CA1292043C - Method for dynamically allocating data channels on a trunked communication system - Google Patents
Method for dynamically allocating data channels on a trunked communication systemInfo
- Publication number
- CA1292043C CA1292043C CA000557939A CA557939A CA1292043C CA 1292043 C CA1292043 C CA 1292043C CA 000557939 A CA000557939 A CA 000557939A CA 557939 A CA557939 A CA 557939A CA 1292043 C CA1292043 C CA 1292043C
- Authority
- CA
- Canada
- Prior art keywords
- data
- channels
- channel
- subscribers
- allocated
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W84/00—Network topologies
- H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
- H04W84/04—Large scale networks; Deep hierarchical networks
- H04W84/08—Trunked mobile radio systems
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W24/00—Supervisory, monitoring or testing arrangements
- H04W24/10—Scheduling measurement reports ; Arrangements for measurement reports
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/20—Control channels or signalling for resource management
- H04W72/23—Control channels or signalling for resource management in the downlink direction of a wireless link, i.e. towards a terminal
Abstract
METHOD FOR DYNAMICALLY ALLOCATING DATA CHANNELS ON A
TRUNKED COMMUNICATION SYSTEM
Abstract Disclosed is a method to dynamically allocate a number of data channel on a trunked radio system (100).
The data activity is monitored during a predetermined time interval. If activity is above a predetermined maximum, an additional channel may be reserved for data use. Conversely, if data traffic is low, a data channel may be reallocated for voice message use. Moreover, should the amount of data traffic among the available data channels be unbalanced, the present method contemplates reassigning subscriber units (114 or 116) to the available data channels to balance the data traffic load, thereby providing superior access time and system performance.
TRUNKED COMMUNICATION SYSTEM
Abstract Disclosed is a method to dynamically allocate a number of data channel on a trunked radio system (100).
The data activity is monitored during a predetermined time interval. If activity is above a predetermined maximum, an additional channel may be reserved for data use. Conversely, if data traffic is low, a data channel may be reallocated for voice message use. Moreover, should the amount of data traffic among the available data channels be unbalanced, the present method contemplates reassigning subscriber units (114 or 116) to the available data channels to balance the data traffic load, thereby providing superior access time and system performance.
Description
METHOD FOR DYNAMICALLY ALLOCATING DATA CHANNELS ON A
TRUNKED COMMUNICATION SYSTEM
Technical Field This invention relates generally to trunked communications systems and more particularly to trunked communication systems that transceive both voice and data.
: Backqround Art In a basic RF trunked system there exists a high degree of flexibility to partition voice conversations between different groups 80 that no one group of users is specifically aware when another group of users makes use of the system. Typically, these groups are subdivided inko subgroups so that calls may be made upon either a group, subgroup or individual basis depending upon the type of communication desired by an initiating subscriber.
To establish a voice communication between a group o~ units operating on a trunked system, a subscriber unit transmits a data packet called an "inbound signalling word" (ISW) on a control channel that is maintainad for such purposes. ~he ISW contains at
TRUNKED COMMUNICATION SYSTEM
Technical Field This invention relates generally to trunked communications systems and more particularly to trunked communication systems that transceive both voice and data.
: Backqround Art In a basic RF trunked system there exists a high degree of flexibility to partition voice conversations between different groups 80 that no one group of users is specifically aware when another group of users makes use of the system. Typically, these groups are subdivided inko subgroups so that calls may be made upon either a group, subgroup or individual basis depending upon the type of communication desired by an initiating subscriber.
To establish a voice communication between a group o~ units operating on a trunked system, a subscriber unit transmits a data packet called an "inbound signalling word" (ISW) on a control channel that is maintainad for such purposes. ~he ISW contains at
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least the requesting unit's unique ID code, which may contain or be used to obtain the requesting subscriber's current talk-group. The requsst is ~orwarded to a central controller, which decodes the request, and transmits on the control channel a data packet called an "outbound signalling word" (OSW) to all subscriber units, which continuously monitor the control channel when not participating in a voice conversation. The oSw is a channel grant which contains the talk-group code of the requesting unit, and the voice channel number a signed for the converRation. The OSW causes the requesting unit to move to the voice channel and commence transmitting, while simultaneously causing all other subscriber units in the same talk-group to move to the voice channel as listening units. In this way a group call is set up.
If, however, all voice channels are in use when a subscriber unit transmits an ISW, the central controller typically sends the requesting subscriber a "busy OSW".
In addition to voice messages, it is desirable to send data information across a trunked radio channel. In some data sy~tems, a subscriber unit sbtains a trunked data communication channel via the same procedure used to obtain a voice chann~l. However, this practice is inefficient and spectrally waste~ul, due to the time it takes for a requesting subscriber to transmit an ISW and receive a channel grant OSW from the central, and the ~ime it takes to set-up and clear-down the call on the voice channel. At contemporary data transmission rates, it i5 anticipated that an entire typical data message would take substantially less ~ime to transmit than the time required to obtain a channel (approximately .5 seconds). Thus, assigning a data channel pursuant to the same procedure as assignlng a voice channel would be wasteful of spectrum and consume precious system time that could be better used to transmit data messages.
Other trunked communication systems desirous to accommodate data traffic have permanently dedicated one ~2~
least the requesting unit's unique ID code, which may contain or be used to obtain the requesting subscriber's current talk-group. The requsst is ~orwarded to a central controller, which decodes the request, and transmits on the control channel a data packet called an "outbound signalling word" (OSW) to all subscriber units, which continuously monitor the control channel when not participating in a voice conversation. The oSw is a channel grant which contains the talk-group code of the requesting unit, and the voice channel number a signed for the converRation. The OSW causes the requesting unit to move to the voice channel and commence transmitting, while simultaneously causing all other subscriber units in the same talk-group to move to the voice channel as listening units. In this way a group call is set up.
If, however, all voice channels are in use when a subscriber unit transmits an ISW, the central controller typically sends the requesting subscriber a "busy OSW".
In addition to voice messages, it is desirable to send data information across a trunked radio channel. In some data sy~tems, a subscriber unit sbtains a trunked data communication channel via the same procedure used to obtain a voice chann~l. However, this practice is inefficient and spectrally waste~ul, due to the time it takes for a requesting subscriber to transmit an ISW and receive a channel grant OSW from the central, and the ~ime it takes to set-up and clear-down the call on the voice channel. At contemporary data transmission rates, it i5 anticipated that an entire typical data message would take substantially less ~ime to transmit than the time required to obtain a channel (approximately .5 seconds). Thus, assigning a data channel pursuant to the same procedure as assignlng a voice channel would be wasteful of spectrum and consume precious system time that could be better used to transmit data messages.
Other trunked communication systems desirous to accommodate data traffic have permanently dedicated one ~2~
- 3 - CM-00262H
or more channels to handling data traffic. While this avoids the access time problem noted above, this technique is contrary to the basic principles of trunked communication syRtems, which strive to allocate channel resources across a plurality o~ users as required.
Therefore, the practice of having dedicated data channels, pPrmanently removed from the channel allocation "pool" of frequencies, is wasteful of spectral resources and leads to inefficient ~ystem operation. Moreover, the dedicated data channsl systems lack the capacity to dynamically redistribute or allocate the data traffic load across the available data channels. Such systems typically permanently assign a subscriber unit to a data channel thereby building in future problems as the number of data subscribers increases on a particular channel.
