JPWO1997034385A1 - Mobile communication systems - Google Patents

Abstract

(57) [Abstract] When there is a data signal of a length that can be transmitted in one slot of a TDMA radio channel, a base station generates a first slot having a mobile station identifier indicating the destination mobile station and the data signal. When there is a data signal of a length that cannot be transmitted in one signal slot, a continuation slot is generated that includes the first slot and at least a portion of the data signal. The base station transmits the first slot in a start slot located at a position determined for each mobile station on the TDMA radio channel, and transmits the continuation slots in slots following the start slot. The mobile station receives the start slot, and stops receiving if the start slot is not the first slot. If the start slot is the first slot, the mobile station determines the mobile station identifier, and stops receiving if the mobile station identifier indicates a mobile station other than the mobile station, and receives the continuation slots if the mobile station identifier indicates the mobile station itself.

Description

[Detailed Description of the Invention] Mobile Communication System Technical Field The present invention relates to a mobile communication system in which base stations and mobile stations communicate using the TDMA method, and in particular to a mobile communication system that can reduce the power consumption of mobile stations receiving data signals using the TDMA method.

Technical Background Conventionally, when a base station communicating using TDMA receives a data signal addressed to a mobile station, it searches for an open slot in the TDMA channel and transmits the data signal in the next available slot. Meanwhile, the mobile station monitors each slot and, if one is included, receives the data signal addressed to itself.

However, for a mobile station to determine whether a slot contains a signal addressed to it, it must first receive and demodulate each slot. It must then read the mobile station identifier contained in that slot and determine whether a signal addressed to it is included. These operations consume power. On the other hand, there is a demand for extending the mobile station's signal standby time while minimizing battery size. To meet this demand, it is desirable to minimize the power consumption required to detect signals addressed to the mobile station.

DISCLOSURE OF THE INVENTION The present invention was conceived in consideration of the above-mentioned circumstances, and aims to provide a mobile communication system that can reduce the power consumption of mobile stations during signal standby by monitoring only the start slot of a TDMA radio channel.

The present invention aims to solve the above problems by providing the following configuration.

(1) In a mobile communication system for transmitting a data signal from a base station to a mobile station using a TDMA radio channel consisting of slots, the base station comprises: means for generating a first slot having a mobile station identifier indicating the destination mobile station and a subsequent slot having at least a portion of the data signal; means for transmitting the first slot in a start slot located at a position on the TDMA radio channel that is determined for each mobile station; and means for transmitting the subsequent slot in the slot following the start slot; and the mobile station comprises means for monitoring the start slot, means for determining the mobile station identifier if the start slot is the first slot, and means for receiving the subsequent slot if the mobile station identifier indicates the mobile station.

Therefore, according to the mobile communication system of the present invention, the mobile station monitors only the start slot, which shortens the operating time of the receiving device compared to when all slots are monitored, thereby reducing battery consumption of the mobile station.

(2) The base station further comprises means for transmitting an empty slot not containing the data signal when the data signal is not present, and the mobile station further comprises means for suspending reception until the next start slot if the start slot is the empty slot or the continuation slot.

Therefore, according to the mobile communication system of the present invention, reception is stopped if the received slot is an empty slot or a signal slot addressed to another mobile station. Therefore, by transmitting multiple signals consecutively, the signal delay time can be reduced.

(3) The base station further comprises means for generating multiple types of synchronization words for the mobile station to synchronize with the slot, and means for transmitting the slot with a synchronization word selected from the multiple types of synchronization words based on whether the slot is the start slot, and the mobile station further comprises means for determining whether the slot is the start slot based on the type of the synchronization word.

Therefore, according to the mobile communication system of the present invention, the mobile station can determine the position of the start slot while simultaneously synchronizing with the slot.

(4) The base station provides a common start slot at a predetermined position on the TDMA radio channel, and when transmitting a common data signal to multiple mobile stations, the base station comprises: means for generating a first slot having a mobile station identifier indicating the multiple mobile stations and a continuation slot having at least a portion of the data signal; means for transmitting the first slot in the common start slot; and means for transmitting the continuation slot in the slot following the common start slot; and the mobile station comprises: means for monitoring the common start slot in addition to the start slot determined for each mobile station; means for determining the mobile station identifier when the common start slot is the first slot; and means for receiving the continuation slot if the mobile station identifier indicating the mobile station is included in the mobile station identifiers.

