MXPA99000199A - Method and apparatus for monitoring the linking activity to avoid the staging of the system in a waste system - Google Patents

Abstract

The present invention relates to a method and apparatus for preventing stagnation of the system in a dispatch system by monitoring the binding activity. The dispatch system is comprised of a set of remote units (10,20,22) that communicate with each other when transmitting one at a time to the group. A remote unit (10) communicates with the other remote units through at least one base station (44). A communication manager (40) grants a remote unit (10) to be the exclusive speaker of the system after the request through the base station serving the requesting remote unit (44). The base station (44) monitors a series of data from the remote unit designated as the system speaker (10) to detect the voice activity. The base station (44) sends a sub-requested request to the communication manager (40) to yield the privilege of the system speaker if the voice activity falls below a predetermined threshold

Description

METHOD AND APPARATUS FOR MONITORING THE LINKING ACTIVITY TO AVOID SYSTEM SETTING IN A DISPATCH SYSTEM I. Field of the Invention This invention relates generally to dispatch systems and, more particularly, to the implementation of a dispatch system in a cellular system. II. DESCRIPTION OF THE RELATED ART In a wireless telephone communication system, many users communicate over a wireless channel to connect to other wired and wireless telephone systems. Communication over the wireless channel can be one of a variety of multiple access techniques. These multiple access techniques include multiple access by time division (TDMA), multiple access by frequency division (FDMA), and multiple access by division of code (CDMA). The CDMA technique has many advantages. In U.S. Patent No. 4,901,307 issued February 13, 1990 to K. Gilhousen et al., Entitled "MULTI ACCESS COMMUNICATION SYSTEM OF DIFFUSED SPECTRUM USING SATELLITE OR TERRESTRIAL REPEATERERS", ("SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM" USING SATELLITE OR TERRESTRIAL REPEATERS ") assigned to the assignee of the present invention and incorporated herein by reference, an exemplary CDMA system is described. In the aforementioned patent, a multiple access technique is disclosed where a large number of users of mobile telephone systems, each having a transceiver, communicate through satellite repeaters, aerial repeaters, or base station transceiver subsystems. terrestrial radio signals that use broadcast signals of CDMA. When using CDMA communications, the frequency spectrum can be reused multiple times, allowing an increase in the capacity of the system user. In the CDMA cellular system, each base station transceiver subsystem provides coverage to a limited geographic area and links the remote units in its coverage area through a cellular system switch to the public switched telephone network (PSTN). When a remote unit moves to the coverage area of a new base station transceiver subsystem, the user's routing is transferred to the new base station transceiver subsystem. The signal transmission path of the base station to the remote unit is referred to as the forward link and the signal transmission path of the remote unit to the base station is referred to as the reverse link.

In a typical wireless telephone communication system, the remote unit may employ a vocoder system that encodes the voice information in a variable speed format. In a variable speed system, the data transmission speed may be decreased due to pauses in voice activity. The lower data rate reduces the level of interference to other users, caused by the transmissions of the remote unit. In the base station, a vocoder system is used to reconstruct the voice information. In addition to the voice information, the data information alone or a mixture of the two can be transmitted by the remote unit. When a remote unit produces its own transmission data, an internal vocoder produces, from digital samples of the voice information, coded data at four different speeds, for example, approximately 8,000 bits per second (bps), 4,000 bps, 2,000 bps and 1,000 bps, based on voice activity during a structure of 20 milliseconds (ms). Each vocoder data structure is formatted with supplementary bits as data structures of 9,600 bps, 4,800 bps, 2,400 bps and 1,200 bps. The higher speed data structures that correspond to a 9,600 bps structure are referred to as a "full speed" structure; a data structure of 4,800 bps is referred to as a "medium speed" structure; a data structure of 2,400 bps is referred to as a "quarter-speed" structure; and a data structure of 1,200 bps is referred to as a "one-eighth speed" structure. In U.S. Patent No. 5,414,796 entitled "VARIABLE SPEED VOCODIFIER", issued May 9, 1995 and assigned to the assignee of the present invention, a vocoder is described which is suitable for application in this environment. When the remote unit receives data from an external source, such as a terminal equipment unit, the remote unit continues to process the data in this variable speed structure format. When the original cellular telephony spectrum licenses were issued by the government, one of the restrictions on the use of the spectrum was that carriers could not provide dispatch services. However, due to the great advantages of the CDMA system and the expenses and problems inherent in the deployment and maintenance of private delivery systems, the government is reexamining this point. The government