JP2007208341A - Base station, mobile station and mobile communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a base station for providing a broadcast service to mobile stations with excellent quality while suppressing collision of signals between the mobile stations. <P>SOLUTION: The base station 100 transmits notice information including a training slot number and a training code to be used by a mobile station 200 going to newly receive the broadcast service or notice information including an idle state of a training slot and a training code by using a broadcast slot. The mobile station 200 uses either of the training slot and the training code specified on the basis of the notice information to transmit a training signal. Then the base station 100 optimizes an adaptive array in response to the reception of the training signal from the mobile station 200 for the mobile station 200 going to receive the broadcast service. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a base station that has an antenna and provides a broadcast service to a plurality of mobile stations, a mobile station, and a mobile communication system.

  In a communication system in which a time division duplex (TDD) method and a time division multiple access (TDMA) are adopted as a radio interface and an antenna of an adaptive array method is provided in a base station, when providing a broadcast service to a mobile station The problem is that as the number of antennas increases, valleys are formed in the directivity pattern.

  For this reason, the base station suppresses the generation of valleys in the directivity pattern by slightly changing the antenna directivity in the time slot that is a communication channel, and the data transmitted by broadcast has the same time. By transmitting a plurality of times in the slot, degradation of communication quality due to valleys in the directivity pattern is suppressed.

For example, in Patent Document 1, the base station transmits paging information as broadcast information a plurality of times, and changes the directivity of the antenna to reduce communication quality due to valleys in the directivity pattern. It is avoiding. However, multiple transmissions of paging information cause a reduction in data rate. For this reason, the mobile station transmits a training signal for adjusting the directivity of the antenna using the uplink time slot toward the base station, as in the case of receiving a unicast signal. On the other hand, the base station that has received this training signal adjusts the antenna directivity (optimization of the adaptive array).
JP-T-2004-511141

  However, when a plurality of mobile stations transmit training signals, there is a possibility that the training signals collide. In order to avoid such collision of training signals, conventionally, as shown in FIG. 10, the base station generates a random number from a mobile station unique number such as ESN (Electric Serial Number) or MEID (Mobile Equipment ID). Using the random number, a time slot and a code spread multiple access (CDMA) code (training code) corresponding to the time slot are selected as a communication channel (TR) for training signals to be allocated to the mobile station. .

  However, even in such processing, if the number of mobile stations increases, training signal collision occurs. In this case, the base station regards a training signal from another mobile station other than any one of the mobile stations as a jamming signal, and performs adaptive array control to suppress deterioration of communication quality due to the jamming signal. As a result, the communication quality at other mobile stations deteriorates.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to improve the quality of broadcast services to mobile stations while avoiding signal collisions between mobile stations. And a mobile station and a mobile communication system.

  The present invention is a base station that has an antenna and transmits broadcast information to a plurality of mobile stations using a part of a plurality of downlink time slots, and corresponds to the downlink time slot that transmits the broadcast information. Communication channel allocating means for allocating a communication channel so that each of the plurality of mobile stations can transmit a signal for adjusting the directivity of the antenna, and transmitted from the mobile station. And a directivity adjusting unit that adjusts the directivity of the antenna with respect to the mobile station when a signal for adjusting the directivity of the antenna using the communication channel is received. .

  According to this configuration, since each mobile station is assigned a different communication channel, even if each mobile station transmits a predetermined signal for adjusting the antenna directivity using the assigned communication channel, collision occurs. Is avoided, and the directivity of the antenna with respect to each mobile station is appropriately adjusted.

  In the base station of the present invention, the communication channel assignment unit may notify the mobile station of information on a communication channel used by the mobile station.

  In the base station of the present invention, the communication channel allocating means may notify the mobile station of information on availability of the communication channel.

  In the base station of the present invention, the communication channel assigning means assigns a communication channel specified based on a time slot in time division multiple access and a code in code division multiple access corresponding to the time slot. Also good.

  In the base station of the present invention, the directivity adjusting means may adjust the directivities of a plurality of antennas.

  In the base station of the present invention, the directivity adjusting means sets the number of predetermined signals for adjusting the directivity of the antenna from the mobile station received by another base station as a first threshold value. When it reaches, the directivity of the antenna may be adjusted with respect to the number of mobile stations exceeding the first threshold.

