WO2017193843A1 - Procédés et dispositifs de prise en charge d'accès à des ressources radio sans licence dans des systèmes de communications sans fil - Google Patents

Procédés et dispositifs de prise en charge d'accès à des ressources radio sans licence dans des systèmes de communications sans fil Download PDF

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Publication number
WO2017193843A1
WO2017193843A1 PCT/CN2017/082804 CN2017082804W WO2017193843A1 WO 2017193843 A1 WO2017193843 A1 WO 2017193843A1 CN 2017082804 W CN2017082804 W CN 2017082804W WO 2017193843 A1 WO2017193843 A1 WO 2017193843A1
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wireless communication
communication device
category
before talk
listen before
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PCT/CN2017/082804
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English (en)
Inventor
Guang Liu
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Jrd Communication Inc.
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Priority to CN201780023834.6A priority Critical patent/CN109417792B/zh
Publication of WO2017193843A1 publication Critical patent/WO2017193843A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/14—Spectrum sharing arrangements between different networks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/04—Wireless resource allocation
    • H04W72/044—Wireless resource allocation based on the type of the allocated resource
    • H04W72/0446—Resources in time domain, e.g. slots or frames
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/04—Wireless resource allocation
    • H04W72/044—Wireless resource allocation based on the type of the allocated resource
    • H04W72/0453—Resources in frequency domain, e.g. a carrier in FDMA
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/20—Control channels or signalling for resource management
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/20—Control channels or signalling for resource management
    • H04W72/23—Control channels or signalling for resource management in the downlink direction of a wireless link, i.e. towards a terminal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W74/00—Wireless channel access
    • H04W74/002—Transmission of channel access control information
    • H04W74/006—Transmission of channel access control information in the downlink, i.e. towards the terminal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W74/00—Wireless channel access
    • H04W74/08—Non-scheduled access, e.g. ALOHA
    • H04W74/0808—Non-scheduled access, e.g. ALOHA using carrier sensing, e.g. carrier sense multiple access [CSMA]
    • H04W74/0816—Non-scheduled access, e.g. ALOHA using carrier sensing, e.g. carrier sense multiple access [CSMA] with collision avoidance

Definitions

  • Embodiments of the present invention generally relate to wireless communication systems and in particular to devices and methods for supporting access to an unlicensed communications channel using a Listen Before Talk (LBT) procedure.
  • LBT Listen Before Talk
  • the invention has particular application, though is not limited to, enhanced Licenced Assisted Access (eLAA) technologies in an LTE (Long Term Evolution) advanced wireless communication system.
  • eLAA enhanced Licenced Assisted Access
  • Wireless communication systems such as the third-generation (3G) of mobile telephone standards and technology are well known.
  • 3G standards and technology have been developed by the Third Generation Partnership Project (3GPP) .
  • the 3 rd generation of wireless communications has generally been developed to support macro-cell mobile phone communications.
  • Such macro cells utilise high power base stations (NodeBs) to communicate with wireless communication devices within a relatively large geographical coverage area.
  • NodeBs base stations
  • wireless communication devices or User Equipment (UEs) as they are often referred to, communicate with a Core Network (CN) of the 3G wireless communication system via a Radio Network Subsystem (RNS) .
  • CN Core Network
  • RNS Radio Network Subsystem
  • a wireless communication system typically comprises a plurality of radio network subsystems, each radio network subsystem comprising one or more cells to which UEs may attach, and thereby connect to the network.
  • Each macro-cellular RNS further comprises a controller, in a form of a Radio Network Controller (RNC) , operably coupled to the one or more NodeBs.
  • RNC Radio Network Controller
  • Communicationsystems and networks have developed towards a broadband and mobile system.
  • the 3rd Generation Partnership Project has developed the so-called Long Term Evolution (LTE) and LTE advanced solutions, namely, an Evolved Universal Mobile Telecommunication System Territorial Radio Access Network, (E-UTRAN) , for a mobile access network, and a System Architecture Evolution (SAE) solution, namely, an Evolved Packet Core (EPC) , for a mobile core network.
