Patent Description:
Mobile communication technologies are moving the world toward an increasingly connected and networked society. The rapid growth of mobile communications and advances in technology have led to greater demand for capacity and connectivity. Other aspects, such as energy consumption, device cost, spectral efficiency, and latency are also important to meeting the needs of various communication scenarios. Various techniques, including new ways to provide higher quality of service, are being discussed. <CIT> relates to channel state feedback reporting in wireless communication networks and in particular to modifications of the procedure for reporting CSI as specified by section <NUM> of 3GPP TS <NUM> V10. and the corresponding RRC protocol as specified by 3GPP TS <NUM> V10. 3GPP Draft, R1-<NUM>, relates to HARQ-ACK and CQI repetition in multiflow HSPA.

This document discloses methods, systems, and devices related to digital wireless communication, and more specifically, to techniques related to transmissions of control information to enhance channel coverage.

The development of the new generation of wireless communication - <NUM> New Radio (NR) communication - is a part of a continuous mobile broadband evolution process to meet the requirements of increasing network demand. <NUM> NR aims to make wireless broadband to have fiber-like performance at a significantly lower cost-per-bit. With new levels of latency, reliability, and security, <NUM> NR will scale to efficiently connect the massive Internet of Things (IoT) architecture, and will offer new types of mission-critical services.

<NUM> communication techniques will likely use high-frequency data transmission. The presence of high-frequency wireless channel path loss, however, can cause poor coverage. Therefore, there is a need to consider ways to enhance coverage for transmission, particularly for uplink (UL) transmissions coverage from a user equipment (UE). It is noted that uplink transmissions are not limited to transmissions from a UE to a base station. Transmissions from a UE to a control unit (e.g., a UE acting as a femto cell) can also be referred to as uplink transmission.

The NR uplink coverage issue needs to be addressed for at least the following deployment scenarios:.

In some of the scenarios discussed above, when UL has coverage issues, UL data traffic relies only on LTE-PUSCH at a low frequency, while NR-PUCCH is maintained at a high frequency (e.g., <NUM>). It is, therefore, desirable to report at least some of the uplink control information with coverage enhancing techniques to obtain equivalent coverage as compared to PUCCH.

Currently, the uplink control information includes at least the channel state information (CSI), also referred to as CSI feedback, and hybrid automatic repeat request acknowledgement (HARQ-ACK) information. The CSI is typically carried on the PUCCH. When CSI is multiplexed with the PUSCH, it is reported independently and processed separately according to control information processing procedures. In order to enhance uplink coverage issues when all data traffic relies on LTE-PUSCH and NR-PUCCH operates at a high frequency, it is desirable to report relevant CSI on a PUSCH channel with a low bit rate.

At the same time, while NR systems support data transmissions based on code block groups (CBGs), all the CBGs in a transport block (TB) are currently scheduled at the same time (e.g., sharing the same HARQ process number). Because the CBGs are not scheduled independently, the HARQ process can only be released after all CBGs of a TB are received correctly, thereby causing limitations of resource scheduling. It is, therefore, also desirable to introduce techniques that allow independent scheduling of the CBGs of a particular TB.

This patent document describes coverage enhancing techniques for uplink control transmission that comprise the following aspects:.

Details of the techniques are further described in the following embodiments.

This embodiment describes exemplary operations that can be performed by a base station. <FIG> shows a flowchart representation of a method <NUM> for wireless communication that can be implemented at a base station. The method <NUM> includes, at <NUM>, transmitting, to a user equipment (UE), a control message based on a transmission mode of a physical channel to schedule a transmission of control information on the physical channel. The method <NUM> also includes, at <NUM>, receiving the transmission of control information on the physical channel.

In some embodiments, the base station first determines a transmission mode of a physical channel. For example, <FIG> shows exemplary uplink transmission modes that are defined in the current 3GPP standards. Additional transmission modes can be determined based on the uplink coverage level of the corresponding UEs. The base station then transmit a downlink control message based on the transmission mode to schedule a transmission of control information on the physical channel.

In some implementations, the downlink control message is scrambled by a <NUM>-bit Radio Network Temporary Identifier (RNTI). In some implementations, a specific DCI format is used to transmit the control message. The control message can include at least one of the items listed in Table <NUM>.

In some embodiments, a simple modulation and coding scheme (MCS), such as low-density parity-check (LDPC) coding and QPSK modulation scheme, can be used for transmitting the uplink control information. For example, both RLC feedback and CSI feedback can be jointly encoded using LDPC and modulated using QPSK. In some embodiments, a CSI report request field is used to indicate for which carrier, carrier group, or carrier set CSI is requested. In some implementations, one wideband CSI can be reported for multiple carriers.

