It is designed with full consideration of PAMR features and various demands of commercial mobile users, and is capable of providing a variety of services to users such as radio dispatch, basic call, packet data services, as well as multiple value-added services like SMS and LBS. It has the following advantages;. Radio dispatch services The GoTa system has all radio dispatch functions of a professional analogue trunking radio system, capable of replacing the existing analogue systems.
These functions include;. Data services The GoTa system supports Location services With a perfect combination of CDMA-based positioning technologies and trunking services, the GoTa system can offer featured and differentiated location service solutions, which can be widely used by industrial users and civil departments in areas of ship navigation, emergency assistance, vehicle management, goods tracking, logistics management, location-based charged service, and etc.
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Green Efforts. The way receiver sensitivity is specified in analog differs from how it is specified in digital. The RF signal level required to create a 20dB signal-to-noise ratio is the acknowledged method of specifying analog receiver sensitivity, whereas the RF signal level at which a specified Bit Error Rate BER is displayed is the acceptable method of specifying digital receiver sensitivity.
Market Restraining Factors: The increased cost of the service Due to the fact that TETRA was developed in order to address the PAMR market with every possible function, complexity and development costs appeared as the most significant contributions to the higher cost of the final product. Multiple user interactions in a TETRA infrastructure necessitate fast and specialized switch nodes which are costly. The number of sites necessary to cover the same area as an existing analog system could be two or more times than that.
With a set cost of site rent, maintenance, frequency license, and backbone links, more sites necessitate a larger initial investment. Liner modulation necessitates the use of expensive technology. In , the software segment acquired a significant revenue share of the terrestrial trunked radio market.
There is a rising demand for software components due to the development of software applications that are majorly facilitating various features such as automatic location messages, remoting radio monitors, accessing voice, and data information. In , the portable segment garnered the maximum revenue share of the terrestrial trunked radio systems market. As the portable devices are compact and handy, they are more convenient to use.
This feature is also called walkie-talkie mode. The direct mode operation accounted for the second-largest revenue share of the terrestrial trunked radio systems in Direct Mode Operation refers to the capability of TETRA radio terminals to connect with one another while operating independently of the network, much like walkie-talkies. In addition, it can also be employed in specific professional settings, such as accidents or unusual conditions. During a chase, for example, two patrol cars may exit the coverage area, but two police units must still communicate.
Both units will be able to continue the interaction and exchange of information in direct mode. In , the military and defense segment garnered the highest revenue share in the terrestrial trunked radio systems market. The increased growth of this segment is attributed to the rising adoption of terrestrial trunked radio systems across the defense sector.
TETRA services are widely being employed in this sector for multiple purposes such as, to communicate with other security authorities and command and control of military police activities, security of crucial objects, and defense material deployment. In , North America procured a significant revenue share of the terrestrial trunked radio systems market. The rising utilization of TETRA technology across the region is due to the rising investment by the government of the US in order to strengthen the defense infrastructure of the nation.
The increased penetration of the technologies and advancements across the defense sector of the US is driving the growth of the market across North America. The market research report covers the analysis of key stake holders of the market. In addition, it would reinforce the daily operations of public safety agencies and first responders with increased coverage of the nationwide TETRA network while assisting emergency services of Romania with improved security and flexibility.
Sep Hytera came into an agreement with Shenzhen Metro Line 12, the rapid transit system for Shenzhen city. Hyteria would supply inclusive integrated communication solutions to the entity. Further, these solutions would establish efficient communication across train drivers, station operation staff, and the control center. In addition, the new product operates by enabling TETRA radio automation through situational triggers and geofencing.
On the repeater receive or talk-in side, we normally feed all the receivers normally one at each transmitter site and sometimes additional receivers at non-transmitter sites into a device called a voter or comparator. This unit electronically checks or compares each receiver signal for its signal to noise ratio and then selects or votes the best signal to be sent to the dispatcher and to be re-broadcast.
The location of the simulcast controller computer and other equipment including the voters that makes simulcast possible is called the prime site and may, or may not, be located at one of the remote site locations. Simulcast can be either single frequency or trunked see next section. Scanning Issues: Same as for duplex operation. Since coverage area is normally larger than for a single repeater, scanners will also be able to monitor over a larger area.
If one of the simulcast transmitters goes out of service, coverage for its area will be reduced. If you are in that area, you may notice a weaker signal or you may stop receiving that system all together. Since the FCC allows only six sites on a license, you may find multiple licenses covering the simulcast system.
