Patent Publication Number: US-10791566-B2

Title: System and method for dynamic channel allocation

Description:
RELATED APPLICATION 
     Pursuant to 35 U.S.C. § 120, this application is a continuation of U.S. patent application Ser. No. 15/641,747, entitled “System and Method for Dynamic Channel Allocation,” filed Jul. 5, 2017, and naming Ronald Lee Bane and Brian J. Austin as inventors, which is a continuation of U.S. patent application Ser. No. 14/935,270, entitled “System and Method for Dynamic Channel Allocation,” filed Nov. 6, 2015, and naming Ronald Lee Bane and Brian J. Austin as inventors, which claims the benefit and priority from U.S. Provisional Patent Application Ser. No. 62/076,473, entitled “System and Method for Dynamic Channel Allocation,” filed Nov. 6, 2014, and naming Ronald Lee Bane and Brian J. Austin as inventors, both of which are incorporated by reference herein for all purposes. 
    
    
     TECHNICAL FIELD 
     This disclosure relates in general to a system and method for dynamic channel allocation in a communications system and, in particular, to an improved system and method for dynamic channel allocation in a land mobile radio system, including a simulcast and a non-simulcast land mobile radio system, using one or more preference indicators. 
     BACKGROUND OF THE DISCLOSURE 
     Land mobile radio (LMR) systems are used by municipalities, governmental entities, including police, fire, medical, and military first responders, and other organizations to provide a private, wireless communications network using mobile and/or stationary radio units to communicate with one another over a specific geographic area. An LMR system can be as simple as two subscriber units communicating between themselves and a site over preset channels, or they can be complex consisting of hundreds of subscriber units and multiple sites. Generally, an LMR system includes a plurality of sites positioned in different locations in the specific geographic area to provide the desired coverage and bandwidth. Each site may include an antenna, a site controller, and a plurality of repeaters that include a transmitter and receiver at designated or desired frequencies. In certain embodiments, the sites, such as the site controllers, may communicate with each other through a backbone data network, such as an IP data network or the Internet, to assist with communications needs between the sites, such as call-setup activities and administrative functions needed for operating an LMR system. 
     An LMR System may, generally, be categorized as simulcast system or a non-simulcast system. In a simulcast trunking LMR system, a channel is comprised of two or more repeaters, each having common transmit frequencies, and common receive frequencies, but located at different geographical locations. The site locations are chosen to provide a wider coverage area than is possible with a single location. In such simulcast systems, repeater failures can result in a reduction in capacity, a reduction in coverage, or both. Consider, for example in a nine channel, three site simulcast LMR system, the failure of a single repeater at one site. If the channel is allowed to be included for use in subsequent communication requests, the RF coverage will suffer, due to the loss of transmit and/or receive functionality in the geographical area normally covered by the failed repeater. If the channel is not allowed to be included for use in subsequent communication requests, the system will operate over the preferred coverage area, but with reduced capacity. In this failure scenario, it is likely that the reduced capacity result is preferred over the reduced coverage area result. 
     Consider an alternate failure scenario where a site loses power, causing all repeaters at that site to fail. If the same preferred action from the previous scenario were applied in this case, all channels would be excluded from subsequent communication requests, resulting in zero capacity for the system. For this failure scenario, the reduced coverage result would be preferred over the zero capacity result. 
     When a call is setup in an LMR system, channels, which are comprised of underlying repeaters at one or more sites, are to be effectively allocated or various problems and disadvantages may occur, such as those just described, including decreased call coverage area, decreased bandwidth or capacity, and call quality. 
     SUMMARY 
     In a first aspect, there is provided a method for dynamic channel allocation in a land mobile radio communications system that includes allocating a control channel and a traffic channel based upon at least one preference indicator. The method may include determining one or more preference indicators for various channels for use in allocating the plurality of channels, wherein each of the plurality of channels is associated with one or more repeaters of a plurality of repeaters located at a plurality of sites of the land mobile radio communications system, determining a priority ranking for use in allocating each of the plurality of channels based at least in part on the one or more preference indicators, and receiving a first channel allocation request to allocate one of the plurality of channels as a control channel. The method may further includes allocating a first one of the plurality of channels as the control channel in response to the first channel allocation request by selecting the first one of the plurality of channels based on the highest ranked channel of the priority ranking for use in allocating each of the plurality of channels, receiving a second channel allocation request to allocate one of the plurality of channels as a traffic channel while the first one of the plurality of channels is allocated as the control channel, and allocating a second one of the plurality of channels as the traffic channel in response to the second channel allocation request by selecting the second one of the plurality of channels based on the then highest ranked channel of the priority ranking for use in allocating each of the plurality of channels. 
