CN107046726B

CN107046726B - Method and apparatus for providing transmission status of unlicensed carrier

Info

Publication number: CN107046726B
Application number: CN201610084100.6A
Authority: CN
Inventors: 孟艳; 刘建国; 陶涛; 谷俊嵘; 叶思根; 沈钢
Original assignee: Nokia Shanghai Bell Co Ltd; Alcatel Lucent SAS
Current assignee: Nokia Shanghai Bell Co Ltd; Alcatel Lucent SAS
Priority date: 2016-02-05
Filing date: 2016-02-05
Publication date: 2020-10-02
Anticipated expiration: 2036-02-05
Also published as: CN107046726A

Abstract

Embodiments of the present disclosure provide methods and apparatus for providing a transmission status of an unlicensed carrier in licensed-assisted access, and methods and apparatus for determining a transmission status of an unlicensed carrier in licensed-assisted access. The method for providing a transmission state of an unlicensed carrier in licensed-assisted access includes: in response to receiving an uplink scheduling grant from a base station, listening for a transmission state of an unlicensed carrier on an uplink channel; and providing an indication of the transmission status to the base station based on the snooping. The embodiments of the present disclosure enable a base station to know a transmission state of an uplink, thereby being able to perform a corresponding operation according to the transmission state of the uplink.

Description

Method and apparatus for providing transmission status of unlicensed carrier

Technical Field

Embodiments of the present disclosure relate generally to wireless communication technologies, and more particularly, to a method and apparatus for providing a transmission state of an unlicensed carrier in a License Assisted Access (LAA), and a method and apparatus for determining a transmission state of an unlicensed carrier in a LAA.

Background

At the 70 th conference of RAN, LTE enhanced licensed assisted access (eLAA-LTE) was approved to support Uplink (UL) operation of the secondary cell (SCell) of LAA in unlicensed spectrum, see in particular proposal RP-152272 ("New WorkItem on enhanced LAA for LTE", Ericsson, Huawei, 2015, 12/7/12/10). In particular, self-scheduling and cross-carrier scheduling of UL transmissions of the licensed spectrum should be supported simultaneously. If the eLAA design complies with the European requirements for Listen Before Talk (LBT) specifications (ETSI EN 301893 (V1.8.0), "harmonic EN coverage of the scientific requirements of the R & TTE Directive," month 2015), the transmitter is required to perform LBT prior to transmission. For cross-carrier scheduling, UL grants (grants) are transmitted from the licensed carriers. Based on the UL grant, a User Equipment (UE) can perform LBT prior to its UL transmission. In this case, only one LBT operation is required for eLAAUL transmission. However, for self-scheduling, the eLAA UL transmission then requires two consecutive LBT operations, namely LBT performed by the eLAA eNB before the UL grant transmission and LBT performed by the UE before the UL data transmission.

In both cases, each scheduled UE should perform LBT for UL transmission after receiving a UL grant from the eNB. If the channel is idle, the UE can transmit data as commanded by the eNB. Otherwise, the UE will not transmit a Physical Uplink Shared Channel (PUSCH). Each UE performs UL transmission based on its own listening result. The uncertainty of the UL transmission will affect the behavior of the eNB.

First, the eNB is not aware of whether the UE has already transmitted. If the eNB blindly decodes the PUSCH (without detecting whether the PUSCH is transmitted or not), in case the eNB cannot correctly decode the PUSCH, it will be unclear by the eNB whether the UE terminated transmission of the PUSCH because the channel is busy, or the UE had transmitted the PUSCH, but the eNB failed to correctly decode the PUSCH. This makes it difficult for the eNB to combine appropriate Hybrid Automatic Retransmission (HARQ) with subsequent retransmissions. Regardless of whether the eNB stores soft bits from this "hypothesized" transmission, performance will degrade when the eNB's soft buffer processing does not match the actual transmission state.

Second, when PUSCH decoding fails, the eNB does not know whether the UE has lost the UL grant or has not transmitted PUSCH because the channel is busy. This makes it difficult for the eNB to perform proper link adaptation for UL grants.

Disclosure of Invention

Therefore, in order to solve or at least partially alleviate the above problems in the prior art, there is a need to introduce a mechanism to let the eNB know the UL transmission status in the LAA.

According to a first aspect of embodiments of the present disclosure, a method for providing a transmission status of an unlicensed carrier is provided. The method comprises the following steps: in response to receiving an uplink scheduling grant from a base station, listening for a transmission state of an unlicensed carrier on an uplink channel; and providing an indication of the transmission status to the base station based on the snooping.

In some embodiments, providing the indication of the transmission status to the base station based on the snooping comprises: providing a signal known to the base station as an indication of the transmission status; and transmitting the known signal to the base station together with uplink data.

In some embodiments, providing a signal known to the base station as the indication of the transmission status comprises: the known signal is provided in a predefined symbol of the scheduled subframe.

In some embodiments, the predefined symbol comprises: a symbol at a middle position of a first slot and a middle position of a second slot of the scheduled subframe.

In some embodiments, the predefined symbol further comprises: a symbol at a start position of at least one of the first slot and the second slot.

In some embodiments, providing the indication of the transmission status to the base station based on the snooping comprises: transmitting signaling to the base station including an indication of the transmission status.

