Method and apparatus for monitoring link activity to prevent system deadlock in a dispatch system

Method and device for monitoring communication line activity in dispatch system to prevent system stall

Background of the invention

The invention relates to a dispatching system, especially a dispatching system configured in a cellular system.

In a radio telephone communication system, multiple users communicate on a radio channel to interconnect wireless and wired telephone systems. Communication on wireless channels can have a variety of different proximity channel technologies, including time division multiplexing (TDMA), frequency division multiplexing (FDMA), and code division multiplexing (CDMA). CDMA technology has several advantages. For a representative CDMA system, see US Patent Application No. 4,901,307, and "SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS" filed by K. Gilhousen et al. On February 13, 1990. People, and this article is listed here as a reference document.

In the above patent application, the multiple multiplexing technologies proposed (there are a large number of mobile phone system users here), each of which requires a transceiver (communication via a satellite adapter), an airborne converter, or the use of CDMA Ground base station transceiver sub-system for spread spectrum communication signals. In communications using CDMA, the frequency can be used multiple times to allow for increased user capacity of the system.

In the CDMA honeycomb system, each base station transceiver subsystem covers a limited geographical area and in this coverage area, the remote control unit is connected to the public switched telephone network (PSTN) via the peak nest system. When a remote control unit moves into the coverage area of a new base station transceiver subsystem, the path called by the user is transmitted to the new base station transceiver subsystem. The signal transmission path from the broadcast channel to the remote control unit is called a forward link, and the path from the remote control unit to the broadcast channel is called a reverse link.

In a representative radio communication system, a remote control unit may use a voice encoder system, which encodes voice information under variable rate data. In a processing rate system, the dispatch transmission rate can be reduced due to the quiescing sound action. The lower dispatch rate reduces the level of interference due to the remote unit transmitting to other users. In a broadcast channel, one of the voice encoder systems of the broadcast channel uses the same audio information. In addition to sound information, there is a person who dispatches the information or a mixture of sound and assignment can be transmitted by the remote control unit.

A remote control unit is a preferred embodiment of a multi-rate voice encoder when a remote control unit is generating its own dispatch for transmission. When the sound or dispatch action reaches a minimum, the multi-rate voice encoder transmits at a lower rate, and when the sound level or dispatch action is high, it transmits at a higher rate. In a preferred embodiment, the internal sound-encoder processes encoding assignments from digital samples of sound information at four different rates, such as 8,000 bits per second (bps), 4,000 bps, 2,000 bps, and 1,000 bps. Based on sound action during 20 ms data. Dispatched by each voice encoder. The overhead bits are used to format the data of the voice encoder into 9,600 bps, 4,800 bps, 2,400 bps, and 1,200 bps. The highest dispatch transmission rate data corresponding to 9,600 bps data is called "full rate" data; 4,800 bps dispatch data is called "half rate", 2,400 bps dispatch data is called "1/4 rate" data, and 1,200 The bps dispatch data is called "1/8 rate" data. A vocoder suitable for this environment can be found in U.S. Patent Application No. 5,414,796, entitled "Variable Rate vocoder", published May 9, 1995, and assigned to the assignee of the present invention. Even when the remote control unit receives assignments such as terminal equipment units from outside resources, the remote control unit continuously processes the assignments in this variable rate data format.

When the government issues a license for the original Peak Nest phone spectrum, the use of this spectrum is restricted to the fact that carriers cannot provide distribution services. However, due to the advantages of the CDMA system and the expenses and problems of each person assigning the use and maintenance of the system, the government will check this requirement again. The government itself can benefit greatly from this service.

Basically, wireless and wired services provide point-to-point services, and dispatch services provide services for one or more people. The distribution services are shared by local police wireless systems, taxi dispatch systems, federal intelligence and secret operations, and general military communications systems.

The basic model of the dispatch system involves the use of a broadcast network. Each broadcast network user monitors a common broadcast forward link signal. If the threshold user wants to talk, he presses a push-to-talk button (PTT), and this is to allow system talker priority. Basically, the voice of the talking user is transmitted from the reverse link to the broadcast link. Ideally, the dispatch system allows ground and wireless proximity systems. When the user of the remote control unit finishes talking, release the PTT button. In response to the remote control unit generating a button to talk about the pause instruction, this ends the priority and makes the system idle, so that other users can use it.

