Control signal design based on a downlink control information format

Methods and apparatuses for preconfigured uplink resource are disclosed. A method at a remote unit comprises transmitting a data in a predefined resource based on a resource configuration; and receiving a control signal in a first search space, wherein the control signal includes at least one of (1) a response to the data; (2) an updated TA; (3) an updated power; (4) an updated data transmission repetition; (5) a flag of retransmission based on dynamic grant or the predefined resource; (6) a fallback indication; and (7) a predefined resource release indication.

FIELD

The subject matter disclosed herein generally relates to wireless communications and, more particularly, to control signal design for preconfigured uplink resource (PUR) configuration.

BACKGROUND

The following abbreviations are herewith defined, some of which are referred to within the following description: Third Generation Partnership Project (3GPP), European Telecommunications Standards Institute (ETSI), Frequency Division Duplex (FDD), Frequency Division Multiple Access (FDMA), Long Term Evolution (LTE), New Radio (NR), Very Large Scale Integration (VLSI), Random Access Memory (RAM), Read-Only Memory (ROM), Erasable Programmable Read-Only Memory (EPROM or Flash Memory), Compact Disc Read-Only Memory (CD-ROM), Local Area Network (LAN), Wide Area Network (WAN), Personal Digital Assistant (PDA), User Equipment (UE), Uplink (UL), Downlink (DL), Evolved Node B (eNB), Next Generation Node B (gNB), Downlink (DL), Central Processing Unit (CPU), Graphics Processing Unit (GPU), Field Programmable Gate Array (FPGA), Dynamic RAM (DRAM), Synchronous Dynamic RAM (SDRAM), Static RAM (SRAM), Liquid Crystal Display (LCD), Light Emitting Diode (LED), Organic LED (OLED), Physical Uplink Shared Channel (PUSCH), Preconfigured Uplink Resource (PUR), Machine type Communication (MTC), MTC Physical Downlink Control Channel (MPDCCH), Narrowband Physical Downlink Control Channel (NPDCCH), Re-Authorization-Request (RAR), Radio Resource Control (RRC), Tracking Area (TA), Modulation and Coding Scheme (MCS), Redundant Version (RV), Acknowledgement (ACK), Negative Acknowledgment (NACK), Downlink Control Information (DCI), Coverage Enhancement (CE), System Information Block (SIB), Random Access Channel (RACH), Early Data Transmission (EDT), System Information (SI), Earthquake and Tsunami Warning System (ETWS), Commercial Mobile Alert System (CMAS).

A basic procedure of uplink transmission based on preconfigured uplink resource (PUR) is shown inFIG.4.

In step 1, UE receives PUR configuration from eNB before transitioning to an IDLE state. In step 2, based on the PUR configuration, UE transmits uplink data in IDLE state. In step 3, UE monitors MPDCCH or NPDCCH for a response to determine whether the uplink data transmission was successful or unsuccessful. Alternatively, the UE may receive a retransmission grant.

After performing uplink transmission based on received PUR configuration, UE expects to receive either an explicit ACK or an explicit NACK or an uplink retransmission grant on MPDCCH or NPDCCH. How to design a unified DCI for different CE modes and how to design an optimized DCI or reduced DCI to improve MPDCCH/NPDCCH detection performance is a big issue for RANI specification.

After the PUSCH transmission, UE has to monitor at least 3 search spaces in IDLE state, i.e. MPDCCH or NPDCCH type 1 common search space for paging, MPDCCH or NPDCCH type 2 common search space for RAR, and PUR search space, which could be designed as common search space for all UEs or UE-specific search space for dedicated PUR. The narrowbands of the three search spaces are RRC-configured separately, which means that the three search spaces may overlap, especially the PUR search space may overlap with MPDCCH or NPDCCH type 1 common search space or with MPDCCH or NPDCCH type 2 common search space in time domain or frequency domain. It is yet unknown how to specify UE's behavior (e.g. which search space UE should monitor) when the PUR search space overlaps with MPDCCH or NPDCCH type 1 common search space or with MPDCCH or NPDCCH type 2 common search space.

In this disclosure, the invention proposes solutions to solve the above-identified problems.

BRIEF SUMMARY

Methods and apparatuses for control signal design are disclosed.

