Method fo group call in mobile communication system and mobile communication system

Method for maintaining group call in mobile communication system and mobile communication system

This application is based on Finnish Patent Application No. 964817 filed on December 2, 1996. The content of the Finnish priority patent is hereby incorporated for reference.

The present invention relates to a method for maintaining a group call in a mobile communication system. The mobile communication system includes: a network infrastructure, and a mobile station communicating with the network infrastructure through a wireless path, the frame structure of which is composed of time slots, and the method It includes the following steps: establishing a group call, where the first mobile station has priority, the mobile stations participating in the group call communicate in the manner of speech item, and the frame structure includes the second mobile station sending the speech item used in its speech item Time slot.

The method of the present invention is particularly suitable for PMR (Private Mobile Radio or Professional Mobile Radio) networks, or relay networks, which are generally corporate networks or private mobile radio networks of official institutions. All channels in these networks are allocated to one or Multiple companies or official institutions. In addition to the number of users, users in these networks have been assigned a group number, which indicates which group call group or user group the user belongs to. Therefore, calls sent to members of a particular group can be switched to all users of the group.

Group call is an important function in PMR network. Group calls are used in situations involving several participants, especially when the entire group must be kept abreast of developments. A group call is a conference call in which all participants can take turns to speak, or send voice items, and listen to each other's speech. In a group call, the entire group can be called through a group identification code. As we all know, many mobile phone systems, especially those used by companies and government agencies, use group calls. In terms of wireless paths, group calls are generally implemented in the form of simple point-to-multipoint calls, in which voice is sent from one speaker to multiple speakers, and the voice items are assigned to the next speaker in a predetermined order. Naturally, group calls can also be implemented in the form of duplex calls.

Here, a call or group call refers to a complex information exchange between two or more parties. The call can consist of one or more voice items. In a half-duplex call, these voice items are serial.

The present invention can be applied to mobile communication systems with digital or analog wireless paths. Analog mobile communication systems are described, for example, in the following publications: MPT 1327, A Signalling Standard for Trunked Private Land Mobile Radio Systems, January 1988, revised and republished in November 1991, and MPT 1343, Performance Specification, January 1988, 1991 Revised and republished in September 2008, both are issued by Radio-communications Agency and published by British Department of Trade and Industry.

An example of a digital mobile phone or mobile communication system to which the present invention can be applied is the TETRA system (Pan European Relay Radio). In fact, the current standard ETS 300 392-2, Radio Equipment and Systems (RES): Trans-European Trunked Radio (TETRA): Voice plus Data (V+D) Part 2: Air interface (AI), March 1996, ETSI, 583 Described in the page. In this system, the distribution of voice items is controlled by the switching and management infrastructure (SwMI) through the base station connected to it.

In FDMA (Frequency Division Multiple Access) systems, the function of sending signaling messages or other data during a call or data call is called in-band signaling. In this system, part of the channel transmission capacity is generally used to replace actual voice or circuit-switched data signaling during a call.

WO A1 91/09481 describes the traffic volume between a first and a second communication unit in a quasi-duplex situation, for example on a direct mode channel. The first communication unit transmits a signal with holes appearing periodically, and the signal also includes a voice information part and an information packet indicating the location of the next hole. The receiving second communication unit sends an interrupt request signal to the first communication unit in the hole indicated by the information packet. The first communication unit receives and processes the interrupt request signal. If the first communication unit determines that the interrupt request signal meets (required) predetermined conditions, it sends an acknowledgement to the receiving second communication unit. The confirmation informs the second communication unit that the first communication unit will interrupt the transmission (for a predetermined length of time), thereby allowing the receiving second communication unit to start the transmission. The second communication unit can thus initiate transmission.

US Patent No. 5,025,442 describes a quasi-duplex mobile phone system that uses a control time slot. During the control time slot, the receiving communication unit is allowed to send an interrupt signal to the sending communication unit to instruct the sending communication unit not to send again, thereby interrupting the transmission. Transmission of the communication unit.

It is also well known that part of the service capacity allocated to users is permanently used for signaling. This method is called out-of-band (channel-specific) signaling.

In ordinary mobile phone networks, such as NMT (Nordic Mobile Telephone) or GSM (Global System for Mobile) systems, all calls generally have the same priority, that is, no user has priority over other users.

In a private wireless network, that is, a relay network, the situation is different. The operation of these PMR networks can enable users who complete certain types of services, such as emergency, or other important tasks to have a higher priority, that is, to exchange their high-priority calls first in congestion.