Note that it is not possible except under some very special circumstances for a receiver user to tell which simulcast transmitter site or combination of sites is providing the signal being received. Sometimes this may be the farthest site, sometimes the closest, but many times will be a combination of two or more of the remote sites. Thus it is inaccurate and confusing to refer to a received simulcast signal by one remote site name instead of the name for the simulcast system or subsystem.
In the older radio systems, one or more groups of users were assigned to a particular pair of frequencies. If no one in any of those groups were talking, the frequency or frequency pair stood idle. At the same time, the groups of users on a different assigned frequency pair may be so busy that each of the groups is constantly waiting for someone to get through talking so they can get a message through.
Thus there was a lot of available airtime wasted. As the number of user groups increased in large metropolitan areas, all available frequencies were assigned to existing user groups King County being a prime example. As new groups such as new police departments or additional precincts in an existing police department were created, no frequencies were available without sharing with an existing user.
A solution, known as trunking was borrowed from the telephone industry. With this technology, several frequency pairs are grouped together and put under the control of a computer called a Trunking Controller. This computer then accepts each request to talk, assigns the next available frequency pair , directs all the radios in the talk group to switch to the assigned frequency pair, and sends a permit to talk tone to the requesting party.
The whole process takes less than half a second. The computer also monitors the activity not the conversation, but the fact the frequency pair is in use. When the frequency pair becomes idle, it is returned to the pool and is available for re-assignment to another user group. By pooling several frequencies, we also pool the unused airtime thus allowing more user-groups to work independently. In this manner we can get 3 to 10 times more use from a given set of frequencies than the old non-trunking method of assigning frequencies to users.
A trunked repeater system can be either single site or simulcast. A simple analogy to trunking is the system used to serve in-person customers at a bank. Formerly, customers got in line at individual teller windows to wait for the teller at that window to assist them. All of us have experienced getting in what appears to be the shortest line, when in fact, the transactions in front of us end up taking longer than anticipated, resulting in a longer wait for service than other lines might have offered.
Also, you may have experience waiting in an assigned line for your type of transaction, even if another window has no waiting customers. Now, many banks have customers form a single queue, and the next available teller waits on the customer at the front of the line. Rather than being stuck with a specific teller line frequency , the trunking system will accept a request to talk and assign whatever frequency is available to the next request in line. When all frequencies are assigned, the system will put all requests in a waiting queue, and is able to prioritize customers in the line.
The next available channel will be assigned to requests with the highest priority. Requests with equal priority will be served on a first-come, first-served basis. Typically, no users should experience any wait except in the event of a major disaster when radio traffic would be unusually high. Scanning Issues: The range that a scanner will work is influenced by the same factors as repeater and simulcast operation, depending on configuration.
Frequency, however, is a very different issue. Since a computer is used to assign the next frequency, sometimes as often as every time a field unit keys up, the scanner needs to be able to follow these assignments just as the field units or it will not follow the conversation. To do this, a special scanner that can either be controlled by an external computer or has the internal circuitry to follow the frequency assignments is required.
Most of the older trunking scanners also need to know all the frequencies in use by the trunking system. Thus, to properly scan, all frequencies used in a trunked system must be programmed into this type of scanner. If you are using one of the computer software products such as Trunker or one of the newest trunking scanners, this is not a requirement, but you must still program the control channel for the system you wish to scan.
Since the FCC allows only six sites on a license and the system may use frequencies from more than one band, you may find multiple licenses covering the trunked or trunked simulcast system. You will need to determine which frequencies on these multiple licenses probably all the frequencies on all the licenses are in use for the trunked system you wish to monitor. When the King County system was first installed Seattle was the first to implement , Seattle recognized this as an issue and made arrangements with the vendor to sell radios to those wishing to scan at the discounted price Seattle paid.
This was an expensive way to scan, but there were no alternatives on the market. Although this offer is still available, Seattle will not program any requested talkgroup, will only program Seattle talkgroups other sub-regions would program their talkgroups , and the radios are several times more expensive than the trunking scanners now on the market.
In a Smartnet trunked repeater system, generally 5 to 28 frequency pairs are grouped together. One of these frequency pairs is called the control channel and is used to convey information between the field units and the trunking system.