In one embodiment, a method at a remote unit comprises transmitting a data in a predefined resource based on a resource configuration; and receiving a control signal in a first search space, wherein the control signal includes at least one of (1) a response to the data; (2) an updated TA; (3) an updated power; (4) an updated data transmission repetition; (5) a flag of retransmission based on dynamic grant or the predefined resource; (6) a fallback indication; and (7) a predefined resource release indication.

In some embodiment, the response to the data is an ACK or a NACK to the data (e.g., the uplink data transmission was successfully or unsuccessfully received). The updated TA is an index of a TA set or an index offset to an index corresponding to previously adopted TA. The updated power is an index of a power set or an index offset to an index corresponding to previously adopted power. The updated data transmission repetition is an index of a data transmission repetition set or an index offset to an index corresponding to previously adopted data transmission repetition.

In some embodiment, the method may further comprise receiving multiple sets of scheduling delay, and determining a set of scheduling delay based on a coverage mode, wherein the control signal further includes an indication of scheduling delay based on the set of scheduling delay. Alternatively, the method may further comprise receiving multiple references scheduling delays, and determining a reference scheduling delay based on a coverage mode, wherein the control signal further includes an indication of scheduling delay based on the reference scheduling delay. In other embodiment, the method may further comprise receiving multiple sets of repetition number, and determining a set of repetition number based on a coverage mode, wherein the control signal further includes an indication of repetition number based on the set of repetition number. Alternatively, the method may further comprise receiving multiple reference repetition numbers, and determining a reference repetition number based on a coverage mode, wherein the control signal further includes an indication of repetition number based on the reference repetition number.

In some embodiment, the resource configuration includes at least one of a scheduling delay set, a repetition number set, a reference scheduling delay and a reference repetition number. In this condition, the control signal further includes an indication of scheduling delay based on the scheduling delay set or the reference scheduling delay, and an indication of repetition number based on the repetition number set or the reference repetition number. The control signal may include a predefined bit pattern, wherein the predefined bit pattern indicates at least one of retransmission based on next predefined resource, fallback and predefined resource release.

In some embodiment, the method further comprises monitoring a second search space for paging message or random access, wherein the second search space is partially or fully overlapped with the first search space in a time or frequency resource. In particular, the method further determines to monitor the first search space or the second search space with one of the following manners: always monitoring the first search space; always monitoring the second search space; based on a search space indication; and based on at least one of a period of paging occasion, a period of the predefined resource, a period of control signal monitoring and a control signal monitoring window.

In some embodiment, the control signal further includes at least one of SI (System Information) modification indication, ETWS (Earthquake and Tsunami Warning System) indication and CMAS (Commercial Mobile Alert System) indication. The method may further comprise receiving a paging message, which includes the response to the data. Alternatively, the method may further comprise receiving a random access response message, which includes the response to the data.

In another embodiment, a remote unit comprises a transmitter that transmits a data in a predefined resource based on a resource configuration; and a receiver that receives a control signal in a first search space, wherein the control signal includes at least one of (1) a response to the data; (2) an updated TA; (3) an updated power; (4) an updated data transmission repetition; (5) a flag of retransmission based on dynamic grant or the predefined resource; (6) a fallback indication; and (7) a predefined resource release indication.

In yet another embodiment, a method at a base unit comprises receiving a data in a predefined resource based on a resource configuration; and transmitting a control signal, wherein the control signal includes at least one of (1) a response to the data; (2) an updated TA; (3) an updated power; (4) an updated data transmission repetition; (5) a flag of retransmission based on dynamic grant or the predefined resource; (6) a fallback indication; and (7) a predefined resource release indication.

In further embodiment, a base unit comprises a receiver that receives a data in a predefined resource based on a resource configuration; and a transmitter that transmits a control signal, wherein the control signal includes at least one of (1) a response to the data; (2) an updated TA; (3) an updated power; (4) an updated data transmission repetition; (5) a flag of retransmission based on dynamic grant or the predefined resource; (6) a fallback indication; and (7) a predefined resource release indication.

