Joe Nielson

Radio Terminology/Basics What is “trunked radio” TETRA

TechnologyStandardsFeaturesTETRA today

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.

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

A radio channel is a single band of frequency that can successfully deliver radio communicationsEither voice or data

The size of the channel, or bandwidth is determined by the channels frequency tolerance and the type of transmissionCannot have channels interfering with each

other

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

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

http://ptolemy.eecs.berkeley.edu/eecs20/sidebars/radio/freqchrt.pdf

TETRA in Europe - 380-385/390-395 MHzAsia Pacific and South America: frequencies 806-824//851-869 MHzAble to operate between 300 to 1000 MHz 

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

Note: Just for an overall picture, other factors can effect the voice quality as well

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 expensiveReally depends on the type of user and

what they need

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

The frequency carrier itself defines who the message gets sent out to

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 systemUnknown what frequency will be used

A talkgroup is used to keep track of who needs to hear what messages

Why the name “Trunked”?

1. Fire: Using channel 1, only Talk Group 1 will hear it

2. Simultaneously Police sends a message

3. 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

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

TETRA at 4 channels per 25 kHz bandwidth

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

Problems with the channel controller could mean problems for everyone

A slightly longer delay for communication set up

Trunking radios are more expensive

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 AgreementAn agreement to lessen

border controls between

distinct countries (1985)

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

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

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

o TETRA uses Time Division Multiple Access (TDMA) in order to increase the number of channels on a given frequency

o It can divide one 25 kHz channel into four separate communication channels

o This creates both a cost savings in frequency needed and the amount of hardware needed per system

1 time slot = 14.167 ms 1 TDMA frame = 4 time slots = 56.67 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

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

Bit value Amount of shift00 None01 1/410 1/211 3/4

Example, not actually what TETRA uses

 Correct Pattern: 00 00 10 00 10 00

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

Bit value

AmplitudePhase shift

000 1 None

001 2 None

010 1 1/4

011 2 1/4

100 1 1/2

101 2 1/2

110 1 3/4

111 2 3/4

Each wave gets shifted from the wave before it

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

16-QAM equates to 16 possible bit values: 0000, 0001 …. 1110, 1111

64-QAM equates to 64 possible bit values: 100000, 110000, …

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.

the decision boundaries of lower order schemes are much larger

The difference in phase is known as “phase jitter”

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…

DMO – Direct Mode Operation AIR IF – Air Interface TEI – Terminal Equipment Interface ISI – Inter-System Interface

Also can interface to: PSTN/ISDN/PABX, WAN/LAN, and internet

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

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

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 4800 9600 14400

3 7200 14400 21600

4 9600 19200 28800

*Protection – protection against data corruption due to noise, or other environmental factors

Technology Unit Narrow Band

Wide Band Broadband

TETRA 1 kbits/s 7.2 to 28.8

TETRA 2 kbits/s 28.8 to 384+

GSM kbits/s 9.6

GPRS kbits/s 115

EDGE kbits/s 144 to 384

3G kbits/s 384 to 2,000

Many organizations are looking at using cellular based services due to the data rates available

Service TETRA GSM 3G

Group call yes no No

Broadcast call yes no No

End-to-End encryption

yes no No

DMO yes no No

Gateways yes no No

Transmit Inhibit yes no No

Simultaneous V & D

yes no No

Receive only yes no No

Access Priority yes no No

Late Entry yes no No

Discreet Listening

yes no No

Service TETRA GSM 3G

Priority call yes no yes

Ambience listening

yes no No

Multiple key encryption

yes no No

Full duplex telephony

yes yes yes

Over air encryption

yes yes yes

Long range capability

yes no No

Area selection yes no No

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

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

“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

TMO

DMO

Dual Watch Mode (Receives from TMO only)

“Back-to-Back”

Gateway Mode

DMO

FAIL

Allows a TETRA terminal to access another TETRA network other than the one it is registered onAssignment of talk groups needs to be

definedBilling of telephony callsEncryption schemes used must be releasedNo need for extra hardware

Only a few systems currently using ISI

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 1Expected 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

3 methods: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 AlgorithmsTEA1, 2, 3, 4 which each have a specific

area of use

Enabling/Disabling of terminals

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

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

BMW’s plant in Dingolfing, GermanyHad multiple analog systems replaced by a

single TETRA systemSDS 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

2008 Beijing Olympics Handled 1.6 million calls a day, Asia's

largest TETRA network90,000 users

Petrom S.A. Petrobrazi Oil RefineryAround 2,000 employees, using SDS for

tracking of employeesDoubled the previous systems capacity

using the same amount of spectrumNew system is also much more scalable

NYC Transit carried out a TETRA pilot in 2011, along with NJ Transit in 2010Both pilots confirmed that TETRA meets

and exceeds their requirements for voice and data communications

TETRA pilot in WisconsinNielson Communications Inc. Green Bay,

WI is comparing their current analog system to a TETRA system

Blue = BestRed = WeakBlack = No signal

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

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%

2010 a record year for terminal shipments (IMS analysis)

Deployment of new networks up 6% and extensions up 8%

Source: TETRA MoU

Source: TETRA MoU

Video Examples

http://www.youtube.com/watch?v=LdKp6M4pKSo&feature=relmfu

http://www.youtube.com/watch?feature=player_embedded&v=LJn2HrJarQM

http://www.youtube.com/watch?v=PVAKRQofNoY&feature=endscreen&NR=1

Trunking BenefitsSpectrum utilization, security, better coverage

TDMA benefitsless 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

Questions

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 http://urgentcomm.com/networks_and_systems/commentary/tetra-north-america-20090617/

Phase Shift Keying. (n.d.). Home - University of Delaware Dept. of Physics & Astronomy. Retrieved March 27, 2012, from http://www.physics.udel.edu/~watson/scen103/projects/96s/thosguys/psk.html

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 http://urgentcomm.com/mobile_voice/mag/digital-trunked-mobile-tetra-0301/index1.html

Signal Harbor. (2005). Understanding trunking. Retrieved from http://www.signalharbor.com/sr/05apr/index.html

Hayes, W. (2003, May 29). What is trunking. Retrieved from http://www.thebriarpatch.org/trunking/

Sources TETRA Association. (n.d.). Tetra. Retrieved from

http://www.tetramou.com/about/page/12027 TETRA Association. (2006, January). Tetra technology advantages & benefits.

Retrieved from http://www.tetramou.com/Library/Documents/Why_TETRA/Technology Benefits.pdf

Krishna, S. (2012, April 12). Non coherent demodulation of pi/4 dqpsk (tetra). Retrieved from http://www.dsplog.com/2010/04/12/non-coherent-demodulation-of-pi4-dqpsk-tetra

Barrus, J. (2012, March 5). Fresh ideas in two-way communications. Retrieved from http://communities.motorola.com/community/two-way_communications/blog

Charan, L. (2006). Complex technology made real. Retrieved from http://www.complextoreal.com

ETSI. (2007, October). Etsi TR 102 580 v1.1.1. Retrieved from http://pda.etsi.org/exchangefolder/tr_102580v010101p.pdf

University of California, Berkeley. (Producer). (2000). The radio spectrum. [Print Photo]. Retrieved from http://ptolemy.eecs.berkeley.edu/eecs20/sidebars/radio/spectrum.gif

Ascom. (n.d.). Tetra - terrestrial trunked radio. Retrieved from http://www.ascom.com/en/tetra-article.pdf