Accordingly, there exists a need for a trunked communicatisn system that can accommodate both voice and data signals, and that operates in true trunked manner to efficiently utilize spectral resources.
Summary of the Invention Accordingly, it is an object of the present invention to provide an improved trunked communication system-It i~ another object of the present invention toprovide a procedure to dynamically allocate data channPls on a trunked radio sy6tem.
It i~ a further object of the present invention to redis~ribut~ or ~alance the data traffic load on ~he parti ular numbsr of data channels currently available.
It is another objert o~ the present invention to provide a rapid and conveni n~ m~thod ~o broadcast system wide data messages to all data subscribers.
Accordingly, these and other objects are achieved by the present invention's dynamic allocation of data channels in a trunked radio sys~em.
or more channels to handling data traffic. While this avoids the access time problem noted above, this technique is contrary to the basic principles of trunked communication syRtems, which strive to allocate channel resources across a plurality o~ users as required.
Therefore, the practice of having dedicated data channels, pPrmanently removed from the channel allocation "pool" of frequencies, is wasteful of spectral resources and leads to inefficient ~ystem operation. Moreover, the dedicated data channsl systems lack the capacity to dynamically redistribute or allocate the data traffic load across the available data channels. Such systems typically permanently assign a subscriber unit to a data channel thereby building in future problems as the number of data subscribers increases on a particular channel.
Accordingly, there exists a need for a trunked communicatisn system that can accommodate both voice and data signals, and that operates in true trunked manner to efficiently utilize spectral resources.
Summary of the Invention Accordingly, it is an object of the present invention to provide an improved trunked communication system-It i~ another object of the present invention toprovide a procedure to dynamically allocate data channPls on a trunked radio sy6tem.
It i~ a further object of the present invention to redis~ribut~ or ~alance the data traffic load on ~he parti ular numbsr of data channels currently available.
It is another objert o~ the present invention to provide a rapid and conveni n~ m~thod ~o broadcast system wide data messages to all data subscribers.
Accordingly, these and other objects are achieved by the present invention's dynamic allocation of data channels in a trunked radio sys~em.
- 4 - CM-00262H
Briefly, according to the invention, a method is disclosed to dynamically allocate a number of data channels on a trunked radio system. The data activity is monitored during a predetermined time interval. If activity is above a predetermined maximum, an additional channel is reservsd for data use. Conversely, if data traffic is low, a data channel i6 reallocated for voice message use. Moreover, should the amount of data traffic between the available data channel~ be unbalanced, the present invention contemplates reassigning subscriber units ~o the available data channels ~o balance the data traffic load, thereby providing superior access time and system performance.
Brief Description of the Drawinq~
The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may be understood by reference to the following description, taken in con;unction with the accompanying drawings, and the saveral figures o~ which like referenced numerals identify like elements, and in which:
Figure l is a block diagram of a trunked radio system that may employ the present invention, Figure 2 i& an illu~tration of the preferred signalling ~ormat for a master data channel;
Figure 3 is an illustration of the preferred signalling for~at for other data channels;
Figure 4 is a ~low diagram illustrating the steps executed by the fixed-end equipment of Figure 1 in accordance with the present invention;
Figure 5a i a flow diagram illustrating the steps executed by the fixed-end equipment of Figure 1 to perform the load leveling of subscriber units to 2~
Briefly, according to the invention, a method is disclosed to dynamically allocate a number of data channels on a trunked radio system. The data activity is monitored during a predetermined time interval. If activity is above a predetermined maximum, an additional channel is reservsd for data use. Conversely, if data traffic is low, a data channel i6 reallocated for voice message use. Moreover, should the amount of data traffic between the available data channel~ be unbalanced, the present invention contemplates reassigning subscriber units ~o the available data channels ~o balance the data traffic load, thereby providing superior access time and system performance.
Brief Description of the Drawinq~
The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may be understood by reference to the following description, taken in con;unction with the accompanying drawings, and the saveral figures o~ which like referenced numerals identify like elements, and in which:
Figure l is a block diagram of a trunked radio system that may employ the present invention, Figure 2 i& an illu~tration of the preferred signalling ~ormat for a master data channel;
Figure 3 is an illustration of the preferred signalling for~at for other data channels;
Figure 4 is a ~low diagram illustrating the steps executed by the fixed-end equipment of Figure 1 in accordance with the present invention;
Figure 5a i a flow diagram illustrating the steps executed by the fixed-end equipment of Figure 1 to perform the load leveling of subscriber units to 2~
- 5 - CM-00262H
available data channels in accordance with the present in~ention;
Figure 5b, is a flow diagram of the steps executed by the fixed-end equipment of Figure 1 to transmit a system message to the subscriber units in accordance with the present invention, and Figure 6 is a flow diagram illustrating the steps executed by th~ data subscribers of Figure 1.
Detailed DescriE~tion of the Preferred Embodiment Referring now to the drawings, and in particular to Figure 1, there is shown a block diagram of a trunked voice/data communication system (100) that may employ the present invention.
The centralized or fixed-end equipment comprises a central controller 102, which is responsible for àilocating the channel resources trepresented here by repeaters 104a-104N) amongst the many subscriber units. Of the available communication channels, one (repeater 104a) is selected to be a voice control channel, which communicates with any trunked subscriber capable of transmitting voice traffic.
Preferably, each of the repeaters 104a-N are capable of operating as a voice channel, control channel, or data channel.
To accommodate data traffic, such repeaters are equipped with a data interface 122. The data interfaces 122 are responsible for encoding outbound data, decoding and error correcting inbound ~ data, repeater control, and providing an interface between the repeater~ and the network controller 108. Alternately, a predetermined subset of the total number of repeaters may be eq~ipped for data or used as a control channel. Typically, the particular repeater selected to be the control channel (104a~ is periodically changed as a control measure.
~The data network comprises at lease one host computer 106, which is coupled (i.e., wireline) to a ::
~f~
available data channels in accordance with the present in~ention;
Figure 5b, is a flow diagram of the steps executed by the fixed-end equipment of Figure 1 to transmit a system message to the subscriber units in accordance with the present invention, and Figure 6 is a flow diagram illustrating the steps executed by th~ data subscribers of Figure 1.
Detailed DescriE~tion of the Preferred Embodiment Referring now to the drawings, and in particular to Figure 1, there is shown a block diagram of a trunked voice/data communication system (100) that may employ the present invention.
The centralized or fixed-end equipment comprises a central controller 102, which is responsible for àilocating the channel resources trepresented here by repeaters 104a-104N) amongst the many subscriber units. Of the available communication channels, one (repeater 104a) is selected to be a voice control channel, which communicates with any trunked subscriber capable of transmitting voice traffic.
Preferably, each of the repeaters 104a-N are capable of operating as a voice channel, control channel, or data channel.
To accommodate data traffic, such repeaters are equipped with a data interface 122. The data interfaces 122 are responsible for encoding outbound data, decoding and error correcting inbound ~ data, repeater control, and providing an interface between the repeater~ and the network controller 108. Alternately, a predetermined subset of the total number of repeaters may be eq~ipped for data or used as a control channel. Typically, the particular repeater selected to be the control channel (104a~ is periodically changed as a control measure.
