JP5178356B2 - Base station and control channel transmission / reception timing maintaining method - Google Patents

Description

  The present invention relates to a base station and a control channel transmission / reception timing maintaining method.

  Currently, a radio communication system configured by a mobile terminal such as a mobile phone or a personal handy-phone system (PHS) terminal has a time division multiple access (TDMA) system and a time division duplex as a multiple access system. Some employ a (TDD: Time Division Duplex) method. In a base station in such a wireless communication system, a carrier for transmitting a signal is divided into time slots having a predetermined time interval, and various information is transmitted to and received from the mobile terminal through a control channel or a communication channel assigned to each time slot. In the base station, when assigning a control channel to a time slot at a predetermined timing, control is performed so that the timing of assigning the control channel to the adjacent base station does not overlap. This is because assigning a control channel to a time slot having the same timing as that of an adjacent base station causes the mutual control channels to become interference waves, thereby hindering communication with the mobile terminal.

  By the way, in the above prior art, a control channel must be assigned to a time slot having a timing different from that of the adjacent base station. Therefore, when restart is performed due to a reset due to various system abnormalities, the adjacent base station transmits the control channel. It is necessary to search for a time slot that does not overlap with the one used in the above and assign a control channel to the searched time slot. Therefore, in the above prior art, when a reset occurs, a processing time for allocating a control channel to a time slot is required until communication with the portable terminal is started even after restarting.

  Further, in the above-described conventional technique, the timings of the time slots in the surrounding base stations and the carriers must be synchronized before the control channel is assigned to the time slots. Therefore, in addition to the time for executing the process of assigning the control channel to the time slot before starting the communication with the mobile terminal, the time for executing the process for synchronizing the timing of the time slot in the surrounding base station and the carrier. It becomes necessary. Therefore, in the above prior art, there is a problem that communication with the portable terminal cannot be started immediately after restart due to the occurrence of reset.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide an apparatus capable of starting communication with a mobile terminal in a shorter time than before after restarting.

  In order to achieve the above object, in the present invention, as a first solution for a base station, communication with a mobile terminal is performed by a time division multiple access method, and a layer 1 processing unit is input from a reference clock signal generation unit. A base station that maintains timing synchronization in a time division multiple access scheme and executes signal transmission control processing in layer 1 based on a reference clock signal, and executes a layer 1 processing unit and a reference when restarting When it is determined that the clock signal generation unit does not need to be restarted, the layer 1 processing unit is notified by instructing the layer 1 processing unit to maintain the time slot used for transmission / reception of the control channel. A control unit that executes restart of each unit other than the clock signal generation unit, and when the layer 1 processing unit receives the instruction, the reference clock signal generation unit Based on the reference clock signal et input, employ a means that transmits a signal to and are time slots using the base station of the adjacent set above receivable signal strength for transmission of the control channel.

  In the present invention, as the second solving means relating to the information processing apparatus, in the first solving means, when the layer 1 processing unit receives the instruction, the reference clock signal input from the reference clock signal generating unit Based on the above, a means is adopted in which the time slot used for transmission of the control channel is set to be equal to or higher than the signal strength that can be received by the adjacent base station, and a signal not subjected to digital modulation is transmitted to the time slot.

  In the present invention, as the third solving means relating to the information processing apparatus, in the first or second solving means, the layer 1 processing unit is configured to transmit data symbols and pilots in time slots used for transmission of control channels. Any one, any two, or all of the symbols and training is set to be equal to or higher than the signal strength that can be received by the adjacent base station.

  Also, in the present invention, as a first solving means related to the control channel transmission / reception timing maintaining method, the layer 1 processing unit communicates with the mobile terminal by the time division multiple access method, and the layer 1 processing unit receives the reference clock input from the reference clock signal generation unit A control channel transmission / reception timing maintaining method in a base station for maintaining timing synchronization in a time division multiple access scheme and executing signal transmission control processing in layer 1 based on a signal, When it is determined that the one processing unit and the reference clock signal generation unit do not need to be restarted, the layer 1 processing unit is notified by instructing the layer 1 processing unit to maintain the time slot used for transmission / reception of the control channel. A step of restarting each unit other than the one processing unit and the reference clock signal generating unit, and the layer 1 processing unit When receiving the instruction, based on the reference clock signal input from the reference clock signal generator, a signal in which the time slot used for transmission of the control channel is set to be equal to or higher than the signal strength that can be received by the adjacent base station The step of transmitting is adopted.