The control information to be transmitted on the physical uplink channel includes at least radio link control (RLC) feedback and/or CSI feedback. Multiple redundant versions of the RLC feedback and/or CSI feedback can be transmitted. The uplink control information is transmitted using resources in the frequency domain. The frequency-domain resources include a start position of physical resource block (PRB) and a number of PRBs. In some cases, the number of PRBs is a fixed number m, which can be predetermined or semi-statically configured by RRC signaling. The uplink control information is also transmitted using resources in the time domain. The time-domain resources include a start position of an OFDM symbol and a number of OFDM symbols. In some implementations, the start position and the number of OFDM symbols are the same in each slot.

In some embodiments, a transport block (TB) or a code block group (CBG) of the control information is transmitted by bundling multiple adjacent slots or mini-slots together. The number of adjacent slots or mini-slots bundled for the transmission can be determined using one of the following ways:.

In some embodiments, all the slots or mini-slots share the same demodulation reference signals (DMRS) for modulation. The position and number of DRMS symbols correspond to the bundled slots. In some implementations, when the number of slots or mini-slots is semi-statically configured using RRC signaling, the position and number of DRMS are also configured using RRC signaling.

After sending a downlink control message to schedule transmissions of the uplink control information, the base station receives the uplink control information transmitted over a bundle of multiple adjacent slots or mini-slots. If the base station detects any error during demodulation of the received data, it may schedule a re-transmission of the control information in one of the following ways:.

In some embodiments, a retransmission based on CBGs can be configured using higher layer signaling. In such cases, the downlink control message sent by the base station includes specific fields to indicate which CBG(s) needs to be retransmitted.

The retransmission of the control information can also be performed using a bundle of multiple adjacent slots or mini-slots. For example, when demodulation errors occur in only one CBG, redundant versions of the CBG can be transmitted using multiple adjacent slots or mini-slots. In another example, when modulation errors occur in two CBGs, redundant versions of the first CBG can be transmitted using the first k adjacent slots or mini-slots, and redundant versions of the second CBG can transmitted using the remaining adjacent slots or mini-slots. Each CBG can include an independent HARQ process number. Each CBG can also include a different redundant version of the control information.

This embodiments describes exemplary operations that can be performed a user equipment (UE). <FIG> shows a flowchart representation of a method <NUM> for wireless communication that can be implemented at a user equipment. The method <NUM> includes, at <NUM>, receiving, from a base station, a control message for scheduling a transmission of control information on a physical channel based on a transmission mode of the physical channel. The method <NUM> also includes, at <NUM>, transmitting, based on the control message, one or more redundant versions of the control information on the physical channel.

The UE can perform blind detection using a specific RNTI to determine a transmission mode of the physical uplink channel. In some implementations, the UE determines whether it should schedule regular data transmission or control information transmission based on the format of the DCI message or a subset of bits in the DCI message. For example, if the DCI message it receives is in a first format (e.g., format X), then the UE will schedule uplink control information transmission accordingly. If the DCI message it receives is in a second format (e.g., format Y), then the UE will schedule regular uplink data transmission. In some cases, both data and control transmissions use the same DCI format, but the DCI message includes one or more bits to indicate whether the transmission should be data or control information.

In some embodiments, a transport block (TB) or a code block group (CBG) of the control information is transmitted using a bundle of multiple adjacent slots or mini-slots. Each slot can be used to transmit a different redundant version of the TB. Alternatively, each slot can be used to transmit a different CBG of the TB.

The multiple adjacent slots or mini-slots can be scheduled using the same parameters. In some implementations, however, each slot or mini-slot can have independent scheduling parameters. The scheduling parameters include at least the following: frequency domain resource allocations, time domain resource allocations, or the MCS. The scheduling parameters also include fields such as HARQ process number, CBGTI, or NDI.

The time domain resource allocation can indicate a start position of the time-domain symbols. For example, the start position can be indicated by an offset value as compared to the last symbol of the downlink control message.

After receiving the downlink control message from the base station, the UE then transmit the control information on the uplink channel.

In some embodiments, the UE jointly encodes a TB of the RLC and/or CSI feedback, and modulates the encoded data using the QPSK modulation scheme. The size of the TB can be ascertained using one or more of the following parameters: the number of layers for codeword mapping, the size of the allocated time-domain and frequency-domain resources, the number of mapped resource elements, the MCS level, or subcarrier spacing (SCS) related parameters. Particularly, when other parameters are the same, SCS has an inverse correspondence with the TBS. For example, a large SCS corresponds to a small TB size, and a small SCS corresponds to a large TB size.

