Patent Application
20250142426
The present disclosure relates to a terminal, a base station, and a communication method.
In the standardization of 5G, New Radio access technology (NR) was specified in 3GPP, and specification of Release 15 (Rel. 15) of NR was published.
However, there is room for further study on a method for improving the accuracy of control on a transmission timing of a signal.
One non-limiting and exemplary embodiment of the present disclosure facilitates providing a terminal, a base station, and a communication method each capable of improving the accuracy of control on a transmission timing of a signal.
A terminal according to an exemplary embodiment of the present disclosure includes: reception circuitry, which, in operation, receives, in a first cell, control information for identifying a reference time in control on a transmission timing of an uplink signal to a second cell that is different from the first cell; and control circuitry, which, in operation, controls the transmission timing based on the control information.
It should be noted that general or specific embodiments may be implemented as a system, an apparatus, a method, an integrated circuit, a computer program, a storage medium, or any selective combination thereof.
According to a non-limiting and exemplary embodiment of the present disclosure, it is possible to improve the accuracy of control on a transmission timing of a signal.
Additional benefits and advantages of the disclosed aspects will become apparent from the specification and drawings. The benefits and/or advantages may be individually obtained by the various embodiments and features of the specification and drawings, which need not all be provided in order to obtain one or more of such benefits and/or advantages.
Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.
NR Rel. 15 has been specified as a radio access technology for terrestrial networks. Meanwhile, an extension of NR to a non-terrestrial network (NTN) such as communication using a satellite and/or a high-altitude platform station (HAPS) has been studied (e.g., NPL 1).
In the NTN environment, a coverage area (e.g., one or more cells) of a satellite for a terminal (may be also referred to as, e.g., user equipment (UE)) on the ground or a terminal located in airspace, such as an aircraft or drone, is formed by a beam from the satellite. In addition, a round trip time (RTT) of radio wave propagation between the terminal and the satellite is determined depending on the altitude of the satellite (e.g., approximately up to 36000 km) and the angle viewed from the terminal, that is, the positional relation between the satellite and the terminal.
For example, NPL 1 mentions that the round trip time (RTT) of radio wave propagation between a base station and a terminal takes up to approximately 540 ms in NTN.
Further. NPL 1 mentions that, in NTN, a differential delay up to approximately 10 ms (e.g., difference between farthest location and closest location from satellite in beam) arises in accordance with a location of a terminal in a beam (or coverage area or cell).
In addition, for example, in the case of a non-geostationary satellite such as a low-earth orbit satellite (LEO), the amount of a propagation delay varies more rapidly than in the terrestrial network because the satellite moves at a high speed of approximately 7.6 km per second.
In NR, for example, in order to align reception timings at a base station (e.g., also referred to as gNB) of signals transmitted from terminals, each of the terminal performs timing control (e.g., timing adjustment) that is based on information (e.g., referred to as “Timing Advance (TA) command”) indicated (notified) by the base station for correcting (adjusting) a timing.
In NTN, since the amount of the propagation delay vanes more rapidly than in the terrestrial network as described above, a terminal calculates the round-trip delay time between the terminal and a base station, corrects the timing, and thereby transmits a signal.
Delay time of a radio link between a terminal and a satellite (e.g., referred to as “service link”) may be calculated based on, for example, location information on the terminal and information on an orbit or a location of the satellite. Note that the location information on the terminal may be acquired by, for example, a Global Navigation Satellite System (GNSS) or the like at the terminal. Further, the information on the orbit or location of the satellite may be indicated (e.g., broadcasted) from a base station to the terminal as “satellite ephemeris information (or satellite ephemeris),” for example.
Meanwhile, delay time of a radio link between a base station or a gateway (GW) on the ground and a satellite (e.g., referred to as “feeder link”) may be calculated, at the terminal, based on a common TA parameter indicated from the base station, for example.
The delay time of the feeder link varies as the satellite moves, so that information on the amount of variation in the delay time, such as a common TA drift and the amount of variation in the common TA drift (common TA drift variation) may be indicated to the terminal as the common TA parameter, in addition to the delay time of the feeder link at a certain point, for example.
As described above, in NTN, the round trip delay time of the service link and the feeder link are corrected (e.g., compensated) on a side of the terminal, and an uplink signal is thus transmitted. This allows the signal transmitted from each terminal to be received within a predetermined time-difference at the base station.
As control information for NTN from the base station to the terminal, at least one of the following information/parameters may be included. The control information for NTN may be indicated to the terminal by, for example, broadcast information such as a System Information Block (SIB). Alternatively, the information may be indicated by parameter NTN-Config.
Here, the epoch time is, for example, a reference time of the satellite ephemeris and common TA parameter. The satellite ephemeris and common TA parameter are generated based on the epoch time, and values thereof at the time of the epoch time are indicated. The terminal may, for example, calculate a satellite location based on the epoch time and the satellite ephemeris information, and calculate the delay time of the feeder link based on the epoch time and the common TA parameter.
Further, the epoch time is not an absolute time and may be represented by a system frame number (SFN) and a subframe number and thus indicated to the terminal, for example.
Incidentally, the satellite ephemeris information may include, for example, the following parameters:
Meanwhile, the common TA parameter may include, for example, the following parameters:
The satellite ephemeris information and common TA parameter are sometimes referred to as assistance information.
The terminal, for example, using at least one of the above parameters included in the control information for NTN, may calculate the amount of feeder-link delay (hereinafter referred to as “feeder-link delay amount”) (round-trip delay), Delaycommon (t), according to the following Equation 1:
Note that the feeder-link delay amount may be delay between a satellite and a timing synchronization reference point (reference point) of an uplink signal
In NR, a terminal in an RRC_IDLE state or an RRC_INACTIVE state performs neighbor cell measurement for cell reselection.
The information on a neighbor cell used in the neighbor cell measurement may be indicated (e.g., broadcasted) from a base station to the terminal, for example. For example, the information on the neighbor cell may be indicated to the terminal by SIB type 2 (SIB 2). The information on the neighbor cell may include, for example, at least one of a radio parameter such as carrier frequency or subcarrier spacing (SCS) and information on a time location of an SSB to be measured, which is called SSB measurement timing configuration (SMTC). Incidentally, the SSB is an abbreviation for Synchronization Signal (SS)/Physical Broadcast Channel (PBCH) block. In the neighbor cell measurement, quality measurement may be performed on, for example, Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), and Signal to Interference and Noise Ratio (SINR) of the neighbor cell.
Further, in NR, for example, a terminal in an RRC_CONNECTED state performs the neighbor cell measurement for handover in accordance with the indication from the base station and then performs the handover.
Information on a neighbor cell used in the neighbor cell measurement for the handover (e.g., which may be same as above-mentioned information on neighbor cell) may be indicated to the terminal by terminal-specific RRC signaling (e.g., dedicated RRC signaling), for example. For example, the information on the neighbor cell may be indicated by an “RRCreconfiguration message” from a base station (e.g., serving cell) to which the terminal is connected.
In NTN, as the information on the neighbor cell, satellite ephemeris information and common TA parameter of the neighbor cell may be indicated. The satellite ephemeris information and common TA parameter of the neighbor cell may be used, for example, by a terminal to adjust a measurement window as a satellite moves; additionally, may be used to adjust a measurement timing of the neighbor cell called SSB based measurement timing configuration (SMTC). Further, when performing the handover, the terminal may perform timing adjustment (TA) for random access transmission (e.g., random access channel (RACH) transmission), using the satellite ephemeris information and common TA parameter of the neighbor cell.
For example, there is room for further study on a method for indicating information on a neighbor cell.
In NR (e.g., Release 16), conditional handover (CHO) has been introduced.
In CHO, for example, a terminal receives in advance an RRCreconfiguration message including a condition for the handover (hereinafter referred to as “HO condition”). For example, a base station that serves as a handover source (e.g., also referred to as source base station, source gNB, or source cell) may transmit a handover request (HO request message) to a base station that serves as a handover target (e.g., also referred to as target base station, target gNB, or target cell). The target base station may transmit a handover request acknowledge (HO request acknowledge message) to the source base station. The source base station may then transmit the RRCreconfiguration message including the HO condition to a terminal (UE) subject to the handover, for example.
The terminal may evaluate (or confirm, determine, monitor) at any time whether the HO condition is satisfied. When the HO condition is satisfied, the terminal may perform the handover and perform processing of accessing a new cell (target base station) (e.g., RACH processing).
For example, in Release16, a condition based on the neighbor cell measurement is used as the HO condition. In the condition based on the neighbor cell measurement, a terminal may perform the handover in a case where, for example, measurement results of RSRP, RSRQ, SINR, and the like of the neighbor cell satisfy the prescribed criteria.
In NTN, as the HO condition, for example, the addition of at least one of a condition based on a timing and a condition based on a location has been discussed, in addition to the condition based on the neighbor cell measurement.