  • LTE Long Term Evolution
  • E-UTRAN Evolved Universal Mobile Telecommunication System Territorial Radio Access Network
  • SAE System Architecture Evolution
  • EPC Evolved Packet Core
  • a macrocell in an LTE system is supported by a base station known as an eNodeB or eNB (evolved NodeB) .
  • Current wireless communications networks operate using licensed radio spectrum in which multiple accesses to the communications resources of the licensed radio spectrum is strictly controlled.
  • Each user of the network is essentially provided a “slice” of the spectrum using a variety of multiple access techniques such as, by way of example only but not limited to, frequency division multiplexing, time division multiplexing, code division multiplexing, and space division multiplexing or a combination of one or more of these techniques.
  • multiple access techniques such as, by way of example only but not limited to, frequency division multiplexing, time division multiplexing, code division multiplexing, and space division multiplexing or a combination of one or more of these techniques.
  • unlicensed radio spectrum may also be used by network operators in order to increase or supplement capacity.
  • a network based on the Long Term Evolution (LTE) /LTE advanced standards has an enhanced downlink that uses a Licensed-Assisted-Access (LAA) procedure to operate on unlicensed spectrum. All communication devices need to complete a LBT (Listen Before Talk) procedure before accessing an unlicensed channel.
  • LBT Listen Before Talk
  • Some LAA techniques use a clear channel assessment (CCA) check on channels of the unlicensed spectrum to determine the presence or absence of other signals prior to using the channel.
  • the base stations eNBs
  • eNBs can start the downlink transmissions on the carriers which are clear and the user equipment or terminals need to monitor the downlink carriers indicated by the base station with signalling.
  • a UE performs a CAA check by using energy detection to determine the presence or absence of other signals on a particular carrier, resource block and/or channel to determine if that carrier, resource block and/or channel is occupied or clear to use.
  • the LBT procedure may be used for LAA carriers from the unlicensed spectrum. Normally carriers from the licensed spectrum are specifically reserved for each UE and thus typically do not require the LBT procedure and/or CCA check.
  • DL (downlink) and UL (uplink) are implemented in different ways, and an eNB can start a DL transmission anytime on any channel while UEs can only start an UL transmission on specific subframes of specific channels allocated by the eNB with UL Grant messages.
  • a UE has comparatively fewer chances to access unlicensed carriers and UL performance may also be disadvantaged as a result.
  • a network element for supporting communications in a wireless communication system, the network element comprising a transmitter circuit arranged to transmit a message, for reception by a wireless communication device in the wireless communication system, comprising information for assisting the wireless communication device to access an unlicensed radio resource, wherein the network element is arranged to configure a Licensed Assisted Access (LAA) uplink channel comprising subframes, each subframe having “n” OFDM symbols, where “n” is an integer, and wherein at least one symbol is blanked to create a gap during which the wireless communication device can perform a Listen Before Talk procedure and wherein the network element is further arranged to configure a Maximum Channel Occupied Time (MCOT) period during which a channel of the unlicensed radio resource may be occupied, and wherein said message includes information relating to at least one of: the position of the gap; .
  • LAA Licensed Assisted Access
  • MCOT Maximum Channel Occupied Time
  • a remaining duration of the MCOT period which is available to the wireless communication device an instruction for the wireless communication device to switch from a Category 4 to a Category 2 Listen Before Talk procedure; an instruction for the wireless communication device to postpone a Category 4 Listen Before Talk procedure following a previous Listen Before Talk procedure failure.
  • the network element may be an eNB.
  • the message may be included in Downlink Control Information.
  • the network element and wireless communication device are arranged to support a Listen Before Talk (LBT) procedure.
  • LBT Listen Before Talk
  • the wireless communication system is an LTE advanced system in which Licensed Assisted Access is supported and which uses a Listen Before Talk procedure. It has been agreed that Listen Before Talk will be classified into four categories. Category 1 has no LBT; Category 2 has LBT without random back-off, Category 3 has LBT with random back-off with fixed size of contention window, Category 4 has LBT with random back-off with variable size of contention window. In 3GPP Release 13, Category 4 has been adopted as the only LBT type for downlink.
  • the instruction for the wireless communication device to switch from a Category 4 to a Category Listen Before Talk procedure may comprise a single bit indicator per subframe.