If the button or talk button on the remote control unit is paused, the remote control unit may have priority to allow the system talker. Therefore, the system resources are expanded, and other remote control units can be prevented from approaching the system, because the remote control unit with the paused audio encoder stops the system. This state is called a system stall, and is of course an extremely unnecessary state. The invention provides a device and a device capable of detecting a system pause and preventing the harmful effects generated by the system.

When a remote control unit user presses the button to talk button, the communication manager can give the remote control unit system talker priority. When the remote control unit has system talker priority, his voice is transmitted to other remote control units that are members of the dispatch system. When the remote control unit uses the release button or talk button, the communication manager rejects the system talker priority of the remote control unit, and therefore the system of other remote control units with system talker priority is also idled. If the button of the remote control unit is stopped, the remote control unit continues the system talker priority, thus preventing other remote control units from being allowed the system talker priority. The present invention monitors the sound action of a signal received from a remote control unit of a broadcast channel. If the sound action is lower than a certain level, it is assumed that the remote control unit no longer needs the system talker priority, and the broadcast channel generates a proxy indicating that the button, that is, the talk button has been released, and transmitted to the communication manager. The personnel will allow the system talker to give priority to another remote control unit.

The features and advantages of the present invention can be further understood from the following description. Please refer to the accompanying drawings when reading: FIG. 1 is a block diagram of a representative dispatch system; and FIG. 2 is a representative step of configuring the present invention.

FIG. 1 shows a representative dispatching system. In a preferred embodiment, the remote control units 10, 20, 22, 24, in particular, can be used as telephones for dispatching units and point-to-point communication. In FIG. 1, the remote control unit 10 is now in operation and the remote control units 20, 22, 24 are passive listeners. The broadcast channel antennas 30, 32, 34 can provide forward-linked broadcast channels to the remote control units 20, 22, 24. The broadcast channel antenna 30 transmits and receives a helpful forward and reverse traffic channel from the remote control unit 10. The help traffic channel is similar to the forward link broadcast channel, except that the remote control unit 10 can receive signal information specific to the remote control unit, such as power control commands. The mobile switching center (MSC) 38 sends a signal from a group of base station transceiver sub-systems, which includes the base station transceiver sub-systems 44, 48, 50. The system includes broadcast channel antennas 30, 32, 34, base station transceiver subsystems 44, 48, 50, and MSC 38 called broadcast channel 28. The communications manager 40 controls the allowable system talker priority, such as to a remote control unit, where the user in the unit has pressed a push-to-talk button (PTT). In a preferred embodiment, air interface signaling and modulation are performed according to a code division multiple access (CDMA) system. See TIA / EIA / IS-95 "Mobile Station-Base Station Compatibility Standard for Dual-Mode "Wideband Spread Spectrum Cellular Systems" is generally referred to as IS-95. In IS-95, a remote control unit is called a mobile unit.

It is known in the art that the base station transceiver subsystem can be divided into three regions. The use of a base station transceiver subsystem here refers to a single area in the base station transceiver subsystem or the base station transceiver subsystem.

In FIG. 1, a two-way connection is established between the mobile remote control unit 10 and the base station transceiver subsystem 44. To become active. The remote control unit 10 transmits a proximity channel message to request a traffic channel from the base station transceiver sub-system 44. Send a proximity message on the proximity channel. The proximity channel is a reverse link channel used by the remote control unit to communicate with the broadcast channel. The proximity channel is a shared slotted random proximity channel. Only one remote control unit of each base station transceiver system in each frequency channel can successfully use the proximity channel. Proximity channels are used for short message exchanges, such as in response to a signal from a pager. A proximity attempt is transmitted by the remote control unit in a string of proximity detection signals. Each proximity detection signal carries the same information, but is transmitted at a higher power than the former. The proximity detection signal is transmitted until the broadcast channel is informed that the signal has been received in the remote control unit.

After the remote control unit 10 has established a communication link, it receives any incoming messages on the forward broadcast channel on the connected traffic channel before assisting. In this way, the remote control unit 10 does not monitor the forward link broadcast channel, but receives all the distribution system information on the link traffic channel before its own assistance. The remote control unit 10 transmits the signal back to the base station transceiver sub-system 44 in the helpful reverse channel. Therefore, the remote control unit 10 has its own forward link signal path, and the specific information of the remote control unit can be included in the transmission. For example, if the remote control unit 10 can operate as a dispatch system and a point-to-point telephone unit, the remote control unit 10 learns from the forward link traffic channel that the incoming point-to-point call is directed to the remote control unit 10.