     In one embodiment of the method, the method further includes updating the priority ranking for use in allocating each of the plurality of channels based at least in part on changes to the one or more preference indicators. 
     In another embodiment of the method, the method further includes periodically updating the priority ranking for use in allocating each of the plurality of channels. 
     In still another embodiment of the method, the method further includes updating the priority ranking for use in allocating each of the plurality of channels based at least in part on changes in at least two or more of the one or more preference indicators. 
     In still yet another embodiment of the method, at least one of the one or more preference indicators includes a channel failure indicator for each of the plurality of channels that corresponds to the current operational indicator of the plurality of repeaters associated with each channel. 
     In one embodiment of the method, the channel failure indicator is determined for each of the plurality of channels and is based on the percentage of operational repeaters associated with a particular channel as compared to the total number of repeaters associated with that particular channel. 
     In yet another embodiment of the method, the one or more preference indicators includes at least one from the group that includes a channel failure indicator, a channel priority indicator, and a radio frequency interference indicator. 
     In still yet another embodiment of the method of dynamic channel allocation, the one or more preference indicators includes a channel failure indicator for each of the plurality of channels that corresponds to the current operational state of the plurality of repeaters associated with each channel, and a channel priority indicator that includes a static ranking of each of the plurality of channels. 
     In another embodiment of the method, the one or more preference indicators includes a channel priority indicator that includes a static ranking of each of the plurality of channels. 
     In yet another embodiment, the one or more preference indicators includes a radio frequency interference indicator that corresponds to radio frequency interference levels for each of the plurality of channels. 
     In one embodiment of the method, the one or more preference indicators includes a high reflected power indicator that corresponds to reflected power levels related to each of the plurality of channels. 
     In still another embodiment of the method, the one or more preference indicators includes at least one from the group that includes a channel failure indicator, a channel priority indicator, a radio frequency interference indicator, a high reflected power indicator, an excessive current drain indicator, a loss of backbone communications indicator, and a channel usage indicator. 
     In yet another embodiment of the method, the land mobile radio communications system is a simulcast land mobile radio communications system. 
     In yet still another embodiment, the land mobile radio communications system is a P25 trunking system. 
     In one embodiment of the method, the land mobile radio communications system includes a plurality of sites positioned at separate locations and in data communication with one another using a data communications network. And in another embodiment of the method, the data communications network is a backbone data communications network. 
     In another embodiment of the method, determining the priority ranking for use in allocating each of the plurality of channels is based on a weighted average of at least a first preference indicator and a second preference indicator of the one or more preference indicators. 
     In still another embodiment of the method, determining the priority ranking for use in allocating each of the plurality of channels is based on a weighted average of at least a first preference indicator and two or more of the indicators from the group including or consisting of a channel priority indicator, a radio frequency interference indicator, a high reflected power indicator, an excessive current drain indicator, a loss of backbone communications indicator, and a channel usage indicator. 
     In a second aspect, there is provided a method for dynamic channel allocation in a land mobile radio communications system that includes determining a first and second preference indicator and allocating a first channel and a second channel based upon at least the first preference indicator. The method may include determining the first preference indicator and the second preference indicator for each of a plurality of channels for use in allocating the plurality of channels associated with one or more repeaters located at a plurality of sites. The first preference indicator includes a channel failure indicator for each of the plurality of channels that corresponds to the current operational state of the plurality of repeaters associated with each such channel, and the second preference indicator is one or more from the group including or consisting of a channel priority indicator, a radio frequency interference indicator, and a high reflected power indicator. The method may further include determining a priority ranking for use in allocating each of the plurality of channels based at least in part on the first preference indicator that includes the channel failure indicator for each of the plurality of channels, receiving a channel allocation request, and allocating a channel in response to the channel allocation request by selecting an available channel based on the priority ranking for allocating each of the plurality of channels. 
     In one embodiment of the method, determining the priority ranking for use in allocating each of the plurality of channels is based at least in part on both the first preference indicator and the second preference indicator. In another embodiment of the method, the second preference indicator for use in allocating the plurality of channels is the channel priority indicator that includes a static ranking of each of the plurality of channels. 
     In yet another embodiment of the method, the second preference indicator for use in allocating the plurality of channels is the radio frequency interference indicator that corresponds to radio frequency interference levels for each of the plurality of channels. 
     In still yet another embodiment of the method, the second preference indicator for use in allocating the plurality of channels is the high reflected power indicator that corresponds to reflected power levels related to each of the plurality of channels. 
     In one embodiment of the method, the second preference indicator for use in allocating the plurality of channels is one from the group including or consisting of the channel priority indicator, the radio frequency interference indicator, a high reflected power indicator, an excessive current drain indicator, a loss of backbone communications indicator, and a channel usage indicator. 