An example of a high-priority call is an emergency call, that is, a call that is established when at least one user needs emergency assistance. An emergency user can initiate an emergency call, or it can be initiated by some other mobile station or a dispatcher controlling the operation. An emergency call can be sent to a chat group, that is, a group call. The members of the chat group not only need to listen to the conversation, but also need to participate in the conversation. In other words, members can send voice items. This is usually necessary, for example, to issue instructions to a group member in an emergency. However, when multiple users speak in turn, users who require a communication connection in an emergency situation cannot always be assigned to voice items as quickly as possible.

However, in a mobile phone system based on the relay method, the mobile station must request voice items from the system, and the system allocates the voice items in chronological order or priority. The system can also interrupt an ongoing voice item.

A problem in the prior art is that during a single call of a single base station or a voice item in a group call of a base station to which the subscriber station that sends the voice item is attached, the prior art mobile communication system protocol, especially the TETRA mobile phone system The capacity of the control channel is very limited. During the voice term, only frame 18 of the TETRA frame structure has an available low-association control channel, that is, once-a-second time slot. Especially in the private mobile wireless networks used by official agencies, emergency group calls are often sent, so users or mobile stations in emergency situations can get enough requests for voice items during the voice items sent by users participating in the group call. Opportunity is very important, and naturally the voice item request is quite easy to succeed.

In the prior art solutions, especially in the TETRA system, the use of low-association signaling channels enables all mobile stations participating in a group call to adopt random access methods, such as the first-try method, by sending voice items Request a signal to request a voice item.

If the second mobile station is sending a voice item and multiple third mobile stations are participating in an emergency group call, and the first mobile station is actually in an emergency situation, at the same time in the 18th frame time slot reserved for the voice item request, or in If a voice item is requested in a part of the time slot, a problem will occur. Next, it may be the turn of a third mobile station to send a voice item request instead of the first mobile station, that is, the mobile station in emergency. For example, the sending request from the third mobile station may conflict with the voice item request sent by the first mobile station. The first mobile station, that is, the mobile station in an emergency situation, cannot deliver its voice item request to the network infrastructure, so the voice item will not be allocated to the first mobile station in an emergency situation.

One way to solve this problem is to allocate a separate uplink channel, time slot or frequency to the priority mobile station so that the voice item request can be delivered immediately. The problem with this scheme is that it wastes wireless resources. It should be noted that if a user is in an emergency or priority situation, the traffic density is unlikely to be higher than normal. In addition, for network facilities, assigning a separate uplink channel to priority users is a complex and non-standardized process.

Another way to solve the above problem is to allow the priority mobile station to send voice item requests on the common control channel. This approach makes the priority mobile station not in the traffic channel, so it may lose the call or at least not receive the sending mobile stations Partially sent.

Another problem with the prior art solution is that when the voice item in the priority group call ends, a random access time period is started, during which mobile stations participating in the group call can request the voice item. In this way, the voice item request of the third mobile station may conflict with the voice item request issued by the first, priority mobile station, and therefore cannot be quickly allocated to the voice item required by the first mobile station. This is particularly important in private mobile wireless networks used by official agencies, where it must be ensured that the voice items of priority mobile stations that may be in emergency situations are quite easy to succeed.

The purpose of the present invention is to solve the above-mentioned problems of the prior art.

The purpose of the present invention is to provide a method by which it can be ensured that priority mobile stations participating in a priority call, for example, voice item requests sent by mobile stations in an emergency situation, can actually reach the network infrastructure, and the latter can actually reach the network infrastructure after receiving the voice item request. After that, the voice item can be accurately assigned to the priority mobile station.

This new method of maintaining group calls can be implemented by the method of the present invention, which is characterized by further including the following steps: only the first mobile station is assigned a time slot or time period, and in these time slots or time periods only the first The mobile station can send a signaling message to the network infrastructure, and send data to the first mobile station and the third mobile station, indicating that only the first mobile station can send the signaling message to the time slot or time period of the network infrastructure , The third mobile station does not send its signaling message in the time slot or time period allocated to the first mobile station.

The present invention also relates to a mobile communication system, including: first, second, and third mobile stations, a mobile switch for forwarding group calls and transmitting and maintaining group calls, the mobile stations participating in the group call Voice item communication, a base station that maintains a frame structure. The aforementioned frame structure includes the time slot used by the second mobile station that transmits the voice item in its voice item.

