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
