Base station device

Abstract

Provided is a base station device for executing time-division multiplexing wireless communication with a terminal that transmits a time-sequenced uplink radio frame at a transmission timing based on an uplink timing advance value, the base station device comprising: a detection unit that detects an interference period between a time-sequenced first downlink radio frame transmitted from a synchronized base station and the time-sequenced uplink radio frame; a base station control unit that corrects the uplink timing advance value on the basis of the position and the length of the interference period in the time-sequenced uplink radio frame; and a base station transmission unit that notifies the terminal of the corrected uplink timing advance value by using one or more base station antennas.

Description

base station equipment

[0001] The present invention relates to a base station device.

[0002] When analog RoF (Radio-over-Fiber) is applied to a communication system, the functions of the communication system's base station may be divided into an aggregation station and a base station (see Non-Patent Document 1). By deploying base stations with simple configurations in wireless areas, a flexible and economical mobile network is realized. Hereinafter, the direction from the terminal to the base station is referred to as "uplink," and the direction from the base station to the terminal is referred to as "downlink."

[0003] Communication systems such as mobile networks often use the Time Division Duplex (TDD) method, which switches between uplink (UL) and downlink (DL) in the same frequency band on a slot-by-slot basis.

[0004] A communication system may be equipped with a timing advance (TA) function (see Non-Patent Document 2). In the timing advance, a timing advance value (TA value) corresponding to the amount of transmission delay in a wireless section is determined. An uplink radio frame is transmitted at a timing earlier than a downlink radio frame by a time period determined by the timing advance value (see Non-Patent Document 3).

[0005] As a result, for example, when an uplink radio frame is transmitted from a terminal to an asynchronous base station (own station), the reception timing of the uplink radio frame at the antenna of the asynchronous base station is synchronized with the reference timing of time division multiplexing of the synchronous base station (other station).

[0006] Kodai Ito, Mizuki Suga, Hirofumi Shirato, Naoki Kita, and Takeshi Onisawa, "Efficient Accommodation of Diverse High-Frequency Band Wireless Systems Using Analog RoF," NTT Technical Journal, 32(3), 15-17, 2020. 3GPP TS 38.211 version 16.7.0 Release 16 3GPP TS 38.133 version 15.3.0 Release 15

[0007] Hereinafter, the timing advance value for uplink transmission will be referred to as the "uplink timing advance value." Hereinafter, the timing advance value for downlink transmission will be referred to as the "downlink timing advance value."

[0008] When a timing advance function is applied to an analog RoF communication system, the central station estimates a transmission delay amount in the analog RoF section (optical section) from the central station to the base station. The central station determines a downlink timing advance value of the central station based on the estimated transmission delay amount in the optical section so that the transmission timing of the downlink radio frame at the base station is synchronized with the reference timing.

[0009] When a timing advance function is applied to an analog RoF communication system, the central station estimates a transmission delay amount in a wireless section from a terminal to a base station. The central station determines an uplink timing advance value for the terminal based on the estimated transmission delay amount in the wireless section so that the reception timing of an uplink wireless frame at the base station is synchronized with a reference timing. The central station notifies the terminal of the uplink timing advance value.

[0010] When a timing advance function is applied to a digital RoF communication system, the central station estimates the amount of transmission delay in the wireless section from the terminal to the base station. The central station determines an uplink timing advance value for the terminal based on the estimated value of the transmission delay in the wireless section so that the reception timing of the uplink wireless frame at the base station is synchronized with the reference timing. The central station notifies the terminal of the uplink timing advance value.

[0011] However, even though there is an error in the estimated value of the transmission delay, the base station (base station device) cannot detect the timing advance error (TAE) caused by the error, and therefore the base station cannot correct the timing advance value to reduce the error.

[0012] In view of the above circumstances, an object of the present invention is to provide a base station device that is capable of detecting an error in a timing advance value and correcting the timing advance value so as to reduce the error.

[0013] One aspect of the present invention is a base station device that performs wireless communication using time division multiplexing with a terminal that transmits time-series uplink radio frames at transmission timing based on an uplink timing advance value, and includes: a detection unit that detects an interference period between a first time-series downlink radio frame transmitted from a synchronized base station and the time-series uplink radio frame transmitted from the terminal; a base station control unit that corrects the uplink timing advance value based on the position and length of the interference period in the time-series uplink radio frame; and a base station transmission unit that notifies the terminal of the corrected uplink timing advance value using one or more base station antennas.