~The data network comprises at lease one host computer 106, which is coupled (i.e., wireline) to a ::
~f~
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network controller 108. The network controller 108 is responsible for data traffic routing and communicating with the central controller 102 to request the allocation of a data channel. Those skilled in the art will appreciate that if the host computer 106, the ne~work controller 108 and the central ¢ontroller 102 are co-located, the intercouplings (124-128) may be direct.
However, should remote locations be desired, such communications may be maintained through the use of data modems as i5 known in the art. Optionally, or additionally, the trunked voice/data communication system 100 may employ one or more radio frequency (RF) coupled host computers 118. The RF hsst 118 communicates as a trunked control station via ~ny suitable data transceiver 120. The primary difference between the wireline host 106 and the RF ho~t 118 is that the data subscribers communicate directly (i.e., viA both the inbound and outbound frequencies of a data equipped repeater) with the RF host, whereas the wireline host 106 transceives all information via the inbound or outbcund fre~uencies of a data equipped repeater. Accordingly, the data network of the present invention may employ several computers in either a centralized or distributed processing arrangement.
Generally, the fixed-end equipment also includes a system manager console 110 that enables the supervisor of a communication service provider to set a number of operational parameters that control the operation of the ~runked communication ystem. Typical examples of such par~meters include the maximum number of assignable data channels (if any), whether voice or data will be the priority traffic, and variou~ threshold values that control when data channel~ may be added or reallocated to voice traffic. Thus, a~ any particular time, the trunked communication system of tha present invention need not have any channels allocated for data traffic.
Conversely, if voice traffic is low, or if data traffic lZ9Z043
network controller 108. The network controller 108 is responsible for data traffic routing and communicating with the central controller 102 to request the allocation of a data channel. Those skilled in the art will appreciate that if the host computer 106, the ne~work controller 108 and the central ¢ontroller 102 are co-located, the intercouplings (124-128) may be direct.
However, should remote locations be desired, such communications may be maintained through the use of data modems as i5 known in the art. Optionally, or additionally, the trunked voice/data communication system 100 may employ one or more radio frequency (RF) coupled host computers 118. The RF hsst 118 communicates as a trunked control station via ~ny suitable data transceiver 120. The primary difference between the wireline host 106 and the RF ho~t 118 is that the data subscribers communicate directly (i.e., viA both the inbound and outbound frequencies of a data equipped repeater) with the RF host, whereas the wireline host 106 transceives all information via the inbound or outbcund fre~uencies of a data equipped repeater. Accordingly, the data network of the present invention may employ several computers in either a centralized or distributed processing arrangement.
Generally, the fixed-end equipment also includes a system manager console 110 that enables the supervisor of a communication service provider to set a number of operational parameters that control the operation of the ~runked communication ystem. Typical examples of such par~meters include the maximum number of assignable data channels (if any), whether voice or data will be the priority traffic, and variou~ threshold values that control when data channel~ may be added or reallocated to voice traffic. Thus, a~ any particular time, the trunked communication system of tha present invention need not have any channels allocated for data traffic.
Conversely, if voice traffic is low, or if data traffic lZ9Z043
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enjoys a priority status or is particularly heavy, one or more channels may be allocated for data communication.
According to the present invention, a predetermined channel ordinarily comprises the first channel to be allocated for data. Preferably, this fir~t as~igned data channel (hereinafter "the master data channel") has the same frequency as any ~ingle ~requency data-only subscribers (116) to provide maximum compatibility with existing data equipment. Alternately, a random channel may be the first assigned data channel, however, the data-only subscribers must scan the available channels to find it. Thus, the present invention prefers to first assign a selected channel, and, thereafter, assign any other data equipped (12Z) channel as an additional data channel.
The present invention allocates dat~ ch nnels for a time interval datexmined by aither the system manager or a default parameter. The length of the allocation period may vary with the time of day, system loading or other such parameters. By reserving a channel for data use over a time period, data channel requests are minimized and spectral efficisncy is maximized since a data subscriber need not request a data channel for each separate data transmission.
As a general principle, the goal of any trunked communication system i5 to effectively allocate the limited channel resources amongst a plurality of subscriber units. The present invention contemplates three classes of subscriber units: voice-only subscribers 112, voice/data subscribers 114, and data-only subscribers 116. The voice-only subscribers 112 are contemplated to be any existing trunked subscrib~r unit having a compatible signalling protocol to allow interaction with the system (lO0). The data-only subscribers (116) are contemplated to be any multiple or single channel data transcaivers such as the RDT 800TM, manufactured by Motorola, Inc., or 129;~043
enjoys a priority status or is particularly heavy, one or more channels may be allocated for data communication.
According to the present invention, a predetermined channel ordinarily comprises the first channel to be allocated for data. Preferably, this fir~t as~igned data channel (hereinafter "the master data channel") has the same frequency as any ~ingle ~requency data-only subscribers (116) to provide maximum compatibility with existing data equipment. Alternately, a random channel may be the first assigned data channel, however, the data-only subscribers must scan the available channels to find it. Thus, the present invention prefers to first assign a selected channel, and, thereafter, assign any other data equipped (12Z) channel as an additional data channel.
The present invention allocates dat~ ch nnels for a time interval datexmined by aither the system manager or a default parameter. The length of the allocation period may vary with the time of day, system loading or other such parameters. By reserving a channel for data use over a time period, data channel requests are minimized and spectral efficisncy is maximized since a data subscriber need not request a data channel for each separate data transmission.
As a general principle, the goal of any trunked communication system i5 to effectively allocate the limited channel resources amongst a plurality of subscriber units. The present invention contemplates three classes of subscriber units: voice-only subscribers 112, voice/data subscribers 114, and data-only subscribers 116. The voice-only subscribers 112 are contemplated to be any existing trunked subscrib~r unit having a compatible signalling protocol to allow interaction with the system (lO0). The data-only subscribers (116) are contemplated to be any multiple or single channel data transcaivers such as the RDT 800TM, manufactured by Motorola, Inc., or 129;~043
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functional equivalent. Of course, receive-only data devices, such as any of the Motorola family of display pagers, may also operate to receive paging data over an assigned data channel. In this way, the trunked system of the present invention accommodates existing equipment, while providing enhanced communication capabilities.
SubsGriber units are typically comprised of either mobile, portable or control stations. Typically, mobile units are understood to be transceivers designed to operate in a vehicle. A portable unit is typically understood to be a transceiving or receive-only device designed primarily to be carried on or about the person.
Conkrol stations are usually permanent or semi-permanent installations in buildings or other such fixed locations.
These are collectively re~erred to herein as subscriber units, which communica~e with one another through the fixed-end equipment.
As previously mentionad, the first data channel allocated is defined as the master data channel, the identity of which is periodically transmitted to all subscribsrs over the control channel. Additionally, or optionally, the identities of all other allocatad data channels are periodically transmit~ed over both the voice control channel and the master da~a channel.
Tho~e skilled in the art will appreciate that some criteria i8 required to decide how to distribute data users when multiple data channels are present.
According to the present invention, the data subscribers (114 and 116) each determine their own assigned data channel by rando~ly selecting one of ~he available data c:hannels .