On the other hand, the passive remote control units 20, 22, and 24 in FIG. 1 do not have a reverse link signal established for any base station transceiver subsystem. Even when the remote control units 20, 22, 24 are passive remote control units, they can still use the proximity channel and the broadcast channel for communication. In the preferred embodiment, the passive remote units 20, 22, 24 use proximity channels to send messages to the base station transceiver subsystem (if they need more power from the forward link broadcast channel). In order to respond to the power request for proximity messages, the base station transceiver subsystem can increase the transmission power level of the forward link broadcast channel.

In a standard CDMA system, this program allocates resources so that the remote control unit can become active, can talk for a few seconds, and process a substantial amount of resources. In a preferred embodiment, when the remote control unit presses a button to talk, it dispatches A set of resources. When the remote control unit releases the button to talk button, resources still help the remote control unit for a period of time. During this period, when the user does not press the button to talk button, the remote control unit is designated as active and in a suspended state. The suspended remote control unit transmits and receives a series of transmission rate messages to maintain the connected power control. According to this method, when the user of the remote control unit presses the button to talk button, the link is completely established and responds immediately. This type of operation can be adapted to the natural conversational use of the dispatch system. When the pause between button press talk actions exceeds a critical value, resources can be released. After the resources have been released, the remote control unit sends an initiation message on the proximity channel to establish a link again. However, only one remote control unit can talk at any time, but more than one remote control unit can be operated.

The operation of the above system can be very different from the standard push-to-talk operation. The configuration of a representative button-to-talk system uses the same frequency or two frequencies. When the user of the remote control unit presses the button to talk button, it transmits on the common frequency and blocks all other signals proximate to the channel, even when other users talk first. In particular, when a talker talks, his receiver is disabled to prevent backtracking. In this way, when the user of the remote control unit presses the button-to-talk button, and his receiver is disabled, he cannot hear his own voice. Therefore, the button of a remote control unit, that is, the talk button is pressed, not only other users cannot request the system, but also the user cannot hear the warning message even when sending an overload message.

In the standard push-to-talk system, there is no requirement for the system talker priority and the corresponding allowable system talker priority. And after the remote control unit has pressed the button-to-talk button, there is no way to override the system talker priority. And in typical systems, it is difficult to detect sound movements. The invention is different. In the preferred embodiment, CDMA multiple proximity technology is used (in another embodiment other multiple proximity technologies may be used). In a CDMA system, more than one remote control unit can be transmitted at the same time and at the same frequency. Even when the remote control unit is continuously transmitting, other remote control units in the area can still use the same frequency to help channels such as proximity channels, forward traffic channels, and forward link broadcast channels. And when the remote control unit is talking and generates a reverse link traffic channel signal, it continuously receives a forward link traffic channel signal. If the voice of the user of the remote control unit is not included after the forward link traffic channel signal, the speaker on the remote control unit can still operate and the specific remote control unit acts as a system talker. In this way, a priority unit can generate an audio message even when a button is pressed to talk about a button.

When the user starts to press the button or talk button, a PTT_on indication is sent from the remote control unit to the broadcast channel. When the user releases the button to talk button, a PTT_off instruction is transmitted from the remote control unit to the broadcast channel. Nominally, until the PTT_off instruction is received, there is no way to allow the button to talk about proximity. In another design concept of the present invention, the positioning button, that is, the talk button is disabled, so that the PTT_off indication cannot be transmitted.

In the preferred embodiment, the remote control unit is the preferred embodiment of a multi-rate voice encoder. When the sound or dispatch action reaches a minimum, the multi-rate voice encoder transmits at a lower rate, and when the sound level or dispatch action is high, it transmits at a higher rate. In a preferred embodiment, the internal sound-encoder processes encoding assignments from digital samples of sound information at four different rates, such as 8,000 bits per second (bps), 4,000 bps, 2,000 bps, and 1,000 bps. Based on sound action during 20 ms data. Dispatched by each voice encoder. The overhead bits are used to format the data of the voice encoder into 9,600 bps, 4,800 bps, 2,400 bps, and 1,200 bps. The highest dispatch transmission rate data corresponding to 9,600 bps data is called "full rate" data; 4,800 bps dispatch data is called "half rate", 2,400 bps dispatch data is called "1/4 rate" data, and 1,200 The bps dispatch data is called "1/8 rate" data. A sound encoder suitable for this environment can be found in U.S. Patent Application No. 5,414,796, entitled "Variable-Rate Sound Encoder", published on May 9, 1995 and assigned to the assignee of the present invention, even when When the remote control unit receives an assignment such as a terminal equipment unit from an external resource, the remote control unit continuously processes the assignment in this variable rate data format. Under the minimum connection assignment, the voice encoder in the present invention transmits 1/8 rate data.

