Patent Description:
In 3GPP LTE Rel-<NUM>, unlicensed spectrum is used for downlink (DL) transmission in the licensed-assisted access (LAA). Listen-before-talk (LBT) is defined for LAA DL, which requires a base station (the eNB) to perform a channel detection procedure before transmission, and requires it to perform the transmission only if this procedure succeeds. One part of the channel detection procedure is that the eNB needs to do energy detection, and compares the received energy to an energy threshold to determine whether the channel is free for specific time duration. The threshold has significant impact on the channel access opportunity of the eNB, and therefore has significant impact on the coexistence of LAA with other networks such as Wi-Fi, or among LAA nodes. Such coexistence mechanisms among LAA systems are disclosed in <NPL>, wherein the disclosure evaluates results for DL transmission without UL in unlicensed spectrum.

In LAA DL, a maximum energy detection threshold (hereinafter referred to as threshold) is defined as a function of:.

In addition, the eNB has the flexibility to use a threshold that is no bigger than the defined maximum energy detection threshold. The specific threshold adaptation mechanism depends on the eNB implementation.

A new work project has been recently approved in Rel-<NUM>, which specifies the support to the LAA UL (uplink) transmission. A channel detection procedure of UL transmission will need to be defined for the user equipment (UE), and an energy detection threshold also needs to be defined accordingly for UL transmissions.

Although there are a lot of similarities between DL and UL, there are also some differences between DL and UL, which may require different considerations about how to defitie the energy detection threshold. It is very important to define a suitable energy threshold, because when an improper threshold is set at an UE, the UE might suffer from either of the following:.

The main differences between DL and UL in the terms of defining the energy detection threshold include:.

Therefore, it is necessary to provide a method of determining a proper energy detection threshold in UL channel detection procedure of LAA, and the above factors should be taken into account in this method.

To solve the problems described above, embodiments of the present disclosure propose a method and apparatus for determining a channel sensing threshold in uplink (UL) channel detection of licensed-assisted access (LAA).

An aspect of the present disclosure provides a method for determining a channel sensing threshold in uplink channel detection of licensed-assisted access, this method comprising: determining parameters associated with the user equipment; and determining a channel sensing threshold for the user equipment based on the parameters as defined in claim <NUM>.

According to the present disclosure, determining parameters associated with the user equipment comprises determining of the following items associated with the user equipment as said parameters:.

According to an embodiment of the present disclosure, determining parameters associated with the user equipment comprises determining whether a hidden node is present.

According to an embodiment of the present disclosure, determining a channel sensing threshold for the user equipment based on the parameters comprises at least one of the following: increasing or decreasing the channel sensing threshold based on at least one of the channel bandwidth and the transmit power; or decreasing the channel sensing threshold based on at least one of presence of another type of radio access point and presence of the hidden node.

According to an embodiment of the present disclosure, determining one or more parameters associated with the user equipment comprises: determining said one or more parameters in a first order; and determining the channel sensing threshold using at least one of said one or more parameters determined in the first order.

According to an embodiment of the present disclosure, determining the channel bandwidth associated with the user equipment comprises: determining a channel bandwidth of an entire system; or determining a channel bandwidth allocated and used for burst transmission of the UE.

According to an embodiment of the present disclosure, determining the transmit power associated with the user equipment comprises: determining a maximum transmit power for the UE; determining an expected transmit power of the burst transmission for the UE; or determining an average transmit power in a time period before the burst transmission for the UE.

According to an embodiment of the present disclosure, determining whether other types of RATs associated with the UE are present comprises at least one of: detecting whether another type of RAT associated with the UE is present; and receiving a signaling indicating whether the other type of RAT associated with the UE is present.

According to an embodiment of the present disclosure, determining whether a hidden node associated with the UE is present comprises: receiving a signaling indicating presence of the hidden node detected by a base station; or receiving a signaling indicating presence of a possible hidden node determined by the base station.