It should also be understood that other bases are available and the particular ba is used in any particular implementation i~ not critical to ~he practice of ~he present invention. Random number (selection) generators are well known in the art, and the particular algorithm used is not critical to ~he practice or understanding of ~2920~3 - g - CM-00262H
the present inventive method. Of course, the particular data channel assignment will depend upon the actual number of data channels currently available. For example, a particular subscriber unit may select data channel one if the current number of data channel~ is tws. If the number of channels is three, channel two may be selected, and so on. O~ course, if there is only one data channel available, all data subscribers will use that channel. In this way, data subscribers may select a data channel and up-load or down-load information to or from the host computer 106 (or 118). As used herein, "up-load" means the transference of data or executable code from a subscriber unit to a ho~t computer. The term 7'down-load" means khe transference o~ data or executable code ~rom a host compu~er to a subscriber unit.
When a particular number of data channels is assigned, ~he central 102 monitors the voice activity, while the network controller 108 monitors the activity on the data channels. This activity monitoring is preferably performed for a predetermined period o~ time.
For example, the monitoring activity may be done by the hour tor half hour~ so that during peak loading times the trunked system (100) can quickly adapt to reallocate the channel resources. If the network controller determines that the data activity on the assigned data channels has exceeded a predetermined supervisor selected threshold, the network controller 108 re~uests the central to allocate another channel for data traffic. Conversely, if the central determines that voice activity has ex eeded a predetermined threshold, the central 102 requests the network controller to relinquish a data channel. In this way, ~he trunked system 100 adapts to reallocate the channel resources.
According to the present invention, reallocation begins by transmitting a "revert to master" command over all currently as~igned data channels. When the subscriber units receive this com~and, ~hey all revert to - 10 - CM-00262~
the master data channel to lis~en for new data channel assignments. The allocated data chann21s may be incremented or decremented by a predetermined number (one of the preferred embodiments) and the new allocation or number of data channels may be broadcast along with the identity of each data channel. The subscriber units receiving this information determine the number of available data channel3 and r~ndomly select an assignment. In this way, the number of data channels can 10 be conveniently incremented or decremented depending upon data traffic.
In addition to o~erall data traffic monitoring, the network controller 108 may determine that the data traffic load on a particular data channel is excessive.
15 Accordingly, the present invention csntemplates a method to balance the data tra~fic over the available data channels. Load leveling may be accomplished by simply transmitting a "revert to master" command over all currently a~signed data channels. When the subscriber units receive this command, they all revert to the master data channel to listen for new data channel assignments.
For load leveling, the actual number of allocated data ahannels may not have changed. The data subscribers are merely forced to randomly re-select a data channel assignment. However, it is possible that the data su~scribers may not be able to effectively re-distribute the data traffic using this simple approach.
Accordingly, the present invention contamplates txansmitting an of~et "seed" to some or all the subscribers for the random selection algori~hm. In this way, there i5 a statistical probability that ~hP load will be spread over the available data channels as opposed to being congested onto a particular data channel. The data traffic may then be monitored over the next opera~ing period, and if the load is still unbalanced a different offse~ seed may be transmi~ted to again redistribute the data load.
~29Z043 Those skilled in the ar~ will appreciate that it is often desirable to communicate with all subscriber units at one time in response to either an emergency, or to distribute a message of general concern. For example, a message announcing some emergency condition, or that the host computer 106 (or 11~) will be down ~or repair are examples of messages that would be convenient to transmit to all subscribers at one time. Accordingly, the present invention achieves this operat$on by transmitting the revert to master command over all allocated data channels. ~11 subscribers respond to this command by listening to ~he master data channel. Just prior to retransmitting the current number of data channels and theix identities (which may be unchanged), a system broadcast message is tran~mitted so that all subscribers may receive the message prior to receiving tha data channel in~ormation. In this way rapid syst~m wide data communication is provided by the present inventive method. After receiving the system message, the data subscribers may return to their assigned data channels.
Referring now to Figure 2, an illustration of the preferred signalling format for the master data channel i8 shown. The signalling format 200 begins with a preamble portion 202, which may include synchronization or framing information for the da~a subscriber units.
Following the preamble 202 is an optional block 204 wherein either a system message or an offset seed may be transmitted to effectuate either the system message operation or the load leveling procedure previously mentioned. Of course, during normal operations format block 204 would not be used and ~he preamble 202 would directly precede block 206~
Basically, block 206 transmits the total number of currently available data channels (b~ it 1, 2, 5, etc. ) in any suitable form. Following block 206 are a plurality of blocks (208a through 208n) which transmit 129Z~43 - 12 - CM-00262~
the identity of the data channels. In the preferred embodiment, the transmitted identity of the data channels is the actual frequency of the channels. Alternately, the channels could be assigned a designated number and the selected ones available ~or data use transmitted.
For example, if a particular system has five channels, it may be convenient to label them 1-5. Then, assuming the subscribers knew the frDquencies, the numbers "4" and "5"
may be transmitted to indicate that channels four and five are the data channels. The preferred method, however, is to transmit the actual ~r2quencies, since this allows for simple expansion of the system, and llmits the amount of info~mation required to reside in the aubscriber units. Therefore, if there is one data channel (i.e., the master data channel~, that frequency will be transmitted in block 208a. If there are five data channels currently available (the master data channel plus four other data channels), those frequencies may be transmitted (for exampla in blocks 208a through 208e), and so on.
After the transmission of the identity of the last available data channel, the master data channel may be used by the subscriber units as a data channel as is illustrated by block 210.
To effectuate a recovery process, in case any particular subscriber unit should temporarily lose its data chann~l assignment, the cen~ral 102 and the network controller 108 may periodically transmit the signalling format 200 over the voice control channel and the master data channel, respectively. If through some error the data channel assignment is lost, the present invention provides that all data mode subscriber units automatically revert ~o the ma~ter data channel. In this way, a subscriber unit may receive the periodic transmissions of the channel as~ignments from the master data channel and return to the proper data channel assig~ment. In the event a subscriber unit loses the l2gz~as3 identity of the master data channel, the present invention further provides that the subscriber units revert to the voice control cbannel to receive the data channal allocatlon information.
Referring now to Figure 3, the preferred format ~or other (i.e., not the ma~ter) daka channels i shown.
Basically, the ~ormat of a data channel 300 begins with a preamble 302, which may include synchronization and fxaming information. ~he preamble 302 precPdes a plurality of variable length data messages 304-308.
As previously mentioned, the request for assignment of a data channel is prohibitively long compared to the typical data message transmission time.
Therefore, the present invention contemplates a subscriber unit going to its assigned data channel and transmitting the data information without re-requesting the channel~ Operating in this manner conserves spectrum and speeds transmission by eliminating the requirement to request a data channel. Of course, there exists the possibility that there will be data collisions on the data channels. However, data collision avoidance mechani3ms and methods are widely known in the art and any suitable data collision avoidance and recovery method will be suitable for use in the present invention.
