1. TETRA Terrestrial trunked radio
Joe Nielson

2. outline Radio Terminology/Basics What is “trunked radio” TETRA
Technology
Standards
Features
TETRA today

3. Radio terminology Base Station – Tower site “repeater” radio
Portable Radio – Hand held, lower power, when compared to Mobile
Mobile Radio – High power when compared to portable radio (larger antenna)
PMR – Professional Mobile Radio, radio systems that are used by public safety, and other organizations that use the above equipment.
Base station is used to re-transmit messages across the known radio network to other registered users
Portable radio is the walkie-talkie style used for its small size
Mobile radio is the kind in a squad car or mobile vehicle, higher power and a larger antenna
Professional (Private) Mobile Radio – radio users who need large coverage areas, instant communications

4. radio basics
The PMR market requires constant reliable communication and needs to allow for capacity increases during major incidents
This makes it necessary to have tower sites to increase the range of communication for portable and mobile radios
Along the M5 motorway in England
Cannot have “no service” areas or dropped calls
High Congestion, service almost unusable
Cannot be in control of tower sites

5. Radio basics
A radio channel is a single band of frequency that can successfully deliver radio communications
Either voice or data
The size of the channel, or bandwidth is determined by the channels frequency tolerance and the type of transmission
Cannot have channels interfering with each other
Channel – a defined frequency used for a single line or channel of communication
Bandwidth – the amount of range that the defined frequency is allowed to travel into

6. bandwidth Ex: Center frequency = 150 kHz (f0)
bandwidth allocation = 50 kHz
Then the 150 kHz frequency cannot be modulated above 175 (f2) kHz, or below 125 (f1) kHz

7. Radio basics
The channel is identified by a distinct frequency, and has to be modulated in order to transport a message across the channel
Some types are frequency, amplitude, phase modulation and pi/4 DQPSK (Differential Quaternary Phase Shift Keying)
Due to technology improvements, it is now possible to have the same amount of channels with less bandwidth
If someone were to purchase a frequency, the frequency purchased would be the “center” frequency.
Frequencies can be purchased through periodic auctions put on by the FCC
Example: AM radio stations typically have better quality than FM stations
50 years ago only VHF band of spectrum was usable for PMR users due to unstable hardware

8. Spectrum overview TETRA in Europe - 380-385/390-395 MHz
The radio spectrum is regulated by the FCC and has well-defined rules for bandwidth utilization.
i.e. how efficient a radio system uses the spectrum that it has available
TETRA in Europe / MHz
Asia Pacific and South America: frequencies // MHz
Able to operate between 300 to 1000 MHz 

9. Analog vs digital
Digital systems use binary numbers and have to encode and decode a voice signal by using a voice codec
The voice signal is translated in a way so that it best represents a voice signal in the codecs reference table
Since something like background noise cannot be translated in the reference table, it makes digital systems good at filtering background noise
CODEC = voice coder/decoder

10. Analog vs digital
Threshold = point at which communication is lost
Note: the digital voice quality is significantly higher for the most part when compared to analog
Many other factors can determine the voice quality such as antenna spacing, transmitted RF power, receiver sensitivity,…
Note: Just for an overall picture, other factors can effect the voice quality as well

11. Analog vs digital
Security is easier to implement on a digital system because encryption algorithms are generally digital themselves
Non-voice services in an analog system would need an entirely separate method, whereas it can be built into digital
Digital radios are much more expensive
Really depends on the type of user and what they need
The best security algorithms are digital
Digital radios are currently more expensive but will change over time
A small police department of 4 officers will not need a multi-million dollar communications system

12. Conventional radio
Only a single channel of frequency is used for each communication path
- predetermined
Not very efficient, especially for critical communications
A pair of frequencies can be used in the same way, (one for North, one for south)
Manual switching
One communication channel is used and it is predetermined what frequency will be used to transmit the message
If the channel is being used and someone else wants to use it, they have to wait for it to open up