In the timing-based CHO, for example, a terminal may perform the handover within a time range indicated in advance. Alternatively, the terminal may, for example, perform the neighbor cell measurement within the time range indicated in advance and perform the handover when a result of the neighbor cell measurement satisfies the prescribed criteria.
In the location-based CHO, for example, a terminal may perform the handover in a case where a distance between a reference location of a cell to which the terminal is connected (e.g., current cell or serving cell) and the terminal is greater than a value indicated in advance. Alternatively, for example, the terminal may perform the handover in a case where the distance between the reference location of the current cell and the terminal is greater than a distance between a reference location of the neighbor cell and the terminal (or greater by prescribed distance).
Thus, in NTN, giving an HO condition to a terminal beforehand allows the handover with a reduced delay even when a cell is switched at high speed as in LEO.
The conditional handover (CHO) has been described, thus far.
As described above, the epoch time indicated from a base station to a terminal in NTN may be represented by the SFN and subframe number.
Here, the information on the epoch time received at the terminal along with the information on the satellite ephemeris and the common TA parameter of the neighbor cell (e.g., cell of gNB 2 in
Note that the term “interpret” may be replaced with, for example, “specify,” “judge,” “determine,” “decide,” “calculate,” or “understand.”
One non-limiting and exemplary embodiment of the present disclosure describes, for example, a method for correctly interpreting epoch time from information received by a terminal, and for improving, at the terminal, the accuracy of estimation of a satellite location using satellite ephemeris and estimation of the amount of a delay of a feeder link using a common TA parameter. For example, the terminal may acquire information for interpreting epoch time of a neighbor cell, from a network-side.
A communication system according to an embodiment of the present disclosure includes base station 100 and terminal 200.
At least one of data generator 101, controller 102, data-transmission processor 103, and data-reception processor 107 illustrated in
Data generator 101, for example, generates a downlink signal to each terminal 200 and outputs the generated downlink signal to data-transmission processor 103. The downlink signal generated by data generator 101 may include at least any of the following signals: user data (e.g., Physical Downlink Shared Channel (PDSCH)); a control signal (e.g., Physical Downlink Control Channel (PDCCH)); a synchronization signal (e.g., SSB); a reference signal (RS); and Medium Access Control (MAC) control information.
Controller 102 may, for example, generate system information (e.g., broadcast information) such as a Master Information Block (MIB) or SIB and specific control information (e.g., RRC control information such as RRCreconfiguration message). Controller 102 outputs the generated information to data-transmission processor 103.
For example, basic control information including an SFN may be indicated to terminal 200 by the MIB. Moreover, for example, the SIB may include information (e.g., minimum required information) for accessing a cell (e.g., base station 100), neighbor cell information for neighbor cell measurement or cell selection, and other broadcast information. The system information (e.g., SIB) may further include control information for NTN including at least one of parameters corresponding to the cell, such as satellite ephemeris, a common TA parameter, epoch time, and a term of validity. Furthermore, the system information (e.g., SIB) may include, for example, information for a neighbor cell in NTN including at least one of parameters corresponding to the neighbor cell, such as satellite ephemeris, a common TA parameter, and epoch time. The information for the neighbor cell in NTN may include information corresponding to each of the other cells (e.g., neighbor cells)
Incidentally, a method for transmitting the information for the neighbor cell (e.g., including at least one of satellites ephemeris, common TA parameter, and epoch time) will be described later.
Further, controller 102 may, for example, perform exchange of cell information or SIB information (e.g., handover request or handover request acknowledge) with other base stations, for the handover or the like.
Data-transmission processor 103, for example, encodes and modulates the signal input from data generator 101 and the signal input from controller 102, and then outputs a modulated signal to radio transmitter 104.
Radio transmitter 104, for example, performs transmission processing such as D/A conversion, up-conversion, and/or amplification on the signal input from data-transmission processor 103, and transmits a radio signal after the transmission processing from antenna 105.
Radio receiver 106, for example, performs reception processing such as down-conversion and/or A/D conversion on the data signal (e.g., Physical Uplink Shared Channel (PUSCH)), control signal (e.g., Physical Uplink Control Channel (PUCCH)), or random access signal (e.g., Physical Random Access Channel (PRACH)) from terminal 200 received via antenna 105, and outputs the signal after the reception processing to data-reception processor 107.
Data-reception processor 107, for example, performs channel estimation, demodulation processing, and decoding processing on the received signal input from radio receiver 106. Data-reception processor 107 outputs the decoded signal.
Next, a configuration example of terminal 200 will be described.
At least one of data-reception processor 203, location-information acquirer 204, timing adjuster 205, and data-transmission processor 206 illustrated in
Radio receiver 202, for example, performs reception processing such as down-conversion and/or A/D conversion on a downlink signal such as a data signal (e.g., PDSCH) and a control signal (e.g., PDCCH) from base station 100 received via antenna 201, and then outputs the signal after the reception processing to data-reception processor 203 and outputs information on a reception timing to timing adjuster 205.
Data-reception processor 203, for example, performs demodulation processing and decoding processing on the received signal input from radio receiver 202 (e.g., PDCCH or PDSCH). The control signal (e.g., PDCCH) may include, for example, assignment information on the downlink data signal (e.g., PDSCH) or assignment information on the uplink data signal (e.g., PUSCH). Additionally, the downlink data signal (e.g., PDSCH) may include user data, for example. The downlink data signal (e.g., PDSCH) may further include broadcast information such as system information, RRC control information (e.g., RRCreconfiguration message). MAC Control Element (MAC CE) control information, a RACH response (may be referred to as, e.g., msg2 or Random Access Response (RAR)), or a TA command.
Further, data-reception processor 203 performs reception processing of information for NTN (e.g., including at least one of satellites ephemeris, common TA parameter, and epoch time) included in the broadcast information or the RRC control information (e.g., RRCReconfiguration message) and of information to be used in the cell selection, the neighbor cell measurement, or the handover, thus outputting the signal after the reception processing to timing adjuster 205.
Location-information acquirer 204, for example, acquires location information on terminal 200 (e.g., information on latitude, longitude, elevation, and the like). The location information on terminal 200 may be acquired by, for example, a GNSS function such as the Global Positioning System (GPS). Location-information acquirer 204 outputs the acquired location information on terminal 200 to timing adjuster 205.
Timing adjuster 205, for example, controls (adjusts) a transmission timing of a transmission signal (uplink signal). Timing adjuster 205 outputs information on the timing adjustment to radio transmitter 207.
For example, timing adjuster 205 may calculate a distance between terminal 200 and a satellite based on the location information on terminal 200 input from location-information acquirer 204 and the satellite ephemeris information input from data-reception processor 203. Timing adjuster 205 may then calculate propagation delay time between the satellite and terminal 200 (e.g., service link) based on the distance between terminal 200 and the satellite and a radio wave propagation speed (approximately 3×108 m/s).
For example, timing adjuster 205 may further calculate propagation delay time between base station 100 and the satellite (e.g., feeder link) based on the common TA parameter input from data-reception processor 203.
Furthermore, timing adjuster 205 may adjust the transmission timing of the uplink signal (e.g., uplink data or RACH signal) using the propagation delay time of each of the service link and feeder link, for example. For example, timing adjuster 205 may perform the timing adjustment such that a signal is received by base station 100 at a prescribed timing by compensating the propagation delay time of each of the service link and feeder link, in accordance with a timing adjustment value (TTA) indicated in the following Equation 2:
In Equation 2. NTA denotes, for example, a TA value indicated by the TA command, NTAoffset denotes offset for the TA value, and Tc denotes a basic time unit. Moreover, TUEspecific denotes a terminal-specific TA value that is based on the service link delay time estimated from the location information on terminal 200 and the location of the satellite, and Tcommon denotes a common TA value that is based on the feeder link delay time calculated from the common TA parameter. The first term of Equation 2 is, for example, similar to that in Rel. 15 NR specifications. In Equation 2, the terminal-specific TA value (TUEspecific) and the common TA value (Tcommon) are added to the value of the first term.
Timing adjuster 205, for example, may perform the timing adjustment in accordance with the timing adjustment value indicated in Equation 2, based on a reception timing of the signal (e.g., SSB signal) that is received from base station 100 and input by radio receiver 202.
Data-transmission processor 206, for example, performs error correction encoding and modulation processing on transmission data to be input, and then outputs the modulated signal to radio transmitter 207. The transmission data may be, for example, a signal (e.g., PUSCH) transmitted with time-and frequency-resources allocated by base station 100 or may be a signal (e.g., also referred to as PRACH signal or msg 1) transmitted in the random access processing.
Radio transmitter 207, for example, performs transmission processing such as D/A conversion, up-conversion, and/or amplification on the signal input from data-transmission processor 206, and transmits a radio signal after the transmission processing from antenna 201. Radio transmitter 207 may, for example, transmit the signal at a timing specified by the information input from timing adjuster 205.
