WO2016122228A1 - Procédé et appareil de contention pour des ressources de canal - Google Patents

Procédé et appareil de contention pour des ressources de canal Download PDF

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Publication number
WO2016122228A1
WO2016122228A1 PCT/KR2016/000941 KR2016000941W WO2016122228A1 WO 2016122228 A1 WO2016122228 A1 WO 2016122228A1 KR 2016000941 W KR2016000941 W KR 2016000941W WO 2016122228 A1 WO2016122228 A1 WO 2016122228A1
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channel
uplink
determining
uplink subframe
timing
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PCT/KR2016/000941
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English (en)
Inventor
Yingyang Li
Chengjun Sun
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Samsung Electronics Co., Ltd.
Beijing Samsung Telecommunications Technology Research Co., Ltd.
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Publication of WO2016122228A1 publication Critical patent/WO2016122228A1/fr

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    • 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]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0006—Assessment of spectral gaps suitable for allocating digitally modulated signals, e.g. for carrier allocation in cognitive radio

Definitions

  • the present disclosure relates to wireless communications, and particularly, to a method and a communication apparatus of occupying uplink/downlink channel resources in an unlicensed band based on a contending mechanism in a long term evolution (LTE) system.
  • LTE long term evolution
  • FIG. 1 is a schematic diagram illustrating a conventional FDD radio frame.
  • each radio frame lasts 10ms and includes 10 subframes.
  • Each subframe lasts 1ms.
  • Each time slot lasts 0.5ms.
  • FIG. 2 is a schematic diagram illustrating a conventional TDD radio frame. In a TDD system, each radio frame lasts 10ms and includes two half frames.
  • Each half frame lasts 5ms.
  • Each half frame includes 8 subframes each of which lasts 0.5ms and 3 special fields, i.e. Downlink Pilot Time Slot (DwPTS), Guarding Period (GP) and Uplink Pilot Time Slot (UpPTS).
  • the 3 special fields have a total duration of 1ms.
  • a downlink transmission time interval (TTI) is defined in a subframe.
  • Uplink/downlink (UL/DL) configurations for a TDD radio frame, as shown in Table 1.
  • D represents a downlink subframe
  • U represents an uplink subframe
  • S represents a special subframe including the 3 special fields.
  • the first n OFDM (Orthogonal Frequency Division Multiplexing) symbols in each downlink subframe may be used for transmitting downlink control information (DCI).
  • DCI include Physical Downlink Control Channel (PDCCH) and other control information.
  • the value of n may be 0, 1, 2, 3 or 4.
  • the other OFDM symbols may be used for transmitting Physical Downlink Shared Channel (PDSCH) or enhanced PDCCH (EPDCCH).
  • PDSCH Physical Downlink Shared Channel
  • EPDCCH enhanced PDCCH
  • PDCCH and EPDCCH respectively bear DCI for allocating uplink channel resources (referred to as UL Grant) and DCI for allocating downlink channel resources (referred to as DL Grant).
  • UL Grant Uplink channel resources
  • DL Grant DCI for allocating downlink channel resources
  • DCI of different UEs is transmitted individually.
  • DL Grant and UL Grant in DCI are also transmitted individually.
  • LTE-advanced LTE-advanced
  • multiple component carriers CC
  • CA carrier aggregation
  • the aggregated carriers constitute downlink and uplink links in the communication system, therefore larger transmission rates can be achieved.
  • Aggregated CCs may adopt the same duplexing manner, i.e., the aggregated CCs may be FDD cells or all of the CCs may be TDD cells.
  • the aggregated CCs may adopt different duplexing manners, i.e., the aggregated CCs may include both FDD cells and TDD cells at the same time.
  • a base station may configure a UE to work in multiple Cells which include a primary cell (Pcell) and multiple secondary cells (Scell).
  • Pcell primary cell
  • Scell secondary cells
  • initial transmission and HARQ re-transmission of the same transport block (TB) are restricted in one CC.
  • HARQ-ACK and channel state information (CSI) in a Physical Uplink Control Channel is only transmitted in a Pcell. This may undermine the flexibility of scheduling of base stations. Effectiveness of HARQ transmission needs to be improved in new scenarios to meet the demand of evolving LTE systems.
  • a UE may be configured with cells operating on an unlicensed band as Scells of the UE.
  • Unlicensed bands generally have already been allocated for other usages, e.g., for radar systems and/or wireless local area network (WiFi) systems defined in 802.11 standards.
  • WiFi systems of 802.11 family operate based on carrier sense multiple access/collision avoidance (CSMA/CA) mechanism.