  • the instruction to postpone a Category 4 Listen Before Talk procedure following a previous Listen Before Talk procedure failure may be indicated by a single bit per subframe.
  • the message transmitted by the network element may include information relating to at least one of an uplink subframe size and an uplink subframe location.
  • the message may include information indicating in which subframe a gap needs to be blanked for LBT procedures for a plurality of wireless communication devices multiplexed onto the LAA uplink channel.
  • a wireless communication device adapted to perform a Listen Before Talk (LBT) procedure and having a receiver circuit for receiving a message from a network element supporting communication in a wireless communication system, wherein the message includes information for assisting the wireless communication device to access an unlicensed radio resource using a Licensed Assisted Access (LAA) uplink channel comprising subframes, each subframe having “n” OFDM symbols, where “n” is an integer, and wherein at least one symbol is blanked to create a gap during which the wireless communication device can perform a Listen Before Talk procedure, and wherein said message includes information relating to at least one of: (i) the position of the gap; (ii) a remaining duration of a Maximum Channel Occupied Time MCOT period which is available to the wireless communication device; (iii) an instruction for the wireless communication device to switch from a Category 4 to a Category Listen Before Talk procedure; (iv) an instruction for the wireless communication device to postpone a Category 4 Listen Before Talk procedure
  • LBT Listen Before Talk
  • the wireless communication device may be a User Equipment or similar mobile communications device.
  • the message further includes information indicating in which subframe a gap needs to be blanked for LBT procedure for a plurality of wireless communication devices multiplexed onto the LAA uplink channel.
  • the wireless communication device may include a signal processor for determining whether a Category 4 Listen Before Talk procedure can be postponed following a previous Listen Before Talk procedure failure on receipt of a message from the network element including information relating to the position of the gap and a remaining duration of the Maximum Channel Occupation Time.
  • the signal processor is arranged to determine if such a a Category 4 Listen Before Talk procedure can be postponed on a subframe by subframe basis.
  • the signal processor is arranged to postpone the Category 4 Listen before talk procedureby one subframe if a Listen Before Talk procedure failed on a previous subframe with a single UE indicated.
  • the wireless communication device includes a signal processor for determining whether the wireless communication device can switch from a Category 4 Listen Before Talk procedure to a Category 2 Listen Before Talk procedure depending on information received from the network element relating to a remaining duration of an Maximum Channel Occupation Time and, optionally, the position of the gap.
  • a method for enabling communications in a wireless communication device in a wireless communication system comprising, at a network element of the wireless communication system, transmitting to the wireless communication device, a message comprising information for assisting the wireless communication device to access an unlicensed radio resource; configuring a Licensed Assisted Access (LAA) uplink channel comprising subframes, each subframe having “n” OFDM symbols, where “n” is an integer, and wherein at least one symbol is blanked to create a gap during which the wireless communication device can perform a Listen Before Talk procedure, configuring a Maximum Channel Occupied Time (MCOT) period during which a channel of the unlicensed radio resource can be occupied, and including in said message information relating to at least one of: (i) the position of the gap; (ii) a remaining duration of the MCOT period which is available to the wireless communication device; (iii) an instruction for the wireless communication device to switch from a Category 4 to a Category 2 Listen
  • LAA Licensed Assisted Access
  • MCOT Maximum
  • the method may also include, at the wireless communication device, determining if a Category 4 Listen Before Talk procedure can be postponed following a previous Listen Before Talk procedure failure.
  • a non-transitory computer readable medium having computer readable instructions stored thereon for execution by a processor to perform the method according to the third aspect.
  • the non-transitory computer readable medium may comprise at least one from a group consisting of: a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a Read Only Memory, a Programmable Read Only Memory, an Erasable Programmable Read Only Memory, EPROM, an Electrically Erasable Programmable Read Only Memory and a Flash memory.
  • Figure 1 is a simplified block diagram of a part of a cellular communication system and operating in accordance with an example embodiment
  • Figure 2 is a first timing diagram illustrating an example of a Licensed Assisted Access method utilising Listen Before Talk procedures
  • Figures 3 and 4 are second and third timing diagrams illustrating an example of a Licensed Assisted Access method for multiple User Equipments.
