JP3001644B2 - Mobile communication system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a mobile communication system in which a base station and a mobile station communicate with each other in a TDMA system, and in particular, reduces power consumption of a mobile station receiving a data signal in a TDMA system. The present invention relates to a mobile communication system.

2. Description of the Related Art Conventionally, when a data signal addressed to a mobile station is generated, a base station communicating by the TDMA method searches for an empty slot in a TDMA channel, and transmits a data signal from the immediately following empty slot. On the other hand, the mobile station monitors each slot, and receives a data signal if a data signal addressed to the mobile station is included.

However, in order for the mobile station to determine whether or not a signal addressed to itself is transmitted in each slot, it is necessary to first receive and demodulate the signal in each slot. Further, it is necessary to read the mobile station identifier included in the signal received in the slot and determine whether or not the signal addressed to the own station is included. Therefore, the power of the mobile station is consumed by these operations. On the other hand, there is a need to extend the signal waiting time of the mobile station and reduce the size of the battery. In order to satisfy this requirement, it is desirable to reduce the power consumption when detecting a signal addressed to the own station as much as possible.

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and is capable of reducing the power consumption of a mobile station when waiting for a signal by monitoring only the start slot of a TDMA radio channel. The purpose is to provide a system.

The mobile communication system according to the present invention has a base station and a plurality of mobile stations, between the base station and each mobile station,
Using a periodic time slot, it is possible to perform data communication via a radio channel, and the base station includes a mobile station identifier including a mobile station identifier of a destination mobile station and a data signal addressed to the mobile station. Transmitting a plurality of slot signals in one or more consecutive time slots starting from one of a plurality of periodic start slots that are part of the periodic time slot; Receiving a slot signal at each of a plurality of starting slots;
When a slot signal including the mobile station identifier of the mobile station is received in a certain start slot, all slot signals addressed to the mobile station are received in one or more slots starting from the start slot. It is.

According to such a mobile communication system, since the mobile station monitors only the start slot, the operation time of the receiving device is shorter than in the case where all the slots are monitored, so that the battery consumption of the mobile station is reduced. be able to.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram illustrating a configuration of a communication system according to a first embodiment.

 FIG. 2 is an explanatory diagram showing the configuration of the data signal 32.

FIG. 3 is an explanatory diagram showing the configuration of the TDMA radio channel 30.

 FIG. 4 is an explanatory diagram showing the configuration of an empty slot.

FIG. 5 is an explanatory diagram showing a configuration of a signal slot for transmitting the data signal 32.

FIG. 6 is an explanatory diagram showing a method of transmitting an empty slot and a signal slot in the TDMA radio channel 30.

FIG. 7 is an explanatory diagram showing an operation of the receiving device 23 when there is no signal to be transmitted from the base station 10 to the mobile stations 20 and 21.

FIG. 8 is an explanatory diagram showing the operation of the receiving device 23 when the start slot 90 is periodically arranged on the TDMA radio channel 30.

FIG. 9 is an explanatory diagram showing the operation of the receiving device 23 when there is a signal to be transmitted from the base station 10 to the mobile station 20.

FIG. 10 is an explanatory diagram showing a method in which the mobile stations 20 and 21 determine the position of the start slot 90.

FIG. 11 is an explanatory diagram showing operations of the mobile stations 20 and 21 when there are two or more signals to be transmitted from the base station 10 to the mobile station 20.

FIG. 12 is an explanatory diagram illustrating an operation example of the base station 10 and the plurality of mobile stations 20 and 21.

FIG. 13 is an explanatory diagram showing operations of the base station 10 and the mobile station 20 when transmitting a common signal to the plurality of mobile stations 20 and 21.

FIG. 14 is an explanatory diagram showing the configuration of the transmission mode signal 87.

 FIG. 15 is an explanatory diagram showing the configuration of the notification signal 80.

 FIG. 16 is an explanatory diagram showing the configuration of the data signal 86.

FIG. 17 is an explanatory diagram showing the operation of the mobile stations 20 and 21 when notifying the arrangement of the start slots 90 and 91 by the notification signal 80.

FIG. 18 shows starting slots 90, 91 or a common starting slot.
FIG. 10 is an explanatory diagram showing the configuration of a slot designation signal 60 for designating the arrangement of 95.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.

