WO2025177421A1 - Base station device - Google Patents

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

The present invention relates to a base station device.

When analog RoF (Radio-over-Fiber) is applied to a communications system, the functions of the communications system's base station may be divided into an aggregation station and a base station (see non-patent document 1). Deploying base stations with simple configurations throughout the wireless area enables the realization of a flexible and economical mobile network. Hereinafter, the direction from the terminal to the base station will be referred to as "uplink," and the direction from the base station to the terminal will be referred to as "downlink."

Communication systems such as mobile networks sometimes use the time division duplex (TDD) method. In the time division duplex method, the uplink (UL) and downlink (DL) are switched in the same frequency band on a slot-period basis.

Communications systems may be equipped with a timing advance (TA) function (see Non-Patent Document 2). Timing advance determines a timing advance value (TA value) that corresponds to the amount of transmission delay in the wireless section. Uplink wireless frames are transmitted at a timing earlier than downlink wireless frames by an amount based on this timing advance value (see Non-Patent Document 3).

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

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), pp. 15-17, 2020. 3GPP TS 38.211 version 16.7.0 Release 16 3GPP TS 38.133 version 15.3.0 Release 15

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."

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

When a timing advance function is applied to an analog 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 the uplink timing advance value for the terminal based on the estimated amount of 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 of the terminal.

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 the terminal's uplink timing advance value based on the estimated amount of 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 terminal's uplink timing advance value.

However, despite the fact that there is an error in the estimated transmission delay, the base station (base station equipment) is unable to detect the timing advance error (TAE: Timing Advance Error) caused by this error. This presents a problem in that the base station is unable to correct the timing advance value to reduce the error.

In light of the above circumstances, the present invention aims to provide a base station device that can detect errors in the timing advance value and then correct the timing advance value to reduce those errors.

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. The base station device includes: a detector 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 controller 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 transmitter that notifies the terminal of the corrected uplink timing advance value using one or more base station antennas.

This invention makes it possible to detect errors in the timing advance value and then correct the timing advance value to reduce those errors.

FIG. 1 is a diagram illustrating an example of the configuration of a communication system in a first embodiment. 10 is a diagram illustrating an example of an interference period when the transmission timing of a radio 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. 10A and 10B are diagrams illustrating an example of an interference period when the transmission timing of a radio frame in a terminal is delayed with respect to the reference timing of time division multiplexing of a synchronized base station (other station) in the first embodiment. 4 is a flowchart illustrating an example of the operation of the communication system in the first embodiment. FIG. 10 is a diagram illustrating an example of the configuration of a communication system according to a modified example of the first embodiment. FIG. 10 is a diagram illustrating an example of the configuration of a communication system in a second embodiment. 10 is a flowchart showing an example of the operation of a communication system in the second embodiment. FIG. 10 is a diagram illustrating an example of the configuration of a communication system in a third embodiment. FIG. 2 is a diagram illustrating an example of a hardware configuration of a communication device in each embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings.
(First embodiment)
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.

The base station 2a comprises 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.

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

The base station 2a (asynchronized 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 error "TAE" in the uplink timing advance value corresponds to the error "t _ER " in the estimated value of the transmission delay amount. Before the uplink timing advance value is corrected, the uplink timing advance value notified to the terminal 3 has not been corrected based on the error "TAE" in the uplink timing advance value. Therefore, in the vicinity of the base station antenna 21, downlink radio frames from the synchronized base station 4 may interfere with uplink radio frames between the base station 2a and the terminal 3.

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

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, since the transmission timing of the downlink radio frames in the base station antenna 21 is synchronized with the reference timing, transmission processing based on the timing advance value (downlink timing advance value) is not required for downlink transmission by the base station transmitter 24.

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 determines an uplink timing advance value based on the estimated value "t _RF " of the amount of transmission delay in the wireless section so that the reception timing of the uplink wireless frame at the base station antenna 21 is synchronized with the reference timing. The base station 2a notifies the terminal 3 of the uplink timing advance value.

The error "TAE" in the uplink timing advance value corresponds to the error "t _ER " in the estimated value of the transmission delay amount in the wireless section. The error "TAE" in the uplink timing advance value causes the transmission timing of the uplink radio frame to become asynchronous with 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.

In addition, at the timing of switching from downlink transmission to uplink transmission, a guard period (GP) may be defined in the special slot of the time-series radio frame. Furthermore, 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 in the timing advance value.