The mobile communication system of the present invention is characterized in that it also includes: allocation means for allocating time slots or time periods to only the first mobile station, so that only the first mobile station can send signaling in a specific time slot or time period The message is sent to the mobile exchange, and the sending device is used to send data to the first mobile station and the third mobile station in the control message, indicating the time slot or time period that only the first mobile station can send, and the third mobile station The control device for preventing the sending of signaling messages in the time slot or time period allocated to the first mobile station.

The present invention also relates to a mobile station that communicates in the form of a group call in a mobile communication system. The mobile station includes a transceiver for sending transmission in a frame structure. The frame structure includes: sending a voice item in a group call. 2. The time slot used by the mobile station in its voice item, and the time period shared by the mobile station that has not sent the voice item for sending signaling messages to the network infrastructure; the control unit; the user interface; and the memory unit.

The mobile station of the present invention is characterized in that the mobile station includes a control unit that, in response to a control message sent by the mobile communication system, prevents a signaling message from being indicated in the control message and allocated to the first mobile station. Sent in a time slot or time period.

The mobile station of the present invention is also characterized in that, in response to the control message sent by the mobile communication system, the transceiver of the mobile station sends a signaling message in the time period indicated by the control message.

The present invention is based on the following idea: to ensure that the participants of the priority group call, such as the mobile station that initiates an emergency call, are allocated signaling capacity at a specific interval so that the mobile station has the opportunity to send a voice item request. Continuously send an indication of its appearance to the system. This is achieved by assigning a random access time slot of the frame structure to the first, priority mobile station, and blocking others participating in the same call, and the third mobile station transmits in the frame structure time slot assigned to the first mobile station. In the present invention, first, the priority mobile station is a mobile station in an emergency, and sends data to the third mobile station participating in the priority group call, indicating that only the first mobile station can send signaling messages to the network infrastructure The time slot or time period of the facility.

The advantages of the method, mobile communication system and mobile station of the present invention are that the present invention ensures that, for example, a mobile station in an emergency situation, especially a priority mobile station, can send a voice item request, and if the mobile station sends a voice item request, the request is also Upon reaching the network infrastructure, the latter can then assign the next voice item to the priority mobile station, such as a mobile station in an emergency.

The present invention will be described in detail below with reference to the accompanying drawings. In the accompanying drawings: Figure 1 shows the frame structure of the TETRA mobile phone system; Figure 2 shows a sequence diagram of a priority group call according to the first embodiment of the present invention; Figure 3 Shows a sequence diagram of a priority group call according to the second embodiment of the present invention; Fig. 4 shows a block diagram of the mobile station of the present invention; Fig. 5 shows an overview of the following situation: according to the present invention, the priority mobile station is given frequent The opportunity to send location data at intervals; Figure 6 shows a block diagram of the mobile communication system of the present invention.

Figure 1 shows the frame structure of the TETRA mobile phone system. In the TETRA protocol, the uplink frequency on the system channel (from the mobile station to the base station) is two time slots behind the downlink direction (from the base station to the mobile station). The system includes a main radio frequency, which has a main signaling channel, and possibly other signaling channels and traffic channels.

In the TETRA frame structure, one superframe includes 60 multiframes, and each multiframe includes 18 TDMA frames. Each TDMA frame is divided into 4 time slots, 101 to 104 in the figure. According to the TETRA standard, a time slot or a part of a time slot in the 18th frame of a multiframe, a time period, such as half a time slot, is allocated as an uplink signaling channel, and other time slots in the frame, such as 101, 103 and 104 can be allocated as traffic channels. In this figure, multiframes are indicated by 1 to 60, frames are indicated by 1 to 18, and time slots are indicated by 1 to 4.

Fig. 2 shows a sequence diagram of a priority group call according to the first embodiment of the present invention. At the beginning of the operation, the user indicates to the system that it is in an emergency situation. The user who gave the instruction may be in an emergency situation himself/herself, or he/she may also be, for example, a dispatcher who detects that the mobile station requesting to participate in the group call is in an emergency situation. The system operates in accordance with the emergency call process: for example, it allocates voice items to the mobile station that initiated the emergency call, and routes the call to the emergency switching level. The method of the present invention relates to a situation where an emergency call is diverted to a group call where other members of the group also have the opportunity to speak. If the mobile station in the conversation group other than the mobile station that is in emergency and needs priority, that is, for example, the second mobile station, sends voice items 201, 202, 203, then the mobile station in emergency is the first mobile station. , The priority mobile station must be able to preempt the voice item of a certain group member when needed.