Embodiment 1 A. Hardware Configuration of Embodiment FIG. 1 is a block diagram illustrating a configuration of a mobile communication system according to the present embodiment. In the figure, the mobile communication system includes a base station 10 and one or more mobile stations 20 and 21, and the base station 10 and the mobile stations 20 and 21 communicate via a TDMA radio channel 30. Further, the base station 10 is provided with a transmitting device 11 for transmitting a signal via the TDMA radio channel 30, and a control device 12 for generating a signal and controlling the operation of the transmitting device 11. On the other hand, the mobile station 20 is provided with a receiving device 23 that receives a signal via the TDMA radio channel 30, and a control device 22 that analyzes the signal and controls the operation of the receiving device 23.

B. Data Structure in Embodiment Here, various data structures transmitted in this embodiment will be described. First, FIG. 2 shows a configuration of a data signal 32 transmitted from the base station 10 to the mobile stations 20 and 21. The data signal 32 includes a mobile station identifier 34 indicating a destination.
And data 36 transmitted to the mobile stations 20 and 21.

FIG. 3 shows a configuration of the TDMA radio channel 30. The TDMA radio channel 30 is composed of continuous slots 40. In the slot 40, a slot type 41 indicating the type of slot, a continuous slot number 42 indicating the number of slots continuously used for transmitting the data signal 32, and a signal unit 43 are transmitted. Then, the data signal 32 is transmitted by being included in one or more signal units 43.

FIG. 4 shows a slot when there is no data signal to be transmitted.
4 shows a configuration of a slot signal transmitted using 40. The slot type 41 indicates that the slot signal is an empty slot signal that does not include a data signal, and the number of continuous slots 42 indicates “0”. The signal section 43 is not used.

Next, FIG. 5A shows a configuration of a slot signal when the data signal 32 is transmitted in a plurality of slots. In the first slot signal, the slot type 41 indicates that it is the first slot. Also, the number of continuous slot signals, that is, “3” is described in the continuous slot number 42. Further, the head portion of the data signal 32 is described in the signal section 43. Next, the slot type 41 of the slot signal following this indicates that the slot signal is a continuous slot signal. Then, the remaining portion of the data signal 32 is described in the signal portion 43 of the continuous slot signal.

By the way, there is a case where the data signal 32 can be transmitted in one slot. In such a case, only a single slot signal as shown in FIG. 5B is transmitted. The slot type 41 of this slot signal indicates that it is the first slot signal, and the number of continuous slots 42 is “0”.

Next, FIG. 6 shows a state where an empty slot signal having no data signal 32 and a slot signal having a data signal are transmitted via the TDMA radio channel 30. In FIG. 6, the hatched slot signals are slot signals including data signals, and the unhatched slot signals are empty slot signals. When the data signal 32 is generated, one or a plurality of slot signals corresponding to the data signal 32 are continuously transmitted. Then, an empty slot signal is transmitted during a period in which no slot signal is transmitted.

C. Operation of Embodiment C.1. Monitoring of Data for Own Station by Mobile Station Next, FIG. 7 shows an operation of the base station 10 when there is no signal to be transmitted to the mobile stations 20 and 21. In such a case, the control device 12
Causes the transmitting device 11 to transmit an empty slot signal in all slots of the TDMA radio channel 30. Here, a slot that occurs at a predetermined timing in the TDMA radio channel 30 is assumed, and this slot is referred to as a “start slot”. The control device 22 of each of the mobile stations 20 and 21 outputs a command to the reception device 23 to start reception in the start slot 90.

When receiving the command, the receiving device 23 receives a signal in the start slot 90 and supplies the signal to the control device 22. Control device 22 detects whether or not the signal received in start slot 90 is an empty slot signal.
If the signal is an empty slot signal, the receiving device 23 determines that no signal addressed to the own station has been generated and stops reception.
To instruct.

Here, as shown in FIG. 8, the start slots 90 are periodically arranged on the TDMA radio channel 30. Thus, the mobile stations 20 and 21 need only monitor the start slot 90.

C.2. Data Transmission to Mobile Station (Single) Next, the operation when transmitting various data to the mobile stations 20 and 21 will be described. The operation when the data signal to be transmitted is singular is described. Let me explain first.

As shown in FIG. 9, the base station 10
The signal generated before the occurrence of is generated is transmitted with the start slot 90 as a starting point. For example, when a data signal 32 to be transmitted to the mobile station 20 occurs at time t10, the control device 1 of the base station 10
2 suspends transmission of the data signal 32 until the start time t11 of the start slot 90. Next, control device 12 causes transmitting device 11 to transmit an empty slot signal up to the slot immediately before start slot 90, and to start transmitting data signal 32 from start slot 90. Then, when the transmission device 11 completes transmission of the data signal 32, the control device 12 causes the transmission device 11 to transmit an empty slot signal.