  • a mobile station (STA) has to check a radio channel before transmitting a signal, and can transmit the signal in the radio channel only when the radio channel remains idle for a certain period of time.
  • the STA may use two mechanisms at the same time to determine the state of the radio channel.
  • the STA may apply carrier sensing to the radio channel, and determine the radio channel is busy when signals from other STAs are detected or a detected signal power exceeds a pre-defined threshold.
  • a physical layer module in the STA may send a clear channel assessment (CCA) report to a higher layer module indicating the radio channel is busy.
  • CCA clear channel assessment
  • WiFi systems of 802.11 family also introduce a virtual carrier sensing technique, i.e., using a network allocation vector (NAV) which indicates the duration in which a radio channel is reserved.
  • NAV network allocation vector
  • Each 802.11 frame includes a duration field, and the value of a NAV in the duration field can be used to determine the radio channel cannot be used for transmitting signals.
  • LTE systems need more spectrum resources to meet the requirement of increasing mobile communications services.
  • a possible solution is to deploy LTE systems on unlicensed bands.
  • multiple LTE systems may be configured to operate on an unlicensed band.
  • the multiple LTE systems may belong to different operators.
  • an LTE device may refer to a base station or a UE for simplicity.
  • an LTE device may check the state of a channel before transmitting signals in the channel, and occupy the channel only when a channel occupation condition is met. The device may occupy the channel for a duration of one or multiple subframe and release the channel to provide an opportunity for other devices to use the channel.
  • FBEs divide channel resources according to a fixed frame periodicity. As shown in FIG. 3, each frame may include channel occupation time and idle time. The channel occupation time is shorter than 10ms, and the idle time is no shorter than 5% of the frame periodicity.
  • a device may check the channel before each frame start, and the CCA time is no less than 20us. The device may occupy channel resources of the frame only when the channel is detected to be idle. LBEs contend for channel resources based on a policy similar to that of WiFi devices.
  • the time unit (TU) of CCA should be no less than 20us.
  • a device may check the channel through CCA within a TU, and occupy the channel if the channel is found to be idle. If the channel is found to be busy, the device may start an extended CCA (ECCA) process, i.e., generate a random number N and set a CCA counter. Each time when the device finds the channel remains idle within a TU, the device may decrease the number in the counter by 1. If the device finds the channel is busy, the device may keep the number in the counter unchanged. When the counter counts down to 0, the device may occupy the channel.
  • the N is a random value in [1, q], and q may be a value ranging from 4 to 32.
  • an LBE may occupy the channel for a maximum of ms.
  • a policy should be made for an LTE system operating on an unlicensed band for contending for channel resources based on the above two possible working modes, to better support LTE UL/DL transmission and to well co-exist with other systems operating on the unlicensed band.
  • Various examples provide a method, an apparatus and a base station of contending for channel resources.
  • the examples provide an effective mechanism for LBEs and FBEs to contend for channel resources and to well co-exist with other systems operating on the same unlicensed band.
  • a method of contending for channel resources may include:
  • ECCA extended clear channel assessment
  • CCA clear channel assessment
  • the procedure of determining the parameter for the ECCA according to the current frame structure may include: determining a currently allowed maximum channel occupation time according to the current frame structure, and adjusting the parameter according to the currently allowed maximum channel occupation time.
  • the procedure of determining the parameter for the ECCA according to the current frame structure may include: determining, by the device, an expected channel occupation time T0 before starting the ECCA, adjusting the parameter according to the T0, and applying the parameter to an ECCA process performed before occupying the channel.
  • the procedure of determining the T0 comprises: determining, by the device, the T0 for each category of downlink signal; or, determining, by the device, the T0 for each channel occupation.
  • the procedure of adjusting the parameter according to the currently allowed maximum channel occupation time comprises: adjusting, by a base station, the parameter according to a smaller value of the T0 and A; wherein the A represents a duration between a time point at which the channel is assessed and a time point at which the next channel occupation is to be ended, the T0 is a length of the expected channel occupation time of the device before the device starts the ECCA.
  • the procedure of adjusting the parameter for the ECCA according to the smaller value of the T0 and the A may include:
  • q 1 is the value of q for the first channel assessment since the last channel occupation in the same direction is ended
  • N 1 is the target random number corresponding to q 1
  • ⁇ (0,1) is a random value between (0,1) corresponding to an initial target random number N 1
  • q k-1 is the value of q used in channel assessment performed when the value of q was last modified
  • N k-1 is a target random number corresponding to q k-1
  • q k is the value of q during the current channel assessment performed by the device.
