WO2018040674A1 - Procédé de transmission de liaison montante, procédé de transmission de liaison descendante, équipement utilisateur et station de base - Google Patents

Procédé de transmission de liaison montante, procédé de transmission de liaison descendante, équipement utilisateur et station de base Download PDF

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Publication number
WO2018040674A1
WO2018040674A1 PCT/CN2017/088781 CN2017088781W WO2018040674A1 WO 2018040674 A1 WO2018040674 A1 WO 2018040674A1 CN 2017088781 W CN2017088781 W CN 2017088781W WO 2018040674 A1 WO2018040674 A1 WO 2018040674A1
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WIPO (PCT)
Prior art keywords
user equipment
symbol
base station
coverage level
transmission delay
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PCT/CN2017/088781
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English (en)
Chinese (zh)
Inventor
张言飞
张武荣
于光炜
温容慧
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华为技术有限公司
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements
    • H04W56/004—Synchronisation arrangements compensating for timing error of reception due to propagation delay
    • H04W56/0045—Synchronisation arrangements compensating for timing error of reception due to propagation delay compensating for timing error by altering transmission time
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/0001—Arrangements for dividing the transmission path
    • H04L5/0003—Two-dimensional division
    • H04L5/0005—Time-frequency
    • H04L5/0007—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT
    • H04L5/001—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT the frequencies being arranged in component carriers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/12—Wireless traffic scheduling
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/20—Control channels or signalling for resource management

Definitions

  • the present invention relates to wireless communication technologies, and more particularly to uplink and downlink transmission.
  • the transmission time of radio waves in the wireless channel is the transmission delay.
  • the transmission delay depends on the distance between the sender and the receiver, as shown in Figure 1.
  • the transmission delay of the signal in the air can reach the order of several tens of microseconds. This will cause the receiving end to receive a signal, the time to determine the symbol boundary and the actual arrival time of the symbol there is a certain deviation, as shown in Figure 2.
  • T0 is the time at which the receiving end considers the symbol i to start, that is, the actual receiving time
  • T1 is the time at which the symbol i actually arrives at the receiving end.
  • T0 and T1 There is a time deviation t between T0 and T1. Therefore, the symbol received by the receiving end is the tail end of the symbol i-1 and the front end of the symbol i, thereby introducing interference between symbols, so that the demodulation performance of the receiving end is deteriorated.
  • the user equipment sends the time advance t, so that the uplink transmission symbol of the user equipment reaches the base station at time T0. If the distance between the user equipment and the base station is different, the time when the uplink symbol arrives at the base station is different, and the base station needs to make timing adjustments for different user equipments. The existing base station cannot implement unified timing adjustment for all user equipments.
  • LTE Long Term Evolution
  • LTE adopts an uplink timing advance (TA, TimeAdvance) mechanism, and adjusts the uplink transmission time of each user equipment to eliminate different transmission delays between user equipments, so that uplink signals of different user equipments arrive at the time alignment of the base station, thereby Guaranteed uplink orthogonality. Therefore, the symbol start positions of all user equipments received by the base station fall within the length of the cyclic prefix (CP, Cycl icPrefix), thereby ensuring demodulation of the base station.
  • the base station determines the uplink timing advance TA value of each user equipment by measuring the random access signal sent by the user equipment, and then sends a specific message to each user equipment to notify each user equipment to adopt The corresponding uplink timing advance TA value transmits an uplink symbol. For the user equipment that is already in the connected state, the base station needs to continuously adjust the uplink timing advance TA value for each user equipment.
  • TA TimeAdvance
  • the base station needs to adjust the uplink timing advance TA value for each user equipment, so at least the following problems exist:
  • the base station needs to send an adjustment command of the uplink timing advance TA value to each user equipment, from a system perspective In view, the signaling overhead is large;
  • the base station calculates the uplink timing advance TA value not only during the initial random access of the user equipment, but also continuously updates the uplink timing advance TA value for the connected user equipment, so the calculation amount of the base station is too large, and the design complexity is high.
  • the demodulation performance of the reception end is often poor due to the transmission delay assembly.
  • the uplink timing advance TA mechanism is adopted, the uplink signal transmission time of each user equipment is adjusted to eliminate different transmission delays between user equipments, which will result in excessive signaling overhead and excessive calculation of base stations. Problems such as excessive storage overhead.
  • the embodiments of the present invention provide an uplink transmission method, a downlink transmission method, a user equipment, and a base station, so as to reduce signaling overhead for uplink transmission and reduce complexity of the base station.
  • an embodiment of the present invention provides an uplink transmission method.
  • the user equipment receives the downlink symbol, and determines the receiving time of the downlink symbol.