Therefore, according to the mobile communication system of the present invention, by distributing slots for each mobile station, it is possible to reduce battery consumption of the mobile stations while ensuring signal transmission to each mobile station. Furthermore, by providing a common start slot at which multiple mobile stations start reception, the delay when transmitting a common signal to multiple mobile stations can be reduced compared to the delay when individual slots are used for each mobile station. Furthermore, since overlapping signal transmissions are eliminated, the utilization efficiency of TDMA radio channels can be improved.

(5) The base station further comprises means for transmitting a notification signal indicating the position of the start slot for each of the mobile stations, and the mobile stations further comprise means for starting reception from the start slot indicated in the notification signal.

Therefore, according to the mobile communication system of the present invention, since the notification signal notifies one or more mobile stations of the presence or absence of a signal, the presence or absence of a data signal can be notified to the mobile stations more quickly than in a case where signals are transmitted sequentially to one or more mobile stations. This reduces the transmission delay of the data signal and improves the utilization efficiency of the TDMA radio channel.

(6) The mobile station further comprises means for transmitting a reception mode indicating whether to monitor all slots or only the start slot, and means for monitoring the slot in the transmitted reception mode; and the base station further comprises means for receiving the reception mode, and means for transmitting the data signal to the mobile station that transmitted the reception mode from the slot immediately following the generation of the data signal when the reception mode indicates that all slots are to be monitored, and means for transmitting the data signal to the mobile station that transmitted the reception mode from the start slot when the reception mode indicates that only the start slot is to be monitored.

Therefore, in the mobile communication system of the present invention, the base station can switch transmission modes upon request from the mobile station. Furthermore, when traffic is heavy or the allowable transmission delay is small, switching to continuous transmission mode allows data to be transmitted as quickly as before. Furthermore, the transmission method can be changed to intermittent transmission mode at the start of communication or during communication, depending on the mobile station's battery consumption limits.

(7) The base station further comprises means for transmitting a slot designation signal including information indicating the position of the start slot, and the mobile station further comprises means for receiving the slot designation signal and means for determining the position of the start slot from the slot designation signal.

Therefore, according to the mobile communication system of the present invention, the arrangement of the start slot and the common start slot can be flexibly determined depending on the situation.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an explanatory diagram showing the configuration of a communication system according to the 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 the configuration of a signal slot for transmitting a data signal 32. As shown in FIG.

FIG. 6 is an explanatory diagram showing a method for transmitting idle slots and signal slots in a TDMA radio channel 30.

FIG. 7 is an explanatory diagram showing the operation of the receiver 23 when the base station 10 has no signal to transmit to the mobile stations 20 and 21.

FIG. 8 is an explanatory diagram showing the operation of the receiver 23 when start slots 90 are periodically placed 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 how mobile stations 20 and 21 determine the location of the starting slot 90.

FIG. 11 is an explanatory diagram showing the operation of mobile stations 20 and 21 when base station 10 has two or more signals to transmit to mobile station 20.

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

FIG. 13 is an explanatory diagram showing the operation of the base station 10 and the mobile station 20 when transmitting a common signal to multiple 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 mobile stations 20 and 21 when notification signal 80 notifies the allocation of start slots 90 and 91.

FIG. 18 is an explanatory diagram showing the configuration of the slot designation signal 60 that designates the placement of the start slots 90, 91, or the common start slot 95.

Best Mode for Carrying Out the Invention An example of an embodiment of the present invention will now be described with reference to the drawings.

(Embodiment 1) A. Hardware Configuration of the Embodiment Figure 1 is a block diagram showing the configuration of a mobile communication system according to this embodiment. In the figure, this mobile communication system includes a base station 10 and one or more mobile stations 20, 21. The base station 10 and the mobile stations 20, 21 communicate via a TDMA radio channel 30. The base station 10 also includes a transmitter 11 that transmits signals over the TDMA radio channel 30 and a controller 12 that generates signals and controls the operation of the transmitter 11. The mobile station 20 also includes a receiver 23 that receives the TDMA radio channel 30 and a controller 22 that analyzes the signals and controls the operation of the receiver 23.

B. Data Structure in the Embodiment Here, various data structures used in this embodiment will be explained. First, Figure 2 shows the structure of a data signal 32 transmitted from base station 10 to mobile stations 20 and 21. This data signal 32 is composed of a mobile station identifier 34 indicating the destination and data 36 to be transmitted to mobile stations 20 and 21.