[0014] According to the present invention, it is possible to detect an error in the timing advance value and then correct the timing advance value so as to reduce the error.

[0015] FIG. 1 is a diagram showing an example of the configuration of a communication system in a first embodiment. FIG. 2 is a diagram showing an example of an interference period in a case where the transmission timing of a wireless frame in a terminal is earlier than the reference timing of time division multiplexing of a synchronized base station (other station) in the first embodiment. FIG. 3 is a diagram showing an example of the interference period in a case where the transmission timing of a wireless frame in a terminal is later than the reference timing of time division multiplexing of a synchronized base station (other station) in the first embodiment. FIG. 4 is a flowchart showing an example of the operation of a communication system in the first embodiment. FIG. 5 is a diagram showing an example of the configuration of a communication system in a modified example of the first embodiment. FIG. 6 is a diagram showing an example of the configuration of a communication system in a second embodiment. FIG. 7 is a flowchart showing an example of the operation of a communication system in the second embodiment. FIG. 8 is a diagram showing an example of the configuration of a communication system in a third embodiment. FIG. 9 is a diagram showing an example of the hardware configuration of a communication device in each embodiment.

[0016] Embodiments of the present invention will be described in detail with reference to the drawings. (First Embodiment) Fig. 1 is a diagram showing an example of the configuration of a communication system 1a in the first embodiment. The communication system 1a is a system that performs wireless communication between a base station and a terminal. The communication system 1a includes a base station 2a (base station device) and a terminal 3. A synchronized base station 4 is installed in advance at a location adjacent to the base station 2a.

[0017] The base station 2a includes a base station antenna 21, a detector 22, a base station controller 23, and a base station transmitter 24. The base station antenna 21 and the base station transmitter 24 (optical section) are connected by an optical fiber. The optical fiber may be a single-mode optical fiber, a multi-mode optical fiber, a single-core optical fiber, or a multi-core optical fiber.

[0018] The terminal 3 includes a terminal antenna 31 , an acquisition unit 32 , a terminal control unit 33 , and a terminal transmission unit 34 .

[0019] The base station 2a (asynchronous base station) notifies the terminal 3 of the uplink timing advance value. The terminal 3 executes a transmission process (advance processing) based on the uplink timing advance value. The error "TAE" of the uplink timing advance value is calculated by multiplying the error "t ＥＲ Before the uplink timing advance value is corrected, the uplink timing advance value notified to the terminal 3 is not corrected based on the uplink timing advance error "TAE." Therefore, in the vicinity of the base station antenna 21, the downlink radio frame of the synchronized base station 4 may interfere with the uplink radio frame between the base station 2a and the terminal 3.

[0020] The communication system 1a in the first embodiment is a digital RoF communication system, in which transmission processing (advance processing) based on a timing advance value (uplink timing advance value) is required only for uplink transmission.

[0021] In digital RoF, the functional unit that performs modulation and demodulation processing is provided in the base station antenna 21. The base station antenna 21 generates downlink radio frames in synchronization with the reference timing of time division multiplexing. Therefore, in the base station antenna 21, the transmission timing of the downlink radio frames is synchronized with the reference timing, so that transmission processing based on a timing advance value (downlink timing advance value) is not required for downlink transmission by the base station transmitter 24.

[0022] The base station 2a estimates the amount of transmission delay in the wireless section from the terminal 3 to the base station 2a. The base station 2a calculates the estimated value of the amount of transmission delay in the wireless section "t" so that the reception timing of the uplink wireless frame at the base station antenna 21 is synchronized with the reference timing. ＲＦ The base station 2 a determines the uplink timing advance value based on the above. The base station 2 a notifies the terminal 3 of the uplink timing advance value.

[0023] The error in the uplink timing advance value, "TAE," is the error in the estimated value of the transmission delay amount in the wireless section, "t ＥＲ ". The error "TAE" in the uplink timing advance value causes the transmission timing of the uplink radio frame to become asynchronous with respect to the reference timing of time division multiplexing. This causes interference (inter-base station interference) between the uplink radio frame of the base station 2a (asynchronized base station) and the downlink radio frame of the synchronized base station 4. The base station 2a detects the error "TAE" in the uplink timing advance value based on the period of inter-base station interference.

[0024] Note that a guard period (GP) may be defined in the special slot of the time-series radio frame at the timing of switching from downlink transmission to uplink transmission. Also, in order to improve the accuracy of timing synchronization, a special slot without a guard period may be used only when estimating and correcting the error of the timing advance value.