In the following, exemplary operations of base station 100 and terminal 200 will be described.
In the present embodiment, for example, base station 100 generates information on epoch time of a neighbor cell (neighbor cell) by using a system frame number (SFN) and a subframe number in a cell (serving cell) of base station 10. For example, base station 100 may convert the SFN and subframe number of the epoch time of the neighbor cell to the SFN and subframe number of the cell of base station 100, regenerate information on the epoch time based on the converted SFN and subframe number, and thus indicate the resultant information to terminal 200 in the cell of base station 100.
Terminal 200 interprets the epoch time of the neighbor cell based on the SFN and subframe number of the connected cell (serving cell) or the cell for which the information on the epoch time has been received.
In the following, a description will be given of a method for transmitting information for a neighbor cell transmitted from base station 100 (including, e.g., satellite ephemeris, common TA parameter, and epoch time) and a method for interpreting the epoch time at terminal 200. By way of example, two methods (Method 1 and Method 2) in the processing at the time of handover will be each described.
In Method 1, base station 100 converts epoch time (e.g., SFN and subframe number) of a neighbor cell to a value that is based on an SFN and a subframe number in base station 100, for example. For example, control information on epoch time indicated from base station 100 to terminal 200 indicates epoch time of base station 100 (e.g., serving cell of terminal 200) corresponding to the epoch time of the neighbor cell.
In the example illustrated in
For example, at the time of handover, gNB 1 which is a base station serving as a handover source (source base station) transmits a handover request (HANDOVER REQUEST) to gNB 2 which is a base station serving as a handover target (target base station) (Processing 1 illustrated in
gNB 1, which is the source base station, receives a handover request acknowledge (HANDOVER REQUEST ACKNOWLEDGE) from gNB 2, which is a target base station (Processing 2 illustrated in
The handover request acknowledge may include, for example, system information used to receive a signal from the target base station (or target cell) and to access the target base station.
The handover request acknowledge may further include, for example, satellite ephemeris information, a common TA parameter, and information on epoch time for satellite 2 forming the target cell (cell 2), as illustrated in
The source base station (gNB 1) indicates, to the UE in cell 1, the control information such as the system information, the satellite ephemeris information, the common TA parameter, the epoch time, and a term of validity of the target cell acquired from the target base station (gNB 2) (Processing 3 illustrated in
Here, in Method 1, as for the epoch time, the source base station (gNB 1) converts (or overwrites) the SFN and subframe number that are based on the timing of the target cell (cell 2) to (with) an SFN and a subframe number that are based on a timing of the source cell (cell 1) of the source base station (gNB 1). In the example illustrated in
The information indicated from the source base station (gNB 1) to the UE may include, for example, information on a handover condition.
In
Further, in a case where a carrier frequency differs between the connected cell and the neighbor cell, for example, the UE may receive a signal from the target cell by opening a reception window at an arrival timing of an SSB signal from the target cell subject to the measurement. Alternatively, for example, the UE may stop reception of the signal from the target cell by closing the reception window at a timing that is different from the arrival timing of the SSB signal from the target cell subject to the measurement. At this time, the UE may estimate propagation delay by using the satellite ephemeris information and common TA parameter of the target cell and then adjust a timing of the reception window based on the estimated propagation delay.
Further, the UE may access (e.g., perform RACH transmission to) the target cell so as to perform the handover (e.g., Processing 4 illustrated in
At this time, for example, the UE may interpret the epoch time of the target cell based on a timing of the SFN and subframe of the cell (source cell) to which the UE is connected. In the example illustrated in
Thus, in Method 1, base station 100 converts the epoch time of the neighbor cell, based on the SFN and subframe number used in base station 100, and then indicates the converted epoch time to terminal 200. This allows, in Method 1, terminal 200 to correctly identify the timing of the epoch time of the neighbor cell even when a signal from the neighbor cell (e.g., signal including SFN of neighbor cell, such as MIB and PBCH) cannot be received.
In Method 1, a case has been described where the epoch time of the neighbor cell is converted based on the SFN and subframe number used in base station 100, but the present disclosure is not limited to this case. For example, base station 100 may indicate, to terminal 200, the epoch time of the neighbor cell generated based on the SFN and subframe number used in base station 100. Alternatively, base station 100 may indicate, to terminal 200, the epoch time of the neighbor cell generated at an external apparatus (e.g., core network, other controllers, or the like) based on the SFN and subframe number used in base station 100. At this time, for the satellite ephemeris and the common TA parameter as well, information or a parameter matching to the epoch time based on the SFN and subframe number used in base station 100 may be generated.
In Method 2, base station 100 indicates, to terminal 200, a value of a difference between an SFN and a subframe number corresponding to epoch time in base station 100 and an SFN and a subframe number corresponding to epoch time in a neighbor cell, in addition to the epoch time of the neighbor cell (e.g., SFN and subframe number). For example, control information on epoch time indicated from base station 100 to terminal 200 indicates a difference between the epoch time of the neighbor cell and the epoch time of base station 10 (e.g., serving cell of terminal 200).
In the example illustrated in
Incidentally, Processing 1 illustrated in
As in Method 1, the source base station (gNB 1) indicates, to the UE (terminal 200) in cell 1, the control information such as the system information, the satellite ephemeris information, the common TA parameter, the epoch time, and a term of validity of the target cell acquired from the target base station (gNB 2) (Processing 3 illustrated in
Here, in Method 2, the source base station (gNB 1) may determine information on a difference (or variation) in the SFN (referred to as, e.g., “SFN difference”) between the target cell (cell 2) and the source cell (cell 1), as for the epoch time. The source base station may acquire the information on the SFN difference by exchanging information with the target base station, for example. In the example illustrated in
In
Further, the UE may access (e.g., perform RACH transmission to) the target cell so as to perform the handover (e.g., Processing 4 illustrated in
For example, the UE may interpret, as the epoch time of the neighbor cell (e.g., target cell), the time obtained by subtracting (or adding) the SFN difference from the epoch time indicated from the source base station (gNB 1), based on a timing of the SFN and subframe used in gNB 1 (source cell) to which the UE is connected. In the example illustrated in
Terminal 200 may use the calculated information to perform timing adjustment of the reception window for the quality measurement of the target cell or timing adjustment when accessing the target cell during execution of the handover.
Thus, in Method 2, base station 100 indicates, to terminal 200, a difference in SFN between the neighbor cell and the cell of base station 100 as well as the epoch time of the neighbor cell. This allows, in Method 2, terminal 200 to identify (derive) the timing of the SFN of the neighbor cell and thus correctly identify the epoch time of the neighbor cell even when a signal from the neighbor cell (e.g., signal including SFN of neighbor cell, such as MIB and PBCH) cannot be received.
Note that the information on the SFN difference may be separately indicated to terminal 200 by the SIB or RRC control information, without limitation to the indication at the time of the handover.
Further, in the example of
Method 1 and Method 2 have been each described, thus far.
For example, information on an SFN is indicated to terminal 200 by at least one of an MIB and PBCH (sometimes referred to as “MIB.PBCH”) broadcasted in each cell. By way of example, when terminal 200 is located in the vicinity of the neighbor cell (e.g., target cell), a reception quality (e.g., Signal to Noise Ratio (SNR)) of a signal from the neighbor cell is high; hence, terminal 200 is highly likely to receive the MIB/PBCH of the neighbor cell and thus obtain the SFN of the neighbor cell. On the other hand, when terminal 200 is located away from the neighbor cell, the SNR of the signal from the neighbor cell is poor; hence, terminal 200 may not receive the MIB/PBCH and not acquire the SFN of the neighbor cell. For example, in the case of a conditional handover, terminal 200 receives information on the neighbor cell (e.g., including epoch time of neighbor cell) from base station 100 prior to an actual timing of the handover. For this reason, at a timing before the actual timing of the handover, terminal 200 is highly likely to be located away from the neighbor cell and is less likely to receive the MIB/PBCH of the neighbor cell (e.g., information on SFN of neighbor cell).
In the present embodiment, for example, in a cell to which terminal 200 is connected, terminal 200 receives control information for identifying epoch time (e.g., reference time) in control on a transmission timing (e.g., including determination of satellite location or calculation of delay time of feeder link) of an uplink signal to a neighbor cell (e.g., RACH), and controls the transmission timing based on the received control information.
For example, terminal 200 can correctly interpret, based on a timing of an SFN and a subframe in a serving cell, the epoch time of the neighbor cell included in the control information (e.g., RRCReconfiguration message or SIB) received from base station 100 that is the serving cell. This allows, for example, terminal 200 to improve the accuracy of estimation of the satellite location and the feeder-link delay amount in the neighbor cell without receiving the information on the SFN and/or subframe number of the neighbor cell by the MIB/PBCH or SIB of the neighbor cell.