  • the clear channel criterion may be: a counting value X in a counter is larger than or equal to N k .
  • a method of contending for channel resources may include:
  • the procedure of performing downlink transmission may include:
  • the base station starting, by the base station, the CCA in a specified uplink subframe, and transmitting downlink data using the channel when the clear channel criterion is satisfied;
  • the specified uplink subframe is the uplink subframe that is currently not scheduled or the uplink subframe for which uplink scheduling information is not detected.
  • a method of contending for channel resources may include:
  • the procedure of determining the start timing of the device may include:
  • timing offset sequence which comprises timing offsets corresponding to different uplink subframe resources
  • the procedure of determining the start timing of the device comprises: configuring, by a base station, a time advance (TA) of the device for the uplink subframe resources; determining, by the device, uplink start timing according to N TA , (N TA +N TAoffset ) ⁇ T s is a pre-defined static offset.
  • TA time advance
  • the procedure of determining the start timing of the device comprises: determining uplink timing of a UE to be advanced by (N TA +N TAoffset +N (2) TAoffset ) ⁇ T s based on receiving timing of a downlink subframe corresponding to the uplink subframe resources, N TA is a TA configured for the UE, N TAoffset is a static offset, and N (2) TAoffset is one of timing offsets defined for different uplink subframe resources.
  • a sequence of N (2) TAoffset may be generated in advance, each value in the sequence represents an offset N (2) TAoffset corresponding to a subframe;
  • the N (2) TAoffset to be used in uplink transmission may be configured via cell-specific signaling.
  • the procedure of determining the start timing of the device comprises: puncturing a starting section of an uplink subframe in a cell while keeping timing of the uplink subframe unchanged so as to change the actual timing of transmitting an uplink signal at a UE.
  • the number of OFDM symbols that are allowed to be punctured at the starting section of the uplink subframe is less than or equal to 3.
  • G is a pre-determined positive integer.
  • a sequence of puncturing duration may be generated in advance, each value in the sequence represents a duration of performing puncturing on a subframe in the specified direction;
  • An apparatus of contending for channel resources may include: an extended clear channel assessment (ECCA) parameter determination unit, a clear channel assessment (CCA) unit and a data transmission unit;
  • ECCA extended clear channel assessment
  • CCA clear channel assessment
  • the ECCA parameter determination unit is configured to determine a parameter for an ECCA according to a current frame structure
  • the CCA unit is configured to perform CCA to obtain a state of a channel in an unlicensed band, and send an instruction to the data transmission unit when determining a clear channel criterion is satisfied according to the parameter;
  • the data transmission unit is configured to occupy the channel for data transmission after receiving the instruction from the CCA unit.
  • An apparatus of contending for channel resources may include: an uplink subframe determination unit, an idle detection unit and a downlink transmission unit;
  • the uplink subframe determination unit is configured to determine an uplink subframe for uplink transmission in a channel according to pre-defined allocation information
  • the idle detection unit is configured to determine an uplink subframe which is currently not scheduled or an uplink subframe for which uplink scheduling information is not detected, and inform the downlink transmission unit to perform downlink transmission using the determined uplink subframe.
  • An apparatus of contending for channel resources may include: a start timing determination unit, a channel assessment unit and a transmission unit;
  • the start timing determination unit is configured to determine a start timing for transmitting a signal in a specified direction within a time period for transmission in the specified direction;
  • the channel assessment unit is configured to assess a channel before the start timing determined by the start timing determination unit, and instruct the transmission unit to transmit a signal using the channel in response to a determination that the channel is idle.
  • LBEs may control channel occupation using the ECCA parameter or perform downlink transmission using unoccupied uplink resources, so as to effectively use resources in unlicensed bands.
  • FBEs may all have opportunity to perform transmission using an unlicensed band by using variable start timing for transmission.
  • FIG. 1 is a schematic diagram illustrating the structure of a conventional FDD radio frame
  • FIG. 2 is a schematic diagram illustrating the structure of a conventional TDD radio frame
  • FIG. 3 is a schematic diagram illustrating a working mechanism of an FBE according to regulations of Europe;
  • FIG. 4 is a schematic diagram illustrating adjusting an ECCA parameter according to a possible channel occupation time
  • FIG. 5 is a schematic diagram illustrating UL resources and DL resources
  • FIG. 6 is a schematic diagram illustrating downlink transmission using idle uplink resources
  • FIG. 7 is a schematic diagram illustrating co-existence realized through adjusting timing of an uplink subframe.