[0025] Next, a detailed configuration example of the communication system 1a will be described. The base station antenna 21 may be an antenna with a fixed direction of directivity of wireless frames (radio waves), or an antenna with a variable direction of directivity of wireless frames. An example of an antenna with a variable direction of directivity of wireless frames is a phased array antenna.

[0026] The base station antenna 21 acquires the uplink timing advance value of the terminal 3 from the base station transmitter 24. The base station antenna 21 transmits a downlink radio frame indicating the uplink timing advance value to the terminal antenna 31. The base station antenna 21 receives, from the terminal antenna 31, the uplink radio frames in time series that have been transmitted at timings based on the uplink timing advance value.

[0027] The detector 22 detects interference periods in time-series uplink radio frames. The position of the interference period (interference position) in the time-series uplink radio frames is represented by, for example, a slot number. The length of the interference period is represented by, for example, the number of symbols in Orthogonal Frequency Division Multiplexing (OFDM). The detector 22 outputs the detection result of the interference period to the base station controller 23.

[0028] The base station control unit 23 determines whether the transmission timing of the uplink radio frame is earlier than the reference timing of time division multiplexing of the synchronized base station (other station) based on the position of the interference period in the time series of the uplink radio frame. The base station control unit 23 determines the error (absolute value) of the uplink timing advance value based on the length of the interference period. Here, the base station control unit 23 may determine the error of the uplink timing advance value based on the average or median of the lengths of the interference periods detected multiple times.

[0029] The base station control unit 23 corrects the uplink timing advance value to reduce an error in the uplink timing advance value. If the base station 2a determines that the reception timing of the uplink radio frame is earlier than the reference timing, the base station control unit 23 decreases the uplink timing advance value to delay the transmission timing of the uplink radio frame from the terminal 3. If the base station 2a determines that the reception timing of the uplink radio frame is later than the reference timing, the base station control unit 23 increases the uplink timing advance value to advance the transmission timing of the uplink radio frame from the terminal 3.

[0030] The base station transmitter 24 outputs the corrected uplink timing advance value to the base station antenna 21. The terminal antenna 31 receives the downlink radio frame indicating the uplink timing advance value from the base station antenna 21. The terminal antenna 31 starts transmitting the uplink radio frame at a timing based on the control of the terminal transmitter 34.

[0031] The acquisition unit 32 acquires the uplink timing advance value from the terminal antenna 31. The terminal control unit 33 controls the timing advance of the terminal transmitter 34 based on the uplink timing advance value. The terminal transmitter 34 controls the demodulation process from the electrical signal to an uplink radio frame in the terminal antenna 31 so as to start transmitting the uplink radio frame based on the control by the terminal control unit 33.

[0032] Next, an example of detecting an interference period will be described. Fig. 2 is a diagram showing an example of an interference period 7 in the first embodiment when the transmission timing of a radio frame (radio frequency signal) in a terminal 3 is earlier than the reference timing of time division multiplexing of a synchronized base station 4 (other station). In the following, as an example, the slot with slot number "SL2" is a special slot in the time series radio frames.

[0033] 2 illustrates an example of time-series radio frames synchronized with the reference timing of the synchronized base station 4 and received by the base station antenna 21. In the special slot with slot number "SL2" in the time-series radio frames synchronized with the reference timing of the synchronized base station 4, a guard period 5 is inserted at the timing of switching between downlink transmission "DL" and uplink transmission "UL." The length of the guard period 5 is, for example, 2 OFDM symbols.

[0034] 2 illustrates an example of time-series radio frames transmitted from terminal 3 based on the uplink timing advance value and received by base station antenna 21. In the special slot with slot number "SL2" in the time-series radio frames transmitted from terminal 3 at the timing of base station 2a (asynchronous base station), a guard period 6 is inserted at the timing of switching between downlink transmission "DL" and uplink transmission "UL." The length of guard period 6 is, for example, 2 OFDM symbols.

[0035] 2, in the special slot with slot number "SL2," there is an interference period 7 between a downlink radio frame transmitted from the synchronized base station 4 and an uplink radio frame transmitted from the terminal 3. The base station control unit 23 determines whether the reception timing of the uplink radio frame at the base station 2a is earlier than the reference timing based on the position of the interference period 7 in the time-series radio frames. If there is an interference period 7 immediately after switching from downlink transmission to uplink transmission (if there is an interference period 7 in the first uplink radio frame), the base station control unit 23 determines that the reception timing of the uplink radio frame at the base station 2a is earlier than the reference timing.