In some embodiments, transmitting signaling to the base station including the indication of the transmission status comprises: acquiring resources of an uplink control channel for transmitting the signaling from the base station; and transmitting the signaling by using the resource of the uplink control channel.

In some embodiments, acquiring resources of an uplink control channel for transmitting the signaling from the base station comprises: acquiring a starting position of the resource configured by the base station in a semi-static manner and an offset configured by the base station in a dynamic manner relative to the starting position.

In some embodiments, obtaining the dynamically configured offset of the base station relative to the starting position comprises: the offset is determined based on a resource allocation for uplink transmission on the unlicensed carrier.

In some embodiments, obtaining the dynamically configured offset of the base station relative to the starting position comprises: receiving a downlink control information message including the offset from the base station.

In some embodiments, acquiring resources of an uplink control channel for transmitting the signaling from the base station comprises: the method comprises the steps of obtaining a plurality of candidate resources configured by the base station in a semi-static mode and an index of one of the candidate resources configured by the base station in a dynamic mode.

In some embodiments, transmitting the signaling using the resources of the uplink control channel comprises: transmitting the signaling in a current subframe or a next subframe of the uplink control channel based on a time at which the listening is performed.

In some embodiments, transmitting signaling to the base station including the indication of the transmission status comprises: transmitting the signaling to the base station by multiplexing the signaling with uplink data before or after discrete Fourier transform.

In some embodiments, multiplexing the signaling with uplink data comprises: the signaling is multiplexed with uplink data on predefined resource elements.

In some embodiments, wherein multiplexing the signaling with uplink data after the discrete fourier transform comprises: the signaling is provided at a start position of a first slot and a start position of a second slot of the scheduled subframe.

In some embodiments, wherein transmitting the signaling comprising the indication of the transmission status to the base station comprises: transmitting the signaling on the unlicensed carrier in response to success of the listening; and transmitting the signaling on the licensed carrier allocated by the base station in response to the failure to listen.

In some embodiments, the method further comprises: in response to success of the sensing, an indication of a starting location of an uplink data transmission is provided to the base station on a licensed carrier allocated by the base station.

In some embodiments, wherein the indication of the starting position indicates one symbol in the scheduled subframe.

According to a second aspect of embodiments of the present disclosure, there is provided a method for determining a transmission status of an unlicensed carrier. The method comprises the following steps: receiving, from a user equipment, an indication of a transmission status of an unlicensed carrier on an uplink channel; and determining a transmission status of the unlicensed carrier based on the indication of the transmission status.

In some embodiments, receiving, from the user equipment, the indication of the transmission status of the unlicensed carrier on the uplink channel comprises: a signal known to a base station is received as an indication of the transmission status, wherein the known signal is received with uplink data.

In some embodiments, receiving a signal known to the base station as the indication of the transmission status comprises: the known signal is received from a predefined symbol of a scheduled subframe.

In some embodiments, receiving, from the user equipment, the indication of the transmission status of the unlicensed carrier on the uplink channel comprises: signaling comprising an indication of the transmission status is received from the user equipment.

In some embodiments, the signalling comprising the indication of the transmission status is received from the user equipment: configuring resources of an uplink control channel for transmitting the signaling for the user equipment; and receiving the signaling on the uplink control channel.

In some embodiments, configuring the resource of the uplink control channel for transmitting the signaling for the user equipment comprises: configuring a starting position of the resource in a semi-static manner; and configuring the offset relative to the starting position in a dynamic manner.

In some embodiments, dynamically configuring the offset relative to the starting position comprises: and sending the downlink control information message comprising the offset to the user equipment.

In some embodiments, configuring the resource of the uplink control channel for transmitting the signaling for the user equipment comprises: configuring a plurality of candidate resources in a semi-static manner; and dynamically configuring an index of one of the plurality of candidate resources.

In some embodiments, receiving the signaling comprising the indication of the transmission status from the user equipment comprises: the signaling is received multiplexed with uplink data before or after performing a discrete fourier transform at the user equipment.

In some embodiments, receiving the signaling multiplexed with uplink data comprises: the signaling multiplexed with the uplink data is received on a predefined resource element.

In some embodiments, receiving the signaling multiplexed with uplink data after performing a discrete fourier transform at the user equipment comprises: the signaling is received at a start position of a first slot and a start position of a second slot of the scheduled subframe.

In some embodiments, the method further comprises: an indication of a starting position for an uplink data transmission is received on the allocated licensed carrier.

In some embodiments, the indication of the starting position indicates one symbol in the scheduled subframe.

According to a third aspect of embodiments of the present disclosure, there is provided an apparatus for providing a transmission status of an unlicensed carrier. The device includes: a listening unit configured to listen to a transmission state of an unlicensed carrier on an uplink channel in response to receiving an uplink scheduling grant from a base station; and a providing unit configured to provide an indication of the transmission status to the base station based on the listening.

In some embodiments, the providing unit is further configured to: providing a signal known to the base station as an indication of the transmission status; and transmitting the known signal to the base station together with uplink data.

In some embodiments, the providing unit is further configured to: the known signal is provided in a predefined symbol of the scheduled subframe.

In some embodiments, the providing unit is further configured to: transmitting signaling to the base station including an indication of the transmission status.

In some embodiments, the providing unit is further configured to: acquiring resources of an uplink control channel for transmitting the signaling from the base station; and transmitting the signaling by using the resource of the uplink control channel.

