CN100361545C - A method of PTT point-to-point call in digital trunking system based on GSM technology - Google Patents

Abstract

The invention provides a method for PTT point-to-point communication of a digital trunking system based on GSM technology, comprising: a PTT calling mobile station sends a request communication message; a base station controller assigns services to the PTT calling mobile station according to the request communication message channel; the base station controller sends the request communication message to the mobile service control center; the mobile service control center notifies the base station controller to send a notification message to the PTT called mobile station; the PTT called mobile station selects a service channel according to the notification message and PTT calling The mobile station communicates. During point-to-point communication, the calling mobile station and the called mobile station take turns occupying the uplink of the wireless service channel and share the downlink to realize point-to-point PTT half-duplex communication; thereby improving the channel utilization rate of the communication system. The invention adopts the group call process when the call is established, thereby shortening the establishment time of communication.

Description

A method of PTT point-to-point call in digital trunking system based on GSM technology

technical field

The invention relates to network communication technology, in particular to a method for PTT point-to-point calling of a digital trunking system based on the GSM technology system.

Background technique

In the existing cluster network technology, cluster private networks are mostly used. Due to the different technologies and standards of each private network, these private networks are independently constructed by each group, which has formed a situation of independent construction, resulting in low frequency utilization efficiency and network construction. Disadvantages such as high cost and network maintenance costs. With the development of trunking communication technology from analog to digital, the construction of trunking network presents a development direction from independent private network construction to cluster common network construction. Due to the advanced technical system of the GSM (Global System for Mobile Communications) system, it has the most extensive user base in the world. Therefore, the development of GSM-based digital trunking system not only has a good technical foundation, but also has a wide user base.

In the GSM-based digital trunking system technology, Europe has formulated a set of international standards GSM-R (Global System for Railway Mobile Communications) for railway mobile communications. It uses GSM communication technology as a service bearer and can provide eMLPP (enhanced multi-level Priority and Preemption Service) service, VGCS (Voice Group Call Service) service and VBS (Voice Group Call Service) service and other basic trunking communication services;

According to the existing European GSM-R process standard specification, when the calling mobile station and the called mobile station in a cell make a point-to-point call with each other, the calling mobile station and the called mobile station will occupy different services. The channel needs to occupy two A interface circuits and use more TRAU (transcoding and rate adaptation unit) units, which is not conducive to cost saving. Considering that the cluster system often needs to apply for additional bandwidth in addition to the public network bandwidth, the number of channels in the cluster system is actually very tight. Therefore, its system capacity is greatly restricted. Therefore, it is urgent to study how to improve the channel utilization of the cluster system topic.

Since the existing process specification of the GSM-R system does not support PTT point-to-point half-duplex communication in the cell, the use of the point-to-point call service of the GSM-R system does not conform to the usage habits of the existing digital trunking system users for the PTT service. For point-to-point calls in the same cell, both the calling party and the called party will occupy a wireless interface channel. Therefore, under the condition that the number of channels in the cell is very limited, the capacity of the system is severely limited; The call process includes the call initiation of the calling mobile station, the response of the called mobile station, the connection and confirmation of the network side and the mobile called party, so it takes a long time to establish a call; therefore, the initial end-to-end voice transmission channel takes a long time to establish. Not suitable for specific cluster business.

Contents of the invention

The purpose of the present invention is to aim at the shortcoming of above-mentioned prior art, provide a kind of method based on the digital trunking system PTT point-to-point call of GSM technical system, to improve channel utilization rate, thereby increase system capacity, and shorten the establishment time of caller and callee communication .

The present invention provides a kind of method that obtains the digital trunking system PTT point-to-point call based on the GSM technical system, comprising:

A. PTT caller mobile station sends a request communication message;

B. The base station controller allocates a service channel for the PTT calling mobile station according to the request communication message;

C. The base station controller sends the request communication message to the mobile service control center;

D. The mobile service control center notifies the base station controller to send a notification message to the PTT called mobile station;

E. The PTT called mobile station selects a service channel to communicate with the PTT calling mobile station according to the notification message.