DETAILED DESCRIPTION

As will be appreciated by one skilled in the art, aspects of the embodiments may be embodied as a system, apparatus, method, or program product. Accordingly, embodiments may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may generally all be referred to herein as a “circuit”, “module” or “system”. Furthermore, embodiments may take the form of a program product embodied in one or more computer readable storage devices storing machine-readable code, computer readable code, and/or program code, referred to hereafter as “code”. The storage devices may be tangible, non-transitory, and/or non-transmission. The storage devices may not embody signals. In a certain embodiment, the storage devices only employ signals for accessing code.

Certain functional units described in this specification may be labeled as “modules”, in order to more particularly emphasize their independent implementation. For example, a module may be implemented as a hardware circuit comprising custom very-large-scale integration (VLSI) circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like.

Any combination of one or more computer readable medium may be utilized. The computer readable medium may be a computer readable storage medium. The computer readable storage medium may be a storage device storing code. The storage device may be, for example, but need not necessarily be, an electronic, magnetic, optical, electromagnetic, infrared, holographic, micromechanical, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing.

A non-exhaustive list of more specific examples of the storage device would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or Flash Memory), portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer-readable storage medium may be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device.

The code may also be loaded onto a computer, other programmable data processing apparatus, or other devices, to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the code executed on the computer or other programmable apparatus provides processes for implementing the functions specified in the flowchart and/or block diagram block or blocks.

FIG.1depicts an embodiment of a wireless communication system100for control signal design. In one embodiment, the wireless communication system100includes remote units102and base units104. Even though a specific number of remote units102and base units104are depicted inFIG.1, one skilled in the art will recognize that any number of remote units102and base units104may be included in the wireless communication system100.

The remote units102may communicate directly with one or more of the base units104via UL communication signals.

The base units104may be distributed over a geographic region. In certain embodiments, a base unit104may also be referred to as an access point, an access terminal, a base, a base station, a Node-B, an eNB, a gNB, a Home Node-B, a relay node, a device, or by any other terminology used in the art. The base units104are generally part of a radio access network that includes one or more controllers communicably coupled to one or more corresponding base units104. The radio access network is generally communicably coupled to one or more core networks, which may be coupled to other networks, like the Internet and public switched telephone networks, among other networks. These and other elements of radio access and core networks are not illustrated, but are well known generally by those having ordinary skill in the art.

In one implementation, the wireless communication system100is compliant with 3GPP 5G new radio (NR). More generally, however, the wireless communication system100may implement some other open or proprietary communication protocol.

The base units104may serve a number of remote units102within a serving area, for example, a cell (or a cell sector) or more cells via a wireless communication link. The base units104transmit DL communication signals to serve the remote units102in the time, frequency, and/or spatial domain.

The control node106is a control plane network element that handles signaling related to mobility and security for the remote units102. For example, the control node106may be a Mobility Management Entity (MME).

FIG.2depicts one embodiment of an apparatus200that may be used in the present invention. The apparatus200represents a single embodiment of the remote unit102. Such remote unit102may include a processor202, a memory204, an input device206, a display208, a transmitter210, and a receiver212. In some embodiments, the input device206and the display208are combined into a single device, such as a touch screen. In certain embodiments, the remote unit102may not include any input device206and/or a display208. In various embodiments, the remote unit102may include at least one of the processor202, the memory204, the transmitter210and the receiver212, and may not include the input device206and/or the display208.

The processor202, in one embodiment, may include or represented by any known controller capable of executing computer-readable instructions and/or capable of performing logical operations. For example, the processor202may be a microcontroller, a microprocessor, a central processing unit (CPU), a graphics processing unit (GPU), an auxiliary processing unit, a field programmable gate array (FPGA), or a similar programmable controller. In some embodiments, the processor202executes instructions stored in the memory204to perform the methods and routines described herein. The processor202is communicatively coupled to the memory204, the input device206, the display208, the transmitter210, and the receiver212.

The input device206, in one embodiment, may include any known computer input device including a touch panel, a button, a keyboard, a stylus, a microphone, or the like. In some embodiments, the input device206may be integrated with the display208, for example, as a touch screen or similar touch-sensitive display. In some embodiments, the input device206includes a touch screen such that text may be input using a virtual keyboard displayed on the touch screen and/or by handwriting on the touch screen. In some embodiments, the input device206includes two or more different devices, such as a keyboard and a touch panel.