Fig. 2 shows, in shaded lines, the continuous time slots of a specific uplink connection or channel for the second mobile station to send its voice items 201, 202, 203. In FIG. 1, for example, the time slot of the first 17th frame in the multiframe is the same time slot, such as time slot 102. The preemption of the priority mobile station is realized as follows: the system notifies the priority mobile station and the third mobile station, that is, other mobile stations that listen to the voice of the second mobile station, that a time slot or time period 204, 205 has been allocated to the first mobile station. The mobile station can send a voice item request. This notification is done by sending signaling messages to at least the first mobile station and the third mobile station. In response to the notification, the third mobile station does not send its signaling message in the time slot or time period allocated to the first mobile station.

According to the present invention, if the first mobile station has no other need to send in the aforementioned time slot or time period 204, 205, that is, there is no voice item request or any other signaling message, it can be required to send an empty transmission, such as an empty PDU (Protocol Data Unit). This makes it possible to achieve the third objective of the present invention: to force a priority mobile station, for example, a mobile station in an emergency situation to continuously declare its existence.

If necessary, the first mobile station can send positioning data in the time slot or time period 204, 205 allocated to it. Then based on the data, the geographic location of the mobile station can be determined. The positioning data may be, for example, GPS (Global Positioning System) position coordinate data. Based on the location data, a positioning system connected to, for example, a mobile communication system or its dispatcher can announce the location of the mobile station every time the first priority mobile station transmits location data. Therefore, it is possible to monitor the position change of the first mobile station, that is, its movement.

The frame structure portion allocated to the first mobile station for sending the voice item request may be the entire time slot, a time period composed of multiple time slots, or a part of a time slot.

The method according to the first embodiment of the present invention includes at least the following steps: first establish at least one group call, so that the frame structure of the mobile communication system includes a plurality of time periods between normal communication time slots, and these time periods are commonly used by the first mobile station. And the third mobile station, used to send signaling messages to the network infrastructure. This involves a situation where the second mobile station is sending a voice item, and first, the priority mobile station wants to be assigned to the next voice item.

In the subsequent allocation step, one or more common time periods are allocated only to the first mobile station for sending signaling messages. Therefore, it is decided to allocate a specific frame, such as the time slot of frame 18 in the frame structure, to be used only for the first mobile station to send signaling messages.

The network infrastructure sends an allocation notification to the first mobile station and the third mobile station, and in response to the notification, the third mobile station does not send its transmission during the aforementioned time period.

Fig. 3 is a sequence diagram of a priority group call according to the second embodiment of the present invention. This embodiment is an improvement of the foregoing first embodiment. Unless otherwise specified, the content described above for the first embodiment also applies to this embodiment. The second embodiment relates to a situation where the second mobile station has established its voice item 301 and terminated it 302. In the prior art, if the voice item is terminated, the mobile station listening to the channel usually allows random access. Then, the mobile station listening to the channel can send a voice item request signal or other signaling message. The goal is to assign a new voice item. The priority mobile station is in a special situation in the following aspects: if it needs to initiate a voice item, it must be able to initiate it as soon as possible. The reason is that the priority mobile station may be in an emergency situation and needs help, so it is requesting help. The priority mobile station can also request the establishment of an emergency call.

Figure 3 shows a situation in which all mobile stations of the group call can immediately preempt first, and secondly, the mobile station has terminated its voice item. The preemption situation is carried out as follows: the network infrastructure of the mobile communication system allocates a certain number of first time slots or time periods 304 to the first mobile station, and at least the third mobile station participating in the group call requests to send random access and signaling messages. In addition, the system allocates the second time slot 305 of the frame structure only to the first or priority mobile station for sending signaling messages, generally voice item requests. The first or priority mobile station and the third mobile station participating in the group call are informed about the allocation. It is also possible to notify the second mobile station that has terminated the voice item. The allocation notification contains at least the following data, which indicates a time slot or time period in which only the first mobile station can send a signaling message. A time slot or time period, such as half a time slot, is allocated to a priority mobile station that may be in an emergency situation, in which only the priority mobile station can send a voice item request. It can be implemented in an appropriate manner, so that priority users, such as users in emergency situations, may not want to preempt the previous call, but still want to be assigned to the next voice item.

If after the second mobile station terminates its voice item 302, the first mobile station is allocated a first idle time slot or time period, the preemption situation 303 will appear prematurely, because the user reacts to the terminated voice item more quickly than when the user detects it. The slot allocation time is slightly later (for example, half a second). Naturally, it is also possible to allocate the time slot to the first mobile station immediately after the second mobile station's voice item is terminated, or to allocate it in any other time slot or time period.