13. Conventional radio
The frequency carrier itself defines who the message gets sent out to
Doesn’t mean a single radio can be programmed to listen to all channels or have all of them programmed in their radio…

14. Trunked radio
Multiple channels are pooled together and used as a shared resource
A trunking controller is used to locate an open channel in the pool of channels and uses it to repeat the message across the system
Unknown what frequency will be used
A talkgroup is used to keep track of who needs to hear what messages
Why the name “Trunked”?
The term trunking refers back to old telephone networks, the connections between them were thick hard lines, and were often covered in lead to reduce interference, thus resembling an elephant trunk
It is unknown at the time the button is pressed what frequency the message will be sent out on

15. Trunked radio Fire: Using channel 1, only Talk Group 1 will hear it
Simultaneously Police sends a message
Trunking controller automatically allocates another channel for TG 2 to use
-Could be a different channel every time
-Each time a user is essentially sending a request to use the system, vs. the actual message
In a trunking system, it is unknown at call set-up time which exact frequency will be used.
The trunking controller picks an available channel and then assigns the talk group to it so the message can retransmitted
In most situations of public safety systems, most radios have all talk groups programmed into their radios

16. Trunking benefits
The main advantage to trunking is that it factors in that not everyone will need channel access at the same time
Therefore, fewer channels are required for the same amount of users
Likewise, with the same number of radio channels, more users can be brought in
A voter can seamlessly transfer an ongoing call to another site if a user is mobile and suddenly goes out of range of a certain site

17. Trunking benefits TETRA at 4 channels per 25 kHz bandwidth
TETRA system utilizing a 25 kHz bandwidth has 4 communication channels, considered narrowband by FCC
TETRA at 4 channels per 25 kHz bandwidth

18. Trunking benefits
Trunking does not increase the amount of simultaneous conversations per channel, it only utilizes the channels more efficiently
If a channel goes down, it can be (almost) seamlessly transferred to another channel

19. Trunking downfalls
Problems with the channel controller could mean problems for everyone
A slightly longer delay for communication set up
Trunking radios are more expensive
Central controller controls everything, fix = have a backup!
Delay caused by the controller searching for an available channel, Not by much, hardly noticed
Expensive due to the lack of competition

20. Tetra introduction Schengen Agreement An agreement to lessen
TETRA is an open standard developed by the European Telecommunications Standards Institute
It was developed for the PMR market in order to solve the problems of congestion and a growing demand for data services
Schengen Agreement
An agreement to lessen
border controls between
distinct countries (1985)
TETRA was originally designed to solve the Schengen agreement which sought to have cross-border communications between certain European countries and also allow citizens to cross borders more freely

21. Tetra introduction
TETRA is in use throughout the world and is considered the first truly open digital private mobile radio standard
The openness allows different equipment from different manufacturers to be able to fully communicate with each other.
It is currently not allowed in the US for multiple reasons, some of which there is debate over, but will be allowed soon
Others: P25, DMR
Other examples in the United States are: P25 – a digital trunking method (expensive), DMR – not fully functional yet
Opposite example: Apple products, only Apple software runs on Apple hardware

22. Tetra introduction
TETRA is currently not fully compliant with certain FCC rules dealing with frequency allocation
The TETRA Association has already requested that the rules be waived and the waivers are currently in progress with some of them already waived
In the future it is likely that the FCC will follow the waivers with a rule-making process to allow TETRA equipment in the US permanently

23. Tetra introduction
Motorola Inc. has many intellectual property rights on TETRA due to the companies effort in developing the standard
The company claims that it would support the use of TETRA in the US, if there is evidence that enough people have a need for it
There are many in the industry that believe Motorola is protecting its P25 business

24. Tetra technology
TETRA uses Time Division Multiple Access (TDMA) in order to increase the number of channels on a given frequency
It can divide one 25 kHz channel into four separate communication channels
This creates both a cost savings in frequency needed and the amount of hardware needed per system

