WO2017215750A1 - Transmitting device, receiving device and methods thereof - Google Patents

Transmitting device, receiving device and methods thereof Download PDF

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Publication number
WO2017215750A1
WO2017215750A1 PCT/EP2016/063765 EP2016063765W WO2017215750A1 WO 2017215750 A1 WO2017215750 A1 WO 2017215750A1 EP 2016063765 W EP2016063765 W EP 2016063765W WO 2017215750 A1 WO2017215750 A1 WO 2017215750A1
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WIPO (PCT)
Prior art keywords
transmission
cdd
transmission parameters
database
data block
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PCT/EP2016/063765
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French (fr)
Inventor
Chaitanya TUMULA
Junshi Chen
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Huawei Technologies Co Ltd
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Huawei Technologies Co Ltd
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Priority to PCT/EP2016/063765 priority Critical patent/WO2017215750A1/en
Publication of WO2017215750A1 publication Critical patent/WO2017215750A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1812—Hybrid protocols; Hybrid automatic repeat request [HARQ]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0667—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of delayed versions of same signal
    • H04B7/0671—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of delayed versions of same signal using different delays between antennas
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1867—Arrangements specially adapted for the transmitter end
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1867—Arrangements specially adapted for the transmitter end
    • H04L1/1896—ARQ related signaling

Definitions

  • the present invention relates to a transmitting device and a receiving device. Furthermore, the present invention also relates to corresponding methods, a database, a computer program, and a computer program product.
  • This Transmission Mode is useful to introduce frequency diversity in flat fading channels, and transmission to users whose CQI is unreliable orfor User Equipment's (UEs) in which Channel Quality Indicator (CQI) measurement is too costly.
  • UEs User Equipment's
  • CQI Channel Quality Indicator
  • the transmitter uses a predefined precoding and cyclic delay matrices to send information to the receiver.
  • a single layer CDD transmission is considered using Orthogonal Frequency Division Multiplexing (OFDM) with N sub subcarriers and N transmit antennas. It was proposed to change the sign (5 0 , 5 1( ... , S W -i ) of data transmitted from different transmit antennas during different HARQ transmission attempts to improve the performance.
  • OFDM Orthogonal Frequency Division Multiplexing
  • a short-coming of the conventional solution is that LTE does not support CDD for single layer transmission. Hence, the the conventional solution is not applicable in current LTE systems. Moreover, the conventional solution does not address the case corresponding to CDD transmission using more than one layer.
  • An objective of embodiments of the present invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions.
  • Another objective of embodiments of the present invention is to provide methods and devices for HA Q transmissions using large-delay CDD mode for more than one transmission layer.
  • the above mentioned and other objectives are achieved with a transmitting device for a wireless communication system, the transmitting device comprising
  • a processor configured to
  • a transceiver configured to
  • NACK Negative Acknowledgement
  • the transmitting device for HARQ transmissions of at least one data block using large-delay CDD mode, it is proposed to use different large-delay CDD transmission parameters (e.g. corresponding to CDD transmission matrices) during different HARQ transmission attempts. Therefore, it is to be noted that the transmitting device according to the first aspect also covers the case of three or more CDD transmissions.
  • the effective channel seen by the receiving device is changed and result in diversity gain therefore improving the system performance between the transmitting device and the receiving device substantially.
  • the processor is configured to
  • the first implementation form of the transmitting device is beneficial for reducing the processing delay associated with the generation of transmission parameters for each CDD transmission.
  • the processor is configured to
  • transmission parameters for CDD transmissions from the database based on at least one of: a HARQ process number, redundancy versions of current and previous CDD transmissions of the HARQ process, new data indicator of the data block, and database indices of the database used during previous CDD transmissions of the HARQ process.
  • the second implementation form of the transmitting device facilitates the selection of transmission parameters of the CDD transmission in an efficient manner by evaluating of a set of logical operations.
  • the transceiver is configured to
  • the first set of transmission parameters related to the first CDD transmission e.g. means that the first set of transmission parameters are used in the first CDD transmission.
  • the third implementation form of the transmitting device is beneficial for the receiving device in the sense that the receiving device can first decode the control signals to obtain the transmission parameters associated with the current CDD transmission and then demodulate the transmitted data blocks.
  • the first control signal indicates a first database index for the first corresponding database entry and the second control signal indicates a second database index for the second corresponding database entry.
  • the fourth implementation form of the transmitting device is advantageous to minimize the number of bits that needs to be conveyed to the receiving device using the control signal. Thereby, overhead is reduced.
  • the transceiver is configured to
  • the fifth implementation form is an alternative to the fourth implementation form of the transmitting device.
  • the transmitting device need not send control signals to the receiving device.
  • the above mentioned and other objectives are achieved with a receiving device for a wireless communication system, the receiving device comprising
  • a transceiver configured to:
  • a processor is configured to
  • a transmission failure may e.g. consist of the receiving device performing demodulation and decoding of the received data block, and performing a cyclic redundancy check (CRC) to validate the correctness of the received data block. If the CRC check is passed, the transmission is successful and the receiving device sends an acknowledgement (ACK) signal to the transmitting device. If the CRC check fails, the transmission is failed and the receiving device sends a negative acknowledgement (NACK) signal to the transmitting device. Also other mechanisms for transmission failure checks are possible.
  • CRC cyclic redundancy check
  • the receiving device can receive and process the signals associated with a data block which was transmitted from a transmitter using different CDD transmissions parameters during different transmission attempts of a HARQ process. Hence, system performance is substantially improved.
  • the transceiver is configured to
  • processor is configured to
  • the first implementation form of the receiving device facilitates the process of demodulation of the data block associated with a given CDD transmission.
  • the receiver first demodulates the control signal associated with a corresponding CDD transmission to obtain the database entry and then demodulates the data block of a CDD transmission.
  • the first control signal indicates a first database index for the first corresponding database entry and the second control signal indicates a second database index for the second corresponding database entry,
  • processor is configured to
  • the second implementation form is beneficial in terms of providing a mechanism to obtain the transmission parameters associated with a CDD transmission of a data block.
  • the transceiver is configured to
  • processor is configured to
  • the third implementation form of the receiving device is advantageous in the sense that the receiving device need not perform any additional decoding of control signals to obtain the transmission parameters associated with a CDD transmission. It can directly obtain the effective channel from the precoded reference signals and using this information, it can perform demodulation of the data block associated with a CDD transmission.
  • a database comprising a plurality of database entries, wherein each database entry includes transmission parameters for a CDD transmission of a HA Q process.
  • the database according to the third aspect provides an advantage in terms of minimizing the overhead associated with the control signaling between the transmitting device and the receiving device.
  • the present solution is not limited thereof.
  • NACK Negative Acknowledgement
  • the method comprises
  • the method comprises selecting transmission parameters for CDD transmissions from the database based on at least one of: a HA Q process number, redundancy versions of current and previous CDD transmissions of the HARQ process, new data indicator of the data block, and database indices of the database used during previous CDD transmissions of the HARQ process.
  • the method comprises
  • the first control signal indicates a first database index for the first corresponding database entry and the second control signal indicates a second database index for the second corresponding database entry.
  • the method comprises transmitting at least one first reference signal precoded with the first set of transmission parameters related to the first CDD transmission,
  • the method comprises
  • the first control signal indicates a first database index for the first corresponding database entry and the second control signal indicates a second database index for the second corresponding database entry,
  • the method comprises
  • the method comprises
  • the present invention also relates to a computer program, characterized in code means, which when run by processing means causes said processing means to execute any method according to the present invention.
  • the invention also relates to a computer program product comprising a computer readable medium and said mentioned computer program, wherein said computer program is included in the computer readable medium, and comprises of one or more from the group: ROM (Read-Only Memory), PROM (Programmable ROM), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically EPROM) and hard disk drive.
  • Fig. 1 shows a transmitting device according to an embodiment of the present invention.
  • Fig. 2 shows a method according to an embodiment of the present invention.
  • Fig. 3 shows a receiving device according to an embodiment of the present invention.
  • Fig. 4 shows another method according to an embodiment of the present invention.
  • Fig. 5 shows the use of different CDD parameters during HARQ transmissions in large-delay CDD mode.
  • Fig. 6 shows a block diagram of a selection logic and a database.
  • Fig. 7 shows a flow chart of the selection logic using database index ID of CDD transmission parameters during HARQ transmissions in large-delay CDD mode.
  • Fig. 8 shows a database comprising CDD transmission parameters.