     In another embodiment of the method, the land mobile radio communications system is a simulcast land mobile radio communications system. 
     In yet another embodiment of this method, the method further includes periodically determining the priority ranking for use in allocating each of the plurality of channels based at least in part on the first preference indicator that includes the channel failure indicator for each of the plurality of channels. 
     In still another embodiment of the method, the method further includes updating the priority ranking for use in allocating each of the plurality of channels based at least in part on changes in the first preference indicator. 
     In yet another embodiment of the method, the method further includes updating the priority ranking for use in allocating each of the plurality of channels based at least in part on changes in the first preference indicator or the second preference indicator. 
     In one embodiment of the method, the allocated channel is a traffic channel configured to exchange voice communications. 
     In another embodiment of the method, the allocated channel is a control channel. 
     In still another embodiment of the method, the channel failure indicator is determined for each of the plurality of channels and is based on the percentage of operational repeaters associated with a particular channel as compared to the total number of repeaters associated with that particular channel. 
     In yet another embodiment of the method, each of the plurality of channels includes one or more repeaters located at a plurality of land mobile radio sites. 
     In one embodiment of the method, the priority ranking for use in allocating each of the plurality of channels is based on a weighted average that includes at least the first preference indicator and the second preference indicator. 
     In another embodiment of the method, determining the priority ranking for use in allocating each of the plurality of channels is based on a weighted average of the first preference indicator and two or more of the indicators from the second preference indicator from the group including or consisting of the channel priority indicator, the radio frequency interference indicator, a high reflected power indicator, an excessive current drain indicator, a loss of backbone communications indicator, and a channel usage indicator. 
     In a third aspect, there is provided a land mobile radio communications system with dynamic channel allocation to provide mobile communications between at least two of a plurality of radio subscriber units. The land mobile radio communications system includes a plurality of sites positioned at separate locations in data communication with one another using a data network, and wherein each of the plurality of sites includes a plurality of repeaters configured to provide a plurality of channels for communications between at least two of the plurality of radio subscriber units, and one or more processors configured to provide dynamic channel allocation. The one or more processors may be configured to provide dynamic channel allocation that includes the capability to determine one or more preference indicators for each of the plurality of channels for use in allocating the plurality of channels, wherein each of the plurality of channels is associated with one or more repeaters of the plurality of repeaters located at the plurality of sites of the land mobile radio communications system, and to determine a priority ranking for use in allocating each of the plurality of channels based at least in part on the one or more preference indicators. The one or more processors may be further configured to provide the capability to receive a first channel allocation request to allocate one of the plurality of channels as a control channel, to allocate a first one of the plurality of channels as the control channel in response to the first channel allocation request by selecting the first one of the plurality of channels based on the highest ranked channel of the priority ranking for use in allocating each of the plurality of channels, to receive a second channel allocation request to allocate one of the plurality of channels as a traffic channel while the first one of the plurality of channels is allocated as the control channel, and to allocate a second one of the plurality of channels as the traffic channel in response to the second channel allocation request by selecting the second one of the plurality of channels based on the then highest ranked channel of the priority ranking for use in allocating each of the plurality of channels. 
     In one embodiment of the LMR system, the one or more processors are further configured to update the priority ranking for use in allocating each of the plurality of channels based at least in part on changes to the one or more preference indicators. 
     In another embodiment of the LMR system, the one or more processors are further configured to periodically update the priority ranking for use in allocating each of the plurality of channels. 
     In yet another embodiment of the LMR system, the one or more processors are further configured to update the priority ranking for use in allocating each of the plurality of channels based at least in part on changes in at least two or more of the one or more preference indicators. 
     In still another embodiment of the LMR system, the at least one of the one or more preference indicators includes a channel failure indicator for each of the plurality of channels that corresponds to the current operational state of the plurality of repeaters associated with each channel. 
     In another embodiment of the LMR system, the channel failure indicator is determined for each of the plurality of channels and is based on the percentage of operational repeaters associated with a particular channel as compared to the total number of repeaters associated with that particular channel. 
     In one embodiment of the LMR system, the one or more preference indicators includes at least one from the group that includes a channel failure indicator, a channel priority indicator, a radio frequency interference indicator, and a high reflected power indicator. 
     In yet another embodiment of the LMR system, the one or more preference indicators includes a channel failure indicator for each of the plurality of channels that corresponds to the current operational state of the plurality of repeaters associated with each channel, and a channel priority indicator that includes a static ranking of each of the plurality of channels. 