  • Figure 5 is a table illustrating relevant parameters utilised by a User Equipment when accessing unlicensed spectrum.
  • an example of part of an LTEcellular communication system operating in accordance with embodiments of the invention is illustrated and indicated generally at 100 and comprises an evolved Node B (eNB) 101 supporting an LTE cell 102.
  • the eNB 101 may support a multiplicity of cells.
  • the evolved Node B 101 comprises a part of a radio access network which in this example is an E-UTRAN.
  • User Equipments 103a, 103b, 103c are located within the area of coverage of the cell 102. Just three User Equipments are shown in FIG. 1 but more or fewer User Equipments may be located in the cell 102 and be in a connected mode at any given time.
  • EPC evolved packet core
  • the 1 includes a Packet Gateway P-GW 104 and a Serving GPRS (General Packet Radio System) Support Node (SGSN) 105.
  • the P-GW 104 is responsible for interfacing the radio access network with a packet data network, eg. a Packet Switched Data Network (PSDN) (such as the Internet) .
  • PSDN Packet Switched Data Network
  • the SSGN 105 performs a routing and tunnelling function for traffic to and from the cell 102, while the P-GW 104 links with external packet networks.
  • the EPC also comprises a Mobility Management Entity 106.
  • the eNB 101 is linked to the SSGN 105 through the Mobility Management Entity (MME) 106.
  • MME Mobility Management Entity
  • the eNB 101 is also connected with the P-GW 104 through the MME 106 and a Service Gateway S-GW 107.
  • the MME 106 handles signalling control and mobility while the S-GW 107 is a local anchor point for user data.
  • the eNB 101 is provided with a receiver circuit 108 and also a transmitter circuit 109 for transmitting messages to one or more User Equipments 103a, 103b, 103c.
  • the messages transmitted include certain information (to be described in further detail below) for assisting a User Equipment to access an unlicensed radio resource which is provided by the eNB in addition to licensed carriers. Unlicensed carriers work together with licensed carriers in Carrier Aggregation.
  • the messages may be included in Downlink Control Information.
  • Each User Equipment 103a, 103b and 3B, 103c includes a receiver 110 for receiving messages from the eNB 101 and a signal processor 111 for determining certain factors, to be described below, based on the information contained in the received messages.
  • a downlink LBT has been specified in 3GPP TS 36.213 and defines four priority classes.
  • a contention window is also defined for each priority and a random value is chosen and used to determine the number of CCAs to be done within one LBT procedure. Choosing a random value minimises the chances of collisions between different eNBs attempting to access the same unlicensed channel.
  • the contention window size can depend on loading of the channel and although a small contention window size can help an eNB to grab a channel quickly, it also limits the time available to the eNB for transmission of data to a comparatively short period.
  • the eNB 101 listens to the unlicensed channel to determine if the channel is already in use by some other device. Once the channel is detected to be free, the eNB 101 starts a defer period followed by a CCA countdown. If, during the countdown period, a signal is detected, then the eNB suspends the countdown until the signal has gone whereupon the countdown procedure is resumed after expiry of another defer period. When the countdown value is equal to zero, the eNB can start its transmission but for no more than a certain number of milliseconds as permitted by the prevailing priority class.
  • the downlink LBT is Category 4.
  • An LBT procedure as agreed by the 3GPP defines a Maximum Channel Occupied Time (MCOT) which identifies a maximum length of a downlink burst that an eNB can transmit on an unlicensed channel.
  • MCOT Maximum Channel Occupied Time
  • the eNB 101 may not use all of this MCOT period and so it has also been agreed that the remaining part can be shared by one or more of the UEs 103a, 103b, 103c in a so-called one-shot or Category 2 LBT procedure.
  • the uplink requires multiplexing of multiple UEs and so the eNB 101 needs to coordinate these multiple devices to access the same channel at the same time.
  • a Licensed Assisted Access uplink transmission in this example is arranged in subframes.
  • Each subframe has ” n” OFDM symbols and at least one symbol is blanked to create a gap.