  According to this configuration, the base station adjusts the antenna directivity to a mobile station that cannot receive adjustment of the antenna directivity by another base station, thereby performing broadcast service to the mobile station. And the number of mobile stations receiving the broadcast service in the entire communication system can be increased.

  Further, the base station of the present invention is configured so that the communication channel allocating means has the mobile station when the number of predetermined signals for adjusting the directivity of the antenna from the mobile station reaches a second threshold value. A part of the communication channel assigned to the mobile station may be transferred to a mobile station that is newly receiving the broadcast service.

  According to this configuration, the base station reassigns a part of the broadcast signal communication channel assigned to the mobile station to the mobile station that intends to newly receive the broadcast service, so that the number of mobile stations that receive the broadcast service. Can be increased.

  Further, the base station of the present invention is characterized in that the directivity adjusting means includes a mobile station located outside the service area and an outer circumference part of the service area when the own station is located on the outer circumference part of the service area of the broadcast service. The directivity of the antenna may be adjusted in the order of a mobile station that moves from a base station cell other than the mobile station to its own cell and a mobile station that exists in a multipath environment.

  According to this configuration, the base station can increase the number of mobile stations that receive the broadcast service in the entire communication system by selecting the target mobile station whose antenna directivity is to be adjusted with an appropriate priority.

  In addition, the present invention is a mobile station that receives broadcast information from a base station, and adjusts the antenna directivity of the base station in an uplink time slot corresponding to a downlink time slot that receives the broadcast information. It has the means to transmit the signal of.

The mobile communication system of the present invention is a mobile communication system comprising a plurality of mobile stations and a base station having an antenna and transmitting broadcast information to the plurality of mobile stations. A station allocates a communication channel so that each of the plurality of mobile stations can transmit a signal for adjusting the directivity of the antenna in an uplink time slot corresponding to a downlink time slot that transmits the broadcast information. Communication channel allocating means, wherein the mobile station has transmission means for transmitting a signal for adjusting the directivity of the antenna using the allocated communication channel, and the base station further includes: ,
Directivity adjusting means for adjusting the directivity of the antenna with respect to the mobile station when receiving a signal transmitted from the mobile station for adjusting the directivity of the antenna using the communication channel; It is characterized by having.

  In the mobile communication system, the communication channel allocating means of the base station divides an uplink time slot corresponding to a downlink time slot for transmitting the distribution information, and the divided time slot Communication channels may be allocated based on codes in code division multiple access corresponding to the divided time slots.

  According to the present invention, even when each mobile station transmits a predetermined signal for adjusting the directivity of the antenna, collision is avoided, and adjustment of the directivity of the antenna with respect to each mobile station is appropriately performed. Broadcast service can be provided with good quality.

  FIG. 1 is a diagram showing a configuration of a communication system (mobile communication system) according to an embodiment of the present invention. In the communication system 1 illustrated in FIG. 1, the base station 100 provides a broadcast service to a plurality of mobile stations 200.

  FIG. 2 is a diagram showing a configuration of the base station 100. As shown in FIG. A base station 100 shown in FIG. 2 includes a plurality of antennas 102, a transmission / reception circuit 104 connected to the antennas 102 and an external network 150, and a control circuit 106 having functions of a communication channel assignment unit and a directivity adjustment unit. Composed. FIG. 3 is an example of the arrangement and directivity pattern of the antenna 102 in the base station 100. In FIG. 3, eight antennas 102 are arranged in a circle, and each antenna 102 has directivity toward the outside. Each antenna 102 is adjusted in directivity with respect to the mobile station 200 (optimization of an adaptive array).

  FIG. 4 is a diagram showing a communication channel structure applied in the communication system 1. FIG. 4 shows a communication channel structure in the TDD-TDMA communication system, and one frame is formed in 5 ms. One frame is divided into six time slots. The first three time slots are uplink communication time slots (uplink slots) corresponding to uplink channels, and the latter three time slots are downlink communication time slots (downlink slots) corresponding to downlink channels. is there. In the channel structure of FIG. 4, the length of the downlink slot is set longer than that of the uplink slot in order to obtain the downlink communication speed.