3 also shows the configuration of a TDMA radio channel 30. This TDMA radio channel 30 is composed of consecutive slots 40. Each slot 40 has a slot type 41 indicating the type of slot, a number of consecutive slots 42 indicating the number of consecutive slots that make up a data signal 32, and a signal portion 43. The data signal 32 is written in one or more signal portions 43.

Figure 4 shows the configuration of a slot 40 when no data signal is included. The slot type 41 indicates an empty slot, and the number of consecutive slots 42 indicates "0." The signal portion 43 is unused.

Next, Figure 5(A) shows the slot configuration when a data signal 32 is transmitted over multiple slots. In the first slot, the slot type 41 indicates that it is the first slot. The number of subsequent slots 42 indicates the number of subsequent slots, i.e., "3." The signal portion 43 contains the beginning of the data signal 32. Next, the slot type 41 of the subsequent slot indicates that it is a subsequent slot. The signal portion 43 of the subsequent slot contains the remaining portion of the data signal 32.

However, it is also possible that the data signal 32 can be transmitted in one slot.

In this case, only a single slot is transmitted, as shown in Figure 5(B). The slot type 41 of this slot indicates that it is the first slot, and the number of consecutive slots 42 is "0."

Next, Figure 6 shows the state in which empty slots without a data signal 32 and signal slots with a signal are transmitted over the TDMA radio channel 30. In Figure 6, hatched slots are signal slots, and unhatched slots are empty slots. When a data signal 32 is generated, one or more corresponding signal slots are transmitted consecutively. During periods when no signal slots are transmitted, empty slots are transmitted.

C. Operation of the Embodiment C.1. Monitoring of Data Destined for Mobile Station Next, Figure 7 shows the operation of the base station 10 when there is no signal to transmit to the mobile stations 20 and 21. In this case, the control device 12 causes the transmitter 11 to transmit an empty slot in all slots of the TDMA radio channel 30. Here, we assume a slot that occurs at a predetermined timing in the TDMA radio channel 30, and refer to this slot as the "start slot." Upon receiving the start slot 90, the control device 22 of the mobile stations 20 and 21 outputs a command to the receiver 23 to begin reception.

Upon receiving this command, the receiver 23 receives the start slot 90 and supplies it to the controller 22. The controller 22 then determines whether the start slot 90 is an empty slot. If it is an empty slot, it determines that no signal addressed to the receiver 23 has been generated and instructs the receiver 23 to stop receiving.

As shown in FIG. 8, start slots 90 are periodically allocated on TDMA radio channel 30. This allows mobile stations 20 and 21 to monitor only start slots 90.

C. 2. Data Transmission to Mobile Station (Single) Next, we will explain the operation when transmitting various types of data to mobile stations 20 and 21. We will first explain the operation when a single data signal is to be transmitted.

As shown in Figure 9, base station 10 transmits signals generated before a certain start slot 90, starting from that start slot 90. For example, when data signal 32 to be transmitted to mobile station 20 occurs at time t10, control device 12 of base station 10 suspends transmission of data signal 32 until transmission start time t11 of start slot 90. Next, control device 12 causes transmitter 11 to transmit empty slots up to the slot immediately preceding start slot 90, and then starts transmitting data signal 32 from start slot 90. Then, when transmitter 11 completes transmission of data signal 32, control device 12 causes transmitter 11 to transmit the empty slot.

The control device 22 of the mobile stations 20 and 21 instructs the receiving device 23 to start receiving a signal at the start slot 90. The receiving device 23 then receives information about the start slot 90 and provides it to the control device 22. The control device 22 determines whether to continue reception based on the slot received from the receiving device 23. That is, the control device 22 continues reception if the slot is the first slot of the data signal 32 addressed to the mobile station, and then instructs the receiving device 23 to stop reception after completing reception of the signal slot containing the data signal 32.

On the other hand, if the start slot 90 is an empty slot or a slot containing a signal addressed to another station, reception is stopped.

Here, using FIG. 10 , we will explain how the mobile stations 20 and 21 determine the location of the start slot 90 on the TDMA radio channel 30. First, each slot contains a synchronization word that the mobile stations 20 and 21 use to synchronize to the slot. When communication begins, the mobile stations 20 and 21 receive successive slots on the TDMA radio channel 30 to synchronize to the slot. In this embodiment, two types of synchronization words 50 and 52 are used. The base station 10 transmits synchronization word 50 in slot 90 and synchronization word 52 in other slots. When communication begins, the mobile stations 20 and 21 receive successive slots and determine that the slot in which they receive synchronization word 50 is the start slot 90. This allows the mobile stations 20 and 21 to determine the location of the start slot 90 while simultaneously synchronizing to the slots.