itself would greatly benefit from such services. While typical wired and wireless telephony service provides point-to-point service, dispatch services provide service from one to many points. The common use of dispatch services are local police radio systems, taxi cab dispatch systems, secret service operations and the Federal Intelligence Commission and military communication systems in general. The basic model of a dispatch system consists of a network of user dissemination. Each user of the broadcast network monitors a forward link signal of common broadcast. If a network user wants to speak, press a push button to talk (PTT) and they are granted the system conferencing privileges. Typically, the voice of the talking user is addressed from the reverse link over the forward link of broadcast. Ideally, the dispatch system allows land and wireless access to the system. When the user of the remote unit has finished speaking, he releases the PTT button. In response, the remote unit generates a push button indication to speak off which terminates the privileges and frees the system for use by other system users. If the push button to speak on a remote unit is pressed, the remote unit can be granted system conferencing privileges. The resources of the system are thus consumed and other remote units can be prevented from accessing the system because the remote unit with the push button to speak pressed is blocking the system. This type of scenario is referred to as system stagnation and is, of course, a highly undesirable state. The present invention is a method and apparatus for detecting the stagnation of the system and truncating its harmful effects. SUMMARY OF THE INVENTION When a user of the remote unit presses the push button to speak, a communications administrator may grant privileges of the system conferrer to the remote unit. When the remote unit has system conferencing privileges, its voice signal is broadcasted to the other remote units that are members of the dispatch system. When the user of the remote unit releases the press to talk button, the communications manager denies the system conferencing privileges to the remote unit and frees the system so that the other remote units have system conferencing privileges. If the push button to talk about the remote unit is pressed, the remote unit retains the system's conferencing privileges thus preventing other remote units from obtaining conferring system conferencing privileges.

The present invention monitors the voice activity of the signal received from the remote unit in the base station. If the voice activity falls below a certain level, it is assumed that the remote unit no longer needs the conferencing privileges of the system and the base station generates a subrrogated indication that the push to talk button has been released, the which is sent to the communications manager. In this way the communications administrator is free to grant the lecturer privileges of the system to another remote unit. BRIEF DESCRIPTION OF THE DRAWINGS The features, objects and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which: Figure 1 is a block diagram of a system of typical office; and Figure 2 is a flow chart showing an exemplary set of steps for implementing the present invention. DESCRIPTION OF THE PREFERRED MODALITY Figure 1 shows a typical dispatch system. In the preferred embodiment, the remote units 10, 20, 22, and 24 can operate both as dispatch units and point-to-point telephones. In Figure 1, the remote unit 10 is currently active and the remote units 20, 22 and 24 are currently passive listeners. The antennas of the base station 30, 32 and 34 can provide the forward link channel of broadcast to the remote units 20, 22 and 24. The antenna of the base station 30 transmits and receives a specialized reverse and forward traffic channel. to and from the remote unit 10. The specialized traffic channel is similar to the forward link broadcast channel except that, for example, the remote unit 10 can receive other signaling information specific to the remote unit such as control commands of energy. The mobile switching center (MSC) 38 coordinates the signaling to and from a set of base station transceiver subsystems that comprise base-staging transceiver subsystems 44, 48 and 50. The system comprising the base station antennas 30, 32 and 34 and the base station transceiver subsystems 44, 48 and 50 and the MSC 38 are referred to as the base station 28. The communication manager 40 controls the network such as granting the system conferencing privilege to a remote unit whose user has Press the Press to Talk button (PTT). In the preferred embodiment, signaling and modulation of the air interface are in accordance with the Code Division Multiple Access (CDMA) system described in "Mobile Station Compatibility Standard-Base Station for Diffused Spectrum Cell Systems Broadband Dual Mode "TIA / EIA / IS-95, generally referred to simply as IS-95. In IS-95, the remote unit is referred to as a mobile station. It is well known in the art that base station transceiver subsystems can be divided by sectors such as into three sectors. When the term base station or base station transceiver subsystems is used herein, it implies that the term may refer to a whole base station transceiver subsystem or to a single sector of a base station transceiver subsystem. In Figure 1, the active remote unit 10 has a bidirectional link established with the base station transceiver subsystem 44. In order to become active, the remote unit 10 sends an