According to an embodiment of the present disclosure, the method further comprises: updating one or more parameters associated with the UE in response to reception of a signaling for updating the channel sensing threshold.

Another aspect of the present disclosure provides an apparatus for determining a channel sensing threshold in uplink channel access of licensed-assisted access, the apparatus comprising: a parameter determination module configured to determine parameters associated with the user equipment; and a channel sensing threshold determination module configured to determine a channel sensing threshold for the user equipment based on the parameters, as defined in claim <NUM>.

According to the present disclosure, the parameter determination module comprises: a channel bandwidth determination unit configured to determine a channel bandwidth associated with the UE; a transmit power determination unit configured to determine a transmit power associated with the UE; a radio access point determination unit configured to determine whether another type of radio access point associated with the UE is present; and optionally a hidden node determination unit configured to determine whether a hidden node associated with the UE is present.

According to an embodiment of the present disclosure, the channel sensing threshold determination module is configured to perform at least one of: increasing or decreasing the channel sensing threshold based on at least one of the channel bandwidth and the transmit power; or decreasing the channel sensing threshold based on at least one of presence of the other type of radio access point and presence of the hidden node.

According to an embodiment of the present disclosure, the parameter determination module is configured to determine said one or more parameters in a first order; and the channel sensing threshold determination module is configured to determine the channel sensing threshold using the parameters determined in the first order.

According to an embodiment of the present disclosure, the channel bandwidth determination unit comprises: a first bandwidth determination unit configured to determine a channel bandwidth of an entire system; and a second bandwidth determination unit configured to determine a channel bandwidth allocated and used for burst transmission of the UE.

According to an embodiment of the present disclosure, the transmit power determination unit comprises: a first transmit power determination unit configured to determine maximum transmit power for the UE; a second transmit power determination unit configured to determine expected transmit power for the burst transmission of UE; or a third transmit power determination unit configured to determine average transmit power in a time period before the burst transmission for the UE.

According to an embodiment of the present disclosure, the radio access point determination unit comprises: a detection unit configured to detect whether another type of radio access point associated with the UE is present; and a receiving unit configured to receive a signaling indicating whether the other type of radio access point associated with the UE is present.

According to an embodiment of the present disclosure, the hidden node determination unit is configured to: receive a signaling indicating presence of the hidden node detected by a base station; or receive a signaling indicating presence of a possible hidden node determined by the base station.

According to an embodiment of the present disclosure, the apparatus further comprises: a parameter updating means configured to update the one or more parameters associated with the UE in response to reception of a signaling for updating the channel sensing threshold.

The method and apparatus for determining the channel sensing threshold discussed in various embodiments herein have the following advantages:.

The figures illustrated here are used to provide further understanding of the present disclosure, and constitute part of the present application. Exemplary embodiments of the present disclosure and depictions thereof are used to explain the present disclosure and do not constitute improper limitations to the present disclosure.

Principles of the present disclosure will now be described with reference to various example embodiments illustrated in the drawings. It should be appreciated that description of those embodiments is merely to enable those skilled in the art to better understand and further implement the present disclosure and is not intended for limiting the scope of the present disclosure in any manner.

<FIG> is a flow chart of a method <NUM> for determining a channel sensing threshold in uplink channel detection of LAA according to an embodiment of the present disclosure. The method <NUM> comprises main steps S110 through S120.

According to the present disclosure, determining parameters associated with the user equipment (namely, step S110) comprise determining the following items associated with the user equipment as said parameters:.

According to an embodiment of the present disclosure, determining a channel bandwidth associated with the user equipment may comprise determining a channel bandwidth of an entire system,.

According to an embodiment of the present disclosure, determining a channel bandwidth associated with the user equipment may comprise determining a channel bandwidth allocated and used for burst transmission of the UE. For example, when the UE uses discontinuous frequency resources for transmission, the channel bandwidth includes only the actual bandwidth that is used by the UE.