  • FIG. 8 is a schematic diagram illustrating co-existence realized through puncturing a starting section of an uplink subframe.
  • an apparatus i.e. UE or base station
  • a communication unit transmitter
  • a control unit controller
  • the communication unit may communicate with a different network node (base station or UE).
  • the control unit controls overall states and operations of the components of the apparatus. This is for ease of description only. That is, the above apparatus may have a different configuration.
  • the apparatus may further include an input unit and a storage unit.
  • the mechanism may include three methods of contending for channel resources. Examples one and two are examples of a method for LBEs, and example three is an example for FBEs. The following describes a few examples of the method of contending for channel resources.
  • the following is a method for LBE.
  • the method may be applied to DL transmission and UL transmission.
  • channel resources of a carrier in an unlicensed band may be not allowed to be used for data transmission in a specified direction within specified time periods.
  • the carrier may be kept idle for some specified time periods and all LTE devices are not allowed to use the carrier for transmission, so that the idle time periods may be used for measuring signals from other systems.
  • some specified subframes on the carrier may be reserved for uplink transmission, and a base station may switch to a receiving state during the specified subframes and are not allowed to transmit downlink signal using the specified subframes.
  • the ECCA herein refers to a process of a device performs CCA and judges whether to occupy a channel.
  • a target random number ceiling q may be obtained according to a target channel occupation time T, and a target random number N may be generated at random according to q.
  • the range of N is 1 to q.
  • the device may check the channel state with a granularity of the duration of a TU. If the channel stays idle within a TU, the device may determine the channel is detected to be idle for one more time. When the number of times the channel is detected to be idle reaches N, the device may occupy the channel for transmitting signals.
  • the target channel occupation time T may be a static value, or a value semi-statically configured via higher-layer signaling.
  • the device may determine an expected target channel occupation time T0, and obtain other parameters for the ECCA according to the T0, and apply the parameters in the whole ECCA process before the next channel occupation.
  • the base station may transmit different types of downlink signal according to the functions to be fulfilled, and accordingly, the expected target channel occupation time T0 may be different.
  • the signals to be transmitted by the base station may be downlink data which generally needs a longer time to transmit more downlink data.
  • the signals to be transmitted by the base station may be discovery signal (DRS) which may occupy fewer subframes.
  • DRS discovery signal
  • the signals to be transmitted by the base station may be reference signals dedicated for CSI measurement, e.g., CRS or CSI-RS, and the expected channel occupation time may be shorter than the duration of a subframe.
  • different types of downlink signals may correspond to different expected channel occupation time T0.
  • ECCA is performed in different manners for different types of downlink signals by taking the expected channel occupation time T0 corresponding to the downlink signals to be transmitted as the target channel occupation time T.
  • the channel occupation time of the device may be different each time for the same type of downlink signals.
  • the target channel occupation time for each time of channel occupation may be determined to be T0, and the ECCA for that time of channel occupation may be performed according to T0.
  • the target channel occupation time T may be adjusted according to currently allowable maximum channel occupation time.
  • an LBE may determine the currently allowable maximum length of channel occupation time according to the current frame structure, and adjust the parameter for ECCA according to the currently allowable maximum length.
  • the length of time between a time point at which the channel is checked and a time point at which the next channel occupation is to be ended is denoted as A.
  • the parameter for the ECCA may include the upper limit q of the target random value generated by the device and the value N of the target random number.
  • the adjusting of the ECCA parameter may be performed before channel assessment of each TU, i.e., the ECCA parameter may be adjusted according to the currently allowable maximum channel occupation time A before CCA within each TU.
  • the ECCA parameter may be adjusted at an interval of plural TUs, i.e., the ECCA parameter may be adjusted before CCA within a TU every plural TUs.
  • the ECCA parameter may be adjusted according to other conditions.
  • the device may adjust the ECCA parameter when the device is to obtain the channel state near a boundary of a subframe, i.e., the ECCA parameter may be adjusted according to the currently allowable maximum channel occupation time A before CCA in a TU at a time near the boundary of a subframe.
  • the device may select the ECCA parameter according to allowable maximum channel occupation time A at the start of CCA during an ECCA process before a channel occupation.
  • the following example describe a detailed process.
  • FIG. 4 it is supposed specific subframes in the channel are periodically assigned for uplink transmission, i.e., 3 consecutive subframes in every 9 subframes are allocated for uplink transmission.
  • a base station starts channel assessment at a position of the CCA time 1, and an expected maximum channel occupation time of the base station is 6ms.