access channel message requesting a traffic channel to the transceiver subsystem of base station 44. The access message is sent over the access channel. The access channel is a reverse link channel used by the remote units to communicate to the base station. The access channel is a shared slotted random access channel. Only one remote unit per sector of the base station transceiver subsystem can successfully use the access channel at a time. The access channel is used for exchanges of short signaling messages such as call origins, answers to pages and records. An access attempt is sent by the remote unit in a series of access tests. Each access test contains the same information but is transmitted at a higher energy level than the previous one. The access tests continue until the recognition of the base station in the remote unit is received. When the remote unit 10 has established a communication link, it receives any signaling present in the forward broadcast channel on a dedicated forward link traffic channel. In this way, the remote unit 10 does not monitor the forward link broadcast channel and still receives all the information from the dispatch system on its own specialized forward link traffic channel. The remote unit 10 is again communicated to the base station transceiver subsystem 44 on a specialized reverse channel. Because the remote unit 10 has its own specialized forward link signal path, the sending of specific messages from the remote unit can be included in the signaling. For example, if the remote unit 10 is capable of operating both a remote dispatch system unit and a point-to-point telephone unit, the remote unit 10 can be informed on the forward link traffic channel that a call point-to-point is being directed to the remote unit 10. On the other hand, in Figure 1, the passive remote units 20, 22 and 24 do not have a reverse link signal established towards any of the base station transceiver subsystems. Even though the remote units 20, 22 and 24 are passive, they can still use the access channel to communicate with the base station. In the preferred embodiment, the passive remote units 20, 22 and 24 use the access channel to signal the base station transceiver subsystem if they are in need of more power from the forward link broadcast channel. In response to the power demand access message, the base station transceiver subsystem may increase the transmit power level of the forward link broadcast channel. In a standard CDMA system, the process of allocating resources in order for the remote unit to become active may take several seconds as well as a substantial amount of processing resources. In order to preserve the resources of the system and avoid the associated delay, in the preferred mode, when a remote unit presses the press button to speak, a set of resources is assigned. When the remote unit releases the press to talk button, the resources remain dedicated to the remote unit for some period of time. During the time when the user is not found pressing the press button to speak, the remote unit is designated as active and is said to be on hold. A remote unit that is waiting sends and receives a series of inactive messages at low speed to preserve control of the link power. In this way, when the user of the remote unit subsequently presses the press button to speak, the link is established completely and is answered immediately. This type of operation accommodates the use of the natural dialogue of a dispatch system. When the pause between push-to-talk activations exceeds a threshold, resources can be released. After the resources have been released, the remote unit must send a source message over an access channel to reestablish a connection. Although it is true that only one remote unit can be found talking at the same time, more than one remote unit can be active. The operation of the system described above can be vastly different from the standard operation of press to talk. A typical speaking press system is implemented by using a common frequency or set of two frequencies. Once the user of a remote unit has pressed the press button to speak, is transmitting over the common frequency and has blocked all others to access the channel. It also blocks the channel by pressing its press button to speak even if another user was speaking first. Typically, while the speaker is talking, his receiver is disabled to avoid feedback. In this way, when the user of the remote unit presses the press button to speak and his receiver is disabled he will not hear his own voice. Therefore, if the press button is pressed to talk about a unit, not only other users can not access the system but the user itself may not be able to hear a warning message even if a modification message is transmitted . In a standard press-to-talk system there is no demand for system conferencing privileges or the corresponding granting of system conferencing privileges. There is also no way to deny the conferencing privileges of the system after a remote join has pressed the push button to speak. Also in a typical system it is difficult to detect voice activity. The present invention is very much different. In the preferred embodiment, a CDMA multiple access technique is used. (Alternative access techniques can be used in the alternative modalities). In a CDMA system, more than one remote unit can transmit on the same frequency at the same time. Even if the remote unit transmits continuously, other remote units in the area continue to be able to use the same frequency to communicate over the