According to an embodiment of the present disclosure, determining a channel bandwidth associated with the user equipment may comprise transmitting a signaling from eNB to the UE to inform the UE which type of channel bandwidth as described above should be used for determining channel sending threshold. For example, the eNB can use one bit (e.g. logic value '<NUM>') to indicate to use the channel bandwidth of the entire system() or use one bit (e.g. logic value '<NUM>') to indicate to use the channel bandwidth allocated and used for burst transmission of the UE.

It is noted that the bandwidth described above and used by the UE is for determining the channel sensing threshold. Therefore, the bandwidth described above is not necessarily same as the bandwidth on which the UE actually performs the channel sensing (or energy detection). For example, the UE may perform energy detection on the bandwidth of the entire system, but the threshold described above is calculated based on the actual allocated bandwidth.

According to an embodiment of the present disclosure, determining a transmit power associated with the UE may comprise determining a maximum transmit power for the UE.

According to an embodiment of the present disclosure, determining a transmit power associated with the UE may comprise an expected transmit power of the burst transmission for the UE, wherein the expected transmit power is estimated by the UE based on UL power control and scheduling information before starting the channel detection procedure, and may be updated during the channel detection procedure as required (e.g. based on open loop power control).

It is noted that there may be some difference between the expected transmit power and the actual transmit power when channel detection procedure succeeds, but the difference is expected to be small.

According to an embodiment of the present disclosure, determining a transmit power associated with the UE may comprise determining an average transmit power in a time period before the burst transmission for the UE. For example, the average can be done within a time window or using an infinite impulse response (IIR) filter.

According to an embodiment of the present disclosure, the eNB may send a signaling to the UE to inform which type of transmit power described above should be used at the UE for determining the channel sensing threshold. For example, the eNB can use one-bit (e.g. logic value '<NUM>') to indicate to use the maximum transmit power or use one-bit (e.g. logic value '<NUM>') to indicate to use the expected transmit power of the burst transmission for the UE.

According to an embodiment of the present disclosure, the UE may detect whether another type of RAT is present by itself without any assist from the eNB.

According to an embodiment of the present disclosure, the eNB can send a signaling to the UE to indicate whether the UE should assume the presence of other RATs when determining a threshold.

According to an embodiment of the present disclosure, the UE may use a combination of the above to determine whether another type of RAT is present.

According to an embodiment of the present disclosure, determining whether a hidden node associated with the UE is present comprises: receiving a signaling indicating presence of a hidden node detected by a base station. For example, when the eNB detects the hidden node issue for the UL transmission from a particular UE, the eNB can lower the threshold by sending a negative offset to the UE, in order to relieve the hidden node problem. The offset is sent to the UE via UE-specific signaling in this case.

According to an embodiment of the present disclosure, determining whether a hidden node associated with the UE is present comprises: receiving a signaling indicating whether a possible hidden node associated with the UE and decided by a base station is present. For example, the eNB may decide to use a negative offset by considering (i) the number of UEs being scheduled in a subframe, (ii) the number of user pairs being scheduled using the same time-frequency resource via MU-MIMO, and/or (iii) the estimated transmit power from the UEs. Again for example, the eNB may decide to use a lower threshold, and eNB can send a negative offset signaling to all the UE via broadcast signaling or UE-specific signaling for any other reason (e.g. coexistence with other LAA/Wi-Fi nodes, some specific deployment topology, etc).

It is appreciated that the signaling for different parameters can be transmitted to the UE separately or in a combined fashion. For example, when the eNB needs to signal both the presence of other RATs and a threshold offset for hidden node to UE, the signal can be one of the following ways:.

According to an embodiment of the present disclosure, determining a channel sensing threshold for the user equipment based on the above parameters (namely, step S120) comprises at least one of: increasing or decreasing the channel sensing threshold based on at least one of the channel bandwidth and the transmit power; or decreasing the channel sensing threshold based on at least one of presence of another type of RAT and presence of the hidden node.