The transmitter210is used to provide UL communication signals to the base unit104and the receiver212is used to receive DL communication signals from the base unit104. In various embodiments, the transmitter210and the receiver212may transmit and receive resources via different cells. Although only one transmitter210and one receiver212are illustrated, the remote unit102may have any suitable number of transmitters210and receivers212. The transmitter210and the receiver212may be any suitable type of transmitters and receivers. In one embodiment, the transmitter210and the receiver212may be part of a transceiver.

FIG.3depicts one embodiment of another apparatus300that may be used in the present invention. The apparatus300includes one embodiment of the base unit104. Furthermore, the base unit104may include at least one of a processor302, a memory304, an input device306, a display308, a transmitter310and a receiver312. As may be appreciated, the processor302, the memory304, the input device306, the display308, the transmitter310, and the receiver312may be substantially similar to the processor202, the memory204, the input device206, the display208, the transmitter210, and the receiver212of the remote unit102, respectively.

Although only one transmitter310and one receiver312are illustrated, the base unit104may have any suitable number of transmitters310and receivers312. The transmitter310and the receiver312may be any suitable type of transmitters and receivers. In one embodiment, the transmitter310and the receiver312may be part of a transceiver.

FIG.5illustrates a schematic diagram of a method according to the present invention. “DL” represents that in steps510and530, data or control signal is transmitted from eNB (not shown inFIG.5) to UE (not shown inFIG.5) while “UL” denotes that in step520, data is transmitted from the UE to the eNB.

Step510ofFIG.5corresponds to step 1 ofFIG.4, in which UE is in an RRC-Connected state. In the step510, PUR configuration is transmitted from eNB to the UE. Step520ofFIG.5corresponds to Step 2 ofFIG.4, during which UE is in an IDLE state while performing data transmission on PUSCH based on the PUR configuration, to the eNB. Step530ofFIG.5corresponds to step 3 ofFIG.4, in which UE is still in the IDLE state while monitoring a search space and expecting to receive explicit ACK or explicit NACK or uplink retransmission grant.

An explicit ACK or an explicit NACK or an uplink retransmission grant will be included in a control signal sent from the eNB.

It is possible to reuse traditional DCI format 6-0A or 6-0B as the control signal. However, a lot of existing fields in the DCI format 6-0A or 6-0B (such as HARQ process number, TPC command, UL index, DAI, SRS request, etc) are useless for the control signal. In view of the above, this disclosure proposes a new DCI (referred to as PUR DCI hereinafter) format to send the control signal.

The PUR DCI according to a first embodiment is described as follows.

The PUR DCI includes a field of ACK/NACK indication. The ACK/NACK indication may be 1 bit to explicitly indicate ACK (for example, value=1) or NACK (for example, value=0). The ACK signal represents that transmission on PUSCH was successfully received by the eNB. The NACK signal, on the other hand, means that transmission on PUSCH was not successfully received at the eNB.

Upon the ACK/NACK indication field indicating an ACK signal, the PUR DCI may further include parameters that may be frequently changing, such as an updated TA, updated power, updated repetition number, etc. Therefore, it is preferable that these frequently changing parameters are also updated along with ACK indication (for example, ACK/NACK indication value=1). Incidentally, the repetition number means the repetition number for the data transmitted on PUSCH.

Each of the above-mentioned parameters such as updated TA, updated power, and updated repetition number included in the control signal may be represented by an index value or an index offset value. The index value refers to an index corresponding to a value in a set, while the index offset value refers to an offset to an index corresponding to the previously adopted value.

For example, suppose the repetition number may be selected from a repetition set of {1, 2, 4, 8, 16, 32, 64, 128}, if the index value is used, then 3 bits that can indicate eight different indices are necessary to indicate one value from the repetition number set {1, 2, 4, 8, 16, 32, 64, 128}. For example, [000] may indicate repetition number being 1, [001] may indicate repetition number being 2, . . . , and [111] may indicate repetition number being 128. On the other hand, if the index offset value is used, then 1 or 2 bits are necessary to indicate the offset depending on a range of the offset. For example, if the range of the offset is {−1, 1}, i.e. one index from the previously indicated index, then 1 bit is enough. In particular, if the previously adopted repetition number is 8, which means that the index corresponding to the repetition number 8 is [011], then [0] may indicate an offset of −1, i.e. the index will be [011]−=[010], which indicates the new repetition number being 4. Similarly, [1] may indicate the offset of 1, i.e. the index will be [011]+1=[100], which indicates the new repetition number being 16. If the range of the offset is set to {−2, −1, 1, 2} or {−2, −1, 0, 1}, 2 bits are necessary to indicate the index offset value.