The control device 22 of the mobile stations 20 and 21 instructs the reception device 23 to start receiving a signal in the start slot 90. Accordingly, the receiving device 23 receives the information in the start slot 90 and supplies the information to the control device 22. The control device 22 is a receiving device
It is determined based on the information received from 23 whether or not to continue the reception. That is, the control device 22 transmits the data signal addressed to its own station.
If it is the first slot signal of 32, the reception is continued, and then the reception device 23 is instructed to stop the reception after the reception of the slot signal including the data signal 32 is completed.

On the other hand, when a free slot signal or a slot signal having a signal addressed to another station is received in the start slot 90, the reception is stopped.

Here, a method in which the mobile stations 20 and 21 determine the position of the start slot 90 on the TDMA radio channel 30 will be described with reference to FIG. First, in each slot, a synchronization word for the mobile stations 20 and 21 to synchronize with the slot is transmitted. When the communication starts, the mobile stations 20 and 21
In each of the slots, the synchronization word is continuously received to synchronize with the slot. In the present embodiment, two types of synchronization words 50 and 52 are employed. Base station 10 transmits synchronization word 50 in slot 90 and transmits synchronization word 52 in the other slots. The mobile stations 20 and 21 continuously receive slots at the start of communication, and determine that "the slot receiving the synchronization word 50 is the start slot 90". This allows mobile station 2
0, 21 can determine the position of the start slot 90 in parallel with synchronizing the slots.

In the above operation, the arrangement of the start slot 90 may be dynamically determined based on the transmission delay of the downlink signal requested by the mobile stations 20 and 21 and the battery consumption. For example, if the signal traffic is low and a large delay from the occurrence of a signal at the base station 10 to the transmission to the mobile stations 20 and 21 is allowed, the interval between the start slots 90 is increased, and a large delay is not allowed. In this case, the interval between the start slots 90 may be reduced.

In the operation described above, since the mobile stations 20 and 21 monitor the arrival of the slot signal addressed to the own station only in the start slot 90, the operation time of the receiving device 23 is shorter than the case where all the slots are monitored. Therefore, mobile stations 20, 21
Battery consumption can be reduced.

C.3. Data Transmission to Mobile Station (Plural) Next, the operation when the base station 10 transmits a plurality of data signals 32 to the mobile stations 20 and 21 will be described. FIG. 11 shows a state where two data signals 32 to be transmitted from the base station 10 exist. When two data signals 32 are generated in the base station 10, the controller 12 suspends transmission of the data signal 32 until the start slot 90. Next, the control device 12 instructs the transmission device 11 to transmit a signal slot including the two data signals 32 from the start slot 90.
These signals are transmitted from 11. Then, when the transmission of the slot signal is completed, the control device 12 causes the transmitting device 11 to transmit an empty slot signal.

The receiving devices 23 of the mobile stations 20 and 21 start receiving signals from the start slot 90 and transmit the signals to the control device 22. Next, the control device 22 determines whether or not to continue the reception based on the signal received from the receiving device 23. That is, if the mobile station identifier 34 indicating the own station is included in the signal portion 43 of the slot signal received in the start slot, the signal is received in the number of continuous slots indicated by the number of continuous slots 42 in the same slot signal. To the receiving device 23 as follows. According to such an instruction, the receiving apparatus 23 receives in a series of continuation slots. After the slot signal is received in these series of continuation slots, the receiving apparatus 23 receives the slot signal in another slot. Then, if the mobile station identifier 34 indicating the own station is included in the slot signal, the slot signal is further received in the number of continuous slots indicated by the continuous slot number 42.

On the other hand, if the received slot signal is an empty slot signal or a slot signal addressed to another mobile station, control device 22 instructs receiving device 23 to stop reception. As described above, in the above-described operation, by continuously transmitting a plurality of signals, the signal delay time can be reduced.

C.4. Broadcasting etc. Next, an operation in the case of transmitting a common signal to a plurality of mobile stations (broadcasting etc.) will be described with reference to FIGS. First, as shown in FIG. 12, base station 10 transmits a signal addressed to mobile station 20 from start slot 90, and transmits a signal addressed to mobile station 21 from start slot 91. The mobile station 20 monitors the arrival of the slot signal addressed to the own station in the start slot 90, and the mobile station 21 monitors the arrival of the slot signal addressed to the own station in the start slot 91.