As illustrated in Figure 3, the lengths of data mes~ages 1, 2 and 3 (304, 306 and 308), are all of a variable duration depending upon the amount of in~ormation to be transmitted. Thu , onca a subscriber unit gains access to a data channel, khe subscriber may transmit data for as long as required to complete a data me~sage. Of course, a second subscriber unit attempting to transmit data may be required ~o wait until the first subscriber has completed transmitting. Thus, a data channel may be in constant or near constan~ use. During period~ of high data channel use, the preamble portion 302 need not be transmitted since the subscribers may stiIl be synchronized to the incoming data. However, if ~92~43 th2 data channel use is low, the network controllzr 108 or a data subscriber may transmit the preamble portion 302 prior to transmitting.
Referring now to Figure 4, there i8 shown a ~low diagram illustrating the steps executed by the ~ixed-end equipment to implement the present invention. The routine begins with initializing step 400, wherein the central controller 102 and the network controller 108 may set aside memory space or perform other such functions as any particular system may requireO The routine next proceeds to step 402, which start~ the period tim r over which the central controller 102 monitors the voice activity and the network controller monitors the data activity. In step 404, the~e m2asurements are taken such as by cal~ulating the air-time billing information or other such suitable means. Following s~ep 404, decision 406 determines whether or not the timer has elapsed. If the timer has not elapsed, a loop is formed with step 404 until decision 406 determines that the timer has expired.
Decision 408 determines whether the voice activity is high when compared to a selected threshold that may be specified by the system supervisor. If the determination Or decision 408 i~ tha~ the voice activity is high, decision 410 determinec whether the current number of data channels minu~ a predetermined offset (one in the pre~erred embodiment) would be less than the minimum number (if any) o~ data channels specified by the system supervisor. I~ so, decision 410 returns co~trol to reference letter A, which re~ets the timer and the routine begins again. If, however, decision 410 dete~mines that removing a channel would no~ be below the minimum allowed data channels, or there is no minimum, the routine proceeds to s~ep 412, which dP-alloca~es a channel from data traffic and returns it to voice traffic. The routine then proceeds to re~erence letter A
of Figure 4.
~Z~43 If the determination of decision 408 is that the voice activity is not high, the routine proceeds to decision 414, which determines whether the data activity is high compared to a predetermined threshold selected by the system supervisor. If the determination of decision 414 is that the data activiky is high, the routine proceeds to decision 416, which determines whether the current number of channels plu~ one (in the preferred embodiment) is greater than the maximum number (if any) specified by the system supervisor. If the determination of decision 416 i8 ~hat the additional channel would exceed the maximum, the routine returns control to reference letter A. If, however, decision 416 determines that the addition of a data channel will not exceed the maximum, the routine proceeds to step 418, which allocates an additional channel ~rom voice traf~ic to data traffic. The routine then returns control to reference letter A of Figure 4.
Additionally, the fixed-end equipment may take traffic priorities into account before the allocation step 418 and the de-allocation step 412. If, for example, a particular system favored voice traffic, an additional data channel may not be allocated if voice traffic were above a predetermined minimum. Alternately, for a system having a data traffic preference, a data channel may not be re-allocated for voice traffic if data traffic was above a predetermined threshold. In the absence.of either a voice ~raffic or data traffic preference, the absolute allocation and de-allocation procedure of Figure 4 is preferred.
Referring ~till to Figure 4, if the determination of 414 is that thP data activity as a whole is not high, the routine proceeds to decision 420 to determine whether the data traffic across all available data channels is balanced or unbalanced. If the determination of decision 420 i~ that the traffic i8 essentially balanced, the routine returns control to reference l~tter A, which resets the timer of step 402. If, however, de~ision 420 determine~ that the data traffic ~s unbalanc2d the roukine proceeds to the load leveling xoutine of Figure 5a.
Referring now to Figure 5a, the steps executed by the network controller 108 to execute a load leveling of data ~ra~fic across the available data channels is described. The routine begins in step 500, which transmits a revert to master command across all data channels. Upon receipt o~ the command, the data subscribers listen to the master data channel and may receive an o~f~et seed parameter or a load level command transmitted as block 204 o~ Figure 2 (502 of Fig. 5a).
The load leveling routine next proceeds to step 504, 15 where the num~er of available data channels and their identities are transmitted over the master data channel.
Of course, the total number may not have changed; instead the offset seed parameter may have been added to ~tatistically redistribute the groups (or subgroups) acxoss the available data channels. After receiving this information, each subscriber randomly re-selects a data channel assignment. Of course, a~ previously mentioned, i~ after monitoring the next transmission period, the data traffic load remains unbalanced, a different offset seed may be transmitted until an acceptable balance is obtained between the data traf~ic and the available data channel resources Re~erring now to Figure 5b, the steps executed by the network controller 108 to broadcast a sys~em wide data message is shown. The rou~ine ~egins in step 506, where the revert to mas er command is tr~nsmitted to all data subscribers. Nex~, in s~ep 508, ~he system message is transmitted (see Figure 2, block 204) to the subscriber units over the master data channel. Following step 508, the current number o~ data chann~ls and their identitie~ ~which may be unchanged) are transmitted in step 510. In thi~ way, a message of general concern may be rapidly and efficiently transmitted to all data subscriber units. Lastly, after step 510, the routine returns to reference letter A of Figure 4.
Referring now to Figure 6, there is shown a flow diagram illustrating the steps executed by a data subscriber unit (114 or 116) in accordance with the present invention. The routine begins in step 600, where the data subscriber performs any initialization steps required in any particular implementation. In step 602, the data subscriber receives the data channel allocation in~ormation from either the voice control channel or the master data channel. Additionally, a subscri~er I5 monitoring the master data channel may receive a system message (see Figure 2). In step 604, the data subscriber randomly selects a data channel from the available data channels. In step 608, the data subscriber operates to receive and transmit data information on the assigned data channel. Decision 610 determines whether a "revert to master" command was received~ If so, the subscriber goes to the master control channel to receive the data channel allocation information in step 612; otherwise, the routine returns to reference letter B to continue data operations.
Decision 614 determines whether the data allocation information contained a system message. If so, the data subscriber stores or plays back the message by any appropriate means. For example, the subscriber can display the message (step 616) on any suitable display means. Optionally, the data subscriber may generate a "hard copy" on a printer, or speech synthesis may be utilized to render the message audible. If the determination of decision 614 is that the data channel allocation information does not contain a system message, the routine proceeds to decision 618.
Decision 618 determines whether the data channel allocation information contained a load leveling command or a new , .
- 18 - lZ92~43 CM-00262H
offset seed. If so, the data sub~criber again randomly selects a data channel assignment 620, which may be different than its previous data channel assignment, and the routine proceeds to reference letter B wherein the subscriber returns to normal data communication.
While a particular embodiment of the invention has been described and shown, it should be understood that the invention i8 not limited thereto since many modi~ications may be made. It i8 therefore contemplated by the present application to co~er any and all such modi~ications that may fall within the true spirit and 8cope 0~ the ba~ic underlying principles disclosed and claimed herein~
What i5 claimed i8:
functional equivalent. Of course, receive-only data devices, such as any of the Motorola family of display pagers, may also operate to receive paging data over an assigned data channel. In this way, the trunked system of the present invention accommodates existing equipment, while providing enhanced communication capabilities.
SubsGriber units are typically comprised of either mobile, portable or control stations. Typically, mobile units are understood to be transceivers designed to operate in a vehicle. A portable unit is typically understood to be a transceiving or receive-only device designed primarily to be carried on or about the person.