  • the user equipment determines, according to the receiving time of the downlink symbol, the sending time of the uplink symbol, and the sending time of the uplink symbol and the downlink symbol.
  • the difference in reception time is a fixed value.
  • the length of the cyclic prefix CP of the uplink symbol is determined by the maximum bidirectional transmission delay.
  • an embodiment of the present invention provides a user equipment.
  • the user equipment includes a receiver and a processor.
  • the receiver is configured to receive a downlink symbol.
  • the processor is configured to determine a receiving time of the downlink symbol, and determine a sending time of the uplink symbol according to the receiving time of the downlink symbol, and a difference between a sending time of the uplink symbol and a receiving time of the downlink symbol is a fixed value.
  • the length of the cyclic prefix CP of the upstream symbol is determined by the maximum bidirectional transmission delay.
  • the user since the difference between the uplink symbol transmission time and the downlink symbol reception time is a fixed value, the user does not need to set the uplink TA value by himself, and overcomes the inter-symbol interference that may be caused by the transmission delay.
  • the robustness of the system reduces the signaling overhead of the uplink timing advance TA.
  • the fixed value is zero.
  • the length of the cyclic prefix CP of the uplink symbol is determined by the maximum bidirectional transmission delay. Specifically, the length of the cyclic prefix CP of the uplink symbol is greater than or equal to the maximum bidirectional transmission delay.
  • the fixed value is determined by the coverage level of the user equipment.
  • the length of the cyclic prefix CP is determined by the maximum bidirectional transmission delay of the user equipment at its coverage level.
  • the maximum bidirectional transmission delay of the user equipment under its coverage level depends on the bidirectional transmission delay corresponding to the upper limit of the coverage level of the user equipment; wherein the coverage level upper limit is under the coverage level.
  • the base stations corresponding to the user equipment are farthest apart.
  • the fixed value is less than or equal to the bidirectional transmission delay corresponding to the lower limit of the coverage level of the user equipment; wherein the lower limit of the coverage level is the closest to the base station under the coverage level.
  • an embodiment of the present invention provides a downlink transmission method.
  • the base station Determining a transmission time of the downlink symbol, and transmitting the downlink symbol; the base station receives the uplink symbol, and the difference between the transmission time of the uplink symbol and the reception time of the downlink symbol is a fixed value; wherein, the length of the cyclic prefix CP of the uplink symbol Determined by the maximum two-way transmission delay.
  • an embodiment of the present invention provides a base station.
  • the base station includes a processor, a transmitter, and a receiver.
  • the processor is configured to determine the transmission time of the downlink symbol.
  • the transmitter is used to transmit downlink symbols.
  • the receiver is configured to receive an uplink symbol, and a difference between a transmission time of the uplink symbol and a reception time of the downlink symbol is a fixed value.
  • the length of the cyclic prefix CP of the uplink symbol is determined by the maximum bidirectional transmission delay.
  • the length of the cyclic prefix CP is determined by the farthest distance supported by the base station.
  • the length of the cyclic prefix CP is determined by the maximum bidirectional transmission delay of the coverage level of the user equipment corresponding to the downlink symbol.
  • the base station sends the fixed value in a multicast manner, and the fixed value is determined by a coverage level of the user equipment corresponding to the base station.
  • the base station provided by the embodiment of the present invention divides the user equipment into different groups according to the coverage level of the user equipment, and the base station can uniformly configure the uplink TA variable for the user equipment in different groups, which is not required for each user compared with the prior art.
  • the device configures the uplink TA variable, and only needs to configure the uplink TA variable for different groups, thereby reducing the signaling overhead for uplink TA value adjustment and reducing the complexity of the base station.
  • the base station transmits an uplink TA command to the user equipment in some or all groups in a multicast manner, where the uplink TA command includes an uplink TA variable.
  • the multicast TA mode is used to facilitate the transmission of the uplink TA command to different groups. If the uplink TA command is transmitted only to the user equipment in the partial group, and the number of uplink TA commands transmitted at this time is reduced, the signaling overhead for the uplink TA value adjustment can be reduced and the complexity of the base station can be reduced.
  • the fixed value is less than or equal to the bidirectional transmission delay corresponding to the lower limit of the coverage level of the user equipment; wherein the lower limit of the coverage level is the closest to the base station under the coverage level.
  • the user equipment in the embodiment of the present invention can determine the uplink TA value autonomously, and the base station does not need to configure the uplink TA value for the user equipment, thereby reducing the signaling overhead for the uplink TA value and reducing the complexity of the base station.
  • 1 is a schematic diagram showing a bidirectional transmission delay in a wireless communication system
  • FIG. 2 is a schematic diagram of deviations between symbol arrival time and symbol reception time in a conventional wireless communication system
  • FIG. 3 is a schematic diagram of an uplink transmission method according to an embodiment of the present invention.