  • the device may select q 1 to be 15 for ECCA according to the value of A, i.e., 6ms, according to the regulations in Europe since the maximum possible downlink occupation time A is 6ms, i.e., a target random number N1 between 1 and 15 is randomly generated, and a counting value in an idle counter is initiated to be 0. Then the device may perform channel assessment, and increase the value in the idle counter by 1 after detecting the channel stays idle in a TU. If the target random number is unchanged, when the value in the idle counter equals to the target random number N1, the device may occupy the channel for data transmission.
  • the base station may adjust the ECCA parameter according to currently remaining maximum possible channel occupation time. For example, supposing a channel occupation condition is not satisfied since the CCA time 1 and the remaining maximum possible downlink occupation time A at CCA time k is 4ms, the device may adjust the ECCA parameter according to the value of A, i.e., 4ms. According to the regulations in Europe, when A is 4ms, the device may select q k to be 10 for performing the ECCA. As such, the device may adjust the target random number according to q k , and the adjusted target random number is denoted as N k . Some methods of processing N k are as follows.
  • a random number N k is randomly generated as the target random number, and the value of N k may be between 1 and q k . If the current value X in the idle counter is larger than or equal to N k , the device may directly occupy the channel for data transmission without performing another CCA. If X is smaller than N k , the device may perform another CCA and increase the value in the idle counter by 1 when the channel is detected to be idle in a TU. If the target random number is unchanged, when the value in the idle counter equals to the target random number N k , the device may occupy the channel for data transmission.
  • an upper limit q of the target random number for each CCA may be determined according to A or T0.
  • the value of q for the first CCA may be denoted as q 1
  • an initial value of the target random number may be denoted as N 1 .
  • An upper limit q k of the target random number for current CCA may be obtained according to currently possible channel occupation time.
  • the target random number generated for the first CCA may be adjusted according to the values of q 1 and q k to obtain the current target random number N k .
  • ⁇ (0,1) is a random value corresponding to N 1 within (0,1)
  • the device may perform another CCA and increase the value in the idle counter by 1 when the channel is detected to be idle in a TU. If the target random number is unchanged, when the value in the idle counter equals to the target random number N k , the device may occupy the channel for data transmission.
  • the time of the first CCA of the device refers to the CCA performed for transmitting new downlink packets since the last time the channel was released after previous downlink transmission was ended.
  • the upper limit q of the target random number for each CCA may be determined according to A or T0, and the upper limit q k of the target random number for the current CCA may be obtained according to the currently possible channel occupation time.
  • the upper limit of the target random number of the previous CCA may be denoted by q k-1
  • the target random number of the previous CCA may be denoted by N k-1 .
  • the current target random number N k may be obtained by adjusting N k-1 according to q k and q k-1 .
  • UL/DL transmission is performed in a time division multiplexing manner.
  • the mechanism of various examples may be applied to downlink transmission.
  • the position of the uplink subframes may be decided by UL grant. When a UE receives a UL grant within subframe n, the UE may determine subframe n+k may be used for uplink transmission according to a timing relation. k is decided by the timing relation from the UL grant to an uplink subframe which includes PUSCH. Although some subframes are allocated for uplink transmission, the UE may not transmit uplink signals because the channel is detected to be busy.
  • a base station may always determine the subframes cannot be used for downlink transmission no matter whether the subframes are used by a UE for transmitting uplink data. That is, the base station does not perform CCA within the time of the subframes, and does not transmit downlink data using the subframes.
  • supposing the subframe configuration periodicity is 9 subframes, and the last 3 subframes in each period may be used for uplink transmission. According to the above example, the last 3 subframes in each period are reserved for uplink transmission only, and downlink transmission are performed in the other 6 subframes in each period.
  • a base station schedules a UE for uplink transmission but all UEs do not transmit uplink signals because the channel is detected to be busy, the subframes actually are not used in uplink transmission. In this situation, the base station cannot transmit data in the subframes even if the channel is in a CCA idle state at the location of the base station, and this is a waste of resources.
  • another method allows a base station to transmit downlink data using uplink resources on which no uplink transmission is scheduled or no uplink signal is detected although uplink transmission is scheduled on the uplink resources.
  • uplink resources may be used for downlink transmission.
  • a subframe or plural consecutive subframes may be used for uplink transmission, but a base station does not semi-statically configure uplink transmission of any UE nor schedule uplink transmission of any UE. Since uplink transmission in subframes are scheduled in advance of at least 4ms, the base station knows there is no uplink signal in the subframes, and may continue downlink transmission which starts before the uplink subframes start within the uplink subframes, i.e., the uplink subframes are actually used for downlink transmission.
