JPH0923473A - Synchronization system between base stations - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain timing synchronization between respective radio base stations through a delay circuit by transmitting a signal sent from a concentrated base station from the antenna of a radio base station and measuring a transmitting time till a signal received by another antenna of the same radio station returns to the concentrated base station. SOLUTION: The concentrated base station 10 and a radio base station 1 are connected to each other by a transmission line which needs the transmission line transmitting time of L1d of a downward line 33 and a transmission line which needs the transmission line transmitting time of L1u of an upward line 34. On the other hand, the concentrated base station 10 and a radio base station 2 are connected to each other by a transmission line which needs the transmission line transmitting time of L2d and a transmission line which needs the transmission line transmitting time of L2u . Thus, bit synchronization between the base stations is made possible by adjusting the transmission timing by the transmitting time difference part of the upward line. On the other hand, the signal is received without the overlap of bursts at the concentrated base station by adjusting the receiving timing by the transmission time difference part of the downward line.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a TDMA-TDD.
(Time Division Multiple A
access-Time Division Duplex
The present invention relates to a method for adjusting a delay between transmission and reception when performing burst modulation and demodulation in a mobile communication method adopting the method x) and a communication method for performing timing synchronization of a transmission frame of a transmission burst among a plurality of radio base stations.

[0002]

2. Description of the Related Art FIG. 3 is a system configuration diagram showing a configuration of a conventional inter-base station synchronization system. This system consists of a centralized base station where modulators and demodulators are centrally arranged, and a modulated signal is transmitted between the wireless base stations by an optical transmission path, and radio waves are transmitted and received from the wireless base station antenna to communicate with the mobile station. . The toll base station is composed of a modulator and a demodulator, an interface circuit for converting a transmission signal of a public network into a modulation / demodulation signal and vice versa, and a timing controller for controlling the timing of the modulator and the demodulator.

The interface circuit converts data from the public network into a data string of a transmission burst, inserts a preamble and a unique word bit required in the burst modulation method, and is inserted on the receiving side for use in a wireless section. The data string is removed and the received data signal is transmitted to the public network at the speed of the public network. The radio base station
It is equipped with a transceiver and antenna that converts modulated signals to radio frequencies and transmits and receives. In the TDMA-TDD system, in order to communicate with a plurality of mobile stations, a modulation signal is divided into a plurality of time slots, and the same radio carrier is used by a burst modulation signal to perform bidirectional communication in a time division manner. Timing control is required for burst modulation and burst demodulation. By changing the timing of modulation / demodulation by the timing controller in the centralized base station to change the transmission / reception timing, the burst modulated signal that is burst-modulated in the centralized base station is transmitted to the wireless base station via the optical transmission line. It is transmitted from the antenna of and received by the mobile station. The burst modulated signal transmitted by the mobile station is received by the antenna of the wireless base station, input to the demodulator of the centralized base station via the optical transmission line, and demodulated into received data.

In burst modulation / demodulation, the modulation burst position is detected by detecting the unique word inserted in the transmission data in the received data. If the received data side and the unique word are always matched and detected, the same reception pattern as the unique word may exist, and the timing position cannot be correctly determined.Therefore, a unique word detection window is installed and matching comparison detection is performed only in the detection window. It is necessary to improve the false detection rate. The detection width of this detection window and the delay amount from the transmission burst are set by the timing between transmission and reception. In the centralized control using the optical transmission line, the position of the reception unique word detection window must be controlled by the timing controller. To measure the transmission line delay, the modulated burst signal sent from the toll base station is returned to the antenna of the wireless base station via the transmission line and returned by the return switch, or the reflected wave is received, and the centralized base station is again transmitted via the transmission line. The round trip propagation delay time of the optical transmission line can be measured by detecting the received unique word with the demodulator of the station and comparing the transmitted unique word with the received unique word. In the TDMA-TDD system, the timings of bursts transmitted by a plurality of radio base stations are synchronized, and the transmission burst phases are aligned by frame synchronization. If transmission is performed in a time slot delayed due to an optical transmission line delay, another radio base station interferes with the next time slot, and interference from the time slot of another station causes the frequency utilization efficiency to decrease. To avoid this, the toll base station needs to anticipate the transmission path delay time and transmit in advance for the transmission path delay time rather than the burst position to be transmitted from the base station, and measure the transmission path length of each radio base station. Assuming that the upstream and downstream optical transmission lines from the centralized base station to the wireless base station have the same length, the burst timing of the modulator is transmitted earlier by half the time.