In some embodiments, the allocated number of PRBs is equal to or smaller than a predetermined number (e.g., three PRBs). The allocated number of OFDM symbols is also equal to or smaller than a predetermined number (e.g., two OFDM symbols). Because the number of PRBs and OFDM symbols can be small, the final TB size is also relatively small.

The UE then repeatedly maps the modulated symbols to different time slots or mini-slots. When the base station schedules the transmission of the control information based on CBGs, the UE determines which CBGs to map to the bundle of slots or mini-slots based on CBGTI.

This embodiments describes details regarding the downlink control message for scheduling uplink control information transmission.

In some embodiments, the base station first determines a transmission mode based on the uplink coverage level of the UE. The base station then transmits a corresponding DCI message based on the transmission mode. In some implementations, the control message is further scrambled by a specific RNTI (e.g., a <NUM>-bit RNTI).

Table <NUM> shows exemplary fields that can be included in the corresponding DCI message. For example, when the RLC feedback indicator is set to <NUM>, the UE needs to jointly encode the RLC feedback with the CSI feedback.

<FIG> shows an example of the process of retransmission of a transport block. In this particular example, the number of slots or mini-slots used for uplink control information transmission is four. In each of the slots, the frequency-domain resources have the same locations. For example, the uplink control information is mapped to PRB8∼PRB10 in frequency domain from slot <NUM> to slot <NUM>. The information is encoded using LDPC and modulated using the QPSK modulation scheme.

When multiple slots or mini-slots are used to transmit the same TB of the uplink control information, they can share the same HARQ process and transmit the same redundant version of the TB. If an error occurs when demodulating data from the slots, the base station can schedule a retransmission of the TB or one of the CBG of the TB. The downlink control message for scheduling the retransmission, therefore, needs to be adjusted to include an indicator (e.g., CBGTI) to indicate which CBG(s) of the TB need to be retransmitted. The retransmission can also share the same HARQ process, same redundant version, and the same NDI, etc., until all CBGs of the TB are demodulated correctly.

In this particular example, the TB has four CBGs. Errors occurred when the base station demodulates CBG1 and CBG2, while CBG3 and CBG4 are demodulated correctly. The base station, therefore, schedules retransmission of only CBG1 and CBG2 in a bundle of four adjacent slots.

<FIG> shows another example of the process of retransmission of a transport block. In this particular example, the bundled slots transmit different CBGs of a TB. Each CBG has an independent NDI, an independent HARQ process number, and an independent RV. For example, CBG1, which has a corresponding HARQ process number <NUM>, is transmitted using slot1 and slot2. CBG2, which has a corresponding HARQ process number <NUM>, is transmitted using slot3 and slot4.

When CBG1 is received correctly by the base station and errors occur during demodulation of CBG2, the base station can schedule the retransmission of CBG2 using the HARQ process corresponding to CBG2. In some implementations, the base station can schedule the retransmission of CBG2 using the HARQ process corresponding to CBG1. In some cases, the base station can use both HARQ processes that correspond to CBG1 and CBG2 to retransmit CBG2 to increase the probability of a successful retransmission.

Table <NUM> shows exemplary fields that can be included in the DCI message to indicate transmission of independent CBGs. Here, M is the number of CBGs configured in a TB, and N is the number of scheduled CBGs. The DCI message can include three parts. The first part includes common downlink control information for all slots or mini-slots, such as subcarrier indicator, frequency-domain resource and time-domain resource allocation information, MCS, power control information, etc. The second part includes downlink control information that is specific to each CBG, such as NDI, HARQ process number, or redundancy version. The third part includes other types of downlink control information, such as CSI measurement triggers.

This embodiments shows exemplary ways of increasing HARQ-ACK coverage when HARQ-ACK information is piggybacked on PUSCH. The HARQ-ACK information includes both HARQ-ACK and HARQ-NACK.

In time domain, HARQ-ACK information can be mapped repetitively to symbols adjacent to DMRS symbols. In some implementations, the repetitive mapping of HARQ-ACK information is done based on DMRS symbols. For example, as shown in <FIG>, each slot has two DMRS symbols: DMRS1 (<NUM>) and DMRS2 (<NUM>'). Two types of HARQ-ACK information are transmitted: HARQ-ACK1 (<NUM>) and HARQ-ACK2 (<NUM>). HARQ-ACK1 (<NUM>) is mapped repetitively to symbols adjacent to DMRS1 (<NUM>), and HARQ-ACK2 (<NUM>) is mapped repetitively to symbols adjacent to DMRS2 (<NUM>').