The request communication message includes a service type message.

The service type message includes PTT point-to-point half-duplex call message and GSM general point-to-point call message.

Described step B further comprises:

B1. The mobile station controller judges whether this call is a PTT point-to-point half-duplex call according to the request communication message. If so, the mobile station controller assigns a service channel to the PTT calling mobile station and executes step B2. Otherwise, it is generally GSM Point-to-point call processing;

B2. The mobile station that initiates the PTT half-duplex call reports a link establishment instruction message on the assigned traffic channel, and occupies the assigned traffic channel;

When the mobile service control center receives the request communication message, it also conducts call qualification examination on the PTT calling mobile station according to the request communication message. If it passes, the mobile service control center notifies the base station controller to send a notification message to the PTT called mobile station , and execute step E, otherwise, cut off the communication between the calling mobile station and the called mobile station, the base station controller releases the traffic channel allocated for the PTT calling mobile console, and ends the call.

Described step C further comprises:

C1. The base station controller selects a circuit from the circuit pool specific to the A interface;

C2. The base station controller connects the selected A interface specific circuit pool circuit with the corresponding base station and the interface Abis ground circuit of the base station controller;

C3. The base station controller forwards the PTT half-duplex calling layer 3 service message to the mobile service controller through the SS No7 signaling link.

The call qualification examination includes: examining whether the calling mobile station has subscribed to the PTT half-duplex call service, and authenticating the calling mobile station.

The notification message described in the step D includes a channel description message and a called mobile station identity message; the channel description message includes a traffic channel assigned to the PTT half-duplex called mobile station, and the called mobile station identity information represents the called mobile station It is called the identity mark of the mobile station identity information.

The step E includes: the called mobile station transfers to the traffic channel allocated for the called mobile station in the channel description message to receive voice.

The traffic channel assigned to the called mobile station in the channel description message is the same as the traffic channel assigned to the calling mobile station.

Described step E further comprises:

When the called mobile station is not communicating with the calling mobile station, the network side sends an uplink idle message on the downlink fast accompanying channel of the traffic channel;

When the uplink is idle, when the user of the calling mobile station presses the PTT key, the calling mobile station sends an uplink channel occupancy request message to the uplink;

The network side sends an uplink occupation permission message on the downlink fast accompanying channel, at this time the calling mobile station can send a voice message to the called mobile station;

The user's voice of the calling mobile station is transmitted upward through the uplink, and after being looped back through the A interface circuit, the voice of the calling mobile station is sent downward on the downlink channel of the traffic channel.

The network side can periodically send the uplink busy message of the traffic channel on the downlink fast accompanying channel of the traffic channel while the user presses the PTT key;

After the called mobile station receives the traffic channel uplink busy message, the called mobile station does not send any information on the uplink;

After the calling mobile station finishes speaking, release the PTT key, and the calling mobile station sends an uplink release message on the uplink;

The network side receives the uplink release message, and periodically sends the uplink idle message on the downlink fast accompanying channel of the traffic channel.

According to the present invention, during point-to-point communication, the calling mobile station and the called mobile station occupy the uplink of the wireless service channel in turn, share the downlink, and realize point-to-point PTT half-duplex communication; thereby improving the communication system channel utilization.

Description of drawings

Figure 1 shows a call flow diagram according to the present invention;

Fig. 2 shows the flowchart of the PTT point-to-point call process of the present invention;

Fig. 3 shows the flow chart of the communication process between the calling mobile station and the called mobile station in the present invention.

Detailed ways

In order to make it easier for those skilled in the art to understand and realize the present invention, the embodiments of the present invention are described in conjunction with the accompanying drawings.