Further, for example, terminal 200 can correctly interpret the epoch time of the neighbor cell even in a case where the MIB/PBCH or SIB of the neighbor cell is not received, such as a case where the terminal is located away from the neighbor cell, thereby correctly determining a term of validity of the indicated information on the neighbor cell.
Therefore, according to the present embodiment, it is possible to improve the accuracy of transmission timing control of an uplink signal.
Incidentally, in a case where the handover is not triggered within the term of validity from the epoch time interpreted with the above-mentioned methods, terminal 200 may determine that the handover has failed and indicate the failure to base station 100. Additionally, after determining that the handover has failed, terminal 200 may receive again an RRCReconfiguration message or SIB updated with a new parameter from base station 100.
Configurations of base station 100 and terminal 200 according to the present embodiment may be the same as in Embodiment 1, for example.
In the present embodiment, for example, base station 100 need not indicate, in a cell of base station 100, satellite ephemeris information, a common TA parameter, and information on epoch time of a target cell to terminal 200 that performs a conditional handover.
For example, base station 100 (e.g., controller 102) may indicate, to terminal 200 that performs a normal handover, the satellite ephemeris information, the common TA parameter, and the information on the epoch time of the target cell by an RRCreconfiguration message at the time of the handover. On the other hand, base station 100 need not indicate, to terminal 200 that performs the conditional handover, the satellite ephemeris information, the common TA parameter, and the information on the epoch time of the target cell. In this case, base station 100 need not acquire these pieces of information from a target base station.
Moreover, in the present embodiment, for example, terminal 200 may receive the satellite ephemeris information, the common TA parameter, and the information on the epoch of the target cell, from the target cell without reception from a cell to which terminal 200 is connected (e.g., source cell or serving cell).
For example, when performing the conditional handover, terminal 200 (e.g., data-reception processor 203) may receive information on NTN (e.g., SIB) from the target cell and thereby acquire the satellite ephemeris information, the common TA parameter, and the information on the epoch time of the target cell, prior to accessing the target cell (e.g., performing RACH transmission). Further, when performing the conditional handover, terminal 200 need not receive the information on the NTN of the target cell (e.g., information on epoch time) from the cell to which terminal 200 is connected (e.g., serving cell or source cell).
For example, terminal 200 accesses the target cell (e.g., performs RACH transmission) after acquiring the satellite ephemeris information, the common TA parameter, and the information on the epoch time of the target cell included in the SIB.
Further, when performing no conditional handover, for example, terminal 200 need not receive the information on the NTN from the target cell.
Terminal 200 may receive the information on the NTN of the target cell prior to the RACH processing on the target cell in the handover from the source cell to the target cell. For example, the SIB for the NTN of the target cell may be received during a period from satisfying a handover condition and triggering the handover to performing RACH transmission.
Further, when accessing the target cell (e.g., performing RACH transmission), for example, terminal 200 (e.g., timing adjuster 205) may perform timing adjustment according to Equation 2 after acquiring the satellite ephemeris information, the common TA parameter, and the information on the epoch time included in the information (e.g., SIB) on the NTN received from the target cell.
In the example illustrated in
The UE (e.g., terminal 200) illustrated in
For example, at the time of the conditional handover, gNB 1 which is a source base station transmits a handover request (HANDOVER REQUEST) to gNB 2 which is a target base station (Processing 1 illustrated in
gNB 1, which is the source base station, receives a handover request acknowledge (HANDOVER REQUEST ACKNOWLEDGE) from gNB 2, which is a target base station (Processing 2 illustrated in
The handover request acknowledge may include, for example, system information used to receive a signal from the target base station (or target cell) and to access the target base station.
Here, when the conditional handover is performed, the handover request acknowledge need not include, for example, satellite ephemeris information, a common TA parameter, and information on epoch time for satellite 2 forming the target cell (cell 2).
The source base station (gNB 1) indicates, to the UE (terminal 200) in cell 1, the system information on the target cell acquired from the target base station (gNB 2) (Processing 3 illustrated in
In
When the handover condition is satisfied, the UE may access (e.g., perform RACH transmission to) the target cell so as to perform the handover (e.g., Processing 4 illustrated in
The UE may then estimate the propagation delay (service link delay and feeder link delay) using the satellite ephemeris information and common TA parameter of the target cell and then perform, based on the estimated propagation delay, transmission of RACH in uplink or the like (e.g., adjustment of transmission timing).
At this time, the UE may interpret the epoch time of the target cell based on a timing of the SFN and subframe of the target cell. In the example illustrated in
Thus, in the present embodiment, for example, in a cell to which terminal 200 is connected, terminal 200 receives, from a neighbor cell, control information for identifying epoch time (e.g., reference time) in control on a transmission timing (e.g., including determination of satellite location or calculation of delay time of feeder link) of an uplink signal to a neighbor cell (e.g., RACH), and controls the transmission timing based on the received control information.
Base station 100 (e.g., source base station) does not indicate the satellite ephemeris information, the common TA parameter, nor the information on the epoch time of the target cell, to terminal 200 that cannot receive the MIB information from the target cell for the conditional handover (e.g., cannot acquire SFN of target cell) and have a possibility of not correctly interrupting the epoch time of the target cell. This can reduce the amount of indication information, e.g., control overhead.
In addition, when approaching the target cell, terminal 200 acquires the satellite ephemeris information, the common TA parameter, and the information on the epoch time that are included in the SIB of the target cell. In this situation, for example, terminal 200 can acquire the SFN of the target cell from the MIB information on the target cell, thus interpreting the epoch time correctly.
Alternatively, terminal 200 may acquire the satellite ephemeris information, the common TA parameter, and the information on the epoch time of the target cell prior to accessing the target cell. For this reason, terminal 200 is likely to have sufficient time to access the target cell after receiving the indication for the conditional handover, and can estimate a timing of the handover execution, from the handover condition; thus, terminal 200 can receive the SIB of the target cell with time to spare.
Therefore, according to the present embodiment, it is possible to improve the accuracy of transmission timing control of an uplink signal.
Configurations of base station 100 and terminal 200 according to the present embodiment may be the same as in Embodiment 1, for example.
In the present embodiment, for example, base station 100 may indicate, to terminal 200, information on epoch time based on an SFN and a subframe number of a target cell acquired from the target cell as is.
For example, base station 100 (e.g., controller 102) may indicate, to terminal 200 that performs a normal handover or a conditional handover, the satellite ephemeris information, the common TA parameter, and the information on the epoch time of the target cell by an RRCreconfiguration message at the time of the handover. Herein, the epoch time may be epoch time that is based on an SFN and a subframe number of a target cell.
Additionally, in the present embodiment, for example, terminal 200 (e.g., data-reception processor 203) receives an RRCReconfiguration message from base station 100 (e.g., serving cell or source cell) and thus acquires the satellite ephemeris information, the common TA parameter, and the information on the epoch time of the target cell.
Further, terminal 200 may acquire, for example, information on an SFN of the target cell from the target cell (e.g., neighbor cell). The information on the SFN of the target cell may be indicated by an MIB/PBCH from the target cell, for example. In one example, terminal 200 may acquire the SFN of the target cell when being located close to the target cell (e.g., when SNR of signal from target cell is enough).
Further, for example, terminal 200 may interpret the epoch time at the time of acquiring the SFN of the target cell and then identify a satellite location and calculate the amount of propagation delay (e.g., TA value) from the satellite ephemeris information and the common TA parameter that are indicated from the source cell.
Further, for example, when performing RACH transmission on the target cell, terminal 200 (e.g., timing adjuster 205) may perform timing adjustment according to Equation 2, based on the satellite ephemeris information, the common TA parameter, and the information on the epoch time of the target cell.
In this manner, terminal 200 receives control information on NTN of the target cell (e.g., including epoch time of target cell) from the cell to which terminal 200 is connected (e.g., source cell or serving cell), and receives, from the target cell, the information on the SFN of the target cell.
In the example illustrated in
The UE (e.g., terminal 200) illustrated in
Note that, in
The source base station (gNB 1) indicates, to the UE in cell 1, the system information, the satellite ephemeris information, the common TA parameter, and the information on the epoch time of the target cell acquired from the target base station (gNB 2) (Processing 3 illustrated in
In
Here, the UE need not interpret the epoch time of the target cell received from the source cell (cell 1) when receiving no MIB/PBCH (e.g., including SFN of target cell) from the target cell (cell 2). For example, terminal 200 may interpret the epoch time of the target cell received from the source cell (cell 1) when approaching the target cell and receiving the MIB/PBCH (e.g., including SFN of target cell) from the target cell (Cell 2).
In the manner described above, the UE receives the satellite ephemeris information, the common TA parameter, and the information on the epoch time of the target cell from the source base station (or source cell), and receives the information on the SFN to interpret the epoch time from the target base station (or target cell).