Two different methods can be addressed in the present invention. In the first method, the user presses a button or talk button. The remote control unit transmits a PTT_on indication and receives a channel designation. However, users do not talk either intentionally or unexpectedly. In addition, no PTT_off was received in the broadcast channel. If you use the talk button without releasing the button, the broadcast channel may not receive the PTT_off indication. If the button is disabled when the button is pressed on the remote control unit, the broadcast channel may not receive the PTT_off indication.

In the second state, which is somewhat the same but not completely improved, the user presses the voice encoder. The remote control unit transmits a PTT_on indication and receives a channel designation. Users talk and send voice communications to other people. However, whether intentionally or unexpectedly, users stop talking for a while. Again, no PTT_off indication was received in the broadcast channel. If the application user does not release the button, the broadcast channel will not receive the PTT_off instruction. If the push-to-talk button is pressed or the remote control unit is disabled, the broadcast channel will not receive the PTT_off indication.

In either state, the system stalls unless a member of the network has indicated that it is a priority user and the intervening remote control unit can be "interrupted". In this state, there is no remote control unit in the network that can cost the talker, and the application vetoes stop. In the present invention, a monitoring link (sound or dispatch) action is applied to prevent this state. The invention can be shared with other agencies to prevent pauses, and the pause system is close, such as the US patent application number _________, whose title is "METHOD AND APPARATUS FOR ACCESS REGULATION AND SYSTEM PROTECTION OF A DISPATCH SYSTEM", June 24, 1996 Filed on the following day and assigned to the assignee of the present invention. Another reference document is US Patent Application No. __________, titled "METHOD AND APPARATUS FOR EFFICIENT SYSTEM ACCESS IN A DISPATCH SYSTEM". And assigned to the assignee of the present invention.

There are several ways to detect link movement. If the vocoder is similar to the vocoder described above, the average number of low-rate data received over a period of time can be determined. This method can also be used on dispatch transmissions. Using this method, if background noise causes occasional high-rate data, a valid continuous sound signal can still be detected. Other fixed-rate digital voice encoders can use different encoding methods depending on whether the audio is audible or non-voice. Broadcast channels can monitor the type of encoding that uses encoded signals to detect link movement. Another way is to monitor the frequency content of the coded signal to determine if sound is present. So it can be discovered earlier when responding to assignments on assignment links. For example, the broadcast channel may simply look up the number of messages in the incoming signal, or compare the average number of bits with a value of 1 compared to the total number of bits.

Fig. 2 is a flowchart showing the basic operation of the present invention. In the preferred embodiment, the system is executed by the broadcast channel 28 (FIG. 1). The system is preferably located in the MSC 38 (Figure 1), and some operations can be performed in the base station transceiver subsystem. In the most general embodiment, the system can be anywhere in the communication system. The system shown in Figure 2 performs one operation on each remote control unit, which allows the system interlocutor priority.

Beginning at start block 100, operation begins when the remote control unit receives permission to allow a system talker (block 102). This allows a representative response to a PTT_on indication received from the remote control unit. The two counts are also set to the starting value in block 102. When the first assignment is transmitted from the remote control unit to the broadcast channel, the broadcast channel determines whether there is sufficient linking action to indicate that a live sound or dispatch communication has been received (block 106). If not, then T₁The count increases with the elapse of the reaction time (block 108). A query is made at block 110 whether a denial of system talker priority has been received. This veto signal is received if the remote control unit releases the button-to-talk button or if the remote control unit interrupts for another remote control unit. If a veto has been received, the flow is terminated in block 114. If no veto signal is received, block 112 is performed. If T₁Count does not exceed critical value₁In block 112, the flow returns to block 106. If T₁Count exceeded threshold₁In block 112, the broadcast channel generates a PTT_off to the communication manager, so the system is idle in block 134 for use by other remote control units.