  Of the three downlink slots, the third downlink slot farthest from the uplink slot is usually a time slot (broadcast slot) used for broadcasting. The third uplink slot which is a pair of the broadcast slot is used for transmitting a training signal for adjusting the directivity of the antenna. This uplink slot is divided into a plurality of TDMA time slots (training slots) for training signals, and each training slot includes a CDMA code (training code) for a plurality of training signals.

  Hereinafter, a first embodiment and a second embodiment regarding the processing of the communication system 1 will be described.

(First embodiment)
FIG. 5 is a diagram for explaining processing of the base station 100 in the first embodiment. The control circuit 106 in the base station 100 uses the broadcast slot to broadcast information including the number and training code of a training slot that is a communication channel to be used by the mobile station 200 that is about to receive a new broadcast service. Then, the data is transmitted via the transmission / reception circuit 104 and the antenna 102.

  The mobile station 200 that is about to receive a new broadcast service identifies a training slot and a training code to be used based on broadcast information from the base station 100, and trains using the identified training slot and training code. Start signal transmission. When the transmission / reception circuit 104 in the base station 100 receives the training signal via the antenna 102, the control circuit 106 adjusts the directivity of the antenna 102 with respect to the transmission source mobile station 200 (optimization of the adaptive array). Do. Further, the control circuit 106 allocates a broadcast slot to the transmission source mobile station 200. Thereafter, the transmission / reception circuit 104 transmits a broadcast signal from the network 150 using the broadcast slot. Thereby, the mobile station 200 can receive a broadcast service with good quality.

  As shown in FIG. 5, the control circuit 106 in the base station 100 holds a matrix of training slots and training codes. In addition, the control circuit 106 holds a training slot and a training code that the mobile station 200 uses for uplink communication. The training slots and training codes used by the mobile station 200 for uplink communication correspond to the shaded portions of the matrix.

  When the quality of the broadcast service does not reach a desired level (for example, when the level of the received signal is equal to or lower than a predetermined value), the mobile station 200 stops transmitting the training signal using the training slot and the training code at that time. Then, transmission of a training signal using another training slot and training code is started.

  The broadcast slot includes a part including broadcast information and a part including a broadcast payload. The transmission / reception circuit 104 in the base station 100 repeatedly transmits the broadcast information through the antenna 102 by a plurality of different adaptive array patterns. Further, the transmission / reception circuit 104 transmits the broadcast payload via the antenna 102 using an optimal adaptive array pattern based on the training signal from the mobile station 200.

(Second embodiment)
FIG. 6 is a diagram for explaining the processing of the base station 100 in the second embodiment. The control circuit 106 in the base station 100 transmits broadcast information including a training slot which is a communication channel and a free state of the training code via the transmission / reception circuit 104 and the antenna 102 using the broadcast slot.

  Based on the broadcast information from the base station 100, the mobile station 200 that is about to receive a broadcast service identifies a training slot and a training code that are not used by other mobile stations 200, and the identified training slot and Start sending training signals using one of the training codes. When the transmission / reception circuit 104 in the base station 100 receives the training signal via the antenna 102, the control circuit 106 optimizes the adaptive array for the transmission source mobile station 200 for the antenna 102. Further, the control circuit 106 allocates a broadcast slot to the transmission source mobile station 200. Thereafter, the transmission / reception circuit 104 transmits a broadcast signal from the network 150 using the broadcast slot. Thereby, the mobile station 200 can receive a broadcast service with good quality.

  As shown in FIG. 6, the control circuit 106 of the base station 100 holds a matrix of training slots and training codes. In addition, the control circuit 106 holds a training slot and a training code that the mobile station 200 uses for uplink communication.

  When the quality of the broadcast service does not reach a desired level (for example, when the level of the received signal is equal to or lower than a predetermined value), the mobile station 200 stops transmitting the training signal using the training slot and the training code at that time. Then, transmission of a training signal using another training slot and training code is started.

  As shown in FIG. 6, the broadcast slot includes a part including broadcast information and a part including a broadcast payload. The base station 100 repeatedly transmits the broadcast information by a plurality of different adaptive array patterns. On the other hand, the base station 100 transmits the broadcast payload using an optimal adaptive array pattern based on the training signal from the mobile station 200.