The number of bits (1 or 2 in the above example) for indicating the index offset is smaller than the number of bits (3 in the above example) for indicating the index. Therefore, the index offset indication is preferable than the index indication since it can reduce the number of bits used for indication.

In the situation when ACK/NACK indication field indicates a NACK, the PUR DCI may further include a retransmission type indicator field. The retransmission type indicator field may be a 1 bit filed to signal UE as to how retransmission should be performed. There are two ways for the UE to perform the retransmission. The first way is for the UE to perform retransmission based on the next PUR resource. The second way is for UE to perform retransmission based on a dynamic scheduling (i.e. upon receiving the uplink retransmission grant included in the PUR DCI). The retransmission type indicator field may be set to [1] to indicate retransmission being based on the next PUR resource or may be set to [0] to indicate retransmission being based on the dynamic scheduling.

In the condition where retransmission is being based on the next PUR resource, some adjustment parameters for the uplink retransmission may also be included in the PUR DCI, such as MCS, RV, repetition number, etc. In particular, MCS is the modulation and code scheme for the uplink retransmission. RV is the redundant version of the uplink retransmission. Repetition number is the repetition number of the uplink retransmission.

In the condition of retransmission being based on the dynamic scheduling, the following parameters may be included in the PUR DCI: resource assignment, scheduling delay, MCS, RV, repetition number, DCI repetition number. Among these parameters, the MCS, the RV and the repetition number have been previously discussed in the condition of retransmission being based on the next PUR resource. Other parameters, i.e. resource assignment, scheduling delay and the DCI repetition number are used for scheduling the uplink retransmission.

A UE may be configured in different coverage modes. There are two coverage enhancement (CE) modes specified for UE in RRC-CONNECTED state, i.e. CEmode A and CEmode B. The CEmode A describes a set of behaviors for no repetition and small number of repetitions for transmission, while the CEmode B describes a set of behaviors for a large number of repetitions to be performed for transmission. For eMTC UE in IDLE state, considering the low mobility feature, it assumes that UE in IDEL state is configured to follow the same coverage mode as in the RRC-CONNECTED state. On the other hand, the UE in IDLE state may alternatively be in CE level 1, 2, 3 or 4 or other CE level definition which may be related to different transmission repetitions. The CE level may also be regarded as CE mode. In different CE modes, the parameters such as scheduling delay set, repetition number set, etc are quite different. Therefore, it is inefficient to configure the parameters (parameter sets) included in the PUR DCI to contain all of possible values for both CEmode A and CEmode B. For example, the repetition number set for CEmode A may be {1, 2, 4, 8, 16, 32, 64, 128} while the repetition number set for CEmode B may be {32, 64, 128, 256, 512, 1024, 2048, 4096}. In this condition, if one repetition number set is configured for both CEmode A and CEmode B, the one repetition number set would be 11, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 40961, and four bits are necessary to indicate one value from the repetition number set {1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096}. On the other hand, three bits are enough for indicating the repetition number set {1, 2, 4, 8, 16, 32, 64, 128} or the repetition number set {32, 64, 128, 256, 512, 1024, 2048, 4096}.

In view of the above, this disclosure proposes that eNB configures two sets of parameters (scheduling delay set, repetition number set) for CEmode A and CEmode B separately via a broadcast channel (e.g., SIB1). UE determines a set of parameters based on its CE mode. For example, the repetition number set is {1, 2, 4, 8, 16, 32, 64, 128} for CEmode A and is {32, 64, 128, 256, 512, 1024, 2048, 4096} for CEmode B. When a UE receives a repetition number index [010] in DCI, the UE in CEmode A will recognize that the repetition number will be configured as 4 based on the repetition number set configured for CEmode A while the UE in CEmode B will recognize that the repetition number will be configured as 128 based on the repetition number set configured for CEmode B.