     In still another embodiment of the LMR system, the one or more preference indicators includes a channel priority indicator that includes a static ranking of each of the plurality of channels. 
     In another embodiment of the LMR system, the one or more preference indicators includes at least one from the group that includes a channel failure indicator, a channel priority indicator, a radio frequency interference indicator, a high reflected power indicator, an excessive current drain indicator, a loss of backbone communications indicator, and a channel usage indicator. 
     In yet another embodiment of the LMR system, the land mobile radio communications system is a simulcast land mobile radio communications system. 
     In still another embodiment of the LMR system, the is a conventional system. 
     In one embodiment of the LMR system, the determination of the priority ranking for use in allocating each of the plurality of channels is based on a weighted average of at least a first preference indicator and a second preference indicator of the one or more preference indicators. 
     In a fourth aspect, there is provided a dynamic channel allocation system configured for use in a land mobile radio communications system that provides mobile communications between at least two of a plurality of radio subscriber units is provided. The land mobile radio communications system includes a plurality of sites in communication with one another and positioned at separate locations, and wherein each of the plurality of sites includes a plurality of repeaters configured to provide a plurality of channels for communication between the at least two of the plurality of radio subscriber units. The dynamic channel allocation system may include one or more processors configured to determine one or more preference indicators for each of the plurality of channels for use in allocating the plurality of channels, wherein each of the plurality of channels is associated with one or more repeaters of the plurality of repeaters located at a plurality of sites of the land mobile radio communications system, and to determine a priority ranking for use in allocating each of the plurality of channels based at least in part on the one or more preference indicators. The one or more processors may be further configured to receive a first channel allocation request to allocate one of the plurality of channels as a control channel, to allocate a first one of the plurality of channels as the control channel in response to the first channel allocation request by selecting the first one of the plurality of channels based on the highest ranked channel of the priority ranking for use in allocating each of the plurality of channels, to receive a second channel allocation request to allocate one of the plurality of channels as a traffic channel while the first one of the plurality of channels is allocated as the control channel, and to allocate a second one of the plurality of channels as the traffic channel in response to the second channel allocation request by selecting the second one of the plurality of channels based on the then highest ranked channel of the priority ranking for use in allocating each of the plurality of channels. 
     In one embodiment of the dynamic channel allocation system, the land mobile radio communications system is a P25 trunking system. 
     In another embodiment of the dynamic channel allocation system, the one or more processors are further configured to update the priority ranking for use in allocating each of the plurality of channels based at least in part on changes in at least two or more of the one or more preference indicators. 
     In yet another embodiment of the dynamic channel allocation system, the at least one of the one or more preference indicators includes a channel failure indicator for each of the plurality of channels that corresponds to the current operational state of the plurality of repeaters associated with each channel. 
     In still another embodiment of the dynamic channel allocation system, the one or more preference indicators includes at least one from the group that includes a channel failure indicator, a channel priority indicator, a radio frequency interference indicator, and a high reflected power indicator. 
     In one embodiment of the dynamic channel allocation system, the one or more preference indicators includes at least one from the group that includes a channel failure indicator, a channel priority indicator, a radio frequency interference indicator, a high reflected power indicator, an excessive current drain indicator, a loss of backbone communications indicator, and a channel usage indicator. 
     In still another embodiment of the dynamic channel allocation system, the determination of the priority ranking for use in allocating each of the plurality of channels is based on a weighted average of at least a first preference indicator and a second preference indicator of the one or more preference indicators. 
     Other aspects, features, and advantages will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, principles of the inventions disclosed. 
    
    
     
       DESCRIPTION OF THE FIGURES 
       The accompanying drawings facilitate an understanding of the various embodiments, and are not necessarily drawn to scale. 
         FIG. 1  is an overview diagram that illustrates an exemplary LMR system with dynamic channel allocation that includes three sites that each include nine repeaters and that each have a designated geographic coverage area, according to an embodiment; 
         FIG. 2  is an overview diagram that illustrates an exemplary site of an LMR system in communication with a mobile radio unit, and including an antenna, a plurality of repeaters, and a site controller with one or more processors, a memory or storage device, and a dynamic channel allocation system, according to one embodiment; 
         FIG. 3  is a flowchart that illustrates an exemplary method for dynamic channel allocation in a land mobile radio communications system that involves using at least one preference indicator, such as a channel failure indicator, to allocate a control channel and a traffic channel, according to an exemplary embodiment; and 
         FIG. 4  is a flowchart that illustrates another exemplary method for dynamic channel allocation in a land mobile radio communications system that includes at least a first preference indicator and a second preference indicator, according to another exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is an overview diagram of an exemplary land mobile radio (LMR) system  100  with dynamic channel allocation. The LMR system  100  includes a first site  102 , a second site  104 , and a third site  106 . The circles around each of the sites indicate an approximate geographic coverage area for such sites of the LMR system  100 . Each of the three exemplary sites of  FIG. 1  include nine repeaters. For example, the first site  102  includes a plurality of repeaters  110 , as illustrated, having nine repeaters. Each such repeater of the plurality of repeaters  110  includes the capability to transmit and receive. Similarly, the second site  104  includes a plurality of repeaters  120 , which also includes nine repeaters similar to the plurality of repeaters  110  of the first site  102 . The third site  106  also includes a plurality of repeaters  130  that includes nine repeaters. 