  • Fig. 9 illustrates signalling according to embodiments of the present invention.
  • Fig. 10 shows performance of embodiments of the present invention.
  • Fig. 1 1 illustrates implementation aspects according to embodiments of the invention.
  • LTE uses the same CDD precoding parameters for all HARQ transmission attempts of a transport block. This may result in a performance degradation in propagation conditions in which the channel has not changed significantly between different HARQ transmission attempts of the same data. Specifically, if the same redundancy version of a transport block is transmitted during HARQ retransmission attempts.
  • W(i) is a precoding matrix
  • D(i) is a delay matrix
  • U is a rotation matrix.
  • w is the Additive White Gaussian Noise (AWGN)
  • x(i) is the data vector transmitted on the considered ith resource element.
  • the elements of x(i) can correspond to either one or two Transport Blocks (TBs). Depending on the number of antenna ports, LTE uses one or two TBs per transmission. In case of two antenna ports, two TBs are used. Whereas, in case of four antenna ports, one or two TBs can be used.
  • the receiver sends a NACK signal corresponding to that erroneous TB to the transmitter using uplink control signalling.
  • the transmitter uses HARQ and retransmits the same transport block using either a different Redundancy Version (RV) or the same RV.
  • RV Redundancy Version
  • the channel gains experienced by the second data transmission attempt will remain the same.
  • both the TBs are in error and the receiver sends two NACK signals to the transmitter corresponding to the two TBs.
  • the received signal on the ith resource element can be expressed as
  • Fig. 1 shows a transmitting device 100 according to an embodiment of the invention.
  • the transmitting device 100 comprises a processor 102 communicably coupled with a transceiver 104.
  • the communication means are illustrated with the arrow between the processor 102 and the transceiver 104 in Fig. 1.
  • the transmitting device 100 also comprises an optional antenna 106 configured for wireless communications in a wireless communication system.
  • the transceiver 104 is communicably coupled to the antenna 106.
  • the processor 102 of the transmitting device 100 is configured to select a first set of transmission parameters for a first CDD transmission of a HARQ process.
  • the processor 102 is further configured select a set of second set of transmission parameters for a second CDD transmission of the HARQ process.
  • the first set of transmission parameters and the second set of transmission parameters differ from each other in at least one transmission parameter.
  • the transceiver 104 is configured to transmit at least one Data Block (DB) precoded with the first set of transmission parameters in a first CDD transmission.
  • the transceiver 104 is further configured to receive a NACK associated with the data block of the first CDD transmission.
  • the transceiver 104 is configured to retransmit the data block precoded with the second set of transmission parameters in a second CDD transmission upon reception of the NACK.
  • DB Data Block
  • the data block may e.g. be a TB, such as the ones used in LTE systems. However, also other forms of "blocks" comprising data may be used with the present solution.
  • Fig. 2 shows a corresponding method 200 which may be executed in a transmitting device 100, such as the one shown in Fig. 1 .
  • the method 200 comprises selecting 202 a first set of transmission parameters for a CDD transmission of a HARQ process.
  • the method 200 further comprises selecting 204 a set of second transmission parameters for a second CDD transmission of the HARQ process.
  • the first set of transmission parameters and the second set of transmission parameters differ from each other in at least one transmission parameter.
  • the method 200 further comprises transmitting 206 at least one data block precoded with the first set of transmission parameters in a first CDD transmission.
  • the method 200 further comprises receiving 208 a NACK associated with the data block of the first CDD transmission.
  • the method 200 further comprises retransmitting 210 the data block precoded with the second set of transmission parameters in a second CDD transmission upon reception of the NACK.
  • Fig. 3 shows a receiving device 300 according to an embodiment of the invention.
  • the receiving device 300 comprises a transceiver 302 communicably coupled with a processor 304.
  • the communication means are illustrated with the arrow between the processor 304 and the transceiver 302.
  • the receiving device 300 also comprises an optional antenna 306 configured for wireless communications in a wireless communication system.
  • the transceiver 302 is coupled to the antenna 306.
  • the transceiver 302 is configured to receive a first CDD transmission comprising a data block of a HA Q process being transmitted using a first set of transmission parameters.
  • the transceiver 302 of the receiving device 300 is further configured to transmit a NACK in response to a transmission failure associated with the data block of the first CDD transmission.
  • the transceiver 302 is configured to receive at least one second CDD transmission comprising the data block of the first CDD transmission being transmitted using a second set of transmission parameters.
  • the first set of transmission parameters and the second set of transmission parameters differ from each other in at least one transmission parameter.
  • the processor 304 is configured to detect the data block of the first CDD transmission using the first set of transmission parameters.
  • the processor 304 is configured to detect the data block of the second CDD transmission using the second set of transmission parameters.
  • Fig. 4 shows a corresponding method 400 which may be executed in a receiving device 300, such as the one shown in Fig. 3.
  • the method 400 comprises receiving 402 a first CDD transmission comprising a data block of a HARQ process being transmitted using a first set of transmission parameters.
  • the method 400 further comprises transmitting 404 a NACK in response to a transmission failure associated with the data block of the first CDD transmission.
  • the method 400 further comprises receiving 406 at least one second CDD transmission comprising the data block of the first CDD transmission being transmitted using a second set of transmission parameters.
  • the first set of transmission parameters and the second set of transmission parameters differ from each other in at least one transmission parameter.
  • the method 400 further comprises detecting 408 the data block of the first CDD transmission using the first set of transmission parameters.
  • the method 400 further comprises detecting 410 the data block of the second CDD transmission using the second set of transmission parameters.
  • An overview of an embodiment of the invention is shown in Fig. 5.
  • Data bits corresponding to at least one DB is encoded using a Forward-Error Correction (FEC) scheme, rate matching is performed and the coded bits are then scrambled at block 1 10.
  • the scrambled coded bits are then mapped onto constellation corresponding to a chosen modulation order at block 1 12.
  • the modulation symbols corresponding to the DB is then mapped onto different transmission layers at block 1 14.
  • the lines corresponding to a second DB is shown with dashed-lines to point out that one can use more than one DB for transmission.
  • the transmit symbol vectors corresponding to different transmission layers are then precoded using the Large-delay CDD precoding at block 1 16.
  • the precoded transmit symbol vectors are finally sent for Resource Element (RE) mapping.
  • RE Resource Element
  • CDD parameter selection 1 18 there is a logic for CDD parameter selection 1 18 connected to the large-delay CDD precoding block 1 16.
  • the CDD parameter selection logic 1 18 is further connected to a CDD parameter database 500 consisting of different CDD parameter choices.
  • the logic for CDD parameter selection 1 18 can be implemented either in Hardware (HW) or in Software (SW), or by a combination thereof.
  • the database 500 of CDD parameters can be stored in programmable or non-programmable memory.
  • the CDD parameter database 500 can be part of the transmitting device 100 or can be a separate memory element elsewhere in the system.
  • FIG. 6 A detailed diagram of the CDD parameter selection logic 1 18 and the CDD parameter database block 500 is shown in Fig. 6.
  • the processor 102 of the transmitting device 100 is configured to select transmission parameters for CDD transmissions from the database 500 based on at least one of: a HARQ process number, Redundancy Versions (RVs) of current and previous CDD transmissions of the HARQ process, New Data Indicator (NDI) of the DB, and database indices of the database 500 used during previous CDD transmissions of the HARQ process.
  • RVs Redundancy Versions
  • NDI New Data Indicator
  • database indices of the database 500 used during previous CDD transmissions of the HARQ process there are three inputs to the CDD parameter selection logic 1 18, namely inputs 11 , I2, and I3.
  • the inputs 11 , I2, and I3 to the selection logic block 1 18 are according to this embodiment:
  • the selection logic 1 18 also comprises, in this embodiment, of a programmable memory 120 configured to store the RV indices of a DB corresponding to a given HARQ process number and the CDD parameter database indices selected during the previous transmissions of a given HARQ process number.
  • the selection logic 1 18 can e.g. perform the following logical operations according to an embodiment in which a plurality of DBs are associated with a HARQ process. With reference to the flow chart shown in Fig. 7:
  • First the selection logic 1 18 checks if all the DBs are carrying new data by checking the NDI flags/bits of all the DBs (I2). This can be performed for example using the logical AND operations of NDI bits of all DBs.
  • the selection logic 1 18 outputs index 1 and the picks the entries corresponding to index 1 of the CDD parameter database 500.