access channel, specialized traffic channels and the forward link broadcast channel, as well as others. Note also that while the remote unit is talking and generating a reverse link traffic channel signal, it continues to receive the forward link traffic channel signal. If the voice of the user of the remote unit is not included in the signal of the forward link traffic channel, the speaker in the remote unit may remain enabled while the remote unit is designated as the system speaker. In this way, a privileged unit could generate a voice message for the remote unit even when its press button is pressed to speak. When the user initially presses the push button to speak, a PTT_out indication is sent from the remote unit to the base station. When the user releases the press to talk button, a PTT_out indication is sent from the remote unit to the base station. Nominally, until the indication of PTT_off is received, no push access can be granted to speak to any other user. One aspect of the present invention is directed to the situation in which the push button to operate in such a way that no indication of off-switch PTT is transmitted. In the preferred embodiment, the remote unit comprises a multi-rate vocoder. A multi-speed vocoder transmits at a low speed when voice or data activity is decreased and transmits at higher speeds when the level of voice or data activity is high. In the preferred embodiment, the internal vocoder produces, from digital samples of the voice information, coded data at four different speeds, for example, approximately 8,000 bits per second (bps), 4,000 bps, 2,000 bps and 1,000 bps, in based on voice activity during a structure of 20 milliseconds (ms). Each vocoder data structure is formatted with supplementary bits as data structures of 9,600 bps, 4,800 bps, 2,400 bps and 1,200 bps. The higher speed data structures that correspond to a 9,600 bps structure are referred to as a "full speed" structure; a data structure of 4,800 bps is referred to as a "half speed" structure; a data structure of 2,400 bps is referred to as a "quarter-speed" structure; and a data structure of 1,200 bps is referred to as a "one-eighth speed" structure. In U.S. Patent No. 5,414,796 entitled "VARIABLE SPEED VOCODIFIER", issued May 9, 1995 and assigned to the assignee of the present invention, a vocoder is described which is suitable for application in this environment. Even when the remote unit receives data from an external source, such as a terminal equipment unit, the remote unit continues to process the data in this variable speed structure format. The present invention can make use of the fact that if a minimum link data is presented, the vocoder sends structures of one-eighth of speed. There are two different scenarios that are addressed by the present invention. In the first scenario, the user presses the press button to speak. The remote unit sends an indication of PPT_out and receives a channel assignment. However, either intentionally or unexpectedly, the user does not speak. Additionally, no indication of PTT_ off at the base station is received. The base station may not receive the indication of PTT_off if the user does not release the press button to speak. The base station may not receive the indication of PTT_off if the button is locked or the remote unit is operating erroneously otherwise. In a similar but slightly different second scenario, the user presses the press button to speak. The remote unit sends a PTT_on indication and receives a channel assignment. The user speaks and sends voice traffic to the other members of the network. However, either intentionally or unexpectedly the user stops talking for a prolonged period of time. Again, no indication of PTT_off is received at the base station. The base station may not receive the indication of PTT_off if the user does not release the press button to speak. The base station may not receive the indication of PTT_off if the button is locked or the remote unit is operating erroneously otherwise. In any scenario, unless one of the members of the network has been designated as a higher priority user and can 'interrupt' the errant remote unit, the system is in stalemate. In such case, no other remote unit in the network can become the speaker, thus disabling the network. The present invention avoids such stagnation by monitoring the link activity (voice or data). The present invention can be used in conjunction with other mechanisms to prevent stagnation and regulate access to the system, such as those described in US Patent Application Serial No. 08 / 671,132 entitled "METHOD AND APPARATUS FOR REGULATION OF ACCESS AND PROTECTION OF SYSTEM OF AN OFFICE SYSTEM ", (" METHOD AND APPARATUS FOR ACCESS REGULATION AND SYSTEM PROTECTION OF A DISPATCH SYSTEM ") which was presented on June 24, 1996 and is assigned to the assignee of the same and in the Patent Application American Series No. 08 / 671,131 entitled "METHOD AND APPARATUS FOR EFFICIENT SYSTEM ACCESS IN AN OFFICE SYSTEM", ("METHOD AND APPARATUS FOR EFFICIENT SYSTEM ACCESS IN A DISPATCH SYSTEMS") which was filed on June 24, 1996 and is assigned to the transferee of the same. There are many ways to detect link activity. If a vocoder similar to that described above is used, the average number of low speed structures received during a period of time can be determined. This method is also applicable to data transmission. In this way, if the background noise causes occasional structures of higher speed, still the lack of a valid continuous voice signal is detected.