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 radio frames (radio waves) or an antenna with a variable direction of directivity of radio frames, such as a phased array antenna.

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 representing the uplink timing advance value to the terminal antenna 31. The base station antenna 21 receives from the terminal antenna 31 a time-series uplink radio frame transmitted at a timing based on the uplink timing advance value.

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

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

The base station control unit 23 corrects the uplink timing advance value to reduce the error in the uplink timing advance value. Here, if it is determined that the reception timing of the uplink radio frame at base station 2a is earlier than the reference timing, the base station control unit 23 decreases the uplink timing advance value, delaying the transmission timing of the uplink radio frame at terminal 3. If it is determined that the reception timing of the uplink radio frame at base station 2a is later than the reference timing, the base station control unit 23 increases the uplink timing advance value, advancing the transmission timing of the uplink radio frame at terminal 3.

The base station transmitter 24 outputs the corrected uplink timing advance value to the base station antenna 21. The terminal antenna 31 receives a downlink radio frame representing the uplink timing advance value from the base station antenna 21. The terminal antenna 31 begins transmitting the uplink radio frame at a timing based on control by the terminal transmitter 34.

The acquisition unit 32 acquires the uplink timing advance value from the terminal antenna 31. The terminal control unit 33 controls the timing advance for the terminal transmission unit 34 based on the uplink timing advance value. The terminal transmission unit 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 of the terminal control unit 33.

Next, an example of detecting an interference period will be described.
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.

The upper part of Figure 2 shows an example of a time-series radio frame synchronized with the reference timing of the synchronized base station 4, which is received by the base station antenna 21. In the special slot with slot number "SL2" in the time-series radio frame 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.

The lower part of Figure 2 shows 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.

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

In FIG. 2, the base station control unit 23 determines the number of symbols in 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 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 that the transmission timing of the uplink radio frame in terminal 3 is delayed by the error in the uplink timing advance value.

Figure 3 shows an example of an interference period 8 in the first embodiment when the transmission timing of a wireless frame at terminal 3 is delayed relative to the reference timing of time division multiplexing at a synchronized base station 4 (other station).

The upper part of Figure 3 illustrates a time-series radio frame synchronized with the reference timing of the synchronized base station 4, and received by the base station antenna 21. The lower part of Figure 3 illustrates a time-series radio frame transmitted from the terminal 3 based on the uplink timing advance value and received by the base station antenna 21.

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

In Figure 3, the base station control unit 23 determines the number of symbols in 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 at terminal 3 is advanced by the error in the uplink timing advance value.

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

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

The base station control unit 23 corrects the uplink timing advance value to shorten interference period 7 or interference period 8 based on the position and length of interference period 7 or interference period 8 in the time-series uplink radio frame (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).

As described above, base station 2a (base station device) performs wireless communication using time division multiplexing with terminal 3. Terminal 3 obtains the uplink timing advance value from base station 2a. Terminal 3 transmits uplink wireless frames in a time series with transmission timing based on the uplink timing advance value.

The detection unit 22 detects interference period 7 or 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 control unit 23 corrects the uplink timing advance value based on the position and length of the interference period 7 or interference period 8 in the time-series uplink radio frame to shorten the interference period 7 or interference period 8. The base station transmission unit 24 notifies the terminal 3 of the corrected uplink timing advance value using the base station antenna 21.

This makes it possible to detect errors in the timing advance value and then correct the timing advance value to reduce those errors. Furthermore, even without synchronizing the time of base station 2a with the highly accurate time of the Global Navigation Satellite System (GNSS), the base station antenna 21 can synchronize the communication timing of base station 2a's time division multiplexing with the reference timing of the time division multiplexing of a synchronized base station (other station).

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

FIG. 5 is a diagram showing an example configuration of a communication system 1a in a modified example of the first embodiment. The communication system 1a includes multiple base stations 2a (base station 2a and one or more other base stations 2a) and a terminal 3.

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 base station 2a-1's radio frames with the reference timing of the time division multiplexing of the synchronous base station 4, as in the first embodiment.

In this way, downstream radio frames from base station 2a-1, whose communication timing is synchronized with the reference timing, may interfere with upstream radio frames transmitted from a terminal 3 subordinate to base station 2a-2, which is adjacent to base station 2a-1. The base station control unit 23 of base station 2a-2 (asynchronous base station) adjacent to base station 2a-1, whose communication timing is synchronized with the reference timing, may synchronize the communication timing of the radio frames of base station 2a-2 with the communication timing of the radio frames of base station 2a-1, as in the first embodiment.