  • UEs may perform an LBT procedure and start transmission immediately after the gap.
  • each subframe is 1 ms long with 14 symbols and either the first and/or second symbol are blanked.
  • the eNB indicates the position of the gaps to the UEs 103a, 103b, 103c.
  • a UE may either perform a Category 2 LBT when its following transmission burst lies within an existing MCOT, or a Category 4 LBT when its following transmission burst cannot be finished within an existing MCOT. If the Category 4 LBT cannot be completed within one gap, it has to continue its LBT procedure in the next gap which will be at least 1 ms later and so on.
  • a UE In order for a UE to select the more appropriate LBT procedure (for example, Category 2 as opposed to Category 4) it is advantageous for a UE to know how much of the MCOT is remaining. For example, a UE will know how long it requires to transmit its data and therefore if it also knows the duration of the remaining MCOT it will be able to deduce if the transmission can be completed within the remaining MCOT window or not. For example, if the UE determines that the transmission would not fall outside the MCOT window then it can perform a Category 2 LBT procedure. If on the other hand the UE determines that its transmission would fall outside the MCOT window, then the UE can choose to perform a Category 4 LBT.
  • a Category 4 LBT may be postponed after a Category 2 LBT fail and under certain circumstances to be explained in more detail below.
  • the remaining MCOT is signalled to the UE by the eNB 101.
  • This information may comprise, for example, 3 bits and is included in the message sent from the eNB in Downlink Control Information.
  • the remaining MCOT can be inferred by the signal processor 111 in the UE by counting down one subframe from the predefined MCOT value whenever the UE detects a downlink transmission. This alternative has a drawback however in the case of a missed detection of a downlink transmission. In such a case, the remaining MCOT would not be decremented. This could result in the UE occupying the unlicensed channel time with an improper LBT.
  • a Category 2 LBT procedure is always preferred for LAA uplink as it helps a UE to grab an unlicensed channel with a higher probability compared with other categories.
  • the eNB 101 sends an instruction to a UE instructing the UE to switch from a Category 4 to a Category 2 LBT procedure under certain circumstances.
  • the instruction can be included in the message transmitted by the eNB in Downlink Control Information.
  • a single bit indication per subframe can be used. If such bit is not sent, then the UE continues to use Category 4 LBT. Alternatively, the UE can deduce whether or not to switch from a Category 4 to a Category 2 LBT procedure from other signalling fields.
  • Case 1 illustrates how a Category 4 LBT can be postponed following an LBT failure.
  • a UE such as 103a of figure 1
  • a UE has failed its first LBT at the commencement of subframe 4 but succeeded in its second LBT one subframe later. So it starts its uplink transmissions from subframe number 5 and keeps transmitting without a break up to the start of subframe 9 whereupon the eNB-initiated MCOT expires.
  • the UE succeeded in its first LBT and so it can start uplink transmissions from subframe number 4 and keep transmitting up to the start of subframe 8 where the eNB MCOT expires.
  • the total transmission duration is no more than the MCOT which has been initiated by the eNB. So a UE can continue another transmission after successful category 4 LBT at the beginning of either subframe 9 for case 1 or subframe 8 for case 2.
  • a Category 4 LBT must be performed in order to comply with regulations. Hence, a category 4 LBT can be deferred in such circumstances such as that in case 1.
  • a signalling indicator is transmitted in a message from the eNB to the UEs to indicate, for each uplink subframe, if a Category 4 LBT can be postponedbyone subframe when an LBT failed on this subframe.
  • the signal processing capability of the UE can determine by how many subframes a category 4 LBT can be postponed following an LBT failure by receiving the message indicating the remaining MCOT duration and knowing the number of subframes which have been allocated and their location.
  • the eNB sends to the UEsin a broadcast manner, one or more parameters indicating how many uplink subframes are allocated and where they are.
  • Such an indicator could be designated “subframe’s size” and could comprise 3 to 4 bits.
  • the allocated subframes for a particular UE do not have to be contiguous.
  • the size of a subframe has to be known to the UE is so it can correctly configure the uplink channel.
  • an information field designated “multiple UEs bitmap one bit per scheduled uplink subframe) is used to indicate to the UEs in which subframes a gap needs to be blanked for an LBT procedure.