The UE may then calculate a satellite location from the satellite ephemeris information and calculate the feeder-link delay amount (e.g., common TA value) from the common TA parameter, based on the interpreted epoch time.
For example, information on an SFN is indicated to terminal 200 by the MIB/PBCH broadcasted in each cell. By way of example, when terminal 200 is located in the vicinity of the neighbor cell (e.g., target cell), a reception quality (e.g., SNR) of a signal from the neighbor cell is high, hence, terminal 200 is highly likely to receive the MIB/PBCH of the neighbor cell and thus obtain the SFN of the neighbor cell. On the other hand, when terminal 200 is located away from the neighbor cell, the SNR of the signal from the neighbor cell is poor; hence, terminal 200 may not receive the MIB/PBCH and not acquire the SFN of the neighbor cell. For example, in the case of a conditional handover, terminal 200 receives information on the neighbor cell (e.g., including epoch time of neighbor cell) from base station 100 prior to an actual timing of the handover. For this reason, at a timing before the actual timing of the handover, terminal 200 is highly likely to be located away from the neighbor cell and is less likely to receive the MIB/PBCH of the neighbor cell (e.g., information on SFN of neighbor cell). In this situation, terminal 200 cannot correctly interpret information on epoch time based on the SFN of the target cell.
By contrast, in the present embodiment, terminal 200 receives, from a cell to which the terminal is currently connected (source cell), the satellite ephemeris information, the common TA parameter of the target cell, and the information on the epoch time that is based on the SFN of the target cell. Additionally, when being located close to the target cell, terminal 200 receives the MIB/PBCH of the target cell from the target cell and thereby acquires the information on the SFN. Thus, in the present embodiment, terminal 200 interprets the epoch time information indicated from the source cell after acquiring the information on the SFN of the target cell. This allows terminal 200 to correctly interpret (or derive) the epoch time that is based on the SFN of the target cell and thus appropriately estimate the satellite location information and the feeder-link delay time.
Alternatively, terminal 200 may acquire the satellite ephemeris information, the common TA parameter, and the information on the epoch time of the target cell prior to accessing the target cell. For this reason, terminal 200 is likely to have sufficient time to access the target cell after receiving the indication for the conditional handover, and can estimate a timing of the handover execution, from the handover condition: thus, terminal 200 can receive the MIB of the target cell with time to spare and perform the timing adjustment (e.g., calculation of TA value) for the RACH transmission.
Incidentally, base station 100 may indicate, to terminal 200, the satellite ephemeris information, the common TA parameter, and the information on the epoch time of the target cell, at a plurality of timings.
For example, in NR, information on an SFN is 10-bit information, taking values ranging from 0 to 1023. Hence, the SFN has one cycle (e.g., referred to as “SFN cycle”) with 1024 frames and is reset to 0 every SFN cycle. For example, since one frame is 10 ms, the SFN is reset every 10.24 seconds. Accordingly, for example, at the time of receiving the MIB/PBCH of the neighbor cell (e.g., target cell) and acquiring (e.g., reading) the SFN of the neighbor cell, terminal 200 cannot possibly determine which SFN of the SFN cycle is referred to by the SFN and subframe number corresponding to the epoch time received in past, as illustrated in
For example, in
Consequently, for example, base station 100 may indicate, to terminal 200, the satellite ephemeris information, the common TA parameter, and the information on the epoch time of the target cell at least every one SFN cycle (e.g., 10.24 seconds), as illustrated in
Here, the satellite ephemeris information, the common TA parameter, and the information on the epoch time of the target cell may be updated with the epoch time represented by the most recent SFN, for example. By way of example, information based on the SFN of SFN cycle 1 is indicated as information indicated in SFN cycle 1, and information based on the SFN of SFN cycle 2 may be indicated as information indicated in SFN cycle 2.
For example, terminal 200 receives the satellite ephemeris information, the common TA parameter, and the information on the epoch time of the target cell by the RRCReconfiguration message, at a plurality of timings. In this case, terminal 200 may determine (or assume) the SFN indicated in the epoch time as an SFN of the same SFN cycle as the timing at which the RRCReconfiguration message has been received. Alternatively, terminal 200 may, for example, determine (or assume) the SFN indicated in the epoch time as the closest SFN from the timing at which the RRCReconfiguration message has been received.
This allows terminal 200 to uniquely identify the SFN indicated by the epoch time, at the time of receiving the MIB of the target cell and acquiring the SFN, thereby interpreting the epoch time correctly.
Incidentally, an example has been described in which the satellite ephemeris information, the common TA parameter, and the epoch time of the target cell are indicated to terminal 200 by the RRCReconfiguration message, but the present disclosure is not limited to this example, and they may be indicated by an SIB. In this case, terminal 200 may receive the corresponding SIB every predetermined interval (e.g., interval of SFN cycles).
The embodiments of the present disclosure have been each described, thus far.
Note that, in the above-described embodiments, an example in a conditional handover has been described, but the present disclosure is not limited to this example, and the same method can be used in a normal handover or in indication of neighbor cell information for cell selection.
Further, in the above-described embodiments, an operation may vary between in the handover and in the cell selection. For example, in the case of the cell selection or the neighbor cell measurement, base station 100 may indicate epoch time, satellite ephemeris, and a common TA parameter that are based on an SFN and a subframe number of base station 100 (i.e., serving cell) to terminal 200 as information on a neighbor cell, whereas, in the case of the handover, the base station may indicate, to terminal 200, epoch time, satellite ephemeris, and a common TA parameter that are based on an SFN and a subframe number of a target base station or a target cell. Further, for example, as information on a neighbor cell used in the cell selection or the neighbor cell measurement, base station 100 may indicate, to terminal 200, epoch time, satellite ephemeris, and a common TA parameter that are based on the SFN and subframe number of base station 100 (i.e., serving cell), whereas, as information on a target cell used in the handover, the base station may indicate, to terminal 200, epoch time, satellite ephemeris, and a common TA parameter that are based on the SFN and subframe number of the target base station or the target cell. In the case of the cell selection or the neighbor cell measurement, terminal 200 may be in a location where the MIB, PBCH, or SIB of the neighbor cell cannot be received, at the time of receiving these pieces of information from base station 100. Thus, the indication, to terminal 200, of the epoch time, the satellite ephemeris, and the common TA parameter that are based on the SFN and subframe number of the serving cell enables terminal 200 to correctly interpret the information on the epoch time by the SFN and subframe timing of the serving cell and thus appropriately control a measurement window using the information on the satellite ephemeris and the common TA parameter. Meanwhile, in the case of the handover, terminal 200 is highly likely to be located in the vicinity of the neighbor cell. Thus, the indication, to terminal 200, of the epoch time, the satellite ephemeris, and the common TA parameter that are based on the SFN and subframe number of the target cell enables terminal 200 to correctly interpret the information on the epoch time because the information on the SFN and subframe of the target cell can be acquired by the MIB/PBCH of the target cell, and thus to access the target cell using the information on the satellite ephemeris and the common TA parameter.
Note that the above-mentioned information on the neighbor cell for the cell selection or the neighbor cell measurement may be broadcasted by an SIB, and the above-mentioned information on the neighbor cell for the handover may be indicated to terminal 200 by an RRCReconfiguration message.
Further, in the above-described embodiments, when the information such as the epoch time, the satellite ephemeris, and the common TA parameter is indicated by an SIB to terminal 200, the epoch time may be implicitly indicated by the first or last subframe (e.g., subframe number) of an SI-window in which the SIB is transmitted. In this case, as the information on the neighbor cell, base station 100 indicates, to terminal 200, the epoch time, the satellite ephemeris, and the common TA parameter that are based on the timing of the SFN and/or subframe of base station 100 (i.e., serving cell). Alternatively, when the epoch time, the satellite ephemeris, and the common TA parameter, which are based on the timing of the SFN and/or subframe of base station 100 (i.e., serving cell), is indicated to terminal 200, the epoch time may be implicitly indicated by the first or last subframe (e.g., subframe number) of an SI-window in which the SIB is transmitted.
Further, in the above-described embodiments, a cell may be an area defined by received power of an SSB or a Channel State Information-Reference Signal (CSI-RS) transmitted from a base station (or satellite) or may be an area defined by a geographical location. Moreover, the cell in the above-described embodiments may be replaced with a beam defined by the SSB.
Further, in the above-described embodiments, the satellite ephemeris information, which is information on a satellite location, may be broadcasted by the system information or held by terminal 200 in advance. The satellite ephemeris information may be updated when communication is possible. Alternatively, terminal 200 may identify a satellite location using information that is different from the satellite ephemeris information.
Further, in the above-described embodiments, a base station may be replaced with a “network.”
Further, in the above-described embodiments, a target cell at the time of handover has been described as an example, but the target cell may be replaced with a neighbor cell. In addition, one aspect of the present disclosure is applicable not only to the handover but also to the neighbor cell measurement for the cell reselection. Moreover, one aspect of the present disclosure is applicable to a procedure called RRC reconfiguration with sync typified by the handover.