Other fixed-rate digital vocoders may use different encoding methods depending on whether the audio signal is voice or noise other than voice. The base station can monitor an indication of the type of coding used to encode the signal in order to detect link activity. Another scheme can monitor the spectral content of the encoded signal in order to determine the presence or absence of voice. The absence of data in the data connection can be even easier to detect. For example, the base station can simply observe the number of transitions in the incoming signal or the average number of bits with value "1" compared to the total number of bits. Figure 2 is a flow chart with which the basic operation of the present invention is explained. In the preferred embodiment, the system is executed by the base station 28 (of figure 1). The system most likely resides in the MSC 38 (of Figure 1) while several of the operations may take place within the base station transceiver subsystems. In the most general mode, the system can be located anywhere in the communications system. The system shown in Figure 2 is executed once for each remote unit to which system conferencing privileges are granted.

Starting from the start block 100, the operation begins when a conferring of system conferencing privileges is received for the remote unit, block 102. Such granting is typically in response to an indication of PTT_out received from the remote unit. Also in block 102, the two counts are fixed at an initial value. As the first data is transferred from the remote unit to the base station, the base station determines whether the link activity is sufficient or not to indicate the reception of an active voice or data communication, block 106. If not, the count Tx is increased to reflect the passage of time, block 108. Block 110 asks whether a denial of system lecturer privileges has been received. Such denial can be received if the remote unit releases the press button to speak or if the remote unit is interrupted by another remote unit. If a negation has been received, the flow ends in block 114. If no negation has been received, the flow continues to block 112. If the count T1 does not exceed the threshold, the threshold- ^ in block 112, the flow it continues back to block 106. If the count Tx exceeds the threshold, the threshold-!, in block 112, the base station generates an indication of overdue PTT to be sent to the communications manager, block 134, thereby releasing the system for used by other remote units. If linkage activity is detected in block 106, a second phase of the flowchart that addresses the second previous scenario is introduced. As the data continues to be transferred from the remote unit to the base station, block 116 monitors the link activity. If there is not sufficient link activity to indicate receipt of an active voice or data communication, the count T2 is increased to reflect the passage of time in block 118. Block 120 asks whether a denial of privileges has been received. lecturer of the system. If a negation has been received, the flow terminates in block 128. If no negation has been received, the flow continues to block 122. If counting T2 does not exceed the threshold, threshold2, in block 122, the flow continues back to block 116. If count T2 exceeds a threshold, threshold 2, in block 122, the base station generates an indication of subtracted shutdown PTT to be sent to the communications manager, block 134, thereby releasing the system for use by other remote units and the flow ends in block 138. If link activity is detected in block 116, the count T2 is reset, block 126. Block 130 asks if a denial of system conferencing privileges has been received. If a negation has been received, the flow terminates in block 136. If no negation has been received, the flow continues to block 116. The mechanism displayed in blocks 106 and 116 for detecting link activity may be the same or different. An example of a link detection mechanism is the counting of the average number of low speed structures received over a certain period. In this way, if the background noise causes an occasional structure of higher speed, still the lack of a valid continuous voice signal is detected. In the preferred embodiment, the structures of the vocoder are transferred over the air at a rate of one per 20 msec. The mechanisms of blocks 106 and 116 can monitor 16 consecutive structures. If 15 out of 16 of the structures comprise one-eighth speed data, the link activity is not sufficient to indicate active use. When the base station sends the indication of the subtracted PTT_out to the communication manager, the communications manager may or may not be able to distinguish the undersigned indication from a clear PTT indication received directly from the remote unit. When the communications manager receives the indication of the outgoing PTT_off, he can respond by sending a denial of system conferencing privileges to the remote unit. If the communication manager can not distinguish between the indication of the removed PTT_out and a indication of the offset PTT generated by the remote unit, it may send the denial in response to each indication of the offset PTT. If you can distinguish between the two, the communication manager only needs to send a denial when an indication of the canceled PTT_out is received. In the preferred embodiment, the negation is sent over the reverse link traffic channel to the remote unit. In response to denial, the remote unit can stop the transmission of an active voice signal and either become inactive or enter a standby state. The remote unit can respond by alerting the user or by taking corrective action. Note that the flow chart shown in Figure 2 operates to be carried out. The upper cycle, generally comprised of blocks 106, 108, 110 and 112, refers to the first scenario. The upper cycle monitors activity until active voice or data communication is received. If the upper cylinder is left, the lower cycle, generally comprised of the blocks 116, 118, 120 and 122, refers to the second scenario. The lower cycle continues to monitor the binding activity of the input signal as the call progresses. Note that the threshold values! and threshold2 do not need to be the same value. If they are selected as the same value, the cycle collapses in a single cycle. In a more general