  • 4 is a schematic diagram of a cyclic prefix of an OFDM symbol
  • 5 is a symbol timing diagram of downlink and uplink transmissions of a base station and multiple terminals according to an embodiment of the present invention
  • FIG. 6 is a schematic diagram of a structure of an OFDM symbol according to an embodiment of the present invention.
  • FIGS. 7-10 are schematic diagrams showing four OFDM symbol structures in four coverage levels according to an embodiment of the present invention.
  • FIG. 11 is a structural block diagram of a user equipment according to an embodiment of the present invention.
  • Figure 12 is a block diagram showing the structure of a base station according to an embodiment of the present invention.
  • the embodiment is applicable to any type of synchronous communication system, and is particularly suitable for a synchronous communication system that transmits over a long distance, for example, an OFDM system that transmits over a long distance.
  • the embodiments of the present invention can be applied to multiple fields, and are particularly applicable to scenarios where a large number of communication nodes exist, for example, smart meter reading and backhaul, sensor data collection and alarm in a factory, intelligent transportation, smart city, and the like. Application scenario.
  • a base station (BS) is a device deployed in a radio access network to provide a wireless communication function for a user equipment.
  • the base station may include various forms of macro base stations, micro base stations, relay stations, access points, and the like.
  • the name of a device having a base station function may be different.
  • an evolved Node B evolved Node B: eNB or eNodeB
  • Node B In the 3G network, it is called Node B and so on.
  • step S301 the base station transmits a downlink symbol, such as transmitting a downlink OFDM symbol.
  • step S302 the user equipment receives the downlink symbol and determines the receiving time of the downlink symbol.
  • the user equipment receives the downlink signal, detects the downlink signal, obtains symbol boundary synchronization, and further determines a receiving time of the downlink symbol, where the downlink symbol is an OFDM symbol.
  • step S303 the user equipment determines the transmission time of the uplink symbol according to the reception time of the downlink symbol, and the difference between the transmission time of the uplink symbol and the reception time of the downlink symbol is a fixed value.
  • the length of the cyclic prefix CP of the uplink symbol is determined by the maximum bidirectional transmission delay.
  • the maximum two-way transmission delay is determined by the farthest distance supported by the base station. Specifically, the maximum two-way transmission delay is equal to twice the farthest distance supported by the base station and the quotient of the speed of light.
  • the structure of the uplink symbol is determined by the length of the cyclic prefix CP of the uplink symbol.
  • the maximum two-way transmission delay is determined by the farthest distance between the coverage level of the user equipment and the base station. Specifically, the maximum two-way transmission delay is equal to a quotient of the upper limit of the coverage level of the user equipment and the distance between the base station and the speed of light; wherein the upper limit of the coverage level refers to the coverage level. Farthest from the base station.
  • the length of the cyclic prefix CP of the upstream symbol is greater than or equal to the maximum two-way transmission delay between the user equipment and the base station.
  • the difference between the time of the uplink symbol transmission and the downlink symbol reception time is a fixed value. Therefore, even if the time for each UE to transmit the uplink symbols may be different, the difference between the time when each UE transmits the uplink symbol and the time when the UE receives the downlink symbol is fixed, thereby unifying the time of the UE uplink symbol transmission. Further, the UE may use the time when the OFDM symbol is received as the time of downlink symbol reception.
  • the time at which the upstream symbol is transmitted can be adjusted by adjusting the fixed value. For example, when the fixed value is set to 0, the time at which the uplink symbol is transmitted is aligned with the time at which the downlink symbol is received.
  • the maximum two-way transmission delay refers to twice the distance between the user equipment and the base station and the quotient of the speed of light.
  • the maximum two-way transmission delay refers to a bidirectional transmission delay between the base station and the farthest distance supported by the base station. That is, the maximum two-way transmission delay is equal to twice the quotient of the farthest distance and the speed of light.
  • the maximum two-way transmission delay refers to the maximum bidirectional transmission of the user equipment under its coverage level. Delay.
  • the maximum bidirectional transmission delay of the user equipment under its coverage level refers to the maximum bidirectional transmission delay corresponding to the upper limit of the coverage level of the user equipment; the upper coverage level refers to the distance from the base station under the coverage level. The farthest.
  • step S304 the user equipment sends the uplink symbol to the base station according to the transmission time of the uplink symbol.
  • step S305 the base station receives the uplink symbol, and the difference between the transmission time of the uplink symbol and the reception time of the downlink symbol is a fixed value; wherein the length of the cyclic prefix CP of the uplink symbol is determined by the maximum bidirectional transmission delay. .