Further, the satellite ephemeris and common TA parameter of the neighbor cell may be indicated by the SIB as the neighbor cell information, and terminal 200 may use these pieces of information at the time of the cell selection or cell reselection in an RRC_IDLE state. Alternatively, at the time of the handover in an RRC_CONNECTED state, the terminal-specific RRC control information may indicate, to terminal 200, information indicating which neighbor cell information is used as the target cell information. This can reduce the amount of indication information to terminal 200.
Further, in the above-described embodiments, terminal 200 may perform the reception quality measurement by using other signals such as a CSI-RS, instead of the SSB signal.
Further, in the embodiments described above, an example has been described in which a GNSS such as GPS or the like (e.g., location detection using satellite signal) is used, but the present disclosure is not limited to this, and the following may be performed: location detection by a terrestrial cellular base station, location detection using WiFi (registered trademark) signal or Bluetooth (registered trademark) signal; location detection using an acceleration sensor or the like; or location detection by a combination of these detection methods, for example. Incidentally, altitude information may be acquired from, for example, an atmospheric pressure sensor.
Further, in the above-described embodiments, the uplink transmission from terminal 200 to base station 100 has been described, but an embodiment of the present disclosure is not limited to this and may be applied to data in a downlink from base station 100 to terminal 200 or in a link between terminals 200 (e.g., sidelink). Further, in the above-described embodiments, the RACH signal transmission has been described as an example of the uplink transmission, but the transmission target is not limited to RACH and may be other signals or channels.
An embodiment of the present disclosure is also applicable for any type of satellite such as a Geostationary Earth Orbit satellite (GEO), medium earth orbit satellite (MEO), LEO, or highly elliptical orbit satellite (HEO). Further, an embodiment of the present disclosure may be applied to non-terrestrial communication such as communication performed by a HAPS or a drone base station.
Further, in the above embodiments, descriptions have been given by taking the NTN environment (e.g., satellite communication environment) as an example, but the present disclosure is not limited to this. The present disclosure may be applied to other communication environments (e.g., at least one terrestrial cellular environment in LTE and NR). For example, an embodiment of the present disclosure may be applied to terrestrial communication in an environment where the cell size is large and the propagation delay between base station 100 and terminal 200 is longer (e.g., equal to or longer than threshold), for example. In addition, an embodiment of the present disclosure may be applied not only to the NTN but also to communication to which handover or cell selection is applied.
Further, in the above-described embodiment, the satellite communication may have a configuration in which the base station functionality is on the satellite (e.g., “regenerative satellite”), or a configuration in which the base station functionality is on the ground and the satellite relays the communication between the base station and a terminal (e.g., “transparent satellite”). In other words, in an embodiment of the present disclosure, for example, the downlink and uplink may be a link between a terminal and the satellite or a link via the satellite.
The parameters in the above-described embodiments are examples and may include other values. For example, an SFN of epoch time, a subframe number of the epoch time, and the number of frames of one cycle of the SFN are not limited to the values given in the above-mentioned examples.
A method for indicating control information from base station 100 to terminal 200 is not limited to the above-mentioned examples, and the control information may be indicated (or broadcasted, instructed, configured) by at least one of system information such as an MIB and an SIB, RRC control information, MAC control information, and downlink control information (DCI), may be previously configured for terminal 200, or may be defined by standards in advance.
The base station may be referred to as a gNodeB or a gNB. Further, the terminal may be referred to as UE.
Time resource units, such as system frames or subframes, may be replaced with slots, time slots, mini slots, frames, or subframes.
Further, any component with a suffix, such as “-er,” “-or,” or “-ar” in the above-described embodiments may be replaced with other terms such as “circuit (circuitry),” “device,” “unit,” or “module.”
Information indicating whether terminal 200 supports the functions, operations, or processing described in the above embodiments may be transmitted (or indicated) from terminal 200 to base station 100 as capability information or capability parameter(s) of terminal 200, for example.
The capability information may include an information element (IE) individually indicating whether terminal 200 supports at least one of the functions, operations, and processing described in the above embodiments. Alternatively, the capability information may include an information element indicating whether terminal 200 supports a combination of any two or more of the functions, operations, and processing described in the above embodiments.
Base station 100, for example, may determine (decide or assume), based on the capability information received from terminal 200, the functions, operations, and processing supported (or unsupported) by terminal 200 that has transmitted the capability information. Base station 100 may perform operations, processing, or control in accordance with a determination result based on the capability information. For example, base station 100 may control communication for NTN, based on the capability information received from terminal 200.
Note that the fact that terminal 200 does not support some of the functions, operations, or processing described in the above embodiment may be interpreted as limitation on such functions, operations, or processing in terminal 200. For example, information or a request related to such limitation may be indicated to base station 100.
Information on the capability or limitation of terminal 200 may be, for example, defined by standards, or implicitly indicated to base station 100 in association with information known in base station 100 or information transmitted to base station 100.
In the present disclosure, a downlink control signal (or downlink control information) related to an exemplary embodiment of the present disclosure may be a signal (or information) transmitted through a Physical Downlink Control Channel (PDCCH) of the physical layer, for example, or may be a signal (or information) transmitted through a Medium Access Control Control Element (MAC CE) or the Radio Resource Control (RRC) of a higher layer. Further, the signal (or information) is not limited to that notified by the downlink control signal, but may be predefined in the specifications (or standard) or may be pre-configured for the base station and the terminal.
In the present disclosure, an uplink control signal (or uplink control information) relating to an exemplary embodiment of the present disclosure may be, for example, a signal (or information) transmitted through a PUCCH of the physical layer or a signal (or information) transmitted through the MAC CE or RRC of the higher layer. Further, the signal (or information) is not limited to that notified by the uplink control signal, and may be predefined in the specifications (or standard) or may be pre-configured for the base station and the terminal. The uplink control signal may be replaced with, for example, uplink control information (UCI), 1st stage sidelink control information (SCI), or 2nd stage SCI.
In an exemplary embodiment of the present disclosure, the base station may be a Transmission Reception Point (TRP), a cluster head, an access point, a Remote Radio Head (RRH), an eNodeB (eNB), a gNodeB (gNB), a Base Station (BS), a Base Transceiver Station (BTS), a master device, a gateway, or the like. Further, in sidelink communication, a terminal may play a role of the base station. Alternatively, the base station may be replaced with a relay device that relays communication between a higher node and a terminal, or may be replaced with a roadside device.
An exemplary embodiment of the present disclosure may be applied to, for example, any of uplink, downlink, and sidelink. For example, an exemplary embodiment of the present disclosure may be applied to a Physical Uplink Shared Channel (PUSCH), a Physical Uplink Control Channel (PUCCH), and a Physical Random Access Channel (PRACH) in the uplink, a Physical Downlink Shared Channel (PDSCH), PDCCH or a Physical Broadcast Channel (PBCH) in the downlink, or a Physical Sidelink Shared Channel (PSSCH), a Physical Sidelink Control Channel (PSCCH), a Physical Sidelink Broadcast Channel (PSBCH) in the sidelink.
Note that PDCCH, PDSCH, PUSCH and PUCCH are examples of a downlink control channel, a downlink data channel, an uplink data channel, and an uplink control channel, respectively. PSCCH and PSSCH are examples of a sidelink control channel and a sidelink data channel. Further, PBCH and PSBCH are examples of broadcast channels, and PRACH is an example of a random access channel.
An exemplary embodiment of the present disclosure may be applied to, for example, either of a data channel or a control channel. For example, a channel in an exemplary embodiment of the present disclosure may be replaced with a data channel including any of PDSCH, PUSCH, and PSSCH or a control channel including any of PDCCH, PUCCH, PBCH, PSCCH, and PSBCH.
In an exemplary embodiment of the present disclosure, a reference signal is a signal known to both of a base station and a mobile station, for example, and may also be referred to as a Reference Signal (RS) or a pilot signal. The reference signal may be any of a Demodulation Reference Signal (DMRS), a Channel State Information-Reference Signal (CSI-RS), a Tracking Reference Signal (TRS), a Phase Tracking Reference Signal (PTRS), a Cell-specific Reference Signal (CRS), or a Sounding Reference Signal (SRS).
In an exemplary embodiment of the present disclosure, the units of time resources are not limited to one or a combination of slots and symbols, but may be, for example, time resource units such as frames, superframes, subframes, slots, time slot, subslots, minislots, or symbols, Orthogonal Frequency Division Multiplexing (OFDM) symbols, Single Carier-Frequency Division Multiplexing (SC-FDMA) symbols, or other time resource units. The number of symbols included in one slot is not limited to any number of symbols exemplified in the above-described embodiments, and may be another number of symbols.
An exemplary embodiment of the present disclosure may be applied to either a licensed band or an unlicensed band.