As shown in FIG. 13, base station 10 transmits data signal 32 transmitted to both mobile station 20 and mobile station 21 in common start slot 95. The mobile station identifier 34 of the data signal 32 indicates both the mobile station 20 and the mobile station 21. here,
The position of the common start slot 95 on the TDMA radio channel 30 is predetermined. Also, the mobile station 20 and the mobile station 21
Common start slot 95 in addition to start slot 90 or 91
To monitor. If the slot signal received in the common start slot 95 includes a signal addressed to the own station, the reception is stopped after the slot signal is received in a slot subsequent to the common start slot 95. On the other hand, if the received slot signal is an empty slot signal or a slot signal addressed to another station, the reception is stopped.

In the operation described above, by distributing the start slots for each mobile station, the battery consumption of the mobile station can be reduced while ensuring signal transmission to each mobile station. In addition, by providing a common start slot 95 in which a plurality of mobile stations start reception in common, a delay in transmitting a signal common to a plurality of mobile stations is reduced when an individual slot is used for each mobile station. Less. TDMA radio channel 30
Use efficiency is increased.

C.5. Mode Switching A conventionally known mobile station continuously monitors the TDMA radio channel 30. Needless to say, such mobile stations and mobile stations that monitor only the start slot 90 based on the present embodiment may coexist. On the other hand, also in the mobile station 20 according to the present embodiment, it is conceivable that the traffic becomes large or the allowable transmission delay becomes small. In such a case, it is preferable that the TDMA radio channel 30 can be continuously monitored.

Therefore, in this embodiment, in such a case, the base station
Under the control of 10, the modes of the mobile stations 20, 21 are switched, and accordingly, the base station 10 can change the transmission mode. Conversely, the base station 10 may switch the transmission mode in response to a request from the mobile stations 20 and 21.

FIG. 14 shows a configuration of a transmission mode signal 87 that requests the base station 10 to switch the transmission mode from the mobile stations 20 and 21. The transmission mode signal 87 includes the mobile station identifier 34, a signal type 82 indicating a transmission mode signal, and transmission mode information 88 indicating a signal transmission method. Transmission mode information 88
Is, for example, a continuous transmission mode to start transmitting a data signal at an arbitrary time, a start slot 90 and a common start slot.
It indicates the intermittent transmission mode in which data signal transmission is started with only 95. The mobile stations 20 and 21 transmit a transmission mode signal 87 to the base station 10 before or during communication. Upon receiving the transmission mode signal 87, the base station 10
The signal is transmitted by the transmission method requested by 21.

According to this operation, when traffic is large or when the allowable transmission delay is small, data can be transmitted as quickly as in the past by switching to the continuous transmission mode. Also, the transmission method can be changed to the intermittent transmission mode at the start of communication and during communication according to the limitation of the battery consumption of the mobile station. Further, the transmission mode signal 87
May change the interval of the start slot.

In the above embodiment, the mobile stations 20 and 21 request the base station 10 to change the transmission mode.However, the present invention is not limited to this.For example, in the base station 10, for each of the mobile stations 20 and 21, Maintain a list of matching transmission modes for each,
The transmission mode of each mobile station 20, 21 may be switched according to the list. Since the mobile stations 20 and 21 are each provided with a mobile station identifier unique to the mobile station, the base station
In 10, the transmission mode for each is held in association with the mobile station identifier. The contents of the list are:
It is set in advance by some input means or the like.

(Second Embodiment) A. Hardware Configuration and Data Structure of the Embodiment The hardware configuration of the present embodiment is the same as that of the first embodiment, but there are some differences in the data structure as described in detail below.

That is, in the present embodiment, the start slot information 85 indicating the position of the start slot 90 of each mobile station is
80, is transmitted from the base station 10 to the mobile stations 20, 21.
The base station 10 may follow the notification signal 80 followed by one or more data signals 86
To the mobile stations 20 and 21.

FIG. 15 shows a configuration of the notification signal 80. The notification signal 80 includes a mobile station identifier 34 for identifying one or more mobile stations that should receive this signal, a signal type 82 indicating a notification signal, and a mobile station identifier list 83. Mobile station identifier list 83
Includes the individual mobile station identifier 84 indicating the destination of each of the one or more signals and the start slot information 85 indicating the position of the start slot of the data signal 86.