[0036] 2, the base station control unit 23 determines the number of symbols in the interference period 7 as the error (absolute value) of the uplink timing advance value. The base station control unit 23 may also determine the sum of the number of symbols in the interference period 7 and the number of symbols in the guard period as the error (absolute value) of the uplink timing advance value. The base station control unit 23 corrects the uplink timing advance value so as to delay the transmission timing of the uplink radio frame in the terminal 3 by the error of the uplink timing advance value.

[0037] FIG. 3 is a diagram showing an example of an interference period 8 in the first embodiment when the transmission timing of a radio frame in a terminal 3 is delayed with respect to the reference timing of time division multiplexing of a synchronized base station 4 (other station).

[0038] The upper part of Fig. 3 illustrates time-series radio frames synchronized with the reference timing of the synchronized base station 4 and received by the base station antenna 21. The lower part of Fig. 3 illustrates time-series radio frames transmitted from the terminal 3 based on the uplink timing advance value and received by the base station antenna 21.

[0039] 3, in the slot with slot number "SL4," there is an interference period 8 between the downlink radio frame transmitted from the synchronized base station 4 and the uplink radio frame transmitted from the terminal 3. In this way, when there is an interference period 8 in the middle of the time-series uplink radio frames, the base station control unit 23 determines that the reception timing of the uplink radio frame at the base station 2a is late with respect to the reference timing.

[0040] 3, the base station control unit 23 determines the number of symbols in the interference period 8 as the error (absolute value) of the uplink timing advance value. The base station control unit 23 corrects the uplink timing advance value so that the transmission timing of the uplink radio frame in the terminal 3 is advanced by the error of the uplink timing advance value.

[0041] In addition, not only when the uplink radio frame is transmitted using the OFDM method (multi-carrier) but also when the uplink radio frame is transmitted using a single carrier, it is possible to determine whether the reception timing of the uplink radio frame at the base station 2a is earlier than the reference timing based on the position of the interference period. Also, it is possible to determine the error (absolute value) of the uplink timing advance value based on the length of the interference period (the number of samples).

[0042] Next, an operation example of the communication system 1a will be described. Fig. 4 is a flowchart showing an operation example of the communication system 1a in the first embodiment. The detection unit 22 detects an interference period 7 or an interference period 8 between a time-series downlink radio frame transmitted from a synchronized base station 4 and a time-series uplink radio frame transmitted from a terminal 3 (step S101).

[0043] The base station control unit 23 corrects the uplink timing advance value based on the position and length of the interference period 7 or 8 in the time-series uplink radio frames so as to shorten the interference period 7 or 8 (step S102). The base station transmission unit 24 notifies the terminal 3 of the corrected uplink timing advance value using the base station antenna 21 (step S103).

[0044] As described above, the base station 2a (base station device) performs time division multiplexing wireless communication with the terminal 3. The terminal 3 acquires an uplink timing advance value from the base station 2a. The terminal 3 transmits uplink wireless frames in time series at transmission timing based on the uplink timing advance value.

[0045] The detector 22 detects an interference period 7 or an interference period 8 between a time-series downlink radio frame (first downlink radio frame) transmitted from the synchronized base station 4 and a time-series uplink radio frame transmitted from the terminal 3. The base station controller 23 corrects the uplink timing advance value based on the position and length of the interference period 7 or the interference period 8 in the time-series uplink radio frame so as to shorten the interference period 7 or the interference period 8. The base station transmitter 24 notifies the terminal 3 of the corrected uplink timing advance value using the base station antenna 21.

[0046] This makes it possible to detect an error in the timing advance value and then correct the timing advance value to reduce the error.Furthermore, even if the time of the base station 2a is not synchronized with the highly accurate time of the Global Navigation Satellite System (GNSS), the base station antenna 21 can synchronize the communication timing of the time division multiplexing of the base station 2a with the reference timing of the time division multiplexing of a synchronized base station (other station).

[0047] (Variation) The synchronized base station 4 may be another base station 2 a (base station device) synchronized with the reference timing of time division multiplexing. A plurality of base stations 2 a (base station 2 a and one or more other base stations 2 a) may be synchronized in a chain with the reference timing of time division multiplexing.