According to an embodiment of the present disclosure, the method <NUM> further comprises an updating step S130 for updating one or more parameters associated with the UE in response to reception of a signaling for updating the channel sensing threshold.

For example, when the threshold needs to be changed/updated, a signaling for changing/updating the threshold may be sent to the UE. For example, whenever there is a change of condition, the eNB sends a semi-static signaling to the UE so that the UE can update the parameters and the channel sensing threshold. This signaling can be delivered to the UE on either licensed or unlicensed carrier.

Alternatively, the necessary parameter(s) such as the threshold offset can be included in downlink control information (DCI) message that carries UL grant. In this case, the UE uses the parameters in this DCI to determine the threshold for the UL transmissions.

Reference is made to a specific example below. This example considers a plurality of parameters stated above and expresses the channel sensing threshold as the following equation (<NUM>):
<MAT>
wherein:.

Referring to the above equation (<NUM>), the UE channel sensing threshold would be decided and specified according to the following items:.

As stated above, the channel bandwidth refers to the bandwidth where the UE delivers (or transmit) its data. Actually, the UE may utilize a portion of the whole bandwidth. The channel sensing could be performed on the rated bandwidth, or on a portion of the bandwidth. Bandwidth is denoted by BWMHz.

Specifically, when there are multiple UEs, one UE may occupy a portion of the system bandwidth in the UL transmission not all of them. Thus, to avoid the interlock among the multiple UEs, the channel sensing bandwidth could be a portion of the system bandwidth. The channel sensing threshold should also adapt to this bandwidth.

On the other hand, the uplink transmission of a UE may spread across the whole bandwidth to satisfy the power spectrum density requirement. Under this case, the BWMHZ should be the whole bandwidth.

The UEs may not occupy the whole bandwidth in the UL transmission. Thus, the threshold adjustment shall be based on the transmitting power (density) of UEs and the subcarriers utilized by the UEs. The configuration of the value of αwould indicate the impact of the transmitting power of the UE on its threshold.

Besides, the PTX could be flexibly adjusted in different time duration.

Another choice is to select the maximum transmitting power of UEs and neglect the PTX.

When the presence of the other type of RAT is detected, the threshold of the UEs would be kept to, e.g., a lower value (Y < <NUM>), so that the UEs could co-exist with them.

If the UE does not have an ability to detect whether other RATs are present, the UE may send a request to the eNB and the eNB could send a signaling to the UE to indicate whether other RATs are present. The presence of another type of RAT could be known to the eNB at deployment stage and configured by operator, however not known to the UE.

If the eNB starts to transmit a signaling to the UE to indicated whether the other type of RAT is present, whereas the UE detects a different results with the signaling. Under this case, the UE could keep a lower threshold, in order to reduce the impact of the other type of RAT.

CCA ED threshold offset is configured by eNB, in order to enable flexible channel access (e.g. using a negative value to avoid hidden node problem) at the UE side. When the eNB observes an abnormal state, possibly caused by hidden node, it would suggest the UE to lower down its threshold, in order to avoid the hidden node problem which is reflected by Y2. The eNB may indicate the offset to UE by downlink signaling.

According to an embodiment of the present disclosure, determining one or more parameters associated with the user equipment (namely, step S110) may further comprise: determining said one or more parameters in a first order; and determining the channel sensing threshold by using at least one of said one or more parameters determined in a first order.

Reference is made to specific examples in <FIG> and <FIG> to illustrate parameter determination in a specific order (e.g., a first order) and corresponding threshold adaptation procedure.

<FIG> is a flow chart for adjusting a channel sensing threshold in uplink channel detection of LAA in the case that the UE can detect another type of RAT according to an embodiment of the present disclosure.

<FIG> is a flow chart for adjusting a channel sensing threshold in uplink channel detection of LAA in the case that the UE cannot detect another type of RAT according to an embodiment of the present disclosure.

For sake of simplicity, in two cases shown in <FIG> and <FIG>, thoughts are only exemplarily given to a two-level threshold for the spectrum sensing of UE. The parameters and variables are set as follows,.