  The following processing is performed together with the processing of the first embodiment or the second embodiment described above. When the number of training signals from each mobile station 200 received by the base station 100 reaches a value obtained by subtracting 1 from the number of antennas, the base station 100 provides a broadcast service to a part of the mobile station 200. Can not do.

  In this case, the following adaptive array optimization process is performed. In FIG. 7, when the number of training signals from each mobile station 200 received by the base station 100a reaches a value obtained by subtracting 1 from the number of antennas, control in another base station 100b adjacent to the base station 100a is performed. The circuit 106 receives training signals from several mobile stations 200 via the antenna 102 and the transmission / reception circuit 104, optimizes the adaptive array for the mobile station 200, and then the transmission / reception circuit 104 receives the antennas. A broadcast signal using a broadcast slot is transmitted via 102. That is, when the base station 100a cannot provide a broadcast service to some mobile stations 200, the other base stations 100b and 100c are in charge of the broadcast service for some mobile stations 200.

  Alternatively, the control circuit 106 in the base station 100 assigns a broadcast slot assigned to a part of another mobile station 200 that has already received the broadcast service to the mobile station 200 that is about to receive the broadcast service. Change. Thereby, in the mobile station 200, although the quality of the broadcast service is slightly lowered, the number of mobile stations 200 that receive the broadcast service can be increased.

  In order to realize such broadcast slot transfer, it is necessary that the time space and the code space of the training signal have sufficient margin for the resources of the adaptive array. Also, since data loss occurs due to a decrease in broadcast slots allocated to other mobile stations 200 that have already received the broadcast service, it is desirable to recover data by interleaving or the like.

  FIG. 8 is a diagram for explaining broadcast slot transfer processing. As shown in FIG. 8, when five broadcast slots are allocated to each of the mobile stations 200a, 200b, 200c, and 200d, when the mobile station 200e newly receives a broadcast service, The control circuit 106 transfers one broadcast slot assigned to each of the mobile stations 200a to 200d to the mobile station 200e one by one. As a result, four broadcast slots are allocated to each of the mobile stations 200a to 200e.

  Next, the selection process of the mobile station 200 that is the target of antenna directivity adjustment by the base station 100 will be described. FIG. 9 is a diagram illustrating a selection process of the mobile station 200 that is a target of antenna directivity adjustment by the base station 100. In FIG. 9, the hatched cells are the cells of the base station 100 a at the outer periphery of the service area, and the dots are the cells of the base station 100 b other than the outer periphery of the service area.

  The base station 100a at the outer periphery of the service area can communicate with the mobile station 200a located outside the service area by optimizing the adaptive array. In this case, in the broadcast service, when the control circuit 106 in the base station 100 a receives the training signal transmitted from the mobile station 200 a via the antenna 102 and the transmission / reception circuit 104, the control circuit 106 in the base station 100 a Perform optimization. Thereby, the mobile station 200a can receive the broadcast signal from the base station 100a.

  Note that mobile station 200a located outside the service area may be able to communicate with only one base station 100a on the outer periphery of the service area. In this case, other base stations other than the base station 100a as described above cannot perform processing such as receiving a training signal from the mobile station 200a and transmitting a broadcast signal. Therefore, when the number of training signals from each mobile station 200 reaches the value obtained by subtracting 1 from the number of antennas, the control circuit 106 in the base station 100a gives priority to the mobile station 200 that is the source of the training signals. , The adaptive array is optimized, and then the transmission / reception circuit 104 transmits a broadcast signal via the antenna 102.

  The priority order is determined as follows. That is, the control circuit 106 in the base station 100a in the outer periphery of the service area moves from the cell of the mobile station 200a located outside the service area and the base station 100b other than the outer periphery of the service area to its own cell. The adaptive array is optimized in the order of the mobile station 200b that is being introduced, a mobile station 200c that has a lot of delayed waves, and is clearly considered to exist in a multipath environment such as a city, and the other mobile station 200d.

  As described above, in the communication system 1 according to the present embodiment, the base station 100 receives broadcast information including a training slot number and a training code to be used by the mobile station 200 that is about to receive a new broadcast service, or training. Broadcast information including the slot and training code availability is transmitted using the broadcast slot, and the mobile station 200 performs training using either the training slot or the training code specified based on the broadcast information. Send a signal. Then, the base station 100 optimizes the adaptive array for the mobile station 200 that receives the broadcast service in response to the reception of the training signal from the mobile station 200, and the training signal is transmitted between the mobile stations 200. A broadcast service can be provided to each mobile station 200 with good quality while suppressing collision.