[0048] 5 is a diagram illustrating an example of the configuration of a communication system 1a according to a modification of the first embodiment. The communication system 1a includes a plurality of base stations 2a (base station 2a and one or more other base stations 2a) and a terminal 3.

[0049] The base station control unit 23 of the base station 2a-1 (asynchronous base station) adjacent to the synchronous base station 4 synchronizes the communication timing of the radio frame of the base station 2a-1 with the reference timing of time division multiplexing of the synchronous base station 4, as in the first embodiment.

[0050] In this way, interference may occur between a downlink radio frame of the base station 2a-1 whose communication timing is synchronized with the reference timing and an uplink radio frame transmitted from a terminal 3 subordinate to the base station 2a-2 adjacent to the base station 2a-1. The base station control unit 23 of the base station 2a-2 (asynchronous base station) adjacent to the base station 2a-1 whose communication timing is synchronized with the reference timing may synchronize the communication timing of the radio frame of the base station 2a-2 with the communication timing of the radio frame of the base station 2a-1, as in the first embodiment.

[0051] In this way, the downlink radio frame of the base station 2a-2, whose communication timing is synchronized with the reference timing, may interfere with the uplink radio frame transmitted from the terminal 3 subordinate to the base station 2a-3 adjacent to the base station 2a-2. The base station control unit 23 of the base station 2a-3 (asynchronous base station) adjacent to the base station 2a-2, whose communication timing is synchronized with the reference timing, may synchronize the communication timing of the uplink radio frame of the base station 2a-3 with the communication timing of the uplink radio frame of the base station 2a-2, as in the first embodiment. In this way, the communication timings of the multiple base stations 2a are synchronized in a chain reaction.

[0052] Second Embodiment The second embodiment is mainly different from the first embodiment in that transmission processing (advance processing) based on a timing advance value (downlink timing advance value) is performed not only for uplink transmission but also for downlink transmission. The second embodiment will be described focusing on the differences from the first embodiment.

[0053] 6 is a diagram showing an example of the configuration of a communication system 1b in the second embodiment. The communication system 1b is a system that performs wireless communication between a base station and a terminal. The communication system 1b includes a base station 2b and a terminal 3. A synchronized base station 4 is installed in advance at a location adjacent to the base station 2b.

[0054] The base station 2b includes a base station 10 and a central station 20b. The base station 10 includes a base station converter 11, a base station measurement unit 12, and a base station antenna 21.

[0055] The central station 20b includes a detection unit 22, a base station control unit 23, a base station transmission unit 24, a base station conversion unit 25, and a base station measurement unit 26. The base station conversion unit 25 and the base station measurement unit 26 may be integrated. The base station conversion unit 11 and the base station conversion unit 25 are connected by an optical fiber.

[0056] The base station 2b (asynchronous base station) notifies the terminal 3 of the uplink timing advance value. The terminal 3 executes transmission processing (advance processing) based on the uplink timing advance value. The uplink timing advance value notified to the terminal 3 is used as an estimate of the transmission delay amount in the wireless section, "t ＲＦ" is based on the estimated value of the transmission delay in the wireless section, "t ＲＦ " is the total transmission delay "t ＲｏＦ +t ＲＦ ,” the estimated value of the transmission delay amount between the base station conversion unit 11 and the base station conversion unit 25 (optical section) “t ＲｏＦ " is obtained by subtracting

[0057] Before the upstream timing advance value is corrected, the estimated transmission delay amount in the optical section, "t ＲｏＦ ” is the error in the estimated value of the transmission delay amount in the optical section, “t ＥＲ The error in the upstream timing advance value, "TAE," is the error in the estimated value of the transmission delay amount in the optical section, "t ＥＲ Therefore, the uplink radio frame of the terminal 3 and the downlink radio frame of the synchronized base station 4 may interfere with each other in the vicinity of the base station antenna 21.

[0058] The communication system 1b in the second embodiment is an analog RoF communication system. The analog RoF may be "BB over Fiber (BBoF)" that transmits baseband (BB) signals over optical fiber, "IF over Fiber (IFoF)" that transmits intermediate frequency (IF) signals over optical fiber, or "RF over Fiber (RFoF)" that transmits radio frequency (RF) signals directly over optical fiber. An analog RoF communication system requires not only upstream transmission processing based on an upstream timing advance value, but also downstream transmission processing based on a downstream timing advance value.