FIG. 16 shows the configuration of the data signal 86. Data signal 86
Comprises a mobile station identifier 34 for identifying a mobile station, a signal type 82 indicating a data signal, and data 36.

B. Operation of Embodiment Next, the operation of the base station 10 and the mobile station 20 will be described with reference to FIG.

The base station 10 receives the data signal 86 addressed to the mobile station 20 and the mobile station 20.
When a data signal 86 addressed to 21 is generated, the mobile station identifier 34 indicating that the mobile station 20 and the mobile station 21 should receive, the individual mobile station identifier 84 of the mobile station 20, and the start slot information 8
5, and a notification signal 80 including the individual mobile station identifier 84 of the mobile station 21 and the start slot information 85 is generated and transmitted from the common start slot 95. Further, a data signal 86 addressed to the mobile station 20 is transmitted from a start slot 90 indicated by start slot information 85 following the individual mobile station identifier 84 of the mobile station 20.
Further, a data signal 86 addressed to the mobile station 21 is transmitted from a start slot 91 indicated by start slot information 85 following the individual mobile station identifier 84 of the mobile station 21. The data signal 86 is transmitted by one or more slots as in FIG.

The mobile station 20 starts reception from a start slot 90 indicated by start slot information 85 following the individual mobile station identifier 84 of the mobile station 20. Then, if the received slot signal is a slot signal to be received by the own station, reception is continued. On the other hand, if the received slot signal is an empty slot signal or a slot signal addressed to another station, the reception is stopped.

Here, it will be explained why the start slot 90 can be a slot addressed to another station. Since the start slot is allocated to each mobile station, reception of information is generally completed before the start slot of another station occurs. However, if the number of serving mobile stations increases and the interval between start slots narrows, or if the traffic for a particular mobile station increases significantly, the particular (to other station) start slot will occur until that particular start slot. This is because the slot of the mobile station is extended.

In the example shown in FIG. 17, since the start slot 90 is the next slot after the common start slot 95, the mobile station 20 receives the data signal 86 following the notification signal 80, and thereafter stops receiving. . Also, since the start slot 91 is far from the common slot 95, the mobile station 21
, The reception is stopped once, and the reception is started again from the start slot 91. Then, the mobile station 21 stops receiving after further receiving the data signal 86.

In the present embodiment, the presence / absence of a signal is notified to one or more mobile stations by the notification signal 80, so that the presence / absence of a data signal in the mobile station can be determined earlier than in the case where signals are sequentially transmitted to one or more mobile stations. Can be notified. Therefore, the transmission delay of the data signal can be reduced. Also, the use efficiency of the TDMA radio channel is improved.

(Modification) Although the embodiment of the invention has been described above, the technical scope of the invention according to the present application is not limited to the above embodiment. The invention described in the claims can be implemented by adding various changes to the above embodiment. It is obvious from the description of the claims that such an invention belongs to the technical scope of the invention according to the present application.

For example, the above embodiment can be variously modified as follows, for example.

The arrangement of the start slots 90 and 91 and the common start slot 95 may be determined by the base station 10 according to a predetermined algorithm. In this case, the base station 10 may notify the base stations 20 and 21 of the arrangement of the start slots 90 and 91 in the first embodiment and the arrangement of the common start slot 95 in the first and second embodiments by the slot designation signal 60.

FIG. 18 shows the configuration of this slot designation signal 60. The slot designation signal 60 is a mobile station identifier 3 for identifying the mobile station 20.
7, a signal type 82 indicating the slot designation signal 60,
And slot information 62. The slot information 62 indicates the arrangement of the start slots 90 and 91 in the first embodiment and the arrangement of the common start slot 95 in the first and second embodiments.

The base station 10, for example, the number of mobile stations, allowable transmission delay,
Using the amount of signals unique to each mobile station, the amount of signals common to a plurality of mobile stations, the signal generation characteristics, and the like as parameters, the start slots 90 and 91 and the common start slot Determine the placement. Then, based on the slot information 62, the mobile stations 20 and 21
The positions of 90, 91 and the common start slot 95 are determined.