The point-to-point call process includes group call process and paging process. The group call process refers to: after the calling mobile station initiates a group call, the network side can directly deliver the call in the group call area after passing the calling qualification examination of the calling mobile station. Notification, the notification can directly include the description information of the group call channel. After receiving the group call notification, the called mobile station directly transfers to the group call channel for receiving, and the calling voice can be transmitted to the called mobile station at this time. Therefore, the group call Paging process The caller and called end-to-end set-up time is short; the paging process refers to: after the calling mobile station initiates an ordinary point-to-point call, the network side passes the call qualification examination of the calling mobile station, and then conducts a call to the called mobile station. Paging, that is, to send a paging message to all the cells under the location area of the called mobile station. After receiving the paging message, the called mobile station needs to establish contact with the network side, send a paging response message to the network side, and the network side receives the paging message. After receiving the paging response message, allocate a channel to the mobile station, and issue an assignment command to the mobile station to assign the called mobile station to the allocated channel. Therefore, the voice end-to-end establishment time of the ordinary point-to-point paging process is long .

The general idea of the present invention is: the PTT point-to-point call of the present invention is a call carried out in a certain cell, and the call of the mobile station goes through the group call process, because the notification message sent to the called mobile station contains the MSISDN of the called user (Mobile Station Integrated Services Digital Network Number) information, the MSISDN information is a mobile station number, written in the SIM (Subscriber Identity Module) card of the mobile station, its role is to uniquely identify a mobile station, therefore, the called mobile station Receive the call of the calling mobile station according to the notification message, so as to realize the point-to-point half-duplex PTT (push to talk) service in the cell. When realizing the PTT point-to-point half-duplex service in the cell, the calling mobile station and the called mobile station share the downlink TCH (traffic channel) and occupy the uplink TCH in turn, and the uplink occupied by the calling mobile station and the called mobile station in turn The mechanism adopts the uplink occupation mechanism in the group call service, and the occupation mechanism can be controlled by BTS (base station), BSC (base station controller) or MSC (mobile switching center), so as to realize PTT fast access. The uplink occupation mechanism refers to: when the uplink state of the point-to-point call is idle, the calling user can initiate an uplink application process by pressing the PTT key. After the uplink application is successful, the uplink state is in a busy state, and the user can speak. At this time, The peer mobile station user can only listen but not speak; the user releases the PTT key to initiate the uplink release process. After the uplink release is successful, the uplink state is idle, and the mobile station can press the PTT key to apply for speaking.

The steps for implementing the PTT point-to-point half-duplex call of the present invention will be described in detail below. In order to distinguish between PTT point-to-point half-duplex calls and GSM general point-to-point calls, a byte is usually used to represent the service type in the first layer 3 message. For example, this byte uses different numbers to represent different services, and a standard protocol can be used Any value not used in (for example: 78H) indicates that this call is a PTT point-to-point half-duplex call. That is to say, as shown in Figure 1, in step 1, the calling mobile station initiates a call, and in step 2, it is judged whether the call initiated by the calling mobile station is a call of PTT point-to-point half-duplex service, if PTT point-to-point half-duplex Duplex service, after the wireless interface access stage, the first layer 3 service message reported is represented as a PTT point-to-point half-duplex service call, and then, in step 3, enter the PTT point-to-point half-duplex service call process, otherwise , in step 4, enter the GSM general point-to-point call process.

If the PTT point-to-point half-duplex call message is expressed in the first access burst, the call message is reported on the uplink random access channel through the access burst; if the SDCCH channel is assigned immediately, the PTT point-to-point half-duplex The call message is reported on the SDCCH (independent dedicated control channel); if the TCH channel is assigned immediately, the PTT point-to-point half-duplex call message is reported on the TCH (traffic channel).