[0059] The central station 20b measures the amount of transmission delay in the analog RoF section (optical section) from the central station 20b to the base station 10. Based on the measurement result of the amount of transmission delay, the central station 20b calculates an estimated value of the amount of transmission delay in the optical section, "t ＲｏＦ The central station 20b determines the estimated value "tＲｏＦ " determines the downlink timing advance value based on the

[0060] The central station 20b estimates the amount of transmission delay in the wireless section from the terminal 3 to the base station 10. The central station 20b calculates the estimated value of the amount of transmission delay in the wireless section "t" so that the reception timing of the uplink wireless frame at the base station 10 is synchronized with the reference timing. ＲＦ The central station 20b determines the error (absolute value) of the uplink timing advance value based on the length of the interference period in the time-series radio frames. The central station 20b corrects the uplink timing advance value based on the error of the uplink timing advance value. The central station 20b notifies the terminal 3 of the uplink timing advance value.

[0061] Next, a detailed configuration example of the communication system 1b will be described. If the analog RoF is "IFoF," the base station antenna 21 (extending antenna) may include a frequency conversion device (not shown). If the analog RoF is "RFoF," the base station antenna 21 (extending antenna) may not include a frequency conversion device (not shown).

[0062] The base station antenna 21 transmits a downlink wireless frame to the terminal antenna 31 based on the electrical signal (RF signal) input from the base station conversion unit 11. The base station antenna 21 outputs an electrical signal (RF signal) based on the uplink wireless frame received from the terminal antenna 31 to the base station conversion unit 11.

[0063] The base station converter 11 (RoF slave device) converts (modulates) an electrical signal (RF signal) input from the base station antenna 21 into an optical signal. The base station converter 11 converts (demodulates) an optical signal input from the base station converter 25 (RoF master device) into an electrical signal (RF signal).

[0064] The base station measurement unit 12 measures the amount of transmission delay in the RoF section (optical section) between the base station conversion unit 11 and the base station conversion unit 25. For example, the base station measurement unit 12 measures the round trip time (RTT) in the section with the base station conversion unit 25 synchronized by the Precision Time Protocol (PTP).

[0065] The detector 22 detects the position and length of an interference period in a time series of radio frames, and outputs the detection result of the interference period to the base station controller 23.

[0066] The base station control unit 23 determines whether the transmission timing of the uplink radio frame is earlier than the reference timing of time division multiplexing of the synchronized base station (other station) based on the position of the interference period in the time series of radio frames. The base station control unit 23 determines the error (absolute value) of the uplink timing advance value based on the length of the interference period in the time series of radio frames.

[0067] The base station control unit 23 calculates an estimated value of the transmission delay amount in the RoF section (optical section) “t ＲｏＦ +t ＥＲ The error in the estimated value of the transmission delay amount, t ＥＲ " becomes sufficiently small. Here, the base station control unit 23 may determine an estimate of the transmission delay amount in the RoF section based on the average or median of the PTP or RTT measurement results obtained by multiple measurements. The base station control unit 23 determines the estimate of the transmission delay amount in the RoF section "t ＲｏＦ +t ＥＲ " determines the downlink timing advance value based on the

[0068] The base station transmitter 24 outputs the corrected uplink timing advance value to the base station antenna 21. Based on the downlink timing advance value, the base station transmitter 24 transmits (early transmits) a downlink frame to the base station converter 25. The downlink frame is, for example, a communication data signal and a time division multiplexing control signal (TDD control signal). By the base station transmitter 24 transmitting the time division multiplexing control signal early, the transmission timing of the downlink radio frame at the base station antenna 21 can be synchronized with the reference timing of time division multiplexing.

[0069] This makes it possible to control the transmission timing of the downlink radio frame at the base station antenna 21 so as to satisfy the time division multiplexing regulation of "within ±1.5 μs" specified in 3GPP (registered trademark).

[0070] The base station conversion unit 25 (RoF master) converts (modulates) the electrical signal (RF signal) input from the base station transmission unit 24 into an optical signal. The base station conversion unit 25 converts (demodulates) the optical signal input to the base station conversion unit 11 (RoF slave) into an electrical signal (RF signal).

[0071] The base station measurement unit 26 measures the amount of transmission delay in the RoF section (optical section) between the base station conversion unit 11 and the base station conversion unit 25. For example, the base station measurement unit 26 performs a measurement process of the round trip time for the base station measurement unit 12 synchronized by the high precision time synchronization protocol.