[0005]

However, in the method described above, when the optical transmission path lengths of the toll base station and the radio base station are different between the uplink and the downlink, a plurality of radio base stations are used. The frame synchronization phases cannot be matched.

In general, since the uplink and downlink transmission path lengths are not always equal, the data transmitted from a plurality of radio base stations cannot be bit-synchronized, and the transmission data is transmitted to two radio base stations apart from each other. Transmit diversity to switch to transmit to mobile station could not be switched.

An object of the present invention is to establish bit synchronization between wireless base stations when there is a transmission path time difference between the wireless base stations on both the upper and lower lines in the transmission path between the centralized base station and a plurality of wireless base stations. And

[0008]

According to the present invention, when the transmission path time between the toll base station and the radio base station is different, the delay measuring device 1 compares the transmission data and the reception data of the radio base station to obtain an optical signal. Measuring the delay time between transmission and reception on the transmission line, and comparing the transmission data of one radio base station by the delay measuring device 2 with the reception data demodulated by the centralized base station via the optical transmission line. By measuring the delay time, the controller calculates the transmission timing change time for the downlink transmission path delay time and the reception timing change time for the uplink transmission path delay time, and the transmission timing is calculated by the delay circuit 1. Is adjusted to establish synchronization among a plurality of radio base stations, and the delay circuit 2 adjusts the reception timing to enable reception at the centralized base station. And butterflies. With conventional technology, the transmission line delay time can be measured separately for the uplink and downlink, and bit synchronization is established between multiple radio base stations when the optical transmission length differs between the uplink and downlink. What you can do is different.

According to the present invention, the timing of a transmission burst transmitted from a radio base station can be synchronized even when the optical transmission path lengths of the uplink and the downlink are different, and another slot from another radio base station can be synchronized. Since the frequency time slot that can be used as a whole can be improved almost twice because it is not interfered with, the frequency utilization efficiency can be improved.

Further, even when the transmission path transmission time between the toll base station and the radio base station is different while the mobile station is busy, the connected radio base station is not transmitted to another radio base station. It is possible to realize non-instantaneous handover that is switched by instantaneous interruption. Further, the inter-cell diversity becomes possible by transmitting the reception data received by the plurality of radio base stations to the centralized base station through the optical transmission line to switch the diversity.

An embodiment of the present invention will be described below with reference to the drawings.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 is a block diagram of an inter-base station synchronization system according to an embodiment of the present invention.

Reference numeral 1 is a public network. 10 toll base stations
An interface circuit for converting a transmission signal from the modulator / demodulator 11 to a public network and vice versa. Concentration of delay time measuring devices 1 and 13 for measuring a round trip transmission delay time from a centralized base station to a wireless base station. Delay measuring devices 2 and 14 for measuring a downlink transmission path delay time from a base station to a certain radio base station, an air propagation time from the base station to another radio base station, and an uplink transmission path delay time from the base station to the toll base station. A timing controller for calculating the delay time of the uplink and the downlink of each transmission line based on the delay times measured by the delay measuring devices 1 and 2, and a delay circuit 1 for adjusting the delay time of the downlink of 15 , 16 delay circuits 2 for adjusting the delay time of the uplink, modulators of 17, a demodulator of 18, and a transmission timing pulse generator of 19 are provided.