Conkrol stations are usually permanent or semi-permanent installations in buildings or other such fixed locations.
These are collectively re~erred to herein as subscriber units, which communica~e with one another through the fixed-end equipment.
As previously mentionad, the first data channel allocated is defined as the master data channel, the identity of which is periodically transmitted to all subscribsrs over the control channel. Additionally, or optionally, the identities of all other allocatad data channels are periodically transmit~ed over both the voice control channel and the master da~a channel.
Tho~e skilled in the art will appreciate that some criteria i8 required to decide how to distribute data users when multiple data channels are present.
According to the present invention, the data subscribers (114 and 116) each determine their own assigned data channel by rando~ly selecting one of ~he available data c:hannels .
It should also be understood that other bases are available and the particular ba is used in any particular implementation i~ not critical to ~he practice of ~he present invention. Random number (selection) generators are well known in the art, and the particular algorithm used is not critical to ~he practice or understanding of ~2920~3 - g - CM-00262H
the present inventive method. Of course, the particular data channel assignment will depend upon the actual number of data channels currently available. For example, a particular subscriber unit may select data channel one if the current number of data channel~ is tws. If the number of channels is three, channel two may be selected, and so on. O~ course, if there is only one data channel available, all data subscribers will use that channel. In this way, data subscribers may select a data channel and up-load or down-load information to or from the host computer 106 (or 118). As used herein, "up-load" means the transference of data or executable code from a subscriber unit to a ho~t computer. The term 7'down-load" means khe transference o~ data or executable code ~rom a host compu~er to a subscriber unit.
When a particular number of data channels is assigned, ~he central 102 monitors the voice activity, while the network controller 108 monitors the activity on the data channels. This activity monitoring is preferably performed for a predetermined period o~ time.
For example, the monitoring activity may be done by the hour tor half hour~ so that during peak loading times the trunked system (100) can quickly adapt to reallocate the channel resources. If the network controller determines that the data activity on the assigned data channels has exceeded a predetermined supervisor selected threshold, the network controller 108 re~uests the central to allocate another channel for data traffic. Conversely, if the central determines that voice activity has ex eeded a predetermined threshold, the central 102 requests the network controller to relinquish a data channel. In this way, ~he trunked system 100 adapts to reallocate the channel resources.
According to the present invention, reallocation begins by transmitting a "revert to master" command over all currently as~igned data channels. When the subscriber units receive this com~and, ~hey all revert to - 10 - CM-00262~
the master data channel to lis~en for new data channel assignments. The allocated data chann21s may be incremented or decremented by a predetermined number (one of the preferred embodiments) and the new allocation or number of data channels may be broadcast along with the identity of each data channel. The subscriber units receiving this information determine the number of available data channel3 and r~ndomly select an assignment. In this way, the number of data channels can 10 be conveniently incremented or decremented depending upon data traffic.
In addition to o~erall data traffic monitoring, the network controller 108 may determine that the data traffic load on a particular data channel is excessive.
15 Accordingly, the present invention csntemplates a method to balance the data tra~fic over the available data channels. Load leveling may be accomplished by simply transmitting a "revert to master" command over all currently a~signed data channels. When the subscriber units receive this command, they all revert to the master data channel to listen for new data channel assignments.
For load leveling, the actual number of allocated data ahannels may not have changed. The data subscribers are merely forced to randomly re-select a data channel assignment. However, it is possible that the data su~scribers may not be able to effectively re-distribute the data traffic using this simple approach.
Accordingly, the present invention contamplates txansmitting an of~et "seed" to some or all the subscribers for the random selection algori~hm. In this way, there i5 a statistical probability that ~hP load will be spread over the available data channels as opposed to being congested onto a particular data channel. The data traffic may then be monitored over the next opera~ing period, and if the load is still unbalanced a different offse~ seed may be transmi~ted to again redistribute the data load.
~29Z043 Those skilled in the ar~ will appreciate that it is often desirable to communicate with all subscriber units at one time in response to either an emergency, or to distribute a message of general concern. For example, a message announcing some emergency condition, or that the host computer 106 (or 11~) will be down ~or repair are examples of messages that would be convenient to transmit to all subscribers at one time. Accordingly, the present invention achieves this operat$on by transmitting the revert to master command over all allocated data channels. ~11 subscribers respond to this command by listening to ~he master data channel. Just prior to retransmitting the current number of data channels and theix identities (which may be unchanged), a system broadcast message is tran~mitted so that all subscribers may receive the message prior to receiving tha data channel in~ormation. In this way rapid syst~m wide data communication is provided by the present inventive method. After receiving the system message, the data subscribers may return to their assigned data channels.
Referring now to Figure 2, an illustration of the preferred signalling format for the master data channel i8 shown. The signalling format 200 begins with a preamble portion 202, which may include synchronization or framing information for the da~a subscriber units.
Following the preamble 202 is an optional block 204 wherein either a system message or an offset seed may be transmitted to effectuate either the system message operation or the load leveling procedure previously mentioned. Of course, during normal operations format block 204 would not be used and ~he preamble 202 would directly precede block 206~
Basically, block 206 transmits the total number of currently available data channels (b~ it 1, 2, 5, etc. ) in any suitable form. Following block 206 are a plurality of blocks (208a through 208n) which transmit 129Z~43 - 12 - CM-00262~
the identity of the data channels. In the preferred embodiment, the transmitted identity of the data channels is the actual frequency of the channels. Alternately, the channels could be assigned a designated number and the selected ones available ~or data use transmitted.
For example, if a particular system has five channels, it may be convenient to label them 1-5. Then, assuming the subscribers knew the frDquencies, the numbers "4" and "5"
may be transmitted to indicate that channels four and five are the data channels. The preferred method, however, is to transmit the actual ~r2quencies, since this allows for simple expansion of the system, and llmits the amount of info~mation required to reside in the aubscriber units. Therefore, if there is one data channel (i.e., the master data channel~, that frequency will be transmitted in block 208a. If there are five data channels currently available (the master data channel plus four other data channels), those frequencies may be transmitted (for exampla in blocks 208a through 208e), and so on.
After the transmission of the identity of the last available data channel, the master data channel may be used by the subscriber units as a data channel as is illustrated by block 210.
To effectuate a recovery process, in case any particular subscriber unit should temporarily lose its data chann~l assignment, the cen~ral 102 and the network controller 108 may periodically transmit the signalling format 200 over the voice control channel and the master data channel, respectively. If through some error the data channel assignment is lost, the present invention provides that all data mode subscriber units automatically revert ~o the ma~ter data channel. In this way, a subscriber unit may receive the periodic transmissions of the channel as~ignments from the master data channel and return to the proper data channel assig~ment. In the event a subscriber unit loses the l2gz~as3 identity of the master data channel, the present invention further provides that the subscriber units revert to the voice control cbannel to receive the data channal allocatlon information.
Referring now to Figure 3, the preferred format ~or other (i.e., not the ma~ter) daka channels i shown.
Basically, the ~ormat of a data channel 300 begins with a preamble 302, which may include synchronization and fxaming information. ~he preamble 302 precPdes a plurality of variable length data messages 304-308.
As previously mentioned, the request for assignment of a data channel is prohibitively long compared to the typical data message transmission time.