  • the selection logic 1 18 performs the following logical operations using the RV indices of the DBs in the current transmission (I3), the HARQ process number (11 ), and RV indices and the database indices used in the previous transmissions of the same DBs accessed from the programmable memory 120.
  • the selection logic 1 18 chooses an index from the CDD parameter database 500 that was not chosen previously during the N max - 1 transmissions corresponding to the same HARQ process number.
  • the selection logic 1 18 may choose an index from the CDD parameter database 500 that was chosen previously during the N max - 1 transmissions corresponding to the same HARQ process number.
  • N max denotes the maximum number of transmissions attempts (including the first transmission) for any DB.
  • the selection logic 1 18 only needs to store the N max previously used index IDs of the parameter database and RVs of the DBs associated with the N max previous transmissions for a given HARQ process number in the programmable memory 120.
  • An example database 500 comprising CDD transmission parameters is shown in Fig. 8.
  • the selection logic in Fig. 7 can select the precoding matrix for et of precoding matrices
  • the selection logic 1 18 may
  • CDD transmission parameters e.g. the delay matrix D(i) and the rotation matrix U during HARQ retransmissions.
  • embodiments of the invention relate to signalling aspects between the transmitting device 100 and the receiving device 300 in a wireless communication system 600.
  • the signalling aspects of one particular embodiment is illustrated in Fig. 9.
  • the dotted line in Fig. 9 only separate two cases described in the following disclosure.
  • the receiving device 300 needs to decode the transmit signal (comprising at least one DB) transmitted by the transmitting device 100 using the proposed solution.
  • the receiving device 300 needs to know which transmission parameters were selected during the transmission of the DB in the current HA Q process.
  • the transmitting device 100 needs in one example to signal the database index of the parameter database 500 it selected for transmission to the receiving device 300.
  • This signalling information can be sent on the control channel as control signals CS1 and CS2 as shown in Fig. 9.
  • the receiving device 300 has an identical copy of the parameter database 500 in its memory and by decoding the database index value sent using the control signals CS1 and CS2, the receiving device 300 can access (illustrated with the arrow) the parameter database 500 as shown in Fig. 9.
  • the database 500 is shown as an external device to the receiving device 300, however the database can be a part of the receiving device 300.
  • the receiving device 300 can perform the demodulation of the precoded DB using these transmission parameters.
  • the transmitting device 100 is configured to transmit a first control signal CS1 indicating a first corresponding database entry for the first set of transmission parameters related to the first CDD transmission.
  • the transmitting device 100 is configured transmit a second control signal CS2 indicating a second corresponding database entry for the second set of transmission parameters related to the second CDD transmission.
  • control signals are not limited to two control signals.
  • a plurality of control signals could be used, wherein each control signal is associated with a corresponding CDD transmission.
  • This principle is also applicable to the use of the reference signals which is explained below.
  • the first control signal CS1 indicates a first database index for the first corresponding database entry and the second control signal CS2 indicates a second database index for the second corresponding database entry.
  • the receiving device 300 is configured to receive a first control signal CS1 indicating a first corresponding database entry of a database 500 for the first set of transmission parameters related to with the first CDD transmission.
  • the receiving device 300 is configured receive a second control signal CS2 indicating a second corresponding database entry for the second set of transmission parameters related to the second CDD transmission.
  • the receiving device 300 is further configured to fetch the first set of transmission parameters from the database 500 based on the first indicated database entry, and detect the DB of the first CDD transmission using the first set of transmission parameters.
  • the receiving device 300 is further configured fetch the second set of transmission parameters from the database 500 based on the second indicated database entry, and to detect the DB of the second CDD using the second set of transmission parameters.
  • the first control signal CS1 indicates a first database index for the first corresponding database entry
  • the second control signal CS2 indicates a second database index for the second corresponding database entry.
  • the processor 304 is configured to fetch the first set of transmission parameters from the database 500 using the first database index, and to fetch the second set of transmission parameters from the database 500 using the second database index.
  • the transmitting device 100 may not signal the transmission parameters on the control channel. Instead the transmitting device 100 can precode reference signals S1 and RS2. The receiving device 300 can then perform the detection of the precoded DB using the precoded reference signals RS1 and RS2.
  • the transmitting device 100 is configured to transmit at least one first reference signal RS1 precoded with the first set of transmission parameters related to the first CDD transmission.
  • the transmitting device 100 is configured transmit at least one second reference signal RS2 precoded with the second set of transmission parameters related to the second CDD transmission.
  • the receiving device 300 is configured receive at least one first reference signal RS1 precoded with the first set of transmission parameters related to the first CDD transmission.
  • the receiving device 300 is configured to receive at least one second reference signal RS2 precoded with the second set of transmission parameters related to the second CDD transmission.
  • the receiving device 300 is configured to estimate a first effective channel matrix for first CDD transmission based on the received first reference signal RS1 .
  • the receiving device 300 is also configured to detect the DB of the first CDD transmission based on the estimated first effective channel, and to estimate a second effective channel matrix for second CDD transmission based on the received second reference signal RS2.
  • the receiving device 300 is further configured to detect the DB of the second CDD transmission based on the estimated second effective channel.
  • the transmitting device 100 may not signal the transmission parameters to the receiving device 300 at all. Furthermore, the reference signals may not be precoded. In such scenarios, the receiving device 300 blindly estimates the transmission parameters using e.g. the maximum likelihood estimation and then performs the data demodulation.
  • embodiments of the invention introduce the change of transmission parameters during different HARQ transmission attempts of given data block(s). By changing the transmission parameters during HARQ transmissions, the effective channel seen by the receiving device 300 is changed during different transmission attempts. This result in performance gain compared to conventional solutions.
  • Fig. 10 The performance of embodiments of the invention with Quadrature Phase Shift Keying (QPSK) modulation is shown in Fig. 10 and the simulation configuration is shown in Table 1 .
  • QPSK Quadrature Phase Shift Keying
  • the performance for the present solution in which the CDD parameters are changed during the retransmission is shown in Fig. 10.
  • the x-axis shows the SNR in dB and the y-axis shows the block error rate (BER).
  • BER block error rate
  • the transmitting device 100 and the receiving device 300 may be part of any suitable communication device, such as a radio network node (RNN) or a user device (UD) which is illustrated in Fig. 11 .
  • RNN radio network node
  • UD user device
  • a shown the radio network node and the user device can comprise a transmitting device 100 and/or a receiving device 300.
  • a radio network node, or base station e.g. a Radio Base Station (RBS), which in some networks may be referred to as transmitter, "eNB”, “eNodeB”, “NodeB” or “B node”, depending on the technology and terminology used.
  • the radio network nodes may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size.
  • the radio network node can be a Station (ST A), which is any device that contains an IEEE 802.1 1 -conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM).
  • MAC Media Access Control
  • PHY Physical Layer
  • a user device or a User Equipment (UE), mobile station, wireless terminal and/or mobile terminal is enabled to communicate wirelessly in a wireless communication system, sometimes also referred to as a cellular radio system.
  • the User Equipment (UE) may further be referred to as mobile telephones, cellular telephones, computer tablets or laptops with wireless capability.
  • the UEs in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another receiver or a server.
  • the UE can be a Station (ST A), which is any device that contains an IEEE 802.1 1- conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM)
  • ST A Station
  • MAC Media Access Control
  • PHY Physical Layer
  • any method according to the present invention may be implemented in a computer program, having code means, which when run by processing means causes the processing means to execute the steps of the method.
  • the computer program is included in a computer readable medium of a computer program product.
  • the computer readable medium may comprises of essentially any memory, such as a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), or a hard disk drive.
  • the present first network node and second network node comprises the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing the present solution.
  • means, units, elements and functions are: processors, memory, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selecting units, switches, interleavers, de-interleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiver units, transmitter units, DSPs, MSDs, TCM encoder, TCM decoder, power supply units, power feeders, communication interfaces, communication protocols, etc. which are suitably arranged together for performing the present solution.
  • the processors of the present devices may comprise, e.g., one or more instances of a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions.
  • CPU Central Processing Unit
  • ASIC Application Specific Integrated Circuit
  • the expression "processor” may thus represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above.
  • the processing circuitry may further perform data processing functions for inputting, outputting, and processing of data comprising data buffering and device control functions, such as call processing control, user interface control, or the like.