  • supposing a previous downlink occupation time of a base station ends before the uplink subframe start, when the base station does not semi-statically configure uplink transmission of any UE nor schedule uplink transmission of any UE, the base station may re-start CCA in the subframes previously allocated for uplink transmission, and occupy the channel for transmitting downlink data when a clear channel criterion is satisfied.
  • supposing a previous downlink occupation time of a base station ends before the uplink subframe start, when the base station semi-statically configures uplink transmission of any UE or schedules uplink transmission of any UE in the uplink subframes, the base station may performs uplink signal detection in the uplink subframes.
  • the base station may re-start CCA in the remaining time of the uplink subframes previously allocated for uplink transmission, and occupy the channel for transmitting downlink data when a clear channel criterion is satisfied.
  • the channel occupation may not be restricted in the remaining time of the uplink subframes, but may continue in subframes for downlink transmission after the uplink subframes end.
  • supposing the subframe configuration periodicity is 9 subframes, and the last 3 subframes in each period may be used for uplink transmission.
  • supposing an uplink subframe set 701 is used for uplink transmission, subsequent downlink transmission resources may start after the uplink subframes end, i.e., the subframe set 702.
  • Supposing a base station has semi-statically configured uplink transmission of a UE or has scheduled uplink transmission of a UE on uplink subframe 703 but no uplink transmission of any UE is detected in uplink subframe 703, the base station may attempt to perform downlink transmission 704 in advance after determining no uplink transmission of any UE is received.
  • the base station may measure signal power in the uplink subframe, or measure the power of DMRS to determine whether there is a UE transmitting uplink signals in the uplink subframe. According to the method, when the base station does not schedule uplink transmission of any UE, or when the base station detects all UEs do not perform uplink transmission as scheduled, the base station may reuse the uplink subframe resources for downlink transmission to make full use of the channel resources.
  • This example describes a modified method for FBE.
  • the method may be applied to DL transmission and UL transmission.
  • the following takes UL transmission as an example to illustrate the method of contending for channel resources.
  • Supposing a work flow of UL transmission in an unlicensed band may include: a base station may first transmit a UL grant to schedule PUSCH of a UE or may semi-statically configure uplink transmission of the UE; the UE may performs CCA before the configured UL subframe, e.g., performing CCA within a TU, and transmit an uplink signal after the channel is detected to be idle. That is, UL transmission of the UE is based on an FBE policy after the base station dynamically schedules or semi-statically allocates resources.
  • Supposing positions of uplink subframes of adjacent cells are aligned to each other, according to the FBE policy, if UEs within an area have different timing, the uplink signal of the UE with earlier timing may keep blocking the uplink signal of the UE with the later timing.
  • This situation of UEs having different timing is likely to happen. That may happen when timing of adjacent cells are asynchronous, or when there are multiple operators within an area and timing of the operators are asynchronous.
  • FBEs are configured to perform CCA periodically at some time points. Since LTE systems support an uplink timing adjustment mechanism, i.e., the uplink timing of a UE is controlled by a base station, the UE may adjust the timing for transmitting uplink signals according to a timing command of a base station. As such, when FBE is applied in LTE systems, the UE may perform CCA before timing for UL transmission specified by the base station. That is, when working according to FBE in LTE UL direction, the UE may not perform CCA periodically, but may perform CCA at adjustable time points according to timing commands from the base station.
  • various examples provide a mechanism in which UEs in a cell changes the start timing for transmitting uplink signals according to a determined rule in each time interval for uplink transmission.
  • a UE may perform CCA in a time period, e.g., in a TU, before the uplink start timing starts, and transmit an uplink signal if the channel is idle, or not occupy the uplink resources this time if the channel is busy.
  • the determined rule for changing the uplink timing may be adopted by all of UEs in the cell, so that all of UEs in the same cell may transmit uplink signal at the same time.
  • the cell may have priority in transmitting uplink signals and occupying the channel.
  • UL timing of a cell is later than other cells, it is equivalent to that the cell actively gives up the channel occupation opportunity to enable other cells that have earlier UL timing to transmit uplink signals.
  • the cells may well co-exist with each other.
  • supposing cells of an operator have synchronized uplink transmission and cells of different operators may be asynchronous, cells of the same operator may adopt the above rule of changing UL timing.
  • the start timing of UL transmission of a UE may be controlled by a base station.
  • the start timing of an uplink subframe is changed by adjusting the value of N TA in calculating the timing advance according to (N TA +N TAoffset ) ⁇ T s . That is, in different time periods for uplink transmission, the start timing of transmitting uplink signals may be changed by configuring different N TA as the timing advance.
