TETRA SYSTEMS - TRAINING


Course Summary

TETRA is a mobile radio technology that is being used for a proposed new police communications system, offered throughout the UK by the Home Office. The system is called Airwave, and in England and Wales the network of masts is being installed by a part of mmO2 plc, known as O2 Airwave. TETRA, like mobile phone systems, uses masts (or ‘base stations’) and handsets that look very like a chunky mobile phone. The masts usually have three poles, and each pole usually has four flattened loops. Some antennae are straight. TETRA offers the user fairly secure communications, that, like all other digital radio technologies, delivers clear speech. It allows users with the radios the ability to talk in a group, and to talk to other users with similar digital systems elsewhere. It has a ‘help’ button that enables the user to call for assistance very quickly. Other facilities, such as looking up police computer information, whilst said to be possible in the future, will not be delivered as promised.
TETRA is a microwave system, like ordinary mobile phones, but the masts ‘talk’ to each other directly. Unlike mobile phone masts, they transmit constantly, 24 hours a day. TETRA messages are sent in pulses or bursts that are transmitted at a frequency coinciding with the electrical frequency of the human brain in its waking state. In a report to the Government, this was declared unsafe, and to be avoided. There are many reasons why it is unsafe, but this message was ignored when the Home Office decided only to consider TETRA systems

TETRA SYSTEMS - OUTLINES


PMR: Private Mobile Radio

􀂉 cost effective mobile communications for private networks
􀂉 many specialised facilities not available in public mobile networks
􀂉 usually stand-alone networks
􀂉 advanced systems allow interconnection with fixed network (voice/data)
􀂉 use of VHF/UHF allow good coverage with small antennas
􀂉 Target users
􀂉 police forces
􀂉 fire brigades
􀂉 emergency health
􀂉 military forces
􀂉 transportation fleets: goods, taxi, buses
􀂉 utilities: electricity, gas, water

PMR systems

􀂉 Basic mobile radio systems
􀂉 simple two-way radio without base stations
􀂉 users within range of each other
􀂉 fixed frequency assignment (sometimes manually selectable)
􀂉 usually no privacy
􀂉 Advanced mobile radio systems
􀂉 cellular network architecture - trunked systems
􀂉 secure communications
􀂉 efficient use of frequency spectrum
􀂉 possibility of shared resources - PAMR: Public Access Mobile Radio
􀂉 examples of technologies: TETRA / TETRAPOL

PMR special requirements (I)

􀂉 Reliability
􀂉 high service availability
􀂉 minimum service still possible in case of large breakdown
􀂉 Centralised / Decentralised operation
􀂉 central dispatch point to organise users
􀂉 possibility of direct mode operation (without central control or any infrastructure al all)
􀂉 Various types of call
􀂉 point-to-point (single user to single user)
􀂉 group (pre-defined number of users)
􀂉 broadcast (all users in the network; all users in a selected area)

PMR special requirements (II)

􀂉 Call set-up
􀂉 sub-second call set-up time
􀂉 PTT - Press To Talk operation
􀂉 usually no need for action to answer
􀂉 Security
􀂉 increased security
􀂉 possibility of end to end encryption
􀂉 Call priorities
􀂉 classes of users with higher priority
􀂉 urgent calls may be able to pre-empt other call types

Telecommunication Services for TETRA Systems

Network architecture
Network functions
Establishing service
Location registration
Register/de-register
Connection restoration
Call re-establishment
Security features
Services supported at the defined system interfaces
Services supported at the defined system gateways
Trunking methods
Message trunking
Transmission trunking
Quasi-transmission trunking

Propagation Models in TETRA Systems

Introduction
Static
Rural Area (RAx
Hilly Terrain (HTx)
Typical Urban (TUx) and Bad Urban (BUx)
Equalizer testing model (EQx)
Sensitivity, interference rejection and nominal performance
Definition of sensitivity
Reference sensitivity levels and reference sensitivity performance
Equivalent signal-to-noise ratio
TETRA Interference rejection
Nominal performance
Sensitivity comparison of TETRA with analogue FM systems
Comparison of co-channel interference rejection of TETRA with analogue FM
Path loss model
Rural Area
Suburban area
Link budget
Signal variability
Area coverage
Noise limited
Coverage for stationary operation
Coverage for moving MSs
Interference limited
Quasi-synchronous operation
Direct mode

Technical Description for TETRA Systems

OSI reference model of a TETRA system
Testable boundaries
Description of MS/BS air interface protocol architecture
Mapping of higher layer data on to the physical layer
Physical layer
Physical resources
TDMA frame structure
Slot structure
Radio transmission burst structure
Slot structure formats within the physical layer
Organization of layer 2 - Data Link Control (DLC)
Logical channels in the lower MAC
Logical channels in the upper MAC
Use of the logical channels and mapping between layers
Physical layer functionality of TETRA System
Lower MAC functionality
How it all hangs together
Broadcast channel
Signalling channel
Traffic channels
Logical channels supporting operation of the physical layer
MAC functionality
Random access procedures
Reserved access procedures
Call set-up procedures
Individual calls
Group calls
Layer 3 functionality
Cell selection and re-selection
Establishing service
Acquiring cell synchronization
Acquiring network information
Cell selection and re-selection in TETRA systems
System modes of operation
Normal mode
Extended mode
TETRA systems minimum mode
Discontinuous downlink transmissions - time sharing mode
MCCH sharing mode
Carrier sharing mode
MS modes of operation
Idle mode
Common signalling and packet mode
Traffic mode
Stealing mechanism
Uplink stealing
Criteria for uplink stealing
Downlink stealing
Reception of downlink transmissions
Energy economy mode
Independent allocation of uplink and downlinks
Classes of MS
MS power classes
MS receiver classes
MS duplex capability
Frequency half duplex operation
Frequency full duplex operation
Support of air-interface encryption
Support of concurrent calls
Data services in Voice plus Data
Short data service
Circuit mode data
Packet mode data
X.25 connection mode packet data
Connectionless mode
Network interconnection

Radio Aspects in TETRA Systems

Area coverage techniques
Single site wide area coverage
Cellular channel re-use
Quasi-synchronous transmission
Time sharing transmission
Antenna diversity
Site diversity
Direct Mode (DM) / trunked gateway
On-frequency repeaters
Comparison of some area coverage techniques
Small active cells versus passive receive only cells
Cellular versus quasi-synchronous
Quasi-synchronous versus time-shared transmission
DM / trunked gateway versus on-frequency repeaters
Radio parameters
Frequency allocation

Co-existence Aspects of TETRA Systems

Introduction
Impact of unwanted emissions near the carrier
Impact of unwanted emissions far from the carrier
Military systems

Other Unleashed Courses' List

Universal Mobile Telecommunications System UMTS and High Speed Packet Access HSPA
Telecommunication architecture and information Technologies
Multicarrier Technologies for 4G Mobile Communications
Certified Wireless Network Administrator ® (CWNA ®)
Global System for Mobile Communications GSM
General Packet Radio Service GPRS and EDGE
Long Term Evolution LTE and LTE Advanced
Wimax Technologies and Deployment
Wireless Local Area Network WLAN
Electricity and Electronics
LTE Implementation EPS System
RF Design and Applications
Wireless Communications
LTE Design in Depth
UMTS In-Depth

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