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

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.

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

Base station 2b includes a base station 10 and a central station 20b. Base station 10 includes a base station converter 11, a base station measurement unit 12, and a base station antenna 21.

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 optical fiber.

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 based on the estimated value "t _RF " of the transmission delay amount in the wireless section. The estimated value "t _RF " of the transmission delay amount in the wireless section is obtained by subtracting the estimated value "t RoF " of the transmission delay amount between the base station conversion unit 11 and the base station conversion unit 25 (optical section) from the total transmission delay amount "t _{RoF +} t _RF " that can be measured by the uplink timing advance function.

Before the uplink timing advance value is corrected, the estimated value "t _RoF " of the transmission delay amount in the optical section includes an error "t _ER " in the estimated value of the transmission delay amount in the optical section. The error "TAE" in the uplink timing advance value corresponds to the error "t _ER " in the estimated value of the transmission delay amount in the optical section. For this reason, the uplink wireless frame of the terminal 3 and the downlink wireless frame of the synchronized base station 4 may interfere with each other in the vicinity of the base station antenna 21.

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

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 results of the amount of transmission delay, the central station 20b determines an estimated value "t _RoF " of the amount of transmission delay in the optical section. Based on the estimated value "t RoF " of the amount of transmission delay in the optical section, the central station 20b determines a downlink timing advance value so that the transmission timing of the downlink radio frame at the base station _{antenna 21} is synchronized with the reference timing.

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 determines an uplink timing advance value based on the estimated value "t _RF " of the amount of transmission delay in the wireless section so that the reception timing of the uplink wireless frame at the base station 10 is synchronized with the reference timing. 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 wireless frames. The central station 20b corrects the uplink timing advance value based on the error in the uplink timing advance value. The central station 20b notifies the terminal 3 of the uplink timing advance value.

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

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.

The base station conversion unit 11 (RoF slave unit) converts (modulates) the electrical signal (RF signal) input from the base station antenna 21 into an optical signal. The base station conversion unit 11 converts (demodulates) the optical signal input from the base station conversion unit 25 (RoF master unit) into an electrical signal (RF signal).

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 performs measurement processing of the round trip time (RTT) in the section with the base station conversion unit 25 synchronized by the Precision Time Protocol (PTP).

The detection unit 22 detects the position and length of interference periods in the time series of radio frames. The detection unit 22 outputs the interference period detection results to the base station control unit 23.

Based on the position of the interference period in the time series of radio frames, the base station control unit 23 determines whether the transmission timing of the uplink radio frame is earlier than the reference timing of the time division multiplexing of the synchronized base station (other station). Based on the length 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.

The base station control unit 23 determines an estimated value of the transmission delay amount in the RoF section (optical section), "t _RoF +t _ER ", based on the measurement results by the base station measurement unit 26. The measurement makes the error "t _ER " in the estimated value of the transmission delay amount sufficiently small. Here, the base station control unit 23 may determine an estimated value of the transmission delay amount in the RoF section based on the average or median value of the measurement results of PTP or RTT measured multiple times. The base station control unit 23 determines a downlink timing advance value based on the estimated value of the transmission delay amount in the RoF section, "t _RoF +t _ER ".

The base station transmitter 24 outputs the corrected uplink timing advance value to the base station antenna 21. The base station transmitter 24 transmits (early transmits) downlink frames to the base station converter 25 based on the downlink timing advance value. The downlink frames are, for example, communication data signals and time division multiplexing control signals (TDD control signals). By the base station transmitter 24 transmitting the time division multiplexing control signals early, the transmission timing of the downlink radio frames at the base station antenna 21 can be synchronized with the reference timing of time division multiplexing.

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

The base station conversion unit 25 (RoF parent device) 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 child device) into an electrical signal (RF signal).

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 round-trip time measurement process on the base station measurement unit 12, which is synchronized using a high-precision time synchronization protocol.

Next, an example of the operation of the communication system 1b will be described.
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 transmitter 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 transmitter 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).

As described above, the base station measurement unit 12 and 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 the 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.

This makes it possible to detect errors in the timing advance value and then correct the timing advance value to reduce those errors. At the base station antenna 21, it is possible to synchronize the communication timing of base station 2b with the reference timing.

(Third embodiment)
The third embodiment is mainly different from the second embodiment 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.