  • the above method for FBE satisfies the requirements of FBE because the timing of starting UL transmission of an FBE is controlled by a base station.
  • UEs that may need to transmit uplink signals may adjust the value of N TA through dedicated signaling before starting UL transmission, thus the signaling overhead is large.
  • the rule of changing start timing of uplink subframes in different UL resources in a cell may be configured, i.e., UEs in a cell may start transmitting uplink signals at different timing positions in different uplink resources.
  • the time advance of a UE in a cell may be changed by adding an offset, denoted as N (2) TAoffset , to the above time advance (N TA +N TAoffset ) ⁇ T s , i.e., the uplink timing of the UE is ahead of receiving timing of a downlink subframe of the UE by (N TA +N TAoffset +N (2) TAoffset ) ⁇ T s .
  • the N (2) TAoffset may be in unit of OFDM symbol length, thus after the N (2) TAoffset is changed for different uplink resources, the timing of an uplink OFDM symbol remains the same although the start timing and end timing of a subframe relative to corresponding downlink subframe are changed.
  • the N (2) TAoffset may be in a smaller unit, denoted as G us, e.g., G may be the length of a TU, i.e., 20 us.
  • the value of N (2) TAoffset may be not negative so that the actual uplink transmission timing of a UE is always advanced compared with corresponding downlink subframe.
  • the value of the advance may be different for each uplink transmission.
  • a larger GP may be reserved to allow adjustment of uplink subframe timing without affecting subsequent downlink subframes.
  • the value of N (2) TAoffset may be all negative, and the value of the delay may be different for each uplink transmission.
  • the uplink transmission timing of the UE is delayed relative to corresponding downlink subframes, thus OFDM symbols at the beginning of a subsequent downlink subframe may be punctured.
  • the larger TA may be configured by a base station so that the actual uplink transmission timing of a UE is advanced relative to a corresponding downlink subframe, and a larger GP may be reserved so that a subsequent downlink subframe is not affected.
  • the value of N (2) TAoffset may be positive, 0 or negative, i.e., the actual uplink transmission timing of a UE relative to a corresponding downlink subframe is sometimes advanced, sometimes postponed. The value of the advance or the delay may be different for each uplink transmission.
  • a sequence for changing the N (2) TAoffset may be generated for each cell.
  • the PCID of a cell may be used as an initiation parameter of random number generator.
  • supposing uplink transmission of cells of the same operator are synchronous, all LTE cells of the same operator may be configured with the same sequence for changing the N (2) TAoffset , and LTE cells of different operators may be configured with different sequences for changing the N (2) TAoffset .
  • the sequence for changing the N (2) TAoffset may be inexplicitly defined by other parameters, thus no extra signaling overhead is generated.
  • the method of generating the sequence for changing the N (2) TAoffset is not limited in various examples.
  • new cell-specific signaling may be used for configuring the N (2) TAoffset to be used in an uplink transmission.
  • the value of N (2) TAoffset may be changed for each uplink transmission, or may be changed for every plural times of uplink transmission.
  • this method includes transmitting occupation signaling for each UE, thus reduces the signaling overhead.
  • the signal power of the UE will block the uplink transmission of UEs in cell 2.
  • the N (2) TAoffset of cell 1 is 0, and the N (2) TAoffset of cell 2 is 3, when the blocking situations are not taken into consideration, the start timing of cell 2 falls ahead of that of cell 1 by 2.5 OFDM symbols, thus a UE in cell 2 can transmit uplink signals.
  • the signal power of the UE will block the uplink transmission of UEs in cell 1.
  • UEs from two cells may occupy resources alternately by changing the value of N (2) TAoffset .
  • uplink subframe timing of a cell may be kept unchanged, and the beginning section of an uplink subframe may be punctured to change the actual timing of uplink transmission of a UE.
  • the time length of the puncturing may be changed, i.e., UEs in a cell may transmit uplink signals at different timing positions on different uplink resources.
  • the puncturing may include puncturing at most N single-carrier frequency division multiple access (SCFDMA) symbols at the beginning section of a subframe in unit of SCFDMA symbols. For example, N may be smaller than or equal to 3 to avoid puncturing a DMRS symbol of the subframe.
  • SCFDMA single-carrier frequency division multiple access
  • the puncturing may be performed in a smaller unit, denoted as G us to puncture at most M ⁇ G us at the beginning section of a subframe.
  • G may equal the length of a TU, i.e., 20us.