In some embodiments, the providing unit is further configured to: acquiring a starting position of the resource configured by the base station in a semi-static manner and an offset configured by the base station in a dynamic manner relative to the starting position.

In some embodiments, the providing unit is further configured to: the offset is determined based on a resource allocation for uplink transmission on the unlicensed carrier.

In some embodiments, the providing unit is further configured to: receiving a downlink control information message including the offset from the base station.

In some embodiments, the providing unit is further configured to: the method comprises the steps of obtaining a plurality of candidate resources configured by the base station in a semi-static mode and an index of one of the candidate resources configured by the base station in a dynamic mode.

In some embodiments, the providing unit is further configured to: transmitting the signaling in a current subframe or a next subframe of the uplink control channel based on a time at which the listening is performed.

In some embodiments, the providing unit is further configured to: transmitting the signaling to the base station by multiplexing the signaling with uplink data before or after discrete Fourier transform.

In some embodiments, the providing unit is further configured to: the signaling is multiplexed with uplink data on predefined resource elements.

In some embodiments, the providing unit is further configured to: the signaling is provided at a start position of a first slot and a start position of a second slot of the scheduled subframe.

In some embodiments, wherein the providing unit is further configured to: transmitting the signaling on the unlicensed carrier in response to success of the listening; and transmitting the signaling on the licensed carrier allocated by the base station in response to the failure to listen.

In some embodiments, wherein the providing unit is further configured to: in response to success of the sensing, an indication of a starting location of an uplink data transmission is provided to the base station on a licensed carrier allocated by the base station.

According to a fourth aspect of embodiments of the present disclosure, there is provided an apparatus for determining a transmission status of an unlicensed carrier. The device includes: a receiving unit configured to receive, from a user equipment, an indication of a transmission status of an unlicensed carrier on an uplink channel; and a determining unit configured to determine a transmission status of the unlicensed carrier based on the indication of the transmission status.

In some embodiments, the receiving unit is further configured to: a signal known to a base station is received as an indication of the transmission status, wherein the known signal is received with uplink data.

In some embodiments, the receiving unit is further configured to: the known signal is received from a predefined symbol of a scheduled subframe.

In some embodiments, the receiving unit is further configured to: signaling comprising an indication of the transmission status is received from the user equipment.

In some embodiments, the apparatus further comprises: a configuration unit configured to configure, by the ue, resources of an uplink control channel for transmitting the signaling; and the receiving unit is further configured to receive the signaling on the uplink control channel.

In some embodiments, the configuration unit is further configured to: configuring a starting position of the resource in a semi-static manner; and configuring the offset relative to the starting position in a dynamic manner.

In some embodiments, the configuration unit is further configured to: and sending the downlink control information message comprising the offset to the user equipment.

In some embodiments, the configuration unit is further configured to: configuring a plurality of candidate resources in a semi-static manner; and dynamically configuring an index of one of the plurality of candidate resources.

In some embodiments, the receiving unit is further configured to: the signaling is received multiplexed with uplink data before or after performing a discrete fourier transform at the user equipment.

In some embodiments, the receiving unit is further configured to: the signaling multiplexed with the uplink data is received on a predefined resource element.

In some embodiments, the receiving unit is further configured to: the signaling is received at a start position of a first slot and a start position of a second slot of the scheduled subframe.

In some embodiments, the receiving unit is further configured to: an indication of a starting position for an uplink data transmission is received on the allocated licensed carrier.

Embodiments of the present disclosure enable a base station to know a transmission state of an uplink, so that corresponding operations, such as appropriate hybrid automatic repeat and repeat combining and link adaptation, can be performed according to the transmission state of the uplink.

Drawings

The features, advantages and other aspects of various embodiments of the present disclosure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which several embodiments of the present disclosure are shown by way of illustration and not limitation. In the drawings:

fig. 1 shows a flow diagram of a method for providing a transmission status of an unlicensed carrier according to a first aspect of an embodiment of the present disclosure;

fig. 2 shows a flow chart of a method for determining a transmission status of an unlicensed carrier according to a second aspect of an embodiment of the present disclosure;

fig. 3 schematically illustrates LBT for multi-subframe scheduling according to an embodiment of the present disclosure;

fig. 4 schematically illustrates LBT for single subframe scheduling according to an embodiment of the present disclosure;

fig. 5 schematically illustrates DMRS transmissions according to an embodiment of the disclosure;

fig. 6 schematically illustrates an enhanced DMRS transmission according to an embodiment of the present disclosure;

fig. 7 schematically shows transmission status indications for the case where data transmission starts at a subframe boundary scheduled for a single subcarrier;

fig. 8 schematically shows transmission status indications for a case where data transmission starts at a subframe boundary scheduled for a plurality of subcarriers;

fig. 9 schematically shows transmission status indications for the case where data transmission starts after a subframe boundary for single subcarrier scheduling;

fig. 10 schematically shows transmission status indications for a case where data transmission is started after a subframe boundary scheduled for a plurality of subcarriers;

fig. 11 schematically illustrates resource multiplexing between PUSCH and explicit signaling according to an embodiment of the present disclosure;

fig. 12 schematically illustrates resource mapping for explicit signaling according to an embodiment of the present disclosure;

fig. 13 illustrates a block diagram of an apparatus for providing a transmission status of an unlicensed carrier according to a third aspect of an embodiment of the present disclosure; and

fig. 14 shows a block diagram of an apparatus for determining a transmission status of an unlicensed carrier according to a fourth aspect of an embodiment of the present disclosure.