Therefore, the present invention contemplates a subscriber unit going to its assigned data channel and transmitting the data information without re-requesting the channel~ Operating in this manner conserves spectrum and speeds transmission by eliminating the requirement to request a data channel. Of course, there exists the possibility that there will be data collisions on the data channels. However, data collision avoidance mechani3ms and methods are widely known in the art and any suitable data collision avoidance and recovery method will be suitable for use in the present invention.
As illustrated in Figure 3, the lengths of data mes~ages 1, 2 and 3 (304, 306 and 308), are all of a variable duration depending upon the amount of in~ormation to be transmitted. Thu , onca a subscriber unit gains access to a data channel, khe subscriber may transmit data for as long as required to complete a data me~sage. Of course, a second subscriber unit attempting to transmit data may be required ~o wait until the first subscriber has completed transmitting. Thus, a data channel may be in constant or near constan~ use. During period~ of high data channel use, the preamble portion 302 need not be transmitted since the subscribers may stiIl be synchronized to the incoming data. However, if ~92~43 th2 data channel use is low, the network controllzr 108 or a data subscriber may transmit the preamble portion 302 prior to transmitting.
Referring now to Figure 4, there i8 shown a ~low diagram illustrating the steps executed by the ~ixed-end equipment to implement the present invention. The routine begins with initializing step 400, wherein the central controller 102 and the network controller 108 may set aside memory space or perform other such functions as any particular system may requireO The routine next proceeds to step 402, which start~ the period tim r over which the central controller 102 monitors the voice activity and the network controller monitors the data activity. In step 404, the~e m2asurements are taken such as by cal~ulating the air-time billing information or other such suitable means. Following s~ep 404, decision 406 determines whether or not the timer has elapsed. If the timer has not elapsed, a loop is formed with step 404 until decision 406 determines that the timer has expired.
Decision 408 determines whether the voice activity is high when compared to a selected threshold that may be specified by the system supervisor. If the determination Or decision 408 i~ tha~ the voice activity is high, decision 410 determinec whether the current number of data channels minu~ a predetermined offset (one in the pre~erred embodiment) would be less than the minimum number (if any) o~ data channels specified by the system supervisor. I~ so, decision 410 returns co~trol to reference letter A, which re~ets the timer and the routine begins again. If, however, decision 410 dete~mines that removing a channel would no~ be below the minimum allowed data channels, or there is no minimum, the routine proceeds to s~ep 412, which dP-alloca~es a channel from data traffic and returns it to voice traffic. The routine then proceeds to re~erence letter A
of Figure 4.
~Z~43 If the determination of decision 408 is that the voice activity is not high, the routine proceeds to decision 414, which determines whether the data activity is high compared to a predetermined threshold selected by the system supervisor. If the determination of decision 414 is that the data activiky is high, the routine proceeds to decision 416, which determines whether the current number of channels plu~ one (in the preferred embodiment) is greater than the maximum number (if any) specified by the system supervisor. If the determination of decision 416 i8 ~hat the additional channel would exceed the maximum, the routine returns control to reference letter A. If, however, decision 416 determines that the addition of a data channel will not exceed the maximum, the routine proceeds to step 418, which allocates an additional channel ~rom voice traf~ic to data traffic. The routine then returns control to reference letter A of Figure 4.
Additionally, the fixed-end equipment may take traffic priorities into account before the allocation step 418 and the de-allocation step 412. If, for example, a particular system favored voice traffic, an additional data channel may not be allocated if voice traffic were above a predetermined minimum. Alternately, for a system having a data traffic preference, a data channel may not be re-allocated for voice traffic if data traffic was above a predetermined threshold. In the absence.of either a voice ~raffic or data traffic preference, the absolute allocation and de-allocation procedure of Figure 4 is preferred.
Referring ~till to Figure 4, if the determination of 414 is that thP data activity as a whole is not high, the routine proceeds to decision 420 to determine whether the data traffic across all available data channels is balanced or unbalanced. If the determination of decision 420 i~ that the traffic i8 essentially balanced, the routine returns control to reference l~tter A, which resets the timer of step 402. If, however, de~ision 420 determine~ that the data traffic ~s unbalanc2d the roukine proceeds to the load leveling xoutine of Figure 5a.
Referring now to Figure 5a, the steps executed by the network controller 108 to execute a load leveling of data ~ra~fic across the available data channels is described. The routine begins in step 500, which transmits a revert to master command across all data channels. Upon receipt o~ the command, the data subscribers listen to the master data channel and may receive an o~f~et seed parameter or a load level command transmitted as block 204 o~ Figure 2 (502 of Fig. 5a).
The load leveling routine next proceeds to step 504, 15 where the num~er of available data channels and their identities are transmitted over the master data channel.
Of course, the total number may not have changed; instead the offset seed parameter may have been added to ~tatistically redistribute the groups (or subgroups) acxoss the available data channels. After receiving this information, each subscriber randomly re-selects a data channel assignment. Of course, a~ previously mentioned, i~ after monitoring the next transmission period, the data traffic load remains unbalanced, a different offset seed may be transmitted until an acceptable balance is obtained between the data traf~ic and the available data channel resources Re~erring now to Figure 5b, the steps executed by the network controller 108 to broadcast a sys~em wide data message is shown. The rou~ine ~egins in step 506, where the revert to mas er command is tr~nsmitted to all data subscribers. Nex~, in s~ep 508, ~he system message is transmitted (see Figure 2, block 204) to the subscriber units over the master data channel. Following step 508, the current number o~ data chann~ls and their identitie~ ~which may be unchanged) are transmitted in step 510. In thi~ way, a message of general concern may be rapidly and efficiently transmitted to all data subscriber units. Lastly, after step 510, the routine returns to reference letter A of Figure 4.
Referring now to Figure 6, there is shown a flow diagram illustrating the steps executed by a data subscriber unit (114 or 116) in accordance with the present invention. The routine begins in step 600, where the data subscriber performs any initialization steps required in any particular implementation. In step 602, the data subscriber receives the data channel allocation in~ormation from either the voice control channel or the master data channel. Additionally, a subscri~er I5 monitoring the master data channel may receive a system message (see Figure 2). In step 604, the data subscriber randomly selects a data channel from the available data channels. In step 608, the data subscriber operates to receive and transmit data information on the assigned data channel. Decision 610 determines whether a "revert to master" command was received~ If so, the subscriber goes to the master control channel to receive the data channel allocation information in step 612; otherwise, the routine returns to reference letter B to continue data operations.
Decision 614 determines whether the data allocation information contained a system message. If so, the data subscriber stores or plays back the message by any appropriate means. For example, the subscriber can display the message (step 616) on any suitable display means. Optionally, the data subscriber may generate a "hard copy" on a printer, or speech synthesis may be utilized to render the message audible. If the determination of decision 614 is that the data channel allocation information does not contain a system message, the routine proceeds to decision 618.
Decision 618 determines whether the data channel allocation information contained a load leveling command or a new , .
- 18 - lZ92~43 CM-00262H
offset seed. If so, the data sub~criber again randomly selects a data channel assignment 620, which may be different than its previous data channel assignment, and the routine proceeds to reference letter B wherein the subscriber returns to normal data communication.