  • the length of the cyclic prefix CP of the upstream symbol is greater than or equal to the maximum two-way transmission delay.
  • the length of the cyclic prefix CP of the uplink symbol is sufficiently long, it is ensured that the time at which the symbol arrives at the base station falls within the CP window of the uplink symbol, thus ensuring that the base station can receive the complete data.
  • the cyclic prefix CP is detailed below.
  • a cyclic prefix CP is added in front of each symbol, that is, the tail end of each OFDM symbol is copied and supplemented to the OFDM symbol.
  • the uplink transmission method provided by the embodiment of the present invention is further described below with reference to FIG.
  • FIG. 5 is a symbol timing diagram of downlink and uplink transmissions of a base station and multiple terminals according to an embodiment of the present invention.
  • the base station transmits downlink symbols to UE1 and UE2 on a uniform time base.
  • the distance between UE1 and UE2 and the base station is different, wherein UE1 is closer to the base station, and UE2 is farther from the base station.
  • T2 there is a time difference between the time when the UE 2 receives the downlink symbol and the time when the UE transmits the downlink symbol. Since UE2 is far from the base station, T2 is greater than T1.
  • the UE in the embodiment of the present invention may determine the time at which the uplink symbol is sent, so that the difference between the sending time of the uplink symbol and the receiving time of the downlink symbol is a fixed value.
  • the fixed value is set to 0 in FIG.
  • the UE1 transmits an uplink symbol to the base station with the reception time of its downlink symbol, and arrives at the base station after the time T1.
  • UE2 sends an uplink symbol to the base station with the reception time of its downlink symbol, and arrives at the base station after time T2.
  • the time difference between the time when the base station receives the uplink symbol of UE1 and the time when the base station transmits the downlink symbol to UE1 is 2T1.
  • the time difference between the time when the base station receives the uplink symbol sent by the UE2 and the time when the base station sends the downlink symbol to the UE2 is 2T2.
  • the length of the CP is sufficiently long, for example, the length of the CP is greater than or equal to the two-way transmission delays 2T1 and 2T2 of the UE1 and the UE2, the time of the symbols of the UE1 and the UE2 received by the base station is guaranteed to be within one CP, that is, It is said that the starting position of the symbols received by the base station falls within one CP range, so that no inter-symbol interference is caused, and thus the decoding performance of the base station is not affected.
  • the fixed value may be other constants other than zero.
  • the fixed value takes the value Td and Td is a non-zero constant.
  • the length of the CP is greater than or equal to 2T1+Td and 2T2+Td, so as to ensure that the symbols of UE1 and UE2 received by the base station are all within one CP, so that no inter-symbol interference is caused, and thus the base station is not affected. Decoding performance.
  • the purpose of setting the CP in the existing OFDM system is to eliminate inter-symbol interference caused by multipath components, and the length of the CP is greater than the maximum multipath delay spread of the wireless channel, and the maximum number of wireless channels is
  • the runoff delay is typically a few to ten microseconds (us).
  • the bidirectional transmission delay is usually several tens of microseconds.
  • the maximum multipath delay spread is usually much smaller than the bidirectional transmission delay. Therefore, the UE is far from the base station
  • CPs in existing OFDM systems generally cannot eliminate inter-symbol interference due to transmission delay.
  • the OFDM symbol structure is different. That is, the structure of the OFDM symbol is determined by the CP length of the OFDM symbol.
  • the embodiment of the present invention designs the cyclic prefix CP length of the OFDM symbol structure, and ensures that the starting positions of the OFDM symbols received by the base station all fall within one CP range.
  • FIG. 6 shows an OFDM symbol structure according to an embodiment of the present invention.
  • the subcarrier spacing of the OFDM system is 3.75 KHz and the sampling frequency is 1.92 MHz.
  • the OFDM symbol structure includes 6 OFDM symbols with sequence numbers 0-5.
  • the data portion of each OFDM symbol uses a discrete Fourier transform IFFT of 512 points, that is, the length of the data portion in each OFDM symbol is 512 samples, and the duration of the data portion is 266.7us.
  • the farthest distance between the UE and the base station can be determined in conjunction with the coverage of the base station or obtained in a priori manner. It is assumed that the farthest distance between the UE covered by the base station and the base station is 10 km. At this time, the maximum two-way transmission delay Tround_trip is twice the one-way transmission delay, namely:
  • each OFDM symbol includes 640 sample points, each of which has a duration of 333.3 us.
  • An OFDM symbol structure includes a total of 3840 sample points, thereby constituting one time slot of 2 milliseconds (ms), that is, 6 OFDM symbols.