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Abstract

The present invention relates to transmitting device and a receiving device. The transmitting device (100) comprising a processor (102) configured to select a first set of transmission parameters for a first Cyclic Delay Diversity, CDD, transmission of a Hybrid Automatic Repeat reQuest, HARQ, process, select a set of second transmission parameters for a second CDD transmission of the HARQ process, wherein the first set of transmission parameters and the second set of transmission parameters differ from each other in at least one transmission parameter, a transceiver (104) configured to transmit a data block precoded with the first set of transmission parameters in a first CDD transmission, receive a Negative Acknowledgement, NACK, associated with the data block of the first CDD transmission, retransmit the data block precoded with the second set of transmission parameters in a second CDD transmission upon reception of the NACK. The receiving device (300) comprising a transceiver (302) configured to receive a first CDD transmission comprising a data block of a HARQ process being transmitted using a first set of transmission parameters, transmit a NACK in response to a transmission failure associated with the data block of the first CDD transmission, receive at least one second CDD transmission comprising the data blocks of the first CDD transmission being transmitted using a second set of transmission parameters, wherein the first set of transmission parameters and the second set of transmission parameters differ from each other in at least one transmission parameter, a processor (304) is configured to detect the data block of the first CDD transmission using the first set of transmission parameters, detect the data block of the second CDD transmission using the second set of transmission parameters. Furthermore, the present invention also relates to a database, corresponding methods, a computer program, and a computer program product.

Description

TRANSMITTING DEVICE, RECEIVING DEVICE AND METHODS THEREOF Technical Field
The present invention relates to a transmitting device and a receiving device. Furthermore, the present invention also relates to corresponding methods, a database, a computer program, and a computer program product.
Background
It is envisioned that for 5G systems, latency requirement will be less than 1 msec. With such short round trip delays, retransmitted data packets may fall within the same coherence interval of the channel, i.e. experience the same channel fading. Because of this, the advantage of the time-diversity with Hybrid-Automatic Repeat reQuest (HARQ) is lost. There should be mechanisms in place to address this issue. As an example, consider the downlink of Long Term Evolution (LTE) open-loop spatial multiplexing mode (TM3 in 3GPP LTE) with large-delay Cyclic Delay Diversity (CDD). This Transmission Mode (TM) is useful to introduce frequency diversity in flat fading channels, and transmission to users whose CQI is unreliable orfor User Equipment's (UEs) in which Channel Quality Indicator (CQI) measurement is too costly. In TM3 large-delay CDD mode, the transmitter uses a predefined precoding and cyclic delay matrices to send information to the receiver.
Previously, in a conventional solution, a single layer CDD transmission is considered using Orthogonal Frequency Division Multiplexing (OFDM) with Nsub subcarriers and N transmit antennas. It was proposed to change the sign (50, 51( ... , SW-i ) of data transmitted from different transmit antennas during different HARQ transmission attempts to improve the performance.
A short-coming of the conventional solution is that LTE does not support CDD for single layer transmission. Hence, the the conventional solution is not applicable in current LTE systems. Moreover, the conventional solution does not address the case corresponding to CDD transmission using more than one layer.
Summary
An objective of embodiments of the present invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions. Another objective of embodiments of the present invention is to provide methods and devices for HA Q transmissions using large-delay CDD mode for more than one transmission layer.
An "or" in this description and the corresponding claims is to be understood as a mathematical OR which covers "and" and "or", and is not to be understand as an XOR (exclusive OR).
The indefinite article "a" in this disclosure and claims is not limited to "one" and can also be understood as "one or more", i.e., plural. The above objectives are solved by the subject matter of the independent claims. Further advantageous implementation forms of the present invention can be found in the dependent claims.
According to a first aspect of the invention, the above mentioned and other objectives are achieved with a transmitting device for a wireless communication system, the transmitting device comprising
a processor configured to
select a first set of transmission parameters for a first Cyclic Delay Diversity, CDD, transmission of a Hybrid Automatic Repeat reQuest, HARQ, process,
select a set of second transmission parameters for a second CDD transmission of the
HARQ process, wherein the first set of transmission parameters and the second set of transmission parameters differ from each other in at least one transmission parameter, a transceiver configured to
transmit a data block precoded with the first set of transmission parameters in a first CDD transmission,
receive a Negative Acknowledgement, NACK, associated with the data block of the first CDD transmission,
retransmit the data block precoded with the second set of transmission parameters in a second CDD transmission upon reception of the NACK.
In the transmitting device according to the first aspect, for HARQ transmissions of at least one data block using large-delay CDD mode, it is proposed to use different large-delay CDD transmission parameters (e.g. corresponding to CDD transmission matrices) during different HARQ transmission attempts. Therefore, it is to be noted that the transmitting device according to the first aspect also covers the case of three or more CDD transmissions.
Furthermore, the expression "at least one data block" is equivalent to "one or more data blocks"
By using the different CDD transmission parameters during different HA Q transmission attempts, the effective channel seen by the receiving device is changed and result in diversity gain therefore improving the system performance between the transmitting device and the receiving device substantially.
In a first possible implementation form of a transmitting device according to the first aspect, the processor is configured to
select transmission parameters for CDD transmissions from a database, wherein database entries of the database each includes transmission parameters for a CDD transmission.
The first implementation form of the transmitting device is beneficial for reducing the processing delay associated with the generation of transmission parameters for each CDD transmission.
In a second possible implementation form of a transmitting device according to the first implementation form, the processor is configured to
select transmission parameters for CDD transmissions from the database based on at least one of: a HARQ process number, redundancy versions of current and previous CDD transmissions of the HARQ process, new data indicator of the data block, and database indices of the database used during previous CDD transmissions of the HARQ process.
The second implementation form of the transmitting device facilitates the selection of transmission parameters of the CDD transmission in an efficient manner by evaluating of a set of logical operations.
In a third possible implementation form of a transmitting device according to the first or second implementation form, the transceiver is configured to
transmit a first control signal indicating a first corresponding database entry for the first set of transmission parameters related to the first CDD transmission,
transmit a second control signal indicating a second corresponding database entry for the second set of transmission parameters related to the second CDD transmission.
The first set of transmission parameters related to the first CDD transmission e.g. means that the first set of transmission parameters are used in the first CDD transmission. The third implementation form of the transmitting device is beneficial for the receiving device in the sense that the receiving device can first decode the control signals to obtain the transmission parameters associated with the current CDD transmission and then demodulate the transmitted data blocks.
In a fourth possible implementation form of a transmitting device according to the third implementation form, the first control signal indicates a first database index for the first corresponding database entry and the second control signal indicates a second database index for the second corresponding database entry.
The fourth implementation form of the transmitting device is advantageous to minimize the number of bits that needs to be conveyed to the receiving device using the control signal. Thereby, overhead is reduced. In a fifth possible implementation form of a transmitting device according to any of the preceding implementation forms of the first aspect or to the first aspect as such, the transceiver is configured to
transmit at least one first reference signal precoded with the first set of transmission parameters related to the first CDD transmission,
transmit at least one second reference signal precoded with the second set of transmission parameters related to the second CDD transmission.
The fifth implementation form is an alternative to the fourth implementation form of the transmitting device. By precoding the reference signals with the transmission parameters associated with a corresponding CDD transmission, the transmitting device need not send control signals to the receiving device.
According to a second aspect of the invention, the above mentioned and other objectives are achieved with a receiving device for a wireless communication system, the receiving device comprising
a transceiver configured to
receive a first CDD transmission comprising a data block of a HA Q process being transmitted using a first set of transmission parameters,
transmit a NACK in response to a transmission failure associated with the data block of the first CDD transmission,
receive at least one second CDD transmission comprising the data block of the first CDD transmission being transmitted using a second set of transmission parameters, wherein the first set of transmission parameters and the second set of transmission parameters differ from each other in at least one transmission parameter,
a processor is configured to
detect the data block of the first CDD transmission using the first set of transmission parameters,
detect the data block of the second CDD transmission using the second set of transmission parameters.
A transmission failure may e.g. consist of the receiving device performing demodulation and decoding of the received data block, and performing a cyclic redundancy check (CRC) to validate the correctness of the received data block. If the CRC check is passed, the transmission is successful and the receiving device sends an acknowledgement (ACK) signal to the transmitting device. If the CRC check fails, the transmission is failed and the receiving device sends a negative acknowledgement (NACK) signal to the transmitting device. Also other mechanisms for transmission failure checks are possible.
The receiving device according to the second aspect can receive and process the signals associated with a data block which was transmitted from a transmitter using different CDD transmissions parameters during different transmission attempts of a HARQ process. Hence, system performance is substantially improved.
