1 / 62

TETRA Terrestrial trunked radio

Joe Nielson. TETRA Terrestrial trunked radio. outline. Radio Terminology/Basics What is “trunked radio” TETRA Technology Standards Features TETRA today. Radio terminology. Base Station – Tower site “repeater” radio Portable Radio – Hand held, lower power, when compared to Mobile

yazid
Download Presentation

TETRA Terrestrial trunked radio

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Joe Nielson TETRATerrestrial trunked radio

  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.

  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

  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

  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

  8. Spectrum overview TETRA in Europe - 380-385/390-395 MHz Asia Pacific and South America: frequencies 806-824//851-869 MHz Able to operate between 300 to 1000 MHz  http://ptolemy.eecs.berkeley.edu/eecs20/sidebars/radio/freqchrt.pdf

  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

  10. Analog vs digital 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

  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

  13. Conventional radio The frequency carrier itself defines who the message gets sent out to

  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”?

  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

  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

  17. Trunking benefits 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

  20. Tetra introduction • 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)

  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

  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 = 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

  26. Tetra technology

  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 valueAmount of shift 00 None 01 1/4 10 1/2 11 3/4  Correct Pattern: 00 00 10 00 10 00

  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

  30. Tetra technology Each wave gets shifted from the wave before it

  31. Tetra technology • 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: 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.

  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

  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

  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

  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 *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

  41. Why not use gsm or 3g?

  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

  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

  47. TETRA Security • 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 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

More Related