When a mobile or portable unit also called field, or subscriber, unit is not listening to a talkgroup conversation, it is monitoring listening to the control channel. A Smartnet system can be either single site or simulcast. Note, also, that there is no requirement to have the frequencies in any particular order. They can be set up in ascending, descending, or some random sequence and the system will work just as well.
It then follows that the frequency order in the scanner does not have a bearing on the scanner operation. Each subscriber unit is assigned a unique ID number. Each talkgroup is also assigned a unique ID number and turning the channel selector knob now selects a talkgroup ID number instead of a frequency.
The system uses these numbers to track and authorize subscriber use of the system. This tracking starts when the subscriber unit is first turned on and then each time the operator changes the talkgroup. The Smartnet trunked system is controlled by a Trunked System Controller which is located in the case of simulcast at what we call the Prime Site along with any simulcast control equipment. The transmitters are located at what we call Remote Sites if simulcast along with the Remote Site Controller.
Note that a Smartnet system can be one site only not simulcast with everything co-located. With the introduction of Smartnet, Motorola also introduced a failure mode called Failsoft. If the trunking system loses its control channel or has certain other failures, it is no longer able to operate in the trunking mode.
So instead of going into a condition that stops all communication, the system enters Failsoft. In this state all transmitters channels turn on and operate in a conventional repeater mode. The subscriber radios are able to recognize this state and switch to a predetermined frequency one of the trunk system frequencies, but not the control channel frequency depending on their selected talkgroup.
In most systems several talkgroups will share a frequency. Some talkgroups may not be assigned a failsoft frequency and these talkgroups will cease to operate during the failsoft period. If a particular failsoft frequency has also failed, the talkgroups assigned to that frequency will also be off the air during failsoft. Scanning Issues: Same as Trunked Repeater operation for single site or simulcast, depending on configuration. The location of the prime site has no bearing on the operation of the scanner.
During Failsoft, all transmitters turn on, whether or not there is an on-going conversation. This means a scanner will stop on each frequency and stay there until intervention by the scanner operator. As much as trunking solved traffic handling ability and simulcast improved wide-area operation, some limitations prevented this from being the panacea we hoped for. Trunking has a limited number of frequencies it can handle limiting the amount of traffic it can carry.
Simulcast has a limited number of sites it can handle limiting the amount of signal delivered to the coverage area- with larger areas getting less signal for a given number of sites. Simulcast requires a transmitter at every site for each frequency whether or not that site is required for a particular call increases the system cost , and requires exclusive frequency usage in a very large area limiting the ability to reuse frequencies- an FCC issue.
So we once again turned to the computer to solve these problems and increase the geographical coverage. Motorola responded to our needs with a system called SmartZone also a Motorola registered trademark which takes two or more Smartnet trunking systems any combination of simulcast and non-simulcast and ties them together with a master computer called the Zone Controller.
Smart Zone allows us to combine the good points of both single site and simulcast trunking to achieve a better overall system. The job of the Zone Controller is to keep track of every radio in use, what site it is using from the Zone Controller perspective, each entire simulcast sub-system no matter how many remote sites it has is called a site and treated as one site , and what talk group that radio is switched to.
When a radio is turned on it affiliates with the system, reporting its ID, site it is on, and talkgroup selected. When a user keys a radio, or changes the channel selector knob, the radio talks to the site it is affiliated with, which in turn passes the information desire to talk or change of talk group to the Zone Controller.
The system thus knows which sites remember an entire simulcast sub-system is just another site as far as the Zone Controller is concerned require the audio for a particular talkgroup. In the case of PTT Press To Talk or keying the radio activation, the Zone Controller then tells all affected site controllers to make a channel available, and ties the audio of these sites together to complete the call.
The individual site controllers then via the control channel tell all of the subscriber units with the talkgroup selected which frequency to listen to. All this happens in less than half a second. Note that, in most cases, if no radio affiliated to a particular site has the talkgroup being talked on selected, the talkgroup audio will not be sent to that site, and anyone scanning that site will not hear the conversation.
Each SmartZone site whether single site or simulcast sub-system can be programmed for Failsoft operation. Those sites that are programmed for failsoft operation can enter the failsoft mode even while the rest of the SmartZone system is operating normally in the wide-area, trunked, mode.
Conversations on a site in failsoft will not be carried on other SmartZone sites. Scanning Issues: With today s scanners, you can only scan the talkgroups of one SmartZone site at a time. Okay great, we now have our RTL offset configured, we know the networks and we have the control channels. The last thing we need to do is figure out how we are going to cover all of the range of the system, if we look at the PERS system we are targeting we see it has the following channels:.