  • the length of the cyclic prefix of each OFDM symbol in the OFDM symbol structure should be greater than or equal to the maximum bidirectional transmission trip to ensure that the base station can receive uplink data of all terminals within the CP range.
  • the maximum two-way transmission delay is the transmission delay of the UE farthest from the base station within the coverage of the base station.
  • the embodiment of the present invention effectively eliminates inter-symbol interference caused by transmission delay by configuring the cyclic prefix CP.
  • the difference between the time of receiving the uplink symbol and the time of receiving the downlink symbol is set to a fixed value, so that the time for all the UEs to send the uplink symbol can be unified, thereby no longer relying on the adjustment of the uplink TA value.
  • the signaling overhead for TA value adjustment is greatly reduced and the base station complexity is reduced.
  • step S303 the user equipment transmits an OFDM symbol as shown in FIG. 6 to the base station according to the time when the uplink symbol is transmitted. Assuming that the OFDM symbol structure is known to the base station, normal subsequent processing of the OFDM symbol can be performed.
  • the downlink OFDM symbol received by the user equipment and the length of the cyclic prefix CP of the transmitted uplink OFDM symbol are used by the base station.
  • the farthest distance supported is determined.
  • the length of the cyclic prefix CP of the OFDM symbol is determined by the distance between the user equipment and the base station.
  • the length of the cyclic prefix CP of the OFDM symbol is determined by the maximum bidirectional transmission delay of the user equipment at its coverage level, as described in more detail below.
  • each coverage level corresponds to one OFDM symbol structure. See Figures 7-10 (not shown in Table 1, see Figures 7-10), and each OFDM structure determines a unique CP duration.
  • Coverage level number Subcarrier spacing Distance between UE and base station CP duration 1 15kHz 0-500m 5.2us/4.7us 2 15kHz 0.5-2.5km 16.7us 3 3.75kHz 0.5-2.8km 20.83us/18.75us 4 3.75kHz 2.5-10km 66.7us
  • the first coverage level is 0-500 m
  • the second coverage level is 0.5-2.5 km
  • the third coverage level is 0.5-3 km
  • the fourth coverage level is 2.5-10 km.
  • the coverage of the first coverage level is small, and may also be referred to as the lowest coverage level and the latest coverage level.
  • the second coverage level may also be referred to as a medium to close coverage level.
  • the third coverage level may be referred to as a medium and long distance coverage level.
  • the coverage of the fourth coverage level is large, and may also be referred to as the highest coverage level and the farthest coverage level.
  • the length of the cyclic prefix CP of the uplink symbol is determined by the farthest distance 500m under the coverage level 1; in the case where the user equipment is in the coverage level 2, the uplink The length of the cyclic prefix CP of the symbol is determined by the longest distance of 2.5 km under the coverage level 2; in the case where the user equipment is in the coverage level 3, the length of the cyclic prefix CP of the upstream symbol is the highest under the coverage level 3 The long distance 2.8 km is determined; in the case where the user equipment is in the coverage level 4, the length of the cyclic prefix CP of the uplink symbol is determined by the farthest distance 10 km under the coverage level 4.
  • the division of coverage levels here is merely exemplary.
  • the correspondence between different coverage levels and the distance between the UE and the base station may be different, and the coverage level may be set to be greater than 4 or less than 4, for example, only 2 or 3 coverage levels may be set.
  • the coverage level may be set to be greater than 4 or less than 4, for example, only 2 or 3 coverage levels may be set.
  • Those skilled in the art can set other coverage levels according to the teachings of Table 1, and details are not described herein again.
  • the maximum bidirectional transmission delay of the user equipment under its coverage level depends on the upper limit of the coverage level of the user equipment and the distance between the base stations; wherein the coverage level upper limit is at the coverage level The base stations are farthest apart.
  • FIG. 7 shows an OFDM symbol structure corresponding to coverage level 1.
  • the OFDM system uses a subcarrier spacing of 15 kHz and a sampling frequency of 1.92 MHz.
  • the OFDM symbol structure at this time is aligned with the 1.4 MHz system bandwidth of LTE.
  • One OFDM symbol structure may include 7 OFDM symbols.
  • the data portion of each OFDM symbol includes 128 sample points, and the data portion has a duration of 66.7 us.
  • the duration of the CP should be greater than or equal to 3.33us, that is, the CP should contain at least 6 sampling points. As shown in FIG.
  • the duration of the CP can be set to 5.2 us or 4.7 us, that is, the CP can include 10 sampling points or 9 sampling points.
  • the CP duration in the first OFDM symbol is 5.2 us, including 10 sample points.
  • the CP duration in other OFDM symbols is 4.7 us, and the CP of each OFDM symbol includes 9 sample points.