     Not shown in  FIG. 1  is a data network, such as a backbone network, which may be implemented as an IP network, that is used to provide data communication between and among the sites of the LMR system  100 . Further, various processors, servers, and supporting hardware may be provided at one or more of the sites, and these are not expressly shown in  FIG. 1 . This may include, depending on the implementation of the LMR system  100 , site controllers provided at each site, or at designated sites. It should be understood that the LMR system  100  may be provided as a P25 system, a trunk system, a conventional system, a simulcast system, a non-simulcast system, or virtually any other implementation of an LMR system. 
     In operation, a radio subscriber unit, which may be a portable or mobile radio and/or a stationary radio unit, is in communication with one or more of the sites of the LMR system  100 , and a request is made to set up a channel for communication with one or more other radio units. In such a case, a dynamic channel allocation system includes one or more preference indicators that may be used to prioritize the available channels so that the appropriate or desired traffic channel is selected when the traffic channel request is received. A control channel may be allocated using the same or similar dynamic channel allocation system and the one or more preference indicators so that an appropriate or desired control channel is set up at startup and at other designated times when a control channel is needed. 
     In a simulcast system, a channel, such as a control channel or a traffic channel, may include a repeater at each of the three sites  102 ,  104 , and  106  that transmits and receives on the same frequency. For example, a channel request to set up a control channel may result in a dynamic channel allocation of a channel that is defined as including a repeater “1” from the plurality of repeaters  110 ,  120 , and  130 , from the various sites of the LMR system  100 . One or more preference indicators may be used to rank the nine channels of the LMR system  100 . In one implementation, a health indicator, which also may be referred to as a channel failure indicator, may be used as the first and only preference indicator. The channel failure indicator may be calculated in a variety of ways. For example, if one of the three repeaters for channel one is not available, a simple percentage of 67% may represent the channel failure indicator of channel one. If all three repeaters of channel one are available, then the health or channel failure indicator may be represented as 100% or as a “1.” As such, the various nine channels of the simulcast LMR system  100  may be ranked so that whenever a channel request is made to use such a channel, the channels may be dynamically allocated according to the ranked priority as provided by the preference indicator, which is illustrated to be a channel failure indicator. 
     In other embodiments, two or more preference indicators may be used to determine how such channels are dynamically allocated. For example, a channel priority indicator may be provided to rank each such channel that is simply a static ranking of the various channels. A radio frequency interference indicator may be used to rank such channels, and such indicator may be from a periodic measurement of RF interference on the various channels so that the ranking may be adjusted to allow for the channel with the least amount of radio interference to be allocated when requested by user. This may significantly improve overall call quality and performance of the LMR system  100 . Of course, this indicator may be weighted as desired and included as part of two or more preference indicators for use in compiling the channel allocation priority. 
     Other preference indicators may include a high reflected power indicator, an excessive current drain indicator, a loss of backbone communications indicator, and a channel usage indicator. For example, a high reflected power indicator, similar to the radio frequency interference indicator, may be implemented using periodic calculations of power being reflected on each such channel. Those channels with more reflected power are considered less desirable and thus would be ranked in a lower priority than those with less reflected power. Similarly, an excessive current drain indicator, such as the current drain provided at a final amplifier or other amplifier of a repeater, may be measured continuously or periodically, and the various repeaters and corresponding channels may then be ranked accordingly. A channel usage indicator may include a ranking of the channels based upon the usage of such channels. As such, in one embodiment, the channels that are less frequently used may be ranked higher to be allocated more frequently in order to even out overall usage of the various repeaters and channels of the LMR system  100 . Finally, and as mentioned previously, a data network, not shown in  FIG. 1 , is provided to allow the various sites, including the first site  102 , the second site  104 , and the third site  106  to communicate with each other. If this data network connection is lost to one or more of the sites, then the loss of backbone communications indicator may be used to provide a dynamic channel allocation or influence the overall channel allocation priority list. 