In order to speed up the PTT point-to-point half-duplex call establishment, if the PTT point-to-point half-duplex call message is the call establishment message reported through the access pulse, the BSC uses the immediate assignment process to assign TCH to the mobile station; for the immediate assignment In the case of the SDCCH channel, when the BSC decodes layer 3 service messages, if it finds a PTT point-to-point half-duplex call setup message in the cell, the BSC assigns a TCH to the mobile station. Since the transmission rate of TCH is much faster than other channels, the setup time of PTT point-to-point half-duplex calls is shortened for these two cases.

Fig. 2 shows a flow chart of the PTT point-to-point call process of the present invention. In step 20, after specifying the TCH to the PTT half-duplex call originating mobile station, the PTT half-duplex call originating mobile station reports a link establishment instruction message on the TCH and occupies the TCH. At this time, the mobile station and the network pass The TCH establishes a dedicated link. In the present invention, in order to speed up the call setup time, the adopted strategy is: that is, to allow the calling mobile station to communicate with the called mobile station on the uplink without passing the qualification examination, and at the same time, the BSC Forward the calling layer 3 service message to the MSC for signing, if qualified, continue the communication, otherwise, cut off the communication between the calling mobile station and the called mobile station.

In order to connect the calling mobile station with the called mobile station, in step 26, the BTS (base station) on the network side sends a notification message on the notification channel. The notification message includes the following information: channel description information and called mobile station identity information; channel description information includes the TCH allocated to the PTT half-duplex called mobile station, and the TCH and the PTT half-duplex call originating mobile station The TCH service channels are completely the same; the identity information of the called mobile station can use the called MSISDN number, and can also use other identity marks representing the identity information of the called mobile station.

In step 27, the called mobile station finds that the identity information of the mobile station represented in the notification message is the same as its own identity information by receiving the notification message on the notification channel, and then the mobile station transfers to the TCH described in the channel description field to receive , since the loopback operation is preset, the PTT point-to-point half-duplex end-to-end transmission channel is completely connected at this time. The PTT half-duplex called mobile station can communicate with the TT calling mobile station.

At the same time, in step 21, the BSC forwards the calling layer 3 service message converted from the request communication message to the MSC, and in step 22, the MSC performs call qualification examination on the calling mobile station, thereby realizing PTT point-to-point calls are controlled. First, the BSC selects a circuit from the specific circuit pool of the A interface and assigns it to the PTT point-to-point half-duplex call. All the A interface circuits in the circuit pool perform loopback at the 64KBPS rate point; the loopback refers to the uplink The 64KBPS speech code stream decoded by the circuit is sent to the speech coder of the downlink circuit. Then, the BSC performs the connection of the selected A interface specific circuit pool circuit and the corresponding Abis (the interface between the base station and the base station controller) ground circuit; the connection refers to the completion of the Abis uplink time slot and the A interface circuit uplink time slot connection and the connection between the downlink time slot of the Abis interface and the downlink time slot of the A interface circuit. Finally, the BSC forwards the PTT half-duplex calling layer three service message to the MSC through the SS No7 signaling link, and the MSC can check the call qualification of the calling mobile station by the message; in step 23, it is judged whether the review is passed, If passed, in step 28, the calling mobile station and the called mobile station continue to make a subsequent call, otherwise, in step 24, the MSC initiates a call release process to the BSC, and the BSC releases all resources of the call, and the resources include : A interface circuit resources, cell wireless channel resources, and disconnect the Abis interface circuit and A interface circuit connection; the call inspection includes: checking whether the mobile station has signed the PTT half-duplex call service, mobile station authentication and other processes .