In the above example, different sets (e.g. different repetition number sets) for CEmode A and CEmode B are broadcasted to the UE. Alternatively, the eNB may send, via PUR configuration, a particular set (e.g. a particular repetition number set and/or a particular scheduling delay set) to a UE to indicate the particular set for that UE. For example, the eNB may send a repetition number set {1, 2, 4, 8, 16, 32, 64, 128} to a UE if the UE is configured as CEmode A while send another repetition number set {32, 64, 128, 256, 512, 1024, 2048, 4096} to another UE if the other UE is configured as CEmode B.

In the above, the set(s) (e.g. repetition number set(s)) is/are broadcasted to or directly sent to the UE. Alternatively, a reference value (for example, the maximum value or the minimum value) contained in a set rather than the set itself may be broadcasted or sent to the UE. As the UE knows in advance the rule for constructing the set from the reference value, the UE may know the set when receiving the reference value. For example, for the repetition number set {1, 2, 4, 8, 16, 32, 64, 128} to be sent to the UE, the eNB may only send a reference repetition number (for example, the maximum repetition number Rmax=128, or the minimum repetition number Rmin=1) to the UE to indicate the repetition number set as {Rmax/128, Rmax/64, . . . , Rmax/2, Rmax}={1, 2, 4, 8, 16, 32, 64, 128}. This is possible because UE knows in advance the rule for constructing the repetition number set {1, 2, 4, 8, 16, 32, 64, 128} from the reference repetition number. Similarly, the eNB may configure multiple (e.g. two) reference values (e.g. reference scheduling delays, reference repetition numbers) for CEmode A and CEmode B separately, and broadcast or directly send them to the UE. For example, the UE may receive multiple reference scheduling delays and determine a reference scheduling delay based on its coverage mode (CEmode A or CEmode B). The UE may receive multiple reference repetition numbers and determine a reference repetition number based on its coverage mode (CEmode A or CEmode B). The reference value might be any value within the set. For example, the reference value may be the maximum value or the minimum value within the set.

The PUR DCI further includes an indication of scheduling delay based on the set of scheduling delay or the reference scheduling delay. The PUR DCI further includes an indication of repetition number based on the set of repetition number or the reference repetition number.

The PUR DCI further includes a fallback indication field. The fallback indication field may be 1 bit and used to indicate the UE to change from IDLE state to RRC-CONNECTED state and perform transmission via EDT (Early Data Transmission) or RACH.

Optionally, the PUR DCI may further include a predefined resource release indication field. The predefined resource release indication field may be 1 bit and used to indicate that the predefined resource configured in resource configuration is released.

Table 1 shows an example of PUR DCI content according to the first embodiment.

Table 1 does not contain the optional predefined resource release indication field. From the Table 1, it can be seen that the PUR DCI includes only 13 bits, that is significantly smaller than DCI format 6-0A or 6-0B. In addition, since different parameter sets (or different reference parameters) may be sent to the UE in advance, it is unnecessary to design two different PUR DCIs for CEmode A and CEmode B separately.

Incidentally, as can be seen from Table 1, except for the ACK/NACK field and the fallback indication field, the same bit may be used for different fields. For example, when the ACK/NACK field is 1 (ACK), there is no retransmission type field. Therefore, the bit for indicating the retransmission type in the condition of the ACK/NACK field being 0 (NACK) may be used for indicating a part of the updated TA.

In the PUR DCI according to the first embodiment, when the transmission on PUSCH by the UE in IDLE state is unsuccessfully received at the eNB, one bit in the PUR DCI is used to explicitly indicate the retransmission being based on the next PUR resource or based on the dynamic scheduling. In the PUR DCI according to a second embodiment, when the transmission on PUSCH by the UE in IDLE state is unsuccessfully received at the eNB, the dynamic scheduling is assumed.

Table 2 shows an example of PUR DCI according to the second embodiment.

According to the second embodiment, the retransmission type field is not included. In the condition of ACK/NACK indication field indicating NACK (ACK/NACK field being set to 0), it is assumed that the retransmission is based on dynamic scheduling.

On the other hand, a predefined bit pattern of the PUR DCI may be used for indicating retransmission based on next PUR configuration. The predefined bit pattern means that one state of one field or one state for several fields in the PUR DCI is reserved. For example, suppose that the field for indicating resource assignment includes 4 bits, when the resource assignment field is [0000], it is not used to indicate resource assignment but used (reserved) to indicate retransmission based on next PUR. For another example, suppose that the field for indicating resource assignment includes 4 bits and the field for indicating scheduling delay includes 3 bits, when the resource assignment field is [0000] and the scheduling delay field is [111], it is used (reserved) to indicate retransmission based on next PUR.