An exemplary embodiment of the present disclosure may be applied to any of communication between a base station and a terminal (Uu-link communication), communication between a terminal and a terminal (Sidelink communication), and Vehicle to Everything (V2X) communication. For example, a channel in an exemplary embodiment of the present disclosure may be replaced with any of PSCCH, PSSCH, Physical Sidelink Feedback Channel (PSFCH), PSBCH, PDCCH, PUCCH, PDSCH, PUSCH, and PBCH.
In addition, an exemplary embodiment of the present disclosure may be applied to either of a terrestrial network or a network other than the terrestrial network (Non-Terrestrial Network (NTN)) using a satellite or a High Altitude Pseudo Satellite (HAPS). In addition, the present disclosure may be applied to a network having a large cell size, and a terrestrial network with a large delay compared with a symbol length or a slot length, such as an ultra-wideband transmission network.
In an exemplary embodiment of the present disclosure, an antenna port refers to a logical antenna (antenna group) formed of one physical antennas or a plurality of physical antennas. For example, the antenna port does not necessarily refer to one physical antenna, and may refer to an array antenna formed of multiple antennas or the like. For example, it is not defined how many physical antennas from the antenna port, and instead, the antenna port is defined as the minimum unit through which a terminal is allowed to transmit a reference signal. The antenna port may also be defined as the minimum unit for multiplication of a precoding vector weighting.
3GPP has been working on the next release for the 5th generation cellular technology (simply called “5G”), including the development of a new radio access technology (NR) operating in frequencies ranging up to 100 GHz. The first version of the 5G standard was completed at the end of 2017, which allows proceeding to 5G NR standard-compliant trials and commercial deployments of terminals (e.g., smartphones).
For example, the overall system architecture assumes an NG-RAN (Next Generation-Radio Access Network) that includes gNBs, providing the NG-radio access user plane (SDAP/PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the UE. The gNBs are interconnected with each other by means of the Xn interface. The gNBs are also connected by means of the Next Generation (NG) interface to the NGC (Next Generation Core), more specifically to the AMF (Access and Mobility Management Function)(e.g., a particular core entity performing the AMF) by means of the NG-C interface and to the UPF (User Plane Function) (e.g., a particular core entity performing the UPF) by means of the NG-U interface. The NG-RAN architecture is illustrated in
The user plane protocol stack for NR (see e.g., 3GPP TS 38.300, section 4.4.1) includes the PDCP (Packet Data Convergence Protocol, see clause 6.4 of TS 38.300), RLC (Radio Link Control, see clause 6.3 of TS 38.300) and MAC (Medium Access Control, see clause 6.2 of TS 38.300) sublayers, which are terminated in the gNB on the network side. Additionally, a new Access Stratum (AS) sublayer (SDAP, Service Data Adaptation Protocol) is introduced above the PDCP (see e.g., clause 6.5 of 3GPP TS 38.300). A control plane protocol stack is also defined for NR (see for instance TS 38.300, section 4.4.2). An overview of the Layer 2 functions is given in clause 6 of TS 38.300. The functions of the PDCP, RLC, and MAC sublayers are listed respectively in clauses 6.4, 6.3, and 6.2 of TS 38.300. The functions of the RRC layer are listed in clause 7 of TS 38.300.
For instance, the Medium Access Control layer handles logical-channel multiplexing, and scheduling and scheduling-related functions, including handling of different numerologies.
The physical layer (PHY) is for example responsible for coding, PHY HARQ processing, modulation, multi-antenna processing, and mapping of the signal to the appropriate physical time-frequency resources. The physical layer also handles mapping of transport channels to physical channels. The physical layer provides services to the MAC layer in the form of transport channels. A physical channel corresponds to the set of time-frequency resources used for transmission of a particular transport channel, and each transport channel is mapped to a corresponding physical channel. Examples of the physical channel include a Physical Random Access Channel (PRACH), a Physical Uplink Shared Channel (PUSCH), and a Physical Uplink Control Channel (PUCCH) as uplink physical channels, and a Physical Downlink Shared Channel (PDSCH), a Physical Downlink Control Channel (PDCCH), and a Physical Broadcast Channel (PBCH) as downlink physical channels.
Use cases/deployment scenarios for NR could include enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), and massive machine type communication (mMTC), which have diverse requirements in terms of data rates, latency, and coverage. For example, eMBB is expected to support peak data rates (20 Gbps for downlink and 10 Gbps for uplink) and user-experienced data rates on the order of three times what is offered by IMT-Advanced. On the other hand, in case of URLLC, the tighter requirements are put on ultra-low latency (0.5 ms for UL and DL each for user plane latency) and high reliability (1-10-5 within 1 ms). Finally, mMTC may preferably require high connection density (1,000,000 devices/km2 in an urban environment), large coverage in harsh environments, and extremely long-life battery for low cost devices (15 years).
Therefore, the OFDM numerology (e.g., subcarrier spacing, OFDM symbol duration, cyclic prefix (CP) duration, and number of symbols per scheduling interval) that is suitable for one use case might not work well for another. For example, low-latency services may preferably require a shorter symbol duration (and thus larger subcarrier spacing) and/or fewer symbols per scheduling interval (aka, TTI) than an mMTC service. Furthermore, deployment scenarios with large channel delay spreads may preferably require a longer CP duration than scenarios with short delay spreads. The subcarrier spacing should be optimized accordingly to retain the similar CP overhead. NR may support more than one value of subcarrier spacing. Correspondingly, subcarrier spacings of 15 kHz, 30 kHz, and 60 kHz . . . are being considered at the moment. The symbol duration Tu and the subcarrier spacing Δf are directly related through the formula Δf=1/Tu. In a similar manner as in LTE systems, the term “resource element” can be used to denote a minimum resource unit being composed of one subcarrier for the length of one OFDM/SC-FDMA symbol.
In the new radio system 5G-NR for each numerology and each carrier, resource grids of subcarriers and OFDM symbols are defined respectively for uplink and downlink. Each element in the resource grids is called a resource element and is identified based on the frequency index in the frequency domain and the symbol position in the time domain (see 3GPP1TS 38.211 v15.6.0).
For example, gNB and ng-eNB hosts the following main functions:
The Access and Mobility Management Function (AMF) hosts the following main functions:
In addition, the User Plane Function (UPF) hosts the following main functions:
Finally, the Session Management Function (SMF) hosts the following main functions:
RRC is higher layer signaling (protocol) used for UE and gNB configuration. With this transition, the AMF prepares UE context data (which includes, for example, a PDU session context, security key, UE Radio Capability, UE Security Capabilities, and the like) and sends it to the gNB with an INITIAL CONTEXT SETUP REQUEST. Then, the gNB activates the AS security with the UE. This activation is performed by the gNB transmitting to the UE a SecurityModeCommand message and by the UE responding to the gNB with the SecurityModeComplete message. Afterwards, the gNB performs the reconfiguration to setup the Signaling Radio Bearer 2 (SRB2) and Data Radio Bearer(s) (DRB(s)) by means of transmitting to the UE the RRCReconfiguration message and, in response, receiving by the gNB the RRCReconfigurationComplete from the UE. For a signaling-only connection, the steps relating to the RRCReconfiguration are skipped since SRB2 and DRBs are not set up. Finally, the gNB indicates the AMF that the setup procedure is completed with INITIAL CONTEXT SETUP RESPONSE.
Thus, the present disclosure provides a 5th Generation Core (5GC) entity (e.g., AMF, SMF, or the like) including control circuitry, which, in operation, establishes a Next Generation (NG) connection with a gNodeB, and a transmitter, which in operation, transmits an initial context setup message to the gNodeB via the NG connection such that a signaling radio bearer between the gNodeB and a User Equipment (UE) is set up. Specifically, the gNodeB transmits Radio Resource Control (RRC) signaling including a resource allocation configuration Information Element (IE) to the UE via the signaling radio bearer. Then, the UE performs an uplink transmission or a downlink reception based on the resource allocation configuration.
The URLLC use case has stringent requirements for capabilities such as throughput, latency and availability. The URLLC use case has been envisioned as one of the enablers for future vertical applications such as wireless control of industrial manufacturing or production processes, remote medical surgery, distribution automation in a smart grid, transportation safety. Ultra-reliability for URLLC is to be supported by identifying the techniques to meet the requirements set by TR 38.913. For NR URLLC in Release 15, key requirements include a target user plane latency of 0.5 ms for UL (uplink) and 0.5 ms for DL (downlink). The general URLLC requirement for one transmission of a packet is a block error rate (BLER) of 1E-5 for a packet size of 32 bytes with a user plane latency of 1 ms.
From the physical layer perspective, reliability can be improved in a number of possible ways. The current scope for improving the reliability involves defining separate CQI tables for URLLC, more compact DCI formats, repetition of PDCCH, or the like. However, the scope may widen for achieving ultra-reliability as the NR becomes more stable and developed (for NR URLLC key requirements). Particular use cases of NR URLLC in Rel. 15 include Augmented Reality/Virtual Reality (AR/VR), e-health, e-safety, and mission-critical applications.