In the above operation, the placement of the start slot 90 may be dynamically determined based on the downlink signal transmission delay and battery consumption required by the mobile stations 20 and 21.

For example, if signal traffic is low and a large delay between the generation of a signal at the base station 10 and its transmission to the mobile stations 20 and 21 can be tolerated, the interval between the start slots 90 can be increased; if a large delay cannot be tolerated, the interval between the start slots 90 can be decreased.

In the operation described above, the mobile stations 20 and 21 monitor only the start slot 90, which shortens the operating time of the receiver 23 compared to when all slots are monitored. This reduces battery consumption in the mobile stations 20 and 21.

C. 3. Data Transmission to Mobile Stations (Multiple) Next, we will explain the operation when transmitting multiple data signals 32 from base station 10 to mobile stations 20 and 21. Figure 11 shows a state in which there are two data signals 32 to be transmitted from base station 10. When two data signals 32 are generated at base station 10, control device 12 suspends transmission of data signals 32 until transmission of start slot 90 begins. Next, control device 12 instructs transmitter 11 to transmit a signal slot containing two data signals 32 from start slot 90, and transmitter 11 transmits these signals. Then, upon completion of transmission of the signal slot, control device 12 instructs transmitter 11 to transmit an empty slot.

The receiving device 23 of the mobile stations 20 and 21 begins receiving signals from the start slot 90 and transmits them to the control device 22. The control device 22 then determines whether to continue reception based on the slots received from the receiving device 23. That is, if the signal portion 43 of the start slot contains a mobile station identifier 34 identifying the mobile station, the control device 22 instructs the receiving device 23 to receive the number of continuation slots indicated by the continuation slot count 42. In accordance with this instruction, the receiving device 23 receives a series of continuation slots. After receiving these continuation slots, the receiving device 23 receives one more slot. If the slot contains a mobile station identifier 34 identifying the mobile station, the control device 22 receives another number of continuation slots indicated by the continuation slot count 42.

On the other hand, if the received slot is an empty slot or a signal slot addressed to another mobile station, the control device 22 instructs the receiving device 23 to stop receiving. In this way, in the above-mentioned operation, by transmitting multiple signals consecutively, the signal delay time can be reduced.

C. 4. Broadcast, etc. Next, using Figures 12 and 13, we will explain the operation when transmitting a common signal to multiple mobile stations (such as broadcast). First, as shown in Figure 12, base station 10 transmits a signal addressed to mobile station 20 in start slot 90 and a signal addressed to mobile station 21 in start slot 91. Start slot 91 has the same configuration as start slot 90. Mobile station 20 monitors start slot 90, and mobile station 21 monitors start slot 91.

As shown in FIG. 13, base station 10 transmits data signal 32 to both mobile station 20 and mobile station 21 from common start slot 95. The mobile station identifier 34 of this data signal 32 identifies both mobile station 20 and mobile station 21. The location of common start slot 95 on TDMA radio channel 30 is predetermined. Mobile station 20 and mobile station 21 monitor common start slot 95 in addition to start slot 90 or 91. If common start slot 95 contains a signal addressed to their own station, they stop receiving after receiving the signal slot following common start slot 95. On the other hand, if the received slot is an empty slot or a signal slot addressed to another station, they stop receiving.

In the above-described operation, by distributing slots for each mobile station, it is possible to reduce battery consumption at each mobile station while ensuring signal transmission to each mobile station. Furthermore, by providing a common start slot 95 at which multiple mobile stations begin reception, the delay when transmitting a common signal to multiple mobile stations is less than the delay when individual slots are used for each mobile station. Furthermore, since overlapping signal transmissions are eliminated, the utilization efficiency of the TDMA radio channel 30 is improved.

C. 5. Mode Switching Conventionally, known mobile stations continuously monitor the TDMA radio channel 30. Of course, such mobile stations may coexist with mobile stations that monitor only the start slot 90 based on this embodiment. However, even with the mobile station 20 according to this embodiment, there may be cases where traffic becomes heavy or the allowable transmission delay becomes small. In such cases, continuous monitoring of the TDMA radio channel 30 would be desirable.