25. Tetra technology 1 time slot = 14.167 ms
1 TDMA frame = 4 time slots = ms
1 muliframe = 18 TDMA frames = 1.02 s
Circuit mode compresses the data frames down to 17 to allow the 18th to be a control frame

26. Tetra technology
Channels in TETRA can be designated for any combination of voice and data

27. Tetra technology
pi/4 DQPSK – pi/4 Differential Quaternary Phase Shift Keying is what TETRA uses for its common TETRA V+D and TEDS control channel
Phase shift keying relies on shifts of the phase of the signal to transmit data, versus shifting the frequency or amplitude
In pi/4 there are four possible phase shifts: -3π/4, +3π/4, +π/4, -π/4

28. Tetra technology Example, not actually what TETRA uses
Bit value Amount of shift
00 None /4 /2 /4
 Correct Pattern:

29. Tetra technology
Quadrature Amplitude Modulation (QAM) is a combination of amplitude modulation and PSK
If two different amplitudes are used, along with 4 different phases, that equates to a total of 8 different possible combinations
QAM is used in Release 2 where TEDS is defined

30. Tetra technology Bit value Amplitude Phase shift 000 1 None 001 2 010
1/4
011
100
1/2
101
110
3/4
111
Each wave gets shifted from the wave before it

31. Tetra technology
Also require better signal to noise ratio, and error rates also increase
In general, the higher order modulations provide higher data rates,
but are more prone to error
** The three different levels of 64-QAM refer to the amount
of interference protection against noise used

32. Tetra technology
16-QAM equates to 16 possible bit values: 0000, 0001 …. 1110, 1111
64-QAM equates to 64 possible bit values: , , …
The higher the amount of possible values, the more chance there is for error since the shifts are closer together
QoS attributes can also be negotiated such as; throughput, delay, priority and reliability.

33. Tetra technology
the decision boundaries of lower order schemes are much larger
The difference in phase is known as “phase jitter”

34. Tetra standards TETRA Release 1:
The original release of TETRA occurred, previously known as the TETRA V & D or voice and data.
Defined the original functionality such as the interfaces, voice and basic (slow) data services
< 20 k bit/s throughput…

35. Tetra Standards DMO – Direct Mode Operation AIR IF – Air Interface
TEI – Terminal Equipment Interface
ISI – Inter-System Interface
AIR IF, and DMO – most complicated and most complex
TEI- facilitates the independent development of mobile data applications.

36. Tetra Standards Also can interface to:
PSTN/ISDN/PABX, WAN/LAN, and internet

37. Tetra Voice and data Group Call – Not unique to TETRA
TETRA provides very fast call set-up time of 300 ms
This would be very difficult to do on a cellular network, since they were primarily designed for one-to-one calls
Pre-Emptive Priority Call (Emergency Call)
Call Retention – protects users from being forced off the network
Pre-Emptive Priority Call – In emergency situations, a user can push a predefined button to give them highest priority access to the network resources. It will even drop current calls on the network if need be.

38. Tetra Voice and data
Priority Call – allows 16 different resource access levels
Dynamic Group Number Assignment (DGNA) – creating talkgroups “on the fly”
Ambience Listening
Busy Queuing
Full-Duplex phone calls: Basically anything that you can do with a regular phone – caller ID, block call, call forward, call hold…
Eliminates the need for a cell phone
Priority Call – Provides different GoS to different users. Ex: Front-line officers
DGNA – Ex. Creating a group for select police, fire and EMS users during a major incident where close coordination is needed
Ambience Listening – ability to place a radio in listen-only mode, without any notification that it is in the mode. Also brings up questions of invasion on privacy.
Busy Queuing – If the network is at full capacity, then a new call will be placed in a queue to later have the request fulfilled in a FIFO manner