The radio base station 1 of 51 is a transceiver of 52,
Equipped with an antenna M of 53 and an antenna S of 54, transmission is performed by either one of the antennas, and reception is performed by transmitting the received waves received by both antennas to a radio base station and selectively switching the one with a higher reception level. This is a configuration for demodulation.

The radio base station 2 of 71 is a transceiver of 72,
Equipped with 73 antennas M and 74 antennas S, it has the same configuration as the radio base station 1 of 51.

The 10 centralized base stations and 51 radio base stations 1 require 33 L _1d transmission path transmission times as downlinks and 34 L _1u transmission path transmission times as uplinks. It is connected by a transmission line. Also, 10
And the wireless base station 2 of 71 are connected by a transmission path of 31 L _2d transmission time and a transmission path of 32 L _2u transmission time.

The following operations are required to measure the transmission time and the spatial transmission time by the above device.

The signal output from the toll base station after being modulated is transmitted to the radio base station 1 through the transmission path of the transmission time L _1d ,
The radio base station 1 converts it to a radio frequency, transmits it from the M antenna of the radio base station 1, receives it at the S antenna of the radio base station 1, converts it to a subcarrier frequency, and transmits it for a transmission time L _1u . It is transmitted to the toll base station via the path and demodulated. At this time, the centralized base station detects a unique word to measure the time from transmission to reception after demodulation to demodulation as a delay time.

Thus, the transmission time of L _1d + L _1u can be measured, and this time is _designated as T ₁₁ .

The measurement method when transmitting from the M antenna of the radio base station 2 and receiving from the S antenna of the radio base station 2 is the same as above.

As a result, the transmission time of L _2d + L _2u can be measured, and this time is _defined as T ₂₂ .

The signal output from the centralized base station after being modulated is output to the radio base station 1 via the transmission path of the transmission time L _1d.
To the radio frequency in the radio base station 1,
The signal is transmitted from the M antenna of the radio base station 1, received by the M antenna of the radio base station 2 via the propagation path of the air propagation time A ₁₂ , converted into the subcarrier frequency by the radio base station 2, and the transmission time L _It is transmitted to the _toll base station via the _2u transmission line and demodulated. At this time, the centralized base station detects the unique word before and after transmission to measure the time from transmission to reception after demodulation to demodulation as delay time.

As a result, the transmission time of L _1d + A ₁₂ + L _2u can be measured, and this time is _defined as T ₁₂ .

The method of measurement when transmitting from the S antenna of the radio base station 1 and receiving at the S antenna of the radio base station 2 via the air propagation path is also the same as above.

Thus, the propagation time of L _2d + A ₁₂ + L _1u can be measured, and this time is _designated as T ₂₁ .

On the basis of these, the transmission line delay time difference is obtained, and the above conditions are defined by the following (1), (2),
This is shown in equations (3) and (4). L _1d + L _1u = T ₁₁ (1) L _2d + L _2u = T ₂₂ (2) L _1d + L _2u + A ₁₂ = T ₁₂ (3) L _2d + L _1u + A ₁₂ = T ₂₁ (4) (3) + (4 ) - (1) - (from _{2), 2A 12 = T 12} + T 21 -T 11 -T 22 (5)

[0027]

[Equation 1]

From (1)-(3), T ₁₁ -T ₁₂ = (L _1u -L _2u ) + A ₁₂ (7) L _1u -L _2u = T ₁₁ -T ₁₂ + A ₁₂ (8) (2)- From (4), T ₁₁ −T ₂₁ = (L _1d −L _2d ) + A ₁₂ (9) L _1d −L _2d = T ₁₁ −T ₂₁ + A ₁₂ (10)

From the above equation (8), the transmission time difference L _1u -L _2u between the uplink from the radio base station 1 to the toll base station and the uplink from the radio base station 2 to the toll base station can be obtained.

From the above equation (10), the transmission time difference L _1d -L _2d between the downlink from the toll base station to the radio base station 1 and the downlink from the toll base station to the radio base station 2 can be obtained.