Detailed Description

The principles of the subject matter described herein will now be described with reference to a number of exemplary embodiments. It should be understood that these embodiments are described merely to enable those skilled in the art to better understand and thereby implement the subject matter described herein, and are not intended to limit the scope of the subject matter described herein in any way.

The term "base station" (BS) as used herein may refer to a node B (NodeB or NB), an evolved node B (eNodeB or eNB), a Remote Radio Unit (RRU), a Radio Head (RH), a Remote Radio Head (RRH), a relay, a low power node, such as a pico base station, a femto base station, and the like.

The term "user equipment" (UE) as used herein refers to any device capable of communicating with a BS. As an example, the UE may include a terminal, a Mobile Terminal (MT), a Subscriber Station (SS), a Portable Subscriber Station (PSS), a Mobile Station (MS), or an Access Terminal (AT).

According to a first aspect of embodiments of the present disclosure, a method for providing a transmission status of an unlicensed carrier is provided. Fig. 1 shows a flow diagram of a method 100 for providing a transmission status of an unlicensed carrier according to a first aspect of an embodiment of the present disclosure. The method 100 may be performed by a UE in a wireless communication network, in particular, the method 100 may be performed by an apparatus 1300 described later herein with reference to fig. 13.

The method 100 begins at step S110. In step S110, the UE listens to the transmission status of the unlicensed carrier on the uplink channel in response to receiving the uplink scheduling grant from the base station. Sensing the transmission status of the unlicensed carrier on the uplink channel may include, for example, performing LBT on the uplink channel. It can be understood that the success of performing interception or LBT on the uplink channel indicates that the uplink channel is in an idle state; and the failure of carrying out interception or LBT failure on the uplink channel indicates that the uplink channel is in a busy state.

Next, in step S120, the UE provides an indication of the transmission status of the unlicensed carrier to the base station based on the listening.

According to a second aspect of embodiments of the present disclosure, there is provided a method for determining a transmission status of an unlicensed carrier. Fig. 2 shows a flow chart of a method 200 for determining a transmission status of an unlicensed carrier according to a second aspect of an embodiment of the present disclosure. The method 200 may be performed by an eNB in a wireless communication network, and in particular, the method 200 may be performed by an apparatus 1400 described later herein with reference to fig. 14.

The method 200 begins at step S210. In step S210, the eNB receives an indication of the transmission status of the unlicensed carrier on the uplink channel from the UE. Next, in step S220, the eNB determines a transmission status of the unlicensed carrier based on the indication of the transmission status.

In the following, the details of the

methods

100 and 200 will be described in connection with two specific embodiments according to the present disclosure.

First embodiment

Before describing two specific embodiments according to the present disclosure, LBT for two scheduling mechanisms (i.e., multi-subframe scheduling and single-subframe scheduling) employed in current LAA systems is first discussed.

Fig. 3 schematically illustrates LBT for multi-subframe scheduling according to an embodiment of the present disclosure. As shown in fig. 3, for multi-subframe scheduling, all UEs scheduled in the same burst transmission may perform LBT simultaneously and start UL transmission (e.g., PUSCH transmission) simultaneously if LBT succeeds. In the case where a plurality of UL subframes are continuously scheduled for the same UE, once the UE starts UL transmission, the UE does not have to perform listening for UL transmission on the remaining subframes in one burst transmission.

Fig. 4 schematically illustrates LBT for single subframe scheduling according to an embodiment of the present disclosure. As shown in fig. 4, for single subframe scheduling, LBT is performed in every UL subframe. In the example shown in fig. 4, the last symbol in each UL subframe is reserved as an idle period for LBT.

Two specific embodiments according to the present disclosure will be described below based on the above two scheduling mechanisms.

In a first embodiment, providing an indication of a transmission status of an unlicensed carrier to a base station based on snooping comprises: providing a signal known to the eNB as an indication of the transmission status; and transmitting the known signal to the eNB together with the uplink data. examples of signals known to the eNB include, but are not limited to: modulated Reference Signal (DMRS) in some embodiments, providing a signal known to the eNB as an indication of the transmission status includes: the known signal is provided in a predefined symbol of the scheduled subframe.

For purposes of illustration, the provision of an indication of the transmission status of an unlicensed carrier will be described below with DMRS as an example of a known signal. However, it should be understood that any other suitable known signal may also be employed, and the scope of the present disclosure is not limited in this respect.

In current LTE systems, DMRS is always transmitted together with data in each subframe over the entire Physical Resource Block (PRB), as shown in fig. 5. Two DMRS symbols, i.e., a symbol at a middle position of the first slot (symbol #3) and a symbol at a middle position of the second slot (symbol #10), are transmitted within one subframe. DMRS is used for channel estimation and UL data demodulation in LTE systems. Accordingly, whether there is UL burst transmission can be determined by detecting whether DMRS exists. The eNB may blindly detect DMRSs transmitted with data in each subframe. After the eNB detects the presence of the DMRS signal, the eNB will know that the UE has transmitted data. Otherwise, it will be assumed that no data is transmitted from the UE.