  According to the present invention, the base station communicates with the mobile terminal by the time division multiple access method, and the layer 1 processing unit is based on the reference clock signal input from the reference clock signal generation unit, in the time division multiple access method. A base station that maintains timing synchronization and performs signal transmission control processing in layer 1 and determines that the layer 1 processing unit and the reference clock signal generation unit do not need to be restarted when restarting Then, a control for notifying the layer 1 processing unit of an instruction to maintain the reservation of the time slot used for transmission / reception of the control channel and executing restart of each unit other than the layer 1 processing unit and the reference clock signal generation unit When the layer 1 processing unit receives the instruction, the layer 1 processing unit transmits the control channel based on the reference clock signal input from the reference clock signal generation unit. It transmits a signal to and are time slots using the base station of the adjacent set above receivable signal strength.

As a result, the base station does not need to search for a slot to which the control channel is allocated and can immediately start transmission / reception of the control channel. Therefore, after restarting, the base station can communicate with the mobile terminal in a shorter time than before. Can start.
Further, in the base station, even during restart, the layer 1 processing unit maintains timing synchronization based on the reference clock signal input from the reference clock signal generation unit. Since it is not necessary to execute the process to synchronize, communication with a portable terminal can be started in a shorter time.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The present embodiment relates to a base station that communicates with a PHS (Personal Handy-phone System) terminal.
FIG. 1 is a schematic configuration diagram illustrating a wireless communication system including a base station A according to the present embodiment. As shown in FIG. 1, the wireless communication system includes a base station A and a PHS terminal B.

The base station A and the PHS terminal B use a time division multiple access (TDMA) system and a time division duplex (TDD) system in an orthogonal frequency division multiple access (OFDMA) system. ) Communication devices that communicate with each other using a communication method that combines methods. The base station A is discretely arranged with a predetermined interval from other base stations (not shown), and communicates with the PHS terminal B in the assigned cell.
The PHS terminal B performs voice communication or data communication by transmitting and receiving signals to and from the base station A.

  As is well known, the OFDMA system means that PHS terminal B and other PHS terminals (not shown) share all subcarriers in an orthogonal relationship, and a group of 24 subcarriers is positioned as one group, and each PHS terminal It is a technology that realizes multiple access by assigning to a network. In the wireless communication system of this embodiment, the above-described OFDMA method is further combined with a TDMA method and a TDD method.

  That is, each group of subcarriers is divided into slots, which are the minimum units, by TDMA, and uplink and downlink are switched every 4 slots by TDD. FIG. 2 is a schematic diagram showing slots in each group of subcarriers in the wireless communication system configured by the base station A according to the present embodiment. In FIG. 2, the vertical axis represents frequency and the horizontal axis represents time. As shown in FIG. 2, 112 slots obtained by multiplying a group of 28 subcarriers in the frequency direction and 4 slots in the time axis direction are allocated to the uplink and the downlink, respectively.

  In this radio communication system, as shown in FIG. 2, among the subcarrier groups, the farthest group in the frequency direction (28 in the frequency direction in FIG. 2) is assigned to the control channel, and the remaining subcarrier groups are communicated. Assign to a channel. Then, the base station A transmits / receives the control channel to / from the PHS terminal B using any slot in the subcarrier group (28 in the frequency direction in FIG. 2) assigned to the control channel. It is assumed that the hatched slot shown in FIG. 2 is used by the base station A as a control channel. Also, one unit obtained by dividing each subcarrier group shown in FIG. 2 as each slot in the time axis direction is referred to as PRU (Physical Resource Units).

  Next, symbols of each subcarrier of the PRU in the control channel will be described with reference to FIG. FIG. 3 is a schematic diagram showing symbols on each subcarrier of the PRU in the control channel of the base station A according to the present embodiment. In FIG. 3, the vertical axis represents frequency and the horizontal axis represents time. As shown in FIG. 3, the PRU in the control channel is composed of 24 subcarriers in the frequency direction. Each subcarrier of the PRU in the control channel is divided into 21 symbols in the time axis direction.