In some implementations, the repetitive mapping of HARQ-ACK is done uniformly for different DMRS symbols. In another example, as shown in <FIG>, each slot has two DMRS symbols: DMRS1 (<NUM>) and DMRS2 (<NUM>'). Two types of HARQ-ACK information are transmitted: HARQ-ACK1 (<NUM>) and HARQ-ACK2 (<NUM>). HARQ-ACK1 (<NUM>) is mapped repetitively to symbols adjacent to one side of DMRS1 (<NUM>) and DMRS2 (<NUM>'), and HARQ-ACK2 (<NUM>) is mapped repetitively to symbols adjacent to the other side of DMRS1 (<NUM>) and DMRS2 (<NUM>').

Here, HARQ-ACK1 (<NUM>) is a HARQ-ACK codeword, and HARQ-ACK2 (<NUM>) is another HARQ-ACK codeword. The codeword size can be determined by the Downlink Assignment Index (DAI) field in the DCI message. Different HARQ-ACK information is encoded independently based on RM encoding, and modulated using BPSK or QPSK modulation scheme.

<FIG> shows an example of a wireless communication system where techniques in accordance with one or more embodiments of the present technology can be applied. A wireless communication system <NUM> can include one or more base stations (BSs) 705a, 705b, one or more wireless devices 710a, 710b, 710c, 710d, and an access network <NUM>. A base station 705a, 705b can provide wireless service to wireless devices 710a, 710b, 710c and 710d in one or more wireless sectors. In some implementations, a base station 705a, 705b includes directional antennas to produce two or more directional beams to provide wireless coverage in different sectors.

The access network <NUM> can communicate with one or more base stations 705a, 705b. In some implementations, the access network <NUM> includes one or more base stations 705a, 705b. In some implementations, the access network <NUM> is in communication with a core network (not shown) that provides connectivity with other wireless communication systems and wired communication systems. The core network may include one or more service subscription databases to store information related to the subscribed wireless devices 710a, 710b, 710c and 710d. A first base station 705a can provide wireless service based on a first radio access technology, whereas a second base station 705b can provide wireless service based on a second radio access technology. The base stations 705a and 705b may be co-located or may be separately installed in the field according to the deployment scenario. The access network <NUM> can support multiple different radio access technologies.

<FIG> is a block diagram representation of a portion of a radio station. A radio station <NUM> such as a base station or a wireless device (or UE) can include processor electronics <NUM> such as a microprocessor that implements one or more of the wireless techniques presented in this document. The radio station <NUM> can include transceiver electronics <NUM> to send and/or receive wireless signals over one or more communication interfaces such as antenna <NUM>. The radio station <NUM> can include other communication interfaces for transmitting and receiving data. Radio station <NUM> can include one or more memories (not explicitly shown) configured to store information such as data and/or instructions. In some implementations, the processor electronics <NUM> can include at least a portion of the transceiver electronics <NUM>. In some embodiments, at least some of the disclosed techniques, modules or functions are implemented using the radio station <NUM>.

It is thus evident that this patent document describes coverage enhancing techniques that allow redundancy in uplink control information (e.g., CSI and/or HARQ-ACK information) to help increase the success rate of demodulating such information and enhance coverage of the uplink channel. Using the disclosed techniques, the transport block size of CSI can be made small to allow the use of a simple modulation and coding scheme (MCS), such as QPSK, for transmissions of such uplink control information. The disclosed techniques also allow transmission of the uplink control information based on both TBs and CBGs using either joint or independent HARQ process(es) to allow flexible scheduling of the transmissions.

From the foregoing, it will be appreciated that specific embodiments of the presently disclosed technology have been described herein for purposes of illustration, but that various modifications may be made without deviating from the scope of the invention. Accordingly, the presently disclosed technology is not limited except as by the appended claims.

Claim 1:
A method for wireless communication performed by a base station, BS, configured to operate in a 3GPP system, comprising:
transmitting, to a user equipment, UE, a control message according to a transmission mode of a physical channel,
wherein the control message is configured to schedule a transmission of control information on the physical channel, the control information including at least channel state information, and
wherein the transmission of the control information comprises transmitting one or more redundant versions of the control information using a plurality of adjacent slots or mini-slots in time domain, and wherein the control information further includes one or more redundant versions of hybrid automatic repeat request acknowledgment, HARQ-ACK, information mapped to adjacent symbols of a demodulation reference signal, DMRS, carried on the physical channel; and
receiving, from the user equipment, the transmission of the control information on the physical channel.