Synchronization between the base stations can be realized by using these transmission time differences. Specific timings of synchronization in the inter-base station synchronization method are shown in FIGS. 4 and 5, and the method is shown below.

As a hypothesis, l _1d -L _2d > 0, L _1u -L _2u
> 0. <Downlink> (1) Transmit from the toll base station to the wireless base station 1. (2) After transmitting to the wireless base station 1, the centralized base station transmits to the wireless base station 2 after l _1d −L _2d time has elapsed. (3) The burst timings received by the wireless base station 1 and the wireless base station 2 from the centralized base station match. <Uplink> (1) The centralized base station receives the radio base station 2. (2) After receiving from the wireless base station 2, the centralized base station receives from the wireless base station 1 after L _1u −L _2u time has elapsed. (3) The bursts from the wireless base stations 1 and 2 can be received by the centralized base station without overlapping.

By this method, L _1d -L _2d <> 0, L _1u
It can be seen that the same realization is possible regardless of -L _2u <> 0.

As is clear from this result, bit synchronization between base stations becomes possible by adjusting the transmission timing by the uplink transmission time difference. In addition, by adjusting the reception timing by the difference in the transmission time of the downlink, reception at the centralized base station is possible without the bursts overlapping.

(Embodiment 2) FIG. 2 is a block diagram of an inter-base station synchronization system according to an embodiment of the present invention.

Reference numeral 1 is a public network. 10 toll base stations
An interface circuit for converting a transmission signal from the modulator / demodulator 11 to a public network and vice versa, a delay measuring device 1 or a concentration base 13 for measuring a round trip transmission delay time from a concentration base station 12 to a radio base station Of the delay measuring devices 2 and 14 for measuring the downlink transmission path delay time from a station to a certain radio base station, the air propagation time from that station to another radio base station, and the uplink transmission path delay time from that to the toll base station. A timing controller that calculates the uplink and downlink delay times of each transmission line based on the delay times measured by the delay measuring devices 1 and 2; a delay circuit 1 that adjusts the downlink delay time of 15; It is equipped with 19 transmission timing pulse generators.

The radio base station 1 of 51 is a transceiver of 52,
53 antenna M, 54 antenna S, 55 modulator,
Equipped with 56 demodulators.

The radio base station 1 of 71 is a transceiver of 72,
73 antenna M, 74 antenna S, 75 modulator,
Equipped with 76 demodulators.

The 10 centralized base stations and 51 radio base stations 1 require 33 L _1d transmission path transmission times as downlinks and 34 L _1u transmission path transmission times as uplinks. It is connected by a transmission line. Also, 10
And the wireless base station 2 of 71 are connected by a transmission path of 31 L _2d transmission time and a transmission path of 32 L _2u transmission time.

Only the transmission / reception timing of the modulator and demodulator need be considered, and the optical transmission line delay amount need not be considered. Compared with the first embodiment, the delay circuit 2 is unnecessary.

Hereinafter, the transmission line delay measuring method and the timing adjusting method are the same as those in the first embodiment.

[0042]

As described above, according to the present invention,
Even if the transmission times of the optical transmission lines between the centralized base station and the radio base stations are different, the radio base stations can be synchronized with each other.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a second embodiment of the present invention.

FIG. 3 is a conventional system configuration diagram.

FIG. 4 is a transmission / reception timing adjustment diagram according to the present invention.

FIG. 5 is a timing diagram of the TDMA-TDD method according to the present invention.