Figure 3 shows the process of communication between the PTT calling mobile station and the PTT called mobile station. The PTT calling mobile station and the PTT called mobile station can take turns to talk and occupy the uplink of the wireless TCH in turn, and the downlink shares ; The specific process is as follows:

When in step 31, that is, when both parties do not speak, the network side sends an uplink idle message on the TCH downlink FACCH (fast accompanying channel);

In step 32, when one party needs to speak, press the PTT key, and the mobile station sends an uplink channel occupancy request message uplink;

In step 33, the network side sends an uplink occupation permission message on the downlink FACCH, and in step 34, the user can speak;

The user voice of the speaking mobile station is transmitted upward through the uplink, and after being looped back through the A interface circuit, the user voice is sent downward on the downlink channel of the TCH;

In step 35, when the user presses the PTT key on the network side, the TCH uplink busy message can be periodically sent on the TCH downlink FACCH channel, and the interval period for sending the message will affect the downlink voice, the present invention It is recommended to use more than 0.5 seconds;

When receiving the uplink busy message, the opposite mobile station can display it to the user through a certain man-machine interface. At this time, the user cannot speak and does not send any information on the uplink;

During the period when the PTT key is pressed, the speaking mobile station can adopt a mute mode for the voice received on the downlink circuit in order to avoid hearing the echo and affecting the quality of the call process;

In step 37, it is judged whether the user releases the PTT key, if the PTT key is released, in step 38, the mobile station sends an uplink release message on the uplink, and other users can send a request to talk message on the uplink, Otherwise, in step 39, keep the uplink busy message, other users can not speak;

The network side receives an uplink release message, and periodically sends an uplink idle message on the TCH downlink FACCH channel;

When the mobile station receives the uplink idle message, it can display it to the user through a certain man-machine interface. At this time, the user can speak;

The uplink can be controlled by the BTS, BSC or MSC. This control will affect the PTT to the uplink front station time, and the PTT preemption time will decrease in turn;

When the PTT half-duplex call ends, the user presses the call end key, and the mobile station reports the call end message to the network side. After receiving the message, the network side starts the call release process and releases the PTT half-duplex call; ends the half-duplex PTT The service can be limited to the calling mobile station, or both the calling mobile station and the called mobile station can release the call;

According to the present invention, since the calling party and the called party only occupy one channel, the traffic capacity of the system is doubled, and the conference bridge resource of the network is saved.

A circuit pool can be designed separately for the PTT service at the A interface, and all circuits in the circuit pool can all adopt the loopback mode at the 64KBPS circuit nodes to realize point-to-point half-duplex, because the present invention does not need the voice distribution resources of the network side network side It can be completed on the base station side without participating in the bottom layer connection of the voice channel, thereby shortening the connection time.

The present invention uses a group call process on a large frame instead of a paging process, thereby saving call establishment time.

In order to utilize the preset resource scheme conveniently, the present invention adopts the strategy that the BSC realizes the preset resource scheme as long as the route selection is completed, and at the same time as the route selection, it also completes the establishment of the network side point-to-point PTT half-duplex transmission channel; through experimental testing , Point-to-point PTT half-duplex call setup time is less than 1 second. The establishment of the end-to-end transmission channel can be controlled at about 500 milliseconds;

Other processes on the base station side (such as the occupation of the uplink) can refer to the related process of the group call service, but the network side does not need to participate in the control of the uplink channel;

The use habit of PTT half-duplex service can completely follow the use habit of the existing trunking digital system for this service;

Although the present invention has been described by the embodiments, those of ordinary skill in the art know that, without departing from the spirit and essence of the present invention, the present invention can have many modifications and variations, and the scope of the present invention is defined by the appended rights Requirements to limit.

Claims (11)