39. Tetra Voice and data Data Services :
Short Data Service – Implemented on the TETRA control channel, only can support up to 256 bytes per message
Packet Data Service – Both connection-oriented and connection-less configurations
Data Rate (bit/s)
No. Time Slots
High Protection*
Protected
Not Protected 1
2400
4800
7200 2
9600
14400 3
21600 4
19200
28800
TETRA also supports Data services on top of the voice services.
*Protection – protection against data corruption due to noise, or other environmental factors

40. Why not use gsm or 3g?
Many organizations are looking at using cellular based services due to the data rates available
Technology
Unit
Narrow Band
Wide Band
Broadband
TETRA 1
kbits/s
7.2 to 28.8
TETRA 2
28.8 to 384+
GSM
9.6
GPRS
115
EDGE
144 to 384 3G
384 to 2,000
One thing that many PMR users are considering is switcing over to a cellular service.
From the table above it looks like a viable option, but data rates are on the lower priority side of things with most PMR users.

41. Why not use gsm or 3g? Service TETRA GSM 3G Group call yes no No
Broadcast call
End-to-End encryption
DMO
Gateways
Transmit Inhibit
Simultaneous V & D
Receive only
Access Priority
Late Entry
Discreet Listening
Service
TETRA
GSM 3G
Priority call
yes no
Ambience listening No
Multiple key encryption
Full duplex telephony
Over air encryption
Long range capability
Area selection
Other services, like the ones shown below are much more useful and important to most PMR users.
Most companies or agencies do not want their employees to have the capabilities to go on facebook anyway.
From the above charts it is apparent that TETRA offers the key services that PMR users want.

42. Why not use gsm or 3g? TETRA was designed for PMR use, by PMR users
Cellular technologies were designed for one-one-communication primarily and therefore do not offer the services needed by PMR users
The higher data rates offered are not of interest to the PMR market
Other features are more important:
Call setup time, (6-9 seconds versus 300 ms)
Reliability, security, must be highly available

43. Tetra DMO
Direct Mode Operation – Allowing TETRA radio terminals to communicate directly with one another while outside of the TETRA network
Allows for local communications when the entire group does not need to be notified - “Back-to-Back mode”
Allows for Trunked Mode Operation extension or “Gateway mode”, an extension back to the network to out-of-range terminals

44. Tetra DMO
“Back-to-Back” – normal DMO operation (nearby communications)
“Gateway Mode” – special equipment can provide communications between both networks
“Dual Watch” – Also allows communication between both networks

45. TETRA ISI
Allows a TETRA terminal to access another TETRA network other than the one it is registered on
Assignment of talk groups needs to be defined
Billing of telephony calls
Encryption schemes used must be released
No need for extra hardware
Only a few systems currently using ISI
Talk Groups – does the roaming user still need to communicate with the original talk groups?
Telephony calls – who should be billed?
Releasing the encryption scheme becomes a security risk

46. TETRA Release 2
Work started around 1999, and was released at the end of 2005
High Speed data with rates almost 10 times greater than that of Release 1
Expected rates of 30 – 400 kbits/s
More voice codecs in order to improve communications with cellular systems
Fully compatible with TETRA Release 1
TMO range extension
Released around end of 2005, started in 1999

47. TETRA Security 3 methods: Supports four AIE Algorithms
Authentication
Used to make sure both the radio is allowed, and if the network is trusted
Air Interface Encryption (AIE)
Protects against eavesdropping
End to End encryption
Supports four AIE Algorithms
TEA1, 2, 3, 4 which each have a specific area of use
Enabling/Disabling of terminals

48. TETRA Data applications
Custom Applications can be created for a TETRA system using SDS, Packet data service, or TEDS
No generic “TETRA SDK” – systems differ on terminal and network side a lot
The SDS on TETRA primarily would only be useful for status messaging or Automatic Vehicle Location, (AVL) due to the low data rate

49. Tetra Data applications
The Packet data service allows for things such as: Database lookup, imaging, or slow scan video.
High speed data could be used for things such as fingerprinting or real time video.
The wide variety of data services offered by TETRA, along with over 350 companies offering solutions, make it an ideal choice for data applications in the PMR market