In a first possible implementation form of a receiving device according to the second aspect, the transceiver is configured to
receive a first control signal indicating a first corresponding database entry of a database for the first set of transmission parameters related to with the first CDD transmission,
receive a second control signal indicating a second corresponding database entry for the second set of transmission parameters related to the second CDD transmission,
wherein the processor is configured to
fetch the first set of transmission parameters from the database based on the first indicated database entry,
detect the data block of the first CDD transmission using the first set of transmission parameters,
fetch the second set of transmission parameters from the database based on the second indicated database entry,
detect the data block of the second CDD using the second set of transmission parameters. The first implementation form of the receiving device facilitates the process of demodulation of the data block associated with a given CDD transmission. The receiver first demodulates the control signal associated with a corresponding CDD transmission to obtain the database entry and then demodulates the data block of a CDD transmission.
In a second possible implementation form of a receiving device according to the first implementation form of the second aspect, the first control signal indicates a first database index for the first corresponding database entry and the second control signal indicates a second database index for the second corresponding database entry,
wherein the processor is configured to
fetch the first set of transmission parameters from the database using the first database index,
fetch the second set of transmission parameters from the database using the second database index.
The second implementation form is beneficial in terms of providing a mechanism to obtain the transmission parameters associated with a CDD transmission of a data block.
In a third possible implementation form of a receiving device according to the second aspect as such, the transceiver is configured to
receive at least one first reference signal precoded with the first set of transmission parameters related to the first CDD transmission,
receive at least one second reference signal precoded with the second set of transmission parameters related to the second CDD transmission,
wherein the processor is configured to
estimate a first effective channel (matrix) for first CDD transmission based on the received first reference signal,
detect the data block of the first CDD transmission based on the estimated first effective channel,
estimate a second effective channel (matrix) for second CDD transmission based on the received second reference signal,
detect the data block of the second CDD transmission based on the estimated second effective channel. The third implementation form of the receiving device is advantageous in the sense that the receiving device need not perform any additional decoding of control signals to obtain the transmission parameters associated with a CDD transmission. It can directly obtain the effective channel from the precoded reference signals and using this information, it can perform demodulation of the data block associated with a CDD transmission.
According to a third aspect of the invention, the above mentioned and other objectives are achieved with a database comprising a plurality of database entries, wherein each database entry includes transmission parameters for a CDD transmission of a HA Q process.
The database according to the third aspect provides an advantage in terms of minimizing the overhead associated with the control signaling between the transmitting device and the receiving device.
A transmitting device or receiving device or database according to the first, second or third aspects, wherein the transmission parameters are any of: a precoding matrix, a delay matrix, and a rotation matrix. However, the present solution is not limited thereof.
According to a fourth aspect of the invention, the above mentioned and other objectives are achieved with method comprising:
selecting a first set of transmission parameters for a first Cyclic Delay Diversity, CDD, transmission of a Hybrid Automatic Repeat reQuest, HARQ, process,
selecting a set of second transmission parameters for a second CDD transmission of the
HARQ process, wherein the first set of transmission parameters and the second set of transmission parameters differ from each other in at least one transmission parameter,
transmitting a data block precoded with the first set of transmission parameters in a first CDD transmission,
receiving a Negative Acknowledgement, NACK, associated with the data block of the first CDD transmission,
retransmitting the data block precoded with the second set of transmission parameters in a second CDD transmission upon reception of the NACK. In a first possible implementation form of a method according to the fourth aspect, the method comprises
selecting transmission parameters for CDD transmissions from a database, wherein database entries of the database each includes transmission parameters for a CDD transmission.
In a second possible implementation form of a method according to the first implementation form, the method comprises selecting transmission parameters for CDD transmissions from the database based on at least one of: a HA Q process number, redundancy versions of current and previous CDD transmissions of the HARQ process, new data indicator of the data block, and database indices of the database used during previous CDD transmissions of the HARQ process.
In a third possible implementation form of a method according to the first or second implementation form, the method comprises
transmitting a first control signal indicating a first corresponding database entry for the first set of transmission parameters related to the first CDD transmission,
transmitting a second control signal indicating a second corresponding database entry for the second set of transmission parameters related to the second CDD transmission.
In a fourth possible implementation form of a method according to the third implementation form, the first control signal indicates a first database index for the first corresponding database entry and the second control signal indicates a second database index for the second corresponding database entry.
In a fifth possible implementation form of a method according to any of the preceding implementation forms of the first aspect or to the first aspect as such, the method comprises transmitting at least one first reference signal precoded with the first set of transmission parameters related to the first CDD transmission,
transmitting at least one second reference signal precoded with the second set of transmission parameters related to the second CDD transmission. According to a fifth aspect of the invention, the above mentioned and other objectives are achieved with method comprising:
receiving a first CDD transmission comprising a data block of a HARQ process being transmitted using a first set of transmission parameters,
transmitting a NACK in response to a transmission failure associated with the data block of the first CDD transmission,
receiving at least one second CDD transmission comprising the data block of the first CDD transmission being transmitted using a second set of transmission parameters, wherein the first set of transmission parameters and the second set of transmission parameters differ from each other in at least one transmission parameter,
detecting the data block of the first CDD transmission using the first set of transmission parameters, detecting the data block of the second CDD transmission using the second set of transmission parameters.
In a first possible implementation form of a method according to the second aspect, the method comprises
receiving a first control signal indicating a first corresponding database entry of a database for the first set of transmission parameters related to with the first CDD transmission, receiving a second control signal indicating a second corresponding database entry for the second set of transmission parameters related to the second CDD transmission,
fetching the first set of transmission parameters from the database based on the first indicated database entry,
detecting the data block of the first CDD transmission using the first set of transmission parameters,
fetching the second set of transmission parameters from the database based on the second indicated database entry,
detecting the data block of the second CDD using the second set of transmission parameters.
In a second possible implementation form of a method according to the first implementation form of the second aspect, the first control signal indicates a first database index for the first corresponding database entry and the second control signal indicates a second database index for the second corresponding database entry,
the method comprises
fetching the first set of transmission parameters from the database using the first database index,
fetching the second set of transmission parameters from the database using the second database index.
In a third possible implementation form of a method according to the second aspect as such, the method comprises
receiving at least one first reference signal precoded with the first set of transmission parameters related to the first CDD transmission,
receiving at least one second reference signal precoded with the second set of transmission parameters related to the second CDD transmission,
estimating a first effective channel (matrix) for first CDD transmission based on the received first reference signal, detecting the data block of the first CDD transmission based on the estimated first effective channel,
estimating a second effective channel (matrix) for second CDD transmission based on the received second reference signal,
detecting the data block of the second CDD transmission based on the estimated second effective channel.
The advantages of the methods according to the fourth aspect or the fifth aspect are the same as those for the corresponding device claims according to the first aspect and the second aspect.
The present invention also relates to a computer program, characterized in code means, which when run by processing means causes said processing means to execute any method according to the present invention. Further, the invention also relates to a computer program product comprising a computer readable medium and said mentioned computer program, wherein said computer program is included in the computer readable medium, and comprises of one or more from the group: ROM (Read-Only Memory), PROM (Programmable ROM), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically EPROM) and hard disk drive.
Further applications and advantages of the present invention will be apparent from the following detailed description.
Brief Description of the Drawings
The appended drawings are intended to clarify and explain different embodiments of the present invention, in which:
Fig. 1 shows a transmitting device according to an embodiment of the present invention. Fig. 2 shows a method according to an embodiment of the present invention.
Fig. 3 shows a receiving device according to an embodiment of the present invention.
Fig. 4 shows another method according to an embodiment of the present invention.
Fig. 5 shows the use of different CDD parameters during HARQ transmissions in large-delay CDD mode.
Fig. 6 shows a block diagram of a selection logic and a database.
Fig. 7 shows a flow chart of the selection logic using database index ID of CDD transmission parameters during HARQ transmissions in large-delay CDD mode.
Fig. 8 shows a database comprising CDD transmission parameters.
Fig. 9 illustrates signalling according to embodiments of the present invention. Fig. 10 shows performance of embodiments of the present invention.
Fig. 1 1 illustrates implementation aspects according to embodiments of the invention.
Detailed Description
In TM3 large-delay CDD transmission mode, in some configurations, LTE uses the same CDD precoding parameters for all HARQ transmission attempts of a transport block. This may result in a performance degradation in propagation conditions in which the channel has not changed significantly between different HARQ transmission attempts of the same data. Specifically, if the same redundancy version of a transport block is transmitted during HARQ retransmission attempts.