  • the OFDM symbol structure composed of 7 OFDM symbols includes a total of 960 sample points, and the total duration of the OFDM symbol structure is 0.5 ms, thereby constituting a complete time slot.
  • FIG. 7 is an example in which one slot includes 7 OFDM symbols. In fact, one slot may also include 6 OFDM symbols, and the principle is the same, and details are not described herein again.
  • FIG. 8 shows an OFDM symbol structure corresponding to coverage level 2.
  • the OFDM system uses a subcarrier spacing of 15 kHz and a sampling frequency of 1.92 MHz.
  • the OFDM symbol structure at this time is aligned with the 1.4 MHz system bandwidth of LTE.
  • One OFDM symbol structure may include 6 OFDM symbols.
  • the data portion of each OFDM symbol includes 128 sample points, and the data portion has a duration of 66.7 us.
  • the duration of the CP should be greater than or equal to 16.7us, that is, the CP should contain at least 32 sampling points. As shown in FIG.
  • the duration of the CP can be set to 16.7 us, that is, the CP can include 32 sampling points.
  • the OFDM symbol structure composed of 6 OFDM symbols includes a total of 960 sampling points, and the total duration of the OFDM symbol structure is 0.5 ms, thereby constituting a complete time slot.
  • the CP duration at this time is the same as the CP duration when the LTE is extended.
  • FIG. 8 is an example in which one slot includes 6 OFDM symbols. In fact, one slot may also include 7 OFDM symbols, and the principle is the same, and details are not described herein again.
  • FIG. 9 shows an OFDM symbol structure covering level 3.
  • the OFDM system uses a subcarrier spacing of 3.75 kHz and a sampling frequency of 1.92 MHz.
  • the OFDM symbol structure at this time is aligned with the 1.4 MHz system bandwidth of LTE.
  • One OFDM symbol structure may include 7 OFDM symbols.
  • the data portion of each OFDM symbol includes 512 sample points, and the data portion has a duration of 266.7us.
  • the duration of the CP should be greater than or equal to 18.7 us, that is, the CP should contain at least 35 sampling points. As shown in FIG.
  • the duration of the CP can be set to 20.83us or 18.75us, that is, the CP can include 40 sampling points or 36 sampling points.
  • the CP duration in the first OFDM symbol is 20.83 us, including 40 sample points.
  • the CP duration in other OFDM symbols is 18.75 us, and the CP of each OFDM symbol includes 36 sample points.
  • the OFDM symbol structure composed of 7 OFDM symbols includes a total of 3840 sample points, and the total duration of the OFDM symbol structure is 2 ms, thereby constituting a complete time slot.
  • the CP duration at this time is the same as the CP duration when LTE is normal.
  • the OFDM symbol structure allows for a round trip delay of approximately 2.8 km.
  • FIG. 9 is an example in which one slot includes 7 OFDM symbols. In fact, one slot may also include 6 OFDM symbols, and the principle is the same, and details are not described herein again.
  • FIG. 10 shows an OFDM symbol structure covering level 4.
  • the OFDM system uses a subcarrier spacing of 3.75 kHz and a sampling frequency of 1.92 MHz.
  • the OFDM symbol structure at this time is aligned with the 1.4 MHz system bandwidth of LTE.
  • One OFDM symbol structure may include 6 OFDM symbols.
  • the data portion of each OFDM symbol includes 512 sample points, and the data portion has a duration of 266.7us.
  • the duration of the CP should be greater than or equal to 66.7us, that is, the CP should contain at least 128 sampling points. As shown in FIG.
  • the duration of the CP can be set to 66.7 us, that is, the CP can include 128 sampling points.
  • the OFDM symbol structure composed of 6 OFDM symbols includes a total of 3840 sample points, and the total duration of the OFDM symbol structure is 2 ms, thereby constituting a complete time slot.
  • the OFDM symbol structure allows for a round trip (two-way transmission) delay of approximately 10 km.
  • FIG. 10 is an example in which a time slot includes six OFDM symbols. In fact, one time slot may also include seven OFDM symbols, and the principle is the same, and details are not described herein again.
  • the length of the cyclic prefix CP included in each OFDM symbol is related to the coverage level of the user equipment.
  • the coverage level of the user equipment is related to the distance between the user equipment and the base station, that is, the coverage level of the user equipment is related to the transmission delay, so that the corresponding OFDM symbol structure can be flexibly set for different levels of transmission delay.
  • the user equipment can determine the OFDM symbol structure corresponding to its coverage level according to its coverage level and by, for example, a lookup manner, whereby the CP overhead due to the use of a single OFDM symbol can be reduced.
  • the OFDM symbol structure corresponding to the farthest coverage level may be selected by default.