[0072] Next, an example of operation of the communication system 1b will be described. FIG. 7 is a flowchart showing an example of operation of the communication system 1b in the second embodiment. The base station measurement unit 12 and the base station measurement unit 26 measure the amount of transmission delay in the optical section from the base station transmission unit 24 to the base station antenna 21 (step S201). The base station control unit 23 determines a downlink timing advance value based on the amount of transmission delay in the optical section (step S202). The base station transmission unit 24 transmits time-series downlink frames to the optical section at transmission timing based on the downlink timing advance value (step S203). The base station antenna 21 transmits time-series downlink radio frames (second downlink radio frames) to the terminal 3 (step S204).

[0073] As described above, the base station measurement unit 12 and the base station measurement unit 26 measure the amount of transmission delay in the optical section from the base station transmitter 24 to the base station antenna 21. The base station control unit 23 determines a downlink timing advance value based on the amount of transmission delay in the optical section. The base station transmitter 24 transmits time-series downlink frames to the optical section at transmission timing based on the downlink timing advance value. The base station antenna 21 transmits time-series downlink radio frames (second downlink radio frames) to the terminal 3.

[0074] This allows the timing advance value to be corrected to reduce the error after detecting the error in the timing advance value, and the base station antenna 21 can synchronize the communication timing of the base station 2b with the reference timing.

[0075] Third Embodiment The third embodiment differs from the second embodiment mainly in that the base station includes two or more base stations. The third embodiment will be described focusing on the differences from the second embodiment.

[0076] 8 is a diagram showing a configuration example of a communication system 1c according to the third embodiment. The communication system 1c is a system that performs wireless communication between a base station and a terminal. The communication system 1b according to the third embodiment may be, for example, an analog RoF communication system or a digital RoF communication system.

[0077] The communication system 1c includes a base station 2c and a terminal 3. A synchronized base station 4 is installed in advance at a location adjacent to the base station 2c. The base station 2c includes two or more base stations 10 and a central station 20c.

[0078] Each base station 10 includes a base station conversion unit 11 , a base station measurement unit 12 , and a base station antenna 21 .

[0079] The central station 20c includes a detection unit 22, a base station control unit 23, a base station transmission unit 24 for each base station 10, a base station conversion unit 25, and a base station measurement unit 26. The central station 20c may include a base station control unit 23 for each base station 10. The base station conversion units 11 and the base station conversion units 25 are connected by optical fiber. The central station 20c may include a switch 27.

[0080] The switch 27 performs a process of switching the path of the electrical signal in a time-division manner. Here, the switch 27 acquires the electrical signal output from the base station 10-1 from the base station conversion unit 25. The switch 27 outputs the electrical signal output from the base station 10-1 to the detection unit 22 and the base station measurement unit 26. The switch 27 acquires the electrical signal output from the base station 10-2 from the base station conversion unit 25. The switch 27 outputs the electrical signal output from the base station 10-2 to the detection unit 22 and the base station measurement unit 26.

[0081] The detector 22 detects the position and length of an interference period in the time-series radio frames for each base station 10. The detector 22 outputs the detection result of the interference period for each base station 10 to the base station controller 23.

[0082] The base station measurement unit 26 measures the amount of transmission delay in the RoF section (optical section) between the base station conversion unit 11 and the base station conversion unit 25 for each base station 10. The base station control unit 23 calculates an estimated value of the amount of transmission delay in the RoF section, "t ＲｏＦ +t ＥＲ ” is used to determine the downlink timing advance value for each base station 10. Here, the error “t ＥＲ " is small enough.

[0083] The base stations 10 are identified, for example, by a wavelength division multiplexing (WDM) method based on an optical signal having a different wavelength for each base station 10. The base stations 10 are identified, for example, based on a delay measurement signal having a different frequency band for each base station 10. The delay measurement signal may be transmitted by a subcarrier-multiplexing (SCM) method in which the same optical wavelength is multiplexed and transmitted.

[0084] The base station control unit 23 determines the error (absolute value) of the uplink timing advance value for each base station 10 based on the length of the interference period in the time-series radio frames. Based on the measurement result by the base station measurement unit 26, the base station control unit 23 calculates the estimated value "t ＲｏＦ +t ＥＲ The base station control unit 23 determines the estimated value of the transmission delay amount in the RoF section, "t ＲｏＦ +t ＥＲ The downlink timing advance value is determined for each base station 10 based on the above.