  • the eNB sends to the UE one or more parameters in a unicast manner indicating how many uplink subframes are allocated and where they are.
  • the allocated subframes for a particular UE do not have to be contiguous.
  • information field designated “multiple UEs bitmap (one bit per scheduled uplink subframe) is used to indicate to the UE in which subframes a gap needs to be blanked for an LBT procedure.
  • a further information field designated “MCOT remaining duration” which may comprise 3 bits is used to send information relating to the remaining MCOT duration which can be utilised by UEs after an eNB has completed its downlink transmissions.
  • this remaining duration is indicated in units of subframe and indicates the remaining duration of the MCOT which was initiated by the eNB. If an uplink transmission can be completed within this remaining period, a category 2 LBT is required. Otherwise, a category 4 LBT is required.
  • This information field could be sent in either a broadcast manner or a unicast manner and if it is sent in the unicast manner to a UE, the eNB can adjust its value according to which subframes the specific UE is scheduled on.
  • FIG. 3 For one frame 301 having a total duration of 10 ms, there are 4 downlink subframes (0 to 3) and six uplink subframes (4 to 9) which are allocated to two UEs, UE1 and UE2, (such as 103a and 103b of figure 1) and a downlink LBT initiates a MCOT of 8 ms.
  • Each UE needs to finish a 25 ⁇ s LBT (that is a one shot/Category 2 LBT) before its uplink transmission commences and if the first 25 ⁇ s LBT fails, the UE needs to wait until the beginning of the next subframe before it can perform another LBT.
  • subframes 4 to 9 are allocated for use by UE1 and subframes 6 to 8 are allocated for use by UE2.
  • subframes 4 to 9 are allocated to UE1 and subframes 4 to 6 are allocated to UE2. Both UEs can use the same subframe but are allocated different resource blocks.
  • the category 4 LBT following failure of a Category 2 LBT by UE1 at subframe 4, the category 4 LBT can be postponed by one subframe because subframe number 4 is unused by either UE and therefore is not included in the MCOT.
  • the category 4 LBT for UE1 cannot be postponed because subframe 4 is allocated to (and therefore assumed to be used by) UE2 and so must be included in the MCOT.
  • a first information field is the ‘uplink subframe size’a nd in these examples of figures 3 and 4, has a value of 6 meaning that a total number of 6 subframes are allocated.
  • a second information field is ‘multiple UEs bitmap’ which identifies location of subframes used by one or multiple UEs. In the case of figure 3, this has the value 001110 meaning that the third, fourth and fifth subframes are allocated to multiple UEs (and the first, second and sixth subframes to one UE only) .
  • the ‘multiple UEs bitmap has the value 111000 meaning that the first, second and third subframes are allocated to multiple UEs (and the fourth, fifth and sixth subframes are allocated to only one) .
  • a third information field is ‘MCOT remaining duration’a nd has a value of 4 meaning that the remaining MCOT duration (after downlink transmissions have finished) comprises four subframes.
  • the signal processing functionality of UE1 can deduce that the Category 4 LBT can be postponed by a least two successive subframes if LBT failure occurs.
  • the signal processing functionality of both UE1 and UE2 can deduce that the Category 4 LBT cannot be postponed following an earlier LBT failure.
  • MCOT duration (after the eNB has completed its downlink transmissions) isequal to 3 (that is 3 ms or three subframes) and this value is transmitted to a UE by the eNB with the uplink grant.
  • Uplink subframes are configured by the eNB and represented by row 501 in figure 5 and numbered 4 to 9.
  • the ‘multiple UEs bitmap’ of 010000 shown in row 502 means that only subframe number 5 is used by more than one UE with the rest being used by one UE only (but not necessarily the same UE each time) .
  • the shaded subframes 4, 5, 7, 8 and 9 are allocated to UE1.
  • Row 503 represents LBT results with an ‘x’s ignifying a Category 2 failure and a ‘V’s ignifying a pass.
  • Row 505 states whether or not a particular subframe is counted as a transmission as far as the remaining MCOT is concerned.
  • Row 506 states the remaining MCOT duration at the end of each subframe as deduced by the UE1.