  That is, the PRU in the control channel is composed of 501 symbols obtained by multiplying 24 subcarriers in the frequency direction and 21 slots in the time axis direction. As shown in FIG. 3, 501 symbols in the PRU are composed of five types of symbols, that is, data symbols, pilot symbols, training symbols, guard symbols, and guard times. In FIG. 3, a solid symbol indicates a data symbol, a lattice pattern symbol indicates a pilot symbol, a diagonal pattern symbol indicates a training symbol, and a dot pattern symbol indicates a guard symbol and a guard time.

  The data symbol is a symbol for transmitting data such as a base station ID in the control channel. The pilot symbol is a symbol used by the PHS terminal B for carrier synchronization, amplitude fluctuation and phase fluctuation amount estimation and reception strength, interference power and jamming power estimation. The training symbol is a symbol that has a cyclic property and is used by the PHS terminal B to synchronize timing in the TDMA-TDD scheme. The guard symbol is a symbol provided to prevent interference between adjacent subcarriers.

  Furthermore, the guard time is a symbol provided to prevent overlapping of PRUs caused by a shift in signal reception timing accompanying a change in the position of the PHS terminal B or the like. In normal times, data symbols, pilot symbols, and training symbols have signal strengths equal to or higher than a predetermined threshold value, and transmit digitally modulated information. Further, the card symbol and the guard time are set to signal strength that is remarkably lower than that of the data symbol, pilot symbol, and training symbol.

Next, the functional configuration of the base station A will be described with reference to FIG. FIG. 4 is a functional block diagram showing a functional configuration of the base station A according to the present embodiment. As illustrated in FIG. 4, the base station A includes a wireless communication unit 1, a wired communication I / F unit 2, and a control unit 3. The wireless communication unit 1 includes a layer 1 processing unit 1a, a layer 2 processing unit 1b, and a reference clock signal generation unit 1c.
The layer 1 processing unit 1a performs digital modulation processing of a transmission signal transmitted to the PHS terminal B via an antenna, digital demodulation processing of a reception signal received from the PHS terminal B via an antenna, detection of communication quality, etc. A signal transmission control process in the physical layer) is executed.
The layer 2 processing unit 1b performs signal transmission control processing in layer 2 (data link layer) such as ARQ (automatic repeat request) control (automatic retransmission control).

  The reference clock signal generation unit 1c generates a reference clock signal by dividing the frequency of a synchronization clock signal input from an exchange (not shown) via the wired communication I / F unit 2, and generates a layer 1 processing unit. This reference clock signal is output to 1a. The layer 1 processing unit 1a then synchronizes timing in the TDMA-TDD system with other base stations (not shown) based on this reference clock signal. Note that the clock signal for synchronization received by the wired communication I / F 2 unit from the exchange is for the purpose of timing synchronization in the TDMA-TDD system, and is transmitted to the base station A and other base stations (not shown). In contrast, it is a signal that is always supplied.

  The wired communication I / F unit 2 is an interface for connecting to other base stations (not shown), exchanges, and the like by wire. Under the control of the control unit 3, various signals such as control signals and audio signals are transmitted. It transmits / receives to / from the exchange and receives a clock signal for synchronization from the exchange. The wired communication I / F unit 2 outputs a synchronization clock signal to the reference clock signal generation unit 1 c and outputs an audio signal or the like to the control unit 3.

  The control unit 3 includes an internal memory including a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), the wireless communication unit 1, the wired communication I / F unit 2, and signal input. It consists of an interface circuit that performs output, and controls the overall operation of the base station A based on a control program stored in the ROM and signals received by the wireless communication unit 1 and the wired communication I / F unit 2 . The control program stored in the ROM includes a control channel transmission / reception timing maintenance program, and the control unit 3 executes control channel transmission / reception timing maintenance processing based on the control channel transmission / reception timing maintenance program. The details of the control process executed by the control unit 3 will be described as the operation of the base station A below.

Next, the operation of the base station A configured as described above will be described with reference to FIG. FIG. 5 is a flowchart showing the operation of the base station A according to this embodiment.
The control unit 3 determines whether or not a system abnormality that causes a restart due to a reset has occurred in any of the units in the base station A (step S1). If it is determined “NO” in step S1, That is, if no system abnormality has occurred in any part of the base station A, the process proceeds to step S1, and if “YES” is determined in step S1, that is, the system abnormality that causes a restart due to reset Occurs in any part of the base station A, the wireless communication unit 1 is caused to transmit a handover instruction to another base station to the PHS terminal existing in its own cell, that is, the PHS terminal B (step S2). ).