[0085] The base station transmitter 24-1 outputs the corrected uplink timing advance value for the base station 10-1 to the base station antenna 21-1, and the base station transmitter 24-2 outputs the corrected uplink timing advance value for the base station 10-2 to the base station antenna 21-2.

[0086] The terminal antenna 31 receives a downlink radio frame indicating an uplink timing advance value from the base station antenna 21-1 for the base station antenna 21-1. The terminal antenna 31 receives a downlink radio frame indicating an uplink timing advance value from the base station antenna 21-2 for the base station antenna 21-2. The terminal antenna 31 starts transmitting the uplink radio frames in chronological order for each base station 10 at a timing based on the control of the terminal transmitter 34.

[0087] As described above, the base station control unit 23 corrects the uplink timing advance value for each of the plurality of base station antennas 21. The base station transmission unit 24 notifies the terminal 3 of the uplink timing advance value corrected for each of the base station antennas 21, using the base station antenna 21.

[0088] This makes it possible to detect errors in the timing advance value and correct the timing advance value to reduce the errors even when there are multiple base stations 10. In each base station antenna 21, the communication timing of the base station 2c can be synchronized with the reference timing.

[0089] The base station control unit 23 and the terminal control unit 33 included in the device of the present invention can each be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network.

[0090] 9 is a diagram illustrating an example of the hardware configuration of the communication device 100 in each embodiment. The example of the hardware configuration of the communication device 100 corresponds to the example of the hardware configuration of the base station (base station device) in each embodiment and the example of the hardware configuration of the terminal in each embodiment.

[0091] The communication device 100 is realized as software by a processor 101, such as a CPU (Central Processing Unit), executing a program stored in a storage device 103 having a non-volatile recording medium (non-transitory recording medium) and a memory 102. The program may be recorded on a computer-readable recording medium. Examples of computer-readable recording media include portable media such as a flexible disk, a magneto-optical disk, a ROM (Read Only Memory), and a CD-ROM (Compact Disc Read Only Memory), and non-transitory recording media such as a hard disk or a solid-state drive (SSD) built into a computer system. The communication unit 104 executes predetermined communication processing.

[0092] The communication device 100 may be realized using hardware including an electronic circuit (electronic circuit or circuitry) using, for example, an LSI (Large Scale Integrated circuit), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array).

[0093] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention.

[0094] The present invention is applicable to communication systems.

[0095] 1a, 1b, 1c...communication system, 2a, 2b, 2c...base station, 3...terminal, 4...synchronized base station, 5...guard period, 6...guard period, 7...interference period, 8...interference period, 10...base station, 11...base station conversion unit, 12...base station measurement unit, 20b, 20c...aggregate station, 21...base station antenna, 22...detection unit, 23...base station control unit, 24...base station transmission unit, 25...base station conversion unit, 26...base station measurement unit, 27...switch, 31...terminal antenna, 32...acquisition unit, 33...terminal control unit, 34...terminal transmission unit, 100...communication device, 101...processor, 102...memory, 103...storage device, 104...communication unit

Claims

1. A base station device that performs wireless communication using time division multiplexing with a terminal that transmits time-series uplink radio frames at transmission timing based on an uplink timing advance value, comprising: a detection unit that detects an interference period between a first time-series downlink radio frame transmitted from a synchronized base station and the time-series uplink radio frame transmitted from the terminal; a base station control unit that corrects the uplink timing advance value based on the position and length of the interference period in the time-series uplink radio frame; and a base station transmission unit that notifies the terminal of the corrected uplink timing advance value using one or more base station antennas.

2. The base station device according to claim 1, wherein the synchronized base station is another base station device synchronized with the reference timing of the time division multiplexing.

3. The base station device according to claim 1, further comprising a measurement unit that measures the amount of transmission delay in the optical section between the base station transmitter unit and the one or more base station antennas, wherein the base station controller determines a downlink timing advance value based on the amount of transmission delay in the optical section, the base station transmitter unit transmits time-series downlink frames at a transmission timing based on the downlink timing advance value, and the one or more base station antennas transmit time-series second downlink radio frames based on the time-series downlink frames to the terminal.

4. The base station device according to claim 1, wherein the base station control unit corrects the uplink timing advance value for each base station antenna in the one or more base station antennas, and the base station transmission unit notifies the terminal of the uplink timing advance value corrected for each base station antenna using the one or more base station antennas.

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