In this embodiment, the base station 10 switches the mode of the mobile stations 20 and 21 under its control in such cases, and the base station 10 can change the transmission mode accordingly. Alternatively, the base station 10 may switch the transmission mode in response to a request from the mobile stations 20 and 21.

14 shows the structure of a transmission mode signal 87 sent from mobile stations 20 and 21 to base station 10 to request a change in transmission mode. The transmission mode signal 87 includes a mobile station identifier 34, a signal type 82 indicating that the signal is a transmission mode signal, and transmission mode information 88 indicating the signal transmission method. The transmission mode information 88 indicates, for example, a continuous transmission mode in which data signal transmission begins at any time, or an intermittent transmission mode in which data signal transmission begins only in start slot 90 and common start slot 95.

Before starting communication or during communication, mobile stations 20 and 21 transmit a transmission mode signal 87 to base station 10. Upon receiving the transmission mode signal 87, base station 10 transmits a signal using the transmission method requested by mobile station 20 or 21.

This operation allows data to be transmitted as quickly as before by switching to continuous transmission mode when traffic is heavy or the allowable transmission delay is small. Furthermore, the transmission method can be changed to discontinuous transmission mode at the start of communication or during communication, depending on the limitations of the mobile station's battery consumption. Furthermore, the interval between start slots may be changed by transmission mode signal 87.

In the above embodiment, the mobile stations 20, 21 request the base station 10 to change the transmission mode. However, this is not limiting. For example, the base station 10 may store a list of transmission modes suitable for each of the mobile stations 20, 21, and switch the transmission mode of each of the mobile stations 20, 21 according to the list.

Each mobile station 20, 21 is assigned a unique mobile station identifier, and base station 10 stores a transmission mode list for each mobile station, corresponding to the mobile station identifier. The contents of this list are preset by some input means or the like.

(Embodiment 2) A. Hardware Configuration and Data Structure of the Second Embodiment The hardware configuration of this embodiment is similar to that of Embodiment 1, but there are some differences in the data structure, as described in detail below.

That is, in this embodiment, start slot information 85 indicating the position of the start slot 90 for each mobile station is transmitted from the base station 10 to the mobile stations 20 and 21 via a notification signal 80. Following the notification signal 80, the base station 10 transmits one or more data signals 86 to the mobile stations 20 and 21.

15 shows the configuration of notification signal 80. Notification signal 80 includes mobile station identifier 34, which identifies one or more mobile stations that should receive the signal, signal type 82, which indicates that the signal is a notification signal, and mobile station identifier list 83. Mobile station identifier list 83 includes individual mobile station identifiers 84, which indicate the destination of each of the one or more signals, and start slot information 85, which indicates the position of the start slot of data signal 86.

FIG. 16 shows the configuration of a data signal 86. The data signal 86 includes a mobile station identifier 34 that identifies the mobile station, a signal type 82 that indicates that the signal is a data signal, and data 36.

B. Operation of the Embodiment Next, the operation of the base station 10 and the mobile station 20 will be described with reference to FIG. 17. First, the base station 10 begins transmitting a notification signal 80 in the common start slot 95. Meanwhile, the mobile stations 20 and 21 begin receiving in the common start slot 95. If the signal type 82 of the received signal indicates a notification signal, the base station 10 reads the start slot information 85 following the individual mobile station identifier 84 of the base station.

When a data signal 86 addressed to mobile station 20 and a data signal 86 addressed to mobile station 21 are generated, base station 10 generates a notification signal 80 including a mobile station identifier 34 indicating that mobile station 20 and mobile station 21 should receive the signal, an individual mobile station identifier 84 and starting slot information 85 for mobile station 20, and an individual mobile station identifier 84 and starting slot information 85 for mobile station 21, and transmits the notification signal 80 in a common starting slot 95. Furthermore, base station 10 transmits data signal 86 addressed to mobile station 20 in a starting slot 90 indicated by the starting slot information 85 following the individual mobile station identifier 84 for mobile station 20. Furthermore, base station 10 transmits data signal 86 addressed to mobile station 21 in a starting slot 91 indicated by the starting slot information 85 following the individual mobile station identifier 84 for mobile station 21. Data signals 86 are transmitted in one or more slots, as in FIG. 5 .

The mobile station 20 starts reception from the start slot 90 indicated by the start slot information 85 following the individual mobile station identifier 84 of the mobile station 20. If the received slot is a slot that the mobile station should receive, the mobile station 20 continues reception. On the other hand, if the received slot is an empty slot or a signal slot addressed to another station, the mobile station 20 stops reception.