The next voice item 306 immediately follows the time slot or time period 305 allocated to the first mobile station for signaling messages. If first, the priority mobile station has requested a voice item, the next voice item 306 can be assigned. Otherwise, the next voice item 306 is allocated to other mobile stations requesting the voice item. After the next voice item, a new time slot or time period 307 of the frame structure follows, where any mobile station except the mobile station that is sending the voice item can send its signaling message to the network infrastructure. If this is defined in the data sent by the network infrastructure, even the time slot or time period can still be allocated to the first mobile station for sending signaling messages.

Figures 2 and 3 show that multiple random access frames are used for the allocation of voice items. After the last voice item, a time slot is reserved for the priority mobile station for sending voice item requests. The random access frame may be a TDMA time slot or part of such a time slot.

In the second embodiment of the present invention, at least the following steps are required. When the second mobile station that has sent the voice item terminates its voice item, in order to send a signaling message, the required number of time slots or time periods are allocated from the frame structure time period of the required length to the third mobile participating in the group call station.

In addition, a time period is allocated from the time period of the required length, which is only used for the first mobile station to send a signaling message. These signaling messages can be, for example, voice item request signaling, status messages, messages notifying the location of the mobile station, or null messages.

Thereafter, a first notification is sent to the mobile stations participating in the group call, indicating that a specific time slot or time period of the frame structure is allocated to the mobile stations participating in the group call. The notification informs the mobile stations participating in the group call that a specific time slot can be used for all mobile stations in the group to send signaling messages.

Then, a second notification is sent to the first mobile station, indicating that the specific second time period of the frame structure is only allocated to the first mobile station for sending the signaling message. Naturally there can be more than one first mobile station.

In response to the first notification, the mobile stations participating in the group call then send a signaling message in the above-mentioned time slot or time period.

In addition, in response to the second notification, the first mobile station may send a transmission in the time period allocated to it.

In the first and second embodiments of the present invention, in response to the allocation data sent by the network infrastructure, the third mobile station stores in its memory data indicating which time period in the frame structure is allocated to the first mobile station.

Figure 4 is a block diagram of the mobile station of the present invention. Fig. 4 shows a typical communication radio unit 400, namely a mobile phone, a mobile station or a subscriber station used by, for example, a user. The function of the transceiver (TX/RX) 401 is to tune to the channel used. The transceiver 401 communicates with the base station or relay station through radio frequency, that is, is divided into TDMA frames and further divided into radio frequency of time slots, of which at least one time slot can be allocated to one or more mobile stations for use as a traffic channel. Connected to the transceiver 401 is the antenna 402, which is connected to the wireless path RP. Usually 60 to 1000 MHz (VHF and UHF range) radio frequency is used, but other frequencies can also be used. On the radio frequency RP, analog modulation can be used, which is usually phase modulation. Other types of modulation can also be used. The signaling can be sent, for example, via a voice frequency sub-carrier (FFSK). The transmission on the wireless path can also be digital. The wireless unit can be tuned to and communicate on upstream and downstream frequencies.

The user interface 405 includes an electroacoustic frequency converter, generally a headset 406 and a microphone 407, and optional buttons for initiating or terminating calls and dialing. Because in the relay system, the transmission on the wireless path RP is preferably non-directional, so the subscriber station usually also has a call button, which must be pressed during the duration of the voice item. The call button is not shown in Figure 4.

The function of the controller 403 is to control the operation of the wireless unit. The controller 403 is connected to a user interface 405, from which it receives pulses such as originating and terminating calls. The controller 403 may also send an acoustic signal or a visual signal to the user through the user interface 405, and these signals are related to the operation of the mobile phone and/or the mobile phone system.

The controller 403 is connected to the transceiver TX/RX 401. The channel used by the transceiver is allocated by the controller 403, the transceiver 401 is tuned to the channel or radio frequency, and an appropriate time slot is allocated by the controller 403. The transceiver 401 is also activated by the controller 403. The controller 403 transmits and receives signaling messages through the transceiver 401. The communication wireless unit or mobile station 400 of the present invention can be used, for example, in a wireless system including a wireless network having at least one base station, a mobile station and optionally one or more relay stations, these relay stations at least one base station and Forwarding traffic between user stations. Here, the communication mobile station includes a memory device 409, a transceiver 401, and a controller 403 for controlling the operation of the mobile station.