While a particular embodiment of the invention has been described and shown, it should be understood that the invention i8 not limited thereto since many modi~ications may be made. It i8 therefore contemplated by the present application to co~er any and all such modi~ications that may fall within the true spirit and 8cope 0~ the ba~ic underlying principles disclosed and claimed herein~
What i5 claimed i8:
Claims (14)
PROPERTY OF PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for allocating data channels on a trunked radio frequency communication system having a control channel and a plurality of channels available for voice or data communication and a plurality of data subscribers, comprising the steps of:
(a) measuring the amount of - data communications during a predetermined interval;
(b) comparing said measured amount of data communications to a predetermined threshold;
(c) changing the number of channels allocated for data communication in response to step (b); and (d) informing said plurality of data subscribers that the number of channels allocated for data communication has been changed.
(a) measuring the amount of - data communications during a predetermined interval;
(b) comparing said measured amount of data communications to a predetermined threshold;
(c) changing the number of channels allocated for data communication in response to step (b); and (d) informing said plurality of data subscribers that the number of channels allocated for data communication has been changed.
2. The method of claim 1, which includes a method for leveling data traffic over at least two channels comprising the steps of;
(a) measuring the amount of data communications over each of the channels allocated for data;
(b) determining whether said measured amount of data communications is uniformly distributed over the channels allocated for data;
(c) in response to step (b) causing all data subscribers to go to the control channel;
(d) transmitting a random number to said data subscribers via said control channel.
(a) measuring the amount of data communications over each of the channels allocated for data;
(b) determining whether said measured amount of data communications is uniformly distributed over the channels allocated for data;
(c) in response to step (b) causing all data subscribers to go to the control channel;
(d) transmitting a random number to said data subscribers via said control channel.
3. The method of claim 2, which includes the step of:
(e) commanding the plurality of data subscribers to randomly re-select a data channel based at least in part on said random number.
(e) commanding the plurality of data subscribers to randomly re-select a data channel based at least in part on said random number.
4. The method of claim 3, wherein the step of measuring comprises calculating the amount of data communications based at least in part on subscriber air-time billing information.
5. The method of claim 4, wherein the step of changing comprises increasing the number of channels allocated for data by a predetermined number of channels.
6. The method of claim 5, wherein said channels allocated for data are increased by one.
7. The method of claim 6, wherein the step of changing comprises decreasing the number of channels allocated for data by a predetermined number of channels.
8. The method of claim 7, wherein said channels allocated for data are decreased by one.
9. In a trunked radio frequency communication system having a plurality of data subscribers, a plurality of data channels, and a control channel, a method for leveling data traffic over said plurality of data channels, comprising the steps of:
(a) measuring the amount of data traffic on each of said plurality of data channels;
(b) determining whether said measured amount of data traffic is uniformly distributed;
(c) in response to step (b) causing said data subscribers to go to said control channel; and (d) transmitting a random number to said data subscribers via said control channel.
(a) measuring the amount of data traffic on each of said plurality of data channels;
(b) determining whether said measured amount of data traffic is uniformly distributed;
(c) in response to step (b) causing said data subscribers to go to said control channel; and (d) transmitting a random number to said data subscribers via said control channel.
The method of claim 9, which includes the step of:
(e) causing said plurality of data subscribers to randomly re-select a data channel assignment based at least in part on said random number
(e) causing said plurality of data subscribers to randomly re-select a data channel assignment based at least in part on said random number
11. A method for communicating on a trunked communication system having a plurality of data subscriber units and at least one central controller and network controller to allocate a plurality of channels for data or at the network controller;
(a) measuring data traffic over the channels allocated for data;
(b) comparing said measured data traffic to a predetermined threshold;
(c): transmitting a data channel request to the central controller as necessary in response to step (b);
(d) transmitting a command signal to the plurality of data subscriber units over a predetermined channel;
(e) transmitting an information signal to the plurality of data subscriber units over a predetermined channel;
at the central controller;
(a) receiving said data channel request from the network controller;
(b) varying the number of allocated data channels in response to said data channel request;
(c) transmitting an information signal to the plurality of subscriber units over a control channel;
at the plurality of data subscriber units;
(a) receiving said command signal;
(b) receiving said information signal from said network controller;
(c) randomly selecting a data channel in response to said information signal from said network controller;
(d) monitoring said selected channel.
(a) measuring data traffic over the channels allocated for data;
(b) comparing said measured data traffic to a predetermined threshold;
(c): transmitting a data channel request to the central controller as necessary in response to step (b);
(d) transmitting a command signal to the plurality of data subscriber units over a predetermined channel;
(e) transmitting an information signal to the plurality of data subscriber units over a predetermined channel;
at the central controller;
(a) receiving said data channel request from the network controller;
(b) varying the number of allocated data channels in response to said data channel request;
(c) transmitting an information signal to the plurality of subscriber units over a control channel;
at the plurality of data subscriber units;
(a) receiving said command signal;
(b) receiving said information signal from said network controller;
(c) randomly selecting a data channel in response to said information signal from said network controller;
(d) monitoring said selected channel.
12. The method of claim 11, which includes the central controller step of transmitting, periodically, the identity of a first allocated data channel over said control channel.
13. The method of claim 11, which includes the central controller step of transmitting the identity of all available data channels over said control channel.
14. The method of claim 12, which includes the network controller step of transmitting the identity of all available data channels over said first allocated channel.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/044,525 US4870408A (en) | 1987-04-30 | 1987-04-30 | Method for dynamically allocating data channels on a trunked communication system |
| US07/044,525 | 1987-04-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1292043C true CA1292043C (en) | 1991-11-12 |
Family
ID=21932875
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000557939A Expired - Lifetime CA1292043C (en) | 1987-04-30 | 1988-02-02 | Method for dynamically allocating data channels on a trunked communication system |
Country Status (11)
| Country | Link |
|---|---|
| US (1) | US4870408A (en) |
| EP (1) | EP0358688B1 (en) |
| JP (1) | JPH0777462B2 (en) |
| KR (1) | KR960006465B1 (en) |
| CA (1) | CA1292043C (en) |
| DE (1) | DE3851146T2 (en) |
| DK (1) | DK590888A (en) |
| FI (1) | FI100073B (en) |
| HK (1) | HK1000359A1 (en) |
| NZ (1) | NZ223890A (en) |
| WO (1) | WO1988008648A1 (en) |
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| HK1000359A1 (en) | 1998-03-06 |
| US4870408A (en) | 1989-09-26 |
| EP0358688A4 (en) | 1992-01-22 |
| KR890700976A (en) | 1989-04-28 |
| DE3851146D1 (en) | 1994-09-22 |
| NZ223890A (en) | 1990-04-26 |
| JPH0777462B2 (en) | 1995-08-16 |
| FI893922A0 (en) | 1989-08-21 |
| DK590888D0 (en) | 1988-10-25 |
| DE3851146T2 (en) | 1995-03-09 |
| DK590888A (en) | 1988-11-03 |
| KR960006465B1 (en) | 1996-05-16 |
| EP0358688A1 (en) | 1990-03-21 |
| EP0358688B1 (en) | 1994-08-17 |
| WO1988008648A1 (en) | 1988-11-03 |
| FI893922A (en) | 1989-08-21 |
| JPH02500317A (en) | 1990-02-01 |
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