Here, we explain why start slot 90 can be a slot for another station. Because start slots are assigned to each mobile station, reception of information typically ends before the start slot of another station occurs. However, if the number of serving mobile stations increases and the interval between start slots becomes shorter, or if traffic to a particular mobile station increases significantly, the slot for that particular mobile station may be extended until the next start slot (for another station) occurs.

In the example shown in FIG. 17, start slot 90 is the slot following common start slot 95, so mobile station 20 receives notification signal 80 followed by data signal 86, and then stops receiving. Also, start slot 91 is far from common slot 95, so mobile station 21 stops receiving after receiving notification signal 80 and then starts receiving again from start slot 91. Mobile station 21 then receives data signal 86 before stopping receiving.

In this embodiment, the notification signal 80 notifies one or more mobile stations of the presence or absence of a signal. This allows the mobile stations to be notified of the presence or absence of a data signal more quickly than when signals are transmitted sequentially to one or more mobile stations. This reduces the transmission delay of the data signal and improves the utilization efficiency of the TDMA radio channel.

(Modifications) Although the above describes an embodiment of the invention, the technical scope of the invention pertaining to this application is not limited to the above embodiment. Various modifications to the above embodiment can be made to realize the invention described in the claims. It is clear from the claims that such inventions fall within the technical scope of the invention pertaining to this application.

For example, the above embodiment can be modified in various ways, for example, as follows.

The base station 10 may determine the arrangement of the start slots 90, 91 and the common start slot 95 using a predetermined algorithm. In this case, the base station 10 may notify the base stations 20, 21 of the arrangement of the start slots 90, 91 in embodiment 1 and the arrangement of the common start slot 95 in embodiments 1 and 2 using a slot designation signal 60.

18 shows the configuration of this slot designation signal 60. The slot designation signal 60 includes a mobile station identifier 37 that identifies the mobile station 20, a signal type 82 that indicates that it is a slot designation signal 60, and slot information 62. The slot information 62 indicates the arrangement of start slots 90 and 91 in the first embodiment and the arrangement of a common start slot 95 in the first and second embodiments.

Base station 10 determines the placement of start slots 90, 91 and common start slot 95 to maximize radio channel utilization efficiency, using parameters such as the number of mobile stations, allowable transmission delay, the amount of signal specific to each mobile station, the amount of signal common to multiple mobile stations, and signal generation characteristics. Mobile stations 20, 21 then determine the locations of start slots 90, 91 and common start slot 95 based on slot information 62.

Alternatively, the slot designation signal 60 may be transmitted over a control TDMA radio channel different from the communication TDMA radio channel 30. In this case, the mobile stations 20 and 21 receive the slot designation signal 60 over the control TDMA radio channel and then switch to the communication TDMA radio channel 30. They then monitor the designated start slots 90 and 91 and the common start slot 95. This allows the allocation of the start slots 90 and 91 and the common start slot 95 to be flexibly determined depending on the situation. The mobile station 20 may also determine the start slots 90 and 91 and the common start slot 95 and notify the base station 10 of these.

───────────────────────────────────────────────────── Continued from the front page (72) Inventor: Katsumi Kobayashi 3-42-5 Higiriyama, Konan-ku, Yokohama, Kanagawa Prefecture -103 (72) Inventor: Tadao Takami 102 Yabe Heights, 3-21-10 Oyabe, Yokosuka, Kanagawa Prefecture (Note) This publication is based on the publication published internationally by the International Bureau of Patents (WIPO). The effect of the international publication of the Japanese patent application (Japanese utility model registration application) related to this publication arises pursuant to Article 184-10, Paragraph 1 of the Patent Act (Article 48-13, Paragraph 2 of the Utility Model Act) and is unrelated to this publication.

