MXPA99000198A - Method and apparatus for efficient system access in a waste system - Google Patents

Abstract

The present invention relates to a method and apparatus for providing access to a dispatch system. A communication manager (40) simultaneously grants a privileged lecture privilege of the system to a remote unit (10) in the system. After a remote unit (10) requests and is designated as the exclusive speaker of the system, no other remote unit (20, 22) can transmit during a first predetermined amount of time. After the first predetermined time has elapsed, any other remote unit (20,22) can request the exclusive lecturer privilege of the system to become the exclusive lecturer of the system. The system-exclusive conferencing privilege15 is revoked by the communication manager (40) to any remote unit that retains the exclusive conferencing privilege of the system for more than a second predetermined amount of time. The exclusive conferencing privilege20 of the system is also revoked after the release of a press button to speak on a remote unit (10). In addition, a liase station (44) in communication with a remote unit (id designated as the exclusive lecturer of the system generate a surrogate injury claim to the communications manager (40) if the exclusive lecturer of the system travels outside the coverage area of the system, loses energy or is destroyed

Description

METHOD AND APPARATUS FOR EFFICIENT SYSTEM ACCESS IN AN OFFICE SYSTEM Background of the Invention I. Field of the Invention This invention relates generally to a dispatch system and, more particularly, to the access regulation in a system. of dispatch. II. Description of the Prior 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 the 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 exposed where a large number of users of the mobile telephone system, each having a transceiver, communicate through satellite repeaters, aerial repeaters or terrestrial base stations using signaling signals. spread spectrum communication 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 geographical area and links the remote units in its coverage area through a system switched to the public switched telephone network (PSTN). When a remote unit moves to the coverage area of a new base station transceiver subsystem, the call routing of the remote unit 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 an exemplary CDMA system, each base station transceiver subsystem transmits a pilot signal having a common pseudorandom noise (PN) broadcast code which is shifted in code phase from the pilot signal of other base station transceiver subsystems. During the operation of the system, the remote unit is provided with a list of code phase offsets corresponding to the surrounding base station transceiver subsystems surrounding the base station transceiver subsystem through which communication is established. The remote unit is equipped with a search element with which it tracks the signal strength of the pilot signal from a group of base station transceiver subsystems that include the surrounding base station transceiver subsystems. In U.S. Patent No. 5,267,261, entitled "SOFT TRANSFER AUXILIARY BY A MOBILE IN A CDMA CELLULAR COMMUNICATION SYSTEM", ("MOBILE ASSISTED SOFT HANDFIND IN A CDMA CELLULAR COMMUNICATION SYSTEM") issued on November 30, 1993, assigned to the The present invention provides a method and system for providing communication with a remote unit through more than one base station transceiver subsystem during the transfer process. When using this system, communication between the remote unit and the end user is not is interrupted by the eventual transfer of an original base station transceiver subsystem to a subsequent base station transceiver subsystem. This type of transfer can be considered a "soft" transfer since communication with the subsequent base station transceiver subsystem is established before communication with the original base station transceiver subsystem is terminated. When the remote unit is in communication with two subsystem base station transceivers, the remote unit combines the signals received from each base station transceiver subsystem in the same manner in which multiple path signals from a common base station transceiver subsystem are combined. In a typical macrocell system, a system controller may be employed to create a single signal for the end user from the signals received by each base station transceiver subsystem. Within each base station transceiver subsystem, the signals received from a common remote unit can be combined before being decoded and thus a total advantage of the multiple received signals is obtained. The decoded result from each base station transceiver subsystem is provided to the system controller. Once a signal has been decoded, it can not be combined with other signals. In this way, the system controller must select among the plurality of decoded signals produced by each base station transceiver subsystem with which communication is established by a single remote unit. The most advantageous decoded signal is selected from the set of signals from the base station transceiver subsystems and the non-chosen signals are simply discarded. Because the remote unit is in communication with the end user through at least one base station transceiver subsystem at all times through the smooth transfer process, no interruption in communication occurs between the remote unit and the user final. A smooth transfer provides significant benefits in its inherent "do rather than interrupt" technique over the conventional "interrupt beforehand" technique used in other cellular communication systems. In a wireless telephone system, maximizing the capacity of the system in terms of the number of simultaneous telephone calls that can be handled is extremely important. The capacity of the system in a broadcast spectrum system can be maximized by controlling the transmission power of each remote unit such that each transmitted signal reaches the receiver of the base station transceiver subsystem at the same level. In a real system, each remote unit can transmit the minimum signal level that produces a signal-to-noise ratio that allows for an acceptable data recovery. If a signal transmitted by a remote unit reaches the receiver of the base station transceiver subsystem at a power level that is too low, the bit error rate may be too high to allow high quality communications due to interference from the other remote units. On the other hand, if the signal transmitted by the remote unit is at an energy level that is too high when it is received in the base station transceiver subsystem, communication with this particular remote unit is acceptable, but this high signal Energy acts as interference for the other remote units. This interference can negatively affect communications with other remote units. Accordingly, to maximize the capacity in an exemplary CDMA broadcast spectrum system, the transmit power of each remote unit within the coverage area of a base station transceiver subsystem is controlled by the base station transceiver subsystem in order to produce the same nominal received signal energy in the base station transceiver subsystem. In the ideal case, the total signal energy received in the base station transceiver subsystem is equal to the received nominal power of each remote unit multiplied by the number of remote units that transmit within the coverage area of the base station transceiver subsystem plus the energy received in the station transceiver subsystem base from the remote units in the coverage area of the surrounding base station transceiver subsystems. It is also desirable to control the relative energy used in each data signal transmitted by the base station transceiver subsystem in response to the control information transmitted by each remote unit. The basic reason for providing such control is to accommodate the fact that in certain locations the forward channel link may be unusually disadvantageous. Unless the energy that is being transmitted to the disadvantageous remote unit is increased, the signal quality may become unacceptable. An example of such a location is a point where the path loss to one or two surrounding base station transceiver subsystems is almost the same as the path loss to the base station transceiver subsystem communicating with the remote unit. In such a location, the total interference would be increased three times over the interference observed by the remote unit at a point relatively close to its base station transceiver subsystem. In addition, the interference that comes from the surrounding base station transceiver subsystems does not weaken in unison with the signal coming from the active base station transceiver subsystem as would be the case for the interference that comes from the active base station transceiver subsystem. A remote unit in such a situation may require an additional signal power of 3 to 4 dB from the active base station transceiver subsystem to achieve adequate performance. At other times, the remote unit can be located where the ratio of signal to interference is unusually good. In such a case, the base station transceiver subsystem could transmit the desired signal by using a transmitter power lower than normal, reducing the interference to other signals that are being transmitted by the system. To achieve the above objectives, a signal-to-interference measurement capability can be provided within the receiver of the remote unit. This measurement is carried out by comparing the energy of the desired signal with the total energy of the interference and noise. If the measured proportion is less than a predetermined value, the remote unit transmits a request to the base station transceiver subsystem for additional energy in the forward link signal. If the ratio exceeds the predetermined value, the remote unit transmits a demand for energy reduction. One method by which the receiver of the remote unit can monitor the proportions of signal to interference is the monitoring of the structure error rate (FER) of the resulting signal. Another way is by measuring the number of cancellations received. The base station transceiver subsystem receives the power adjustment demands from each remote unit and responds by adjusting the energy assigned to the corresponding forward link signal by a predetermined amount. The adjustment is typically small, such as in the order of 0.5 to 1.0 dB, or about 12%. The rate of energy change may be somewhat slower than that used for the reverse link, perhaps once per second. In the preferred embodiment, the dynamic range of the adjustment is typically limited such as 4 dB less than nominal to about 6 dB greater than the nominal transmission power. The base station transceiver subsystem must also consider the energy demands made by the other remote units when deciding whether it meets the demands of any particular remote unit. For example, if the base station transceiver subsystem is loaded in its capacity, additional power demands can be granted, but only 6% or less, instead of 12% normal. In this regime, a demand for energy reduction would still be granted at the normal 12% change. When the original cellular telephony licenses were issued by the government, one of the restrictions on the use of the spectrum was that carriers could not provide dispatch system services. However, due to the great advantages of the CDMA system and the expenses and inherent problems of unemployment and maintenance of private delivery systems, the government is re-examining this point. The government itself would greatly benefit from such services. While the typical wired and wireless telephony service provides point-to-point service, the 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 press to talk (PTT) button. Typically, the voice of the talking user does address from the reverse link over the forward link of broadcast. Ideally, the dispatch system allows terrestrial access and connected by cable to the system. When a remote unit that is part of a dispatch system presses the press button to speak, you would like to start talking immediately. However, in conventional wireless systems, a noticeable amount of time is necessary to establish a link before the user can be talking. The present invention is an efficient solution for system access. The present invention also provides means for regulating and protecting access to the system in a dispatch system. SUMMARY OF THE INVENTION When a remote unit initially 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 a certain period of time. During the time when the user does not press the push button to speak, the remote unit and the base station transceiver subsystems send a low speed series of inactive structures to each other to preserve link power control. 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 natural use of a dispatch system. The time during which a remote unit is found by pressing the press button to speak is divided into two different periods. During the first period of time, full priority of use of the system is given to the remote unit once it has been granted to be the lecturer of the system. When the first period of time expires, a second period of time begins. During the second period of time, if any other remote unit presses the press button to speak, the first remote unit is prevented and the system's conferencing privileges are denied. The remote switch unit is granted to be the lecturer of the system. Typically, when the press to speak button is released, the remote unit sends a PTT_out indication to the base station. The base station passes the indication of PTT_off to the communication manager so that the communications administrator can grant a new remote unit to be the system speaker. However, if a remote unit has been granted as the lecturer of the system and during that time it leaves the coverage area of the system, the remote unit is unable to transmit an indication of PTT_off to the base station. The base station is aware that the remote unit has left the coverage area but the communications manager does not. In response to the output of the remote unit, the base station generates a subtracted PTT_address indication to be sent to the communications manager. The communication manager responds by denying the lecturer access of the system to the remote unit and thereby freeing other remote units to become the system lecturer. 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 shows a typical dispatch system; Figures 2A and 2B are an implementation of an exemplary block diagram of an immobilization time system; Figures 3A and 3b are an implementation of exemplary block diagrams for access regulation and system protection of a dispatch system; And Figure 4 shows a more detailed representation of a typical dispatch system. 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 an active speaker 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 dedicated forward and reverse traffic channel. to the remote unit 10. The dedicated traffic channel is similar to the forward link broadcast channel except that, for example, the remote unit 10 can receive other remote unit-specific signaling information such as power control commands. In the preferred embodiment, the energy control in the dedicated traffic channel link with the remote unit 10 is carried out as set forth in U.S. Patent No. 5,056,109 entitled "METHOD AND APPARATUS FOR CONTROLLING TRANSMISSION ENERGY IN A SYSTEM CELLULAR CELLULAR TELEPHONY OF CDMA ", (" METHOD AND APPARATUS FOR CONTROLLING TRANSMISSION POWER IN A CDMA CELLULAR MOBILE TELEPHONE SYSTEM ") issued on October 8, 1991, assigned to the assignee of the present invention. The mobile switching center (MSC) 38 coordinates signaling to and from all base station transceiver subsystems such as the base station 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 "The Mobile Station Compatibility Standard-Base Station for Diffused Spectrum Cell Systems Broadband Dual Mode "(" Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular Systems ") 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 is assumed 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 for the base station transceiver subsystem sector can successfully use the access channel at a time. The access channel is used for exchanges of short signaling messages such as call origins, responses to pages and registers. 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 an acknowledgment is received from the base station in the remote unit. When the remote unit 10 has established a communication link, 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 dedicated forward link traffic channel. The remote unit 10 is again communicated to the base station transceiver subsystem 44 on a dedicated reverse channel. In the preferred embodiment, the energy control over the forward and reverse links is carried out as described above in accordance with IS-95. Because the remote unit 10 has its own dedicated 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 as 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. Note that if the remote units 20, 22 and 24 are completely passive, the individual base station transceiver subsystems may not realize if the remote units are in their corresponding coverage areas. Even if a remote unit registers with the base station transceiver subsystem when it enters the coverage area of a base station transceiver subsystem, the base station transceiver subsystem has no way of knowing when the remote unit has left the base station's coverage area. base station transceiver subsystem. 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 can increase the transmit power level of the forward link broadcast channel. When a remote unit initiates a connection, a series of transactions must take place to allocate resources. For example, Figure 4 shows a more detailed representation of a typical dispatch system. In Figure 4, the CDMA interconnection subsystem 216, the call control processor 224 and the system controller 218 can be included within the MSC 38 of Figure 1. To initiate a connection, the remote unit 200 sends a message of origin on an access channel comprising a PTT_only indicating that the press to talk button has been pressed. The base station 210A receives the message and sends a message to the system controller 218 through the CDMA interconnection subsystem 216. The system controller 218 sends a message back to the base station 210A, which in response sends a message about the paging channel to the remote unit 200, acknowledging receipt of the access message. The system controller 218 must notify the call control processor (CCP) 224, which pays attention to the call. The call control processor 224 manages any number of services that may be demanded (e.g., point-to-point services, push-to-talk services, data services, or secure voice services). If the call control processor 224 issues a grant to allocate resources, the call control processor 224 allocates the system resources within the various entities. Both hardware and software resources are allocated to handle the call. For example, the modulator / demodulator pair 212 is assigned in the base station 210A. The CDMA interconnection system (CIS) 216 connects the modulator / demodulator pair 212 to the system controller 218. Within the system controller 218, the selector 220A is assigned to handle the call. From selector 22OA, switch 226 is used to connect the call to the PSTN or connect the call back to the system controller 218. The address designations of the allocated resources and the control information must be passed between the various entities for establish a path of the remote unit 200 to the PSTN. That said, more than 30 messages should be sent to establish a traffic channel. Note that the PTT on indication is passed to the communications manager (not shown). The exemplary embodiment of Figure 4 is used to illustrate the allocation of resources. Of course, other architectures could be used in conjunction with the present invention. In addition to different architectures, the functions can be distributed among the equipment elements different from that shown in Figure 1 and Figure 4. For example, the communication manager function can be integrated into the general system controller equipment or the selectors. The communication of messages and the allocation of resources can take from one to three seconds. For a normal point-to-point call, even a three-second delay is tolerable and probably not noticeable to the end user. Typically, when a user places a point-to-point call, he must wait while the destination telephone rings. Three additional seconds do not greatly affect the amount of time you must wait for a response. Contrasting the operation of the point-to-point system with the operation of a press-to-speak dispatch system, in a dispatch system, when the user of the remote unit presses the press button to speak he would like to start speaking immediately. A delay of three seconds is not acceptable for him. A typical dispatch system specifies a maximum delay time of 300 or 400 milliseconds. A process for pre-allocation of resources is detailed in co-pending US Patent Application No. 08 / 661,690 entitled "METHOD AND APPARATUS FOR ACCELERATED RESPONSE TO A DEMAND FOR ALLOCATION OF RESOURCES IN AN OFFICE SYSTEM" ("METHOD AND APPARATUS FOR ACCELERATED RESPONSE TO RESOURCE ALLOCATION REQUEST IN DISPATCH SYSTEM ") which was filed on June 11, 1996 and is assigned to the assignee of the present invention. In addition to the pre-allocation process, the present invention reduces the number of resource allocation demands by retaining the assigned link for some period of time after the press to speak button is released. The present invention is effective whether or not a pre-allocation process is used. 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, he is transmitting over the common frequency and has blocked all others from accessing the channel. It also blocks the channel by pressing its press button to speak even if another user was speaking first. Also, typically to avoid feedback, while the speaker is talking his receiver is disabled. To avoid feedback, when the user of the receiving unit presses the push button to speak, his receiver is disabled so that he does 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 thec.

User himself 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 resources or the corresponding granting of resources. There is also no way to deny access after a remote unit has pressed the press button to speak. The present invention is very much different. Note that a CDMA multiple access technique is used in the preferred mode. (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, dedicated 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. In a standard CDMA system, the process of receiving a grant when allocating resources and the process of allocating resources can take several seconds as well as a substantial amount of processing resources. In order to preserve the resources of the system and to avoid the associated delay, in the preferred modality detailed below, when a remote unit presses the push 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. Figures 2A and 2B are an implementation of exemplary block diagrams of a standby time system. "Standby time" is the term used to describe the state in which the remote unit is active and a dedicated link is assigned, but during which the remote unit is not the lecturer of the system. 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 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 Figures 2A and 2B is executed once for each remote unit that generates a PTT_on indication. The flow begins in the start block 100. If the remote unit is not yet active, the base station processes a request for a grant of resource allocation and resources are assigned to the remote unit. In block 102, an indication of PTT_out from the remote unit is received and the link is passed to the communication manager. Also in block 102, parameter T3 is set as the initial value. Block 106 asks if the communications manager has rejected system conferencing privileges. If another remote unit has already been designated as the system lecturer, system conferencing privileges can not be granted to the remote unit. If a clear PTT indication has been received from the remote unit, the remote unit is denied system conferencing privileges. As described extensively with respect to Figures 3A and 3B, the communications administrator may deny system conferencing privileges after granting system conferencing privileges if another demand for system conferencing privileges is received. The communications administrator may also deny system conferencing privileges after granting system conferencing privileges if the remote unit has had system conferencing privileges for more than a predetermined amount of time. If the answer is no, the flow continues to block 112. If a remote unit that has been granted system conferencing privileges moves outside of the system coverage area or if power is removed from the remote unit or if the remote unit is destroyed, the remote unit is unable to communicate an indication of PTT_off to the base station. The base station is aware that the remote unit has left the coverage area but the communications manager does not. In response to the output of the remote unit, the base station generates a PTT_supplied indication subrrogated for the remote unit. The communications manager responds by denying system conferencing privileges to the remote remote unit and therefore frees the system to be used by other remote units.

Block 112 asks if the service option is connected. If the base station is receiving valid structures from the remote unit, the service option is connected. If not, the remote unit may have moved out of the system coverage area or may have lost power or may have been destroyed and the flow continues to block 114. In block 114, the base station generates the indication of overdue PTT and the send to the communications manager. The base station then processes a request to break the link. Execution of the standby time system is completed and the flow ends in block 128. Going back to block 112, if the service option is connected, the flow continues back to block 106. Block 106 asks if the communications administrator has denied system conferencing privileges. If the answer is yes, the flow continues in block 118. Blocks 118, 120, 122, 124 and 126 implement the time-out feature. When the remote unit is in 'wait', it sends and receives inactive structures to preserve the link. Inactive structures fill the system with data so that system resources remain allocated and power control in forward and reverse links continue to work. Block 118 asks whether the service option is connected in the same way as block 112. If the option is not connected, the remote unit may have moved out of the system coverage area or may have lost power or may have been destroyed. In such case, the allocated resources can be released for use by another remote unit and the flow continues to block 126. In block 126, the base station processes a link break. The execution of the time-out system is completed and the flow ends in block 128. If the service option is switched on, the flow continues from block 118 to block 120. In block 120, T3 is increased to reflect the step of weather. In block 122, the current value of T3 is compared to a threshold. If the value of T3 exceeds the threshold, in block 126 the base station processes a link break. The execution of the time-out system is completed and the flow ends in block 128. If the value of T3 does not exceed the threshold, the flow continues to block 124. If during this time the user of the remote unit presses the button From press to talk and the remote unit generates a PTT_on indication, the communications administrator can grant system conferencing privileges to the remote unit. Block 124 asks whether system conferencing privileges have been granted to the remote unit. If not, the flow continues back to block 118 and the remote unit continues to wait. If a conferring of conferencing privileges is received from the system, the value T3 is reset, block 108, and the flow continues back in block 106. Note that if a remote unit wishes to preserve the link and continue on hold longer than that the standby time parameter T3 designates, the user of the remote unit can 'key in' the press button to speak by pressing and quickly releasing the push button to speak. By such action, the remote unit generates a positive response to the question in block 124. The value T3 is reset in block 108. Because the press-to-talk button is released quickly, a positive response is generated in response to the question of block 106 and the remote unit starts waiting again for the total duration of T3. As noted above, when the user initially presses the push button to speak, a PTT_out indication is sent from the remote unit to the communications manager. When the user releases the press to talk button, a PTT_out indication is sent from the remote unit to the communications manager. Nominally, until the indication of PTT_off is received, press access can not be given to speak to any other user. One aspect of the present invention addresses the situation in which the press button to speak or in which a general interruption without priority is operating erroneously. Figures 3A and 3B are an implementation of exemplary block diagrams of a system for access regulation and system protection of a dispatch system. In this case, the communications manager divides the time into three periods, beginning the time when a remote unit presses the press button to speak. During the first period, the remote unit has exclusive control over the link since no other remote unit in the same range can interrupt it. When the first period ends, the second period begins. During the second period, the remote unit is interruptible by other remote units of the same range and possibly lower. If no other remote unit presses the push button to speak, the remote unit remains as the designated system speaker. If another remote unit presses the push button to speak, the communications manager sends a denial to the original remote unit about the system conferencing privileges and grants the system conferencing privileges to the remote interrupter unit. If no interruption is received during the second period, after the end of the second period, the communication manager sends a denial to the remote unit about the system conferencing privileges even if no other remote unit attempts to use the system. The purpose behind the denial of privileges after the expiration of the second period of time even if no other user tries to access the system, is the integrity of the system. If the remote unit is using the system in a valid way to communicate, you can restart the connection by simply releasing and pressing the push button to speak. On the other hand, if the remote unit has been disabled and is unable to generate the indication of PTT_off, system resources are not wasted. For example, if the push button to talk about the remote unit is pressed, it continues to unnecessarily consume system resources. Also if the system is designed so that the lecturer of the remote unit is disabled when the press button is pressed to speak, the release of the link after the end of the second period re-enables the lecturer and the remote unit is able to receive messages one more time. In the preferred embodiment, when the second period expires or when the remote unit is interrupted by another remote unit, the communication manager generates a denial of system conferencing privileges. In response, the remote unit begins to remain 'on hold' as described above. Although it is on hold, system resources remain allocated to the remote unit and the remote unit is not subject to resource allocation delays after pressing the press button to speak during the time it is on hold. Figures 3A and 3B are an implementation of exemplary block diagrams of a system for access regulation and system protection of a dispatch system and begin with block 140. In block 140 as well as in blocks 142 and 144, No system conferencing privileges have been granted to any remote units at this time. In block 142, a system conferencing privilege request for a remote unit, typically a PTT_on indication, is received by the communications manager. In block 144, the communication manager grants system conferencing privileges to the remote unit. Also in block 144, T1 is set at an initial value. Block 146 asks if a request for system conferencing privileges has been received from another remote unit. If so, block 138 asks if the remote switch unit is of a higher rank. If not, in block 154, the communication manager issues a rejection of the demand for system conferencing privileges. As noted above, in response to the denial, the remote switch unit may begin to standby and the assigned link remains preserved. Whether or not a request for system conferencing privileges is received, the flow continues to block 148 where T- is incremented to reflect the passage of time and the flow continues to block 150. Block 150 asks whether received a request for rejection of system conferencing privileges, typically in the form of a PTT_out indication, from the remote unit. If so, the flow is directed back to block 142 and the process waits for the next demand for system conferencing privileges. If not, the flow continues to block 152, which asks if it exceeds a threshold L. If not, the flow continues back in block 146 and the remote unit remains as a system lecturer and? continues to increase. If Tx exceeds threshold17 the first uninterruptible period ends and the second uninterruptible period begins.

We return again to block 138 which asks if the remote switch unit is of a higher rank. In the preferred mode, if the remote switch unit has a higher range, it can interrupt the remote unit even during the first period. Accordingly, if the response to block 138 is positive, the flow continues in block 168. The communication manager sends a denial of system conferencing privileges to the remote unit in block 168. In block 170, the administrator of Communications also sends a grant of system conferencing privileges to the remote switch unit. T- is set at an initial value. The flow continues back to block 146. Block 156 sets the value T2 to an initial value. Block 158 increases T2 to indicate the passage of time. Block 160 asks whether a request for denial of system conferencing privileges has been received, generally in the form of a PTT_out indication, from the remote unit. If so, the second period is truncated and the operation continues in block 142 when the next demand for system conferencing privileges is received. If a demand for system conferencing privileges is not received, the flow proceeds to block 162. Block 162 asks whether a request for conferring system conferencing privileges has been received from a remote interrupter unit. In the preferred mode, any other remote unit may interrupt the remote unit. In an alternative mode, only any other remote unit that has an equal or higher range can interrupt the remote unit. If the answer in block 162 is yes, the communication manager sends a denial of system conferencing privileges to the remote unit in block 168. In block 170, the communication manager also sends a granting of conferencing privileges to the remote unit. system to the remote switch unit. T. is set at an initial value. The flow continues back to block 146. If no demand for system conferencing privileges has been received from a remote interrupter unit, the flow continues from block 162 to block 164. Block 164 asks whether the value of T2 exceeds threshold2. Otherwise, the second period continues back in block 158. If threshold 2 has been exceeded, in block 166 the communication manager sends a denial of system conferencing privileges to the remote unit. And the system starts again in block 142. There are many variations and implementations that fall within the scope of the present invention. An implementation may comprise all elements of the present invention and not exactly follow the flow diagrams of Figures 2A and 2B and Figures 3A and 3B. For example, interruptions could be used instead of periodic questions in the status of the indications that have been received. Obviously, the blocks can be rearranged 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 enable any person skilled in the art to use the present invention. The various modifications to these modalities will be readily 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. In this way, 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 (24)

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.
2. A method for providing access in a dispatch system, said dispatch system having a plurality of remote units, at least one base station, a communications manager and a mobile switching center, comprising the steps of: establishing a resource of communication to be used by a first remote unit; claim a privilege of exclusive lecturer of the system by said first remote unit from said communications administrator; and granting said exclusive lecturer privilege of the system to said first remote unit.
3. The method according to claim 1, characterized in that the granting stage comprises the steps of: determining that no remote unit already holds said exclusive lecturer privilege of the system; and granting said exclusive system privilege to said first remote unit.
4. The method according to claim 1, characterized in that the granting stage comprises the steps of: determining that a second remote unit already holds said exclusive lecturer privilege of the system and determining the amount of time that said second remote unit has held said privilege of exclusive speaker of the system; and granting said privileged system lecturer privilege to said first remote unit and revoking said system exclusive lecturer privilege of said second remote unit if said second remote unit has held said exclusive lecturer privilege of the system for more than a first amount of time. default The method according to claim 1, characterized in that the granting stage comprises the steps of: determining that a second remote unit already holds said exclusive lecturer privilege of the system; and granting said first remote unit said exclusive system privilege and revoking said exclusive conferencing privilege of the system of said second remote unit if said first remote unit has a greater rank than said second remote unit.
5. The method according to claim 1, characterized in that it further comprises the step of: revoking said exclusive lecturer privilege of the system to any remote unit holding said exclusive lecturer privilege of the system for more than a first predetermined amount of time.
6. The method according to claim 1, characterized in that it further comprises the step of: revoking, by said combination manager, said exclusive lecturer privilege of the system of said first remote unit holding said exclusive lecturer privilege of the system after reception of a transfer request sent by said first remote unit; retaining said communication resource to be used by said first remote unit for a first predetermined amount of time after receipt of said assignment request; and breaking said communication resource by said communication manager after the expiration of said first predetermined amount of time.
7. The method according to claim 6, characterized in that the step of retaining said communication resource comprises the step of sending and receiving a series of inactive structures between at least one of said base stations and said first remote unit.
8. The method according to claim 7, characterized in that said series of inactive structures comprises energy control information.
9. The method according to claim 6, characterized in that said assignment demand comprises the release of a press button to speak in said first remote unit.
10. 10. The method according to claim 6, characterized in that it also comprises the step of: generating a surrender request surrogate by means of at least one of said base stations after the occurrence of a predefined event; and transmit said demand for surrendered assignment to said communications administrator.
11. The method according to claim 10, characterized in that said predefined event comprises that said first remote unit holding said exclusive lecturer privilege of the system moves out of the coverage area of said dispatch system.
12. The method according to claim 10, characterized in that said predefined event comprises that said first remote unit holding said exclusive lecturer privilege of the system loses power.
13. The method according to claim 10, characterized in that said predefined event comprises that said first remote unit holding said exclusive lecturer privilege of the system is destroyed.
14. 14. An apparatus for providing access in a dispatch system, said dispatch system having a plurality of remote units, at least one base station, a communications manager and a mobile switching center, said apparatus comprising: means for establishing a link communication between at least one of said remote units and said communications administrator; means for generating a lending privilege request message exclusive to the system by a first remote unit; and means, placed in said communications manager, to grant or deny said exclusive lending privilege request of the system to said first remote unit.
15. The apparatus according to claim 14, characterized in that it further comprises: means for retaining said communication link for a predetermined amount of time after said exclusive system conferencing privilege has been revoked to said first remote unit.
16. 16. The apparatus according to claim 14, characterized in that it further comprises said at least one base station, each configured to generate a subrrogated message to demand that said exclusive lecturer privilege of the system be revoked to said first remote unit that holds said privilege of lecturer exclusive of the system after the occurrence of a predetermined event.
17. The apparatus according to claim 16, characterized in that said predetermined event comprises that said first remote unit moves out of a coverage area of said dispatch system.
18. 18. The apparatus according to claim 16, characterized in that said predetermined event comprises an energy failure of said first remote unit.
19. 19. The apparatus according to claim 16, characterized in that said predetermined event is the destruction of said first remote unit.
20. The apparatus according to claim 14, characterized in that it further comprises: means for generating a transfer request indicative of the release of a press button to speak of said first remote unit.
21. The apparatus according to claim 20, characterized in that said communications manager revokes said exclusive lecture state from the system to said first remote unit after the reception of said assignment request message.
22. 22. The apparatus according to claim 14, characterized in that said communications manager comprises: a stopwatch to measure the elapsed time during which said first remote unit holds said privilege of exclusive lecturer of the system; a detector to determine that a second remote unit has requested said exclusive lecturer privilege from the system; and means for determining when said elapsed time has exceeded a predetermined first time and a second predetermined time.
23. 23. The apparatus according to claim 14, characterized in that said communication retention means further comprise: means for generating inactive structures to provide inactive information structures by said base station to a remote standby unit; and means for generating inactive structures to provide inactive information structures by means of one of said remote units to said communications administrator. The method according to claim 23, characterized in that said series of inactive structures comprises energy control information. SUMMARY A method and apparatus to provide access to a dispatch system is discussed. A communication manager (40) simultaneously grants a privileged lecture privilege of the system to a remote unit (10) in the system. After a remote unit (10) requests and is designated as the exclusive speaker of the system, no other remote unit (20, 22) can transmit during a first predetermined amount of time. After the first predetermined time has elapsed, any other remote unit (20, 22) can request the exclusive lecturer privilege of the system and become the exclusive lecturer of the system. The exclusive lecturer privilege of the system is revoked by the communication manager (40) to any remote unit that retains the exclusive lecturer privilege of the system for more than a second predetermined amount of time. The exclusive lecture privilege of the system is also revoked after the release of a press button to speak on a remote unit (10). In addition, a base station (44) in communication with a remote unit (10) designated as the exclusive lecturer of the system will generate a surrogate assignment request to the communications manager (40) if the exclusive lecturer of the system travels outside the coverage area of the system. system, loses energy or is destroyed.