     Two or more of the various preference indicators may be used to dynamically allocate a channel. For example, a first preference indicator may include the channel failure indicator and this may be provided a certain “weighting” in determining how the various channels and underlining repeaters are dynamically ranked for allocation. A second preference indicator, such as a radio frequency interference indicator, may provide another “weighting” in determining how to allocate the various channels. This weighting may be provided in any of a variety of ways, including equal weighting, unequal weighting, and secondary weighting in the event that the first or prior preference indicator does not distinguish one channel from another. For example, if the channel failure indicator is the first preference indicator, and the repeaters for two particular channels are in service and operational, then no distinction can be made between the two channels based on the channel failure indicator. The secondary preference indicator may include a radio frequency interference indicator that indicates that one channel is preferable or has less RF interference than the second channel. As such, the preferred channel may be ranked and dynamically allocated prior to the other, less desirable, channel. 
     In a preferred embodiment, a channel failure indicator (aka a channel health indicator) is used as a first preference indicator and it is maintained or determined for each channel in a system. This numerical representation provides a relative channel preference among the various channels and takes into account repeater failure status for each such channel. In another implementation, the radio frequency or RF interference indicator is determined or detected by comparing a duration of consecutive RSSI samples of unassigned channels over a threshold level against a configured duration (assigning the minimum value to the RFII factor). In such a case, an RF interference detection is cleared when the detection mechanism fails to detect for a configured duration of time. In another implementation of the radio frequency interference indicator, RF interference is detected or measured using a moving average of RF level on each channel at a time when a channel is unassigned or unallocated. In other embodiments, the channel priority indicator is simply a static list of rankings of the various channels of the LMR system  100 . 
     Although not specifically shown in  FIG. 1 , the dynamic channel allocation may be performed by a site controller, or other server or processor(s) that may be implemented at one or more of the various sites of the LMR system  100 . In a simulcast embodiment, the site controller may be implemented at each of the three sites of the LMR system  100 , with one of the site controllers designated as the active site controller to perform the dynamic channel allocation as provided and described herein. The remaining site controllers are provided as hot standby or available in the event the primary or active site controller fails. In other implementation of the LMR system  100 , such as in a non-simulcast LMR system, each of the sites may include a site controller or one or more processors to provide the dynamic channel allocation for each such site. In such a case, a control channel is designated at each location, and such control channel is used as various traffic channels are allocated during the operation of the LMR system  100 . The allocation of various channels may use the dynamic channel allocation methods and processes described and provided herein. As previously mentioned, the various preference indicators and rankings may be performed periodically or may be adjusted upon a change in one or more of the preference indicators. 
       FIG. 2  is an overview diagram that illustrates an exemplary site  102 , such as site  102  of  FIG. 1 , of an LMR system that is in communication with a mobile radio unit  170 . The site  102  includes an antenna  150 , shown communicating with the mobile radio unit  170 , as well as the plurality of repeaters  110 , which, as in  FIG. 1 , includes nine repeaters, in this particular embodiment. The site  102  also includes a site controller  160 , which may be implemented as one or more servers or computers and will include one or more processors  162 , memory and/or storage  164 , and a dynamic channel allocation system  166 , which is shown in  FIG. 2  at the dashed box. The dynamic channel allocation system  166  may be implemented in software or code using a site controller  160  or using an external system dedicated for such application, or using a distributed processing system at different locations. In one implementation, the dynamic channel allocation system  166  is implemented using instructions carried out by the one or more processors  162  of the site controller  160 . 
     Just as in  FIG. 1 , the backbone data network connecting the site  102  to other sites of an LMR system is not specifically shown. In a simulcast LMR system, an active site controller  160  may be provided at one or more of the sites of the LMR system, or at a separate location that is in communication with the one or more sites of the LMR system. In a non-simulcast system, each site of the LMR system will generally have its own site controller, and such site controller may be configured or implemented to carry out the dynamic channel allocation as described herein. In other embodiments, a dedicated computer or system is provided to provide such dynamic channel allocation functionality. 
       FIG. 3  is a flow chart that illustrates an exemplary method  300  for dynamic channel allocation in an LMR system. The method  300  includes using at least one preference indicator, such as the channel failure indicator (which also may be referred to as a health preference indicator) to allocate a control channel and/or one or more traffic channels in an LMR system. 
     The method  300  for dynamic channel allocation begins at  302  where one or more preference indicators for a plurality of channels are determined. For example, in a simulcast system where each of the various channels are made up of repeaters located at each of the plurality of sites of the LMR system, various preference indicators may be determined or measured to assist with determining how to dynamically allocate such channels when a request is made to allocate either a control channel or a traffic channel. Of course, a control channel is generally initially allocated at startup and is used to assist with allocating traffic channels thereafter. It should be understood, that the allocation of both the control channel and the various traffic channels may be allocated using the dynamic channel allocation as provided and described herein. In other implementations, either the control channel is allocated using dynamic channel allocation or the traffic channels are allocated using the dynamic channel allocation, as may be provided in a particular implementation or embodiment. 