FIG. 8 is a diagram showing an example configuration of a communication system 1c in 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 in the third embodiment may be, for example, an analog RoF communication system or a digital RoF communication system.

Communication system 1c includes base station 2c and terminal 3. Synchronous base station 4 is installed in advance at a location adjacent to base station 2c. Base station 2c includes two or more base stations 10 and a central station 20c.

Each base station 10 comprises a base station conversion unit 11, a base station measurement unit 12, and a base station antenna 21.

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 via optical fiber. The central station 20c may also include a switch 27.

The switch 27 performs the 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 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 base station measurement unit 26.

The detection unit 22 detects the position and length of interference periods in the time series of radio frames for each base station 10. The detection unit 22 outputs the interference period detection results for each base station 10 to the base station control unit 23.

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 determines the downlink timing advance value for each base station 10 based on the estimated value "t _RoF +t _ER " of the amount of transmission delay in the RoF section. Here, the error "t _ER " in the estimated value of the amount of transmission delay is sufficiently small.

The base stations 10 are identified, for example, by wavelength division multiplexing (WDM) based on optical signals with different wavelengths for each base station 10. The base stations 10 are identified, for example, by delay measurement signals with different frequency bands for each base station 10. The delay measurement signals may be transmitted using subcarrier multiplexing (SCM), in which the same optical wavelength is multiplexed and transmitted.

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. The base station control unit 23 determines the estimated value "t _RoF + t _ER " of the transmission delay amount in the RoF section (optical section) for each base station 10 based on the measurement results by the base station measurement unit 26. The base station control unit 23 determines the downlink timing advance value for each base station 10 based on the estimated value "t _RoF + t _ER " of the transmission delay amount in the RoF section.

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. 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.

For base station antenna 21-1, terminal antenna 31 receives downlink radio frames representing the uplink timing advance value from base station antenna 21-1. For base station antenna 21-2, terminal antenna 31 receives downlink radio frames representing the uplink timing advance value from base station antenna 21-2. The terminal antenna 31 begins transmitting uplink radio frames in chronological order for each base station 10 at a timing based on control by the terminal transmitter 34.

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

As a result, even if there are multiple base stations 10, it is possible to detect errors in the timing advance value and correct the timing advance value to reduce those errors. At each base station antenna 21, it is possible to synchronize the communication timing of the base station 2c with the reference timing.

The base station control unit 23 and terminal control unit 33 provided 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 over a network.

(Hardware configuration)
9 is a diagram illustrating an example of a 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 a hardware configuration of a base station (base station device) in each embodiment and the example of a hardware configuration of a terminal in each embodiment.

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 in memory 102. The program may be recorded on a computer-readable recording medium. Examples of computer-readable recording media include portable media such as flexible disks, optical magnetic disks, ROMs (Read Only Memory), and CD-ROMs (Compact Disc Read Only Memory), as well as non-transitory recording media such as hard disks or solid state drives (SSDs) built into computer systems. The communication unit 104 executes the specified communication processing.

The communication device 100 may be realized using hardware including electronic circuits (electronic circuits 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).

The above describes in detail an embodiment of the present invention with reference to the drawings, but the specific configuration is not limited to this embodiment and includes designs that do not deviate from the gist of the present invention.

The present invention is applicable to communication systems.

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...Aggregator 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 (4)

A base station device that performs time division multiplexing wireless communication with a terminal that transmits time-series uplink wireless frames at transmission timing based on an uplink timing advance value,
a detection unit that detects an interference period between a first downlink radio frame in time series transmitted from a synchronized base station and an uplink radio frame in time series transmitted from the terminal;
a base station control unit that corrects the uplink timing advance value based on a position and a length of the interference period in the time-series uplink radio frames;
a base station transmitter that notifies the terminal of the corrected uplink timing advance value using one or more base station antennas. 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. a measurement unit that measures a transmission delay amount in an optical section between the base station transmitter unit and the one or more base station antennas,
the base station control unit determines a downlink timing advance value based on the transmission delay amount in the optical section;
the base station transmitter transmits downlink frames in time series at transmission timing based on the downlink timing advance value;
The base station device according to claim 1 , wherein the one or more base station antennas transmit, to the terminal, second downlink radio frames in a time series based on the downlink frames in the time series. the base station control unit corrects the uplink timing advance value for each base station antenna among the one or more base station antennas;
The base station device according to claim 1 , wherein the base station transmitter notifies the terminal of the uplink timing advance value corrected for each of the base station antennas using the one or more base station antennas.