  As described above, the base station according to the present invention suppresses a collision of a predetermined signal for adjusting the antenna directivity between mobile stations, and provides a broadcast service to the mobile stations with good quality. It can be provided and is useful as a base station.

It is a figure which shows the structure of a communication system. It is a figure which shows the structure of a base station. It is an example of the arrangement | positioning and directivity pattern of an antenna. It is a figure which shows a communication channel structure. It is a figure explaining the process of the base station in 1st Example. It is a figure explaining the process of the base station in 2nd Example. It is a figure explaining the optimization process of an adaptive array. It is a figure explaining the transfer process of a broadcast slot. It is a figure explaining the selection process of the mobile station used as the object of antenna directivity adjustment. It is a figure explaining the process of the conventional base station.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Communication system, 100 Base station, 102 Antenna, 104 Transmission / reception circuit, 106 Control circuit, 200 Mobile station.

Claims (11)

A base station having an antenna and transmitting broadcast information to a plurality of mobile stations using a part of a plurality of downlink time slots,
A communication channel that allocates a communication channel so that each of the plurality of mobile stations can transmit a signal for adjusting the directivity of the antenna in an uplink time slot corresponding to a downlink time slot that transmits the broadcast information. Assigning means;
Directivity adjusting means for adjusting the directivity of the antenna with respect to the mobile station when receiving a signal transmitted from the mobile station for adjusting the directivity of the antenna using the communication channel; A base station characterized by comprising:   The base station according to claim 1, wherein the communication channel allocating means notifies the mobile station of information on a communication channel used by the mobile station.   2. The base station according to claim 1, wherein the communication channel allocating unit notifies the mobile station of information on availability of the communication channel.   4. The communication channel allocating unit allocates a communication channel specified based on a time slot in time division multiple access and a code in code division multiple access corresponding to the time slot. The base station described in Crab.   The base station according to claim 1, wherein the directivity adjusting unit adjusts directivities of a plurality of antennas.   The directivity adjusting means is configured to detect the first signal when the number of predetermined signals for adjusting the directivity of the antenna from the mobile station received by another base station reaches a first threshold value. The base station according to any one of claims 1 to 5, wherein the directivity of the antenna is adjusted for a number of mobile stations exceeding a threshold value.   The communication channel allocating unit is configured to perform communication for broadcast signals already allocated to the mobile station when the number of predetermined signals for adjusting the directivity of the antenna from the mobile station reaches a second threshold value. 7. The base station according to claim 1, wherein a part of the channel is transferred to a mobile station that is newly receiving a broadcast service.   The directivity adjusting means is configured to automatically detect a mobile station located outside the service area and a base station cell other than the outer circumference of the service area when the own station is located outside the service area of the broadcast service. The base station according to any one of claims 1 to 7, wherein the directivity of the antenna is adjusted in the order of a mobile station moving to a station cell and a mobile station existing in a multipath environment. A mobile station that receives broadcast information from a base station,
Means for transmitting a signal for adjusting the directivity of the antenna of the base station in an uplink time slot corresponding to a downlink time slot for receiving the broadcast information;
A mobile station characterized by that. In a mobile communication system comprising a plurality of mobile stations and a base station having an antenna and transmitting broadcast information to the plurality of mobile stations,
The base station
Communication channel allocation for allocating a communication channel so that each of the plurality of mobile stations can transmit a signal for adjusting the directivity of the antenna in an uplink time slot corresponding to a downlink time slot for transmitting the broadcast information Having means,
The mobile station
Transmitting means for transmitting a signal for adjusting the directivity of the antenna using the allocated communication channel;
The base station further comprises:
Directivity adjusting means for adjusting the directivity of the antenna with respect to the mobile station when receiving a signal transmitted from the mobile station for adjusting the directivity of the antenna using the communication channel; Having
A mobile communication system. The communication channel allocation means of the base station is
Dividing an uplink time slot corresponding to a downlink time slot for transmitting the distribution information, and determining a communication channel based on the divided time slot and a code in code division multiple access corresponding to the divided time slot assign,
The mobile communication system according to claim 10.

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