Further, the slot designation signal 60 may be transmitted on a TDMA wireless channel for control different from the TDMA wireless channel 30 for communication. In this case, the mobile stations 20 and 21 receive the slot designation signal 60 on the control TDMA radio channel, and then
Switch to wireless channel 30. After that, the designated start slots 90 and 91 and the common start slot 95 are monitored.
Thus, the arrangement of the start slots 90 and 91 and the common start slot 95 can be flexibly determined according to the situation. The mobile station 20 may determine the start slots 90 and 91 and the common start slot 95 and notify the base station 10.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Katsumi Kobayashi 3-42-5-103 Higashiyama, Konan-ku, Yokohama-shi, Kanagawa Prefecture (72) Tadao Takami 3-21-10 Oyabe, Yokosuka-shi, Kanagawa 102 Oyabe Heights 102 (56 ) References JP-A-2-203632 (JP, A)

Claims (13)

(57) [Claims] A base station and a plurality of mobile stations, wherein the base station and each of the mobile stations can communicate with each other via a radio channel using a periodic time slot; The base station transmits one or more slot signals including a mobile station identifier of a destination mobile station and a data signal addressed to the mobile station to a plurality of periodic start slots that are part of the periodic time slot. Transmitting in one or more consecutive time slots starting from one of the following: each mobile station receives a slot signal in each of the periodic plurality of start slots, and the mobile station of the mobile station in a certain start slot When a slot signal including an identifier is received, all slot signals addressed to the mobile station are received in one or more slots starting from the start slot. Mobile communication system to be. 2. The mobile station, wherein the slot signal includes a continuous slot number indicating the number of subsequent slot signals, and wherein the slot signal received in the start slot includes a mobile station identifier corresponding to the mobile station. 2. The mobile communication system according to claim 1, wherein if the number of consecutive slot signals is equal to the number of continuous slots included in the slot signal, the number of continuous slot signals is subsequently received. 3. The base station transmits an empty slot signal not including a data signal when there is no data signal to be transmitted to the mobile station, and the mobile station transmits the empty slot signal or the empty slot signal in the start slot. 2. The reception of a slot signal including a mobile station identifier of a mobile station other than the mobile station is stopped until the next start slot.
Or the mobile communication system according to 2. 4. The mobile station further receives a slot signal immediately after receiving the number of continuous slot signals corresponding to the number of continuous slots, and the slot signal includes a mobile station identifier designating the mobile station. If there is no mobile station, the receiving operation is stopped, and if the slot signal includes a mobile station identifier designating the mobile station, all subsequent slot signals addressed to the mobile station are received. 3. The mobile communication system according to claim 1. 5. The mobile communication system according to claim 1, wherein said different start slot is determined for each mobile station. 6. The mobile communication system according to claim 1, wherein the start slot may overlap among a plurality of mobile stations. 7. The base station transmits a notification signal indicating the start slot corresponding to the mobile station, and the mobile station starts receiving a slot signal in the start slot indicated by the notification signal. The mobile communication system according to claim 1, wherein: 8. The mobile station, comprising: a first receiving mode for monitoring a slot signal transmitted from the base station only in the start slot; and a mobile station for monitoring a slot signal transmitted from the base station in all time slots. Second to monitor
The base station, when the mobile station is in the second reception mode, the data signal to the mobile station, immediately after the data signal is generated And transmitting the data signal to the mobile station from the start slot when the mobile station is in the first reception mode. Mobile communication system. 9. The mobile communication system according to claim 8, wherein the mobile station notifies the base station of a selected one of the first reception mode and the second reception mode. 10. The base station transmits a first synchronization word in the start slot, and transmits a second synchronization word in a time slot other than the start slot. The mobile communication system according to claim 1, wherein reception timing is synchronized with the start slot by receiving first and second synchronization words. 11. The base station transmits a common data signal to the plurality of mobile stations in a predetermined common start slot, and a receiving device of the mobile station transmits the common data signal in the common start slot. The mobile communication system according to claim 1, wherein the mobile communication system receives a signal. 12. A base station device of a mobile communication system that communicates with a plurality of mobile stations via a wireless channel using a periodic time slot, wherein a data signal to be transmitted to one mobile station is provided. Is given, the data signal and the one or more slot signals including the mobile station identifier of the mobile station, the one or more starting from one of the periodic start slots which is a subset of the periodic time slot or A base station apparatus transmitting in a plurality of continuous time slots. 13. A mobile station apparatus that communicates with a base station of a mobile communication system via a wireless channel using a periodic time slot, wherein the periodic time slot is a subset of the periodic time slot. If a slot signal is received from the base station in a start slot and a slot signal addressed to the mobile station is received in a certain start slot, all of the slot signals addressed to the mobile station in one or a plurality of time slots starting from the start slot are received. A mobile station device receiving a slot signal.