Moreover, technology enhancements targeted by NR URLLC aim at latency improvement and reliability improvement. Technology enhancements for latency improvement include configurable numerology, non slot-based scheduling with flexible mapping, grant free (configured grant) uplink, slot-level repetition for data channels, and downlink pre-emption. Pre-emption means that a transmission for which resources have already been allocated is stopped, and the already allocated resources are used for another transmission that has been requested later, but has lower latency/higher priority requirements. Accordingly, the already granted transmission is pre-empted by a later transmission. Pre-emption is applicable independent of the particular service type. For example, a transmission for a service-type A (URLLC) may be pre-empted by a transmission for a service type B (such as eMBB). Technology enhancements with respect to reliability improvement include dedicated CQI/MCS tables for the target BLER of 1E-5.
The use case of mMTC (massive machine type communication) is characterized by a very large number of connected devices typically transmitting a relatively low volume of non-delay sensitive data. Devices are required to be low cost and to have a very long battery life. From NR perspective, utilizing very narrow bandwidth parts is one possible solution to have power saving from UE perspective and enable long battery life.
As mentioned above, it is expected that the scope of reliability in NR becomes wider. One key requirement to all the cases, for example, for URLLC and mMTC, is high reliability or ultra-reliability. Several mechanisms can improve the reliability from radio perspective and network perspective. In general, there are a few key potential areas that can help improve the reliability. Among these areas are compact control channel information, data/control channel repetition, and diversity with respect to frequency, time and/or the spatial domain. These areas are applicable to reliability improvement in general, regardless of particular communication scenarios.
For NR URLLC, further use cases with tighter requirements have been envisioned such as factory automation, transport industry and electrical power distribution. The tighter requirements are higher reliability (up to 10-6 level), higher availability, packet sizes of up to 256 bytes, time synchronization up to the extent of a few μs (where the value can be one or a few μs depending on frequency range and short latency on the order of 0.5 to 1 ms (in particular a target user plane latency of 0.5 ms), depending on the use cases).
Moreover, for NR URLLC, several technology enhancements from physical layer perspective have been identified. Among these are PDCCH (Physical Downlink Control Channel) enhancements related to compact DCI, PDCCH repetition, increased PDCCH monitoring. Moreover, UCI (Uplink Control Information) enhancements are related to enhanced HARQ (Hybrid Automatic Repeat Request) and CSI feedback enhancements. Also PUSCH enhancements related to mini-slot level hopping and retransmission/repetition enhancements are possible. The term “mini-slot” refers to a Transmission Time Interval (TTI) including a smaller number of symbols than a slot (a slot comprising fourteen symbols).
The 5G QoS (Quality of Service) model is based on QoS flows and supports both QoS flows that require guaranteed flow bit rate (GBR QoS flows) and QoS flows that do not require guaranteed flow bit rate (non-GBR QoS Flows). At NAS level, the QoS flow is thus the finest granularity of QoS differentiation in a PDU session. A QoS flow is identified within a PDU session by a QoS flow ID (QFI) carried in an encapsulation header over NG-U interface.
For each UE, 5GC establishes one or more PDU sessions. For each UE, the NG-RAN establishes at least one Data Radio Bearer (DRB) together with the PDU session. e.g., as illustrated above with reference to
In the present disclosure, thus, an application server (e.g., AF of the 5G architecture), is provided that includes: a transmitter, which in operation, transmits a request containing a QoS requirement for at least one of URLLC, eMMB and mMTC services to at least one of functions (such as NEF, AMF, SMF, PCF, and UPF) of the 5GC to establish a PDU session including a radio bearer between a gNodeB and a UE in accordance with the QoS requirement; and control circuitry, which, in operation, performs the services using the established PDU session.
The present disclosure can be realized by software, hardware, or software in cooperation with hardware. Each functional block used in the description of each embodiment described above can be partly or entirely realized by an LSI such as an integrated circuit, and each process described in the each embodiment may be controlled partly or entirely by the same LSI or a combination of LSIs. The LSI may be individually formed as chips, or one chip may be formed so as to include a part or all of the functional blocks. The LSI may include a data input and output coupled thereto. The LSI herein may be referred to as an IC, a system LSI, a super LSI, or an ultra LSI depending on a difference in the degree of integration.
However, the technique of implementing an integrated circuit is not limited to the LSI and may be realized by using a dedicated circuit, a general-purpose processor, or a special-purpose processor. In addition, a FPGA (Field Programmable Gate Array) that can be programmed after the manufacture of the LSI or a reconfigurable processor in which the connections and the settings of circuit cells disposed inside the LSI can be reconfigured may be used. The present disclosure can be realized as digital processing or analogue processing.
If future integrated circuit technology replaces LSIs as a result of the advancement of semiconductor technology or other derivative technology, the functional blocks could be integrated using the future integrated circuit technology. Biotechnology can also be applied.
The present disclosure can be realized by any kind of apparatus, device or system having a function of communication, which is referred to as a communication apparatus. The communication apparatus may comprise a transceiver and processing/control circuitry. The transceiver may comprise and/or function as a receiver and a transmitter. The transceiver, as the transmitter and receiver, may include an RF (radio frequency) module and one or more antennas. The RF module may include an amplifier, an RF modulator/demodulator, or the like. Some non-limiting examples of such a communication apparatus include a phone (e.g., cellular (cell) phone, smart phone), a tablet, a personal computer (PC) (e.g., laptop, desktop, netbook), a camera (e.g., digital still/video camera), a digital player (digital audio/video player), a wearable device (e.g., wearable camera, smart watch, tracking device), a game console, a digital book reader, a telehealth/telemedicine (remote health and medicine) device, and a vehicle providing communication functionality (e.g., automotive, airplane, ship), and various combinations thereof.
The communication apparatus is not limited to be portable or movable, and may also include any kind of apparatus, device or system being non-portable or stationary, such as a smart home device (e.g., an appliance, lighting, smart meter, control panel), a vending machine, and any other “things” in a network of an “Internet of Things (IoT).”
The communication may include exchanging data through, for example, a cellular system, a wireless LAN system, a satellite system, etc., and various combinations thereof.
The communication apparatus may comprise a device such as a controller or a sensor which is coupled to a communication device performing a function of communication described in the present disclosure. For example, the communication apparatus may comprise a controller or a sensor that generates control signals or data signals which are used by a communication device performing a communication function of the communication apparatus.
The communication apparatus also may include an infrastructure facility, such as, e.g., a base station, an access point, and any other apparatus, device or system that communicates with or controls apparatuses such as those in the above non-limiting examples.
A terminal according to an exemplary embodiment of the present disclosure includes: reception circuitry, which, in operation, receives, in a first cell, control information for identifying a reference time in control on a transmission timing of an uplink signal to a second cell that is different from the first cell; and control circuitry, which, in operation, controls the transmission timing based on the control information.
In an exemplary embodiment of the present disclosure, the control information indicates the reference time of the first cell corresponding to the reference time of the second cell.
In an exemplary embodiment of the present disclosure, the control information indicates the reference time of the second cell and a difference between the reference time of the second cell and the reference time of the first cell.
In an exemplary embodiment of the present disclosure, the reception circuitry receives the control information from the second cell without reception from the first cell.
In an exemplary embodiment of the present disclosure, the reception circuitry receives the control information prior to random access processing on the second cell in handover from the first cell to the second cell.
In an exemplary embodiment of the present disclosure, the reception circuitry receives the control information from the first cell and receives information on a system frame number of the second cell from the second cell.
In an exemplary embodiment of the present disclosure, the reception circuitry receives the control information at least every one cycle of a system frame.
A base station according to an exemplary embodiment of the present disclosure includes: control circuitry, which, in operation, determines, in a first cell, control information for identifying a reference time in control on a transmission timing of an uplink signal to a second cell that is different from the first cell, and transmission circuitry, which, in operation, transmits the control information.
A communication method according to an exemplary embodiment of the present disclosure includes: receiving in a first cell, by a terminal, control information for identifying a reference time in control on a transmission timing of an uplink signal to a second cell that is different from the first cell; and controlling, by the terminal, the transmission timing based on the control information.
A communication method according to an exemplary embodiment of the present disclosure includes: determining in a first cell, by a base station, control information for identifying a reference time in control on a transmission timing of an uplink signal to a second cell that is different from the first cell; and transmitting the control information by the base station.
The disclosure of Japanese Patent Application No. 2022-020566, filed on Feb. 14, 2022, including the specification, drawings and abstract, is incorporated herein by reference in its entirety.
An aspect of the present disclosure is useful for radio communication systems.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-020566 | Feb 2022 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/035876 | 9/27/2022 | WO |