Consider a 2x2 multiple-input multiple-output (MIMO) system which uses large-delay CDD transmission, if we consider ith Resource Element (RE) of an Orthogonal Frequency Division Multiplexing (OFDM) system, we have the received signal during the 1st transmission attempt as:
ri = HWm xi + w = H[ J] [J e_°J[J e ] (0 + w Equation 1
Heff
Where W(i) is a precoding matrix, D(i) is a delay matrix, and U is a rotation matrix. These parameter values are specified in the LTE standard. The symbol Heff = HW(i)D(i)U is the effective channel coefficient matrix seen by the receiver, w is the Additive White Gaussian Noise (AWGN), and x(i) is the data vector transmitted on the considered ith resource element. The elements of x(i) can correspond to either one or two Transport Blocks (TBs). Depending on the number of antenna ports, LTE uses one or two TBs per transmission. In case of two antenna ports, two TBs are used. Whereas, in case of four antenna ports, one or two TBs can be used.
Assuming that two TBs are used for transmission, if the data of any of the two TBs is received in error after the 1st transmission, i.e., failing cyclic redundancy check (CRC), the receiver sends a NACK signal corresponding to that erroneous TB to the transmitter using uplink control signalling. The transmitter then uses HARQ and retransmits the same transport block using either a different Redundancy Version (RV) or the same RV.
If the coherence interval of the channel is larger or if the retransmission interval smaller, then the channel gains experienced by the second data transmission attempt will remain the same. Let us assume that after the 1st transmission, both the TBs are in error and the receiver sends two NACK signals to the transmitter corresponding to the two TBs. During the second transmission attempt, assuming that the same V is used during retransmission of the erroneous TBs, the received signal on the ith resource element can be expressed as
r2 = Heffx{i) + w Equation 2
Since Heff remains the same between two transmission attempts, the receiver only sees a signal-to-noise ratio (SNR) improvement but no diversity gain because of HARQ.
According to embodiments of the invention it is proposed to use different CDD transmission parameters during different HARQ transmission attempts and thereby provide a diversity gain. Accordingly, Fig. 1 shows a transmitting device 100 according to an embodiment of the invention. The transmitting device 100 comprises a processor 102 communicably coupled with a transceiver 104. The communication means are illustrated with the arrow between the processor 102 and the transceiver 104 in Fig. 1. In this particular embodiment the transmitting device 100 also comprises an optional antenna 106 configured for wireless communications in a wireless communication system. Hence, the transceiver 104 is communicably coupled to the antenna 106.
The processor 102 of the transmitting device 100 is configured to select a first set of transmission parameters for a first CDD transmission of a HARQ process. The processor 102 is further configured select a set of second set of transmission parameters for a second CDD transmission of the HARQ process. The first set of transmission parameters and the second set of transmission parameters differ from each other in at least one transmission parameter. The transceiver 104 is configured to transmit at least one Data Block (DB) precoded with the first set of transmission parameters in a first CDD transmission. The transceiver 104 is further configured to receive a NACK associated with the data block of the first CDD transmission. The transceiver 104 is configured to retransmit the data block precoded with the second set of transmission parameters in a second CDD transmission upon reception of the NACK.
The data block may e.g. be a TB, such as the ones used in LTE systems. However, also other forms of "blocks" comprising data may be used with the present solution.
Fig. 2 shows a corresponding method 200 which may be executed in a transmitting device 100, such as the one shown in Fig. 1 . The method 200 comprises selecting 202 a first set of transmission parameters for a CDD transmission of a HARQ process. The method 200 further comprises selecting 204 a set of second transmission parameters for a second CDD transmission of the HARQ process. The first set of transmission parameters and the second set of transmission parameters differ from each other in at least one transmission parameter. The method 200 further comprises transmitting 206 at least one data block precoded with the first set of transmission parameters in a first CDD transmission. The method 200 further comprises receiving 208 a NACK associated with the data block of the first CDD transmission. The method 200 further comprises retransmitting 210 the data block precoded with the second set of transmission parameters in a second CDD transmission upon reception of the NACK.
Fig. 3 shows a receiving device 300 according to an embodiment of the invention. The receiving device 300 comprises a transceiver 302 communicably coupled with a processor 304. The communication means are illustrated with the arrow between the processor 304 and the transceiver 302. In this particular embodiment the receiving device 300 also comprises an optional antenna 306 configured for wireless communications in a wireless communication system. Hence, the transceiver 302 is coupled to the antenna 306.
The transceiver 302 is configured to receive a first CDD transmission comprising a data block of a HA Q process being transmitted using a first set of transmission parameters. The transceiver 302 of the receiving device 300 is further configured to transmit a NACK in response to a transmission failure associated with the data block of the first CDD transmission. The transceiver 302 is configured to receive at least one second CDD transmission comprising the data block of the first CDD transmission being transmitted using a second set of transmission parameters. The first set of transmission parameters and the second set of transmission parameters differ from each other in at least one transmission parameter. The processor 304 is configured to detect the data block of the first CDD transmission using the first set of transmission parameters. The processor 304 is configured to detect the data block of the second CDD transmission using the second set of transmission parameters.
Fig. 4 shows a corresponding method 400 which may be executed in a receiving device 300, such as the one shown in Fig. 3. The method 400 comprises receiving 402 a first CDD transmission comprising a data block of a HARQ process being transmitted using a first set of transmission parameters. The method 400 further comprises transmitting 404 a NACK in response to a transmission failure associated with the data block of the first CDD transmission. The method 400 further comprises receiving 406 at least one second CDD transmission comprising the data block of the first CDD transmission being transmitted using a second set of transmission parameters. The first set of transmission parameters and the second set of transmission parameters differ from each other in at least one transmission parameter. The method 400 further comprises detecting 408 the data block of the first CDD transmission using the first set of transmission parameters. The method 400 further comprises detecting 410 the data block of the second CDD transmission using the second set of transmission parameters. An overview of an embodiment of the invention is shown in Fig. 5. Data bits corresponding to at least one DB is encoded using a Forward-Error Correction (FEC) scheme, rate matching is performed and the coded bits are then scrambled at block 1 10. The scrambled coded bits are then mapped onto constellation corresponding to a chosen modulation order at block 1 12. The modulation symbols corresponding to the DB is then mapped onto different transmission layers at block 1 14. In Fig. 5, the lines corresponding to a second DB is shown with dashed-lines to point out that one can use more than one DB for transmission. The transmit symbol vectors corresponding to different transmission layers are then precoded using the Large-delay CDD precoding at block 1 16. The precoded transmit symbol vectors are finally sent for Resource Element (RE) mapping.
In an embodiment of the invention, which is also illustrated in Fig. 5, there is a logic for CDD parameter selection 1 18 connected to the large-delay CDD precoding block 1 16. The CDD parameter selection logic 1 18 is further connected to a CDD parameter database 500 consisting of different CDD parameter choices. The logic for CDD parameter selection 1 18 can be implemented either in Hardware (HW) or in Software (SW), or by a combination thereof. The database 500 of CDD parameters can be stored in programmable or non-programmable memory. The CDD parameter database 500 can be part of the transmitting device 100 or can be a separate memory element elsewhere in the system.
A detailed diagram of the CDD parameter selection logic 1 18 and the CDD parameter database block 500 is shown in Fig. 6. Generally, the processor 102 of the transmitting device 100 is configured to select transmission parameters for CDD transmissions from the database 500 based on at least one of: a HARQ process number, Redundancy Versions (RVs) of current and previous CDD transmissions of the HARQ process, New Data Indicator (NDI) of the DB, and database indices of the database 500 used during previous CDD transmissions of the HARQ process. In the particular example in Fig. 6 there are three inputs to the CDD parameter selection logic 1 18, namely inputs 11 , I2, and I3. The inputs 11 , I2, and I3 to the selection logic block 1 18 are according to this embodiment:
• The HARQ process number in which a DB is transmitted during a CDD transmission, 11.
· NDI flag/bits of the DB (i.e. for each DB of the HARQ process), I2.
• RV of current CDD transmission of the DB in the given HARQ process, I3. The selection logic 1 18 also comprises, in this embodiment, of a programmable memory 120 configured to store the RV indices of a DB corresponding to a given HARQ process number and the CDD parameter database indices selected during the previous transmissions of a given HARQ process number.