In particular, DMRS has good autocorrelation and cross-correlation of Constant Amplitude Zero Autocorrelation (CAZAC) sequences, which are envelope sequences with zero autocorrelation. Once the selected number of resource blocks is known, the length of the CAZAC sequence is fixed, and thus the mapping of frequency domain locations is also fixed. This means that the eNB has full knowledge of the DMRS for each UE, since scheduling is performed by the eNB. There is one OFDM symbol for DMRS in each slot, so the eNB can correlate between the received signal and the DMRS in the DMRS symbol. The correlation peak may indicate the presence of DMRS or indicate the presence of UL transmissions. For example, if the correlation peak is above a predetermined threshold, it may be considered that data was transmitted on the unlicensed carrier; otherwise, no data is considered to be transmitted.

If multiple DMRSs are transmitted in multiple symbols of a subframe, a UL transmission may be considered to be present in the subframe as long as the presence of a DMRS in one symbol is detected; otherwise, no UL transmission is considered to be present.

For a multi-subframe scheduling scenario, to reduce the complexity of detection, DMRS detection operations may be performed only on the first subframe of a burst transmission. However, DMRS detection performance may be improved if DMRS detection for multiple subframes is jointly employed. For example, as long as DMRS is detected to be present in one of the subframes, it can be considered that UL transmission is present in the burst transmission; otherwise, no UL transmission is considered to be present.

Since the interference of the unlicensed spectrum is bursty, the strength of the interference may be different for each OFDM symbol in one subframe. For example, a shorter WiFi packet (e.g., ACK/RTS/CTS, etc.) may affect only one or two OFDM symbols, while a longer WiFi packet may affect multiple subframes. Therefore, DMRS detection may be inaccurate due to the presence of bursty interference in the LAA system. For example, if both DMRS symbols are corrupted by WiFi interference, the results of DMRS detection may be erroneous.

Further, the length of the DMRS sequence depends on the number of resource blocks allocated to the UE. If the length of the DMRS sequence is too short due to the small number of allocated resource blocks, the performance of DMRS detection may not be good enough.

To improve the performance of DMRS detection, enhanced DMRS transmissions with increased density in the time domain, which density is configurable, may be employed to achieve greater diversity gain. For example, the DMRS may be transmitted in more OFDM symbols of the entire subframe. For example, in addition to transmitting the DMRS in a symbol at the middle position of the first slot and the middle position of the second slot of the subframe (as shown in fig. 5), the DMRS may be additionally transmitted in a symbol at the start position of at least one of the first slot and the second slot of the subframe. Fig. 6 schematically illustrates enhanced DMRS transmissions according to an embodiment of the present disclosure. In the example shown in fig. 6, the DMRS is additionally transmitted in a symbol (i.e., symbol #7) at the start position of the second slot of the subframe. Alternatively, the DMRS may be additionally transmitted in any other symbol. For example, the DMRS may be additionally transmitted in a symbol (i.e., symbol #0) of a start position of a first slot of a subframe. As the DMRS density increases, channel estimation and detection performance may be improved. On the other hand, the complexity of DMRS detection may slightly increase and overhead may also increase. Therefore, a tradeoff between detection performance and overhead is needed.

Enhanced DMRS transmissions according to embodiments of the present disclosure may also be used to enhance the performance of DMRS detection when multiple starting locations of data transmission are supported. For example, transmission of data may begin at two symbols. If the starting position of data transmission is at symbol #7, only one DMRS symbol is transmitted in the second slot in case of the transmission scheme shown in fig. 5. This may lead to unacceptable DMRS detection performance. In this case, additional DMRS symbols may be used to improve DMRS detection performance. Also, the position of the additional DMRS symbol may be different due to a difference in a starting position of UL transmission. For example, when UL transmission starts at symbol #0, the location of the additional DMRS symbol may be at symbol # 0; and when UL transmission starts at symbol #7, the location of the additional DMRS symbol may be at symbol # 7.

Second embodiment

In a second embodiment, providing an indication of the transmission status to the eNB based on the listening for the transmission status of the unlicensed carrier comprises: transmitting signaling to the eNB including an indication of the transmission status. In other words, in the second embodiment, display signaling is employed to carry an indication of the transmission status of the unlicensed carrier to inform the eNB whether there is an actual UL transmission. The explicit signaling may be transmitted on a licensed carrier or on an unlicensed carrier. For example, when LBT is successful, the UE may transmit the explicit signaling on the unlicensed carrier; and when LBT fails, the UE may transmit the explicit signaling on the licensed carrier allocated by the eNB.

In the case where the display signaling is employed to carry an indication of the transmission status of the unlicensed carrier, the UE may, for example, employ any of the following three options for transmission.

First option

In a first option, the explicit signaling is transmitted on the UL control channel (e.g., PUCCH) on the licensed carrier or (if an unlicensed carrier is supported) on the unlicensed carrier.

To be able to transmit this explicit signaling on the UL control channel, the eNB should signal the UE's resources of the UL control channel (e.g., PUCCH resources) for the transmission of this explicit signaling. The resource indication may be made via semi-static signaling, dynamic signaling, or a combination thereof.

As one example, the eNB configures a starting location of the resource in a semi-static manner and an offset from the starting location in a dynamic manner. In this example, the UE may determine the offset based on a resource allocation for uplink transmission on the unlicensed carrier.