[Explanation of symbols]

1 Public network 10 Centralized base station 11 Interface circuit 12 Delay measuring device 1 13 Delay measuring device 2 14 Timing controller 15 Delay circuit 1 16 Delay circuit 2 17 Modulator 18 Demodulator 19 Timing pulse generator 31, 33 From centralized base station Downlink optical transmission line to radio base station 32,34 Uplink optical transmission line from radio base station to toll base station 51,71 Radio base station 52,72 Radio base station transceiver 53,73 Radio base station In antenna M 54,74 Antenna in radio base station S 55,75 Modulator in radio base station 56 76 Demodulator in radio base station

Claims (3)

[Claims] 1. A mobile communication system having a plurality of radio base stations coupled to the toll base station via a transmission path, for transmitting and receiving radio waves from an antenna of the radio base station to communicate with a mobile station, The radio base station has at least transmitting and receiving antennas, the signal transmitted from the toll base station is transmitted from the antenna of the radio base station, and the signal received by another antenna of the same radio base station is transmitted to the toll base station. By measuring the propagation time to return and the propagation time until the same signal received by another radio base station returns to the toll base station, timing synchronization is established between the radio base stations via a delay circuit. The inter-base station synchronization method characterized by. 2. A modulated signal is transmitted between a centralized base station in which modulators / demodulators are centrally arranged and a wireless base station through a transmission path, and radio waves are transmitted and received from an antenna of the wireless base station to communicate with a mobile station. In the mobile communication system, the toll base station compares the transmission data and the reception data of the radio base station with the modulator and demodulator and the interface circuit for converting the transmission signal of the public network into the modulation and demodulation signal and vice versa. The delay measuring device 1 for measuring the delay time between transmission and reception of the optical transmission line is compared with the reception data demodulated by the centralized base station through the optical transmission line by receiving the transmission data of the wireless base station by another wireless base station. A delay measuring device 2 for measuring the delay time,
A delay circuit 1 capable of varying the delay amount of transmission data, a delay circuit 2 capable of varying the delay amount of received data, and a delay measuring device 1
And a timing controller that calculates a transmission / reception timing adjustment amount based on the measurement value of the delay measuring device 2 and a timing pulse generator that generates a reference timing necessary to control the timing adjustment amount. It is equipped with a transceiver that converts and transmits to and receives radio frequencies, and an antenna. The delay measuring device 1 compares the transmission data and reception data of a certain radio base station to measure the delay time between transmission and reception on an optical transmission line. By measuring the delay time by comparing the received data demodulated by the centralized base station through the optical transmission path with the transmission data of the certain radio base station received by the delay measuring device 2 by another radio base station, The controller calculates the transmission timing change time for the downlink transmission path delay time and the reception timing change time for the uplink transmission path delay time, and sends it by the delay circuit 1. Establishing synchronization between a plurality of radio base stations by adjusting the timing, by adjusting the reception timing by the delay circuit 2, an inter-base station synchronization method characterized by receiving a centralized base station. 3. Mobile communication in which a signal is transmitted between a toll base station and a radio base station equipped with a modulator / demodulator through a transmission path, and radio waves are transmitted and received from an antenna of the radio base station to communicate with a mobile station. In the system, the centralized base station compares the transmission signal of the public network with the modulation / demodulation signal and vice versa, and compares the transmission data and the reception data of the wireless base station with the delay between the transmission and reception of the optical transmission line. A delay measuring device 1 for measuring time and a delay measuring device for measuring a delay time by comparing transmission data of a wireless base station received by another wireless base station and demodulated by a centralized base station through an optical transmission line. 2, a delay circuit 1 that can vary the delay amount of transmission data, a timing controller that calculates a transmission / reception timing adjustment amount from the measured values of the delay measuring device 1 and the delay measuring device 2, and a necessary for controlling it. The radio base station is provided with a timing pulse generator for generating quasi-timing, the radio base station is provided with a modulator / demodulator, a transceiver for transmitting and receiving a modulated signal by converting to a radio frequency, and an antenna. The transmission data of the base station and the reception data are compared to measure the delay time between transmission and reception of the optical transmission line, and the transmission data of one radio base station is received by another radio base station by the delay measuring device 2 and the optical transmission is performed. By comparing the received data demodulated by the centralized base station through the transmission path and measuring the delay time, the transmission timing change time for the downlink transmission path delay time and the reception timing change time for the uplink transmission path delay time Is calculated by the controller and the transmission timing is adjusted by the delay circuit 1 to establish synchronization among a plurality of radio base stations.