situation, the threshold! has a value smaller than threshold2. It is assumed that if a user initially presses the press button to speak, it is because he has something he wants to communicate. If you do not start communicating the message immediately it is probably because there is an error or an intentional attempt to stall the system. Threshold2 is greater because once the user has begun to speak, it is assumed that he can stop during the conversation. Threshold! it can have a value such as 5 - 10 seconds. The threshold 2 may have a value such as 10-20 seconds. In the most general mode, the present invention is a method and apparatus for monitoring the absence of voice or data information in a push to talk system in order to avoid system stagnation. Of course, the general principles illustrated in Figure 2 could be applied to very different modalities. For example, the lower speed structure may not be a one-eighth speed structure in an alternative mode. The present invention would also prevent stalling if a microphone or other voice path component failed in the remote unit such as if no voice signal was transmitted from the remote unit. There are many variations and implementations that fall within the scope of the present invention. An implementation may comprise all the elements of the present invention and not exactly follow the flowcharts of Figure 2. For example, it is explicit in the above diagram that if at any time the base station receives an indication of PTT_ off from the remote unit, the process of the flow chart is completely aborted. Obviously, the same effect could be achieved by using interruptions instead of periodic questions. The blocks can also be reordered within the flow without affecting the operation of the system. Note also that although the text here refers to remote 'units', some of the units can be units connected by cable. The prior description of the preferred embodiments is provided to allow any person skilled in the art to make or use the present invention. The various modifications to those modalities will readily become apparent to those skilled in the art, and the generic principles defined herein may be applied to other modalities without the use of the inventive faculty. Thus, the present invention is not intended to be limited to the modalities shown herein but to be in accordance with the broadest scope consistent with the principles and novel features set forth herein.

Claims (23)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and therefore the property described in the following claims is claimed as property. A method for preventing stagnation in a dispatch system where a set of remote units communicates with each other by transmitting one to the group at a time, characterized in that it comprises the steps of: receiving at a base station from a remote unit , a demand to be a lecturer of the system; receiving at said base station from a communications administrator a grant to be a lecturer of the system for said remote unit; monitoring a series of data from said remote unit in said base station to detect voice activity; and sending, via said base station, to said communications manager a sub-demand to desist as said lecturer from the system of said remote unit if said voice activity falls below a threshold.
2. 2. A method for preventing stagnation in a speech oppress system characterized in that a single remote unit can be designated as a system lecturer at the same time, comprising the steps of: monitoring the link activity of a remote unit that is currently located designated as said lecturer of the system; and sending a denial of system conferencing privileges to said remote unit if a lack of link activity is detected.
3. The method according to claim 2, characterized in that said step of monitoring comprises the steps of: examining a spectral content of a signal received from said remote unit; comparing said spectral content with said first predetermined threshold; and determining a lack of link activity if said spectral content is less than said first predetermined threshold.
4. The method according to claim 2, characterized in that a signal received from said remote unit comprises digital data and wherein said examination stage comprises the steps of: examining the transitions between logical states of "1" and "0" in said digital data; and determining that said lack of link activity exists if an average number of said transitions falls below a first predetermined threshold.
5. The method according to claim 2, characterized in that a signal received from said remote unit comprises digital data and wherein said monitoring step comprises the steps of: determining an average number of occurrences of the logical state of "1" in said digital data compared to a total amount of digital data received; and determining that said lack of link activity occurs if said average number of occurrences is below a first threshold or above a second threshold.
6. The method according to claim 2, characterized in that a signal from said remote unit comprises variable speed data organized in structures, each structure having one of a set of preselected data transmission rates that also comprise the step of evaluating said structures to determine such lack of link activity.
7. The method according to claim 2, characterized in that a signal from said remote unit comprises variable speed data organized in structures, each structure having one of a set of preselected data transmission rates and wherein said monitoring stage further comprises the steps of: determining an average number of structures received from said remote unit at a rate lower than said set of preselected data transmission rates; and determining whether said lack of link activity occurs if said average number of structures exceeds a first threshold for a first amount of time.
8. 8. The method according to claim 7, characterized in that said monitoring step further comprises the steps of: determining an initial presence of link activity if a number of structures are received at a different speed than said lower speed of said set of transmission rates of preselected data; and determining that said lack of link activity occurs after detecting said initial presence of link activity if said average number of structures exceeds a second threshold for a second amount of time.