As another example, the eNB configures a starting location of the resource in a semi-static manner and an offset from the starting location in a dynamic manner. In this example, the eNB sends a Downlink Control Information (DCI) message to the UE including the offset. Currently, the DCI message is used to carry the UL grant. According to this example, a field in the DCI message may be additionally employed to indicate the frequency shift.

As yet another example, the eNB configures a plurality of candidate resources in a semi-static manner and configures an index of one of the plurality of candidate resources in a dynamic manner. In this example, the eNB sends a DCI message including the index to the UE.

The offset from the resource start position, which is configured in a dynamic manner, and the index of one of the multiple candidate resources provides the eNB with some flexibility in resolving possible PUCCH resource collisions between UEs.

In LAA, data transmission (e.g., PUSCH transmission) may be started at or immediately after a subframe boundary of a scheduled subframe. Depending on the location of the LBT slot. One candidate LBT scheme is: a single LBT slot is fixedly immediately before the PUSCH transmission. The LBT slot before PUSCH transmission may be located before the start position of the UL subframe or the boundary of the UL subframe. In the LBT slot, the eNB and the UE are not allowed to transmit any signal. Once the UE succeeds in performing LBT, the UE starts PUSCH transmission. The UE that failed to perform LBT will terminate the PUSCH transmission.

PUSCH may start in the middle of one subframe after LBT success if partial subframe transmission is supported.

Thus, the explicit signaling may be transmitted in a current subframe or a next subframe of an uplink control channel based on the time at which LBT is performed. Specifically, the UE may transmit in any one of the following three cases.

a) Case 1: starting data transmission at subframe boundary

For this case, LBT may be performed at the last symbol of the previous subframe. The explicit signaling is transmitted on a configured PUCCH resource on a licensed or unlicensed carrier in the current subframe.

For example, for single subframe scheduling as shown in fig. 7, LBT is performed in each UL subframe. Thus, an indication of the transmission status of the unlicensed carrier should be transmitted in each subframe. Further, signaling comprising the indication is transmitted on the PUCCH of the current subframe. If the signaling is transmitted on the unlicensed carrier, a shortened format of the PUCCH may be employed. The shortened format of PUCCH does not use the last symbol in the subframe, leaving the last symbol to the next subframe for LBT.

As another example, for multi-subframe scheduling as shown in fig. 8, LBT is performed only in the first subframe of a burst transmission. Thus, the explicit signaling need only be transmitted in the first subframe of the burst transmission, and need not be transmitted in the remaining subframes of the burst transmission. Thereby, the signaling overhead is reduced compared to the case of single subframe scheduling.

b) Case 2: starting data transmission after subframe boundary

For this case, LBT may be performed at a subframe boundary and data transmission may start after the subframe boundary (i.e., at symbol # 2).

If the explicit signaling is transmitted on the configured PUCCH resource on the licensed carrier, it should be transmitted on the PUCCH of the next subframe, as shown in fig. 9 and 10. For example, as shown in fig. 9 and 10, indication signaling for data transmission of subframe #1 is transmitted in subframe #2 of the licensed carrier.

c) Case 3: starting data transmission after subframe boundary

This explicit signaling may be transmitted using the modified PUCCH if LBT success is known after the start time of the subframe in which PUSCH transmission on the unlicensed carrier is made. For this case, the transmission may start in the middle of a subframe.

For example, if PUSCH transmission on the unlicensed carrier begins at OFDM symbol #1, then since OFDM symbol #0 is reserved for LBT, Sounding Reference Signal (SRS), or any other purpose, and OFDM symbol #0 cannot be used for PUCCH, PUCCH physical layer transmission would need to be modified accordingly to accommodate the smaller number of OFDM symbols in the first slot. This may be achieved, for example, by employing an orthogonal cover of shortened length in the time domain in combination with a predefined mapping.

As another example, if PUSCH transmission is allowed to start at OFDM symbol #7 (i.e., PUSCH transmission in the second slot of a subframe), the explicit signaling may be transmitted with a modified PUCCH that reuses the second slot of the legacy PUCCH signal. In this case, to avoid the eNB confusing full subframe transmission and partial subframe transmission, an indication of the starting position of the uplink data transmission may be provided to the eNB on the grant carrier allocated by the eNB in response to success of LBT. In other words, the indication of the starting position may indicate whether the uplink data transmission is a full subframe transmission or a partial subframe transmission. Additional signaling may be employed to carry an indication of the starting position, wherein the indication of the starting position indicates one symbol in the scheduled subframe.

As one example, for the case where the explicit signaling is transmitted on the PUCCH on the licensed carrier, the UE and eNB may perform the following procedure.

Upon receiving an uplink scheduling grant (which includes resource allocation for PUSCH transmission on the unlicensed carrier) on either the licensed carrier (for cross-carrier scheduling) or the unlicensed carrier (for self-scheduling), the UE listens for UL resources on the unlicensed carrier at the beginning of the UL scheduled subframe or before the boundary of the UL scheduled subframe.

The resources for explicit signaling may be configured by the eNB. For example, certain PUCCH resources in the licensed carrier are allocated to the UE to transmit the signaling. The UE-specific resources may be implicitly determined based on the unlicensed spectrum resource allocation.