  • Row 507 states the category of LBT carried out at a particular subframe.
  • subframe 4 the UE1 performs a Category 2 (25 microsecond) LBT.
  • This LBT fails.
  • subframe 4 is scheduled to a single UE, (bitmap value 0) and UE 1 knows it is the only one scheduled on this subframe. So when the LBT fails, because the UE1 knows that this subframe is not used by any other UE, it can be excluded from the remaining MCOT duration. Hence, at the end of subframe 4 the remaining MCOT duration value has not changed and still remains at 3.
  • Subframe number 5 is scheduled to multiple UEs (bitmap value equal to 1) and the UE1 knows it is just one of the several UEs scheduled. So when theLBT fails, UE1 cannot know if this subframe is used by any other UE or not. Hence this subframe must be counted in the transmission duration. Therefore after subframe 5 the remaining MCOT duration is reduced by one and now equals 2.
  • Subframe number 6 is scheduled to a single UE and UE1 is not scheduled on this subframe (blank) . So UE1 cannot know if this subframe is used by another UE or not. This subframe must be counted in the transmission duration. So after subframe 6, the MCOT remaining duration is reduced by 1 down to a value of 1.
  • Subframe number 7 is similar to subframe number 4 in that it is only scheduled to UE1 and UE1 failed its LBT on subframe 7 in this example and so this frame is not counted in the transmission duration. So after subframe 7 the remaining MCOT duration is not reduced and remains at 1.
  • Subframe number 8 is only scheduled to UE1 and UE1 passed its LBT (indicated by the letter V in the table) and occupied this subframe. After subframe 8 the remaining MCOT duration is reduced by 1 down to 0 which means from the beginning of subframe number 9 a Category 4 LBT is required.
  • the UE can determine when to perform a category 4 LBT. This determination can be performed by the signal processor in the UE.
  • the UE is not configured to deduce remaining MCOT durations on a subframe by subframe basis as described above with reference to figure 5, but instead relies on signalling from the eNB.
  • a ‘remaining MCOT duration parameter’ can be included in one common DCI message to multiple UEs.
  • a UE monitors the downlink signalling. If no downlink signalling is received then the UE defaults to a Category 4 LBT. If downlink signalling is received and the ‘remaining MCOT duration parameter indicates a remaining duration of zero, then the UE must perform a Category 4 LBT.
  • the UE performs a Category 2 LBT in the first subframe and a Category 4 LBT in the next subframe. If downlink signalling is received and theremaining MCOT duration parameter is of 2 or more, then a Category 2 LBT can be performed in the first two and/or the following subframes.
  • the UE is not configured to determine whether a Category 4 LBT can be postponed or not but instead relies on signalling from the eNB.
  • An additional field equalling either 0 or 1, where a 0 means that a postponement is permitted if LBT fails on this subframe and a 1 means that it is not permitted, can be used. Taking the example of Figure 5, the table below illustrates this.
  • Subframe number 5 is a no because another UE is multiplexed and may use this subframe.
  • Subframe 6 is also a no because this subframe is scheduled to another UE.All the other subframes are yes, the Category 4 LBT can be postponed once the 25 ⁇ s LBT fails. The same number of subframes can be postponed as the number of subframes which have a failed LBT and a ‘yes’a t the same time.
  • subframe number 6 can be removed from the above signalling as it is not scheduled to UE1 and UE1 knows that. This option uses more downlink signalling but keeps everything and under the control of the eNB.
  • the signal processing functionality of the embodiments of the invention may be achieved using computing systems or architectures known to those who are skilled in the relevant art.
  • Computing systems such as, a desktop, laptop or notebook computer, hand-held computing device (PDA, cell phone, palmtop, etc. ) , mainframe, server, client, or any other type of special or general purpose computing device as may be desirable or appropriate for a given application or environment can be used.
  • the computing system can include one or more processors which can be implemented using a general or special-purpose processing engine such as, for example, a microprocessor, microcontroller or other control module.
  • the computing system can also include a main memory, such as random access memory (RAM) or other dynamic memory, for storing information and instructions to be executed by a processor.