The above-identified predefined bit pattern can be also used to indicate releasing PUR resource and/or fallback indication. That is, a second predefined bit pattern of the PUR DCI may be reserved for indicating releasing PUR resource. For example, suppose that the field for indicating resource assignment includes 4 bits and the field for indicating scheduling delay includes 3 bits, when the resource assignment field is [1111] and the scheduling delay field is [000], it is used (reserved) to indicate releasing PUR resource. A third predefined bit pattern of the PUR DCI may be reserved for indicating fallback. For example, suppose that the field for indicating repetition number includes 2 bits and the field for DCI repetition number includes 2 bits, when the repetition number field is [11] and the DCI repetition number field is [00], it is used (reserved) to indicate to fall back to EDT or RACH procedures.

In the above first and second embodiments, the UE monitors a search space where it expects to receive PUR DCI. The search space may be a common search space for all UEs or a UE-specific search space for a dedicated PUR (both are referred to as a PUR search space). That is to say, after data is transmitted on PUSCH, UE will monitor the PUSCH search space.

However, in IDLE state, UE also has to monitor the MPDCCH or NPDCCH type 1 common search space for paging and MPDCCH or NPDCCH type 2 common search space for RAR.

There is a possibility that the PUR search space might overlap with the type 1 common search space for paging or with the type 2 common search space for RAR in time or frequency domain. The overlapping may be a full or partial overlapping. In the condition of overlapping, the UE has to determine which search space to monitor.

A third embodiment proposes several options in the condition of search space overlapping.

In a first option, the UE is not required to monitor the MPDCCH or NPDCCH type 1 common search space or MPDCCH or NPDCCH type 2 common search space if either of the search space overlaps with the PUR search space. That is to say, the UE only monitors the PUR search space when the PUR search space overlaps with the MPDCCH or NPDCCH type 1 common search space or with the MPDCCH or NPDCCH type 2 common search space.

In a second option, the UE is not required to simultaneously monitor the PUR search space and the type 1 common search space or the type 2 common search space. That is to say, it is up to UE implementation that determines whether the UE monitors the PUR search space or monitors the type 1 common search space and the type 2 common search space. For example, the UE may always monitor the PUR search space. Alternatively, the UE may always monitor MPDCCH or NPDCCH type 1 common search space or the MPDCCH or NPDCCH type 2 common search space.

In a third option, the UE is expected to monitor the search space configured by the eNB. In the condition of search space overlapping, the eNB configures the UE which search space (the PUR search space or the type 1 common search space or the type 2 common search space) should be monitored.

In a fourth option, the UE is expected to monitor the search space determined by at least one of {period of paging occasion, period of predefine resource, period of control signal period, control signal monitoring window, etc}. For example, if the period of paging occasion is larger than a first threshold, the search space is always MPDCCH or NPDCCH type 1 common search space. If the control signal monitoring window is smaller than a second threshold, the search space is always PUR search space.

Due to search space overlapping, the paging message may be missed by the UE, for example, by the reason that the UE chooses or is required to monitor the PUR search space while the MPDCCH or NPDCCH type 1 common search space is not monitored. In this condition, urgent paging information (for example, SI modification, ETWS and CMAS) can be included in the PUR DCI transmitted within the PUR search space. The PUR DCI may reserve some bits (or some states of particular fields) for urgent paging information indication.

On the other hand, if the PUR DCI is missed due to the search space overlapping, ACK/NACK information can be included in paging DCI (the DCI derived by searching the type 1 common search space for paging), for example by using a predefined bit pattern of the paging DCI, i.e. the reserved bits or unused states or combined states of several fields, to indicate the ACK or NACK to the uplink transmission based on PUR. In particular, the ACK/NACK information is included in the paging DCI when the type 1 common search space will be searched in the condition of search space overlapping. Similarly, the ACK/NACK information may be included in RAR DCI (the DCI derived by searching the type 2 common search space for RAR) in a similar manner, especially when the type 2 common search space will be searched in the condition of search space overlapping.