  After step S2, the control unit 3 determines whether or not a system abnormality that causes a restart due to reset has occurred in the reference clock signal generation unit 1c (step S3), and if “YES” is determined in step S3 In other words, when a system abnormality that causes a restart due to reset occurs in the reference clock signal generation unit 1c, the layer 1 processing unit 1a, the layer 2 processing unit 1b, the reference clock signal generation unit 1c, wired communication The entire base station A including the I / F unit 2 and the control unit 3 is restarted, that is, restarted after wireless communication is completely stopped (step S4).

  If the control unit 3 determines “NO” in step S3, that is, if the system abnormality that causes the restart due to the reset has not occurred in the reference clock signal generator 1c, the cause of the restart due to the reset Is determined in the layer 1 processing unit 1a (step S5), and if it is determined "YES" in step S5, that is, the system abnormality that causes the restart due to reset is the layer 1 If it occurs in the processing unit 1a, in step S4, the entire base station A is restarted, that is, restarted with the wireless communication completely stopped.

  If it is determined “NO” in step S5, that is, if a system abnormality that causes a restart due to reset has not occurred in the layer 1 processing unit 1a, the control unit 3 controls the layer 1 processing unit 1a. A base station A including a layer 2 processing unit 1b other than the layer 1 processing unit 1a, the reference clock signal generating unit 1c, and the wired communication I / F unit 2 and the control unit 3 is notified of a channel transmission / reception timing maintenance instruction (step S6). Is restarted, that is, restart that does not completely stop the wireless communication (step S7).

  When the layer 1 processing unit 1a receives the control channel transmission / reception timing maintenance instruction from the control unit 3, the layer 1 processing unit 1a communicates with other base stations (not shown) based on the reference clock signal input from the reference clock signal generation unit 1c. Timing synchronization in the TDD scheme is continued (step S8), and the signal strength of the data symbols, pilot symbols, and training symbols in the PRU of the slot used for transmission of the control channel exceeds the level that can be received by the adjacent base station. A signal that is not set and is not subjected to digital modulation is transmitted to the data symbol, pilot symbol, and training symbol (step S9). In step S9, the data symbols, pilot symbols, and training symbols become sine waves by not performing digital modulation on the data symbols, pilot symbols, and training symbols.

  For example, when the control channel is transmitted using the hatched slot shown in FIG. 2, in step S8, the layer 1 processing unit 1a determines the data symbol in the PRU in the hatched slot of the downlink (transmission). The signal strength of the pilot symbol and the training symbol is set to a level that can be received by the adjacent base station. As a result, the base station adjacent to the base station A receives the signal transmitted from the base station A, and recognizes that the hatched slot shown in FIG. 2 is used for transmission / reception of the control channel. While the base station A is restarting, this slot is not used for transmission / reception of the control channel by the adjacent base station.

  When the restart is completed after step S9, the control unit 3 causes the layer 1 processing unit 1a to start transmission / reception of a normal control channel using the secured slot (step S10).

  As described above, in the base station A, when the control unit 3 has to execute restart by reset due to a system abnormality, there is no need to restart the layer 1 processing unit and the reference clock signal generation unit 1c. When each unit including the control unit 3 is restarting, the layer 1 processing unit 1a communicates with other base stations based on the reference clock signal input from the reference clock signal generation unit 1c. Timing synchronization in the TDMA-TDD scheme is continued, and the signal strength of data symbols, pilot symbols, and training symbols in the PRU of the slot used for control channel transmission is set to a level that can be received by the adjacent base station And digitally modulate data symbols, pilot symbols and training symbols. To transmit no signal.

As a result, the base station A does not need to search for a slot to which the control channel is allocated after restarting, and can immediately start transmission / reception of the control channel. Communication with can be started.
Furthermore, in the base station A, the layer 1 processing unit 1a also communicates with other base stations based on the reference clock signal input from the reference clock signal generation unit 1c even during restart of each unit including the control unit 3. Since the synchronization of the timing in the TDMA-TDD system is continued, it is not necessary to execute the process of synchronizing the timing in the TDMA-TDD system with other base stations after the restart, so that the mobile terminal Communication can be started.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, For example, the following modifications can be considered.
(1) In the base station A of the above embodiment, the layer 1 processing unit 1a transmits three symbols, ie, a data symbol, a pilot symbol, and a training symbol, to the adjacent base station in order to secure a slot used for transmission / reception of the control channel. Although the signal strength is set to be higher than the level that can be received by the station, the present invention is not limited to this.
For example, any one of data symbols, pilot symbols, and training symbols, or any two symbols may be set to a signal strength equal to or higher than a level that can be received by an adjacent base station.