  • the CP overhead may be partially increased, it is possible to avoid the phenomenon that the inter-symbol interference due to the transmission delay cannot be overcome due to the shortage of the CP length, thereby enhancing the robustness of the system.
  • the OFDM symbol structure corresponding to the coverage level 2 may be selected. It is also possible to choose to cover the OFDM symbol structure corresponding to level 3. For example, when it is required to make the length of the CP small, the OFDM symbol structure corresponding to the coverage level 2 is selected; when it is required to make the length of the CP larger, the OFDM symbol structure corresponding to the coverage level 3 can be selected. When the UE determines that its distance from the base station is close to 2.5 km, or is greater than 2.5 km and less than 2.8 km, the OFDM symbol structure corresponding to the coverage level 3 may be selected.
  • the UE can determine the transmission time of the uplink symbol. For example, the UE makes the difference between the transmission time of the uplink symbol and the reception time of the downlink symbol a fixed value, and the fixed value may be set to zero.
  • the UE may determine the receiving time of the downlink symbol according to the time of the OFDM symbol received from the base station. For example, the time at which the OFDM symbol is received is taken as the downlink symbol reception time.
  • the inventive embodiments reduce the CP overhead associated with the use of a single OFDM symbol by using a plurality of differently structured OFDM symbols.
  • the user equipment obtains the fixed value in a multicast manner.
  • the base station divides the user equipment into different groups according to the coverage level of the user equipment. For example, according to the setting of Table 1, the UE is divided into four groups corresponding to coverage level 1, coverage level 2, coverage level 3, and coverage level 4, respectively.
  • the base station uniformly configures uplink TA variables for user equipments in different groups.
  • the uplink TA value is less than or equal to the bidirectional transmission delay corresponding to the lower coverage level of the coverage level of the user equipment, and the lower coverage level is the closest to the base station under the coverage level.
  • the TA variable is uniformly configured, and the value of the TA variable may be 0.
  • the TA variables are uniformly configured. Since the one-way transmission distance corresponding to the lower limit of the coverage level of the coverage level 2 and the coverage level 3 is 500 m, the value of the TA variable may be 3.3 us.
  • the TA variable is uniformly configured. Since the one-way transmission distance corresponding to the lower limit of the coverage level 4 is 2.5 km, the value of the TA variable may be 16.7 us.
  • the embodiment of the present invention does not need to configure an uplink TA variable for each user equipment, and only needs to configure an uplink TA variable for different groups, thereby reducing the signaling overhead for uplink TA value adjustment and reducing the base station. the complexity.
  • the base station sends an uplink TA command to the user equipment in some or all groups in a multicast manner, where
  • the upstream TA command includes an upstream TA variable.
  • the UE may perform subsequent operations according to the received TA command.
  • the base station facilitates the transmission of uplink TA commands to different groups through multicast. It is worth noting that the base station can only send uplink TA commands to user equipments in some groups. For other user equipments, the TA setting method in the prior art can be adopted. If the base station only transmits the uplink TA command to the user equipment in the partial group, the number of uplink TA commands sent by the base station will be reduced, thereby partially reducing the signaling overhead for the uplink TA value and reducing the complexity of the base station.
  • the uplink transmission method provided by the embodiment of the present invention has been described. It should be noted that the method steps S201-S205 in this embodiment may be completed by independent functional modules or independent physical devices, or in the same functional module or the same physical device.
  • an embodiment of the present invention provides a user equipment 140.
  • the user equipment 140 includes a receiver 141, a processor 142, and a transmitter 143.
  • Receiver 141 is configured to receive downlink symbols from a base station, such as receiving OFDM symbols.
  • receiver 141 is operative to condition (eg, filter, amplify, downconvert, digitize, etc.) the signals received from the antenna and provide input samples to obtain downlink OFDM symbols from the base station.
  • condition eg, filter, amplify, downconvert, digitize, etc.
  • the processor 142 is configured to determine a receiving time of the downlink symbol, and determine, according to the receiving time of the downlink symbol, a sending time of the uplink symbol, and a difference between a sending time of the uplink symbol and a receiving time of the downlink symbol is a fixed value.
  • the length of the cyclic prefix CP of the uplink symbol is determined by the maximum bidirectional transmission delay. For example, the length of the cyclic prefix CP of the symbol is greater than or equal to the maximum bidirectional transmission delay.
  • the processor 142 performs control management on the action of the UE, and is used to perform processing performed by the UE in the foregoing embodiment.
  • the processor 142 is configured to determine a coverage level of the UE. In case the coverage level of the user equipment is not determined, the length of the cyclic prefix CP of the OFDM symbol is determined by the farthest distance supported by the base station. In the case of the coverage level determination of the user equipment, the length of the cyclic prefix CP of the OFDM symbol is determined by the maximum bidirectional transmission delay of the user equipment at its coverage level.