     Proceeding next to step  304 , a priority ranking is determined based on a one or more preference indicators. In the case of only one preference indicator being used, and in a preferred embodiment, a channel failure indicator is used to rank the various channels. This helps ensure that fully functioning channels that include all or most repeaters are allocated first. This provides better overall performance to users of such an LMR system. Depending on a particular embodiment, the priority ranking of the method  300  as provided in  304  may be implemented using a weighted average of two or more preference indicators, as previously discussed, or may use succeeding preference indicators until a preferred channel is identified. 
     Proceeding next to  306 , a first channel allocation request is received, such as when the LMR system is first operational or at a later time, and a control channel is allocated at  308  as indicated in the method  300 . The allocation of the control channel is provided using the dynamic channel allocation based on the one or more preference indicators previously described. Once the control channel is allocated, the method  300  proceeds next to step  310 . At  310 , a second channel allocation request is received, and the current priority ranking for the various channels is accessed at step  312 , where the highest priority ranked channel is then allocated as a traffic channel. Successive traffic channel allocations may then be allocated by proceeding back to step  310  where a third channel allocation request may be received and the next priority ranking is used to allocate such a request. Of course, the priority ranking in the various one or more preference indicators may be periodically updated, continuously updated, and/or updated as conditions and/or characteristics of the LMR system change. For example, a radio interference indicator, a high reflected power indicator, or an excessive current drain indicator may all vary over time depending on the operational characteristics and conditions of the various sites, repeaters and channels of the LMR system. 
     The channel failure indicator corresponds to the current operational state of the plurality of repeaters associated with a channel in a simulcast LMR system, and it may be calculated based upon a percentage or value equal to or less than one. In one implementation, this may be used as the initial determination for ranking and allocating the various channels, while a channel priority indicator, which is simply a static ranking of each of the plurality of channels, may be used as a second or third preference indicator. Of course, a variety of other preference indicators may be used such as a radio frequency interference indicator, a high reflected power indicator, an excessive current drain indicator, which measures the current drain and an amplifier of a repeater, a loss of backbone communications indicator, and a channel usage indicator. Any of a number of these indicators may be used so that a dynamic channel allocation may be provided. Ultimately, a priority ranking is provided so that when a channel request is received by the LMR system, a preferred or desired channel may be expeditiously allocated. 
       FIG. 4  is a flowchart that illustrates another exemplary method  400  for dynamic channel allocation in an LMR system. The method  400  begins at block  402  where a first preference indicator is determined for each of the plurality of channels. In this embodiment, the first preference indicator includes a channel failure indicator, which may be thought of as a health indicator of the various channels. As previously discussed, the channel failure indicator is based upon the operational status of the one or more repeaters that make up each of the plurality of channels. Proceeding next to  404 , a second preference indicator is determined for each of the plurality of channels. The second preference indicator may include one or more of the preference indicators and include a channel priority indicator, a radio frequency interference indicator, and a high reflected power indicator, which may be implemented using testing or measurement equipment to periodically or continuously measure the reflected power of the various channels. 
     The method  400  proceeds next to  406  where a priority ranking is determined for use in dynamically allocating each of the plurality of channels. This priority ranking is determined based at least in part on the first preference indicator, which includes the channel failure indicator. It may also be partially based on the second preference indicator as well. 
     Proceeding next to  408 , in operation, an LMR system may periodically receive channel allocation requests. In such a case, the method  400  proceeds to  410  where a channel is dynamically allocated based upon the current priority ranking of the various available channels. As previously discussed and as provided above in  FIG. 4 , the priority ranking may be determined based on a channel failure indicator and various one or more secondary preference indicators. 
     An overview of certain implementations, examples, and embodiments of a system and method dynamic channel priority is provided below. When channel requests are made by a subscriber radio on a P25 control channel, a channel is selected from the pool of available traffic channels. When the pool of available traffic channels contains channels with different priorities, the traffic channel with the highest priority is chosen. When there is more than one channel with the same highest priority, the one that was least recently used is chosen, in order to distribute the allocation of channels with common priority. 
     In a preferred embodiment, the channel allocation priority is dynamically determined using a weighting of channel health and a configured static channel priority, as previously discussed in connection with the channel failure indictor and the channel priority indicator. A user configurable static channel priority exists for each channel in the system. This may range from 1-28, in one embodiment, with 1 being the highest static priority. Channel health, or the channel failure indicator, may be expressed as a percentage of the number of sites having fully operational repeaters for that channel, rounded to the nearest percent. (0-100). 