The indication of the transmission status of the unlicensed carrier may be expressed as follows. For example, one bit (b1) may be introduced as follows: b 1-0 indicates no data transfer, and b 1-1 indicates data transfer.

In the case where the channel is unoccupied, the UE performs PUSCH transmission on the allocated resources and transmits the indication to the eNB on the allocated PUCCH via the licensed carrier (i.e., b1 ═ 1). In the case where the channel is occupied, the UE will not transmit PUSCH on the unlicensed band and transmit this indication to the eNB on the allocated PUCCH via the licensed carrier (i.e., b1 ═ 0). The indication may be transmitted at the current subframe (for the case of starting transmission at a subframe boundary) or at the next subframe (for the case of starting transmission after a subframe boundary). In particular, for multi-subframe scheduling, an indication of the transmission status of the first subframe within one burst transmission is transmitted to reduce the overhead due to transmitting the same indication of the transmission status of multiple scheduled subframes within one transmission burst.

The eNB will decide whether to decode the data according to the indication. Specifically, for the case where transmission starts after a subframe boundary, the eNB should first buffer the PUSCH of the current subframe and decide whether to decode the data after the indication is received from the UE in the next subframe. An alternative, but equivalent eNB implementation may be: the eNB performs detection of the indication and PUSCH decoding in parallel. Upon detecting the absence of PUSCH transmission, the eNB may stop PUSCH decoding or discard soft buffer bits. Otherwise, the eNB continues PUSCH decoding. In particular, for multi-subframe scheduling, the eNB need only receive an indication of the transmission status of the first subframe of one burst transmission and take the same decoding decision as the first subframe for the other remaining subframes.

As previously described, to avoid the eNB confusing full subframe transmission and partial subframe transmission, an indication of the starting position of the uplink data transmission may be provided to the eNB on the licensed carrier in response to success of LBT. For example, an additional signaling may be introduced to carry the indication of the starting position. For example, one bit (b2) is introduced as follows: b 2-0 indicates full subframe transmission, and b 2-1 indicates partial subframe transmission.

Second option

In a second option, the UE transmits the signaling to the eNB by multiplexing the explicit signaling with uplink data (e.g., PUSCH transmission) prior to Discrete Fourier Transform (DFT).

In particular, the explicit signaling and PUSCH transmissions may be multiplexed on the unlicensed carrier in a manner similar to multiplexing Uplink Control Information (UCI) and PUSCH transmissions in legacy LTE systems. Alternatively, the explicit signaling and PUSCH transmission may be multiplexed on the licensed carrier, if present.

In the LTE system, control signaling (e.g., ACK/NACK, CQI, etc.) is multiplexed with PUSCH transmission, as shown in fig. 11. This explicit signaling including an indication of the transmission status of the unlicensed carrier may be encoded and modulated in the same manner as ACK/NACK. The location of Resource Elements (REs) may be predefined such that the explicit signaling is multiplexed with PUSCH transmissions on the predefined REs. For example, four possible positions of REs of symbol #2, symbol #4, symbol #9, and symbol #11, i.e., 5, 6, 7, and 8, may be predefined to transmit the explicit signaling, as shown in fig. 11. The number of REs used to transmit this explicit signaling may be configurable, depending on the desired detection performance.

For example, if PUSCH transmission on the unlicensed carrier is started at symbol #0 or symbol #1, the explicit signaling may be transmitted on predefined REs of symbol #2 and symbol # 4. If PUSCH transmission on the unlicensed carrier is started in the middle of a subframe (i.e., symbol #7), this explicit signaling may be multiplexed with PUSCH transmission only in the second slot (i.e., symbol #9 and symbol # 11).

Further, to avoid the eNB confusing full subframe transmission and partial subframe transmission, an indication of a starting position of the uplink data transmission may be provided to the eNB on the licensed carrier in response to success of the LBT.

Third option

In a third option, the UE transmits the signaling to the eNB by multiplexing the explicit signaling with uplink data (e.g., PUSCH transmission) after a Discrete Fourier Transform (DFT) (i.e., before an inverse fast fourier transform).

In particular, the explicit signaling may be carried over a separate physical channel/signaling, starting at the PUSCH transmission. Since this can be a single bit or very few bits, a limited number of REs can be employed to achieve satisfactory detection performance. The location of the RE may be predefined. This requires considering the different number of PRBs allocated to PUSCH transmission. The bits are encoded with simple block coding, scrambled, and modulated with QPSK. In principle, the design of this channel can be very similar to the PCFICH in DL. One advantage of this approach is that if PUSCH is allowed to start in the middle of a subframe, the detection of this signaling automatically informs the starting position of the PUSCH transmission. Note that this does not exclude the possibility of transmitting this explicit signaling together with other information in the same physical channel/signaling.

Fig. 12 schematically shows a resource mapping for explicit signaling, illustrating one example of possible locations for explicit signaling transmission, according to an embodiment of the present disclosure. Eight REs of symbol #0 and symbol #7 are predefined to transmit the explicit signaling to support full subframe transmission and partial subframe transmission.

For example, if PUSCH transmission on the unlicensed carrier is started at symbol #0, the explicit signaling should be transmitted on the predefined REs of symbol # 0. If PUSCH transmission on the unlicensed carrier is started at symbol #7, this explicit signaling should be transmitted on the predefined REs of symbol # 7. Thus, the eNB, upon detecting the explicit signaling, can distinguish whether the transmission is a full subframe transmission or a partial subframe transmission.