Using one or more of the above mentioned inputs, for a given HARQ process number, 11 , the selection logic 1 18 can e.g. perform the following logical operations according to an embodiment in which a plurality of DBs are associated with a HARQ process. With reference to the flow chart shown in Fig. 7:
1 . First the selection logic 1 18 checks if all the DBs are carrying new data by checking the NDI flags/bits of all the DBs (I2). This can be performed for example using the logical AND operations of NDI bits of all DBs.
2. If all the DBs are carrying new data (i.e. output of the logical AND operation is 1 ), then the selection logic 1 18 outputs index 1 and the picks the entries corresponding to index 1 of the CDD parameter database 500.
3. If any of the DBs are NOT carrying new data (output of the logical AND operation is 0), then the selection logic 1 18 performs the following logical operations using the RV indices of the DBs in the current transmission (I3), the HARQ process number (11 ), and RV indices and the database indices used in the previous transmissions of the same DBs accessed from the programmable memory 120.
4. If RV indices corresponding to any of the DBs in the current transmission have been used previously for the same DB corresponding to the same HARQ process number, the selection logic 1 18 chooses an index from the CDD parameter database 500 that was not chosen previously during the Nmax - 1 transmissions corresponding to the same HARQ process number.
5. If the RV indices corresponding to any of the DBs in current transmission have not been used previously for the same DB corresponding to the same HARQ process number, the selection logic 1 18 may choose an index from the CDD parameter database 500 that was chosen previously during the Nmax - 1 transmissions corresponding to the same HARQ process number.
In the steps listed above for the selection logic 1 18, Nmax denotes the maximum number of transmissions attempts (including the first transmission) for any DB. Hence, the selection logic 1 18 only needs to store the Nmax previously used index IDs of the parameter database and RVs of the DBs associated with the Nmax previous transmissions for a given HARQ process number in the programmable memory 120. An example database 500 comprising CDD transmission parameters is shown in Fig. 8. For each database index Identity (ID), there are a set of CDD transmission parameters. These transmission parameters can e.g. be precoding matrices, delay matrices and rotation matrices. If the entries corresponding to all the index IDs in Fig. 8 are the same, we obtain the conventional transmission mechanism in LTE. In the proposed solution, we may have different entries corresponding to different index IDs in the parameter database. For two different index IDs in Fig. 8, some of the CDD precoding parameter entries may be the same. As an example, for the two-layer large-delay CDD mode transmission in LTE systems assume that the maximum number of transmission attempts Nmax for any TB be 4. If the same RVs are transmitted for the two TBs (a TB corresponds to a DB) during 4 transmission attempts as in Chase-combining HARQ, the selection logic in Fig. 7 can select the precoding matrix for et of precoding matrices
Figure imgf000018_0001
precoding parameter database 500.
For first transmission, the selection logic 1 18 may select = = [ ] , and for the second transmission attempt of the two TBs, the selection logic 1 18 may select = \ ^], and for the third transmission attempt of the two TBs the selection logic 1 18 may select W(i) = ι Γΐ 1
, and for the fourth transmission attempt of the same TBs the selection logic 1 18 may
2 [j ~j.
select W(i) = i [J ^J.
The above example is only to provide detailed examples of the present solution and the database indices and CDD transmission parameters used in the explanation can take on any suitable values. Moreover, one may also change the other CDD transmission parameters, e.g. the delay matrix D(i) and the rotation matrix U during HARQ retransmissions.
Furthermore, embodiments of the invention relate to signalling aspects between the transmitting device 100 and the receiving device 300 in a wireless communication system 600. The signalling aspects of one particular embodiment is illustrated in Fig. 9. The dotted line in Fig. 9 only separate two cases described in the following disclosure. The receiving device 300 needs to decode the transmit signal (comprising at least one DB) transmitted by the transmitting device 100 using the proposed solution. For this purpose, the receiving device 300 needs to know which transmission parameters were selected during the transmission of the DB in the current HA Q process. For this purpose, the transmitting device 100 needs in one example to signal the database index of the parameter database 500 it selected for transmission to the receiving device 300. This signalling information can be sent on the control channel as control signals CS1 and CS2 as shown in Fig. 9.
The receiving device 300 has an identical copy of the parameter database 500 in its memory and by decoding the database index value sent using the control signals CS1 and CS2, the receiving device 300 can access (illustrated with the arrow) the parameter database 500 as shown in Fig. 9. In Fig. 9 the database 500 is shown as an external device to the receiving device 300, however the database can be a part of the receiving device 300. After obtaining the transmission parameters used at the transmitting device 100 for the transmission of the DB during current HARQ process, the receiving device 300 can perform the demodulation of the precoded DB using these transmission parameters.
Accordingly, in an embodiment of the invention the transmitting device 100 is configured to transmit a first control signal CS1 indicating a first corresponding database entry for the first set of transmission parameters related to the first CDD transmission. The transmitting device 100 is configured transmit a second control signal CS2 indicating a second corresponding database entry for the second set of transmission parameters related to the second CDD transmission.
It is however noted that the present solution is not limited to two control signals. For example, a plurality of control signals could be used, wherein each control signal is associated with a corresponding CDD transmission. This principle is also applicable to the use of the reference signals which is explained below.
In an example, the first control signal CS1 indicates a first database index for the first corresponding database entry and the second control signal CS2 indicates a second database index for the second corresponding database entry. Correspondingly, the receiving device 300 is configured to receive a first control signal CS1 indicating a first corresponding database entry of a database 500 for the first set of transmission parameters related to with the first CDD transmission. The receiving device 300 is configured receive a second control signal CS2 indicating a second corresponding database entry for the second set of transmission parameters related to the second CDD transmission. The receiving device 300 is further configured to fetch the first set of transmission parameters from the database 500 based on the first indicated database entry, and detect the DB of the first CDD transmission using the first set of transmission parameters. The receiving device 300 is further configured fetch the second set of transmission parameters from the database 500 based on the second indicated database entry, and to detect the DB of the second CDD using the second set of transmission parameters. In an example, the first control signal CS1 indicates a first database index for the first corresponding database entry and the second control signal CS2 indicates a second database index for the second corresponding database entry. The processor 304 is configured to fetch the first set of transmission parameters from the database 500 using the first database index, and to fetch the second set of transmission parameters from the database 500 using the second database index.
In an alternate embodiment, the transmitting device 100 may not signal the transmission parameters on the control channel. Instead the transmitting device 100 can precode reference signals S1 and RS2. The receiving device 300 can then perform the detection of the precoded DB using the precoded reference signals RS1 and RS2.
Accordingly, according to an embodiment the transmitting device 100 is configured to transmit at least one first reference signal RS1 precoded with the first set of transmission parameters related to the first CDD transmission. The transmitting device 100 is configured transmit at least one second reference signal RS2 precoded with the second set of transmission parameters related to the second CDD transmission.
Correspondingly, the receiving device 300 is configured receive at least one first reference signal RS1 precoded with the first set of transmission parameters related to the first CDD transmission. The receiving device 300 is configured to receive at least one second reference signal RS2 precoded with the second set of transmission parameters related to the second CDD transmission. Further, the receiving device 300 is configured to estimate a first effective channel matrix for first CDD transmission based on the received first reference signal RS1 . The receiving device 300 is also configured to detect the DB of the first CDD transmission based on the estimated first effective channel, and to estimate a second effective channel matrix for second CDD transmission based on the received second reference signal RS2. The receiving device 300 is further configured to detect the DB of the second CDD transmission based on the estimated second effective channel.
In yet another implementation which is not illustrated in Fig. 9, the transmitting device 100 may not signal the transmission parameters to the receiving device 300 at all. Furthermore, the reference signals may not be precoded. In such scenarios, the receiving device 300 blindly estimates the transmission parameters using e.g. the maximum likelihood estimation and then performs the data demodulation. As aforementioned, embodiments of the invention introduce the change of transmission parameters during different HARQ transmission attempts of given data block(s). By changing the transmission parameters during HARQ transmissions, the effective channel seen by the receiving device 300 is changed during different transmission attempts. This result in performance gain compared to conventional solutions.
The performance of embodiments of the invention with Quadrature Phase Shift Keying (QPSK) modulation is shown in Fig. 10 and the simulation configuration is shown in Table 1 .
Table 1 Simulation Configuration
Figure imgf000021_0001
The performance for the present solution in which the CDD parameters are changed during the retransmission is shown in Fig. 10. The x-axis shows the SNR in dB and the y-axis shows the block error rate (BER). In the scenario in which the channel coefficients remain constant during both transmission attempts, by changing the CDD parameters as in the present solution (denoted "Proposed Method" in Fig. 10), a significant performance improvement is achieved over conventional solutions.
