUSCH channel; and select DM-RS references from a received DM-RS sequence or and the PUSCH payload for channel estimation. The channel estimator unit 418 is configured to obtain improved channel estimates by dynamically reducing a despreading factor in Variable Spreading Factor Orthogonal Cover Code (VSFOCC) based on a Partial port occupancy (P-Poi) at a Base-station. Further the interpolator is configured to interpolate the channel estimates obtained to estimate the channel over NPRB subcarriers. The channel estimator unit 418 is further configured to input the determined channel estimates to an equalizer module and perform one or more of demodulation, scrambling, Low-Density Parity-Check (LDPC) processing and CRC detachment of the inputted channel estimates. The scheduling decisions comprises at least one of user pairing details, user layers, Modulation and Coding Scheme (MCS) assignment and resource assignment across time frequency grids. The bit processing comprises at least one of Code Block segmentation, LDPC Encoding, Rate-Matching, Code-block concatenation and Scrambling at ULSCH (Uplink transport block).

[0039] The Scheduling Aware UE Port Mapper Unit 416 is further configured to perform a Hybrid automatic repeat request (HARQ) Process for each transport block by storing different Redundancy version (RV) of the data for each code-block corresponding to the ULSCH for retransmission and schedule HARQ retransmissions based on CRC failure and data corresponding to HARQ process data maintained in a HARQ buffer. The Scheduling Aware UE Port Mapper Unit 416 is further configured to perform port assignment for reference signal (DM-RS) ports based on a Scheduling Information structure, where the Scheduling Information structure to assign the DM-RS ports comprises of data layers, allocated MCS and a plurality of antenna ports.

[0040] The channel estimator unit 418 performs channel estimation through at least one of least square, OCC de-spreading, frequency domain interpolation and denoising and time axis interpolation of DMRS reference signals. Here the PUSCH resources to be mapped to time-frequency grid is derived from the Scheduling Information and the PUSCH data generated from the one or more UEs are combined through a Precoder, mapped to antennae through Antenna Mapping and subjected to orthogonal frequency-division multiplexing (OFDM) Modulation and Radio Processing at the UE.

[0041] The priority QoS scheduler 402 herein creates the scheduling information based on the PHY measurements and buffer status of the uplink PDU from the higher layers.

[0042] FIG. 5 is flow chart illustrating a method of enabling transmission of uplink signal in a Multi-User Multiple Input Multiple-Output (MU-MIMO) system through dynamic DM-RS port allocation in a 5G New Radio network, according to the embodiments of the present disclosure. At step 502, the priority Quality of Service (QoS) scheduler creates a scheduling information and a scheduling decision for MU-MIMO Scheduling of a plurality of User equipment's (UE's). At 504, the scheduling information is transmitted as Downlink Control Indicator (DCI) payload bits over a Physical Downlink Control Channel (PDCCH) to the one or more paired UEs. At 506, one of more paired UEs of the plurality of UE's is demultiplexed based on the scheduling information. At step 508, a Physical Uplink Shared Channel (PUSCH) Modulation is performed based on the scheduling information extracted from the PDCCH from the one or more paired UEs. At step 510, a Cyclic Redundancy Check (CRC) encoding and bit processing of the DCI payload bits obtained from each of the one or more UE's is performed. The method further comprises at step 512, performing, at a receiver, at least one of data modulation mapping, layer mapping, precoding and resource mapping of a processed DCI payload bit data. At step 514, an antenna resource remapping and beam combining on the PUSCH channel is performed. The method further comprises at step 516, a resource de-mapper at the receiver selects DM-RS references from a received DM-RS sequence or and the PUSCH payload for channel estimation. At step 518, the channel estimator unit obtains improved channel estimates by dynamically reducing a despreading factor in Variable Spreading Factor Orthogonal Cover Code (VSFOCC) based on a Partial port occupancy (P-Poi) at a Base-station. At step 520, the channel estimates obtained are interpolated using a liner or DFT interpolator to estimate the channel over N.sub.PRB subcarriers.

[0043] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification.