Method of assigning a control channel as a temporary voice/data transmitting one in a radio communication system

The subject of the invention is a method of designating a control channel as a temporary audio / data channel in radio communication systems, in particular wide area long distance radio communication systems, ensuring the increase of efficiency of such systems by efficient allocation of limited resources.

Broad area RF systems typically include remote broadcast stations, such as boost stations, that support a number of subscriber assemblies in the system, also known as radios. Subscriber teams can be portable radios, mobile radios, control panels or two-way radios.

U.S. Patent No. 5 054 109 discloses a long-range radio communication system that includes a base translation station and a plurality of sets of mobile and / or portable radio transmitters. When all communication channels are occupied, not only the initiating device is informed that it has been put in the queue for requesting channel allocation, but also the called devices in the corresponding called set receive an indication that they were put in the queue as a result. This indication may, for example, be an acoustic and / or visual indication from an indicator lamp, light emitting diode or liquid crystal display. In this way, each mobile or portable radio device of the set receives advance notification that it will have a conversation in a moment. Such a mobile or portable radio device is therefore notified immediately when the system can provide channel allocation to the calling device that a call will be received. The user of such a set, receiving this type of advance notification instead of leaving his vehicle or turning off his radio device, for example to take a long break, will receive information that the radio device is ready because a call is to be made.

U.S. Patent No. 4,434,506 relates to a system for protecting a control channel against interference waves in a radio communication system.

A typical long-range radio system has two to twenty amplification units per station. In a system with 20 reinforcement assemblies, 19 of them may be provided for acoustic / data channels, hereinafter referred to as acoustic, while one amplification assembly is provided for a control channel that transmits / receives control signals to / from subscriber assemblies in the system. Some systems use all available channels as acoustic channels. The control function in such systems is usually implemented using either a fixed wired network connecting the amplifying units or by means of inaudible control signals in some of the acoustic channels. In any case, the control movement reduces the efficiency of the system, whose primary task is to ensure acoustic communication between its subscriber groups.

The first example of this problem is a small, low density system with two acoustic channels and one control channel. When the number of users is relatively small (e.g. 100-300), two active acoustic channels are sufficient to maintain an acceptable level of service to users. As the number of active subscriber groups increases, there is a need to increase the capacity of the acoustic channels in the system. The addition of a new sound channel to such a small system will be a solution to this problem excluded for cost reasons. Therefore, users must accept the reduced system performance until they can request the addition of a new amplifier for acoustic communications.

As a second example, you can take a large system with a high density, having many acoustic channels and one control channel. When the number of users is relatively small for such a multi-channel system (e.g., 3000-5000), one control channel is sufficient to maintain an acceptable level of service for users. When the number of active subscriber teams increases, however, there may be a need to increase the capacity of control channels in the system. The addition of a new permanent control channel to support a temporary increase in the number of users, as in the example with a small system, is a solution to this problem also excluded due to cost.

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Users must therefore accept the reduced system efficiency until the addition of a new control channel can be justified by the cost.

There is therefore a need for a long-range radio system that provides the ability to implement a temporary acoustic channel or control channel, as needed, using existing equipment. Such a system should enable dynamic assignment of control and communication means, while ensuring an acceptable level of telecommunications services for subscriber teams in the system.

Method of determining the control channel as a temporary acoustic / data channel in radio communication systems in order to maintain a specific level of telecommunications services in a radio communication system having many radio devices, a limited number of acoustic channels, a control channel in which control signals are sent, and a central controller allocating acoustic channels through the control channel, consisting of receiving, from the requesting radio device among many radio devices, the demand for an audio channel, and determining whether all the audio channels are occupied, according to the invention is characterized in that it is determined when it is determined that all the audio channels are occupied, the current state of the actual load the control channel and in response to this determination the current control channel is allocated as a temporary audio channel.

During the assignment, the transmission status of the audio signal on the control channel is broadcast on the current control channel.

Preferably, the step of reassigning the new control channel is used.

In the new control channel, a signal is sent recommending that the words of the incoming signaling be given in said new control channel. Also preferably the state of the current load of the radio communication system is determined.

The method according to the invention also compares the current load condition with the load threshold, this load threshold being taken as the maximum telecommunications traffic level at which telecommunications services can be maintained at least at a predetermined level without using said current control channel.

In an alternative embodiment of the invention, the method of determining the configuration of control channels in a radio communication system having a radio device, central controller, limited number of acoustic channels and dynamic configuration of control channels, whereby the radio device receives the words of signaling coming from the central controller and transmits the words of signaling to the central controller, where these incoming and outgoing signaling words are used to facilitate access to a limited number of audio channels, it is characteristic that the first signal is received indicating that the current control channel is designated as the audio channel, set in response to the first signal, queues of further words of the incoming signaling of the request and at a later time those queued words of the incoming signaling to the central controller are suitable. When setting the queue, priority is given to the further words of the request being received, and a second signal is received indicating that the new control channel has been re-determined.

However, during transmission, in addition, in response to this second signal meaning, queued words of incoming request signal via the new control channel are suitable.

Thus, according to the invention, the control channel can be temporarily used as an audio / data channel. After receiving a communication channel request from one of many subscriber assemblies, the controller determines the current state of the system load. If all audio channels are occupied, the controller instructs, if appropriate, the current control channel to act as the audio channel.

The subject of the invention will be described in the examples shown in the drawing, in which Fig. 1A shows a typical low-density long range radio communication system in a simplified graphic form, Fig. 1B - a high-density long range radio communication system in a simplified graphic form, Fig. 2A - simplified block diagram

174 809 illustrating the principle of the central controller, Fig. 2B - detailed block diagram illustrating the program for determining the acoustic mode of operation in the control channel of Fig. 2A, Fig. 2C block diagram illustrating the program for determining the acoustic mode of operation in the control channel of Fig. 2A, Fig. 3 - simplified block diagram showing the operation of the subscriber team, Fig. 4 - a simplified block diagram showing the operation of the central controller according to an alternative embodiment of the present invention, Fig. 5A - a simplified block diagram showing the algorithm used to activate / deactivate a configuration with multiple control channels, Fig. 5B - a graphic illustration of the relationship between the control channel movement and the number of control channels needed to handle such traffic, fig. 6 - simplified block diagram showing the operation of the controller for call service, Fig. 7 simplified block diagram showing the subscriber registration operation, Fig. 8A - simplified block diagram showing the operation of sending the subscriber's call, while Fig. 8B shows the simplified block diagram of the operation of receiving the subscriber's call.

Figure 1A is a simplified graphic illustration of a small long-range radio communication system 100. The amplification station shown includes one control channel 102 and two acoustic channels 104, 106. Control channel 102 is used to control access to / from acoustic channels 104, 106. All three channels are directed by a central controller 101, for example from Motorola, part number T5313 (so-called Startsite ™).

It should be noted that embodiments of the present invention will be described for a system using FM frequency modulation in RF frequency channels (i.e. frequency pairs), but similar communication systems can be and often are implemented using other signal transfer techniques, e.g., split multiplication TDM time, with FDM frequency division etc.

Subscriber groups 108-112, hereinafter referred to as radios, may be portable, mobile radios, control panels or radiotelephones. For example, car radios 109 and 111 may connect through acoustic channel 106, while radios 110 and 112 may connect through acoustic channel 104. Radio 108 is slow and in this state can supervise control channel 102 pending inclusion in the communication system. In such a small arrangement, for example with only two acoustic channels to be assigned to users less than 200, the control channel 102 will probably be free most of the time.

The large, high-density system 150 shown in Fig. 1B has multiple acoustic channels 154, 156 and 157 and one control channel 152. When the number of users with 158-161 radios is relatively small for such a multi-channel system (e.g. 3000-5000), one control channel is sufficient to maintain an acceptable level of service to users.

The present invention uses a time in which the control channel is free to provide additional acoustic connectivity. The implementation of this idea consists in creating the possibility for the control channel to act temporarily as an acoustic channel during periods of high acoustic movement and minimal control movement. The main advantage of converting the control channel into an acoustic channel is that it avoids the need to install additional hardware components (e.g. acoustic receivers) to meet the increased demand for acoustic communications in a specific area covered by the communications system.

Figure 2A is a block diagram of the operation of the central controller 101 according to one embodiment of the present invention, wherein in the description of the drawings, the respective block of diagrams are assigned the corresponding numerals.

The operation of the central controller 201 begins when an audio channel request is received 203 from the radio. Then a 205 decision is made, which determines whether all audio channels are currently occupied or not. If all the acoustic channels (e.g. 104, 106) are not currently occupied, i.e. there is at least one available audio channel, central controller 101 sends 207 outbound signaling word OSW for normal channel assignment via the current control channel 102 and is still waiting for channel requests. If it is determined that all audio channels are occupied, then the central processor 101 tries to determine 209 whether to introduce voice mode in the control channel

174 809 (hereinafter VOC) or not. A decision is then made which determines whether or not the VOC 211 flag described later has been set by the determination program 209. If the VOC flag was not set, for example, the central controller 101 found that entering VOC mode would not be appropriate at this time, the central controller sends 213 OSW word for normal control channel occupancy and returns to wait for further audio channel requests. If the VOC flag is set, the central controller enters the VOC 215 operating mode. The above-mentioned operating sequence is a preferred embodiment of the invention, but it should be noted that the VOC mode can be entered unconditionally when an additional audio channel is needed. The determination program 209, described later, is used to ensure that the time when the system lacks a control channel is minimal, so that overall system operation is relatively stable over time.

Upon completion of VOC 215, which is described later, the central controller produces 217 updates of channel assignment for existing calls and occupations (e.g., repeats the outgoing signal words representing active calls and occupations started in blocks 207, 213, these repetitions being intended for the last subscribers attached). The central controller 101 then generates the word OSW in the reassigned control channel. Send words ISW 219 (inbound signaling) and returns to normal operation. Sending outgoing signaling word Send words ISW recommends to all subscriber teams in the system whose requests are queued to be sent in the reassigned control channel.

Figure 2B shows a detailed block diagram 230 of the 209 VOC determination program. This program is used to determine whether the current state of the system allows you to delete the control channel. If it is determined that the system can temporarily withstand the loss of the control channel in order to take over the audio conversation, this program searches for the best candidate for this conversation. The program starts by deleting the VOC flag 231 (which can be simply binary information placed at a certain address in RAM in the central control computer) to initialize the program in the default mode. The value of the VOC flag will determine whether VOC mode is on or off, with binary one being on and binary zero being off. The program then checks 232 whether the percentage of traffic taking place only through the control channel is greater than the predetermined threshold percentage (i.e. the percentage of the total number of connections made in the control channel at a given time) or not. A large percentage of traffic only on the control channel typically means that connections on the control channel are more important than calls and the control channel should not be liquidated. The threshold should be set at a level that, based on the current operation, represents the maximum percentage of traffic only in the control channel to maintain an acceptable level of system operation. In a preferred embodiment, this threshold is set to a value of approximately 63%, which value may vary depending on the required system operation.

If the percentage of connections only on the control channel is greater than the predefined threshold, processing of the control channel is delayed 234. In the preferred embodiment, the delay is equal to the average ACL talk length, typically of the order of 5-7 s (ACL measurement is known in telecommunications). The processing delay by a time equal to the current average conversation length in the system gives the system a reasonable chance to find an available audio channel before processing the control channel. If the percentage of calls only on the control channel is not greater than the predefined threshold value, the 236 most active audio channel is selected, i.e. the audio channel that has had the longest conversation. Then, decision 238 is taken, which determines whether the length of the conversation in the selected audio channel is greater than the current ACL in the system or not. If not, the processing of the control channel is delayed 240 by a predetermined time, which in the preferred embodiment is equal to the current ACL value in the system. The processing delay by this time anticipates that each current conversation is relatively new and will not be a new candidate for the control channel if the currently active control channel was processed for acoustic operations.

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After the appropriate delay has elapsed, a decision is made 242 that determines whether an audio channel is available (e.g., released during the delay discussed above) to accept a call without having to take over the control channel or not. If an audio channel is available, the controller assigns 246 audio channel requests to the newly released audio channel. The controller then clears 248 VOC flag before exiting the 250 program.

Returning now to decision 238, if the length of the selected conversation is greater than ACL, 234 is set to the VOC flag and the controller takes the next highest priority request before exiting 250 from the program. Similarly, if there are no available audio channels (as determined by decision 242), the VOC flag is set 244 and the controller takes the next highest priority request before it exits 250 from the program.

Figure 2C is a detailed block diagram 215 showing operation 260 in VOC mode. When the decision to enter the VOC mode is made, the central controller sends 262 OSW words of VOC status (a special signal sent on the control channel informing the radio that the control channel can be taken over). The controller then assigns the OCW to assign the 264 standard channel to the current control channel (which can be any channel that can be controlled, i.e. communication channel equipped with hardware and software necessary for coding and decoding control signals) of a radio transceiver sending a request for use as a temporary audio channel. The central controller converts the 266 existing control channel into a low-speed LSD data transmission channel to enable acoustic movement (e.g., subacoustic data transmission speed of 150 bits per second). An LSD signal, meaning that VOC mode has been activated, is then sent 268 on all audio channels.

At this point, the system 100 shown in Fig. 1A actually has no control channel through which the assignment of the acoustic channels for subsequent acoustic movement would take place. You must therefore minimize the time the system is in this state so that you can accept incoming requests. The central controller therefore looks for the first possibility of assigning the control channel role to either a processed audio channel or another audio channel suitable to act as a control channel. To do this, a decision is made 270, which determines whether or not any end of EOT transmission status has been detected in any audio channel. If an EOT signal has not yet been detected in any of the audio channels, the program loop closes and the program continues to control the audio channels, looking for this end of transmission state. If an EOT signal has been detected, a decision is made 272 that determines whether this particular audio channel is suitable as a control channel or not. If it is not suitable as a control channel, the controller enables the 274 time unit of information. In a preferred embodiment, the use of the information time unit ensures that the transmission is not so short that it causes problems such as terminating the connection before the second subscriber team responds.

The program then checks 276 to determine if another radio has been turned on (that is, it did not initiate transmission). If another radio initiates a conversation, for example by pressing the radio's PTT button, the program loop closes to decision 270 to search for the end signal. If the system is free for new subscribers, that is, no new radios are turned on, a decision is made 277, which determines whether the information time group has finished its work or not. If not, the program loop closes to decision 276 to look for another team for inclusion. After the operating time of the information timer has elapsed, the central controller 101 sends 278 a group disconnect signal (e.g., 300 bits per second) ending the current conversation. The program then returns to decision 270, looking for another end of EOT transmission state.

Referring again to Decision 272, if it is found that a newly released audio channel is suitable for being a control signal, then the central controller assigns it 280 as a control channel. The 282 so-called last queue of the central controller users is currently updating, which assigns priority to users depending on when their conversations have ended. In favorable

174 In the 809 embodiment, it is ensured that the user who last terminated his conversation via the EOT signal receives the highest priority of receiving the next free audio channel if requested. The end VOC status signal (a special signal informing the radio that the control channel assignment is changing) is then sent 284 on all audio channels and the 286 program ends.

Figure 3 is a simplified block diagram 300 showing the operation 302 of a radio or subscriber assembly, as in the preferred embodiment with the possibility of using the VOC mode. The radio constantly controls the current control channel (assigned by the conversation group identifier) ​​to stay in communication in the system 100. Decision 304 is made, which determines whether the subscriber's team is still receiving the words OSW or not. If the team no longer receives the words OSW (which is an indication that the team may be out of reach or lost), then the lost time team is started. This delay (e.g., 200 ms in the preferred embodiment) is used to enable normal, temporary signal loss in a specific area of ​​the system, so that the radio does not prematurely abandon the control channel. Then a decision is made 310 determining whether the lost time team has finished its work or not. If not, the program closes the loop and continues to search for received OSW words in the current control channel. If the operation time has expired, the radio searches 326 acoustic channels capable of acting as a control channel (e.g. from a list of items stored in the radio's memory), looking for control signals. Then a decision is made 328 whether VOC LSD signal (VOC mode with low data rate) was detected in some of the tested audio channel (see Fig. 2C, 268) or not. After checking this, if the radio does not detect the VOC LSD signal, the subscriber searches 332 normal control channel list before returning to normal operation. If the LSD VOC signal was detected in the tested audio channel, the radio enters 330 in VOC mode.

Returning to decision 304, if the radio is still receiving the word OSW, a decision is made 306 determining whether or not the OSW word VOC has been received. If not, the radio processes 308 OSW words in the normal way and continues to look for other OSW words. If a VOC status OSW word is received, the radio enters 312 in VOC mode. At the moment, decision 314 is made, which determines whether the radio has been assigned to the conversation (i.e. a newly assigned control channel directs OSW assignments for this team or its conversation group) or not. If so, then the radio tunes 316 audio to transmit signals on the normal audio channel and searches 318 the list of audio channels capable of acting as a control channel. Similarly, if the designated control channel does not reach this team or its conversation group, 318 list of acoustic channels capable of playing the role of the control channel is searched. At this time, the radio program with a one-time loss (i.e., which joined when 328 VD LSD was detected) also searches 318 list of acoustic channels capable of acting as a control channel.

During the search, a decision is made 320 determining whether the channel capable of acting as a control channel has been found or not. If not, a decision is made 322 whether the radio PTT button has been pressed or not. If the transmit button has not been enabled, the radio returns to search operation 318. If the transmit button has been pressed, the ISW request is placed in queue 324 in the internal memory of the radio (e.g. RAM), and then the subscriber unit returns to search operation 318. In a preferred embodiment of the invention, queued requests receive rank or priority, so that emergency requests have priority over normal audio communications.

If the control channel has been re-determined, i.e. a channel capable of acting as a control channel has been found in decision making, then the radio transmits 334 queued emergency type or other predetermined priority type. As a result, high priority requests first receive the option of accessing previously requested funds without having to be explicitly instructed to grant them. At this time, the radio controls 336 a newly designated control channel, looking for the words OSW. Give the words ISW (a special signal informing the radio that the VOC mode has ended

174 809 and queued requests should be sent via the control channel). Then a decision is made 338 whether or not the Send the ISW words signal has been received. If not, the radio is still controlling 336 the current control channel, looking for an indication that the VOC mode is not working. If the OSW word is received. Send ISW words, the radio transmits 340 all queuing requests (e.g. failure requests (which have not yet been sent) from its internal buffer before it returns to normal operation.

Figure 4 shows a simplified block diagram 400 showing the operation of a central controller during registration of a subscriber or radio. This program starts when the central controller receives a 401 registration request on one of the active control channels, e.g. on control channel A or B. It should be noted that in one embodiment of the present invention, the central controller uses a database to track the specific control channel used by each subscriber in the system. In an alternative embodiment, there may not be any tracking using the database and all signaling is done redundantly in all active control channels. Upon receipt of the registration request, the central processor 403 restores control channel information for the radio having the identifier of that assembly from a portion of the database, if used, for that radio. If the registration request came in an acceptable control channel (i.e. either in the only active control channel or in the same control channel as restored from the database), then the controller sends the word OSW confirmation 409 and the registration process is completed 411. In the event that the central controller contains a database and the request came in a control channel other than the one that was restored 403, then the central processor directs the 407 assembly to the correct control channel. Then the 409 OSW confirmation word is sent and the registration of this team is completed.

Figure 5A is a simplified block diagram 500 showing the activation / deactivation process that ends when there is more than one active control channel in the system. Starting from only one control channel, the central processor assesses the load status of a particular active control channel 502. In a preferred embodiment of the present invention, the load of the motion control channel is measured as a parameter defined as the number of new OSW words per second NOPS. This parameter is understandable in this technical field and is usually a good indicator of the control channel load at any time.

Figure 5B is a graphic illustration of how to make the transition decision from one control channel to two and vice versa. An abscissa 505 gives the number of new OSW words per second, while an ordinate 507 gives the number of control channels active in the system. Point 501 on the graph means that when the NOPS parameter has already reached the upper load threshold, e.g. 27, the control channel receives a recommendation to increase the number of control channels. If the operation is already carried out with two control channels, the algorithm determines when it is possible to return to using one control channel, i.e. at the lower load threshold. In the preferred embodiment, this is done at point 503 when the NOPS parameter value drops to 12. 509 indicates the spacing of this parameter, which in the preferred embodiment is intended to ensure that the system will not switch between working with one and working with two control channels during some operating time. The so-called. the hysteresis effect can be changed (i.e. increase or decrease the 509 interval to optimize system performance).

Returning to Fig. 5A, if the load 504 of a single control channel is greater than 27 NOPS, there is no need to switch to work with two control channels and the program still evaluates 502 the traffic load. If, on the other hand, the load is greater than 27, then the central controller activates the second control channel 506. After doing so, this controller directs 508 all free units to the second control channel, e.g. control channel B. For those systems that have a database, the database is then partitioned 510 to indicate which assemblies and groups of assemblies are assigned to which control channels. The controller then evaluates the 512 system traffic load with two control channels, i.e. using the average NOPS parameter as the criterion. The system keeps using the second control channel until load

174 409 traffic will decrease 514 below 12 NOPS, after which the teams using channel B are directed 516 to channel A. This steering is typically done using standard OSW signaling. Finally, if the central controller has a database, the database partitioning is removed 518 and all assemblies in the system are marked as using the same designated control channel.

The flow of conversation handling by the central controller is shown in Fig. 6 in a simplified block diagram 600. After waiting 601 and receiving a channel request, the central controller sends 605 the word OSW either channel assignment or channel occupation. In the controller without using the database, the word OSW is sent in the control channel where the request came. For those systems that use the database in the central controller, before sending the word OSW 605 response, the central controller routes the 603 radio that sends a request to the correct control channel if it is not already on the designated control channel. After the subscriber starts the call, the central controller determines whether the call is still active 607 or not. This can be done using the known EOT signaling, after which the program ends 613. During the conversation, the central controller repeatedly transmits 609 OSW words for that conversation in the control channel related to the request. These OSW repeating words are used to collect later subscribers and other subscriber teams that may have temporarily lost communication with the control channel. In a system that does not have a database, the central controller then sends 611 signals in the acoustic channel indicating the source of the call request (i.e. which control channel sent the request). This inaudible signaling is used to keep talk group assemblies together on the same control channel without having to memorize the control channel independently for each unit.

Figure 7 shows a simplified block diagram 700 of a subscriber registration operation. After switching on the power 702 or changing the group assignment, the subscriber (radio) transmits 704 the word ISW registration requests. If the radio is routed 706 to a different control channel, then it switches to frequency 708 of the correct control channel. If there is no referral to a new control channel or after switching to the correct control channel, the radio waits for receiving the 710 confirmation OSW word. After receiving the subscriber registration program is terminated 712. If the confirmation OSW word is not received, the radio simply re-transmits the registration request 704 and tries to register again.

Figure 8A shows a simplified block diagram 800 of a call broadcast operation for a subscriber's radio. After broadcasting 801 the PTT word OSW, the radio checks if it has been directed 803 to another control channel. If so, then the radio switches 805 to the correct control channel. If there is no such referral, or after switching to the correct control channel, the radio searches for the word OSW for busy or channel assignment. If the radio receives the 807 busy OSW word, then it still controls the control channel, looking for channel allocation. Similarly, if channel assignment has not been received 809, the radio is still searching for a busy signal or a channel assignment signal. In a preferred embodiment, the radio will search for 4 s for either busy words or OSW words for channel allocation, this time being treated as appropriate if the system is operating correctly. After this 4 s time, as determined by the time unit, has elapsed, the radio stops the transmission attempt and is switched off. After receiving the channel assignment, the radio switches 811 to the assigned audio channel and transmits its information. This information is then transmitted continuously until the 813 transmit button is released, which means the end of the 815 broadcast transmission.

Figure 8B shows a simplified block diagram 850 of a call reception operation on the radio. After receiving the 851 channel assignment for a new call, the radio switches to the designated 853 audio channel and controls that channel. In an alternative embodiment (without the driver database), the radio receives 855 control channel identifier to return to it after receiving an inaudible call from the audio channel. This ensures that the directed radio from the talk group takes with it all the other radios in that talk group after referral. The conversation continues 857 until the EOT signal is received, followed by the 859 tuning of the audio circuit. The radio then switches to the appropriate control channel 861

174 809 according to the inaudibly received 855 identifier signal (on systems without database) or on the control channel from which the request originates (on systems with database) before the receive operation is completed 863.

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