1. a method for digital trunking system PTT point-to-point communication based on GSM technology, is characterized in that, comprises: A. PTT caller mobile station sends a request communication message; B. The base station controller allocates a service channel for the PTT calling mobile station according to the request communication message; C. The base station controller sends the request communication message to the mobile service control center; D. The mobile service control center notifies the base station controller to send a notification message to the PTT called mobile station; E. The PTT called mobile station selects a service channel to communicate with the PTT calling mobile station according to the notification message. 2. the method for point-to-point communication of digital trunking system PTT based on GSM technology as claimed in claim 1, is characterized in that, described request communication message comprises service type message. 3. the method for the digital trunking system PTT point-to-point communication based on GSM technology as claimed in claim 2, is characterized in that, described service type message comprises PTT point-to-point half-duplex call message and GSM general point-to-point call message. 4. the method for the digital trunking system PTT point-to-point communication based on GSM technology as claimed in claim 1 or 3, described step B further comprises: B1. The mobile station controller judges whether this call is a PTT point-to-point half-duplex call according to the request communication message. If so, the mobile station controller assigns a service channel to the PTT calling mobile station and executes step B2. Otherwise, it is generally GSM Point-to-point call processing; B2. The mobile station that initiates the PTT half-duplex call reports a link establishment instruction message on the assigned traffic channel, and occupies the assigned traffic channel; 5. the method for the digital trunking system PTT point-to-point communication based on GSM technology as claimed in claim 1, is characterized in that, When the mobile service control center receives the request communication message, it also conducts call qualification examination on the PTT calling mobile station according to the request communication message. If it passes, the mobile service control center notifies the base station controller to send a notification message to the PTT called mobile station , and execute step E, otherwise, cut off the communication between the calling mobile station and the called mobile station, the base station controller releases the traffic channel allocated for the PTT calling mobile console, and ends the call. 6. the method for the digital trunking system PTT point-to-point communication based on GSM technology as claimed in claim 1, is characterized in that, described step C further comprises: C1. The base station controller selects a circuit from the circuit pool specific to the A interface; C2. The base station controller connects the selected A interface specific circuit pool circuit with the corresponding base station and the interface Abis ground circuit of the base station controller; C3. The base station controller forwards the PTT half-duplex calling layer 3 service message to the mobile service controller through the SS No7 signaling link. 7. the method for the digital trunking system PTT point-to-point communication based on GSM technology as claimed in claim 5, is characterized in that, described call qualification examination comprises: examine whether the calling mobile station signs PTT half-duplex calling service, to calling The mobile station performs authentication. 8. the method for the digital trunking system PTT point-to-point communication based on GSM technology as claimed in claim 1, is characterized in that, comprises channel description message and called mobile station identity message in the notification message described in the described step D; The channel description message includes the service channel allocated to the PTT half-duplex called mobile station, and the called mobile station identity information represents the identity of the called mobile station identity information. 9. the method for the digital trunking system PTT point-to-point communication based on GSM technology as claimed in claim 8, is characterized in that, described step E comprises: called mobile station forwards to the channel description message for called mobile station distribution The traffic channel is used to receive voice. 10. The method for PTT point-to-point communication of digital trunking system based on GSM technology as claimed in claim 9, characterized in that, in the channel description message, the traffic channel allocated for the called mobile station is the same as that assigned for the calling mobile station. The business channel is the same. 11. The method for PTT point-to-point communication of digital trunking system based on GSM technology as claimed in claim 1, 9 or 10, characterized in that said step E further comprises: When the called mobile station is not communicating with the calling mobile station, the network side sends an uplink idle message on the downlink fast accompanying channel of the traffic channel; When the uplink is idle, when the user of the calling mobile station presses the PTT key, the calling mobile station sends an uplink channel occupancy request message to the uplink; The network side sends an uplink occupation permission message on the downlink fast accompanying channel, at this time the calling mobile station can send a voice message to the called mobile station; The user's voice of the calling mobile station is transmitted upward through the uplink, and after being looped back through the A interface circuit, the voice of the calling mobile station is sent downward on the downlink channel of the traffic channel. The network side can periodically send the uplink busy message of the traffic channel on the downlink fast accompanying channel of the traffic channel while the user presses the PTT key; After the called mobile station receives the traffic channel uplink busy message, the called mobile station does not send any information on the uplink; After the calling mobile station finishes speaking, release the PTT key, and the calling mobile station sends an uplink release message on the uplink; The network side receives the uplink release message, and periodically sends the uplink idle message on the downlink fast accompanying channel of the traffic channel.

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