(2) In the base station A of the above embodiment, at the time of restart, the layer 1 processing unit 1a transmits data symbols, pilot symbols, and training symbols adjacent to each other in order to secure a slot used for control channel transmission / reception. Although the signal strength is set to a level that can be received by the base station, the present invention is not limited to this.

  For example, when the signal strength of the signal transmitted by the layer 1 processing unit 1a is high at the time of restart, the layer 1 processing unit 1a uses the signal strength of the data symbol, pilot symbol, and training symbol for transmission / reception of the control channel. You may make it lower to the lowest level which can ensure a slot, ie, the lowest level which the other adjacent base station can recognize that the said slot is used for transmission / reception of a control channel. This makes it easier for the PHS terminal B to connect to the other adjacent base station based on the signal transmitted by the other adjacent base station instead of the restarting base station A.

It is a schematic diagram which shows the radio | wireless communications system comprised by the base station A which concerns on one Embodiment of this invention. It is a schematic diagram which shows the slot in each group of the subcarrier in the radio | wireless communications system comprised by the base station A which concerns on one Embodiment of this invention. It is a schematic diagram which shows the symbol in each subcarrier of PRU in the control channel of base station A which concerns on one Embodiment of this invention. It is a functional block diagram which shows the function structure of the base station A which concerns on one Embodiment of this invention. It is a flowchart which shows operation | movement of the base station A which concerns on one Embodiment of this invention.

Explanation of symbols

A ... base station, B ... PHS terminal, 1 ... wireless communication unit, 1a ... layer 1 processing unit, 1b ... layer 2 processing unit, 1c ... reference clock signal generation unit, 2 ... wired communication I / F unit, 3 ... control Part

Claims (4)

The layer 1 processing unit communicates with the mobile terminal by the time division multiple access method, and the layer 1 processing unit maintains synchronization of the timing in the time division multiple access method based on the reference clock signal input from the reference clock signal generation unit. A base station that executes signal transmission control processing,
When executing the restart, if it is determined that the layer 1 processing unit and the reference clock signal generation unit do not need to be restarted, an instruction to maintain the reservation of the time slot used for transmission / reception of the control channel is issued. A controller that notifies the layer 1 processor and restarts each unit other than the layer 1 processor and the reference clock signal generator;
When the layer 1 processing unit accepts the instruction, the layer 1 processing unit can receive a time slot used for transmission of the control channel based on the reference clock signal input from the reference clock signal generation unit. A base station that transmits a signal set to be higher than an intensity.   When the layer 1 processing unit receives the instruction, the adjacent base station can receive the time slot used for transmission of the control channel based on the reference clock signal input from the reference clock signal generation unit. The base station according to claim 1, wherein the base station transmits a signal that is set to be equal to or higher than the signal strength and is not subjected to digital modulation in the time slot.   The layer 1 processing unit has a signal strength higher than the signal strength at which the adjacent base station can receive any one, any two, or all of the data symbols, pilot symbols and training in the time slot used for transmission of the control channel. The base station according to claim 1, wherein the base station is set as follows. The layer 1 processing unit communicates with the mobile terminal by the time division multiple access method, and the layer 1 processing unit maintains synchronization of the timing in the time division multiple access method based on the reference clock signal input from the reference clock signal generation unit. A control channel transmission / reception timing maintaining method in a base station that executes signal transmission control processing,
When executing the restart, if it is determined that the layer 1 processing unit and the reference clock signal generation unit do not need to be restarted, an instruction to maintain the reservation of the time slot used for transmission / reception of the control channel is issued. A step of notifying the layer 1 processing unit and restarting each unit other than the layer 1 processing unit and the reference clock signal generation unit;
When the layer 1 processing unit accepts the instruction, the layer 1 processing unit can receive a time slot used for transmission of the control channel based on the reference clock signal input from the reference clock signal generation unit. Transmitting a signal set at a strength or higher,
A transmission / reception timing maintaining method comprising:

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