To cover the various channels they are usually For the system listed above we can see the lowest frequency is We also need to find the correct centre frequency for the device thats not on an audio channel because of something called a DC offset. The centre frequency just means where the device is tuned to and will do half the bandwidth to the lower bound and half to the higher bound.
If we had to calculate it for ours and we could cover all 2. Now we have the target system we are looking at, picked the right SDRs for the job and we have the center frequencies we wish to go for, we can now configure everything for trunk-recorder.. You can view all the talk groups on the radioreference website:. Once you have added it browse to the config screen where you will need to copy the example config, something like:. If you are feeling a little braver, I have included a script to help you automatically upload all the groups.
Then you can run the file to upload all of the groups from your OpenMHz file format and you should see the following. We need to tell trunk recorder what kind of config we are looking at what the frequencies are, what our devices are, all information we have had before , so to do that we need two files, our talk group config in trunk recorder format and a config file. The talk group file we already figured out earlier, just remember to keep the right format, from here on out we are using it in trunk recorder format.
The other file is the config consisting of two main parts, one is the sources, which tell trunk recorder what the SDRs that you have are and how they should be configured, and the other is the systems that we are connecting to. Analog and Digital Recorders — These are the number of recorders you will have for your setup, a recorder determines how many recordings can happen at one time.
So if there are 10 calls at a time you will need 10 recorders, however these do add overhead to your resource usage. Depending on if your system is analog or digital you will have to adjust this. Analog and Digital Levels — This is a level from that you can set for how much amplification the audio will go through, if your audio is too soft, try putting these up. The system also has a ton of options and these will depend largely on what system you are trying to listen to, however a common format will look like this:.
Bandplan is something that is unique to smartnet systems, and you will see the above message listed that tells me I need to use this type, for options for other settings refer to the trunk-recoder documentation near the bottom of this page. But as this is a super common setting I have kept this in.
Note that there are also two extra fields for uploadserver and capturedir which are probably okay left as is. Now all we have left is to install our application and setup the config for it. You have the options of running this natively, within a virtual machine or on docker linux only.
I would recommend a virtual machine if this is your first time setting it up and especially ubuntu desktop since you can see what is going on with gqrx when you want to setup the config file and to check any options. Or you can use docker under linux if you are going to be running this in a permanent setting.
I am, it rules! Create a new virtual machine and install ubuntu Remember to attach your SDR to the virtual machine! In the terminal window you can run the following commands:. The installer will kickoff and before long you should see the message that it has been completed. This will then prepare and build the image for you, and may take some time, but we only need to do it once! This will interactively run the docker container and you should see the same output as the virtual image. Once you are happy with how it runs you may want to run it in detached mode in the background with the following.
It was really awesome to see this working, definitely something to make me think about radio again and I think it has a lot of appeal for us radio noobs. I could definitely see further work being done here to do even more awesome things like speach-to-text to notify if any keywords are heard, trying to track the radios within the talk groups and what times they are used and maybe even some enhancements on the openmhz side!
On the surface, it seems straightforward: A control channel allows users to share a section of bandwidth rather than take up one complete channel, allowing for greater usage of the frequency range. This is a pretty extensive guide. Thank you for putting this together. Have you tried using the software called Unitrunker? I use it to monitor local comms here in Vacaville and even gave a presentation of in at our local ham radio club on Ham Radio TV on youtube.
Thank you for this write-up. I know in years past, it was a requirement to have one SDR listening to the control channel and a second one tuning to the talkgroup conversations. Is this still a requirement or best practice? And what specific SDR models would you recommend?
Thanks for the kind words! With regards to the amount of SDRs it depends on the system, but many of the systems have the control channel very close to the usable channels for the radios and as such a single RTLSDR can cover a large portion of the space. It will look at the entire 2. I ended up posting an issue on github but was able to figure it out before getting a response. I had some issues with the HackRF drifting due to environmental temperature changes, and was planning on buying a GPS clock for reference, but it seemed overly temperamental.
Trunked radio systems centrally manage a pool of channels, and intelligently switch users to whatever channel is open at a given time. For a trunked system, those communication paths, or trunks, are channels. A trunked radio system is a computer-controlled network that. For readers desiring an understanding of the basics of radio trunking, this report features a brief overview of the concepts and basic technology involved.