Claims (14)

[Claims] 1. A mobile communication system for transmitting a data signal from a base station to a mobile station using a TDMA radio channel consisting of slots, wherein the base station comprises: means for generating a first slot having a mobile station identifier indicating the destination mobile station and subsequent slots having at least a portion of the data signal; means for transmitting the first slot in a start slot located at a position on the TDMA radio channel determined for each mobile station; and means for transmitting the subsequent slots in the slots following the start slot; and the mobile station comprises: means for monitoring the start slot; means for determining the mobile station identifier if the start slot is the first slot; and means for receiving the subsequent slots if the mobile station identifier indicates the mobile station. 2. The mobile communication system according to claim 1, further comprising: means for transmitting an empty slot not including the data signal when the data signal is not present; and means for suspending reception until the next start slot if the start slot is the empty slot or the continuation slot. 3. The mobile communication system according to claim 1 or 2, wherein the first slot includes information indicating the number of consecutive consecutive slots, and the mobile station is equipped with means for receiving the consecutive slots up to the final slot constituting the data signal based on the number of consecutive consecutive slots. 4. The mobile communications system of claim 3, wherein the base station comprises: means for generating the first slot and the subsequent slots of a plurality of data signals; means for consecutively transmitting the first slot and the subsequent slots of the plurality of data signals in the start slot and the slots following the start slot; and the mobile station further comprises: means for receiving a slot following the last slot; means for terminating reception if the subsequent slot is not the first slot; means for determining the mobile station identifier if the subsequent slot is the first slot; means for terminating reception if the mobile station identifier indicates a mobile station other than the mobile station itself; and means for receiving subsequent slots following the first slot if the mobile station identifier indicates the mobile station itself. 5. The mobile communication system according to any one of claims 1 to 4, wherein the start slot is allocated on the TDMA radio channel based on the delay tolerance of the data signal and the traffic of the data signal. 6. A mobile communication system according to any one of claims 1 to 5, wherein the start slots for a plurality of the mobile stations are respectively arranged on the TDMA radio channel. 7. The mobile communications system according to any one of claims 1 to 6, further comprising means for the base station to transmit a notification signal indicating the position of the start slot for each of the mobile stations, and means for the mobile stations to start reception from the start slot indicated by the notification signal. 8. The mobile communication system according to any one of claims 1 to 7, further comprising a second mobile station that monitors all slots transmitted from the base station, and wherein the base station further comprises means for transmitting the data signal to the second mobile station from an available slot immediately after the data signal is generated. 9. The mobile communications system according to any one of claims 1 to 8, wherein the base station further comprises: means for retaining whether each of the plurality of mobile stations has a first reception mode or a second reception mode; means for identifying whether the mobile station has the first or second reception mode based on the mobile station identifier of the mobile station; means for transmitting the data signal to the mobile station in the next available slot immediately after the data signal is generated if the mobile station has the second reception mode; and means for transmitting the data signal to the mobile station in the start slot if the mobile station has the first reception mode. 10. The mobile communication system according to claim 9, wherein the mobile station monitors only the start slot in the first reception mode, and monitors all slots in the second reception mode. 11. The mobile communication system according to any one of claims 1 to 10, wherein the mobile station further comprises: means for transmitting a receive mode indicating whether to monitor all slots or only the start slot; and means for monitoring the slots in the transmitted receive mode; and the base station further comprises: means for receiving the receive mode; means for, when the receive mode indicates that all slots are to be monitored, transmitting the data signal to the mobile station that transmitted the receive mode from the slot immediately following the generation of the data signal; and means for, when the receive mode indicates that only the start slot is to be monitored, transmitting the data signal to the mobile station that transmitted the receive mode from the start slot. 12. The mobile communications system according to any one of claims 1 to 11, wherein the base station further comprises: means for generating multiple types of synchronization words for the mobile station to synchronize with the slot; and means for transmitting the slot with a synchronization word selected from the multiple types of synchronization words based on whether the slot is the start slot; and the mobile station further comprises means for determining whether the slot is the start slot based on the type of the synchronization word. 13. The mobile communication system according to any one of claims 1 to 12, wherein the base station further comprises means for transmitting a slot designation signal including information indicating the position of the start slot, and the mobile station further comprises means for receiving the slot designation signal and means for determining the position of the start slot from the slot designation signal. 14. The mobile communications system according to any one of claims 1 to 14, characterized in that the base station provides a common start slot at a predetermined position on the TDMA radio channel, and when transmitting a common data signal to multiple mobile stations, comprises: means for generating a first slot having a mobile station identifier indicating the multiple mobile stations and a continuation slot having at least a portion of the data signal; means for transmitting the first slot in the common start slot; and means for transmitting the continuation slot in the slot following the common start slot; and the mobile station comprises: means for monitoring the common start slot in addition to the start slot determined for each mobile station; means for determining the mobile station identifier when the common start slot is the first slot; and means for receiving the continuation slot if a mobile station identifier indicating the mobile station is included in the mobile station identifiers.