If a linking action is detected in block 106, the second phase of the flow is entered, where the second state is located. While the dispatch continues to be transmitted from the remote control unit to the broadcast channel, the link action is monitored in block 116. Increase T if there is insufficient linking action to indicate the receipt of a motion sound or dispatch communication₂The count is based on the passage of reaction time (block 118). At block 120, a query is received as to whether a veto signal of the system talker priority has been received. If a veto signal is received, the process is terminated in block 128. If no veto signal is received, block 122 continues. If T₂Count does not exceed critical value₂(Block 122), go to Block 116. If T₂Count exceeded threshold₂(Block 122), the broadcast channel generates a PTT_off and transmits it to the communication manager, so the system is idle in block 134 for use by other remote control units, and the process is terminated in block 138. If a linking action is detected in block 116, return to T₂Count (block 126). Block 130 asks if a veto signal has been received for the system talker's priority. If a veto signal has been received, the process ends in block 136. If no veto signal is received, the process of block 116 continues.

The mechanisms used in blocks 106, 116 to detect linking actions may be the same or different. An example of a link detection mechanism is counting the average number of rate data received over a period of time. Using this method, if the background noise produces occasional high-rate data, it can still detect the lack of effective continuous sound signal. In the preferred embodiment, the data of the voice encoder is transmitted over the air at a rate of one data every 20 msec. The agencies in blocks 106, 116 can monitor 16 consecutive data. If 15 of the 16 data contains a 1/8 rate dispatch, the link action is not sufficient to indicate that the action is in use.

When the broadcast channel transmits the communication manager proxy PTT_off instruction, the communication manager may or may not recognize receiving the proxy instruction from PTT_off directly from the remote control unit. When the communication manager instructs multiple agents PTT_off, the system manager can transmit a veto signal of the priority of the system talker to the remote control unit. If the communication manager cannot identify the agent's PTT_off instruction and the remote control unit that generates the PTT_off instruction, it can send the required signal without each PTT_off instruction it receives. If the two cannot be identified, the agent PTT_off is often received, and the communication manager only needs to send a veto signal. In the preferred embodiment, the negative signal is transmitted to the remote control unit on the reverse link traffic channel. In order to respond to the veto signal, the remote control unit may pause to transmit a movable sound signal and become inactive or enter a suspended state.

Note the operation of the flowchart of FIG. 2. Above the loop (generally containing blocks 106, 108, 110, and 112) is related to the first state. The upper loop counts the linked actions monitored until a motion sound is received or a communication is dispatched. If the upper loop is actuated, the lower loop generally including blocks 116, 118, 120, and 122 is related to the first state. When the call is in progress, the upper loop continuously enters the signal linking action. Note the critical value₁, Critical value₂It is not necessary to have the same value. If you choose the same value for both, the circuit becomes a single circuit. In most general cases, the critical value₁Less than critical₂. It is assumed that if the user presses the voice encoder at the beginning, it is because he needs to have some signals to communicate. If communication has not started immediately, the system may be stopped due to errors or internal intentions. Because once the user starts talking, it is no longer a threshold₂, Which assumes a pause during the conversation. Critical value₁The value is 5-10 seconds. Critical value₂The value can be 10-20 seconds.

In most general embodiments, the present invention is a method and device for monitoring the disappearance of sound or dispatch information in a push-to-talk system. However, the general principle in FIG. 2 can be used in many different embodiments. For example, the maximum transmission rate data may not be 1/8 rate data in different embodiments. If a microphone or other sound path fails in the remote control unit, the present invention can prevent a pause so that no sound signal is dispatched in the remote control unit.

There are many variations and configurations within the viewpoint of the present invention. A configuration may contain all the elements of the invention and does not necessarily have to follow the flowchart of FIG. 2. For example, it appears in the above figure that if the broadcast channel receives a PTT_off message from the remote control unit at any time, all the process procedures are abandoned. Obviously, the same effect can be achieved by using interrupts instead of periodic challenges. And the order of the blocks in the process can be rearranged without affecting the operation of the system. Moreover, it should be noted that even referred to as "remote control unit", some units may be wireless units.

The above description of the preferred embodiment is based on the fact that those skilled in the art can use the present invention. Those skilled in the art can make various modifications to these embodiments, and the derivative principle defined in the text can be used in other embodiments without the device of the present invention. Therefore, the description in the text is not to limit the present invention, but to explain the principle of the present invention and the salient features in the text.