Based on the above parameters and variables, the threshold could be written as follows if there is no hidden node:.

Based on the above parameters and variables, the threshold could be written as follows if there is a hidden node:.

Thoughts are given below to the case in which LAA co-exists with another type of RAT, e.g., Wi-Fi. When UE is able to detect the other type of RATs, the threshold adaption (adjustment) procedures is shown in <FIG>; the threshold adaption procedure is shown in <FIG> when the UE is not able to detect the other type of RAT.

As shown in <FIG> (namely, when UE is able to detect the other type of RATs):.

As shown in <FIG> (namely, when UE cannot be able to detect the other type of RAT),.

It is noted that it is not always necessary to present all steps in <FIG> and <FIG> as discussed above. It is also not necessary to follow the exact order presented in the flow shown in <FIG> and <FIG>. The involved steps and execution order are only exemplary and not restrictive. Those skilled in the art may appreciate that threshold adjustment procedures involving more or fewer parameters and additional parameters should also fall within the scope of the present disclosure.

<FIG> is a block diagram of an apparatus <NUM> of determining a channel sensing threshold in uplink channel detection of LAA according to an embodiment of the present disclosure. The apparatus <NUM> comprises: a parameter determination module <NUM> configured to determine parameters associated with the user equipment; and a channel sensing threshold determination module <NUM> configured to determine a channel sensing threshold for the user equipment based on the parameters.

According to the present disclosure, the parameter determination module <NUM> comprises: a channel bandwidth determination unit configured to determine a channel bandwidth associated with the UE; a transmit power determination unit configured to determine a transmit power associated with the UE: a radio access point determination unit configured to determine whether another type of radio access point associated with the UE is present. According to an embodiment of the present disclosure, the parameter determination module <NUM> comprises a hidden node determination unit configured to determine whether a hidden node is present.

According to an embodiment of the present disclosure, the channel sensing threshold determination module <NUM> is configured to perform at least one of: increasing or decreasing the channel sensing threshold based on at least one of the channel bandwidth and the transmit power; or decreasing the channel sensing threshold through at least one of presence of another type of radio access point and presence of the hidden node.

According to an embodiment of the present disclosure, wherein the parameter determination module <NUM> is configured to: determine said one or more parameters in a first order; and the channel sensing threshold determination module <NUM> is configured to determine the channel sensing threshold using at least one of the one or more parameters determined in the first order.

According to an embodiment of the present disclosure, the channel bandwidth determination unit comprises: a first bandwidth determination unit configured to determine channel bandwidth of the entire system; and a second bandwidth determination unit configured to determine channel bandwidth allocated and used for burst transmission of the UE.

According to an embodiment of the present disclosure, the transmit power determination unit comprises: a first transmit power determination unit configured to determine a maximum transmit power for the UE; a second transmit power determination unit configured to determine an expected transmit power for burst transmission of the UE; or a third transmit power determination unit configured to determine an average transmit power in a time period before the burst transmission of the UE.

According to an embodiment of the present disclosure, the radio access point determination unit comprises: a detection unit configured to detect whether another type of radio access points associated with the UE are present; and a receiving unit configured to receive a signaling indicating whether the other type of radio access point associated with the UE is present.

According to an a-nea-etaimed embodiment of the present disclosure, the hidden node determination unit is configured to: receive a signaling indicating presence of the hidden node detected by a base station; or receive a signaling indicating presence of a possible hidden node determined by the base station.

Claim 1:
A method (<NUM>) of determining a channel sensing threshold in uplink channel access of licensed-assisted access, comprising:
Determining (S110) parameters associated with user equipment, wherein determining the parameters associated with the user equipment comprises:
determining the following items associated with the user equipment as the parameters:
channel bandwidth;
a transmit power;
whether another type of radio access point is present; and
determining (S120) the channel sensing threshold for the user equipment based on the parameters:
channel bandwidth;
a transmit power, and
whether another type of radio access point is present.