9. The method according to claim 8, characterized in that said second amount of time is greater than said first amount of time.
10. 10. A method for preventing stagnation in a dispatch system characterized in that it comprises the steps of: establishing a communication resource to be used by a first remote unit as a lecturer of the system; receiving a system conferencing privilege claim from said first remote unit; granting said system lecturer privilege to said first remote unit; receiving a traffic signal from said first remote unit; monitor the link activity in said traffic signal; and denying said system lecturer privilege to said first remote unit if said link becomes inactive.
11. The method according to claim 10, characterized in that the link is defined as inactive after said link activity decreases below a predetermined level.
12. The method according to claim 10, characterized in that it further comprises the step of reserving said communication resources for use by said first remote unit subject to a subsequent demand to become said lecturer of the system without requiring the repetition of said step of establishing said communication resource.
13. The method according to claim 10, characterized in that said traffic signal is a multiple access signal by code division.
14. The method according to claim 10, characterized in that said traffic signal is a timeslot multiple access signal.
15. The method according to claim 10, characterized in that said step of denying said system conferencing privilege to said first remote unit comprises the steps of: sending, from a base station to a communications manager, a sub-term request to terminate said system conferencing privilege in said first remote unit; respond to said sublicense request by sending a denial of conferencing privilege of the system of said communication manager to said base station; and sending said conferencing privilege denial of the system of said base station to said first remote unit.
16. The method according to claim 15, characterized in that it further comprises the steps of: sending a shutdown indication, releasing the demand for said system conferencing privilege, from said first remote unit to said base station; sending a request to terminate said system conferencing privileges from said first remote unit from said base station to said communications manager in response to said shutdown indication; and sending said denial indication of said communication manager to said base station.
17. The method according to claim 10, characterized in that said traffic signal of said first remote unit comprises variable speed data organized in structures, each structure having a set of preselected data transmission rates, wherein said monitoring stage further comprises the steps of: determining in said base station, an average number of structures in said traffic signal to a lower one of said set of preselected data transmission rates; and determining that said linkage activity has fallen below said predetermined level if said average number of structures exceeds a first threshold for a first amount of time.
18. The method according to claim 17, characterized in that said monitoring step further comprises the steps of: detecting in said base station an initial presence of said link activity; and determining that said binding activity has fallen below said predetermined level after detecting said initial presence of said binding activity when said average number of structures exceeds a second threshold for a second amount of time.
19. The method according to claim 18, characterized in that said step of detecting said initial presence of link activity comprises the step of detecting, in said traffic channel, a number of structures at a data rate different from said lower data rate. said data transmission speeds.
20. 20. A system for preventing stagnation in a dispatch system characterized in that it is configured to service remote units, said system comprising: a remote unit, designated as a lecturer of the system, which sends variable speed data to broadcast the transmission to a set of other remote units; a base station receiving said variable rate data, monitors said variable rate data to detect link activity and broadcasts said variable data transmission rate to said set of other remote units; and a communications manager receiving a deregistered remote unit release indication signal from said base station if said link activity falls below a predetermined level and which issues a release indication signal to said base station for transmission to said remote unit, in order to order said remote unit to cease the transmission of said variable speed data.
21. 21. An apparatus that prevents stagnation in a push to talk system characterized in that a single remote unit can be designated as a system conferrer at any point in time, comprising: means for monitoring the link activity of a first remote unit that said lecturer of the system is currently designated; and means for sending a denial of system conferencing privileges to said first remote unit if a lack of link activity is detected.
22. 22. The apparatus according to claim 21, characterized in that a signal from said first remote unit comprises variable speed data organized in structures, each structure having one of a set of preselected data transmission rates wherein said monitoring means further comprise means for determining an average number of structures received from said first remote unit to a lower one of said set of preselected data transmission rates; and means for detecting said average number of structures exceeding a first threshold during a first amount of time as said lack of link activity. The apparatus according to claim 21, characterized by said monitoring means further comprising: means for detecting an initial presence of link activity if a number of structures are received at a different speed than a lower one of said set of transmission rates of preselected data; and means for determining said lack of binding activity after detecting said initial presence of binding activity if said average number of structures exceeds a second threshold for a second amount of time.