  • M may be selected so as to avoid puncturing a DMRS symbol in a subframe. If the punctured portion at the beginning section of a subframe are not whole SCFDMA symbols, the UE may transmit filling signals until the start of the next whole SCFDMA symbol, and then transmit uplink signals. The filling signals are used for occupying the channel.
  • a sequence for changing the puncture time may be generated for each cell.
  • the PCID of a cell may be used as an initiation parameter of random number generator.
  • supposing uplink transmission of cells of the same operator are synchronous, all LTE cells of the same operator may be configured with the same sequence for changing the puncture time, and LTE cells of different operators may be configured with different sequences for changing the puncture time.
  • the method of generating the sequence for changing the puncture time is not limited in various examples. According to the method, the sequence for changing the puncture time may be inexplicitly defined by other parameters, thus no extra signaling overhead is generated. In an example, new cell-specific signaling may be used for configuring the puncture time to be used in an uplink transmission.
  • the length of the puncture time may be changed for each uplink transmission, or may be changed for every plural times of uplink transmission.
  • this method includes transmitting occupation signaling for each UE, thus reduces the signaling overhead.
  • supposing the uplink timing of cell 2 falls behind that of cell 1 by half of an SCFDMA symbol.
  • UEs from different cells may have the opportunity to occupy the resources.
  • the start timing of cell 2 falls behind that of cell 1 by 1.5 SCFDMA symbols, thus a UE in cell 1 can transmit uplink signals.
  • the signal power of the UE will block the uplink transmission of UEs in cell 2.
  • the start timing of cell 1 falls ahead of that of cell 1 by 2.5 SCFDMA symbols, thus a UE in cell 2 can transmit uplink signals.
  • the signal power of the UE will block the uplink transmission of UEs in cell 1.
  • UEs from two cells may occupy resources alternately by changing the length of puncture time.
  • the apparatus may include an ECCA parameter determination unit, a CCA unit and a data transmission unit.
  • the ECCA parameter determination unit may determine a parameter for an ECCA according to a current frame structure.
  • the CCA unit may perform CCA to obtain a state of a channel in an unlicensed band, and send an instruction to the data transmission unit when determining a clear channel criterion is satisfied according to the parameter.
  • the data transmission unit may occupy the channel for data transmission after receiving the instruction from the CCA unit.
  • the apparatus may include an uplink subframe determination unit, an idle detection unit and a downlink transmission unit.
  • the uplink subframe determination unit may determine an uplink subframe for uplink transmission in a channel according to pre-defined allocation information.
  • the idle detection unit may determine an uplink subframe which is currently not scheduled or an uplink subframe for which uplink scheduling information is not detected, and inform the downlink transmission unit to perform downlink transmission using the determined uplink subframe.
  • the apparatus may include a start timing determination unit, a channel assessment unit and a transmission unit.
  • the start timing determination unit may determine a start timing for transmitting a signal in a specified direction within a time period for transmission in the specified direction.
  • the channel assessment unit may assess a channel before the start timing determined by the start timing determination unit, and instruct the transmission unit to transmit a signal using the channel in response to a determination that the channel is idle.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

Divers exemples concernent un procédé de contention pour des ressources du canal. Un dispositif peut déterminer un paramètre pour une évaluation de canal dégagé étendue (CCA étendue, ECCA) d'après une structure de trame actuelle, exécuter une CCA afin d'obtenir un état d'un canal dans une bande sans licence, et occuper le canal en réponse à une détermination selon laquelle un critère de canal dégagé est satisfait selon le paramètre. Selon divers exemples, des canaux dans une bande sans licence peuvent être occupés raisonnablement, et le système peut ainsi coexister avec d'autres systèmes opérant sur la bande sans licence.
PCT/KR2016/000941 2015-01-29 2016-01-28 Procédé et appareil de contention pour des ressources de canal WO2016122228A1 (fr)

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CN112534928A (zh) * 2018-08-09 2021-03-19 Oppo广东移动通信有限公司 传输信息的方法、终端设备和网络设备
CN111278152B (zh) * 2019-01-04 2022-02-08 维沃移动通信有限公司 信道占用方法、帧周期指示方法、帧周期确定方法及设备
CN112738905B (zh) * 2019-02-21 2022-04-29 华为技术有限公司 随机接入的方法和装置
CN115696624A (zh) * 2021-07-21 2023-02-03 中兴通讯股份有限公司 信道共享方法、设备和存储介质

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CN118138118A (zh) * 2024-05-08 2024-06-04 天津讯联科技有限公司 一种vdes上下行通信协同分配数据信道资源的方法

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