  • the maximum bidirectional transmission delay of the user equipment under its coverage level depends on the upper limit of the coverage level of the user equipment and the distance between the base stations; wherein the upper limit of the coverage level is the distance from the base station under the coverage level. The farthest.
  • the fixed value is less than or equal to the bidirectional transmission delay corresponding to the lower limit of the coverage level of the user equipment; wherein the lower limit of the coverage level is the closest to the base station under the coverage level.
  • the embodiment of the present invention sets the difference between the transmission time of the uplink symbol and the reception time of the downlink symbol to a fixed value, and sets the OFDM symbol structure according to the maximum bidirectional transmission delay, thereby reducing the uplink TA signaling overhead.
  • the transmitter 143 is configured to send an uplink symbol to the base station, and the difference between the transmission time of the uplink symbol and the reception time of the downlink symbol is a fixed value, and the length of the cyclic prefix CP of the uplink symbol is determined by the maximum bidirectional transmission delay.
  • transmitter 143 is operative to condition (e.g., analog convert, filter, amplify, upconvert, etc.) output samples and generate an uplink signal that is transmitted via an antenna to a base station in the above-described embodiments.
  • condition e.g., analog convert, filter, amplify, upconvert, etc.
  • Figure 11 only shows a simplified design of the user equipment.
  • the user equipment may include any number of transmitters, receivers, processors, controllers, memories, communication units, etc., and all user equipments that can implement the present invention are within the scope of the present invention.
  • FIG. 12 is a schematic diagram of a base station according to an embodiment of the present invention.
  • the base station 150 includes a processor 151, a transmitter 152, and a receiver 153.
  • the processor 151 is configured to determine a transmission time of the downlink symbol, for example, determine a transmission time of the downlink OFDM symbol.
  • the transmitter 152 is configured to transmit a downlink symbol according to a transmission time of the downlink symbol determined by the processor 151.
  • the receiver 153 is configured to receive an uplink symbol, and a difference between a transmission time of the uplink symbol and a reception time of the downlink symbol is a fixed value; wherein a length of the cyclic prefix CP of the uplink symbol is determined by a maximum bidirectional transmission delay. For example, the length of the cyclic prefix CP of the uplink symbol is greater than or equal to the maximum bidirectional transmission delay.
  • the length of the cyclic prefix CP of the OFDM symbol is determined by the farthest distance supported by the base station.
  • the length of the cyclic prefix CP of the OFDM symbol is determined by the maximum bidirectional transmission delay of the coverage level of the user equipment of the downlink symbol.
  • the maximum bidirectional transmission delay of the coverage level of the user equipment depends on the upper limit of the coverage level and the distance between the base stations; wherein the coverage level upper limit is the farthest from the base station under the coverage level. At the office.
  • the transmitter 142 is configured to transmit the fixed value in a multicast manner, and the fixed value is determined by the coverage level of the user equipment of the downlink symbol.
  • the fixed value is less than or equal to the bidirectional transmission delay corresponding to the lower limit of the coverage level of the user equipment corresponding to the downlink symbol, where the lower limit of the coverage level is the distance from the base station under the coverage level of the user equipment of the downlink symbol.

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  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
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Abstract

Des modes de réalisation de la présente invention concernent le domaine technique des communications, en particulier un procédé de transmission de liaison montante, un procédé de transmission de liaison descendante, un équipement utilisateur et une station de base. Le procédé de transmission de liaison montante comprend les étapes suivantes : un équipement utilisateur reçoit un symbole de liaison descendante et détermine le temps de réception du symbole de liaison descendante ; et l'équipement utilisateur détermine le temps de transmission d'un symbole de liaison montante en fonction du temps de réception du symbole de liaison descendante, une différence entre le temps de transmission du symbole de liaison montante et le temps de réception du symbole de liaison descendante étant une valeur constante, et la longueur d'un préfixe cyclique du symbole de liaison montante étant déterminée selon une période de retard de transmission bidirectionnelle maximale. Avec la solution fournie par les modes de réalisation de la présente invention, un équipement utilisateur peut déterminer par lui-même une avance temporelle (TA, "time advance") de liaison montante, et une station de base n'est pas requise pour configurer individuellement des variances de TA de liaison montante pour différentes unités d'équipements utilisateurs, réduisant ainsi le surdébit de signalisation ainsi que la complexité d'une station de base.
PCT/CN2017/088781 2016-08-29 2017-06-16 Procédé de transmission de liaison montante, procédé de transmission de liaison descendante, équipement utilisateur et station de base WO2018040674A1 (fr)

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