50. Tetra users BMW’s plant in Dingolfing, Germany
Had multiple analog systems replaced by a single TETRA system
SDS message is sent whenever there is a fault on the production line
If no one accepts, the system re-sends the message up to three times, and then gets transferred to a manager
If more than one person accepts, only one of them will be given instructions to attend the fault
- If no team representative is able to accept, the system resends the SDS up to three times, after which the request is escalated to a supervisor who then makes the final decision with regards to job allocation.
- If more than one operative accepts the repair job, only one of them will be automatically selected to receive instructions to attend the fault. -

51. Tetra users 2008 Beijing Olympics Petrom S.A. Petrobrazi Oil Refinery
Handled 1.6 million calls a day, Asia's largest TETRA network
90,000 users
Petrom S.A. Petrobrazi Oil Refinery
Around 2,000 employees, using SDS for tracking of employees
Doubled the previous systems capacity using the same amount of spectrum
New system is also much more scalable

52. Tetra in the us
NYC Transit carried out a TETRA pilot in 2011, along with NJ Transit in 2010
Both pilots confirmed that TETRA meets and exceeds their requirements for voice and data communications
TETRA pilot in Wisconsin
Nielson Communications Inc. Green Bay, WI is comparing their current analog system to a TETRA system

53. Tetra pilot in US
Blue = Best
Red = Weak
Black = No signal

54. Tetra pilot in US
Connected the TETRA system to an IP-based phone system for full duplex phone calls, also had AVL capabilities
In summary the results of signal coverage compared to other systems is about the same as TETRA
Loud background noise is filtered out very well on a TETRA system
Easy radio interface to train and use
Busted the myth of needing more hardware for a TETRA system
Clear audio and voice even in noisy environments
Radio interfaces resemble a cell phone

55. Tetra current market
As of 2010, total TETRA contracts has grown to 465
TETRA is operating in over 125 countries
Over the next four years, the Compound Annual Growth Rate of TETRA is expected to grow by 15%

56. Tetra current market
2010 a record year for terminal shipments (IMS analysis)
Deployment of new networks up 6% and extensions up 8%
Source: TETRA MoU

57. Tetra current market
Source: TETRA MoU

58. Video Examples

59. Tetra summary Trunking Benefits TDMA benefits
Spectrum utilization, security, better coverage
TDMA benefits
less hardware = less cost, concurrent voice and data
Unique TETRA services; ISI, DMO, security features, DGNA, full duplex phone calls.. Etc
Increased competition due to openness means cheaper products and solutions

60. Questions

61. Sources
References
Is TETRA on its way to North America? - Urgent Communications article. (n.d.). Urgent Communications magazine online | Formerly MRT magazine. Retrieved March 25, 2012, from
Phase Shift Keying. (n.d.). Home - University of Delaware Dept. of Physics & Astronomy. Retrieved March 27, 2012, from
Unrequited love | Many in the U.S. are smitten with TETRA, and they don’t understand why they can’t have it. (n.d.). Urgent Communications magazine online | Formerly MRT magazine. Retrieved March 25, 2012, from
Signal Harbor. (2005). Understanding trunking. Retrieved from
Hayes, W. (2003, May 29). What is trunking. Retrieved from

62. Sources
TETRA Association. (n.d.). Tetra. Retrieved from
TETRA Association. (2006, January). Tetra technology advantages & benefits. Retrieved from Benefits.pdf
Krishna, S. (2012, April 12). Non coherent demodulation of pi/4 dqpsk (tetra). Retrieved from
Barrus, J. (2012, March 5). Fresh ideas in two-way communications. Retrieved from
Charan, L. (2006). Complex technology made real. Retrieved from
ETSI. (2007, October). Etsi TR v Retrieved from
University of California, Berkeley. (Producer). (2000). The radio spectrum. [Print Photo]. Retrieved from
Ascom. (n.d.). Tetra - terrestrial trunked radio. Retrieved from