     In one example, the dynamic channel allocation priority may be determined as provided by the following weighting: Total Dynamic Channel Allocation Priority=(29−StaticPriority)+(100*ChannelHealth). The constants 29, and 100, are chosen such that the overall Dynamic Channel Allocation Priority may include of a 5 digit number, in this embodiment, represented as HHHSS, where HHH is Channel Health (000-100), and SS is Static Priority (01-28). In this particular embodiment, this places more significance on the channel health than its static priority, even when there is only a single working repeater out of a potential of over 300 sites. 
     Various failure scenarios may include the following: 
     Failure Scenario 1: consider the failure scenario of a nine channel, three site system, with one repeater failure, and some or all channels with a static channel priority of 15. The eight fully operational channels have a Dynamic Priority of Channel Health=3/3*100=100, and an overall weighted Total Dynamic Channel Allocation Priority=(29−15)+(100*100)=10014, while the one channel with the failed repeater has a weighted Total Dynamic Channel Allocation Priority=(29−15)+(100*67)=6714. In this case, the eight fully operational channels would be assigned before considering the use of the channel with one non-operational repeater. This results in full RF coverage except when the system reaches maximum capacity. 
     Failure Scenario 2: consider the failure scenario of a nine channel, three site system, with nine repeater failures at one site, and some or all channels with a static channel priority of 15. In such a situation, the channels have a weighted Total Dynamic Channel Allocation Priority=(29−15)+(100*67)=6714. In this case, the channels may have equal priority, resulting in full capacity, but with reduced RF coverage. The same method can be applied to selecting a preferred control channel. 
     In an alternative embodiment, the channel allocation priority may be dynamically determined using a combination of channel health, the absence of RF interference, and a configured static channel priority. As in the preferred embodiment, a user configurable static channel priority is provided for each channel in the system. This ranges from 1-28, in this embodiment, with 1 being the highest static priority. As in the preferred embodiment, the Channel health, or the channel failure indicator, may be expressed as the percentage of the number of sites having fully operational repeaters for that channel, rounded to the nearest percent. (0-100). The RF Interference (RFI) Indicator (RFII) is an assessment of the quality of the channel in consideration of detected RF interference, ranging from 0-100, where 100 indicates no RFI detected, and 0 indicates the worst level of RFI detected. This may be referred to as the RF interference indicator. In this embodiment, there are only two levels of RFI, 0 and 100. RFII is initially assumed to be at 100, i.e., no interference. The receive signal strength is sampled once per second, in this example. While a channel is not assigned for traffic, the number of consecutive samples at or above a configured threshold is used to indicate the presence of RF interference on the channel. After reaching this threshold, the RFII is set to 0 and stays at 0 until the detection of RFI, using this method, results in no RFI detected for a configured duration of time, at which time the RFII is set to 100. 
     In this alternative embodiment, the weighted Total Dynamic Channel Allocation Priority=(29−StaticPriority)+(100*RFII)+(100000*ChannelHealth). The constants 29, 100, and 100000, are chosen such that the overall Total Dynamic Channel Allocation Priority will be an eight digit number in this embodiment, represented as HHHIIISS, where where HHH is Channel Health (000-100), III is Interference Indicator (000-100), and SS is Static Priority (01-28). In this alternative embodiment, this places most significance on the channel health, followed by RF Interference, and finally static priority. 
     In the foregoing description of certain embodiments, specific terminology has been resorted to for the sake of clarity. The disclosure, however, is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes other technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as “left” and right”, “front” and “rear”, “above” and “below”, “first” and “second”, and the like are used as words of convenience to provide reference points or distinction points and are not to be construed as limiting terms or as time dependent terms. 
     In this specification, the word “comprising” is to be understood in its “open” sense, that is, in the sense of “including”, and thus not limited to its “closed” sense, that is the sense of “consisting only of”. A corresponding meaning is to be attributed to the corresponding words “comprise”, “comprised” and “comprises” where they appear. 
     In addition, the foregoing describes only some embodiments of the invention(s), and alterations, modifications, additions and/or changes can be made thereto without departing from the scope and spirit of the disclosed embodiments, the embodiments being illustrative and not restrictive. 
     Furthermore, invention(s) have described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention(s). Also, the various embodiments described above may be implemented in conjunction with other embodiments, e.g., aspects of one embodiment may be combined with aspects of another embodiment to realize yet other embodiments. Further, each independent feature or component of any given assembly may constitute an additional embodiment.