The present invention relates to a mobile station of a mobile communication system communicating in a group call. The mobile station includes a transceiver for sending a transmission in a frame structure including the following: a second mobile station sending a group call voice item in its voice The time slot used in the item is commonly used for the time period of the mobile station that has not sent the voice item, and this time period is used to send signaling messages to the network infrastructure.

Below we will mainly describe a mobile station whose operation mode is the same as the third mobile station described above for the method steps. The mobile station of the present invention includes a control unit C1 that, in response to a control message sent by the mobile communication system, prevents the sending of a signaling message during the time slot or time period allocated to the first mobile station and indicated by the control message.

In response to the control message sent by the network infrastructure, the memory unit 409 of the mobile station stores in its memory device 409 specific time slots indicating the system frame structure allocated to other mobile stations, that is, the data of the first mobile station in this method step. .

Below we will mainly describe a mobile station whose operation mode is the same as the first mobile station described above for the method steps.

In response to the control message sent by the mobile communication system, the transceiver 401 of the priority mobile station sends a signaling message during the time period indicated by the control message.

In response to the transmission reminder sent by the mobile communication system, the transceiver 401 of the priority mobile station starts sending its transmission in the time slot indicated by the transmission reminder contained in the control message.

Figure 5 illustrates a situation in which the priority mobile station 50 is given the opportunity to transmit location data at frequent intervals in accordance with the present invention. In a mobile communication system, it may happen that the mobile station 501 loses a call. This may especially occur when a transmission relay or a quasi-transmission relay is used in the channel allocation of a mobile communication system. Therefore, if it is desired to ensure that the mobile station in an emergency situation can actually participate in the call at any time, the mobile station must be required to periodically send the presence indication. If it is found that the mobile station is not participating in the call, the mobile communication system, generally the switch of the system, can initiate the call notification on the control channel, because the mobile station that has exited the call may return to the control channel after losing the call. In addition, the occurrence of the periodic indication is very useful in operation, for example because it enables the dispatcher who monitors the emergency call to be notified that the wireless communication with the user's mobile station has been lost in an emergency.

If the positioning device (AVL-GPS) and GPS (Global Positioning System) are available, the present invention can be used to increase the transmission frequency in an emergency, so that any changes in the position of the mobile station can be accurately recorded. When there is no need to use the signaling instant for preemption, the signaling instant allocated to the mobile station can be used to send this type of information. The difference between the position data transmission in the standard case and the emergency case is shown in FIG. 5. It can be seen from the figure that, if necessary, when the mobile station participates in a group call, the mobile station can be given more opportunities to send its location data to the system. This is especially important when the mobile station is in an emergency situation, for example.

Fig. 6 shows a block diagram of the mobile communication system of the present invention. The present invention relates to a mobile communication system, including a first M1, a second M2 mobile station, and a third M3 mobile station, and a network infrastructure INFRA, including a switch MX for forwarding group calls and transmissions, and for maintaining group calls GC, The mobile stations M1, M2, and M3 participating in the group call communicate in the form of voice items, and the base station BS is used to maintain the frame structure that includes the time used by the second mobile station M2, which is sending the voice item, in its voice item. Gap. The innovative mobile communication system also includes an allocating device A for allocating time slots or time periods only to the first mobile station M1, so that only the first mobile station M1 can report to the network in a specific time slot or time period. The infrastructure sends signaling messages.

The mobile communication system of the present invention also includes a sending device T for sending data to the first mobile station M1 and the third mobile station M3 in a control message, indicating which time slot or time period only the first mobile station M1 can send . The innovative mobile communication system also includes a control device R in the third mobile station to prevent signaling messages from being sent in the time slot or time period allocated to the first mobile station M1.

The frame structure of the mobile communication system includes a time period common to the first mobile station M1 and the third mobile station M3 for sending signaling messages to the base station BS.

In this innovative mobile communication system, the allocating device A is used to allocate a specific time period of the public time period to only the first mobile station M1 for sending signaling messages, and the sending device T is used to send to the third mobile station M3 The control message indicates that the time period of the frame structure is allocated to the first mobile station.

The innovative mobile communication system also includes a control device C, which instructs the second mobile station M2 to terminate its voice item in response to the signaling message sent by the first mobile station M1, and a sending device T2, which responds to the signaling message sent by the first mobile station M1. The signaling message is sent to the first mobile station.

The drawings and the above description are only used to illustrate the idea of the present invention. Within the scope of the claims, the method of the present invention, the mobile communication provider and the mobile station may vary. Although the present invention is mainly described above for the TETRA mobile communication system, the present invention can also be used in other types of mobile communication systems.