According to a third aspect of embodiments of the present disclosure, there is provided an apparatus for providing a transmission status of an unlicensed carrier. Fig. 13 illustrates a block diagram of an apparatus 1300 for providing a transmission status of an unlicensed carrier according to a third aspect of an embodiment of the present disclosure. Apparatus 1300 may be implemented in a UE, for example.

As shown in fig. 13, apparatus 1300 comprises: a listening unit 1310 configured to listen to a transmission state of an unlicensed carrier on an uplink channel in response to receiving an uplink scheduling grant from a base station; and a providing unit 1320 configured to provide an indication of the transmission status to the base station based on the listening.

According to a fourth aspect of embodiments of the present disclosure, there is provided an apparatus for determining a transmission status of an unlicensed carrier. Fig. 14 shows a block diagram of an apparatus 1400 for determining a transmission status of an unlicensed carrier according to a fourth aspect of an embodiment of the present disclosure. Apparatus 1400 may be implemented in an eNB, for example.

As shown in fig. 14, the apparatus 1400 includes: a receiving unit 1410 configured to receive, from a user equipment, an indication of a transmission status of an unlicensed carrier on an uplink channel; and a determining unit 1420 configured to determine a transmission status of the unlicensed carrier based on the indication of the transmission status.

In general, the various example embodiments of this disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Certain aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While aspects of embodiments of the disclosure have been illustrated or described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that the blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

Also, blocks in the flow diagrams may be viewed as method steps, and/or as operations that result from operation of computer program code, and/or as a plurality of coupled logic circuit elements understood to perform the associated functions. For example, embodiments of the present disclosure include a computer program product comprising a computer program tangibly embodied on a machine-readable medium, the computer program containing program code configured to implement the above-described methods.

Within the context of this disclosure, a machine-readable 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 machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination thereof. More detailed examples of a machine-readable storage medium include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical storage device, a magnetic storage device, or any suitable combination thereof.

Computer program code for implementing the methods of the present disclosure may be written in one or more programming languages. These computer program codes may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the computer or other programmable data processing apparatus, cause the functions/acts specified in the flowchart and/or block diagram block or blocks to be performed. The program code may execute entirely on the computer, partly on the computer, as a stand-alone software package, partly on the computer and partly on a remote computer or entirely on the remote computer or server.

Additionally, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In some cases, multitasking or parallel processing may be beneficial. Likewise, while the above discussion contains certain specific implementation details, this should not be construed as limiting the scope of any invention or claims, but rather as describing particular embodiments that may be directed to particular inventions. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination.

Various modifications, adaptations, and exemplary embodiments of the foregoing disclosure may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. Any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments of this disclosure. Moreover, the foregoing description and drawings present instructive benefits, and other embodiments of the present disclosure set forth herein will occur to those skilled in the art to which these embodiments of the present disclosure pertain.

It is to be understood that the embodiments of the disclosure are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A method for providing a transmission status of an unlicensed carrier, comprising:

in response to receiving an uplink scheduling grant from a base station, listening for a transmission state of an unlicensed carrier on an uplink channel; and

providing an indication of the transmission status to the base station based on the snooping,

wherein providing an indication of the transmission status to the base station based on the overhearing comprises:

providing a signal known to the base station as an indication of the transmission status; and

transmitting the known signal to the base station together with uplink data,

wherein providing a signal known to the base station as an indication of the transmission status comprises:

the known signal is provided in a predefined symbol of a scheduled subframe.

2. The method of claim 1, wherein the predefined symbol comprises:

a symbol at a middle position of a first slot and a middle position of a second slot of the scheduled subframe.

3. The method of claim 2, wherein the predefined symbol further comprises:

a symbol at a start position of at least one of the first slot and the second slot.

4. A method for determining a transmission status of an unlicensed carrier, comprising:

receiving, from a user equipment, an indication of a transmission status of an unlicensed carrier on an uplink channel; and

determining a transmission status of the unlicensed carrier based on the indication of the transmission status,

wherein receiving, from the user equipment, the indication of the transmission status of the unlicensed carrier on the uplink channel comprises:

receiving a signal known to a base station as an indication of the transmission status, wherein the known signal is received with uplink data,

wherein receiving a signal known to the base station as the indication of the transmission status comprises:

receiving the known signal from a predefined symbol of a scheduled subframe.

5. The method of claim 4, wherein the predefined symbol comprises:

6. The method of claim 5, wherein the predefined symbol further comprises:

7. An apparatus for providing a transmission status of an unlicensed carrier, comprising:

a listening unit configured to listen to a transmission state of an unlicensed carrier on an uplink channel in response to receiving an uplink scheduling grant from a base station; and

a providing unit configured to provide an indication of the transmission status to the base station based on the overhearing,

transmitting the known signal to the base station together with uplink data,

the known signal is provided in a predefined symbol of a scheduled subframe.

8. An apparatus for determining a transmission status of an unlicensed carrier, comprising:

a receiving unit configured to receive, from a user equipment, an indication of a transmission status of an unlicensed carrier on an uplink channel; and

a determining unit configured to determine a transmission status of the unlicensed carrier based on the indication of the transmission status,

receiving the known signal from a predefined symbol of a scheduled subframe.