When the channel coefficients for the second transmission attempt changes independently compared to the channel during the first transmission attempt, the proposed method of using different CDD parameters during different retransmissions has the same performance of using the same CDD parameters during all transmission attempts. However, as mentioned in the background section of this disclosure, as the delay requirement in wireless communication systems reduces, the systems operate in scenarios in which the channel coefficients remain constant for all HARQ transmission attempts of data blocks. The transmitting device 100 and the receiving device 300 may be part of any suitable communication device, such as a radio network node (RNN) or a user device (UD) which is illustrated in Fig. 11 . A shown the radio network node and the user device can comprise a transmitting device 100 and/or a receiving device 300. A radio network node, or base station, e.g. a Radio Base Station (RBS), which in some networks may be referred to as transmitter, "eNB", "eNodeB", "NodeB" or "B node", depending on the technology and terminology used. The radio network nodes may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. The radio network node can be a Station (ST A), which is any device that contains an IEEE 802.1 1 -conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM).
A user device or a User Equipment (UE), mobile station, wireless terminal and/or mobile terminal is enabled to communicate wirelessly in a wireless communication system, sometimes also referred to as a cellular radio system. The User Equipment (UE) may further be referred to as mobile telephones, cellular telephones, computer tablets or laptops with wireless capability. The UEs in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another receiver or a server. The UE can be a Station (ST A), which is any device that contains an IEEE 802.1 1- conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM) Furthermore, any method according to the present invention may be implemented in a computer program, having code means, which when run by processing means causes the processing means to execute the steps of the method. The computer program is included in a computer readable medium of a computer program product. The computer readable medium may comprises of essentially any memory, such as a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), or a hard disk drive. Moreover, it is realized by the skilled person that the present first network node and second network node comprises the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing the present solution. Examples of other such means, units, elements and functions are: processors, memory, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selecting units, switches, interleavers, de-interleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiver units, transmitter units, DSPs, MSDs, TCM encoder, TCM decoder, power supply units, power feeders, communication interfaces, communication protocols, etc. which are suitably arranged together for performing the present solution.
Especially, the processors of the present devices may comprise, e.g., one or more instances of a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The expression "processor" may thus represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above. The processing circuitry may further perform data processing functions for inputting, outputting, and processing of data comprising data buffering and device control functions, such as call processing control, user interface control, or the like. Finally, it should be understood that the present invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.

Claims

1 . Transmitting device for a wireless communication system (600), the transmitting device (100) comprising
a processor (102) configured to
select a first set of transmission parameters for a first Cyclic Delay Diversity, CDD, transmission of a Hybrid Automatic Repeat reQuest, HARQ, process,
select a set of second transmission parameters for a second CDD transmission of the HARQ process, wherein the first set of transmission parameters and the second set of transmission parameters differ from each other in at least one transmission parameter, a transceiver (104) configured to
transmit a data block precoded with the first set of transmission parameters in a first CDD transmission,
receive a Negative Acknowledgement, NACK, associated with the data block of the first CDD transmission,
retransmit the data block precoded with the second set of transmission parameters in a second CDD transmission upon reception of the NACK.
2. Transmitting device (100) according to claim 1 , wherein the processor (102) is configured to select transmission parameters for CDD transmissions from a database (500), wherein database entries of the database (500) each includes transmission parameters for a CDD transmission.
3. Transmitting device (100) according to claim 2, wherein the processor (102) is configured to select transmission parameters for CDD transmissions from the database (500) based on at least one of: a HARQ process number, redundancy versions of current and previous CDD transmissions of the HARQ process, new data indicator of the data block, and database indices of the database (500) used during previous CDD transmissions of the HARQ process.
4. Transmitting device (100) according to claim 2 or 3, wherein the transceiver (104) is configured to
transmit a first control signal (CS1 ) indicating a first corresponding database entry for the first set of transmission parameters related to the first CDD transmission,
transmit a second control signal (CS2) indicating a second corresponding database entry for the second set of transmission parameters related to the second CDD transmission.
5. Transmitting device (100) according to claim 4, wherein the first control signal (CS1 ) indicates a first database index for the first corresponding database entry and the second control signal (CS2) indicates a second database index for the second corresponding database entry.
6. Transmitting device (100) according to any of the preceding claims, wherein the transceiver (104) is configured to
transmit at least one first reference signal (RS1 ) precoded with the first set of transmission parameters related to the first CDD transmission,
transmit at least one second reference signal (RS2) precoded with the second set of transmission parameters related to the second CDD transmission.
7. Receiving device for a wireless communication system (600), the receiving device (300) comprising
a transceiver (302) configured to
receive a first CDD transmission comprising a data block of a HARQ process being transmitted using a first set of transmission parameters,
transmit a NACK in response to a transmission failure associated with the data block of the first CDD transmission,
receive at least one second CDD transmission comprising the data blocks of the first
CDD transmission being transmitted using a second set of transmission parameters, wherein the first set of transmission parameters and the second set of transmission parameters differ from each other in at least one transmission parameter,
a processor (304) is configured to
detect the data block of the first CDD transmission using the first set of transmission parameters,
detect the data block of the second CDD transmission using the second set of transmission parameters.
8. Receiving device (300) according to claim 7, wherein the transceiver (302) is configured to receive a first control signal (CS1 ) indicating a first corresponding database entry of a database (500) for the first set of transmission parameters related to with the first CDD transmission,
receive a second control signal (CS2) indicating a second corresponding database entry for the second set of transmission parameters related to the second CDD transmission, wherein the processor (304) is configured to fetch the first set of transmission parameters from the database (500) based on the first indicated database entry,
detect the data block of the first CDD transmission using the first set of transmission parameters,
fetch the second set of transmission parameters from the database (500) based on the second indicated database entry,
detect the data block of the second CDD using the second set of transmission parameters.
9. Receiving device (300) according to claim 8, wherein the first control signal (CS1 ) indicates a first database index for the first corresponding database entry and the second control signal (CS2) indicates a second database index for the second corresponding database entry, wherein the processor (304) is configured to
fetch the first set of transmission parameters from the database (500) using the first database index,
fetch the second set of transmission parameters from the database (500) using the second database index.
10. Receiving device (300) according to claim 7, wherein the transceiver (302) is configured to receive at least one first reference signal (RSI ) precoded with the first set of transmission parameters related to the first CDD transmission,
receive at least one second reference signal (RS2) precoded with the second set of transmission parameters related to the second CDD transmission,
wherein the processor (304) is configured to
estimate a first effective channel for first CDD transmission based on the received first reference signal (RS1 ),
detect the data block of the first CDD transmission based on the estimated first effective channel,
estimate a second effective channel for second CDD transmission based on the received second reference signal (RS2),
detect the data block of the second CDD transmission based on the estimated second effective channel.
1 1. Database (500) comprising a plurality of database entries, wherein each database entry includes transmission parameters for a CDD transmission of a HARQ process.
12. Transmitting device (100) or receiving device (300) or database (500) according to any of the preceding claims, wherein the transmission parameters are any of: a precoding matrix (W), a delay matrix (D), and a rotation matrix (U).
13. Method (200) comprising:
selecting (202) a first set of transmission parameters for a first Cyclic Delay Diversity, CDD, transmission of a Hybrid Automatic Repeat reQuest, HARQ, process,
selecting (204) a set of second transmission parameters for a second CDD transmission of the HARQ process, wherein the first set of transmission parameters and the second set of transmission parameters differ from each other in at least one transmission parameter,
transmitting (206) a data block precoded with the first set of transmission parameters in a first CDD transmission,
receiving (208) a Negative Acknowledgement, NACK, associated with the data block of the first CDD transmission,
retransmitting (210) the data block precoded with the second set of transmission parameters in a second CDD transmission upon reception of the NACK.
14. Method (400) comprising:
receiving (402) a first CDD transmission comprising a data block of a HARQ process being transmitted using a first set of transmission parameters,
transmitting (404) a NACK in response to a transmission failure associated with the data block of the first CDD transmission,
receiving (406) at least one second CDD transmission comprising the data blocks of the first CDD transmission being transmitted using a second set of transmission parameters, wherein the first set of transmission parameters and the second set of transmission parameters differ from each other in at least one transmission parameter,
detecting (408) the data block of the first CDD transmission using the first set of transmission parameters,
detecting (410) the data block of the second CDD transmission using the second set of transmission parameters.
15. Computer program with a program code for performing a method according to claim 13 or 14 when the computer program runs on a computer.
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