  • main memory such as random access memory (RAM) or other dynamic memory
  • main memory also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by the processor.
  • the computing system may likewise include a read only memory (ROM) or other static storage device for storing static information and instructions for a processor.
  • ROM read only memory
  • the computing system may also include an information storage system which may include, for example, a media drive and a removable storage interface.
  • the media drive may include a drive or other mechanism to support fixed or removable storage media, such as a hard disk drive, a floppy disk drive, a magnetic tape drive, an optical disk drive, a compact disc (CD) or digital video drive (DVD) read or write drive (R or RW) , or other removable or fixed media drive.
  • Storage media may include, for example, a hard disk, floppy disk, magnetic tape, optical disk, CD or DVD, or other fixed or removable medium that is read by and written to by media drive.
  • the storage media may include a computer-readable storage medium having particular computer software or data stored therein.
  • an information storage system may include other similar components for allowing computer programs or other instructions or data to be loaded into the computing system.
  • Such components may include, for example, a removable storage unit and an interface , such as a program cartridge and cartridge interface, a removable memory (for example, a flash memory or other removable memory module) and memory slot, and other removable storage units and interfaces that allow software and data to be transferred from the removable storage unit to computing system.
  • the computing system can also include a communications interface.
  • a communications interface can be used to allow software and data to be transferred between a computing system and external devices.
  • Examples of communications interfaces can include a modem, a network interface (such as an Ethernet or other NIC card) , a communications port (such as for example, a universal serial bus (USB) port) , a PCMCIA slot and card, etc.
  • Software and data transferred via a communications interface are in the form of signals which can be electronic, electromagnetic, and optical or other signals capable of being received by a communications interface medium.
  • computer program product may be used generally to refer to tangible media such as, for example, a memory, storage device, or storage unit.
  • These and other forms of computer-readable media may store one or more instructions for use by the processor comprising the computer system to cause the processor to perform specified operations.
  • Such instructions generally referred to as ‘computer program code’ (which may be grouped in the form of computer programs or other groupings) , when executed, enable the computing systemto perform functions of embodiments of the present invention.
  • the code may directly cause a processor to perform specified operations, be compiled to do so, and/or be combined with other software, hardware, and/or firmware elements (e.g., libraries for performing standard functions) to do so.
  • the software may be stored in a computer-readable medium and loaded into computing systemusing, for example, removable storage drive.
  • a control module in this example, software instructions or executable computer program code
  • the processor in the computer system when executed by the processor in the computer system, causes a processorto perform the functions of the invention as described herein.
  • inventive concept can be applied to any circuit for performing signal processing functionality within a network element. It is further envisaged that, for example, a semiconductor manufacturer may employ the inventive concept in a design of a stand-alone device, such as a microcontroller of a digital signal processor (DSP) , or application-specific integrated circuit (ASIC) and/or any other sub-system element.
  • DSP digital signal processor
  • ASIC application-specific integrated circuit
  • aspects of the invention may be implemented in any suitable form including hardware, software, firmware or any combination of these.
  • the invention may optionally be implemented, at least partly, as computer software running on one or more data processors and/or digital signal processors or configurable module components such as FPGA devices.
  • the elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed, the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

L'invention concerne un procédé permettant de prendre en charge l'accès à un canal de communications sans licence à l'aide d'une procédure d'écoute avant la parole (LBT) dans un système LTE, qui comprend des paramètres dans un message d'informations de commande de liaison descendante envoyé par un eNB (101) à un équipement utilisateur (103a) pour aider l'équipement utilisateur à accéder plus efficacement au canal sans licence. Un paramètre concerne la durée du MCOT restant (temps maximum occupé par le canal). Dans un mode de réalisation, l'équipement d'utilisateur a la capacité de déterminer si une procédure LBT de catégorie 4 peut être reportée suite à une défaillance d'une précédente procédure LBT.
PCT/CN2017/082804 2016-05-13 2017-05-03 Procédés et dispositifs de prise en charge d'accès à des ressources radio sans licence dans des systèmes de communications sans fil WO2017193843A1 (fr)

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GB2550200A (en) 2017-11-15
GB2550200B (en) 2021-08-04

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